不同外部约束条件下的住房保障供给模式选择

实物配租和货币补贴是两种主要的住房保障模式,二者各有优缺点。影响住房保障供给模式选择的外部约束条件主要有四个:政府财政收入水平、城市建设土地资源、城市住房存量以及城镇化不同阶段。本文以住房保障供给模式的成本收益为视角,基于我国35个大中城市的数据分析了不同外部约束条件下当前各城市最优和次优的住房保障供给模式。     

近紫外芯片激发三基色荧光粉制作的白光LED

使用发射波长为395～400 nm的近紫外LED芯片来激发发射峰值波长分别在615,505和445 nm的红绿蓝三基色荧光粉,建立三基色荧光粉混光理论模型,制作不同色温下高显色指数白光发光二极管,研究其光电特性。实验结果表明,采用近紫外激发的三基色白光器件色温为3 000～9 000 K范围内,其显色指数均能保持在80～90之间;当色温大于5 000 K时,显色指数可以达到85;测试结果与理论计算吻合良好。最后,实验证明加入TiO2粉末可消除白光LED中残余近紫外线,三基色荧光粉白光LED色度参数受工作电流变化的影响较小。     

利用遥感和GIS监测旱情的方法研究

主要以山东，河南两省为例，探讨了利用ＮＯＡＡ／ＡＶＨＲＲ图像资料监测大面积表的几种研究方法，并对每种方法的优缺点进行了评估。结果表明，几种方法结合使用并借助地理信息系统，进行大面积的旱情监测是可行的，另外还进行了利用机载雷达图像监测河北省土壤水分的方法尝试研究，分析表明微波遥感监测土壤水分具有广阔的应用前景，可以利用星载ＳＡＲ图像资料作进一步的分析研究，从而获取微波监测土壤水分的最佳波段和最佳极化     

Extraction of selected rare earth elements from anthracite acid mine drainage using supercritical CO_2 via coagulation and complexation

Rare earth elements(REEs) are valuable raw materials which are in great demand in modern high technology industries.Developing methods to produce/recover REEs from waste is significant to the national security of any developed country.This study was focused on investigating the use of supercritical CO2(sCO_2) to extract REEs from anthracite acid mine drainage(AMD).Four different mine drainage water source locations at Blaschak Coal Corp.in Pennsylvania,USA were selected for sample collection.An extraction process was developed and demonstrated for two of those water sources containing the highest concentration of REEs.A method involving metal ion coagulation,their dissolution from the sludge into a concentrated aqueous HNO_3 solution,complexation with organic ligands and sCO_2 extraction was developed to recover REEs from AMD.Specifically,sodium aluminate(NaAlO_2) was used as the coagulant to concentrate REEs from the AMD into a solid precipitate.Consequently,over 99%of the REEs in AMD is concentrated in the remaining sludge.During the coagulation process,the effects of pH and NaAlO_2 concentration on REE precipitation were investigated.Fuming nitric acid(HNO_3) was used to digest the pre-concentrated sludge and tributyl phosphate(TBP) was used to form REE/TBP/HNO_3,a non-polar complex with selected REEs,specifically,cerium(Ce),lanthanum(La) and neodymium(Nd).HNO_3 concentration and organic/aqueous phase ratio were considered as the variables to improve complexation efficiency.Dynamic extraction experiments using sCO_2 and REE/TBP/HNO_3 solutions were then conducted at optimal conditions of 60℃ and 20 MPa.The overall REE extraction efficiencies are found to increase with the atomic number of the REE.As a result,the average overall REE extraction efficiencies of 41.8%,40.1% and 58.2% for Ce,La and Nd,respectively,are obtained.The potential improvements in the overall extraction efficiency are also discussed.     

高压输电换流阀晶闸管控制单元电磁兼容测试方法研究

重点研究了换流阀控制单元TCU的实际运行电磁环境,提出了可能导致TCU运行失败或异常的几种电磁骚扰源,并针对换流阀与控制电路之间的电气联系、空间关系论证了骚扰信号注入部位的适用性。提出了有别于IEC标准的测试方法,并进一步验证了测试方法的合理性和可行性。通过对实测结果的分析,证实了现场应用中因电磁骚扰导致晶闸管及换流阀错误控制、换相失败的原因,并进一步论证了所提出的测试方法的合理性。     

基于机器学习的铆接质量数字化检测系统

为实现铆接质量数字化检测和质量追溯,提出基于机器学习的铆接质量数字化检测方法。使用CCD摄像机对铆接部位进行图像采集,然后进行中值滤波、Canny边缘检测、图像形态学处理等,实现铆接部位裂纹检测和特征信息提取。利用改进的粒子群优化最小二乘支持向量机算法建立铆接质量检测模型,并使用检测样本对模型进行检验。对不合格的铆接进行质量追溯,应用专家系统判断产生缺陷的原因。在某型号飞机装配车间对原型系统进行应用验证。结果表明：所设计的系统检测准确率达96%,可提高铆接质量检测效率、统一检测标准、减少工人劳动。     

