Principle Of Interference Research Articles

Characteristics of the propagation of partial discharge ultrasonic signals on a transformer wall based on Sagnac interference

The acoustic emission (AE) method has been widely recognized for the detection of incipient insulation fault phenomenon (partial discharge, PD) in power transformers, nevertheless, the installation and placement of AE sensors should be taken into full consideration. In this manuscript, a three-dimensional multiphysics model was established and simulated to research the characteristics of the propagation in the transformer wall. Furthermore, a piezoelectric transducer was used to detect PD ultrasonic signals and verify the simulation results in the laboratory. To ensure the accuracy of the detection, an optical fiber sensor based on the Sagnac interference principle was designed and adopted. The variation of the amplitude of the ultrasonic signal with distance reveals the characteristics of the ultrasonic signal propagating in the transformer wall. The distribution of sound pressure on the upper and lower surfaces of the simulation model proved that ultrasonic waves propagate in the form of symmetrical Lamb waves in the transformer wall. Moreover, the amplitude of the AE attenuates due to absorption and refraction loss, and local fluctuations on account of acoustic interference. Thus, a stable signal detected by an AE sensor does not represent the absence of PD in a transformer. To improve the reliability of AE detection, it is proposed in this manuscript that repeated movement of the AE sensor is necessary to obtain a suitable measurement position. Similarly, it is necessary to adjust the position of the AE sensor in order to locate the PD source well. In addition, this study is expected to provide a theoretical analysis and a fiber sensor to address the problem of sensor placement in AE detection.

Fully Dielectric Rod Antenna Arrays with Integrated Power Divider

Abstract This paper presents an overview of fully dielectric antenna arrays with integrated dielectric power dividers developed at Technische Universität Darmstadt as an extension of previous work. The power dividers are based on the principle of multimode interference and offer one- and two-dimensional power division in a single step, which allows the realization of small and lightweight devices. In order to prove the concept, 1 × 4 and 4 × 4 fully dielectric antenna arrays with integrated power dividers milled from Rexolite are designed, realized and characterized, operating between 90 GHz and 105 GHz. To assess miniaturization and beamsteering capabilities, three 1 × 4 arrays composed of different materials, Rexolite, Preperm L300 and Preperm L440, are compared regarding gain, size, weight and element spacing. Depending on array size and material, gain is between 12.5 dBi and 22 dBi, accompanied with sidelobe levels below - 7.5. All demonstrators are realized by milling, but the designs show the potential to be 3D printed or injection molded for large scale manufacturing.

The Role of MicroRNAs in Genome Response to Plant-Lepidoptera Interaction.

RNA interference is a known phenomenon of plant immune responses, involving the regulation of gene expression. The key components triggering the silencing of targeted sequences are double-stranded RNA molecules. The regulation of host–pathogen interactions is controlled by miRNA molecules, which regulate the expression of host resistance genes or the genes of the pathogen. The review focused on basic principles of RNA interference as a gene-silencing-based defense mechanism and the role of miRNA molecules in insect genomes. RNA interference as a tool for plant protection management is discussed. The review summarizes current miRNA-based biotechnology approaches for plant protection management.

The cancellation of human sounds using synthesized soundwaves

The principle of destructive interference is applied to reduce or eliminate the spoken sound in order to increase speech privacy. This research is divided into two parts: the synthesis of sound from formula, using both analytical linguistics and physical approaches, and the actual cancellation of simple to complex sounds in the real world setting. The results suggested that in a real-world setting, up to 60% intensity reduction could be repeatedly detected. When the complexity of the sound is increased, difference in interference pattern could be detected between sounds in frequency range within the human hearing spectrum. Furthermore, it is found that the generation of negative sound using the four formants is not comprehensive enough to interfere effectively with actual sound, therefore the spectral slice is needed to synthesize more complex sounds. After testing various variations, it is found that using 11 most intense frequency components adjusted in proportion according to each original amplitude best cancel the widest range of human sound samples. This method was used to test the effectiveness of actual human sound cancellation. Though effective cancellation was detected in the high frequencies range of the sound spectrum, other frequency ranges were barely affected. The difference between cancellation patterns of each frequency range might need investigating before the cancellation of human sound can be effectively applied in real life.

Study on Linear and Nonlinear Coupling Damage Model of BGA Solder Joint

Due to the complex and changeable environment in space, the ball grid array (BGA) has become one of the most important form of the electronic package in aerospace industry. As the main factors which affect the reliability of electronic products, temperature and vibration will lead to creep and fatigue respectively. Based on the damage mechanism, taking SnAgCu solder joints as the research object, the relationship between the resistance and the damage index are established by using the micro-conductive model of resistance. The mathematical model between stress cycle and damage value is established by damage mechanics. Then, the linear and nonlinear interaction models are established to simulate the initial and mature damage of solder joints respectively based on the principle of area interference. Finally, Monte Carlo method is used to simulate the growth of the crack, concluding that it’s suitable for the linear model when the damage index is less than 0.155 and the nonlinear model is suitable when the damage index is more than 0.155.

