Maximum Peak Value Research Articles

Influence of the different stress paths on rock deformation memory effects using the deformation rate analysis method

Deformation memory effect (DME) is a common property of the rock. A method called Deformation Rate Analysis (DRA) which is based on DME provides a brand-new approach to measuring in situ stress. When rock DME is applied in engineering, it is necessary to solve the problem that which stress peak is corresponding to in situ stress. The standard square samples made of sandstone and granite were selected to investigate the rock DME under different stress paths. Then a memory theoretical model based on multi-surface sliding friction hysteresis is used to analyze the mechanisms of rock DME. The results show that: (1) Rocks always remember the maximum peak stress from preloading, regardless of the sequence of multiple preloading; (2) Multi-memory exists in tests because we found another inflection in DRA curve; (3) The memory model based on sliding friction hysteresis shows the precision of memory information formation increases as the historical maximum peak value gets closer to the measurement load, but multi-memory does not exist in theoretical analysis. The conclusion provides the rule of rock DME under different stress path which would benefits in in situ stress reconstruction.

Hemispheric Sunspot Number Prediction for Solar Cycles 25 and 26 Using Spectral Analysis and Machine Learning Techniques

The present study uses machine learning and time series spectral analysis to develop a novel technique to forecast the sunspot number (SN) in both hemispheres for the remainder of Solar Cycle 25 and Solar Cycle 26. This enables us to offer predictions for hemispheric SN until January 2038 (using the 13-month running average). For the Northern hemisphere, we find maximum peak values for Solar Cycles 25 and 26 of 58.5 in April 2023 and 51.5 in November 2033, respectively (root mean square error of 6.1). For the Southern hemisphere, the predicted maximum peak values for Solar Cycles 25 and 26 are 77.0 in September 2024 and 70.1 in November 2034, respectively (root mean square error of 6.8). In this sense, the results presented here predict a Southern hemisphere prevalence over the Northern hemisphere, in terms of SN, for Solar Cycles 25 and 26, thus continuing a trend that began around 1980, after the last period of Northern hemisphere prevalence (which, in turn, started around 1900). On the other hand, for both hemispheres, our findings predict lower maxima for Solar Cycles 25 and 26 than the preceding cycles. This fact implies that, when predicting the total SN as the sum of the two hemispheric forecasts, Solar Cycles 24 – 26 may be part of a centennial Gleissberg cycle’s minimum, as was the case in the final years of the 19th century and the start of the 20th century (Solar Cycles 12, 13, and 14).

Summary of seven Swedish case reports on the microwave syndrome associated with 5G radiofrequency radiation.

The fifth generation, 5G, for wireless communication is currently deployed in Sweden since 2019/2020, as well as in many other countries. We have previously published seven case reports that include a total of 16 persons aged between 4 and 83 years that developed the microwave syndrome within short time after being exposed to 5G base stations close to their dwellings. In all cases high radiofrequency (RF) radiation from 4G/5G was measured with a broadband meter. RF radiation reached >2,500,000 to >3,180,000 μW/m2 in peak maximum value in three of the studies. In total 41 different health issues were assessed for each person graded 0 (no complaint) to 10 (worst symptoms). Most prevalent and severe were sleeping difficultly (insomnia, waking night time, early wake-up), headache, fatique, irritability, concentration problems, loss of immediate memory, emotional distress, depression tendency, anxiety/panic, dysesthesia (unusual touched based sensations), burning and lancinating skin, cardiovascular symptoms (transitory high or irregular pulse), dyspnea, and pain in muscles and joints. Balance disorder and tinnitus were less prevalent. All these symptoms are included in the microwave syndrome. In most cases the symptoms declined and disappeared within a short time period after the studied persons had moved to a place with no 5G. These case histories are classical examples of provocation studies. They reinforce the urgency to inhibit the deployment of 5G until more safety studies have been performed.

