Physical Thickness Research Articles

Effects of Compression Ratio and Phenolic Resin Concentration on the Properties of Laminated Compreg Inner Oil Palm and Sesenduk Wood Composites

Due to its inferior properties, oil palm wood (OPW) extracted from the inner layer of the oil palm (Elaeis guineensis) trunk, referred as inner OPW in this study, is frequently regarded as a waste. Phenolic resin treatment and lamination of inner OPW with other hardwoods may be an excellent way to improve the properties of the inner OPW. In this study, inner OPW were treated with two different concentrations (15% and 20%) of low molecular weight phenol formaldehyde resin (LmwPF) and compressed at different compression ratios (10%, 20%, and 30%). The physical and mechanical properties of the modified inner OPW’s were evaluated according to British Standards (BS) 373: 1957. The results revealed that inner OPW treated with the highest compression ratio (30%) and resin concentration (20%) exhibited the highest weight percent gain, polymer retention and density. In the following phase of the research, the treated inner OPW was used as the core layer in the fabrication of a three-layer laminated compreg hybrid composites, with untreated and treated sesenduk (Endospermum diadenum) wood serving as the face and back layers. The compression ratios of 10% and 20% and resin concentrations of 10% and 20% were used in this phase of study as laminated boards made with 30% compression ratio failed. The findings showed that resin concentration had a significant impact on both the inner OPW and the laminated compreg hybrid panels. Markedly, higher resin concentrations (20%) resulted in improved physical properties, i.e., thickness swelling and water absorption, as well as enhanced mechanical properties (modulus of rupture and modulus of elasticity). Although compression ratios had no significant effect on the properties of the laminated products, those compressed at higher compression ratios (20%) performed slightly better than the panels compressed at lower compression ratios (10%).

The Properties of Particleboard Composites Made from Pleurotus ostreatus Baglog Waste Using Citric Acid and Sucrose Adhesive

Pleurotus ostreatus (PO) is one of the edible mushrooms cultivated in baglog as the medium. Baglog’s productive age is around 4-5 weeks. The more PO produced, the amount of baglog waste also increases. The main component of baglog is wood sawdust, which contains lignocellulose; therefore, baglog has great potential to be used as a raw material for making particleboard. This research aims to make particleboard from baglog waste and determine the effect of the type and adhesive concentration on the physical and mechanical properties of the particleboard that is produced. Particleboard is made by mixing baglog waste, whose particle size is 40 mesh, with citric acid and sucrose adhesives whose concentrations are varied between 50%, 60%, and 70%. Furthermore, the particleboard was formed using a hot press machine (200 °C, 10 MPa) for 15 minutes. The obtained particleboard will be analyzed for its physical properties, including density, moisture content, water absorption, thickness swelling, morphology, and mechanical properties, including modulus of rupture (MOR) and modulus of elasticity (MOE). The test refers to the JIS A 5908-2003 type 8 standard. As a result, particleboard made using citric acid adhesive (citric acid 70%; C70) has a better physical and mechanical properties compared to sucrose adhesive, with a density value of 0.86 g/cm³, moisture content of 4.118%, thickness expansion of 3.992%, water absorption capacity of 36.89%, 13.456%, MOR 9.682 MPa, and MOE 1.455 GPa.

Oxygen A-band absorption spectroscopy with solar photon counting and lithium niobate nanophotonic circuits

Oxygen A-band measurements can provide important information about cloud top height, cloud physical and optical thickness, and surface atmospheric pressure. So far, O2 A-band measurements are typically made with spectrometers at a spectral resolution of 40 p.m. (such as in the OCO-2 satellite) or a coarser resolution. This paper reports a new CubeSat measurement concept with higher spectral resolution over the O2 A-band using integrated photonic circuits and solar photon counting techniques. An integrated Micro-ring filter (MRR) chip with 10 p.m. resonant linewidth with an extinction ratio of 25 dB or higher is designed, fabricated, and used for precise measurements of the atmospheric oxygen A-band absorption line-shapes around 770 nm. With solar-photon counting and using a narrow-band filter made of an integrated, fast-swept MRR on lithium niobate on insulator (LNOI), we have demonstrated a high-resolution measurement of the O2 A-band absorption spectrum, exhibiting good agreement with the HITRAN database.

