Long-period gratings (LPGs) are written in the fibers un-preheated and preheated. The influence of residual stress on trimming resonance wavelengths by heating the LPGs is investigated comparing the post-heating changes of the transmission characteristics. It becomes evident that the residual stress relaxation shifts resonance wavelengths to shorter wavelengths quickly and the glass structure modification moves them to longer wavelengths slowly. The relaxation rate of the glass structure drops rapidly with the decrease in heating temperature, and the influence of the residual stress relaxation appears more strongly at the early stage of heating at a lower temperature. The trimming wavelength range can be broadened on the short wavelength side by decreasing the heating temperature. We could adjust resonance wavelengths without significant peak loss changes by the residual stress relaxation before writing LPGs, though the trimming range becomes narrow.

The present paper describes a quality enhancement of speech corrupted by additive background noise in a single channel system. The proposed approach is based on the introduction of perceptual criteria using a frequency-weighting filter in a subtractive-type enhancement process. This newly developed algorithm allows for an automatic adaptation in the time and frequency of the enhancement system and finds a suitable noise estimate according to the frequency of the corrupted speech. Experimental results show that the proposed approach can efficiently remove additive noise related to various types of noise corruption.

Two ways of introducing alternation for context-free grammars and pushdown automata are compared. One is the usual way which combines "states" with alternation [1], [4], [7], and the other is the way used in [6] to define the alternating context-free grammar, i.e., alternation is governed by the variables of the grammar. In this paper the latter way is taken over to define a new type of alternating pushdown automaton by combining the "pushdown symbols" of the pushdown automaton with alternation. We have derived a characterization of the original alternating context-free grammars in terms of such a new type of alternating pushdown automaton without states. It is also shown that, if (non-alternating) states are introduced as an additional feature for this type of pushdown automaton, then the resulting alternating pushdown automaton has exactly the same expressive power as the original alternating pushdown automaton.

A new radio-frequency (RF) radiated immunity/susceptibility test method using four-septum TEM cell is proposed. A rotating-EM field can be generated inside the cell by feeding four-different RF DSB-SC signals to four septa arranged in the cell. Since a polarization plane of the rotating-EM field rotates in a low speed, the immunity/susceptibility test for the EM field with various polarizations can be conducted more easily. In this paper, a technique for generating the rotating-EM field in the cell is investigated. The basic characteristics of the cell and the rotating-EM field by using the technique are clarified. To verify the validity of this test method, a RF radiated susceptibility of a printed circuit board is measured. The measured results are verified by comparing with the theoretical results based on modified telegrapher's equations.

A proactive cluster-based distance vector routing protocol based on DSDV protocol is proposed for mobile ad hoc networks. A network is divided into a number of clusters, each cluster having a clusterhead that directly connects the other nodes in the same cluster. Each clusterhead broadcasts update request (UREQ) messages at reqular intervals or in an event driven manner to its neighbor clusterheads. In this way, clusterheads update their own global routing tables that give a path among all clusterheads. In this process, multiple local paths from source clusterhead to its neighbor clusterheads are established as well. A node having a packet to send forwards the packet to its own clusterhead. The clusterhead determines next clusterhead with respect to the destination clusterhead by looking up its own global routing table. Then, the packet is delivered to the next clusterhead along a local path. The advantages of this protocol are threefold. The size of a global routing table is small since it has entries only for clusterheads. A UREQ message travels up from the initiating clusterhead to neighbor clusterheads. Hence, the convergence range of a update request is at least nine times as wide as that of DSDV or CGSR, increasing the correctness of routing. Lastly, a technique to bypass clusterheads, whenever possible, on the fly during packet transmission is presented, to reduce route length as well as to prevent clusterheads from becoming congested. Simulation results show that PCDV outperforms some key protocols of the same category greatly.