Assessment of the azimuthal loads variation by a bi-rotor configuration

Multi wind turbine configurations are emerging in the offshore wind energy market. The modelling of the aerodynamics of these systems is challenging, due to the small lateral distance between rotors and the subsequent interaction between wakes. Previous analysis in the literature showed that, due to this interaction, multi wind turbine concepts present the advantage of an increment in power production, if the rotors are laterally aligned. However, the counterpart in the variation of the blade loads throughout the revolution, has yet to be analysed in depth. This study focuses on the differences observed in azimuthal cycles of blade aerodynamic loads in side-by-side bi-rotor configurations, as an initial analysis of their potential impact on fatigue loads. The analysis has been developed using two aerodynamic codes, with different levels of fidelity. These models are: a Free Vortex filament Method (FVM) combined with an unsteady Lifting Line (LL) model, and a URANS-blade resolved approach. The simulations show that the sectional blade loads are affected by the adjacent rotor, changing the shape of the aerodynamic load cycles along the azimuth. The load azimuthal distributions predicted by a FVM and a URANS models have been compared, showing agreement on the shape of the cycle with slight differences on maximum peak values, specially at the inner sections of the blade. The FVM model has predicted increments in the blade load cycles, with respect to a single rotor case, with a maximum amplitude of a 3% for out-of-plane forces, and a 8% for in-plane forces. The difference in the azimuthal position of both rotors (phase shift angle) mainly affects the azimuthal shape and not so much the characteristic amplitude of these cycles. Finally, including geometric angles as tilt or pre-cone, produces imbalances between the blade sectional forces of the different rotors.

Genome-wide identification and expression analysis of the SPL transcription factor family and its response to abiotic stress in Pisum sativum L

Squamous promoter binding protein-like (SPL) genes encode plant-specific transcription factors (TFs) that play essential roles in modulating plant growth, development, and stress response. Pea (Pisum sativum L.) is a coarse grain crop of great importance in food production, biodiversity conservation and molecular genetic research, providing genetic information and nutritional resources for improving agricultural production and promoting human health. However, only limited researches on the structure and functions of SPL genes exist in pea (PsSPLs). In this study, we identified 22 PsSPLs and conducted a genome-wide analysis of their physical characteristics, chromosome distribution, gene structure, phylogenetic evolution and gene expression patterns. As a result, the PsSPLs were unevenly distributed on the seven chromosomes of pea and harbored the SBP domain, which is composed of approximately 76 amino acid residues. The phylogenetic analysis revealed that the PsSPLs clustered into eight subfamilies and showed high homology with SPL genes in soybean. Further analysis showed the presence of segmental duplications in the PsSPLs. The expression patterns of 22 PsSPLs at different tissues, developmental stages and under various stimulus conditions were evaluated by qRT-PCR method. It was found that the expression patterns of PsSPLs from the same subfamily were similar in different tissues, the transcripts of most PsSPLs reached the maximum peak value at 14 days after anthesis in the pod. Abiotic stresses can cause significantly up-regulated PsSPL19 expression with spatiotemporal specificity, in addition, four plant hormones can cause the up-regulated expression of most PsSPLs including PsSPL19 in a time-dependent manner. Therefore, PsSPL19 could be a key candidate gene for signal transduction during pea growth and development, pod formation, abiotic stress and plant hormone response. Our findings should provide insights for the elucidating of development regulation mechanism and breeding for resistance to abiotic stress pea.

The role of nanosize dependence of dislocation and surface roughness concentrations to calculate lattice thermal conductivity in In0.53Ga0.47As nanofilms

ABSTRACT Systematic empirical relations were established for the nanosize-dependent surface roughness, ϵ ( D ) , dislocations, N D ( D ) , and effective length to examine their effects on the temperature-dependent lattice thermal conductivity (LTC) within the framework of the Morelli-Callaway model for In0.53Ga0.47As alloy films with thicknesses ranging from 10 to 70 and 1400 nm, the latter representing the material’s bulk state. The results were analyzed for film thicknesses of 2, 5, 200, and 500 nm, under the assumption that electrons and impurities are unaffected by nanosize, while a small alloy parameter significantly and sensitively alters the LTC curve in medium and high-temperature regions. According to these new findings, and considering phonon scattering processes, the LTC’s temperature dependence is sufficiently reduced at the nanoscale and fits well with the available reported experimental findings. It was also discovered that the LTC’s peak maximum value and its corresponding temperature are influenced by the film’s dislocation concentration, surface roughness, and thickness. Unravelling the complex interplay between nanosize-dependent dislocation and surface roughness concentrations becomes critical for a thorough knowledge when examining the delicate nuances of LTC in In0.53Ga0.47As nanofilms. Finally, the Morelli-Callaway-based model has been modified to calculate LTC for nanofilms without fitting parameters, provided their related bulk state values are known.

