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In the process of improving coalbed permeability through pulse hydraulic fracturing, the cyclic loading effect influences the characteristics of micropores in coal matrix, thus affecting the process of gas migration. Therefore, it is essential to investigate the effect of cyclic loading on the pore structure of coal. Seven groups of loading tests at different frequencies and amplitudes were conducted on anthracite coal obtained from Shanxi Province, China, using a fatigue-testing machine. Subsequently, using a PoreMaster GT-60 Mercury-intrusion apparatus, the influence of the frequency and amplitude on the structural characteristics (including mercury-injection and mercury-ejection curves, pore size distribution, porosity, and specific surface area) of pores in coal samples was analyzed. Finally, the law and mechanism of action of the loading frequency and amplitude on pores in coal samples were comprehensively analyzed. The test results showed that, in the case of maintaining the sine-wave amplitude unchanged during loading while altering the loading frequency, the overall porosity and pore volume rise at different degrees. The growth of the loading frequency presents a more significant promotive effect on the initiation and development of pores and fractures. Moreover, it drives the transformation of micropores and transition pores into mesopores and macropores, thus increasing the proportion of seepage pores. Under the condition of large sine-wave amplitude during loading, macropores and mesopores are subjected to the repeated action of the external force, thereby reducing the overall porosity. In addition, the volume of the seepage pores declines, and the number of the coalesced pores decreases. Finally, in light of these results, the implications of frequency and amplitude selection in the process of pulse hydraulic fracturing are discussed. Therefore, the results of this research will provide an important theoretical basis for the field application of pulse hydraulic fracturing technology in coal mines.

The development of thermoelectric measurement technology at nanoscale is a challenging task. Here, a novel MEMS-based dual temperature control (DTC) measurement method for thermoelectric properties of individual nanowires was proposed. Different from conventional thermal bridge testing devices, this DTC thermoelectric testing device can obtain the thermoelectric properties by independently control ambient temperature and temperature difference between two ends of the nanowires through two separate resistance thermometers without auxiliary heating devices. The reliability of the model and the testing accuracy were verified by accurately measuring the thermal conductivity, electrical conductivity, and the absolute value of the Seebeck coefficient of VO2 nanowires.

Surface charges inside a nanopore determine the zeta potential and ion distributions and play a significant role in affecting ion transport and the sensitivity of detecting biomolecules. It is of great importance to study the fluctuation of surface charges with the salt concentration and pH in various applications of nanopores. Herein, we proposed a theoretical model to predict the surface charge density of a Si3N4 nanopore, in which both silanol and amine groups were taken into account. It was demonstrated that the surface charge density in the Si3N4 nanopore changes not only with pH but also with the salt concentration. The theoretical model could well predict the experimental results with different salt concentrations, pH values, and pore sizes. The effect of surface functional groups on the isopotential point (pHiep) of the Si3N4 nanopore was also systematically studied. The results indicated that the silanol groups are major determinants of the surface charge, but the influences of the amine groups should not be ignored because the small number of amine groups can change pHiep dramatically. The pHiep value of the Si3N4 nanopore was measured as 4.1, and the ratio of amine over silanol was ascertained as 0.013.

This study investigated the corrosion damage and bearing characteristics of bridge pile foundations under a dry-wet-freeze-thaw cycle of composite salt in an alpine salt marsh area using an in situ test, laboratory test, and numerical simulations. The in situ test showed that the dry-wet-freeze-thaw cycle has little effect on the quality of the concrete specimens and rebar. The area of the rebar at a depth of 0.25 m had the highest corrosion rate of 91%. The application of epoxy resin on the surface improved erosion resistance. After one year of outdoor dry-wet-freeze-thaw cycle test, due to the interaction of compound salts, the quality of specimens is reduced under the denudation of chloride ions, while the mass of specimens is increased by the corrosion products formed under the joint action of carbonate and sulfate, resulting in less obvious change of specimen quality, the antierosion coefficient of the specimens decreased, the maximum loss rate of compressive strength was 38.2%, and the pile foundation began to deteriorate. The laboratory test showed that expansive substances, such as Friedel salt, appeared in the concrete specimens of pile foundation during 225 cycles of dry-wet-freeze-thaw cycles, the relative dynamic elastic modulus was reduced by 60.9%, the antierosion coefficient was reduced to 0.51, and the compressive strength loss rate was 65.9%. As such, the pile foundation was seriously damaged. The numerical simulation shows that, with an increase of the peeling thickness and the corrosion depth, the bearing capacity of the pile foundation will gradually decrease after 8 years. Without maintenance, the bearing capacity of a pile foundation will decrease by 34.45% in the 20th year.

