• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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• pp.64-71
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• 2009

A 3-D rehabilitation robot system is developed in this paper. The robot system is for the rehabilitation of upper extremities, especially the shoulder and elbow joints, and has 3-D workspace for enabling occupational therapy to recover physical functions in activities of daily living(ADL). The rehabilitation robot system, which is driven by actuators, has 1 DOF in horizontal rotational motion and 2 DOF in vertical rotational motion, where all actuators are set on the ground. Parallelogram linkage mechanisms lower the equivalent inertia of the control elements as well as control forces. Also the mechanisms have high mechanical rigidity for the end effector and the handle. Passive motion mode experiments have been performed to evaluate the proposed robot system. The results of the experiments show and excellent performance in simulating spasticity of patients.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.194-198
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• 2008

The necessities of development of foundation having minimized occupying area and construction time are required for overpass in the downtown area by which bimodal tram will pass a crossway. We are studying a single column drilled pier foundation which is continuous from pier to pile foundation. Due to the increased resisting moment by reinforced steel which is ranged from the upper part of pile to lower part of column above ground, it can be possible to make a smaller pile-section and lessen the bar reinforcing. And for the excavation work is possible with smaller equipment, this foundation has a improved constructability and economical efficiency. This foundation needs smaller amount of concrete and has a small self-weight. It has an effect on improving resistance against earthquake due to improved ductility in addition to improved rigidity by interaction between concrete and steel.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.1
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• pp.96-101
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• 2001

In designing the greenhouse structures, snow and wind loads must be estimated on the basis of the probability of occurrence of snow or wind storms of a given intensity. The recurrence interval chosen depends on the standard durable years and safety factors of the greenhouse. This study was carried out to find the standard durable years of pipe framed greenhouses. Bend test for metallic materials was conducted on samples of galvanized steel pipes being used in greenhouse frames. A secular change of collapse loads and flexural rigidity for galvanized steel pipes were analyzed with the parts buried in the ground and exposed in the atmosphere. From those experimental results and corrosion rate of galvanized film, the standard durable years for pipe framed greenhouses are estimated as follows ; the small scale pipe houses of movable type is 7∼8 years and the large scale pipe houses of fixed type is 14∼15 years.

• Advances in nano research
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• v.11 no.6
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• pp.641-648
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• 2021

In this article, the dynamic parameters (frequencies, mode shapes, damping ratios) of the scaled concrete structure and the dynamic parameters (frequencies, mode shapes, damping ratios) of the entire outer surface of titanium dioxide, 80 micron in thickness are compared using operational modal analysis method. Ambient excitation was provided from micro tremor ambient vibration data on ground level. Enhanced Frequency Domain Decomposition (EFDD) was used for the output only modal identification. From this study, a good correlation between mode shapes was found. Titanium dioxide applied to the entire outer surface of the scaled concrete structure has an average of 11.78% difference in frequency values and 10.15% in damping ratios, proving that nanomaterials can be used to increase rigidity in structures, in other words, for reinforcement. Another important result determined in the study was the observation of the adherence of titanium dioxide and similar nanomaterials mentioned in the introduction to concrete structure surfaces was at the highest level.

• Advances in nano research
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• v.12 no.1
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• pp.65-72
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• 2022

The dynamic properties (frequencies, mode shapes, damping ratios) of the scaled WPC warehouse are compared using the operational modal analysis approach to the dynamic parameters (frequencies, mode shapes, damping ratios) of the full outer surface of titanium dioxide, 70 micron in thickness. Micro tremor ambient vibration data on ground level was used to provide ambient excitation. For the output-only modal identification, Enhanced Frequency Domain Decomposition (EFDD) was used. This study discovered a strong correlation between mode shapes. Titanium dioxide applied to the entire outer surface of the scaled WPC warehouse results in an average 14.05 percent difference in frequency values and 7.61 percent difference in damping ratios, demonstrating that nanomaterials can be used to increase rigidity in structures, or for reinforcement. Another significant finding in the study was the highest level of adherence of titanium dioxide and similar nanomaterials mentioned in the introduction to WPC structure surfaces.

• Smart Structures and Systems
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• v.26 no.2
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• pp.195-211
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• 2020

Among anti-seismic technologies, base isolation is a very effective means of mitigating damage to structural and nonstructural components, such as equipment. However, most seismic isolation systems are designed for mitigating only horizontal seismic responses because the realization of a vertical isolation system (VIS) is difficult. The difficulty is primarily due to conflicting isolation stiffness demands in the static and dynamic states for a VIS, which requires sufficient rigidity to support the self-weight of the isolated object in the static state, but sufficient flexibility to lengthen the isolation period and uncouple the ground motion in the dynamic state. To overcome this problem, a semi-active VIS, called the piezoelectric inertia-type vertical isolation system (PIVIS), is proposed in this study. PIVIS is composed of a piezoelectric friction damper (PFD) and a leverage mechanism with a counterweight. The counterweight provides an uplifting force in the static state and an extra inertial force in the dynamic state; therefore, the effective vertical stiffness of PIVIS is higher in the static state and lower in the dynamic state. The PFD provides a controllable friction force for PIVIS to further prevent its excessive displacement. For experimental verification, a shaking table test was conducted on a prototype PIVIS controlled by a simple controller. The experimental results well agree with the theoretical results. To further investigate the isolation performance of PIVIS, the seismic responses of PIVIS were simulated numerically by considering 14 vertical ground motions with different characteristics. The responses of PIVIS were compared with those of a traditional VIS and a passive system (PIVIS without control). The numerical results demonstrate that compared with the traditional and passive systems, PIVIS can effectively suppress isolation displacement in all kinds of earthquake with various peak ground accelerations and frequency content while maintaining its isolation efficiency. The proposed system is particularly effective for near-fault earthquakes with long-period components, for which it prevents resonant-like motion.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.1
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• pp.37-47
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• 2007

