Time-Domain Pulse Waveform Correction for Pulsed Electric Field Measurement in Microwave Cable with Frequency-Dependent Loss

정재훈,김천호,류지헌 한국전자파학회 2021 Journal of Electromagnetic Engineering and Science Vol.21 No.5

This paper presents a method that corrects pulse waveforms distorted by the frequency-dependent loss of microwave cables in measuring pulsed electric fields (PEFs). Because the distortion resulting from the microwave cable disrupts accurate PEF measurements, the distorted pulse should be corrected for precise PEF effect testing. The proposed correction method is achieved by a transfer function that is determined by ABCD parameters calculated from the scattering parameters of the cable. A 10-m microwave cable is tested to validate the proposed method, where the input pulse is a 2-ns sine pulse of a single cycle. Here, the output pulse, scattering parameters, and cable resistance are measured. These measurement results are used to represent the transfer function in MATLAB for the proposed correction method. The test results show that the corrected pulse obtained from the transfer function has an error of 4.5% in the peak-to-peak voltage and an error of 0.8% in the bipolar pulse width compared to the reference input pulse. The errors of PEF measurement decrease dramatically by using the proposed correction method. Moreover, the correction method is validated for various pulse durations, pulse shapes, and cable types.

Investigation on the effect of slot pulse jet on centrifugal pump performance

Renhui Zhang,Lichen Yun 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.2

To improve centrifugal pump cavitation performance, the slot pulse jet pump is proposed. The slot is designed directly on the impeller shroud near the suction side of the blade leading edge. The slots are alternately blocked by the cambered prominence, which is designed at the impeller front side chamber along the circumferential direction. The leakage flow from the front side chamber flows into the slot alternately, and the pulse jet is formed near the blade inlet. Because of the strong shear, the pulse jet is more efficient than steady jet in terms of energy transmission. Based on the numerical simulation, the hydraulic performances of the slot pulse jet pumps with two different pulse frequencies are compared with the slot steady jet pump. The calculation result shows that with the increase of flow rate, the head and efficiency of the three kinds of pumps are basically the same. The cavitation performance of slot pulse jet pump is better than that of slot steady jet pump, especially for slot pulse jet pump Ⅱ. The distribution of pressure difference acted on the slot appears to be jagged, and the pulse frequency is consistent with shaft frequency or its harmonic frequency. The amplitude of the pressure fluctuation on slot jet pump Ⅱ is much higher than that of the slot pulse jet pump Ⅰ. The vapor volume distribution in the middle span of the impeller for slot pulse jet pump is less than that of slot steady jet pump. So, the pulse jet is an effective way to further improve the cavitation performance of slot steady jet pump, and NPSHr is significantly decreased, especially at design condition.

