Low-energy Zone Research Articles

Structural basis to identify a target site in Shiga toxin for the inhibitor discovery against growth of Shiga toxin-producing E. coli

BackgroundCertain peptides that bind Shiga toxin 2 (Stx2) have been reported to treat Shiga toxin-producing Escherichia coli (STEC) infections. However, their mechanisms of action remain unknown. STEC infections lead to serious diseases, such as hemolytic uremic syndrome, in humans. Antibiotic therapy is usually not recommended because of the major challenges of antibiotic resistance and SOS repair. Currently, there is no human vaccine for STEC infection, leaving rehydration therapy as the recommended supportive therapy. Therefore, there is a need for targeted therapeutic intervention to inhibit STEC growth. The purpose of this study was to evaluate the interaction of five known peptides with Stx2 to identify a more suitable peptide based on structural changes. These peptides have been used to inhibit the growth of STEC.ResultsThe current study demonstrated that only tetravalent peptide (TVP) out of 5 common peptides interrupted the Y77-E259 interaction of Stx2, making it active by exposing active site, which ultimately leads to STEC cell death. We also demonstrated that amino acids R170 and F171 of Stx2 in the docked complex of Stx2 and TVP form a helix-loop-helix (HLH). This might lead to the differential expression of genes regulated by Stx2 and ultimately inhibit STEC growth. However, in the case of Stx2-ribosomal P-stalk, these residues did not form HLH. The 3D refined model of TVP showed a low MolProbity score and low energy zones in the ANOLEA profile compared to the original one. Moreover, the low radius of gyration of the refined TVP suggests that it is more compact than the original TVP. Therefore, TVP is a suitable drug candidate for the inhibition of STEC growth. However, the low antigenicity of TVP makes it unsuitable as a drug candidate. We also evaluated three antibiotics that have been used as active ingredients in FDA-approved peptides. Only Oritavancin diphosphate showed strong polar interactions with Y77-E259 and also had the highest binding affinity.ConclusionsPotential drug candidates that inhibit or interrupt the interaction between Y77-E259 and have high antigenicity, low toxicity, and no allergenicity should be explored against the growth of STEC.

Simulation of Particle Breakage in Vibration Mill Based on Tavares Model

In this paper, discrete element simulation software EDEM and Tavares crushing model were used to carry out numerical simulation research on the motion characteristics and crushing characteristics of materials in the MZ100 vibration mill during the grinding process. The influence of material characteristics, shape characteristics and filling rate of grinding media, vibration frequency, and amplitude of vibration mill on the efficiency and effect of vibration mill was analyzed. The factors affecting the distribution characteristics of the rotary center of mass and the low-energy region of the grinding medium in the grinding cavity are discussed. The extreme inflection point of the crushing efficiency of the grinding material in the grinding cavity with respect to the increase of the excitation frequency is obtained. In order to improve the grinding efficiency and reduce the low energy zone, the optimum process parameters of eccentric vibration grinding were discussed, which provided theoretical guidance for the efficient crushing of grinding materials.

Wind regime and sand transport in the mid-course of ten tributaries of the Yellow River, Inner Mongolia of China

Better understanding the wind regimes and dune activity criteria are pre-requisites for the successful planning of any sand dune fixation project and hence have a high priority. To fully understand wind energy conditions and the intensity of aeolian activity, we investigated the wind conditions, sand-transporting potential, and sand-transporting capacity of the basins of mid-course ten tributaries of the Yellow River through field observations and indoor analyses. 1) The analysis of wind energy, which is based on sand transport potential, demonstrates that there is substantial spatial variation within the study area. The western part, which is located near the Kubuqi Desert, qualifies as a high wind energy zone. In contrast, the central part belongs to the medium wind energy zone, whereas the eastern part is categorized as a low wind energy zone. Even though there are notable differences in the sand transport potential characteristics across different time scales, the direction of the synthesized sand transport potential tends to be consistent, predominantly leaning towards the southeast. This orientation provides the requisite energy for the sand material to be transported into the river. 2) The prevailing sand-producing wind direction at various timescales in the research area was dominated by westward (W, WNW, NW) and northward (NNW, N) winds, with distinct seasonality. This seasonal variability was especially prominent in spring, which saw the highest frequency of aeolian activity and the largest volume of sand transport. Autumn and winter exhibited similar patterns, and, in the summer, it was the lowest 3) The relationship between sand-transporting potential and sand-transporting capacity, which is a crucial aspect of aeolian geomorphology, could be adequately depicted using a fitting function based on the temporal patterns of wind speed. During periods of high wind, the sand-transporting potential and sand-transporting capacity of the basins of the ten tributaries followed a power function relationship. Conversely, during periods of low wind, they followed an exponential function relationship. These results imply that spring should be deemed as the crucial period for wind-sand prevention and control. Additionally, emphasis should be placed on the western part, which is situated close to the sand source area, as the primary prevention and control zone.

