This paper proposes fabrication process of a pyramidal electromagnetic (EM) absorber made by natural rubber. The advantage of this research is to generate value-added latex from Thai rubber and to reduce number of chemical absorber by using natural rubber based absorber. The proposed absorber in the research is mainly made from latex with carbon black filler. The proposed absorber is in the form of rubber foam which provides suitable characteristics to serve as an EM absorber. The results of this research are chemical formulas for fabrication of pyramidal rubber foam with carbon black filler. The fabrication cost is very low when compared to an available commercial absorber. The electrical properties of the proposed EM absorber are measured. Also the reflectivity is measured and compared well with a commercial EM absorber.

In this paper, a printed inverted-F antenna for radiating circularly polarized wave around its resonant frequency is proposed. To get good axial ratio at the frequency band with 10dB-return loss, a rectangular element is loaded at the feeding line perpendicularly. The axial ratio and the frequency giving the minimum axial ratio can be adjusted by the ratio of the length to the width of the whole antenna and by the dimension of the loaded rectangular element. The operational principle for circular polarization is explained using the electric current distributions. Moreover, the approach of the enhancement for the bandwidth is discussed. The simulated and measured bandwidths of the 10dB-return loss with a 3dB-axial ratio are 2.375GHz-2.591GHz (216MHz) and 2.350-2.534GHz (184MHz), respectively. The proposed antenna's dimension is 0.067λ2c (λc is the wavelength at the center frequency). The proposed antenna is compact and planar, and is therefore useful for circular polarization in the ISM band.

Two kinds of composite right/left-handed coaxial lines (CRLH CLs) are designed for an antenna element. The dispersion relations of the infinite periodic CRLH CLs are designed to occur -1st resonance at around 700 MHz, respectively. The designed CRLH CLs comprise a monopole and a choke structure for antenna elements. To verify the resonant modes and frequencies, the monopole structure, the choke structure, and the antenna element which is combined the monopole and the choke structures are simulated by eigenmode analysis. The resonant frequencies correspond to the dispersion relations. The monopole and the choke structures are applied to the coaxially fed antenna. The proposed antenna matches at 710 MHz and radiates. At the resonant frequency, the total length of the proposed antenna which is the length of the monopole structure plus the choke structure is 0.12 wavelength. The characteristics of the proposed antenna has been compared with that of the conventional coaxially fed monopole antenna without the choke structure and the sleeve antenna with the quarter-wavelength choke structure. The radiation pattern of the proposed antenna is omnidirectional, the total antenna efficiency is 0.73 at resonant frequencies, and leakage current is suppressed lesser than -10 dB at resonant frequency. The propose antenna is fabricated and measured. The measured |S11| characteristics, radiation patterns, and the total antenna efficiency are in good agreement with the simulated results.

In order to provide an alternative solution of human machine interfaces, this paper proposed to recognize 10 human hand gestures regularly used in the consumer electronics controlling scenarios based on a three-dimensional radar array. This radar array was composed of three low cost 24GHz K-band Doppler CW (Continuous Wave) miniature I/Q (In-phase and Quadrature) transceiver sensors perpendicularly mounted to each other. Temporal and spectral analysis was performed to extract magnitude and phase features from six channels of I/Q signals. Two classifiers were proposed to implement the recognition. Firstly, a decision tree classifier performed a fast responsive recognition by using the supervised thresholds. To improve the recognition robustness, this paper further studied the recognition using a two layer CNN (Convolutional Neural Network) classifier with the frequency spectra as the inputs. Finally, the paper demonstrated the experiments and analysed the performances of the radar array respectively. Results showed that the proposed system could reach a high recognition accurate rate higher than 92%.

