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特集 レジリエンス, Research Article, インフラ整備による衣食住環境の改善や抗生物質の普及によって、とりわけ先進国における人間の主要な死因は感染症疾患から非感染症疾患にシフトし、公衆衛生対策も肥満、糖尿病、高血圧などの慢性疾患予防により重点があてられてきた。そうした中、2019 年末に中国武漢市から発生したとされる新型コロナウイルス感染症（COVID-19）が猛威をふるった。先進国を中心に世界の死者数は300 万人を超え（2021年5月現在）、PCR 検査の普及からワクチン開発およびその配分の透明性まで、現代医療体制への信頼が世界中で脅かされている。人獣共通感染症であるCOVID-19 は、ウイルス（一次）感染と病院での細菌（二次）感染との関係性を露わにし、人間を中心に行われてきた医療の非弾力性が問われるきっかけにもなっている。本稿では、国際保健学者の山本太郎のレジリエンス論を借りながら、微生物とヒトとの共生の視点から、レジリエンスを維持する社会－生態系システムとしての医療について論じる。COVID-19 にまつわる２つの事例をふまえ、（1）可塑性、（2）多様性、（3）持続可能性の３つの側面から医療のレジリエンスについて試論を提示する。そして最後の節では、「プラネタリーヘルス」の視点を紹介し、地球と人類の健康を互いに創りあげる方法と可能性を探る。, City planning, improvements in personal hygiene and medical innovations over the past two centuries led to the decline in infectious disease mortality in most parts of the world. As a consequence of this so-called epidemiological transition, modern public health concerns and policies have become increasingly structured around non-communicable diseases (NCDs), such as diabetes, obesity or hypertension. It is in this context that the new type of coronavirus (COVID-19) emerged from Wuhan, China, in late 2019. More than 3 million deaths worldwide as of May, 2021 combined with often low levels of transparency regarding the availability of PCR tests or the development and distribution of vaccines have considerably damaged the trust in modern healthcare systems around the world. COVID-19, a zoonotic disease, illustrates the systemic vulnerability and inflexibility of modern, anthropocentric infrastructures such as public healthcare systems. The causal relation between primary (viral) and multiple secondary (bacterial) infections in overloaded hospital settings is an obvious example. In this essay, we start from the medical notion of resilience to discuss the importance of coexistence with microorganisms for a more resilient healthcare system, by which we mean a ‘social-ecological system.’ The two different cases, 2009H1N1 influenza and antimicrobial resistance, introduced and discussed here are related to the COVID-19 pandemic in important systemic ways and will allow us to highlight three aspects of resilience in healthcare: (1) plasticity, (2) diversity and (3) sustainability. In the last section, we discuss the concept of planetary health that we hope can help us imagine better ways of protecting the health of both humans and the planet in pandemic and post-pandemic times.

It has been shown using an Al-4.0 mass%Cu alloy as a demonstration material that hot extrusion with the use of a specially-designed die, which is called a heteromorphic die, leads to grain refinement and improvement in ductility. The heteromorphic die consists of two plates and one spacer. One plate is called a strain-giving die and has six holes of 5 mm in diameter, while the other plate is called a shape-giving die and has one rectangular hole of 9 mm×15 mm in side length. The spacer separates these plates at a distance of 10 mm and gives a space between them. The Al-Cu alloy billet was hot-extruded from the strain-giving die into the space between the two dies to produce six thin bars, and all the six bars passed together through the shape-giving die to become a thick rectangular bar. The rectangular bar produced by the present extrusion was tensile-tested at room temperature and the results were compared with those of the un-extruded billet and the bar produced by a conventional hot extrusion using only the shape-giving die. The elongation of the specimens made of the billet, the bar extruded by the conventional method and the one extruded using the present heteromorphic die were 21, 35 and 57%, respectively. The largest elongation found in the sample extruded using the present heteromorphic die should be due to the fine recrystallized grain structure in that sample. It is suggested that the recrystallization is induced by a large strain generated in the present heteromorphic die due to the friction at the large contact area between the die hole wall and the alloy.

