• Asian-Australasian Journal of Animal Sciences
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• 제33권10호
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• pp.1610-1616
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• 2020

Objective: This study was to evaluate the effect of husbandry systems and strains on cecum microbial diversity of Jingyang chickens under the same dietary conditions. Methods: A total of 320 laying hens (body weight, 1.70±0.15 kg; 47 weeks old) were randomly allocated to one of the four treatments: i) Silver-feathered hens in enrichment cages (SEC) with an individual cage (70×60×75 cm), ii) Silver-feathered hens in free range (SFR) with the stocking density of 1.5 chickens per ten square meters, iii) Gold-feathered hens in enrichment cages (GEC), iv) Gold-feathered hens in free range (GFR). The experiment lasted 8 weeks and the cecum fecal samples were collected for 16S rDNA high throughput sequencing at the end of experiment. Results: i) The core microbiota was composed of Bacteroidetes (49% to 60%), Firmicutes (21% to 32%) and Proteobacteria (2% to 4%) at the phylum level. ii) The core bacteria were Bacteroides (26% to 31%), Rikenellaceae (9% to 16%), Parabacteroides (2% to 5%) and Lachnoclostridium (2% to 6%) at the genus level. iii) The indexes of operational taxonomic unit, Shannon, Simpson and observed species were all higher in SFR group than in SEC group while in GEC group than in GFR group, with SFR group showing the greatest diversity of cecum microorganisms among the four groups. iv) The clustering result was consistent with the strain classification, with a similar composition of cecum bacteria in the two strains of laying hens. Conclusion: The core microbiota were not altered by husbandry systems or strains. The free-range system increased the diversity of cecal microbes only for silver feathered hens. However, the cecum microbial composition was similar in two strain treatments under the same dietary conditions.

• Food Science and Biotechnology
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• 제15권5호
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• pp.792-798
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• 2006

The probiotic characteristics of a total of 137 lactic acid bacterial strains isolated from soybean paste were investigated. Among those tested, the D37 strain was selected as a probiotic bacteria due to its acid and bile tolerance, and its strong anti-cancer and antibacterial activities. The D37 strain showed highly stable viability at acidic pH for 2 hr, and was very stable in 10% bovine bile. The viability of human colon cancer HT-29 cells was inhibited more than 60% at a $200\;{\mu}/mL$ concentration of D37 cell-free culture supernatant, and the degree of inhibition was concentration-dependent. The D37 strain showed a wide range of antibacterial activities against food-borne pathogenic bacteria such as Escherichia coli O157, Listeria spp., Vibrio spp., Salmonella spp., and Staphylococcus aureus. According to phenotypic characteristics and the utilization of various sugars, the D37 strain was identified as Lactobacillus cellobiosus.

• Preventive Nutrition and Food Science
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• 제16권1호
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• pp.37-44
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• 2011

The potential probiotic of a total of 15 Bacillus species isolated from Korean soybean paste (doenjang) was evaluated. Among those tested, the CSY191 and CSY388 strains were selected as probiotic bacteria due to their acid and bile tolerance, respectively. These strains were classified as Bacillus subtilis based on morphological, physiological, and chemotaxonomic features as well as on phylogenetic analysis based on their 16S rDNA sequences. These strains CSY191 and CSY388 showed a significant survival with rate range of 30.0 to 58.3% and of 31.0% to 58.1%, respectively, under artificial gastric acidic conditions at pH 3.0. These CSY191 and CSY388 strains appeared to have high antimicrobial activity against Salmonella Typhimurium, Bacillus cereus and Listeria monocytogenes. Also, methanol extractions (surfactin-like compounds) of strain CSY191 and strain CSY388 activated RAW264.7 microphages and induced the production of nitric oxide (NO) in a concentration-dependent manner, respectively. Therefore, strain CSY191 and strain CSY388 can be used as potential probiotics.

