Anew method in system design of ejecting devices of missiles is first presented.Some important points are dis-cussed,which guid the research and development of new ejecting devices of missileg,amd provid the foundatio...Anew method in system design of ejecting devices of missiles is first presented.Some important points are dis-cussed,which guid the research and development of new ejecting devices of missileg,amd provid the foundation flr thw design of mew ejecting device is provided.The system design includes the distribution of techmology specifica-tion,3-D solid modeling of ejecting devices of missiles im-ported from abroad,the design of pmeumatic device sys-tem,the design of ejecting mechanism system,the predic-tion of reliability and the experimental analysis,etc.展开更多
The title compound [Ag(CH3CONHC(S)NH2)2](NO3) has been prepared by hydrothermal synthesis and characterized by single-crystal X-ray diffraction. It crystallizes in mo-noclinic, space group P21/c with Mr = 406.20 (C6H1...The title compound [Ag(CH3CONHC(S)NH2)2](NO3) has been prepared by hydrothermal synthesis and characterized by single-crystal X-ray diffraction. It crystallizes in mo-noclinic, space group P21/c with Mr = 406.20 (C6H12Ag N5O5S2), a = 12.0680(6), b = 6.8056(5), c = 18.0173(1) ? b = 111.383(4), V = 1377.9(2) 3, Z = 4, Dc = 1.958 g/cm3 , F(000) = 808, = 1.789 mm-1, R = 0.0361 and wR = 0.1015. Of 4185 reflections ((2)max = 55.00?, 3147 were unique (Rint = 0.0174) and 2820 with I > 2(I) were used to solve the structure. The silver(I) atom adopts V-shape geometry with the AgS bond distance of 2.4271(7) and 2.7229(9) , respectively. Seven atoms of one acetylthiocarbamide ligand are coplanar, while only four atoms of another acetylthio-carbamide ligand are fairly planar. The [Ag(CH3CONHC(S)NH2)2]+ cation and nitrate anion NO3- are connected by hydrogen bonds to form a three dimensional hydrogen bonding network..展开更多
A hybrid approach is presented to investigate the dynamic behavior of anaxially slide-spin flexible rocket with nonlinear clearance. The equations of motion of the flexiblerocket are derived based upon Euler-Bernoulli...A hybrid approach is presented to investigate the dynamic behavior of anaxially slide-spin flexible rocket with nonlinear clearance. The equations of motion of the flexiblerocket are derived based upon Euler-Bernoulli beam theory and Hamilton principle and the finiteelement method. The characteristics of clearance between the spinning rocket and launcher areconsidered to be piecewise linear. Numerical solution is developed by direct integration method anddemonstrates the validity of the method. The coupled dynamic behavior of axial motion and transversevibrations of rocket are analyzed, and the influences of axially moving acceleration, spin speed,linking stiffness of elastic 'shoes', and the nonlinearity of clearance on the motion attitude ofrocket are studied.展开更多
Semi-empirical molecular orbital calculations were performed on heterocyclic aromatic amines(HCAs). The relationship between the structures and the carcinogenicities can be rationally elucidated by the models based on...Semi-empirical molecular orbital calculations were performed on heterocyclic aromatic amines(HCAs). The relationship between the structures and the carcinogenicities can be rationally elucidated by the models based on the metabolism of HCAs and the Di-region theory. The degree of easiness for the formation of Di-region electrophilic centers determines the carcinogenic activity. There is a good linear relationship between the observed carcinogenicities and the PM3 calculated parameters, with r=0.973 and F=29.8>F ** 0.01 .展开更多
A general method of constructing proxy blind signature is proposed based on multilinear transform. Based on this method, the four proxy blind signature schemes are correspondently generated with four different signatu...A general method of constructing proxy blind signature is proposed based on multilinear transform. Based on this method, the four proxy blind signature schemes are correspondently generated with four different signature equations, and each of them has four forms of variations of signs. Hence there are sixteen signatures in all, and all of them are proxy stronglyblind signature schemes. Furthermore, the two degenerated situations of multi-linear transform are discussed. Their corresponding proxy blind signature schemes are shown, too. But some schemes come from one of these degenerate situations are proxy weakly-blind signature scheme.The security for proposed scheme is analyzed in details. The results indicate that these signature schemes have many good properties such as unforgeability, distinguish-ability of proxy signature,non-repudiation and extensive value of application etc.展开更多
