'Crystal bridge' for measuring the equivalent electrical parameters of piezoelectric crystals

The methods and instrumentation for carrying out precise measurements of the equivalent electrical parameters of piezoelectric crystals have been developed. An accuracy exceeding 0.05% has been achieved with low power dissipation in the crystal permitting the use of this system at low temperatures and particularly in applications concerning the detection of gravitational radiation.     

Intermodulation Distortion of FDM-FM in Injection-Locked Oscillator

When an injection-locked oscillator is used to amplify a frequency division multiplexing-frequency modulation FDM-FM signal, second- and third-order distortions are found to exist. Explicit expressions are derived that give the signal-to-distortion ratio (NPR) as a function of the locking bandwidth, frequency offset, and various modulation parameters. These formulas are believed to be valid within the limits of the assumptions made.     

High accuracy quartz crystal thin film monitor

A quartz resonator thin film monitor of exceptionally high accuracy and resolution has been developed. It is capable of providing measurements with an effective resolution of 0.001 nm and a corresponding relative accuracy of about 1% for a 0.100-nm-thick film of gold. A novel dual oscillator and mixer using integrated circuits is also described.     

Controlling structural failure modes during an impact in the presence of uncertainties

A methodology to enforce a given structural dynamic behavior during an impact while accounting for uncertainty is presented. The approach is based on locating structural fuses that weaken the structure locally and help enforce a deformation mode. The problem of enforcing the crushing of a tube impacting a rigid wall is chosen. In order to find the positions of the fuses, the method identifies distinct structural dynamic behaviors using designs of experiments and clustering techniques. The changes in behavior are studied with respect to variations of the fuse positions and random parameters, such as the thickness. Based on the probabilistic distributions, a measure of the likelihood of occurrence of global buckling is defined. The positions of the fuses are defined using an optimization problem in terms of the likelihood of global buckling and the amount of absorbed energy in the tube. A first formulation of the problem considers variability in the tube’s thickness only. A second formulation also accounts for uncertainties in the positions of the fuses.     

A kernel trick for sequences applied to text-independent speaker verification systems

This paper presents a principled SVM based speaker verification system. We propose a new framework and a new sequence kernel that can make use of any Mercer kernel at the frame level. An extension of the sequence kernel based on the Max operator is also proposed. The new system is compared to state-of-the-art GMM and other SVM based systems found in the literature on the Banca and Polyvar databases. The new system outperforms, most of the time, the other systems, statistically significantly. Finally, the new proposed framework clarifies previous SVM based systems and suggests interesting future research directions.     

