• 환경위생공학
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• 제15권3호
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• pp.50-56
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• 2000

In this study, sewage were treated with operating Two-step Aeration System and conventional activated sludge process together in a condition. At the same HRT 8hr of Two-step Aeration System and Activated Sludge Process, BOD treatment efficiency of 1st sedimentation basin effluent 36.9% by Two-step Aeration system was 12.3% higher than 24.65 by Activated Sludge Process and the COD treatment efficiency 39.8% by two-step Aeration System was 11.6.3% higher than 28.2% by Activated Sludge Process. BOD and COD treatment efficiencies of 2nd sedimentation basin effluent were 88.1% and 85.6% Two-step Aeration System and were 83.8% and 82.3% Activated Sludge Process. In the first treatment, as BOD was relatively removed a lot, F/M ratio 0.17, $0.21{\cdot}BOD/kg{\cdot}MLSS.d$ was maintained by Activated Sludge Process. Therefore it was proved that organic matter treatment efficiency by Two-step Aeration System os Higher than by Activated Sludge Process in a aeration time 8hr. $NH_4^{+}-N$ treatment efficiencies were 55.5% by Two-step Aeration System and 39.75 by Activated sludge Process. $NO_3^{-}-N$ concentration in 2nd. sedimentation basin effluent were 3.33% by Two-step Aeration System and 2.36% by Activated Sludge Process. From this result, Two-step Aeration System was proved more advantageous treatment process for nitrification than Activated Sludge Process. The fluctuation range of BOD, COD and SS concentration in 2nd sedimentation basin effluent $16~33mg/{\ell}$, $15~23mg/{\ell}$ and $14~22mg/{\ell}$ by Two-step Aeration System was smaller than $16~57mg/{\ell}$, $15~25mg/{\ell}$ by Activated sludge Process. Overall the fluctuation range in 2nd sediment basin effluent by was smaller than by Activated Sludge Process. As a result, it is possible for this Two-step Aeration with no facility investment and a little of operation condition change in a conventional sewage treatment plant to get stability and nitrification of treatment water quality.

• 소성∙가공
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• 제20권5호
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• pp.357-361
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• 2011

A beryllium copper alloy(C1720) sheet was stretch-drawn using different processes. A hemispherical punch was first used and the forming behavior was examined. Then, cylindrical cups with a hemispherical head were produced by either one-step drawing or two-step forming(sequential stretch forming-drawing). The one-step drawing showed the better formability than two-step forming. However, the two-step forming was the superior process in terms of attaining shape accuracy.

• 대한기계학회논문집
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• 제12권5호
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• pp.984-991
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• 1988

본 연구에서는 유압관로에서 액주분리를 수반하는 유체 과도현상의 압력파형 에 때때로 관측되는 2단적 압력상승현상의 발생기구를 실험 및 이론적인 추론, 특성곡 선법을 사용한 수치해석을 통하여 명확히 구명함을 목적으로 한다.

• 생명과학회지
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• 제31권4호
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• pp.385-388
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• 2021

벼 육종을 위한 약 배양은 기존 육종 방법을 사용하여 새로운 품종을 개발하는데 최소 6세대에 필요한 시간을 크게 줄여 동형접합자를 신속하게 생산하는 방법이다. 이 약 배양기술은 방법론적 관점에서 더 많은 녹색 식물을 얻을 기회를 제공하며, 약 배양에서 시간과 노력을 절약하는 배양의 효율성을 높이기 때문에 중요하다. 본 연구에서는 배양액과 배양 방법이 다른 1단계와 2 단계 배양의 캘러스 유도율과 녹색 식물 재분화율로 비교하였다. 1단계 배양은 하나의 배지에서 캘러스 유도 및 식물 재생을 허용하는 반면, 2 단계 배양은 두 개의 다른 배지에서 유도 및 식물 재분화가 필요하다. 이 연구에서는 1 단계 및 2 단계 배양으로 벼 꽃밥의 캘러스 유도와 식물 재생률을 비교했다. 캘러스 형성률은 1 단계 배양의 경우 13.0 %, 2 단계 배양의 경우 8.6%로 2 단계 배양보다 1 단계 배양에서 4.4% 더 높았다. 식물 재분화율은 1 단계 배양에서 1.0%, 2 단계 배양에서 3.0 %로 1 단계 배양보다 2단계 배양에서 식물체 재분화율이 3배 더 높았다. 이것은 2 단계 배양이 반수체 생산을 위한 1 단계 배양보다 더 효율적임을 시사한다.

• 한국재료학회지
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• 제34권2호
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• pp.116-124
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• 2024

