The performance of devices based on two dimensional (2D) materials is significantly affected upon prolonged exposure to atmosphere. We analyzed time based environmental degradation of electrical properties of HfS2 field effect transistors. Atmospheric entities like oxygen and moisture adversely affect the device surface and reduction in drain current is observed over period of 48 hours. Two corrective measures, namely, PMMA passivation and vacuum annealing, have been studied to address the diminution of current by contaminants. PMMA passivation prevents the device from environment and reduces the effect of Coulomb scattering. Improvement in current characteristics signifies the importance of dielectric passivation for 2D materials. On the other hand, vacuum annealing is useful in removing contaminants from the affected surface. In order to figure out optimum process conditions, properties have been studied at various annealing temperatures. The improvement in drain current level was observed upon vacuum annealing within optimum range of annealing temperature.

In IEEE802.11 Wireless Local Area Networks (WLANs), frame collisions occur drastically when the number of wireless terminals connecting to the same Access Point (AP) increases. It causes the decrease of the total throughput of all terminals. To solve this issue, the authors have proposed a new media access control (MAC) method, Synchronized Phase MAC (SP-MAC), based on the synchronization phenomena of coupled oscillators. We have addressed the network environment in which only uplink flows from the wireless terminal to an AP exist. However, it is necessary to take into consideration of the real network environment in which uplink and downlink flows are generated simultaneously. If many bidirectional data flows exist in the WLAN, the AP receives many frames from both uplink and downlink by collision avoidance of SP-MAC. As a result, the total throughput decreases by buffer overflow in the AP. In this paper, we propose a priority control method based on SP-MAC for avoiding the buffer overflow in the AP under the bidirectional environment. Also, we show that the proposed method has an effect for improving buffer overflow in the AP and total throughput by the simulation.

In this paper, the effect of a nitrogen-doped (N-doped) LaB6 interfacial layer (IL) on p-type pentacene-based OFET was investigated. The pentacene-based OFET with top-contact/back-gate geometry was fabricated. A 2-nm-thick N-doped LaB6 interfacial layer deposited on an 8-nm-thick SiO2 gate insulator. A 10-nm-thick pentacene film was deposited by thermal evaporation at 100°C followed by Au contact and Al back gate electrodes formation. The fabricated OFET showed normally- off characteristics and a steep subthreshold swing (SS) of 84 mV/dec. from ID-VG and ID-VD characteristics. Furthermore, the aging characteristics of 6 months after the fabrication were investigated and it was found that VTH and SS were stable when the N-doped LaB6 IL was introduced at the interface between SiO2 gate insulator and pentacene.

The translation based language model (TRLM) is state-of-the-art method to solve the lexical gap problem of the question retrieval in the community-based question answering (cQA). Some researchers tried to find methods for solving the lexical gap and improving the TRLM. In this paper, we propose a new dependency based model (DM) for the question retrieval. We explore how to utilize the results of a dependency parser for cQA. Dependency bigrams are extracted from the dependency parser and the language model is transformed using the dependency bigrams as bigram features. As a result, we obtain the significant improved performances when TRLM and DM approaches are effectively combined.

The region that includes the register file is a hot spot in high-performance cores that limits the clock frequency. Although multibanking drastically reduces the area and energy consumption of the register files of superscalar processor cores, it suffers from low IPC due to bank conflicts. Our skewed multistaging drastically reduces not the bank conflict probability but the pipeline disturbance probability by the second stage. The evaluation results show that, compared with NORCS, which is the latest research on a register file for area and energy efficiency, a proposed register file with 18 banks achieves a 39.9% and 66.4% reduction in circuit area and in energy consumption, while maintaining a relative IPC of 97.5%.

In this paper, an adaptive updating probabilistic model is proposed to track an object in real-world environment that includes motion blur, illumination changes, pose variations, and occlusions. This model adaptively updates tracker with the searching and updating process. The searching process focuses on how to learn appropriate tracker and updating process aims to correct it as a robust and efficient tracker in unconstrained real-world environments. Specifically, according to various changes in an object's appearance and recent probability matrix (TPM), tracker probability is achieved in Expectation-Maximization (EM) manner. When the tracking in each frame is completed, the estimated object's state is obtained and then fed into update current TPM and tracker probability via running EM in a similar manner. The highest tracker probability denotes the object location in every frame. The experimental result demonstrates that our method tracks targets accurately and robustly in the real-world tracking environments.

