• 콘크리트학회지
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• 제10권6호
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• pp.313-323
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• 1998

고성능 AE감수제를 사용한 콘크리트의 유동성 유지성능은 고성능 AE감수제의 주성분 및 사용량, 사용방법과 광물질 혼화재의 종류 및 혼합률 등에 따라서 영향을 받는다. 본 연구에서는 주성분이 다른 3종류의 고성능 AE감수제의 사용량과 사용방법을 변화시키고 분말도가 다른 3종류의 고로슬래그 미분말을 활용하여 시멘트풀, 모르터 및 콘크리트의 유동성 유지성능과 강도특성을 비교고찰하여 효율적인 유동성 유지방안을 제시하고자 하였다. 연구결과 고성능AE감수제를 사용한 콘크리트의 유동성 유지성능은 경과시간에 따른 시멘트 입자의 응집성과 밀접한 상관성이 있으며 나프탈린계 고성능 AE감수제의 사용과 고로슬래그 미분말의 분말도가 작고 혼합률이 클수록 모르터 및 콘크리트의유동성 유지성능이 현저히 향상되었다. 한편 고성능AE감수제의 종류에 관계없이 30분후 첨가방법이 유동성 유지성능 및 강도향상에 있어서 일석이조의 좋은 성과가 있었다.

• 한국전문물리치료학회지
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• 제23권4호
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• pp.16-26
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• 2016

Background: Deficiencies in the ability to maintain balance are common in elderly. Augmented feedback such as knowledge of results (KR) can accelerate learning and mastering a motor skill in older people. Objects: We designed this study to examine whether one session of Wii-Fit game with self-regulated KR is effective for elderly people, and to compare the effect of two different timings of self-regulated KR conditions. Methods: Thirty-nine community-dwelling elders, not living in hospice care or a nursing home, participated in this study. During acquisition, two groups of volunteers were trained in 10 blocks of a dynamic balancing task under the following 2 conditions, respectively: (a) a pre-trial self-regulated KR ($n_1=18$), or (b) a post-trial self-regulated KR ($n_2=21$). Immediate retention tests and delayed retention tests of balancing performance were administered in 15 minutes and 24 hours following acquisition period, respectively. Results: In both groups, significant improvements of balancing performances scores were observed during the acquisition period. Regardless of the group, mean of balancing performance scores on retention tests were well-maintained from the final session. There were no significant differences between groups in balancing performance scores during the acquisition period (p>.05); however, the post-trial self-regulated KR group exhibited significantly higher balancing performance scores in both the immediate retention test and delayed retention test than that of the pre-trial self-regulated KR group (p<.05). Conclusion: Therefore, subjects who regulated their feedback after a dynamic balancing task, during the acquisition period, experienced more efficient motor learning during the retention period than did subjects who regulated their feedback before a dynamic balancing task. Accordingly, in case of presenting the KR of motor learning in clinical settings to elders who reduced dynamic balance abilities, the requesting time of KR is imperative according to self-estimation processes as well as types of KR and practice.

• 한국습지학회지
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• 제12권2호
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• pp.67-73
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• 2010

본 연구는 오염이 심한 유수지를 지속적으로 양호한 수질로 유지하기 위한 효율적 방안을 모색하고자 수행되었다. 유수지 수질을 양호하게 유지하려면 외부로부터 유입되는 비점오염원의 유입 차단이 필요하다. 본 연구에서는 이의 방안으로 다공성 슬래그의 활용을 제안하였다. 다공성 슬래그 넷트를 유수지에 설치하는 경우의 수질 변화를 알아보기 위하여 오염물질의 제거 정도를 실험하였다. 그 결과 접촉 시간과 인 제거 효율 간에는 높은 상관관계($r^2=0.9765$)를 나타내어 접촉시간이 처리효율에 미치는 중요한 인자임을 알 수 있었으며, 인과 부유물질은 조제 시료, 생물학적 처리수, 하수 모두 다공성 슬래그 충전상을 통과하면서 높은 효율로 제거됨을 확인할 수 있었다. 이로부터 비점오염원의 유입 방지를 위하여 유수지 수중 내부와 외부 호안에 다공성 슬래그 충전상의 설치방안을 제안하였다.