Responsive regularity of neurons in the hindlimb region of primary somatosensory cortex to different temperature thermal needle stimulation of "Zusanli"(ST36) in mice.

To study the regularity of central response to thermal needle stimulation of "Zusanli" (ST36) at different temperature, and to analyze the temperature difference of central responses. Six male C57BL/6j adult mice were used in the present study. For observing activities of neurons in the hindlimb region of left primary somatosensory cortex (S1HL, A/P=0.46 mm, M/L=1.32 mm, D/V=-0.14 mm) by using a fast high-resolution miniature two-photon microscopy (FHIRM-TPM), the mice were anesthetized with 3% isoflurane (inhalation), with its head fixed in a stereotaxic apparatus, then, adeno-associated virus (AAV-hSyn-GCaMP6f-WPRE-hGHpA, for showing intracellular calcium transients in neurons transfected) was injected into the left S1HL region using a micro-syringe after scalp surgical operation. The mice's right ST36 were stimulated using internal thermal needles with the temperature being 43 ℃, or 45 ℃, or 47 ℃, separately. Image J software and MATLAB 2020b software were used to process the image data of neuronal calcium activity (Ca2+ signaling) in the left S1HL region, including the instant maximum calcium peak value (ΔF/F) in 2 s, instant calcium spike frequency in 2 s, short-term calcium peak value (ΔF/F) in 3.5 min, short-term calcium spike frequency in 3.5 min, calcium peak duration in 3.5 min, maximum calcium peak value (ΔF/F) at the 1st , 2nd and 3rd min, and calcium spike frequency at the 1st, 2nd and 3rd min after thermal needle stimulation. In comparison with the normal temperature needle stimulation, the instant intracellular maximum calcium peak value, instant calcium spike frequency, short-term maximum calcium peak value, short-term calcium spike frequency, and calcium peak duration of S1HL neurons in response to 43 ℃, 45 ℃ and 47 ℃ internal thermal needle stimulation of ST36 were significantly increased (P<0.001, P<0.01). Comparison among the 43 ℃, 45 ℃ and 47 ℃ thermal needle stimulation showed that the 45 ℃ thermal needle stimulation was obviously superior to 43 ℃ and 47 ℃ thermal needle stimulation in increasing instant calcium spike frequency, short-term calcium spike frequency and calcium peak duration of S1HL neurons (P<0.001, P<0.01). The 47 ℃ thermal needle stimulation was stronger than 43 ℃ and 45 ℃ thermal needle stimulation in increasing the instant maximum calcium peak value (P<0.001). The maximum calcium peak value was apparently higher (P<0.001) at the 2nd min than that at the 1st and 3rd min after 43 ℃, 45 ℃ and 47 ℃ thermal needle stimulation. No significant differences were found in the short-term maximum calcium peak value among the 3 thermal needle stimulation and in the calcium spike frequency among the 3 time points after 43 ℃, 45 ℃ and 47 ℃ thermal needle stimulation. S1HL neurons respond to all 43 ℃, 45 ℃ and 47 ℃ thermal needle stimulation of ST36 in mice, while more actively to 45 ℃ thermal needle stimulation.

Crashworthiness of AAG joints with a foam aluminum layer gusset plate

The gusset joint is the most widely used joint system in an aluminum alloy single-layer reticulated shell structure; it plays a vital role in the spatial grid structure. In this paper, the effects of different thicknesses of aluminum alloy gusset plates on the dynamic response and failure modes of aluminum alloy gusset (AAG) joints were studied by impact tests of three specimens. The test results show that the failure modes of AAG joints are a slight depression of the gusset plate, the local buckling of members, the local distortional buckling of members, and tearing of the lower flange and a web of members. The AAG joint inclines along the direction of the failed member and collapses. The finite element model of the AAG joint was established using ANSYS software. The stress, displacement, and deformation modes in the test and numerical simulation results were compared and analyzed, and the rationality of the numerical simulation results was verified. Based on the failure mode of the specimens, a design method for improving the impact resistance of AAG joints with aluminum foam layer gusset plate (AFLGP) is proposed. The numerical simulation results show that an AAG joint with an AFLGP effectively reduces the maximum peak value of impact loads through the deformation of the aluminum foam. In the elastic and elastic-plastic stages, AAG joint with AFLGP had better impact resistance, and the energy absorbed by its rods was 25.44% ∼ 30.36% lower than that of AAG joints alone. Finally, the influence of the thickness of the AFLGP on the impact force and energy absorption of the AAG joint was studied. The aluminum foam gusset layer plate is approximately twice as thick as the aluminum alloy gusset plate had the best protection effect on the AAG joint.

