Coefficients for solution of the analytical freezing equation in the range of states for rapid solidification of biological systems

Solution of the classical solidification heat transfer problem for many biological applications involves states for which roots of the transcendental equation associated with the governing differential equation are not available. These roots are calculated and presented for conditions that characterize a large ratio of solid to liquid phase thermal conductivities and diffusivities and large differences between the initial and final temperatures for the cooling process.     

High-energy optically pumped molecular lasers in the 13- and 16-microm regions

This paper describes the construction of an optically pumped laser device. The device utilizes a line-tunable CO2 TEA laser as a source to optically pump a cell which is capable of cooling candidate laser gases down to approximately 150 degrees K. Laser outputs of 750 mJ in the 13-microm region and 100 mJ in the 16-microm region are obtained by pumping NH3 and CF4 respectively with 10 J of CO2 laser radiation. The measured conversion efficiencies are 15% for NH3 and 3% for CF4. These lasers can be used to photodissociate polyatomic molecules and are attractive sources for practical laser isotope separation.     

A microcomputer-based system for rapid on-line stereological analysis in the SEM

A microcomputer-based image analysis system for the SEM is described. Through two digital-to-analog convertors it controls the position of the electron beam on the specimen inside the microscope. A raster of 128 × 128 pixels is created. At each pixel the signal from the BSE detector is sampled an operator-defined number of times and the median values of the resulting data streams are stored temporarily in the memory of the computer. Stored images may be redisplayed on the visual and record CRTs of the SEM or saved onto a diskette for subsequent recall and analysis. The 256 grey level image is reduced to one having only 64 grey levels and the distribution of the number of counts falling into any of these bins is displayed on the computer monitor, or output to a plotter or printer. The number of counts in each bin represents stereologically the area (and hence volume) fraction of the sample with that grey level. Three levels of threshold may be applied to give four slices in the image. Area (and hence volume) fractions are then calculated, as is the intercept value between slices. This data is output to a printer. An abbreviated program has also been written to permit greater automation of the analysis of samples of bone. Included is a further reduction in the number of grey levels to 16, and the provision of control for an automatic stage. Although presently being applied to the study of samples of mineralised biological tissues this system could be used for any investigation requiring rapid and simple stereological analysis of specimens in the SEM.     

An in-vacuum x-ray diffraction microscope for use in the 0.7-2.9 keV range

A dedicated in-vacuum coherent x-ray diffraction microscope was installed at the 2-ID-B beamline of the Advanced Photon Source for use with 0.7-2.9 keV x-rays. The instrument can accommodate three common implementations of diffractive imaging; plane wave illumination; defocused-probe (Fresnel diffractive imaging) and scanning (ptychography) using either a pinhole, focused or defocused probe. The microscope design includes active feedback to limit motion of the optics with respect to the sample. Upper bounds on the relative optics-to-sample displacement have been measured to be 5.8 nm(v) and 4.4 nm(h) rms/h using capacitance micrometry and 27 nm/h using x-ray point projection imaging. The stability of the measurement platform and in-vacuum operation allows for long exposure times, high signal-to-noise and large dynamic range two-dimensional intensity measurements to be acquired. Finally, we illustrate the microscope's stability with a recent experimental result.     

A compound carbon thermometer for the temperature range 0.3-100 K

A compound carbon thermometer consisting of an abreast connection of a carbon Speer resistor and a carbon Allen-Bradley resistor was tested in the temperature interval 0.3-100 K, an interval which generally requires two independent resistors to be covered. The characteristics, sensitivity, and analytical handling of the resistance versus temperature data are discussed and compared with the corresponding behavior of other thermometers. The satisfactory performance of the compound carbon device contributes to the extension of wide-range thermometry to 0.3 K.     

