In this study, we evaluated the electro-optical characteristics and structural stability in curved state of dye-doped liquid crystal (LC) gel film for stretchable displays. As the results, maximum contrast ratio of 6.7:1 and suppression of LC flow were achieved by optimum of blend condition such as gelator and dye concentration.

In this paper, we review a super-steep subthreshold slope (SS) (<1 mV/dec) body-tied (BT) silicon on insulator (SOI) metal oxide semiconductor field effect transistor (MOSFET) fabricated with 0.15 µm SOI technology and discuss the possibility of its use in ultralow voltage applications. The mechanism of the super-steep SS in the BT SOI MOSFET was investigated with technology computer-aided design simulation. The gate length/width and Si thickness optimizations promise further reductions in operation voltage, as well as improvement of the ION/IOFF ratio. In addition, we demonstrated control of the threshold voltage and hysteresis characteristics using the substrate and body bias in the BT SOI MOSFET.

This paper proposes a novel pseudo multi-exposure image fusion method based on a single image. Multi-exposure image fusion is used to produce images without saturation regions, by using photos with different exposures. However, it is difficult to take photos suited for the multi-exposure image fusion when we take a photo of dynamic scenes or record a video. In addition, the multi-exposure image fusion cannot be applied to existing images with a single exposure or videos. The proposed method enables us to produce pseudo multi-exposure images from a single image. To produce multi-exposure images, the proposed method utilizes the relationship between the exposure values and pixel values, which is obtained by assuming that a digital camera has a linear response function. Moreover, it is shown that the use of a local contrast enhancement method allows us to produce pseudo multi-exposure images with higher quality. Most of conventional multi-exposure image fusion methods are also applicable to the proposed multi-exposure images. Experimental results show the effectiveness of the proposed method by comparing the proposed one with conventional ones.

Smallcells have recently emerged as a potential approach for local area deployments that can satisfy high data rate requirements, reduce energy consumption and enhance network coverage. In this paper, we work on maximizing the weighted sum energy efficiency (WS-EE) for densely deployed smallcell networks. Due to the combinatorial and the general fractional program nature of the resource allocation problem, WS-EE maximization is non-convex and the optimal joint resource blocks (RBs) and power allocation is NP-hard. To solve this complex problem, we propose to decompose the primal problem into two subproblems (referred as RBs allocation and power control) and solve the subproblems sequentially. For the RBs allocation subproblem given any feasible network power profile, the optimal solution can be solved by maximizing throughput locally. For the power control subproblem, we propose to solve it locally based on a new defined pricing factor. Then, a distributed power control algorithm with guaranteed convergence is designed to achieve a Karush-Kuhn-Tucker (KKT) point of the primal problem. Simulation results verify the performance improvement of our proposed resource allocation scheme in terms of WS-EE. Besides, the performance evaluation shows the tradeoff between the WS-EE and the sum rate of the smallcell networks.

In this paper, we consider coded multi-input multi-output (MIMO) systems with low-density parity-check (LDPC) codes and space-time block code (STBC) in MIMO channels. The LDPC code takes the role of a channel code while the STBC provides spatial-temporal diversity. The performance of such coded MIMO system has been shown to be excellent in the past. In this paper, we present a performance analysis for an upper bound on probability of error for coded MIMO schemes. Compared to previous works, the proposed approach for the upper bound can avoid any explicit weight enumeration of codewords and provide a significant step for the upper bound by using a multinomial theorem. In addition, we propose a log domain convolution that enables us to handle huge numbers, e.g., 10500. Comparison of system simulations and numerical evaluations shows that the proposed upper bound is applicable for various coded MIMO systems.

