Switching Phenomena Research Articles

The Phenomenon Of Code Switching And Code Mixing In English Learning Classroom

The diversity of languages in Indonesia has sundry errors such as gaps, errors in interpreting other languages, and others. It means, it also applies when in the process of learning foreign languages at school, especially English. Thus, learning English is difficult to build a positive spirit in learning, making students active and responsive in the learning process. Therefore, this study focuses on examining the types of code-switching and code-mixing in learning English in schools. This study uses a qualitative paradigm, using a descriptive case study type of research. Therefore, the researcher sets the goal to describe the data as it occurs in the phenomenon under study. This study is the occurrence of code-switching and code-mixing events in learning English at school. In this study, the researcher used guided semi structured interviewed as a data collection technique. The data from this study was analyzed based on the steps used, namely identifying the data, classifying the data, and describing the data according to the research objectives. The results of this study are the determinants of code-switching and code-mixing from teachers or students. Then, there are types of each between code-mixing and code-switching.

Experimental study on flow and turbulence characteristics of jet impinging on cylinder using three-dimensional Lagrangian particle tracking velocimetry

When a round jet impinges on a convex cylindrical surface, complex three-dimensional (3D) flow structures occur, accompanied by the Coanda effect. To characterize the flow and turbulence properties of the general system, ensemble averages of 3D Lagrangian particle tracking velocimetry measurements were taken. The radial bin-averaging method was used in post-processing the tracked particles and corresponding instantaneous velocity vectors to generate appropriate ensemble-averaged statistics. Two impinging angles were selected, and at a fixed Reynolds number, the ensemble-averaged volumetric velocity field and turbulent stress tensor components were measured. The flow and turbulence characteristics of the impinging jet on the cylinder were notably different based on the impinging angle, especially in the downstream region. Surprisingly, the attached wall jet with a half-elliptic shape was abruptly thickened in the wall-normal direction, similar to the axis switching phenomenon observed in elliptic jets in the case of oblique impingement. In the jet-impinging region, the flow spread in all directions with high mean vorticity values. With the development of a 3D curved wall jet, both the Coanda effect and centrifugal force played a significant role in the flow behavior. A notable feature of the self-preserving region was the similarity of mean velocity profiles with scaling by the maximum velocity and the jet half-width for both impinging angle cases. Local isotropy of turbulent normal stresses was observed in this region, supporting the existence of self-preservation in the 3D curved wall jet. The volumetric ensemble-averaged Reynolds stress tensor revealed strong inhomogeneous turbulence in the boundary layer region and the curvature effect on the Reynolds shear stress in the free shear layer.

Geometric Phase Flat Optical Gratings with High Diffraction Angle Based on Dual‐Frequency Nematic Liquid Crystal

AbstractDiffractive optical elements (DOEs) are increasingly used as lightweight and compact solutions in photonic devices. Steering of light and manipulation of the polarization can be efficiently obtained with the help of photo‐aligned liquid crystal (LC) devices. 1D LC diffraction gratings are studied that are based on the geometric phase principle and demonstrate that the optical functionality can be substantially broadened by using dual frequency LC. Switching between a highly efficient diffractive and a transmissive state is obtained by adjusting the frequency of the applied electric field. Compared to commonly studied 1D nematic LC diffraction gratings, the steering efficiency over large diffraction angles is strongly increased. By using an appropriate electric‐field treatment, the efficiency for first‐order diffraction of red light over an angle of 12.6° increases from 60% to 90%. Moreover, additional switching phenomena are observed at intermediate voltage treatments, leading to enhanced tunability of the DOEs. The origin of this behavior is explained with the help of finite element Q‐tensor simulations for the director configuration.

Anisotropic mass transport enables distinct synaptic behaviors on 2D material surface

Anisotropy is an intrinsic property in crystals with low structural symmetry, and such well-textured materials usually show distinct electronic transport and optical properties along different lattice orientations, offering wide applications in electronic and photonic devices. As a typical low-symmetry materials, crystalline GeSe with orthorhombic structure shows large electric and optical anisotropies. In this work, we take advantage of the anisotropic mass transport and filamentary growth of Ag ions on the GeSe surface to fabricate planar memristive devices which show directional memory and transient switching phenomena. The anisotropic switching behaviors stem from the distinct morphology of metallic filaments that are directionally dependent on the mobility of ions, e.g., ions diffusing along the low-barrier direction tend to form stark conductive channels while those with low mobility only entail slim and weak dendrites, which have been clearly observed under electronic microscopy. The functionality could be utilized to mimic various synaptic events, such as long-term memory enabled by stable conductive channels and short-term memory by the spontaneous rupture of weak filaments, all implemented in one physical device. Two integration schemes based on the anisotropic devices are designed and demonstrated for different application scenarios, paving the way for its applications in multifunctional brain-inspired computing systems.

