The excessive buildup of neurotoxicα-synuclein plays a pivotal role in the pathogenesis of Parkinson's disease,highlighting the urgent need for innovative therapeutic strategies to promoteα-synuclein clearance,p...The excessive buildup of neurotoxicα-synuclein plays a pivotal role in the pathogenesis of Parkinson's disease,highlighting the urgent need for innovative therapeutic strategies to promoteα-synuclein clearance,particularly given the current lack of disease-modifying treatments.The glymphatic system,a recently identified perivascular fluid transport network,is crucial for clearing neurotoxic proteins.This review aims to synthesize current knowledge on the role of the glymphatic system inα-synuclein clearance and its implications for the pathology of Parkinson's disease while emphasizing potential therapeutic strategies and areas for future research.The review begins with an overview of the glymphatic system and details its anatomical structure and physiological functions that facilitate cerebrospinal fluid circulation and waste clearance.It summarizes emerging evidence from neuroimaging and experimental studies that highlight the close correlation between the glymphatic system and clinical symptom severity in patients with Parkinson's disease,as well as the effect of glymphatic dysfunction onα-synuclein accumulation in Parkinson's disease models.Subsequently,the review summarizes the mechanisms of glymphatic system impairment in Parkinson's disease,including sleep disturbances,aquaporin-4 impairment,and mitochondrial dysfunction,all of which diminish glymphatic system efficiency.This creates a vicious cycle that exacerbatesα-synuclein accumulation and worsens Parkinson's disease.The therapeutic perspectives section outlines strategies for enhancing glymphatic activity,such as improving sleep quality and pharmacologically targeting aquaporin-4 or its subcellular localization.Promising interventions include deep brain stimulation,melatonin supplementation,γ-aminobutyric acid modulation,and non-invasive methods(such as exercise and bright-light therapy),multisensoryγstimulation,and ultrasound therapy.Moreover,identifying neuroimaging biomarkers to assess glymphatic flow as an indicator ofα-synuclein burden could refine Parkinson's disease diagnosis and track disease progression.In conclusion,the review highlights the critical role of the glymphatic system inα-synuclein clearance and its potential as a therapeutic target in Parkinson's disease.It advocates for further research to elucidate the specific mechanisms by which the glymphatic system clears misfoldedα-synuclein and the development of imaging biomarkers to monitor glymphatic activity in patients with Parkinson's disease.Findings from this review suggest that enhancing glymphatic clearance is a promising strategy for reducingα-synuclein deposits and mitigating the progression of Parkinson's disease.展开更多
This article describes the effects of some factors on the tip clearance flow in axial linear turbine cascades. The measurements of the total pressure loss coefficient are made at the cascade outlets by using a five-ho...This article describes the effects of some factors on the tip clearance flow in axial linear turbine cascades. The measurements of the total pressure loss coefficient are made at the cascade outlets by using a five-hole probe at exit Mach numbers of 0.10, 0.14 and 0.19. At each exit Mach number, experiments are performed at the tip clearance heights of 1.0%, 1.5%, 2.0%, 2.5% and 3.0% of the blade height. The effects of the non-uniform tip clearance height of each blade in the pitchwise direction are also studied. The results show that at a given tip clearance height, generally, total pressure loss rises with exit Mach numbers proportionally. At a fixed exit Mach number, the total pressure loss augments nearly proportionally as the tip clearance height increases. The increased tip clearance heights in the tip regions of two adjacent blades are to be blame for the larger clearance loss of the center blade. Compared to the effects of the tip clearance height, the effects of the exit Mach number and the pitchwise variation of the tip clearance height on the cascade total pressure loss are so less significant to be omitted.展开更多
Alzheimer's disease,the primary cause of dementia,is characterized by neuropathologies,such as amyloid plaques,synaptic and neuronal degeneration,and neurofibrillary tangles.Although amyloid plaques are the primar...Alzheimer's disease,the primary cause of dementia,is characterized by neuropathologies,such as amyloid plaques,synaptic and neuronal degeneration,and neurofibrillary tangles.Although amyloid plaques are the primary characteristic of Alzheimer's disease in the central nervous system and peripheral organs,targeting amyloid-beta clearance in the central nervous system has shown limited clinical efficacy in Alzheimer's disease treatment.Metabolic abnormalities are commonly observed in patients with Alzheimer's disease.The liver is the primary peripheral organ involved in amyloid-beta metabolism,playing a crucial role in the pathophysiology of Alzheimer's disease.Notably,impaired cholesterol metabolism in the liver may exacerbate the development of Alzheimer's disease.In this review,we explore the underlying causes of Alzheimer's disease and elucidate the role of the liver in amyloid-beta clearance and cholesterol metabolism.Furthermore,we propose that restoring normal cholesterol metabolism in the liver could represent a promising therapeutic strategy for addressing Alzheimer's disease.展开更多
Metamorphic mechanism has the advantages of variable topology and variable degrees of freedom, which can realize the requirements of multi-conditions and multi-tasks, and has a good application prospect. The configura...Metamorphic mechanism has the advantages of variable topology and variable degrees of freedom, which can realize the requirements of multi-conditions and multi-tasks, and has a good application prospect. The configuration transformation is prominent feature of the metamorphic mechanism. The number of constraints or properties of the kinematic pairs provided by the metamorphic kinematic pairs will change under certain conditions, its dynamic performance is much more complex than that of traditional kinematic pairs with immutable constraints. However, the clearance model about traditional kinematic pairs with immutable constraints established by long-term research is difficult to be directly applied to the metachromatic kinematic pairs. Referring to the experience of the traditional kinematic pairs with immutable constraints, the continuous contact model of Metamorphic Groove pin pair with clearance is established. According to the traditional continuous contact model of the kinematic pairs with immutable constraints, the forces between the elements of kinematic pair of the mechanism with clearance and the ideal mechanism without clearance are regarded as the same, and the inertia force and inertia moment of the components are also calculated according to the acceleration of the ideal mechanism. The clearance is regarded as a massless virtual bar with length r. For the rotating pair part, the massless virtual bar length r is the difference between the radius of the shaft and the hole, and for the sliding pair part, the massless virtual bar length r is half of the difference between the height of the slider and the guide groove. According to the new mechanism without gap after adding the imaginary bar, kinetic energy and potential energy of the system are calculated for the two configurations of mechanism with metamorphic Groove pin pair with clearance. The kinetic energy and potential energy of the system are calculated according to the new mechanism without clearance after adding the massless virtual bar. The kinetic energy, potential energy and generalized force are substituted into the Lagrangian equation to obtain the motion equation of the metamorphic mechanism, which lays the foundation for the dynamic performance study of the mechanism with metamorphic groove pin pair with clearance.展开更多
