检索结果-内蒙古大学图书馆

Two- and three-dimensional numerical analysis of gradient and parasitic gradient fields of a three-channel surface gradient coil for magnetic resonance imaging

引用

IEEE TRANSACTIONS ON MAGNETICS 1996年第1期32卷 195-207页

作者： Shi, FA Ludwig, R Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA USA

For many organ-specific magnetic resonance imaging (MRI) applications, surface gradient coils (SGCs) offer an attractive alternative to the whole-body gradient coils presently employed in MR scanners. This investigation develops a 2D and 3D numerical analysis and design strategy based on the magnetic scalar and vector potentials to obtain the field strength and field linearity within a localized imaging area. It is demonstrated that for a predefined volume of interest, a given planar SGC configuration can achieve up to 80 Gauss/cm magnetic field gradient, which significantly exceeds the 1-3 Gauss/cm of whole-body coils based on the same current excitation of 100 A and inductance employed in typical whole-body instruments. In order to test the accuracy of our numerical design, a G(y) gradient coil was fabricated. It is found that the measured field distribution is in excellent agreement with our 3D theoretical predictions. Furthermore, this G,, gradient coil was installed in a GE CSI II 2 Tesla 15 cm bore MRI instrument which permits a direct comparison of the image quality with the computer predicted field linearity. Therefore, this numerical modeling approach proves very useful in analyzing and ultimately optimizing planar SGC coils for organ-specific MRI applications.

关键词： Numerical analysis Coils Magnetic resonance imaging Linearity Gaussian processes Instruments Magnetic fields Inductance Testing Magnetic field measurement

来源：评论

学校读者我要写书评

暂无评论

FINITE-ELEMENT ANALYSIS OF LOSSY DIELECTRIC WAVE-GUIDES

引用

IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 1994年第6期42卷 1025-1031页

作者： LEE, JF Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA USA

This paper presents a full-wave analysis of lossy dielectric waveguides using a hybrid vector finite element method. To avoid the occurrences of spurious modes in the formulation, edge elements and first-order nodal finite element basis functions are used to span the transverse and the z components of the electric field, respectively. Furthermore, the direct matrix solution technique with minimum degree of reordering has been combined with the modified Lanczos algorithm to solve for the resultant sparse generalized eigenmatrix equation efficiently.

关键词： Dielectric losses Finite element methods Integrated circuit modeling Integrated circuit interconnections Electromagnetic waveguides Transmission line matrix methods Frequency Maxwell equations Predictive models LAN interconnection

来源：评论

学校读者我要写书评

暂无评论

ENSURING GPS NAVIGATION INTEGRITY USING RECEIVER AUTONOMOUS INTEGRITY MONITORING

引用

IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE 1995年第10期10卷 31-34页

作者： MICHALSON, WR Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA

The many advantages of Global Positioning System (GPS) based navigation have created a tremendous amount of interest in using GPS as the primary navigation aid onboard commercial and civil aircraft. Even in the presence of Selective Availability, the accuracy of GPS is sufficient to guide aircraft point-to-point between airports without requiring other navigation aids such as VOR or DME, Unfortunately, there is a finite probability that a GPS satellite will fail, causing the transmission of potentially misleading navigation information. Thus, before GPS can be widely adopted as a navigation aid, techniques must be devised to detect any possible failures and notify the user prior to the degradation of navigation accuracy. This paper discusses the problem of detecting possible GPS satellite failures using a technique called Receiver Autonomous Integrity Monitoring (RAIM).

关键词： Global Positioning System Satellite navigation systems Aircraft navigation Clocks Equations Degradation computerized monitoring Aircraft propulsion Availability Earth

来源：评论

学校读者我要写书评

暂无评论

QUADRATIC ASSIGNMENT PROBLEMS GENERATED WITH THE PALUBETSKIS ALGORITHM ARE DEGENERATE

引用

IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-FUNDAMENTAL THEORY AND APPLICATIONS 1994年第7期41卷 481-484页

作者： CYGANSKI, D VAZ, RF VIRBALL, VG Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA USA

The quadratic assignment problem (QAP) is a combinatorial optimization problem that arises in many applications such as the allocation of processes in distributed computer systems. The QAP is NP-hard and therefore no algorithms are known for solving the QAP in polynomial time. For this reason a variety of heuristic methods have been proposed for this problem. In order to evaluate heuristics, Palubetskis proposed an algorithm that generates QAPs with known optimal solution value. We show in this paper that given a Palubetskis instance (but not its optimal value) the corresponding optimal value can be determined via a linear program, polynomial in the input data, i.e., in polynomial time. This implies that problems generated by the Palubetskis method belong to a simple and degenerate subclass of QAPs and are therefore not appropriate for algorithm testing. The proof technique suggests moreover a new lower bound for Euclidean QAPs.

