AIM To investigate the underlying mechanisms of the protective role of remote ischemic perconditioning (RIPerC) in rat liver transplantation. METHODS Sprague-Dawley rats were subjected to sham, orthotopic liver transp...AIM To investigate the underlying mechanisms of the protective role of remote ischemic perconditioning (RIPerC) in rat liver transplantation. METHODS Sprague-Dawley rats were subjected to sham, orthotopic liver transplantation (OLT), ischemic postconditioning (IPostC) or RIPerC. After 3 h reperfusion, blood samples were taken for measurement of alanine aminotransferase, aspartate aminotransferase, creatinine (Cr) and creatinine kinase-myocardial band (CK-MB). The liver lobes were harvested for the following measurements: reactive oxygen species (ROS), H2O2, mitochondrial membrane potential (Delta psi m) and total nitric oxide (NO). These measurements were determined using an ROS/H2O2, JC1 and Total NOx Assay Kit, respectively. Endothelial NO synthase (eNOS) was analyzed by reverse transcription-polymerase chain reaction (RTPCR) and western blotting, and peroxynitrite was semiquantified by western blotting of 3-nitrotyrosine. RESULTS Compared with the OLT group, the grafts subjected to RIPerC showed significantly improved liver and remote organ functions (P < 0.05). ROS (P < 0.001) including H2O2 (P < 0.05) were largely elevated in the OLT group as compared with the sham group, and RIPerC (P < 0.05) reversed this trend. The collapse of Delta psi m induced by OLT ischemia/reperfusion (I/R) injury was significantly attenuated in the RIPerC group (P < 0.001). A marked increase of NO content and phosphoserine eNOS, both in protein and mRNA levels, was observed in liver graft of the RIPerC group as compared with the OLT group (P < 0.05). I/R-induced 3-nitrotyrosine content was significantly reduced in the RIPerC group as compared with the OLT group (P < 0.05). There were no significant differences between the RIPerC and IPostC groups for all the results except Cr. The Cr level was lower in the RIPerC group than in the IPostC group (P < 0.01). CONCLUSION Liver graft protection by RIPerC is similar to or better than that of IPostC, and involves inhibition of oxidative stress and up-regulation of the PI3K/Akt/eNOS/NO pathway.展开更多
A modified mixed strengthening model was proposed for describing the yield strength of particle reinforced aluminum matrix composites.The strengthening mechanisms of the composites were analyzed based on the microstru...A modified mixed strengthening model was proposed for describing the yield strength of particle reinforced aluminum matrix composites.The strengthening mechanisms of the composites were analyzed based on the microstructures and compression mechanical properties.The distribution uniformity of reinforcements and cooperation relationship among dislocation mechanisms were considered in the modified mixed strengthening model by introducing a distribution uniformity factor u and a cooperation coefficient fc,respectively.The results show that the modified mixed strengthening model can accurately describe the yield strengths of Al3Ti/2024Al composites with a relative deviation less than1.2%,which is much more accurate than other strengthening models.The modified mixed model can also be used to predict the yield strength of Al3Ti/2024Al composites with different fractions of reinforcements.展开更多
AIM To investigate the protective mechanism of mitofusin-2 (Mfn2) in rat remote ischemic perconditioning (RIC) models and revalidate it in alpha mouse liver-12 (AML-12) hypoxia cell lines. METHODS Sprague-Dawley rats ...AIM To investigate the protective mechanism of mitofusin-2 (Mfn2) in rat remote ischemic perconditioning (RIC) models and revalidate it in alpha mouse liver-12 (AML-12) hypoxia cell lines. METHODS Sprague-Dawley rats were divided into three groups (n = 6 each): sham, orthotopic liver transplantation and RIC. After operation, blood samples were collected to test alanine aminotransferase and aspartate aminotransferase. The liver lobes were harvested for histopathological examination, western blotting (WB) and quantitative real-time (qRT)-PCR. AML-12 cell lines were then subjected to normal culture, anoxic incubator tank culture (hypoxia) and anoxic incubator tank culture with Mfn2 knockdown (hypoxia + Si), and data of qRT-PCR, WB, mitochondrial membrane potential (Delta psi m), apoptosis, endoplasmic reticulum Ca2+ concentrations and mitochondrial Ca2+ concentrations were collected. RESULTS Both sham and normal culture groups showed no injury during the experiment. The RIC group showed amelioration of liver function compared with the orthotopic liver transplantation group (P < 0.05). qRTPCR and WB confirmed that Mfn2-mitochondrial Ca2+ uptake 1/2 (MICUs) axis was changed (P < 0.005). In AML-12 cell lines, compared with the hypoxia group, the hypoxia + Si group attenuated the collapse of..m and apoptosis (P < 0.005). The endoplasmic reticulum Ca2+ decrease and mitochondrial Ca2+ overloading observed in the hypoxia group were also attenuated in the hypoxia + Si group (P < 0.005). Finally, qRT-PCR and WB confirmed the Mfn2-MICUs axis change in all the groups (P < 0.005). CONCLUSION Mfn2 participates in liver injury in rat RIC models and AML-12 hypoxia cell lines by regulating the MICUs pathway.展开更多
Background:Remote ischemic perconditioning(RIPerC)has been demonstrated to protect grafts from hepatic ischemia-reperfusion injury(IRI).This study investigated the role of exosomes in RIPerC of liver grafts in rats.Me...Background:Remote ischemic perconditioning(RIPerC)has been demonstrated to protect grafts from hepatic ischemia-reperfusion injury(IRI).This study investigated the role of exosomes in RIPerC of liver grafts in rats.Methods:Twenty-five rats(including 10 donors)were randomly divided into five groups(n=5 each group):five rats were used as sham-operated controls(Sham),ten rats were for orthotopic liver transplantation(OLT,5 donors and 5 recipients)and ten rats were for OLT+RIPerC(5 donors and 5 recipients).Liver architecture and function were evaluated.Results:Compared to the OLT group,the OLT+RIPerC group exhibited significantly improved liver graft histopathology and liver function(P<0.05).Furthermore,the number of exosomes and the level of P-Akt were increased in the OLT+RIPerC group.Conclusions:RIPerC effectively improves graft architecture and function,and this protective effect may be related to the increased number of exosomes.The upregulation of P-Akt may be involved in underlying mechanisms.展开更多
Diamond coatings possess numerous excellent properties,making them desirable materials for high-performance surface applications.However,without a revolutionary surface modification method,the surface roughness and fr...Diamond coatings possess numerous excellent properties,making them desirable materials for high-performance surface applications.However,without a revolutionary surface modification method,the surface roughness and friction behavior of diamond coatings can impede their ability to meet the demanding requirements of advanced engineering surfaces.This study proposed the thermal stress control at coating interfaces and demonstrated a novel process of precise graphenization on conventional diamond coatings surface through laser induction and mechanical cleavage,without causing damage to the metal substrate.Through experiments and simulations,the influence mechanism of surface graphitization and interfacial thermal stress was elucidated,ultimately enabling rapid conversion of the diamond coating surface to graphene while controlling the coating’s thickness and roughness.Compared to the original diamond coatings,the obtained surfaces exhibited a 63%-72%reduction in friction coefficients,all of which were below 0.1,with a minimum of 0.06,and a 59%-67%decrease in specific wear rates.Moreover,adhesive wear in the friction counterpart was significantly inhibited,resulting in a reduction in wear by 49%-83%.This demonstrated a significant improvement in lubrication and inhibition of mechanochemical wear properties.This study provides an effective and cost-efficient avenue to overcome the application bottleneck of engineered diamond surfaces,with the potential to significantly enhance the performance and expand the application range of diamond-coated components.展开更多
