• Journal of the Korea Society of Computer and Information
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• v.15 no.8
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• pp.13-21
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• 2010

One of the most distinguished features of the DHP association rules mining algorithm is that it counts the support of hash key combinations composed of k items at phase k-1, and uses the counted support for pruning candidate large itemsets to improve performance. At this time, it is desirable for each hash key combination to have a separate count variable, where it is impossible to allocate the variables owing to memory shortage. So, the algorithm uses a direct hashing mechanism in which several hash key combinations conflict and are counted in a same hash bucket. But the direct hashing mechanism is not efficient because the distribution of hash key combinations is unvalanced by the characteristics sourced from the mining process. This paper proposes a mapped perfect hashing function which maps the region of hash key combinations into a continuous integer space for phase 3 and maximizes the efficiency of direct hashing mechanism. The results of a performance test experimented on 42 test data sets shows that the average performance improvement of the proposed hashing mechanism is 7.3% compared to the existing method, and the highest performance improvement is 16.9%. Also, it shows that the proposed method is more efficient in case the length of transactions or large itemsets are long or the number of total items is large.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.6
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• pp.106-112
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• 2001

Unfortunately, the area without economical efficiency, especially the far distance sea, is much lower than that of a urban area-built-up area. It should be promoted the equivalent level to a urban area in the light of future-oriented universal service. Actually, Because propagation environment of mobile communication in the sea is greatly different from that for inland focused on built-up area, a propagation prediction model in the sea should be distinguished from inland-based one. Accordingly, the purpose of this study is to suggest the propagation prediction model for the sea service as a method to minimize unnecessary facilities investment and maintenance caused by additional or new building of a base station. If mobile phone service for far distance sea is provided by expanding limited communication zone of narrow band CDMA mobile communication whose spread band FA is 1.2288MHz. Suggested propagation prediction model includes five parameters to minimize facilities investment of a base station and maximize channel capacity: equivalent line of sight, chip delay by PN code, antenna altitude, power of base station and gain of antennas. Finally, suggested propagation prediction model is simulated and, the results are examined for its utility by comparing with loss of free space.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.5
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• pp.88-98
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• 2011

Recently, according as the importance of GIS(geography information system) database security is embossed, much researches had been achieved about GIS network security. But most such researches are weak against sourceful illegal reproductions and distributions of GIS vector data map. In this paper, we proposed an efficient layer unit contents based partial encryption technique in the vector map compression domain to prevent illegal distributions and unauthorized accesses. This method achieves a partial encryption about each central coordinate and directional parameters of a MCA(minimum coding attribute) that is created at the vector map compression processing in the vector space. First, the position encryption is applied as permutating randomly the center coordinate of each record that is minimum unit of vector map shape. And second, the direction encryption that changing shapes of vector map topography is applied as encrypting the direction of vertices's coordinates of each record. In experimental results, we confirmed that our proposed method can encipher the large volumed vector map data effectively in low computational complexity. Also, we could minimize the decline of compression efficiency that occurred by conventional contents based encryption schemes using AES or DES algorithms.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.3
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• pp.50-62
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• 2015

Recently, Subway Line No. 9, described as a 'hell-like' subway for its recorded load factor of max. 240% due to the opening of the 2nd phase extension section, has been causing problems of recurrent congestion in a subway station building. A recurrent congestion in the station building becomes a factor to offend rail users and to reduce the efficiency of railway management. This study aims to establish the methodology for effect evaluation of information provided to rail users, and conducts a gate metering case study considering the congested conditions at a platform among the methodologies for effect evaluation. The metering effect evaluation by load factor was conducted through selecting the micro simulation and pedestrian simulation tool grafting a gate metering. As a result, it was confirmed that, if gate metering is performed, the service level and pedestrian density of a platform by load factor would improve. In other words, if metering is conducted at a platform, it is possible to control the load factor in the waiting space of a platform. Therefore, it was judged through this study that it is possible to set up the index for effect evaluation of information provided to manage congestion of rail users, and establish the methodology for effect evaluation of information provided to rail users through a program.

• Korean Journal of Optics and Photonics
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• v.25 no.4
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• pp.216-220
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• 2014

We have synthesized a $CaMgSi_2O_6:Eu^{2+}$ blue phosphor via a solid-state reaction method. The $CaMgSi_2O_6:Eu^{2+}$ phosphor has monoclinic structure with a space group of C2/c (15), and an emission band peaking at 450 nm (blue) due to the $4f^7-4f^65d$ transition of the $Eu^{2+}ion$. The emission intensity at $100^{\circ}C$ is 54% of the value at room temperature. A white LED was fabricated by integrating a UV LED (400 nm) with our blue phosphor plus two commercial green and red phosphors. The white LED shows a color temperature of 3500 K with a color rendering index of 87 (x = 0.3936, y = 0.3605), and a luminous efficiency of 18 lm/W. The white LED shows a luminance maintenance of 97% after operation at 350 mA for 400 hours at $85^{\circ}C$.

