Continuously transferring cold atoms in caesium double magneto-optical trap

We have established a caesium double magneto-optical trap （MOT） system for cavity-QED experiment, and demonstrated the continuous transfer of cold caesium atoms from the vapour-cell MOT with a pressure of - 1 × 10^-6 Pa to the ultra-high-vacuum （UHV） MOT with a pressure of - 8 × 10^-8 Pa via a focused continuous-wave transfer laser beam. The effect of frequency detuning as well as the intensity of the transfer beam is systematically investigated, which makes the transverse cooling adequate before the atoms leak out of the vapour-cell MOT to reduce divergence of the cold atomic beam. The typical cold atomic flux got from vapour-cell MOT is - 2 × 10^7 atoms/s. About 5 × 10^6 caesium atoms are recaptured in the UHV MOT.

The charge transfer via a double helix DNA

This paper reports a double helix model of charge transfer in DNA molecule. The calculated results show that the transmission characteristics of DNA are not only related to the longitudinal transfer but also to the helicity of molecule. It finds that there are four transmission bands centred at 0.92, 3.07, 7.75 and 8.87eV, also the width and intensity of bands corresponding to the helix direction are less than that of the longitudinal direction. With the increase of hopping energy, transmission bands become wide so that the transmission ability is enhanced.

Droplet transfer behavior of the stainless steel coated electrode with double-layer coating

In this paper, the droplet transfer behavior of the stainless steel coated electrode with double layer coating is researched by means of those experimental methods, such as high speed camera, collecting droplet in water, surfacing on the steel plate et al. The results show that the droplet transfer indexes of coated electrode are mainly controlled by the size of droplet, which affects the transfer behavior of droplet. The distribution characteristic of the droplet size of the electrode affects the numerical relationship among droplet transfer indexes. The metallurgical process of the coated electrode with double layer coating is carried out continuously in different zones. The main reason for the coated electrode with double layer coating gaining excellent usability quality is that the droplets realize the 'quasi flux wall guided transfer pattern'.

Electron transfer properties of double quantum dot system in a fluctuating environment

Using the innovative method of the additional Bloch vector,the electron transfer properties of a double quantum dot(DQD) system measured by a quantum point contact(QPC) in a fluctuating environment are investigated.The results show that the environmental noises in transverse and longitudinal directions play different roles in the dynamical evolution of the open quantum systems.Considering the DQD with symmetric energy level,the Fano factor exhibits a slight peak with the increase of transverse noise amplitude σ_(T),which provides a basis for distinguishing dynamical phenomena caused by different directional fluctuation noises in symmetric DQD structures by studying the detector output.In the case of asymmetric DQD,the dependence of a detector current involving the level displacement is distinct when increasing the transverse noise damping coefficient τ_(T) and the longitudinal noise damping coefficient τ_(ε) respectively.Meanwhile,the transverse noise damping coefficient τ_(T) could significantly reduce the Fano factor and enhance the stability of the quantum system compared with the longitudinal one.The Fano factors with stable values as the enhancement of noise amplitudes show different external influences from the detector measurement,and provide a numerical reference for adjusting the noise amplitudes in both transverse and longitudinal directions appropriately in a microscopic experimental process to offset the decoherence effect caused by the measurements.Finally,the research of average waiting time provides unique insights to the development of single electron transfer theory in the short-time limit.

Quantum Information Transfer from a Double Quantum Dot System to a Cavity Field

In this paper, we propose a scheme to realize quantum information transfer from a double quantum dot （DQD） system to a quantized cavity field. The DQD and the cavity field are treated as a two-state charge qubit and a continuous-variable system, respectively. It is shown that quantum information encoded in the two-state DQD system can be transferred to quantum states of the cavity field with a continuous-variable basis through appropriate projective measurements with respect to the DQD.

Theoretical study on the mechanism for the excited-state double proton transfer process of an asymmetric Schiff base ligand

Excited-state double proton transfer(ESDPT)in the 1-[(2-hydroxy-3-methoxy-benzylidene)-hydrazonomethyl]-naphthalen-2-ol(HYDRAVH_(2))ligand was studied by the density functional theory and time-dependent density functional theory method.The analysis of frontier molecular orbitals,infrared spectra,and non-covalent interactions have crossvalidated that the asymmetric structure has an influence on the proton transfer,which makes the proton transfer ability of the two hydrogen protons different.The potential energy surfaces in both S_(0)and S_1 states were scanned with varying O-H bond lengths.The results of potential energy surface analysis adequately proved that the HYDRAVH_(2)can undergo the ESDPT process in the S_1 state and the double proton transfer process is a stepwise proton transfer mechanism.Our work can pave the way towards the design and synthesis of new molecules.

