• Computers and Concrete
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• 제29권2호
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• pp.107-115
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• 2022

With the improvements in computer technologies, utilization of image processing techniques has increased in many areas (such as medicine, defence industry, other industries etc.) Many different image processing techniques are used for surface analysis, detection of manufacturing defects, and determination of physical and mechanical characteristics of composite materials. In this study, cementitious composites were obtained by addition of Grounded Granulated Blast-Furnace Slag (GGBFS), Styrene Butadiene polymer (SBR), and Grounded Granulated Blast-Furnace Slag and Styrene Butadiene polymer together (GGBFS+SBR). Expanded Polystyrene (EPS) beads were added to these cementitious composites in different ratios (20%, 40% and 60%). The mechanical and physical characteristics of the composites were determined, and homogeneity indexes of the composites were determined by image processing techniques to determine EPS distribution forms in them. Physical and mechanical characteristics of the produced samples were obtained by applying consistency, density, water absorption, compressive strength (7 and 28 days), flexural strength (7 and 28 days) and tensile splitting strength (7 and 28 days) tests on them. Also, visual examination by using digital microscope, and image analysis by using image processing techniques with open source coded ImageJ program were performed. As a result of the study, it is determined that GGBFS and SBR addition strengthens the adhesion sites formed as it increases the adhesion power of the mixture and helps to get rid of the segregation problem caused by EPS. As a result of the image processing analysis it is demonstrated that GGBFS and SBR addition has positive contribution on homogeneity index.

• Geomechanics and Engineering
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• 제31권1호
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• pp.99-112
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• 2022

The present study examines the natural frequencies (NFs) of perfect/imperfect functionally graded sandwich beams (P/IP-FGSBs), which are composed of a porous core constructed of functionally graded materials (FGMs) and a homogenous isotropic metal and ceramic face sheets resting on elastic foundations. To accomplish this, the material properties of the FGSBs are assumed to vary continuously along the thickness direction as a function of the volume fraction of constituents expressed by the modified rule of the mixture, which includes porosity volume fraction represented using four distinct types of porosity distribution models. Additionally, to characterize the reaction of the two-parameter elastic foundation to the Perfect/Imperfect (P/IP) FGSBs, the medium is assumed to be linear, homogeneous, and isotropic, and it is described using the Winkler-Pasternak model. Furthermore, the kinematic relationship of the P/IP-FGSBs resting on the Winkler-Pasternak elastic foundations (WPEFs) is described using trigonometric shear deformation theory (TrSDT), and the equations of motion are constructed using Hamilton's principle. A closed-form solution is developed for the free vibration analysis of P/IP-FGSBs resting on the WPEFs under four distinct boundary conditions (BCs). To validate the new formulation, extensive comparisons with existing data are made. A detailed investigation is carried out for the effects of the foundation coefficients, mode numbers (MNs), porosity volume fraction, power-law index, span to depth ratio, porosity distribution patterns (PDPs), skin core skin thickness ratios (SCSTR), and BCs on the values of the NFs of the P/IP-FGSBs.

• 한국지진공학회논문집
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• 제28권1호
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• pp.33-39
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• 2024

Understanding the behavior of soil under cyclic loading conditions is essential for assessing its response to seismic events and potential liquefaction. This study investigates the effect of non-plastic fines content (FC) on excess pore pressure generation in medium-density sand-silt mixtures subjected to strain-controlled cyclic direct simple shear (CDSS) tests. The investigation is conducted by analyzing excess pore pressure (EPP) ratios and the number of cycles to liquefaction (Ncyc-liq) under varying shear strain levels and FC values. The study uses Jumunjin sand and silica silt with FC values ranging from 0% to 40% and shear strain levels of 0.1%, 0.2%, 0.5%, and 1.0%. The findings indicate that the EPP ratio increases rapidly during loading cycles, with higher shear strain levels generating more EPP and requiring fewer cycles to reach liquefaction. At 1.0% and 0.5% shear strain levels, FC has a limited effect on Ncyc-liq. However, at a lower shear strain level of 0.2%, increasing FC from 0 to 10% reduces Ncyc-liq from 42 to 27, and as FC increases further, Ncyc-liq also increases. In summary, this study provides valuable insights into the behavior of soil under cyclic loading conditions. It highlights the significance of shear strain levels and FC values in excess pore pressure generation and liquefaction susceptibility.

