稻城传统藏式民居的自发式更新

面对旅游发展中民居的更新改造,针对藏区稻城传统藏式民居的地域性自然及文化特征,本文提出以个体追求为主导,自下而上进行的自发式更新改造。其中,专业设计重在全面的思考与分析,适度的引导与限定,准确的定量与预估,协助个体进行功能与空间的优化配置。进而归纳实践中自发式更新具体在空间扩张、功能重组、物料选择及文化传承方面的方式,并结合稻城一民居改造项目加以阐述。     

提升建筑工程现场施工管理的策略

建筑工程现场施工管理是一个技术性非常强的过程,并且贯穿整个建筑工程。本文对目前建筑工程现场施工管理存在的问题进行了分析,并且提出了相应的解决策略。     

TDR水分计标定试验分析

土体含水量是控制非饱和土特性不可或缺的状态变量,快捷、准确地测量该变量成为推动非饱和土研究的重要环节。TDR水分计测定含水量具有方便、快速、经济的优点。围绕TDR测量原理,开展了探测体积、测量误差的标定试验,并在操作中总结出了TDR水分计的安装经验,结果表明:两针型TDR水分计探测范围集中在1.7倍探针间距的圆柱体内;针对砂土和黄土,TDR测量值比烘干含水量稍大,两者间可采用三次多项式拟合修正。为确保TDR水分计为实际应用提供准确可靠的水分数据,未来室内试验和室外监测使用前需预先进行标定。     

珊瑚礁地质条件下水泥土搅拌桩抗渗性能研究

为研究珊瑚礁特殊地质条件下水泥土搅拌桩的抗渗性能,以海南岛某基坑止水工程为背景,通过原状土室内渗透试验与现场取芯试验,获得了膨润土外加剂水泥土的抗渗变化规律。研究表明：①水泥土搅拌桩在珊瑚礁特殊地质条件下的止水工程中具有良好的适用性。②早期水泥对水泥土渗透性的影响大于膨润土,后期由于膨润土的密实效应,膨润土对渗透性能的影响大于水泥,且随着膨润土掺入量的增加,水泥土渗透系数逐渐减小,抗渗能力增强。研究成果对珊瑚礁地质中工程止水具有一定的借鉴意义。     

类芬顿体系研发及其处理苯酚能力研究

为解决传统均相芬顿体系反应后产生大量含铁污泥、药剂使用量过大等问题,以Fe、Cu和C烧结制备非均相类芬顿体系催化剂,研究催化剂中各物质的最佳配比,考察催化剂的烧结温度和时间对催化剂比表面积和催化效能等方面的影响。通过试验得到各物质的最佳配比为Fe∶C=4∶1、Cu含量为7%、Na2Si O3含量为5%,此时对COD和苯酚的去除率分别为92.61%和98.60%。BET和化学试验结果表明,最优烧结温度和烧结时间分别为850℃和3 h,此条件下利用Fe、Cu和C制备的类芬顿催化剂具有良好的比表面积、平均孔径及催化效果。     

陀螺稳定平台速度环的离散自抗扰控制

针对陀螺稳定平台在高精度定位下的控制精度受到速度环电机在低速运动时非线性摩擦力影响的问题,文章设计了一种改进策略的自抗扰控制器,将原系统中的非线性摩擦力与电机不同转向时的模型误差统一视为系统扰动,采用扩张状态观测器对这个扰动进行估计,前馈到控制量中进行校正。理论分析了一阶离散系统上扩张状态观测器的推导过程和稳定性条件,并采用遗传算法工具箱对针对平台所设计的扩张状态观测器的参数进行辨识。在仿真实验中,我们首先分析了所设计的扩张状态观测器的开环性能,然后将所设计的自抗扰控制器与实际系统采用的PI控制器的控制精度进行了对比分析。文章为进一步提高陀螺稳定平台的控制性能,提供了一种新的高精度的控制策略。     

Facile fabrication of hierarchically flowerlike Ag microstructure for SERS application

Hierarchically flowerlike Ag microstructure with uniform silver nanosheets as building blocks has been facilely prepared on a composite film surface via in situ reduction of Ag⁺ by a polyaniline component. The morphology of the as-prepared Ag microstructure is determined by the reaction duration, not the concentration of Ag⁺ in the reaction process. The complex geometry, rough surface, and interlaced nanosheets of the hierarchical Ag microstructure create interstitial sites and thus result in enhanced Raman signals.     