황소개구리(Lithobates catesbeianus)의 소리 특성 변화에 따른 선호도 연구

곽민경,구교성,장이권 한국양서ㆍ파충류학회 2022 한국양서·파충류학회 학술대회 Vol.2022 No.07

무미 양서류는 번식, 공격, 방어, 등을 위해 울음소리를 주로 이용한다. 그중에서도 대표적 으로 번식 울음은 종특이적으로 진화하는 성질로 개체의 생식 능력, 건강, 크기 등에 대한 정 보를 전달하는 역할을 한다. 침입외래종 황소개구리(Lithobates catesbeianus)는 세계 100대 악성 외래종으로 국내에서도 1950년대 식용 목적으로 처음 도입되어 토종 생태계에 큰 위협 을 끼치고 있다. 황소개구리의 경우 대부분 인위적인 소리를 이용한 연구만 진행됐을 뿐 자 연적인 소리의 소리 특성에 관한 연구는 미비하다. 황소개구리 종에 대한 이해와 번식 울음 을 이용한 새로운 개체 수 조절 방안 제시를 위해 황소개구리의 소리 특성 변화에 따른 선호 도 연구의 필요성이 대두된다. 이에 본 연구는 먼저 국내 서식하는 황소개구리 번식 울음의 특성을 분석하여 이를 바탕으로 번식 울음의 선호도를 검증한 후, 번식 울음소리의 특성 변 화에 따른 선호도 차이를 연구하고자 한다. 연구에 사용된 황소개구리 소리는 2021년 6~8월 충청남도 태안군 일대에서 녹음하여 총 17개체의 55개의 번식 울음, 123개의 croak을 확보하 였다. 수집된 음원의 분석 결과, peak frequency는 219.0±14.5 Hz, croak duration은 744.8±118.8 ms, pulse rate은 81.2±14.9 pulse/s로, 이를 바탕으로 소리 특성이 조정하여 유인 음향이 제작되었다. 1차 실험으로는 유인 음향으로 녹음된 자연적인 소리, 이를 바탕으로 만 들어진 인위적인 소리, 그리고 유인 음향이 없는 경우 세 가지에 대한 현장 비교 실험으로 진행되었다. 총 두 개의 연구 지점에서 실험이 진행되었으며, 총 66개체의 황소개구리가 포획 되었다. χ² 검정 결과, 두 지점에서 모두 유인 음향의 차이보다 지점 내 포획 장치의 위치의 차이가 더 유의미했다. 위 결과를 바탕으로 2차 실험인 소리 특성 변화 실험은 총 세 개의 지점에서 진행되었으며, 한 지점 내 총 세 가지로 조정된 소리 특성을 유인 음향으로 사용하 였다. peak frequency 특성 변화 실험 지점에서는 high frequency (254 Hz), median frequency (218 Hz), low frequency (193 Hz), croak duration 특성 변화 실험 지점에서는 short croak duration (430 ms), median croak duration (750 ms), long croak duration (1100 ms), pulse rate 특성 변화 실험 지점에서는 high pulse rate (136 pulse/s), median pulse rate (80 pulse/s), low pulse rate (50 pulse/s), 총 세 개의 스피커에서 각기 다른 소리 특성 의 음향을 출력하였다. 본 연구의 결과를 통해 황소개구리가 선호하는 번식 울음의 종특이적 인 선호도를 연구하여 이후 생태계 보전 및 종 관리 방안에 대한 새로운 접근을 제시할 수 있다.

Frequency-Modulated Pulse-Amplification Method for Reducing Pulse Shape Distortion

Jihoon Jeong,Seryeyohan Cho,Seungjin Hwang,Tae Jun Yu 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.11

To reduce the laser pulse shape distortion accompanying the amplification process and achieve an intended output pulse shape in the Nd:YAG amplifier chain, we propose a frequency-modulated pulse-amplification method. Assuming carrier-frequency-modulated seed pulses, we numerically simulate the pulse amplification in an Nd:YAG amplifier chain where severe distortion occurs. For the calculation, we develop a modified Frantz-Nodvik equation, which enables two inputs with different carrier frequencies. The simulation results indicate that the temporal contrast of the seed pulse needed to obtain a at output pulse shape is reduced by 16 - 25 dB when frequency modulation is applied.

Frequency Domain Processing Techniques for Pulse Shape Modulated Ultra Wideband Systems

Gordillo, Alex Cartagena,Kohno, Ryuji The Korea Institute of Information and Commucation 2007 Journal of communications and networks Vol.9 No.4

In this paper, two frequency domain signal processing techniques for pulse shape modulation(PSM) ultra wideband(UWB) systems are presented. Firstly, orthogonal detection of UWB PSM Hermite pulses in frequency domain is addressed. It is important because time domain detection by correlation-based receivers is severely degraded by many sources of distortion. Pulse-shape, the information conveying signal characteristic, is deformed by AWGN and shape-destructive addition of multiple paths from the propagation channel. Additionally, because of the short nature of UWB pulses, timing mismatches and synchronism degrade the performance of PSM UWB communication systems. In this paper, frequency domain orthogonality of the Hermite pulses is exploited to propose an alternative detection method, which makes possible efficient detection of PSM in dense multipath channel environments. Secondly, a ranging method employing the Cepstrum algorithm is proposed. This method is partly processed in the frequency domain and can be implemented without additional hardware complexity in the terminal.

