Compression Properties and Energy Absorption of A Novel Double Curved Beam Negative Stiffness Honeycomb Structures

This paper presents the design of a novel honeycomb structure with a double curved beam.The purpose of this design is to achieve vibration isolation for the main engine of an offshore platform and reduce impact loads.An analytical formula for the force-displacement relationship of the honeycomb single-cell structure is presented based on the modal superposition method.This formula provides a theoretical basis for predicting the compression performance of honeycomb structures.The effects of structural geometric parameters,series and parallel connection methods on the mechanical and energy absorption properties are investigated through mathematical modeling and experimental methods.Furthermore,the study focuses on the vibration isolation and impact resistance performance of honeycomb panels.The results show that the designed honeycomb structure has good mechanical and energy absorption performance,and its energy absorption effect is related to the geometric parameters and series and parallel connection methods of the structure.The isolation efficiency of the honeycomb with 4 rows and 3 columns reaches 38%.The initial isolation frequency of the isolator is 11.7 Hz.

Preparation and Properties of Magnesium Oxysulfide Cement Based Foam Board Absorbing Material

In order to better solve the problem of electromagnetic pollution in the civil building cement,to improve the absorption capacity of magnesium oxysulfide cement based materials,and to better use sulfur oxide magnesium cement foamed sheet for improvement of electromagnetic industry,this paper uses the excellent microwave absorbing properties of ferrite and the modified sulfur oxide magnesium cement foam board,and discusses the microwave absorbing performance,aiming at improving the electromagnetic pollution in daily life.The effects of ferrite and silicon carbide doping on microwave absorption properties of modified magnesium oxysulfate cement were studied.At the same time,the wave absorbing properties of the corresponding samples were detected by bow method,and the causes of the corresponding phenomena were analyzed by scanning electron microscopy (SEM).The results show that the lowest reflectance of the material is-17.9 dB at 34.1 GHz and the average reflectance of the whole band is-15.9 dB under the target frequency band of 26.5-40 GHz.Under the action of external magnetic field,the absorbing particles are affected by magnetization force,magnetic dipole and resistance coupling,and play the absorbing effect in the cement base solidified completely in the electromagnetic field environment.The lowest reflectance is-17.3dB at 36.4GHz and the average reflectance is-14.3dB for the whole band.

On the Radiative Properties of Ice Clouds:Light Scattering, Remote Sensing,and Radiation Parameterization

Presented is a review of the radiative properties of ice clouds from three perspectives： light scattering simulations, remote sensing applications, and broadband radiation parameterizations appropriate for numerical models. On the subject of light scattering simulations, several classical computational approaches are reviewed, including the conventional geometric-optics method and its improved forms, the finite-difference time domain technique, the pseudo-spectral time domain technique, the discrete dipole approximation method, and the T-matrix method, with specific applications to the computation of the singlescattering properties of individual ice crystals. The strengths and weaknesses associated with each approach are discussed.With reference to remote sensing, operational retrieval algorithms are reviewed for retrieving cloud optical depth and effective particle size based on solar or thermal infrared（IR） bands. To illustrate the performance of the current solar- and IR-based retrievals, two case studies are presented based on spaceborne observations. The need for a more realistic ice cloud optical model to obtain spectrally consistent retrievals is demonstrated. Furthermore, to complement ice cloud property studies based on passive radiometric measurements, the advantage of incorporating lidar and/or polarimetric measurements is discussed.The performance of ice cloud models based on the use of different ice habits to represent ice particles is illustrated by comparing model results with satellite observations. A summary is provided of a number of parameterization schemes for ice cloud radiative properties that were developed for application to broadband radiative transfer submodels within general circulation models（GCMs）. The availability of the single-scattering properties of complex ice habits has led to more accurate radiation parameterizations. In conclusion, the importance of using nonspherical ice particle models in GCM simulations for climate studies is proven.