快速成形零件变形分析

快速成形零件变形是因为树脂固化中存在从液态向固态变化过程中产生的收缩,零件的变形与受力情况有关,而且受零件的尺寸、形状、位置的影响,采用二次曝光工艺,使得部分收缩自由释放,减少收缩对零件的影响,可以明显改善零件的变形。     

基于平场光栅的分光光度计在生化分析仪中的应用

采用先进的全息凹面平场光栅作为分光元件和后分光光度测量结构,结合生化分析仪的应用,完成软硬件系统的设计。以硅光电二极管阵列作为探测器,同时接收8路光信号。MSC1210、TUSB3410分别作为核心控制和接口单元,简化电路设计易于程序升级改造。并以电子学方法实现双波长测量。提高测量的准确性和测量效率。     

Experimental analysis of properties of materials for rapid prototyping

Rapid prototyping (RP) can substantially shorten the time and reduce the cost of developing a new product from the initial idea to production. Rapid prototyping can help in recognizing the basic defects whose subsequent correction may prove very expensive, especially if they have already been made when the product is ready for production. There are also many restrictions of RP procedures, primarily in the number of available materials and their properties, which may differ significantly from the properties of end product materials. In this work, based on the stipulated standards of the 3D printing machines (ZPrinter 310 Plus) and the hybrid Polyjet technique (Objet Eden 330), adequate test specimens were made. Furthermore, with adequate equipment, we carried out the analysis of the dimensions, roughness of surfaces, and mechanical properties of prototype test specimens. Then, based on the data obtained by testing of properties, we provided a critical commentary regarding the data stipulated by their producers.     

光度法测定茶叶中铅结果的不确定度分析

对4- (2-吡啶偶氮)-间苯二酚(PAR)分光光度法测定茶叶中铅含量的方法进行不确定度评价。通过分析不确定度来源和量化计算,得到分析方法的扩展不确定度为4.2 μ g/g。茶叶中铅含量可表示为(40±4.2) μ g/g。     

Design and analysis of an infrared range sensor system for floor-state estimation

Most blind and vision-impaired people use a white cane or a guide dog to aid their walking. The conventional white cane helps the user to perceive the environment simply by identifying the presence of nearby obstacles. In the present study, three infrared range sensors were used to identify the floor state. The sensor system, affixed to the user’s belt, does not require swinging motion or any other movement by the user. The three sensors are configured radially, and the design parameters are selected based on the sensor characteristics. The main difference from the conventional range sensor system for the blind is that the infrared range sensor system identifies three discrete states (even surface, ascending stair, descending stair). The condition for the state transition was derived from a sensor system model. Additionally, the effects of sensor system movement were verified by covariance analysis.     

Accuracy analysis of a mobile mapping system for close range photogrammetric projects

Image-based mapping solutions require accurate exterior orientation parameters independently of the cameras used for a survey. This paper analyses the inclusion of up to two stereo-based geometric constraints in the form of baseline distance and convergence angle between camera axes to boost the integrated sensor orientation performance on outdoor close-range projects. A terrestrial low-cost mobile mapping GNSS/IMU multi-camera system is used to test the performance of the stereo-based geometric constraint on a weak geometric network in a stop-and-go survey. The influence of the number of control points (CPs) is analysed to confirm the performance and usability of the geometric constraints in real live terrestrial projects where far from ideal setups can exist across the survey. Improvements in image residuals up to 9 times and deviation errors better than 1 cm are expected when at least three CPs are incorporated into the adjustment.     

A wind tunnel for anemometer calibration in the range of 0.2-1.25 m/s

In order to calibrate different types of anemometers in a low-speed range (0.2-1.25 m/s) using pressure measurements, a wind tunnel has been built and characterized. The wind tunnel has a low-speed section and a high-speed section. The wind tunnel calibration has been performed by means of comparison of airspeed at the test cross section (low-speed) and at the reference cross section (high-speed). Measurements have been taken with a calibrated hot-wire anemometer and static and total probes respectively. A linear fitting is used to relate reference and test airspeed. A model based on mass conservation law has been developed. Calculations have been made with and without introducing the effect of the speed profile. Uncertainties of the experimental calibration are presented.     

PE Lambda850型高精度紫外-可见分光光度计使用经验

根据日常使用经验,提出了Lambda850紫外可见分光光度计使用中应注意的几个问题.     

