• Journal of Korea Water Resources Association
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• v.37 no.7
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• pp.569-579
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• 2004

Recently, the extreme drought is often occurred due to the global warming and the serious weather changes. Also, the problems of the water pollution In the developed areas, the oppositions from people in the upper stream area and water concession from the local governments affect the national request to get more clean water resources in upper stream of the undeveloped areas. It also brings on the necessity of recognition for water supply managements. Therefore, as the water demand is rapidly changes in the metropolitan areas, the capability of water supply from the north Han river basin dams should be appropriately investigated. In this study, we developed a simulation system using STELLA (equation omitted) software environment, a shared vision model, to analyze the possibility of the stable water supply from north Han river basin dams. Also, three different rules are applied on this model by dividing the water level to minimum(Rule 1), medium(Rule 2) and maximum(Rule 3). Using the rules, the safety yield changes are analyzed for dam rule curve of the reservoir and hydropower release.

• Journal of Korea Water Resources Association
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• v.32 no.5
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• pp.525-535
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• 1999

An optimal unit commitment model for efficient management of water and energy resources in a basin using combined mixed integer programming is developed. The combined mixed integer programming model is able to solve the inconsistency problem that may occur from mixed integer programming models. The technique which enables the use of conditional constraints and either-or constraints in the linear programming is also suggested. As a result of applying the combined mixed integer programming model to Lower Colorado River Basin in United States. the basin efficiency is decreased by 1.53% from the results of the mixed integer programming, while it is increased by 0.67% from the results of the historical operation. It is found that the decreased allowable error between power supplies and demands in the combined mixed integer programming causes the decreased basin efficiency.

• Journal of the Korean Institute of Rural Architecture
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• v.20 no.1
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• pp.69-76
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• 2018

This study is to research technical measures for improving energy efficiency in the conservation and reuse of historic buildings focused on the recent research trends and case studies of the west. These measures are broadly classified into three types, the passive measures for saving energy and increasing comfort, the most cost-effective energy saving strategies, and the renewable energy sources. Firstly, the passive measures are divided into the elements and systems. The passive elements are awnings and overhanging eaves, porches, shutters, storm windows and doors, and shade trees. There are also the natural ventilation systems such as the historic transoms, roofs and attics to improve airflow and cross ventilation to either distribute, or exhaust heat. Secondly, the most cost-effective energy efficiency strategies are the interior insulation, airtightness and moisture protection, and the thermal quality improvement of windows. The energy efficiency solutions of modern buildings are the capillary-active interior insulation, the airtightness and moisture protection of interior walls and openings, and the integration of the original historic window into the triple glazing. Beyond the three actions, the additional strategies are the heat recovery ventilation, and the illumination system. Thirdly, there are photovoltaic(PV) and solar thermal energy, wind energy, hydropower, biomass, and geothermal energy in the renewable energy sources. These energy systems work effectively but it is vital to consider its visual effect on the external appearance of the building.

• Geomechanics and Engineering
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• v.11 no.4
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• pp.531-552
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• 2016

The greenschist in the Jinping II Hydropower Station in southwest China exhibits continuous creep behaviour because of the geological conditions in the region. This phenomenon illustrates the time-dependent deformation and progressive damage that occurs after excavation. In this study, the responses of greenschist to stress over time were determined in a series of laboratory tests on samples collected from the access tunnel walls at the construction site. The results showed that the greenschist presented time-dependent behaviour under long-term loading. The samples generally experienced two stages: transient creep and steady creep, but no accelerating creep. The periods of transient creep and steady creep increased with increasing stress levels. The long-term strength of the greenschist was identified based on the variation of creep strain and creep rate. The ratio of long-term strength to conventional strength was around 80% and did not vary much with confining pressures. A quantitative method for predicting the failure period of greenschist, based on analysis of the stress-strain curve, is presented and implemented. At a confining pressure of 40 MPa, greenschist was predicted to fail in 5000 days under a stress of 290 MPa and to fail in 85 days under the stress of 320 MPa, indicating that the long-term strength identified by the creep rate and creep strain is a reliable estimate.

• Geomechanics and Engineering
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• v.12 no.4
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• pp.595-609
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• 2017

Due to high in-situ stress and brittleness of rock mass, the surrounding rock masses of underground caverns are prone to appear splitting failure. In this paper, a kind of loading-unloading variable elastic modulus model has been initially proposed and developed based on energy dissipation principle, and the stress state of elements has been determined by a splitting failure criterion. Then the underground caverns of Dagangshan hydropower station is analyzed using the above model. For comparing with the monitoring results, the entire process of rock splitting failure has been achieved through monitoring the splitting failure on side walls of large-scale caverns in Dagangshan via borehole TV, micro-meter and deformation resistivity instrument. It shows that the maximum depth of splitting area in the downstream sidewall of the main power house is approximately 14 m, which is close to the numerical results, about 12.5 m based on the energy dissipation model. As monitoring result, the calculation indicates that the key point displacement of caverns decreases firstly with the distance from main powerhouse downstream side wall rising, and then increases, because this area gets close to the side wall of main transformer house and another smaller splitting zone formed here. Therefore it is concluded that the energy dissipation model can preferably present deformation and fracture zones in engineering, and be very useful for similar projects.