AIM:To determine an optimal cutoff value for abnormal splenic artery diameter/proper hepatic artery diameter(S/P) ratio in cirrhosis-induced portal hypertension.METHODS:Patients with cirrhosis and portal hypertension(...AIM:To determine an optimal cutoff value for abnormal splenic artery diameter/proper hepatic artery diameter(S/P) ratio in cirrhosis-induced portal hypertension.METHODS:Patients with cirrhosis and portal hypertension(n = 770) and healthy volunteers(n = 31) underwent volumetric computed tomography threedimensional vascular reconstruction to measure the internal diameters of the splenic artery and proper hepatic artery to calculate the S/P ratio.The cutoff value for abnormal S/P ratio was determined using receiver operating characteristic curve analysis,and the prevalence of abnormal S/P ratio and associations between abnormal S/P ratio and major complications of portal hypertension were studied using logistic regression.RESULTS:The receiver operating characteristic analysis showed that the cutoff points for abnormal splenic artery internal diameter and S/P ratio were > 5.19 mm and > 1.40,respectively.The sensitivity,specificity,positive predictive value,and negative predictive value were 74.2%,45.2%,97.1%,and 6.6%,respectively.The prevalence of an abnormal S/P ratio in the patients with cirrhosis and portal hypertension was 83.4%.Patients with a higher S/P ratio had a lower risk of developing ascites [odds ratio(OR) = 0.708,95%CI:0.508-0.986,P = 0.041] and a higher risk of developing esophageal and gastric varices(OR = 1.483,95%CI:1.010-2.175,P = 0.044) and forming collateral circulation(OR = 1.518,95%CI:1.033-2.230,P = 0.034).After splenectomy,the portal venous pressure and maximum and mean portal venous flow velocities were reduced,while the flow rate and maximum and minimum flow velocities of the hepatic artery were increased(P < 0.05).CONCLUSION:The prevalence of an abnormal S/P ratio is high in patients with cirrhosis and portal hypertension,and it can be used as an important marker of splanchnic hemodynamic disturbances.展开更多
The aerospace community widely uses difficult-to-cut materials,such as titanium alloys,high-temperature alloys,metal/ceramic/polymer matrix composites,hard and brittle materials,and geometrically complex components,su...The aerospace community widely uses difficult-to-cut materials,such as titanium alloys,high-temperature alloys,metal/ceramic/polymer matrix composites,hard and brittle materials,and geometrically complex components,such as thin-walled structures,microchannels,and complex surfaces.Mechanical machining is the main material removal process for the vast majority of aerospace components.However,many problems exist,including severe and rapid tool wear,low machining efficiency,and poor surface integrity.Nontraditional energy-assisted mechanical machining is a hybrid process that uses nontraditional energies(vibration,laser,electricity,etc)to improve the machinability of local materials and decrease the burden of mechanical machining.This provides a feasible and promising method to improve the material removal rate and surface quality,reduce process forces,and prolong tool life.However,systematic reviews of this technology are lacking with respect to the current research status and development direction.This paper reviews the recent progress in the nontraditional energy-assisted mechanical machining of difficult-to-cut materials and components in the aerospace community.In addition,this paper focuses on the processing principles,material responses under nontraditional energy,resultant forces and temperatures,material removal mechanisms,and applications of these processes,including vibration-,laser-,electric-,magnetic-,chemical-,advanced coolant-,and hybrid nontraditional energy-assisted mechanical machining.Finally,a comprehensive summary of the principles,advantages,and limitations of each hybrid process is provided,and future perspectives on forward design,device development,and sustainability of nontraditional energy-assisted mechanical machining processes are discussed.展开更多
Owing to reliability and high strength-to-weight ratio,large thin-walled components are widely used in the aviation and aerospace industry.Due to the complex features and sequence involved in the machining process of ...Owing to reliability and high strength-to-weight ratio,large thin-walled components are widely used in the aviation and aerospace industry.Due to the complex features and sequence involved in the machining process of large thin-walled components,machining deformation of component is easy to exceed the specification.In order to address the problem,it is important to retain the appropriate finishing allowance.To find the overall machining deformation,finishing allowance-induced deformation(web finishing allowance,sidewall finishing allowance)and initial residual stress-induced deformation were considered as major factors.Meanwhile,machined surface residual stress-induced deformation,clamping stress-induced deformation,thermal deformation,gravity-induced deformation and inertial force-induced deformation were neglected in the optimization model.Six-peak Gaussian function was introduced to fit the initial residual stress.Based upon the obtained function of initial residual stress,a deformation prediction model between initial residual stress and finishing allowance was established to attain the finishing allowanceinduced deformation.In addition,linear programming optimization model based on the simplex algorithm was developed to optimize the overall machining deformation.Results have concluded that the overall machining deformation reached the minimum value when sidewall finishing allowance and web finishing allowance varied between 1 and 2 mm.Additionally,web finishing allowance-induced deformation and sidewall finishing allowance-induced deformation were1.05 mm and 0.7 mm.Furthermore,the machining deformation decreased to 0.3–0.38 mm with the application of optimized finishing allowance allocation strategy,which made 39–56%reduction of the overall machining deformation compared to that in conventional method.展开更多
AIM: To optimize the perfusates used for hypothermicmachine perfusion(HMP).METHODS: Sprague-Dawley rats were assigned randomly to three groups(n = 12 per group) that received either saline, University of Wisconsin col...AIM: To optimize the perfusates used for hypothermicmachine perfusion(HMP).METHODS: Sprague-Dawley rats were assigned randomly to three groups(n = 12 per group) that received either saline, University of Wisconsin coldstorage solution(UW) or histidine-tryptophan-ketoglutarate solution(HTK) as the perfusate. Each group was divided into two subgroups: static cold storage(SCS) and HMP(n = 6 per subgroup). The liver graft was retrieved according to the method described by Kamada. For the SCS group, the graft was directly placed into cold perfusate(0-4?℃) for 6 h after liver isolation while the portal vein of the graft was connected to the perfusion machine for the HMP group. Then the perfusates were collected at different time points for analysis of aspartate aminotransferase(AST), alanine transaminase(ALT) and lactate dehydrogenase(LDH) levels. Liver tissues were obtained for evaluation of histology, dry/wet weight(D/W) ratio, and malondialdehyde(MDA) and adenosine-triphosphate(ATP) levels. The portal vein pressure and velocity were monitored in real time in all HMP subgroups.RESULTS: Comparison of HMP and SCS: Regardless of the perfusate, HMP improved the architecture of donor graft in reducing the congestion around sinusoids and central vein and maintaining sinusoid lining in morphology; HMP improved liver function in terms of ALT, AST and LDH, especially during the 3-6 h period(SCS vs HMP using saline: ALT3, 225.00 ± 105.62 vs 49.50 ± 18.50, P = 0.047; LDH3, 1362.17 ± 563.30 vs 325.75 ± 147.43, P = 0.041; UW: LDH6, 2880.14 ± 948.46 vs 2135.00 ± 174.27, P = 0.049; HTK, AST6, 307.50 ± 52.95 vs 185.20 ± 20.46, P = 0.041); HMP decreased MDA level(saline, 2.79 ± 0.30 vs 1.09 ± 0.09, P = 0.008; UW, 3.01 ± 0.77 vs 1.23 ± 0.68, P = 0.005; HTK, 3.30 ± 0.52 vs 1.56 ± 0.22, P = 0.006). Comparison among HMP subgroups: HTK showed less portal vein resistance than UW and saline(vs saline, 3.41 ± 0.49 vs 5.00 ± 0.38, P < 0.001; vs UW, 3.41 ± 0.49 vs 4.52 ± 0.63, P = 0.007); UW reduced edema most efficiently(vs saline, 0.68 ± 0.02 vs 0.79 ± 0.05, P = 0.013), while HTK maintained ATP levels best(vs saline, 622.60 ± 29.11 vs 327.43 ± 44.66, P < 0.001; vs UW, 622.60 ± 29.11 vs 301.80 ± 37.68, P < 0.001).CONCLUSION: HMP is superior to SCS in maintaining both architecture and function of liver grafts. Further, HTK was found to be the optimal perfusate for HMP.展开更多
Traumatic injuries in the central nervous system,such as traumatic brain injury and spinal cord injury,are associated with tissue inflammation and the infiltration of immune cells,which simultaneously affect the self-...Traumatic injuries in the central nervous system,such as traumatic brain injury and spinal cord injury,are associated with tissue inflammation and the infiltration of immune cells,which simultaneously affect the self-renewal and differentiation of neural stem cells.Howeve r,the tissue repair process instigated by endogenous neural stem cells is incapable of restoring central nervous system injuries without external intervention.Recently,resident/peripheral immune cells have been demonstrated to exert significant effects on neural stem cells.Thus,the resto ration of traumatic injuries in the central nervous system by the immune intervention in neural stem cells represents a potential therapeutic method.In this review,we discuss the roles and possible mechanisms of immune cells on the selfrenewal and differentiation of neural stem cells along with the prognosis of central nervous system injuries based on immune intervention.Finally,we discuss remaining research challenges that need to be considered in the future.Further elucidation of these challenges will fa cilitate the successful application of neural stem cells in central nervous system injuries.展开更多