Currently,it is still a challenge to develop an organic photosensitizer(PS)with outstanding near-infrared absorption,low O2dependence,precise tumor targeting and rapid clearance through the kidney to improve the overa...Currently,it is still a challenge to develop an organic photosensitizer(PS)with outstanding near-infrared absorption,low O2dependence,precise tumor targeting and rapid clearance through the kidney to improve the overall outcome of phototherapy.In this study,we have designed an organic PS(Nc PB)with an excellent near-infrared light absorption through a refined molecular strategy.Meanwhile,Nc PB was assembled into nanoparticles with different sizes(Nano Nc PB-1 and Nano Nc PB-0)by a supramolecular modulation strategy.As the results,the nanoparticle with an ultra-small size(Nano Nc PB-1)generated a large number of superoxide anion(O_(2)^(·-))in a low-O_(2)-dependent manner and release plenty of heat.Furthermore,the results of in vivo experiments demonstrated that Nano Nc PB-1 actively accumulated in tumor tissues and showed a 92%tumor inhibition after photodynamic and photothermal combination therapy.More importantly,Nano Nc PB-1 could be rapidly cleared from the body of mice via the renal pathway,which alleviates potential side effects of prolonged retention of PS in the circulation.展开更多
Joint clearances in antenna pointing mechanisms lead to uncertainty in function deviation. Current studies mainly focus on radial clearance of revolute joints, while axial clearance has rarely been taken into consider...Joint clearances in antenna pointing mechanisms lead to uncertainty in function deviation. Current studies mainly focus on radial clearance of revolute joints, while axial clearance has rarely been taken into consideration. In fact, own?ing to errors from machining and assembly, thermal deformation and so forth, practically, axial clearance is inevitable in the joint. In this study, an error equivalent model(EEM) of revolute joints is proposed with considering both radial and axial clearances. Compared to the planar model of revolute joints only considering radial clearance, the journal motion inside the bearing is more abundant and matches the reality better in the EEM. The model is also extended for analyzing the error distribution of a spatial dual?axis("X–Y" type) antenna pointing mechanism of Spot?beam antennas which especially demand a high pointing accuracy. Three case studies are performed which illustrates the internal relation between radial clearance and axial clearance. It is found that when the axial clearance is big enough, the physical journal can freely realize both translational motion and rotational motion. While if the axial clearance is limited, the motion of the physical journal will be restricted. Analysis results indicate that the consideration of both radial and axial clearances in the revolute joint describes the journal motion inside the bearing more precise. To further validate the proposed model, a model of the EEM is designed and fabricated. Some suggestions on the design of revolute joints are also provided.展开更多
Combining practical engineering projects, this article analyzes the design strategies for the reconstruction and expansion of insufficient clearance sections in highway interchanges. This includes an overview of the p...Combining practical engineering projects, this article analyzes the design strategies for the reconstruction and expansion of insufficient clearance sections in highway interchanges. This includes an overview of the project, a comparison of design options for insufficient clearance in interchanges, and the main design strategies for reconstruction and expansion. It is hoped that this analysis can provide a reference for the design of such road reconstruction and expansion projects.展开更多
BACKGROUND Chronic hepatitis B(CHB)patients rarely achieve functional cure with initial pegylated interferon alpha-2b(Peg-IFNα-2b)therapy.Validated tools to guide retreatment candidates are lacking.We hypothesized th...BACKGROUND Chronic hepatitis B(CHB)patients rarely achieve functional cure with initial pegylated interferon alpha-2b(Peg-IFNα-2b)therapy.Validated tools to guide retreatment candidates are lacking.We hypothesized that clinical indicators predict hepatitis B surface antigen(HBsAg)clearance during retreatment.AIM To develop a prediction model for HBsAg clearance in Peg-IFNα-2b retreatment.METHODS In this retrospective cohort study,we enrolled 135 CHB/compensated cirrhosis patients receiving Peg-IFNα-2b retreatment after initial non-clearance at Tianjin University Central Hospital(2017-2025).Predictors were identified through univariate Cox,least absolute shrinkage and selection operator,and multivariate Cox regression.Model performance was assessed via receiver operating characteristic analysis and Harrell’s C-index,with risk stratification by X-tile optimization.RESULTS HBsAg clearance rate was 20.74%(28/135).Independent predictors included:Combination nucleos(t)ide analogue(NA)therapy during initial treatment[hazard ratio(HR)=0.276,95%confidence interval(CI):0.092-0.833],baseline HBsAg at retreatment(HR=0.571,95%CI:0.410-0.795),HBsAg decline after initial treatment(HR=2.050,95%CI:1.108-3.793),and treatment interval(HR=1.013/week,95%CI:1.008-1.018).The retreatment HBsAg clearance prediction score(RHCP-S)demonstrated area under the curve of 0.920(95%CI:0.863-0.946),sensitivity of 92.3%,specificity of 79.3%.Clearance rates differed significantly:RHCP-S challenge group(≤74 points):3.45%,RHCP-S probable group(74-110 points):29.63%,RHCP-S dominant group(≥110 points):80.95%(P<0.001).CONCLUSION The overall HBsAg clearance rate with Peg-IFNα-2b retreatment was 20.74%(28/135).The RHCP-S model identifies optimal retreatment candidates(≥110 points)with 80.95%clearance probability,associated with the absence of combination NA therapy during initial treatment,greater initial HBsAg decline,longer intervals,and lower retreatment HBsAg.展开更多
Mechanical vibration sputum clearance is commonly used for airway clearance.However,existing handheld vibration-assisted expectorators confront several challenges including operator’s hand fatigue and a high risk of ...Mechanical vibration sputum clearance is commonly used for airway clearance.However,existing handheld vibration-assisted expectorators confront several challenges including operator’s hand fatigue and a high risk of cross-infection between medical staff and patients.To address these issues,this study presents a novel design for an intelligent percussion-based sputum clearance robot.The robot is designed to assist medical staff in providing percussion-based sputum clearance nursing for patients.Initially,the structure of the robot is designed based on the environmental conditions in the intensive care unit(ICU).To mitigate the impact of the vibrations generated by the vibration percussion head on the robotic arm operation,a fixture equipped with a vibration damper is designed to ensure that the robot’s standard functionality remains unaffected.Furthermore,a human back detection(HBD)framework constructed from multi-subtask modules is proposed to address the shortcomings of existing robotic systems in terms of human perception capabilities.These modules are designed to accurately identify and map the anatomical features of the human back.This effectively improves the capability of the robot to interact with the human body.Based on this framework,the robotic arm is controlled precisely to emulate the percussion strategies employed by physicians.Finally,extensive experiments are conducted in a real-world setting with multiple participants.The results indicate that the robot could provide percussion-based sputum clearance nursing that is practically equivalent to the operations by medical staff.展开更多
The existence of the aeroengine casing,limited monitoring points,and multi-fault characteristics make obtaining the rotor’s vibration transmission characteristics challenging,resulting in difficulties accurately iden...The existence of the aeroengine casing,limited monitoring points,and multi-fault characteristics make obtaining the rotor’s vibration transmission characteristics challenging,resulting in difficulties accurately identifying the rotor unbalance.This paper utilizes a high-frequency composite sensor to monitor the engine’s blade tip clearance(BTC)and extracts unbalanced information from BTC signals for rotor dynamic balancing,while avoiding the need for the once per revolution(OPR)sensor.First,the vibration characteristics of the rotor-blade system under multi-fault conditions are investigated.Then,based on BTC measurement,a none OPR method and an unbalance identification method are proposed,in which the radial vibration of the blade tip in the BTC signals at different speeds is extracted and operated in the time domain to obtain the rotor unbalanced vibration,the signal is reconstructed,and cross-correlation analysis is used to accurately identify the magnitude and phase of the unbalanced signal.Finally,a rotor test bench is utilized for experimental verification.The results reveal that the dynamic balancing method based on the BTC signal can more precisely identify the rotor unbalance than the traditional rotor dynamic balancing method.The application of this technique will effectively improve engine health management and fault prediction.展开更多
