• Journal of Korea Multimedia Society
• /
• v.9 no.5
• /
• pp.576-584
• /
• 2006

Content-based video matching is measuring a similarity of video signature compared to the original clip and copies of media. Specially, it is very important to match the exact frame position, but it depends on frame rate, noise condition and compression format of video. Ordinal signature shows good performance than other video signatures under normal condition but the previous didn't try to find the uniqueness and robustness. Hua et al. performed a uniqueness test under compressed in different formats or frame size. However, they used other compression format image instead of noise in robustness test. This paper proposes robustness test method using several noise models and analyzes the performance of robustness and uniqueness.

• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.211-214
• /
• 2000

본 논문은 전자파 장해 및 복사내성 측정의 대용 시험시설로 활용될 수 있는 전자파 잔향실의 전자기장 특성에 관하여 연구하였다. 전자파 잔향실 내부 균일성을 확보하기 위하여, 음향효과의 극대화를 위해 인간의 가청 주파수대인 16-20,000Hz 범위, 음속(340 m/sec)에 적용하여 활용되고 있는 Shroeder Quadratic Residue Diffuser를 무선 주파수 대역 30 KHz -3 THz인 범위로 확장, 3가지 형태의 Diffuser를 설계하여 잔향실 내부에 적용하였다. FDTD(Finite-Difference Time-Domain) 수치해석 방식을 이용하여 잔향실 내부의 필드 특성을 조사한 결과 Diffuser를 부착한 3 가지 형태 모두 치대 tolerance $\pm$3dB 이내의 필드 균일도를 나타내었으며, Type 3, 대칭형 구조의 Diffuser 형태가 효율이 가장 우수하다는 결과를 나타내었다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.1
• /
• pp.51-62
• /
• 2002

EMI/EMS 측정을 위해서는 주변 전자파 잡음(background noise)이 낮은 야외시험장(Open Area Test Site)이 가장 바람직하나, 근래 전자(전기 기기 사용의 증가와 방송.무선통신 시스템의 다양화로 인한 인공잡음(artificial noise)의 증대로 조건에 부합된 부지 선정이 어렵고, 설치 비용이 매우 크며 날씨 변화에 따라 시험 계획이 변경 될 수도 있는 단점이 있다. 전자파 분-무반사실(Semi Anechoic Chamber)은 대부분의 환경 잡음을 감쇠시키므로 야외시험장처럼 장소의 구애를 받지 않아 도시나 혹은 제품 생산지 가까이에 설치 운용이 가능하다. 그러나 큰 설치 공간과 많은 시설 유지 비용을 필요로 하며, 저주파 대역에서는 반사에 의한 공진을 완전히 제거할 수 없어 성능이 떨어진다. 또한, 최근 컴퓨터 CPU의 동작주파수가 급속하게 높아지고 PCS, IMT-2000 등과 같은 이동전화의 사용주파수도 계속해서 높아짐에 다라 미연방통신위원회(Federal Communication Commission)에서는 5㎓까지의 복사 방출 시험을 요구하고 있다. IEC 61000-4-3 복사 내성 시험규격도 휴대폰 주파수인 2㎓까지 확장되었으며 IMT-2000, Bluetooth 등 새로운 이동통신서비스가 속속 개발됨에 따라 18㎓ 까지 시험 주파수가 확장되는 추세이다. 그러나, 현재 국내 각 연구실에서 보유하고 있는 야외시험장이나 전자파 반-무반사실의 경우 1㎓이상에서의 시험이 곤란하여 수 ㎓주파수대역에서 시험이 가능한 복사 및 내성시험 시설이 필요하게 되었다. 이러한 문제점들을 해결하기 위해 고안된 대용 측정 시설 중 대표적인 것이 TEM 셀이나 GTEM셀과 같은 TEM 도파관(waveguide) 형태의 장비들이다. 이들은 본래 EMS 측정을 위한 장비이지만 협소한 공간이나 외부와의 전자파 간섭의 우려가 없고, 설치가 비교적 자유로워 여러 연구기관에서 도파관 원리를 이용한 측정 방식을 연구(개발하여 범용적인 전자파 적합성 측정 장비로서 활용하고 있다. 야외시험장과 무반사실 등이 안테나에 의한 피시험기기 주변 공간에서의 1점 측정으로 인해 시험 시간이 많아 소요되는 공통적인 단점이 있는 반면, TEM 도파관에 의한 측정은 일단 피시험기기의 모델링 정보만 얻어지면 계산에 의해 EMI 측정을 바로 할 수 있다. <표 1>에서 현재 상용화되어 사용되고 있는 TEM/GTEM 셀, 야외 시험장 및 전자파 무반사실에 대해 EMI 측정과 관련된 몇 가지 사안에 대해 비교하였다. 본 문서에서는 야외시험장이나 전자파 반-무반사실 등과 같은 기존 EMI/EMS 측정 시설의 단점을 보완하고, 광대역 특성을 갖는 대용 측정 시설로서의 TEM 도파관에 대해 소개하고 야외시험장 결과와의 상관관계 알고리즘 및 표준화 동향에 대해 기술하였다. 2절에서는 대표적인 TEM 도파관 구조의 측정 시설인 TEM 셀과 GTEM 셀의 전기적.구조적 특징에 대해 간단히 기술하고, 3절에서는 TEM 셀과 GTEM 셀에서이 측정결과를 이용하여 야외 시험장 결과를 얻어내는 상관관계 알고리즘에 대해 기술하였다. 4절에서는 IEC/CISPR와 TC77에서의 표준화 활동을 중심으로 현재 진행중인 TEM 도파관 관련 표준화 동향과 내용에 대해 기술하고자 한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.2
• /
• pp.227-233
• /
• 2001

