Diversity and structural composition of species in dipterocarp forests:a study from Fasiakhali Wildlife Sanctuary, Bangladesh

Fasiakhali Wildlife Sanctuary is a protected area composed of tropical remnant rainforest that harbor substantial number of large,old Garjan（Dipterocarpus spp.）trees.The present study assessed composition,structure and diversity of the species in this protected area.A total of 32 trees species were recorded with DBH ≥ 11 cm belonging to 24 genera and 19 families.The forest is low in plant diversity as represented by Shannon–Wiener diversity and Simpson Dominance indices.Dipterocarpus turbinatus was the most dominant species with maximum relative density,frequency,dominance,and importance value index.Syzygium firmum and Tectona grandis followed in terms of dominance.The structural composition indicated higher number of individuals in the medium growth classes（41 to 〈 511 cm DBH and 16–20 m height ranges）,whereas D.turbinatus was the only species that dominated most of the growth classes.Poor stem density in lower growth classes indicated meager recruitment of regeneration which may be due to lower annual precipitation,increased grazing and encroachments.This study will help to understand the patterns of tree species composition and diversity in the remnant dipterocarp forests of Bangladesh.It will also contribute to identifying threatened plants to undertake D.turbinatus based conservation and sustainable management of the Fasiakhali Wildlife Sanctuary.

Structural composition of oligomeric and polymeric proanthocyanidins from diff erent parts of grape pomace

Grape pomace is one of the most abundant solid by-products generated during winemaking,rich in bioactive compounds,i.e.,proanthocyanidins.The major objective of this work was to characterize structurally oligomeric and polymeric proanthocyanidins of diff erent parts of grape pomace(seed,skin,and stem).Column chromatography techniques were used to isolate oligomeric and polymeric proanthocyanidins fractions from diff erent parts of grape pomace.The purifi ed grape seed proanthocyanidins were used to assess the effi ciency of the three most frequently-used acidic degradation methods,using benzyl mercaptan,phloroglucinol,and cysteamine as nucleophiles.The structural characterization of proanthocyanidins in the different parts of grape pomace was further performed by the phloroglucinolysis and ESI-MS analysis.The results showed signifi cant diff erences in the structural composition of proanthocyanidins among diff erent parts of pomace.A positive correlation was found between the mean degree of polymerization and percentage of galloylation,in both oligomeric and polymeric fractions.The results provided useful information for the preparation of diff erent proanthocyanidins products from grape pomace.

Suppression of Co(Ⅱ)ion deposition and hazards:Regulation of SEI film composition and structure

Despite the presence of Li F components in the solid electrolyte interphase(SEI)formed on the graphite anode surface by conventional electrolyte,these Li F components primarily exist in an amorphous state,rendering them incapable of effectively inhibiting the exchange reaction between lithium ions and transition metal ions in the electrolyte.Consequently,nearly all lithium ions within the SEI film are replaced by transition metal ions,resulting in an increase in interphacial impedance and a decrease in stability.Herein,we demonstrate that the SEI film,constructed by fluoroethylene carbonate(FEC)additive rich in crystalline Li F,effectively inhibits the undesired Li^(+)/Co^(2+)ion exchange reaction,thereby suppressing the deposition of cobalt compounds and metallic cobalt.Furthermore,the deposited cobalt compounds exhibit enhanced structural stability and reduced catalytic activity with minimal impact on the interphacial stability of the graphite anode.Our findings reveal the crucial influence of SEI film composition and structure on the deposition and hazards associated with transition metal ions,providing valuable guidance for designing next-generation electrolytes.

Compositional and structural evolution of the titanium dioxide formation by thermal oxidation

Titanium oxide films were prepared by annealing DC magnetron sputtered titanium films in an oxygen ambient. X-ray diffraction （XRD）, Auger electron spectroscopy （AES） sputter profiling, MCs^＋-mode secondary ion mass spectrometry （MCs^＋-SIMS） and atomic force microscopy （AFM） were employed, respectively, for the structural, com- positional and morphological characterization of the obtained films. For temperatures below 875 K, titanium films could not be fully oxidized within one hour. Above that temperature, the completely oxidized films were found to be rutile in structure. Detailed studies on the oxidation process at 925K were carried out for the understanding of the underlying mechanism of titanium dioxide （TiO2） formation by thermal oxidation. It was demonstrated that the formation of crystalline TiO2 could be divided into a short oxidation stage, followed by crystal forming stage. Relevance of this recognition was further discussed.