The robust H∞ control problem for discrete-time uncertain systems is investigated in this paper. The uncertain systems are modelled as a polytopic type with linear fractional uncertainty in the vertices. A new linear...The robust H∞ control problem for discrete-time uncertain systems is investigated in this paper. The uncertain systems are modelled as a polytopic type with linear fractional uncertainty in the vertices. A new linear matrix inequality (LMI) characterization of the H∞ performance for discrete systems is given by introducing a matrix slack variable which decouples the matrix of a Lyapunov function candidate and the parametric matrices of the system. This feature enables one to derive sufficient conditions for discrete uncertain systems by using parameter-dependent Lyapunov functions with less conservativeness. Based on the result, H∞ performance analysis and controller design are carried out. A numerical example is included to demonstrate the effectiveness of the proposed results.展开更多
Ab initio calculations at the B3LYP/3-21G^(**), HF/3-21G>^(**) and ONIOM(HF/3-21G^(**): AM1) levels of the theory in combination with counterpoise procedure for BSSE correction were performed on HMX dimers. There e...Ab initio calculations at the B3LYP/3-21G^(**), HF/3-21G>^(**) and ONIOM(HF/3-21G^(**): AM1) levels of the theory in combination with counterpoise procedure for BSSE correction were performed on HMX dimers. There exist two O...H intermolecular contacts and the dispersion forces are dominant in the dimers. The corrected binding energies of the dimer are -15.10 and -17.81 kJ/mol at the HF/3-21G^(**) and \{ONIOM(HF/3-21G^(**): AM1) \}levels, respectively. The calculation by the B3LYP method gives irrational corrected binding energies though it produces similar intermolecular distances as those produced by the HF or \{ONIOM\} method. The geometrical parameters, the contact distances and the binding energies demonstrated, for the first time, the validity of the ONIOM method applied in the calculation of the parameters of intermolecular interactions.展开更多
Differential pulse voltammetry(DPV) was applied to the determination of alkaline phosphatase(ALP) activity in human serum with phenyl phosphate as the substrate. Phenyl phosphate can enzymatically be hydrolyzed to pro...Differential pulse voltammetry(DPV) was applied to the determination of alkaline phosphatase(ALP) activity in human serum with phenyl phosphate as the substrate. Phenyl phosphate can enzymatically be hydrolyzed to produce phenol which is quantified by DPV at +660 mV(vs.Ag/AgCl) in the concentration range of 2.0_100 μmol/L. The standard curve for ALP is linear over the range from 0.06 to 1000 U/L with a relative standard deviation of 3.0%. The conditions for the enzymatic reaction and voltammetric detection were optimized and the kinetic constants were also examined.The human serum samples were tested by this method and the results were in good agreement with those obtained by the routine p-nitrophenyl phosphate spectrophotometric method.展开更多
The structures,the binding energies and the thermodynamic properties of formamide and hydroxyacetonitrile(HAN) dimers have been studied by means of the self\|consistent \%ab initio\% Hartree\|Fock and the second\|orde...The structures,the binding energies and the thermodynamic properties of formamide and hydroxyacetonitrile(HAN) dimers have been studied by means of the self\|consistent \%ab initio\% Hartree\|Fock and the second\|order Mφller\|Plesset correlation energy correction methods. The counterpoise procedure was used to check the basis set superposition error(BSSE) of the binding energies. There exist cyclic structures in a formamide dimer(Ⅰ),a HAN dimer(Ⅱ) and their heterodimer(Ⅲ). The corrected binding energies for dimers Ⅰ,Ⅱ and Ⅲ are respectively -45.53,-45.83 and -43.89 kJ/mol at the MP2/aug\|cc\|p VDZ//HF/\{aug\|cc\|p VDZ\} level. The change of the Gibbs free energies(Δ\%G\%) in the process of Ⅰ+Ⅱ→2Ⅲ was predicted to be -2.74 kJ/mol at 298.15 K. Dimer Ⅲ can be spontaneously produced in the mixture of formamide and HAN,which is in agreement with the experimental fact that most cyanohydrins are capable of interacting with dipeptide cyclo\|His\|Phe(CHP).展开更多
The state feedback design for singularly perturbed systems described in Delta operator is considered. The composite state feedback controller for slow and fast subsystems is designed by using the direct method. The ob...The state feedback design for singularly perturbed systems described in Delta operator is considered. The composite state feedback controller for slow and fast subsystems is designed by using the direct method. The obtained results can bring previous conclusions of continuous and discrete time systems into the unified Delta framework. A simulation example is presented to demonstrate the validity and efficiency of the design.展开更多