Platinum(Pt)supported on Zinc(Zn)modified silicalite-1(S-1)zeolite(denoted as Pt-Zn/S-1)was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time.Both Le...Platinum(Pt)supported on Zinc(Zn)modified silicalite-1(S-1)zeolite(denoted as Pt-Zn/S-1)was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time.Both Lewis and Bronsted acid sites were detected in Pt-Zn/S-1 catalyst by means of FT-IR adsorption of NH3 experiment,which were identified as mostly weak and medium ones.Besides,Pt and Zn species showed strong interaction,as revealed by the TPR(Temperature-programmed reduction)and XPS(X-ray photoelectron spectroscopy)experiments.Pt-Zn/S-1 catalyst exhibited excellent aromatization function rather than isomerization and cracking side reactions in the conversion of n-hexane.Pulse experimental study showed that 75.6%of n-hexane conversion and 76.8%of benzene selectivity were obtained over Pt0.1-Zn60/S-l catalyst at 550℃ and under atmospheric pressure.By spectroscopy tests and pulse experimental results,it was concluded that the n-hexane aromatization over Pt-Zn/S-1 catalyst follows a metal-acid bifunctional mechanism.Furthermore,with the assistance of Zn,the electron-deficient Pt species in Pt-Zn/S-1 showed good sulfur tolerance performance.展开更多
In the machining process of aircraft monolithic parts,the initial residual stress redistribution and structural stiffness evolution often lead to unexpected distortions.On the other hand,the stress redistribution and ...In the machining process of aircraft monolithic parts,the initial residual stress redistribution and structural stiffness evolution often lead to unexpected distortions.On the other hand,the stress redistribution and stiffness reduction during the machining process depend on the material removal sequence.The essence of the stress redistribution is releasing the initial elastic strain energy.In the present study,the influence of the material removal sequence on the energy release is studied.Moreover,a novel optimization method is proposed for the material removal sequence.In order to evaluate the performance of the proposed method,the mechanism of the machining distortion is firstly analyzed based on the energy principle.Then a calculative model for the machining distortion of long beam parts is established accordingly.Moreover,an energy parameter related to the bending distortion and the procedure of the material removal sequence optimization is defined.Finally,the bending distortion analysis and material removal sequence optimization are performed on a long beam with a Z-shaped cross-section.Furthermore,simulation and experiments are carried out.The obtained results indicate that the optimized sequence results in a low distortion fluctuation and decreases the bending distortion.展开更多
Covalent organic frameworks(COFs)are a novel type of crystalline porous organic polymer materials recently developed.It has several advantages in chromatographic separation field,such as high thermal stability,porosit...Covalent organic frameworks(COFs)are a novel type of crystalline porous organic polymer materials recently developed.It has several advantages in chromatographic separation field,such as high thermal stability,porosity,structural regularity,and large specific surface area.Here,a novel spherical COF 1,3,5-tris(4-aminophenyl)benzene(TAPB)and 2,5-bis(2-propyn-1-yloxy)-1,4-benzenedicarboxaldehyde(BPTA)was developed as an electrochromatographic stationary phase for capillary electrochromatography separation.The COF TAPB-BPTA modified capillary column was fabricated via a facile in situ growth method at room temperature.The characterization results of scanning electron microscopy(SEM),Fourier transform infrared(FT-IR)spectroscopy,and X-ray diffraction(XRD)confirmed that COF TAPB-BPTA were successfully modified onto the capillary inner surface.The electrochromatography separation performance of the COF TAPB-BPTA modified capillary was investigated.The prepared column demonstrated outstanding separation performance toward alkylbenzenes,phenols,and chlorobenzenes compounds.Furthermore,the baseline separations of non-steroidal anti-inflammatory drugs(NSAIDs)and parabens with good efficiency and high resolution were achieved.Also,the prepared column possessed satisfactory precision of the intra-day runs(n=5),inter-day runs(n=3),and parallel columns(n=3),and the relative standard deviations(RSDs)of the retention times of tested alkylbenzenes were all less than 2.58%.Thus,this new COF-based stationary phase shows tremendous application potential in chromatographic separation field.展开更多
Amines have been considered as promising candidates for post-combustion CO2 capture. A mechanistic understanding for the chemical processes involved in the capture and release of CO2 is important for the rational desi...Amines have been considered as promising candidates for post-combustion CO2 capture. A mechanistic understanding for the chemical processes involved in the capture and release of CO2 is important for the rational design of amines. In this study, the structural effects of amines on the kinetic competition among three typical products（carbamates, carbamic acids and bicarbonate） from amines ＋ CO2 were investigated, in contrast to previous thermodynamic studies to tune the reaction of amines with CO2 based on desirable reaction enthalpy and reaction stoichiometry. We used a quantum chemical method to calculate the activation energies（Ea） for the reactions of a range of substituted monoethanolamines with CO2 covering three pathways to the three products. The results indicate that the formation of carbamates is the most favorable, among the three considered products. In addition, we found that the Eavalues for all pathways linearly correlate with pK aof amines, and more importantly, the kinetic competition between carbamate and bicarbonate absorption pathways varies with p Kaof the amines, i.e. stronger basicity results in less difference in Ea. These results highlight the importance of the consideration of kinetic competition among different reaction pathways in amine design.展开更多
Different factors affecting the efficiency of the orifice energy dissipator were investigated based on a series of theoretical analyses and numerical simulations. The main factors investigated by dimension analysis we...Different factors affecting the efficiency of the orifice energy dissipator were investigated based on a series of theoretical analyses and numerical simulations. The main factors investigated by dimension analysis were identified, including the Reynolds number （Re）, the ratio of the orifice diameter to the inner diameter of the pipe （ did ）, and the ratio of distances between orifices to the inner diameter of the pipe （ LID ）. Then, numerical simulations were conducted with a k-ε two-equation turbulence model. The calculation results show the following： Hydraulic characteristics change dramatically as flow passes through the orifice, with abruptly increasing velocity and turbulent energy, and decreasing pressure. The turbulent energy appears to be low in the middle and high near the pipe wall. For the energy dissipation setup with only one orifice, when Re is smaller than 105, the orifice energy dissipation coefficient K increases rapidly with the increase of Re. When Re is larger than l05, K gradually stabilizes. As diD increases, K and the length of the recirculation region L1 show similar variation patterns, which inversely vary with diD. The function curves can be approximated as straight lines. For the energy dissipation model with two orifices, because of different incoming flows at different orifices, the energy dissipation coefficient of the second orifice （K2） is smaller than that of the first. If LID is less than 5, the K value of the LID model, depending on the variation of/（2, increases with the spacing between two orifices L, and an orifice cannot fulfill its energy dissipation function. If LID is greater than 5, K2 tends to be steady; thus, the K value of the LID model gradually stabilizes. Then, the flow fully develops, and L has almost no impact on the value of K.展开更多
