• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.2
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• pp.121-143
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• 2010

To investigate the effect of implant types and bone resorption on the fracture characteristics. 4 types of Osstem$^{(R)}$Implant were chosen and classified into external parallel, internal parallel, external taper, internal taper groups. Finite elements analysis was conducted with ANSYS Multi Physics software. Fatigue fracture test was performed by connecting the mold to the dynamic load fatigue testing machine with maximum load of 600N and minimum load of 60N. The entire fatigue test was performed with frequency of 14Hz and fractured specimens were observed with Hitachi S-3000 H scanning electron microscope. The results were as follows: 1. In the fatigue test of 2 mm exposed implants group, Tapered type and external connected type had higher fatigue life. 2. In the fatigue test of 4 mm exposed implants group, Parallel type and external connected types had higher fatigue life. 3. The fracture patterns of all 4 mm exposed implant system appeared transversely near the dead space of the fixture. With a exposing level of 2 mm, all internally connected implant systems were fractured transversely at the platform of fixture facing the abutment. but externally connected ones were fractured at the fillet of abutment body and hexa of fixture or near the dead space of the fixture. 4. Many fatigue striations were observed near the crack initiation and propagation sites. The cleavage with facet or dimple fractures appeared at the final fracture sites. 5. Effective stress of buccal site with compressive stress is higher than that of lingual site with tensile stress, and effective stress acting on the fixture is higher than that of the abutment screw. Also, maximum effective stress acting on the parallel type fixtures is higher. It is careful to use the internal type implant system in posterior area.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.73-82
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• 2009

Injectable calcium phosphate cement (CPC) has been used as bone substitute successfully due to good biocompatibility and osteoconductivity. One of the important mechanical characteristics of CPC is flowablility, which can be evaluated by measuring rheological parameters. However, there have been few studies that measured rheological properties of CPC. The purpose of this study was to evaluate the effects of temperature and concentrations of 2 kinds of setting solutions, hydroxyprophyl methylcellulose (HPMC) and polyacrylic acid (PAA), on rheological properties of CPC. The CPC used was dicalcium phosphate dihydrate (DCPD). Rheological properties of CPC paste were measured using rheometer. The effect of concentrations of each solution (2% and 1% HPMC and 35% and 17.5% PAA) was evaluated. The effect of temperature ($25^{\circ}C$ and $37^{\circ}C$) on the rheological properties of CPC was also investigated. The statistical analysis was carried out with Mann-whitney test with Bonferronis collection. CPC with both setting solutions showed shear thinning behavior. Higher concentrations of setting solution (2% HPMC and 35% PAA) produced significantly higher viscosity than lower concentrations of setting solution (1% HPMC and 17.5% PAA). CPC with HPMC showed significantly higher viscosity at $37^{\circ}C$ that at $25^{\circ}C$. CPC with PAA showed lower viscosity at $37^{\circ}C$ than at $25^{\circ}C$, although the difference was not statistically significant. The results showed that CPC with HPMC or PAA solutions are pseudoplastic and the concentrations of setting solutions and temperature may have an effect on the rheological properties of CPC paste. These results showed that the flowability of injectable CPC could be improved by use of increasing frequency of oscillation. In clinical practice, the use of ultrasonic vibration would be helpful in application of injectable CPC. CPC with HPMC could be more easily applicated at $25^{\circ}C$ than $37^{\circ}C$. The use of lower concentrations of HPMC and PAA solution would be beneficial in terms of flowability.

• The Korean Journal of Air & Space Law and Policy
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• v.33 no.1
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• pp.227-260
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• 2018