Excited-State Double Proton Transfer of 1,8-Dihydroxy-2-Naphthaldehyde:a MS-CASPT2//CASSCF Study

Excited-state double proton transfer(ESDPT)is a controversial issue which has long been plagued with theoretical and experimental communities.Herein,we took 1,8-dihydroxy-2-naphthaldehyde(DHNA)as a prototype and used combined complete active space selfconsistent field(CASSCF)and multi-state complete active-space second-order perturbation(MS-CASPT2)methods to investigate ESDPT and excited-state deactivation pathways of DHNA.Three different tautomer minima of S1-ENOL,S1-KETO-1,and S1-KETO-2 and two crucial conical intersections of S1 S0-KETO-1 and S1 S0-KETO-2 in and between the S0 and S1 states were obtained.S1-KETO-1 and S1-KETO-2 should take responsibility for experimentally observing dual-emission bands.In addition,two-dimensional potential energy surfaces(2 D-PESs)and linear interpolated internal coordinate paths connecting relevant structures were calculated at the MS-CASPT2//CASSCF level and confirmed a stepwise ESDPT mechanism.Specifically,the first proton transfer from S1-ENOL to S1-KETO-1 is barrierless,whereas the second one from S1-KETO-1 to S1-KETO-2 demands a barrier of ca.6.0 kcal/mol.The linear interpolated internal coordinate path connecting S1-KETO-1(S1-KETO-2)and S_(1) S0-KETO-1(S1 S0-KETO-2)is uphill with a barrier of ca.12.0 kcal/mol,which will trap DHNA in the S_(1) state while therefore enabling dual-emission bands.On the other hand,the S1/S0 conical intersections would also prompt the S_(1) system to decay to the S_(0) state,which could be to certain extent suppressed by locking the rotation of the C5-C8-C9-O10 dihedral angle.These mechanistic insights are not only helpful for understanding ESDPT but also useful for designing novel molecular materials with excellent photoluminescent performances.

Influence of the Inclination Angle on Mixed Convection and Heat Transfer in a“T”Shaped Double Enclosure

The effect of the tilt angle on mixed convection and related heat transfer in a“T”shaped double enclosure with four heated obstacles on the bottom surface is numerically investigated.The considered obstacles are constantly kept at a relatively high(fixed)temperature,while the cavity’s upper wall is cooled.The finite volume approach is used to solve the mass,momentum,and energy equations with the SIMPLEC algorithm being exploited to deal with the pressure-velocity coupling.Emphasis is put on the influence of the tilt angle on the solution symmetry,flow structure,and heat exchange through the walls.The following parameters and related ranges are considered:Rayleigh number 104≤Ra≤5.105,tilt angle 0°≤φ≤90°,Reynolds number 100≤Re≤1000,Prandtl number Pr=0.72,block height B=0.5,opening width C=0.15,and distance between blocks D=0.5.The results reveal different branches of solutions on varying Re andφ.They also show that the symmetry of the solution regarding the P_(2)axis is retained for all cases with no tilt and for values of Re between 100 and 1000.

Effect of Solvent Polarity on Excited-State Double Proton Transfer Process of 1,5-Dihydroxyanthraquinone

The excited-state double proton transfer(ESDPT)properties of 1,5-dihydroxyanthraquinone(1,5-DHAQ)in various solvents were investigated using femtosecond transient absorption spectroscopy and the DFT/TDDFT method.The steady-state fluorescence spectra in toluene,tetrahydrofuran(THF)and acetonitrile(ACN)solvents presented that the solvent polarity has an effect on the position of the ESDPT fluorescence emission peak for the 1,5-DHAQ system.Transient absorption spectra show that the increasing polarity of the solvent accelerates the rate of excited state dynamics.Calculated potential energy curves analysis further verified the experimental results.The ESDPT barrier decreases gradually with the increase of solvent polarity from toluene,THF to ACN solvent.It is convinced that the increase of solvent polarity can promote the occurrence of the ESDPT dynamic processes for the 1,5-DHAQ system.This work clarifies the mechanism of the influence of solvent polarity on the ESDPT process of 1,5-DHAQ,which provides novel ideas for design and synthesis of new hydroxyanthraquinone derivatives.

Mechanism of Excited State Double Proton Transfer in 2-Amino-3-Methoxypyridine and Acetic Acid Complex

The excited-state double-proton transfer （ESDPT） mechanism of 2-amino-3-methoxypyridine and acetic acid com- plex is studied by the density functional theory （DFT） and time-dependent DFT with CAM-B3LYP functional. The complex is connected through two different types of inter-molecular hydrogen bonds. After photo-excitation, both hydrogen bonds get strengthened, which can facilitate the ESDPT reaction. The scanned potential energy curve along the proton transfer coordinate indicates that the ESDPT reaction proceeds in a stepwise pattern.

