分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-04-06
摘要: A new direct summation method, named as polyhedron method, is proposed to calculate Madelung energy. This method calculates sums of electrostatic interactions over sets of neutral polyhedron unit pairs rather than conventional ion pairs; this gives Madelu
分类: 材料科学 >> 材料科学(综合) 提交时间: 2017-03-30
摘要: In this work, 12-tungestocobaltic acid based organic-inorganic hybrid material, [Bmim)(6)CoW12O40 (CoW) was synthesized and applied as a synergist in polypropylene (PP)/intumescent flame retardant (IFR) composites. The flame retardant properties were inve
分类: 材料科学 >> 材料科学(综合) 提交时间: 2017-03-30
摘要: In this work, 12-tungestocobaltic acid based organic-inorganic hybrid material, [Bmim)(6)CoW12O40 (CoW) was synthesized and applied as a synergist in polypropylene (PP)/intumescent flame retardant (IFR) composites. The flame retardant properties were inve
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-04-06
摘要: We studied the optical properties of silica colloids suspensions made of nanospheres having an average diameter of 50, 90, 120, and 300 nm in electric field. It was illustrated that a colloidal suspension with a particle size of 120 nm shows a dramatic ch
提交时间: 2017-04-06
摘要: Aluminum hypophosphite (AHP) was introduced into polylactide/intumescent flame retardant (PLA/IFR) systems by melt blending. The flame retardant and thermal properties of the PLA composites were investigated. The results suggest that a synergistic effect
分类: 物理学 分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-12-28
摘要: Light top squarks (stops) and light higgsinos are the key features of natural supersymmetry (SUSY), where the higgsinos χ?1± and χ?1,20 are nearly degenerate and act as the missing transverse energy (ET) at the LHC. Besides the pair production via strong
分类: 物理学 分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-12-28
摘要: The maximal U(1)LU(1)LU(1)_L supersymmetric inverse seesaw mechanism (MLSIS) provides a natural way to relate asymmetric dark matter (ADM) with neutrino physics. In this paper we point out that MLSIS is a natural outcome if one dynamically realizes the in
分类: 地球科学 >> 空间物理学 提交时间: 2017-03-31
摘要: Ulysses magnetic and plasma data are used to study hourly-scale Alfv{\'e}nic fluctuations in the solar polar wind. The calculated energy ratio $R^2_{v_A}$(cal) of inward to outward Alfv{\'e}n waves is obtained from the observed Wal{\'e}n slope through an analytical expression, and the observed $R^2_{v_A}$(obs) is based on a direct decomposition of original Alfv{\'e}nic fluctuations into outward- and inward-propagating Alfv{\'e}n waves. The radial variation of $R^2_{v_A}$(cal) shows a monotonically increasing trend with heliocentric distance $r$, implying the increasing local generation or contribution of inward Alfv{\'e}n waves. The contribution is also shown by the radial increase in the occurrence of dominant inward fluctuations. We further pointed out a higher occurrence ($\sim 83\%$ of a day in average) of dominant outward Alfv{\'e}nic fluctuations in the solar wind than previously estimated. Since $R^2_{v_A}$(cal) is more accurate than $R^2_{v_A}$(obs) in the measurement of the energy ratio for dominant outward fluctuations, the values of $R^2_{v_A}$(cal) in our results are likely more realistic in the solar wind than previously estimated and than $R^2_{v_A}$(obs) in our results. The duration ratio $R_T$ of dominant inward to all Alfv{\'e}nic fluctuations increases monotonically with $r$, and is about two or more times that from {\it Voyager 2} observations at $r \geq 4$~AU. Finally, from the variation trend in our results, a higher (lower) occurrence rate is expected at $r 4$~AU) for dominant outward Alfv{\'e}nic fluctuations, and opposite variations are expected for dominant inward fluctuations. Simultaneously, $R^2_{v_A}$(cal) and $R_T$ will be expected to be smaller at $r 4$~AU. These results reveal new qualitative and quantitative features of Alfv{\'e}nic fluctuations therein compared with previous studies and put constraints on modelling the variation of solar wind fluctuations.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Heat accumulation is a severe problem for high-power light-emitting diodes (LEDs). Here, we introduce a thermostable and transparent lateral heat spreader as an additional heat-escaping channel of an LED chip to improve the thermal management of LED devices. The lateral heat spreader was prepared based on a silver nanowire (AgNW)/polyimide composite comprising a thin polyacrylate layer soldering a conductive AgNW network to confine the nanowires to the surface of a polyimide film and to obtain low contact resistance between the nanowires. The AgNW/polyimide composite film has a figure-of-merit sheet resistance of 7 ohm sq 1 with 76% transmittance at 550 nm. After heating at 200 C for 168 h, the sheet resistance increases to 16 ohm sq 1. The thermal conductivity and thermal diffusivity are 130.2 W m 1 K 1 and 60.5 mm2 s 1, respectively, which are comparable to those of a commercial copper foil. A demonstration shows the core temperature in a thermal diffusion apparatus can be lowered by 9 C. The experimental data combined with computational simulation indicate the Joule heating could be drawn away efficiently along the lateral heat spreader.