Electrocatalytic carbon dioxide reduction is a promising technology for addressing global energy and environmental crises. However, its practical application faces two critical challenges: the complex and energy-inten...Electrocatalytic carbon dioxide reduction is a promising technology for addressing global energy and environmental crises. However, its practical application faces two critical challenges: the complex and energy-intensive process of separat-ing mixed reduction products and the economic viability of the carbon sources (reactants) used. To tackle these challenges simultaneously, solid-state electrolyte (SSE) reactors are emerging as a promising solution. In this review, we focus on the feasibility of applying SSE for tandem electrochemical CO_(2) capture and conversion. The configurations and fundamental principles of SSE reactors are first discussed, followed by an introduction to its applications in these two specific areas, along with case studies on the implementation of tandem electrolysis. In comparison to conventional H-type cell, flow cell and membrane electrode assembly cell reactors, SSE reactors incorporate gas diffusion electrodes and utilize a solid electro-lyte layer positioned between an anion exchange membrane (AEM) and a cation exchange membrane (CEM). A key inno-vation of this design is the sandwiched SSE layer, which enhances efficient ion transport and facilitates continuous product extraction through a stream of deionized water or humidified nitrogen, effectively separating ion conduction from product collection. During electrolysis, driven by an electric field and concentration gradient, electrochemically generated ions (e.g., HCOO- and CH3COO-) migrate through the AEM into the SSE layer, while protons produced from water oxidation at the anode traverse the CEM into the central chamber to maintain charge balance. Targeted products like HCOOH can form in the middle layer through ionic recombination and are efficiently carried away by the flowing medium through the porous SSE layer, in the absence of electrolyte salt impurities. As CO_(2)RR can generate a series of liquid products, advancements in catalyst discovery over the past several years have facilitated the industrial application of SSE for more efficient chemicals production. Also noteworthy, the cathode reduction reaction can readily consume protons from water, creating a highly al-kaline local environment. SSE reactors are thereby employed to capture acidic CO_(2), forming CO_(3)^(2-) from various gas sources including flue gases. Driven by the electric field, the formed CO_(3)^(2-) can traverse through the AEM and react with protons originating from the anode, thereby regenerating CO_(2). This CO_(2) can then be collected and utilized as a low-cost feedstock for downstream CO_(2) electrolysis. Based on this principle, several cell configurations have been proposed to enhance CO_(2) capture from diverse gas sources. Through the collaboration of two SSE units, tandem electrochemical CO_(2) capture and con-version has been successfully implemented. Finally, we offer insights into the future development of SSE reactors for prac-tical applications aimed at achieving carbon neutrality. We recommend that greater attention be focused on specific aspects, including the fundamental physicochemical properties of the SSE layer, the electrochemical engineering perspective related to ion and species fluxes and selectivity, and the systematic pairing of consecutive CO_(2) capture and conversion units. These efforts aim to further enhance the practical application of SSE reactors within the broader electrochemistry community.展开更多
Electrocatalytic CO_(2)-to-CO conversion is crucial for advancing sustainable processes,and providing essential feedstocks for the chemical industry.Cobalt phthalocyanine(CoPc)is a well-established molecular catalyst ...Electrocatalytic CO_(2)-to-CO conversion is crucial for advancing sustainable processes,and providing essential feedstocks for the chemical industry.Cobalt phthalocyanine(CoPc)is a well-established molecular catalyst for this conversion;however,maintaining high selectivity at industrially relevant current densities remains a significant challenge.Herein,we present a Co–N_(5)local structure anchored on nitrogen-doped carbon nanotubes through axial nitrogen coordination engineering to CoPc(CoPc/N-CNTs).The catalyst demonstrates near-unity CO selectivity and a high CO turnover frequency,peaking at 19.2 s^(−1)across a wide range of overpotentials.In flow cell tests,CoPc/N-CNTs achieve a CO Faradaic efficiency exceeding 95%at a current density of−800 mA cm^(−2).When integrated into a membrane electrode assembly,it maintained over 90%CO Faradaic efficiency at an industrial-scale current of−5 A for up to 20 h.Mechanistic studies revealed that Co–N_(5)active sites accelerate*COOH formation and inhibit deeper*CO reduction to CH_(3)OH while reducing HER activity by lowering H_(2)O surface coverage.These findings offer a delicate catalyst design that enables the efficient and sustained conversion of CO_(2)to CO.展开更多
Determining the electronic structure of La_(3)Ni_(2)O_(7)is an essential step towards uncovering its superconducting mechanism.It is widely believed that the bilayer apical oxygens play an important role in the bilaye...Determining the electronic structure of La_(3)Ni_(2)O_(7)is an essential step towards uncovering its superconducting mechanism.It is widely believed that the bilayer apical oxygens play an important role in the bilayer La_(3)Ni_(2)O_(7)electronic structure.Applying the hybrid exchange–correlation functionals,we obtain a more accurate electronic structure of La_(3)Ni_(2)O_(7)at its high-pressure phase,where the bonding dz2 band is below the Fermi level owing to the apical oxygen.The symmetry properties of this electronic structure and its corresponding tight-binding model are further analyzed.We find that the antisymmetric part is highly entangled,leading to a minimal nearly degenerate two-orbital model.Then,the apical oxygen vacancies effect is studied using the dynamical cluster approximation.This disorder effect strongly destroys the antisymmetric b Fermi surface,leading to the possible disappearance of superconductivity.展开更多
The impacts of the Luzon Strait transport on shallow meridional overturning circulation(SMOC)in the South China Sea(SCS)have been pointed out by previous studies,but the issue whether the Luzon Strait transport domina...The impacts of the Luzon Strait transport on shallow meridional overturning circulation(SMOC)in the South China Sea(SCS)have been pointed out by previous studies,but the issue whether the Luzon Strait transport dominates the SMOC formation still remains open.The Helmholtz decomposition is applied based on the ocean general circulation model for the earth simulator products to address this issue.Results show that the motion caused by the Luzon Strait transport is characterized as an obvious southward flow between 13°N and 20°N.After this motion being removed,the clockwise winter SMOC and the anticlockwise summer SMOC can still exist significantly.The SMOC existence and its seasonal variation are also reproduced in the numerical simulation with the Luzon Strait closed.Both results of the Helmholtz decomposition and numerical experiment suggest that the SMOC formation and its seasonal variation are not dominated by the Luzon Strait transport.The SCS monsoon is the primary driving factor for the SMOC,which is related to the physical processes within the SCS.展开更多
