Symbol rate and modulation level-controlled adaptivemodulation/TDMA/TDD system for high-bit-rate wireless data transmission

This paper proposes a time-division multiple-access/time-division duplex (TDMA/TDD)-based symbol rate and modulation level-controlled adaptive modulation system for high-bit-rate data transmission. The proposed system controls both the symbol rate and modulation level for the next transmission time slot according to the estimated carrier power to noise spectral density ratio (C/N₀) and delay spread for the time slot to achieve higher bit rate and higher transmission quality as well as higher delay-spread immunity. It is demonstrated by computer simulation and laboratory experiments that the proposed system can achieve a higher average bit rate with higher transmission quality in comparison with the fixed-rate quaternary phase-shift keying (QPSK) system and modulation level-controlled adaptive modulation system in both flat Rayleigh and frequency-selective fading environments. The simulated and experimental results also show that the proposed adaptive modulation techniques can be applied to 1-2-Mb/s indoor and outdoor microcellular systems with its delay spread of up to 250 ns and its terminal mobility of up to pedestrian speed without employing any special antifrequency-selective fading techniques, such as the adaptive equalizer and space diversity     

Analysis of spatial smoothing effect of short‐term fluctuation of global solar radiation based on data including quantization error

Photovoltaic (PV) systems are attracting attention as one of the promising countermeasures against global warming and the environmental issues. However, the generation output from PV systems is generally unstable and unpredictable. Therefore, large penetration of PV systems may cause some serious impacts on power system operation, such as load frequency control, voltage regulation, etc. Estimation of the influences of PV system installation is becoming important, but it requires simultaneous multipoint solar radiation measurements. The Japan Meteorological Business Support Center has provided 1‐minute meteorological data observed in Japan, but its solar radiation data includes quantization errors. This paper proposes a regeneration method for solar radiation data including quantization errors. It also analyzes the spatial smoothing effect of global solar radiation fluctuations. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(3): 55–63, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21274     

Direct writing of semiconducting polythiophene and fullerene derivatives composite from bulk heterojunction solar cell by inkjet printing

The direct writing approach of poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) composite from bulk-heterojunction (BHJ) solar cell was efficiently addressed by inkjet printing technology using conventional chlorobenzene ink solution. The structure of inkjet-printed P3TH:PCBM BHJ film was fabricated by the repetitive direct writing of new line overlapped partially on former line. The best structure of P3HT:PCBM film for BHJ solar cell was observed from inkjet printing condition of around 50% of droplet overlaps with 2 wt.% BHJ ink at 25 °C of substrate temperature. The maximum power conversion efficiency reached 2.83% with an open circuit voltage of 0.62 V, a short circuit current density of 8.60 mA/cm², and a fill factor of 0.53 under air mass 1.5 G irradiation (100 mW/cm²).     

Nonlinear motion correction of respiratory-gated lung SPECT images

We propose a method for correcting the motion of the lungs between different phase images obtained by respiratory-gated single photon emission computed tomography (SPECT). This method is applied to SPECT images that show a preserved activity distribution in the lungs such as 99m-Tc macro aggregated albumin (99m-Tc-MAA) perfusion images and 99m-Tc-Technegas ventilation images. In the proposed method, an objective function, which consists of both the degree of similarity between a reference image and a deformed image, and the smoothness of deformation is defined and optimized using a simulated annealing algorithm. For the degree of similarity term in the objective function, an expansion ratio, defined as the ratio of change in local volume due to deformation, is introduced to preserve the total activity during the motion correction process. This method was applied to data simulated from computer phantoms, data acquired from a physical phantom, and 17 sets of clinical data. In all cases, the motion correction between inspiration and expiration phase images was successfully achieved.     

Chemical stability of γ-butyrolactone-based electrolytes for aluminum electrolytic capacitors

γ-Butyrolactone-based electrolytes have been used as the operating electrolytes for aluminum electrolytic capacitors. The chemical stability of these electrolytes at elevated temperatures has been examined by monitoring the decrease in their electrolytic conductivities. The deteriorated electrolytes were analyzed by gas and liquid chromatography and the conductivity decrease was directly correlated with the loss of acid components. In quaternary ammonium hydrogen maleate/γ-butyrolactone electrolytes, the maleate anion decomposed by decarboxylation resulting in a complex polymer containing polyester and polyacrylate structures. Quaternary ammonium benzoate/γ-butyrolactoneelectrolytes decomposed by SN2 reactions giving alkyi benzoates and trialkylamines. The deterioration of the carboxylate salt/γ-butyrolactone electrolytes was accelerated by electrolysis.     