As the performance of the box-type multiple launch rocket system(BMLRS)improves,its mechanical structures,particularly the plane clearance design between the slider on the rocket and the guide inside the launch canist...As the performance of the box-type multiple launch rocket system(BMLRS)improves,its mechanical structures,particularly the plane clearance design between the slider on the rocket and the guide inside the launch canister,have grown increasingly complex.However,deficiencies still exist in the current launch modeling theory for BMLRS.In this study,a multi-rigid-flexible-body launch dynamics model coupling the launch platform and rocket was established using the multibody system transfer matrix method and the Newton-Euler formulation.Furthermore,considering the bending of the launch canister,a detection algorithm for slider-guide plane clearance contact was proposed.To quantify the contact force and friction effect between the slider and guide,the contact force model and modified Coulomb model were introduced.Both the modal and launch tests were conducted.Additionally,the modal convergence was verified.By comparing the modal experiments and simulation results,the maximum relative error of the eigenfrequency is 3.29%.thereby verifying the accuracy of the developed BMLRS dynamics model.Furthermore,the launch test validated the proposed plane clearance contact model.Moreover,the study investigated the influence of various model parameters on the dynamic characteristics of BMLRS,including launch canister bending stiffness,slider and guide material,slider-guide clearance,slider length and layout.This analysis of influencing factors provides a foundation for future optimization in BMLRS design.展开更多
Lateral clearance on the inside of horizontal curves is required by all geometric design guidelines in order to provide at least stopping sight distance. There already exist graphical models, analytical models, and de...Lateral clearance on the inside of horizontal curves is required by all geometric design guidelines in order to provide at least stopping sight distance. There already exist graphical models, analytical models, and design charts for determining minimum clearance offsets to meet the requirement. Some of these models determine the offsets based on constant design sight distance values on the assumption that drivers negotiate horizontal curves at constant speed. Therefore, those models are suitable for sites where there is no difference in speeds between tangent and curved sections. Past studies have reported that there are sites where drivers decelerate on entering horizontal curves and accelerate on departing from the curves. At those sites stopping sight distance for a given driver varies with driver location due to variable speed. This paper presents an analytical model and a chart for determining minimum offsets needed to provide desired sight distances at horizontal curves with variable operating speeds. At those sites the offsets yield roadside clearance boundaries that have transition arcs with performances that are similar to those of elliptical arcs. Therefore, practitioners may choose to use elliptical equations or equations and the chart developed herein. Results of this study will be of value to practitioners in the area of roadside design.展开更多
Active control of turbine blade tip clearance continues to be a concern in design and control of gas turbines. Ever increasing demands for improved efficiency and higher operating temperatures require more stringent t...Active control of turbine blade tip clearance continues to be a concern in design and control of gas turbines. Ever increasing demands for improved efficiency and higher operating temperatures require more stringent tolerances on turbine tip clearance. In this paper, a turbine tip clearance control apparatus and a model of turbine tip clearance are proposed; an implicit active generalized predictive control （GPC）, with auto-regressive （AR） error modification and fuzzy adjustment on control horizon, is presented, as well as a quantitative analysis method of robust per- turbation radius of the system. The active clearance control （ACC） of aero-engine turbine tip clear- ance is evaluated in a lapse-rate take-off transient, along with the comparative and quantitative analysis of the stability and robustness of the active tip clearance control system. The results show that the resultant active tip clearance control system with the improved GPC has favorable steadystate and dynamic performance and benefits of increased efficiency, reduced specific fuel consump- tion, and additional service life.展开更多
Experiment and numerical simulation technique are used to investigate the tip leakage flow in an axial fan with tip clearance at the design condition. The flow field in the tip region of fan is measured using a PDA (P...Experiment and numerical simulation technique are used to investigate the tip leakage flow in an axial fan with tip clearance at the design condition. The flow field in the tip region of fan is measured using a PDA (Particle Dynamics Analysis) system. The flow is surveyed across the whole passage at fifteen axial locations (from the 100% axial chord in front of the leading edge to the 100% axial chord behind the trailing edge), mainly focusing on the outer 90% blade span. Both experiment measurement and numerical simulation indicates the leakage flow originated from the tip clearance along the chord rolls up into three dimensional spiral structure to form leakage flow vortex. The interaction of leakage flow and main flow will produce the low velocity zone, and block the flow. The leakage flow almost occupies the most part of flow passage behind the trailing edge.展开更多
Thin-walled tube numerical control （NC） bending is a tri-nonlinear physical process with multi-defect and multi-die constraints. The clearance on each contact interface is the major factor to indicate the contact co...Thin-walled tube numerical control （NC） bending is a tri-nonlinear physical process with multi-defect and multi-die constraints. The clearance on each contact interface is the major factor to indicate the contact conditions. A three-dimensional-finite element （3D-FE） model is established to consider the realistic dynamic boundary conditions of multiple dies under ABAQUS/Explicit platform. Combined with experiment, numerical study on bending behavior and bendability under different clearance between tube and various dies is conducted in terms of wrinkling, wall thinning and cross section deformation. The results show that （1）with smaller clearance of tube-wiper die and tube-mandrel, the wrinkling can be restrained while the wall thinning It and cross-section deformation Id increase; while excessive small clearance blocks tube materials to flow past tangent point and causes piles up, the onset of wrinkling enhances It and Id. （2）Both It and Id decrease with smaller clearance of tube-pressure die; the wrinkling possibility rises with larger clearance on this interface if the mandrel’s freedom along Y-axis is opened; smaller clearance of tube-bend die prevents wrinkling while increases It, and the clearance on this interface has little effect on Id. （3）A modified Yoshida buckling test （YBT） is used to address the wrinkling mechanisms under normal constraints in tube bending： the smaller clearance may restrain wrinkling efficiently; the smaller wall thickness, the less critical clearance needed; the critical clearance for tube bending 38 mm×1 mm×57 mm （tube outer diameter×wall thickness×centerline bending radius） equals about 20% of initial wall thickness.展开更多
