• 대한토목학회논문집
• /
• 제28권2C호
• /
• pp.83-94
• /
• 2008

본 연구에서는 흙의 미소변형에서 대변형까지 고려할 수 있는 유효응력해석을 이용하여 매립지반에 대한 액상화 및 진동으로 발생하는 침하량을 예측하였다. 유효응력모델은 진동 중에 발생하는 과잉간극수압을 계산하여 이에 따른 흙의 강성저하와 수반되는 지반의 변위를 모델링하였다. 진동으로 인한 지반의 변형률 수준이 작은 경우에 적합한 등가선형해석을 이용한 액상화 평가를 실시하여 유효응력모델을 이용한 예측법과 비교하였다. 등가선형해석에서 계산된 전단응력비에 해당하는 표준관입시험치를 국내에서 발생 가능한 지진규모와 실트질 함유량에 따라 콘관입저항치로 환산한 값과 현장에서 계측된 콘관입저항치를 서로 비교하여 액상화 가능성을 예측하였다. 두 곳의 인천지역 매립지에 대한 액상화 해석을 위하여 매립지에서 계측된 콘관입저항치와 전단파 속도를 이용하여 입력 물성값을 결정하였다. 인천 매립지에 대한 두 액상화 해석 방법의 결과는 액상화 발생 여부에서 유사하였으며 깊이에 따른 연속적인 액상화 판정과 얇은 층의 액상화 예측이 가능하여 액상화 예측의 정밀도를 높였다. 유효응력모델을 이용한 액상화 해석 결과는 지표면 아래 20m 이내에서 초기 유효수직응력의 40%~70% 정도의 과잉간극수압이 발생하였으며 이로 인하여 지표면에서 10cm 미만의 침하가 발생하였다.

• 한국축산식품학회지
• /
• 제40권4호
• /
• pp.512-526
• /
• 2020

Synthetic nitrite is considered an undesirable preservative for meat products; thus, controlling synthetic nitrite concentrations is important from the standpoint of food safety. We investigated 1,000 species of microorganisms from various kimchi preparations for their potential use as a starter culture for the production of nitrites. We used 16S rRNA gene sequence analysis to select a starter culture with excellent nitrite and nitric oxide productivity, which we subsequently identified as Staphylococcus hominis subspecies hominis WiKim0113. That starter culture was grown in NaCl (up to 9%; w/v) at 10℃-40℃; its optimum growth was observed at 30℃ at pH 4.0-10.0. It exhibited nonproteolytic activity and antibacterial activity against Clostridium perfringens, a bacterium that causes food poisoning symptoms. Analysis of Staphylococcus hominis subspecies hominis WiKim0113 with an API ZYM system did not reveal the presence of β-glucuronidase, and tests of the starter culture on 5% (v/v) sheep blood agar showed no hemolytic activity. Our results demonstrated the remarkable stability of coagulase-negative Staphylococcus hominis subspecies hominis WiKim0113, especially in strain negative for staphylococcal enterotoxins and sensitive to clinically relevant antibiotics. Moreover, Staphylococcus hominis subspecies hominis WiKim0113 exhibited a 45.5% conversion rate of nitrate to nitrite, with nitrate levels reduced to 25% after 36 h of culturing in the minimal medium supplemented with nitrate (200 ppm). The results clearly demonstrated the safety and utility of Staphylococcus hominis subspecies hominis WiKim0113, and therefore its suitability as a starter culture.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2008년도 추계학술대회논문집
• /
• pp.71-81
• /
• 2008

This paper proposes a spectral element which can represent dynamic responses in high frequency domain such as Lamb waves on a thin plate. A two layer beam model under 2-D plane strain condition is introduced to simulate high-frequency dynamic responses induced by piezoelectric layer (PZT layer) bonded on a base plate. In the two layer beam model, a PZT layer is assumed to be rigidly bonded on a base beam. Mindlin-Herrmann and Timoshenko beam theories are employed to represent the first symmetric and anti-symmetric Lamb wave modes on a base plate, respectively. The Bernoulli beam theory and 1-D linear piezoelectricity are used to model the electro-mechanical behavior of a PZT layer. The equations of motions of a two layer beam model are derived through Hamilton's principle. The necessary boundary conditions associated with electro mechanical properties of a PZT layer are formulated in the context of dual functions of a PZT layer as an actuator and a sensor. General spectral shape functions of response field and the associated boundary conditions are formulated through equations of motions converted into frequency domain. A detailed spectrum element formulation for composing the dynamic stiffness matrix of a two layer beam model is presented as well. The validity of the proposed spectral element is demonstrated through comparison results with the conventional 2-D FEM and the previously developed spectral elements.

