• Toxicological Research
• /
• 제18권2호
• /
• pp.107-116
• /
• 2002

Arsenic (As) is a ubiquitous element found in several forms in foods and water. Although certain foods, such as marine fish, contain substantial levels of organic arsenic forms, they are relatively low in toxicity compared to inorganic forms. in contrast, arsenic in drinking water is predominantly inorganic and highly toxic. Chronic ingestion of arsenic-contaminated drinking water is therefore the major pathway posing potential risk to human hearth. since the early 1990s in Bangladesh ozone, arsenic exposure has caused more than 7,000 deaths and uncounted thousands shout symptoms of long-term arsenic poisoning. Significant portion of world populations are exposed to low to moderate levels of arsenic of parts per billion (ppb) to hundreds of ppb. As a consequence, the World Health Organization (WHO) and U.S. environmental health agencies, such as the Environmental Protection Agency (EPA) made arsenic their highest priority. Recently, the WHO, European Union (EU), and US. EPA lowered an acceptable level of 10 ppb for arsenic in drinking water In this article, various health effects of arsenic in drinking water were reviewed and the current status for risk assessment to regulate arsenic in drinking water was discussed.

• 한국생산제조학회지
• /
• 제21권6호
• /
• pp.946-953
• /
• 2012

When water shortage has been getting worse recently, toilet water-saving is one of the most effective way to solve the water shortage. Therefore, in this study, toilet flushing performance was investigated with VOF(Volume Of Fluid) model to obtain the basic design data for the development of high-efficiency toilets. The result showed that the shorter trapway, the longer the flushing duration time. However, the shorter trapway is found to have disadvantage in exhausting dirt due to relatively weak siphon and higher curvature. Since the remaining water in a trapway appears to help siphon, it is also an important factor in developing high-efficiency toilets. Although higher water level in the water tank shows better performance in flushing, lower water level is preferred to save water. Too low water level may cause dirt to clog the trapway due to relatively weak siphon.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2022년도 학술발표회
• /
• pp.458-458
• /
• 2022

It is essential to reduce global carbon emissions, mainly from energy use. The water supply and distribution sector is a vital part of human society and is one of the primary energy consumers. The procurement and distribution of water require electricity to operate the pump to deliver water to users with sufficient pressure. As the water users are spatially distributed over a wide area, the energy required to deliver water to each user differs depending on the corresponding supplying element (reservoir, tank, pipe, pump, and valve). This difference in energy required for each user also comes with a difference in pressure availability which affects the level of service for individual users and the whole network. Typically, there is a disproportion where users close to the source experience excessively high pressure with low energy consumption. In contrast, remote users need more energy to get the minimum pressure. This study proposes the Energy Return Index (ERI) to quantify the pressure return from particular energy consumption to supply water to each node. The disproportionality can be quantified and identified in the network using the proposed ERI. The index can be applied to optimize the network elements such as pump operation and tank location/size to reach a balanced energy consumption with the appropriate level of service.

• 한국농공학회논문집
• /
• 제56권6호
• /
• pp.113-119
• /
• 2014

This study aims to evaluate the behavior of poorly-compacted raised reservoir levee with water level raising by using centrifugal model test. From the test results, it seems that the hydraulic fracturing at the core of the raised reservoir levee with low degree of compaction possibly occurs due to the drastical increase of pore water pressure by water level raising. Additionally, the continuous infiltration may induce crack and/or sinkhole on the surface of the poorly-compacted raised reservoir levee owing to the increase of the subsidences at the crown and the front side of that. Therefore, reasonable construction management for the compaction of the raised reservoir levee is needed.