• 한국축산식품학회지
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• 제44권1호
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• pp.146-164
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• 2024

Owing to the residual toxicity and adverse health effects of chemical preservatives, there is an increasing demand for using natural preservatives in food. Although many natural extracts have been evaluated, research on their antibacterial effects remains insufficient. Therefore, this study aimed to explore the possibility of developing Psidium guajava, Ecklonia cava, and Paeonia japonica (Makino) Miyabe & Takeda extracts as natural food preservatives. Further, the effect of mixing these extracts on microbial growth and quality was evaluated during the refrigeration of sausages. Optimal mixing ratios were determined based on the minimum inhibitory and bactericidal concentrations of each mixed extract against the Listeria monocytogenes, Salmonella spp. and Escherichia coli. D-optimal mixing design optimization tool was further used to obtain an optimum mixing ratio of Formulation 1 (F1). The antibacterial activity of F1 increased with increasing concentration, with similar activities at 0.5% and 1%. The sausages with synthetic or natural preservatives showed significantly lower lipid oxidation than those of the control and grapefruit extract-treated sausages after 4 wk of refrigeration. Total plate counts were observed only in the control and treatment groups stored for 3 wk, and no significant effect of ascorbic acid was observed. Compared to the other samples, sausages with added natural extracts showed the highest overall acceptability scores initially and after 4 wk. Therefore, similar amounts of grapefruit seed and natural extracts had the same effect on microbiological analysis and lipid rancidity during sausage storage. Hence, this mixture can serve as a potential natural preservative in meat products.

• Steel and Composite Structures
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• 제51권3호
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• pp.271-288
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• 2024

The primary objective of this study is to investigate the production and performance characteristics of structural concrete incorporating varying proportions (0%, 25%, and 50% by volume) of pumice stone, as well as aluminum lathe as an additive at 0%, 1%, 2%, and 3%, under fire conditions. The experiment will be conducted over a period of up to 1 hour, at temperatures ranging from 24℃, 200℃, 400℃ and 600℃. For the purpose of this, a total of twelve test samples were manufactured, and then tests of compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS) were performed on these samples.Next, a comparison was made between the obtained values and the influence of temperature. To achieve this objective, the manufactured samples were placed at temperatures of 200℃, 400℃, and 600℃ for a duration of 1 hour, and were subjected to the influence of temperature.These values at 24 ℃ were then contrasted with the CS results obtained from test samples that were subjected to the temperature effect for an hour at 200 ℃, 400 ℃, and 600 ℃. A comprehensive analysis of the test outcomes reveals that the incorporation of aluminum lathe wastes into a mixture results in a significant reduction in the compressive strength of the concrete. As a result of this adjustment, the CS values dropped by 32.93%, 45.70%, and 52.07%, respectively. Furthermore, It was shown that testing the ratios of pumice stone alone resulted in a decrease in CS outcomes. Additionally, it was found that the presence of higher temperatures is clearly the primary factor contributing to the decrease in the strength of concrete. Due to elevated temperatures, the CS values decreased by 19.88%, 28.27%, and 38.61% respectively.After this investigation, an equation that explains the connection between CS and STS was provided through the utilization of the data of the experiments that were carried out.

• 한국건설순환자원학회논문집
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• 제12권2호
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• pp.111-120
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• 2024

본 논문에서는 홍수와 같은 재해시 비탈면 긴급 복구를 위한 보수재료를 제조하기 위한 일환의 연구로써, 플라이애시 혼합율에 따른 모르타르, 현무암 섬유 보강에 따른 모르타르를 각각 제조하여 보수재료의 기초 품질 특성에 미치는 특성을 평가하였다. 긴급 복구를 위한 보수재료는 각각의 특성으로부터 최적의 플라이애시 사용량을 선정하였으며, 현무암 섬유 혼합에 따른 기초 품질 향상을 위하여 화학혼화제 및 증점제의 최적 사용량을 도출하였다. 특히 하이볼륨 플라이애시는 알려진 장점으로 인하여 고성능 감수제 사용량 감소 및 작업성 향상이 가능함을 확인하였으며, 증점제 효과와 함께 섬유 뭉침 현상을 해소할 수 있는 것으로 나타났다. 본 실험결과를 통하여 얻어진 보수재료는 초기재령 강도를 중점으로 평가하여 긴급 복구를 위한 보수재료로써의 활용 가능성을 제시하고자 하였다.

