Gender and walking speed effects on plantar pressure distribution for adults aged 20-60 years

This study investigates gender and walking speed (80%, 100%, 120% and 140% of preferred walking speed (PWS)) effects on plantar pressure parameters. In total, 30 healthy males and females, aged between 20 to 60 years, participated in this study. A plantar pressure measurement device was used to measure the peak pressure, peak force and contact area in six plantar zones. The results indicate that males had higher peak pressure and peak force in the medial toe and forefoot, as well as greater contact area in the central forefoot and heel areas. Females had greater contact area in the midfoot. Increased walking speed caused a significant increase in most of the response measures and the increase became more obvious when the speed was higher than 120% PWS. Although there was no significant interaction between gender and PWS, some gender differences were found. PRACTITIONER SUMMARY: Using percentage PWS provides a new perspective to discuss the effects of gender and walking speed on plantar pressure distribution. This study's findings can be very useful for footwear and orthotics design for different genders.     

An investigation of stability limits while holding a load

The objective of this study was to investigate the effects of load height and foot placement on the functional base of support (FBOS) limits and the postures that participants used when they reached their FBOS limits. Twelve young male participants were tested while holding a 12-kg load at reach (above their heads), at shoulder and knuckle height, and unladen under both wide and narrow foot placements. The FBOS limits and the centre of pressure (COP) excursion length were calculated based on data from a force platform. Postural angles when participants reached their FBOS limits were calculated from records of a 2-D motion analysis system. The results showed that the load height had greater effect on the posterior FBOS limit. As the load height decreased, the COP excursion length decreased. Participants were prone to using a hip strategy to maintain postural balance when reaching their FBOS limits. Quantitative data of FBOS limits and postural control while participants hold a load at various heights when reaching their FBOS limits is of value for designing a safe materials handling workplace.     

An anthropometric survey of Indian schoolchildren aged 3-5 years

Kindergartens of age group 3-5 years, a distinct and small subgroup of Indian schoolchildren, need special emphasis on human factors. The paper presents the results of an anthropometric survey conducted on schoolchildren. These data, previously lacking in India, can be of benefit for the designers of kindergartens. A set of 81 different body dimensions was taken from a sample of 198 children of age group 3-4 years and 4.1-5 years. Simple anthropometric techniques were used to collect the data. Statistical analyses of the data have been presented in a tabular form for designers as well as for non-technical users. It is emphasized that such data have to be developed at the national level, including every ethnic group, or on a regional basis. Designers, manufacturers and importers of goods should have access to these data.     

Anthropometric characteristics of Japanese aged 0-59 years by analysis of a unified correlation matrix

Abstract

The correlation coefficient of each measured item pair for each partial group of similar-age, same-gender subjects is used to produce correlation coefficients for the entire subject group. Manipulation of the resulting equation yields a unified correlation matrix. Principal component analysis using this equation is applied to the anthropometric data of about 40 000 Japanese men and women 0-59 years old. As the distribution of subject age is not uniform, the number of subjects in each group is corrected for in the analysis, and the influence of this non-uniformity on the analytical results is investigated. An analysis for each individual partial group is also performed, and the physical features represented by the obtained principal factors are examined. Finally, the items crucially affecting each principal factor are shown to vary with age and gender.     

Estimates for a measure of stability robustness via a Lyapunov matrix equation

The upper and lower bounds of an existing measure for stability robustness are obtained in terms of the solution to a Lyapunov matrix equation for nominal systems. This measure is exact, in the sense that it gives a necessary and sufficient condition for the stability of perturbed systems for a certain class of perturbations. The results enable us to assess the measure using the solution to a Lyapunov equation.     

Surface curvature as a measure of image texture

Methods from the theory of surfaces in differential geometry are applied to the gray tone intensity and absorbance surfaces defined by a digital image. In particular, the first fundamental form, the second fundamental form, the two principal curvatures, the Gaussian curvature, and mean curvature from classical differential geometry are presented. New curvatures are introduced which appear to be more appropriate for the purposes of image texture. For each curvature, a texture feature is generated. These features are applied to biological cell nuclei and it is found that they are useful for purposes of discrimination.     

