• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.53-60
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• 2017

Fly ash(FA) which is a byproduct in the coal combustion in thermal power plant contributes to pore structure densification due to pozzolanic reaction, and this leads to long-term strength development and excellent resistance to chloride penetration. In the work, compressive strength and chloride resistance in OPC(Ordinary Portland Cement) and FA-based concrete are evaluated, and the relationships are investigated considering ages. For the work, 3 different W/B (Water to Binder) ratios of 37%, 42%, and 47% are prepared, and 3 substitution ratio of fly ash(0%, 30%, and 50%) are considered as well. At the age of 28 days and 180 days, test results of compressive strength, diffusion coefficients based on Tang's method, and passed charges referred to ASTM C 1202 and KS F 2711 are obtained. With increasing replacement ratio of FA and decreasing W/B, the resistances to chlorides(diffusion coefficient and passed charge) are improved, and the results at the age of 180 days decrease to only 15% level at the age of 28 days due to pozzolanic reaction in FA 50 mixture, which shows that resistance to chloride is much dependent on age effect than strength development. After 180 days, more clear linear relationships are observed between strength and resistance to chloride.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.6
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• pp.445-452
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• 2015

Software reliability in the software development process is an important issue. Software process improvement helps in finishing with reliable software product. Infinite failure NHPP software reliability models presented in the literature exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. In this paper, proposes the reliability model with log and power intensity function (log linear, log power and exponential power), which made out efficiency application for software reliability. Algorithm to estimate the parameters used to maximum likelihood estimator and bisection method, model selection based on mean square error (MSE) and coefficient of determination($R^2$), for the sake of efficient model, was employed. Analysis of failure, using real data set for the sake of proposing log and power intensity function, was employed. This analysis of failure data compared with log and power intensity function. In order to insurance for the reliability of data, Laplace trend test was employed. In this study, the log type model is also efficient in terms of reliability because it (the coefficient of determination is 70% or more) in the field of the conventional model can be used as an alternative could be confirmed. From this paper, software developers have to consider the growth model by prior knowledge of the software to identify failure modes which can be able to help.

• Journal of Environmental Health Sciences
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• v.48 no.2
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• pp.75-85
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• 2022

Background: Various types of semi-volatile organic compounds (SVOCs) exist in the public's living environment. They occur in different forms in terms of their physical and chemical properties and partition coefficients. As a consequence, indoor exposure to SVOCs occurs via various routes, including inhalation of air and airborne particles, skin contact, and dust intake. Objectives: To propose a method for assessing human exposure to the SVOCs occurring in the air of an indoor environment, the concentrations of SVOCs in house dust and organic films measured in a real residential environment were estimated in terms of gas-phase concentration using the partition coefficient. Assessment of inhalation exposure to SVOCs was performed using this method. Methods: Phthalates were collected from samples of house dust and organic films from 110 households in a real residential environment. To perform an exposures assessment of the phthalates present in organic films, gas-phase concentration was calculated using the partition coefficient. The airborne gas-phase concentrations of phthalates from the house dust and organic films were estimated and exposure assessment was performed based on the assumption of inhalation exposure from air. Results: As a result of the exposure assessment for gas-phase phthalates from house dust and organic films, preschool children showed the highest level of inhalation of phthalates, followed by school children, adults, and adolescents. Conclusions: This study includes the limitation of not considering different SVOCs exposure pathways in the health impact assessment, including those of phthalates in the indoor living environment. However, this study has the significance of performing exposure assessment based on exposure to SVOCs present in indoor air that originated from organic films in the indoor residential environment. Therefore, the results of this study should be useful as basic data for exposure and health risk assessments of SVOCs associated with organic films in the indoor environment.

• Journal of the Korean Geotechnical Society
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• v.24 no.11
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• pp.71-77
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• 2008

In this study, CPT-based methodology for estimating the ultimate lateral resistance, $p_u$, is proposed and verified for lateral loaded piles in sandy soil. Preexistent methods estimating the ultimate lateral resistance, $p_u$, and the ultimate lateral capacity, $H_u$, of pile have been based on the vertical effective stress, relative density, and the coefficient of lateral earth pressure. Similarly, cone resistance $q_c$ in pure sandy soil is expressed by those essential factors. As correlation between $p_u$ and $q_c$ are normalized with average effective stress ${\sigma}_m$, estimation methodology for the lateral loaded pile of $p_u$ in sandy soil is proposed. The method is verified by calibration chamber test results in pure sand. The standard derivation of estimated $p_u$ is 0.279, and COV (Coefficient Of Variation) of estimated $p_u$ is 0.272. These results showed that the estimated pus by the method are analogous with the measured $p_us$ in calibration chamber test.

• Journal of Broadcast Engineering
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• v.20 no.3
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• pp.449-463
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• 2015

Video object tracking is important for variety of applications, such as security, video indexing and retrieval, video surveillance, communication, and compression. This paper proposes an object tracking method in HEVC bitstreams. Without pixel reconstruction, motion vector (MV) and size of prediction unit in the bitstream are employed in an Spatio-Temporal Markov Random Fields (ST-MRF) model which represents the spatial and temporal aspects of the object's motion. Coefficient-based object shape adjustment is proposed to solve the over-segmentation and the error propagation problems caused in other methods. In the experimental results, the proposed method provides on average precision of 86.4%, recall of 79.8% and F-measure of 81.1%. The proposed method achieves an F-measure improvement of up to 9% for over-segmented results in the other method even though it provides only average F-measure improvement of 0.2% with respect to the other method. The total processing time is 5.4ms per frame, allowing the algorithm to be applied in real-time applications.