Electromagnetic field characteristics of Reverberation chamber, which could be applicable for an alternative test facility of electromagnetic interference and radiated electromagnetic susceptibility have been investigated. To obtain the required field uniformity of reverberation chamber, Schroeder method Quadratic Residue Diffuser was designed to be applied to chamber. In this paper, 3 different types of diffusers depending on diffuser's periodic direction have been used to investigate field characteristics of each type by using FDTD numerical method. The results show all 3 types of reverberation chambers have below $\pm$3 dB tolerance of field uniformity characteristics, and the symmetrical, type 3, structure show better results among them.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.5
• /
• pp.839-848
• /
• 2000

This paper presents the results of an electromagnetic field analysis for a reverberation chamber that is an alternative method of a shielded anechoic chamber, which is widely used for the analysis and measurement of electromagnetic interference and immunity test. Inside the defined test volume of the rectangular and triangular type, the Schroeder Quadratic Residue Diffuser was employed. FDTD(Finite-Difference Time-Domain) simulation method was applied to produce the field characteristics inside those reverberation chambers. According to the results, field uniformities on the aforementioned two types of reverberation chambers were correlated within $\pm$3dB, and $\pm$4.4dB tolerances, and rectangular type reverberation chamber shows an independent polarization result.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.3
• /
• pp.291-298
• /
• 2016

In this paper, we studied about the radiated emission of EFT(Electrical Fast Transient)/Burst signal, referenced IEC-61000-4-4 of the international EMC standard and its effect on EUT(Equipment Under the Test) when EFT/Burst signal (Conducted noise) induced on a power cable to EUT. Firstly, we set up test sample by the standard and +4 kV standard signal is induced by EFT/Burst signal generator with 1 m length power cable for 1 minute. Consequently, we found not only induced EFT/Burst signal along power line, but also directly radiated emission signal from EFT/Burst signal generator (Radiated emission noise of EFT/Burst). The radiated emission signal of EFT/Burst was 30 dB which is higher than limit of CISPR 22 which is international EMC standard. Moreover, we measured the electric field strength by changing distance from maximum radiated emission point to electric field strength tester. As a result, this electric field strength was 23 V/m which is higher than international EMC standard test level(CISPR 24). Therefore, it was confirmed that the probability of malfunction may be high when radiated emission of EFT/Burst noise exists near the EUT.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.4
• /
• pp.18-24
• /
• 2010

