检索结果-南通市图书馆

Electrogastrography: Poor correlation with antro-duodenal manometry and doubtful clinical usefulness in adults

World Journal of Gastroenterology 2007年第38期13卷 5101-5107页

作者： shahab Abid Greger Lindberg Karolinska Institutet Department of Medicine Division of Gastroenterology and Hepatology Karolinska University Hospital Huddinge Stockholm 14186 Sweden

AIM: To investigate if there is a correlation between electrical activity measured by electrogastrography (EGG) and contractile activity of the stomach as measured by antroduodenal manometry (ADM). We also studied whether the underlying motility disorder could be predicted from EGG parameters. METHODS: We compared 21 parameters measured from EGG with 8 parameters measured from ADM. The ability of EGG to identify the underlying diagnosis was tested by comparing EGG parameters for each diagnosis group against other patients. The study comprised recordings from 148 patients and 125 females. Their median age was 45 (range 17-76) years. RESULTS: We found few and weak correlations between EGG and ADM. Specifically the correlation between parameters reflecting the response to meal was poor (r = -0.07, P = 0.39). The discriminatory power of EGG for underlying motility disorder was also low. Patients with slow transit constipation (STC) showed a lower postprandial power in normogastric (3.7 ± 0.5 vs 4.0 ± 0.5) and tachygastric (3.5 ± 0.4 vs 3.7 ± 0.4) regions, a lower percentage of time with normogastria [87.2 (56.5-100)% vs 95.7 (0-100)%], and a higher percentage of time with tachygastria [9.3 (0-33)% vs 3.5 (0-100)%] and bradygastria [1.8 (0-20)% vs 0 (0-17.1)%]. Patients with irritable bowel syndrome had a higher percentage of time with normogastria [96.5 (62.5-100)% vs 93.3 (0-100)%] and a less unstable dominant frequency as measured by the instability coefficient [15 (3-77) vs 24 (2-72)]. CONCLUSION: EGG and ADM seem to measure different aspects of gastric motor activity but cannot show a spatial correlation. The diagnostic value of EGG is poor, but EGG may have some value for the identification of patients with STC.

关键词： Antroduodenal manometry Correlation Diagnostic use Electrogastrography Functional bowel disorders Physiopathology

来源：

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

Regenerative energy management of electric drive based on Lyapunov stability theorem

引用

Journal of Modern Power Systems and Clean Energy 2019年第2期7卷 321-328页

作者： shahab SABZI Mehdi ASADI Hassan MOGHBELI Department of Electrical Engineering Arak University of Technology

In recent years, urban rail systems have developed drastically. In these systems, when induction electrical machine suddenly brakes, a great package of energy is produced. This package of energy can be stored in energy storage devices such as battery, ultra-capacitor and flywheel. In this paper, an electrical topology is proposed to absorb regenerative braking energy and to store it in ultracapacitor and ***-capacitor can deliver the stored energy to DC grid and charge the battery for auxiliary applications such as lighting and cooling systems The proposed system is modeled based on large signal averaged modeling, which leads to the simplicity of calculations. The control system is based on Lyapunov stability theorem which guarantees system stability. Also, an energy management algorithm is proposed to control energy under braking and steady-state conditions. Finally,the simulation results validate the effectiveness of the proposed control and energy management system.

关键词： DC/DC converter Lyapunov stability Bidirectional converter Energy management system(EMS) Ultra-capacitor Battery Switching function

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Fabrication of a highly efficient new nanocomposite polymer gel for controlling the excess water production in petroleum reservoirs and increasing the performance of enhanced oil recovery processes

引用

Chinese Journal of Chemical Engineering 2021年第4期34卷 385-392页

作者： Sajad Asadizadeh shahab Ayatollahi Bahman ZareNezhad Faculty of Chemical Petroleum and Gas EngineeringSemnan UniversitySemnanIran Chemical and Petroleum Engineering Department Sharif University of TechnologyTehranIran

A new nanocomposite polymer gel is synthesized for reduction of excess water production in petroleum reservoirs at real operating *** new nanocomposite gel contains SiO2 nanoparticles,partially hydrolyzed polyacrylamide(HPAM)and chromium *** pressure and high temperature tests using porous carbonate core are carried out to evaluate the effects of nanoparticles on the synthesized polymer gel *** is shown that the residual resistance factor ratio of water to oil using the synthesized polymer gel nanocomposite in this work is much higher than that of the ordinary polymer *** presented results confirm the high performance of the synthesized nanocomposite polymer gel for decreasing the water flow through porous carbonate bed.A mathematical model for description of oil and water flow behavior in the presence of synthesized nanocomposite polymer gel is also *** presented nano polymer gel leads to considerable cost saving in enhanced oil recovery(EOR)processes.

