• Journal of the Korea Society of Computer and Information
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• v.13 no.2
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• pp.243-250
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• 2008

The coverage algorithm based on Boustrophedon path has been known to be the most efficient in places without or less obstacles If the map of an environmental area thru SLAM algorithm can be obtainable. However, the efficiency of the coverage algorithm based on Boustrophedon path drops drastically when obstacles are complex. In this paper, we propose and implement a new algorithm, which we call Group-k, that efficiently handles the complex area. The Group-k algorithm groups the obstacles and prioritizes the covering sequences with complex rank of the groups. Implementation-based experiments show about 20% improved performance when applying the nor- algorithm, compared to the Boustrophedon path algorithm.

• Journal of Digital Contents Society
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• v.14 no.3
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• pp.349-356
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• 2013

Products of Wi-Fi devices in recent years offer higher throughput and have longer signal coverage which also bring unnecessary signal interference to neighboring wireless networks, and result in decrease of network throughput. Signal interference is an inevitable problem because of the broadcast nature of wireless transmissions. However it could be optimized by reducing signal coverage of wireless devices. On the other hand, smaller signal coverage also means lower transmission power and lower data throughput. Therefore, in this paper, we analyze the relationship among signal strength, coverage and interference of Wi-Fi networks, and as a tradeoff between transmission power and data throughput, we propose a range-aware Wi-Fi network scheme which controls transmission power according to positions and RSSI(Received Signal Strength Indication) of Wi-Fi devices and analyze the efficiency of the proposed scheme by simulation.

• Journal of the Korean Statistical Society
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• v.31 no.2
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• pp.143-152
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• 2002

In an effort to make a right choice among ratio estimation strategies and PPS sampling strategies, we conduct an empirical investigation of the relative performances of three ratio estimation strategies and four PPS estimation strategies using a set of 12 natural populations. The quality of a strategy is measured in the traditional way, namely with the consideration of efficiency, achieved coverage rate of the nominal 99% confidence interval and approach to normality (asymmetry).

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.5
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• pp.688-699
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• 2017

Model-based test, a well-known method of the black box tests, is consisted of the following four steps : model construction using requirement, test case generation from the model, execution of a SUT (software under test) and detection failures. Among models constructed in the first step, state-based models such as UML standard State Machine are commonly used to design event-based embedded systems (e.g., weapon control systems). To generate test cases from state-based models in the next step, coverage-based techniques such as state coverage and transition coverage are used. Round-trip path coverage technique using W-Method, one of coverage-based techniques, is known as more effective method than others. However it has a limitation of low failure observability because the W-Method technique terminates a testing process when arrivals meet states already visited and it is hard to decide the current state is completely same or not with the previous in the case like the GUI environment. In other words, there can exist unrevealed faults. Therefore, this study suggests a Extended W-Method. The Extended W-Method extends the round-trip path to a final state to improve failure observability. In this paper, we compare effectiveness and efficiency with requirement-item-based technique, W-Method and our Extended W-Method. The result shows that our technique can detect five and two more faults respectively and has the performance of 28 % and 42 % higher failure detection probability than the requirement-item-based and W-Method techniques, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.11
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• pp.5464-5488
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• 2019

The multi-population genetic algorithm in multi-target paths coverage has become a top choice for many test engineers. Also, information sharing strategy can improve the efficiency of multi-population genetic algorithm to generate multi-target test data; however, there is still space for some improvements in several aspects, which will affect the effectiveness of covering the target path set. Therefore, a multi-target paths coverage strategy is proposed by improving multi-population genetic algorithm based on individual information sharing among populations. It primarily contains three aspects. Firstly, the behavior of the sub-population covering corresponding target path is improved, so that it can continue to try to cover other sub-paths after covering the current target path, so as to take full advantage of population resources; Secondly, the populations initialized are prioritized according to the matching process, so that those sub-populations with better path coverage rate are executed firstly. Thirdly, for difficultly-covered paths, the individual chromosome features which can cover the difficultly-covered paths are extracted by utilizing the data generated, so as to screen those individuals who can cover the difficultly-covered paths. In the experiments, several benchmark programs were employed to verify the accuracy of the method from different aspects and also compare with similar methods. The experimental results show that it takes less time to cover target paths by our approach than the similar ones, and achieves more efficient test case generation process. Finally, a plug-in prototype is given to implement the approach proposed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1599-1610
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• 2019

