令和3年7月大雨により，西日本を中心として甚大な洪水被害が発生した．平成30年7月豪雨では長時間降 雨が続いたのに対して，令和3年7月大雨では短時間に急激に降水量が増加し，中小河川を中心として平成 30年豪雨に匹敵する規模の洪水が生じた．この結果，多くの河川で河岸侵食や河川沿いの道路，堤防の陥 没等の被害が生じた．広島県三原市を流れる沼田川水系仏通寺川では堰下流での河岸侵食被害が数か所確 認された．堰などの横断構造物下流では，波状跳水や潜り噴流などの激しい乱れを伴う流れ場となるため，洗堀，吸出しを引き起こす可能性がある．洪水時に河岸侵食の危険度評価と同時に被災メカニズムの把握 を行うことは河川管理の上で重要となる．本論文では，現地観測結果を示し，仏通寺川を対象とした洪水 流解析及び河岸侵食のあった箇所を対象とした流れの三次元解析より，中小河川における横断構造物下流 で発生する被災のメカニズムについて考察した．

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　本論文では，大規模な地形変化を伴う阿賀野川河口砂州の開口解析を安定かつ高い精度で実施するために，先に著者らが定式化した斜面勾配を考慮した一般底面流速解析法(GBVC法)および河床変動の解析方法を修正した．観測史上最大流量を記録した阿賀野川平成23年7月洪水を対象とし，河口砂州の開口過程の影響が現れている観測水面形の時間変化のデータを用い，修正した解析法に基づき洪水流・河床変動解析を行った．十分発達した河口砂州上を越流する流れと流砂運動を高精度に計算することで，河岸浸食による砂州の崩落を考慮せずとも，河口砂州開口過程および開口後の横断面形状を再現でき，力学的考察から河口砂州の開口機構を説明した．

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There is increasing interest in flow configurations around banks for a reliable bank protection. We have proposed a new numerical analysis method, Bottom Velocity Computation method based on depth integrated model for three-dimensional flow configurations in laboratory channel and field experimental channel with large scale. While the method provided good agreement with measured data in laboratories, results in the large scale experiment were not enough to reproduce flow configurations, because complex velocity distributions and turbulence motions in the vicinity of bottom depend on variations of complex geometries and bed material distributions in rivers. In this paper, the applicability of the bottom velocity computation method for flows with large scale is discussed by using measured data of field experiment in the Asa river.

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At flow attacking points against bank protection works in the steep rivers, local three-dimensional flows and free-surface spatial-temporal fluctuations cause river bed scouring and bank erosion. Three- dimensional flow structures and free-surface fluctuations are important to understand river bed scouring and bank erosion against bank protection works in steep rivers.

In this study, we have two objectives. First, we show structures of three-dimensional flows and free- surface fluctuations against flow attacking points by using the computation results of the General Bottom Velocity Computation method. Second, we show the evaluation method of forces brought by three- dimensional flows around gravel river bank. As a result, forces of three-dimensional flows and free- surface fluctuations are clarified in relation to bank erosions, and the forces on gravel river bank are evaluated by the vector sum of bottom pressure gradient and bottom shear stress.

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Recent advancements of computational technology and developments of numerical scheme allow us to calculate detail flow structures in rivers with quasi-3D and 3D calculation methods. While the conventional wall law for rough bed has been used for the boundary condition on rough bed, its applicability to those detail calculations is questionable. This paper proposed a non-equilibrium wall law for rough bed with momentum equations for bottom vorticity and roughness layers and discussed its applicability through the theoretical considerations of the magnitude of each terms of the governing equations for the non-equilibrium wall law. We applied the present non-equilibrium wall law employed by the BVC method (BVC-NWL) to the real scale 3D flow in front of structures measured in the Joganji River field experiment. The calculation results by BVC-NWL provided better agreement with measured data than the BVC method with the equivalent wall law (BVC-EWL).

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It is important for designs of river structures to understand not only local scale phenomena around structures but also large scale phenomena such as unsteadiness of a flood flow and behaviors of sandbars. Although a numerical model has been applied to various practical problems with the recent progress of computational technique, most of applications of a 3D model have been confined to local scale phenomena in a narrow area. To calculate 3D local flow around a structure integrally with 2D large scale phenomena in a wide area, this paper proposes a practical computation method for flows over structures based on the general bottom velocity computation method of a depth integrated model. It is demonstrated that the method is able to calculate a water surface profile and a pressure distribution for a rapidly varied flow over a structure and vertical structures of a flow in a hydraulic jump. And erosion processes of a embankment are explained by the method coupled with non-equilibrium sediment transport model.

