• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.28 no.10
• /
• pp.414-419
• /
• 2016

Air flow measurement is a fundamental and important task for testing, adjusting, and balancing of HVAC system. However, it is difficult to carry out in the field due to the large size and weight of the flow meter. In this study, for the purpose of developing a small and portable flow meter, we proposed a different method of static pressure measurement and verified it experimentally. In the proposed method, static pressure difference was measured by inserting a tube inside the chamber before and after the nozzles. The results were compared with measurements according to the ANSI/ASHRAE standard. The results were in good agreement, indicating that the inserted tube method could be used for static pressure measurement of a portable flow meter. The proposed method eliminates the pressure tubes that are attached outside, which results in smaller size and easy handling.

• Journal of Biosystems Engineering
• /
• v.11 no.2
• /
• pp.4-13
• /
• 1986

뿌리작물(作物)을 수확(收穫)하기 위(爲)하여 진동(振動)을 이용(利用)한 4절(節)링크로 구성(構成)되는 시작기(試作機)를 설계(設計), 제작(製作) 및 실험을 수행(遂行)하였다. 수확기(收穫機)의 작동중(作動中) 발생(發生)하는 불균형력(不均衡力)을 상쇄(相殺)시키기 위(爲)한 힘의 평형장치(平衡裝置)를 설계(設計)하기 위(爲)하여 각(各) 요소(要素)의 가속도(加速度) 및 동력학적(動力學的)인 힘을 분석(分析)하였고, 진동기구(振動機構)에 의(依)하여 발생(發生)되는 이론적(理論的)인 토크와 측정(測定)된 토크를 비교분석(比較分析)하였다. 설계(設計)된 힘의 평형장치(平衡裝置)는 불균형력(不均衡力)의 대부분(大部分)을 상쇄(相殺)시켜주고, 이론적(理論的)인 토크는 실측(實測)토크의 변화경향(變化傾向)과 잘 일치(一致)하였다.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.10
• /
• pp.1159-1165
• /
• 2011

The recording density of HDD is increasing in ratio of 100% each year. Because the increasing of recording density requires the feature of high rotation, fixation and low-noise, fluid hydrodynamic bearing(FDB) has been paid attention to overcome a limitation in ball bearing. Most of researches related to improving performance of FDB have been studied in Japan which has 80% more market share of HDD spindle motor assembly. Main subject of studies are about for the design of the groove shape, manufacturing process of fluid dynamic bearing, performance evaluation and measurement. In HDD, non-repeatable runout(NRRO) is most important parameter which determines the performance of HDD spindle system because NRRO is unpredictable that cannot be compensated in head/slider servo system. In this study, performance evaluation system can measure dynamic behaviors were designed and methodology for calculating imbalance, RRO, and NRRO were proposed.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.19 no.4
• /
• pp.1088-1091
• /
• 2005

This study was designed to research whether Dinamika can yield a suitable diagnosis for Activity of Autonomic Nene System on stroke. The testing of Dinamika was carried out at Oriental Medical Centar of Dong-Eui University with the participation of 27 patients. The results of Dinamika examinations shows as follows : Group A(the rising of a parasympathetic nerve system) is 0 persons. And Group B(the balancing autonomic none system) is 4 persons. Group C(the rising of a sympathetic nerve system) is 23 persons. There are 7 persons that it is difference of more than $20\%$ between B1 (the control ability of autonomic nerve system) and B2(the potential energy to control autonomic nerve system), 11 person that B1 and B2 are less than $10\%$, 1 person that B1 and B2 are balanced about $60\%$, 8 person that it is balanced domain from $10\%\;to\; 60\%$ between B1 and B2. According to this study on activity of autonomic nerve system using Dinamika on Stroke, these results suggest that 27 patients evidence the problem of autonomic none systems.

• Restorative Dentistry and Endodontics
• /
• v.28 no.2
• /
• pp.156-161
• /
• 2003

The purpose of this study is to evaluate the polymerization ability of three different light sources by microhardness test. Stainless steel molds of 1, 2, 3, 4 and 5 mm in thickness of 7 mm in diameter were prepared. The hybrid composite Z100 was packed into the hole of the mold and curing light was activated for designated time. Three different light sources, conventional halogen, light emitting diode, and plasma arc, were used for curing of composite. Two different curing times applied ; one is to follow the manufacturers recommendation and the other is to extend the curing time of LED and plasma arc for balancing the light energy with halogen. Immediately after curing, the Vickers hardness was measured at the bottom of specimen. The results were as follows. 1 The composite cured with LED showed equal to higher microhardnesss than halogen. 2. The composite was cured with plasma arc by manufacturers recommendation showed lowest micro-hardness at all thickness. However, when curing time was extended, microhardness was higher than the others. In conclusion, this study suggested that plasma arc needs properly extended curing time.

