Densification mechanisms of spark plasma sintering: multi-step pressure dilatometry

The effects of electrical current and mechanical pressure on the densification of spherical copper powder during spark plasma sintering (SPS) are examined. A novel multi-step pressure dilatometry method is introduced to compare the constitutive behavior of the copper powder under nearly equivalent current-insulated and current-assisted SPS process conditions. The strain rate sensitivity agrees with that predicted for a dislocation climb-controlled creep densification mechanism for both processing setups. Accelerated densification rate leading to a higher final relative density is observed for the current-assisted SPS.     

Performance of a Manufacturing Cell with Increased Product Mix

We investigate the impact of increasing the number of items made in a cell on its performance. The optimal lotsizes of production and queuing delays are both shown to increase with increased product mix. However, these adverse effects diminish as more items are assigned to the cell. We also examine a strategy of sequencing which attempts to minimize the number of setups by looking ahead in the queue and processing all items for which the machine is already setup. In the case of similar items, it is found that this sequencing policy results in little savings in setup time.     

Measuring pressure of pulsed plasma flows by quadrature interferometry techniques

We have developed a new method for measuring the gaskinetic pressure of corpuscular flows in pulsed plasma that employs a probe in the form of an acoustic rod incorporated in the optical scheme of a laser interferometer. This method has been used to study the temporal dynamics of the pressure of corpuscular flows emerging from a micropinch discharge of the low-inductance vacuum spark type. Due to a large dynamic range (～10⁵), the proposed method can be implemented in a large variety of plasma setups with a broad range of parameters.     

Statistical reasoning in diagnostic problem-solving—The case of flow-rate measurements

There are various methods for measuring flow rates in rivers, but all of them have practical issues and challenges. A period of exceptionally high water levels revealed substantial discrepancies between two measurement setups in the same waterway. Finding a causal explanation of the discrepancies was important, as the problem might have ramifications for other flow-rate measurement setups as well. Finding the causes of problems is called diagnostic problem-solving. We applied a branch-and-prune strategy, in which we worked with a hierarchy of hypotheses, and used statistical analysis as well as domain knowledge to rule out options. We were able to narrow down the potential explanations to one main suspect and an alternative explanation. Based on the analysis, we discuss the role of statistical techniques in diagnostic problem-solving and reasoning patterns that make the application of statistics powerful. The contribution to theory in statistics is not in the individual techniques but in their application and integration in a coherent sequence of studies – a reasoning strategy.     

Analysis and approximation for the performance of a workstation with various types of setups

Setups commonly exist in flexible manufacturing systems. Modelling the queue time correctly is of fundamental importance in evaluating the performance of manufacturing systems. An insightful classification is the first step towards correct modelling. Through the observation of practical production lines, two types of setups are classified: state-induced setups and product-induced setups. The product-induced setups can be a changeover setup or a replacement setup. Changeover setups are induced by switching manufacturing processes between products, whereas replacement setups are caused by changing components or consumables. Approximate models for the mean queue time of different setup types are proposed based on their distinct properties. The proposed models are validated with simulations and perform well in the examined cases.     

Lot streaming with attached setups in three-machine flow shops

Lot streaming is the process of splitting a job or lot to allow overlapping between successive operations in a multistage production system. This use of transfer lots usually results in a significantly shorter makespan for the schedule. We study the structural properties of schedules which minimize the makespan for a single job with attached setup times in a flow shop. The structure of the optimal schedules is more complex than in the case with no setups or detached setups, as it may follow a much larger variety of patterns. Using the structural insights obtained, however, it is possible to find the optimal solution with s sublots in O(s) time for the three-machine case.     

Application of frustrated total internal reflection devices to analytical laser spectroscopy

Novel implementations of single-fiber laser-induced breakdown spectroscopy and laser-induced fluorescence spectroscopy systems that gated light switches based on frustrated total internal reflection are described. The switching devices are largely wavelength independent, with full temporal and spatial separation of laser and fluorescence light. Wavelength-independent beam separation or beam combination schemes can be implemented for coaxial optical setups, e.g., in single-fiber or telescopic experimental arrangements. Selected practical examples of schemes for qualitative and quantitative analytical spectroscopy are discussed.     