• 한국광학회지
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• 제12권4호
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• pp.294-299
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• 2001

최근에 구조물의 안전 감시를 위하여 광섬유 센서를 개발하기 위한 연구가 활발하게 진행되고 있다. 따라서 본 연구에서는 구조물의 넓은 면적에 분포되어있는 변형률을 한 개의 광섬유 라인으로 측정하기 위한 광섬유 BOTDA(Brillouin Optical Time Domain Analysis) 센서를 개발하는 연구를 수행하였다. 광섬유 BOTDA 센서는 2개의 광전 변조기 (electro-optic modulator)를 사용하여 간단하게 구성하였다. 광섬유의 변형률 측정실험을 통하여 광섬유의 전체길이 4.8km중에 변형률이 가해진 10m 구간의 변형률을 200회 평균화 처리된 신호로부터 브릴루앙 주파수 천이를 측정함에 의하여 정확하게 측정할 수 있음을 보였다. 또한 삼성전자의 단일모드 광섬유의 경우 변형률 측정 실험을 통하여 변형률 감지도가 4.81 MHz/0.01%임을 알 수 있었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.96-102
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• 2006

Because of the increasing need to use clayey soil as the backfill in reinforced soil structures and embankment material, nonwoven geotextiles with the drain capability have been receiving much attention. However, there are few studies of the deformation behavior of nonwoven geotextiles at geosynthetics reinforced soil structures in the field because the nonwoven geotextile, which has low tensile stiffness and higher deformability than geogrids and woven geotextiles, is difficult to measure its deformation by strain gauges and to prevent the water from infiltrating. This study proposes a new, more convenient method to measure the deformation behaviour of nonwoven geotextile by using a strain gauge; and examines the availability of the method by conducting laboratory tests and by applying it on two geosynthetics reinforced soil (GRS) walls in the field. A wide-width tensile test conducted under confining pressure of 7kPa showed that the local deformation of nonwoven geotextile measured with strain gauges has a similar pattern to the total deformation measured with LVDT. In the field GRS walls, nonwoven geotextile showed a larger deformation range than the woven geotextile and geogrid; however, the deformation patterns of these three reinforcement materials were similar. The function of strain gauges attached to nonwoven geotextile in the walls works normally for 16 months. Therefore, the method proposed in this study for measuring nonwoven geotextile deformation by using a strain gauge proved useful.

• 한국지반공학회논문집
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• 제21권6호
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• pp.127-135
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• 2005

부산점토에 대한 변형률 속도 의존적인 압밀특성을 분석하기 위해 다양한 변형률 속도의 일정 변형률(CRS) 압밀시험과 하중제어 압밀시험을 수행하였다. 부산점토에 대한 실내시험 결과에서 선행압밀하중은 압밀과정 동안에 유발되는 변형률 속도에 의존적이고 선행압밀하중에 대해 정규화시킨 압밀곡선은 유일하다는 것을 알 수 있었다. CRS 시험에서 얻어진 압밀계수 및 투수계수는 정규압밀영역에서 변형률 속도에 관계없이 일정한 값에 수렴함을 알 수 있었다. 또한 하중제어 압밀시험을 통해서 전응력이 일정한 상태에서 간극수압이 증가하는 Mandel-Cryer 효과를 볼 수 있었다. 그리고 장시간의 하중제어 압밀시험을 통해 선행압밀하중 부근에서 흙 구조의 붕괴로 인하여 급격한 간극수압의 증가현상이 관찰되었다.

• 대한기계학회논문집A
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• 제41권3호
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• pp.193-198
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• 2017

Alloy 617은 초고온가스로(VHTR)의 중간열교환기(IHX)의 유력한 후보 재료 중의 하나이다. $850^{\circ}C$의 고온에서 Alloy 617 용접재의 저사이클 피로 거동을 고찰하기 위하여, 완전 양진 변형률제어 피로시험이 0.6에서 1.5%의 전변형률범위에서 수행되었다. 용접재 시험편은 V-그루브 형상의 가스텅그스텐아크 용접한 용접 패드로부터 가공되었다. 피로수명은 전변형률범위가 증가할수록 감소하였다. 모든 실험조건에서 Alloy 617 용접재 시험편의 반복 응력 반응 거동은 초기 수 사이클에서 반복 변형률 경화현상을 나타내었다. 또한 모든 피로 균열의 발생과 전파는 입내파괴의 파손 모드를 보였다.

