检索结果-南通市图书馆

Weakening of the anisotropy of surface roughness in ultra-precision turning of single-crystal silicon

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2015年第4期28卷 1273-1280页

作者： Wang Minghai Wang ben Zheng Yaohui Key Laboratory of Fundamental Science for National Defense of Aeronautical Digital Manufacturing Process Shenyang Aerospace University School of Mechanical Engineering & Automation Beijing University of Aeronautics & Astronautics

Ultra-precision machining causes materials to undergo a greatly strained deformation process in a short period of *** effect of shear strain rates on machining quality, in particular on surface anisotropy, is a topic deserving of research that has thus far been *** study analyzes the impact of the strain rate during the ultra-precision turning of single-crystal silicon on the anisotropy of surface *** on the establishment of cutting models considering the tool rake angle and the edge radius, this is the first research that takes into account the strain rate dislocation emission criteria in studying the effects of the edge radius, the cutting speed, and the cutting thickness on the plastic deformation of single-crystal *** results of this study show that the uses of a smaller edge radius, faster cutting speeds, and a reduced cutting thickness can result in optimally uniform surface roughness, while the use of a very sharp cutting tool is essential when operating with smaller cutting thicknesses.A further finding is that insufficient plastic deformation is the major cause of increased surface roughness in the ultra-precision turning of brittle *** this basis, we propose that the capacity of single-crystal silicon to emit dislocations be improved as much as possible before brittle fracture occurs, thereby promoting plastic deformation and minimizing the anisotropy of surface roughness in the machined workpiece.

关键词： Anisotropy of surface roughness Cutting speed Edge radius Single-crystal silicon Strain rate Ultra-precision turning Weakening

Particulate matter(PM(2.5)) exposure season-dependently induces neuronal apoptosis and synaptic injuries

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2017年第4期29卷 336-345页

作者： Minjun Chen ben Li Nan Sang College of Environment and Resource Research Center of Environment and HealthShanxi University

Epidemiological studies have shown that particulate matter 2.5（PM（2.5）） not only increases the incidence of cardiopulmonary illnesses but also relates to the development of neurodegenerative diseases. Considering that PM（2.5）is highly heterogeneous with regional disparity and seasonal variation, we investigated whether PM（2.5）exposure induced neuronal apoptosis and synaptic injuries in a season-dependent manner. The results indicated that PM（2.5）altered the expression of apoptosis-related proteins（mainly bax and bcl-2）, activated caspase-3 and caused neuronal apoptosis. Additionally, PM（2.5）decreased the levels of synaptic structural protein postsynaptic density（PSD-95） and synaptic functional protein N-methyl-D-aspartate（NMDA） receptor subunit（NR2B） expression. These effects occurred in a season-dependent manner, and PM（2.5）collected from the winter showed the strongest changes. Furthermore, the effect was coupled with the inhibition of phosphorylated extracellular signal-regulated kinase 1/2（p-ERK1/2） and phosphorylated c AMP-response element binding protein（p-CREB）. Based on the findings, we analyzed the correlations between the chemical composition of PM（2.5）samples and the biological effects, and confirmed that winter PM（2.5）played a major role in causing neuronal apoptosis and synaptic injuries among different season samples.

关键词： Particulate matter(PM(2.5)) Season-dependent effect Neuronal apoptosis Synaptic injury

Automatic Fall Detection Using Membership Based Histogram Descriptors

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2017年第2期32卷 356-367页

作者： Mohamed Maher ben Ismail Ouiem Bchir College of Computer and Information Sciences King Saud University Riyadh 11495 KSA

t We propose a framework for automatic fall detection based on video visual feature extraction. The proposed approach relies on a membership histogram descriptor that encodes the visual properties of the video frames. This descriptor is obtained by mapping the original low-level visual features to a more discriminative descriptor using possibilistic memberships. This mapping can be summarized in two main phases. The first one consists in categorizing the low-level visual features of the video frames arid generating homogeneous clusters in an unsupervised way. The second phase uses the obtained membership degrees generated by the clustering process to compute the membership based histogram descriptor （MHD）. For the testing stage, the proposed fall detection approach categorizes unlabeled videos as ＂Fall＂ or ＂Non-Fall＂ scene using a possibilistic K-nearest neighbors classifier. The proposed approach is assessed using standard videos dataset that simulates patient fall. Also, we compare its performance with that of state-of-the-art fall detection techniques.

