Electron heating mode transitions in dual frequency capacitive discharges

The authors consider electron heating in the sheath regions of capacitive discharges excited by a combination of two frequencies, one much higher than the other. There is a common supposition that in such discharges the higher frequency is the dominant source of electron heating. In this letter, the authors discuss closed analytic expressions quantifying the Ohmic and collisionless electron heating in a dual frequency discharge. In both cases, the authors show that the lower frequency parameters strongly influence the heating effect. Moreover, this influence is parametrically different, so that the dominant heating mechanism may be changed by varying the low frequency current density

A model for tailored-waveform radiofrequency sheaths

The sheath physics of radiofrequency plasmas excited by a sinusoidal waveform is reasonably well understood, but the existing models are complicated and are not easily extended to the more complex waveforms recently introduced in applications. Turner and Chabert (2014 Appl. Phys. Lett. 104 164102) proposed a model for collisionless sheaths that can easily be solved for arbitrary waveforms. In this paper we extend this model to the case of collisional sheaths in the intermediate pressure regime. Analytical expressions are derived for the electric field, the electric potential and the density profiles in the sheath region. The collisionless and collisional models are compared for a pulsed-voltage waveform

A New Multivariate Statistical Model for Change Detection in Images Acquired by Homogeneous and Heterogeneous Sensors

International audienceRemote sensing images are commonly used to monitor the earth surface evolution. This surveillance can be conducted by detecting changes between images acquired at different times and possibly by different kinds of sensors. A representative case is when an optical image of a given area is available and a new image is acquired in an emergency situation (resulting from a natural disaster for instance) by a radar satellite. In such a case, images with heterogeneous properties have to be compared for change detection. This paper proposes a new approach for similarity measurement between images acquired by heterogeneous sensors. The approach exploits the considered sensor physical properties and specially the associatedmeasurement noise models and local joint distributions. These properties are inferred through manifold learning. The resulting similarity measure has been successfully applied to detect changes between many kinds of images, including pairs of optical images and pairs of optical-radar images

Periodic formation and propagation of double layers in the expanding chamber of an inductive discharge operating in Ar/ SF 6 mixtures

International audienceIt has previously been shown ͓Tuszewski et al., Plasma Sources Sci. Technol. 12, 396 ͑2003͔͒ that inductive discharges in electronegative gases are subject to two types of instability: the source instability related to the E to H transition and a transport instability, occurring downstream when an expanding chamber is present. These two types of instability are observed in our " helicon " reactor operated without a static magnetic field in low-pressure Ar/ SF 6 mixtures. Temporally and spatially resolved measurements show that, in our experiment, the downstream instability is a periodic formation and propagation of a double layer. The double layer is born at the end of the source tube and propagates slowly to the end of the expansion region with a velocity of 150 m s −1

Lifespan Modeling of Insulation Materials for Low Voltage Machines: films and twisted pairs

This paper deals with the modeling of insulation material lifespan in a partial discharge regime. Accelerated aging tests are carried out to determine the lifespan of polyesterimide insulation films under different various stress conditions. The insulation lifespan logarithm is modeled as a function of different factors: the electrical stress logarithms and of an exponential form of the temperature. The model parameters, or so-called factor effects, is estimated on a training set. The significance of the factors is evaluated through the analysis of variance (ANOVA). In a first step, the design of experiment method (DoE) is considered. The associated lifespan model is linear with respect to the factors. This method is well-known for reducing the number of experiments while providing a good accuracy. In a second step, the response surface method (RSm) is considered. This method takes also into account some second order terms and thus possible interactions between the stress factors. Performance of the two methods are analyzed and compared on a test set. </p

Variable Importance Assessment in Lifespan Models of Insulation Materials: A Comparative Study

International audienceThis paper presents and compares different methods for evaluating the relative importance of variables involved in insulation lifespan models. Parametric and non-parametric models are derived from accelerated aging tests on twisted pairs covered with an insulating varnish under different stress constraints (voltage, frequency and temperature). Parametric models establish a simple stress-lifespan relationship and the variable importance can be evaluated from the estimated parameters. As an alternative approach, non-parametric models explain the stress-lifespan relationship by means of regression trees or random forests (RF) for instance. Regression trees naturally provide a hierarchy between the variables. However, they suffer from a high dependency with respect to the training set. We show that RF provide a more robust model while allowing a quantitative variable importance assessment. Comparisons of the different models are performed on different training and test sets obtained through experiments

