Maximum Propagation Distance Research Articles

Study on plasma expansion model of primary discharge on spacecraft solar array

In the space plasma environment, primary discharge may occur on the solar array and evolve into a destructive sustained arc, which threatens the safe operation of the spacecraft. Based on the plasma expansion fluid theory, a new multicomponent plasma expansion model is proposed in this study, which takes into account the effects of ion species, ion number, initial discharge current, and Low Earth Orbit (LEO) plasma environment. The expansion simulation of single-component and multicomponent ions is carried out respectively, and the variations of plasma number density, expansion distance, and speed during the expansion process are obtained. Compared with the experimental results, the evolution of propagation distance and speed is closed and the error is within a reasonable range, which verifies the validity and rationality of the model. The propagation characteristics of the primary discharge on the solar array surface and the influence of the initial value on the maximum propagation distance and the propagation current peaks are investigated. This study can provide important theoretical support for the propagation and evolution of the primary discharge and the key behavior of the transition to secondary discharge on spacecraft solar array.

Piperazine pyrophosphate-functionalized Ni-MOF metal framework: Fabrication and synergistic explosion suppression mechanisms

Dust explosion suppression is crucial for ensuring safe industrial operations. To explore composite explosion suppression powders with higher performance, piperazine pyrophosphate (PAPP)-functionalized nickel-based metal–organic framework (PAPP@Ni-MOF) synergistic suppression materials were designed and synthesized. The effectiveness of this suppressant in inhibiting the explosion flame and intensity of polypropylene (PP) dust was investigated using explosion flame propagation and explosion pressure test apparatus. The results indicate that the combination of N/P elements and Ni-MOF exhibits excellent catalytic carbonization performance. Adding 50 wt% PAPP@Ni-MOF can completely inhibit the propagation of PP explosion flames and the rise in explosion pressure. The maximum propagation distance of the explosion flame was reduced by 78.07 %, the overall flame propagation speed decreased by 84.54 %, and the maximum explosion pressure was reduced by 76.87 %. Through characterization experiments, the products before and after the explosion were analyzed. Combined with molecular dynamics (MD) simulation results, the efficient synergistic explosion suppression mechanism of PAPP@Ni-MOF for PP dust was revealed from the perspectives of thermal conduction isolation, key radical recombination, and volatile gas adsorption.

Effects of explosion-venting interlayer within utility tunnels on the characteristics of natural gas explosions

With the rapid expansion of the national economy and strategic adjustments to the energy structure, natural gas, a crucial clean energy source, encounters significant safety challenges during transportation in utility tunnels, owing to its flammable and explosive nature. To effectively address the current issues in response technologies for gas explosions in utility tunnels, such as inadequate control over the flame propagation range, limited attenuation of overpressure, and the mechanical impact damage effects on the internal structures of the utility tunnels and surrounding buildings, a small-scale experimental platform was constructed independently. This platform is designed to explore how the area and position of vents affect the characteristics of methane explosions within tunnels, utilizing the explosion venting mechanism. The results indicate that, for the same venting position, the maximum flame propagation distance, speed, and peak overpressure all decrease as the venting area increases. When the vent is located at position 1 in each compartment, the reduction in maximum flame propagation distance and speed is the most significant. The maximum decrease in peak overpressure occurs at venting position 2. When the venting position is closer to the ignition source, the rate of explosion overpressure rise and the explosion index both decrease with an increase in venting area, with the most significant reduction occurring at venting position 1. Conversely, when the venting position is farther from the ignition source, the rate of explosion overpressure rise and the explosion index actually increase, with the most significant increase occurring at venting position 4. The research findings offer a theoretical foundation and scientific guidance for developing new technologies aimed at mitigating gas explosion disasters in utility tunnels through internal venting.

