A higher order finite element algorithm for the unsteady Navier-Stokes equations

A higher order element, the Tocher 10 or C₀ Cubic on triangles, is the base for formulation of a finite element algorithm for numerical calculation of fluid flows governed by the unsteady Navier-Stokes equations. Results from the calculation of supersonic free shear layer flow are numerically accurate and in excellent agreement with finite difference solutions. Diverse characteristics for these two classes of methods emerge when the requirements of core storage and computer time are considered.     

A characterization of stiffly stable linear multistep methods

A theorem expressing geometric conditions necessary and sufficient for the stiff stability of a linear multistep method is obtained. A corollary to this theorem provides sufficient conditions for stiff stability, for the class of algorithms characterized by a single essential root. By applying the Schur-Cohn criterion and employing a computerized algebraic manipulation program, the result provides a first step towards an exhaustive search technique for determining a continuum of members of this class.     

多输出隔离电源利用次级侧同步后置稳压器实现高效率

引言许多通讯、服务器和其他应用领域都需要多输出电压的隔离电源，但是对所有的输出电压都提供严密调节是令电源设计工程师们头疼的事。一般的，设计者在每个辅助输出端加一个线性调节器，但线性调节器的效率非常低，限制了它的低输出电流应用。另一个选择是用一个降压转换器作为后调节器。这种方法有较好的效率，但是如果后调节器在初级输出端级联的话，电源需要一个更大的输出电感和电容，或者如果用多个副线圈的话将需要附加的整流器、电感和电容器。附加的电源转换级和元器件增加了传导损耗。另一个选择是用磁放大后调节器，它的效率很…     

资源枯竭下的建筑学——世界建筑师大会感言

2002年5月，联合国发布了由1100名科学家联合调查撰写的《全球环境望》，这份报告勾勒出30年后地球遇到的一系列生态和物种延续危机，人口爆炸，普遍缺水，粮食灾荒，矿藏耗尽。     

Improvement in the slotted wall boundary condition by numerical methods

The constant coefficient in the classical slotted wall boundary condition is expressed as a line integral of the slot-induced, rapidly varying velocity. Aerodynamic panel methods which employ a vector continuous loading concept in order to minimize panel leakage are used to compute the inviscid flow through periodic slots, from which the slotted wall coefficient is evaluated by means of numerical integration. This approach is expected to yield improved results, inasmuch as no idealizations in slat geometry are required. For the first time, the method affords the capability to obtain insight into the effects upon the slotted wall coefficient of minor alterations in slat shape, such as geometry changes which leave invariant the openness and thickness ratios. The coefficient is numerically evaluated for slat shapes typical of test section design.     

中国建筑和《时代建筑》100期

《时代建筑》是中国建筑革命和上海这地方的产物。中国30年的变革天翻地覆,由此推动的建筑活动适应和服务于整个国家机器和社会经济活动,中国20世纪末21世纪初的建筑热潮让世界刮目相看。建设数量、投入的资金,资源和人力巨大,政府、企业和私人发展商对建筑和开发的兴趣空前高涨。城市建设,城市设计代替或带动了建筑设计。建筑类型不断出新、多样,以适应社会和居民持续提高的生活水平和要求。节能标准、新技术和材料不断面世,环境观和可持续发展在建筑评价中的份量越来越重;国营设计院实行自负盈亏、私人事务所逐渐占到市场的大多数。建筑设计竞赛和招投标成为行业内的游戏规则,     

Influence of urea fertiliser formulation, urease inhibitor and season on ammonia loss from ryegrass

This paper reports the results of experiments to determine whether ammonia (NH₃) loss can be reduced and nitrogen (N) use efficiency improved by using two relatively new commercial urea formulations rather than granular urea and urea ammonium nitrate. Four nitrogen treatments were applied at a rate of 40 kg N ha^?1: granular urea, ‘Green Urea? 14’ [containing 45.8 % N as urea and ‘Agrotain^®’ (N-(n-butyl) thiophosphoric triamide) @ 5 L t^?1 of urea as a urease inhibitor], ‘Nhance’, a fine particle spray [containing 46 % N as urea, ‘Agrotain’ @ 1 L t^?1 of urea and gibberellic acid (applied at a rate of 10 g ha^?1)] and urea ammonium nitrate in solution (UAN) surface applied. Ammonia loss was determined in autumn and spring using a micrometeorological method. In autumn, use of the Green Urea and Nhance reduced NH₃ loss from the 30 % of applied N lost from the granular urea to 9 and 23 % respectively. Loss from all treatments in spring was very small (<2 % of applied N), because 4 mm of rain fell within 24 h of application onto an already wet site. The use of the Nhance and Green Urea instead of granular urea did not result in increased agronomic efficiency or recovery efficiency of the applied N, and this is most likely due to the presence of sufficient available N from both fertiliser application and the soil. A ¹⁵N study recovered 72.8 % of the applied N in the plants and soil, and showed that 30 % of the total N taken up by the plant was derived from the fertiliser, and 70 % from the soil.     

Towards international: China-aided stadiums in the developing world

Foreign aid is a form of international relationship between countries. Building projects are a major form of foreign aid. In the past 60 years, China has constructed over 1400 buildings in the developing world, and many of them are stadiums. This study explores how China exported its overseas-aided stadiums in the developing world and considers the importance of these buildings from an architectural perspective. Through an examination of firsthand materials, this study explains the historic vicissitude of China-aided stadium architecture, analyzes the architectural features of these buildings, and presents case studies of representative examples from each historic stage. The investigation of these buildings from three periods in the 20th and 21st centuries fills a gap in the study of Chinese architecture and modern architectural history.     

Surface potentials and layer charge distributions in few-layer graphene films

Graphene-derived nanomaterials are emerging as ideal candidates for postsilicon electronics. Elucidating the electronic interaction between an insulating substrate and few-layer graphene (FLG) films is crucial for device applications. Here, we report electrostatic force microscopy (EFM) measurements revealing that the FLG surface potential increases with film thickness, approaching a "bulk" value for samples with five or more graphene layers. This behavior is in sharp contrast with that expected for conventional conducting or semiconducting films, and derives from unique aspects of charge screening by graphene's relativistic low energy carriers. EFM measurements resolve previously unseen electronic perturbations extended along crystallographic directions of structurally disordered FLGs, likely resulting from long-range atomic defects. These results have important implications for graphene nanoelectronics and provide a powerful framework by which key properties can be further investigated.