Measurement Distance Research Articles

Single-Cut Scattered Field Transformation Applicable for Differences in the Radar Ranges of Transmitter and Receiver

This paper proposes a new single-cut scattered field transformation method. The method extends the existing radiation reflector model to the case where the measurement distances from a target under test to a transmitter (TX) and a receiver (RX) are different. The method is applied to bistatic measurements by using the monostatic to bistatic equivalence theorem (MBET). The new method is based on the Born approximation and has features: (1) a scattered field including not only a far-field but a near-field can be predicted from measured near-field samples, where the measurement distances from a target under test to the TX and RX can be different, (2) the scattered field with a zero bistatic angle and the field with the non-zero bistatic angle where the MBET holds can be predicted, (3) the computational time is practical for a large target, and (4) the implementation of the code is easy. The algorithm of the method has simply three steps: inverse Fourier transformation (FT) is implemented with the measured near-field samples, the samples with inverse FT are multiplied by a novel weighting factor, and the scattered field is predicted by taking FT of the weighted samples. The proposed method is experimentally and numerically verified.

Analysis and optimization of temperature measurement distance on the infrared temperature measurement accuracy of a building envelope

Due to the measuring distance, there are variable degrees of temperature measurement differences when infrared temperature monitoring technology is employed to take the temperature of a building envelope, which can directly lead to distortion in the detection of the building envelope temperature. In order to address this issue, temperature data from 20 sets of different measurement locations were acquired through field testing analyzing the building envelope and the interior latex-painted wall. By fitting polynomials to the temperature error and distance curves, a model of the temperature-distance compensation function was produced. According to the results, it is possible to precisely estimate the temperature of latex-painted interior walls at a distance of 0.25 meters using an instrument. The temperature-distance compensation model is executed as the measurement distance increases, resulting in a maximum error rate of 1% for temperature readings after compensation. Before adjustment, the error rate in measuring temperature was 4.9%; after adjustment, it is 3.9%.

Over-the-Air Noise Temperature Measurement

Noise temperature is one of the key performances of RF components, such as the amplifiers in those receivers and transmitters. It is essential to measure the noise temperature accurately; however, the traditional conduction method is no longer suitable for those components with integrated antennas, e.g., antennas in packages (AiP) or antenna on chip (AoC). This paper proposes a solution for noise temperature measurement based on the over-the-air (OTA) method. First, the concept and the problem of noise temperature for those devices integrated with RF components and radiation elements are reviewed, the proposed OTA noise temperature measurement and calibration methods are presented, the measurement systems are set up and at both C band and millimeter-wave band with different measurement distances under both transmitting and receiving states are demonstrated in detail, and the measured results are compared and discussed which verifies that this proposed method is technically feasible for the OTA noise temperatures with high accuracy.

Error Comparison of CNFFFT and Hankel Method in RCS Near-Field to Far-Field Transformation

At present, there are mainly two kinds of image-based near-field to far-field transformation (NFFFT) algorithms: Hankel method and circular near-field-to-far-field transformation (CNFFFT). Due to the approximation in the measurement distance, the accuracy of Hankel method is lower than that of CNFFFT. However, the implementation of CNFFFT is complex and time-consuming. It is necessary to determine the detailed relationship between the transformation error and the near-field test distance for both algorithms to provide a basis for the choice of which algorithm to use. In this paper, the effect of the near-field test distance approximation of the two algorithms is obtained by simulating 4, 5, and 9 scattering point models. Meanwhile, an accurate comparison method for two NFFFT algorithms under different test distances is proposed.

Absorbing Material of Button Antenna with Directional Radiation of High Gain for P2V Communication.

