Current Spectrum Research Articles

Sensorless Control of IPMSM Drives Using High-Frequency Pulse Voltage Injection With Random Pulse Sequence for Audible Noise Reduction

Saliency tracking based sensorless control schemes of interior permanent magnet synchronous motor (IPMSM) are generally troubled by the audible noise induced by high-frequency (HF) signal injection and the estimation error caused by voltage distortions. Aiming at that, a novel sensorless control strategy of IPMSM drives using HF pulse voltage injection with random pulse sequence (HFPVI-RPS) is proposed. Firstly, the conventional HFPVI method could restrain the impact of voltage distortions, and its mechanism is briefly reviewed. Then, based on that, a novel injected form that injecting HF pulse signals with random pulse sequence into the estimated d-axis is designed to eliminate discrete harmonics in the current power spectra density (PSD) and broaden the current PSD to a wide range. The audible noise can be reduced as much as possible. Further, a signal demodulation scheme matched with the injected form of HFPVI-RPS is proposed for the accurate extraction of rotor position. The PSD analysis of the HFPVI and proposed HFPVI-RPS methods is carried out, and the PSD comparison between reported methods and HFPVI-RPS method is given. Eventually, the effectiveness of the proposed sensorless control strategy is verified on a 750W IPMSM drive platform.

Relaxation behaviour of pristine and ZnO impregnated PS nanocomposite films using thermally stimulated depolarization current technique

Thermally stimulated depolarization current studies of pristine and ZnO doped nanocomposite films (at 5, 10, 15 & 20 wt% of ZnO) have been investigated at different poling temperatures and polarizing fields. Peaks corresponding to glass transition temperature (α1 and α2-peaks) relaxation, space-charge relaxation (ρ-peaks) and γ-relaxation were observed in thermograms of pristine and doped films. The change in peak height and peak positions with increase in doping concentration and poling parameters i.e., EP & TP results to the trapping or detrapping of the charge carriers. The anomalous behaviour of PS/ZnO nanocomposite films towards TSD current spectra observed near the glass transition temperature indicates the phase transitions. Changes in different relaxations may be attributed to the structural deformation of the samples due to doping and supported by FTIR and SEM results. Moreover, some molecular parameters like activation energy (Ea) and relaxation times (τ) were estimated.

New measurement method of displacement susceptibility based on time‐domain current and potential combined spectra

AbstractDisplacement susceptibility is a very important parameter to characterise the displacement polarisation of dielectrics. Two methods based on the time‐domain current and potential combined spectra are proposed to measure the displacement susceptibility. One is based on the time‐domain polarisation current and decay potential combined spectra, and the other is based on the time‐domain depolarisation current and recovery potential combined spectra. The principle of the proposed methods are verified by simulation. In addition, a measurement system for the two proposed methods is built and is used to measure the displacement susceptibility of transparent organic glass and opaque nonlinear field grading materials. The experimental results are compared with those of the present optical method and the frequency‐domain method. Simulation and experimental results show that the proposed methods for the measurement of displacement susceptibility are feasible and practical, which lays a foundation for the research on the polarisation characterisation of dielectrics.

Numerical Investigation on the Effect of Electrical Parameters on the Discharge Characteristics of NS-SDBD

There are numerous scientific and engineering fields where the surface dielectric barrier discharge driven by nanosecond pulses (NS-SDBD) has important applications. To improve its performance, more research is still needed on the effects of electrical parameters on the NS-SDBD actuator’s discharge characteristics. In this study, a two-dimensional numerical model based on 13 discharge particle chemical processes was constructed using a numerical simulation approach, producing findings for the NS-SDBD actuator’s voltage–current (V-A) characteristics, discharge profile, and spectrum analysis. Additionally, a comprehensive investigation into the trends and underlying mechanisms of the effects of the voltage amplitude, pulse width, rise time, and fall time parameters on the discharge behavior of the NS-SDBD actuator was carried out. The results show that higher voltage amplitudes increase the maximum current and electron density, which enhances the plasma excitation effect. The peak power deposition during the second discharge is also raised by longer pulse widths and rise times, whereas the total power deposition during the second discharge is decreased by longer fall times.

