Fabrication of one-dimensional programmable-height nanostructures via dynamic stencil deposition

Dynamic stencil deposition (DSD) techniques offer a variety of fabrication advantages not possible with traditional lithographic processing, such as the ability to directly deposit nanostructures with programmable-height profiles. However, DSD systems have not enjoyed widespread usage due to their complexity. We demonstrate a simple, low-profile, portable, one-dimensional nanotranslation system that facilitates access to nanoscale DSD abilities. Furthermore we show a variety of fabricated programmable-height nanostructures, including parallel arrays of such structures, and suggest other applications that exploit the unique capabilities of DSD fabrication methods.     

用差热天平对锅炉垢成分进行研究

本着节约能源,笔者采用差热天平对锅炉垢进行了实验性研究,探讨了锅炉垢的主要成分,提出了锅炉使用中应注意的问题.     

Nondestructive proximate testing of plastic deformations by differential thermal EMF measurements

A method for nondestructive proximate testing of plastic deformations in metals and alloys by measuring the differential thermal emf is considered. Using an instrument that was developed for this problem, thermal emf measurements were performed on several specimens of steels of different types on which notches were made as zones of expected localization of plastic deformations. During extension of specimens, the thermal emf was measured in the plastic-deformation zone. A linear decrease in the thermal emf was observed; the maximum change occurred just before specimen fracture.     

Fractal prediction model of thermal contact conductance of rough surfaces

The thermal contact conductance problem is an important issue in studying the heat transfer of engineering surfaces,which has been widely studied since last few decades,and for predicting which many theoretical models have been established.However,the models which have been existed are lack of objectivity due to that they are mostly studied based on the statistical methodology characterization for rough surfaces and simple partition for the deformation formats of contact asperity.In this paper,a fractal prediction model is developed for the thermal contact conductance between two rough surfaces based on the rough surface being described by three-dimensional Weierstrass and Mandelbrot fractal function and assuming that there are three kinds of asperity deformation modes:elastic,elastoplastic and fully plastic.Influences of contact load and contact area as well as fractal parameters and material properties on the thermal contact conductance are investigated by using the presented model.The investigation results show that the thermal contact conductance increases with the increasing of the contact load and contact area.The larger the fractal dimension,or the smaller the fractal roughness,the larger the thermal contact conductance is.The thermal contact conductance increases with decreasing the ratio of Young’s elastic modulus to the microhardness.The results obtained indicate that the proposed model can effectively predict the thermal contact conductance at the interface,which provide certain reference to the further study on the issue of heat transfer between contact surfaces.     

A round-robin test of thermal desorption spectroscopy with quadrupole mass spectrometers calibrated by standard conductance element

The results of a round-robin test of thermal desorption spectroscopy (TDS) in which the quadrupole mass spectrometer of each participant was calibrated in-situ by a standard conductance element are reported. The desorption rate from three commercially available reference materials was quantified from the calibration results, and compared among the three participants. The total reported desorption amounts of hydrogen and argon molecules from the reference materials showed agreement within about 10%. The degree of equivalence of three TDS apparatuses was discussed. It is also shown that the quantification of the gas desorption amounts yields us the appropriate relative ratio between desorbed gas species.     

更换桥梁支座实时监测技术

本文介绍了对北京地铁运营公司更换桥梁支座过程的实时监测技术.     

A new thermal property measurement technique by modified pattern search method

The high temperature thermal properties of materials are critical in industrial production and theoretic simulation. However, these properties are not always readily available. In this paper, a new technique was developed to obtain the temperature dependent thermal conductivity and specific heat through only one experiment. More importantly, this experiment was very convenient, since only thermal cycle recording was necessary. In addition, the finite element method and pattern search method were applied to optimize the supposed thermal property values. In order to avoid the convergence difficulty of the classical pattern search method, the step size adjusting function was rewritten. A solid sample and a particle like sample were selected to verify the measurement technique. The verification experiment showed that the thermal property results were accurate to some extent.     

