Design procedure of class-E amplifier for off-nominal operation at 50% duty ratio

Design equations for satisfying the off-nominal operating condition [i.e., only the zero-voltage switching (ZVS) condition] of the Class-E amplifier with a linear shunt capacitance at a duty ratio D=0.5 are derived. A new parameter s (V/s), called the slope of switch voltage when the switch turns on is introduced to obtain an image of the distance from the nominal conditions. By examining off-nominal Class-E operation degree of the design freedom of the Class-E amplifier increases by one. In addition various amplifier parameters such as operating frequency, output power, and load resistance range can be set as design specifications. For example, the peak switch voltage and switch current can be taken into account in the design procedure. Examples of a design procedure of the Class-E amplifier for off-nominal operation are given. The theoretical results were verified with PSpice simulation and experiments.     

Hydrothermal Formation of Hydroxyapatite Layers on the Surface of Type-A Zeolite

Type-A zeolite evenly covered with hydroxyapatite thin layers was prepared using hydrothermal treatment at 120°C for 8 h under autogenous pressure. The hydroxyapatite needlelike nanocrystals, 100–200 nm in diameter and 30 nm in thickness, were grown under the reaction between discharged Ca²⁺ ions from type-A zeolite and PO₄³⁻ ions in (NH₄)₃PO₄ solution. The preferential orientations of the c -axis of hydroxyapatite crystals perpendicular to a zeolite surface were observed using transmission electron microscopy. The crystal structure of type-A zeolite was not destroyed under the reaction, but the surface morphology was changed only with complete covering of scaly hydroxyapatite particles.     

Modifying ability of Ql-free coal-tar pitch to develop optical anisotropy in co-carbonizations

Carbonization properties of a Ql-free coal-tar pitch (CTP-ASM) prepared by selective precipitation were studied to evaluate it as a source for needle-coke. Its modifying ability for production of needlecoke in co-carbonizations with principal carbonizing substances which gave cokes of mozaic texture in single carbonizations was estimated by changing mixing ratios. The shape and size of the anisotropic optical texture in the co-carbonized coke were measured by point counting. CTP-ASM and Ashland A240, of eight additives, had the highest modifying ability in the co-carbonizations with Khafji vacuum residue. Both contained ca. 6% benzene-insolubles (Bl), and had f_a values of ≈0.9. Other additives of either lower or higher Bl or f_a showed less modifying ability. The modifying susceptibility of principal carbonizing substances varies with their structure and properties. Based on a systematic investigation of co-carbonizations the compatibility between a principal carbonizing substance and an additive is discussed from a viewpoint of their structural parameters.     

Crystal growth and structure analysis of twin-free monoclinic hydroxyapatite

Single crystals of hydroxyapatite were grown by a flux method using Ca₃(PO₄)₂ and Ca(OH)₂ under 100 MPa of Ar gas. The crystals obtained had stoichiometric composition of Ca₁₀(PO₄)₆(OH)₂ and some of them were twin-free single crystals. From X-ray diffraction analyses, the space group was confirmed to be monoclinic P2₁/b with cell parameters a=0.9419(3) nm, b=1.8848(6) nm, c=0.6884(2) nm, and =119.98(2)°. The detailed crystal structure was determined with a reliability factor R_w=0.033; the O atoms of OH were located just on the 2₁ axis while the H atoms of OH occupied the positions a little deviated from the 2₁ axis. The origin of this structure was ascribed to the formation of hydrogen bonds between the H atoms of the OH ions and the specific O atoms of the PO₄ ions.     

In-Flight Nitridation of Molybdenum Disilicide Powders by an Induction Plasma

The in-flight nitridation of MoSi₂ powder particles was attempted in an argon-nitrogen induction plasma, with and without tail gas quenching. The inductive power level, reactor pressure, plasma-gas composition, and quantity of quench gas, as well as the species of quench gas, were investigated to obtain substantial nitridation of the MoSi₂ powder particles. Under investigated conditions, ∼2.8 wt% of nitrogen was incorporated into the MoSi₂ powder particles.     