Recently, as the use of drones increases, the risk of drone accidents and third-party property damage is also increasing. In Korea, due to the recent increase in drone use, accidents have been frequently reported in the media. The number of reports from citizens, and military and police calls regarding illegal or inappropriate drone use has also been increasing. Drone operators may be responsible for paying damages to third parties due to drone accidents, and are liable for paying settlements due to illegal video recording. Therefore, it is necessary to study the idea of providing drone insurance, which can mitigate the liability and risk caused by drone accidents. In the US, comprehensive housing insurance covers damages caused by recreational drones around the property. In the UK, when a drone accident occurs, the drone owner or operator bears strict liability. Also, in the UK, drone insurance joining obligation depends on the weight of the drones and their intended use. In Germany, in the event of personal or material damage, drone owner bears strict liability as long as their drone is registered as an aircraft. Germany also requires by law that all drone owners carry liability insurance. In Korea, insurance is required only for "ultra-light aircraft use businesses, airplane rental companies and leisure sports businesses," where the aircraft is "paid for according to the demand of others." Therefore, it can be difficult to file claims for third party damages caused by unmanned aerial vehicles in personal use. Foreign insurance companies are selling drone insurance that covers a variety of damages that can occur during drone accidents. Some insurance companies in Korea also have developed and sell drone insurance. However, the premiums are very high. In addition, drone insurance that addresses specific problems related to drone accidents is also lacking. In order for drone insurance to be viable, it is first necessary to reduce the insurance premiums or rates. In order to trim the excess cost of drone insurance premiums, drone flight data should be accessible to the insurance company, possibly provided by the drone pilot project. Finally, in order to facilitate claims by third parties, it is necessary to study how to establish specific policy language that addresses drone weight, location, and flight frequency.

• Tuberculosis and Respiratory Diseases
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• v.48 no.4
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• pp.487-499
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• 2000

Background : Acute lung injury is an hypoxic respiratory failure resulting from damage to the alveolar-capillary membrane, which can be developed by a variety of systemic inflammatory diseases. In this study the therapeutic effects of intra-tracheal pulmonary surfactant instillation was evaluated in the intratracheal endotoxin induced acute lung injury model of a rat. Methods : Twenty Sprague-Dawley rats were divided into 4 groups, and normal saline (2 ml/kg, for group 1) or LPS (5 mg/kg, for group 2, 3, and 4) was instilled into the trachea respectively. Either normal saline (2 ml/kg, for group 1 & 2, 30 min later) or bovine surfactant (15 mg/kg, 30 min later for group 3, 5 hr later for group 5) was instilled into the trachea. The therapeutic effect of intratracheal surfactant therapy was evaluated with one chamber body plethysmography (respiratory frequency, tidal volume and enhanced pause), ABGA, BAL fluid analysis (cell count with differential, protein concentration) and pathologic examination of the lung. Results : Intratracheal endotoxin instillation increased the respiration rate decreased the tidal volume and int creased the Penh in all group of rats. Intratracheal instillation of surfactant decreased Penh, increased arterial oxygen tension, decreased protein concentration of BAL fluid and decreased lung inflammation at both times of administration (30 minute and 5 hour after endotoxin instillation). Conclusion : Intratracheal instillation of surfactant can be a beneficial therapeutic modality as discovered in the acute lung injury model of rats induced by intratracheal LPS intillation. It deserves to be evaluated for treatment of human acute lung injury.

• Tuberculosis and Respiratory Diseases
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• v.46 no.6
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• pp.826-835
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• 1999

Background : The $\beta_2$ adrenergic receptor ($\beta_2$ AR) polymorphisms occurring at amino acid position 16 (Arg to Gly), 27 (Gln to Glu), 34 (Val to Met), and 164 (Thr to Ile) are known to be functionally relevant and also disease-modifying in subjects with asthma. However the contribution of these polymorphisms to the development of the asthmatic phenotype or other markers for allergic disease remains to be established. Methods : 109 patients with bronchial asthma and 42 healthy person were included. Serum total IgE, allergen specific IgE, and skin prick test were performed to all of the subjects. $\beta_2$ AR polymorphisms were checked by mutated allele specific amplification (MASA) method. Results : The results were as follows. The frequencies of $\beta_2$ AR polymorphisms in asthmatic patients and healthy person were not statistically different(p>0.05). There was no association between $\beta_2$ AR polymorphisms of amino acid position 16, 27, 34 and the existence of atopy among asthmatic patients(p>0.05). Between asthmatic patients with or without elevated IgE level and $\beta_2$ AR polymorphisms of amino acid position 16, 27, 34, there was no statistically significant association(p>0.05). Conclusion : There was no difference in frequency of the $\beta_2$ AR polymorphism between asthmatic patients and healthy person. In the bronchial asthma, association of $\beta_2$ AR polymorphism and atopy/serum total IgE was not found.