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: First-principles calculations combined with XRD simulations are performed to systematically study crystal structures, bonding characteristics and electronic structures of LixCoSiO4 (x = 2.0, 1.5, 1.0) polymorphs with symmetries Pmn21-DP and Pbn21. The calculated average voltages by lithium extraction agree well with available experiments. CoO4 tetrahedron is the key structural unit to track the process of delithiation. The oxidation of CoO4 tetrahedron results in a special pattern of bonding characteristic, which corresponds to spin ordering and may be observable in XRD spectra according to simulation. We find delithiated phases are intrinsic Mott insulators, electronic band gaps change from Mott− Hubbard-type to charge-transfer-type during lithium removing. The swapping of near-gap states is associated with the contraction of the oxidized CoO4 units, indicating Peierls distortions that may be the physical origin of capacity degrading of Co−silicate chemistry.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: In this paper, flexible Ag electrodes with a hexagonal micromesh structure were fabricated on PET substrate using a photolithography technique. The effect of film thickness on optical and electrical properties of Ag electrodes was investigated systematically. Furthermore, these flexible transparent Ag mesh electrodes were firstly applied to a polymer dispersed liquid crystal (PDLC) device and its performance was evaluated. All of the Ag electrodes exhibited a high average transmittance of about 80.2–85.0% in the visible range (400–800 nm), and the minimum sheet resistance value reached 8.2 U sq 1. The prepared Ag mesh also showed an excellent performance of adhesion and bending, demonstrating its superior durability. The PDLC device based on Ag mesh electrodes showed comparable performance with that using ITO electrodes, indicating that the Ag mesh film can be a good substitution for ITO electrodes in PDLC devices and may find practical application in large area flexible devices.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: We reported the favorable cathode buffer layer based on a blend of ZnO nanoparticles (NPs) and TiO2 nanorods (NRs) applied to inverted solar cells. In addition to the high optical transmittance, the resultant blend film gave a relatively dense film with lower roughness than that of the respective single-component film. This improved the interface contact between the buffer layer and photoactive layer and therefore reduced the contact resistance and leakage current. Moreover, the combination of NRs and NPs increased the efficiency of electron transport and collection by providing both a direct path for electron transport from TiO2 NRs and a large contact area between ZnO NPs and the active layer. Consequently, both the short-circuit current density (Jsc) and fill factor (FF) in the device were improved, leading to an improvement of the device performance. The best power conversion efficiency (PCE) based on the blend film as the buffer layer reached 8.82%, which was preferable to those of a single ZnO NP film (7.76%) and a TiO2 NR-based device (7.66%). KEYWORDS: ZnO nanoparticles, TiO2 nanorods, blend film, cathode buffer layer, inverted solar cells
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: In this paper, we reported that ZnO nanoparticles (NPs) film modified with C60 pyrrolidine tris-acid ethyl ester (PyC60) was used as cathode buffer layer in inverted polymer solar cells. The resultant device with a blend of PTB7:PC71BM as photoactive materials exhibited an open-circuit voltage (Voc) of 0.753 V, a short-circuit current (Jsc) of 16.04 mA cm 2, a fill factor (FF) of 72.5%, and an overall power conversion efficiency (PCE) of 8.76%. It was higher than the control devices based on sole ZnO NPs film or ZnO: PyC60 hybrid film as cathode buffer layer. It was found that the morphology improvement of ZnO/PyC60 film contributed to reducing series loss and interfacial charge recombination. In addition, it improved the interfacial contact with photoactive layer. The results increased electron injection and collection efficiency, and improved FF.