• Journal of Drive and Control
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• v.12 no.4
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• pp.60-70
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• 2015

A front-end loader (FEL) mounted on an agricultural tractor is one of the most commonly used implements for farm work. However, when the tractor carries material using the bucket attached to the FEL on a sloping ground, the materials can spill or roll back over the operator due to the tilted body, thereby requiring the bucket surface to remain level at a constant value regardless of varying slopes. In this study, an active system for controlling the angle of the FEL bucket on a tractor based on the real-time measurement of ground slopes was developed to enable the bucket to constantly remain level. A FEL simulator operated based on an electro hydraulic proportional valve (EHPV) was constructed in the laboratory to develop a proportional-integral-derivative (PID) controller forming a virtual electronic control unit (ECU) on the computer, which could automatically adjust the bucket angles depending on varying input angles while sending SAE-J1939 associated messages via CAN BUS to the EHPV. The different parameter values for the PID controller due to the gravity effect of the bucket were determined using a manual PID tuning method while assuming that the tractor travels on either an ascending slope or a descending slope. The developed PID control-based self-leveling system showed a mean of steady-state errors of within $1^{\circ}$ and a mean of delayed times of ~ 0.8s when the step input of $+20^{\circ}$ was given, implying that the developed system and control algorithm would be effective in maintaining the bucket angle at a certain value. Future studies include the improvement of the control algorithm to reduce such a time delay as well as the application of the developed algorithm to the FEL mounted on a tractor tested at a testing ground.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.283-292
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• 1996

This study was performed to determine the physical properties of rice hull and straw which could be used for an optimum design and operation of the handling facilities for these rice crop by-products. The properties measured were kinetic friction coefficient , bulk density, and dynamic and static angle of repose. Rice hulls with moisture content of 13% and 21% were used throughout the test while rice straws of 10% and 16% moisture were chopped into 10mm length and used for the test. Friction coefficient was calculated from the horizontal traction forces measurement when a container holding the mass of rice hull and straw was pulled over mild steel. PVC, stainless steel, and galvanized steel surface by a universal testing machine. Bulk density was measured by an apparatus consisting of filling fundel and a receiving vessel. Dynamic angle of repose which is the angle at which the material will stand when piled was calculated from the photos of bulk samples after they were flowed by gravity and accumulated on a circular surface. Static angle of repose which is the angle between the horizontal and the sloping side of the material left in the container when discharging was also measured in the similar way. Results and conclusions from this study are summarized as follows . 1. Kinetic friction coefficient of both rice hull and straw were in the range of 0.26 -0.52 and increased with the moisture content. The magnitude of friction increased in the order of galvanized steel, stainless steel, PVC ,and mild steel. 2. Bulk densities of rice hull decreased while those of rice straw increased with moisture content increase . Average bulk densities of rice hull and straw were 96.8 and 74.7kg/㎥, respectively. 3. Average dynamic angle of repose for rice straw was 32.6$^{\circ}$ and those for 13% and 21% moisture rice hull were 38.9$^{\circ}$ and 44.9$^{\circ}$ , respectively. 4. Static angles of repose for both rice hull and straw showed increase with the moisture content. The values were 75.2\ulcorner and 80.2$^{\circ}$ for 13% and 21% moisture rice hull, respectively. Rice straws having 10% and 16% moisture content showed 87.3% and 89.2$^{\circ}$ static angle of repose, respectively.

• Journal of Korea Water Resources Association
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• v.43 no.2
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• pp.153-165
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• 2010

Large-Scale Particle Image Velocimetry (LSPIV) is an extension of particle image velocimetry (PIV) for measurement of flows spanning large areas in laboratory or field conditions. LSPIV is composed of six elements - seeding, illumination, recording, image transformation, image processing, postprocessing - based on PIV. Possible error elements at each step of Mobile LSPIV (MLSPIV), which is a mobile version of LSPIV, in field applications are identified and summarized the effect of the errors which were quantified in the previous studies. The total number of elemental errors is 27, and five error sources were evaluated previously, seven elemental errors are not effective to the current MLSPIV system. Among 15 elemental errors, four errors - sampling time, image resolution, tracer, and wind - are investigated through an experiment at a laboratory to figure out how those errors affect to velocity calculation. The analysis to figure out the effect of the number of images used for image processing on the velocity calculation error shows that if over 50 images or more are used, the error due to it goes below 1 %. The effect of the image resolution on velocity calculation was investigated through various image resolution using digital camera. Low resolution image set made 3 % of velocity calculation error comparing with high resolution image set as a reference. For the effect of tracers and wind, the wind effect on tracer is decreasing remarkably with increasing the flume bulk velocity. To minimize the velocity evaluation error due to wind, tracers with high specific gravity is favorable.