직각 펄스를 이용한 Cu 전기도금에서 주파수가 도금층 특성에 미치는 영향

閔炳承,鄭元燮,金麟坤 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.12

Recently, copper electrodeposits having more fine grains are required in the lead frame manufacturing process such as lead bending and wire bonding. These processes could not be achieved with a conventional DC copper electrodeposits, which resulted in a cracking or poor bonding with lead wire. In this study, square pulse current was conducted in order to overcome these problems. Prior to plating, the substrate was electropolished, cleaned in deionized water, activated in 5% H_2SO_4 and then transferred immediately to the plating solution. The deposition thickness was 1 ㎛. Cu was electro-plated onto A42(Fe 58% + Ni 42 alloy) sheet from cyanide-Cu bath by DC and high frequency pulse current. Morphology of plating surface was studied by the scanning probe microscope and optical microscope. The corrosion resistance of each plated specimens were studied by A.C Impedance test. Some of our results are summarized as follows; The cathode current efficiency was increased with increasing pulse frequency. XRD analysis shows that microstructure of high frequency pulse deposits develops into more anisotropic pattern than that of DC deposit. Corrosion resistance increased with increase in pulse frequency.

참개구리(Rana nigromaculata)의 짝짓기 소리의 구조와 변이

박시룡,양서영 한국생태학회 1997 Journal of Ecology and Environment Vol.20 No.6

The structure and variation of the mating call in Rana nigromaculata was studied in a population at Da-rak, Chong-won, Chung-buk (36$\circ$ 37' latitude, 127$\circ$ 21' longitude) in Korea. The mating call consists of 3 to 8 pulse groups divided by clear silent intervals. Each pulse group is also composed of fine pulses. Temperature and body size affect the temporal and spectral characteristics of the mating call. Pulse, pulse group repetition rate and dominant frequency rise with increasing temperature, whereas pulse grouprepetition rate and dominant frequency decrease with increasing body size. A playback experiment was designed to establish the effect of a potential intruder on male calling. During the stimulus periods, resident males markedly decreased the pulse repetition rate, and icreased the rate of pulse groups, dominant frequency, and the number of call groups. This results indicate that this species responds in a graded fashion when interacting with other individuals.

듀티 싸이클 및 펄스 주파수가 TiAlN 코팅막의 미세구조와 기계적 특성에 미치는 영향에 관한 연구

전성용,황주연,Chun, Sung-Yong,Hwang, Ju Yeon 한국세라믹학회 2014 한국세라믹학회지 Vol.51 No.5

This paper presents the effects of pulse plasma parameters such as duty cycle and pulse frequency on the properties of TiAlN coatings deposited by asymmetric bipolar pulsed DC magnetron sputtering systems. The results show that, with decreasing duty cycle and increasing pulse frequency, the coating morphology changes from a columnar structure to a dense structure with finer grains. Pulsed sputtered TiAlN coatings showed higher hardness, higher residual stress, and smaller grain sizes than did DC prepared TiAlN coatings. Moreover, residual stress and nanoindentation hardness of pulsed sputtered TiAlN coatings increased with increasing pulse frequency. Meanwhile, the surface roughness decreased continuously with increasing pulsed DC frequency up to 50 kHz.