Investigations on physical, structural, elastic, optical and radiation shielding properties of boro-tellurite glasses for radiation waste management applications

The boro-tellurite glasses with the chemical composition 29B2O3+20TeO2+50MO +1Dy2O3 containing different modifiers (where M = Ba, Li2, Sr, Ca, Mg and Zn) have been produced via conventional melt quenching method. The elastic, structural, physical, optical bandgap properties and the high energy photon shielding behavior of the produced glasses were extensively inspected through appropriate characterization techniques. The X-ray diffraction (XRD) pattern confirms amorphous character of the as-quenched samples. The Fourier-Transform Infrared (FTIR) spectral analysis reveals the presence of functional groups by the way of their stretching and bending vibrational modes. The estimation of parameters like Boron–Boron separation (dB−B), Bond density (n0), oxygen molar volume (V0), and Oxygen Packing Density (OPD) were facilitated to understand the detailed structural modifications and the moduli of elasticity (E, K, G, σ) parameters were determined for the fabricated the boro-tellurite glasses. The barium incorporated present boro-tellurite glass possess lower OPD and higher average molecular weight and it might make the glass network densely packed. To ensure the radiation protection ability, defending parameters such as equivalent atomic number, mass attenuation coefficient (MAC), Effective electron density, half-value layer (HVL), mean free path (MFP) and build-up factors of the titled glasses were determined employing the user friendly Phy-X software. Barium cations added boro-tellurite glass found to have the shortest MFP and HVL, as well as the lowest EBF in the low and intermediate energy zones indicating the potential for using the barium cations incorporated boro-tellurite glass as alternatives for conventional concretes in shielding and waste management applications.

Hydrocarbon generation and organic matter enrichment of limestone in a lacustrine mixed sedimentary environment: A case study of the Jurassic Da'anzhai member in the central Sichuan Basin, SW China

The hydrocarbon generation effectiveness of lacustrine limestone has been gradually proven. The Da'anzhai Member limestone is the most important Jurassic oil-producing layer in the central Sichuan Basin, and the characteristics of limestone organic matter are often overlooked. 175 typical samples of different lithologies from 19 wells were systematically analyzed to determine hydrocarbon generation, controlling factors and formation models by analyses of organic matter, minerals, elements, isotopes and petrography. (1) Lacustrine paleoenvironments can be beneficial for the enrichment of organic matter in limestone. A favorable environment would be a quiet, low-energy zone in a warm and humid climate with an appropriate supply of terrestrial inputs. (2) Lacustrine limestone has a higher organic matter conversion rate, and a lower hydrocarbon generation threshold than argillaceous source rocks, and can be effective source rock. (3) The mud-bearing shell limestone from the forebeach to the lake slope is thick, with a relatively high abundance of organic matter, and its hydrocarbon generation is effective. This study can clarify the effectiveness and enrichment of the limestone organic matters in the study area, and contribute to an understanding of hydrocarbon generation for full-rock system in a lacustrine mixed sedimentary environment.