抄紙方向に対して傾斜角をつけて切り出したコピー用紙を用いて引張試験を行い，応力-ひずみ関係を求めた。数理塑性理論に基づいて非線形領域における応力-ひずみ関係を相当応力-相当塑性ひずみ関係に変換し，理論の適用性について検討した。その結果，様々な傾斜角における相当応力-相当塑性ひずみ関係は互いによく一致しており，数理塑性理論が適用可能であることが示唆された。, Uniaxial tensile tests were conducted for off-axis copy paper to obtain stress-strain curves. It was shown that the stress-strain responses strongly depend on the off-axis angles. The nonlinear regions of the off-axis angle-dependent stress-strain relationships were transformed into the equivalent stress-equivalent plastic strain counterparts based on the mathematical theory of plasticity taking into account a Hill-type anisotropic yield criterion. The equivalent relationships were demonstrated to coincide almost uniquely regardless of the off-axis angles. This implied that the nonlinear stress-strain responses of copy paper can be predicted appropriately by using the mathematical theory of plasticity.

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Fiber metal laminates (FML) are composites laminated by fiber reinforced plastics (FRP) and aluminum alloy. GLARE, one of the FML laminated by Glass Fiber Reinforced Plastics and aluminum alloy, has been applied to an upper fuselage panel in an Airbus A380. The precise stress distribution of the out of plane components has not been discussed around the contact hole boundary, though several papers applied the three dimensional (3D) finite element method (FEM) to GLARE for delamination failure analysis. This paper applies 3D-FEM to a GLARE pin joint and obtains the characteristic stresses near the contact region. Effects of material properties and plasticity on the distribution and magnitude of stresses are discussed together with previous results of Carbon FML obtained by the present authors. It was found that within the practical range of material properties and loading stroke, their effects on the stress distribution are small and that the magnitude depends on them. A model that relates the out of plane normal stress σ ZZ with the longitudinal stiffness of FRP is presented, which explains well the several numerical results.

In this paper, the crushing behavior of cylindrical conic absorber with corrugated surface subjected to axial compressive loading is studied by using finite element method. The role of corrugation is to control the deformation pattern and to decrease the fluctuation in the load-displacement curve. The effect of taper is to increase the crushing span. The deformation mode for taper corrugated circular tubes can be classified into progressive crush mode, in which compressive force fluctuates with the wrinkles forming one after another, and simultaneous crush mode, in which compressive force increases uniformly. A mode classification chart is produced for various combinations of wavelength, wave-altitude and taper angle. The cone with corrugated surface is superior to the cylinder with corrugated surface for energy absorption rate.

私たちが行ってきた長期記憶の分子機構の研究について解説します。長期記憶の形成に関わる遺伝子・分子の探索と機能解析について簡単に触れた後，シナプス形態の可塑性と記憶の関連，記憶を正確に保存する神経細胞レベルのメカニズムであるシナプスタグ，そして最後に神経新生と恐怖記憶の処理過程について述べます。