Development and degradation of graphitic microtexture in carbon nanospheres under a morphologically restrained condition

Graphitic microtexture in carbon nanospheres (CNSs, average diameter = 500–1000 nm) formed by a heat-treatment between 2000 °C and 2900 °C was investigated with XRD, Raman spectrum, SEM and TEM. By the heat-treatment up to 2000 °C, CNS particles in any size were polyhedronized. In the microtexture of polyhedronized CNS particles thus obtained, graphitic stacking structure of aromatic layers was well developed in the polyhedron face regions, while an aggregation of column-like crystallite was confirmed in the polyhedron ridge region. It was also shown that some ridges of CNSs with the average diameter over 700 nm were collapsed by the heat-treatment at 2900 °C. These collapses include an exfoliation of aromatic layers in which the torn layers have hairpin-like microtexture at their ends, and a crack of layer stacks with adjacent layer stacks. According to a direct examination with TEM, it was clarified that a ratio of ridges with either type of damage to a total number of ridges is obviously higher in CNS particles with larger diameter. This phenomenon was discussed in relation to the high crystallinity in the polyhedron face regions and the aggregation of structural defects in the ridge regions.     

Electrochemical properties of quaternary ammonium borodiglycolates and borodioxalates

Quaternary ammonium borodiglycolates and borodioxalates were prepared by the reaction of quaternary ammonium tetrahydroxyborates with glycolic acid and oxalic acid, respectively. These compounds are used as the electrolyte salts of aluminum electrolytic capacitors. Their molar conductivities, limiting molar conductivities and oxidation potentials in γ-butyrolactone were higher than those of borodisalicylates and borodicatecholates due to the lack of aromatic rings. Their film-forming ability of anodic aluminum oxide in γ-butyrolactone electrolytes containing a small amount of water was poor, because both anodic dissolution and oxidation occurred simultaneously.     

Effects of a turbocharger cut out system on vibration characteristics of a propulsion shafting system and a large low speed marine diesel engine

To cope with the long term recession in the shipping industry due to oversupply of ships and high oil prices and due to reinforcement of environmental regulations to reduce greenhouse gas emission from ships, large container vessels built recently have ultra-long stroke engines with high propulsion efficiency. For these, de-rated engine and tuning technologies are used to reduce fuel oil consumption. However, previously built vessels were optimized for high ship speed. In these case, lowering ship speed to reduce ship operating cost does not provide similar benefits. Therefore, engine manufacturers have developed a turbocharger cut-out system to reduce fuel oil consumption at low speed. This has the advantage of reducing fuel consumption at low speeds, but also has the characteristic of producing higher torsional exciting force than is typical in existing engines for low load ranges. In this paper, the performance and dynamic characteristics of a marine diesel engine were reviewed after applying a turbocharger cut-out system. Then the effects on the engine body vibration and the torsional vibration were examined for a corresponding propulsion shafting system in a Panamax container-vessel equipped with a turbocharger cut-out system optimized for slow steaming. As a result, the torsional vibratory stress in shafts was increased. This had a larger effect on the X-mode shape of the engine body vibration and on the upper structure vibration, when one of three turbochargers was cut out.     

Effects of cyclic carbonates as additives to γ-butyrolactone electrolytes for rechargeable lithium cells

γ-Butyrolactone (GBL) has a high boiling point, a low freezing point, a high flashing point, a high dielectric constant and a low viscosity. GBL is a very preferable solvent for lithium ion batteries. However, GBL readily undergoes reductive decomposition on the surface of the negative electrodes, and it forms a solid electrolyte interphase (SEI) with a large resistance. It is causing deterioration of battery performances. In this work, effects of cyclic carbonates as additives to GBL electrolytes were investigated. As these carbonates, ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), vinylethylene carbonate (VEC), and phenylethylene carbonate (PhEC) were investigated using LiCoO₂/graphite cells. The effects of these additives were evaluated from the viewpoints of improvement of the battery performance and suppression of the reductive decomposition of GBL. VC, VEC and PhEC were effective to suppress the excess reductive decomposition of GBL. Battery performances were improved and the following results were obtained from the electrochemical measurements of LiCoO₂/graphite cells with GBL-based electrolytes. Residual capacity was high in the order of VEC > VC > PhEC. Rate capability was high in the order of PhEC > VC > VEC. These additives have advantages and disadvantages. By optimizing electrolyte formulation, the performances of Li-ion batteries using GBL-based electrolytes will be improved further.