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排序方式: 共有414条查询结果,搜索用时 46 毫秒
121.
Daisuke Murai Atsushi Kawamoto Tsuguo Kondoh 《International journal for numerical methods in engineering》2020,121(10):2246-2261
This article describes a numerical solution to the topology optimization problem using a time-evolution equation. The design variables of the topology optimization problem are defined as a mathematical scalar function in a given design domain. The scalar function is projected to the normalized density function. The adjoint variable method is used to determine the gradient defined as the ratio of the variation of the objective function or constraint function to the variation of the design variable. The variation of design variables is obtained using the solution of the time-evolution equation in which the source term and Neumann boundary condition are given as a negative gradient. The distribution of design variables yielding an optimal solution is obtained by time integration of the solution of the time-evolution equation. By solving the topology optimization problem using the proposed method, it is shown that the objective function decreases when the constraints are satisfied. Furthermore, we apply the proposed method to the thermal resistance minimization problem under the total volume constraint and the mean compliance minimization problem under the total volume constraint. 相似文献
122.
123.
Pariya Thanatuksorn Kazuhito Kajiwara Toru Suzuki 《Journal of the science of food and agriculture》2009,89(3):363-371
BACKGROUND: High levels of oil in fried products has been recognized as causing health problems. The formation of microstructure during frying is one factor that influences oil absorption. Above the glass transition temperature (Tg), the physical properties of a polymer influences the formation of structure. The ball‐milling process changes the physicochemical properties of wheat flour constituents. The present study investigated the effects of physicochemical changes in wheat flour by the ball‐milling process on structure formation and oil absorption in wheat flour dough model. RESULTS: Dough samples were made from wheat flour that had been ball‐milled for 0 to 10 h and then fried in frying oil at 150 °C for 1–7 min. Thermal properties of wheat flour, structure alteration, and textural properties of fried samples were evaluated. As compared with samples made of non‐milled flour, samples made from milled flour had smaller pores and higher oil absorption. The fracture force of a fried sample prepared from non‐milled flour was lower than that of a sample prepared from milled flour. CONCLUSION: Ball‐milling affected the microstructure formation in fried wheat flour dough, and subsequently oil absorption. The crispness of a sample prepared from non‐milled wheat flour is higher than that of a sample prepared from ball‐milled wheat flour. This may be due not only to a plasticization effect, but may also be dependent on microstructure. Copyright © 2008 Society of Chemical Industry 相似文献
124.
Makoto Takahashi Toshiyuki Miyauchi Kengo Sawada Hiroyuki Ishikawa Shoji Sato Masahiro Tahashi Koichi Wakita Sadao Ohkido Motohisa Honda Asami Murai Masato Kamiya Masanori Matubara 《Journal of the American Ceramic Society》2009,92(3):578-584
The preparation of large-scale YBa2 Cu3 O7− x superconductor samples was investigated. This method is based on plastic forming using a slurry consisting of YBa2 Cu3 O7− x particles and a sol solution made up of multimetallic hydroxide particles (YBa2 Cu3 (OH) x colloidal particles) and poly(vinyl) alcohol (PVA). The effects of adding PVA on the product, the crystallinity, and the superconducting properties of the sample were investigated. It was found that PVA acted as a protective colloid in the sol solution and stabilized YBa2 Cu3 (OH) x colloidal particles, and that the role of PVA changed from a thickener to a flocculant during drying so that the formability/workability of the green sheet sample was improved and large samples (about 80 mm × 80 mm × 3 mm) without large cracks were obtained after firing. The samples became superconducting at 91.5±0.5 K ( T con ) and the full transition temperature ( T coff ) was 88.5±1.5 K. The critical current density ( J c ) of the sample prepared from the slurry containing 1 wt% PVA was 713±150 A/cm2 at 77 K. This J c value was improved to 2300 A/cm2 by heat treatment at 773 K under an oxygen atmosphere. 相似文献
125.
Chotika Viriyarattanasak Naoko Hamada-Sato Manabu Watanabe Kazuhito Kajiwara Toru Suzuki 《Food chemistry》2011
The percentage of metmyoglobin (%metMb) in aqueous meat extracts of bigeye and bluefin tuna and beef samples were estimated using previously reported equations derived from the absorption spectra of horse Mb. The results demonstrate that in an aqueous extract, the difference in %metMb estimated by the different equations was negligible for beef samples. Conversely, in an aqueous tuna extract, different %metMb values were obtained with the different equations. The discrepancy in the tuna sample results might be due to differences in absorption spectra for horse and tuna Mb. Therefore, a new set of equations derived from the absorption spectra of bigeye tuna Mb, reported by Matsuura and Hashimoto (1955), was established. The accuracy of the proposed equations was compared with the cyanmetmyoglobin (cyanmetMb) method. The results show that the total Mb concentrations estimated by our proposed equations were in good agreement with the results obtained by the conventional cyanmetMb method (R2 = 0.984). Therefore, the new set of proposed equations is valid for the spectrophotometric determination of the relative proportions of Mb derivatives and total Mb concentration in aqueous tuna meat extracts. 相似文献
126.