Non-destructive optical testing of the products obtained using additive manufacturing

Developing of additive manufacturing and the use of additive technologies at all stages of the product life cycle entails the necessity of developing methods providing control of their characteristics. Here we consider application of the optical measurement procedures to the objects of complicated shape. Products manufactured by the methods of additive technologies may have defects such as delamination, starved joint, porosity, warp, stress-strain state, roughness, etc. We present the devices designed and developed on the principles of interference, structured light and holography at the «VNIIOFI» Federal State Unitary Enterprise to identify the defects in the products of additive technologies. The advantages and shortcomings of the interference microscope, scanner-profilometer, and shearograph are examined with regard to the control of the aforementioned types of geometric defects. The special feature of the contact-free methods is the possibility of control of different types of materials: metals and dielectrics, transparent, reflective, scattering and composite materials. The results of experimental study aimed at detection of the surface and subsurface defects are presented. Interferograms and results of phase reconstruction are presented both for reflective and transparent objects. Defects of the refractive index of the microcavity made of an optical fiber were detected. Metrological characteristics of optical devices for non-destructive testing of products are estimated. Standards for calibration and graduation of the optical devices considered in the study were manufactured and tested. The use of specially developed standards makes it possible to use these methods both for qualitative assessment of the objects of complicated shape and flaw detection and for quantitative estimation of their characteristics.

Design of One-Bit Magnitude Comparator using Photonic Crystals

Abstract At present, photonic crystals (PhCs) are used to design various combinational and sequential circuits. In this paper, an all-optical one-bit magnitude comparator is proposed using PhC waveguide without using nonlinear material. It is based on beam interference principle, using T-shaped lattice with silicon dielectric rods in air background. It is demonstrated through finite-difference time-domain simulation and verified numerically using MATLAB simulation. The size of PhC lattice structure can be as small as 19.167a×19.167a, where ‘a’ is the lattice constant of the PhC.

Traceable atomic force microscope based on monochromatic light interference

Atomic force microscope (AFM) is widely applied to the measurement of the micro-nano structures due to its three-dimensional spatial resolution of sub-nanometer. However, the height measurement traceability in the z-axis is complex to be implemented in conventional AFMs. In this paper, a traceable AFM is developed based on the monochromatic light interference (MLI) principle without probe calibration. The height change of the AFM's probe is directly detected by extracting the phase change of the MLI fringes on the probe tip with the Hilbert transform based phase extraction algorithm, and the three-dimensional surface topography is reconstructed with a surface recovery algorithm. The configuration of tracing to the wavelength of the monochromatic light in real-time further improves the measurement accuracy of the MLI-AFM. A prototype MLI-AFM is established to demonstrate its measurement accuracy enhancement.

A Self-Referencing Intensity-Based Fabry–Perot Cavity for Curvature Measurement

In this article, a self-referencing intensity-based fiber optic sensor relying on the principle of Fabry-Perot interference is proposed and demonstrated to measure curvature. The sensor is manufactured producing an air bubble cavity between two sections of multimode fiber. By detecting optical power variations at specific wavelengths, it was possible to measure curvature, enabling this sensor as a self-referencing system. For this setup, the achieved curvature sensitivity was 0.561 ± 0.014 dB/m -1 , with a correlation factor up to 0.997, within the measurement range of 0.0-0.8 m -1 . The proposed system has several features, including the self-referencing characteristic and its structure simplicity in terms of measuring procedure, making it a useful system.

Surface profile measurement of doped silicon using near-infrared low-coherence light.

A scanning interferometry system based on near-infrared low-coherence interferometry by using a superluminescent diode (SLD) as the light source is presented. The system cannot only measure the surface profile of doped double-sided polished silicon but also measure its optical thickness and refractive index. The measurement system uses near-infrared CCD to detect interferometric light in the near infrared, based on the Michelson interference principle. SLD has low temporal and high spatial coherence and high penetration to doped silicon wafers; thus, higher visibility can be obtained when measuring the rear side. Meanwhile, the optical thickness measured by low coherent scanning interference is compared with the optical thickness obtained by spectrally resolved interferometry to verify the accuracy of the system. Due to the periodic characteristics of interference fringes, the coherence length of the narrowband light source is usually greater than the path length difference of the interferometer. It gives the measurement a phase ambiguity of 2π, which may severely limit the application of the measurement. However, the short coherent length SLD light source used in the project can avoid 2π phase ambiguity problems. Besides, this system can perform full scanning in a larger step and achieve rapid on-line measurement of the target surface.

