• Journal of Korea Water Resources Association
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• v.53 no.7
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• pp.533-543
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• 2020

In order to provide information for proper management of groundwater resources, it is necessary to estimate the rise time of groundwater level by calculating the delay time between the time series of precipitation and groundwater level and to understand the characteristics of groundwater level variation. In this study, total delay time (TDT) and cross correlation coefficient between the moving averaged precipitation generated by using the moving average method to take into account the preceding precipitation and the groundwater level were calculated and analyzed for the nine groundwater level monitoring wells in the Pyoseon watershed in the southeast of Jeju Island. As a result, when the moving averaged precipitation was used, the correlation with the groundwater level was higher in all monitoring wells than in the case of using the raw precipitation, so that it was possible to more clearly estimate the delay time between precipitation and groundwater level. When using the moving averaged precipitation, it had cross correlation coefficients of up to 0.57 ~ 0.58 with the time series data of the groundwater level, and had a relatively high correlation when considering the preceding precipitation of about 24 days on average. The TDT was about 32 days on average, and it was confirmed that the consideration of preceding precipitation plays an important role in estimating the TDT because the days of moving averaged precipitation greatly influences the calculation of the TDT. In addition, through the use of moving averaged precipitation, we found an error in estimating the TDT due to the use of raw precipitation. Through the method of estimating the TDT used in this study and the use of the R code for estimating the TDT presented in the appendix of this paper, it will be possible to estimate the TDT for other regions in the future relatively easily.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.6
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• pp.327-340
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• 2017

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.

• Journal of Korea Water Resources Association
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• v.48 no.7
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• pp.553-566
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• 2015

Acoustic Doppler Current Profilers(ADCPs) have capability to concurrently capitalize three-dimensional velocity vector and bathymetry with highly efficient and rapid manner, and thereby enabling ADCPs to document the hydrodynamic and morphologic data in very high spatial and temporal resolution better than other contemporary instruments. However, ADCPs are also limited in terms of the inevitable unmeasured regions near bottom, surface, and edges of a given cross-section. The velocity in those unmeasured regions are usually extrapolated or assumed for calculating flow discharge, which definitely affects the accuracy in the discharge assessment. This study aimed at scrutinizing a conventional extrapolation method(i.e., the 1/6 power law) for estimating the unmeasured regions to figure out the accuracy in ADCP discharge measurements. For the comparative analysis, we collected spatially dense velocity data using ADV as well as stationary ADCP in a real-scale straight river channel, and applied the 1/6 power law for testing its applicability in conjunction with the logarithmic law which is another representative velocity law. As results, the logarithmic law fitted better with actual velocity measurement than the 1/6 power law. In particular, the 1/6 power law showed a tendency to underestimate the velocity in the near surface region and overestimate in the near bottom region. This finding indicated that the 1/6 power law could be unsatisfactory to follow actual flow regime, thus that resulted discharge estimates in both unmeasured top and bottom region can give rise to discharge bias. Therefore, the logarithmic law should be considered as an alternative especially for the stationary ADCP discharge measurement. In addition, it was found that ADCP should be operated in at least more than 0.6 m of water depth in the left and right edges for better estimate edge discharges. In the future, similar comparative analysis might be required for the moving boat ADCP discharge measurement method, which has been more widely used in the field.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.1
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• pp.27-31
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• 1985

To get well matured farm yard manure from ricestraw as quickly as possible during winter season, straw piles wrapped with polyethylene film and/or straw thatch were stored in the vinyl house or open air. Their maturities and changes of temperature in heap were investigated from the beginning of December 1983 to March of next year. Heat increment in vinyl house was high $2-5^{\circ}C$ than at open air at the lowest temperature but it didn't rise over the freezing point. However, the highest temperature was arisen over than $20^{\circ}C$ averagely at the vinylhouse compared to those of open air during three months. Temperature in piles of straw manure was reached to about $70^{\circ}C$ in maximum and rose again very rapidly after repiling in the vinyl house, whereas increment of temperature after repiling was delayed and took long times to reach the maximum temperature at open air. Wrapping with P.E. film also affected the insulation of decomposing heat of straw pile and promoted the repeat of piling even at open air. By these results, ricestraw would be decomposed rapidly by insulation with P.E. film in the vinyl house and could be reached to matured compost for application to field on next spring season. P.E. film covered for vinyl house was endured until May of next year without tear by weathering.

