• Korean Journal of Agricultural Science
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• v.41 no.1
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• pp.35-40
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• 2014

This study was carried out to evaluate the Salmonella cross contamination at retail chicken meat outlets in Kandy, Sri Lanka and to identify the risk factors for Salmonella contamination at retail chicken meat outlets. Fifteen retail chicken meat outlets in Kandy area were randomly selected. Pre-tested questionnaires were used to collect data for identifying risk factors of Salmonella cross contamination at retail outlets and swab samples from meat contact surfaces/utensils were obtained. Out of 57 swab samples collected from meat contact surfaces/utensils, the overall prevalence of Salmonella cross contamination was 21%. Weighing scale (33%), meat containing trays/buckets (27%) and cutting board (25%) showed the highest percentage of Salmonella prevalence whereas knife and showcase showed relatively low percentages, 14% and 9%, respectively. Retail chicken outlets with slaughtering facilities had a significantly higher prevalence of Salmonella cross contamination than those without slaughtering facilities. This higher rate of Salmonella cross contamination at retail chicken meat outlets could be attributed to lack of proper cold chains and minimal facilities, and poor level of hygiene in those outlets.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1014-1020
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• 2003

We have developed the ultrasonic polishing system to get super finishing that consist of machine part that can rotate and travel the main shaft with power 1.5kW, ultrasonic generator with frequency 20kHz. By using this system we were investigated the characteristics of ultrasonic polishing and deduced the major facters which affect the surface roughness by the experimental plans for three different materials such as ceramic, glass, and wafer, and so could be obtained following results. We could be obtained the excellent surface for hard-to-difficult cutting materials. The rotating speed could be found to be major factor influencing the surface roughness. In the case of ceramic and wafer, we were able to obtain good surface roughness when the feed rate and ultrasonic output is higher. In the case of glass, the surface roughness becames worse when ultrasonic output is higher because of increasing of load affacting on the particles in slurry.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.60-67
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• 2012

In the study, the effect grinding condition on the workpiece arithmetical average roughness(Ra) to 10 steps leading to cutting each section with the spindle rotational speed 8000rpm and feed rate 150mm/min of grinding in GC(green silicon carbide) grinding processing after heat treatment and non heat treatment of SCM415 material. Also the following conclusions were obtained analysis of stress distribution displacement and finite elements method(FEM) on assemble parts with 3+2 axis simultaneous control through grinding and gave a load 11kg on ATC arm both sides gave a load of 11kg. For the centerline average roughness(Ra) in the heat and non-heat treatment work pieces, which were appeared the most favorable in the fifth section were $0.511{\mu}m$ and $0.514{\mu}m$, that were shown in the near the straight line section was the smallest deformation of curve. In addition, the bad surface roughness appeared on the path is too long by changing angle, the more inclined depth of cut, because the chip discharging is not smoothly.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.3
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• pp.125-130
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• 2017

In this study, the influence of various factors on surface roughness was investigated using the Taguchi experimental method through high-speed machining processing. Feed rate, pitch, tool diameter, and depth of cut are widely applied to high-speed machining conditions for mold production. Each of these factors was implemented and classified into three levels; then, after high speed machining, surface roughness was measured, the S/N ratio was analyzed, and the influence on the surface roughness of control factors was analyzed quantitatively by ANOVA. Using this information, a mathematical model for predicting surface roughness was derived from multiple regression analysis. This mathematical model enables the surface roughness value after high-speed machining to be predicted at the production stage, before machining, for a wide range of machining conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.113-116
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• 2003

To maximize the productivity in machining molds and dies, machine tools should operate at high speeds. During the high speed operation of moving frames or spindles, vibration problems are apt to occur if the machine tool structures are made of conventional steel materials with inferior damping characteristics. However, self-excited vibration or chatter is bound to occur during high speed machining when cutting speed exceeds the stability limit of machine tool. Chatter is undesirable because of its adverse effect on surface finish, machining accuracy, and tool lift. Furthermore, chatter is a major cause of reducing production rate because, if no remedy can be found, metal removal rates have to be lowered until vibration-free performances is obtained. Also, the resonant vibration of machine tools frequently occurs when operating frequency approaches one of their natural frequencies because machine tools have several natural frequencies due to their many continuous structural elements. However, these vibration problems are closely related to damping characteristics of machine tool structures. This paper presents the use of polymer concrete and sandwich structures to overcome vibration problems. The polymer concrete has high potential for machine tool bed due to its good damping characteristics with moderate stiffness. In this study, a polymer concrete bed combined with welded steel structure i.e., a hybrid structure was designed and manufactured for a high-speed gantry-type milling. Also. its dynamic characteristics were measured by modal tests.

• Journal of the Korea Safety Management & Science
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• v.16 no.3
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• pp.45-54
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• 2014

The average injury rate in sawmilling industry for the last 5 years is 4.99%, which means that more than 200 injuries have occurred in that industry every year. Because the first step in risk assessment is the hazard identification, it is very important to know how to define the hazard and nature of harm. We analyzed 643 accident records of three years(2010-2012) and carried out site survey for the same cases. As a result, the most common types of work at the time of injury in sawmilling industry were removing jammed wood 81(12.8%), wood carrying task 52(8.1%), wood cutting 49(7.6%), travelling table log band saw 41(6.4%), maintenance 37(5.8%) etc. In addition, there were statistically significant differences in some analysis factors such as injured body parts, employment size, and handling material among different working places. Therefore, it is concluded that differentiated prevention efforts are necessary in each workplace.