Processing microchannels inside laminated aluminum nitride high-temperature co-fired ceramics(AlN HTCC) packaging, a typical difficult-to-cut ceramic, can effectively solve the heatdissipation problem of integrated ch...Processing microchannels inside laminated aluminum nitride high-temperature co-fired ceramics(AlN HTCC) packaging, a typical difficult-to-cut ceramic, can effectively solve the heatdissipation problem of integrated chips used in smart skin. In order to improve the processing efficiency and quality of AlN, the machinability of AlN after laser chemical milling(LCM) was studied through the milling force, machined surface quality, surface defects, formation mechanism, and tool wear. This study established a milling force model that can predict the milling forces of AlN and analyses the reasons for the improvements in the milling force based on experimental data and predicted data. The results from the model and experiments demonstrated that the milling force of the laser chemical milling assisted micro milling(LCAMM) decreased by 85%–90% and 85%–95%, respectively, due to the amount of removal of a single edge was more uniform and the actual inclination angle increased during the cutting process in LCAMM. Moreover, the machined surface quality improved by 65%–76% after LCM because of less tool wear, fewer downward-propagating cracks generated during each feed, and the surface removal mode transformed from intergranular fracture to transgranular fracture, which effectively reducing tool wear and improving tool life. Finally, when feed per tooth and depth of cut were 0.4 μm/z and 5 μm, the optimal machined surface quality was obtained, with a roughness of 64.6 nm Therefore, milling after LCM can improve the machinability of AlN and providing a feasibility for the high-quality and efficient machining of microchannels.展开更多
The variable air volume(VAV)air conditioning system is with strong coupling and large time delay,for which model predictive control(MPC)is normally used to pursue performance improvement.Aiming at the difficulty of th...The variable air volume(VAV)air conditioning system is with strong coupling and large time delay,for which model predictive control(MPC)is normally used to pursue performance improvement.Aiming at the difficulty of the parameter selection of VAV MPC controller which is difficult to make the system have a desired response,a novel tuning method based on machine learning and improved particle swarm optimization(PSO)is proposed.In this method,the relationship between MPC controller parameters and time domain performance indices is established via machine learning.Then the PSO is used to optimize MPC controller parameters to get better performance in terms of time domain indices.In addition,the PSO algorithm is further modified under the principle of population attenuation and event triggering to tune parameters of MPC and reduce the computation time of tuning method.Finally,the effectiveness of the proposed method is validated via a hardware-in-the-loop VAV system.展开更多
In recent years,gait-based emotion recognition has been widely applied in the field of computer vision.However,existing gait emotion recognition methods typically rely on complete human skeleton data,and their accurac...In recent years,gait-based emotion recognition has been widely applied in the field of computer vision.However,existing gait emotion recognition methods typically rely on complete human skeleton data,and their accuracy significantly declines when the data is occluded.To enhance the accuracy of gait emotion recognition under occlusion,this paper proposes a Multi-scale Suppression Graph ConvolutionalNetwork(MS-GCN).TheMS-GCN consists of three main components:Joint Interpolation Module(JI Moudle),Multi-scale Temporal Convolution Network(MS-TCN),and Suppression Graph Convolutional Network(SGCN).The JI Module completes the spatially occluded skeletal joints using the(K-Nearest Neighbors)KNN interpolation method.The MS-TCN employs convolutional kernels of various sizes to comprehensively capture the emotional information embedded in the gait,compensating for the temporal occlusion of gait information.The SGCN extracts more non-prominent human gait features by suppressing the extraction of key body part features,thereby reducing the negative impact of occlusion on emotion recognition results.The proposed method is evaluated on two comprehensive datasets:Emotion-Gait,containing 4227 real gaits from sources like BML,ICT-Pollick,and ELMD,and 1000 synthetic gaits generated using STEP-Gen technology,and ELMB,consisting of 3924 gaits,with 1835 labeled with emotions such as“Happy,”“Sad,”“Angry,”and“Neutral.”On the standard datasets Emotion-Gait and ELMB,the proposed method achieved accuracies of 0.900 and 0.896,respectively,attaining performance comparable to other state-ofthe-artmethods.Furthermore,on occlusion datasets,the proposedmethod significantly mitigates the performance degradation caused by occlusion compared to other methods,the accuracy is significantly higher than that of other methods.展开更多
High-volume fraction silicon particle-reinforced aluminium matrix composites(Si/Al)are increasingly applied in aerospace,radar communications,and large-scale integrated circuits because of their superior thermal condu...High-volume fraction silicon particle-reinforced aluminium matrix composites(Si/Al)are increasingly applied in aerospace,radar communications,and large-scale integrated circuits because of their superior thermal conductivity,wear resistance,and low thermal expansion coefficient.However,the abrasive and adhesive wear caused by the hard silicon reinforcement and the ductile aluminium matrix leads to significant tool wear,decreased machining efficiency,and compromised surface quality.This study combines theoretical analysis and cutting experiments to investigate polycrystalline diamond(PCD)tool wear during milling of 70 vol%Si/Al composite.A key contribution of this work is the development of a tool wear model that incorporates reinforcement particle characteristics,treating them as ellipsoidal structures,which enhances the accuracy of predicting abrasive and adhesive wear mechanisms.The model is based on abrasive and adhesive wear mechanisms,and can analyze the interaction between silicon particles,aluminium matrix,and tool components,thus providing deeper insights into PCD tool wear processes.Experimental validation of the model shows a good agreement with the results,with a mean deviation of approximately 10%.The findings on the tool wear mechanism reveal that,as tool wear progresses,the proportion of abrasive wear increases from 40%in the running-in stage to 75%in the rapid wear stage,while adhesive wear decreases.The optimal machining parameters of 120 m·min^(–1) cutting speed(v_(c))and 0.04 mm·z^(–1) feed rate(f_(z)),result in tool life of 33 min and surface roughness(S_(a))of 2.2μm.The study uncovers the variation patterns of abrasive and adhesive wear during the tool wear process,and the proposed model offers a robust framework for predicting tool wear during the machining of high-volume fraction Si/Al composites.The research findings also offer key insights for optimizing tool selection and machining parameters,advancing both the theoretical understanding and practical application of PCD tool wear.展开更多
基金Supported by National Natural Science Foundation of China,No.81421062the Science and Technology Bureau of Zhejiang Province,China,No.2016C33145+1 种基金the National Natural Science Foundation of China,No.81470891the 863 National High Technology Research and Development Program of China for young scientist No.2015AA020923
文摘AIM To investigate the underlying mechanisms of the protective role of remote ischemic perconditioning (RIPerC) in rat liver transplantation. METHODS Sprague-Dawley rats were subjected to sham, orthotopic liver transplantation (OLT), ischemic postconditioning (IPostC) or RIPerC. After 3 h reperfusion, blood samples were taken for measurement of alanine aminotransferase, aspartate aminotransferase, creatinine (Cr) and creatinine kinase-myocardial band (CK-MB). The liver lobes were harvested for the following measurements: reactive oxygen species (ROS), H2O2, mitochondrial membrane potential (Delta psi m) and total nitric oxide (NO). These measurements were determined using an ROS/H2O2, JC1 and Total NOx Assay Kit, respectively. Endothelial NO synthase (eNOS) was analyzed by reverse transcription-polymerase chain reaction (RTPCR) and western blotting, and peroxynitrite was semiquantified by western blotting of 3-nitrotyrosine. RESULTS Compared with the OLT group, the grafts subjected to RIPerC showed significantly improved liver and remote organ functions (P < 0.05). ROS (P < 0.001) including H2O2 (P < 0.05) were largely elevated in the OLT group as compared with the sham group, and RIPerC (P < 0.05) reversed this trend. The collapse of Delta psi m induced by OLT ischemia/reperfusion (I/R) injury was significantly attenuated in the RIPerC group (P < 0.001). A marked increase of NO content and phosphoserine eNOS, both in protein and mRNA levels, was observed in liver graft of the RIPerC group as compared with the OLT group (P < 0.05). I/R-induced 3-nitrotyrosine content was significantly reduced in the RIPerC group as compared with the OLT group (P < 0.05). There were no significant differences between the RIPerC and IPostC groups for all the results except Cr. The Cr level was lower in the RIPerC group than in the IPostC group (P < 0.01). CONCLUSION Liver graft protection by RIPerC is similar to or better than that of IPostC, and involves inhibition of oxidative stress and up-regulation of the PI3K/Akt/eNOS/NO pathway.
