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The study describes the recoverable strain in Ti-24Nb-4Zr-8Sn (wt.%) alloy with cellular structure having rhombic dodecahedron and topology-optimised unit cell fabricated by electron beam melting. At a certain cyclic strain, the recoverable strain in rhombic dodecahedron structure was greater in comparison to topology-optimised structure because of different stress distribution on struts. The cellular structure of Ti-24Nb-4Zr-8Sn alloy with rhombic dodecahedron unit cell had larger recoverable strain in comparison to Ti-6Al-4V cellular structure. This behaviour is attributed to higher strength to modulus ratio (σ/E) and superelasticity of Ti-24Nb-4Zr-8Sn alloy. [ABSTRACT FROM AUTHOR]

A novel combined system, integrated with a flashing Ranking cycle and humidification dehumidification (HDH) desalination unit, is proposed to achieve the energy utilization from geothermal water. The flashed steam is used to generate power while the remaining water is applied to heat the seawater for water production. Based on the coupling relation between the power and desalination unit, conservation equations based on the thermodynamic laws are constituted. Energy and entropy analysis of the combined system are achieved for determining the power and water production. Furthermore, the influence principles from the spraying temperature and terminal temperature difference of the seawater heater on the overall performance of the combined system are also focused. The simulation results indicate that the maximal net power from the flashing Rankine cycle reaches 157.0 kW when the flashing temperature is 375.15 K. Due to the leading role to determine total efficiency of the combined system, maximum values of 711.85 kg h −1 for the water production and 43.98% for the total efficiency are obtained when the flashing temperature is 378.15 K. Furthermore, it is also obtained that a lower value both for the seawater spraying temperature and terminal temperature difference of the seawater heater can help to improve the performance of the combined system. [ABSTRACT FROM AUTHOR]

Nerve growth factor (NGF) is widely expressed in the nervous system and best understood for its neuronal function. The present study was designed to describe the characteristics of hair follicles and the expression pattern of NGF and its receptor, tyrosine kinase receptor (TrkA), in the skin of Liaoning cashmere goats during hair follicle cycling. Results of hematoxylin and eosin staining revealed that there was a high ratio of secondary to primary follicles, with more active secondary follicles during anagen phase than other phases. The results of quantitative real-time polymerase chain reaction and western blot showed that both NGF and TrkA mRNA and protein levels were persistently detected in the skin tissue during hair follicle cycling. Furthermore, NGF and TrkA mRNA and protein levels during anagen were significantly higher than that during catagen. Using immunohistochemistry, the especially high immunoreactivities of TrkA in the outer root sheath (ORS) and NGF in the internal root sheath (IRS) and ORS were observed during anagen of hair follicles. Meanwhile, NGF and TrkA immunoreactivities were also observed in the epidermis of cashmere goats at similar expression levels as hair follicles. ORS cells were isolated from secondary follicle, and NGF treatment experiments were also studied. Result show that 20 ng/mL or 100 ng/mL NGF could significantly promote the proliferation of ORS cells in vitro, but the promotion could be blocked by the addition of 20 ng/mL K252a, the inhibitor of TrkA. The present study indicates that NGF might be involved in the reconstruction and growth of hair follicles through TrkA tyrosine kinase dependent pathways. [ABSTRACT FROM AUTHOR]

Experimental measurements clearly reveal the presence of bulk superconductivity in the CsPb x Bi 4− x Te 6 (0.3≤ x ≤1.0) materials, i.e. the first member of the thermoelectric series of Cs[Pb m Bi 3 Te 5+ m ], these materials have the layered orthorhombic structure containing infinite anionic [PbBi 3 Te 6 ] − slabs separated with Cs + cations. Temperature dependences of electrical resistivity, magnetic susceptibility, and specific heat have consistently demonstrated that the superconducting transition in Cs 0.96 Pb 0.25 Bi 3.75 Te 6.04 occurs at T c =3.1 K, with a superconducting volume fraction close to 100% at 1.8 K. Structural study using aberration-corrected STEM/TEM reveals a rich variety of microstructural phenomena in correlation with the Pb-ordering and chemical inhomogeneity. The superconducting material Cs 0.96 Pb 0.25 Bi 3.75 Te 6.04 with the highest T c shows a clear ordered structure with a modulation wave vector of q ≈ a */2+ c */1.35 on the a – c plane. Our study evidently demonstrates that superconductivity deriving upon doping of narrow-gap semiconductor is a viable approach for exploration of novel superconductors. [ABSTRACT FROM AUTHOR]

Highlights: [•] We study a viscoelastic column subject to parametric excitation whose damping is governed by fractional derivatives. [•] We find the multiple bifurcation solutions, jump phenomenon and saddle-node analytically. [•] Nonlinear fractional derivative and time delay are investigated. [•] We find that the fractional order, time delay and material modulus ratio can increase the stability. [•] New criteria of stability determination for fractional order derivatives are established. [Copyright &y& Elsevier]

