• Journal of the Korean Society of Safety
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• v.14 no.2
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• pp.3-10
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• 1999

Fatigue crack growth rates in commercial plate of high strength Al 7075-T651 were investigated for the T-L direction in air, water and sea water. In this paper the effect of cyclic load wave-form(trapezoid and triangle) on fatigue crack growth rates in air, water and sea water environments were investigated using standard LEFM testing procedures. It was founded that the fatigue crack growth behaviors were not affected by cyclic load wave-forms. In region II (stable crack growth region), the fatigue crack growth behaviors were insensitive to cyclic load wave-forms and were sensitive to environment i.e. fatigue crack growth behaviors were higher in sea water than in air for all cyclic load wave-form. The result of fractographical morphology in air, water and sea water by SEM showed obvious dimple rupture and typical striation in air, but transgranular fracture surface in water and sea water. The values m are not affected by corrosion environments but C are different values.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2001.12a
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• pp.27-30
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• 2001

A inventory management system of the manufacturing industry has a model of different kinds according to the objective and the situation. A inventory management system needs superior system technique in demand forecast, economical efficiency, reliability and application for stable supply of the finished goods, the raw materials and the parts. This paper proposes a demand forecast method based on fuzzy structured neural network, which uses min-operation and trapezoid membership function of fuzzy rules. So we can have an intelligent inventory management system for optimized decision-making of forecasting data with expert's opinion in fuzzy environment. This inventory management system used an intelligence agent and it could be adapted to asystemenvironmentchangeinorder.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.2
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• pp.129-134
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• 2017

The process of producing a fish trap frame is very complicated and manual, so it is expensive, the quality of the product is unstable, the quality is not guaranteed, the durability is weak, and it cannot be used for a long time. Therefore, we made a fish trap frame-making machine to reduce the manpower and costs and to make robust products. This machine cuts the wire of mild steel to a certain size and then makes the connecting parts into a trapezoid shape by spot welding. In this study, the weld point shear strength between manual and automatic operation was compared and analyzed.

• School Mathematics
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• v.3 no.2
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• pp.447-473
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• 2001

Since the greater part of mathematical concepts have been developed in the direction of “from the concrete and realistic aspects to the abstract level”, children should be secured to learn mathematics genetically with various manipulative materials. The aim of this study is to instigate the active use of geoboards in mathematics classroom. To achieve this arm, we first embodied the several significances on the use of geoboards in mathematics instruction. And we then performed an instruction that children discover and justify the formula related to the area of trapezoid by exploring with geoboards, and analyzed the instructional episode to support our assertion about some secure merit accompanied by using geoboards. From this study, we obtained the conclusion that geoboard activity contains many significances such as children can explore congruence, symmetry, similarity, fundamental properties of figures, and pattern. Futhermore, geoboard activity enable children to transform a figure into other equivalently, develop spatial sense, have basic experiences for coordinate geometry, build a concrete model to explain abstract ideas, and foster the ability of problem solving and mathematical thinking.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.570-573
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• 2001

This paper presents the characteristics of Switched Reluctance Motor (SRM) based on 3D Equivalent Magnetic Circuit Network Method (3D EMCNM). 3D EMCNM supplements magnetic equivalent circuit by numerical technique using distributive magnetic circuit parameters. However in case of SRM the previous 3D EMCNM which uses fan shape element is not proper for analysis. This paper solved this problem by developing the trapezoid element and verified the validity of the suggested element by comparing the results of 3D EMCNM with 2D FEM.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.342-344
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• 2006

This paper present a method of current control for torque ripple reduction in brushless dc motor which have a trapezoid back EMF. In such drives the current ripples are generated by motor inductance in stator windings and the back EMF. The ripples suppression techniques that are practically effective in high speed as well as in low speed regions are rarely found. The proposed method here is based on a strategy that the commutation intervals of the incoming ang the outgoing phases can be equalized by a proper PWM control.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.95-99
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• 1994

Robot engineering is developed mainly in the field of intelligibility such as a manipulation. Considering the popularization of robots in the future, however, a robot should be studied from a viewpoint of saving energy because a robot is a kind of machine with a energy conversion. This paper deals with minimizing an energy consumption of a manipulator which is driven in a point-to-point control method. When a manipulator carries a heavy payload toward gravitation or the links are de-accelerated for positioning, the motors at joints generate electric energy. Since this energy can be regenerated to the source by using a chopper, the energy consumption of a manipulator is only heat loss by an electric and a frictional resistance of the motors. The minimization of the sum of these losses is reduced Lo a two-points boundary-value problem of an non-linear differential equation. The solutions are obtained by the generalized Newton-Raphson method in this paper. The energy consumption due to the optimum angular velocity patterns of two joints of a two-links manipulator is compared with conventional velocity patterns such as quadratic and trapezoid.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.79-80
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• 2009

Compression stress distribution used to concrete structure design substitutes equivalent rectangle, trapezoid and parabola-rectangle stress block for actual concrete stress distribution. Presently, rectangular stress block of Korea Concrete Design Code is equal to it of ACI code that doesn't reflect the material feature of the high strength concrete. The study does an experiment on concrete compression stress distribution to know the material feature of the concrete used in korea.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.7
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• pp.584-590
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• 2001

An inventory management system of manufacturing industry has a model of different kinds according to the objective and the situation. An inventory management system needs superior system technique in demand forecast, economical efficiency, reliability and application for stable supply of the finished goods, the raw materials and the parts. This paper proposes a demand forecast method based on fuzzy structured neural network, which uses min-operation and trapezoid membership function of fuzzy rules. So we can construct an intelligent inventory management system that make optimized decision-making for forecasting data with expert s opinion in fuzzy environment. The inventory management system uses intelligence agent and it could be adapted to a system environment change in order.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.550-555
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• 2003

When a shock wave arrives at an open end of tube, an impulse wave is discharged from the tube exit and complicated flow is formed near tube exit. The flow field is influenced by the cross-sectional geometry of tube exit, such as circular, square, rectangular, trapezoid and etc. In the current study, three-dimensional propagation characteristics of impulse wave discharged from the tube exit with non-circular cross section are numerically investigated using a CFD method. Total variation diminishing (TVD) scheme is used to solve the three-dimensional, unsteady, compressible Euler equations. Computations are performed for the Mach numbers of the incident shock wave $M_{s}$ below 1.5. The results obtained show that the peak pressure of the impulse wave and propagation directivity depends on the cross-sectional geometry of tube exit and the Mach number of incident shock wave.