Quasi-soliton control in optical lattices with longitudinal exponentially modulation

The dynamical evolution of one-dimensional quasi-soliton in Kerr-type linear-nonlinear optical lattices with the exponential asymptotically longitudinal modulation is investigated. The optical lattice features both the transverse linear refractive index modulation and the nonlinear coefficient periodically modulation. The analytical solutions of the integral beam center, the mean square of the beam width, and the critical incident angle are obtained by adopting the effective particle approach. The dynamical trapping and switching phenomena have been observed. Moreover, the introduction of the longitudinal modulation improves greatly the mobility of the soliton. The propagation states of the quasi-soliton can be controlled by varying a variety of parameters, such as the depths of the linear nonlinear lattices, the form factor and the incident angle of soliton, as well as the asymptotic rate of longitudinal modulation. Thus our results offer a new opportunity for the all optical manipulation of light beam.

NiSi: New Venue for Antiferromagnetic Spintronics.

Envisaging antiferromagnetic spintronics pivots on two key criteria of high transition temperature and tuning of underlying magnetic order using straightforward application of magnetic field or electric current. Here, weshow that NiSi metal can provide suitable new platform in this quest. First, ourstudy unveils high temperature antiferromagnetism in single crystal NiSi with TN ⩾ 700 K. Antiferromagnetic order in NiSi is accompanied by the non-centrosymmetric magnetic character with small ferromagnetic component in a-c plane. Second, wefind that NiSi manifests distinct magnetic and electronic hysteresis responses to field applications due to the disparity in two moment directions. While magnetic hysteresis is characterized by one-step switching between ferromagnetic states of uncompensated moment, electronic behavior is ascribed to metamagnetic switching phenomena between non-collinear spin configurations. Importantly, the switching behaviors persist to high temperature. The properties underscore the importance of NiSi in the pursuit of antiferromagneticspintronics. This article is protected by copyright. All rights reserved.

Linear and symmetric synaptic weight update characteristics by controlling filament geometry in oxide/suboxide HfOx bilayer memristive device for neuromorphic computing

Memristive devices have been explored as electronic synaptic devices to mimic biological synapses for developing hardware-based neuromorphic computing systems. However, typical oxide memristive devices suffered from abrupt switching between high and low resistance states, which limits access to achieve various conductance states for analog synaptic devices. Here, we proposed an oxide/suboxide hafnium oxide bilayer memristive device by altering oxygen stoichiometry to demonstrate analog filamentary switching behavior. The bilayer device with Ti/HfO2/HfO2−x(oxygen-deficient)/Pt structure exhibited analog conductance states under a low voltage operation through controlling filament geometry as well as superior retention and endurance characteristics thanks to the robust nature of filament. A narrow cycle-to-cycle and device-to-device distribution were also demonstrated by the filament confinement in a limited region. The different concentrations of oxygen vacancies at each layer played a significant role in switching phenomena, as confirmed through X-ray photoelectron spectroscopy analysis. The analog weight update characteristics were found to strongly depend on the various conditions of voltage pulse parameters including its amplitude, width, and interval time. In particular, linear and symmetric weight updates for accurate learning and pattern recognition could be achieved by adopting incremental step pulse programming (ISPP) operation scheme which rendered a high-resolution dynamic range with linear and symmetry weight updates as a consequence of precisely controlled filament geometry. A two-layer perceptron neural network simulation with HfO2/HfO2−x synapses provided an 80% recognition accuracy for handwritten digits. The development of oxide/suboxide hafnium oxide memristive devices has the capacity to drive forward the development of efficient neuromorphic computing systems.

Quantitative Analysis of Isoform Switching in Cancer.