Abstract: In order to help water supply utilities improve water supply management, offer early warning and control water pipeline leakage, so as to provide clean water to residents, many instruments are installed to monitor hydraulic and water quality conditions along the water pipelines. However, one of the challenges of such tremendous monitor system is its limited power resources to make the smart sensors and sensor networks operate continuously and safely due to poor site conditions. In this paper, a novel vertical-axis water turbine has been developed for hydropower harness inside water pipelines when extra water head can be consumed. The small hydro power generated can be used for power supply to the data collection systems in underground and congested locations or to maintenance work at remote locations. The device was developed through CFD (Computational Fluid Dynamic) simulation and lab tests. The performance of the developed water turbines and the flow characteristics inside water pipes were simulated using the ANSYS CFD packages: FLUENT and Gambit. After the simulation, a number of prototypes were fabricated and tested to measure the real power output and verify the simulated results. The results indicate that the simulation outcomes can offer a good guidance for the rotor design even though the difference between the simulation and experimental results is fairly large. The results also show that the rotor with a hollow structure combined with an eye-shaped slanted block in a pipeline could generate the maximum power as compared with other types of vertical-axis rotors. Furthermore, the simulation and test results of different generation turbines offer valuable information for developing hydropower harness device in confined conditions. [Copyright &y& Elsevier]

Abstract: The nonlinear single-mode dynamic behaviour of the viscoelastic arch whose damping is governed by fractional derivatives is considered. A set of ordinary differential equations is derived for the primary resonance and is solved by the residue harmonic homotopy to obtain all the steady state solutions. A parametric study is carried out to determine the influence of the viscoelastic damping characteristics of the material on the responses. Both the fractional order and material modulus ratio are effective in enhancing the stability of the structure. Multiple bifurcation solutions, jump phenomenon, saddle-node are observed analytically without numerical integration and are confirmed by numerical integration. [Copyright &y& Elsevier]

Abstract: This research investigates the design constraints and potential of applying the remote source solar lighting system to the enclosed lift lobbies of high-rise residential buildings in Hong Kong. No natural light is usually provided to these lift lobbies, which depend on electric lighting for illumination. The application of conventional light pipes requires minimum 3m headroom and is not feasible to be applied in the high-rise residential buildings of 2.8m floor height in Hong Kong. A remote source solar lighting system is specifically designed to solve the headroom problem. The daylighting system uses small diameter side-emitting fiber optic as light transmission medium. The factors of solar altitude, solar azimuth angle and solar irradiance are investigated. The shadowing effects caused by neighboring buildings and the supporting framework are analyzed in details. Design parameters of the natural daylight system are defined. Design guidelines and a model design are developed as a reference for building designers in designing a remote source solar lighting system. The design addresses both the functional application as well as the esthetic design. The remote source daylighting system can be integrated into the architectural design of the external facade and lift lobbies. [Copyright &y& Elsevier]

Abstract: A solar rechargeable battery is constructed by use of a hybrid TiO2/poly(3,4-ethylenedioxythiophene, PEDOT) photo-anode and a ClO4 − doped polypyrrole counter electrode. Here, the dye-sensitized TiO2/PEDOT photo-anode serves for positive charge storage and a p-doped PPy counter electrode acts for electron storage in LiClO4 electrolyte. The proposed device demonstrates a rapid photo-charge at light illumination and a stable electrochemical discharge in the dark, realizing an in situ solar-to-electric conversion and storage. [Copyright &y& Elsevier]

Abstract: When seeking a solution in series form, the number of terms needed to satisfy some preset requirements is unknown in the beginning. An iterative formulation is proposed so that when an approximation is available, the number of effective terms can be doubled in one iteration by solving a set of linear equations. This is a new extension of the Newton iteration in solving nonlinear algebraic equations to solving nonlinear differential equations by series. When Fourier series is employed, the method is called the residue harmonic balance. In this paper, the fractional order van der Pol oscillator with fractional restoring and damping forces is considered. The residue harmonic balance method is used for generating the higher-order approximations to the angular frequency and the period solutions of above mentioned fractional oscillator. The highly accurate solutions to angular frequency and limit cycle of the fractional order van der Pol equations are obtained analytically. The results that are obtained reveal that the proposed method is very effective for obtaining asymptotic solutions of autonomous nonlinear oscillation systems containing fractional derivatives. The influence of the fractional order on the geometry of the limit cycle is investigated for the first time. [Copyright &y& Elsevier]