• Journal of Plant Biotechnology
• /
• 제31권4호
• /
• pp.267-271
• /
• 2004

국내 고구마 율미 품종의 배발생 캘러스를 Agrobacterium 매개 방법을 이용하여 형질전환 식물체를 개발하였다. 배발생 캘러스를 7일 동안 전배양 한 후 Agrobacterium과 2일 간 공동배양할 경우 일시적인 형질전환 효율이 가장 높았다. Agrobacterium과의 공동배양 후 배발생 캘러스를 1mg/L 2,4-D, 100mg/L kanamycin, 400mg/L claforan 이 첨가된 선발배지에서 4주 간격으로 계대배양하였다. 선발된 kanamycin 저항성 캘러스를 2,4-D를 제거한 선발배지로 옮겨 체세포배를 유도하였으며 이후 소식물체로 발달하였다. Southern 분석으로 1-3 copy의 GUS 유전자가 고구마 염색체내로 도입되었음을 확인하였다. 또한 조직학적 분석으로 GUS 유전자가 형질전환 고구마의 배발생 캘러스, 재분화 식물체의 잎, 엽병, 및 뿌리 조직에서 강하게 발현됨을 알 수 있었다.

• 한국미생물학회:학술대회논문집
• /
• 한국미생물학회 2001년도 추계학술대회
• /
• pp.16-25
• /
• 2001

A genomic library of biphenyl-degrading strain Comamonas sp. SMN4 was constructed by using the cosmid vector pWE15 and introduced into Escherichia coli. Of 1,000 recombinant clones tested, two clones that expressed 2,3-dihydroxybiphenyl 1,2-dioxygenase activity were found (named pNB 1 and pNB2). From pNB1 clone, subclone pNA210, demonstrated 2,3-dihydroxybiphenyl 1,2-dioxygenase activity, is isolated. 2,3-Dihydroxybiphenyl 1,2-dioxygenase (23DBDO, BphC) is an extradiol-type dioxygenase that involved in third step of biphenyl degradation pathway. The nucleotide sequence of the Comamonas sp. SMN4 gene bphC, which encodes 23DBDO, was cloned into a plasmid pQE30. The His-tagged 23DBDO produced by a recombinant Escherichia coli, SG 13009 (pREP4)(pNPC), and purified with a Ni-nitrilotriacetic acid resin affinity column using the His-bind Qiagen system. The His-tagged 23DBDO construction was active. SDS-PAGE analysis of the purified active 23DBDO gave a single band of 32 kDa; this is in agreement with the size of the bphC coding region. The 23DBDO exhibited maximum activity at pH 9.0. The CD data for the pHs, showed that this enzyme had a typical a-helical folding structures at neutral pHs ranged from pH 4.5 to pH 9.0. This structure maintained up to pH 10.5. However, this high stable folding strucure was converted to unfolded structure in acidic region (pH 2.5) or in high pH (pH 12.0). The result of CD spectra observed with pH effects on 23DBDO activity, suggested that charge transition by pH change have affected change of conformational structure for 23DBDO catalytic reaction. The $K_m$ for 2,3-dihydroxybiphenyl, 3-metylcatechol, 4-methylcatechol and catechol was 11.7 $\mu$M, 24 $\mu$M, 50 mM and 625 $\mu$M.

• 한국가스학회지
• /
• 제1권1호
• /
• pp.49-55
• /
• 1997

폭발압력은 가연성 혼합가스의 폭발시 발생되는 에너지의 변환형태로 가스폭발 사고시 구조물의 파괴와 피해는 주로 폭발압력과 열에 의해 발생한다. 본 연구에서는 몇 종류의 탄화수소와 산소의 혼합물에 대하여 폭발특성과 폭발연소시 발생되는 에너지와의 관계를 규명하고자 하였다. 폭발실험 용기는 L/D가 1이고 부피가 $5916cm^3$인 원주형 용기를 사용하였으며 폭발압력은 strain형 압력센서를 사용하여 오실로스코프로 측정하였다. 실험에 사용된 탄화수소는 메탄, 에틸렌, 프로판, 부탄이었으며 실험의 변수로는 산화제인 산소와의 혼합기의 농도 변화이었다. 실험결과 폭발압력은 연소열에 강한 의존성을 갖고 있음을 알 수 있었으며 이 관계를 이용하여 연소특성으로부터 폭발압력의 예측이 가능할 것으로 생각된다.

• 한국소음진동공학회논문집
• /
• 제17권7호
• /
• pp.572-578
• /
• 2007

Two stroke low speed diesel engines are widely used for marine propulsion or as power plant prime mover. These engines have many merits which includes higher thermal efficiency, mobility and durability. Yet various annoying vibrations occur sometimes in ships or at the plant itself. Of these vibrations, torsional vibration is very important and dictates a careful investigation during the engme's initial design stage for safe operation. With the rule and limit on torsional vibration in place, shaft strength fatigue due to torsional vibration however demands further analysis which possibly can be incorporated in the classification societies' rule and limit. In addition, the shaft's torsional vibration stresses can be calculated equivalently from accumulated fatigue cycles number due to transient torsional vibration in time domain. In this paper, authors suggest a new estimation method combined with Palmgren-Miner equation. A 6S70MC-C ($25,320ps{\times}91rpm$) engine for ship propulsion was selected as a case study. Angular velocity was measured, instead of shaft's strain, for simplified measurement and it was converted to torsional vibration stress for accumulated fatigue cycle numbers in shafting life time. Likewise, the accumulated fatigue calculation was compared with shaft fatigue strength limit. This new method can be further realized and confirmed in ship with two stroke low speed diesel engine.

