• The Korean Journal of Quaternary Research
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• v.21 no.1
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• pp.15-26
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• 2007

A wide tree-ring data network from Western Himalayan region as well as from Central and Peninsular India have been established by the Indian Institute of Tropical Meteorology (IITM), Pune, India. This includes several ring width and density chronologies of Himalayan conifers (Pinus, Picea, Cedrus, Abies)covering entire area of Western Himalaya and teak (Tectona grandis L.F.) from central and peninsular India. Many of these chronologies go back to $15^{th}$ century. Tree-ring based reconstructed pre-monsoon (March-April-May) summer climate of Western Himalaya do not show any significant increasing or decreasing trend since past several centuries. High altitude tree-ring chronologies near tree line-glacier boundary are sensitive to the winter temperature. Unprecedented higher growth in recent decades is closely associated with the warming trend over the Himalayan region. Dendroclimatic analysis of teak (Tectona grandis) from Central and Peninsular India show significant relationship with pre-monsoon and monsoon climate. Moisture index over the region indicates strong association with tree-ring variations rather than the direct influence of rainfall. It is evident that, two to three consecutive good monsoon years are capable of maintaining normal or above normal tree growth, even though the following year is low precipitation year.

• The Transactions of the Korea Information Processing Society
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• v.4 no.10
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• pp.2615-2628
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• 1997

In this paper, a new codebook design algorithm is proposed. It uses a DCT map based on two-dimensional discrete cosine of transform (2D DCT) and finite state vector quantizer (FSVQ) when the vector quantizer is designed for image transmission. We make the map by dividing input image according to edge quantity, then by the map, the significant features of training image are extracted by using the 2D DCT. A master codebook of FSVQ is generated by partitioning the training set using binary tree based on tree-structure. The state codebook is constructed from the master codebook, and then the index of input image is searched at not master codebook but state codebook. And, because the coding of index is important part for high speed digital transmission, it converts fixed length codes to variable length codes in terms of entropy coding rule. The huffman coding assigns transmission codes to codes of codebook. This paper proposes single-side growing huffman tree to speed up huffman code generation process of huffman tree. Compared with the pairwise nearest neighbor (PNN) and classified VQ (CVQ) algorithm, about Einstein and Bridge image, the new algorithm shows better picture quality with 2.04 dB and 2.48 dB differences as to PNN, 1.75 dB and 0.99 dB differences as to CVQ respectively.

• Journal of The Korean Association of Information Education
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• v.1 no.1
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• pp.49-59
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• 1997

In this thesis, To provide the base of effective data access methods, performance of some indexing techniques used gent-Tally are compared. They are classified as primary key and multikey. For primary key method, made a comparative analysis on Static index. Dynamic index and Hashing. For multikey indexing method K-d tree, K-d-B tree, Inverted file and Grid file of which characteristics are compared. In many applications, multikey indexings are more requested, but are not supplied enough. So, to satisfy users' request - more fast, more exact and to be applied according to the trend of being huge database systems, it is requested more study about multikey data access methods.

• The KIPS Transactions:PartD
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• v.15D no.6
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• pp.755-766
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• 2008

Recently, NAND flash memory is becoming into the spotlight as a next-generation storage device because of its small size, fast speed, low power consumption, and etc. compared to the hard disk. However, due to the distinct characteristics such as erase-before-write architecture, asymmetric operation speed and unit, disk-based systems and applications may result in severe performance degradation when directly implementing them on NAND flash memory. Especially when a B-tree is implemented on NAND flash memory, intensive overwrite operations may be caused by record inserting, deleting, and reorganizing. These may result in severe performance degradation. Although ${\mu}$-tree has been proposed in order to overcome this problem, it suffers from frequent node split and rapid increment of its height. In this paper, we propose Log-Structured B-Tree(LSB-Tree) where the corresponding log node to a leaf node is allocated for update operation and then the modified data in the log node is stored at only one write operation. LSB-tree reduces additional write operations by deferring the change of parent nodes. Also, it reduces the write operation by switching a log node to a new leaf node when inserting the data sequentially by the key order. Finally, we show that LSB-tree yields a better performance on NAND flash memory by comparing it to ${\mu}$-tree through various experiments.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.29B no.7
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• pp.11-22
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• 1992

In this paper, a new indexing technique is proposed for efficient evaluation of nested queries on aggregation hierarchy in object-oriented data model. As an index data structure, an extended $B^{+}$ tree is introduced in which instance identifier to be searched and path information used for update of index record are stored in leaf node and subleaf node, respectively. the retrieval and update algorithm on the introduced index data structure is provided. Comparisons under a variety of conditions are given with current indexing techniques, showing improved performance in cost, i.e., the total number of pages accessed for retrieval and update.

