• Journal of Biosystems Engineering
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• v.2 no.1
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• pp.7-24
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• 1977

This paper is the forth and fifth one of the study on balanced type oscillating mole drainer. In the light of the results from previous reports about the model tests, some design criteria were established and a prototype machine was set up for experimental purpose. Motion characteristics and functionof the each parts of the machine were checked and analyzed. After that, performance tests of the prototype machine were carried out in thefield. Obtained results are summarized as follows ; 1. Ten centimeter of the bullet diameter was determined so as to be able to attach it to the tractors with capacity of 30 PS to 40 PS. 2. To maintain the balance between the moments of the front shank and rear shank, the oscillating amplitude of the rear bullet was determined to be larger than that of the front bullet. At the same time , the oscillating direction of the rear bullet was designed with the inclines of ten to thirty degrees. 3. An octagonal dynamo transduced was developed for measuring the compressive force of the upper link is measuring the draft force of the machine. Acceptable linear relationship between forces and strain responses from O.D.T. was obtained. 4. Analysing the balancing mechanism of the acting part of the machine , it was found that the total draft force of the machine was equal to the difference between the sum of the draft force produced from the right and left side bending moments of the lower drawber and the compressive force on the upper link. 5. There are acceptable linear relationship between the strain and twisting moment by driving shaft, and between strain and shank moment. Above results enable us to carry out the field experiment with prototype machine. 6. When the test machine was used in the field, it was possible to reduce the oscillating acceleration by forty percent in average as compared it with the single bullet mole drainer. 7. When the test machine was used under the oscillating condition, the dratt torce was reduced by 27 percent to 59 percent as compared it with the test machine under non-oscillating condition, while the draft force was increased by 7 percent to 20 percent as compared it with the mole drainer having oscillating single bullet. The reasoning behind this fact was considered as the resistance force due to the rear shank and bullet. 8. As the amplitude and frequency of the bullet were increased, the torque was increased accordingly. This tendency could be varied with the various characteristics of the given soils. And the larger frequency and amplitute, the more increasing oscil\ulcornerlating power but decreasing draft brce were needed, and draft force was increased as the velocity was increased.9. When the amplitude of the rear bullet was designed to be larger than that of the front bullet, the minimum value of the moment was lowered and oscillating acceleration was reduced. And when the oscillating direction of the rear bullet was declined back\ulcornerwards, oscillating acceleration was increased along with the increasing angle of decli\ulcornernation. When the test machine was operated in high speed, the difference between maximum moments and minimum ones became narrow. This varying magnitude of moments appeared on the moment oscillogram seems to be correlated to the oscillating acceleration and draft force. 10. From the analysis of variance, it was found that those factors such as frequency, amplitude, and operating velocity significantly affected in the oscillating acceleration, the draft resistance, the torque, the moment, and the total power required. And interaction between frequency and amplitude affected in the oscillating acceleration. 11. Within the given situation of this study, the most preferable operating conditions of the test machine were 7 Hz in oscillating frequency, 0.54 m/sec in operating velocity, and 39.1 mm in oscillating amplitude of front and rear bullets. However, it is necessary to select the proper frequency and magnitude of oscillation depending on the soil properties of the field in which the mole drainer is practiced by use of a bal1nced type oscillating mole drainer. 12. It is recommended that a comparative study of the mole drainers would be performed in the near future using two separate balanced oscillating bullet with the one which is operated by oscillating the movable bullet in a single cylinder or other balanced type which may be single oscillating bullet with spring, damper or balancing weight, and that of thing. To expand the applicability of the balanced type oscillating mole drainer in practical use, it is suggested to develop a new mechanism which perform mole drain with vinyl pipe or filling material such as rice hull.

• Journal of the Korean Society of Food Culture
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• v.16 no.2
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• pp.137-146
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• 2001

Purpose of this study was to investigate the health status and life style of middle-aged people in Daejon. The subjects expressed more fear for disease as getting older(p<0.01). Sixty six percent of the subjects have suffered in the past or suffer at present certain kinds of disease. The older they are, the more disease they have. The alimentary disease, neuralgia, and arthritis were the most popular disease. The eye strain and exhaustion of body were indicated more frequently in fifties than in thirties or forties(p<0.01). They considered excercise as the most important factor to maintain health status, and then moderation in diet, relaxation, rest, decrease of alcohol intake, no smoking. Forty three percent of them were non-drinker. The number of drinker was four times more in male than female and increased as getting younger(p<0.01). Only male revealed smoker and 29% of them smoked 10-20 cigarettes per day. The number of smoker decreased as getting older(p<0.01). Male played exercise more regularly than female and subjects have better exercise habit as getting older(p<0.01). This study suggests that practical programs for self-health control should be developed for playing exercise regularly for female and for considering nutrition, no smoking, and no drinking in the daily life for male.

