• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.9
• /
• pp.732-736
• /
• 2016

Air conditioning part designs are moving towards higher efficiency and productivity. The expansion device is one of the core parts of an air conditioning system and controls the refrigerant quantity, evaporation load, compression capacity, and condensation capacity. In this study, an electronic expansion valve for two working fluids ($CO_2$ and R134a) was developed for air conditioning systems in vehicles. The valve uses an eccentric cam driving structure instead of a lead screw to decrease manufacturing costs and increase productivity. The pressure resistance and flow rate performance was evaluated using numerical analysis. At maximum operation conditions and burst pressure conditions with $CO_2$, the maximum stresses on the valve model were about 98 MPa and 223 MPa, respectively. The maximum flow rates of $CO_2$ and R134a with different orifice openings were about 550 kg/h and 386 kg/h, respectively. The performance with R134a was verified by experiments.

• Journal of the Institute of Convergence Signal Processing
• /
• v.13 no.2
• /
• pp.83-90
• /
• 2012

In this paper, an intelligent visual surveillance system based on a NIOS II embedded platform is implemented. By this time, embedded based visual surveillance systems were restricted for a special purpose because of high dependence upon hardware. In order to improve the restriction, we implement a flexible embedded platform, which is available for various purpose of applications. For high speed processing of software based programming, we improved performance of the system which is integrated the SOPC type of NIOS II embedded processor and image processing algorithms by using software programming and C2H(The Altera NIOS II C-To-Hardware(C2H) Acceleration Compiler) compiler in the core of the hardware platform. Then, we constructed a server system which globally manage some devices by the NIOS II embedded processor platform, and included the control function on networks to increase efficiency for user. We tested and evaluated our system at the designated region for visual surveillance.

• Korean Journal of Remote Sensing
• /
• v.20 no.2
• /
• pp.125-137
• /
• 2004

In case of using image sequence taken from a moving camera along a road in an urban area, general video mosaicing technique based on a single baseline cannot create 2-D image mosaics. To solve the drawback, this paper proposed a new image mosaicing technique through 3-D multi-baselines that can create image mosaics in 3-D space. The core of the proposed method is that each image frame has a dependent baseline, an equation of first order, calculated by using ground control point (GCP) of optical flows. The proposed algorithm consists of 4 steps: calculation of optical flows using hierarchical strategy, calculation of camera exterior orientation, determination of multi-baselines, and seamless image mosaics. This paper realized and showed the proposed algorithm that can create efficient image mosaics in 3-D space from real image sequence.

• The Journal of Information Systems
• /
• v.30 no.4
• /
• pp.21-42
• /
• 2021

Purpose In order for companies to continue to grow, they should properly manage human resources, which are the core of corporate competitiveness. Employee turnover means the loss of talent in the workforce. When an employee voluntarily leaves his or her company, it will lose hiring and training cost and lead to the withdrawal of key personnel and new costs to train a new employee. From an employee's viewpoint, moving to another company is also risky because it can be time consuming and costly. Therefore, in order to reduce the social and economic costs caused by employee turnover, it is necessary to accurately predict employee turnover intention, identify the factors affecting employee turnover, and manage them appropriately in the company. Design/methodology/approach Prior studies have mainly used logistic regression and decision trees, which have explanatory power but poor predictive accuracy. In order to develop a more accurate prediction model, XGBoost is proposed as the classification technique. Then, to compensate for the lack of explainability, SHAP, one of the XAI techniques, is applied. As a result, the prediction accuracy of the proposed model is improved compared to the conventional methods such as LOGIT and Decision Trees. By applying SHAP to the proposed model, the factors affecting the overall employee turnover intention as well as a specific sample's turnover intention are identified. Findings Experimental results show that the prediction accuracy of XGBoost is superior to that of logistic regression and decision trees. Using SHAP, we find that jobseeking, annuity, eng_test, comm_temp, seti_dev, seti_money, equl_ablt, and sati_safe significantly affect overall employee turnover intention. In addition, it is confirmed that the factors affecting an individual's turnover intention are more diverse. Our research findings imply that companies should adopt a personalized approach for each employee in order to effectively prevent his or her turnover.

• Nuclear Engineering and Technology
• /
• v.54 no.5
• /
• pp.1674-1685
• /
• 2022

The ball valve is an important device in the pipeline transportation system of nuclear power plants. Its operational stability and safety directly affect the normal working of nuclear power plants. In this study, the transient numerical simulation of the opening and closing process of a ball valve was conducted on the basis of the flow interruption capability experiment of the ball valve by using the moving mesh method and inlet and outlet variable boundary conditions. The flow rate and pressure difference with time of the opening and closing process of the ball valve were studied. The internal flow characteristics of the ball valve under different relative openings were analyzed in conjunction with the typical back-step flow structure. Results show that the transient numerical results agree well with the experimental results. The internal flow characteristics of the ball valve are similar at the same opening during opening and closing process. At small opening, the spool and outlet channels easily form a back-step flow structure. The disappearance and generation of backflow vortices during opening and closing occur at 85% opening and 75% opening, respectively. With the decrease in opening degree, the difference in vortex core area in the flow channel of the ball valve spool in the opening and closing process gradually appears. The research results provide some reference value for the design and optimization of ball valves.

• Smart Media Journal
• /
• v.12 no.5
• /
• pp.46-57
• /
• 2023

As the COVID-19 pandemic and the development of IT technology have led to the gradual popularization of remote and telecommuting, cloud computing technology is advancing, and cyber attack techniques are becoming more sophisticated and advanced. In response to these trends, companies are increasingly moving away from traditional perimeter-based security and adopting Zero Trust to strengthen their security. Zero Trust, based on the core principle of doubting and not trusting everything, identifies all traffic and grants access permissions through a strict authentication process to enhance security. In this paper, we analyze the background of Zero Trust adoption and the adoption policies and trends of countries that are proactively promoting its implementation. Additionally, we propose necessary efforts from governments and organizations to strengthen corporate security and considerations for companies when applying Zero Trust.

