• International Journal of Railway
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• v.2 no.4
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• pp.139-146
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• 2009

Vehicle braking in non-electrified rail systems wastes energy. Advanced flywheel technology presents a way to capture and reuse this braking energy to improve vehicle efficiency and so reduce the operating costs and environmental impact of diesel trains. This paper highlights the suitability of flywheels for rail vehicle applications, and proposes a novel mechanical transmission system to apply regenerative braking using a flywheel energy storage device. A computational model is used to illustrate the operation and potential benefits of the energy storage system.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.6
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• pp.553-559
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• 2015

The purpose of this research is to develop a gait assistive device to enhance the gait stability and training efficiency of stroke patients. The configuration of this device is mainly composed of a motored wheel and a single cane whose lower end is attached to a motored wheel frame. A patient can feel haptic information from continuous ground contact from the wheel while walking through the grip handle. In addition, the wheeled cane can avoid using excessive use of the patient's upper limb for weight support and motivate the patient to use a paralyzed lower limb more actively. Moreover, the proposed device can provide intuitive and safe user interaction by integrating a force sensor and a tilt sensor equipped to the cane frame, and a switch sensor at the cane's handle. The admittance control has been implemented for the patient to change the walking speed intuitively by using the interaction forces at the handle. A hemi-paretic stroke patient participated in the walking assistive experiments as a pilot study to verify the effectiveness of the proposed haptic cane system. The results showed that the patient could improve walking speed and muscle activations during walking with a constant speed mode of the haptic cane. Moreover, the patient could maintain the preferred walking speeds and gait stability regardless of the magnitude of resistance forces with the admittance control mode of the haptic cane. The proposed robotic gait assistive device with a simple and intuitive mechanism can provide efficient gait training modes to stroke patients with high possibilities of widespread utilizations.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.240.2-240.2
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• 2013

The device scale of flash memory was confronted with quantum mechanical limitation. The next generation memory device will be required a break-through for the device scaling problem. Especially, graphene is one of important materials to overcome scaling and operation problem for the memory device, because ofthe high carrier mobility, the mechanicalflexibility, the one atomic layer thick and versatile chemistry. We demonstrate the hybrid memory consisted with the metal-oxide quantum dots and the mono-layered graphene which was transferred to $SiO_2$ (5 nm)/Si substrate. The 5-nm thick secondary $SiO_2$ layer was deposited on the mono-layered graphene by using ultra-high vacuum sputtering system which base pressure is about $1{\times}10^{-10}$ Torr. The $In_2O_3$ quantum dots were distributed on the secondary $SiO_2$2 layer after chemical reaction between deposited In layer and polyamic acid layer through soft baking at $125^{\circ}C$ for 30 min and curing process at $400^{\circ}C$ for 1 hr by using the furnace in $N_2$ ambient. The memory devices with the $In_2O_3$ quantum dots on graphene monolayer between $SiO_2$ thin films have demonstrated and evaluated for the application of next generation nonvolatile memory device. We will discuss the electrical properties to understating memory effect related with quantum mechanical transport between the $In_2O_3$ quantum dots and the Fermi level of graphene layer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.91-96
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• 2012

The retract actuator makes the landing gear retract or extend during take-off and landing of an aircraft. To prevent folding of landing gear that has remained in the extended state because of an unexpected external disturbance, an internal locking device is applied to the retract actuator. The locking device is restrained with another internal component by oil pressure supplied to the retract actuator, and this restraint makes the locking of the actuator possible. Because locking and unlocking are repeated during retraction and extension of the landing gear, the locking device takes repeated identical loads, and the possibility of fatigue failure exists. In this study, the process and results of fatigue analysis for the locking device are presented, and the appropriateness of the analysis result is verified using a fatigue test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.49-58
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• 2019

The Scientific balloon is a flight system that could recover an entire platform at the end of the mission. The recovery takes place mainly in low-density populated areas, taking into account for the possible damage to the human life and public safety. In Republic of Korea, on the other hand, marine recovery should be considered due to the dense mountainous terrain and restrictions of the peninsula. In this operating environment, the envelope must be recovered because of severe marine pollution that may occur after the splashdown. Therefore, in this study, the separation device that consists of a location tracker and the waterproof system were developed. The device includes data transmission/reception, separation, and waterproof systems which are manufactured considering the environmental condition of the Korea. The performance of the device and the trajectory of the envelope were verified by conducting a separation test of a 20km platform at a target altitude and the recovery of the zero-pressure balloon.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.485-485
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• 2009