An increasing number of drivers are relying on digital map navigation systems in vehicles or mobile phones to select optimal driving routes in order to save time and improve safety. In the near future, digital map nav...An increasing number of drivers are relying on digital map navigation systems in vehicles or mobile phones to select optimal driving routes in order to save time and improve safety. In the near future, digital map navigation systems are expected to play more important roles in transportation systems. In order to extend current navigation systems to more applications, two fundamental problems must be resolved: the lane-level map model and lane-level route planning. This study proposes solutions to both problems. The current limitation of the lane-level map model is not its accuracy but its flexibility;this study proposes a novel seven-layer map structure, called as Tsinghua map model, which is able to support autonomous driving in a flexible and efficient way. For lane-level route planning, we propose a hierarchical route-searching algorithm to accelerate the planning process, even in the presence of complicated lane networks. In addition, we model the travel costs allocated for lane-level road networks by analyzing vehicle maneuvers in traversing lanes, changing lanes, and turning at intersections. Tests were performed on both a grid network and a real lane-level road network to demonstrate the validity and efficiency of the proposed algorithm.展开更多
AIM: To evaluate the effectiveness and safety of early nasogastric enteral nutrition (NGEN) for patients with severe acute pancreatitis (SAP). METHODS: We searched Cochrane Central Register of Controlled Trials (Issue...AIM: To evaluate the effectiveness and safety of early nasogastric enteral nutrition (NGEN) for patients with severe acute pancreatitis (SAP). METHODS: We searched Cochrane Central Register of Controlled Trials (Issue 2, 2006), Pub-Medline (1966-2006), and references from relevant articles. We included randomized controlled trials (RCTs) only, which reported the mortality of SAP patients at least. Two reviewers assessed the quality of each trial and collected data independently. The Cochrane Collaboration’s RevMan 4.2.9 software was used for statistical analysis. RESULTS: Three RCTs were included, involving 131 patients. The baselines of each trial were comparable. Meta-analysis showed no significant differences in mortality rate of SAP patients between nasogastric and conventional routes (RR = 0.76, 95% CI = 0.37 and 1.55, P = 0.45), and in other outcomes, including time of hospital stay (weighted mean difference = -5.87, 95% CI = -20.58 and 8.84, P = 0.43), complication rate of infection (RR = 1.41, 95% CI = 0.62 and 3.23, P = 0.41) or multiple organ defi ciency syndrome (RR = 0.97, 95% CI = 0.27 and 3.47, P = 0.97), rate of admission to ICU (RR = 1.00, 95% CI = 0.48 and 2.09, P = 0.99) or conversion to surgery (RR = 0.66, 95% CI = 0.12 and 3.69, P = 0.64), as well as recurrence of re-feeding pain and adverse events associated with nutrition. CONCLUSION: Early NGEN is a breakthrough in the management of SAP. Based on current studies, early NGEN appears effective and safe. Since the available evidence is poor in quantity, it is hard to make an accurate evaluation of the role of early NGEN in SAP.Before recommendation to clinical practice, further high qualified, large scale, randomized controlled trials are needed.展开更多
AIM： To assess the economics of various chemotherapeutic regimens for advanced gastric cancer （AGC）, and to select the best cost-effective regimen for the common Chinese patients. METHODS： Data source used in this...AIM： To assess the economics of various chemotherapeutic regimens for advanced gastric cancer （AGC）, and to select the best cost-effective regimen for the common Chinese patients. METHODS： Data source used in this study was the Chinese Biomedical Disk Database. Patients were diagnosed as AGC and any regimen was eligible. Outcome measures included median survival time （MST） and percentage of complete and partial response （CR＋PR）. Economic statistics was per capita direct medical cost （DMC） of a single cycle. TreeAge Pro Healthcare 2007 software was used to carry out costeffectiveness and incremental cost-effectiveness analysis. Sensitivity analyses were applied by altering willingness- to-pay and annual discount rate, and also re-analyzed by excluding the studies with apparent heterogeneity. RESULTS： Seven retrospective economics studies on 760 patients were included. S-fluorouracil-based regimens were universal, and also some new agents were involved, such as docetaxel, paclitaxel, andoxaliplatin. By processing analysis, we could recommend etoposide, leucovorin and 5-fluorouracil （ELF） regimen as preference, with a DMC/MST ratio of 2543 RBM/11.7 mo and a DMC/CR＋PR ratio of 2543 RMB/53.3%. Uraciltegafur, etoposide and cisplatin （FEP） or 5-fluorouracil, adrimycin/epirubin and mitomycin （FAM） regimens could be regarded as optional first-line chemotherapy for AGC in common Chinese patients. With no regard for willingness-to-pay, the docetaxel, cisplatin and 5-fluorouracil （DCF） regimen could be chosen as either a first- or a second-line chemotherapy, with a DMC/CR＋PR ratio of 9979 RMB/56.3%. CONCLUSION： 5-fluorouracial regimens are still considered the mainstream for AGC, while new agents such as taxanes are optional. More randomized clinical trials are required before any mandatory recommendation of certain regimens for patients with AGC in China is made.展开更多
BACKGROUND Intraductal papillary mucinous neoplasms(IPMNs)are non-invasive pancreatic precursor lesions that can potentially develop into invasive pancreatic ductal adenocarcinoma.Currently,the International Consensus...BACKGROUND Intraductal papillary mucinous neoplasms(IPMNs)are non-invasive pancreatic precursor lesions that can potentially develop into invasive pancreatic ductal adenocarcinoma.Currently,the International Consensus Guidelines(ICG)for IPMNs provides the basis for evaluating suspected IPMNs on computed tomography(CT)imaging.Despite using the ICG,it remains challenging to accurately predict whether IPMNs harbor high grade or invasive disease which would warrant surgical resection.A supplementary quantitative radiological tool,radiomics,may improve diagnostic accuracy of radiological evaluation of IPMNs.We hypothesized that using CT whole lesion radiomics features in conjunction with the ICG could improve the diagnostic accuracy of predicting IPMN histology.AIM To evaluate whole lesion CT radiomic analysis of IPMNs for predicting malignant histology compared to International Consensus Guidelines.METHODS Fifty-one subjects who had pancreatic surgical resection at our institution with histology demonstrating IPMN and available preoperative CT imaging were included in this retrospective cohort.Whole lesion semi-automated segmentation was performed on each preoperative CT using Healthmyne software(Healthmyne,Madison,WI).Thirty-nine relevant radiomic features were extracted from each lesion on each available contrast phase.Univariate analysis of the 39 radiomics features was performed for each contrast phase and values were compared between malignant and benign IPMN groups using logistic regression.Conventional quantitative and qualitative CT measurements were also compared between groups,viaχ2(categorical)and Mann Whitney U(continuous)variables.RESULTS Twenty-nine subjects(15 males,age 71±9 years)with high grade or invasive tumor histology comprised the"malignant"cohort,while 22 subjects(11 males,age 70±7 years)with low grade tumor histology were included in the"benign"cohort.Radiomic analysis showed 18/39 precontrast,19/39 arterial phase,and 21/39 venous phase features differentiated malignant from benign IPMNs(P<0.05).Multivariate analysis including only ICG criteria yielded two significant variables:thickened and enhancing cyst wall and enhancing mural nodule<5 mm with an AUC(95%CI)of 0.817(0.709-0.926).Multivariable post contrast radiomics achieved an AUC(95%CI)of 0.87(0.767-0.974)for a model including arterial phase radiomics features and 0.834(0.716-0.953)for a model including venous phase radiomics features.Combined multivariable model including conventional variables and arterial phase radiomics features achieved an AUC(95%CI)of 0.93(0.85-1.0)with a 5-fold cross validation AUC of 0.90.CONCLUSION Multi-phase CT radiomics evaluation could play a role in improving predictive capability in diagnosing malignancy in IPMNs.Future larger studies may help determine the clinical significance of our findings.展开更多
