bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluorine-regulated surface chemical state of titanium dioxide (TiO
Authors: Liao Xin , Fang Jimin , Yang Lingling , Xu Zhijie , Wang Xun
Published: March 2021

Environmental context As a new type of photocatalytic material, nano-titanium dioxide can be applied in the field of energy and environmental protection. This research uses ammonium bifluoride to modify the titanium dioxide and analyses it in combination with interface chemistry theory, and finds that its photocatalytic efficiency has been greatly improved. This provides new ideas for wastewater treatment and pollutant degradation. Abstract Titanium dioxide (TiO2) was prepared by hydrothermally adjusting titanium sulfate with ammonium hydrogen fluoride. The UV-visible absorption spectra show that there was no significant redshift in the absorption sideband of the sample, but the addition of ammonium hydrogen fluoride affected the morphology and microstructure of the sample. When the molar ratio of F to Ti was 1.5, the specific surface area of TiO2 more than doubled, the surface complexation mode changed significantly and the number of surface-active sites increased by a factor of 16.24. The photocatalytic degradation measurements show that the decolourisation rate of the photocatalyst prepared by fluorine control was increased by 40 % compared with the uncontrolled sample. The analysis of the combined state of the catalyst surface shows that the photocatalytic degradation efficiency and the amount of deprotonated TiO− as well as the number of positively charged oxidation states of methylene blue are clearly correlated. Furthermore, the number of active sites of the catalyst increased and the electrostatic interaction between fluorine and titanium formed a F-Ti dipole moment, which intensified the interaction between the negatively charged TiO− ion and the positively charged quinone methylene blue molecule. The lone pair electron of N in the quinone methylene blue molecule and the 3d orbital of Ti formed a metastable complex through coordination, and demethylation of the methylene blue molecules was completed.
Experimental evidence of the importance of multitrophic structure for species persistence
Authors: Bartomeus Ignasi , Saavedra Serguei , Rohr Rudolf P. , Godoy Oscar
Published: March 2021

Significance

It has been unclear whether understanding how biodiversity is maintained requires us to study species interactions within and across trophic levels simultaneously. Achieving this task remains, however, challenging for practical and theoretical reasons. Here, integrating a simple but detailed experimental plant–pollinator community and a tractable mathematical framework, we show that biodiversity is strongly affected by species competitive interactions among plants and among pollinators, as well as the mutualistic effects between pollinators on plants. Furthermore, we show that experimentally preventing some species to interact can modify the rest of the interactions and affect idiosyncratically the probability of species persistence. These effects are only observable within the empirical evaluation and not with traditional simulation approaches.
Parties and voices
Authors: Luke K. K.
Published: March 2021

Since Harvey Sacks’ early observations on collaborative sentence-making, the joint production of turns has become a topic of abiding interest amongst conversation analysts. This paper offers a thematic review of the literature by looking into a number of issues surrounding joint productions, including their forms and interactional uses, major types and sub-types, syntactic and pragmatic contributions, unity and variation across languages, and reasons for its inherent fascination as a conversational practice. By re-examining a number of key concepts and distinctions, including completion, extension, projection, continuation, collaboration, and affiliation/disaffiliation, the paper offers a critical assessment of their perspicuity and usefulness for our understanding of joint production as a general phenomenon (which includes both co-completions and increments). In the second part of the paper, it is suggested that two further concepts be added to the analyst’s toolbox, namely, ‘parties’ (Schegloff 1995) and ‘voices’ (Bakhtin 1981). It is argued that with these notions, one would be better placed to explain the curious status of joint productions as at once collaborative and yet at the same time potentially transformative or even subversive. The overriding goal is conceptual clarification of this field, which hopefully will help place further research on firmer ground.
Understanding the impact of supporting conceptual information design
Authors: Pontis Sheila
Published: March 2021

This article argues that supporting conceptual information design should be a priority as it could better equip
design practitioners for their jobs. Findings from a longitudinal evaluation of a tool – MapCI Cards – using multiple methods to
assess the impact of supporting conceptual design in professional practice are reported here. Internal and external factors
emerged as having an adverse influence on information designers’ responses to conceptual design. Increased conceptual design
awareness and more confident decisions resulted from working with a support tool. Structure, flexibility, and externalizations are
indicated as possible ways to effectively support conceptual information design. The article ends with recommendations for future
support tools.
Linguistic structures in social interaction
Authors: Mushin Ilana , Doehler Simona Pekarek
Published: March 2021

