목적 : 본 연구는 동공크기 변화에 따른 굴절이상과 고위수차를 노안 전후의 연령군으로 분류하고 비교 분석하여 노안 처방 등의 임상에 도움이 될 수 있는 정보를 제공하고자 한다. 방법 : 안질환 및 굴절교정 수술을 받은 경험이 없는 20세~80세의 성인 남녀를 20~40세 그룹과 45~80세 두 그 룹으로 나누어 굴절이상과 고위수차를 측정하였다. 동공크기 변화에 따른 굴절이상과 고위수차의 비교는 Paired-T test를 이용하였고, 연령에 따른 상관분석은 Pearson correlation으로 실시하였다. 결과 : 20~40세 대상자의 등가구면 굴절력은 동공크기 3 mm에서 –3.193±2.494 D, 5 mm에서 –3.386±2.451 D로 0.193 D 근시도가 증가하였으며, 45~80세 대상자의 등가구면 굴절력은 동공크기 3 mm에서 0.015±1.340 D, 5 mm에서 –0.054±1.566 D로 0.069 D 근시도가 증가하였다. 또한 동공크기 3 mm에서 20~40세 대상자보다 45~80세 대상자의 코마수차는 0.026 μm, 구면수차는 0.016 μm, 트레포일수차는 0.037 μm, 비점수차는 0.012 μ m, 콰트레포일수차는 0.022 μm 증가하였다. 결론 : 노안교정을 위한 누진굴절력렌즈 처방 시 시력을 저하시킬 수 있는 동공크기나 고위수차를 참고하여 처 방해야 할 것으로 생각된다.

In in vitro fermentation studies, feed samples can either be included in the in vitro rumen medium using filter bags or can be directly dispersed. The objective of this study was to investigate the effects of different pore sizes of filter bags on the rumen fermentation characteristics in an in vitro system. Corn, soybean meal, and timothy were ground to pass through a 1.0-mm screen and were formulated in the ratio of 70:7:23 based on DM, respectively. The formulated experimental diet (2g/DM) was put in F57 filter bags and R510 nylon bags (Ankom®) which pore sizes were 25 and 50 μm, respectively. An in vitro study was conducted to determine the rumen fermentation characteristics for 3, 6, 12, 24, and 48 h and rumen microbial community at 48 h of incubation. A significantly higher production of gas was observed in the R510 bags than in F57 at all the incubation times (p<0.01). IVDMD (p<0.01) and IVNDFD (p<0.01) were significantly higher, whereas pH (p<0.01) and NH3-N (p<0.01) were lower when R510 bags were used. In the VFA composition, acetate and butyrate were significantly higher (p<0.01) in R510 bags, and propionate and total VFA concentration did not differ (p=0.55 and 0.25, respectively) between F57 and R510 bags. The log copy numbers of bacteria and protozoa did not differ (p=0.69 and 0.94, respectively) between F57 and R510 bags, whereas those of fungi were significantly higher in R510 than in F57 bags (p<0.01). Therefore, the use of R510 may reflect actual rumen fermentation characteristics more precisely than those of F57 because increased gas production, nutrient digestibility and acetate, butyrate proportion were founded in R510.

