Jinsheng Kang

Fluctuating asymmetry and preferences for sex-typical bodily characteristics

Body size and shape seem to have been sexually selected in a variety of species, including humans, but little is known about what attractive bodies signal about underlying genotypic or phenotypic quality. A widely used indicator of phenotypic quality in evolutionary analyses is degree of symmetry (i.e., fluctuating asymmetry, FA) because it is a marker of developmental stability, which is defined as an organisms ability to develop toward an adaptive end-point despite perturbations during its ontogeny. Here we sought to establish whether attractive bodies signal low FA to observers, and, if so, which aspects of attractive bodies are most predictive of lower FA. We used a 3D optical body scanner to measure FA and to isolate size and shape characteristics in a sample of 77 individuals (40 males and 37 females). From the 3D body scan data, 360° videos were created that separated body shape from other aspects of visual appearance (e.g., skin color and facial features). These videos then were presented to 87 evaluators for attractiveness ratings. We found strong negative correlations between FA and bodily attractiveness in both sexes. Further, sex-typical body size and shape characteristics were rated as attractive and correlated negatively with FA. Finally, geometric morphometric analysis of joint configurations revealed that sex-typical joint configurations were associated with both perceived attractiveness and lower FA for male but not for female bodies. In sum, body size and shape seem to show evidence of sexual selection and indicate important information about the phenotypic quality of individuals.

Parameter optimization by Taguchi methods for finishing advanced ceramic balls using a novel eccentric lapping machine

Abstract The final finishing process of advanced ceramic balls used in hybrid precision bearings constitutes two-thirds of the total manufacturing cost, and hence effective and economic finishing methods and processes are critical to their widespread application. A novel eccentric lapping machine is designed and manufactured. Hot isostatically pressed silicon nitride ball blanks (diameter 13.25mm) are used to investigate the feasibility of accelerating the ball finishing process while maintaining high surface quality. Taguchi methods are used during the first step of finishing to optimize lapping parameters; the L9 (34) four-parameter, three-level orthogonal array is used to design the experiment. Experimental results reveal that this novel eccentric lapping method is very promising; a material removal rate of 40 μm/h is achievable. The optimum lapping condition is found to be high speed, high load and high paste concentration with 60 μm diamond particles. The analysis of variance shows that the most significant lapping parameter is lapping load, which accounts for 50 per cent of the total, followed by lapping speed (31 per cent); the particle size and paste concentration only account for 12 per cent and 7 per cent respectively. A comparison with previous lapping experiments and the mechanism of material removal are also discussed briefly.

Body shape preferences: associations with rater body shape and sociosexuality.

There is accumulating evidence of condition-dependent mate choice in many species, that is, individual preferences varying in strength according to the condition of the chooser. In humans, for example, people with more attractive faces/bodies, and who are higher in sociosexuality, exhibit stronger preferences for attractive traits in opposite-sex faces/bodies. However, previous studies have tended to use only relatively simple, isolated measures of rater attractiveness. Here we use 3D body scanning technology to examine associations between strength of rater preferences for attractive traits in opposite-sex bodies, and raters’ body shape, self-perceived attractiveness, and sociosexuality. For 118 raters and 80 stimuli models, we used a 3D scanner to extract body measurements associated with attractiveness (male waist-chest ratio [WCR], female waist-hip ratio [WHR], and volume-height index [VHI] in both sexes) and also measured rater self-perceived attractiveness and sociosexuality. As expected, WHR and VHI were important predictors of female body attractiveness, while WCR and VHI were important predictors of male body attractiveness. Results indicated that male rater sociosexuality scores were positively associated with strength of preference for attractive (low) VHI and attractive (low) WHR in female bodies. Moreover, male rater self-perceived attractiveness was positively associated with strength of preference for low VHI in female bodies. The only evidence of condition-dependent preferences in females was a positive association between attractive VHI in female raters and preferences for attractive (low) WCR in male bodies. No other significant associations were observed in either sex between aspects of rater body shape and strength of preferences for attractive opposite-sex body traits. These results suggest that among male raters, rater self-perceived attractiveness and sociosexuality are important predictors of preference strength for attractive opposite-sex body shapes, and that rater body traits –with the exception of VHI in female raters– may not be good predictors of these preferences in either sex.

A novel eccentric lapping machine for finishing advanced ceramic balls

Abstract Advanced ceramic balls are used extensively in hybrid precision ball bearings and show advantages in high speed, high temperature, high load and hostile environment. Finishing these balls with high quality, good efficiency and low cost is critical to their widespread application. A brief review of the methods for finishing ceramic balls is presented. The design of a novel eccentric lapping machine for finishing advanced ceramic balls is described. The kinematics of eccentric lapping is analysed and discussed, the symbolic expressions for the ball spin angular speed, ωc, ball spin angle, β, and ball circulation angular speed, ωc, are derived and numerical solutions are plotted. Two kinds of hot isostatically pressed (HIPed) silicon nitride ball blanks (13.25–13.50mm in diameter) were lapped and polished to 12.700 mm using this machine. A maximum material removal rate of 68 μm/h was achieved at the lapping step, which is much higher than by the traditional concentric lapping method. The polished ball surface roughness, Ra, value is 0.003 μm, and the ball roundness is 0.08–0.09 μm, which is above grade 5 and close to grade 3 of the precision bearing ball specification. This machine can be used as a prototype to develop a larger-scale machine for production.

