• 한국소음진동공학회논문집
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• 제20권10호
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• pp.983-990
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• 2010

Reduction of acoustic loads of space launch vehicles can be achieved by acoustic absorbers satisfying strict cleanness requirements. This limited the use of general porous materials and requires non-porous sound absorbers. Micro-perforated panel absorbers(MPPA) is one of promising sound absorbers satisfying the cleanness requirement for launch vehicles. However, its applicability was limited to low sound pressure levels according to the acoustic impedance model of micro-perforated panels. In this paper the applicability of micro-perforated panel absorbers at high incident sound pressure was investigated in experimental ways. The absorption characteristics of a micro-perforated panel absorber was simulated according to its design variables, e.g., minute hole diameters and aperture ratios. It was shown that optimal design can be readily done by using proposed design charts. Experiments were conducted to measure acoustic properties of the designed micro-perforated panel absorbers. The results showed that acoustic resistance increases rapidly as incident sound pressure level does but change of acoustic reactance can be neglected in a practical point of view. This caused the decrease of peak value of absorption coefficient at high incident sound pressure level, but the amount of reduction can be accepted in practice. The major advantage of the micro-perforated panel absorber(wide absorption bandwidth) was still kept at high sound pressure level.

• 정보관리연구
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• 제43권2호
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• pp.199-222
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• 2012

한국인들의 국제활동 증대에 따라 외국인들과의 접촉이 증가하였으며 활동의 주체인 한국인 개인을 외국인이 식별해야 하는 필요가 증대되고 있다. 개인을 식별해주는 것은 개인의 이름(personal name)이며, 한글(Hangeul, Korean alphabet)을 모르는 외국인이 한국인을 식별할 수 있도록 하려면 한국인명을 로마자로 표기하는 음성번역(phonetic translation)이 필요하다. 한국인명의 로마자표기 실태를 보면 다양한 형식이 혼용되고 있어 혼돈이 벌어지고 있다. 한국인명을 로마자로 표기하는 과정에서 발생하는 혼돈은 크게 한국인명을 표기하기 위한 로마자 자모의 선택과 표기형식의 상이함에서 비롯된다. 본 연구는 한국인명의 로마자표기를 위한 형식을 검토하여 최적안을 제안하는 것을 목적으로 하였다. 이를 위해 한국과 서구간의 인명 구조와 사용관행의 차이를 살펴보고, 한국인명의 로마자표기의 의미와 관련쟁점을 정리하였으며, 현재 사용되고 있는 다양한 표기형식을 유형화하였다. 이를 기반으로 한국인명의 로마자표기에 사용되고 있는 다양한 형식을 검토하고 최적안이라 판단되는 표기형식을 제안하였다.

• 한국추진공학회지
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• 제17권4호
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• pp.1-9
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• 2013

능동형 대함 유도탄 기만기의 추진 시스템 요구 조건 및 저장성 액체 이원추진제 로켓 엔진의 적용 가능성을 파악하기 위해 개념 설계를 수행하였다. 이미 미국과 오스트레일리아에서 공동 개발하여 운용 중인 Nulka의 제원을 통해 시스템의 기본적인 무게, 크기 등을 가정하였고, 1,000 N 급 과산화수소/케로신 로켓 엔진과 가압식 추진제 공급 방식으로 추진 시스템을 가정하였다. 이를 바탕으로 최적 궤적을 설계하였고 그 결과를 통해 하부 시스템들의 무게 분포를 예측하고 실현 가능성을 확인하였다. 그 결과, 100초 이상의 운용 시간, 엔진 재점화, 그리고 최대 지상 추력 1,000 N의 경우 최소 35%까지의 추력 제어 성능이 추진 시스템의 요구 조건으로 도출 되었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.387-392
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• 2006

The recent on indoor air problem has led to many studies on the methods and effects of ventilation for better indoor air quality. Although natural ventilation is the most effective and energy-saving method in residental housings, the small size of openable window has been a problem in high-rise residential buildings to ventilate only through natural ventilation. Consequently, the installation of mechanical ventilation system has been a requirement in residential buildings, and has caused other problems such as increase of energy consumption and SBS. Hybrid ventilation which uses forces of both natural and mechanical power has been introduced to solve the problem of increase in energy consumption with natural ventilation. In this paper, two types of hybrid ventilation systems in residential building were introduced. One type was with natural ventilation through vent grille in the window, and another type was with natural ventilation through ceiling duct while both types used mechanical ventilation system with the outlets. The indoor temperature distribution and pollution density distribution in summer while operating the ceiling air conditioner were analyzed through CFD simulation. In this paper, the optimal location of diffusers to achieve thermal comfort would be proposed.

