• The Journal of the Acoustical Society of Korea
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• v.12 no.2
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• pp.5-13
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• 1993

The purpose of this paper is to suggest and analyze the parallel algorithm for merging two heaps, on SIMD-SM-R parallel computer. In order to create the parallel algorithm for merging two heaps, we have classified two subproblems. For the first method, to select node p as a LEVEL-FIND function, Wyllie(19) suggests the method with time complexity O(log n) while this thesis has O(log(n/k)). For the second method, to merge two subheap, our algorithm has O(log(n/k)*log(n)) using max(2**(i-1), 「(m+1)/4」)'s processors while Dekel and Sahni(4)'s method and Hong's method(18) have O(log m). Also our parallel algorithm's EPU is close to 1 and so has an optimal speed-up ratio.

• Wind and Structures
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• v.17 no.4
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• pp.419-433
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• 2013

This paper investigates the vertical profiles of horizontal mean wind speed and direction based on the synchronized measurements from a Doppler radar profiler and an anemometer during 16 tropical cyclones at a coastal site in Hong Kong. The speed profiles with both open sea and hilly exposures were found to follow the log-law below a height of 500 m. Above this height, there was an additional wind speed shear in the profile for hilly upwind terrain. The fitting parameters with both the power-law and the log-law varied with wind strength. The direction profiles were also sensitive to local terrain setups and surrounding topographic features. For a uniform open sea terrain, wind direction veered logarithmically with height from the surface level up to the free atmospheric altitude of about 1200 m. The accumulated veering angle within the whole boundary layer was observed to be $30^{\circ}$. Mean wind direction under other terrain conditions also increased logarithmically with height above 500 m with a trend of rougher exposures corresponding to lager veering angles. A number of empirical parameters for engineering applications were presented, including the speed adjustment factors, power exponents of speed profiles, and veering angle, etc. The objective of this study aims to provide useful information on boundary layer wind characteristics for wind-resistant design of high-rise structures in coastal areas.

• Journal of Advanced Navigation Technology
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• v.24 no.3
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• pp.198-204
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• 2020

This paper designs a electromagnetic-log (EM-Log) aided navigation filter for maritime environment without global navigation satellite system (GNSS). When navigation is performed for a long time, Inertial navigation system (INS)'s error gradually diverges. Therefore, an integrated navigation method is used to solve this problem. EM-Log sensor measures the velocity of the vehicle. However, since the measured velocity from EM-Log contains the speed of the sea current, the aided navigation filter is required to estimate the sea current. This paper proposes a single model filter and interacting multiple (IMM) model filter methods to estimate the sea current and analyzes the influence of the sea current model on the filter. The performance of the designed aided navigation filter is verified using a simulation and the improvement rate of the filter compared to the pure navigation is analyzed. The performance of single model filter is improved when the sea current model is correct. However, when the sea current model is incorrect, the performance decreases. On the other hands, IMM model filter methods show the stable performance compared to the single model.

• Korean Journal of Agricultural and Forest Meteorology
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• v.26 no.2
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• pp.115-125
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• 2024

Wind is a meteorological factor that has a significant impact on agriculture. Gust cause damage such as fruit drop and damage to facilities. In this study, low-altitude wind speed prediction was performed by applying physical models to Local Ensemble Prediction System (LENS). Logarithmic Law (LOG) and Power Law (POW) were used as the physical models, and Korea Ministry of Environment indicators and Moderate Resolution Imaging Spectroradiometer (MODIS) data were applied as indicator variables. We collected and verified wind and gust data at 3m altitude in 2022 operated by the Rural Development Administration, and presented the results in scatter plot, correlation coefficient, Root Mean Square Error (RMSE), Normalized Root Mean Square Error (NRMSE), and Threat Score (TS). The LOG-applied model showed better results in wind speed, and the POW-applied model showed better results in gust.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.438-441
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• 2000

In this paper, Turbo rode is describing a performance near the Shannon's channel capacity limit. So, basic theory of turbo code and MAP,Log-MAP decoding algorithm was arranged. The foundation of this using VHDL, Log-MAP turbodecoder was implemented by Altera´s FLEX10K CPLD.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.3
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• pp.165-173
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• 2018

