Phenomenological features of diaphragm discharge

Flame formations of relatively little-studied diaphragm discharge in water at low energy of discharge (up to 10 J) are investigated. Its particular features show up in the fundamental difference in shape between the anode and cathode flames on both sides of the diaphragm, in the difference in variation of their shape and size with the variation of electrical conductivity of the medium, in polar development of flames from the diaphragm to their electrodes, in the possibility of existence of “half-breakdowns”, and in the difference between them depending on polarity, in a special form of cathode breakdown.     

An analysis of the reasons for the reduction in reliability of machinery structures under low temperature climate conditions

The influence of low temperature on the reliability of machine parts and on the characteristics of strength of steels and their weld joints is analyzed. It is established that a drop in temperature in impact cyclic loading causes a decrease in fatigue resistance of weld joints of low-alloy steels and a corresponding increase in relative frequency of crack formation in them. A comparison of experimental and service data shows that the increase in service relative frequency of crack formation in welded machine parts at reduced temperature is an indication of their fatigue origin. It was concluded that the increase in the frequency of failures of welded machine parts with a reduction in temperature observed under service conditions is caused by a reduction in their fatigue resistance and an increase in the tendency of their materials toward brittle fracture.     

铝合金的动态再结晶

本文展现了当前铝及铝合金动态再结晶研究的一些进展。分析了铝合金动态再结晶的特点和材料状态,形变条件对动态再结晶的影响。指出了铝合金动态再结晶研究在理论,实际生产中的意义和铝合金动态再结晶研究的方向。     

The 55 mph limits and front-to-rear collisions involving autos and large trucks

The effects of the establishment of 55 mph limits on front-to-rear crashes involving automobiles and trucks were examined. Since the establishment of 55 mph limits resulted in a reduction in the difference between the reported average speed of automobiles and large trucks, it provided an opportunity to examine the effects of speed differences on the. frequency of crash involvement of these vehicles. Principal results of the study were as follows: In 1974, the year of the introduction of 55 mph speed limits, a substantial reduction in the number of front-to-rear crashes involving an automobile and tractor trailer on higher speed roads occurred in the states whose experience was examined. A substantial decline in the number of front-to-rear crashes involving an auto and single body truck on higher speed roads also occurred in 1974 in these states. The decline in the number of front-to-rear crashes involving an automobile and tractor trailer on higher speed roads was primarily the result of a major decline in the number of crashes in which an auto struck a tractor trailer in the rear. The number of crashes in which a tractor trailer struck an auto in the rear declined by a much smaller percentage. The decline in the number of front-to-rear crashes involving an automobile and single body truck on higher speed roads resulted from comparable decreases in the number of crashes in which an auto struck a single body truck in the rear and those in which a single body truck struck an auto in the rear. Prior to the establishment of 55 mph limits, tractor trailers struck automobiles in the rear in more than half of the front-to-rear crashes involving these vehicles on both higher and lower speed roads. Because the major decline in the number of crashes in which autos struck tractor trailers in the rear following the introduction of the new limits was not matched by as large a decline in the number of crashes in which tractor trailers struck autos in the rear, there was a significant increase in the proportion of front-to-rear crashes involving an automobile and tractor trailer in which the tractor trailer struck the automobile in the rear on higher speed roads. Prior to the establishment of 55 mph limits, single body trucks struck automobiles in the rear in more than half of the front-to-rear crashes involving these vehicles on both higher and lower speed roads. However, single body trucks struck autos in the rear in a lower proportion of their front-to-rear crashes with autos than did tractor trailers. The proportion of front-to-rear crashes involving an automobile and single body truck in which an auto was struck in the rear by a single body truck was not significantly affected by the establishment of 55 mph limits.     

21世纪之初工程哲学在东西方的同时兴起

科学哲学和技术哲学都是首先在欧美国家兴起的,可是,工程哲学却是于21世纪之初在中国和欧美发达国家同时兴起和基本同步发展的。文章简要介绍了2002年以来工程哲学在中国和欧美国家发展的重要事件和已经发表的重要著作,最后,简要评论了东、西方工程哲学发展的主要特点。     

Unconventional fractional quantum Hall effect in monolayer and bilayer graphene

The commensurability condition is applied to determine the hierarchy of fractional fillings of Landau levels in monolayer and in bilayer graphene. The filling rates for fractional quantum Hall effect (FQHE) in graphene are found in the first three Landau levels in one-to-one agreement with the experimental data. The presence of even denominator filling fractions in the hierarchy for FQHE in bilayer graphene is explained. Experimentally observed hierarchy of FQHE in the first and second Landau levels in monolayer graphene and in the zeroth Landau level in bilayer graphene is beyond the conventional composite fermion interpretation but fits to the presented nonlocal topology commensurability condition.     

