Adaptive Beam-Frequency Allocation Algorithm with Position Uncertainty for Millimeter-Wave MIMO Systems

Envisioned for fifth generation (5G) systems, millimeter-wave (mmWave) communications are under very active research worldwide. Although pencil beams with accurate beamtracking may boost the throughput of mmWave systems, this poses great challenges in the design of radio resource allocation for highly mobile users. In this paper, we propose a joint adaptive beam-frequency allocation algorithm that takes into account the position uncertainty inherent to high mobility and/or unstable users as, e.g., Unmanned Aerial Vehicles (UAV), for whom this is a major problem. Our proposed method provides an optimized beamwidth selection under quality of service (QoS) requirements for maximizing system proportional fairness, under user position uncertainty. The rationale of our scheme is to adapt the beamwidth such that the best trade-off among system performance (narrower beam) and robustness to uncertainty (wider beam) is achieved. Simulation results show that the proposed method largely enhances the system performance compared to reference algorithms, by an appropriate adaptation of the mmWave beamwidths, even under severe uncertainties and imperfect channel state information (CSIs).Comment: 5 pages, 6 figures, 1 table, 1 algorith

<ORIGINAL ARTICLE>ESR spin trapping study on ascorbic acid as a scavenger of hydroxyl and hydrogen radicals

The present study was carried out to confirm the usefulness of the ESR spin trapping technique for detecting and measuring short-lived radicals and to clarify the ability of ascorbic acid as a radical scavenger against radicals generated from irradiated human serum. One hundred μl of human serum was irradiated with 1 Gy of X-ray radiation coexisting with 35 μl of DETAPAC, 50 μl of various concentrations (2×10^M～60×10^M) of ascorbic acid, and 15 μl of DMPO. After irradiation at each concentration, the ESR signals were recorded using an ESR spectrometer. These signals were identified, and then normalized as the relative signal intensities against the standard signal intensity of manganese oxide marker. The relative signal intensities were plotted, and the results showed that the signals were from DMPO-OH and DMPO-H, showing the generation of ・OH and ・H, and that the relative signal intensities obtained at each concentration decreased as the concentration of ascorbic acid increased

Power and Beam Optimization for Uplink Millimeter-Wave Hotspot Communication Systems

We propose an effective interference management and beamforming mechanism for uplink communication systems that yields fair allocation of rates. In particular, we consider a hotspot area of a millimeter-wave (mmWave) access network consisting of multiple user equipment (UE) in the uplink and multiple access points (APs) with directional antennas and adjustable beam widths and directions (beam configurations). This network suffers tremendously from multi-beam multi-user interference, and, to improve the uplink transmission performance, we propose a centralized scheme that optimizes the power, the beam width, the beam direction of the APs, and the UE - AP assignments. This problem involves both continuous and discrete variables, and it has the following structure. If we fix all discrete variables, except for those related to the UE-AP assignment, the resulting optimization problem can be solved optimally. This property enables us to propose a heuristic based on simulated annealing (SA) to address the intractable joint optimization problem with all discrete variables. In more detail, for a fixed configuration of beams, we formulate a weighted rate allocation problem where each user gets the same portion of its maximum achievable rate that it would have under non-interfered conditions. We solve this problem with an iterative fixed point algorithm that optimizes the power of UEs and the UE - AP assignment in the uplink. This fixed point algorithm is combined with SA to improve the beam configurations. Theoretical and numerical results show that the proposed method improves both the UE rates in the lower percentiles and the overall fairness in the network

<ORIGINAL>Microradiography in the differentiation and definite diagnosis of odontomas

The present study evaluated the usefulness of microradiography in differentiny and making a definite diagnosis of odontomas. A surgically removed odontoma from a 14-year-old girl was used here. The specimen was sectioned at approximately 100μm thickness and ground to 50μm. Microradiographic images were obtained using soft X-ray equipment (Sofron, Japan) under the conditions of : tube voltage, 10kVp ; tube current, 5mA ; FSD 7.5cm ; and exposure time, 20min. The images were evaluated by comparing to images obtained by histological procedures. The results showed that the microradiographic images had almost the same resolution as that of the microscopic images