Semi-floating ring bearing（SFRB） is developed to control the vibration of turbocharger rotor. The outer clearance of SFRB affects the magnitude and frequency of nonlinear whirl motion, which is significant for the d...Semi-floating ring bearing（SFRB） is developed to control the vibration of turbocharger rotor. The outer clearance of SFRB affects the magnitude and frequency of nonlinear whirl motion, which is significant for the design of turbocharger. In order to explore the effects of outer clearance, a transient finite element analysis program for rotor and oil film bearing is built and validated by a published experimental case. The nonlinear dynamic behaviors ofrotor-SFRB system are simulated. According to the simulation results, two representative subsynchronous oscillations excited by the two hearings respectively are discovered. As the outer clearance of SFRB increases from 24 ~tm to 60 pro, the low-frequency subsynchronous oscillation experiences three steps, including a strong start, a gradual recession and a combination with the other one. At the same time, the high-frequency subsynchronous oscillation starts to appear gradually, then strengthens, and finally combines. If gravity and unbalance are neglected, the combination will start starts from high rotor speed and extents to low rotor speed, just like a ＂zipper＂. It is found from the quantitative analysis that when the outer clearance increases, the vibration amplitude experiences large value firstly, then reduction, and suddenly increasing after combination. A useful design principle of SFRB outer clearance for minimum vibration amplitude is proposed： the outer clearance value should be chosen to keep the frequency of two subsynchronous oscillations clearly separated and their amplitudes close.展开更多
The inner and outer oil film dynamic characteristic coefficients of floating ring bearings（FRBs） change due to the manufacturing tolerance of the floating ring, journal and intermediate, which leads to high-speed tu...The inner and outer oil film dynamic characteristic coefficients of floating ring bearings（FRBs） change due to the manufacturing tolerance of the floating ring, journal and intermediate, which leads to high-speed turbocharger＇s vibration too large and even causes nonlinear vibration accident. However, the investigation of floating ring bearing manufacturing tolerance clearance on the rotordynamic characteristics is less at present. In order to study the influence law of inner and outer clearance on turbocharger vibration, the rotor dynamic motion equations of turbocharger supported in FRBs are derived by analyzing the size relations between floating ring, journal and intermediate for the inner and outer oil film clearances, the time transient response analysis for combination of FRBs clearance are developed. A realistic turbocharger is taken as a research object, the FE model of the turbocharger with FRBs is modeled. Under the conditions of four kinds of limit state bearing clearances for inner and outer oil film, the nonlinear transient analyses are performed based on the established FE dynamic models of the nonlinear rotor-FRBs system applied incentive combinations of gravity and unbalance force, respectively. From the waterfall, the simulation results show that the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different under the four kinds of bearing manufacturing tolerance limit clearances, and fractional frequency does not appear in the turbocharger and the amplitude is minimum under the ODMin/IDMax bearing manufacturing tolerance clearances. The turbocharger vibration is reduced by controlling the manufacturing tolerance clearance combinations of FRBs, which is helpful for the dynamic design and production-manufacturing of high-speed turbocharger.展开更多
Variable nozzle turbine （VNT） has become a popular variable geometry turbine （VGT） technology for the diesel engine application. Nozzle clearance, which can＇t be avoided on the hub and shroud side of the VNT turb...Variable nozzle turbine （VNT） has become a popular variable geometry turbine （VGT） technology for the diesel engine application. Nozzle clearance, which can＇t be avoided on the hub and shroud side of the VNT turbine due to the pivoting stators, can lead to turbine performance deterioration. However, its mechanism is still not clear. In this paper, numerical investigation, which is validated by experiment, is carried out to study the mechanism of the nozzle clearance＇s effect on the turbine performance. Firstly, performance of the mixed flow turbine with fixed nozzle clearances tested on flow bench. Performance of the tested turbine with the same nozzle clearance is numerically simulated. The numerical result agrees well with the test data, which proves correct of the numerical method. Then the turbine performance with different nozzle clearances is numerically analyzed. The research showed that with nozzle clearance, flow loss in the nozzle increases at first and it reaches the maximum value when the clearance ratio is 5%. Flow at the exit of the nozzle becomes less uniform with nozzle clearance. The negative incidence angle of the rotor also increases with nozzle clearance and leads to more incidence angle loss in the rotor. The low energy fluid formed in the nozzle due to the nozzle clearance migrates from hub to shroud side in the rotor, which is another main reason for the rotor＇s performance degradation. The present research exposed the mechanism of the dramatically decrease of the turbine performance with nozzle clearance： （a） The loss associated with the nozzle leakage increases with the nozzle clearance; （b） The flow loss grows up quickly in the rotor due to the incidence angle loss and migration of the low energy fluid from hub to shroud side.展开更多
BACKGROUND: Acute liver failure(ALF) is an acute severe deterioration of liver function with high mortality. Early and accurate prognostic assessment of patients with ALF is critically important. Although the model fo...BACKGROUND: Acute liver failure(ALF) is an acute severe deterioration of liver function with high mortality. Early and accurate prognostic assessment of patients with ALF is critically important. Although the model for end-stage liver disease(MELD) scores and King’s College Hospital(KCH) criteria are well-accepted as predictive tools, their accuracy is unsatisfactory.The indocyanine green(ICG) clearance test(ICGR15, ICG retention rate at the 15 minutes) is a sensitive indicator of liver function. In this study, we investigated the efficacy of the ICGR15 for the short-term prognosis in patients with ALF. We compared the predictive value of ICGR15 with the MELD scores and KCH criteria.METHODS: Sixty-nine patients who had been diagnosed with ALF were recruited retrospectively. ICGR15 had been performed by ICG pulse spectrophotometry and relevant clinical and laboratory indices were analyzed within 24 hours of diagnosis.In addition, the MELD scores and KCH criteria were calculated.RESULTS: The three-month mortality of all patients was 47.83%.Age, serum total bilirubin and creatinine concentrations,international normalized ratio for prothrombin time, ICGR15,MELD scores and KCH criteria differed significantly between surviving and deceased patients. A positive correlation was observed between ICGR15 and MELD scores(r=0.328, P=0.006).The ICGR15-MELD model, Logit(P)=0.096×ICGR15+0.174 ×MELD score–9.346, was constructed by logistic regression analysis. The area under the receiver operating characteristic curve was 0.855. When set the cut-off point to-0.4684, the sensitivity was 87.90% and specificity, 72.20%. The area under the receiver operating characteristic curve of the ICGR15-MELD model(0.855) was significantly higher than that of the ICGR15(0.793), MELD scores(0.776) and KCH criteria(0.659).Based on this cut-off value, the patients were divided into two groups. The mortality was 74.36% in the first group(ICGR15-MELD≥-0.4686) and 13.33% in the second group(ICGR15-MELD<-0.4686), with a significant difference between the two groups(χ2=25.307, P=0.000).CONCLUSION: The ICGR15-MELD model is superior to the ICGR15, MELD scores, and KCH criteria in predicting the shortterm prognosis of patients with ALF.展开更多
The tip leakage flow between a blade and a casing wall has a strong impact on compressor pressure rise capability, efficiency, and stability. Consequently, there is a strong motivation to look for means to minimize it...The tip leakage flow between a blade and a casing wall has a strong impact on compressor pressure rise capability, efficiency, and stability. Consequently, there is a strong motivation to look for means to minimize its impact on performance. This paper presents the potential of passive tip leakage flow control to increase the aerodynamic performance of highly loaded compressor blades. Experimental investigations on a linear compressor cascade equipped with blade winglets mounted to the blade tips have been carried out. Results for a variation of the tip clearance and the winglet geometry are presented. Current results indicate that the use of proper tip winglets in a compressor cascade can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction-side winglets are aerodynamically superior to the pressure-side or combined winglets. The suction-side winglets are capable of reducing the exit total pressure loss associated with the tip leakage flow and the passage secondary flow to a significant degree.展开更多