Abstract: In metropolitan cities like Hong Kong where land value is high, highrise commercial and residential buildings with “central core” design are developed. The lift lobbies in the buildings are usually located in the centre of the building to free up peripheral areas to provide valuable exterior view. The lift lobbies have no window provisions and electric lighting is switched on for 24h continuously consuming non-renewable energy. Different types of light guides/light pipes have been proven to be capable to transfer daylight into deep floor plan during both clear sky and overcast periods. However, the thickness of light guide requires 3m headroom clearance for installation whilst the headroom of the highrise buildings is usually limited to 2.8m in order to build more storeys. In this research, a remote source lighting system (RSL) is introduced to illuminate the enclosed lift lobbies. The system composed of prismatic light pipe and optic fiber to address the problem of limited headroom. Simulation of the system was carried out and reported in the paper, indicating that this lighting system can solve the energy consumption problem in the lift lobby in terms of renewable energy use and natural lighting application. This research concentrates on highrise residential buildings. [Copyright &y& Elsevier]

Abstract: This paper reports the investigation results of the energy payback time (EPBT) and greenhouse-gas payback time (GPBT) of a rooftop BIPV system (grid-connected) in Hong Kong to measure its sustainability. The 22kWp PV array is facing south with inclined angle of 22.5°. The hourly solar irradiance and ambient air temperature from 1996 to 2000 were used as weather data input. The annual power output was found to be 28,154kWh. The embodied energy for the whole system in the lifespan was 205,816kWh, including 71% from PV modules and 29% from balance of system (BOS). The percentage of embodied energy for silicon purification and processing reached 46%. The EPBT of the PV system was 7.3years, and the GPBT was estimated to be 5.2years considering fuel mixture composition of local power stations. This paper also discussed the EPBTs for different orientations, ranging from 7.1years (optimal orientation) to 20.0years (west-facing vertical PV façade). The results show that the ‘sustainability’ of a PV system is affected by its installation orientation and location. Choosing locations and orientations with higher incident solar irradiance is one key for the sustainability of BIPV technology applications. [ABSTRACT FROM AUTHOR]

Abstract: The transmission electron microscopy observations of the charge ordering (CO) which governs the electronic polarization in clearly show the presence of a remarkable phase separation at low temperatures. Two CO ground states are found to adopt the charge modulations of and , respectively. Our structural study demonstrates that the incommensurately -modulated state is chiefly stable in samples with relatively lower oxygen contents. Data from theoretical simulations of the diffraction suggest that both - and -modulated phases have ferroelectric ordering. The effects of oxygen concentration on the phase separation and electric polarization in this layered system are discussed. [Copyright &y& Elsevier]

Abstract: The shading-type building-integrated photovoltaic (BIPV) claddings can act as power generators as well as external shading devices of a building, which reduce the energy consumption of the building. However, there is little information about energy impacts of different tilt angles of the shading-type BIPV claddings. By considering the typical meteorological conditions of Hong Kong, the energy performance of the shading-type BIPV claddings, in terms of the electricity generation and the cooling load reduction, is analyzed in this paper. The optimum tilt angle of PV modules for maximum electricity generation is found to be 20° instead of local latitude. Combining electricity generation and cooling load reduction, it can be concluded that the optimum tilt angles for the first type of the shading-type BIPV claddings vary from 30° to 50°, while the optimum tilt angle for the second type is 0°. [Copyright &y& Elsevier]

Abstract: The structural features of the “5M” martensitic phase in Ni2FeGa alloys have been determined by electron diffraction using the multi-slice least-squares (MSLS) method. The results demonstrate that the “5M” phase contains an evident cooperative effect of monoclinic distortion and sinusoidal modulation along the [110] c direction. Theoretical simulations based on our refined data suggest that the “5M” martensitic phase observed in Ni–Fe–Ga and Ni–Mn–Ga has visible common behaviors in both stacking sequence and local structural distortion. Considering the cooperative effect of monoclinic distortion and sinusoidal modulation, we demonstrate that the “7M” martensitic phase could adopt two equivalent structural phases corresponding with the stacking sequences of and , respectively. [Copyright &y& Elsevier]

Abstract: We systemically studied the OH-terminated diamond (001) surfaces by first-principles calculations. A set of network structures are investigated, two of them are found to be energetically favored over a recently proposed anti-parallel configuration [S.J. Sque, R. Jones, P.B. Briddon, Phys. Rev. B 73 (2006) 085313]. The transition paths and barriers between the anti-parallel configuration and the network structures are calculated. Furthermore, using ab initio molecular dynamics, a scissor mode of pseudo-water molecules in vibrational spectra was found, which is in well agreement with available experiments. [Copyright &y& Elsevier]

Abstract: Transmission electron microscopy (TEM) investigations on Nd2/3− x Li3 x TiO3 with x=0.14 reveal a rich variety of structural features in the samples prepared under different conditions, such as superstructures, anti-phase domains, and nano-chessboard structures. Our careful analysis shows that these structural phenomena can be fundamentally understood as the combination of structural effects of (Nd, Li)-ordering along the 〈001〉p direction and the spinodal decomposition along the 〈100〉p/〈010〉p direction. The coexistence of phase separation and cation ordering can lead to visible nano-structural complexities in many crystals, as the typical results, the regular lamella structure, nano-chessboard structures and anti-phase boundaries have been extensively studied. [Copyright &y& Elsevier]