Spatial and temporal variability of colored dissolved organic matter absorption properties in the Taiwan Strait

Spatial and temporal variability of the absorption properties of colored dissolved organic matter （CDOM） in the Taiwan Strait was investigated in summer （July to August of 2006） and winter （from December 2006 to January of 2007） seasons. The CDOM absorption coefficient at 280 nm （a 280 ） showed a decreasing trend from nearshore to offshore areas while the spectral slope coefficient parameter calculated between wavelengths 275–295 nm （S 275 295 ） showed an increase, indicative of decreasing aromaticity and molecular weight of the CDOM. The average a 280 in winter （1.47 ± 0.50 m ^-1 ） was significantly higher than in summer （1.10 ± 0.41 m ^-1 ）, while the average S 275 295 in winter （26.7 ± 5.2 μm^- 1 ） was significantly lower than in summer （30.6 ± 5.5 μm^- 1 ）, demonstrating clear seasonal variation in CDOM abundance and properties in the Taiwan Strait. A three-end- member conservative mixing model showed that local terrestrial CDOM inputs from several rivers along the western coast were small （〈5%）. However, the distribution of CDOM in the Taiwan Strait is mainly controlled by water mass movement [i.e., the Zhe-min Coastal Current （ZCC） and the Kuroshio Branch Current （KBC） in winter and the South China Sea Water （SCSW） in summer]. Biological activity was also an important factor affecting the distribution of CDOM in the offshore region in summer months.

Electromagnetic Shielding and Absorption Properties of Fiber Reinforced Cementitious Composites

In order to investigate the electromagnetic shielding effectiveness （SE） and absorbing properties of fiber reinforced concrete, steel fiber, carbon fiber and synthetic polyvinyl alcohol （PVA） fiber reinforced concrete were researched. The results show that with the increase of fiber Volume fraction, the SE and trend of frequency change of corresponding fiber reinforced concrete are enhanced. When the volume content of steel fiber is 3%, the SE of concrete is above 50 dB and its frequency is above 1.8 GHz. Moreover, in the range of 8-18 GHz, steel fiber, carbon fiber and PVA fiber all can improve the microwave absorption properties of concrete. The concrete with 0.5% carbon fiber can achieve the best absorbing property, the minimum reflectivity is about -7 dB; while steel fiber optimal volume fraction is 2%. The reflectivity curve of PVA fiber reinforced concrete fluctuates with the frequency, and the minimum value of the reflectivity is below -10 dB. The results show that fiber reinforced concrete could be used as EMI（electromagnetic interference） prevention buildings by attenuating and reflecting electromagnetic wave energy.

Effect of particle size on the preparation and microwave absorption properties of FeSiAl magnetically soft alloy hollow microspheres

FeSiAl magnetically soft alloy hollow microspheres(MSAHMs) were prepared by self-reactive quenching technology based on Fe + Si + AI + KNO_3 reactive systems, in order to obtain absorbents with light weight, low frequency and high efficiency. Firstly, twice-balling adhesive precursor method was used to obtain FeSiAl magnetically soft alloy agglomerate powders. Then agglomerate powders with the mesh number of 150-240, 240-325 and 325-400 were sprayed through the flame field into the quenching water. At last, FeSiAl MSAHMs with coarse(average at 86.97 μm), medium(average at 52.16 μm) and fine particles(average at 31.80 μm) were got. Effect of particle size on the phases and microwave absorption properties in low frequency band was studied by XRD and vector network analyzer. The results show that,Fe_3 Si_(0.7)Al_(0.3) and Fe_3 Si_(0.5)Al_(0.5) appear in the phase components of FeSiAl MSAHMs,which is important to improve the microwave absorption properties in low frequency. In addition, the real part(ε′) and imaginary part(ε″) of complex permittivity, the real part(μ′) and imaginary part(μ″) of complex permeability of FeSiAl MSAHMs all present the trend of fine particles > medium particles > coarse particles. The microwave absorption properties in low frequency are improved with the increasing of particle size, and the absorption peak moves to lower frequency range. The properties of fine particles are the best. Their matching thickness of samples is at 5 mm, and the minimum reflectivity is-43 dB at this thickness. The absorption frequency band lower than-10 dB is 4.6-7.6 GHz with a bandwidth of 3 GHz.