This article provides a review on X-ray pulsar-based navigation(XNAV).The review starts with the basic concept of XNAV,and briefly introduces the past,present and future projects concerning XNAV.This paper focuses on ...This article provides a review on X-ray pulsar-based navigation(XNAV).The review starts with the basic concept of XNAV,and briefly introduces the past,present and future projects concerning XNAV.This paper focuses on the advances of the key techniques supporting XNAV,including the navigation pulsar database,the X-ray detection system,and the pulse time of arrival estimation.Moreover,the methods to improve the estimation performance of XNAV are reviewed.Finally,some remarks on the future development of XNAV are provided.展开更多
AIM： To determine the most cost-effective hemofiltration modality for early management of severe acute pancreatitis （SAP） in China. METHODS： We carried out a search of Pub-Medline and Chinese Biomedical Disk datab...AIM： To determine the most cost-effective hemofiltration modality for early management of severe acute pancreatitis （SAP） in China. METHODS： We carried out a search of Pub-Medline and Chinese Biomedical Disk database. Controlled clinical trials on Chinese population were included in the analysis. The four decision branches that were analyzed were： continuous or long-term veno-venous hemofiltration （CVVH/LVVH）, short-term veno-venous hemofiltration （SVVH）, SVVH plus peritoneal dialysis （PD）, and non-hemofiltration control group. The effectiveness of the technique was determined by survival rate, complications prevention and surgery preservation. The total cost of hospitalization was also assessed. RESULTS： The SVVH only technique was the least costly modality, $5809 （44449 RMB）, and was selected as the baseline treatment modality. SVVH only arm achieved the lowest C/E ratio in terms of overall survival, complications prevention and surgery preservation. In incremental cost-effectiveness analysis, the CWH/ LVVH only and the control arms were inferior to other techniques. Sensitivity analysis showed SVVH only and SVVH plus PD arms overlapped in C/survival ratio. CONCLUSION： The role of early veno-venous hemofiltration as an alternative therapy for SAP remains controversial. However, we propose that early use of short-term high-volume veno-venous hemofiltration would have a beneficial impact on the management of SAP.展开更多
Intelligent vehicles are advancing at a fast speed with the improvement of automation and connectivity,which opens up new possibilities for different cyber-attacks,including in-vehicle attacks(e.g.,hijacking attacks)a...Intelligent vehicles are advancing at a fast speed with the improvement of automation and connectivity,which opens up new possibilities for different cyber-attacks,including in-vehicle attacks(e.g.,hijacking attacks)and vehicle-to-everything communicationattacks(e.g.,data theft).These problems are becoming increasingly serious with the development of 4G LTE and 5G communication technologies.Although many efforts are made to improve the resilience to cyber attacks,there are still many unsolved challenges.This paper first identifies some major security attacks on intelligent connected vehicles.Then,we investigate and summarize the available defences against these attacks and classify them into four categories:cryptography,network security,software vulnerability detection,and malware detection.Remaining challenges and future directions for preventing attacks on intelligent vehicle systems have been discussed as well.展开更多
Using renewable energy to drive carbon dioxide reduction reaction(CO_(2)RR)electrochemically into chemicals with high energy density is an efficient way to achieve carbon neutrality,where the effective utilization of ...Using renewable energy to drive carbon dioxide reduction reaction(CO_(2)RR)electrochemically into chemicals with high energy density is an efficient way to achieve carbon neutrality,where the effective utilization of CO_(2) and the storage of renewable energy are realized.The reactivity and selectivity of CO_(2)RR depend on the structure and composition of the catalyst,applied potential,electrolyte,and pH of the solution.Besides,multiple electron and proton transfer steps are involved in CO_(2)RR,making the reaction pathways even more complicated.In pursuit of molecular-level insights into the CO_(2)RR processes,in situ vibrational methods including infrared,Raman and sum frequency generation spectroscopies have been deployed to monitor the dynamic evolution of catalyst structure,to identify reactive intermediates as well as to investigate the effect of local reaction environment on CO_(2)RR performance.This review summarizes key findings from recent electrochemical vibrational spectrosopic studies of CO_(2)RR in addressing the following issues:the CO_(2)RR mechanisms of different pathways,the role of surface-bound CO species,the compositional and structural effects of catalysts and electrolytes on CO_(2)RR activity and selectivity.Our perspectives on developing high sensitivity wide-frequency infrared spectroscopy,coupling different spectroelectrochemical methods and implementing operando vibrational spectroscopies to tackle the CO_(2)RR process in pilot reactors are offered at the end.展开更多
Gradient nanostructure was introduced to enhance the strength and ductility via deformation incompatibility accommodated by geometrical necessary dislocations for most metallic materials recently.However,few intensive...Gradient nanostructure was introduced to enhance the strength and ductility via deformation incompatibility accommodated by geometrical necessary dislocations for most metallic materials recently.However,few intensive researches were carried out to investigate the effect of gradient structure on the deformation twin evolution and resulting performance improvements.In the present paper,we produced gradient-structured AZ31 Mg alloy with fine-grain layers,parallel twin laminates and a coarse-grain core from two upmost surfaces to the center of plate.Surprisingly,this architected Mg alloy exhibited simultaneous enhancement of strength and ductility.Subsequent microstructural observations demonstrated that abundant twin-twin interactions resulting from higher strength and multi-axial stress state could make great contributions to the increase of work-hardening capability.This was further proved by the measurement of full-field strain evolution during the plastic deformation.Such a design strategy may provide a new path for producing advanced structure materials in which the deformation twinning works as one of the dominant plasticity mechanisms.展开更多
BACKGROUND: Currently, serum amylase and lipase are the most popular laboratory markers for early diagnosis of acute pancreatitis with reasonable sensitivity and specificity. Urinary trypsinogen-2 (UT-2) has been incr...BACKGROUND: Currently, serum amylase and lipase are the most popular laboratory markers for early diagnosis of acute pancreatitis with reasonable sensitivity and specificity. Urinary trypsinogen-2 (UT-2) has been increasingly used but its clinical value for the diagnosis of acute pancreatitis and post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis has not yet been systematically assessed. DATA SOURCES: A comprehensive search was carried out using PubMed (MEDLINE), Embase, and Web of Science for clinical trials, which studied the usefulness of UT-2 as a diagnostic marker for acute pancreatitis. Sensitivity, specificity and the diagnostic odds ratios (DORs) with 95% confidence interval (CI) were calculated for each study and were compared with serum amylase and lipase. Summary receiver-operating curves were conducted and the area under the curve (AUC) was evaluated. RESULTS: A total of 18 studies were included. The pooled sensitivity and specificity of UT-2 for the diagnosis of acute pancreatitis were 80% and 92%, respectively (AUC=0.96, DOR=65.63, 95% CI: 31.65-139.09). The diagnostic value of UT-2 was comparable to serum amylase but was weaker than serum lipase. The pooled sensitivity and specificity for the diagnosis of post-ERCP pancreatitis were 86% and 94%, respectively (AUC=0.92, DOR=77.68, 95% CI: 24.99-241.48).CONCLUSIONS: UT-2 as a rapid test could be potentially used for the diagnosis of post-ERCP pancreatitis and to an extent, acute pancreatitis. Further studies are warranted to confirm these results.展开更多