基金Projects (51875121,51405100) supported by the National Natural Science Foundation of ChinaProjects (2014M551233,2017T100237) supported by the China Postdoctoral Science Foundation+2 种基金Project (ZR2017PA003) supported by the Natural Science Foundation of Shandong Province,ChinaProject (2017GGX202006) supported by the Plan of Key Research and Development of Shandong Province,ChinaProject (2016DXGJMS05) supported by the Plan of Science and Technology Development of Weihai,China
文摘A modified mixed strengthening model was proposed for describing the yield strength of particle reinforced aluminum matrix composites.The strengthening mechanisms of the composites were analyzed based on the microstructures and compression mechanical properties.The distribution uniformity of reinforcements and cooperation relationship among dislocation mechanisms were considered in the modified mixed strengthening model by introducing a distribution uniformity factor u and a cooperation coefficient fc,respectively.The results show that the modified mixed strengthening model can accurately describe the yield strengths of Al3Ti/2024Al composites with a relative deviation less than1.2%,which is much more accurate than other strengthening models.The modified mixed model can also be used to predict the yield strength of Al3Ti/2024Al composites with different fractions of reinforcements.
基金Supported by Science and Technology Innovation Talents Support Plan,Department of Education,Henan Province,China,No.17HASTIT044China Postdoctoral Science Foundation,No.2017M610374
文摘AIM To investigate the protective mechanism of mitofusin-2 (Mfn2) in rat remote ischemic perconditioning (RIC) models and revalidate it in alpha mouse liver-12 (AML-12) hypoxia cell lines. METHODS Sprague-Dawley rats were divided into three groups (n = 6 each): sham, orthotopic liver transplantation and RIC. After operation, blood samples were collected to test alanine aminotransferase and aspartate aminotransferase. The liver lobes were harvested for histopathological examination, western blotting (WB) and quantitative real-time (qRT)-PCR. AML-12 cell lines were then subjected to normal culture, anoxic incubator tank culture (hypoxia) and anoxic incubator tank culture with Mfn2 knockdown (hypoxia + Si), and data of qRT-PCR, WB, mitochondrial membrane potential (Delta psi m), apoptosis, endoplasmic reticulum Ca2+ concentrations and mitochondrial Ca2+ concentrations were collected. RESULTS Both sham and normal culture groups showed no injury during the experiment. The RIC group showed amelioration of liver function compared with the orthotopic liver transplantation group (P < 0.05). qRTPCR and WB confirmed that Mfn2-mitochondrial Ca2+ uptake 1/2 (MICUs) axis was changed (P < 0.005). In AML-12 cell lines, compared with the hypoxia group, the hypoxia + Si group attenuated the collapse of..m and apoptosis (P < 0.005). The endoplasmic reticulum Ca2+ decrease and mitochondrial Ca2+ overloading observed in the hypoxia group were also attenuated in the hypoxia + Si group (P < 0.005). Finally, qRT-PCR and WB confirmed the Mfn2-MICUs axis change in all the groups (P < 0.005). CONCLUSION Mfn2 participates in liver injury in rat RIC models and AML-12 hypoxia cell lines by regulating the MICUs pathway.
基金This study was supported by the Public Projects of Zhe-jiang Province(LGF21H030006)the Major Science and Tech-nology Projects of Hainan province(ZDKJ2019009)+2 种基金Research Project of Jinan Microecological Biomedicine Shandong Laboratory(JNL-2022002A,JNL-2022023C)Research Unit Project of Chinese Academy of Medical Sciences(2019-I2M-5-030)Innovative Re-search Groups of National Natural Science Foundation of China(81721091).
文摘Background:Remote ischemic perconditioning(RIPerC)has been demonstrated to protect grafts from hepatic ischemia-reperfusion injury(IRI).This study investigated the role of exosomes in RIPerC of liver grafts in rats.Methods:Twenty-five rats(including 10 donors)were randomly divided into five groups(n=5 each group):five rats were used as sham-operated controls(Sham),ten rats were for orthotopic liver transplantation(OLT,5 donors and 5 recipients)and ten rats were for OLT+RIPerC(5 donors and 5 recipients).Liver architecture and function were evaluated.Results:Compared to the OLT group,the OLT+RIPerC group exhibited significantly improved liver graft histopathology and liver function(P<0.05).Furthermore,the number of exosomes and the level of P-Akt were increased in the OLT+RIPerC group.Conclusions:RIPerC effectively improves graft architecture and function,and this protective effect may be related to the increased number of exosomes.The upregulation of P-Akt may be involved in underlying mechanisms.
基金support from the National Natural Science Foundation of China(NSFC)[No.52475464,52475463]National Natural Science Foundation of Jiangsu Province(No.BK20231442)+4 种基金the Fundamental Research Funds for the Central Universities(No.NS2024032)the International Joint Laboratory of Sustainable Manufacturing,Ministry of Education and the Fundamental Research Funds for the Central Universities(No.NG2024007)China Scholarship Council(No.202206830048)the Foundation of the Graduate Innovation Center,Nanjing University of Aeronautics and Astronautics(No.kfjj20200510)Funding for Outstanding Doctoral Dissertation in NUAA(No.BCXJ23-09)。
文摘Diamond coatings possess numerous excellent properties,making them desirable materials for high-performance surface applications.However,without a revolutionary surface modification method,the surface roughness and friction behavior of diamond coatings can impede their ability to meet the demanding requirements of advanced engineering surfaces.This study proposed the thermal stress control at coating interfaces and demonstrated a novel process of precise graphenization on conventional diamond coatings surface through laser induction and mechanical cleavage,without causing damage to the metal substrate.Through experiments and simulations,the influence mechanism of surface graphitization and interfacial thermal stress was elucidated,ultimately enabling rapid conversion of the diamond coating surface to graphene while controlling the coating’s thickness and roughness.Compared to the original diamond coatings,the obtained surfaces exhibited a 63%-72%reduction in friction coefficients,all of which were below 0.1,with a minimum of 0.06,and a 59%-67%decrease in specific wear rates.Moreover,adhesive wear in the friction counterpart was significantly inhibited,resulting in a reduction in wear by 49%-83%.This demonstrated a significant improvement in lubrication and inhibition of mechanochemical wear properties.This study provides an effective and cost-efficient avenue to overcome the application bottleneck of engineered diamond surfaces,with the potential to significantly enhance the performance and expand the application range of diamond-coated components.