The flexural capacity of a single micropile is small, and some additional materials need to be built into the steel pipe to increase the flexural and tensile capacity of the structure. This...

In this study, a novel ternary nanocomposite, graphene-cerium oxide/porous polyaniline (rGO-CeO2/porous PANI), was synthesized via in situ polymerization and electrochemical reduction methods. A series of characterization such as SEM, XRD, and FTIR for the as-prepared composites proved that the ternary nanocomposite with well-connected nanosheets and porous structure has been successfully synthesized. The electrochemical performance testing illustrated that the electrochemical capacitance of rGO-CeO2/porous PANI nanocomposite could reach 454.8 F g−1 at 1.0 A g−1 when the mass ratio of CeO2 and porous PANI was 1:4. And the specific capacitance retained 70.23% after 10000 cycles at a current density of 5.0 A g−1 in 1.0 mol L−1 H2SO4 electrolyte. In comparison to the other nanomaterials, the excellent electrochemical performance of rGO-CeO2/porous PANI nanocomposite is attributed to good electrical conductivity and large specific surface area brought from graphene and porous PANI, energy density and better cycle life derived from CeO2, and synergetic contribution among the three components. Thus, the rGO-CeO2/porous PANI nanocomposite is a promising electrode material for supercapacitor.

Bulk metallic glasses (BMGs) with amorphous structure have excellent mechanical and chemical properties. In polishing process, it is hard but important to maintain amorphous state to keep original properties of BMGs, which are easily crystallized in traditional mechanical polishing and long-pulse laser polishing. In this paper, we first propose to use femtosecond laser double-pulse irradiation to smooth the surface of Zr-based BMG and make it free of laser-induced periodic surface structures and crystallization. Here, the smooth surface with half decreasing in roughness (Sa) to 111 nm is achieved by optimized parameters with laser pulse energy 0.06 μJ of the first pulse, energy ratio 40% of the first to the second pulse and time delay 20 ps. Obvious transition from a coarse surface to a smooth one occurs at near 10 ps time delay and 40% energy ratio. Mobility enhancement of molten materials guarantees the removal of undesirable surface structures through surface tension and gravity. Crystallization is avoided due to rapid heating and cooling under femtosecond laser double-pulse irradiation. A smoothed BMG surface obtained by this method verifies its feasibility in BMGs polishing.

In this paper, three-dimensional periodic numerical model for fully developed flow in a cross wavy primary surface recuperator for a microturbine system is built. The performance of flow and heat transfer is analyzed. The fields of flow and temperature in a gas and air channel are obtained. Different working conditions are numerically simulated. Numerical results are compared with experimental data concerned. Analysis results show that the flow in the gas and air channel is anti-symmetry along the centre of channel. The flow of fluid is fluctuant. The flow velocity of gas is much higher than that of air. The thermal ratio of cross wavy primary surface recuperator can reach 95.2%. The thermal ratio decreases with the improvement of gas inlet temperature. When gas inlet temperature increases by 100 K, the thermal ratio decreases by about 1%. The thermal ratio increases with the reduction of flow rate in the channel. When flow rate reduces by 40%, the thermal ratio increases by about 4%. The research results can be used to guide checking the performance of a recuperator.

