• International Journal of Fluid Machinery and Systems
• /
• v.10 no.2
• /
• pp.146-153
• /
• 2017

Sediment flow through hydropower components causes hydro-abrasive erosion resulting in loss of efficiency, interruptions in power production and downtime for repair/maintenance. Online instruments are required to measure/capture the variations in sediment parameters along with collecting samples manually to analyse in laboratory for verification. In this paper, various sediment parameters viz. size, concentration (TSS), shape and mineral composition relevant to hydro-abrasive erosion were measured and discussed with respect to a hydropower plant in Himalayan region, India. A multi-frequency acoustic instrument was installed at a desilting chamber to continuously monitor particle size distribution (PSD) and TSS entering the turbine during 27 May to 6 August 2015. The sediment parameters viz. TSS, size distribution, mineral composition and shape entering the turbine were also measured and analysed, using manual samples collected twice daily from hydropower plant, in laboratory with instruments based on laser diffraction, dynamic digital image processing, gravimetric method, conductivity, scanning electron microscope, X-ray diffraction and turbidity. The acoustic instrument was able to capture the variation in TSS; however, significant deviations were found between measured mean sediment sizes compared to values found in the laboratory. A good relation was found for turbidity ($R^2=0.86$) and laser diffraction ($R^2=0.93$) with TSS, which indicated that turbidimeter and laser diffraction instrument can be used for continuous monitoring of TSS at the plant. Total sediment load passed through penstock during study period was estimated to be 15,500 ton. This study shall be useful for researchers and hydropower managers in measuring/monitoring sediment for hydro-abrasive erosion study in hydropower plants.

• Journal of Internet Computing and Services
• /
• v.3 no.5
• /
• pp.31-39
• /
• 2002

A rapid growth of internet and sudden increase of multimedia data demands for high-speed transfer media and if optimizec usage from the interface system. To achieve this level of network bandwidth, multiple NICs for support of high-speed network bandwidth have been developed and studied. Furthermore, the use of multiple NICs can provide high-speed LAN environment without large network environment modification, supports backward compatibility of current system and reduce overhead. However. if system failure is caused by SPOF(Single Point of Failure) fault of large-capacity multiple NICs, incredible loss will be met because it services large capacity of multimedia data, Therefore, to prevent loss coming from faults, we describe 'Fault tolerance of multiple NICs', which use the fault prevention mechanism. Considering inefficiency of availability and serviceability that is occurred with existing TMR, Primary-Standby approach and Watchdog time mechanism, we propose and design the efficient fault tolerance mechanism, which minimize down time as changing of detection period dynamically. Consequently, the fault tolerance mechanism proposed for reducing overhead time when the fault is occurred, should minimize system downtime overall.

• Tunnel and Underground Space
• /
• v.13 no.6
• /
• pp.455-464
• /
• 2003

Four assessment systems for planning and evaluation of TBM tunnelling are discussed, and their characteristics and input data are analyzed. Two of the systems are determined to be adequate for post-evaluation of TBM performance because the time, such as repair time, downtime, installation time and transport time, must be included for calculations. The others are adequate for pre-planning because the basic data of the systems consist of only the basic properties of rocks and rock masses, and the specification of TBM. In order to apply these assessment systems, a number of equations, graphs and charts are generally required, which seems to be very inconvenient and complicated. In this study, therefore, a user-friendly program operated on Windows system is developed, and each system can be selected by the corresponding input data. It will be possible fer tunnel engineers to select a system according to their objectives and available input data, and to apply the system to TBM tunnel project.

• Journal of Applied Reliability
• /
• v.16 no.4
• /
• pp.295-304
• /
• 2016

Purpose: This paper presents an application of Markov Process to reliability and availability analysis. In order to do that of analysis, we set up a specific case of Tablet PC and it's usage scenario. The case has it some spares and maintenance and repair processes. Methods: Different configurations of the tablet PC and as well as their functions are defined. The system configuration and calculated failure rates of components are modeled from Windchill Quality Solution. Two models, without a spare and with spare, are created and compared using Markov Process. The Matlab numerical analysis is used to simulate and show the change of state with time. Availability of the system is computed by determining the time the system stays in different states. Results: The mission availability and steady-state condition availability in accordance with the mission are compared and the availability of the system with spares have improved availability than without spares. Simulated data shows that downtime of the system increased which results in greater availability through the consideration of spares. Conclusion: There's many techniques and methods to do reliability and availability analysis and mostly are time-independent assumptions. But Markov Process, even though its steady-state and ergodic properties, can do time analysis any given time periods.

• Journal of Korean Critical Care Nursing
• /
• v.9 no.1
• /
• pp.40-50
• /
• 2016

Purpose: Continuous renal replacement therapy (CRRT) has become the preferred dialysis method to support critically ill children and neonates with acute kidney injury. Using CRRT on neonates has increased, but reports about experience are limited. The aim of this study is to describe the clinical application, outcomes, and complications of CRRT in children and neonates. Methods: A retrospective review was performed in 135 children and 36 neonates who underwent CRRT at a tertiary hospital from 2008 to 2015. Results: At the initiation of CRRT, the median age of children was 72 months and the corrected age of neonates was 37.1 weeks. Median body weight of neonates was 3.2 kg. In neonates, initial degree of fluid overload [FO%], blood flow rate [BFR] and ultrafiltration rate [UFR] rate during CRRT were higher than in children. Median real time of CRRT was 90.5 and 53.5 hours in children and neonates, respectively. Downtime of CRRT was 0.7 and 1.3 hours/day. Median mortality rates (44.4% vs.47.2%) and complication rates were similar between the groups. Conclusion: CRRT can be used for a wide range of critically ill children and neonates. Different application methods of CRRT can contribute to increased survival of neonates.