Assessment of sustainability of machining Ti-6Al-4V under cryogenic condition using energy map approach

Sustainability of a manufacturing system is of significant importance to its overall efficiency and output. The issue becomes more pertinent during the machining of hard to cut titanium alloys which draws excessive amount of energy. Process map are effective tools that readily provides machinability information of materials of manufacturing importance to process planners. Titanium alloys, owing to their usage in high volumes, are well-mapped but only under dry conditions. The current research focuses on the development of energy consumption map of titanium alloy Ti-6Al-4V employing single point turning under cryogenic conditions. Cryogenic cooling is known for its convenience for green manufacturing as opposed to conventional coolant. Cutting speed and feed rate are used as variable machining parameters over a wide spectrum using full factorial design of experimentation. Energy consumption is represented by specific cutting energy due to its machine-tool independent nature. The map region was demarcated into low, moderate and high energy zones. Analysis of the developed novel map revealed underlying mechanics of machining and provided deeper insight into the factors effecting energy consumption. Energy consumption was found to be more dependent on cutting speed than feed rate. Tool chip contact length was found to decrease due to the reduction of slip region under cryogenic conditions. Analysis of chip morphology revealed that chip shear angle and compression ratio decreased with increase in cutting speed resulting in higher energy consumption. The significance of cryogenic map is also underscored in its utility on the shop floor for selection of optimum machining parameters for higher productivity in addition to its sustainable and environmental friendly nature. In comparison with dry energy map, a reduction in energy up to 16% is observed which highlights the sustainability of cryogenic energy map. The utility of cryogenic energy map can also be ascertained from the fact that productivity can be increased by 156% in terms of material removal rate by careful selection of appropriate machining parameters. Overall, the developed cryogenic map is a vital asset of manufacturing systems as it collectively serves the purpose of sustainability and cleaner production.

Petrographic and geochemical characteristics of oncolites in the Ediacaran Dengying Formation of the Upper Yangtze Area, China: Implications for their Paleo-environment

The Ediacaran Period represents a critical transition in the Earth's evolution, which could be potentially revealed by analyzing the oncolites formed during this period. This study investigates the genesis of oncolites in the Ediacaran Dengying Formation in the Yangba profile, Nanjiang County, Sichuan Basin. Moreover, efforts are made to analyze the effects of terrigenous input from perspectives of rare earth elements, probe into the variation of redox conditions via the microscopic analysis of trace elements, and exemplify the coupling relationship between the oxygen isotope, strontium isotope, paleosalinity (indicated by Z values), and sea level variation. The oncolites in the Yangba profile are generally featured by thin skins and dispersal grains and are highly differentiated in size and shape. A large number of microbial laminated fabrics and framboidal pyrite are developed in the dark laminae, and the former is yellow-green under the fluorescence microscope. According to the 13C-enrichment and petrographic analyses, oncolites and organic matter should be autochthonously formed by geochemical processes linked to microbial mats. Three cycles of sedimentary microfacies formed in subtidal low-energy zone and subtidal high-energy zone, and ten upward-coarsening cycles of oncolites are identified vertically, which, together with the vertical variations of δ18O and 87Sr/86Sr, indicate that the sea level has experienced six stages of variations during the deposition of the 2nd Member of the Ediacaran Dengying Formation (Deng-II Member): namely, transgression, lowstand fluctuating regression, transgression, continuous regression, transgression, and again lowstand fluctuating regression. Negative Ce anomalies (Ce/Ce*) and low V/Cr and low V/(V + Ni) ratios indicate the presence of molecular O2 in the water column, whereas characteristic Ni/Co, U/Th, and framboidal pyrite suggest the contemporaneous presence of anoxic water. The oncolites are suggested to be rarely impacted by terrigenous input, as is evident by the Er/Nd ratio of < 0.1, the average Y/Ho ratio of 35, the average La/Yb ratio of 36, and the Z value of > 130. To conclude, Upper Yangtze Deng-II Member oncolites are exemplified to be of microbial origins; the marine redox structure is featured by a temporarily stratified, oxygenated water body and a less oxygenated deeper water body during the Ediacaran, and frequent change of seawater energy, which are consistent with the Ediacaran seawater properties.

