The disk allocation problem examined in this paper is finding a method to distribute a Binary Cartesian Product File on multiple disks to maximize parallel disk I/O accesses for partial match retrieval. This problem is known to be NP-hard, and heuristic approaches have been applied to obtain suboptimal solutions. Recently, efficient methods such as Binary Disk Modulo (BDM) and Error Correcting Code (ECC) methods have been proposed along with the restrictions that the number of disks in which files are stored should be a power of 2. In this paper, a new Disk Allocation method based on Genetic Algorithm (DAGA) is proposed. The DAGA does not place restrictions on the number of disks to be applied and it can allocate the disks adaptively by taking into account the data access patterns. Using the schema theory, it is proven that the DAGA can realize a near-optimal solution with high probability. Comparing the quality of solution derived by the DAGA with the General Disk Modulo (GDM), BDM, and ECC methods through the simulation, shows that 1) the DAGA is superior to the GDM method in all the cases and 2) with the restrictions being placed on the number of disks, the average response time of the DAGA is always less than that of the BDM method and greater than that of the ECC method in the absence of data skew and 3) when data skew is considered, the DAGA performs better than or equal to both BDM and ECC methods, even when restrictions on the number of disks are enforced.

Recently the study and implementation of elliptic curve cryptosystems (ECC) have developed rapidly and its achievements have become a center of attraction. ECC has the advantage of high-speed processing in software even on restricted environments such as smart cards. In this paper, we concentrate on complete software implementation of ECC over a prime field on a 16-bit microcomputer M16C (10 MHz). We propose a new type of prime characteristic of base field suitable for small and fast implementation, and also improve basic elliptic arithmetic formulas. We report a small and fast software implementation of a cryptographic library which supports 160-bit elliptic curve DSA (ECDSA) signature generation, verification and SHA-1 on the processor. This library also includes general integer arithmetic routines for applicability to other cryptographic algorithms. We successfully implemented the library in 4 Kbyte code/data size including SHA-1, and confirmed a speed of 150 msec for generating an ECDSA signature and 630 msec for verifying an ECDSA signature on M16C.

In this paper, we will discuss a map synthesis system which handles static information (geographic objects) as well as dynamic information (traffic conditions, weather, etc. ). In addition to geographic thesauruses used in the previous systems, we will use co-existence relationships to improve the quality of maps generation. The system is considered to be general purpose (not restricted to car navigation nor travel maps) and can generate arbitrary maps according to the user's specification. It is very difficult for a user to specify a query which corresponds to the required map, because map description is not easy. The system should automatically generate missing information or find errors in the user specification. For the purpose we use geographic domain thesauruses which contain aggregation and other geographic relationships as well as conventional thesaurus hierarchy. In this paper, we will discuss to use co-existence relationships to enhance ability to select geographic objects automatically. Co-existence specifies relationships among geographic objects which should appear in a map together although they may not have geographic relationship by thesauruses. By utilizing co-existence relationships, a user can acquire much more understandable maps.

This paper proposes a new framework of managing virtual spaces based on spatial databases as an extension of VRML-based systems. The framework is suitable for treating continuous virtual spaces and for managing the quality of service (QoS) of the virtual spaces depending on user's operations and situations of computer resources. Levels of detail (LoD) of 3D objects is the most important rule for rendering scenes dynamically while managing the QoS. This paper describes a method of managing the QoS depending on the LoD in the form of spatial queries. An advantage of the framework is that spatial databases can incrementally construct virtual spaces in clients using differential descriptions based on VRML, that is, DVRML, proposed in this paper. Dynamic spatial data such as avatar's movement and real-time multimedia data such as videos should be shared by all participants in a virtual space in real time. Our framework can also handle dynamic spatial data by means of real-time updating of some spatial objects in spatial databases as well as static spatial data. We developed some experimental applications based on the framework in order to prove that it is feasible for networked virtual spaces with video components.

In ordinary digital signature schemes, anyone can verify signatures with signer's public key. However it is not necessary for anyone to be convinced a justification of signer's dishonorable message such as a bill. It is enough for a receiver only to convince outsiders of signature's justification if the signer does not execute a contract. On the other hand there exist messages such as official documents which will be first treated as limited verifier signatures but after a few years as ordinary digital signatures. We will propose a limited verifier signature scheme based on Horster-Michels-Petersen's authenticated encryption schemes, and show that our limited verifier signature scheme is more efficient than Chaum-Antwerpen undeniable signature schemes in a certain situation. And we will propose a convertible limited verifier signature scheme based on our limited verifier signature scheme, and show that our convertible limited verifier signature scheme is more efficient than Boyar-Chaum-Damg rd-Pedersen convertible undeniable signature schemes in a certain situation.