Abstract: The vanadium bronzes ()- A x V 2O5 (A=Na+, Ag+, Ca2+, Cu+) are investigated by electron energy-loss spectroscopy (EELS), X-ray absorption near edge spectroscopy and electronic structure calculations. We analysed the fine structural features of experimental spectra in the low-loss region and the vanadium L2,3 and oxygen K ionization edges in correlation with electronic structure of this quasi-one-dimensional conducting system. The different energy separations on the fine structures of the vanadium L3 edge and oxygen K edge arising from ligand field splitting suggest charge disproportionation occurring in ()- A x V 2O5 materials at room temperature. Based on the analysis of the highly-damped valence electron plasmon peak for these materials, the charge distribution among different chains and ladders is briefly discussed. [Copyright &y& Elsevier]

Abstract: Powerful visible upconversion fluorescence intensities of Er3+ in novel bismuth gallate glasses (LKBBG) and common tellurite glasses (TZN) with low phonon energies and high refractive indices have been compared. Under the same measurement condition, Er3+-doped LKBBG glasses show the stronger upconversion emission intensities than Er3+-doped common tellurite glasses (TZN). The visible upconversion emission bands peaked at 531, 548 and 668nm have been confirmed that two photons contribute to these upconversion processes. The maximum phonon energy obtained in LKBBG glasses is 673cm−1, which is 65cm−1 lower than that in common tellurite glasses, indicating that LKBBG glasses almost possess the lowest maximum phonon energy in all of the oxide glasses. All analyses support that Er3+-doped LKBBG glasses are promising materials for fabricating visible upconversion devices. [Copyright &y& Elsevier]

Abstract: The ground state of Na0.5CoO2 has been calculated using the full potential local orbital method and local density approximation plus Hubbard (); the results demonstrate that charge and orbital ordering evidently exist in the present system in association with the antiferromagnetic state. Notable structural features observed between 300 and 30 K have been carefully examined using in situ TEM investigations, a superstructure with a wave vector of , becoming commonly visible below , can be interpreted as the charge/orbital ordering on the Co1 and Co2 sites. Moreover, we have also observed another notable superstructure with below the phase transition of , which suggests a more complicated orbital ordered state existing at lower temperatures. [Copyright &y& Elsevier]

Abstract: Layered Sr0.35CoO2 has been synthesized by means of an ion exchange reaction from Na0.7CoO2. Resistivity measurements show that this material can be either metallic or semiconducting depending on the annealing conditions. The magnetic susceptibility of the sample increases with decreasing temperature, showing a Curie–Weiss behavior in high temperatures. Transmission electron microscopy observations reveal the presence of two superstructures arising respectively from the intercalated Sr-ordering (a compositional modulation) with q 1 = a*/3+ b*/3 and a periodic structural distortion (a transverse structural modulation) with q 2 = a*/2. [Copyright &y& Elsevier]

Abstract: Tin phosphide (Sn4P3) with a layered structure was synthesized by direct ball-milling method and tested for possible use as an electroactive anode material in alkaline aqueous solution. The experimental results demonstrated that the Sn4P3 electrode could deliver a discharge capacity of 775mAh/g at the constant current of 200mA/g, 716mAh/g at 2000mA/g and 511mAh/g at 5000mA/g respectively, showing a superiorly high rate capability in alkaline aqueous solution. The excellent electrochemical activity of the Sn4P3 material is found to arise from the cooperative interaction of the P and Sn atoms in the layered crystalline structure, in which the Sn atom layers serve as a conductive framework providing an electronic passage for the 5-electron oxidation of the P atoms. [Copyright &y& Elsevier]

Abstract: The superconductivity in Na0.3Co1−x M x O2 ·1.3H2O and the charge ordering in Na0.5Co1−x M x O2 have been investigated for M=Mn and Ti substitution for Co. Single-phased Na0.5Co1−x M x O2 (0⩽ x ⩽0.1, M=Mn, Ti) materials were prepared by Na deintercalation from Na0.75Co1−x M x O2; the hydrated Na0.3Co1−x M x O2 ·1.3H2O (0⩽ x ⩽0.1, M=Mn, Ti) materials were prepared by Na deintercalation and then water intercalation. Measurements of physical properties demonstrated that the superconductivity in Na0.3Co1−x M x O2 ·1.3H2O is evidently influenced by the Co-site doping and completely ceases at x =0.02 for Mn doping and x =0.01 for Ti doping. Analysis of resistivity and magnetization on Na0.5Co1−x M x O2 revealed that Mn doping has much stronger influence than Ti doping on both the charge ordering and the low-temperature physical properties. [Copyright &y& Elsevier]

