• Tribology and Lubricants
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• 제9권1호
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• pp.62-69
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• 1993

Friction and wear behavior of a carbon/carbon composite material for aircraft brake material was experimentally investigated. Friction and wear test setup was designed and built for the experiment. Friction and wear tests were conducted under various sliding conditions. Friction coefficients were measured and processed by a data acquisition system and amount of wear measured by a balance. Stainless steel disk was used as the counterface material. Temperature was also measured by inserting thermocouple 2.5 mm beneath the sliding surface of the carbon/carbon composite specimen. Wear surfaces were observed by SEM, and analyzed by EDAX. The experimental results showed that sliding speed and normal force did not have significant effects on friction coefficient and wear factor of the composite. Temperature increase just below the surface was not large enough to cause any thermal degradation or oxidation which occurred at higher temperature when tested by TGA. Wear film was generated both on the specimen and on the counterface at relatively low sliding speed but cracks, grooves, and wear debris were observed at high sliding speed. Friction coefficient remained almost constant when the sliding speed or normal load was varied. It is believed that the adhesive and abrasive components contributed mainly to the friction coefficient. Wear behavior at low sliding speed was governed by wear film formation and adhesive wear mechanism. At high speed, fiber orientation, ploughing by counterface asperities, and fiber breakage dominated wear of the carbon/carbon composite.

• Journal of Ginseng Research
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• 제9권1호
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• pp.15-23
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• 1985

The study was carried out to confirm the changes of soil physico-chemical properties and population of Fusarium solani by soil managements at preplanning fields for ginseng cultivation. Soil porosity and aggregation had been significantly increased during the managements while exchangeable nitrogen content and bulk density of the soil had been decreased. Available phosphate and exchangeable potassium content, in addition, seemed to be slightly increased. And soil aggregation showed positive correlation with clay, organic matter, soil moisture, and Ca content in the soil but negative with K content. Decrease rate of NH4-N and NO3-N content after soil managements were 55% and 41% in average, respectively. And better decrease effect for NH4-N was obtained in sand loam soil whereas no effect for NO3-N with soil textures. The more ploughing seemed to result in less propagules of F solani in the soil, however there was non significant decrease in population of the pathogen after the soil management. Number of F. solani in soil was significantly less in the fields where gramineous and leguminous crops had been grown as a precrop than other crops tested. Meanwhile there was no correlation between soil texture and population of the pathogen in the soil.

• Journal of Forest and Environmental Science
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• 제25권1호
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• pp.49-55
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• 2009

The present study analyses the effect of land use on the vegetation of some desert ecosystems in Abu Dhabi, United Arab Emirates (UAE). Three sites were selected to represent different types of land use, inside Umm Al-Banadeq forest, outside the forest and along Abu Dhabi-Al Ain Trucks Road. In total, fifty-two stands were examined; including a matrix of 14 species ${\times}$ 52 stands. Based on species cover data, stands were classified using TWINSPAN and ordinated using DCA. Four vegetation groups were generated at level three of classification. Zygophyllum mandavillei was dominant in most vegetation groups; Heliotropium bacciferum dominated vegetation groups inhabited the forest. Species richness, species turnover, relative evenness and relative concentration of dominance of forest vegetation groups were 2.8, 5.7, 0.7, and 2.0, respectively. The differences were attributed to both natural variability and forestry-induced changes, including change in land use, drainage and ploughing and shading by trees. Vegetation group inhabited Abu Dhabi-Al Ain Trucks Road, that were dominated by Haloxylon salicornicum and Zygophyllum mandavillei have high total cover (8.8 m per $m^{-1}$). Most community and vegetation attributes were significantly higher inside the forest than outside. Human interventions and environmental factors affected species diversity and abundance of these communities.