Modelling dynamically driven global cloud formation microphysics in the HAT-P-1b atmosphere

ABSTRACT Insight into the formation and global distribution of cloud particles in exoplanet atmospheres continues to be a key problem to tackle going into the JWST era. Understanding microphysical cloud processes and atmospheric feedback mechanisms in three-dimensional (3D) has proven to be a challenging prospect for exoplaneteers. In an effort to address the large computational burden of coupling these models in 3D simulations, we develop an open source, lightweight, and efficient microphysical cloud model for exoplanet atmospheres. ‘Mini-cloud’ is a microphysical based cloud model for exoplanet condensate clouds that can be coupled to contemporary general circulation models (GCMs) and other time-dependent simulations. We couple mini-cloud to the Exo-FMS GCM and use a prime JWST target, the hot Jupiter HAT-P-1b, as a test case for the cloud formation module. After 1000+ of days of integration with mini-cloud, our results show a complex 3D cloud structure with cloud properties relating closely the dynamical and temperature properties of the atmosphere. Current transit and emission spectra data are best fit with a reduced cloud particle number density compared to the nominal simulation, with our simulated JWST NIRISS SOSS spectra showing promising prospects for characterizing the atmosphere in detail. Overall, our study is another small step in first principles 3D exoplanet cloud formation microphysical modelling. We suggest that additional physics not included in the present model, such as coagulation, are required to reduce the number density of particles to appropriately observed levels.

Two-Wire Power Line Microwave Communication Using Low-Loss Modes

A closed-form solution for the common and differential modal currents induced on a pair of infinitely long parallel conductors by a source, field coupled to a power line, is derived. For lossy conductors, the current consists of a continuous spectrum of radiation modes and (for the common mode) a modified low-loss Sommerfeld–Goubau (SG) mode and (for the differential mode) a quasi-TEM mode. This model is used to investigate the influence of a parallel conductor on microwave power line communication systems. When the complete current spectrum is used, it is shown that the SG mode is not the primary reason why low-loss communication is possible on power lines for distances on the order of 100 m. Nevertheless, and consistent with previous research, microwave communication using power lines has advantages over free space communication, and for typical parameters, the performance of these systems can be enhanced if the power line contains more than one conductor.

Rotor Bar Fault Diagnosis in Indirect Field–Oriented Control-Fed Induction Motor Drive Using Hilbert Transform, Discrete Wavelet Transform, and Energy Eigenvalue Computation

The most powerful technology in the condition-based maintenance (CBM) framework for rotating machinery is fault detection (FD) and fault diagnosis (FDS). This paper investigates the broken rotor bar (BRB) FDS utilizing Hilbert transform (HT), discrete wavelet transform (DWT), and energy eigenvalue (EEV) computation with the induction motor (IM) drive handled by the indirect field orientation control (IFOC). The stator current spectrum, which the HT collects, is utilized to determine BRB degradation. The DWT decomposes the signal while the fast Fourier transform (FFT) recovers the signal’s frequency and amplitude factors. The EEV of the motor current in the signal determines the degree of the malfunction and provides a better method for recognizing errors. The DWT is used to overcome the Fourier analysis’s drawbacks and is primarily dedicated to non-stationary signals. While DWT is used, the malfunctioning BRB’s stator current signal is restrained from its original amplitude. The results demonstrate that the proposed method can identify and diagnose faults in an IM drive even under different loads.

Scientific Realism and Anti-Realism Through the Lens of Sunnī Divine Action Models

ABSTRACT Scientific realism and anti-realism, in various forms, frame many philosophical discussions about what constitutes a successful scientific theory. This paper explores this within an Islamic framework by examining the Sunnī theological tradition's various divine action models (DAMs) for their possible impact upon the theological reception of scientific realism and anti-realism, concluding that the tradition would be committed to an agnostic stance on the question. This enables the tradition to remain relevant to a broad spectrum of future scientific developments and changing intellectual currents.

Identification of Terahertz Link Modulation in Atmospheric Weather Conditions

With the rapid increase of wireless connectivity, current spectrum resources are not enough for significant requirements for large data capacity. Research interests are moving towards the high-frequency band in the terahertz range for wider bandwidth. However, multipath scattering and induced time delay, suffered by terahertz links propagating in outdoor weather, lead inevitably to increasing expenses in baseband signal processing. This trades away the advantage of low time latency and high stability, which are commonly considered as important merits of terahertz wireless communication techniques. To reduce the burden in signal processing and explore the feasibility of modulation identification in the terahertz band, a method of wireless link modulation identification is considered as a potential solution. In this work, it is investigated theoretically by employing two kinds of neural networks: the convolutional neural network (CNN) and the long short-term memory network (LSTM). Link deterioration caused by different atmospheric weather is introduced into the theoretical model, and the performance of this method is evaluated. Results show that the identification accuracy of the constructed neural networks can be up to 99%, which means such a method is efficient for identification of the modulation format of terahertz wireless links under different weather conditions. This work demonstrates the feasibility of modulation identification in outdoor terahertz communication scenarios and provides specific references.

