Slow Propagation Research Articles

Slow Propagation in Some Disordered Quantum Spin Chains

We introduce the notion of transmission time to study the dynamics of disordered quantum spin chains and prove results relating its behavior to many-body localization properties. We also study two versions of the so-called Local Integrals of Motion (LIOM) representation of spin chain Hamiltonians and their relation to dynamical many-body localization. We prove that uniform-in-time dynamical localization expressed by a zero-velocity Lieb-Robinson bound implies the existence of a LIOM representation of the dynamics as well as a weak converse of this statement. We also prove that for a class of spin chains satisfying a form of exponential dynamical localization, sparse perturbations result in a dynamics in which transmission times diverge at least as a power law of distance, with a power for which we provide lower bound that diverges with increasing sparseness of the perturbation.

Extremely Slow Fatigue Crack Propagation of High Strength steel in Very High Cycle Regime

Extremely Slow Fatigue Crack Propagation of High Strength steel in Very High Cycle Regime

Research on analogue of electromagnetically induced transparency effect based on asymmetric structure all-dielectric metamaterial

The electromagnetically induced transparency (EIT), which is a result of destructive interference between different excitation paths in a three-energy-level atomic medium, makes opaque probe light transparent over a range of frequencies. As this EIT effect is usually accompanied with strong dispersion, it has potential applications such as slow light propagation, optical buffering, nonlinear optics, optical sensing, etc. However, for conventional quantum EIT effect which requires stable gas lasers and low temperature environment, the implementation of EIT in chip-scale applications is severely hampered by the scathing experimental requirements. Recently, the EIT-like effect in metamaterials, which are constructed by designing the artificial subwavelength functional elements and arranging the spatial sequences, attracts tremendous attention because of its advantages, such as room temperature manipulability, large bandwidth, and small sizes. In addition, the high-quality factor(<i>Q</i>) value obtained by EIT-like effect has great significance in designing the metamaterial-based devices. In this paper, we design an EIT-like metamaterial with such a structure. The unit cell of the proposed metamaterial is constructed by two asymmetric silicon blocks embedded on a silicon dioxide substrate. Meanwhile, we analyze its optical properties and EIT-like effects by using three-dimension (3D) FDTD method. Based on the coupled Lorentz model, the EIT-like effect of the designed metamaterial is investigated. Then, by employing the electric field distribution on the surface of the metamaterial, and combining with the three-level atomic system, the mechanism of the EIT-like effect is analyzed in detail. We find that the EIT-like effect in the proposed metamaterial has high <i>Q</i> value (<i>Q</i> ≈ 8616) and the high transmission (<i>T</i> = 96%). By changing the length of the silicon block to destroy the asymmetry of the metamaterial structure, an active tuning EIT-like effect is realized. Furthermore, the metamaterial structure has the advantages of low loss, easy preparation, and active-controllability. This study represents an innovative approach to designing the EIT-like metamaterial, which is expected to be useful for designing active tunable slow-light devices and highly sensitive optical sensors.

Home Energy Management Algorithm Based on Deep Reinforcement Learning Using Multistep Prediction

In recent years, home energy management systems (HEMS), which enable the automatic control of electrical equipment and home appliances, have been attracting attention as a method for saving electricity at home. HEMS achieve energy saving by visualizing energy consumption at home and controlling energy consuming equipment such as air conditioners. The optimum control law is difficult to attain, owing to uncertainties related to power demand and power supply from the electrical equipment. Deep reinforcement learning has been used to address energy optimization problems for home environments. However, in HEMS, several components such as heating, ventilation, and air conditioning (HVAC) systems, storage batteries, and electric water heaters are simultaneously controlled, and therefore, the action space becomes extremely large. Therefore, it may not be feasible to fully learn the rare experience using traditional deep reinforcement learning methods due to the large size of the state-action space and slow propagation of delayed rewards. In this study, we propose an energy management algorithm that uses the Dual Targeting Algorithm to strongly learn the experience of acquiring high returns using the quick propagation of delayed rewards via multistep returns. The proposed energy management algorithm is applied to a HEMS learning experiment to control a storage battery and an HVAC system, and its performance is compared to that of a Deep Deterministic Policy Gradient-based energy management system. As a result, it is confirmed that the proposed method can reduce the number of hours deviating from the comfort temperature range by about 17% compared to the existing method.