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反射型力ラーLCDは近い将来急速に普及すると予測される高機能携帯情報端末のキーデバイスになるものと考えられる.このLGDは反射と散乱の機能の点から,3種類に分類することができる,現在,低電圧駆動,広視野角,高速応答性,中間調表示,フルカラー表示などが達成されており,視賢角をある程度隈定すれば高品位のペーパーホワイトディスプレイを実現できる見込みである.将来的には携帯情報端末のみでなく,目の疲労の少ない,高品位の情報用モニターディスプレイとして広く適用される可能性がある.

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We have studied by computer simulation the electro-optical properties of a single-polarizer reflective TN-LCD (R-TN LCD) that combines a reflector and pixel electrodes. We found that R-TN LCD provided a high-brightness, high-contrast and achromatic display by optimization of cell parameters when a retardation film was applied between the polarizer and the LC cell. With these optimized conditions, we have fabricated 24-cm (9.5-in.) -diagonal VGA monochrome and 512-color R-TN LCDs. We achieved a reflectance of monochrome and color-R-TN LCD of more than 180 and 90% respectively within ±15 degree of the detector angle, with peak reflectance comparable with the standard white (BaSO₄), the maximum contrast ratio of both is 6 : 1. These values are acceptable for reflective LCDs.

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The optimal conditions of the conductivity anisotropy ratio _??_ and the dielectric an-isotropyΔε were studied on DSM-type liquid crystal display devices. It was proved that when _??_ was mae as large as possible and Ac was between -0. 2 and -0.05 for parallel-aligned cell and about -0.2 for vertically-aligned cell, high contrast could be obtained at a low applied voltage. However, the do dependence of contrast in the vicinity of the optimal value of Δε became less significant with increasing _??_.

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　段落ち下流湾曲部における流れ構造を，実験や3次元数値計算より考察し，種々の跳水によって異なる河岸侵食危険性を明らかにした．直線・蛇行水路における実験結果との比較から，標準k-εモデルを用いたRANS方程式による3次元計算によって，段落ち下流湾曲部における水深を良好に再現することを示した．蛇行水路における横断面流速分布の計算結果より，潜り噴流と波状跳水では湾曲部における流速分布が異なり，波状跳水では潜り噴流と比べ，湾曲部において強い二次流が発生することを明らかにした．これは，段落ちがない場合と比べ，流速の鉛直分布の勾配が大きくなり，遠心力の鉛直勾配も大きくなるためと考えられる．よって，段落ち下流湾曲部において波状跳水が発生する場合，強い二次流が発生するため外岸沿いの河岸侵食危険度が高まる可能性を示した．

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Accurate estimation of discharge hydrograph during flood events has been one of the most important issues in River Engineering. In this study numerical simulations of flood flows in a compound meandering channel are carried out using a 2-d numerical model to discuss the possibility to reproduce the discharge hydrograph only with the information on water levels. It is demonstrated that the numerical simulation with water level hydrographs at upstream and downstream boundaries can well reproduce the discharge hydrograph at the section in the middle reach and hence that the discharge hydrograph at upstream end is not always necessary. It is also shown that since discharge hydrograph is very sensitive to the magnitude of floodplain roughness, even a record of flood discharge at high water stage, not necessarily at the flood peak, may give good estimation of floodplain roughness, leading to highly accurate estimation of discharge hydrograph.

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土石流やそれに伴う土砂・洪水氾濫の被害軽減のためにはこれらのきっかけとなる山地斜面での地下水位変動を明らかにする必要がある．本研究では山地斜面における岩盤内・表層地下水位の降雨に対する変動特性を岩盤内・表層地下水位の観測を行い，地下水位変動と実効雨量の相関から，地下水位変動の時間スケールを評価し，考察した．そして，降雨に対する水位変動の遅れ時間と実効雨量の半減期が地表面からの地下水位で表されることを明らかにし，降雨から表層，岩盤内地下水位を予測するモデルを構築した．このモデルを用い，岩盤内地下水位の長期的な変化を予測できることを示した．また，山地斜面の岩盤内地下水位の変化を明らかにすることで，山地貯留量と流出予測における新たな知見を示した．岩盤内地下水位の高低で半減期の大小が変わり，地下水位が低いときは半減期が大きくなるため河川への流出量もそれに伴い小さくなることを明らかにした．