Constant Wideband Compressive Spectrum Sensing for Sparse and Nonsparse Signals With Low-Rank Matrix Recovering and Prior Knowledge Mining

In cognitive radios (CR), compressive spectrum sensing (CSS) is a promising technique to detect wideband spectrum holes with reduced sampling rate requirement of analog-to-digital converter (ADC). It is implied in compressive sensing (CS) that the minimum sampling rate is determined by the sparsity order of the observed wideband signal. Unfortunately, the sparsity order is previously unknown and dynamically varies. Meanwhile, CS technology fails to work efficiently for the nonsparse spectrum case. For example, the CSS performance degenerates significantly for low signal-to-noise ratio (SNR) scenarios since the observed signal becomes nonsparse in frequency domain. To overcome the above-mentioned challenges, we propose a novel CSS algorithm with temporally-correlated prior knowledge mining (TPKM-CSS) to detect spectrum holes without a prior sparsity order information. The proposed scheme can handle both the sparse and nonsparse spectrum cases. The proposed solution has three contributions: firstly, CR implements multiple parallel sampling simultaneously to acquire wireless spectrum signals, which have a low-rank spectrum matrix. Secondly, the temporal correlation between continuous CS data is further exploited to improve the estimation accuracy of the current spectrum. Finally, the theoretical performance of the proposed TPKM-CSS is evaluated, wherein the cumulative distribution function (CDF) of the spectrum reconstruction error is derived in the closed form. The simulation results show that the proposed scheme works well for both sparse and nonsparse spectrum scenarios. Compared with the CSS schemes that are based on low-rank matrix recovery (LMR-CSS), maximizing correlation (MC), iterative compressive filtering (ICF), or Bayesian CS (BCS), the proposed scheme yields the superior performance in terms of the probability of detection and the probability of false alarm, especially for nonsparse signals. Furthermore, the simulated statistical performance of the spectrum reconstruction error matches well the theoretical CDF curve.

Analytical Calculation of the DC-Link Current Harmonics in Active Power Filter Considering Coupling Effect

Current harmonic is an important factor in power converters' DC-link design. Its accurate derivation is conducive to estimating the reliability of DC-link capacitors. In active power filter (APF), due to its wide output bandwidth, the DC link suffers current harmonics on a broader spectrum, and the coupling effects among compensated harmonics make the derivation in this application more complex. However, the traditional methods in voltage source inverters (VSIs) usually assume the output current to be a simple sinusoid, or only calculate the root mean square (RMS) values. They cannot readily illustrate the coupling effect, nor discriminate between different modulation strategies. This paper presents a general method for APF to solve the DC-link current harmonics under any operation condition. Using Double-Fourier theory, a new variable called ‘harmonic factor’ is defined to describe the coupling effect among compensated harmonics. Then the DC-link current spectrum is quantitatively derived with the low-frequency compensated harmonics and the switching-frequency ripple currents. Finally, the simulation and experiment of a 2-level 100-A APF verify the theoretical analysis.

Spectrum Management for Local Mobile Communication Networks

Spectrum management is a complex topic that divides stakeholders' perspectives. Recently, a major paradigm shift has taken place with the emergence of local 4G and 5G networks via local spectrum licensing models in several countries, allowing different stakeholders to establish their own mobile communication networks within specific facilities, such as a factories and ports. These local mobile communication networks can serve mobile network operators' (MNOs) end users, closed user groups, or a mix, resulting in operations under different regulatory conditions. Their emergence relies on spectrum availability in the given location, which is managed by national regulators. Local spectrum availability can be increased with spectrum sharing where two or more radio systems operate in the same band, but stakeholder views differ - some promote it while others object it. This paper analyzes the most recent spectrum management developments from the viewpoint of emerging local mobile communication networks considering the role of spectrum sharing. The analysis reveals how differently the countries have prepared for the new business opportunity arising from local mobile communication networks in their spectrum awarding decisions and quantifies current spectrum availability for establishing local 5G networks. The results show varying spectrum management approaches taken by the regulators. Especially, local spectrum licenses appear in the most recent spectrum awards. To realize a large number of local 4G/5G and future 6G networks, spectrum sharing will become critical and needs to be clearly defined and understood to mitigate currently strong stakeholders' objection.

