• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.301-304
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• 2001

The analog multiplier is very useful building block in many circuits such as filter, frequency-shifter, and modulators. In recent year, The main design issue of circuit designer is low-voltage/low-power system design, because of all systems are recommended very integrated system and portable system In this paper, the proposed the four-quadrant analog multiplier is using the bulk-driven techniques. The bulk-driven technique is very useful technique in low-voltage system, compare with gate-driven technique. therefore the proposed analog multiplier is operated in 1V supply voltage. And the proposed analog multiplier is low power dissipation compare with the others. therefor the proposed analog multiplier is convenient in low-voltage/low-power in system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.425-428
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• 2017

This paper describes a full-wave rectifiers for energy harvesting circuit using a vibrational energy. The designed circuit is applied to the negative voltage converter with the body-bias technique using the Beta-multiplier so that the power efficiency is excellent even at the low voltage, and the comparator is designed as the bulk-driven type. The proposed circuit is designed with $0.35{\mu}m$ CMOS process, and The designed chip occupies $931{\mu}m{\times}785{\mu}m$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.533-536
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• 2016

This paper describes a vibrational energy harvesting circuit with MPPT control. A high-performance AC-DC converter of which the efficiency is improved by using body-bias technique and bulk-driven technique is proposed and applied for the vibrational energy harvesting circuit design. MPPT (Maximum Power Point Tracking) control function is implemented using the linear relationship between the open-circuit voltage of a vibrational device and its MPP voltage. The designed MPPT control circuit traces the maximum power point by periodically sampling the open circuit voltage of a vibrational device, makes the reference voltages using sampled voltage and delivers the maximum available power to load. The proposed circuit is designed with a $0.35{\mu}m$ CMOS process, and the chip area is $1.21mm{\times}0.98mm$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.477-480
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• 2015

In this paper a low-voltage vibration energy harvesting circuit with MPPT(Maximum Power Point Tracking) control is proposed. By employing bulk-driven technique, the minimum operating voltage of the proposed circuit is as low as 0.8V. The designed MPPT control circuit traces the maximum power point by periodically sampling the open circuit voltage of a full-wave rectifier circuit connected to the piezoelectric device output and delivers the maximum available power to load. The proposed circuit is designed using a $0.35{\mu}m\;CMOS$ process, and the chip area including pads is $1.33mm{\times}1.31mm$. Simulation results show that the maximum power efficiency of the designed circuit is 85.49%.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.451-454
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• 2015

This paper introduces 3 type of OTAs with $0.35-{\mu}m$ standard CMOS technology for Low-Power, Low-Voltage. The first type is a two-stage OTA designed to operate with a 1-V VDD and it has $1.774{\mu}W$ low power consumption. All transistors are operating in strong inversion. It takes Gm-Enhancement techniques to compensate gm, which is lowered by Bulk-Driven technique and has an Wide swing current mirror for low voltage operation and a Class-A output. The second type is a Two-stage OTA designed to operate with a 0.8-V VDD and It has 52nW low power consumption and 112dB high gain. The current mirror uses Composite Transistor binding Gates of two MOSFET to raise Rout which is similar with cascode structure. The third type is a Two-stage OTA designed to operate with a 0.6-V VDD and It has 160nW low power consumption and 72dB high gain. It takes Level Shift technique by Common Gate structure to amplify signals without additional bias voltage at second stage.

• Journal of Mechanical Science and Technology
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• v.15 no.8
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• pp.1188-1195
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• 2001

A numerical analysis has been carried out to investigate the influences of thermosolutal convection on the heat and mass transfer and solute segregation in crystals grown by the vertical Bridgman technique. The governing equations are solved by a finite-volume method using the power law scheme and the SIMPLE algorithm in which body-fitted coordinate system has been used. A primary convective cell driven by thermal gradients forms in the bulk of the domain, while a secondary convective cell driven by solutal gradients forms near interface. As the solutal Rayleigh number increases, secondary cell becomes to be stronger and has a great influence on the radial concentration along the interface.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1320-1327
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• 2013

