• Journal of the Korean Wood Science and Technology
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• 제47권4호
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• pp.425-441
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• 2019

목재수피의 음향성능을 파악하고자 6가지 수종의 목재수피를 삭편으로 절삭하여 몇 가지 비중조건과 두께로 만든 후 흡음율과 음향투과손실을 전달함수법과 전달행렬법으로 각각 측정하였다. 그 결과, 편백나무수피가 두께 100 mm 일 때의 100-6400 Hz 평균흡음율은 0.90이며 두께 50 mm 일때의 100-6400 Hz 평균흡음율은 0.84이다. 특히 두께 100 mm 일 때의 경우, 1 KHz의 주파수영역에서의 흡음율은 약 100%에 근접하는 높은 흡음율을 나타내었다. 음향투과손실은 측정주파수범위에서 편백나무수피는 500 Hz에서 15.30 dB의 투과손실을 나타내었고 1000 Hz 수치는 15.73 dB이었다. 10 mm 두께의 합판을 수피파티클 배면에 추가한 후에는 투과손실이 20-30 dB 증가하였다. 목재수피는 친환경적이면서 기존의 석고보드보다 흡음율이 높고 음향투과손실이 크게 나타나서 음향성능이 우수한 건축재료로 고려될 수 있다고 생각된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(4)
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• pp.13-16
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• 2001

In the Dedicated Short Range Communication (DSRC) system channel, a large number of bit errors occur because of Additive White Gaussian Noise (AWGN) and fading. When an image data is transmitted under the condition, reconstructed image quality is significantly degraded. In this paper, as an alternative to the error correcting code and/or automatic repeat request scheme, we propose an error recovery scheme for image data transmission. We first analyze how transmission errors in the DSRC system channel degrade image quality. Then, in order to improve image quality, we propose error resilient and concealment schemes for still image transmission using DCT-based fixed length coding, hamming code, cyclic redundancy check, and interleaver. Finally, we show its performance by an experiment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.432-434
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• 2004

Bluetooth is a promising wireless personal area network technology and is on the verge of being ubiquitously deployed over wide range of devices. This paper aims to implement a wireless network for image transmission using Bluetooth technology. The characteristics of Bluetooth are small size, low band width and low power consumption, However, there are some difficulties in implementing a wireless radio network using Bluetooth since a lot of repeaters may needed when Bluetooth depends a role of host on personal computer for data transmission. In this paper, a method to implement a wireless radio network is proposed and applied for image transmission using a small size microprocessor for each Bluetooth.

• 오토저널
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• 제15권3호
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• pp.36-46
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• 1993

In CVT vehicle, the engine speed is completely decoupled from the vehicle speed within the range from maximum transmission ratio to minimum transmission ratio. This allows the engine to operate in optimal state(e.g. best fuel economy or maximum power mode.) In this study, the CVT control algorithm for optimal operation of engine is suggested. In order to implement the real time digital control of electro-hydraulic CVT system, a software called CVTCON has been developed. CVTCON also includes the CVT operation module, (2) system test module, (3) system control module and (4) data management module. By using the CVTCON and the electro-hydraulic CVT system, two modes of experiments were carried out: constant throttle opening mode and acceleration mode. From the experimental result, it was found that the algorithm suggested in this study showed optimal operation of the CVT system.

• 전자공학회논문지A
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• 제31A권10호
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• pp.31-38
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• 1994

In this paper, the leaky wave readiation characteristics of a microstrip rectangular patch array is presented. The reflection and transmission characteristics are analyzed using the equivalent transmission line method. Since the leaky wave is generated from the periodic array, using the Floquet'theorem, leaky wave frequency range is predicted and confirmed by the measured reflection and transmission characterstics of the array. A 17 element microstrip patch array at X-Band is designed and tested. Teh scattering Characteristics show good agreement woth those obtained from the equivalent transmission line analysis. The radiatio characteristics at 10GHz using this method show about 3${\circ}$ shift in main lobe angle compared with measured results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 C
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• pp.1376-1378
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• 1999

Most conventional protection relays are based on processing information in the spectrum that is close to or at power frequency. It is, however, widely known that faults on transmission lines produce frequency components of a wide range In this respect, this paper describes the basis of a Protection technique for transmission lines which utilises high-frequency components. Fault-generated signals caused by post-fault and the signal derived from stack tuner is connected to the coupling capacitor of CVT. Digital signal processing is then applied to the captured information to determine whether the fault is inside or outside the Protected zone, and to discriminate the fault type on transmission line.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.628-632
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• 2001

Experimental approach was investigated to improve gear rattle noise of a small car. During the development of a small car serious problem occurred inside the transmission gear units. The transmission was a carried over system from a less powered predecessor. Several components of suspicion were investigated, and applied to reduce rattle noise. In general, backlash, the assembly gaps, and the clutch disk rattle induce gear rattle noise. Above mentioned improvements were applied to reduce the noise, but still problem remained. Meanwhile, the temperature inside the gearbox was reported to be unusually high and the life of transmission oil quality deteriorated drastically, Temperature increment caused the large gap between the bearing outer diameter and the transmission housing. Large gap made the gear shaft assembly move intermittently and impact each other. The tighter control of the assembly gap allowed the rotating shafts smoothly and reduced the gear rattle noise even in the high temperature range.

• 소음진동
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• 제8권5호
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• pp.807-813
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• 1998

Transmission loss of the simple expansion chamber with multiple inlet and outlet ports is obtained. Transfer matrices which represent the relation between the power variables(pressure and velocity) of inlets and outlets depend on the input relatons as well as the acoustic system parameters(i.e. geometry of the chamber, wall admittance, etc.). The analysis has been performed analytically, including the effects of higher order modes for the 2-inlet/1-outlet, 1-inlet/2-outlet and 2-inlet/2-outlet systems. This study yeilds that phase difference between the inlet ports can significantly increase the transmission loss in low frequency range.

• Journal of information and communication convergence engineering
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• 제7권3호
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• pp.372-376
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• 2009

In this paper, new and simple optical transmission link with fixed dispersion management (DM) scheme, i.e., pre(post) compensation and residual dispersion per span (RDPS) are fixed to net residual dispersion (NRD) = 0 ps/nm, and optical phase conjugator (OPC) having optimal position depending on launch power in WDM transmission system is proposed. Also, effective launch power range of WDM channels resulting 1 dB eye opening penalty (EOP) is induced as a function of OPC position. First, it is confirmed that, for applying DM into WDM transmission link fixed pre(post)compensation and RDPS, which are independence on exact system parameters except launch power, sufficiently are used in WDM links, but OPC with optimal position is needed for effective compensating impairments of WDM channels. And, it is confirmed that effective launch power is broader in case of RDPS = 100 ps/nm than in RDPS = 50 ps/nm. But, it is shown that the best OPC position offset is -0.6 km from a point of view of power window, which is defined as difference between maximum and minimum effective launch power.

• Journal of information and communication convergence engineering
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• 제8권6호
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• pp.677-681
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• 2010

This paper proposes a transmission probability control scheme for enhancing the performances of FSA-based RFID system. In order to maximize the system performance, the number of tags attempting to transmit their identifiers in a frame should be kept at a proper level. The reader calculates the transmission probability according to the number of tags within the identification range of reader and then broadcasts it to tags. Tags, in which their slot counter values reach to zero, attempt to transmit their identifiers with the received probability. Simulation results show that the proposed scheme can offer better throughput and delay performance than the conventional one regardless of the number of tags.