Influence of component parameters on propagation characteristics of foaming polyurethane grout in rock fractures

Polyurethane grouting is an important technical solution used for seepage prevention and mechanical reinforcement of fractured rock. Various components of polyurethane grout significantly affect the grout properties and propagation behavior. The present study focuses on the crucial role of component parameters in controlling the propagation process and designing grouting parameters for foaming polyurethane grout. A coupled modeling approach combining chemical reactions and flow field analysis is developed to investigate the polyurethane foaming process. The proposed modeling approach is validated by comparing simulation results with experimental data from the literature. The influence of key component parameters: isocyanate index, initial water concentration and physical blowing agent, on the propagation characteristics (including propagation distance, maximum pressure, final density, reaction time and maximum temperature) of foaming polyurethane grout in rock fractures are further analyzed. The results reveal two distinct types of effects caused by the components, i.e., a monotonic relationship and a parabolic trend. Critical values are identified for the impact of isocyanate index on maximum propagation distance, final density and characteristic time, as well as for the influence of physical blowing agent on maximum propagation distance, final density and maximum pressure. Other parameters demonstrated a monotonic relationship. Additionally, a quantitative assessment is conducted to evaluate the impact of multiple components on propagation characteristics. The finding indicates that the initial water concentration has a significant effect on all properties, while isocyanate index exerts a more pronounced impact on reaction time and maximum temperature. The effect of the physical blowing agent is relatively minor compared to other factors. This study is helpful for material selection and proportioning of polyurethane grout in practical engineering applications.

Polygonal Laguerre-Gauss beams

We demonstrate that Laguerre-Gauss (LG) beams can have a polygonal distribution with the radial and azimuthal components, the so-called polygonal Laguerre-Gauss beams. These light beams are generated with a linear and trigonometric phase function of the angular coordinate which transform the Perfect LG beams with a lens. The polygonal Laguerre-Gauss beams preserve their distribution within a maximum propagation distance without diffraction similar to that used in the propagation-invariant light fields. We expect that these polygonal Laguerre-Gauss beams will be a method for creating any distribution controlling the radial and azimuthal components; moreover, they can be a proposal to control the number of the ring structures of the light beams.

Experimental investigation for the effect of bust pressure on hydrogen explosion venting

A series of experiments are carried out to investigate the effect of burst pressure on hydrogen explosion venting in a 20 L square vessel. Pressure buildup and flame evolution are recorded using piezoelectric pressure transducers, high speed camera, high speed infrared camera and schlieren system. The results show that both the maximum explosion pressure (Pmax) inside and outside the vessel increase with the increasing burst pressure, and the Pmax in the external space decreases rapidly with the increase of the distance from the vent port. Compared to the burst pressure of 0 kPa, the Pmax inside the vessel and at 1200 mm increased by 79.1 % and 153.6 %, respectively, when the burst pressure was 325 kPa. The venting flame surface during the propagation is smoother with the increasing burst pressure, the width and area of the flame also increases. There is little effect of burst pressure on the maximum flame propagation distance (Lmax), but with the increase of burst pressure, the flame propagation time is shortened and the average propagation velocity is increased. The venting flame propagation time is shortened from 5.0 ms to 3.5 ms with the burst pressure increases from 0 kPa to 325 kPa. The high temperature zone of venting flame is mainly distributed in the flame front, while the maximum flame temperature (Tmax) gradually increases with the increase of burst pressure. The increase in burst pressure results in an increase in the turbulence intensity inside the vessel and an advance in the time to stabilization inside the vessel. Furthermore, the moment at which flow backflow occurs at the vent port is advanced from 16.5 ms to 8.5 ms with the increase in burst pressure.

Compact planar meta‐lenses for nondiffracting surface wave deflection

AbstractA novel planar lens structure is proposed by using metasurfaces to convert cylindrical‐like surface wave to inclined nondiffracting wave with a deflection angle. Based on the geometric optics, the refractive index distribution of the surface wave lens is derived. A square metal ring‐shaped metasurface cell is used for realizing small refractive index whilst two opposite E‐shaped metal patches are used to form the meta‐cell with large refractive index. By adjusting the size of meta‐cells, the desired refractive index distribution is obtained after optimization. Measured results show that the inclined nondiffractive surface wave can be achieved with the maximum propagation distance of 99.72 mm at the tilted angle of 26.8°, which are consistent with the full‐wave simulation and numerical calculation results. The proposed meta‐lens achieves compact size, large titled angle, and long nondiffraction propagation distance, therefore could be well utilized in surface wave communication and nondestructive detection of surface defects.

