仿生沟槽锥形结构多种环境下油滴的自运输研究

目的虽然传统锥形结构可以实现水下油滴的定向运动,但在复杂环境中连续自适应的油滴自运输仍然是一个挑战。为此研发一种新型沟槽锥形结构表面,以实现多种环境下高效的油滴自运输。方法受到水稻叶各向异性沟槽结构和仙人掌刺不对称锥形结构的启发,采用飞秒激光直写扫描系统在聚四氟乙烯上下表面加工沟槽锥形结构。借助接触角测试平台表征结构表面的润湿性,并通过扫描电子显微镜对表面微沟槽形貌进行分析。使用高速相机记录结构在水环境、水-空气界面和空气中的油滴运输过程,并以此为基础分析研究结构在多种环境下的油滴自运输能力。结果沟槽锥形结构实现了在水下、空气中及水-空气界面多种环境下油滴的连续自运输,并且展示出优于传统锥形结构的高效水下油滴自运输能力,收集速率达到112.17 mm/s。结论利用沟槽锥形结构良好的结构扩展性、无须消耗能源或外力驱动的操作模式和优异的油滴自运输能力,制备了水下自驱动集油装置,展示了该结构的潜在应用。

多孔超疏水表面疏水稳定性与集气性能研究

基于仿生学思想,使用激光在铝板表面加工出凹槽和微槽的复合微纳形态,并在凹槽内加工出微孔作为气体通道。结果表明,复合微纳结构具有气泡自传输和气体收集特性,在石油化工、生物医学等领域的应用前景广阔。虽然近年来的研究已经实现了微气泡在非对称润湿结构中的定向运动,但对其在减少阻力方面的应用还没有很好的研究。本文使用纳秒激光处理500 µm厚的铝板,实现了气泡的自发定向传输。这种特殊的微结构采用低表面能材料进行处理,以提供更好的抗静水压力和气泡收集能力。

Flow variability along a vegetated natural stream under various sediment transport rates

The influence of vegetation and sediment on flow characteristics in open channels cannot be neglected. To study the flow variability under the effects of the instream natural vegetation and sediment supply, experiments were conducted with varied water and sediment supply in a movable bed of a river prototype. The instantaneous threedimensional velocities near two types of vegetation patches(the shrub and the weed) and along the centerline of the main channel with vegetation belts were measured using a 3-D side-looking acoustic Doppler velocimetry. The experimental results show that both the instream vegetation and sediment supply strongly affect the flow and turbulence characteristics. In the case of vegetation patches, both the shrub and weed have a considerable influence on the distribution of the streamwise velocity and turbulence intensity of their surrounding water. The streamwise velocity distribution followed as J-shape and linear shape around the weed and shrub under different experimental conditions. The turbulence intensity was large at the top of the weed and shrub;the shrub had its greatest influence on the downstream water flow. In the case of vegetation belts,the streamwise velocity along the centerline of the main channel exhibited an S-shape, J-shape and linear shape at different locations under varied water,vegetation structures and riverbed configurations.The turbulence intensity along the centerline of the main channel ranged from 0.0 to 0.1. The upstream turbulence intensity was affected considerably by a sediment supply, while the downstream turbulence intensity changed with the varied vegetation characteristics and riverbed topography. The second flow coefficient M-value increased longitudinally and was almost positive along the centerline of the main channel, implying that the rotational direction of the secondary current cell was clockwise.

Modeling vertical heat transport in the wave affected surface layer of the ocean

In considering the vertical heat boundary approximation for the free surface applied. However, due to the existence of the transport problems in the upper ocean, the flat upper and the horizontal homogenous hypothesis are usually wave motion, the application of this approximation may result in some errors to the solar irradiation since it decays quickly in respect to the actual thickness of the water layer below the surface; on the other hand, due to the fluctuation of the water layer depth, it is improper to neglect the effects of the horizontal advection and turbulent diffusion since they also contribute to the vertical heat transport. A new model is constructed in this study to reflect these effects. The corresponding numerical simulations show that the wave motion may remarkably accelerate the vertical heat transferring process and the variation of the temperature in the wave affected layer appears in an oscillating manner.

