检索结果-内蒙古大学图书馆

作者： Avraam, D.G. Halkides, T.I. Liguras, D.K. Bereketidou, O.A. Goula, M.A. Prefecture Authority of Imathia Section of Town-Planning and Environment GR-59100 Veria Greece Technological Educational Institute of Western Macedonia Pollution Control Technologies Department GR-50100 Koila Kozani Greece HELBIO S.A. Hydrogen and Energy Production Systems Patras Science Park Stadiou Street Platani GR-26504 Rio Greece University of Western Macedonia Department of Mechanical Engineering Bakola and Sialvera GR-50100 Kozani Greece

An experimental and theoretical study for the biogas steam reforming reaction over 5%Ru/Al2O3 catalyst have been performed. An apparatus was constructed for the conduction of the experiments, the core of which was a tube reactor, filled with the catalyst in form of pellets. The inlet gas mixture consisted of CH4 and CO2 in various composition ratios as a model biogas and steam. A theoretical model of the process was developed. The experimental reactor was modelled as an isothermal pseudo homogeneous fixed bed reactor. Internal and external transport phenomena were neglected and appropriate effectiveness factors were employed instead. A physical properties model was used for the calculation of the physicochemical properties of the real mixture. Five reactant species, CH4, CO 2, H2O, CO and H2, were included in the model, whereas the feed consisted of the first three. Steam reforming and water gas shift were the main reactions. Experimental results and theoretical predictions match closely, stability of the catalyst was assured and an optimal operational window was identified, at GHSV = 10,000-20,000 h-1, T = 700-800 °C, CH4/CO2 = 1.0-1.5 and H2O/CH 4 = 3.0-5.0. © 2010 Published by Elsevier Ltd on behalf of Professor T. Nejat Veziroglu.

关键词： Catalysis

来源：评论

学校读者我要写书评

暂无评论

On the estimation of robustness and filtering ability of dynamic biochemical networks under process delays, internal parametric perturbations and external disturbances

引用

Mathematical Biosciences 2009年第2期222卷 92-108页

作者： Chen, Bor-Sen Chen, Po-Wei Lab. of Control and Systems Biology Department of Electrical Engineering National Tsing-Hua University 101 Section 2 Kuang Fu Road Hsin-chu 300 Taiwan

Inherently, biochemical regulatory networks suffer from process delays, internal parametrical perturbations as well as external disturbances. Robustness is the property to maintain the functions of intracellular biochemical regulatory networks despite these perturbations. In this study, system and signal processing theories are employed for measurement of robust stability and filtering ability of linear and nonlinear time-delay biochemical regulatory networks. First, based on Lyapunov stability theory, the robust stability of biochemical network is measured for the tolerance of additional process delays and additive internal parameter fluctuations. Then the filtering ability of attenuating additive external disturbances is estimated for time-delay biochemical regulatory networks. In order to overcome the difficulty of solving the Hamilton Jacobi inequality (HJI), the global linearization technique is employed to simplify the measurement procedure by a simple linear matrix inequality (LMI) method. Finally, an example is given in silico to illustrate how to measure the robust stability and filtering ability of a nonlinear time-delay perturbative biochemical network. This robust stability and filtering ability measurement for biochemical network has potential application to synthetic biology, gene therapy and drug design. © 2009 Elsevier Inc. All rights reserved.

关键词： Linear matrix inequalities

来源：评论

学校读者我要写书评

暂无评论

Automated diagnostic approaches for defective rolling element bearings using minimal training pattern classification methods

Automated diagnostic approaches for defective rolling elemen...

引用

4th World Congress on engineering Asset Management: engineering Asset Lifecycle Management, WCEAM 2009

作者： Gryllias, K.C. Yiakopoulos, C. Antoniadis, I. School of Mechanical Engineering Machine Design and Control Systems Section Dynamics and Structures Laboratory Athens 15773 Greece

ISBN: (纸本)9781849960021

Rolling Element Bearings consist one of the most widely used industrial machine elements, being the interface between the stationary and the rotating part of the machine. Due to their importance a plethora of monitoring methods and fault diagnosis procedures have been developed, in order to reduce maintenance costs, improve productivity, and prevent malfunctions and failures during operation which could lead to the downtime of the machine. Towards this direction, among different automatic diagnostic methods, the Support Vector Machine (SVM) method has been shown to present a number of advantages. Support Vector Machine is a relatively new computational learning method based on Statistical Learning Theory and combines fundamental concepts and principles related to learning, well-defined formulation and self-consistent mathematical theory. The key aspects about the use of SVMs as a rolling element bearing health monitoring tool are the lack of actual experimental data, the optimal selection of the type and the number of input features, and the correct selection of the kernel function and its corresponding parameters. A large number of input features have been proposed, being divided in two big categories: A) Traditional signal statistical features in the time domain, such as mean value, rms value, variance, skewness, kurtosis etc, B) Frequency domain based indices, such as energy values obtained at characteristic frequency bands of the measured and the demodulated signals. In this paper, the structure and the performance of a Support Vector Machine based approach for rolling element bearing fault diagnosis is presented. The main advantage of this method is that the training of the SVM is based on a model describing the dynamic behavior of a defective rolling element bearing, enabling thus the direct application of the SVM to experimental measurements of defective bearings, without the need of training the SVM with experimental data of a defective bearing.