Change detection for optical and radar images using a Bayesian nonparametric model coupled with a Markov random field

International audienceThis paper introduces a Bayesian non parametric (BNP) model associated with a Markov random field (MRF) for detecting changes between remote sensing images acquired by homogeneous or heterogeneous sensors. The proposed model is built for an analysis window which takes advantage of the spatial information via an MRF. The model does not require any a priori knowledge about the number of objects contained in the window thanks to the BNP framework. The change detection strategy can be divided into two steps. First, the segmentation of the two images is performed using a region based approach. Second, the joint statistical properties of the objects in the two images allows an appropriate manifold to be defined. This manifold describes the relationships between the different sensor responses to the observed scene and can be learnt from a training unchanged area. It allows us to build a similarity measure between the images that can be used in many applications such as change detection or image registration. Simulation results conducted on synthetic and real optical and synthetic aperture radar (SAR) images show the efficiency of the proposed method for change detection

Pemberdayaan Masyarakat Pesisir Pulau Untungjawa Dalam Upaya Meningkatkan Kesadaran Hukum Dan Kemandirian Nelayan

Kelurahan Pulau Untung Jawa merupakan salah satu dari enam kelurahan di wilayah kepulauan Seribu atau satu di antara tiga kelurahan di wilayah kecamatan Kepulauan Seribu Selatan. Penduduk Pulau Untung Jawa sebagian besar adalah masyarakat pribumi yang silsilahnya berasal dari Pulau Untung Jawa dan perpindahan masyarakat Pulau Ubi Besar tanggal 13 Februari 1954. Kelurahan Pulau Untung Jawa merupakan kawasan andalan Wisata Pemukiman yang mempunyai peranan penting dalam mewujudkan visi kabupaten yaitu: Sebagai Taman dan Ladang Kehidupan Bahari yang Berkelanjutan Penelitian ini menemukan model pemberdayaan yang tepat bagi masyarakat pesisir pulau UntungJawa dan menganalisis upaya peningkatan kesadaran hukum dan kemandirian nelayan Pulau UntungJawa. Penelitian ini termasuk dalam penelitian deskriptif kualitatif dengan pendekatan sosiologis, atau dalam penelitian hukum biasa disebut normatif terapan/normatif empiris. Model pemberdayaan yang bertujuan membangun kemandirian nelayan pulau UntungJawa dapat dilaksanakan dengan kerjasama dan partisipasi masyarakat. Perlu sinergitas antara peran pemerintah baik aparat kelurahan dan instansi terkait lainnya, LSM yang peduli atau pun Perusahaan, kampus maupun masyarakat nelayan itu sendiri. Terdapat faktor pendukung dan faktor penghambat yang harus diperhatikan dan dicarikan solusinya. Faktor pendukung antara lain sudah terbangun konsep kesadaran dalam melakukan segala macam kegiatan yang sesuai dengan hukum yang ada, potensi wisata dan produksi perikanan, aparat Kelurahan yang cukup aktif dan kesiapan SDM untuk memotivasi diri dan menerima pendampingan serta berbagai pelatihan. Adapun faktor penghambatnya antara lain: terbatasnya modal, faktor alam, sarana prasarana, kurangnya gairah wisata, daya minat beli dan daya minat permainan air, tidak adanya penghasillan rutin, honor pekerja yang kurang dari UMP, SDM, dan kurangnya kesadaran hukum, bantuan hukum dan perlindungan hukum

Risk indicators affecting honeybee colony survival in Europe: one year of surveillance

International audienceAbstractThe first pan-European harmonized active epidemiological surveillance program on honeybee colony mortality (EPILOBEE) was set up across 17 European Member States to estimate honeybee colony mortality over winter and during the beekeeping season. In nine Member States, overwinter losses were higher and statistically different from the empirical level of 10 % under which the level of overwinter mortality was considered as acceptable with usual beekeeping conditions. In four other countries, these losses were lower. Using multivariable Poisson regression models, it was showed that the size of the operation and apiary and the clinically detected varroosis, American foulbrood (AFB), and nosemosis before winter significantly affected 2012–2013 overwinter losses. Clinically detected diseases, the size of the operation and apiary, and the non-participation to a common veterinary treatment significantly affected 2013 summer losses. EPILOBEE was a prerequisite to implement future projects studying risk factors affecting colony health such as multiple and co-exposure to pesticides