• Journal of the Korean Society for Heat Treatment
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• v.5 no.4
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• pp.201-208
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• 1992

An experimental study of the constitutive response of precipitation-strengthened Al-0.55wt% Zr alloy, which consists of an Al matrix precipitation-strengthened by coherent particles, ${\beta}^{\prime}(Al_3Zr)$ with $L1_2$ structure has been performed. The deformation response of the materials has been examined by stress relaxation test at 573K, 623K and 673K. It was found that there exist the threshold stress during stress relaxation and threshold stress results from the presense of ${\beta}^{\prime}(Al_3Zr)$ particles. The ratio of threshold stress and Orowan stress decreased gradually with increasing temperature. The resistance to climb-pass of particles was independent of particles size for a fixed volume fraction although the threshold for bowing and particles cutting are sensitive to the particles dimensions. The smaller particles cutted by dislocations. This behavior of dislocations in this alloy was explained in terms of the small value antiphase boundary energy. The dislocation networks wrere more extensive in spesimens subjected to stress relaxation and there were numerous areas that have a high denstiy of jogged dislocation. This experiment results indicate that the rate controlling stress relaxation process is the climb of edge dislocation over particles.

• Explosives and Blasting
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• v.18 no.3
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• pp.89-97
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• 2000

최근 노후화 된 콘크리트 및 털 구조물에 대하여 환경 공해가 발생하지 않는 해체 기술의 필요성이 급증하고 있어서 이에 대한 연구가 활발히 이루어지고 있다. 그 결과 콘크리트 구조물을 일시에 해체하기 위하여 사용되고 있던 화약을 이용한 발파해체공법 및 군용 폭파 공법 등으로부터 응용되어 특수한 형태의 크기로 제작된 성형폭약을 철골구조물에 부착시킨 후 이를 폭발 시켜서 순간적으로 철골구조물의 철판(또는 빔이나 기타 부자재)을 절단 해체할 수 있게 되었다. 그 동안은 성형폭약의 폭발절단 효과에 영향을 주는 요소들인 대상 구조물의 재질 및 형상, 두께와 강도 특성, 성형폭약의 형상, 폭약의 종류, 장약량, Liner의 종류, Stand-off Distance, 성형폭약의 폭 및 너비, 기폭방법에 따른 영향과 폭발 절단시 발생되는 폭풍압에 의한 진동 및 소음의 영향 등에 대한 연구가 대부분이었다. 따라서 본 연구에서는 성형폭약의 주 구성요소인 화약과 금속성 Liner를 유연성이 탁월하고 조성 성분들의 혼합성과 성형성이 우수한 가소화제를 사용하여 제작된 성형폭약의 가소화 정도가 폭발절단력에 미치는 영향을 검토하였다. 이를 위하여 본 연구는 PETN 과 RDX 화약이 각각 25wt% 및 75wt%로 흔합된 화약원료를 85wt%로 하고 폴리이소부틸렌(P.I.B) 성분이 80 wt% 이상인 폴리부텐(P.B) 7wt% 와 부틸고무 4wt% 그리고 디에칠헥실세바케이트 4wt%로 구성된 가소화제를 사용하여 실험하였다.

• Journal of the Korean Ceramic Society
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• v.48 no.2
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• pp.152-159
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• 2011

The green and hard machining characteristics of dental ceramics are of great interest to dental industry. The green bodies of TZP/$Al_2O_3$ composites were prepared by the cold isostatic pressing, and machined on the CNC lathe using PCD (polycrystalline diamond) insert under various machining conditions. With increasing nose radius of PCD insert, surface roughness initially increased due to increased cutting resistance, but decreased by the onset of sliding fracture. The lowest surface roughness was obtained at spindle speed of 1,300 rpm and lowest feed rate. Hard bodies were prepared by pressureless sintering the machined green bodies at several temperatures. The grinding test for sintered hard body was conducted using electroplated diamond bur with different grit sizes. During grinding, grain pull out in the composite was occurred due to thermal expansion mismatch between the alumina and zirconia. The strength of the composite decreased with alumina contents, due to increased surface roughness and high monoclinic phase transformed during grinding process. The final polished samples represented high strength by the elimination of a phase transformation layer.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.714-719
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• 2011

The surface roughness depending on the machining method is very important because is produce a finished product through riveting, sealing, bonding, and special paint in order to curb the turbulence and air resistance which occur between the sheets. Aluminum alloy 2024 which is widely used for interior and exterior material of aircraft are tested. Jin-young JW-60C wire cutting machine was used in this experiment. In this paper, the experimental investigation has been performed to find out the influence of the surface roughness and surface shape characteristics on the wire-cut EDM of discharge energy in aluminium alloy 2024. The selected experimental parameters are peak current, no-load voltage, off time and feed rate. The experimental results give the guideline for selecting reasonable machining parameters. The high discharge energy on the idle time, almost no change in surface roughness can be seen.