小管径空调器的优化设计

空调器采用小管径铜管可以有效地降低空调器换热器的成本,大幅降低空调器的充注量,此技术被称为MicroGroove^TM小管径技术。但用小管径直接替换大管径时会给空调器的性能带来影响,因此需要重新设计换热器。本文提出了小管径空调器的优化设计方法,主要包括采用基于图论的仿真方法设计制冷剂流路及换热器结构,采用空调器系统仿真软件预测优化后的系统性能。本文以单冷空调器和冷暖两用的空调器为例进行小管径空调器的优化设计,总结了用小直径管替代大直径管用于空调器优化设计的准则。     

Effects of ball milling on microstructure and electrical properties of sol–gel derived (Bi0.5Na0.5)0.94Ba0.06TiO3 piezoelectric ceramics

A citrate sol–gel method was investigated for synthesizing lead-free piezoelectric compositions of (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ (BNT) and the effect of ball milling on the sintering, microstructure and electrical properties of BNT ceramics was emphasized. The thermal analysis and X-ray diffraction results show that crystalline powders with a single perovskite structure can be obtained when calcined at 600 °C for 3 h. The average particle size of as-calcined powder and electrical properties of sintered samples were obviously dependent on an additional ball milling. Because of well-dispersed superfine powders (∼100 nm), the BNT ceramics can be well densified at temperature 50 °C lower than that by mixed-oxide method and conventional sol–gel method and as a result exhibit enhanced electrical properties of a piezoelectric constant d₃₃ ∼ 180 pC/N and a planar electromechanical coupling factor k_p ∼ 0.29.     

Probing Distinctive Electron Conduction in Multilayer Rhenium Disulfide

Charge carrier transport in multilayer van der Waals (vdW) materials, which comprise multiple conducting layers, is well described using Thomas–Fermi charge screening (λ_TF) and interlayer resistance (R_int). When both effects occur in carrier transport, a channel centroid migrates along the c‐axis according to a vertical electrostatic force, causing redistribution of the conduction centroid in a multilayer system, unlike a conventional bulk material. Thus far, numerous unique properties of vdW materials are discovered, but direct evidence for distinctive charge transport behavior in 2D layered materials is not demonstrated. Herein, the distinctive electron conduction features are reported in a multilayer rhenium disulfide (ReS₂), which provides decoupled vdW interaction between adjacent layers and much high interlayer resistivity in comparison with other transition‐metal dichalcogenides materials. The existence of two plateaus in its transconductance curve clearly reveals the relocation of conduction paths with respect to the top and bottom surfaces, which is rationalized by a theoretical resistor network model by accounting of λ_TF and R_int coupling. The effective tunneling distance probed via low‐frequency noise spectroscopy further supports the shift of electron conduction channel along the thickness of ReS₂.     

开发知识级问题求解建模

开发知识级问题求解建模正在导致知识工程的重大变革。鉴于知识表示的本体论可以作为开发知识级建模的基础理论，我们提出描述问题求解过程组织的本体论ＲＡ和刻划领域世界结构的本体论ＯＴ，并设计了基于这两个本体论的问题求解建模方法。由于面向知识级建模分析的特点，支持该方法的建模环境ＫＭＥＰＳ有效地克服了面向符号级实现的知识工程的弱点。     

Water-soluble MnO nanocolloid for a molecular T1 MR imaging: a facile one-pot synthesis, in vivo T1 MR images, and account for relaxivities

A facile one-pot synthesis of a water-soluble MnO nanocolloid (i.e., D-glucuronic acid-coated MnO nanoparticle) is presented. The MnO nanoparticle in the MnO nanocolloid was coated with a biocompatible and hydrophilic D-glucuronic acid, and its particle diameter was nearly monodisperse and ranged from 2 to 3 nm. The average hydrodynamic diameter of the MnO nanocolloid was estimated to be 5 nm. The MnO nanoparticle was nearly paramagnetic down to T=3 K. The MnO nanocolloid showed a high longitudinal water proton relaxivity of r1=7.02 s(-1) mM(-1) with the r2/r1 ratio of 6.83 due to five unpaired S-state electrons of Mn(II) ion (S=5/2) as well as a high surface to volume ratio of the MnO nanoparticle. High contrast in vivo T1 MR images were obtained for various organs, showing the capability of the MnO nanocolloid as a sensitive T1 MRI contrast agent. The suggested three key-parameters which control the r1 and r2 relaxivities of nanocolloids (i.e., the S value of a metal ion, the spin structure, and the surface to volume ratio of a nanoparticle) successfully accounted for the observed r1 and r2 relaxivities of the MnO nanocolloid.     

电动汽车牵引无限变速器的传动特性研究

设计了用于电动汽车传动系统的牵引无限变速器(TIVT).在分析其基本结构和工作原理的基础上,系统地分析了其核心部件的运动学和动力学特性,建立了传动比、滑动率、传递转矩和传动效率的数学模型,进而利用仿真软件ADMAS对其主要传动特性进行了分析研究和数值计算.结果表明,当输入转速不变时,输出转速随操纵环摆动角的变化而变化;当动力传动部件之间纯滚动或滑动率较小时,牵引无限变速器的传动效率较高,合理的设计可使传动效率达到99%.以某型号纯电动汽车为计算实例,其它条件完全相同时,匹配TIVT的电动汽车续驶里程较原车增加8.8km.     

A novel ethanol gas sensor based on ZnO-microwire

One-dimensional (1D) ZnO microwires were successfully synthesized by chemical vapor deposition and their structural and morphological properties were analyzed by X-ray diffraction and scanning electron microscopy, demonstrating that the microwires were single crystalline with perfect hexagonal structure and smooth surface. Using these 1D microstructures, we fabricated a novel ZnO-based ethanol gas sensor. Operating at room temperature, the sensor was found to have good sensing characteristics. The reliability and stability of the sensor could be improved by connecting multiple 1-wire devices (1-WD) in parallel into a multi-wires device. In interior natural lighting environment and under 3 V bias, the response and recovery time of the 1-WD to 200 ppm ethanol gas were <10 s and about 300 s, respectively, and the minimum and maximum detection limit were about 2 and 200 ppm, respectively. A sensing model was proposed for discussing the performance of the sensor. The simplicity in fabrication, low power consumption and low cost make the sensor suitable for practical application in many fields, especially in identifying driving under the influence and chemical industry monitoring.     

环境管理体系阶段性实施指南(ISO14005)促进欧盟生态管理与审核计划(EMAS)与环境管理体系体系(ISO14001)的协调实施

ISO14005:2010《分阶段实施环境管理体系指南》国际标准融入了环境声明、环境绩效评价、环境信息交流等重要环境管理工具的使用,使得通过ISO14001环境管理体系认证的组织在附加实施标准中的一些要素后可实现与EMAS的符合.