• 한국분무공학회지
• /
• 제9권3호
• /
• pp.15-21
• /
• 2004

The removal of the dusts in the subway stations, tunnels, factories and buildings becomes issue for comfortable indoor and outdoor conditions. There has been used an automatic self-cleaning filter system to collect the dusts. In general, the collected particles are removed by water spray nozzles. The new design for improving the cleaning efficiency of collected dusts and reducing the supplied water is the concept of the plane array of demister filters and the twin-fluid nozzle for mixing compressed air and water in the automatic self-cleaning filter system. Results show that the cleaning efficiency of twin-nozzle filter systems is 99.1%, compared to 47% in the conventional filter system. Therefore the automatic self-cleaning filter system using twin-fluid nozzle filter systems reduces water supplied in the filter system, and increases cleaning efficiency and drying efficiency.

• 한국농촌건축학회논문집
• /
• 제24권2호
• /
• pp.45-52
• /
• 2022

Of the 17,106 domestic reservoirs(as of December 2020), 14,611 are older than 50 years, and these old reservoirs will gradually increase over time. The injection grouting method is most applied to the reinforcement method of the aging reservoir. However, the injection grouting method is not accurate in uniformity and reinforced area. An laboratory model test was conducted to evaluate the applicability of the deep mixing method, which compensated for these shortcomings, as a reservoir reinforcement method. As a result of calculating the hydraulic conductiveity for each method through the model test results, the injection grouting method was calculated as a hydraulic conductiveity value that was about 7.5 times larger than that of the deep mixing method. As a result of measuring the water level change in the laboratory model test, it was found that the water level change decreased in the injection method and deep mixing method compared to the non-reinforcement method. In addition, deep mixing method showed a water level change of about 15% based on 40 hours compared to the injection method, indicating that the water-reducing effect was superior to that of the injection method.

• 한국음향학회지
• /
• 제37권1호
• /
• pp.21-30
• /
• 2018

수동 시역전 기법은 시공간적인 집속효과를 통해 다중경로 채널응답에 의한 인접 심볼간 간섭의 영향을 줄임으로써 수중통신 시스템의 오류 성능을 향상시킬 수 있는 방법이다. 이러한 수동 시역전 기법은 일반적으로 시역전 결합에 사용되는 수신신호가 많을수록 큰 공간 다이버시티 이득을 얻기 때문에 많은 수의 수신기를 사용할 때 우수한 통신 성능을 얻을 수 있다. 본 논문에서는 제한된 개수의 수신기를 사용하더라도 많은 수의 수신기를 사용할 때와 근접한 통신 성능을 얻을 수 있는 수신기의 개수와 조합에 대해 분석한다. 분석을 위해 2015년 5월에 제주 남서쪽 해역에서 수행된 SAVEX15(Shallow-water Acoustic Variability Experiment 2015) 실험 데이터를 활용한다. 음향채널이 존재하는 채널 특성 때문에 에너지가 집중되는 수심이 존재하였고 에너지가 집중되는 수심에 존재하는 수신기를 포함하여 수동 시역전 결합을 할 때, 일부의 수신기만을 사용하여 최적에 가까운 통신 성능을 도출할 수 있음을 보인다.

• 한국물환경학회지
• /
• 제39권4호
• /
• pp.343-355
• /
• 2023

After the implementation of the total pollution load control system, the effect of improving river water quality by expanding investments in basic environmental facilities, inducing operational efficiency, and reducing the load of various pollutants was clear. However, since the implementation of the system, the management of non-point pollutants has been neglected; management focused on specific substances (biochemical oxygen demand (BOD) and total phosphorus (T-P)) and lacked specific cause analysis and action plans, failed to establish a relationship between water quality and pollution load, failed to reflect stakeholder demands for river water quality management, and failed to apply technical conditions. Therefore, to overcome the limitations raised and achieve a practical and efficient advanced total pollution system, the current system was partially improved and will continue to be improved. This study analyzed the performance and limitations of the total pollution system and introduced recent improvements and the contents that are being improved. The main contents included reducing emissions and reduction monitoring, using water quality tele-monitoring system (TMS) data and self-measurement data, adding population-inducing facilities, and adjusting regional development projects from 20 to 30 multi-family housing units, currentizing each pollutant source according to the roadmap. If the system is improved in a developmental direction and responds to various changes, it will be a more practical and effective policy.

