자동점적관수에 의한 토성별 수분함량 및 장력 변화특성 비교 연구

김학진,안성욱,한경화,최진용,정선옥,노미영,허승오 (사) 한국생물환경조절학회 2013 생물환경조절학회지 Vol.22 No.4

Maintenance of adequate soil tension or content during the period of crop growth is necessary to support optimum plant growth and yields. A better understanding of soil tension and content for precision irrigation would allow optimal soil water condition to crops and minimize the adverse effects of water stress on crop growth and development. This research reports on a comparison of soil water tension and content variations in differently textured soils over time under drip irrigation using two different water management methods, i.e. pulse time and required water irrigation methods. The pulse time-based irrigation was performed by turning the solenoid valve on and off for preset times to allow the wetting front to disperse in root zone before additional water was applied. The required water estimation method was a new water control logic designed by Rural Development Administration that applies the amount of water required based on a conversion of the measured water tension into water content. The use of the pulse time irrigation method under drip irrigation at a high tension of −20 kPa and high temperatures over 30oC was not successful at maintaining moisture tensions within an appropriate range of 5 kPa because the preset irrigation times used for water control could not compensate for the change in evapotranspiration during day and night. The response time and pattern of water contents for all of the tested soils measured with capacitance-based sensor probes were faster and more direct than those of water tensions measured with porous and ceramic cup-based tensiometers when water was applied, indicating water content would be a better control variable for automatic irrigation. The required water estimation-based irrigation method provided relatively stable control of moisture tension,even though somewhat lower tension values were obtained as compared to the target tension of −20 kPa, indicating that growers could expect to be effective in controlling low tensions ranging from −10 to −20 kPa with the required water estimation system. 본 연구에서는 토성에 따른 물의 이용효율을 높이면서재배 작물의 생산성을 최대화하기 위한 효율적인 자동관개 로직을 개발하고자, 수분장력값을 관수 개시점으로하여 물 공급 유지와 멈춤을 간헐적으로 수행하는 펄스형 관개방식과 측정한 수분장력값을 이용하여 토양수분량을 예측해 재배작물에 적합한 물량을 추가 투입하는필요물량계산 관수방식을 적용하여 토성이 다른 실험베드에서 2년간 토마토 작물을 재배하면서 토양수분 함량과 장력의 변화를 측정비교하였다. 물공급 30초와 멈춤30분 및 15분 조건을 이용한 펄스형 관수방식과 필요물량계산 방식에서 얻어진 수분장력값은 목표한 −20kPa 조건에 비해 각각 −42~−8kPa, −20~−10kPa로 나타나 필요물량 계산방식이 균일한 수분장력을 유지하는 측면에서는 유리하였으나 토양수분상태는 상대적으로 습하였다. 공시 토성 모두에서 수분함량은 수분장력에 비해 시간반응이 빠르면서 물공급에 따라 비례적으로 증가하는 경향이 뚜렷하였다. 수분변화 값은 펄스형 관수와 필요물량계산 관수방식의 경우 사양토 기준으로 각각 17~24%, 19~31%로서 펄스형 관수방식이 수분변화 값이 작으면서 시간에 따라 안정적인 값을 유지한 것으로 나타났는데 이는 물공급에 따른 수분함량의 시간변화가 수분장력에 비해 뚜렷하게 빠름과 관계가 있는 것으로 판단하였다. 이러한 결과로부터 펄스형 관수방식은 수분함량값을 이용하여 수분을 조절하는 것이 유리함을 의미한다.

고전적인 4차 룬게-쿠타 방법을 이용한 피킹 스위치 수치 해석

노영수(Young-Su Roh) 대한전기학회 2020 전기학회논문지 Vol.69 No.2

A peaking switch plays a crucial role reducing the rise time of the high voltage output pulse from the Blumlein pulse forming line. An equivalent circuit in which the peaking switch is modelled as a series combination of inductor and resistor in parallel with a capacitor, is used to generate the output voltage waveform and to numerically analyze how much the rise time of the output voltage pulse changes at various conditions under the assumption that the input voltage is a Gaussian pulse whose rise time is ∼5 ns. Simultaneous ordinary differential equations for variables such as arc current, resistance, and output voltage, are derived from the equivalent circuit, and solved by the classical forth-order Runge-Kutta method. Simulation results show that the rise time can be extremely reduced up to 425 ps at a pressure of 17 atm.

