Overlay networks, such as P2P, Grid, and CDN, have been widely deployed over physical IP networks. Since simultaneous overlay networks compete for network resources, their selfish behaviors to improve their application-oriented QoS disrupt each other. To enhance the collective performance and improve the QoS at the application level, we consider so-called the overlay network symbiosis where overlay networks cooperate with each other. In this paper, we proposed a cooperative mechanism for hybrid P2P file-sharing networks, where peers can find more files and exchange files with more peers. Through simulation experiments, we verified the effectiveness of cooperation from view points of application and system.

To provide application-oriented network services, a variety of overlay networks are deployed over physical IP networks. Since they share and compete for the same physical network resources, their selfish behaviors affect each other and, as a result, their performance deteriorates. Our research group considers a model of overlay network symbiosis, where overlay networks coexist and cooperate to improve their application-level quality of service (QoS) while sustaining influences from the physical network and other overlay networks. In this paper, we especially focus on Peer-to-Peer (P2P) networks among various overlay networks. We propose a mechanism for pure P2P networks of file-sharing applications to cooperate with each other. In our proposal, cooperative peers establish logical links among two or more P2P networks, and messages and files are exchanged among cooperative P2P networks through these logical links. For efficient and effective cooperation, we also propose an algorithm for selection of cooperative peers and a caching mechanism to avoid putting too much load on cooperative peers and cooperating networks. Simulation results show that our proposed mechanism improves the search efficiency of P2P file-sharing applications and reduces the load in P2P networks.

The perfect matched layer (PML) is formulated for the use in the constrained interpolation profile (CIP) method. Numerical results are presented to examine the performance of the proposed formulation of the PML in the case of two-dimensional TM wave. The results show that the proposed methods suppress the reflection effectively in comparison with the natural absorbing boundary condition of the CIP method. We have two methods to formulate the PML, and it is shown that the both methods have equal characteristics.

The protein threading problem with profiles is known to be efficiently solvable using dynamic programming. In this paper, we consider a variant of the protein threading problem with profiles in which constraints on distances between residues are given. We prove that protein threading with profiles and constraints is NP-hard. Moreover, we show a strong hardness result on the approximation of an optimal threading satisfying all the constraints. On the other hand, we develop two practical algorithms: CLIQUETHREAD and BBDPTHREAD. CLIQUETHREAD reduces the threading problem to the maximum edge-weight clique problem, whereas BBDPTHREAD combines dynamic programming and branch-and-bound techniques. We perform computational experiments using protein structure data in PDB (Protein Data Bank) using simulated distance constraints. The results show that constraints are useful to improve the alignment accuracy of the target sequence and the template structure. Moreover, these results also show that BBDPTHREAD is in general faster than CLIQUETHREAD for larger size proteins whereas CLIQUETHREAD is useful if there does not exist a feasible threading.

We have developed a 32-bit, 32-word, and 9-read, 7-write ported register file. This register file has several circuits and techniques for reducing the impact of process variation that is marked in recent process technologies, voltage variation, and temperature variation, so called PVT variation. We describe these circuits and techniques in detail, and confirm their effects by simulation and measurement of the test chip.

This study is devoted to a half-wave dipole with a conductor plane at a distance much smaller than a quarter wavelength which we designate as an ultra low profile dipole (ULPD) antenna in this paper. The concerns of ULPD antenna are the feeding method and the impedance matching, because the input impedance usually tends to be lowered by the existence of a metallic structure in its proximity. In this paper, we propose a ULPD antenna with an excellent impedance matching and a coaxial feed built within the antenna structure so that the external matching and a balun are not required. A coaxial cable is used as a feed line and extended to be a half of a half wavelength dipole. The other half is made up of a parasitic element, which is connected to the outer conductor of the coaxial radiator. To make a matching, the outer conductor of the coaxial radiator is stripped off at a suitable length, and the total length of a dipole is considered for its resonance at a desired frequency of 2 GHz. The experiment has been conducted. The results show the return loss of -27 dB and the maximum gain of 9 dBi in the normal direction to the conductor plane. The computational results are also obtained, which agree well with the experimental results.

Flash bulk files downloading in style of P2P through perpendicular pattern becomes more popular recently. Many peers download different pieces of shared files from the source in parallel. They try to reconstruct complete files by exchanging needed pieces with other downloading peers. The throughput of entire downloading community, as well as the perceived downloading rate of each peer, greatly depends on uploading bandwidth contributed by every individual peer. Unfortunately, without proper built-in incentive mechanism, peers inherently tend to relentlessly download while intentionally limiting their uploading bandwidth. In this paper, we propose a both effective and efficient incentive approach--Reciprocity, which is only based on end-to-end measurement and reaction: a peer caps uploading rate to each of its peers at the rate that is proportional to its downloading rate from that one. It requires no centralized control, or electronic monetary payment, or certification. Preliminary experiments' results reveal that this approach offers favorable performance for cooperative peers, while effectively punishing defective ones.

