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Biomedical subjects

J G Kreifeldt

Publications and source records attributed to J G Kreifeldt.

6 recordsLinked to original sources
PubMed1996

The use of computer-generated bivariate charts in anthropometric design.

The design of workspaces and consumer products using the bivariate approach is an important, but cumbersome process because of the general unavailability of the proper bivariate charts and the calculations required. This paper presents a simplified method for bivariate anthropometric design using computer generated charts. These charts are created based on the assumption that the appropriate anthropometric data can be adequately represented by the bivariate normal distribution. Four basic bivariate design types are chosen for the study and the ability to derive other types from them is detailed. This paper presents the necessary charts and tables for quick and easy reference in order to determine cutoffs based on the simplifying assumption that the bivariate target percentage will be met by using either equal or complementary univariate cutoff values for each variable as determined by the design problem. Examples show how to use the charts and tables for different design types.

Journal Article↗
PubMed1993

A new approach to input device key design using fingerprints.

A new approach to designing input device keys is proposed, and a TV remote controller is used as an example to demonstrate the new approach for studying the relationship between fingerprints and key geometry. One hundred subjects' fingerprints of thumbs and index fingers of both hands were collected, and a computer program was used for converting the fingerprint to a bitmap form. Subsequently, the data were analysed to provide some guidelines for determining the key size and key shape for the input device. Finally, the fingerprints were used to study the pattern of finger press and the justification for keycap curvature for finger placement. The results showed that the new approach can be useful in guiding designers of input device keys. A further benefit of this study is in providing a more systematic approach with considerable general potential for studying input device keys.

Journal Article↗
PubMed1980

A systematic study of the plaque removal efficiency of worn toothbrushes.

This study described a new in vivo methodology for measuring and comparing plaque removal efficiencies of different toothbrush designs and used it to quantify the loss of plaque removal efficiency of worn toothbrushes, as well as to elucidate the causes. Worn toothbrushes produce statistically significant and large decreases in plaque removal ability depending upon their state of wear. While both bristle matting and bristle tapering contribute to this loss, the former appears to be the more potent. Thus brush designs that are resistant to bristle matting should show markedly superior durability. An indirect conclusion from the bristle tapering results is that the softer a brush, the less plaque it will remove. As a practical conclusion, it is recommended that a standard toothbrush be discarded when it shows signs of matting, regardless of age.

Adolescent↗
PubMed1979

Moment of inertia: psychophysical study of an overlooked sensation.

The distribution of mass in an object held in the hand, as described by its moment of inertia, is a fundamental and potent but largely unrecognized contributor to the object's "feel." A limited set of experiments has produced Weber fractions for human differential sensitivity to this property in the approximate range of 1/5 to 1/3, which is about ten times the Weber fraction reported for lifted weights.

Biophysical Phenomena↗