• Korean Journal of Optics and Photonics
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• v.24 no.6
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• pp.331-337
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• 2013

A large optical surface is fabricated by grinding, polishing and figuring. The grinding process is the most rapid and has the largest amount of fabrication of all processes. If we measure the surface precisely and rapidly in the grinding process, it is possible to improve the efficiency of the fabrication process. Since the surface of grinding process is rough and not shiny, it is not easy to measure the surface using light so that we cannot use an interferometer. Therefore, we have to measure the surface using a mechanical method. We can measure the surface under the grinding process by using a laser tracker which is a portable 3-dimensional coordinate measuring machine. In this paper, we used the laser tracker to measure the surface error of 1 m diameter spherical mirror. This measurement result was compared to that of an interferometer. As a result, surface measurement error was found to be $0.2{\mu}m$ rms (root mean square) and $2.7{\mu}m$ PV (Peak to Valley), which is accurate enough to apply to the rough surface under the grinding stage.

• Journal of the Korean Geographical Society
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• v.50 no.6
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• pp.607-619
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• 2015

It is important to detect trails accurately for finding a proper management. We examined the applicability of KOMPSAT imagery to detect trails and found that it could be an efficient alternative to track trails correctly. We selected K2 and K3 imagery with different spatial resolution. Then, we processed each imagery to get NDVI, SAVI, and SC data. And then, we identified trails by object-based analysis and network analysis. Finally, we evaluated the potential trails with F-measurement and Jaccard coefficient which are based on correctness and completeness. The results show that the applicability is quite different in each case. Among them, especially the SC data with K3 shows the most highest value; correctness of detecting legal trails is 0.44 and completeness of that is 0.54. F-measurement and Jaccard coefficient are 0.49 and 0.32. In general, although there is a limit in detecting trails by using only KOMPSAT imagery, the usefulness of KOMPSAT imagery can be a higher considering its cost efficiency and availability of acquiring periodic data.

• Journal of Bio-Environment Control
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• v.21 no.4
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• pp.459-465
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• 2012

This study analyzed the effect of semi-rigid rafter-purlin cross-linking connection and driven steel pipe base on the static behavior of plastic greenhouse (PG). To promote the time and cost efficiency of the assembly process, each cross-linking connections of space arch type grid that consists of rafter and purlin is linked with steel-wire buckles, and each end of the rafters was driven directly to the ground to support the PG structure. However, in the design process, cross-linking connections and bases are idealized by being categorized as fully rigid or frictionless pinned, which does not appropriately reflect actual conditions. This study takes a full-scale loading test of PG and analyzes the effect of member cross-linking connections and driven steel pipe base on the behavior of a structure. The analysis provided a basis for determining the rigidity factor of member cross-linking nodes needed for finite element analysis, and the reliability of the result regarding the static behavior of PG.

• Journal of Navigation and Port Research
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• v.29 no.5 s.101
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• pp.389-394
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• 2005

The additional moment occurs because the superstructures of VLFS are influenced by wave loads instead of earthquake loads. In order to reduce the additional moment, this study used the semi-rigid connections which lie between fully rigid and pinned. If the semi-rigid connections are used for superstructures of VLFS, the moment of beams can be reduced and more economical construction will be possible. This study aims to show the effect of wave loads on structure and the efficiency of the semi-rigid connections due to wave loads by analyzing the time history responses. The dynamic behaviors of the rigid frame are compared with those of the semi-rigid frame considering of static loads, wave loads and combination loads for a four-bay, three-story frames. The semi-rigid connection type is a steel tubular column with square external-diaphragm connections and the time history analysis is used for the dynamic responses. The additional moment responses due to wave loads increase $33\%$ in the rigid frame, $26\%$ in the semi-rigid frame with the spring model.

• The KIPS Transactions:PartC
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• v.14C no.5
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• pp.431-438
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• 2007

RFID system is core technology that construct ubiquitous environment for replacement of barcode technology. Use ratio of RFID system rapidly increase because the technology has many good points such as identification speed, storage space, convenience etc. But low-cost tag operates easily by query of reader, so the system happened user privacy violent problem by tag information exposure. The system studied many ways for security application, but operation capability of low-cost tag is about $5K{\sim}10K$ gates, but only $250{\sim}3K$ gates allocated security part. So it is difficult to apply security to the system. Therefore, this scheme uses dividing 64 bits and reduces arithmetic, so proposed scheme provide mutual authentication that can apply to low-cost RFID system. Existing methods divide by 4 and used 96 bits. However, that reduces 32 bits length for lightweight and reduced from communication number of times of 7 times to 5 times. Also, because offer security by random number than existing scheme that generate two random numbers, that is more efficient. However, uses hash function for integrity that was not offered by XOR arithmetic and added extension of proposed scheme. Extended scheme is not offered efficiency than methods that use XOR arithmetic, but identification distance is mode that is proposed secure so that can use in for RFID system.