• 한국지반공학회논문집
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• 제36권12호
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• pp.69-76
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• 2020

Back-to-Back 보강토옹벽은 좁은 구간에 양립하는 옹벽의 형식을 가지기 때문에 벽체간의 이격거리에 따라 보강재가 겹치게 되어 보강재 간의 상호작용에 의한 응력 변화와 일체화된 상태에서 전체가 거동하는 문제 등으로 설계단계에서 신중한 접근이 필요하나 현재 국내에 정형화된 설계기준이나 지침이 전무한 상태이다. 본 연구는 이러한 Back-to-Back 보강토옹벽에 대해 옹벽폭 대 높이비(옹벽폭비, Wb/H)에 따른 최적 보강길이비에 대해 고찰하였다. 옹벽폭비는 FHWA 설계기준의 Case II에 해당하는 1.1H, 1.4H, 1.7H, 2.0H, 높이는 일반적으로 가장 많이 적용되고 있는 3.0m, 5.0m, 7.0m, 10.0m를 대상으로 하였으며, 각 조건에서 수치해석을 통해 FHWA 설계기준의 적정성과 옹벽의 높이 및 옹벽폭비에 따른 최적 보강길이비를 제안하였다.

• 한국세라믹학회지
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• 제38권11호
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• pp.1037-1041
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• 2001

저온(32$0^{\circ}C$)에서 SiH$_4$와 $N_2$O 가스의 혼합을 통해 플라즈마화학기상증착(PECVD)법을 이용하여 실리카 광도파로의 클래딩막으로 사용되는 SiO$_2$후막을 제조하였다. 증착변수가 SiO$_2$후막의 특성에 미치는 영향을 살펴보기 위해 $N_2$O/SiH$_4$flow ratio와 RF power에 변화를 주었다. $N_2$O/SiH$_4$ flow ratio가 감소함에 따라 증착속도는 2.9 $mu extrm{m}$/h), 굴절률은 thermal oxide의 굴절률(n=1.46)에 근접하였다.

• 대한약침학회지
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• 제12권4호
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• pp.97-110
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• 2009

Objective : The purpose of this study is to determine the effect of Hominis Placenta Pharmacopuncture(HPP) on lower limb spasticity control in stroke patients. Methods : Twenty stroke patients with Leg spasticity were randomly divided into two groups, a Distilled water Pharmacopuncture(group I) and a HPP(group II). The number of Pharmacopuncture was 5 times a week and acupuncture treatment was 3 times a week for 3 weeks. Modified Ashworth Scale(MAS), H-reflex/M-response ratio(H/M ratio), Berg Balance Scale(BBS) and Time Up & Go(TUG) were used for evaluation of spasticity control before experiment, after 1 week, 2 weeks, 3 weeks. Results : Group I showed significant improvement(p$<$.05) in BBS but no significant improvement in MAS, H/M ratio, and TUG. Group II showed significant improvement(p$<$.05) in MAS, BBS, and TUG, but no significant improvement in H/M ratio. The results showed significant difference in TUG, but no significant difference in MAS, H/M ratio and BBS between 2 groups. Conclusion : These results showed that HPP might decrease lower limb spasticity and increase leg motor function in stroke patients. Further studies will be required to examine more cases in the long period for the effect on lower limb in spasticity by HPP.

• 상하수도학회지
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• 제37권6호
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• pp.311-324
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• 2023

As an advanced study on the method of calculating the target revenue water ratio of local waterworks through the leakage component analysis method proposed by Kim et al. (2022), this study developed a model to calculate the achievable revenue water ratio within the specified project cost, the required project cost to achieve the specified target revenue water ratio, and the economically appropriate target revenue water ratio level by considering the leakage reduction cost and leakage reduction benefit for each revenue water ratio improvement strategy, and conducted an applicability evaluation of the developed model using actual field data. The procedure for calculating the target revenue water ratio of local waterworks considering economics proposed in this study consists of three stages: physical data linkage model construction, leakage component analysis, and economic analysis, and the applicability was evaluated for Zone H with branch type and the Zone M network type. As a result of the application, it was calculated that approximately 32.5 billion won would be required to achieve the target revenue water ratio of 70% in the Zone H, and approximately KRW 10.5 billion would be required to achieve the target revenue water ratio of 75% in the Zone M. If the business scale of Zones H and M was corrected to 10,000 m³/day of water usage, the required project cost for a 1% improvement in the revenue water ratio of Zone H was calculated to be 0.7642 billion won and 0.4715 billion won for Zone M.

• 상하수도학회지
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• 제23권5호
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• pp.669-678
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• 2009

The reduction of excess activated sludge from petrochemical plant was investigated by the electro fenton (E-Fenton) process using electrogenerated hydroxyl radicals which lead to mineralization of activated sludge to $CO_2$, water and inorganic ions. Factors affecting the disintegration efficiency of excess activated sludge in E-Fenton process were examined in terms of five criteria: pH, $H_2O_2/Fe^{2+}$ molar ratio, current density, initial MLSS (mixed liquid suspended solids) concentration, $H_2O_2$ feeding mode. TSS total suspended solid and $TCOD_{cr}$ reduction rate increased with the increasing $H_2O_2/Fe^{2+}$ molar ratio and current density until 42 and $6.7 mA/cm^2$, respectively but further increase of $H_2O_2/Fe^{2+}$ molar ratio and current density would reduce the reduction rate. On the other hand, as expected, increasing pH and initial MLSS concentration of activated sludge decreas TSS and $TCOD_{cr}$ reduction rate. The E-Fenton process was gradually increased during first 30 minutes and then linearly proceed till 120 minutes. The optimal E-Fenton condition showed TSS reduction rate of 62~63% and $TCOD_{cr}$ (total chemical oxygen demand) reduction rate of 55~56%. Molar ratio $H_2O_2/Fe^{2+} = 42$ was determined as optimal E-Fenton condition with initial $Fe^{2+}$ dose of 5.4 mM and current density of $6.7{\sim}13.3 mA/cm^2$, initial MLSS of 7,600 mg/L and pH 2 were chosen as the most efficient E-Fenton condition.