• Tuberculosis and Respiratory Diseases
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• v.48 no.3
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• pp.365-376
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• 2000

Background : Ever since Flexible Fiberoptic Bronchoscopy was introduced into clinical practice, it has played an important role in both diagnosis and therapy of respiratory diseases. Repeated bronchoscopic examinations is are not so uncommon. This study was designed prospectively to assess the clinical availability of the Repeated Flexible Bronchoscopy (RFB). Methods : Pre-established indications were as follows : 1) To confirm diagnosis or the cell type in proven malignancy 2) to diagnose or locate hemoptysis 3) to follow-up or confirm recurrence 4) to use in therapy. We performed RFB and analyzed the data in 156 patients during 28-month period. Results : The frequency of RFB was 23.0%. The indication for diagnosis or cell type of malignancy was 25 cases, of which 2 cases were confirmed by a third bronchoscopic examination and 3 cases by surgical procedures. Localization of the bleeding site was confirmed in 53.8%. RFB for small cell lung cancer yielded more information on residual or recurred lesion not apparent even with the CT scan in 30%. Previous cases of bronchostenosis due to endo-bronchial tuberculosis was shown to have worsened in 66.7%. Therapeutic manipulations were done in 126 cases, and bronchial suction was most common. Complications showed decreasing tendency with repeated examinations. Conclusion : The RFB for diagnosis or cell type of malignancy was useful in that comfirmation of diagnosis was possible in 85.7% of malignancy. More aggressive procedures should be employed including TBLB or TBNA. The RFB showed possible usefulness in the follow-up of patients with small cell lung cancer. For the patients with hemoptysis or endobronchial tuberculosis, the RFB did not the significance did not show significance because its results did not influence the diagnosis, therapy or clinical course.

• Tuberculosis and Respiratory Diseases
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• v.54 no.4
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• pp.367-377
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• 2003

Background : It is well known that only 10% of those infected with Mycobacterium tuberculosis actually develop clinical disease, indicating the existence of host genetic factors regulating disease expression. In this study, we investigated HLA-DRB1 and -DQB1 gene polymorphisms in Korean patients with pulmonary tuberculosis (PTB). Methods : HLA-DRB1 and -DQB1 gene polymorphisms were investigated in 67 PTB patients without previous treatment history, 38 drug-sensitive (DS) and 29 multidrug-resistant (MDR) cases, and 200 healthy controls. HLA-DRB1 typing was done using reverse SSO (sequence specific oligonucleotide) and PCR-SSCP (single strand conformational polymorphism) methods and DQB1 typing was done using PCR-RFLP (restriction fragment length polymorphism), PCR-SSCP and PCR-SSP (sequence specific primer) methods. Results : Among the PTB patients, MDR-TB cases showed frequencies of DRB1*0701 and *08032 increased by about two-fold compared to those of normal controls, and likewise for their associated DQB1 alleles, DQB1*0202 and *0601 (15.5% vs. 34.5%, p=0.01). The frequency of HLA-DQB1*0609 was significantly increased in PTB patients (4.0% vs. 14.9%, p=0.004), showing similar increases in both DS and MDR cases. There was also an association of HLA alleles with the clinical severity of the disease according to the extent of lung lesion. Significantly increased frequencies of DRB1*08032 (4.2% vs. 32.6%, p=0.007) and DQB1*0601 (12.5% vs. 34.9%, p=0.047) were observed in more advanced (moderately & far advanced/DS and far advanced/MDR), compared with less advanced (minimal/DS and moderately advanced/MDR) lung lesions. Although DRB1*0701, DQB1*0202 and DQB1*0609 showed significant increases in different subsets of the disease, these HLA alleles did not show consistent association with disease severity. Conclusion : HLA-DRB1*08032 and DQB1*0601 alleles were associated with genetic susceptibility to MDR-TB in Korean patients, and also with disease severity and progression of PTB.

• Tuberculosis and Respiratory Diseases
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• v.55 no.6
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• pp.579-588
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• 2003

