Parallel Path Research Articles

The influence of the Kubo number on the transport of energetic particles

We discuss the interaction between charged energetic particles and magnetized plasmas by using analytical theory. Based on the unified nonlinear transport (UNLT) theory we compute the diffusion coefficient across a large scale magnetic field. To achieve analytical tractability we use a simple Gaussian approach to model the turbulent magnetic fields. We show that the perpendicular diffusion coefficient depends only on two parameters, namely the Kubo number and the parallel mean free path. We combine the aforementioned turbulence model with the UNLT theory and we solve the corresponding integral equation numerically to show how these two parameters control the perpendicular diffusion coefficient. Furthermore, we consider two extreme cases, namely the case of strong and suppressed pitch-angle scattering, respectively. For each case we consider small and large Kubo numbers to achieve a further simplification. All our analytical findings are compared with formulas which are known in diffusion theory.

Waving the flag for development communication: Why there is still hope for communication research

From the debated Modernisation paradigm all the way to the participatory and inclusive approaches for social change, development communication research has given rise to a stimulating scholarly discussion that has introduced both theoretical and evidence-based claims, which are contributing constructively to the evolvement of this discipline. By addressing a number of points that have been raised as evidence of a decline in communication research, this article discusses how development communication research has followed a parallel but different path from other areas of communication research and has slowly but successfully made an important contribution to the field of communication.

MULTI-SPACECRAFT OBSERVATIONS AND TRANSPORT MODELING OF ENERGETIC ELECTRONS FOR A SERIES OF SOLAR PARTICLE EVENTS IN AUGUST 2010

ABSTRACT During 2010 August a series of solar particle events was observed by the two STEREO spacecraft as well as near-Earth spacecraft. The events, occurring on August 7, 14, and 18, originated from active regions 11093 and 11099. We combine in situ and remote-sensing observations with predictions from our model of three-dimensional anisotropic particle propagation in order to investigate the physical processes that caused the large angular spreads of energetic electrons during these events. In particular, we address the effects of the lateral transport of the electrons in the solar corona that is due to diffusion perpendicular to the average magnetic field in the interplanetary medium. We also study the influence of two coronal mass ejections and associated shock waves on the electron propagation, and a possible time variation of the transport conditions during the above period. For the August 18 event we also utilize electron observations from the MESSENGER spacecraft at a distance of 0.31 au from the Sun for an attempt to separate between radial and longitudinal dependencies in the transport process. Our modelings show that the parallel and perpendicular diffusion mean free paths of electrons can vary significantly not only as a function of the radial distance, but also of the heliospheric longitude. Normalized to a distance of 1 au, we derive values of λ ∥ in the range of 0.15–0.6 au, and values of λ ⊥ in the range of 0.005–0.01 au. We discuss how our results relate to various theoretical models for perpendicular diffusion, and whether there might be a functional relationship between the perpendicular and the parallel mean free path.

Optical system design of the Dyson imaging spectrometer based on the Fery prism

Imaging spectrometer has obtained wide development since rich feature information can be obtained by it; now, we focus on its high spectral resolution and miniaturization. In this paper, we design the Dyson imaging spectrometer system based on Fery prism. The average spectral resolution is 4.3 nm and the structure of the total length is 229 mm. It is a small, high-spectrometer imaging system. The front and rear surface of the traditional prism are plane, but the surfaces of the Fery prism are spherical, which can provide some optical power to realize imaging function and produce the dispersion effect. The Fery prism does not need to be placed in the parallel optical path, which simplifies the collimator lens and the imaging lens and are necessary in the prism spectrometer, making it possible to obtain a compact spectrometer. Full-spectrum transmittance of the prism is up to 94 %. Compared to the convex grating, the energy efficiency is greatly improved, and the free spectral range is wider, and its dispersion will not bring higher-order spectral aliasing problem. The small high spectrometer only includes two components. Its spectral range is from 400 to 1000 nm, covering the near-ultraviolet to near-infrared. The various aberrations of the typical spectrum are corrected. The spectrometer is excellent in performance.