Vehicular communication systems can be used to enhance the safety level of road users by exchanging safety/warning messages. In this paper, an absorbing material on a button antenna is proposed for pedestrian-to-vehicle (P2V) communication, which provides safety service to road workers on the highway or in a road environment. The button antenna is small in size and is easy to carry for carriers. This antenna is fabricated and tested in an anechoic chamber; it can achieve a maximum gain of 5.5 dBi and an absorption of 92% at 7.6 GHz. The maximum distance of measurement between the absorbing material of the button antenna and the test antenna is less than 150 m. The advantage of the button antenna is that the absorption surface is used in the radiation layer of the antenna so that the antenna can improve the radiation direction and gain. The absorption unit size is 15 × 15 × 5 mm3.

Digital Management of Teaching Cases in Colleges and Universities Based on Cluster Analysis

The necessity of digital management of teaching cases is mainly reflected in the aspects of improving teaching quality, facilitating retrieval and storage, achieving cross-platform sharing, conducting real-time updating, saving resources, and carrying out data analysis and evaluation. However, there are still some defects in the existing management models or methods, which lead to difficulties in data storage and retrieval, and affect the utilization efficiency of teaching resources. To this end, this article takes the Chinese language and literature major as an example, and studies the digital management of teaching cases in colleges and universities based on cluster analysis. First of all, it quantifies the quality of digital management of teaching cases, enables resource demanders to accurately select digital resources of teaching cases that meet their teaching or learning needs through the evaluation index of service quality when faced with diversified digital resources of teaching cases in colleges and universities. The clustering algorithm is used to mine potential topics and patterns in teaching cases, which improves the classification efficiency of teaching cases and enables educators to have a deeper understanding of teaching content and educational needs. It uses "absolute index", "incremental index" and "fluctuation index" to construct the similarity measurement distance function of the basic attributes of teaching cases in colleges and universities and uses the Ward method based on variance analysis to classify the characteristics of teaching cases in colleges and universities. Experimental results verify the effectiveness of the proposed method.

The Influence of a Photometric Distance on Luminance Measurements

Luminance measurements are the least frequent of all photometric measurements. This article characterizes and systematizes the various methods of luminance measurement. In particular, the method of direct luminance measurement using modern luminance meters (ILMD) is described in detail. This paper presents the results of the study on the influence of the measurement distance on the luminance measurement results. Two ILMD meters (laboratory and portable) and a luminance standard were used in this study. The conducted research showed that an incorrectly chosen measuring distance can lead to significant measurement errors of up to several tens of percent. In addition, the possible impact of incorrect measurements on the design of an interior lighting installation was presented. It was shown that the selected interior lighting installation can consume more than 40 percent more electricity compared to the installation based on the correct luminance measurements of the luminaires with diffuse shades. In the final stage of the study, the definition of the photometric test distance for luminance measurements using ILMD was proposed. The test results can be particularly useful for the luminance measurements of OLEDs or the luminaires with diffuse luminous character. However, these results can also be used for luminance measurements of other light sources and luminaires.

300 km ultralong fiber optic DAS system based on optimally designed bidirectional EDFA relays

Optical fiber distributed acoustic sensing (DAS) based on phase-sensitive optical time domain reflectometry (φ-OTDR) is in great demand in many long-distance application fields, such as railway and pipeline safety monitoring. However, the DAS measurement distance is limited by the transmission loss of optical fiber and ultralow backscattering power. In this paper, a DAS system based on multispan relay amplification is proposed, where the bidirectional erbium-doped fiber amplifier (EDFA) is designed as a relay module to amplify both the probe light and the backscattering light. In the theoretical noise model, the parameters of our system are carefully analyzed and optimized for a longer sensing distance, including the extinction ratio (ER), span number, span length, and gain of erbium-doped fiber amplifiers. The numerical simulation shows that a bidirectional EDFA relay DAS system can detect signals over 2500 km, as long as the span number is set to be more than 100. To verify the effectiveness of the scheme, a six-span coherent-detection-based DAS system with an optimal design was established, where the cascaded acoustic-optic modulators (AOMs) were used for a high ER of 104 dB. The results demonstrate that the signal at the far end of 300.2 km can be detected and recovered, achieving a high signal-to-noise ratio of 59.6 dB and a high strain resolution of 51.8pε/Hz at 50 Hz with a 20 m spatial resolution. This is, to the best of our knowledge, a superior DAS sensing distance with such a high strain resolution.