Background : The hospital-acquired pneumonia is the most common nosocomial infection. Recently, the Acinetobacter baummannii infections are rapidly increasing, especially the frequency of Multi-drug resistant A. baumannii. Therefore we assessed clinical features and prognosis of patients in the ICU with Multi-drug resistant A. baumannii from the sputum culture using the Clinical Pulmonary Infection Score(CPIS). Method : The medical records of 43 patients with Multi-drug resistant A. baumannii from sputum culture who were suspected had clinically pneumonia and admitted to the ICU from January 2000 to July 2002 were retrospectively analyzed. Results : 19 patients were CPIS greater than 6 and 24 patients were CPIS less than or equal to 6. Mean age for the former was $71{\pm}11$ years old, and the latter was $61{\pm}19$ years old. The mean APACHE II score on admission and on sputum study was not different between two groups($17.4{\pm}5.7$ vs $18.5{\pm}6.1$, p=0.553, $20{\pm}6$ vs $17{\pm}8$, p=0.078). But the mortality rate was 73.7% for the former, and 16.7% for the latter(p<0.001). Conclusion : In ICU patients who had clinically suspected pneumonia with sputum culture positive for Multi-drug resistant A. baumannii, the mortality was significantly higher if CPIS was greater than 6.

• Tuberculosis and Respiratory Diseases
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• v.60 no.1
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• pp.76-82
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• 2006

Background : The objective of this study was to understand sleep-related problems, and to determine whether the sleep questionnaires is a clinically useful method in patients who need polysomnography. Methods : Subjects were patients who performed polysomnography and who asked to answer a sleep questionnaires at the Sleep Disorders Clinic of St. Paul's Hospital, Catholic University of Korea. Baseline characteristics, past medical illness, behaviors during sleep-wake cycle, snoring, sleep-disordered breathing and symptoms of daytime sleepiness were analyzed to compare with data of polysomnography. Results : The study population included 1081 patients(849 men, 232 female), and their mean age was $44.2{\pm}12.8years$. Among these patients, 38.9% had an apnea-hypopnea index(AHI)<5, 27.9% had $5{\leq}AHI<20$, 13.2% had $20{\leq}AHI<40$, and 20.0% had $40{\leq}AHI$. The main problems for visiting our clinic were snoring(91.7%), sleep apnea(74.5%), excessive daytime sleepiness(8.0%), insomnia(4.3%), bruxism(1.1%) and attention deficit(0.5%). The mean value of frequency of interruptions of sleep was 1.6 and the most common reason was urination(46.3%). Epworth Sleepiness Scale(ESS) had a weak correlation with AHI(r=0.209, p<0.01). When we performed analysis of sleep questionnaires, there were significant differences in the mean values of AHI according to the severity of symptoms including snoring, daytime sleepiness, taking a nap and arousal state after wake(p<0.05). Conclusion : On the basis of statistical analysis of sleep questionnaires, the severity of subjective symptoms such as ESS, snoring, daytime sleepiness and arousal state after wake correlated with the AHI significantly. Therefore the sleep questionnaires can be useful instruments for prediction of the severity of sleep disorder, especially sleep-disordered breathing.

• Tuberculosis and Respiratory Diseases
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• v.63 no.6
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• pp.480-485
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• 2007

Background: Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible. COPD has systemic effects, such as skeletal muscle dysfunction and abnormal weight loss. It also has been suggested that COPD is related to other chronic disease, such as cardiovascular disease, osteoporosis, and anemia. The aim of this study was to evaluate a symptom questionnaire and laboratory findings in subjects with air flow limitation. Methods: We evaluated a symptom questionnaire and laboratory findings in subjects with airflow limitation detected by spirometry in conjunction with the Second Korean National Health and Nutrition Examination Survey. A total of 9,243 adults over the age of 18 were recruited. Among the adults, we finally analyzed 2,217 subjects who met the acceptability and repeatability criteria of spirometry, showed normal findings on chest radiography, and were older than 40 years of age. Results: There were 288 subjects with airflow limitation as determined by spirometry. The frequency of respiratory symptoms such as cough, sputum and wheezing were significantly higher in subjects with airflow limitation (p <0.01). Hemoglobin and hematocrit levels were higher in subjects with airflow limitation (hemoglobin level 13.98 mg/dL vs. 13.62 mg/dL, hematocrit 42.10% vs. 40.89%; p<0.01). The HDL cholesterol level was lower in subjects with airflow limitation (44.95 mg/dL vs. 45.60 mg/dL; p<0.01). There was no significant difference in the total cholesterol, triglyceride, blood urea nitrogen, creatinine, and fasting glucose levels. Conclusion: In subjects with airflow limitation, prevalence of respiratory symptoms was higher than in normal spirometry subjects and the levels of hemoglobin and the hematocrit were higher. The HDL cholesterol level was lower in subjects with airflow limitation.