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PARAMETER DEPENDENCE OF STEAM EXPLOSION LOADS AND PROPOSAL OF A SIMPLE EVALUATION METHOD
Kiyofumi Moriyama,박현선 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.7
The energetic steam explosion caused by contact between the high temperature moltencore and water is one of the phenomena that may threaten the integrity of the containmentvessel during severe accidents of light water reactors (LWRs). We examined thedependence of steam explosion loads in a typical reactor cavity geometry on selectedmodel parameters and initial/boundary conditions by using a steam explosion simulationcode, JASMINE, developed at Japan Atomic Energy Agency (JAEA). Among the parameters,we put an emphasis on the water pool depth that has significance in terms of accidentmitigation strategies including cavity flooding. The results showed a strong correlationbetween the load and the premixed mass, defined as the mass of the molten material inlow void zones (void fraction < 0.75). The jet diameter and velocity that comprise the flowrate were the primary factors to determine the premixed mass and the load. The waterpool depth also showed a significant impact. The energy conversion ratio based on theenthalpy in the premixed mass was in a narrow range ~4%. Based on this observation, weproposed a simplified method for evaluation of the steam explosion load. The resultsshowed fair agreement with JASMINE.
Animal models of Alzheimer's disease and evaluation of anti-dementia drugs
Yamada, Kiyofumi,Nabeshima, Toshitaka 한림대학교 환경·생명과학연구소 2002 [일송 국제심포지엄] 노화와 만성퇴행성 신경질환 Vol.- No.4
Alzheimer's disease(AD) is the most common cause of progressive decline of cognitive function in aged humans, and is characterized by the presence of numerous senile plaques and neurofibrillary tangles accompanied by neuronal loss. Some, but not all, of the neuropathological alterations and cognitive impairment in AD can be reproduced genetically and pharmacologically in animals. It should be possible to discover novel drugs that slow the progress or alleviate the clinical symptoms of AD by using these animal models. We review the recent progress in the development of animal models of AD and discuss how to use these model animals to evaluate novel anti-dementia drugs.
Moriyama, Kiyofumi,Park, Hyun Sun Atomic Energy Society of Japan 2016 Journal of nuclear science and technology Vol.53 No.10
<P>We modified JASMINE code, a fuel-coolant interaction simulation code developed at Japan Atomic Energy Agency (JAEA), to extend the applicability for ex-vessel melt coolability assessment. The modification included addition of a melt particle size distribution model based on an empirical correlation and a simple non-local radiation heat transfer model, improvement in the treatment of melt particle generation, and re-agglomeration of settled particles. The modified code was tested by simulating melt jet breakup experiments, namely selected cases of ALPHA/GPM series with alumina-zirconia mixture and steel melt by JAEA, and FARO experiments with urania-zirconia mixture by Joint Research Center Ispra. Simulation results showed that the code reproduces the experimental results well for the cases with a deep subcooled water pool where the melt breaks up completely. On the other hand, significant underestimation of heat removal from the melt and overestimation of agglomeration of settled melt was encountered for conditions with a shallow or saturation temperature water pool. The melt agglomeration behavior in the simulation was sensitive to model parameters on the agglomeration criterion and heat transfer depending on conditions.</P>
Roles of Matrix Metalloproteinases and Their Targets in Epileptogenesis and Seizures
Hiroyuki Mizoguchi,Kiyofumi Yamada 대한정신약물학회 2013 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.11 No.2
Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) remodel the pericellular environment by regulating the cleavage of extracellular matrix proteins, cell surface components, neurotransmitter receptors, and growth factors,which together regulate cell adhesion, synaptogenesis, synaptic plasticity, and long-term potentiation. Increased MMP activity and dysregulation of the balance between MMPs and TIMPs have also been implicated in various pathological conditions. Recent studies have suggested that prolonged seizures are associated with high MMP levels in serum and neural tissues, and certain extracellular macromolecule targets may influence the pathogenesis of epilepsy and seizure. In this review, we discuss the roles of MMP activation in animal models of epilepsy
Preparation of Activated Carbon from Wastepaper and Adsorption of Endocrine Disrupting Chemicals
TAKAYUKI OKAYAMA,KIYOFUMI MATSUSHITA,HIROMA SASUZUKI,MASAHIRO SHIMADA 한국펄프·종이공학회 2006 한국펄프종이학회 기타 간행물 Vol.- No.-
Activated carbon is proposed as a new application of wastepaper recycling other than the paper-making. Waste kraft bag is considered to be a suitable raw material for activated carbon because of its low ash content. Small pellets of wastepaper squeezed out from the continuous kneader were carbonized in a nitrogen atmosphere and activated using carbon dioxide. The BET specific surface areas of activated carbon prepared from waste kraft bag was 1,285 ㎡/g, which is higher than commercially available activated carbons. The activated carbon prepared from wastepaper has a well-developed porous structure, particularly in mesopore and macropore ranges. As a result, activated carbon with iodine adsorption capacity of 1,400 ㎎/g was obtained from waste kraft bag. In this paper, adsorption amount of Bisphenol A (BPA) was determined to investigate adsorbability of activated carbon from waste kraft bag. Adsorption measurements were on solutions ranging from 0.1 ㎍/L to 100 ㎎/L. The activated carbon from waste kraft bag gave higher BPA adsorbabilities over a wide range, compared with commercially available activated carbons.