On-chip generation of Bessel–Gaussian beam via concentrically distributed grating arrays for long-range sensing

Bessel beam featured with self-healing is essential to the optical sensing applications in the obstacle scattering environment. Integrated on-chip generation of the Bessel beam outperforms the conventional structure by small size, robustness, and alignment-free scheme. However, the maximum propagation distance (Zmax) provided by the existing approaches cannot support long-range sensing, and thus, it restricts its potential applications. In this work, we propose an integrated silicon photonic chip with unique structures featured with concentrically distributed grating arrays to generate the Bessel–Gaussian beam with a long propagation distance. The spot with the Bessel function profile is measured at 10.24 m without optical lenses, and the photonic chip’s operation wavelength can be continuously performed from 1500 to 1630 nm. To demonstrate the functionality of the generated Bessel–Gaussian beam, we also experimentally measure the rotation speeds of a spinning object via the rotational Doppler Effect and the distance through the phase laser ranging principle. The maximum error of the rotation speed in this experiment is measured to be 0.05%, indicating the minimum error in the current reports. By the compact size, low cost, and mass production potential of the integrated process, our approach is promising to readily enable the Bessel–Gaussian beam in widespread optical communication and micro-manipulation applications.

Performance analysis of an SDM-WDM multicore optical fiber link

Analytical evaluation of inter-channel and inter-core coupling induced crosstalk including Amplified Spontaneous Emission (ASE) noise in a single mode 7-core homogeneous multi-core optical fiber (MCF) based Space Division Multiplexed Wavelength Division Multiplexing (SDM-WDM) communication system with distributed Raman amplifier is presented. The Stimulated Raman Scattering (SRS) induced crosstalk impairment including ASE noise and inter-core and inter-channel coupling induced crosstalk at the output of any core with excitation into other core of the MCF is investigated. Signal to Crosstalk plus Noise Ratio (SCNR) is determined at the output of photo detector of the excited core. Finally, Bit Error Rate (BER) performance results are evaluated for different system parameters, viz. WDM channel number, channel spacing, propagation distance, pump power etc. It is noticed that BER deteriorates with SRS induced crosstalk and ASE noise, which is worsened further by the effect of inter-core crosstalk (IC-XT). The maximum acceptable propagation distance for a desired value of BER and other system parameters considering inter-channel crosstalk (Ich-XT), IC-XT including SRS induced crosstalk and ASE noise is also evaluated analytically. For example, to maintain a particular BER (10E-9, say) we need to increase the input signal power from 2.5dBm to 5.5dBm while increasing the WDM channels from 12 to 16 considering only the SRS and ASE noise. On the other hand, we need to increase the input signal power from 5.5dBm to 9.0dBm to increase the WDM channels from 12 to 16 when the IC-XT is added up with the SRS and ASE noise. The maximum allowable pump power considering the collective impact of Ich-XT and IC-XT including SRS and ASE noise is determined for a given value of BER (10E-9). Power penalty versus WDM channel spacing at a given BER value (10E-10), link distance and pump power at different WDM channels is also evaluated and presented.

Generation and propagation of Airy beams and 1-inch diameter focusing optics using three-dimensional-printed polymer optics