• Structural Engineering and Mechanics
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• v.63 no.4
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• pp.521-536
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• 2017

Reinforced concrete core-wall structures with buckling-restrained brace outriggers are interesting systems which have the ability to absorb and dissipate energy during strong earthquakes. Outriggers can change the energy demand in a tall building. In this paper, the energy demand was studied by using the nonlinear time history analysis for the mentioned systems. First, the structures were designed according to the prescriptive codes. In the dynamic analysis, three approaches for the core-wall were investigated: single plastic hinge (SPH), three plastic hinge (TPH) and extended plastic hinge (EPH). For SPH approach, only one plastic hinge is allowed at the core-wall base. For TPH approach, three plastic hinges are allowed, one at the base and two others at the upper levels. For EPH approach, the plasticity can extend anywhere in the wall. The kinetic, elastic strain, inelastic and damping energy demand subjected to forward directivity near-fault and ordinary far-fault earthquakes were studied. In SPH approach for all near-fault and far-fault events, on average, more than 65 percent of inelastic energy is absorbed by buckling-restrained braces in outrigger. While in TPH and EPH approaches, outrigger contribution to inelastic energy demand is reduced. The contribution of outrigger to inelastic energy absorption for the TPH and EPH approaches does not differ significantly. The values are approximately 25 and 30 percent, respectively.

• Journal of Ecology and Environment
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• v.38 no.1
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• pp.67-74
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• 2015

Three strains of the green microalga Botryococcus braunii (JJS, KCM, and KJD) were isolated from different water bodies in Korea and grown as batch cultures in the laboratory. The effects of different growth media and temperatures on the growth rate were investigated, as well as the effect of temperature on the total lipid content and lipid profile. All three strains had the highest growth rates in BG-11 medium and at $25^{\circ}C$. Maximal lipid production ($gL^{-1}$) was at $30^{\circ}C$ in the JJS strain and at $25^{\circ}C$ in the KCM and KJD strains. However, all the three strains produced the greatest percent dry weight of total lipids at $15^{\circ}C$ and had the lowest percent dry weight of total lipids at $25^{\circ}C$. In general, oleic acid, linolenic acid, and behenic acid were the most common fatty acids in all three strains. However, the three strains varied considerably in their fatty acid profiles at different culture temperatures.

• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.129-140
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• 1999

This study presents test results of RC beams strengthened by steel plates, carbon fiber sheets(CFS) and aramid fiber sheets(AFS) for increasing flexural and shear resistance. The test was performed with different parameters including the type of strengthening materials, flexural-strengthening methods and shear-strengthening methods. In case of flexural test, RC beams are initially loaded to 70% of the ultimate flexural capacity and in case of shear test loaded to 60 or 80 percent of the ultimate shear capacity and subsequently reinforced with steel plates, CFS and AFS. Experimental data on strength, steel strain, deflection, and mode of failure of the reinforced beams were obtained, and comparisons between the different shear reinforced schemes and the non-strengthened control beams were made. The test results showed that damaged RC beams strengthened by steel plates, CFS and AFS have more improved the flexural and shear capacity. For the beams with external reinforcement by steel plates, aramid fiber sheets and carbon fiber sheets increases in ultimate strength of 4 to 21, 17 to 43 and 26 to 36 percent were respectively achieved. Initial load had small effect on strength after reinforcement, but an important influence on deflection. One sheet reinforced was stronger than two sheets reinforced but less deflected than two sheets reinforced.

• Journal of the Korean Wood Science and Technology
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• v.21 no.3
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• pp.61-66
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• 1993

24mm-thick specimens from three species of plantation-grown softwood were press dried under two platen pressures of 1.75kgf/$cm^2$ and 3.50kgf/$cm^2$ to obtain drying information regarding to drying rate, thickness shrinkage and drying defects. The influence of platen pressure on drying fare in range of moisture content (30 to 10 percent) increased for pitch pine and larch, but reduced for korean white pine at higher pressure. Thickness shrinkage was increased at the higher pressure, and estimated thickness shrinkage at final MC of 10 percent became unrealistically greater for specimens containing higher final moisture content under the great influence of compressive strain. The effects of pressure on the amount of surface checks and honeycombing were different from species used. These species should have applied lower temperature than 177$^{\circ}C$ in this study to reduce surface checks and honeycombing.

