Partially Cooled Shocks: Detectable Precursors in the Warm/hot Intergalactic Medium

I present computations of the integrated column densities produced in the post-shock cooling layers and in the radiative precursors of partially cooled fast shocks as a function of the shock age. The results are applicable to the shock-heated warm/hot intergalactic medium which is expected to be a major baryonic reservoir and contain a large fraction of the so-called missing baryons. My computations indicate that readily observable amounts of intermediate and high ions, such as C IV, N V, and O VI, are created in the precursors of young shocks, for which the shocked gas remains hot and difficult to observe. I suggest that such precursors may provide a way to identify and estimate the "missing" baryonic mass associated with the shocks. The absorption-line signatures predicted here may be used to construct ion-ratio diagrams, which will serve as diagnostics for the photoionized gas in the precursors. In my numerical models, the time evolution of the shock structure, self-radiation, and associated metal-ion column densities are computed by a series of quasi-static models, each appropriate for a different shock age. The shock code used in this work calculates the non-equilibrium ionization and cooling, follows the radiative transfer of the shock self-radiation through the post-shock cooling layers, takes into account the resulting photoionization and heating rates, follows the dynamics of the cooling gas, and self-consistently computes the photoionization states in the precursor gas. I present a complete set of the age-dependent post-shock and precursor columns for all ionization states of the elements H, He, C, N, O, Ne, Mg, Si, S, and Fe as functions of the shock velocity, gas metallicity, and magnetic field. I present my numerical results in convenient online tables

State-Dependent Computation Using Coupled Recurrent Networks

Although conditional branching between possible behavioral states is a hallmark of intelligent behavior, very little is known about the neuronal mechanisms that support this processing. In a step toward solving this problem, we demonstrate by theoretical analysis and simulation how networks of richly interconnected neurons, such as those observed in the superficial layers of the neocortex, can embed reliable, robust finite state machines. We show how a multistable neuronal network containing a number of states can be created very simply by coupling two recurrent networks whose synaptic weights have been configured for soft winner-take-all (sWTA) performance. These two sWTAs have simple, homogeneous, locally recurrent connectivity except for a small fraction of recurrent cross-connections between them, which are used to embed the required states. This coupling between the maps allows the network to continue to express the current state even after the input that elicited that state iswithdrawn. In addition, a small number of transition neurons implement the necessary input-driven transitions between the embedded states. We provide simple rules to systematically design and construct neuronal state machines of this kind. The significance of our finding is that it offers a method whereby the cortex could construct networks supporting a broad range of sophisticated processing by applying only small specializations to the same generic neuronal circuit

Skip Ring/Circular Skip List: Circular Linked List Based New Data Structure

A linked list is a data structure consisting of a group of nodes which together represent a sequence. Linked lists are used in skip list data structures. They consist of a layered structure and all nodes are in the bottom layer. These nodes are reduced to half towards upper layers and thus a pyramid-like structure is formed, which facilitates search, insertion and removal operations. A circular linked list is a type of linked list in which the last node of the list points back to the first node. Our new data structure, skip ring, is created with the help of circular linked list and skip list data structures. In circular linked list, operations are performed on a single round robin list. However, our new data structure consists of circular link lists formed in layers which are linked in a conical way. Time complexity of search, insertion and deletion equals to O (lg N) in an N-element skip ring data structure. Therefore, skip ring data structure is employed more effectively (O(lg N)) in circumstances where circular linked lists (O(N)) are used. Keywords: Skip Ring, Circular Skip List, Circular Linked List, Skip List, Data Structure

Spiral Growth Manufacturing (SGM) – A Continuous Additive Manufacturing Technology for Processing Metal Powder by Selective Laser Melting

Spiral growth manufacturing is a new innovative powder based rapid manufacturing technique. The innovation exists in the methodology in which powder layers are deposited. Unlike other pre-placed powder systems, the deposited layers move relative to the location at which they are processed. This is made possible by a rotating build drum into which powder is deposited, in spiralled layers, from a stationary hopper. With this configuration powder can be continuously deposited and levelled and simultaneously processed, eliminating delays in the build cycle. Stainless steel and cobalt-chrome powder is selectively melted using a 100W flash lamp pumped Nd:YAG laser. This paper reports on factors affecting build rate and on build strategies for creating a number of axis-symmetric thin and thick walled cylinders. Experimental results suggest that build rate for thin walled structures bonded to a substrate will ultimately be governed by tangential movements of the powder particles when frictional forces are not sufficient to accelerate the particles along a curved path, provided that enough laser power is available for melting. Even melt pool balling, which is evident when melting one layer at high speeds, diminishes in multiple layer builds due to re-melting and infilling.Mechanical Engineerin

Magnetic bilayer-skyrmions without skyrmion Hall effect

Arising from emergent electromagnetic field of magnetic skyrmions due to their nontrivial topology, the skyrmion Hall effect might be a roadblock for practical applications since any longitudinal motions of skyrmions in nanotrack is accompanied by a transverse motion. A direct consequence of such an effect is easy destruction of skyrmions at the nanotrack edges during their fast motions along the nanotrack, despite their topological protection. Here we propose an entirely novel solution of completely inhibiting such skyrmion Hall effect without affecting its topological properties based on a antiferromagnetic-coupling bilayer system. We show that a pair of magnetic skyrmions can be nucleated in such a bilayer system through vertical current injection or converted from a current-driven domain-wall pair. Once nucleated, the skyrmion pair can be displaced through current-induced spin torque either from a vertical injected current or in-plane current. The skyrmion Hall effect is completely suppressed due to the cancellation of back-action forces acting on each individual skyrmion, resulting in a straight and fast motion of skyrmions along the current direction. This proposal will be of fundamental interests by introducing the bilayer degree of freedom into the system. Moreover, it provides an easy way to engineer the transport properties of the skyrmionic devices to achieve desired performance, making it highly promising for practical applications such as ultradense memory and information-processing devices based on skyrmions