• Korean Journal of Veterinary Research
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• v.21 no.2
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• pp.151-159
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• 1981

An investigation on various causes of milking disturbances resulting from injuries and abnormalities of mammary system were made in 2,179 Holstein cows. To perform this investigation, 69 dairy farms of the suburban area of Seoul city, Gyeonggi-do and Chungnam provinces were andomly selected and subjected. Diagnosis was made by means of inspection and palpation of teat, insertion of teat canula, checking milk machines, anamneses and farm records. This investigation was, actively done from March 1977 to February 1979, The results obtained were summerized as follows; 1. It was found that 446 cows, accounting for 20.48% of 2,179 cows inspected, had supernumerary teats. Among them 53.59% had one, 43.72% had two, 2.47% had three, and 0.22% had four supernumerary teats, respectively. 2. Dry off quarters were found in 158 quarters which turned out to be 1.8% of 8,716 quarters inspected. Among dry off quarters, 62.02% seemed to be caused by mastitis, 30.37% by acquired teat obstructions, and 7.59% by congenital blind teats and glands respectively. 3. Teat sphincter stenosis was found in 154 teats of 50 cows, which represents 1.76% of 8,716 teats and 2.29% of 2,179 cows inspected, respectively. Among 154 teats with teat sphincter stenosis, 138 teats (85.7%) of 33 cows were found to be congenital and revealed highest incidence. 4. Loose sphincter was found in 78 teats of 36 cows, which figure 0.89% of 8,7l6 teats and 1.69% of 2,179 cows inspected, respectively. Among 78 teats with loose sphincter, 52 teats (66.66%) of 13 cows were found to be congenital and revealed highest incidence. 5. Injured teat tip caused by over milking of milk machine, was found in 229 teats of 156 cows, which figure 2.63% of 8,716 teats and 7.15% of 2,179 cows observed, respectively. 6. Other miscellaneous injuries and congenital abnormalities of teats and udders were diagnosed as follows: The teat laceration was found in 34 teats (0.39% of 8,716 teats), fissure of teat skin in 24 teats (0.28% of 8,716 teats), stricture of teat cistern in 21 teats (0.24% of 8,716 teats), teat fistula in 12 teats (0.14% of 8,716 teats), papillomas on testes in 8 teats (0.09% of 8,716 teats). Knothole orifice in 7 teats (0.08% of 8,716 teats), subcutaneous abscess of udder in 5 quarters (0.05% of 8,716 teats), membraneous obstruction of teat cistern in 4 teats (0.05% of 8,716 teats), and congenital short teat in 8 teats (0.09% of 8,716 teats), respectively.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.33-41
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• 2020

The landing gear of an aircraft is a device that absorbs and dissipates shock energy transmitted from the ground to the fuselage. Among the landing gears, the semi-active MR damper landing gear is supposed to show high-shock absorption efficiency under various landing conditions and secure the stability when out of control. In the case of the MR damper landing gear using an annular channel rather than orifice, Amesim, a commercial multi-physics program, is considered as more useful than the conventional two-degree-of-freedom model because the damping force generated by the pressure drop through the flow annular path can cause cavitation in the low-pressure chamber of the MR damper with a specific internal structure. In this paper, the main dynamic characteristics of the MR damper landing gear with an annular type flow path structure has been analyzed under the condition of cavitation. Based on the analysis results using Amesim, a design guideline for the MR damper flow path that prevents cavitation has been proposed based on the modification of the arrangement of internal components of the damper. The guideline was verified through a drop simulation.

• Journal of Periodontal and Implant Science
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• v.29 no.1
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• pp.51-63
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• 1999

Exposure of the root surface due to gingival recession after periodontal surgery, elicit pain response when exposed to mechanical, heat, chemical or osmotic irritation. Especially patients treated with periodontal surgery, show high frequency. There have been reports that the 1 out of 7 patients complains of dentinal hypersensitivity. There have been many studies on the clinical effects of various materials on the treatment of dentinal hypersensitivity. The purposes of this study were to evaluate the effect of sodium chloride and potassium oxalate and to observe the relationship between the dentinal hypersensitivity and surface characteristics such as dentinal tubule size and number. This study included 20 teeth which were scheduled for extraction and had no pulpal disease. These teeth were divided into Root planing group, EDTA group, NaCl group and Oxalate group. Dentinal hypersensitivity is measured by tactile, pressured air and cold water using NRS (Numerical Rating Scales). Teeth were extracted under local anesthesia and each specimen was sectioned to a size about 3 X 5 mm and was examined under the scanning electron microscope (X2,000) The results were as follows, 1. The EDTA group exhibited significantly increased dentinal hypersensitivity comparing with the other groups. 2. The NaCl and Oxalate groups showed significantly reduced dentinal hypersensitivity comparing with the EDTA group. 3. As a method for dentinal hypersensitivity measurement, it was presumed thet tactile sensitivity test was not sensitive method but air blast test and cold water test were adequate method. 4. In a SEM study, the root planing group exhibited amorphous smear layer and showed no dentinal tubule orifice, but the EDTA group showed the large number of dentinal tubules. On the other hand, the NaCl and Oxalate groups did not show exposed dentinal tubules. The NaCl group showed more rough root surface than the EDTA group, and the Oxalate group showed many participates to be presumed as calcium oxalate particle. As the results from this study, root planing couldn't expose the dentinal tubule and NaCl and potassium oxalate occluded exposed dentinal tubule effectively. Dentinal hypersensitivity has close relationship with the exposure of dentinal tubules, especially with it's size and number.