Gd2-xEux(MoO4)3 red phosphors are synthesized by using co-precipitation method.X-ray diffraction(XRD),scanning electron microscopy(SEM) and fluorescence spectrum are used to characterize the structure and luminescent property of the samples.The luminescent properties of Gd2-xEux(MoO4)3 with various concentration of Eu3+ are investigated in detail.The results show that three dominant bands locate at 394,465,534 nm.The emission spectra exhibit the most intense emission at 589 nm and 613 nm,especially the later which is corresponding to the 5D0→7F2 transition of the Eu3+.With the increase of the concentration of Eu3+,the luminescent intensity of the phosphors is gradually increased.When x=0.6(i.e.Gd1.4Eu0.6-(MoO4)3),the luminescent intensity of the red phosphor is the strongest.

A digital microfluidic chip by electrostatic manipulation was designed and fabricated for a micro total analysis system.The principle of the electrostatic manipulation was proposed and the fabrication processes and experimental platform were demonstrated.For the chip,the silicon was taken as a substrate,a silicon oxide film as the insulating layer,a TiW/Au film as the electrode array,a Si3N4 film as the dielectric layer,and the fluorocarbon polymer as the hydrophobic layer.With an open structure instead of complex sandwich structure,the chip just needed a coplanar controlling electrode with one layer,so the process was simplified greatly.As the electrode array was embeded in the SiO2,the electric leakage from poor step coverage and dielectric breakdown at the margin were prevented.Furthermore,with thin dielectric layer and fine hydrophobic layer,the manipulating voltage was reduced greatly.Experiments show that,by controlling the sequence of voltage to the electrode array,the droplet can be transported smoothly in the two-dimension planes with a programmable manner at a low voltage of 20 V,and the maximum speed has reached 96 mm/s.The digital microfluidic chip can be used in a Lab-on-chip due to its simple structure and IC compatible fabrication processes.

An optical wavelength demultiplexer with the etched diffraction grating (EDG) on the silicon-on-insulator (SOI) material is demonstrated. Fabricated by the wet-anisotropic-etching method, 90° turning mirrors are used to bend waveguides, and the size of the EDG-based demultiplexer is minimized to only 16×2.5 mm2. The crosstalk is below −16 dB. The on-chip loss is about 9.97 dB, which is composed of about 8.72 dB excess loss and 1.25 dB diffraction loss. The polarization-dependent central wavelength shift is below 0.13 nm, and the polarization-dependent loss is about 0.35 dB. The sources of the crosstalk and loss are discussed in details, and the related measures to improve the performance are also presented.

Nanoscale vacuum electronics has been receiving much attention recently with the design and fabrication of vacuum field emission transistors and other devices. The performance and lifetime of these devices depend on the material choice for the emitters. Silicon carbide is a robust material with appealing work function and established fabrication processes. Field emission properties of SiC nanoemitters under different cathode–anode gaps are studied in this work with the aid of focused ion beam etching to control the gap precisely. When the electrode gap is as small as 20 nm, a considerable decrease in voltage and increase in field emission current are seen. When the electrode gap is decreased progressively, the emission current increases exponentially at a fixed collector voltage, and the absence of current saturation is ideal for device scaling. Simulations and Fowler–Nordheim equation are used to analyze the field emission characteristics. The emission is enhanced for both extremely short gaps and sharp ...

According to our previous results on the magnesium-based exhaust gas cleaning system (Mg-EGCS), PAHs and total oil content were the main factors affecting the COD in the wastewater. In this work, three kinds of adsorption materials were investigated and macroporous resin was selected for oil removal. The effects of the dosage of macroporous resin, adsorption time and the flow rate were studied, and thermodynamics equation was used to characterize the adsorption process. The results showed that macroporous resin is a good candidate for oil removal from desulphurization wastewater on board, and the COD after treatment can meet the discharge criteria set by the International Maritime Organization (IMO).

A compact optical demultiplexer with etched diffraction grating (EDG) is designed and fabricated on a silicon-on-insulator (SOI) material. Several 90? turning mirrors are used to bend the waveguides, and the size of the EDG-based demultiplexer is minimized to only 16?1.7?mm2. The crosstalk is about -18?dB. The on-chip loss is about 18.2?dB, which is composed of about 16.9?dB excess loss and 1.3?dB diffraction loss. Measures to improve the performance are discussed.

