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Publications (62)
A series of hydraulic experiments were conducted for quantitative evaluation on the detachment effect of benthic algae on uneven riverbeds caused by sediment loading. We focused on the shielding part created by the exposure height of gravel and the width between pieces of gravel. The experimental results showed that the shielding was affected by bo...
Bloom of nuisance filamentous green algae on riverbed in regulated river reaches has been an aquatic environmental problem. Algae population dynamics contain growth and abrasion, the latter being due to mechanical disturbances by sediment-laden flows during flood events. A recent experimental study revealed that the abrasion of algae population fol...
Water environmental variables have been reasonably described as subexponentially decaying processes. In this short paper, we apply a theory of superstatistics, the statistics of doubly random variables, to recently obtained experimental data of the benthic algae detachment in water flows created in a laboratorial flume. We show that the survival cu...
This study applies the theory of stochastic control to an environmental project planning to counteract against the sediment starvation problem in river environments. This can be considered as a time‐average inventory problem to time‐discretely control a continuous‐time system driven by a non‐smooth jump process under habit formation disturbing proj...
We analyze a new mathematical model to evaluate performance of recent sediment-based environmental restoration projects from a stochastic viewpoint along with applications. We focus on unique jump-driven non-smooth dynamics governing streamflows and sediment storage subject to impulsive human interventions to replenish the sediment. We derive a non...
We formulate a new two-variable river environmental restoration problem based on jump stochastic differential equations (SDEs) governing the sediment storage and nuisance benthic algae population dynamics in a dam-downstream river. Controlling the dynamics is carried out through impulsive sediment replenishment with discrete and random observation/...
We formulate a new two-variable river environmental restoration problem based on jump stochastic differential equations (SDEs) governing the sediment storage and nuisance benthic algae population dynamics in a dam-downstream river. Controlling the dynamics is carried out through impulsive sediment replenishment with discrete and random observation/...
A recent river environmental restoration problem is approached from a standpoint of stochastic control of hybrid regime‐switching diffusion processes with discrete and costly observations. This setting harmonizes with real problems because continuously obtaining environmental and ecological information is difficult, and is often costly. The main pr...
We consider a new simple stochastic single-species population dynamics model for understanding the flow-regulated benthic algae bloom in uncertain river environment: an engineering problem. The population dynamics are subject to regime-switching flow conditions such that the population is effectively removed in a high-flow regime while it is not re...
A primitive mathematical model for population control in natural environment is formulated under a unified regular‐impulse stochastic control formalism. This kind of mathematical models, although they are candidates of the models of population control, seem not to be well studied. In this paper, the impulse control uses deteriorating items and is s...
In saline aquaculture ponds in the tropics, intermittent rainfall during the rainy season can cause salinity stratification, and strong solar radiation can cause thermal stratification. The combination of these factors may result in thermohaline convection in the ponds. Thermohaline convection in a closed saline water body can in turn induce heat s...
A Hamilton–Jacobi–Bellman Quasi-Variational Inequality (HJBQVI) for a river environmental restoration problem with wise-use of sediment is formulated and its mathematical properties are analyzed. A finite difference scheme with a penalization technique is then established for solving the HJBQVI. The scheme is free from any iterative solvers and is...
A stochastic differential game for cost-effective restoration of river environment based on sediment wise-use, an urgent environmental issue, is formulated. River restoration here means extermination of harmful algae in dam downstream. The algae population has weak tolerance against turbid river water flow, which is why the sediment is focused on i...
The Sanriku coastal area suffered serious damage from the Great East Japan Earthquake that occurred on March 11, 2011. Four years have passed since the earthquake, and reconstruction of the aquaculture industry is progressing. In order to achieve sustainable development and promotion, it is necessary to correctly understand the environment of the S...
The objective of this study was to evaluate the effect of soil moisture condition and irrigation regime on the bioelectric potential of crops with different growth stages. The bioelectric potential of broccoli (Brassica oleracea var. italica) plants at the initial and mid-growth stages was measured under different soil moisture conditions and irrig...
Suspended sediment, which is an important water quality characteristic concerning effluents from agricultural areas, was studied in relatively small rivers that drain agricultural watersheds with considerable rice paddy areas. Suspended sediment load (SL) was observed daily for thirty three months and analysed--applying data stratification. Suspend...
