This article proposes a versatile model of a multiservice queueing system with elastic traffic. The model can provide a basis for an analysis of telecommunications and computer network systems, internet network systems in particular. The advantage of the proposed approach is a possibility of a determination of delays in network nodes for a number of selected classes of calls offered in modern telecommunications networks.

On SNS (Social Networking Services), detecting Sybils is an urgent demand. The most famous approach is called “SybilRank” scheme where each node evenly distributes its trust value starting from honest seeds and detects Sybils based on the trust value. Furthermore, Zhang et al. propose to avoid trust values from being distributed into Sybils by pruning suspicious relationships before performing SybilRank. However, we point out that the above two schemes have shortcomings that must be remedied. In the former scheme, seeds are concentrated on the specific communities because they are selected from nodes that have largest number of friends, and thus the trust value is not evenly distributed. In the latter one, a sophisticated attacker can avoid graph pruning by making relationships between Sybil nodes. In this paper, we propose a robust seed selection and graph pruning scheme to detect Sybil nodes more accurately. To more evenly distribute trust value into honest nodes, we first detect communities in the SNS and select honest seeds from each detected community. And then, by leveraging the fact that Sybils cannot make dense relationships with honest nodes, we also propose a graph pruning scheme based on the density of relationships between trusted nodes. We prune the relationships which have sparse relationships with trusted nodes and this enables robust pruning malicious relationships even if the attackers make a large number of common friends. By the computer simulation with real dataset, we show that our scheme improves the detection accuracy of both Sybil and honest nodes.

An application of laser annealing process, which is used to form the P-type Base junction for high-performance low-voltage power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), is proposed. An equivalent shallow-junction structure for P-Base junction with uniform impurity distribution is achieved by adopting green laser annealing of pulsed mode. Higher impurity activation for the shallow junction has been achieved by the laser annealing of melted phase than by conventional RTA (Rapid Thermal Annealing) of solid phase. The application of the laser annealing technology in the fabrication process of Low-Voltage U-MOSFET is also examined.

Given a set of positive-weighted points and a query rectangle r (specified by a client) of given extents, the goal of a maximizing range sum (MaxRS) query is to find the optimal location of r such that the total weights of all points covered by r is maximized. In this paper, we address the problem of processing MaxRS queries over road network databases and propose two new external memory methods. Through a set of simulations, we evaluate the performance of the proposed methods.

Enforcing access control policies in Information-Centric Networking (ICN) is difficult due to there being multiple copies of contents in various network locations. Traditional Access Control List (ACL)-based schemes are ill-suited for ICN, because all potential content distribution servers should have an identical access control policy or they should contact a centralized ACL server whenever their contents are accessed by consumers. To address these problems, we propose a distributed capability access control scheme for ICN. The proposed scheme is composed of an internal capability and an external capability. The former is included in the content and the latter is added to a request message sent from the consumer. The content distribution servers can validate the access right of the consumer through the internal and external capabilities without contacting access control policies. The proposed model also enhances the privacy of consumers by keeping the content name and consumer identification anonymous. The performance analysis and implementation show that the proposed scheme is feasible and more efficient than other access control schemes.

An application of laser annealing process, which is used to form the shallow P-type Base junction for 20-V planar power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) is proposed. We demonstrated that the fabricated devices integrated with laser annealing process have superior electrical characteristics than those fabricated according to the standard process. Moreover, the threshold voltage variation of the devices applied by the new annealing process is effectively suppressed. This is due to that a uniform impurity distribution at the channel region is achieved by adopting laser annealing. Laser annealing technology can be applied as a reliable, effective, and advantageous process for the low-voltage power MOSFETs.

This paper claims to use a new question expansion method for question classification in cQA services. The input questions consist of only a question whereas training data do a pair of question and answer. Thus they cannot provide enough information for good classification in many cases. Since the answer is strongly associated with the input questions, we try to create a pseudo answer to expand each input question. Translation probabilities between questions and answers and a pseudo relevant feedback technique are used to generate the pseudo answer. As a result, we obtain the significant improved performances when two approaches are effectively combined.

Tor is the most popular and well-researched low-latency anonymous communication network provides sender privacy to Internet users. It also provides recipient privacy by making TCP services available through “hidden service”, which allowing users not only to access information anonymously but also to publish information anonymously. However, based on our analysis of the hidden service protocol, we found a special combination of cells, which is the basic transmission unit over Tor, transmitted during the circuit creation procedure that could be used to degrade the anonymity. In this paper, we investigate a novel protocol-feature based attack against Tor's hidden service. The main idea resides in fact that an attacker could monitor traffic and manipulate cells at the client side entry router, and an adversary at the hidden server side could cooperate to reveal the communication relationship. Compared with other existing attacks, our attack reveals the client of a hidden service and does not rely on traffic analysis or watermarking techniques. We manipulate Tor cells at the entry router to generate the protocol-feature. Once our controlled entry onion routers detect such a feature, we can confirm the IP address of the client. We implemented this attack against hidden service and conducted extensive theoretical analysis and experiments over Tor network. The experiment results validate that our attack can achieve high rate of detection rate with low false positive rate.

