• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.3
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• pp.62-72
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• 2022

In this study, a miniaturized GPS band(L₁ : 1.575 GHz) antenna that can be mounted on a small drone is proposed. The miniaturization was designed by applying the perturbation method based on the λ/4 microstrip antenna and lengthening the current path at the edge of the patch. The miniaturized antenna was fabricatred such that it could be attached to the surface of styrofoam(ε_r=1.06, t=10 mm) having a size of 10 mm × 9 mm × 10 mm (0.05 λ × 0.05 λ × 0.05 λ). The thickness and length of the feeding line and the spacing between short stubs were adjusted for impedance matching. S₁₁ was found to be -18.8 dB at the center frequency of the fabricated antenna, 1.575 GHz. The radiation pattern measurement results show that the maximum gain of E_θ is 1.87 dBi in 0 directions in the xz-plane, and that E_θ is an omnidirectional characteristic with an average gain of -1.7 dBi in the yz-plane. It was found that the antenna can be used as an ultra-small microstrip antenna, which can be mounted on a small dron for GPS, and is capable of preserving a reduction ratio of 98.8% as compared to a λ/2 microstrip patch antenna.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.6
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• pp.706-711
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• 1997

Low supply of water is generally the most serious factor limiting rice production. The experiment was conducted to identify the reasonable method for minimum irrigation under ridge direct seeding on dry paddy, at National Honam Agricultural Experiment Station, RDA in 1996. The results showed that the reduction ratio of irrigation water was high in order of furrow irrigation at 15-day>furrow irrigation at 10-day>flooding irrigation at 10-day>, and furrow irrigation at 5-day intervals. However, milled rice yield was high in the furrow irrigation at 5-day intervals and in flooding irrigation at 10-day intervals due to high ripened grain as compared with other treatments indicating two treatments were the most reasonable irrigation methods in terms of saving the labor cost and water supply as well as the admittable yield performance.

• Journal of the Korea Society for Simulation
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• v.18 no.3
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• pp.103-112
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• 2009

In a nuclear power plant (NPP), periodic sensor calibrations are required to assure sensors are operating correctly. However, only a few faulty sensors are found to be calibrated. For the safe operation of an NPP and the reduction of unnecessary calibration, on-line calibration monitoring is needed. In this paper, principal component-based Auto-Associative support vector regression (PCSVR) was proposed for the sensor signal validation of the NPP. It utilizes the attractive merits of principal component analysis (PCA) for extracting predominant feature vectors and AASVR because it easily represents complicated processes that are difficult to model with analytical and mechanistic models. With the use of real plant startup data from the Kori Nuclear Power Plant Unit 3, SVR hyperparameters were optimized by the response surface methodology (RSM). Moreover the statistical techniques are integrated with PCSVR for the failure detection. The residuals between the estimated signals and the measured signals are tested by the Shewhart Control Chart, Exponentially Weighted Moving Average (EWMA), Cumulative Sum (CUSUM) and generalized likelihood ratio test (GLRT) to detect whether the sensors are failed or not. This study shows the GLRT can be a candidate for the detection of sensor drift.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.3
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• pp.239-251
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• 2023

The aim of this study is to evaluate the effect of noise-filtering earplugs on the hearing ability of dentists wearing them during noise-induced dental procedures. Pure tone audiometry and distortion product otoacoustic emission (DPOAE) tests were conducted at the initial visit and 1 year later to evaluate the hearing ability of the participants. As a result of the study, the pure tone average of the group wearing earplugs decreased significantly compared to the group not wearing earplugs, indicating an improvement in hearing. However, the signal-to-noise ratio of the DPOAE tests did not show a significant difference. These findings suggest that noise-filtering earplugs may have some effectiveness in preventing hearing loss. However, since the 1-year observation period may not be adequate to identify changes in hearing, a follow-up study with an extended follow-up period is necessary.

• Korean journal of aerospace and environmental medicine
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• v.29 no.2
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• pp.72-76
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• 2019

Over the last decade, human brucellosis (HB) has become a principal zoonosis in Korea. The objective of this study was observing the epidemiological trends of the extensive eradication programs for bovine brucellosis (BB) outbreaks-associated HB in Korea from 2002 to 2013. The raw data analysis in this study was obtained from the website of brucellosis outbreaks by Korea Center for Disease Control and Prevention (KCDC) and Animal and Plant Quarantine Agency (QIA), Korea, 2002~2013. The number of cases of BB outbreaks-associated HB in Korea was increased after 2003 and peaked in 2006 before decreasing thereafter. There were a total of 89,240 infected BB in domestic cattle with a cumulative incidence rate (CIR) of 611.8 per 100,000 cattle; during the same period there were a total of 703 cases of HB with a CIR of 0.12 per 100,000 persons. Moreover, the correlation coefficient of brucellosis outbreaks between cattle and human was highly significant (r=+0.985). The attack ratio of HB was 7.88 per 1,000 BB cases. All of the control measures of HB were applied in the extensive eradication programs for brucellosis outbreaks of infection source in domestic animals and contributed significantly to the reduction in the outbreaks of HB in Korea.

• Composites Research
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• v.20 no.4
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• pp.31-41
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• 2007

Dome shape design methods of Filament Winding (FW) composite pressure vessel, which can suggest various dome contour according to the external loading conditions, were investigated analytically and numerically. The performance indices(PV/W) of the pressure vessels with same cylinder radius and boss opening but different dome shape were evaluated by finite element analysis under the internal pressure loading condition. The analysis results showed that as the dome shape becomes flat, the performance index decreases significantly due to the reduced burst pressure. Especially, for the case of the high value of the parameter ro, the ratio between the radii of the cylinder part and the boss opening, the flat dome is disadvantageous in the aspect of the weight reduction, and additional reinforcing dome design technique should be required to increase the burst pressure. For example, above ro=0.54 condition, the dome shape change according to the loading condition could cause the low burst pressure and increase of composite weight in dome region and is not recommendable except for the special case that maximum inner volume or sufficient space between skirt and dome is the primary design objective. However, at ro=0.35, the dome shape change brings not so significant differences in the performance of FW vessel.