STA/LTA 알고리즘에 기반한 콘크리트의 초음파 도착시간 자동 추출 연구

이승현,이주원,최하진,강현구 한국콘크리트학회 2024 콘크리트학회논문집 Vol.36 No.2

본 연구에서는 콘크리트에서 초음파 신호의 도착시간을 결정하는 특정 시간구간을 랜덤하게 적용한 STA/LTA 알고리즘을 제안하고 시뮬레이션 및 실험 데이터에 대해 상세 해석을 진행하여 성능을 검증하였다. Comsol Multiphysics 프로그램과 실제 UPV 장비를 사용하여 무근콘크리트와 철근콘크리트 모델에서 직접법과 간접법을 통해 측정된 초음파 신호를 기반으로 AIC, Hinkley Criterion, Amplitude Threshold-picker 알고리즘과 특정 시간구간을 랜덤하게 적용한 STA/LTA 알고리즘의 편차값을 비교하여 성능 평가를 실시하였다. 이후 무근콘크리트와 철근콘크리트에서의 결과 비교를 통해 재료의 복합성이 신호에 미치는 영향을 평가하였으며, 직접법과 간접법 사용의 비교를 통해 간접법이 초음파 신호에 미치는 영향에 대해 평가를 실시하였다. 그 결과, 특정 시간구간을 랜덤하게 적용한 STA/LTA 알고리즘이 타 알고리즘에 비해 더 우수한 성능을 보였으며, 실험보다 시뮬레이션에서, 철근콘크리트보다 무근콘크리트에서, 간접법보다 직접법에서 더 낮은 편차값을 가짐을 확인하였다. In this study, the STA/LTA algorithm with a specific time interval applied randomly for determining signal arrival time in concrete was developed and validated. The performance evaluation included comparing deviation values of the AIC (akaike information criterion), Hinkley Criterion, and Amplitude Threshold-picker algorithms, as well as the STA/LTA algorithm with a specific time interval applied randomly. This comparison relied on ultrasonic signals measured through both direct and indirect methods in models of non-reinforced and reinforced concrete. The signals were measured in simulations and experiments using the Comsol Multiphysics software along with actual UPV equipment. Following this, a comparison of the results between non-reinforced and reinforced concrete was conducted to assess the impact of material heterogeneity on the signals. Additionally, a comparison between the direct and indirect methods was performed to evaluate the effect of the indirect method on ultrasonic signals. As a result, the STA/LTA algorithm with a specific time interval applied randomly setting exhibited superior performance compared to other algorithms. It had lower bias values, especially in simulations as opposed to experiments, in non-reinforced concrete compared to reinforced concrete, and with the direct method rather than the indirect method.

