Response of rainfed bread and durum wheat to source,level and timing of nitrogen fertilizer on two Ethiopian Vertisols: II. N uptake,recovery and efficiency

In trials conducted at 2 highland Vertisol sites in Ethiopia in 1990 and 1991, 2 locally popular wheat cultivars, 1 spring bread wheat (Triticum aestivum L.) and 1 durum wheat (T. durum Desf.), were supplied with nitrogen (N) fertilizer at 0, 60 and 120 kg N ha^–1 in the form of large granular urea (LGU), standard urea prills or ammonium sulfate. N was applied all at sowing, all at mid-tillering or split-applied between these two stages (1/3:2/3). While durum wheat exhibited the highest N concentration in grain and straw, bread wheat, because of its higher productivity, resulted in a greater grain and total N uptake. In general, split application of N and use of LGU as N source enhanced grain and total N uptake, apparent N recovery and agronomic efficiency of N, particularly under severe water-logging stress. Where significant, the interactions among the experimental factors substantiated the superior responsiveness of the bread wheat cultivar to fertilizer N, and the beneficial effects of split N application and LGU as an N source. Split application of N tended to nullify the positive effects of LGU, presumably by approximating the delayed release of N achieved with LGU. Considering the potential benefits to Ethiopian peasant farmers and consumers, split application of N should be advocated, particularly on water-logged Vertisols; LGU could be an advantageous N source assuming a cost comparable to the conventional N source urea.     

Preparation and mechanical behavior of Mg-based bulk metallic glasses and their matrix composite

Mg87-xCuxDy13(x=22,27,32) bulk metallic glasses (BGMs) with a diameter of 6-8 mm and in-situ Mg phase reinforced Mg70Cu17Dy13 BMG matrix composite with a diameter of 3 mm have been prepared by copper mould casting. The glass forming ability (GFA) of Mg-Cu-Dy alloys have been investigated by differential scanning calorimetry (DSC) and X-Ray diffraction (XRD) and tne mechanical properties have been measured. Results show that Mg87-xCuxDy13(x=22,27,32) alloys in the Mg-Cu-Dy alloy system exhibit excellent GFA, and Mg60Cu27Dy13 alloy has the largest GFA among these alloys. And In-situ Mg phase reinforced Mg70Cu17Dy13 BMG matrix composite exhibits some work hardening and a high fracture compressive strength of 702.38 MPa and some plastic strain of 0.81%. The improvement of the mechanical properties is attributed to the fact that the Mg phase distributed in the amorphous matrix of the alloy has some effective load bearing and plastic deformation ability to restrict the expanding of shear bands and cracks and produce its own plastic deformation.     

利用直流输电抑制交直流系统次同步振荡的仿真研究

在交直流联合输电系统中，由于大机组轴系的弹直流系统常规控制扔相互作用，可能引起形态复杂的振荡一次同步振荡（ＳＳＯ）。但是直流系统是一个快速可控的有源系统，因而有可能通过分析与研究ＳＳＯ的机理和规律，采用适当的ＨＶＤＣ控制措施，变消极影响为积极因素反过来抑制大轴的扭振。本文从ＨＶＤＣ控制系统出发利用次同步振荡时的特征表现，给ＨＶＤＣ设计了一个附加控制器。仿真结果表明该顺能有效的抑制镒同步振荡。     

添加Cu和T6下Mg2Si/Al复合材料的组织与性能

采用铸造法制备原位自生亚共晶Al-10Mg₂Si复合材料,研究Cu和T6热处理对该复合材料组织与力学性能的影响。结果表明:适量Cu的添加能显著减小共晶Mg₂Si相晶粒尺寸,使其晶体结构由粗大的长条状和汉字状转变为细小的条状和纤维状;同时使针状的β-Al₅Fe Si相转变为细小的不规则富Cu颗粒。经T6热处理后,质量分数为1.5%的Cu复合材料中的共晶Mg₂Si相完全球化。质量分数为1.5%的Cu添加同时提高了材料铸态下的抗拉强度(R_m)、屈服强度(R_p0.2)和伸长率(A),达317、169 MPa和2.3%,比未添加Cu提高了42.2%、24.3%和53.3%;经T6热处理的R_m和R_p0.2值分别增至332、181 MPa,而A值保持不变。同时,材料由脆性断裂完全转变为韧性断裂。     

Tubular shaped composites made from polythiophene covalently linked to Prato functionalized N-doped carbon nanotubes