Mass propagation through direct and indirect organogenesis in three species of genus Zephyranthes and ploidy assessment of regenerants through flow cytometry.

Genus Zephyranthes consists of economically important plant species due to their high ornamental value and presence of valuable bioactive compounds. However, this genus propagates by asexual division only which gives slow propagation rate. Plant tissue culture has the potential to provide efficient techniques for rapid multiplication and genetic improvement of the genus. In this work, a dual in vitro regeneration system through callus mediated shoot regeneration and direct shoot regeneration in species Zephyranthes candida, Zephyranthes grandiflora and Zephyranthes citrina was investigated. Bulb, leaf and root explants were cultured on Murashige and Skoog (MS) medium amended with different plant growth regulators (PGR's) viz. 2,4-dichlorophenoxyacetic acid (2,4-D), 1-Naphthalene acetic acid (NAA), 6-benzyl amino purine (BAP), N-phenyl-N'-1,2,3 -thiadiazol-5-ylurea (TDZ), 6-Furfuryl- aminopurine (KIN) alone or in combinations for callus induction and regeneration. Only bulb explants showed callus induction and regeneration response on different PGR combinations with a varied response in callus induction percentage, callus color and callus texture. Creamish compact callus (CC) was induced on 2 mg L[Formula: see text] 2,4-D, brown friable callus (BF) on 2 mg L[Formula: see text] NAA + 1 mg L[Formula: see text] BAP and green friable callus (GF) callus on 1 mg L[Formula: see text] KIN + 3 mg L[Formula: see text] NAA. The maximum shoot multiplication from different callus types (indirect organogenesis) was achieved on 2 mg L[Formula: see text] BAP alone without combinations. Bulb explants of Z. grandiflora induced maximum callus induction percentage (86.4%) and shoot regeneration percentage (83.5%) with the maximum 08 shoots per 150 mg callus mass. The induction and regeneration response was followed in the order of Z. grandiflora > Z. candida > Z. citrina. Similarly, maximum direct organogenesis from bulb explants was obtained in Z. grandiflora (93.3%) followed by Z. candida (91.5%) and Z. citrina (90.4%) on 3 mg L[Formula: see text] TDZ amended MS media. Adventitious root induction was achieved on 2 mg L[Formula: see text] IBA with a maximum of 8 roots per shoot. The in vitro raised plantlets were successfully acclimatized in the field with 85% survival efficiency. The genome size (2C DNA content) of the field-grown plants and in vitro regenerated plants, evaluated through flow cytometry technique, were similar and showed no ploidy changes. An efficient mass propagation protocol was established for obtaining plants with unaltered genome size in the three species of Zephyranthes.

Keep, break and breakout in food chains with two and three species.

In this paper, through Rosenzweig-MacArthur predator-prey model we study the cyclic coexistence and stationary coexistence and discuss temporal keep and break in the food chain with two species. Then species' diffusion is considered and its effect on oscillation and stability of the ODE system is studied concerning the two different states of coexistence. We find in cyclic coexistence temporal oscillation of population is translated into spatial oscillation although there is fluctuation at the beginning of population waves and finally more stable population evolution is observed. Furthermore, the presence of spatial diffusion of the species can lead to steady wavefront propagation and alter the population distribution in the food chain with two and three species. We show that lower-level species with slow propagation will limit higher-level species and help to keep food chain in space, but through fast propagation lower-level species can survive in a new space without predation and realize a breakout in the linear food chain.

SLOW SURFACE ELECTROMAGNETIC WAVES AT THE METASURFACE / DISSIPATIVE DIELECTRIC INTERFACE

The possibilities of the slow surface electromagnetic waves propagation along the flat boundary of a metasurface with a dissipative dielectric are studied. The metasurface is a thin flat slab of metamaterial with simultaneously negative permittivity and permeability with "amplification". All media were assumed to be isotropic. Dispersion dependences are obtained for the eigenmodes of such a waveguide structure. The possibility of full compensation of the energy losses of surface waves by the appropriate choice of the “gains” values is demonstrated.

