Waves Past Porous Structures in a Two-layer Fluid

Havelock’s type of expansion theorems, for an integrable function having a single discontinuity point in the domain where it is defined, are utilized to derive analytical solutions for the radiation or scattering of oblique water waves by a fully extended porous barrier in both the cases of finite and infinite depths of water in two-layer fluid with constant densities. Also, complete analytical solutions are obtained for the boundary-value problems dealing with the generation or scattering of axi-symmetric water waves by a system of permeable and impermeable co-axial cylinders. Various results concerning the generation and reflection of the axisymmetric surface or interfacial waves are derived in terms of Bessel functions. The resonance conditions within the trapped region are obtained in various cases. Further, expansions for multipole-line-source oblique-wave potentials are derived for both the cases of finite and infinite depth depending on the existence of the source point in a two-layered fluid.     

Robust Stabilization of Delayed Singular Systems with Linear Fractional Parametric Uncertainties

This paper deals with the problem of robust stabilization for delayed singular systems with parametric uncertainties. The parametric uncertainties are assumed to be of a linear fractional form involving all system matrices. Necessary and sufficient conditions for quadratic stability and quadratic stabilization are obtained. Moreover, the results generalize and improve previous works on delayed singular systems with norm-bounded parametric uncertainties. A strict linear matrix inequality (LMI) design approach is developed such that, when the LMI is satisfied, a desired robust state feedback control law can be constructed. A numerical example is provided to demonstrate the application of the proposed method.     

A Novel Terahertz Rat-Race Hybrid Coupler Based on PPDW

A novel rat-race hybrid coupler based on parallel-plate dielectric waveguide (PPDW) is proposed. PPDW has been proposed as a basic terahertz transmission line for its remarkable simple structure and comparatively low attenuation at terahertz frequency band. It can be applied to design many terahertz components. In this paper, a (3 N + 3/2) × lambda circumference PPDW rat-race hybrid coupler operating at quasi-TE₁₀ mode is studied. The investigation results show that, at 0.34 THz, the transmission losses of the two split output ports are both equals −3.2 dB; the return loss at its input port is below −20 dB; the insertion loss at each split transmission port is less than 0.2 dB; and the two isolated ports show good isolation of above 20 dB. Therefore, it will have wide potential applications at terahertz frequency band.     

Comparative Assessment of Adaptive Body-Bias SOI Pass-Transistor Logic

A very low voltage transconductor for video frequency range applications and compatible with standard CMOS technology is described. In the proposed transconductor, except the DC level shifter circuit (DCLS), the whole transconductor uses the main supply voltage [which can be as low as 1.5 V in a standard 0.6 μm CMOS technology] while the DCLS uses a simple charge-pump circuit as its supply voltage and has a very low current consumption. In addition, proper common-mode sense and charge-pump circuits are developed for this low-voltage application. Meanwhile, some techniques to improve the frequency response, linearity, and noise performance of the proposed transconductor are described. In a standard 0.6 μm CMOS technology and single 1.5 V supply, simulations show that the proposed transconductor futures a THD of −50 dB for 1.4 V_pp and 10 MHz input signal and −60 dB for 1.4 V_pp and 1 MHz signal where the threshold voltage of MOS transistors could be as high as 1 V. Based on the proposed transconductor, a lowpass filter with 700 kHz to 8 MHz programmable cutoff frequency and a bandpass 10.7 MHz second order filter were implemented. Armin Tajalli received the B.Sc. from Sharif University of Technology (SUT), Tehran, Iran, in 1997, and M.Sc. from Tehran Polytechnic University, Tehran, Iran, in 1999. From 1998 he has joint Emad Co. as a senior design engineer were he has worked on several industrial and R&D projects on analog and mixed-mode ICs. He received the award of the Best Design Engineer from Emad Co., 2001, the Kharazmi Award of Industrial Research and Development, Iran, 2002, and Presidential Award of the Best Iranian Researchers, in 2003. He is now working toward his PhD degree at SUT. His current interests are design of high speed circuits for telecommunication systems. Mojtaba Atarodi received the B.S.E.E. from Amir Kabir University of Technology (Tehran Polytechnic) in 1985, and M.Sc. degree in electrical engineering from the University of California, Irvine, in 1987. He received the Ph.D. degree from the University of Southern California (USC) on the subject of analog IC design in 1993. From 1993 to 1996 he worked with Linear Technology Corporation as a senior analog design engineer. Since then, he has been consulting with different IC companies. He is currently a visiting professor at Sharif University of Technology. He has published more than 30 technical papers in the area of analog and mixed-signal integrated circuit design as well as analog CAD tools.     