Effect of incorporation of wheat bran, rice bran and banana peel powder on the mesostructure and physicochemical characteristics of biscuits.

Various types of natural fiber-rich ingredients are added into bakery-based products to improve their fiber content for health promotional purposes. But the majority of these products usually include exotic dietary fiber components. The aim of this study was to develop biscuits incorporated with wheat bran, rice bran and banana peel powder and to evaluate the effects on physicochemical properties and sensory acceptability of these different biscuit samples. Wheat bran, rice bran and banana peel powder was used to substitute refined wheat flour in biscuit samples at different levels (0, 5, 10, 15, 20, 25, and 30%). The effect of wheat bran, rice bran and banana peel powder incorporation on proximate composition, physical characteristics, texture profile, color and sensory evaluation of biscuit samples were investigated. The moisture content of the product showed a significant (p ≤ 0.01) decreasing trend while as protein showed increasing trend with increasing level of incorporation of wheat bran, rice bran and banana peel powder. Also there was a considerable effect on L*(darkness to lightness), a*(greeness to redness), and b*(blueness to yellowness) values of biscuit samples. Among the physical parameters diameter and thickness decreased non-significantly (p ≤ 0.01) with the addition of different fibers whereas spread ratio and weight increases. Sensory attributes showed a significant (p ≤ 0.01) increasing trend with an increase in the level of incorporation of different fibers. Based on sensory evaluation biscuits prepared with 15% wheat bran, 15% rice bran, and 10% banana peel powder were rated best. The biscuits were packed in high density polyethylene (HDPE) boxes and were analyzed on different intervals viz. 0, 30, and 60th day. In samples of optimized biscuits, the ash content, protein, fat and color exhibited a non- significant tendency of declining over storage. It was discovered that the ash content dropped from0.86 to 0.67% in Wb4, 0.95 to 0.75% in Rb4, and 1.15to 0.92% in Bpp3. However there was a considerable increase in moisture content during storage.

(Invited) Thin-Film Transistor Accumulation-Mode Modeling

Analytical equations are developed for electrostatic assessment of accumulation-mode thin-film transistors (TFTs) so that potential, electric field, and accumulation layer free electron concentration profiles may be generated. Additionally, equations are derived for plotting TFT trap density versus surface potential, based on accurate extraction of the channel mobility as a function of gate voltage. A key factor in formulating these device physics equations is distinguishing between a ‘long-base’ or ‘short-base’ channel thickness. A ‘long-base’ (‘short-base’) channel thickness is defined to occur when the accumulation layer thickness (as calculated in the normal manner) is less than (greater than) the physical thickness of the channel layer. The electrostatic equations derived herein are applied to the analysis of two amorphous oxide semiconductor (AOS) TFTs with differing channel layers, i.e., a 40 nm amorphous indium gallium zinc oxide (a-IGZO) or a 7 nm amorphous indium zinc oxide (a-IZO). Application of these equations suggests that optimal TFT performance is obtained when the channel layer thickness is chosen to be similar to its Debye length. Estimated trap densities of these two AOS TFTs are found to be quite similar. Therefore, the superior mobility performance of the a-IZO TFT compared to the a-IGZO TFT is ascribed to the smaller effective mass of a-IZO, assuming that the maximum (no trapping) drift mobility in the channel is established by the thermally-limited diffusive mobility.