作物の生産性を規定する主要因の一つは、水である。作物が栽培されている圃場においでは、土壌環境は一定であることはむしろまれで、常に変動している。さらに空間的にも不均一である。このことは研究者の間ではっきりと認識されているとは言えず、水ストレス耐性と作物根系の発達と機能との関係を考える上では､たいへん重要な視点である。作物が栽培されている圃場においては、栽培期間中、長期にわたって乾燥あるいは過湿ストレスが続く場合より、むしろ乾燥と過湿の間で土壌水分条件が変動することの方が実態に近いと考えられる。このような変動は、乾燥や過湿の単独のストレスに比べ、根の発育と機能にとってより厳しいストレス要因として働く可能性がある。この間題をイネについて考えてみる。世界的にみるとイネ栽培地域の約半分が天水田(rainfed lowlandrice field)で、灌漑設備が整っていない。この天水田における最大の収量制限要因は、水ストレスである。天水田には、深さ2Ocmあたりに硬盤層という不透水層が存在し、そのため一時的に湛水状態となる場合がある。すなわち、硬盤層より下の心土は通常、湿潤状態であるが、硬盤層より上の作土は不定期な降雨によって嫌気的と好気的条件を繰り返し、その際に起こる水ストレスが生産性の低下を招く。このように、天水田における水ストレスは、畑状態で起こる単純な乾燥ストレスとは質的に異なるものである。さらには、世界的な水不足に対応して、灌漑設備が整っている水田においても、節水栽培技術の開発が急がれているが、ここでも共通の問題が存在する｡このような,時間的･空間的に不均一な土壌条件下で、イネ根系はどのような形質を具備すべきか?環境条件に対して反応し、形態を変化させる能力を可塑性と呼ぶ。そこで、茎葉部より分配された光合成産物を効率よく利用して、変動する土壌環境、とくにストレス環境に応答して、個体の成長を安定させるような能力を有する、すなわち可塑性の大きい振系が、機能的に高いと考えることができる。しかし一方、この可塑性という形質は、遺伝学的にはたいへん扱いにくく、これをまともに取り上げるような育種プログラムもこれまでにはなかった。しかしこの形質は､作物のストレス耐性と密接に関連している可能性が高く、注目する必要がある。本論文では、主として筆者らがこれまでに行ってきた研究成果をもとに、土壌環境の中で、とくに水ストレス耐性を中心に、作物根の発育や機能が果たす役割を、可塑性をキーワードに考えてみたい。Among the various soil conditions, the soil moisture effect is probably most commonly recognized. Soil environment is rarely constant but continues to change and is heterogeneous in space as well. These facts are quite important when the root development and function are analyzed in relation to their roles in water stress. During cropping period, it may be rather common that soil moisture conditions fluctuate between drought and excess in moisture than that the conditions continue to be either of them. It is important to note that such fluctuation can be more stressful as compared with singly consistent stress of either drought and excess in moisture on crop root development and function. In case of rice, more than a half of areas planted with rice is rainfed lowland field without irrigation. The most severe constraints to production there is water stress. Under rainfed lowland conditions, a hardpan that is water impermeable tends to be formed approximately 20 cm below soil surface, and thus waterlogged conditions can temporally appear. In other words, subsoil below the hardpan is usually wet while the topsoil above the hardpan is often exposed to frequent wet and dry cycles that are caused by irregular rainfall, and such water stress can cause substantial reduction in growth and yield of rice plants. As such, the water stress under rainfed lowland conditions is essentially different from the simple drought stress under upland conditions. Furthermore, global trend of water scarcity badly demands the development of water-saving rice production technology in irrigated rice fields, which however inherently contains the similar problem of water stress as rainfed lowlands. Then what kinds of root traits should rice plants possess under such heterogeneous soil environment in time and space? A root system of a crop plant is an integration of component roots with dissimilar morphology, anatomy and possibly physiological functions. They are different also in developmental responses to various environments. The ability of the plant to change its morphology as environmental conditions change is known as phenotypic plasticity. The root system that is high in function may be defined as that developmentally responds to environmental changes in a way that it stabilizes the whole plant growth, i.e., plastic root system. Such trait is difficult to be dealt with genetically and thus has been rarely incorporated in any breeding program. This paper aims to briefly review our research outputs with related areas on root system development and function in relation to the stress tolerance, especially that of water stress, of crop plants., The proceedings included herein are the papers presented in the Seventh ICCAE Open Forum held in October 20th, 2006 at Nagoya University, Japan.

In this paper, the collapse behaviors of thin plate with corrugated cross-section subjected to three-point bending are studied by using the finite element method. In order to estimate the energy-absorption characteristics of the beam, it is vital to understand the relation of load and displacement. It is found that the load decreases by flattening of the cross-section of the beam, and the flattening shape can be quantitatively expressed by using curvature radius of the plane of the top and bottom in the cross-section. Based on an idea that the external work is mainly expended by the flattening deformation of the cross-section, a new prediction method is proposed for estimating the relation of load and displacement. Its validity is verified by comparing with the numerical results by FEM under various conditions.

The thinning processing of crystal grain boundary lines and calculation of strain of crystal grains are programmed for estimation of the non-uniform deformation behavior of crystal grains in polycrystalline material. The thinning processing of crystal grain boundary line is calculated by image processing based on Hilditch method. Logarithmic strains are calculated by measuring maximum distances of grain boundaries of respective grains at every degree interval from the loading direction. The strain distribution in all direction for a grain is approximated with an ellipse using the method of least squares and the principal strain are obtained as the long and the short axes of the ellipse. The calculation accuracy of these programs is examined in detailed., 紀要論文

In this paper, the elastoplastic bending collapse of cylindrical tube subjected to statically pure bending is studied by using finite element method (FEM). It is revealed in the case of infinite length that the moment of the elastoplastic cylindrical tube is controlled by flattening ratio of tube. Also, it is shown that the flattening ratio of tube can be expressed by axial and circumferential stress as a function of the material and geometrical properties and curvatures. Based on these facts, an approximate numerical method to estimate the maximum moment of cylindrical tubes is proposed, and its validity is shown by comparing with numerical results of FEM.