PURPOSES : Concrete pavement is excellent in structural performance and durability. However, its functionality – such as noise and skid resistance – is a shortcoming. Functionality such as noise reduction and skid resistance of concrete pavement is affected by the texture surface, and the texture surface is classified according to the length of the wavelength. In recent years, Fine-size exposed aggregate concrete pavement has been applied, which has excellent structural performance and durability, and secures functionalities such as noise reduction and long-term skid resistance by randomly forming texture surface. Fine-size exposed aggregate concrete pavements are constructed by removing the surface cement binder to randomly expose coarse aggregate and their functionality is mainly governed by the surface texture. However, deteriorated concrete by tire-pavement friction and deicing agent may cause abrasion and aggregate loss on the surface texture; thus reducing their functional performances. Abrasion is created by the thin cutoff of aggregate texture under repeated tire-pavement friction. In addition, aggregate loss is defined by the detachment of aggregates from cement binder. This study aims to evaluate the abrasion and aggregate loss of Fine-size exposed aggregate concrete pavement surface texture under tire-pavement friction and scaling tests. METHODS : In the study, abrasion and aggregate loss of tining and exposed aggregate concrete surface treatments were evaluated. Deterioration of each surface treatment was replicated by scaling test under ASTM C 672 test method. Afterward, abrasion test was conducted by ASTM C779 to simulate the tire-pavement friction under traffic. Consequently, abrasion and aggregate loss were measured. RESULTS : Abrasion depth of non-scaling tining, 10-mm EACP, and 8-mm EACP was 1.76, 1.12, and 1.01mm, respectively. Compared to scaling surface treatments, the difference of abrasion depth in tining texture was the largest with value of 0.4mm. For both textures of finesize exposed aggregate concrete, abrasion depth difference was about 0.1mm. Moreover, The 10-mm EACP exhibited a 2.6% of aggregate loss rate caused by tire-pavement friction before conducting concrete deterioration test. After 40-cycle scaling test, aggregate loss increased up to 12.2%. For 8-mm EACP, aggregate loss rate was 1.7% on non-scaling concrete. Further, this rate was magnified up to 7.3% for the 40-cycle scaling concrete. CONCLUSIONS : Under non-scaling or scaling tests, fine-size exposed aggregate concrete pavement showed better abrasion resistance than tining texture since tining was formed by aggregates and cement binder. Additionally, rate of aggregate loss was significant when EACP experienced the deicing agent under numerous cycles of freeze-thaw action.

As a case study on aspect ratio behavior, Kaolin, zeolite, TiO2, pozzolan and diatomaceous earth minerals are investigated using wet milling with 0.3 mm media. The grinding process using small media of 0.3 pai is suitable for current work processing applications. Primary particles with average particle size distribution D50, ~6 μm are shifted to submicron size, D50 ~0.6 μm after grinding. Grinding of particles is characterized by various size parameters such as sphericity as geometric shape, equivalent diameter, and average particle size distribution. Herein, we systematically provide an overview of factors affecting the primary particle size reduction. Energy consumption for grinding is determined using classical grinding laws, including Rittinger's and Kick's laws. Submicron size is obtained at maximum frictional shear stress. Alterations in properties of wettability, heat resistance, thermal conductivity, and adhesion increase with increasing particle surface area. In the comparison of the aspect ratio of the submicron powder, the air heat conductivity and the total heat release amount increase 68 % and 2 times, respectively.

This study collected and analyzed the fishing process of existing fishing boat and newly built fishing boat by using the video observation methods to understand the improvement of fishing operation efficiency and safety according to the scale change of coastal composite fishing boat. The fishing operation efficiency was calculated by analyzing the frequency of movement, the movement distance and the moving time per basket used in the fishing process to derive the improvement of the newly built fishing boat compared to the existing fishing boat. It was confirmed that the mean frequency of movements decreased to 13.9%, the average moving time decreased to 21.8%, the mean movement distance increased to 20.5% and the movement through the top of gunwale did not occur. Movement of frequency, increased and time according to the fishing operation were directly affected by the width of side passages and the presence or absence of walking obstruction such as bulwark stay, hatch coaming and fishing gears on deck. The results of this study are expected to be used as basic data for redesigning into a safe and efficient coastal composite fishing boat in the future.

Aluminum (Al) - based powders have attracted attention as key materials for 3D printing because of their excellent specific mechanical strength, formability, and durability. Although many studies on the fabrication of 3Dprinted Al-based alloys have been reported, the influence of the size of raw powder materials on the bulk samples processed by selective laser melting (SLM) has not been fully investigated. In this study, AlSi10Mg powders of 65 μm in average particle size, prepared by a gas atomizing process, are additively manufactured by using an SLM process. AlSi10Mg powders of 45 μm average size are also fabricated into bulk samples in order to compare their properties. The processing parameters of laser power and scan speed are optimized to achieve densified AlSi10Mg alloys. The Vickers hardness value of the bulk sample prepared from 45 μm-sized powders is somewhat higher than that of the 65 μm-sized powder. Such differences in hardness are analyzed because the reduction in melt pool size stems from the rapid melting and solidification of small powders, compared to those of coarse powders, during the SLM process. These results show that the size of the powder should be considered in order to achieve optimization of the SLM process.

