Geometrical structures and fundamental characteristics of microwavestepped-impedance resonators

λ_g/4-,λ_g/2-, and λ_g-type transmission-line stepped-impedance resonators (SIRs) have been proposed and various practical applications have been reported on the basis of the analysis related to each resonator. This paper standardizes these three types of SIRs and systematically summarizes their fundamental characteristics, such as resonance conditions, resonator length, spurious (higher order) responses, and equivalent circuits. Practical applications which employ features of three types of SIRs are investigated with demonstrations of specific structures. Original design formulas with respect to λ_g-type dual-mode resonators are analytically derived. Advanced SIR's using composite material and multisteps are also introduced and their availability is discussed     

Augmented placental production of leptin in preeclampsia: possible involvement of placental hypoxia

Preeclampsia (PE) is a hypertensive disorder, which develops in late pregnancy and is usually associated with placental hypoxia and dysfunction. We have recently demonstrated that leptin is a novel placenta-derived hormone in humans and suggested its significance in human pregnancy (see Ref. 19). To explore the changes in the leptin production in placenta in PE, we measured the plasma leptin level and placental leptin messenger RNA expression in pregnant women with PE. Plasma leptin levels in preeclamptic women were elevated significantly, compared with gestational age- and body mass index-matched normal pregnant women (P < 0.0001). Plasma leptin levels in the severe PE group were significantly higher than those in the mild PE group (P < 0.0001). Plasma leptin levels in preeclamptic women were reduced, soon after the placental delivery, to those expected for their body mass indices. Northern blot analysis revealed that leptin messenger RNA levels are increased in the placentas from preeclamptic women, compared with normal pregnant women. Leptin secretion was increased significantly in a human trophoblastic cell line (BeWo cells) cultured under hypoxic conditions (5% O2), compared with those cultured under standard conditions (20% O2; P < 0.01). The present study demonstrated that placental production of leptin is augmented in severe PE, probably because of placental hypoxia, thereby suggesting the possible significance of leptin as a marker of placental hypoxia in severe PE.     

A study on sodium spray combustion

Sodium spray combustion was studied through experiments and analysis, in order to clarify the burning rate, pressure and temperature transients in a sodium spray fire. In the experiments, about 400 g sodium was sprayed in a closed vessel of 2 m³, containing nitrogen and 0–21 vol% oxygen. Pressure, temperature and oxygen concentration were measured during and after sodium injection. The experimental results revealed that the temperature in the spray outer region was higher than that of inner region and observed oxygen consumption was not more than 80% of that expected for complete combustion of sodium. To analyze the experiments, a computer program SOFIA-II was developed based on an analytical single droplet combustion model and a two-dimensional temperature and oxygen concentration distribution model in the vessel. The calculated pressure agreed with the experimental pressure on the whole and the peak pressure difference was within 10% error.     

Low-temperature processable Sn-doped ZnO films as electron transporting layers for perovskite solar cells

Charge-transporting processable layers at a low temperature is a challenge for fabricating novel, highly stable and flexible optoelectronic devices. In fact, the crystallization of metal oxide usually needs to be processed under a high-temperature to obtain excellent semiconducting properties. In this work, Sn-doped ZnO (TZO) thin films, as electron transporting layers (ETLs) in perovskite solar cells, were prepared via sol–gel method at a temperature of less than 180 °C. The effects of annealing temperature on the properties of TZO thin films were investigated. It was found that the electrical properties of the TZO films were improved with increasing annealing temperature. In addition, an elemental composition analysis revealed that a temperature of only 140 °C sufficed for converting the precursor gel film into TZO film. The perovskite solar cell, which utilized a low-temperature TZO thin film, yielded a better power conversion efficiency than one with high-temperature ETLs (180 °C). These results imply that discovering low-temperature ETL processing for sol–gel enables good-quality metal oxide ETL, which can also be used in flexible solar cell applications.

     

The Great Buddha Project: Digitally Archiving,Restoring, and Analyzing Cultural Heritage Objects

This paper presents an overview of our research project on digital preservation of cultural heritage objects and digital restoration of the original appearance of these objects. As an example of these objects, this project focuses on the preservation and restoration of the Great Buddhas. These are relatively large objects existing outdoors and providing various technical challenges. Geometric models of the great Buddhas are digitally achieved through a pipeline, consisting of acquiring data, aligning multiple range images, and merging these images. We have developed two alignment algorithms: a rapid simultaneous algorithm, based on graphics hardware, for quick data checking on site, and a parallel alignment algorithm, based on a PC cluster, for precise adjustment at the university. We have also designed a parallel voxel-based merging algorithm for connecting all aligned range images. On the geometric models created, we aligned texture images acquired from color cameras. We also developed two texture mapping methods. In an attempt to restore the original appearance of historical objects, we have synthesized several buildings and statues using scanned data and a literature survey with advice from experts.     

Analytical study on effect of ring geometry on frequency shift of piezoelectric ring-shaped resonator

Ring-shaped resonators with one and four-point-outer-pinned supports have been designed in this work. The ring-shaped resonator reacts with a mass perturbation to provide eigenstate or frequency shifts which could transfer to electrical signals by piezoelectric effect. The aforementioned ring-shaped resonator is mainly comprised with a multilayer of Pt/Ti/PZT/Pt/Ti/SiO₂ deposited on the silicon-on-insulator wafer and expected to be a contour mode. In order to estimate the sensitivity of the ring-shaped resonator against the mass perturbation, the theoretical analysis was conducted by ANSYS from two aspects including: (a) the view point of geometrical design and (b) the mass application methodology. When a mass perturbation (i.e., a liquid droplet) of 10?pg is homogeneously contacting on the top electrode of the resonator, frequency shifts from 2.11 to 4.07?kHz could be obtained when excited in the contour mode. Furthermore, the more stabled vibration behavior of resonator with four-point-pinned supports was approved by the computer stimulation of ANSYS analysis results.