Earticle

In South Korea, frog farming has been permitted to protect Mountain brown frogs which continuously declining and have used as traditional dish resources. Despite of various breeding attempts over last 10 years, successful farming are still rare largely due to the lack of appropriate food items and poor disease managements. This study was conducted to provide useful information on appropriate density and temperature farming conditions to reduce potential pathogens in frog farms. Our study first explores the effects of different temperature and density treatments on the growth and the time to metamorphosis of Rana dybowskii tadpoles. Second, we determined how those two treatments affect the number of bacterial and fungal colonies on the skin and in the liver and heart of metamorphosed juveniles. Our results showed that the temperature treatment affected the growth of tadpoles and the time to metamorphosis unlike the density treatment. The snout-vent length was longer and the time to metamorphosis was greater in low temperature group than those in other temperature groups. Temperature treatment also induced significant differences in the number of bacterial and fungal colonies detected in the examined organs. The number of bacterial and fungi colonies was higher in ambient and low temperature groups than those in the high temperature and field-control group for the three organs. Density treatment showed significant difference only in the number of bacterial colonies. Medium and high density treatment groups had more bacterial colonies than low treatment group and field-control group commonly in the three organs. Our results suggest that 1) low density (10 tadpoles / 20L water) could be better for farming to reduce potential bacterial diseases, 2) low temperature (1℃ below than ambient temperature) might be selected for bigger metamorphosed juveniles, but 1℃ higher temperature than ambient temperature could be better to manage potential bacterial and fungal diseases.

A mixture of alcohol and water is commonly used as antifreeze, liquor, and the fundamental solvents for the manufacture of cosmetics, pharmaceuticals, and inks in our daily life. Since various properties of alcohol water mixtures such as density, boiling or melting point, viscosity, and dielectric constant are determined by their mixing ratio, it is very important to know the mixing ratio to predict their properties. One of simple method to find the mixing ratio is measuring the density of the mixtures. However, it is not easy to predict the mixing ratio from the density of the mixtures because the relationship between mixing ratio and density has not been established well. The relationship is dependent on the relative sizes of solute and solvent molecules, and their interactions. Recently, an empirical model to predict the density of glycerol water mixture from their mixing ratio has been introduced. The suggested model is simple but quite accurate for glycerol water mixture. In this article, we investigated the applicability of this model to different alcohol water mixtures. Densities for six different alcohol water mixtures containing various alcohols (e.g., ethylene glycol, 1,3-propane diol, propylene glycol, methanol, ethanol, and 1-propanol) were simulated and compared to experimentally measured ones to investigate the applicability of the model proposed for glycerol water mixtures to other alcohol water mixtures. The model predicted the actual density of all alcohol water mixtures tested in this article with high accuracy at various ratios. This model can probably be used to predict the mixing ratio of other alcohol water mixtures from their densities beyond 6 alcohols tested in this article from their densities.

The anatomical properties of unproductive oil palm stems (OPS) and their correlation with density were studied from the core to the bark at the bottom, middle, and top sections for effective utilization. Observations of anatomical features were performed with optical and scanning electron microscopy, while density measurements were conducted with an electronic densimeter (MH-330A; Omena, China). The number of vascular bundles (VBN) increased from core to bark and decreased from top to bottom. The fiber bundle area (FBA) increased from core to bark and from top to bottom. Fiber length (FL), width (FW), and wall thickness (FWT) decreased from the bottom to the top, whereas the fiber lumen diameter (FLD) increased. FL across all sections showed a decreasing trend from core to bark. Radial variations in FW, FLD, and FWT differed across sections. The fiber derivative values in the inner part of the middle section were comparable to those in the top section, predominantly showing third-grade pulp quality. In contrast, the bottom section exhibited the characteristics similar to the outer part of the middle section, where fibers were largely classified as fourth-grade pulp. Density was found to have a positive correlation with VBN, while FBA, FL, and FW exhibited a negative, though statistically insignificant, relationship with oven-dry density. No correlation was observed between FWT, FLD, and OPS density.To conclude, distinct variations in quantitative anatomical characteristics were observed within the OPS, suggesting that fiber properties can serve as indicators of stem quality. In general, fiber quality declined from the top to the bottom sections and from the core outward.