The permeation characteristics and the burst strength of nylon 12 membranes treated with heat in various solutions such as aqueous solutions of formic acid, formic acid/formalin, and sodium hydroxide/ formalin were investigated under various conditions. They were significantly influenced by the treatment solution, temperature and time, and the concentration of acid and alkali in the treatment solution. In particular, nylon 12 membranes treated with formic acid/formalin remarkably improved the permeation characteristics and the burst strength. These phenomena were discussed from the standpoint of the effective pore size and pore number in the membrane, and the form and aggregation of polymer molecules forming the membrane. 相似文献
127.
CC Moore SH Mellon J Murai PK Siiteri WL Miller 《Canadian Metallurgical Quarterly》1993,133(1):368-375
Both cortisol and aldosterone bind to and activate the mineralocorticoid receptor. Cortisol concentrations are generally 100- to 200-fold higher than aldosterone concentrations, yet mineralocorticoids clearly exert effects different from glucocorticoids. One hypothesis is that 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which converts cortisol to biologically inactive cortisone, protects the mineralocorticoid receptor from cortisol. The circulating concentrations of cortisol in the squirrel monkey are 20- to 50-fold higher than human cortisol concentrations, yet this animal has no evidence of glucocorticoid or mineralocorticoid excess. We used this experiment of nature to test the hypotheses that the known (hepatic) form of 11 beta-HSD protects renal mineralocorticoid receptors from the action of cortisol and that it modulates glucocorticoid concentrations in target tissues. Using a long oligonucleotide based on the rat sequence, we cloned the squirrel monkey 11 beta-HSD complementary DNA and gene. The encoded monkey amino acid sequence is 75% and 91% identical to the corresponding rat and human sequences, respectively. The tissue abundance of the messenger RNA for the monkey enzyme was similar to or less than that seen for the rat and human enzymes. Both the monkey and human 11 beta-HSD complementary DNAs were cloned into an expression vector and used to transfect cultures of Chinese hamster ovary cells. Both vectors were transcribed and translated into equivalent amounts of 11 beta-HSD enzyme. The monkey enzyme was slightly more efficient than the human enzyme in converting [3H]cortisol to cortisone, and estimates of the Michaelis-Menten constant and maximum velocity of both enzymes are similar. These data indicate that the abundance and activity of the hepatic form of 11 beta-HSD are insufficient to inactivate the very high concentrations of cortisol in the squirrel monkey, suggesting that this form of 11 beta-HSD does not defend the mineralocorticoid receptor or protect tissues from high cortisol concentrations. Rather, this enzyme appears to favor conversion of cortisone to cortisol, thus maximizing tissue concentrations of cortisol to overcome glucocorticoid resistance associated with a 50% reduction in glucococorticoid receptors. 相似文献
128.
S Ichiyama K Nakashima K Shimokata M Ohta Y Shimizu K Ooe H Igarashi T Murai 《Canadian Metallurgical Quarterly》1997,175(3):723-726
Streptococcus pyogenes can cause severe infections, such as toxic shock-like syndrome (TSLS). The transmission and pathogenesis of TSLS are poorly understood, and information is needed to develop prevention strategies. Four cases were identified in which the organism was transmitted among patients with TSLS and their family members. DNA macrorestriction endonuclease analysis using pulsed-field gel electrophoresis demonstrated the spread of S. pyogenes clones that caused TSLS among the family members. Although 14 persons related to the case-patients experienced only colonization or self-limited disease, 3 developed invasive infections (pneumonia, severe pharyngitis requiring hospitalization, and puerperal sepsis). These findings indicate that antimicrobial prophylaxis for close contacts of patients with TSLS should be considered and reinforce the need for further studies on epidemic control of TSLS. 相似文献
129.
Abeyratne S.G. Horikawa J. Murai Y. Lipo T.A. 《Power Electronics, IEEE Transactions on》1997,12(2):201-212
A new AC/AC power converter topology, in which all the switches operate in a resonant fashion to reduce switching losses, is proposed. The topology enables conduction-period control of individual current pulses, whereby pulse-width modulation (PWM) could be achieved to a fair degree of accuracy with the associated controller. The scheme implements current peak (resonant) limiting by a simple diode clamp. Improved switch utilization (voltage × current) and reduced part-count could be cited as the merits of the circuit over the previous soft-switched current-sourced AC/AC configurations. It is experimentally verified that the output PWM controller could be used to implement constant V/F operation, and the results are presented. In-depth design criteria for the topology that gives optimized voltage stresses are presented. A charge-based, line current feed-forward, mode-controller is introduced at the input and digitally verified. Feasibility of the simultaneous control over both input power-factor and smooth input-output line currents are studied and the digital verification is presented 相似文献
130.