• 한국정보통신설비학회:학술대회논문집
• /
• 2008.08a
• /
• pp.45-50
• /
• 2008

Many applications of sensor network require connection to the Internet. The transmission protocol of traditional sensor network was designed within the sensor network itself. However, based on 6LoWPAN which can be accessed using IPv6, direct connection is possible between the sensor network and the TCP/IP network outside. Transmission of data in applications of sensor network falls into two main categories. One is a small packet that is periodically produced such as packet related to temperature and humidity. The other is a relatively large packet that brings about network overheads such as images. We investigated the conformance test and pros and cons of application data over the transmission protocol of Zigbee and 6LoWPAN. As a result, both Zigbee and 6LoWPAN have shown low rate of loss for periodic data and have in creased reliability of data transfer. When transmitting streaming image data, both ACK, non ACK mode of Zigbee and UDP of 6LoWPAN minimized transmission time but suffered the consequences of high packet loss. Even though TCP of 6LoWPAN required a long transmission time, we were able to confirm that no loss has occurred.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.24 no.11
• /
• pp.846-853
• /
• 2014

High performance intake silencer with low pressure drop are developed for a household oxygen generator. First, the acoustic power of the target oxygen generator are experimentally evaluated according to ISO code. Then, the transmission loss of and the flow characteristics inside the existing intake silencer are predicted and analyzed. On a basis of these results, two intake silencers are proposed, which are designed to induce the swirling flow inside the intake silencer and thus to reduce the flow loss. The predicted TL and the pressure drop for these two new silencers are compared to the existing one, which shows that the proposed ones have higher TL as well as low pressure drop. The reason for these improvements are explained by investigating the flow characteristics of the new silencers in detail.

• Current Optics and Photonics
• /
• v.1 no.1
• /
• pp.65-72
• /
• 2017

We propose a nearly lossless, compact, electrically modulated vertical directional coupler, which is based on the controllable evanescent coupling in a previously proposed graphene-assisted total internal reflection (GA-FTIR) scheme. In the proposed device, two single-mode waveguides are separate by graphene-$SiO_2$-graphene layers. By changing the chemical potential of the graphene layers with a gate voltage, the coupling strength between the waveguides, and hence the coupling length of the directional coupler, is controlled. Therefore, for a properly chosen, fixed device length, when an input wave is launched into one of the waveguides, the ratio of their output powers can be controlled electrically. The operation of the proposed device is analyzed, with the dispersion relations calculated using a model of a one-dimensional slab waveguide. The supermodes in the coupled waveguide are calculated using the finite-element method to estimate the coupling length, realistic devices are designed, and their performance was confirmed using the finite-difference time-domain method. The designed $3{\mu}m$ by $1{\mu}m$ device achieves an insertion loss of less than 0.11 dB, and a 24-dB extinction ratio between bar and cross states. The proposed low-loss device could enable integrated modulation of a strong optical signal, without thermal buildup.

• Korean Journal of Materials Research
• /
• v.29 no.11
• /
• pp.664-669
• /
• 2019

In this paper, a water-based green polymer mud is synthesized by simple compounding method. Effects of different kinds of tackifiers, their molecular weight on the viscosity of polymer mud and the effects of different fluid loss additives on mud fluid loss are studied. The results show that when polystyrene and anionic polyacrylamide with molecular weight of 8 ~ 10 million are used as the main thickening ingredient, polymer mud with high viscosity and high stability can be obtained. When the prepared polymer mud is formulated as NPAM: PEO: Hydroxypropyl cellulose(HPC) : Water = 42:10:10:100000 (unit: kg), the viscosity can reach 20.6 s, the filtration loss in 7.5 min is 24 mL, and the sand content is only 0.1 %. Compared with traditional bentonite mud, the green environment-friendly polymer mud has the advantages of small amount of waste, low environmental pollution, and low pulping cost, and can meet the construction needs for most topography and geomorphology drilling engineering.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.3
• /
• pp.69-74
• /
• 2018

Large industrial motors require a large area because of the high risk of shutdown accidents and large industrial accidents due to the lowering of the dielectric strength of the armature windings and overheating problems. Therefore, there is a demand for a large-capacity motor that has small size, light weight, and excellent dielectric strength compared with conventional motors. Superconducting motors have advantages of high efficiency and output power, low size, low weight, and improved stability. This results from greatly increasing the magnetic field generation by using superconductive field coils in rotating machines such as generators and motors. It is very important to design and analyze the cooling system to lower the critical temperature of the wires to achieve superconducting performance. In this study, a field loss analysis and low-temperature heat transfer analysis of the cooling system were performed through the conceptual design of a 100-HP high-temperature superconducting synchronous motor. The field loss analysis shows that a uniform pore magnetic flux density appears when high-temperature superconducting wire is used. The low-temperature heat transfer analysis for gaseous neon and liquid neon showed that a flow rate of 1 kg/min of liquid neon is suitable for maintaining low-temperature stability of the high-temperature superconducting wire.

• Journal of Korean Institute of Industrial Engineers
• /
• v.20 no.4
• /
• pp.99-111
• /
• 1994

Toguchi method is a systematic technique for designing high quality product at low cost. There are three steps in the Toguchi method, 1)system design, 2)parameter design, and 3)tolerance design. This paper considers the tolerance design for multiple performance characteristics which is practically important. We present two tolerance design procedures : grade selection and tolerance determining procedures. In grade selection procedure a scheme is presented that minimizes the sum of the price of low-level characteristics and the expected loss due to the variations of high-level characteristics. In tolerance determining procedure we determine the tolerances of the low-level characteristics.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.4B no.1
• /
• pp.20-23
• /
• 2004

BLDCMs are widely used in many industries. In certain specialized areas, they need to have high efficiency, high power rate and produce a low volume of noise, etc. In this study, a new type of slotless BLDCM is proposed that has no cogging torque, low iron loss and low volume as compared to commonly used BLDCMs. With a high performance magnet and coreless compact winding structure similar to those employed in linear synchronous motors, motor volume is reduced. The proposed motor has been put been through various experiments arid has demonstrated acceptable results for industry applications.

• Journal of Advanced Marine Engineering and Technology
• /
• v.16 no.5
• /
• pp.77-84
• /
• 1992

In the most of acoustic system with low flow rate and low pressure level, one-dimensional, linear modeling techniques are used very well. At low frequency, the tube is modeled as inertia element and cavity as capacitance element, and to extend the range of frequency normal mode oscillators are represented. Bond graph modelling techniques are proposed to predict TL (Transmission Loss) and time response which is impossible by transfer matrix in muffler system. A simple acoustic filter which consists of several tubes and cawities is analyzed in both time and frequency domain.

• Proceedings of the KIPE Conference
• /
• 2005.07a
• /
• pp.266-268
• /
• 2005

A new synchronous switch controlled transient current build-up zero voltage switching (TCB-ZVS) forward converter is proposed. The proposed converter is suitable for the low-voltage and high-current applications. The features of the proposed converter are low conduction loss of magnetizing current, no additional circuit for the ZVS operation, high efficiency, high power density and low EMI noise throughout all load conditions.

• ETRI Journal
• /
• v.28 no.3
• /
• pp.355-363
• /
• 2006

This paper presents a low-cost RF parameter estimation technique using a new RF built-in self-test (BIST) circuit and efficient DC measurement for 4.5 to 5.5 GHz low noise amplifiers (LNAs). The BIST circuit measures gain, noise figure, input impedance, and input return loss for an LNA. The BIST circuit is designed using $0.18\;{\mu}m$ SiGe technology. The test technique utilizes input impedance matching and output DC voltage measurements. The technique is simple and inexpensive.