Investigation of photon attenuation factors for TeO2-Bi2O3–B2O3 glass systems using SRIM codes, EPICS2017 library and Phy-X/PSD

We aimed to examine the photon shielding characteristics of the TeO2-Bi2O3-B2O3 ternary glass system using EPICS2017 library and Phy-X/PSD software. Seven glass systems, TeBiB1-TeBiB7, with varying TeO2, Bi2O3, and B2O3 compositions were examined. The mass attenuation coefficient (MAC) evaluated with EPICS2017 (MACEPICS2017) is slightly lower than MAC derived from Phy-X/PSD software (MACPhy-X/PSD) by an average of 0.24%. MACEPICS2017 is in good agreement with MACPhy-X/PSD at all the examined energies. Substituting an atom fraction of Bi2O3 with TeO2 and/or B2O3 resulted in the decrease of the total atomic cross-section of the glass, which in turn decreases the MAC. The linear attenuation coefficient (LAC) has comparatively higher values in the low energy zone (1.034–1.563 cm−1 at 0.347 MeV), and the lowest values were reported at 2.506 MeV (in order of 0.2 cm−1). TeBiB1 has relatively higher LAC than TeBiB2-TeBiB7 glasses, whereas TeBiB6 and TeBiB7 glasses have nearly the same LAC and they possess lower LAC than the remaining glasses. The half-value layer (HVL) at 0.347 MeV takes the following values: 0.443 cm for TeBiB1, 0.532 cm for TeBiB2, 0.537 cm for TeBiB3, 0.541 cm for TeBiB4, 0.545 cm for TeBiB5, 0.670 cm for TeBiB6 and 0.670 cm for TeBiB7. The sequence of HVL is TeBiB6 > TeBiB7 > TeBiB2 > TeBiB3 > TeBiB4 > TeBiB5 > TeBiB1. The tenth value layer results revealed that the TeBiB1- TeBiB7 samples are good attenuators to the low energetic radiation. We found that TeBiB1 has the thinnest TVL (equals 4.439 cm, at 0.826 MeV), while TeBiB6 has the thickest TVL.

Experimental study on separation of lumpish coal and gangue using X-ray

ABSTRACT The recognition of lumpish coal and gangue of different coal sorts was conducted using X-ray technique. Gas coal, fat coal and coking coal were used in this study, and the ash content was found to roughly increase linearly with the density independently of coal sort. Al2O3, SiO2, Fe2O3 and SO3 were detected to be the major oxides for the increase in ash content as the density increased. The gray value of coal was larger than that of gangue and decreased with the increase in thickness and density independently of coal sort and energy zone. The gray value in the high energy zone was found to overlap with that in the low energy zone. Material attribute value (R) was applied for estimating the accuracy of the recognition, and the highest accuracy was given at R = 1.3.

Ecological risk and enrichment of potentially toxic elements in the soil and eroded sediment in an organic vineyard (Tokaj Nagy Hill, Hungary)

Potentially toxic elements (PTEs), such as Cu, Zn, Pb, Ni, Cr, and Co, can accumulate in vineyard soils due to repeated uses of inorganic pesticides and chemical or organic fertilizers. In sloping vineyards, PTEs can also be moved by soil erosion resulting in their accumulation in low-energy zones within the landscape, adversely affecting the soil environment. Our study evaluated the ecological risk related to the pseudo-total and bioavailable PTE contents (Zn, Pb, Co, Ni, Cr, and Cu) in the soil and eroded sediment samples from an organic vineyard in Tokaj (NE Hungary). The contamination status and the ecological risk of target PTEs were assessed by calculating the contamination factor, the pollution load index, the ecological risk factor, and the ecological risk index. The median pollution load indices of 1.15, 1.81, and 1.10 for the topsoil, the sediments, and the subsoil, respectively, demonstrate a moderate multi-element contamination case in the organic vineyard. Target PTEs tented to show increased concentrations in eroded sediments with the highest enrichment ratio (3.36) observed for Cu (Cu in the sediment/Cu in the topsoil), revealing a preferential movement of Cu-rich soil particles by overland flow. Moreover, PTEs were present in the sediments in more bioavailable forms (except Ni, Cr), assessed by an extraction procedure with EDTA. The ecological risk index (< 90) based on the studied PTEs showed an overall low ecological risk in the vineyard. Copper was the predominant factor of the ecological risk. Moreover, the highest ecological risk factor (24.6) observed for the bioavailable Cu content in an eroded sediment sample (representing 82% of the total ecological risk) shows that Cu accumulation in sloping vineyards is an ecological risk, particularly in the sedimentation zones. The high proportions of bioavailable Cu in the vineyard’s soil represent an increasing ecological risk over time, related to repeated treatments of vine plants with Cu-based pesticides.

