Linear Boolean classification, coding and "the critical problem"

The problem of constructing a minimal rank matrix over GF(2) whose kernel does not intersect a given set S is considered. In the case where S is a Hamming ball centered at 0, this is equivalent to finding linear codes of largest dimension. For a general set, this is an instance of "the critical problem" posed by Crapo and Rota in 1970. This work focuses on the case where S is an annulus. As opposed to balls, it is shown that an optimal kernel is composed not only of dense but also of sparse vectors, and the optimal mixture is identified in various cases. These findings corroborate a proposed conjecture that for annulus of inner and outer radius nq and np respectively, the optimal relative rank is given by (1-q)H(p/(1-q)), an extension of the Gilbert-Varshamov bound H(p) conjectured for Hamming balls of radius np

Voice Shoppers: From Information Gaps to Choice Gaps in Consumer Markets

Recent years have seen exponential growth in the use of voice shoppers – artificial intelligence–based algorithms installed on digital voice assistants, such as Alexa and Google Assistant, that buy products based on verbal requests received from consumers. This game-changing switch to semi-automated shopping is shaking up markets by reshaping consumer–supplier relationships, as well as the business models of suppliers and search services. Voice shoppers benefit consumers by offering speedier and more sophisticated transactions while reducing search and transaction costs. At the same time, consumers’ voluntary delegation of their search powers and product selection creates what we call a “choice gap,” wherein the voice shopper chooses the product to be offered to the consumer. This gap is distinct from the commonly recognized information gap, which exists when suppliers possess more information than consumers. The choice gap might create a misalignment between consumer preferences and the products actually sold, which harms consumers as well as the function of markets. Yet market forces cannot be relied upon to remedy this market failure. Despite the significant consequences of this market failure, the negative effects of the choice gap are currently undertreated. Consumer protection and antitrust laws are ill-suited to the task. To remedy this, we suggest that transactions conducted by voice shoppers be reviewed under agency law. Agency law enables the application of fiduciary, performance, and information duties that protect consumers’ interests in the transaction, rather than consumer choice. Such duties can reduce the choice gap, improve consumer welfare, and restore market performance. Our findings and suggestions have relevance well beyond voice shoppers, for technologies which completely automate consumer choice without any human involvement, which are the future of commerce

Numerical and Experimental Analyses of Vibrations of Annular Plates with Multiple Eccentric Holes

This paper deals with the free transverse vibrations of annular plates with geometrical discontinuities in form of eccentric holes and rims. The finite element method and experimental studies are used. Solid and shell finite element models are employed in the numerical analysis using the commercial ANSYS software. The calculated results are verified by the original experimental data via innovative laser measurement techniques. Numerical and experimental results of this study adequately describe the phenomenon of dividing natural frequency values corresponding to the mode shapes, where the number of nodal diameters is a factor of the number of through holes. The proposed procedure of analysis of transverse vibrations of annular plates with eccentric through holes arranged over the specified radius is recommended for engineering applications

Broadcasting in Noisy Radio Networks

The widely-studied radio network model [Chlamtac and Kutten, 1985] is a graph-based description that captures the inherent impact of collisions in wireless communication. In this model, the strong assumption is made that node $v$ receives a message from a neighbor if and only if exactly one of its neighbors broadcasts. We relax this assumption by introducing a new noisy radio network model in which random faults occur at senders or receivers. Specifically, for a constant noise parameter $p \in [0,1)$, either every sender has probability $p$ of transmitting noise or every receiver of a single transmission in its neighborhood has probability $p$ of receiving noise. We first study single-message broadcast algorithms in noisy radio networks and show that the Decay algorithm [Bar-Yehuda et al., 1992] remains robust in the noisy model while the diameter-linear algorithm of Gasieniec et al., 2007 does not. We give a modified version of the algorithm of Gasieniec et al., 2007 that is robust to sender and receiver faults, and extend both this modified algorithm and the Decay algorithm to robust multi-message broadcast algorithms. We next investigate the extent to which (network) coding improves throughput in noisy radio networks. We address the previously perplexing result of Alon et al. 2014 that worst case coding throughput is no better than worst case routing throughput up to constants: we show that the worst case throughput performance of coding is, in fact, superior to that of routing -- by a $\Theta(\log(n))$ gap -- provided receiver faults are introduced. However, we show that any coding or routing scheme for the noiseless setting can be transformed to be robust to sender faults with only a constant throughput overhead. These transformations imply that the results of Alon et al., 2014 carry over to noisy radio networks with sender faults.Comment: Principles of Distributed Computing 201