Crystal microstructure, infrared absorption, and microwave electromagnetic properties of (La_(1-x)Dy_x)_(2/3)Sr_(1/3)MnO_3

The manganite perovskite polycrystal samples of （La1-xDyx）2/3Sr1/3MnO3 （x = 0, 0.1, 0.2, 0.35, and 0.5） doped with Dy were prepared by solid state reaction in atmosphere to measure their X-ray diffraction （XRD） patterns, scanning electric microscope （SEM） images, infrared absorption spectra, and microwave electromagnetic properties. The displacement of the XRD peaks of the samples was found, and the 2θ increases from 0.05o to 0.5o. The grains of undoped La2/3Sr1/3MnO3 not only have the greatest size, but also the most regular shape. The size of the grains decreases as the Dy doping content increases from 0 to 0.5. The infrared absorption spectra of all samples were measured at room temperature. An absorption peak corresponding to the stretching vibration mode of Mn-O bonds appears within the range of 591-629 cm-1. The absorption peak shifts from a higher frequency to a lower one with the decrease of the average ionic radius of A-site. The frequency de- pendence of microwave-absorbing properties, imaginary components of the complex magnetic permeability μ＂ and dielectric permeability ε＂ for all samples was measured at room temperature from 8 to 13 GHz. The results show that the loss of microwave absorption can be attrib- uted to both the magnetic and electric losses. The increase of Dy content not only enhances the microwave absorption but also causes the displacement of the absorption peaks.

Effects of Organic Selenium on Growth Properties, Selenium Absorption and Utilization, Antioxidant Activity and Immunity in Weaning Piglets

This experiment was conducted to determine the influences of adding organic selenium (Se) on growth properties, Se absorption and utilization, immunity and antioxidant activity in diets of Duroc weaning piglets. This study was performed on 36 (average weight 7.6 kg) weaning piglets. The weaning piglets were randomly allocated to 1 of 4 homogeneous treatments (A, control treatment, no added Se;B, Sodium selenite, 0.3 mg Se/kg feed;C, yeast Se, 0.3 mg Se/kg;D, DL-methionine Se 0.3 mg Se/kg). Every treatment had 3 replicates, every replicate had 3 piglets. The experiment lasted for 35 d, with the first 7 d for adaptation. Feed intake, residual and contaminated feed were recorded every day. Every piglet weight was weighted respectively at beginning and end of experiment. Daily intake, gain weight and feed conversion rates of every replicate were calculated finally. Se concentrations of serum, blood antioxidant and immunity index were analyzed in the 36th d of experiment. The results showed average daily gain of treatment C was significant higher (P 0.05) and D had higher trend than that of treatment A and B (P = 0.06) respectively. And feed and gain ratio of C and D had trends to lower than them of A and B (P = 0.14). However, all the intake of every week and whole period had no significant differences among treatments (P > 0.05). At same time, except for the Immunoglobulin M of treatment D and C was higher than that of treatment A and B significantly (P < 0.05), all the other Se contents of serum, immunity indexes, blood cell parameters and enzymatic activities had no significant differences among treatments (P > 0.05). But they took on some obvious trends. For example, the Se contents and glutathione peroxidase activities increased successively in order of treatment A, B, C and D;the blood urea nitrogen and total bilirubin of treatment A had higher trend than that of other treatments (P = 0.06). All in all, adding to organic Se in basal diets could improve the animal’s healthy levels, growth properties and Se utilization to some extent. Relatively speaking, the DL-methionine Se had more advantages compared to yeast Se.

Scattering and absorption of particles by a black hole involving a global monopole

Under the conditions that the wavelength of a particle is much larger than its radius of central mass, and the Schwarzschild field is weak, the scattering of a particle has been studied by many researchers. They obtained that scalar and vector particles abide by Rutherford＇s angle distribution by using the low level perturbation method and the scattered field＇s approximation in a weak field. The scattering cross section of a photon coincides with the section in Newton＇s field of point mass. We can obtain the photon＇s polarization effect by calculating the second-order perturbation in the linear Schwarzschild field. This article discusses the scattering and absorption of a particle by a black hole involving a global monopole by using the aforesaid method.

Effect of Accelerated Aging Temperature under Artificial Seawater on the Properties of Carbon Fiber/Epoxy Composites and the Erosion Mechanism

In order to explore the effect of artificial accelerated aging temperature on the performance of carbon fiber/epoxy resin composites,we used artificial seawater as the aging medium,designed the aging environment of seawater at different temperatures under normal pressure,and studied the aging behavior of carbon fiber/epoxy composites.The infrared spectroscopy results show that,with the increase of aging temperature,the degree of hydrolysis of the composite is greater.At the same time,after 250 days of aging of artificial seawater at regular temperature,40 and 60 ℃,the moisture absorption rates of composite materials were 0.45%,0.63%,and 1.05%,and the retention rates of interlaminar shear strength were 91%,78%,and 62%,respectively.It is shown that the temperature of the aging environment has a significant impact on the hygroscopic behavior and mechanical properties of the composite,that is,the higher the temperature,the faster the moisture absorption of the composite,and the faster the decay of the mechanical properties of the composite.