基金Supported by Grants from Beijing Municipal Health Bureau, No.2011-2-18the Capital Health Development Special Funds, No.2011-2018-03
文摘AIM:To determine an optimal cutoff value for abnormal splenic artery diameter/proper hepatic artery diameter(S/P) ratio in cirrhosis-induced portal hypertension.METHODS:Patients with cirrhosis and portal hypertension(n = 770) and healthy volunteers(n = 31) underwent volumetric computed tomography threedimensional vascular reconstruction to measure the internal diameters of the splenic artery and proper hepatic artery to calculate the S/P ratio.The cutoff value for abnormal S/P ratio was determined using receiver operating characteristic curve analysis,and the prevalence of abnormal S/P ratio and associations between abnormal S/P ratio and major complications of portal hypertension were studied using logistic regression.RESULTS:The receiver operating characteristic analysis showed that the cutoff points for abnormal splenic artery internal diameter and S/P ratio were > 5.19 mm and > 1.40,respectively.The sensitivity,specificity,positive predictive value,and negative predictive value were 74.2%,45.2%,97.1%,and 6.6%,respectively.The prevalence of an abnormal S/P ratio in the patients with cirrhosis and portal hypertension was 83.4%.Patients with a higher S/P ratio had a lower risk of developing ascites [odds ratio(OR) = 0.708,95%CI:0.508-0.986,P = 0.041] and a higher risk of developing esophageal and gastric varices(OR = 1.483,95%CI:1.010-2.175,P = 0.044) and forming collateral circulation(OR = 1.518,95%CI:1.033-2.230,P = 0.034).After splenectomy,the portal venous pressure and maximum and mean portal venous flow velocities were reduced,while the flow rate and maximum and minimum flow velocities of the hepatic artery were increased(P < 0.05).CONCLUSION:The prevalence of an abnormal S/P ratio is high in patients with cirrhosis and portal hypertension,and it can be used as an important marker of splanchnic hemodynamic disturbances.
基金supported by the National Natural Science Foundation of China(Nos.52075255,92160301,52175415,52205475,and 92060203)。
文摘The aerospace community widely uses difficult-to-cut materials,such as titanium alloys,high-temperature alloys,metal/ceramic/polymer matrix composites,hard and brittle materials,and geometrically complex components,such as thin-walled structures,microchannels,and complex surfaces.Mechanical machining is the main material removal process for the vast majority of aerospace components.However,many problems exist,including severe and rapid tool wear,low machining efficiency,and poor surface integrity.Nontraditional energy-assisted mechanical machining is a hybrid process that uses nontraditional energies(vibration,laser,electricity,etc)to improve the machinability of local materials and decrease the burden of mechanical machining.This provides a feasible and promising method to improve the material removal rate and surface quality,reduce process forces,and prolong tool life.However,systematic reviews of this technology are lacking with respect to the current research status and development direction.This paper reviews the recent progress in the nontraditional energy-assisted mechanical machining of difficult-to-cut materials and components in the aerospace community.In addition,this paper focuses on the processing principles,material responses under nontraditional energy,resultant forces and temperatures,material removal mechanisms,and applications of these processes,including vibration-,laser-,electric-,magnetic-,chemical-,advanced coolant-,and hybrid nontraditional energy-assisted mechanical machining.Finally,a comprehensive summary of the principles,advantages,and limitations of each hybrid process is provided,and future perspectives on forward design,device development,and sustainability of nontraditional energy-assisted mechanical machining processes are discussed.
基金co-supported by the National Natural Science Foundation of China(No.51405226)Postgraduate Research&Practice Innovation Program of Jiangsu Province of China(No.KYCX19_0165)。
文摘Owing to reliability and high strength-to-weight ratio,large thin-walled components are widely used in the aviation and aerospace industry.Due to the complex features and sequence involved in the machining process of large thin-walled components,machining deformation of component is easy to exceed the specification.In order to address the problem,it is important to retain the appropriate finishing allowance.To find the overall machining deformation,finishing allowance-induced deformation(web finishing allowance,sidewall finishing allowance)and initial residual stress-induced deformation were considered as major factors.Meanwhile,machined surface residual stress-induced deformation,clamping stress-induced deformation,thermal deformation,gravity-induced deformation and inertial force-induced deformation were neglected in the optimization model.Six-peak Gaussian function was introduced to fit the initial residual stress.Based upon the obtained function of initial residual stress,a deformation prediction model between initial residual stress and finishing allowance was established to attain the finishing allowanceinduced deformation.In addition,linear programming optimization model based on the simplex algorithm was developed to optimize the overall machining deformation.Results have concluded that the overall machining deformation reached the minimum value when sidewall finishing allowance and web finishing allowance varied between 1 and 2 mm.Additionally,web finishing allowance-induced deformation and sidewall finishing allowance-induced deformation were1.05 mm and 0.7 mm.Furthermore,the machining deformation decreased to 0.3–0.38 mm with the application of optimized finishing allowance allocation strategy,which made 39–56%reduction of the overall machining deformation compared to that in conventional method.
基金Supported by National Science and Technology Major Project,No.2012ZX10002-017Natural Science Foundation of China for Innovative Research Group,No.81121002+4 种基金National Natural Science Foundation of China,No.81000137 and No.81470891The Qianjiang Talent Program of Zhejiang Province,China,No.2012R10045the Scientific Research Program for the Returned Overseas Chinese Scholars,Ministry of Health,China,No.J20112008National High Technology Research and Development Program of China for Young Scientists(863 Program),No.2015AA020923Ministry of Education,Zhejiang Province,China,No.Y201328095
文摘AIM: To optimize the perfusates used for hypothermicmachine perfusion(HMP).METHODS: Sprague-Dawley rats were assigned randomly to three groups(n = 12 per group) that received either saline, University of Wisconsin coldstorage solution(UW) or histidine-tryptophan-ketoglutarate solution(HTK) as the perfusate. Each group was divided into two subgroups: static cold storage(SCS) and HMP(n = 6 per subgroup). The liver graft was retrieved according to the method described by Kamada. For the SCS group, the graft was directly placed into cold perfusate(0-4?℃) for 6 h after liver isolation while the portal vein of the graft was connected to the perfusion machine for the HMP group. Then the perfusates were collected at different time points for analysis of aspartate aminotransferase(AST), alanine transaminase(ALT) and lactate dehydrogenase(LDH) levels. Liver tissues were obtained for evaluation of histology, dry/wet weight(D/W) ratio, and malondialdehyde(MDA) and adenosine-triphosphate(ATP) levels. The portal vein pressure and velocity were monitored in real time in all HMP subgroups.RESULTS: Comparison of HMP and SCS: Regardless of the perfusate, HMP improved the architecture of donor graft in reducing the congestion around sinusoids and central vein and maintaining sinusoid lining in morphology; HMP improved liver function in terms of ALT, AST and LDH, especially during the 3-6 h period(SCS vs HMP using saline: ALT3, 225.00 ± 105.62 vs 49.50 ± 18.50, P = 0.047; LDH3, 1362.17 ± 563.30 vs 325.75 ± 147.43, P = 0.041; UW: LDH6, 2880.14 ± 948.46 vs 2135.00 ± 174.27, P = 0.049; HTK, AST6, 307.50 ± 52.95 vs 185.20 ± 20.46, P = 0.041); HMP decreased MDA level(saline, 2.79 ± 0.30 vs 1.09 ± 0.09, P = 0.008; UW, 3.01 ± 0.77 vs 1.23 ± 0.68, P = 0.005; HTK, 3.30 ± 0.52 vs 1.56 ± 0.22, P = 0.006). Comparison among HMP subgroups: HTK showed less portal vein resistance than UW and saline(vs saline, 3.41 ± 0.49 vs 5.00 ± 0.38, P < 0.001; vs UW, 3.41 ± 0.49 vs 4.52 ± 0.63, P = 0.007); UW reduced edema most efficiently(vs saline, 0.68 ± 0.02 vs 0.79 ± 0.05, P = 0.013), while HTK maintained ATP levels best(vs saline, 622.60 ± 29.11 vs 327.43 ± 44.66, P < 0.001; vs UW, 622.60 ± 29.11 vs 301.80 ± 37.68, P < 0.001).CONCLUSION: HMP is superior to SCS in maintaining both architecture and function of liver grafts. Further, HTK was found to be the optimal perfusate for HMP.