Effects of magnetogastrography sensor configurations in tracking slow wave propagation

Magnetogastrography (MGG) is a non-invasive method of assessing gastric slow waves (SWs) by recording the resultant magnetic fields. MGG can capture both SW frequency and propagation, and identify SW dysrhythmias that are associated with motility disorders. However, the impact of the restricted spatial coverage and sensor density on SW propagation tracking performance is unknown. This study simulated MGG using multiple anatomically specific torso geometries and two realistic SW propagation patterns to determine the effect of different sensor configurations on tracking SW propagation. The surface current density mapping and center-of-gravity tracking methods were used to compare four magnetometer array configurations: a reference system currently used in GI research and three hypothetical higher density and coverage arrays. SW propagation patterns identified with two hypothetical arrays (with coverage over at least the anterior of the torso) correlated significantly higher with simulated realistic 3 cycle-per-minute SW activity than the reference array (p = 0.016, p = 0.005). Furthermore, results indicated that most of the magnetic fields that contribute to the performance of SW propagation tracking were located on the anterior of the torso as further increasing the coverage did not significantly increase performance. A 30% decrease in sensor spacing within the same spatial coverage of the reference array also significantly increased correlation values by approximately 0.50 when the signal-to-noise ratio was 5 dB. This study provides evidence that higher density and coverage sensor layouts will improve the utility of MGG. Further work is required to investigate optimum sensor configurations across larger anatomical variations and other SW propagation patterns.

Propagation of gas explosions of different volumes in a large test tunnel

ABSTRACT With the continuous development of coal science and technology, gas explosion disasters have become an important factor in restricting efficient and intensive coal mining which threaten safe production in coal mines. In a large test tunnel, gas explosion propagation tests were conducted by taking gas-air mixtures with different volumes of 50 m3, 100 m3, and 200 m3 as explosion sources. The results demonstrate that, at a given gas concentration, the larger the volume of the gas-air mixture, the stronger the explosive power and the further the flame propagates. The pressure near the explosion source does not necessarily the maximum value in the whole gas explosion process. In the increasing propagation distance, explosion pressure does not linearly attenuate but fluctuates along the tunnel. The flame propagation velocity increases and then decreases throughout the explosion in three stages: a slow propagation stage at the beginning of an explosion, an accelerated propagation stage, and a decelerated propagation stage before flame extinction. Shock waves generated by a gas explosion interact and influence explosion flames and there is a positive feedback mechanism that promotes their mutual interaction. The conclusions provide an important theoretical basis for preventing gas explosion accidents and formulating active measures for explosion suppression in underground coal mines.

The effect of chronic nausea on gastric slow wave spatiotemporal dynamics in children

Chronic nausea in adolescents with functional gastrointestinal disorders is an increasingly reported but poorly understood symptom that negatively affects quality of life. Functional gastrointestinal disorders are known to correlate closely with slow wave rhythm disturbances. The ability to characterize gastric electrophysiologic perturbations in functional nausea patients could provide potential diagnostic and therapeutic tools for nausea patients. We used high-resolution electrogastrograms (HR-EGG) to measure gastric slow wave parameters in pediatric chronic nausea patients and healthy subjects both pre- and postprandial. We computed the dominant frequency, percentage power distribution, gastric slow wave propagation direction, and speed from HR-EGG. We observed significant differences in the dominant frequency and power distributed in normal and bradyarrhythmia frequency ranges when comparing patients and healthy subjects. Propagation patterns in healthy subjects were predominantly anterograde, while patients exhibited a variety of abnormalities including retrograde, anterograde, and disrupted patterns. There was a significant difference in the preprandial mean slow wave direction between healthy subjects (222°±22°) and patients (103°±66°; p˂0.01), although the postprandial mean direction between healthy subjects and patients was similar (p=0.73). No significant difference in slow wave propagation speed was found between patients and healthy subjects in either pre- (p=0.21) or postprandial periods (p=0.75). The spatiotemporal characterization of gastric slow wave activity using HR-EGG distinguishes symptomatic chronic nausea patients from healthy subjects. This characterization may in turn inform and direct clinical decision-making and lead to further insight into its pathophysiology.