Electronic Transport Properties of Spin-Crossover Magnet Fe（Ⅱ）-N4S2 Complexes

Spin-crossover （SCO） magnets can act as one of the most possible building blocks in molec- ular spintronics due to their magnetic bistability between the high-spin （HS） and low-spin （LS） states. Here, the electronic structures and transport properties through SCO magnet Fe（II）-N4S2 complexes sandwiched between gold electrodes are explored by performing exten- sive density functional theory calculations combined with non-equilibrium Green＇s function formalism. The optimized Fe-N and Fe-S distances and predicted magnetic moment of the SCO magnet Fe（II）-N4S2 complexes agree well with the experimental results. The reversed spin transition between the HS and LS states can be realized by visible light irradiation according to the estimated SCO energy barriers. Based on the obtained transport results, we observe nearly perfect spin-filtering effect in this SCO magnet Fe（II）-N4S2 junction with the HS state, and the corresponding current under small bias voltage is mainly contributed by the spin-down electrons, which is obviously larger than that of the LS case. Clearly, these theoretical findings suggest that SCO magnet Fe（II）-N4S2 complexes hold potential applications in molecular spintronies.

Negative Differential Resistance and Spin-Filtering Effects in Zigzag Graphene Nanoribbons with Nitrogen-Vacancy Defects

We explore the electronic and transport properties of zigzag graphene nanoribbons （GNRs） with nitrogen-vacancy defects by performing fully self-consistent spin-polarized density functional theory calculations combined with non-equilibrium Green＇s function technique. We observe robust negative di erential resistance （NDR） effect in all examined molecular junctions. Through analyzing the calculated electronic structures and the bias-dependent transmission coefficients, we find that the narrow density of states of electrodes and the bias-dependent effective coupling between the central molecular orbitals and the electrode subbands are responsible for the observed NDR phenomenon. In addition, the obvious di erence of the transmission spectra of two spin channels is observed in some bias ranges, which leads to the near perfect spin-filtering effect. These theoretical findings imply that GNRs with nitrogenvacancy defects hold great potential for building molecular devices.

Paste-like self-flowing transportation backfilling technology based on coal gangue

A paste-like self-flowing pipeline transportation backfilling technology with coal gangue as aggregate is proposed to remove the potential damage caused by coal gangue piles. As well, the difficult problems of recovering high quality safety coal pillars and deep mining of the Suncun Coal Mine （SCM）, Xinwen Coal Group, Shandong are resolved. The physical-chemical properties of coal gangue, optimized proportion of materials, backfilling system and craft in the SCM were studied in the laboratory and then an industrial test was carried out on high quality coal pillars under a town. The results show that finely crushed kaolinized and fresh gangue with granularity less than 5 mm can be used as aggregate with fly ash to replace part of the cement and a composite water reducer as an additive, accounting for 1.0%-1.5% of the total amount of cement and fly ash. The recommended proportion is l（cement）：4（fly ash）： 15（coal gangue）, with a mass fraction of 72%-75%, rheoiogical paste-like properties and a strength of more than 0.7 MPa at 7 d. The sequence of adding cement, fly ash, water reducer and then coal gangue ensures that the suspended state of the slurry, reducing the wear and jam of pipelines. The working face is advancing continuously by the alternating craft of building block walls with coal gangue and backfilling mined-out gobs with paste-like slurry. The recovery rate is as high as 90% with a backfilling cost of 36.9 YuarffL good utilization of coal gangue and no subsidence on the surface. This technology provides a good theoretical basis and application experience for coal mines, cement backfilling with paste-like slurry.

Spin-Polarized Transport Through a Quantum Dot Coupled to Ferromagnetic Leads： Kondo Correlation Effect

We investigate the linear and nonlinear transport through a single level quantum dot connected to two ferromagnetic leads in Kondo regime, using the slave-boson mean-field approach for finite on-site Coulomb repulsion. We find that for antiparallel alignment of the spin orientations in the leads, a single zero-bias Kondo peak always appears in the voltage-dependent differential conductance with peak height going down to zero as the polarization grows to P = 1.For parallel configuration, with increasing polarization from zero, the Kondo peak descends and greatly widens with the appearance of shoulders, and finally splits into two peaks on both sides of the bias voltage around P ～ 0.7 until disappearing at even larger polarization strength. At any spin orientation angle θ, the linear conductance generally drops with growing polarization strength. For a given finite polarization, the minimum linear conductance always appears at θ = π.

Transport Through a Precessing Spin Coupled to Noncollinearly Polarized Ferromagnetic Leads

The quantum electronic transport through a precessing magnetic spin coupled to noncollinearly polarized ferromagnetic leads （F-MS-F） has been studied in this paper. The nonequilibrium Green function approach is used to calculate local density of states （LDOS） and current in the presence of external bias. The characters of LDOS and the electronic current are obtained. The tunneling current is investigated for different precessing angle and different configurations of the magnetization of the leads. The investigation revea/s that when the precessing angle takes θ 〈 π /2 and negative bias is applied, the resonant tunneling current appears, otherwise, it appears when positive bias is applied. When the leads are totally polarized and the precessing angel takes O, the tunneling current changes with the configuration of two leads; and it becomes zero when the two leads are antiparallel.

