We successfully fabricated split alignment sleeves for single-mode operation with the injection-molding technique using both thermosetting epoxy resin and thermoplastic polyetherimide (PEI) resin. The relationship between the surface smoothness and the connection-loss characteristics of these injection-molded plastic sleeves was investigated. We made two-dimensional contour maps of the outer and inner surfaces of the plastic sleeves using the measured surface roughness. There were many contour lines on both the outer and inner surfaces of the PEI sleeve. In contrast, the epoxy sleeves had very smooth surface profiles. An offset Δr was estimated by using the inner-surface roughness data of the sleeve-ferrule contact regions. The connection loss of the sleeve increased as the Δr value increased. The measured losses agree fairly well with the theoretical losses estimated by using the Δr values. The PEI sleeves exhibited large Δr values, and one-third of them had large connection losses of > 0.5 dB. In contrast, the epoxy sleeves had very small Δr values of < 0.6 µm, and exhibited an average loss of < 0.1 dB.

We present novel semiconductor technologies of ZnO epitaxial films with using laser molecular-beam epitaxy method. Exciting optical properties such as room temperature lasing in ZnO nanocrystalline films and quantum size effects in ZnO/MgxZn1-xO superlattices were observed. By developing crystalline quality with using lattice-matched substrates, we could control resistivity of the doped ZnO films from 10-3 Ωcm to 104 Ωcm. These results would provide us an opportunity to construct a monolithic array consisted of light emitting devices and field effect transistors towards a possible flat panel display.

This paper shows how a divisive state clustering algorithm that generates acoustic Hidden Markov models (HMM) can benefit from a tied-mixture representation of the probability density function (pdf) of a state and increase the recognition performance. Popular decision tree based clustering algorithms, like for example the Successive State Splitting algorithm (SSS) make use of a simplification when clustering data. They represent a state using a single Gaussian pdf. We show that this approximation of the true pdf by a single Gaussian is too coarse, for example a single Gaussian cannot represent the differences in the symmetric parts of the pdf's of the new hypothetical states generated when evaluating the state split gain (which will determine the state split). The use of more sophisticated representations would lead to intractable computational problems that we solve by using a tied-mixture pdf representation. Additionally, we constrain the codebook to be immutable during the split. Between state splits, this constraint is relaxed and the codebook is updated. In this paper, we thus propose an extension to the SSS algorithm, the so-called Tied-mixture Successive State Splitting algorithm (TM-SSS). TM-SSS shows up to about 31% error reduction in comparison with Maximum-Likelihood Successive State Split algorithm (ML-SSS) for a word recognition experiment.

With the continuing growth of the World Wide Web (WWW) services over the Internet, the demands for rapid image transmission over a network link of limited bandwidth and economical image storage of a large image database are increasing rapidly. In this paper, a classified binary-tree-structured Self-Organizing Feature Map neural network is proposed to design image vector codebooks for quantizing images. Simulations show that the algorithm not only produces codebooks with lower distortion than the well-known CVQ algorithm but also can minimize the edge degradation. Because the adjacent codewords in the proposed algorithm are updated concurrently, the codewords in the obtained codebooks tend to be ordered according to their mutual similarity which means more compression can be achieved with this algorithm. It should also be noticed that the obtained codebook is particularly well suited for progressive image transmission because it always forms a binary tree in the input space.

