• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.2
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• pp.323-330
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• 2017

The millimeter wave band is in the extremely high frequency band whose frequency and wavelength are 30-300GHz and 10-1mm respectively. When the obstacles block the propagation path which is not Line-of-Sight (LoS), due to a high propagation loss, it is hard to receive a signal in the millimeter wave band. Therefore When the path loss is measured in the millimeter wave band, the signal which is not distinguished from the noise is observed. Consequently, the path loss data which is limited in certain value is observed in the high propagation loss environment. If the original least square is implemented without taking the limitation of certain value into account, the path loss exponent may be underestimated. In this paper, the performance of Tobit Maximum Likelihood Estimation, Heckman Two-stage Model and Truncation Regression Model which can estimate properly in the censoring or truncated environments are compared.

• Journal of KIISE:Databases
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• v.29 no.3
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• pp.217-229
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• 2002

Regular path expressions are primary elements for formulating queries over the semistructured data that does not assume the conventional schemas. In addition, the query pruning is an important optimization technique to avoid useless traversals in evaluating regular path expressions. However, the existing query pruning often fails to fully optimize multiple regular path expressions, and the previous methods that post-process the result of the existing query pruning must check exponential combinations of sub-results. In this paper, we present a new query pruning technique that consists of the preprocessing phase and the pruning phase. Our two-phase query pruning is affective in optimizing multiple regular path expressions, and is more scalable than the previous methods in that it never check the exponential combinations of sub-results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.12
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• pp.935-942
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• 2014

The ride quality investigation is on-going topic in the car industry since its global standard has not evaluated and it is difficult to point out one part that hinders the ride quality. Since the traditional transfer path analysis that is widely used in car industry to investigate the ride quality requires a lot of test time to process the full data so that there are problems to conduct in industry. Based on these disadvantages, new approaches have developed such as OPAX(operational path analysis with eXogeneous inputs) and OTPA(operational transfer path analysis) for last decades. The OTPA only requires the operational data for evaluate the contribution of vibration sources and the OPAX has advantage of using parametric model to estimate the operating load and needs a minimum set of extra tests with excitation. In this paper, for evaluating the hindrance of ride quality two methods are used and the result is compared with another result of a car having higher ride quality.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.5
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• pp.179-186
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• 2014

Current networks such as social network, web page link, traffic network are big data which have the large numbers of nodes and edges. Many applications such as social network services and navigation systems use these networks. Since big networks are not fit into the memory, existing in-memory based analysis techniques cannot provide high performance. Frontier-Expansion-Merge (FEM) framework for graph search operations using three corresponding operators in the relational database (RDB) context. FEM exploits an index table that stores pre-computed partial paths for efficient shortest path discovery. However, the index table of FEM has low hit ratio because the indices are determined by distances of indices rather than the possibility of containing a shortest path. In this paper, we propose an method that construct index table using high degree nodes having high hit ratio for efficient shortest path discovery. We experimentally verify that our index technique can support shortest path discovery efficiently in real-world datasets.

• Journal of the Korean Society for Railway
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• v.18 no.2
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• pp.149-156
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• 2015

It is necessary to determine real path for urban railway users in order to allocate revenues between urban railway organizations. Out of several algorithms used to determine optimal routes, the k-path algorithm based on link-label has been utilized. However, this k-path algorithm has certain flaws. For example, optimal route can change depending on the travel and walking time, transfer penalty, and so on. Also, this algorithm cannot take into account the characteristics of users, who prefer express train to normal trains. In this paper, an algorithm is proposed to determine one single optimal route based on the traffic card data. This method also can search for an optimal path in conjunction with the railway timetable.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.8
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• pp.1011-1017
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• 2019

This paper proposes reinforcement learning to solve the node-disjoint path problem which establishes multipath for reliable data transmission in wireless ad-hoc networks. The node-disjoint path problem is a problem of determining a plurality of paths so that the intermediate nodes do not overlap between the source and the destination. In this paper, we propose an optimization method considering transmission distance in a large-scale wireless ad-hoc network using Q-learning in reinforcement learning, one of machine learning. Especially, in order to solve the node-disjoint path problem in a large-scale wireless ad-hoc network, a large amount of computation is required, but the proposed reinforcement learning efficiently obtains appropriate results by learning the path. The performance of the proposed reinforcement learning is evaluated from the viewpoint of transmission distance to establish two node-disjoint paths. From the evaluation results, it showed better performance in the transmission distance compared with the conventional simulated annealing.

• The Transactions of the Korea Information Processing Society
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• v.3 no.7
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• pp.1924-1937
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• 1996

In this paper, we propose a ESP(Extended Scan Path) architecture for multi- board testing. The conventional architectures for board testing are single scan path and multi-scan path. In the single scan path architecture, the scan path for test data is just one chain. If the scan path is faulty due to short or open, the test data is not valid. In the multi-scan path architecture, there are additional signals in multi-board testing. So conventional architectures are not adopted to multi-board testing. In the case of the ESP architecture, even though scan paths either short or open, it doesn't affect remaining other scan paths. As a result of executing parallel BIST and IEEE 1149.1 boundary scan test by using, he proposed ESP architecture, we observed to the test time is short compared with the single scan path architecture. Because the ESP architecture uses the common bus, there are not additional signals in multi-board testing. By comparing the ESP architecture with conventional one using ISCAS '85 bench mark circuit, we showed that the architecture has improved results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.2
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• pp.146-153
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• 2013

The IR-UWB radar system radiates a pulse whose width is several hundred pico sec at Tx antenna and check the time to receive the pulse that reflected from target to measure the TOA. In this paper, we present a new algorithm which supplement the conventional ranging algorithm for more accurate estimation. We get received signal data using IR-UWB Radar module which equipped a NVA6000 UWB Transceiver and analysis the data of multi-path. Consequently, we found the property of UWB multi-path signal, which best fit a Gamma distribution. so we present a algorithm using Gamma-distribution and compared a performance with conventional ranging algorithm.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.3
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• pp.206-210
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• 2009

In this paper, we propose a new routing scheme based on multi-path routing which provides uniform energy consumption for all nodes. This scheme adds a new type of root node for constructing multi-path. The sink node delegates some partial roles to these root nodes. Such root nodes carry out path establishment independently. As a result, each nodes consume energy more uniformly and the network life-time will be extended. Through simulation, we confirmed that energy consumption of the whole network is scattered and the network life-time is extended. Moreover, we show that the proposed routing scheme improves the performance of network compared to previous routing strategies as the number of source nodes increases.

• ETRI Journal
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• v.39 no.2
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• pp.213-221
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• 2017

The advent of wireless access in vehicular environments (WAVE) technology has improved the intelligence of transportation systems and enabled generic traffic problems to be solved automatically. Based on the IEEE 802.11p standard for vehicle-to-anything (V2X) communications, WAVE provides wireless links with latencies less than 100 ms to vehicles operating at speeds up to 200 km/h. To date, most research has been based on field test results. In contrast, this paper presents a numerical analysis of the V2X broadcast throughput limit using a path loss model. First, the maximum throughput and minimum delay limit were obtained from the MAC frame format of IEEE 802.11p. Second, the packet error probability was derived for additive white Gaussian noise and fading channel conditions. Finally, the maximum throughput limit of the system was derived from the packet error rate using a two-ray path loss model for a typical highway topology. The throughput was analyzed for each data rate, which allowed the performance at the different data rates to be compared. The analysis method can be easily applied to different topologies by substituting an appropriate target path loss model.