Utilization of different size waste melamine impregnated paper as an adhesive in the manufacturing of particleboard

In this study, the efficiency of waste melamine impregnated paper (WMIP) as an adhesive; effects of WMIP usage with different sizes and amounts as a resin in three-layer particleboard manufacturing on mechanical, physical, surface roughness properties and formaldehyde emission values were investigated. Three-layer particleboards were manufactured with three different sizes (small, medium and large) and four different rates (10, 15, 20, 25% of total board weight) of WMIP. Mechanical (bending strength, modulus of elasticity, internal bond strength, surface soundness, screw withdrawal strength), physical (density, thickness swelling, water absorption, Brinell hardness, and surface roughness) properties and formaldehyde contents of the samples were determined according to relevant standards. As a result of the study, it was determined that WMIP still has some uncured adhesive with curing ability in it. The size and amount of WMIP had a statistically significant effect on the particleboard properties (Mechanical, Physical Formaldehyde emission and surface roughness). While the mechanical and physical properties improved as the amount of WMIP increased, these values deteriorated as the size of the WMIP increased. The best mechanical and physical results were obtained by using small-size WMIP at the rate of 25% and all the panel groups produced with small-size WMIP (except 10% ratio) have achieved the mechanical values required in the standard. In all particleboard groups produced, only the one with 25% of the small-size WMIP used group was provided with the standard requirements for thickness swelling properties. For optimal performance (the least rough surface characteristics), the formulation of the panels should contain small WMIP sizes and a 20% WMIP ratio. The findings also showed that increasing the WMIP ratio has resulted in better mechanical properties. Through this study, some technological properties of three-layer particleboard produced with WMIPs were determined and potential utilization of WMIPs in particleboard manufacturing as an adhesive was demonstrated.

Design and Performance Analysis of Zinc Oxide Thin Film Transistor (ZnO2TFT) with High-k Dielectric Materials

ZnO has been extensively used as oxide in the thin film electronics industry because of its performance advantages such as electrical and optical properties. This study represents the design and optimization of the ZnO thin film transistor (TFT). The characteristics of the device are studied using the software Silvaco TCAD ATLAS. The improvement in the performance of the device has been observed in optimizing dielectric layer thickness ([Formula: see text]). Further SiO2oxide layer is replaced with the high-[Formula: see text] dielectric to improve its performance. The use of high-[Formula: see text] dielectric gives the concept of equivalent oxide thickness (EOT) in which physical thickness (PT) of the dielectric layer is increased without increasing electric thickness (effective thickness), which improves the reliability of the device. The electrical parameters extracted for the low-[Formula: see text] SiO2 ([Formula: see text]) at thickness (TSiO2) 50[Formula: see text]nm are [Formula: see text][Formula: see text]A, [Formula: see text][Formula: see text]A, [Formula: see text], [Formula: see text][Formula: see text]V/decade, [Formula: see text][Formula: see text]V. The high performance of the device has been achieved using Al2O3and HfO2as the dielectric material.

Variety of Approaches for Generating Volume of Aquara-6 Sunflower Seeds

Sunflower is a major oilseed crop in the world. Its seeds are applied to extract oil which gives high nutritional value and can be kept longer than other vegetable oils. In this article, we focus on Aquara-6 sunflower in order to study the way for generating volume of seeds on each head. The distinctive features for this type of sunflower are high yield and large flowers. The aims of this study are to present five ways to calculate the volumes of Aquara-6 sunflower seeds for each head and to compare these methods to volume measurement by replacing them with water of all seeds. This is collected from the physical grain, including width, length, and thickness, of each sunflower head in order to prepare data for calculating volumes of five methods. After that they are estimated via five methods from three regions on sunflower heads and on the whole heads. Moreover, we analyze the comparison between the estimated volumes and the actual volumes of fifteen sunflower heads. The results show that the best way to approximate the volume of seeds on each head is the square pyramid's formular and the second way is the circular cylinder's formular. These methods can be alternative ways to generate the volume of sunflower seeds in the future. In addition, this can be helpful to study the moisture content, especially in the drying process.

