Validity of Vertical Jump Measuring Devices

The vertical jump has been used to assess athleticism in explosive sports. Field measuring methods have been recently introduced to the market. Some of these devices have been previously validated, however, they have not been validated by an independent research institute nor have been concurrently validated in the same training session. PURPOSE: This research intends to conduct an independent validation of alternative vertical jump devices and to validate multiple devices within the same training session. METHODS: 50 physically active University students were recruited for this study. The subjects performed a self-paced 5 minute jog on a treadmill as part of the general warm-up followed by an 8 minute specific dynamic warm up. Subjects then performed a familiarization phase on the force plates, which consisted of 3 repetitions of the countermovement jump (CMJ); in order to control for individual technical differences and intra-subject variability, subjects were instructed to perform a CMJ at a 90 degree angle squat for each repetition. Subjects then performed a CMJ at the researchers signal for 3 repetitions. We placed an accelerometer based device (Push-Band) on the subjects waist, an Iphone 7plus was used to record and analyze the subject’s CMJ on two video apps (MyJump2 and What’sMyVert), and a photoelectric cells system (optojump) bars were placed next to the force plates; the later were used as the gold standard for the vertical jump measure. 3 researchers measured synchronically each CMJ. A data analysis was conducted on IBM SPSS 23. An Intra-class correlation was used to analyze the correlation between devices. RESULTS: Compared to the force plates, the MyJump2 app showed a nearly perfect correlation (r=.968). The Whats’myVert video app and PushBand showed a moderate-large correlation (r=.619 and r=.641 respectively). Lastly, the Optojump showed a moderate correlation of r= .492. CONCLUSION: We observed a nearly perfect correlation of the MyJump2 app, this correlation appears to be consistent to a previous validation study. The What’sMyVert app showed a large correlation to the force plates, and to our knowledge, this is the first study looking at the validation of this app. We found some inconsistency between our data from the PushBand accelerometer and the Optojump to what has been previously published. In summary, based on our data, the video apps appear to be an excellent alternative to costly laboratory and field devices

Bloom Filters, Adaptivity, and the Dictionary Problem

The Bloom filter---or, more generally, an approximate membership query data structure (AMQ)---maintains a compact, probabilistic representation of a set S of keys from a universe U. An AMQ supports lookups, inserts, and (for some AMQs) deletes. A query for an x in S is guaranteed to return "present." A query for x not in S returns "absent" with probability at least 1-epsilon, where epsilon is a tunable false positive probability. If a query returns "present," but x is not in S, then x is a false positive of the AMQ. Because AMQs have a nonzero probability of false-positives, they require far less space than explicit set representations. AMQs are widely used to speed up dictionaries that are stored remotely (e.g., on disk/across a network). Most AMQs offer weak guarantees on the number of false positives they will return on a sequence of queries. The false-positive probability of epsilon holds only for a single query. It is easy for an adversary to drive an AMQ's false-positive rate towards 1 by simply repeating false positives. This paper shows what it takes to get strong guarantees on the number of false positives. We say that an AMQs is adaptive if it guarantees a false-positive probability of epsilon for every query, regardless of answers to previous queries. First, we prove that it is impossible to build a small adaptive AMQ, even when the AMQ is immediately told whenever it returns a false positive. We then show how to build an adaptive AMQ that partitions its state into a small local component and a larger remote component. In addition to being adaptive, the local component of our AMQ dominates existing AMQs in all regards. It uses optimal space up to lower-order terms and supports queries and updates in worst-case constant time, with high probability. Thus, we show that adaptivity has no cost