Modulation of impedance matching of hollow cubic carbon with semi-closed structure for effective microwave absorption

In this paper, a certain degree of semi-closed structure was successfully introduced in hollow cubic carbons (HCCs) by selective dissolution of phenolic resin (PR)/NaCl precursor by acetone. The impedance matching of the HCCs absorber was improved, which in turn lead to the enhancement of the electromagnetic wave absorption capacity. By controlling the selective dissolution time of acetone, HCCs with different degrees of integrity were formed, and the degree and mechanism of the influence of the semi-closed structure of HCCs on the wave absorbing properties were investigated by analyzing the microstructure and physical phase composition of HCCs. From the scanning electron microscope photographs, it can be seen that with the increase of the acetone treatment time of HCCs, the samples gradually appeared a certain degree of semi-closed structure. With the extension of the acetone treatment time to 60 min, the structure of the HCCs was seriously damaged, at which time the impedance matching of the wave-absorbing materials was seriously deteriorated, and the electromagnetic wave absorption performance was also decreased. Among them, the electromagnetic wave absorption performance of HCCs30min is the most outstanding, specifically, when the loading rate is 10 wt%, the maximum absorption peak value of HCCs30min with a thickness of 2.7 mm reaches −41.1 dB, and the corresponding absorption bandwidth is 3.8 GHz (8.9 GHz–12.7 GHz). The experiment confirms that the existence of the degree of structural integrity can affect the impedance matching and wave absorption performance of HCCs.

Intelligent Method for Corrosion Detection and Quantification in Aircraft Lap Joints Using Pulsed Eddy Current

Nondestructive evaluation using pulsed eddy current (PEC) has remarkable capabilities for the detection and characterization of hidden corrosion in multilayer structures. Previous works proposed maximum peak value, time-to-peak, and time-to-zero crossing of PEC signals for hidden corrosion detection. In practice, there are two important noise sources: probe liftoff and interlayer gap. These noise sources disable the aforementioned components in defect detection and classification. This paper delivers a new intelligent method for detection and classification of corrosion defects in two-layer structures at the presence of gap and liftoff. Application independent component analysis and principal component analysis to PEC signals for features extraction and Fisher’s linear discriminant method for classification provide an automatic material loss characterization in multilayer structures. Comparing the results with conventional methods based on PEC signals shows the importance of post-processing methods in the detection and quantification of corrosion.

Estimation on magnetic entropy change and specific heat capacity through phoenomological model for Heusler melt spun ribbon of Ni47Mn40−x Si x In3 (x = 1, 2 and 3)

Abstract In this, we report the temperature-dependent magnetization [M(T)] in two distinct magnetic fields of 0.5 T and 5 T for Ni47Mn40−x Si x In3 (x = 1, 2, and 3) alloys. Using a phenomenological model and Maxwell’s thermodynamic relation, the values of the magnetic entropy change and specific heat capacity are calculated, and their values are also compared. The maximum magnetic entropy change and specific heat capacity peak values for different magnetic fields are both steadily reduced for the samples with x = 1 to 3 samples, which is followed by an increase in relative cooling power value. In comparison to 0.5 T magnetic field, the samples investigate the highest values of magnetic entropy change (3.32, 2.81, 2.01 J kg−1 K−1) and specific heat capacity (32.37, 14, 4.32 J kg−1 K−1) with a magnetic field of 5 T. According to this finding, the sample is more responsible for the magnetic field than chemical pressure.

Polymer Nanocomposites Based on Nanosized Substituted Ferrites (NiZn)1-xMnxFe2O4 on the Surface of Carbon Nanotubes for Effective Interaction with High-Frequency EM Radiation.