• 대한금속재료학회지
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• 제50권12호
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• pp.873-882
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• 2012

Dual Phase (DP) steel which has a soft ferrite phase and a hard martensite phase reveals both high strength and high ductility and has received increased attention for use in automotive applications. To conduct structural analysis to verify vehicle safety, highly credible experimental results are required. In this study, tensile tests were performed in a strain rate range from $10^{-4}/s$ to 300/s for Sink Roll-Less (SRL) hot-dip metal coated sheets. Collision properties were estimated through simulation by LS-DYNA using the stress-strain curve obtained from the tensile test. The simulation results were compared with the actual crash test results to confirm the credibility of the simulation. In addition, a tensile test and a crash test with 2% prestrain and a baking (PB) specimen were evaluated identically because automotive steel is used after forming and painting. The mechanical behaviors were improved with an increasing strain rate regardless of the PB treatment. Thus, plastic deformation with an appropriate strain rate is expected to result in better formability and crash characteristics than plastic deformation with a static strain rate. The ultimate tensile strength (UTS) and absorbed energy up to 10% strain were improved even though the total elongation decreased after PB treatment, The results of the experimental crash test and computer simulation were slightly different but generally, a similar propensity was seen.

• Computers and Concrete
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• 제29권1호
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• pp.15-29
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• 2022

Concrete-filled steel tubes (CFSTs) are increasingly used as composite sections in structures owing to their excellent load bearing capacity. Therefore, predicting the mechanical behavior of CFST sections under axial compression loading is vital for design purposes. This paper presents the first study on the nonlinear analysis of heated CFSTs with high-strength concrete core containing steel fiber and waste tire rubber under axial compression loading. CFSTs had steel fibers with 0, 1, and 1.5% volume fractions and 0, 5, and 10% rubber particles as sand alternative material. They were subjected to 20, 250, 500, and 750℃ temperatures. Using flow rule and analytical analysis, a model is developed to predict the load bearing capacity of steel tube, and hoop strain-axial strain relationship, and axial stress-volumetric strain relationship of CFSTs. An elastic-plastic analysis method is applied to determine the axial and hoop stresses of the steel tube, considering elastic, yield, and strain hardening stages of steel in its stress-strain curve. The axial stress in the concrete core is determined as the difference between the total experimental axial stress and the axial stress of steel tube obtained from modeling. The results show that steel tube in CFSTs under 750℃ exhibits a higher load bearing contribution compared to those under 20, 250, and 500℃. It is also found that the ratio of load bearing capacity of steel tube at peak point to the load bearing capacity of CFST at peak load is noticeable such that this ratio is in the ranges of 0.21-0.33 and 0.31-0.38 for the CFST specimens with a steel tube thickness of 2 and 3.5 mm, respectively. In addition, after the steel tube yielding, the load bearing capacity of the tube decreases due to the reduction of its axial stiffness and the increase of hoop strain rate, which is in the range of about 20 to 40%.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(4)
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• pp.182-187
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• 1996

Deformation characteristics of miniature plate tensile specimens have been studied to develop the thickness requirement and a correlation to estimate the mechanical properties of bulk material from miniature specimen data. The material used was a SA 508 C1.3 reactor pressure vessel steel and the thicknesses of miniature tensile specimens varied from ().12 m to 2 mm. The effects of thickness on the tensile deformation properties such as strength, ductility, and necking characteristics were analyzed. The yield and ultimate tensile strengths were independent of specimen thickness when the thickness was larger than about 0.2 mm. The uniform and total elongations decreased as the specimen thickness decreased. It was also observed that the uniform strain component in the width direction decreased with decrease in the specimen thickness, however, that in the thickness direction was rather constant in total thickness range studied. Based on this observation and a relationship between the necking angle and the ratio between strain components, a correlation between the uniform elongations of miniature specimen and standard specimen was derived. The uniform elongations calculated by this new correlation agreed well with the measured values.