• Journal of the Korean Geophysical Society
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• v.3 no.2
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• pp.127-138
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• 2000

This study was conducted to examine the differences between dynamic and static elastic constants by use of some laboratory tests of cement mortar specimens which have different water/cement mixing ratios. Specific gravity measurement, ultrasonic velocity estimating and uniaxial compression test were adopted to acquire the dynamic and static elastic constants. Digital data acquisition and processing enhanced the accuracy of estimating the velocities of specimens drastically, Also, the method using the gradient of propagation delay time in according to increment of specimen length more enhanced the accuracy than the method using the only one specimen length over total propagation time. The correlation between density and the P and S wave velocity of specimens shows reliable positive relation and the correlation between density and the strength of uniaxial compression has the similar relationship. The dynamic Young's modulus $(E_D)$ is alway greater than the static Young's modulus $(E_S)$ and there is increasing tendency of the ratio $(E_D/E_S)$ according to the increase of density or strength of the specimens. On the other hand, there is no typical relationship between dynamic Poisson's ratio $({\nu}_D)$ and static Poisson's ratio $({\nu}_S)$ and just the ratio of ${\nu}_D/{\nu}_S$ ranges front 69 to 122 %.

• Journal of the Korea Convergence Society
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• v.12 no.9
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• pp.185-191
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• 2021

In our study, we evaluated possibility of distillation process introduction for Korean Rubus coreanus balsamic vinegar production development, has a less complicated and more rapid process leading to higher production volumes and cost savings. In order to investigate the applicability of concentrated vinegar fraction (CVF) and distilled vinegar fraction (DVF) obtained from the distillation process as balsamic and distillation vinegar, acidity, pH, and specific gravity (S.G.) were measured for the vinegar fraction obtained from the distillation process. The acidity of final CVF (60% of initial volume) obtained 4 types of vinegar (acidity; 4.42, 4.84, 5.61, and 6.35) were increased mean 38.1%, compared to initial acidities. Especially, acidity and pH of the final CVF was similar to balsamic vinegar. In addition, acidity of DVF also increased and it of the final fraction was 4.41%, 4.95%, 5.88%, and 6.72%, respectively. And it was suggested that the final DVF could be used as distilled vinegar. In this study, it was confirmed that vinegar can be effectively concentrated through the distillation process, and distilled vinegar can be produced at the same time. However, it is thought that the introduction of the distillation process can be decided only after additional biochemical characteristics such as organic acid content and antioxidant activity measurement for each vinegar fraction are analyzed.

• Korean Journal of Heritage: History & Science
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• v.50 no.2
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• pp.40-61
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• 2017

This study investigated material characteristics of composition and variable strength measurement using physicochemical and petrographic analysis for lime-soil mixture barrier tombs of Guri Galmae site in Joseon Dynasty. The tomb barriers are composed mainly of microcrystalline calcite, quartz, feldspar and mica with lime matrix. The lime matrix shows compact sheet texture, and some samples show hydration aggregates with needle-shaped textures. Gypsum occurred as a secondary process where carbonization reactions were poor. Concentrations of CaO in the tomb barrier very widely ranged from 4.43 to 36.19 wt.%, specific gravity and absorption ratio of the materials show of 1.35 to 1.62 and 20.1 to 32.6%, respectively. As the rebound hardness, the materials ranged from 10.0 to 28.4 (mean 15.7). The values are higher in the $-90^{\circ}$ direction rather than in the $0^{\circ}$ direction with the consequence that the values indicate more strength toward the vertical direction. Difference in strength by directions was caused by the directions of the tomb barriers, which is related to the processes in each stage. In the tomb barriers, ultrasonic velocity and unconfined compressive strength ranged from 1,049.2 to 1,728.9m/s and under 5.00MPa, respectively. Variation patterns between the two are very similar in values. As the result of composition and strength, the materials of higher contents on CaO are higher in strength values. Generally, techniques and skills to make the lime-soil mixture barriers are interpreted as low qualities in relatively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.8
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• pp.531-540
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• 2022

In this paper, we present an algorithm that identifies artillery type and rapidly predicts the impact point based on the IMM filter. The ballistic trajectory equation is used as a system model, and three models with different ballistic coefficient values are used. Acceleration was divided into three components of gravity, air resistance, and lift. And lift acceleration was added as a new state variable. The kinematic condition that the velocity vector and lift acceleration are perpendicular was used as a pseudo-measurement value. The impact point was predicted based on the state variable estimated through the IMM filter and the ballistic coefficient of the model with the highest mode probability. Instead of the commonly used Runge-Kutta numerical integration for impact point prediction, a semi-analytic method was used to predict impact point with a small amount of calculation. Finally, a state variable initialization method using the least-square method was proposed. An integrated algorithm including artillery type identification, impact point prediction and initialization was presented, and the validity of the proposed method was verified through simulation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.40-48
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• 2023