The large-scale cast steel has been used in broad fields of industries, such as power generation, construction, vessels, and automobiles. In the solidification process of a hummer used for press machine, for example, sometimes defects such as shrinkage cavity, segregation and cracks appear at hummer's surface. Shrinkage cavity and segregation can be predicted by performing non-steady state heat transfer analysis ; and therefore such two types of defects can be eliminated by using chills which control solidification process. However, uneven cooling rates at different regions of the large-scale cast steel generate thermal stresses, which cause solidification cracks, between the chills. For causing those cracks, thermal stress may be important ; however, there have been few studies for this thermal stress analysis. In this study, a three dimensional thermal elasto-plastic stress analysis has been performed by using finite element method in connection with three dimensional non-steady state heat transfer analysis, including interaction between the temperature and stress field. The results provide further understanding of the observed solidification crack failure for large-scale cast steel.

Molecular dynamics simulations of tensile deformation of amorphous metals with dispersed nanocrystalline particles were performed in order to reveal the particle size effects on Young's modulus and the flow stress through all crystal volume fraction from 0% (amorphous) to 100% (nanocrystalline metal). The analysis model used in this research contains 32 nano-scaled crystal-particles with random orientation in a unit cell. It became clear that the Young's modulus of the nano-composite is increased as the average particle radius and the crystal volume fraction increase. On the other hand, the flow stress is not affected by the particle size when the crystal volume fraction is lower than 60%. The particle size effects appear gradually for higher crystal volume fraction models. This phenomenon is caused by an increase of the fraction of the grain boundary to the entire interface. We also demonstrate that the elastic constants can be estimated with a higher accuracy by employing a self-consistent compliance model based on the equivalent inclusion method. The Lennard-Jones potential, modified to enforce the continuity at the cut off distance, was used as an interatomic potential. The potential parametes were defined based on Inoue's three basic principles.

In this paper, large scale molecular dynamics simulations of tensile deformation of amorphous metals with a nanocrystalline particle were performed in order to clarify the effect of particle size and crystal volume fraction on the deformation property and the strength. It became clear that the size effects of particle are very small, and the influence of the crystal volume fraction is large. The elastic modulus and the flow stress become large as the crystal volume fraction increases. After yielding of the amorphous phase, the stress of the crystal phase still increases. Thus, the flow stress of the composite increases after yielding. It prevents plastic localization and improves the ductility. When the crystal volume fraction is small, the stress distribution is homogeneous in the particle including near the amorphous-crystal interface. Therefore, chances of the originating deformation are small, the inside-particle plastic deformation hardly occurs. When the crystal volume fraction is high, the particles undergo plastic deformation even with small global deformations. After yielding of the crystal particle, the flow stress decreases, because defects are introduced into the crystal. It is expected that the ideal crystal volume fraction which improve the ductility may exist. Lennard-Jones potential which is modified to enforce the continuity at the cut off distance was used. The potential parametes were defined based on Inoue's three basic principles.

In order to clarify the deformation behavior of polycrystalline metals, formulation based on crystal slips is incorporated into the rigid-finite element analysis. The rate-dependent type constitutive relation is assumed for the crystal slips and the compressibility is assumed for the material in order to avoid the singularity of the stress-strain matrix used in numerical analysis. Based on the analysis, a numerical example is shown.

