• 한국지반환경공학회 논문집
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• 제14권7호
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• pp.5-12
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• 2013

지반을 굴착하고 지하매설물을 설치한 후 뒤채움하는 시공에 있어 뒤채움재에 의한 하중은 지하매설물의 안정성을 저감시키고, 이로 인해 각종 파손이 발생한다. 이러한 문제점을 해결하기 위해 여러 산업 부산물을 이용하여 관의 변형을 일으키지 않고 소정의 강도를 가질 수 있는 뒤채움재를 개발하기 위해 다양한 연구가 진행되고 있다. 본 연구에서는 화력발전소의 산업부산물인 석탄회를 활용한 뒤채움재를 사용하여 그 중 CLSM에 대한 물리적 특성 기준에 가장 적합한 배합비를 선택하여 현장시험을 실시하였고, 수치해석을 수행하여 실험결과의 신뢰성을 높였으며 뒤채움 후 DB-24 하중을 재하하여 하중재하 전 후의 지표침하량, 매설관의 변형률을 분석하였다. 그 결과 현장실험과 수치해석 모두 비슷한 결과를 얻었고 침하량은 2mm 이하로 나타났으며 매설관의 변형률은 최대 0.006으로 나타났다.

• 한국과학교육학회지
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• 제21권1호
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• pp.59-75
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• 2001

이 연구는 개념생태 구성요소 중 학습자가 지닌 동기 심리적 관점의 측면에서 수행되었다. 즉 학습자가 학습동기와 관련하여 과학학습에 대한 개념을 어떻게 구성하고 있는가에 대하여 정성적인 방법으로 연구하였다. 수도권에 소재한 '가나' 고등학교 2학년 학생 3명의 사례를 제시하였다. 연구의 신뢰도와 타당도를 위하여 자료의 수집과 분석 의 전과정 동안 삼각측정법을 사용하였다. 면담, 직접 및 간접 관찰, 문서를 통한 자료 수집을 하여 분석한 후, 사례 연구를 하였다. 연구 결과, 학습자들의 과학 학습에 대한 열정은 과학 학습에 대한 관점과 관련되는 것으로 나타났다. 과학 학습에 대한 학습자들의 관점은 지식의 본성, 학습의 본성, 인식론적 확신 근거를 포함한 과학 및 과학 수업에 대한 관점에 영향을 받았다. 이러한 과학학습관은 학습자들의 자아 효능과 과학학습 동기에 영향을 주는 것으로 보여진다.

• 한국수자원학회논문집
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• 제31권6호
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• pp.757-768
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• 1998

6개의 수조와 1개의 펌프장을 갖고 있는 대심도 지하관로 배수시스템에서 발생하는 복잡한 서어징 현상을 강체수주이론에 의한 비선형 상태방정식에 의해서 해석하였다. 상태방정식은 각 수조에서의 유량연속방정식과 비선형항을 갖는 지하관로의 운동 방정식으로부터 구성된다. 홍수의 유입량과 펌프의 유출량을 장방형 펄스(pulse)로 하고 유출유량과 전유입유량이 같다고 한다면 비선형 상태방정식에 의한 각 수조수위의 진동은 선형화 방정식에 의한 결과와 잘 일치 하고 있다. 이것은 관로저항의 영향이 적고 이것을 무시한 자유진동해석이 타당하다는 것을 나타내는 것이다. 자유진동 방정식은 6개의 고유모드를 갖는다. 그 중 하나는 강체모드이며 유출유량이 전유입유량과 다를 때에 나타나며 이러한 6개의 고유모드는 유입유출조건에 의해서 여러 가지 서어징 현상을 구성한다. 강체모드가 존재하기 때문에 실제의 홍수 유입량에 대응한 고도의 펌프운전이 요구된다.