Revolving doors can impede rapid evacuation during fire emergencies due to their structural characteristics, which pose a potential hazard. This study utilized the Pathfinder simulation software to analyze and compare the Required Safe Egress Time (RSET) and occupant density based on revolving door passage speed and utilization rates under different evacuation scenarios. When both revolving doors and swing doors were operational, or when revolving doors were closed and only swing doors were used, areas with an occupant density exceeding 3 persons per square meter were observed in the entrance area. However, when revolving doors were deactivated and the width of swing doors was expanded, a reduction in RSET was observed, and no areas with an occupant density exceeding 3 persons per square meter were identified. Therefore, buildings equipped with revolving doors should acknowledge the risks associated with their use. They must ensure sufficiently wide emergency exits or implement systems that allow revolving doors to open during emergencies to facilitate efficient evacuation. Furthermore, it is crucial to establish additional regulations governing the operation and safety standards of revolving doors during emergency scenarios.

본 연구는 돈군의 크기를 달리했을 때 육성돈의 행동 특 성을 파악하기 위해 실시되었다. 돈사별 합사 밀도(6개체, 10개체, 13개체)를 달리하고 합사후 1일, 20일, 40일에 하루 8시간씩 돼지의 행동을 디지털 캠코더를 이용하여 촬영하 였다. 촬영된 영상을 바탕으로 육성돈의 행동 유형별 지속 시간과 빈도를 분석하였다. 휴식 행동이 전체 연구기간 동 안 가장 많은 부분을 차지하였다. 기타 개체유지행동과 기 타 사회 행동을 제외한 모든 육성돈의 행동은 돈군별로 유 의한 차이를 보이는 것으로 나타났다. 적대 행동과 벨리 노우징, 인접한 돈방 개체와의 상호작용, 꼬리 물기 및 승 가 행동은 고밀도 돈사에서 다른 돈사에 비해 매우 높았 다. 육성돈의 일당증체량과 유형별 행동 사이의 관계를 분 석한 결과, 적대 행동과 벨리 노우징, 승가 행동이 일당증체량과 부의 상관관계가 있었다. 고밀도 돈방에서 육성돈 의 공격적 성향이 매우 높은 것으로 나타났다. 본 연구 결 과 육성돈의 합사 밀도는 공격 행동을 비롯한 다양한 행동 에 영향을 미치는 것으로 판단된다.

This study was conducted to clarify behaviors of growing pigs between different group size (low density: 1.65 m2/pig, medium density: 0.99 m2/pig and high density: 0.76 m2/pig). The growing pigs were housed in each group size and observed with the aid of video technology for 8 consecutive hours in days 1, 20 and 40 days after mixing. Most of self-maintenance and social behaviors, exclude other self-maintenance and other social behaviors, were significantly different among group sizes. Inactive behavior was most common during the study period. The behaviors of agonistic, belly nosing, interaction with adjacent pen, tail biting and mounting were significantly higher in high density than in low and medium densities. Agonistic, belly nosing and mounting behaviors were negatively correlated with average daily gained body weight. This study reveals a higher level of aggression in high density than in low and midium densities. It is concluded that behaviors of growing pigs are critically affected by group size.

교통밀도는 교통수요와 가장 직접적인 관계가 있으므로 거시적인 지표 중에서 가장 중요하 다고 알려져 있으며(Traffic Engineering, 2004), 특정시각 주어진 거리 안의 존재하는 차량의 대 수로 정의한다. 하지만, 밀도는 기상과 도로조건 및 비용 상의 문제로 인하여 현장에서 직접 수집이 어렵다. 이런 이유로 속도와 교통량보다 상대적으로 연구가 활발하게 이루어지지는 않 아 수집방법에 관한 다양한 시도뿐만 아니라 측정된 값의 정확도에 관한 연구가 많이 부족하 다. 이에 본 논문에서는 밀도를 측정할 수 있는 방법으로 여러 대의 카메라 영상을 정합 (synthesis)하는 기술을 활용하였다. 이러한 밀도수집시스템으로 수집한 밀도를 정의에 기반 한 참값으로 선정하고, 이 값을 전통적인 측정방법들로 산출한 밀도와 비교하였다. 비교결과, 관 계식(fundamental equation)을 이용한 산출방법으로 산출한 밀도 값이 참값과 비교하여 RMSE(Root Mean Square Error)가 1.8-2.5로 가장 참값에 가깝다. 또한 향후 밀도를 직접 수집할 때 유의하여할 수집 간격 등의 간과하기 쉬운 이슈사항을 순간밀도와 평균밀도를 산출하여 알 아보았다. 실험 사이트의 실제 교통상황은 LOS B임에도 불구하고, 초 당 순간밀도는 최대 (16veh/km)에서 최소 2(veh/km)의 값이 다양하게 관측되어 교통상황의 판단이 어려웠다. 하지 만 30초 간격으로 15분 평균밀도는 8.3-7.9(veh/km)로 정확하게 LOS B를 판단하였다.

