检索结果-内蒙古大学图书馆

Intersubband Transitions in InxGa1-xAs/AlGaAs Multiple Quantum Wells for Long Wavelength Infrared Detection

MRS Online Proceedings Library 2003年第1期744卷 1-6页

作者： Workman, Clayton L. Wang, Zhiming Ma, Wenquan George, Christi E. Panneer Selvam, R. Salamo, Gregory J. Zhou, Qiaoying Omar Manasreh, M. Center for Semiconductor Physics in Nanostructures (C-SPIN) and the Microelectronics-Photonics Program University of Arkansas Fayetteville USA Department of Electrical and Computer Engineering University of New Mexico Albuquerque USA

We report on intersubband transitions in InxGa1-xAs/AlGaAs multiple quantum wells (MQWs) grown by molecular beam epitaxy. The conduction band offset for this material system is larger than that of the well known GaAs/AlGaAs system, thus making it possible to design, grow, and fabricate quantum well infrared photodetectors operational beyond the 14 μm spectral region with minimized dark current. We have grown InxGa1-xAs/AlGaAs MQWs with indium compositions ranging from x = 0.08 to 0.20 verified by in situ RHEED oscillations, band offset measurements, and high-resolution X-ray diffraction. Band-to-band transitions were verified by photoluminescence measurements, and intersubband transitions were measured using Fourier transform infrared (FTIR) spectroscopy. Due to the high strain and introduction of dislocations associated with the high indium content, wells with indium compositions above ∼ 0.12 did not result in intersubband transitions at silicon doping levels of 2×1018 cm-3. A thick linear graded InxGa1-xAs buffer was grown below the MQW structures to reduce the strain and resulting dislocations. Intersubband transitions were measured in InxGa1-xAs wells with indium compositions of x = 0.20 and greater when grown on top of the linear graded buffer. In addition to these results, FTIR measurements on InGaAs/AlGaAs MQW multi-color, long-wavelength infrared detector structures are reported.

关键词：

来源：评论

学校读者我要写书评

暂无评论

A Microsensor Based on a Microcantilever Patterned with an Environmentally Sensitive Hydrogel

引用

MRS Online Proceedings Library 2003年第1期729卷 481-486页

作者： Zachary Hilt, J. Gupta, Amit K. Bashir, Rashid Peppas, Nicholas A. NSF Program on Therapeutic and Diagnostic Devices Purdue University West Lafayette USA Biomaterials and Drug Delivery Laboratories School of Chemical Engineering Purdue University West Lafayette USA Department of Electrical and Computer Engineering Purdue University West Lafayette USA Department of Biomedical Engineering Purdue University West Lafayette USA

A process was developed for patterning thin films of environmentally sensitive hydrogels onto silicon microcantilevers. Microcantilevers have been shown to be ultra-sensitive transducers for chemical, physical, and biological microsensors. By patterning environmentally sensitive hydrogels onto silicon microcantilevers, novel microsensors were prepared for MEMS and BioMEMS applications. Specifically, a cross-linked poly(methacrylic acid) (PMAA) network containing significant amounts of poly(ethylene glycol) dimethacrylate (PEGDMA) was studied. This hydrogel exhibits a swelling dependence on pH. By increasing the environmental pH above the pKa of PMAA to cause ionization of the carboxylic acid groups, electrostatic repulsion is produced along the main polymer chain causing the polymer network to expand and swell. Therefore, a pH change induces swelling or shrinking of the polymer network and creates stress on the microcantilever surface causing it to bend. In this study, silicon microcantilevers were fabricated on p-type (100) SOI wafers. Covalent adhesion was gained between the polymer and the silicon surface through the modification of the silicon surface with ?-methacryloxypropyl trimethoxysilane. Hydrogels were patterned onto the silicon microcantilevers utilizing a mask aligner to allow for precise positioning. The micropatterned hydrogels were analyzed using optical microscopy and profilometry. The bending response of patterned cantilevers with a change in environmental pH was observed, providing proof-of-concept for a MEMS/BioMEMS sensor based on microcantilevers patterned with environmentally sensitive hydrogels.

关键词：

来源：评论

学校读者我要写书评

暂无评论

A multi-paradigm simulator for simulating complex adaptive supply chain networks

A multi-paradigm simulator for simulating complex adaptive s...