• 한국해양학회지:바다
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• 제18권1호
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• pp.47-52
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• 2013

생태계 질소 순환 연구에서 동위원소 추적자를 이용한 실험은 그 유용성에도 불구하고, 무기 질소의 안정동위원소 측정이 어려워 자료의 생산이 활발하지 못한 형편이다. Gardner et al. (1996)은 HPLC (high performance liquid chromatography)를 이용하여 비교적 간편하고 정밀하게 암모늄의 동위원소 비를 측정하는 방법을 개발해 질소순환 연구에 활발하게 활용하였다. 그러나 일반적이지 않은 syringe 펌프가 필요해 다른 실험실에 이 시스템이 도입되지는 못하였다. 본 연구에서는 최신 HPLC 펌프 기술을 활용하여 Dr. Gardner 그룹 이후 최초로 암모늄 동위원소비 측정 시스템을 구축하였다. 표준시료 측정 결과 RTS (retention time shift)는 안정동위원소 비와 좋은 상관관계를 보였다. 이 시스템은 측정 자료를 디지털 형태로 변환하는 장치까지 갖추어 컴퓨터 프로그램을 이용한 다양한 자료처리가 가능하다. 특히 Matlab$^{(R)}$ 이용하여 retention time 계산에 peak 면적을 이용함으로써 측정의 정확성을 높이고, 직선성을 향상할 수 있었다. 영산강 하구 해수를 가지고 실시한 $^{15}N$-암모늄 첨가 실험에서 $^{15}N/^{14}N$ 비율 변화를 HPLC-RTS법을 통해 측정하였으며, 식물성 플랑크톤에 의한 암모늄 섭취와 재광물화 과정을 각각 독립적으로 측정하는 것이 가능했다.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제21권2호
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• pp.331-345
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• 2007

본 연구에서는 중학생들이 수학 평가 결과를 어떻게 파지하는지를 탐구하고자 하였다. 이를 위해, 측정시기, 문항 유형, 성적, 평가요소 등을 학생들이 평가결과를 파지하는데 중요한 요인이라고 보고 이 변인들과 관련된 학생들의 평가결과 파지 유형을 분류하였다. 이를 토대로, 두 명의 연구 참여자를 선정하여 심층면담을 진행함으로써 그들의 평가에서 핵심적인 역할을 하는 요소가 무엇이며 그것이 향후에 어떤 형태로 파지되어 나타나는지를 분석함으로써 중학생들의 수학과 평가 결과의 파지 유형을 분석하였다.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2003년도 춘계학술발표논문집
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• pp.80-92
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• 2003

The water retention of coating colors can be accurately measured by devices such as an AA-GWR water retention meter whose principle of measurement is based on pressure filtration of coatings under an externally applied air pressure over a certain period of time. It was hypothesized that such devices could be also used to determine the immobilization solids(IMS) of coating colors by determining a sudden drop in the rate of dewatering, that is, a sudden change in the drainage curves. To test this hypothesis, the immobilization solids of coating colors containing various thickeners and water retention additives at different levels were first accurately measured by a modified immobilization tester based on the well-known gloss drop method, and then their values were compared with those obtained by an AA-GWR water retention tester. They agreed very well and showed that the mean of the solids differences is 0.36% in the IMS points between both methods. This good agreement was not surprising because both test methods are based on the same end-point, that is, the immobilization solids point at which menisci begin to form at the coating surface. Theoretical considerations supporting this new method for measuring the immobilization solids of coating colors are presented and some recommendations for the test method are discussed. Also, the effect of various thickeners and water retention additives on the properties and printability of coated papers is discussed.

• Bulletin of the Korean Chemical Society
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• 제20권10호
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• pp.1159-1164
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• 1999

The study investigated the effect of carrier composition (ionic strength and pH) on the retention of various proteins in flow field-flow fractionation (Flow FFF) as well as the conformational change of Bovine Serum Albumin (BSA) with urea concentration, storage time and temperature. The study found that the retention of protein in Flow FFF increased with the ionic strength of the carrier liquid. Most proteins were well solubilized at pH = 7-8. The hydrodynamic diameters obtained from Flow FFF retention data agree well with theoretical values. The retention increased and the peak shape became distorted at extreme pH conditions of the carrier solution. The selected carrier composition for comparison between the literature value of proteins was 0.05 M tris buffer solution with a pH of 8. Storing BSA at 4 ±2℃ over a period of three months resulted in slow dimerization. Also, in case of the storage of BSA at 37 ±5℃ for one week, the retention of both BSA monomer and dimer increased with the urea concentration. Finally, the structural composition of specific enzymes: malonyl-CoA decarboxylase (MCDC) and malonyl-CoA synthesis (MCS) was determined by using Flow FFF at specific carrier solutions. The molecular weight of the natural MCDC was determined to be 208 kDa, which means it is a homotetramer, while that of the MCS was determined to be 47 kDa, which means it is a monomer.