• Journal of Korea Water Resources Association
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• v.34 no.6
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• pp.617-625
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• 2001

Peace dam constructed against the water attack had stopped in the first step, linked with Hwacheon dam through bypass tunnels and had an effect of flood surcharging in its pocket on Hwacheon dam downstream. To study the utility of Peace dam, the flood control effects of Peace dam and the restricted water level (RWL) in Hwacheon dam were reviewed and identified with operating Hwacheon dam system. Analysing the results the ideas of expanding the usability of the water resources in Hwacheon dam system were suggested. To do that, the criteria and the model of reservoir operation were established frist and the optimization of the operation have done. Based on the results the performance of the optimization was evaluated as an reference coefficient with relative value of the registered data to the optimized. And examining several alternatives for the RWL in Hwacheon reservoir operation made more feasible RWL suggested. And its economic benefit was also reckoned.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.1
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• pp.91-100
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• 1985

This study is on the gate operation of dams, which are for the hydropower and multipurpose in Han River Basin, considering the safety under the emergency. The results of the study on the safety of dams in Han River Basin associated with the gate operation of dams against the design flood flow and the combined inflow are as follows; 1) The empirical formula (1) can be used for gate operation with the informations of reservoir's water level and the inflow. 2) The applicability of the multiple regression formula (2) among the gate opening area, inflow, water level, and outflow is assured. 3) From the safety analysis of dams for the emergency by the procedures developed in this study, six dams are safe except Soyanggang, Euiam, and Cheongpyung Dam, but the above three dams can be safe with the lowering of the starting water level of gate opening by the pre-discharges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.141-149
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• 1993

Production of hydro-energy is random in its output amount due to the characteristics of the reservoir inflows. Therefore, it is necessary to provide the rationality in determining the amount of energy for a supply contract. This study presents a methodology for determining reasonably reliable amount of the energy supply considering the energy sale-incomes associated with the penalties which are subject to inflow-reliabilities. The objective function consists of the returns of energy sales and the risk-loss function to reflect statistically relevant risks. A range of the coefficient of the risk-loss function was figured out by its sensitivity analysis. The risk-loss herein means the penalty which should be paid by the energy supplier in case that the level of the energy supply is behind the contracted amount. And the reliability of reservoir inflow is defined by the exceedance probability of the inflow. The log-normal distribution was accepted as the probability density function of monthly inflows on the level of significance at 5%. Golden-ratio searching was applied to identify the optimal reliability and Incremental Dynamic Programming was used to maximize generation of the hydro-power energy in reservoir operation. The algorithm was the applied to the Daechung multi-purpose reservoir and hydro-power plant system in order to verify its usefulness.

• Geomechanics and Engineering
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• v.14 no.3
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• pp.271-281
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• 2018

A jointed rock slope stability evaluation was simulated by a discontinuous deformation analysis numerical method to investigate the process and safety factors for different crack distributions and different overloading situations. An optimized method using Discontinuous Deformation Analysis for Rock Failure (DDARF) is presented to perform numerical investigations on the jointed rock slope stability evaluation of the Dagangshan hydropower station. During the pre-processing of establishing the numerical model, an integrated software system including AutoCAD, Screen Capture, and Excel is adopted to facilitate the implementation of the numerical model with random joint network. These optimizations during the pre-processing stage of DDARF can remarkably improve the simulation efficiency, making it possible for complex model calculation. In the numerical investigations on the jointed rock slope stability evaluations using the optimized DDARF, three calculation schemes have been taken into account in the numerical model: (I) no joint; (II) two sets of regular parallel joints; and (III) multiple sets of random joints. This model is capable of replicating the entire processes including crack initiation, propagation, formation of shear zones, and local failures, and thus is able to provide constructive suggestions to supporting schemes for the slope. Meanwhile, the overloading numerical simulations under the same three schemes have also been performed. Overloading safety factors of the three schemes are 5.68, 2.42 and 1.39, respectively, which are obtained by analyzing the displacement evolutions of key monitoring points during overloading.

• Advances in concrete construction
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• v.9 no.5
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• pp.449-457
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• 2020

The influence of subsequent curing on the performance of fly ash contained mortar under steam curing was studied. Mortar samples incorporated with different content (0%, 20%, 50% and 70%) of Class F fly ash under five typical subsequent curing conditions, including standard curing (ZS), water curing(ZW) under 25℃, oven-dry curing (ZD) under 60℃, frozen curing (ZF) under -10℃, and nature curing (ZN) exposed to outdoor environment were implemented. The unsteady chloride diffusion coefficient was measured by rapid chloride migration test (RCM) to analyze the influence of subsequent curing condition on the resistance to chloride penetration of fly ash contained mortar under steam curing. The compressive strength was measured to analyze the mechanical properties. Furthermore, the open porosity, mercury intrusion porosimetry (MIP), x-ray diffraction (XRD) and thermogravimetric analysis (TGA) were examined to investigate the pore characteristics and phase composition of mortar. The results indicate that the resistance to chloride ingress and compressive strength of steam-cured mortar decline with the increase of fly ash incorporated, regardless of the subsequent curing condition. Compared to ZS, ZD and ZF lead to poor resistance to chloride penetration, while ZW and ZN show better performance. Interestingly, under different fly ash contents, the declining order of compressive strength remains ZS>ZW>ZN>ZD>ZF. When the fly ash content is blow 50%, the open porosity grows with increase of fly ash, regardless of the curing conditions are diverse. However, if the replacement amount of fly ash exceeds a certain high proportion (70%), the value of open porosity tends to decrease. Moreover, the main phase composition of the mortar hydration products is similar under different curing conditions, but the declining order of the C-S-H gels and ettringite content is ZS>ZD>ZF. The addition of fly ash could increase the amount of harmless pores at early age.