• Journal of KIISE:Computing Practices and Letters
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• v.16 no.1
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• pp.11-16
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• 2010

This paper compares and studies scheduling methods to reduce jitter in real-time control systems. While previous research has focused on dynamic-priority scheduling schemes, this paper focuses on fixed-priority scheduling which is more widely used. It is pointed out that previously defined jitter measures might not be useful in enhancing the control performance of a real-time task because the measures are relative values. We present a new jitter measure and a new scheduling scheme for fixed-priority tasks. The experimental results through simulation show that the new scheduling scheme reduces jitter and enhances control performance.

• ETRI Journal
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• v.41 no.5
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• pp.626-636
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• 2019

A novel algorithm for joint user selection and optimal power allocation for Stackelberg game-based revenue maximization in a downlink non-orthogonal multiple access (NOMA) network is proposed in this study. The condition for the existence of optimal solution is derived by assuming perfect channel state information (CSI) at the transmitter. The Lagrange multiplier method is used to convert the revenue maximization problem into a set of quadratic equations that are reduced to a regular chain of expressions. The optimal solution is obtained via a univariate iterative procedure. A simple algorithm for joint optimal user selection and power calculation is presented and exhibits extremely low complexity. Furthermore, an outage analysis is presented to evaluate the performance degradation when perfect CSI is not available. The simulation results indicate that at 5-dB signal-to-noise ratio (SNR), revenue of the base station improves by at least 15.2% for the proposed algorithm when compared to suboptimal schemes. Other performance metrics of NOMA, such as individual user-rates, fairness index, and outage probability, approach near-optimal values at moderate to high SNRs.

• Advances in materials Research
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• v.2 no.4
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• pp.221-235
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• 2013

To obtain bronze with good mechanical properties and high wear resistance, a new bronze (CADZ) is proposed on the basis of various fundamental information. The CADZ consists of the elements Al10.5, Fe4.2, Sn3.7 and Ni3.1, and its design is based on Cu-Al10.5 alloy. The Cu-10.5%Al is very hard and brittle. To obtain the high material ductility of the Cu-10.5%Al alloy, an attempt was made to add a few percent of Sn. Moreover, to make high strength of the Cu alloy, microstructure with small grains was created by the proper amount of Fe and Ni (Fe/Ni = 0.89). The mechanical properties of the CADZ sample have been examined experimentally, and those were compared with commercial bronzes. The tensile strength and wear resistance of CADZ are higher than those for commercial bronzes. Although the ductility of CADZ is the lower level, the strain to failure of CADZ is about 2.0~5.0% higher than that for the Cu-Al10.5 alloy. Details of the microstructural effects on the mechanical properties in the CADZ sample were further discussed using various experimental results.

• Journal of the Korean Solar Energy Society
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• v.28 no.5
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• pp.85-95
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• 2008

Photovoltaic conditioning systems normally use a maximum power point tracking (MPPT) technique to deliver the highest possible power to the load continuously when variations occur in the insolation and temperature. A unique method of tracking the maximum power points (MPPs) and forcing the boost converter system to operate close to these points is presented through deriving small-signal model and transfer function of boost converter considering input capacitor. This paper aims at modeling boost converter including fairly large equivalent series resistance(ESR) of input reservoir capacitor by state-space-averaging method and PWM switch model. In the future, properly designed controller for compensation will be constructed in 3kw real system for maximum photovoltaic power tracking control.

• Journal of Korea Multimedia Society
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• v.24 no.10
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• pp.1435-1448
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• 2021

Recent years, due to the direct or indirect damages caused by meteorological disasters more and more attention have been paid to natural disasters. At same time, diversified and multi-sensory interactive meteorological services is increasingly demanded. In this study, novel interactive meteorological service was compared with the traditional communication methods. Combining with case studies and systems creation, a virtual reality weather simulation framework was proposed, and a realistic virtual game environment providing real-time and historical weather information was created. The primary goal of this study is to build a weather display cabinet game system by using virtual reality technology, and promoting public's understanding of the principles of weather changes. With the interactive games in realistic scenarios, public's awareness for disasters prevention could be promoted. It is helping to change public's traditional understanding of meteorological theories, and will provide a more convenient way for the public to explore more effective weather forecasts. The simulation system is supported by VR technology. It was combined with Leap Motion interactive equipment to make popularization games for weather science. T-test data analysis showed that the application of VR technology in weather games has strong operability and interactivity.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2888-2898
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• 2021