AIM: To investigate the role of prophylactic antibiotics in the reduction of mortality of severe acute pancreatitis (SAP) patients, which is highly questioned by more and more randomized controlled trials (RCTs) and m...AIM: To investigate the role of prophylactic antibiotics in the reduction of mortality of severe acute pancreatitis (SAP) patients, which is highly questioned by more and more randomized controlled trials (RCTs) and metaanalyses. METHODS: An updated meta-analysis was performed. RCTs comparing prophylactic antibiotics for SAP with control or placebo were included for meta-analysis. The mortality outcomes were pooled for estimation, and re-pooled estimation was performed by the sensitivity analysis of an ideal large-scale RCT. RESULTS: Currently available 11 RCTs were included. Subgroup analysis showed that there was significant reduction of mortality rate in the period before 2000, while no significant reduction in the period from 2000 [Risk Ratio, (RR ) = 1.01, P = 0.98]. Funnel plot indi-cated that there might be apparent publication bias in the period before 2000. Sensitivity analysis showed that the RR of mortality rate ranged from 0.77 to 1.00 with a relatively narrow confidence interval (P < 0.05). However, the number needed to treat having a minor lower limit of the range (7-5096 patients) implied that certain SAP patients could still potentially prevent death by antibiotic prophylaxis. CONCLUSION: Current evidences do not support prophylactic antibiotics as a routine treatment for SAP, but the potentially benefited sub-population requires further investigations.展开更多
How to completely remove the water from ionic liquids(ILs)is difficult for researchers because of the hygroscopicity of ILs.In order to study the hygroscopicity of ILs,two kinds of ILs,1-Butyl-3-methylimidazolium hexa...How to completely remove the water from ionic liquids(ILs)is difficult for researchers because of the hygroscopicity of ILs.In order to study the hygroscopicity of ILs,two kinds of ILs,1-Butyl-3-methylimidazolium hexafluorophosphate([Bmim][PF6])and 1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)([Bmim][NTf_(2)])were investigated by molecular dynamics simulations.Although[Bmim][PF6]and[Bmim][NTf_(2)]are hydrophobic,both of the ILs could absorb water molecules from the vapor.In this work,the process of absorbing water from the vapor phase was studied,and the water molecules could disperse into the IL.Aggregation was observed with increasing the water concentration.Although the absorbed water increases obviously,the amount of free water and small cluster in the ILs does not change significantly and always stays at a certain level.The amount of free water and small cluster in[Bmim][PF6]is more than that in[Bmim][NTf_(2)],which is consistent with their hydrophobicity.In addition,the liquid-vacuum and liquid–liquid interfaces of the ILs were simulated and analyzed in detail.The number density distribution and angle distribution indicated that[Bmim]+cations arrangement regularly at the IL-vacuum interface.The butyl chain point to the vacuum,while the imidazlium ring is close to the IL phase region and perpendicular to the interface.While at the IL-water interface,the cations and anions are disordered.展开更多
The gun-track launch system is a new special launch device that connects the track outside the muzzle.Because it is constrained by the track,the characteristics of development of the muzzle jet differ from those of th...The gun-track launch system is a new special launch device that connects the track outside the muzzle.Because it is constrained by the track,the characteristics of development of the muzzle jet differ from those of the traditional muzzle jet.Specifically,it changes from freely developing to doing so in a constrained manner,where this results in an asymmetric direction of flow as well as spatio-temporal coupling-induced interference between various shock waves and the formation of vortices.In this background,the authors of this article formulate and consider the development and characteristics of evolution of the muzzle jet as it impacts a constrained moving body.We designed simulations to test the gun-track launch system,and established a numerical model based on the dynamic grid method to explore the development and characteristics of propagation of disturbances when the muzzle jet impacted a constrained moving body.We also considered models without a constrained track for the sake of comparison.The results showed that the muzzle jet assumed a circumferential asymmetric shape,and tended to develop in the area above the muzzle.Because the test platform was close to the ground,the muzzle jet was subjected to reflections from it that enhanced the development and evolution of various forms of shock waves and vortices in the muzzle jet to exacerbate its rate of distortion and asymmetric characteristics.This in turn led to significant differences in the changes in pressure at symmetric points that would otherwise have been identical.The results of a comparative analysis showed that the constrained track could hinder the influence of reflections from the ground on the muzzle jet to some extent,and could reduce the velocity of the shock waves inducing the motion of the muzzle as well as the Mach number of the moving body.The work here provides a theoretical basis and the requisite technical support for applications of the gun-track launch system.It also sheds light on the technical bottlenecks that need to be considered to recover high-value warheads.展开更多
As an attractive class of metallic materials,single-phase CrCoNi medium-entropy alloy(MEA)has drawn much attention recently regarding their deformation behaviors,but the dynamically mechanical responses of this alloy ...As an attractive class of metallic materials,single-phase CrCoNi medium-entropy alloy(MEA)has drawn much attention recently regarding their deformation behaviors,but the dynamically mechanical responses of this alloy at high strain rates remain less studied,especially coupled with extremely low temperatures.In this study,the dynamic deformation behaviors of this CrCoNi MEA were systematically investigated at room temperature(RT)of 298 K and liquid nitrogen temperature(LNT)of 77 K using the split Hopkinson pressure bar(SHPB).This alloy exhibited a combination of higher yield strength and stronger hardening rate upon dynamic compressive deformation when the loading conditions become much harsher(higher strain rate or lower temperature).Detailed microstructure analyses indicated that the strong strain hardening ability during dynamic deformation was mainly attributed to the continuous formation of nanoscale deformation twins.Furthermore,as loaded at LNT,multi-directional deformation twins were activated.Meanwhile,due to the interaction between Shockley partial dislocations and twin boundaries,large-sized deformation-induced FCC-HCP phase transformations at a micrometer scale were also observed within the grains,which not only accommodated the plasticity but also played an important role in improving the hardening capability owing to the appearance of newly generated interfaces.展开更多
基金This work was supported by the National Key R&D Program of China(2022YFB4102000 and 2022YFA1505100)the NSFC(22472038)the Shanghai Science and Technology Innovation Action Plan(22dz1205500).
