In conventional inverters, the linear modulation range is limited to a maximum voltage space vector radius of 0.866 times the dc link voltage (<inline-formula><tex-math ...notation="LaTeX">\text{V}_\text{dc}</tex-math></inline-formula>), which corresponds to a maximum peak fundamental phase voltage of 0.577 <inline-formula><tex-math notation="LaTeX">\text{V}_\text{dc}</tex-math></inline-formula>. Beyond this, the inverter enters the overmodulation region, where the operation transitions to a six-step mode causing the voltage space vector to trace a hexagonal locus. This results in phase voltage waveforms with significant lower order harmonic content leading to torque ripples in the motor shaft and undesired harmonic losses. Thus, the achievable speed range of the induction motor in the linear modulation range is effectively limited to 90.5% of its full base speed. In contrast, the proposed five-level inverter topology generates a circular voltage space vector locus with a radius of up to 0.955 <inline-formula><tex-math notation="LaTeX">\text{V}_\text{dc}</tex-math></inline-formula> resulting in a maximum peak fundamental phase voltage of 0.637 <inline-formula><tex-math notation="LaTeX">\text{V}_\text{dc}</tex-math></inline-formula>. Thus, the linear modulation range is extended to full base speed and is independent of the load power factor. The proposed power circuit is based on two standard three-level neutral point clamped inverters and can be realized by two readily available three-level NPC inverter IC packages. Standard space vector pulsewidth modulation techniques can be employed for switching pulse generation.
Most compact binary systems are expected to circularize before the frequency of emitted gravitational waves (GWs) enters the sensitivity band of the ground based interferometric detectors. However, ...several mechanisms have been proposed for the formation of binary systems, which retain eccentricity throughout their lifetimes. Since no matched-filtering algorithm has been developed to extract continuous GW signals from compact binaries on orbits with low to moderate values of eccentricity, and available algorithms to detect binaries on quasicircular orbits are suboptimal to recover these events, in this paper we propose a search method for detection of gravitational waves produced from the coalescences of eccentric binary black holes (eBBH). We study the search sensitivity and the false alarm rates on a segment of data from the second joint science run of LIGO and Virgo detectors, and discuss the implications of the eccentric binary search for the advanced GW detectors.
Nipah Virus (NiV) is a highly fatal emerging zoonotic virus and a potential threat to global health security. Here we describe the characteristics of the NiV outbreak that occurred in Kerala, India, ...during May-June 2018.
We used real-time reverse transcription polymerase chain reaction analysis of throat swab, blood, urine, and cerebrospinal fluid specimens to detect NiV. Further, the viral genome was sequenced and subjected to phylogenetic analysis. We conducted an epidemiologic investigation to describe the outbreak and elucidate the dynamics of NiV transmission.
During 2-29 May 2018, 23 cases were identified, including the index case; 18 were laboratory confirmed. The lineage of the NiV responsible for this outbreak was closer to the Bangladesh lineage. The median age of cases was 45 years; the sex of 15 (65%) was male. The median incubation period was 9.5 days (range, 6-14 days). Of the 23 cases, 20 (87%) had respiratory symptoms. The case-fatality rate was 91%; 2 cases survived. Risk factors for infection included close proximity (ie, touching, feeding, or nursing a NiV-infected person), enabling exposure to droplet infection. The public health response included isolation of cases, contact tracing, and enforcement of hospital infection control practices.
This is the first recorded NiV outbreak in South India. Early laboratory confirmation and an immediate public health response contained the outbreak.
This article proposes an 18-switch five-level inverter topology for induction motor (IM) drives, enabling an extended linear modulation range (LMR) till full base speed. The power circuit consists of ...a conventional NPC three-level inverter and a standard two-level inverter feeding the opposite phase winding ends of an open-ended winding IM. The proposed inverter achieves a voltage space vector radius of <inline-formula> <tex-math notation="LaTeX">0.955~{V}_{\text {dc}} </tex-math></inline-formula> and a maximum peak fundamental phase voltage of <inline-formula> <tex-math notation="LaTeX">0.637~{V}_{\text {dc}} </tex-math></inline-formula> in its LMR compared to a conventional five-level inverter with the corresponding figures of 0.866 and <inline-formula> <tex-math notation="LaTeX">0.577~{V}_{\text {dc}} </tex-math></inline-formula>, respectively. This improvement arises from the fact that in the overmodulation region spanning from 0.577 to <inline-formula> <tex-math notation="LaTeX">0.637~{V}_{\text {dc}} </tex-math></inline-formula>, the standard five-level inverter operates in a six-step mode, resulting in the voltage space vector trace a hexagonal path producing a lower-order harmonic-rich phase voltage. The proposed power circuit effectively addresses this issue by ensuring a circular locus for the voltage space vector up to a radius of <inline-formula> <tex-math notation="LaTeX">0.955~{V}_{\text {dc}} </tex-math></inline-formula> resulting in a maximum peak fundamental voltage of <inline-formula> <tex-math notation="LaTeX">0.637~{V}_{\text {dc}} </tex-math></inline-formula>. Consequently, it extends the linear speed range of the motor to the full base speed without lower-order harmonic problems.
