• 공업화학
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• 제18권2호
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• pp.162-167
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• 2007

본 연구에서는 Clostridium beijerinckii Donker 1926을 이용한 연속식 혐기성 소화공정에서 수소 생산과 동력학적 특성을 고찰하였다. 기질은 glucose를 사용하였고, 0.5, 0.25, 0.125일의 체류시간 (hydraulic retention time, HRT)에서 실험이 이루어졌으며, 모든 HRT의 조건에서 탄산화물은 99% 이상의 제거효율를 나타내었다. 체류시간이 짧을수록, COD 제거율은 낮은 반면에, 전체 가스 중에서 수소 가스 함량과 수소 발생량이 높게 나타났다. 또한, 정상상태에서, 증식 수율과 수소가스 생성 수율은 각각 0.27 g-VSS/g- glucose, 0.26 L/g-glucose로 나타났다. 본 실험에 사용된 균주를 glucose와 같이 당 성분이 함유된 폐수처리에 적용하면 수소를 생산할 수 있으며, 이러한 실험 결과들을 잘 활용하면 대체에너지로서, 실제적인 수소가스 생산 시스템에 적용할 수 있을 것이다.

• 한국전문물리치료학회지
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• 제8권1호
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• pp.9-19
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• 2001

During therapy sessions, feedback is often provided concurrently by the physical therapist as the patient attempts to perform a movement and after the movement attempt. This feedback is provided to enhance the patient's balance abilities. However, recent studies in nondisabled populations have suggested that frequent feedback may be detrimental to retention or learning of motor skills. This study compared the effects of 100% relative frequency of knowledge of performance (KP) with 66% relative frequency of KP for motor learning on balance retraining in patients with hemiplegia. Twenty patients with hemiplegic were randomly assigned to one of two experimental groups. The acquisition phase consisted of 16 blocks of 5 trials for 2 days (80 total practice trials). The retention phase consisted of 2 blocks of a short-term retention test, one day after the end of the acquisition phase and a long-term retention test, one week after the end of the short-term retention test. In the 100% feedback condition, participants received feedback after every practice trial. A faded KP schedule was used in the 66% condition. No significant differences were found between the two groups during all experimental phases (acquisition and retention phases), (p>.05). However, there were significant decreases in balance index for both groups of acquisition phase (p<.05). These results suggest that 66% relative frequency of KP is not more effective than 100% relative frequency of KP with respect to retention over time when hemiparetic patients attempt to learn balance.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2000년도 제26회 펄프종이기술 국제세미나
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• pp.1-10
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• 2000

The development of paper machines, increasing machine speeds with new, mostly low basis weight and/or high ash content paper grades, as well as the fact that several trends regarding process items have increased the sensitivity of papermaking. At the same time, papermakers are looking for flexibility in the production line. We can say that with all PMs the biggest benefits with the lowest capital spending can be achieved by focusing on improved wet end management. In order to manage wet end chemistry on a paper machine, our goal is to control sub-process through which we can influence the operation of the entire wet end with maximum effect. Key measurements and controls are-white water consistency control which is the most effective way to control retention - charge demand measurement and control which takes care of concentration of the anionic material entering to PM -ash measurements and controls which are deeply related to retention and paper quality This paper presents and concentrates to two of these key controls ; retention and charge. The purpose of charge control is to give the process control the tools to react to changes caused by amount of dissolved and colloida material incoming to wet end system. It is called coagulation or fixing control. Retention control is then taking care of retention aid flow to the process by responding any changes seen in white water consistency. It is called flocculation control. Each of these solutions separately , and even more effectively all together, stabilize the wet end operations and so greatly improve the produced paper quality and machine runnability. Practical results will be presented and they are referring to the latest mill cases. We have developed the first wet end measuring system in the late 1980s and control solutions based on this modern measuring technology were completely updated in 1990s. This paper introduces the principle, operation , and results of our unique wet end analyzers (retention and charge ) which are at the level of automation solutions as a part of paper machine quality control Especially our newest member of the platform , on-line charge analyzer has reached and set new standards to the on-line charge monitoring.