• Journal of Power Electronics
• /
• v.14 no.5
• /
• pp.946-956
• /
• 2014

Cascaded H-Bridge (CHB) converters can be directly connected to medium-voltage grids without using transformers and they possess the advantages of large capacity and low harmonics. They are significant tools for providing grid connections in large-capacity renewable energy systems. However, the reliability of a grid-connected CHB converter can be seriously influenced by the number of power switching devices that exist in the structure. This paper proposes a fault-tolerant control strategy based on double zero-sequence voltage injection and DC voltage optimization to improve the reliability of star-connected CHB converters after one or more power units have been bypassed. By injecting double zero-sequence voltages into each phase cluster, the DC voltages of the healthy units can be rapidly balanced after the faulty units are bypassed. In addition, optimizing the DC voltage increases the number of faulty units that can be tolerated and improves the reliability of the converter. Simulations and experimental results are shown for a seven-level three-phase CHB converter to validate the efficiency and feasibility of this strategy.

• Proceedings of the KIPE Conference
• /
• 2018.07a
• /
• pp.165-167
• /
• 2018

본 논문은 다권선 변압기를 이용한 능동 셀 밸런싱 회로의 에너지 전달 효율을 향상시킬 수 있는 스위칭 방식을 제안한다. 다권선 변압기를 이용한 밸런싱 회로는 셀 당 하나의 스위치가 사용되며, 하나의 변압기 권선을 두 개의 셀이 공유하는 구조를 가져 다른 능동 셀 밸런싱 회로보다 소량의 능동 소자 및 수동 소자가 사용되는 장점을 갖는다. 이 밸런싱 회로는 직렬 셀 전압의 분포에 따라 에너지를 공급하는 소스 셀과 에너지를 받는 목표 셀을 선택하여 벅-부스트 및 플라이백 방식으로 동작한다. 하지만, 플라이백 동작에서 기존의 스위칭 방식을 사용할 경우, 변압기의 커플링 계수의 영향으로 인해 밸런싱 과정 중 비-목표 셀로 전달되는 에너지가 발생하게 된다. 이는 에너지 전달 효율을 감소시켜 셀 밸런싱 과정 중 새로운 셀 불균형 현상을 초래한다. 본 논문에서는 플라이백 동작에서 변압기의 커플링 영향을 최소화하여 셀 밸런싱을 효과적으로 수행할 수 있는 스위칭 방식을 제안하였다. 제안한 스위칭 방식의 성능은 1 W급 시작품을 이용한 실험을 통하여 검증되었다.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.10 no.5
• /
• pp.281-296
• /
• 2015

This paper describes a novel disaster evacuation system using embedded systems such as smart devices for crisis and emergency management. In indoor environments deployed with the Bluetooth Low Energy(BLE) beacons, smart devices detect their indoor positions from beacon messages and interact with Map Server(MS) and Route Server(RS) in the Internet over the LTE and/or Wi-Fi functions. The MS and RS generate an optimal path to the nearest emergency exit based on a novel graph generation method for less route computation, called the Disaster Evacuation Graph(DEG), for each smart device. The DEG also enables efficient processing of some constraints in the computation of route, such as load balancing in situation of different capacities of paths or exits. All data interfaces among three system components, the MS, RS, smart devices, have been defined for modular implementation of our disaster evacuation system. Our experimental system has been deployed and tested in our building thoroughly and gives a good evidence that the modular design of the system and a novel approach to compute emergency route based on the DEG is competitive and viable.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.12
• /
• pp.1740-1744
• /
• 2017

This paper describes the preparation and characteristics of a battery capacitor and module for solar power system. A cylindrical 30,000F battery capacitor ($60{\times}138mm$) was assembled by using the $LTO(Li_4Ti_5O_{12})$ electrode as an anode and $NMC(LiNiMnCoO_2)-LCO(LiCoO_2)$ as a cathode. The battery capacitor has reduced energy density and power density under high CC(constant current) and CP(constant power) conditions. Battery capacitor module (16V, 11Ah) was fabricated using an asymmetric hybrid capacitor with a capacitance of 30,000F. In order to determine the characteristics of the battery capacitor Module for solar power system, battery capacitor cells were connected in series with active balancing circuit. As a result of measuring the 100w LED lamp, it was discharged at the voltage of 15V~10V, and the compensation time at discharge was measured to be about 4979s. Experimental results show that it can be applied to applications related to solar power system by applying battery capacitor module.

• Journal of Korea Multimedia Society
• /
• v.25 no.8
• /
• pp.1075-1084
• /
• 2022

Internet of Things(IoT) has become a key available technology for efficiently implementing device to device(D2D) services in various domains such as smart home, healthcare, smart city, agriculture, energy, logistics, and transportation. A lightweight publish/subscribe(Pub/Sub) messaging protocol not only establishes data dissemination pattern but also supports connectivity between IoT devices and their applications. Also, a Pub/Sub broker is deployed to facilitate data exchange among IoT devices. A scalable edge-based publish/subscribe (Pub/Sub) broker overlay networks support latency-sensitive IoT applications. In this paper, we design a hypercube grid quorum(HGQ) for distributed Pub/Sub systems based IoT applications. In designing HGQ, the network of hypercube structures suitable for the publish/subscribe model is built in the edge layer, and the proposed HGQ is designed by embedding a mesh overlay network in the hypercube. As their applications, we propose an HGQ-based mechansim for dissemination of the data of sensors or the message/event of IoT devices in IoT environments. The performance of HGQ is evaluated by analytical models. As the results, the latency and load balancing of applications based on the distributed Pub/Sub system using HGQ are improved.