On the Presence and Thermalization of Cold Ions in the Exhaust of Antiparallel Symmetric Reconnection

Using fully kinetic 2.5 dimensional particle-in-cell simulations of anti-parallel symmetric magnetic reconnection, we investigate how initially cold ions are captured by the reconnection process, and how they evolve and behave in the exhaust. We find that initially cold ions can remain cold deep inside the exhaust. Cold ions that enter the exhaust downstream of active separatrices, closer to the dipolarization front, appear as cold counter-streaming beams behind the front. In the off-equatorial region, these cold ions generate ion-acoustic waves that aid in the thermalization both of the incoming and outgoing populations. Closest to the front, due to the stronger magnetization, the ions can remain relatively cold during the neutral plane crossing. In the intermediate exhaust, the weaker magnetization leads to enhanced pitch angle scattering and reflection. Cold ions that enter the exhaust closer to the X line, at active separatrices, evolve into a thermalized exhaust. Here, the cold populations are heated through a combination of thermalization at the separatrices and pitch angle scattering in the curved magnetic field around the neutral plane. Depending on where the ions enter the exhaust, and how long time they have spent there, they are accelerated to different energies. The superposition of separately thermalized ion populations that have been accelerated to different energies form the hot exhaust population.

Experimental characterization of a novel ventilation system for multi-story buildings with continuous curtain walls

PurposeThe purpose of this paper is to present the results of an experimental campaign conducted on a recently developed fire protection system (FPS), specifically designed for installation on continuous glass curtain walls systems typical of multi-story buildings.Design/methodology/approachThe authors will first present the theoretical derivation of the relevant parameters to characterize and predict the fire evolution and probability of flashover, according to existing codes and standards. Then, the results of two full-scale tests will be presented in terms of temperature fields, thermal gradients and position of the neutral plane.FindingsThe experimental evidence shows how the proposed system is able to dramatically reduce internal temperatures in the rooms interested by the fire, also allowing for safer evacuation procedures by increasing the height of the neutral plane.Originality/valueThe novel window frame element comprises an automatic doubly convergent aperture system that induces ventilation in the compartment by increasing internal convection in the rooms subject to the fire. This allows for an efficient dispersion of hot gases and fumes and a drastic improvement in safety for both the occupants and firefighting operators. The theoretical results are then compared to the experimental evidence to evaluate the performance of the proposed ventilation system in the context of existing standards and design procedures.

Head Position and Posturography: A Novel Biomarker to Identify Concussion Sufferers

Balance control systems involve complex systems directing muscle activity to prevent internal and external influences that destabilize posture, especially when body positions change. The computerized dynamic posturography stability score has been established to be the most repeatable posturographic measure using variations of the modified Clinical Test of Sensory Integration in Balance (mCTSIB). However, the mCTSIB is a standard group of tests relying largely on eyes-open and -closed standing positions with the head in a neutral position, associated with probability of missing postural instabilities associated with head positions off the neutral plane. Postural stability scores are compromised with changes in head positions after concussion. The position of the head and neck induced by statically maintained head turns is associated with significantly lower stability scores than the standardized head neutral position of the mCTSIB in Post-Concussion Syndrome (PCS) subjects but not in normal healthy controls. This phenomenon may serve as a diagnostic biomarker to differentiate PCS subjects from normal ones as well as serving as a measurement with which to quantify function or the success or failure of a treatment. Head positions off the neutral plane provide novel biomarkers that identify and differentiate subjects suffering from PCS from healthy normal subjects.

PERANCANGAN TIANG PANCANG DENGAN TAHANAN FRIKSI NEGATIF

Development in Jakarta took place the most, but the condition of the land in Jakarta ehich was dominated by sof soil was becoming an obstacle. Landfill is one way that can be done to strengthen or improve soft soil. But if this landfill causes a settlement in soil around the pile is bigger than the settlement in the pile, there will be negative skin friction which will cause the pile to be pulled down. This study aims to analyze and compare the magnitude of the influence of negative skin friction caused by the pile by using the undrained parameter, drained parameter, Meyerhof empirical, and Vesic empirical to analyze the carrying capacity of the pile and determine the neutral plane and negative skin friction with the Fellenius method and Prakash & Sharma methods. From the results of the analysis,negative skin friction does not accur in the pile that ends hard soil while it occurs in soil that ends soft soil. The location of neutral plane between the Fellenius method and Prakash & Sharma is not too different. But piles that experience negative skin friction need to be redesign. Changes in diameter of this pile can reach 2.5 times the initial size. Pembangunan di Jakarta sangat banyak, tetapi kondisi tanah di Jakarta yang didomisasi oleh tanah lunak mnjdi kendala. Timbunan menjadi salah satu cara yang dapt dilakukan untuk memperkuat atau memperbaiki tanah lunak. Tetapi apabila timbunan ini menyebabkan penurunan tanah di sekitar tiang lebih besar daripada penurunan tiang maka akan timbul gesekan antara selimut tiang dengan tanah ke arah bawah yang akan menyebabkan tiang tertarik ke bawah. Gaya geser ke bawah ini dikenal sebagai gesekan selimt negatif. Studi ini bertujuan untuk menganalisis dan membandingkan besarnya pengaruh gesekan selimut negatif akibat timbunan dengan menggunakan metode undrained parameter, drained parameter, empiris Meyerhoff, dan empiris Vesic untuk menganalisis daya dukung tiang serta penentuan titik netral dan friksi negatif dengan metode Fellenius dan Prakash & Sharma. Dari hasil analisis, gesekan selimut negative tidak terjadi di tiang yang berujung tanah keras sedangkan terjadi di tanah pada tanah yang berujung tanah lunak. Letak tiitk netral antara metode Fellenius dan Prakash & Sharma tidak terlalu berbeda. Tetapi tiang yang mengalami friksi negatif perlu didesain ulang ukurannya. Perubahan diameter tiang ini bisa mencapai 2.5 kali dari ukuran awal.