For advanced data-oriented applications in distributed environments, effective information is frequently obtained by integrating or merging various autonomous information sources. There are many problems: how to search information sources, how to resolve their heterogeneity, how to merge or integrate target sources, how to represent information sources with a common protocol, and how to process queries. We have proposed a new language, QUIK, as an extension of a deductive object-oriented database (DOOD) language, QUIXOTE, and extend typical mediator systems. In this paper, we discuss various features of QUIK: programming capabilities as integrating an exchange model and mediator specifications, merging subsumption relations for maintaining consistency, searching alternative information sources by hypothesis generation, and identifying objects.

We examine crossing waveguides with three channels consisting of nonlinear material by means of FD-BPM (Finite Difference Beam Propagation Method). Specifically, we investigate how the insertion of a multimode waveguide into the crossing section of both 13 and 23 structures influences the switching characteristics of output power. We then confirm that these structures can be favorably applied to a wide variety of all-optical devices for integrated optics such as intensity-dependent optical switches, optical power distributors and so on.

This paper proposes the radio ATM entrance network with radio links connecting between access points and wired backbone ATM networks for wireless ATM access. In order to reduce the interference power among the radio entrance links, the Power and Modulation Level Controlled Radio method is newly proposed, the method controls not only modulation level but also the transmission power according to the ATM cell traffic intensity. Theoretical analysis shows that the proposed method can increase the carrier to noise plus interference power ratio and can reduce the average cell loss rate compared with the conventional Modulation Level Controlled Radio method in case that there is the interference power among the radio ATM entrance links.

In recent years, several global network systems using non-stationary satellites have been proposed. Some of them are announced to start services within years. We also have several experimental systems with stratospheric aircrafts. In the future, the radio communication system using stratospheric aircrafts will be one of the promising media for personal communications. The question of how to establish the optimal communication under such circumstance seems to be still open. In this paper, performance evaluations of wireless communication systems using LEO satellites and stratospheric aircrafts are proposed. We will show some proper communication parameters to improve competence of mobile communication in the such systems as well.

This paper proposes a novel signal transmission scheme for helicopter satellite communications. The proposed scheme is based on time diversity, and combined with a novel algorithm to suppress an influence of carrier phase slip. In the proposed scheme, carrier phase slip is detected in cross correlation processing of the received signal, and is effectively suppressed. The proposed scheme thus makes it possible to employ coherent phase shift keying modulation to achieve bit error rate performance superior to that of differential phase shift keying modulation even in the low carrier-to-noise power ratio environment.

In this paper, the surface impedance boundary condition (SIBC) for a dispersive lossy medium backed by a perfect conductor is implemented in computation of electromagnetic (EM) scattering using the finite difference time domain (FDTD) method. The dispersion of the surface impedance is incorporated into FDTD update equations by using the piecewise linear recursive convolution (PLRC) approach. The validity of the proposed method is confirmed numerically.

The objective of thinning is to reduce the amount of information in image patterns to the minimum needed for recognition. Thinned image helps the extraction of important features such as end points, junction points, and connections from image patterns. The ultimate goal of parallel algorithms is to minimize the execution time while producing high quality thinned image. Though much research has been performed for parallel thinning algorithms, there has been no systematical approach for comparing the execution speed of parallel thinning algorithms. Several rough comparisons have been done in terms of iteration numbers. But, such comparisons may lead to wrong guides since the time required for iterations varies from one algorithm to the other algorithm. This paper proposes a formal method to analyze the performance of parallel thinning algorithms based on PRAM (Parallel Random Access Machine) model. Besides, the quality of skeletons, robustness to boundary noise sensitivity, and execution speed are considered. Six parallel algorithms, which shows relatively high performance, are selected, and analyzed based on the proposed analysis method. Experiments show that the proposed analysis method is sufficiently accurate to evaluate the performance of parallel thinning algorithms.

Call tracking data contains a calling address, called address, service type, and other useful attributes to predict a customer's calling activity. Call tracking data is becoming a target of data mining for telecommunication carriers. Conventional data-mining programs control the number of association rules found with two types of thresholds (minimum confidence and minimum support), however, often they generate too many association rules because of the wide variety of patterns found in call tracking data. This paper proposes a new method to reduce the number of generated rules. The method proposed tests each generated rule based on Akaike Information Criteria (AIC) without using conventional thresholds. Experiments with artificial call tracking data show the high performance of the proposed method.

