The thin film organic photovoltaic cells (OPVs) using organic semiconductors are inferior to oxgen-resistance and water-resistance, and the OPVs have a drawback that the photoelectric conversion efficiency (η) is low. For high efficiency of the OPVs, control of bulk heterojunction (BHJ) structure in the active layer is demanded. Therefore, it is thought that we can control the BHJ structure easily if we can bring a change in the aggregated structure and the crystallinity of the BHJ structure by introducing the third component that is different from the organic semiconductor into the activity layer. In this study, we introduced peptide consisting of phenylalanine of 2 molecules into the active layer prepared by poor solvent addition effect for the organic thin film solar cells and intended to try high efficiency of the organic thin film solar cells and examined the electrochemistry characteristic of the cells.

In this paper, we consider cloud-assisted Peer-to-Peer (P2P) video streaming systems, in which a given video stream is divided into several sub-streams called stripes and those stripes are delivered to all subscribers through different spanning trees of height two, with the aid of cloud upload capacity. We call such a low latency delivery of stripes a 2-hop delivery. This paper proves that if the average upload capacity of the peers equals to the bit rate of the video stream and the video stream is divided into a stripes, then 2-hop delivery of all stripes to n peers is possible if the upload capacity assisted by the cloud is 3n/a. If those peers have a uniform upload capacity, then the amount of cloud assistance necessary for the 2-hop delivery reduces to n/a.

Aimed at long-term monitoring of daily office conversations without recording the conversational content, a system is presented for estimating acoustic nonverbal information such as utterance duration, utterance frequency, and turn-taking. The system combines a sound localization technique based on the sound energy distribution with 16 beam-forming microphone-array modules mounted in the ceiling for reducing the influence of multiple sound reflection. Furthermore, human detection using a wide field of view camera is integrated to the system for more robust speaker estimation. The system estimates the speaker for each utterance and calculates nonverbal information based on it. An evaluation analyzing data collected over ten 12-hour workdays in an office with three assigned workers showed that the system had 72% speech segmentation detection accuracy and 86% speaker identification accuracy when utterances were correctly detected. Even with false voice detection and incorrect speaker identification and even in cases where the participants frequently made noise or where seven participants had gathered together for a discussion, the order of the amount of calculated acoustic nonverbal information uttered by the participants coincided with that based on human-coded acoustic nonverbal information. Continuous analysis of communication dynamics such as dominance and conversation participation roles through nonverbal information will reveal the dynamics of a group. The main contribution of this study is to demonstrate the feasibility of unconstrained long-term monitoring of daily office activity through acoustic nonverbal information.

This paper proposes a speaker-phonetic i-vector modeling method for text-dependent speaker verification with random digit strings, in which enrollment and test utterances are not of the same phrase. The core of the proposed method is making use of digit alignment information in i-vector framework. By utilizing force alignment information, verification scores of the testing trials can be computed in the fixed-phrase situation, in which the compared speech segments between the enrollment and test utterances are of the same phonetic content. Specifically, utterances are segmented into digits, then a unique phonetically-constrained i-vector extractor is applied to obtain speaker and channel variability representation for every digit segment. Probabilistic linear discriminant analysis (PLDA) and s-norm are subsequently used for channel compensation and score normalization respectively. The final score is obtained by combing the digit scores, which are computed by scoring individual digit segments of the test utterance against the corresponding ones of the enrollment. Experimental results on the Part 3 of Robust Speaker Recognition (RSR2015) database demonstrate that the proposed approach significantly outperforms GMM-UBM by 52.3% and 53.5% relative in equal error rate (EER) for male and female respectively.

With the rising importance of information security, the necessity of implementing better security measures in the physical layer as well as the upper layers is becoming increasing apparent. Given the development of more accurate and less expensive measurement devices, high-performance computers, and larger storage devices, the threat of advanced attacks at the physical level has expanded from the military and governmental spheres to commercial products. In this paper, we review the issue of information security degradation through electromagnetic (EM)-based compromising of security measures in the physical layer (i.e., EM information security). Owing to the invisibility of EM radiation, such attacks can be serious threats. We first introduce the mechanism of information leakage through EM radiation and interference and then present possible countermeasures. Finally, we explain the latest research and standardization trends related to EM information security.