Unique Slow Crack Growth Behavior of Isotactic Polypropylene: The Role of Shear Layer-Spherulites Layer Alternated Structure.

With the development of polymer science, more attention is being paid to the longevity of polymer products. Slow crack growth (SCG), one of the most important factors that reveal the service life of the products, has been investigated widely in the past decades. Here, we manufactured an isotactic polypropylene (iPP) sample with a novel shear layer–spherulites layer alternated structure using multiflow vibration injection molding (MFVIM). However, the effect of the alternated structure on the SCG behavior has never been reported before. Surprisingly, the results showed that the resistivity of polymer to SCG can be enhanced remarkably due to the special alternated structure. Moreover, this sample shows unique slow crack propagation behavior in contrast to the sample with the same thickness of shear layer, presenting multiple microcracks in the spherulites layer, which can explain the reason of the resistivity improvement of polymer to SCG.

In-depth comparison of polyamide 12 parts manufactured by Multi Jet Fusion and Selective Laser Sintering

Abstract Recently, the possibility of producing medium-to-large batches has increased the interest in polymer powder bed fusion technologies such as selective laser sintering (SLS) and multi jet fusion (MJF). Only scant data about the characterization of parts produced by MJF can be found in the literature, and fatigue behavior studies are absent. This study analyzes the material properties of Polyamide 12 (PA12) powders and printed specimens using both SLS and MJF technologies. The morphology, crystalline phases, density, porosity, dimensional accuracy, and roughness are measured and compared; tensile and fatigue tests are performed to assess the effect of the technologies on the mechanical behavior of the produced structures. In addition, lattice structure specimens obtained by different geometric modeling approaches are tested to understand the influence of modeling methods on the fatigue life. The PA12 powders printed by both SLS and MJF mainly show by X-Ray Diffraction γ-phase and a small shoulder of α-phase. The crystallinity decreases after printing the powders both in SLS and MJF technology. The printed parts fabricated using the two technologies present a total porosity of 7.95% for SLS and 6.75% for MJF. The roughness values are similar, Ra ≈ 11 µm along the building direction. During tensile tests, SLS samples appear to be stiffer, with a lower plastic deformation than MJF samples, that are tougher than SLS ones. Fatigue tests demonstrate higher dispersion for MJF specimens and an enhancement of fatigue life for both SLS and MJF printed lattice structures modeled with a novel geometric modeling approach that allows the creation of smoother surfaces at nodal points. Scanning electron microscopy on fracture surfaces shows a brittle failure for the SLS tensile specimens, a more ductile failure for the MJF tensile specimens, a crazing failure mechanism for the SLS fatigue tested samples, and a crack initiation and slow growth and propagation for the MJF fatigue tested samples.

Slow propagation of 2 GHz acoustical waves in a suspended GaAs phononic waveguide on insulator

Optoelectronic oscillators have dominated the scene of microwave oscillators in the last few years thanks to their great performances regarding frequency stability and phase noise. However, miniaturization of such devices is an up-to-date challenge. Recently, devices based on a phonon–photon interaction have gathered a lot of interest thanks to their extreme compactness and working frequency directly in the GHz. In this frame, a still-missing element to obtain long-term frequency stability performances is an on-chip delay within the feedback loop. Here, we experimentally show filtering and slow propagation of 2 GHz acoustic waves on a Gallium Arsenide membrane heterogeneously integrated on a silicon wafer. By engineering the dispersion of an acoustical waveguide, we evidence a group velocity below 1000 m/s for the mode able to propagate. Thus, an integrated delay implementation is at reach for potential improvement of opto-acoustic devices such as optomechanical oscillators or wireless applications.