MobileNAT: A New Technique for Mobility Across Heterogeneous Address Spaces

We propose a new network layer mobility architecture called Mobile NAT to efficiently support micro and macro-mobility in and across heterogeneous address spaces common in emerging public networks. The key ideas in this architecture are as follows: (1) Use of two IP addresses – an invariant virtual IP address for host identification at the application layer and an actual routable address at the network layer that changes due to mobility. Since physical address has routing significance only within a domain, it can be a private address and therefore, does not deplete the public IP address resource. (2) New DHCP enhancements to distribute the two addresses. (3) A new signaling element called Mobility Manager (MM) that uses Middlebox Communication (MIDCOM) framework to signal the changes in packet processing rules to the Network Address Translators (NATs) in the event of node mobility. Our proposal does not require any modifications to the access networks and can seamlessly co-exist with the existing Mobile IP mechanisms and therefore, can be used to provide seamless mobility across heterogeneous wireline and wireless networks. We report implementation details of a subset of our ideas in a testbed with Windows XP clients and Linux based NATs. Milind M. Buddhikot is a Member of Technical Staff in the Center for Networking Research at Lucent Bell Labs, Holmdel, NJ. Milind holds a Doctor of Science (D. Sc.) in computer science (July 1998) from Washington University in St. Louis, and a Master of Technology (M.Tech.) in communication engineering (December 1988) from the Indian Institute of Technology (I.I.T), Bombay. His current research interests are in the areas of systems and protocols for integrated public wireless networks, authentication and dynamic key exchange protocols, Voice-over-IP (VOIP) networks, and sensor and ad-hoc networks. He has authored over 26 research papers and 9 patent submissions in the areas of design of multimedia systems and protocols, layer-4 packet classification, MPLS path routing, authentication and dynamic key exchange, and 802.11/3G integration. Milind currently serves as the Associate Editor of the IEEE/ACM Transactions on Networking. He also served as a co-guest-editor of IEEE Network magazine’s March 2001 Special issue on Fast IP Packet forwarding and Classification for Next Generation Internet Services. He has served in the capacity of a tutorial chair for IEEE LCN 94, 95, as a publicity chair for NOSSDAV97, and as a program committee member for MMCN 2001, 2003, IEEE ICNP2002, 2003 and IEEE LCN 93-2000 conferences. Adiseshu Hari received a Doctorate in Computer Science from Washington University in St. Louis in 1999, and has since been at Bell Labs, Lucent Technologies, where he’s worked on projects related to network design and optimization. He’s currently looking at design issues in large scale SIP based VoIP networks. Kundan N. Singh received a B.E.(Hons) degree in Computer Science from Birla Institute of Technology and Science in India, M.S. in Computer Science from Columbia University, and is continuing his studies towards Ph.D. degree in the same field at Columbia University in New York City. As a research assistant in the Internet Real-Time Lab at Columbia University, he is doing research on Internet telephony, SIP-H.323 signaling gateway, unified messaging systems and multimedia conferencing. Scott Miller is the Director of the High Speed Mobile Data Research department at Bell Labs in Holmdel, New Jersey. He has B.S. and M.S. degrees in electrical engineering from Cooper Union in New York City. His current research involves the integration of 802.11 and 3G wireless data service and the related mobile networking issues concerning seamless mobility, authentication, security, roaming, and accounting. Prior to his work on 802.11/3G integration, Scott has led several systems research efforts in wireless applications, implementing novel systems for wireless messaging, speech-driven directory services, wireless instant messaging, carrier-based content billing, and multi-media content adaptation.This revised version was published online in August 2005 with a corrected cover date.     

Unsupervised Segmentation of Stereoscopic Video Objects: Constrained Segmentation Fusion Versus Greedy Active Contours

In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.     

Study on BMT Millimeter Wave Dielectric Resonators

The microwave dielectric properties and microstructures of Ba(Mg_1/3Ta_2/3)O₃ (BMT) ceramics were investigated. In order to reduce the evaporation of MgO at high temperature, burying in MgO powders sintered BMT ceramics. The relationship between the composition and Q value of BMT ceramics was discussed. Dielectric resonators using in millimeter wave band have been designed and fabricated. Their attenuations at central resonation frequency (τ_f) are less than 35dB. Temperature coefficients of resonant frequency are adjustable and less than 2 ppm/°C.     

Analysis of Inner-Scale Effect on Atmosphere Scintillation for Infrared Laser Beam Propagating on Earth-Space Paths

On Earth-space paths, based on ITU-R C _n ² (h) model, by means of a modification of the Rytov method that incorporates an amplitude spatial frequency filter function under strong fluctuation conditions, considering atmospheric turbulence inner-scale, an expression is developed for the scintillation index of a visible or a near and middle infrared laser beam wave that is valid under moderate to strong irradiance fluctuations. The quantitative analyses of scintillation index are done by this analytic model for laser Gaussian collimated beam wave at visible or near and middle infrared wave band. The results agree with theoretic analysis scintillation. This scintillation model can be converted into a Gaussian beam wave model with finite inner-scale on horizontal sight paths of invariable C _n ².     

Two-view tomography of low-temperature plasma

Emission tomography is a promising method for the diagnostics of thelateral uniformity of plasma components. However, the technological features of microelectronics allow one to use a strictly limited number of views, which adversely affects the quality of the reconstruction. The earlier proposed model of local inhomogeneities (MLI) allows one to resolve the diagnostic difficulties of the lateral homogeneity of the components of low-temperature plasma in the case of the two-view fan-like scanning scheme. In this work, the model is supplemented taking into account an additional factor affecting the accuracy of the tomographic reconstruction, namely, the dependence of the radiation intensity recorded by the optical angular sensor upon the distance to the radiating plasma particle. This was taken into account for the tomographic reconstruction using the method of the maximum entropy, which is basic for MLI.