关键词： Support vector machines

来源：评论

学校读者我要写书评

暂无评论

Comparison of criteria for optimal demodulation of defective rolling element bearings vibration response with complex shifted morlet wavelets (CSMW)

Comparison of criteria for optimal demodulation of defective...

引用

16th International Congress on Sound and Vibration 2009, ICSV 2009

作者： Gryllias, Konstantinos C. Antoniadis, Ioannis A. National Technical University of Athens School of Mechanical Engineering Machine Design and Control Systems Section Athens 15773 Greece

ISBN: (纸本)9781615677368

Complex Shifted Morlet Wavelets (C.S.M.W.) present a number of advantages over other similar methods. Since Morlet Wavelets are modulated in the time domain by a Gaussian shaped time window (and for this reason are also known as Gabor wavelets), they present the optimal resolution simultaneously in the time and in the frequency domain. Moreover, compared to the Discrete Wavelet Transform (DWT), they lead to a continuous (and thus more accurate) approximation in both time and frequency domains. Furthermore, it should be noted that although CWT is been considered as more computationally intensive than the DWT, relevant algorithms may overcome this disadvantage to a significant degree. In addition, contrary to the traditional Morlet Wavelet Transform, CSMW results to complex wavelet coefficients in the time domain, thus enabling the direct calculation of the signal envelope by the magnitude of the wavelet coefficients, in a quite similar way to the traditional Hilbert Transform. Finally, in contrast to the classical concept of "scaling" the wavelet in the time or frequency domain, which allows the identification of only the wavelet scale, the concept of shifting the Morlet wavelet in the frequency domain allows the simultaneous optimal selection of both the wavelet parameters necessary to identify it as a proper filter in the frequency domain: The center frequency and the bandwidth. Concerning the optimal selection of these last two parameters, a number of criteria have been proposed: a) The signal Entropy, b) The Crest Factor c) The Number of the wavelet amplitude Peaks exceeding a threshold, d) A Smoothness Index factor. A number of application cases are presented and the effectiveness of the different Criteria is examined and compared. None of these criteria presents an overall optimum behavior in all test cases considered.

关键词： Discrete wavelet transforms

来源：评论

学校读者我要写书评

暂无评论

Doppler effect minimization in the spectra emitted by moving vehicles by the application of a Harmonic Signal Detection (HARD) Method

Doppler effect minimization in the spectra emitted by moving...

引用

6th International Conference on Condition Monitoring and Machinery Failure Prevention Technologies 2009

作者： Yiakopoulos, C.T. Gryllias, K.C. Antoniadis, I.A. National Technical University of Athens School of Mechanical Engineering Machine Design and Control Systems Section Dynamics and Structures Laboratory Athens 15773 Greece

ISBN: (纸本)9781618390097

On-line fault diagnosis of moving vehicles is of increasing importance, especially if the diagnosis can be performed from a stationary byside station near the way of the moving vehicle. The diagnostically interesting information of a moving vehicle is available in the acoustic signal which is emitted by the source. However, the Doppler effect introduces a spectrum smear depending on the speed of the moving source, which shifts the interesting frequencies to different bands. A method is presented that allows the acquired information to be connected to the proper running of the moving vehicle, indicating the useful carrier frequencies of the source signals. The basic idea is based on the Harmonic Signal Detection Method. Since this method is a special parametric method performing directly in the time domain, it can track on-line the instantaneous speed of the moving object. The estimated speed variation of the moving object can be used to fix the problem of the frequency distortion introduced by the Doppler effect. The paper includes results of the proposed technique to simulated data and to an experimental measurement which was taken by a moving rail vehicle.

关键词： Doppler effect

来源：评论

学校读者我要写书评

暂无评论

Demodulation of defective rolling element bearings vibration response with Complex Shifted Wavelets (CSMW) using a Peak Energy Criterion (PEC)

Demodulation of defective rolling element bearings vibration...