关键词： fall detection possibilistic approach feature extraction clustering

MONOTONE APPROXIMATION TO A SYSTEM WITHOUT MONOTONE NONLINEARITY

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2000年第2期18卷 207-224页

作者： Yuan-ming Wang ben-yu Guo Department of Mathematics East China Normal UniversityShanghai 200062China School of Mathematical Sciences Shanghai Normal UniversityShanghai 200234China

Presents information on a study which proposed a monotone approximation for a system without monotone nonlinearity. Concept of ordered pair of supersolution and subsolution for the resulting problem; Numerical results.

关键词： monotone approximation systems without monotone nonlinearity

Laparoscopic dissection of the hepatic node:The trans lesser omentum approach

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastrointestinal Oncology 2020年第1期12卷 77-82页

作者： Offir ben-Ishay Department of General Surgery Rambam Health Care Campus

BACKGROUND Diagnosis of lympho-proliferative diseases is sometimes *** lymph node biopsy is the standard of *** percent of the patients will present with abdominal or retroperitoneal lymphadenopathy *** in endoscopic techniques allow for access to fine needle biopsy in complicated areas,but this often does not meet the standard guidelines for *** To investigate the results of laparoscopic excisional biopsy of the hepatic node(LEBHN)through a trans lesser omentum *** Data of all patients undergoing LEBHN were collected retrospectively from patients’electronic charts over a period of 1 *** collected included age,gender,suspected disease,number of previous biopsies and biopsy method,surgical approach,intraoperative complications,operative time,post-operative complications,mortality,and final *** Six patients were operated in this technique during the time frame of the study,66.6%(n=4)were females,and median age was 55 years(range:25-72 years).We present no conversions from laparoscopy to laparotomy,and mean operating time was 51.2 *** length of hospital stay was 1 d,and morbidity and mortality were *** importantly,this technique offered definite diagnosis and appropriate treatment in all *** diagnosis included two patients with lymphoma(Hodgkin and Follicular),two patients with sarcoidosis,and two patients with reactive lymph nodes with no evidence of *** In conclusion,this technique seems to be feasible and safe and may offer a simple approach for a definite diagnosis for what seems to be a complicated anatomical area.

关键词： Lymph node Diagnosis Lymphoma Laparoscopy Biopsy Retroperitoneum

A review of the current state of biofuels production from lignocellulosic biomass using thermochemical conversion routes

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2019年第7期27卷 1523-1535页

作者： Paola Ibarra-Gonzalez ben-Guang Rong Department of Chemical Engineering Biotechnology and Environmental Technology University of Southern Denmark

The rapid increase in energy demand,the extensive use of fossil fuels and the urgent need to reduce the carbon dioxide emissions have raised concerns in the transportation *** renewable and sustainable sources have become the ultimate solution to overcome the expected depletion of fossil *** conversion of lignocellulosic biomass to liquid(BtL)transportation fuels seems to be a promising path and presents advantages over first generation biofuels and fossil ***,development of BtL systems is critical to increase the potential of this resource in a sustainable and economic *** of lignocellulosic BtL transportation fuels,such as,gasoline,diesel and jet fuel can be accomplished through various thermochemical processes and processing *** major steps for the production of BtL fuels involve feedstock selection,physical pretreatment,production of bio-oil,upgrading of bio-oil to transportation fuels and recovery of value-added *** present work is aiming to give a comprehensive review of the current process technologies following these major steps and the current scenarios of biomass to liquid facilities for the production of biofuels.

