• 한국도로학회논문집
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• 제17권6호
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• pp.27-32
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• 2015

PURPOSES : It is difficult to estimate tunnel stability because of lack of timely information during tunnel excavation. Tunnel deformability refers to the capacity of rock to strain under applied loads or unloads during tunnel excavation. This study was conducted to analyze a methods of pre-evaluation of stability during tunnel construction using the critical strain concept, which is applied to the results of tunnel settlement data and unconfined compression strength of intact rock or rock mass at the tunnel construction site. METHODS : Based on the critical strain concept, the pre-evaluation of stability of a tunnel was performed in the Daegu region, at a tunnel through andesite and granite rock. The critical strain concept is a method of predicting tunnel behavior from tunnel crown settlement data using the critical strain chart that is obtained from the relationship between strain and the unconfined compression strength of intact rock in a laboratory. RESULTS : In a pre-evaluation of stability of a tunnel, only actually measured crown settlement data is plotted on the lower position of the critical strain chart, to be compared with the total displacement of crown settlement, including precedent settlement and displacement data from before the settlement measurement. However, both cases show almost the same tunnel behavior. In an evaluation using rock mass instead of intact rock, the data for the rock mass strength is plotted on the lower portion of the critical strain chart, as a way to compare to the data for intact rock strength. CONCLUSIONS : From the results of the pre-evaluation of stability of the tunnel using the critical strain chart, we reaffirmed that it is possible to promptly evaluate the stability of a tunnel under construction. Moreover, this research shows that a safety evaluation using the actual instrumented crown settlement data with the unconfined compression strength of intact rock, rather than with the unconfined compression strength of a rock mass in the tunnel working face, is more conservative.

• Smart Structures and Systems
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• 제20권2호
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• pp.139-150
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• 2017

The structural strain plays a significant role in structural condition assessment of in-service bridges in terms of structural bearing capacity, structural reliability level and entire safety redundancy. Therefore, it has been one of the most important parameters concerned by researchers and engineers engaged in structural health monitoring (SHM) practices. In this paper, an SHM system instrumented on the Jiubao Bridge located in Hangzhou, China is firstly introduced. This system involves nine subsystems and has been continuously operated for five years since 2012. As part of the SHM system, a total of 166 fiber Bragg grating (FBG) strain sensors are installed on the bridge to measure the dynamic strain responses of key structural components. Based on the strain monitoring data acquired in recent two years, the strain-based structural condition assessment of the Jiubao Bridge is carried out. The wavelet multi-resolution algorithm is applied to separate the temperature effect from the raw strain data. The obtained strain data under the normal traffic and wind condition and under the typhoon condition are examined for structural safety evaluation. The structural condition rating of the bridge in accordance with the AASHTO specification for condition evaluation and load and resistance factor rating of highway bridges is performed by use of the processed strain data in combination with finite element analysis. The analysis framework presented in this study can be used as a reference for facilitating the assessment, inspection and maintenance activities of in-service bridges instrumented with long-term SHM system.

• 콘크리트학회논문집
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• 제23권5호
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• pp.627-636
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• 2011

최근 고강도 콘크리트의 폭렬 방지용 보강 섬유로서 폴리프로필렌 섬유를 대신하여 나일론 섬유의 사용이 증가됨에 따라 고온에 노출된 나일론 섬유를 혼입한 고강도 콘크리트의 폭렬 및 역학적 특성에 관한 실험적 연구가 수행되고 있다. 그러나, 고온을 받은 나일론 섬유 보강 고강도 콘크리트에 관한 연구는 주로 폭렬 특성, 압축강도 및 탄성계수에 대한 평가만이 수행되고 있으며, 열팽창 변형, 전체 변형, 크리프 변형 및 과도 변형과 같은 거동은 평가된 바가 없다. 따라서 이 연구에서는 W/B 0.30~0.15에 따른 나일론 섬유를 혼입한 고강도 콘크리트에 대하여 열팽창 변형, 전체 변형, 크리프 및 과도 변형 등을 평가하였다. 실험 결과, 나일론 섬유는 고온을 받은 나일론 섬유를 혼입한 고강도 콘크리트의 성능에 특별한 영향을 미치지 않는 것으로 보였으며, 나일론 섬유 보강 고강도 콘크리트는 섬유를 혼입하지 않은 고강도 콘크리트 또는 보통 강도 콘크리트보다 큰 과도 변형을 나타냈다.

