The regions with shear stress and mean velocity gradient of opposite sign often exist in complex turbulent shear flows.In these cases,the eddy viscosity hypothesis breaks down.Hinze regards the,departure from eddy vis...The regions with shear stress and mean velocity gradient of opposite sign often exist in complex turbulent shear flows.In these cases,the eddy viscosity hypothesis breaks down.Hinze regards the,departure from eddy viscosity hypothesis as a result from transportation of mean momentum over distance by the large structures and arrives at a shear stress expression including the second order derivatives of the mean velocity.However,his expression greatly overestimates the shear stress.This implies that the flow particles are unlikely to have enough memory of the mean momentum over distance.By assuming the departure from eddy viscosity hypothesis as a result from transportation of the shear stress contained in smaller eddies over distance by the large structures,the present author has arrived at a new shear stress expression.The shear stress estimated so far is in good agreement with the experiments.展开更多
The interference alignment （IA） algorithm based on FDPM subspace tracking （FDPM-ST IA） is proposed for MIMO cognitive network （CRN） with multiple primary users in this paper. The feasibility conditions of FDPM-S...The interference alignment （IA） algorithm based on FDPM subspace tracking （FDPM-ST IA） is proposed for MIMO cognitive network （CRN） with multiple primary users in this paper. The feasibility conditions of FDPM-ST IA is also got. Futherly, IA scheme of secondary network and IA scheme of primary network are given respectively without assuming a priori knowledge of interference covariance matrices. Moreover, the paper analyses the computational complexity of FDPM-ST IA. Simulation results and theoretical calculations show that the proposed algorithm can achieve higher sum rate with lower computational complexity.展开更多
Heavy biodegraded crude oils have larger numbers of coeluting compounds than nonbiodegraded oils, and they are typically not resolved with conventional gas chromatography（GC）. This unresolved complex mixture（UCM） ...Heavy biodegraded crude oils have larger numbers of coeluting compounds than nonbiodegraded oils, and they are typically not resolved with conventional gas chromatography（GC）. This unresolved complex mixture（UCM） has been investigated using comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry（GC×GC-To FMS） within a set of biodegraded petroleums derived from distinct sedimentary basins, including northwestern Sichuan（Neoproterozoic, marine）, Tarim（Early Paleozoic, marine）, Bohai Bay（Eocene, saline/brackish） and Pearl River Mouth（Eocene, freshwater）. In general, the hydrocarbons that constitute the UCM in petroleum saturate fractions can be classified into three catalogues based on the distributions of resolved compounds on two dimensional chromatograms. Group 1 is composed mainly of normal and branched alkanes, isoprenoid alkanes and monocyclic alkanes; Group 2 comprises primarily terpanes ranging from two to five rings, and Group 3 is dominated by monoaromatic hydrocarbons such as tetralins and monoaromatic steranes. In addition, the UCM is source dependent and varies between oil populations. i.e., the UCM of petroleum derived from Precambrian and Early Paleozoic marine, Eocene saline/brackish and freshwater source rocks is specifically rich in higher homologues of A-norsteranes, series of 1,1,3-trimethyl-2-alkylcyclohexanes（carotenoid-derived alkanes）, and tetralin and indane compounds, respectively.展开更多
The novel complex [K(18-C-6)]_2 [Cd(mnt)_2] [18-C-6 = 18-crown-6, mnt =1,2-dicyanoethene-1,2-dithiolate, C_2S_2-(CN)_2^(2-)] was synthesized and characterized by elementalanalysis, IR spectrum and X-ray diffraction an...The novel complex [K(18-C-6)]_2 [Cd(mnt)_2] [18-C-6 = 18-crown-6, mnt =1,2-dicyanoethene-1,2-dithiolate, C_2S_2-(CN)_2^(2-)] was synthesized and characterized by elementalanalysis, IR spectrum and X-ray diffraction analysis. The complex displays two-dimensional networkstructure of [K(18-C-6)] complex segments and [Cd(mnt)_2] complex segment bridged by S-K-S, S-K-Nand N-K-N interactions between adjacent [K(18-C-6)] and [Cd(mnt)_2] units.展开更多
