• 한국분무공학회지
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• 제18권1호
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• pp.1-8
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• 2013

In this paper an experimental study is presented to investigate the dynamic behavior of impacting droplet onto a liquid film. The main parameters are the droplet velocity and the thickness of the liquid film. Photographic images are presented to show the formation of crown, central jet and disintegrating droplet from the central jet. The emphasis is on presenting the time evolution of crown diameter, crown height, central jet height and the size of disintegrating droplet from the central jet. The diameter and height of crown are higher for faster droplet and thinner liquid film. On the other hand, the height of central jet are higher for faster droplet and thicker liquid film. The size of disintegrating droplet from the central jet heavily depends on the droplet velocity; Larger droplet is produced with faster falling droplets.

• 한국레이저가공학회지
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• 제8권2호
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• pp.7-12
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• 2005

The material processing of UV nanosecond pulse laser cannot be avoided the material shape change and contamination caused by interaction of base material and laser beam. Nowadays, ultra short pulse laser shorter than nanosecond pulse duration is used to overcome this problem. The advantages of this laser are no heat transfer, no splashing material, no left material to the adjacent material. Because of these characteristics, it is so suitable for micro material processing. The processing of sapphire wafer was done by UV 355nm, green 532nm, IR 1064nm. X-Y motorized stage is installed to investigate the proper laser beam irradiation speed and cycles. Also, laser beam fluence and peak power are calculated.

• 한국식생활문화학회지
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• 제25권3호
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• pp.251-261
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• 2010

This paper examines the dining tendencies of Koreans toward meat dishes and their related factors, with 301 people residing in Korea as subjects. We questioned this population on their restaurant choices, eating habits, preferences and a dislike with respect to method of cooking. All age groups, with the exception of 50~60 year-olds, were found to consume meat dishes in specialized restaurants. The selection factor for restaurants varied, depending on the age group: affordable cost was the most important factor for whom under 20 year-old. Whereas 20-40 year-old people considered taste and ambience the most for choosing restaurant. The 50-60 year-old people found to seek for convenient restaurant. In terms of the most preferred parts of beef, 20-30 year-old people preferred tenderloin (42.3%) while 40-60 year-old people preferred sirloin (45.6% and 41.2% each). All the other age groups preferred ribs the most (It was also found that) men preferred the rib parts and women preferred tenderloin. With respect to pork, all age groups preferred pork belly, with the highest response rate in the under 20 age group. When consuming meat dishes, 91.0% of respondents pointed to roasting as the most frequent preparation method, the reason being good taste was deemed the highest number of responses. In a survey on preference for stewed meats, 74.8% of the sample pool was found to prefer stew dishes but 24.9% of respondents provided negative answers, the reason for dislike was found to be poor taste for women, and both a long preparation time and poor taste for men. In fact, regardless of marital status, a high number of responses were given for poor taste as the reason for disliking stew dishes. Based on the examined factors for inconveniences in preparing meat dishes, the most common inconvenience factor was the odor of meat left on clothes after the dining experience, followed by the smoke generated in roasting meat, and the safety risk involved with changing the grill. In terms of stir fry preparation, the negative thoughts were due to the splashing of food and spices while cooking, followed by the meat odor left on clothes after dining experience, and the sanitation level of the cooking containers. For deep frying the sanitation level of cooking containers was the biggest reason for dislike, followed by splashing of food when preparing. Lastly, it was indicated that the problem of steaming method was a difficulty of judging the portion, on the top of this, people found that the sanitation level of cooking container and a long preparation time were also the problem of this cooking method.

• 한국분무공학회지
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• 제11권2호
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• pp.89-97
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• 2006

An inviscid axisymmetric model capable of predicting droplet bouncing and the detailed pre-impact motion, influenced by the ambient pressure, has been developed using boundary element method (BEM). Because most droplet impact simulations of previous studies assumed that a droplet was already in contact with the impacting substrate at the simulation start, the previous simulations could not accurately describe the effect of the gas compressed between a failing droplet and the impacting substrate. To properly account for the surrounding gas effect, an effect is made to release a droplet from a certain height. High gas pressures are computationally observed in the region between the droplet and the impact surface at instances just prior to impact. The current simulation shows that the droplet retains its spherical shape when the surface tension energy is dominant over the dissipative energy. When increasing the Weber number, the droplet surface structure is highly deformed due to the appearance of the capillary waves and, consequently, a pyramidal surface structure is formed; this phenomenon was verified with our experiment. Parametric studies using our model include the pre-impact behavior which varies as a function of the Weber number and the surrounding gas pressure.