• Journal of Biomedical Engineering Research
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• v.19 no.1
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• pp.59-68
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• 1998

Digital hearing aids offer many advantages over conventional analog hearing aids. With the advent of high speed digital signal processing chips, new digital techniques have been introduced to digital hearing aids. In addition, the evaluation of new ideas in hearing aids is necessarily accompanied by intensive subject-based clinical tests which requires much time and cost. In this paper, we present an objective method to evaluate and predict the performance of hearing aid systems without the help of such subject-based tests. In the hearing impairment simulation(HIS) algorithm, a sensorineural hearing impairment medel is established from auditory test data of the impaired subject being simulated. Also, the nonlinear behavior of the loudness recruitment is defined using hearing loss functions generated from the measurements. To transform the natural input sound into the impaired one, a frequency sampling filter is designed. The filter is continuously refreshed with the level-dependent frequency response function provided by the impairment model. To assess the performance, the HIS algorithm was implemented in real-time using a floating-point DSP. Signals processed with the real-time system were presented to normal subjects and their auditory data modified by the system was measured. The sensorineural hearing impairment was simulated and tested. The threshold of hearing and the speech discrimination tests exhibited the efficiency of the system in its use for the hearing impairment simulation. Using the HIS system we evaluated three typical hearing aid algorithms.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.365-376
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• 1999

The importance of finishing and polishing the restoration has been described by several authors. The final step provides for improved metallurgical properties, better marginal adaptation, reduced plaque accumulation. Unfortunately, finishing of the restorations can produce damage from temperature rises at the pulpal wall. The aim of this study was to determine the changes in temperature can be occurred during the use of finishing and polishing instruments under a variety of conditions. ; with or without a water coolant, intermittent or continuous operation, high or low rotation speed, remaining dentin thickness and various restorative materials. Class V preparations were cut on extracted molars and restored with composite resin(Z 100), resin-modified glass ionomer cements(Dyract, Fuji II LC), and amalgam. Finishing was done with aluminum oxide coated disc($Sof-lex^{(R)}$ polishing disc, 3M, USA). The following results were obtained. 1. The rise of temperature during polishing of amalgam restorations was the highest among the all experimental groups except polishing with water coolant(P<0.05). However, there were no statistical differences in temperature rises between Z 100, Dyract and Fuji II LC(P>0.05). 2. The intrapulpal temperature was greatly influenced by the applied time, and intermittent polishing was showed significantly lower temperature rises than continuous polishing(P<0.01). 3. The intrapulpal temperature was increased according to the application of polishing regard less of using water coolant. However, polishing with water coolant showed significantly lower temperature in the pulp than not used water coolant(P<0.01).

• Economic and Environmental Geology
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• v.45 no.5
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• pp.487-502
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• 2012

This paper is focused on mineral compositions, microstructures and distributional characters of remained grains in the fault rocks collected from a fault developed in Yongdang-ri, Yangbuk-myeon, Gyeongju City, Korea, using X-ray diffraction (XRD), optical microscope, laser grain size analysis and fractal dimension analysis methods. The exposed fault core zone is about 1.5 meter thick. On the average, the breccia zone is 1.2 meter and the gouge zone is 20cm thick, respectively. XRD results show that the breccia zone consists predominantly of rock-forming minerals including quartz and feldspar, but the gouge zone consists of abundant clay minerals such as chlorite, illite and kaolinite. Mineral vein, pyrite and altered minerals commonly observed in the fault rock support evidence of fault activity associated with hydrothermal alteration. Fractal dimensions based on box counting, image analysis and laser particle analysis suggest that mineral grains in the fault rock underwent fracturing process as well as abrasion that gave rise to diminution of grains during the fault activity. Fractal dimensions(D-values) calculated by three methods gradually increase from the breccia zone to the gouge zone which has commonly high D-values. There are no noticeable changes in D-values in the gouge zone with trend being constant. It means that the bulk-crushing process of mineral grains in the breccia zone was predominant, whereas abrasion of mineral grains in the gouge zone took place by continuous fault activity. It means that the bulk-crushing process of mineral grains in the breccia zone was predominant, whereas abrasion of mineral grains in the gouge zone took place by continuous fault activity. Mineral compositions in the fault zone and peculiar trends in grain distribution indicate that multiple fault activity had a considerable influence on the evolution of fault zones, together with hydrothermal alteration. Meanwhile, fractal dimension values(D) in the fault rock should be used with caution because there is possibility that different values are unexpectedly obtained depending on the measurement methods available even in the same sample.

• Horticultural Science & Technology
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• v.29 no.4
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• pp.317-325
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• 2011

This study was conducted to examine the effect of supplemental lighting on the growth and yield of hydroponically grown sweet pepper (Capsicum annuum L. cv. sprit) under low levels of natural light in winter. The plants were treated with natural light only (control), 3-hour supplemental lighting before sunrise, after sunrise and after sunset with high pressure sodium (HPS, 400W). As the result of these three treatments, the supplemental lighting promoted photosynthesis in the low light intensity condition and particularly photosynthesis was more active right after sun rise in the morning, 1.5-$3.0{\mu}molCO_2{\cdot}m^{-2}{\cdot}s^{-1}$ comparing to those of supplemental lighting after sunset, 0.5-$1.5{\mu}molCO_2{\cdot}m^{-2}{\cdot}s^{-1}$. Transpiration rate and stomatal conductance sharply increased with supplemental lighting after sunrise then they decreased again after turning the lights off. Stomatal size was observed $32.2{\mu}m^2$ after supplemental lighting, whereas the size of the natural light was almost closed at $7.7{\mu}m^2$. The average plant height of sweet papper cv. spirit was 185 cm before sunrise, 188 cm after sunrise and 208 cm after sunset with supplemental lighting for 3hours while the control was 171 cm. With supplemental lighting a better number of fruit set per plant was measured 4.3 before and after sunrise, 3.7 after sunset but 2.6 in the control. Interestingly, there were no significant differences in the sugar content ($^{\circ}Brix$) degree between treatment of supplemental lighting, whereas slight differences between seasons were seen. The marketable fruit yield of sweet pepper (cv. spirit) was $116.0kg{\cdot}ha$ with supplemental lighting, whereas the control (natural light only) was $75.8kg{\cdot}ha$. Despite of spending electricity and depreciation cost, the economic analysis showed net income with supplemental lighting after sunrise was 51% higher than control treatment in cv. spirit.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.35 no.6
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• pp.553-562
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• 2017