To create materials that interact effectively with electromagnetic (EM) radiation, new nanosized substituted ferrites (NiZn)1-xMnxFe2O4 (x = 0, 0.5, and 1) anchored on the surface of multi-walled carbon nanotubes (CNTs) have been synthesized. The concentration of CNTs in the (NiZn)1-xMnxFe2O4/CNT system was from 0.05 to 0.07 vol. fractions. The dielectric and magnetic characteristics of both pristine (NiZn)1-xMnxFe2O4 ferrites and (NiZn)1-xMnxFe2O4/CNT composite systems were studied. The introduction of (NiZn)1-xMnxFe2O4/CNT composites into the amorphous epoxy matrix allows to tailor absorbing properties at the high-frequency by effectively shifting the maximum peak values of the absorption and reflection coefficient to a region of lower frequencies (20-30 GHz). The microwave adsorption properties of (NiZn)1-xMnxFe2O4/0.07CNT-ER (x = 0.5) systems showed that the maximum absorption bandwidth with reflection loss below -10 dB is about 11 GHz.

Study on Deformation Behavior and Mechanical Properties of 42CrMo High-Strength Steel with Multi-Station Warm Upsetting

In order to find out the deformation behavior and mechanical properties of 42CrMo steel under warm upsetting conditions, the Gleeble-3500 thermal simulation testing machine was used to carry out a warm upsetting physical simulation experiment on 42CrMo steel. By controlling deformation temperature, strain rate, and constant temperature deformation pass, the microstructure evolution rule under different warm upsetting conditions was analyzed, and its hardness value was measured. Then, the simulation experiment is carried out based on the Deform-3D finite element platform. The results show that, with the increase in deformation temperature, 42CrMo steel has a temperature rise softening effect, which significantly reduces the peak value of rheological stress. At 650 °C, the maximum peak value of rheological stress is only 45.3% of that of cold upsetting deformation at room temperature, and the stress-strain curve tends to be gentle at the plastic deformation stage, which is the most suitable temperature for warm upsetting deformation. The maximum peak flow stress of 42CrMo steel increases with the increase in strain rate, but the number of deformation channels has little influence on the stress-strain curve. The warm, upsetting deformation can refine the internal grain structure significantly, and the grain refinement mechanism is mechanical crushing. When the temperature is slightly higher, the broken grain will recover, and the grain size will grow. During the process of warm upsetting, the strain rate has a great influence on the microhardness of the sample. The deformation pass has little influence on the hardness, and the hardness increases slightly with the increase in the deformation pass. Through the Deform-3D simulation, the correlation coefficient R and the average absolute relative error (AARE) between the simulation value and the experimental value were calculated, and the correlation coefficient R-value was 0.9948, and the average absolute relative error (AARE) was 2.05%, indicating that the simulation can accurately reflect the relationship between displacement and applied load.

Field-induced Bose–Einstein condensation in zigzag spin chain KGaCu(PO4)2

Single crystals of GaKCu(PO4)2 were synthesized using the hydrothermal method, and subsequent measurements of specific heat, magnetic susceptibility, and high-field magnetization were performed. A broad peak is observed in the magnetic susceptibility and specific heat curves, with the maximum values appearing at about 11.5 K and 5.29 K, respectively. The highest maximum peak value of susceptibility is observed when the magnetic field is applied along the c-axis, followed by the a-axis, b-axis, and polycrystalline samples. These indicate that the system exhibits one-dimensional magnetism and the magnetic easy axis is the c axis. The magnetization at 2 K reveals the occurrence of a field-induced Bose–Einstein condensation (BEC) phase within the magnetic field range of approximately 8−12 T. High-field magnetization up to 40 T indicates that the compound reaches magnetization saturation as the field exceeds H s = 12 T. Through systematic measurements, a field-temperature (H−T) phase diagram was constructed, and dome-like phase boundaries were observed. The findings suggest that GaKCu(PO4)2 is a spin gap system and a promising candidate for studying BEC of magnons due to its phase transition boundary occurring at low magnetic fields.

