W2C is synthesized through a reaction-sintering process from an ultrafine-W and WC powder mixture using spark plasma sintering (SPS). The effect of various parameters, such as W:WC molar ratio, sintering temperature, and sintering time, on the synthesis behavior of W2C is investigated through X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) analysis of the microstructure, and final sintered density. Further, the etching properties of a W2C specimen are analyzed. A W2C sintered specimen with a particle size of 2.0 μm and a relative density over 98% could be obtained from a W-WC powder mixture with 55 mol%, after SPS at 1700℃ for 20 min under a pressure of 50 MPa. The sample etching rate is similar to that of SiC. Based on X-ray photoelectron spectroscopy (XPS) analysis, it is confirmed that fluorocarbon-based layers such as C-F and C-F2 with lower etch rates are also formed.

This study evaluated effects of the addition of garlic powder allicin (GPA) mixture on rumen fermentation with methane in Hanwoo steer. On in vitro trial, two experimental groups were used: control (without GPA) and treatment group (addition of 0.1% GPA mixed with the basal concentrate). Similar to in vitro trial, two experimental groups were used in vivo trial. Five Hanwoo steers (3 steers in one group and 2 in another group; average body weight = 500 ± 43 kg) were assigned by crossover design for 20 d consists of 15 d diet adaptation and 5 d data collection in each experimental period. Daily feed intake and enteric methane production were recorded by an automated head chamber system. The results of in vitro study showed that the GPA treatment group had higher acetic acid (24.30 vs 23.45 mmol/L) and butyric acid (16.55 vs 15.47 mmol/L) concentrations, but lower CH4 production (1.40 vs 2.71 mmol/ml) after 24 h of incubation compared to the control (p<0.05). Total gas, propionic acid, total volatile fatty acid (VFA), and acetic acid: propionic acid ratio were not affected by treatment after 24 h incubation. In the in vivo experiment, rumen pH and VFA were not significantly different between treatments (p>0.05), except acetic acid, which was significantly higher in GPA mixture group (60.97 vs 53.94 mM) than in the control group (p<0.05). Furthermore, no significant differences were recorded in CH4 production (g/d) and CH4 yield (g/kg DMI) between the two groups (p>0.05). In conclusion, the addition of 0.1% GPA mixture reduced CH4 proudcition on in vitro trial, but no effect on in vivo trial.

PURPOSES : Asphalt pavements are damaged by various causes, such as cracks, potholes due to climate, and traffic environment. Asphalt aging has a significant effect on cracks, which may also form potholes. The purposes of this study are to estimate the change in asphalt binder and mixture performance and to correlate the physicochemical changes of the asphalt binder and mixture performance with aging. METHODS : The aging process of the asphalt was determined in the laboratory, based on the methods used in previous studies. In terms of consistency (stiffness), crack-resistance performance, moisture susceptibility, SK investigated the binder part, and Shoreki investigated the mixture part depending on the aging time. RESULTS : The consistency (stiffness) and brittleness of both the asphalt binder and mixture tended to increase with aging. In particular, the crack-resistance performance of the asphalt binder (G*sinδ, ductility, and ΔTc) and mixture (flexural fatigue test and Cantabro test) deteriorated because of asphalt aging. Furthermore, the aging mechanisms (oxidation and polymerization) were identified based on the chemical structure analysis. CONCLUSIONS : It is confirmed that the aging affected the chemical composition change and the physical properties of the asphalt. Asphalt pavements are significantly affected by the aging characteristics of the binder. It is concluded that the crack-resistance performance of the mixture decreases with aging due to these physical and chemical changes.

This study was conducted to find out the effects of seed mixture using new domestic grass varieties orchardgrass ‘Onnuri’ and tall fescue ‘Greenmaster’ on botanical composition and dry matter productivity from 2015 to 2018 in oversown hilly pasture, the central northern area of Korea. This experiment was consisted of 4 mixed grasses (Treatment 1 : tall fescue oriented mixture with imported varieties; Treatment 2 : orchardgrass oriented mixture with imported varieties; Treatment 3 : orchardgrass oriented mixture with domestic varieties, Treatment 4 : tall fescue oriented mixture with domestic varieties). Evaluation of seasonal changes in botanical composition of pasture showed that orchardgrass was the highest in all treatments, ranging from 46 to 89% and Kentucky bluegrass was the second highest in all treatments. Treatment 3 (7,633 kg ha-1) and Treatment 4 (7,570 kg ha-1), mixed grasses using domestic varieties, were showed the highest dry matter yield than Treatment 1(6,950 kg ha-1) and Treatment 2 (6,934 kg ha-1), which were mixed grasses using introduced varieties. Therefore, these results showed that the orchard grass oriented grasses mixture with domestic varieties was good for grassland vegetation and productivity in oversown hilly pasture, the central northern area of Korea.

