• The Journal of the Acoustical Society of Korea
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• v.14 no.1E
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• pp.73-82
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• 1995

This paper presents a data structure that implements a mergeable double-ended priority queue ; namely, an improved relaxed min-max-pair heap. It suggests a sequential algorithm to merge priority queues organized in two relaxed min-max heaps : kheap and nheap of sizes k and n, respecrively. This new data sturuture eliminates the blossomed tree and the lazying method used to merge the relaxed min-max heaps in [8]. As a result, the suggested method in this paper requires the time complexity of O(log(log(n/k))*log(k)) and the space complexity of O(n+), assuming that $k{\leq}{\lfloor}log(size(nheap)){\rfloor}$ are in two heaps of different sizes.

• The Transactions of the Korea Information Processing Society
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• v.5 no.5
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• pp.1162-1171
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• 1998

This paper presents a data structure that implements a mergable double-ended priority queue : namely an improved relaxed min-max-pair heap. By means of this new data structure, we suggest a parallel algorithm to merge priority queues organized in two relaxed heaps of different sizes, n and k, respectively. This new data-structure eliminates the blossomed tree and the lazying method used to merge the relaxed min-max heaps in [9]. As a result, employing max($2^{i-1}$,[(m+1/4)]) processors, this algorithm requires O(log(log(n/k))${\times}$log(n)) time. Also, on the MarPar machine, this method achieves a 35.205-fold speedup with 64 processors to merge 8 million data items which consist of two relaxed min-max heaps of different sizes.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.10
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• pp.935-941
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• 2016

Predicting and evaluating ship manoeuvring characteristics are very important not only for the design stage, but also for the existing vessels. There are several ways to predict ship's manoeuvrability and most of them are highly connected with the estimation of hydrodynamic coefficients. This paper presents a new estimation method using the system identification with mathematical algorithms for estimating hydrodynamic coefficient in the ship's mathematical model. Specifically a double ended ferry which equips four azimuth propulsion systems were chosen as benchmark ship and a set of benchmark data which is generated in the fast time simulation software was provided to conduct mathematical optimization process. Also the initial values for the optimization were borrowed from the empirical regression formulas of the simulation software of Rheinmetall Defence ship simulator. Therefore the newly suggested mathematical optimization algorithm gave a successful result for estimation hydrodynamic coefficients. Proper optimization conditions of the objective function and constraints were also verified during the study.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1532-1539
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• 2019

This paper analyzes a new method for reducing boiling water reactor fuel temperature during a Loss of Coolant Accident (LOCA). The method uses a device called Reverse Flow Restriction Device (RFRD) at the inlet of fuel bundles in the core to prevent coolant loss from the bundle inlet due to the reverse flow after a large break in the recirculation loop. The device allows for flow in the forward direction which occurs during normal operation, while after the break, the RFRD device changes its status to prevent reverse flow. In this paper, a detailed simulation of LOCA has been carried out using the U.S. NRC's TRACE code to investigate the effect of RFRD on the flow rate as well as peak clad temperature of BWR fuel bundles during three different LOCA scenarios: small break LOCA (25% LOCA), large break LOCA (100% LOCA), and double-ended guillotine break (200% LOCA). The results demonstrated that the device could substantially block flow reversal in fuel bundles during LOCA, allowing for coolant to remain in the core during the coolant blowdown phase. The device can retain additional cooling water after activating the emergency systems, which maintains the peak clad temperature at lower levels. Moreover, the RFRD achieved the reflood phase (when the saturation temperature of the clad is restored) earlier than without the RFRD.

• Journal of Korean Critical Care Nursing
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• v.10 no.1
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• pp.51-62
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• 2017

Purpose: This study aimed to understand the essence of experiences of patients and family members during flexible visiting in an intensive care unit (ICU). Methods: This is a qualitative study using interviews with open ended questions. We used Colaizzi's method of phenomenological interpretation. Results: Flexible visiting in the ICU impacted the patients and their families in various ways. The following categories were extracted from the patients' experiences with flexible visiting: 1) the opportunity to feel the presence of the family and 2) the burden of unrestricted visiting. The following categories were extracted from the families' experiences with flexible visiting: 1) psychological comfort by convenience 2) being aware of health care professionals and critical care nursing in the intensive care unit, and 3) double trouble. Conclusions: These results showed that flexible visiting in the ICU affected the patients and their families positively and negatively. Therefore, nursing staff need to design psychological and social interventions that address the needs of patients and their families.

• Journal of Sensor Science and Technology
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• v.21 no.2
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• pp.114-120
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• 2012

This paper describes the design, fabrication and testing of a micromachined resonant accelerometer consisting of a symmetrical pair of proof masses and double-ended tuning fork(DETF) oscillators. Under the external acceleration along the input axis, the proof mass applies forces to the oscillators, which causes a change in their resonant frequency. This frequency change is measured to indicate the applied acceleration. Pivot anchor and leverage mechanisms are adopted in the accelerometer to generate larger force from a proof mass under certain acceleration, which enables increasing its scale factor. Finite element method analyses have been conducted to design the accelerometer and a silicon on insulator(SOI) wafer with a substrate glass wafer was used for fabricating it. The fabricated accelerometer has a scale factor of 188 Hz/g, which is shown to be in agreement with analysis results.