• Journal of Biomedical Engineering Research
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• v.22 no.5
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• pp.403-412
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• 2001

The Present study analyzed the pressure-flow characteristics of a Korean shunt valve. Changes in the characteristic currie depending on the design parameters were also investigated. The Korean shunt valve used in the present study was constant pressure type and our analyses were validated through experiments. We applied fluid-structure interaction to solve the flow dynamic Problem because the small diaphragm in the valve was made from flexible silicone elastomers. Considering the material nonlinearity of the hyper-elastic material. the Mooney-Rivlin approximation was employed. The results of the numerical analyses were close to the experimental results The major Pressure drop was observed to happen in the small diaphragm. The slope of the pressure-flow characteristic curve was computed to be 0.37mm$H_2O$.hr/cc, which was similar to the average value of commercial shunt valves. 0.40mm$H_2O$.hr/cc. Therefore. our valves analyzed in the Present study showed a Proper Pressure control characteristics of the constant pressure type shunt valves. The opening pressure could be controlled by adjusting the amount of predeflection of the valve diaphragm. In order to obtain opening pressures of 25mm$H_2O$ and 80mm$H_2O$, respectively, and the required predeflection was found to be 10.2$\mu$m and 35.3$\mu$m. The flow orifice size was found to be within 10$\mu$m during valve operation Therefore, Precision design and manufacturing techniques are necessary for successful operations of the shunt valve. The study indicated the amount of predeflection as well as the magnitude of corner rounding of the diaphragm edge are important design parameters to influence the slope of the pressure-flow characteristic curve.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.416-426
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• 1999

The objective of this study is to confirm the effect of dentine bonding primer application on penetration of sealant. Extracted permanent molars were used to compare penetration success rate of control group (sealant application only) and experimental groups (sealant application after applying the primers of $Scotchbond^{TM}$ Multi-Purpose system and $All-Bond^{(R)}$ 2 system). The following results were obtained: 1. The experimental groups using the primers showed increased sealant penetration success rate to the base of fissure when compared to control group but there was no statistically significant differences(p>0.05). 2. The depth, width and 'depth/width' value of fissure had statistically significant effect on sealant penetration success rate(p<0.05). 3. The penetration success rate decreased about 0.9 times as the depth of fissure increased every $25{\mu}m$, and increased about 1.1 times as the width of the fissure orifice increased every $25{\mu}m$ and decreased about 0.6 times as the 'depth/width' value increased every 1. From the above results, it can be concluded that assure morphology had a great effect on sealant penetration and for better penetration, use of dentine bonding primer can be helpful but it needs more study in clinical bases.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.1
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• pp.114-118
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• 2009

Sialolithiasis is the formation of calcific concretions within the ductal system of major or minor salivary glands. The submandibular gland is most involved because of its high viscosity of the saliva and the long, curved duct. It may occur at any age but, it is most common in middle-aged adults and rare in childhood. Clinical symptoms in sialolithiasis are variable but, swelling is the most common, followed by the pain. Clinical examination and radiographic examination(panoramic and mandibular occlusal radiographs, sialography, intraoral-, extraoral- ultrasound, CT scan, MRI and sialoendoscopy) can help to confirm a diagnosis and localize a stone. The treatment is surgical intervention, either removal of the sialolith or sialoadenectomy. However, non-invasive techniques including shock-wave lithotripsy, $CO_2$ laser and endoscopic treatment used in selected cases. A 5-Year-old girl referred from private practice for evaluation of a yellowish mass on the floor of the mouth. She complained that it had became three times bigger than four months ago when it was found for the first time and she had some pain on submandibular gland area occasionally. On physical examination, a firm and yellowish mass could be seen at the orifice of the submandibular duct. Diagnosis is the submandibular sialolithiasis in the anterior Wharton`s duct. Under local anesthesia, stone was removed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.6
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• pp.343-351
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• 2014

The reflection and transmission coefficients of waves due to perforated wall are mainly determined by both the porosity and wall thickness of the perforated wall and the period and nonlinearity of incident waves. Among them the wall thickness is very important because it affects the head loss coefficient and the inertia length of the wall. However, by employing the head loss coefficient derived for sharp crested orifice, the previous researches have neglected, or incorrectly considered the effect of wall thickness on the head loss coefficient. Even though it is considered, the effect of the inertia length is neglected in some empirical formulae. Thus, the effect of wall thickness on the reflection and transmission coefficients of waves is not properly considered. In this study comprehensive experiments are conducted for the perforated walls with various thicknesses, and the results are compared with those predicted by the empirical formulae. As a result it is found that the existing formulae can not properly consider the effect of wall thickness, and it is confirmed that a new formula which can correctly consider the effect of wall thickness on the head loss coefficient is necessary.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.4
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• pp.299-304
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• 2013