Vital area identification (VAI) is an essential procedure for the design of physical protection systems (PPSs) for nuclear power plants (NPPs). The purpose of PPS design is to protect vital areas. VAI has been improved continuously to overcome the shortcomings of previous VAI generations. In first-generation VAI, a sabotage fault tree was developed directly without reusing probabilistic safety assessment (PSA) results or information. In second-generation VAI, VAI model was constructed from all PSA event trees and fault trees. While in third-generation VAI, it was developed from the simplified PSA event trees and fault trees. While VAIs have been performed for NPPs in full-power operations, VAI for NPPs in low-power and shutdown (LPSD) operations has not been studied and performed, even though NPPs in LPSD operations are very vulnerable to sabotage due to the very crowded nature of NPP maintenance. This study is the first to research and apply VAI to LPSD operation of NPP. Here, the third-generation VAI method for full-power operation of NPP was adapted to the VAI of LPSD operation. In this study, LPSD VAI for a few plant operational states (POSs) was performed. Furthermore, the operation strategy of vital areas for both full-power and LPSD operations was discussed. The LPSD VAI method discussed in this paper can be easily applied to all POSs. The method and insights in this study can be important for future LPSD VAI that reflects various LPSD operational states. Regulatory bodies and electric utilities can take advantage of this LPSD VAI method.

• ETRI Journal
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• v.43 no.5
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• pp.825-834
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• 2021

Based on its simplicity and user-friendly characteristics, OpenMP has become the standard model for programming on shared-memory architectures. Checkpointing-aided parallel execution (CAPE) is an approach that utilizes the discontinuous incremental checkpointing technique (DICKPT) to translate and execute OpenMP programs on distributed-memory architectures automatically. Currently, CAPE implements the OpenMP execution model by utilizing the DICKPT to distribute parallel jobs and their data to slave machines, and then collects the results after executing these distributed jobs. Although this model has been proven to be effective in terms of performance and compatibility with OpenMP on distributed-memory systems, it cannot fully exploit the capabilities of multicore processors. This paper presents a novel execution model for CAPE that utilizes two levels of parallelism. In the proposed model, we add another level of parallelism in the form of multithreaded processes on slave machines with the goal of better exploiting their multicore CPUs. Initial experimental results presented near the end of this paper demonstrate that this model provides significantly enhanced CAPE performance.

• Journal of Multimedia Information System
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• v.8 no.3
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• pp.197-202
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• 2021

Bitcoin and blockchain are often making headlines not only on TV or media but also among the public in today's society. These technologies have been developed after the risk of the centralized financial system came to the fore during the 2007 global financial crisis. Since then, an anonymous inventor called Satoshi Nakamoto penned the bitcoin white paper where a blockchain-based reference implementation was introduced. Bitcoin was able to achieve unprecedented growth by positioning itself as one of the top global currencies in terms of market capitalization after five years since its development. The pace of Vietnam's economic development is notably fast among Asian nations, while the nation was expected to be a Southeast Asian blockchain hub but they have banned virtual currency trading recently. However, they've also designated the State Bank of Vietnam (SBV) as a responsible agency for the research of blockchain-based cryptocurrencies, the construction of a service ecosystem, and their test operations. The fast-growing economy, increasing number of smartphone users, and the Vietnam government's support policies for startups substantiate these efforts. Therefore, this paper attempts to study the current status of Vietnam's blockchain technology that has been considered to be the center of blockchain systems right behind Singapore, and its implications for Korean companies.

• The Korean Journal of Emergency Medical Services
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• v.25 no.3
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• pp.127-143
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• 2021

Purpose: The purpose of the study is to investigate the actual state of activity on domestic and foreign civil anti-disaster organizations, related suggestions, and development plans. Methods: This study used the documentary survey research method and the technical approach method. Civil anti-disaster organizations' information was derived from detailed scholarly monographs, specialty publications, and previous studies of master doctorate dissertation. Results: Volunteer Fire Department and voluntary crime prevention groups show problems related to budgetary deficits and volunteer deficiency. In order to resolve these issues, laws must be enacted to guarantee interest and support. In addition, the Citizen Corps Active in Disaster (CAIND) organization requires a dedicated salary system to address the investment of its workforce and the cost of heavy equipment. Moreover, deficiencies were revealed regarding the lack of systems in support of occupational education and training. In conclusion, several weak points require close attention. Conclusion: The results of this comparative analysis study about the domestic and foreign civil anti-disaster organizations provide insight into identity materialization and concept establishment.

• Smart Structures and Systems
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• v.23 no.2
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• pp.207-214
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• 2019

Achieving a pervious concrete (PC) with appropriate physical and mechanical properties used in pavement have been strongly investigated through the use of different materials specifically from the global waste materials of the populated areas. Discarded tires and the rubber tire particles have been currently manufactured as the recycled waste materials. In the current study, the combination of polymer, silica fume and rubber aggregates from rubber tire particles have been used to obtain an optimized PC resulting that the PC with silica fume, polymer and rubber aggregate replacement to mineral aggregate has greater compressive and flexural strength. The related flexural and compressive strength of the produced PC has been increased 31% and 18% compared to the mineral PC concrete, also, the impact resistance has been progressed 8% compared to the mineral aggregate PC and the permeability with Open Graded Fraction Course standard (OGFC). While the manufactured PC has significantly reduced the elasticity modulus of usual pervious concrete, the impact resistance has been remarkably improved.