The Mechanical and Self-Sensing Performance of Reactive Powder Cement Concrete with Nano-Stainless Steel Powder

In order to prepare cement concrete with high mechanical properties and durability, nano-stainless steel powder reactive powder cement concrete (RPC) was manufactured. The dosage of nano-stainless steel powder ranged from 0% to 1.2% by the total volume of the RPC. In this study, the compressive and flexural strengths of the RPC with nano-stainless steel powder were determined, the dry shrinkage rate of the RPC was tested and the electrical resistance and alternating current (AC) impedance spectrum of the RPC were measured; moreover, the corresponding strain-sensing properties were investigated, and the scanning electron microscope (SEM) was used for observing the microstructures of the RPC. The results showed that the RPC with 1.0% nano-stainless steel powder exhibited the threshold values of the mechanical strengths. The maximum flexural strength and compressive strength were 16.1% and 14.2% higher than the minimum values. The addition of the nano-stainless steel powders reduced the dry shrinkage rate by 12.1%–39.8%. The electrical resistance of the RPC decreased in the form of the cubic function with the volume fraction of the stainless steel powders. The 1.0% nano-stainless steel powder was the threshold value for the electrical resistance and piezoresistive performance. The relationship between the electrical reactance and electrical resistance fitted well with the quadratic function. As obtained from the SEM results, the addition of the nano-stainless steel powder could effectively improve the compactness of the hydration products.

The spectrum of in vitro maturation in clinical practice: the current insight.

In vitro oocyte maturation (IVM) has been used worldwide. Despite the long-term implementation, the uptake of this procedure to complement current in vitro fertilization (IVF) remains low. The main reason is likely due to the non-synchronization of protocol and definition criteria, leading to difficulty in collective proper outcome data worldwide and, thus, lack of understanding of the exact IVM procedure. The review aims to consolidate the current clinical practice of IVM by dissecting relevant publications to be tailored for a current spectrum of clinical practice. Nevertheless, the background theories of oocyte maturation were also explored to provide a comprehensive understanding of the basis of IVM theories. Additional discussion of other potential uses of IVM in the future, such as in ovarian tissue cryopreservation known as OTO-IVM for fertility preservation and among women with diminished ovarian reserve, was also explored. Otherwise, future collaboration among all IVM centers is paramount for better collection of clinical data to provide valid recommendations for IVM in clinical practice, especially in molecular integrity and possible DNA alteration if present for IVM offspring outcome safety purposes.

Role of the single-particle dynamics in the transverse current autocorrelation function of a liquid metal.

A recent simulation study of the transverse current autocorrelation of the Lennard-Jones fluid [Guarini et al., Phys. Rev. E 107, 014139 (2023)] revealed that this function can be perfectly described within the exponential expansion theory [Barocchi et al., Phys. Rev. E 85, 022102 (2012)]. However, above a certain wavevector Q, not only transverse collective excitations were found to propagate in the fluid, but a second oscillatory component of unclear origin (therefore called X) must be considered to fully account for the time dependence of the correlation function. Here, we present an extended investigation of the transverse current autocorrelation of liquid Au as obtained by abinitio molecular dynamics in the very wide range of wavevectors 5.7 ≤ Q ≤ 32.8 nm-1 in order to also follow the behavior of the X component, if present, at large Q values. A joint analysis of the transverse current spectrum and its self-portion indicates that the second oscillatory component arises from the longitudinal dynamics, as suggested by its close resemblance with the previously determined component accounting for the longitudinal part of the density of states. We conclude that such a mode, albeit featuring a merely transverse property, fingerprints the effect of longitudinal collective excitations on single-particle dynamics, rather than arising from a possible coupling between transverse and longitudinal acoustic waves.

MXene@Hydrogel composite nanofibers with the photo-stimulus response and optical monitoring functions for on-demand drug release

The photo-stimulus response has the advantage of non-invasiveness, which could be used to control the “on” and “off” of drug release achieving on-demand release. Herein, we design a heating electrospray during electrospinning to prepare photo-stimulus response composite nanofibers consisting of MXene@Hydrogel. This heating electrospray enables to spray MXene@Hydrogel during the electrospinning process, and the hydrogel is uniformly distributed which cannot be achieved by the traditional soaking method. In addition, this heating electrospray can also overcome the difficulty that hydrogels are hard to be uniformly distributed in the inner fiber membrane.The “on” and “off” state of drug release could be controlled by light. Not only near infrared (NIR) light but also sunlight could trigger the drug release, which could benefit outdoor use when cannot find NIR light. Evidence by hydrogen bond has been formed between MXene and Hydrogel, the mechanical property of MXene@Hydrogel composite nanofibers is significantly enhanced, which is conducive to the application of human joints and other parts that need to move. These nanofibers also possess fluorescence property, which is further used to real-time monitor the in-vivo drug release. No matter the fast or slow release, this nanofiber can achieve sensitive detection, which is superior to the current absorbance spectrum method.

