• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.145-152
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• 1999

This paper presents the principle and experimental results of a non-contact surface roughness measurement by means of screen projected pattern of lase beam reflected from a polished surface. In the reflected laser beam pattern especially from a fine surface like ground or polished one, light intensity varies from the center fo the image to its boundary as the Gaussian distribution. The standard deviation of a light intensity distribution is assumed to be a good non-contact estimator for measuring the surface roughnes, because the light reflectivity is known to be well related with the surface roughness. This method doesn't need to discriminate between the specularly reflected light and the diffusely reflected one, whereas the scattered laser intensity method must do. Nor it needs to adjust the change of light intensity caused by environmental lights or specimen materials. Reflected laser beam pattern narrowly spreads out in the vertical direction to tiny scratches on the polished surface due to abrasives. The deeper the scratch the more the dispersion, which means the rougher surface. The standard deviation of the pattern is nearly in proportion to the surface roughness. Measurement errors by this method are shown to be below 10 percent compared with those obtained by a common contact method. The inclination of measuring unit from the normal axis causes the measurement errors up to 10 percent for an angle of 4 degree. Therefore the proposed method can be used as an on-the-machine quick roughness estimator within 10 percent measurement error.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.672-680
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• 2017

A solar photovoltaic system is composed of a module mounting structure, supporting trunk, and a control unit that supplies generated electrical power to an external power grid or a load. The efficiency of the system depends on the incident solar light, so the mounting structure is installed to face the sun. However, because the sun always moves, systems that track the sun have better efficiency than fixed systems. The structure experiences wind pressure, snow load, seismic load, and structure weight. The wind pressure has the most serious effect on the structure. The pressure was obtained using finite element method for various gaps between modules and angles between the panel and the ground. The wind pressure is lowest when the gap is zero, and it increases with the inclination angle. Based on the results, a mounting structure module was designed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.4 no.3_4
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• pp.79-91
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• 1971

A boat seine has been used as a major fishing gear for catching anchovy (Engraulis japonica) in the southern coastal waters of Korea since 1920s. The original seine was operated by two rowing boats as the haul seine. The rowing boats were, in recent, replaced by powered boats. The net size was enlarged by more than three times the original nit as they began to by operated in the deeper waters of approximately sixty meters. However, there are many problems in the efficiency of the fishing gear to be improved. The authors studied on the hydrodynamic resistance and performance of the boat seine net of the 1/10 scale model in tow. The results are summaried as follows. 1. The hydrodynamic resistance converted from model experiment into the full scale is: $$R_1=30,000\;v^{1.2}\;(0.2{\leqq}v{\leqq}1.0)$$ $$R_2=16,000\;v^2\;(0.2{\leqq}v{\leqq}0.6)$$ where $R_1$ and $R_2$ denote the resistance of whole gear and of bag net in kg respectively, and v the speed of flow in m/sec. 2. In the extension wing, approximately seventy percent of the length of the ground rope from the towing end to the inside-wing slopes down from sea level toward the sea bottom, while the thirty percent of the inside of it remains parallel with th: 5:a level. The performance is regarded to b: inefficient for driving fish shoal into the inside-wing, especially for the shoal diving suddenly. 3. At the towing speed higher than 0.2 m/sec, the trailing edge of the inside-wing is blown backward beyond the seaming line connecting the inside-wing and the mouth of the bag net. It is regarded as an unreasonable performance to drive the fish shoal smoothly into the bag net. 4. At the towing speed higher than 0.2 m/sec, the posterior end of the lower bosom is lifted up above the level of the ground rope of the inside-wing. It is considered that the fish shoal diving suddenly can escape through the discrepancy between the lower bosom and the sea bottom, even if the ground rope of the inside-wing sweeps the sea bottom. 5. The angle of inclination of the upper bosom is estimated as $35\~40^{\circ}$. It seems that the inclination is too steep to drive smoothly the fish shoal diving toward the sea bottom into the bag net. 6. In structure, circumference of the posterior section of the bag net is wider by 1.3 times that of the anterior section. Actually in towing at a speed higher than 0.2m/sec, however, the circumference of the posterior section becomes smaller than that of the anterior section. It is recommended to be designed in a long cylindrical form.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.189-199
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• 2015

Our country's leading granite weathered soil of the ground slope failures that occur in cutting slope most cases, it does not require in-depth to the shear strength most of the surface layer is affected by weathering (1~2 m) at a shallow depth close to the ground, it is important to identify the reliability. Based on the result obtained in actual field investigation, the field slope type was classified by each type of wedge slope, Infinite slope, finite slope -I and finite slope -II, and the slope stability was examined respectively. In addition, using the numerical analysis results, the relationship between the slope inclination angle and safety factor was analyzed and it tried to offer basic data to which the stability in the field slope was able to be estimated by analyzing the safety factor change of the slope according to the slope type. In this study, classified into four types of natural slope, safety factor estimation method by slope types is proposed through the numerical analysis. However, some limit exists in generalizing in this research because it does not test various case studies. Therefore, the case study of a wide range of various sypes to assess the safety of various types slope can be made, accommodate a wide range of field conditions reasonable risk evaluation criteria may be derived.