An artificial neural networks(ANNs) based gear material selection hybrid intelligent system is established by analyzing the individual advantages and weakness of expert system (ES) and ANNs and the applications in mat...An artificial neural networks(ANNs) based gear material selection hybrid intelligent system is established by analyzing the individual advantages and weakness of expert system (ES) and ANNs and the applications in material select of them. The system mainly consists of tow parts: ES and ANNs. By being trained with much data samples, the back propagation (BP) ANN gets the knowledge of gear materials selection, and is able to inference according to user input. The system realizes the complementing of ANNs and ES. Using this system, engineers without materials selection experience can conveniently deal with gear materials selection.展开更多
The application of the random binary phase coded signal in the CW radar system has been limited by the difficulty to isolate the transmission and reception signal. In order to make use of the random binary phase coded...The application of the random binary phase coded signal in the CW radar system has been limited by the difficulty to isolate the transmission and reception signal. In order to make use of the random binary phase coded signal, the random binary phase coded pulse radar (RBPC-PR) system has been studied. First, the average ambiguity function (AAF) of the RBPC-PR signal has been analyzed. Then, a statistical method of reducing the range sidelobe (RSL) is presented. Finally, a signal processing scheme of the RBPC-PR is devdoped. The simulation results show that by using the scheme, the jamming immunity of the system, the resolution and accuracy of distance and velocity have been improved, and the distance and velocity vagueness caused by periods can also be removed. The RSL can be reduced over 30 dB by the statistical average method, thus the probability ambiguity caused by random noise can be avoided.展开更多
The method of extracting the basic features of part from the file of STEPAP214 of 3-D model is proposed. All faces in the file are the minimal elements. The combination isdone for the faces with geometry restrictions ...The method of extracting the basic features of part from the file of STEPAP214 of 3-D model is proposed. All faces in the file are the minimal elements. The combination isdone for the faces with geometry restrictions and some attributes by the theory of the bestalphabetic tree which is constructed by HU--TUCKER algorithm in combination principle. So the basicfeatures could be attained. This provides the research basis to the more share and integration ofCAD information in the virtual enterprises. Finally, a case is used to illustrate the validity ofthe approach.展开更多
The technology of plasma arc was used to modify the interface adhesion between c hromium coating and steel substrate. The interface microstructure was studied as a function of plasma arc processing parameters. Microst...The technology of plasma arc was used to modify the interface adhesion between c hromium coating and steel substrate. The interface microstructure was studied as a function of plasma arc processing parameters. Microstructure analysis was per formed by optical microscopy, scanning electron microscopy and electron probe. T he microhardness distribution along the depth of a cross-section of the chromium coating and the substrate was measured. The results show the energy density of transferred plasma arc is obviously higher than plasma non-transferred arc. The molten interface was obtained by plasma transferred arc. Interfaces between chro mium coating and steel substrate can be divided by plasma non-transferred arc in to three classes: non-molten, a little molten and molten. Good interface bonding was obtained by proper process parameters. The microhardness of chromium coatin g decreases with increasing energy density of plasma arc.展开更多
The structure of chiral N-ethyl-N-(2,3,4,6-tetra-O-acetyl-b-D-glycosyl)-thio- carbamide was determined by X-ray diffraction method. It crystallizes in the monoclinic system, space group P21 with a = 7.6560(15), b = 10...The structure of chiral N-ethyl-N-(2,3,4,6-tetra-O-acetyl-b-D-glycosyl)-thio- carbamide was determined by X-ray diffraction method. It crystallizes in the monoclinic system, space group P21 with a = 7.6560(15), b = 10.311(2), c =14.181(3) ? b =100.88(3), C17H26N2O9S, Mr = 434.46, V = 1099.3(4) ?, Z = 2, Dc = 1.312 g/cm3, F(000) = 460, m = 0.196 mm-1, R = 0.0704 and wR = 0.1655. The total independent reflections were 5098, of which 1875 were observed with I ≥2s(I). The hexopyranosyl ring adopts a chair conformation. All the ring substituents are in the equatorial positions. The acetoxylmethyl group is in the gauche-gauche conformation. The S atom is in synperiplanar conformation, while the NCNC linkage is antiperiplanar. X-ray analysis shows that the absolute configuration of the chiral carbon atom at C(1) was proved to be b-form. The 1H NMR spectra and IR are in good agreement with the result of crystallography analysis. The NH…O intermolecular hydrogen bonds link the molecules into infinite chains connected by CH…O interactions.展开更多
