• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.4
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• pp.1337-1358
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• 2015

In this paper, we present an analytical and simulated study on the performance of adaptive vehicular ad hoc networks (VANET) priority based on Transmission Distance Reliability Range (TDRR) and data type. VANET topology changes rapidly due to its inherent nature of high mobility nodes and unpredictable environments. Therefore, nodes in VANET must be able to adapt to the ever changing environment and optimize parameters to enhance performance. However, there is a lack of adaptability in the current VANET scheme. Existing VANET IEEE802.11p's Enhanced Distributed Channel Access; EDCA assigns priority solely based on data type. In this paper, we propose a new priority scheme which utilizes Markov model to perform TDRR prediction and assign priorities based on the proposed Markov TDRR Prediction with Enhanced Priority VANET Scheme (MarPVS). Subsequently, we performed an analytical study on MarPVS performance modeling. In particular, considering five different priority levels defined in MarPVS, we derived the probability of successful transmission, the number of low priority messages in back off process and concurrent low priority transmission. Finally, the results are used to derive the average transmission delay for data types defined in MarPVS. Numerical results are provided along with simulation results which confirm the accuracy of the proposed analysis. Simulation results demonstrate that the proposed MarPVS results in lower transmission latency and higher packet success rate in comparison with the default IEEE802.11p scheme and greedy scheduler scheme.

• Journal of information and communication convergence engineering
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• v.2 no.4
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• pp.214-218
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• 2004

In this paper, we have analyzed TCP performance over wireless correlated fading links with and without Snoop protocol. For a given value of the packet error rate, TCP performance without Snoop protocol is degraded as the fading is getting fast (i.e. the user moves fast). When Snoop protocol is introduced in the base station, TCP performance is enhanced in most wireless environments. Especially the performance enhancement derived from using Snoop protocol is large in fast fading channel. This is because packet errors become random and sporadic in fast fading channel and these random packet errors (mostly single packet errors) can be compensated efficiently by Snoop protocol's local packet retransmissions. But Snoop protocol can't give a large performance improvement in slow fading environments where long bursts of packet errors occur. Concerning to packet error rate, Snoop protocol results in the highest performance enhancement in the channel with mid-high values of packet error rate. This means Snoop protocol cannot fully fulfill its ability under too low or too high packet error rate environments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.43-49
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• 2017

In this paper, we propose the scheduling scheme of IEEE802.15.4e TSCH which is not specified in standard specification. The proposed scheme schedules the link by cooperating among the devices. A new device scans EBs(Enhanced Beacons) from network. An advertiser device broadcasts an enhanced beacon frame including links information on allocated channel offset and time-slots, and a new device can determine its own channel offset and time-slot. It's performance on maximum throughput and minimum delay is evaluated by comparing the proposed approach with a typical single channel IEEE802.15.4.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3272-3285
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• 2016

Recently, Vector of Locally Aggregated Descriptors (VLAD) has been proposed to index image by compact representations, which encodes powerful local descriptors and makes significant improvement on search performance with less memory compared against the state of art. However, its performance relies heavily on the size of the codebook which is used to generate VLAD representation. It indicates better accuracy needs higher dimensional representation. Thus, more memory overhead is needed. In this paper, we enhance VLAD image representation by using two level hierarchical-codebooks. It can provide more accurate search performance while keeping the VLAD size unchanged. In addition, hierarchical-codebooks are used to construct multiple inverted files for more accurate non-exhaustive search. Experimental results show that our method can make significant improvement on both VLAD image representation and non-exhaustive search.

• Korean Journal of Radiology
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• v.23 no.6
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• pp.598-614
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• 2022

While ultrasound (US) is considered an important tool for hepatocellular carcinoma (HCC) surveillance, it has limited sensitivity for detecting early-stage HCC. Abbreviated MRI (AMRI) has recently gained popularity owing to better sensitivity in its detection of early-stage HCC than US, while also minimizing the time and cost in comparison to complete contrast-enhanced MRI, as AMRI includes only a few essential sequences tailored for detecting HCC. Currently, three AMRI protocols exist, namely gadoxetic acid-enhanced hepatobiliary-phase AMRI, dynamic contrast-enhanced AMRI, and non-enhanced AMRI. In this study, we discussed the rationale and technical details of AMRI techniques for achieving optimal surveillance performance. The strengths, weaknesses, and current issues of each AMRI protocol were also elucidated. Moreover, we scrutinized previously performed AMRI studies regarding clinical and technical factors. Reporting and recall strategies were discussed while considering the differences in AMRI protocols. A risk-stratified approach for the target population should be taken to maximize the benefits of AMRI and the cost-effectiveness should be considered. In the era of multiple HCC surveillance tools, patients need to be fully informed about their choices for better adherence to a surveillance program.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.3
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• pp.155-166
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• 2008

