• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1149-1155
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• 2007

The transition area between a bridge and an earthwork is one of the weakest area of track because of the track geometry deterioration caused unequal settlement of backfill of abutment. In case of a ballastless track, the approach slab is installed to prevent the phenomenon. But, if there is occurred the inclined displacement on the approach slab by a settlement of the foundation or formation, the track is also under the inclined displacement. And this defect causes reducing the running stability of a vehicle, the riding comfort of passengers, and the deteriorations of track by excessive impact subjected to the track. In this study, parametric studies were performed to know what is the allowable displacement limit on the approach slab to avoid such a bad effect. The length and amount of unequal settlement of the approach slab was adopted as parameter for numerical analysis. And car body accelerations, variations of wheel force and rail stress and uplift force induced on a fastener clip are investigated. From the result, resonable settlement limits of an approach slab according to slab length was suggested.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.8
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• pp.462-467
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• 2009

Researches and developments on BEMS are performed world-widely through sustainable management in various conditions. However, there are many obstacles to adapt the system in existing buildings because it needs highly expensive equipments, which are designed for newly built buildings, to install. Therefore, there are numerous limits exist when applying the BEMS in established buildings. The purpose of this study estimates the optimization of RF output power in WSN(Wireless Sensor Networks), which is the essential technology to develop PEMS. The results of this study is as follows ; 1) Applying WSN technique in buildings was possible. 2) As RF output power increases, the number of relay node reduced, therefore, the WSN showed more stability. 3) When estimating optimal RF output power in school, it should be considered between the number of relay node and RF output power. 4) Considering battery consumption and possibility of reception, the best suited RF output power is -20dbm in apartment house.

• Journal of the Korean Society of Physical Medicine
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• v.11 no.4
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• pp.79-84
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• 2016

PURPOSE: The purpose of this study was to investigate effects of Horse riding simulator exercise on pain, dysfunction and dynamic balance in adults with nonspecific chronic low back pain. METHODS: In this study, total 19 college students usually complain of low back pain who were randomly divided into the horse riding simulator exercise group (n=10), lumbar strengthening exercise group (n=9) were recruited. Each group carried out for 30 minutes exercise three times a week for 4 weeks. Horse riding simulator exercise group carried out 15 minutes horse riding simulator exercise and 15 minutes lumbar strengthening exercise. Lumbar strengthening exercise group carried out 30 minutes lumbar strengthening exercise. Visual analogue scale (VAS) were measured for evaluation back pain. Korean oswestry disability index (KODI) were measured for dysfunction. Limits of stability (LOS) were measured for dynamic balance. RESULTS: VAS, KODI, LOS results showed a significant change within both horse riding simulator exercise group, lumbar strengthening exercise group. CONCLUSION: Present study suggested that the horse riding simulator exercise can improve back pain, dysfunction, dynamic balance. Horse riding simulator exercise provides more convenience, interest and motivation than conversional therapy and it could be a possible approach to adults with nonspecific chronic low back pain.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.5
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• pp.701-707
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• 2006

Disinfectant residual should be maintained to achieve biological stability during distribution of treated water. The wide distribution of retention times associated with storage and transport of water in a network and the reactivity of disinfectants make it difficult to maintain adequate residuals at critical locations. Rechlorination at some intermediate locations may reduce the total disinfectant dose while keeping residuals within specified limits throughout the water distribution system. In order to select the adequate location of rechlorination for achieving to maintain of residual chlorine throughout the distribution system, EPANET was used in this study. EPANET was well predicted chlorine transport and residual loss in the distribution system. Location of rechlorination was selected to maintain 0.4mg/L of residual chlorine throughout a water distribution system by field investigation and model simulation. The quantity of chlorine may reduced 36.7% and provided smooth residual between 0.42 and 0.60mg/L, when rechlorination would be used continuously at strategic location within the distribution system.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.11
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• pp.1627-1633
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• 2012

This study was to evaluate the feasibility of recycling the solids separated from swine wastewater treatment process as a fuel source for heat production and to provide a data set on the gas emissions and combustion properties. Also, in this study, the heavy metals in ash content were analyzed for its possible use as a fertilizer. Proximate analysis of the solid recovered from the swine wastewater after flocculation with organic polymer showed high calorific (5,330.50 kcal/kg) and low moisture (15.38%) content, indicating that the solid separated from swine wastewater can be used as an alternative fuel source. CO and NOx emissions were found to increase with increasing temperature. Combustion efficiency of the solids was found to be stable (95 to 98%) with varied temperatures. Thermogravimetry (TG) and differential thermal analysis (DTA) showed five thermal effects (four exothermic and one endothermic), and these effects were distinguished in three stages, water evaporation, heterogeneous combustion of hydrocarbons and decomposition reaction. Based on the calorific value and combustion stability results, solid separated from swine manure can be used as an alternative source of fuel, however further research is still warranted regarding regulation of CO and NOx emissions. Furthermore, the heavy metal content in ash was below the legal limits required for its usage as fertilizer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.11
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• pp.916-923
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• 2009