The additive manufacture of polymer optical elements has the promise of reducing component weight, providing new design capabilities, and enhanced performance for a wide variety of military and commercial optical systems. We review progress in the development of three-dimensional (3D)-printed gradient index (GRIN) lenses and optical phase masks. The 3D printing process uses a modified commercial inkjet printer and ultraviolet curable polymers that have specific nanoparticles added to them to modulate the index of refraction. Complex optical phase masks for the generation of Airy laser beams and polymer GRIN lenses to replace conventional glass lenses used in a telescope or riflescope are created. The generation and propagation of Airy beams using these polymer-generated optical phase masks have been investigated and analyzed through experimentation, simulations, and comparison with recent theoretical predictions. Airy beams have been generated using the conventional approach with a spatial light modulator and compared to the 3D printed optical phase masks. The maximum nondiffracting propagation distance of an aperture truncated Airy beam was experimentally measured. The results show that the maximum nondiffracting propagation distance of a laboratory generated Airy beam is proportional to x02, the Airy beam waist size squared. The size of the Gaussian envelope beam has a weaker effect on the Airy beam propagation distance. The experimental results were compared with current theoretical models. A set of 1-inch-diameter 100-mm focal length polymer GRIN lenses have been made using 3D printing. Transmission and modulation transfer function results for the lenses are reported.

Explosion Flame and Pressure Characteristics of Nonstick Coal Dust and the Inhibition of Explosion Suppressants

Nonstick coal is widely distributed in the world and is an important resource for human beings. The explosion characteristics and explosion suppression of nonstick coal dust are increasingly concerning. In this paper, the flame and pressure characteristics of a nonstick coal dust explosion are studied, and the suppression effect of SiO2, KCl, and NH4H2PO4 on the explosion is analyzed. It is concluded that the maximum propagation distance of a nonstick coal dust explosion flame is 0.59 m, the maximum pressure is 0.63 MPa, and the maximum pressure rise rate is 40.79 MPa/s. The explosion suppression effect of SiO2 is worse than that of KCl, but the inhibition effect of NH4H2PO4 is the best among the three kinds of explosion suppressants. When the mass percentage of NH4H2PO4 dust mixed with coal dust is 70%, the coal dust explosion is completely suppressed. It absorbs a certain amount of heat to promote the chemical reaction, which plays a certain role in controlling the explosion process, and its explosion suppression mechanism includes both physical and chemical explosion suppression.

6G Network Architecture Using FSO-PDM/PV-OCDMA System with Weather Performance Analysis

This paper presents a novel 160 Gbps free space optics (FSO) communication system for 6G applications. Polarization division multiplexing (PDM) is integrated with an optical code division multiple access (OCDMA) technique to form a PDM-OCDMA hybrid. There are two polarization states: one is X-polarization generated from adjusting the azimuthal angle of a light source at 0° while the other is Y-polarization which is generated by adjusting the azimuthal angle of a light source at 90°. Each polarization state is used for the transmission of four independent users. Each channel is assigned by permutation vector (PV) codes and carries 20 Gbps data. Four different weather conditions are considered for evaluating the performance of our proposed model. These weather conditions are clear air (CA), foggy conditions (low fog (LF), medium fog (MF), and heavy fog (HF)), dust storms (low dust storm (LD), moderate dust storm (MD), heavy dust storm (HD)), and snowfall (wet snow (WS) and dry snow (DS)). Bit error rate (BER), Q-factors, maximum propagation range, channel capacity, and eye diagrams are used for evaluating the performance of the proposed model. Simulation results assure successful transmission of 160 Gbps overall capacity for eight channels. The longest FSO range is 7 km which occurred under CA while the minimum is achieved under HD, which is 0.112 km due to large attenuation caused by HD. Within fog conditions, the maximum propagation distances are 1.525 km in LF, 1.05 km in MF, and 0.85 km in HF. Likewise, under WS and DS, the proposed system can support transmission distances of 1.15 km and 0.28 km, respectively. All these transmission distances are achieved at BER less than 10−5.