引用

6th International Conference on Condition Monitoring and Machinery Failure Prevention Technologies 2009

作者： Gryllias, Konstantinos C. Antoniadis, Ioannis A. National Technical University of Athens School of Mechanical Engineering Machine Design and Control Systems Section Dynamics and Structures Laboratory Athens 15773 Greece

ISBN: (纸本)9781618390097

Complex Shifted Morlet Wavelets (CSMW) can be used for the demodulation of the vibration response of defective rolling element bearings, as they present a number of advantages. The most important is that according to this method, the maximal timefrequency resolution is obtained, while the magnitudes of the complex wavelet coefficients in the time domain lead directly to the required envelope. However, the key element for the successful application of the method is the optimal selection and location of the corresponding necessary time-frequency window both in the time and in the frequency domains. For this reason, a Peak Energy Criterion (PEC) is proposed in order to tune the relevant wavelet window by choosing simultaneously in an optimal way and automatically both the center frequency and the bandwidth. A number of application cases are presented and the criterion demonstrates excellent behavior as it combines the benefits of energy based criteria, with criteria characterizing the spikiness of the response.

关键词： Demodulation

来源：评论

学校读者我要写书评

暂无评论

A morphological index for fault detection and trending in defective gearboxes

A morphological index for fault detection and trending in de...

引用

16th International Congress on Sound and Vibration 2009, ICSV 2009

作者： Gryllias, K.C. Yiakopoulos, C.T. Antoniadis, I.A. Guminski, R. Radkowski, St. National Technical University of Athens School of Mechanical Engineering Machine Design and Control Systems Section Athens 15773 Greece Warsaw University of Technology Institute of Machine Design Fundamentals ul. Narbutta 84 02-524 Warszawa Poland

ISBN: (纸本)9781615677368

Gearboxes consist one of the most widely used industrial machine parts. Due to its importance, a plethora of monitoring methods and fault diagnosis procedures have been developed in order to reduce maintenance costs, improve productivity, and prevent malfunctions and failures during operation which could lead to downtime of machinery. Thus, it is crucial to detect accurately and on time fault symptoms. Typical faults of gears include pitting, chipping and even tooth cracking. The development of a local fault at a gear often introduces both amplitude and phase modulations at the vibration measured signals. A remarkable number of frequency based signal processing methods have been proposed for gear fault identification and detection, including Ceptrum Analysis, Hilbert Transformation, Cyclostationary Analysis, Deconvolution Filters and different Time-Frequency Analysis methods, such as wavelets. The aforementioned methods, although they present a quite effective behaviour in the detection of defects, usually require complex and sophisticated analysis and as a result there are some important obstacles in using them in an automated manner without the presence of special trained personnel Moreover, a number of traditional time domain signal processing methods have been developed, such as the root mean square of the signal, the crest factor, the kurtosis, the shape factor, the impulse factor and the recently introduced morphological analysis. Morphological Signal Processing is closely related to mathematical morphology. Its basic concept is to modify the geometrical features of a signal in the time domain in order to construct a kind of envelop. In this paper Morphological Analysis and the resulting Morphological Index is applied to a set of vibration measurements from a gearbox prior to tooth breakage. Morphological Index, as is shown at the results, seems to be able to monitor the evolution of the potential fault, providing a clear warning prior to the breakage of the t

关键词： Mathematical morphology

来源：评论

学校读者我要写书评

暂无评论

Design and operational concepts for reusable rocket engine

Design and operational concepts for reusable rocket engine

引用

45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

作者： Yoshida, Makoto Takada, Satoshi Naruo, Yoshihiro Niu, Kenichi 1 Koganezawa Kimigaya Kakuda Miyagi 981-1525 Japan Mitsubishi Heavy Industries Co. Ltd. 1200 Higashi-tanaka Komaki Aichi 485-8561 Japan Tribology Technology Section Space Transportation Mission Directorate Japan Department of Space Systems and Astronautics ISAS 3-1-1 Yoshinodai Sagamihara Kanagawa 229-8510 Japan Liquid Rocket Design Section Engine and Control Equipment Engineering Department Japan

ISBN: (纸本)9781563479762

A 40kN rocket engine, Pilot Engine, is being developed in Japan. Pilot Engine development has been initiated relating to the reusable sounding rocket, which is also developed in Japan. This rocket vertically takes off, reaches to 120km altitude, lands vertically on the launch site and is launched again within several days. This rocket will provide observation mission chances with low cost and with quickness utilizing the advantages of reusability. ··This program has been authorized as a technology demonstration phase, and most of the technologies required for the vehicle are to be demonstrated in a few years. In order to realize this rocket concept, the engines installed on the rocket should have features of reusability, long life, deep throttling and health monitoring. ··Those have not yet been established in Japanese rocket engines. ··To solve the engineering subjects about those features, a new design methodology, advanced engine simulations and engineering testing are focused in the Pilot Engine development. Especially in engineering testing, limit condition data is acquired and new diagnostic techniques. Those can be applied utilizing mobility of small size hardware. In this paper, development status of Pilot Engine is mentioned, including fundamental design, engineering tests and operation and maintenance schedule. © 2009 by the American Institute of Aeronautics and Astronautics, Inc.

