25 research outputs found
An EOQ model with stock dependent demand and imperfect quality items
This paper deals with an economic order quantity model where demand is stock
dependent. Items received are not of perfect quality and each lot received
contains percentage defective imperfect quality items, which follow a
probability distribution. Two cases are considered. 1) Imperfect quality
items are held in stock and sold in a single batch after a 100 percent
screening process. 2) A hundred percent screening process is performed but
the imperfect quality items are sold as soon as they are detected.
Approximate optimal solutions are derived in both cases. A numerical example
is provided in order to illustrate the development of the model. Sensitivity
analysis is also presented, indicating the effects of percentage imperfect
quality items on the optimal order quantity and total profit
On the Twisted Superconformal Structure in Gravity Coupled to Matter
It is shown that the two dimensional gravity, described either in the
conformal gauge (the Liouville theory) or in the light cone gauge, when coupled
to matter possesses an infinite number of twisted superconformal
symmetries. The central charges of the algebra for the two gauge choices
are in general different. Further, it is argued that the physical states in the
light cone gauge theory can be obtained from the Liouville theory by a field
redefinition.Comment: Plain Tex, 13 pages, IC/93/81, UG-3/9
Optimal replenishment and sales team initiatives for pharmaceutical products – A mathematical model
AbstractThe paper addresses an inventory model of pharmaceutical products where the demand rate of the customers increases with the volume of the initiatives of the sales team. In this model, the deterioration of the product varies depending on on-hand inventory. The volume of sales team initiatives is a control variable. It is dependent on on-hand inventory and vice versa. The profit function of the farm is formulated by the trading of inventory costs, purchasing costs, losses due to deterioration and sales team initiative costs, considering inflation and the time value of the monetary cost and profit parameters. Finally, the profit function is maximized by a variation of the calculus method. A numerical example is given to justify our model
On N=1 Superconformal Algebra in the Non-Critical Bosonic String Theory
In a recent work it has been shown that the bosonic strings could be embedded
into a special class of fermionic strings. We argue that the
superpartners of any physical state in the spectrum of this fermionic string is
non-physical. So, there is no supersymmetry in the space of physical states and
the embedding is, in this sense, ``trivial''. We here propose two different
constructions as possible candidates of non-trivial embeddings of the
non-critical bosonic strings into some special class of fermionic strings
of which one is the non-critical NSR string. The BRST charge of the
fermionic strings in both cases decompose as ,
where is the BRST charge of the bosonic string.Comment: 12 pages, Plain tex, UG-2/9
Observations on the Topological Structure in 2d Gravity Coupled to Minimal Matter
By using a bosonization we uncover the topological gravity structure of
Labastida, Pernici and Witten in ordinary gravity coupled to
minimal models. We study the cohomology class associated with the fermionic
charge of the topological gravity which is shown to be isomorphic to that of
the total charge. One of the ground ring generators of string
theory is found to be in the equivariant cohomology of this fermionic charge.Comment: 13 pages, plain tex, UG-5/94 Some clarifying statements and two new
references adde
String Theory as a Constrained Topological Sigma Model
It has been argued by Ishikawa and Kato that by making use of a specific
bosonization, string theory can be regarded as a constrained
topological sigma model. We generalize their construction for any
minimal model coupled to two dimensional (2d) gravity and show that the
energy--momentum tensor and the topological charge of a constrained topological
sigma model can be mapped to the energy--momentum tensor and the BRST charge of
string theory at zero cosmological constant. We systematically study
the physical state spectrum of this topological sigma model and recover the
spectrum in the absolute cohomology of string theory. This procedure
provides us a manifestly topological representation of the continuum Liouville
formulation of string theory.Comment: 12 pages, Latex file, UG-9/9
Remarks on the Additional Symmetries and W-Constraints in the Generalized KdV Hierarchy
Additional symmetries of the -reduced KP hierarchy are generated by the
Lax operator and another operator , satisfying = 0
for and with the condition that = 0, = 1, 2,..... We show explicitly that the
generators of these additional symmetries satisfy a closed and consistent
W-algebra only when we impose the extra condition that .Comment: 10 pages, Plain Te
BRST Cohomology Ring in NSR String Theory
The full cohomology ring of the Lian-Zuckerman type operators (states) in
Neveu-Schwarz-Ramond (NSR) string theory is argued to be
generated by three elements , and in analogy with the corresponding
results in the bosonic case. The ground ring generators and are
non-invertible and belong to the Ramond sector whereas the higher ghost number
operators are generated by an invertible element with ghost number one less
than that of the ground ring generators and belongs to either Neveu-Schwarz
(NS) or Ramond (R) sector depending on whether we consider (even, even) or
(odd, odd) series coupled to supergravity. We explicitly construct these
operators (states) and illustrate our result with an example of pure Liouville
supergravity.Comment: 16 pages, Latex, no figure
Proper acceleration, geometric tachyon and dynamics of a fundamental string near D branes
We present a detailed analysis of our recent observation that the origin of
the geometric tachyon, which arises when a D-brane propagates in the
vicinity of a stack of coincident NS5-branes, is due to the proper acceleration
generated by the background dilaton field. We show that when a fundamental
string (F-string), described by the Nambu-Goto action, is moving in the
background of a stack of coincident D-branes, the geometric tachyon mode can
also appear since the overall conformal mode of the induced metric for the
string can act as a source for proper acceleration. We also studied the
detailed dynamics of the F-string as well as the instability by mapping the
Nambu-Goto action of the F-string to the tachyon effective action of the
non-BPS D-string. We qualitatively argue that the condensation of the geometric
tachyon is responsible for the (F,D) bound state formation.Comment: 26 pages, v2: added references, v3: one ref. updated, to appear in
Class. and Quant. Gravit