• International Journal of Highway Engineering
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• v.11 no.3
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• pp.129-139
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• 2009

The transportation network is a critical infrastructure in the event of natural and human caused disasters such as rainfall, snowfall, and terror and so on. Particularly, the transportation network in an urban area where a large number of population live is subject to be negatively affected from such events. Therefore, efficient traffic operation plans are required to assist rapid evacuation and effective detour of vehicles on the network as soon as possible. Recently, ubiquitous communication and sensor network technology is very useful to improve data collection and connection related emergency information. In this study, we develop a specific algorithm to provide evacuation route and detour information only for vehicles under emergency situations. Our algorithm is based on shortest path search technique and dynamic traffic assignment. We perform the case study to evaluate model performance applying hypothetical scenarios involved terror. Results show that the model successfully describe effective path for each vehicle under emergency situation.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.29-34
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• 2017

Factors of Zero-Energy Building are divided into active and passive factor. Passive factor means insulation, heat bridge of building like insulation, windows and doors, awning, outside etc. and active factor means energy output and efficiency coefficient. Energy output of active factor is achieved by new generating energy. This study anticipated how many effects will be produced when not new generating energy but Vehicle to Building; V2B, bi-directional charging and discharging technology, is applied to Zero-Energy Building. In new generating energy, power generation will be anticipated by geography and climate, but in V2B, several input variable like user's discharging intention and number of usable charger etc. should be considered. We can check how much V2B contribute to the Zero-Energy Building by anticipated results, and that results should be anticipated by using probabilitic method because there is few statistical data. This study anticipate change of charging and discharging pattern, based by Demand Response slot, by using monte carlo method among the probabilitic methods.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.495-501
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• 2016

Mineral oil has been widely used as an insulating oil for electrical transformers for a long time, but the necessity of employing new insulation oil such as vegetable oil has been increased due to urgent needs for the biodegradability when it leaks and also for the thermal stability at a higher operation temperature. Although specific periods are required between the production and consumption, there are still short of the data to prove the insulation oils' storage stability depending upon various circumstances and their resources. Thus, this paper demonstrates the insulation oils' oxidation characteristics of both mineral and vegetable oils when each was exposed to different environments for 12 weeks. From this test, some properties including total acid number, water content and dielectric breakdown were changed under specific conditions and resources. Vegetable oils showed higher hydrophilicity and water saturation than those of mineral oils due to their molecular compositions. Under sunlight exposure condition, all insulation oils oxidized and changed their properties when exposing to the direct light, regardless of the resource used.

• Journal of the Korean Society for Railway
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• v.11 no.4
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• pp.349-356
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• 2008

Put Safety-critical systems related to the railway communications are currently undergoing changes. Mechanical and electro-mechanical devices are being replaced by programmable electronics that are often controlled remotely via communication networks. Therefore designers and operators now not only have to contend with component failures and user errors, but also with the possibility that malicious entities are seeking to disrupt the services provided by theirs systems. Recognizing the safety-critical nature of the types of communications required in rail control operations, the communications infrastructure will be required to meet a number of safety requirements such as system faults, user errors and the robustness in the presence of malicious attackers who are willing to take determined action to interfere in the correct operation of a system. This paper discusses the safety strategies employed in the railway communications and proposes a security mechanism for Korean railway communication system. We present the developed communication safety evaluation tool based on the proposed security mechanism and also evaluate its protecting capability against the threats of masquerading, eavesdropping, and unauthorized message manipulation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3D
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• pp.295-306
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• 2008

The Intersection is inner traffic facilities and the space where the roads are intersected and connected. And also, the Intersection is the decision-making section for drivers to select the route according to the geometric structure and operation method. However decision-making section cause to raise car accidents rate because it imposes a heavy burden on drivers. In that reason, many countries such as Europe use the Roundabouts to reduce the numbers of decision making and collision. In Korea, the kinds of method are just introduced and it is using now but there are no exact standards. Hence, this study suggests the process to evaluate and determine the types of Intersection which are based on the traffic flow (congestion) and traffic safety (accidents). Firstly, this study presents the number of accident at each Intersection which is depended on the traffic volume. Secondly, this study calculates and analysis the accident at signalized Intersection, non-signalized Intersection and Roundabout by TSIS-NETSIM program. Thirdly, this study concludes the best suitable Intersection type through the materials which are mentioned before.

• KIPS Transactions on Software and Data Engineering
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• v.4 no.6
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• pp.253-260
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• 2015

When we buy items in online stores, it is common to face recommended items that meet our interest. These recommendation system help users not only to find out related items, but also find new things that may interest users. Recommendation system has been widely studied and various models has been suggested such as, collaborative filtering and content-based filtering. Though collaborative filtering shows good performance for predicting users preference, there are some conditions where collaborative filtering cannot be applied. Sparsity in user data causes problems in comparing users. Systems which are newly starting or companies having small number of users are also hard to apply collaborative filtering. Content-based filtering should be used to support this conditions, but content-based filtering has some drawbacks and weakness which are tendency of recommending similar items, and keeping history of a user makes recommendation simple and not able to follow up users preference changes. To overcome this drawbacks and limitations, we suggest weighted window assisted user history based recommendation system, which captures user's purchase patterns and applies them to window weight adjustment. The system is capable of following current preference of a user, removing useless recommendation and suggesting items which cannot be simply found by users. To examine the performance under user and data sparsity environment, we applied data from start-up trading company. Through the experiments, we evaluate the operation of the proposed recommendation system.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.9
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• pp.385-396
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• 2017

Many IoT platforms have been proposed for various IoT devices, from low-end to high-end performance. We previously proposed a new IoT platform called MinT that supports the operation of the sensing devices and network communication. In the proposed platform, the things can flexibly connect to each other and efficiently share their information. Most IoT platforms, including the MinT, support thread pooling to quickly process requests. However, using a thread pool with a fixed thread count can cause network delay and inefficient energy consumption. In this paper, we propose an enhanced method to manage the thread pool efficiently by adjusting the number of threads every cycle to regulate the device's performance. In particular, we aim to improve the performance of the Interaction Thread Pool Group, which is responsible for analyzing, processing, and re-transmitting the received packets. The experiment shows that the improved method increases the average throughput by approximately 25% compared to the existing platforms. Finally, using the proposed method, the MinT can reduce the transmission delay and energy consumption of devices in the IoT environment.

