• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.6C
• /
• pp.495-505
• /
• 2010

In this paper, the effect of Near-Far Problem (NFP) among distributed nodes in OFDMA-based Wireless Mesh Networks (WMNs) is analyzed by investigating statistical characteristics of Time Difference of Arrival (TDoA) and Desired-to-Undesired power Ratio (DUR). In order to overcome the effects of Inter-Symbol Interference (ISI), Inter-Carrier Interference (ICI), and Inter Link Interference (ILI), caused by TDoA in WMNs, we derive effective SINR for each subcarrier, and then, propose the optimal starting point of FFT window which can minimize BER for each subcarrier. In addition, we propose a subcarrier-based Zero Forcing - 2 Dimensional Ordered Successive Interference Cancellation (ZF-2DOSIC) technique for signal detection in WMNs with TDoA. It is verified by simulation that the effective SINR and uncoded BER performances of the proposed signal detection technique for OFDMA-based WMNs are significantly improved, compared with those of conventional technique.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.24 no.2
• /
• pp.163-170
• /
• 2018

The purpose of this study is to describe quantitatively the characteristics and the structure of the Act on the development, management, etc. of Marinas (the Marinas Act) by analysing its provisions using semantic network analysis. The method of semantic network analysis has its advantages in overcoming limitations of the traditional content analysis method, as it is easy for the user to understand the structure and the shape of a network by figuring out the structural network among words. The object of the analysis is the full text of Marinas Act recently revised from Chapters 1 to 4, while partial analysis is carried out respectively for each chapter from Chapters 2 to 4. The structural characteristic of the Marinas Act shows that the act focuses on the development of marinas, as its main goal is interpreted to set up hardwares and to construct facilities rather than to promote the marina industry itself. Even though some clauses for human capital development and business development are included, they are of less importance compared to the development of marina facilities. This study provides some basic information on the structural characteristics of the current act, which can be referred to in subsequent studies. In the future, it also needs to be complemented through comparative analysis with government policy outcomes and performance of diverse analytical approaches.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.24 no.5
• /
• pp.495-503
• /
• 2014

In recent days, a study of the intrusion detection system collecting and analyzing network data, packet or logs, has been actively performed to response the network threats in computer security fields. In particular, Bayesian network has advantage of the inference functionality which can infer with only some of provided data, so studies of the intrusion system based on Bayesian network have been conducted in the prior. However, there were some limitations to calculate high detection performance because it didn't consider the problems as like complexity of the relation among network packets or continuos input data processing. Therefore, in this paper we proposed two methodologies based on K-menas clustering to improve detection rate by reforming the problems of prior models. At first, it can be improved by sophisticatedly setting interval range of nodes based on K-means clustering. And for the second, it can be improved by calculating robust CPT through applying weighted-leaning based on K-means clustering, too. We conducted the experiments to prove performance of our proposed methodologies by comparing K_WTAN_EM applied to proposed two methodologies with prior models. As the results of experiment, the detection rate of proposed model is higher about 7.78% than existing NBN(Naive Bayesian Network) IDS model, and is higher about 5.24% than TAN(Tree Augmented Bayesian Network) IDS mode and then we could prove excellence our proposing ideas.

• Korean journal of applied entomology
• /
• v.21 no.2 s.51
• /
• pp.61-67
• /
• 1982

The strawberry cultivar Hokowase showing rapid wilting and death around harvest time was first found in the fold at Woongcheon, Chungnam province in 1974. The fungus, Fusarium oxysporum was isolated frequently from the crown, petiole and root of strawberry plants collected from Woongcheon and was pathogenic to Hokowase. The fungus abundantly produced micro-and macro-conidia and chiamydospore on PSA. The size of micro conidia, macro conidia and Chlamydospores was $5.0\~13.0\times2.5\~3.0,\;12.8\~62.5\times2.5\times50\mu\;and\;7.5\~13.8\times5.5\~12.5\mu$, respectively. Mycelial growth of the fungus was best between $25\~30^{\circ}C$ on PSA. The disease at Woongcheon occurred from the end of March and incidence of the disease increased from the beginning of May reaching $40.2\%$ of diseased Plants at the 1st part of June. In laboratory and field evaluation tests with twelve fungicides, Difolatan, Benlate T and Tospin M showed some control effects against the disease although they did not show ignificant differences in effects compared with that of the non-treatment. The cultivar Yachiyo, Daehak 1, Line 10-2, and Senga Sengana were highly resistant, and Harunoka and Empire were moderate resistant whereas Northwest and Hokowase were highly susceptible to the fungus under field condition.

• The KIPS Transactions:PartA
• /
• v.11A no.6
• /
• pp.459-468
• /
• 2004

Sharing XML trees on mobile devices has become more and more popular. Optimistic replication of XML trees for mobile devices raises the need for reconciliation of concurrently modified data. Especially for reconciling the modified tree structures, we have to compare trees by node mapping which takes O($n^2$) time. Also, using semantic based conflict resolving policy is often discussed in the literature. In this research, we focused on an efficient reconciliation method for mobile environments, using edit scripts of XML data sent from each device. To get a simple model for mobile devices, we use the XML list data sharing model, which allows inserting/deleting subtrees only for the repetitive parts of the tree, based on the document type. Also, we use keys for repetitive part subtrees, keys are unique between nodes with a same parent. This model not only guarantees that the edit action always results a valid tree but also allows a linear time reconciliation algorithm due to key based list reconciliation. The algorithm proposed in this paper takes linear time to the length of edit scripts, if we can assume that there is no insertion key conflict. Since the previous methods take a linear time to the size of the tree, the proposed method is expected to provide a more efficient reconciliation model in the mobile environment.