In this paper, the crystallization behaviors and transport properties are investigated for a-Ge/Bi bilayers annealed at different temperatures. For 200 nm/100 nm bilayers, it is found that the orientations of Bi in the bilayers annealed at 200°C and 340°C are preferred, as well as the original one. But they are random when the bilayers are annealed at temperatures between 240°C and 300°C. For 200 nm/50 nm bilayers, the orientations of Bi are always preferred. Corresponding to the orientations mentioned above, the minimum on the R(300 K)-Ta curve appears only in the case of 200 nm/100 nm bilayers.

Using Mössbauer spectra and x-ray diffraction patterns, annealed mechanically alloyed Fe - Cu has been investigated in this paper. It is found that in [Formula: see text], after it has been milled, fcc-Cu has transformed into bcc-Cu, and some Cu atoms have diffused into the Fe. After the alloy has subsequently been annealed, it is found that bcc-Cu has transformed back into fcc-Cu, while the Cu atoms in the Fe have been separated. In [Formula: see text], after being milled, an fcc-Fe-rich phase has been formed, and after the alloy has subsequently been annealed, this has transformed back to bcc-Fe. The shorter the milling time and the higher the annealing temperature, the faster the transformation. In [Formula: see text], after it has been annealed, the fcc-Fe-rich phase has transformed to bcc-Fe also, and the fcc-Cu-rich phase remains when the annealing temperature increases. All of these results show that the fcc-Fe-rich phase in the milled samples is a metastable phase - it will transform to stable bcc-Fe when it is annealed - while the long-milling-product fcc-Cu-rich phase is a stable phase.

Two-dimensional gas-liquid direct-contact heat-mass transfer in vertical pipe of CWS entrained-flow gasifier was simulated using VOF multiphase flow model. Water vapor diffusion in the syngas, surface tension and radiation heat transfer were considered when establishing the mathematics model. The corresponding experiment was conducted to validate the simulation results, and the numerical prediction of the temperature distribution was in a good agreement with experiment. With this model, the vapor concentration and the flow pattern of the falling water film with or without phase change were predicted.

In this paper, we present a novel technology to realize a doubly clamped nanobeam, which is preferred to cantilever because of its higher natural frequency with a same dimension, as a piezoresistive mass sensor. Ar selective bombardment was applied on a 200 nm thick doubly clamped nanobeam to form a piezoresistor in a Wheaston bridge along with other ordinary resistors. The device was electrostatically actuated and readout piezoresistively. The achieved merit product of Q-factor and f0 in air is as high as 3.5 times 108 , which hints a better mass detection resolution compared with its counterpart of micro cantilever, while our approach is simple and easily controlled.

Superconducting quantum interference device (SQUID) amplifier is best known for its low input impedance, low noise and low power consumption. Nowadays it is widely used for detecting the weak signals. Compared with other methods, the Nb/Al-AlOx/Nb structure Josephson junction based SQUID has the advantages of high transition temperature, high voltage flux modulation index and good heat recycle ability, wide critical voltage range, so it is a very good option for making SQUID amplifier. In this work, we fabricate the overdamped Josephson junction and washer dc SQUID, and test the I-V characteristics at He3 3 K stage temperature and calculate the current resolution of SQUID. The result of SQUID modulation property is good. The magnification becomes larger after increasing the input line number of loops, and the system noise becomes smaller after the join of the LC filter. This work is very important for designing and manufacturing transition edge sensor readout circuits.

In this paper, based on the inductively coupled plasma (ICP) etching and KOH wet etching techniques, the fabrication of integrated waveguide turning mirror (IWTMs) is presented.

Our investigation of in situ observations on electronic and mechanical properties of nano materials using a scanning electron microscope (SEM) and a transmission electron microscope (TEM) with the help of traditional micro-electro-mechanical system (MEMS) technology has been reviewed. Thanks to the stability, continuity and controllability of the loading force from the electrostatic actuator and the sensitivity of the sensor beam, a MEMS tensile testing chip for accurate tensile testing in the nano scale is obtained. Based on the MEMS chips, the scale effect of Young's modulus in silicon has been studied and confirmed directly in a tensile experiment using a transmission electron microscope. Employing the nanomanipulation technology and FIB technology, Cu and SiC nanowires have been integrated into the tensile testing device and their mechanical, electronic properties under different stress have been achieved, simultaneously. All these will aid in better understanding the nano effects and contribute to the designation and application in nano devices.

