This paper presents an examination of classical scattering models for radar cross sections deciduous leaves, such as the generalised Rayleigh-Gans (GRG) model and physical optics (PO) model. The PO employs resistive sheet approximation in this study. validity regions analytical microwave from leaves are investigated by comparison with precise numerical results method moment. It was found that GRG extend their estimating amplitudes thickness a lossy dielectric disk decreases. can be used...

The root mean square (rms) height s and autocorrelation length l are commonly used as the surface roughness input parameters to scattering models. Whereas it is well known that of a natural soil underestimated with short profile, not clear how much affect backscattering coefficients for various incidence angles polarizations. In this paper, simulated measured profiles computed using integral equation method analyzed answer question. A 4000lmacr-long rough generated numerically, where lmacr...

We propose a novel contactless ultrasonic method for monitoring the hardening behavior of cementitious materials. The goal this is to obtain high-quality data compare unique process between rapid setting cement (RSC) and ordinary Portland (OPC) mortars without physical coupling surface specimens. To monitor materials, conventional approaches use contact or embedded-type sensors, which limit field application. Our solution measure leaky Rayleigh waves at interface air allows estimation state...

In this study, we present a method to estimate the depth of near-surface shallow delamination in concrete using noncontact micro-electromechanical system (MEMS) ultrasonic sensor array and an optimization-based data processing approach. The proposed approach updates bulk wave velocities tested element by solving optimization problem reference scanning collected from full-depth region. Subsequently, is estimated separate problem. Numerical simulations laboratory experiments were conducted...

The compressive strength of early aged concrete was estimated using obtained shear modulus derived by leaky Rayleigh wave velocity. To obtain without interference from other factors, a unique testing configuration implemented contactless ultrasonic method, which offers the advantages being non-invasive and non-destructive. A parametric study conducted to examine influence material properties air temperature on development velocity in joint half-space. results indicate that is primary factor...

Soil moisture has been considered a key variable in governing the terrestrial ecosystem. However, it is challenging to preserve indigenous soil characteristics using conventional monitoring methods that require maximum contacts. To overcome this issue, we developed non-destructive method of evaluating contactless ultrasonic system. This system was designed measure leaky Rayleigh waves at air-soil joint-half space. The influences on were explored under sand, silt, and clay controlled...

Developments in air-coupled testing hardware impact-echo (IE) tests have enabled new levels of scanning for concrete bridge decks. A tooth gear IE system has been developed using gears as impactors and microelectromechanical systems (MEMS). Since the moves generates impacts itself, this collects a large amount test data across field continuously. The contact duration two different is evaluated mechanism compared to conventional steel ball impactor by high-speed camera. measurements were...

A recently developed contactless ultrasonic testing scheme is applied to define the optimal saw-cutting time for concrete pavement. The system improved using wireless data transfer field applications, and signal processing analysis are proposed evaluate modulus of elasticity early-age concrete. Numerical simulation leaky Rayleigh wave in joint-half space including air performed demonstrate procedure. hardware algorithms experimentally validated with a comparison procedures. In addition,...

본 논문에서는 주파수 및 토양의 수분 함유량 변화에 따라 지뢰 탐지용 지표투과레이더의 수신신호를 분석하였다. 한국 표준 토양인 식양토를 기준으로 유전율, 도전율 전자파 감쇄 손실을 계산하였고, FDTD를 이용하여 다양한 주파수에 따른 탐지 영상을 생성하였다. 레이더의 표적 신호 대 클러터 비(SCR) 수신 전력을 분석하였으며, 가변 채널 방식이 토양 조건에서 지표 투과레이더에 적합함을 보였다. Return signals of a ground penetrating radar(GPR) for mine detection at various frequencies and soil moisture contents are analyzed in this paper. We first compute the dielectric constant, conductivity attenuation loss based on clay loam which is Korea standard soil. The...

The backscattering coefficients of a bare soil surface were measured using an L-band polarimetric scatterometer, which used to verify the validities scattering models and inversion algorithms. moisture contents roughness parameters (the RMS height correlation length) also from surface. with these compared coefficients. retrieved coefficients, parameters. This paper shows that agree measurements, results.

This paper presents an inversion algorithm for retrieving the volumetric soil moisture content and surface rms height from measured backscattering coefficients of a vegetation canopy. The polarimetric tall-grass field are using scatterometer at L-band. water-cloud scattering model canopy obtained by data-fitting with measurements. Then, roughness retrieved genetic algorithm. tall-grass-covered compared in-situ ground truth data, good agreements between those values shown.

We propose a micromachined 2x2 optical switch with variable attenuation. The proposed features expandability and integration utilizing four 45° micromirrors driven by electrostatic comb actuators. These can move independently to reflect and/or partially block the signal. In order reduce insertion loss caused long path length, module employed anti-reflection coated lensed fibers. Two pairs of fibers were aligned in each single trench at both sides for cost-effective packaging. device was...