Impact of connection between specimen and load plate on viscoelastic material response of hot mix asphalt

In routine testing of hot mix asphalt (HMA) cyclic compression tests (CCT) are carried out to assess the permanent deformation behavior. However, CCTs can also be employed for determining the material response within the linear viscoelastic domain in terms of stiffness and phase lag, when a frequency and temperature sweep is considered. In the compressive domain two test setups are possible regarding the connection between load plate and specimen: The specimen is either firmly connected (glued) to the load plates, which prevents transverse strain at the end planes, or the specimen is placed between the load plates without firm connection. In this case friction-reducing additives (e.g. silicone grease) applied to the end planes of the specimen help to create a more homogeneous strain distribution over the height of the specimens, since limited transverse strain are also be activated at the end planes of the specimen. This paper investigates whether these two test setups produce comparable results in terms of viscoelastic material reaction of HMA. Therefore, CCTs were run on HMA-specimens with the two test setups. Data evaluation was carried out by means of regression analysis with a standard sine and an advanced function containing the first harmonic oscillation term. It is shown that the parameters of the first harmonic term are able to describe the magnitude and shape of a distorted sine. Data from force and axial deformation signals are analyzed as well as the derived viscoelastic material reaction. From the findings of the study it can be concluded that cyclic material tests in the compressive domain are capable of describing the viscoelastic material behavior of HMA regardless of the connection between specimen and load plates and that they are comparable to results of a well-established, standardized stiffness test, the 4-point-bending test. It is also shown that the regression analysis with the advanced function can be employed to analysis the quality of response of the test machine. Thus, technical limits of test machines and deformation sensors can be detected by using the regression analysis with the advanced approximation function.     

Identification of linear systems in the presence of nonlineardistortions

This paper treats the identification of linear systems in the presence of nonlinear distortions. It extends the theory developed for measurement setups where the input is exactly known and the output is observed with errors (output error framework) to measurement setups where both the input and output are observed with errors (errors-in-variables framework). An appropriate measurement strategy and identification algorithm are presented     

Characterizing nonlinear RF circuits for their in-band signaldistortion

This work presents a theoretical discussion on the ability of traditional noise power ratio (NPR) setups to characterize the in-band signal distortion of general RF circuits. It is shown that NPR tests are optimistic in estimating co-channel distortion, as they are blind for the signal-correlated components. Therefore, an alternative standard for co-channel distortion specification and the associated measurement setups are theoretically proposed and experimentally validated     

Dual Experimental Approach for Thermal Impacts on Electromagnetic Behavior of Electronic Circuit Board Configurations

Some effects of physical parameters, such as temperature, on electromagnetic emission or susceptibility of electronic circuit boards are nonnegligible and can be enforced by new integrated complex electronic structures. This paper describes experimental improvements proposed on near-field and radiated-mode test setups, including the temperature parameter. New experimental investigations and methodology are driven to estimate the real external thermal impacts on electromagnetic behavior and compliance. With pertinent characterization results, a review of wideband frequency modifications of electromagnetic compatibility (EMC) responses on electronic configurations with active digital devices and a printed circuit board (PCB) wire network is presented and analyzed.     

Kinematic and deformation parameter measurement by spatiotemporal analysis of an interferogram sequence

In recent years, optical interferometry has been applied to the whole-field, noncontact measurement of vibrating or continuously deforming objects. In many cases, a high resolution measurement of kinematic (displacement, velocity, and acceleration, etc.) and deformation parameters (strain, curvature, and twist, etc.) can give useful information on the dynamic response of the objects concerned. Different signal processing algorithms are applied to two types of interferogram sequences, which were captured by a high-speed camera using different interferometric setups: (1) a speckle or fringe pattern sequence with a temporal carrier and (2) a wrapped phase map sequence. These algorithms include Fourier transform, windowed Fourier transform, wavelet transform, and even a combination of two of these techniques. We will compare these algorithms using the example of a 1D temporal evaluation of interferogram sequences and extend these algorithms to 2D and 3D processing, so that accurate kinematic and deformation parameters of moving objects can be evaluated with different types of optical interferometry.     

Optical Omega network: a compact implementation technique

We propose a technique for the compact implementation of an optical Omega network. This technique utilizes the concept that both the perfect-shuffle interconnection and the switching stages can be realized by the same procedures, i.e., duplicate, shift, superimpose, and mask. As a result, a single set of optics is sufficient to realize the whole Omega network in a time-multiplexed recursive manner. Optical setups were designed and a proof-of-principle experiment was performed.     