Recently, the Services Oriented Architectures (SOA) have been recognized as the key to the integration and interoperability of different applications and systems that coexist in an organization. However, even though the use of SOA has increased, some applications are unable to use it. That is the case of mission critical information applications, whose requirements such as high reliability, non-stop operation, high flexibility and high performance are not satisfied by conventional SOA infrastructures. In this article we present a novel approach of combining SOA with Autonomous Decentralized Systems (ADS) in order to provide an infrastructure that can satisfy those requirements. We have named this infrastructure Autonomous Decentralized Service Oriented Architecture (ADSOA). We present the concept and architecture of ADSOA, as well as the Loosely Couple Delivery Transaction and Synchronization Technology for assuring the data consistency and high reliability of the application. Moreover, a real implementation and evaluation of the proposal in a mission critical information system, the Uniqueness Verifying Public Key Infrastructure (UV-PKI), is shown in order to prove its effectiveness.

Web Service Composition (WSC) has been well recognized as a convenient and flexible way of service sharing and integration in service-oriented application fields. WSC aims at selecting and composing a set of initial services with respect to the Quality of Service (QoS) values of their attributes (e.g., price), in order to complete a complex task and meet user requirements. A major research challenge of the QoS-aware WSC problem is to select a proper set of services to maximize the QoS of the composite service meeting several QoS constraints upon various attributes, e.g. total price or runtime. In this article, a fast algorithm based on QoS-aware sampling (FAQS) is proposed, which can efficiently find the near-optimal composition result from sampled services. FAQS consists of five steps as follows. 1) QoS normalization is performed to unify different metrics for QoS attributes. 2) The normalized services are sampled and categorized by guaranteeing similar number of services in each class. 3) The frequencies of the sampled services are calculated to guarantee the composed services are the most frequent ones. This process ensures that the sampled services cover as many as possible initial services. 4) The sampled services are composed by solving a linear programming problem. 5) The initial composition results are further optimized by solving a modified multi-choice multi-dimensional knapsack problem (MMKP). Experimental results indicate that FAQS is much faster than existing algorithms and could obtain stable near-optimal result.

Distributed antenna systems (DASs) combined with multi-user multiple-input multiple-output (MU-MIMO) transmission techniques have recently attracted significant attention. To establish MU-MIMO DASs that have wide service areas, the use of a dynamic clustering scheme (CS) is necessary to reduce computation in precoding. In the present study, we propose a simple method for dynamic clustering to establish a single cell large-scale MU-MIMO DAS and investigate its performance. We also compare the characteristics of the proposal to those of other schemes such as exhaustive search, traditional location-based adaptive CS, and improved norm-based CS in terms of sum rate improvement. Additionally, to make our results more universal, we further introduce spatial correlation to the considered system. Computer simulation results indicate that the proposed CS for the considered system provides better performance than the existing schemes and can achieve a sum rate close to that of exhaustive search but at a lower computational cost.

In this study, our recent research activities on nanophotonic devices with semiconductor quantum nanostructures are reviewed. We have developed a technique for nanofabricating of high-quality and high-density semiconductor quantum dots (QDs). On the basis of this core technology, we have studied next-generation nanophotonic devices fabricated using high-quality QDs, including (1) a high-performance QD laser for long-wavelength optical communications, (2) high-efficiency compound-type solar cell structures, and (3) single-QD devices for future applications related to quantum information. These devices are expected to be used in high-speed optical communication systems, high-performance renewable energy systems, and future high-security quantum computation and communication systems.

Fan-in/fan-out devices are necessary for the construction of multi-core fiber communication systems. A fan-out device using a capillary is proposed and made by connecting a tapered fiber bundle and a multi-core fiber. The tapered fiber bundle is elongated so that the core arrangement and the mode field diameter (MFD) of single-core fibers agree with those of the multi-core fiber. Suppressing the MFD change is necessary to reduce the coupling loss of the fan-out device. While elongating the fiber bundle, the MFD decreases at the beginning until the core reaches a certain core diameter, and then it begins to increase. We suppress the MFD change of the fan-out device by using this phenomenon. The average insertion loss at both ends of a multi-core fiber was approximately 1.6dB when the fabricated fan-in/fan-out devices were connected to the multi-core fiber.

Wi-Fi P2P has been deployed extensively in mobile devices. However, Wi-Fi P2P is not efficient because it requires an IP layer connection for transmitting even short messages to nearby devices, especially in high density or highly mobile environments owing to the fact that a user on the move has difficulty selecting service-available devices, and a user device has to frequently connect to and be released from nearby devices. This paper proposes a new messaging framework that enables application-level messages to be exchanged between nearby devices with no IP layer connectivity over Wi-Fi P2P. The pre-association messaging framework (PAMF) supports both broadcast and unicast transmission to maximize the delivery success rate, considering the number of peers and messages. Evaluations of PAMF conducted under real scenarios show that application-level messages can be exchanged within a few seconds, with high success rate. PAMF provides high portability and extensibility because it does not breach the Wi-Fi P2P standard. Moreover, the demonstrations show that PAMF is practical for new proximity services such as local marketing and urgent messaging.