Analysis of phase-controlled resonant DC-AC inverters with class Eamplifier and frequency multipliers

This paper presents a minute analysis and experimental results of phase-controlled resonant DC-AC inverters with class E amplifiers and frequency multipliers. The circuit is composed of two identical class E amplifiers or frequency multipliers, which are used as DC-AC inverters and connected in parallel. The two inverters are driven at the same switching frequency, and the overall output power of the circuit can be controlled by varying the phase shift between the drive voltages of the two inverters. The circuit can regulate the output voltage at a constant switching frequency. The measured efficiency was over 93% at an output power of 0.98 W and a switching frequency of 0.5 MHz for both of the inverters with amplifier and frequency doubler     

Class DE current-source parallel resonant inverter

This paper introduces a Class DE current-source parallel resonant inverter, along with its design procedure and experimental results. This circuit offers several desirable features. First, the proposed circuit lacks harmonic components of input current over the voltage-source inverters. Second, the source pin of the MOSFET is directly connected to the ground, so that it is not necessary to use a complicated gate-drive circuit. Third, by maintaining zero-current switching, power loss by the parasitic inductor at turn-off decreases. The measured efficiency is over 90% at the output power of 3.5 W and the operating frequency of 0.5 MHz     

On site experiments of the slanted soil treatment systems for domestic gray water.

In order to make a breakthrough for the acute problem of water shortage in the world, the key words "decentralization and re-use" are very important for new sustainable sanitation systems that will be developed. Therefore, we focused on a new treatments system called "a slanted soil treatment system" which combines a biotoilet system with a domestic grey water treatment system. Because this system is a low cost and compact system, the system can be easily introduced to homes in urban areas or in the suburbs of cities in many developing countries. In this study, we performed on site experiments carried out on Shikoku Island, Japan, for several years. We obtained the following results. The slanted soil treatment system could remove organic pollutants and total nitrogen and total phosphorus in grey water effectively. Furthermore, the system performance became high in the case of the high concentration of the influent water. The nitrification reaction and denitrification reaction were speculated to exist due to aerobic zones and anaerobic zones present in the slanted soil treatment system. The slanted soil treatment system could perform for approximately 3 years with zero maintenance. The plug flow model of 1st order reaction kinetics could describe the reaction in the slanted soil treatment system. However, it is necessary to improve the system to maintain the performance in all seasons.     

Hydroxyapatite pattern formation in PVA gels

Sodium hydroxide solution was allowed to diffuse from the edge of an acidic poly(vinyl alcohol) gel sheet containing dissolved calcium and phosphate ions, and calcium phosphate was observed to precipitate as the pH rose. The precipitation pattern changed depending on the solute concentration near the reaction front; precipitate “walls” were formed in areas in which the calcium phosphate concentration was higher or the sodium hydroxide concentration was lower than the conditions for homogeneous precipitation, and within a very limited concentration combination of calcium phosphate and sodium hydroxide, a regular stripe pattern with a pitch of about 100 μm was formed. The calcium phosphate precipitate obtained was a single phase of hydroxyapatite. It was also found that apatite ceramic sheets with periodic porous structures or with undulate patterns could be manufactured by sintering gels with stripe patterns.     

Reconnaissance report on geotechnical damage caused by a localized torrential downpour with emergency warning level in Kyushu,Japan

Kumamoto and Kogoshima prefectures are located in the southern Kyushu district of western Japan. In July 2020, a warm, humid air front triggered the delayed rains of the rainy season, resulting in torrential rains in many parts of Japan, especially in Kyushu. In particular, heavy downpours occurred in the southern Kyushu district on July 4th, causing severe damage to much of the infrastructure. Details could not be analyzed as usual because some branch office of local government were also damaged by floods. The spatial distribution of precipitation in the Kuma River basin, in the southern part of Kumamoto, was characterized by the uniformity of 400–500 mm on July 3rd and 4th. Finally, emergency warnings of torrential rain were issued for the southern Kumamoto and the northern Kagoshima Prefectures by Japan Meteorological Agency (JMA) at 4:50 a.m., July 4th, 2020. Then, the active rain front gradually shifted towards northern Kyushu. Again, torrential rain fell on northern Kyushu in the afternoon due to a stagnant rainy season front, and the JMA issued an emergency warning for a localized torrential downpour for parts of Fukuoka, Saga and Nagasaki prefectures at 4:30 pm. Gradually, the damage status involving geodisasters such as several types of slope failures, road subsidence, damage of the river levee was reported by local governments in each area where there had been emergency warnings.Based on the brief report of the pre-investigation team from the Kyushu branch of the Japan Geotechnical Society (JGS) in the first week after the disaster on July 4th, the geo-research teams investigated the following: 1) landslides; 2) damaged roads; 3) damaged river levees, and 4) any geotechnical infrastructures which were partially damaged and may be even more severely damaged by the next torrential rain. This reconnaissance report introduces the geological features in Kyushu, the analysis of precipitation distribution and geotechnical damages on the slope failures, road failures and river embankments based on reports obtained from July 4th to August 31st, 2020.