Dependence of Structural and Optoelectrical Properties on the Composition of Electron Beam Evaporated Zn_xCd_(1-x)S Thin Films

Thin films of ZnxCd1-xS have been prepared by electron beam evaporation of a mixture of ZnS & CdS powders. The films are deposited onto sodalime glass slides under similar conditions.The composition of the films is varied from CdS to ZnS (x=0 to 1). The films show a regular change in color from toner red to orange yellow as Zn concentration increases to maximum.These films are characterized for their optical, electricaI and structural properties. The bandgap value of ZnxCd1-xS films is found to vary linearIy from 2.20 eV to 3.44 eV with change in the x value from 0 to 1. The resistivity of these films is in the range of 171.0 Ωcm to 5.5× 106Ωcm for x=0~0.6. All the samples show cubic structure after annealing in air at 250℃ for 40 min.The lattice constant ao varies from 0.5884 nm to 0.54109 nm linearly.

In-situ additive manufacturing of high strength yet ductility titanium composites with gradient layered structure using N_(2)

It has always been challenging work to reconcile the contradiction between the strength and plasticity of titanium materials.Laser powder bed fusion(LPBF) is a convenient method to fabricate innovative composites including those inspired by gradient layered materials.In this work,we used LPBF to selectively prepare Ti N/Ti gradient layered structure(GLSTi)composites by using different N_(2)–Ar ratios during the LPBF process.We systematically investigated the mechanisms of in-situ synthesis Ti N,high strength and ductility of GLSTi composites using microscopic analysis,TEM characterization,and tensile testing with digital image correlation.Besides,a digital correspondence was established between the N_(2) concentration and the volume fraction of LPBF in-situ synthesized Ti N.Our results show that the GLSTi composites exhibit superior mechanical properties compared to pure titanium fabricated by LPBF under pure Ar.Specifically,the tensile strength of GLSTi was more than 1.5times higher than that of LPBF-formed pure titanium,reaching up to 1100 MPa,while maintaining a high elongation at fracture of 17%.GLSTi breaks the bottleneck of high strength but low ductility exhibited by conventional nanoceramic particle-strengthened titanium matrix composites,and the hetero-deformation induced strengthening effect formed by the Ti N/Ti layered structure explained its strength-plasticity balanced principle.The microhardness exhibits a jagged variation of the relatively low hardness of 245 HV0.2 for the pure titanium layer and a high hardness of 408 HV0.2 for the N_(2) in-situ synthesis layer.Our study provides a new concept for the structure-performance digital customization of 3D-printed Ti-based composites.

Preparation of Flower-like Copper Foam Supported Co_(3)O_(4) Electrocatalyst and Its Hydrogen Evolution Performance

Flower-like copper foam Co_(3)O_(4) catalysts(Co_(3)O_(4)/CF) were prepared by hydrothermal method.The crystalline structure and microscopic morphology of the prepared samples were characterized by using X-ray diffractometer(XRD) and scanning electron microscope(SEM),and the electrochemical properties were investigated by an electrochemical workstation.The experimental results show that the Co_(3)O_(4) catalysts are successfully prepared on the foamed copper support by hydrothermal method,and the material’s morphology is mainly flower cluster.When the current density is 10 mA·cm^(-2),the overpotential value of the Co_(3)O_(4)/CF catalyst is 141 mV,lower than that of blank support.The electrochemical impedance(EIS) spectrum shows that the R_(ct )value of the Co_(3)O_(4)/CF catalyst decreases,and the Coulomb curves of double-layer show that the electrochemically active area of the Co_(3)O_(4)/CF catalyst efficiently increases compared with that of the blank support.Therefore,the as-obtained Co_(3)O_(4)/CF catalyst exhibits a good hydrogen evolution rate,showing great applicability potential in the catalytic electrolysis of water for hydrogen production.