Abstract: Transmission electron microscopy (TEM) observations reveal the presence of complex superstructures and remarkable phase separation in association with Na-ordering phenomenon in γ-Na0.5CoO2. Resistivity and magnetization measurements indicate that three phase transitions at the temperatures of 25, 53 and 90K, respectively, appear commonly in γ-Na0.5CoO2 samples. Under a high pressure up to 10kbar, the low-temperature transport properties show certain changes below the charge order transition; under an applied magnetic field of 7T, phase transitions at around 25 and 53K, proposed fundamentally in connection with alternations of magnetic structure and charge ordering maintain almost unchanged. [Copyright &y& Elsevier]

Abstract: Structural and physical properties of Na x CoO2 and superconducting Na x CoO2·yH2O hydrates have been systematically investigated. Raman scattering measurements reveal that the five active phonons in Na x CoO2·yH2O system change systematically with the H2O intercalation and modification of superconductivity, in particular the A 1g and E 1g modes in correlation with oxygen movements. Incoherent inelastic neutron scattering (IINS) study on the local structure of H2O-layers in Na x CoO2·yH2O (0≤y≤1.8) suggests the presence of three types of clusters, H3O+, H5O+ and ice-Ih like weakly bonded water, among CoO2 sheets. Electron energy loss (EEL) analysis on Na0.33CoO2·yH2O (0≤y≤1.3) indicates certain notable changes in the electronic structure during hydration. Microstructure and structural phase transitions accompanied with local atomic ordering in the charge-ordered phase Na0.5CoO2 have been investigated along with the hexagonal–orthorhombic phase transition. [Copyright &y& Elsevier]

Abstract: The electronic structure of Sr0.35CoO2, structurally analogous to the layered Na x CoO2, has been evaluated using the local spin density approximation (LSDA). We find that evident c-dispersions appear in both the and a 1g Co-derived bands, demonstrating the existence of a notable interplanar interaction in Sr0.35CoO2. The LSDA+U calculation reveals that the electronic structure, in particular the band splitting between the spin-up and spin-down electrons, changes evidently along with the increase of the effective on-site Coulomb interaction U. Analysis of theoretical and experimental electron energy-loss spectra (EELS) for the oxygen K-edge and the Co L23-edge suggests that the on-site interaction (U) in Sr0.35CoO2 is less than 3eV which is noticeably weaker than the estimated value (from 5 to 8eV) in the Na x CoO2 materials. [Copyright &y& Elsevier]

Abstract: The nonstoichiometric Na x CoO2 system exhibits extraordinary physical properties that correlate with temperature and Na concentration in its layered lattice without evident long-range structure modification when conventional crystallographic techniques are applied. For instance, Na0.7CoO2, a thermodynamically stable phase, shows large thermoelectric power; water-intercalated Na0.33CoO2·1.3H2O is a newly discovered superconductor with T c∼4K, and Na0.5CoO2 exhibits an unexpected charge ordering transition at around T co∼55K. Recent studies suggest that the transport and magnetic properties in the Na x CoO2 system strongly depend on the charge carrier density and local structural properties. Here we report a combined variable temperature transmission electron microscopy and Raman scattering investigation on structural transformations in Na0.5CoO2 single crystals. A series of structural phase transitions in the temperature range from 80 to 1000K are directly identified and the observed superstructures and modulated phases can be interpreted by Na-ordering. The Raman scattering measurements reveal phase separation and a systematic evolution of active modes along with phase transitions. Our work demonstrates that the high mobility and ordering of sodium cations among the CoO2 layers are a key factor for the presence of complex structural properties in Na x CoO2 materials, and also demonstrate that the combination of electron diffraction and Raman spectroscopy measurements is an efficient way for studying the cation ordering and phase transitions in related systems. [Copyright &y& Elsevier]

With the rapid increase in Building Integrated Photovoltaic (BIPV) systems and the popularity of photovoltaic (PV) applications, a simple but accurate model to calculate the power output of P V modules is crucial for evaluating systems. In addition, in the analysis of energy payback, two factors, the power output (maximum power output) model of PV modules and the representative local weather data, affect calculations of the energy savings and the payback time of BIPV systems. Most studies take the efficiency of PV modules as constant when calculating the energy payback time of PV systems, and ignore the influence of solar radiation and temperature on the results of the calculation. This study tries to develop one simple, practical, yet more accurate model for describing the characteristics of the power output of PV modules. It develops a model for describing the I–V characteristics of PV modules according to the equivalent circuits of solar cells, by which an accurate but complicated model of the maximum power output (MPO) can be achieved. Taking this MPO model as a benchmark, two other application models from other studies are evaluated and examined. One simplified application model for describing the maximum power output of PV modules is then derived from the results of the simulation. Once the solar radiation on PV panels and the ambient temperature are known, the power output of BIPV systems or PV systems can be calculated accurately and easily. [ABSTRACT FROM AUTHOR]