The projective transformation of the special semi-symmetric metric recurrent connection is studied in this paper. First of all, an invariant under this transformation is granted; Secondly, by inducing of the invariant...The projective transformation of the special semi-symmetric metric recurrent connection is studied in this paper. First of all, an invariant under this transformation is granted; Secondly, by inducing of the invariant and making use of the properties that the corresponding covariant derivative keeps being fixed under the distinctness connection, the curvature tensor expression of the Riemannian manifold is posed at the same time.展开更多
This paper is concerned with the H2 estimation and control problems for uncertain discretetime systems with norm-bounded parameter uncertainty. We first present an analysis result on H2 norm bound for a stable uncerta...This paper is concerned with the H2 estimation and control problems for uncertain discretetime systems with norm-bounded parameter uncertainty. We first present an analysis result on H2 norm bound for a stable uncertain system in terms of linear matrix inequalities (LMIs). A solution to the robust H2 estimation problem is then derived in terms of two LMIs. As compared to the existing results, our result on robust H2 estimation is more general. In addition, explicit search of appropriate scaling parameters is not needed as the optimization is convex in the scaling parameters. The LMI approach is also extended to solve the robust H2 control problem which has been difficult for the traditional Riccati equation approach since no separation principle has been known for uncertain systems. The design approach is demonstrated through a simple example.展开更多
In this paper,a Slotted Stepped-Impedance Resonator (SSIR) is proposed.Due to the slots in the low-impedance section of the conventional SIR,the new resonator has a lower fundamental resonance f0 and can provide a pot...In this paper,a Slotted Stepped-Impedance Resonator (SSIR) is proposed.Due to the slots in the low-impedance section of the conventional SIR,the new resonator has a lower fundamental resonance f0 and can provide a potential finite transmission zero fz close to f0.Based on the proposed SSIR,a fourth-order Chebychev BandPass Filter (BPF) is designed at f0=1 GHz.The measured results show that a better than-65 dB rejection is achieved on both the lower and the upper stopband.Moreover,the new filter has a wide-30 dB rejection upper stopband from 1.13f0 to 6.52f0.The fabricated filter exhibits a size of The new filter has a planar topology and is easily integrated with modern portable communication systems.展开更多
文摘Anew method in system design of ejecting devices of missiles is first presented.Some important points are dis-cussed,which guid the research and development of new ejecting devices of missileg,amd provid the foundation flr thw design of mew ejecting device is provided.The system design includes the distribution of techmology specifica-tion,3-D solid modeling of ejecting devices of missiles im-ported from abroad,the design of pmeumatic device sys-tem,the design of ejecting mechanism system,the predic-tion of reliability and the experimental analysis,etc.
基金This work was supported by the Natural Science Foundation of Shandong province (No.Y2002B06) and Science Research Foundation of Qingdao University of Science and Technology (No. 03Z08)
文摘The title compound [Ag(CH3CONHC(S)NH2)2](NO3) has been prepared by hydrothermal synthesis and characterized by single-crystal X-ray diffraction. It crystallizes in mo-noclinic, space group P21/c with Mr = 406.20 (C6H12Ag N5O5S2), a = 12.0680(6), b = 6.8056(5), c = 18.0173(1) ? b = 111.383(4), V = 1377.9(2) 3, Z = 4, Dc = 1.958 g/cm3 , F(000) = 808, = 1.789 mm-1, R = 0.0361 and wR = 0.1015. Of 4185 reflections ((2)max = 55.00?, 3147 were unique (Rint = 0.0174) and 2820 with I > 2(I) were used to solve the structure. The silver(I) atom adopts V-shape geometry with the AgS bond distance of 2.4271(7) and 2.7229(9) , respectively. Seven atoms of one acetylthiocarbamide ligand are coplanar, while only four atoms of another acetylthio-carbamide ligand are fairly planar. The [Ag(CH3CONHC(S)NH2)2]+ cation and nitrate anion NO3- are connected by hydrogen bonds to form a three dimensional hydrogen bonding network..