As real-time embedded systems are required to accommodate various tasks with different levels of criticality, scheduling algorithms for MC (Mixed-Criticality) systems have been widely studied in the real-time systems community. Most studies have focused on MC uniprocessor systems whereas there have been only a few studies to support MC multiprocessor systems. In particular, although the ZL (Zero-Laxity) policy has been known to an effective technique in improving the schedulability performance of base scheduling algorithms on SC (Single-Criticality) multiprocessor systems, the effectiveness of the ZL policy on MC multiprocessor systems has not been revealed to date. In this paper, we focus on realizing the potential of the ZL policy for MC multiprocessor systems, which is the first attempt. To this end, we design the ZL policy for MC multiprocessor systems, and apply the policy to EDF (Earliest Deadline First), yielding EDZL (Earliest Deadline first until Zero-Laxity) tailored for MC multiprocessor systems. Then, we develop a schedulability analysis for EDZL (as well as its base algorithm EDF) to support its timing guarantee. Our simulation results show a significant schedulability improvement of EDZL over EDF, demonstrating the effectiveness of the ZL policy for MC multiprocessor systems.

Peer code review is key to ensuring the absence of software defects. To reduce review costs, software developers adopt code convention checking tools that automatically identify maintainability issues in source code. However, these tools do not always address the maintainability issue for a particular project. The goal of this study is to understand how code review fixes conditional statement issues, which are the most frequent changes in software development. We conduct an empirical study to understand if-statement changes through code review. Using review requests in the Qt and OpenStack projects, we analyze changes of the if-conditional statements that are (1) requested to be reviewed, and are (2) revised through code review. We find the most frequently changed symbols are “( )”, “.”, and “!”. We also find project-specific fixing patterns for improving code readability by association rule mining. For example “!” operator is frequently replaced with a function call. These rules are useful for improving a coding convention checker tailored for the projects.

A new projection-based color-to-gray conversion method is proposed in this letter. In the proposed method, an objective function which considers color contrasts in an input image is defined. Projection coefficients are determined by minimizing the objective function. Experimental results show the validity of the proposed method.

Binary sparse representation based on arbitrary quality metrics and its applications are presented in this paper. The novelties of the proposed method are twofold. First, the proposed method newly derives sparse representation for which representation coefficients are binary values, and this enables selection of arbitrary image quality metrics. This new sparse representation can generate quality metric-independent subspaces with simplification of the calculation procedures. Second, visual saliency is used in the proposed method for pooling the quality values obtained for all of the parts within target images. This approach enables visually pleasant approximation of the target images more successfully. By introducing the above two novel approaches, successful image approximation considering human perception becomes feasible. Since the proposed method can provide lower-dimensional subspaces that are obtained by better image quality metrics, realization of several image reconstruction tasks can be expected. Experimental results showed high performance of the proposed method in terms of two image reconstruction tasks, image inpainting and super-resolution.

This paper proposes a directional noise suppressor with a specified constant beamwidth for directional interferences and diffuse noise. A directional gain is calculated based on interchannel phase difference and combined with a spectral gain commonly used in single-channel noise suppressors. The beamwidth can be specified as passband edges of the directional gain. In order to implement frequency-independent constant beamwidth, frequency-proportionate directional gains are defined for different frequencies as a constraint. Evaluation with signals recorded by a commercial PC demonstrates good agreement between the theoretical and the measured directivity. The signal-to-noise ratio improvement and the PESQ score for the enhanced signal are improved by 24.4dB and 0.3 over a conventional noise suppressor. In a speech recognition scenario, the proposed directional noise suppressor outperforms both the conventional nondirectional noise suppressor and the conventional directional noise suppressor based on phase based T/F filtering with a negligible degradation in the word error rate for clean speech.

Once a bug is reported, it is a major concern whether or not the bug is resolved (closed) soon. This paper examines seven metrics quantifying the amount of clues to the early close of reported bugs through a case study. The results show that one of the metrics, the similarity to already-closed bug reports, is strongly related to early-closed bugs.

This paper discusses VDT syndrome from the point of view of the viewing distance between a computer screen and user's eyes. This paper conducts a series of experiments to show an impact of the viewing distance on task performance. In the experiments, two different viewing distances of 50cm and 350cm with the same viewing angle of 30degrees are taken into consideration. The results show that the long viewing distance enables people to manipulate the mouse more slowly, more correctly and more precisely than the short.