Data Reconstruction in Internet Traffic Matrix

Traffic matrix is an abstract representation of the traffic volume flowing between sets of source and destination pairs.It is a key input parameter of network operations management,planning,provisioning and traffic engineering.Traffic matrix is also important in the context of OpenFlow-based networks.Because even good measurement systems can suffer from errors and data collection systems can fail,missing values are common.Existing matrix completion methods do not consider traffic exhibit characteristics and only provide a finite precision.To address this problem,this paper proposes a novel approach based on compressive sensing and traffic self-similarity to reconstruct the missing traffic flow data.Firstly,we analyze the realworld traffic matrix,which all exhibit lowrank structure,temporal smoothness feature and spatial self-similarity.Then,we propose Self-Similarity and Temporal Compressive Sensing(SSTCS) algorithm to reconstruct the missing traffic data.The extensive experiments with the real-world traffic matrix show that our proposed SSTCS can significantly reduce data reconstruction errors and achieve satisfactory accuracy comparing with the existing solutions.Typically SSTCS can successfully reconstruct the traffic matrix with less than 32%errors when as much as98%of the data is missing.

Spin Transport in a Rashba Ring-Quantum Dot System Pumped by Microwave Fields

We report a theoretical study on producing electrically spin-polarized current in the Rashba ring with parallel double dots embedded, which are subject to two time-dependent microwave fields. By means of the Keldysh Green＇s function method, we present an analytic result of the pumped current at adiabatic limit and demonstrate that the interplay between the quantum pumping effect and spin-dependent quantum interference can lead to an arbitrarily controllable spin-polarized current in the device. The magnitude and direction of the charge and spin current can be effectively modulated by system parameters such as the pumping phase difference, Rashba precession phase, and the dynamic phase difference of electron traveling in two arms of ring; moreover, the spin-polarization degree of the charge current can also be tuned in the range [-∞, ＋∞]. Our findings may shed light on the all-electric way to produce the controllable spin-polarized charge current in the field of spintronics.

Spin-Polarized Transport through a Quantum Dot Coupled to Ferromagnetic Leads and a Mesoscopic Ring

Using an equation of motion technique, we investigate the spin-polarized transport through a quantum dot coupled to ferromagnetic leads and a mesoseopie ring by the Anderson Hamiltonian. We analyze the transmission probability of this system in both the equilibrium and nonequilibrium cases, and our results reveal that the transport properties show some noticeable characteristics depending upon the spin-polarized strength p, the magnetic flux Ф and the number of lattice sites NR in the mesoseopic ring. These effects might have some potential applications in spintronics.

Pedestrianisation and Parking Policy as a Solution towards Green Transport Plan： A Case Study of Zagreb

Strategy of development trends in this moment and at this stage of the traffic comes from understanding the possibilities of the implementation of measures to raise the quality of movement and life in the city. It also includes planning and implementation of targeted interventions in the transport network or facilities. Mobility is a complex process in the area, starting from the departure from the apartment, using various means of transportation, a number of activities in different goals until to return to the location of the apartment. It thus requires extensive transport infrastructure in the form of walkways, bicycle paths, street and railway network. At the same time, reshaping of public transport facilities is needed in which the pedestrian, biker and green concept shall be the main elements of the new spatial conditions. Pedestrian zones development in the city means to create pedestrian areas and green islands in all the places in the city where possible. This process is essential for the transformation of public spaces, in particular, transport corridors. To accomplish the concept of the green transport plan, the need for change in the parking policy is emphasized. This should be an integral part of the city planning and should go hand in hand with the traffic policy.

Wave-Vector and Temperature-Dependent Electron Transport in a Magnetic Nanostructure Modulated by Bias

We theoretically investigate the wave-vector and temperature-dependent electron transport in a magneticnanostructure modulated by an applied bias.The large spin-polarization can be achieved in such a device,and the degreeof spin-polarization strongly depends on the transverse wave-vector and the temperature.These interesting propertiesmay be helpful to spin-polarize electrons into semiconductors,and this device may be used as a spin filter.

Effect of Force Adaptation in Mechanics

Discovery of effect of force adaptation in mechanics is presented. The discovery is based on use of the mobile closed mechanical contour for force transfer from the mechanism input link to an output link, According to discovery the motion transfer can be carried out by Assur structural group in the form of the mobile closed contour, and the output link is the link with one degree of freedom. The received mechanical system includes an input link, an output link and the closed contour placed between them as fourth class Assur structural group. The kinematic chain has two degrees of freedom. However the closed contour imposes an additional constraint on relative motion of its links. The carried out discovery allows providing the variable transfer ratio only due to the variable external load. Mechanical properties of the closed contour allow providing the required transfer ratio independently, smart and automatically.