In this paper, we proposed a method for radar modulation identification based on the measurement of inequality in the frequency domain. Gini's coefficient was used to exploit the inequality in the powers of spectral components. The maximum likelihood classifier was used to classify the detected radar signal into four types of modulations: unmodulated signal (UM), linear frequency modulation (LFM), non-linear frequency modulation (NLFM), and frequency shift keying (FSK). The simulation results demonstrated that the proposed method achieves an overall identification accuracy of 98.61% at a signal-to-noise ratio (SNR) of -6dB without a priori information such as carrier frequency, pulse arrival times or pulse width.

Cyclic codes are a subclass of linear codes and have applications in consumer electronics, data storage systems, and communication systems as they have efficient encoding and decoding algorithms. In this letter, a class of four-weight binary cyclic codes are presented. Their weight distributions of these cyclic codes are also settled.

A dual-hop amplify-and-forward (AF) relaying system with beamforming is analyzed over η-µ fading channels that includes Nakagami-m, Nakagami-q (Hoyt), and Rayleigh fading channels as special cases. New and exact expressions for the outage probability (OP) and average capacity are derived. Moreover, a new asymptotic analysis is also conducted for the OP and average capacity in terms of basic elementary functions which make it easy to understand the system behavior and the impact of channel parameters. The viability of the analysis is verified by Monte Carlo simulations.

This paper presents the design and characterization of an E-band 16×16-slot monopulse array antenna with full-corporate-feed fabricated by the commercially available batch process of diffusion bonding of laminated copper plates. The antenna is multi-layered, and consists of vertically-interconnected radiating elements, a corporate-feed circuit and a comparator. It has four input ports for different excitations. Sum and difference beams in different cut-planes for monopulse operation can be generated. The antenna has a quasi-planar profile, and a total size of 13.31 λ0×13.31λ0×1.52λ0 (λ0 is the wavelength at the design frequency of 78.5GHz). The antenna demonstrates a wide operation bandwidth of 17.2 (70-87.2) GHz for VSWR < 2. At 78.5GHz: 1) for the sum beam, there is a 32.6-dBi realized gain (83% antenna efficiency) and a 33.3-dBi directivity (95% aperture efficiency); 2) for the difference beams in the E-, H-, 45°-, and 135°-planes, the null depths are -53.0, -58.0, -57.8, and -65.6dB, respectively. Across the full operation band where the sum main-beam and difference null are able to consistently point at the boresight, the antenna also demonstrates excellent performance in terms of high gain, high efficiency, high isolation, low cross-polarization, and distinguished monopulse capability.

This paper presents a soft-error-tolerant memory-control circuit for SRAM-based field programmable gate arrays (FPGAs). A potential obstacle to applying such FPGAs to safety-critical industrial control systems is their low tolerance. The main reason is that soft errors damage circuit-configuration data stored in SRAM-based configuration memory. To overcome this obstacle, the soft-error tolerance must thus be improved while suppressing the circuit area overhead, and data stored in external memory must be protected when a fault occurs on the FPGA. Therefore, a memory-control circuit was developed on the basis of a dual-modular-redundancy (DMR) architecture. This memory controller has a repair and retry scheme that repairs damaged circuit-configuration data and re-executes unfinished accesses after the repair. The developed architecture reduces circuit redundancy below that of a commonly used triple-modular-redundancy (TMR) architecture. Moreover, a write-invalidation circuit was developed to protect data in external memory, and an external-memory-state recovery circuit was developed to enable resumption of memory access after fault repair. The developed memory controller was implemented in a prototype circuit on an FPGA and evaluated using the prototype. The evaluation results demonstrated that the developed memory controller can operate successfully for 1.03×109 hours (at sea level). In addition, its circuit area overhead was found to be sufficiently smaller than that of the TMR architecture.

In order to realize solid-state drives (SSDs) with high performance, low energy consumption and high reliability, storage class memory (SCM)/multi-level cell (MLC) NAND flash hybrid SSD has been proposed. Algorithm of the hybrid SSD should be designed according to SCM specifications and workload characteristics. In this paper, SCMs are used as non-volatile cache. Cache operation guidelines and optimal SCM specifications for the hybrid SSD are provided for various workload characteristics. Three kinds of non-volatile cache operation for the hybrid SSD are discussed: i) write cache, ii) read-write cache without space control (RW cache) and iii) read-write cache with space control (RW cache w/ SC). SSD workloads are categorized into eight according to read/write ratio, access frequency and access data size. From evaluation result, the write cache algorithm is suitable for write-intensive workloads and read-cold-sequential workloads, while the RW cache algorithm is suitable for read-cold-random workloads to achieve the highest performance of the hybrid SSD. In contrast, as for read-hot-random workloads, write cache is appropriate when the SCM capacity is less than 3% of the NAND flash capacity. On the other hand, RW cache should be used in case that SCM capacity is more than 5% of NAND flash capacity. The effect of Memory-type SCM (M-SCM) and Storage-type SCM (S-SCM) on the hybrid SSD performance is also analyzed. The M-SCM latency is below 1 us (high speed) but the capacity is only 2% of the NAND flash capacity (small capacity). On the other hand, the S-SCM capacity is assumed to be 5% of the NAND flash capacity (large capacity) but S-SCM speed is larger than 1 us (low speed). If the additional SCM cost is limited to 20% of MLC NAND flash cost, up to 7-times and 8-times performance improvement are achieved in write-hot-random workload and read-hot-random workloads, respectively. Moreover, if the additional SCM cost is the same as MLC NAND flash cost, M-SCM/MLC NAND flash hybrid SSD achieves 24-times performance improvement.