• Asian-Australasian Journal of Animal Sciences
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• 제10권1호
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• pp.64-69
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• 1997

A study was conducted on the effects of ploughing on physiological responses of male and female Bali-cattle. A $2{\times}2{\times}6{\times}8$ factorial design (2 seasons, 2 sexes, 6 days and 8 consecutive time of measurements every 30 minutes) was employed. Responses during the cool/humid season were lower than hot/dry; respiration rate (RR) was 52 vs 75/min, rectal temperature(RT) was 39.1 vs $39.5^{\circ}C$ and skin temperature (ST) was 37.1 vs $37.6^{\circ}C$. Within sexes, males were less tolerant than females in that their RR (66 vs 61 breath/min), RT (39.4 vs $39.2^{\circ}C$) and ST (37.6 vs $37.1^{\circ}C$) were each higher than females during work. With increasing time, during the average 2.5 h working period gradual increases in RR, RT and ST were recorded and the overall increases of 84 breath/min, $1.9^{\circ}C$ and $13.8^{\circ}C$ respectively (p < 0.001). Packed cell volume (PCV) data indicated significant difference between sexes, time and season (p < 0.001, p < 0.05 and p < 0.001 respectively). Within time (before and after 2.5 h working) the PCV decreased from 27.4 to 25.6%.

• 수산해양기술연구
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• 제50권2호
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• pp.162-168
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• 2014

The friction and wear characteristics of the rubber matrix composites filled with nano sized silica particles were investigated at ambient temperature by pin-on-disc friction test. The volume fraction of silica particles was 19%. The cumulative wear volume and wear rate of these materials on counterpart roughness were determined experimentally. The major failure mechanisms were lapping layers, deformation of matrix, ploughing, debonding of particles, fracture of particles and microcracking by scanning electric microscopy photograph of the tested surface. The cumulative wear volume showed a tendency to increase with increase of sliding distance. The wear rate of these composites tested indicated low value as increasing the sliding distance.

• 소성∙가공
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• 제13권8호
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• pp.716-722
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• 2004

Effects of sliding speed, applied load, and thickness of PMMA (Poly Methyl Methacrylate) coating layers on their dry sliding frictional and wear behavior were investigated. Sliding wear tests were carried out using a pin-on-disk wear tester. The PMMA layer was coated on Si wafer by a spin coating process with two different thicknesses, $1.5\mu\textrm{m}$ and $0.8\mu\textrm{m}$. AISI 52100 bearing steel balls were used as a counterpart of the PMMA coating during the wear. Normal applied load and sliding speed were varied. Wear mechanisms of the coatings were investigated by examining worn surfaces using an SEM. Friction coefficient of the coatings decreased with the increase of the applied load. Both adhesion and deformation of the coating determined the coefficient. The thicker PMMA layer with the thickness of $1.5mutextrm{m}$ showed lower friction coefficient than the thinner layer under most test conditions. Effects of sliding speed and applied load on the frictional behavior were varied depending on the thickness of the coating layer.

• Tribology and Lubricants
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• 제31권6호
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• pp.287-293
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• 2015

Laser surface texturing (LST), a surface engineering modification, has been considered as one of the new processes used to improve tribological characteristics of materials by creating artificially patterned microstructure on the contact surface of mechanical components. In LST technology, the laser is optimized to obtain or manufacture the dimples with maximum precision. The micro-dimples reduce the coefficients of friction and also improve the wear resistance of materials. This study investigates the effect of dimple density is investigated. For this purpose, a ball-on-disc type tester is used with AISI 52100 bearing steel as the test material. Discs are textured with a 5% and 10% dimple density. Experimental work is performed with normal loads of 5 N, 10 N, and 15 N under a fixed speed of 150 rpm at room temperature. The effect of the textured surface is compared to that of the untextured one. Experimental results show that the textured surface yields lower friction coefficients compared to those of untextured surfaces. Specifically, the 10% dimple density textured surface shows better friction reduction behavior than the 5% dimple density textured sample, and has an 18% improvement in friction reduction compared with the untextured samples. Microscopic observation using a scanning electron microscope (SEM) shows that the major friction mechanisms of the AISI 52100 bearing steel are adhesion, plastic deformation, and ploughing.

