• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2011년도 춘계학술대회
• /
• pp.333-335
• /
• 2011

In the transmitting process of image processing system, images always be corrupted by impulse noise, especially random-valued impulse noise. So removing the random-valued impulse noise is very important, but it is also one of the most difficult case in image processing. The most famous method is the standard median filter, but at edge, the filter has a special feature which has a tendency to decrease the preserve. As a result, we proposed a filter that detection random-valued impulse noise firstly, next to use efficient method to remove the noise and preserve the details. And through the simulation, we compared with the algorithms and indicated that proposed method significant improvement over many other existing algorithms.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 C
• /
• pp.1555-1557
• /
• 2001

To compare the lightning impulse measurement capabilities of high voltage laboratory, a lightning impulse voltage measuring system from HUT is circulated around the world. This paper presents test results after second round of this worldwide exercise. KERI's impulse voltage measuring system compared with the circulating reference measuring system from HUT at voltage levels of 80, 160, 240, 320 and 400 kV. Three impulse shapes were used, i.e. full smooth lightning impulse with both short (0.84 $\sim$ 0.95 ${\mu}s$) and long front (1.45 $\sim$ 1.56 ${\mu}s$), and chopped impulse with time to chopped impuse. Impulse peak value ($U_p$) and time parameters ($T_1$, $T_2$ and $T_c$) according to IEC 60060-1 were compared.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
• /
• pp.67-71
• /
• 2003

The propagation characteristics of the impulse wave discharged from the exit of a perforated pipe is investigated through a simple shock tube facility. The pressure histories and directivities of the impulse wave propagating outside from the exit of pipe with several different configurations are analyzed for the range of the incident weak shock wave Mach number between 1.02 and 1.2. In the shock tube experiments, the impulse wave are visualized by a Schlieren optical system for the purpose of understanding its propagation characteristics. The experimental results show that for the near sound field the impulse noise strongly propagates toward to the pipe axis, but for the far sound field the impulse noise uniformly propagates toward to the omnidirections, indicating that the directivity pattern is almost same regardless of the pipe type. Especially, it is shown that the perforated pipe has a little performance to reduce the impulse noise only for the near sound field

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 춘계학술대회논문집
• /
• pp.852-855
• /
• 2004

This experimental study describes the propagation characteristics of the impulse noise emitted from the exit of a straight pipe attached to the open end of a simple shock tube. The sound pressure level and directivity of the impulse noise propagating from the exit of pipe with several different diameters are measured in the far sound fold for the range of the incident shock wave Mach number between 1.07 and 1.26. The experimental results showed that the peak values of impulse noises had a strong dependance on the exit diameter of a pipe and the shock wave Mach number. The impulse noise had the directivity propagating toward to the pipe axis and the characteristics of inverse square law of propagation distance. Moreover, it was shown that the one-third octave band SPL of impulse noise was almost constant regardless of the frequency band.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
• /
• pp.61-62
• /
• 2009

This paper describes the characteristics of lightning impulse current of ZnO block for transmission line arrester with external gap. The ageing parameters of lightning arresters ate impulse current, moisture ingress, temperature ageing and so on. Especially it is important to estimate the change of electrical characteristics by impulse current. Total energy applied to the ZnO arrester each time is $4/10{\mu}s$, 30kA and $2/20{\mu}s$, 10kA impulse current. Before and After the test, the residual voltage variation of varistors passed was below 5%. According to the test, it is thought that the ZnO arrester shows good stability with impulse current test.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.792-797
• /
• 2003

A helical vane is applied to reduce the magnitude of the impulse wave discharged from the exit of a duct. A shock tube with an open end is used to investigate the effect of the helical vanes on the impulse wave magnitude. Four different types of helical vanes are installed into the low-pressure tube of shock tube. The magnitude of the incident shock wave is varied below 1.25, and the magnitude of impulse wave is measured using a pressure transducer mounted on a wedge probe. Instant images of the impulse wave are obtained by means of the Schlieren optical method. The present experimental results show that the helical vane considerably reduces the magnitude of the impulse wave and the vane effects are more remarkable for stronger incident shock wave.

• 한국전자파학회논문지
• /
• 제14권11호
• /
• pp.1121-1126
• /
• 2003

본 논문에서 트랜지스터를 이용하여 Ultra Wide Bandwidth(UWB)통신 시스템의 구성 요소의 하나인 임펄스 발생기를 설계하였다. 이 펄스 발생기는 두 가지 스텝으로 이루어져 있다. 첫 번째 스텝에서 트랜지스터 스위칭 동작과 스위칭 동작에 걸리는 시간을 이용하여 트랜지스터의 가우시안 펄스를 만든다. 두 번째 스텝에서 고 대역 통과 필터를 이용하여 모노싸이클 임펄스로 변환시킨다. 결과인 임펄스의 크기는 약 +/-250 ㎷ 정도이고, 펄스의 폭은 0.9 ns로서 펄스폭은 트랜지스터의 동작 시간과 일치하였다.

• Structural Engineering and Mechanics
• /
• 제42권3호
• /
• pp.363-381
• /
• 2012

This study is aimed at providing an efficient analytical model to obtain pressure- impulse diagram of one-way reinforced concrete slabs subjected to different shapes of air blast loading using single degree of freedom method (SDOF). A tri-linear elastic perfectly plastic SDOF model has been used to obtain the pressure-impulse diagram to correlate the blast pressure and the corresponding concrete flexural damage. In order to capture the response history for the slab, a new approximately SDOF method based on the conventional SDOF method is proposed and validated using published test data. The influences of pulse loading shape on the pressure-impulse diagram are studied. Based on the results, a pressure-impulse diagram generation method using SDOF and an analytical equation for the pressure-impulse diagram is proposed to different damage levels and different blast loading shapes.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
• /
• pp.458-459
• /
• 2007

This paper describes the characteristics of lightning impulse current of ZnO block for transmission line arrester with external gap. The ageing parameters of lightning arresters are impulse current, moisture ingress, temperature ageing and so on. Especially it is important to estimate the change of electrical characteristics by impulse current. Total energy applied to the ZnO arrester each time is $4/10{\mu}s$, 30kA and $2/20{\mu}s$, 10kA impulse current. Before and After the test, the residual voltage variation of varistors passed was below 5%. According to the test, it is thought that the ZnO arrester shows good stability with impulse current test.

• 한국환경과학회지
• /
• 제12권12호
• /
• pp.1261-1267
• /
• 2003

On the basis of the distribution of particle size measured by laser diffraction spectrometers, this research was carried out to investigate the characteristics of mist removal with the change of operating condition in the plasma reactor of impulse streamer corona. The operating parameters in this experiment were power of impulse streamer corona, gas velocity, impulse generation time, gas temperature, and SOx/NOx concentration. The collection efficiency T(d) was estimated by the distribution of particle size in the collection zone through the advanced model.