1,834 research outputs found
Invariance: a Theoretical Approach for Coding Sets of Words Modulo Literal (Anti)Morphisms
Let be a finite or countable alphabet and let be literal
(anti)morphism onto (by definition, such a correspondence is determinated
by a permutation of the alphabet). This paper deals with sets which are
invariant under (-invariant for short).We establish an
extension of the famous defect theorem. Moreover, we prove that for the
so-called thin -invariant codes, maximality and completeness are two
equivalent notions. We prove that a similar property holds in the framework of
some special families of -invariant codes such as prefix (bifix) codes,
codes with a finite deciphering delay, uniformly synchronized codes and
circular codes. For a special class of involutive antimorphisms, we prove that
any regular -invariant code may be embedded into a complete one.Comment: To appear in Acts of WORDS 201
Completing circular codes in regular submonoids
AbstractLet M be an arbitrary submonoid of the free monoid Aâ, and let XâM be a variable length code (for short a code). X is weakly M-complete iff any word in M is a factor of some word in Xâ [J. NĂ©raud, C. Selmi, Free monoid theory: Maximality and completeness in arbitrary submonoids, Internat. J. Algebra Comput. 13 (5) (2003) 507â516]. Given a regular submonoid M, and given an arbitrary code XâM, we are interested in the existence of a weakly M-complete code XË that contains X. Actually, in [J. NĂ©raud, Completing a code in a regular submonoid, in: Acts of MCUâ2004, Lect. Notes Comput. Sci. 3354 (2005) 281â291; J. NĂ©raud, Completing a code in a submonoid of finite rank, Fund. Inform. 74 (2006) 549â562], by presenting a general formula, we have established that, in any case, such a code XË exists. In the present paper, we prove that any regular circular code XâM may be embedded into a weakly M-complete one iff the minimal automaton with behavior M has a synchronizing word. As a consequence of our result an extension of the famous theorem of SchĂŒtzenberger is stated for regular circular codes in the framework of regular submonoids. We study also the behaviour of the subclass of uniformly synchronous codes in connection with these questions
Embedding a -invariant code into a complete one
Let A be a finite or countable alphabet and let be a literal
(anti-)automorphism onto A * (by definition, such a correspondence is
determinated by a permutation of the alphabet). This paper deals with sets
which are invariant under (-invariant for short) that is,
languages L such that (L) is a subset of L.We establish an extension
of the famous defect theorem. With regards to the so-called notion of
completeness, we provide a series of examples of finite complete
-invariant codes. Moreover, we establish a formula which allows to
embed any non-complete -invariant code into a complete one. As a
consequence, in the family of the so-called thin --invariant codes,
maximality and completeness are two equivalent notions.Comment: arXiv admin note: text overlap with arXiv:1705.0556
Topologies for Error-Detecting Variable-Length Codes
Given a finite alphabet , a quasi-metric over , and a
non-negative integer , we introduce the relation such that holds whenever . The
error detection capability of variable-length codes is expressed in term of
conditions over . With respect to the prefix metric, the factor
one, and any quasi-metric associated with some free monoid (anti-)automorphism,
we prove that one can decide whether a given regular variable-length code
satisfies any of those error detection constraints.Comment: arXiv admin note: text overlap with arXiv:2208.1468
Methods for minimizing performance degradation caused by branch delays
The presence of branch instructions in an instruction stream may adversely affect the performance of a processor by introducing significant delays in the execution process. As processors become more pipelined, the impact these delays have upon performance increases. This thesis investigates why delays occur when branch instructions are encountered. It also summarizes various hardware methodologies which can alleviate the performance degradation due to these delays. Simulation results show that these hardware methodologies can improve branch performance by up to 45 percent. Some branches are inherently necessary in order to implement programming decisions. However, the use of branches within programs can inadvertently cause significant performance degradation. This thesis analyzes several methods to implement a programming decision and the performance of each method, thus providing insight into programming guidelines which can be followed to improve branch performance. Measurements of these software techniques show performance improvements of up to 178 percent
Coding âWhatâ and âWhenâ in the Archer Fish Retina
Traditionally, the information content of the neural response is quantified using statistics of the responses relative to stimulus onset time with the assumption that the brain uses onset time to infer stimulus identity. However, stimulus onset time must also be estimated by the brain, making the utility of such an approach questionable. How can stimulus onset be estimated from the neural responses with sufficient accuracy to ensure reliable stimulus identification? We address this question using the framework of colour coding by the archer fish retinal ganglion cell. We found that stimulus identity, âwhatâ, can be estimated from the responses of best single cells with an accuracy comparable to that of the animal's psychophysical estimation. However, to extract this information, an accurate estimation of stimulus onset is essential. We show that stimulus onset time, âwhenâ, can be estimated using a linear-nonlinear readout mechanism that requires the response of a population of 100 cells. Thus, stimulus onset time can be estimated using a relatively simple readout. However, large nerve cell populations are required to achieve sufficient accuracy
Scheduling and shop floor control in commercial airplane manufacturing
Thesis (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; in conjunction with the Leaders for Manufacturing Program at MIT, 2005.Includes bibliographical references (p. 73-75).Boeing is the premier manufacturer of commercial jetliners and a leader in defense and space systems. Competition in commercial aircraft production is increasing and in order to retain their competitive position, Boeing must strive to improve their operations by reducing costs. Boeing factories today still schedule and monitor the shop floor much as they have for the past 100 years. This thesis compares and contrasts several different methods for shop floor control and scheduling including Boeing's barcharts, Toyota production system, critical chain, and dynamic scheduling. Each system is will be analyzed with respect to how it handles variability in labor output required and how that affects which products are typically made under each system. In additional to qualitative comparisons, discrete event simulations comparing the various strategies will be presented. Areas for future simulation study are also discussed. The recommended approach for commercial airplane assembly is critical chain. A suggested implementation plan is presented along with methods to ease acceptance.by Vikram Neal Sahney.S.M.M.B.A
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