Pulse-width modulated (PWM) inverters are known to generate common mode voltages which cause motor bearing currents in the induction motor drives. They also result in leakage currents which act as ...sources of conducted electromagnetic interference in the drive system. The common mode voltage generated by a conventional three-level inverter can be eliminated by switching only the voltage space vectors which do not produce the common mode voltage. This paper presents a PWM switching strategy to eliminate common mode voltage using the open-end winding configuration for the induction motor. The switching strategy presented in this paper, does not generate any alternating common mode voltages in the drive system and hence the electrostatic coupling of the common mode voltage, which results in the bearing currents and the leakage currents, is avoided. The proposed scheme is devoid of neutral point voltage fluctuations and does not require neutral point clamping diodes, when compared to the common mode elimination scheme based on the conventional three-level inverter topology. Also, the present scheme uses a single dc-link with half the voltage compared to the conventional three-level inverter based scheme.
A multilevel inverter for generating 17 voltage levels using a three-level flying capacitor inverter and cascaded H-bridge modules with floating capacitors has been proposed. Various aspects of the ...proposed inverter like capacitor voltage balancing have been presented in the present paper. Experimental results are presented to study the performance of the proposed converter. The stability of the capacitor balancing algorithm has been verified both during transients and steady-state operation. All the capacitors in this circuit can be balanced instantaneously by using one of the pole voltage combinations. Another advantage of this topology is its ability to generate all the voltages from a single dc-link power supply which enables back-to-back operation of converter. Also, the proposed inverter can be operated at all load power factors and modulation indices. Additional advantage is, if one of the H-bridges fail, the inverter can still be operated at full load with reduced number of levels. This configuration has very low dv/dt and common-mode voltage variation.
Transparent glasses are widely used for making optical and electronic devices. Transparent 20SrO–(15−x)Bi
2
O
3
−xCeO
2
–65B
2
O
3
(0 ≤ x ≤ 5, mol%) glasses are prepared via melt-quench technique and ...characterized using UV–visible and Fourier transform infrared spectroscopy (FT-IR) spectra. The ac conductivities of the glasses increase within the addition of CeO
2
. The physical parameter, density of the glass samples are characterized by Archimedes’ method. The optical absorption studies show that the present glass system behaves as a direct band gap semiconductor. The FT-IR studies show that the glasses are made up of BO
4
and BO
3
structural units. The conductivity analysis suggests that the charge transport occurs through the participation of nonbridging oxygen atoms.
Research on antioxidant biomarkers can generate profound insights into the defense mechanisms of fish larvae against different stressors and can reveal manipulation strategies for improved growth and ...survival. However, the number of samples to process and unavailability of required infrastructure in larval-rearing facilities limit the immediate processing, requiring the preservation of specimens. Silver pompano (
Trachinotus blochii
), a potential marine aquaculture species, shows a low larval survival rate due to poorly developed antioxidant mechanism. In this context, 39 storage conditions, including three storage temperatures and different buffers, were scrutinized to select the most suitable preservation strategy for five important antioxidant biomarkers of fish larvae, viz
.
catalase activity, superoxide dismutase (SOD) activity, measurement of lipid peroxidation, reduced glutathione (GSH), and ascorbic acid contents. The paper proposes the optimum larval storage conditions for these five evaluated antioxidant biomarkers to generate similar results in preserved and non-preserved larval samples. Larval samples preserved in PBS at lower temperatures (− 20 °C and − 80 °C) are recommended for evaluating catalase activity and ascorbic acid content. Catalase activity can also be evaluated by preserving the larval samples at − 20 °C or − 80 °C without buffers. Larval samples held in PBS or without any buffers at − 20 °C and at − 80 °C were found to be suitable for SOD and GSH evaluation, respectively. Preservation in 50% glacial acetic acid at − 80 °C or − 20 °C was preferred for the lipid peroxidation assays. Apart from methodological perspectives, the paper provides insights into the dynamics of larval antioxidant profiles of
T. blochii
, for the first time.
Graphical Abstract
Glass ceramics in the 20MO.55Bi2O3.25B2O3 (M=Sr, Ba) system were prepared by conventional melt quenching method, followed by heat treatment. XRD patterns show that the crystalline phase boron ...sillenite (Bi24B2O39) was formed on thermal treatment. The variation in the microstructure of the sample as a function of crystallization temperature was studied using scanning electron microscopy. The structural changes due to heat-treatment of the glasses have been explained on the basis of the changes in FT-IR and FT-Raman spectra. The glass ceramics in the present study have relatively high dielectric constant and low dielectric loss.
•Bi24B2O39 crystalline phase have been prepared in the 20MO.55Bi2O3.25B2O3 (M=Sr, Ba) glass system.•The formation of BiO3 units is favored during the conversion of glass into glass ceramics.•The glass ceramics prepared have high dielectric constants and low dielectric loss.
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