1,666 research outputs found
Problems with interpretation of He ground state
The continuum of He nucleus is studied theoretically in a three-body
He++ model basing on the recent information concerning He
spectrum [Golovkov, \textit{et al.}, Phys. Rev. C \textbf{76}, 021605(R)
(2007)]. The He ground state (g.s.) candidate with structure
for new g.s. energy of He is predicted to be at about
MeV. The peak in the cross section associated with this state may be
shifted to a lower energy (e.g. MeV) when He is populated in
reactions with Li due to peculiar reaction mechanism. Formation of the
low-energy ( keV) ``alternative'' ground state with structure
is highly probable in He in the case of considerable
attraction (e.g. fm) in the s-wave He channel, which properties are
still quite uncertain. This result either questions the existing experimental
low-energy spectrum of He or place a limit on the scattering length in
He channel, which contradicts existing data.Comment: 14 pages, 13 figures, 1 tabl
Static deflection control of flexible beams by piezo-electric actuators
This study deals with the utilization of piezo-electric actuators in controlling the static deformation of flexible beams. An optimum design procedure is presented to enable the selection of the optimal location, thickness and excitation voltage of the piezo-electric actuators in a way that would minimize the deflection of the beam to which these actuators are bonded. Numerical examples are presented to illustrate the application of the developed optimization procedure in minimizing the structural deformation of beams of different materials when subjected to different loading and end conditions using ceramic or polymeric piezo-electric actuators. The results obtained emphasize the importance of the devised rational procedure in designing beam-actuator systems with minimal elastic distortions
Hartman effect and spin precession in graphene
Spin precession has been used to measure the transmission time \tau over a
distance L in a graphene sheet. Since conduction electrons in graphene have an
energy-independent velocity v, one would expect \tau > L/v. Here we calculate
that \tau < L/v at the Dirac point (= charge neutrality point) in a clean
graphene sheet, and we interpret this result as a manifestation of the Hartman
effect (apparent superluminality) known from optics.Comment: 6 pages, 4 figures; v2: added a section on the case of
perpendicularly aligned magnetizations; v3: added a figur
Superconducting Coherent States for an Extended Hubbard Model
An extended Hubbard model with phonons is considered. q-coherent states
relative to the superconducting quantum symmetry of the model are constructed
and their properties studied. It is shown that they can have energy expectation
lower than eigenstates constructed via conventional processes and that they
exhibit ODLRO.Comment: 7 pages, 3 figure
Supervision in the extension service in Helmand Arghandab Valley Authority, Afganistan
"A special problem #400 presented to the Department of Extension Education, University of Missouri, Columbia, in partial fulfillment of the requirements for the degree, Master of Science in Extension Education."Supervision is a process by which subordinates are assisted to perform their activities with increasing satisfaction to themselves, to people with whom they work and to the organization. The principal aim of Extension supervision is maximum growth and development of people. Yet, our recent supervisory practices are incongruent with this philosophy. Supervision is considered synonymous to administration and the supervisor major purpose is to make sure that subordinates do not deviate from the administrative rules and regulations. The chief duty of supervisor is inspection of the execution of plans, policies and procedures that are formulated at the higher level of administrative hierarchy. Extension activities are carried out through the H.A.V.A. Agricultural Division. The top administrative authorities who formulate the Extension programs are highly qualified experts; however, they should pay little attention to the significance of human relations. Supervision by most of them therefore, is conceived as a process of commanding subordinates to follow orders and to act according to direction given to them. The writer has a strong belief in the philosophy of democratic supervision. Democracy anywhere is participatory group life enjoyed by free individuals having the greatest opportunities for participation. Plans, policies, methods, techniques, and procedures of implementation are determined by the group. In here, central determination and direction techniques are replaced by a cooperative and coordinated group efforts. People are invited to take part in the development of plans and decisions which are likely to affect their lives. In the light of this philosophy, supervision must be based upon sound principles of human relations. Supervisor must possess a sound knowledge of the principles of supervision and continuous training in their application to his situation. With concept as such, this paper is condensed from reading of volumes of books and literature which are related to the subject. I hope this will be a valuable guide, not only to myself but to all of those who serve as supervisor in the Extension Service of Afghanistan.Introduction -- A look into the past history of extension service in Helmand-Arghandab Valley, Afghanistan -- The significance of extension supervision -- The supervisor as a leader -- Principles of supervision -- Characteristics of effective supervision -- Qualities necessary to the success of supervisors -- Characteristics and traits of extension supervisors -- Functions of the extension supervisor -- Evaluating the supervisor's performance -- Conclusion and recommendation for the extension service in Helmand-Arghandab Valley, Afghanistan.Includes bibliographical references (pages 78-82
Coherent state quantization of paragrassmann algebras
By using a coherent state quantization of paragrassmann variables, operators
are constructed in finite Hilbert spaces. We thus obtain in a straightforward
way a matrix representation of the paragrassmann algebra. This algebra of
finite matrices realizes a deformed Weyl-Heisenberg algebra. The study of mean
values in coherent states of some of these operators lead to interesting
conclusions.Comment: We provide an erratum where we improve upon our previous definition
of odd paragrassmann algebra
The -matrix inverse scattering approach for coupled channels with different thresholds
The inverse scattering method within the -matrix approach to the two
coupled-channel problem is discussed. We propose a generalization of the
procedure to the case with different thresholds.Comment: 20 pages, 3 figure
Threshold Effects in Multi-channel Coupling and Spectroscopic Factors in Exotic Nuclei
In the threshold region, the cross section and the associated overlap
integral obey the Wigner threshold law that results in the Wigner-cusp
phenomenon. Due to flux conservation, a cusp anomaly in one channel manifests
itself in other open channels, even if their respective thresholds appear at a
different energy. The shape of a threshold cusp depends on the orbital angular
momentum of a scattered particle; hence, studies of Wigner anomalies in weakly
bound nuclei with several low-lying thresholds can provide valuable
spectroscopic information. In this work, we investigate the threshold behavior
of spectroscopic factors in neutron-rich drip-line nuclei using the Gamow Shell
Model, which takes into account many-body correlations and the continuum
effects. The presence of threshold anomalies is demonstrated and the
implications for spectroscopic factors are discussed.Comment: Accepted in Physical Review C Figure correcte
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