• 지질공학
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• 제24권3호
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• pp.311-322
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• 2014

Limestone bodies under the tectonic environment have experienced various tectonic processes, and also changed the stress state. In this study, calcite twins found in limestones of the Joseon Supergroup and Pyeongan Supergroup in the northeastern part of the Ogcheon Belt, South Korea were measured, then the paleostress (i.e., the maximum shortening axis) was reconstructed using the new calcite strain gauge (NCSG) technique. The average twin thickness and average twin intensity increase as the total twin strain increases. We utilize the appearance of twins, the average twin thickness and average twin intensity, and the total twin strain to estimate that the observed calcite twins were produced at temperatures of < $200^{\circ}C$ in the Joseon Supergroup and $170^{\circ}C$ in the Pyeongan Supergroup. In the Joseon Supergroup, the dominant direction of the maximum shortening axis WNW-ESE to NW-SE; NE-SW shortening is also observed. The maximum shortening axes in the Pyeongan Supergroup are oriented NW-SE and NE-SW. The NE-SW direction of maximum shortening is associated with the occurrence of the Songrim orogeny of the Paleozoic to Early Jurassic, and the NW-SE direction of maximum shortening correlates to the Daebo orogeny of the Early Jurassic to Late Jurassic. It is thus concluded that the paleostress across the study area changed from NE-SW to NW-SE during the Mesozoic.

• Journal of Animal Science and Technology
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• 제54권6호
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• pp.435-442
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• 2012

This study was conducted to isolate and identify the lactic acid bacteria (LAB) from spent mushroom substrates (SMS) for the effective anaerobic fermentation to utilize SMS as an animal feed and to determine the optimal medium conditions for their growth. At first, a total of 23 strains were isolated from the ensiled SMS based on the LAB counts and pH tested. Then, a total of 16 strains which rapidly produce lactate and decreased the pH, were selected for a screening test. The optical density (OD), pH, and yellow clear zone were tested for the selected 16 strains. Among the strains, KU5 strain had wider yellow clear zone and lower pH and KU13 strain had higher OD at 24 hr of incubation and wider yellow clear zone compared to other strains and control strain (Lactobacillus plantarum KCCM 12116). Accordingly, KU5 and KU13 strains were finally selected. The KU5 and KU13 were identified as Lactobacillus plantarum by the 16S rRNA sequencing. The KU5 strain was named as Lactobacillus plantarum KU5, and the KU13 strain was named as Lactobacillus plantarum KU13. Lactobacillus plantarum KU5 and Lactobacillus plantarum KU13 were registered at the National Center for Biotechnology Information (NCBI). Access number of Lactobacillus plantarum KU5 was HQ542227 and that of Lactobacillus plantarum KU13 was HQ542228. The optimal medium conditions for growth of KU5 and KU13 were soybean meal 2% and formulated feed 2%, respectively.

• 한국식품영양학회지
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• 제20권4호
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• pp.363-368
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• 2007

Traditional kochujang samples were collected from the folk village in Sunchang to find the major microbial composition and correlation between the taste and the microbial properties. Among the 29 samples, 17 samples showed Bacillus licheniformis as dominant strain with 11 samples Bacillus subtilis and 1 sample Staphylococcus pasteuri. Subdominant strain of 17 samples was Bacillus licheniformis with 12 samples Bacillus subtilis. Dominant strain numbers varied in rage of $6.60{\sim}8.38$ logCFU/g with subdominant strain number $5.90{\sim}7.86$ logCFU/g and total microbial number $6.64{\sim}8.56$ logCFU/g respectively. Bacterial type number varied in range of $6{\sim}18$ with the average 10.5 types. Fungi were found only in 2 samples and identified all to be Aspergillus oryzae. Yeasts were found in 25 samples. The dominant yeast strain of 23 samples was identified to be Zygosaccharomyces pseudorouxii and that of 2 samples Zygosaccharomyces rouxii. Yeast type variety showed that only single type was found in 15 samples, 2 types in 8 samples, 3 types in 1 sample and 4 types in 1 sample. Fungal number was 3.90 and 4.08 logCFU/g and yeast numbers varied in range of $3.90{\sim}6.43$ logCFU/g. The sensory scores of kochujang showed positive correlation with type numbers, but no significant correlation with the other microbial properties like total bacterial number, dominant bacterial number, subdominant bacterial number and dominant yeast number.