We theoretically demonstrate the imaging properties of a complex two-dimensional(2D) face-centered square lattice photonic crystal(PC) made from germanium cylinders in air background. The finitedifference time-domain(...We theoretically demonstrate the imaging properties of a complex two-dimensional(2D) face-centered square lattice photonic crystal(PC) made from germanium cylinders in air background. The finitedifference time-domain(FDTD) method is employed to calculate the band structure and simulate image construction. The band diagram of the complex structure is significantly compressed. Negative refraction occurs in the second energy band with negative phase velocity at a frequency of 0.228(2πc/a), which is lower than results from previous studies. Lower negative refraction frequency leads to higher image resolution. Numerical results show that the spatial resolution of the system reaches 0.7296λ, which is lower than the incident wavelength.展开更多
A novel two-dimensional network manganese(Ⅱ) polymer complex [Mn(O2CCH2CI)2-(phen)]n has been synthesized and characterized by elemental analysis and IR spectrum. The crystal structure of title complex has also been ...A novel two-dimensional network manganese(Ⅱ) polymer complex [Mn(O2CCH2CI)2-(phen)]n has been synthesized and characterized by elemental analysis and IR spectrum. The crystal structure of title complex has also been determined, which is in monoclinic of a space group P21/c with the following unit cell parameters at 294K: a=1.9738(4) nm, b =1.1384(2) nm, c =0.74915(14) nm, V =1.6795(5) nm3, Z= 2.展开更多
The copper(Ⅱ) complex [Cu_3(nta)_2(azpy)_2(H_2O)_2]·6H_2O (nta =nitrilotriacetate, azpy = 4,4′-azobispyridine) has been synthesized and characterized. The X-rayanalysis reveals that there are two kinds of copp...The copper(Ⅱ) complex [Cu_3(nta)_2(azpy)_2(H_2O)_2]·6H_2O (nta =nitrilotriacetate, azpy = 4,4′-azobispyridine) has been synthesized and characterized. The X-rayanalysis reveals that there are two kinds of copper(Ⅱ) coordination environments. Cu(1) has adistorted square plane symmetry and Cu(2) has a distorted octahedral symmetry. Cu(1) is linked toCu(2) through nta and bound to Cu(1C) by azpy, and Cu(2) is linked to Cu(2A) through azpy, whichextends to two-dimensional network with large rhombus 1.2 nm x 1.7 nm.展开更多
THE photosystem Ⅱ light-harvesting chlorophyll a/b protein complex (LHC Ⅱ) is a kind of integral membrane protein complex in the thylakoid membranes of chloroplasts from higher plants and green algae, and its most i...THE photosystem Ⅱ light-harvesting chlorophyll a/b protein complex (LHC Ⅱ) is a kind of integral membrane protein complex in the thylakoid membranes of chloroplasts from higher plants and green algae, and its most important biological function is light harvesting and展开更多
In an attempt to synthesize supra-molecular complex of copper(II) with mixed ligands in a solution reaction of Cu(ClO 4) 2·6H 2O with 4,5-diazafluorene-9-one (dafo) and o-phthalic acid, the bright blue col...In an attempt to synthesize supra-molecular complex of copper(II) with mixed ligands in a solution reaction of Cu(ClO 4) 2·6H 2O with 4,5-diazafluorene-9-one (dafo) and o-phthalic acid, the bright blue column-like crystal [Cu(dafo) 2(H 2O) 2]-(ClO 4) 2 was obtained. Its structure was determined by single-crystal X-ray diffraction study. The crystal belongs to monoclinic system, space group P2(1)/n with cell dimensions: a=0.7947(3) nm, b=1.2021(5) nm, c=1.3190(5) nm, α=90.000(5)°, β=90.000(5)°, γ= 90.000(5)°, V=1.2600(9) nm 3, Z=2, F(000)=670, M r=662.83, D c=1.747 g/cm 3, μ (Mo Kα)=1.154 mm -1, R 1=0.0455, wR 2=0.1041. The analysis of the crystal structure indicates that the complex has a two-dimensional network structure which is formed by hydrogen bonds.展开更多