본 연구는 3개의 종돈회사가 보유하고 있는 6곳의 GGP 농장에서 분만한 Yorkshire종의 번식기록을 이용하여 농장과 산차간의 상호작용효과를 구명하는데 있다. 총산자수와 생존산자수의 평균은 각각 13.4±3.6두와 12.5±3.4두였으며, LSO와 LDO의 평균 세대간격은 각각 17.5개월과 22.0개월로 추정되었다. 산차별 총산자수 기록의 분포는 A(10), B(21), C(30) 그룹과 B(20), B(22), C(31) 그룹에서 뚜렷한 차이를 나타내었으며, 농장×산차의 상호작용효과는 고도의 유의차(P < 0.01)가 인정되었다. Model Ⅱ에서 추정된 유전력과 반복력은 총산자수에서 각각 0.13과 0.21, 생존산자수에서 각각 0.11과 0.19로 나타났다. 총산자수의 육종가를 이용하여 선발된 분만 기록이 있는 개체의 top 1% 비율은 ModelⅠ에서 A(10)농장이 67.4%로 가장 높았고 B(20), C(30), B(21)순이었으나, ModelⅡ에서 B(22)농장이 35.8%로 가장 높았고, B(20) 34.7%, B(21) 12.6%순이었다. 총산자수의 육종가를 이용하여 선발된 자손의 기록이 있는 씨수퇘지들의 top 1% 비율은 ModelⅠ에서 A(10)농장이 55.6%로 가장 높았으나 ModelⅡ에서 C(31)농장이 33.3%로 가장 높았고 B(20)과 B(21) 22.2%순이었다.

본 연구에 이용되는 국내 재래 흑염소는 유전적 자원을 보존하고 품종을 유지하기 위하여 소규모 집단에서 고도의 근친교배를 수행하고 있어 유전적 자질의 다양성이 저해되고 있을 것으로 우려되었다. 따라서 본 연구는 국내 재래흑염소 경상대계통 집단의 유전체 정보를 활용하여 재래흑염소 집단의 유전적 특성과 유효집단의 크기를 추정하고자 실시하였다. 국내 재래 흑염소의 유전체 정보는 Illumina Goat SNP 50k chip (illumina, inc., San Diego, CA)의 정보를 분석하여 연구에 이용하였다. 각 염색체의 인접 표지인자 와의 연관불평형 (Linkage Disequilibrium)은 0.225로 추정이 되었다. 또한, 표지인자 사이의 거리가 증가함에 따라 연관불평형의 값은 감소되는 것으로 나타났다. 국내 재래 흑염소의 유효집단크기는 최근의 세대로 오는 경우 감소하는 추세를 보였으며, 13세대에서 유효집단의 크기는 29두로 추정되었다. 재래 흑염소 경상대계통은 낮은 연관불평형 값과 유효집단 크기를 보여 유전적 자원의 다양성이 낮을 것으로 보이며, 이를 해결하기 위한 계획적인 교배와 품종 집단의 크기를 키우기 위한 대책이 필요할 것으로 사료된다.

Powder characteristics, such as density, size, shape, thermal properties, and surface area, are of significant importance in the powder bed fusion (PBF) process. The powder required is exclusive for an efficient PBF process. In this study, the particle size distribution suitable for the powder bed fusion process was derived by modeling the PBF product using simulation software (GeoDict). The modeling was carried out by layering sintered powder with a large particle size distribution, with 50 μm being the largest particle size. The results of the simulation showed that the porosity decreased when the mean particle size of the powder was reduced or the standard deviation increased. The particle size distribution of prepared titanium powder by the atomization process was also studied. This study is expected to offer direction for studies related to powder production for additive manufacturing.

