The effects of Cu content on the microstructure and mechanical properties of thixoformed Al-6Si-xCu-0.3Mg(x= 3,4,5and 6,mass fraction,%) alloys were studied.The samples were thixoformed at 50%liquid content and severa...The effects of Cu content on the microstructure and mechanical properties of thixoformed Al-6Si-xCu-0.3Mg(x= 3,4,5and 6,mass fraction,%) alloys were studied.The samples were thixoformed at 50%liquid content and several of the samples were treated with the T6 heat treatment.The samples were then examined by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray(EDX) spectroscopy and X-ray diffraction(XRD) analysis,as well as hardness and tensile tests.The results show that the cooling slope casting and thixoforming process promote the formation of very fine and well distributed intermetallic compounds in the aluminium matrix and the mechanical properties of the alloys increase considerably compared with the permanent mould casting.The results also reveal that as the Cu content in the alloy increases,the hardness and tensile strength of the thixoformed alloys also increase.The ultimate tensile strength,yield strength and elongation to fracture of the thixoformed heat-treated Al-6Si-3Cu-0.3Mg alloy are 298 MPa,201 MPa and 4.5%,respectively,whereas the values of the thixoformed heat-treated alloy with high Cu content(6%) are 361 MPa,274 MPa and 1.1%,respectively.The fracture of the thixoformed Al-6Si-3Cu-0.3Mg alloy shows a dimple rupture,whereas in the alloy that contains the highest Cu content(6%),a cleavage fracture is observed.展开更多
The development of a pseudo-one pot synthesis of 3（5）,4-dinitropyrazole enabled us to use it as a starting material for energetic plasticisers. Its acidic proton allowed simple derivatisation on one of the ring nitr...The development of a pseudo-one pot synthesis of 3（5）,4-dinitropyrazole enabled us to use it as a starting material for energetic plasticisers. Its acidic proton allowed simple derivatisation on one of the ring nitrogens. The thermal characteristics of two derivatives were evaluated. For instance, the N-allyl compound was a liquid with very low glass transition temperature, whereas the N-propargyl compound was a sticky solid at ambient temperature. The two compounds were both thermally stable according to STANAG 4582.展开更多
Composition is the operation of replacing variables in a polynomial with other polynomials. The main question in this paper is: when does composition commute with universal Groebner basis computation? We prove that th...Composition is the operation of replacing variables in a polynomial with other polynomials. The main question in this paper is: when does composition commute with universal Groebner basis computation? We prove that this happens iff the composition is single variable. This has a natural application in the computation of universal Groebner bases of composed polynomials.展开更多
This paper presents a new approach to solve mixed-variable unit commitment(UC) problems with non-smooth cost functions based on a generalized pattern search filter(GPS-filter) algorithm. A GPS-filter algorithm does no...This paper presents a new approach to solve mixed-variable unit commitment(UC) problems with non-smooth cost functions based on a generalized pattern search filter(GPS-filter) algorithm. A GPS-filter algorithm does not require any information about the gradient of the objective function while searching for an optimum solution. At the same time, it is available for solving mixed-variable optimization problems, which is very suitable for UC. A new suitable discrete neighborhood structure with UC characteristics is proposed to improve GPS-filter efficiently. A lot of multiple units' states are fixed before search; hence, the polling search of discrete variable is efficient for a few uncertain units. Numerical experiments are included to demonstrate the proposed approach's ability to handle the highly nonlinear, discontinuous, non-smooth cost functions and mixed variables of the UC problem.展开更多
基金Universiti Teknikal Malaysia Melaka (UTeM) and the Ministry of Education Malaysia for financial support of this studyUniversiti Kebangsaan Malaysia (UKM) for the financial support under research grants GUP-2012-040 and AP-2012-014
文摘The effects of Cu content on the microstructure and mechanical properties of thixoformed Al-6Si-xCu-0.3Mg(x= 3,4,5and 6,mass fraction,%) alloys were studied.The samples were thixoformed at 50%liquid content and several of the samples were treated with the T6 heat treatment.The samples were then examined by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray(EDX) spectroscopy and X-ray diffraction(XRD) analysis,as well as hardness and tensile tests.The results show that the cooling slope casting and thixoforming process promote the formation of very fine and well distributed intermetallic compounds in the aluminium matrix and the mechanical properties of the alloys increase considerably compared with the permanent mould casting.The results also reveal that as the Cu content in the alloy increases,the hardness and tensile strength of the thixoformed alloys also increase.The ultimate tensile strength,yield strength and elongation to fracture of the thixoformed heat-treated Al-6Si-3Cu-0.3Mg alloy are 298 MPa,201 MPa and 4.5%,respectively,whereas the values of the thixoformed heat-treated alloy with high Cu content(6%) are 361 MPa,274 MPa and 1.1%,respectively.The fracture of the thixoformed Al-6Si-3Cu-0.3Mg alloy shows a dimple rupture,whereas in the alloy that contains the highest Cu content(6%),a cleavage fracture is observed.
文摘The development of a pseudo-one pot synthesis of 3（5）,4-dinitropyrazole enabled us to use it as a starting material for energetic plasticisers. Its acidic proton allowed simple derivatisation on one of the ring nitrogens. The thermal characteristics of two derivatives were evaluated. For instance, the N-allyl compound was a liquid with very low glass transition temperature, whereas the N-propargyl compound was a sticky solid at ambient temperature. The two compounds were both thermally stable according to STANAG 4582.
基金This paper is aided financially by Youth Item in the Education Department of Hunan Province(03B047) Natural Science Fund in China( 10371036).
文摘Composition is the operation of replacing variables in a polynomial with other polynomials. The main question in this paper is: when does composition commute with universal Groebner basis computation? We prove that this happens iff the composition is single variable. This has a natural application in the computation of universal Groebner bases of composed polynomials.
基金Project Supported by National Natural Science Foundation of China(51277034,51377027)
文摘This paper presents a new approach to solve mixed-variable unit commitment(UC) problems with non-smooth cost functions based on a generalized pattern search filter(GPS-filter) algorithm. A GPS-filter algorithm does not require any information about the gradient of the objective function while searching for an optimum solution. At the same time, it is available for solving mixed-variable optimization problems, which is very suitable for UC. A new suitable discrete neighborhood structure with UC characteristics is proposed to improve GPS-filter efficiently. A lot of multiple units' states are fixed before search; hence, the polling search of discrete variable is efficient for a few uncertain units. Numerical experiments are included to demonstrate the proposed approach's ability to handle the highly nonlinear, discontinuous, non-smooth cost functions and mixed variables of the UC problem.