The HAN which is an ionic liquid is a non-toxic monopropellant with high storability, and its specific impulse can be increased by blending methanol, thereby it can substitute the hydrazine. The HAN was synthesized by acid-base reaction of hydroxylamine and nitric acid, and the blending ratio of HAN and methanol is 8.2:1. The iridium catalyst was used to decompose the HAN, and 1 N class thruster with shower head type injector having one orifice was used to evaluate the HAN/Methanol propellant. The thermal stability of distributor was increased by using ceramic material to endure the high temperature of product gas. The preheating temperature of catalyst should be $400^{\circ}C$ at least for the complete decomposition. The feeding pressure should be increased to increase the $C^*$ efficiency, thereby the decomposition performance was decreased upstream catalyst, and the performance of thruster was decreased. The fine metal mesh was inserted after the injector to improve the atomization of propellant, thereby it can settle the performance decrease problem. The phenomenon of performance decrease was remarkably improved owing to the insertion of fine metal mesh.

• Journal of Chest Surgery
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• v.8 no.2
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• pp.109-118
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• 1975

This is a report on four cases of the lobar emphysema due to proximal bronchial obstruction in the Department of Thoracic Surgery, Hanyang University Hospital, during the period of three and half years from 1972 to 1975. First case, a two years old male child was referred to our Department with the lobar emphysema of the lower lobe of the right lung with pneumonia. This emphysema was developed after aspiration of a piece of peanut. Bronchoscopy revealed that the bronchus of the right lower lobe was obstructed with the foreign body, however removal of the peanut through bronchoscope was not attempted because of corruption and softening of the peanut. The removal of the peanut by bronchotomy was performed after subsiding of acute phase of pulmonary infection. Postoperative course was uneventful and the emphysema was disappeared. Second case, a twenty months old female baby was referred to our Department with lobar emphysema of the lower lobe of the left lung. The emphysema was suddenly developed with coughing and dyspneic symptoms and the diagnosis was made roentgenologically. She gave a history of reccurrent infections of the respiratory tract after birth. Bronchoscopy showed an obstruction of the left main bronchus with the growing of fibrinous tissue on the bronchial mucosa. The protruded tissue in the left main bronchus taken out about O.8ml with biopsy forceps for histological examination. After this procedure, the emphysema of the left lung was disappeared. Histological finding was reported to be a chronic inflammatory granulation tissue. Third case, a two and half years old male child was referred to our Department with roentgenological lobar emphysema. Two weeks prior to admission he had an episode of sudden onset of coughing attack with dyspnea. Bronchoscopy revealed that the bronchus of the left lower lobe was obstructed with a mass which was strongly suspected of a neoplastic tissue. At operation, there was found a perforation of enlarged tuberculous lymph node in the bronchus of the left lower lobe and protrusion of granulation tissue into the bronchus. Ruptured orifice on themembranous wall of the left lower lobe bronchus was closed with interrupted suture after the" removal of a perforated tuberculous lymph node. Postoperative course was uneventful and antituberculous chemotherapy was given. Fourth case, a 47 years old man was admitted to our Department with the complaint of severe dyspnea of few months duration. Twenty years ago, he had a history of lung tuberculosis and was treated for many years. X-ray examination including tomography and bronchography revealed that the upper lobe of the right lung was destroyed with cavities, the lower lobe was completely shrunk, and the right middle lobe was strongly overdistended with narrowing bronchial trees. Differential bronchospirometry and lung scanning confirmed that the respiratory function of the affected lung was impaired almost totally. The value of the right lung was calculated on 6% of oxygen uptake, 1% of Minute volume, and 32% of vital capacity. The right pneumonectomy was performed under the careful consideration of anesthetic and surgical procedures. Postoperative course was uneventful and the respiratory function was improved nearly to the normal level.evel.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.183-189
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• 1997

This study was performed to Investigate size of droplet sprinkled from mini-sprinkler. Twelve different kinds of the sprinkler having various structures and sizes of nozzle orifices were selected and tested. Diameters of the droplet reached at several distances from a sprinkler were measured by a machine vision system and the volume median diameters (VMM) were determined statistically. The size of droplet was not affected much by the size of nozzle orifice of a sprinkler but was rather more affected by structure of the sprinkler, especially by the shape of spreader of the sprinkler. Experiment of varying pressure of sprinkling water validated that the size of droplet was inversely proportional to water pressure powered by 1/3. Hence the size of droplet at any water pressure could be easily estimated from experimental data. The size of droplet increased as travel distance of the droplet increases in a relationship of and order function. The size of droplet of the tested sprinkler were in the ranges of 100-300fm within 1m of droplet travel distance, 230~470${\mu}{\textrm}{m}$ within 1~2m of droplet travel distance and 300~770${\mu}{\textrm}{m}$ within 2~3m of droplet travel distance.