Traffic engineering refers to techniques to accommodate traffic efficiently by dynamically configuring traffic routes so as to adjust to changes in traffic. If traffic changes frequently and drastically, the interval of route reconfiguration should be short. However, with shorter intervals, obtaining traffic information is problematic. To calculate a suitable route, accurate traffic information of the whole network must be gathered. This is difficult in short intervals, owing to the overhead incurred to monitor and collect traffic information. In this paper, we propose a framework for traffic engineering in cases where only partial traffic information can be obtained in each time slot. The proposed framework is inspired by the human brain, and uses conditional probability to make decisions. In this framework, a controller is deployed to (1) obtain a limited amount of traffic information, (2) estimate and predict the probability distribution of the traffic, (3) configure routes considering the probability distribution of future predicted traffic, and (4) select traffic that should be monitored during the next period considering the system performance yielded by route reconfiguration. We evaluate our framework with a simulation. The results demonstrate that our framework improves the efficiency of traffic accommodation even when only partial traffic information is monitored during each time slot.

This paper presents a design for the perpendicular-corporate feed in a four-layer circularly-polarized parallel-plate slot array antenna. We place a dielectric layer with adequate permittivity in the region between the coupling-aperture and the radiating-slot layers to remove x-shaped cavity walls completely in the radiating part of a conventional planar corporate-feed waveguide slot array antenna. To address fabrication constraints, the dielectric layer consists of PTFE and air. It excites a strong standing wave in the region and so provides 2×2-element subarrays with uniform excitation. None of the slot layers are in electrical contact due to air gaps between the slot layers. The four-layer structure with apertures for circular polarization contributes to wideband design for axial ratios because of the eigenmodes in the desired band. We realize an 11.9% bandwidth for axial ratios of less than 3.0dB as confirmed by measurements in the 60GHz band. At the design frequency, the measured realized gain is 32.7dBi with an antenna efficiency of 75.5%.

The separating redundancy is an important property in the analysis of the error-and-erasure decoding of a linear block code. In this work, we investigate the separating redundancy of the duals of first-order generalized Reed-Muller (GRM) codes, a class of nonbinary linear block codes that have nice algebraic properties. The dual of a first-order GRM code can be specified by two positive integers m and q and denoted by R(m,q), where q is the power of a prime number and q≠2. We determine the first separating redundancy value of R(m,q) for any m and q. We also determine the second separating redundancy values of R(m,q) for any q and m=1 and 2. For m≥3, we set up a binary integer linear programming problem, the optimum of which gives a lower bound on the second separating redundancy of R(m,q).

In 2017, Shirase proposed a variant of Elliptic Curve Method combined with Complex Multiplication method for generating certain special kinds of elliptic curves. His algorithm can efficiently factorize a given composite integer when it has a prime factor p of the form 4p=1+Dv2 for some integer v, where -D is an auxiliary input integer called a discriminant. However, there is a disadvantage that the previous method works only for restricted cases where the class polynomial associated to -D has degree at most two. In this paper, we propose a generalization of the previous algorithm to the cases of class polynomials having arbitrary degrees, which enlarges the class of composite integers factorizable by our algorithm. We also extend the algorithm to more various cases where we have 4p=t2+Dv2 and p+1-t is a smooth integer.

Frequency-hopping sequence (FHS) sets with low-hit-zone (LHZ) have Hamming correlations maintained at a low level as long as the relative time delay between different sequences are limited in a zone around the origin, and thus can be well applied in quasi-synchronous (QS) frequency-hopping multiple-access (FHMA) systems to reduce the mutual interference between different users. Moreover, the periodic partial Hamming correlation (PPHC) properties of employed LHZ-FHS sets usually act as evaluation criterions for the performances of QS-FHMA systems in practice. In this letter, a new class of LHZ-FHS sets is constructed via interleaving techniques. Furthermore, these new LHZ-FHS sets also possess optimal PPHC properties and parameters not included in the related literature.