Intelligent services have expanded as Internet of Things (IoT) technology has evolved and new requirements emerge to accommodate various services. One new requirement is transmitting data over long distances with low-power. Researchers have developed low power wide area (LPWA) network technology to satisfy the requirement; this can improve IoT network infrastructure and increase the range of services. However, network coverage expansion causes several problems. The traffic load is concentrated at a specific gateway, which causes network congestion and leads to decreased transmission efficiency. Therefore, the approach proposed in this paper attempts to recognize and then avoid congestion through gateway channel hopping. The LPWA network employs multiple channels, so wireless channel hopping is available in a gateway. Devices that are not delay sensitive wait for the gateway to reappear on their wireless channel; delay sensitive devices change the wireless channel along the hopping gateway. Thus, the traffic load and congestion in each wireless channel can be reduced improving transmission efficiency. The proposed approach's performance is evaluated by computer simulation and verified in terms of transmission efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1133-1141
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• 2009

In this paper, we present a distributed fault-tolerant topology control protocol that configure a wireless sensor network to achieve k-connectivity and (k+1)-coverage. One fundamental issue in sensor networks is to maintain both sensing coverage and network connectivity in order to support different applications and environments, while some least active nodes are on duty. Topology control algorithms have been proposed to maintain network connectivity while improving energy efficiency and increasing network capacity. However, by reducing the number of links in the network, topology control algorithms actually decrease the degree of routing redundancy. Although the protocols for resolving such a problem while maintaining sensing coverage were proposed, they requires accurate location information to check the coverage, and most of active sensors in the constructed topology maintain 2k-connectivity when they keep k-coverage. We propose the fault-tolerant topology control protocol that is based on the theorem that k-connectivity implies (k+1)-coverage when the sensing range is at two times the transmission range. The proposed distributed algorithm does not need accurate location information, the complexity is O(1). We demonstrate the capability of the proposed protocol to provide guaranteed connectivity and coverage, through both geometric analysis and extensive simulation.

• Journal of Electrochemical Science and Technology
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• v.14 no.1
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• pp.21-30
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• 2023

This work presents a correlation between the behavior of formic acid oxidation (FAO) on various Bi-modified Pt(poly) disk electrodes and their morphologies observed on Bi-modified Pt(111) disk electrodes using electrochemical scanning tunneling microscopy (EC-STM) to understand the effects of Bi on Pt. To distinguish the FAO activities of Bi on Pt and plain Pt around Bi, additional Pt was intentionally deposited using two different routes: direct route and iodine route. In direct route, Pt was directly deposited on Bi islands and plain Pt sites around Bi islands, while in iodine route, Pt was exclusively deposited on Bi islands by protecting plain Pt sites with adsorbed iodine. Thus, a comparison of FAO performances on the two Bi-modified Pt electrodes with additional Pt (deposited in the different ways) disclosed a difference in FAO performances on plain Pt sites and Bi islands. When Bi coverage was ~0.04, the Bi deposits were scattered Bi islands enhancing FAO on Pt(poly). The additional Pt deposits using direct route increased FAO efficiency, while the ones using iodine route slightly decreased FAO current. The EC-STM observations indicated that Pt deposits around Bi islands, not on Bi islands, were responsible for the FAO current increase on Bi-modified Pt(poly). The FAO efficiency on Bi-modified Pt(poly) with a Bi coverage of ~0.25 increased by a factor of 2. However, the additional Pt deposits using the two Pt deposition routes notably decreased the FAO current. The dependency of FAO on Bi coverage was discussed in terms of electronic effect and ensemble effect.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3233-3240
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• 2012

We demonstrated the combined applications of online protein digestion using trypsin immobilized enzyme reactor (IMER) and dual tandem mass spectrometry with collisionally activated dissociation (CAD) and electron transfer dissociation (ETD) for tryptic peptides eluted through the trypsin-IMER. For the trypsin-IMER, the organic and inorganic hybrid monolithic material was used. By employing the trypsin-IMER, the long digestion time could be saved with little or no sacrifice of the digestion efficiency, which was demonstrated for standard protein samples. For three model proteins (cytochrome c, carbonic anhydrase, and bovine serum albumin), the tryptic peptides digested by the IMER were analyzed using LC-MS/MS with the dual application of CAD and ETD. As previously shown by others, the dual application of CAD and ETD increased the sequence coverage in comparison with CAD application only. In particular, ETD was very useful for the analysis of highly-protontated peptide cations, e.g., ${\geq}3+$. The combination approach provided the advantages of both trypsin-IMER and CAD/ETD dual tandem mass spectrometry applications, which are rapid digestion (i.e., 10 min), good digestion efficiency, online coupling of trypsin-IMER and liquid chromatography, and high sequence coverage.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.11
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• pp.21-27
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• 2013

This paper proposes an adaptive modulation based incremental hop selection scheme which improves network coverage in half-duplex multi-hop networks. The proposed scheme guarantees wide coverage through the operation of multi-hop network while preventing spectral efficiency loss due to the usage of multiple time phases in the half-duplex protocol. Also, we evaluate the average spectral efficiency performance over Nakagami-m fading channel. The simulation results show that the proposed scheme outperforms the existing schemes and the derived evaluation is valid.