• Transactions of the Korean Society of Automotive Engineers
• /
• v.3 no.5
• /
• pp.47-55
• /
• 1995

Cylindrical chokes are used widely as components of hydraulic equipments. The dynamic charac teristics between flowrate and pressure drop through the cylindrical chokes were discussed by the frequency characteristics of the chokes. It was assumed no pressure recovery occured at the downstream neighborhood of the choke. The pulsating jetflow from outlet of cylindrical chokes shows very complex behaviours which are quite different from the steady jetflow but it is not clarified quantitatively. In order to utilize the chokes as a flowmeter, it is indispensable to discuss the estimation of the dynamics of pressure drop in the downstream jetflow region of cylindrical chokes. In this experimental study, the dynamic behaviours of the jetflow in the downstream region of cylindrical chokes are investigated precisely by using flow visualization. In the results of experimental sutdy, it is clarified that the retachment length depended on pressure wave is compared with it depended on velocity wave.

• Nuclear Engineering and Technology
• /
• v.49 no.3
• /
• pp.484-494
• /
• 2017

In industrial plants such as nuclear power plants, system operations are performed by embedded controllers orchestrated by Supervisory Control and Data Acquisition (SCADA) software. A targeted attack (also termed a control aware attack) on the controller/SCADA software can lead a control system to operate in an unsafe mode or sometimes to complete shutdown of the plant. Such malware attacks can result in tremendous cost to the organization for recovery, cleanup, and maintenance activity. SCADA systems in operational mode generate huge log files. These files are useful in analysis of the plant behavior and diagnostics during an ongoing attack. However, they are bulky and difficult for manual inspection. Data mining techniques such as least squares approximation and computational methods can be used in the analysis of logs and to take proactive actions when required. This paper explores methodologies and algorithms so as to develop an effective monitoring scheme against control aware cyber attacks. It also explains soft computation techniques such as the computational geometric method and least squares approximation that can be effective in monitor design. This paper provides insights into diagnostic monitoring of its effectiveness by attack simulations on a four-tank model and using computation techniques to diagnose it. Cyber security of instrumentation and control systems used in nuclear power plants is of paramount importance and hence could be a possible target of such applications.

• Nuclear Engineering and Technology
• /
• v.53 no.3
• /
• pp.911-919
• /
• 2021

In this paper, the design stress intensity values for the plate-type fuel assembly for research reactor are presented. Through a tensile test, the material properties of the cladding (aluminum alloy 6061) and structural material (aluminum alloy 6061-T6), in this case the yield and ultimate tensile strengths, Young's modulus and the elongation, are measured with the temperatures. The empirical equations of the material properties with respect to the temperature are presented. The cladding undergoes several heat treatments and hardening processes during the fabrication process. Cladding strengths are reduced compared to those of the raw material during annealing. Up to a temperature of 150 ℃, the strengths of the cladding do not significantly decrease due to the dislocations generated from the cold work. However, over 150 ℃, the mechanical strengths begin to decrease, mainly due to recrystallization, dislocation recovery and precipitate growth. Taking into account the uncertainty of the 95% probability and 95% confidence level, the design stress intensities of the cladding and structural materials are established. The presented design stress intensity values become the basis of the stress design criteria for a safety analysis of plate-type fuels.

• Journal of Distribution Science
• /
• v.20 no.2
• /
• pp.91-100
• /
• 2022

Purpose: The sports industry is a major form of leisure and entertainment, but the industry was tremendously affected by the Covid-19 pandemic. This study gives solutions for sports leisure retail stores to the effects of the Covid-19 crisis on consumers' sports products purchasing habits and then gives a logical conclusion regarding the findings of the topic. Research design, data and methodology: Scant research is available to feedback for owners and managers of sports leisure retail stores which elements could be considered to recover their business prior to the pandemic. For achieving this, this study investigated total 284 responses in the retail stores and conducted the ANOVA analysis to compare the level of intensity on the impact Covid 19 pandemic. Results: Our findings suggests that there was a statistically recognizable difference at the significance level of probability between the mean value of the impact index of Covid 19 pandemic and key recovery strategies, indicating the high degree of Covid 19 impact can be reducing by four solutions. Conclusions: Finally, this study concludes the specific entertainment elements that influence the purchasing behavior of consumers will ensure that the Sports industry deals with its internal problems first without necessarily looking at the outside factors such as the pandemic.