In this introductory paper to the inaugural volume of the journalInteractional Linguistics, we raise the question of what a theory of language might look like once we factor time into explanations of regularities in linguistic phenomena. We first present a historical overview that contextualises interactional approaches within the broader field of linguistics, and then focus on temporality as a key dimension of language use in interaction. By doing so, we discuss issues of emergence and its consequences for constituency and dependency, and of projection and its relation to action formation within and across languages. Based on video-recorded conversational data from French and Garrwa (Australian), we seek to illustrate how the discipline of linguistics can be enriched by attending to the temporal deployment of patterns of language use, and how this may in turn modify what we understand to be language structure.
Nonstatistical behavior of the photoionization of spin–orbit doublets
Authors: Püttner Ralph , Martins Jessica B , Marchenko Tatiana , Travnikova Oksana , Guillemin Renaud , Journel Loïc , Ismail Iyas , Goldsztejn Gildas , Koulentianos Dimitris , Céolin Denis , Rocco Maria Luiza Miranda , Piancastelli Maria Novella , Simon Marc , Keating David A , Rasadi Munasinghe C , Deshmukh Pranawa C , Manson Steven T
Published: March 2021

The photoionization branching ratios of spin–orbit doublets are studied both experimentally and theoretically at energies several keV above threshold. The results show significant relativistic effects for Ar 2p in the autoionizing region below the 1s threshold, and large many-body effects for Xe 3d and 4d in the vicinity of the L-shell thresholds. The branching ratios in Xe are also found to vary significantly over very broad multi-keV energy regions both above and below the inner-shell thresholds. In addition, the Ar 2p study confirms experimentally the decades-old theoretical prediction that the nonresonant branching ratio does not approach the statistical (nonrelativistic) value, and, in fact, progressively diverges from statistical with increasing photon energy.
Vitrification is a spontaneous non-equilibrium transition driven by osmotic pressure
Authors: Wang J Galen , Zia Roseanna N
Published: March 2021

Persistent dynamics in colloidal glasses suggest the existence of a non-equilibrium driving force for structural relaxation during glassy aging. But the implicit assumption in the literature that colloidal glasses form within the metastable state bypasses the search for a driving force for vitrification and glassy aging and its connection with a metastable state. The natural relation of osmotic pressure to number-density gradients motivates us to investigate the osmotic pressure as this driving force. We use dynamic simulation to quench a polydisperse hard-sphere colloidal liquid into the putative glass region while monitoring structural relaxation and osmotic pressure. Following quenches to various depths in volume fraction ϕ (where ϕ
RCP ≈ 0.678 for 7% polydispersity), the osmotic pressure overshoots its metastable value, then decreases with age toward the metastable pressure, driving redistribution of coordination number and interparticle voids that smooths structural heterogeneity with age. For quenches to 0.56 ⩽ ϕ ⩽ 0.58, accessible post-quench volume redistributes with age, allowing the glass to relax into a strong supercooled liquid and easily reach a metastable state. At higher volume fractions, 0.59 ⩽ ϕ < 0.64, this redistribution encounters a barrier that is subsequently overcome by osmotic pressure, allowing the system to relax toward the metastable state. But for ϕ ⩾ 0.64, the overshoot is small compared to the high metastable pressure; redistribution of volume stops as particles acquire contacts and get stuck, freezing the system far from the metastable state. Overall, the osmotic pressure drives structural rearrangements responsible for both vitrification and glassy age-relaxation. The connection of energy, pressure, and structure identifies the glass transition, 0.63 < ϕ
g ⩽ 0.64. We leverage the connection of osmotic pressure to energy density to put forth the mechanistic view that relaxation of structural heterogeneity in colloidal glasses occurs via individual particle motion driven by osmotic pressure, and is a spontaneous energy minimization process that drives the glass off and back to the metastable state.
Durable, magnetic-responsive melamine sponge composite for high efficiency, in situ oil–water separation
Authors: Niu Haifeng , Qiang Zhe , Ren Jie
Published: March 2021