The traffic of the future metro network will dynamically change not only in volume but also in destination to support the application of virtualization technology to network edge equipment such as cloud edges to achieve cost-effectiveness. Therefore, the future metro network will have to accommodate traffic cost-effectively, even though both the traffic volume and the traffic destination will change dynamically. To handle to this trend, in this paper, we propose a future metro network architecture based on Next-Generation Passive Optical Network Stage 2 systems that offers cost-effectiveness while supporting virtual machine migration of cloud edges. The basic idea of the proposed method is sharing a burst-mode receiver between the continuous-mode transmitters and burst-mode transmitters. In this paper, we show the feasibility and effectiveness of the proposed method with experiments on prototype systems, and simulations for the preliminary evaluation of network capital expenditure.

Software defect prediction (SDP) plays a significant part in allocating testing resources reasonably, reducing testing costs, and ensuring software quality. One of the most widely used algorithms of SDP models is Naive Bayes (NB) because of its simplicity, effectiveness and robustness. In NB, when a data set has continuous or numeric attributes, they are generally assumed to follow normal distributions and incorporate the probability density function of normal distribution into their conditional probabilities estimates. However, after conducting a Kolmogorov-Smirnov test, we find that the 21 main software metrics follow non-normal distribution at the 5% significance level. Therefore, this paper proposes an improved NB approach, which estimates the conditional probabilities of NB with kernel density estimation of training data sets, to help improve the prediction accuracy of NB for SDP. To evaluate the proposed method, we carry out experiments on 34 software releases obtained from 10 open source projects provided by PROMISE repository. Four well-known classification algorithms are included for comparison, namely Naive Bayes, Support Vector Machine, Logistic Regression and Random Tree. The obtained results show that this new method is more successful than the four well-known classification algorithms in the most software releases.

We propose a method for accurately identifying people using temporal and spatial changes in local movements measured from video sequences of body sway. Existing methods identify people using gait features that mainly represent the large swinging of the limbs. The use of gait features introduces a problem in that the identification performance decreases when people stop walking and maintain an upright posture. To extract informative features, our method measures small swings of the body, referred to as body sway. We extract the power spectral density as a feature from local body sway movements by dividing the body into regions. To evaluate the identification performance using our method, we collected three original video datasets of body sway sequences. The first dataset contained a large number of participants in an upright posture. The second dataset included variation over the long term. The third dataset represented body sway in different postures. The results on the datasets confirmed that our method using local movements measured from body sway can extract informative features for identification.

The security analysis of Keccak, the winner of SHA-3, has attracted considerable interest. Recently, some attention has been paid to distinguishing Keccak sponge function from random permutation. In EUROCRYPT'17, Huang et al. proposed conditional cube tester to recover the key of Keccak-MAC and Keyak and to construct practical distinguishing attacks on Keccak sponge function up to 7 rounds. In this paper, we improve the conditional cube tester model by refining the formulation of cube variables. By classifying cube variables into three different types and working the candidates of these types of cube variable carefully, we are able to establish a new theoretical distinguisher on 8-round Keccak sponge function. Our result is more efficient and greatly improves the existing results. Finally we remark that our distinguishing attack on the the reduced-round Keccak will not threat the security margin of the Keccak sponge function.

In this paper, we consider full-duplex (FD) relay networks with filter-and-forward (FF)-based multiple relays (FD-FF), where relay filters jointly mitigate self-interference (SI), inter-relay interference (IRI), and inter-symbol interference. We consider the filter design problem based on signal-to-noise-plus-interference ratio maximization subject to a total relay transmit power constraint. To make the problem tractable, we propose two methods: one that imposes an additional constraint whereby the filter responses to SI and IRI are nulled, and the other that makes i.i.d. assumptions on the relay transmit signals. Simulation results show that the proposed FD-FF scheme outperforms a conventional FF scheme in half-duplex mode. We also consider the filter design when only second-order statistics of channel path gains are available.

