• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 1999.06a
• /
• pp.145.1-149
• /
• 1999

In Computer Graphics, Phong shading algorithm is essential and also sufficient for producing realistic images. In this paper, we propose an approach taking only two additions and one memory access for shading a pixel. A Phong-Shading table is used for storing the values of diffuse and specular components of the Phong reflection model. The intensity of a pixel can be obtained by table lookup. The performance of proposed method is almost the same as Gouraud shading.

• Journal of Power Electronics
• /
• v.18 no.5
• /
• pp.1489-1500
• /
• 2018

Partial shading analysis of large-scale photovoltaic (PV) arrays has recently become a theoretically and numerically challenging issue, and it is necessary for PV system designers. The main contributions of this study are the following: 1) A PSIM-based macro-model was employed because it is remarkably fast, has high precision, and has no convergence issues. 2) Three types of equivalent macro-models were developed for the transformation of a small PV sub-array with uniform irradiance to a new macro-model. 3) On the basis of the proposed new macro-model, a tearing method was established, which can divide a large-scale PV array into several small sub-arrays to significantly improve the efficiency improvement of a simulation. 4) Three platforms, namely, PSIM, PSpice, and MATLAB, were applied to evaluate the proposed tearing method. The proposed models and methods were validated, and the value of this research was highlighted using an actual large-scale PV array with 2420 PV modules. Numerical simulation demonstrated that the tearing method can remarkably improve the simulation efficiency by approximately thousands of times, and the method obtained a precision of nearly 6.5%. It can provide a useful tool to design the optimal configuration of a PV array with a given shading pattern as much as possible.

• Journal of the Korea Computer Graphics Society
• /
• v.20 no.4
• /
• pp.1-7
• /
• 2014

The volume rendering has become an important technique in many applications along with hardware development. Understanding and perception of volume visualization benefit from visual cues which are available from shading. Better visual cues can be obtained from global illumination models but it's huge amount of computation and extra GPU memory need cause a lack of interactivity. In this paper, in order to improve visual cues on volume rendering, we propose an image space occlusion shading model which requires no additional resources.

• KIEAE Journal
• /
• v.13 no.4
• /
• pp.21-26
• /
• 2013

Shading devices have become an integral part of the daylighting strategy for sustainable classroom design. The louver type is newly designed shading devices which provide more view to the outside and protect from outside condition such as snow or rain. The purpose of this study is to compare the daylight performance of traditional and louver type overhang and lightshelf. The room dimension was $7.5m{\times}9.0m{\times}3.0m$. The length of shading devices was calculated by Palmero's study. The length of the traditional and louver type overhang was 455mm, 1210mm and lightshelf was 350/810mm, 625/555mm respectively. For the study, the Radiance 2.0 was used to evaluate the illuminance and uniformity ratios. And scale model were used to evaluate sunpatch area on the floor in model was calculated. The results showed that the louver type lightshelf was suitable for spring and summer, and louver type overhang was suitable for winter.

• Agricultural and Biosystems Engineering
• /
• v.1 no.2
• /
• pp.73-80
• /
• 2000

Aerodynamics in a naturally ventilated multi-span greenhouse with plants was analyzed numerically by the computational fluid dynamics (CFD) simulation. To investigate the potential application of CFD techniques to greenhouse design and analysis, the numerical results of the CFD model were compared with the results of a steady-state mass and energy balance numerical model. Assuming the results of the mass and energy balance model as the standard, reasonably good agreement was obtained between the natural ventilation rates computed by the CFD numerical model and the mass and energy balance model. The steady-state CFD model during a sunny day showed negative errors as high as 15% in the morning and comparable positive errors in the afternoon. Such errors assumed to be due to heat storage in the floor, benches, and greenhouse structure. For a west wind of 2.5 m s$^{-1}$ , the internal nonporous shading screens that opened to the east were predicted to have a 15.6% better air exchange rate than opened to the west. It was generally predicted that the presence of nonporous internal shading screens significantly reduced natural ventilation if the horizontal opening of the screen for each span was smaller that the effective roof vent opening.