基金supported by the National Natural Science Foundation of China,No.81971031(to ZL)the National Key Research and Development Program of China,No.2022YFE0210100(to JFC)+7 种基金the National Natural Science Foundation of China(Original Exploration Project),No.82151308(to JFC)the National Natural Science Foundation of China(Research Fund for International Senior Scientists),No.82150710558(to JFC)Science&Technology Initiative STI2030-Major Projects,No.2021ZD0203400(to JFC)Key Research and Development Program of Zhejiang Province,No.2023C03079(to JFC)Scientific Research Starting Foundation of Oujiang Laboratory(Zhejiang Laboratory for Regenerative Medicine,Vision and Brain Health),No.OJQDSP2022007(to JFC)Project of State Key Laboratory of Ophthalmology,Optometry and Visual Science,Wenzhou Medical University,No.J01-20190101(to JFC)Scientific Research Starting Foundation of Wenzhou Medical University,No.QTJ12003(to JFC)Department of Science and Technology of Zhejiang Province,No.2023ZY1011(to JFC)。
文摘The excessive buildup of neurotoxicα-synuclein plays a pivotal role in the pathogenesis of Parkinson's disease,highlighting the urgent need for innovative therapeutic strategies to promoteα-synuclein clearance,particularly given the current lack of disease-modifying treatments.The glymphatic system,a recently identified perivascular fluid transport network,is crucial for clearing neurotoxic proteins.This review aims to synthesize current knowledge on the role of the glymphatic system inα-synuclein clearance and its implications for the pathology of Parkinson's disease while emphasizing potential therapeutic strategies and areas for future research.The review begins with an overview of the glymphatic system and details its anatomical structure and physiological functions that facilitate cerebrospinal fluid circulation and waste clearance.It summarizes emerging evidence from neuroimaging and experimental studies that highlight the close correlation between the glymphatic system and clinical symptom severity in patients with Parkinson's disease,as well as the effect of glymphatic dysfunction onα-synuclein accumulation in Parkinson's disease models.Subsequently,the review summarizes the mechanisms of glymphatic system impairment in Parkinson's disease,including sleep disturbances,aquaporin-4 impairment,and mitochondrial dysfunction,all of which diminish glymphatic system efficiency.This creates a vicious cycle that exacerbatesα-synuclein accumulation and worsens Parkinson's disease.The therapeutic perspectives section outlines strategies for enhancing glymphatic activity,such as improving sleep quality and pharmacologically targeting aquaporin-4 or its subcellular localization.Promising interventions include deep brain stimulation,melatonin supplementation,γ-aminobutyric acid modulation,and non-invasive methods(such as exercise and bright-light therapy),multisensoryγstimulation,and ultrasound therapy.Moreover,identifying neuroimaging biomarkers to assess glymphatic flow as an indicator ofα-synuclein burden could refine Parkinson's disease diagnosis and track disease progression.In conclusion,the review highlights the critical role of the glymphatic system inα-synuclein clearance and its potential as a therapeutic target in Parkinson's disease.It advocates for further research to elucidate the specific mechanisms by which the glymphatic system clears misfoldedα-synuclein and the development of imaging biomarkers to monitor glymphatic activity in patients with Parkinson's disease.Findings from this review suggest that enhancing glymphatic clearance is a promising strategy for reducingα-synuclein deposits and mitigating the progression of Parkinson's disease.
基金National Natural Science Foundation of China (10377011)
文摘This article describes the effects of some factors on the tip clearance flow in axial linear turbine cascades. The measurements of the total pressure loss coefficient are made at the cascade outlets by using a five-hole probe at exit Mach numbers of 0.10, 0.14 and 0.19. At each exit Mach number, experiments are performed at the tip clearance heights of 1.0%, 1.5%, 2.0%, 2.5% and 3.0% of the blade height. The effects of the non-uniform tip clearance height of each blade in the pitchwise direction are also studied. The results show that at a given tip clearance height, generally, total pressure loss rises with exit Mach numbers proportionally. At a fixed exit Mach number, the total pressure loss augments nearly proportionally as the tip clearance height increases. The increased tip clearance heights in the tip regions of two adjacent blades are to be blame for the larger clearance loss of the center blade. Compared to the effects of the tip clearance height, the effects of the exit Mach number and the pitchwise variation of the tip clearance height on the cascade total pressure loss are so less significant to be omitted.
基金financially supported by the Science and Technology Innovation Program of Hunan Province,No.2022RC1220(to WP)China Postdoctoral Science Foundation,No.2022M711733(to ZZ)+2 种基金the National Natural Science Foundation of China,No.82160920(to ZZ)Hebei Postdoctoral Scientific Research Project,No.B2022003040(to ZZ)Hunan Flagship Department of Integrated Traditional Chinese and Western Medicine(to WP)。
文摘Alzheimer's disease,the primary cause of dementia,is characterized by neuropathologies,such as amyloid plaques,synaptic and neuronal degeneration,and neurofibrillary tangles.Although amyloid plaques are the primary characteristic of Alzheimer's disease in the central nervous system and peripheral organs,targeting amyloid-beta clearance in the central nervous system has shown limited clinical efficacy in Alzheimer's disease treatment.Metabolic abnormalities are commonly observed in patients with Alzheimer's disease.The liver is the primary peripheral organ involved in amyloid-beta metabolism,playing a crucial role in the pathophysiology of Alzheimer's disease.Notably,impaired cholesterol metabolism in the liver may exacerbate the development of Alzheimer's disease.In this review,we explore the underlying causes of Alzheimer's disease and elucidate the role of the liver in amyloid-beta clearance and cholesterol metabolism.Furthermore,we propose that restoring normal cholesterol metabolism in the liver could represent a promising therapeutic strategy for addressing Alzheimer's disease.
文摘Metamorphic mechanism has the advantages of variable topology and variable degrees of freedom, which can realize the requirements of multi-conditions and multi-tasks, and has a good application prospect. The configuration transformation is prominent feature of the metamorphic mechanism. The number of constraints or properties of the kinematic pairs provided by the metamorphic kinematic pairs will change under certain conditions, its dynamic performance is much more complex than that of traditional kinematic pairs with immutable constraints. However, the clearance model about traditional kinematic pairs with immutable constraints established by long-term research is difficult to be directly applied to the metachromatic kinematic pairs. Referring to the experience of the traditional kinematic pairs with immutable constraints, the continuous contact model of Metamorphic Groove pin pair with clearance is established. According to the traditional continuous contact model of the kinematic pairs with immutable constraints, the forces between the elements of kinematic pair of the mechanism with clearance and the ideal mechanism without clearance are regarded as the same, and the inertia force and inertia moment of the components are also calculated according to the acceleration of the ideal mechanism. The clearance is regarded as a massless virtual bar with length r. For the rotating pair part, the massless virtual bar length r is the difference between the radius of the shaft and the hole, and for the sliding pair part, the massless virtual bar length r is half of the difference between the height of the slider and the guide groove. According to the new mechanism without gap after adding the imaginary bar, kinetic energy and potential energy of the system are calculated for the two configurations of mechanism with metamorphic Groove pin pair with clearance. The kinetic energy and potential energy of the system are calculated according to the new mechanism without clearance after adding the massless virtual bar. The kinetic energy, potential energy and generalized force are substituted into the Lagrangian equation to obtain the motion equation of the metamorphic mechanism, which lays the foundation for the dynamic performance study of the mechanism with metamorphic groove pin pair with clearance.