• 한국수산과학회지
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• 제26권6호
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• pp.519-528
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• 1993

해수중에서 유처리제에 의해 유화${\cdot}$분산된 Bunker-C유의 생분해도와 이로 인해 나타나는 용존산소소비를 연구할 목적으로 국내에서 시판 중인 유처리제 및 국내 연안에 있어 유류오염사고의 주종을 이루고 있는 Bunker-C유에 대한 TOD분석과 원소분석을 행하고, 또한 Bunker-C유/유처리제 혼합물에 대해 천연해수를 이용한 생분해 실험을 행한 결과를 요약하면 다음과 같다. 1. 1mg의 Bunker-C유는 3.16mg의 TOD를 나타내는 반면에 1mg의 유처리제는 2.80mg의 TOD값을 나타내었다. 2. Bunker-C유는 $87.3\%$의 탄소와 $11.5\%$의 수소를 함유하였으며, 유처리제는 $76.5\%$의 탄소와 $12.2\%$의 수소를 함유하였다. Bunker-C유와 유처리제 중 어느 시료에서도 질소는 검출되지 않았다. 3. 천연해수 중에서 일정량의 Bunker-C유(4mg/l)에 대하여 유처리제를 $10:1{\sim}10:5$의 혼합비율로 첨가한 Bunker-C유/유처리제 혼합물에 관해서 정리하면, 혼합물의 $BOD_5$는 $0.34{\sim}2.06mg/l$였고 $BOD_{20}$는 $1.05{\sim}5.47mg/l$였다. 또한 혼합비율이 증가함에 따라 혼합물의 BOD는 증가하였다. 혼합물은 생분해도($BOD_5$/TOD)가 $3{\sim}11\%$로서 저율 분해군에 속하였다. 또한 혼합비율이 10:1에서 10:5로 증가함에 따라 혼합물의 생분해도는 $3\%$에서 $11\%$로 증가하였다. 혼합물의 탈산소계수($K_1$)는 $0.072{\sim}0.097/day$였으며, 혼합물의 최종산소요구량($L_o$)은 $1.113mg/l{\sim}6.746mg/l$로서 혼합비율이 증가함에 따라 최종산소요구량도 증가하였다.

• 한국식품저장유통학회지
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• 제24권3호
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• pp.431-439
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• 2017

생맥산 원료인 맥문동, 오미자 및 인삼의 최적 혼합비율을 설정하고자 맥문동, 오미자 및 인삼 혼합추출물을 제조하여 이화학적 특성 및 생리활성을 조사하였다. 맥문동, 오미자 및 인삼 혼합추출물의 추출수율은 25.33-33.87%이었으며, 총 폴리페놀 및 총 플라보노이드 함량은 오미자의 혼합비율이 높은 추출물(ME1)에서 각각 1.01 g/100 g 및 0.07 g/100 g으로 가장 높은 값을 나타내었고, 총 당 함량은 맥문동의 혼합비율이 높은 추출물(MEC)에서 22.83 g/100 g으로 가장 높은 값을 나타내었다. DPPH radical 및 ABTS radical 소거활성은 ME1 추출물에서 각각 26.79% 및 21.09%로 가장 우수한 radical 소거활성을 나타내었으며, superoxide radical 소거활성 및 FRAP 활성 또한 ME1 추출물에서 각각 67.83% 및 $295.47{\mu}M$로 가장 우수한 항산화 활성을 나타내었다. 맥문동, 오미자 및 인삼 혼합추출물의 생리활성을 확인한 결과, $H_2O_2$에 의해 산화적 손상된 폐상 피세포인 L-132 세포의 생존율은 51.43%를 나타낸 반면 ME1 추출물($1,000{\mu}g/mL$)은 81.22%로 가장 높은 세포보호 효과를 나타내었다. LPS로 자극을 유도한 대식세포주인 RAW264.7 세포는 인삼의 혼합비율이 높은 ME2 추출물($1,000{\mu}g/mL$)은 $7.48{\mu}M$로 가장 적은 nitric oxide 생성량을 나타내어 nitric oxide 생성을 억제하였다. 따라서 본 연구에서는 동의보감 및 일반적으로 많이 이용하고 있는 MEC 추출물보다 ME1 및 ME2 추출물에서 항산화 활성 및 면역조절능이 우수함을 확인하여, 새로운 생맥산 혼합비율을 이용한 항산화 활성 및 면역조절용 기능성 식품 소재 개발이 가능할 것으로 사료된다.