The role of atmospheric forcings and WRF physical set-up on convective initiation over Córdoba, Argentina

The accurate determination of the location and timing of convective initiation (CI) is a crucial aspect of forecasting and high impact weather warning systems associated with deep convection. Central Argentina, particularly the Sierras de Córdoba (SDC), is characterized by the regular occurrence of deep convective cells that reach supercell characteristics producing large hail and occasionally tornadoes.In order to analyze the sensitivity of the CI over SDC, an ensemble of 12 simulations with the WRF model at convection-permitting resolution (3 km.) was carried out to study a marginal supercell initiated on October 17, 2017 at the SDC foothills. The ensemble was built using 3 different microphysics (MP) parameterizations (WSM6, Thompson and Morrison) and 2 planetary boundary layer (PBL) parameterizations (Yonsei University and Mellor Yamada Janjic). Also, the sensitivity of initial and boundary conditions is considered by forcing the model with 2 different global analyses: the European Centre for Medium-Range Weather Forecast (ECMWF) model, and the Global Data Assimilation System (GDAS).The two different forcing data show low-level moisture differences, which later modulate the life-cycle of the simulated cells. A tracking algorithm was used to capture their life-cycle, and CI was detected at both the hills and the plains. Simulations forced with ECMWF analyses tend to show better results with characteristics closer to the ones observed including: initiation over the eastward slope of SDC, stronger cells and slow propagation. Among all simulations analyzed, the best performance was obtained with the combination of Thompson MP and Yonsei University PBL schemes.

An analysis of the propagation of impact elastic waves in isotropic and anisotropic materials

In order to study the propagation law of impact elastic waves on the platform better, an experimental platform is built with isotropic and anisotropic materials to explore the propagation law of impact elastic waves on the platform. The influences of platform materials, yarn arrangement directions, comparisons of longitudinal waves and transverse waves and lamination experiments on the propagation of impact stress waves are analyzed, respectively. The results of experiments show that the transverse waves along the fiber arrangement direction have the fastest propagation speed and the longitudinal waves have the slowest propagation speed in anisotropic materials. The speed of stress waves in lamination experiment is arranged from large to small: the epoxy resin lamination, the organic glass lamination, an epoxy resin thick plate, an organic glass thick plate. Adding arranged fibers with high acoustic velocity regularly when designing impact-resistant composite materials is beneficial to the transmission and spread of elastic waves. The impact isolating materials can be whole designed as a layered structure. A certain number of 90° zigzag structures can also be arranged at the edge of the materials to enhance the effect of protection.

Space-based microgravity experiments on flame spread over randomly distributed n-decane-droplet clouds: Anomalous behavior in flame spread

The first combustion experiments aboard the Japanese Experiment Module “Kibo” on the International Space Station, titled “Elucidation of Flame Spread and Group Combustion Excitation Mechanism of Randomly Distributed Droplet Clouds (Group Combustion)” were conducted in 2017 in order to bridge the gap between droplet combustion and spray combustion through flame spread over droplet arrays, droplet-cloud elements and randomly distributed droplet clouds. n-Decane droplets were distributed randomly on a SiC-fiber lattice, and the flame spread and group-combustion excitation were observed. During the flame spread near the group-combustion-excitation limit, two types of anomalous behavior appeared: large-scale ignition and re-burning by a slow flame propagation in a burned area. We successfully simulated similar phenomena by a flame-spread experiment using droplet-cluster arrays. The large-scale ignition phenomenon is caused by the ignition of a flammable mixture generated by heating multiple droplets existing outside the local flame-spread limit. The re-burning phenomenon by the slow flame propagation in a burned area is caused by the ignition of a flammable mixture diluted by the combustion products after the radiative extinction of the group flame. There is the possibility of a cool-flame appearance in both phenomena.

Accelerating Heat-Initiated Radical Reactions of Organic Halides with Tin Hydride Using Flow Microreactor Technologies

AbstractWe herein report that flow microreactors can promote an efficiency of radical chain reactions. The chain reactions with a fast propagation step can be accelerated by virtue of an efficient heat-transfer character of the microreactors, whereas the yield of those reactions with a slow propagation step was increased by flow microreactors. Moreover, the yield was further increased by a sequential addition of the initiators, which was allowed by a flow-sequential-addition system.