Vehicular ad hoc network (VANET) is an emerging technology for the future intelligent transportation systems (ITS). How to design an efficient routing protocol for VANET is a challenging task due to the high mobility and uneven distribution of vehicles in urban areas. This paper proposes a backbone-based approach to providing the optimal inner-street relaying strategy. The virtual backbone is created distributively in each road segment based on the newly introduced stability index, which considers the link stability between vehicles and the mobility of vehicles. We also deploy the roadside unit (RSU) at intersections to determine the next path for forwarding data. The RSU gathers a global view of backbone vehicles on each road connected to the junction and analyzes the performance of the backbone as a basis of routing path selection. Simulation results show that the proposed protocol outperforms the conventional protocols in terms of packet delivery ratio and end-to-end delay.

Multi-static Primary Surveillance Radar (MSPSR) has recently attracted attention as a new surveillance technology for civil aviation. Using multiple receivers, Primary Surveillance Radar (PSR) detection performance can be improved by synthesizing the reflection characteristics which change due to the aircraft's position. In this paper, we report experimental results from our proposed optical-fiber-connected passive PSR system with transmit signal installed at the Sendai Airport in Japan. The signal-to noise ratio of experimental data is evaluated to verify moving target detection. In addition, we confirm the operation of the proposed system using a two-receiver setup, to resemble a conventional multi-static radar. Finally, after applying time correction, the delay of the reflected signal from a stationary target remains within the expected range.

It is well known that the power transfer efficiency (PTE) of a wireless power transfer (WPT) system is maximized at a specific coupling coefficient under the fixed system parameters. For an adaptive WPT system, various attempts have been made to achieve the maximum PTE by changing the system parameters. Applying the input matching networks to the WPT system is one of the most popular implementation methods to change the source impedance and improve the PTE. In this paper, we derive the optimum source condition for the given load and the achievable maximum PTE under the optimum source condition in a closed-form. Furthermore, we propose a method to estimate the input impedance, without feedback information, and an input matching network structure that transforms the source impedance into the optimum source obtained from the estimated input impedance. The proposed technique is successfully implemented at a resonant frequency of 13.56MHz. The experimental results are in close agreement with the theoretical achievable maximum PTE and show that the use of only a single matching network can sufficiently achieve a PTE close to the ideal maximum PTE.

We propose a novel bit error rate (BER) analysis model of weighted-type fractional Fourier transform (WFRFT)-based systems with WFRFT order offset Δα. By using the traditional BPSK BER analysis method, we deduce the equivalent signal noise ratio (SNR), model the interference in the channel as a Gaussian noise with non-zero mean, and provide a theoretical BER expression of the proposed system. Simulation results show that its theoretical BER performance well matches the empirical performance, which demonstrates that the theoretical BER analysis proposed in this paper is reliable.

Pilot contamination due to pilot reuse in adjacent cells is a very serious problem in massive multi-input multiple-output (MIMO) systems. Therefore, proper pilot allocation is essential for improving system performance. In this paper, we formulate the pilot allocation optimization problem so as to maximize uplink sum rate of the system. To reduce the required complexity inherent in finding the optimum pilot allocation, we propose a low-complexity pilot allocation algorithm, where the formulated problem is decoupled into multiple subproblems; in each subproblem, the pilot allocation at a given cell is optimized while the pilot allocation in other cells id held fixed. This process is continued until the achievable sum rate converges. Through multiple iterations, the optimum pilot allocation is found. In addition, to improve users' fairness, we formulate fairness-aware pilot allocation as maximization problem of sum of user's logarithmic rate and solve the formulated problem using a similar algorithm. Simulation results show that the proposed algorithms match the good performance of the exhaustive search algorithm, meanwhile the users' fairness is improved.

