• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2102-2107
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• 2007

GSHP systems are used for air-conditioning systems in commercial buildings, schools, and factories because of low operating and maintenance costs. These systems use the earth as a heat source in heating and a heat sink in cooling mode. Ground heat exchangers are classified by a horizontal and vertical type according to the installation method. Vertical type is usually constructed by placing small diameter high density polyethylene tube in a vertical borehole. Vertical tube sizes range from 20 to 40 mm nominal diameter. Borehole depth range between 100 and 200 m depending on local drilling conditions and available equipment. In this study, to evaluate the performance of single u-tube with bentonite grouting, single u-tube with broken stone grouting and double u-tube bentonite grouting of vertical ground heat exchangers, test sections are buried on the earth and experimental apparatus is installed. Therefore the heat transfer performance and pressure loss of these are estimated.

• Structural Engineering and Mechanics
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• v.41 no.2
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• pp.285-297
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• 2012

An inverse approach is presented for calculating the flexibility coefficient of open-side cracks in the cross sectional of beams. The cracked cross section is treated as a massless rotational spring which connects two segments of the beam. Based on the Euler-Bernoulli beam theory, the differential equation governing the forced vibration of each segment of the beam is written. By using a mathematical manipulation the time dependent differential equations are transformed into the static substitutes. The crack characteristics are then introduced to the solution of the differential equations via the boundary conditions. By having the time history of transverse response of an arbitrary location along the beam, the flexibility coefficient of crack is calculated. The method is applied for some cracked beams with solid rectangular cross sections and the results obtained are compared with the available data in literature. The comparison indicates that the predictions of the proposed method are in good agreement with the reported data. The procedure is quite general so as to it can be applicable for both single-side crack and double-side crack analogously. Hence, it is also applied for some test beams with double-side cracks.

• The Journal of Korean Association of Computer Education
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• v.5 no.2
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• pp.39-48
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• 2002

It is general that the ICAI(Intelligent Computer Assisted Instruction) consists of 4 modules. Export module, Teacher module, Student module and Interface module. In each module construction, there should be some rules to control strategies efficiently and systematically that are related to the texts and assessment instruments, assessment results and evaluation, feedback, etc. It is necessary to use a method to classify the curriculum into sections with units and to represent the identified relationships between them. These relationships are available to all the process of learning, assessment, evaluation and feedback. In this paper, we propose the method to represent these units and relationships as a graph. In addition, we implement an internet-based courseware authoring tool to support the environment in which several expert can construct concurrently the courseware with cooperation between them.

• Journal of Welding and Joining
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• v.35 no.1
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• pp.43-48
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• 2017

Pulse TIG (Tungsten Inert Gas) welding is often considered the most difficult of all the welding processes commonly used in industry. Because the welder must maintain a short arc length, great care and skill are required to prevent contact between the electrode and the workpiece. Pulse TIG welding is most commonly used to weld thin sections of stainless steel, non-ferrous metals such as aluminum, magnesium and copper alloys. It is significantly slower than most other welding techniques and comparatively more complex and difficult to master as it requires greater welder dexterity than MIG or stick welding. The problems associated with manual TIG welding includes undercutting, tungsten inclusions, porosity, Heat affected zone cracks and also the adverse effect on health of welding gun operator due to amount of tungsten fumes produced during the welding process. This brings the necessity of automation. Hence, In this paper an attempt has been made to build a customerized setup of Pulse TIG welding based on through review of Pulse TIG welding parameters. The cost associated for making automated TIG is found to be low as compared to SPM (Special Purpose machines) available in the market.

• Journal of the Korean Society of Safety
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• v.23 no.3
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• pp.58-64
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• 2008

In order to identify the exact behavior of corbel section, the horizontal force acting on corbel section should be considered as well as the vertical force. In this study, a new corbel section, which is economical and easy to construct, is developed by evaluating the exact strength of the section. Experiments were performed to verify the strengths of the proposed sections comparing with those of the currently used section. The summary of the experiment results are as follows: 1) In order to minimize the horizontal force effect, it was found that the use of pre-stressing was most effective, and that TB type corbel section is a most efficient section in terms of economy and workability. 2) The experimentally obtained strength of corbel section matched well with that estimated using shear friction theory. Therefore, it is concluded that shear friction theory would be very useful if a precise crack angie in the corbel section, which is pre-stressed by PS strings and threaded bolts, is available.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.3
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• pp.317-322
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• 2012

The low speed aerodynamic characteristics for a modified sonic arc airfoil which is designed by using the nose shape function of sonic arc, the shape function of NACA four-digit wing sections, and Maple are experimentally investigated. The small rotor blades of a modified sonic arc and NACA0012 airfoil are precisely fabricated with a commercially available light aluminum(Al 6061-T6) and are spin tested over a low speed range (3000rpm-5000rpm). In a consuming power comparison, the consuming powers of NACA0012 are higher than that of modified sonic arcs at each pitch angle. The measured rotor thrust for each pitch angle is used to estimate the rotor thrust coefficient according to momentum theory in the hover state. The value of thrust coefficients for both two airfoils at each pitch angle show almost constant values over the low Mach number range. However, the rotor thrust coefficient of NACA0012 is higher than that of the modified sonic arc at each pitch angle. In conclusion, the aerodynamic performance of NACA0012 is better than that of modified sonic arcs in the low speed regime. This test model will provide a convenient platform for improving the aerodynamic performance of small scale airfoils and for performing design optimization studies.