文摘Electrocatalytic carbon dioxide reduction is a promising technology for addressing global energy and environmental crises. However, its practical application faces two critical challenges: the complex and energy-intensive process of separat-ing mixed reduction products and the economic viability of the carbon sources (reactants) used. To tackle these challenges simultaneously, solid-state electrolyte (SSE) reactors are emerging as a promising solution. In this review, we focus on the feasibility of applying SSE for tandem electrochemical CO_(2) capture and conversion. The configurations and fundamental principles of SSE reactors are first discussed, followed by an introduction to its applications in these two specific areas, along with case studies on the implementation of tandem electrolysis. In comparison to conventional H-type cell, flow cell and membrane electrode assembly cell reactors, SSE reactors incorporate gas diffusion electrodes and utilize a solid electro-lyte layer positioned between an anion exchange membrane (AEM) and a cation exchange membrane (CEM). A key inno-vation of this design is the sandwiched SSE layer, which enhances efficient ion transport and facilitates continuous product extraction through a stream of deionized water or humidified nitrogen, effectively separating ion conduction from product collection. During electrolysis, driven by an electric field and concentration gradient, electrochemically generated ions (e.g., HCOO- and CH3COO-) migrate through the AEM into the SSE layer, while protons produced from water oxidation at the anode traverse the CEM into the central chamber to maintain charge balance. Targeted products like HCOOH can form in the middle layer through ionic recombination and are efficiently carried away by the flowing medium through the porous SSE layer, in the absence of electrolyte salt impurities. As CO_(2)RR can generate a series of liquid products, advancements in catalyst discovery over the past several years have facilitated the industrial application of SSE for more efficient chemicals production. Also noteworthy, the cathode reduction reaction can readily consume protons from water, creating a highly al-kaline local environment. SSE reactors are thereby employed to capture acidic CO_(2), forming CO_(3)^(2-) from various gas sources including flue gases. Driven by the electric field, the formed CO_(3)^(2-) can traverse through the AEM and react with protons originating from the anode, thereby regenerating CO_(2). This CO_(2) can then be collected and utilized as a low-cost feedstock for downstream CO_(2) electrolysis. Based on this principle, several cell configurations have been proposed to enhance CO_(2) capture from diverse gas sources. Through the collaboration of two SSE units, tandem electrochemical CO_(2) capture and con-version has been successfully implemented. Finally, we offer insights into the future development of SSE reactors for prac-tical applications aimed at achieving carbon neutrality. We recommend that greater attention be focused on specific aspects, including the fundamental physicochemical properties of the SSE layer, the electrochemical engineering perspective related to ion and species fluxes and selectivity, and the systematic pairing of consecutive CO_(2) capture and conversion units. These efforts aim to further enhance the practical application of SSE reactors within the broader electrochemistry community.
基金the National Key Research and Development Program of China(2022YFA1505700)the Fundamental Research Funds for the Central Universities(ZYGX2022J012)+2 种基金the NSFC(52171201,22278067,22322201,22201272)the Central Government Funds of Guiding Local Scientific and Technological Development for Sichuan Province(2024ZYD0152)the Natural Science Foundation of Sichuan Province(2025NSFJQ0017,2024NSFSC1107,2024NSFSC1104,2023NSFSC0094)。
文摘Electrocatalytic CO_(2)-to-CO conversion is crucial for advancing sustainable processes,and providing essential feedstocks for the chemical industry.Cobalt phthalocyanine(CoPc)is a well-established molecular catalyst for this conversion;however,maintaining high selectivity at industrially relevant current densities remains a significant challenge.Herein,we present a Co–N_(5)local structure anchored on nitrogen-doped carbon nanotubes through axial nitrogen coordination engineering to CoPc(CoPc/N-CNTs).The catalyst demonstrates near-unity CO selectivity and a high CO turnover frequency,peaking at 19.2 s^(−1)across a wide range of overpotentials.In flow cell tests,CoPc/N-CNTs achieve a CO Faradaic efficiency exceeding 95%at a current density of−800 mA cm^(−2).When integrated into a membrane electrode assembly,it maintained over 90%CO Faradaic efficiency at an industrial-scale current of−5 A for up to 20 h.Mechanistic studies revealed that Co–N_(5)active sites accelerate*COOH formation and inhibit deeper*CO reduction to CH_(3)OH while reducing HER activity by lowering H_(2)O surface coverage.These findings offer a delicate catalyst design that enables the efficient and sustained conversion of CO_(2)to CO.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.NSFC-12494590,NSFC-12174428,and NSFC-12274279)the New Cornerstone Investigator Programthe Chinese Academy of Sciences Project for Young Scientists in Basic Research(Grant No.2022YSBR-048).
文摘Determining the electronic structure of La_(3)Ni_(2)O_(7)is an essential step towards uncovering its superconducting mechanism.It is widely believed that the bilayer apical oxygens play an important role in the bilayer La_(3)Ni_(2)O_(7)electronic structure.Applying the hybrid exchange–correlation functionals,we obtain a more accurate electronic structure of La_(3)Ni_(2)O_(7)at its high-pressure phase,where the bonding dz2 band is below the Fermi level owing to the apical oxygen.The symmetry properties of this electronic structure and its corresponding tight-binding model are further analyzed.We find that the antisymmetric part is highly entangled,leading to a minimal nearly degenerate two-orbital model.Then,the apical oxygen vacancies effect is studied using the dynamical cluster approximation.This disorder effect strongly destroys the antisymmetric b Fermi surface,leading to the possible disappearance of superconductivity.
基金The National Natural Science Foundation of China under contract No.42076003.
文摘The impacts of the Luzon Strait transport on shallow meridional overturning circulation(SMOC)in the South China Sea(SCS)have been pointed out by previous studies,but the issue whether the Luzon Strait transport dominates the SMOC formation still remains open.The Helmholtz decomposition is applied based on the ocean general circulation model for the earth simulator products to address this issue.Results show that the motion caused by the Luzon Strait transport is characterized as an obvious southward flow between 13°N and 20°N.After this motion being removed,the clockwise winter SMOC and the anticlockwise summer SMOC can still exist significantly.The SMOC existence and its seasonal variation are also reproduced in the numerical simulation with the Luzon Strait closed.Both results of the Helmholtz decomposition and numerical experiment suggest that the SMOC formation and its seasonal variation are not dominated by the Luzon Strait transport.The SCS monsoon is the primary driving factor for the SMOC,which is related to the physical processes within the SCS.
