• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.6
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• pp.752-757
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• 2017

Analysis has been performed for the penetration of a long-rod into MMC/Ceramic layered armour system with several shot test and a series of simulations. Two types of MMC plate have been fabricated by a liquid pressing method; A356/45%vol.%SiCp with a uniform distribution of SiC particle and Al7075/45%vol.B4Cp with B4C particle. The mechanical properties were measured with the high-speed split Hopkins bar test, hardness test and compression test. The popular Simplified Johnson-Cook model was adopted to represent the material characteristics for FEM simulations. The performance of the MMC applied armour system has been made by comparing with the semi-infinite mild steel target using the depth of penetration(DOP). The results show that placing ceramic front layer provides a certain gain in protection, and that placing another ductile front layer provides a further gain. The application of MMC is found to be attractive.

• PNF and Movement
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• v.18 no.1
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• pp.65-75
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• 2020

Purpose: The purpose of this study was to investigate the differences in muscle thickness and ground reaction force of the vastus medialis oblique and vastus lateral oblique muscles during squats at ankle angles of toe 0°, toe in 10°, and toe out 10°. Methods: In this study, 9 male and 17 female students in their 20s participated in a randomized controlled trial and were compared according to the ankle angles of toe 0°, toe in 10°, and toe out 10°. To determine the reliability and measurement of muscle thickness according to ankle angle using ultrasound equipment and muscle thickness, the participants' ankle angles-toe 0°, toe in 10°, and toe out 10°-were measured three times at the vastus medialis oblique and vastus lateralis oblique muscles during squats. At the same time, the maximum vertical ground reaction force was measured with a force plate. A total of three measurements were taken and averaged, and two minutes of squat movements were assessed between ankle angles to prevent target action. Results: The results of this study illustrated that the reliability of the vastus medialis oblique muscles and vastus lateralis oblique muscles in ankle angle was high. The difference in muscle thickness was significantly greater in comparing the toe out 10° angle with the toe 0° angle than between toe in 10° and toe out 10° in vastus medialis oblique and vastus lateralis oblique (p < 0.05). There was no statistically significant difference between the ankle angle of toe 0° and toe in 10° (p > 0.05). The maximum vertical ground reaction force was significantly greater at toe out 10° than at the ankle angle of toe 0° and toe out 10° and between toe in 10° and toe out 10° (p < 0.05). There was no statistically significant difference in the comparison between toe 0° and toe in 10° (p > 0.05). Conclusion: Squatting at an ankle angle of toe out 10° increases the dorsi flexion; thus, the stability of the ankle and the thickness of both oblique muscles increased to perform more effective squats. In addition, as the base of support widens, it is thought that the stability of the posture increases so that squat training can be performed safely.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.1-6
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• 2005

Analogue physical modelling using granular materials (i.e., sandbox experiments) has been applied with great success to a number of geological problems at various scales. Such physical experiments can also be simulated numerically with the Discrete Element Method (DEM). In this study, we apply the DEM simulation to the collision between the Indian subcontinent and the Eurasian Plate, one of the most significant current tectonic processes in the Earth. DEM simulation has been applied to various kinds of dynamic modelling, not only in structural geology but also in soil mechanics, rock mechanics, and the like. As the target of the investigation is assumed to be an assembly of many tiny particles, DEM simulation makes it possible to treat an object with large and discontinuous deformations. However, in DEM simulations, we often encounter difficulties when we examine the validity of the input parameters, since little is known about the relationship between the input parameters for each particle and the properties of the whole assembly. Therefore, in our previous studies (Yamada et al.,2002a,2002b,2002c), we were obliged to tune the input parameters by trial and error. To overcome these difficulties, we introduce a numerical biaxial test with the DEM simulation. Using the results of this numerical test, we examine the validity of the input parameters used in the collision model. The resulting collision model is quite similar to the real deformation observed in eastern Asia, and compares well with GPS data and in-situ stress data in eastern Asia.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.27-35
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• 2019

The existing middle-long span railway bridge has been mainly applied to steel box girder bridges. However, the steel box girder bridges have disadvantages in securing the space under the bridge, and the main girder is made of a thin plate box shape, resulting in a ringing noise due to the vibration. Many complaints about noise have been raised. For this reason, there is a need for the development of long railway bridges that can replace steel box girder bridges. In this paper, the characteristics of the steel composite railway bridge currently developed were introduced and a time history analysis was conducted using MIDAS Civil reflecting the speed of KTX load for 40m and 50m bridges. In addition, from the analysis results, the dynamic behavior of target bridges were verified and it was examined whether they meet the dynamic performance criteria proposed in the railway design standards. As a result, all of the bridges under review satisfied the dynamic safety criteria, however, in case of 40m of span, the vertical acceleration value was very large. In order to solve this problem, authors proposed the improvement plan and corrected the cross section to confirm that the vertical acceleration decreased.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.1
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• pp.59-69
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• 2021

