iPhone 手机掘金     

Daniel Lyons  陈大为 《海外英语》2009,(4):44-46

仅需为Apple手机写个小应用软件,有的孩子在自己的卧室里就能赚个百万美元。  相似文献   

Direct measurements of the frequency-dependent dielectrophoresis force     

Ming-Tzo Wei  Joseph Junio    H. Daniel Ou-Yang 《Biomicrofluidics》2009,3(1)

Dielectrophoresis (DEP), the phenomenon of directed motion of electrically polarizable particles in a nonuniform electric field, is promising for applications in biochemical separation and filtration. For colloidal particles in suspension, the relaxation of the ionic species in the shear layer gives rise to a frequency-dependent, bidirectional DEP force in the radio frequency range. However, quantification methods of the DEP force on individual particles with the pico-Newton resolution required for the development of theories and design of device applications are lacking. We report the use of optical tweezers as a force sensor and a lock-in phase-sensitive technique for analysis of the particle motion in an amplitude modulated DEP force. The coherent detection and sensing scheme yielded not only unprecedented sensitivity for DEP force measurements, but also provided a selectivity that clearly distinguishes the pure DEP force from all the other forces in the system, including electrophoresis, electro-osmosis, heat-induced convection, and Brownian forces, all of which can hamper accurate measurements through other existing methods. Using optical tweezers-based force transducers already developed in our laboratory, we have results that quantify the frequency-dependent DEP force and the crossover frequency of individual particles with this new experimental method.  相似文献   

Event-based discrete-time multi-agent consensus over signed digraphs with communication delays     

Lulu Li  Jianquan Lu  Daniel W.C. Ho 《Journal of The Franklin Institute》2019,356(18):11668-11689

The ability to ensure the desired performance of the cooperative-antagonistic multi-agent networks (MANs) in the presence of communication constraints is an important task in many applications of real systems. In this paper, under the proposed event-triggered condition (ETC), different types of consensus are obtained under different network topology. We concentrates on the event-based bipartite consensus. It is shown that under the proposed ETC (i) the addressed cooperative-antagonistic network with arbitrary communication delays reaches bipartite consensus provided that the network is balanced; (ii) the network model reaches zero if the network is unbalanced. Further, to avoid the continuously verifying the triggering condition, a self-triggered algorithm is proposed for realizing the bipartite consensus of the network model. A numerical example is given to illustrate the effectiveness of the theoretical results.  相似文献   

Causality in medicine,and its relation to action,mechanisms, and probability     

Auker-Howlett  Daniel  Wilde  Michael 《Metascience》2019,28(3):387-391

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Varieties of innovation and business survival: Does pursuit of incremental or far-ranging innovation make manufacturing establishments more resilient?     

Timothy R. Wojan  Daniel Crown  Anil Rupasingha 《Research Policy》2018,47(9):1801-1810

The transition from an industrial economy to an innovation economy poses two critical questions for the manufacturing sector in advanced countries. First, given the diffusion of modern manufacturing practices around the world, what level of innovation (incremental, more far-ranging, or radical) is most likely to support a resilient domestic manufacturing sector? Second, are assumed differences in the innovative capacity across space likely to hasten the decline of rural manufacturing? To answer these questions this research combines comprehensive measures of self-reported innovation able to reliably differentiate incremental and more far-ranging innovation with establishment-level data able to examine the geographical distribution of these different innovation strategies. The data used for the analysis includes a two-period panel of manufacturing establishments surveyed in 1996 and 2013 with annual employment data indicating survival in the intervening years. Our findings suggest that long-surviving manufacturing plants overwhelmingly gravitate away from non-innovation strategies toward incremental or more far-ranging innovation orientations. A survival advantage of far-ranging innovation over incremental innovation is observed for standalone firms. We do not identify a difference in the innovation orientations of rural and urban manufacturing establishments.  相似文献   

Modification of Mikhailov stability criterion for fractional commensurate order systems   总被引：1，自引：1，他引：0  

Jessica Mendiola-Fuentes  Daniel Melchor-Aguilar 《Journal of The Franklin Institute》2018,355(5):2779-2790

In this paper we present the modification of the Mikhailov stability criterion for linear fractional commensurate order systems. The modification consists in determining the appropriate measure for the total argument change depending on the highest fractional order ${\alpha }_n=n\alpha$ of the system and not only on the integer n as stated in the literature. The validity of the result is illustrated by means of several examples.  相似文献   

Predictive ability of the medicine ball chest throw and vertical jump tests for determining muscular strength and power in adolescents     

Daniel A. Hackett  Timothy B. Davies  Denis Ibel  Stephen Cobley  Ross Sanders 《Measurement in physical education and exercise science》2018,22(1):79-87

