冲击式水轮机性能换算的新理论提案(Ⅱ)

对冲击式水轮机的内部流动进行了探讨,着重研究了喷嘴以后的自由二相流,发现冲击式水轮机存在着与反击式水轮机不同的流动机理及其对应的不同比尺效应;并指出非定常自由流随工况变化的比尺效应对性能预测的影响;同时大流量区水斗切口出流的增加会引起负比尺效应明显增加.     

FORMATION OF SOCIAL NORMS IN COMMUNICATING AGENTS WITH COGNITIVE FRAMEWORKS

1 IntroductionWe study how individuals' actions form social norms and the actions are edicted by thenorms in a social system. Action is a set of oriented processes[1], namelyl individualsl acttoward some objects, whether intelltionally or unintentionally. Orientations to objects fromindividuals are conceived as structured or patterned in a social system. Namelyl there are someconsistencies or regularities between the orientations and actions of dtherelit indi.id.al,[21. 'Thestructure forms th…     

A case study of WebGIS technology for distance learning between Korea and Japan

Recently, some case study of distance learning by internet line are widely carried out. Until now, the cultural or friendship exchange was a main purpose using distance learning program. In our research group, a distance learning which connected 3 sites (Nagasaki and Omura and Kagoshima in Japan) was tried as a domestic example[1]. In this case, internet exclusive line and portable telephone were utilized for DVTS technical support of distance learning. Nowadays, the international distance learning for education is also beginning. Our research group also tried international distance learning between Kwangju city of Korea and Nagasaki city of Japan using DVTS techniques with the tools of WebGIS education materials.     

Materials chemistry: a synthetic enamel for rapid tooth repair

The conventional treatment of dental caries involves mechanical removal of the affected part and filling of the hole with a resin or metal alloy. But this method is not ideal for tiny early lesions because a disproportionate amount of healthy tooth must be removed to make the alloy or resin stick. Here we describe a dental paste of synthetic enamel that rapidly and seamlessly repairs early caries lesions by nanocrystalline growth, with minimal wastage of the natural enamel.     

Avian flu: isolation of drug-resistant H5N1 virus

The persistence of H5N1 avian influenza viruses in many Asian countries and their ability to cause fatal infections in humans have raised serious concerns about a global flu pandemic. Here we report the isolation of an H5N1 virus from a Vietnamese girl that is resistant to the drug oseltamivir, which is an inhibitor of the viral enzyme neuraminidase and is currently used for protection against and treatment of influenza. Further investigation is necessary to determine the prevalence of oseltamivir-resistant H5N1 viruses among patients treated with this drug.     

Molecular identification of a renal urate anion exchanger that regulates blood urate levels

Urate, a naturally occurring product of purine metabolism, is a scavenger of biological oxidants implicated in numerous disease processes, as demonstrated by its capacity of neuroprotection. It is present at higher levels in human blood (200 500 microM) than in other mammals, because humans have an effective renal urate reabsorption system, despite their evolutionary loss of hepatic uricase by mutational silencing. The molecular basis for urate handling in the human kidney remains unclear because of difficulties in understanding diverse urate transport systems and species differences. Here we identify the long-hypothesized urate transporter in the human kidney (URAT1, encoded by SLC22A12), a urate anion exchanger regulating blood urate levels and targeted by uricosuric and antiuricosuric agents (which affect excretion of uric acid). Moreover, we provide evidence that patients with idiopathic renal hypouricaemia (lack of blood uric acid) have defects in SLC22A12. Identification of URAT1 should provide insights into the nature of urate homeostasis, as well as lead to the development of better agents against hyperuricaemia, a disadvantage concomitant with human evolution.     

Stacking of conical molecules with a fullerene apex into polar columns in crystals and liquid crystals

Polar liquid crystalline materials can be used in optical and electronic applications, and recent interest has turned to formation strategies that exploit the shape of polar molecules and their interactions to direct molecular alignment. For example, banana-shaped molecules align their molecular bent within smectic layers, whereas conical molecules should form polar columnar assemblies. However, the flatness of the conical molecules used until now and their ability to flip have limited the success of this approach to making polar liquid crystalline materials. Here we show that the attachment of five aromatic groups to one pentagon of a C(60) fullerene molecule yields deeply conical molecules that stack into polar columnar assemblies. The stacking is driven by attractive interactions between the spherical fullerene moiety and the hollow cone formed by the five aromatic side groups of a neighbouring molecule in the same column. This packing pattern is maintained when we extend the aromatic groups by attaching flexible aliphatic chains, which yields compounds with thermotropic and lyotropic liquid crystalline properties. In contrast, the previously reported fullerene-containing liquid crystals all exhibit thermotropic properties only, and none of them contains the fullerene moiety as a functional part of its mesogen units. Our design strategy should be applicable to other molecules and yield a range of new polar liquid crystalline materials.