• 한국건설관리학회논문집
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• 제20권4호
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• pp.3-12
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• 2019

VE 분석은 사용자의 다양한 요구사항을 명확히 정의하여 기능과 성능을 확보함은 물론 비용절감이 가능한 대안을 제안하여야 한다. 하지만 현행 국내 VE 프로젝트는 프로젝트 참여자간 효과적, 효율적 커뮤니케이션의 어려움과 제약된 시간으로 인해 VE 기능분석에 대한 명확한 정의가 어려운 실정이다. 이로 인해 주로 국내 VE의 결과는 기존 시설 기능을 유지하면서 비용절감을 수행하는 방향으로 포커스 되어 있다. 따라서 본 연구는 VE 수행의 본래 취지에 맞추어서 사용자에 적합한 최적의 기능을 확보함은 물론 비용절감이 가능하도록 프로젝트 VE 참여자의 집단적, 협력적 방식이 가능한 QFD-VE 모델을 제안한다. QFD-VE 기법은 첫째, 요구기능의 정의 및 수정, 요구기능의 중요도 설정에 대하여 집단의사결정 적용이 가능하며, 둘째 VE 대안에 대한 인접시스템의 간섭, 충돌 여부를 프로젝트 VE 참여자가 협력적으로 검토할 수 있는 기법이다. 본 연구는 향후 QFD-VE 기법을 이용한 전산시스템 구현을 위해 수학적 모델을 함께 제시하였다.

• 농업생명과학연구
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• 제52권6호
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• pp.13-25
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• 2018

Appropriate water level is the primary factor for the optimal yield of crop plants. The required water level varies according to the variety of the crops. In the present study, we investigated the optimum requirement of groundwater level(GWL) to grow sorghum and adzuki bean under paddy field soil. Here, we cultivated sorghum and adzuki bean using lysimeter filled with paddy soil under GWL 0 cm(NT) and GWL(20, 40 cm) where GWL 20 cm is maintained as a waterlogging condition. The plant growth promoting attributes were measured on the first day after treatment(0 DAT), 10 DAT and 20 DAT. The results showed that the growth parameter such as shoot length, leaf length, leaf width, and stem thickness of both sorghum and adzuki bean were constantly increased and were found higher at GWL 40 cm(except stem thickness and leaf width in sorghum at 20 DAT). The physiological parameters such as chlorophyll content and stomatal conductance were also found higher at GWL 40 cm in all DAT. In addition, the elements like P and K contents in adzuki bean, and Ca content in sorghum were constantly increased and was found higher in GWL 40 cm at all DAT. These results suggest that the GWL of 40 cm is appropriate for production of sorghum and adzuki bean especially in case of paddy soil.

• Journal of Korean Neurosurgical Society
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• 제62권6호
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• pp.712-722
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• 2019

Objective : Although magnetic resonance guided focused ultrasound (MRgFUS) has been used as minimally invasive and effective neurosurgical treatment, it exhibits some limitations, mainly related to acoustic properties of the skull barrier. This study was undertaken to identify skull characteristics that contribute to optimal ultrasonic energy transmission for MRgFUS procedures. Methods : For ex vivo skull experiments, various acoustic fields were measured under different conditions, using five non-embalmed cadaver skulls. For clinical skull analyses, brain computed tomography data of 46 patients who underwent MRgFUS ablations (18 unilateral thalamotomy, nine unilateral pallidotomy, and 19 bilateral capsulotomy) were retrospectively reviewed. Patients' skull factors and sonication parameters were comparatively analyzed with respect to the cadaveric skulls. Results : Skull experiments identified three important factors related skull penetration of ultrasound, including skull density ratio (SDR), skull volume, and incidence angle of the acoustic rays against the skull surface. In clinical results, SDR and skull volume correlated with maximal temperature (Tmax) and energy requirement to achieve Tmax (p<0.05). In addition, considering the incidence angle determined by brain target location, less energy was required to reach Tmax in the central, rather than lateral targets particularly when compared between thalamotomy and capsulotomy (p<0.05). Conclusion : This study reconfirmed previously identified skull factors, including SDR and skull volume, for successful MRgFUS; it identified an additional factor, incidence angle of acoustic rays against the skull surface. To guarantee successful transcranial MRgFUS treatment without suffering these various skull issues, further technical improvements are required.

