5,154 research outputs found
A mathematical modelling study of an athlete's sprint time when towing a weighted sled
No full textThis is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s12283-013-0114-2.This study used a mathematical model to examine the effects of the sled, the running surface, and the athlete on sprint time when towing a weighted sled. Simulations showed that ratio scaling is an appropriate method of normalising the weight of the sled for athletes of different body size. The relationship between sprint time and the weight of the sled was almost linear, as long as the sled was not excessively heavy. The athlete’s sprint time and rate of increase in sprint time were greater on running surfaces with a greater coefficient of friction, and on any given running surface an athlete with a greater power-to-weight ratio had a lower rate of increase in sprint time. The angle of the tow cord did not have a substantial effect on an athlete’s sprint time. This greater understanding should help coaches set the training intensity experienced by an athlete when performing a sled-towing exercise
np-CECADA: Enhancing Ubiquitous Connectivity of LoRa Networks
No full textLong Range Wide Area Networks (LoRaWAN) offer ubiquitous communications for The Internet of Things (IoT). However, there are many challenges in rolling out LoRaWAN - mainly scalability, energy efficiency, Packet Reception Ratio (PRR), and keeping the channel access as simple as unslotted ALOHA. To this end, we design non-persistent Capture Effect Channel Activity Detection Algorithm (np-CECADA), which is a novel, distributed protocol for the MAC layer of LoRaWAN. It utilizes Channel Activity Detection (CAD), which is a built-in imperfect mechanism for channel sensing and minimal feedback from the gateways. In np-CECADA each device independently adapts backoff times based on the traffic in its vicinity and the transmission power based on the heuristically inferred probability of capturing the channel. To achieve this, first, we carried out an extensive on-field evaluation to measure the effectiveness of CAD and capture effect in LoRa. Using them we designed np CECADA and developed ns-3 modules. Packet Reception Ratio of np-CECADA is 15.74× and 5.13× higher than vanilla LoRaWAN and p-CARMA, respectively. Channel utilization is 11.24× higher compared to LMAC. Further, on a testbed of 30 LoRa devices np-CECADA outperforms LoRaWAN up to 5 times.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Embedded System
Beyond P^NP = NEXP
No full text. Buhrman and Torenvliet created an oracle relative to which P NP = NEXP and thus P NP = P NEXP . Their proof uses a delicate finite injury argument that leads to a nonrecursive oracle. We simplify their proof removing the injury to create a recursive oracle making P NP = NEXP. In addition, in our construction we can make P = UP = NP " coNP. This leads to the curious situation where LOW(NP) = P but LOW(P NP ) = NEXP, and the complete p m - degree for P NP collapses to a p-isomorphism type. 1 Introduction In 1978, Seiferas, Fischer and Meyer [SFM78] showed a very strong separation theorem for nondeterministic time: For time constructible t 1 (n) and t 2 (n), if t 1 (n + 1) = o(t 2 (n)) then NTIME(t 1 (n)) does not contain NTIME(t 2 (n)). Thus we have a huge gap between nondeterministic polynomial time (NP) and nondeterministic exponential time (NEXP). We would also expect then a separation between P NP and P NEXP . Indeed, we have some evidence for that direction:..
Some Comments on Functional Self-Reducibility and the NP Hierarchy
No full textIn Valiant [11] and Schnorr [9], concepts of "functional self-reducibility" are introduced and investigated. We concentrate on the class NP and on the NP hierarchy of Meyer and Stockmeyer [7] to further investigate these ideas. Assuming that the NP hierarchy exists (specifically, assuming that we show that, while every complete set in is functionally self-reducible, there exist sets in which are not functionally self-reducible
P≠NP
No full textHere, the author tries to build the structure of the Theory of computation based on considering time as a fuzzy concept.
In fact, there are reasons to consider time as a fuzzy concept. In this article, the author doesn’t go to this side but note that Brower and Husserl views on the concept of time were similar [8]. Some reasons have been given for it in [3].