PURPOSES : In many European countries, the fine-size exposed aggregate concrete pavement (EACP) technique has been adopted for a quiet pavement. However, different noise reduction levels were reported based on the mixture design and texture conditions. This study aims to suggest a quality control condition for achieving low-noise texture and a mixture design procedure for exposed aggregate concrete overlay (EACO), which will provide the optimum mixture of the surface texture that can reduce the tire-pavement noise. METHODS : The tire-pavement noise is highly influenced by the pavement surface texture. The surface texture of the EACP can be quantified by the mean texture depth (MTD) and the exposed aggregate number (EAN). The optimum condition for the low-noise texture of the EACP was investigated herein based on the analysis of the review of the texture conditions and noise measurement in many EACP sites. RESULTS : The MTD and EAN criteria can be derived according to the investigated relationship between noise and texture condition. The optimum mixture design to satisfy these criteria can be achieved by controlling the maximum size of the coarse aggregate and the S/a. CONCLUSIONS: This study aimed to suggest a quality control condition for achieving low-noise texture and an optimum mixture design for EACO. As a result, we found that the early traffic opening of EACO can be achieved by using high early-strength cement.

미국선녀벌레에 방제효과가 높은 3종 (데리스, 시트로넬라, 계피)의 식물추출물과 보조제 (잔탄검과 실리콘 계열 화합물)를 함유하는 조성물을 개발하였다. 이 조성물은 인삼 재배지에서 미국선녀벌레 방제효과가 90% 이상으로 높았다. 또한 다른 흡즙성 해충에도 살충률이 높아 PLS (positive list system) 전면 시행에 따른 대응방안으로 활용이 가능할 것으로 생각된다.

Reliability analysis of the components frequently starts with the data that manufacturer provides. If enough failure data are collected from the field operations, the reliability should be recomputed and updated on the basis of the field failure data. However, when the failure time record for a component contains only a few observations, all statistical methodologies are limited. In this case, where the failure records for multiple number of identical components are available, a valid alternative is combining all the data from each component into one data set with enough sample size and utilizing the useful information in the censored data. The ROK Navy has been operating multiple Patrol Killer Guided missiles (PKGs) for several years. The Korea Multi-Function Control Console (KMFCC) is one of key components in PKG combat system. The maintenance record for the KMFCC contains less than ten failure observations and a censored datum. This paper proposes a Bayesian approach with a Dirichlet mixture model to estimate failure time density for KMFCC. Trends test for each component record indicated that null hypothesis, that failure occurrence is renewal process, is not rejected. Since the KMFCCs have been functioning under different operating environment, the failure time distribution may be a composition of a number of unknown distributions, i.e. a mixture distribution, rather than a single distribution. The Dirichlet mixture model was coded as probabilistic programming in Python using PyMC3. Then Markov Chain Monte Carlo (MCMC) sampling technique employed in PyMC3 probabilistically estimated the parameters’ posterior distribution through the Dirichlet mixture model. The simulation results revealed that the mixture models provide superior fits to the combined data set over single models.

A two-phase flow in mini-channels is consist with various flow regimes (such as bubble slug, annular, churn flow) according to gas and liquid phase flow rates. A previous researches revealed that in a case of slug flow in hydrophobic mini-channels, gas and liquid phase are perfectly separated by interfaces and triple contact line. In this study, the single dry slug flow experiments in circular mini-channel (D = 1.018 mm) are conducted to observe interfacial break-up phenomena in high capillary number range (Ca < 0.02). The slug is consist with D.I. water or D.I. water-ethanol binary mixtures (5% and 10%, mole fraction). On the base of previous researches, we calculate the pressure drop at moving triple contact line. In an addition, a single dry slug flow is visualized by using high-speed camera. Through the experiment, three regimes of pressure drop are observed; steady, loss, separation. As a result, criteria between steady and loss regimes is closely related to capillary number, and criteria between loss and separation regimes is related to surface tension.

PURPOSES : This study aimed to estimate road pavement life expectancy using Bayesian Markov Mixture Hazard Model, to support infrastructure asset management. In addition, the life expectancies for the pavement condition index were compared among regional construction and management administrations. METHODS : Eleven years of National Highway road pavement monitoring data fused with ESAL (Equivalent Single Axle Loads), SNP (Structural Number of Pavement, an indicator of structural capacity), and average low temperature, total rainfall, and de-icing were used for the deterioration modeling. Deterioration modeling was performed through the Bayesian Markov Mixture Hazard Model. RESULTS : The expected life expectancy of the crack was estimated at 12.28 to 18.51 years, rut depth was estimated at 15.93 to 25.3 years, and the International Roughness Index was estimated at 10.44 to 14.33 years. It was also confirmed that the heterogeneity factor proposed in the Bayesian Markov Mixture Hazard Model could be used to analyze group characteristics and differences in the benchmark. CONCLUSIONS: This study provided important information in that it compared the life expectancies and structural characteristics of the pavement condition indexes among regional construction and management administrations. Based on this result, it is expected that a pavement structure design and maintenance strategy suitable for deterioration characteristics among regional construction and management administrations will be established.