Recently, large-scale offshore and coastal structures have been constructed owing to the increasing interest in eco-friendly energy development. To achieve this, precise simulations of waves are necessary to ensure the safe operations of marine structures. Several experiments are required in the field to understand the offshore wave; however, in terms of scale, it is difficult to control variables, and the cost is significant. In this study, numerical waves under various wave conditions are produced using a piston-type wavemaker, and the produced wave profiles are verified by comparing with the results from a numerical wave tank (NWT) modeled using the smoothed particle hydrodynamics (SPH) method and theoretical equations. To minimize the effect by the reflected wave, a mass-weighted damping zone is set at the right end of the NWT, and therefore, stable and uniform waves are simulated. The waves are generated using the linear and Stokes wave theories, and it is observed that the numerical wave profiles calculated by the Stokes wave theory yield high accuracy. When the relative depth is smaller than two, the results show good agreement irrespective of the wave steepness. However, when the relative depth and wave steepness are larger than 2 and 0.04, respectively, the errors are negligible if the measurement position is close to the excitation plate. However, the error is 10% or larger if the measurement position is away from the excitation location. Applicable target wave ranges are confirmed through various case studies.

• Journal of the Korea Society for Simulation
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• v.30 no.1
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• pp.55-63
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• 2021

As a study on ballistic protection performance of a weapon system that is used in combat simulation, this paper aims to propose an improvement effect of the ballistic protection performance varying with incident angle of a bullet. For this, live-fire ballistic tests were performed to determine either complete penetration(CP) and partial penetration(PP) of three types of general armor plates made of uniformly rolled steel plates against a small caliber threat using 5.45 mm bullets with various speed. The major test parameter was the material of the weapon system and incident angle of the bullet with the target. Further, to quantitatively analyze the ballistic protection performance, three existing measurement methods were used for ballistic limit velocity. The test results showed that the ballistic protection performance with the incident angle of 30 degrees was 4% to 14% varying with the material of the armor plates greater than that of 0 degrees, which was approximately 1.1 times the performance improvement on average when compared to the conventional angle of incidence of the 0 degree. Those test results are expected to contribute to developing a more realistic combat simulation addressing the parameter improving the ballistic protection performance of an armor plate.

• Journal of the Korean Geotechnical Society
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• v.25 no.9
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• pp.45-55
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• 2009

The quality of railroad trackbed fills has been controlled by field measurements of density and bearing resistance of plate-load tests. The control measures are compatible with the design procedures whose design parameter is $k_{30}$ for both ordinary-speed railways and high-speed railways. However, one of fatal flaws of the design procedures is that there are no simple laboratory measurement procedures for the design parameters ($k_{30}$ or, $E_{v2}$ and $E_{v2}/E_{v1}$) in design stage. To overcome the defect, the compressional wave velocity was adopted as a control measure, in parallel with the advent of the new design procedure, and its measurement technique was proposed in the preliminary investigation. The key concept of the quality control procedure is that the target value for field compaction control is the compressional wave velocity determined at optimum moisture content using modified compaction test, and direct-arrival method is used for the field measurements during construction, which is simple and reliable enough for practice engineers to access. This direct-arrival method is well-suited for such a shallow and homogeneous fill lift in terms of applicability and cost effectiveness. The sensitivity of direct-arrival test results according to the compaction quality was demonstrated at a test site, and it was concluded that compressional wave velocity can be effectively used as quality control measure. The experimental background far the companion study (Park et al., 2009) was established through field and laboratory measurements of the compressional wave velocity.

• Journal of Plant Biotechnology
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• v.33 no.1
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• pp.57-62
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• 2006

Several methods for determining the response of corn to glyphosate were investigated to provide a fast and reliable method for identifying glyphosate-resistant corn in vivo. Two bioassays were developed. One assay is named 'whole plant / leaf growth assay', in which the herbicide glyphosate is applied on the upper part of 3rd leaf and the growth of herbicide-untreated 4th leaf is measured at 3 day after treatment. in this assay, the leaf growth of conventional corn was inhibited in a dose dependent from 50 to $1600{\mu}g/mL$ of glyphosate and growth inhibition at $1600{\mu}g/mL$ was 55% of untreated control. The assay has the potential to be used especially in the case that the primary cause of glyphosate resistance is related with a reduction of the herbicide translocation. Another assay is named 'leaf segment / shikimate accumulation assay', in which the four excised leaf segments ($4{\times}4mm$) are placed in each well of a 48-well microtiter plate containing $200{\mu}L$ test solution and the amount of shikimate is determined after incubation for 24 h in continuous light at $25^{\circ}C$. In this assay, 0.33% sucrose added to basic test solution enhanced a shikimate accumulation by 3 to 4 times and the shikimate accumulation was linearly occurred from 2 to $8{\mu}g/mL$ of glyphosate, showing an improved response to the method described by Shaner et al. (2005). The leaf segment / shikimate accumulation assay is simple and robust and has the potential to be used as a high throughput assay in the case that the primary cause of glyphosate resistance is related with EPSPS, target site of the herbicide. Taken together, these two assays would be highly useful to initially select the lines obtained after transformation, to investigate the migration of glyphosate-resistant gene into other weeds and to detect a weedy glyphosate-resistant corn in field.

