Suitable Incidence Angle Research Articles

Design of a New-Type Electro-Optical Sensor Based on the Total-Internal Reflection Theory in Heterodyne Interferometry

In this paper, a new-type electro-optical sensor based on the total-internal reflections theory in heterodyne interferometry is proposed. The sensor is designed as a semi-circle shape. It is made of BK7 glass with the refractive index of 1.51509. And the end surface of the sensor is designed as a micro-mirror. The phase difference between s-and p-polarizations at the output of the optical fiber sensor can be obtained when a heterodyne optical source is launched into the electro-optical sensor at a suitable incident angle. By numerical calculation, the resolution of the system by using the intensity method can reach refractive index unit (RIU) in the measurement range of. The electro-optical sensor could be valuable for chemical, biological and biochemical sensing. It is with some advantages, such as, high resolution and stability, high sensitivity and real-time measurement.

Theoretical modeling of low-attenuation lamb wave modes generation in three-layer adhesive joints using angle beam transducer

IN THIS PAPER, AT FIRST THE ATTENUATION OF LAMB WAVES IN THREE-LAYER ADHESIVE JOINTS, INCLUDING TWO ELASTIC PLATES BONDED TOGETHER BY A VISCOELASTIC ADHESIVE LAYER, IS INVESTIGATED USING GLOBAL MATRIX METHOD AND THEN SUITABLE INCIDENCE ANGLE IS THEORETICALLY CALCULATED TO GENERATE LOW-ATTENUATION LAMB WAVES USING ANGLE BEAM TRANSDUCER. THEORETICAL BOUNDARY VALUE PROBLEM IN THREE-LAYER ADHESIVE JOINTS WITH PERFECT BOND AND TRACTION-FREE BOUNDARY CONDITIONS ON THEIR OUTER SURFACES IS SOLVED TO FIND A COMBINATION OF FREQUENCIES AND MODES WITH LOWEST ATTENUATION. CHARACTERISTIC EQUATION IS DERIVED BY APPLYING CONTINUITY AND BOUNDARY CONDITIONS IN THREE-LAYER JOINTS USING GLOBAL MATRIX METHOD. PHASE VELOCITY DISPERSION CURVES AND ATTENUATION INTENSITY PLOT IN HIGH AND LOW FREQUENCIES ARE OBTAINED WITH NUMERICAL SOLUTION OF THIS EQUATION BY A COMPUTER CODE FOR A THREE-LAYER JOINT, INCLUDING AN ALUMINUM REPAIR PATCH BONDED TO THE AIRCRAFT ALUMINUM SKIN BY A LAYER OF VISCOELASTIC EPOXY ADHESIVE. TO VALIDATE THE NUMERICAL SOLUTION RESULTS OF CHARACTERISTIC EQUATION, WAVE STRUCTURE CURVES ARE PLOTTED FOR A SPECIAL MODE IN TWO DIFFERENT FREQUENCIES IN THE ADHESIVE JOINT. ALSO, TRANSDUCER INCIDENCE ANGLE IS CALCULATED IN TERMS OF FREQUENCY FOR DIFFERENT MODES USING THEORETICAL METHOD TO GENERATE LAMB WAVE MODES WITH LOW ATTENUATION LEVEL BY ANGLE BEAM TRANSDUCER. THESE MODES ARE RECOGNIZABLE BY TRANSDUCERS IN INSPECTIONS WITH LAMB WAVES BECAUSE OF LOW ATTENUATION LEVEL.

Bistatic measurements for the estimation of rice crop variables using artificial neural network

An outdoor rice crop bed (4×4m2) was specially prepared for a bistatic ground based scatterometer measurements at various growth stages of rice crop from transplanting to ripening stage at like polarizations (HH- and VV-) in the angular range of 20–70° at the steps of 5°. The computed scattering coefficients showed increasing behavior from transplanting to reproductive stage and started decreasing at ripening stage. The angular dependency of scattering coefficient was found to decrease initially with age and became negligible near the ripening stage of rice crop. The polynomial regression analysis showed higher values of coefficient of determination (R2) at 30° incidence angle for both like polarizations. Two types of feed forward back propagation neural network (FFBPNN) models were developed for the estimation of rice crop growth variables namely FFBPANN-I and FFBPANN-II model. The FFBPANN-I model was developed with one input neuron (HH- or VV-polarized scattering coefficient) and one output neuron (biomass or leaf area index or plant height or chlorophyll content) while the FFBPANN-II model was developed with two input neurons (HH- and VV-polarized scattering coefficient) and four output neurons (biomass, leaf area index, plant height and chlorophyll content). Performances of both the types of FFBPANN models were found good for the estimation of rice crop variables. However, the performance of FFBPANN-II model was found better in comparison to the FFBPANN-I model at suitable incidence angle 30°.