타코펄스 불균일성 보정이 포함된 펄스간 시간 측정방법

손준원(Jun-Won Son) 한국항공우주학회 2022 韓國航空宇宙學會誌 Vol.50 No.4

펄스간 시간측정방법은 이상적인 조건에서는 정확한 반작용휠 속도를 측정할 수 있지만, 실제로는 타코펄스 불균일성 때문에 측정속도 오차가 존재한다. 본 연구에서는 불균일성을 극복하는 방법을 살펴본다. 우선 휠을 특정한 속도로 회전시켜서 타코펄스 불균일성을 측정하는 방법을 소개한다. 이렇게 획득된 불균일성 정보를 이용하여 실시간으로 측정오차를 보정하는 방법을 제안한다. 해당 방법은 펄스간 시간 측정방법의 카운트와 사전 측정된 불균일 정보로부터 속도 후보군을 계산하고, 이중에서 실제속도와 가장 가까운 값을 선택한다. 시뮬레이션을 통해서 제안된 방법이 타코펄스 불균일성을 극복하고 정확한 속도를 측정하며 빠른 휠속도 제어도 가능함을 보인다. In ideal configuration, elapsed-time method can measure the exact reaction wheel speed. But in real configuration, the speed measurement error exists due to tacho pulse non-uniformity. In this research, we study the method which overcome the non-uniformity effects. First, we introduce the method which spin the wheel at the specific speed and measure the non-uniformity. Then, we propose the real-time measurement error correction method which uses the obtained non-uniformity information. This method calculate the speed candidates from the elapsed-time method’s counts and non-uniformity information, and choose the closest speed to the real speed. Through simulation, we show that proposed method measure the exact speed regardless of non-uniformity, and fast wheel speed control is possible.

Advances for the time-dependent Monte Carlo neutron transport analysis in McCARD

Sang Hoon Jang,Hyung Jin Shim Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.7

For an accurate and efficient time-dependent Monte Carlo (TDMC) neutron transport analysis, several advanced methods are newly developed and implemented in the Seoul National University Monte Carlo code, McCARD. For an efficient control of the neutron population, a dynamic weight window method is devised to adjust the weight bounds of the implicit capture in the time bin-by-bin TDMC simulations. A moving geometry module is developed to model a continuous insertion or withdrawal of a control rod. Especially, the history-based batch method for the TDMC calculations is developed to predict the unbiased variance of a bin-wise mean estimate. The developed methods are verified for three-dimensional problems in the C5G7-TD benchmark, showing good agreements with results from a deterministic neutron transport analysis code, nTRACER, within the statistical uncertainty bounds. In addition, the TDMC analysis capability implemented in McCARD is demonstrated to search the optimum detector positions for the pulsed-neutron-source experiments in the Kyoto University Critical Assembly and AGN201K.

Interactions of a short-pulsed plane acoustic wave with complex rigid objects: a numerical study

Sangmo Kang 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9

In this paper, we numerically study interactions of a short-pulsed plane acoustic wave with complex rigid objects by solving the linearized Euler equations. For the study, our numerical approach implements an immersed boundary method to satisfy the no-penetration condition on the surface of rigid objects, together with a fully-explicit staggered-grid finitedifference time-domain method having perfectly matched layers. First, we validate our approach for acoustic wave scattering by a circular cylinder, a well-known benchmark problem. Subsequently, we extend our simulations to two representative problems, namely interactions with a circular cylinder and a plano-concave lens which are of paramount interest in terms of acoustic force and acoustic focusing, respectively. Our simulations allow us to better understand the main mechanism of propagation, reflection, and scattering of acoustic waves as a result of interaction with rigid objects. In addition, the effects of pulse width on the interactions are closely investigated.

SRM의 DC linke 전압리플을 고려한 단일 펄스 구동 방식의 특성 해석

李聖九(Sung-Gu Lee),鄭大成(Dae-Sung Jung),李柱(Ju Lee) 대한전기학회 2008 전기학회논문지 Vol.57 No.11

This paper deals the characteristic analysis of Switched Reluctance Motor(SRM) driven by single-pulse mode considering dc link voltage ripple. Two dimensional time-stepped Finite Element Method(FEM) is used to analyze the characteristic of SRM driven by single-pulse mode with dc link voltage ripple. The analysis results is verified by experimental test.