Modern information technologies have facilitated the collection of data to assess various aspects of rice production such as yield, quality, soil properties and growth conditions. Currently, farmers can identify any variation of these indicators within a field, between fields or with other farmers. However, a comprehensive analytical method to iden...
The energy consumption and green house gas emissions associated with rice production in rice terraces were estimated by using the life cycle assessment (LCA) method. We conducted a survey on two farmers in Hoshino village, Fukuoka Prefecture, Japan. The energy consumptions for farmers A and B were 29,254 MJ/ha/Year and 29,637 MJ/ha/Year, respective...
Water quality characterization is important, and often, the first step in watershed water quality management. The characterization activity centers on the quantification of water quality parameters relevant to the monitoring objective and the analyses of the impact of the parameters on the state of water body. This study characterizes the general w...
The floating culture system is a water purification method using the ability of plants for nutrient removal. Since the appropriate management of the floating culture system in eutrophied water depends on the characteristics of the water body, like its shape or depth, it is impossible to make a general guideline. Therefore, as part of constructing a...
This study was conducted in a shallow reservoir for agriculture to examine the response characteristics of the internal seiche to wind action in a closed water body. A observational results revealed that the frequency characteristics of the wave of density interface change with time corresponding to the unsteady wind action, and that the time delay...
The characteristics of thermal convection in a closed water body with
shallow area were examined by experiment for measuring water temperature
and flow visualization experiment. An experiment for measuring water
temperature and the theoretical analysis of the characteristics of the
mixed layer revealed that the horizontal convection based on the de...
We investigated the estimation of the inorganic nitrogen concentration (INC) in irrigation water using electrical conductivity (EC) measurements for its application to fertilizer management in rice production. Data on the INC and EC of irrigation water were collected throughout the rice growth seasons of 2008 and 2009 from five water systems locate...
The objective of this study is clarification of the relationship between plant bioelectrical potential and water consumption environment, including transpiration, irrigation, and water stress. Experiments are conducted to clarify the relationship; to extract the plant bioelectrical potential, spectral analysis is introduced. The result indicates th...
The objective of this study was to obtain basic data, in order to discuss the type of farming in which rice is produced sustainably in rice terraces. Working hours, production costs, and income associated with rice production were surveyed on two farmers (farmer A, farmer B) in Hoshino Village, Fukuoka Prefecture, Japan. As a result, the working ho...
We developed a model for estimation of diurnal variation of water temperature in a paddy field with an emphasis on field-use, and we evaluated this model by comparing the data measured at 2 paddy fields managed by 2 different farmers. In addition, the factors influencing estimation error were examined and the feasibility of the model was discussed...
The objective of this study was to provide useful reference data on the effects of environmental factors on rice production in rice terraces. Environmental indicators, such as meteorology, soil properties, and water quality, were measured in the rice terraces of Hoshino Village, Fukuoka Prefecture. The results revealed that during the ripening peri...
The characteristics of thermal convection in a closed water body with compound cross section were ezamined by experiment for measuring water temperature and flow visualization experiment, and considered the influence of the horizontal convection based on the horizontal density difference. A experiment for measuring water temperature revealed that t...
In a closed water body with compound cross section, we examined the effects of horizontal convection based on the horizontal density difference on the characteristics of thermal convection generated by radiational cooling at water surface. An experiment for measureing water temperature revealed that the fluid exchange was done by the horizontal con...
Between 2006 and 2008, we surveyed the rice production in Hoshino village, Fukuoka prefecture, Japan, and examined the quality of irrigation water in this region. Through the survey, we obtained data for the 3 paddy fields where the same cultivar (Yumetsukushi) was cultivated in irrigation water with a wide range of inorganic nitrogen concentration...
Rice production in the rice terrace region was investigated, using three paddy fields located at different altitudes in different water systems in Hoshino village, Fukuoka prefecture, Japan. The effects of air temperature, nitrogen concentration in irrigation water, and cultivation practices of individual farmers were assessed, based on the growth...