The performance evaluation of a new building is becoming more important because efficient design alone is often not sufficient to deliver an efficient building. However, there is a lack of standard evaluation methods to measure the energy performance of a new construction that has Energy Conservation Design Measures(ECDMs). This study presents an enhanced method based on calibrated whole-building simulation for evaluating the energy performance of new commercial buildings and demonstrates its use using a case-study building, including: an Energy Use Index(EUI) comparison with sub-metered data and an evaluation of the performance of specific ECDMs. The use of this method has determined that the case-study building was shown to use approximately 47% less energy than the base-case building that has the same shape and function as the case-study building(i.e., calibrated as-built simulation mode]), but doesn't include the simulated ECDMs.

• Advances in nano research
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• v.17 no.2
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• pp.157-165
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• 2024

This paper discusses the importance of carbon nanotubes (CNTs) in enhancing performance and resistance of tennis rackets with the application of nanotechnology. This paper discusses how nanomaterials work toward making the equipment lighter, stronger, and more durable by combining CNTs with composite materials in Tennis Rackets. Distinctive properties of the CNTs, such as the very high strength-to-weight ratio and exceptional mechanical resilience, have been exploited in racket performance optimization for better power transmission, increased control on shots, and improved durability. Resistance to wear and tear is discussed in terms of the life of a CNT-enhanced tennis racket and its continued performance with time. The findings imply that the CNTs increase the security and overall performance of tennis rackets, hence promising further innovation in sports technology equipment and the various performances expected from users.

• Journal of Information Processing Systems
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• v.5 no.1
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• pp.11-18
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• 2009

As well as providing various APIs for the development of inference engines and storage models, Jena is widely used in the development of systems or tools related with Web ontology management. However, Jena still has several problems with regard to the development of real applications, one of the most important being that its query processing performance is unacceptable. This paper proposes a storage model to improve the query processing performance of the original Jena storage. The proposed storage model semantically classifies OWL elements, and stores an ontology in separately classified tables according to the classification. In particular, the hierarchical knowledge is managed, which can make the processing performance of inferable queries enhanced and stores information. It enhances the query processing performance by using hierarchical knowledge. For this paper an experimental evaluation was conducted, the results of which showed that the proposed storage model provides a improved performance compared with Jena.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.2
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• pp.1-9
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• 2019

In a ground-source heat pump (GSHP) system, a vertical ground heat exchanger (GHE) is widely accepted due to a higher thermal performance. In the vertical GHE, grout (also called grouting material) plays an important role in the heat transfer performance and the initial installation cost of the GHE. Bentonite-based grout has been used in practice because of its high swelling potential and low hydraulic conductivity. This study evaluated the thermo-physical properties of the bentonite-based grouts through lab-scale measurements. In addition, we conducted performance simulation to analyze the effect of mixed ratio of grouts on the design length and thermal performance of the vertical GHE. The simulation results show that thermally-enhanced grouts improve the heat transfer performance of the vertical GHE and thus reduce the design length of GHE pipe.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.47 no.2
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• pp.93-106
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• 2024

As the complexity and uncertainty of international construction projects increase, the importance of risk management capabilities in the construction industry has become more pronounced. Accordingly, Enterprise Risk Management (ERM) has become a widely adopted approach among organizations as a new way for more effective risk management. Despite its growing application, research related to ERM is still in its infancy, and most of the existing studies have been limited to financial industries. Therefore, this study aims to empirically examine the influence of ERM's core elements on project risk management (PRM) and project performance within construction firms. Our findings indicate that the key ERM components-organization, policy, and culture-significantly enhance PRM processes, underscoring their critical role and importance. Additionally, effective PRM positively affects project outcomes, highlighting its significance for construction companies engaged in international projects. While ERM does not directly impact project performance, it indirectly improves outcomes through enhanced PRM capabilities. It suggests that ERM will contribute to the firm's performance by improving the firm's PRM capability through policies and a risk-focused culture corresponding to the adopted ERM organization and system..