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81.
Sunggook Park Zhichao Song Lance Brumfield Alborz Amirsadeghi Jaejong Lee 《Applied Physics A: Materials Science & Processing》2009,97(2):395-402
In thermal nanoimprint lithography, temperature is one of the most important process parameters. Temperature is not only important
for the flow of resist during molding but also for demolding, the process by which the imprint stamp is removed from the molded
resist/substrate. This is because thermal stress and friction and adhesion forces generated at the stamp/resist interface
and the mechanical strength of the resist are all dependent on temperature. In this paper, we demonstrate via both experimentation
and numerical simulation that an optimal temperature (T
d) leading to minimal deformation of molded resist exists for demolding. The ease of demolding was directly accessed by measuring
demolding force at different T
d for a Si stamp/PMMA/Si substrate system of 4-in.-diameter using a mechanical tester. Numerically, the demolding process for
a simple two-dimensional model of a Si stamp/poly(methyl methacrylate) (PMMA) resist/Si substrate system was simulated using
a finite-element method for different T
d, assuming viscoelasticity of the PMMA resist and temperature dependence of friction coefficients at the stamp/PMMA interface.
We found that a temperature leading to the minimum in both the demolding force and the normalized stress vs. T
d curves exists below the glass transition temperature of the PMMA resist, from which the optimal T
d was derived. 相似文献
82.
S.L. Young H.Z. Chen C.C. Lin J.B. Shi Lance Horng Y.T. Shih 《Journal of magnetism and magnetic materials》2006
Magnetic and transport properties of (La0.7Pb0.3MnO3)1−xAgx composites are explored in this study. Ferromagnetism is gradually attenuated due to the magnetic dilution with increase of Ag content percentage. Clearly irreversible behavior in the zero-field cooling and field cooling curves at a low field caused by the competition between the magnetization and magnetic domain orientation processes has been observed as x increases. Saturation magnetization decreases as x increases, while ferromagnetic transition temperature remains around 346 K for all composites. The resistivity decreases significantly for (La0.7Pb0.3MnO3)1−xAgx composites. It is suggested that introduction of Ag into the niche of grain boundaries forms artificial conducting network and improves the carriers to transport. However, enhancement of magnetoresistance has been observed for the system. 相似文献
83.
84.
Lance Horng G. Chern M. C. Chen P. C. Kang D. S. Lee 《Journal of magnetism and magnetic materials》2004,270(3):389-396
Epitaxial thin films of Fe3O4 and CoFe2O4 on MgO (0 0 1) substrates were grown by molecular beam epitaxy at low temperature growth process. Magnetization and hysteresis loop of both films were measured to investigate magnetic anisotropic properties at various temperatures. Anomalous magnetic properties are found to be correlated with crystalline, shape, and stress anisotropies. The Fe3O4 film below Verwey structural transition has a change in crystal structure, thus causing many anomalous magnetic properties. Crystalline anisotropy and anomalous magnetic properties are affected substantially by Co ions. The saturation magnetization of Co–ferrite film becomes much lower than that of Fe3O4 film, being very different from the bulks. It indicates that the low temperature growth process could not provide enough energy to have the lowest energy state. 相似文献
85.
Lee HI Benton PM Laryukhin M Igarashi RY Dean DR Seefeldt LC Hoffman BM 《Journal of the American Chemical Society》2003,125(19):5604-5605
A recent high-resolution X-ray crystallographic study (1.16 A) of the Azotobacter vinelandii nitrogenase MoFe protein revealed a previously undetected electron density associated with the active site FeMo-cofactor. The density is located inside the cluster at the center of the "trigonal prism" of six irons and is assigned to a species "X". The identity of species X was not resolved, although the electron density is consistent with a single N, O, or C atom. One proposal is that X is an N atom that derives from and exchanges with N from N2 during catalysis. In the present study, we have examined this possibility by employing 14N and 15N isotopes of N2 along with ENDOR and ESEEM spectroscopies. The WT MoFe protein and alpha-359Arg-->Lys and alpha-381Phe-->Leu variants were allowed to turn over in the presence of 14N2 or 15N2, and then were examined as resting enzymes by ENDOR and ESEEM at X- and Q-bands to look for all 14N and 15N signals coupled to the electron spin of the FeMo-cofactor and to determine if any exchanged during turnover. We have found five peaks in Q-band pulsed ENDOR spectra that appear to arise not only from previously reported N1/N2, which give rise to the ESEEM, but also from one or two additional coupled nitrogens. None of the ENDOR and ESEEM signals vanish or are altered by catalytic turnover with 15N2, and no new 15N signal is detected, leading to the conclusion that if species X is a nitrogen atom, it does not exchange during dinitrogen reduction. 相似文献
86.
87.
In addition to the classic orthogonal polynomials which satisfy second order differential equations, there are a number of orthogonal polynomials which satisfy differential equations of orders four or six. Like the classic sets, they have distributional weight functions, are the eigenfunctions for certain self-adjoint boundary-value problems, and sometimes are involved with indefinite boundary-value problems.The purpose of this survey is to summarize the work of the last decade and to exhibit the state of the art as it now stands. Of particular interest is the development of the theory of singular Sturm-Liouville systems, which is so necessary in order to describe the boundary-value problems associated with these polynomials. 相似文献
88.
E. Christopher Lance 《Acta Mathematica》1983,151(1):209-230
89.
A ringH
q which is aq-analog of the universal enveloping algebra of the Heisenberg Lie algebraU(h) is constructed, and its ring theoretic properties are studied. It is shown thatH
q has a factor ringA
q which is a simple domain with properties that are compared to the Weyl algebra. A secondq-analogH
q ofU(h) is constructed, andH
q is shown to be a primitive ring. 相似文献
90.
Suppose that all the nonzero one-sided or two-sided ideals of an algebra have finite codimension. To what extent must the algebra be p.i. or primitive? 相似文献