• Structural Engineering and Mechanics
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• v.59 no.1
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• pp.153-186
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• 2016

This paper addresses temperature-dependent nonlinear vibration and instability of embedded functionally graded (FG) pipes conveying viscous fluid-nanoparticle mixture. The surrounding elastic medium is modeled by temperature-dependent orthotropic Pasternak medium. Reddy third-order shear deformation theory (RSDT) of cylindrical shells are developed using the strain-displacement relations of Donnell theory. The well known Navier-Stokes equation is used for obtaining the applied force of fluid to pipe. Based on energy method and Hamilton's principal, the governing equations are derived. Generalized differential quadrature method (GDQM) is applied for obtaining the frequency and critical fluid velocity of system. The effects of different parameters such as mode numbers, nonlinearity, fluid velocity, volume percent of nanoparticle in fluid, gradient index, elastic medium, boundary condition and temperature gradient are discussed. Numerical results indicate that with increasing the stiffness of elastic medium and decreasing volume percent of nanoparticle in fluid, the frequency and critical fluid velocity increase. The presented results indicate that the material in-homogeneity has a significant influence on the vibration and instability behaviors of the FG pipes and should therefore be considered in its optimum design. In addition, fluid velocity leads to divergence and flutter instabilities.

• Advanced Composite Materials
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• v.18 no.3
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• pp.265-285
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• 2009

Off-axis compressive deformation behavior of a unidirectional CFRP laminate at high temperature and its strain-rate dependence in a quasi-static range are examined for various fiber orientations. By comparing the off-axis compressive and tensile behaviors at an equal strain rate, the effect of different loading modes on the flow stress level, rate-dependence and nonlinearity of the off-axis inelastic deformation is elucidated. The experimental results indicate that the compressive flow stress levels for relatively larger off-axis angles of $30^{\circ}$, $45^{\circ}$ and $90^{\circ}$ are about 50 percent larger than in tension for the same fiber orientations, respectively. The nonlinear deformations under off-axis tensile and compressive loading conditions exhibit significant strain-rate dependence. Similar features are observed in the fiber-orientation dependence of the off-axis flow stress levels under tension and compression and in the off-axis flow stress differential in tension and compression, regardless of the strain rate. A phenomenological theory of viscoplasticity is then developed which can describe the tension-compression asymmetry as well as the rate dependence, nonlinearity and fiber orientation dependence of the off-axis tensile and compressive behaviors of unidirectional composites in a unified manner. It is demonstrated by comparing with experimental results that the proposed viscoplastic constitutive model can be applied with reasonable accuracy to predict the different, nonlinear and rate-dependent behaviors of the unidirectional composite under off-axis tensile and compressive loading conditions.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.39-45
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• 2008

The most important elements in flexible pavement design criteria are stress and strain distributions. To obtain reasonable stress and strain distributions in pavements, moving wheel loads must be applied to analyze the pavement responses. In this study, finite element analysis was used to identify the three-dimensional states using the vehicle load into a constant-position / time-variable load (25, 50 and 80km/hr). In an elastic system, the strain is the same in both longitudinal and transverse directions under a single wheel. However, the same is not necessary in a viscoelastic system. Test results showed that the maximum values between transverse and longitudinal strains the bottom of asphalt concrete base layers under 25km/hr were were about 40 percent.

• The Plant Pathology Journal
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• v.23 no.1
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• pp.22-25
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• 2007

Biocontrol activity of five strains of selected rhizo-bacteria were tested in tomato against bacterial wilt caused by Ralstonia solanacearum. After root bacterization the plants were grown in a perlite-hydroponic system. Upon challenge inoculation with the pathogen, all of the rhizobacterial strains efficiently suppressed the bacterial wilt in tomato in various rates, at maximum by the strain, Bacillus vallismortis strain EXTN-1. While the percent of infected plants in the non-bacterized control plants were 95%, it was only 65% in plants pre-treated with EXTN-1. It was also demonstrated that the movement of R. solanacearum within the stem was significantly hampered when the plants were root bacterized. As EXTN-1 has no antagonistic properties against R. solanacearum, the bacterial wilt was probably suppressed by a mechanism other than antibiosis. Previously, the strain had been proven to produce an efficient elicitor for inducing systemic resistance in many crops. As the present study confirmed that EXTN-1 has the ability for reducing the pathogen spread in tomato, the strain could be effectively used as a potential biocontrol agent against bacterial wilt.