关键词： Polynomials Transmission line matrix methods Cost function Distributed computing Testing Minimization Linear matrix inequalities Symmetric matrices Application software Resource management

来源：评论

学校读者我要写书评

暂无评论

True and false energy-saving devices

引用

IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS 1997年第6期33卷 1439-1443页

作者： Emanuel, AE Electrical and Computer Engineering Department Worcester Polytechnic Institute Worcester MA USA

This paper explains the mystifying performance of a nonlinear capacitance used as a passive energy-saving device (ESD), According to the law of energy conservation, such ESD's cannot improve motor efficiency, Theoretical and experimental studies prove that the bulk of the perceived ''energy savings'' is caused by the current transformers phase-angle error.

关键词： energy-saving devices power factor correction

来源：评论

学校读者我要写书评

暂无评论

ANALYTICAL AND NUMERICAL TREATMENT OF PULSED WAVE-PROPAGATION INTO A VISCOUS-FLUID

引用

IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL 1995年第4期42卷 789-792页

作者： LUDWIG, R LEVIN, PL Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA USA

A transient analytical expression for the propagation of pulsed ultrasound through a viscous fluid is derived by evaluating the Laplace transform in the complex domain. The numerical solution of the viscous wave equation without any restricting approximations is developed for a full space with an impulsive excitation at the origin. Different values of the viscosity coefficient for a given sound speed clearly delineate the transition from a pure parabolic, or diffusive to a pure hyperbolic or wave propagation behavior. This region is often of crucial importance from a practical point of view as ultrasonic instrumentation in medical imaging and nondestructive testing must compensate not only for phase differences due to propagation delays but also for pulse distortion due to attenuation mechanisms in the medium of interest.

关键词： Nondestructive Testing pulse distortion Propagation delay Fluid Numerical viscous fluids Medical imaging Viscosity coefficients Laplace transform Wave equation point of view

来源：评论

学校读者我要写书评

暂无评论

The impact of indoor environmental quality on tourist accommodation ratings using guest reviews

引用

Building and Environment 2025年 280卷

作者： Zhang, Fan Seshadri, Karthick Liu, Shichao Santamouris, Matthaios School of Engineering and Built Environment Griffith University SouthportQLD Australia Department of Computer Science and Engineering National Institute of Technology Andhra Pradesh Tadepalligudem India Department of Civil Environmental Architectural Engineering Worcester Polytechnic Institute MA United States High Performance Architecture School of Built Environment University of New South Wales SydneyNSW Australia

Guest satisfaction is pivotal for the hospitality industry, yet the role of Indoor Environmental Quality (IEQ) in shaping guest ratings remains inadequately explored. This study addresses this gap by leveraging web-mining, natural language processing and the Three-Factor Theory to analyse guest reviews of Australian hotels and serviced apartments listed on ***. Findings indicate that most IEQ factors—thermal comfort, indoor air quality, luminous environment, acoustics, space, facilities, cleanliness, and layout—function as Basic Factors. While deficiencies in these areas drive dissatisfaction, their adequacy alone does not significantly enhance satisfaction. Notably, exterior view serves as an Excitement Factor in budget accommodations (three stars or below) but transitions to a Basic Factor in luxury settings. Among all IEQ factors, cleanliness, indoor air quality, and acoustics had the strongest negative impacts when underperforming, whereas satisfactory exterior views, cleanliness, and available space positively influenced guest ratings. The COVID-19 pandemic intensified these effects, heightening guest sensitivity to IEQ deficiencies (e.g., poor air quality) while elevating expectations for high-performing attributes like exterior views and available space. Overall, IEQ factors accounted for 32.8 % of customer ratings in budget hotels and 23.9 % in luxury accommodations. The findings underscore the necessity of ensuring satisfactory performance across all IEQ factors, particularly cleanliness and indoor air quality, while strategically enhancing exterior views and spatial configuration to optimize guest satisfaction. These insights provide hospitality managers and policymakers with data-driven guidance for enhancing guest satisfaction and operational resilience in post-pandemic hospitality settings. © 2025 The Author(s)

关键词： Indoor air pollution

来源：评论

学校读者我要写书评

暂无评论

Area Determination of Diabetic Foot Ulcer Images Using a Cascaded Two-Stage SVM-Based Classification