关键词： Biofuels Lignocellulosic biomass Process route Thermochemical conversion Upgrading Separation

Numerical study on shock-accelerated heavy gas cylinderswith diffusive interfaces

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2019年第4期35卷 750-762页

作者： Dongdong Li ben Guan Ge Wang College of Aerospace and Civil Engineering Harbin Engineering University Harbin 150001 China

Interactions of shock wave and heavy gas cylinders with different diffusive interfaces are numerically investigated. Comparisons among these interfaces are made in terms of cylinder morphology, wave system evolution, fluids mixing, and circulation generation. Navier-Stokes equations are solved in the present work to simulate the complex multi-fluid flow. The fifth-order weighted essentially non-oscillatory scheme is used to compute the numerical flux. The influence of interface diffusion is revealed by the numerical results. The cylinders with similar geometric scale but different diffusion interface have great similarities in the hydrodynamic characteristics, including the interface morphology, shock focusing and molecular mixing, as well as circulation deposition. For the cases with more serious interface diffusion, the cylinder develops into more regular vortex pairs. The diffusive interface greatly mitigates the strength of the reflected shock wave and weakens the shock focusing capability. Some interface structural features are also recorded and analyzed. The diffusive interface brings about slower molecular mixing and less circulation generation. The circulation deposition on different interfaces is quantitatively investigated and compared with the theoretical models. The theoretical models are found to be applicable to the scenarios of diffusive interfaces.

关键词： Shock bubble interaction Interfacial instability Diffusive interface Circulation model

MODELING AND FORECASTING OF STOCK MARKETS UNDER A SYSTEM ADAPTATION FRAMEWORK

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2012年第4期25卷 641-674页

作者： Xiaolian ZHENG ben M.CHEN The Department of Electrical & Computer Engineering The National University of Singapore

This paper adopts the concept of dynamic feedback systems to model the behavior of financial markets, or more specifically, the stock market from a dynamic system point of view. Based on a feedback adaptation scheme, the authors model the movement of a stock market index within a framework that is composed of an internal dynamic model and an adaptive filter. The output-error model is adopted as the internal model whereas the adaptive filter is a time-varying state space model with instrumental variables. Its input-output behavior, and internal as well as external forces are then identified. Special attention has also been paid to the recent financial crisis by examining the movement of Dow Jones Industrial Average （DJIA） as an example to illustrate the advantage of the proposed framework. Supported by time-varying causality tests, five influential factors from economic and sentiment aspects are introduced as the input of this framework. Testing results show that the proposed framework has a much better prediction performance than the existing methods, especially in complicated economic situations. An application of this framework is also presented with focuses on forecasting the turning periods of the market trend. Realizing that a market trend is about to change when the external force begins to exhibit clear patterns in its frequency responses, the authors develop a set of rules to recognize this kind of clear patterns. These rules work well for stock indexes from US, China and Singapore.

关键词： Complex systems financial modeling financial systems market forecasting system economics.

Numerical analysis for impacts of nozzle end-clearances on aerodynamic performance and forced response in a VNT turbine

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2018年第5期31卷 1030-1040页

作者： ben ZHAO Leilei WANG Hongjun HOU Michigan State University East Lansing 48824 USA Hebei University of Engineering Handan 056038 China

It has been well known that nozzle end-clearances in a Variable Nozzle Turbine（VNT）are unfavorable for aerodynamic performance, especially at small openings, and efforts to further decrease size of the clearances are very hard due to thermal expansion. In this paper, both the different sizes of nozzle end-clearances and the various ratios of their distribution at the hub and shroud sides were modelled and investigated by performing 3D Computational Fluid Dynamics（CFD） and Finite Element Analysis（FEA） simulations with a code of transferring the aerodynamic pressure from the CFD results to the FEA calculations. It was found that increasing the size of the nozzle end-clearances divided equally at the hub and shroud sides deteriorates turbine efficiency and turbine wheel reliability, yet increases turbine flow capacity. And, when the total nozzle endclearances remain the same, varying nozzle end-clearances＇ distribution at the hub and shroud sides not only shifts operation point of a VNT turbine, but also affects the turbine wheel vibration *** with nozzle hub clearance, the shroud clearance is more sensitive to both aerodynamic performance and reliability of a VNT turbine. Consequently, a possibility is put forward to improve VNT turbine efficiency meanwhile decrease vibration stress by optimizing nozzle end-clearances＇ distribution.

关键词： Clearance Forced response Mode analysis Performance Reliability Variable Nozzle Turbine(VNT)