• Korean Journal of Environmental Biology
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• v.32 no.3
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• pp.159-167
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• 2014

In this study, I examined the water quality and phytoplankton community in aquaculture laver farm in the southwest part of Aphae-do, South Korea, based on the young leaf stage, middle leaf stage, and adult leaf stage of laver thallus from October, 2013 to January, 2014. It was observed that the Aphae laver farm, as located in shallow waters, was found to have a serious resuspsension of the surface sediments due to physical disturbance caused by winds and tidal mixing. Such a resuspension of surface sediments coupled with nutrients supply obstructs light penetration into the sea for its huge amount of total suspended matters. As a result for this reason, it was viewed toimpedthe growth of phytoplankton was impeded as it also competes with laver to absorb the same kinds of nutrients as laver does during the laver growth period in winter. Such elements of the marine environment in Aphae laver farm are in contrast with the environment of Japan, where nutrients including dissolved inorganic nitrogen, in particular, are insufficient to cause the recent laver bad harvest, discoloration and quality degradation while large diatoms, with their higher nutrients absorption efficiency than laver, generate winter red tide. In other words, an important factor to maintain the high laver production in the southern parts of West Sea of Korea was found to be the marine environment of its laver farms where large diatoms are prevented from growing due to nutrients supply and dense seston weights from resuspended matters by physical disturbances.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1726-1732
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• 2008

Injection molding is one of plastic forming technology which can easily mass-produce plastic parts with various and even complex shape. The technology has lots of difficulties in making a good part due to phase change of material, high applied pressure, and fast melt flow speed in the cavity. To overcome the problems, they had to make trial and error method until the CAE(Computer Aided Engineering) could be a tool for concurrent engineering. In this paper, we investigate the optimal design for a plastic DVD tray part by systematic approach of the commercial CAE program. In design, we should consider two objectives which are both dimensional stability and cost-down. The dimension of the part is crucial because the tray should carry a DVD correctly, but the part is too thin to injection-mold easily. In order to improve the moldability, the mold is designed in the form of stack mold which is a kind of 4 hot runner system. In first, we changed the stack-mold system with one hot-runner to cost down, and decided the optimal position of the gate. After that, we investigate the effect of both the layout of cooling channels and the cooling temperature on the shrinkage of the DVD tray. A optimal simulation approach, the gate design is 2Gate#3 and the layout is Case2 cooling line as the optimal temperature of $70^{\circ}C$. The Moldflow and PC+ABS are used for the CAE program and material respectively.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.4
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• pp.204-208
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• 2000

Little information is available for the temporal variation in air temperature profile within rice canopies under development, while much works have been done for a fully developed canopy. Fine wire thermocouples of 0.003 mm diameter (chromel-constantan) were installed at 10 vertical heights by a 10 cm step in a paddy rice field to monitor the air temperatures over and within the developing rice canopy from one month after transplanting (June 29) to just before heading (August 24). According to a preliminary analysis of the data, we found neither the daytime temperature maximum nor the night time minimum at the active radiation surface (the canopy height with maximum leafages) during this period, which is a typical profile of a fully developed canopy. Air temperature within the canopy never exceeded that above the canopy at 1.5 m height during the daytime. Temporal march of the within-canopy profile seemed to be controlled mainly by the ambient temperature above the canopy and the water temperature beneath the canopy, and to some extent by the solar altitude, resulting in alternating isothermal and inversion structures.

• Journal of Plant Biotechnology
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• v.29 no.1
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• pp.37-40
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• 2002

Sweet potato is a crop vegetatively propagated by vine cuttings, an ineffective method for maintaining pathogene-free stock plants. As an alternative method, single-node cultures of virus-free plantlets derived from apical meristem in sweet potato (cv. Yulmi) was examined. Effective pH range, sugar concentration and nodal order were investigated to establish an in vitro mass propagation system with high quality virus-free stock plantlets to farmhouse. Although the plantlets grew at wide range of pH, the most effective pH of the medium was 4.8 in single-node cultures. High sugar concentration of 60∼80 g/L resulted in increased growth response in shoot length, root length, number of node, leaf area and fresh and dry weight of shoot and root, whereas reducing sugar contents below 6% was showed reduced growth response. The first node including meristem tip was the best for the rapid growth of plantlets and the other nodes also showed a very similar growth response. Uniform plantlet can be obtained massively at the same time by culture of single node except for the first node including meristem tip. In conclusion, the most effective pH range and sugar concentration of medium for the growth of plantlets via single-node cultures was 4.8, 60∼80 g/L respectively. The first node was the best for the rapid propagation of plantlets in nodal order.

• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.355-364
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• 2014

The restrained volume changes of concrete due to variations of temperature and moisture produce transverse cracks in continuously reinforced concrete tracks (CRCTs). Such cracks are known to significantly affect the behaviors and long-term performance of CRCT. To investigate the effects of the transverse cracks on the behavior of CRCT and to develop more reasonable maintenance standards for cracks, in this study, the stress distribution of the track concrete layers (TCL) and the hydraulically stabilized base course (HSB) with transverse cracks were numerically predicted by a three dimensional finite element analysis when CRCT was subjected to train loads. The results indicate that the bending stresses of TCL and vertical stresses at the interfaces between TCL and HSB increased as the cracks were deepened. In addition, vertical stresses were locally concentrated near reinforcing steel in cracks in TCL when full-depth cracks developed, which may lead to punch-outs in CRCTs. Comparably, the effects of crack width and spacing were not as significant as crack depth. This study indicates that ensuring the long-term performance of CRCTs requires adequate maintenance not only for crack width and spacing but also for crack depth. Our results also show that locating HSB joints between sleepers is beneficial to the long-term performance of CRCTs.

• Journal of the Society of Disaster Information
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• v.17 no.1
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• pp.120-127
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• 2021

Purpose: In this study, the effect of changes in the variables related to water droplets on the spray density on the floor in the analysis of the water mist fire protection system using FDS was analyzed. Method: When the spray of the water mist nozzle was analyzed in FDS, Particles Per Seconds, Particle Velocity, Size Distribution, and Spray Pattern Shape that can be set in relation to droplets were input to review the analyzed results. Result: In the analysis results, when the number of particles per second was set above a certain value, the spray density of the floor was similar. In the case of Particle Velocity, as the velocity decreases, the spray density of the central portion increases but decreases at a distance of 0.15m or more. From the analysis of the change in the size distribution function, it was found that an increase in the 𝛾 value increases the spray density of the central part, but the value at a remote location decreases. Compared to the result of applying the Gaussian distribution, the median value decreases dramatically when the uniform distribution is applied, but the value at the adjacent position increases. Conclusion: Variables related to the droplet properties of the FDS affect the spray density of the floor. Therefore, in order to increase the reliability of results before performing analyses such as fire suppression or cooling, a sufficient review of input variables is required.

• Journal of the Korean Orthopaedic Association
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• v.56 no.4
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• pp.326-333
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• 2021

Purpose: A retrograde intramedullary nail is commonly used to treat femoral shaft and distal femur fractures. The authors analyzed the treatment results and the factors affecting the period of bone union for thirty-five patients treated with a retrograde intramedullary nail. Materials and Methods: Thirty-five patients who could be followed up for more than twelve months after the treatment with retrograde intramedullary nailing were analyzed retrospectively. The treatment results and the relationship between the period of bone union and the patient's age, sex, comminution of fracture, presence of open fracture, location of the fracture, and accompanying fractures were evaluated. Results: The average bone union time was 4.50 months. The period of bone union was unaffected by the age, sex, location, and presence of open fractures but was affected by the presence of comminution and accompanying fractures. Conclusion: Retrograde intramedullary nailing is effective for distal and shaft of fractures of the femur. The period of bone union is affected by the presence of comminution and accompanying fractures.

• Korean Journal of Environment and Ecology
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• v.36 no.1
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• pp.30-55
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• 2022