Thin-film transistor accumulation-mode modeling

Analytical equations are developed for electrostatic assessment of accumulation-mode thin-film transistors (TFTs) so that potential, electric field, and accumulation layer free electron concentration profiles may be generated. Additionally, equations are derived for plotting TFT trap density versus surface potential, based on accurate extraction of the channel mobility as a function of gate voltage. A key factor in formulating these device physics equations is distinguishing between a ‘long-base’ or ‘short-base’ channel thickness. A ‘long-base’ (‘short-base’) channel thickness is defined to occur when the accumulation layer thickness (as calculated in the normal manner) is less than (greater than) the physical thickness of the channel layer. The electrostatic equations derived herein are applied to the analysis of two amorphous oxide semiconductor (AOS) TFTs with differing channel layers, i.e., a 40 nm amorphous indium gallium zinc oxide (a-IGZO) or a 7 nm amorphous indium zinc oxide (a-IZO). Application of these equations suggests that optimal TFT performance is obtained when the channel layer thickness is chosen to be similar to its Debye length. Estimated trap densities of these two AOS TFTs are found to be quite similar. Therefore, the superior mobility performance of the a-IZO TFT compared to the a-IGZO TFT is ascribed to the smaller effective mass of a-IZO, assuming that the maximum (no trapping) drift mobility in the channel is established by the thermally-limited diffusive mobility.

A Three-Dimensional Transition Interface Model for Bolt Joint

Bolt connection is an important component in mechanical structure which significantly affects the dynamic property of the whole structure. In this paper, a three-dimensional transition interface model which contains geometric and physical parameters is proposed to model the bolted joint based on the contact analysis. The geometric parameters and the physical parameters are used to characterize the influence of contact area and contact pressure which are related to connection parameters such as material, roughness, connection thickness, and tightening force, respectively. After that, the geometric parameter identification method is proposed, and the geometric parameter database of bolt joints for machine tools is constructed based on the Kriging interpolation method. Then, the model updating method based on the combination of modal parameters and frequency response function is proposed to identify the physical parameters and thickness of the three-dimensional transition interface model. The database of the transition interface model is constructed after verifying the validity of the proposed model. Finally, an engineering example of an engraving machine tool is used to check the practicability of the proposed transition interface model and the usage of the constructed parameter database.

Seismic interpretation pitfalls caused by interference effects, exemplified by seismic modeling of outcropping chalk successions

Interference and inherent resolution limitations are well-recognized problems in reflection seismic data and have over time led to misinterpretations. Acquisition of seismic data containing a broad range of frequencies, including high frequencies, does not solve this problem but merely moves the problem to a finer scale. Forward seismic modeling of known geologic scenarios is a valuable tool for studying anticipated seismic responses of successions with a given set of geologic and/or rock physical characteristics and for predicting interpretational challenges. We perform finite-difference-based seismic forward modeling on a conceptual geologic model derived from outcropping chalk sections in southeast Denmark and evaluate possible pitfalls that may hamper interpretation of seismic data acquired from strata with similar characteristics. We demonstrate that interbedded strata with contrasting physical properties and variable thickness can result in interference effects resembling faults and fractures. The result has significance for characterization, e.g., geothermal sites, potential CO2 storage targets, groundwater reservoirs, and hydrocarbon exploration sites, in which the proper imaging of faults and fractures from seismic data is an essential task.

Directional Damping of Plasmons at Metal-Semiconductor Interfaces.

