• 폴리머
• /
• 제34권1호
• /
• pp.14-19
• /
• 2010

여러 원인에 의한 석조문화재의 풍화 손상을 저지할 목적으로 아크릴계 고분자를 이용하는 가압함침 보존 처리방법에서 함침된 고분자와 무기물질인 석재와의 친화성을 높이도록 silane계 아크릴 단량체의 사용을 연구하였다. 기본 단량체인 methyl metacrylate(MMA)에 vinyl trimethoxy silane(VTMS)의 함량을 변화시키고 라디칼 중합으로 MMA-VTMS 공중합체를 얻어 이들 공중합체의 유리전이온도, 평균분자량, 그리고 저장탄성률의 변화를 평가하여 benzoyl peroxide (BPO) 1 wt%, 중합시간 8시간, 그리고 VTMS 5 mol% 혼합의 경우(PMV5)가 최적 혼합비율과 중합조건임을 알 수 있었다. 실제 국내산 화강암과 풍화된 암석의 시편을 함침 보존처리한 후 수분 흡수율, 충격특성, 내산성 및 접착특성 등을 측정한 결과 MMA 단독 사용과 비교하여 PMV5의 경우 모든 특성에 있어서 개선되는 것을 확인하였다.

• 한국물환경학회지
• /
• 제34권2호
• /
• pp.210-215
• /
• 2018

It is difficult to count colonial cyanobacteria Microcystis cells since the thickness of colonies is constrained by amorphous mucilage, making it impossible to estimate the number of cells. Disaggregation of Microcystis colonies into single cell is needed to improve the accuracy and precision of cell density estimation of naturally collected samples. Uultrasonic treatment method is commonly used owing to the simplicity and immediacy of the procedure. However, amplitude, frequency, and duration of ultrasonic treatment also cause cell loss during the experiment. Optimal ultrasonic treatment has not been standardized yet. Therefore, the objective of this study was to investigate optimal ultrasonic treatment by analyzing cell density and colony numbers. We collected colonial Microcystis from Changnyeong-Haman weir area in Nakdong River during harmful algal boom period from September to October in 2017. Ultrasonic treatment method was applied to disrupt colonies into single cells to enumerate cell density. Among treatment conditions, results from continuously treated for 100 seconds were found to be the optimum to reduce colonies to a suspension of single cell without cell losses under high and low density of Microcystis cells. Lugol iodine fixed cells followed by sonication showed less negative impact of cell damage within the optimal treatment time (100 seconds). Furthermore, disaggregated cells treated by sonication enables microscopic observation more easily since gas vacuoles were collapsed to facilitate sedimentation of cells under the counting chamber for quantitative enumeration of buoyant Microcystis cells.

• 플랜트 저널
• /
• 제10권4호
• /
• pp.35-41
• /
• 2014

축열조는 집단에너지를 공급하는 지역의 고도와 열부하에 따라 높이와 용량이 결정된다. 이는 축열조의 수두를 이용하여 열배관망에 압력을 가하고 배관망내의 비등을 방지하며 온도변화에 따라 체적이 팽창하면 이를 흡수하고 수축 시에는 부족한 중온수를 배관망에 공급하는 기능을 해야 하기 때문이다. 또한, 축열조의 역할은 주로 열수요량의 변화가 심한 계절별 주간 야간 시간대에 적절한 용량을 갖추고 잉여 열량을 저장한 후 필요한 시간대에 지역난방 열원으로 이용하면 열생산 설비의 운전 조건에 영향을 받지 않으면서 독자적으로 지역난방 열수요를 공급할 수 있는 장점이 있다. 본 연구는 지역난방에 건설되어 운영 중인 축열조 27기 중 폴리우레탄 폼의 단열 재료로 시공된 18기의 축열조에 대하여 단열재의 재질과 축열조의 운전방법에 따른 단열재의 손상원인에 대한 고찰과 단열재 손상이 축열조 부식에 어떠한 영향을 미치는지 고찰하였다.

