• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.164-167
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• 2005

In this paper, the design and characteristics of a ${\pi}-shaped$ ultrasonic motor which is applicable to optical zoom operation of lenssystem for mobile phone are investigated. Its desi후 and simulation of performances are carried out by FEM (finite element method) commercial software. As a simulation result, by applying voltage with single phase, a combined vibration is produced at the surface of an arm of stator. The prototype of motor is fabricated and its outer size is 8*4*2 $mm^3$ including the cylindrical steel rod of 2 mm in diameter as rotor. The motor exhibits a maximum speed of 500 rpm and a power consumption of 0.3 W when driven at 20 Vpp and 64 kHz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1229-1234
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• 2001

There are three items, which are panhead displacement, tilting angle of pan head, required moment of main shaft, which representing kinematic performance of pantograph. Kinematic variables effective on kinematic performance are length of each components and installation angle, In this study, cost function is defined with 3 items, By this cost function, length of thrust rod was optimized. Finite element analysis was used to consider structural soundness. Finite element model was qualified by comparison between analysis result with experiment result. By qualified F.E, model various severe condition was simulated to consider structural soundness.

• Korean Journal of Environmental Biology
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• v.39 no.3
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• pp.289-292
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• 2021

Henricia specimen was collected from the East Sea of Korea using fishing nets. The specimen was identified as Henricia hayashii (Djakonov 1961), belonging to the family Echinasteridae of the order Spinulosida. This species can be distinguished from other Henricia species by slender arms (R/r=7.4), constricted arm base, six to thirty-five slender spinelets, open-meshed, reticulated abactinal skeleton comprising semi-triangular, rod-like form, and small ossicles present inside the papular areas. This species superficially resembles H. reniossa in terms of its body size but differs in the shape and arrangement of the abactinal and actinal plates. To date, two genera of Echinasteridae, Aleutihenricia and Henricia, including a total of 14 species, have been reported in Korea. Herein, the morphological characteristics of H. hayashii are described, and photographs are provided.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.6
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• pp.523-531
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• 2008

In hole type CPTu equipment which combines the concepts of inhole test method and piezocone test method was newly developed in order to evaluate the dynamic properties of marine soils. It is possible to perform inhole type CPTu without any additional source device because the source and receiver are contained inside the cone rod, which is different from the conventional seismic cone system. In this study, laboratory tests using kaolinite as soft soil and numerical simulations using finite element method were carried out to investigate the effects of several parameters including test methods and soil conditions on the test results from inhole type CPTu and to find out the optimum test method. It was found that it is necessary to maintain the length of swing arm as well as the distance between source and receiver consistently to obtain the rigorous test results. The laboratory test and numerical results also reveal that contrary to the input wave frequency, the water content of soil layer and the disturbance due to the installation of swing arm apparently affect the shear wave velocity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1901-1907
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• 2010

A hydraulic cylinder is a primary component of an excavator and is used for activating attachments such as boom, arm, and bucket. Generally, the cylinder is prone to structural problems such as buckling and fatigue failure caused by cyclic high pressure. Therefore, the safety margin for fatigue, yield, and buckling during the design lifetime should be evaluated at the durability-design stage. The durability design includes basic and detailed stages. In the basic design, the principal dimensions of the rod and tube are determined by considering the working force, speed, and range with respect to yield and buckling. In the detailed design, the dimensions of the rod notch, welds, tube end, gland, orifice, and cushion ring are determined by considering the fatigue safety. We present and discuss the overall procedure for durability design and the related analysis techniques.

• Advances in Traditional Medicine
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• v.9 no.2
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• pp.142-148
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• 2009

Anxiety disorders are one of the serious problems which need proper therapy devoid of side effects of presently available medicines. The present study evaluates the anxiolytic and sedative activity of leaf galls of Piper nigrum Linn. in Swiss Albino mice. The pet. ether, chloroform, ethyl acetate and ethanol extracts of leaf galls of Piper nigrum Linn were obtained by continuous soxhlet extraction. The prepared extracts were found to be safe up to 2000 mg/kg body weight of mice in the acute toxicity study. Each extract was assessed for anxiolytic activity in Swiss Albino mice by elevated plus Maze, open field test, rota rod test and phenobarbitone induced sleeping time test. In the Elevated Plus Maze test, the pet.ether extract and chloroform extract at a dose of 50 mg/kg b.w. orally, significantly (P < 0.01) increased the number of entries and time spent in open arm comparable with standard diazepam at the dose of 10 mg/kg. b.w. p.o. In the open field test, pet. ether extract (50 mg/kg b.w. p.o.) showed significant increase (P < 0.01) in ambulation and activity in the center. Chloroform extract (50 mg/kg b.w p.o.) was significant (P < 0.05) for both ambulation and center activity. Pet. ether extract (50 mg/kg b.w. p.o) also showed significant activity (P < 0.01) in rota rod test. All the results are comparable with standard diazepam at the dose of 1 mg /kg b.w, p.o. Moreover all the extracts showed significant (P < 0.01) increase in the phenobarbitone induced sleeping time among which pet.ether showed more prominent activity (36%) comparable with control. The results revealed that, the active pet.ether extract and chloroform extract of leaf galls of Piper nigrum Linn is worthwhile to develop the bioactive principle for anxiolytic activity.

• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.241-245
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• 2006

In this paper, the design and characteristics of a $\pi-shaped$ ultrasonic motor that is applicable to optical zoom operation of a lens system for mobile phones are investigated. Its design and simulation of performances are carried out by FEM (finite element method) commercial software. As a simulation result, by applying voltage with single phase, a combined vibration is produced at the surface of a stator arm. A prototype of the motor is fabricated and its outer size is $8*4*2mm^3$ including the cylindrical steel rod of 2 mm in diameter as the rotor. The motor exhibits a maximum speed of 500 rpm and a power consumption of 0.3 W when driven at 20 Vpp and 64 kHz.

• Safety and Health at Work
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• v.11 no.1
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• pp.80-87
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• 2020

Background: Residential and commercial cleaning is a part of our daily routine to maintain sanitation around the environment. Health care of professionals involved in such cleaning activities has become a major concern all over the world. The present study investigates the risk of musculoskeletal disorders in professional cleaners involved in floor mopping tasks. Methods: A cross-sectional study was performed on 132 mopping professionals using a modified Nordic questionnaire. The Pearson correlation test was implemented to study the association of perceived pain with work experience. The muscle strain and postural risk were evaluated by means of three-channel electromyography and real-time motion capture respectively of 15 professionals during floor mopping. Results: Regarding musculoskeletal injuries, risk was reported majorly in the right hand, lower back, left wrist, right shoulder, left biceps, and right wrist of the workers. Work experience had a low negative association with MSDs in the left wrist, right wrist, right elbow, lower back, and right lower arm (p < 0.01). Surface EMG showed occurrence of higher muscle activity in upper trapezius and biceps brachii (BB) muscles of the dominant hand and flexor carpi radialis and BB muscles of the nondominant hand positioned at the upper and lower portion of the mop rod, respectively. Conclusion: Ergonomic mediations should be executed to lessen the observed risk of musculoskeletal injuries in this professional group of workers.

• The Journal of Korea Robotics Society
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• v.16 no.2
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• pp.137-146
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• 2021

When controlling manipulator, degree of freedom is lost in singularity so specific joint velocity does not propagate to the end effector. In addition, control problem occurs because jacobian inverse matrix can not be calculated. To avoid singularity, we apply Deep Deterministic Policy Gradient(DDPG), algorithm of reinforcement learning that rewards behavior according to actions then determines high-reward actions in simulation. DDPG uses off-policy that uses 𝝐-greedy policy for selecting action of current time step and greed policy for the next step. In the simulation, learning is given by negative reward when moving near singulairty, and positive reward when moving away from the singularity and moving to target point. The reward equation consists of distance to target point and singularity, manipulability, and arrival flag. Dual arm manipulators hold long rod at the same time and conduct experiments to avoid singularity by simulated path. In the learning process, if object to be avoided is set as a space rather than point, it is expected that avoidance of obstacles will be possible in future research.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.498-505
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• 2024

In this paper, a cable-driven endoscopic manipulator (CEM) is designed for the Chinese latest compact fusion reactor. The whole CEM arm is more than 3000 mm long and includes end vision tools, an endoscopic manipulator/control system, a feeding system, a drag chain system, support systems, a neutron shield door, etc. It can cover a range of ±45° of the vacuum chamber by working in a wrap-around mode, etc., to meet the need for observation at any position and angle. By placing all drive motors in the end drive box via a cable drive, cooling, and radiation protection of the entire robot can be facilitated. To address the CEM motion control problem, a discrete trajectory tracking method is proposed. By restricting each joint of the CEM to the target curve through segmental fitting, the trajectory tracking control is completed. To avoid the joint rotation angle overrun, a joint limit rotation angle optimization method is proposed based on the equivalent rod length principle. Finally, the CEM simulation system is established. The rationality of the structure design and the effectiveness of the motion control algorithm are verified by the simulation.