The effect of Ni/Co-doping on electronic structures and optical properties of cubic Ca2Ge

The electronic structures and optical properties of the intrinsic, Ni-, Co-, and CoNi-doped models of cubic Ca2Ge alloys have been investigated by using the plane wave ultra-soft pseudopotential method based on the density functional theory. The doped metal ions cause lattice distortion (the lattice constant decreases slightly) and enhance the built-in electric field. As a result, in the low energy zone, the dielectric constant, the refractive index, and the extinction coefficient increase; with the appearance of impurity bands, the width of the band gap reduces significantly; and the absorption spectrum redshifts, indicating a stronger response in the infrared band, and a higher light utilization efficiency. In addition, the CoNi-doped results in the best enhancement in optical properties in the low energy region.

Changing the paleo-depositional environment in the last 2300 years: a study through sedimentology and geochemistry of a sediment core, western Bay of Bengal

The sediment core collected at a water depth of 260.2 m off Mahanadi, western Bay of Bengal was analyzed for grain size fractions, clay minerals, and major and trace elements to understand changing depositional environments, source and processes with time, from ~ 2300 cal yr before present (BP) to the year of the collection (2014). Age was estimated using accelerator mass spectrometer (AMS) 14C dates of two planktonic foraminifera samples. The core was divided into six distinct zones based on the significant changes in the sediment components and clay minerals. The presence of higher than average clay and smectite and lower silt and illite, in Zone II (2000 years BP–1070 cal yr BP) and Zone V (300–130 cal yr BP) revealed their deposition in low energy conditions, while, Zone III (1070 to 530 cal yr BP) and Zone VI (132 cal yr BP to present) exhibited higher silt and illite and lower clay and smectite than average suggesting their deposition in a high energy environment. Similar depositional environments observed between Zones II and V and also between Zones III and VI indicated the reoccurrence of similar hydrodynamic conditions with time. Zone II represents the Roman Warm Period and part of the early Medieval Warm Period, while, zone V corresponds to the retreating phase of the Little Ice Age. High Al in zone III and fluctuating trend in zone VI indicates higher Al release along with silt and illite from physical weathering in a cold and arid climate, while, smectite showed a positive correlation with Ti indicating the source of Ti and smectite as basic igneous rocks released during the enhanced southwest monsoon and warm climate. Mn and Zn distribution revealed fluctuations in the Oxygen Minimum Zone (OMZ) intensity to changing hydrodynamic conditions and depositional environments. The present study revealed changing depositional environments in the western Bay of Bengal with time with respect to changing material influx, reflecting fluctuating monsoons and climate.

BaO–Li2O–B2O3 glass systems: Potential utilization in gamma radiation protection

In this work, MCNP5 code and Phy-X/PSD software were used to report different shielding parameters for the BaO–Li2O–B2O3 glass systems. The radiation shielding parameters were evaluated for photon energies between 284 and 2506 keV. The mass attenuation coefficient (μ/ρ) demonstrated a strong energy dependence at the low energy zone (284 keV<E < 662 keV), while having a weak energy dependence at high energies. The maximum μ/ρ is found for the glass sample with 40 mol% of BaO and is equal to 0.127 cm2/g at 0.347 MeV and 0.067 cm2/g at 0.826 MeV. The transmission factor (TF) was determined and the results show an increasing trend as energy increases, implying that more gamma photons can penetrate the BaLiB1 and BaLiB9 glasses at higher energies. For the glass with 40 mol% of BaO, the TF at 0.511 MeV lies within the range of 0.916 (when x = 0.25 cm) and 0.743 (when x = 0.85 cm). It was also found that the TF for BaLiB9 (the glass with 40 mol% of BaO) is lower than that for BaLiB1. The TF results showed that the greater the amount of BaO in the glass samples, the more efficient the sample will be as a shield. The tenth value layer (TVL) was observed to increase with increasing energy, reaching a maximum value at 2506 keV. The half value layer (HVL) data suggested that with an increase in the photon energy, a reduction in shielding occurs, improving the penetration of the photons through the BaLiB1– BaLiB9 glasses. The mean free path (MFP) values varied within the range of 4.046–11.208 cm for BaLiB1 and 1.631–6.814 cm for BaLiB9.