Electromagnetic wave absorption and mechanical properties of SiC nanowire/low-melting-point glass composites sintered at 580°C in air

Si C nanowires are excellent high-temperature electromagnetic wave (EMW) absorbing materials. However, their polymer matrix composites are difficult to work at temperatures above 300℃, while their ceramic matrix composites must be prepared above 1000℃ in an inert atmosphere. Thus, for addressing the abovementioned problems, SiC/low-melting-point glass composites were well designed and prepared at 580℃ in an air atmosphere. Based on the X-ray diffraction results, SiC nanowires were not oxidized during air atmosphere sintering because of the low sintering temperature. Additionally, SiC nanowires were uniformly distributed in the glass matrix material. The composites exhibited good mechanical and EMW absorption properties. As the filling ratio of SiC nanowires increased from 5wt%to 20wt%, the Vickers hardness and flexural strength of the composite reached HV 564 and 213 MPa, which were improved by 27.7%and 72.8%, respectively, compared with the low-melting-point glass. Meanwhile, the dielectric loss and EMW absorption ability of SiC nanowires at 8.2–12.4 GHz were also gradually improved. The dielectric loss ability of low-melting-point glass was close to 0. However, when the filling ratio of SiC nanowires was 20wt%, the composite showed a minimum reflection loss (RL) of-20.2 dB and an effective absorption (RL≤-10 dB) bandwidth of2.3 GHz at an absorber layer thickness of 2.3 mm. The synergistic effect of polarization loss and conductivity loss in SiC nanowires was responsible for this improvement.

Combination of a biopharmaceutic classification system and physiologically based pharmacokinetic models to predict absorption properties of baicalein in vitro and in vivo

Objective: To determine the in vitro and in vivo absorption properties of active ingredients of the Chinese medicine, baicalein, to enrich mechanistic understanding of oral drug absorption.Methods: The Biopharmaceutic Classification System(BCS) category was determined using equilibrium solubility, intrinsic dissolution rate, and intestinal permeability to evaluate intestinal absorption mechanisms of baicalein in rats in vitro. Physiologically based pharmacokinetic(PBPK) model commercial software GastroPlus~(TM) was used to predict oral absorption of baicalein in vivo.Results: Based on equilibrium solubility, intrinsic dissolution rate, and permeability values of main absorptive segments in the duodenum, jejunum, and ileum, baicalein was classified as a drug with low solubility and high permeability. Intestinal perfusion with venous sampling(IPVS) revealed that baicalein was extensively metabolized in the body, which corresponded to the low bioavailability predicted by the PBPK model. Further, the PBPK model predicted the key indicators of BCS, leading to reclassification as BCS-II. Predicted values of peak plasma concentration of the drug(C_(max)) and area under the curve(AUC)fell within two times of the error of the measured results, highlighting the superior prediction of absorption of baicalein in rats, beagles, and humans. The PBPK model supported in vitro and in vivo evidence and provided excellent prediction for this BCS class II drug.Conclusion: BCS and PBPK are complementary methods that enable comprehensive research of BCS parameters, intestinal absorption rate, metabolism, prediction of human absorption fraction and bioavailability, simulation of PK, and drug absorption in various intestinal segments across species. This combined approach may facilitate a more comprehensive and accurate analysis of the absorption characteristics of active ingredients of Chinese medicine from in vitro and in vivo perspectives.

