• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.19-26
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• 2001

• Transactions on Electrical and Electronic Materials
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• v.17 no.4
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• pp.183-188
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• 2016

This paper presents the design and characterization of wide band ohmic microswitch with an actuation voltage as low as 20~25 V, and a restoring force of 14.1 μN. The design of the proposed switch is primarily composed of an electrostatic actuator, bridge membrane, cantilever (beam) and coplanar waveguide, suspended over the substrate. The analysis shows an insertion loss of −0.002 dB at 1GHz and remains as low as −0.35 dB, even at 100 GHz. The isolation loss of the switch is sustained at −21.09 dB at 100GHz, with a peak value of −99.58 dB at 1 GHz and up-state capacitance of 4 fF. To our knowledge, this is the first demonstration of a series contact switch, which works over a wide bandwidth (DC-100 GHz) and with such a high and sustained isolation, even at high frequencies and with an excellent figure of merit (f_c=1/2.pi.Ron.Cu= 39.7 THz).

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.199-202
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• 2006

The objective of this study is to propose methods of controlling the wake behind a sphere for drag reduction using the suboptimal control theory and surrogate management framework, respectively. The Reynolds numbers considered is 300 at which the base flow is unsteady planar symmetric. Given the cost function defined as the square of the difference between the target pressure (potential-flow pressure) and real flow pressure on the sphere surface, the suboptimal control makes the flow steady axisymmetric and produces drag reduction. Based on the actuation profile from the suboptimal control, the optimal wavy actuation profile is obtained using the surrogate management framework and produces drag reduction.

• Transactions on Electrical and Electronic Materials
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• v.16 no.4
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• pp.173-178
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• 2015

In lieu of the excellent radio frequency (RF) performance of microelectromechanical system ( MEMS) switches, these micro switches need higher actuation voltage for their operation. This requirement is secondary to concerns over the swtiches’ reliability. This paper reports high reliability operation of RF MEMS switches with low voltage requirements. The proposed switch is optimised to perform in the Q-band, which results in actuation voltage of just 16.4 V. The mechanical stress gradient in the thin micro membrane is computed by simulating von Mises stress in a multi-physics environment that results in 90.4 MPa stress. The computed spring constant for the membrane is 3.02 N/m. The switch results in excellent RF performance with simulated isolation of above 38 dB, insertion loss of less than 0.35 dB and return loss of above 30 dB in the Q-band.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.6
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• pp.553-562
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• 2015

This paper presents a strategy and an algorithm for levitation control of an over-actuated passive maglev tray system. The passive maglev tray system has more actuators than its degrees of freedom. The actuators of the system are switching when the tray travels longitudinally. Furthermore, the levitation forces of the actuators are non-homogeneous because the actuation devices are not in the moving platform. These characteristics make a limit in using conventional control approaches for levitation. For smooth actuator switching, the actuator force generation should be dependent on longitudinal positions of the tray. To enable constant pose tracking, this research introduces a control strategy and a control algorithm based on integral controllers on virtual variables. The states of the tray are estimated using a Kalman filter and fed to the proposed controller. The performances of the proposed control strategy and the algorithm are validated through tests.

• Transactions of The Korea Fluid Power Systems Society
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• v.7 no.4
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• pp.23-31
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• 2010

As the analysis and design technologies for electro-magnetic actuation has advanced over the years, proportional solenoid valve is gaining acceptance in wide range of industrial and commercial applications because of its superior characteristics over the conventional AOV or MOV, such as improved performance, reduced maintenance costs. This research deals with the position controller design of two-stage flow control solenoid valve. Investigation of steady-state characteristics and dynamic model identification for pilot disc is performed. Least square method to minimize the error magnitude of frequency response between the closed-loop and target system is applied to the design of PI-controller gains. From the experiments of step and frequency response, it is concluded that the controller meets the performance specification of target system, which verifies the usefulness of controller design method for proportional solenoid valve.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.1
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• pp.102-122
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• 2017

