• The KIPS Transactions:PartA
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• v.14A no.7
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• pp.421-434
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• 2007

Among many other CG generated natural scenes, the representation of ocean surfaces is one of the most complicated and time-consuming problem because of its large extent and complex surface movement. We present a hybrid method to represent and animate unbound deep-water ocean surfaces by utilizing graphics processor as both simulation and rendering core. Our technique is mainly based on spectral approaches that generate a high-detailed height field using Fourier transform on a 2D regular grid. Additionally, we incorporate Gerstner model and generate low-detailed height field on a 2D projected grid in order to represent large waves and main structure of ocean surface. There is no interruption between CPU and GPU, and no need to transfer simulation results from the system memory to graphics hardware because the entire simulation and rending processes are done on graphics processor. As a result we can synthesize and render realistic water surfaces in real-time. Proposed techniques are readily adoptable to real-time applications such as computer games that have heavy work load on CPU but still demand plausible natural scenes.

• KIISE Transactions on Computing Practices
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• v.23 no.8
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• pp.473-480
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• 2017

In recent years, semiconductor-based storage devices such as flash memory (SSDs) have been developed to high performance. In addition, a trend has been observed of optimally utilizing resources such as the central processing unit (CPU) and memory of the internal controller in the storage device according to the needs of the application. This concept is called In-Storage Processing (ISP). In a storage device equipped with the ISP function, it is possible to process part of the operation executed on the host system, thus reducing the load on the host. Moreover, since the data is processed in the storage device, the data transferred to the host are reduced. In this paper, we propose a method to optimize graph query processing by utilizing these ISP functions, and show that the optimized graph processing method improves the performance of the graph 500 benchmark by up to 20%.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.393-400
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• 2014

Structures are often subject to vehicle collision which can be accidental or terrorist attack. Previous research shows that the damage in major columns may result in progressive collapse of a whole building. This study investigates the performance of a steel column standing on a reinforced concrete footing subjected to a vehicle collision. The size and the axial load of the steel column are determined based on the assumption that it is the first story corner column in a typical three-story building with six meter span length. The finite element model of a eight-ton single unit truck provided by the NCAC (National Crash Analysis Center) is used in the numerical analysis. The finite element analysis is performed using the LS-DYNA, and the results show that the behavior of the column subjected to car impact depends largely on the column-foundation connection detail.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.1
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• pp.25-30
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• 2016

It is critical to forecast the maximum daily and monthly demand for power with as little error as possible for our industry and national economy. In general, long-term forecasting of power demand has been studied from both the consumer's perspective and an econometrics model in the form of a generalized linear model with predictors. Time series techniques are used for short-term forecasting with no predictors as predictors must be predicted prior to forecasting response variables and containing estimation errors during this process is inevitable. In previous researches, seasonal exponential smoothing method, SARMA (Seasonal Auto Regressive Moving Average) with consideration to weekly pattern Neuron-Fuzzy model, SVR (Support Vector Regression) model with predictors explored through machine learning, and K-means clustering technique in the various approaches have been applied to short-term power supply forecasting. In this paper, SARMA and intervention model are fitted to forecast the maximum power load daily, weekly, and monthly by using the empirical data from 2011 through 2013. $ARMA(2,\;1,\;2)(1,\;1,\;1)_7$ and $ARMA(0,\;1,\;1)(1,\;1,\;0)_{12}$ are fitted respectively to the daily and monthly power demand, but the weekly power demand is not fitted by AREA because of unit root series. In our fitted intervention model, the factors of long holidays, summer and winter are significant in the form of indicator function. The SARMA with MAPE (Mean Absolute Percentage Error) of 2.45% and intervention model with MAPE of 2.44% are more efficient than the present seasonal exponential smoothing with MAPE of about 4%. Although the dynamic repression model with the predictors of humidity, temperature, and seasonal dummies was applied to foretaste the daily power demand, it lead to a high MAPE of 3.5% even though it has estimation error of predictors.

• Journal of Broadcast Engineering
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• v.16 no.2
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• pp.258-273
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• 2011

This paper designs and implements a multi-view 3D video player system which is operated faster than existing video player systems. The structure for obtaining the near optimum speed in a multi-processor environment by parallelizing the component modules is proposed to process large volumes of multi-view image data at high speed. In order to use the concurrency of bottleneck, we designed image decoding, synthesis and rendering modules in a pipeline structure. For load balancing, the decoder module is divided into the unit of viewpoint, and the image synthesis module is geometrically divided based on synthesized images. As a result of this experiment, multi-view images were correctly synthesized and the 3D sense could be felt when watching the images on the multi-view autostereoscopic display. The proposed application processing structure could be used to process large volumes of multi-view image data at high speed, using the multi-processors to their maximum capacity.

