• Journal of Korean Neurosurgical Society
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• v.61 no.1
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• pp.97-104
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• 2018

Objective : Diffusion-weighted magnetic resonance imaging (DW-MRI) has proven useful in the study of the natural history of ischemic stroke. However, the potential of DW-MRI for the evaluation of chronic subdural hematoma (CSDH) has not been established. In this study, we investigated DW-MRI findings of CSDH and evaluated the impact of the image findings on postoperative outcomes of CSDH. Methods : We studied 131 CSDH patients who had undergone single burr hole drainage surgery. The images of the subdural hematomas on preoperative DW-MRI and computed tomography (CT) were divided into three groups based on their signal intensity and density : 1) homogeneous (iso or low) density on CT and homogeneous low signal intensity on DW-MRI; 2) homogeneous (iso or low) density on CT and mixed signal intensity on DW-MRI; and 3) heterogeneous density on CT and mixed signal intensity on DW-MRI. On the basis of postoperative CT, we also divided the patients into 3 groups of surgical outcomes according to residual hematoma and mass effect. Results : Analysis showed statistically significant differences in surgical (A to B : p<0.001, A to C : p<0.001, B to C : p=0.129) and functional (A to B : p=0.039, A to C : p<0.001, B to C : p=0.108) outcomes and treatment failure rates (A to B : p=0.037, A to C : p=0.03, B to C : p=1) between the study groups. In particular, group B and group C showed worse outcomes and higher treatment failure rates than group A. Conclusion : CSDH with homogeneous density on CT was characterized by signal intensity on DW-MRI. In CSDH patients, performing DW-MRI as well as CT helps to predict postoperative treatment failure or complications.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.277-279
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• 2005

Recently, due to the increase of power conversion devices and nonlinear loads with the development of information, communication and control technologies, the instantaneous minute interruption factors such as voltage & current harmonics, surge occurring frequency, instantaneous voltage variation, voltage unbalance, flicker etc. have greatly threatened the power quality, and the deterioration of electric power facilities and the functional error of controllers are increasing. As such an instantaneous minute interruption appears to be small and local, accurate evaluation with measurement is difficult and total analysis system is required through a wide range of power quality effect analysis such as the simultaneous measurement on various power supply phenomena and the analysis on the interrelation with system loads. Most of conventional power quality diagnosis equipments have beer developed and applied, which were able to measure the stability rate of frequency, the stability rate of voltage, the electricity-failure duration etc, However, they were insufficient to analyze the system present situation, understand the cause of the failure occurred by the problem of power quality and analyze out the phenomena. Accordingly, this study will address the development of the system for a wide range of power quality diagnosis over the present level, the system for supporting the determination such as the analysis on risk factors, failure mode and impact, the system for harmonic evaluation based on international standards(IEC 61000 Series) and the total power quality diagnosis network & system with the extension and openness as a local and national-scale broadband power quality diagnosis system.

• Journal of IKEEE
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• v.24 no.2
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• pp.385-391
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• 2020

Overcurrent and abnormal voltages in the distribution system can cause not only burden of power plant but also damage to customers. As a result, researches related to the distribution automation have been widely conducted by utilizing a real time digital simulation to improve the reliability of power supply through rapid failure handing, reduction of power failure intervals and failure recovery. However, the distribution automation systems using the real time digital simulator are expensive and limited to verify actual hardwares. Therefore, in this paper, an external hardware devices was developed based on the distribution system analysis results of the digital simulator. And real-time simulation and functional verification are implemented by the real feeder remote terminal units used in distribution automation. The effectiveness of the proposed system is verified through several experiments.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.7-18
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• 2005

Over the past twenty years, the maintenance system has been developed and its importance has been increased. For the effective maintenance of the urban transit, we have developed the maintenance system based on the concept of RCM(Reliability Centered Maintenance). RCM analysis is a systematic approach to developing a cost-effective maintenance strategy based on the various components's reliability of the system in question. It is performed according to process that includes the following steps; definition of function and functional failures of the systems, construction of RB D(Reliability Block Diagram), performance of FMEA(Failure Modes & Effects Analysis) and calculation of the reliability index. The final process of RCM is to determine appropriate failure maintenance strategies. This paper aims to define the procedure of maintenace based on the concept of RCM for urban transit. The key for a successful maintenance system is an automated scheduling to the maximum extent possible and timely executions. The developed system issues maintenance plan and repair request based on analyzed data and maintenance experience.

• Journal of Chest Surgery
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• v.24 no.7
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• pp.663-668
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• 1991

To evaluate risks, complications and mortality of reoperations on heart valve prosthesis, we reviewed clinical records of 53 patients who underwent reoperation because of prosthetic valve failure[PVF], from Jan 1959 through Jun. 1991. They had undergone 48 mitral, 10 aortic valve rereplacement Primary tissue failure was the main cause of reoperation : it occurred in 51 valves at a mean postoperative interval of 58 months. Calcification and collagen disruption of prosthesis were main causes of primary tissue failure in macro and micropathology, In 3 failing mechanical prostheses, paravalvular leak was in 2 cases, another one case had the thrombi at the hinge portion. If conditions such as emergency operation with or without endocarditis, thromboembolism and advanced NYHA functional class are prevented, we think that reoperative valve replacement has similar morbidity and mortality to initial valve replacement surgery. But our sturdy represents higher mortality [22.6%] because of late surgical intervention failing the prevention of conditions leading to myocardial damage. In conclusion if the tearing, calcification, and a new murmur were detected the early reoperation should be considered to increase late survival.

