摘要 :
Mixture of asphalt binder and filler, called mastics in this paper are often assumed to behave as simple viscoelastic materials; simply binders stiffened by filler. It will be shown in this paper that this is an oversimplification...
展开
Mixture of asphalt binder and filler, called mastics in this paper are often assumed to behave as simple viscoelastic materials; simply binders stiffened by filler. It will be shown in this paper that this is an oversimplification. Stiffening is only one way in which the addition of mineral filler changes the properties of asphalt stiffer binder. In fact, mastics behave quite differently than simply stiffer binder. These differences include changes in the material properties with aging and time and magnitude of loading that are of technical and scientific interest.
收起
摘要 :
A melal-semiconductor-metal (M-S-M) model for quantitative analysis of current-voltage (I-V) characteristics of semiconducting nanowires is described and applied to fit experimental I-V curves of Bi_2S_3 nanowire transistors. The ...
展开
A melal-semiconductor-metal (M-S-M) model for quantitative analysis of current-voltage (I-V) characteristics of semiconducting nanowires is described and applied to fit experimental I-V curves of Bi_2S_3 nanowire transistors. The I-V characteristics of semiconducting nanowires are found to depend sensitively on the contacts, in particular on the Schottky barrier height and contact area, and the M-S-M model is shown to be able to reproduce all experimentally observed I-V characteristics using only few fitting variables. A procedure for decoupling contact effects from that of the intrinsic parameters of the semiconducting nanowires, such as conductivity, carrier mobility and doping concentration is proposed, demonstrated using experimental I-V curves obtained from Bi_2S_3 nanowires and compared with the field-effect based method.
收起
摘要 :
We present improved parameterized algorithms for the feedback vertex set problem on both unweighted and weighted graphs. Both algorithms run in time O(5~k kn~2). The algorithms construct a feedback vertex set of size at most k (in...
展开
We present improved parameterized algorithms for the feedback vertex set problem on both unweighted and weighted graphs. Both algorithms run in time O(5~k kn~2). The algorithms construct a feedback vertex set of size at most k (in the weighted case this set is of minimum weight among the feedback vertex sets of size at most k) in a given graph G of n vertices, or report that no such feedback vertex set exists in G.
收起
摘要 :
Two novel functional ladder-like polysilsesquioxanes with double-chain macromolecular backbones and nonlinear optical (NLO) chromophore-containing side chains for NLO applications (NLO-T_1 and NLO-T_2) were synthesized successfull...
展开
Two novel functional ladder-like polysilsesquioxanes with double-chain macromolecular backbones and nonlinear optical (NLO) chromophore-containing side chains for NLO applications (NLO-T_1 and NLO-T_2) were synthesized successfully for the first time via the introduction of the NLO chromophores to the side chains of the ladderlike polychloroprpylsilsesquiox- ane (Cl-T_1) and ladderliek poly(4-chlromethylphenyl)ethysilsesquioxane (Cl-T_2), respectively, by an etherification reaction.
收起
摘要 :
Semiconducting carbon nanotubes (CNTs) are considered as the most promising channel material to construct ultrascaled field-effect transistors, but the perfect sp2 C─C structure makes stable doping difficult, which limits the ele...
展开
Semiconducting carbon nanotubes (CNTs) are considered as the most promising channel material to construct ultrascaled field-effect transistors, but the perfect sp2 C─C structure makes stable doping difficult, which limits the electrical designability of CNT devices. Here, an inner doping method is developed by filling CNTs with 1D halide perovskites to form a coaxial heterojunction, which enables a stable n-type field-effect transistor for constructing complementary metal–oxide–semiconductor electronics. Most importantly, a quasi-broken-gap (BG) heterojunction tunnel field-effect transistor (TFET) is first demonstrated based on an individual partial-filling CsPbBr3/CNT and exhibits a subthreshold swing of 35 mV dec−1 with a high on-state current of up to 4.9 µA per tube and an on/off current ratio of up to 105 at room temperature. The quasi-BG TFET based on the CsPbBr3/CNT coaxial heterojunction paves the way for constructing high-performance and ultralow power consumption integrated circuits.
收起
摘要 :
A novel kind of alcohol-soluble ladderlike polyslisesquioxane having side-chain with amino terminal groups (NH2-T) was first prepared by reduction of nitro terminal groups on the side chains of ladderlke polynitrosilsesquioxane (N...
展开
A novel kind of alcohol-soluble ladderlike polyslisesquioxane having side-chain with amino terminal groups (NH2-T) was first prepared by reduction of nitro terminal groups on the side chains of ladderlke polynitrosilsesquioxane (NO2-T) with a nearly 100/100 conversion rate. The parent polymer NO2-T was synthesized by stepwise coupling polymerization. As starting monomer, 3-(4-nitrophenoxy)propyltrichlorosilane (M) was synthesized by hydrosilylation of the corresponding allyic derivative with trichlorosilane in the presence of dicyclopentadienylplatinum(II) chloride (Cp2PtCl2) catalyst in a high yield.
收起
摘要 :
The electrochemical NO_x reduction reactions, involving nitrate and nitrite
reduction reactions (NO_3~−RR and NO_2~−RR), have emerged as promising
approaches for both NO_3~− and NO_2~− removal, and ammonium (NH_3)
synthesis...