• Journal of Biosystems Engineering
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• v.38 no.4
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• pp.240-247
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• 2013

Purpose: This study was conducted to develop a rubber-crawler type vehicle as a traveling device for harvesting water-dropwort cultivated in water contained paddy rice field in winter season. Methods: A commercial rubber-crawler type vehicle was used to investigate application of rubber crawler to the paddy rice field as preliminary test. As the result of the preliminary test, a both prototype traveling device with rubber crawlers for a water-dropwort harvest was designed with inclination of $45^{\circ}$ at the front-end and rear-end of crawler under the basic water depth of 0.6 m in the paddy rice field. The device was fabricated and attached to the experimental harvesting test devices on the front of the prototype vehicle. The size of the prototype crawler vehicle with a harvesting part is $2,800{\times}1,460{\times}1,040 $ (mm) ($L{\times}W{\times}H$) with weight of 9.21 kN (maximum). Sizes of the crawler of prototype vehicle are ground contact length of 900 mm, width of 180 mm, height of 1,070 mm and distance between center to center of crawlers of 720 mm. The side-overturn angle of the prototype was $26.4^{\circ}$. Results: Driving performance of the prototype vehicle in water contained paddy field were good at both forward and reverse (backward) directions as weights were applied. The drawbar pull and the maximum sinking depth of the prototype vehicle were 3.5 kN and 0.13 m respectively at water depth of 0.5 m, when the weight and bearing capacity of the prototype rubber crawler in the paddy field were 8.51 kN and 26.3 $kN/m^2$, respectively. Conclusions: Results of the driving test performance of the prototype crawler in paddy rice field at the water depth of 0.5 m were satisfactory. The prototype had enough drawbar pull and driving ability in the deep water contained paddy field.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.97-102
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• 2007

Though the stability analysis of soil slopes widely employs the limit equilibrium method, the study on the jointed rock slopes must consider the direction of joint and the characteristics of Joint at the same time. This study analyzes the result of the change in the factors which show the characteristics of discontinuity and the shape factor of rock slopes, and so on, in an attempt to validate the propriety as to the interpretation of jointed rock slope stability which uses the general finite element program. First, the difference depending on the flow rules was compared, and the factor effect study was conducted. The selected independent variables included the direction of joint which displays the mechanical characteristics of discontinuity, adhesive cohesion, friction angle, the inclination and height of rock slope which reveal the shape of slope and surcharge load. And the horizontal displacement was numerically interpreted at the 1/3 point below the slope, a dependent variable, to compare the relative degree of factor effects. The findings of study on factor effects led to the validation that the result of horizontal displacement for each factor satisfied various engineering characteristics, making it possible to be applied to stability interpretation of jointed rock slope. A modelling is possible, which considers the application of the result of real geotechnical surveys & laboratory studies and the non-linear characteristics when designing the rock slope. In addition, the stress change which may result from the natural disaster, such as precipitation, and the construction, can be expressed. Furthermore, as the complicated rock condition and the ground supporting effect can be considered through FEM, it is considered to be very useful in making an engineering decision on the cut-slope, reinforcement and so on.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.1-7
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• 2018

A folding solar power system is a stand-alone system and is a structure with solar panels attached. It consists of supporting parts and folding parts for ease of movement. While the efficiency of solar panels is also important to produce electricity by maximizing the power efficiency of solar panels, the most important thing is structure stability. The folding solar power structure intended to be developed in this study is a collapsible structure that is easy to move and install into systems that can produce electricity from grid to independent. Since these structures are installed outdoors, wind loads, snow cover, etc. In this paper, the wind loads most affected by the folding solar power generation structure were obtained using the MeshFree Finite Element Method. MeshFree is a program that makes it easier for users to interpret by simplifying the mesh tasks required by an existing analysis. The analysis showed that the greater the angle of inclination of the wind to the ground, the greater the wind load. In addition, reliability was ensured by wind load testing.