• Radiation Oncology Journal
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• v.16 no.3
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• pp.337-345
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• 1998

Purpose : To obtain the uniform dose at limited depth to entire surface of the body, the dose characteristics of degraded electron beam of the large target-skin distance and the dose distribution of the six-dual electron fields were investigated Materials and Method : The experimental dose distributions included the depth dose curve, spatial dose and attenuated electron beam were determined with 300 cm of target-skin distance (TSD) and full collimator size (35*35 $cm^2$ on TSD 100 cm) in 4 MeV electron beam energy. Actual collimated field size of 105 cm * 105 cm at the distance of 300 cm could include entire hemibody. A patient was standing on step board with hands up and holding the pole to stabilize his/her positions for the six-dual fields technique. As a scatter-degrader, 0.5 cm of acrylic plate was inserted at 20 cm from the body surface on the electron beam path to induce ray scattering and to increase the skin dose. Results : The full width at half maximum(FWHM) of dose profile was 130 cm in large field of 105*105 $cm^2$ The width of $100\pm10\%$ of the resultant dose from two adjacent fields which were separated at 25 cm from field edge for obtaining the dose unifomity was extended to 186 cm. The depth of maximum dose lies at 5 mm and the 80$\%$ depth dose lies between 7 and 8 mm for the degraded electron beam by using the 0.5 cm thickness of acrylic absorber. Total skin electron beam irradiation (TSEBI) was carried out using the six dual fields has been developed at Stanford University. The dose distribution in TSEBI showed relatively uniform around the flat region of skin except the protruding and deeply curvatured portion of the body, which showed excess of dose at the former and less dose at the latter. Conclusion : The percent depth dose, profile curves and superimposed dose distribution were investigated using the degraded electron beam through the beam absorber. The dose distribution obtained by experiments of TSEBI showed within$\pm10\%$ difference except the protruding area of skin which needs a shield and deeply curvatured region of skin which needs boosting dose.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.3
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• pp.127-137
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• 2007

To confirm whether or not the Electrochemical Disinfection System (EDS) meet with the D-2 regulation established by IMO (International Maritime Organization), the biological treatment efficacy of the EDS was assessed using three groups of natural marine plankton (bacteria, $10-50\;{\mu}m$ and $>50\;{\mu}m$ sized organisms). Influent water was passed through the EDS under the flow velocity ($23.8\;m^3/hr$) and test design was consisted of control (no treatment) and experimental (10 ppm and 30 ppm) condition for total residual chlorine (TRC). And the biological condition of the influent water followed the standards established by the guidelines for the approval of ballast water management systems. The disinfection efficacy of the $10-50\;{\mu}m$ sized organisms (phytoplankton) was assessed by three kinds of measurements using photomicroscope, epifluorescence microscope and fluorometer (fumer Designs 10-AU). After being passed through the EDS, all motile phytoplankton lost their motility under photomicroscope, the colour of chlorophyll fluorescence fumed from red into green under epifluorescence, and the high chlorophyll fluorescence (Expt. 1: 6.95, Expt. 2: 7.11) detected by fluorometer decreased into value not detected. These results indicated phytoplankton community was totally killed after electrochemical disinfection treatment. Survivorship of the larger organisms than $50\;{\mu}m$ was determined based on the appendage's movement under a stereomicroscope. Natural assemblage collected from ambient seawater was killed shortly after being passed through the EDS, whereas some Artemia remained alive. However, no live Artemia was found after 24 hour further exposure to each TRC concentration (10 and 30 ppm) under darkness. After electrochemical treatment, the target bacteria such as aerobes, coliform and Escherichia coli were completely killed on the basis of CFU (colony forming unit) on Petrifilm plate ($3\;M^{TM}$) after 48 hr incubation. Moreover, no regrowth was found in the three groups of plankton during five days under additional exposure to the treated water. These results indicated that the disinfection efficiency of the EDS on the three groups of plankton satisfy D-2 regulation.