Recent carrier-grade networks use many network elements (switches, routers) and servers for various network-based services (e.g., video on demand, online gaming) that demand higher quality and better reliability. Network log data generated from these elements, such as router syslogs, are rich sources for quickly detecting the signs of critical failures to maintain service quality. However, log data contain a large number of text messages written in an unstructured format and contain various types of network events (e.g., operator's login, link down); thus, genuinely important log messages for network operation are difficult to find automatically. We propose a proactive failure-detection system for large-scale networks. It automatically finds abnormal patterns of log messages from a massive amount of data without requiring previous knowledge of data formats used and can detect critical failures before they occur. To handle unstructured log messages, the system has an online log-template-extraction part for automatically extracting the format of a log message. After template extraction, the system associates critical failures with the log data that appeared before them on the basis of supervised machine learning. By associating each log message with a log template, we can characterize the generation patterns of log messages, such as burstiness, not just the keywords in log messages (e.g. ERROR, FAIL). We used real log data collected from a large production network to validate our system and evaluated the system in detecting signs of actual failures of network equipment through a case study.

This paper proposes optimal beam patterns of analog beamforming for SU (Single User) massive MIMO (Multi-Input Multi-Output) transmission systems. For hybrid beamforming in SU massive MIMO systems, there are several design parameters such as beam patterns, the number of beams (streams), the shape of array antennas, and so on. In conventional hybrid beamforming, rectangular patch array antennas implemented on a planar surface with linear phase shift beam patterns have been used widely. However, it remains unclear whether existing configurations are optimal or not. Therefore, we propose a method using OBPB (Optimal Beam Projection Beamforming) for designing configuration parameters of the hybrid beamforming. By using the method, the optimal beam patterns are derived first, and are projected on the assumed surface to calculate the achievable number of streams and the resulting channel capacity. The results indicate OBPB with a spherical surface yields at least 3.5 times higher channel capacity than conventional configurations.

Semitransparent organic solar cells were fabricated using lamination process. The devices were realized by using two independent substrates with transparent indium-tin-oxide electrode. One substrate was coated with poly(ethylenedioxy-thiophene)/poly(styrenesulfonate) layer and active layer of poly(3-hexylthiophene-2,5-diyl) (P3HT) and (6,6)-phenyl-C61 butyric acid methyl ester mixture. Another substrate was coated with ultra-thin polyethylenimine ethoxylated. The two substrates were laminated using hot press system. The device exhibited semitransparency and showed typical photovoltaic characteristics with open voltage of 0.59 V and short circuit current of 2.9 mA/cm2.

Photophysical properties of water-soluble porphyrin were studied in aqueous solutions with/without DNA and in DNA solid films. Ultrathin films were prepared from aqueous DNA solutions by a spin-coating method on glass or on gold nanoparticles (AuNPs). Remarkable enhancement of phosphorescence was observed for porphyrin immobilized in DNA films spin-coated on AuNPs, which was attributed to the electric field enhancement and the increased radiative rate by localized surface plasmon resonance of AuNPs.

Photon upconversion (UC) is a technique to convert long wavelength light into short wavelength light. UC fluorescence by triplet-triplet annihilation (TTA) follows a mechanism involving two kinds of molecules as sensitizer and emitter. In this study, we constructed the photon UC dyes system that was applicable to weak excitation light and convert the red light into yellow light in high efficiency. The present result will be useful for the purpose of application to optical elements and light medical care.

Organic photoconductors (OPC) have been an important research and development topics for high quality electrophotography. By using electric field induced optical second harmonic generation (EFISHG) measurement, we can probe carrier processes in electrophotographic processes such as photo carrier generation, carrier separation, and carrier transportation for copier image production. We here selectively probe charge generation and accumulation in charge generation layer and charge transport layer in multilayer structure OPCs. We studied charge accumulation in OPC under illumination (wavelength 635nm) of double-layer-type OPC with structure of hole transport layer coated on charge generation layer. The result showed that light absorption efficiently produces free holes and electrons in the charge generation layer, followed by excessive hole accumulation at the CG/CT interface due to photo-conducting effect of CG layer. The short-wavelength irradiation at 405nm induced photovoltaic effect. These results demonstrated that the EFISHG measurement is useful to selectively probe carrier process in one layer of the multilayer OPC and to the discussion of carrier process for electrophotographic image productions.