In this study, we investigated the microstructure and piezoelectric properties of 0.96(K_0.456Na_0.536)Nb_0.95Sb_0.05-0.04Bi_0.5(Na_0.82K_0.18)_0.5ZrO₃ (KNNS-BNKZ) ceramics based on one-step and two-step sintering processes. One-step sintering led to significant abnormal grain (AG) growth at temperatures above 1,085 ℃. With increasing sintering temperature, piezoelectric and dielectric properties were enhanced, resulting in a high d₃₃ = 506 pC/N for one-step specimen sintered at 1,100 ℃ (one-step 1,100 ℃ specimen). However, for one-step 1,115 ℃ specimen, a slight decrease in d₃₃ was observed, emphasizing the importance of a high tetragonal (T) phase fraction for superior piezoelectric properties. Achieving a relative density above 84 % for samples sintered by the one-step sintering process was challenging. Conversely, two-step sintering significantly improved the relative density of KNNS-BNKZ ceramics up to 96 %, attributed to the control of AG nucleation in the first step and grain growth rate control in the second step. The quantity of AG nucleation was affected by the duration of the first step, determining the final microstructure. Despite having a lower T phase fraction than that of the one-step 1,100 ℃ specimen, the two-step specimen exhibited higher piezoelectric coefficients (d₃₃ = 574 pC/N and k_p = 0.5) than those of the one-step 1,100 ℃ specimen due to its higher relative density. Performance evaluation of magnetoelectric composite devices composed of one-step and two-step specimens showed that despite having a higher g₃₃, the magnetoelectric composite with the one-step 1,100 ℃ specimen exhibited the lowest magnetoelectric voltage coefficient, due to its lowest k_p. This study highlights the essential role of phase fraction and relative density in enhancing the performance of piezoelectric materials and devices, showcasing the effectiveness of the two-step sintering process for controlling the microstructure of ceramic materials containing volatile elements.

• Journal of the Korean Wood Science and Technology
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• 제44권6호
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• pp.913-922
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• 2016

This study attempted to measure molecular weight (MW) of melamine-urea-formaldehyde (MUF) resins prepared by two different synthesis methods: the one-step MUF resins were synthesized in one batch procedure, while the two-step MUF resins were prepared by a physical mixing of urea-formaldehyde (UF) resin with melamine-formaldehyde (MF) resin that had been synthesized in a separate procedure. The properties of medium density fiberboard (MDF) panels bonded with two types of MUF resins were also investigated. MWs of these MUF resins were measured using gel permeation chromatography (GPC). In addition, this study measured the MWs of one-step MUF resin during its synthesis procedure. The performance of two types of MUF resins was evaluated by determining properties of MDF panels prepared in laboratory. As the synthesis procedure progressed, both number average MW ($M_n$) and weight average MW ($M_w$) of one-step MUF resin gradually increased, while the polydispersity index (PDI) decreased. And low Mw species of the resin predominantly decreased as the synthesis step progressed. The one-step MUF resin showed greater $M_n$ and $M_w$ than those of the two-step ones even though the PDI values of both resins were very similar each other. As expected, the one-step MUF resin resulted in better properties of MDF panels than those of two-step resins. In particular, the one-step MUF resin provided better internal bond (IB) strength and thickness swelling (TS) with MDF panels than those of two-step ones, indicating better water resistance of the one-step resin. These results suggest that the preparation method of MUF resins have a great impact on the MW and final panel properties.

• 대한전기학회논문지
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• 제45권4호
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• pp.568-573
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• 1996

The amorphous silicon films deposited by low pressure chemical vapor deposition are crystallized by the various annealing techniques including low-temperature furnace annealing and two-step annealing. Two-step annealing is the combination of furnace annealing at 600 [.deg. C] for 24 h and the sequential furnace annealing at 950 [.deg. C] 1h or the excimer laser annealing. It s found that two-step annealings reduce the in-grain defects significantly without changing the grain boundary structure. The performance of the poly-Si thin film transistors (TFTs) produced by employing the tow-step annealing has been improved significantly compared with those of one-step annealing. (author). 13 refs., 6 figs., 1 tab.

• 한국학교보건학회지
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• 제1권1호
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• pp.148-159
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• 1988

For the evaluation of physical assessment by school nurses, this study was designed in two steps physical assessment. The first step is the primary health screening by school health nurses. The second step is the Physicians' physical examination of ill health students selected by school nurses. This study was conducted on a total of 3,525 students of three primary schools located in urban, township, and rural area during the period from May to June, 1987, all data were collected through direct observation & survey method. The main findings are as follows 1. The number of ill health students selected by two step method was more than that of one step method by the physician. 2. The types of ill health students selected by two step method had more diversity than that of one step method by the physician. 3. Budgets and time consumption for two step method were more reductive than that of one step method by the physician.

• 한국표면공학회지
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• 제36권4호
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• pp.339-346
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• 2003

Stainless steel wire has been used in industry, dental and medical parts. Especially, it has been used widely for the dental orthodontic materials. The orthodontic wire requires good mechanical properties, such as elastic strength, combined with a high resistance to corrosion. To increase elastic strength and good corrosion resistance, drawing methods(one-step and two-step drawing) have been used and the electrochemical characteristics of drawed wire have been researched using potentiodynamic method in 0.9％NaCl and field emission scanning electron microscope. The one-step drawed wire showed the formation of rough surface. The hardness and tensile strength of two-step drawed wire increased. For the case of two-step drawed wire, the corrosion resistance and pitting potential increased compared with one-step drawed wire due to the drawing induced small surface roughness, such as scratch. The passivation and active current density decreased as the reduction in area for drawing increased.

• 한국전기전자재료학회논문지
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• 제13권2호
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• pp.95-100
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• 2000

For the well-controlled growing in-situ heavily phosphorus doped polycrystalline Si films directly on Si wafer by reduced pressure chemical vapor deposition, a study is made of the two step growth. When in-situ heavily phosphorus doped Si films were deposited directly on Si (100) wafer, crystal structure in the film is not unique, that is, the single crystal to polycrystalline phase transition occurs at a certain thickness. However, the well-controlled polycrtstalline Si films deposited by two step growth grew directly on Si wafers. Moreover, the two step growth, which employs crystallization of grew directly on Si wafers. Moreover, the two step growth which employs crystallization of amorphous silicon layer grown at low temperature, reveals crucial advantages in manipulating polycrystal structures of in-situ phosphorous doped silicon.