• Archives of Plastic Surgery
• /
• v.40 no.4
• /
• pp.409-413
• /
• 2013

Background Buried non-incisional double-eyelid blepharoplasty is a popular aesthetic procedure. Although various modified continuous suture techniques have been used to create a more natural appearance and to reduce downtime, complications such as loosening of the double fold, asymmetry, and foreign body reactions have been observed. Methods This study included 250 patients who underwent double-eyelid blepharoplasty between March 1997 and November 2012 using a modified single-knot continuous buried non-incisional technique. With 4 stab incisions in the upper eyelids, one of two needles loaded with double-armed 7-0 nylon was passed in one direction alternately through the dermis and the conjunctiva, while the other needle was passed subconjunctivally in the opposite direction. Both ends of the sutures were knotted within a lateral stab incision of the upper eyelids and were buried in the orbicularis oculi muscle. Results Most patients displayed satisfactory aesthetic results, and no significant complications occurred. There was no obvious regression of the double fold; however, 3 patients required reoperation to correct loosening of the fold on one side during the follow-up period. One patient presented with the suture knot subcutaneously, and the knot was removed in the clinic. Conclusions The modified single-knot continuous buried non-incisional technique is a simple and less time-consuming method for a durable double fold and provides satisfactory aesthetic results.

• Journal of radiological science and technology
• /
• v.8 no.2
• /
• pp.29-45
• /
• 1985

Computed Tomography Scanner (CT) is highly expensive in operation as well as purchasing. That reason may cause not only to increase the burden of patients but also to waste the capital resources leading to financial difficulties. However the numbers of CT installed throughout the country is increasing, because of efficiency in medical care, patient's concern, competitions among the hospitals within the same area. In the non-Metropolitan area the scanners were expected to be less utilized and less profitable. Nine hospitals equipped with the CT were studied on the utilization of that equipment during the period from November 1984 to February 1985 in non-Metropolitan area and break-even point in one hospital was analyzed for estimating profitabilities. The results were as follows ; 1. Among those nine hospitals, four hospitals had less than 400 beds, which is one of the restrictive minimum standards on the installation of Whole-body Computed Tomography Scanner. 2. The operating time during the normal operation period was longer than those of any other studies, but the accumulated down time was also longer than those of any other studies. The average number of scanning per week for each CT was 45, while the estimated number of for the break-even point was 56.7 cases. 3. When the downtime was excluded in calculating the average operation would be much closer to the cases for the break-even point. Therefore the break-down of the equipment was to be a main cause of the low profitability. 4. The average scanning rate for head area was 33.6%, however three of the nine hospitals showed about 20%. 5. If scanning ratio for the body parts excepting head was increased, the number of scanning for the break-even point would be diminished. 6. The small size hospital especially located near the Metropolitan area showed largest loss in the CT operation. In purchasing the highly expensive equipments in hospitals, demand should be taken into account and planning is recommended.

• Journal of IKEEE
• /
• v.24 no.3
• /
• pp.691-698
• /
• 2020

The installation cost or the magnitude of the fault current varies depending on the grid connection method of the offshore wind farm. Therefore, there is a need for an efficient power grid connection method considering the capacity and location of the complex. In particular, most power cables in offshore wind farms use 3-core considering cost and efficiency. In the event of a failure such as a short circuit, the entire cable must be replaced, which can lead to significant losses in terms of cost, considering repair costs and turbine downtime. Therefore, in this paper, a radial, ring, and molding method is introduced into a 100 MW wind farm to be installed at Jeju offshore, and a three-phase short circuit failure is performed using a PSCAD/EMTDC program to perform computer analysis. I would like to propose a suitable power grid connection method.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.42 no.4
• /
• pp.939-949
• /
• 2017

Prognostics and health management(PHM) is actively utilized by industry as an essential technology focusing on accurately monitoring the health state of a system and predicting the remaining useful life(RUL). An effective PHM is expected to reduce maintenance costs as well as improve safety of system by preventing failure in advance. With these advantages, PHM can be applied to the battery system which is a core element to provide electricity for devices with mobility, since battery faults could lead to operational downtime, performance degradation, and even catastrophic loss of human life by unexpected explosion due to non-linear characteristics of battery. In this paper we mainly review a recent progress on various models for predicting RUL of battery with high accuracy satisfying the given confidence interval level. Moreover, performance evaluation metrics for battery prognostics are presented in detail to show the strength of these metrics compared to the traditional ones used in the existing forecasting applications.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.24 no.1
• /
• pp.96-101
• /
• 2014

Wind power is the fastest growing renewable energy source in the world and it is expected to remain so for some times. Recently, there is a constant need for the reduction of Operational and Maintenance(O&M) costs of Wind Energy Conversion Systems(WECS). The most efficient way of reducing O&M cost would be to utilize CMS(Condition Monitoring System) of WECS. CMS allows for early detection of the deterioration of the wind generator's health, facilitating a proactive action, minimizing downtime, and finally maximizing productivity. There are two types of faults such as mass unbalance and aerodynamic asymmetry which are related to wind turbine's rotor faults. Generally, these faults tend to generate various vibrations. Therefore, in this work a simple fault detection algorithm based on spectrums of vibration signals and simple max-min decision logic is proposed. Furthermore, in order to verify its feasibility, several simulation studies are carried out by using GH-bladed software.