• Spatial Information Research
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• v.6 no.2
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• pp.125-132
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• 1998

The I/O performance for spatial queries is extremely important since the handling of huge amount of multidimensional data is required in spatial databases for geographic information systems. Therefore, we describe representative spatial access methods handling complex spatial objects, z-transform B tree, KDB tree, R tree, MAX tree, to increase I/O performance. In addition, we measure the performance of spatial indexing schemes by testing against various realistic data and query sets. Results from the benchmark test indicates that MAX outperforms other indexing schemes on insertion, range query, spatial join. MAX tree is expected to use as index scheme organizing storage system of GIS in the future.

• Journal of Korea Multimedia Society
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• v.8 no.6
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• pp.729-734
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• 2005

In order to access XML data stored in object databases, an efficient index scheme is inevitable. There have been several index schemes that can be used to efficiently retrieve XML data stored In object databases, but they are all the single path indexes that support indexing along a single schema path. Henee, if a query contains an extended path which is denoted by wild character ('*'), a query processor has to examine multiple index objects, resulting in poor performance and inconsistent index management. In this paper, we propose MPI (Multi-Path Index) scheme as a new index scheme that provides the functionality of multiple path indexes more efficiently, while it uses only one index structure. The proposed scheme is easy to manage since it considers the extended path as a logically single schema path. It is also practical since it can be implemented by little modification of the B -tree index structure.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.1
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• pp.12-23
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• 2001

Extended path expressions are used to denote multiple paths concisely by using '$\ast$' character. They are convenient for expressing OQL queries to retrieve XML data stored in OODBs. In this paper, we propose a multi-path index scheme as a new index scheme to efficiently process queries with extended path expressions. Our proposed index scheme allocates a unique path identifier for every possible single path in an extended path expression and provides functionalities of both a single path indexing and multiple path indexing through the composition of index key and path identifier while using only a index structure. The proposed index scheme provides better performance than single-path index schemes, and is practical since it can be implemented by little modification of leaf records of a B+-tree index.

• Journal of KIISE:Databases
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• v.35 no.3
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• pp.218-230
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• 2008

The temporal aggregate in temporal databases is an extension of the conventional aggregate to include the time on the range condition of aggregation. It is a useful operation for Historical Data Warehouses, Call Data Records, and so on. In this paper, we propose a structure for the temporal aggregation with multiple selection predicates, called the ITA-tree, and an aggregate processing method based on the structure. In the ITA-tree, we transform the time interval of a record into a single value, called the T-value. Then, we index records according to their T-values like a $B^+$-tree style. For possible hot-spot situations, we also propose an improvement of the ITA-tree, called the eITA-tree. Through analyses and experiments, we evaluate the performance of the proposed method.

• Journal of Korea Multimedia Society
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• v.9 no.12
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• pp.1529-1541
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• 2006

Moving objects have been widely employed in traffic and logistic applications. Spatio-temporal aggregations mainly describe the moving object's behavior in the spatial data warehouse. The previous works usually express the object moving in some certain region, but ignore the object often moving along as the trajectory. Other researches focus on aggregation and comparison of trajectories. They divide the spatial region into units which records how many times the trajectories passed in the unit time. It not only makes the storage space quite ineffective, but also can not maintain spatial data property. In this paper, a spatio-temporal aggregation index structure for moving object trajectory in constrained network is proposed. An extended B-tree node contains the information of timestamp and the aggregation values of trajectories with two directions. The network is divided into segments and then the spatial index structure is constructed. There are the leaf node and the non leaf node. The leaf node contains the aggregation values of moving object's trajectory and the pointer to the extended B-tree. And the non leaf node contains the MBR(Minimum Bounding Rectangle), MSAV(Max Segment Aggregation Value) and its segment ID. The proposed technique overcomes previous problems efficiently and makes it practicable finding moving object trajectory in the time interval. It improves the shortcoming of R-tree, and makes some improvement to the spatio-temporal data in query processing and storage.