• Tribology and Lubricants
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• v.34 no.1
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• pp.33-41
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• 2018

This paper describes a new test rig for identification of rotordynamic force coefficients of squeeze film dampers (SFDs) in automotive turbochargers (TCs). Prior studies have mainly concentrated on relatively large-sized SFDs used in aircraft engines, turbocompressors, and turbopumps. The main objective of the current study is to propose a test rig for identification of dynamic force coefficients of small-sized SFDs (a journal diameter of ~11 mm). The current test rig consists of a journal, a SFD cartridge, four support rods, an upper structure, a data acquisition (DAQ) system, and an oil circulation unit. The annular gaps between the journal outer surface and SFD cartridge inner surface create SFD film lands. The damper has two parallel film lands separated by a central groove, having an axial length and depth of 3 mm. Each film land has a length of 4 mm with a $40{\mu}m$ radial clearance. The static load and dynamic impact tests identify the structural characteristics (i.e., stiffness and natural frequency) of the journal and assembled test rig. The measurements show good agreement with predictions. The SFD performance data from this test rig will be used to develop innovative TC rotor systems with improved NVH and reliability characteristics incorporating advanced SFD technology.

• Journal of Biosystems Engineering
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• v.38 no.3
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• pp.171-179
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• 2013

Purpose: A simulator for the design and performance evaluation of a tractor with a hydro-mechanical transmission (HMT) was developed. Methods: The HMT consists of a hydro-static unit (HSU), a swash plate control system, and a planetary gear. It was modeled considering the input/output relationship of the torque and speed, and efficiency of HSU. Furthermore, a dynamic model of a tractor was developed considering the traction force, running resistance, and PTO (power take off) output power, and a tractor performance simulator was developed in the co-simulation environment of AMESim and MATLAB/Simulink. Results: The behaviors of the design parameters of the HMT tractor in the working and driving modes were investigated as follows; For the stepwise change of the drawbar load in the working mode, the tractor and engine speeds were maintained at the desired values by the engine torque and HSU stroke control. In the driving mode, the tractor followed the desired speed through the control of the engine torque and HSU stroke. In this case, the engine operated near the OOL (optimal operating line) for the minimum fuel consumption within the shift range of HMT. Conclusions: A simulator for the HMT tractor was developed. The simulations were conducted under two operation conditions. It was found that the tractor speed and the engine speed are maintained at the desired values through the control of the engine torque and the HSU stroke.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.92-98
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• 2014

Spacer is a construction material for maintaining cover depth and steel installation, however several problems like staining, leakage, and cracking are currently issued due to performance degradation and unsatisfactory dimensional stability of spacer. Plastic composite is widely used for prevention of brittle failure in cement based material, which yields improvement of crack resistance and ductile failure. This study is for development and applicability evaluation of high strength spacer with slag cement for environmental load reduction and plastic composite like polypropylene fiber, nylon fiber, and glass fiber. For this work, unit weight of 4 different plastic fibers are evaluated through preliminary tests. Physical tests including compressive, flexural, and tensile strength and durability tests including absorption, permeability, length change, crack resistance, carbonation, and freezing and thawing are performed. Through various tests, optimum plastic fiber is selected and manufacturing system for high strength spacer with the selected fiber is developed. Dimensional stability of the developed spacer is evaluated through field applicability evaluation.

• Journal of the Korean Geosynthetics Society
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• v.9 no.3
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• pp.57-65
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• 2010

The main objective of this study is to investigate the time-dependent deformation of EPS blocks under repeated loading conditions which is the one of the flexible pavement structure. The study comprised of both the experimental work and analytical modeling in order to understand the behavior of EPS blocks under repeated loading. The analytical modeling included the selection of a suitable model for describing the deformation behavior observed under repeated loading conditions, investigating the relationship among the unit weight, deformation and applied stress, analyzing the effect of repeated load on deformation. The test results were compared with the Findley's theory and model analysis with the results of this research under repeated loading conditions. Both Modified Findley's model and the proposed model can be adopted to illustrate the deformation behavior of EPS blocks under repeated loads.

• Journal of Welding and Joining
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• v.7 no.3
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• pp.19-27
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• 1989

Both the SS41 steel and the M.E.F(martensite encapsulated islands of frrite) dual phase steel made of SS41 steel by heat treatment were welded by friction welding, and then manufactured machinemade Vnotch standard Charpy impact specimens and precracked with a fatigue system at BM(base metal), HAZ(heat affected zone) and WZ(weld interface Zone). The impact test of them was performed with an instrumented impact test machine at a number of temperatures in constant loading velocity and the dynamic fracture characteristics were studied on bases of the absorbed energy, dynamic fracture toughness and fractography from the test. The results obtained are as follows; At the room temperature, the absorbed energy is HAZ.geq.WZ.geq.BM in case of the M.E.F. dual phase steel: BM.geq.HAZ.geq.WZ in case of the SS41 steel, HAZ.geq.BM.geq.WZ at the low temperature. The absorbed energy is decreased markedly with the temperature lowering; it is highly dependent on the temperature. The dynamic fracture toughness of the M.E.F. dual phase steel is HAZ.geq.WZ.geq.BM at the room temperature; BM.geq.WZ.geq.HAZ below-60.deg. C. Therefore the reliability of friction welding is uncertain at the low temperature(below-60.deg. C). The dynamic fracture toughness of the SS41 steel; HZA.geq.WZ.geq.BM at overall temperature region. The flaw formed by rotational upsetting pressure was shown y SEM; in this region. The absorbed energy per unit area and dynamic fracture toughness were low relative to other region.