Decision Making on Behalf of Children: Understanding the Role of the Harm Principle

Thirty years ago, Buchanan and Brock distinguished between guidance principles and interference principles in the setting of surrogate decision making on behalf of children and incompetent adult patients. They suggested that the best interest standard could serve as a guidance principle, but was insufficient as an interference principle. In this issue of The Journal of Clinical Ethics, Ross argues that the best interest standard can serve as neither a guidance or interference principle for decision making on behalf of children, but that her model of constrained parental autonomy can serve as both. I will argue that Buchanan and Brock were correct that a single model or standard cannot serve as both a guidance and interference principle in pediatrics and that the best interest standard is a sufficient guidance principle. The harm principle fulfills the conditions necessary for an interference principle, at least insofar as deciding when state intervention to interfere with parental decision making is justified.

Comparative performance analysis of relative humidity sensor based on intermodal interference using tapered square no-core optical fiber and tapered cylindrical optical fiber

This work presents the computational evaluation of a new model for relative humidity sensor based on the principle of intermodal interference using a square-section no-core tapered optical fiber compared to a classical cylindrical tapered optical fiber sensor. Attempting at a new application of this type of sensor, simulations were carried out in the range of up to 60% of relative humidity, the main interest range of the pharmaceutical industry. Several materials were used in its modeling and an analysis was developed in its constructive dimensions, in order to verify the influence of each of them on the sensor performance.

Design and analysis of all‐optical 1‐to‐2 line decoder based on linear photonic crystal

A new design of 1-to-2 line all-optical logic decoder has been proposed based on a two-dimensional photonic crystal (PhC) structure. The decoder operates based on the principle of optical interference within the PhC waveguides. An optical bias has been used to generate high-logic states at zero input conditions. Simulations explore a high contrast ratio, in the order of 11.3 dB, for both the output ports of the device. Response times have been calculated from the transient responses of the output ports, and are found as 0.65 and 0.77 ps for the ports 1 and 2, respectively. These results in a bit rate of ≃625 Gbps, considering the worst-case scenario. Phase sensitivity analysis has also been performed which shows that the device output is quite sensitive to the differences in phases of the bias and signals. However, a strategy has been proposed to make the same insensitive to the phase changes. Finally, the small footprint (in the order of 234 μm 2 ); standard operating wavelength; and silicon-based design of the decoder, along with its said merits, make the device highly potential for on-chip photonic-integrated-circuit applications.

Fitting algorithm for interferometric spectrum of fiber Fabry-Perot cavity acoustic sensors

Fiber Fabry-Perot cavity acoustic sensors have been widely used in some fields recently due to its advantages such as high sensitivity, resistance to electromagnetic interference, etc. In order to control the performance of the sensors, it is necessary to precisely adjust the cavity length. In order to obtain the cavity length efficiently and accurately, a fitting algorithm for interference spectrum is proposed in this paper. The base of the algorithm is the principle of light interference and the key of the algorithm is to find the peaks and valleys of the interference spectrum. Experimental results show that the algorithm has a high fitting degree.

Suppression effectiveness research on multi-level EMI filter in thermal electromagnetic interactive filed of explosion-proof three-level NPC converter

As a system, the explosion-proof three-level NPC (Neutral-Point-Clamped) converter has the characteristics of nonlinear, high complexity, and multiple thermal electromagnetic fields, among which multiple magnetic fields interfere with each other and affect the system stability. In order to solve this problem, the conducted electromagnetic interference principle was analyzed in the converter filed firstly in this paper, and transmission paths were illustrated as well. Secondly, on the basis of IGBT (Insulated Gate Bipolar Translator) transient state analysis, the EMI (Electro-Magnetic Interference) mechanism analysis of three-level converter power devices was completed for EMI filter design. Finally, a novel multi-level EMI filter was designed to weaken mutual interference of small magnetic field group in the system and to solve the EMI suppression problem of inner cavity interaction of explosion-proof three-level NPC converter. The research target is to optimize the filter and enhance the system ability of resistance to thermal and electromagnetic interference. The suppression effectiveness of multi-level EMI filter was proved by the experiment conducted on a 1 MW (Million Watt) explosion-proof three-level NPC converter platform.

Laboratory design and practice for undergraduates: Using RNAi to modulate gene expression

RNA interference is a gene silencing phenomenon mediated by short double-stranded RNAs, which has become a widely used research technology for reverse genetics. In order to make students understand the technology better, the students were required to select target genes, to design small interfering RNAs (siRNAs) and primers, and then to test the effect of gene silencing mediated by siRNAs. Taking the fifth group in 2018 as an example, Mus musculus acyl-CoA synthetase long-chain family member 1 (Acsl1) was selected as the target gene, two pairs of siRNAs targeting Acsl1 mRNA were designed and transfected into 3T3-L1 by electroporation, then the total RNAs were extracted and synthesized to cDNA, and the expression levels of mRNAs were finally tested by relative quantitative PCR. The results showed that both pairs of siRNAs had more than 60% silencing effects. In the past three years, about 83% of the students completed all the experiments successfully and screened out at least a pair of effective siRNA. This teaching practice for undergraduates enhances students' understanding of RNA interference principle and technology, and exercises students' lab experience and scientific research ability.