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: We used cesium stearate (CsSt) to modify the interface of the electron- extracting contact in inverted organic solar cells. Surface microstructure, optical properties, and electrical characterization as well as exciton generation rate and dissociation probability were investigated to understand the impact of CsSt on the interface contact. The results indicated that by incorporation of CsSt, the surface morphology and energy level as well as conductivity of a zinc oxide (ZnO) film were improved. On the basis of the above properties, highly efficient inverted organic solar cells have been demonstrated by using a ZnO nanoparticle film and CsSt stacked bilayer structure as the cathode interfacial layer. The insertion of a CsSt layer between the ZnO film and active layer improved the electron extraction efficiency, and a high power conversion efficiency (PCE) of 8.69% was achieved. The PCE was improved by 20% as compared to the reference device using a ZnO-only electron extraction layer.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: In this study, (001) and (101)-orientated polycrystalline SnO films were respectively fabricated. The preferred orientation conversion was observed by modifying the stoichiometry of the SnO films. It was revealed that the O-rich and Sn-rich SnO films favor (001) and (101) grain orientations, respectively. Moreover, based on the Raman selection rule and our experimental results, the 110 cm 1 Raman peak is assigned to the low- frequency Eg mode of SnO. The Raman intensity ratio between the 110 cm 1 and 210 cm 1 peak of SnO increases with the relative texture coefficient of the (101) grain orientation but decreases with that of the (001) one, demonstrating that the Raman characteristic information could be used as fingerprint recognition to mutually predict the crystallographic texture of SnO films.
提交时间: 2017-05-02
摘要: Polycrystalline ZnSnN2 thin films were successfully prepared by DC magnetron sputtering at room temperature. Both the as-deposited and annealed films showed n-type conduction, with electron concentration varying between 1.6 x 10[18] and 2.3 x 10[17] cm[-3
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: In this paper, Ga-doped ZnO (GZO) thin films are deposited on glass substrates by radio frequency magnetron sputtering for low loss plasmonic applications. The effects of Ga2O3 content in the target and substrate temperature on the electrical, structural and optical properties of GZO films are investigated. Film with the highest carrier concen- tration of 7.0 × 1020 cm− 3 was obtained at a Ga2O3 content of 5 wt% in the target under room temperature deposi- tion. With increasing deposition temperature, the lowest electrical resistivity of 3.8 × 10− 4 Ω cm was acquired at a deposition temperature of 200 °C. The values of plasmonic resonances wavelength could be changed from 1.35 to 2.39 μm by adjusting the carrier concentration. Material absorption losses in these GZO films are 10 times lower than that of conventional Ag films at telecommunication wavelengths. These results make GZO a promising low-loss plasmonic material operating at telecommunication wavelengths.
提交时间: 2017-05-02
摘要: Heterovalent Sn2O3 nanosheets were fabricated via an oxidation annealing process and the formation mechanism was investigated. The temperature required to complete the phase transformation from Sn3O4 to Sn2O3 was considered. Two contrasting experiments sh
提交时间: 2017-05-02
摘要: Memristive devices have been widely employed to emulate biological synaptic behavior. In these cases, the memristive switching generally originates from electrical field induced ion migration or Joule heating induced phase change. In this letter, the Ti/Z
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: In the preliminary design process of switched reluctance machine (SRM), adjusting the number of wingding turns or cross-sectional area of conductor to optimize windings design has dramatic effects on the performances like torque density, efficiency and thermal dissipation and so on. However, the difficulty exists on how to guarantee these performances while optimizing winding design. This paper proposes an analytical optimization design method based on an regulation model of ampere density and coil space factor, which can directly determine the optimal number of winding turns, the cross- sectional area of conductor, the ampere density and the coil space factor. And a MATLAB pre-design program has been developed to provide two design schemes respectively with and without the optimization model. The comparison analysis has been further carried out with finite element analysis (FEA). The simulation results verify that the performances can be highly improved with the proposed optimization model.