Pressure drop measurement on forced flow cable conductors

Forced flow cable conductors being developed for use in LCP coils and other large superconducting magnets utilize supercritical helium flowing through narrow, uneven channels with large cooling surfaces. Extensive measurements on pressure drop of a variety of samples were performed. It is found that the friction factor versus Reynolds number plots of all the data are clustered together and behave in a universal way. A factor of two to three higher in friction factor than the smooth tube value in turbulent helium flow regime can be expected for this type of conductor.     

Some problems in long-term prevention of streptococcal infection among children with rheumatic heart disease in Taiwan

In Taiwan, rheumatic fever (RF) and rheumatic heart disease (RHD) remain widespread and constituting a health problem. The long-term prevention of streptococcal infections among rheumatic children has also failed to prevail, and yet has seldom been emphasized. Therefore, recurrence of RF remained prevalent. For an appraisal of the difficulties in the administration of long-term medication prophylaxis, a prospective study was started in 1967. One hundred and five consecutive cases of RF and RHD were followed up for more than 1 year to 6 years with an average of 4.4 years. One hundred and two cases received monthly injections of benzathine penicillin G for 6 months to 6 years, of whom 10 were switched to daily sulfa drugs; 1 case had oral penicillin daily for 6 years; in 12 cases, sulfa drugs were given for 6 months to 5 years. Fifty-one cases (48.6 %) stayed well in the program; 22 (21.0 %) stayed but were not compliant; 32 (30.4 %) dropped out soon or after staying in for more than 1 year. Major risk factors leading to non-compliance are; 1) apparent recovery from the illness or resumption of the normal activity; 2) cram session at school; 3) lack of easy medical care system; and 4) shortage of active participation by the health workers and general practitioners. The present study confirmed that the long-term prevention of streptococcal infection was effective and contributed to the decline of RF recurrence rate from more than 30 % down to 6%. Our study implicates that this important preventive program can not be achieved just only by the hospital staff, but should be approached jointly by all doctors, health and social workers, school teachers and the parents.     

医用血泵微机智能监控及信息管理系统

针对国内手术过程自动化程度低的现状，设计了医用血泵微机智能监控及信息管理系统，中给出了系统的硬件设计和软件实现方法。系统具有可靠性高、测控精度高、成本低效率高等特点，解决了目前国内手术操作过程中控制输液流量精度低的难题。     

Dielectric constants of single-wall carbon nanotubes at various frequencies

A cylindrical rod composed of a uniform mixture of single-wall carbon nanotubes and alumina powders dissolved in paraffin was inserted in the center of a radio frequency cavity. The complex dielectric constant of carbon tubes at various frequencies was measured by a resistance-inductance-capacitance (RLC) meter and a microwave network analyzer. The cylindrical rod benefits the protection of the sample from adsorbing moisture and preventing the rod from filling with air, thus making accuracy experiment values. The real part and the imaginary part of the dielectric constants of single-wall carbon nanotubes are, respectively, increase and decrease in magnitudes as frequency increases satisfactorily in complying with the portray from the free electron Drude model.     

In Vitro Propagation of XXY Undifferentiated Mouse Spermatogonia: Model for Fertility Preservation in Klinefelter Syndrome Patients

Klinefelter syndrome (KS) is characterized by a masculine phenotype, supernumerary sex chromosomes (usually XXY), and spermatogonial stem cell (SSC) loss in their early life. Affecting 1 out of every 650 males born, KS is the most common genetic cause of male infertility, and new fertility preservation strategies are critically important for these patients. In this study, testes from 41, XXY prepubertal (3-day-old) mice were frozen-thawed. Isolated testicular cells were cultured and characterized by qPCR, digital PCR, and flow cytometry analyses. We demonstrated that SSCs survived and were able to be propagated with testicular somatic cells in culture for up to 120 days. DNA fluorescent in situ hybridization (FISH) showed the presence of XXY spermatogonia at the beginning of the culture and a variety of propagated XY, XX, and XXY spermatogonia at the end of the culture. These data provide the first evidence that an extra sex chromosome was lost during innate SSC culture, a crucial finding in treating KS patients for preserving and propagating SSCs for future sperm production, either in vitro or in vivo. This in vitro propagation system can be translated to clinical fertility preservation for KS patients.     

An image system for fast positioning and accuracy inspection of ball grid array boards

An image, in-process inspection and accuracy positioning system has been developed as automated measurement machine to deal with ball grid array type printed circuit boards (PCB). A new technique is proposed to automate the boundary scan and circularity estimation. The attributes of a pixel at a pad or hole are calculated from the RGB color on PCB image. Here we introduce the idea of the least-square circle to find the center of the holes and pads. The value of alignment shift can be obtained according to the four images in a special image capturing procedures. If the circle of the pad and hole can be determined correctly, the vision system can easily inspect the local deviation when positioning table locates the PCB on the image capturing point. The results of positioning and inspection are presented and evaluated including through hole locations, alignment calculation, system calibration, and statistical functions.     

Application of on-wafer TRL calibration on the measurement ofmicrowave properties of Ba0.5Sr0.5TiO3films

A series of Al/Ba_0.5Sr_0.5TiO₃ (BST) /sapphire multi-layered coplanar waveguide (CPW) transmission lines of different geometries and thin-film configurations was fabricated. We employed an accurate on-wafer Through-Line-Reflect (TRL) calibration technique and quasi-TEM analysis to measure the dielectric constant, loss tangent, and tunability of BST thin films using this CPW structure. Experimental results show that the overall insertion loss is less than 3 dB/cm even at frequencies as high as 20 GHz, which is the lowest obtained to date for metal/BST CPW devices. This result indicates that, with optimized impedance matching, normal conductors are also possibly suitable for fabricating low-loss tunable phase-shifter devices     

Tailoring the Surface Chemical Reactivity of Transition‐Metal Dichalcogenide PtTe2 Crystals

PtTe₂ is a novel transition‐metal dichalcogenide hosting type‐II Dirac fermions that displays application capabilities in optoelectronics and hydrogen evolution reaction. Here it is shown, by combining surface science experiments and density functional theory, that the pristine surface of PtTe₂ is chemically inert toward the most common ambient gases (oxygen and water) and even in air. It is demonstrated that the creation of Te vacancies leads to the appearance of tellurium‐oxide phases upon exposing defected PtTe₂ surfaces to oxygen or ambient atmosphere, which is detrimental for the ambient stability of uncapped PtTe₂‐based devices. On the contrary, in PtTe₂ surfaces modified by the joint presence of Te vacancies and substitutional carbon atoms, the stable adsorption of hydroxyl groups is observed, an essential step for water splitting and the water–gas shift reaction. These results thus pave the way toward the exploitation of this class of Dirac materials in catalysis.     

谱相关技术及其在潜艇结构振动信号传递特性分析中的应用

由于潜艇结构的复杂性,有限元方法和时域相关方法在分析结构振动信号传递特性时精度欠佳。针对上述问题,提出了定量分析结构振动信号传递特性的谱相关技术,该技术通过结构两侧振动信号分析结构对振动信号组成成分的影响,避免了有限元精确建模困难与振动信号通过复杂结构时波形失真较大的难题。将该技术应用于潜艇缩比模型不同结构振动信号传递特性分析中,定量分析结果表明该技术能很好地分析不同结构的振动信号传递特性。     

PoC技术探析

PTT又称为“一键通”,是一种实现walkie—talkie功能的移动话音业务。基于公众蜂窝移动通信网络的PTT业务称为PoC业务。文章主要介绍PoC技术、PoC协议和发展趋势。