Design of Multi-Layer Protocol Architecture using Hybrid Optimal Link State Routing (HOLSR) Protocol for CR Networks

There is a lack of spectrum due to the rising demand for sensing device communication and the inefficient use of the existing available spectrum. Through opportunistic access to licenced bands, which does not obstruct the primary sensory users (PU), it is feasible to enhance the inefficient use of the current sensor device frequency spectrum. Cognitive settings are a demanding environment in which to carry out tasks like sensor network routing and spectrum access since it is difficult to access channels due to the presence of PUs. The basic goal of the routing problem in sensor networks is to establish and maintain wireless sensor multihop paths between cognitive sensor nodes. The frequency to be used as well as the number of hops at each sensor node along the path must be determined for this assignment. In order to improve performance while using less energy, scientists suggested a unique adaptive cross-layer optimisation subcarrier distribution technique with the HOLSR protocol for wireless sensor nodes. Throughput and energy consumption parameters are used to analyse the sensor network architecture protocol that has been developed. The energy usage of the sensor nodes in the network has increased by 50%. The performance of the proposed HOLSR algorithm is assessed using the simulation results, and the results are contrasted with those of a conventional multicarrier (MC) system in terms of bit error rate and throughput.

Determination of Seismic Load for Buildings using Different Response Spectra and Application on Different Methods of Analysis

The response spectra defined in the appropriate Euro standards from the first and second generation (EN 1998–1 and EN 1998-1-1), which determine the seismic load for common buildings, are critically presented first. To avoid a reduction in earthquake loading on structures using response spectra, only a few points of the response spectra in the second generation of EN 1998-1-1 are determined by applying the probabilistic concept of seismic hazard assessment. The comparison of current response spectra in EN 1998–1 is made with the uniform hazard spectra (UHS). The comment and application of the second generation of EN 1998-1-1 is a novelty that is introduced in this paper. On the basis of response spectra presented here according to EN 1998–1 and EN 1998-1-1 and other spectra obtained from real and artificial records, comparative different methods of analysis on one regular simple eight-story reinforced concrete frame structure are illustrated to find out how the kind of spectra and used methods of analysis influence the story displacements and story drifts of one simple regular structure. So, at the same time, the reader will be informed not only about novelties in the second generation of EN 1998-1-1 as far as response spectra are concerned but also understand the implication of various response spectra on the methods of analysis of building structures.

SPS preparation of La10Si6O27 and the effect of sintering temperature on electrical conductivity

La10Si6O27 powder was synthesized by a high-energy ball milling method and its sintered body was prepared by spark plasma sintering (SPS) technology. Phase structure, microscopic morphology, density, porosity and oxide ion conductivity of La10Si6O27 were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Archimedes method and alternating current (AC) impedance spectrum, respectively. XRD results showed the ball-milled powder could form apatite-type La10Si6O27 at 1400 ℃. The crystal structure of La10Si6O27 sintered body remained stable. SEM results showed that La10Si6O27 sintered body using SPS sintering method had better sintering between grains and a large reduction in open pores compared to conventional sintering. Grains of the sintered body were clearly visible and the grain size was uniform, about 1 µm. Archimedes method analysis showed relative density of La10Si6O27 sintered body is 100%, and open porosity is 0. Electrical conductivity of La10Si6O27 sintered body has an Arrhenius relationship with temperature.

Identification of the High Mannose N-Glycan Isomers Undescribed by Conventional Multicellular Eukaryotic Biosynthetic Pathways.

N-linked glycosylation is one of the most important post-translational modifications of proteins. Current knowledge of multicellular eukaryote N-glycan biosynthesis suggests high mannose N-glycans are generated in the endoplasmic reticulum and Golgi apparatus through conserved biosynthetic pathways. According to conventional biosynthetic pathways, four Man7GlcNAc2 isomers, three Man6GlcNAc2 isomers, and one Man5GlcNAc2 isomer are generated during this process. In this study, we applied our latest mass spectrometry method, logically derived sequence tandem mass spectrometry (LODES/MSn), to re-examine high mannose N-glycans extracted from various multicellular eukaryotes which are not glycosylation mutants. LODES/MSn identified many high mannose N-glycan isomers previously unreported in plantae, animalia, cancer cells, and fungi. A database consisting of retention time and CID MSn mass spectra was constructed for all possible MannGlcNAc2 (n = 5, 6, 7) isomers that include the isomers by removing arbitrary numbers and positions of mannose from canonical N-glycan, Man9GlcNAc2. Many N-glycans in this database are not found in current N-glycan mass spectrum libraries. The database is useful for rapid high mannose N-glycan isomeric identification.