Traffic Density is the most important of the three primary macroscopic traffic stream parameters, because it is most directly related to traffic demand(Traffic Engineering, 2004). It is defined as the number of existing vehicles within a given distance at a certain time. However, due to weather, road conditions, and cost issues, collecting density directly on the field is difficult. This makes studies of density less actively than those of traffic volume or velocity. For these reasons, there is insufficient attempts on divers collecting methods or researches on the accuracy of measured values. In this paper, we used the ‘Density Measuring System’ based on the synthesise technology of several camera images as a method to measure density. The collected density value by the ‘Density Mesuring System’ is selected as the true value based on the density define, and this value was compared with the density calculated by the traditional measurement methods. As a result of the comparison, the density value using the fundamental equation method is the closest to the true value as RMSE shows 1.8 to 2.5. In addition, we investigated some issues that can be overlooked easily such as the collecting interval to be considered on collecting density directly by calculating the moment density and the average density. Despite the actual traffic situation of the experiment site is LOS B, it is difficult to judge the real traffic situation because the moment density values per second are observed max 16.0 (veh/km) to min 2.0 (veh/km). However, the average density measured for 15 minutes at 30-second intervals was 8.3-7.9 (veh/km) and it indicates precisely LOS B.

To confirm the effect of alkaline water drinking on the red blood cell density, the participants were divided into two groups, purified water (PW) drinking group (n=10) and alkaline water(AW) drinking group (n=10). Two uL of blood was collected before drinking water, and at 10 minutes, 30 minutes, 1 hour, and 2 hours after drinking 15mL/kg within 10 minutes. Blood was on the slide glass under light microscope, red blood cells were counted from taken by 400 times. Also, to confirm the effect of alkaline water drinking on the properties of urine, urine was collected before drinking water and when it feel nature calls after drinking. Urobilinogen, glucose, bilirubin, ketone body, gravity, RBC, protein, WBC, pH and MDA in urine were investigated. Purified water (pH 6.9, +372mV) was produced only by physical filtering using commercial purified filter. AW (pH 9.2, +203.8mV) was prepared by Mineral water ionizer (Blue QQTM, Eagle Eye America Inc., Korea). Red blood cell density was showed lower tendency in AW group than PW group until an hour after drinking, and especially lowest tendency in 30 minutes (p<0.05). But two hours later, it was showed tendency to back to normal. ROS was showed low tendency both AW and TW groups after drinking. AW group was lower than PW group. Urobilinogen, glucose, bilirubin, ketone body and protein were showed low tendency both AW and PW. But pH was showed rising trends both AW (p<0.001) and PW group (p<0.01). Alkaline water is absorbed faster to the blood compared to the tap water and have higher antioxidant effect than PW group.

The light weight foamed concrete has many advantages. Because there are many pores in the matrix of concrete at the viewpoint of the insulation and fire resistance. Therefore it has been used in applications requiring insulation. The insulation property of light weight foamed concrete varies according to density. Also, density is varies according to hardened matrix and pore rate. The purpose of the experiment is to know the thermal properties of light weight foamed concrete according to the change of density and the shape of iron plate, when heating the light weight foamed concrete. The results of this experiment are as follows. The higher density of concrete, the lower temperature of that. This tendency is not same as that of ordinary light weight foamed concrete. It seems that temperature decrease of concrete can be affected by vapor phenomenon of inner water of concrete when concrete is heated. The specimen of density 0.9 is showed lowest temperature. Also, the perforated specimen was efficient in preventing temperature increase.