• Asian-Australasian Journal of Animal Sciences
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• 제11권6호
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• pp.732-738
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• 1998

Three crossbred gilts weighing $61{\pm}2kg$ ($mean{\pm}SD$) and three gilts weighing $52{\pm}3kg $ on the day before the first treatment began (d -1) were used for each of two experiments (Exp. 1 and Exp. 2), respectively. In Exp. 1, all pigs were fed the experimental diet (CP 19%) from d -7 to the end of study (d 21) to verify that nitrogen retention is constant during the 21 -d period. In Exp. 2, pigs were fed the control diet (CP 15.5 %) from d -7 to d 8 and then the low-lysine diet from d 9 to d 16 in order to determine how rapidly dietary changes in amino acid composition results in a new equilibrium for nitrogen metabolism. The amount of urine nitrogen loss was not different over 21 days (p > 0.10). Rates of nitrogen retention were not different among pigs (p > 0.10) nor over time (p > 0.10). Average nitrogen retention during the period was 1.00 g/kg $BW^{0.75}$ per day. The apparent biological value was 41%, which did not change over the 3-week period (p > 0.10). The overall efficiency of nitrogen use for nitrogen retention was 35% (Exp. 1). The amount of nitrogen loss in urine and the efficiency of nitrogen utilization for nitrogen gain reached a new equilibrium within 2 to 3 d after the diet was changed. The low-lysine diet resulted in a 20% increase of nitrogen loss in urine (p < 0.001) and a 9% decline in efficiency of nitrogen use for nitrogen retention (p < 0.001). Nitrogen retention while the pigs were fed the control diet was also higher than the retention when pigs were fed the low lysine diet (p < 0.001). The efficiency of nitrogen use for nitrogen retention in pigs fed the control diet was 57% (Exp. 2), which was higher (p < 0.001) than that from pigs fed the low-lysine diets (52%).

• Archives of Pharmacal Research
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• 제20권6호
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• pp.637-642
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• 1997

Degradation of a compound with a hydroxyl group during the course of its diffusion across the skin was investigated. Based on the experimental findings of ashortened retention time of a degradant peak from post-diffusion samples and from the ability to evaporate radioactivity from such samples, it seems that during diffusion the parent compound degrades into a more hydrophilic product which is then oxidized. A tritium label at the carbon with a hydroxyl group was released as a tritiated water. When the post-diffusion samples were left open to the air allowing evaporation of water, there was a corresponding decrease in radioactivity of such samples. There was a linear relationship between the time left open and the fraction of radioactivity lost. When such samples were fractionated by HPLC, and then had their radioactivities measured by scintillation counting, two peaks wre identified. The first peak, which may be attributable to tritiated water, was eluted at the same retention time as the solvent front. The second peak eluted at the retention time of the parent compound. When the evaporation/loss of radioactivity experiment was repeated using a $^{14}C$-labeled compound there was no significant loss of radioactivity, indicating that the earlier loss with $^{3}H$-labeled compound was related to the formation and loas sof tritiated water.

• 대한치과교정학회지
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• 제46권1호
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• pp.36-41
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• 2016

Objective: The aim of this study was to evaluate retention practices commonly employed by orthodontists. The objectives were to identify the types of retainer frequently used and to investigate the variations in retention practice. Methods: A total of 97 orthodontists were randomly selected, and a questionnaire consisting of 25 multiple-choice questions sent to them by mail. Upon receiving of the completed questionnaires, the data were statistically analyzed. Results: A total of 32 responses were received; among these, 59.4% of orthodontists' practiced is in a government setting and 40.6% were in private practice. A vacuum-formed retainer was the most commonly used removable retainer for both maxillary (46.9%) and mandibular (46.9%) arches, followed by a Hawley retainer (maxilla, 43.8%; mandible, 37.5%), and a fixed retainer (maxilla, 3.1%; mandible, 9.4%). Of the responding orthodontists, 78.1% prescribed full-time wear (more than 20 h per day) for a duration of 3-9 months for a maxillary arch, compared to 71.9% for the mandibular arch. Only 18.8% of the orthodontists prescribed part-time wear of the retainer for the maxillary arch, compared to 21.9% for the mandibular arch. The majority of orthodontists did not instruct their patients to stop wearing removable retainers (71.9%) or fixed retainers (66.8%) at any specific time and they preferred their patients to continue wearing retainers. Conclusions: Vacuum-formed retainers are the most commonly used retainers among orthodontists. The majority of orthodontists prescribed full-time wear for more than 20 h per day with a duration of 3-9 months and preferred indefinite use of the retainer.