Parametric study on contact sensors for MASW measurement-based interfacial debonding detection for SCCS

Steel-concrete composite structures(SCCS)have been widely used as primary load-bearing components in large-scale civil infrastructures.As the basis of the co-working ability of steel plate and concrete,the bonding status plays an essential role in guaranteeing the structural performance of SCCS.Accordingly,efficient non-destructive testing(NDT)on interfacial debondings in SCCS has become a prominent research area.Multi-channel analysis of surface waves(MASW)has been validated as an effective NDT technique for interfacial debonding detection for SCCS.However,the feasibility of MASW must be validated using experimental measurements.This study establishes a high-frequency data synchronous acquisition system with 32 channels to perform comparative verification experiments in depth.First,the current sensing approaches for high-frequency vibration and stress waves are summarized.Secondly,three types of contact sensors,namely,piezoelectric lead-zirconate-titanate(PZT)patches,accelerometers,and ultrasonic transducers,are selected for MASW measurement.Then,the selection and optimization of the force hammer head are performed.Comparative experiments are carried out for the optimal selection of ultrasonic transducers,PZT patches,and accelerometers for MASW measurement.In addition,the influence of different pasting methods on the output signal of the sensor array is discussed.Experimental results indicate that optimized PZT patches,acceleration sensors,and ultrasonic transducers can provide efficient data acquisition for MASW-based non-destructive experiments.The research findings in this study lay a solid foundation for analyzing the recognition accuracy of contact MASW measurement using different sensor arrays.

STRUCTURAL EVOLUTION OF UNDERCOOLED SINGLE-PHASE Ni-2wt%Pb MONOTECTIC ALLOY

The structural evolution of undercooled single-phase Ni-2wt%Pb monotectic alloy was systematically investigated by the method of molten glass denucleating combined with superheating cycle. Within the achieved undercooling range of 22 to 280 K, the solidification structure undergoes three changes at 22 K, 88 K and 187 K, respectively. With the increase of undercooling, common dendrites, the first class granular grains, undercooled dendrites and the second class granular grains come out one after the other. Analytical results show that the granulation mechanism of the first class granular grains is owing to dendrite remelting and recrystallization, and the granulation mechanism of the second is owing to dendrite break-up and recrystallization.

A Review of Structural Health Monitoring Techniques as Applied to Composite Structures

Structural Health Monitoring(SHM)is the process of collecting,interpreting and analysing data from structures in order to determine its health status and the remaining life span.Composite materials have been extensively use in recent years in several industries with the aim at reducing the total weight of structures while improving their mechanical properties.However,composite materials are prone to develop damage when subjected to low to medium impacts(i.e.1-10 m/s and 11-30 m/s respectively).Hence,the need to use SHM techniques to detect damage at the incipient initiation in composite materials is of high importance.Despite the availability of several SHM methods for the damage identification in composite structures,no single technique has proven suitable for all circumstances.It must be noted that the amount of techniques available nowadays is too extensive to be comprehensively reviewed in a single paper.Therefore,the focus will be on techniques that can serve as a starting point for studies focusing on damage detection,localisation,assessment and prognosis on certain kinds of structures.Thus,the line of thought behind the search and the structure of this review is a result of objectives beyond the scope of the paper itself.Nevertheless,it was considered that,once the above was understood,an updated synopsis such as this could also be useful for other researchers in the same field.

Floristic Composition, Structure and Soil Properties of Mixed Deciduous Forest and Deciduous Dipterocarp Forest: Case Study in Madan Watershed, Myanmar

Patterns of woody regeneration in terms of species composition and diversity were studied in mixed deciduous forest (MDF) and deciduous dipterocarp forest (DDF) in Minbyin reserved forest of Lewe Township. A total of 57 plant species of MDF belonging to 28 families and 342 individuals and 25 plant species of DDF consist of 15 families and 285 individuals were identified. Plant species diversity was quantitatively higher in the MDF (H' = 3.68) compared to the DDF (H' = 2.39). Tectona grandis showed the highest density (30), dominance (4.40 m2) and IVI (27.01) of MDF and Dipterocarpus tuberculatus also composed the highest density (109), dominance (9.02 m2) and IVI (81.87) in DDF. The smallest diameter class (10 - 20 cm) comprised with 29 species, 103 individuals in MDF and 18 species, 85 individuals in DDF. The size class distribution displayed a reverse J-shaped pattern. The largest numbers of species were concentrated in the smallest height class in both investigated forests because of height and diameter distribution is closely related. The total densities of seedlings and saplings were 1219 and 531 ha-1 in MDF and 988 and 444 ha-1 in DDF respectively. Although soil texture of (40 - 50 cm) and (90 - 100 cm) were sandy clay loam in mixed deciduous forest, the other layers of both investigated forests were sandy loam.