This study examined the predictive ability of the medicine ball chest throw and vertical jump for muscular strength and power in adolescents. One hundred and ninety adolescents participated in this study. Participants performed trials of the medicine ball chest throw and vertical jump, with vertical jump peak power calculated via an estimation equation. One-repetition maximum and peak power for the chest press and leg press were assessed using pneumatic exercise machines. The medicine ball chest throw strongly correlated with chest press one-repetition maximum and peak power, while the vertical jump peak power strongly correlated with leg press one-repetition maximum and peak power. The predictive ability of medicine ball chest throw was better than vertical jump peak power for muscular strength and power when controlling for sex, age, height, weight, and maturation, and was not affected by involvement in sports. Results show good predictive ability of the medicine ball chest throw for muscular strength and power in adolescents, while predictable ability of vertical jump peak power is weakened when other factors are taken into account.  相似文献   

‘The East’ strikes back. Ultras Dynamo,hyper-stylization,and regimes of truth     

Daniel Ziesche 《Sport in Society》2018,21(6):883-901

Abstract

This case study deals with Ultras Dynamo, the leading group in the active fan scene of Eastern German (the term Eastern Germany is used within this paper to refer to the territory on which the GDR existed from 1949 to 1990; it entails the federal states Brandenburg, Mecklenburg-Vorpommern, Sachsen, Sachsen-Anhalt, Thuringia and the eastern part of Berlin) side SG Dynamo Dresden (throughout the paper, the club’s full name ‘Sportgemeinschaft Dynamo Dresden’ will be shortened using either Dynamo Dresden or simply Dynamo. Among the fans, the club is mostly called SGD (abbreviation of Sport[G]emeinschaft Dynamo) which is also used on flags, banners and in fan chants). The paper analyses styles of self-representation of the active fan scene at Dynamo and critically analyses the claim made by the group to being apolitical. The process of collective identity construction is linked to media images of the group and a ‘regime of truth’ is identified: a self-sustaining and interdependent cycle which overarches the process of image- and identity-construction at Dynamo Dresden and which can be traced back to processes of labelling, stigmatization and secondary deviance.  相似文献   

Physiological implications of preparing for a natural male bodybuilding competition     

Lachlan Mitchell  Gary Slater  Daniel Hackett  Nathan Johnson  Helen O’connor 《European Journal of Sport Science》2018,18(5):619-629

This study aimed to describe the body composition and physiological changes which take place during the in-season and recovery periods of a group of natural bodybuilders. Natural male bodybuilders (n?=?9) were assessed 16 (PRE16), 8 (PRE8), and 1 (PRE1) week(s) before, and 4 (POST4) weeks after a bodybuilding competition. Assessments included body composition, resting metabolic rate (RMR), serum hormones, and 7-day weighed food and training diaries. Change in parameters was assessed using repeated-measures analysis of variance. Dietary protein intake remained high throughout the study period (2.8–3.1?g?kg^?1?d^?1). Fat mass (FM) was significantly reduced from PRE16 to PRE1 (8.8?±?3.1 vs. 5.3?±?2.4?kg, P?.01). There was a small decrease in lean mass (LM) from PRE8 to PRE1 (71.8?±?9.1 vs. 70.9?±?9.1?kg, P?P?>?.05). Large reductions in total and free testosterone (16.4?±?4.4 vs. 10.1?±?3.6?nmol?L^?1, P?. 116.8?±?76.9?pmol?L^?1, P?. 19.9?±?7.6?nmol?L^?1, P?. 72.5?±?8.5?kg, P?. 25.4?±?9.3?nmol?L^?1, P?相似文献   

Assessment of passive drag in swimming by numerical simulation and analytical procedure     

Tiago M. Barbosa  Rui Ramos  António J. Silva  Daniel A. Marinho 《Journal of sports sciences》2018,36(5):492-498

The aim was to compare the passive drag-gliding underwater by a numerical simulation and an analytical procedure. An Olympic swimmer was scanned by computer tomography and modelled gliding at a 0.75-m depth in the streamlined position. Steady-state computer fluid dynamics (CFD) analyses were performed on Fluent. A set of analytical procedures was selected concurrently. Friction drag (D_f), pressure drag (D_pr), total passive drag force (D_f+pr) and drag coefficient (C_D) were computed between 1.3 and 2.5 m · s^?1 by both techniques. D_f+pr ranged from 45.44 to 144.06 N with CFD, from 46.03 to 167.06 N with the analytical procedure (differences: from 1.28% to 13.77%). C_D ranged between 0.698 and 0.622 by CFD, 0.657 and 0.644 by analytical procedures (differences: 0.40–6.30%). Linear regression models showed a very high association for D_f+pr plotted in absolute values (R² = 0.98) and after log–log transformation (R² = 0.99). The C_D also obtained a very high adjustment for both absolute (R² = 0.97) and log–log plots (R² = 0.97). The bias for the D_f+pr was 8.37 N and 0.076 N after logarithmic transformation. D_f represented between 15.97% and 18.82% of the D_f+pr by the CFD, 14.66% and 16.21% by the analytical procedures. Therefore, despite the bias, analytical procedures offer a feasible way of gathering insight on one’s hydrodynamics characteristics.  相似文献