• 펄프종이기술
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• 제32권5호
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• pp.44-53
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• 2000

The development of paper machines, increasing machine speeds with new, mostly low basis weight and/or high ash content paper grades, as well as the fact that several trends regarding process items have increased the sensitivity of papermaking. At the same time, papermakers are looking for flexibility in the production line. We can say that with all PMs, the biggest benefits with the lowest capital spending can be achieved by focusing on improved wet end management. In order to manage wet end chemistry on a paper machine, our goal is to control subprocesses through which we can influence the operation of the entire wet end with maximum effect. Key measurements and controls are - white water consistency control which is the most effective way to control retention. - charge demand measurement and control which takes care of concentration of the anionic material entering to PM. - ash measurements and controls which are deeply related to retention and paper quality. This paper presents and concentrates to two of these key controls: retention and charge. The purpose of charge control is to give the process control the tools to react to changes caused by amount of dissolved and colloidal material incoming to wet end system. It is called coagulation or fixing control. Retention control is then taking care of retention aid flow to the process by responding any changes seen in white water consistency. It is called flocculation control. Each of these solutions separately, and even more effectively all together, stabilize the wet end operations and so greatly improve the produced paper quality and machine runnability. Practical results will be presented and they are referring to the latest mill cases. We have developed the first wet end measuring system in the late 1980s and control solutions based on this modern measuring technology were completely updated in 1990s. This paper introduces the principle, operation, and results of our unique wet end analyzers (retention and charge) which are at the level of automation solutions as a part of paper machine quality control. Especially our newest member of the platform, on-line charge analyzer has reached and set new standards to the on-line charge monitoring.

• 대한환경공학회지
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• 제30권2호
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• pp.175-180
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• 2008

본 연구는 Fill-Contact-Settle-Decant-Idle의 공정으로 구성된 활성슬러지 공정인 SBR(Sequencing bach reactor)공정에서 수리학적 체류시간을 24시간으로 하여 운전하였으며, 세포외 폴리머의 생성량, 흡착량, 제거율 등과 SRT와의 상관관계에 대한 특성을 조사하였다. 본 실험의 목적은 활성슬러지 시스템에서 다양한 SRT를 통한 생물흡착 특성을 결정하기 위한 것이다. 연구 결과 SRT(Sludge retention time)가 증가함에 따라 단위 미생물당 유기물 흡착율 및 제거율이 감소하는 것으로 나타났으며 단위 미생물당 생성되는 세포외 폴리머 양도 감소하는 것으로 나타났다. 생물흡착효율은 SRT가 증가할수록 높았고 SRT 30일에서 그 값은 53.2%였다. 하지만 단위 미생물당 생물흡착량은 SRT 2일에서(48.6 mg COD/gVSS) 가장 높게 관찰되었다. SRT에 따른 EPS량은 TSS, TCOD$_{Cr}$ 그리고 TKN에 의해 정량적으로 분석하였다. 상기의 결과로 인하여 슬러지의 플록 형성을 방해하여 슬러지의 침강성을 저해하며, COD 제거효율을 감소시키는 결과를 초래하는 것으로 사료된다. 따라서 미생물을 이용한 생물학적 공정 운영시 EPS의 특성을 고려하여 SRT, MLSS 유지, 유기물 부하량 등의 설계 인자를 적정히 선정하여 운영하는 것이 필요할 것으로 판단된다.

• Journal of Multimedia Information System
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• 제5권4호
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• pp.235-244
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• 2018

Potential maximum soil moisture retention (S) is a dominant parameter in the Soil Conservation Service (SCS; now called the USDA Natural Resources Conservation Service (NRCS)) runoff Curve Number (CN) method commonly used in hydrologic modeling for event-based flood forecasting (SCS, 1985). Physically, S represents the depth [L] soil could store water through infiltration. The depth of soil moisture retention will vary depending on infiltration from previous rainfall events; an adjustment is usually made using a factor for Antecedent Moisture Conditions (AMCs). Application of the method for continuous simulation of multiple storms has typically involved updating the AMC and S. However, these studies have focused on a time step where S is allowed to vary at daily or longer time scales. While useful for hydrologic events that span multiple days, this temporal resolution is too coarse for short-term applications such as flash flood events. In this study, an approach for deriving a time-variable potential maximum soil moisture retention curve (S-curve) at hourly time-scales is presented. The methodology is applied to the Napa River basin, California. Rainfall events from 2011 to 2012 are used for estimating the event-based S. As a result, we derive an S-curve which is classified into three sections depending on the recovery rate of S for soil moisture conditions ranging from 1) dry, 2) transitional from dry to wet, and 3) wet. The first section is described as gradually increasing recovering S (0.97 mm/hr or 23.28 mm/day), the second section is described as steeply recovering S (2.11 mm/hr or 50.64 mm/day) and the third section is described as gradually decreasing recovery (0.34 mm/hr or 8.16 mm/day). Using the S-curve, we can estimate the hourly change of soil moisture content according to the time duration after rainfall cessation, which is then used to estimate direct runoff for a continuous simulation for flood forecasting.