Injury of flexor halluics longus tendon in amateur marathon runners results in abnormal plantar pressure distribution: observational study

ObjectiveTo analyze the changes of plantar pressure in amateur marathon runners with flexor halluics longus (FHL) tendon injury using the Medtrack-Gait plantar pressure measurement system, and to explore whether the plantar pressure data can be used as an index for the diagnosis of injury.MethodsA total of 39 healthy amateur marathon runners without any ankle joint symptoms were recruited. Dynamic and static plantar pressure data were measured using the pressure plate of Medtrack-Gait. According to MRI imaging findings, whether the FHL tendon was injured or not was judged, and the dynamic and static data were divided into the injury group and control group. The data with statistically significant differences between the two groups were used to make the receiver operating characteristic (ROC) curve.ResultThe maximum contact area (PA) of the first metatarsal(M1) region, the maximum load-bearing peak value (PW) and the time pressure integral (PMPTI) of the second metatarsal(M2) region in the injury group were lower than those in the control group, respectively (P < 0.05). The maximum contact area (PA) of the fifth metatarsal(M5) region was higher than that in the control group (P < 0.05). The area under curve (AUC) value of the ROC curve of the PA of M1 region, the PW and PMPTI of M2 region were statistically (P < 0.05).ConclusionFHL tendon injury resulted in decreased PA in M1, decreased PW and PMPTI in M2, and increased PA in the M5 region, suggesting that FHL tendon injury resulted in a force shift from the medial to the lateral side of the foot. The PA of M1, PW and PMPTI of M2 have certain diagnostic value for early FHL injury in amateur marathon runners.

Combined inhibition effect of vacuum chamber and inert gas on LPG explosion

In order to investigate combined inhibition effect of vacuum chamber and inert gas on Liquefied petroleum gas (LPG) explosion, the explosion experiment was carried out on the self-built gas explosion experiment pipe (L/D = 47.5). The flame propagation and explosion pressure characteristics of LPG were investigated at different vacuum degrees and 10% CO2 volume fraction (VF). The results showed that it is feasible to use a photosensitive solenoid valve to open the vacuum chamber. The Photoreceptor Solenoid Valve can open the vacuum chamber in time; Compared to add only 10% CO2, after installing the vacuum chamber, the maximum pressure peaks were all delayed; The pressure drops rapidly and a short period of negative pressure appeared, and the negative pressure duration becomes shorter as the vacuum degree increases; At various vacuum degrees levels, the maximum pressure peak value occurs at 0.06 vacuum degrees, primarily due to the combined influence of residual fuel quantity, Helmholtz oscillation, and turbulence near the flame front. The Pmax in the pipe and the flame intensity at any position is lower than that when only adding 10% CO2; high vacuum is more conducive to extinguish the flame and increase the thickness of the flame; the pumping effect of the vacuum chamber inhibits the rise of explosion pressure and flame propagation velocity. The combined explosion suppression is more effective on LPG explosions compared to add only 10% CO2. When selecting vacuum degree, it is important to consider the impact of the opening time and different vacuum degree within the vacuum chamber on pressure formation and flame propagation.

Synthesis of nanosized spinel ferrites MnFe2O4 on the surface of carbon nanotubes for the creation of polymer composites with enhanced microwave absorption capacity

Currently, the creation of new protective materials able to absorb the electromagnetic (EM) radiation is an important direction strongly linked to the use of high-tech electronics which leads to EM pollution in a wide range of high frequencies. The wide-band absorption and large bandwidth are two important factors affected the absorbing performance of materials. In this research, the development of polymer nanocomposites based on the multi-walled carbon nanotubes (CNTs) as a conductive component modified by manganese ferrite (MnFe2O4) nanoparticles as a magnetic component made it possible to increase the efficiency of absorption of EM waves in the frequency range 1–41 GHz as a result of good impedance matching characteristics in comparison with pure manganese ferrite. Finally, the absorption coefficient of EM waves in the frequency range of 5–20 GHz for MnFe2O4/0.065 vol.%CNT nanocomposites about 2.5–3 times higher than for MnFe2O4. The present work shows, that the introduction of MnFe2O4/CNT composites into the both amorphous (epoxy resin) and crystalline (polychlorotrifluoroethylene) polymer matrices makes it possible to manage microwave absorbing properties as well as a shift of the region of frequencies of maximum peak values of the absorption coefficient and reflection loss. The obtained relations prove that by the change of the amount of the modifying component (MnFe2O4) on the surface of carbon nanotubes, the content of the MnFe2O4/CNT nanocomposite in the polymer matrixes, and the thickness of the polymer composites it is possible to control the absorption coefficient and reflection loss of EM waves in the high frequency range. The MnFe2O4/0.044CNT–PCTFE and MnFe2O4/0.065CNT–epoxy resin composites exhibit higher bandwidth in relation to other reported composites or structures at the same thickness.

