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91.
The analysis of the rotation of a ferromagnetic ellipsoid suspended in a Newtonian fluid and subjected to a uniform magnetic field is extended to include a long, slender cylindrical fiber which is magnetically saturated. Experimental observations of rotating nickel cylinders with aspect ratiosL/D ranging from 5 to 40 agree with the theoretical predictions that: (1) the proper magnetoviscous time constant for the motion is
MV =
s/µ
0
M
s
2
, (2) larger fiber aspect ratios result in considerably longer orientation times; and (3) the strength of the applied external field has only a slight effect on the overall fiber rotation, and has no effect on the maximum angular velocity achieved. Quantitative agreement of theory and experiments is obtained for fibers withL/D 20; for the shorter fibers, the theory tends to overpredict the fiber rotation rate by as much as 30%.
D
diameter of the cylinder
-
D
P
(r)
position-dependent demagnetization tensor, implicitly defined in eq. (2.5)
-
D
xx,D
yy,D
zz
volume-averaged demagnetizing factors for an ellipsoid equivalent to a uniformly magnetized cylinder, defined in eq. (2.6)
-
H
i
;H
i
magnetic field inside a ferromagnetic body; magnitude ofH
i
-
H
0;H
0
magnetic field applied by external sources; magnitude ofH
0
-
k
geometric parameter in the hydrodynamic resistance of a body rotating in a Newtonian fluid, eq. (2.2)
-
L
length of the cylinder
-
L
(h);L
z
(h)
hydrodynamic torque exerted on a rotating body; thez-component ofL
(h) on the cylinder
-
L
(m);L
z
(m)
magnetic torque exerted on a magnetic body in a magnetic field, eq. (2.4); thez-component ofL
(m) on the cylinder
-
M
the magnetization of a magnetic material
-
M
s
the saturation magnitude ofM, approached by all ferromagnetic materials asH
i becomes large
-
r
position vector of a point within a ferromagnetic body
-
V
volume of a magnetic particle
-
x, y, z
rectangular coordinate axes fixed in the cylinder according to figure 1
-
angle of inclination of the axis of the cylinder with respect toH
0
-
shear rate
-
small parameter of slender body theory,=1/ln (2L/D)
-
s
constant viscosity of the suspending fluid
-
µ
0
the magnetic permeability of free space,µ
0=4 · 10–7 H/m
-
MV
the magnetoviscous time constant, a characteristic time for a process involving a competition of viscous and magnetic stresses
-
1
the first normal-stress coefficient
-
;
z
angular velocity of a rotating body; angular velocity of a cylinder about thez-axis,
z =– d/dt 相似文献
92.
Kristie C. Armstrong 《Talanta》2010,82(2):675-431
A bismuth bulk electrode (BiBE) has been investigated as an alternative electrode for the anodic stripping voltammetric (ASV) analysis of Pb(II), Cd(II), and Zn(II). The BiBE, which is fabricated in-house, shows results comparable to those of similar analyses at other Bi-based electrodes. Metal accumulation is achieved by holding the electrode potential at −1.4 V (vs. Ag/AgCl) for 180 s followed by a square wave voltammetric stripping scan from −1.4 to −0.35 V. Calibration plots are obtained for all three metals, individually and simultaneously, in the10-100 μg L−1 range, with a detection limit of 93, 54, and 396 ng L−1 for Pb(II), Cd(II), Zn(II), respectively. A slight reduction in slope is observed for Cd(II) and Pb(II) when the three metals are calibrated simultaneously vs. individually. Comparing the sensitivities of the metals when calibrated individually vs. in a mixture reveals that Zn(II) is not affected by stripping in a mixture. However, Pb(II) and Cd(II) have decreasing sensitivities in a mixture. The optimized method has been successfully used to test contaminated river water by standard addition. The results demonstrate the ability of the BiBE as an alternative electrode material in heavy metal analysis. 相似文献
93.
