New techniques for multi-component flow velocity measurement using high-frequency pulsed diode lasers

The application of high-frequency pulsed laser diodes for fringe-type laser Doppler anemometry allows multi-component flow velocity measurements by using only one receiver and one signal processing chain. This is effected by synchronization of the laser pulses with the sampling process of the data acquisition system. Consequently, an identical wavelength can be used for all components. The experimental verification of this new technique is described. The technique permits the design of miniaturized and low cost optical flow sensors which can be used for low and high speed flows.     

Real-time and label-free detection of chloramphenicol residues with specific molecular interaction

Molecular measurements with specific or non-specific molecular interaction are usually reported by using different methods. This paper shows a method for small-molecular label-free measurements in real time with specific and non-specific molecular interaction based on surface plasmon resonance. The quantitative measurement of glucose with non-specific molecular interaction was performed simply to validate our self-built angle-dependent surface plasmon resonance system, which showed a good sensitivity and stability, such as that of Fourier transform infrared spectrometer. As application, we present the measurement of chloramphenicol residues with specific molecular interaction employing an indirect competitive immunoreaction by using the same surface plasmon resonance system with a limit of detection about 0.5 ng mL⁻¹, which shows a potential application for food safety.     

Computation and analysis of the workspace of a reconfigurable parallel robotic system

A reconfigurable robotic system permits multiple configurations having different characteristics, using mostly modularized building blocks. The goal of this paper is to investigate how the shape, dimensions and the distribution of singularities in the workspace for different configurations, with different degrees of freedom, of a reconfigurable robotic system, are changed. The computation of the workspace is based on the modularity property of the system. The presented results are also experimentally validated.     

Resolution abilities and measuring depth of High-Frequency densitometry on wood samples

The High-Frequency (HF) densitometry measures relative density variations on wood samples utilizing the dielectric properties in wood. This method is based on the propagation of an electric stray field through the surface-near region of a wood sample. We studied experimentally the penetration depth and the differentiation abilities of the HF-densitometry method on wood samples. Two experimental approaches showed that penetration depth is related to the geometrical dimensions of the micro-electrode measuring system. Characteristic patterns of the HF-output signal were used to determine the resolution abilities of each HF-probe. Due to a very small integration area geometric structures of earlywood cells of Norway spruce were indicated by stepwise profiles in the HF-output signal pattern. With the High-Frequency densitometry it was possible to distinguish different cell structures due to their variations in wood density up to a resolution of 1 μm. In addition it was possible to determine wood density variations at various resolution levels. Based on the respective resolution abilities and penetration depths of five different purpose-built HF-probes we show the optimal operating conditions for measurements on wood of this indirect densitometry method.     

Semiautomated methods for cancellous bone histomorphometry using a general-purpose video image analysis system

Semiautomated methods are used to measure elongated, curved and complex branching profiles and isolated perimeter segments in monochrome video images with a general-purpose analysis system. These methods are used to make the major primary measurements of bone histomorphometry. Accuracy and reproducibility of the image acquisition, processing and measurement system is documented by measuring a semicircular standard of known dimensions. Semiautomated applications of the Ar/Le method for measuring areas and perimeters, and calculating lengths and widths of osteoid seams, lengths of mineralization labels and mineral apposition rate, wall width, indirect measurements of eroded, osteoclastic and osteoblastic perimeters without tracing, and measurement of mineralized or total cancellous bone area and perimeter gave values comparable to measurements of the same parameters by tracing or grid counting techniques with equal or better reproducibility and much greater efficiency. Intraindividual variation in measuring multiple bone biopsies was comparable to that reported with current standard methods. Major sources of variability for semiautomated methods were image magnification and selection of profile edges by thresholding, and sources of variability for manual methods are image magnification, numbers of orthogonal intercepts, tracing speed and accuracy of the algorithm used to measure traced pixels. Semiautomated methods are accurate, reproducible and rapid methods suitable for bone histomorphometry.     