The shield tunneling method has been increasingly employed to minimize environmental damages and civil complaints in the populated and developed area. A lining segment, which is a main structure of the shield tunnel, consists of joints. Conventional foreign and domestic design data have been commonly used for design practices without a specific verification of structural analysis models, design load, and the effect of soil characteristics on the performance of lining segment. In this study, the suitability of existing analytic models used for the design of shield tunnel lining segment has been evaluated through a comparison between analytical and numerical solutions. Based on the evaluation of their suitability performed in the study, a full-circumferential beam jointed spring model (1R-S0) is proposed for design practices by considering user's convenience, the applicability of field conditions and the accuracy of analysis result. By using the proposed model, the parameter analysis was performed to investigate the effects of joint stiffness, ground rigidity, joint distribution and the number of joints on the behavior of lining segment. Parameters considered in the investigation have been appeared to affect the behavior of lining segment. Among those parameters, joint stiffness has been appeared to have the most significant effect on the bending moment and displacement of lining segment.

• Journal of the Korean Society for Railway
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• v.19 no.6
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• pp.792-801
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• 2016

Standard Penetration Test (SPT) and Cone Penetration Test (CPT) are widely used in geotechnical investigation methods for railway roadbed. However, SPT can not be used on the Railway track, since the equipment may contact to the electric lines. However, a portable equipment can be used for geotechnical investigation without electrical hazard. Dynamic Cone Penetrometer (DCP) is one of representative portable equipments. A normal portable DCP has usually not enough driving energy and the rigidity of cone-rod, so it is impossible to investigate the required investigate penetration depth. In this study, The adaptability of Pagani cone test which is one of portable dynamic cone penetrometer is studied and compared with SPT-N data. As a result of this study, the proposed correlation factors between Pagani cone test and SPT-N values after corrections is 1.48 for sandy soil and 1.33 for clayey soil.

• Journal of the Korean GEO-environmental Society
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• v.5 no.3
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• pp.51-60
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• 2004

In Korea there are recently many attempts to expand a temporary soil nailing system into a permanent soil nailing system since the first construction in 1993. In the soil nailing system, the rigid facing walls act on restraining the deformation of the ground. These are purposed to minimize the damage of adjacent buildings or underground structures. In Korea, to minimize the relaxation of the ground, the soil nailing system in the downtown area is often used experientially together with braced cuts, sheet pile walls, soil cement walls (SCW), or jet grouting walls. However, for the conservative design, the confining effects by the stiff facing have been ignored because the proper design approach of considering the facing stiffness has not been proposed. In this study, various laboratory model tests are carried out to examining the influence the rigidity of facings on the global safety of soil nailing system. Also, the parametric studies using the numerical technique as shear-strength reduction technique are carried out. In the parametric study, the thickness of concrete facing walls is changed to identify the effects of the facing wall stiffness.

• Journal of Biosystems Engineering
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• v.9 no.1
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• pp.11-21
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• 1984

This study was intended to analyze the dynamic force system which induced the shattering of paddy grains. A model to predict the shattering of paddy grains was developed, and physical quantities, such as mass distribution and rigidity of rice plant, needed for evaluating the minimum shattering forces were also measured. Under the assumption that rice plant right before harvesting is a vibratory system, the mathematical model of the vibratory system was developed and solved with the varied conditions of forcing functions. The results of the study were summarized as follows: 1. The shattering of grain occurred at the abscission layer of grain by the bending moments resulted from the impact force due to the collision of panicles of rice plant. 2. The vibratory model developed for milyang 23 rice variety was analyzed to give the natural frequencies of 7-9 Hz, which were closely related with the excitation frequencies of 4-10 Hz caused by various machine parts besides engine. Thus, avoiding the resonance should be taken into consideration in the design of the harvesting machinery. 3. It was analyzed to predict the lowest frequency that could develop the shattering when the excitation force was applied to the lower end of stem. The lowest frequency for the Milyang 23 rice variety ranged from 8.33 Hz to 11.66 Hz as the amplitude varied from 1 cm to 2.5 cm. 4. The degree of shattering depended upon the magnitude of the impact force and its application point. For Milyang 23 rice variety, the minimum impact force developing the shattering was $5g_f$ when it was applied at 1 cm above the lower end of stern and $1g_f$ when applied at 5 cm above the lower end of stem. 5. The minimum colliding velocity of the panicle, when it was on the ground that would just develop the shattering, was given as follows, $$V=\sqrt{\frac{K_t}{m_g}{\cdot}{{\phi}^2}}$$ where V : The colliding velocity of the panicle against ground to cause the shatteering of rice grain. (cm/sec) $K_t$ : The minimum spring constant for bending at the abscission layer of grain. (dyne-cm/rad) ${\phi}$ : The minimum shattering angle of grain (rad) $m_g$ : The maximum mass of grain. (g).