Lucie Loukotková Eva Tesařová Zuzana Bosáková Pavel Repko Daniel W. Armstrong 《Journal of separation science》2010,33(9):1244-1254
Retention and enantioseparation behavior of ten 2,2′‐disubstituted or 2,3,2′‐trisubstituted 1,1′‐binaphthyls and 8,3′‐disubstituted 1,2′‐binaphthyls, which are used as catalysts in asymmetric synthesis, was investigated on eight chiral stationary phases (CSPs) based on β‐CD, polysaccharides (tris(3,5‐dimethylphenylcarbamate) cellulose or amylose CSPs) and new synthetic polymers (trans‐1,2‐diamino‐cyclohexane, trans‐1,2‐diphenylethylenediamine and trans‐9,10‐dihydro‐9,10‐ethanoanthracene‐(11S,12S)‐11,12‐dicarboxylic acid CSPs). Normal‐, reversed‐phase and polar‐organic separation modes were employed. The effect of the mobile phase composition was examined. The enantiomeric separation of binaphthyl derivatives, which possess quite similar structures, was possible in different enantioselective environments. The substituents and their positions on the binaphthyl skeleton affect their properties and, as a consequence, the separation system suitable for their enantioseparation. In general, the presence of ionizable groups on the binaphthyl skeleton, substitution with non‐identical groups and a chiral axis in the 1,2′ position had the greatest impact on the enantiomeric discrimination. The 8,3′‐disubstituted 1,2′‐binaphthyl derivatives were the most easily separated compounds in several separation systems. From all the chiral stationary phases tested, cellulose‐based columns were shown to be the most convenient for enantioseparation of the studied analytes. However, the polymeric CSPs with their complementary behavior provided good enantioselective environments for some derivatives that could be hardly separated in any other chromatographic system. 相似文献
94.
Michal Zapadlo Ján Krupčík Pavel Májek Daniel W. Armstrong Pat Sandra 《Journal of chromatography. A》2010,1217(37):5859-5867
The orthogonality of three columns coupled in two series was studied for the congener specific comprehensive two-dimensional GC separation of polychlorinated biphenyls (PCBs). A non-polar capillary column coated with poly(5%-phenyl–95%-methyl)siloxane was used as the first (1D) column in both series. A polar capillary column coated with 70% cyanopropyl-polysilphenylene-siloxane or a capillary column coated with the ionic liquid 1,12-di(tripropylphosphonium)dodecane bis(trifluoromethane-sulfonyl)imide were used as the second (2D) columns. Nine multi-congener standard PCB solutions containing subsets of all native 209 PCBs, a mixture of 209 PCBs as well as Aroclor 1242 and 1260 formulations were used to study the orthogonality of both column series. Retention times of the corresponding PCB congeners on 1D and 2D columns were used to construct retention time dependences (apex plots) for assessing orthogonality of both columns coupled in series. For a visual assessment of the peak density of PCBs congeners on a retention plane, 2D images were compared. The degree of orthogonality of both column series was, along the visual assessment of distribution of PCBs on the retention plane, evaluated also by Pearson's correlation coefficient, which was found by correlation of retention times tR,i,2D and tR,i,1D of corresponding PCB congeners on both column series. It was demonstrated that the apolar + ionic liquid column series is almost orthogonal both for the 2D separation of PCBs present in Aroclor 1242 and 1260 formulations as well as for the separation of all of 209 PCBs. All toxic, dioxin-like PCBs, with the exception of PCB 118 that overlaps with PCB 106, were resolved by the apolar/ionic liquid series while on the apolar/polar column series three toxic PCBs overlapped (105 + 127, 81 + 148 and 118 + 106). 相似文献
95.
We have directly resolved shock structures in pure aluminum in the first few hundred picoseconds subsequent to a dynamic load at peak stresses up to 43 GPa and strain rates in excess of 10(10) s(-1). For strong shocks we obtain peak stresses, strain rates, and rise times. From these data, we directly validate the invariance of the dissipative action in the strong shock regime, and by comparing with data obtained at much lower strain rates show that this invariance is observed over at least 5 orders of magnitude in the strain rate. Over the same range, we similarly validate the fourth-power scaling of the strain rate with the peak stress (the Swegle-Grady relation). 相似文献
96.