关键词： Engines

来源：评论

学校读者我要写书评

暂无评论

Nanofabrication of three-dimensional imprint diamond molds by ECR oxygen ion beams using polysiloxane

Nanofabrication of three-dimensional imprint diamond molds b...

引用

作者： Shuji, Kiyohara Tomoyuki, Kashiwagi Hirofumi, Takikawa Yuichi, Kurashima Yoshio, Taguchi Yoshinari, Sugiyama Electric and Control System Engineering Course Faculty of Advanced Engineering Maizuru National College of Technology 234 Aza Shiroya Maizuru Kyoto 625-8511 Japan Department of Electrical and Electronic Engineering Toyohashi University of Technology Toyohashi Aichi 441-8580 Japan Department of Mechanical Systems Engineering University of Yamanashi 4-3-11 Takeda Kofu Yamanashi 400-8511 Japan Application and Technical Section ELIONIX INC 3-7-6 Motoyokoyama Hachioji Tokyo 192-0063 Japan

We have investigated the nanofabrication of three-dimensional (3D) chemical vapor deposited (CVD) diamond molds in Electron Cyclotron Resonance (ECR) oxygen ion beam etching technologies using polysiloxane [-R2SiO-]n as an electron beam (EB) mask and a room-temperature (RT)-imprint resist material. The polysiloxane exhibited a negative-exposure characteristic and its sensitivity was 5:5 × 10 -5 C/cm2. The maximum etching selectivity of polysiloxane film against diamond film was 4.7, which was obtained under the following ECR oxygen ion etching conditions: ion energy of 400 eV, ion incidence angle of 0 ° , microwave power of 100 W, gas pressure of 1:4 × 10 -2 Pa and stage temperature of 24 ° C. The diamond molds of cone and tetragonal pyramid dots were fabricated with polysiloxane mask in EB lithography technology using the RT-nanoimprint lithography (NIL) process. The dots are 500, 600, 700, 800, 900 nm in diameter and width respectively. The pitch between the dots is 2 μm, and each dot has a height of about 1 μm. It was found that the optimum imprinting pressure and its depth obtained after the press for 5 min were 0.5 MPa and 0.5 μm respectively. The resulting diameter of each imprinted polysiloxane pattern was in good agreement with that of the 3D-diamond mold. We carried out the RT-NIL process for the fabrication of diamond nanopatterns, using the 3D-diamond molds that we developed. © 2009 The Surface Science Society of Japan.

关键词： Room temperature

来源：评论

学校读者我要写书评

暂无评论

systems architecture for the next generation COMPASS software

Systems architecture for the next generation COMPASS softwar...

引用

2008 Annual Conference of the Transportation Association of Canada: Transportation - A Key to a Sustainable Future, TAC/ATC 2008

作者： Morala, Emmanuel Wong, Hoi Wong, Kam Control Systems Unit Advanced Traffic Management Section Ministry of Transportation of Ontario Canada Software Engineering Systems Engineering Division Delcan Canada

COMPASS is a freeway traffic management system implemented by the Ontario Ministry of Transportation (MTO). Through prompt detection and management of freeway incidents and the provision of accurate and timely traffic information to motorists and the public at large, it improves safety, optimizes capacity and delivers a better level of service to motorists on Ontario's major highways. The first generation of the COMPASS software was deployed in 1990. It has far exceeded its designed life and had undergone numerous functional enhancements and systems expansions. As a preliminary step towards the development of the Next Generation COMPASS Software (NGCS), the need for systems Architecture was identified that provides the framework in implementing the NGCS. Through this exercise, we reviewed and identified functions that will continue to be supported, the lessons learned from years of operational experience, application of the latest software technologies that are end-user friendly and reduce development and maintenance costs. The Intelligent Transportation System (ITS) standards were also examined and we identified the applicable user services that will be adopted and formulated strategic plans for implementation that minimize downtime of the existing operational system. The NGCS will be gradually developed over time as the data and technologies required become available. The functional requirements therefore have also been grouped under different deployment terms (namely, short, medium and long term) based on their readiness and user requirements.

关键词： Intelligent systems

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：