PURPOSES : The feasibilities of cohesive elastoplastic contact model and discrete element method (DEM) for asphalt concrete mixture compaction process were evaluated. METHODS : The contact models that were used to simulate the dynamic behavior of construction materials were reviewed. The characteristics of cohesive elastoplastic models were discussed from the perspective of integration with existing contact models. Two asphalt mixtures that were fabricated with specific aggregate gradations and binder contents were compacted according to the Superpave gyratory compaction specification. The parameters for the model were determined via trial-and-error method. The heights of the specimens were plotted with respect to number of gyrations. The results of the laboratory tests were compared to those of numerical simulations. The displacement of particles in asphalt mixture specimen was also visualized to understand the effect of gyratory compaction on asphalt mixture specimen. RESULTS : The DEM model exhibited a significant friction coefficient dependency on compaction degree and slop. The DEM model with parameters determined through trial and error demonstrated reasonable simulation results in terms of specimen height at a gyration number. CONCLUSIONS: Even though a little discrepancy was observed between the results of the experimental test and numerical simulation, a combination of DEM with cohesive elastoplastic contact model seems to be applicable for the simulation of asphalt mixture compaction in laboratory. However, the model needs to be enhanced to be used for more realistic compaction processes, including heat transfer, phase change, and vibratory loading.

Herbal medicine has been the basis for medical treatments through much of human history, and such traditional medicine is still widely practiced today. Modern medicine makes use of many plant-derived compounds as the basis for pharmaceutical drugs. In traditionally, Achyranthes aspera, Safflower (Carthamus tinctorius) seed and Acanthopanax senticosus have been used for the treatment and prevention of bone-related diseases. In this study, we investigated the pharmacological effect of mixture of Achyranthes aspera, Safflower (Carthamus tinctorius) seed and Acanthopanax senticosus and the other herbs. Two types of enzymes were used to enhance the extraction components of amino acid, mineral content, free sugar, and flavor recovery in extracting natural herbal mixtures(NME). We evaluated regulation of osteogenic differentiation in human bone marrow mesenchymal stem cells using alkaline phosphatase staining, alizarin red S staining and RT-PCR. The CCK-8 assay indicated that NME had no cytotoxicity but increased cell survival. In addition, NME promoted the mineralization and expression of osteogenic differention marker genes in human bone marrow mesenchymal stem cells. Therefore, NME has an effect of promoting proliferation and osteogenic differentiation of human mesenchymal stem cell.

The effects of lactic acid bacteria (LAB) mixtures on low moisture Italian ryegrass (IRG) silage fermentation was evaluated in field conditions. The experiment was categorized into two groups: Un-inoculated (Control) and Inoculated with LAB mixture for four storage periods (45, 90, 180, and 365 days, respectively). Silage inoculated with the LAB mixture had the lowest pH with highest lactic acid production than the control from beginning at 45-365 days at all moistures. Higher LAB counts were observed in inoculated silages than the control silages at whole experimental periods. It is a key reason for the rapid acidification and higher lactic acid production in silages during the storage periods. Overall results suggest that an adding of LAB mixture had positive effects on the increasing aerobic stability of silage and preserved its quality for an extended duration.

브로일러의 생산성과 닭고기의 품질에 미치는 Bacillus. subtillus, Streptomyces galilaeus 및 Sphingobacteriaceae로 구성된 사료용 복합생균제(PFM, probiotic feed mixture)의 효과를 조사하였다. 병아리 (Ross 308) 240마리를 4개의 처리구로 나누어 35일간 사육하였다. 처리구는 사료용 복합 생균제를 함유하지 않은 대조구(CON, control), 일반생균제(CP3, commercial probiotics 0.3%), 사료용 복합 생균제 3(PFM3, 사료용 복합 생균제 0.3%), 사료용 복합 생균제 5(PFM5, 사료용 복합 생균제 0.5%)로 구분하였다. 체중은 CON과 비교할 때 CP3, PFM3, PFM5가 높았고 PFM3, PFM5는 CP3에 비해 우수하였다(p<0.05). F낭, 흉선, 비장의 무게 및 IgG 수준은 CON과 비교할 때 PFM3, PFM5 및 CP3에서 증가하였으며 PFM3, PFM5는 CP3에 비해 높았다(p<0.05). 맹장의 Lactobacillus 균수는 PFM3, PFM5 및 CP3를 섭취한 브로일러가 CON에 비해서 높았으나 E.coli, Salmonella, coliforms, 총 호기성 균수는 감소하였다(p<0.05). PFM3 및 PFM5를 섭취한 닭가슴살의 보수력은 CON 및 CP3와 비교할 때 증가하였다(p<0.05). 결론적으로 Bacillus subtillus, Streptomyces galilaeus 및 Sphingobacteriaceae를 포함하는 사료용 복합생균제 0.3%가 브로일러의 생산성과 닭고기 품질향상에 기여할 수 있음을 나타낸다.