Anti-dementia Activity of Nobiletin, a Citrus Flavonoid: A Review of Animal Studies
Akira Nakajima,Kiyofumi Yamada,Yasushi OHIZUMI 대한정신약물학회 2014 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.12 No.2
Alzheimer’s disease (AD), the most common form of dementia among the elderly, is characterized by the progressive declineof cognitive function and has a detrimental impact worldwide. Despite intensive laboratory and clinical research over the lastthree decades, pharmacological options for the prevention and effective long-term treatment of AD are not currently available. Consequently, successful therapeutic and preventive treatments for AD are needed. When researching materials from naturalresources having anti-dementia drug activity, we identified nobiletin, a polymethoxylated flavone from the peel of Citrus depressa. Nobiletin exhibited memory-improving effects in various animal models of dementia and exerted a wide range of beneficial effectsagainst pathological features of AD including amyloid-β (Aβ) pathology, tau hyperphosphorylation, oxidative stress, cholinergicneurodegeneration and dysfunction of synaptic plasticity-related signaling, suggesting this natural compound could become anovel drug for the treatment and prevention of AD.
마이크로 구조 표면에서의 임계열유속 증진에 관한 실험적 연구
김설하(Kim Seol Ha),Kiyofumi Moriyama,박현선(Hyunsun Park),김무환(Moo Hwan Kim) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
It is well known that microstructures of a heating surface significantly enhances critical heat flux (CHF) of pool boiling due to the surface roughness-amplified capillary force. We suggest the limitation of the capillary effect induced by the surface roughness, by modelling a capillary wicking flow and a permeable liquid flow on the microstructured surface. Then, the critical size of microstructure for CHF delay were calculated, and evaluated in pool boiling experiments on the microfabricated structured surfaces. The experimental results also demonstrated that the CHF enhancement by roughness was limited by the permeable liquid flow, rewetting performance through structured surface.
Masakazu Kobayashi,Junji Akaki,Kiyofumi Ninomiya,Masayuki Yoshikawa,Osamu Muraoka,Toshio Morikawa,Masato Odawara 한국식품영양과학회 2021 Journal of medicinal food Vol.24 No.1
The number of diabetes mellitus and borderline diabetes cases is increasing and poses a serious problem worldwide. Plants of the genus Salacia are known to have α-glucosidase inhibitory activity and to lower postprandial hyperglycemia. Two randomized, double-blind, placebo-controlled clinical trials were conducted to evaluate the efficacy of Salacia chinensis extract. Study 1 was a single-dose crossover study of 150, 300, or 600 mg of Salacia extract or placebo to determine the dose dependency of the effect on postprandial hyperglycemia. The duration of the washout period between each experimental day was a minimum of 6 days. Study 2 was a 12-week, multiple-dose, parallel-group study to evaluate the effects of 600 mg/day of Salacia extract on blood glucose parameters. In Study 1, Salacia induced significant dose-dependent suppression of postprandial blood glucose, insulin, and their incremental area under the curve values. The dose of 600 mg appeared to have the most significant effect. In Study 2, Salacia significantly improved several blood glucose-related parameters, such as hemoglobin A1c, and glucose tolerance after glucose challenge. These results suggest that S. chinensis extract may have beneficial effects in patients with diabetes.