• Journal of Aerospace System Engineering
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• v.18 no.2
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• pp.12-20
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• 2024

The application of reinforcement design to ensure the structural safety of electronics in small satellites is limited by the spatial constraints of the satellite structure during launch vibrations. Additionally, a reliable evaluation approach is needed for mounting highly integrated devices that are susceptible to fatigue failure. Although the Steinberg fatigue failure theory has been used to assess the structural integrity of electronic devices, recent studies have highlighted its theoretical limitations. In this paper, we propose a structural methodology based on the critical strain theory to design the digital control unit (DCU) of the X-band SAR payload component for the small SAR technology experimental project (S-STEP), a small satellite constellation. To validate the design, we conducted modal and random analyses using simplified modeling techniques. Based on our methodology, we ultimately demonstrated the structural safety of the electronics through analysis results, safety margin derivation, and functional tests conducted both before and after the launch test.

• Korean Journal of Radiology
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• v.25 no.1
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• pp.24-32
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• 2024

Despite improvements in operative techniques and perioperative care, post-hepatectomy liver failure (PHLF) remains the most serious cause of morbidity and mortality after surgery, and several risk factors have been identified to predict PHLF. Although volumetric assessment using imaging contributes to surgical simulation by estimating the function of future liver remnants in predicting PHLF, liver function is assumed to be homogeneous throughout the liver. The combination of volumetric and functional analyses may be more useful for an accurate evaluation of liver function and prediction of PHLF than only volumetric analysis. Gadoxetic acid is a hepatocyte-specific magnetic resonance (MR) contrast agent that is taken up by hepatocytes via the OATP1 transporter after intravenous administration. Gadoxetic acid-enhanced MR imaging (MRI) offers information regarding both global and regional functions, leading to a more precise evaluation even in cases with heterogeneous liver function. Various indices, including signal intensity-based methods and MR relaxometry, have been proposed for the estimation of liver function and prediction of PHLF using gadoxetic acid-enhanced MRI. Recent developments in MR techniques, including high-resolution hepatobiliary phase images using deep learning image reconstruction and whole-liver T1 map acquisition, have enabled a more detailed and accurate estimation of liver function in gadoxetic acid-enhanced MRI.

• Toxicological Research
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• v.11 no.1
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• pp.15-21
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• 1995

Several populations of lymphocytes possess receptors for autonomic neurotransmitter, which make lymphocytes susceptible to autonomic stimulation. This study was to evaluate the functional alternation of effector cells of the immune system. Female Balb/C mice, 15-20 g, were injected with MA subcutaneously under various conditions. Mixed lymphocyte reaction (MLR) showed certain T cell subsets were affected by MA. The level of interleukin-2 (IL-2) production was inhibited due to a defect in expression of the IL-2 receptor. In mice injected with 20 mg MA/kg, 1 day before assay, phagocytosis of peritoneal macrophages showed $14.07\pm3%$, which was similar degree to 5 mg MA/kg treatment for 4 consecutive days. Phagocytosis was almost recovered to that of control after 4 day in 20 mg/kg injected mice. Maximum inhibition of plaque forming cell (PFC) occurred when MA was given early, indicating the inductive time point of antibody production was affected. The cortisol level increased in the MA treated group (0.05, 0.20, and $0.08{\mu}g$/dl for control, low, and high dose-MA treated mice, respectively). Based on these results, MA has general suppression effects on the immune systems by functional alteration of effector cells. Considering the increment of serum cortisol levels, MA partially impacts the neuroendocrine system to lead to failure of immune response.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.4
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• pp.419-426
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• 2017

In implant restorations, it is difficult for the patient to percept any symptoms. In addition, they are absent of shock absorbers, which can lead to mechanical failure if stress distribution is not considered. Since maxillary anterior multiple-implant restorations play a significant role in guiding the functional movement of the mandible by distributing lateral force, it is crucial to form appropriate occlusion. The use of the T-scan system is more advantageous in assessing 'dynamic occlusion', such as the change of occlusion over time, the amount of tooth contact during functional movement, and assessing the occlusion in the less-visible posterior teeth. The case is reported as it has satisfactory results in harmonious anterior guidance of a maxillary anterior multiple-implant restoration using T-scan analysis.

• Journal of Chest Surgery
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• v.53 no.3
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• pp.121-126
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• 2020

Background: The aim of this study was to analyze the clinical outcomes of autogenous brachiocephalic arteriovenous fistulas and to investigate the factors associated with 1-year patency after initiation of hemodialysis. Methods: We retrospectively reviewed the medical records of 41 patients who underwent surgery to create an autogenous brachiocephalic arteriovenous fistula between January 2015 and December 2017, received hemodialysis at the same hospital for longer than 1 year, and were monitored for their vascular access status. Intraoperative flow was measured using transit-time ultrasonography. Results: The 1-year primary and secondary patency rates were 61% (n=25) and 87.8% (n=36), respectively. The functional group (subjects who required no intervention to maintain patency within the first year after hemodialysis initiation) displayed a significantly higher median intraoperative flow rate (450 mL/min) than the non-functional group (subjects who required intervention at least once regardless of 1-year patency) (275 mL/min) (p=0.038). Based on a receiver operating characteristic curve analysis, all patients were additionally subdivided into a high-flow group (>240 mL/min) and a low-flow group (≤240 mL/min). The high-flow group included a significantly greater number of functional brachiocephalic arteriovenous fistulas than the low-flow group (74.2% vs. 20%, respectively; p=0.007). Conclusion: Transit-time flow, as measured with intraoperative transit-time ultrasonography, was associated with patency without the need for intervention at 1 year after initiation of hemodialysis.