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Reach envelopes are very useful for the design and layout of controls. In building reach envelopes, one of the key problems is to represent the reach limits accurately and conveniently. Spherical harmonics are proved to be accurate and convenient method for fitting of the reach capability envelopes. However, extensive study are required on what components of spherical harmonics are needed in fitting the envelope surfaces. For applications in the vehicle industry, an inevitable issue is to construct reach limit surfaces with consideration of the seating positions of the drivers, and it is desirable to use population envelopes rather than individual envelopes. However, it is relatively inconvenient to acquire reach envelopes via a test considering the seating positions of the drivers. In addition, the acquired envelopes are usually unsuitable for use with other vehicle models because they are dependent on the current cab packaging parameters. Therefore, it is of great significance to construct reach envelopes for real vehicle conditions based on individual capability data considering seating positions. Moreover, traditional reach envelopes provide little information regarding the assessment of reach difficulty. The application of reach envelopes will improve design quality by providing difficulty-rating information about reach operations. In this paper, using the laboratory data of seated reach with consideration of the subjective difficulty ratings, the method of modeling reach envelopes is studied based on spherical harmonics. The surface fitting using spherical harmonics is conducted for circumstances both with and without seat adjustments. For use with adjustable seat, the seating position model is introduced to re-locate the test data. The surface fitting is conducted for both population and individual reach envelopes, as well as for boundary envelopes. Comparison of the envelopes of adjustable seat and the SAE J287 control reach envelope shows that the latter is nearly at the middle difficulty level. It is also found that the abilities of reach envelope models in expressing the shape of the reach limits based on spherical harmonics depends both on the terms in the model expression and on the data used to fit the envelope surfaces. [ABSTRACT FROM AUTHOR]

This paper aimed to identify the reach capabilities of 26 seated subjects considering the reach difficulty, orientation and other potential factors, and to find a method to model the minimum reach capability surfaces for fixed and adjustable seats. The reach capability radius was used as a measure of the reach capability and theoretically modeled. Based on the test data of seated reach, the distribution of the reach capability radius was analyzed. The strategy to select the minimum reach envelopes was constructed to accommodate a sufficient percentage of the target population for both fixed and adjustable seats. For adjustable seats, a method was developed to derive the reach capability data from the tested individual reach capability data by introducing seating position models to re-position the individual reach capability data. An application case was realized based on the cab packaging data of a mini-van, and the minimum reach envelopes of different difficulties were created and validated to accommodate 90% of the target population. [ABSTRACT FROM AUTHOR]

Fractionated samples of d,l-poly(lactic acid) (PLA) were prepared and the dielectric normal mode relaxation was studied for dilute and semi-dilute solutions of the PLA in a good solvent benzene. Results indicate that in the dilute regime the normal mode relaxation time is proportional to [η]Mw in agreement with the Rouse–Zimm theory, where [η] and Mw denote the intrinsic viscosity and weight average molecular weight, respectively. The dielectric relaxation strength which is proportional to the mean square end-to-end distance 〈r2〉 increases with increasing Mw with the power of 2ν, where ν is the excluded volume parameter determined from [η]. The relaxation time in the semi-dilute regime increases with increasing concentration C due to increases of the entanglement density and the friction coefficient. The relaxation time corrected to the iso-friction state agrees approximately with the dynamic scaling theories. The relaxation strength decreases with increasing concentration indicating that 〈r2〉 decreases on account of the screening of the excluded volume effect. The concentration dependence of 〈r2〉 agrees approximately with the scaling theory proposed by Daoud and Jannink. [Copyright &y& Elsevier]