基金This project is supported by Science Foundation of Shanghai Municipal Co-mmission of Education, China(No.98AJ01) Provincial Natural Science Foundation of Shanghai, China(No.03ZR14032).
文摘A hybrid approach is presented to investigate the dynamic behavior of anaxially slide-spin flexible rocket with nonlinear clearance. The equations of motion of the flexiblerocket are derived based upon Euler-Bernoulli beam theory and Hamilton principle and the finiteelement method. The characteristics of clearance between the spinning rocket and launcher areconsidered to be piecewise linear. Numerical solution is developed by direct integration method anddemonstrates the validity of the method. The coupled dynamic behavior of axial motion and transversevibrations of rocket are analyzed, and the influences of axially moving acceleration, spin speed,linking stiffness of elastic 'shoes', and the nonlinearity of clearance on the motion attitude ofrocket are studied.
基金the National Natural Science Foundation of China(No.2 0 0 4 2 0 0 1) and by the Postdoctoral Foundation ofthe Ministry of Education P.R.China
文摘Semi-empirical molecular orbital calculations were performed on heterocyclic aromatic amines(HCAs). The relationship between the structures and the carcinogenicities can be rationally elucidated by the models based on the metabolism of HCAs and the Di-region theory. The degree of easiness for the formation of Di-region electrophilic centers determines the carcinogenic activity. There is a good linear relationship between the observed carcinogenicities and the PM3 calculated parameters, with r=0.973 and F=29.8>F ** 0.01 .
基金Supported by the Fundamental Research Program of Commission of Science Technology and Industry for National Defence (No.J1300D004)
文摘A general method of constructing proxy blind signature is proposed based on multilinear transform. Based on this method, the four proxy blind signature schemes are correspondently generated with four different signature equations, and each of them has four forms of variations of signs. Hence there are sixteen signatures in all, and all of them are proxy stronglyblind signature schemes. Furthermore, the two degenerated situations of multi-linear transform are discussed. Their corresponding proxy blind signature schemes are shown, too. But some schemes come from one of these degenerate situations are proxy weakly-blind signature scheme.The security for proposed scheme is analyzed in details. The results indicate that these signature schemes have many good properties such as unforgeability, distinguish-ability of proxy signature,non-repudiation and extensive value of application etc.
基金This work was partially supported by RGC Grant 7103/01P and the open project of the state key Laboratory of intelligent and Systems,Tsinghua University(No.0406).
文摘The robust H∞ control problem for discrete-time uncertain systems is investigated in this paper. The uncertain systems are modelled as a polytopic type with linear fractional uncertainty in the vertices. A new linear matrix inequality (LMI) characterization of the H∞ performance for discrete systems is given by introducing a matrix slack variable which decouples the matrix of a Lyapunov function candidate and the parametric matrices of the system. This feature enables one to derive sufficient conditions for discrete uncertain systems by using parameter-dependent Lyapunov functions with less conservativeness. Based on the result, H∞ performance analysis and controller design are carried out. A numerical example is included to demonstrate the effectiveness of the proposed results.
基金Supported by the National Natural Science Foundation of China(No.2 0 1730 2 8) and the Postdoctoral Foundation of theMinistry of Education of China
文摘Ab initio calculations at the B3LYP/3-21G^(**), HF/3-21G>^(**) and ONIOM(HF/3-21G^(**): AM1) levels of the theory in combination with counterpoise procedure for BSSE correction were performed on HMX dimers. There exist two O...H intermolecular contacts and the dispersion forces are dominant in the dimers. The corrected binding energies of the dimer are -15.10 and -17.81 kJ/mol at the HF/3-21G^(**) and \{ONIOM(HF/3-21G^(**): AM1) \}levels, respectively. The calculation by the B3LYP method gives irrational corrected binding energies though it produces similar intermolecular distances as those produced by the HF or \{ONIOM\} method. The geometrical parameters, the contact distances and the binding energies demonstrated, for the first time, the validity of the ONIOM method applied in the calculation of the parameters of intermolecular interactions.