• 한국자원식물학회:학술대회논문집
• /
• 한국자원식물학회 2018년도 추계학술대회
• /
• pp.64-64
• /
• 2018

The genus Cenchrus (Poaceae), containing ca. 97 species, is distributed throughout Australia, Africa and Indian sub-continent and which was introduced to the United States and Mexico for use in improved pasture. In Korea, especially Daecheong Island, it is one of the most hazardous invasive plant, which causes serious environmental threats, biodiversity damages and physically negative impact on humans and animals. It can cause serious damage to farms, fields and white sand beaches. However, the chloroplast (cp) genome sequences and information of Cenchrus longispinus have been not addressed, so we provide the complete cp genome of Cenchrus longispinus using next-generation sequencing technology. The size of cp genomes of this Daecheong Island species (Cenchrus longispinus) is 137,144 bp, and it shows a typical quadripartite structure. Consisting of the large single copy (LSC; 80,223 bp), small single copy (SSC; 12,449 bp), separated by a pair of inverted repeats (IRs; 22,236 bp). This cp genome contains 75 unique genes, 4 rRNA coding genes, 33 tRNA coding genes and 21 duplicated in the IR regions, with the gene content and organization are similar to other Poaceae cp genomes. Our comparative analysis identified four cpDNA regions (rpl16, rbcL, ndhH and ndhF) from three Cenchrus species, two Setaria species and one Pennisetum species which may be useful for molecular identification.

• 소성∙가공
• /
• 제25권1호
• /
• pp.36-42
• /
• 2016

Fiber metal laminates (FMLs) are well known for improved fatigue strength, better impact resistance, superior damage tolerance and slow crack growth rate compared to traditional metallic materials. However, defects and loss of strength of a composite material can occur due to the vertical load from the punch during the joining with a dissimilar material using a conventional clinching method. In the current study, tapered-hole clinching was an alternative process used to join Al 5052 and FMLs. The tapered hole was formed in the FML before the joining. For the better understanding of static and dynamic characteristics, a clinched joining followed by a tensile-shear test was numerically simulated using the finite element analysis. The design parameters were also evaluated for the geometry of the tapered hole by the Taguchi method in order to improve and compare the lateral joining strength of the clinched joint. The influence of the neck thickness and the undercut were evaluated and the contribution of each design parameter was determined. Then, actual experiments for the joining and tensile-shear test were conducted to verify the results of the numerical simulations. In conclusion, the appropriate combination of the design parameters can improve the joining strength and the cross-sections of the tapered-hole clinched joint formed in the actual experiments were in good agreement with the results of the numerical simulations.

• KIEAE Journal
• /
• 제14권6호
• /
• pp.93-97
• /
• 2014

Curtain wall system of office buildings has recently become very common in Korea. As the multi-layer curtain glazing is exposed to outdoor environment, it is very subjected to direct environmental impact. Consequently, breakage and cracks of glazing due to heat expansion is frequently observed. This study explores various causes and aspects for destruction of multi-layer glazing. A sensitivity analysis was performed on the basis that thermal changes causes damage to the multi-layer glazing. Air temperature in air cavity within the multi-layer glazing was examined to find its effect on multi-layer glazing breakage. Analysis showed high deflection to depth ratio of 1:1.8 and that higher the aspect ratio, smaller is the deflection. Allowable pressure showed that the weakest value is for aspect ratio of 1:2.9. Sensitivity analysis by the area of the glazing showed that as area of glazing becomes higher, allowable pressure and deflection-depth ratio becomes smaller. For allowable pressure and allowable deflection-depth within air cavity, the glazing breakage occurred at least $107^{\circ}C$. The results from glazing breakage by thermal factor shows that it is hard to break the glazing with only an increase in air cavity temperature in multi-layer glazing applied in buildings.

• 한국인터넷방송통신학회논문지
• /
• 제14권6호
• /
• pp.93-98
• /
• 2014

고유가 시대에 대체 에너지를 찾고, 개인의 건강 증진 추세에 따라 점점 자전거를 이용하는 사람이 증가하고 있고, 이에 따라 자전거 교통사고 또한 증가되고 있다. 자전거 교통사고의 경우, 탑승자에게 사고의 충격량이 고스란히 전달되기 때문에 신체적 위험도가 높다. 그렇기 때문에 스스로 사고를 신고하기 어려워 사고에 대한 신속한 대응을 하지 못 할 수가 있다. 그래서 본 논문에서는 사고 발생 시 자전거에 장착된 사고 알림 장치를 통해 사고를 감지하고 감지된 신호를 바탕으로 GPS 장치에 의해 사고 위치 확인 후, 스마트폰의 어플리케이션을 이용하여 문자전송 및 사고위치 정보를 전송함으로서 탑승자의 안전성을 향상시키는 목적으로 자전거 사고 알림 시스템을 개발하였다. 그리고 실험을 통해 사고 발생 이후 2차 피해를 막기 위한 신속한 사고 대응 방법을 구축하여 구현한 시스템의 효율성을 확인할 수 있었다.