ConspectusOver the past decade, it has been shown that surface plasmons can enhance photoelectric conversion in photovoltaics, photocatalysis, and other optoelectronic applications through their plasmonic absorption and damping processes. However, plasmonically enhanced devices have yet to routinely match or exceed the efficiencies of traditional semiconductor devices. The effect of plasmonic losses dissipates the absorbed photoenergy mostly into heat and that has hampered the realization of superior next-generation plasmonic optoelectronic devices. Several approaches are being explored to alleviate this situation, including using gain to compensate for the plasmonic losses, designing and synthesizing alternative low-loss plasmonic materials, and reducing activation barriers in plasmonic devices and physical thicknesses of photoabsorber layers to lower the plasmonic losses. A newly proposed plasmon-induced interfacial charge-transfer transition (PIICTT) mechanism has proven to be effective in minimizing energy loss during interfacial charge transfer. The PIICTT leads to a damping of metallic plasmonics by directly generating excitons at the plasmonic metal/semiconductor heteronanostructures. This novel concept has been proven to overcome some of the limitations of electron-transfer inefficiencies, renewing a focus on surface plasmon damping processes with the goal that the plasmonic excitation energies of metal nanoparticles can be more efficiently transferred to the adjacent semiconductor components in the absence and presence of an effective interlayer of carrier-selective blocking layer (CSBL). Several theoretical and experimental studies have concluded that efficient plasmon-induced ultrafast hot-carrier transfer was observed in plasmonic-metal/semiconductor heteronanostructures. The PIICTT mechanism may well be a general phenomenon at plasmonic metal/semiconductor, metal/molecule, semiconductor/semiconductor, and semiconductor/molecule heterointerfaces. Thus, the PIICTT presents a new opportunity to limit energy loss in plasmonic-metal nanostructures and increase device efficiencies based on plasmonic coupling. The nonradiative damping of surface plasmons can impact the energy flux direction and thereby provide a new process beyond light trapping, focusing, and hot carrier creation.In this Account, we draw much attention to the benefits of interfacial plasmonic coupling, highlighting recent pioneering discoveries in which plasmon-induced interfacial charge- and energy-transfer processes enable the generation of hot charge carriers near the plasmonic-metal/semiconductor interfaces. This process is likely to increase the photoelectric conversion efficiency, constituting "plasmonic enhancement". We also discuss recent advances in the dynamics of surface plasmon relaxation and highlight exciting new possibilities for plasmonic metals and their interactions with strongly attached semiconductors to provide directional energy fluxes. While this new research area comes on the heels of much elaborate research on both metal and semiconductor nanomaterials, it provides a subtle but important refinement in understanding the optoelectronic properties of materials with far-reaching consequences from fundamental interface science to technological applications. We hope that this Account will contribute to a more systematic description of interface-coupled plasmonics, both fundamentally and in terms of applications toward the design of plasmonic heterostructured devices.

The effect of konjac glucomannan and Aloe vera gel concentration on physical and mechanical properties of edible film

Glucomannan from konjac can be used as an ingredient for edible films. However, the use of glucomannan as an edible film has a high water vapour transmission rate and water solubility. Aloe vera is known to have the ability to reduce water vapour transmission and solubility, thus, it is suitable to improve these properties of glucomannan edible film. The purpose of this study was to determine the effect, interaction, and best treatment between three levels of glucomannan flour concentration (1%, 1.3%, 1.6%) and the addition of Aloe vera gel (0%, 5%, 10%) on the physical (thickness, water-solubility, optical transparency) as well as mechanical characteristics (tensile strength, elongation at break, water vapour transmission rate) of the edible film using randomized block factorial experimental design. The results showed that there were interactions between the concentration of glucomannan flour and the addition of Aloe vera gel on the elongation of the film. Glucomannan flour addition had a significant effect on thickness, solubility, tensile strength, and elongation of edible films. The addition of Aloe vera gel significantly affected the elongation of the edible film. The best treatment in this study was the treatment with 1.6% glucomannan flour and 10% Aloe vera gel which obtained a thickness value of 0.105 mm; tensile strength 0.854 MPa; elongation 9.53%; water solubility 54.72%; transparency 2.925 A.mm-1 ; and WVTR value 3.889 g.m-2 .day-1 .