The Response of a Broadband Light Source for an Optical Fiber Sensor Based on Surface Plasmon Resonance Technology

In this paper, the study on response of a broadband light source for an optical fiber sensor (OFS) based on surface plasmon resonance (SPR) technology is presented. The OFS is made of a multimode optical fiber which cladding was removed and coated with two layers of metal films. As a broadband light source is launched into the OFS at a suitable incident angle, we can obtain the intensity at the output of the optical fiber sensor. With the structure, the refractive index detection can be made by the SPR spectra that are obtained by an Optical Spectrum Analyzer (OSA). The OFS could be valuable for chemical, biological and biochemical sensing, etc. It has some advantages, such as, high resolution and stability, small size and real-time measurement.

Design of a Reflective Type Optical Fiber Sensor Based on Multiple Total-Internal Reflections Theory in Heterodyne Interferometry

In this paper, a reflective type optical fiber sensor (OFS) based on multiple total internal reflections in heterodyne interferometry is proposed. The sensor is made of a multimode optical fiber which cladding was removed and polished as a top shape. And the end surface of the sensor is designed as a micro-mirror. As a heterodyne optical source is launched into the optical fiber sensor at a suitable incident angle, we can obtain the phase difference between s-and p-polarizations at the output of the optical fiber sensor. By numerical simulation, it is clear that the resolution of the system by using the intensity method can reach refractive index unit (RIU) at least in the measurement range of. The OFS could be valuable for chemical, biological and biochemical sensing. It has some merits, such as, high resolution and stability, small size and real-time measurement.

Estimation of kidney bean crop variables using ground-based scatterometer data at 9.89 GHz

Crop variables were estimated using ground-based multi-temporal, multi-angle and co-polarized scatterometer X-band data at 9.89 GHz. An outdoor crop-bed was prepared to observe the scatterometer response at VV and HH polarizations in the incidence angle range from 20° to 70°. Soil moisture (SM) and crop variables, including leaf area index (LAI), leaf water area index (LWAI) and plant height (PH), of a kidney bean crop at different stages of growth were measured. The aim of this study was to estimate the crop variables and to determine how the variables interact with microwaves. We found that LAI correlated better than LWAI with the microwave backscattering coefficient σ0 (at 9.89 GHz) and the correlation with PH was lower, at the most suitable incidence angle of 40°. The value of σ0 increased with an increase in LAI at both polarizations. The crop variables retrieved by inversion of the cloud model and a polarization-based model were compared with another model based on least squares optimization. The results are promising for the estimation of crop variables, particularly LAI.

THE EFFECT OF SOIL TEXTURE IN SOIL MOISTURE RETRIEVAL FOR SPECULAR SCATTERING AT C-BAND

The objective of this paper is to analyze the behavior of specular scattering for difierent soil texture flelds at various soil moisture (mv) and analyze the data to retrieve the soil moisture with minimizing the efiect of the soil texture. To study the soil texture efiect on specular scattering 10 difierent soil flelds were prepared on the basis of change in soil constituents (i.e., percentage of sand, silt and clay) and experiments were performed in both like polarizations (i.e., HH-polarization and V V -polarization) at various incidence angles (i.e., varying incidence angle from 25 - to 70 - in step of 5 - ). Angular response of specular scattering coe-cients (ae - in HH-polarization and ae - vv in V V -polarization) were analyzed for difierent soil texture flelds with varying soil moisture content whereas the surface roughness condition for all the observations were kept constant. The changes in specular scattering coe-cient values were observed with the change in soil texture flelds with moisture for both like polarizations. Further, copolarization ratio (P = ae - /ae -) study was performed and it was observed that the dependency of copolarization ratio for change in soil texture fleld at constant soil moisture is less prominent whereas the value of copolarization ratio is varying with variation of moisture content. This emphasizes that copolarization ratio may be minimizing the efiect of soil texture while observing the soil moisture on specular direction. Regression analysis is carried out to select the best suitable incidence angle for observing the moisture and texture at C-band in specular direction and 60 - incidence angle was found the best suitable incidence angle. An empirical relationship between P and mv was developed for the retrieval of mv and the obtained relationship gives a good agreement with observed mv. In addition, mv was also retrieved

