• Journal of Energy Engineering
• /
• v.2 no.1
• /
• pp.95-103
• /
• 1993

A conceptual thermoelectric heat pump(cooling mode) of small capacity is designed. Its performance is investigated through parametric analysis. COP and cooling capacity decease as the ambient temperature increases with ${\mu}$, J, T$\sub$wi/, fixed. To design a system of fixed capacity comes to calculate ${\mu}$ and J when T$\sub$wi/, and T$\sub$a/ are given. As v is fixed by semi-conductor manufacturers, optimum combination of n and I should be searched for ν. Optimum current could be calculated using ${\mu}$-J curve and optimum value of ${\mu}$. COR$\sub$R/ increases as water flow rate increases and T$\sub$a/ decreases. The effect of heat transfer coefficient at hot(heat releasing) side is more significant than that at cold(heat absorbing) side.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.3407-3412
• /
• 2007

The performance characteristics of the polymer electrolyte fuel cells (PEFCs) were investigated under various humidification conditions at steady-state and transient conditions. The PEFC studied in this study was characterized by I-V curves in potentiostatic mode. The I-V curves representing steady-state performance were obtained from OCV to 0.25V, and the dynamic performance responses were obtained at some points of voltages. The anodic external humidification was applied and the humidity was controlled from 20% to 100%. The effects of relative humidity of hydrogen were measured with the dry air at the cathode. At high voltage region, the performance at high temperature was higher, but at low voltage region, low temperature condition showed the higher performance. The dynamic responses were observed at the instant when the voltage of the PEFC was changed. It was observed that the performance reached steady-state earlier with the increase of temperature.

• Journal of Advanced Marine Engineering and Technology
• /
• v.29 no.4
• /
• pp.443-452
• /
• 2005

The purpose of this study is experimentally to analyze the effects of intake port swirl, injection system and turbocharger on the engine performance and the emission characteristics in a V8 type turbocharger intercooler D.I. diesel engine of the displacement 16.7L, and to suggest the improvement of engine performance. Generally to enhance engine power, TCI diesel engine is put to practically use turbocharged intercooler in order to increase volume efficiency which is cooled boost air. As results of considering the factors of the intake port of swirl ratio 2.25, compression ratio 17.5. re-entrant $8.5^{\circ}$ combustion bowl, nozzle hole diameter ${\phi}0.33{\ast}3+{\phi}0.35{\ast}2$. nozzle protrusion 3.18mm, injection timing BTDC $12^{\circ}CA$ and turbocharger(compressor 0.6A/R+46Trim. turbine 1.0 A/R+57Trim) is the best in the full load in the engine performance and the exhaust characteristics of NOx concentration. Therefore. their factors are appropriated as intake system, injection and turbocharger system.

• Korean Chemical Engineering Research
• /
• v.56 no.4
• /
• pp.469-473
• /
• 2018

When pure hydrogen was supplied to the stationary PEMFC generally using the reforming gas, its characteristics were compared with the vehicle PEMFC. The effect of varying the amount of hydrogen supply to the anode on the overall performance was compared. The variation of hydrogen supply in the range of 1.0~1.7 excess (stoi.) had little effect on the OCV of stationary and vehicle MEA (Membrane and Electrode Assembly). At 0.7 V, the current density of the stationary MEA was about 16% higher than that of the vehicle MEA. I-V performance, impedance, and LSV were measured with varying relative humidity. Both OCV and electrolyte membrane resistances decreased with increasing relative humidity. The hydrogen permeability of the stationary MEA was lower than that of the vehicle MEA, showing that the durability of the stationary membrane could be higher than that of the vehicle membrane.

• Journal of the Korean Applied Science and Technology
• /
• v.29 no.4
• /
• pp.594-598
• /
• 2012

Polymer electrolyte membrane fuel cell(PEMFC) performance degrades seriously when sulfur dioxide and hydrogen sulfide are contaminated in the fuel gas at anode and air source at cathode, respectively. This paper reveals the effect of the combined sulfur impurity poisoning on both PEMFC cathode and anode parts through measuring electrical performance on single FC operated under 1 ppm to 10 ppm impurity gases. The severity of $SO_2$ and $H_2S$ poisoning depended on concentrations of impurity gases under optimum operating conditions($65^{\circ}C$ of cell temperature and 100 % relative humidity). Sulfur adsorption occured on the surface of Pt catalyst layer on MEA. In addition, MEA poisoning by impurity gases were cumulative. After four consecutive poisonings with 1, 3, 5 to 10 ppm, the fuel cell performance of PEMFC was decrease upto 0.54 V(76 %) from 0.71 V.