Nanostructured Carbon Materials for Li-S and Li-Se Batteries

Novel energy storage systems with high energy density and reduced cost has drawn significant attention due to the emerging storage application, such as commercial electronic devices, electrical vehicles, and grid storage systems. Conventional Li-ion batteries, however, are hard to meet the requirement for those applications in near future due to the theoretical energy density limit. Therefore, advanced batteries with different chemistry which could provide higher capacity and energy density are necessary for further development. Among many candidates, Lithium-sulfur battery (Li-S) has been recognized as one promising system due to its high gravimetric energy density and low material cost, which is superior to most of current Li-ion batteries. Besides sulfur, selenium (Se) has also been involved in the battery study, since it shares similar lithiation/delithiation mechanism to sulfur. In addition, although with lower gravimetric capacity than sulfur, the better electrical conductivity and less shuttling behavior make selenium parallel path of the sulfur system. Due to their dissolution nature of both Li-S and Li-Se systems, supporting materials which provide a robust framework with sufficient internal space and reactive sites, are critical for the chemistry. Although there were many candidates for the supporting material in Li-S and Li-Se batteries, such as metal oxides and graphene based materials, porous carbon materials are still dominant for a practical point of view. Relatively low cost, Industrial scale production and convenient handling make porous carbon materials superior to other supporting materials. Here we present a summary of our work on several porous carbon materials as the supporting material, which help enable high S/Se loading on both material level and electrode level, for the Li-S and Li-Se batteries. We will demonstrate the preparation, characterization and electrochemical performance of the carbon materials. The comparison of corresponding Li-S and Li-Se will be also described. Besides carbon materials, we will also discuss about our study on the influence of polymer binder and electrolyte on the optimized electrodes on both Li-S and Li-Se systems. Further discussions on the battery design and cell-level energy density estimation will be also addressed.

The hydrolysis mechanism and kinetic analysis for COS hydrolysis: A DFT study

Density Functional Theory (DFT) was utilized to study the hydrolysis mechanism and kinetic analysis of carbonyl sulfide (COS). The structures of reactants (R), transition states (TS), intermediates (IM) and products (P) were analyzed and a conclusion reached that hydrolysis mechanism of COS occurs in two paths with One path as a C=S path and the other as a C=O path and all featuring potential for forming H2S and CO2. Function change analysis of COS hydrolysis indicated the rate-determining step of COS hydrolysis was the first elementary reaction as OH and H in H2O attacked C=O and S=O in COS, respectively, with the two paths parallel and competitive and the C=S path more reactionary than the C=O path. Influence on each elementary reaction was also not consistent with reaction temperature increase. The study also included further investigation of the COS catalytic hydrolysis.

Direct observation of charge state in the quasi-one-dimensional conductor Li0.9Mo6O17

The quasi-one-dimensional conductor Li0.9Mo6O17 has been of great interest because of its unusual properties. It has a conducting phase with properties different from a simple Fermi liquid, a poorly understood “insulating” phase as indicated by a metal-“insulator” crossover (a mystery for over 30 years), and a superconducting phase which may involve spin triplet Cooper pairs as a three-dimensional (p-wave) non-conventional superconductor. Recent evidence suggests a density wave (DW) gapping regarding the metal-“insulator” crossover. However, the nature of the DW, such as whether it is due to the change in the charge state or spin state, and its relationship to the dimensional crossover and to the spin triplet superconductivity, remains elusive. Here by performing 7Li-/95Mo-nuclear magnetic resonance (NMR) spectroscopy, we directly observed the charge state which shows no signature of change in the electric field gradient (nuclear quadrupolar frequency) or in the distribution of it, thus providing direct experimental evidences demonstrating that the long mysterious metal-“insulator” crossover is not due to the charge density wave (CDW) that was thought, and the nature of the DW gapping is not CDW. This discovery opens a parallel path to the study of the electron spin state and its possible connections to other unusual properties.

Structural basis for promiscuous PAM recognition in type I-E Cascade from E. coli.

Clustered regularly interspaced short palindromic repeats (CRISPRs) and the cas (CRISPR-associated) operon form an RNA-based adaptive immune system against foreign genetic elements in prokaryotes. Type I accounts for 95% of CRISPR systems, and has been used to control gene expression and cell fate. During CRISPR RNA (crRNA)-guided interference, Cascade (CRISPR-associated complex for antiviral defence) facilitates the crRNA-guided invasion of double-stranded DNA for complementary base-pairing with the target DNA strand while displacing the non-target strand, forming an R-loop. Cas3, which has nuclease and helicase activities, is subsequently recruited to degrade two DNA strands. A protospacer adjacent motif (PAM) sequence flanking target DNA is crucial for self versus foreign discrimination. Here we present the 2.45 Å crystal structure of Escherichia coli Cascade bound to a foreign double-stranded DNA target. The 5'-ATG PAM is recognized in duplex form, from the minor groove side, by three structural features in the Cascade Cse1 subunit. The promiscuity inherent to minor groove DNA recognition rationalizes the observation that a single Cascade complex can respond to several distinct PAM sequences. Optimal PAM recognition coincides with wedge insertion, initiating directional target DNA strand unwinding to allow segmented base-pairing with crRNA. The non-target strand is guided along a parallel path 25 Å apart, and the R-loop structure is further stabilized by locking this strand behind the Cse2 dimer. These observations provide the structural basis for understanding the PAM-dependent directional R-loop formation process.

