A SIMULATION STUDY OF THE SIZE AND POWER OF SOME TWO-SAMPLE TESTS FOR UNEQUALLY CENSORED SURVIVAL DATA (RANK TESTS, LOGRANK, PROPORTIONAL HAZARDS, WILCOXON TESTS, EXPONENTIAL DISTRIBUTION)

Sizes and power of selected two-sample tests of the equality of survival distributions are compared by simulation for small samples from unequally, randomly-censored exponential distributions. The tests investigated include parametric tests (F, Score, Likelihood, Asymptotic), logrank tests (Mantel, Peto-Peto), and Wilcoxon-Type tests (Gehan, Prentice). Equal sized samples, n = 18, 16, 32 with 1000 (size) and 500 (power) simulation trials, are compared for 16 combinations of the censoring proportions 0%, 20%, 40%, and 60%. For n = 8 and 16, the Asymptotic, Peto-Peto, and Wilcoxon tests perform at nominal 5% size expectations, but the F, Score and Mantel tests exceeded 5% size confidence limits for 1/3 of the censoring combinations. For n = 32, all tests showed proper size, with the Peto-Peto test most conservative in the presence of unequal censoring. Powers of all tests are compared for exponential hazard ratios of 1.4 and 2.0. There is little difference in power characteristics of the tests within the classes of tests considered. The Mantel test showed 90% to 95% power efficiency relative to parametric tests. Wilcoxon-type tests have the lowest relative power but are robust to differential censoring patterns. A modified Peto-Peto test shows power comparable to the Mantel test. For n = 32, a specific Weibull-exponential comparison of crossing survival curves suggests that the relative powers of logrank and Wilcoxon-type tests are dependent on the scale parameter of the Weibull distribution. Wilcoxon-type tests appear more powerful than logrank tests in the case of late-crossing and less powerful for early-crossing survival curves. Guidelines for the appropriate selection of two-sample tests are given. ^

Social relations and power

This paper presents an explanatory typology of social relations which moves forward from those habitual and known by social disciplines, and labels the three types: actions - strategies - institutions . We set out to research characteristics, specificities, relevance of and differences between each type, as well as their interactions and interweaving, which make up the complexity of social relations. Moreover, mutual interdependence between the said social categories is established, which corresponds to a new conceptualization of power . This avoids traditional reductionism and rescues rarely taken-into-account capacities and determinations. The pair "social relations and power" makes up a necessary and indispensable framework to tackle the various problems of the social world.

Secret and power in social life

Secret and power constitute two fundamental instances of the social world. Secret takes care of the concealment of things and of social processes. Secret is also a power device. Power is the social capacity to do, create, not doing and stop from doing. Secret and power get mutual feedback. Power uses the secret to protect his potential, be it what may, to increment its operative strength. Secret uses the power to achieve its aims and proposals. Social sciences seem to ignore the huge explanatory capacity of these two interrelated concepts, and even more, their powerful intervention in societies.

Social relations and power

This paper presents an explanatory typology of social relations which moves forward from those habitual and known by social disciplines, and labels the three types: actions - strategies - institutions . We set out to research characteristics, specificities, relevance of and differences between each type, as well as their interactions and interweaving, which make up the complexity of social relations. Moreover, mutual interdependence between the said social categories is established, which corresponds to a new conceptualization of power . This avoids traditional reductionism and rescues rarely taken-into-account capacities and determinations. The pair "social relations and power" makes up a necessary and indispensable framework to tackle the various problems of the social world.

Secret and power in social life

Secret and power constitute two fundamental instances of the social world. Secret takes care of the concealment of things and of social processes. Secret is also a power device. Power is the social capacity to do, create, not doing and stop from doing. Secret and power get mutual feedback. Power uses the secret to protect his potential, be it what may, to increment its operative strength. Secret uses the power to achieve its aims and proposals. Social sciences seem to ignore the huge explanatory capacity of these two interrelated concepts, and even more, their powerful intervention in societies.

Secret and power in social life

Secret and power constitute two fundamental instances of the social world. Secret takes care of the concealment of things and of social processes. Secret is also a power device. Power is the social capacity to do, create, not doing and stop from doing. Secret and power get mutual feedback. Power uses the secret to protect his potential, be it what may, to increment its operative strength. Secret uses the power to achieve its aims and proposals. Social sciences seem to ignore the huge explanatory capacity of these two interrelated concepts, and even more, their powerful intervention in societies.