• Journal of the Korean housing association
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• v.22 no.4
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• pp.43-50
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• 2011

In an aging society, as the number of people with disabilities increases concerns are raised about the quality of life of these people and their access to a safe environment becomes important. The purpose of this study is to find out the value of accessibility as an attribute of housing. To estimate the value of accessible, barrier-free housing, this study uses the Contingent Valuation Method (CVM) and analyzes the factors which affect the Willingness To Pay (WTP) of survey respondents by using Survival Analysis. In addition, the importance and satisfaction of barrier-free facilities in the dwellings of survey respondents was investigated. Since aging could be an important factor in influencing the need for accessibility, this study surveyed two age groups, one group (212 respondents) of people below the age of 65 and the other (162 respondents) of people above 65. The results of this study show that respondents would pay on average 2.67% more for being barrier-free when answering an open-ended question and 3.87% more for barrier-free housing when using the double referendum model. This is the increase in value that the respondents perceive as a consequence of removing all the architectural barriers from a dwelling. On average, elderly respondents would pay 2.99% of housing price for accessible features compared to 4.40% of the younger group. However, if the elderly who have willingness to pay for accessibility, the value the older group put on barrier-free housing was higher than the value perceived by the younger group. Factors that influence the WTP are importance of barrier-free facilities, education level and housing type. The value of dwellings without barriers estimated in this study shows the potential size and value of this kind of housing market to the housing development sector.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.6
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• pp.66-76
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• 2023

The government recently implemented policies to improve transportation for the disabled passengers. On the other hand, metropolitan public transport still lacks adequate services for these individuals. Many new cities lack urban rail lines and focus on high-floor buses for expansion. Wheelchair users can only access to double-decker low-floor seat express buses for intercity travel. This study examined the necessity and rationale for introducing low-floor seat buses by estimating the user's willingness to pay through a contingent valuation method. Two methods for eliciting the willingness to pay were adopted: open-ended and dichotomous choice questions. The binomial logit model was used to estimate the willingness to pay. The results indicated that the general public is willing to pay an additional 126.7 Korean won, while the disabled passengers are willing to pay an additional 117.5 Korean won. When translated into annual economic benefits, this amounts to approximately 35 billion Korean won.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.18 no.1
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• pp.19-25
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• 2022

Nuclear Power Plants (NPP) should be designed to have sufficient safety margins and to ensure seismic safety against earthquake that may occur during the plant life time. After the 9.12 Gyeongju earthquake accident, the structural integrity of nuclear power plants due to the beyond design basis earthquake is one of key safety issues. Accordingly, it is necessary to conduct structural integrity evaluations for domestic NPPs under beyond design basis earthquake. In this study, the Level 3 LBB (Leak Before Break) evaluation was performed by considering the beyond design basis earthquake for the surge line of a OPR1000 plant of which design basis earthquake was set to be 0.2g. The beyond design basis earthquake corresponding to peak ground acceleration 0.4g at the maximum stress point of the surge line was considered. It was confirmed that the moment behaviors of the hot leg and pressurized surge nozzle were lower than the maximum allowable loading in moment-rotation curve. It was also confirmed that the LBB margin could be secured by comparing the LBB margin through the Level 2 method. It was judged that the margin was secured by reducing the load generated through the compliance of the pipe.

• Nuclear Engineering and Technology
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• v.18 no.3
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• pp.200-208
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• 1986

The loss of coolant accident based on a double-ended cold leg break is analyzed with the discharge coefficient (Ca) of 0.4. This analysis covers the whole transient period from the start of depressurization to the complete refilling of the core by using RELAP4/MOD6-EM and RELAP4/ MOD6-HOT CHANNEL for the system thermal-hydraulics and the fuel performance during the blowdown phase respectively, and RELAP4/MOD6-FLOOD and TOODEE2 during the reflood phase. A simple analytical method has been developed to account for the lower plenum filling by approximating steam-water countercurrent flows and superheated wall effects at the downcomer during the refill period. Based on the informations. at the time of EOB (end-of-bypass), the refill duration time and the initial reflooding temperature were estimated and compared with the results from the RELAP4/MOD6, resulting in a good agreement. In addition, some parametric studies on the EOB were performed. The form loss coefficient between upper head and upper downcomer was found to be sensitive to the occurrence of the spurious EOB. Appropriate form loss coefficients should be taken into account to avoid the flow oscillations at the downcomer. The analyses with the six and three volume core nodalizations, respectively, show much similar trends in the system thermal-hydraulic performance, but the former case is recommended to obtain good results.