Spacecraft Pose Estimation Based on Different Camera Models

Spacecraft pose estimation is an important technology to maintain or change the spacecraft orientation in space. For spacecraft pose estimation, when two spacecraft are relatively distant, the depth information of the space point is less than that of the measuring distance, so the camera model can be seen as a weak perspective projection model. In this paper, a spacecraft pose estimation algorithm based on four symmetrical points of the spacecraft outline is proposed. The analytical solution of the spacecraft pose is obtained by solving the weak perspective projection model, which can satisfy the requirements of the measurement model when the measurement distance is long. The optimal solution is obtained from the weak perspective projection model to the perspective projection model, which can meet the measurement requirements when the measuring distance is small. The simulation results show that the proposed algorithm can obtain better results, even though the noise is large.

Ultrasonic needle hydrophone calibration in air by a parabolic off-axis mirror focused beam using three-transducer reciprocity

An acoustic field distribution investigation in air requires a small receiving sensor. Needle hydrophones seem to be an attractive solution, and it has previously been demonstrated that needle hydrophones designed for use in water can be used in air. The metrology problem is that an absolute sensitivity calibration is needed, because needle hydrophones are not characterized in air, especially for frequencies below 1 MHz, which is of interest for air-coupled ultrasound. Conventional, three-transducer/microphone reciprocity calibration requires measurements to be done in the far field. However, when transducer diameter is large and the frequency is high, the required measurement distance becomes very large: 3 m for a 20 mm source, transmitting at 1 MHz. Large propagation distance leads to high attenuation and nonlinear effects in air propagation, and distortion and losses accumulate. Small needle hydrophones have low sensitivity, so that high excitation amplitudes would be required, which can lead to transducer heating and increase nonlinearity effects. A derivative of the three-transducer reciprocity calibration method is proposed, where a large aperture transducer is focused onto a hydrophone, using hybrid of plane wave and spherical wave reciprocity. Use of a focused source minimizes the frequency-dependent diffraction effects, and the spherical wave approximation is valid at the focal distance, and low level excitation signals can be used. Focusing is accomplished using a parabolic off-axis mirror. Calibration is in transmission, which reduces the complexity of the electrical measurements. The corresponding equations have been derived for this setup. Calibration of the transducer and needle hydrophone absolute sensitivity is obtained.

Dependence of turbulence estimations on nacelle lidar scanning strategies

Abstract. Through numerical simulations and the analysis of field measurements, we investigate the dependence of the accuracy and uncertainty of turbulence estimations on the main features of the nacelle lidars' scanning strategy, i.e., the number of measurement points, the half-cone opening angle, the focus distance and the type of the lidar system. We assume homogeneous turbulence over the lidar scanning area in front of a Vestas V52 wind turbine. The Reynolds stresses are computed via a least-squares procedure that uses the radial velocity variances of each lidar beam without the need to reconstruct the wind components. The lidar-retrieved Reynolds stresses are compared with those from a sonic anemometer at turbine hub height. Our findings from the analysis of both simulations and measurements demonstrate that to estimate the six Reynolds stresses accurately, a nacelle lidar system with at least six beams is required. Further, one of the beams of this system should have a different opening angle. Adding one central beam improves the estimations of the velocity components' variances. Assuming the relations of the velocity components' variances as suggested in the IEC standard, all considered lidars can estimate the along-wind variance accurately using the least-squares procedure and the Doppler radial velocity spectra. Increasing the opening angle increases the accuracy and reduces the uncertainty on the transverse components, while enlarging the measurement distance has opposite effects. All in all, a six-beam continuous-wave lidar measuring at a close distance with a large opening angle provides the best estimations of all Reynolds stresses. This work gives insights on designing and utilizing nacelle lidars for inflow turbulence characterization.