PURPOSES: The noise problem in concrete pavements has an adverse effect to the road user or nearby residents and is generated by the contact between a tire and the pavement surface. Exposed aggregate concrete pavements have been adopted to solve the tire-pavement noise problem in the United States and Europe. However, the efficiency of the coagulation retarder and exposure equipment used for this kind of pavement has not yet been investigated. Therefore, this study aims to evaluate the ability of the coagulation retarder and exposure equipment in producing the optimum exposed aggregate texture to achieve low pavement noise. A method for the exposure time selection has also been introduced here. METHODS: Sodium gluconate retarders were selected for use in this study. The retarder-water ratios of 1:1, 1:2, and 1:3 were investigated. The retarder was sprayed on a fresh concrete surface with rates of 200 g/m2, 300 g/m2, and 400 g/m2. The aggregates were then exposed to the surface using a steel brush and a water jet. The efficiencies for the low-noise texture, workability, and environmental impact produced by the two exposure devices were estimated. The EAN and the MTD were investigated according to the exposure time. RESULTS : The aggregates were exposed after the retarder was sprayed on the fresh concrete surface; the exposure lasted for 18 h to 26 h each time. The retarder-water ratio of 1:2 and the spraying rate of 300 g/m2 produced an optimum surface texture for low noise. Additionally, the steel brush performed more effectively in exposing aggregate to the surface compared to the water jet. The selected exposure time window (ETW) was 28 h to 35 h. CONCLUSIONS : The optimum retarder was the sodium gluconate retarder with a retarder-water ratio of 1:2 and a spraying rate of 300 g/m2. The steel brush showed a good performance in exposing the aggregates and showing the efficiency of the coagulation retarder in the given environment so as to produce the quality control condition. The ETW was influenced by the construction, mixture design, and construction environment; however, the selected ETW in this study was 26 h~35 h.

PURPOSES : In many European countries, the fine-size exposed aggregate concrete pavement (EACP) technique has been adopted for a quiet pavement. However, different noise reduction levels were reported based on the mixture design and texture conditions. This study aims to suggest a quality control condition for achieving low-noise texture and a mixture design procedure for exposed aggregate concrete overlay (EACO), which will provide the optimum mixture of the surface texture that can reduce the tire-pavement noise. METHODS : The tire-pavement noise is highly influenced by the pavement surface texture. The surface texture of the EACP can be quantified by the mean texture depth (MTD) and the exposed aggregate number (EAN). The optimum condition for the low-noise texture of the EACP was investigated herein based on the analysis of the review of the texture conditions and noise measurement in many EACP sites. RESULTS : The MTD and EAN criteria can be derived according to the investigated relationship between noise and texture condition. The optimum mixture design to satisfy these criteria can be achieved by controlling the maximum size of the coarse aggregate and the S/a. CONCLUSIONS: This study aimed to suggest a quality control condition for achieving low-noise texture and an optimum mixture design for EACO. As a result, we found that the early traffic opening of EACO can be achieved by using high early-strength cement.

섬에 유입된 고양이(Felis catus)는 외래 포식자로서 섬 고유종의 멸종이나 절멸, 생물 다양성 감소 등의 직접적인 요인으로 작용할 수 있다. 본 연구는 제주도의 부속섬인 마라도(N 33° 07′, E 126° 16′)에 유입되어 서식하는 고양이의 개체군 현황과 행동권, 서식지 이용특성을 파악하기 위해 실시되었다. 2018년 3월부터 2018년 7월까지 직접관찰과 포획-재포획법을 통해 개체수 추정 결과, 번식 가능한 성체 총 20마리를 확인하였다. 이 중 10마리에 GPS 무선추적장치를 부착하여 추적한 결과 고양이의 행동권 크기는 12.05±6.99 ha (95% KDE: kernel density estimation), 핵심서식지 크기는 1.60±0.77 ha (50% KDE)로 나타났다. 성별에 따른 행동권과 핵심서식지의 크기는 통계적으로 유의하지 않았고, 10마리 중 8마리가 먹이획득이 쉬운 인간 거주지역을 핵심서식지로 이용하였다. 또한 마라도에 번식하는 멸종위기종인 뿔쇠오리(Synthliboramphus wumizusume)의 번식지에 5마리, 섬개개비(Locustella pleskei)의 번식지에 6마리가 접근하는 것을 각각 확인하였다. 본 연구는 마라도의 고양이 개체수와 행동권에 대한 정보를 최초로 파악하였으며, 특히 고양이 행동권 분석을 통해 철새와 멸종위기종에 대한 가해 가능성을 제시하였다. 철새와 멸종위기 조류의 서식지인 마라도에서 발생할 수 있는 고양이의 피해를 줄이기 위해 향후 고양이의 포식압, 고양이와 멸종위기 조류 개체군의 변동에 대한 모니터링에 관한 연구와 함께, 필요시 고양이 개체군 관리방안을 마련할 필요가 있을 것으로 판단된다.