基金the National Key Research and Development Program of China (2018YFB0105000)the National Natural Science Foundation of China (61773234 and U1864203)+2 种基金the Project of Tsinghua University and Toyota Joint Research Center for AI Technology of Automated Vehicle (TT2018-02)the International Science and Technology Cooperation Program of China (2016YFE0102200)the software developed in the Beijing Municipal Science and Technology Program (D171100005117001 and Z181100005918001).
文摘An increasing number of drivers are relying on digital map navigation systems in vehicles or mobile phones to select optimal driving routes in order to save time and improve safety. In the near future, digital map navigation systems are expected to play more important roles in transportation systems. In order to extend current navigation systems to more applications, two fundamental problems must be resolved: the lane-level map model and lane-level route planning. This study proposes solutions to both problems. The current limitation of the lane-level map model is not its accuracy but its flexibility;this study proposes a novel seven-layer map structure, called as Tsinghua map model, which is able to support autonomous driving in a flexible and efficient way. For lane-level route planning, we propose a hierarchical route-searching algorithm to accelerate the planning process, even in the presence of complicated lane networks. In addition, we model the travel costs allocated for lane-level road networks by analyzing vehicle maneuvers in traversing lanes, changing lanes, and turning at intersections. Tests were performed on both a grid network and a real lane-level road network to demonstrate the validity and efficiency of the proposed algorithm.
文摘AIM: To evaluate the effectiveness and safety of early nasogastric enteral nutrition (NGEN) for patients with severe acute pancreatitis (SAP). METHODS: We searched Cochrane Central Register of Controlled Trials (Issue 2, 2006), Pub-Medline (1966-2006), and references from relevant articles. We included randomized controlled trials (RCTs) only, which reported the mortality of SAP patients at least. Two reviewers assessed the quality of each trial and collected data independently. The Cochrane Collaboration’s RevMan 4.2.9 software was used for statistical analysis. RESULTS: Three RCTs were included, involving 131 patients. The baselines of each trial were comparable. Meta-analysis showed no significant differences in mortality rate of SAP patients between nasogastric and conventional routes (RR = 0.76, 95% CI = 0.37 and 1.55, P = 0.45), and in other outcomes, including time of hospital stay (weighted mean difference = -5.87, 95% CI = -20.58 and 8.84, P = 0.43), complication rate of infection (RR = 1.41, 95% CI = 0.62 and 3.23, P = 0.41) or multiple organ defi ciency syndrome (RR = 0.97, 95% CI = 0.27 and 3.47, P = 0.97), rate of admission to ICU (RR = 1.00, 95% CI = 0.48 and 2.09, P = 0.99) or conversion to surgery (RR = 0.66, 95% CI = 0.12 and 3.69, P = 0.64), as well as recurrence of re-feeding pain and adverse events associated with nutrition. CONCLUSION: Early NGEN is a breakthrough in the management of SAP. Based on current studies, early NGEN appears effective and safe. Since the available evidence is poor in quantity, it is hard to make an accurate evaluation of the role of early NGEN in SAP.Before recommendation to clinical practice, further high qualified, large scale, randomized controlled trials are needed.
基金Supported by Multidisciplinary Treatment Project of Gastrointestinal Tumors, West China Hospital, Sichuan University,the Scientific Foundation of West China Hospital of Sichuan University
文摘AIM： To assess the economics of various chemotherapeutic regimens for advanced gastric cancer （AGC）, and to select the best cost-effective regimen for the common Chinese patients. METHODS： Data source used in this study was the Chinese Biomedical Disk Database. Patients were diagnosed as AGC and any regimen was eligible. Outcome measures included median survival time （MST） and percentage of complete and partial response （CR＋PR）. Economic statistics was per capita direct medical cost （DMC） of a single cycle. TreeAge Pro Healthcare 2007 software was used to carry out costeffectiveness and incremental cost-effectiveness analysis. Sensitivity analyses were applied by altering willingness- to-pay and annual discount rate, and also re-analyzed by excluding the studies with apparent heterogeneity. RESULTS： Seven retrospective economics studies on 760 patients were included. S-fluorouracil-based regimens were universal, and also some new agents were involved, such as docetaxel, paclitaxel, andoxaliplatin. By processing analysis, we could recommend etoposide, leucovorin and 5-fluorouracil （ELF） regimen as preference, with a DMC/MST ratio of 2543 RBM/11.7 mo and a DMC/CR＋PR ratio of 2543 RMB/53.3%. Uraciltegafur, etoposide and cisplatin （FEP） or 5-fluorouracil, adrimycin/epirubin and mitomycin （FAM） regimens could be regarded as optional first-line chemotherapy for AGC in common Chinese patients. With no regard for willingness-to-pay, the docetaxel, cisplatin and 5-fluorouracil （DCF） regimen could be chosen as either a first- or a second-line chemotherapy, with a DMC/CR＋PR ratio of 9979 RMB/56.3%. CONCLUSION： 5-fluorouracial regimens are still considered the mainstream for AGC, while new agents such as taxanes are optional. More randomized clinical trials are required before any mandatory recommendation of certain regimens for patients with AGC in China is made.
基金Supported by National Cancer Institute of the National Institutes of Health,No. R37CA229810Biostatistics Core Facility at the H.Lee Moffitt Cancer Center and Research Institute,an NCI designated Comprehensive Cancer Center,No. P30-CA076292
文摘BACKGROUND Intraductal papillary mucinous neoplasms(IPMNs)are non-invasive pancreatic precursor lesions that can potentially develop into invasive pancreatic ductal adenocarcinoma.Currently,the International Consensus Guidelines(ICG)for IPMNs provides the basis for evaluating suspected IPMNs on computed tomography(CT)imaging.Despite using the ICG,it remains challenging to accurately predict whether IPMNs harbor high grade or invasive disease which would warrant surgical resection.A supplementary quantitative radiological tool,radiomics,may improve diagnostic accuracy of radiological evaluation of IPMNs.We hypothesized that using CT whole lesion radiomics features in conjunction with the ICG could improve the diagnostic accuracy of predicting IPMN histology.AIM To evaluate whole lesion CT radiomic analysis of IPMNs for predicting malignant histology compared to International Consensus Guidelines.METHODS Fifty-one subjects who had pancreatic surgical resection at our institution with histology demonstrating IPMN and available preoperative CT imaging were included in this retrospective cohort.Whole lesion semi-automated segmentation was performed on each preoperative CT using Healthmyne software(Healthmyne,Madison,WI).Thirty-nine relevant radiomic features were extracted from each lesion on each available contrast phase.Univariate analysis of the 39 radiomics features was performed for each contrast phase and values were compared between malignant and benign IPMN groups using logistic regression.Conventional quantitative and qualitative CT measurements were also compared between groups,viaχ2(categorical)and Mann Whitney U(continuous)variables.RESULTS Twenty-nine subjects(15 males,age 71±9 years)with high grade or invasive tumor histology comprised the"malignant"cohort,while 22 subjects(11 males,age 70±7 years)with low grade tumor histology were included in the"benign"cohort.Radiomic analysis showed 18/39 precontrast,19/39 arterial phase,and 21/39 venous phase features differentiated malignant from benign IPMNs(P<0.05).Multivariate analysis including only ICG criteria yielded two significant variables:thickened and enhancing cyst wall and enhancing mural nodule<5 mm with an AUC(95%CI)of 0.817(0.709-0.926).Multivariable post contrast radiomics achieved an AUC(95%CI)of 0.87(0.767-0.974)for a model including arterial phase radiomics features and 0.834(0.716-0.953)for a model including venous phase radiomics features.Combined multivariable model including conventional variables and arterial phase radiomics features achieved an AUC(95%CI)of 0.93(0.85-1.0)with a 5-fold cross validation AUC of 0.90.CONCLUSION Multi-phase CT radiomics evaluation could play a role in improving predictive capability in diagnosing malignancy in IPMNs.Future larger studies may help determine the clinical significance of our findings.