关键词： Petroleum Excess water Nanocomposite Polymer gel Nanoparticle EOR

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Hot deformation behavior of microstructural constituents in a duplex stainless steel during high-temperature straining

引用

International Journal of Minerals,Metallurgy and Materials 2013年第10期20卷 953-960页

作者： Amir Momeni shahab Kazemi Ali Bahrani Materials Science and Engineering Department Hamedan University of Technology Department of Materials Engineering Faculty of EngineeringBu Ali Sina University

The hot deformation characteristics of 1.4462 duplex stainless steel （DSS） were analyzed by considering strain partitioning between austenite and ferrite constituents. The individual behavior of ferrite and austenite in microstructure was studied in an iso-stress condition. Hot compression tests were performed at temperatures of 800-1100~C and strain rates of 0.001-1 s-1. The flow stress was modeled by a hyperbolic sine constitutive equation, the corresponding constants and apparent activation energies were determined for the studied alloys. The constitutive equation and law of mixture were used to measure the contribution factor of each phase at any given strain. It is found that the contribution factor of ferrite exponentially declines as the Zener-HoUomon parameter （Z） increases. On the contrary, the austenite contribution polynomially increases with the increase of Z. At low Z values below 2.6. x 1015 （lnZ---35.5）, a negative contribution factor is determined for austenite that is attributed to dynamic recrystallization. At high Z values, the contribution factor of austenite is about two orders of magnitude greater than that of ferrite, and therefore, austenite can accommodate more strain. Microstructural characterization via electron back-scattered diffraction （EBSD） confirms the mechanical results and shows that austenite recrystallization is possible only at high temperature and low strain rate.

关键词： duplex stainless steel compression testing strain partitioning high temperature operations deformation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A hybrid deterministic-stochastic model for spouted beds

引用

Particuology 2019年第1期17卷 104-113页

作者： shahab Golshan Reza Zarghami Navid Mostoufi Process Design and Simulation Research Centre. School of Chemical Engineering. College of Engineering University of Tehran. TehranIran

A new hybrid deterministic-stochastic model is developed and used to simulate a slot-rectangular spouted *** model includes deterministic and stochastic steps that are executed in *** simulation starts with the deterministic part of the model,in which the computational fluid dynamics-discrete element method (CFD-DEM) equations are solved for 1 s to give the initial velocity distribution of the *** stochastic part is then executed,with the hydrodynamics of the bed taken from the velocity distributions acquired in the first step through Monte Carlo sampling.A full deterministic (CFD-DEM) simulation of the bed is also conducted for comparison with the proposed hybrid ***,the proposed hybrid is validated using experimental data from the *** validations are based on the axial and lateral velocity distributions of the particles and the bed *** effects of the cell size and number of sampling steps on the accuracy of the model are also *** performance of the proposed model is compared with the CFD-DEM results in terms of the computation time and the rate of solid circulation in the *** hybrid model is found to have shorter runtimes than the CFD-DEM approach.

关键词： CFD–DEM Monte Carlo Spouted bed Hydrodynamics Solid circulation rate

来源：

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

Simulation of Vortex-Induced Vibrations of A Cylinder Using ANSYS CFX Rigid Body Solver

引用

China Ocean Engineering 2017年第1期31卷 79-90页

作者： IZHAR Abubakar QURESHI Arshad Hussain KHUSHNOOD shahab University of Engineering and Technology Lahore Pakistan University of Engineering and Technology Taxila Pakistan

This article simulates the vortex-induced oscillations of a rigid circular cylinder with elastic support using the new ANSYS CFX rigid body solver. This solver requires no solid mesh to setup FSI（Fluid Structure Interaction）simulation. The two-way case was setup in CFX only. Specific mass of the cylinder and flow conditions were similar to previous experimental data with mass damping parameter equal to 0.04, specific mass of 1 and Reynolds number of 3800. Two dimensional simulations were setup. Both one-degree-of-freedom and two-degree-of-freedom cases were run and results were obtained for both cases with reasonable accuracy as compared with experimental ***-figure XY trajectory and lock-in behavior were clearly captured. The obtained results were satisfactory.

关键词： cylinder solver Reynolds vortex freedom Vortex circular satisfactory figure captured

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Full field reservoir modeling of shale assets using advanced data-driven analytics

引用

Geoscience Frontiers 2016年第1期7卷 11-20页

作者： Soodabeh Esmaili shahab D.Mohaghegh Asset Development Team North OperationCalifornia Resources CorporationCalifornia 90024USA West Virginia University 345-E Mineral Resources Bldg.P.O.Box 6070MorgantownWV 26506USA

Hydrocarbon production from shale has attracted much attention in the recent years. When applied to this prolific and hydrocarbon rich resource plays, our understanding of the complexities of the flow mechanism（sorption process and flow behavior in complex fracture systems- induced or natural） leaves much to be desired. In this paper, we present and discuss a novel approach to modeling, history matching of hydrocarbon production from a Marcellus shale asset in southwestern Pennsylvania using advanced data mining, pattern recognition and machine learning technologies. In this new approach instead of imposing our understanding of the flow mechanism, the impact of multi-stage hydraulic fractures, and the production process on the reservoir model, we allow the production history, well log, completion and hydraulic fracturing data to guide our model and determine its behavior. The uniqueness of this technology is that it incorporates the so-called ＂hard data＂ directly into the reservoir model, so that the model can be used to optimize the hydraulic fracture process. The ＂hard data＂ refers to field measurements during the hydraulic fracturing process such as fluid and proppant type and amount, injection pressure and rate as well as proppant concentration. This novel approach contrasts with the current industry focus on the use of ＂soft data＂（non-measured, interpretive data such as frac length, width,height and conductivity） in the reservoir models. The study focuses on a Marcellus shale asset that includes 135 wells with multiple pads, different landing targets, well length and reservoir properties. The full field history matching process was successfully completed using this data driven approach thus capturing the production behavior with acceptable accuracy for individual wells and for the entire asset.

