Possible acception criteria for structure functions

This paper deals with the verification of thermal transient evaluation implementations. This subject is relevant because e.g. the upcoming standard will describe the thermal transient measurement as a standard method to estimate the junction-to-case thermal resistance [1], [2], thus anybody can create their own implementation of the evaluation method. We have to have a method to verify these implementations. For this reason we examined the result of the NID (Network Identification by Deconvolution) method from different aspects. For these examinations we defined a multilayer structure as a reference structure and we analytically expressed the unit-step response and the cumulative structure function of this structure. Using the unit-step response as an input data set for the implementation in question we got an approximation of the structure function. Analysing this and the reference RC network we could define a practical maximum tolerance for the deviation between the analytical and the calculated functions.     

Polycarbonate films metalized with a single component molecular conductor suited to strain and stress sensing applications

The paper reports all-organic strain and stress sensitive films that use electrical monitoring approach. The films were prepared by self-metallizing polycarbonate films with the single component molecular conductor [Au(α-tpdt)₂]⁰ (tpdt = 2,3-thiophenedithiolate). It was shown that [Au(α-tpdt)₂]⁰ by its nature is able to form metallic solid material with low crystallinity. Electromechanical tests demonstrated that the developed films are strain-resistive materials with advanced elastic properties: their electrical resistance varies linearly with uniaxial elongation up to relative strain being of 1.0% that is about five times larger than that for conventional metals. The gauge factor of the films is 4.4 and stress sensitivity is 30 Ω/bar. The processing characteristics of polycarbonate films, self-metalized with a metallic [Au(α-tpdt)₂]⁰-based layer, make them potentially useful for engineering flexible, lightweight, strain and pressure sensors. Due to electromechanical characteristics these films are suited to strain sensing applications requiring miniature strain control in a wide deformation range.     

MEMS助力推动下一代无线通信

未来的无线通信系统将具备各种新功能并高度微型化。而且,3代和4代多模/多波段无线终端设备将为新业务、互联网与Mcommerce(移动电子商务)数据、以及静态/视频图象提供网络连接。此外,终端设备也应具备更多新功能来吸引更多终端用户。微电子 机械(microelectromechanical,MEM)元件与系统可提高创新性3代产品的集成化水平,并可调整器件的特性和工作方式,因此可降低3代 图 产品的尺寸和成本。它们还将为 　　　无线系统带来新的体系结构和功耗管理特征。此外,MEMS还将推动新功能、传感器、执行器在无线终端设备上的集成。用户接口需要采用新的技术解决方案。微机械传感器和麦克风已经有元件形式的产品,它们可以被看作是更复杂、包括若干集成化传感器元件的智能系统的一个组成部分。对移动终端来说,娱乐和游戏功能是新功能开发的重要推动力,传感器和执行器也是如此。微反射镜和微透镜为照相机和显示器的实现带来了新的可能,如投影显示。因此MEMS将极大地促进未来无线系统的发展。本文将对 MEMS 在无线通信发展 中的应用进行探讨,首先讨论微系统 化、多功能器件在紧凑系统中的集成、...     

Enhanced efficiency and frequency assignment by optimizing the base stations location in a mobile radio network