The Key Influence of Fluid in Metamorphic Rock Preserves, Mineral Assemblages, Compositions and Structures: Study from High-Pressure Eclogite and Its Amphibolization in the Western Dabie Mountains,Central China

The most of high/ultrahigh-pressure(HP/UHP)terranes of the world are characterized by the occurrence of numerous pods,lenses or layered blocks of eclogite and amphibolites(e.g.O’Brien,1997;Elvevold and Gilotti,2000;Zhang et al.,2003;and references there in).Field and petrological features suggest that amphibolites should

In-service Structural Health Monitoring of a Full-scale Composite Horizontal Tail

In-service structural health monitoring（SHM） technologies are critical for the utilization of composite aircraft structures. We developed a Lamb wave-based in-service SHM technology using built-in piezoelectric actuator/sensor networks to monitor delamination extension in a full-scale composite horizontal tail. The in-service SHM technology combine of damage rapid monitoring（DRM） stage and damage imaging diagnosis（DID） stage allows for real-time monitoring and long term tracking of the structural integrity of composite aircraft structures. DRM stage using spearman rank correlation coeffi cient was introduced to generate a damage index which can be used to monitor the trend of damage extension. The DID stage based on canonical correlation analysis aimed at intuitively highlighting structural damage regions in two-dimensional images. The DRM and DID stages were trialed by an in-service SHM experiment of CFRP T-joint. Finally, the detection capability of the in-service SHM technology was verified in the SHM experiment of a full-scale composite horizontal tail. Experimental results show that the rapid monitoring method effectively monitors the damage occurrence and extension tendency in real time; damage imaging diagnosis results are consistent with those from the failure model of the composite horizontal tail structure.

On the Impact of Manufacturing Uncertainty in Structural Health Monitoring of Composite Structures: A Signal to Noise Weighted Neural Network Process

This article investigates the potential impact of manufacturing uncertainty in composite structures here in the form of thickness variation in laminate plies, on the robustness of commonly used Artificial Neural Networks (ANN) in Structural Health Monitoring (SHM). Namely, the robustness of an ANN SHM system is assessed through an airfoil case study based on the sensitivity of delamination location and size predictions, when the ANN is imposed to noisy input. In light of the observed poor performance of the original network, even when its architecture was carefully optimized, it had been proposed to weigh the input layer of the ANN by a set of signal-to-noise (SN) ratios and then trained the network. Both damage location and size predictions of the latter SHM approach were increased to above 90%. Practical aspects of the proposed robust SN-ANN SHM have also been discussed.

The Minaret of the Great Mosque in Algiers,a Structural Challenge

The Great Mosque in Algiers will be the third largest mosque in the world and its minaret the highest. The region has a high seismic risk. The project designed by a German team of architects and engineers is under construction and will be finished by 2016. Due to the minaret slenderness and to the special composite structure chosen to withstand lateral loading, the structural design faced some challenging aspects. The paper presents the design philosophy, some significant structural features and details of the minaret structure.

RECOGNITION OF STRUCTURAL DIAGRAM OF MACHINE TOOL SPEED CHANGE SYSTEM WITH ANY COMPOSITE RATIO

The speeds of output shaft of a machine tool ni=n1E are expressed by the exponentvalues Ej of series ratio . Based on this expression, the inherert law of differences between expo-nents of driven points from the same drive pair and the same driving point and of correspordingdriving points A method for finding out the exponents of the range ratio hat been given accordingto the law and it is called coordinate diagram method. Finally, a mathematical model is constiuctedand a computer programme is designed.