基金the National Natural Science Foundation of China(No.61703413)the Science and Technology Innovation Program of Hunan Province,China(No.2021RC3078).
文摘This article provides a review on X-ray pulsar-based navigation(XNAV).The review starts with the basic concept of XNAV,and briefly introduces the past,present and future projects concerning XNAV.This paper focuses on the advances of the key techniques supporting XNAV,including the navigation pulsar database,the X-ray detection system,and the pulse time of arrival estimation.Moreover,the methods to improve the estimation performance of XNAV are reviewed.Finally,some remarks on the future development of XNAV are provided.
基金Supported by The National Natural Science Foundation of China, No.30500684 and Clinical Research Foundation for Residency Granted by the Cooperative Project of West China Hospital and Daiichi Pharmaceutical Co. Ltd., the level Ⅰ
文摘AIM： To determine the most cost-effective hemofiltration modality for early management of severe acute pancreatitis （SAP） in China. METHODS： We carried out a search of Pub-Medline and Chinese Biomedical Disk database. Controlled clinical trials on Chinese population were included in the analysis. The four decision branches that were analyzed were： continuous or long-term veno-venous hemofiltration （CVVH/LVVH）, short-term veno-venous hemofiltration （SVVH）, SVVH plus peritoneal dialysis （PD）, and non-hemofiltration control group. The effectiveness of the technique was determined by survival rate, complications prevention and surgery preservation. The total cost of hospitalization was also assessed. RESULTS： The SVVH only technique was the least costly modality, $5809 （44449 RMB）, and was selected as the baseline treatment modality. SVVH only arm achieved the lowest C/E ratio in terms of overall survival, complications prevention and surgery preservation. In incremental cost-effectiveness analysis, the CWH/ LVVH only and the control arms were inferior to other techniques. Sensitivity analysis showed SVVH only and SVVH plus PD arms overlapped in C/survival ratio. CONCLUSION： The role of early veno-venous hemofiltration as an alternative therapy for SAP remains controversial. However, we propose that early use of short-term high-volume veno-venous hemofiltration would have a beneficial impact on the management of SAP.
文摘Intelligent vehicles are advancing at a fast speed with the improvement of automation and connectivity,which opens up new possibilities for different cyber-attacks,including in-vehicle attacks(e.g.,hijacking attacks)and vehicle-to-everything communicationattacks(e.g.,data theft).These problems are becoming increasingly serious with the development of 4G LTE and 5G communication technologies.Although many efforts are made to improve the resilience to cyber attacks,there are still many unsolved challenges.This paper first identifies some major security attacks on intelligent connected vehicles.Then,we investigate and summarize the available defences against these attacks and classify them into four categories:cryptography,network security,software vulnerability detection,and malware detection.Remaining challenges and future directions for preventing attacks on intelligent vehicle systems have been discussed as well.
文摘Using renewable energy to drive carbon dioxide reduction reaction(CO_(2)RR)electrochemically into chemicals with high energy density is an efficient way to achieve carbon neutrality,where the effective utilization of CO_(2) and the storage of renewable energy are realized.The reactivity and selectivity of CO_(2)RR depend on the structure and composition of the catalyst,applied potential,electrolyte,and pH of the solution.Besides,multiple electron and proton transfer steps are involved in CO_(2)RR,making the reaction pathways even more complicated.In pursuit of molecular-level insights into the CO_(2)RR processes,in situ vibrational methods including infrared,Raman and sum frequency generation spectroscopies have been deployed to monitor the dynamic evolution of catalyst structure,to identify reactive intermediates as well as to investigate the effect of local reaction environment on CO_(2)RR performance.This review summarizes key findings from recent electrochemical vibrational spectrosopic studies of CO_(2)RR in addressing the following issues:the CO_(2)RR mechanisms of different pathways,the role of surface-bound CO species,the compositional and structural effects of catalysts and electrolytes on CO_(2)RR activity and selectivity.Our perspectives on developing high sensitivity wide-frequency infrared spectroscopy,coupling different spectroelectrochemical methods and implementing operando vibrational spectroscopies to tackle the CO_(2)RR process in pilot reactors are offered at the end.
基金This work was financially supported by National Natural Science Foundation of China(Grant Nos.11772268 and 12025205).The authors would like to appreciate the researchers in Nanjing university of science and technology for their support in preparation of gradient structured materials.
文摘Gradient nanostructure was introduced to enhance the strength and ductility via deformation incompatibility accommodated by geometrical necessary dislocations for most metallic materials recently.However,few intensive researches were carried out to investigate the effect of gradient structure on the deformation twin evolution and resulting performance improvements.In the present paper,we produced gradient-structured AZ31 Mg alloy with fine-grain layers,parallel twin laminates and a coarse-grain core from two upmost surfaces to the center of plate.Surprisingly,this architected Mg alloy exhibited simultaneous enhancement of strength and ductility.Subsequent microstructural observations demonstrated that abundant twin-twin interactions resulting from higher strength and multi-axial stress state could make great contributions to the increase of work-hardening capability.This was further proved by the measurement of full-field strain evolution during the plastic deformation.Such a design strategy may provide a new path for producing advanced structure materials in which the deformation twinning works as one of the dominant plasticity mechanisms.