• Journal of Korean Society of Forest Science
• /
• v.111 no.1
• /
• pp.115-124
• /
• 2022

This study was conducted to obtain basic data that could help prevent damage caused by slow-moving landslides (land-creep). Specifically, the geological, topographic, and physical characteristics of land-creep were analyzed in Jiphyeon-myeon, Jinju-si. The first and second analyzed land-creeps occurred in 1982 and 2019, respectively. The area damaged in the second land-creep was about 11.5-fold larger than that damaged in the first land-creep. The dominant constituent rock in the land-creep area was sedimentary rock, which seems to be weakly resistant to weathering. The areas that collapsed due to land-creep were related to the presence of separated rocks between the bedding plane in the estimated activity surface over the slope direction and the vertically developed joint surface. Thus, surface water and soil debris were introduced through the gaps of separated rocks. Additionally, the areas collapsed due to the combination of the bedding plane and joint surface shale and sandstone showed an onion structure of weathered outcrop from the edge to inner part caused by weathering from ground water. Consequently, core stones were formed. The study area was a typical area of land-creep in a mountain caused by ground water. Land-creep was classified into convex areas of colluvial land-creep. The landslide-risk rating in the study area was classified into three and five classes. The flow of ground water moved to the northeast and coincided with the direction of the collapse. Soil bulk density in the collapsed area was lower than that in ridge area, which was rarely affected by land-creep. Thus, soil bulk density was affected by the soil disturbance in the collapsed area.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.25 no.5
• /
• pp.1131-1141
• /
• 2015

In this paper, we proposed a new approach of machine learning based method for detecting game-bots from normal players in MMORPG by inspecting the player's action log data especially in-game money increasing/decreasing event log data. DBSCAN (Density Based Spatial Clustering of Applications with Noise), an one of density based clustering algorithms, is used to extract the attributes of spatial characteristics of each players such as a number of clusters, a ratio of core points, member points and noise points. Most of all, even game-bot developers know principles of this detection system, they cannot avoid the system because moving a wide area to hunt the monster is very inefficient and unproductive. As the result, game-bots show definite differences from normal players in spatial characteristics such as very low ratio, less than 5%, of noise points while normal player's ratio of noise points is high. In experiments on real action log data of MMORPG, our game-bot detection system shows a good performance with high game-bot detection accuracy.

• The Korean Society of Law and Medicine
• /
• v.11 no.2
• /
• pp.113-145
• /
• 2010

Nowadays, it is surely the quack which stands as one of the most controversial, problematic. the quack has been a consistent target of contested public protection strategies in the past few centuries in many countries. Recently, complementary and alternative medicine (CAM) is increasingly utilized and accepted by patients and providers throughout the health care system in the world, most accounts attribute this growing acceptability to the shortcomings of conventional medicine, the appeal of CAM's core beliefs, and the growing body of research indicating that CAM actually works. However, the governments of western countries have called for measures to ensure that the public are protected from incompetent and dangerous practitioners. Common to these controversies has been a suggestion to ban, exclude or limit the medical practice of those deemed to be damaging rather than improving the health of individuals as a measure of public protection. This article describes the experiences of western counties' health care system which is moving in a more pluralistic direction. By examining the ways in which regulatory efforts in the countries have come to address what is invariably described as a growing interest in CAM, this study show how the problem of CAM/quackery today is increasingly located in an ethical field of practitioner competency, qualifications, conduct, responsibility and personal professional development, regardless of the form of therapy in question. Many countries developed a series of measures and strategies to contain the acceptance of CAM groups, such as insisting on scientific evidence of safety and efficacy, resisting integration of CAM with conventional medicine and opposing government support for research and education. In a sense, those countries' movements serve to protect not only patients, but the dominant position of medicine and its allied professions, and to maintain existing jurisdictional boundaries within the healthcare system. The popular support for CAM will require that health professional stakeholders continue to address the challenges this poses, and at the same time protect their position at healthcare system. To cope with the quack, professional body, public sector and health authorities should consider the safety of consumers of healthcare and responding to the demands of the community for CAM therapies as well as the claims of the established healthcare professions. Finally, some implications for future health care were suggested.

• Journal of Intelligence and Information Systems
• /
• v.13 no.3
• /
• pp.47-61
• /
• 2007

In SCM (supply chain management), companies are pursuing a new approach through which overall functions within the supply chain, ranging from material purchase to production, distribution, and sales are designed, planned, and managed in an integrated way. The core functions among them are production planning and distribution planning. As these problems are mutually related, they should be dealt with simultaneously in an integrated manner. SCM is large-scale and multi-stage problems. Also, its various kinds of internal or external factors can, at any time, dynamically bring a change to the existing plan or situation. Recently, many enterprises are moving toward an open architecture for integrating their activities with their suppliers, customers and other partners within the supply chain. Agent-based technology provides an effective approach in such environments. Multi-agent systems have been proven suitable to represent domains such as supply chain networks which involve interactions among manufacturing organization, their customers, suppliers, etc. with different individual goals and propriety information. In this paper, we propose a multi-agent system based on the genetic algorithm that make it possible to integrate the production and distribution planning on a real-time basis in SCM. The proposed genetic algorithm produced near optimal solution and we checked that there is a great difference in the results between integrated planning and non-integrated planning.