Over the past 8 years, multiple studies examined the phenomenon of isoform switching in human cancers and discovered that isoform switching is widespread, with hundreds to thousands of such events per cancer type. Although all of these studies used slightly different definitions of isoform switching, which in part led to a rather poor overlap of their results, they all leveraged transcript usage, a proportion of the transcript's expression in the total expression level of the parent gene, to detect isoform switching. However, how changes in transcript usage correlate with changes in transcript expression is not sufficiently explored. In this article, we adopt the most common definition of isoform switching and use a state-of-the-art tool for the analysis of differential transcript usage, SatuRn, to detect isoform switching events in 12 cancer types. We analyze the detected events in terms of changes in transcript usage and the relationship between transcript usage and transcript expression on a global scale. The results of our analysis suggest that the relationship between changes in transcript usage and changes in transcript expression is far from straightforward, and that such quantitative information can be effectively used for prioritizing isoform switching events for downstream analyses.

Controlled Switching of Bistable Nanophase Domains on a Silicon Surface.

Switching the crystalline phase of a material via electrostatic control is a proven strategy for developing memory devices such as memristors that are based on nonvolatile resistance switching phenomena. However, phase switching in atomic-scale systems is often difficult to control and poorly understood. Here, we explore nonvolatile switching of long 2.3 nm wide bistable nanophase domains in a Sn double-layer structure grown on Si(111), using a scanning tunneling microscope. We identified two mechanisms for this phase switching phenomenon. First, the electrical field across the tunnel gap continuously tunes the relative stability of the two phases and favors one over the other depending on the tunneling polarity. The second mechanism involves carrier injection into empty Sn orbitals. The coupling between these relatively long-lived hot electrons and surface phonons induces a lattice instability at sufficiently large tunneling current and provides access to a hidden metastable state of matter. This hidden state is nonvolatile but can be erased by choosing the appropriate tunneling conditions or raising the temperature. Similar mechanisms could possibly be exploited in phase-change memristor and field effect devices.

Comparative analysis of low-frequency noise based resistive switching phenomenon for filamentary and interfacial RRAM devices

We investigate the low-frequency noise (LFN) characteristics of resistive switching random access memory (RRAM) devices with metal–insulator–metal structures of TiN/Ti/TiO2/TiN (filamentary) and TiN/Ti/TiO2/HfO2/TiN (interfacial). By comparing filamentary and interfacial RRAM devices, we stipulate guidelines for noise sources according to the resistance states or resistive switching mechanisms of RRAM device. In filamentary RRAM devices, the dominant noise source in the low resistance state is the localized oxygen vacancies, whereas the noise characteristics in the high resistance state represent a bulk effect. In interfacial RRAM devices, the noise characteristics in both resistance states represent the bulk effect. The physical mechanism of the multilevel cell operation is inferred by the I–V characteristics in both Icc and Vreset control modes. Specifically, the changes in the structure of the conductive filament inside the switching layer can be confirmed through LFN measurement.

Resistive Switching: Physics, Devices and Applications

Resistive Switching: Physics, Devices and Applications

Bistable Resistive Memory Switches fabricated by Floating Thin Films of Conjugated Polymers

The layer-by-layer (LBL) fabrication of conjugated polymer (CPs) thin films while preserving their microstructural features by solution processing is highly desired for compact and flexible electronic circuits. However, it is cumbersome and challenging owing to the unavoidable damage to the underlying layers. To circumvent this issue, the unidirectional floating-film transfer method (UFTM) was utilized for the LBL fabrication of oriented CP thin films on the orthogonal liquid surfaces. Further, resistive bistable memory switches were fabricated by sandwiching a layer of metal nanostructures between the LBL-fabricated oriented CP thin films. The resistive switching phenomena were realized by utilizing the applied bias-dependent charge trapping, holding, and recombination on the available states at vacuum-deposited aluminum nanostructures. The effect of CP backbone conformation on the vertical charge transport was also analyzed via a comparative study of three thiophene-based polymers namely RR-P3HT, PBTTT, and PTB-7. It was revealed that CPs with relatively fewer hydrophobic side chains was more favorable for the facile vertical charge transport due to its preferred face-on conformation on the hydrophilic liquid substrate used in UFTM. It was demonstrated that a non-volatile bistable resistive memory switch fabricated using UFTM-processed oriented thin films of PTB-7 exhibited a remarkably high on-off ratio of 1.5 × 106 with high durability.