The I/O Complexity of Computing Prime Tables

International audienceWe revisit classical sieves for computing primes and analyze their performance in the external-memory model. Most prior sieves are analyzed in the RAM model, where the focus is on minimizing both the total number of operations and the size of the working set. The hope is that if the working set fits in RAM, then the sieve will have good I/O performance, though such an outcome is by no means guaranteed by a small working-set size. We analyze our algorithms directly in terms of I/Os and operations. In the external-memory model, permutation can be the most expensive aspect of sieving, in contrast to the RAM model, where permutations are trivial. We show how to implement classical sieves so that they have both good I/O performance and good RAM performance, even when the problem size N becomes huge—even superpolynomially larger than RAM. Towards this goal, we give two I/O-efficient priority queues that are optimized for the operations incurred by these sieves

Evaluación preliminar comparativa de la radiación solar y potencial energético entre dos ciudades de la frontera México y Estados Unidos

Ponencia presentada en: VII Congreso de la Asociación Española de Climatología: clima, ciudad y ecosistemas, celebrado en Madrid entre el 24 y 26 de noviembre de 2010.[ES]La radiación solar es uno de los recursos energéticos más importantes de nuestro planeta. Actualmente ha cobrado importancia y se ha incrementado el interés para utilizar el recurso solar como un elemento renovable y no contaminante. Es bajo este contexto que en esta comunicación se presenta la evaluación y se realiza un comparativo de las mediciones de radiación solar global y potencial energético estimado. Estas mediciones se realizaron con piranómetros instalados en la ciudad de Mexicali, Baja California, al noroeste de México y en la ciudad de Yuma, Arizona, en el suroeste de Estados Unidos. A estas dos ciudades las separan 96 km., ambas ciudades han mostrado un desarrollo sostenido, y climáticamente se caracterizan porque anualmente se presentan una gran cantidad de días soleados, temperaturas cálidas extremas y muy poca precipitación. Los resultados muestran diferencias tanto en el comportamiento como en la intensidad de las mediciones a pesar de su cercanía, lo que parece ser un indicativo de que los flujos a meso-escala parecen dominar a los sistemas sinópticos que prevalecen en la región. El potencial energético es estimado mediante la propuesta de aprovechamiento de varios umbrales. Con esta estimación se proyecta el aprovechamiento energético si se utilizara el recurso solar y se muestra la cantidad equivalente de gases de efecto invernadero que se dejarían de producir. Este estudio comparativo no tiene precedente en México y son pocos los datos medidos que a nivel regional se tienen lo que demuestra su importancia para las propuestas de estrategias de mitigación en el cambio climático.[EN]Solar radiation is one of the most important energy resources of our planet. It has now become important and has increased the interest to use the solar resource as a renewable and clean element. It is in this context that this paper presents the evaluation and makes a comparison of measurements of global solar radiation and estimated energy potential. These measurements were made with pyranometer installed in the city of Mexicali, Baja California, northwestern Mexico and the city of Yuma, Arizona, in the southwestern United States. These two cities are separate by 96 km. Both cities have shown a sustained development, and are characterized climatically because annually presents a large number of sunny days, extremes warm temperatures and little precipitation. The results show differences in both, behavior and in the intensity measurements despite their closeness, which appears to be an indication that the meso-scale flows appear to dominate the synoptic systems that prevail in the region. The energy potential is estimated by the proposed use of several thresholds. With this estimate the energy use is projected if the solar resource use and displays the equivalent amount of greenhouse gases that would stop production. This comparative study is unprecedented in Mexico, and few measured data at the regional level are demonstrating their importance to the proposed mitigation strategies on climate change

Bostonia: 1998-1999, no. 1, 3-4

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Wear testing of aerospace self-lubricating bearing liner materials [Abstract]