Investigation of collaborative research trends in Indian medical sciences: 1900–1945

The decade beginning 1925 is important in the history of medical science in modern India. This is evident from the bibliometric study of the publications in theIndian Medical Gazette, from 1900 to 1945. The paper studies the evolution of collaboration in the field of medical sciences during this period. In order to do so the study determines the: (i) pattern of collaboration in basic and applied research in medical science; (ii) trends in the multiplicity of authors; and (iii) the type of collaboration for the period 1900–1945. The collaborative and authorship trends discussed in the paper suggests that medical science was still in the developing stage in India in the period 1900–1945, and there was a possibility of its expansion in the near future.     

In vivo and in vitro tracking of erosion in biodegradable materials using non-invasive fluorescence imaging

The design of erodible biomaterials relies on the ability to program the in vivo retention time, which necessitates real-time monitoring of erosion. However, in vivo performance cannot always be predicted by traditional determination of in vitro erosion, and standard methods sacrifice samples or animals, preventing sequential measures of the same specimen. We harnessed non-invasive fluorescence imaging to sequentially follow in vivo material-mass loss to model the degradation of materials hydrolytically (PEG:dextran hydrogel) and enzymatically (collagen). Hydrogel erosion rates in vivo and in vitro correlated, enabling the prediction of in vivo erosion of new material formulations from in vitro data. Collagen in vivo erosion was used to infer physiologic in vitro conditions that mimic erosive in vivo environments. This approach enables rapid in vitro screening of materials, and can be extended to simultaneously determine drug release and material erosion from a drug-eluting scaffold, or cell viability and material fate in tissue-engineering formulations.     

5G时代动态可变式校标设计及延展应用

目的探讨5G时代中国高校如何通过具有高识别度和多元变化的校标设计及延展应用,提升中国高校的国际品牌形象,助力中国高校的国际化进程。方法通过比较研究中国137所“双一流”高校与QS世界大学排名前100强高校的校标,以图像分析和统计学的方法揭示中国高校校标设计高度雷同化、辨识度低的现状,指出常见的圆形范式校标在国际竞争和品牌传播中所存在的局限性;借鉴西方品牌形象设计的成功案例,寻找5G时代中国高校校标设计的创新理念、设计方向以及具体的延展应用方法。结论强调独特性、高识别性的校标设计在高校品牌传播中的重要性,并创造性地提出了“动态可变式”校标设计及延展应用在5G时代必将成为高校品牌形象传播的主流趋势和重要手段。     

Effect of micro-randomness on macroscopic properties and fracture of laminates

Composite materials demonstrate a considerable extent of heterogeneity. A non-uniform spatial distribution of reinforcement results in variations of local properties of fibrous laminates. This non-uniformity not only affects effective properties of composite materials but is also a crucial factor in initiation and development of damage and fracture processes that are also spatially non-uniform. Such randomness in microstructure and in failure evolution is responsible for non-uniform distributions of stresses in composite specimens even under externally uniform loading, resulting, for instance, in a random distribution of matrix cracks in cross-ply laminates. The paper deals with statistical features of a distribution of carbon fibres in a transversal cross-sectional area in a unidirectional composite with epoxy matrix, based on various approaches used to quantify its microscopic randomness. A random character of the fibres’ distribution results in fluctuations of local elastic moduli in composites, the bounds of which depend on the characteristic length scale. A lattice model to study damage and fracture evolution in laminates, linking randomness of microstructure with macroscopic properties, is discussed. An example of simulations of matrix cracking in a carbon fibre/epoxy cross-ply laminate is given.     