• Steel and Composite Structures
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• v.47 no.1
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• pp.91-102
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• 2023

To study the evaluation standard and control limit of mortar filling layer void length, in this paper, the train sub-model was developed by MATLAB and the track-bridge sub-model considering the mortar filling layer void was established by ANSYS. The two sub-models were assembled into a train-track-bridge coupling dynamic model through the wheel-rail contact relationship, and the validity was corroborated by the coupling dynamic model with the literature model. Considering the randomness of fastening stiffness, mortar elastic modulus, length of mortar filling layer void, and pier settlement, the test points were designed by the Box-Behnken method based on Design-Expert software. The coupled dynamic model was calculated, and the support vector regression (SVR) nonlinear mapping model of the wheel-rail system was established. The learning, prediction, and verification were carried out. Finally, the reliable probability of the amplification coefficient distribution of the response index of the train and structure in different ranges was obtained based on the SVR nonlinear mapping model and Latin hypercube sampling method. The limit of the length of the mortar filling layer void was, thus, obtained. The results show that the SVR nonlinear mapping model developed in this paper has a high fitting accuracy of 0.993, and the computational efficiency is significantly improved by 99.86%. It can be used to calculate the dynamic response of the wheel-rail system. The length of the mortar filling layer void significantly affects the wheel-rail vertical force, wheel weight load reduction ratio, rail vertical displacement, and track plate vertical displacement. The dynamic response of the track structure has a more significant effect on the limit value of the length of the mortar filling layer void than the dynamic response of the vehicle, and the rail vertical displacement is the most obvious. At 250 km/h - 350 km/h train running speed, the limit values of grade I, II, and III of the lengths of the mortar filling layer void are 3.932 m, 4.337 m, and 4.766 m, respectively. The results can provide some reference for the long-term service performance reliability of the ballastless track-bridge system of HRS.

• Journal of agriculture & life science
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• v.50 no.3
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• pp.31-41
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• 2016

This study was conducted to develop a handy earth auger for use in sloppy and rugged forest terrains in order to reduce labor cost which comprises a major part of the production costs in forest afforestation projects. The first prototype is developed consist of two parts, the soil-digging screw and the battery power source. The specifications of the first prototype screw are: length of 170mm, a top diameter of 60mm, bottom diameter of 47mm, 23° angle for each helix, and a 50mm awl-head tip. The use of a single line of screw was selected for reduced weight. In addition, a power source of rotary DC Motor(WD-6G2425, WONILL, Korea) with a maximum torque of 30kgf-cm, rotation of 20-30rpm, K6G30C decelerator with a reduction ratio of 30:1 which could be used with no load for 48 was operated. In consideration of its weight, a lithium battery was utilized in line with the goal of developing a lightweight auger. In order to evaluate the performance of the first prototype, test sites were selected as 6 areas. The rotational force was found to be highest in area A(Solid area), followed by areas F(Mounted slope 40° area) and E(Mounted slope 30° area). It was also observed that in general, the rotational force increased along with the increase in soil depth with the maximum rotational force recorded at 10cm.

• Environmental and Resource Economics Review
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• v.32 no.2
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• pp.107-126
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• 2023

This study analyzes the financial efficiency of the early scappage support system using the benefit and cost analysis. To do so, we use comprehensive administrative data on the early scrappage of old diesel vehicles. The result shows that the benefit-cost ratio was greater than 1 before 2020, but it appeared to be less than 1 after 2020. This indicates that despite recent reforms to increase the subsidy of early scrappage of old diesel vehicles, the rate of the benefit of air quality improvement is not as fast as the increase in system operation cost of this system. The benefit of air quality improvement depends on how much the operating period is shortened due to early scrappage support system. The earlier this period is brought forward, the more likely it is that the benefits of early scrappage will exceed the costs. Upon examining the results of this study, it was found that when the scrappage timing is brought forward by 5 years, the B/C for 98% of the samples becomes 1, greatly securing financial efficiency. Therefore, it is important for the government to reform the system so that it can influence the decision of old diesel vehicle owners on the timing of scrappage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6C
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• pp.321-329
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• 2008

In this study, a series of column test as a way in order to make up for the weakness point of the conventional acceleration method were conducted to both propose the suction board drain method and grapes the specific improvement character of this method as a result of a sort of plastic drain board and a phase of vacuum pressure conditions. On this occasion, the study focused on computing the effective factors of the fittest Suction board drain method affected by each condition through confirming the settlement generated during the test, the water content reduction and stress increase effect occurred arising from the test, and the ratio of consolidation related to the improvement period. In accordance with the shape of core and that whether the core is attached to the filter(pocket or adhesion), the castle type of adhesion and the column type of pocket are more efficient than the others as a consequence of the test to find out the improvement effect depending on each drainage such as a castle type, coil type, harmonica type, column type of pocket and a castle of the adhesion. In case of the step suction pressure, the shorter the period of $-0.8\;kg/cm^2$ as a final step of the suction pressure is, the better the improvement is. In addition, the correlation between degree of consolidation per each suction pressure level and duration of application was drawn as a curve and the point of inflection on this curve was provided to determine the duration period to maximize the consolidation.