Determination and analysis of ionization/excitation distributions for alpha particles in silicon detectors

As known, the detector response function in the detection of alpha particles is characterized by the following distributions: electronic excitation and ionization, electron–hole pair statistics, and electronic noise contribution. The distribution due to the ionization–excitation process is of particular relevance, because it is not Gaussian and contributes essentially to the asymmetry of the alpha lines. For this work, we adapted the well-known code SRIM, to obtain and analyze the ionization/excitation distributions for alpha-particles in silicon, in a wide range of energies from 0.5 to 10 MeV. These curves were later well-fitted to a function corresponding to the convolution of a Gaussian with exponentials truncated in the low-energy zone of the distribution. A detailed study about the dependence of all the fitting parameters on energy was performed. The parametrization carried out in this work can also be an useful tool to generate the corresponding ionization–excitation curves required in the task of reproducing real alpha-particle spectra.

The Phenomenon of Bistable Phase Difference Intervals in the Times-Frequency Vibration Synchronization System Driven by Two Homodromy Exciters

A vibration system with two homodromy exciters operated in different rotational speed is established to investigate whether the phenomenon of bistable phase difference intervals exists in the times-frequency vibration synchronization system. Some constructive conclusions are proposed. (1) By introducing an average angular velocity perturbation parameter ε0 and two sets of phase difference perturbation parameters and ε2, the frequency capture criterion and the necessary criteria for realizing the times-frequency vibration synchronization are derived. The corresponding stability analysis is carried out. (2) By the theoretical analysis and experiments, it is verified that the times-frequency vibration synchronization system exists the phenomena of bistable phase difference interval. That is, the phase differences between the two homodromy exciters are stable around 180 degrees when they are located at a short distance; the antiphase synchronization phenomenon appears. On the contrary, they are stable around 0 degrees at the in-phase synchronization state. (3) Because of the two homodromy exciters operating in the different rotational speed, the vibration system obtains relatively complex compound motion trajectories; the corresponding application is investigated by adding a feeding material chamber. The times-frequency vibration synchronization system can be used to design the vibration mill for reducing its low-energy zone and developing chaotic mixing equipment for obtaining a better mixing effect.

CALCULATION OF CROSS SECTIONS AND ASTROPHYSICAL S-FACTORS AT 0-5 MeV ENERGY RANGE FOR 8Li (α, n)11B REACTION

Explaining the origin and evolution of elements is one of the most important problems in astrophysics. The r-process in the current nucleosynthesis scenario; roughly responsible for the production of half of the nuclei heavier than iron. 8Li(α,n)11B reaction plays an important role in the r-process of this scenario because of being a cosmic radiation induced reaction. In particular, it is important to know the change with energy in the low energy zone for testing the accuracy of the model calculations. In this study, the astrophysical S-factors of the 8Li(α,n)11B reaction and the probability of reaction at low energies were calculated in the 0-5 MeV energy range. TALYS 1.8 code was used for the theoretical calculations. The obtained theoretical values were compared with experimental data obtained from the EXFOR database.

Study of Top-down and Bottom-up Approaches by Using Design of Experiment (DoE) to Produce Meloxicam Nanocrystal Capsules.

In order to investigate the correlation among energy input-related, drug-related, and stabilizer-related aspects for both top-down and bottom-up nanocrystal production, meloxicam nanosuspensions (NS) were produced by using three different methods (low-energy wet milling, high-pressure homogenization, and precipitation) and each method was optimized by using design of experiment (DoE). Box-Behnken design of 3 factors and 3 levels was applied for the optimization of each method. All the three models were found to be significant and the optimized process parameters were used for production of NS, respectively. Interestingly, by comparison of the top-down and bottom-up approaches, the influence of energy input (homogenization pressure or milling speed) from the instruments seemed not significant for top-down compared with bottom-up for this drug. Different mechanisms of homogenization (relatively high energy zone) and milling (relatively low energy zone) led to obtained various significant correlations for each method. Capsules containing nanocrystals were successfully produced by using a novel method applying NS (after wet bead milling and homogenization processes) as wetting agent for direct capsuling and showed superiority regarding as dissolution rate compared with the traditional two-step method (freeze-dried powder used for capsuling as the first step). Different NS preparation methodologies proved to have a direct influence on the following capsuling process and consequently, in the dissolution rate. This study also proved that residual DMSO in nanosuspension after precipitation process could affect the freeze-drying process, which might further alter the redispersion and influence the downstream processes.