Operation and Qualification of Coaxial Plasma Gun Modes With a Gas Puff Inlet

We describe the design, operation, and qualification of a coaxial plasma gun (CPG) in a low-pressure environment with a gas puff inlet. This infrastructure enables a CPG to operate in the deflagration mode followed by snowplow plasma sheath formation. These modes inject radially expanding and axially propagating plasma sheaths into a low-pressure residual background. This manuscript details the pulse power delivery circuit, including automatic logic control of subcircuits. High-speed camera images (12800 frames/s) of the formed plasma elucidate the ionization of an axially propagating plasma. Long-exposure images (1.3 s) capture the full propagation distance of the plasmoid. Rogowski coil current diagnostics elucidate the timing of a self-crowbar discharge that delineates between deflagration and snowplow modes. An empirically determined 50-ms gas puff duration resulted in a maximum plasma propagation distance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 23$ </tex-math></inline-formula> cm. Shorter durations did not ionize a sufficient amount of gas for elongated axial propagation, whereas longer durations suppressed axial plasma sheath expansion. This type of gas injection CPG device is now qualified for use in CPG experiments that require the snowplow mode and maximum mean free path of fast ions resulting from various plasma heating mechanisms. These include CPG operation within external magnetic fields in which significant plasma propagation distance is required, including solar physics experiments and space propulsion development.

Mutually guided light and particle beam propagation

The polarizability of atoms and molecules gives rise to optical forces that trap particles and a refractive index that guides light beams, potentially leading to a self-guided laser and particle beam propagation. In this paper, the mutual interactions between an expanding particle beam and a diffracting light beam are investigated using an axisymmetric particle-light coupled simulation. The nonlinear coupling between particles and photons is dependent on the particle beam radius, particle density, particle velocity and temperature, polarizability, light beam waist, light frequency (with respect to the resonance frequency), and light intensity. The computational results show that the maximum propagation distance is achieved when the waveguiding effect is optimized to single-mode operation. The application of the coupled beam propagation as a space propulsion system is discussed.

Survey on encode biometric data for transmission in wireless communication networks

The aim of this research survey is to review an enhanced model supported by artificial intelligence to encode biometric data for transmission in wireless communication networks can be tricky as performance decreases with increasing size due to interference, especially if channels and network topology are not selected carefully beforehand. Additionally, network dissociations may occur easily if crucial links fail as redundancy is neglected for signal transmission. Therefore, we present several algorithms and its implementation which addresses this problem by finding a network topology and channel assignment that minimizes interference and thus allows a deployment to increase its throughput performance by utilizing more bandwidth in the local spectrum by reducing coverage as well as connectivity issues in multiple AI-based techniques. Our evaluation survey shows an increase in throughput performance of up to multiple times or more compared to a baseline scenario where an optimization has not taken place and only one channel for the whole network is used with AI-based techniques. Furthermore, our solution also provides a robust signal transmission which tackles the issue of network partition for coverage and for single link failures by using airborne wireless network. The highest end-to-end connectivity stands at 10 Mbps data rate with a maximum propagation distance of several kilometers. The transmission in wireless network coverage depicted with several signal transmission data rate with 10 Mbps as it has lowest coverage issue with moderate range of propagation distance using enhanced model to encode biometric data for transmission in wireless communication.

Experiment on influence of inert powder on deflagration of oil shale dust research

AbstractTo study the effect of inert powder on the deflagration of oil shale dust, the Hartmann tube experiment device and 20 L spherical explosion experiment device were used. The effects of three kinds of inert powder (KH2PO4, NaHCO3, Al(OH)3) and widely used rock powder (CaCO3) on the deflagration of oil shale dust in different proportions were studied. The results show that the four inert powders can effectively dilute the concentration of oil shale dust cloud, slow down the reaction rate, delay the flame propagation, and reduce the maximum flame propagation speed. When 50 wt% KH2PO4, NaHCO3, CaCO3, Al(OH)3 inert powder is added, the maximum flame propagation speed is 44.14%, 41.11%, 31.79%, 58.96%, and the maximum explosion pressure drop is 70.0%, 66.0%, 59.5%, 77.0%. When Al(OH)3 was added at 10 wt%, 30 wt%, and 50 wt%, the combustion time of oil shale was extended to 162.7, 223.4, and 321.5 ms, respectively. With the addition of Al(OH)3, the time from ignition time to maximum explosion pressure of oil shale dust increases gradually, the maximum flame propagation distance is shortened obviously, the maximum flame propagation speed and maximum explosion pressure drop the most, and the effect of inhibiting oil shale dust deflagration flame is the best.