Novel Synthesis Method of Nonst0ichiometric Na2-xlrO3 Crystal Structure, Transport and Magnetic Properties

Transition metal oxides with 4d or 5d metals are of great interest due to the competing interactions, of the Coulomb repulsion and the itineracy of the d-electrons, opening a possibility of building new quantum ground states. Particularly the 5d metal oxides containing Iridium have received significant attention within the last years, due to their unexpected physical properties, caused by a strong spin orbit coupling observed in It（IV）. A prominent example is the Mott-insulator Sr2IrO4. Another member of this family, the honeycomb lattice compound Na2IrO3, also being a Mott-insulator having, most probably, a Kitaev spin liquid ground state. By deintercalating sodium from Na2IrO3, the authors were able to synthesize a new honeycomb lattice compound with more than 50% reduced sodium content. The reduction of the sodium content in this layered compound leads to a change of the oxidation state of iridium from ＋ IV to ＋ V/＋ VI and a symmetry change from C2/c to P-3. This goes along with significant changes of the physical properties. Besides the vanishing magnetic ordering at 15 K, also the transport properties changes and instead insulating semiconducting properties are observed.

Steering Multiple Reverse Current into Unidirectional Current in Deterministic Ratchets

Recent investigations have shown that with varying the amplitude of the external force, the deterministic ratchets exhibit multiple current reversals, which are undesirable in certain circumstances. To control the multiple reverse current to unidirectional current, an adaptive control law is presented inspired from the relation between multiple reversaJs current and the chaos-periodic/quasiperiodic transition of the transport velocity. The designed controller can stabilize the transport velocity of ratchets to steady state and suppress any chaos-periodic/quasiperiodic transition, namely, the stable transport in ratchets is achieved, which makes the current sign unchanged.

Conductance Oscillations in Spin Field-Effect Transistors

Ballistic spin transport in spin field-effect transistors is studied by taking into account the Rashba spinorbit coupling, interracial scattering, and band mismatch. It is shown that the spin conductance oscillation with the semiconductor channel length is a superimposition of the Rashba spin precession and spin interference oscillations. They have different oscillation periods π/κR and π/κ with κR the Rashba wavevector and κ the Fermi wavevector of the semiconductor channel, and play different parts of slow and rapid oscillations, depending upon the relative magnitude of π/κR and π/κ. Only at κ = κR does the spin conductance exhibit oscillations of a single period. Two types of different behaviors of the tunnelling magnetoresistance are discussed.

International Price Shocks Transmission： The Case of Rice in Togo

The objective of the paper was to examine the relationship between the world rice price and the rice price in Togo using the linear and nonlinear co-integration tests. The author used the monthly prices for Togo local rice market and international market. The results show that the rice prices on the local market are integrated to international market. The elasticity of the long-term transmission is high. The threshold autoregression （TAR） model reveals an asymmetric transmission with a magnitude that varies depending on the nature of shock. Price increases in international markets are transmitted more rapidly to the local markets than price reductions. These results might be explained by the market power of traders, transport costs and government intervention.

High-strength super-hydrophobic double-layered PBO nanofiberpolytetrafluoroethylene nanocomposite paper for high-performance wave-transparent applications

Poly(p-phenylene-2,6-benzobisoxazole)nanofiber(PNF)paper is facing unprecedented challenges in enhancing the interaction between the PNFs and improving its hydrophobicity.In this work,a sol–gel film transformation approach was developed to fabricate high-strength PNF paper.Iron ions formed coordination bonds between PNFs to obtain a preforming three-dimensional,interconnective nanofiber network.Subsequently,polytetrafluoroethylene(PTFE)particles were sprayed onto the surface of the paper,followed by thermal treatment to obtain double-layered PTFE-P/PNF nanocomposite paper.The nanocomposite paper presents incredible tensile strength(271.6 MPa,increased by 52.9%),folding endurance,super-hydrophobicity,and self-cleaning performances.Moreover,it exhibits low dielectric constant(2.06)and dielectric loss tangent(0.0133)values.According to the wave-transparent model for a doublelayered dielectric established by Maxwell’s equations,the wave-transparent coefficients of electromagnetic waves incident from both sides of the paper are 97.6%(PNF side)and 96.0%(PTFE/P(S-co-BCB-coMMA)side),respectively.The PTFE-P/PNF nanocomposite paper possesses great potential in the fields of wave-transparent applications.