展开
The electrochemical NO_x reduction reactions, involving nitrate and nitrite
reduction reactions (NO_3~−RR and NO_2~−RR), have emerged as promising
approaches for both NO_3~− and NO_2~− removal, and ammonium (NH_3)
synthesis under ambient conditions. However, the incorporation and
stabilization of sulfur dopants in the catalysts for efficient NO_x reduction are
rarely explored, leading to an unclear effect of sulfur on the NO_x reduction
mechanism. Herein, sulfur-doped Cu_2O (S-Cu_2O) nanoneedle arrays via in
situ electrochemical treatment are synthesized. The S-Cu_2O catalyst
possesses excellent durability and selectivity for NH_3 over a wide range of
potentials in NO_3~−RR, attaining a maximum NH_3 Faradaic efficiency of 94%
at −0.6 V_(RHE) and a maximum NH_3 yield as high as 1.06 mmol h~(−1) cm~(−2). In
NO_3~−RR, the sulfur dopant can accelerate the step from NO_2~− to NH_3,
contributing superior performance in NO_2~−RR and assembled Zn−NO_2~−
battery device. Density functional theory (DFT) calculations reveal that the
presence of sulfur can enhance the initial step of *NO_3 adsorption, lower the
reaction barriers for the formation of *NHO intermediate, and activate the
H_2O dissociation process. The work sheds light on the role of sulfur in
enhancing electrocatalytic performance and provides a unique perspective for
understanding the NO_x reduction mechanism.
收起
摘要 :
A washoff rate equation for stormwater pollutants is presented based on linear buildup of pollutant mass in the watershed. The expression was applied to residential and open land areas that have not previously been considered even...
展开
A washoff rate equation for stormwater pollutants is presented based on linear buildup of pollutant mass in the watershed. The expression was applied to residential and open land areas that have not previously been considered even though these areas are major sources of metals, nutrients, and bacteria in stormwater runoff. The transport coefficient c was determined from the nearly constant portion of the hydrograph at the peak of each runoff event. Values of c (cm"1) for seven metals, i.e., Zn, Cu, Cd, Ni, Pb, Hg, and Ag (3.03±1.34-6.10±2.55 cm~(-1)), TSS, BOD_5, total phosphorus (TP), E. coli, and fecal coliform (2.12 ± 0.907-7.16 ± 2.72 cm~(-1)) were estimated using this equation. The washoff rate was developed to reflect mixed land uses based on mass deposition and effective area. The order of transport coefficients for metals is Pb>Ag>Zn>Cu>Ni>Hg>Cd reflecting decreasing particle association. For all parameters this order is TSS>fecal coliform>E. co!i>Pb>BOD_5 BOD_5>Ag>Zn>Cu>Ni>Hg>Cd>TP. The washoff rate and a related pollutant concentration model are expected to be useful for the development of best management practices for stormwater.
收起
摘要 :
The electronic circular dichroism (ECD), optical rotation dispersion (ORD), and vibrational circular dichroism (VCD) spectra of a pair of enantiomers, I.e. 3 and 4, of a bicyclo[3.1.0]hexane derivative have been measured in aceton...
展开
The electronic circular dichroism (ECD), optical rotation dispersion (ORD), and vibrational circular dichroism (VCD) spectra of a pair of enantiomers, I.e. 3 and 4, of a bicyclo[3.1.0]hexane derivative have been measured in acetonitrile and acetonitrile-d_3, respectively. Extensive conformational searches at the B3LYP/6-311++G~(**) level have been carried out for 3, which has four OH and one N_3 functional groups. For the bicyclo[3.1.0]hexane ring of 3, the boat-like conformers have been found to be much more stable than the chair-like conformers, while the number and the strength of the intramolecular hydrogen bonds have been identified as the dominant factors in the relative stability among the boat-like and among the chair-like conformers. DFT simulations of the ECD, ORD and VCD spectra have been performed for all low energy conformers at the B3LYP/6-311++G~(**) and B3LYP/aug-cc-pVDZ level. Implicit continuum polarization model has been used to account for solvent effects in all these chiroptical measurements. Comparison of the DFT simulations with the experimental data shows that all three chiroptical properties yield the same absolute configuration assignment for 3. This work demonstrates that using multiple chiroptical spectroscopic methods in combination with DFT calculations allows one to determine absolute configurations with high confidence for chiral carbohydrates and their analogues, which possess a large number of rotatable bonds.
收起
摘要 :
In this paper, Ti-6Al-4V matrix composites reinforced with 5% or 10% TiB and TiC were in situ synthesized by common casting and hot-forging technology utilizing the reaction between titanium and B4C. The phase constituents were id...
展开
In this paper, Ti-6Al-4V matrix composites reinforced with 5% or 10% TiB and TiC were in situ synthesized by common casting and hot-forging technology utilizing the reaction between titanium and B4C. The phase constituents were identified by XRD while transus temperatures were determined by DSC and metallography. The evolution of microstructures was studied by optical microscopy. The effects of reinforcements on the microstructures, tensile properties and fractures at room temperature were discussed. The results show that yield strength and ultimate tensile strength increased significantly while ductility decreased with reinforcements increasing. Fracture type turned to brittle when reinforcements increased.
收起
