55,854 research outputs found

### Kinematics of the Broad Line Region in M81

A new model is presented which explains the origin of the broad emission
lines observed in the LINER/Seyfert nucleus of M81 in terms of a steady state
spherically symmetric inflow, amounting to 1 x 10^-5 Msun/yr, which is
sufficient to explain the luminosity of the AGN. The emitting volume has an
outer radius of ~1 pc, making it the largest broad line region yet to be
measured, and it contains a total mass of ~ 5 x 10^-2 Msun of dense, ~ 10^8
cm^-3, ionized gas, leading to a very low filling factor of ~ 5 x 10^-9. The
fact that the BLR in M81 is so large may explain why the AGN is unable to
sustain the ionization seen there. Thus, the AGN in M81 is not simply a scaled
down quasar.Comment: Accepted for Publication in ApJ 7/21/0

### Degeneracies when T=0 Two Body Interacting Matrix Elements are Set Equal to Zero : Talmi's method of calculating coefficients of fractional parentage to states forbidden by the Pauli principle

In a previous work we studied the effects of setting all two body T=0 matrix
elements to zero in shell model calculations for $^{43}$Ti ($^{43}$Sc) and
$^{44}$Ti. The results for $^{44}$Ti were surprisingly good despite the
severity of this approximation. In this approximation degeneracies arose in the
T=1/2 I=$({1/2})^-_1$ and $({13/2})^-_1$ states in $^{43}$Sc and the T=1/2
$I=({13/2})_2^-$, $({17/2})^-_1$, and $({19/2})_1^-$ in $^{43}$Sc. The T=0
$3_2^+$, $7_2^+$, $9_1^+$, and $10_1^+$ states in $^{44}$Ti were degenerate as
well. The degeneracies can be explained by certain 6j symbols and 9j symbols
either vanishing or being equal as indeed they are. Previously we used Regge
symmetries of 6j symbols to explain these degeneracies. In this work a simpler
more physical method is used. This is Talmi's method of calculating
coefficients of fractional parentage for identical particles to states which
are forbidden by the Pauli principle. This is done for both one particle cfp to
handle 6j symbols and two particle cfp to handle 9j symbols. The states can be
classified by the dual quantum numbers ($J_{\pi},J_{\nu}$)

### Umklapp scattering as the origin of $T$-linear resistivity in the normal state of high-$T_c$ cuprate superconductors

The high-temperature normal state of the unconventional cuprate
superconductors has resistivity linear in temperature $T$, which persists to
values well beyond the Mott-Ioffe-Regel upper bound. At low-temperature, within
the pseudogap phase, the resistivity is instead quadratic in $T$, as would be
expected from Fermi liquid theory. Developing an understanding of these normal
phases of the cuprates is crucial to explain the unconventional
superconductivity. We present a simple explanation for this behavior, in terms
of umklapp scattering of electrons. This fits within the general picture
emerging from functional renormalization group calculations that spurred the
Yang-Rice-Zhang ansatz: umklapp scattering is at the heart of the behavior in
the normal phase.Comment: v1 6+1 pages, 4 figures; v2 6+2 pages, 4 figures; v3 6 + 2.5 pages, 5
figure

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### Time Resolved Spectroscopy Of Cataclysmic Variables - SS Cygni

NSF AST76-23882, AST 79-06340McDonald Observator

### Children's suggestibility in relation to their understanding about sources of knowledge

In the experiments reported here, children chose either to maintain their initial belief about an object's identity or to accept the experimenter's contradicting suggestion. Both 3â to 4âyearâolds and 4â to 5âyearâolds were good at accepting the suggestion only when the experimenter was better informed than they were (implicit source monitoring). They were less accurate at recalling both their own and the experimenter's information access (explicit recall of experience), though they performed well above chance. Children were least accurate at reporting whether their final belief was based on what they were told or on what they experienced directly (explicit source monitoring). Contrasting results emerged when children decided between contradictory suggestions from two differentially informed adults: Threeâ to 4âyearâolds were more accurate at reporting the knowledge source of the adult they believed than at deciding which suggestion was reliable. Decision making in this observation task may require reflective understanding akin to that required for explicit source judgments when the child participates in the task