This paper presents the improvement of the field uniformity in a reverberation chamber which can be substitute an anechoic chamber for the electromagnetic interference (EMI) and immunity test. Nowadays, there are many EMI issues due to the increasing use of wireless local area network (LAN), digital multimedia broadcasting (DMB), and mobile internet. With this reason, this paper studied the field characteristics in a reverberation chamber for 2.3 GHz band. In this paper, the finite difference time domain (FDTD) method is used to analyze the field characteristics in a reverberation chamber. To improve the field uniformity in the reverberation chamber, this paper adopted a 2D cubical residue diffuser (CRD) with varying the disposition and number of CRD. For each case, the tolerance and standard deviation of the electric field strength are evaluated. In comparison with the reverberation chamber without any CRD, the reverberation chamber with two CRDs showed improved results; 1.98 dB improvement in standard deviation and 3.6 dB improvement in tolerance.

• Journal of IKEEE
• /
• v.23 no.3
• /
• pp.1088-1091
• /
• 2019

In this paper, a real-time monitoring system for environmental safety by living area is proposed. The proposed system is designed to measure radiation, fine dust and basic living information (temperature) using fixed and mobile measuring equipment, and constitutes a web database that stores data received from the equipment. It also develops web programs for displaying received data on PCs and mobile phones. The results of testing the performance of the system by an authorized testing agency showed that the radiation measurement range was measured in the range of $10{\mu}Sv/h$ to 10mSv/h, which is comparable to the world's highest level, and that the accuracy was measured between ${\pm}6.7$ and ${\pm}8.7$ percent of the measurement uncertainty was measured and normal operation at or below the international standard of ${\pm}15$ percent. In addition, the temperature test was conducted on a section of $-20^{\circ}C$ to $50^{\circ}C$ and normal operation was confirmed in response to the temperature change. Stability of radiated electromagnetic waves was ensured by a suitable judgment. The product's testing in general and high and low temperature environments for about four months after the prototype was made confirmed to be more than five years of durability. The measurement range and accuracy of fine dust sensors are compared with those of companies that measure the air environment, and the performance level is similar through the air quality measurement register.

• Fire Science and Engineering
• /
• v.31 no.3
• /
• pp.63-72
• /
• 2017

This study fabricated a low-voltage 10 circuit distribution board based on the KEMC (Korea Electrical Manufacturers Cooperative) 2102-610 standard and performed a characteristics assessment of the developed 10 circuit distribution board to secure product stability. The developed 10 circuit distribution board is designed to have the characteristics of insulation materials, as well as resistance to corrosion ultraviolet radiation and mechanical impact. The developed distribution board is fabricated to have an appropriate protection class of enclosure, electric shock prevention and protection circuits, switchgear and its components, internal electrical circuits and connectors, external conduct terminal, insulation characteristics, temperature rise test, heat resistance, etc. The developed 10 circuit distribution board consists of a single phase circuit and 3-phase circuits. It is possible to measure in real time the leakage current generated from the load distribution line by installing a sensor module at the load side of each of the branched switchgears. In addition, it is possible to increase a circuit according to the use and purpose of the load and to also manage and check the load in real time. Temperature rise tests were performed on the developed 10 circuit distribution board at 18 places including the inlet connection, main circuit and distribution circuit bus bars and bus bar supports, etc. The highest temperature of $65.3^{\circ}C$ was measured at the R-Phase of the connection of the MCCB power supply for the branch circuit bus bar and a temperature rise of $61.6^{\circ}C$ was measured at the T-Phase of the load side. When applying thermal stress to an MCCB for 6 hours at $180^{\circ}C$ using a heat resistant experimental device, it was found that the actuator lever was transformed and moved in the tripped state.