Validity and reliability of a novel device for bilateral upper extremity functional measurements

Background and objective

This study was designed to establish the validity and reliability of a new device that measures bilateral shoulder and elbow range of motion (ROM) and grip force performance in vivo. A further aim was to investigate the control of inter-limb grip force coordination during isometric force-maintenance tasks. Validity of the ROM and grip force measurements was examined using a validated clinical goniometer and standard weights.

Subjects

Twenty-one healthy adults (six female, 15 male; mean ± standard deviation age = 23.05 ± 3.51) were recruited for this study.

Design

All subjects were asked to perform tests to evaluate the validity and reliability of ROM, grip force maximum voluntary contraction (MVC) and coordination control measurements.

Results

The ROM and grip force measurements were linearly correlated with criterion standards. For reliability testing, all of the intraclass correlation coefficient values were >0.99. The inter-limb grip force coordination control task showed that the force modulation timing during dominant-to-non-dominant hand transition was longer than the non-dominant-to-dominant hand transition (p < 0.05).

Conclusions

These results demonstrate that this device is valid and reliable when used to measure shoulder and elbow ROM and grip force of both hands. Isometric force-maintenance tasks also indicated changes in inter-limb grip force control.     

Time perception as a workload measure in simulated car driving

In experimental studies using flight simulations subjects’ duration estimates have shown to be an effective indicator of cognitive task demands. In this study we wanted to find out whether subjective time perception could serve as a measure of cognitive workload during simulated car driving. Participants drove on a round course of a driving simulator consisting of three different environments with different levels of task demands. Drivers were required to perform a time-production task while driving the vehicle. Electrodermal activity and subjective ratings of mental workload (SWAT) were recorded simultaneously. The length of produced intervals increased significantly in more complex driving situations, as did electrodermal activity and subjective ratings of mental workload. Thus, time production is a valid indicator of cognitive involvement in simulated driving and could become a valid method to measure the current mental workload of car drivers in various traffic situations.     

Defining locality as a problem difficulty measure in genetic programming

A mapping is local if it preserves neighbourhood. In Evolutionary Computation, locality is generally described as the property that neighbouring genotypes correspond to neighbouring phenotypes. A representation has high locality if most genotypic neighbours are mapped to phenotypic neighbours. Locality is seen as a key element in performing effective evolutionary search. It is believed that a representation that has high locality will perform better in evolutionary search and the contrary is true for a representation that has low locality. When locality was introduced, it was the genotype-phenotype mapping in bitstring-based Genetic Algorithms which was of interest; more recently, it has also been used to study the same mapping in Grammatical Evolution. To our knowledge, there are few explicit studies of locality in Genetic Programming (GP). The goal of this paper is to shed some light on locality in GP and use it as an indicator of problem difficulty. Strictly speaking, in GP the genotype and the phenotype are not distinct. We attempt to extend the standard quantitative definition of genotype-phenotype locality to the genotype-fitness mapping by considering three possible definitions. We consider the effects of these definitions in both continuous- and discrete-valued fitness functions. We compare three different GP representations (two of them induced by using different function sets and the other using a slightly different GP encoding) and six different mutation operators. Results indicate that one definition of locality is better in predicting performance.     