基金the National Natural Science Foundation of China(Nos.T2322004 and 22078066)。
文摘Currently,it is still a challenge to develop an organic photosensitizer(PS)with outstanding near-infrared absorption,low O2dependence,precise tumor targeting and rapid clearance through the kidney to improve the overall outcome of phototherapy.In this study,we have designed an organic PS(Nc PB)with an excellent near-infrared light absorption through a refined molecular strategy.Meanwhile,Nc PB was assembled into nanoparticles with different sizes(Nano Nc PB-1 and Nano Nc PB-0)by a supramolecular modulation strategy.As the results,the nanoparticle with an ultra-small size(Nano Nc PB-1)generated a large number of superoxide anion(O_(2)^(·-))in a low-O_(2)-dependent manner and release plenty of heat.Furthermore,the results of in vivo experiments demonstrated that Nano Nc PB-1 actively accumulated in tumor tissues and showed a 92%tumor inhibition after photodynamic and photothermal combination therapy.More importantly,Nano Nc PB-1 could be rapidly cleared from the body of mice via the renal pathway,which alleviates potential side effects of prolonged retention of PS in the circulation.
基金Supported by National Natural Science Foundation of China(Grant Nos.51635002(Key Program),51605011,51275015)
文摘Joint clearances in antenna pointing mechanisms lead to uncertainty in function deviation. Current studies mainly focus on radial clearance of revolute joints, while axial clearance has rarely been taken into consideration. In fact, own?ing to errors from machining and assembly, thermal deformation and so forth, practically, axial clearance is inevitable in the joint. In this study, an error equivalent model(EEM) of revolute joints is proposed with considering both radial and axial clearances. Compared to the planar model of revolute joints only considering radial clearance, the journal motion inside the bearing is more abundant and matches the reality better in the EEM. The model is also extended for analyzing the error distribution of a spatial dual?axis("X–Y" type) antenna pointing mechanism of Spot?beam antennas which especially demand a high pointing accuracy. Three case studies are performed which illustrates the internal relation between radial clearance and axial clearance. It is found that when the axial clearance is big enough, the physical journal can freely realize both translational motion and rotational motion. While if the axial clearance is limited, the motion of the physical journal will be restricted. Analysis results indicate that the consideration of both radial and axial clearances in the revolute joint describes the journal motion inside the bearing more precise. To further validate the proposed model, a model of the EEM is designed and fabricated. Some suggestions on the design of revolute joints are also provided.
文摘Combining practical engineering projects, this article analyzes the design strategies for the reconstruction and expansion of insufficient clearance sections in highway interchanges. This includes an overview of the project, a comparison of design options for insufficient clearance in interchanges, and the main design strategies for reconstruction and expansion. It is hoped that this analysis can provide a reference for the design of such road reconstruction and expansion projects.
基金Supported by the Tianjin Health Research Project(Key Project),No.TJWJ2024ZD004Tianjin Key Medical Discipline(Specialty)Construction Project,No.TJYXZDXK-034A.
文摘BACKGROUND Chronic hepatitis B(CHB)patients rarely achieve functional cure with initial pegylated interferon alpha-2b(Peg-IFNα-2b)therapy.Validated tools to guide retreatment candidates are lacking.We hypothesized that clinical indicators predict hepatitis B surface antigen(HBsAg)clearance during retreatment.AIM To develop a prediction model for HBsAg clearance in Peg-IFNα-2b retreatment.METHODS In this retrospective cohort study,we enrolled 135 CHB/compensated cirrhosis patients receiving Peg-IFNα-2b retreatment after initial non-clearance at Tianjin University Central Hospital(2017-2025).Predictors were identified through univariate Cox,least absolute shrinkage and selection operator,and multivariate Cox regression.Model performance was assessed via receiver operating characteristic analysis and Harrell’s C-index,with risk stratification by X-tile optimization.RESULTS HBsAg clearance rate was 20.74%(28/135).Independent predictors included:Combination nucleos(t)ide analogue(NA)therapy during initial treatment[hazard ratio(HR)=0.276,95%confidence interval(CI):0.092-0.833],baseline HBsAg at retreatment(HR=0.571,95%CI:0.410-0.795),HBsAg decline after initial treatment(HR=2.050,95%CI:1.108-3.793),and treatment interval(HR=1.013/week,95%CI:1.008-1.018).The retreatment HBsAg clearance prediction score(RHCP-S)demonstrated area under the curve of 0.920(95%CI:0.863-0.946),sensitivity of 92.3%,specificity of 79.3%.Clearance rates differed significantly:RHCP-S challenge group(≤74 points):3.45%,RHCP-S probable group(74-110 points):29.63%,RHCP-S dominant group(≥110 points):80.95%(P<0.001).CONCLUSION The overall HBsAg clearance rate with Peg-IFNα-2b retreatment was 20.74%(28/135).The RHCP-S model identifies optimal retreatment candidates(≥110 points)with 80.95%clearance probability,associated with the absence of combination NA therapy during initial treatment,greater initial HBsAg decline,longer intervals,and lower retreatment HBsAg.
基金Supported by National Key R&D Program of China(Grant No.2021YFC0122700).
文摘Mechanical vibration sputum clearance is commonly used for airway clearance.However,existing handheld vibration-assisted expectorators confront several challenges including operator’s hand fatigue and a high risk of cross-infection between medical staff and patients.To address these issues,this study presents a novel design for an intelligent percussion-based sputum clearance robot.The robot is designed to assist medical staff in providing percussion-based sputum clearance nursing for patients.Initially,the structure of the robot is designed based on the environmental conditions in the intensive care unit(ICU).To mitigate the impact of the vibrations generated by the vibration percussion head on the robotic arm operation,a fixture equipped with a vibration damper is designed to ensure that the robot’s standard functionality remains unaffected.Furthermore,a human back detection(HBD)framework constructed from multi-subtask modules is proposed to address the shortcomings of existing robotic systems in terms of human perception capabilities.These modules are designed to accurately identify and map the anatomical features of the human back.This effectively improves the capability of the robot to interact with the human body.Based on this framework,the robotic arm is controlled precisely to emulate the percussion strategies employed by physicians.Finally,extensive experiments are conducted in a real-world setting with multiple participants.The results indicate that the robot could provide percussion-based sputum clearance nursing that is practically equivalent to the operations by medical staff.
基金supported by the Key Program of National Natural Science Foundation of China(No.92160203)National Natural Science Foundation of China(No.92360306).