Mistagogiczny charakter odnowienia przyrzeczeń chrzcielnych

The postconciliar turn towards baptismal spirituality is visible in appreciation of the renewal ritual of baptismal promises. In the early centuries of Christianity the very presence of catechumens during the first part of Sunday liturgy and the rite of sending them away reminded the congregation of the central role of the baptismal covenant in the life of Christians. The old division into the Mass of Catechumens and Mass of the Faithful was a reflection of that. Today the Church makes a reference to Baptism in the Sunday aspersion. In the liturgical year cycle the period of paschal preparation (Lent) creates a parallel formation path for catechumens and the Christian faithful who accompany them. During the Easter Vigil, which constitutes the pivotal point of the liturgical year and the principal time for catechumens to get baptised, the whole Church renews baptismal promises. Parents and godparents renew them when children are baptised, while the youth do during Confirmation. Also the administration of Viaticum should be preceded by a renewal of the profession of faith. The renewal of baptismal promises is envisaged by a ritual celebrated during major exorcisms. The typical editions of postconciliar liturgical books provide the text of questions and suggest answers in the singular form, which implies a personalistic dimension of the renewal. It is an element of the permanent mystagogy of the Sacrament of Baptism.

Parallel All-Pairs Shortest Path Algorithm: Network Decomposition Approach

The all-pairs shortest path algorithms compute the shortest paths between all node pairs in a network. This paper presents a parallel algorithm for the all-pairs shortest path problem with a network decomposition approach. The algorithm decomposes the network into a set of independent augmented directed acyclic subnetworks that can be efficiently processed in parallel. The shortest path computation for each subnetwork provides a subset of the all-pairs shortest paths in the original network. The superiority of the new algorithm was verified through comparing its performance against that of the parallel single-origin shortest path algorithm. The execution times were compared for hypothetical and real-world networks with different sizes. A percentage of improvement in the execution time of about 50% was recorded for the transportation network of a large metropolitan area.

Fixation Strength of Caudal Pedicle Screws after Posterior Lumbar Interbody Fusion with the Modified Cortical Bone Trajectory Screw Method.

Study DesignClinical case series.PurposeIn the posterior lumbar interbody fusion (PLIF) procedure in our institute, the cephalad screw trajectory follows a mediolateral and caudocephalad directed path according to the original cortical bone trajectory (CBT) method. However, the starting point of the caudal screw is at the medial border of the pedicle on an articular surface of the superior articular process, and the trajectory takes a mediolateral path parallel to the cephalad endplate. The incidence of caudal screw loosening after PLIF with this modified CBT screw method was investigated, and significant risk factors for caudal screw loosening were evaluated.Overview of LiteratureA biomechanical study of this modified caudal screw trajectory using the finite element method reported about a 20% increase in uniaxial yield pullout load compared with the traditional trajectory. However, there has been no clinical study concerning the fixation strength of this modified caudal screw trajectory.MethodsThe subjects were 193 consecutive patients who underwent single-level PLIF with modified CBT screw fixation. Caudal screw loosening was checked in computed tomography at 6 months after surgery, and screw loosening was defined as a radiolucency of 1 mm or more at the bone-screw interface.ResultsThe incidence of caudal screw loosening after lumbosacral PLIF (46.2%) was significantly higher than that after floating PLIF (6.0%). No significant differences in sex, brand of the instruments, and diameter and length of the caudal screw were evident between patients with and without caudal screw loosening. Patients with caudal screw loosening were significantly older at the time of surgery than patients without caudal screw loosening.ConclusionsFixation strength of the caudal screw after floating PLIF with this modified CBT screw technique was sufficiently acceptable. Fixation strength after the lumbosacral procedure was not.