This study entailed non-destructive micro-computed tomography and chromaticity distribution (histogram) analysis of tomographic images with the aim of characterizing the physical properties including the internal structure and density of five samples of lime plaster collected from lime-comprised Goguryeo mural tombs dated to the 4th–6th centuries. Non-destructive micro-computed tomography analysis identified the layered structure of the walls, the distribution of component minerals, and the size and distribution of pores. Chromaticity distribution analysis of cross-sectional images identified density trends in component materials. Combining these methods is an effective research approach for determining the physical properties of plaster while minimizing damage to research materials.

This study experimentally evaluated the long-term thermal degradation of expanded polystyrene (EPS) insulation collected from aged buildings. Thirty-five field samples with service lives ranging from 13 to 31 years were tested using the heat flow meter method in accordance with ISO 8301 and KS L 9016 to measure thermal conductivity (λ) and density (ρ). The measured thermal conductivity varied between 0.037 and 0.050 W/(m·K), with an average of 0.044 W/(m·K), representing approximately a 2–20% increase compared with the KS reference values for new EPS. The average density decreased by about 40% relative to the initial reference level. A strong negative correlation was observed between density and thermal conductivity (r = –0.732, p < 0.05), while a weak-to-moderate positive relationship was identified between density reduction and the increase in thermal conductivity (r = 0.41, p < 0.05). These findings suggest that density loss and microcell structural degradation are likely major contributing factors to the thermal performance degradation of aged EPS insulation. The regression models derived from this study provide foundational reference data for establishing correction factors that reflect the degraded thermal properties of aged insulation in building energy performance assessments and the green remodeling applications.

For experimental studies on the production of MR fluid for MR dampers, MR fluid with a viscosity of 506 cP and a density of 2.6 g/cc was produced. In order for MR fluid to have suitable performance for MR dampers, it is important to select surfactants, magnetic particles, base oil, and characteristic additives to obtain high damping force and maintain physical and chemical properties. In order to investigate the redispersibility of MR fluid, viscosity, density, saturation magnetic flux density, dispersibility, and temperature effects were evaluated. A particle size distribution meter and a vibrating magnetometer were used, and a yield stress and redispersion device were developed to obtain the yield stress of the MR fluid. The recovery rate of MR fluid was approximately 97% at 0.2% succinic acid coating and 8% anti-settling agent. And when current is applied, the viscosity increases by more than 90% due to magnetic properties.

본 논문은 국내 신성장 산업을 중심으로 무역경쟁력을 분석하여, 산업의 성장 가능성에 미치 는 영향력에 대해 분석하였다. 분석은 수출시장점유율, 현시비교우위지수(RCA), 근접도 (Proximity), 밀도(Density) 분석을 하였다. 주요 분석 결과는 다음과 같다. 첫째, 한국의 수출 증 가율이 높은 품목은 반도체, 전기자동차, 첨단신소재, 바이오 헬스케어 4개 산업이며, 로봇, 2 차전지, 디스플레이 산업은 낮게 나타났다. 둘째, 시장점유율 분석 결과 첨단신소재, 반도체, 2차전지 순으로 점유율이 높게 나타났으며, 디스플레이 산업은 점유율 약화를 나타냈다. 셋째, 현시비교우위지수 분석 결과 바이오헬스케어 산업을 제외하고는 대부분 1 이상으로 나타났으 며, 디스플레이산업과 로봇산업의 지수 감소가 나타났다. 넷째, Density 분석 결과 분석 대상 7개 산업의 Density는 0.4 이하의 지표를 나타내고 있어, 산업 확장 능력은 보통 수준으로 분석 되었다. 본 연구 결과는 우리나라의 신성장 산업은 수출시장점유율과 현시비교우위지수 등에 서 상대적 우위를 나타내고 있으나, 지수 추이는 감소 추세를 나타내고 있고, 산업 확장 능력 또한 낮은 수준으로 분석되었다. 따라서 제품 R&D 강화와 혁신기업에 대한 정부 지원, 기업의 마케팅 능력 강화를 통한 산업 성장 촉진이 요구된다.

