Hye-jung Cho

High-Efficiency Active DMFC System for Portable Applications

We propose a highly efficient active direct-methanol fuel cell system for portable application in this paper. The system is composed of a fuel cell stack, mechanical parts, a smart battery, and circuit parts. The mechanical parts consist of several pumps, a mixer, a liquid separator, and heat exchange modules. The battery enables the operation of the mechanical parts and powers the output load during the start-up state. It can also improve the system dynamic characteristics by providing or absorbing the power when the load varies. Furthermore, the battery can also provide peak power at overload. The circuit parts consist of two buck-boost converters and a control circuit. The first-stage buck-boost converter maintains the constant stack current and charges the battery. The second-stage buck-boost converter regulates the output voltage. Buck-boost converters use synchronous rectifiers to increase the power conversion efficiency. In order to ensure a highly efficient and a highly reliable operation, four operating modes (battery discharging mode, start-up mode, hybrid mode, and shut-down mode) are defined and operating algorithms are proposed. These control modes facilitate the cold start at start-up and increase fuel efficiency. All control functions are implemented in software with a single-chip microcontroller MSP430F5438. A 25-W prototype is implemented to support the theoretical analysis.

WACA: WearAble Device Based Home Control Assistant Framework

In this paper, we have analyzed requirements and pain points of legacy wearable-based IoT and smart home services. In conventional system, we are required to wear additional accessory devices, and to move to specific areas to control and manage the home devices. In order to solve these restrictions, we have implemented WACA framework by using well-known general wearable devices. We also present the gesture-interaction based device control architecture using the wearable devices to provide more efficient and valuable smart home services. Based on the experiment results, we show that the proposed system has the potential as wearable device-based universal control assistance architecture.

Design and Implementation of an Easy-Setup Framework for Personalized Cloud Device

With the popularization of Public Cloud services, requirements for Personal Cloud services with more enhanced security and independent personalized storage are also increasing. In order to provide Personal Cloud services, a variety of Home Cloud devices available in the home have been introduced. Based on the analysis of these devices and previous researches, we extracted critical restrictions regarding the initial configuration such as the complex procedures, limitation of installation environment, and the problem that users wasted a lot of time for its setup. Thus, we propose a novel wireless network-based Easy-Setup framework using smartphones and Android-based personal cloud devices-HomeSync in order to improve these restrictions. In addition, we constructed an experiment test-bed to validate the effectiveness of our proposed framework. Finally, we present the results of the comparative experiments compared with previous researches in terms of consumption time and initial setup procedures.

Self-Amorphizing Gas Cluster Ion Beam Technology and Combination with Laser Spike Anneal for Highly Scaled Source Drain Junction

High energy borane (B2H6) gas cluster ion beam (GCIB) successfully enables a sub-10 nm box-shaped dopant profile without channeling tail, and steep gradient (2.5 nm/dec) in lateral direction. pFET using GCIB source/drain extension shows superior suppression of short channel effects and reduces the dependency of drive current on gate overlap capacitance variation for scaled devices. Moreover, the perimeter leakage component in p+/n-well junction was reduced compared to the conventional co-implantation process with pre-amorphization, which might come from novel self-amorphization mechanism by energized clusters without foreign impurities such as Ge and F. For further scaled devices, GCIB can provide more efficient boron activation by laser spike annealing (LSA) while maintaining the scaled extension profile by combination with the reduced temperature spike RTA

Valveless Small Gas Pump

In this article, a small valveless gas pump based on a synthetic jet actuator is developed. Instead of a check or active valve, a special flow control structure in consideration of synthetic jet characteristics is designed to realize valve function. A small-sized prototype of this pump is presented. Numerical simulation by using a simplified fluid model is conducted. The results reveal that the present small valveless pump can achieve gas pumping with large flow rate. However, it is also noted that in one operation cycle, there exists a period when a small amount of backflow appears. This paper was presented at the Micro/Nanoscale Energy Conversion Transport 2004; August 9–12 at Inje University, Korea.