Most mobile radio networks have been planned based on the classical cellular concept. However, alternative planning strategies that lead to more efficient network configurations are necessary due to the fact that the traffic density is generally far from constant throughout the service area, making necessary the relocation of base stations inside the traffic hotspots. If the traffic is characterized in a discrete way, the optimization of base stations location resembles vector quantization, a well-known problem in signal processing. In this paper, we use this analogy to propose a mobile radio network planning algorithm. Simulation results show that higher trunking efficiency as well as improved frequency assignment can be obtained if an existing mobile radio network is redesigned using the presented strategy. Raúl Chávez-Santiago was born in Oaxaca City, Mexico. He obtained the B.Sc. degree in communications and electronics engineering in 1997 from the School of Mechanical and Electrical Engineering (ESIME-IPN), and the M.Sc. degree in electrical engineering in 2001 from the Center of Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN) in Mexico City. He has professional experience as Computer Networking Engineer, and Research and Teaching Assistant. Currently, he is completing his studies toward the Ph.D. degree at Ben-Gurion University (BGU) of the Negev, Israel. In 2002, he received the URSI Young Scientist Award. His main research interests are the optimal planning of radio communication networks, the electromagnetic compatibility of terrestrial and satellite radio systems, and the efficient use of the radio spectrum. He is an IEEE and IEICE student member, and a URSI radio scientist. Avi Raymond was born in Yavne, Israel. He received the B.Sc. and M.Sc. degrees in electrical engineering from Ben-Gurion University (BGU) of the Negev in 2000 and 2005, respectively. He worked for two years in a communication company in the field of Telephony and Broadband Services. He also worked as a Research Assistant in the communications laboratory at BGU. He currently works at Elta Electronic Industries Ltd. as System Engineer and pursues studies toward a second M.Sc. degree in systems engineering at the Technion Institute of Technology, Haifa, Israel. His research interests are the optimization algorithms for frequency assignment in cellular networks. Vladimir Lyandres was born in 1944, in Vologda, Russia. He received the M.Sc. degree in communications engineering in 1966 and the Ph.D. degree in communications theory in 1972 from the State University of Telecommunications (SUT), Saint Petersburg, Russia. He was with SUT until 1990 holding a position of Senior Scientific Associate and working on research and development of digital transmission systems, modeling of radio communication channels and algorithms of frequency planning for broadcasting and cellular systems. Since 1991 he holds a position of Researcher at the communications laboratory and Professor at the Department of Electrical and Computer Engineering, Ben-Gurion University (BGU) of the Negev, Israel. His research interests include synthesis of Markov models, combinatorial optimization, and adaptive power loading. He is a senior member of IEEE and member of IEICE.     

Multilayered Distributed Routing for Power Efficient MANET Performance

In this paper a new power efficient routing algorithm for MANETs with self-organizing and self-routing features is described and its performance analyzed in different simulation scenarios. The algorithm has the logic of a non-cooperative routing algorithm based on the evaluation of a weight parameter, the latter being a function of properties of the MANET nodes related to the nominal available power and the transmission range. A self-estimation of this weight parameter for each node is introduced in the routing process based on the status and functional history of the node. The routing is based on network layering, formation of service areas in each layer and choice of nodes from these areas to have the functionality of default gateways. The proposed algorithm, named service zone gateway prediction (SZGP), is a hybrid type of routing mechanism, incorporating pre-computed multipath hop-by-hop distributed routing, with a periodically updated hierarchical multilayered structure. The results from the simulation experiments show that the performance of the proposed SZGP algorithm in relation to the basic performance parameters such as packet delivery ratio, delay and throughput are similar to those of the well-known AODV algorithm, but in relation to power efficiency the proposed algorithm outperforms AODV significantly. This is due to the fact that such an approach reduces the overall number of broadcasts in the network and ensures a reliable and energy efficient connection by balancing the load among the nodes.     

BCI Competition 2003--Data sets Ib and IIb: feature extraction from event-related brain potentials with the continuous wavelet transform and the t-value scalogram

The t-CWT, a novel method for feature extraction from biological signals, is introduced. It is based on the continuous wavelet transform (CWT) and Student's t-statistic. Applied to event-related brain potential (ERP) data in brain-computer interface (BCI) paradigms, the method provides fully automated detection and quantification of the ERP components that best discriminate between two samples of EEG signals and are, therefore, particularly suitable for classification of single-trial ERPs. A simple and fast CWT computation algorithm is proposed for the transformation of large data sets and single trials. The method was validated in the BCI Competition 2003, where it was a winner (provided best classification) on two data sets acquired in two different BCI paradigms, P300 speller and slow cortical potential (SCP) self-regulation. These results are presented here.     