Transient magneto-optical spectrum of photoexcited electrons in the van der Waals ferromagnet Cr2Ge2Te6

Femtosecond optical control of magnetic materials shows promise for future ultrafast data storage devices. To date, most studies in this area have relied on quasimonochromatic light in magneto-optical pump-probe experiments, which limited their ability to probe semiconducting and molecule-based materials with structured optical spectra. Here, we demonstrate the possibility of extracting the magneto-optical spectrum of the electrons in the conduction band in the two-dimensional van der Waals ferromagnet ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$ (CGT), which is made possible due to broadband probing in the visible spectrum. The magneto-optical signal is a sum of contributions from electrons in the conduction and valence bands, which are of opposite sign for CGT. Depending on the probe wavelength used, this difference could lead to an erroneous interpretation that the magnetization direction is reversed after excitation, which has important consequences for understanding spin toggle switching phenomena.

Doping modulated ion hopping in tantalum oxide based resistive switching memory for linear and stable switching dynamics

Artificial intelligence (AI) has demonstrated that automated machines could eventually replace human mental labor. However, AI is only settled in restricted environments with high computing resources and power supply. Artificial neural networks are currently implemented at the software level, necessitating the constant retrieval of synaptic weight among devices. Physically composing neural networks with emerging nonvolatile memories (eNVMs) can directly map synaptic weight and accelerate AI computing. Resistive switching memory (RRAM) is a promising in-memory computing unit, but challenges regarding nonideal properties remain unsolved. In particular, nonlinear conductance update is a major issue that hinders the performance of neural networks with RRAMs. In this study, metal cation doping was introduced to tantalum oxide-based RRAM to reveal the ionic hopping behavior, which is the essence of the resistive switching phenomena. Controlled dopant concentrations and a further understanding of ionic hopping alleviated nonlinear conductance modulation up to ∼1.46, while sustaining proper resistive switching window of ∼10.

Temporal-spatial analysis on multi-mode interaction of a flexible pipe subject to external current and internal flow

The vortex-induced vibration (VIV) in relation to a flexible pipe is numerically studied in order to examine the coupled effects occurring between the external shear current and the varying density internal flow. The analysis is performed using numerical methods and interpreted with position-frequency-energy (PFE) and time-frequency-energy (TFE) illustrations. The results indicate that the external shear current and varying density internal flow play different roles in affecting the VIV response. Due to temporal-spatial multi-mode competition, the phenomenon of mode switching is captured, showing alternating amplitude trough and peak in the TFE spectrum. The vibration response at the amplitude trough is commonly characterized by a wide range of frequencies, but the vibration response at the amplitude peak is usually dominated by a single frequency or a narrow range of frequencies. Based on the analysis related to spanwise waveforms, it is found that the standing wave commonly corresponds to a relatively stable equilibrium state of energy transfer between fluid-structure and mode-mode at local segments, and that the traveling waveform corresponds to an unsteady status of energy transfer between fluid-structure along the pipe span. Finally, through the contrast analysis of lift force and vibration response, one can find that the lift force along the pipe span is highly periodic and is in phase with the vibration displacement.

Resistive Switching and Current Conduction Mechanisms in Hexagonal Boron Nitride Threshold Memristors with Nickel Electrodes

AbstractThe 2D insulating material hexagonal boron nitride (h‐BN) has attracted much attention as the active medium in memristive devices due to its favorable physical properties, among others, a wide bandgap that enables a large switching window. Metal filament formation is frequently suggested for h‐BN devices as the resistive switching (RS) mechanism, usually supported by highly specialized methods like conductive atomic force microscopy (C‐AFM) or transmission electron microscopy (TEM). Here, the switching of multilayer hexagonal boron nitride (h‐BN) threshold memristors with two nickel (Ni) electrodes is investigated through their current conduction mechanisms. Both the high and the low resistance states are analyzed through temperature‐dependent current–voltage measurements. The formation and retraction of nickel filaments along boron defects in the h‐BN film as the resistive switching mechanism is proposed. The electrical data are corroborated with TEM analyses to establish temperature‐dependent current–voltage measurements as a valuable tool for the analysis of resistive switching phenomena in memristors made of 2D materials. The memristors exhibit a wide and tunable current operation range and low stand‐by currents, in line with the state of the art in h‐BN‐based threshold switches, a low cycle‐to‐cycle variability of 5%, and a large On/Off ratio of 107.