Vibration Analysis of a Low-Power Reduction Gear

Free vibrations of a low-power reduction gear engaged with a hydraulic pump of the test rig are discussed. Vibration analysis is performed with the finite element representation and commercial ANSYS program. Vibration analysis of an examined system is conducted in the two stages. The natural frequencies of free transverse vibrations of the gears are first generated, and on the basis of the Campbell diagrams, the excitation speeds for several natural frequencies of examined gears are calculated. Then the free vibrations of a reduction gear are analyzed, and two computational cases are presented. In the first case, only the mass and geometry of all parts of the body are considered. In the second case, the mass of tooth gears is also taken into account. Based on the FE models, the first ten natural frequencies and natural mode shapes of a reduction gear are calculated. Then, these results are used to estimate the stress level in the walls of the body for a permissible acceleration value. As expected, smaller stress values for a permissible acceleration value are obtained for the second finite element model of the system. The problems discussed here can be helpful for engineers dealing with the dynamics of gear systems

Neue Methoden zur Bekämpfung des Echten Mehltaus im Ökologischen Landbau

Blattoberflächen-modifizierende Salzapplikationen sollten als Bekämpfungsmittel gegen Echten Mehltau an Tomaten und Gurken getestet werden hinsichtlich folgender Eigenschaften: - Wirkung verschiedener Salze - Blattverträglichkeit - Untersuchung der unterschiedlichen Wirkungsmechanismen mittels REM - Übertragbarkeit in praxisnahe Versuche. Die verschiedenen Salzlösungen und Kombinationen aus diesen Salzen unterschieden sich deutlich in ihrer Wirkung auf Gurkenmehltau. Die beste Wirkung ergab sich mit allenfalls geringer Schädigung des Blattes mit 0,1% MnCl2, 1 % Patentkali (K2SO4/MgSO4) und 1% Knöterichextrakt. MnCl2 liegt auf Grund seines niedrigen Deliqueszenzpunktes ständig gelöst auf der Blattoberfläche vor, wogegen sich Knöterichextrakt und Patentkali auf der Blattoberfläche in einer Art „Salzkriechen“ verteilen durch häufigen Wechsel zwischen Trocknen und Wiederverflüssigung. Salzschäden ließen sich verringern durch Zusatz von Netzmitteln zur Sprühlösung. Rasterelektronische Visualisierung zeigte für alle untersuchten Lösungen einen direkt toxischen Effekt auf die Mehltausporen und ihre Hyphen in jeder Entwicklungsphase des Pilzes. Eine Verbesserung des Nährstoffstatus der Pflanzen scheidet als Wirkungsmechanismus aus, da alle Pflanzen optimal ernährt waren und die Behandlungen zu keinen signifikanten Veränderungen der Nährstoffgehalte in den Blättern führten. Besonders chloridische Salze führten z.T. zu erheblicher Nekrotisierung der Blätter. Da diese Salzlösungen jedoch auch in geringer Konzentration in der Lage waren, die Ausbreitung des Echten Mehltau effektiv zu verhindern, sollten Möglichkeiten zur Mikrodosierung dieser Salze geprüft werden. Extreme Witterungsbedingungen im Sommer 2003 führten dazu, dass Praxistests nicht ausgeführt oder normal beendet werden konnten. Es gilt jedoch als sicher, dass einige der untersuchten Salzmischungen in geringen Konzentrationen (zw. 0,1 und 1%) den Befall mit Echten Mehltaupilzen effektiv reduzieren können, ohne Blattoberflächen zu schädigen

USORT: AN EFFICIENT HYBRID OF DISTRIBUTIVE PARTITIONING SORTING

A new hybrid of Distributive Partitioning Sorting is described and tested against Quicksort on uniformly distributed items. Pointer sort versions of both algorithms are also tested

The influence of continuous casting and extrusion processes on the properties and structure of CuNi2Si alloy and the morphology of the Ni-Si phase precipitates

CuNiSi alloys are widely used in various mechanical and electrical applications. These group of materials, due to the phenomena of precipitation hardening, are able to obtain high mechanical properties with also relatively high electrical properties. In the article authors compare two different types of products, made from the CW111C alloy i.e. rods which were continuously cast on the horizontal laboratory casting set-up (low degree of structure refinement) and rods commercially extruded with high degree of structure refinement. The presented results of experimental work characterize the tested materials in terms of their chemical composition, mechanical and electrical properties depending on the manufacturing process, as well as reveal their structures and the effect of heat treatment on the morphology of the Ni-Si precipitates

ON THE COMPUTATION OF MINIMUM ENCASING RECTANGLES AND SET DIAMETERS

Two new algorithms are described for the following problems: given a set of N points in the plane determine (i) the rectangle of minimum area which will completely cover (or encase) the set and (ii) the two points that are farthest apart (diameter of the set). Both algorithms have O(NlogN) time complexity and are based upon a similar strategy