환경특성에 따른 집박쥐의 반향정위(Echolocation) 시그널 분석

정철운 ( Chul Un Chung ),한상훈 ( Sang Hoon Han ),김성철 ( Sung Chul Kim ),이정일 ( Chong Il Lee ) 한국환경생태학회 2009 한국환경생태학회지 Vol.23 No.6

환경특성에 따른 집박쥐(Pipistrellus abramus)의 반향정위 변화를 분석하기 위하여 2009년 4월부터 8월까지 경상북도 경주시 천북면 일원의 주간 휴식장소를 대상으로 실시하였다. 환경특성 유형은 일몰 후 출현순간, 출현 후 이동, 논 경작지, 산림 가장자리, 개방공간, 주택단지 등 6개 유형으로 구분하여 비교하였다. 분석결과 환경특성에 따른 차이 및 서식지간 이동과 먹이포획을 위한 비행 사이에서는 차이가 있는 것으로 나타났다. 외부 환경으로의 출현 순간에서는 짧은 시간의 FM 시그널만 확인되었으며, 개방 공간에서는 긴 시간의 CF 시그널 형태의 음을 이용하는 것으로 나타났다. 그 외 환경특성에서는 펄스의 형태적인 차이는 있었지만 FM과 CF 시그널을 혼합하여 이용하는 것으로 확인되었다. 먹이포획을 위한 비행과 서식지간 이동을 위한 비행에서는 펄스의 지속시간을 제외한 펄스 간격, 최고 진동수, 개시부와 종결부 진동수에서는 두 가지 비행패턴 사이에서 유의적인 차이가 확인되었다. 출현순간을 제외하고 서식지간 이동을 위한 비행시에는 곤충의 반향을 감지하여 곤충의 탐색에 적합한 협대역의 FM 시그널과 긴 펄스 지속시간을 가지는 형태를 보였으며, 먹이포획을 위한 비행에서는 폭넓은 탐색과 정확한 위치파악을 위한 광대역의 FM 시그널과 짧은 시간의 펄스 지속시간을 갖는 것으로 확인되었다. This study was conducted to analyze the changes in the echolocation of Pipistrellus abramus according to environmental characteristics. The survey was conducted in the day-roosting site of P. abramus located in Gyeongju City (North Gyeongsang Province) from April to August, 2009. The environmental characteristics during the research were classified in six categories: the emergence time after sunset moving time from day roost to feeding areas; rice fields; forest edges; open spaces; and residential areas. Analysis results showed that there are differences in environmental characteristics and also differences between the moving time to the habitat and the moving time to capture preys. At the emergence time from day roost, Pipistrellus abramus used a FM signal with a short pulse-duration. In open spaces, however, they used a CF signal with a long pulse-duration. In different environmental situations, they used both FM and CF signals, although the types of pulse which they used were different. Except pulse-duration, there were significant differences in pulse-interval, peak-frequency, starting-frequency and ending-frequency between the movement among habitats and the movement to capture preys. Except the emergence time from day-roost, they showed a narrow band FM signal and a long pulse-duration that are suitable to search for insects by sensing echoes of insects when they moved among their habitats. When they were out to capture their preys, they showed a broad band FM signal and a short pulse-duration which enabled them to widely search and accurately locate their preys.

Frequency Synchronization of Three-Phase Grid-Connected Inverters Controlled as Current Supplies

Fu, Zhenbin,Feng, Zhihua,Chen, Xi,Zheng, Xinxin,Yin, Jing The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

In a three-phase system, three-phase AC signals can be translated into two-phase DC signals through a coordinate transformation. Thus, the PI regulator can realize a zero steady-state error for the DC signals. In the control of a three-phase grid-connected inverter, the phase angle of grid is normally detected by a phase-locked loop (PLL) and takes part in a coordinate transformation. A novel control strategy for a three-phase grid-connected inverter with a frequency-locked loop (FLL) based on coordinate transformation is proposed in this paper. The inverter is controlled as a current supply. The grid angle, which takes part in the coordinate transformation, is replaced by a periodic linear changing angle from $-{\pi}$ to ${\pi}$. The changing angle has the same frequency but a different phase than the grid angle. The frequency of the changing angle tracks the grid frequency by the negative feedback of the reactive power, which forms a FLL. The control strategy applies to non-ideal grids and it is a lot simpler than the control strategies with a PLL that are applied to non-ideal grids. The structure of the FLL is established. The principle and advantages of the proposed control strategy are discussed. The theoretical analysis is confirmed by experimental results.