引用

Simulation Winter Conference

作者： Pathak Dilts Biswas Management of Technology Program (EECS) Vanderbilt University Nashville TN USA Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN USA

This paper introduces a multi-paradigm dynamic system simulator based on discrete time and discrete event formalism for simulating a supply chain as a complex adaptive system. Little is known about why such a diversity of supply chain structures exist. Simulating dynamic supply chain networks over extended periods using the multi-paradigm dynamic system simulator allows us to observe the emergence of different structures. The simulator is implemented using a software agent technology, where individual agents represent firms in a supply chain network. In this paper, we present an example scenario run on the simulator and the preliminary results that have been observed. This multi-paradigm tool provides a valuable investigation instrument for real life supply chain problems.

关键词： Adaptive systems Supply chains Vehicle dynamics Discrete event simulation Manufacturing industries Technology management Software agents Supply chain management Procurement computer industry

来源：评论

学校读者我要写书评

暂无评论

Probabilistic contention window control in 802.11 WLANs

Probabilistic contention window control in 802.11 WLANs

引用

IEEE Pacific Rim Conference on Communications, computers and Signal Processing

作者： E.M. Cheung G.W. Wong R.W. Donaldson Science One Program University of British Columbia Vancouver BC Canada Department of Electrical and Computer Engineering University of British Columbia Vancouver BC Canada

In IEEE 802.11 wireless local area networks (WLANs); the binary exponential backoff (BEB) algorithm is used in the medium access control (MAC) protocol to resolve contortion problems. Unfortunately, BEB has been shown to be highly short-term unfair. In this paper, we propose a probabilistic contention window control mechanism to improve the fairness of the backoff procedure and we evaluate its performance on real-time applications such as voice over IP and video conferencing. Simulation results reveal improvements in fairness and throughput, without detriment to delay and jitter.

关键词： Wireless LAN Media Access Protocol Access protocols Wireless application protocol Ethernet networks Wireless sensor networks Space stations Intelligent networks Electronic mail Internet telephony

来源：评论

学校读者我要写书评

暂无评论

Frequency domain analysis of heart rate variability in sleep disordered breathing

Frequency domain analysis of heart rate variability in sleep...

引用

Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： S. Vijendra K. Behbehani J.R. Burk E.A. Lucas D.H. Dao H. Nazeran Biomedical Engineering Program University of Texas Arlington USA Sleep Consultants Inc. Fort Worth TX USA Department of Electrical and Computer Engineering University of Texas El Paso TX USA

Frequency domain analysis of the R-R intervals was performed in subjects with and without sleep disordered breathing (SDB). Data from Physionet's Apnea-ECG database as well as data collected at our sleep disorders clinic were used for this study. 15-minute ECG epochs were selected from polysomnography data. Power spectrum analysis of the resampled R-R interval series (1.2 Hz) was performed using Welch's averaged periodogram method. Normalized power in two bands, AB/sub 1/ (0.019 to 0.071 Hz) and AB/sub 2/ (0.019 to 0.036 Hz) were used to compare the impact of SDB events on the spectrum of R-R intervals. Normalized AB/sub 1/ power produced a sensitivity of 76% and a specificity of 100% in the data from the Apnea-ECG database. The same parameter produced a sensitivity of 76% and specificity of 52% in the data collected at our sleep laboratory. This difference in the results may be attributed to the severity and duration of SDB events present in the two datasets.

关键词： Frequency domain analysis Heart rate variability Sleep Electrocardiography Databases Performance analysis Neural networks Biomedical engineering Data analysis Laboratories

来源：评论

学校读者我要写书评

暂无评论

Carbon nanotube growth from Cu-Co alloys for field emission applications

Carbon nanotube growth from Cu-Co alloys for field emission ...

引用

IEEE International Conference on Vacuum Microelectronics (IVMC)

作者： W. Hofmeister W.P. Kang Y.M. Wong J.L. Davidson Interdisciplinary Graduate Program in Material Science Vanderbilt University Nashville TN USA Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN USA

We have used Cu-Co alloy to generate uniform distribution of Co precipitates, and successfully grown CNTs by CVD on the Cu support.

关键词： Carbon nanotubes Conducting materials Transistors Application software Cobalt alloys Copper alloys Materials science and technology Hydrocarbons Chemical vapor deposition Nanocrystals

来源：评论

学校读者我要写书评

暂无评论

A new maximum power point tracking controller for photovoltaic power generation

A new maximum power point tracking controller for photovolta...