Instant 3D design concept generation and visualization by real-time hand gesture recognition

3D conceptual design is a creative process. While the designers are in the inspirational mode, they want to quickly express the design ideas in 3D and visualize it in real time without obstacle. In an exploration of a new, natural and more user friendly interface to assist rapid 3D conceptual generation and visualization, a prototype system of hand gesture and motion capture based user interface has been proposed and implemented. In this paper, we present the framework and components of this real time 3D conceptual generation and visualization system. Hand gestures were designed with the consideration of ease to use and the suitability for real time continuous recognition. Rule-based intelligent menu/icons were designed which changes the prompts according to the design process and expected operations. Real time hand gesture recognition was realized by skeleton model based template matching, and the use of hidden Markov models (HMMs). The recognized hand gestures become command script in OpenSCAD environment, and the 3D design concept was instantly generated and displayed on the screen. A case study was conducted for the initial evaluation of the system.

Generating 3D architectural models based on hand motion and gesture

This paper presents a novel method for rapidly generating 3D architectural models based on hand motion and design gestures captured by a motion capture system. A set of sign language-based gestures, architectural hand signs (AHS), has been developed. AHS is performed on the left hand to define various components of architecture, while location, size and shape information is defined by the motion of Marker-Pen on the right hand. The hand gestures and motions are recognized by the system and then transferred into 3D curves and surfaces correspondingly. This paper demonstrates the hand gesture-aided architectural modeling method with some case studies.

The effects of material combination and surface roughness in lubricated silicon nitride/steel rolling contact fatigue

Four kinds of commercially finished 12.7 mm HIPed silicon nitride bearing balls with surface roughness values R ranging a from 0.002 to 0.016 mm were tested using a four-ball rolling configuration. They were rolling against two types of steel testing balls with different surface roughness and hardness, in fully lubricated condition at a maximum compressive stress of 6.58 GPa and at a speed of 10 000 rpm for over 135 million stress cycles. Rolling track surfaces were examined by microscope, SEM, 3D surface analysis and interference profilometry. Experiment results show that the composite surface roughness are most influential. The shape of the surface topography of silicon nitride are not very sensitive. The slight difference in steel hardness may lead to significant differences in steel fatigue life. 2002 Elsevier Science Ltd. All rights reserved.

Rolling contact fatigue performance of HIPed Si3N4 with different surface roughness

Abstract Accelerated rolling contact fatigue four-ball tests were performed on hot isostatically pressed (HIPed) silicon nitride/steel contacts under lubricated condition using a PLINT TE92/HS microprocessor controlled rotary tribometer at a maximum compressive stress of 6.58 GPa and at a speed of 10,000 rpm for 135–200 million stress cycles. Rolling track surfaces were examined by optical microscopy, SEM, 3-D surface analysis, atomic force microscopy and interference profilometry. Experimental results show that with an initial roughness value R a from 0.016 to 0.094 μm, the surfaces became smoother during testing and surface pitting (10–20 μm) occurred. For the surfaces with a roughness value R a from 0.002 to 0.008 μm, the surfaces became rougher and lubricant oil residues were deposited at the edges of rolling track. Some small and shallow surface pitting 2–3 μm in size was also observed. Some scratch marks left on the surface by the previous lapping process were further extended during testing. R a and R q are still most important roughness parameters in relation to rolling contact behaviour. The effects of other surface roughness parameters, such as the shape of the valley, R sk and R ku are not obvious in this study.

The influence of heterogeneous porosity on silicon nitride/steel wear in lubricated rolling contact

Heterogeneous porosity is detected on the surface and subsurface of hot isostatically pressed (HIPed) silicon nitride spherical rolling elements. The extent of the localised porosity accounts for an area of 6% of the rolling element surface and 4% of the material volume. An experimental investigation using a rotary tribometer is described to compare the lubricated rolling wear mechanisms and performance of HIPed silicon nitride with heterogeneous porosity defect in contact with steel. A brief review of previous investigations is presented. Localised porosity detection using white and violet light microscopy with post-test evaluation is described. Discussions, micro-hardness measurements and scanning electron microscopy illustrations are presented. Critical localised porosity size is evaluated from experimental results.

Comparison of four-ball and five-ball rolling contact fatigue tests on lubricated Si3N4/steel contact

Abstract Accelerated four-ball and five-ball rolling tests were performed on HIPed Si 3 N 4 ball samples (rough lapped with surface roughness value R a 0.08 μm and R q 0.118 μm) in fully lubricated condition. The contact load and the stress cycles per minute for four-ball rolling and five-ball rolling tests were maintained the same. The rolling track appearances of five-ball tests reveal severe sliding occurred. In one case, the opposite arc cracks were generated all over the two sides of the rolling track, and this could not be explained by simplified kinematics model. The failure mechanisms were discussed, which suggest the sliding on the two sides of the track was in the opposite direction.