With advances in ubiquitous environments, user demand for easy data-lookup is growing rapidly. Not only users but intelligent ubiquitous applications also require data-lookup services for a ubiquitous computing framework. This paper proposes a backward-compatible, searchable virtual file system (S-VFS) for easy data-lookup. We add search functionality to the VFS, the de facto standard abstraction layer over the file system. Users can find a file by its attributes without remembering the full path. S-VFS maintains the attributes and the indexing structures in a normal file per partition. It processes queries and returns the results in a form of a virtual directory. S-VFS is the modified VFS, but uses legacy file systems without any modification. Since S-VFS supports full backward compatibility, users can even browse hierarchically with the legacy path name. We implement S-VFS in Linux kernel 2.6.7-21. Experiments with randomly generated queries demonstrate outstanding lookup performance with a small overhead for indexing.

One approach to accommodating IP traffic on a wavelength division multiplexing (WDM) network is to construct a logical topology, establishing a set of lightpaths between nodes. The lightpaths carry IP traffic but do not require any electronic packet processing at intermediate nodes, thereby reducing the load on those nodes. When the IP and WDM networks have independent routing functions, however, the lightpaths in the WDM network may not be fully utilized by the IP router. It is therefore necessary to integrate the two routing mechanisms in order to utilize resources efficiently and adapt to changes in traffic. In this paper, we propose an integrated routing mechanism for IP over WDM networks. The key idea is to first prepare a set of virtual-links representing the lightpaths that can be established by the WDM network, then calculate the minimum cost route on an IP network including those links. Our simulation results show that when traffic patterns do not change, the throughput of our method is almost the same as that of a logical topology optimally designed for a given traffic demand. When traffic patterns change, the throughput of our method is about 50% higher than that of the logical topology.

In numerical simulations of microwave structures using the alternating-direction implicit finite-difference time-domain (ADI-FDTD) method, the time marching scheme comprises two sub-iterations, where different updating schemes for evaluating E and H fields at each sub-iteration can be adopted. In this paper, the E-field implicit-updating (EFIU) and H-field implicit-updating (HFIU) schemes are compared with each other especially with regard to the implementation of local boundary conditions.

We propose constant-round protocols for interval tests, equality tests, and comparisons where shared secret inputs are not given bitwise. In [9]. Damgård et al. presented a novel protocol called the bit-decomposition, which can convert a polynomial sharing of an element in prime field Zp into sharings of bits. Though, by using the bit-decomposition protocol, those protocols can be constructed with constant round complexities theoretically, it involves expensive computation, leading to relatively high round and communication complexities. In this paper, we construct more efficient protocols for those protocols without relying on the bit-decomposition protocol. In the interval test protocol, checking whether a shared secret exists in the known interval is reduced to checking whether a bitwise-shared random secret exists in the appropriate interval. In the comparison protocol, comparing two shared secrets is reduced to comparing the two secrets viaindirectly where p is an odd prime for an underlying linear secret sharing scheme. In the equality test protocol, checking whether two shared secrets are equal is reduced to checking whether the difference of the two secrets is zero and furthermore checking whether the difference is a zero is reduced to checking quadratice residuosity of a random secret in a probabilistic way.

The latest LSIs still lack performance in pattern matching and picture recognition. Living organisms, on the other hand, devote very little energy to processing of this type, suggesting that they operate according to a fundamentally different concept. There is a notable difference between the two types of processing: the most similar pattern is always chosen by the conventional digital pattern matching process, whereas the choice made by an organism is not always the same: both the most similar patterns and other similar patterns are also chosen stochastically. To realize processing of this latter type, we examined a calculation method for stochastically selecting memorized patterns that show greater similar to the input pattern. Specifically, by the use of a random voltage sequence, we executed stochastic calculation and examined to what extent the accuracy of the solution is improved by increasing the number of random voltage sequences. Although calculation of the Manhattan distance cannot be realized by simply applying stochastic computing, it can be done stochastically by inputting the same random voltage sequence to two modules synchronously. We also found that the accuracy of the solution is improved by increasing the number of random voltage sequences. This processor operates so efficiently that the power consumption for calculation does not increase in proportion to the number of memorized vector elements. This characteristic is equivalent to a higher accuracy being obtained by a smaller number of random voltage sequences: a very promising characteristic of a stochastic associative processor.