Effect of Diffusivity on the Pseudospinodal Decomposition of the γ′ Phase in a Ni-Al Alloy

The effect of diffusivity on pseudospinodal decomposition of γ′ (Ni₃Al) phase precipitation was investigated in a Ni-Al alloy using the diffuse interface phase field model. The γ′ phase microstructure, coarsening dynamics and interfacial composition width between the γ and γ′ phases were studied as a function of the diffusivity magnitude. Increasing the diffusivity results in a reduced number of γ′ nuclei, and accelerated growth and coarsening of the γ′ phase. The cube of the γ′ average radius versus time shows a linear relation during coarsening, and the Al concentration in the γ matrix follow the relations \(\Delta c_{\text{Al}}^{\gamma } \sim t^{ - 1/ 3}\) regardless of the diffusivity magnitude. The γ/γ′ interfacial composition width decreases with increased diffusivity and average radius. An obvious Al concentration depleted region is present at the γ/γ′ interface during the nucleation and growth stage of γ′ phase indicates that growth occurs by down-hill diffusion in the matrix γ phase. That combined with the gradual increase in γ′ composition demonstrates that pseudospinodal decomposition is the transformation mechanism.     

MWCNT-H2O纳米流体对静态真空闪蒸制冰实验的影响

在蒸馏水中加入多壁碳纳米管（MWCNT）纳米粒子,选用亲水性非离子型表面活性剂TNWDIS为分散剂。经过超声波震荡,配制分散均匀稳定的MWCNT-H₂O纳米流体。利用静态真空闪蒸实验台,设定系统压力为100Pa,研究在吸附作用下多壁碳纳米管纳米粒子浓度、粒径、TNWDIS与MWCNT配比对闪蒸制取冰浆实验的影响。结果表明,多壁碳纳米管的加入可消除闪蒸制冰的相变蓄冷阶段、缩短液相降温时间使流体更早出现过冷现象;20～40nm粒径的MWCNT纳米粒子使用TNWDIS进行分散,质量分数范围在0.075%～0.15%时多壁碳纳米管纳米流体分散均匀稳定、达到最佳效果,其中质量分数为0.1%的纳米流体最大降低水的过冷度达62.2%;过冷度随着MWCNT纳米粒子粒径的增大而升高,闪蒸率基本维持在40%,但含冰率呈现非线性变化;20～40nm粒径的MWCNT纳米粒子使用TNWDIS配制成质量分数为0.1%的纳米流体,TNWDIS与MWCNT的分散配比建议采用0.5∶1,过冷度基本维持在2℃。     

相变材料复合八水氢氧化钡的制备及热性能

纯八水氢氧化钡相变蓄热材料在使用过程中存在凝固过冷、相分离及体积变化等问题,因此需要对其进行相应的改性研究。本文根据相变蓄热材料成核机理,以八水氢氧化钡为相变蓄热材料基材,一水氢氧化钡及去离子水作为复合添加剂,制备了混合比例为95.1% Ba（OH）₂·8H₂O+2% Ba（OH）2·H₂O+2.9% H₂O的复合相变蓄热材料。对该复合相变蓄热材料进行了热性能测试,结果表明：复合相变蓄热材料的平均热导率为1.2W/（m·K）、相变潜热值为263.7kJ/kg;在复合相变蓄热材料融化过程中进行升温-压力实验,测试数据显示容器内部的相对压力不超过0.09MPa;利用恒温金属浴仪器对该复合相变蓄热材料进行300次融化/凝固循环实验,测试数据显示复合相变蓄热材料过冷度增加量0.7℃、相变潜热值降低0.796%。改性后的复合相变蓄热材料相变温度适宜、热性能稳定,可推广应用于中低温相变储热系统。     

Rotation errors in numerical manifold method and a correction based on large deformation theory

Numerical manifold method (NMM) is an effective method for simulating block system, however, significant errors are found in its simulation of rotation problems. Three kinds of errors, as volume expansion, stress vibration, and attenuation of angular velocity, were observed in the original NMM. The first two kind errors are owing to the small deformation assumption and the last one is due to the numerical damping. A large deformation NMM is proposed based on large deformation theory. In this method, the governing equation is derived using Green strain, the large deformation iteration and the open-close iteration are combined, and an updating strategy is proposed. The proposed method is used to analyze block rotation, beam bending, and rock falling problems and the results prove that all three kinds of errors are eliminated in this method.