• 대한전기학회논문지:전력기술부문A
• /
• 제48권10호
• /
• pp.1251-1258
• /
• 1999

The water level control of a steam generator in the unclear power plant is an important process. Most of the water level controllers of the actual plant are PID controllers. But they have limitations in appling for tracking the set point and getting rid of disturbances, so there are some defects to apply in the actual ground even though many research works represented the resolutions to solve it. In this paper, it is suggested that the established simple PID controller in low power has the ability to remove disturbances and trace the set-point, and then possesses the real-time self-tuning function according to the variety of moving peculiarity of a plant. This function realized by making use of fuzzy logic. PID parameters are formulated by a variable ${\alpha}$ and made it fluctuate by a fuzzy inference according to level error and level error change. This mechanism makes application of actual plant effective as well as taking advantage of improving the efficiency of water level controller by way of adding the function of self-tuning instead of replacing PID controller. The computer simulation of this scheme shows the improved performance compare to conventional PID controller.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2005년도 추계 학술대회논문집
• /
• pp.39-44
• /
• 2005

In HANARO, a multi-purpose research reactor of 30 MWth, the emergency water supply system consists essentially of an emergency water storage tank located in the level of about thirteen meter (13 m) above the reactor core, a three inch ('3\%') diameter water injection pipe line including injection valves from the tank to the reactor cooling inlet pipe and a test loop to do periodic system performance test. When the water level of the reactor pool comes down to the extremely low due to a loss of reactor pool water accident the emergency water stored in the tank should be fed to the core by the gravity force and at that time the design flow rate is eleven point four kilogram per second (11.4 kg/s). But it is impossible periodically to measure the injection flow rate under the emergency condition because the normal water level should be maintained during the reactor operation. This paper describes a flow network analysis to simulate the flow rate under the emergency condition. As results, it was confirmed through the analysis results that the calculated flow rate agrees with the design requirement under the emergency condition.

• 한국소음진동공학회논문집
• /
• 제17권3호
• /
• pp.226-234
• /
• 2007

This study aims to evaluate noise emission from water supply and drain installations in apartment bathroom. These noise were one of the most annoying noise sources in apartment houses. Especially, drain plumbing system have used bellow bathroom ceiling, it was very discomfort to hear the noise in bellow apartment. Noise of closets and faucets were measured which were main noise source, then these noise were evaluate and analyzed the emitting characteristics varying the supplying water pressure. As increasing the water pressure, also total noise level of the water supplying stool noise and faucet noise were increased. Especially the water closet showed remarkably the increasing noise level in middle and high frequency bandwidth, while the noise level of faucets increased in $50\;Hz{\sim}250\;Hz$ of low frequency bandwidth. Vortex closet were favorable to syphon closet, and lever faucet were favorable to conventional lavatory faucet on reducing the noise. Above these results could be used in basic data establishing KS (Korean Standard) for evaluation and rating procedure and measures reducing these noise.

• Geomechanics and Engineering
• /
• 제30권2호
• /
• pp.201-210
• /
• 2022

This paper presents a study regarding the influence of various water levels on the characteristics of subgrade mud pumping through a self-developed test instrument. The characteristics of mud pumping are primarily reflected by axial strain, excess pore water pressure, and fine particle migration. The results show that the axial strain increases nonlinearly with an increase in cycles number; however, the increasing rate gradually decreases, thus, an empirical model for calculating the axial strain of the samples is presented. The excess pore water pressure increases rapidly first and then decreases slowly with an increase in cycles number. Furthermore, the dynamic stress within the soil first rapidly decreases and then eventually slows. The results indicate that the axial strain, excess pore water pressure, and the height and weight of the migrated fine particles decrease significantly with a low water level. In this study, when the water level is 50 mm lower than the subgrade soil surface, the issue of subgrade mud pumping no longer exist.