基金supported by grants from the National Natural Science Foundation of China(2009SZ0201)National Institute of Health Research UK
文摘BACKGROUND: Currently, serum amylase and lipase are the most popular laboratory markers for early diagnosis of acute pancreatitis with reasonable sensitivity and specificity. Urinary trypsinogen-2 (UT-2) has been increasingly used but its clinical value for the diagnosis of acute pancreatitis and post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis has not yet been systematically assessed. DATA SOURCES: A comprehensive search was carried out using PubMed (MEDLINE), Embase, and Web of Science for clinical trials, which studied the usefulness of UT-2 as a diagnostic marker for acute pancreatitis. Sensitivity, specificity and the diagnostic odds ratios (DORs) with 95% confidence interval (CI) were calculated for each study and were compared with serum amylase and lipase. Summary receiver-operating curves were conducted and the area under the curve (AUC) was evaluated. RESULTS: A total of 18 studies were included. The pooled sensitivity and specificity of UT-2 for the diagnosis of acute pancreatitis were 80% and 92%, respectively (AUC=0.96, DOR=65.63, 95% CI: 31.65-139.09). The diagnostic value of UT-2 was comparable to serum amylase but was weaker than serum lipase. The pooled sensitivity and specificity for the diagnosis of post-ERCP pancreatitis were 86% and 94%, respectively (AUC=0.92, DOR=77.68, 95% CI: 24.99-241.48).CONCLUSIONS: UT-2 as a rapid test could be potentially used for the diagnosis of post-ERCP pancreatitis and to an extent, acute pancreatitis. Further studies are warranted to confirm these results.
基金Supported by The National Natural Science Foundation of China,No. 81072910
文摘AIM: To investigate the role of prophylactic antibiotics in the reduction of mortality of severe acute pancreatitis (SAP) patients, which is highly questioned by more and more randomized controlled trials (RCTs) and metaanalyses. METHODS: An updated meta-analysis was performed. RCTs comparing prophylactic antibiotics for SAP with control or placebo were included for meta-analysis. The mortality outcomes were pooled for estimation, and re-pooled estimation was performed by the sensitivity analysis of an ideal large-scale RCT. RESULTS: Currently available 11 RCTs were included. Subgroup analysis showed that there was significant reduction of mortality rate in the period before 2000, while no significant reduction in the period from 2000 [Risk Ratio, (RR ) = 1.01, P = 0.98]. Funnel plot indi-cated that there might be apparent publication bias in the period before 2000. Sensitivity analysis showed that the RR of mortality rate ranged from 0.77 to 1.00 with a relatively narrow confidence interval (P < 0.05). However, the number needed to treat having a minor lower limit of the range (7-5096 patients) implied that certain SAP patients could still potentially prevent death by antibiotic prophylaxis. CONCLUSION: Current evidences do not support prophylactic antibiotics as a routine treatment for SAP, but the potentially benefited sub-population requires further investigations.
基金financial support from the National Science Fund for Excellent Young Scholars(21722610)Taishan Scholars Program of Shandong Province(tsqn201909091)。
文摘How to completely remove the water from ionic liquids(ILs)is difficult for researchers because of the hygroscopicity of ILs.In order to study the hygroscopicity of ILs,two kinds of ILs,1-Butyl-3-methylimidazolium hexafluorophosphate([Bmim][PF6])and 1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)([Bmim][NTf_(2)])were investigated by molecular dynamics simulations.Although[Bmim][PF6]and[Bmim][NTf_(2)]are hydrophobic,both of the ILs could absorb water molecules from the vapor.In this work,the process of absorbing water from the vapor phase was studied,and the water molecules could disperse into the IL.Aggregation was observed with increasing the water concentration.Although the absorbed water increases obviously,the amount of free water and small cluster in the ILs does not change significantly and always stays at a certain level.The amount of free water and small cluster in[Bmim][PF6]is more than that in[Bmim][NTf_(2)],which is consistent with their hydrophobicity.In addition,the liquid-vacuum and liquid–liquid interfaces of the ILs were simulated and analyzed in detail.The number density distribution and angle distribution indicated that[Bmim]+cations arrangement regularly at the IL-vacuum interface.The butyl chain point to the vacuum,while the imidazlium ring is close to the IL phase region and perpendicular to the interface.While at the IL-water interface,the cations and anions are disordered.
文摘The gun-track launch system is a new special launch device that connects the track outside the muzzle.Because it is constrained by the track,the characteristics of development of the muzzle jet differ from those of the traditional muzzle jet.Specifically,it changes from freely developing to doing so in a constrained manner,where this results in an asymmetric direction of flow as well as spatio-temporal coupling-induced interference between various shock waves and the formation of vortices.In this background,the authors of this article formulate and consider the development and characteristics of evolution of the muzzle jet as it impacts a constrained moving body.We designed simulations to test the gun-track launch system,and established a numerical model based on the dynamic grid method to explore the development and characteristics of propagation of disturbances when the muzzle jet impacted a constrained moving body.We also considered models without a constrained track for the sake of comparison.The results showed that the muzzle jet assumed a circumferential asymmetric shape,and tended to develop in the area above the muzzle.Because the test platform was close to the ground,the muzzle jet was subjected to reflections from it that enhanced the development and evolution of various forms of shock waves and vortices in the muzzle jet to exacerbate its rate of distortion and asymmetric characteristics.This in turn led to significant differences in the changes in pressure at symmetric points that would otherwise have been identical.The results of a comparative analysis showed that the constrained track could hinder the influence of reflections from the ground on the muzzle jet to some extent,and could reduce the velocity of the shock waves inducing the motion of the muzzle as well as the Mach number of the moving body.The work here provides a theoretical basis and the requisite technical support for applications of the gun-track launch system.It also sheds light on the technical bottlenecks that need to be considered to recover high-value warheads.
基金supported by the National Natural Science Foundation of China(Grant No.12102363)the China National Funds for Distinguished Young Scientists(Grant No.12025205).
文摘As an attractive class of metallic materials,single-phase CrCoNi medium-entropy alloy(MEA)has drawn much attention recently regarding their deformation behaviors,but the dynamically mechanical responses of this alloy at high strain rates remain less studied,especially coupled with extremely low temperatures.In this study,the dynamic deformation behaviors of this CrCoNi MEA were systematically investigated at room temperature(RT)of 298 K and liquid nitrogen temperature(LNT)of 77 K using the split Hopkinson pressure bar(SHPB).This alloy exhibited a combination of higher yield strength and stronger hardening rate upon dynamic compressive deformation when the loading conditions become much harsher(higher strain rate or lower temperature).Detailed microstructure analyses indicated that the strong strain hardening ability during dynamic deformation was mainly attributed to the continuous formation of nanoscale deformation twins.Furthermore,as loaded at LNT,multi-directional deformation twins were activated.Meanwhile,due to the interaction between Shockley partial dislocations and twin boundaries,large-sized deformation-induced FCC-HCP phase transformations at a micrometer scale were also observed within the grains,which not only accommodated the plasticity but also played an important role in improving the hardening capability owing to the appearance of newly generated interfaces.