Sensor design and evaluation for on-machine probing of extruded tool joints

This paper describes the design and evaluation of two contact probes used to measure the length and bore concentricity of cylindrical, extruded tool joints while clamped in a production lathe spindle. The probes consisted of an LVDT, a spring-preloaded shaft supported by linear bearings used to isolate the LVDT from side loads, and a hardened steel sphere to contact the rough surface. For bore concentricity measurements, a parallelogram leaf-type flexure and 45° surface was used to transfer radial deviations to the spindle/part/LVDT axis. The LVDT output was used in conjunction with the lathe turret position to determine the extruded part dimensions prior to machining. Experimental results are provided for measurements of multiple parts; variations in length, internal diameter, and bore concentricity are compared to the nominal dimensions. Additionally, a calibration artifact is described which enabled evaluation of the measurement accuracies for the two probes. Given the pre-machining part dimensions, it is shown how this information can be used to select from a pre-defined matrix of part programs to reduce cycle time and machining cost.     

Geometry-oriented knowledge-based system for preliminary process design of cold-forged parts

This paper presents an integrated architecture of a geometry-oriented knowledge-based process-design system (GEOPDE) for multistage cold forging of solid and hollow parts. It deals with the unit processes of upsetting, forward extrusion, backward extrusion and with combinations of these processes. By using the notion of group technology, the forging processes and forging part geometries are classified. With Prolog as the building tool, the inherited backward chaining reasoning was used for solving the deduction problems. The formation approach, such as “generate and test” and backtracking control strategy, was also employed for generating weighted alternative process plans. Using design rules, empirical formulae and material properties as integrated knowledge, the billet dimensions and the forging sequences are generated automatically once the product dimensions are given by the user. The developed system is a prototype expert system for the preliminary process design of cold-forged products for the forging industry.     

A Remote Injection Moulding Simulation System Based on the Internet and the Web

The application service provider (ASP) has become a potential e-business model and software application using an ASP instead of the customer’s local installation is expanding rapidly. An approach to building up a remote ASP-oriented simulation tool on the World Wide Web, based on a distributed processing architecture is presented in this paper. The construction approach and key techniques of the system are described in detail. This distributed processing environment can also be used to set up other remote simulation systems.     

Three-dimensional heat transfer analysis of LENSTM process using finite element method

Laser-engineered net shaping, referred to as LENS^TM process, is an additive manufacturing technique for building metallic parts, layer by layer, by direct deposition of metal powders in a melt pool created by a focused laser beam. The process involves rapid melting and solidification of a controlled amount of injected metal powders as a laser beam scans over each layer building the structure from the bottom to the top. Due to its unique capability to deposit precise amounts of powder material at a desired location, the LENS^TM process finds potential application in rapid tooling, prototyping, precision repair work, and manufacture of complex, intricate components with varying compositions. The peak temperature and thermal cycle experienced by each layer influence the final mechanical properties and dimensional accuracy of the part. An understanding and quantitative knowledge of the peak temperature, melt pool dimensions, and thermal cycles experienced in the deposited layers are essential for a priori selection of the process parameters in LENS^TM technique. It is important to ensure that the deposited layers have the desired dimensions, good interlayer bonding, and requisite mechanical properties. In an attempt to understand the process parameters to be used in achieving the desired nature of deposition, a three-dimensional model is developed based on finite element method to numerically simulate heat transfer phenomenon in LENS^TM process considering deposition of SS316 powders on a substrate of the same material. The computed temperature profiles are first validated with experimental results reported in the literature. The influence of process parameters on peak temperature, thermal cycles, and melt pool dimensions are studied subsequently. The continuous movement of laser and synchronized activation of elements depicting addition of powder particles are incorporated through an externally written user subroutine and using the element deactivation and activation features in the commercial finite element software ABAQUS 6.7. A unique non-dimensional parameter specific to LENS^TM process is defined considering the combined influence of process parameters and material properties. The non-dimensional parameter is further used to serve as a guideline for the selection of appropriate process parameters that can result in a steady melt pool dimension, thereby ensuring a target layer width with good interlayer bonding.     