The AuGe-alloy source and drain (S/D) formed on SiO2/Si(100) by the lithography process was investigated for the scaling of the organic field-effect transistors (OFETs) with bottom-contact geometry. The S/D was fabricated by the lift-off process utilizing the resist of OFPR. The OFETs with minimum channel length of 2.4 µm was successfully fabricated by the lift-off process. The fabrication yield of Au S/D was 57%, while it was increased to 93% and 100% in case of the Au-1%Ge and Au-7.4%Ge S/D, respectively. Although the mobility of the OFETs with Au-7.4%Ge S/D was decreased to 1.1×10-3 cm2/(Vs), it was able to be increased to 5.5×10-2 cm2/(Vs) by the surface cleaning utilizing H2SO4/H2O2 mixture solution (SPM) and post metallization annealing (PMA) after lift-off process, which was higher than that of OFET with Au S/D.

In this work, we report the in situ growth of gold nanoparticles (AuNPs) for the improvement of a transmission surface plasmon resonance (T-SPR) sensor to detect human immunoglobulin G (IgG). Human IgG was immobilized on an activated self-assembled monolayer of 11-mercaptoundecanoic on a gold-coated grating substrate. The T-SPR system was also used to monitor the construction of sensor chips as well as the binding of IgG and anti-IgG conjugated with AuNPs. After specific adsorption with IgG, the T-SPR signal was further enhanced by the in situ growth of AuNPs bound with anti-IgG. Using AuNP conjugation and in situ growth of bound AuNPs, the sensitivity of the IgG immunosensor was improved by two orders of magnitude compared with that without conjugated AuNPs.

Copper (Cu) electroless plating was conducted on planar and microstructured polydimethylsiloxane (PDMS) substrates. In this study, organic thin films terminated with nitrogen (N)-containing groups, e.g. poly (dimethylaminoethyl methacrylate) brush (PDMAEMA), aminopropyl trimethoxysilane monolayer (APTES), and polydopamine (PDA) were used to anchor palladium (Pd) catalyst. While electroless plating was successfully promoted on all sample surfaces, PDMAEMA was found to achieve the best adhesion strength to the PDMS surfaces, compared to APTES- and PDA-covered PDMS substrates, due to covalent bonding, anchoring effects of polymer chains as well as high affinity of N atoms to Pd species. Our process was also successfully applied to the electroless plating of microstructured PDMS substrates.

Improvement of output and lifetime is a problem for biofuel cells. A structure was adopted in which gelation mixed with agarose and fuel (fructose) was sandwiched by electrodes made of graphene-coated carbon fiber. The electrode surface not contacting the gel was exposed to air. In addition, grooves were added to the gel surface to further increase the oxygen supply. The power density of the fuel cell was examined in terms of the electrode area exposed to air. The output increased almost in proportion to the area of the electrode exposed to air. Optimization of the concentration of fuel, gel, and the amount of enzyme at the cathode were also examined. The maximum power density in the proposed system was approximately 121μW/cm2, an enhancement of approximately 2.5 times that in the case of using liquid fuel. For the power density after 24h, the fuel gel was superior to the fuel liquid.

The demand for enzymatic biofuel cells (EBFCs) as power sources or auxiliary power sources for small devices is expected to increase in the near future. EBFCs have advanced properties and do not require a separator, depending on the substrate specificity of the enzyme. Two direct electron transfer (DET)-type enzymes were used to modify anodes (length 5mm, width 4mm) by a chemical modification method using a condensation agent. The DET-type enzymes used in this study were pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) with glucose as a reaction substrate and fructose dehydrogenase (FDH) using fructose as a reaction substrate. Carboxyl groups were attached to multi-walled carbon nanotubes (MWCNTs) that act as catalyst carriers, activated to other functional groups, and reacted with the amino groups of the enzyme by the condensation agent to form covalent bonds. As a result, the upper limit of the concentration, considered to be the reaction limit, was raised as compared with that of EBFC modified with only one kind of enzyme for each electrode prepared by the same process. The output voltage was 0.155V, and the maximum power density was 80.08µW/cm2.