• Structural Engineering and Mechanics
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• v.90 no.4
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• pp.357-370
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• 2024

Due to the fact that the mechanism of the effects of temperature and initial geometric imperfection on low-velocity impact problem of axially moving plates is not yet clear, the present paper is to fill the gap. In the present paper, the nonlinear dynamic behavior of axially moving imperfect graphene platelet reinforced metal foams (GPLRMF) plates subjected to lowvelocity impact in thermal environment is analyzed. The equivalent physical parameters of GPLRMF plates are estimated based on the Halpin-Tsai equation and the mixing rule. Combining Kirchhoff plate theory and the modified nonlinear Hertz contact theory, the nonlinear governing equations of GPLRMF plates are derived. Under the condition of simply supported boundary, the nonlinear control equation is discretized with the help of Gallekin method. The correctness of the proposed model is verified by comparison with the existing results. Finally, the time history curves of contact force and transverse center displacement are obtained by using the fourth order Runge-Kutta method. Through detailed parameter research, the effects of graphene platelet (GPL) distribution mode, foam distribution mode, GPL weight fraction, foam coefficient, axial moving speed, prestressing force, temperature changes, damping coefficient, initial geometric defect, radius and initial velocity of the impactor on the nonlinear impact problem are explored. The results indicate that temperature changes and initial geometric imperfections have significant impacts.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.425-430
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• 2014

Floor coverings and Mats are for children are economical and has excellent workability, as well as they can reduce floor impact noise effective. "When these floorings contact to impact source, they are deformed and change impact force characteristics that strikes floor structure. It is important to measure the impact force spectrum of floorings in order to evaluate reduction of floor impact noise for floorings. In experimental test of floor impact noise and impact force for 14 PVC vinyl floor coverings and 16 mats for children, we confirmed that the impact force spectrum directly related to the floor impact noise spectrum.

• Steel and Composite Structures
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• v.48 no.3
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• pp.305-320
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• 2023

The mechanical properties of polymeric composites are degraded under elevated temperatures due to the effect of temperature on the mechanical behavior of the resin and resin fiber interfaces. In this study, the effect of temperature on the impact response of the carbon fiber reinforced plastics (CFRP) was investigated at low-velocity impact (LVI) using a drop-weight impact tester machine. All the composite plates were fabricated using a vacuum infusion process with a stacking sequence of [45/0_2/-45/90_2]s, and a thickness of 2.9 mm. A group of the specimens was exposed to an environment with a temperature cycling at the range of -30 ℃ to 65 ℃. In addition, three other groups of the specimens were aged at ambient (28 ℃), -30 ℃, and 65 ℃ for ten days. Then all the conditioned specimens were subjected to LVI at three energy levels of 10, 15, and 20 J. To assess the behavior of the damaged composite plates, the force-time, force-displacement, and energy-time diagrams were analyzed at all temperatures. Finally, radiography, optical microscopy, and scanning electron microscopy (SEM) were used to evaluate the effect of the temperature and damages at various impact levels. Based on the results, different energy levels have a similar effect on the LVI behavior of the samples at various temperatures. Delamination, matrix cracking, and fiber failure were the main damage modes. Compared to the samples tested at room temperature, the reduction of temperature to -30 ℃ enhanced the maximum impact force and flexural stiffness while decreasing the absorbed energy and the failure surface area. The temperature increasing to 65 ℃ increased the maximum impact force and flexural stiffness while decreasing the absorbed energy and the failure surface area. Applying 200 thermal cycles at the range of -30 ℃ to 65 ℃ led to the formation of fine cracks in the matrix while decreasing the absorbed energy. The maximum contact force is recorded under cyclic temperature as 5.95, 6.51 and 7.14 kN, under impact energy of 10, 15 and 20 J, respectively. As well as, the minimum contact force belongs to the room temperature condition and is reported as 3.93, 4.94 and 5.71 kN, under impact energy of 10, 15 and 20 J, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1078-1081
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• 2004

A robot manipulator is usually operated in two modes: free motion and constraint motion depending on whether the robot comes into contact with the environment or not. At the moment of contact, impact occurs, and sometimes, it possibly degrade the robot's performance by vibration and at worst, shortens its lifetime. In this article, a new proposed algorithm is described by introducing a command signal modification method on the basis of impedance control and a validity of the proposed algorithm is demonstrated by showing a simulation and an experiment.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.175-180
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• 1993

The nonlinear integro-differential equations of motion of a two-link structurally flexible planar manipulator executing contact tasks are presented. The equations of motion are derived using the extended Hamilton's principle and the Galerkin criterion. Also, Models for the wrist-force sensor and impact that occurs when the manipulator's end point makes contact withthe environment are presented. The dynamic models presented can be used to studythe dynamics of the system and to design controllers.

