[Show abstract][Hide abstract] ABSTRACT: A 16-channel monolithically integrated distributed feedback (DFB) laser array with arrayed waveguide gratings (AWGs) multiplexer and semiconductor optical amplifier (SOA) has been fabricated using nanoimprint technology. Selective lasing wavelength with 200 GHz frequency space has been obtained. The typical threshold current is between 20 mA and 30 mA. The output power is higher than 1 mW with 350 mA current in SOA. The side mode suppression ratio (SMSR) of the spectrum is better than 40 dB.
[Show abstract][Hide abstract] ABSTRACT: High temperature heat treatments were conducted for as-cast N08028 alloy to obtain various microstructures with different amounts of σ-phase, and then hot compression tests were carried out using Gleeble-3500 thermo-mechanical simulator in deformation temperature range from 1100 to 1200 °C and strain rate range from 0.01 to 1 s−1. For the same initial microstructure, the flow stress was observed to increase with increasing the strain rate and decreasing the deformation temperature, while for the same deformation condition, the flow stress was found to increase with increasing the amount of σ-phase in the initial microstructure. Moreover, dynamic recrystallization was found to be the main dynamic soften mechanism. On this basis, Arrhenius-type constitutive equations and artificial neural network (ANN) model with back-propagation learning algorithm were established to predict hot deformation behavior of the alloy. Furthermore, the parameters of constitutive equations were found to be dependent on the initial microstructure, which was also as one of the inputs for the ANN model. Suitability of the two models was evaluated by comparing the accuracy, correlation coefficient and average absolute relative error, of the prediction. It is concluded that the ANN model is more accurately than the constitutive equations.
[Show abstract][Hide abstract] ABSTRACT: Starting from a proposed theoretical two-phase boundary model for the film condensation of ambient air on a cryogenic horizontal tube (Zhao et al., 2014), we conducted an experimental study on the film condensation of superheated vapours for further study. Condensation experiments were performed for the R134a vapour with various superheating outside a horizontal tube cooled by inside flowing cryogenic nitrogen gas. The reduction of experimental data to obtain condensation-side heat transfer coefficient was accomplished by using two different approaches, individually, which were tube wall measurement technique and modified Wilson plot technique. The results obtained under different conditions were compared with each other, in which a certain divergence existed acceptably. The result shows that the condensation heat transfer coefficient increases by 9.79% when the superheating changes from 39.5 K to 131.9 K. Meanwhile, the condensation heat transfer performance becomes worse due to the combination of condensation and natural convection as the cooling capacity inside the tube is smaller than the critical heat flux. This phenomenon is only available for the condensation of superheated vapour especially for the higher superheating. The condensation heat transfer coefficients from experimental measurement in this paper are compared with the simulated results from the two-phase boundary model previously presented, and a good agreement is reached.KeywordsFilm condensationSuperheated vapoursR134aModified Wilson plot technique
[Show abstract][Hide abstract] ABSTRACT: The monolithic integration of 1.5-µm four channels phase shift distributed feedback lasers array (DFB-LD array) with 4×1 multi-mode interference (MMI) optical combiner is demonstrated. A home developed process mainly consists of butt-joint regrowth (BJR) and simultaneous thermal and ultraviolet nanoimprint lithography (STU-NIL) is implemented to fabricate gratings and integrated devices. The threshold currents of the lasers are less than 10 mA and the side mode suppression ratios (SMSR) are better than 40 dB for all channels. Quasi-continuous tuning is realized over 7.5 nm wavelength region with the 30 °C temperature variation. The results indicate that the integration device we proposed can be used in wavelength division multiplexing passive optical networks (WDM-PON).