引用

IEEE Transactions on Biomedical engineering 2017年第9期64卷 2098-2109页

作者： Wang, Lei Pedersen, Peder C. Agu, Emmanuel Strong, DIane M. Tulu, Bengisu Department of Electrical and Computer Engineering Worcester Polytechnic Institute WorcesterMA01609 United States Department of Electrical and Computer Engineering Worcester Polytechnic Institute United States Department of Computer Science Worcester Polytechnic Institute United States Foisie School of Business Worcester Polytechnic Institute United States

The standard chronic wound assessment method based on visual examination is potentially inaccurate and also represents a significant clinical workload. Hence, computer-based systems providing quantitative wound assessment may be valuable for accurately monitoring wound healing status, with the wound area the best suited for automated analysis. Here, we present a novel approach, using support vector machines (SVM) to determine the wound boundaries on foot ulcer images captured with an image capture box, which provides controlled lighting and range. After superpixel segmentation, a cascaded two-stage classifier operates as follows: In the first stage, a set of k binary SVM classifiers are trained and applied to different subsets of the entire training images dataset, and incorrectly classified instances are collected. In the second stage, another binary SVM classifier is trained on the incorrectly classified set. We extracted various color and texture descriptors from superpixels that are used as input for each stage in the classifier training. Specifically, color and bag-of-word representations of local dense scale invariant feature transformation features are descriptors for ruling out irrelevant regions, and color and wavelet-based features are descriptors for distinguishing healthy tissue from wound regions. Finally, the detected wound boundary is refined by applying the conditional random field method. We have implemented the wound classification on a Nexus 5 smartphone platform, except for training which was done offline. Results are compared with other classifiers and show that our approach provides high global performance rates (average sensitivity = 73.3%, specificity = 94.6%) and is sufficiently efficient for a smartphone-based image analysis. © 2017 IEEE.

关键词： Support vector machines

来源：评论

学校读者我要写书评

暂无评论

NUMERICAL IMPLEMENTATION AND MODEL PREDICTIONS OF A UNIFIED CONSERVATION LAW DESCRIPTION OF THE ELECTROMAGNETIC ACOUSTIC TRANSDUCTION PROCESS

引用

IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL 1992年第4期39卷 481-488页

作者： LUDWIG, R Department of Electrical and Computer Engineering Worcester Polytechnic Institute Worcester MA USA

A numerical formulation and its computer implementation of the electro-acoustic transduction process governing an electromagnetic acoustic transducer are discussed. Based on momentum law descriptions of the underlying physical concepts, a multistage finite element, finite difference procedure is developed to predict the acoustic wave radiation into an isotropic half space due to an excitation coil driven by a high-frequency, pulsed current. To demonstrate the flexibility of this novel approach, the acoustic wave generation efficiency of constant versus variable lift-off wire pair configurations of a meander coil suspended over a metallic specimen is examined in two dimensions. It will be shown for the Lorentz force density induced by 5 and 8 wire pair meander coils that a variable wire lift-off creates a more uniform volume force density in the metallic specimen and consequently produces more efficient broad band surface waves as compared to the conventional fixed lift-off arrangement. Furthermore, the directivity patterns of these finite aperture, pulsed elastic wave phenomena exhibit behaviors that cannot be adequately predicted by simple analytical formulas.

关键词： Predictive models Numerical models Coils Acoustic waves Electromagnetic radiation Acoustic transducers Finite element methods Finite difference methods Acoustic pulses Pulsed electroacoustic methods

来源：评论

学校读者我要写书评

暂无评论

FFT COMPUTATION WITH SYSTOLIC ARRAYS, A NEW ARCHITECTURE

引用

IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-ANALOG AND DIGITAL SIGNAL PROCESSING 1994年第4期41卷 278-284页

作者： BORIAKOFF, V Electrical and Computer Engineering Department Worcester Polytechnic Institute Worcester MA USA

The use of the Cooley-Tukey algorithm for computing the 1-d FFT lends itself to a particular matrix factorization which suggests direct implementation by linearly-connected systolic arrays. Here we present a new systolic architecture that embodies this algorithm. This implementation requires a smaller number of processors and a smaller number of memory cells than other recent implementations, as well as having all the advantages of systolic arrays. For the implementation of the decimation-in-frequency case, word-serial data input allows continuous real-time operation without the need of a serial-to-parallel conversion device. No control or data stream switching is necessary. computer simulation of this architecture was done in the context of a 1024 point DFT with a fixed point processor, and CMOS processor implementation has started.

关键词： FAST FOURIER TRANSFORM ONLINE PROCESSING SYSTOLIC ARRAYS VLSI

来源：评论

学校读者我要写书评

暂无评论

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

请选择保存的检索档案：

请选择收藏分类：

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

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

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：