多重信号分选(MUltiple SIgnal Classification,MUSIC)算法是波达方向(Direction-Of-Arrival,DOA)估计的最重要算法之一,但庞大的计算量使其工程实用性大打折扣。为降低MUSIC的计算量,该文基于子空间旋转(Subspace Rotation Technique,S...多重信号分选(MUltiple SIgnal Classification,MUSIC)算法是波达方向(Direction-Of-Arrival,DOA)估计的最重要算法之一,但庞大的计算量使其工程实用性大打折扣。为降低MUSIC的计算量,该文基于子空间旋转(Subspace Rotation Technique,SRT)变换思想提出了一种高效改进算法,即SRT-MUSIC算法。SRT-MUSIC利用秩亏特性对噪声子空间矩阵按行分块并以旋转变换得到降维噪声子空间,进而基于该降维噪声子空间与导向矢量的正交性构造空间谱估计信号DOA。理论分析表明:SRT-MUSIC能有效避免空间谱搜索中的冗余运算,从而成倍降低算法的计算量。对于大阵元、少信号情况,所提算法计算效率优势更为明显。仿真实验证明了SRT-MUSIC的有效性和高效性。展开更多
文摘The regions with shear stress and mean velocity gradient of opposite sign often exist in complex turbulent shear flows.In these cases,the eddy viscosity hypothesis breaks down.Hinze regards the,departure from eddy viscosity hypothesis as a result from transportation of mean momentum over distance by the large structures and arrives at a shear stress expression including the second order derivatives of the mean velocity.However,his expression greatly overestimates the shear stress.This implies that the flow particles are unlikely to have enough memory of the mean momentum over distance.By assuming the departure from eddy viscosity hypothesis as a result from transportation of the shear stress contained in smaller eddies over distance by the large structures,the present author has arrived at a new shear stress expression.The shear stress estimated so far is in good agreement with the experiments.
基金the National Nature Science Foundation of China under Grant No.61271259 and 61301123,the Chongqing Nature Science Foundation under Grant No.CTSC2011jjA40006,and the Research Project of Chongqing Education Commission under Grant No.KJ120501 and KJ120502
文摘The interference alignment （IA） algorithm based on FDPM subspace tracking （FDPM-ST IA） is proposed for MIMO cognitive network （CRN） with multiple primary users in this paper. The feasibility conditions of FDPM-ST IA is also got. Futherly, IA scheme of secondary network and IA scheme of primary network are given respectively without assuming a priori knowledge of interference covariance matrices. Moreover, the paper analyses the computational complexity of FDPM-ST IA. Simulation results and theoretical calculations show that the proposed algorithm can achieve higher sum rate with lower computational complexity.
基金funded by the National Natural Science Foundation of China(Grant No.41172126)the State Key Laboratory of Petroleum Resources and Prospecting(PRP/indep-2-1402)
文摘Heavy biodegraded crude oils have larger numbers of coeluting compounds than nonbiodegraded oils, and they are typically not resolved with conventional gas chromatography（GC）. This unresolved complex mixture（UCM） has been investigated using comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry（GC×GC-To FMS） within a set of biodegraded petroleums derived from distinct sedimentary basins, including northwestern Sichuan（Neoproterozoic, marine）, Tarim（Early Paleozoic, marine）, Bohai Bay（Eocene, saline/brackish） and Pearl River Mouth（Eocene, freshwater）. In general, the hydrocarbons that constitute the UCM in petroleum saturate fractions can be classified into three catalogues based on the distributions of resolved compounds on two dimensional chromatograms. Group 1 is composed mainly of normal and branched alkanes, isoprenoid alkanes and monocyclic alkanes; Group 2 comprises primarily terpanes ranging from two to five rings, and Group 3 is dominated by monoaromatic hydrocarbons such as tetralins and monoaromatic steranes. In addition, the UCM is source dependent and varies between oil populations. i.e., the UCM of petroleum derived from Precambrian and Early Paleozoic marine, Eocene saline/brackish and freshwater source rocks is specifically rich in higher homologues of A-norsteranes, series of 1,1,3-trimethyl-2-alkylcyclohexanes（carotenoid-derived alkanes）, and tetralin and indane compounds, respectively.
文摘The novel complex [K(18-C-6)]_2 [Cd(mnt)_2] [18-C-6 = 18-crown-6, mnt =1,2-dicyanoethene-1,2-dithiolate, C_2S_2-(CN)_2^(2-)] was synthesized and characterized by elementalanalysis, IR spectrum and X-ray diffraction analysis. The complex displays two-dimensional networkstructure of [K(18-C-6)] complex segments and [Cd(mnt)_2] complex segment bridged by S-K-S, S-K-Nand N-K-N interactions between adjacent [K(18-C-6)] and [Cd(mnt)_2] units.