A method for indoor navigation based on magnetic beacons using smartphones and tablets

Outdoor navigation using GPS receivers installed in various types of consumer electronics devices, especially smartphones and tablet computers has become very common. However, indoor navigation can be problematic as GPS signals are blocked by ceilings and building walls and accuracy is on the order of building dimensions. In present work we propose using an array of magnetic beacons for localizing a receiver equipped with a magnetic sensor. A smartphone or a tablet computer with an internal magnetometer can be employed as a receiver. Exploiting smartphones and tablets for indoor navigation is a great advantage when considering convenience, simplicity and low cost. The navigation area is covered by magnetic beacons deployed in known locations. Each beacon generates an AC magnetic field with a unique signature enabling the receiver to distinguish between beacons. The signature may feature a specific single frequency tone, a combination of frequencies, or any other modulated signal. A software application running on the receiver enables self-localization by means of detection and identification of the nearest beacon. A system prototype has been developed and used to test the proposed method in field conditions. Experimental results show successful localization, which paves the way for a full scale development of an effective indoor navigation system. The good results together with simple implementation make the proposed method attractive for a wide range of indoor localization applications, including: pedestrian and robot navigation, inbuilding rescue missions, vision impaired assistance, and location aware services, just to mention a few.     

An artefact for traceable freeform measurements on coordinate measuring machines

The present paper describes an artefact based approach to obtain traceability of freeform measurements on coordinate measuring machines. First, the requirements for the traceability of freeform measurements and a strategy for the development of a feasible solution are presented. A new concept of artefact, called the “Modular Freeform Gauge” (MFG) has been developed. It is based on physical modeling of a given freeform surface by a combination of items with regular geometry, well calibrated on their dimensions and form. The relative position is accounted for during the procedure; this information is used to generate a “calibrated” CAD model as reference for freeform measurements. The architecture of the artefact, its collocation in the traceability chain, and the calibration procedure are described.Finally, a procedure for the uncertainty assessment of actual freeform measurements is presented. The work here described has been focused on implementation of the uncertainty assessment procedure for freeform measurements on turbine blades. A task-specific Modular Freeform Gauge was developed for this application.     

Image-based measurement of the dimensions and of the axis straightness of hot forgings

Non-contact measurement of shapes and dimensions is currently quite a common issue. A lot of systems with different speeds and accuracies are in the market. Measurement of high temperature objects is, however, a very special task which ensures a specific solution. This paper presents a measurement system composed of two high resolution single-lens reflex cameras and a software application, which is designed for the fast measurement of shapes and dimensions of rotationally symmetric forgings. The software computes the length, diameter, and straightness of the axis, based on a 3D model constructed from four boundary curves of the forging captured in two images. Experimental measurements have shown an error of up to 2% for the length measurement and 1% for the diameter measurement. Results are available in a few seconds. The proposed measurement approach based on boundary curves shows a great potential for practical use in forging plants.     

The Noded graph approach to stack analysis

The tolerance chart is a graphical method for representing the manufacturing dimensions of a workpiece or assembly, at all stages of its manufacture. The chart provides an intermediate control system of checks and balances to ensure that processing dimensions and tolerances will meet those specified on the print. Tolerance charts are generally used in studying the dimensional problems on individual parts. However, they have proved tedious in their application to assemblies. This paper presents a simple and systematic approach to the process of tolerance stack analysis. The Noded graph model is constructed, representing the given and the unknown dimensions. Links are then established, using the model, which help to formulate the stack path of interest into a linear equation. The equation is used to complete the tolerance stack analysis module. This will be explained using a variety of geometric dimensioning and tolerancing examples. In addition, it is simple and hence easy to practise and very logical.     

