Modal analysis of radial-resonator waveguide diode mounts

A method of calculating the driving-point and transfer admittances of waveguide diode mounts with radial resonators is presented. The method is applicable to a variety of mount configurations, including the widely used resonant-cap mount. The analysis uses multimodal admittance matrices to represent the radial regions and their coupling and includes the influence of the waveguide boundary conditions. The analysis proceeds by first determining (from the matching of tangential fields at the common boundary) the coupling between radial regions in the form of a mode-coupling matrix. By multiplying this matrix with the generalized admittance matrices of connecting radial regions to form an overall admittance matrix, the driving-point and transfer admittances for a general radial-resonator mount can be extracted. The method is demonstrated by application to the resonant-cap mount. The accuracy of the analysis is confirmed by comparison with experimental results     

Effects of CEE and Feedback Error on Performance for AF-ORS with PSA-CE Schemes Over Quasi-Static Rayleigh Fading Channels

In this paper, we propose the analytical approach for amplify-and-forward (AF) opportunistic relaying schemes (ORS). When operation of AF-ORS consists of relay selection and data transmission phases based on pilot symbol assisted-channel estimation (PSA-CE) methods over quasi-static Rayleigh fading channels, we show that the relay selection phase can be implemented by pilots symbols transmission for source-relay and relay-destination. Moreover, the feedback method for the selected relay index is proposed to have a simple fashion. Then, we investigate the effects of both a channel estimation error and an estimated noise variance, which are obtained by PSA-CE methods, on the received signal-to-noise ratio (SNR). The average SNR loss is also derived in terms with the number of pilots in PSA-CE methods. Moreover, the average symbol error rate, the outage probability, and the normalized channel capacity of the ORS are derived in approximated closed-form expressions for an arbitrary link SNR when the channel state information in the source-relay-destination link is estimated based on transmitted pilots symbols. As the number of pilot symbols, the derived analytical approach is verified, and by comparing it with simulation results, the accuracy is demonstrated. In addition, it is verified that the effect of the feedback error can be neglected for PAS-CE methods over quasi-static fading channels.     

Self-Organization of Microlens Arrays Caused by the Spin-Coating-Assisted Hydrophobic Effect

A simple, low-cost, low-temperature, and shape-controllable approach has been demonstrated to fabricate polymer microlens arrays (MLAs). By using microcontact printing of the self-assembled monolayers and then spin coating, the microlenses were able to organize themselves on the patterned glass substrate. High-quality MLAs made of NOA65 prepolymer with lens-diameters of 50, 75, and 100 mum have been fabricated by this method. Lens shapes can be controlled by changing the spin rates of the prepolymer coating. Optical measurements have revealed an excellent light-collecting capability from the fabricated MLAs. It is anticipated that the technique will be ideally suited to low-cost and high-volume production     

Nitride-Based High-Power Flip-Chip LED With Double-Side Patterned Sapphire Substrate

A nitride-based high-power flip-chip (FC) light-emitting diode (LED) with a double-side patterned sapphire substrate (PSS) was proposed and realized. Under 350-mA current injection, it was found that forward voltages were 3.24, 3.26, and 3.25 V for the conventional FC LED, FC LED prepared on PSS, and FC LED with double-side PSS, respectively. It was found that the 350-mA LED output powers were 79.3, 98.1, and 121.5 mW for the conventional FC LED, FC LED prepared on PSS, and FC LED with double-side PSS, respectively. In other words, we can enhance the electroluminescence intensity by 53% without increasing operation voltage of the fabricated LED     

ECG measurement on a chair without conductive contact

For the purpose of long-term, everyday electrocardiogram (ECG) monitoring, we present a convenient method of ECG measurement without direct conductive contact with the skin while subjects sat on a chair wearing normal clothes. Measurements were made using electrodes attached to the back of a chair, high-input-impedance amplifiers mounted on the electrodes, and a large ground-plane placed on the chair seat. ECGs were obtained by the presented method for several types of clothing and compared to ECGs obtained from conventional measurement using Ag-AgCl electrodes. Motion artifacts caused by usual desk works were investigated. This study shows the feasibility of the method for long-term, convenient, everyday use.     

Pixel‐Structured Scintillator with Polymeric Microstructures for X‐Ray Image Sensors

We introduce a pixel‐structured scintillator realized on a flexible polymeric substrate and demonstrate its feasibility as an X‐ray converter when it is coupled to photosensitive elements. The sample was prepared by filling Gd₂O₂S:Tb scintillation material into a square‐pore‐shape cavity array fabricated with polyethylene. For comparison, a sample with the conventional continuous geometry was also prepared. Although the pixelated geometry showed X‐ray sensitivity of about 58% compared with the conventional geometry, the resolving power was improved by about 70% above a spatial frequency of 3 mm^?1. The spatial frequency at 10% of the modulation‐transfer function was about 6 mm^?1.     

Distributed Multirobot Exploration and Mapping

Efficient exploration of unknown environments is a fundamental problem in mobile robotics. We present an approach to distributed multirobot mapping and exploration. Our system enables teams of robots to efficiently explore environments from different, unknown locations. In order to ensure consistency when combining their data into shared maps, the robots actively seek to verify their relative locations. Using shared maps, they coordinate their exploration strategies to maximize the efficiency of exploration. This system was evaluated under extremely realistic real-world conditions. An outside evaluation team found the system to be highly efficient and robust. The maps generated by our approach are consistently more accurate than those generated by manually measuring the locations and extensions of rooms and objects.     

Efficient geocasting with multi-target regions in mobile multi-hop wireless networks

Geocasting, a variation on the notion of multicasting, is a mechanism to deliver messages of interest to all nodes within a certain geographical target region. Although several geocasting protocols have already been proposed for multi-hop wireless networks, most of these algorithms consider a “single” target region only. Here, when more than one target regions need to receive the same geocast messages, multiple transmissions need to be initiated separately by the message source. This causes significant performance degradation due to redundant packet transmissions, and it becomes more severe as the number of target regions increase. To solve this problem, we propose a basic scheme and its variations which utilize the geometric concept of “Fermat point” to determine the optimal junction point among multiple geocast regions from the source node. Our simulation study using ns-2 shows that the proposed schemes can effectively reduce the overhead of message delivery while maintaining a high delivery ratio in mobile multi-hop wireless networks.