2004, 19(3):129-135. DOI: 10.3871/j.1004-7220.2004.3.135.
Abstract:Objective To investigate the effect of vasal viscoelasticity on wall shear stress of pulsatile flow under the influence of Rolling Massage. Methods A hemodynamic model for simulating arterial periodic oscillatory and axial blood flow with a local mild stenosis was formed. Blood was assumed to be Newtonian liquid and vessel wall was assumed to be with linear viscoelasticity. Under the influence of Rolling Massage, the effect of horizontal compression induced an axial vessel stenosis. Pattern of blood flow was found to fit with the linearized Navier-Stokes equation. Results The average shear stress, maximal shear stress and instantaneous shear stress, as well as the maximal wall shear stress behind the maximal stenostic vessel segment, which were measured at 31cm away from the entrance of the vessel, were dependent on both viscous coefficient of vessel and changes in manipulative frequency of Rolling Message. Conclusion The wall shear stress changed significantly under Rolling Massage an...更多d it agreed with the fact that Rolling Massage can remove blood stasis. 还原
2004, 19(3):136-141. DOI: 10.3871/j.1004-7220.2004.3.141.
Abstract:Objective Porcelain-fused-to-metal (PFM) is widely used in oral clinic because of its intensity of metal and finery of porcelain. However porcelain often flakes off in the interface of metal and porcelain. To investigate this problem,the interfacial intensity of different thickness ratios is studied for analyzing the failure mechanism. Methods Moiré interferometry was applied in experimental study of four-point bending specimens with interfacial crack and no interfacial crack and results of experiment are compared with that of finite element analysis. Results Displacement field and stress field of crack tip are obtained. Simultaneously,fracture density and stress parameter of interface are also calculated. Besides,specimen fabrication process and experimental method are also introduced. Conclusion Because of mid-layer place of metal-porcelain cross section moved along with layer ratio,so it can be concluded that thickness ratio has great influence for fracture intensity.
2004, 19(3):142-146. DOI: 10.3871/j.1004-7220.2004.3.146.
Abstract:Objective To simplify the structures of human upper extremity into a two rigid-body system by establishing a dynamic model based on a numerical equation approach. Methods Using Carerden angle as the generalized coordinates and applying the multi-rigid-body dynamic theory to establish dynamic equation; Using the MATHEMATICA calculation software to solve the equation numerically in the active and the converse solution, respectively and results were subsequently compared. Results The dynamic equation of the upper extremity with two rigid-body and numeric solution were obtained. The Carerden angle calculated by the known active force, which was calculated in the equation as the known motion, was accordance with that which was given when the motion was known. At one time the peak point appeared in the converse solution. Conclusion The MATHEMATICA software was a convenient approach, which was able to resolve the complex two rigid-body system equations in the upper extremity. In order to avoid the peak point, the evaluation should be conducted within a defined range with confined error range so that the solution obtained was acceptable.
2004, 19(3):147-150. DOI: 10.3871/j.1004-7220.2004.3.150.
Abstract:Objective A three dimensional finite element model of the revised total hip is established to study the stem stress distributions and to provide a theoretical foundation for the clinical practice. Methods The main mechanicel properties of the stem under different conditions of external loadings is calculated and analyzed in detail using ABAQUS finite element software. Results ① The stem stress increases as the load angle α increases under different boundary conditions and load conditions. ② The stem stress is significantly affected by boundary conditions. ③ All the stress values are in direct proportion to the load values, but the stress distribution curves change shape with respect to load value. Conclusion ① The patients after total hip replacement should avoid the activity of large range of motion of the hip joint(α<30°).② The stresses in all load conditions increase rapidly with load angle α(α>25°) increasing when only the lower third part of the stem is in contact with the bone, so the femur fracture or the stem rupture can easily take place if there is an accidental impact.③ When the stem is not in perfect contact with the human femur, the stem stress is still large even when the range of motion of the patient's hip joint is small.