• The KIPS Transactions:PartD
• /
• v.15D no.4
• /
• pp.451-462
• /
• 2008

Recently, with the advent of applications using locations of moving objects, it becomes crucial to develop efficient index schemes for spatio-temporal databases. The $TPR^*$-tree is most popularly accepted as an index structure for processing future-time queries. In the $TPR^*$-tree, the future locations of moving objects are predicted based on the CBR(Conservative Bounding Rectangle). Since the areas predicted from CBRs tend to grow rapidly over time, CBRs thus enlarged lead to serious performance degradation in query processing. Against the problem, we propose a new method to adjust CBRs to be tight, thereby improving the performance of query processing. Our method examines whether the adjustment of a CBR is necessary when accessing a leaf node for processing a user query. Thus, it does not incur extra disk I/Os in this examination. Also, in order to make a correct decision, we devise a cost model that considers both the I/O overhead for the CBR adjustment and the performance gain in the future-time owing to the CBR adjustment. With the cost model, we can prevent unusual expansions of BRs even when updates on nodes are infrequent and also avoid unnecessary execution of the CBR adjustment. For performance evaluation, we conducted a variety of experiments. The results show that our method improves the performance of the original $TPR^*$-tree significantly.

• Journal of the Korea Society of Computer and Information
• /
• v.20 no.5
• /
• pp.1-12
• /
• 2015

NAND flash memory has being used for storage systems widely, because it has good features which are low-price, low-power and fast access speed. However, NAND flash memory has an in-place update problem, and therefore it needs FTL(flash translation layer) to run for applications based on hard disk storage. The FTL includes complex functions, such as address mapping, garbage collection, wear leveling and so on. Futhermore, implementation of the FTL on low-power embedded systems is difficult due to its memory requirements and operation overhead. Accordingly, many index data structures for NAND flash memory have being studied for the embedded systems. Overall performances of the index data structures are enhanced by a decreasing of page write counts, whereas it has increased page read counts, as a side effect. Therefore, we propose an index management method using a page mapping log table in $B^+$-Tree based on NAND flash memory to decrease page write counts and not to increase page read counts. The page mapping log table registers page address information of changed index node and then it is exploited when retrieving records. In our experiment, the proposed method reduces the page read counts about 61% at maximum and the page write counts about 31% at maximum, compared to the related studies of index data structures.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.7
• /
• pp.22-31
• /
• 2008

Cognitive radio should imply a proper sensing technique for detecting the presence of licensed users to identify the unused spectrum holes. Besides this, this information should also be used to opportunistically provide communication among secondary users. At the same time the performance of the primary user should not be declined by the secondary users. The detection of licensed users may be significantly difficult for shadowing effect. To prevail over this problem cooperative spectrum sensing, In which the combined observation information gained by multiple secondary users is employed to achieve higher performance of detection, has been inspected. However, the primary challenge of cooperative sensing lays in its ability to detect the presence of licensed user quickly and accurately. In this paper, we have used UltraWideBand (UWB) to detect the presence of licensed users and transmit the sensing information among the nodes of the network. UWB has the capability of transmitting data at a very high rate. It is unique in co-existence capability with narrow band systems. Here, we have shown that the detection probability of licensed user is improved by means of transmitting the spectrum sensing information via UWB. We also have analyzed the throughput of the proposed technique and compared the result with existing sensing method.

• Journal of Korea Port Economic Association
• /
• v.28 no.3
• /
• pp.235-257
• /
• 2012

Recently the role of ports has been changed to satisfy flexibly needs of demands in global economy. A new concept for ports is not just a place for international trade but an important nodal point in logistics chain. The changing environment like this trend creates a high degree of uncertainty and leaves port managers confused with the question how to respond effectively to dynamic market. The latest studies provide that the port must have a good hinterland to achieve competitive advantages in a logistics chain. Korean Government announced "The Master Development Plan for Port Logistics Parks in Korea" in 2006. This contains the plan of hinterland construction of Busan New Port to achieve the status of logistics hub in Asian market. Previous studies rely solely on traditional DCF(discounted cash flow) analysis for investment of hinterland. However DCF method does not include irreversibility, uncertainty and the choice of timing for investment project. This thesis introduces a ROPM(real options pricing model) which overcomes the limitations of traditional valuation methods. The option valuations in this study utilize the Black-Scholes model, the binomial model and the MonteCarlo simulation to value investment opportunity of a port hinterland. In this thesis, an attempt is made to modify the NPV criterion by incorporating the real options approach, and its application is demonstrated in a hinterland construction investment plan. This research has conducted an empirical analysis by calculating economic value of the investment for a hinterland of Busan New Port.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.5
• /
• pp.37-42
• /
• 2002

Artificial neural networks are efficient computing techniques that are widely used to solve complex problems in many fields. In this paper a liquefaction potential was estimated by using a back propagation neural network model applicated to cyclic triaxial test data, soil parameters and site investigation data. Training and testing of the network were based on a database of 43 cyclic triaxial test data from 00 sites. The neural networks are trained by modifying the weights of the neurons in response to the errors between the actual output values and the target output value. Training was done iteratively until the average sum squared errors over all the training patterns were minimized. This generally occurred after about 15,000 cycles of training. The accuracy from 72% to 98% was shown for the model equipped with two hidden layers and ten input variables. Important effective input variables have been identified as the NOC,$D_10$ and (N$_1$)$_60$. The study showed that the neural network model predicted a CSR(Cyclic shear stress Ratio) of silty-sand reasonably well. Analyzed results indicate that the neural-network model is more reliable than simplified method using N value of SPT.