Spectrally recycling space-time wave packets

'Space-time' (ST) wave packets are propagation-invariant pulsed optical beams that travel rigidly in linear media without diffraction or dispersion at a potentially arbitrary group velocity. These unique characteristics are a result of spatio-temporal spectral correlations introduced into the field; specifically, each spatial frequency is associated with a single temporal frequency (or wavelength). Consequently, the spatial and temporal bandwidths of ST wave packets are correlated, so that exploiting an optical source with a large temporal bandwidth or achieving an ultralow group velocity necessitate an exorbitantly large numerical aperture. Here we show that `spectral recycling' can help overcome these challenges. 'Recycling' or `reusing' each spatial frequency by associating it with multiple distinct but widely separated temporal frequencies allows one to circumvent the proportionality between the spatial and temporal bandwidths of ST wave packets, which has been one of their permanent characteristics since their inception. We demonstrate experimentally that the propagation invariance, maximum propagation distance, and group velocity of ST wave packets are unaffected by spectral recycling. We also synthesize a ST wave packet with group velocity c/14.3 (c is the speed of light in vacuum) with a reasonable numerical aperture made possible by spectral recycling.

The effects of Tx./Rx. pointing errors on the performance efficiency of local area optical wireless communication networks

Abstract This study presents the effects of Tx./Rx. pointing errors on the performance efficiency of local area optical wireless communication networks. The received signal power and max Q factor are measured in the presence of vertical-cavity surface-emitting lasers (VCSELs) bias current and modulation current at maximum propagation distance for the wireless network. The signal is enhanced with increasing of bias and modulation peak currents of the VCSEL device. The optimum received power and max. Q factor is also examined at Tx./Rx. the pointing error of 0.1 mrad and propagation reach of 5 km at available bit rates transmission of 10 Gb/s.

Lens-based phase retrieval under spatially partially coherent illumination—Part I: Theory

We present a novel approach of phase retrieval using a 4f-imaging system, for the specific case of spatially partially coherent illumination. The theoretical investigation presented in Part I is based on scalar diffraction theory in combination with a heuristic approach. We find that the intensity of the de-focused speckle fields across the image plane shows sufficient contrast for phase retrieval, as long as the radius of the point spread function of the imaging system is well below the radius of the correlation area (spatial coherence) in the object plane. We also derive a useful relation, which allows to determine the requirements towards the essential parameters of an experimental setup, such as maximum propagation distance, diameter of the source, illumination distance and the numerical aperture of the imaging system. The consecutive paper, Part II, describes shape measurement based on the present treatise.

Generation of nondiffraction beams by using graphene‐based metasurface in terahertz regime

AbstractIn this article, a graphene‐based reflective metasurface which can generate Bessel beams at arbitrary directions is proposed at 1.52 THz. It chooses the classical cross structure as the unit cell and extends the coverage of the reflection phase to 360° by adjusting two key parameters while maintaining a relatively high‐reflection amplitude. Combined with the excellent impedance characteristics of graphene in the terahertz regime and the long energy transmission distance of the nondiffraction beam, the reflective metasurface finally realize the pseudo‐Bessel beam with a maximum propagation distance of about 3358.85 um and a deflection of about 15° in yoz‐plane as expected. Two forms of efficiency are proposed for the metasurface, one is the focusing efficiency, the other is the conventional radiation efficiency. The simulation results show that the former shows a trend of increasing first and then decreasing, which conforms to the beam‐forming property of Bessel beam; the latter can be basically maintained at high value of 70% within the nondiffraction propagation distance, which conforms to the energy transmission characteristic of the nondiffraction beam. All the studies show that the graphene‐based metasurface combined with the nondiffraction theory has the advantages of highly controllable beam deflection, long focusing distance, and high‐energy transfer efficiency in the terahertz regime, so it will have a broad application prospect in terahertz telecommunication, wireless energy transmission, near‐field detecting, imaging and many other fields.