• Journal of Chest Surgery
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• v.33 no.6
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• pp.469-475
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• 2000

Background: Thoracic aortomyoplasty is one of the surgical treatment for heart failure and has advantages over artificial heart or intraaortic balloon pumps. It uses autogenous skeletal muscles and solves problems such as energy source. However its use in clinical settings has been limited. This preliminary study was designed to develop surgical technique and to determine the effect of acute descending thoracic aortomyoplsty. Material and Method: Thirteen adult Mongrel dogs were used. The left latissimus dorsi muscle was wrapped around the descending aorta under general anesthesis. Swan-Ganz and microtipped Millar catheter were used for the hemodynamics and endocaridial viability ratio. Data were collected with myostimulator on and off in normal hearts and the ischemic hearts. Result: In normal hearts, the mean aortic diastolic pressure increased from 72$\pm$15mmHg at baseline to 78$\pm$13mmHg with stimulator on. Coronary perfusion pressure increased from 61$\pm$11mmHg to 65$\pm$9mmHg. Diastolic time increased from 0.288$\pm$0.003 msec to 0.290$\pm$0.003msec. Systolic time decreased from 0.164$\pm$0.002msec to 0.160$\pm$0.002 msec. Endocardial viability ratio increased from 1.21$\pm$0.22 to 1.40$\pm$0.18. In ischemic hearts, mean aortic diastolic pressure incrased from 56$\pm$21mmHg at baseline to 61$\pm$15mmHg with stimulator on. Coronary perfusion pressure increased from 48$\pm$17mmHg to 52$\pm$15mmHg. Diastolic time increased from 0.290$\pm$0.003 msec to 0.313$\pm$0.004msec. Systolic time decreased from 0.180$\pm$0.002 msec to 0.177$\pm$0.003 msec. Endovascular viability ratio increased from 0.9$\pm$0.31 to 1.1$\pm$0.31. The limited number of cases ruled out the statistic significance. Conclusion: Descending thoracic aortomyoplasty is a simple operation designed to use patient's own skeletal muscles. It trends to increase diastolic augmentation and coronary perfusion pressure. Modification of surgical technique and stimulator protocol would maximize the effect to assist the heart.

• Journal of Chest Surgery
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• v.31 no.7
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• pp.668-673
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• 1998

During the past several years, the maze operation has become the most effective method of treatment for chronic atrial fibrillation. When the maze procedure is done concomittantly with other cardiac operations, surgeons, in their initial experiences, may be concerned about the additional operative risks and uncertainty of the results. We performed the Cox-maze III procedure in six cases of chronic atrial fibrillation associated with mitral, mitral & aortic, or coronary arterial disease. Maze III procedure was done with open mitral commissurotomy(3 cases), mitral valve replacement(1 case), aortic and mitral valve replacement(1 case), and two-vessel coronary bypass graft(1 case). In spite of rather prolonged aortic cross clamp time, cardiac recovery was uneventful in all cases. No cases required reexploration for postoperative bleeding. All patients showed regular sinus rhythms immediate or between 2 and 20 days postoperateratively. Transient postoperative supraventricular arrhythmarias were easily controlled by various antiarrhythmic agents. In follow up evaluations, all cases showed regular sinus rhythm on ECG and the right and left atrial transport function was confirmed by Doppler echocardiography in all except one. Though our experience was limited in case number, the Cox-maze III procedure was effective in controlling the chronic atrial fibrillation without serious additional operative risks.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.3
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• pp.379-389
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• 2022

The number of public transportation users has dropped drastically due to COVID-19. In this work, my survey was conducted to uncover the factors that influence citizens' travel patterns. Data were collected and logistic regression analysis on the shifts in transportation was undertaken. Additionally, an importance-performance analysis was carried out to investigate how to effectively operate public transportation systems and improve facilities. The main research findings were as follows: First, the more individuals were concerned about COVID-19 (+) and being infected when using public transportation (+), the greater the tendency to switch to private transportation modes. Secondly, when it came to personal traits, respondents who could drive a car (+) or owned a car (+)or did more online shopping (+) or used public transportation for trips (+) tended to switch over, compared with respondents who could not drive or did not own a caror used public transportation to commute. In addition, respondents who were vaccinated (-) or had more household members tended not to switch transportation modes, compared with those who were not vaccinated or had fewer household members. Third, it is important to continue the following efforts to safeguardhygiene linked to public transportation: wearing masks, disinfecting hands, controlling diseases, and general cleaning. The conclusion was that it is important to put traffic congestion and ventilation issues first, especially in regards public transportation, which was not rated as satisfactory enough compared to its importance. The research findings can provide useful basic data when establishing countermeasures to the current COVID-19 circumstances in the areas of public transportation operation and management and in the event of an infectious disease outbreak in the future.