A Low-Cost Experimental Setup to Characterize Piezoelectric Cantilever Bimorphs

Hysteresis is a common phenomenon in nonlinear systems. Piezoelectric bimorphs show hysteretic behavior when operating as actuators. Tools that produce the characterization of these devices are available; they use high-cost setups that measure deformations with resolutions on the order of nanometers. In this paper, a new low-cost experimental setup that uses coupled infrared detectors to investigate the behavior of piezoelectric actuators is discussed. The tool, providing deformation measurements with a resolution on the order of 10 , is intended to produce a rough estimation of the device behavior and is of interest for research and educational purposes. Low cost, easy reproducibility in research and educational laboratories, a contactless measurement strategy, an inset calibration facility, and a suitable user interface are the main features of the tool developed. Notes on the uncertainty introduced by the tool when estimating bimorph deformations are given. Moreover, a case study that concerns the characterization of a piezoelectric bimorph actuator is discussed to illustrate the performance of the system developed in a real case.     

Fracture of steel beam to box column connections

Abstract

This study is aimed at examining the behavior of the beam to interior box column connection. Cruciform type test setups are selected with the column under constant gravity load while both beams under gradually increased cyclic loading in opposite directions to simulate earthquake load. The tearing strength of the column plate by the transmitted out‐of‐plane load from the beam web is analyzed by yield line theory. A simplified method is proposed to establish the relationship between the thickness of beam web and column plate. A series of experimental studies are also conducted to examine the effect of a diaphragm plate on the transmission of applied force from beam flanges. Based on the results of this study, suggestions are made for the design and construction of beam to box column connections to achieve better strength and ductility.     

Optical setups for probabilistic bipartite and tripartite entanglement generation and quantum teleportation in optical networks

In this work we present optical setups for a polarization encoded qubit, based only on common linear optical devices, which implement probabilistic bipartite and tripartite entanglement generation, as well probabilistic quantum teleportation. The setups can be implemented with current technology and they permit the realization of several quantum communication protocols.     

Influence of the steel plate on the friction behavior of automotive wet disk clutches

Friction behavior is the key parameter for the design of automotive wet disk clutches. On the one hand, the Coefficient of Friction (CoF) level should be high to transmit torque efficiently. On the other hand, the clutch requires a positive slope of the CoF over sliding speed for good controllability, high comfort, and a low tendency to shudder. Clutches used in automatic or dual-clutch transmissions mostly use organic friction lining. These friction systems tend to have low CoF at low sliding speeds due to their high requirements regarding shifting comfort. Nevertheless, they show high values of CoF at high sliding speeds.

This study investigates the influence of different steel plate finishes on friction behavior in different application-relevant operation modes such as brake shift, unsteady slip, and micro slip. Each of these operation modes requires an accurate CoF measurement at different sliding speed ranges. Therefore, we use different test rig setups. We characterize the steel plates by their areal surface topography measured with an optical system using focus variation. We discuss differences in the friction behavior of the corresponding tribological systems at different operating conditions.

Results show an influence of the steel plate surface finish on the CoF level. Therefore, the surface finish of the steel plate influences the functional behavior of wet disk clutches and engineers should consider the surface finish in the early design phase. We discuss the correlation between commonly used surface parameters and friction parameters.

     

Measurement of RF Emissions From Electrostatic Discharges Between Charged Insulators

This paper focuses on the measurement of the electromagnetic radiation from electrostatic discharges between charged insulators that are electrostatically coupled to conductors. To observe this phenomenon in a controlled environment, various basic experimental setups were assembled in a semianechoic chamber, consisting of a metal antenna, a table tennis ball, and a dielectric plane positioned on a ground plane. We provide a phenomenological discussion and present the obtained results. Finally, we propose an equivalent circuit that is capable of representing the investigated phenomenon, and we report results of further test setups that aim at confirming some of our conjectures.     

Lot splitting to minimize average flow-time in a two-machine flow-shop

Lot splitting is a technique for accelerating the flow of work by splitting job lots into sublots, In this paper we investigate the lot splitting scheduling problem in a two-machine flow-shop environment with detached setups and with batch availability. The performance measure considered is the average flow-time which is indicative of the increasingly important manufacturing lead-time. Our contribution is both theoretic and practical for the case of general (not necessarily equal) sublots. We identify properties of the optimal solution and develop a solution procedure to solve the problem. We then present a computational study which indicates that our solution technique is very efficient.     

Numerical wave optical analysis of microlens array telescopes and comparison with experimental results

We present a numerical wave optical model to describe the complex behavior of coaxial and decentered microlens-array-based telescopes illuminated by an incoherent angular spectrum of plane waves. With the use of this model we have been able to observe major performance differences between Galilean and Keplerian setups, which to our knowledge were not described before. The results of the simulations are compared with experimental results; the images of multimode fiber end faces are characterized with respect to transfer efficiency and intensity distribution. The results are also explained by use of modified existing analytical models.