본 논문은 기상 모델의 미세구름물리 모수화 과정 내의 눈송이의 질량-크기 관계가 지표 강수 모의에 미치는 영향에 대해 연구에 관한 것이다. WDM6와 WSM6 미세구름물리 모수화 방안이 연구를 위해 사용되었다. 실제 관측된 자료를 바탕으로 산출된 Thompson의 눈송이의 질량-크기 관계를 도입하여 WDM6와 WSM6 내의 눈송이의 질량-크기 관계식을 대체하였다. 이상적인 스콜선과 한반도 겨울철 강수 사례에 대해 수정된 WDM6와 WSM6를 사용하여 민감도 실험을 실시하였다. 결과적으로, 대기 하층에서는 싸락눈과 빗방울의 혼합비가 증가하였고 눈송이의 혼합비는 감소하였다. 이러한 혼합비와 지표 강수의 변화는 빗방울과 눈송이의 충돌 및 병합 과정과 싸락눈의 융해 과정에 기인한 것으로 분석되었다.

The present study examined changes in surface shape and pore size observed in carbon black particles isothermally oxidized in an air atmosphere according to their burn-off ratio. Carbon black materials were fed into a horizontal tubular furnace in an air atmosphere when the inside temperature reached 600 °C. Subsequently, while changing the isothermal oxidation time, carbon black samples with different burn-off ratios were obtained, i.e., 10.5, 20.0, 30.4, 41.0, 49.9, 59.8, 71.1, and 81.0%. The scanning electron microscope analysis revealed that the observed carbon black particles were in the form of aggregated primary particles, and that there was no change in the particle size of these primary particles as the burn-off process proceeded. The latter observation supported the observation that pores were formed in the carbon black samples during the burn-off process. Notably, the Brunauer–Emmett–Teller analysis exhibited hysteresis curves, indicating that the corresponding adsorption isotherms were of IV-type. It was also found that the area of the hysteresis curves increased as the burn-off process proceeded. The specific surface area of the raw carbon black sample was 58.00 m2/g, while that of the 81.0% sample was about 4.1 times the figure at 240.27 m2/g. The total pore volume VT was 0.17 cm3/g for the raw sample, and it was much higher for the 81.0% sample at 0.58 cm3/g. The transmission electron microscope analysis showed that the raw carbon black particles had a spherical shape with a smooth surface, but inner pores were not observed. In the 49.9% sample, pores with a size of about 5 nm were observed inside carbon black particles. Notably, the size of the pores observed in the 81.0% sample was about 20 nm and the large pores were created by the collapsing and merging of the smaller pores by oxidation.

목적 : 본 연구에서는 각기 다른 조명에서 조절반응과 동공의 크기 측정을 동적으로 하고 그에 따른 조절과 동공의 동적 변화가 시기능에 어떠한 영향을 미치는지 알아보고자 하였다. 방법 : 연구대상은 안과적 수술 경력이 없는 17명(23.06±0.51세)을 대상으로 하였고 기본검사를 통해 나안시력이 0.8 이상인 인원을 대상자로 선정하였다. 3개의 조명 조건(명소시, 박명시, 암소시)에서 개방형 자동굴절검 사기(WAM-5500)를 통해 5 Hz로 조절 및 동공크기를 동적으로 측정하였으며 조절자극은 40 cm, 40~30 cm, 30 cm, 30∼20 cm, 20 cm에서 5초간 주었다. 더불어 원거리 시력 및 대비감도를 측정하였다. 결과 : 명소시 상태에서 조절반응량이 가장 높았으며 암소시 상태에서 조절반응량이 가장 낮게 나타났다(p ＜0.050). 동공의 크기 변화는 명소시 상태에서 동공의 크기가 가장 작게 측정되었고, 암소시 상태에서 동공 크기가 가장 크게 측정되었다(p＜0.050). 시력과 대비감도에서도 명소시 상태에서 모두 가장 높은 수치를 나타냈으며, 암소시 상태에서 시력과 대비감도 모두 가장 낮게 측정되었다(p＜0.050). 결론 : 본 연구의 결과로 다른 조명 조건하에서 조절자극이 변화될 때 조절반응량과 동공크기가 연속적으로 변화됨을 알 수 있었다. 낮은 조도에서 조절반응량은 조절자극보다 낮게 나타났고 시력 및 대비감도 모두 저하되었다. 이것은 정적인 상태에서도 조절의 지속적인 변화를 나타낸다. 그러므로 조절 또는 시기능 검사 시 동적 측정이 필요할 것으로 사료된다.