Disorder-induced trapping and antitrapping of vortices in type-II superconductors

We study the features of the superconductivity nucleation and vortex configurations in superconductors with modulated disorder. Using the Ginzburg-Landau-type theory with spatially varying diffusion coefficient, we uncover and explain the switching between the vortex-defect attraction to the repulsion upon the increase in the external magnetic field. It is shown that for rather weak applied magnetic fields, a superconducting nucleus localized near the region with the suppressed diffusion coefficient possesses a nonzero vorticity whereas the increase in the magnetic field can lead to a transition into the state with zero winding number. We demonstrate the manifestations of this switching phenomenon in superconductors with a large number of defects by performing numerical simulations of the vortex structures in superconductors with periodic spatial profiles of the diffusion coefficient. The obtained results clarify the physics of the vortex arrangement in several classes of the superconducting materials including one-dimensional superlattices and nanopatterned superconductors with regular arrays of the defects characterized by the increased concentration of nonmagnetic impurities.

Threshold Switching by Bipolar Avalanche Multiplication in Ovonic Chalcogenide Glasses

AbstractAn ovonic threshold switch (OTS) based on chalcogenide glasses finds application as a selecting device in storage class memory (SCM) arrays. The OTS operation relies on the threshold switching, where the device switches from the off to the on state without phase transition, then the device turns off almost immediately as the voltage is reduced below a certain holding value. The physics behind the switching phenomenon has attracted wide interest due to the complicated interplay between electronic transport, joule heating and phase transition. In this work, it is shown that the current‐voltage characteristic close to the switching point carries the fingerprint of carrier multiplication. The physical mechanism of threshold switching is then explained by bipolar impact ionization leading to avalanche multiplication, which in turn gives rise to the typical S‐shaped characteristic. Numerical simulations by this physics‐based model account for the measured switching properties, namely threshold voltage and current, at various chalcogenide thicknesses and compositions. These results provide the theoretical framework for future design and optimization of OTS in memory and computing applications.

The pervasiveness of language contact: Evidence from negative existentials in Romeyka/Turkish code-switching

This paper investigates the morpho-syntactic features of language contact in the endangered Greek dialect Romeyka with Turkish. We analyze the use of the borrowed negative existential jok to (a) determine its role in Romeyka’s negation patterns (b) examine the effects of contact in Romeyka through cross-linguistic comparisons of jok with Turkish and forms of the dialect as spoken in Greece and (c) apply the identified grammatical patterns of jok to Myers-Scotton’s linguistic explanations for the code switching phenomena in the Matrix Language Turnover Hypothesis. The analysis demonstrates the pervasive influence of Turkish on the morpho-syntax of Romeyka through the incorporation of Turkish grammatical structures. We observe changes in the fundamental predicate grammar that are aligned with Turkish and that are inconsistent with Pontic’s existential constructions where the verb indicating existence is used. The patterns of contact confirm the Matrix Language hypothesis and provide evidence that indicate that Romeyka may be undergoing language turnover. Our findings are relevant to further understanding code switching among speakers of minority languages and assessing the vitality of Romeyka in Turkey.

PIDHIRTSI GROUP OF SITES OF THE KYIV DNIPRO REGION OF SCYTHIAN AGE

The paper reveals the issue of population switch in the Kyiv Dnipro region which occurred gradually from the end of the 7th to the 5th centuries BCE. It is related to the origin of the Pidhirtsi group of sites. In historiography since 1950—1960s two hypotheses on this topic have been developed: the integration version based on the diffusion of forest-steppe and Mylograd cultural elements and autochthonous one. Nowadays, after the discovery of new archaeological sites and revision of the chronology, the more progressive research direction is processual migration archeology. The design of the approach is multidisciplinary. The population switch phenomenon is connected to the climate caused migrations of the forest population of Mylograd culture to the Upper and Middle Dnipro regions. In such circumstances with a range of cross-cultural contacts, the Pidhirtsi group of sites was formed.
 The settlement structure reconstructed on the basis of the material culture changes in correlation with geo informational analysis of the sites for two chronological periods. The impulses of the Mylograd population were caused by the economic crisis and paleoclimatic situation, in fact cooling and increasing humidity. The first diffusion occurred at the end of 7th century BCE and traced after burial complexes. The peak of population switch took place in the end of 6th — beginning 5th centuries BCE. As an example of material culture change were revised the materials of Bortnychi settlement explored in the 1950s. In the area of the Mylograd culture was observed decreasing of the anthropogenic activity. The forest steppe population inhabited the Left Bank Dnipro — Don region.
 Reconstruction of the cultural and historical context on the forest and forest-steppe frontier is a necessary approach for understanding the regional settlement system. Long-range interdisciplinary paleoclimatic studies of the Kyiv Dnipro region are a prospective direction for future research.