Purpose : This paper analyzes the trade competitiveness of domestic new growth industries and analyzes the influence they have on the growth potential of industries. Research design, data, methodology : The analysis period is 2015-2021, and the analysis target is based on 6 units of industry HS codes in 7 new growth industry fields. The analysis included export market share, current comparative advantage index (RCA), proximity, and density. Results : As a result of the current comparative advantage index analysis, most of them were above 1 except for the bio-healthcare industry, and the display industry and robot industry showed a decrease in the index. As a result of the density analysis, the density of the seven industries subject to analysis was below 0.4, and the industry's expansion ability was analyzed to be at a normal level. Conclusions : In order to grow new growth industries, it is necessary to promote industrial growth by strengthening product R&D, government support for innovative companies, and strengthening companies' marketing capabilities.

재난 및 재해 상황시 이동관리전략을 신속히 마련하기 위해서는 특정 도로구간을 통행하는 교통류의 특징과 도로의 위상학적 구조 등을 사전에 파악해야 할 필요성이 있다. 이는 도로관 리자가 미시적 도로단위별로 취약성을 평가한 후 재난·재해 상황에 대비한 적절한 모니터링과 관리방안을 설정하는데 중요한 근거가 될 수 있기 때문이다. 따라서 본 연구에서는 도시부 도 로링크별 취약성 평가를 위하여 공간밀도, 시간점유율, 네트워크 매개중심성 지표를 제시하였 으며, 거리 및 밀도기반 클러스터링 분석을 통하여 각 링크그룹별로 가지고 있는 시공간 및 위상학적 취약성을 정의하였다. 본 연구를 통해 제시된 결과는 도로 링크를 집단별로 특성화 하여 취약성을 관리하는 것에 활용될 수 있으며, 재난·재해 시 우선 통제지점 선정 및 최적경 로 제시를 위한 기초자료로도 활용 가능할 것으로 기대된다.

It is necessary to grasp the characteristics of traffic flow passing through a specific road section and the topological structure of the road in advance in order to quickly prepare a movement management strategy in the event of a disaster or disaster. It is because it can be an essential basis for road managers to assess vulnerabilities by microscopic road units and then establish appropriate monitoring and management measures for disasters or disaster situations. Therefore, this study presented spatial density, time occupancy, and betweenness centrality index to evaluate vulnerabilities by road link in the city department and defined spatial-temporal and topological vulnerabilities by clustering analysis based on distance and density. From the results of this study, road administrators can manage vulnerabilities by characterizing each road link group. It is expected to be used as primary data for selecting priority control points and presenting optimal routes in the event of a disaster or disaster.

고고성지가 입지하고 있는 공간의 특징을 GIS 공간기술을 통해 분석하는 것은 중국고대의 통 치와 지배가 관철되는 장소를 선택하는 배경에 대해서 정치적인 원인 이외에 지형과의 관계를 통해 나타날 수 있는 새로운 기준을 제시하고자 하는 것이다. 이를 바탕으로 성시의 형성과정의 실제의 모습을 고찰해 볼 수 있다고 생각한다. 중국고대사 연구의 분야에서 고고자료의 활용은 매우 중요한 과제이다. 고고성지의 목록이 축 적되어 가고 있는 상황에서 진한시대사 연구에서는 잘 주목하지 않았던 성시자료를 자연환경과 의 관계 속에서 논의 해보고자 한다. 구체적으로 考古城址의 입지분석을 통해서 이루어지는데 이 때 고고성지의 위치는 평면도상의 위치를 말하는 것이 아니라 지형과의 관계를 반영하고 있는 위치 를 말한다. GIS기술은 고고유적이 가지고 있는 위치 및 공간정보를 통합적으로 관리하고 분석하 여 지도에 표시할 수 있는 도구이기 때문에 위치정보를 기반으로 하여 위에서 제시한 성시의 위치 와 주변지형과의 관계에 대하여 다양한 검토가 가능하다. 이 논문에서는 QGIS라는 오픈소스 개방형 GIS프로그램을 이용하여 유적의 위치와 지형도 등 의 공간정보를 공간데이터 기반으로 정리하여 한대의 성시가 형성되는 과정을 한 대 의 취락유 적인 고고성지와 묘지의 정량적인 공간분석을 하였다. 지형의 起伏을 수치화한 DEM(Digital Elevation Model, 수치표고모델)을 사용하여 취락들이 입지한 지형을 분석하였다. 이 수치표고모 델인 DEM을 이용하여 지형의 경사, 사면방향, 표고에 기반한 유적의 위치의 특징을 분포도를 통 해 제시하였다. 고고성지가 입지하고 있는 공간의 특징을 GIS 공간기술을 통해 분석하는 것은 중국고대의 통 치와 지배가 관철하기 위한 장소가 입지하는 원인을 정치, 경제적인 것 이외에 주변 환경과의 관계 를 중심으로 살펴서 城市의 형성원인에 나타난 통치의 방식과 그 변화의 또 다른 원인을 규명하 는 것이 연구의 목적이라고 할 수 있다.