Kinetics and Mechanism of Oxidation of S2O32− by a Co‐Bound μ‐Amido‐μ‐Superoxo Complex

ABSTRACTIn acetate buffer media (pH 4.5–5.4) thiosulfate ion (S2O32−) reduces the bridged superoxo complex, [(NH3)4CoIII(μ‐NH2,μ‐O2)CoIII(NH3)4]4+ (1) to its corresponding μ‐peroxo product, [(NH3)4CoIII(μ‐NH2,μ‐O2)CoIII(NH3)4]3+ (2) and along a parallel reaction path, simultaneously S2O32− reacts with 1 to produce the substituted μ‐thiosulfato‐μ‐superoxo complex, [(NH3)4CoIII(μ‐S2O3,μ‐O2)CoIII(NH3)4]3+ (3). The formation of μ‐thiosulfato‐μ‐superoxo complex (3) appears as a precipitate which on being subjected to FTIR shows absorption peaks that support the presence of Co(III)‐bound S‐coordinated S2O32− group. In reaction media, 3 readily dissolves to further react with S2O32− to produce μ‐thiosulfato‐μ‐peroxo product, [(NH3)4CoIII(μ‐S2O3,μ‐O2)CoIII(NH3)4]2+ (4). The observed rate (k0) increases with an increase in [TThio] ([TThio] is the analytical concentration of S2O32−) and temperature (T), but it decreases with an increase in [H+] and the ionic strength (I). Analysis of the log At versus time data (A is the absorbance of 1 at time t) reveals that overall the reaction follows a biphasic consecutive reaction path with rate constants k1 and k2 and the change of absorbance is equal to {a1 exp(–k1t) + a2 exp(–k2t)}, where k1 > k2.

Machining of curved geometries with constant engagement tool paths

End milling of the curved surfaces is characterized by significant amount of engagement variation along the tool path which results in deflection-induced surface error on the machined components. Feed rate regulation cannot be used in this case to minimize the surface errors as it necessitates continuous change in feed rate along the tool path which deteriorates surface finish and lowers productivity. Another approach in the form of tool path modification scheme was also proposed in the literature to minimize engagement variation at corners of a pocket. This approach has been effective in reducing fluctuations of engagement at corners and cannot be applied directly in machining of curved geometries where engagement variation is continuous along the entire tool path. Keeping these limitations in focus, a new methodology is proposed in this article to minimize surface error variation that modifies machining strategy for the curved components. The strategy proposes machining of the curved components into two different stages: first, generating the modified semi-finishing geometry using algorithm proposed in this article and then producing the desired geometry using conventional contour parallel tool path. The methodology generates the modified semi-finishing geometry such that the engagement offered is constant when a finishing pass is made. The effectiveness of the proposed methodology has been verified by performing computational studies and machining experiments on typical curved geometries. It is observed that the proposed methodology is quite effective in minimizing the variation in the surface error on the machined components.

Decoupling electrical and thermal properties in antimony telluride based artificial multilayer for high thermoelectric performance

In this work, Sb2Te3/Poly(3,4-ethylenedioxythiophene)/Sb2Te3 sandwich structure was artificially fabricated. This leads to a simultaneous increase of electrical conductivity and decrease of thermal conductivity by tailoring electric flow along the more-electrically conductive parallel path and thermal flow blocked across the less-thermally conductive perpendicular direction. The maximum of thermoelectric figure of merit was increased by 116%, reaching 1.3 at 523 K.

Hybrid-Excited Doubly Salient Synchronous Machine With Permanent Magnets Between Adjacent Salient Stator Poles

A novel stator hybrid-excited, parallel flux path, synchronous machine of doubly salient topology is proposed. It has the novel features of: 1) hybrid dc field and permanent magnet (PM) excitation in the stator; 2) magnets placed in the slots between adjacent salient stator poles; and 3) the magnetic poles of PMs arranged, such that the flux premagnetizes the stator, but it is in a direction to oppose the dc excitation flux. The electromagnetic characteristics of the machine are analyzed on open-circuit and load. Since the new machine topology is developed from the variable-flux machine (VFM), a comparison of their electromagnetic torque and machine losses is conducted. The average electromagnetic torque of the hybrid-excited machine can be increased by 18% for fixed copper loss in comparison with the VFM due to the reduction of magnetic saturation in the stator. It is also shown that at high temperatures some risk of PM demagnetization exists when excited with dc and armature currents due to fringing flux that exists between the stator and the rotor poles. However, this affects only a very small area of the PMs. The performance of the hybrid-excited machine is predicted by a 2-D finite-element analysis and experimentally validated.

Space Time State Trellis Codes for MIMO Systems Using Reconfigurable Antennas

We present a novel class of space time trellis codes based on super quasi-orthogonal space time codes for a reconfigurable antenna system. We call them space time state trellis codes (STSTCs). We design for 4 trellis states and both 2 and 4 branch trellis structures for BPSK and QPSK constellations. The proposed codes take advantage of the additional degrees of diversity offered by reconfigurable antennas and changing propagation states. They achieve full rate, full diversity and high coding gain. Simulation results demonstrate their good performance. STSTCs achieve the diversity order expected of four transmit antennas while using only two reconfigurable transmit antennas. Our code out performs the existing super orthogonal space time trellis code, which fails to achieve full diversity in a reconfigurable antenna system. The proposed 4 trellis state STSTC is designed based on the following performance criteria: minimum coding gain distance of the minimum return path (CGD MRP), performance factor (PF), rank of the partial valid path (RPVP) on top of traditional minimum coding gain distance of parallel path (CGD PP). We show through analysis and simulations that minimum CGD PP is not a sufficient criteria and that additional performance gains are provided by considering the CGD MRP.