The development of durable and high-performance absorbents for in situ oil–water separation is of critical importance for addressing severe water pollution in daily life as well as for solving accidental large-scale oil spillages. Herein, we demonstrate a simple and scalable approach to fabricate magnetic-responsive superhydrophobic melamine sponges by in situ deposition of PDA coatings and Fe3O4 nanoparticles, followed by surface silanization with low surface energy 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PTOS) layer. The prepared melamine sponge composite (PTOS-Fe3O4@PDA/MF) not only exhibits a very high water contact angle of 165 ± 1.5° and an excellent ability to uptake a variety of oils and organic solvents (e.g. up to 141.1 g/g for chloroform), but also shows robust durability and superior recyclability. The PTOS-Fe3O4@PDA/MF sponge can also efficiently separate oils (or organic solvents) and water, as demonstrated by different model systems including immiscible oil–water solution mixture and miscible water–oil (W/O) emulsion (stabilized by surfactants). Furthermore, the PTOS-Fe3O4@PDA/MF sponge is able to in situ recover organics from water using a peristaltic pump, which gives it significant advantages over other traditional batch processes for oil–water separation. We believe that the PTOS-Fe3O4@PDA/MF sponge provides a very promising material solution to address oil–water separation, especially for the large-scale problems that have been long-time challenges with conventional sorption methods.
Modeling intra-fractional abdominal configuration changes using breathing motion-corrected radial MRI
Authors: Liu Lianli , Johansson Adam , Cao Yue , Kashani Rojano , Lawrence Theodore S , Balter James M
Published: March 2021

Abdominal organ motions introduce geometric uncertainties to gastrointestinal radiotherapy. This study investigated slow drifting motion induced by changes of internal anatomic organ arrangements using a 3D radial MRI sequence with a scan length of 20 min. Breathing motion and cyclic GI motion were first removed through multi-temporal resolution image reconstruction. Slow drifting motion analysis was performed using an image time series consisting of 72 image volumes with a temporal sampling rate of 17 s. B-spline deformable registration was performed to align image volumes of the time series to a reference volume. The resulting deformation fields were used for motion velocity evaluation and patient-specific motion model construction through principal component analysis (PCA). Geometric uncertainties introduced by slow drifting motion were assessed by Hausdorff distances between unions of organs at risk (OARs) at different motion states and reference OAR contours as well as probabilistic distributions of OARs predicted using the PCA model. Thirteen examinations from 11 patients were included in this study. The averaged motion velocities ranged from 0.8 to 1.9 mm min−1, 0.7 to 1.6 mm min−1, 0.6 to 2.0 mm min−1 and 0.7 to 1.4 mm min−1 for the small bowel, colon, duodenum and stomach respectively; the averaged Hausdorff distances were 5.6 mm, 5.3 mm, 5.1 mm and 4.6 mm. On average, a margin larger than 4.5 mm was needed to cover a space with OAR occupancy probability higher than 55%. Temporal variations of geometric uncertainties were evaluated by comparing across four 5 min sub-scans extracted from the full scan. Standard deviations of Hausdorff distances across sub-scans were less than 1 mm for most examinations, indicating stability of relative margin estimates from separate time windows. These results suggested slow drifting motion of GI organs is significant and geometric uncertainties introduced by such motion should be accounted for during radiotherapy planning and delivery.
Rapid rotational magneto-acousto-electrical tomography with filtered back-projection algorithm based on plane waves
Authors: Sun Tong , Hao Penghui , Chin Chien Ting , Deng Dingqian , Chen Tiemei , Chen Yi , Chen Mian , Lin Haoming , Lu Minhua , Gao Yi , Chen Siping , Chang Chunqi , Chen Xin
Published: March 2021