• Journal of the Korean Society of Safety
• /
• v.38 no.1
• /
• pp.18-24
• /
• 2023

Severe natural disasters and man-made attacks such as terrorism are causing unprecedented disruptions in power systems. Due to rapid climate change and the aging of energy infrastructure, both the frequency of failure and the level of damage are expected to increase. Resilience is a concept proposed to respond to extreme disaster events that have a low probability of occurrence but cause enormous damage and is defined as the ability of a system to recover to its original function after a disaster. Resilience is a comprehensive indicator that can include system performance before and after a disaster and focuses on preparing for all possible disaster scenarios and having quick and efficient recovery actions after an incident. Various studies have been conducted to evaluate resilience, but studies on economic damage considering the duration of a power outage are scarce. In this study, we propose an optimal algorithm that can identify failures after an extreme disaster and restore the load on the distribution system through emergency distributed power generation input and system reconfiguration. After that, the cost of power outage damage is analyzed by applying VoLL and CDF according to each restoration strategy.

• Journal of the Korean Society of Industry Convergence
• /
• v.27 no.2_1
• /
• pp.257-268
• /
• 2024

Soccer is type of sport that carries a high risk of injury. Injury is not only cause in the unlucky soccer carrier and also team performance as well as financial effects can be worse since soccer is a team-based game. The duration of recovery from a soccer injury typically relies on its type and severity. Therefore, we conduct this research in order to predict the probability of players injury type using machine learning technologies in this paper. Furthermore, we compare different machine learning models to find the best fit model. This paper utilizes various supervised classification machine learning models, including Decision Tree, Random Forest, K-Nearest Neighbors (KNN), and Naive Bayes. Moreover, based on our finding the KNN and Decision models achieved the highest accuracy rates at 70%, surpassing other models. The Random Forest model followed closely with an accuracy score of 62%. Among the evaluated models, the Naive Bayes model demonstrated the lowest accuracy at 56%. We gathered information about 54 professional soccer players who are playing in the top five European leagues based on their career history. We gathered information about 54 professional soccer players who are playing in the top five European leagues based on their career history.

• Journal of Korea Water Resources Association
• /
• v.51 no.8
• /
• pp.703-711
• /
• 2018

Water distribution system (WDS) pipe bursts are caused from excessive pressure, pipe aging, and ground shift from temperature change and earthquake. Prompt detection of and response to the failure event help prevent large-scale service interruption and catastrophic sinkhole generation. To that end, this study proposes a improved Western Electric Company (WECO) method to improve the detection effectiveness and efficiency of the original WECO method. The original WECO method is an univariate Statistical Process Control (SPC) technique used for identifying any non-random patterns in system output data. The improved WECO method multiples a threshold modifier (w) to each threshold of WECO sub-rules in order to control the sensitivity of anomaly detection in a water distribution network of interest. The Austin network was used to demonstrated the proposed method in which normal random and abnormal pipe flow data were generated. The best w value was identified from a sensitivity analysis, and the impact of measurement frequency (dt = 5, 10, 15 min etc.) was also investigated. The proposed method was compared to the original WECO method with respect to detection probability, false alarm rate, and averaged detection time. Finally, this study provides a set of guidelines on the use of the WECO method for real-life WDS pipe burst detection.