Causes behind the formation of a walled city are specifically examined through the analysis of ancient walled cities in their locations. Here, the location of a walled city reflects its relations with its surrounding geographical features instead of its position on a ground plan. The GIS technology offers a tool to manage and analyze comprehensively the location and spatial information of ancient relics and mark them on a map. It allows researchers to carry out various reviews of walled cities in their locations and relations with their surrounding geographical features mentioned above based on their location information. By analyzing the spatial features of ancient fortress sites with the GIS space technology, researchers can provide a new set of criteria for backgrounds to select places to rule and dominate in ancient China based on their relations with their surrounding geographical features other than political causes. These can offer a basis to examine the actual formation of a walled city. In the field of research on ancient Chinese history, the utilization of archeological materials poses a very important task. In a situation where the lists of ancient fortress sites were piling up, this study set out to discuss materials about walled cities, which had not received much attention in the study of Qin and Han Dynasties and their history, their relations with their sur rounding natural environments. The study conducted quantitative spatial analysis of ancient fortress sites and cemeteries, which were settlement relics from Han, to figure out the formation process of a walled city in Han b y arranging their spatial information including their locations and topographical maps based on spatial data with an open source GIS program called QGIS. Using a digital elevation model(DEM), which translates topographical elevations into numbers, the investigator analyzed the geographical features of the places where settlements were located. Using the DEM, the study presented the characteristics of relics' locations in a distribution chart based on the inclines, incline directions, and altitudes of their geographical features. By analyzing the spatial features of the locations of ancient fortress sites with the GIS space technology, the present study aimed to examine the causes behind the places of rule and dominance in ancien t China in their r elations with their surrounding environments other than political and economic causes and identify new causes in the formation of walled cities o ther than the me thods of rule and their changes.

본 연구는 문화재 방사선 조사에서 고려하지 않았던 산란 방사선의 영향을 확인하기 위해 관전압 (kVp) 과 필름-바닥 거리(film-floor-distance: FFD) 납스크린 배치를 달리하여 평가하였다. 연구결과, 실험시편의 투과농도와 산란 방사선의 투과 농도는 관전압에 따라 증가되었다. 실험시편의 투과농도는 평균 1.4 D의 편차를 보이며, 60 kVp에서 0.17 D, 160 kVp에서 1.54 D, 220 kVp에서 2.97 D로 확인되었다. 산란 방사선의 평균 투과농도는 60 kVp에서 0.10 D, 160 kVp에서 0.40 D, 220 kVp에서 0.46 D로 확인되었다. FFD 거리가 바닥면과 멀어질수록 관전압(60 kVp-160 kVp)구간의 경우 투과농도 (D)가 커지는 경향을 보였으나, 고전압(160 kVp-220 kVp)구간은 FFD 거리 증가에 따른 투과농도 변화가 확인되지 않았다. 납스크린 없는 조건과 바닥면(floor)을 납스크린으로 대체한 경우는 FFD 50 mm, 100 mm, 200 mm 거리에서 산란 방사선이 확인되었고, FFD 0 mm 거리는 확인되지 않았다. 식별률은 관전압 160 kVp에 서 FFD에 따라 2.08~2.67% 범위이며, 관전압 220 kVp에서는 2.67~3.33% 범위로 측정되었다.

This study was conducted to evaluate the effects of scattering radiation, which was not considered in the cultural Heritage radiography, by evaluating the relationship between the tube voltage (unit: kVp), film-floor-distance(FFD), and lead screen layout. The density (unit: D) of the test specimens and the scattered radiation increased with the tube voltage. The density of the test specimens showed an average deviation of 1.4 D; it was 0.17 D at 60 kVp, 1.54 D at 160 kVp, and 2.97 D at 220 kVp. The mean density of the scattered radiation was 0.10 D at 60 kVp, 0.40 D at 160 kVp, and 0.46 D at 220 kVp. The density tended to increase when the tube voltage ranged between 60 kVp and 160 kVp, as the FFD distance increased. However, a change in the permeation density was not observed for high voltages(160 kVp-220 kVp). Scattered radiation was observed when FFD was 50 mm, 100 mm, and 200 mm and no lead screen was used and the bottom surface was replaced with the lead screen. No scattered radiation was observed when FFD was 0 mm. The identification rate ranged from 2.08% to 2.67%, according to the FFD, for a 160 kVp tube voltage, and from 2.67% to 3.33% for a 220 kVp tube voltage