In this paper, two different electromagnetic energy harvesters using bulk micromachined silicon spiral springs and Polydimethylsiloxane (PDMS) packaging technique have been fabricated, characterized, and compared to generate electrical energy from ultra-low ambient vibrations under 0.3g. The proposed energy harvesters were comprised of a highly miniaturized Neodymium Iron Boron (NdFeB) magnet, silicon spiral spring, multi-turned copper coil, and PDMS housing in order to improve the electrical output powers and reduce their sizes/volumes. When an external vibration moves directly the magnet mounted as a seismic mass at the center of the spiral spring, the mechanical energy of the moving mass is transformed to electrical energy through the 183 turns of solenoid copper coils. The silicon spiral springs were applied to generate high electrical output power by maximizing the deflection of the movable mass at the low level vibrations. The fabricated energy harvesters using these two different spiral springs exhibited the resonant frequencies of 36Hz and 63Hz and the optimal load resistances of $99{\Omega}$ and $55{\Omega}$, respectively. In particular, the energy harvester using the spiral spring with two links exhibited much better linearity characteristics than the one with four links. It generated $29.02{\mu}W$ of output power and 107.3mV of load voltage at the vibration acceleration of 0.3g. It also exhibited power density and normalized power density of $48.37{\mu}W{\cdot}cm-3$ and $537.41{\mu}W{\cdot}cm-3{\cdot}g-2$, respectively. The total volume of the fabricated energy harvesters was $1cm{\times}1cm{\times}0.6cm$ (height).

• Journal of Welding and Joining
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• v.14 no.6
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• pp.119-130
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• 1996

Welding is one of the important technologies in shipbuilding industry. Automation and productivity promotion of welding contribute to the cost saving of ship production. The quality and productivity of welding are dependent on the quality and suitability of technical information supplied by engineering parts. This paper describes the research results of welding information system for ship. The system can be used for the development of CIMS for shipbuilding. For this work, the welding information related to the ship Production were analyzed in detail. Object-oriented technique is applied to represent the complex and various welding information. To process the extend amount of the welding information of ship, database system was constructed. A pilot system for the bulk carrier ship was developed and can be used with ease by programming of event-driven method and implementaion of graphical user interlace.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.1
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• pp.142-156
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• 2015

A new method for ship Inner Shell optimization, which is called Parametric Inner Shell Optimization Method (PISOM), is presented in this paper in order to improve both hull performance and design efficiency of transport ship. The foundation of PISOM is the parametric Inner Shell Plate (ISP) model, which is a fully-associative model driven by dimensions. A method to create parametric ISP model is proposed, including geometric primitives, geometric constraints, geometric constraint solving etc. The standard optimization procedure of ship ISP optimization based on parametric ISP model is put forward, and an efficient optimization approach for typical transport ship is developed based on this procedure. This approach takes the section area of ISP and the other dominant parameters as variables, while all the design requirements such as propeller immersion, fore bottom wave slap, bridge visibility, longitudinal strength etc, are made constraints. The optimization objective is maximum volume of cargo oil tanker/cargo hold, and the genetic algorithm is used to solve this optimization model. This method is applied to the optimization of a product oil tanker and a bulk carrier, and it is proved to be effective, highly efficient, and engineering practical.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2515-2517
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• 1998

The micro fresnel lens(MFL) was modeled and fabricated on a XY-stage electrostatically driven by comb actuator. The modeled MFL was approximated as a step shape with 4-phase and 4-zone plate. The focal length and diameter of the MFL is 20mm and 912${\mu}m$, respectively. The XY-stage suspending the MFL is designed to generate a large static displacement up to about 20${\mu}m$. On SOI substrates, we first fabricated MFL using the RIE(reactive Ion etching) technology and then patterned and etched bulk silicon to make XY-stage. After the fabrication of all structures on top side of the SOI substrates. $Si_3N_4$ was deposited for passivation of all structures using PECVD(plasma enhanced chemical vapor deposition). All the MFL systems width comb drive actuator were released by KOH etching from the bottom side of the SOI wafer using double-sided alignment technique. In fabrication of MFL, a dry etching conditions is established in order to improve surface roughness and to control the etched depth.