交流调速电梯中的电能质量

因为人们越来越多地使用非线性负载，电网中就存在电源质量问题。在交流传动系统中广泛使用功率变换器，由于其非线性的工作运行状态，导致电压发生畸变，从而影响敏感设备的性能。本文试图分析由功率变换器供电的电梯交流传动系统对电源质量的影响。敏感电气设备和电梯交流传动系统都连接到0．4kV输电线路上。因功率逆变器导致的电压畸变能够导致系统故障甚至电气设备中部分元件的损坏。     

Modeling of Dynamic Effects in a Laser-Driven Semiconductor Switch of High-Power Microwaves

Problems of high-power microwaves penetrating into and reflecting from a semiconductor (silicon) plate with non-stationary processes are investigated. The plate is the basis of switches activated by laser-driven photoconductivity which changes its properties when heated by the switched microwave power. Analytical criteria for the stationary solutions of the activated (quasi-metallic) and deactivated (dielectric) states of the switch under the conditions of high-power microwave heating and external cooling are found. Results of numerical simulations are also given for the problems of the switch activation by microwave heating initiated by pulsed laser radiation, which increases the carrier density rapidly. Numerical simulations are carried out using the finite-difference time-domain method with the unsplit perfectly matched layer absorbing boundary conditions. We demonstrate various types of solutions depending on the basic parameters of the problems - microwave field intensity, laser pulse energy and semiconductor doping.     

Advances in reflective oxygen saturation monitoring with a novel in-ear sensor system: results of a human hypoxia study

Pulse oximetry is a well-established, noninvasive photoplethysmographic method to monitor vital signs. It allows us to measure cardiovascular parameters, such as heart rate and arterial oxygen saturation, and is considered an essential monitoring tool in clinical routine. However, since many of the conventional systems work in transmission mode, they can only be applied to the thinner or peripheral parts of the body, such as a finger tip. This has the major disadvantage that, in case of shock-induced centralization and a resulting drop in perfusion, such systems cannot ensure valid measurements. Therefore, we developed a reflective in-ear sensor system that can be worn in the ear channel like a headphone. Because the sensor is integrated in an ear mold and positioned very close to the trunk, reliable measurement is expected even in case of centralization. An additional advantage is that the sensor is comfortable to wear and has considerable resistance to motion artifacts. In this paper, we report on hypoxia studies with ten healthy participants which were performed to analyze the system with regard to the detection of heart rate and arterial oxygen saturation. It was shown earlier that, due to the high signal quality, heart rate can easily be detected. Using the conventional calculation principle, based on Beer-Lambert's law combined with a single-point calibration method, we now demonstrate that the detection of arterial oxygen saturation in the human ear canal is possible using reflective saturation sensors.     

Cyclobutadiene–C60 Adducts: N‐Type Materials for Organic Photovoltaic Cells with High VOC

New tetraalkylcyclobutadiene–C₆₀ adducts are developed via Diels–Alder cycloaddition of C₆₀ with in situ generated cyclobutadienes. The cofacial π‐orbital interactions between the fullerene orbitals and the cyclobutene are shown to decrease the electron affinity and thereby increase the lowest unoccupied molecular orbital (LUMO) energy level of C₆₀ significantly (ca. 100 and 300 meV for mono‐ and bisadducts, respectively). These variations in LUMO levels of fullerene can be used to generate higher open‐circuit voltages (V_OC) in bulk heterojunction polymer solar cells. The tetramethylcyclobutadiene–C₆₀ monoadduct displays an open‐circuit voltage (0.61 V) and a power conversion efficiency (2.49%) comparable to the widely used P3HT/PCBM (poly(3‐hexylthiophene/([6,6]‐phenyl‐C61‐butyric acid methyl ester) composite (0.58 V and 2.57%, respectively). The role of the cofacial π‐orbital interactions between C₆₀ and the attached cyclobutene group was probed chemically by epoxidation of the cyclobutene moiety and theoretically through density functional theory calculations. The electrochemical, photophysical, and thermal properties of the newly synthesized fullerene derivatives support the proposed effect of functionalization on electron affinities and photovoltaic performance.