We consider a bisimilarity control problem for transition systems. For this control problem, a necessary and sufficient condition for its solvability and a method for synthesizing a state feedback controller have been presented in the literature. However, the state of the system to be controlled is not necessarily observable. In this paper, we synthesize an observer-based output feedback controller for the bisimilarity control problem under a certain condition, and show that this output feedback controller is a solution to the control problem.

One of the patterns that the design of parallel file systems has to solve stems from the difficulty of handling the metadata-intensive I/O generated by parallel applications accessing a single large directory. We demonstrate a middleware design called SFS to support existing parallel file systems for distributed and scalable directory service. SFS distributes directory entries over data servers instead of metadata servers to offer increased scalability and performance. Firstly, SFS exploits an adaptive directory partitioning based on extendible hashing to support concurrent and unsynchronized partition splitting. Secondly, SFS describes an optimization based on recursive split-ordering that emphasizes speeding up the splitting process. Thirdly, SFS applies a write-optimized index structure to convert slow, small, random metadata updates into fast, large, sequential writes. Finally, SFS gracefully tolerates stale mapping at the clients while maintaining the correctness and consistency of the system. Our performance results on a cluster of 32-servers show our implementation can deliver more than 250,000 file creations per second on average.

In this letter, the problem of how to set reserve prices so as to improve the primary user's revenue in the second price-sealed auction under the incomplete information of secondary users' private value functions is investigated. Dirichlet process is used to predict the next highest bid based on historical data of the highest bids. Before the beginning of the next auction round, the primary user can obtain a reserve price by maximizing the additional expected reward. Simulation results show that the proposed scheme can achieve an improvement of the primary user's averaged revenue compared with several counterparts.

Recent small cube satellites use higher frequency bands such as Ku-band for higher throughput communications. This requires high-frequency link in an earth radio station as well. As one of the solutions, we propose usage of bidirectional radio-on-fiber link employing a wavelength multiplexing scheme. It was numerically shown that the response linearity of the electro-absorption modulator integrated laser (EML) is sufficient and that the spurious emissions are lower enough or can be reduced by the radio-frequency filters. From the frequency response and the single-sideband phase noise measurements, the EML was proved to be used in a radio-on-fiber system of the cube satellite earth station.

Broadcasting and communications networks can be used together to offer hybrid broadcasting services that incorporate a variety of personalized information from communications networks in TV programs. To enable these services, many different applications have to be run on a user terminal, and it is necessary to establish an environment where any service provider can create applications and distribute them to users. The danger is that malicious service providers might distribute applications which may cause user terminals to take undesirable actions. To prevent such applications from being distributed, we propose an application authentication protocol for hybrid broadcasting and communications services. Concretely, we modify a key-insulated signature scheme and apply it to this protocol. In the protocol, a broadcaster distributes a distinct signing key to each service provider that the broadcaster trusts. As a result, users can verify that an application is reliable. If a signed application causes an undesirable action, a broadcaster can revoke the privileges and permissions of the service provider. In addition, the broadcaster can update the signing key. That is, our protocol is secure against leakage of the signing key by the broadcaster and service providers. Moreover, a user terminal uses only one verification key for verifying a signature, so the memory needed for storing the verification key in the user terminal is very small. With our protocol, users can securely receive hybrid services from broadcasting and communications networks.

This paper proposes Fast Fourier Transform (FFT) based orthogonal beam selection method at the user terminals (UTs) to reduce the number of nulls for the other users except an intended user by the Block Diagonalization (BD) algorithm in multiuser MIMO (MU-MIMO) sytems. The BD algorithm has been proposed in order to realize MU-MIMO broadcast transmission with a realistic signal processing burden. The BD algorithm cancels inter-user interference by creating the weights so that the channel matrixes for the other users are set to be zero matrixes. However, when the number of transmit antennas is equals to the total number of received antennas, the transmission rate by the BD algorithm is decreased. The proposed method realizes the performance improvement compared to the conventional BD algorithm without the burden on the UTs. It is verified via bit error rate (BER) evaluation that the proposed method is effective compared to the conventional BD algorithm and antenna selection method. Moreover, the effectiveness of proposed method is verified by the performance evaluation considering medium access control (MAC) layer in a comparison with the conventional BD algorithm which needs the channel state information (CSI) feedback. Because the proposed method can be easily applied to beamforming without the CSI feedback (implicit beamforming), it is shown that the propose method is effective from a point of view on the transmission efficiency in MU-MIMO system.