• 한국방재학회:학술대회논문집
• /
• 2007.02a
• /
• pp.163-167
• /
• 2007

For numerical analysis of a tidal flow, a two-dimensional hydrodynamic model is developed by solving the nonlinear shallow-water equations. The governing equations are discretized explicitly with a finite difference leap-frog scheme and a first-order upwind scheme on adaptive hierarchical quadtree grids. The developed model is verified by applying to prediction of tidal behaviors. The calculated tidal levels are compared to available field measurements. A very reasonable agreement is observed.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.39 no.5
• /
• pp.494-499
• /
• 1990

A new compact hierarchical representation method image is proposed. This method represents a binary image with the set of decimal numbers. Each decimal number represents the pattern of nonterminal node(gray node) in the quadtree. This pattern implies the combination of its four child nodes. The total number of gray nodes is one third of that terminal nodes. We show that gray tree method is efficient comparing with others which have been studied.

• Water Engineering Research
• /
• v.1 no.3
• /
• pp.187-197
• /
• 2000

This paper describes an adaptive quadtree-based 2DH wave-current interaction model which is able to predict wave breaking, shoaling, refraction, diffraction, wave-current interaction, set-up and set-down, mixing processes (turbulent diffusion), bottom frictional effects, and movement of the land-water interface at the shoreline. The wave period-and depth-averaged governing equations are discretised explictly by means of an Adams-Bashforth second-order finite difference technaique on adaptive hierarchical staggered quadtree grids. Grid adaptation is achieved through seeding points distributed according to flow criteria(e.g. local current gradients). Results are presented for nearshore circulation at a sinusoidal beach. Enrichment permits refined modelling of important localised flow features.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.7
• /
• pp.1613-1623
• /
• 1996

In this paper, an image coding scheme using removal of isolated coefficients and quadtree structure in wavelet transformed domain, is suggested. The number of significant coefficients can be reduced by quantizing in different stages according to the weights of the each band. The quadtree structure preseves the location information while significantly reducing the number of bits required to represent the locality of an image. To increase the efficienty of the wavelet transformed images using quadtree, the energy of the isolated coefficients is analyzed and those with low energy are eliminated. Furthermore, to control the bit rate the entropy of each block is sorted according to its energy concentration and the number of bits required for encoding, and the blocks with low energy are removed to achieve the desired compression rate.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.13 no.1
• /
• pp.1-8
• /
• 2001

Wave-induced currents drive nearshore transport processes, and hence an accurate understanding of wave-current interaction is required for proper management of coastal zone. This paper presents details of an adaptive quadtree grid based numerical model of the coupled wave climate and depth-averaged current field. The model accounts for wave breaking, shoaling, refraction, diffraction, wave-current interaction, set-up and set-down, mixing processes, bottom friction effects, and movement of land-water interface at the shoreline. The wave period- and depth-averaged governing equations arc discrctized explicitly by means of an Adarns¬Bashforth second-order finite difference technique on adaptive hierarchical staggered quadtree grids. Results from the numerical model are in reasonable agreement with the laboratory data of longshore current generated by oblique waves on a plane beach (Visser 1980, 1991).

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.5
• /
• pp.1825-1839
• /
• 2015

The final draft of the latest video coding standard, High Efficiency Video Coding (HEVC), was approved in January 2013. The coding efficiency of HEVC surpasses its predecessor, H.264/MPEG-4 Advanced Video Coding (AVC), by using only half of the bitrate to encode the same sequence with similar quality. However, the complexity of HEVC is sharply increased compared to H.264/AVC. In this paper, a method is proposed to decrease the complexity of intra coding in HEVC. Early pruning and an early splitting strategy are applied to the quadtree structure of coding tree units (CTU) and residual quadtree (RQT). According to our experiment, when our method is applied to sequences from Class A to Class E, the coding time is decreased by 44% at the cost of a 1.08% Bjontegaard delta rate (BD-rate) increase on average.

• Journal of Korea Spatial Information System Society
• /
• v.5 no.1 s.9
• /
• pp.65-74
• /
• 2003

Location-based service is an important spatiotemporal database application area that provides the location-aware information of wireless terminals via positioning devices such as GPS. With the rapid advances of wireless communication systems, the requirement of mobile application areas including traffic, mobile commerce and supply chaining management became the center of attention for various research issues in spatiotemporal databases. In this paper we present the A-Quadtree, an efficient indexing method for answering location-based queries where the movement vector information (e.g., speed and velocity) is not presented. We implement the A-Quadtree with an index structure for object identifiers as a.Net component to apply the component to multiplatforms. We present our approach and describe the performance evaluation through various experiments. In our experiments, we compare the performance with previous approaches and show the enhanced efficiency of our method.

• Journal of the Korea Computer Graphics Society
• /
• v.17 no.2
• /
• pp.17-26
• /
• 2011

This paper presents an interactive progressive image transmission method, which enables a remote user to interactively select and transmit preferred regions from an index image. Our enhanced quadtree decomposition using PSNR-based rules and new implicit quadtree coding provide better rate-distortion performance than previous quadtree coders as well as leading bit plane methods. An adaptive traversal of child nodes is introduced for better visual display of restored images. Depth-first traversal combined with breadth-first traversal of the quadtree to accomplish interactive transmission as presented, results in a method that provides competitive performance at a low level of computational complexity. Moreover, our decoding requires only simple arithmetic which is enabling our method to be used for real-time mobile applications.

• The KIPS Transactions:PartA
• /
• v.11A no.3
• /
• pp.173-180
• /
• 2004

Quadtree, which 11 a hierarchical data structure, is a very important data structure to represent images. The linear quadtree representation as a way to store a quadtree is efficient to save space compared with other representations. Therefore, it has been widely studied to develop efficient algorithms to execute operations related to quadtrees. The region expansion is an operation to expand images by a given distance and the scaling If an operation to scale images by a given scale factor. In this paper, we present algorithms to perform the region expansion and scaling of images represented by quadtrees, using three-dimensional n${\times}$n${\times}$n processors on RMESH(Reconfigurable MESH). These algorithms have constant time complexities by using efficient basic operations to route the locational codes of quadtree on the hierarchical structure of n${\times}$n${\times}$n RMESH.

• Journal of KIISE:Computer Systems and Theory
• /
• v.31 no.1_2
• /
• pp.10-18
• /
• 2004

Quadtree, which is a hierarchical data structure, is a very important data structure to represent binary images. The linear quadtree representation as a way to store a quadtree is efficient to save space compared with other representations. Therefore, it has been widely studied to develop efficient algorithms to execute operations related with quadtrees. The operations of unaligned linear quadtrees, which are operations among the linear quadtrees with different origin, are able to perform the translated or rotated images efficiently. And this operations requires alignment of the linear quadtrees. In this paper, we present an efficient algorithm to perform alignment of unaligned linear quadtrees, using three-dimensional $n{\pm}n{\pm}n$ processors on RMESH(Reconfigurable MESH). This algorithm has constant-time complexity by using efficient basic operations to route the locational codes of quardtree on the hierarchical structure of $n{\pm}n{\pm}n$ RMESH.