A fundamental problem in a pure Peer-to-Peer (P2P) file sharing system is how to protect the anonymity of peer nodes when providing efficient data access services. Most of existing work mainly focus on how to provide the initiator anonymity, but neglect the anonymity of the responder. In this paper, we propose a multicast-based protocol, called Mapper, for efficient file sharing with mutual anonymity. By seamlessly combining the technologies of multi-proxy and IP multicast together, the proposed protocol guarantees mutual anonymity during the entire session of file retrieval. Furthermore, Mapper replicates requested files inside the multicast group, so file distribution can be adjusted adaptively and the cost for multicast can be further reduced. Results of both simulations and theoretical analyses demonstrate that Mapper possesses the merits of scalability, reliability, and high adaptability.

Machine learning and data mining algorithms are increasingly being used in the intrusion detection systems (IDS), but their performances are laggard to some extent especially applied in network based intrusion detection: the larger load of network traffic monitoring requires more efficient algorithm in practice. In this paper, we propose and design an anomaly intrusion detection (AID) system based on the vector quantization (VQ) which is widely used for data compression and high-dimension multimedia data index. The design procedure optimizes the performance of intrusion detection by jointly accounting for accurate usage profile modeling by the VQ codebook and fast similarity measures between feature vectors to reduce the computational cost. The former is just the key of getting high detection rate and the later is the footstone of guaranteeing efficiency and real-time style of intrusion detection. Experiment comparisons to other related researches show that the performance of intrusion detection is improved greatly.

This paper proposes a Java online plug-in mechanism that can be used to modify any part in a system file coded in Java, even while the part is running, without service interruption. The Java-related plug-in capabilities are devised by using the plug-in functional elements offered by the existing C++ online plug-in that we proposed. In particular, measures on how to deal with the use of Just In Time compilation and inline expansion are considered. New linkage and file-back up techniques are proposed for this purpose. Case studies reveal its wide applicability and the degree of memory area saving effects. Evaluation proves this mechanism does not affect the performance of ordinary service processing. It is expected to be used in practice for Java-based service processing such as VoIP and Instant Messaging.

This paper presents a novel low-power register file based on adiabatic logic. The register file consists of a storage-cell array, address decoders, read/write control circuits, sense amplifiers, and read/write drivers. The storage-cell array is based on the conventional memory cell. All the circuits except the storage-cell array employ CPAL (complementary pass-transistor adiabatic logic) to recover the charge of large node capacitance on address decoders, bit-lines and word-lines in fully adiabatic manner. The minimization of energy consumption was investigated by choosing the optimal size of CPAL circuits for large load capacitance. The power consumption of the proposed adiabatic register file is significantly reduced because the energy transferred to the large capacitance buses is mostly recovered. The energy and functional simulations are performed using the net-list extracted from the layout. HSPICE simulation results indicate that the proposed register file attains energy savings of 65% to 85% as compared to the conventional CMOS implementation for clock rates ranging from 25 to 200 MHz.

A folded loop antenna for handsets has already been introduced and shown as one of balance-fed antennas for handsets, which is very effective to mitigate the antenna performance degradation due to the body effect. In order to meet the requirements for the latest handsets such as low profile and small size, a folded loop antenna is modified. The antenna, which is possibly built in the handsets, is newly proposed. Low profile and small size is achieved by consisting of the half of low profile folded loop antenna, which has a structure folded loop elements sideways so that the antenna can be placed on the ground plane (GP). In the analysis, the electromagnetic simulator based on the FDTD (Finite Difference Time Domain) method is used and the design parameters useful in practical operation are found. The electromagnetic simulator based on the Method of Moment (MoM) is used to calculate the current distribution on the antenna element and the GP. An example of low profile and small size antenna which has wideband characteristics are designed based on these parameters, and the antenna characteristics such as VSWR, the current distributions and the radiation patterns are compared with Planar Inverted-F Antenna (PIFA), which is one of conventional built-in antennas for handset. As a result, it has been confirmed that the physical volume of the antenna, which has been introduced here, becomes smaller than that of PIFA. In addition, the radiation efficiency of these antennas is measured and the results are compared with each other.