• Asian-Australasian Journal of Animal Sciences
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• 제8권4호
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• pp.325-328
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• 1995

The experiment was conducted to study the comparative pathology of hemic system among three different broiler chicken strains i.e. Hubbard (H), Lohmann (L) and Indian River (IR) suffering from experimentally induced Hydropericardium Syndrome (HPS). For this 50 chicks of each strain were inoculated with HPS inoculum at the age of 21 days and other 50 chicks of each broiler strain were kept as uninoculated control. After slaughtering each bird of both groups was subjected to pathological examination of heart, spleen and aorta and also for determining routine haematological parameters. The maximum values of Total Erythrocyte Count (TEC), heterophils and thrombocytes and the minimum values of Total Leukocyte Count (TLC) and Hemoglobin (Hb) content were found in H broiler strain. Percentage of monocytes, basophils and eosinophils also showed maximum decrease in H broiler chicken strain. Gross pathological lesions in the inoculated birds revealed that the heart showed ballooning due to distention of pericardial sac with pericardial fluid. Haemorrhages on the epicardium and flabbiness of the myocardium. Under the microscope, degenerative changes in myocardial tissue were seen. Lesions in the spleen included splenomegaly and haemorrhagic spots. Aorta showed flabbiness of the wall and disruption of endothelium. It is concluded that there is a marked difference in susceptibility of HPS among three different commercial broiler strains. The Hubbard broiler strain is more susceptible which is followed by the Indian River and Lohmann respectively.

• 한국의류산업학회지
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• 제22권2호
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• pp.250-260
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• 2020

The purpose of the present study was to explore the most effective body region and cooling temperature to alleviate heat strain of workers in hot environments. We developed liquid cooling hood, vest, sleeves and socks and applied the water temperatures of 10, 15, 20, and 25℃ through the liquid cooling garments in a hot and humid environment (33℃ air temperature and 70% RH air humidity). A healthy young male participated in a total of 16 experimental trials (four cooling garments × four cooling temperatures) with the following protocol: 10-min rest, 40-min exercise on a treadmill and 10-min recovery. The results showed that rectal temperature, mean skin temperature, and ratings of perceived exertion during exercise; heart rate and diastolic blood pressure during recovery; and total sweat rate were lower for the vest condition than other garment conditions(p < .05). However, there was no differences in mean skin temperature among the four cooling garments when we compared the values converted by covering area(%BSA). When we classified the results by cooling temperature, there were no consistent differences in thermoregulatory and cardiovascular responses among the four temperatures, but 25℃ water temperature was evaluated as being the most ineffective cooling temperature in terms of subjective responses. In conclusion, the results indicated that wearing cooling vest with < 20℃ cooling temperature can alleviate heat strain of workers in hot and humid environments. If the peripheral body regions are cooled with liquid cooling garments, larger cooling area with lower cooling temperature than 10℃ would be effective to reduce heat strain of workers. Further studies with a vaild number of subjects are required.

• 대한기계학회논문집
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• 제11권2호
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• pp.191-197
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• 1987

본 논문에서는 이상과 같이 그 중요성이 인정되는 작은 표면피로균열의 성장 특성을 조사하기 위하여 연강과 중탄소강에 두 종류의 작은 표면결함을 가공한 네가지 종류의 시험편을 제작하고, 응력비 R=-1인 소야식 회전굽힘 피로시험을 통하여 작은 표면결함이 피로강도에 미치는 영향과 그 성장특성을 조사한 후 응력확대계수 K를 사 용하는 방법과 반복전스트레인 확대계수범위 .DELTA. $K_{\epsilon}$t/를 비교 검토하여 그 유효성 을 조사하고 이를 파괴역학적 측면에서 고찰하였다.다.

• Geomechanics and Engineering
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• 제24권2호
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• pp.179-191
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• 2021

In this study, the strength and failure mechanism of red sandstones with combined defects were investigated by uniaxial compression tests on red sandstones with different crack angles using two-dimensional particle flow code numerical software, and their mechanical parameters and failure process were studied and analyzed. The results showed that the mechanical characteristics such as peak strength, peak strain, and elastic modulus of the samples with prefabricated combined defects were significantly inferior than those of the intact samples. With increasing crack angle from 15° to 60°, the weakening area of cracks increased, elastic modulus, peak strength, and peak strain gradually reduced, the total number of cracks increased, and more strain energy was released. In addition, the samples underwent initial brittle failure to plastic failure stage, and the failure form was more significant, leading to peeling phenomenon. However, with increasing crack angle from 75° to 90°, the crack-hole combination shared the stress concentration at the tip of the crack-crack combination, resulted in a gradual increase in elastic modulus, peak strain and peak strength, but a decrease in the number of total cracks, the release of strain energy reduced, the plastic failure state weakened, and the spalling phenomenon slowed down. On this basis, the samples with 30° and 45° crack-crack combination were selected for further experimental investigation. Through comparative analysis between the experimental and simulation results, the failure strength and final failure mode with cracks propagation of samples were found to be relatively similar.