In this paper, a sensor-based monitoring system was established to analyze the long-term behavioral characteristics of the caisson quay wall, a representative structural type in port facilities. Data was collected over a period of approximately 10 months. Based on existing literature, anomalous behaviors of port facilities were classified, and a measurement system was selected to detect them. Monitoring systems were installed on-site to periodically collect data. The collected data was transmitted and stored on a server through LTE network. Considering the site conditions, inclinometers for measuring slope and crack meters for measuring spacing and settlement were installed. They were attached to two caissons for comparison between different caissons. The correlation among measured data, temperature, and tidal level was examined. The temperature dominated the spacing and settlement data. When the temperature changed by approximately 50 degrees, the spacing changed by 10 mm, the settlement by 2 mm, and the slope by 0.1 degrees. On the other hand, there was no clear relationship with tidal level, indicating a need for more in-depth analysis in the future. Based on the characteristics of these collected database, it will be possible to develop algorithms for detecting abnormal states in gravity-type quay walls. The acquisition and analysis of long-term data enable to evaluate the safety and usability of structures in the event of disasters and emergencies.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.383-392
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• 2016

This study is to evaluate the physical and mechanical properties on the Ipseok-dae columnar joints of Mt. Mudeung National Park. For these purposes, physical and mechanical properties as well as discontinuity property on the Mudeungsan tuff, measurement of vibration and local meteorology around columnar joints, and ground deformation by self-weight of columnar joints were examined. For the physical and mechanical properties, average values were respectively 0.65% for porosity, 2.69 for specific gravity, 2.68 g/cm³ for density, and 2411 m/s for primary velocity, 323 MPa for uniaxial compressive strength, 81 GPa Young's modulus, and 0.25 for Poisson's ratio. For the joint shear test, average values were respectively 3.15 GPa/m for normal stiffness, 0.38 GPa/m for shear stiffness, 0.50 MPa for cohesion, and 35° for internal friction angle. The JRC standard and JRC chart was in the range of 4~6, and 1~1.5, respectively. The rebound value Q of silver schmidt hammer was 57 (≒ 90 MPa). It corresponds 20% of the uniaxial compressive strength of intact rock. The maximum vibration value around the Ipseok=dae columnar joints was in the range of 0.57 PPV (mm/s)~2.35 PPV (mm/s). The local meteorology of surface temperature, air temperature, humidity, and wind on and around columnar joints appeared to have been greatly influenced the weather on the day of measurement. For the numerical analysis of ground deformation due to its self-weight of the Ipseok-dae columnar joints, the maximum displacement of the right ground shows when the ground distance is approximately 2 m, while drastically decreased by 2~4 m, thereafter was insignificant. The maximum displacement of the middle ground shows when the ground distance is approximately 0~2 m, while drastically decreased by 3~10 m, thereafter was insignificant. The maximum displacement of the left ground shows when the ground distance is approximately 5~6 m, while drastically decreased by 6~10 m, thereafter was insignificant.

• Journal of radiological science and technology
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• v.27 no.2
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• pp.29-33
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• 2004

Until early 1980s we have lived without thinking that radon ruins our health. But, scientists knew truth that radon radioactive danger is bedeviling on indoor that we live for a long time. Specially, interest about effect that get in danger and injury for Radon and human body is inactive in our country. Recently, with awareness for Radon contamination, We inform about importance and danger of Radon in some station of the Seoul subway, indoor air of school facilities and We had interest with measure and manages. Usually, Radon gas emitted in base of building enters into indoor through building floor split windage back among radon or indoor air of radon daughter nucleus contamination is increased. Therefore, indoor radon concentration rises as there are a lot of windages between number pipe of top and bottom and base that enter crack from estrangement of the done building floor, underground to indoor. Thus, Radon enters into indoor through architecture resources water as well as, kitchen natural gas for choice etc., but more than about 85% from earth's crust emit. Danger and injury of health by Radon and Radon daughter nucleus that is indicated for cause of lung cancer incerases content of uranium of soil rises specially from inside pit of High area and a mine, cave, hermetical space with house. Safe sub-officer of radon concentration can not know and danger always exists large or small during. So, Important thing reduces danger of lung cancer by lowering concentration of Radon within house and building. Therefore, is thought that need general house Radon concentration measurement, measured Radon concentration monthly using Sintillator radon monitor. Study finding appeared high all underground market 1 year than the ground, and the winter appeared high than the summer. Specially, month that pass over 4pCi in house that United States Environmental Protection Agency advises appeared in underground, and appeared and know Radon exposure gravity by 4 months during 12 months. Therefore, Thinking that establishment and regulation of norm and preparation of reduction countermeasure about Radon are pressing feels, and inform result that measure Radon concentration.