文摘We theoretically demonstrate the imaging properties of a complex two-dimensional(2D) face-centered square lattice photonic crystal(PC) made from germanium cylinders in air background. The finitedifference time-domain(FDTD) method is employed to calculate the band structure and simulate image construction. The band diagram of the complex structure is significantly compressed. Negative refraction occurs in the second energy band with negative phase velocity at a frequency of 0.228(2πc/a), which is lower than results from previous studies. Lower negative refraction frequency leads to higher image resolution. Numerical results show that the spatial resolution of the system reaches 0.7296λ, which is lower than the incident wavelength.
基金supported by the National Natural Science Foundation of China(Grant No.20271041)Shaanxi Province Natural Science Foundation(Grant No.2002B04).
文摘A novel two-dimensional network manganese(Ⅱ) polymer complex [Mn(O2CCH2CI)2-(phen)]n has been synthesized and characterized by elemental analysis and IR spectrum. The crystal structure of title complex has also been determined, which is in monoclinic of a space group P21/c with the following unit cell parameters at 294K: a=1.9738(4) nm, b =1.1384(2) nm, c =0.74915(14) nm, V =1.6795(5) nm3, Z= 2.
文摘The copper(Ⅱ) complex [Cu_3(nta)_2(azpy)_2(H_2O)_2]·6H_2O (nta =nitrilotriacetate, azpy = 4,4′-azobispyridine) has been synthesized and characterized. The X-rayanalysis reveals that there are two kinds of copper(Ⅱ) coordination environments. Cu(1) has adistorted square plane symmetry and Cu(2) has a distorted octahedral symmetry. Cu(1) is linked toCu(2) through nta and bound to Cu(1C) by azpy, and Cu(2) is linked to Cu(2A) through azpy, whichextends to two-dimensional network with large rhombus 1.2 nm x 1.7 nm.
文摘THE photosystem Ⅱ light-harvesting chlorophyll a/b protein complex (LHC Ⅱ) is a kind of integral membrane protein complex in the thylakoid membranes of chloroplasts from higher plants and green algae, and its most important biological function is light harvesting and
文摘In an attempt to synthesize supra-molecular complex of copper(II) with mixed ligands in a solution reaction of Cu(ClO 4) 2·6H 2O with 4,5-diazafluorene-9-one (dafo) and o-phthalic acid, the bright blue column-like crystal [Cu(dafo) 2(H 2O) 2]-(ClO 4) 2 was obtained. Its structure was determined by single-crystal X-ray diffraction study. The crystal belongs to monoclinic system, space group P2(1)/n with cell dimensions: a=0.7947(3) nm, b=1.2021(5) nm, c=1.3190(5) nm, α=90.000(5)°, β=90.000(5)°, γ= 90.000(5)°, V=1.2600(9) nm 3, Z=2, F(000)=670, M r=662.83, D c=1.747 g/cm 3, μ (Mo Kα)=1.154 mm -1, R 1=0.0455, wR 2=0.1041. The analysis of the crystal structure indicates that the complex has a two-dimensional network structure which is formed by hydrogen bonds.
文摘多重信号分选(MUltiple SIgnal Classification,MUSIC)算法是波达方向(Direction-Of-Arrival,DOA)估计的最重要算法之一,但庞大的计算量使其工程实用性大打折扣。为降低MUSIC的计算量,该文基于子空间旋转(Subspace Rotation Technique,SRT)变换思想提出了一种高效改进算法,即SRT-MUSIC算法。SRT-MUSIC利用秩亏特性对噪声子空间矩阵按行分块并以旋转变换得到降维噪声子空间,进而基于该降维噪声子空间与导向矢量的正交性构造空间谱估计信号DOA。理论分析表明:SRT-MUSIC能有效避免空间谱搜索中的冗余运算,从而成倍降低算法的计算量。对于大阵元、少信号情况,所提算法计算效率优势更为明显。仿真实验证明了SRT-MUSIC的有效性和高效性。