• 콘크리트학회논문집
• /
• 제23권4호
• /
• pp.441-448
• /
• 2011

이 연구에서는 실리카퓸 및 수축 저감제, 팽창재, 고성능 감수제의 혼입을 변수로 한 초고성능 시멘트 복합체(UHPCC)의 초기 수축 거동을 평가하기 위하여 화학수축 및 자기수축 실험을 수행하고, 응결 측정 결과와 비교하여 UHPCC의 자기건조 시작 시점에 대하여 분석하였다. 실험 결과, 실리카퓸 및 수축 저감제는 초기 화학수축을 증가시키는 경향을 보였으며, 고성능 감수제는 시멘트와 배합수의 수화 반응을 지연시키고 화학수축을 저감시키는 것으로 나타났다. 수축 저감제와 팽창재를 조합하여 적용한 경우 약 49%의 자기수축 저감 효과를 보였으며, 팽창재는 경화를 촉진 시키는 것으로 나타났다. 또한 UHPCC는 다수의 섬유 혼입과 낮은 물-결합재비에 의해 초결 이전부터 자기건조 현상이 발생하는 것으로 나타났다.

• 콘크리트학회논문집
• /
• 제24권3호
• /
• pp.233-240
• /
• 2012

하이브리드 SHCC는 마이크로 섬유에 의한 마이크로 균열제어와 매크로 섬유에 의한 매크로 균열제어 성능이 뛰어나 다양한 분야에 적용가능성이 높은 재료로서 활발히 연구되고 있다. 그러나 SHCC는 부배합으로 자기수축에 의한 수축균열을 고려하여야 한다. 따라서 이 연구에서는 PE섬유와 강섬유가 함께 혼입된 팽창형 하이브리드 SHCC의 역학적 특성을 평가하고자 하였다. 하이브리드 SHCC의 역학적 특성을 평가하고자 W/B(45%, 30%, 20%)와 팽창재 대체유무(0%, 10%)를 변수로하였다. 시험은 수축, 압축, 직접인장 및 휨 시험을 수행하였다. 각 실험들을 통한 성능평가결과 10%의 팽창재를 대체한 W/B 30%의 하이브리드 SHCC에서 역학적 성능 개선이 가장 우수하였다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.2129-2134
• /
• 2004

The present study has been conducted to develop a heat pump system using river water of temperature energy which not only belongs to unutilized energy but is a kind of good heat source due to maintain its temperature in a certain degree regardless of seasonal variation. The system did not meet the proposed performance after setup. In this paper, the system performance affected by refrigerant Oil, by pressure drop, or by other factors has been discussed. The followings were obtained : (1) Refrigerant Oil mixture rate was 2.5 in weight percentage, (2) Pressure drop through evaporator was 29.1kPa($3.1^{\circ}C$ in saturated tempearture) (3) Pressure drop from the end of evaporator to compressor inlet was 39.8kPa($4.0^{\circ}C$ in saturated tempearture). (4) The system performance can to be improved by modifying a part of pipe line to compressor, and reducing pressure drop through heat exchangers.