We introduce a notion of watermarking for cryptographic functions and propose a concrete scheme for watermarking cryptographic functions. Informally speaking, a digital watermarking scheme for cryptographic functions embeds information, called a mark, into functions such as one-way functions and decryption functions of public-key encryption. There are two basic requirements for watermarking schemes. A mark-embedded function must be functionally equivalent to the original function. It must be difficult for adversaries to remove the embedded mark without damaging the original functionality. In spite of its importance and usefulness, there have only been a few theoretical works on watermarking for functions (or programs). Furthermore, we do not have rigorous definitions of watermarking for cryptographic functions and concrete constructions. To solve the problem above, we introduce a notion of watermarking for cryptographic functions and define its security. Furthermore, we present a lossy trapdoor function (LTF) based on the decisional bilinear Diffie-Hellman problem problem and a watermarking scheme for the LTF. Our watermarking scheme is secure under the symmetric external Diffie-Hellman assumption in the standard model. We use techniques of dual system encryption and dual pairing vector spaces (DPVS) to construct our watermarking scheme. This is a new application of DPVS.

In the model of no-dictionary searchable symmetric encryption (SSE) schemes, the client does not need to keep the list of keywords W. In this paper, we first show a generic method to transform any passively secure SSE scheme to a no-dictionary SSE scheme such that the client can verify search results even if w ∉ W. In particular, it takes only O(1) time for the server to prove that w ∉ W. We next present a no-dictionary SSE scheme such that the client can hide even the search pattern from the server.

Homomorphic encryption (HE) is useful to analyze encrypted data without decrypting it. However, by using ordinary HE, a user who can decrypt a ciphertext that is generated by executing homomorphic operations, can also decrypt ciphertexts on which homomorphic evaluations have not been performed, since homomorphic operations cannot be executed among ciphertexts which are encrypted under different public keys. To resolve the above problem, we introduce a new cryptographic primitive called Homomorphic Proxy Re-Encryption (HPRE) combining the “key-switching” property of Proxy Re-Encryption (PRE) and the homomorphic property of HE. In our HPRE, original ciphertexts (which have not been re-encrypted) guarantee CCA2 security (and in particular satisfy non-malleability). On the other hand, re-encrypted ciphertexts only guarantee CPA security, so that homomorphic operations can be performed on them. We define the functional/security requirements of HPRE, and then propose a specific construction supporting the group operation (over the target group in bilinear groups) based on the PRE scheme by Libert and Vergnaud (PKC 2008) and the CCA secure public key encryption scheme by Lai et al. (CT-RSA 2010), and prove its security in the standard model. Additionally, we show two extensions of our HPRE scheme for the group operation: an HPRE scheme for addition and an HPRE scheme for degree-2 polynomials (in which the number of degree-2 terms is constant), by using the technique of the recent work by Catalano and Fiore (ACMCCS 2015).

Underwater optical wireless communication has been merely a theory for a long time because light sources are too weak to use them as emitters for communications. In the past decade, however, underwater optical wireless communications have used laser diodes or light emitting diodes as emitters with visible light in high brightness with low power consumption. Recently, they have become practical. As described in this paper, recent trends of underwater optical wireless communication study, practical modems and prospective uses of underwater optical wireless communication are presented first. Next, optical characteristics of the seawater in various conditions are explained based on the experimental data measured using the profiler for underwater optics produced especially for this study. Then the prototype underwater optical wireless communication modem developed by our team is introduced. It was tested in several sea areas, which confirmed bi-directional communication in the 120m range at 20Mbps and a remote desktop connection between under water vehicles at 100m range. In addition, one modem was set in air; other was set in water. The modems mutually communicated directly through the sea surface.

As a modulation scheme for optical wireless communication, there is MPolSK (multilevel polarization shift keying) that modulates a state of polarization of light. MPolSK has a problem that it is severely affected by mismatched polarization axes. Although MDPolSK (multilevel differential PolSK) can overcome the problem, it is susceptible to noise, and its SER (symbol error rate) degrades as compared to MPolSK. In this paper, we propose one kind of MDPolSK that estimates the mismatched polarization axes in the receiver. We analyzed SER of the proposed scheme by computer simulations. The result shows that the proposed scheme is not affected by the mismatched polarization axes, and it provides a good SER as compared to the conventional MDPolSK. In addition, we modified the constellation used in the proposed scheme to improve SER.