The Next Generation Internet Initiative was launched in the U.S. to advance key networking technologies that will enable a new wave of applications on the Internet. Now, in its third year, the program has launched and fostered over one hundred new research projects in partnership with academic, industrial and government laboratories. One key research area that has been emphasized within the program is the next-generation optical networking. Given the ever increasing demand for network bandwidth, and the recent phenomenal advances in WDM technologies, the Next Generation Internet is expected to be an IP-based optical WDM network. As IP over WDM networking technologies mature, a number of important architectural, management and control issues have surfaced. These issues need to be addressed before a true Next Generation Optical Internet can emerge. This paper provides a brief introduction to the overall goals and activities of DARPA's NGI program and describes the key architectural, management, and control issues for the Optical Internet. We review the different IP/WDM networking architectural models and their tradeoffs. We outline and discuss several management and control issues and possible solutions related to the configuration, fault, and performance management of IP over dynamic WDM networks. We present an analysis and supporting simulation results demonstrating the potential benefits of dynamic IP over WDM networks. We then discuss the issues related to IP/WDM traffic engineering in more detail, and present the approach taken in the NGI SuperNet Network Control and Management Project funded by DARPA. In particular, we motivate and present an innovative integrated traffic-engineering framework for re-configurable IP/WDM networks. It builds on the strength of Multi-Protocol Label Switching (MPLS) for fine-grain IP load balancing, and on the strength of Re-configurable WDM networking for reducing the IP network's weighted-hop-distance, and for expanding the bottleneck bandwidth.

We propose a variation of the Context Tree Weighting algorithm for tree source modified such that the growth of the context resembles Lempel-Ziv parsing. We analyze this algorithm, give a concise upper bound to the individual redundancy for any tree source, and prove the asymptotic optimality of the data compression rate for any stationary and ergodic source.

We consider the problem of embedding complete binary trees into 2-dimensional tori with minimum (edge) congestion. It is known that for a positive integer n, a 2n-1-vertex complete binary tree can be embedded in a (2n/2+1)(2n/2+1)-grid and a 2n/2 2n/2-grid with congestion 1 and 2, respectively. However, it is not known if 2n-1-vertex complete binary tree is embeddable in a 2n/2 2n/2-grid with unit congestion. In this paper, we show that a positive answer can be obtained by adding wrap-around edges to grids, i.e., a 2n-1-vertex complete binary tree can be embedded with unit congestion in a 2n/2 2n/2-torus. The embedding proposed here achieves the minimum congestion and an almost minimum size of a torus (up to the constant term of 1). In particular, the embedding is optimal for the problem of embedding a 2n-1-vertex complete binary tree with an even integer n into a square torus with unit congestion.

Flow control algorithm in high speed networks is a resource-sharing policy implemented in a distributed manner. This paper introduces a novel concept of backlog balancing and demonstrates its application to network flow control and congestion control by presenting a rate-based flow control algorithm for ATM networks. The aim of flow control is to maximize the network utilization for achieving high throughput with tolerable delay for each virtual circuit (VC). In a resource-sharing environment, this objective may also cause network congestion when a cluster of aggressive VC's are contending for the same resource at a particular node. The basic idea of our algorithm is to adjust the service rate of each node along a VC according to backlog discrepancies between neighboring nodes (i.e., to reduce the backlog discrepancy). The handshaking procedure between any two consecutive nodes is carried out by a link-by-link binary feedback protocol. Each node will update its service rate periodically based on a linear projection model of the flow dynamics. The updated service rate per VC at a node indicates its explicit demand of bandwidth, so a service policy implementing dynamic bandwidth allocation is introduced to enforce such demands. Simulation study has validated the concept and its significance in achieving the goal of flow control and yet preventing network congestion at the same time.

We study how to generalize a key agreement and password authentication protocol on the basis of the well known hard problems such as a discrete logarithm problem and a Diffie-Hellman problem. The key agreement and password authentication protocol is necessary for networked or internetworked environments to provide the user knowledge-based authentication and to establish a new cryptographic key for the further secure session. The generalized protocol implies in this paper to require only weak constraints and to be generalized easily in any other cyclic groups which preserve two hard problems. The low entropy of password has made it difficult to design such a protocol and to prove its security soundness. In this paper, we devise a protocol which is easy to be generalized and show its security soundness in the random oracle model. The proposed protocol reduces the constraints extremely only to avoiding a smooth prime modulus. Our main contribution is in solving the password's low entropy problem in the multiplicative group for the generalization.