基金supported by the National Natural Science Foundation of China,Nos.82172527 and 81972138 (to LLW)。
文摘Traumatic injuries in the central nervous system,such as traumatic brain injury and spinal cord injury,are associated with tissue inflammation and the infiltration of immune cells,which simultaneously affect the self-renewal and differentiation of neural stem cells.Howeve r,the tissue repair process instigated by endogenous neural stem cells is incapable of restoring central nervous system injuries without external intervention.Recently,resident/peripheral immune cells have been demonstrated to exert significant effects on neural stem cells.Thus,the resto ration of traumatic injuries in the central nervous system by the immune intervention in neural stem cells represents a potential therapeutic method.In this review,we discuss the roles and possible mechanisms of immune cells on the selfrenewal and differentiation of neural stem cells along with the prognosis of central nervous system injuries based on immune intervention.Finally,we discuss remaining research challenges that need to be considered in the future.Further elucidation of these challenges will fa cilitate the successful application of neural stem cells in central nervous system injuries.
基金financially supported by the National Natural Science Foundation of China (21603023)
文摘Platinum(Pt)supported on Zinc(Zn)modified silicalite-1(S-1)zeolite(denoted as Pt-Zn/S-1)was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time.Both Lewis and Bronsted acid sites were detected in Pt-Zn/S-1 catalyst by means of FT-IR adsorption of NH3 experiment,which were identified as mostly weak and medium ones.Besides,Pt and Zn species showed strong interaction,as revealed by the TPR(Temperature-programmed reduction)and XPS(X-ray photoelectron spectroscopy)experiments.Pt-Zn/S-1 catalyst exhibited excellent aromatization function rather than isomerization and cracking side reactions in the conversion of n-hexane.Pulse experimental study showed that 75.6%of n-hexane conversion and 76.8%of benzene selectivity were obtained over Pt0.1-Zn60/S-l catalyst at 550℃ and under atmospheric pressure.By spectroscopy tests and pulse experimental results,it was concluded that the n-hexane aromatization over Pt-Zn/S-1 catalyst follows a metal-acid bifunctional mechanism.Furthermore,with the assistance of Zn,the electron-deficient Pt species in Pt-Zn/S-1 showed good sulfur tolerance performance.
基金the National Natural Science Foundation of China(No.51405226)。
文摘In the machining process of aircraft monolithic parts,the initial residual stress redistribution and structural stiffness evolution often lead to unexpected distortions.On the other hand,the stress redistribution and stiffness reduction during the machining process depend on the material removal sequence.The essence of the stress redistribution is releasing the initial elastic strain energy.In the present study,the influence of the material removal sequence on the energy release is studied.Moreover,a novel optimization method is proposed for the material removal sequence.In order to evaluate the performance of the proposed method,the mechanism of the machining distortion is firstly analyzed based on the energy principle.Then a calculative model for the machining distortion of long beam parts is established accordingly.Moreover,an energy parameter related to the bending distortion and the procedure of the material removal sequence optimization is defined.Finally,the bending distortion analysis and material removal sequence optimization are performed on a long beam with a Z-shaped cross-section.Furthermore,simulation and experiments are carried out.The obtained results indicate that the optimized sequence results in a low distortion fluctuation and decreases the bending distortion.
基金supported by the National Natural Science Foundation of China(Grant Nos.:82073808,81872828,and 81573384).
文摘Covalent organic frameworks(COFs)are a novel type of crystalline porous organic polymer materials recently developed.It has several advantages in chromatographic separation field,such as high thermal stability,porosity,structural regularity,and large specific surface area.Here,a novel spherical COF 1,3,5-tris(4-aminophenyl)benzene(TAPB)and 2,5-bis(2-propyn-1-yloxy)-1,4-benzenedicarboxaldehyde(BPTA)was developed as an electrochromatographic stationary phase for capillary electrochromatography separation.The COF TAPB-BPTA modified capillary column was fabricated via a facile in situ growth method at room temperature.The characterization results of scanning electron microscopy(SEM),Fourier transform infrared(FT-IR)spectroscopy,and X-ray diffraction(XRD)confirmed that COF TAPB-BPTA were successfully modified onto the capillary inner surface.The electrochromatography separation performance of the COF TAPB-BPTA modified capillary was investigated.The prepared column demonstrated outstanding separation performance toward alkylbenzenes,phenols,and chlorobenzenes compounds.Furthermore,the baseline separations of non-steroidal anti-inflammatory drugs(NSAIDs)and parabens with good efficiency and high resolution were achieved.Also,the prepared column possessed satisfactory precision of the intra-day runs(n=5),inter-day runs(n=3),and parallel columns(n=3),and the relative standard deviations(RSDs)of the retention times of tested alkylbenzenes were all less than 2.58%.Thus,this new COF-based stationary phase shows tremendous application potential in chromatographic separation field.
基金supported by the National Natural Science Foundation of China (Nos. 21207016, 21325729)the Fundamental Research Funds for the Central Universities (No. DUT12RC(3)07)+1 种基金the Liaoning Provincial Education Department (No. L2012021)Program for Changjiang Scholars and Innovative Research Team in University (No. IRT_13R05)
文摘Amines have been considered as promising candidates for post-combustion CO2 capture. A mechanistic understanding for the chemical processes involved in the capture and release of CO2 is important for the rational design of amines. In this study, the structural effects of amines on the kinetic competition among three typical products（carbamates, carbamic acids and bicarbonate） from amines ＋ CO2 were investigated, in contrast to previous thermodynamic studies to tune the reaction of amines with CO2 based on desirable reaction enthalpy and reaction stoichiometry. We used a quantum chemical method to calculate the activation energies（Ea） for the reactions of a range of substituted monoethanolamines with CO2 covering three pathways to the three products. The results indicate that the formation of carbamates is the most favorable, among the three considered products. In addition, we found that the Eavalues for all pathways linearly correlate with pK aof amines, and more importantly, the kinetic competition between carbamate and bicarbonate absorption pathways varies with p Kaof the amines, i.e. stronger basicity results in less difference in Ea. These results highlight the importance of the consideration of kinetic competition among different reaction pathways in amine design.