• 한국산림과학회지
• /
• 제33권1호
• /
• pp.1-32
• /
• 1977

황폐림지(荒廢林地)의 토양(土壤)이 배지(培地)로 될 때 경사별(傾斜別) 토양수분상태(土壤水分狀態)를 파악(把握)하고 여러가지 토양수분상태(土壤水分狀態)가 피복용(被覆用)의 식물(植物)의 생장(生長)에 미치는 영향과 피복식물(被覆植物)의 수분요구도(水分要求度) 및 내건성(耐乾性)을 관찰(觀察), 조사(調査)하고 토양수분(土壤水分)이 결핍(缺乏)된 환경에서 시비효과(施肥效果) 및 수분이용(水分利用) 효율(效率)을 구명(究明)하므로서 보다 합리적(合理的)이며 효과적(效果的)인 황폐림지(荒廢林地) 지피식생조성방법(地被植生造成方法)에 관련(關聯)되는 이론적(理論的) 배경(背景)을 모색(摸索)하기 위하여 본(本) 연구(硏究)가 실시(實施) 되었다. 본(本) 연구과정(硏究過程)은 야외시험(野外試驗)과 온실시험(溫室試驗)으로 구성(構成)되어 있으며 야외(野外) 시험(試驗)은 건기(乾期)와 우기(雨期)에 걸쳐 3 경사지(傾斜地)에서 4 시비수준(施肥水準) 2 파종방법(播種方法)에 대한 피복식물(被覆植物)(아까시나무, 싸리, 새)의 생장상태(生長狀態)를 조사분석(調査分析) 하였다. 온실시험(溫室試驗) 3 수분처리(水分處理), 4 시비수준(施肥水準)에 대한 피복식물(被覆植物)의 생장(生長)을 신장생장(伸長生長), 중량생장(重量生長)으로 조사분석(調査分析) 하였다. 현지(現地)의 입지환경(立地環境) 및 토양수분상태(土壤水分狀態)의 변화(變化)를 측정(測定)하기 위하여 기온(氣溫) 온도(溫度), 강우량(降雨量) 등(等)이 조사부분(調査分析) 되었고 토양수분측정용(土壤水分測定用) Soil cell을 경사별(傾斜別)로 모두 24개(個) 설치(設置) 조사(調査)하였다. 화강편마암(花崗片麻岩)을 모재(母材)로 하는 본황폐림지(本荒廢林地)는 경사도(傾斜度)에 따라 토심(土深) 및 토성(土性)이 다르게 나타나며 이러한 토양조건(土壤條件)은 경사도별(傾斜度別) 토양수분체계(土壤水分體系)를 지배(支配)한다. 완경사지(緩傾斜地) ($17^{\circ}$)는 토심(土深)이 20cm 이상(以上)이며 토성(土性)은 양토(壤土)로서 우기(雨期)동안에 토양수분(土壤水分)은 항상 위조점(萎凋點) 이상(以上)의 유효수분(有效水分)을 보지(保持)하고 있으며, 중경사지(中傾斜地)($25^{\circ}$)는 토심(土深)이 15cm, 토성(土性)은 사질양토(砂質壤土)로서 우기(雨期)동안 토양수분(土壤水分)은 때때로 위조점(萎凋點) 가까이 까지 떨어졌다. 그러나 급경사지(急傾斜地) ($37^{\circ}$)는 토심(土深)은 10cm, 토성(土性)은 사질양토(砂質壤土)로서 우기(雨期)에도 토양수분(土壤水分)이 때때로 위조점(萎凋點) 이하(以下)로 떨어졌다. (표(表) 6 참조) 이상(以上)과 같은 연구(硏究)에 의하여 얻어진 결과(結果)를 요약(要約)하면 다음과 같다. 1. 본연구재료(本硏究材料)로 쓰인 3가지 식물(植物)의 초기생장기간중(初期生長期間中)의 수분요구도(水分要求度)의 상대적(相對的) 수준(水準)을 분석(分析)할 때 다음과 같은 결론(結論)을 얻을 수 있다. 즉(卽) 아까시 나무는 수분요구도(水分要求度)가 높고 (자연보수력수준(自然保水力水準) 내건성(耐乾性)은 비교적(比較的) 약(弱)하다. 싸리는 수분요구도(水分要求度)가 낮고(유효수분(有效水分)의 50%수준(水準)) 내건성(耐乾性)은 강(强)하다. 새는 수분요구도(水分要求度)가 보통(普通)이며 내건성(耐乾性)은 비교적(比較的) 약(弱)하다. 2. 피복용(被服用) 식물(植物)의 토양수분(土壤水分) 조건(條件)에 따른 시비효과(施肥效果)는 수분(水分)이 적을 때에는 잘 나타나지 않으나 수분(水分)이 충분(充分)할 때에는 매우 잘 나타난다. 즉(卽) 토양수분(土壤水分)과 시비처리(施肥處理)의 상호작용(相互作用)이 식물생장(植物生長)에 미치는 영향은 매우 크다. 3. 피복용(被服用) 식물(植物)의 토양수분조건(土壤水分條件)에 따른 양분요구도(養分要求度)는 다음과 같다. 초기생장시(初期生長時) 토양수분(土壤水分)이 건조(乾燥)하면 3 식물(植物)이 모두 낮은 시비수준(施肥水準)에서 생장(生長)이 좋고 토양수분(土壤水分)이 적윤(適潤)하면 아까시 나무와 새는 높은 시비수준(施肥水準)에서 생장(生長)이 좋게 나타난다. 후기생장시(後期生長時) 3 식물(植物) 모두 토양수분수준(土壤水分水準) 의 증가(增加)와 함께 높은 시비수준(施肥水準)이 생장(生長)에 주는 효과(效果)가 컸다. 4. 시비수준별(施肥水準別) 수분이용효율(水分利用效率)은 아까시 나무와 새의 경우 건조지(乾燥地)에 있어서는 낮은 시비수준(施肥水準)(1g 수준(水準))의 수분이용효율(水分利用效率)이 높고 적윤지(適潤地)에 있어서는 높은 시비수준(施肥水準)(3g 수준(水準))의 수분이용효율(水分利用效率)이 높았다. 싸리의 경우 모든 수분조건하(水分條件下)에서 공(共)히 낮은 시비수준(施肥水準)(1g 수준(水準))의 이용효율(利用效率)이 높았다. 5. 아까시 나무와 싸리는 인산(燐酸)의 요구도(要求度)가 인정(認定)되나 새는 인정(認定)되지 않으며 황폐림지(荒廢林地) 토양수분결핍(土壤水分缺乏)은 식물(植物)의 인산흡수(燐酸吸收)를 저해(沮害)한다.