• 한국직업건강간호학회지
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• 제6권1호
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• pp.53-71
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• 1997

Across sectional study was performed to evaluate the chronic effects on central nerve system(CNS) of cumulative exposure of complex organic solvents, using neurobehavioral test. Subjects were 66 (male) dock yard painters of some large ship industry which is located in Ulsan. The neurobehavioral test battery used in this study was NCTB (Neurabehavioral Core Test Battery recommended by WHO(World Health Organization), which consisted of 7 items-Profile of mood states (POMS), Simple reaction time, Santa Ana dexterity test. Digit span, Digit symbol, Benton visual retention test and Pursuit aiming. The subjects were classified by 3 groups according to duration of employment(group 1 ; less than 9 years, group 2 ; 10-14 years, group 3 ; more than 15 years). The results of performance were analyzed considering of work duration, age, educational level, alcohol drinking, smoking and testing time as confounding factors. Benton visual retention test, pursuit aiming correct dot and sum of dot showed significant differences among the groups, and decreased with increasing work duration. It indicated that the mean scores of performance ability were lowering according to work duration. Besides, the tests that didn't show statistical significances but showed linear trends were depression-dejection, vigor, fatigue of POMS, slowest time of simple reaction time and digit span forward. Most of the neurobehavioral test items were correlated with age and educational level. After controlling of confounding factors-age and educational level, the results followed ; digit span backward was different significantly. Tension-anxiety, depression-dejection, anger-hostility of POMS, SD and slowest time of simple reaction time, Santa Ana dexterity test non-preferred hand, digit span forward, Benton visual retention test and pursuit aiming correct dot decreased with increasing of work duration. The correlation analysis was done in order to find out the relationship between subjective symptom and the scores of neurobehavioral core test battery. According to the results of analysis there were no items that had statistical significant relationship(p<0.05).

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.325-328
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• 2000

The control of the data retention time is a main issue for realizing future high density dynamic random access memory. In this paper, we propose the new implantation scheme by gate-related ion beam shadowing effect and buffer-enhanced $\Delta$ Rp increase using buffered N- implantation with tilt and 4X-rotation that is designed on the basis of the local-field-enhancement model of the tail component. We report an excellent tail improvement of the retention time distribution attributed to the reduction of electric field across the cell junction due to the redistribution of N- concentration which is intentionally caused by Ion Beam Shadowing and Buffering Effect using tilt implantation with 4X-rotation.

• 한국환경보건학회지
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• 제26권4호
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• pp.15-20
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• 2000

The studies of swine wastewater treatment aim to development of process using soil microorganism. Removal rate of swine wastewater containing organic matter was 99 percent in case of high loading rate. Microorganism was devoted to improve the treatment efficiency of the process. According to the result obtained from biological treatment of high loading rate swine wastewater. Hydraulic retention time was 2.3 days in unit process of biological phosphorus removal. BO $D_{rm}$ / $P_{rm}$ ratio was 1122 in room temperature anaerobic process and 355.6 in mesophilic anaerobic process. And then phosphorus removal rate mesophilic anaerobic process was 3 time as much as than room temperature acaerobic process.

• Membrane and Water Treatment
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• 제1권4호
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• pp.253-271
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• 2010

A theoretical study for the flux enhancement by pulsation of transmembrane pressure is presented for osmotic pressure controlled ultrafiltration under laminar flow regime. The transient velocity profile is solved analytically using Green's function method. Time dependent convective diffusive equation is solved to quantify the membrane surface concentration and the permeate flux, numerically. The effects of the amplitude and frequency of pulsation on flux, surface concentration and observed retention are studied.