增长主义价值观转变背景下的收缩城市复兴策略比较——以美国与德国为例

近年来发达国家收缩城市现象日益严峻,且导致了日趋复杂的城市问题,逐步引起了专家学者对收缩问题的重视和应对。其中,美国和德国的应对策略颇具代表性。本文从分析美国与德国在应对收缩时所具有的不同价值观的背景入手,通过对克利夫兰和马格德堡不同的应对范式的比较研究发现:以美国为代表的大部分发达国家延续利用传统的增长主义价值范式应对收缩,通过刺激性投资项目的建设带动城市不断增长,却导致收缩效应的强化;而德国率先转变收缩价值观——采用关注城市存量空间的精简主义价值取向,应对收缩取得良好效果。通过此比较性视角研究,本文希望为我国正确认识城市收缩现象——转变传统增长主义价值观提供思路和借鉴,并冀图从中得到我国复兴收缩城市的有益启示。     

一种转化钻柱振动能量的井底高压喷射钻井装置

通过转化井下钻柱振动能量来增加井底钻井液喷射压力是提高钻井速度的重要途径,而现有技术还未能充分合理地利用钻柱振动能量。为此,基于井下钻柱振动能量的利用理论,提出了钻井液井下增压、增排量的井底高压喷射钻井理念,设计出了井底高压喷射钻井装置,并对其进行了数值仿真研究。结果表明:(1)井底高压喷射钻井装置可以将钻柱振动能量有效转化给井底钻井液从而实现井下高压喷射钻井;(2)井底高压喷射钻井装置增加了喷嘴钻井液过流流量,在?215.9 mm井眼中,其输出的钻井液流量可以提高5 L/s;(3)增大了钻井液喷射压力,喷嘴处钻井液脉冲压力最高达到11.3 MPa;(4)深井内井底高压喷射钻井装置应用效果比上部地层更加显著。结论认为,井底高压喷射钻井装置为高压喷射钻井技术的实现提供了一种新的手段,可以解决现有高压喷射钻井技术设备费用昂贵、安全性差、适用范围有限的问题。     

Transformation of the Β-Triketone Pesticides Tembotrione and Sulcotrione by Reactions with Ozone: Kinetic Study,Transformation Products,Toxicity and Biodegradability

Rate constants between ozone and triketone herbicides, tembotrione and sulcotrione, were determined between pH 2 and 12. Both compounds are completely transformed within seconds by ozone under real water treatment conditions. A reaction pathway was proposed based on the identification of transformation products. Toxicity evaluation using Vibrio fischeri test showed that a residual toxicity remained even after degradation of the major by-products, but biodegradation significantly increased from 50% to 70% for molar ozone to pesticide ratios from 0 to 2. Thus, ozonation coupled with biological treatment would drastically reduce the risk associated to the presence of triketone herbicides.     

形变与连接——高密度校园空间试验:深圳外国语学校国际部设计

高密度是近年中小学校园建设中常见的空间现象,论文以深圳市外国语学校国际部的设计过程为例,分别从空间作用力、形变、连接等基本概念出发,探讨了高密度条件下校园空间设计方法与应用。以此强调设计过程中建筑师对城市环境、项目构成及使用者需求等方面的认识和理解。     

Shape memory strains and temperatures in the extreme

It is well known that the achievement of high transformation strains in shape memory alloys (SMAs) has been curtailed by plastic deformation mediated via dislocation slip. In particular, the utilization of SMAs at high temperatures is also hindered by plastic slip. In this paper, an overview of the most important SMAs is provided by constructing transformation strain, transformation temperature, and slip resistance plots to put existing works in perspective. To this plots, we added results on NiTiHf alloys which impart both high temperature capability and high slip resistance at unprecedented levels. The remarkable finding is that NiTiHf alloys can undergo transformation strains near 20% and transformation temperatures exceeding 400 °C.     

Wet chemistry synthesis of ZnO crystals with hexamethylenetetramine(HMTA): Understanding the role of HMTA in the formation of ZnO crystals

ZnO crystals have been prepared via a simple aqueous solution route using zinc acetate-hexamethylenetetramine (HMTA) solution. To understand the role of HMTA in the formation processes of ZnO crystals, concentration measurements of Zn(II) remaining in the solution as well as SEM and XRD analyzes of the solid product have been made at regular intervals. The results demonstrated that the HMTA concentration has determinative effects on the growth rate of obtained ZnO products by controlling the composition of zinc complex species and mediating the transformation rate of building blocks. XRD results revealed the single phase nature with the wurtzite structure of the as prepared ZnO rods. X-ray photoelectron spectroscopy confirmed high purity of the ZnO rods. By varying the concentration of HMTA in the solution, the average size of rods was varied from 5 μm to 10 μm. Photoluminescence spectra indicated that the photoluminescent intensity of the emission peak at 380 nm increase to different degree with increasing HMTA concentration. These results revealed that the concentration of HMTA plays a vital role to control the properties of ZnO crystals.     

Energy consideration for variant selection in precipitation on dislocations

Preferential precipitation on dislocations has been discussed by considering interaction energy between transformation strains to change the crystal structure and stress fields around dislocations. For quantitative calculation, precipitation of the hcp a phase from the bcc b matrix in a Ti alloy is analyzed. A previous experiment shows that a certain variant of precipitates among crystallographically equivalent ones was formed preferentially on a given dislocation. The present analysis is successful in explaining such variant selection. Comparison with other studies has revealed that the stress always plays an important role in the early stage of phase transformation to change the crystal structure.     

Data Format Transferring for FIB Microfabrication

Data format transformation is very important for 2D and 3D nanofabrication of FIB technology because only one map file format with the extension name XBM is available in FIB workstation software. This XBM format has only a few drawing functions which limits the bitmap editor when creating a complicated map file such as a spiral or a gear. Therefore, it is necessary to make use of specialised software which can transfer map files created by other drawing software such as AutoCAD and CorelDRAW into the FIB machine in the required XBM map file format. The method of transferring a map file created by AutoCADR14 into the XBM format file is discussed in detail in this paper. It is available for practical FIB micromanufacturing.     

三相并网型逆变器矢量控制技术实现

本文介绍了三相并网型逆变器矢量控制技术的实现过程,包括三相并网型逆变器电路建模以及根据模型设计控制系统,得到PL控制器参数。仿真结果和实验结果均验证了控制系统设计的有效性,体现了矢量控制技术用于三相并网逆变器控制的实用性和优越性。