펄스 수축방식 기반의 지연버퍼를 이용한온-칩 디지털 온도센서

윤승찬,김태운,최호용 한국전기전자학회 2019 전기전자학회논문지 Vol.23 No.2

This paper proposes a CMOS temperature sensor using inverter delay chains of the same size based on the pulseshrinking method. A temperature-pulse converter (TPC) uses two different temperature delay lines with inverter chainsto generate a pulse in proportion to temperature, and a time-digital converter (TDC) shrinks the pulse using inverterchains of the same size to convert pulse width into a digital value to be insensitive to process changes. The chip wasimplemented with a 0.49 ㎛ x 0.23 ㎛ area using a 0.35 ㎛ CMOS process with a supply voltage of 3.3V. Themeasurement results show a resolution of 0.24 °C/bit for 9-bit data for a temperature sensor range of 0 °C to 100 °C. 본 논문은 동일 크기의 인버터 체인을 가진 지연 버퍼를 사용한 펄스 수축방식에 기반된 CMOS 온도 센서를 제안한다. 온도 센서는 2 개의 서로 다른 온도 지연 라인을 가진 온도에 비례하여 펄스를 생성하는 온도-펄스 변환기( TPC)와 공정 변화에 민감하지 않도록 동일 크기를 가진 인버터 체인을 사용하여 펄스를 수축하여 디지털 값으로 변환하는 시간-디지털 변환기(TDC)로 구성된다. 칩은 공급 전압이 3.3 V인 0.35 ㎛ CMOS 공정을 이용하여 0.49 ㎛ x 0.23 ㎛의 면적으로 구현되었다. 측정 결과 0 °C~100 °C의 온도 센서 범위에 분해능은 9-비트 데이터에서 0.24°C/bit를 가진다.

Wavelet변환을 이용한 초음파 잡음신호의 제거에 관한 연구

박익근,이정순 한국공작기계학회 1999 한국생산제조학회지 Vol.8 No.1

Recently, advanced signal analysis which is called "Time-Frequency Analysis" has been developed. Wavelet and Wigner Distribution are used to the method. Wavelet transform(WT) is applied to time-frequency analysis of waveforms obtained by an ultrasonic pulse-echo technique. The Gabor function is adopted as the analyzing wavelet. Wavelet analysis method is an attractive technique for evaluation of material characterization evaluation. In this paper, the feasibility of suppression of ultrasonic background noise signal using WT has been presented. These results suggest that ultrasonic background noise signal can be suppressed and enhanced even for SNR of 20.8 dB. This property of the WT is extremely useful for the detecting flaw echos embedded in background noise.

Seismic Vulnerability Analysis of Multi-main-span High Pier Continuous Rigid-frame Bridge in Terms of Cloud Method

Jingang Zhao,Hongyu Jia,Yulin Zhan 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.6

Due to the complex canyon topography in southwestern regions of China, several multi-main-span high pier continuous rigid-frame bridges (MHPCRFBs) are built to meet the special terrain. Owing to the great effect of high-order modes, the seismic responses of MHPCRFBs are more complicated than the conventional signal main span continuous rigid-frame bridges. However, there has been very limited researches focus on the seismic vulnerability of MHPCRFBs. This study selects a practical five-span (three main span) high pier continuous rigid-frame bridge as a study object to investigate the seismic vulnerability of MHPCRFBs under near-field pulse-like seismic wave excitation. And a finite element model of the example bridge is built by OpenSees incorporating the influence of abutment, and simultaneously100 near-field pulse-like seismic waves are chosen to research their effect on the seismic vulnerability of the MHPCRFB. The dynamic nonlinear time-history analyses are carried out to record the peak demand values of the example bridge under three seismic excitation calculation cases (longitudinal earthquake, biaxial earthquake, and triaxial earthquake). Thirty-three intensity measures are compared with respect to two statistical parameters including correlation efficient and root mean square error, the peak ground velocity (PGV) turns out to be the optimal intensity measure for seismic vulnerability analysis of MHPCRFB. Subsequently, by using the analysis procedures of the cloud method, the seismic vulnerability curves of MHPCRFB are developed and compared. The results of this study show that the bottom and top areas of the high piers are more fragile at the slight and moderate damage stages along longitudinal direction, and only the bottom areas are prone to damage along transverse direction. And the seismic wave excitation directions have an obvious influence on the seismic damage probability of the MHPCRFB. In addition, the zone with larger failure probabilities of the lower pier is significantly longer than the higher pier. The obtained results provide helpful reference for the seismic-resistant design and consolidation of MHPCRFBs, shed light on the lower pier of MHPCRFBs should be paid high concern to the anti-seismic design.