スギ・落葉広葉樹林の林冠ギャップ下と閉鎖林冠下におけるスギ若木の当年枝(モジュール)の長さ分布, 当年枝当たりの成長点数, 葉の形態, 当年枝の伸長様式, 葉齢を調べた.閉鎖林冠下における当年枝の長さ分布は正規分布であったが, 林冠ギャップ下では長い当年枝が見られ正に歪んだ分布となっていた.当年枝当たりの成長点は閉鎖林冠下(1.4個)よりも林冠ギャップ下(3.0個)で有意に多かった.当年枝の単位長さ当たりの針葉数と当年枝の単位長さ当たりの重さは閉鎖林冠下の方が有意に小さかったが, 軸に対する針葉の開度は林冠ギャップ下の方が有意に小さかった.当年枝の伸長期間は3ケ月前後と長期に及び, 林冠ギャップ下は閉鎖林冠下の1.6倍となっていた.これらの結果から, 光資源が乏しい閉鎖林冠下のスギ若木は針葉の重複回避によって効率的な同化生産のための調整を行う一方で, 比較的短い伸長期間にともなう成長点が少ない短くて軽い当年枝を伸ばすことによって樹冠の増加を抑えていることが明らかになった.また葉齢は閉鎖林冠下で有意に高かったが, これは被陰への対応に伴う若木の着葉量減少を葉の長寿命化によって補おうとした行動と推察された., Morphology, structure and dynamics of current-year shoots (modules) of Cryptomeria japonica saplings were studied in canopy gaps and in closed canopy of a natural conifer-hardwood forest. Shoot length distribution was normal in closed canopy while the distribution skewed positively in canopy gaps. The number of growing points per shoot in closed canopy (1.4) was significantly lower than that in canopy gaps (3.0). The number of needles per shoot length and the shoot weight per shoot length were significantly lower in closed canopy although the open angle of needle along shoot was significantly lower in canopy gaps. The periods of shoot elongation (> 3 months) in canopy gaps was 1.6 times longer than that in closed canopy. These results clarified that C. japonica saplings adjust needle morphology to achieve efficient photosynthesis through avoiding mutual shading among needles and reduce the increment of crown by producing shorter and lighter shoots with lower number of growing points in the light limited condition of closed canopy. In addition, needle longevity was significantly higher in closed canopy, suggesting that C. japonica saplings compensate the reduced amount of needles by prolonging needle longevity in closed canopy.

A plastic constitutive theory incorporating the directional dependence of the plastic strain increment dε^p on the stress increment dσ' was proposed by Goya and Ito. The expression was given in terms of two transition parameters μ(α) and β(α) which denote the magnitude and the direction angle of the plastic increment, where α denotes the direction angle of the stress increment measured from a particular direction n_N, named "natural direction", in which the direction of the stress increment coincide with that of the plastic strain increment. In this report, a computer code for a finite element polycrystalline model is used for the numerical investigation of the variation of the two constitutive parameters μ(α) and β(α) of anisotropic plastic materials. The results show that the approximate functions for the two transition parameters are numerically determined and the direction dependence rule can be naturally extended for anisotropic plastic materials. It is also suggested that several quadratic functions used for classical plastic potential may be introduced for the natural direction potential whose normal is identical to the natural direction., 論文

The purpose of the study in this paper is to establish analytical approaches by which the failure behaviors of the locally thin-walled piping can be simulated well against seismic loading. The summary of results obtained through the present study is as follows. Fully three dimensional elasto-plastic analyses have been carried out for the locally thin-walled piping by using ABAQUS. It has been found that the ratcheting behavior observed in the experiment can be simulated well through the finite element analysis.

「塑性」と「衝撃」とをキーワードとする基礎的研究の成果を要約したものである。骨組構造や部材が繰り返し荷重や衝撃の厳しい載荷を受けた時, どの様な過程を経て, 終局状態, あるいは構造物としての使命を果たし得ない状態に至るかを主として理論的に究めた。, Summary is presented of past studies, upon the author's retirement, on the topics of "plasticity" and "impulsive loading" in the context of structural behaviour. Aggravating processes are theoretically analyzed for framed structures and their constituent members under repeated loading or severe pulse loads being lead to the ultimate state or the final state, in which the structures become unserviceable as such. Principal results are expressed in the original papers in the form of closed-form solutions for idealized situations.

In the first part of this paper, a series of systematic experiments of 5083 AI alloy are carried out at 833 K to elucidate the characteristic features of superplastic deformation under multiaxial loading conditions. Proportional deformation tests at constant strain-rates show that the initial yield stresses obey the Prager-Drucker criterion. It is also shown that under constant strain-rate tests the material hardens under tension, while it softens under compression. Significant strain-rate dependence of the flow stresses is elucidated for tension, compression and torsion loadings. In the second part of the paper, the constitutive model of superplasticity formulated in the previous paper is improved to obtain better description of the drop of the flow stress due to cavity growth under tension loading. For this purpose, the concept of effective stress and the strain equivalence principle of continuum damage mechanics are introduced into the model, and the relevant evolution equations are modified. Comparison of the results of the proposed model with those of the corresponding experiments shows that the proposed model gives better predictions than previously proposed by the authors.