• Applied Biological Chemistry
• /
• 제36권1호
• /
• pp.38-44
• /
• 1993

1) OBT mutant는 Clostridium saccharoperbutylacetonicum ATCC 13564(N1-4주(株))로부터 UV light와 butanol tolerance에 의해 분리했다. 동 돌연변이주(株)는 16.46g/l(1.4배 증가)의 부타놀과 4.6g/l(1.5배 증가)의 아세톤을 생산하고 전체 용매는 21.47g/l를 생산했다. 이 결과는 n-butanol을 생산하는 clostridial bacteria에서 error-prone pathway를 통한 misrepair의 약한 효과가 UV light와 butanol tolerance에 의해서 극복되었다는 것을 제시했다. 2) glucose 발효에 비교해서 mannitol 발효에서 OBT mutant는 acetone과 acetic acid는 생산되지 않았다. 전체용매에 대한 n-butanol과 ethanol의 비는 각각 10.3%와 10.6%씩 증가되었고 전체적으로는20.9% 증가된 반면, acetone의 비는 21.2%가 감소되었다. 또한 전체 용매에 대한 n-butanol의 최대비는 94.8%까지 증가하였다. 이들 결과는 산화합물(acetone, acetic acid, butyric acid)이 환원화합물(n-butanol, ethanol)로 전환된 것을 의미했다. 따라서 mannitol은 부산물인 산화합물을 제거하는데 사용할 수 있다.

• Journal of Applied Biological Chemistry
• /
• 제52권4호
• /
• pp.163-169
• /
• 2009

A total of 155 microbial strains were isolated from the Korean traditional soybean paste based on their morphological features on the growth of agar plate. Among the isolated strains, a total of 28 strains were capable of hydrolyzing isoflavone glycoside to isoflavone aglycone efficiently in the soybean paste. Finally, two strains, K123-1 and SI, were selected because of their resistance to 15% NaCl and ability to convert isoflavone glycoside to isoflavone aglycone efficiently during the fermentation of soybean paste. The isolated strains K123-1 and SI were identified to be Pichia guilliermondii and Candida fermentati, respectively, using the partial 26S rDNA sequence analysis and phylogenic analysis. Pichia guilliermondii K123-1 and Candida fermentati SI converted daidzin to daidzein up to 96% and 95%, respectively, and genistin to genistein up to 92% when soybean pastes were fermented at $30^{\circ}C$ for 20 days with a single isolated strain. Pichia guilliermondii K123-1 and Candida fermentati SI were able to grow in the presence of 15% NaCl on both liquid medium and agar plate. We think that Pichia guilliermondii K123-1 and Candida fermentati SI might be one of good candidates for making functional soybean paste because they are isolated from the Korean traditional soybean paste and have a good ability to convert isoflavone glycosides to isoflavone aglycones and a high salt tolerance.

• Journal of Microbiology and Biotechnology
• /
• 제25권6호
• /
• pp.893-902
• /
• 2015

Various Lactobacillus reuteri strains were screened for the ability to convert glycerol to 1,3-propanediol (1,3-PDO) in a glycerol-glucose co-fermentation. Only L. reuteri DSM 20016, a well-known probiotic, was able to efficiently carry out this bioconversion. Several process strategies were employed to improve this process. Co²⁺ addition to the fermentation medium, led to a high product titer (46 g/l) of 1,3-PDO and to improved biomass synthesis. L. reuteri DSM 20016 produced also ca. 3 µg/g of cell dry weight of vitamin B₁₂, conferring an economic value to the biomass produced in the process. Incidentally, we found that L. reuteri displays the highest resistance to Co²⁺ ions ever reported for a microorganism. Two waste materials (crude glycerol from biodiesel industry and spruce hydrolysate from paper industry) alone or in combination were used as feedstocks for the production of 1,3-PDO by L. reuteri DSM 20016. Crude glycerol was efficiently converted into 1,3-PDO although with a lower titer than pure glycerol (33.3 vs. 40.7 g/l). Compared with the fermentation carried out with pure substrates, the 1,3-PDO produced was significantly lower (40.7 vs. 24.2 g/l) using cellulosic hydrolysate and crude glycerol, but strong increases of the maximal biomass produced (2.9 vs 4.3 g/l CDW) and of the glucose consumption rate were found. The results of this study lay the foundation for further investigations to exploit the biotechnological potential of L. reuteri DSM 20016 to produce 1,3-PDO and vitamin B₁₂ using industry byproducts.