Throughout this article, the author presents the Theory of Computation with Fuzzy Time. Given the classic definition of Turing Machine, the concept of Time is modified to Fuzzy time. This new term calls as Theory TC* [2] and this type of computation “Fuzzy time Computation”. We have relatively large number of fundamental unsolved problems in Complexity Theory. In the new theory, some of the major obstacles and unsolved problems have been solved [2]. It should be noted that in this article, the writer considers fuzzy number associated to instants of time as a symmetric one. The point about the symmetry is in the proof of Lemma 3, although it is generalizable.
In particular, the new classes of complexity Theory, P*, NP*, BPP* in the TC* analogues to the definitions of P, NP, BPP defines as their natural alternative definition. Here, we will see P*≠ NP*, P*= BPP*. Finally, we have Theorem 4
A Dynamic-Programming Heuristic for Regular Grid-Graph Partitioning
No full textPrevious researchers have demonstrated that striping heuristics produce very good (and, in some cases, asymptotically optimal) partitions for regular grid graphs. These earlier methods differed in the domains of application and the stripe-height selection process, and did not have polynomial run-time guarantees.
In this paper, we transform the stripe selection problem for general grid graphs into a shortest path problem. The running time for the entire process of transforming the problem and solving for the shortest path is polynomial with respect to the length of input for the original problem. Computational results are presented that demonstrate improved solution quality for general domains
P≠NP
No full textHere, the author tries to build the structure of the Theory of computation based on considering time as a fuzzy concept.
In fact, there are reasons to consider time as a fuzzy concept. In this article, the author doesn’t go to this side but note that Brower and Husserl views on the concept of time were similar [8]. Some reasons have been given for it in [3].
Throughout this article, the author presents the Theory of Computation with Fuzzy Time. Given the classic definition of Turing Machine, the concept of Time is modified to Fuzzy time. This new term calls as Theory TC* [2] and this type of computation “Fuzzy time Computation”. We have relatively large number of fundamental unsolved problems in Complexity Theory. In the new theory, some of the major obstacles and unsolved problems have been solved [2]. It should be noted that in this article, the writer considers fuzzy number associated to instants of time as a symmetric one. The point about the symmetry is in the proof of Lemma 3, although it is generalizable.
In particular, the new classes of complexity Theory, P*, NP*, BPP* in the TC* analogues to the definitions of P, NP, BPP defines as their natural alternative definition. Here, we will see P*≠ NP*, P*= BPP*. Finally, we have Theorem 4
NP vyhledávací problémy
No full textTitle: NP search problems Author: Tomáš Jirotka Department: Department of Algebra Supervisor: Prof. RNDr. Jan Krajíček, DrSc. Abstract: The thesis summarizes known results in the field of NP search pro- blems. We discuss the complexity of integer factoring in detail, and we propose new results which place the problem in known classes and aim to separate it from PLS in some sense. Furthermore, we define several new search problems. Keywords: Computational complexity, TFNP, integer factorization.
Primal-Dual Bilinear Programming Solution of the Absolute Value Equation
No full textWe propose a finitely terminating primal-dual bilinear programming algorithm for the solution of
the NP-hard absolute value equation (AVE): Ax ? |x| = b, where A is an n � n square matrix. The
algorithm, which makes no assumptions on AVE other than solvability, consists of a finite number of
linear programs terminating at a solution of the AVE or at a stationary point of the bilinear program.
The proposed algorithm was tested on 500 consecutively generated random instances of the AVE with
n =10, 50, 100, 500 and 1,000. The algorithm solved 88.6% of the test problems to an accuracy of
1e ? 6
The presence of a zero in an integer linear recurrent sequence is NP-hard to decide
No full textWe show that the problem of determining if a given integer linear recurrent sequence has a zero-a problem that is known as "Pisot's problem"-is NP-hard. With a similar argument we show that the problem of finding the minimal realization dimension of a one-letter max-plus rational series is NP-hard. This last result answers a folklore question raised in the control literature on the max-plus approach to discrete event systems. Our results are simple consequences of a construction due to Stockmeyer and Meyer. (C) 2002 Elsevier Science Inc. All rights reserved
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