• Journal of KIISE:Information Networking
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• v.33 no.6
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• pp.428-437
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• 2006

Wireless ad-hoc routing has been extensively studied and many clever schemes have been proposed over the last several years. One class of ad-hoc routing is geographic routing where each intermediate node independently selects the next hop using the given location information of destination. Geographic routing, which eliminates the overhead of route request packet flooding, is scalable and suitable for large scale ad hoc networks. However, geographic routing may select the long detour paths when there are voids between a source and a destination. In this paper, we propose a novel geographic routing approach called Geographic Landmark Routing(GLR). GLR recursively discovers the intermediate nodes called landmarks and constructs sub-paths that connect the subsequent landmarks. Simulation results on various network topologies show that GLR significantly improves the performance of geographic routing.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.1
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• pp.75-79
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• 2010

Wireless sensor networks (WSN) are widely used in many applications. WSN acquires the data of surrounding environments with sensors attached to each node. It is important to design sensor networks that can communicate energy-efficiently as well as to get sensor readings with high accuracy. In this paper, we propose a novel routing scheme that assures high accuracy and significantly reduces data transmission costs in WSN with faults. First, we organize a number of network topologies randomly for routing sensor readings to the base station. Because every sensor node is connected each other with a single path, redundant transmissions are not incurred. It can reduce unnecessary transmissions and guarantee final sensor readings with high accuracy. To show the superiority of our scheme, we compare it with an existing multi-path routing scheme. In the result, our scheme has similar accuracy as the existing scheme and reduces unnecessary data transmissions by about 70% over the existing technique.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1037-1047
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• 2017

The Differential Power Processing (DPP) converter is a promising multi-module photovoltaic inverter architecture recently proposed for photovoltaic systems. In this paper, a DPP converter architecture, in which each PV-panel has its own DPP converter in shunt, performs distributed maximum power point tracking (DMPPT) control. It maintains a high energy conversion efficiency, even under partial shading conditions. The system architecture only deals with the power differences among the PV panels, which reduces the power capacity of the converters. Therefore, the DPP systems can easily overcome the conventional disadvantages of PCS such as centralized, string, and module integrated converter (MIC) topologies. Among the various types of the DPP systems, the feed-forward method has been selected for both its voltage balancing and power transfer to a modified H-bridge inverter that needs charge balancing of the input capacitors. The modified H-bridge multi-level inverter had some advantages such as a low part count and cost competitiveness when compared to conventional multi-level inverters. Therefore, it is frequently used in photovoltaic (PV) power conditioning system (PCS). However, its simplified switching network draws input current asymmetrically. Therefore, input capacitors in series suffer from a problem due to a charge imbalance. This paper validates the operating principle and feasibility of the proposed topology through the simulation and experimental results. They show that the input-capacitor voltages maintain the voltage balance with the PV MPPT control operating with a 140-W hardware prototype.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.9-18
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• 1995

The use of CAD/CAM systems is growing fast in the shipbuilding industry. To develope a geometric modeler, the existing CAD/CAM systems have been analysed. Because existing systems have closed architectures, it is not easy to investigate the internal structures. However, new trends in the software engineering, open architectured systems, pose some possibility to develope the geometric modeler. Several geometric modelers are analysed to extract component functions and modules. ACIS of the Spatial Technology, AIS of the CAM-I consortium, the STEP part for the geometry and topology, CAD*I of the ESPRIT project, and domestic modelers are investigated. Based on this analysis, a reference model which shows the framework of the modeler is proposed. With the data structure supporting non-manifold topologies, the reference model can be used to encourage a cooperative development program.