• Journal of Ocean Engineering and Technology
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• v.32 no.3
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• pp.151-157
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• 2018

Offshore structures are exposed to low- and high-frequency responses due to environmental loads, and fatigue damage models are used to calculate the fatigue damage from these. In this study, we tried to optimize the main parameters used in fatigue damage calculation to derive a new fatigue damage model. A total of 162 bi-modal spectra using the elliptic equation were defined to describe the response of offshore structures. To calculate the fatigue damage from the spectra, time series were generated from the spectra using the inverse Fourier transform, and the rain-flow counting method was applied. The considered optimization variables were the size of the frequency increments, ratio of the time increment, and number of repetitions of the time series. In order to obtain optimized values, the fatigue damage was calculated using the parameter values proposed in previous work, and the fatigue damage was calculated by increasing or decreasing the proposed values. The results were compared, and the error rate was checked. Based on the test results, new values were found for the size of the frequency increment and number of time series iterations. As a validation, the fatigue damage of an actual tension spectrum found using the new proposed values and fatigue damage found using the previously proposed method were compared. In conclusion, we propose a new optimized calculation process that is faster and more accurate than the existed method.

• Journal of Soil and Groundwater Environment
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• v.20 no.3
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• pp.74-82
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• 2015

A method to filter out the effect of river stage fluctuations on groundwater level was designed using an artificial neural network-based time series model of groundwater level prediction. The designed method was applied to daily groundwater level data near the Gangjeong-Koryeong Barrage in the Nakdong river. Direct prediction time series models were successfully developed for both cases of before and after the barrage construction using past measurement data of rainfall, river stage, and groundwater level as inputs. The correlation coefficient values between observed and predicted data were over 0.97. Using the time series models the effect of river stage on groundwater level data was filtered out by setting a constant value for river stage inputs. The filtered data were applied to the hybrid water table fluctuation method in order to estimate the groundwater recharge. The calculated ratios of groundwater recharge to precipitation before and after the barrage construction were 11.0% and 4.3%, respectively. It is expected that the proposed method can be a useful tool for groundwater level prediction and recharge estimation in the riverside area.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.839-844
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• 2003

For mass and volume reduction, input demultiplxer and output multiplexer of satellite transponder widely adopt dual-mode waveguide filters fer channel filters. Generally, channel filters of the input demultiplexer are doubly terminated and channel filters of manifold output multiplexer should be singly terminated fur correct operation. This paper gives a tuning method using short-ended dummy cavity for dual-mode cavity filters. Tuning is based on the match of the computed and measured phase response of reflection coefficient. This proposed method is applied to 4-pole dual-mode doubly terminated elliptic response filter and 6-pole dual-mode singly terminated elliptic response filter for demonstration of this new tuning method. It is shown that this method shows good agreement between the experimental and computed results.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.883-898
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• 2019

This paper employs computational tools to predict power increase (or speed loss) and propulsion performances in waves of KVLCC2. Two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved using finite volume method; and a realizable k-ε model has been applied for the turbulent closure. The free-surface is obtained by solving a VOF equation. Sliding mesh method is applied to simulate the flow around an operating propeller. Towing and self-propulsion computations in calm water are carried out to obtain the towing force, propeller rotating speed, thrust and torque at the self-propulsion point. Towing computations in waves are performed to obtain the added resistance. The regular short head waves of λ/LPP = 0.6 with 4 wave steepness of H/λ = 0.007, 0.017, 0.023 and 0.033 are taken into account. Four methods to predict speed-power relationship in waves are discussed; Taylor expansion, direct powering, load variation, resistance and thrust identity methods. In the load variation method, the revised ITTC-78 method based on the 'thrust identity' is utilized to predict propulsive performances in full scale. The propulsion performances in waves including propeller rotating speed, thrust, torque, thrust deduction and wake fraction, propeller advance coefficient, hull, propeller open water, relative rotative and propulsive efficiencies, and delivered power are investigated.

• Journal of the Korean Dietetic Association
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• v.11 no.2
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• pp.159-169
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• 2005

The purpose of this study was to assess the energy expenditure and investigate the relationship between related variables in 70 female university students. Resting energy expenditure estimated by Harris-Benedict formula, WHO/NAO/FAO formula and various formulas based on body weight and body surface area were 1366.9$\pm$74.4kcal/day, 1287.8$\pm$106.6kcal/day, 1171.4$\pm$155.8kcal/day and 1342.0$\pm$97.4kcal/day. Measured resting energy expenditure by indirect calorimetry(Model : Metavine and TrueOne2400) were 1582.0$\pm$150.1kcal/day and 1268.2$\pm$152.9kcal/day, respectively. Average step number per day was 11981.2$\pm$3014.4 steps and average step number per hour was 746.1$\pm$198.0 steps/hr. Daily energy expenditure by using Harris-Benedict formula, body weight formula, body surface area formula, WHO/NAO.FAO formula and 15-min check list formula were 2374.7$\pm$249.6kcal, 2033.5$\pm$313.2kcal, 2331.2$\pm$266.0kcal, 2240.8$\pm$185.5kcal and 2195.5$\pm$398.3kcal. Meanwhile energy intake of subjects was 1714.9$\pm$551.2 kcal. Daily energy expenditure has positive correlation(r=0.262) with daily step number. And there was significant positive correlations(r=0.35-0.68) between various daily energy expenditures and muscle mass. These results suggested that increase of daily step number by using pedometer is good method to increase daily energy expenditure. In particular, increase in step number can reinforce the amounts of muscle.