Users’ participation in requirements gathering for smart phones applications in emerging markets

This study presents insights from using requirements gathering techniques for country-specific customization of smart phones in two emerging markets, Iran and Turkey. In each country, a group of users participated in requirements gathering sessions that were aimed at developing design ideas for overcoming country-specific usability problems. Using qualitative content analysis, it was found that in each country some specific interaction activities were considered more when participants generated design ideas for country-specific usability problems. It was also found that even for similar usability problems, participants suggested country-specific solutions. Therefore, it is suggested that participation of local users in the design process should not be limited to identification of usability problems, but should also include the problem-solving phase that is usually a phase in design and development processes in which requirements gathering techniques are being used.     

Mechanical and thermo‐physical properties of high‐density polyethylene modified with talc

The aim of this study was to examine the physical, mechanical, and thermo‐physical properties of high‐density polyethylene (HDPE) modified with talc. Different weight fractions of talc (up to 35 wt %) were compounded with an HDPE matrix containing 2.5 wt % of carbon black (CB) in a twin‐screw compounder. The composites were then processed by injection moulding to obtain specimens for testing. The results indicate that CB causes a significant decrease in the toughness, while talc not only enhances the thermal conductivity and thermo‐physical properties of the composites but can also play a role in compensating for the negative effects of CB on impact resistance. The experimental data show that the presence of CB reduces the impact resistance of HDPE by up to 34%, while addition of up to 8 wt % talc can return this value to close to that of pure HDPE. No significant effect on the composite tensile yield and fracture strength was observed for either component at all concentrations. The thermal conductivity, thermal diffusivity, and specific density values of the composites increased almost linearly, but the increase in moisture absorption in the long term showed nonlinear behavior in the concentration range of the experiment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Forming limit prediction of anisotropic material subjected to normal and through thickness shear stresses using a modified M–K model

In some recent sheet metal forming processes such as hydroforming and incremental forming processes, normal and through thickness stresses are induced over the metal sheet, and therefore, prediction of forming limits requires considering effect of these stresses. In this investigation, a modified M–K model has been utilized to consider general stress state including normal and through thickness shear stresses on anisotropic metal sheet. This is achieved by assuming additional force equilibrium and geometrical compatibility between groove and matrix, and the numerical model has been solved by Newton–Raphson method to calculate the limiting strains. Forming limit diagrams resulting from this model have been evaluated with some published experimental data, and a good accordance between the results has been observed. It has also been concluded that exertion of normal and through thickness stresses enhances forming limits significantly.     

A Parametric Model for Multispectral Scanners

Efficient acquisition and utilization of remotely sensed data require an extensive a priori evaluation of the performance of the basic data collection unit, the multispectral scanner. The objective of the research described in this paper is the development of a parametric model to analytically evaluate the response of a multispectral scanner in any operational environment and to provide the necessary information in selecting a set of optimum parameters. In this paper the multispectral scanner spatial characteristics are represented by a linear shift-invariant multiple-port system where the N spectral bands comprise the input processes. The scanner characteristic function, the relationship governing the transformation of the input spatial and hence spectral correlation matrices through the systems, is developed. Specific cases for Gaussian point spread functions are examined. The integration of the scanner spatial model and a parameter classification error estimator provides the necessary technique to evaluate the performance of a multispectral scanner. A set of test statistics is specified and the corresponding output quantities computed by the characteristic function. Two sets of classification accuracies, one at the input and one at the output, are estimated. The scanner's instantaneous field of view is changed and the variation of output classification performance computed.     

Measurement of stand-sit and sit-stand transitions using a miniature gyroscope and its application in fall risk evaluation in the elderly

A new method of evaluating the characteristics of postural transition (PT) and their correlation with falling risk in elderly people is described. The time of sit-to-stand and stand-to-sit transitions and their duration were measured using a miniature gyroscope attached to the chest and a portable recorder placed on the waist. Based on a simple model and the discrete wavelet transform, three parameters related to the PT were measured, namely, the average and standard deviation of transition duration and the occurrence of abnormal successive transitions (number of attempts to have a successful transition). The comparison between two groups of elderly subjects (with high and low fall-risk) showed that the computed parameters were significantly correlated with the falling risk as determined by the record of falls during the previous year, balance and gait disorders (Tinetti score), visual disorders, and cognitive and depressive disorders (p < 0.01). In this study, the wavelet transform has provided a powerful technique for enhancing the pattern of PT, which was mainly concentrated into the frequency range of 0.04-0.68 Hz. The system is especially adapted for long-term ambulatory monitoring of elderly people.     

Comments on earthquake response spectra

Statistical summaries have been carried out on a large number of earthquake records to examine the influences of geological conditions, duration of strong motion, and peak ground acceleration on ground motion and response spectra. The results indicate that the peak ground velocity-acceleration ratio is substantially lower for records on rock deposits than those on alluvium, and it is lower for records with a peak ground acceleration greater than 0.20 g than those with acceleration less than 0.20 g. For each influence the spectral bounds defined as the product of mean ground motion and mean plus one standard deviation amplifications are computed for five damping coefficients and compared to those for alluvium deposits without consideration of duration and acceleration level.     

Conductivity as a tool for evaluating the homogeneity of sintered discs of transition metal oxides

Sintered discs can be prepared and made conducting for a number of transition metal oxides. It can be shown that room temperature resistivity measurements are an important tool in determining reproducibility for such materials. Several transition metal oxide systems have been chosen to illustrate the importance of these measurements.     

Controlling first four moments for robust optimization

The paper addresses the solution of robust moment-based optimization problems after a multipoint reformulation. The first four moments are considered (i.e. mean, variance, skewness and kurtosis) going beyond classical engineering optimization based on the control of the mean and variance . In particular, the impact on the design of a control of the third and fourth moments are discussed. The multipoint formulation leads to discrete expressions for the moments. linking moment-based and multipoint optimizations. The linearity of the sums in the discrete moments permits an easy evaluation of their gradients with respect to the design variables. Optimal sampling issues are analyzed and a procedure is proposed to quantify the confidence level on the robustness of the design. The proposed formulation is fully parallel and the time-to-solution is comparable to single-point situations. It is applied to three problems: an analytical least-square minimization problem, a shape optimization problem with a reduced-order model, and a full aircraft shape optimization robust over a range of transverse winds.     

A Computational Study of Soot Formation in Methane Air Co-Flow Diffusion Flame Under Microgravity Conditions

An in-house developed code has been used to predict soot formation in a methane air co flow diffusion flame at normal gravity and at lower gravity levels of 0.5 G, and 0.0001 G (microgravity). There is an augmentation of soot formation at lower gravity levels because of lower buoyancy induced acceleration leading to an increased residence time. The peak temperature at microgravity is reduced by about 50 K than that at normal gravity level. The axial velocity under normal gravity and reduced gravity show negative values (relatively small in magnitude) near the wall at axial height beyond 15 cm; but axial velocity is never negative in microgravity condition. Peak value of soot volume fraction at 0.5 G and microgravity multiplies by a factor of ～3 and ～7, respectively of that at normal gravity. The zone of peak soot volume fraction shifts away from the axis towards the wings, as gravity level is lowered. In comparison to soot volume fraction, the factors of amplification of soot number density at reduced gravity and at microgravity are comparatively lower at 1.2 and 1.5 of that at normal gravity respectively. On the other hand, mean soot particle sizes at reduced gravity and microgravity increase to 1.5 and 2 times of that at normal gravity respectively.