• Parasites, Hosts and Diseases
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• v.59 no.2
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• pp.139-148
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• 2021

This study was carried out to provide information on the taxonomic classification and analysis of mitochondrial genomes of Spirometra theileri. One strobila of S. theileri was collected from the intestine of an African leopard (Panthera pardus) in the Maswa Game Reserve, Tanzania. The complete mtDNA sequence of S. theileri was 13,685 bp encoding 36 genes including 12 protein genes, 22 tRNAs and 2 rRNAs with absence of atp8. Divergences of 12 protein-coding genes were as follow: 14.9% between S. theileri and S. erinaceieuropaei, 14.7% between S. theileri and S. decipiens, and 14.5% between S. theileri with S. ranarum. Divergences of 12 proteins of S. theileri and S. erinaceieuropaei ranged from 2.3% in cox1 to 15.7% in nad5, while S. theileri varied from S. decipiens and S. ranarum by 1.3% in cox1 to 15.7% in nad3. Phylogenetic relationship of S. theileri with eucestodes inferred using the maximum likelihood and Bayesian inferences exhibited identical tree topologies. A clade composed of S. decipiens and S. ranarum formed a sister species to S. erinaceieuropaei, and S. theileri formed a sister species to all species in this clade. Within the diphyllobothridean clade, Dibothriocephalus, Diphyllobothrium and Spirometra formed a monophyletic group, and sister genera were well supported.

• Journal of Power Electronics
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• v.19 no.4
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• pp.846-857
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• 2019

Voltage step-down converters are very popular in distributed power systems, voltage regular modules, electric vehicles, etc. However, a high step-down voltage ratio is required in many applications to prevent the traditional buck converter from operating at extreme duty cycles. In this paper, a series capacitor interleaved buck converter with a soft switching technique is proposed. The DC voltage ratio of the proposed converter is half that of the traditional buck converter and the voltage stress across the one main switch and the diodes is reduced. Moreover, by paralleling the series connected auxiliary switch and the auxiliary inductor with the main inductor, zero voltage transition (ZVT) of the main switches can be obtained without increasing the voltage or current stress of the main power switches. In addition, zero current turned-on and zero current switching (ZCS) of the auxiliary switches can be achieved. Furthermore, owing to the presence of the auxiliary inductor, the turned-off rate of the output diodes can be limited and the reverse-recovery switching losses of the diodes can be reduced. Thus, the efficiency of the proposed converter can be improved. The DC voltage gain ratio, soft switching conditions and a design guideline for the critical parameters are given in this paper. A loss analysis of the proposed converter is shown to demonstrate its advantages over traditional converter topologies. Finally, experimental results obtained from a 100V/10V prototype are presented to verify the analysis of the proposed converter.

• Journal of Power Electronics
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• v.19 no.4
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• pp.881-893
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• 2019

This paper proposes a practical sliding-mode controller design for shaping the impedances of cascaded boost-converter power decoupling circuits for reducing the second order harmonic ripple in photovoltaic (PV) current. The cascaded double-boost converter, when used as power decoupling circuit, has some advantages in terms of a high step-up voltage-ratio, a small number of switches and a better efficiency when compared to conventional topologies. From these features, it can be seen that this topology is suitable for residential (PV) rooftop systems. However, a robust controller design capable of rejecting double frequency inverter ripple from passing to the (PV) source is a challenge. The design constraints are related to the principle of the impedance-shaping technique to maximize the output impedance of the input-side boost converter, to block the double frequency PV current ripple component, and to prevent it from passing to the source without degrading the system dynamic responses. The design has a small recovery time in the presence of transients with a low overshoot or undershoot. Moreover, the proposed controller ensures that the ripple component swings freely within a voltage-gap between the (PV) and the DC-link voltages by the small capacitance of the auxiliary DC-link for electrolytic-capacitor elimination. The second boost controls the main DC-link voltage tightly within a satisfactory ripple range. The inverter controller performs maximum power point tracking (MPPT) for the input voltage source using ripple correlation control (RCC). The robustness of the proposed control was verified by varying system parameters under different load conditions. Finally, the proposed controller was verified by simulation and experimental results.