CNG 차량의 경우 압력센서를 이용하여 CNG의 양을 계측하고 있다. 그러나 주변 환경 조건에 따라 정확한 양을 파악하는데 어려움이 있어 운전자에게 불안감을 조성하게 된다. 본 연구는 CNG 연료 시스템에서 CNG의 양을 정밀하게 측정하기 위한 기초 연구로써 CNG 연료량 검출 시스템을 모사하여 측정방법을 제시하고자 한다. 실험은 Type-3의 CNG 탱크에 초음파 센서를 적용한 연료량 검출 모사장치 구현하였다. 그리고 내부의 압력은 압축공기를 이용하여 100 bar 에서 0 bar 까지 5 bar 단위로 저감시키면서 초음파 센서의 수신 신호를 검증하였다. 그 결과 탱크 내 압력이 감소함에 따라 초음 파 센서의 출력 신호가 감쇠하는 것을 알 수 있었고, 다소 차이는 있었지만 선형성을 띄고 있는 것을 확인할 수 있었다.

The amount of CNG was measured using a pressure sensor in the case of CNG vehicles. However, the current measurement method causes anxiety to the driver because it is difficult to measure the detailed amount of CNG according to various environmental conditions. This study was performed to measure the amount of CNG in CNG fuel system, and presented the method of measurement by simulating the detection system of CNG. In this experiment, a detection simulator with an ultrasonic sensor in CNG tank of Type-3 was designed, and the reception signal of the ultrasonic sensor was verified by reducing the pressure from 100 bars to 0 bars (increment=5 bars) using compressed air. As a result, the output signal voltage of the ultrasonic sensor decreased as the pressure in the tank decreased, and the it was verified that the shape of the graph was linearity.

In order to identify the environmental factors that cause the dysoxic water, the water temperature difference(del_temp), salinity difference(del_sal), density difference(del_rho), Brunt-Väisälä frequency(bvf), Richardson Number(ri_num) Logistic regression analysis was performed on the six explanatory variables of difference(del_z). Mcfadden R ^ 2 of the regression model was 0.7422 and the explanatory power of the model was good. According to ANOVA analysis, the temperature difference, stratigraphy stability(bvf) and Richardson number were significant in the generation of dysoxic water, and salinity difference was not significant. In particular, the p-value for the temperature difference was 2.2 * 10 ^-16, close to zero. Therefore, it was found that the water temperature difference between the surface layer and the bottom layer is the most influential factor in the occurrence of dysoxic water in Dangdong Bay. As a result of estimating the probability of occurrence of dysoxic water by using the depth difference and water temperature difference among the above six explanatory variables, the probability of occurrence of dysoxic water is 70% when water depths are 5m, 10m, 15m and 20m, The temperature differences were about 8℃, 6℃, 5℃ and 3℃, respectively.