2004, 19(3):151-156. DOI: 10.3871/j.1004-7220.2004.3.156.
Abstract:Objective Study the effect of load-dropping form on simulation result of osteoporosis based on the numerical model of postmenopausal osteoporosis. Methods Numerical model of postmenopausal osteoporosis was established based on the anisotropic bone remodelling model and mechanostat system combined wifh finite element method. Results Bone mass loses over 25% relative to premenopause when the load descends 20% due to fall of muscular strength and decrease of activities after menopause. Conclusion The result of research showed that both biomechanic factor and physiological factor can lead to osteoporosis,while the form of load descending had little influence upon result.
2004, 19(3):157-159. DOI: 10.3871/j.1004-7220.2004.3.159.
Abstract:Objective To study viscoelasticity of the cancellous bone at femoral neck of fresh cadavers of Chinese nationality. Methods Tensile stress relaxation experiment was conducted for cancellous bone of femoral neck using Shimadzu AUTOGRAPH electronic universal testing machine at 90 degrees、0 degree, and 45 degrees, respectively: Results By using logarithmic regression analysis, the functions and curves of reduced stress relaxation of tested cancellous bone were obtained. Conclusion The results of the experiment show that the largest stress relaxation of the cancellous bone of femoral neck was found in samples tested at 90 degrees as compared with that tested at 0 degree and 45 degrees. These results suggested that the cancellous bone at femoral neck was anisotropic.
2004, 19(3):160-165. DOI: 10.3871/j.1004-7220.2004.3.165.
Abstract:Objective To derive the circumferential stress on elastic tube in a biologic body using mathematics and mechanics analysis. Methods To calculate the formula of circumferential stress (σ θ) on an elastic tube. Results The σ θ on elastic tube is approximately equate to ΔP · r o/D(ΔP,r o and D are the pressure,the mean radius of the tube wall and the thickness of the wall,respectively),with the absolute error δσ θ=ΔP/2,and relative error δσ θ/σ θ = D/2r o.The semi-exactitude formula of the circumferential stress was ΔPrD-P 1+P 22,with the absolute error δσ θ=ΔP2-(P 1+P 2)D2r 0,and relative error δσ θ/σ θ=1σ θΔP2-D(P 1+P 2)2r 0.It was found that the highest circumferential stress exists in small artery of human. Conclusion The approximate formula of circumferential stress and the absolute error is accepted,which is easy for the application.The small artery is trend to be split due to the highest circumferential stress present.
2004, 19(3):166-169. DOI: 10.3871/j.1004-7220.2004.3.169.
Abstract:Objective To compare the mechanical properties of ilium, scapula, and fibula used for reconstruction of metatarsus deficit. Methods Bone defect was simulated at the first to third metatarsus and fourth to fifth metatarsus using a 3-D foot skeletal model. Defects were then reconstructed using ilium, fibula, and scapula, respectively. The displacements and stresses of the reconstructed defects were evaluated using finite element analysis. Results Variations were shown in displacements and stresses among different metatarsus defects, with the largest variation in the deficit of the first to third metatarsus. The use of ilium for metatarsus defect reconstruction revealed the lowest values in the maximum displacement and stress as compared with scapula and fibula. Conclusion Based on mechanical analysis, it was recommended to repair the bony defects involving several metatarsuses and ilium was the most preferred skeleton for reconstruction.
2004, 19(3):170-172. DOI: 10.3871/j.1004-7220.2004.3.172.
Abstract:Objective To investigate the relation between the skeletal age and the rate of tooth movement. Methods Twenty-three female patients was included in this study.The age for those patients ranged from 12 to 14 years old (mean 13.4).All patients were required the removal of first premolars in both arches.Assessment of the skeletal age was made with a hand radiograph before treatment.Comparatively constant force of 150 grams was used for canine retraction.The rate of canine movement was measured. Results Using comparatively constant force to move canine distally,large individual differences were found in the rate of canine movement.There was no linear correlation between chronological age and the rate of canine retraction.But there was a linear relationship between the skeletal age and the rate of canine retraction.The canines moved distally more slowly followed skeletal age increasing. Conclusion The rate of tooth movement varied among individuals.Skeletal age seems to be a critical factor in regulating rate of tooth movement.