The hyperfine magnetic field (HMF) distributions obtained from the M\"ossbauer spectra of the alloys ${\mathrm{Fe}}_{\mathit{x}}$${\mathrm{Cu}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$ prepared by ball milling are studied. The HMF of the samples milled for 160 h decrease from 30 to 24 T when the Fe proportion x decreases from 0.8 to 0.6 and 0.5, while, for x=0.6 as the milling time t changes from 10 to 40 and 160 h, the proportion of the high fields in the HMF distribution decreases gradually, and the proportion of middle fields increases. These results agree with the results from x-ray diffraction and extended x-ray-absorption fine structure (EXAFS). Furthermore, a weak magnetic phase (10 T) is found from the M\"ossbauer spectra. The proportion of this phase remain at about 10% when x and t change. With the results of x-ray diffraction and EXAFS, three phases can be deduced in these samples: bcc Fe, fcc Fe rich, and fcc Cu rich.

Nanoscale refinement on a (100) oriented silicon-on-insulator (SOI) wafer was introduced by using tetra-methyl-ammonium hydroxide (TMAH, 25 wt%) anisotropic silicon etchant, with temperature kept at 50 °C to achieve precise etching of the (111) crystal plane. Specifically for a silicon nanowire (SiNW) with oxide sidewall protection, the in situ TMAH process enabled effective size reduction in both lateral (2.3 nm/min) and vertical (1.7 nm/min) dimensions. A sub-50 nm SiNW with a length of microns with uniform triangular cross-section was achieved accordingly, yielding enhanced field effect transistor (FET) characteristics in comparison with its 100 nm-wide pre-refining counterpart, which demonstrated the feasibility of this highly controllable refinement process. Detailed examination revealed that the high surface quality of the (111) plane, as well as the bulk depletion property should be the causes of this electrical enhancement, which implies the great potential of the as-made cost-effective SiNW FET device in many fields.

A turning mirror is a key component in compact optical waveguide devices and high-density integrated optics. An improved two-step method for fabrication of high-quality, compact turning mirrors in silicon-on-insulator materials is proposed. First, inductively coupled plasma etching is applied to produce the turning mirror, which keeps the turning mirror compact; then silicon wet anisotropic etching is applied to enhance the quality of the turning mirror by of its polishing surface, correcting its orientation, and improving the verticality. The shape of the turning mirror fabricated by the two-step method is hexagonal or octagonal, matching the optical field of the rib waveguide well. A large effective mirror size to reflect light waves and reduced shrinkage of the mirror size during etching guarantee that a mirror produced by this two-step method will be more compact than previously designed mirrors.

The behaviors in annealed Ge/Fe multi-layer have been investigated. It is found that the temperature of crystallization and compound-production at the surface is higher than that in the bulk. The abnormal Raman spectra are analyzed and the relationship between the phases and the magnetism during annealing is also discussed.

By using the Debye-Hückel equation and the Poisson equation, the almost one-dimensional ionic conductive behaviors of α-LiIO3 have been analysed theoretically. The current across the boundaries between the crystal and metallic electrodes is con-sidered to be limited by rate processes. The asymmetry of the ± c-directions due to spontaneous polarization of the crystal has been taken into consideration. The explicit expression derived for the apparent DC conductivity is satisfactory in explaining the characteristic behavior of α-LiIO3, e.g., the dependence of conductivity on applied voltage, as shown experimentally in [1]. The functional relationship between the AC dielectric constant and the bias field (cf. [1]) is interpreted partially by following the approach given in [2]. It is also pointed out that the weak current constantly flowing through the wire connecting the end surfaces of opposite polarity of an α-LiIO3 single crystal (cf. [3]), as well as similar phenomena observed in our own laboratory on poled ferroelectrics such as BaxSr1-xNb2O6(x～1/3), are caused by the crystal-line polarity EMF. This EMF coexists with the spontaneous, polarization Ps.