Blueweb is a self-organizing Bluetooth-based multihop network equipped with a scatternet formation algorithm and a modified source routing protocol. In this paper, we first review the basic Blueweb network. Then we focus on a heuristic automatic configuration algorithm which can be used to partition a large-scale Blueweb network. This algorithm contains three main functional blocks including route master selection, node assignment, and subnet number decision. The route master selection block selects new route masters at a low computation cost. The node assignment block assigns nodes to each newly configured subnet in order to minimize the average route query cost. The subnet number decision block determines the optimal number of subnet which achieves the largest system performance improvement ratio at minimum operation cost. With these three functional blocks, optimal network configuration for Blueweb routing protocol can be determined. Computer simulations show that a configured Blueweb achieves higher network capacity than an unconfigured Blueweb.

This report presents Dual Field-modulating-Plates (Dual-FP) technology for a 28 V operated high power GaAs heterojunction FET (HJFET) amplifier. A developed HJFET has two FP electrodes; the 1st-FP is connected to the gate and the 2nd-FP to the ground. The 2nd-FP suppresses the drain current dispersion effectively cooperating with the 1st-FP, and it can also reduce the gate-drain parasitic capacitance. The developed push-pull amplifier, with four Dual-FPFET chips, demonstrated 55.1 dBm (320 W) output power with a 14.0 dB linear gain and a drain efficiency of 62% at 2.14 GHz. Under two-carrier W-CDMA signals, it showed a high drain efficiency of 30% and low third-order Inter-modulation distortion of -37 dBc at output power of 47.5 dBm.

Two-dimensional discrete wavelet transform (DWT) for processing image is conventionally designed by line-based architectures, which are simple and have low complexity. However, they suffer from two main shortcomings - the memory required for storing intermediate data and the long latency of computing wavelet coefficients. This work presents a new block-based architecture for computing lifting-based 2-D DWT coefficients. This architecture yields a significantly lower buffer size. Additionally, the latency is reduced from N2 down to 3N as compared to the line-based architectures. The proposed architecture supports the JPEG2000 default filters and has been realized in ARM-based ALTERA EPXA10 Development Board at a frequency of 44.33 MHz.

With the rapid development of wireless network technologies, heterogeneous networks with wired and wireless links are becoming common. However, the performance of TCP data transmission deteriorates significantly when a TCP connection traverses such networks, mainly because of packet losses caused by the high bit error rate of wireless links. Many solutions for this problem have been proposed in the past literature. However, most of them have various drawbacks, such as difficulties in their deployment by the wireless access network provider and end users, violation of TCP's end-to-end principle by splitting the TCP connection, or inapplicability to IP-level encrypted traffic because the base station needs to access the TCP header. In this paper, we propose a new mechanism without such drawbacks to improve the performance of TCP over wired and wireless heterogeneous networks. Our mechanism employs a receiver-based approach, which does not need modifications to be made to the sender TCP or the base station. It uses the ACK-splitting method for increasing the congestion window size quickly in order to restrain the throughput degradation caused by packet losses due to the high bit error rate of wireless links. We evaluate the performance of our mechanism and show that our mechanism can increase throughput by up to 94% in a UMTS network. The simulation results also show that our mechanism does not significantly deteriorate even when the receiver cannot perfectly distinguish whether packet losses are due to network congestion or bit errors on the wireless links.

We consider the capacitated multi-source multicast tree routing problem (CMMTR) in an undirected graph G=(V,E) with a vertex set V, an edge set E and an edge weight w(e) ≥ 0, e ∈ E. We are given a source set S ⊆ V with a weight g(e) ≥ 0, e ∈ S, a terminal set M ⊆ V-S with a demand function q : M → R+, and a real number κ > 0, where g(s) means the cost for opening a vertex s ∈ S as a source in a multicast tree. Then the CMMTR asks to find a subset S′⊆ S, a partition {Z1,Z2,...,Zl} of M, and a set of subtrees T1,T2,...,Tl of G such that, for each i, ∑t∈Ziq(t) ≤ κ and Ti spans Zi∪{s} for some s ∈ S′. The objective is to minimize the sum of the opening cost of S′and the constructing cost of {Ti}, i.e., ∑s∈S′g(s)+w(Ti), where w(Ti) denotes the sum of weights of all edges in Ti. In this paper, we propose a (2ρUFL+ρST)-approximation algorithm to the CMMTR, where ρUFL and ρST are any approximation ratios achievable for the uncapacitated facility location and the Steiner tree problems, respectively. When all terminals have unit demands, we give a ((3/2)ρUFL+(4/3)ρST)-approximation algorithm.

