Transverse momentum correlations of quarks in recursive jet models

In the symmetric string fragmentation recipe adopted by PYTHIA for jet simulations, the transverse momenta of successive quarks are uncorrelated. This is a simplification but has no theoretical reason. Transverse momentum correlations are naturally expected, for instance, in a covariant multiperipheral model of quark hadronization. We propose a simple recipe of string fragmentation which lead to such correlations. The definition of the jet axis and its relation with the primordial transverse momentum of the quark is also discussed.Comment: 7 pages, 3 figures, 1 tabl

Double stratification effects on unsteady electrical MHD mixed convection flow of nanofluid with viscous dissipation and Joule heating

The problem of unsteady mixed convection electrical magnetohydrodynamic (MHD) flow and heat transfer induced due to nanofluid over a permeable stretching sheet using Buongiorno model is investigated. The transverse electric and magnetic fields are considered in the flow field, while in the heat convection is associated with the thermal radiation, heat generation/absorption, viscous and Ohmic dissipations, and chemical reaction is incorporated in the mass diffusion. A similarity transformation is used to reduce the boundary layer governing equations which are partial differential equations to nonlinear differential equations and then solved numerically using implicit finite difference scheme. The nanofluid velocity and temperature are sensitive to an increase in the electric field, which resolved the problem of sticky effects due to the magnetic field. Destructive chemical reaction increases the level nanoparticles concentration while reversed behave happened in the case of the generative chemical reaction. Heat source boosts the fluid temperature while as opposite occurred with the heat sink. Thermal and concentration stratifications decreased the fluid temperature and the nanoparticles concentration profiles. Buoyancy ratio parameter reduced the Nusselt and Sherwood numbers whereas mixed convection parameter increases for higher values. A comparison with the previous study available in literature has been done and found an excellent agreement with the published dat

Machine learning for prediction models to mitigate the voltage deviation in photovoltaic-rich distributed network

The voltage deviation is one of the most crucial power quality issues that occur in electrical power systems. Renewable energy plays a vital role in electrical distribution networks due to the high economic returns. However, the presence of photovoltaic systems changes the nature of the energy flow in the grid and causes many problems such as voltage deviation. In this work, several predictive models are examined for voltage regulation in the Jordanian Sabha distribution network equipped with photovoltaic farms. The augmented grey wolf optimizer is used to train the different predictive models. To evaluate the performance of models, a value of one for regression factor and a low value for root mean square error, mean square error, and mean absolute error are used as standards. In addition, a comparison between nineteen predictive models has been made. The results have proved the capability of linear regression and the gaussian process to restore the bus voltages in the distribution network accurately and quickly and to solve the shortening in the voltage dynamic response caused by the iterative nature of the heuristic algorithm. 

Chondrocalcinose articulaire révélatrice d’une hypercalcémie hypocalciurique familiale: à propos d’une observation

L'hypercalcémie hypocalciurique familiale (HHF) est une maladie bénigne à transmission autosomique dominante, caractérisée par une hypercalcémie persistante béhigne, une hypocalciurie, et des concentrations de  parathormone (PTH) normales ou modérément élevées, sans complication secondaire à l'hypercalcémie. Nous rapportons l'observation d'un patient ayant présenté une chondrocalcinose articulaire révélatrice d'une HHF. A travers cette observation nous essayons de décrire les aspects épidémiologiques, les caractéristiques cliniques, et paracliniques de cette association