9,915 research outputs found
Thermal expansion of CaFe2As2: effect of cobalt doping and post-growth thermal treatment
We report thermal expansion measurements on Ca(Fe_(1-x)Co_x)_2As_2 single
crystals with different thermal treatment, with samples chosen to represent
four different ground states observed in this family. For all samples thermal
expansion is anisotropic with different signs of the in-plane and c-axis
thermal expansion coefficients in the high temperature, tetragonal phase. The
features in thermal expansion associated with the phase transitions are of
opposite signs as well, pointing to a different response of transition
temperatures to the in-plane and the c-axis stress. These features, and
consequently the inferred pressure derivatives, are very large, clearly and
substantially exceeding those in the Ba(Fe_(1-x)Co_x)_2As_2 family. For all
transitions the c-axis response is dominant
Ankle fracture surgery on a pregnant patient complicated by intraoperative emergency caesarian section.
We report the case of a woman in the third trimester of pregnancy who sustained an ankle fracture dislocation that could not be adequately closed reduced. After discussions with the patient, her obstetrician, and the anesthesiologists, she was indicated for surgical fixation. A heart tone monitor was used to assess fetal health during the procedure. During surgical incision, the fetus went into distress, and an emergency caesarian section was performed. After delivery of the infant and abdominal closer, surgery was completed. Due to a cohesive team effort, both the patient and her infant had excellent outcomes. There are many important considerations in the surgical management of the pregnant patient with traumatic orthopaedic injuries. Of especial importance to the orthopaedic surgeon is the impact of patient positioning on uteroplacental blood flow. This report discusses factors that should be taken into account by any orthopaedist who plans to operate on a pregnant patient
Equivalence after extension for compact operators on Banach spaces
In recent years the coincidence of the operator relations equivalence after
extension and Schur coupling was settled for the Hilbert space case, by showing
that equivalence after extension implies equivalence after one-sided extension.
In this paper we investigate consequences of equivalence after extension for
compact Banach space operators. We show that generating the same operator ideal
is necessary but not sufficient for two compact operators to be equivalent
after extension. In analogy with the necessary and sufficient conditions on the
singular values for compact Hilbert space operators that are equivalent after
extension, we prove the necessity of similar relationships between the
-numbers of two compact Banach space operators that are equivalent after
extension, for arbitrary -functions.
We investigate equivalence after extension for operators on
-spaces. We show that two operators that act on different
-spaces cannot be equivalent after one-sided extension. Such
operators can still be equivalent after extension, for instance all invertible
operators are equivalent after extension, however, if one of the two operators
is compact, then they cannot be equivalent after extension. This contrasts the
Hilbert space case where equivalence after one-sided extension and equivalence
after extension are, in fact, identical relations.
Finally, for general Banach spaces and , we investigate consequences
of an operator on being equivalent after extension to a compact operator on
. We show that, in this case, a closed finite codimensional subspace of
must embed into , and that certain general Banach space properties must
transfer from to . We also show that no operator on can be
equivalent after extension to an operator on , if and are
essentially incomparable Banach spaces
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Design and finite element mode analysis of noncircular gear
The noncircular gear transmission is an important branch of the gear transmission, it is characterized by its compact structure, good dynamic equilibration and other advantages, and can be used in the automobile, engineering machine, ship, machine tool, aviation and spaceflight field etc. Studying on the dynamics feature of noncircular gear transmission can improve the ability to carry loads of, reduce the vibration and noise of, increase the life of the noncircular gear transmission machine, provides guidance for the design of the noncircular gear, and has significant theories and practical meanings. In this paper, the gear transmission technique is used to studied the design method of the noncircular gear, which contains distribution of teeth on the pitch curve, designs of the tooth tip curve and the tooth root curve, design of the tooth profile curve, the gear system dynamics principle is introduced to establish dynamics model for the noncircular gear; basic theory of finite element and mode analysis method are applied, finite element model for the noncircular gear is established, natural vibration characteristic of the noncircular gear is studied. And the oval gear is taken as an example, the mathematics software MathCAD, the 3D modeling software UG and the finite element software ABAQUS are used to realize precise 3D model of the oval gear. The finite element method is used, the natural vibration characteristic of the oval gear is studied, the main vibration types and natural frequencies of the oval gear and that of the equivalent cylindrical gears are analyzed and compared, the conclusions received reflect the dynamics performance of the oval gear, and solid foundation is laid for dynamics research and engineering application of the oval gear transmission
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