Elderly people often use a cane to walk; it is an important part of their daily life. The cane must be made of a light weight material of high stiffness. In addition, stress relaxation on impact is required to make the cane easy to grasp. All these factors are affected by the shape design. Therefore, an effective shape design considering the stress relaxation on impact load and the weight of the cane is important. Traditionally, straight-type canes are widely used in the market. In this study, a bioinspired shape design methodology is proposed to produce canes. The basis vector method is used, and a multi-objective design optimization for minimizing the total volume and the maximum stress is performed. A sequential approximate optimization is then adopted to determine the Pareto optimal solutions. The superiority of the proposed method over the straight-type cane is confirmed through numerical results. The optimal cane shapes have more than 90% lower impact stress than the straight-type canes. Finally, a prototype of the optimized cane is produced using the braiding technology. Carbon fiber reinforced plastic is the selected cane material owing to its light weight and high stiffness.

Keywords

Biology, Cane design, Shape optimization, Multi-objective design optimization, Breading technology

Paper information

[Advance Publication] (Proper information for citation will be announced after formal publication)

We have performed numerical simulations to examine saccular cerebral aneurysm formation at the outer curve of a bent artery. A U-shaped arterial geometry with torsion, which was modeled on part of the human internal carotid artery, has been employed. A new numerical model was proposed to take into account proliferation as well as degradation of the arterial wall. Proliferation of the arterial wall was modeled by surface area expansion in high wall shear stress region. Based on wall shear stress distribution on the artery, we have investigated aneurysm formation for the following three conditions: (a) strength degradation of the wall, (b) proliferation of the wall, and (c) both strength degradation and proliferation of the wall. A saccular aneurysm shape was not observed when considering only arterial wall degradation up to 90%. However, the saccular shape formed when proliferation of the arterial wall was also taken into consideration. The resultant shape was consistent with clinical observations. Our findings have suggested that a saccular aneurysm may not be formed by degradation of the arterial wall alone, but also require its proliferation.

Keywords

Cerebral Aneurysm, Growth, Modeling, Wall Shear Stress, Numerical Analysis

Paper information

Yuji SHIMOGONYA, Takuji ISHIKAWA, Yohsuke IMAI, Daisuke MORI, Noriaki MATSUKI and Takami YAMAGUCHI, “Formation of Saccular Cerebral Aneurysms May Require Proliferation of the Arterial Wall: Computational Investigation”, Journal of Biomechanical Science and Engineering, Vol. 3, No. 3 (2008), pp.431-442 . doi:10.1299/jbse.3.431

Stokesian dynamics method based on the approximation of the additivity of velocities was employed to analyze the mechanical behavior of the primary thrombus under the blood flow. The mechanical interactions in the platelet-platelet aggregation and the platelet-surface adhesion via biological macromolecules such as von Willebrand factor and fibrinogen was modeled by the Voigt model. The process of the primary thrombus destruction was simulated under different levels of the mechanical interaction using the developed method. When the binding force was weak, which corresponds to the decline of the platelet function in the bleeding diseases, it was demonstrated that the platelets did not efficiently reside on the injured site of the vessel wall. The results show that our modeling can qualitatively demonstrate the effect of the mechanical interaction via adhesive macromolecules on the destruction process of the primary thrombus. Our modeling could be a powerful tool to better understand the physiological hemostatic mechanism as well as the pathology of the thrombosis and the bleeding disorders.<br />

Keywords

Stokesian Dynamics, Platelet, Plasma Proteins, Bleeding Diseases, Thrombosis

Paper information

Koichiro YANO, Daisuke MORI, Ken-ichi TSUBOTA, Takuji ISHIKAWA, Shigeo WADA and Takami YAMAGUCHI, “Analysis of Destruction Process of the Primary Thrombus Under the Influence of the Blood Flow”, Journal of Biomechanical Science and Engineering, Vol. 2, No. 1 (2007), pp.34-44 . doi:10.1299/jbse.2.34