• The Journal of Korea Robotics Society
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• v.14 no.3
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• pp.203-210
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• 2019

This paper proposes a hand-controller mechanism for manually controlled endoscopic surgical instruments. A wire-driven mechanism is typically adapted for endoscopic surgical tools because motors cannot be embedded to the joints due to the size limitation. The wire-driven mechanism requires length control of wires that are pulled and released according to the desired joint angle. It is difficult for the operator to control individual wire lengths intuitively. The hand-controller mechanism should be able to control the wires easily without complex processes. For this purpose, we propose a mechanism that can control the wire lengths with a simple mechanical structure and its optimal design method using genetic algorithm. We show the simulation and experimental results to confirm the proposed mechanism and design methods are useful for the manually controlled endoscopic surgical instrument.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.81.1-81.1
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• 2019

Linear sausage oscillations of a cylinder embedded in a plasma with an azimuthal magnetic field, created by a current on the surface of the cylinder, are studied. Such a plasma configuration could be applied to modelling demonstrate that the lowest radial harmonic of the sausage mode is in the trapped regime for all values of the parallel wave number. In the long-wavelength limit, phase and group speeds of this mode are equal to the Alfven speed in the external medium. It makes the oscillation period to be determined by the ratio of the parallel wavelength, e.g., double the length of an oscillating loop, to the external Alfven speed, allowing for its seismological estimations. The application of the results obtained to the interpretation of long-period (longer than 20-30 s) oscillations of emission intensity detected in solar coronal structure, gives reasonable estimations of the external Alfven speed. Cutoff values of the parallel wavenumber for higher radial harmonics are determined analytically. Implications of this finding to the observational signatures of fast magnetoacoustic wave trains guided by the plasma non-uniformity are discussed.

• Smart Structures and Systems
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• v.23 no.5
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• pp.429-447
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• 2019

The present study analyzed free vibration of the three-layered micro annular/circular plate which its core and face sheets are made of saturated porous materials and FG-CNTRCs, respectively. The structure is subjected to magneto-electric fields and magneto-electro-mechanical pre loads. Mechanical properties of the porous core and also FG-CNTRC face sheets are varied through the thickness direction. Using dynamic Hamilton's principle, the motion equations based on MCS and FSD theories are derived and solved via GDQ as an efficient numerical method. Effect of different parameters such as pores distributions, porosity coefficient, pores compressibility, CNTs distribution, elastic foundation, multi-physical pre loads, small scale parameter and aspect ratio of the plate are investigated. The findings of this study can be useful for designing smart structures such as sensor and actuator.

• The Journal of Korea Robotics Society
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• v.16 no.2
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• pp.164-171
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• 2021

This paper proposes a continuum mechanism for manually controlled endoscopic surgical instruments. The wire-driven mechanism is typically adapted for endoscopic surgical tools because motors cannot be embedded to the joints due to the size limitation. However, the conventional wire-driven mechanism has inherent problems caused by redundancy, such as deflection and low precision. It does not have operating force and manipulability for surgery. Therefore, a method to increase the force of the continuum mechanism using a multi-wire with simple mechanical structure is proposed. Moreover, for intuitive operation, a hand-controller mechanism that can manipulate the length of the wire without complex process is proposed. Finally, we show that the proposed mechanism and methods are applicable to endoscopic surgical tools through simple experiments.

• Journal of information and communication convergence engineering
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• v.20 no.4
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• pp.235-241
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• 2022

A dispersion map was proposed to improve the compensation effect of a distorted WDM (wavelength division multiplexed) channel in a dispersion-managed link coupled with optical phase conjugation. The dispersion map is an origin-symmetric structure around the optical phase conjugator in the middle of the transmission path. In addition, the dispersion map has a form in which a constant dispersion accumulation pattern is repeated regularly. Through simulation, we confirmed that the application of the origin-symmetric dispersion map with a repetitively shaped configuration was more effective in compensating for the distorted WDM channel than in the dispersion-managed link with a conventional dispersion map. In addition, we confirmed that the compensation effect could be increased when the cumulative dispersion distribution of the origin-symmetric distribution map had a positive value in the first half section and a negative value in the second half section. Further, we observed that as the number of repeated dispersion accumulation patterns increased, the residual dispersion per span should also be increased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.58-59
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• 2020

The change of temperature and humidity in early-age concrete has a great influence on the durability of the structure. In this study, a reliable wireless sensor network system and a concrete embedded type Compressive strength prediction sensor were designed using the Arduino platform. The accuracy of the compressive strength prediction sensor was verified through a mock-up experiment, and it was confirmed that the experiment had sufficient accuracy to be used in the field environment.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.32-33
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• 2021

The corrosion of the embedded steel rebars and the consequent deterioration of the reinforced concrete structure has become a challenging concern to the construction industries for the fiscal deficit. However, corrosion inhibitors are potential and being widely used for corrosion mitigation to solve such problems. This study has been focused on the mixed type of corrosion inhibitor where one component of the corrosion inhibitor is organic and another one is inorganic material. 0.1 (M) triethanolamine (TEA) and 0.01 (M) sodium hexametaphosphate (SHMP) have been mixed in distilled water to produce the mixed inhibitor. Studies of the steel rebar corrosion in chloride contaminated (3.5 wt.% NaCl) concrete pore (CCCP) solution has been conducted using different concentrations of corrosion inhibitor. Electrochemical impedance spectroscopy (EIS) method is involved to understand the corrosion behaviour of the steel rebars at different exposure durations.

• Educational Technology International
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• v.12 no.1
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• pp.1-20
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• 2011

The study described in this paper examined the effectiveness of a multimedia case-based learning environment to teach technology integration to Korean pre-service teachers. The structure and philosophy behind the use of embedded video in an online, multimedia system and the data collected from 103 pre-service teachers are presented and discussed. The overall finding shows that there was no significant difference from pre- to posttest among the lecture, the case-based, and the mixed environment groups. However, low prior knowledge students improved more when they learned about technology integration with the mixed method than with the case-based method alone. Discussion about this result and its educational implications conclude the paper.

• Journal of applied mathematics & informatics
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• v.42 no.1
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• pp.49-64
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• 2024

When setting up a structure with an embedded shallow arch, there is a phenomenon where the end of the arch moves. To study the so-called moving domain problem, one try to transform a considered noncylindrical domain into the cylindrical domain using the transform operator, as well as utilizing the method of penalty and other approaches. However, challenges arise when calculating time derivatives of solutions in a domain depending on time, or when extending the initial conditions from the non-cylindrical domain to the cylindrical domain. In this paper, we employ the transform operator to prove the existence and uniqueness of weak solutions of the shallow arch equation on the moving domain as clarifying the time derivatives of solutions in the moving domain.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.4
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• pp.17-24
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• 2014

In this paper, we propose a CMOS FM RX front-end structure with an automatic tunable input matching network and implement it using a 65nm CMOS technology. The proposed FM RX front-end is designed to change the resonance frequency of the input matching network at the low noise amplifier (LNA) according to the channel frequency selected by a phase-locked loop (PLL) for maintaining almost constant sensitivity level when an embedded antenna type with high frequency selectivity characteristic is used for FM receiver. The simulation results of implemented FM front-end show about 38dB of voltage gain, below 2.5dB of noise figure, and -15.5dBm of input referred intercept point (IIP3) respectively, while drawing only 3.5mA from 1.8V supply voltage including an LO buffer.