Femtosecond laser ablation elemental mass spectrometry

Laser ablation mass spectrometry (LA-MS) has always been an interesting method for the elemental analysis of solid samples. Chemical analysis with a laser requires small amounts of material. Depending on the analytical detection system, subpicogram quantities may be sufficient. In addition, a focused laser beam permits the spatial characterization of heterogeneity in solid samples typically with micrometer resolution in terms of lateral and depth dimensions. With the advent of high-energy, ultra-short pulse lasers, new possibilities arise. The task of this review is to discuss the principle differences between the ablation process of short (>1 ps) and ultra-short (<1 ps) pulses. Based on the timescales and the energy balance of the process that underlies an ablation event, it will be shown that ultra-short pulses are less thermal and cause less collateral damages than longer pulses. The confinement of the pulse energy to the focal region guarantees a better spatial resolution in all dimensions and improves the analytical figures of merit (e.g., fractionation). Applications that demonstrate these features and that will be presented are in-depth profiling of multi-layer samples and the elemental analysis of biological materials.     

基于 AUTOCAD 带约束的图形参数化建库工具研究

研究了一种参数化建立标准件库的方法，提出了基于几何约束的参数化的模型，它在几何拓扑关系及尺寸链基础上，以尺寸为主要驱动机制，通过参数驱动与约束驱动来更改图形数据库从而达到参数化的目的。该方法不仅适于单视图变参，同时也解决了模型实体的多视图联动变参问题，并已在叶片精铸模压型标准件上得到实现与应用。     

Note: Frequency-conversion photonic Doppler velocimetry with an inverted circulator

Photonic Doppler velocimetry (PDV) is a fiber-based interferometer used in dynamic compression research. Conventional PDV systems are simple to construct but do not perform well in all measurement conditions, while universal PDV systems that support many different configurations are complex and expensive. A simpler approach is the use of external, inverted circulators which can be added and removed in a modular fashion. This technique permits frequency-conversion measurements with a conventional PDV system. Using a correction to remove baseline effects, frequency conversion systems can resolve low velocity transients that conventional PDV cannot.     

PSV and marker detection techniques for investigating the wake of an oscillating cylinder in a large wind tunnel

Although Particle Image Velocimetry techniques are widely used in the experimental investigation of the flow structure around obstacles, the application of these techniques in wind tunnels is frequently limited by the dimension of the areas involved, which make the image acquisition set-up expensive.This paper examines the use of Particle Streak Velocimetry (PSV) and marker detection techniques to measure the flow field around bodies with relatively large dimensions. In spite of its minimal requirements in terms of acquisition set-up, the method permits the investigation of complex phenomena.The tests described in the paper were carried out in air using a rigid cylinder, free to oscillate in a wind tunnel. Coupling PSV and marker detection techniques with the phase average of the measured velocity fields, the evolution of vortex shedding behind a cylinder with a diameter of 200 mm was measured with an acquisition area of about 1000×1200 mm.     

A NEW,AUTOMATED, MULTIANGULAR RADIOMETER INSTRUMENT FOR TOWER-BASED OBSERVATIONS OF CANOPY REFLECTANCE (AMSPEC II)

Plant photosynthesis is critical for understanding carbon cycling at landscape and global scales. While tower-based measurements of CO₂ have enhanced our knowledge of ecosystem fluxes, scaling these measurements globally is difficult. Satellite observations provide full, global coverage and hold the potential of spatially continuous measurements of ecosystem fluxes, but the requirements for modeling these fluxes from satellite-derived surface parameters are not well understood. This article describes the further development of a tower-mounted, automated, multiangular spectroradiometer system (AMSPEC II) used to study the relationships between canopy-reflectance and plant-physiological processes from multiangular observations, thereby facilitating a comprehensive modeling of the bidirectional reflectance distribution of the canopy. A Webcam permits simultaneous monitoring of phenological changes over time.     

An Automatic Range-Switching Modification for Direct-Reading Specific Conductance Measurements

ABSTRACT

An analysis system was developed to automatically determine specific conductance on samples at the rate of 30 per hour over a range of 1-15,000 μmho/cm with a precision of 1 percent or less. The system consists of custom designed digital electronic circuitry which modifies a commercially available direct-reading conductivity meter. This modification permits automatic range switching of the meter so that measurements are made under optimum conditions.