• The Journal of Advanced Prosthodontics
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• v.9 no.3
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• pp.195-199
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• 2017

PURPOSE. The objective of this study was to determine the cumulative survival rate (CSR) and associated risk factors of Implantium implants by retrospective clinical study. MATERIALS AND METHODS. Patients who received Implantium implants (Dentium Co., Seoul, Korea) at Korea University Guro Hospital from 2004 to 2011 were included. The period between the first surgery and the last hospital visit until December 2015 was set as the observation period for this study. Clinical and radiographic data were collected from patient records, including all complications observed during the follow-up period. Kaplan-Meier analysis was performed to examine CSR. Multiple Cox proportional hazard model was employed to assess the associations between potential risk factors and CSR. RESULTS. A total of 370 implants were placed in 121 patients (mean age, 56.1 years; range, 19 to 75 years). Of the 370 implants, 13 failed, including 7 implants that were lost before loading. The 10-year cumulative survival rate of implants was 94.8%. The multiple Cox proportional hazard model revealed that significant risk factor of implant failure were smoking and maxillary implant (P<.05). CONCLUSION. The 10-year CSR of Implantium implants was 94.8%. Risk factors of implant failure were smoking and maxillary implant.

• Journal of Periodontal and Implant Science
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• v.38 no.4
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• pp.589-594
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• 2008

Purpose: Osseointegration of implants in patients with pneumatized maxillary sinuses is difficult to achieve due to the deficiency of available bone in the posterior maxilla after loss of teeth. Maxillary sinus elevation is a method to overcome this problem. In this study, we evaluated the implant survival rate and the relationship between implant survival in patients with sinus elevation by the lateral approach. Materials and Methods: A total of 48 patients were consecutively treated with sinus elevation by the lateral approach between February 2003 & August 2006 at the dental hospital of Chonbuk National university. A total of 113 implants were placed. The mean healing period was 7.1 months and implants were placed after a mean period of 5.6 months. The mean observation period was 21.8 months. Results: Out of the 113 implants placed, fifteen failed, resulting in a survival rate of 86.7%, 18 cases of sinus membrane perforation were observed out of 65 sinuses treated. 33 implants were placed in a perforated site and 10 failed, representing a 60.7% implant survival. 80 implants were placed in a nonperforated site and 5 failed, representing a 92.6% implant survival. Conclusions: Implant placement with sinus elevation is an acceptable treatment for short term results. Sinus membrane perforation and postoperative complications, however, may have an effect on implant failure.

• Clinical and Experimental Pediatrics
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• v.49 no.4
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• pp.446-450
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• 2006

Congenital central hypoventilation syndrome (CCHS) or Ondine's curse is a very rare sleep disorder that is the result of a congenital failure of the autonomic control of ventilation caused by insensitivity of the chemoreceptor to hypercapnea during sleep. Gastrointestinal motility disorders, particularly a congenital megacolon (Hirschsprung disease) is often combined with CCHS. This combination can be explained by a defect in the migration of neuronal cells from the neural crest (neurocristopathy) during the intrauterine period. A diagnosis of CCHS is made by confirming the failure of adequate ventilation in response to hypercapnea and hypoxia during sleep and the exclusion of other diseases. Young infants frequently show atypical clinical courses, and their conditions are frequently complicated with the long-term sequela of hypoxemic episodes. Therefore, a high index of suspicion and active treatment with mechanical ventilation are important for reducing recurrent hypoxemic episodes in the neonatal period. This paper reports the follow up of a case of CCHS in a neonate who showed frequent intractable apnea and cyanosis and was given artificial mechanical ventilation during sleep.