### The Texas banking crisis and the payments system

The Federal Reserve System plays a crucial role in the payments system that is especially important during periods of financial turmoil. In this article, Robert Clair, Joanna Kolson, and Kenneth Robinson explain the process and the risks involved in clearing checks in the private sector. They compare these processes and risks with the essentially risk-free check-clearing service the Federal Reserve System offers. During banking crises, they hypothesize, banks will increase their check-clearing through the Federal Reserve to minimize their risk exposure. A model of Federal Reserve check-clearing volume is constructed and estimated. The empirical results show that during banking crises, Federal Reserve check- processing volume rises as banks seek safer methods of clearing checks. Consequently, Federal Reserve payment services are important tools in minimizing the disruptive effects of banking crises on the economy.Banks and banking - Texas ; Payment systems

### Studies of implicit and explicit solution techniques in transient thermal analysis of structures

Studies aimed at an increase in the efficiency of calculating transient temperature fields in complex aerospace vehicle structures are reported. The advantages and disadvantages of explicit and implicit algorithms are discussed and a promising set of implicit algorithms with variable time steps, known as GEARIB, is described. Test problems, used for evaluating and comparing various algorithms, are discussed and finite element models of the configurations are described. These problems include a coarse model of the Space Shuttle wing, an insulated frame tst article, a metallic panel for a thermal protection system, and detailed models of sections of the Space Shuttle wing. Results generally indicate a preference for implicit over explicit algorithms for transient structural heat transfer problems when the governing equations are stiff (typical of many practical problems such as insulated metal structures). The effects on algorithm performance of different models of an insulated cylinder are demonstrated. The stiffness of the problem is highly sensitive to modeling details and careful modeling can reduce the stiffness of the equations to the extent that explicit methods may become the best choice. Preliminary applications of a mixed implicit-explicit algorithm and operator splitting techniques for speeding up the solution of the algebraic equations are also described

### Evaluation of the SPAR thermal analyzer on the CYBER-203 computer

The use of the CYBER 203 vector computer for thermal analysis is investigated. Strengths of the CYBER 203 include the ability to perform, in vector mode using a 64 bit word, 50 million floating point operations per second (MFLOPS) for addition and subtraction, 25 MFLOPS for multiplication and 12.5 MFLOPS for division. The speed of scalar operation is comparable to that of a CDC 7600 and is some 2 to 3 times faster than Langley's CYBER 175s. The CYBER 203 has 1,048,576 64-bit words of real memory with an 80 nanosecond (nsec) access time. Memory is bit addressable and provides single error correction, double error detection (SECDED) capability. The virtual memory capability handles data in either 512 or 65,536 word pages. The machine has 256 registers with a 40 nsec access time. The weaknesses of the CYBER 203 include the amount of vector operation overhead and some data storage limitations. In vector operations there is a considerable amount of time before a single result is produced so that vector calculation speed is slower than scalar operation for short vectors

### Some aspects of algorithm performance and modeling in transient analysis of structures

The status of an effort to increase the efficiency of calculating transient temperature fields in complex aerospace vehicle structures is described. The advantages and disadvantages of explicit algorithms with variable time steps, known as the GEAR package, is described. Four test problems, used for evaluating and comparing various algorithms, were selected and finite-element models of the configurations are described. These problems include a space shuttle frame component, an insulated cylinder, a metallic panel for a thermal protection system, and a model of the wing of the space shuttle orbiter. Results generally indicate a preference for implicit over explicit algorithms for solution of transient structural heat transfer problems when the governing equations are stiff (typical of many practical problems such as insulated metal structures)

### Brayton-cycle radioisotope heat-source design study. Phase II /preliminary design/ report

Brayton cycle radioisotope heat source desig

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