[Show abstract][Hide abstract] ABSTRACT: A series of sulfonated polyimide (SPI)/boehmite (AlOOH) (5.0, 10.0, 15.0, 20.0 wt.%) composite membranes are fabricated by blending for vanadium redox flow battery (VRFB) application. SEM images illustrate the compatibility between SPI and AlOOH. Both EDS and XRD results verify the existence of AlOOH in the SPI/AlOOH composite membrane, and FT-IR spectrums show the interaction between SPI and AlOOH. The SPI/AlOOH membranes have improved stability in 0.1 mol L−1 VO2
+ + 3.0 mol L−1 H2SO4 solutions at 40 °C than pure SPI membrane. The SPI/AlOOH-10 % membrane possesses the highest proton selectivity among all SPI/AlOOH membranes. The VRFB with the SPI/AlOOH-10 % membrane presents a higher coulombic efficiency (94.30–97.60 %) and energy efficiency (83.10–64.78 %) at the current density ranged from 20 to 80 mA cm−2 than that with Nafion 117 membrane. The open circuit voltage tests show that the SPI/AlOOH-10 % membrane has longer self-discharge time (117 h) compared with Nafion 117 (72 h). Furthermore, the cycling charge-discharge tests indicate that the SPI/AlOOH-10 % membrane has good operation stability in VRFB system. Therefore, the low-cost SPI/AlOOH membrane with excellent battery performance exhibits a great potential for application in VRFB.
Journal of Solid State Electrochemistry 12/2014; 18(12):3479-3490. DOI:10.1007/s10008-014-2574-0 · 2.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ambient air condensation on a cryogenic horizontal tube is investigated using a newly built mathematical model, in which the liquid film and the vapor boundary layer are coupled together with a major emphasis on the effect of buoyancy. Based on the model, the heat transfer coefficients and the film thickness as well as the interfacial shear are obtained under different conditions to investigate the effects on the flow and heat transfer characteristics of the superheating between vapor and film, the buoyancy in the boundary layer and the subcooling between wall and film. In addition to the flow and heat transfer characteristics of air, the other four different vapors, i.e. H2O, R134a, methane (CH4), argon (Ar), are also discussed. The results show that the superheating has a more significant contribution to the increase of heat transfer coefficient for air comparing to the other vapors, e.g. in the cases of superheating ΔT∞ = 100 and 200 K the mean heat transfer coefficient increases by 10.3% and 24.3% for air, while it increases by only 1.8% and 3.9% for H2O. In contrast to superheating, the subcooling has a negative effect on the increase of heat transfer coefficient. Noteworthy, the buoyancy plays a non-negligible role on the flow and heat transfer characteristics of superheated air condensation. The analytical results are of great importance in the design and improvement of ambient-heated cryogenic vaporizer (AHCV).
[Show abstract][Hide abstract] ABSTRACT: The Ni-NiO-Cu Metal-Insulator-Metal (MIM) tunnel diodes were fabricated through electrochemical deposition and thermal oxidation in the confined nanochannels of anodic aluminum oxide templates. Scanning electron microscopy (SEM) investigation reveals the diodes have a contact area of about 0.008 mu m(2), and transmission electron microscopy (TEM) shows that the thickness of NiO insulator layers ranges from 2 nm to 12 nm. The current-voltage (I-V) characteristics of the MIM diodes as prepared exhibit the nonlineara behavior with values strongly depending on the thermal oxidation time and the best zero bias sensitivity is 7.3 V-1 at bias voltage (V-bias) of 0.1 V.
[Show abstract][Hide abstract] ABSTRACT: Objective:
To elucidate the role of A39S mutation of DJ-1 in the onset of Parkinson's disease (PD) and identify genes for which expressions are abnormally regulated by A39S DJ-1 mutation.
We established HEK293 cell lines which stably expressed empty vector, wild-type DJ-1 and A39S mutated DJ-1 respectively. DNA microarrays were used to identify genes for which expressions change in wild-type DJ-1 cells and A39S DJ-1 mutant cells.
Compared with the cell line expression empty vector, we identified 42 differentially regulated genes (including 14 up-regulated genes and 28 down-regulated genes) in the wildtype DJ-1 cells and 8 differentially regulated genes (including 6 up-regulated genes and 2 downregulated genes) in the A39S DJ-1 mutant cells. Compared with the wild-type DJ-1 cells, only the expression of UGT2B7 gene was down-regulated in A39S DJ-1 mutant cells. These differentially regulated genes were mainly related to signal transduction, regulation of transcription, apoptosis and metabolism.