• 분석과학
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• 제24권1호
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• pp.15-23
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• 2011

본 연구에서는 미지 대사물질 동정을 위해 GC-TOF/MS의 양이온 화학적 이온화 방법(positive chemical ionization, $CI^+$)을 이용, 정확한 질량 값(accurate mass)과 동위원소 비(isotope ratio) 측정을 위한최적 조건을 확립하였다. 분자이온 $[M+H]^+$ 세기를 증가시킬 수 있는 high mass tune 방법이 사용되었으며, 화합물들의 분리 및 감도에 따른 검출조건이 고려되어 졌다. 24종의 trimethylsilyl (TMS)기로 유도체화 된 표준 대사물질들을 분석한 결과 $[M+H]^+$의 경우 이론 값 과의 절대평균오차는 6.8 ppm이였으며, 동위원소 비(M+1/M, M+2/M)의 경우는 각각 1.5%와 1.7%였다. 얻어진 질량 값과 동위원소 비를 원소조성 알고리즘에 적용한 결과 21개의 화합물의 구조식이 2순위 내에서 일치하였다.

• 한국세라믹학회지
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• 제28권11호
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• pp.885-891
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• 1991

Calcium hydroxyapatite have been synthesized by a direct precipitation reaction between 0.05 M calcium hydroxide suspension and 0.3 M orthophosphoric acid solution. 0.01 M calcium hydroxide solution was added during the reaction in order to increase the total Ca/P mol ration and reaction pH of the solution. The stoichiometric hydroxyapatite was synthesized over 1.75 as total Ca/P mol ratio, but the calcium-deficient hydroxyapatite was prepared under 1.725 as total Ca/P mol ratio. The nonstoichiometry of the precipitates were interpreted in terms of the pH change during the reaction.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.975-976
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• 2006

The present paper is a parameter study of zinc flake production using a Simoloyer CM01 horizontal high energy rotary ball mill. The manufactured flakes have a dimension in thickness (t) < $1{\mu}m$ and diameters (d) 5-100 ${\mu}m$, consequently a ratio d/t up to 200. The flake geometry is mainly controlled by the variation of process parameters such as rotary speed of the rotor, ratio of powder/ball charge, load ratio of the system, process temperature, operating model and the quantity of process control agent (PCA). The Zn flakes were characterized by SEM, tap densitometry, laser diffraction and water coverage measurement.

• Geomechanics and Engineering
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• 제2권1호
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• pp.29-44
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• 2010

Vertical vibration tests were conducted using model footings of different size and mass resting on the surface of finite sand layer with different height to width ratios which was underlain by either rigid concrete base, under both dry and saturated condition. The effect of saturation on the damping ratio of finite sand stratum underlain by a rigid base has been verified and compared with the results obtained for the case of finite dry sand stratum underlain by the rigid base. Comparison of results of the experimental study showed that the damping in both the cases is less than 10%. The damping ratio obtained for finite saturated sand stratum is marginally lower than that obtained on finite dry sand stratum at H/B ratio of 0.5. The difference between the two cases becomes significant when the H/B ratio increases to 3.0, indicating the significant influence of soil moisture on damping ratio of foundation- soil system with increase in the thickness of the finite sand stratum. Comparison of the predicted damping ratio for a homogeneous sand stratum with the experimental damping ratio obtained corresponding to the height to width ratio of 3.0 of the finite sand stratum underlain by the rigid concrete base indicates a significant reduction in damping ratio of the foundation-soil system for both the cases.

• 대한치과교정학회지
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• 제17권1호
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• pp.7-13
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• 1987

This study was conducted to clarify the relationship of hyoid bone position to tongue position and mandible when malocclusion is categorized in the bilateral and in the vertical components. Five groups of samples (normal occlusion, unilateral and bilateral cross-bite, openbite, deep-bite) were selected for his investigation by utilizing the cephalograms. On the basis study, the following conclusions were obtained; 1. In the normal group. the mean hyoid position (H-M) was $9.83{\pm}4.27mm$. The mean distance of hyoid body to tongue dorsum (H-T) was $52.17{\pm}6.70mm$. The ratio of H-M/H-T was $18.59\%$. 2. In all malocclusion groups, the hyoid position (H-M) was found to be larger than that of the norm except the deep overbite group 3. The tongue dorsum position (H-T) was increased, compared to that of norm, in all malocclusion groups. 4. Hyoid position (H-M) was found to show high correlation to the ratio of H-M/H-T, H-T, PI-T (0.890, 0.699, 0.455). 5. The hyoid position (H-M) was found to show low correlation to the measurements of mandible, but among them the ODI was found to show conversely a little higher correlation against hyoid position (H-M).