• Korean Journal of Computational Design and Engineering
• /
• v.13 no.1
• /
• pp.1-7
• /
• 2008

Data compression becomes increasingly an important issue for reducing data storage spaces as well as transmis-sion time in network environments. In 3D geometric models, the normal vectors of faces or meshes take a major portion of the data so that the compression of the vectors, which involves the trade off between the distortion of the images and compression ratios, plays a key role in reducing the size of the models. So, raising the compression ratio when the normal vector is compressed and minimizing the visual distortion of shape model's shading after compression are important. According to the recent papers, normal vector compression is useful to heighten com-pression ratio and to improve memory efficiency. But, the study about distortion of shading when the normal vector is compressed is rare relatively. In this paper, new normal vector compression method which is clustering normal vectors and assigning Representative Normal Vector (RNV) to each cluster and using the angular deviation from actual normal vector is proposed. And, using this new method, Visually Undistinguishable Lossy Compression (VULC) algorithm which distortion of shape model's shading by angular deviation of normal vector cannot be identified visually has been developed. And, being applied to the complicated shape models, this algorithm gave a good effectiveness.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.18 no.7
• /
• pp.913-921
• /
• 1993

Texture mapping is mostly used as an image synthesis method in the model-based coding system. An image synthesis using this method uses only the texture information of a front face-view. Therefore, when the model is rotated, texture mapping may produce an awkward image in point of shading. In this paper. a new texture mapping method considering shading effect is studied, and also the ear's wireframe and changes of hair are suplemented for the relation. The experimental results show that the proposed method yields the synthesized images with reasonably natural quality.

• Journal of Bio-Environment Control
• /
• v.11 no.2
• /
• pp.93-100
• /
• 2002

This study was carried out not only to develop CFD model for numerically simulating fog cooling system but also to verify the validity of the developed model by data measured in fag cooling greenhouse. In addition the developed model was applied to investigate the effects of spraying water temperature, spraying water amount, spraying interval and evaporation percentage on the performance of the fog cooling system. According to the simulation results, the temperature differences between the measured and predicted temperatures at each measurement point were $0.1~1.4^{\circ}C$ in case of no shading and $0.2~2.3^{\circ}C$ in close of shading. The humidity differences were 0.3~6.0% and 0.7~10.6%, respectively in the cases of no shading and shading. Because the predicted data showed a good agreement with the measured ones, the developed model is supposed to be able to predict the cooling effect of the fog cooling system. The performance of fog cooling system was greatly influenced by spraying water amount, spraying interval and evaporation percentage, but it was not influenced by spraying water temperature.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.45 no.4
• /
• pp.98-106
• /
• 2003

In order to set up structural improvement strategy against meteorological disasters of the shading structures in ginseng fields, structural safety analyses as well as some case studies of structural damage patterns were carried out. According to the results of structural safety analysis, allowable safe snow depth for type B(wood frame with single span) was 25.9 cm, and those for type A(wood frame with multi span) and type C and D (steel frame with multi span) were 17.6 cm, 25.8 cm, and 20.0 cm respectively. So types of shading structures should be selected according to the regional design snow depth. An experiential example study on meteorological disasters indicated that a strong wind damage was experienced once every 20 years, and a heavy snow damage once every 9.5 years. The most serious disasters were caused by heavy snow and it was found that a half break and complete collapse of structures were experienced by about 70% of snow damage. In addition to maintenance, repair and reinforcement, it is also recommended that improved model of shading structures for ginseng cultivation should be developed as a long term countermeasures against meteorological disasters.

• Journal of the Korean Solar Energy Society
• /
• v.31 no.6
• /
• pp.32-39
• /
• 2011

This study is about the installation of the solar cell modules. The solar cell modules are built by the tree-mimic structure, and the performance is compared with that of the flat-plate type solar cell module installation. The mathematical tree model, which was suggested by Fisher and Honda, is utilized to determine the location of the solar cell modules for the tree-mimic type. The experiment shows that the generated electric power of the flat-plate type is higher than that of the tree-mimic type by 30% for one month of July. This lower performance for the tree-mimic type comes from the shading effects among the solar cell modules. The theoretical calculation for the absorbed solar radiation on the two types of solar cell installation shows that the tree-mimic type is higher than the flat-plate type by 8.5%. The shading area for the tree-mimic model is calculated with time by using the 3D-CAD, which will be utilized for the optimization of the tree-mimic model in the future.