Paul Konitzer (1894–1947): Hygieniker,Amtsarzt, Sozialmediziner,Gesundheitspolitiker

Paul Konitzer was one of the outstanding and well-known physicians in the years after the World War II in East-Germany. THe paper describes his professional way as hygienist, social medical, municipal physician and last but not least as health politician in the times of four different political regimes: the imperial era in Germany till 1918, the time of "Weimarer Republic" till 1933, the Nazi dictatorship till 1945 and the early years in the Soviet occupation zone of Germany. The life of Konitzer is a typical example of the fate of a German doctor in the first half of the 20th century. Konitzer was arrested in February 1947 by the Soviet Military Government in Berlin in connection with some political troubles and reproach with a typhus epidemic in a German camp for Russian Prisoners of War in the Nazi era. On April 22nd 1947 he died in prison of Dresden by suicide without condemnation.     

Microbial stability evaluation of cement-based waste forms at different waste to cement ratio

An evaluation of the effect of differences in chromium nitrate to cement ratio on the microbial stability of a chromium nitrate/cement waste form, as reflected in the leaching of chromium, calcium, magnesium and aluminum; was carried out in this study. An increase in the proportion of chromium in the waste form from 4.8 to 8.7% had no noticeable effect on microbial stability, with the total chromium leached essentially unchanged. Further increases in the proportion of chromium in the waste form from 8.7 to 10.7%, and from 10.7 to 15.9% resulted in a substantial decrease in microbial stability, with 3-fold and 1.3-fold increase in the total chromium leached, respectively, observed. For calcium, increases in the chromium proportion were accompanied with increases in the total calcium leached even though the increases were not in direct proportion to the increases in chromium proportion. For magnesium and aluminum, increases in the proportion of chromium within the range 4.8-10.7% were accompanied with increases in the total respective metals leached, with minor variation for each metal. On the whole, the maximum percentage chromium leached from the different waste forms was substantially lower than those of the other metals.     

Citation delay in interdisciplinary knowledge exchange

As part of a larger project to investigate knowledge flows between fields of science, westudied the differences in speed of knowledge transfer within and across disciplines. The agedistribution of references in three selections of articles was analysed, including almost 800.000references in journal publications of the United Kingdom in 1992, 700.000 references inpublications of Germany in 1992, and more than 11 million references in the world total ofpublications in 1998.The rate of citing documented knowledge from other disciplines appears to differ sharplyamong disciplines. For most of the disciplines the same ratio's are found in the three data sets.Exceptions show interesting differences in the interdisciplinary nature of a field in a country. Wefind a general tendency of a citation delay in case of knowledge transfer between different fieldsof science: citations to work of the own discipline show less of a time lag than citations to work ina foreign discipline. Between disciplines typical differences in the speed of incorporatingknowledge from other disciplines are observed, which appear to be relatively independent of timeand place: for each discipline the same pattern is found in the three data sets. The disciplinespecific characteristics found in the speed of interdisciplinary knowledge transfer may be point ofdeparture for further investigations. Results may contribute to explanations of differences incitation rates of interdisciplinary research.     

Leukaemia following childhood radiation exposure in the Japanese atomic bomb survivors and in medically exposed groups

Incidence and mortality risks of radiation-associated leukaemia are surveyed in the Japanese atomic bomb (A-bomb) survivors exposed in early childhood and in utero. Leukaemia incidence and mortality risks are also surveyed in 16 other studies of persons who received appreciable doses of ionizing radiation in the course of treatment in childhood and for whom there is adequate dosimetry and cancer incidence or mortality follow-up. Relative risks tend to be lower in the medical series than in the Japanese A-bomb survivors. The relative risks in the medical studies tend to diminish with increasing average therapy dose. After taking account of cell sterilisation and dose fractionation, the apparent differences between the relative risks for leukaemia in the Japanese A-bomb survivors and in the medical series largely disappear. This suggests that cell sterilisation largely accounts for the discrepancy between the relative risks in the Japanese data and the medical studies. Excess absolute risk has also been assessed in four studies, and there is found to be more variability in this measure than in excess relative risk. In particular, there is a substantial difference between the absolute risk in the Japanese atomic bomb survivor data and those in three other (European) populations. In summary, the relative risks of leukaemia in studies of persons exposed to appreciable doses of ionizing radiation in the course of treatment for a variety of malignant and non-malignant conditions in childhood are generally less than those in the Japanese A-bomb survivor data. The effects of cell sterilisation can largely explain the discrepancy between the Japanese and the medical series.     