• Asian-Australasian Journal of Animal Sciences
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• 제28권1호
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• pp.50-57
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• 2015

This study was conducted to investigate the effect of soybean meal (SM) and soluble starch (SS) on biogenic amine production and microbial diversity using in vitro ruminal fermentation. Treatments comprised of incubation of 2 g of mixture (expressed as 10 parts) containing different ratios of SM to SS as: 0:0, 10:0, 7:3, 5:5, 3:7, or 0:10. In vitro ruminal fermentation parameters were determined at 0, 12, 24, and 48 h of incubation while the biogenic amine and microbial diversity were determined at 48 h of incubation. Treatment with highest proportion of SM had higher (p<0.05) gas production than those with higher proportions of SS. Samples with higher proportion of SS resulted in lower pH than those with higher proportion of SM after 48 h of incubation. The largest change in $NH_3$-N concentration from 0 to 48 h was observed on all SM while the smallest was observed on exclusive SS. Similarly, exclusive SS had the lowest $NH_3$-N concentration among all groups after 24 h of incubation. Increasing methane ($CH_4$) concentrations were observed with time, and $CH_4$ concentrations were higher (p<0.05) with greater proportions of SM than SS. Balanced proportion of SM and SS had the highest (p<0.05) total volatile fatty acid (TVFA) while propionate was found highest in higher proportion of SS. Moreover, biogenic amine (BA) was higher (p<0.05) in samples containing greater proportions of SM. Histamines, amine index and total amines were highest in exclusive SM followed in sequence mixtures with increasing proportion of SS (and lowered proportion of SM) at 48 h of incubation. Nine dominant bands were identified by denaturing gradient gel electrophoresis (DGGE) and their identity ranged from 87% to 100% which were mostly isolated from rumen and feces. Bands R2 (uncultured bacterium clone RB-5E1) and R4 (uncultured rumen bacterium clone L7A_C10) bands were found in samples with higher proportions of SM while R3 (uncultured Firmicutes bacterium clone NI_52), R7 (Selenomonas sp. MCB2), R8 (Selenomonas ruminantium gene) and R9 (Selenomonas ruminantium strain LongY6) were found in samples with higher proportions of SS. Different feed ratios affect rumen fermentation in terms of pH, $NH_3$-N, $CH_4$, BA, volatile fatty acid and other metabolite concentrations and microbial diversity. Balanced protein and carbohydrate ratios are needed for rumen fermentation.

• 한국식품과학회지
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• 제50권1호
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• pp.76-82
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• 2018

본 연구에서는 식물성 원료인 콩에 물의 비율을 달리하여 발효우유 베이스(base)를 제조하고, 식물성 젖산균인 김치 젖산균 L. plantarum와 식초 젖산균인 B. acidiproducens를 접종하여 제조한 발효우유의 물리 화학적 특성을 알아보고자 하였다. 콩과 물의 비율은 1:1인 것이 다른 비율보다 실험결과에서 이상적인 값을 보였다. L. plantarum 발효우유와 B. acidiproducens 발효우유는 pH와 산도, 생균수에서 대조군으로 사용한 YF 발효우유보다 낮은 값을 나타내었으나 발효우유 제조 규격에 적합한 수준이었다. L. plantarum 발효우유는 발효완료시점의 생균수에서 B. acidiproducens 발효우유보다 유의적으로 높은 값을 나타내었으나 (p<0.05) 완성된 발효우유의 향과 전체적 기호도에서 낮은 평가를 받았는데, 이는 발효우유의 신맛과 향으로 인한 결과로 사료된다. B. acidiproducens VG1 발효우유는 L. plantarum YD09 발효우유와 pH, 산도, 색도, 당도 및 점성에서 유사한 결과 값을 보였고, 생균수에서는 L. plantarum 발효우유보다 낮은 값을 나타내었지만, 관능검사에서 높은 선호도를 보였다. 결론적으로 김치 젖산균인 L. plantarum YD09과 식초에서 분리한 B. acidiproducens VG1은 시판되는 YF 균주보다 발효 초기 pH값이 높은 경향을 보였으나 발효가 완료된 시점에서 발효우유로써 규격에 합하는 결과 값을 나타낸 것으로 보아 발효우유 제조에 적합한 것으로 사료되며, 콩과 물의 비율을 1:1로 정하여 제조하는 것이 생균수가 높고, 커드 형성이 잘 되는 발효우유를 제조할 수 있을 것으로 보인다. 그리고 L. plantarum 보다 B. acidiproducens VG1을 사용하여 발효우유를 제조할 경우 신맛이 덜하고 시판되는 ABT-4 (YF)만큼 기호도가 높은 발효우유를 제조할 수 있을 것으로 사료된다.