Conduction Properties and Scattering Mechanisms in F-doped Textured Transparent Conducting SnO_2 Films Deposited by APCVD

Transparent conducting F-doped texture SnO2 films with resistivity as low as 5× 10-4 Ω ·cm,with carrier concentrations between 3.5 × 1020 and 7× 1020 cm-3 and Hall mobilities from 15.7 to 20.1 cm2/(V/s) have been prepared by atmosphere pressure chemical vapour deposition (APCVD). These polycrystalline films possess a variable preferred orientation, the polycrystallite sizes and orientations vary with substrate temperature. The substrate temperature and fluorine flow rate dependence of conductivity, Hall mobility and carrier conentration fOr the resultingfilms have been obtained. The temperature dependence of the mobiity and carrier concentrationhave been measured over a temperature range 16～400 K. A systematically theoretical analysis on scattering mechanisms for the highly conductive SnO2 films has been given. Both theoretical analysis and experimental results indicate that for these degenerate, polycrystalline SnO2 ：F films in the low temperature range (below 100 K), ionized impurity scattering is main scattering mechanism. However, when the temperature is higher than 100 K, the lattice vibration scattering becomes dominant. The grain boundary scattering makes a small contribution to limit the mobility of the films.

Effects of heat treatment on dynamic compressive properties and energy absorption characteristics of open-cell aluminum alloy foams

The effects of heat treatment on the dynamic compressive properties and energy absorption characteristics of open cell aluminum alloy foams (Al-Mg-Si alloy foam and Al-Cu-Mg alloy foam) produced by infiltrating process were studied. Two kinds of heat treatment were exploited: age-hardening and solution heat treating plus age-hardening (T6). The split Hopkinson pressure bar (SHPB) was used for high strain rate compression test. The results show that both age-hardened and T6-strengthened foams exhibit improved compression strength and shortened plateau region compared with that of foams in as-fabricated state under high strain rate compression, and the energy absorption capacity is also influenced significantly by heat treatment. It is worthy to note that omitting the solution treating can also improve the strength and energy absorbed much.

Structure and electrochemical performance of delafossite AgFeO_(2)nanoparticles for supercapacitor electrodes

Delafossite AgFeO_(2)nanoparticles with a mixture of 2H and 3R phases were successfully fabricated by using a simple co-precipitation method.The resulting precursor was calcined at temperatures of 100,200,300,400,and 500℃to obtain the delafossite AgFe0_(2)phase.The morphology and microstructure of the prepared AgFeO_(2)samples were characterized by using field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),N_(2) adsorption/desorption,X-ray absorption spectroscopy(XAS),and Xray photoelectron spectroscopy(XPS)techniques.A three-electrode system was employed to investigate the electrochemical properties of the delafossite AgFeO_(2)nanoparticles in a 3 M KOH electrolyte.The delafossite AgFeO_(2)nanoparticles calcined at 100℃(AFO100)exhibited the highest surface area of 28.02 m^(2)·g^(-1)and outstanding electrochemical performance with specific capacitances of 229.71 F·g^(-1)at a current density of 1 A·g^(-1)and 358.32 F·g^(-1)at a scan rate of 2 mV·s^(-1).This sample also demonstrated the capacitance retention of 82.99% after 1000 charge/discharge cycles,along with superior specific power and specific energy values of 797.46 W·kg^(-1)and 72.74Wh·kg^(-1),respectively.These findings indicate that delafossite AgFeO_(2)has great potential as an electrode material for supercapacitor applications.

Influence of Density on Compressive Properties and Energy Absorption of Foamed Aluminum Alloy

The foamed aluminum alloys with different densities were fabricated by melt foaming technique. The compressive properties and energy absorption of the foamed aluminum alloy with different densities were analyzed. The results reveal that the compressive stress-strain curves follow the typical behavior of cellu- lar foams with three deformation stages. Under the same strain, the energy absorption capability decreases with the decrease of density. However, with increasing the strain, the energy absorption efficiency of foamed metal increases initially and then decreases. The lower the density, the longer the plateau region, within the range of high strain, the energy absorption efficiency is always high.

Analysis on characteristics of aerosol absorption and scattering over Zhangye, China

The first China-US joint dust field experiment was carried out by Lanzhou University, Chinese Academy of Sciences, China Me- teorological Administration, and University of Maryland, the Department of Energy （DOE）, USA, from April to June, 2008. The observation sites are located at Zhangye National Climatological Observatory, Semi-Arid Climate and Environment Observatory of Lanzhou University （SACOL）, and Jingtai with the Mobile Facilities of SACOL. The measurements of Particle Soot Absorp- tion Photometer and TSI Integrating Nephelometer are used to analyze the aerosol absorption and scattering characteristics over Zhangye. The results are： the aerosol absorption, total scattering, and backscattering coefficients present similar diurnal variation trends with their bi-peaks at 08：00 and 22!00, and they are generally higher in nighttime than in daytime. Their monthly average coefficient is the highest in April, and the!l drops in succession in May and June. Frequency analysis of aerosol single scattering albedo （SSA） shows that the magnitudes＇0f SSA at 450, 550, and 700 nm are mainly within 0.7q3.9. The maximum frequency of SSA at 450 and 700 nm distribute at 0.8, and at 0.85 for 550 nm. The averages of SSA at 450, 550, and 700 nm are 0.72, 0.75, and 0.68, respectively.