A Novel Method for Ocean Wind Speed Detection Based on Energy Distribution of Beidou Reflections.

The Global Navigation Satellite System Reflectometry (GNSS-R) technique exploits the characteristics of reflected GNSS signals to estimate the geophysical parameters of the earth’s surface. This paper focuses on investigating the wind speed retrieval method using ocean scattered signals from a Beidou Geostationary Earth Orbit (GEO) satellite. Two new observables are proposed by computing the ratio of the low energy zone and the high energy zone of the delay waveform. Coastal experimental raw data from a Beidou GEO satellite are processed to establish the relationship between the energy-related observables and the sea surface wind. When the delay waveform normalized amplitude (this will be referred to as “threshold” in what follows) is 0.3, fitting results show that the coefficient of determination is more than 0.76 in the gentle wind scenario (<10 m/s), with a root mean square error (RMSE) of less than 1.0 m/s. In the Typhoon UTOR scenario (12.7 m/s~37.3 m/s), the correlation level exceeds 0.82 when the threshold is 0.25, with a RMSE of less than 3.10 m/s. Finally, the impact of the threshold and coherent integration time on wind speed retrieval is discussed to obtain an optimal result. When the coherent integration time is 50 milliseconds and the threshold is 0.15, the best wind speed retrieval error of 2.63 m/s and a correlation level of 0.871 are obtained in the UTOR scenario.

Influence of boron contents on microstructure, mechanical properties and shielding effect of Fe–W–C alloy

By using vacuum sintering method, the shielding materials made of iron-tungsten-carbon-boron (Fe–W–C–B) alloys with different boron (B) contents were prepared. The influences of different B contents on mechanical properties, shielding performance and microstructures of the alloys were investigated. The research results showed that with increasing B content, the fracture of alloys changed from plastic to brittle fractures and the higher the B content was, the more serious the brittle fracture. Moreover, the content of brittle amorphous phase FeWB increased and therefore the hardness and density of alloys increased at first and then reduced. When the B content was 2.5%, the alloy phase was mainly composed of Fe2B, Fe3(C, B) and α-Fe phases, with compact microstructure, shown as continuous network microstructure and tiny, long, round rod-like microstructure. In this case, the density, tensile strength and hardness of alloys were 10.05 g/cm3, 410 MPa and 468 HV, respectively. The γ-ray shielding performance of the alloy reduced at first, then increased and finally declined with the increase of B contents. When the B content was 1.5%, the half-value thickness reached to the minimum (about 6.36 mm). The transmittance of neutron shields reduced at first and then increased in a low-energy zone (0–4 MeV). When the B content was 2.5%, the alloys showed the lowest transmittance about 0.10842.

Ab-initio calculations of chemical and optoelectronic properties of 7-atom Pt-Y [Y = Li, Na, K

Using density functional theory, we investigated structural, chemical, electronic, and optical properties of the 7 neutral atom Pt-Y [Y = Li, Na, K] pure and nanoalloys. The generalized gradient approximation and ultrasoft pseudopotential are considered. Interesting results are achieved. In particular, Pt6Li cluster shows a higher absolute value of the binding energy (BE) whereas in all other Pt7-mYm systems, this value decreases when m increases. The more the atomic radius increases, the less the resulting alkali metal nanoclusters are cohesive. The most stable structure of Pt7-mYm cluster is obtained when m = 4 for Li and Na atoms, whereas for K atom, this occurs for m = 3. Moreover, the calculated absorption spectra of the Pt7-mYm (m = 2, 4, 6) have revealed that the doping with Li, Na, and K widens the absorption band. Also, the absorption spectra obtained are more pronounced in the low energy zone. It appears that the electron absorption strength is high in low excitation energy zone. On the other hand, the nanoclusters with m = 1, 3, 5, 7 (odd numbers of electrons) showed metallic character with absorption spectra that could not be easily guessed through the present numerical calculations. The nanoclusters Pt7-mYm with even numbers of dopant atoms showed semiconductor properties with the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap increasing as the number of doping atoms increases.