文摘Different factors affecting the efficiency of the orifice energy dissipator were investigated based on a series of theoretical analyses and numerical simulations. The main factors investigated by dimension analysis were identified, including the Reynolds number （Re）, the ratio of the orifice diameter to the inner diameter of the pipe （ did ）, and the ratio of distances between orifices to the inner diameter of the pipe （ LID ）. Then, numerical simulations were conducted with a k-ε two-equation turbulence model. The calculation results show the following： Hydraulic characteristics change dramatically as flow passes through the orifice, with abruptly increasing velocity and turbulent energy, and decreasing pressure. The turbulent energy appears to be low in the middle and high near the pipe wall. For the energy dissipation setup with only one orifice, when Re is smaller than 105, the orifice energy dissipation coefficient K increases rapidly with the increase of Re. When Re is larger than l05, K gradually stabilizes. As diD increases, K and the length of the recirculation region L1 show similar variation patterns, which inversely vary with diD. The function curves can be approximated as straight lines. For the energy dissipation model with two orifices, because of different incoming flows at different orifices, the energy dissipation coefficient of the second orifice （K2） is smaller than that of the first. If LID is less than 5, the K value of the LID model, depending on the variation of/（2, increases with the spacing between two orifices L, and an orifice cannot fulfill its energy dissipation function. If LID is greater than 5, K2 tends to be steady; thus, the K value of the LID model gradually stabilizes. Then, the flow fully develops, and L has almost no impact on the value of K.
基金supported by the National Natural Science Foundation of China(NSFC)[No.51905270]National Natural Science Foundation of Jiangsu Province(No.BK20231442)the China Postdoctoral Science Foundation(No.2023M731659).
文摘Processing microchannels inside laminated aluminum nitride high-temperature co-fired ceramics(AlN HTCC) packaging, a typical difficult-to-cut ceramic, can effectively solve the heatdissipation problem of integrated chips used in smart skin. In order to improve the processing efficiency and quality of AlN, the machinability of AlN after laser chemical milling(LCM) was studied through the milling force, machined surface quality, surface defects, formation mechanism, and tool wear. This study established a milling force model that can predict the milling forces of AlN and analyses the reasons for the improvements in the milling force based on experimental data and predicted data. The results from the model and experiments demonstrated that the milling force of the laser chemical milling assisted micro milling(LCAMM) decreased by 85%–90% and 85%–95%, respectively, due to the amount of removal of a single edge was more uniform and the actual inclination angle increased during the cutting process in LCAMM. Moreover, the machined surface quality improved by 65%–76% after LCM because of less tool wear, fewer downward-propagating cracks generated during each feed, and the surface removal mode transformed from intergranular fracture to transgranular fracture, which effectively reducing tool wear and improving tool life. Finally, when feed per tooth and depth of cut were 0.4 μm/z and 5 μm, the optimal machined surface quality was obtained, with a roughness of 64.6 nm Therefore, milling after LCM can improve the machinability of AlN and providing a feasibility for the high-quality and efficient machining of microchannels.
基金supported by the National Natural Science Foundation of China(No.61903291)Key Research and Development Program of Shaanxi Province(No.2022NY-094)。
文摘The variable air volume(VAV)air conditioning system is with strong coupling and large time delay,for which model predictive control(MPC)is normally used to pursue performance improvement.Aiming at the difficulty of the parameter selection of VAV MPC controller which is difficult to make the system have a desired response,a novel tuning method based on machine learning and improved particle swarm optimization(PSO)is proposed.In this method,the relationship between MPC controller parameters and time domain performance indices is established via machine learning.Then the PSO is used to optimize MPC controller parameters to get better performance in terms of time domain indices.In addition,the PSO algorithm is further modified under the principle of population attenuation and event triggering to tune parameters of MPC and reduce the computation time of tuning method.Finally,the effectiveness of the proposed method is validated via a hardware-in-the-loop VAV system.
基金supported by the National Natural Science Foundation of China(62272049,62236006,62172045)the Key Projects of Beijing Union University(ZKZD202301).
文摘In recent years,gait-based emotion recognition has been widely applied in the field of computer vision.However,existing gait emotion recognition methods typically rely on complete human skeleton data,and their accuracy significantly declines when the data is occluded.To enhance the accuracy of gait emotion recognition under occlusion,this paper proposes a Multi-scale Suppression Graph ConvolutionalNetwork(MS-GCN).TheMS-GCN consists of three main components:Joint Interpolation Module(JI Moudle),Multi-scale Temporal Convolution Network(MS-TCN),and Suppression Graph Convolutional Network(SGCN).The JI Module completes the spatially occluded skeletal joints using the(K-Nearest Neighbors)KNN interpolation method.The MS-TCN employs convolutional kernels of various sizes to comprehensively capture the emotional information embedded in the gait,compensating for the temporal occlusion of gait information.The SGCN extracts more non-prominent human gait features by suppressing the extraction of key body part features,thereby reducing the negative impact of occlusion on emotion recognition results.The proposed method is evaluated on two comprehensive datasets:Emotion-Gait,containing 4227 real gaits from sources like BML,ICT-Pollick,and ELMD,and 1000 synthetic gaits generated using STEP-Gen technology,and ELMB,consisting of 3924 gaits,with 1835 labeled with emotions such as“Happy,”“Sad,”“Angry,”and“Neutral.”On the standard datasets Emotion-Gait and ELMB,the proposed method achieved accuracies of 0.900 and 0.896,respectively,attaining performance comparable to other state-ofthe-artmethods.Furthermore,on occlusion datasets,the proposedmethod significantly mitigates the performance degradation caused by occlusion compared to other methods,the accuracy is significantly higher than that of other methods.
基金supported by the National Natural Science Foundation of China(Grant No.52075255)the Jiangsu Provincial Science and Technology Plan(Grant No.BZ2023005).
文摘High-volume fraction silicon particle-reinforced aluminium matrix composites(Si/Al)are increasingly applied in aerospace,radar communications,and large-scale integrated circuits because of their superior thermal conductivity,wear resistance,and low thermal expansion coefficient.However,the abrasive and adhesive wear caused by the hard silicon reinforcement and the ductile aluminium matrix leads to significant tool wear,decreased machining efficiency,and compromised surface quality.This study combines theoretical analysis and cutting experiments to investigate polycrystalline diamond(PCD)tool wear during milling of 70 vol%Si/Al composite.A key contribution of this work is the development of a tool wear model that incorporates reinforcement particle characteristics,treating them as ellipsoidal structures,which enhances the accuracy of predicting abrasive and adhesive wear mechanisms.The model is based on abrasive and adhesive wear mechanisms,and can analyze the interaction between silicon particles,aluminium matrix,and tool components,thus providing deeper insights into PCD tool wear processes.Experimental validation of the model shows a good agreement with the results,with a mean deviation of approximately 10%.The findings on the tool wear mechanism reveal that,as tool wear progresses,the proportion of abrasive wear increases from 40%in the running-in stage to 75%in the rapid wear stage,while adhesive wear decreases.The optimal machining parameters of 120 m·min^(–1) cutting speed(v_(c))and 0.04 mm·z^(–1) feed rate(f_(z)),result in tool life of 33 min and surface roughness(S_(a))of 2.2μm.The study uncovers the variation patterns of abrasive and adhesive wear during the tool wear process,and the proposed model offers a robust framework for predicting tool wear during the machining of high-volume fraction Si/Al composites.The research findings also offer key insights for optimizing tool selection and machining parameters,advancing both the theoretical understanding and practical application of PCD tool wear.