GPS (Global Positioning System) receiver among various sensors mounted on UAV (Unmanned Aerial Vehicle) helps to perform various functions such as hovering flight and waypoint flight based on GPS signals. GPS receiver can be used in an environment where GPS signals are smoothly received. However, recently, the use of UAV has been diversifying into various fields such as facility monitoring, delivery service and leisure as UAV's application field has been expended. For this reason, GPS signals may be interrupted by UAV's flight in a shadow area where the GPS signal is limited. Multipath can also include various noises in the signal, while flying in dense areas such as high-rise buildings. In this study, we used analytical photogrammetry and auto tracking total station technique for 3D positioning of UAV. The analytical photogrammetry is based on the bundle adjustment using the collinearity equations, which is the geometric principle of the center projection. The auto tracking total station technique is based on the principle of tracking the 360 degree prism target in units of seconds or less. In both techniques, the target used for positioning the UAV is mounted on top of the UAV and there is a geometric separation in the x, y and z directions between the targets. Data were acquired at different speeds of 0.86m/s, 1.5m/s and 2.4m/s to verify the flight speed of the UAV. Accuracy was evaluated by geometric separation of the target. As a result, there was an error from 1mm to 12.9cm in the x and y directions of the UAV flight. In the z direction with relatively small movement, approximately 7cm error occurred regardless of the flight speed.

• Journal of the Korean Society of School Health
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• v.14 no.1
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• pp.131-143
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• 2001

The primary aim of this dissertation is to contribute to the improvement of methods in physical examination by providing quality information for the current school system and advice for improving status. Present status, controversial points and possible remedies in physical examination were analyzed on a frequency and percentage basis. An $x^2$-test was used to verify the statistics between the results from the examination and each variable. In case of multiple categories of variables, an $x^2$ cs was adopted. Chronological data as well as both total and sampling physical examination data verified the statistics using an $x^2$-test. This thesis is based both on the data from middle school health care specialists in Gyunggi Province and on the analysis of physical examinations reported from local schools to the municipal education agency from 1997 to 1999. The results of the study are as follows: First, according to the survey, only 29.0% of the total schools had their school doctors examine all the students while most of the educational institutions failed to implement the whole process of physical examination on the list. It also turned out that the more students the schools have, the lower the rate of implementation of physical examination by school doctors(p=0.014). Second, the average time a school doctor spends for checkup turned out to be approximately 1.7 minutes per student This means that the quality of the physical examination is not guaranteed in the process. Third, 47.7% of those surveryed say that a dental examination was performed, each taking 21.24 seconds on average. In addition, it shows that some 31.5% wanted to have a task force team for dental checkups at the local health center. Given the fact that dental caries among students is progressively on the rise, the dental health centers that are now set up in some elementary schools should be expanded to cover the whole educational institution in order to raise awareness of the importance of dental care. Fourth, 48.5% of those surveyed say that a comprehensive physical examination should be adopted to promote the health of high schoolers. Since it takes a lot of public funds to implement a comprehensive method, it is essential to make sure that in-depth studies should be based on the frequency and methods of physical examination. Fifth, regarding such diseases among 3rd year middle school students in 1999, statistics shows that there was a slight difference in the prevalence rate of color blindness, and allergic diseases for male students ; and color blindness, hearing disturbance and allergic disease for female students. For those items, however, it is too little to say that there is a significant difference and accordingly it is assumed to be a problem of the measuring process. Sixth, the result of analysis on the sample physical examination and the total physical examination of the year 1999 shows as follows: For male students in the 3rd year of middle school, a slight difference appeared to those students in 11 items including eye problems and eye disease, otitis media, tonsillar hypertrophy, spinal shape, respiratory urinary allergic disease and other abnormal diseases(p<0.05). Particularly, the prevalence rate between students with and without disease was shown to be two times more in the following: eye problems, otitis media, tonsill hypertrophy, allergic diseases, etc. For female students in the 3rd year, prevalence rate showed little difference in 14 items(p<0.05). For items including eye problem, otitis media, tonsill hypertrophy, allergic disease, etc. it was shown that the rate was two times more between students with and without diseases. Physical examinations under the current school system are not producing any fundamental results for the health of the students. Methods and results are not trustworthy. Accordingly, a drastic overhaul of the current practices is needed in frequency, methods and items on the list in order to promote the health of the students. Cost-benefit studies as well as political considerations to ensure the development of efficient methods for physical examination are urgently needed at this moment.