• Computers and Concrete
• /
• 제32권2호
• /
• pp.185-206
• /
• 2023

This article aimed to explore the optimization of mineral admixtures and retarding admixture for high-performance concrete. In essence, fresh concrete can be regarded as a mixture in which both coarse and fine aggregates are suspended in a cement-based matrix paste. Based on this view, the test procedure was divided into three progressive stages of binder paste, mortar, and concrete to explore their rheological behavior and mechanical properties respectively. At each stage, there were four experimental control factors, and each factor had three levels. In order to reduce the workload of the experiment, the Taguchi method with an L9(3⁴) orthogonal array and four controllable three-level factors was adopted. The test results show that the use of the Taguchi method effectively optimized the composition of high-performance concrete. The slump of the prepared concrete was above 18 cm, and the slump flow was above 50 cm, indicating that it had good workability. On the other hand, the 28-day compressive strength of the hardened concretes was between 31.3-59.8 MPa. Furthermore, the analysis of variance (ANOVA) results showed that the most significant factor affecting the initial setting time of the fresh concretes was the retarder dosage, and its contribution percentage was 62.66%. On the other hand, the ANOVA results show that the most significant factor affecting the 28-day compressive strength of the hardened concretes was the water to binder ratio, and its contribution percentage was 79.05%.

• Journal of Biosystems Engineering
• /
• 제29권3호
• /
• pp.217-224
• /
• 2004

This research was conducted to test the feasibility of utilizing high-pressure water jets of over 1.0㎫ as a means of breaking and peeling garlic bulbs. High-pressure plunger pumps and flat-spray nozzles of varying orifice diameters and spray angles were utilized to supply water jets into a prototype peeling chamber made of transparent acrylic plates. Water jets were discharged from a total of six nozzles installed in such a way that three parallel nozzles face the other three. The cross-sectional area of the peeling chamber and the installation angle of the nozzles had critical effects on peeling performance. Small cross-sectional area was required so that total impact force of water jets on garlic could be increased. The optimum installation angles were around 4, 8, and 16$^{\circ}$ for the nozzles having 15, 40, and 65$^{\circ}$ spray angles, respectively. Best performance with 61.4% of completely-peeled garlics was obtained at a pressure of 1.94㎫ and a flow rate of 9.07 $\ell$/min for each nozzle. The peeling efficiency of the system was generally unsatisfactory due to the limited flow rate of the plunger pumps utilized. For better performance, it is recommended to increase flow rate while reducing operating pressure by utilizing other type of pumps.

• 한국수자원학회논문집
• /
• 제57권9호
• /
• pp.585-598
• /
• 2024

자연재해를 사전에 대비하고 효율적인 수자원 관리를 하기 위해서는 수문모형의 구조적 특성이 예측 성능에 미치는 영향을 파악하고 불확실성을 최소화하여 수문예측의 정확도를 향상시키는 것이 중요하다. 본 연구에서는 모형의 구조가 상이한 준분포형과 집중형 GR4J 모형을 순차 자료동화 기법과 연계 적용하여 하천 유량 모의성능에 미치는 영향을 분석하였다. 이를 위해 남강댐 유역에 대해 앙상블 칼만 필터(Ensemble Kalman Filter, EnKF)와 파티클 필터(Particle Filter, PF) 기법을 적용하였다. 모의결과, 두 수문모형의 Kling-Gupta efficiency (KGE) 지표는 파티클 필터 적용시 0.749(집중형), 0.831(준분포형)로, 집중형 모형 보다 준분포형 모형에서 0.082(11.0%) 향상되었다. 또한, 자료동화와 관련된 하이퍼-매개변수 중 기상강제력(강수, 잠재증발산) 불확실성이 모의성능에 미치는 영향을 분석하였다. 집중형 모형은 수문자료동화 기법에 따라, 준분포 형 모형은 각 하위유역에 따라 최적 성능을 얻기 위한 불확실성 조건이 상이하였다. 한편, 자료동화 성능에 보정 및 검정기간의 비율이 미치는 영향을 평가한 결과, 앙상블 칼만 필터는 보정기간이 짧아질수록 자료동화 성능은 감소하였으나, 파티클 필터는 상대적으로 영향을 적게 받았다. 또한, 자료동화의 최적성능을 얻기 위해서는 모형 구조에 따른 적절한 하이퍼-매개변수와 보정기간 선정이 중요함을 확인하였다.