Udo Krüger Charts TechnoTeam's Journey

Udo Krüger Charts TechnoTeam's Journey

Geometric Brownian information engine: Essentials for the best performance.

We investigate a geometric Brownian information engine (GBIE) in the presence of an error-free feedback controller that transforms the information gathered on the state of Brownian particles entrapped in monolobal geometric confinement into extractable work. Outcomes of the information engine depend on the reference measurement distance x_{m}, the feedback site x_{f}, and the transverse force G. We determine the benchmarks for utilizing the available information in an output work and the optimum operating requisites for best achievable work. Transverse bias force (G) tunes the entropic contribution in the effective potential and hence the standard deviation (σ) of the equilibrium marginal probability distribution. We recognize that the amount of extractable work reaches a global maximum when x_{f}=2x_{m} with x_{m}∼0.6σ, irrespective of the extent of the entropic limitation. Because of the higher loss of information during the relaxation process, the best achievable work of a GBIE is lower in an entropic system. The feedback regulation also bears the unidirectional passage of particles. The average displacement increases with growing entropic control and is maximum when x_{m}∼0.81σ. Finally, we explore the efficacy of the information engine, a quantity that regulates the efficiency in utilizing the information acquired. With x_{f}=2x_{m}, the maximum efficacy reduces with increasing entropic control and shows a crossover from 2 to 11/9. We discover that the condition for the best efficacy depends only on the confinement lengthscale along the feedback direction. The broader marginal probability distribution accredits the increased average displacement in a cycle and the lower efficacy in an entropy-dominated system.

A pipeline robot system for monitoring soil water content distribution

Monitoring soil water content (SWC) distribution is crucial for better understanding soil water dynamics and accurate hydrological modeling. In this study, a pipeline robot system for monitoring SWC distribution is designed to improve the current technical problems of insufficient measurement distance and low positioning accuracy of the existing SWC monitoring platform. The system consists of a pipeline robot, a fixed base station and a PVC pipe. The robot could fit into a 55-mm-diameter PVC pipe to measure SWC distribution horizontally, vertically, or at any angle to the horizontal direction. The base station serves as a data collector and also supplies power and distance information for recharging and positioning the robot, respectively. A series of tests for evaluating the performance of the pipeline robot system were conducted. Field experiments were also conducted to monitor soil water infiltration and horizontal distribution of SWC of crop root zone at three plots. The results showed that the minimum radius of volume of sensitivity of the dielectric sensor is about 2.25 cm. The robot for mobile measurement performed stable both in horizontal and vertical directions and the response of the dielectric sensor output to different dielectric materials is significant. The accumulated error of the encoder is effectively decreased from 4.3% to 1.2% by correcting the position error using the laser ranging sensor. The measured SWCs during the calibration experiment were highly correlated with those obtained by the drying method (R2 = 0.990 and RMSE = 0.0181 cm3 cm−3). The results of the field experiments demonstrated that the system is feasible for monitoring soil water infiltration in the vertical direction and SWC distributions of crop root zone horizontally at the three plots, indicating that the potential application of the developed system for long-term monitoring of SWC distribution under field conditions in the near future.

Feasibility of Stress Wave-Based Debond Defect Detection for RCFSTs Considering the Influence of Randomly Distributed Circular Aggregates with Mesoscale Homogenization Methodology.