The mechanism of oxygen reduction at MnO2-catalyzed air cathode was investigated by measurements of polarization curves in wide OH− concentrations, oxygen pressures and using different crystalline MnO2 catalysts. It is found that the oxygen reduction at MnO2 catalyst is accompanied with the reduction of MnO2 and the catalytic activities of MnO2 is closely related to the electrochemical activities of MnO2. Based on the experimental determination of the reaction orders of OH−, O2 and the intermediate Mn3+ ion, we propose a chemical oxidation mechanism for the catalytic oxygen reduction, in which oxygen reduction proceeds through chemical oxidation of the discharge product of MnO2 rather than through a direct two-electron reduction. The rate expression derived from this mechanism can very well explain the observed polarization properties and the concentration dependence of oxygen reduction. [Copyright &y& Elsevier]

This paper describes a simulation model for analyzing the probability of power supply failure in hybrid photovoltaic–wind power generation systems incorporating a storage battery bank, and also analyzes the reliability of the systems. An analysis of the complementary characteristics of solar irradiance and wind power for Hong Kong is presented. The analysis of local weather data patterns shows that solar power and wind power can compensate well for one another, and can provide a good utilization factor for renewable energy applications. For the loss of power supply probability (LPSP) analysis, the calculation objective functions and restraints are set up for the design of hybrid systems and to assess their reliability. To demonstrate the use of the model and LPSP functions, a case study of hybrid solar–wind power supply for a telecommunication system is presented. For a hybrid system on the islands surrounding Hong Kong, a battery bank with an energy storage capacity of 3 days is suitable for ensuring the desired LPSP of 1%, and a LPSP of 0% can be achieved with a battery bank of 5 days storage capacity. [Copyright &y& Elsevier]

Abstract: Polycrystalline and single crystalline samples of CaFe2As2 were prepared by using different fabrication routes. These samples show evident differences in both phase transition temperatures and transport properties depending on fabrication conditions. TEM observations reveal a rich variety of structural phenomena in these materials, such as a tweed-like pattern in self-flux samples, a structural modulation along the 〈110〉tetra direction in the polycrystalline sample, and complex dislocation networks in the Sn-flux samples. Careful analysis shows that the twinning domains arising from the tetragonal-to-orthorhombic phase transition belong to the δ-type. [Copyright &y& Elsevier]

Abstract: SrMn2As2 single crystals were grown by the Sn flux method. Structural features of these crystals were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD results show that the single crystal has a rhombohedral structure and grows along the c-axis direction. The microstructure and layered structural features of this material have been examined by SEM and high-resolution TEM observations. The measurements of in-plane resistivity as a function of temperature demonstrate that SrMn2As2 undergoes a phase transition of semiconductor–insulator at a low temperature; the active energies are estimated to be Δ=0.64 and 0.29eV for two distinct regions. Magnetic measurements show a clear antiferromagnetic (AFM) transition at about T N =125K. Therefore, the SrMn2As2 material is an AFM insulator at low temperatures and could be a potential parent compound for superconductors. [Copyright &y& Elsevier]

The role of δ-Fe in hydrogen embrittlement (HE) of 17-4 PH steel is studied in this work. Scanning Kelvin probe force microscopy result indicates that δ-Fe is a hydrogen trapping site. Accordingly, δ-Fe can reduce the hydrogen concentration of surrounding martensite and prior austenite grain boundaries (PAGBs) and imped the brittle fracture along lath boundaries and PAGBs, which can be beneficial to the HE resistance improvement. However, a cleavage fracture of δ-Fe can occur under the synergetic action of hydrogen-enhanced localized plasticity (HELP) and hydrogen enhancement of the strain-induced generation of vacancies (HESIV). These findings indicate a new path to improving HE resistance of high strength martensitic steels. • SKPFM result shows that hydrogen tends to segregate in delta ferrite. • Delta ferrite acting as a hydrogen trapping site decreases the tendency of brittle fracture. • Hydrogen segregation in delta ferrite leads to a strain localization and a subsequent transgranular cleavage fracture. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of GH690 alloy is investigated in the temperature range of 950–1200°C and a strain rate of 10−3s−1 to 2s−1. It is found that the flow stress increases with strain, and then decreases as it reaches a peak flow stress. On the basis of the experiment data, processing maps are developed using the dynamic materials model (DMM). The processing maps exhibit two domains. One is the stable region occurring in the temperature range of 1120–1180°C and the strain rate of 0.0325–0.447s−1, the other is the instability zone occurring in the temperature range of 950–1180°C and the strain rate of 0.18–2s−1. Under the guidance of the processing maps, a rolling experiment is carried out, and it is found that the yield strength, ultimate tensile strength and elongation of the plate are 565MPa, 685MPa and 51.13% respectively. [ABSTRACT FROM AUTHOR]