Underwater vehicles use Inertial Navigation System (INS) with high-performance Inertial Measurement Unit (IMU) for high precision navigation. However, when underwater navigation is performed for a long time, the INS error gradually diverges, therefore, an integrated navigation method using auxiliary sensors is used to solve this problem. In terms of underwater vehicles, the vertical axis error is primarily compensated through Vertical Channel Damping (VCD) using a depth gauge, and an integrated navigation filter can be designed to perform horizontal axis error and sensor error correction using a speedometer such as Electromagnetic-Log (EM-Log). However, since EM-Log outputs the forward direction relative speed of the vehicle with respect to the sea and sea current, INS correction filter using this may cause a rather large error. Although it is possible to design proper filters if the exact model of the sea current is known, it is impossible to know the accurate model in reality. Therefore, this study proposes an INS/EM-Log integrated navigation filter with the function to estimate sea current using an Interacting Multiple Model (IMM) filters, and the performance of this filter is analyzed through a simulation performed in various environments.

• Ocean and Polar Research
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• v.37 no.4
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• pp.333-340
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• 2015

The contrast (fish body to medium ratio) of density and sound speed were measured to estimate acoustic scattering from small juvenile cod (Gadus macrocephalus) with the Kirchhoff-Ray Mode backscatter model. The density contrast was measured by the density-bottle method and the sound speed contrast was estimated by the time of flight method. The results revealed that the measured density contrasts of juvenile cod varied between 1.003 and 1.029 (mean = 1.014, S.D. = 0.01). On the other hand, sound speed contrasts varied between 1.039 and 1.041 (mean = 1.041, S.D. = 0.001). The relationship between averaged target strength (TS) and total length (TL) established by the model were <$TS_{38kHz}$> = 20log(TL) - 68.8 and <$TS_{38kHz}$> = 20log(TL) - 69.4, respectively.

• Journal of Korean Society of Forest Science
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• v.84 no.2
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• pp.218-225
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• 1995

In this paper, a mechanical analysis model for steep-slope log-skidding operations of a rubber-tired tractor is discussed and the applicability of the model is investigated. The model largely consists of mathematical analysis models for log drag, dynamic vehicle weight distributions and soil-vehicle traction. For the case study, a theoretical data set for log skidding operations is used in investigating the effect of the factors influencing the results of mechanical analysis or the productivity of skidding operations. The analyses include 1) the effect of log choking methods on tangential log-skidding force, 2) the effects of the change in travel speed and log load on the required input power to the wheels and 3) the log skidding performance of a two-wheel drive compared with that of a four-wheel drive.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.190-196
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• 2009

In this paper, performance of a turbo-coded OFDM system is analyzed and simulated in a power line communication channel. Since the power line communication system typically operates in a hostile environment, turbo code has been employed to enhance reliability of transmitted data. The performance is evaluated in terms of bit error probability. As turbo decoding algorithms, MAP (maximum a posteriori), Max-Log-MAP, and SOVA (soft decision Viterbi output) algorithms are chosen and their performances are compared. From simulation results, it is demonstrated that Max-Log-MAP algorithm is promising in terms of performance and complexity. It is shown that performance is substantially improved by increasing the number of iterations and interleaver length of a turbo encoder. The results in this paper can be applied to OFDM-based high-speed power line communication systems.

• Journal of KIISE:Databases
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• v.37 no.5
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• pp.238-249
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• 2010

Flash memory has been studied as a storage medium in order to improve the performance of the system using its high computing speed in the DBMS field where frequent data access is needed. The most difficulty using the flash memory is the performance degradation and the life span shortening of flash memory coming from inefficient in-place update. Log based approaches have been studied to solve inefficient in-place update problem in the DBMS where write operations occur in smaller size of data than page frequently. However the existing log based approaches suffer from the frequent merging operations, which are the principal cause of performance deterioration. Thus is because their fixed log area management can not guarantee a sufficient space for logs. In this paper, we propose non-fixed log area management technique that can minimize the occurrence of the merging operations by promising an enough space for logs. We also suggest the cost calculation model of the optimal log sector number minimizing the system operation cost in a block. In experiment, we show that our non-fixed log area management technique can have the improved performance compared to existing approaches.