关键词： Reservoir modeling Data driven reservoir modeling Top-down modeling Shale reservoir Modeling Shale

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Simulation of Vortex-Induced Vibrations of A Cylinder Using ANSYS CFX

引用

China Ocean Engineering 2014年第4期28卷 541-556页

作者： Abu Bakar IZHAR Arshad Hussain QURESHI shahab KHUSHNOOD University of Engineering & Technology Lahore Pakistan University of Engineering & Technology Taxila Pakistan

In this paper, vortex-induced vibrations of a cylinder are simulated by use of ANSYS CFX simulation code. The cylinder is treated as a rigid body and transverse displacements are obtained by use of a one degree of freedom spring damper system. 2-D as well as 3-D analysis is performed using air as the fluid. Reynolds number is varied from 40 to 16000 approx., covering the laminar and turbulent regimes of flow. The experimental results of （Khalak and Williamson, 1997） and other researchers are used for validation purposes. The results obtained are comparable.

关键词： vortex-induced vibrations ANSYS CFX flow induced vibrations fluid structure interaction

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Viscous fingering and its effect on areal sweep efficiency during waterflooding: an experimental study

引用

Petroleum Science 2019年第1期16卷 105-116页

作者： Zahra Kargozarfard Masoud Riazi shahab Ayatollahi Enhanced Oil Recovery (EOR) Research Centre IOR-EOR Research Institute Shiraz University Department of Petroleum Engineering School of Chemical and Petroleum Engineering Shiraz University Enhanced Oil Recovery (EOR) Research Center School of Chemical and Petroleum Engineering Sharif University of Technology

Viscous fingering is one of the main challenges that could reduce areal sweep efficiency during waterflooding in oil reservoirs. A series of waterflooding experiments were carried out in a Hele-Shaw cell at ambient temperature during which areal sweep efficiency was estimated and techniques to ease the fingering problem were examined. The onset and propagation of viscous fingers were monitored as a function of both injection rate and injection/production positions. Image processing techniques were utilized to quantitatively investigate the propagation of fingers. The experimental results show that, under specific conditions, increasing the number of finger branches could improve the areal sweep efficiency, whereas growth of a single narrow finger has a negative impact on oil displacement efficiency. According to the obtained results,increasing the injection rate improves the areal sweep efficiency up to a critical rate at which viscous fingers start to *** impact of heterogeneity of the medium on distributing the viscous fingers was also investigated by introducing two different arrangements of fractures in the model. The results show that fractures perpendicular to the direction of flow would distribute the displacing water more uniformly, while fractures in the direction of flow would amplify the unfavorable sweep efficiency.

关键词： Viscous fingering Areal sweep efficiency Front instability Mobility ratio Fractures Hele-Shaw cell

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effect of salts and their interaction with ingenious surfactants on the interfacial tension of crude oil/ionic solution

引用

Chinese Journal of Chemical Engineering 2020年第1期28卷 224-235页

作者： Mostafa Lashkarbolooki Roohollah Parvizi shahab Ayatollahi Ebrahim Ghaseminejad Raeeni School of Chemical Engineering Babol Noshirvani University of TechnologyBabolIran Department of Chemical Engineering Islamic Azad UniversityIran School of Chemical and Petroleum Engineering Sharif University of TechnologyTehranIran National Iranian South Oil Company Iran

Understanding the roles of asphaltene and resin as natural surfactants existed in crude oil can enlighten contradicting reported results regarding interfacial tension(IFT) of crude oil/aqueous solution as a function of salinity and ion type. In this way, this study is aimed to investigate the effect of these natural surface active agents on IFT of with special focus on SO4^2-anion and Mg^2+cation. Two different synthetic oil solutions of 8 wt% of the extracted asphaltene and resin dissolved in toluene are prepared, and then IFT values are measured. After that,the obtained results are compared with the IFT of intact crude oil in contact with the same saline solutions examined in the previous stage. The obtained results showed a synergistic effect of Na2SO4+ MgCl2 solution unlike the MgSO4+ MgCl2 and CaSO4+ MgCl2 solutions on IFT reduction of resin at MgCl2 concentration of 15000 mg·kg^-1. In summary, it is found that the affinity of asphaltene molecules towards the interface of oleic phase/ionic solution leads to higher IFT variation.

关键词： IFT Resin Asphaltene Mg^2+ SO4^2-

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：