Distraction as a measure of presence: using visual and tactile adjustable distraction as a measure to determine immersive presence of content in mediated environments

To assess and improve the user experience in entertainment products, developers need results of evaluation methods, which in detail measure the relationship between the mediated content and the resulting media experience. This paper proposes a method applying adjustable distraction (AD) to determine presence as immersion (Lombard and Ditton in At the heart of it all: the concept of presence, Department of Broadcasting, Telecommunications and Mass Media, Temple University, 1997) at selectable events (approximated real-time). Two experiments were conducted to investigate its applicability in computer games and movies with respectively visual and tactile AD. The first experiment examined whether the experienced intensity in a survival-shooter game, measured through questionnaires, was proportional to results from the AD method. The intrusiveness of the AD method was also addressed in the experiment by comparing the immersive presence ratings in a between-groups design. The second experiment investigated whether heart rate measurements, intensity ratings and the results of the AD method with vibration as the distraction signal were proportional when test participants watched a movie clip. The outcome of the first experiment indicated that no significant intrusion is caused by the method. In addition, results showed no proportionality between the AD method and intensity ratings. However, as the AD measurements were supported by flow theory, it might be that the results from the AD method using visual distraction are giving a more comprehensive indication of presence as immersion (rather than just the intensity dimension). The second experiment revealed proportionality between the intensity ratings and the heart rate measurements, while the results from the tactile AD method were not proportional. We suspect that this was caused by the great variance found across the test participants’ thresholds of perceivable vibration. Because of this, it is suggested that a thorough screening process is conducted pre-test if the AD method should apply vibration as the distracting stimulus.     

On stability of a class of positive linear functional difference equations

We first give a sufficient condition for positivity of the solution semigroup of linear functional difference equations. Then, we obtain a Perron–Frobenius theorem for positive linear functional difference equations. Next, we offer a new explicit criterion for exponential stability of a wide class of positive equations. Finally, we study stability radii of positive linear functional difference equations. It is proved that complex, real and positive stability radius of positive equations under structured perturbations (or affine perturbations) coincide and can be computed by explicit formulae. Pham Huu Anh Ngoc and Toshiki Naito are supported by the Japan Society for Promotion of Science (JSPS) ID No. P 05049.     

New sets of stability criteria as a generalization of Markov's stability theorem

In this paper new sets of algebraic stability criteria for linear time-invariant continuous-time systems are presented as a generalization of Markov's stability theorem. They are expressed as a series of inequalities for the Hankel determinants whose elements consist of the two kinds of Taylor coefficients associated with the characteristic polynomial of the systems. Results are derived that have close relations to the continued-fraction expansion and Padé approximation theory.     

Distance to second cluster as a measure of classification confidence

Most image classification algorithms rely on computing the distance between the unique spectral signature of a given pixel and a set of possible clusters within an n-dimensional feature space that represents discrete land cover categories. Each scrutinized pixel will ultimately be closest to one of the predefined clusters; different classification algorithms differ in the details of which cluster is considered as closest or most likely, but in general the selected algorithm will label each pixel with the label of the closest cluster. However, pixels expressing virtually identical distances to two or more clusters identify a limitation of this typical classification approach. Conditions for limitations to distance based classification algorithms include when distances are long and the pixel may not clearly belong to any single category, may represent mixed land cover, or can be easily confused spectrally between two or more categories. We propose that retention of the distance to the second closest cluster can shed light on the confidence with which label assignment proceeds and present several examples of how such additional information might enhance accuracy assessments and improve classification confidence. The method was developed with simplicity as a goal, assuming the classification has already been performed, and standard clustering reports are available. Over a test site in central British Columbia, Canada, we illustrate the described technique using classified image data from a nation-wide land cover mapping project. Calculation of multi-spectral Euclidean distances to cluster centroids, standardized by cluster variance, allows comparison of all potential class assignments within a unified framework. The variable distances provide a measure of relative confidence in the actual classification at the level of individual pixels.     

Privacy as a right or as a commodity in the online world: the limits of regulatory reform and self-regulation

The increased use of the internet and information technology to enable online transactions, distribute information and customer reviews through ecommerce and social networking sites, online advertising, and data mining is both creating efficiencies and challenging our privacy. This paper highlights the growing fear that current federal and state laws in the United States are not adequate to protect the privacy of the data collected while we process electronic transactions or browse the internet for information. The notion of efficiency and cost-benefit are used to justify a certain level of privacy loss, thus treating privacy as a commodity to be transacted rather than a right to be defended. To address developing concerns about personal privacy invasions, we discuss the role and limits that both government regulation and self-regulation play in protecting our privacy.     

