Topology optimization for designing strain-gauge load cells

Load cells are used extensively in engineering fields. This paper describes a novel structural optimization method for single- and multi-axis load cell structures. First, we briefly explain the topology optimization method that uses the solid isotropic material with penalization (SIMP) method. Next, we clarify the mechanical requirements and design specifications of the single- and multi-axis load cell structures, which are formulated as an objective function. In the case of multi-axis load cell structures, a methodology based on singular value decomposition is used. The sensitivities of the objective function with respect to the design variables are then formulated. On the basis of these formulations, an optimization algorithm is constructed using finite element methods and the method of moving asymptotes (MMA). Finally, we examine the characteristics of the optimization formulations and the resultant optimal configurations. We confirm the usefulness of our proposed methodology for the optimization of single- and multi-axis load cell structures.     

Debittering of enzymatic hydrolysates using an aminopeptidase from the edible basidiomycete Grifola frondosa

Bitter peptide solutions, prepared by the enzymatic hydrolysis of soy protein and milk casein, were treated with an aminopeptidase from the edible basidiomycete Grifola frondosa. As the incubation time elapsed, the amount of free amino acids released increased and the bitterness of the enzyme reaction mixtures decreased. However, the debittering of the milk casein hydrolysate by the aminopeptidase was less effective than that observed for the soy protein hydrolysate. Hydrophobic amino acids such as valine, leucine, phenylalanine, tyrosine, and isoleucine were preferentially released from the bitter solutions by the action of the aminopeptidase.     

Decreased interleukin-6 level in the cerebrospinal fluid of patients with Alzheimer-type dementia

We examined IL-6 levels in the cerebrospinal fluid (CSF) of patients clinically diagnosed with Alzheimer-type dementia (ATD) and with vascular dementia (VD) and of age-matched normal subjects. The IL-6 levels in the CSF of ATD, but not VD patients, were significantly decreased. In the early onset ATD patients (disease onset < 65 years), IL-6 levels were reduced to 21% of the control level. The IL-6 levels in the CSF were not associated with the severity of the dementia or the duration of the disease since the identification of the first symptoms.     

An evaluation of splenopancreatic disconnection as a modification of the distal splenorenal shunt, studied in nonalcoholic patients by sequential angiography

To evaluate the validity and complications of modifying the distal splenorenal shunt (DSRS) by performing splenopancreatic disconnection (SPD), hemodynamic changes in the portal system were assessed by visceral angiography in 93 patients with nonalcoholic portal hypertension during early postoperative follow-up after DSRS. There were 40 patients who underwent DSRS alone and 53 who underwent DSRS plus SPD. Early follow-up angiography showed that portal vein perfusion was well maintained, and that the diameter of the portal vein had decreased significantly by the same degree in both groups. Hepatofugal collaterals for the shunt had developed to a greater extent in the DSRS group, while they were almost completely absent in the DSRS with SPD group. Nevertheless, partial portal vein thrombosis was not detected in the DSRS group, although it was seen in seven (13.2%) of the patients who underwent DSRS plus SPD, in whom the left proximal splenic vein was not visible. The proximal splenic vein was seen in significantly less of the DSRS with SPD patients (47.2%) than the DSRS group patients (85%). In conclusion, SPD more effectively prevented the early postoperative development of collateral pathways for the shunt compared with standard DSRS; however, the possible stagnation of blood flow in the left proximal splenic vein may predispose to a risk of partial portal vein thrombosis developing during the early postoperative period after DSRS with SPD.     