Double side polishing process has been used for various industrial applications, such as polishing of semiconductor substrates and flat panel display glasses. In wafer manufacturing, double side polishing process is applied to improve wafer flatness and to minimize particle generation from wafers in device manufacturing processes, which is recognized as one of the most important processes. Whereas the kinematical modeling and analysis results of single side polishing, extensively used for chemical-mechanical polishing (CMP) in device manufacturing, are well investigated, the studies in conjunction with double side polishing are barely carried out, due to the complication of polishing system and the uncertainty of wafer motion in the carrier. This paper suggests the derivation of kinematical model with consideration of carrier and wafer motion in double side polishing, and then presents the effect of kinematical parameters on material removal amount and its non-uniformity. The kinematical analysis results help to understand the double side polishing process and to control the polishing results.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.2032-2033
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• 2007

There has been increasing interests of condition monitoring and diagnosis for electric equipment, which lead to the development of this system domestic and abroad. In the past, operators' interest was how to quickly repair and restore the electric equipments after failure. But, due to the North American Blackout in 2003 and the aging of equipments, users have paid attention to the condition based monitoring of electric equipment to prevent a fault like outrage. GIS-PDS("GIS Preventive and Diagnosis System") requiresa large amount of measurement data with timeliness for monitoring and analysis of real-time state of GIS(Gas Insulated Switchgear). We developed the timeliness-guaranteed communication device for GIS-PDS.

• Design & Manufacturing
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• v.15 no.4
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• pp.65-71
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• 2021

In the early days of laser invention, it was simply used as a measuring tool, but as lasers became more common, they became an indispensable processing tool in the industry. Short-wavelength lasers are used to make patterns on wafers used in semiconductors depending on the wavelength, such as CO2 laser, YAG laser, green laser, and UV laser. At first, the hole of the PCB board mainly used for electronic parts was not thin and the hole size was large, so a mechanical drill was used. However, in order to realize product miniaturization and high integration, small hole processing lasers have become essential, and pattern exposure for small hole sizes has become essential. This paper intends to analyze the characteristics through patterns by exposing the PCB substrate through DMD and polygon scanner, which are different optical systems. Since the optical systems are different, the size of the patterns was made the same, and exposure was performed under the optimal conditions for each system. Pattern characteristics were analyzed through a 3D profiler. As a result of the analysis, there was no significant difference in line width between the two systems. However, it was confirmed that dmd had better pattern precision and polygon scanner had better productivity.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.35-43
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• 2017

The three-dimensional integrated circuit (3D-IC) is a general trend for the miniaturized and high-performance electronic devices. The through-silicon-via (TSV) is the advanced interconnection method to achieve 3D integration, which uses vertical metal via through silicon substrate. However, the TSV based 3D-IC undergoes severe thermo-mechanical stress due to the CTE (coefficient of thermal expansion) mismatch between via and silicon. The thermo-mechanical stress induces mechanical failure on silicon and silicon-via interface, which reduces the device reliability. In this paper, the thermo-mechanical reliability of TSV based 3D-IC is reviewed in terms of mechanical fracture, heat conduction, and material characteristic. Furthermore, the state of the art via-level and package-level design techniques are introduced to improve the reliability of TSV based 3D-IC.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.9
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• pp.707-713
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• 2006

To improve heating performance of the heat pump in winter season, refrigerant heating device was applied to conventional heat pump. The refrigerant heating device operates at the heating capacity does not enough to the heating load requirement of the conditioning space. When the discharge air temperature of the indoor heat exchanger goes down to below $40^{\circ}C$ which is criterion for comfort of the occupants in the conditioning space, the system also starts. The refrigerant heating system has new concept of auxiliary heating device for heat pump in winter. In this study, the system performance was analyzed through experiments and parametric study was conducted to improve the COP and control strategies.