Nowadays more people have started using their mobile phone to access information they need from anywhere at anytime. In advanced mobile technology, Location Service allows users to quickly pinpoint their location as well as makes a recommendation to fascinating events. However, users desire more appropriate recommendation services. In other words, the message service should push a message at a proper place in time. In consequence, customers obtain a higher level of satisfaction. In this paper, we propose a framework of time, place, purpose and personal profile based recommendation service. We illustrate scenarios in "push", "pull" and "don't disturb" services, where our DB queries can recommend the relevant message to users. The three factors: time, place and purpose are mutually dependent and the basic rules to analyze the essential data are summarized. We also create algorithms for DB query. We are filtering messages by one important factor: personal profile such as user's preference and degree of preference. Furthermore, we discuss an implementation of the prototype system, including results of experimental evaluation.

A single-mode fiber employing a trench index profile for indoor wiring is proposed to realize low-bending loss and low-splice loss simultaneously. The designs and the advantages of the fiber over fibers with conventional step index profiles are described. The characteristics of manufactured fibers with trench index profiles are also described. One of the manufactured fibers realizes a bending loss of 0.018 dB/turn at 1550 nm for a bending radius of 7.5 mm, and a splice loss of 0.19 dB at 1550 nm in mechanical splicing to a conventional single mode fiber simultaneously. Other one of the fibers realizes a bending loss of 0.011 dB/turn at 1550 nm for a bending radius of 5 mm, and the splice loss is 0.37 dB at 1550 nm simultaneously. A total loss of a fiber employing the trench index is small and stable against the fluctuation of MFD.

We discuss a typical profile of the k-error linear complexity for balanced binary exponent periodic sequences and the number of periodic distinct sequences by their profiles. A numerical example with period 16 is also shown.

The 70-GHz band propagation characteristics of two different hot-spot zones are measured and analyzed: (1) a transmitter fixed to a ceiling servicing the area beneath it (type A), and (2) a transmitter fixed to a wall servicing the area in front of it (type B). Measurements were made in two different settings, a lobby and a train. The results show that zone B produces a smaller delay spread in relation to distance. A comparison of the use of vertical and circular polarization shows that circular polarization produces a smaller delay spread in the type B zone. The results also indicated that the function of the delay spread value for the distance in a lobby and train in type B zone.

The current paper presents the design, analysis, and implementation of a low-profile resonant dc-to-dc converter that utilizes a coreless printed circuit board transformer as a substitute for the conventional magnetic core-based transformer. A prototype series resonant converter, fabricated in a 40 mm80 mm area with a 4 mm thickness while achieving the maximum efficiency of 85% at a 58 W output power, is used as an example to address the theoretical and practical issues involved in the design, analysis, and implementation of a PCB transformer-based low-profile dc-to-dc converter.

By using distributed database systems, many advantages can be obtained such as database management cost, efficiency, and high integrity of systems through allocating fragments to many distributed sites with horizontal/vertical fragmentation of global database schema. To minimize costs, distributed algorithms must be applied so that database fragments are allocated to optimal sites. It is useful to replicate fragments, such as allocating many copies in many sites including load balancing. But there are too many possible combinations of each site and fragment, making it impossible to find a solution in real time, i.e., it is an NP-complete problem. This paper proposes near optimal heuristic algorithms for minimizing cost by defining a cost model based on read and update queries that are requested in many sites. Various factors are applied to the proposed algorithms for sizing efficient network resources that compute database transactions as remote query or update requests for consistency in replicated database systems. For network load balancing, incoming network traffic table is defined in each site. A request transaction from unallocated sites to allocated sites can be accessed properly at any other replicated sites by using the network traffic table. Finally, some experimental results verified the proposed algorithms by comparing actual cases of database allocation.

Performance of selective Rake (SRake) receiver is evaluated for direct sequence ultra wideband (DS-UWB) communications considering an independent Rayleigh channel having exponentially decaying power delay profile (PDP). BEP performances are shown. The results obtained are compared with similar results in a channel having flat PDP. Assumption of a flat PDP is found to predict the optimum spreading bandwidth to be lower and sub-optimum operating performance beyond optimum spreading bandwidth to be severely worse than that is achievable in a channel having exponentially decaying PDP by employing an SRake receiver having fixed number of combined paths. Optimum spreading bandwidth for SRake in a channel having exponentially decaying PDP is shown to be much larger than the one in a channel having flat PDP; that is specifically a good-news for UWB communications. Effects of partial band interference are also investigated. Interference is found to be less effective in exponentially decaying PDP.

DualFS is a next-generation journaling file system which has the same consistency guaranties as traditional journaling file systems but better performance. This paper introduces three new enhancements which significantly improve DualFS performance during normal operation, and presents different experimental results which compare DualFS and other traditional file systems, namely, Ext2, Ext3, XFS, JFS, and ReiserFS. The experiments carried out prove, for the first time, that a new file system design based on separation of data and metadata can significantly improve file systems' performance without requiring several storage devices.