• 한국조경학회지
• /
• 제14권3호
• /
• pp.21-31
• /
• 1987

The overuse in the outdoor recreation lands has been deteriorating the natural resources and landscapes. So this study was executed to measure the users'impacts on vegetation and soil at Hwaum Temple District Campsite in the Mt. Jiri National Park, the southern part of Korea. Five sites were sampled in the study area according to the extent of impact observed. Then the users'densities and impacts on vegetation and soil were measured at each site. According to the result of this study, the numbers of species and individuals and the coverage of lower-layer vegetation showed outstanding changes by only light use. The numbers of species and individuals of middle-layer vegetation, species diversity indices, change rate in species composition of lower and middle-layer vegetation, damage rate of forces, contents of clay, soil moisture and organic matters, exchangeable base ions, soil hardness, organic matter depth and bare area of the campsite showed conspicuous changes from the site 4(19.6men / 1,000㎡). Especially, the self-repair of vegetation was impossible as the result of analysis of soil hardness and the formation of natural vegetation was expected to be difficult as the result of vegetation sturcture analysis over the users'average density of 19.6men /1,000㎡. The campsite management of this area shall be proposed as follows to prevent serious deterioration of natrual environment. A limitation of the present use and a conservation on soil and vegetation should be required at the site 4 and 5. Specially, prevention of camping recreation and artificial rehabilitation are necessary at the site 5(24. 3 men/1000㎡)

• International Journal of Concrete Structures and Materials
• /
• 제9권3호
• /
• pp.345-367
• /
• 2015

Past earthquakes have signaled the increased collapse vulnerability of mainshock-damaged bridge piers and urgent need of repair interventions prior to subsequent cascading hazard events, such as aftershocks, triggered by the mainshock (MS). The overarching goal of this study is to quantify the collapse vulnerability of mainshock-damaged substandard RC bridge piers rehabilitated with different repair jackets (FRP, conventional thick steel and hybrid jacket) under aftershock (AS) attacks of various intensities. The efficacy of repair jackets on post-MS resilience of repaired bridges is quantified for a prototype two-span single-column bridge bent with lap-splice deficiency at column-footing interface. Extensive number of incremental dynamic time history analyses on numerical finite element bridge models with deteriorating properties under back-to-back MS-AS sequences were utilized to evaluate the efficacy of different repair jackets on the post-repair behavior of RC bridges subjected to AS attacks. Results indicate the dramatic impact of repair jacket application on post-MS resilience of damaged bridge piers-up to 45.5 % increase of structural collapse capacity-subjected to aftershocks of multiple intensities. Besides, the efficacy of repair jackets is found to be proportionate to the intensity of AS attacks. Moreover, the steel jacket exhibited to be the most vulnerable repair intervention compared to CFRP, irrespective of the seismic sequence (severe MS-severe or moderate AS) or earthquake type (near-fault or far-fault).

• 한국생산제조학회지
• /
• 제20권1호
• /
• pp.47-52
• /
• 2011

It is well known that stiffness of composites depends on layup sequence of CFRP(carbon fiber reinforced plastics) laminates because the layup of composite laminates influences their properties. Ultrasonic NDE of composite laminates is often based on the backwall echoes of the sample. A pair of such transducers was mounted in a holder in a nose-to-nose fashion to be used as a scanning probe on composites. Miniature potted angle beam transducers were used (Rayleigh waves in steel) on solid laminates of composites. Experiments were performed to understand the behavior of the transducers and the nature of the waves generated in the composite (mode, wave speed, angle of refraction). C-scan images of flaws and impact damage were then produced by combining the pitch-catch probe with a portable manual scanner known as the Generic Scanner ("GenScan"). The pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to fiber orientation of the CFRP composites, including low level porosity, ply waviness, and cracks. Therefore, it is found that the experimentally Rayleigh wave variation of pitch-catch ultrasonic signal was consistent with numerical results and one-side ultrasonic measurement might be very useful to detect the defects.