Nanotechnology has provided a set of tools that the engineers can use to design and manufacture integrated nano devices, which are capable of performing sensing, computing, data storing and actuation. One of the main hurdles for nano devices has been the amount of power that it can generate for transmission of data. In this paper, we proposed cooperative nano communication in the Terahertz (THz) Gap frequency band to increase the range of transmission. Outage probability (OP) performances for the proposed cooperative nano communication networks in the THz band (0.1 - 10THz) have been evaluated for the following scenarios; A) A single decode-and-forward (DF) relay over independent identically distributed (i.i.d.) Rayleigh fading channels, B) DF multi-relay network with best relay selection (BRS) over i.i.d. Rayleigh fading channels, and C) DF multi-relay network with multiple hops with BRS over i.i.d. Rayleigh fading channels. The results show that the transmission distance can be improved significantly by employing DF relays. Also, it is shown that by increasing the number of hops in a relay the OP performance is marginally degraded. The analytical results have been verified by Monte-Carlo simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.7
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• pp.986-992
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• 2021

To stabilize closed-loop wireless control systems, the state-of-the-art approach receives the individual sensor measurements at the controller and then sends the computed control signal to the actuators. We propose an over-the-air controller scheme where all sensors attached to the plant transmit scaled sensing signals simultaneously to the actuator, and the actuator then computes the feedback control signal by scaling the received signal. The over-the-air controller essentially adopts the over-the-air computation concept to compute the control signal for closed-loop wireless control systems. In contrast to the state-of-the-art sensor-to-controller and controller-to-actuator communication approach, the over-the-air controller exploits the superposition properties of multiple-access wireless channels to complete the communication and computation of a large number of sensing signals in a single communication resource unit. Therefore, the proposed scheme can obtain significant benefits in terms of low actuation delay and low resource utilization with a simple network architecture that does not require a dedicated controller.

• Transactions on Electrical and Electronic Materials
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• v.17 no.2
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• pp.92-97
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• 2016

This paper presents design and simulation of wide band RF microswitch that uses electrostatic actuation for its operation. RF MEMS devices exhibit superior high frequency performance in comparison to conventional devices. Similar techniques that are used in Very Large Scale Integration (VLSI) can be employed to design and fabricate MEMS devices and traditional batch-processing methods can be used for its manufacturing. The proposed switch presents a novel design approach to handle reliability concerns in MEMS switches like dielectric charging effect, micro welding and stiction. The shape has been optimized at actuation voltage of 14-16 V. The switch has an improved restoring force of 20.8 μN. The design of the proposed switch is very elemental and primarily composed of electrostatic actuator, a bridge membrane and coplanar waveguide which are suspended over the substrate. The simple design of the switch makes it easy for fabrication. Typical insertion and isolation of the switch at 1 GHz is -0.03 dB and -71 dB and at 85 GHz it is -0.24 dB and -29.8 dB respectively. The isolation remains more than - 20 db even after 120 GHz. To our knowledge this is the first demonstration of a metal contact switch that shows such a high and sustained isolation and performance at W-band frequencies with an excellent figure-of merit (fc=1/2.pi.Ron.Cu =1,900 GHz). This figure of merit is significantly greater than electronic switching devices. The switch would find extensive application in wideband operations and areas where reliability is a major concern.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.5
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• pp.247-251
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• 2004

We report highly improved yield strength of nickel thin film, prepared using electroplating. The micro-scaled nickel cantilever is found to have significantly higher yield strength than bulk nickel. For the yield strength test, the heights of the micro-scaled cantilever were varied up to 60 ${\mu}{\textrm}{m}$ and electrostatic force was used for actuation. Stress of the bent cantilever was estimated using the FEM large deflection model. The yield strength of the thin nickel film is found to be over five times higher than that of the bulk nickel previously published. Results from this study indicate that metal microstructures can be used for MEMS applications requiring large deflection.