Sensitivity analysis of a directional potential drop sensor for creep monitoring

Recent research efforts indicated that directional potential drop (PD) measurements could be exploited for in-situ creep monitoring. The present work investigates the sensitivity of such measurements with a square-electrode configuration to geometrical and material variations caused by creep. This measurement technique is based on a modification of the conventional PD technique as it measures simultaneously two resistance values in orthogonal directions. Under uniaxial stress condition, the ratio of the lateral and axial resistances is roughly proportional to the applied strain. Experimental tests showed that small anisotropic changes in the resistance ratio caused by directional effects of creep can be distinguished from potentially far larger isotropic changes caused by non-directional reversible and irreversible thermal effects. The sensitivity of the square-electrode PD sensor to geometrical and material variations was analyzed separately and the analytical predictions were validated by experimental tests in both cases. The directional PD technique was found to exhibit high sensitivity that allows the detection of elastic and plastic strains as low as 0.05%. Additional experimental results from an accelerated 400-hour creep test are presented to demonstrate the feasibility of this technique to monitor creep degradation in 304 stainless steel at 600 °C.     

‘Creating futures that would otherwise not be’ – Reflections on the Greater Helsinki Vision process and the making of metropolitan regions

In 2007, the Greater Helsinki Vision 2050 ideas competition was held and attracted international interest, with more than one hundred submissions, out of which ultimately nine were chosen as winners. The ideas competition was a voluntary joint effort of the fourteen municipalities composing the Greater Helsinki Area. In principle, the competition can be understood as the shared effort to create ‘futures that would otherwise not be’ (Albrechts). One possible future is actually the formation of a metropolitan region in Finland, which does not yet exist, at least in any formal sense. Even though it does not yet exist, the making of a metropolis is high on the agenda of many actors in Finland. This article explores the how and why of this competition, the results, the implications and its complications. For that purpose, it will develop a framework to understand the situation, addressing the particularities of the Finnish territory and policy. It will present and comment on the Greater Helsinki Vision competition and also its follow-up process. After this, the article will also reflect on the current academic and planning debate regarding metropolitan regions, their existence and function, and their ambivalences for societal and territorial development. The final conclusions will look into theoretical aspects of ‘vision making’, post-modern planning, and how a territorial response capacity can be shaped to create different futures.     

Comments on “What the Back of the Object Looks Like: 3D Reconstruction from Line Drawings without Hidden Lines”

I comment on a paper describing a method for deducing the hidden topology of an object portrayed in a 2D natural line drawing. The principal problem with this paper is that it cannot be considered an advance on (or even an equal of) the state of the art as the approach it describes makes the same limiting assumptions as approaches proposed 10 years ago. There are also important omissions in the review of related work.     

Assessing the risk of “Kirkendall voiding” in Cu3Sn

A common location of sporadic, usually unpredictable, premature failures of both SnPb and Pb-free solder joints is within the intermetallic bond to one of the contact pads. Cu pads tend to be less prone to such defects than Ni/Au coated pads, but one phenomenon is a cause of growing concern for high reliability applications. Sporadic intermetallic problems are notoriously difficult to screen for, but at least a number of them are detectable right after assembly. However, the occasional formation of a network of voids within the Cu₃Sn layer forming when soldering to Cu pads is rarely noticeable until much later. To make matters worse, efforts to establish practical engineering tests for purposes of identification and screening have usually not been successful.The root cause of the so-called ‘Kirkendall voiding’ has been shown to be associated with the quality of the electroplated Cu, apparently as determined by the incorporation of minute amounts of specific organic impurities. The present work describes and discusses a series of potential tests that allow the sorting of electroplated Cu in terms of its propensity for Cu₃Sn voiding during soldering and subsequent aging. The times and efforts involved in these tests differ greatly, as do their effectiveness and accuracy. Individual tests may therefore be useful at various stages from supplier qualification to monitoring of batch to batch variations.     

How much do incentives affect car purchase? Agent-based microsimulation of consumer choice of new cars—Part I: Model structure,simulation of bounded rationality,and model validation

This article presents an agent-based microsimulation capable of forecasting the effects of policy levers that influence individual choices of new passenger cars. The fundamental decision-making units are households distinguished by sociodemographic characteristics and car ownership. A two-stage model of individual decision processes is employed. In the first stage, individual choice sets are constructed using simple, non-compensatory rules that are based on previously owned cars. Second, decision makers evaluate alternatives in their individual choice set using a multi-attributive weighting rule. The attribute weights are based on a multinomial logit model for cross-country policy analysis in European countries. Additionally, prospect theory and the notion of mental accounting are used to model the perception of monetary values. The microsimulation forecasts actual market observations with high accuracy, both on the level of aggregate market characteristics as well as on a highly resolved level of distributions of market shares. The presented approach is useful for the assessment of policies that influence individual purchase decisions of new passenger cars; it allows accounting for a highly resolved car fleet and differentiated consumer segments. As a result, the complexity of incentive schemes can be represented and detailed structural changes can be investigated.     

De-embedding parasitic components from propagation constant calculations

We present a novel technique for extracting transition structure circuit elements from microwave transmission lines. Using a full-wave Maxwell Equation simulator and microwave circuit software tools, data were generated from a prototype 2.5-dimensional coaxial line-like structure and used as a test vehicle to ascertain the effectiveness of this method. Our results confirm the method's value as a new tool for the design of microwave components.     

A practical evaluation of spectrum-based fault localization

Spectrum-based fault localization (SFL) shortens the test–diagnose–repair cycle by reducing the debugging effort. As a light-weight automated diagnosis technique it can easily be integrated with existing testing schemes. Since SFL is based on discovering statistical coincidences between system failures and the activity of the different parts of a system, its diagnostic accuracy is inherently limited. Using a common benchmark consisting of the Siemens set and the space program, we investigate this diagnostic accuracy as a function of several parameters (such as quality and quantity of the program spectra collected during the execution of the system), some of which directly relate to test design. Our results indicate that the superior performance of a particular similarity coefficient, used to analyze the program spectra, is largely independent of test design. Furthermore, near-optimal diagnostic accuracy (exonerating over 80% of the blocks of code on average) is already obtained for low-quality error observations and limited numbers of test cases. In addition to establishing these results in the controlled environment of our benchmark set, we show that SFL can effectively be applied in the context of embedded software development in an industrial environment.