In this paper, we propose an IEEE 802.15.10-based layer 2 routing (L2R) method with a load balancing algorithm; the proposal considers fairness in terms of the cumulative number of sending packets at each terminal to resolve the packet concentration problem for the IEEE 802.15.4-based low-power consumption wireless smart utility network (Wi-SUN) systems. The proposal uses the accumulated sending times of each terminal as a weight in calculating each path quality metric (PQM) to decide multi-hopping routes with load balancing in the network. Computer simulation of the mesh network with 256 terminals shows that the proposed routing method can improve the maximum sending ratio (MSR), defined as the ratio of the maximum sending times to the average number of sending times in the network, by 56% with no degradation of the end-to-end communication success ratio (E2E-SR). The proposed algorithm is also experimentally evaluated by using actual Wi-SUN modules. The proposed routing method also improves the MSR by 84% with 70 terminals. Computer simulations and experiments prove the effectiveness of the proposed method in terms of load balancing.

With the development of wireless network technology and popularization of mobile devices, the Wireless Local Area Network (WLAN) has become an indispensable part of our daily life. Although the 802.11-based WLAN provides enormous convenience for users to access the Internet, it also gives rise to a number of security issues. One of the most severe threat encountered by Wi-Fi users is the evil twin attacks. The evil twin, a kind of rogue access points (RAPs), masquerades as a legitimate access point (AP) to lure users to connect it. Due to the characteristics of strong concealment, high confusion, great harmfulness and easy implementation, the evil twin has led to significant loss of sensitive information and become one of the most prominent security threats in recent years. In this paper, we propose a passive client-based detection solution that enables users to independently identify and locate evil twins without any assistance from a wireless network administrator. Because of the forwarding behavior of evil twins, proposed method compares 802.11 data frames sent by target APs to users to determine evil twin attacks. We implemented our detection technique in a Python tool named ET-spotter. Through implementation and evaluation in our study, our algorithm achieves 96% accuracy in distinguishing evil twins from legitimate APs.

In an approximately synchronized (AS) code-division multiple-access (CDMA) communication system, zero correlation zone (ZCZ) sequences can be used as its spreading sequences so that the system suppresses multiple access interference (MAI) and multi-path interference (MPI) fully and synchronously. In this letter, the mutually orthogonal (MO) ZCZ polyphase sequence sets proposed by one of the authors are improved, and the resultant ZCZ sequences in each set arrive at the theoretical bound regarding ZCZ sequences under some conditions. Therefore, the improved MO ZCZ sequence sets are optimal.

We developed and applied a new circuit, called the “Self-controllable Voltage Level (SVL)” circuit, not only to expand both “write” and “read” stabilities, but also to achieve a low stand-by power and data holding capability in a single low power supply, 90-nm, 2-kbit, six-transistor CMOS SRAM. The SVL circuit can adaptively lower and higher the word-line voltages for a “read” and “write” operation, respectively. It can also adaptively lower and higher the memory cell supply voltages for the “write” and “hold” operations, and “read” operation, respectively. This paper focuses on the “hold” characteristics and the standby power dissipations (PST) of the developed SRAM. The average PST of the developed SRAM is only 0.984µW, namely, 9.57% of that (10.28µW) of the conventional SRAM at a supply voltage (VDD) of 1.0V. The data hold margin of the developed SRAM is 0.1839V and that of the conventional SRAM is 0.343V at the supply voltage of 1.0V. An area overhead of the SVL circuit is only 1.383% of the conventional SRAM.

This paper theoretically revisits linear passive two-port systems from the viewpoint of power transfer. Instead of using the conventional S21 magnitude, we propose generalizing the kQ product as a figure of merit for two-port performance evaluation. We explore three examples of power transfer schemes, i.e. inductive, capacitive, and resistive channels. Starting from their voltage-current equations, the kQ formula is analytically derived for each scheme. The resultant formulas look different in appearance but are all physically consistent with ωM/R, which stems from the original definition of kQ product in a primitive transformer. After comprehensively learning from the three examples, we finally extend the theory to a black-box model that represents any kind of power transfer channel. In terms of general two-port Z-parameters, useful mathematical expressions are deduced for the optimum load, input impedance, and maximum power transfer efficiency. We also supplement the theory with helpful graphics that explain how the generalized kQ behaves as a function of the circuit parameters.