• Animal Bioscience
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• 제35권7호
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• pp.949-954
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• 2022

Objective: The present study is aimed at phenotypic characterization and mitochondrial d-loop analysis of indigenous "Diara" buffalo population, which are mostly confined to the villages on the South and North Gangetic marshy plains in the Bihar state of India. These buffaloes are well adapted and are best suited for ploughing and puddling the wet fields meant for paddy cultivation. Methods: Biometric data on 172 buffaloes were collected using a standard flexible tape measure. Animals are medium in size; the typical morphometric features are long head with a broad forehead and moderately long and erect ears. Genomic DNA was isolated from unrelated animals. The mtDNA d-loop 358-bp sequence data was generated and compared with 338 sequences belonging to riverine and swamp buffaloes. Results: Based on the mitochondrial d-loop analysis the Diara buffaloes were grouped along with the haplotypes reported for riverine buffalo. Sequence analysis revealed the presence of 7 mitochondrial D loop haplotypes with haplotype diversity of 0.9643. Five of the haplotypes were shared with established swamp breeds and with Buffalo population of Orissa in India. Conclusion: Morphometric analyses clearly shows distinguishing features like long and broad forehead which may be useful in identification. The germplasm of Diara buffalo is much adapted to the marshy banks of river Ganga and its tributaries. It constitutes a valuable genetic resource which needs to be conserved on priority basis.

• Advances in materials Research
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• 제11권3호
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• pp.237-250
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• 2022

The cone bolts with expanded front ends supply improved anchoring performances and increase energy absorbing capacities due to ploughing in the grouted drills. Within this study, use of a novel energy absorber for the cone bolt heads were investigated to assess its design in terms of supplying high support performances. Additionally, different grout material designs were tested to investigate whether the energy absorption capacities of the rock bolts can be improved using a silicone based thermoset polymer (STP) additive. To determine load bearing and energy absorption capacities, a series of deformation controlled pull-out tests were carried out by using bolt samples grouted in rock blocks. According to the results obtained from this study, maximum load bearing capacities of cone bolts are similar and mostly depend on the steel material strength, whereas the energy absorption capacity was determined to significantly vary in accordance with the displacement limits of the shanks. As a result of using STP additive and new polyamide absorber rings, displacement limits without the steel failure increase. The STP additive was found to improve the energy absorption capacities of grouted cone bolts. The absorber rings designed within this study were also assessed to be highly effective and able to double up the energy absorption capacities of the cone bolts.

• 한국토양비료학회지
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• 제17권3호
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• pp.207-211
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• 1984

1976년(年)부터 1979년(年)까지 군증산왕(郡增産王) 이상(以上)의 쌀 다수확(多收穫) 수상(受賞) 농가포장(農家圃場)을 무작위(無作爲)로 102개소(個所) 선정(選定)하여 비배관리(肥培管理)와 토양특성(土壤特性)을 조사(調査) 분석(分析)하고 수량(收量)과의 상관(相關)을 구(求)하였다. 다수확답(多收穫畓)에서는 토양개량제(土壤改良劑)의 시용량(施用量)이 일반답(一般畓)보다 많았고 고위수량답(高位收量畓)일 수록 간단관수(間斷灌水), 심경(深耕) 등(等) 요인별(要因別) 토양개량(土壤改良) 실시비율(實施比率)이 높아졌다. 다수확답(多收穫畓)은 토양유형(土壤類型), 적성등급(適性等級), 배수등급별(排水等級別) 구분(區分)에 따라 수량(收量)의 차이(差異)가 거의 없었다. 다수확답(多收穫畓)의 토성(土性)은 70% 이상(以上)이 양토(壤土) 내지 미사질양토(微砂質壤土)였으나 식토(埴土) 또는 사토(砂土)에도 분포(分布)되어 있었다. 작토층(作土層)의 이화학적(理化學的) 특성(特性)은 일반답(一般畓)보다 훨씬 양호(良好)한 수준(水準)이었고, 토양(土壤)의 이화학적(理化學的) 요인(要因)과 수량(收量)과의 상관(相關)을 보면 토양유형(土壤類型)에서 수량(收量)과 작토심(作土深) 및 보비능(保肥能) 간(間)에는 정(正)의 상관(相關)이 있었지만 다른 성분(成分)들은 토양유형별(土壤類型別)로 경향(傾向)이 다르게 나타났다.