Language Transfer Evidence in the Acquisition of Double Object Construction by Chinese EFL Learners

Based on the theory of language transfer in second language acquisition, this study explored the dynamic acquisition of English double object construction by Chinese EFL learners through comparative analysis. Altogether 120 subjects participated in this experiment and were required to take the proofreading exercise in limited time. The experimental results showed that Chinese EFL learners at different levels of proficiency acquired the core subclass of double object construction better than peripheral ones;meanwhile, learners at higher levels of proficiency outperformed those at lower levels, especially in the peripheral types. Relevant theoretical interpretations were given thereafter to the above research findings, with the hope to shed some light on the learning of double object construction by Chinese EFL learners.

A study on improvement of expression of human G－CSF cDNA transferred with retroviral double－copy vector

In order to overcome the interference of the internal promoter in retroviral vector with a foreign DNA expression, we used the double-copy vector(DC vector) system to improve the effect of transduced gene expression.Human G-CSF cDNA was inserted into the Bgl Ⅱ site of the polyclonal sites within the U3 region of the 3'long terminal repeat(3'-LTR) in the vector(N2A). After being identified, the gene was transduced into Ψ-2 packaging cell line by using the electroporation method. Consequently, the gene was duplicated in the infected cells, and transferred to the 5'-LRT, and then placed outside the retroviral transcriptional unit. After two weeks the neomycin resistance positive colonies were grown in the G-418 medium. The supernatant virus was titred and then transferred to NIH3T3 cells. The G-CSF value of positive clone N2AG7-4 was up to 53. 3 U/106 cells. Southern blot and Northern blot analysis showed that the chimeric gene faithfully duplicated in the cells infected with the corresponding virus and generated two copies with one in each LTR.

Effect of laser power on metal transfer in laser-double arcs P-MAG hybrid welding with single power source

The effect of laser power on metal transfer is studied under conditions of alternating combustion of double arcs in order to develop the welding process of the laser-double arcs pulsed metal active gas （P-MAG） hybrid welding with single power. Different laser power corresponds to different interactive mechanisms of laser and arc and to different methods of metal transfer in the hybrid welding. When the laser power ascends from 500 W to 1 500 W, the methods of metal transfer change from the complex transfer of one droplet per pulse, one droplet two pulses and one droplet much more pulses during the mixture of globular and projected transfer of the lead wire, and from one droplet two pulses and one droplet three pulses during globular transfer of the follow wire to the methods of the metal transfer of both lead wire and follow wire are stable one droplet two pulses and one droplet three pulses when the metal transfer is mainly globular. The arc sharps and pressure of droplet are altered with the laser power changing. The compression of the arcs is strengthened by the laser and the offset of the center of droplet mass is much more obvious with the increasing of the laser power.

Numerical Simulation of Double Diffusive Mixed Convection in a Horizontal Annulus with Finned Inner Cylinder

The present work relates to a numerical investigation of double diffusive mixed convection around a horizontal annulus with a finned inner cylinder.The solutal and thermal buoyancy forces are sustained by maintaining the inner and outer cylinders at uniform temperatures and concentrations.Buoyancy effects are also considered,with the Boussinesq approximation.The forced convection effect is induced by the outer cylinder rotating with an angular velocity(ω)in an anti-clockwise direction.The studies are made for various combinations of dimensionless numbers;buoyancy ratio number(N),Lewis number(Le),Richardson number(Ri)and Grashof number(Gr).The isotherms,isoconcentrations and streamlines as well as both average and local Nusselt and Sherwood numbers were studied.A finite volume scheme is adopted to solve the transport equations for continuity,momentum,energy and mass transfer.The results indicate that the use of fins on the inner cylinder with outer cylinder rotation,significantly improves the heat and mass transfer in the annulus.

Techno-economic analysis of single U-tube and double U-tube heat exchangers in Chongqing area

On the basis of practical projects in Chongqing,the thermal performance of heat exchangers (single U-tube type and double U-tube type) of the ground-source heat pump (GSHP) system in the hot summer was obtained and analyzed. The data obtained from test could match with the result deduced from theoretical calculation. From the test results,the cooling capacity of double U-tube is 1.6 times that of single U-tube. Taking cost per depth per watt Clq as the evaluation standard,Clq of single U-tube is 4.69 RMB$/W,and Clq of double U-tube is 3.14 RMB$/W. The double U-tube heat exchangers usage should be prioritized.