A simple methodology to produce tubular nitrogen-doped carbon nanotube/polythiophene covalently linked composites is described. Nitrogen doped carbon nanotubes (N-CNTs) were made by the floating catalyst CVD method using toluene, ferrocene and tetramethylethylenediamine (TMEDA) as reagents. Functionalization of the N-CNTs was achieved using 3-thiophenecarboxaldehyde and N-methylglycine in 1,2-dichlorobenzene (Prato reaction). Elemental analysis showed nitrogen incorporation of N into the N-CNTs (1.8%) and also the N-methylglycine functionalized N-CNTs (f-N-CNTs; 6.2%). A series of f-N-CNT/thiophene monomer mixtures (weight ratios 1:3, 1:10 and 1:20) were used to make f-N-CNT/polythiophene tubular composites. As the amount of thiophene monomer was increased, the overall diameter of the polymer layer attached onto the N-CNTs increased. Polymer thickness also varied with reaction time (1 h, 12 h and 24 h). The combination of acid functionalization and N–doping gives the best coverage of the CNTs by polythiophene, in which the polythiophene preferentially binds to the f-N-CNTs to give tubular structures.     

Accumulation of chylomicron remnants in homozygous subjects with familial hypercholesterolaemia

Despite the obvious differences between the USA and UK health care systems, they share the characteristics of being motivated and managed in relation to cost and process rather than quality (the improved health status of patients). Whilst governments and insurers across the world use the rhetoric of quality, they, as epitomized by the behaviours of UK and USA decision makers, fail to define, measure and implement quality outcome policies. These behaviours are examined and some of their causes are explored briefly. Competition, as designed and used in public (e.g. UK National Health Service) and private (e.g. USA managed care) markets is shown to fail both to identify quality outcome targets and to provide evidence-based and efficient mechanisms to motivate decision makers to be orientated towards continuous quality outcome improvement in health care. A central policy challenge is, consequently, not just the measurement of quality outcomes but also their management into practice.     

PDA系统及其在卷取机上的应用

针对由高精度传动控制、位置控制、压力控制以及快速连锁控制等组成的卷取控制系统，介绍了开发PDA数据采集系统的组态、网络集成和软件配置等。分析了系统的组态和分析方法的应用。PDA系统的应用，解决了过程数据的高速采集、存贮和分析技术等难题，为分析设备和工艺控制状况提供了技术平台和分析手段，解决了生产过程数据的录入的难题，具有推广应用价值。     

Ring-opening Metathesis Co-polymerization of a C60-cyclopentadiene Cycloadduct and Norbornene with the Grubbs Second-generation Catalyst

A series of C₆₀-containing polymers were synthesized by the co-polymerization of a C₆₀-cyclopentadiene cycloadduct and norbornene in varying ratios. The polymerization was facilitated by a catalytic amount of Grubbs second generation catalyst and the co-polymers formed were investigated by spectroscopic and thermal techniques.     

Multi‐criteria decision evaluation in groundwater zones identification in Moyale‐Teltele subbasin,South Ethiopia

The conventional approaches such as ground‐based surveys and exploratory drilling for groundwater investigation are time‐consuming and uneconomical. Systematic organisation of data of characteristics of any terrain, evaluation of inter‐thematic, interclass dependencies and variability, and also analysing cumulative effect on the development of groundwater regime is the best approach which the current decade requires. This is proved by generation of the thematic information on the above factors through remote sensing technique, and integration in geographic information system (GIS) for evaluation using multi‐criteria decision‐making techniques. This paper presents the results of the attempt made to identify the groundwater potential zones in the Moyale‐Teltele Sub basin of the Genale Dawa River Basin in South Ethiopia using the integrated approaches of remote sensing and geographic information systems. Six geologic, physiographic, and hydrologic factors were applied namely: lithology, structure, geomorphology, slope, land cover, and drainage. Weighted Overlay Analysis using multicriteria decision technique is implemented to produce the groundwater potential map of the area. This result is further verified by groundwater yield data of boreholes and springs collected in the field and from previous reports. The validation revealed that the result is in good conformity with the actual yield of the wells and springs.     

用于三电平逆变器的IGBT提高DC／AC转换的效率

当我们谈论效率时，我们主要指的是电力效率。然而，这种用法并不是效率一次本身的完整含义。在电力电子应用巾，工程师在开发新产品过程中的追求的主要目标是以最大限度地发挥不同类型的效率，如电效率和热效率，以及优化谐波失真和产品整体的尺寸。