When we address a water quality problem in some closed water bodies, it is very important to solve the relationship between the disturbances and flow. Turbulent and convective flows may be induced by mechanical and thermal disturbances, respectively. Disturbances induce the circulation flow of water environmental substance and the water quality dep...
The attenuation of heat flux at the water surface with aquatic plants was examined by hydraulic experiments to consider the
influence of aquatic plants on the magnitude of thermal disturbance in the closed water body. First of all, the experiment
measuring temperatures on surface of leaf revealed the thermal conductivity of the leaf which is peculi...
Thermal stratification is one of the important features in closed water bodies, which primarily depend on meteorological conditions,
and has strong impact on the ecological environment in lakes or reservoirs. Data monitored in 3days were analyzed for factors
that affect heat mixing processes to examine the diurnal stratification cycles in the Shiki...
In closed water bodies which the inflow and outflow are usually small, vertical transportation based on the formation of water temperature stratification, the problem of water quality pollution due to the inhibition of mixing easily occur, especially the problems become serious in shallow water bodies. The main reasons that drive the formation and...
The generation and development of thermal convection based on inhomogeneous water surface cooling were examined by hydraulic
and numerical experiments to examine the characteristics of thermal convection in a closed water body with aquatic plants.
A visualization experiment revealed the structural characteristics of a whirlpool when thermal convect...
Hydraulic experiments were examined to investigate the characteristics of thermal convection based on inhomogeneous water surface cooling in a closed water body where aquatic plants grew thickly. We demonstrated the process of the generation and development of thermal convection from the results of water temperature measurement experiments. This ex...
Variables characterizing ambient environmental conditions (such as barometric pressure, solar radiation, rainfall, temperature, relative humidity, and wind speed) were measured between June and October in 2006 at the rice terraces in Hoshino village, Fukuoka prefecture. Differences in the environmental conditions of the three paddy fields located a...
A real time sensing technique for detecting lodging posture of crops was investigated using a laser scanner. In the laboratory experiment, posture profiles of a wheat bunch with four lodging directions (left, right, front, back) and three lodging angles (40°, 62°, 80°) were measured, and the profiles were assessed through comparisons with digital i...
Water quality is one of the main characteristics of water storage reservoirs or lakes. A water quality profile, in both of spatial and temporal variations, plays a very important role in assessment and management of lake water quality. In order to have deeply understanding of the lake water quality parameters, some observation plans were decided fo...
In areas where irrigation facilities are not available or in mountainous areas, reservoirs are used for paddy rice culture
in Japan. Water temperature must be adequately maintained because it affects water quality and has a significant impact on
the growth and yield of the rice crop. Stratification of water in a reservoir occurs due to heat storage...
Vertical profiles of wind velocity in and around a rice canopy at three different growing stages were experimentally investigated using a wind tunnel. The vertical profiles were measured between rows of rice bunches and above bunches in a rice canopy, and between rows and behind bunches outside the canopy. Each vertical profile was compared with th...
A contributing factor on a water quality issue in a closed water body is in a sedimentation and a deposition of pollutants due to a domination of flow stagnation. Therefore, with regard to the preservation and improvement of the water quality in the water body, it is important to understand the response of the fluid to thermal and mechanical turbul...
In some closed water bodies with little inflow and outflow, because the flow is gentle, hydraulic characteristics are different from a river or an irrigation canal. When there is no disturbance, fluid is stratified based on vertical density distribution. In these bodies, the main dynamics of the water environmental substance depends on the wind cur...
In some closed water bodies with little inflow and outflow, a flow is gentle and its water quality gets worse by developing stratification. And its main dynamics of flow are circulation flow based on wind action on a water surface (mechanical disturbance) and a thermal convective flow by solar radiation. (thermal disturbance) In the present researc...
In some closed water bodies with little inflow and outflow, a flow is loose. So it has the different hydraulic characteristics from a river or an irrigation canal. When there is no disturbance, fluid is stratified based on vertical density distribution. In these bodies, the main dynanucs of the water environmental substance depends on a mechanical...
In some closed water bodies, the fluids are generally stratified based on vertical density differences. The causes of density these differences can be categorized as being due to temperature, salt levels, and turbidity. In addition, the dynamics of water environmental substances are induced by wind-induced turbulence, which is based on mechanical d...