• 산업경영시스템학회지
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• 제40권2호
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• pp.145-149
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• 2017

One of the challenges facing precision manufacturers is the increasing feature complexity of tight tolerance parts. All engineering drawings must account for the size, form, orientation, and location of all features to ensure manufacturability, measurability, and design intent. Geometric controls per ASME Y14.5 are typically applied to specify dimensional tolerances on engineering drawings and define size, form, orientation, and location of features. Many engineering drawings lack the necessary geometric dimensioning and tolerancing to allow for timely and accurate inspection and verification. Plus-minus tolerancing is typically ambiguous and requires extra time by engineering, programming, machining, and inspection functions to debate and agree on a single conclusion. Complex geometry can result in long inspection and verification times and put even the most sophisticated measurement equipment and processes to the test. In addition, design, manufacturing and quality engineers are often frustrated by communication errors over these features. However, an approach called profile tolerancing offers optimal definition of design intent by explicitly defining uniform boundaries around the physical geometry. It is an efficient and effective method for measurement and quality control. There are several advantages for product designers who use position and profile tolerancing instead of linear dimensioning. When design intent is conveyed unambiguously, manufacturers don't have to field multiple question from suppliers as they design and build a process for manufacturing and inspection. Profile tolerancing, when it is applied correctly, provides manufacturing and inspection functions with unambiguously defined tolerancing. Those data are manufacturable and measurable. Customers can see cost and lead time reductions with parts that consistently meet the design intent. Components can function properly-eliminating costly rework, redesign, and missed market opportunities. However a supplier that is poised to embrace profile tolerancing will no doubt run into resistance from those who would prefer the way things have always been done. It is not just internal naysayers, but also suppliers that might fight the change. In addition, the investment for suppliers can be steep in terms of training, equipment, and software.

• 한국가금학회지
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• 제34권4호
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• pp.301-318
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• 2007

Marek's disease (MD) is a highly contagious lymphoproliferative disease of poultry caused by the oncogenic herpesvirus designated Marek's disease virus (MDV). MD has a worldwide distribution and is thought to cause an annual loss over US$ one billion to the poultry industry. Originally described as a paralytic disease, today MD is mostly manifested as an acute disease with tumors in multiple visceral organs. MD is controlled essentially by the widespread use of live vaccines administered either in ovo into 18-day-old embryos or into chicks immediately after they hatch. In spite of the success of the vaccines in reducing the losses from the disease in the last 30 years, MDV strains have shown continuous evolution in virulence acquiring the ability to overcome the immune responses induced by the vaccines. During this period, different generations of MD vaccines have been introduced to protect birds from the increasingly virulent MDV strains. However, the virus will be countered each new vaccine strategy with ever more virulent strains. In spite of this concern, currently field problem from MD is likely to be controled by strategy of using bivalent vaccine. But, potential risk factors for outbreak of MD are still remained in this condition. The major factors can be thought that improper handling and incorrect administration of the vaccine, infection prior to establishment of immunity, suppression of immune system by environmental stress and outbreaks of more virulent MDV strain by using vaccine and genetic resistance of host.

• 상하수도학회지
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• 제30권5호
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• pp.579-586
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• 2016

In many countries in order to manage corrosion of water treatment process, it is currently using Langelier index (LI). However, management of the Larson's ratio (LR) to compare corrosion management and LI which can be generated by the water treatment process is required. In this study, in order to ensure data LR, factors associated with the actual corrosion resistance of water treatment plant was measured. Using the measured data, the model equation can be estimated alkalinity, and using the statutory water quality data, LR and alkalinity is estimated. At comparison of the measured value and estimated value of alkalinity, it appeared in $R^2$ = 0.629, using the statutory water quality data and estimated alkalinity model, LR and alkalinity (Whole water treatment plants : 472) is estimated. Concentration of estimated alkalinity is 0.5 mg/L to 107.5 mg/L (average : 23.2 mg/L), and LR is 0.1 to 10 (average : 1.3). At tendency to corrosion of investigated LR, "No metal tendency" (>0.5) is 39 water treatment plants, 8.26 %, and "corrosion metal tendency" is 433 water treatment plants, 91.74%.