Location Management in PCS Networks by Caching Two-Level Forwarding-Pointers

One of the challenging tasks in Personal Communication Services (PCS) is to efficiently maintain the location of PCS subscribers who move from one region to another (hereafter called mobile users). When a mobile user receives a call, the network has to quickly determine its current location. The existing location management scheme suffers from high signaling traffic in locating the mobile users. Two-level forwarding pointer scheme has been proposed from per-user forwarding pointer scheme to reduce the cost of signaling traffic. In this paper, we enhance the two-level forwarding pointer scheme. When a mobile user moves from its current Registered Area (RA), which is served by Mobile Switching Center (MSC), to another RA the local switch that acts as a parent of those two MSCs maintains this movement in its memory (hereafter called cache entry). A cache entry is used to locate rapidly the mobile user instead of querying the Home Location Register (HLR) and waiting for its reply. HLR is centralized in the network and far away from the mobile users so that the signaling traffic crossing it is expensive. Sometimes the cache entry may be failed to reach the mobile user then a two-level forwarding pointers will be created from the corresponding Visitor Location Register (VLR), attached to its MSC, through a correct path to locate the mobile user. Thus, there is a saving in cost of querying the underlying HLR. The analytical results indicate that such proposal efficiently reduces the signaling traffic cost for all values of Call to Mobility Ratio (CMR), this is especially considerable when CMR ≥1, without any increase in the call setup delay. Salah M. Ramadan (samohra@yahoo.com) received the BS and MS degrees from Computers Engineering Department, Al-Azhar University, Cairo, Egypt, in 1995 and 2002, respectively. From 2002, he was a Ph.D. student in Computers Engineering Department at Al-Azhar University and is currently pursuing the Ph.D. degree, where he is a research assistant in the Wireless Networks Branch. His research interests include traffic management in ATM networks, routing protocols, mobility management in PCS networks, and mobile computing. He is currently an instructor in Cisco Academy, Egypt. Ahmed M. El-Sherbini (Sherbini@mcit.gov.eg) received the Ph.D. in Electrical and Communication Engineering, Case Western University, U.S.A. March 1983 and M.Sc. in Communication Engineering, Cairo University, Giza, Egypt, June 1980. (M. Sc. Research Studies at the Ecole Nationale Superieure des Telecommunications (ENST), Paris, France). He is the Director, National Telecommunication Institute – Ministry of Communications and Information Technology, Egypt and Professor of Electrical and Communication Engineering Dept. Faculty of Engineering, Cairo University, Egypt. M. I. Marie received his B.Sc., M.Sc. and Ph.D. in electronic and communication engineering from Cairo University on 1972, 1981, 1985, respectively. Now he is a professor of communications at Computer and System Engineering department Al-Azhar University, Cairo, Egypt. His fields of interest includes digital communication, computer networks and protocols development. M. Zaki (azhar@mailer.scu.eun.eg) is the professor of software engineering, Computer and System Engineering Department, Faculty of Engineering, Al-Azhar University at Cairo. He received his B.Sc. and M.Sc. degrees in electrical engineering from Cairo University in 1968 and 1973 respectively. He received his Ph.D. degrees in computer engineering from Warsaw Technical University, Poland in 1977. His fields of interest include artificial intelligence, soft computing, and distributed system.     

Application of terrain analysis to the mapping and spatial pattern analysis of subsurface geological fractures of Kuala Lumpur limestone bedrock,Malaysia

Subsurface geological fractures in karst terrain are often associated with unpredictable environmental and geotechnical engineering problems. This requires precise mapping and an understanding of the distribution of geological fractures on multi-scales. To extract and investigate surface and subsurface geological fractures on such scales, multi-scales, this study presents two approaches. The first involves geological prediction and visual interpretation of terrain parameters using a digital elevation model (DEM). The second is an automatic detection method using a topographical fabric algorithm that uses a DEM to create a map of ridges, which represent the footwalls of geological fractures, and valleys (channels), which reflect geological fracture zones. Unlike wavelet analysis and the Fourier transform, which use optical remote-sensing images, the integration of visual interpretation and a topographical fabric algorithm is capable of the extraction and spatial correlation of subsurface geological fractures. This method was applied to Kuala Lumpur limestone bedrock in Malaysia, by focusing on the adjacent mountainous areas and the geometries of ex-opencast mining ponds. The spatial correlation of the extracted surface geological fractures was clarified by rose diagrams and semivariogram models. Spatial correlation shows that the Malaysian peninsula, surface and subsurface geological fractures and the geometry of ex-opencast mining ponds share similar trends. The results obtained using this methodology is compared to those of subsurface geological fractures reported by means of geophysical surveying and field investigation. This proposed method may be useful for mapping geological fractures in areas of high soil moisture, where geophysical surveying is difficult and/or not available, and is also highly applicable in other parts of Malaysia or Southeast Asia, permitting a better understanding of the geotectonics and geotechnical engineering setting of the study area.     

DSP-PML algorithm for open region DNG meta-material FDTD simulations

The digital signal processing (DSP) algorithms developed for digital filters and the perfectly matched layer (PML) formulations are incorporated with the finite difference time domain (FDTD) method to model open region double-negative (DNG) meta-material electromagnetic problems. In the proposed approach, the dielectric parameters of each FDTD unit cell are interpreted as an infinite impulse response digital filter which can be implemented efficiently using the transpose direct form II. A numerical example carried out in a two-dimensional domain is included to show the validity of the proposed formulation.