The effects of configuration of fuel and air tubes on the flame stabilization were experimentally investigated in half-closed combustors. Flame behaviors and stabilities of methane, propane, and DME flames were compared by changing tube diameters and the locations of the fuel and air tubes. It was found that flammability limits are significantly affected by the outlet boundary condition, which disturbs compositions of burned and unburned mixtures near the flame base. And it was found that there exist critical inner tube heights, over which flame stability is determined only by the fuel flow rate. Conclusively, flame stabilization is governed by the flame propagation velocity in an ordinary mixing flow and the non-uniform mixture concentration in the combustion space which is affected by flow recirculation and the combustor configuration. The compositions of $NO_x$ and CO were compared to know basic characteristics of methane, propane, and DME flames.

• Journal of Power Electronics
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• v.12 no.3
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• pp.495-502
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• 2012

This paper presents an improved grid voltage control strategy for wind farms with doubly-fed induction generators (DFIGs) connected to distribution networks based on an analysis of the operation limits of DFIG systems. A modified reactive power limit calculation method in different operation states is proposed and a reactive power control strategy during grid voltage dips/rises is further discussed. A control strategy for compensating unbalanced grid voltage, based on DFIG systems, by injecting negative sequence current into the grid through the grid side converter (GSC) is proposed. In addition, the negative current limit of the GSC is discussed. The distribution principle of the negative sequence current among the different DFIG systems in a wind farm is also introduced. The validity of the proposed voltage control strategy is demonstrated by Matlab/Simulink simulations. It is shown that the stability of a wind farm and the power grid can be improved with the proposed strategy.

• Journal of the Korean Society of Combustion
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• v.20 no.1
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• pp.32-42
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• 2015

The combustion instability was experimentally investigated in model gas turbine combustor with dual swirl burner. When such instability occurs, a strong coupling between pressure oscillation and unsteady heat release excites a self-sustained acoustic wave which results in a loud sound, and can even cause fatal damage to the combustor and entire system. In present study, to understand the combustion instability with a premixed mixture, the detailed periods of pressure and heat release data in unstable flame mode were investigated by various measurement methods at relatively rich condition and lean condition near flammable limits. Also, to prepare the utilization of synthetic natural gas (SNG) fuel in gas turbine system, an investigation was conducted using a simulated SNG including methane as a reference fuel to examine the effects of $H_2$ content on flame stability. These results provide that the instability due to flash-back behaviour like CIVB phenomenon occurred at rich condition, while the repetition of relighting and extinction caused the oscillation of lean condition near flammable limit. From the analysis of $H_2$ content effects, it is also confirmed that the instability frequency is proportional to the laminar burning velocity at both rich and lean condition.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.1
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• pp.81-87
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• 2016

Cloud computing technologies are utilized and merged in various domains. Cloud computing technology-based personal cloud service technologies provide mobility and free access by using user centered storages and smart devices such like smart phones and table PCs. Therefore, we should overcome limits on the storage by solving the capacity problems of devices to provide security services in the personal cloud environments It can be addressable to provide the convenience of various security technologies. However, there are some security threats inherited from existing cloud environments and the possibilities of information leakage when devices are lost or stolen. Therefore, we designed a framework for providing secure cloud services by adding objects, such as user authorization, access tokens, set permissions by key generation, and key management assignments, for user management in personal cloud environments. We analyzed the stability of the proposed framework in terms of irreverent use and abuse, access to insiders, and data loss or leakage. And we evaluated the proposed framework in terms of the security with access control requirements in personal cloud environments.

• Journal of Korean Orthopaedic Sports Medicine
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• v.2 no.2
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• pp.119-126
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• 2003

The shoulder is a complex joint and, by virtue of having a large range of motion, is inherently unstable, relying on the surrounding soft tissue structures for stability. The bony joint consists of the glenoid, acromion, and humoral head, while the soft tissues include the glenoid labrum, the glenohumeral ligaments. and coracoacromial ligament as well as the muscles of the rotator cuff, the long head of the biceps, and the scapulothoracic muscles. Dysfunction in any one of these components can cause shoulder problems. The throwing motion involves a series of phases that stress to their limits the dynamic and static restraints of the glenohumeral and scapulothoracic joints. . Therefore, maintaining a balance of proper biomechanical forces is essential to avoiding shoulder injuries in throwing athletes. Over the last decade, signficant advances have been made in the study and understanding of the shoulder mechanics, and pathophysiology of injury. Additionally, advances in surgical techniques, particularly arthroscopy , have aided in the diagnosis of and the developement of less invasive surgical treatments for injuries that do not respond to nonoperative measures. In this article, we reviewed the pathophysiology of injuries , diagnostic techniques, and surgical management of shoulder injuries in throwing athletes .