• 한국환경농학회지
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• 제24권4호
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• pp.379-385
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• 2005

중금속으로 오염된 폐수를 처리하기 위하여 다양한 처리 방법들이 제시되고 있으나, 최근에는 미생물을 이용한 중금속 처리 방법에 대한 관심이 높아지고 있다. 따라서 중금속으로 오염된 토양에서 중금속에 대하여 강한 내성과 우수한 생물흡착능력을 동시에 가지고 있는 미생물 CPB를 분리하여 중금속에 대한 내성, 흡착 능력 및 흡착의 최적조건을 조사하였다. 중금속에 대한 내성은 전체적으로 $400mg{\ell}^{-1}$ 이상의 농도에서도 높은 내성을 보였으며, 생장 저해도는 단일 중금속 보다 중금속이 복합으로 존재 할 경우 더 크게 나타났다. 중금속 흡착 능력은 Pb>Cd>Cu>Zn의 순으로 흡착 능력이 나타났다. 외형적 흡착형태는 중금속의 종류에 따라 세포 표면 및 세포 막 부근에 electron dense particles들이 형성되었으며, 이는 EDS 분석을 통하여 중금속 화합물인 것으로 확인되었다. 중금속을 흡착하는데 있어 전반적인 최적 pH는 $5{\sim}7$범위였고, 최적 온도는 $25{\sim}35^{\circ}C$이다.

• 한국환경농학회지
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• 제18권1호
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• pp.28-34
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• 1999

전국의 16개 휴 ${\cdot}$ 폐광 지역에서 토양중 중금속함량과 식생조사를 실시한 결과를 요약하면 다음과 같다. 조사 휴 ${\cdot}$ 폐광산 대부분의 경우 피복식물이 없는 나대지로 존재하고 있었고 유기물함량, CEC 등이 낮은 값을 가지고 있는 등 대체로 척박한 토양조건을 가지고 있었으며 특정 중금속으로 인한 오염의 정도가 토양환경보전법상의 우려기준과 대책기준을 초과하는 지점도 있었다. 식물종들의 분포를 조사한 결과 목본은 소나무, 아카시나무 등이, 초본은 쑥과 억새의 출현빈도가 높았다. 쑥은 지상부에 Zn과 Cd를 각각 1,191, 26.35mg/kg을 함유하였고, 패랭이꽃은 Cu를 405mg/kg 함유하여 체내 농도가 가장 높은 것으로 조사되었다. 체내 중금속함량, 건물생산량, 생육기간등을 고려할 때 쑥, 억새, 달맞이꽃등이 토양정화식물로서의 가치가 있다고 생각된다. 앞으로 쑥을 비롯한 내성이 있는 식물종에 대한 조사는 물론 생리적 특성, 토양조건, 기후조건 등에 대한 지속적 연구가 뒤따라야 할 것으로 생각된다.

• 한국환경과학회지
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• 제33권4호
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• pp.257-268
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• 2024

This study investigated the growth characteristics of Euonymus japonicus, Hedera helix, and Peperomia puteolata treated with different calcium chloride (CaCl₂) concentrations to evaluate salt tolerance limits in hydroculture cultivation. Six concentrations of CaCl₂ (0, 1, 2, 5, 10, and 15 g·L^-1 referred to as Cont., C1, C2, C5, C10, and C15) were applied to solution - grown plant species. The survival rate, growth index, plant height, plant width, leaf width, leaf length, number of leaves, and relative chlorophyll contents were measured at monthly intervals. Euonymus japonicus, Hedera helix, and Peperomia puteolata survived up to C2, C5, and C10 at each CaCl₂ concentration. The Euonymus japonicus was higher in the C1 treatment than in the Cont. for most growth characteristics. Hedera helix had the highest leaf width, leaf length, and number of leaves in the Cont., a significant difference was observed compared with the C1 treatment. The chlorophyll content did not differ significantly between the C5 and Cont. treatments. The leaf width and length of Peperomia puteolata were greater in the C2 and C1 treatments than in the Cont., whereas the number of leaves and chlorophyll content were the highest in C5. Dry weight analysis revealed that Euonymus japonicus, Hedera helix, and Peperomia puteolata were the lowest in the Cont. treatments. Euonymus japonicus was 74% in C15, and Hedera helix, and Peperomia puteolata were analyzed at approximately 37%- 50% and 9%-14%, respectively, regardless of the concentration in the CaCl₂ treatment groups. In indoor hydroponic cultivation, the salt tolerance limit concentrations of Euonymus japonicus, Hedera helix, and Peperomia puteolata are 2, 5, and 10 g·L^-1, respectively, indicating that hydroculture management techniques should be applied at higher concentrations.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.190-197
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• 2004

In order to consider statistical properties of probability variables used in the structural analysis, the conventional approach using the safety factor based on past experience usually estimated the safety of a structure. Also, the real structures could only be analyzed with the error in estimation of loads, material characters and the dimensions of the members. But the errors should be considered systematically in the structural analysis. In this paper, we estimated the probability of failure of the pressure vessel. And also, this paper presents sensitivity values of the random variable. Finally, we show that reliability index and probability of failure can present the tolerance limit of dimension of randam variables.

• 품질경영학회지
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• 제35권4호
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• pp.147-158
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• 2007

Owing to the rapid growth in automated manufacturing systems, screening inspection becomes an attractive practice for removing nonconforming items, and it has been suggested that inspection will essentially become an inherent part of modem manufacturing processes. In this paper, we propose rectifying screening inspections which allow quality practitioners to use performance and surrogate variables interchangeably in real-time applications. Two screening inspections are considered; a statistically-based screening inspection to reduce the current proportion of nonconforming items to a specified AOQ(average outgoing quality) after screening, and an economically-based screening inspection where the tolerance limit is determined so that the expected total cost is minimized. It is assumed that the performance variable and the surrogate variable are jointly normally distributed. For two screening inspections, methods of finding the optimal solutions are presented and numerical examples are also given.

• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1093-1101
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• 2002

Continuous fiber ceramic composites (CFCCs) have advantages over monolithic ceramics : Silicon Nitride composites are not well used for application because of their low fracture toughness and fracture strength, but CFCCs exhibit increased toughness for damage tolerance, and relatively high stiffness in spite of low specific weight. Thus it is important to characterize the fracture resistance and properties of new CFCCs materials. Tensile and flexural tests were carried out for mechanical properties and the fracture resistance behavior of a SCS6 fiber reinforced Si$_3$N$_4$ matrix CFCC was evaluated. The results indicated that CFCC composite exhibit a rising R curve behavior in flexural test. The fracture toughness was about 4.8 MPa$.$m$\^$1/2 , which resulted in a higher value of the fracture toughness because of fiber bridging. Mechanical properties as like the elastic modulus, proportional limit and the ultimate strength in a flexural test are greater than those in a tensile test. Also a numerical modeling of failure process was accomplished for a flexural test. This numerical results provided a good simulation of the cumulative fracture process of the fiber and matrix in CFCCs.

• Ocean and Polar Research
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• 제23권4호
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• pp.401-410
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• 2001

Global climate change will alter many such properties of the Southern Ocean as temperature, circulation, stratification, and sea-ice extent. Such changes are likely to influence the species composition and activity of Antarctic marine microorganisms (protists and bacteria) which playa major role in deter-mining the concentration of atmospheric $CO_2$ and producing precursors of cloud condensation nuclei. Direct impacts of climate change on Antarctic marine microorganisms have been determined for very few species. Increasing water temperature would be expected to result in a southward spread of pelagic cyanobacteria, coccolithophorids and others. Growth rates of many species would be expected to increase slightly but nutrient limitation, especially micronutrients, is likely to result in a negligible increase in biomass. The extent of habitats would be reduced for those organisms presently living close to the upper limit of their thermal tolerance. Increased UVB irradiance is likely to favour the growth of those organisms tolerant of UVB and may change the trophic structure of marine communities. Indirect effects, especially those as a consequence of a diminution of the amount of sea-ice and increased upper ocean stratification, are predicted to lead to a change in species composition and impacts on both trophodynamics and vertical carbon flux.

• 환경위생공학
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• 제13권2호
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• pp.115-120
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• 1998

This Study was performed to investigate the contents of aflatoxin $B_{1}$ in cereal, pulse, nuts and these products of domestic and import. These results were as follows. 1. Average concentration(in ${\mu}g/kg$) of aflatoxin $B_{1}$ in domestic foods were 2.6 in cereal, 3.9 in pulse, 4.2 in nuts and 1.4 grain products. The contents of aflatoxin B$_{1}$ in pulse and nuts were much higher than those of cereal and grain products. But their values were still within $10{\mu}g/kg$ the maximum residual level of aflatoxin $B_{1}$ for food of Korea. 2. Average contents of aflatoxin $B_{1}$ in import foods were 4.8, 5.4, 6.0, $3.8{\mu}g/kg$ for cereal pulse , nuts and popcorn & peanuts butter, respectively. And these values were found to be below the maximum residual level ($10{\mu}g/kg$) of aflatoxin $B_{1}$ for food of Korea. 3. The concentration of aflatoxin $B_{1}$ in 2 samples of domestic and 9 samples of import foods were over the tolerance limit for aflatoxin $B_{1}$ in food of Korea. Therefore, the hygienic managements of the foods should be required during storage and circulation at market.

• 한국응용곤충학회지
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• 제19권1호
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• pp.31-34
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• 1980

선충 밀도에 따른 피해정도와 피해허용 한계수준을 알기 위하여 Pot시험을 실시한 결과 접종 2개월후부터 밀도별로 생육차가 나타났으며 씨스트 16마리 이상 접종구는 무접종에 비하여 생육과 근류발육이 현저하게 떨어졌다. 또한 접종선충수가 적을수록 증식이 잘되어 수확시의 씨스트수는 처리구간에 별차이가 없었다. 피해 허용한계 밀도는 파종시 토양 500g당 씨스트 20개내외였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.784-789
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• 2001

In order to investigate the fracture behaviors(penetration modes) and the resistance to penetration during ballistic impact of cold-rolled Al 5052 H34 alloy laminates, anodized Al 5052 H34 alloy laminates, and Al 5052 H34 alloy after cold-rolling, ballistic testing was conducted. In general, superior armor material is brittle materials which have a high hardness. Ballistic resistance of these materials was measured by protection ballistic limit(V50), a statical velocity with 50% probability for incomplete penetration. Fracture behaviors and ballistic tolerance, described by penetration modes, are observed respectfully, resulting from V50 test and Projectile Through Plate(PTP) test at velocities greater than V50. PTP tests were conducted with 0$^{\circ}$obliquity at room temperature using 5.56mm ball projectile. V50 tests with 0$^{\circ}$obliquity at room temperature were also conducted with projectiles that were able to achieve near or complete penetration during PTP tests. Surface Hardness, resistance to penetration, and penetration modes of Al 5052 H34 alloy laminates compared to those of cold-rolled Al 5052 H34 alloy laminates and anodized Al 5052 H34 alloy laminates anodized Al 5052 H34 alloy after cold-rolling.