引用

Annual IEEE Conference on Applied Power Electronics Conference and Exposition (APEC)

作者： Yang Chen K. Smedley F. Vacher J. Brouwer Department of Electrical and Computer Engineering University of California Irvine Irvine CA USA Advanced Power & Energy Program University of California Irvine Irvine CA USA

This paper proposes a new maximum power point tracking (MPPT) method in combination with one-cycle control for photovoltaic power generation. This control scheme is based on the automatic current-adjusting feature of one-cycle control. The output current of the inverter can be adjusted according to the voltage of the photovoltaic (PV) array so as to extract the maximum power from it. In the mean time, one-cycle control guarantees that the output current is in the same shape of and in phase with the grid voltage. All these are accomplished in one power stage and a simple control circuit. No detection and calculation of power are needed. Compared with previously proposed approaches, this method is much more efficient and more cost-effective and yet exhibits excellent performance. The principle is explained qualitatively and extensive experiments have been carried out to verify and validate the proposed method.

关键词： Photovoltaic systems Solar power generation Circuits Voltage Control systems Inverters Costs Power generation Automatic control Shape control

来源：评论

学校读者我要写书评

暂无评论

Non-linear interferometric vibrational imaging

Non-linear interferometric vibrational imaging

引用

Conference on Lasers and Electro-Optics (CLEO)

作者： J.S. Bredfeldt D.L. Marks S. Hambir D. Dlott S.A. Boppart Department of Electrical and Computer Engineering University of Illinois Urbana-Champaign USA School of Chemical Sciences University of Illinois Urbana-Champaign USA Department of Electrica1 and Computer Engineering Bioengineering Program College of Medicine University of Illinois Urbana-Champaign Urbana IL USA

来源：评论

学校读者我要写书评

暂无评论

Pricing mediated bandwidth allocation for the next generation Internet

Pricing mediated bandwidth allocation for the next generatio...

引用

IEEE Conference and Exhibition on Global Telecommunications (GLOBECOM)

作者： B.M. Ninan M. Devetsikiotis Operations Research Program North Carolina State University Raleigh NC USA Department of Electrical and Computer Engineering North Carolina State University Raleigh NC USA

In this paper, we model users of next generation services by means of utility differentiated classes. Noncooperative game theory is employed to explain user behavior with respect to the network price. Rate control algorithms for attaining such a noncooperative Nash equilibrium are then presented. We extend our previous model of a single link fed by Poisson traffic to encompass a generic network and non-Poisson traffic. These results can be applied to a wide variety of future networks ranging from LSPs in MPLS networks to wavelength paths in WDM networks.

关键词： Pricing Channel allocation Internet Communication system traffic control Traffic control WDM networks Microeconomics Control systems Bandwidth Telecommunication traffic

来源：评论

学校读者我要写书评

暂无评论

Realization adaptive strategies and a comparison of Fourier bandwidth, Shannon bandwidth, and Campbell bandwidth

Realization adaptive strategies and a comparison of Fourier ...

引用

Data Compression Conference (DCC)

作者： Wenye Tang Tao He J.D. Gibson Globespan Virata Inc. Red Bank NJ USA Electrical Engineering Department Southern Methodist University Dallas TX USA Media Arts and Technology Program & Electrical and Computer Engineering University of California at Santa Barbara Santa Barbara CA USA

In 1960, Campbell derived a quantity that he defined as the coefficient rate of a random process that involves the process spectral entropy. However, no potential applications of the coefficient rate were identified. Two new derivations of Campbell's rate coefficient rate are presented. One derivation solidifies the interpretation of this quantity as a coefficient rate and allows definition of an effective bandwidth for the process. The second derivation implies a new approach for realization adaptive source compression. The coefficient rate can be used for realization adaptive coefficient selection in a sequence of source representations. Furthermore, the effective bandwidth is designated as Campbell bandwidth and contrasted with Fourier bandwidth and Shannon bandwidth. Several specific examples are presented that illustrate the differences among the three quantities.

关键词： Bandwidth Entropy Random processes Electronic mail Image coding Speech processing Discrete cosine transforms Energy measurement Helium Codes

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：