Topology optimization for fluid–thermal interaction problems under constant input power

This paper deals with density-based topology optimization considering fluid and thermal interactions, in which the Navier–Stokes and heat transport equations are coupled. We particularly focus on designing heat exchangers. In the engineering context, heat exchangers are designed while considering a certain amount of input power. Therefore it is important to maximize the performance of a heat exchanger under a constant input power. In this paper we propose a way to control the input power by introducing an extra integral equation. To be more precise, in the fluid analysis, the inlet pressure is determined by solving the extra integral equation together with the Navier–Stokes equation. By doing this we can keep the inlet power constant even when the flow channels are changed in the optimization process. Consequently, the system of equations of the fluid field takes an integrodifferential form. On the other hand, in the heat transport analysis, a single governing equation is defined for simultaneously modeling both the solid and fluid parts. The design variable is a fluid fraction whose distribution represents the topology of the solid and fluid domains. When designing heat exchangers, two different heat conditions are considered in the formulation of the optimization problems, namely temperature-dependent and temperature-independent heat sources. Through the numerical examples for designing flow channels in a heat exchanger, it is shown that distinct topologies can be obtained according to the input power and the heat source conditions.     

General topology optimization method with continuous and discrete orientation design using isoparametric projection

A general topology optimization method, which is capable of simultaneous design of density and orientation of anisotropic material, is proposed by introducing orientation design variables in addition to the density design variable. In this work, the Cartesian components of the orientation vector are utilized as the orientation design variables. The proposed method supports continuous orientation design, which is out of the scope of discrete material optimization approaches, as well as design using discrete angle sets. The advantage of this approach is that vector element representation is less likely to fail into local optima because it depends less on designs of former steps, especially compared with using the angle as a design variable (Continuous Fiber Angle Optimization) by providing a flexible path from one angle to another with relaxation of orientation design space. An additional advantage is that it is compatible with various projection or filtering methods such as sensitivity filters and density filters because it is free from unphysical bound or discontinuity such as the one at θ = 2π and θ = 0 seen with direct angle representation. One complication of Cartesian component representation is the point‐wise quadratic bound of the design variables; that is, each pair of element values has to reside in a given circular bound. To overcome this issue, we propose an isoparametric projection method, which transforms box bounds into circular bounds by a coordinate transformation with isoparametric shape functions without having the singular point that is seen at the origin with polar coordinate representation. A new topology optimization method is built by taking advantage of the aforementioned features and modern topology optimization techniques. Several numerical examples are provided to demonstrate its capability. Copyright © 2014 John Wiley & Sons, Ltd.     

A single oral administration of conjugated linoleic acid enhanced energy metabolism in mice

We investigated the effect of a single oral administration of conjugated linoleic acid (CLA) on energy metabolism in mice. Male Std ddY mice were orally administered CLA (5 mL/kg weight) or linoleic acid (5 mL/kg weight) (both solutions at concentrations of 73.5%) as a control. Oxygen consumption was significantly greater in the CLA-administered mice than in the control mice. Respiratory quotient was slightly lower in the CLA-administered mice than in the control mice. We calculated fat and carbohydrate oxidation from oxygen consumption and respiratory quotient. Fat oxidation in the CLA-administered mice was significantly higher than in the control mice, and there was no difference in carbohydrate oxidation. Serum concentrations of noradrenalin and adrenalin in the CLA administered mice were significantly higher than in the control mice. These results suggested that CLA enhanced sympathetic nervous activity and energy metabolism.     

Monotonicity in Optimal Policy of a Flexible Manufacturing Cell Feeding Several Production Lines

This paper deals with an optimal part selection problem tominimize the expected cost, in an automated manufacturing system in which a flexible manufacturing cell produces different parts for several production lines. The optimal control problem is formulated as an undiscounted semi-Markov decision process. Properties of the optimal policy are analyzed. Moreover, sufficiency conditions are derived for the optimal policy to be of control iimit type.     

Investigation of nitrate salts for solar latent heat storage

Solar thermal applications require some means of thermal energy storage. Amongst several storage concepts, latent heat storage is quite suitable because of its high storage density and almost constant temperature during charging and discharging. The temperature range between 200 and 300°C is considered to be important for solar total energy systems. In this temperature range, sodium nitrate and its mixed salts with other nitrates including eutectic and off-eutectic salts are candidates.

The present paper deals with heat transfer in a latent heat storage unit utilizing these salts. A method of rough estimation of the thermal conductivity of the storage materials is described, and the temperature history of the storage material experimentally obtained is compared with numerical solutions and found to be in reasonably good agreement.

It is seen that the temperature of the heat transfer surface quickly drops soon after the appearance of a solid phase due to low thermal conductivity of these salts. Ways to avoid this temperature drop are discussed.     

Active properties of thermally excited titanium dioxide/silica composite material for the decomposition of gaseous toluene

Decomposition of gaseous toluene and oxidation of CO on thermally excited titanium dioxide (TiO₂)/silica (SiO₂) composite material were investigated using a simple flow system. TiO₂/SiO₂ composite bead was superior to TiO₂ (anatase) or TiO₂/alumina in the thermally excited activation for toluene decomposition. The composite effect of TiO₂/SiO_2, bead was recognized in our study. ESR studies showed the existence of Ti³⁺ in the material. This means that oxygen vacancy would be generated by thermally excitation of TiO₂ in the composite material.     

Computed tomography analysis of causes of local failure in radiotherapy for cervical carcinoma

BACKGROUND: The authors analyzed the radiation dose to the periphery of the cervix and area of the cervix in relation to local failure of radiotherapy for carcinoma of the cervix using computed tomography (CT) images. METHODS: Between 1981-1990, 127 consecutive patients were treated with definitive radiotherapy. Ninety-nine of these patients had CT images taken at the time of intracavitary therapy. Of these 99 patients, 80 were eligible for this analysis. After CT scanning, isodose curves relative to the point A dose were superimposed on the CT images. The minimum percent dose and minimum dose at the periphery of the cervix were estimated. The area of the cervix also was measured. These factors were examined in relation to the local tumor control rate. RESULTS: Histograms of both the minimum percent dose and the cervical area showed significant differences between the local control and local failure groups (P <0.001). The local control rates were related to both the minimum percent dose and the cervical area, and differed significantly over and below the values of 60% and 18 cm2 (P <0.001 each), respectively. The local control patients, over and below the line: Y = -0.220X + 21.2, in which X (gray [Gy]) and Y (Gy) are the whole pelvis dose and the minimum dose, respectively, could be well differentiated with significance (91.7% vs. 25.0%; P <0.001). CONCLUSIONS: Computed tomography analysis indicated that the local tumor control rate was related strongly to the minimum percent dose, the cervical area, and the pair of whole pelvis and minimum dose values. These factors were found to be more useful than the point A dose in predicting local tumor control.     

Preventive effect of germinated barley foodstuff on diarrhea induced by water-soluble dietary fiber in rats

The two cases presented illustrate the diagnostic difficulties and recommend an approach to use in patients in whom features of acute renal allograft rejection and posttransplant lymphoproliferative disorder (PTLD) appear simultaneously in allograft biopsies. Both patients developed acute allograft rejection episodes in the early post-transplant period followed by severe immunosuppression (OKT-3) and active Epstein-Barr virus infection. In addition to early recognition of light microscopic features of PTLD, immunohistology and in situ hybridization for EBV complement the diagnostic work-up and provide clues to the prompt diagnosis of rapidly developing PTLD affecting the allograft even in the face of persisting rejection.