• 대한원격탐사학회지
• /
• 제16권2호
• /
• pp.117-133
• /
• 2000

We studied the sea level variations at Kerguelen island in the South Indian Ocean with ARGOS data and meteorological data during about 1 year(May 1993~April 1994) through using filter, spectral analysis, coherency and phase, and found characteristics for the two oceanic signal levels(detided oceanic signal level, h$_{detided}$ and seasonal oceanic level, h$_{corr.ib}$). The forms of atmospheric pressure variations are good agreed to between ARGOS data and meteorological data in the observed periods. This Kerguelen area shows the inflow of an air temperature(gain of a radiant heat) into the sea water and the stagnation of high atmospheric pressure bands in summer, and the outflow of a sea water temperature(loss of sensible and latent heat) toward the atmosphere and the stagnation of low atmospheric pressure bands in winter. The seasonal difference of sea level between summer and winter is about 1.6cm. Both the detided oceanic signal level(h$_{detided}$) variation and the inverted barometer level(h$_{ib}$) variation have a strong correlation for T>1day period bands. The characteristics of h$_{detided}$ variation are not decided by the influence of any meteorological distributions (atmospheric pressure), but the influence of other factors(bottom water temperature) for T>2days periods bands. h$_{corr.ib}$ plays a very important role of sea level variation in the observed periods (especially T>about 180days period bands).