The paper describes a novel method for testing the wear rates of liner materials for self-lubricating bearings. The apparatus differs from similar machines in that it is designed for reciprocating contact, to simulate motions encountered in helicopter main rotor pitch link bearings, and is designed to test up to 4 samples at the same time, reducing the effect of variability in environmental conditions. This paper describes key aspects of the test rig along with initial results. Self-lubricating bearings have been in widespread use since the mid-1950s, predominantly in the aerospace industry where they have the advantage of being low maintenance components. They usually consist of a spherical bearing with the inner and outer elements separated by a composite glass fibre / PTFE resin-bonded textile liner. Previous work found that the wear of typical composite liners has three distinct phases – initial wear in, steady-state wear phase, final wear-out, and that humidity and environmental temperature can have a strong influence. Typical bearing-scale tests are long duration, and so a method of accounting for environmental factors and allowing the rapid screening of materials and test conditions is described here as an aid to technology development

Political parties and democratic consolidation in post-communist societies

Political parties have a central role to play in democratic consolidation, yet we know comparatively little about how effectively they represent social cleavages in newly emerging democracies. Using the Lipset–Rokkan framework, this article examines the role of parties in articulating social cleavages in 14 established and 6 emerging democracies using the Comparative Study of Electoral Systems datasets. The results show that the social cleavages in the emerging democracies are similar to those of the established democracies, with religion and class predominating. Parties appear to be less effective in representing social cleavages in the emerging than in the established democracies

Regional biaxial mechanical data of the mitral and tricuspid valve anterior leaflets

The collective data associated with this article presents the biaxial mechanical behavior for six smaller, delimited regions of the mitral valve and tricuspid valve anterior leaflets. Each data set consists of five columns of data, specifically: (i) biaxial testing protocol ID, (ii) circumferential stretch, (iii) radial stretch, (iv) circumferential membrane tension, and (v) radial membrane tension. For further elaboration regarding methodologies or results of the biaxial mechanical characterization please refer to the companion article Laurence, 2019.Support from the American Heart Association Scientist Development Grant (SDG) Award (16SDG27760143) is gratefully acknowledged. CHL was in part supported by the institutional start-up funds from the School of Aerospace and Mechanical Engineering (AME) and the research funding through the Faculty Investment Program from the Research Council at the University of Oklahoma (OU). DL, CR, and SJ were supported by the Mentored Research Fellowship from the Office of Undergraduate Research at OU. DL and CR were supported by the Undergraduate Research Opportunities Program from the Honors College at OU. We also acknowledge undergraduate researchers Jacob Richardson and Ryan Bodlak for their assistance with the biaxial mechanical testing.Ye

Observations of Binary Stars with the Differential Speckle Survey Instrument. IX. Observations of Known and Suspected Binaries, and a Partial Survey of Be Stars

We report 370 measures of 170 components of binary and multiple star systems, obtained from speckle imaging observations made with the Differential Speckle Survey Instrument at Lowell Observatory's Discovery Channel Telescope in 2015 through 2017. Of the systems studied, 147 are binary stars, 10 are seen as triple systems, and 1 quadruple system is measured. Seventy-six high-quality non-detections and fifteen newly resolved components are presented in our observations. The uncertainty in relative astrometry appears to be similar to our previous work at Lowell, namely linear measurement uncertainties of approximately 2 mas, and the relative photometry appears to be uncertain at the 0.1 to 0.15 magnitude level. Using these measures and those in the literature, we calculate six new visual orbits, including one for the Be star 66 Oph, and two combined spectroscopic-visual orbits. The latter two orbits, which are for HD 22451 (YSC 127) and HD 185501 (YSC 135), yield individual masses of the components at the level of 2 percent or better, and independent distance measures that in one case agrees with the value found in the Gaia DR2, and in the other disagrees at the 2-$\sigma$ level. We find that HD 22451 consists of an F6V+F7V pair with orbital period of $2401.1 \pm 3.2$ days and masses of $1.342 \pm 0.029$ and $1.236 \pm 0.026$ $M_{\odot}$. For HD 185501, both stars are G5 dwarfs that orbit one another with a period of $433.94 \pm 0.15$ days, and the masses are $0.898 \pm 0.012$ and $0.876 \pm 0.012$ $M_{\odot}$. We discuss the details of both the new discoveries and the orbit objects