基金the National Natural Science Foundation of China(No.2 0 0 75 0 13) and China Postdoctoral Science Foun-dation(No.2 0 0 30 33492 )
文摘Differential pulse voltammetry(DPV) was applied to the determination of alkaline phosphatase(ALP) activity in human serum with phenyl phosphate as the substrate. Phenyl phosphate can enzymatically be hydrolyzed to produce phenol which is quantified by DPV at +660 mV(vs.Ag/AgCl) in the concentration range of 2.0_100 μmol/L. The standard curve for ALP is linear over the range from 0.06 to 1000 U/L with a relative standard deviation of 3.0%. The conditions for the enzymatic reaction and voltammetric detection were optimized and the kinetic constants were also examined.The human serum samples were tested by this method and the results were in good agreement with those obtained by the routine p-nitrophenyl phosphate spectrophotometric method.
文摘The structures,the binding energies and the thermodynamic properties of formamide and hydroxyacetonitrile(HAN) dimers have been studied by means of the self\|consistent \%ab initio\% Hartree\|Fock and the second\|order Mφller\|Plesset correlation energy correction methods. The counterpoise procedure was used to check the basis set superposition error(BSSE) of the binding energies. There exist cyclic structures in a formamide dimer(Ⅰ),a HAN dimer(Ⅱ) and their heterodimer(Ⅲ). The corrected binding energies for dimers Ⅰ,Ⅱ and Ⅲ are respectively -45.53,-45.83 and -43.89 kJ/mol at the MP2/aug\|cc\|p VDZ//HF/\{aug\|cc\|p VDZ\} level. The change of the Gibbs free energies(Δ\%G\%) in the process of Ⅰ+Ⅱ→2Ⅲ was predicted to be -2.74 kJ/mol at 298.15 K. Dimer Ⅲ can be spontaneously produced in the mixture of formamide and HAN,which is in agreement with the experimental fact that most cyanohydrins are capable of interacting with dipeptide cyclo\|His\|Phe(CHP).
基金This work was supported by the National Natural Science Foundation of China (No. 60474078,60304001).
文摘The state feedback design for singularly perturbed systems described in Delta operator is considered. The composite state feedback controller for slow and fast subsystems is designed by using the direct method. The obtained results can bring previous conclusions of continuous and discrete time systems into the unified Delta framework. A simulation example is presented to demonstrate the validity and efficiency of the design.
文摘An artificial neural networks(ANNs) based gear material selection hybrid intelligent system is established by analyzing the individual advantages and weakness of expert system (ES) and ANNs and the applications in material select of them. The system mainly consists of tow parts: ES and ANNs. By being trained with much data samples, the back propagation (BP) ANN gets the knowledge of gear materials selection, and is able to inference according to user input. The system realizes the complementing of ANNs and ES. Using this system, engineers without materials selection experience can conveniently deal with gear materials selection.
文摘The application of the random binary phase coded signal in the CW radar system has been limited by the difficulty to isolate the transmission and reception signal. In order to make use of the random binary phase coded signal, the random binary phase coded pulse radar (RBPC-PR) system has been studied. First, the average ambiguity function (AAF) of the RBPC-PR signal has been analyzed. Then, a statistical method of reducing the range sidelobe (RSL) is presented. Finally, a signal processing scheme of the RBPC-PR is devdoped. The simulation results show that by using the scheme, the jamming immunity of the system, the resolution and accuracy of distance and velocity have been improved, and the distance and velocity vagueness caused by periods can also be removed. The RSL can be reduced over 30 dB by the statistical average method, thus the probability ambiguity caused by random noise can be avoided.
基金This project is supported by Key Laboratory Program of National Defense-Science Foundation of China (No.51458030103BQ0205)Prorincial Natural Science Foundation of Jiangsu, China (No.BK2003094).