In this paper we modeled and analyzed the ridge type InGaAlAs/InP semiconductor laser with lateral current confinement structure, and optimized the design for the ridge wave guide with the current confinement. We proposed and fabricated the ridge type InGaAlAs/InP laser with a cost effective selective undercut etching method and demonstrated the improvement of the ridge laser performance. This paper provides a solution to solve the cost/yield issue for conventional BH (buried hetero-structure) type laser and performance issue for conventional ridge type laser.

In human-computer interaction, Fitts' law has been applied in one-dimensional pointing task evaluation for some decades, and the usage of effective target width (We) in Fitts' law has been accepted as an international standard in ISO standards 9241-9 [4]. However, the discussion on the concrete methods for calculating We has not been developed comprehensively nor have the different methods of calculation been integrated. Therefore, this paper focuses on a detailed description and a comparison of the two main We calculation methods. One method is mapping all the abscissa data in one united relative coordinate system to perform the calculation (called CC method) and the other is dividing the data into two groups and mapping them in two separate coordinate systems (called SC method). We tested the accuracy of each method and compared both methods in a highly controlled experiment. The experiments' results and data analysis show that the CC method is better than the SC method for human computer interface modeling. These results will be instrumental for future application of Fitts' law.

In the age of pervasive computing, ubiquitous collaboration has become an every-day life paradigm. Without an ideal computing infrastructure, issues with ubiquitous collaboration, such as network unreliability, platform heterogeneity, and client's resource constraints, are inevitable. The traditional replication scheme copes with network unreliability by replicating all the objects of a shared application together at once. This is, however, suitable for neither cooperative applications nor mobile computing devices. These problems can be naturally addressed by using a fine-grained replication scheme that enables a portion of the application objects to be replicated. This paper presents an object-oriented middleware that is capable of dynamically and transparently replicating remotely shared Java applications in a partially and on-demand incremental manner. It is also able to maintain various consistency semantics and enables the coexistence of fine-grained replications and conventional remote method invocations. Empirical results indicate several practical benefits of the middleware.

Heterogeneous distributed computing environments are well suited to meet the fast increasing computational demands. Task scheduling is very important for a heterogeneous distributed system to satisfy the large computational demands of applications. The performance of a scheduler in a heterogeneous distributed system normally has something to do with the dynamic task flow, that is, the scheduler always suffers from the heterogeneity of task sizes and the variety of task arrivals. From the long-term viewpoint it is necessary and possible to improve the performance of the scheduler serving the dynamic task flow. In this paper we propose a task scheduling method including a scheduling strategy which adapts to the dynamic task flow and a genetic algorithm which can achieve the short completion time of a batch of tasks. The strategy and the genetic algorithm work with each other to enhance the scheduler's efficiency and performance. We simulated a task flow with enough tasks, the scheduler with our strategy and algorithm, and the schedulers with other strategies and algorithms. We also simulated a complex scenario including the variant arrival rate of tasks and the heterogeneous computational nodes. The simulation results show that our scheduler achieves much better scheduling results than the others, in terms of the average waiting time, the average response time, and the finish time of all tasks.

The completeness (i.e. confluent and terminating) property is an important concept when using a term rewriting system (TRS) as a computational model of functional programming languages. Knuth and Bendix have proposed a procedure known as the KB procedure for generating a complete TRS. A TRS cannot, however, directly handle higher-order functions that are widely used in functional programming languages. In this paper, we propose a higher-order KB procedure that extends the KB procedure to the framework of a simply-typed term rewriting system (STRS) as an extended TRS that can handle higher-order functions. We discuss the application of this higher-order KB procedure to a certification technique called inductionless induction used in program verification, and its application to fusion transformation, a typical kind of program transformation.