Magneto-acousto-electrical tomography (MAET) is designed to produce conductivity images with high spatial resolution for a conducting object. In a previous study, for an irregular conductor, transverse scanning and rotational methods with a focus transducer were combined to collect complete electrical information. This kind of method, however, is time-consuming because of the transverse scanning procedure. In this study, we proposed a novel imaging method based on plane ultrasound waves and a new aspect of projection in rotational MAET. In the proposed method, we achieved the projection in each rotation angle by using plane waves rather than mechanical scanning of the focus waves along the transverse direction. Thus, the imaging time was significantly saved. To verify the proposed method, we derived a measurement formula containing a lateral integration, which built the relationship between the measurement formula and the projection under each rotation angle. Next, we constructed two different numerical models to compute magneto-acousto-electrical signals by using a finite element method and reconstructed the corresponding conductivity parameter images based on a filtered back-projection algorithm. Then, simulated signals under different signal-to-ratios (6, 20, 40, and 60 dB) were generated to test the performance of the proposed algorithm. To improve the image quality, we further analysed the influence of the filters and the frequency scaling factors embedded in the filtered back-projection algorithm. Moreover, we computed the L2 norm of the error in case of different frequency scaling factors and measurement noises. Finally, we conducted a phantom experiment with a 64-element linear phased array transducer (center frequency of 2.7 MHz) and reconstructed the conductivity parameter images of the circular phantom with an elliptical hole. The experimental results demonstrated the feasibility and time-efficiency of the proposed rapid rotational MAET.
Development and characterization of an LED-based detector for dosimetry in diagnostic radiology
Authors: Damulira Edrine , Yusoff Muhammad Nur Salihin , Omar Ahmad Fairuz , Mohd Taib Nur Hartini
Published: March 2021

Light-emitting diodes (LEDs) could be a potential dosimetry candidate because they are radiation hard, spectrally selective, direct band gap, and low-cost devices. Thus, an LED-based detector prototype was designed and characterized for dosimetry. A 20 × 20 cm2 array of surface mount device LED chips was sandwiched in photovoltaic mode between two intensifying screens to form a dosimetric system. The system was enclosed in a light-tight air cavity using black vinyl tape. The screens converted diagnostic x-ray beams into fluorescent blue light. LEDs, applied in detector mode, converted the fluorescent light into radiation-induced currents. A digital multimeter converted the analog currents into digital voltage signals. Prototype characterization was executed using (a) IEC 61267’s RQR 7 (90 kVp) and RQR 8 (100 kVp) beam qualities, and (b) low (25 mAs) and high (80 mAs) beam quantities. A standard dosimeter probe was simultaneously exposed with the prototype to measure the prototype’s absorbed dose. In all exposures, the x-ray beams were perpendicularly incident on both the dosimeter and prototype, at a fixed source to detector distance-60 cm. The LED array prototype’s minimum detectable dose was 0.139 mGy, and the maximum dose implemented herein was ∼13 mGy. The prototype was 99.18% and 98.64% linearly sensitive to absorbed dose and tube current–time product (mAs), respectively. The system was ±4.69% energy, ±6.8% dose, and ±7.7% dose rate dependent. Two prototype data sets were 89.93% repeatable. We fabricated an ultrathin (5 mm), lightweight (130 g), and a relatively low-cost LED-based dosimetric prototype. The prototype executed a simple, efficient, and accurate real-time dosimetric mechanism. It could thus be an alternative to the current passive dosimetric systems.
Onset detection in surface electromyographic signals across isometric explosive and ramped contractions: a comparison of computer-based methods
Authors: Crotty Evan D , Furlong Laura-Anne M , Hayes Kevin , Harrison Andrew J
Published: March 2021