A technique and setup for obtaining the differential conductance of resonant-tunneling structures

A technique for obtaining the differential conductance within the negative differential resistance region for resonant-tunneling and tunneling heterostructures is developed. An experimental setup for this technique is created and tested with a resonant tunneling diode device.     

A new method of two-phase flow measurement by orifice plate differential pressure noise

The mechanism of differential pressure noise of orifices in two-phase flow has been investigated and a theoretical model has been developed for measurement of the double parameters, i.e. mass flow rate as well as phase fraction (steam quality). The model has been proved in a set of orifice experiments in a two-phase flow system at a pressure range of 5.8–12.1 MPa and steam quality of 0.05–0.95, and a practical model has been fitted. The r.m.s. errors of mass flow rate and steam quality estimated by the model are 9.0 and 6.5%, respectively. The results of the studies create a method to measure double parameters of two-phase flow at once using only a single orifice.     

Note: Thermal conductivity measurement of individual poly(ether ketone)/carbon nanotube fibers using a steady-state dc thermal bridge method

Customized engineered fibers are currently being used extensively in the aerospace and automobile industries due to the ability to "design in" specific engineering characteristics. Understanding the thermal conductivity of these new fibers is critical for thermal management and design optimization. In the current investigation, a steady-state dc thermal bridge method (DCTBM) is developed to measure the thermal conductivity of individual poly(ether ketone) (PEK)/carbon nanotube (CNT) fibers. For non-conductive fibers, a thin platinum layer was deposited on the test articles to serve as the heater and temperature sensor. The effect of the platinum layer on the thermal conductivity is presented and discussed. DCTBM is first validated using gold and platinum wires (25 μm in diameter) over a temperature ranging from room temperature to 400 K with ±11% uncertainty, and then applied to PEK/CNT fibers with diverse CNT loadings. At a 28 wt. % CNT loading, the thermal conductivity of fibers at 390 K is over 27 Wm(-1)K(-1), which is comparable to some engineering alloys.     

A model of thermal contact conductance at high real contact area fractions

Thermal contact conductance (TCC) is studied in the whole range of real contact area fractions between zero and unity. For this purpose, a two-scale model is developed in which the effective (macroscopic) TCC coefficient is obtained from the solution of the heat conduction problem at the scale of asperities. Additional thermal resistance at the real contact spots is included in the model. The model is applied for several real 3D roughness topographies for which the effective TCC coefficient is determined as a function of the real contact area fraction and the local TCC coefficient at real contact spots. An analytical function is found which approximates this relationship in the whole range of parameters, and a characteristic length-scale parameter is introduced which characterizes the effective TCC properties of a rough surface.     

High-accuracy differential measurement of ultrasonic velocity in liquids

An improved technique for measuring very accurately the difference in sound velocity between two liquids is described. The technique, which can be used over a frequency range from 1 to 100 MHz, uses a differential cell that is completely submerged in a thermostatically controlled fluid and a phase-sensitive detection scheme accurate to 2x10(-4) signal periods. Measurements of the velocity difference between water and dilute NaCl solutions (3x10(-5) to 6.6x10(-4) M), accurate to +/-0.02 cm s(-1) (relative accuracy 1 part in 10(7)), are presented.     

激光差动共焦曲率半径测量系统的研制

针对国内高精度曲率半径计量需求,研制一套激光差动共焦曲率半径测量系统.该系统采用差动共焦定焦技术,利用轴向光强响应曲线的过零点精确对应物镜聚焦焦点这一特性,借助过零点对被测件的猫眼和共焦位置进行精密瞄准定位,通过干涉测长技术获取两点间的距离,继而实现曲率半径的高精度测量.该测量系统的机电控制由主控软件完成,可实现机电扫描、数据采集及数据处理,自动化程度高.实验证明,该系统定焦灵敏度高,受环境波动影响小,测量精度可达3×10-6,满足了高精度曲率半径的计量需求.     