• Journal of Chest Surgery
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• v.28 no.1
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• pp.23-30
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• 1995

From January 1985 to December 1992, of 1257 patients who underwent a heart valve replacement 210 [16.8% underwent reoperation on prosthetic heart valves, and 6 of them had a second valve reoperation. The indications for reoperation were structural deterioration [176 cases, 81.5% , prosthetic valve endocarditis [25 cases, 11.6% , paravalvular leak [12 cases, 5.6% , valve thrombosis [2 cases, 0.9% and ascending aortic aneurysm [1 case, 0.4% . Prosthetic valve failure developed most frequently in mitral position [57.9% and prosthetic valve endocarditis and paravalvular leak developed significantly in the aortic valve [40%, 75% [P<0.02 . Mean intervals between the primary valve operation and reoperation were 105.3$\pm$28.4 months in the case of prosthetic valve failure, 61.5$\pm$38.5 months in prosthetic valve endocarditis, 26.8$\pm$31.2 months in paravalvualr leak, and 25.0$\pm$7.0 months in valve thrombosis. In bioprostheses, the intervals were in 102.0$\pm$23.9 months in the aortic valve, and 103.6$\pm$30.8 months in the mitral valve. The overall hospital mortality rate was 7.9% [17/26 : 15% in aortic valve reoperation [6/40 , 6.5% in reoperation on the mitral prostheses [9/135 and 5.7% in multiple valve replacement [2.35 . Low cardiac output syndrome was the most common cause of death [70.6% . Advanced New York Heart Association class [P=0.00298 , explant period [P=0.0031 , aortic cross-clamp time [P=0.0070 , prosthetic valve endocarditis [P=0.0101 , paravalvularr leak [P=0.0096 , and second reoperation [P=0.00036 were the independent risk factors, but age, sex, valve position and multiple valve replacement did not have any influence on operative mortality. Mean follow up period was 38.6$\pm$24.5 months and total patient follow up period was 633.3 patient year. Actuarial survival at 8 year was 97.3$\pm$3.0% and 5 year event-free survival was 80.0$\pm$13.7%. The surgical risk of reoperation on heart valve prostheses in the advanced NYHA class patients is higher, so reoperation before severe hemodynamic impairment occurs is recommended.

• Journal of The Korean Institute of Defense Technology
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• v.5 no.1
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• pp.1-6
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• 2023

The number of test samples was calculated by setting the reliability growth management test period considering the weapon system development period. The optimal reliability growth management test design condition was 80% reliability, 60% confidence level, and 6 months of test period. At this time, it was analyzed that 4 test samples were required if 0 failure occurred, and 9 test samples were required if 1 failure occurred. Using the method of determining the number of samples presented in this paper, it can be used as a basis for acquiring a budget for the number of samples for reliability growth management when switching from the exploratory development stage to the system development stage.

• Journal of Korean Neurosurgical Society
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• v.49 no.4
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• pp.217-221
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• 2011

Objective : This paper presents data from a retrospective study of endoscopic third ventriculostomy (ETV) in patients with shunt malfunction and proposes a simple and reasonable post-operative protocol that can detect ETV failure. Methods : We enrolled 19 consecutive hydrocephalus patients (11 male and 8 female) who were treated with ETV between April 2001 and July 2010 after failure of previously placed shunts. We evaluated for correlations between the success rate of ETV and the following parameters : age at the time of surgery, etiology of hydrocephalus, number of shunt revisions, interval between the initial diagnosis of hydrocephalus or the last shunt placement and ETV, and the indwelling time of external ventricular drainage. Results : At the time of ETV after shunt failure, 14 of the 19 patients were in the pediatric age group and 5 were adults, with ages ranging from 14 months to 42 years (median age, 12 years). The patients had initially been diagnosed with hydrocephalus between the ages of 1 month 24 days and 32 years (median age, 6 years 3 months). The etiology of hydrocephalus was neoplasm in 7 patients; infection in 5; malformation, such as aqueductal stenosis or megacisterna magna in 3; trauma in 1; and unknown in 3. The overall success rate during the median follow-up duration of 1.4 years (9 days to 8.7 years) after secondary ETV was 68.4%. None of the possible contributing factors for successful ETV, including age (p=0.97) and the etiology of hydrocephalus (p=0.79), were statistically correlated with outcomes in our series. Conclusion: The use of ETV in patients with shunt malfunction resulted in shunt independence in 68.4% of cases. Age, etiology of hydrocephalus, and other contributing factors were not statistically correlated with ETV success. External ventricular drainage management during the immediate post-ETV period is a good means of detecting ETV failure.