Abstract: The residue harmonic balance is developed for coupled systems exemplified by the damped Duffing resonator driven by a van der Pol oscillator. This technique combines the features of harmonic balance and parameter bookkeeping to obtain approximate solutions to any desired accuracy. For the two degrees of freedom system, the zeroth-order approximation uses just one Fourier term resulting in a set of two nonlinear algebraic equations that can be solved analytically. The unbalanced residue due to Fourier truncation is improved by solving linear equations that automatically increase the number of terms to balance the previous truncation completely. Highly accurate bifurcation frequencies for various parameters are obtained and are verified by numerical integration results. The effects of the coupling stiffness on the angular frequency and amplitude of steady state response are investigated. The effects of the nonlinear damping are also studied. [Copyright &y& Elsevier]

The two main objectives of this article are (1) to determine the bifurcating periodic responses accurately and to study the effects of time delay and feedback gain on the steady state response in autonomous oscillators by means of the residue harmonic balance method; and (2) to study the dynamics of both the autonomous and non-autonomous Duffing-van der Pol oscillators with delayed position feedback as examples. The results of the steady state response to frequency and amplitude excitation versus the time delay, positive and negative feedback gains are studied. Both saddle-node and subcritical Hopf bifurcations are found and discussed. The obtained second-order solutions are in excellent agreement with numerical integration results. By combining both harmonic balance and polynomial homotopy continuation techniques, the superharmonic resonance responses of the non-autonomous oscillator are investigated in order to obtain all possible steady state solutions. The effects of the feedback gains and time delay on the steady state response are found analytically. It is shown that the fundamental and superharmonic amplitudes decrease with increasing feedback gain. Furthermore, the multiple symmetric solutions of the response amplitudes versus those of external excitation are detected when time delay becomes smaller. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a powerfully analytical technique is proposed for predicting and generating the steady state solution of the fractional differential system based on the method of harmonic balance. The zeroth-order approximation using just one Fourier term is applied to predict the parametric function for the boundary between oscillatory and non-oscillatory regions of the fractional van der Pol oscillator. The unbalanced residues due to Fourier truncation are considered iteratively by solving linear algebraic equations to improve the accuracy of the solutions successively. The highly accurate solutions to the angular frequency and limit cycle of fractional van der Pol oscillator are obtained and compared. The results reveal that the technique described in this paper is very effective and simple for obtaining asymptotic solution of nonlinear system having fractional order derivative. [Copyright &y& Elsevier]

Abstract: A new approach that the iterative homotopy harmonic balancing is presented for charactering and predicting analytical approximations of conservative oscillator with strong odd-nonlinearity in the paper. The new technique does not depend upon small parameter assumption and incorporates the salient features of both methods of the parameter-expansion and the harmonic balance. The results of applying this procedure to the studied examples that the cubic–quintic Duffing equation and Duffing-harmonic equation show the high accurate, simplicity and efficiency of the approach. The approach can be easily extended to other nonlinear oscillators. [Copyright &y& Elsevier]

Abstract: This paper presents the measurements of mean and fluctuating forces on an NACA0012 airfoil over a large range of angle (α) of attack (0–90°) and low to small chord Reynolds numbers (Rec ), 5.3×103–5.1×104, which is of both fundamental and practical importance. The forces, measured using a load cell, display good agreement with the estimate from the LDA-measured cross-flow distributions of velocities in the wake based on the momentum conservation. The dependence of the forces on both α and Rec is determined and discussed in detail. It has been found that the stall of an airfoil, characterized by a drop in the lift force and a jump in the drag force, occurs at Rec ⩾1.05×104 but is absent at Rec =5.3×103. A theoretical analysis is developed to predict and explain the observed dependence of the mean lift and drag on α. [ABSTRACT FROM AUTHOR]

Abstract: A polytriphenylamine (PTPAn)-modified separator was prepared simply by impregnating triphenylamine monomers into a commercial Celgard separator and in situ polymerizing the monomers into electroactive phase by oxidant ozone. This type of electroactive separator can transform from an insulating state to a conductive state at overcharged voltage of ∼3.7V (vs. Li+/Li) and act as a self-actuating potential-switchable separator for overcharge protection of LiFePO4/C Li-ion batteries. The experimental results demonstrated that this electroactive separator can reversibly control the cell''s voltage at the safe value less than 4.15V at high rate overcharge of 2C current without obvious negative impact on the normal charge–discharge performances of the commercial LiFePO4/C batteries even at prolonged overcharge cycling, showing a potential application in 3.6V-class lithium-ion batteries. [Copyright &y& Elsevier]