Hardening charactertic of carbon steels have been discussed by comparing the flow curves with the shape and distribution of cementite. The complicated microstructure state induding lamellar or granular cementite has been quantitatively estimated with one parameter, Sv, in stereology. Magnitude of intemal structure variable, A∞,capable to express hardening ability has been eva1uated from each experimental flow curve in accordance with the random barriぽ'stheory. A good correlation between Sv and A∞has been found. It is clarfied that hardening ability of lamellar cementite is larger than that of granular cementite. These results suggest that the random barriers theory can be applicable for describing any

The plastic deformation of TiN thin films was considered by the hardness anisotropy of these films with the (111) and (200) preferred orientation. These hardness were measured by the nano-indentation technique as have already been reported. The plastic deformation of TiN films were caused by indentation of the trigonal diamond tip, and the evidence of this phenomenon was given by the cross-sectional SEM observation and the TED analysis. The influence of difference of residual stress and grain size on the hardness anisotropy was restrictive, and the hardness anisotropy can be explained by the anisotropy of the yield stress calculated by Schmid's law. This relationship suggests the existence of {100} slip system of TiN crystal. The TEM observation of brittle cracks of TiN films also makes it clear that these cracks caused not by the cleavage fracture but by the intergranular fracture.

本文は静水圧に依存する異方性材料の降伏関数について考察したものである．まずはじめに，Hillの異方性降伏関数を静水圧依存型に拡張した代表的な降伏関数であるPariseauの降伏関数の力学的意味を考察することによりその適用範囲を明確にした．次に，材料主軸方向の異方性の割合が静水圧応力に依存して変化するような直交異方性材料に対して，従来の基本的な降伏関数の自然な拡張として与えられるより一般化した異方性降伏関数について考察し，新たな静水圧依存型異方性降伏関数を提案した．この降伏関数は，降伏曲面の大きさと偏差平面の形状が共に静水圧応力に依存するものである．また，この異方性降伏関数に含まれる材料パラメータをごく一般的な試験によって決定する方法が示された．最後に，異方性岩盤材料に対する試験結果と計算値の比較がなされ，提案する降伏関数が従来の降伏関数に比較して，異方性の表現性に優れていることを示した．, A new anisotropic yield function was proposed for the hydrostatic stress dependent materials. This function consists of an idea that each independent components of a stress tensor is multiplied by the arbitrary coefficient corresponding to each anisotropic principal axis. Both of a meridian of this yield surface and a shape of the deviatoric stress plane are dependent upon hydrostatic pressure. It was shown that a number of classical yield functions are derived from the proposed yield function as special cases.The material parameters included in the proposed yield function ware evaluated by using a nonlinear optimization programming method with certain constraint conditions. This method can evaluate the material parameters only by conventional uniaxial and triaxial compression tests, and do not require any difficult tests as simple shear tests or uniaxial tention tests for rock like materials.To prove the usefulness of the proposed yield function and material parameter evaluation method, the numerical analysis results for various anisotropic rock materials were compared with the experimental results. The conclusions are as follows;・ the numerical results of yield strength have good agreement to the experimental results for various anisotropic rock materials,・ the minimum yield stress occurs at an orientation angle within 30 and 45 degree to a principal axis of anisotropy,・ an orientation angle that the minimum yield stress occurs increases according to hydrostatic pressure,・ the ratio of anisotropy decreases acoording to hydrostatic pressure.By this results, it was shown that the proposed yield function has good expression for the mechanical characteristics of anisotropic materials.

A simple method for structural analysis of honeycomb sandwich construction (HSC), which is used as light weight and high stiffness material, was given. It was shown that a rigidity of honeycomb material is very influential to the stiffness of HSC when HSC is subjected to bending load, and elastic and plastic moduli of rigidity are given by honeycomb parameters such as cell size and cell wall thickness. Therefore the authors proposed the finite element model for structural analysis of HSC, which can simulate the HSC deformed behavior without detailed hexagnal mesh. The analyses results given by proposed model agreed with the results of the experiment and the detaied meshing analyses. This model doesn't reduce the precision but reduce much time for pre-post processes and analyses., ハニカムの幾何形状から3軸方向の等価ヤング率，等価横弾性係数， 等価ポアソン比を決定し，要素の剛性マトリックスに組み込んだ．