文摘The method of extracting the basic features of part from the file of STEPAP214 of 3-D model is proposed. All faces in the file are the minimal elements. The combination isdone for the faces with geometry restrictions and some attributes by the theory of the bestalphabetic tree which is constructed by HU--TUCKER algorithm in combination principle. So the basicfeatures could be attained. This provides the research basis to the more share and integration ofCAD information in the virtual enterprises. Finally, a case is used to illustrate the validity ofthe approach.
文摘The technology of plasma arc was used to modify the interface adhesion between c hromium coating and steel substrate. The interface microstructure was studied as a function of plasma arc processing parameters. Microstructure analysis was per formed by optical microscopy, scanning electron microscopy and electron probe. T he microhardness distribution along the depth of a cross-section of the chromium coating and the substrate was measured. The results show the energy density of transferred plasma arc is obviously higher than plasma non-transferred arc. The molten interface was obtained by plasma transferred arc. Interfaces between chro mium coating and steel substrate can be divided by plasma non-transferred arc in to three classes: non-molten, a little molten and molten. Good interface bonding was obtained by proper process parameters. The microhardness of chromium coatin g decreases with increasing energy density of plasma arc.
基金The authors would like to thank the Educational Administration Key Project of Shandong province+8 种基金 (No. J01C05) the Outstanding Adult-young Scientific Research Encouraging Foundation of Shandong
文摘The structure of chiral N-ethyl-N-(2,3,4,6-tetra-O-acetyl-b-D-glycosyl)-thio- carbamide was determined by X-ray diffraction method. It crystallizes in the monoclinic system, space group P21 with a = 7.6560(15), b = 10.311(2), c =14.181(3) ? b =100.88(3), C17H26N2O9S, Mr = 434.46, V = 1099.3(4) ?, Z = 2, Dc = 1.312 g/cm3, F(000) = 460, m = 0.196 mm-1, R = 0.0704 and wR = 0.1655. The total independent reflections were 5098, of which 1875 were observed with I ≥2s(I). The hexopyranosyl ring adopts a chair conformation. All the ring substituents are in the equatorial positions. The acetoxylmethyl group is in the gauche-gauche conformation. The S atom is in synperiplanar conformation, while the NCNC linkage is antiperiplanar. X-ray analysis shows that the absolute configuration of the chiral carbon atom at C(1) was proved to be b-form. The 1H NMR spectra and IR are in good agreement with the result of crystallography analysis. The NH…O intermolecular hydrogen bonds link the molecules into infinite chains connected by CH…O interactions.
文摘The projective transformation of the special semi-symmetric metric recurrent connection is studied in this paper. First of all, an invariant under this transformation is granted; Secondly, by inducing of the invariant and making use of the properties that the corresponding covariant derivative keeps being fixed under the distinctness connection, the curvature tensor expression of the Riemannian manifold is posed at the same time.
文摘This paper is concerned with the H2 estimation and control problems for uncertain discretetime systems with norm-bounded parameter uncertainty. We first present an analysis result on H2 norm bound for a stable uncertain system in terms of linear matrix inequalities (LMIs). A solution to the robust H2 estimation problem is then derived in terms of two LMIs. As compared to the existing results, our result on robust H2 estimation is more general. In addition, explicit search of appropriate scaling parameters is not needed as the optimization is convex in the scaling parameters. The LMI approach is also extended to solve the robust H2 control problem which has been difficult for the traditional Riccati equation approach since no separation principle has been known for uncertain systems. The design approach is demonstrated through a simple example.
文摘In this paper,a Slotted Stepped-Impedance Resonator (SSIR) is proposed.Due to the slots in the low-impedance section of the conventional SIR,the new resonator has a lower fundamental resonance f0 and can provide a potential finite transmission zero fz close to f0.Based on the proposed SSIR,a fourth-order Chebychev BandPass Filter (BPF) is designed at f0=1 GHz.The measured results show that a better than-65 dB rejection is achieved on both the lower and the upper stopband.Moreover,the new filter has a wide-30 dB rejection upper stopband from 1.13f0 to 6.52f0.The fabricated filter exhibits a size of The new filter has a planar topology and is easily integrated with modern portable communication systems.