Double BP Q-Learning Algorithm for Local Path Planning of Mobile Robot

Aiming at the dimension disaster problem, poor model generalization ability and deadlock problem in special obstacles environment caused by the increase of state information in the local path planning process of mobile robot, this paper proposed a Double BP Q-learning algorithm based on the fusion of Double Q-learning algorithm and BP neural network. In order to solve the dimensional disaster problem, two BP neural network fitting value functions with the same network structure were used to replace the two Q value tables in Double Q-Learning algorithm to solve the problem that the Q value table cannot store excessive state information. By adding the mechanism of priority experience replay and using the parameter transfer to initialize the model parameters in different environments, it could accelerate the convergence rate of the algorithm, improve the learning efficiency and the generalization ability of the model. By designing specific action selection strategy in special environment, the deadlock state could be avoided and the mobile robot could reach the target point. Finally, the designed Double BP Q-learning algorithm was simulated and verified, and the probability of mobile robot reaching the target point in the parameter update process was compared with the Double Q-learning algorithm under the same condition of the planned path length. The results showed that the model trained by the improved Double BP Q-learning algorithm had a higher success rate in finding the optimal or sub-optimal path in the dense discrete environment, besides, it had stronger model generalization ability, fewer redundant sections, and could reach the target point without entering the deadlock zone in the special obstacles environment.

Qualitative Properties and Numerical Solution of the Kolmogorov-Fisher Type Biological Population Task with Double Nonlinear Diffusion

In the present work we study the global solvability of the Kolmogorov-Fisher type biological population task with double nonlinear diffusion and qualitative properties of the solution of the task based on the self-similar analysis. In additional, in this paper we consider the model of two competing population with dual nonlinear cross-diffusion.

Numerical simulation for 2D double-diffusive convection(DDC) in rectangular enclosures based on a high resolution upwind compact streamfunction model Ⅰ: numerical method and code validation

A high resolution upwind compact streamfunction numerical algorithm for two-dimensional(2D)double-diffusive convection(DDC)is developed.The unsteady Navier-Stokes(N-S)equations in the streamfunction-velocity form and the scalar temperature and concentration equations are used.An optimized third-order upwind compact(UCD3 opt)scheme with a low dispersion error for the first derivatives is utilized to approximate the third derivatives of the streamfunction in the advection terms of the N-S equations and the first derivatives in the advection terms of the scalar temperature and concentration equations.The remaining first derivatives of the streamfunction(velocity),temperature,and concentration variables used in the governing equations are discretized by the fourth-order compact Pade(SCD4)schemes.With the temperature and concentration variables and their approximate values of the first derivatives obtained by the SCD4 schemes,the explicit fourth-order compact schemes are suggested to approximate the second derivatives of temperature and concentration in the diffusion terms of the energy and concentration equations.The discretization of the temporal term is executed with the second-order Crank-Nicolson(C-N)scheme.To assess the spatial behavior capability of the established numerical algorithm and verify the developed computer code,the DDC flow is numerically solved.The obtained results agree well with the benchmark solutions and some accurate results available in the literature,verifying the accuracy,effectiveness,and robustness of the provided algorithm.Finally,a preliminary application of the proposed method to the DDC is carried out.

A double closed loop APFC control with feed-forward

In order to improve the steady state performance,dynamic response and power factor of traditional power factor correction(PFC)digital control method and reduce the harmonic distortion of input current,a double closed loop active power factorcorrection(APFC)control method with feed-forward is proposed.Firstly,the small signal model of Boost PFC control systemis built and the system transfer function is deduced,and then the parameters of the main device with Boost topology is estimated.By means of the feed-forward,the system can quickly respond to the change in input voltage.Furthermore,the use ofvoltage loop and current loop can achieve input current and output voltage regulation Simulink modeling shows that this methodcan effectively control the output voltage in case of input voltage largely fluctuating,improve the system dynamic response abilityand input power factor,and reduce the input current harmonic distortion

Visualization of Double-Diffusive Convection and Unsteady Solidification on a Vertical Circular Cylinder

This paper describes experimental results on the solidification process over the vertically positioned circular cylinder, placed in an aqueous solution of sodium nitrate, where the aqueous solution in the vessel is heated from the bottom. After the initiation of solidification by cooling the cylinder below the liquidus temperature, the pure ice formation on the cylinder causes the rejection of solute into the surrounding aqueous solution. The solute enriched vertical fluid layer over the ice then falls on the bottom of the vessel due to its higher density, and accumulates there. This process results in the formation of solute rich and hot horizontal layer (heavy layer), underlying the relatively cold but less concentrated fluid layer (light layer). As this process advances, however, because of the continuing influx of solute rich fluid, the lower heavy layer occupies more space, and the interface of the two layers rises slowly. The pH indicator method has been successfully employed in order to visualize the flows during this process. In this report, we document the evolution of both temperature and flow fields in the aqueous solution quantitatively, as the solidification progresses and the density discontinuity of the two layers rises.