铜合金中铁元素的快速分析研究

使用快速元素分析仪对铜合金中铁元素的发射光谱进行了分析研究,结果表明,可有效的解决铜合金中铁元素的现场快速分析问题。铜合金中铁元素的快速定性分析及定量分析可以使用Fe261.19nm谱线组和Fe274.93nm谱线组。分析系统记录了材料光谱,使现场快速分析具备可追溯性,为质量控制提供了条件。     

Operating a triple stack microchannel plate-phosphor assembly for single particle counting in the 12-300 K temperature range

An assembly consisting of a stack of three microchannel plates (MCPs) and a phosphor screen anode has been operated over the temperature range from 300 to 12 K. We report on measurements at 6.4 kHz (using an alpha source) and with dark counts only (15 Hz). Without any particle source, the MCP bias current decreased by a factor of 2.1 x 10(3) when the temperature was lowered from 300 to 12 K. Using the alpha source, and a photomultiplier tube (PMT) to monitor the phosphor screen anode, we first observed an increase in the decay time of the phosphor from 12 to 45 mus when the temperature was decreased from 300 to 100 K while the decay time then decreased and reached a value of 5 mus at 12 K. The pulse height distribution from the PMT was measured between 300 and 12 K and shows a spectrum typical for a MCP phosphor setup at 300 K and 12 K but is strongly degraded for intermediate temperatures. We conclude that the present MCP-phosphor detector assembly is well suited for position-sensitive particle counting operation at temperatures down to at least 12 K even for count rates beyond 6 kHz. This result is crucial and an important part of ongoing developments of new instrumentation for investigations of, e.g., interactions involving complex molecular ions with internal quantum state control.     

高能压力机螺杆摩擦面粗糙度选用和抛光

对粗糙度与打击力、摩擦系数曲线、配偶零件等各方面进行了分析,所选用的粗糙度值和抛光方法,技术上先进,经济上合理,为设计同类结构提供了一种参考。     

RF CMOS transceiver at 2.4 GHz in wearables for measuring the cardio-respiratory function

This paper presents a radio-frequency (RF) transceiver for operation in the 2.4 GHz ISM band. The RF CMOS transceiver can be supplied with only 1.8 V, and it was designed to establish wireless links for distances up to 10 m, for a maximum baud-rate of 250 Kbps with a Bit Error Probability less than 10⁻⁶. The transmitter can deliver a output power of 0 dBm with a consumption of only 11.2 mW, while the receiver has sensitivity of −60 dBm and consumes only 6.3 mW. The goal of RF CMOS transceiver is for co-integration with sensors in the same die using microsystems techniques. The target application of such microsystems is in wearables (e.g., in wireless electronic shirts) for measuring biomedical data of patients. The wireless electronic shirt (WES) measures the heart rate and the respiratory frequency, and at the same time it allows patients to maintain their mobility.     

华北石化炼油装置应用全馏程等在线分析技术提高油品质量和轻质油收率

华北石化公司依托中石油及华北油田优势,注重发展过程中管理和技术两大要素,引进国外同类企业的全套管理模式,提高企业运行效率.技术上不断引进当前先进的技术及设备,提高炼油过程的技术水平,如:率先在装置馏出口应用油品质量在线分析及APC先进控制,提高馏出口产品合格率保证产品质量,提高轻质油收率等,使公司得以快速发展,由二十几年前几十万吨/年原油加工能力的小规模炼厂,达到了当今一千万吨/年加工量的规模.     

An apparatus for simultaneous measurement of electrical conductivity and thermopower of thin films in the temperature range of 300-750 K

An automated apparatus capable of measuring the electrical conductivity and thermopower of thin films over a temperature range of 300-750 K is reported. A standard dc resistance measurement in van der Pauw geometry was used to evaluate the electrical conductivity, and the thermopower was measured using the differential method. The design of the instrument, the methods used for calibration, and the measurement procedure are described in detail. Given the lack of a standard National Institute of Standards and Technology (Gaithersburg, Md.) sample for high temperature thermopower calibration, the disclosed calibration procedure shall be useful for calibration of new instruments.