• Tuberculosis and Respiratory Diseases
• /
• v.58 no.3
• /
• pp.213-229
• /
• 2005

The first and the longest criminal indictment case of Korean medico-legal battle, so called BORAMAE Hospital Incident, was finally on its end by Korean Supreme Court's decision on June 24, 2004, after 7 years long legal dispute via Seoul District Court and Seoul Superior Appeal Court's decision. Boramae Hospital case was the first Korean legal case of Withdrawing Life-sustaining treatment of mechanical respirator on 58 years old Extradural Hematoma victim who was on Respirator under Coma after multi-organ failure postoperatively(APACHE II score: 34-39). Two physicians who have involved patient's care and had helped to make discharge the Near-death patient to home after repeated demand of patient's wife, due to economic reason, were sentenced as homicidal crime. This review article will discuss the following items with the review of US cases, Quinlan(1976), Nancy Cruzan(1990), Barber (1983), Helen Wanglie(1990), Baby K (1994) and Baby L cases, along with Official Statement of ATS and other Academic dignitaries of US and World.: [1] Details of Boramae Hospital incident, medical facts description and legal language of homicidal crime sentence. [2] The medical dispute about the legal misinterpretation of patient's clinical status, regarding the severity of the victim with multi-organs failure on Respirator under coma with least chance of recovery, less than 10% probability. [3] Case study of US, of similar situation. [4] Introduction of ATS official Statement on Withdrawing/ Withholding Life sustaining treatment. [5] Patient Autonomy as basic principle. [6] The procedural formality in Medical practise for keeping the legitimacy. [7] The definition of Medical Futility and its dispute. [8] Dying in Dignity and PAS(Physician Assisted Suicide)/and/or Euthanasia [9] The Korean version of "Dying in Dignity", based on the Supreme Court's decision of Boramae Hospital incident (2004.6.24.) [10] Summary and Author's Note for future prospects.

• Journal of Information Processing Systems
• /
• v.6 no.3
• /
• pp.413-434
• /
• 2010

Wireless sensor networks are usually characterized by dense deployment of energy constrained nodes. Due to the usage of a large number of sensor nodes in uncontrolled hostile or harsh environments, node failure is a common event in these systems. Another common reason for node failure is the exhaustion of their energy resources and node inactivation. Such failures can have adverse effects on the quality of the real-time services in Wireless Sensor Networks (WSNs). To avoid such degradations, it is necessary that the failures be recovered in a proper manner to sustain network operation. In this paper we present a dynamic Energy efficient Real-Time Job Allocation (ERTJA) algorithm for handling node failures in a cluster of sensor nodes with the consideration of communication energy and time overheads besides the nodes' characteristics. ERTJA relies on the computation power of cluster members for handling a node failure. It also tries to minimize the energy consumption of the cluster by minimum activation of the sleeping nodes. The resulting system can then guarantee the Quality of Service (QoS) of the cluster application. Further, when the number of sleeping nodes is limited, the proposed algorithm uses the idle times of the active nodes to engage a graceful QoS degradation in the cluster. Simulation results show significant performance improvements of ERTJA in terms of the energy conservation and the probability of meeting deadlines compared with the other studied algorithms.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.10 s.352
• /
• pp.46-54
• /
• 2006

In this paper, we propose a digital transceiver that can overcome the problems which current analog transceivers have. For the proposed transceiver, we assumed a frequency resource that consists of discrete and narrow channels. We also assumed that person-to-group, group-to-group, as well as person-to-person, voice and data communications with moderate security should be devisedand the data rate is 1 Mbps with simultaneous voice and data. Frequency hewing spread spectrum (FH-SS) and differential 8-PSK (D8PSK) were adopted for security reasons and bandwidth constraints, and for the reduction of implementation complexity, respectively. For the carrier and the symbol timing recovery, the structure of the preamble was proposed based on the IEEE 802.11 FHSS frame format to improve detection probability. The computer simulation results and power budget analysis implies that the proposed system can be usedin simple wireless communications in place of such as analog walkie-talkies.