Analysis of frequency-dependent lossy transmission lines is very important for designing the high-speed VLSI, MCM and PCB. The frequency-dependent parameters are always obtained as tabulated data. In this paper, a new curve fitting technique of the tabulated data for the moment matching technique in the interconnect analysis is presented. This method based on Chebyshev interpolation enhances the efficiency of the moment matching technique.

The mapping from a global routing to a feasible detailed routing in a number of 2D array routing structures has been shown to be an NP-complete problem. These routing structures include the Xilinx style routing architecture, as well as architectures with significantly higher switching flexibility. In response to this complexity, a different class of FPGA routing structures called Greedy Routing Architectures (GRAs) have been proposed. On GRAs, optimally routing each switch box, in a specified order, leads to an optimal chip routing. Because routing each switch box takes polynomial time, the mapping problem on GRAs can be solved in polynomial time. In particular, an H-tree GRA with W2+2W switches per switch box (SpSB) and a 2D array GRA with 4W2+2W SpSB have been proposed. In this paper, we improve on these results by introducing an H-tree GRA with W2/2+2W SpSB and a 2D array GRA with 3.5W2+2W SpSB. These new GRAs have the same desirable mapping properties of the previously described GRAs, but use fewer switches.

A double-layer Associative Memory System (AMS) based on the Cerebella Model Articulation Controller (CMAC) (CMAC-AMS), owing to its advantages of simple structures, fast searching procedures and strong mapping capability between multidimensional input/output vectors, has been successfully used in such applications as real-time intelligent control, signal processing and pattern recognition. However, it is still suffering from its requirement for a large memory size and relatively low precision. Furthermore, the hash code used in its addressing mechanism for memory size reduction can cause a data-collision problem. In this paper, a new high-order Associative Memory System based on the Newton's forward interpolation formula (NFI-AMS) is proposed. The NFI-AMS is capable of implementing high-precision approximation to multivariable functions with arbitrarily given sampling data. A learning algorithm and a convergence theorem of the NFI-AMS are proposed. The network structure and the scheme of its learning algorithm reveal that the NFI-AMS has advantages over the conventional CMAC-type AMS in terms of high precision of learning, much less required memory size without the data-collision problem, and also has advantages over the multilayer Back Propagation (BP) neural networks in terms of much less computational effort for learning and fast convergence rate. Numerical simulations verify these advantages. The proposed NFI-AMS, therefore, has potential in many application areas as a new kind of associative memory system.

This paper proposes a method to reduce the context switching time using a register bank to store contexts of working tasks. Hardware cost and performance were measured by modeling the register bank and controller in VHDL. Following results were obtained: (1) The controller can be implemented with a much smaller amount of hardware cost compared to that of the register bank, which is realized by SRAM module. (2) Context switching time can be reduced to less than 50% compared to that by software implementation. (3) Combination of the proposed architecture with our previous work (RTOS implemented in HW) gives us much higher performance of a hard real-time system.

A fuel cell energy system is under development for supply of generated electrical energy to telecommunications equipment. It is a cogeneration system; the heat energy recovered is used to cool the telecommunications equipment. For this system, a method is described for controlling a new DC interconnection converter. Its DC interconnection characteristics are also discussed. The new converter controls its input current to the fuel cell rated current at maximum and can operate stably even when the fuel cell voltage decreases. This allows good DC interconnection characteristics to be obtained in both the steady state and the transient state.

The importance of technology retargeting for hard IPs is getting increased. However, recent advances in process technologies make layout reuse too complicated to be done by conventional compactors. As an efficient approach, this paper proposes a flexible layout abstraction model and a new layout synthesis algorithm. The synthesis algorithm provides a concurrent procedure of detailed wiring, compaction, and transistor layout generation by using a scan line to get better layout results than conventional compactors. We have applied this method to the technology retargeting of actual cell layouts and have achieved quite good results comparable to hand-crafted designs.

This paper proposes a high-level synthesis system for datapath design of digital processing hardwares. The system consists of four phases: (1) DFG (data-flow graph) generation, (2) scheduling, (3) resource binding, and (4) HDL (hardware description language) generation. In (1), the system does not generate only one best DFG representing a given behavioral description of a hardware, but more than one good DFGs representing it. In (2) and (3), several synthesis tools can be incorporated into the system depending on the required objectives. Thus we can obtain more than one datapath candidates for a behavioral description with their area and performance evaluation. In (4), the best datapath design is selected among those candidates and its hardware description is generated. The experimental results for applying the system to several benchmarks show the effectiveness and efficiency.