This paper focuses on a single BSA (Basic Service Area) in an infrastructure network and studies the performance of the IEEE 802.11 standard MAC protocol by means of simulation. The MAC protocol supports DCF (Distributed Coordination Function) and PCF (Point Coordination Function). The simulation model includes both data transmission with the DCF and H.263 video transmission with the PCF. In the simulation we assume that the channel transmission rate is 2 Mbps and use the system parameters specified in the standard for the DSSS (Direct Sequence Spread Spectrum) physical layer. We evaluate the performance of this protocol in terms of throughput and MPDU (MAC Protocol Data Unit) delay for various values of the CFP (Contention Free Period) repetition interval and the CFP maximum duration. Numerical results show that if the CFP repetition interval is set too long, video MPDU delay becomes very large periodically; therefore, average video MPDU delay deteriorates. We also find that as the CFP maximum duration decreases, the number of video terminals that can be accommodated in the system decreases. Furthermore, how channel transmission errors affect the performance of the protocol is examined. A two-state continuous-time Markov model is used as a burst error model. As a result, we see that for a small number of video terminals, the average video-MPDU-delay performance does not deteriorate drastically for larger values of bit error rate.

Shared memory multiprocessors are frequently used as compute servers with multiple parallel programs executing at the same time. In such environments, an operating system switches the contexts of multiple processes. When the operating system switches contexts, in addition to the cost of saving the context of the process being swapped out and that of bringing in the context of the new process to be run, the cache performance of processors also can be affected. The blocked algorithm improves cache performance by increasing the locality of memory references. In a blocked program using this algorithm, program performance can be significantly affected by the reuse of a block loaded into a cache memory. If frequent context switching replaces the block before it is completely reused, the cache locality in a blocked program cannot be successfully exploited. To address this problem, we propose a preemption-safe policy to utilize the cache locality of blocked programs in a multiprogrammed system. The proposed policy delays context switching until a block is fully reused within a program, but also compensates for the monopolized processor time on processor scheduling mechanisms. Our simulation results show that in a situation where blocked programs are run on multiprogrammed shared-memory multiprocessors, the proposed policy improves the performance of these programs due to a decrease in cache misses. In such situations, it also has a beneficial impact on the overall system performance due to the enhanced processor utilization.

In this paper, some properties of domain tree languages of top-down pushdown tree transducers (domain(t-PDTT) or t-PDTTD) are shown. It is shown that (1) for any L1, L2 in context-free language (CFL), L1L2yielde(t-PDTTD) (where yielde is an extended yield), (2) yielde(t-PDTTε0DF) is closed under homomorphisms, where t-PDTTε0 is a t-PDTT which can not proceed generations after reading a constant symbol σ and t-PDTTε0DF denotes a domain tree language of t-PDTTε0 with a final state translation, and (3) yielde(t-PDTTε0DF) is the class of recursively enumerable languages, and consequently yielde(t-PDTTD) is the class of recursively enumerable languages.

The constriction resistance of an electric contact has frequently been obtained using a model of only one circular contact spot of radius a. However, cases of a single contact spot are extremely rare as the interface of the electrical contact actually consists of numerous micro-contact spots. A contact is therefore regarded as the aggregate of several micro-contact spots, which are referred to collectively as a cluster. The constriction resistance of the cluster can be calculated as the sum of the self-resistance and mutual resistance of individual micro-contact spots. In the present study, this model is expanded slightly for practical application by normalizing a previous theoretical formula. In order to obtain the constriction resistance for contacts between composite materials and mating metals, EPMA analysis is applied so as to determine real micro-contact spots. Theoretical calculations of the constriction resistance of multiple contact spots is shown to be reasonably consistent with experimental results. In addition, the contact of a composite material and a mating metal is shown to be made up of multispots. The current was recognized experimentally to flow more easily at micro-contact spots in the cluster periphery. These experimental findings coincide with simulation results obtained by theoretical calculations.