• Journal of the Korea Society of Computer and Information
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• v.24 no.4
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• pp.169-176
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• 2019

Wireless sensor networks are used to monitor and control areas in a variety of military and civilian areas such as battlefield surveillance, intrusion detection, disaster recovery, biological detection, and environmental monitoring. Since the sensor nodes are randomly placed in the area of interest, separation of the sensor network area may occur due to environmental obstacles or a sensor may not exist in some areas. Also, in the situation where the sensor node is placed in a non-relocatable place, some node may exhaust energy or physical hole of the sensor node may cause coverage hole. Coverage holes can affect the performance of the entire sensor network, such as reducing data reliability, changing network topologies, disconnecting data links, and degrading transmission load. It is possible to solve the problem that occurs in the coverage hole by finding a coverage hole in the sensor network and further arranging a new sensor node in the detected coverage hole. The existing coverage hole detection technique is based on the location of the sensor node, but it is inefficient to mount the GPS on the sensor node having limited resources, and performing other location information processing causes a lot of message transmission overhead. In this paper, we propose an Adjacent Matrix-based Hole Coverage Discovery(AMHCD) scheme based on connectivity of neighboring nodes. The method searches for whether the connectivity of the neighboring nodes constitutes a closed shape based on the adjacent matrix, and determines whether the node is an internal node or a boundary node. Therefore, the message overhead for the location information strokes does not occur and can be applied irrespective of the position information error.

• Korean Journal of Plant Taxonomy
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• v.50 no.4
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• pp.385-394
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• 2020

To elucidate the molecular phylogeny of Neottia japonica, which is a terrestrial orchid distributed in East Asia, the internal transcribed spacer (ITS) of nuclear DNA and the matK of chloroplast DNA were used. A total 22 species of 69 accessions for ITS and 21 species of 114 accessions for matK phylogeny were analyzed with the maximum parsimony and Bayesian methods. In addition, we sought to establish a correlation between the distribution, morphology of the auricles and genetic association of N. japonica with phylogenetic data. The phylogenetic results suggest that N. japonica is monophyletic and a sister to N. suzukii in terms of the ITS phylogeny, while it is paraphyletic with N. suzukii in terms of the matK phylogeny. N. japonica and N. suzukii show similar morphologies of the lip and column, they both flower in April, and they are both distributed sympatrically in Taiwan. Therefore, it appears to be clear that N. japonica and N. suzukii are close taxa within Neottia, although there is incongruence between the nrDNA and cpDNA phylogenies of N. japonica. The incongruence between the two datasets may have various causes, meaning that further studies are needed to confirm the evolutionary process of N. japonica. The phylogenetic status of N. kiusiana, which was not included in previous studies, was as a sister to N. nidus-avis. Meanwhile, the ITS and matK phylogenies are unsuitable for identifying genetic associations with the characteristic of auricles. The phylogenetic topologies of Korean, Taiwanese and mainland Chinese individuals suggest that the populations of N. japonica in Korea originated from China's mainland and island areas. The characterization of regional gene differences could provide useful preliminary data for future studies.

• International Journal of Computer Science & Network Security
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• v.22 no.6
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• pp.390-399
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• 2022

Cyber security and resilience are phrases that describe safeguards of ICTs (information and communication technologies) from cyber-attacks or mitigations of cyber event impacts. The sole purpose of Risk models are detections, analyses, and handling by considering all relevant perceptions of risks. The current research effort has resulted in the development of a new paradigm for safeguarding services offered online which can be utilized by both service providers and users. customers. However, rather of relying on detailed studies, this approach emphasizes task selection and execution that leads to successful risk treatment outcomes. Modelling intelligent CSGs (Cyber Security Games) using MLTs (machine learning techniques) was the focus of this research. By limiting mission risk, CSGs maximize ability of systems to operate unhindered in cyber environments. The suggested framework's main components are the Threat and Risk models. These models are tailored to meet the special characteristics of online services as well as the cyberspace environment. A risk management procedure is included in the framework. Risk scores are computed by combining probabilities of successful attacks with findings of impact models that predict cyber catastrophe consequences. To assess successful attacks, models emulating defense against threats can be used in topologies. CSGs consider widespread interconnectivity of cyber systems which forces defending all multi-step attack paths. In contrast, attackers just need one of the paths to succeed. CSGs are game-theoretic methods for identifying defense measures and reducing risks for systems and probe for maximum cyber risks using game formulations (MiniMax). To detect the impacts, the attacker player creates an attack tree for each state of the game using a modified Extreme Gradient Boosting Decision Tree (that sees numerous compromises ahead). Based on the findings, the proposed model has a high level of security for the web sources used in the experiment.