Argon metastables in HiPIMS: validation of the ionization region model by direct comparison to time resolved tunable diode-laser diagnostics

The volume plasma interactions of high power impulse magnetron sputtering (HiPIMS) discharges operated with a Ti target is analyzed in detail by combining time-resolved diagnostics with modeling of plasma kinetics. The model employed is the ionization region model (IRM) with an improved and detailed treatment of the kinetics of the argon metastable (Arm) state, called m-IRM. The diagnostics used is tunable diode-laser absorption spectroscopy (TD-LAS) of the Arm state, which gives the line-of-sight density integrated along the laser path parallel to the target surface. The TD-LAS recordings exhibit quite complex temporal evolutions Arm(t), with distinct features that are shown to reflect the time evolution of the plasma (the electron density and temperature), and of the argon gas (gas rarefaction and refill). The Arm(t) function is thus a tracer for the most important aspects of internal discharge physics, and therefore suitable for model testing and validation. The IRM model is constructed to be locked to obey specific experimental macroscopic discharge parameters, specifically the discharge current ID(t) and the voltage UD(t). It has to this purpose been run with the appropriate process gas pressures (from 0.67 to 2.67 Pa), with the experimentally applied voltage pulse profiles UD(t), and with the resulting current pulse profiles ID(t) (with maxima from 0.5 to 70 A). It is shown that the model reproduces the features in the TD-LAS measurements: both the Arm(t) evolution in single pulses, and how the pulse shapes change with gas pressure and with pulse amplitude. The good agreement between the measurements and model output is in this work taken to validate the basic assumptions of the m-IRM. In addition, the m-IRM results have been used to unravel the connections between volume plasma kinetics and various features recorded in the TD-LAS measurement, and to generalize the foremost characteristics of the studied discharges.

Transit Time Multipath Ultrasonic Flowmeter: An Issue on Acoustic Path Arrangement

The multipath ultrasonic flow meter using transit time measurement is being widely used for industrial gas flow measurement. Since the AGA report no. 9 has released, the application of this flowmeter in natural gas metering system has become a technical standard. Currently, the commerical multipath ultrasonic flowmeter employs parallel acoustic path arrangement which consists of four, five or six pairs of ultrasonic transducer. This paper discusses an issue on the acoustic path arrangement of multipath ultrasonic flowmeter in an asymmetric flow profile. From this study, the parallel path arrangement gives relatively inconsistent measurement results when the flow velocity profile was asymmetric.

An efficient contour parallel tool path generation for arbitrary pocket shape without uncut regions

With the aim of improving productivity in pocket machining the uncut regions are one of the most influencing factors on the tool path length and cutting time. We are interested in two kinds of uncut regions; the corner uncuts that appear between the passes and the center uncut. In this paper we have developed a new analytical model of tool path for machining pockets in 2½D with contour parallel offset for an arbitrary shape of pocket boundary whether line-line or line-arc. For the corner uncuts we propose a novel coefficient which ensures the ideal cover area between passes without letting behind any uncut region. For the center uncut we propose an automatically additional reduced looping with a passage segment that depends on the center uncut region geometry. For the purpose of the validation of this new developed method some selected numerical examples are presented. The obtained results show that our new approach minimizes both the tool path length and the machining time compared to other methods. Thus this new method offers an efficient contour parallel offset of tool path generation and an optimized machining.

Path planning and tracking for vehicle parallel parking based on preview BP neural network PID controller

In order to diminish the impacts of external disturbance such as parking speed fluctuation and model uncertainty existing in steering kinematics, this paper presents a parallel path tracking method for vehicle based on preview back propagation (BP) neural network PID controller. The forward BP neural network can adjust the parameters of PID controller in real time. The preview time is optimized by considering path curvature, change in curvature and road boundaries. A fuzzy controller considering barriers and different road conditions is built to select the starting position. In addition, a kind of path planning technology satisfying the requirement of obstacle avoidance is introduced. In order to solve the problem of discontinuous curvature, cubic B spline curve is used for curve fitting. The simulation results and real vehicle tests validate the effectiveness of the proposed path planning and tracking methods.