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The movement and development of the local scour is associated with the sandbar movement and transformation. The local scour around the river structure increases the risk of the structure failures. Therefore it is important for structures maintenance and management to clarify the characteristics and grain compositions of the sandbar. So, we surveyed the grain composition of sandbar in the Tama River in 2008. And we show the movement and transformation of the sandbar during the 2007 flood, which is the largest Tama River flood in recent years, using the digital map data and the cross section survey data. Then, the characteristics of sandbar movement and transformation and grain size composition of the sandbar are discussed. And we develop numerical model for bed and grain composition variation during the 2007 flood by the quasi-3D flow and bed variation model with segment mixture.

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The electrooptic characteristics of cholesteric-nematic mixtures were studied in relation to surface alignment, layer thickness (d) and helical pitch (p). It was made clear that their characteristics could be consistently understood by taking the ratio (d/p) of layer thickness to helical pitch into consideration, and the optimum value of d/p for display devices was about 0.7 for the parallel-aligned cell (parallel cell) and about 0.5 for the vertical-aligned cell (vertical cell).

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本研究は，河床上の自由水面を有する跳水流と地盤中の浸透流を同時に計算する数値実験を行い，固定床水理実験による検証で，河川流と浸透流の空間情報を同時に得ることが可能であることを示した．数値実験から，跳水位置の手前で浸透流が河床に抜けてそこのブロックが受ける揚力と抗力が大きくなり，ブロックの有効重量による摩擦抵抗力を上回ってブロックが滑動する．これはブロック流失の実験結果に一致する．数値実験を通して，床止め工の下に透水性の高い基礎材料を設けると揚圧が下がり，床止め工を一体構造からブロック構造に変更すると，揚圧は大きく低下することが分かった．さらに，遮水矢板は前部に設けると揚圧の減殺に効果があり，後部に設けるとパイピング防止に効果が高いことが示された．

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It is widely accepted that early rehabilitation programs are required for patients with spinal cord injury (SCI) immediately after injury. However many patients with SCI are admitted to rehabilitation facilities only after a long interval in Japan. The purpose of this study was to investigate how early rehabilitation contributes to improve their activities of daily living (ADLs) in Japan. The present multicenter study examined the status of SCI rehabilitation in Japan, and sought to determine the natural course of SCI and the effect early intervention has on rehabilitation. Sixteen Rosai hospitals and one college of medicine participated in our study. One hundred twenty-three SCI patients (admitted between April 1994 and March 1997, 104 men, 19 women; mean age, 48.8±17.7yr) were divided into an early rehabilitation group and a delayed group and were retrospectively assessed by using the American Spinal Cord Injury (ASIA) and International Medical Society of Paraplegia (IMSOP) classification of ASIA/IMSOP 1992 version. The motor recovery rate (MRR) was defined as (ASIA motor score at discharge-ASIA motor score at admission)/(100-ASIA motor score at admission). The regression lines for FIM^TM instrument score and ASIA motor score were determined for 6 subgroups (early or delayed tetraplegia, central cord injury, paraplegia) by the MRR staging. The regression lines for physical or cognitive FIM score and ASIA motor score were also determined for 6 subgroups. Three stages were obtained: acute stage: 2 weeks postinjury; recovery stage: 2 weeks to 6 months postinjury; and chronic stage: more than 6 months postinjury. Regression lines showed that rehabilitation improved physical functional independence for ASIA motor score, especially in the early rehabilitation subgroups. There was no correlation between cognitive FIM score and ASIA motor score in 6 subgroups. The present findings suggested that SCI rehabilitation contributed to good ADLs for motor function and early SCI rehabilitation hastens and promotes improvement in ADLs by enhancing ADLs for function.

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We developed a new method for measuring LC property constants. The method uses a type of VR oriented film where the LC direction is perpendicular to the rubbing direction, uses the tilt of the electrical field to control the tilting direction of LC, and uses CV characteristics to determine LC property constants. Threshold voltage, elastic and dielectric constants can now be found and accurately measured from CV characteristic measurements by linear approximation in the high-voltage range through this method.

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