Accurate prediction of signal waveform in the convergence zone of the South China Sea based on frequency shift compensation

In a deep-sea environment in the South China Sea, a towed sound source is near the surface, and the acoustic signal is received by the vertical array of submersible buoys. The correlation values between the predicted and the measured signal waveform of the first two convergence zones (CZs) are poor, both below 0.5. The sea condition of the test area is good, the hydrological environment changes little in the horizontal direction. The analysis shows that when the underwater acoustic waveform is predicted, due to the relative motion of the transmitting and receiving elements, the channel dispersion caused by the Doppler effect leads to signal distortion. Therefore, the sampling frequency is broadened by 0.125 times to both ends, and the frequency shift corresponding to the maximum value of the waveform correlation peak is used as the optimal compensation for Doppler frequency offset. The results calculated by the RAM model show that the predicted and measured signal waveforms are in good agreement, and the correlation degree is significantly improved. Among them, the average normalized correlation values of the measured and predicted waveforms at different receiving depths in the first and second CZs are 0.84 and 0.82, respectively.

Study on failure characteristics of baking-free bricks with wrap-shell aggregate

Using sediment at the bottom of rivers and lakes as raw materials to prepare non-fired wrap shell aggregate (WSLAs) and using wrap shell aggregates to replace natural crushed stones to prepare baking-free bricks is a means of resource utilization. In this paper, using harmless treated sludge and other cementitious material mix as the core and cement as the shell, the wrap shell aggregate baking-free bricks were prepared and its damage characteristics were studied. By means of physical test and image processing, the mechanical properties of the baking-free brick under different aggregate substitution rate and grading conditions were analyzed. At the same time, the existing image analysis method is compared to select the most suitable method to study the damage characteristics of the baking-free brick, and further explore the meso-mechanism of the baking-free brick and the development and evolution of the crack under different substitution rates. The main research contents and conclusions are as follows: (1) Based on image processing technology, Multifractal spectroscopy and Grey Level Co-occurrence Matrix are faster, lower cost, and more accurate image analysis methods. These two methods make the development and evolution of cracks more convincing through quantitative analysis when exploring the damage characteristics of the wrap shell aggregate baking-free brick. (2) The fracture width Δa, maximum peak value and Δf are linear with the substitution rate, indicating that with the increase of the substitution rate, the fracture diversity is higher, the fracture complexity is higher, and the fracture propagation is wider and richer. (3) When GLCM analysis is used, the correlation between fracture characteristic values and the substitution rate is also linear, and the results show that the energy and correlation decrease with the increase of WSLAs substitution rate. Entropy and contrast increase with the increase of WSLAs substitution rate. (4) Both multifractal spectrum and gray level co-occurrence matrix can well reflect the fracture characteristics under different CAWS substitution rates. From the perspective of fracture complexity, the entropy linear correlation degree of gray level co-occurrence matrix is better than that of multifractal spectrum, which can simply and intuitively reflect the fracture expansion degree. The grayscale level co-existence matrix divides the crack expansion form into four different levels for more detailed research. For crack propagation, the two methods can be compared and verified at the same time to provide reference value for further engineering applications.

Transition between continuous and discrete spectra of high-wavenumber turbulence in neutral gas pressure scan experiments on a linear magnetized plasma

Spectral transition between continuous and discrete spectra has been observed in high-wavenumber turbulence excitation experiments. The transition appeared in neutral gas scanning, which shows that continuous spectra dominate at low gas pressures and discrete spectra dominate at high gas pressures. Both spectra have well smaller spatial scale than the ion effective Larmor radius. The discrete spectra have 6–11 peaks and maximum peak values at 4th or 5th peak. Correlation length analysis reveals that the continuous component is turbulent and the discrete component is coherent. The bicoherence analysis shows that the turbulent spectra have finite nonlinear coupling, whereas the discrete spectra have no corresponding coupling.