Physical-Mechanical properties of wood based composite reinforced with recycled polypropylene and cowpea (Vigna unguiculata Walp.) husk

The need for a sustainable environment and biomass valorization has encouraged research on the recycling of agro and industrial wastes into roofing tiles, ceiling boards, particleboards and furniture. In this study, eco-friendly panels were produced from cowpea husk (CPH), wood chips (WC) and recycled polypropylene (rPP) at different CPH/WC weight percentages and a fixed weight of rPP as binder. The panels were produced by hot compression molding at 150 °C under 2.5 MPa and tested for mechanical (impact strength, modulus of rupture (MOR), modulus of elasticity (MOE)) and physical properties (water absorption (WA), thickness swelling (TS) and density). Fourier transform infra-red spectroscopy (FTIR) was used to study the functional groups in the composite board and raw materials used in addition to the chemical composition. Grey relational analysis was used to optimize performance to a single response, optimal performance was achieved with 80% WC and 20% CPH giving 9.41% water absorption, 15.28% thickness swelling, 1137 kg/m3 density, 0.127 J/mm impact, MOR of 17.96 MPa and MOE of 741.56 MPa. The physical properties evaluated satisfy the American National Standards Institute (ANSI) A 208.1 standard and confirms that the CPH, WC and rPP mixture can be used for the production boards with good dimensional stability and/or for use in applications where load bearing is not required in the construction industry such as ceiling boards and wall claddings.

Quebracho Tannin Bio-Based Adhesives for Plywood.

Wood-based products are traditionally bonded with synthetic adhesives. Resources availability and ecological concerns have drawn attention to bio-based sources. The use of tannin-based adhesives for engineered wood products has been known for decades, however, these formulations were hardly used for the gluing of solid wood because their rigidity involved low performance. In this work, a completely bio-based formulation consisting of Quebracho (Schinopsis balancae) extract and furfural is characterized in terms of viscosity, gel time, and FT-IR spectroscopy. Further, the usability as an adhesive for beech (Fagus sylvatica) plywood with regard to press parameters (time and temperature) and its influence on physical (density and thickness) and mechanical properties (modulus of elasticity, modulus of rupture and tensile shear strength) were determined. These polyphenolic adhesives presented non-Newtonian behavior but still good spreading at room temperature as well as evident signs of crosslinking when exposed to 100 °C. Within the press temperature, a range of 125 °C to 140 °C gained suitable results with regard to mechanical properties. The modulus of elasticity of five layered 10 mm beech plywood ranged between 9600 N/mm2 and 11,600 N/mm2, respectively, with 66 N/mm2 to 100 N/mm2 for the modulus of rupture. The dry state tensile shear strength of ~2.2 N/mm2 matched with other tannin-based formulations, but showed delamination after 24 h of water storage. The proposed quebracho tannin-furfural formulation can be a bio-based alternative adhesive for industrial applicability for special plywood products in a dry environment, and it offers new possibilities in terms of recyclability.

The Effect of Linear Low-Density Polyethylene and Palm Kernel Shell Ash Mixture on the Physical, Mechanical and Degradation Properties of Paving Blocks

The aim of this research was to evaluate the physical-mechanical parameters of paving stones obtained on the basis of the mixture of linear low-density polyethylene (LLDPE) and palm kernel shell ash (PKSA) waste. The ratio of LLDPE to PKSA waste (% weight) was varied in five treatments: A0 (100:0), A1 (97.5:2.5), A2 (95:5), A3 (92.5:7.5), A4 (90:10) and A5 (87.5:12.5). The physical appearance, thickness, compressive strength, water absorption, and morphological characteristics of the paving blocks were observed. The blocks were observed at ambient temperature, exposed to sunlight, and placed on the ground surface on day 0 and day 365. The results showed that addition of PKSA waste decreased the compressive strength but increased the water absorption capacity without a significant effect on the thickness of the paving blocks. Observation after 365 days showed insignificant decreases of compressive strength and thickness, whereas the water absorption capacity increased slightly. Small cracks and more voids in the surface, and more brittleness were observed. To summarize, composites of LLDPE and PSKA as filler have physical-mechanical properties that can be used for road pavement blocks.