• Annual Conference of KIPS
• /
• 2018.10a
• /
• pp.216-217
• /
• 2018

IEEE 1609.2 표준은 WAVE (Wireless Access in Vehicular Environment) 표준에서 차량간(V2V, Vehicle-to-Vehicle) 혹은 차량과 인프라간(V2I, Vehicle-to-Infrastructure)통신 상의 응용 메시지 보호를 위해 제정되었다. 이 표준은 메시지 이증 및 무결성 검증을 위하여 NIST p256 타원 곡선 커브 기반의 ECDSA 전자서명 기법을 사용한다. 매우 복잡한 도신 상의 출퇴근 환경에서는 수백대의 자동차가 전송하는 메시지를 정상적으로 처리하기 위하여, 차량의 OBU(On-Board Unit) 혹은 노상의 RSU(Road-Side Unit)에서 서명된 메시지의 검증 성능이 매우 중요한 이슈가 될 수 있다. 본 논문에서는 V2X 통신에서 효율적인 ECDSA 서명 검증을 위하여, OBU 혹은 RSU 환경에서 CPU 상의 병렬 처리 성능을 테스트 한 후 시사점을 살펴본다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.5
• /
• pp.526-531
• /
• 2014

Vehicular communications have been receiving much attention in intelligent transport systems(ITS) by combining communication technology with automobile industries. In general, vehicular communication can be used for vehicle-to-vehicle(V2V) and vehicle-to-infrastructure( V2I) communication by adopting IEEE802.11p/1609 standard which is commonly known as wireless access in vehicular environment(WAVE). WAVE system transmits signal in 5.835~5.925 GHz frequency band with orthogonal frequency division multiplexing(OFDM) signaling. In this paper, after 32 bit processed the channel monitoring in MAC(Media Access Control) layer of WAVE system implemented according to IEEE 802.11p standard, data were received and we evaluated the performance, we built the test bed consisting of OBU(On Board Unit) in the real expressway. We transmitted WSM(WAVE Short Message) and received WSM between OBU wirelessly. And then, we calculated channel occupancy time per one frame and throughput, and evaluated the performance.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.3
• /
• pp.1691-1699
• /
• 2014

IEEE developing WAVE specifications are able to support V2V and V2I wireless communications, and these functionalities can be used to enhance vehicle operational safety. To overcome any security weaknesses that are inherent in wireless communications, WAVE specification should support message encryption and authentication functions. In this study, we have implemented WAVE security algorithms in IEEE P1609.2 with openssl library and C language. We have verified the normal operation of implemented software, using the test vectors of related specifications, and measured their performance. Our software is platform independent, and can be used for the full implementation of WAVE specification.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2010.10a
• /
• pp.54-57
• /
• 2010

Vehicular Ad-hoc Network the core technology of ITS supports safety service or information service to driver and passenger on the roads utilizing V2V and V2I communication. WAVE, the standard of the vehicular ad hoc networks, adopts IEEE 802.11p as MAC protocol and includes the channel coordination algorithm to utilize multiple channels. However, this standard shows the problem related with QoS guarantee of urgent data for driver's safety and the limitation of the performance improvement. In this paper, we introduce WAVE-based Multi-channel MAC protocols that have proposed to resolve above problems and describe their features.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.2
• /
• pp.6-14
• /
• 2007

In this paper, we propose and observe the Adaptive Modulation system with optimal Turbo Coded V-BLAST (Vertical-Bell-lab Layered Space-Time) technique that is applied the extrinsic information from MAP (Maximum A Posteriori) Decoder in decoding Algorithm of V-BLAST: ordering and slicing. The extrinsic information is used by a priori probability and the system decoding process is composed of the Main Iteration and the Sub Iteration. And comparing the proposed system with the Adaptive Modulation system using conventional Turbo Coded V-BLAST technique that is simply combined V-BLAST with Turbo Coding scheme, we observe how much throughput performance has been improved. In addition, we observe the proposed system using STD (Selection Transmit Diversity) scheme. As a result of simulation, Comparing with the conventional Turbo Coded V-BLAST technique with the Adaptive Modulation systems, the optimal Turbo Coded V-BLAST technique with the Adaptive Modulation systems has better throughput gain that is about 350 Kbps in 11 dB SNR range. Especially, comparing with the conventional Turbo Coded V-BLAST technique using 2 transmit and 2 receive antennas, the proposed system with STD (Selection Transmit Diversity) scheme show that the improvement of maximum throughput is about 1.77 Mbps in the same SNR range.