Biosynthesis of silver nanoparticles in collagen gel improves their medical use in periodontitis treatment

Silver nanoparticles (AgNP) suspensions were biosynthesized by silver ions reduction in the presence of collagen, a nontoxic, organic polymer, intending to improve their medical use in periodontitis treatment. Spectrophotometric measurements showed a time- and concentration-dependent increase of AgNP formation in each suspension variant. Transmission electron microscopy revealed spherical morphology of AgNP in collagen and their mean diameter size was around 30?nm. The particle size distribution and zeta potential values of AgNP in collagen were determined by dynamic light scattering measurements. The surface charge of AgNP in collagen was positive, while commercial AgNP stabilized in citrate had negative surface charge. In vitro cytotoxicity testing of AgNP in collagen showed that they were biocompatible with human gingival fibroblasts in a wider range of concentrations than commercial nanoparticles. The antibacterial activity of AgNP in collagen against two pathogenic strains present in the periodontal pocket was dose-dependent and higher than that of AgNP in citrate. All these results demonstrated that AgNP prepared in collagen gel had improved properties, like small diameter, positive surface charge, high biocompatibility in human gingival fibroblasts, efficiency against bacterial growth and, thus, better therapeutic potential in periodontal disease treatment.     

基于PG的复合改性沥青路用性能对比

沥青路面低温性能是寒区沥青路面设计的主要指标之一,现有的单一改性沥青低温性能不能满足寒区沥青路面PG技术规范的要求。本研究根据黑龙江省常用道路沥青低温性能的PG试验评定结果,研究开发了几种复合改性沥青,以满足黑龙江省寒区沥青路面低温性能的要求。研究内容包括：黑龙江省沥青路面PG分区与PG_m-n标准的确定,黑龙江省道路沥青PG性能评定,复合改性沥青的研究开发与性能评定等。研究结果表明,黑龙江省道路沥青基本满足PG_m-n技术标准的高温性能要求,但均不满足PG_m-n技术标准的低温性能要求。复合改性沥青基本满足或接近黑龙江省道路沥青的PG_m-n低温性能标准。研究结果对改善黑龙江省沥青路面的低温性能具有一定的理论与实用价值。     

FGH96合金反复镦拔与挤压缺陷对比分析

对FGH96合金反复镦拔变形与挤压变形两种制坯工艺的夹杂缺陷水平进行了比较,并分析了不同变形状态下非金属夹杂物的形变特性。结果表明:反复镦拔变形后,锻件内检测到的非金属夹杂物数量有不同程度的增多,超标缺陷成倍增长;而FGH96合金挤压+等温锻造变形后,锻件内检测到的非金属夹杂物数量明显减少,纯净度水平有大幅提高。从微观夹杂物形貌的变形特性来看,等温锻造变形时在垂直于变形方向合金中夹杂物缺陷的尺寸增大;反复镦拔变形时,合金中原有非金属夹杂物缺陷聚集使可检测到的缺陷面积增大;而在挤压变形过程中,夹杂物缺陷在挤出方向被拉长成不连续的线状,每个方向上夹杂物的面积均减小;FGH96合金挤压+等温锻造变形后夹杂缺陷的大小主要由挤压变形后夹杂缺陷破碎情况决定;因此大挤压比变形可有效破碎合金中非金属夹杂物,改善锻件质量。     

Research performance in key medical universities in China observed from the scientific productivity

Research activities in the life sciences during the past few years, have increased appreciably in China, both in regard to relative output of publications and in their impact on the international research community. The purpose of this study is to analyze and evaluate quantitatively the scientific productivity of key medical universities in China by using CBMdisc, MEDLINE and SCI databases. The results showed that Tongji Medical University ranks first in terms of paper output in Chinese and in English languages, while Beijing Medical University is placed second in output but is first in citation impact. Shanghai Medical University had the top annual paper output per scientist, with 2.53 papers in Chinese and 0.13 papers in English. The results also showed that the coverage of Chinese biomedical publications by western indexing services is very poor.     

功率超声在金属熔体成形中的作用效应及其可视化研究进展

主要介绍功率超声在金属熔体成形领域中的作用,详述了超声在铸造成形、辅助焊接成形中细化晶粒、除气除杂、强化焊缝、减小残余应力、促进界面润湿等方面的应用和作用机理。针对超声空化气泡的高速摄影及金属熔体中晶体生长的同步辐射X射线成像观察的研究进展,提出将高速摄影与同步辐射X射线成像结合起来,通过原位观察方法研究超声波与液态金属媒质的相互作用机理,为进一步促进超声在金属熔体成形中的应用提供理论指导。