• The KSFM Journal of Fluid Machinery
• /
• v.10 no.5
• /
• pp.54-63
• /
• 2007

A barrel is a high length-to-diameter ratio cylinder that is influenced by environmental factors such as sunlight, precipitation, wind and clouds. Cross-barrel temperature differences caused by uneven heating or cooling lead to thermal deformation that degrades accuracy. Therefore, a barrel is covered by thermal shrouds to minimize the type of thermal deformation, "fall-of-shot". In this paper, an analytical and experimental study is presented to design the thermal shrouds for a gun barrel and to evaluate the thermal shroud effect. First, an analytical study on the thermal shroud effect to minimize thermal deformation of a gun barrel by sunlight and wind is performed. The coupled analysis of thermal fluid dynamics of the air flow between a barrel and thermal shrouds and thermal stresses of a barrel Is performed to clarify both the thermal shroud effect and the drift in gun muzzle orientation by thermal deformation. Second, experiments are carried out to test and evaluate the thermal shroud effect on the performance of a gun barrel. The drift in gun muzzle orientation against the solar radiation is confirmed by the experiments, and the results well agree with the analytical estimation. Third, three principal design factors that are presumed to have an effect on the performance of the thermal shrouds are also analyzed; sorts of shroud materials, wall-thickness of thermal shrouds, and distance of the gap between a barrel and thermal shrouds.

• YAKHAK HOEJI
• /
• v.54 no.3
• /
• pp.157-163
• /
• 2010

A high-performance liquid chromatography (HPLC) with DAD detector and electrospray ionization mass spectrometry (ESI-MS) was established for the simultaneous determination of coniferin (1), loganic acid (2), demethylsecologanol (3), sweroside (4) and loganin (5) from caulis Lonicera joponica. The optimal chromatographic conditions were obtained on an ODS column ($5{\mu}m$, $4.6{\times}150mm$) with the column temperature $35^{\circ}C$. The mobile phase was composed of (A) water with 0.1% formic acid and (B) methanol with 0.1% formic acid using a gradient elution, the flow rate was 0.3 ml/min. Detection wavelength was set at 254 nm. All calibration curves showed good linear regression ($r^2$>0.998) within test ranges. The developed method provided satisfactory precision and accuracy with overall intra-day and interday variations of 0.16~3.28% and 0.14~1.99%, respectively, and the overall recoveries of 99.39~105.89% for the five compounds analyzed. The verified method was successfully applied to quantitative determination of the two types (phenolic compounds and iridoids) of bioactive compounds in 24 commercial caulis L. japonica samples from different markets in Korea and China. The analytical results demonstrated that the contents of the five analytes vary significantly with sources.

• Journal of the East Asian Society of Dietary Life
• /
• v.22 no.4
• /
• pp.558-565
• /
• 2012

The objective of this study was to develop a predictive growth model for Bacillus cereus in nutrient broth and validate the developed growth model in blanched vegetables. After inoculating B. cereus into nutrient broth, growth of B. cereus was investigated at 13, 17, 24, 30 and $35^{\circ}C$. Lag time (LT) decreased while specific growth rate (SGR) increased with an increase in storage temperature. Growth of B. cereus was not observed at temperatures lower than $12^{\circ}C$. Secondary growth models were developed to describe primary model parameters, including LT and SGR. Model performance was evaluated based on bias factor ($B_f$) and accuracy factor ($A_f$). In addition, we inoculated B. cereus into blanched vegetables stored at 13, 24, $35^{\circ}C$ and observed the growth kinetics of B. cereus in five different blanched vegetables. Growth of B. cereus was most delayed on Doraji at $13^{\circ}C$ and was not observed on Gosari at $13^{\circ}C$. Growth of B. cereus at $35^{\circ}C$ was significantly (p<0.05) slower on Gosari than on other blanched vegetables. The developed secondary LT model for broth in this study was suitable to predict growth of B. cereus on Doraji and Gosari, whereas the SGR model was only suitable for predicting the growth of B. cereus on mung bean sprout.

• Journal of the Optical Society of Korea
• /
• v.18 no.5
• /
• pp.523-530
• /
• 2014

Machine material and structural strain are critical factors for appraising mechanical properties and safety. Particularly in three and four-point bending tests, which appraise the deflection and flexural strain of an object due to external force, measurements are made by the crosshead movement or deflection meter of a universal testing machine. The Digital Image Correlation (DIC) method is one of the non-contact measurement methods. It uses the image analyzing method that compares the reference image with the deformed image for measuring the displacement and strain of the objects caused by external force. Accordingly, the advantage of this method is that the object's surface roughness, shape, and temperature have little influence. However, its disadvantage is that it requires extensive time to compare the reference image with the deformed image for measuring the displacement and strain. In this study, an algorithm is developed for DIC that can improve the speed of image analysis for measuring the deflection and strain of an object caused by a three-point bending load. To implement this algorithm for improving the speed of image analysis, LabVIEW 2010 was used. Furthermore, to evaluate the accuracy of the developed fast correlation algorithm, the deflection of an aluminum specimen under a three-point bending load was measured by using the universal test machine and DIC measurement system.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.17 no.4
• /
• pp.365-374
• /
• 2004