Improvement of scattering correction for in situ coastal and inland water absorption measurement using exponential fitting approach

The absorption coefficient of water is an important bio-optical parameter for water optics and water color remote sensing. However, scattering correction is essential to obtain accurate absorption coefficient values in situ using the nine-wavelength absorption and attenuation meter AC9. Establishing the correction always fails in Case 2 water when the correction assumes zero absorption in the near-infrared(NIR) region and underestimates the absorption coefficient in the red region, which affect processes such as semi-analytical remote sensing inversion. In this study, the scattering contribution was evaluated by an exponential fitting approach using AC9 measurements at seven wavelengths(412, 440, 488, 510, 532, 555, and 715 nm) and by applying scattering correction. The correction was applied to representative in situ data of moderately turbid coastal water, highly turbid coastal water, eutrophic inland water, and turbid inland water. The results suggest that the absorption levels in the red and NIR regions are significantly higher than those obtained using standard scattering error correction procedures. Knowledge of the deviation between this method and the commonly used scattering correction methods will facilitate the evaluation of the effect on satellite remote sensing of water constituents and general optical research using different scatteringcorrection methods.

Electromagnetic and Microwave Absorption Properties of Carbonyl-Iron/Fe91Si9 Composites in Gigahertz Range

Carbonyl-iron/Fe91Si9 composites for thin microwave absorbers were firstly prepared by a simple blending technique. The patterns of carbonyl-iron and Fe91Si9 were characterized by scanning electron microscope (SEM). The complex permittivity, permeability and microwave absorption properties of the composites were studied in the frequency range of 2 - 7GHz by a HP8720B vector network analyzer. Complex permittivity and permeability decrease gradually with increasing weight percentage of Fe91Si9 in the composites, the variation of permittivity was very large but the variation of permeability was very small. The composites exhibited excellent microwave absorption properties with increasing Fe91Si9 content. The reflection loss (RL) values less than –20 dB were obtained in the 3.7 - 6.7 GHz frequency range for the paraffin matrix composites with 80 wt% carbonyl-iron/Fe91Si9 powders (weight ratio of carbonyl-iron to Fe91Si9 was 1:1), with thickness of 4.0 - 2.4 mm, respectively. The optimal RL of –45 dB was observed at 5.2 GHz with a matching thickness (dm) of 3.0 mm. The excellent microwave absorption properties were attributed to a better electromagnetic impedance match and a higher electric resistivity.

Mechanical Properties and Energy Absorption of Integrated AlSi10Mg Shell Structures with BCC Lattice Infill

Shell-infill structures comprise an exterior solid shell and an interior lattice infill,whose closed features yield superior comprehensive mechanical performance and light weight.Additive manufacturing(AM)can ensure the fabrica-tion of complex structures.Although the mechanical behaviors of lattice structures have been extensively studied,the corresponding mechanical performances of integrated-manufactured shell structures with lattice infills should be systematically investigated due to the coupling effect of the exterior shell and lattice infill.This study investigated the mechanical properties and energy absorption of AlSi10Mg shell structures with a body-centered cubic lattice infill fabricated by AM.Quasi-static compressive experiments and corresponding finite element analysis were conducted to investigate the mechanical behavior.In addition,two different finite element modeling methods were compared to determine the appropriate modeling strategy in terms of deformation behavior.A study of different parameters,including lattice diameters and shell thicknesses,was conducted to identify their effect on mechanical performance.The results demonstrate the mechanical advantages of shell-infill structures,in which the exterior shell strengthens the lattice infill by up to 2.3 times in terms of the effective Young’s modulus.Increasing the infill strut diameter can improve the specific energy absorption by up to 1.6 times.