• Tribology and Lubricants
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• v.30 no.3
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• pp.146-155
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• 2014

In this study, we conduct fretting corrosion tests on tin-plated brass coupons to investigate the effect of temperature on fretting corrosion for various span amplitudes. We prepare a coupled fretting corrosion specimens using a tin-plated brass coupon with a thickness of $10{\mu}m$. One specimen is a flat coupon and the other specimen is a coupon with a protuberance in 1 mm radius, which is produced using 2 mm diameter steel ball. We conduct fretting corrosion tests at $25^{\circ}C$, $50^{\circ}C$, $75^{\circ}C$, $100^{\circ}C$ by rubbing the coupled coupons together at the contact between the flat and protuberance coupons. We measure electric resistance of the contact during the fretting corrosion test period. There is increase in resistance with fretting cycles. It is found that rate of increase in electric resistance becomes faster with increase in testing temperature. Magnitude of friction coefficient increases with fretting span amplitudes. And, change in friction coefficient becomes desensitized to the increment in span amplitude. Assuming that failure cycle is the cycle with an electric resistance of $0.01{\Omega}$, we find that failure lifetime ($N_f$) decreases with increase in testing temperature. Furthermore, based on the assumption that the damage rate of the connector is inversely related to the failure cycle, we calculate the activation energy for fretting damage to be 13.6 kJ/mole by using the Arrhenius equation. We propose a method to predict failure cycle at different temperatures for span amplitudes below $30{\mu}m$. Friction coefficients generally increase with increase in span amplitude and decrease in testing temperature.

• Journal of Navigation and Port Research
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• v.30 no.6 s.112
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• pp.525-531
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• 2006

In the port, the yard crane is very important. If a container crane or a transfer crane is broken down, it costs a lot because of the delay of work during the period of repair or reorder. But, we don't have enough spare parts because of the high cost. It is necessary to maintain high reliability of the crane through effective preventive maintenance and failure analysis. In this paper, we analyse the function and failure mechanism of the transfer crane which is a main equipment in the yard Also, we standardize failures and maintenance works using the historical data of failure and maintenance. This study which is a basic work for effective equipment operation and maintenance will support reliability engineers to decide the optimal design of the next generation equipment and operational policy of equipment.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.4
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• pp.145-152
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• 2019

All machines deteriorate in performance over time. The phenomenon that causes such performance degradation is called deterioration. Due to the deterioration, the process mean of the machine shifts, process variance increases due to the expansion of separate interval, and the failure rate of the machine increases. The maintenance model is a matter of determining the timing of preventive maintenance that minimizes the total cost per wear between the relation to the increasing production cost and the decreasing maintenance cost. The essential requirement of this model is that the preventive maintenance cost is less than the failure maintenance cost. In the process mean shift model, determining the resetting timing due to increasing production costs is the same as the maintenance model. In determining the timing of machine adjustments, there are two differences between the models. First, the process mean shift model excludes failure from the model. This model is limited to the period during the operation of the machine. Second, in the maintenance model, the production cost is set as a general function of the operating time. But in the process mean shift model, the production cost is set as a probability functions associated with the product. In the production system, the maintenance cost of the equipment and the production cost due to the non-confirming items and the quality loss cost are always occurring simultaneously. So it is reasonable that the failure and process mean shift should be dealt with at the same time in determining the maintenance time. This study proposes a model that integrates both of them. In order to reflect the actual production system more accurately, this integrated model includes the items of process variance function and the loss function according to wear level.

• Journal of Veterinary Clinics
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• v.26 no.1
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• pp.17-22
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• 2009

Pimobendan is a recently developed cardiac drug which is useful to control moderate to severe congestive heart failure (CHF) from chronic mitral valvular diseases (CMVI). Because of controversy related to the efficacy and safety of pimobendan in dogs, the optimal efficacy and safety of pimobendan was assessed in 20 dogs with CMVI in this study. Scores for quality of life, respiratory failure, circulatory failure and heart failure were evaluated along with radiographical and echocardiographical assessments for about 2 months period after the addition of pimobendan into the regular cardiac medications. This study proved clear evidence that pimobendan had beneficial therapeutic effects in dogs with advanced CMVI, without particular adverse effects. However, further studies are warranted to address the drug interaction with other cardiac therapeutics and to assess therapeutic effects in CHF from other type of heart diseases in dogs and other animals.