• Korea-Australia Rheology Journal
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• v.13 no.2
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• pp.97-106
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• 2001

Three-dimensional flow analysis was performed by using the control volume finite-element method for design of a profile extrusion die. Because polymer melt behavior is complicated and cross-sectional shape of the profile extrusion die is changing continuously, the fluid flow within the die must be analyzed three-dimensionally. A commercially available polypropylene is used for theoretical and experimental investigations. Material properties are assumed to be constant except for the viscosity. The 5-constant modified Cross model is used for the numerical analysis. A test problem is examined in order to verify the accuracy of the numerical method. Simulations are performed for conditions of three different screw speeds and three different die temperatures. Predicted pressure distribution is compared with the experimental measurements and the results of the previous two-dimensional study. The computational results obtained by using three dimensional CVFEM agree with the experimental measurements and are more accurate than those obtained by using the two-dimensional cross-sectional method. The velocity profiles and the temperature distributions within several cross-sections of the die are given as contour plots.

• Natural Product Sciences
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• v.17 no.1
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• pp.45-50
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• 2011

Sophisticated modern research tools for evaluation of medicinal plants are available but microscopic methods are one of the simplest and cheapest methods to establish the identity of the source materials. Pharmacognostical investigation of the dried, powdered and anatomical sections of the fruits of Trachyspermum roxburghianum (DC) Craib was carried out to determine its macro and microscopical characteristics along with its physical constants. Externally, the fruits, yellowish or greenish brown in colour are elongated, elliptical, slightly curved, prominently ridged and longitudinal. As seen in transectional views of the fruits from Trachyspermum roxburghianum, the mericarp has concave sides called commissural surfaces and a convex outer side called the dorsal surface. The mericarp has three primary ridges alternating with two secondary ridges on the dorsal side. On the commissural side, there are two primary ridges which are lateral in position and two secondary ridges in the commissural side. The seed is attached to the pericarp by a short stalk called a raphe. Circular, four-lobed calcium oxalate crystals are fairly abundant in the endosperm. Phytochemical studies revealed the presence of phenolic compounds, triterpenoids, proteins and sugars. The pharmacognostical profile of the fruits will assist in standardization for quality, purity and sample identification.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.466-469
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• 2007

Heat pumps are used for air-conditioning systems in commercial buildings, schools, and factories because of low operating and maintenance costs. These systems use the earth as a heat source in heating mode and a heat sink in cooling mode. Ground heat exchangers are classified by a horizontal type and vertical type according to the installation method. A horizontal type means that a heat exchanger is laid in the trench bored in 1.2 to 1.8 m depth. And a vertical type is usually constructed by placing small diameter high density polyethylene tube in a vertical borehole. Vertical tube sizes range from 20 to 40 mm nominal diameter. Borehole depth range between 100 and 200 m depending on local drilling conditions and available equipment. In this study, to evaluate the performance of single u-tube with bentonite grouting, single u-tube with broken stone grouting and double n-tube bentonite grouting of vertical ground heat exchangers, test sections are buried on the earth and experimental apparatus is installed. Therefore the heat transfer performance and pressure loss of these are estimated.

• Advances in Computational Design
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• v.1 no.1
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• pp.1-25
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• 2016

Domes are architectural and elegant structures which cover a vast area with no interrupting columns in the middle, and with suitable shapes can be also economical. Domes are built in a wide variety of forms and specialized terms are available to describe them. According to their form, domes are given special names such as network, lamella, Schwedler, ribbed, and geodesic domes. In this paper, an optimum topology design algorithm is performed using the enhanced colliding bodies optimization (ECBO) method. The network, lamella, ribbed and Schwedler domes are studied to determine the optimum number of rings, the optimum height of crown and tubular sections of these domes. The minimum volume of each dome is taken as the objective function. A simple procedure is defined to determine the dome structures configurations. This procedure includes calculating the joint coordinates and element constructions. The design constraints are implemented according to the provision of LRFD-AISC (Load and Resistance Factor Design-American Institute of Steel Constitution). The wind loading act on domes according to ASCE 7-05 (American Society of Civil Engineers). This paper will explore the efficiency of various type of domes and compare them at the first stage to investigate the performance of these domes under different kind of loading. At the second stage the wind load on optimum design of domes are investigated for Schwedler dome. Optimization process is performed via ECBO algorithm to demonstrate the effectiveness and robustness of the ECBO in creating optimal design for domes.