Generation of a high-quality partially coherent dark hollow beam with a multimode fiber

We report the experimental generation of a high-quality partially coherent dark hollow beam (DHB) by coupling a partially coherent beam into a multimode fiber (MMF) with a suitable incidence angle. The interference experiment of the generated partially coherent DHB passing through double slits is demonstrated. It is found that the coupling efficiency of the MMF, the quality, and the coherence of the generated partially coherent DHB are closely controlled by the coherence of the input beam.

A study of ultrasonic propagation for ultrasonic flow rate measurement

For the purpose of accurate flow measurement, an automatic three-dimensional (3D) sound field measurement system has been developed, and an experimental study has been conducted on ultrasonic properties. By using this system, ultrasonic sound pressure distributions and radiation angles in water have been measured. According to Snell’s law, the ultrasonic transmission properties can be obtained on the basis of incidence angle, acoustic impedance, basic frequency of ultrasound, and material and thickness of the metallic plate. However, this law cannot be applied to certain cases where an ultrasonic incident wave passes through a metallic plate and turns into a longitudinal wave, a shear wave and a Lamb wave. Consequently, the ultrasonic propagation paths have been investigated experimentally at various angles of incidence. From the experiments, it was confirmed that the ultrasonic beam paths change with incidence angles. Hence, the most suitable incidence angle has been determined from the result of measurements. Velocity measurements using an ultrasonic velocity profiler were made at various incidence angles. The accuracy of measuring flow rates changed with the incidence angles. The optimal incidence angle determined from 3D field measurements was found to yield the most accurate flow rates.

Polarization Ratio Approach to Retrieve the Bare Surface Roughness at X-Band

An observation has been carried out at different incidence angle by X-band scatterometer to retrieve the surface roughness when moisture was kept constant. Polarization ratio approach has been proposed to retrieve the surface roughness at constant moisture. A co-polarized (Horizontal-Horizontal; HH and Vertical-Vertical; VV) ratio (p=σ0HH/ σ0VV) ratio based model is proposed to retrieve the bare surface roughness. The regression analyses have been carried out to pre-decide the suitable incidence angle to observe the surface roughness (0.5 to 4.18 cm) at X-band. It was found that the suitable incidence angle to observe surface roughness (0.5 to 4.18 cm) at X-band with co-polarization ratio is 35° and least square optimization (LSE) method has been applied to retrieve the surface roughness when moisture is kept constant. The retrieved values of rms heights are in good agreement (root mean square error, RMSE-1.22) with observed values of rms heights. The significance of the results has been tested by F-ratio test and it was found quite significant. This type of results are helpful to use the microwave techniques to assess the surface roughness by the air-borne or space borne sensor and propose the suitable angle of incidence to observe the surface roughness at X-band.

21416 超音波流速分布式流量計測法に関する基礎研究 : 金属平板透過における超音波伝播特性(せん断流の計測,OS.4 流れの計測と制御)

The purpose of this study is to measure flow rates with high accuracy by using ultrasound. Experimental study has been conducted on ultrasonic properties which are necessary for the measurement. An automatic measurement system which can measure spatial-temporal sound pressure distributions has been developed. According to Snell's law, the ultrasonic propagation paths can be obtained on the basis of incidence angle, acoustic impedance, basic frequency of ultrasound, and material and thickness of metallic plate. However this law can't be applied to certain cases where an ultrasonic incident wave passes through a metallic plate and turns into a longitudinal wave, a shear wave and a Lamb wave. Consequently the ultrasonic propagation paths have been investigated experimentally at various angles of incidence and plate thickness. The most suitable incidence angle has been determined from the result of measurements, and flow rates will be measured.