Objective. Accurate identification of surface electromyography (EMG) muscle onset is vital when examining short temporal parameters such as electromechanical delay. The visual method is considered the ‘gold standard’ in onset detection. Automatic detection methods are commonly employed to increase objectivity and reduce analysis time, but it is unclear if they are sensitive enough to accurately detect EMG onset when relating them to short-duration motor events. Approach. This study aimed to determine: (1) if automatic detection methods could be used interchangeably with visual methods in detecting EMG onsets (2) if the Teager–Kaiser energy operator (TKEO) as a conditioning step would improve the accuracy of popular EMG onset detection methods. The accuracy of three automatic onset detection methods: approximated generalized likelihood ratio (AGLR), TKEO, and threshold-based method were examined against the visual method. EMG signals from fast, explosive, and slow, ramped isometric plantarflexor contractions were evaluated using each technique. Main results. For fast, explosive contractions, the TKEO was the best-performing automatic detection method, with a low bias level (4.7 ± 5.6 ms) and excellent intraclass correlation coefficient (ICC) of 0.993, however with wide limits of agreement (LoA) (−6.2 to +15.7 ms). For slow, ramped contractions, the AGLR with TKEO conditioning was the best-performing automatic detection method with the smallest bias (11.3 ± 32.9 ms) and excellent ICC (0.983) but produced wide LoA (−53.2 to +75.8 ms). For visual detection, the inclusion of TKEO conditioning improved inter-rater and intra-rater reliability across contraction types compared with visual detection without TKEO conditioning. Significance. In conclusion, the examined automatic detection methods are not sensitive enough to be applied when relating EMG onset to a motor event of short duration. To attain the accuracy needed, visual detection is recommended. The inclusion of TKEO as a conditioning step before visual detection of EMG onsets is recommended to improve visual detection reliability.
Features of the EEDF formation in the dusty plasma of the positive column of a glow discharge
Authors: Li Shubo , Rabadanov K M , Bogdanov E A , Kudryavtsev A A , Ashurbekov N A , Yuan Chengxun , Zhou Zhongxiang
Published: March 2021

In this paper, the formation of the electron energy distribution function (EEDF) in the argon dusty plasma of the positive column of glow discharge at low pressure is investigated. A model for calculating EEDF in the local approximation is adapted to find the nonlocal EEDF via the Holstein–Tsendin model. The results show that, contrary to the prevalent opinion in the literature, the presence of dust has little effect on the EEDF up to the limiting values of the density of dust particles that can be injected into the plasma for the considered conditions. It is also shown that, when obtaining the nonlocal EEDF, the spatial profiles of the axial (heating) and radial (ambipolar) fields should be chosen from a self-consistent solution. Additionally, the differences between the local and nonlocal EEDFs increase in the peripheral regions of the discharge due to a sharp decrease of fast electrons in the nonlocal case. Significant changes in the form of the nonlocal EEDF along the radius also lead to noticeable changes in other characteristics of the electrons in this area, especially for those with a large energy threshold (e.g. due to excitation, ionization).
Electron–neutral bremsstrahlung radiation fingerprints the initial stage of nanosecond discharge in liquid water
Authors: Bílek Petr , Tungli Ján , Hoder Tomáš , Šimek Milan , Bonaventura Zdeněk
Published: March 2021

We postulate that basic radiative signatures observed during the initial phases of nanosecond discharge in liquid water can be attributed to the electron–neutral bremsstrahlung process. Principal characteristics of the radiation collected from developing luminous filaments consist of a sharp decrease in the emission intensity at the short-wavelength side of the spectra, followed by a maximum and subsequent decrease in intensity towards near-infrared wavelengths. All these radiative features can be attributed to the electron–neutral bremsstrahlung produced by a bell-like energy distribution of the electrons. Such an electron energy distribution function is coherent with the concept of electric field emission into electrostriction-induced nanovoids. The findings of this work help in elucidating the hitherto unclear mechanism(s) of plasma generation in liquid water.
Obtaining the unperturbed plasma potential in low-density, low-temperature plasmas
Authors: Causa Federica , Gervasini Gabriele , Uccello Andrea , Granucci Gustavo , Ricci Daria , Rispoli Natale
Published: March 2021

A method is proposed to effectively obtain plasma parameters in low-density, low-temperature plasmas that are easily perturbed by Langmuir probes. The methodology is based on the perimeter sheath expansion method because it provides a simple, but effective interpretation of the Langmuir probe characteristics and, in particular, of the non-saturating trend of the ion saturation due to the expansion of the probe sheath. However, the perimeter sheath expansion method is proposed here in a modified version with a dual purpose: to permit the verification of the Child–Langmuir dependence of the sheath thickness from the potential and, most importantly, to properly assess the plasma potential. When probe perturbation is significant the proposed method provides an effective correction term for the plasma potential. The resulting sheath voltage is consistent in all analysed cases and in close agreement with the expected value for cylindrical probes in Ar. The method is applied to Ar plasmas here, but because no specific assumption was made on the atomic species, it may be applicable to other situations of interest.
Electron power absorption in radio frequency driven capacitively coupled chlorine discharge
Authors: Proto A , Gudmundsson J T
Published: March 2021