• 한국물환경학회지
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• 제35권1호
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• pp.35-42
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• 2019

Urbanization has led to extreme changes in land use on urban watersheds. Most cities are becoming residential, commercial and industrial areas, making infiltration and storage of rainfall less favorable. The demand for LID (Low Impact Development) technology is increasing in order to mitigate this water cycle distortion and return to existing hydrological conditions. The LID technique is effective in reducing runoff by permeating the urban impervious area. However, considering the limit of the installation area and the financial requirement of the installation, there is not much research on the linkage of each LID component technology for optimum efficiency according to the appropriate scale. In this study, the effects of the LID facilities applied to the target site were simulated using the SWMM model, suggesting the optimal linkage method considering interconnectivity, and applying the effects as an existing installation of individual facilities. The water balance at the time of application of the LID technology, short-term and long-term rainfall event were compared. Also, the individual application and the linkage application were compared with each other. If each component technology has sufficient processing size, then linkage application is more effective than individual application.

• Journal of Dental Anesthesia and Pain Medicine
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• 제21권2호
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• pp.129-137
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• 2021

Background: Inappropriate use of intravenous and inhaled anesthetics may be dangerous in infants undergoing facial cleft surgeries. This study primarily aimed to compare the effect of infraorbital nerve block on sevoflurane requirement in infants undergoing cheiloplasty. Intraoperative opioid consumption, hemodynamics, blood glucose levels, extubation time, and delirium were also compared. Methods: This prospective, randomized, double-blinded study was conducted in 34 infants undergoing cheiloplasty under general anesthesia. After induction, group A received bilateral infraorbital nerve block with 0.5 mL of 0.5% bupivacaine and group B 0.5 mL saline. An increase in heart rate or blood pressure > 20% was managed by increasing sevoflurane by 2-2.5%, followed by fentanyl 0.5 ㎍/kg bolus. The chi-square test and independent-sample t-test were used where applicable. Results: Demographics, duration of surgery, and intravenous fluids used were comparable between the groups. Compared to group A, patients in group B had significantly higher consumption of fentanyl (14.2 ± 4.4 ㎍ vs. 22.1 ± 6.2 ㎍) and sevoflurane (14.2 ± 4.8 mL vs. 26.8 ± 15.6 mL). Intraoperative hemodynamic parameters were significantly lower in group A, the number of times increases in hemodynamic parameters occurred, and fentanyl supplemental bolus was required remained significantly lower in group A than in group B. Intraoperative glycemic levels remained higher in group B, and the extubation time was significantly shorter in group A than in group B (4.40 ± 1.60 min vs. 9.2 ± 2.18 min). Group A had a lesser occurrence of postoperative delirium. Conclusion: Supplemental infraorbital block in infants undergoing cheiloplasty under general anesthesia resulted in significantly decreased anesthetic requirements and optimal hemodynamic and glycemic levels with faster extubation and lesser delirium.

• Structural Monitoring and Maintenance
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• 제8권4호
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• pp.329-344
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• 2021

The use of structural control devices to minimize structural response to seismic/dynamic excitations has attracted increased attention in recent years. The use of magnetorheological (MR) dampers as a control device have captured the attention of researchers in this field due to its flexibility, adaptability, easy control, and low power requirement compared to other control devices. However, little attention has been paid to the effect of configuration and number of dampers installed in a structure on responses reduction. This study assesses the control of a five-story structure using one and two MR dampers at different stories to determine the optimal damper positions and configurations based on performance indices. This paper also addresses the fail-safe current value to be applied to the MR damper at each floor in the event of feedback or control failure. The model is mathematically simulated in SIMULINK/MATLAB environment. Linear control strategies for current at 0 A, 0.5 A, 1 A, 1.5 A, 2 A, and 2.5 A are implemented for MR dampers, and the response of the structure to these control strategies for different configurations of dampers is compared with the uncontrolled structure. Based on the performance indices, it was concluded that the dampers should be positioned starting from the ground floor, then the 2^nd floor followed by 1^st and rest of the floors sequentially. The failsafe value of current for MR dampers located in lower floors (G+1) should be kept at a higher value compared to dampers at top floors for effective passive control of multi-story structures.