In order to efficiently investigate the effect of the mesoscale heterogeneity of a concrete core and the randomness of circular coarse aggregate distribution on the stress wave propagation procedure and the response of PZT sensors in traditional coupling mesoscale finite element models (CMFEMs), firstly, a mesoscale homogenization approach is introduced to establish coupling homogenization finite element models (CHFEMs) with circular coarse aggregates. CHFEMs of rectangular concrete-filled steel tube (RCFST) members include a surface-mounted piezoelectric lead zirconate titanate (PZT) actuator, PZT sensors at different measurement distances, a concrete core with mesoscale homogeneity. Secondly, the computation efficiency and accuracy of the proposed CHFEMs and the size effect of representative area elements (RAEs) on the stress wave field simulation results are investigated. The stress wave field simulation results indicate that the size of an RAE limitedly affects the stress wave fields. Thirdly, the responses of PZT sensors at different measurement distances of the CHFEMs under both sinusoidal and modulated signals are studied and compared with those of the corresponding CMFEMs. Finally, the effect of the mesoscale heterogeneity of a concrete core and the randomness of circular coarse aggregate distribution on the responses of PZT sensors in the time domain of the CHFEMs with and without debond defects is further investigated. The results show that the mesoscale heterogeneity of a concrete core and randomness of circular coarse aggregate distribution only have a certain influence on the response of PZT sensors that are close to the PZT actuator. Instead, the interface debond defects dominantly affect the response of each PZT sensor regardless of the measurement distance. This finding supports the feasibility of stress wave-based debond detection for RCFSTs where the concrete core is a heterogeneous material.

Large-Area Monitoring of Radiofrequency Electromagnetic Field Exposure Levels from Mobile Phone Base Stations and Broadcast Transmission Towers by Car-Mounted Measurements around Tokyo

Car-mounted measurements of radiofrequency electromagnetic exposure levels were carried out in a large area around Tokyo. Prior to the electric field (E-field) measurements using a car, the effect of the car body was evaluated in an anechoic chamber. The measurements between May 2021 and February 2022 were carried out within a radius of 100 km centering on Nihonbashi, Tokyo, with a measurement distance of about 13,800 km. The measurement results were averaged in the reference area mesh (1 km2). It was found that the E-field strengths of FM/TV frequency bands are lower than that of mobile phone base stations. It was also found that the E-field strength of only the 5G frequency band is approximately 20–30 dB lower than that of all mobile phone systems. However, note that it is possible to depend on the data traffic of 5G. The E-field strength of all bands is higher in Tokyo than in other prefectures. Additionally, repeated measurements were carried out to investigate the reproducibility of the measured E-field. The standard deviation is less than 3 dB along the same route, and a similar tendency of E-field strength by the car to the time-averaged results of spot measurements in the past was confirmed. Finally, the relationship of E-field strength with population density was investigated. It was found that the E-field strength from mobile phone base stations has a positive relationship with population density.

Scanning Scheme for Underwater High-Rise Pile Cap Foundation Based on Imaging Sonar

This study developed a sonar scanning scheme for underwater high-rise pile cap foundations (HRPCFs) to improve the efficiency of bridge inspection and prolong structural durability. First, two key factors in the measurement point arrangement that significantly affect the accuracy of sonar measurement—the appropriate range of measurement distance and the pitch angle—were determined experimentally. Subsequently, an assembled platform was designed to firmly hold the sonar and conveniently move it under strong currents to effectively provide clear images of the pile. A strategy was developed to determine the appropriate number and horizontal and vertical positions of the measurement points around each pile in the pile group, particularly to avoid the obstruction of signal propagation caused by adjacent piles and pile caps. The method was applied to the scanning of an underwater high-rise pile cap foundation of a bridge, and the results showed that the scanning ranges of the imaging sonar at all arranged measurement points were not affected by adjacent piles. The imaging sonar carried by the proposed platform could obtain clear images stably at a water speed of ~2.0 m/s and obtain all surface data of the pile quickly and completely.

Agreement of Corneal Diameter and Anterior Chamber Depth Measurements with the IOLMaster 500 and the IOLMaster 700 Optical Biometers in Myopic Eyes.