Parameter Design of Linear Frequency Modulated Excitation Waveform for Ultrasonic Nondestructive Testing of Metallic Materials

Linear frequency modulated (LFM) pulses are used as excitation sources for the ultrasonic nondestructive testing of metallic materials. The detection resolution relies on both the bandwidth of the LFM pulse and the amplitude spectrum of the transducer. A bandwidth selection method to analyze the effect of the LFM bandwidth on the inspection results was proposed, as well as to select an optimized LFM bandwidth corresponding to different transducers. Meanwhile, an ultrasonic through- transmission technique to test four different pairs of transducers excited by LFM signals with different bandwidth was used. Experimental results show that the time resolution significantly improves with an increase in the LFM bandwidth. Optimum parameter is achieved when the LFM bandwidth is close to the \(-\) 12 dB bandwidth \(B_{-12\hbox {dB}}\) of the transducer, and it then remains roughly stationary. The results were confirmed by carrying out ultrasonic LFM time-of flight diffraction (LFM-TOFD) testing for a steel plate with three buried defects employing a pair of 10 MHz transducers. The waveforms of the echoes extracted from these defects become narrower with an increase in the exciting bandwidth. In addition, the diffracted waves from the upper and lower tips of the 2 mm defect can be distinguished when the LFM bandwidth is close to the \(-\) 12 dB bandwidth of the 10 MHz transducer. The proposed bandwidth selection method can enhance the efficiency and precision of the actual ultrasonic LFM detection and is suitable for different ultrasonic testing systems, transducers and inspection requirements.     

Visible Light Photocatalytic Properties and Thermochromic Phenomena of Nanostructured BiOCl Microspheres

Black nanostructured Bi OCl microspheres were directly synthesized by a hydrothermal method. The black balllike Bi OCl microspheres and black flower-like Bi OCl microspheres were obtained using different surfactant.The color of the Bi OCl microspheres turned from black to white when being annealed at 400℃ in air for 3 h and could be recovered to black by exposure to ultraviolet light for a few hours. The photocatalytic activity of both the black and the white Bi OCl microspheres was characterized by the photo-degradation of methyl orange dye under visible light irradiation. The black ball-like nanostructure Bi OCl displayed the best photocatalytic activity, compared with the white Bi OCl and the black flower-like Bi OCl. It can degrade the methyl orange dye to 20% within 70 min under visible light irradiation. The high activity of the Bi OCl ball-like sphere may own to its special morphology, strong absorption in visible light range and the existence of oxygen vacancies.     

Oxidation Resistance Coatings of Ir – Zr and Ir by Double Glow Plasma

Oxidation resistance coatings of Ir-40 at.% Zr and Ir were produced onto Mo substrates by double glow plasma technology. The oxidation resistances of the coatings were evaluated at high temperature. Ir-Zr coating consisted of two layers： the primary layer close to the substrate was composed of dense columnar grains and the second layer was composed of dense grains of nanometric size. The mass gain of Ir coating above 800℃ was about 1.35% due to the formation of solid IrO2. The mass loss of Ir coating was about 5.3% due to the formation of gaseous oxide IrO3 when being held at 1227 ℃ for 30 min. The substrate was protected more effectively by multilayer than monolayer coating of Ir in oxidizing environment. The Ir-Zr coating was well bonded to the substrate after oxidation at 800℃. After oxidation at 1000℃, the Ir-Zr coating was poorly bonded to the substrate. The oxidation resistance of Ir-Zr coating was poor due to high content of Zr.