ジーンターゲティング法により特定の遺伝子の発現が抑制されたマウスを作製することが可能となった．このようなマウスをノックアウトマウスと呼んでいる．ノックアウトマウスを利用することにより，様々な蛋白質の生体内における機能を解析する新しい手法が提供された．近年，実に様々なノックアウトマウスが作製されているが，その一つにNMDA型グルタミン酸受容体（NMDA受容体）のサブユニットをコードする遺伝子に欠 損をもつNMDA受容体サブユニットノックアウトマウスがある．NMDA受容体は中枢神経系の様々な生理的，病理的現象との関連が指摘されている重要な受容体である．また近年この受容体のサブユニットをコードするいくつかの遺伝子がクローニングされ，NMDA受容体の多様性が認識されるにともない，中枢神経シナプスにおいて機能しているNMDA受容体のサブユニット構造や，NMDA受容体の多様性の生理的意義についての関心が高まってきた．このような背景のもと，ここ数年，次々にNMDA受容体サブユニットをノックアウトしたマウスが作製され，これらを用いた研究の成果が蓄積されつつある．この間行われた解析も，生理学的，組織化学的分析から行動科学的観察まで，実に多様である．本稿ではNMDA受容体や可塑性研究においてノックアウトマウスが果たしつつある役割と問題点などを概説する．, The N-methyl-D-aspartate (NMDA) type of glutamate receptors is thought to be essential in many central actions of neurotransmitter glutamate, including learning, memory, neurodevelopment and neurodegenerative disorders. Recent molecular cloning has revealed that the NMDA receptor has multiple subunits with distinct distribution, properties and regulation. This implies that NMDA receptors are different in molecular architecture and functional properties, depending on the brain region and developmental stage. To clarify the significance of the molecular diversity of NMDA receptors in vivo, a gene-targeting technique was applied to NMDA receptor subunit genes and several strains of mutant mice lacking targeted NMDA receptor subunit molecules were created. Using these NMDA receptor subunit knockout mice, ivarious physiological, histological and behavioral analyses were performed. ln this article, after bridfly reviewing recent findings, we discuss the advantages and disadvantages of the NMDA receptor subunit knockout mouse as a tool for the studies of NMDA receptors and synaptic plasticity.

A thin plate is heated locally by a laser beam and simultaneously, a large thermal elastic plastic stress-strain state is generated in the heated, thin surface layer. This state can lead to plate bending upon cooling. The bending configuration depends mostly on the plate geometry, and heating and cooling process. We presents some experimental results of bending the plate in V-, U- and concave shapes. A model of this process is constructed and the theoretical predictions are carried out based on FEM analysis using eleastic-plastic theory. Bending angles obtained experimentally and theoretically are in good agreement.

Some materials used to fabricate machines and structures have a strain rate dependence in their stress-strain characteristics at room temperature. In such materials, the deformation and strength depend on the loading velocity. We propose a noncontact evaluation technique using infrared thermography of macroscopic plastic deformation. To detect the heat generated during plastic deformation, an infrared thermal video system (TVS-2100) was employed. The relationship between the plastic deformation and temperature rise of the specimen surface was determined by analytical simulation of elasto/viscoplastic FE analysis coupled with transient heat conduction analysis. The experimental and numerical results are in good agreement, and the effect of the loading rate and the applicability of this evaluation technique by infrared thermography was demonstrated.

Assuming a spherical void in an infinite rigid plastic material, Gurson proposed a yield function for isotropic porous solids. It is, however, well known that the Gurson model gives harder response than those predicted by experimentation on actual porous solids. In numerical studies to check the validity of Gurson's model, most of the past researchers have introduced a cubic unit cell model, in which a spherical void is placed at the center of the cube. The cubic model can be a good approximation of a porous solid, if the void volume fraction is very small. The cubic model, however, may be not appropriate for the study of porous solids with high ratio of void volume fraction since the model automatically introduces an orthotropy effect due to the geometrically repetitive distribution of voids in three orthogonal axis directions. This research will propose a new unit cell model which is appropriate for the study of the yield functions for isotropic porous materials. The model is also favorable for the study of the anisotropic effect due to the void shape because the unit cell includes less of the anisotropy based on the distribution than the cubic model does., 論文

A constitutive law of plastic deformation has been proposed by Goya and Ito, and can incorporate the stress increment directional dependence of plastic strain increment ε^p. The law is developed through the introduction of two transition parameters μ(α) and β(α), which denote the magnitude and the direction angle of the plastic strain increment, respectively, and are defined to be functions of the direction angle of the stress increment. In this report, the law is implemented in an F. E. M. code for deformation analysis. A plane strain tension problem is analyzed for investigation of the effect of these parameters on the occurrence of the shear band. The results show that the clear shear does not appear when the calculation is performed using B_=π/6, which corresponds to the degree of the directional dependence for the corners of the Tresca yield locus., 論文