Biomedical Engineering: Applications, Basis and Communications

A numerical approach was proposed to investigate the wear behavior occurred in the artificial hip joints in this paper. In the numerical simulations, the wear coefficients taken from pin-on-disk tests were introduced into the wear analysis model to assess the wear rates of polyethylene acetabular cups against metallic or ceramic femoral heads. For the established material combinations, different values of polyethylene wear rates were obtained respectively, which were not necessarily the realistic one as expected in vivo but could be confirmed after further discussion on the wear mechanism involved in wear tests. Current results indicated that the polyethylene/ceramic couples represented better wear performances than the polyethylene/metal couples. Furthermore, the ratio of wear rates for polyethylene cups against alumina and the metallic femoral heads was 0.5, which agreed well with that deduced from clinical studies or laboratory hip simulators. It is obvious that these comparable wear behaviors observed from clinics or laboratory studies also can be found by means of the numerical simulation.

The consensus of the normal magnitude of lumbosacral curve has not been achieved. The Cobb's angle cannot depict the whole contour of this curve. For practical applications, a clearer image of these curves and their aging changes should be further investigated. This study aimed to provide a more consolidate concept of normal lumbosacral curves for clinician through a computerized reconstruction method.

Standing lateral radiographs of lumbosacral spine in 82 normal adults were used for reconstructing the sagittal lumbosacral curves. The geometric characteristics of these curves according to the gender and age groups were studied. Using standing lateral radiographs, reconstruction of the lumbosacral curves was performed through digitization, programming and computation. These curves and related parameters were normalized and averaged for analyzing the differences of gender and age.

The most anteriorward and horizontal vertebrae usually occurred on the L4 and L3 in any gender and age groups. The sacral inclination angle did not change obviously with the increasing ages. A tendency of L1 shifting backward was noted in the age groups of 40 to 60 and above 60 years old. The sagittal lumbosacral curves can be easily reconstructed by digitizing lateral radiographs, The aging changes of lumbosacral curves could be qualitatively described as the flattening of lower lumbar curve and the rearward inclination of upper lumbar curve. The changes occurred obviously above 40 years old. Although individual variations existed, the aging changes and the geometric characteristics such as the most anteriorward or horizontal vertebrae could be used as an important guideline during therapy or surgical correction.

Computers play an increasingly important role in daily lives due to rapid developments in information and computer technology. Computers as instruments for physical rehabilitation are becoming more and more prominent. This paper introduces an improved measurement of grip strength through use of a pressure sensitive hand dynamometer. This system can reliably assess a user's grip strength through recording sudden changes in load cell sensors using a circuit and A/D adapter. The analyzed data is directly displayed on an LCD (Liquid Crystal Display) or is transformed and saved in a data record file via a PC interface. The compiled data can be combined with a patient's case history and stored in a database as future reference for clinical use. The system is more efficient, cheaper to operate and more convenient to use than comparable systems currently used by doctors to monitor and analyze the progress of a patient's individually designed rehabilitation program.

In this study, Newtonian flows passing through three-dimensional curved and straight axissymmetrical stenotic tubes are investigated. The geometry effects and Reynolds numbers of 100, 200, 400, and 600 on the formation of the shear rate over arterial walls are studied. It is noted that geometric effects on flow features such as velocity profiles, pressure and wall shear stress distributions in the post-stenotic region are significant. The location of maximum wall shear stress is found to relate to the geometric effect much than the Reynolds number effect.

In this study, the OptoTrak system was employed to collect the articulating surface measurements of the human knee for the femur, tibia and patella in three experimented specimens. Furthermore, a rigorous mathematical reconstruction procedure that estimates reconstruction error was completed by employed the relative analysis tools. The results show, the measurements for each session were able to reconstruct the three-dimensional calibration to a precision of 0.02mm. On the other word, the OptoTrak can be used to obtain the precise measurements of analytical surface of the human knee joint.

Opening windows is frequently done to refresh the indoor air for the occupants. To maintain the cleanliness and freshness of the indoor air, more outdoor air is needed. But its high temperature and humidity are harmful to the thermal comfort of the indoor environment. Therefore, determining the amount of outdoor air allowed to enter the room is very important for the optimum conditioning of the indoor air. The ASHRAE comfort charts indicate the percentage of subjects feeling comfortable during various combinations of dry-bulb temperature, humidity, and air movement. A set of mathematical expressions were proposed to model the charts in order to calculate the comfort degree of the outdoor air automatically with its temperature and humidity. In this paper, the measurement of temperature and humidity was completed by a self-developed digital method. Besides, the comfort level of the sampled air was also simultaneously determined by this digital method based on the mathematical model of comfort charts. The system implemented based on our method is portable. This will let us make good use of the outdoor air and controll the ventilation machine more effectively.