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121.
Ngo Quang Huy Trinh Thi Bich Nguyen Van Suc 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(1):129-133
Summary The paper presents a procedure to prepare soil samples for U and Th isotope measurement by alpha-spectrometry after coprecipitation
with LaF3. In this procedure the reduction of U(VI) to U(IV) was performed by Zn metal in 4M HCl solution. The recoveries of chemical
separation equal to eU-chemistry = 78±4% for uranium and eTh-chemistry = 82±4% for thorium. Canberra alpha-spectrometer was used with PIPS detectors of A-1200-37-AM Model of 1200 mm2 active area. The counting efficiency of the measuring system equals to ecounting = 18% and the total efficiencies were eU = ecounting .eU-chemistry = 14.0±0.7% for uranium and eTh = ecounting .eTh-chemistry = 14.7±0.7% for thorium. The recoveries of chemical separation were rather high (about 80%), that leads to the use of a small
weight of soil sample (about 0.5 g). The efficiencies were also stable, that allows analyzing the soil sample without using
radiotracers. They are advantages of the sample preparation procedure of this work. 相似文献
122.
For the methylsilsesquioxane film whose optical birefringence is almost zero, it was recently reported that its vertical thermal expansion coefficient (CTE) was approximately one order of magnitude larger than the lateral CTE. Though the birefringence is not an absolute predictor of anisotropic behavior, the discrepancy in both the CTEs was so remarkable that it was essential to investigate whether the anisotropy was intrinsic property or not. If the effect of Poisson's ratio is considered in the calculation of the vertical CTE and when elastic modulus measured by surface acoustic wave spectroscopy is used in the assessment of the lateral CTE, both the CTEs are coincident with each other. Therefore, it can be concluded that the discrepancy in the CTEs can be attributed to a higher in‐plane polymer chain orientation but it can also arise from the misleadingly assumed modulus and Poisson's ratio. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3109–3120, 2006 相似文献
123.
Young Wook Kim Seong-Deog Yang 《Proceedings of the American Mathematical Society》2006,134(11):3379-3390
We prove the existence of an infinite family of complete spacelike maximal surfaces with singularities in Lorentz-Minkowski three-space and study their properties. These surfaces are distinguished by their number of handles and have two elliptic catenoidal ends.
124.
Summary Cold neutrons at the external neutron guide laboratory (ELLA) of the KFA Jülich are used to demonstrate their profitable application
for multielement characterization of biological materials. The set-up and experimental conditions of the Prompt Gamma Cold
Neutron Activation Analysis (PGCNAA) device is described in detail. Results for C, H, N, S, K, B, and Cd using synthetic standards
and the “ratio” technique for calculation are reported for several reference materials and prove the method to be reliable
and complementary with respect to the elements being determined by INAA.
IAEA fellow at the KFA from 6. 3. 91 to 2. 9. 91 on contract No. VIE/9016R. 相似文献
125.
We consider a stowage-planning problem of arranging containers on a container ship in the maritime transportation system. Since containers are accessible only from the top of the stack, temporary unloading and reloading of containers, called shifting, is unavoidable if a container required to be unloaded at the current port is stacked under containers to be unloaded at later ports on the route of the ship. The objective of the stowage planning problem is to minimize the time required for shifting and crane movements on a tour of a container ship while maintaining the stability of the ship. For the problem, we develop a heuristic solution method in which the problem is divided into two subproblems, one for assigning container groups into the holds and one for determining a loading pattern of containers assigned to each hold. The former subproblem is solved by a greedy heuristic based on the transportation simplex method, while the latter is solved by a tree search method. These two subproblems are solved iteratively using information obtained from solutions of each other. To see the performance of the suggested algorithm, computational tests are performed on problem instances generated based on information obtained from an ocean container liner. Results show that the suggested algorithm works better than existing algorithms. 相似文献
126.
Let D be a digraph. The competition-common enemy graph (CCE graph) of D has the same set of vertices as D and an edge between vertices u and v if and only if there are vertices w and x in D such that (w,u), (w,v), (u,x), and (v,x) are arcs of D. We call a graph a CCE graph if it is the CCE graph of some digraph. In this paper, we show that if the CCE graph of a doubly partial order does not contain C4 as an induced subgraph, it is an interval graph. We also show that any interval graph together with enough isolated vertices is the CCE graph of some doubly partial order. 相似文献
127.
Kim Dang Phung 《Journal of Differential Equations》2007,240(1):92-124
Using Fourier integral operators with special amplitude functions, we analyze the stabilization of the wave equation in a three-dimensional bounded domain on which exists a trapped ray bouncing up and down infinitely between two parallel parts of the boundary. 相似文献
128.
C.X. Gao F.C. Yu S.Y. Jeong A.R. Choi P. Parchinskiy D.J. Kim H.J. Kim Y.E. Ihm C.G. Kim C.S. Kim 《Journal of magnetism and magnetic materials》2006
GaMnN and Be-codoped GaMnN were grown via molecular beam epitaxy using a single GaN precursor and their structural and magnetic properties were examined. X-ray diffraction and superconducting quantum interference device (SQUID) measurements revealed that the grown layers are homogeneous without precipitates. The saturation magnetization of GaMnN has increased from ∼4 to ∼16 emu/cm3 via codoping of Be. The d–d exchange interaction between Mn atoms was discussed for the ferromagnetism of GaMnN. 相似文献
129.
Laser cleaning of a photoresist (PR) on a glass substrate using ns-pulsed Nd:YAG laser was studied. The direction of the substrate facing the laser beam was varied as a main parameter as well as the power of the laser beam. The backward irradiation (BWI) of the third harmonic beam (355 nm) completely removed 1.2 μm thick PR layer with three pulses at 1.5 J/cm2 leaving no residues behind; while the forward irradiation (FWI) at the same condition just partially cleaned it. To investigate the difference of removal mechanisms between irradiation directions, the size distributions of particulates generated during laser cleaning were observed using an optical particle counter. The concentration of micron-sized particulates increased with increasing laser fluence up to 1 J/cm2 for FWI and 0.5 J/cm2 for BWI and then decreased at higher fluences because the target was a very thin film. The concentration of larger particulates for BWI was much higher than that for FWI implying the difference in removal mechanisms. In consideration of the size characteristics of the particulates and the temperature profiles of the PR layer, the most probable distinct mechanism for the BWI would be a blasting due to high temperature at the PR/glass interface. The particulate number concentration decreased rapidly after the completion of cleaning, suggesting that the measurement of the particulate concentration could detect the progress of the cleaning. Our results demonstrated that the backward irradiation will be useful for the laser cleaning of film-type contaminants on an optically transparent substrate. 相似文献
130.
Oil migration in filled chocolates limits shelf life due to texture changes and loss of visual appeal. Spatial and temporal
oil concentration changes of a two-layer chocolate and peanut butter filling system, which models a filled chocolate, were
monitored by magnetic resonance imaging. Formulations of chocolate varied with respect to particle size, milk fat content
and emulsifier level. Sorption-time experimental data was used to establish the best fit diffusion coefficient for a Fickian
diffusion model. On the basis of the comparison of spatial experimental data to the model, Fickian diffusion alone does not
account for oil migration.
Authors' address: Michael J. McCarthy, Department of Food Science and Technology, University of California, One Shields Avenue,
Davis, CA 95616, USA 相似文献