2004, 19(3):173-175. DOI: 10.3871/j.1004-7220.2004.3.175.
Abstract:Objective To discuss the situation of autonomic neuropathy in the patients with chronic renal failure (CRF) by Heart Rate variability(HRV). Methods HRV were studied by 24-hour Holter in 20 healthy people for control,77 patients with CRF (30 patients with azotemia and 47 patients with uremia). Results HRV in CRF group was significantly lower than in control group.SDNN (85.28±19.96),SDANN Index (75.55±22.47),r-MSSD (19.22±11.82),PNN 50 (6.7±14.79) (P<0.01).There is no significant difference between azotemia and uremia. Conclusion There was dysfunction of autonomic neuropathy in the patients with chronic renal failure.By the HRV analysis we found that HRV was decreased in the azotemia patient,which suggested that there was autonomic neuropathy lesion in the early stage of CRF.
2004, 19(3):176-179. DOI: 10.3871/j.1004-7220.2004.3.179.
Abstract:Objective To study the biomechanical characteristics of a new preventslide clavicular nail for treatment of clavicular fracture. This study was made to provide some biomechanical evidences for better clinical operation. Methods 9 adult clavicles were divided into 3 groups randomly, and made a model for the middle and lateral fractures. Those 3 groups was fixed with prevent-slide clavicular nail(PSCN), 4 holes steel plate(4SP) or kirschner's pin(KP), respectively. The biomechanical test was performed and the stress was analyzed. Results (1)Bending strength of internal fixation with 4SP and PSCN were close to normal specimen group(NS) (P>0.05);but KP group was less than normal specimen group (P<0.05).(2) Torsional strength and stiffness of internal fixation with 4SP and PSCN were less than NS group,but more than KP group (P<0.05).(3) Anti-putout strength and stiffness of internal fixation 4SP and PSCN were larger than KP group (P<0.05); Anti-putout power of internal fixation with PSCN were larger than KP group (P<0.05).(4) Stress shielding of internal fixation with PSCP were less than 4SP group (P<0.05). Conclusion The strength and stiffness of PSCN was larger than that of KP,and was close to 4SP.The stress shielding of PSCN was the less.The internal fixation with PSCN is an ideal method for treating clavicular fracture.
2004, 19(3):180-183. DOI: 10.3871/j.1004-7220.2004.3.183.
Abstract:Objective Using two kinds of imagine processing software (GETCT and MedGraphics),which were developed by our institute,the modeling human pelvis 3-D FE models can be more easier. Methods CT imagine processing,contour lines of cross-sections information processing,numerical finite element analyses. Results Those two software can be used to establish the 3-D finite element model of the human pelvis precisely and quickly. Conclusion According to the software referred above and some existing software,it is easy to construct human pelvis 3-D finite element models and analyse.The results of finite element analyses indicate that methods,introduced in this paper,can be used to model human pelvis 3-D FE models.
2004, 19(3):184-187. DOI: 10.3871/j.1004-7220.2004.3.187.
Abstract:Objective To establish a mathematical model of carotid baroreceptors based on matlab / Simulink plateform. Methods This mathematic model was composed of three parts, including carotid sinus baroreceptor afferent path, sympatric nerve together with vagus nerve efferent path, and reflex effector. The model was validated using animal experimental results. Results It was found that the results of the model analysis were similar to that obtained from rat carotid reflex experiment. Conclusion The structure of the model was clear and extendable, suggesting that the model could be used as an alternative method for animal experiments.
2004, 19(3):188-192. DOI: 10.3871/j.1004-7220.2004.3.192.