To assess the agreement in automated corneal diameter (CD) and anterior chamber depth (ACD, measured from corneal epithelium to lens) distances measurements between the IOLMaster 500 and 700 optical biometers in myopic eyes. One hundred and sixteen eyes of 116 myopic patients aged between 21 to 60 years were included in this study. Measurements of CD and ACD distances were taken with each biometer for all patients in the same session. A t-test and a p-value less than 0.05 was considered statistically significant when the measurements were compared. The agreement between biometers was studied by applying a Bland-Altman analysis. The mean CD values obtained using the IOLMaster 500 and 700 biometers were 12.26±0.35 mm and 12.13±0.34 mm, respectively. The mean ACD distance values were 3.61±0.29 mm and 3.62±0.31, for the IOLMaster 500 and 700 biometers, respectively. There were statistically significant differences between the two devices only for CD measurements (p<0.001), but not for ACD measurements (p=0.26). The limits of agreement obtained were wide in both types of measurements, being 0.422 mm for the CD distance and 0.389 mm for the ACD distance. There were statistically significant differences between the IOLMaster 500 and 700 biometers regarding CD but not in ACD measurements in healthy myopic eyes. These differences could be clinically significant in some cases. According to these results, medical judgement should be used to assess whether the two devices could be used interchangeably for CD and ACD measurements during the clinical practice.

High-Efficiency Diagnosis of Antenna Radiation Characteristics Based on Scanning Optic-Induced Plasma Scattering Technology

This article presents an innovative quasi-real-time antenna near-field diagnosis method, by scanning a laser-induced plasma on a silicon wafer and imaging the field with the synchronously produced scattered signals. Several approaches have been devised to adapt to the antenna diagnosis scenarios. By using the multilayer matching approach, the issue of multiple reflection disturbance between the aperture and silicon wafer is avoided, especially for large aperture antennae at high frequencies. The accuracy of near-field distribution is improved, and far-field patterns can be transformed directly. The experimental results of a Ka-band 20 dB standard antenna agree well with the simulation results. Diagnosis of radiation states in the reactive near-field region is demonstrated, and the resonate modes of a 2.4 GHz Wi-Fi patch antenna at different frequencies are clearly observed. The experiments of a TM01 mode antenna verify the full polarization diagnosis ability of the method, and the linear polarization component is measured with the help of a polarization grid. The demonstrated diagnosis method has the advantages of high efficiency, ultraclose measurement distance, and superresolution and provides a highly promising and widely available method for antenna diagnosis.

RANCANG BANGUN ALAT KEHADIRAN OTOMATIS MENGGUNAKAN QRCODE DILENGKAPI DENGAN PENGUKUR SUHU BADAN DAN CUCI TANGAN

At the beginning of 2020 the world was shocked by the outbreak of the corona virus which infected almost all countries in the world. WHO since January 2020 has declared the world to be in a global emergency related to the Covid-19 virus. As a preventive measure, every public facility and shop must have hand washing equipment, check body temperature before entering the room so that people who have a high temperature must go to the doctor, this also applies to schools to prevent new clusters in the educational environment. In this journal, the presence of a QRCODE-based automatic tool using the MLX90614 temperature sensor to measure body temperature is connected to the Arduino UNO microcontroller and displayed on the LCD in the form of temperature sensor measurement data and OLED displays QRCODE data scanned using the presence application. The Sensor Module MLX90614 has an IR sensitive thermopile detector chip and a signal conditioning ASIC integrated in the sensor packing model TO-39. The signal conditioning in the form of a low noise amplifier, 17-bit ADC and a powerful DSP unit achieves the accuracy and high resolution of the thermometer. The attendance application is made forAndroid smartphones, students can scan the QRCODE to make attendance through an application on an Android smartphone, so using the QRCODE can speed up and simplify receiving information obtained on the smartphone application. Testing of the prototype tool was carried out at Pupuan One Roof Public Middle School 6, a trial was carried out with several students, the lowest measurement difference was 0.2 °C and the highest was 0.5 °C with a measurement distance of 5 cm from the sensor surface. The prototype can be used for attendance from checking temperature, washing hands and making attendance from a smartphone then the data is submitted and stored in the Firebase database.