Toughening alpha-Ti by dislocation-induced phase transformation at crack tips

In this paper, molecular dynamics simulation was used to investigate the crack propagation along the {101‾1} twin boundary in titanium bi-crystals during uniaxial tensile deformation. The whole deformation process can be divided into two periods according to the crack propagation speed: (1) the quick crack propagation period in the early deformation stage and (2) the slow crack propagation period in the later deformation stage. The results show although the pyramidal and basal stacking faults induced from crack tips can reduce the stress concentration in the early deformation stage, they are nonetheless inadequate to inhibit the quick crack propagation with a velocity over 100 m/s. Comparatively, the formation of new face-centered cubic (FCC) grains at crack tips in the later deformation stage can blunt the crack, retard crack propagation and thus promote the toughness of the material. The nucleation and growth of the newly formed FCC grains are controlled by different mechanisms. During the quick crack propagation period, complex interactions between <c+a> partial dislocations on pyramidal planes and <a> dislocations on prismatic planes induce retained stacking faults in FCC lamella and new pyramidal stacking faults in hexagonal close-packed (HCP) matrix. The retained stacking faults develop into FCC nuclei as the tensile strain increases. During the slow crack propagation period, the FCC nuclei grow towards HCP phase and develop into a coarser grain that pins the further propagation of the adjacent crack tip. The growth of FCC nuclei is governed by a prismatic-type phase transformation mechanism, which involves atomic shear, shuffle and extra lattice distortion.

Analisis Mutu Sie Reuboh Dalam Kemasan (Ready to Eat) Selama 7 Hari Penyimpanan

Sie reuboh is a traditional cuisine from Aceh Besar district which use red meat, tallow, vinegar and some blended spices. Normally, Acehnese cooks this cuisine in with traditional clay pot. As cooking utensil, clay pot is vulnerable to breakage and has slow heat propagation compared to stainless steel pot which has long usage and good heat conductor. The use of packaging such as nylon plastic and aluminum foil in storage is also expected to affect the quality of sie reuboh. This study aims to find out sensory profile of produced sie reuboh by using ten attributes (colour/brightness, aroma (sour, spicy, meaty), flavor (hot spicy, sour, salty, umami) and texture (tenderness, chewiness). Sie reuboh was cooked in two types of cooking ware (earth clay pot and stainless steel pot) and then store in nylon and aluminum foil packaging for 7 days. The obtained data is statistical analyzed with ANOVA and DMRT. The results showed that attribute sour aroma, hot spicy flavor, umami and tenderness of sie reuboh cooked with stainless steel has higher notes, whereas other attributes showed no significant effect. Type of packaging also showed no significant effect for these ten attributes except sour aroma. As conclusion, it can be stated that stainless steel provides sie reuboh with better sensory properties compare to clay pot.

Scalable Adaptive Networking for the Internet of Underwater Things

Internet-of-Underwater-Things (IoUT) systems comprising tens or hundreds of underwater acoustic communication nodes will become feasible in the near future. The development of scalable networking protocols is a key enabling technology for such IoUT systems, but this task is challenging due to the fundamental limitations of the underwater acoustic communication channel: extremely slow propagation and limited bandwidth. The aim of this article is to propose the JOIN protocol to enable the integration of new nodes into an existing IoUT network without the control overhead of typical state-of-the-art solutions. The proposed solution is based on the capability of a joining node to incorporate local topology and schedule information into a probabilistic model that allows it to choose when to join the network to minimize the expected number of collisions. The proposed approach is tested in numerical simulations and validated in two sea trials. The simulations show that the JOIN protocol achieves fast convergence to a collision-free solution, fast network adaptation to new nodes, and negligible network disruption due to collisions caused by a joining node. The sea trials demonstrate the practical feasibility of this protocol in real underwater acoustic network deployments and provide valuable insight for future work on the tradeoff between control overhead and reliability of the JOIN protocol in a harsh acoustic communication environment.