A39S mutated DJ-1 may disturb the transcriptional activities of DJ-l and involve in the pathogenesis of PD.
Zhong nan da xue xue bao. Yi xue ban = Journal of Central South University. Medical sciences 04/2014; 39(4):325-32. DOI:10.3969/j.issn.1672-7347.2014.04.001
[Show abstract][Hide abstract] ABSTRACT: An analytical model for dissolution kinetics of secondary phase particles upon isothermal annealing has been proposed. Considering the interactions of solute diffusion fields in front of the secondary phase/matrix interface upon dissolution, a Johnson–Mehl–Avrami type equation, subjected to necessary modification, was derived, in combination with a classic dissolution model for single-particle system. Compared with the semiempirical dissolution models, which are used to fit the experimental results and phase-field method simulation, the current model follows an analogous form, but with the time-dependent kinetic parameters. Distinct from the model fitting work published recently, the current model is derived from the diffusion-controlled transformation theory, while the modeling quality is guaranteed by the physically realistic model parameters. On this basis, the current model calculation leads to a clear relationship between the secondary phase volume fraction and the time. Accordingly, model predictions for isothermal θ′ dissolution in Al–3.0wt%–Cu alloy and silicon dissolution in Al–0.8wt%–Si alloy were performed; good agreement with the published experimental data has been achieved.
[Show abstract][Hide abstract] ABSTRACT: This paper investigates the feasibility of applying a compressed air powertrain to mine rescue vehicles, which require strict explosion-proof and flame-proof characteristics. Based on both simulation and preliminary tests of a single-cylinder air-powered engine prototype, the concept of compressed air powertrain for a rescue vehicle is proposed. Compared to conventional internal combustion engines, the exhaust emissions of the proposed air-powered engine concept are innoxious and its gas temperature is very low, which guarantees the safety and explosion-proof requirements. Preliminary selection and matching of both a transmission and final gear reduction are carried out, considering vehicle traction and air consumption performance characteristics. Simulation results show that given properly designed drivetrain gear ratios, the air-powered rescue vehicle can reach a speed of 7 km/h with gear 1 on a 30% slope road. Compared to current products, its feasibility in driving mileage and traction performance are further confirmed.
[Show abstract][Hide abstract] ABSTRACT: We have demonstrated the cause of low minority carrier lifetime corresponding to the edge zone of casting multicrystalline silicon ingots and its influence on the performance of solar cells. It is found that the concentration of substitutional carbon, interstitial oxygen, and dislocation density have no direct correlation with the low minority carrier lifetime in the edge zone. However, the distribution of interstitial iron exactly coincides with the minority carrier lifetime, indicating that iron contamination is mainly responsible for the lifetime degradation. After phosphorus diffusion gettering process, the low carrier lifetime region became narrower, and the concentration of interstitial iron is reduced by almost one order of magnitude. However, the carrier lifetime in the edge zone cannot be raised to average level. After celling process, the internal quantum efficiency map of the edge zone has a lower response to the long wavelength light, in accordance with the minority carrier lifetime distribution in this region. Therefore, the solar cells based on edge zones exhibit slightly lower efficiency than those conventional ones.
[Show abstract][Hide abstract] ABSTRACT: The paper proposes a novel pneumatic-fuel hybrid system, which combines a traditional internal combustion engine (ICE) and a pneumatic engine. One important merit of this concept is that the system can recover waste from cooling water of internal combustion engine to optimize the working process of pneumatic engine, and thus to improve the entire efficiency of the hybrid system. Meanwhile, energy-saving effect due to lower cooling fan power can be achieved on ICE by waste heat recovery of pneumatic engine. Based on thermodynamic analysis, an experimental system is designed and established for verification. The experimental results show that the performance of pneumatic engine is improved when the waste heat recovery concept of the hybrid system is applied. Then an application example on a 4-cylinder engine is analyzed and discussed using numerical simulation. The results show that the fan power of the ICE cooling system can be saved up to 50% by applying the hybrid system. Considering the appreciable improvements on the energy efficiency with only limited system modifications when the concept is applied to traditional ICE based power systems, the proposed hybrid concept has the potential to serve as an alternative technology aiming for energy saving and emission reduction.