This study conducted a flora survey in the areas of Mt. Sambong (282m) and Mt. Jaung (263m), located in Paju-si, Gyeonggi-do. A total of 434 taxa, including 6 forms, 34 varieties, 11 subspecies, 383 species, 271 genera, and 94 families, were surveyed in the two mountain areas. The ferns were identified as 24 taxa from 10 families, the gymnosperms as 8 taxa from 2 families, the dicotyledonous plants as 322 taxa from 73 families, and the monocotyledonous plants as 80 taxa from 9 families. Five taxa, including Salix koriyanagi, Cimicifuga heracleifolia, Forsythia koreana, Paulownia coreana, and Hemerocallis hakuunensi, were identified as the Korean endemic plants. Eight taxa, including Cimicifuga heracleifolia, Tylophora floribunda, and Iris minutiaurea as Vulnerable species, andAristolochia contorta, Viola diamantiaca, Lithospermum erythrorhizon, Lilium distichum, andArisaema heterophyllumas Least Concern species, were designated as rare and endangered plants designated by the Korea Forest Service. The invasive alien plants were 40 taxa, including Rumex crispus, Phytolacca americana, Cerastium glomeratum, Silene armeria, Chenopodium album, Chenopodium ficifolium, Magnolia obovata, Potentilla supina, Amorpha fruticosa, Medicago sativa, Robinia pseudoacacia, Trifolium repens, Euphorbia supina, Hibiscus trionum, and Oenothera biennisaccounting for 9.2 percent of the 434 taxa of the surveyed plants. As this area is a mountainous area close to settlement facilities, it is believed that ecological preservation measures and measures of specialized plants should be implemented.

• Journal of Korea Water Resources Association
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• v.55 no.spc1
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• pp.1211-1222
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• 2022

Abnormal condition inevitably occurs during operation of water distribution system (WDS) and requires the isolation of certain areas using isolation valves. In general, the determination of the optimal location of isolation valves considered minimization of hydraulic failures as isolation of certain areas causes a change in hydraulic states (e.g., flow direction, velocity, pressure, etc.). Water quality failure can also be induced by changes in hydraulics, which have not been considered for isolation valve system design. Therefore, this study proposes a new isolation valve system design methodology to prevent unexpected water quality failure events. The new methodology considers flow direction change ratio (FDCR), which accounts for flow direction changes after isolation of the area, as a constraint while reliability is used as the objective function. The optimal design model has been applied to a synthetic grid network and the results are compared with the traditional design approach. Results show that considering FDCR can eliminate flow direction changes while average pressure and coefficient of variation of pressure, velocity, and hydraulic geodesic index (HGI) outperform compared to the traditional design approach. The proposed methodology is expected to be a useful approach to minimizing unexpected consequences by traditional design approaches.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2021.04a
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• pp.31-31
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• 2021

본 연구는 서부 DMZ 및 접경지역에 속하고 인천광역시 강화군 강화읍에 위치한 퇴모·혈구산(466m) 을 대상으로 수행되었다. 강화군은 우리나라에서 4번째로 넓은 면적의 섬으로 알려져있고, 인천광역시 서북부 경기만의 한강 하구에 위치하고 있으며, 서쪽으로는 석모도 등 부속섬과 서해안, 북쪽으로는 북 한의 황해도 연백시, 동쪽으로는 김포시와 강화대교와 강화초지대교가 육지로 연결되어 있다. 2019년 4 월부터 2020년 10월까지 7회에 걸쳐 계절별로 식물상 조사를 진행하였다. 본 연구에서 확인된 해명산 일대에 분포하는 관속식물의 현황은 92과 257속 353속 4아종 41변종 4품종 총 402분류군으로 확인되었다. 양치식물은 6과 9속 10종 2변종 12분류군, 나자식물은 3과 4속 8종 총 8분류군, 쌍자엽식물은 74과 198속 268종 4아종 30변종 3품종 등 305분류군, 단자엽식물은 9과 46속 67종 9변종 1품종 등 77분류군으로 조사되었다. 또한, 식물구계학적 특정식물 IV급은 등 1분류군, III급은 물박달나무, 병아리꽃나무 등 6분 류군, II급은 갯장구채, 꼬리조팝나무 등 8분류군, I급은 야산고비, 일엽초 등 20분류군으로 파악되었 다. 희귀식물은 산림청 지정 희귀식물 취약종(VU)에 속하는 산들깨와 약관심종(LC)에 속하는 쥐방울덩굴 등 총 2분류군이 확인되었다. 특산식물은 백운산원추리 및 병꽃나무 등 4분류이 파악되었다. 침입외래식물은 애기수영 및 유럽점나무도물 등 39분류군으로 확인되었고, 생태계교란식은 가시박 등 4분류군으로 파악되었다. 주변의 신산저수지 및 고비고개에 큰 공사가 진행되고있어 침입외래식물의 개체수는 크게 증가할 것으로 예측었다. 따라서 장기적인 생태계 보전대책 수립이 필요하다고 판단된다.