• Journal of Microbiology and Biotechnology
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• 제26권2호
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• pp.270-276
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• 2016

Extended-spectrum β-lactamases (ESBLs), particularly those of the CTX-M types, are the predominant resistance determinants of Escherichia coli that are rapidly spreading worldwide. To determine CTX-M types, E. coli isolates were collected from retail chickens (n = 390) and environmental samples from chicken farms (n = 32) and slaughterhouses (n = 67) in Korea. Fifteen strains harboring bla_CTX-M genes were isolated from 358 E. coli isolates. The most common CTX-M type was eight of CTX-M-15, followed by six of CTX-M-1 and one of CTX-M-14. The bla_CTX-M genes were identified in the isolates from retail chickens (n = 9), followed by feces, water pipes, floors, and walls. Conjugations confirmed the transferability of the plasmids carrying bla_CTX-M genes to the recipient E. coli J53 strain. Furthermore, eight addiction systems carried by the replicons in CTX-M types were confirmed. The dominant system was identified as ccdAB, vagCD, and pndAC in donor strains and transconjugants. The clonal relationship between the two strains carrying bla_CTX-M genes indicates that E. coli may transmit from the farm to retail chickens, suggesting a possible public health risk. Our findings demonstrate that the detection of CTX-M types in E. coli isolates is important for tracking ESBL production in animals, and suggest linkage of multiple addiction systems in plasmids bearing bla_CTX-M genes.

• Journal of Microbiology and Biotechnology
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• 제20권10호
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• pp.1457-1462
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• 2010

Three types of serotypically atypical Shigella flexneri isolates were collected between 2007 and 2008 from Korean patients at the Korea National Institute of Health (NIH). These atypical isolates were characterized and compared with serologically typical S. flexneri. The first grouping of 11 atypical isolates displayed agglutination only with polyB antiserum and exhibited no reaction with any typing or grouping sera (PolyB:un). The second group of 3 isolates displayed reactions with typing sera IV, but also did not bind with any grouping sera (IV:un). The third group of 14 isolates exhibited a plural agglutination pattern, reacting with typing sera II, and two grouping sera (II:(3)4,7(8)). Amongst these atypical isolates, isolates belonging to IV:un and II:(3)4,7(8) exhibited greater antibiotic resistance, in particular to ampicillin, streptomycin, and trimethoprim-sulfamethoxazole, than typical S. flexneri strains. Furthermore, all II:(3)4,7(8) strains harbored integrons. This study suggests that these multiple antibiotic-resistant atypical S. flexneri are new subserotypes of S. flexneri that await further serological classification.

• Journal of Microbiology and Biotechnology
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• 제24권4호
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• pp.431-439
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• 2014

We report the construction of two Bacillus subtilis expression vectors, pBNS1/pBNS2. Both vectors are based on the strong promoter P43 and the ampicillin resistance gene expression cassette. Additionally, a fragment with the Shine-Dalgarno sequence and a multiple cloning site (BamHI, SalI, SacI, XhoI, PstI, SphI) were inserted. The coding region for the amyQ (encoding an amylase) signal peptide was fused to the promoter P43 of pBNS1 to construct the secreted expression vector pBNS2. The applicability of vectors was tested by first generating the expression vectors pBNS1-GFP/pBNS2-GFP and then detecting for green fluorescent protein gene expression. Next, the mannanase gene from B. pumilus Nsic-2 was fused to vector pBNS2 and we measured the mannanase activity in the supernatant. The mannanase total enzyme activity was 8.65 U/ml, which was 6 times higher than that of the parent strain. Our work provides a feasible way to achieve an effective transformation system for gene expression in B. subtilis and is the first report to achieve B. pumilus mannanase secretory expression in B. subtilis.

• Journal of Welding and Joining
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• 제35권3호
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• pp.68-74
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• 2017

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E71T-1C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, Intragranular polygonal ferrite and grainboundary ferrite were formed only in first layer of weld metal. Another layers consisted of acicular ferrite and $Widmannst{\ddot{a}}tten$ ferrite. The amount of acicular ferrite was increased with decreasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered martensite and lower bainite. Lower and upper bainite were formed in heat affected zone of carbon steel. Tensile strengths of dissimilar metal welds decreased with increasing heat inputs. Dissimilar metal welds showed a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals welds showed that the weight loss rate by corrosion below 170 hours was decreased with increasing heat inputs due to the increase of the amount of acicular ferrite.