A case of recurrent esophageal cavernous hemangioma increasing rapidly after surgery

AIM: This study was designed to stress the importance of early diagnosis of fetomaternal hemorrhage (FMH) in attempt to prevent the subsequent adverse outcome on the fetus and the newborn. PATIENTS AND METHODS: Nine newborns were admitted because of neonatal anemia to our neonatal unit from October 1989 through September 1995. The diagnosis of FMH was made by the sigma diagnostic fetal hemoglobin that is the Kleihauer test in our hematologic laboratory. Other causes of neonatal anemia have been ruled out. RESULTS: Seven out of the nine cases have expressed early signs of fetal distress in term of abnormal fetal monitoring and/or thick meconium associated with decreased fetal movements. At birth, a wide clinical spectrum depending on the amount of the hemorrhage was seen, ranging from mild anemia with no symptoms (four cases), hypovolemic shock (one case), respiratory distress syndrome (two cases) and maladjustment to extra-uterine life (one case). There was one death at 48 hours after birth; one infant survived with severe encephalopathy. CONCLUSION: These results indicate that it is mandatory to carry out a Kleihauer test whenever a high suspicious index of FMH is faced or an unexplained neonatal anemia is found.     

Analytical approach to SF/sub 6/ breakdown under transient conditions

Under many circumstances, the initiation of breakdown can be viewed as conversion of energy stored in the electric field (capacitive energy) to thermal energy which converts matter in a thin channel from a nonconducting state to a conducting plasma. This paper analyzes this process in the context of breakdown in SF/sub 6/ as a prelude to future papers which treat the subject of breakdown under highly inhomogeneous thermal field, quasihomogeneous electric field conditions.     

Topology optimization using a reaction–diffusion equation

This paper presents a structural topology optimization method based on a reaction–diffusion equation. In our approach, the design sensitivity for the topology optimization is directly employed as the reaction term of the reaction–diffusion equation. The distribution of material properties in the design domain is interpolated as the density field which is the solution of the reaction–diffusion equation, so free generation of new holes is allowed without the use of the topological gradient method. Our proposed method is intuitive and its implementation is simple compared with optimization methods using the level set method or phase field model. The evolution of the density field is based on the implicit finite element method. As numerical examples, compliance minimization problems of cantilever beams and force maximization problems of magnetic actuators are presented to demonstrate the method’s effectiveness and utility.     

Isogeometric topology optimization of anisotropic metamaterials for controlling high-frequency electromagnetic wave

This study presents a level set–based topology optimization with isogeometric analysis (IGA) for controlling high-frequency electromagnetic wave propagation in a domain with periodic microstructures (unit cells). The high-frequency homogenization method is applied to characterize the macroscopic high-frequency waves in periodic heterogeneous media whose wavelength is comparative to or smaller than the representative length of a unit cell. B-spline basis functions are employed for the IGA discretization procedure to improve the performance of electromagnetic wave analysis in a unit cell and topology optimization. Also, to keep the same order of continuity on the periodic boundaries as on other element edges in the domain, we propose the extended domain approach, while incorporating Floquet periodic boundary condition (FPBC). Two types of optimization problems are taken as examples to demonstrate the effectiveness of the proposed method in comparison with the standard finite element analysis (FEA). The optimization results provide optimized topologies of unit cells qualified as anisotropic metamaterials with hyperbolic and bidirectional dispersion properties at the macroscale.     

Dynamic tensile properties of carbon fiber composite based on thermoplastic epoxy resin loaded in matrix-dominant directions

The dynamic tensile properties of carbon fiber (CF) composite loaded in the matrix-dominant direction are experimentally determined. In this study, thermoplastic epoxy resin is used as a matrix of the CF composite. A dynamic tensile test is performed using a tension-type split Hopkinson bar technique. The experimental results show that there are not linear relationships between tensile strength and strain rate in case of the 10°, 30° and 45° specimens, although the tensile strength of CF composite, whose matrix is typical thermosetting epoxy resin, linearly increases with the strain rate for all fiber orientation angles. From the fracture surface observation, it is found that the ductile fracture of the matrix can be observed only when 10° off-axis specimen is tested under dynamic loading condition. It is inferred that the softening of the thermoplastic epoxy resin in the vicinity of interface area takes place with increasing strain rate.