We analyze the performance of soft handoff used as intergroup handoff in the fiber-optic cellular system. Performance is evaluated in view of blocking and handoff refused probability. The numerical results show that the smaller the handoff region or the more the channel, the larger the system capacity.

Ferromagnetic Co77Cr20Ta3 layers were deposited on a Pt seed layer by a facing targets sputtering apparatus. The Co-Cr-Ta and Pt crystallites revealed better c-axis orientation at a substrate temperature Ts above 200C. Relatively high perpendicular coercivity Hc⊥ of 2.5 kOe was obtained for the bilayered film with a Co-Cr-Ta layer thickness, δCo, of 50 nm deposited at Ts of 250C. Although the Co-Cr-Ta/Pt medium with δCo of 100 nm exhibited lower recording density than a Co-Cr-Ta/Cr longitudinal one, its noise level became small at the high-density recording range. Measurement of the anomalous Hall voltage clarified that the bilayered film with δCo as small as 30 nm revealed larger perpendicular magnetization than the single layer. The Pt seed layer is effective for depositing thin ferromagnetic Co-Cr-Ta layers below 100 nm in thickness.

This paper describes how to generate, analyze and design a novel current-mode filter model using tunable multiple-output operational transconductance amplifiers and grounded capacitors (MO-OTA-Cs) for synthesizing both transmission poles and zeros. Transfer functions of low-order, high-order, general type, and special type are realized based on the filter model. The theory focuses mainly on establishing a relationship between the cascaded MO-OTA-Cs and the multiple-loop feedback matrix, which makes the structural generation and design formulas. Adopting the theory allows us to systematically generate many interesting new configurations along with some known structures. All the filter architectures contain only grounded capacitors, which can absorb parasitic capacitances and require smaller chip areas than floating ones. The paper also presents numerical design examples and simulation results to confirm the theoretical analysis.

The interconnect analysis of on- and off-chips is very important in the design of high-speed signal processing, digital communication, and microwave electronic systems. When the interconnects are characterized by sampled data via electromagnetic analysis, the circuit-level simulation of the network requires rational approximation of the sampled data. Since the frequency band of the sampled data is more than 10 GHz, the rational function must fit into it at many frequency points. The rational function is approximated using the orthogonal least-squares method. With an increase in the number of the fitting data, the least-squares method suffers from a singularity problem. To avoid this, the sampled data are hierarchically approximated in this paper. Moreover, to reduce the computational cost of the circuit-level simulation, the parameter matrix of the interconnects is approximated by a rational matrix with one common denominator polynomial, and the selective orthogonalization procedure is presented.

This paper presents a three-dimensional polarimetric detection result of targets buried in snowpack by synthetic aperture FM-CW radar system. Since the FM-CW radar is suitable for short range sensing and can be equipped with fully polarimetric capability, we further extended it to a polarimetric three-dimensional SAR system. A field experiment was carried out to image and detect targets in a natural snowpack of 280 cm deep. The polarimetric detection and identification schemes are the polarimetric filtering, three-component decomposition, and the power polarization anisotropy coefficient. These approaches to acquired data show the usefulness of three-dimensional polarimetric FM-CW SAR system.

A constraint resolution scheme in the Hopfield-type neural network named "Neuron Filter" is presented for efficiently solving combinatorial optimization problems. The neuron filter produces an output that satisfies the constraints of the problem as best as possible according to both neuron inputs and outputs. This paper defines the neuron filter and shows its introduction into existing neural networks for N-queens problems and FPGA board-level routing problems. The performance is evaluated through simulations where the results show that our neuron filter improves the searching capability of the neural network with the shorter computation time.

In this letter, we remark a well-known nonlinear filtering technique realize immediate effect to suppress the influence of the additive measurement noise in the input to a set theoretic linear blind deconvolution scheme. Numerical examples show ε-separating nonlinear pre-filtering techniques work suitably to this noisy blind deconvolution problem.