Adamson P Andreopoulos C Armstrong R Auty DJ Ayres DS Backhouse C Barr G Bishai M Blake A Bock GJ Boehnlein DJ Bogert D Cavanaugh S Cherdack D Childress S Choudhary BC Coelho JA Coleman SJ Corwin L Cronin-Hennessy D Danko IZ de Jong JK Devenish NE Diwan MV Dorman M Escobar CO Evans JJ Falk E Feldman GJ Frohne MV Gallagher HR Gomes RA Goodman MC Gouffon P Graf N Gran R Grant N Grzelak K Habig A Harris D Hartnell J Hatcher R Himmel A Holin A Huang X Hylen J Ilic J Irwin GM Isvan Z Jaffe DE 《Physical review letters》2011,106(18):181801
Measurements of neutrino oscillations using the disappearance of muon neutrinos from the Fermilab NuMI neutrino beam as observed by the two MINOS detectors are reported. New analysis methods have been applied to an enlarged data sample from an exposure of 7.25×10(20) protons on target. A fit to neutrino oscillations yields values of |Δm(2)|=(2.32(-0.08)(+0.12))×10(-3) eV(2) for the atmospheric mass splitting and sin(2)(2θ)>0.90 (90% C.L.) for the mixing angle. Pure neutrino decay and quantum decoherence hypotheses are excluded at 7 and 9 standard deviations, respectively. 相似文献
97.
J. Glister G. Ron B.W. Lee R. Gilman A.J. Sarty S. Strauch D.W. Higinbotham E. Piasetzky K. Allada W. Armstrong J. Arrington H. Arenhövel A. Beck F. Benmokhtar B.L. Berman W. Boeglin E. Brash A. Camsonne J. Calarco J.P. Chen S. Choi E. Chudakov L. Coman B. Craver F. Cusanno J. Dumas C. Dutta R. Feuerbach A. Freyberger S. Frullani F. Garibaldi J.-O. Hansen T. Holmstrom C.E. Hyde H. Ibrahim Y. Ilieva C.W. de Jager X. Jiang M.K. Jones Hyekoo Kang A. Kelleher E. Khrosinkova E. Kuchina G. Kumbartzki J.J. LeRose R. Lindgren P. Markowitz S. May-Tal Beck E. McCullough D. Meekins 《Physics letters. [Part B]》2011
98.
D. Brynn Hibbert Nicholas Armstrong John H. Vine 《Accreditation and quality assurance》2011,16(7):339-345
Racehorses given a slurry of sodium bicarbonate (known colloquially as a ‘milkshake’) before a race have elevated concentrations of carbon dioxide in their blood. Racing administrators have reacted to this attempt to enhance the performance of the animal by setting limits to ‘total carbon dioxide’ (TCO2, the sum of carbon dioxide, carbonic acid, carbonate and bicarbonate) in prerace samples of plasma. The threshold limit for TCO2 in the rules of racing is an amount concentration of 36.0 mmol/L, with further action ensuing if the reported concentration is greater than an action limit that is calculated from the knowledge of the measurement uncertainty. At present in Australia, the action limit is 37.0 mmol/L, which is based on a combined standard measurement uncertainty of 0.22 mmol/L. From data obtained in a 1997 study in 515 normal racehorses, we have established the distribution (as a probability density function, PDF) of TCO2. This is combined with data from Australian laboratories of 126 horses that were tested following a positive screen, out of which 78 were confirmed positive. We employ the maximum entropy method to establish the PDFs and then apply Bayes Theorem to answer the question ‘given the measured TCO2 concentration what is the probability that a horse has been administered bicarbonate’? The distributions are not normal, which precludes simple approaches that calculate standard deviations from the data. For an action level of 37.0 mmol/L, there is a chance of only 1 in 2 020 000 that a nondoped horse will be judged to be doped, which implies this present threshold is unlikely to lead to conviction of an innocent trainer. 相似文献
99.
100.
Grant F. Armstrong 《Applied Mathematical Finance》2013,20(4):197-208
In this paper we study window barrier options, where a single constant continuously-monitored barrier prevails for a period that commences strictly after the start date of the option and terminates strictly before expiry. We determine valuation formulae within a limited deterministic term-structure in terms of trivariate normal distribution functions. These formulae offer a generalization of the valuation formulae for partial barrier options given by Heynan and Kat. 相似文献