Numerical investigation of the mechanical behavior of the backfill–rock composite structure under triaxial compression

To ensure safe and economical backfill mining,the mechanical response of the backfill–rock interaction system needs to be understood.The numerical investigation of the mechanical behavior of backfill–rock composite structure(BRCS)under triaxial compression,which includes deformation,failure patterns,strength characteristics,and acoustic emission(AE)evolution,was proposed.The models used in the tests have one rough interface,two cement–iron tailings ratios(CTRs),four interface angles(IAs),and three confining pressures(CPs).Results showed that the deformation,strength characteristics,and failure patterns of BRCS under triaxial compression depend on IA,CP,and CTR.The stress–strain curves of BRCS under triaxial compression could be divided into five stages,namely,compaction,elasticity,yield,strain softening,and residual stress.The relevant AE counts have corresponding relationships with different stages.The triaxial compressive strengths of composites increase linearly with the increase of the CP.Furthermore,the CP stress strengthening effect occurs.When the IAs are45°and 60°,the failure areas of composites appear in the interface and backfill.When the IAs are 75°and 90°,the failure areas of composites appear in the backfill,interface,and rock.Moreover,the corresponding failure modes yield the combined shear failure.The research results provide the basis for further understanding of the stability of the BRCS.

Failure characteristics and the damage evolution of a composite bearing structure in pillar-side cemented paste backfilling

A backfilling body-coal pillar-backfilling body(BPB)structure formed by pillar-side cemented paste backfilling can bear overburden stress and ensure safe mining.However,the failure response of BPB composite samples must be investigated.This paper examines the deformation characteristics and damage evolution of six types of BPB composite samples using a digital speckle correlation method under uniaxial compression conditions.A new damage evolution equation was established on the basis of the input strain energy and dissipated strain energy at the peak stress.The prevention and control mechanisms of the backfilling body on the coal pillar instability were discussed.The results show that the deformation localization and macroscopic cracks of the BPB composite samples first appeared at the coal-backfilling interface,and then expanded to the backfilling elements,ultimately appearing in the coal elements.The elastic strain energy in the BPB composite samples reached a maximum at the peak stress,whereas the dissipated energy continued to accumulate and increase.The damage evolution curve and equation agree well with the test results,providing further understanding of instability prevention and the control mechanisms of the BPB composite samples.The restraining effect on the coal pillar was gradually reduced with decreasing backfilling body element's volume ratio,and the BPB composite structure became more vulnerable to failure.This research is expected to guide the design,stability monitoring,instability prevention,and control of BPB structures in pillar-side cemented paste backfilling mining.

Design of Multi-layered Protection Against Guided Mortar Threats Yhrough Numerical Modeling

The trade—off between protection and weight is a constant consideration when designing a portable protective solution.Greater mobility is a desirable attribute and protection must therefore adapt,prompting a demand for lightweight,simple to construct,low-cost and effective ballistic protection systems.High strength and ductility,wave spreading capability and good energy absorption are key properties for ballistic protection.Four materials,polycarbonate,Kevlar?-epoxy,polyurethane foam,and aluminium alloy,possess these properties and were selected for analysis by numerical simulation.Multilayered configurations were proven to be an optimal solution,by exploiting the advantages of each material without having large penalties of mass and cost.Numerical modelling using ANSYS AUTODYN?is used to simulate monolithic and multi-layered target configurations,to obtain the penetration mitigation performance.The results are analysed to select configurations based on different requirements,such as lowest cost,lowest mass,best performance,and optimal configuration which balanced the three key parameters mentioned.The optimal configuration of Aluminium,Kevlar-Epoxy,Polyurethane,and Polycarbonate has layers with thickness of 7,3,38,2 mm respectively with a total mass of 7.97 kg,total cost of$39.86 and penetration of 29.34%(14.67 mm).Polynomial relationships between performance and mass/cost are also determined.

Composite wave-absorbing structure combining thin plasma and metasurface

In order to solve the thickness dependence of plasma absorption of electromagnetic waves and further reduce the backward radar scattering cross section(RCS)of the target,we designed a novel composite structure of a metasurface and plasma.A metasurface with three absorption peaks is designed by means of an equivalent circuit based on an electromagnetic resonance type metamaterial absorber.The reflection and absorption of the composite structure are numerically and experimentally verified.The finite integration method was used to simulate a composite structure of finite size to obtain the RCS.The experimental measurements of electromagnetic wave reflection were conducted by a vector network analyzer(Keysight N5234A)and horn antennas,etc.The research showed that the absorption capacity of this composite structure was substantially improved compared to either the plasma or the metasurface,and it is more convenient for application due to its low plasma thickness requirement and easy fabrication.