• 대한임상독성학회지
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• 제14권1호
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• pp.33-36
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• 2016

Purpose: This study was conducted to identify the characteristics associated with sulfuric acid injury in the emergency department. Methods: Data were collected retrospectively from January 2007 to December 2015 on all sulfuric acid injuries presenting to the emergency department in Gu-mi Soonchunhyung University Hospital. Patients injured by sulfuric acid were recorded over a nine year study period and collected data included demographics, injury mechanism, injured body part, hospital care and final diagnosis. Results: A total of 26 cases were identified. Most patients were male (88.5%) and the face was the most commonly injured body part. The most common mechanism of injury was splashing injury. A total of 16 (61.5%) patients were identified as having lesions worse than second degree burns. Conclusion: Sulfuric acid can cause severe and fatal skin burn. When working with sulfuric acid, acid proof protect clothing, goggles and glove should be worn. Furthermore, safety education and workplace environment improvement are necessary to reduce sulfuric acid injury.

• 한국가시화정보학회지
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• 제13권1호
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• pp.49-53
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• 2015

Recently, researches for droplet impact phenomena have been faced a new phase in the direction of studying the effect of complex external conditions (e.g. wettability, temperature, morphology, electric field, etc.) for depth understanding and precise controlling in various applications. Hence, here we investigated the electrified droplet impact phenomena, because there were few quantitative researches for electrified droplet impact when we considering many real applications such as electrospray, electrohydrodynamic (EHD) jet printing. To observe interaction effect of surface charge between substrate and droplet simultaneously, micro-droplets with various Reynolds number (Re) and Weber number (We) were dripped on super-hydrophobic surface with existence and nonexistence of electrical surface charge. It shows three kinds of impact behaviors, fully bouncing, partial bouncing, and splashing with different We. Also, charged droplet bounced higher on electrically charged surface than on non-charged surface. Additionally, transition regions of three impact behaviors were classified quantitatively with water hammer pressure value, which means instant pressure inside droplet at the impact moment.

• 동력기계공학회지
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• 제1권1호
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• pp.70-79
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• 1997

Ni-base self-fluxing alloy powder particles were flame sprayed onto the SS400 mild steel substrate surface. The effects of both substrate temperature and spraying distance on the splat behavior of sprayed particles were examined. The results obtained are summarized as follows: 1) In the splat behavior of Ni-base self-fulxing alloy particles sprayed onto the SS400 mild steel substrate, splashing was observed under the room temperature condition. On the contrary, it showed circular plate pattern in the substrate temperature range over 373K. 2) It was cleared that there was close relationship between mechanical properties of coating layer and splat behavior of sprayed particles. 3) From the experimental results, optimum spraying conditions showed excellent mechanical properties in the case of Ni-base self fluxing alloy sprayed onto the SS400 mild substrate were 473K of substrate temperature and 250mm of spraying distance.

• Design & Manufacturing
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• 제14권3호
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• pp.57-62
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• 2020

In the drug delivery system industry, the technology with even split injection becomes important for maximizing efficiency and minimizing the side effects. In conventional drug delivery system, infection can occur due to pain and splashing. Also, various applications are impossible due to disposable use, and it is the reason to avoid to use this system because of the complexity of the driving method. Therefore, in this study, a painless drug delivery device is developed for non-pain with electrical insulation breakdown method. Finite elements analysis was used to evaluate the ejection characteristics of drugs according to the shape of the micro ejection nozzle. The effect of the number of holes in the micro nozzle, the length of the nozzle and the inner shape of the nozzle on the drug discharge characteristics were analyzed.

• 설비공학논문집
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• 제8권3호
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• pp.361-374
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• 1996

In general, a cooling tower has two major noise sources, one is the fan and the other is the falling water. The fan noise is produced by passage of its blades through the air and radiates from the fan stack. Noises from the falling water are caused by splashing and dropping of water cascading over the internal filler of the cooling tower and into the basin and radiate from the louvered face. In this paper, the noise measurements and its frequency analysis are carried out for the locations facing the louvered side and near the fan stack referring the related code and standards in order to study the noise characteristics of the induced-draft cooling tower, especially for the buildings. As a result, it is found that for every doubling of distance from the noise source the noise level decreases by 2~4dBA in the near field with reflect surfaces and decreases by about 6dBA also in the far field without reflect surfaces. As a supplement to the noise measurements, a computer program with simple algorithm is developed in order to estimate the noise level at a distance from the cooling tower, so that the user could apply and modify it for the particular boundary conditions easily.

• 대한조선학회논문집
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• 제42권6호
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• pp.559-565
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• 2005

As the wave impinges on and overtops the structure, a large highly aerated region is created in front of the structure and water splashs on top of the structure. The broken wave in front of the structure and associated green water on top of the structure are highly aerated containing not only a large number of bubbles but also very large sizes of bubbles. In this paper, the velocity field of the highly aerated region and the splashing water on the top is measured using a modified PIV method incorporating the traditional PIV method with the shadowgraphy technigue by correlating the ' texture ' of the bubble images. The velocity fields of a plunging wave impacting on a structure in a two-dimensional wave flume is measured. It is found that the maximum fluid particle velocity in flout of the structure during the impinging process is about 1.5 times the phase speed of the wave, while the maximum horizontal velocity above the top is less than the phase speed, It is also found that the dam breaking solution does not work well in predicting the green water velocity.