본 연구는 대학생 프로젝트 팀의 리더십 네트워크 특성이 팀 몰입과 팀 성과에 미치는 영향을 검증하고자 하였다. 이는 리더십 연구에 있어 전통적인 접근법이라 할 수 있는 수직적 리더십과 최근 환경의 변화에 부응하기 위해 학계와 실무에서 많은 관심을 받고 있는 공유리더십을 함께 고려하여 팀 기반 환경에 적합한 리더십을 규명하기 위한 의미 있는 연구라 할 수 있다. 본 연구에서는 팀 내 리더십 영향력 패턴을 보다 잘 파악하기 위해 사회네트워크 접근법을 활용하였다. 기존 선행연구들을 토대로 본 연구에서는 리더십 네트워크의 중심성이 팀 몰입과 팀 성과에 정(+)의 영향을 미칠 것이라는 가설과 함께 리더십 네트워크의 밀도 역시 팀 몰입과 팀 성과에 정(+)의 영향을 미칠 것이라는 가설을 설정하였다. 가설 검증을 위해 81개 대학생 프로젝트 팀의 374명의 학생들을 대상으로 설문조사를 실시하였다. 본 연구의 가설검증 결과 리더십 네트워크의 중심성과 밀도 모두 팀 몰입과 팀 성과에 정(+)의 유의한 영향을 주는 것으로 나타났다. 이러한 결과는 중심성과 밀도 모두 팀 내에서 팀 몰입과 팀 성과를 증진시키는 요인으로 작용하고 있음을 의미한다. 나아가 팀 내에서 높은 중심성과 높은 밀도의 특성을 갖는 리더십 네트워크는 함께 공존할 수 있으며 중심성과 밀도 각각의 긍정적인 영향력이 상호 보완적인 역할을 수행하면서 팀 몰입과 팀 성과를 설명하는 요인들로 작용함을 의미한다. 연구결과를 토대로 연구의 한계 및 향후 연구방향을 제시하였다.

Leadership is considered crucial for enabling team effectiveness, but most existing research on team leadership has focused narrowly on the influence of an individual team leader, thus largely neglecting leadership provided by team members. Current forms of teamwork that emphasize knowledge-based work rely on employees who have high levels of expertise and seek autonomy in how they apply their knowledge and skills and therefore desire greater opportunity to shape and participate in the leadership functions for their teams. Utilizing social network approach, we investigated density and centrality of leadership in team and their influence on team commitment and team performance, in order to better capture these overall patterns of influence. The purpose of this study is to examine the effects of leadership network characteristics on team commitment and team performance. Based on prior literature, this study derives following hypotheses. H1. Leadership network centrality will be positively related to team commitment. H2. Leadership network centrality will be positively related to team performance. H3. Leadership network density will be positively related to team commitment. H4. Leadership network density will be positively related to team performance. To test the proposed hypotheses in our study, we collected data via a survey with a sample of 81 university student teams, comprising 374 respondents (on average 4.38 per team). Centrality and density were measured by 3 items from Kent & Moss(1990). The measurement of centrality and density can be measured by tie type among team members(Balkundi & Harrison, 2006). Team commitment was measured by scale from Van der Vegt, Emans & Van de Vliert(2000) on a 4-item scale. Team performance was measured by 11-item scale from Henderson & Lee(1992), Hoegl & Gemuenden(2001), Gemuenden & Lechler(1997). Items were rated on a 7-point Likert-type scale ranging from 1 to 7. The major findings are as follows: First, centrality of leadership network was positively associated with team commitment and team performance. Mangers should therefore ensure that each team has a clear and shared sense of direction, prepares working plans, prioritize and allocate team tasks and promote and establish norms of participations and workload sharing. Second, density of leadership network was also positively associated with team commitment and team performance. The findings suggest that organizations should help develop strong shared leadership patterns within their teams to bolster effectiveness. Organizations can promote shared leadership by setting expectations and encouraging members when teams initially form to view themselves and their fellow team members as leaders and to engage in shred, mutual leadership. Using a network-based measure of centrality and density, which better captures the patterns of mutual influence inherent in the construct, the findings provide several important theoretical and practical implications regarding leadership network characteristics in the team context and future research directions are discussed.

This experimental study was performed to investigate the mechanical characteristics of surface treated coarse aggregates and concrete using them, And, the applicability was confirmed and increasing effect in compressive strength was evaluated. Here, Surface treating is to remove the mortar paste bonded on the surface of recycled coarse aggregates and the grade of surface treatment which is the principal test variable is the number of drum rotation in Los-Angeles abrasion test. Test result showed the increase of about 30% in compressive strength was developed when recycled coarse aggregates treated with 300 rotations were used in the concrete. However, there was no increase in the concrete using recycled coarse aggregate treated with more than 300 rotations. Considering the limit of increase in compressive strength and the cost effectiveness in surface treating, the grade of surface treating with 300 rotations was the optimized one. The characteristics of recycled coarse aggregate, density, absorption, and unit weigh, was linearly improved with the increase of the grade of surface treatment. Loss in weigh in abrasion test showed high rate in increase in the range of 100 rotations and low rate in the range of more than 100 rotations. The slump in the concrete with recycled coarse aggregate linearly increase with the increase of the grade of surface treatment.