文摘The existence of the aeroengine casing,limited monitoring points,and multi-fault characteristics make obtaining the rotor’s vibration transmission characteristics challenging,resulting in difficulties accurately identifying the rotor unbalance.This paper utilizes a high-frequency composite sensor to monitor the engine’s blade tip clearance(BTC)and extracts unbalanced information from BTC signals for rotor dynamic balancing,while avoiding the need for the once per revolution(OPR)sensor.First,the vibration characteristics of the rotor-blade system under multi-fault conditions are investigated.Then,based on BTC measurement,a none OPR method and an unbalance identification method are proposed,in which the radial vibration of the blade tip in the BTC signals at different speeds is extracted and operated in the time domain to obtain the rotor unbalanced vibration,the signal is reconstructed,and cross-correlation analysis is used to accurately identify the magnitude and phase of the unbalanced signal.Finally,a rotor test bench is utilized for experimental verification.The results reveal that the dynamic balancing method based on the BTC signal can more precisely identify the rotor unbalance than the traditional rotor dynamic balancing method.The application of this technique will effectively improve engine health management and fault prediction.
基金supported by National Natural Science Foundation of China(Grant No.92266201).
文摘As the performance of the box-type multiple launch rocket system(BMLRS)improves,its mechanical structures,particularly the plane clearance design between the slider on the rocket and the guide inside the launch canister,have grown increasingly complex.However,deficiencies still exist in the current launch modeling theory for BMLRS.In this study,a multi-rigid-flexible-body launch dynamics model coupling the launch platform and rocket was established using the multibody system transfer matrix method and the Newton-Euler formulation.Furthermore,considering the bending of the launch canister,a detection algorithm for slider-guide plane clearance contact was proposed.To quantify the contact force and friction effect between the slider and guide,the contact force model and modified Coulomb model were introduced.Both the modal and launch tests were conducted.Additionally,the modal convergence was verified.By comparing the modal experiments and simulation results,the maximum relative error of the eigenfrequency is 3.29%.thereby verifying the accuracy of the developed BMLRS dynamics model.Furthermore,the launch test validated the proposed plane clearance contact model.Moreover,the study investigated the influence of various model parameters on the dynamic characteristics of BMLRS,including launch canister bending stiffness,slider and guide material,slider-guide clearance,slider length and layout.This analysis of influencing factors provides a foundation for future optimization in BMLRS design.
文摘Lateral clearance on the inside of horizontal curves is required by all geometric design guidelines in order to provide at least stopping sight distance. There already exist graphical models, analytical models, and design charts for determining minimum clearance offsets to meet the requirement. Some of these models determine the offsets based on constant design sight distance values on the assumption that drivers negotiate horizontal curves at constant speed. Therefore, those models are suitable for sites where there is no difference in speeds between tangent and curved sections. Past studies have reported that there are sites where drivers decelerate on entering horizontal curves and accelerate on departing from the curves. At those sites stopping sight distance for a given driver varies with driver location due to variable speed. This paper presents an analytical model and a chart for determining minimum offsets needed to provide desired sight distances at horizontal curves with variable operating speeds. At those sites the offsets yield roadside clearance boundaries that have transition arcs with performances that are similar to those of elliptical arcs. Therefore, practitioners may choose to use elliptical equations or equations and the chart developed herein. Results of this study will be of value to practitioners in the area of roadside design.
文摘Active control of turbine blade tip clearance continues to be a concern in design and control of gas turbines. Ever increasing demands for improved efficiency and higher operating temperatures require more stringent tolerances on turbine tip clearance. In this paper, a turbine tip clearance control apparatus and a model of turbine tip clearance are proposed; an implicit active generalized predictive control （GPC）, with auto-regressive （AR） error modification and fuzzy adjustment on control horizon, is presented, as well as a quantitative analysis method of robust per- turbation radius of the system. The active clearance control （ACC） of aero-engine turbine tip clear- ance is evaluated in a lapse-rate take-off transient, along with the comparative and quantitative analysis of the stability and robustness of the active tip clearance control system. The results show that the resultant active tip clearance control system with the improved GPC has favorable steadystate and dynamic performance and benefits of increased efficiency, reduced specific fuel consump- tion, and additional service life.
文摘Experiment and numerical simulation technique are used to investigate the tip leakage flow in an axial fan with tip clearance at the design condition. The flow field in the tip region of fan is measured using a PDA (Particle Dynamics Analysis) system. The flow is surveyed across the whole passage at fifteen axial locations (from the 100% axial chord in front of the leading edge to the 100% axial chord behind the trailing edge), mainly focusing on the outer 90% blade span. Both experiment measurement and numerical simulation indicates the leakage flow originated from the tip clearance along the chord rolls up into three dimensional spiral structure to form leakage flow vortex. The interaction of leakage flow and main flow will produce the low velocity zone, and block the flow. The leakage flow almost occupies the most part of flow passage behind the trailing edge.
基金National Natural Science Foundation of China (59975076, 50905144)State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology (09-10)+1 种基金NPU Foundation for Fundamental Research (JC201028)Fund of the State Key Laboratory of Solidification Process-ing in NWPU
文摘Thin-walled tube numerical control （NC） bending is a tri-nonlinear physical process with multi-defect and multi-die constraints. The clearance on each contact interface is the major factor to indicate the contact conditions. A three-dimensional-finite element （3D-FE） model is established to consider the realistic dynamic boundary conditions of multiple dies under ABAQUS/Explicit platform. Combined with experiment, numerical study on bending behavior and bendability under different clearance between tube and various dies is conducted in terms of wrinkling, wall thinning and cross section deformation. The results show that （1）with smaller clearance of tube-wiper die and tube-mandrel, the wrinkling can be restrained while the wall thinning It and cross-section deformation Id increase; while excessive small clearance blocks tube materials to flow past tangent point and causes piles up, the onset of wrinkling enhances It and Id. （2）Both It and Id decrease with smaller clearance of tube-pressure die; the wrinkling possibility rises with larger clearance on this interface if the mandrel’s freedom along Y-axis is opened; smaller clearance of tube-bend die prevents wrinkling while increases It, and the clearance on this interface has little effect on Id. （3）A modified Yoshida buckling test （YBT） is used to address the wrinkling mechanisms under normal constraints in tube bending： the smaller clearance may restrain wrinkling efficiently; the smaller wall thickness, the less critical clearance needed; the critical clearance for tube bending 38 mm×1 mm×57 mm （tube outer diameter×wall thickness×centerline bending radius） equals about 20% of initial wall thickness.