Social relations and power

This paper presents an explanatory typology of social relations which moves forward from those habitual and known by social disciplines, and labels the three types: actions - strategies - institutions . We set out to research characteristics, specificities, relevance of and differences between each type, as well as their interactions and interweaving, which make up the complexity of social relations. Moreover, mutual interdependence between the said social categories is established, which corresponds to a new conceptualization of power . This avoids traditional reductionism and rescues rarely taken-into-account capacities and determinations. The pair "social relations and power" makes up a necessary and indispensable framework to tackle the various problems of the social world.

STC power for 15MW of PV comparing nameplate, initial power and power after 4 years

To date, the majority of quality controls performed at PV plants are based on the measurement of a small sample of individual modules. Consequently, there is very little representative data on the real Standard Test Conditions (STC) power output values for PV generators. This paper presents the power output values for more than 1300 PV generators having a total installed power capacity of almost 15.3 MW. The values were obtained by the INGEPER-UPNA group, in collaboration with the IES-UPM, through a study to monitor the power output of a number of PV plants from 2006 to 2009. This work has made it possible to determine, amongst other things, the power dispersion that can be expected amongst generators made by different manufacturers, amongst generators made by the same manufacturer but comprising modules of different nameplate ratings and also amongst generators formed by modules with the same characteristics. The work also analyses the STC power output evolution over time in the course of this 4-year study. The values presented here could be considered to be representative of generators with fault-free modules.

Looking for business models in digital media and content industries

International Conference on Dynamics of the Media and Content Industry. European Forum for Science and Industry.

Spherical collectors versus bare tethers for drag, thrust, and power generation

Deorbit, power generation, and thrusting performances of a bare thin-tape tether and an insulated tether with a spherical electron collector are compared for typical conditions in low-Earth orbit and common values of length L = 4−20 km and cross-sectional area of the tether A = 1−5 mm2. The relative performance of moderately large spheres, as compared with bare tapes, improves but still lags as one moves from deorbiting to power generation and to thrusting: Maximum drag in deorbiting requires maximum current and, thus, fully reflects on anodic collection capability, whereas extracting power at a load or using a supply to push current against the motional field requires reduced currents. The relative performance also improves as one moves to smaller A, which makes the sphere approach the limiting short-circuit current, and at greater L, with the higher bias only affecting moderately the already large bare-tape current. For a 4-m-diameter sphere, relative performances range from 0.09 sphere-to-bare tether drag ratio for L = 4 km and A = 5 mm2 to 0.82 thrust–efficiency ratio for L = 20 km and A = 1 mm2. Extremely large spheres collecting the short-circuit current at zero bias at daytime (diameters being about 14 m for A = 1 mm2 and 31 m for A = 5 mm2) barely outperform the bare tape for L = 4 km and are still outperformed by the bare tape for L = 20 km in both deorbiting and power generation; these large spheres perform like the bare tape in thrusting. In no case was sphere or sphere-related hardware taken into account in evaluating system mass, which would have reduced the sphere performances even further.

Spherical collectors versus bare tethers for drag, thrust, and power generation

Performances of ED-tethers using either spherical collectors or bare tethers for drag, thrust, or power generation, are compared. The standard Parker-Murphy model of current to a full sphere, with neither space-charge nor plasmamotion effects considered, but modified to best fit TSS1R results, is used (the Lam, Al'pert/Gurevich space-charge limited model will be used elsewhere) In the analysis, the spherical collector is assumed to collect current well beyond its random-current value (thick-heath). Both average current in the bare-tether and current to the sphere are normalized with the short-circuit current in the absence of applied power, allowing a comparison of performances for all three applications in terms of characteristic dimensionless numbers. The sphere is always substantially outperformed by the bare-tether if ohmic effects are weak, though its performance improves as such effects increase.

On the generative equations of fractal self-similarity in granular media and the related PSD models

The physical appearance of granular media suggests the existence of geometrical scale invariance. The paper discuss how this physico-empirical property can be mathematically encoded leading to different generative models: a smooth one encoded by a differential equation and another encoded by an equation coming from a measure theoretical property.

Iterative bit- and power allocation in correlated MIMO systems

In this contribution a novel iterative bit- and power allocation (IBPA) approach has been developed when transmitting a given bit/s/Hz data rate over a correlated frequency non-selective (4× 4) Multiple-Input MultipleOutput (MIMO) channel. The iterative resources allocation algorithm developed in this investigation is aimed at the achievement of the minimum bit-error rate (BER) in a correlated MIMO communication system. In order to achieve this goal, the available bits are iteratively allocated in the MIMO active layers which present the minimum transmit power requirement per time slot.