Steel bridges, which have been damaged by load and corrosion, need repair or strengthening. That is a cause of decreasing the durability of structure. In order to solve these problems, welding repair and strengthening methods can be considered. In general, cutting and welding procedure is carried out during the repair welding. Therefore, the investigation of the behavior of residual stress and deformation generated by cutting and welding is very important for safety of structure. Residual stress and deformation produced by gas cutting and arc welding were analyzed using 2D and 3D thermal elasto-plastic FEM. According to the results, the magnitude of temperature was analyzed by 2D-FEM is smaller than that was analyzed using the 3D-FEM at the start and end edge of flange. And the magnitude and distribution of residual stress of perpendicular direction of the cutting line and welding line was analyzed by the 2D-FEM was similar to that was analyzed by 3D-FEM. Therefore, it is possible to predict cutting and welding residual stress by 2D and 3D FEM.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.5 no.3 s.18
• /
• pp.23-28
• /
• 2005

This study defined engineering mechanism and compensation method to establish reference pressure of smoke control zone with atmospheric pressure that is compensated for temperature. The reliable pressure differential sensor was developed by establishing the specifications, algorithms and constructing engineering data. The development of pressure differential sensor can cut down number of processes, manufacturing and installation cost by removing pressure measurement pipe established separately for non smoke control zone, and improve the accuracy of pressure differential by embedding pressure measurement ports for non smoke control zone. More correct and reliable pressure differentials can be obtained by the central control rather than the existent individual control. This will provide the basics and the flexibility to the integral smoke control system and accordingly improve the performance of disaster prevention.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.12
• /
• pp.70-78
• /
• 2000

A novel capacitance deviation-to-time interval converter based on ramp-integration is presented. It consists of two current mirrors, two schmitt triggers, and control digital circuits by the upper and lower sides, symmetrically. Total circuit has been with discrete components. The results show that the proposed converter has a linearity error of less than 1% at the time interval(pulse width) over a capacitance deviation from 295 pF to 375 pF. A capacitance deviation of 40pF and time interval of 0.2 ms was measured for sensor capacitance of 335 pF. Therefore, the high-resolution can be known by counting the fast and stable clock pulses gated into a counter for time interval. The application of a novel capacitance deviation-to time interval converter to a digital humidity controller is also presented. The presented circuit is insensitive to the capacitance difference in disregard of voltage source or temperature deviation. Besides the accuracy, it features the small MOS device count integrable onto a small chip area. The circuit is thus particularly suitable for the on-chip interface.

• Journal of the Korea Concrete Institute
• /
• v.17 no.6 s.90
• /
• pp.871-878
• /
• 2005

Reinforced concrete columns exposed to fire experience severe deterioration in material properties and subsequent structural capacities. Degree of losses in structural capacity of a column due to fire-damage mainly depends on the amount of heat transferred into the column during the fire. A reasonable heat transfer model of fire-damaged reinforced concrete column needs to take into account the heat-dependent nonlinear properties of heat conductivity and heat capacity of concrete as well as the evaporation of moistures in a section during the fire. Compared to the previously suggested models, the developed model in this study has included all these parameters in its numerical expressions based on explicit finite difference method. The developed model could predict the temperature changes with a reasonable accuracy for the columns exposed to fire.

• Journal of the Korea Concrete Institute
• /
• v.14 no.4
• /
• pp.556-565
• /
• 2002

The concrete bridge decks on the main girder will usually develop initial cracks in the longitudinal or the transverse direction due to dry shrinkage and temperature change, and as the bridge decks age the crack will gradually develop in different directions due to repeated cyclic loads. The strengthening direction of the concrete bridge deck is a very important factor in improving proper structural behavior. Therefore, in this study, theoretical analyses of strengthened bridge decks were performed using the nonlinear finite element method. To improve the accuracy of the analytical result, boundary conditions and material property of strengthening material was simulated by laboratory condition and test results, respectively. The effect of the strengthening direction and the amount of strengthening material were estimated and compared to the experimental results. The efficiency of the strengthened bridge decks by strengthening variables such as the amount, width and thickness of CFS was observed.

• Journal of the Korean earth science society
• /
• v.38 no.1
• /
• pp.11-23
• /
• 2017

The short term predictability of wind resources is an important factor in evaluating the economic feasibility of a wind power plant. As a method of improving the predictability, a Bayesian Kalman filter is applied as the model data postprocessing. At this time, a statistical training period is needed to evaluate the correlation between estimated model and observation data for several Kalman training periods. This study was quantitatively analyzes for the prediction characteristics according to different training periods. The prediction of the temperature and wind speed with 3-day short term Bayesian Kalman training at Taebaek area is more reasonable than that in applying the other training periods. In contrast, it may produce a good prediction result in Ieodo when applying the training period for more than six days. The prediction performance of a Bayesian Kalman filter is clearly improved in the case in which the Weather Research Forecast (WRF) model prediction performance is poor. On the other hand, the performance improvement of the WRF prediction is weak at the accurate point.