A remote sensing assessment of pest infestation on sorghum

The damage caused by the pest to crop is well known. The major aspects of remote sensing are timely estimates of agriculture crop yield, prediction of pest. Therefore, in this paper, an attempt has been made to investigate the utility and potential application of microwave remote sensing for detection of pest infestation within sorghum field. The studies were made on crop sorghum (Meethi Sudan) that is a forage variety and the pest observed was a species of grasshopper. The beds of crop sorghum were specially prepared for pests as well as microwave scattering measurements. In first phase of study, dependence of occurrence of pests on sorghum plant parameters (i.e., crop covered moist soil (SM), plant height (PH), leaf area index (LAI), percentage biomass (BIO), total chlorophyll (TC)) have been observed and analyzed and it was noticed that pests were more dependent on sorghum chlorophyll than other plant parameters, while climatic conditions were taken as constant. An empirical relationship has been developed between occurrence of pests and TC with quite significant values of coefficient of determination ( r 2 = 0.82). These crop parameters are easily assessable through microwave remote sensing and therefore they can form the basis for prediction of pest remotely. In the second phase of this study, several observations were carried out for various growth stages of sorghum using scatterometer for both like polarizations (i.e., HH- and VV-) and different incidence angles at X-band (9.5 GHz). Linear regression analysis was carried out to obtain the best suitable incidence angle and polarization to assess the sorghum TC. VV-pol gives better results than HH-pol and incidence angle should be more than 40° for both like polarizations for assessing the sorghum TC at X-band. A negative correlation has been obtained between TC and scattering coefficient with the r 2 values (0.69 and 0.75 for HH- and VV-pol, respectively). The TC assessed by the microwave measurements was helpful to estimate the occurrence of pests on sorghum. Based on both phase of study an algorithm is proposed to estimate the number of pest on sorghum by remote sensing method. There is a quite good agreement between observed occurrence of pest and assessed occurrence of pest.

Imaging of electrochemical enzyme sensor on gold electrode using surface plasmon resonance

Three types of imaging, namely layer structure, electrochemical reaction, and enzyme sensor response, were achieved by applying surface plasmon resonance (SPR) measurement to an electrochemical biosensor. We constructed glucose oxidase based mediator type sensors on a gold electrode by spotting the mediator that contained horseradish peroxidase and spin coating the glucose oxidase film. The layer structure of the sensor was imaged by means of angle scanning SPR measurement. The single sensor spot (about 1 mm in diameter) consisted of about 100×100 pixels and its spatial structure was imaged. The multilayer structure of the enzyme sensor had a complex reflectance–incident angle curve and this required us to choose a suitable incident angle for mapping the redox state. We chose an incident angle that provided the most significant reflection intensity difference by using data obtained from two angle scanning SPR measurements at different electrode potentials. At this incident angle, we controlled the electrochemical states of the spotted mediator in cyclic voltammetry and imaged the degree to which the charged site density changed. Finally, we mapped the enzymatic activity around the mediator spot by the enzymatic reoxidation of pre-reduced mediator in the presence of glucose.

A Fabric Defect Valuation Method by Using Expert System

Fabric inspector can recognize the fabric defects because they can observe not only the light and darkness but also the brilliance or gloss on the fabric surface. So, in order to distinguish the fabric defects by the machine, it is also necessary to deal with such information as gathered by inspectors. In this paper, a new method has been developed to distinguish the fabric defects. The laser light is irradiated on the fabric surface and then the diffused light is measured cross 360 degrees to create a reflection pattern.Because there are many naps and twists on the fabric surface irregularly, so the distribution of diffused light will be varied according to the incidence angle of laser. We know that if the light is irradiated on the fabric surface with some suitable angle and the signal is detected at some suitable angle the informations about the fabric defect could be extracted at its maximum. The experiment, has shoun that the most suitable incidence angle is 25 degrees and the most suitable measurement angle is 75 degrees.By using pinhole and filter in the optical path, we can normally detect the signal even if not in the darkroom. And when the pinhole diameter was 0.7mm, we detected the signal with averaging the ripple of the noises due to the thread naps and twists, and without losing the defect signal. Here the measured area (S) is given by the next equation.S=πa2/4cosθwhere a is the pinhole diameter, and θ is the measurement angle.In this experiment, we found that the reflection pattern on th fabric surface was dependent on the fabric construction. The pattern from normal part of the fabric was symmetric, while that from an abnormal part was distorted and the aspect of being distorted was due to the kind of defects. Also the similar reflection patterns can be detected from the same sort defects, but the identical one practically does not appear again even if from the same sort of defect.To recognize the fabric defect with the reflection pattern, the table reasoning method was introduced. Firstly twelve characteristic parameters were sampled from the reflection pattern to investigate the relations between the refection patterns and the fabric defects, then an expert system has been developed to identify the fabric defects.