The development of smart devices has led to the growth of Location-Based Social Networking Services (LBSNSs). In this paper, we introduce an l-Close Range Friends query that finds all l-hop friends of a user within a specified range. We also propose a query processing method on Social Grid Index (SGI). Using real datasets, the performance of our method is evaluated.

Nowadays, with the extensive use of smart devices, the amount of mobile data is experiencing an exponential growth. As a result, accommodating the large amount of traffic is important for the future 5G mobile communication. Millimeter-wave band, which has a lot of spectrum resources to meet the demand brought by the growth of mobile data, is becoming an important part of 5G technology. In order to mitigate the high path loss brought by the high frequency band, beamforming is often used to enhance the gain of a link. In this paper, we propose an iteration-based beamforming method for planar phased array. When compared to a linear array, a planar phased array points a smaller area which ensures a better link performance. We deduce that different paths of millimeter-wave channel are approximately orthogonal when the antenna array is large, which forms the basis of our iterative approach. We also discuss the development of the important millimeter-wave device-phase shifter, and its effect on the performance of the proposed beamforming method. From the simulation, we prove that our method has a performance close to the singular vector decomposition (SVD) method and is superior to the method in IEEE802.15.3c. Moreover, the channel capacity of the proposed method is at most 0.41bps/Hz less than the SVD method. We also show that the convergence of the proposed method could be achieved within 4 iterations and a 3-bit phase shifter is enough for practical implementation.

This paper studies a novel iterative detection algorithm for data detection in orthogonal frequency division multiplexing systems in the presence of phase noise (PHN) and channel estimation errors. By simplifying the maximum a posteriori algorithm based on the theory of variational inference, an optimization problem over variational free energy is formulated. After that, the estimation of data, PHN and channel state information is obtained jointly and iteratively. The simulations indicate the validity of this algorithm and show a better performance compared with the traditional schemes.

This study introduces large-scale field experiments of VoiceTra, which is the world's first speech-to-speech multilingual translation application for smart phones. In the study, approximately 10 million input utterances were collected since the experiments commenced. The usage of collected data was analyzed and discussed. The study has several important contributions. First, it explains system configuration, communication protocol between clients and servers, and details of multilingual automatic speech recognition, multilingual machine translation, and multilingual speech synthesis subsystems. Second, it demonstrates the effects of mid-term system updates using collected data to improve an acoustic model, a language model, and a dictionary. Third, it analyzes system usage.

A 1.9GHz film bulk acoustic resonator (FBAR)-based low-phase-noise complementary cross-coupled voltage-controlled oscillator (VCO) is presented. The FBAR-VCO is designed and fabricated in 0.18µm CMOS process. The DC latch and the low frequency instability are resolved by employing the NMOS source coupling capacitor and the DC blocked cross-coupled pairs. Since no additional voltage headroom is required, the proposed FBAR-VCO can be operated at a low power supply voltage of 1.1V with a wide voltage swing of 0.9V. An effective phase noise optimization is realized by a reasonable trade-off between the output resistance and the trans-conductance of the cross-coupled pairs. The measured performance shows the proposed FBAR-VCO achieves a phase noise of -148dBc/Hz at 1MHz offset with a figure of merit (FoM) of -211.6dB.

A linear-correction method is developed for source position and velocity estimation using time difference of arrival (TDOA) and frequency difference of arrival (FDOA) measurements. The proposed technique first obtains an initial source location estimate using the first-step processing of an existing algebraic algorithm. It then refines the initial localization result by estimating via weighted least-squares (WLS) optimization and subtracting out its estimation error. The new solution is shown to be able to achieve the Cramer-Rao lower bound (CRLB) accuracy and it has better accuracy over several benchmark methods at relatively high noise levels.