Suspended sediment rating curves in small agricultural rivers draining a seasonally-cultivated watershed were established using two kinds of function regression models: the direct power function and the detransformed logarithmic function. Amelioration procedures, i.e. data stratification and seasonal data clustering, were introduced to make the fun...
2002年夏季の諌早湾において貧酸素水塊の現地観測を実施し,得られた結果に基づき貧酸素水塊の挙動特性を把握するとともに,密度躍層形成について検討した.その結果,まず,諌早湾においては観測期間(6月27日~8月31日)中に7月初旬と8月初旬の2回,小潮期に貧酸素水塊が形成され,これは密度躍層の存在と密接に関係することが認められた.つぎに,密度躍層の形成については,その支配因子である表層と底層間の塩分濃度差および水温差と降水量,潮差および風速との関係を検討した.表層と底層間の塩分濃度差および水温差と降水量については,4日前の諌早湾周辺7地点のアメダス降水量の平均値との間に強い相関があることがわかった.表層と底層間の塩分濃度差および水温差と潮差との関係については,潮差が2m未満の小潮時に比較して潮...
有明海湾奥西部海域での貧酸素現象の発生状況を把握するため,1972年から2002年までの浅海定線調査の観測値を用いて,底層の貧酸素現象の検討を行った.その結果,溶存酸素濃度は毎年夏季(6月~9月)に低下し,冬場に回復する年周期を繰り返していること,および溶存酸素濃度で4.3mg/Lを下回る貧酸素化現象が多くの観測地点で確認された.つぎに,統計的に有意な変化傾向の有無について検討を行う目的で,浅海定線調査の溶存酸素濃度データについて,正規確率分布によるあてはめを行った.その紘果,底層の溶存酸素濃度には明らかな経年的変化傾向は認められなかった.また,夏期に発生する底層の貧酸素化については,表層と底層の密度差に密接に関係することがわかった. This study focus on finding...
第1章 序論 1.1 はじめに 1.2 研究背景 第2章 閉鎖性水域における水生植物 2.1 水生植物群落の構造 2.2 水生植物の生活型 2.3 水生植物の生活型による湖沼の分類 2.4 水生植物による浄化作用 2.5 水生植物利用手法 2.6 密度流とその安定性 2.7 成層水域に及ぼす風の効果 第3章 密度2 成層場の乱流構造に関する実験 3.1 実験装置 3.2 浮遊性植物模擬方法 3.3 実験方法 3.4 空気の密度の決定方法 3.5 代表風速と空気の摩擦速度 3.6 塩分濃度と電圧の関係 3.7 塩水の密度の決定方法 3.8 水平,鉛直方向流速の算定 3.9 密度2 成層流における乱流構造 第4章 乱流構造に関する実験結果および考察 4.1 水平方向流速および乱れ強度 4.2 鉛...
The information of electric conductivity (EC) was investigated as an indicator for estimating total nitrogen concentration (T-N) in irrigation water. Water quality indicators, such as T-N, EC, and concentration of metallic elements and anions, were measured at rice terraces in Hoshino village, Yame-gun, Fukuoka prefecture, Japan. The rice terraces...
邦彦 濱上 寿人 井上 健 森- [...]
Yasumaru Hirai
We examined the influence of the aquatic plants given to the magnitude of thermal disturbance in the closed water body by hydraulic experiments which examined attenuation of underwater illuminance and the thermal boundary in the covered part which depending on the kind of the aquatic plant and the vegetation density. As the result, it is understood...
We aimed to obtain the fundamental data of the fertilizer characteristics of nitrogen in liquid compost (LC), which is produced from organic wastes such as human waste and sewage sludge. The rice cultivar Hinihokari was cultivated in pots, and 5 combinations of basal fertilization and topdressing using chemical fertilizer and LC were applied in the...
秀和 吉岡 邦彦 濱上 健 森- [...]
Kunihiko Hamagami
Numerical experiments were conducted by means of the k- ε turbulent model to understand the three dimensional turbulent structure of the wind induced flow in the closed water body. First, three types of the k- ε models were evaluated in terms of their adaptabilities to the wind induced flow. Next, the Low Reynolds number k- ε model, which had the b...