Abstract: We prepared the metastable T′-phase La2−x Ln x CuO4 (Ln=Sm and Y) cuprates by a coprecipitation technology, which cannot be acquired by conventional solid-state reaction. The selective stabilization of T′- and T-phase was studied via altering synthesis temperature and pressure. The structural phase diagram for T- and T′-phase is obtained in La2−x Ln x CuO4 system. All these samples show semiconducting behavior, and no superconductivity was observed down to 2K even after reduction. Magnetic measurement shows a Curie–Weiss-like paramagnetic behavior. [Copyright &y& Elsevier]

Abstract: The electronic structure of β-Na0.33V2O5 has been evaluated using the first-principle density functional theory approach. All energy bands near the Fermi surface (FS) disperse principally along the b-axis direction indicating the quasi-one-dimensionality of this system. The theoretical simulation of the optical property yields reasonable explanations for the notable features revealed in the measurements of the optical spectroscopy. Superconductivity appearing under a pressure of 8GPa has been discussed in connection with the pressure-induced structural and bands alternations. It is suggested that the strong interchain coupling could play a key role in the appearance of superconductivity. The electron correlation effects on the electronic structure have also been calculated and discussed in comparison with photoemission data. [Copyright &y& Elsevier]

A nanocrystalline Li[Li0.12Ni0.32Mn0.56]O2 powder was synthesized by a pyrolysis method using polyacrylate salts as the precursor compounds. XRD and TEM results demonstrated that the Li[Li0.12Ni0.32Mn0.56]O2 powder has a layered structure as α-NaFeO2 and has an average particle size of 50–70nm. The charge–discharge experiments show that the Li[Li0.12Ni0.32Mn0.56]O2 electrode can deliver a reversible capacity of ∼140mAhg-1 cycling at 2.5–4.5V and can still remain 94% of its initial capacity after 10 cycles, showing a great promise for future applications. [Copyright &y& Elsevier]

A novel positive-temperature-coefficient (PTC) electrode was prepared by coating a thin layer of epoxy-carbon PTC material in between the electroactive LiCoO2 layer and the electrode substrate and used for self-actuating thermal cut-off of Li-ion batteries when the batteries are overheated. Experimental results from cyclic voltammetry, impedance spectrometry and charge–discharge measurements demonstrate that the PTC electrode exhibits normal electrochemical behaviors at ambient temperature, but shows an enormous increase in the resistance at the temperature range of 100–130 °C. This PTC behavior of the electrode provides a current-limiting effect, acting as a reversible thermal shutdown switch for rechargeable lithium batteries. [Copyright &y& Elsevier]

A novel Ba–Fe–Si/C composite was prepared by mechanical ball milling and lithium insertion reactions on the composite electrode were investigated by cyclic voltammetry, charge–discharge measurements, XRD and XPS spectroscopy. It is demonstrated that the composite electrode not only possesses sufficiently high reversible capacity of ca. 420 mA h/g, but also exhibits strong capacity retention with indiscernible capacity decay during charge–discharge cycling. The improved cycling ability of the composite is suggested from a cooperative action by inactive FeSi2 and BaSi2 matrix and outer graphite shell, which both buffer the volumetric changes of the active Si phase and provide a good connection for electronic and ionic conduction during lithium insertion and extraction processes. [Copyright &y& Elsevier]

This paper proposes a novel combined system, driven by industrial waste heat, to satisfy the simultaneous demand both for power and freshwater. The concept of organic Rankine cycle is applied to achieve the power generation, while a humidification dehumidification desalination unit is introduced to provide freshwater. For the purpose of efficient energy utilization, the internal energy of the discharged brine and preheated seawater is recovered. Based on the energetic and entropic analysis, the thermodynamic performance of the combined system is simulated, and the influence laws, mainly from the condensing temperature, terminal temperature difference of the recuperator and mass flow rate ratio of the feed seawater, are revealed. Finally, the economic viewpoint of the power and water combined system is also focused. The results show that maximum values of 13.1 kW for the net output power, and 208kgh−1 for the water production can be acquired, when isobutane is applied as the working fluid. It is found that lower condensing temperature and terminal temperature difference of the recuperator indicate a higher water production, while the total efficiency can be further determined in combination with the energy input. It is also discovered that the mass flow rate ratio of the feed seawater is a critical parameter to influence the system performance, although the final effect will be restricted by the entropy generation rate of the system components. Through the comparison among the combined systems, the advantages of the current type are proved by the unit area and cost of production. With respect to the economic performance, a fixed investment for the entire combined system, 49934€, the cost of production with 0.0032€L−1 for water and 0.063€kW−1h−1 for the electricity are obtained. It is also revealed that the production cost can be compressed with higher share of revenues, operation hours and design lifetime. • A power and water combined system, with ORC and HDH units coupled, is proposed. • Energetic and entropic analysis of the proposed system are achieved. • Influence laws from the critical parameters on the system performance are revealed. • Economic performance of the combined system is also focused. [ABSTRACT FROM AUTHOR]