[Show abstract][Hide abstract] ABSTRACT: Electrodeionization (EDI) was used for the removal of Sr2+ from simulated wastewater. The effects of several operational variables, including the flow rate, the initial pH, and the Sr2+ concentration, were investigated, respectively. The optimum operational parameters are as follows: the initial pH of feed solution is 7.0, the flow rate and the concentration of feed solution are 1.0 L h−1 and 50 mg L−1. Under these conditions, the residual Sr2+ concentration is as low as 0.0415 mg L−1 after 200 min of EDI process, the energy consumption is 7.66 kW h m−3, and the current efficiency 9.17%.
Desalination and water treatment 11/2013; 53(8):1-9. DOI:10.1080/19443994.2013.861773 · 1.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Predictions of thermal and pressurization performance in a liquid hydrogen (LH2) tank during liquid discharge is of significance to the design and optimization of a rocket pressurization system. In this paper, a computational fluid dynamic (CFD) model is introduced to simulate the pressurized discharge event of LH2 tank. The wall region together with the fluid region is simultaneously considered as the computational domain, and low-Re k–ε model is applied to account for the fluid-wall heat exchange effect. Liquid–vapor phase change effect is also involved in the model. Comparison of the numerical results with existing experimental data suggests that the CFD model has a good adaptability in pressurization computation. Detailed characteristics, such as pressurant gas requirement, pressure altering history, and temperature distribution inside the tank, can be obtained by the model. The difference of pressurant gas, selecting helium or vapor H2, may result in the variations in pressure and temperature histories. Pressurization by vapor H2 supplies a higher pressure and also a temperature rise, which is significant to consider the selection of pressurant gas. The influences of phase change effect and injector structure on pressurization behaviors are also analyzed. The computational results show that liquid–vapor phase change has a slight influence on the pressurization behaviors. Significant pressure decay at the beginning stage of process may occur in the case of no-diffuser injector application since the incoming gas is excessively cooled by cold LH2. The results show that the present CFD model has a good adaptability in the prediction of pressurization behaviors and is a useful tool for the design and optimization of a pressurization system.
[Show abstract][Hide abstract] ABSTRACT: A fiber optic current sensor based on a polarization-rotated reflected interferometer has been constructed. A special spun highly birefringent fiber is designed and achieved for the sensor by heating and spinning commercial linearly birefringent fiber. In contrast with conventional fibers, the fiber integrates a function of a quarter wave plate. Particularly, fabricating and working principle of the current sensor head using the fiber are expounded. The sensor achieves an accuracy with 0.5% and good linearity shown in temperature dependence (a temperature drift of 0.008%/ °C) over a temperature range 40 °C -70 °C. Further, under simple temperature compensation, the sensor accuracy is within ±0.1% over in a wide range of current and temperature ranges.
[Show abstract][Hide abstract] ABSTRACT: The solidification of UNS N08028 alloy subjected to different cooling rates was studied, where primary austenite dendrites occur predominantly and different amounts of sigma phase form in the interdendritic regions. The solidification path and elemental segregation upon solidification were simulated using the CALPHAD method, where THERMO-CALC software packages and two classical segregation models were employed to predict the real process. It is thus revealed that the interdendritic sigma phase is formed via eutectic reaction at the last stage of solidification. On this basis, an analytical model was developed to predict the evolution of nonequilibrium eutectic phase, while the isolated morphology of sigma phase can be described using divorced eutectic theory. Size, fraction, and morphology of the sigma phase were quantitatively studied by a series of experiments; the results are in good agreement with the model prediction.
Metallurgical and Materials Transactions A 07/2013; 44(7). DOI:10.1007/s11661-013-1657-3 · 1.73 Impact Factor