Triple-wavelength quantitative phase imaging with refractive index measurement

A method to quantitatively measure the refractive index (RI) and the topography of transparent samples is proposed. Three quantitative phase images at different wavelengths are firstly obtained by using a quadriwave lateral shearing interferometry (QLSI) technique, and then the RIs at the three wavelengths and the physical thickness distribution of the sample are independently calculated with the help of Cauchy's dispersion formula. Neither the highly dispersive medium nor the manual operation of changing the surrounding medium is required. From the measured RIs, the composition of the sample can be identified besides the topography of the sample. Both simulation and experimental results verified the effectiveness and feasibility of the proposed method.

Usage Opportunities of Pomegranate (Punica Granatum) Peel Dried with Dif-ferent Methods in Whole Wheat Flour Chips

In this study, pomegranate peels were dried using three different drying methods, vacuum, microwave and convective. Dried peels were ground into powder and replaced (0, 5 and 10%) with whole wheat flour in chips formulation to enhance functional properties of chips. Some physical (diameter, thickness, spread ratio and weight), chemical (total phenolic content and antioxidant activity), color and texture properties of chips samples were determined. While the chips obtained with addition of microwave dried peels were brighter, higher values of yellowness were determined with vacuum dried peels. The increased ratio of pomegranate peel powder caused a decrease in diameter and spread ratio values of chips. The utilization of 10% pomegranate peel powder decreased the hardness of the chips samples. The addition of pomegranate peel powder was increased in total phenolic content and antioxidant activity of chips. As a result, pomegranate peel powder can be used as a functional ingredient in snacks product formulation.

Quantification of physical soil crust thickness and its effects on runoff and sediment yield

AbstractPhysical soil crusts will form on most soils during and after rainfall and it has important effects on the runoff and sediment on slopes. However, objective and effective methods for quantifying the characteristics of physical soil crusts (such as the thickness) are not currently available. A new method was used for determining the thickness of physical soil crusts based on X‐ray computed tomography (CT) in order to quantify the thickness of the structural crust (SC) and depositional crust (DC) for two typical erodible soils comprising granite red soil (GRS) and Quaternary red clay (QRC) in the red soil region of southern China. The pores in the GRS and QRC were characterized as finely and densely spatially distributed, with an average porosity of 15.47% and a range of 1.66–28.83%. The soil porosity increased rapidly in the 0‐to‐3‐mm depth, but the porosity of the SC and DC soil samples generally decreased or was stable in the 3‐to‐30‐mm depth. The average thickness of the soil crust was 1.31 mm, and the average thicknesses of SC and DC were 1.16 and 1.46 mm, respectively. The thickness of SC of GRS decreased with the slope, whereas the thickness of DC of QRC generally increased with the slope. The thickness of SC increased with runoff yield and its contribution rate to the runoff and sediment yield cannot be neglected. The study provides a method for the objective quantification of physical soil crust and can deepen the research on slope erosion process and influencing factors.

High-dispersive mirror for pulse stretcher in femtosecond fiber laser amplification system

We present a high-dispersive multilayer mirror for pulse stretching in a femtosecond fiber laser amplification system. The designed mirror contains 54 layers with a total physical thickness of 7.3 μm, which can provide a positive group delay dispersion (GDD) of 600 fs2 and a high reflectance over 99.9% from 1010 to 1070 nm. The samples were prepared by dual ion beam sputtering. The measured transmittance matches well with the theoretical result. The GDD characteristics of samples were tested by home-made white light interferometer. The measured GDD is higher than the design results, an average GDD of +722 fs2 from 1010 nm to 1070 nm. The mirrors were employed in a Yb-doped large-mode-area photonic crystal fiber amplification system. An input pulse compressed by the gratings with autocorrelation function of 83 fs is obtained with a stretched FWHM of 1.29 ps after 28 bounces between the dispersive mirrors. The results show that the multilayer dispersive mirror could be an effective and promising technique for pulse stretching in femtosecond amplification systems.