Factors affecting stepladder stability during a lateral weight transfer: a study in healthy young adults

A fall from a stepladder is often initiated by a loss of lateral stability. An inverted pendulum model of the human, validated by experiment, was used to determine the feasible range of whole-body center of mass (COM) states for which weight can be transferred laterally on a ladder tread without a ladder rail losing contact with the ground ("no lift-off" stability region). The results show that the size of the feasible no lift-off region was inversely proportional to the height of the tread above the ground, the distance of the stance foot from the ipsilateral rail, and lateral ground inclination angle. For given initial COM kinematics on a tread height equal to 40% human body height, a stance-foot location equal to one-eighth tread width and a 3.5 degrees ground inclination had approximately equivalent effects on the no lift-off region size. Ladder stability was three times more sensitive to tread height than to foot location. Laterally-exerted impulsive hand-tool forces should generally be limited to 8% body weight. These findings can lead to improved ladder designs and safety instructions for stepladder users.     

An experimental evaluation of instantaneous self-assessment as a measure of workload

Instantaneous self-assessment (ISA) is a technique that has been developed as a measure of workload to provide immediate subjective ratings of work demands during the performance of primary work tasks such as air traffic control. This paper reports a study that compared the results of ISA with those gathered from other established workload evaluation techniques; subjective ratings collected at the end of the task, mean heart rate and heart rate variability, and error in the primary task of tracking. ISA ratings were found to be correlated significantly with the post-task ratings of workload, heart rate variability, and task performance. Generally each of the techniques was sensitive to variations in task difficulty. However, performance on the primary tracking task was found to be poorer during periods when ISA responses were required, regardless of whether they were spoken or manual responses. This finding suggests that the usefulness of the technique is limited in comparison to less intrusive measures of workload.     

The negativity of Wigner function as a measure of quantum correlations

In this paper, we study comparatively the behaviors of Wigner function and quantum correlations for two quasi-Werner states formed with two general bipartite superposed coherent states. We show that the Wigner function can be used to detect and quantify the quantum correlations. However, we show that it is in fact not sensitive to all kinds of quantum correlations but only to entanglement. Then, we analyze the measure of non-classicality of quantum states based on the volume occupied by the negative part of the Wigner function.     

A study of fitness distance correlation as a difficulty measure in genetic programming

We present an approach to genetic programming difficulty based on a statistical study of program fitness landscapes. The fitness distance correlation is used as an indicator of problem hardness and we empirically show that such a statistic is adequate in nearly all cases studied here. However, fitness distance correlation has some known problems and these are investigated by constructing an artificial landscape for which the correlation gives contradictory indications. Although our results confirm the usefulness of fitness distance correlation, we point out its shortcomings and give some hints for improvement in assessing problem hardness in genetic programming.     

Spectral variations of coastal water irradiance as a measure of phytoplankton pigments

Spectral irradiance data were collected along the coast of British Columbia, Canada, using a submersible spectroradiometer. The corresponding hydrographic observations show that in general, the surface layer where the irradiance measurements were taken, is a well mixed layer. The spectral variations of the data are interpreted with respect to the changes of chlorophyll α and phaeo-pigment concentrations measured at the same time. Optical properties such as spectral attenuation and back scattering coefficients are estimated from the data. The back scattering coefficient is approximated by an expression obtained from theoretical analysis.

For remote sensing applications, the intercomparisons of algorithms of Gordon et al. (1980) and Kim et al. (1980) are presented. The results indicate that a linear form of the relationship is suitable for estimating the amount of chlorophyll α + phaeopigments in the coastal water of the inshore region. This may be explained by the variations of diffuse reflectance ratio between wavelengths 420 and 560 nm corresponding to the absorption maximum and minimum due to the presence of phytoplankton pigments in the sea water.