基金Supported by National Natural Science Foundation of China(Grant No51506108)
文摘Semi-floating ring bearing（SFRB） is developed to control the vibration of turbocharger rotor. The outer clearance of SFRB affects the magnitude and frequency of nonlinear whirl motion, which is significant for the design of turbocharger. In order to explore the effects of outer clearance, a transient finite element analysis program for rotor and oil film bearing is built and validated by a published experimental case. The nonlinear dynamic behaviors ofrotor-SFRB system are simulated. According to the simulation results, two representative subsynchronous oscillations excited by the two hearings respectively are discovered. As the outer clearance of SFRB increases from 24 ~tm to 60 pro, the low-frequency subsynchronous oscillation experiences three steps, including a strong start, a gradual recession and a combination with the other one. At the same time, the high-frequency subsynchronous oscillation starts to appear gradually, then strengthens, and finally combines. If gravity and unbalance are neglected, the combination will start starts from high rotor speed and extents to low rotor speed, just like a ＂zipper＂. It is found from the quantitative analysis that when the outer clearance increases, the vibration amplitude experiences large value firstly, then reduction, and suddenly increasing after combination. A useful design principle of SFRB outer clearance for minimum vibration amplitude is proposed： the outer clearance value should be chosen to keep the frequency of two subsynchronous oscillations clearly separated and their amplitudes close.
基金Supported by National Natural Science Foundation of China(Grant Nos.51205121,51375162)Scientific Research Foundation of Hunan Provincial Education Department of China(Grant No.13A023)Postgraduate Innovation Foundation of Hunan University of Science and Technology,China(Grant No.S140020)
文摘The inner and outer oil film dynamic characteristic coefficients of floating ring bearings（FRBs） change due to the manufacturing tolerance of the floating ring, journal and intermediate, which leads to high-speed turbocharger＇s vibration too large and even causes nonlinear vibration accident. However, the investigation of floating ring bearing manufacturing tolerance clearance on the rotordynamic characteristics is less at present. In order to study the influence law of inner and outer clearance on turbocharger vibration, the rotor dynamic motion equations of turbocharger supported in FRBs are derived by analyzing the size relations between floating ring, journal and intermediate for the inner and outer oil film clearances, the time transient response analysis for combination of FRBs clearance are developed. A realistic turbocharger is taken as a research object, the FE model of the turbocharger with FRBs is modeled. Under the conditions of four kinds of limit state bearing clearances for inner and outer oil film, the nonlinear transient analyses are performed based on the established FE dynamic models of the nonlinear rotor-FRBs system applied incentive combinations of gravity and unbalance force, respectively. From the waterfall, the simulation results show that the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different under the four kinds of bearing manufacturing tolerance limit clearances, and fractional frequency does not appear in the turbocharger and the amplitude is minimum under the ODMin/IDMax bearing manufacturing tolerance clearances. The turbocharger vibration is reduced by controlling the manufacturing tolerance clearance combinations of FRBs, which is helpful for the dynamic design and production-manufacturing of high-speed turbocharger.
基金supported by Advanced Boost System Development for Diesel HCCI Application of DOE(Grant No. DE-FC26-07-NT43280)
文摘Variable nozzle turbine （VNT） has become a popular variable geometry turbine （VGT） technology for the diesel engine application. Nozzle clearance, which can＇t be avoided on the hub and shroud side of the VNT turbine due to the pivoting stators, can lead to turbine performance deterioration. However, its mechanism is still not clear. In this paper, numerical investigation, which is validated by experiment, is carried out to study the mechanism of the nozzle clearance＇s effect on the turbine performance. Firstly, performance of the mixed flow turbine with fixed nozzle clearances tested on flow bench. Performance of the tested turbine with the same nozzle clearance is numerically simulated. The numerical result agrees well with the test data, which proves correct of the numerical method. Then the turbine performance with different nozzle clearances is numerically analyzed. The research showed that with nozzle clearance, flow loss in the nozzle increases at first and it reaches the maximum value when the clearance ratio is 5%. Flow at the exit of the nozzle becomes less uniform with nozzle clearance. The negative incidence angle of the rotor also increases with nozzle clearance and leads to more incidence angle loss in the rotor. The low energy fluid formed in the nozzle due to the nozzle clearance migrates from hub to shroud side in the rotor, which is another main reason for the rotor＇s performance degradation. The present research exposed the mechanism of the dramatically decrease of the turbine performance with nozzle clearance： （a） The loss associated with the nozzle leakage increases with the nozzle clearance; （b） The flow loss grows up quickly in the rotor due to the incidence angle loss and migration of the low energy fluid from hub to shroud side.
基金supported by a grant from the Foundation of the Ministry of Health,China(2008ZX1005)
文摘BACKGROUND: Acute liver failure(ALF) is an acute severe deterioration of liver function with high mortality. Early and accurate prognostic assessment of patients with ALF is critically important. Although the model for end-stage liver disease(MELD) scores and King’s College Hospital(KCH) criteria are well-accepted as predictive tools, their accuracy is unsatisfactory.The indocyanine green(ICG) clearance test(ICGR15, ICG retention rate at the 15 minutes) is a sensitive indicator of liver function. In this study, we investigated the efficacy of the ICGR15 for the short-term prognosis in patients with ALF. We compared the predictive value of ICGR15 with the MELD scores and KCH criteria.METHODS: Sixty-nine patients who had been diagnosed with ALF were recruited retrospectively. ICGR15 had been performed by ICG pulse spectrophotometry and relevant clinical and laboratory indices were analyzed within 24 hours of diagnosis.In addition, the MELD scores and KCH criteria were calculated.RESULTS: The three-month mortality of all patients was 47.83%.Age, serum total bilirubin and creatinine concentrations,international normalized ratio for prothrombin time, ICGR15,MELD scores and KCH criteria differed significantly between surviving and deceased patients. A positive correlation was observed between ICGR15 and MELD scores(r=0.328, P=0.006).The ICGR15-MELD model, Logit(P)=0.096×ICGR15+0.174 ×MELD score–9.346, was constructed by logistic regression analysis. The area under the receiver operating characteristic curve was 0.855. When set the cut-off point to-0.4684, the sensitivity was 87.90% and specificity, 72.20%. The area under the receiver operating characteristic curve of the ICGR15-MELD model(0.855) was significantly higher than that of the ICGR15(0.793), MELD scores(0.776) and KCH criteria(0.659).Based on this cut-off value, the patients were divided into two groups. The mortality was 74.36% in the first group(ICGR15-MELD≥-0.4686) and 13.33% in the second group(ICGR15-MELD<-0.4686), with a significant difference between the two groups(χ2=25.307, P=0.000).CONCLUSION: The ICGR15-MELD model is superior to the ICGR15, MELD scores, and KCH criteria in predicting the shortterm prognosis of patients with ALF.
基金the National Natural Science Foundation of China(Grant No.:51076018)the Fundamental Research Funds for the Central UniversitiesSpecialized Research Fund for the Doctoral Program of Higher Education
文摘The tip leakage flow between a blade and a casing wall has a strong impact on compressor pressure rise capability, efficiency, and stability. Consequently, there is a strong motivation to look for means to minimize its impact on performance. This paper presents the potential of passive tip leakage flow control to increase the aerodynamic performance of highly loaded compressor blades. Experimental investigations on a linear compressor cascade equipped with blade winglets mounted to the blade tips have been carried out. Results for a variation of the tip clearance and the winglet geometry are presented. Current results indicate that the use of proper tip winglets in a compressor cascade can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction-side winglets are aerodynamically superior to the pressure-side or combined winglets. The suction-side winglets are capable of reducing the exit total pressure loss associated with the tip leakage flow and the passage secondary flow to a significant degree.