Multilevel reflectance switching of ultrathin phase-change films

Several design techniques for engineering the visible optical and near-infrared response of a thin film are explored. These designs require optically active and absorbing materials and should be easily grown on a large scale. Switchable chalcogenide phase-change material heterostructures with three active layers are grown here using pulsed laser deposition. Both Fabry–Perot and strong interference principles are explored to tune the reflectance. Robust multilevel switching is demonstrated for both principles using dynamic ellipsometry, and measured reflectance profiles agree well with simulations. We find, however, that switching the bottom layer of a three-layer device does not yield a significant change in reflectance, indicating a maximum in accessible levels. The pulsed laser deposition films grown show promise for optical display applications, with three shown reflectance levels.

Phase modulation characteristics analysis of liquid crystal spatial light modulator under oblique incidence.

A correction method for obtaining the phase modulation curves of liquid crystal spatial light modulator (LCSLM) systems under oblique incidence is proposed. Considering the reflection and refraction of the interface, the influence of oblique incidence on the LCSLM phase modulation was simulated and analyzed by solving the extended Jones matrix. The polarization interference principle was applied to construct a phase modulation system, the phase modulation was measured at different incident angles, and the measured data were subjected to Fourier fitting. The phase modulation curve was corrected to a straight line using the inverse interpolation method, and the lookup table (LUT) for the gray level and phase was then generated through the line coordinates. The measured results revealed that a larger angle of oblique incidence led to a smaller range of phase modulation. For LCSLM to function over a range from 0 to 2π, the oblique incidence angle should be less than 45°. Experimental results using 25° as an example confirmed the validity of the LUT. The correlation coefficient R between the phase modulation curve and the ideal linear curve was 0.9893, and the root-mean-square error was 0.1888. At incident angles from 0° to 45°, the linearity of the corrected LUT was as good as that of the LUT for vertical incidence, thereby laying the foundation for high-precision beam pointing control.

Multiband notch filter based guided-mode resonance for mid-infrared spectroscopy

A dielectric guided-mode resonance (GMR) notch filter with multiple channels was designed to operate in the mid-wave infrared (MWIR, 3∼4μm). The transmission characteristics of filters were analyzed using a finite difference time domain (FDTD) method. In the structure of notch filter, two different periodic (p1=1.6μm and p2=2.0μm) silicon (Si) grating waveguide layers (GWLs) are constructed on the CaF2 substrate. Si waveguide layer thickness and CaF2 cladding layer thickness were designed based on optical interference principle to give maximum transmission across the MWIR. The transmission spectrum presents two narrow band located at 3.410μm and 3.833μm with not only a high bandstop coefficient (>99%), but also a broadband high transmission (>90%) off-resonance. The resonant wavelengths can be flexible modulated in wide range by changing grating periods or filling factors, and it is proved that filter is stable and useful in actual atmospheric conditions. Because of the good performance in the bandstop features, the multiband GMR notch filter designed in this method may have a potential for a variety of imaging or detection applications.

CPU-GPU architecture for active noise control

Active noise control (ANC) is a technology which lowers the noise level by using the principle of destructive interference of sound wave. Performance of active noise control, generally, is highly related to the number of reference transducers, secondary speakers, and error microphones. However, the more number of transducers, microphones and speakers are used for improving ANC performance, the higher computational requirements of such an ANC algorithm would be. Currently, limited computational efficiency of conventional DSP systems hinders the possible maximum noise reduction performance of ANC. In the previous research, for figuring out the limited ANC performance issues due to a lack of computational efficiency, graphics processing units (GPU), which possesses significant parallel computational efficiency, is utilized for ANC algorithms. However, ANC algorithms with GPU computations in the previous researches have limitations on the fact that they are designed in frequency domain structure due to a block data transfer between central processing units (CPU) and GPU, which suffers from a block delay in control signals. Therefore, throughout this research, we proposed a CPU-GPU architecture for ANC algorithms, which does not suffer from the problems of frequency domain algorithms and take advantage of GPU computation. Also, we suggested important factors needed to be concerned when an ANC algorithm based on CPU-GPU architecture is being developed. The feasibility of the proposed CPU-GPU architecture for ANC algorithms is shown with an example of implementing the proposed CPU-GPU architecture on multichannel delayless subband ANC algorithm.