The prediction and measurement of thermal contact resistance

Apart from safety, one of the most important aspects governing industrial processes is the economy of performance. Demands for higher efficiencies and the use of higher power densities and temperatures require more and more detailed information on the design parameters associated with the prediction of performance. Invariably, such parameters can only be arrived at experimentally. This is due to the nature and complexity of modern technological systems, as a result of the number of variables involved. One such aspect which is becoming increasingly important is the effect of thermal distortion when thermal energy transfer takes place between one solid conducting medium and another. This paper is concerned with various experimental techniques which have been developed to analyse surfaces, and the prediction and measurement of thermal contact resistance when a heat flux is present. The paper then discusses a technique which may be applied to determine the effects of interfacial distortion on bolted joint systems. This is by way of an iterative process employing finite elements and experimentally determined boundary conditions.     

Pyrometric temperature measurement of ceramic thermal shock samples

The determination of critical failure parameters during thermal shock requires a time and space resolved temperature measurement of the sample. High frequency pyrometry is a suitable technique for such a measurement task, which usually requires the knowledge of the optical properties of the investigated material. Another challenge is the infrared transparency of materials to be checked in the wavelength range of the pyrometer. The thermal shock disks are very thin, due to the need of homogeneous temperature distribution and to maintain a two-dimensional problem. To allow a pyrometric temperature measurement a universal calibration method for high frequency infrared cameras has been developed. Pyrometry in various media was demanded, as well as the estimation of optical properties (reflection, transmittance and emission) for the selected ceramics to be tested.     

高热稳定性测风Fabry-Perot干涉仪标准具的设计

针对星载测风Fabry-Perot(F-P)干涉仪的核心部件F-P标准具的热稳定性对测风精度的影响,从标准具结构设计角度(材料、形状和固定方式)分析了标准具的热稳定性,并给出最优设计方案.通过对光学元件结构尺寸的优化设计,得出了F-P标准具光学元件的最佳形状尺寸,即平板厚度为25 mm,间隔元件的角度为40°.采用柔性结构固定方式,计算了F-P标准具机械结构的形状尺寸.最后基于有限元法,分析了光学组件和整个标准具的热变形.分析结果显示,当环境温度变化0.1℃时,光学组件平板中心间隔变化量为0.64 nm,整个标准具平板中心间隔变化量为0.28 nm,通光口径边缘处间隔变化量为0.2 nm,相对于波长λ为630 nm的气辉光谱线约为λ/2 250和λ/3 150,并且平板间隔变化量沿着径向向外逐渐减小.得到的结果显示,优化设计后的结构参数满足风速为5 m/s时测量精度对热稳定性的要求,同时满足力学性能要求.     

DSC、MDSC测定物质比热容的比较

实验用TA公司具有DSC、MDSC两种模式、具备先进Tzero技术的热流型DSCQ200热分析仪测定物质的比热容。对如何运用传统方法及调制方法测定物质的比热容进行了详细阐述;以氯化钾、苯甲酸、去离子水为测试样,对两种方法所得实验结果进行了分析比较。     

Analytical estimation of measurement uncertainty in surface plate calibration by the Moody method using differential levels

Surface plate quality influences the calibration of artifacts, instruments, working gauges and, by extension, the quality of manufactured parts. A statement of uncertainty for the surface plate calibration is needed for conformance testing and for estimating uncertainty in calibrations that rely on the surface plate. An analytical approach to the estimate of uncertainty for a common measurement method is given. The residual height at each position on the surface is expressed in terms of the measurement parameters and the measured angles. Uncertainty of each residual height value is then derived following the common methods for propagation of uncertainty. The maximum uncertainty is at the center of the surface and the calculated bounds on error compare well with values of closure from actual measurements. The uncertainty of height values is proportional to the spacing of the measurement positions and to the squareroot of the number of positions. Using data from many plates of various size and quality, a generalized uncertainty in flatness for the measurement method was estimated. The derivations also allow calculations for specific applications. Finally, a method is proposed for reporting uncertainty in surface slope which is required for estimating uncertainties of items calibrated on a surface plate.