• Carbon letters
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• v.14 no.3
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• pp.162-170
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• 2013

The performance of graphene-based electronic devices is critically affected by the quality of the graphene-metal contact. The understanding of graphene-metal is therefore critical for the successful development of graphene-based electronic devices, especially field-effect-transistors. Here, we provide a review of the peculiar properties of graphene-metal contacts, including work function pinning, the charge transport mechanism, the impact of the process on the contract resistance, and other factors.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.06a
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• pp.177-182
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• 1999

With the recent evolutionary progress in network and terminal technologies, current videoconference systems are in the level of practical use. The existing systems, however, would not be fully useful for decision making process since eyes of users can not always be in contact that makes it difficult to read the expression of participants. In this paper, we discuss the principle and the impact of“MONJUnoCHIE System”a videoconference system with eye contact using a special display device called“Glass Vision”.

• Journal of Korean Society of Rural Planning
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• v.5 no.2 s.10
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• pp.56-65
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• 1999

Recently, new concept and paradigm of 'Environmentally-Friendliness' is taking a growing interest in environmental planning and design. This study is to establish the evaluation model for environmentally-friendliness of 'Tourism Farms' in rural areas by LISREL structural equation model. A questionnaire survey was conducted for deputy manager group and expert group. As the Result of LISREL structural equation model, the environmentally-friendliness of tourism farms is composed of three categories. First, conservation of global environment (Low Impact), second, friendliness to surrounding nature(High Contact), and third, environmental health and amenities (Health & Amenity). Five indicators, such as (1)saving of energy and water resource, (2)reduction and reuse of garbage, (3)natural purification of sewage disposal, (4)utilization of natural energy, (5)campaign and education programs of environmentally-friendliness, were affecting the first category, i.e., conservation of global environment(Low Impact). Friendliness to surrounding nature (High Contact) is affected by 3 indicators, (1)contact to nature and diverse green areas, (2)water intimate & contact areas, (3)natural ecology observation by biotope. Finally, the dimension of environmental health and amenity is affected by 3 indicators, (1)nature affinity by farming experience, (2)environmental-friendliness of soil & crops by organic farming, (3) campaign and education programs of environmentally-friendliness. Total coefficient of determination of the structural equation model by LISREL was 0.897, which showed high explanatory power.

• Journal of the Korean Institute of Landscape Architecture
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• v.27 no.3
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• pp.69-79
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• 1999

Recently, new concept and paradigm of 'Environmentally-Friendless' is taking a growing interest in environmental planning and design. This study is to develop the new approach of sustainable development, and to establish the indicators for environmentally-friendliness of "Tourism Farms" in rural areas. A questionnaire survey was conducted for deputy manager group and expert group. The environmentally-friendliness of tourism farms is composed of three categories, conservation of global environment(Low Impact), friendliness to surrounding nature(High Contact), and environmental health and amenities (Health '||'&'||' Amenity). Four indicators, such as saving of energy and water resource, reduction and reuse of garbage, natural purification of sewage disposal, and utilization of natural energy, were affecting the first category, i.e., conservation of global environment(Low Impact). And, friendliness to surrounding nature (High Contact) is affected by 3 indicators, such as contact to nature and diverse green areas, water intimate '||'&'||' contact areas, and natural ecology observation by biotope. Finally, the dimension of environmental health and amenity is affected by 3 indicators, such as nature affinity by farming experience, environmental-friendliness of soil '||'&'||' crops by organic farming, campaign and education programs of environmentally-friendliness. From the result of Importance-Performance Analysis(IPA) for 10 indicators, environmentally-friendliness was recommended as 'Concentrate Here'. And, the content validity of 10 indicators for 3 categories was examined by factor analysis. The result showed as the same as hypothetical model, which proved the validity of hypothetical model.

• Structural Engineering and Mechanics
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• v.43 no.2
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• pp.199-209
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• 2012

Two carbon fiber composite laminates, $[0/90]_{2S}$ and $[0/+45/90/-45]_S$, were considered in this work to find out the perforation threshold energy to complete the perforation process and the corresponding maximum contact force. Explicit finite element commercial software, LS-DYNA, was used to predict these values. According to the simulation results, these two types of composite laminates were tested by using a vertical drop-weight testing machine. After testing, the damage condition of these specimens were observed and compared with the results from finite element analysis. The testing results indicate that the perforation threshold energy is 6 Joules for $[0/90]_{2S}$ and 7 Joules for $[0/+45/90/-45]_S$, which is in good agreement with the simulation results. Also, the maximum contact force at the case of perforation threshold energy is the lowest as compared to the maximum contact forces occurring at the impact energy that is larger or less than the perforation threshold energy.