Particle-in-cell Monte Carlo collision simulations and Boltzmann term analysis are applied to study the origination and properties of the electric field and the electron power absorption within the electronegative core of a capacitively coupled discharge in chlorine as the pressure is varied from 1 to 50 Pa. The capacitively coupled chlorine discharge exhibits high electronegativity and high electric field develops within the electronegative core. It is found that the electron power absorption increases and the ion power absorption decreases as the pressure is increased. At 1 Pa the electron power absorption is due to both the pressure and ohmic terms. At the higher pressures >10 Pa the ohmic term dominates and all the other contributions to the electron power absorption become negligible. Therefore, the discharge becomes increasingly ohmic with increased pressure and eventually behaves as a resistive load.
Analysis of temperature dependent dark current mechanisms for long-wavelength infrared p-on-n HgCdTe detectors
Authors: Li Xun , Wang Xi , Lin Chun , Wei Yanfeng , Zhou Songmin , Sun Quanzhi
Published: March 2021

The dark current density versus voltage (J–V) curve of long-wavelength infrared (LWIR) p-on-n mercury cadmium telluride (HgCdTe, MCT) photodiode is measured in the temperature range of 40 K–130 K in this study. The dark current mechanisms, namely diffusion, generation–recombination (GR), trap-assisted tunneling, band-to-band tunneling (BBT) and shunt current, are investigated for LWIR p-on-n MCT diode at different temperatures. The results show that the dark current is dominated by diffusion current at low reverse bias when the operating temperature is above 65 K. As the operating temperature decreases, GR current and shunt current gradually become the main ingredient of dark current. In the high reverse bias region, the contribution of BBT mechanism accounts for the largest proportion when the operating temperature is below 75 K. The extracted fitting parameters show that the donor concentration in the n-type region of p-on-n MCT diode display better temperature stability compared with that of n-on-p diodes. Because the thermal excitation effect increases with the increase of temperature, the equivalent trap level moves from shallow acceptor level to deep acceptor level, and the trap density increases from 1.1 × 1010 to 6.0 × 1012 cm−3 when the operating temperature is increased from 80 K to 130 K.
Liquid vaporization actuated soft structures with active cooling and heat loss control
Authors: Lee Han-Joo , Loh Kenneth J
Published: March 2021

Soft robotic systems that are inspired by nature utilize soft materials to perform various tasks in diverse environments. One promising method to control their movement is by utilizing liquid vaporization. In most cases, liquid with high vapor pressure is injected into hollow cavities inside the elastomer. Heating the system vaporizes the liquid, and the structure is inflated by the generated gas. However, there is a significant time lag between powering the system and structural actuation due to the slow increase in temperature that is exacerbated by heat loss. Simply using materials with low thermal conductivity can improve actuation, but the reduced heat loss concurrently increases cooling time during the reversing process. Furthermore, underwater actuation through vaporization remains a challenge, since heat loss becomes even more significant. To address these issues, this study aims to develop a system that can actively control heat loss to enhance both actuation and cooling while performing consistently even in extreme environments. First, double-walled structures were fabricated with silicone elastomer to drastically lower thermal conductivity. Next, a thermoelectric device was installed on the bottom layer to heat and cool the sealed liquid by reversing current flow. The low thermal conductivity of the double-walled structure enhanced actuation performance, while actively cooling the system with the thermoelectric device accelerated the reversing process. Structures with single- and double-layered walls were tested underwater to validate their performance. Finite element models verified the effects of wall designs on heat transfer and structural mechanics. Demonstration of enhanced reversible actuation of the system was performed using a soft anemone-like structure operated underwater.
An ultrawide-zero-frequency bandgap metamaterial with negative moment of inertia and stiffness
Authors: Yang Leiyu , Wang Lifeng
Published: March 2021

Metamaterials have demonstrated great potential for controlling wave propagation since they are flexibly adjustable. A new one-dimensional metamaterial model with both a negative effective moment of inertia and negative effective stiffness is proposed. A negative effective moment of inertia and negative effective stiffness can be achieved by adjusting the structural parameters in certain frequency ranges. Bandgaps in the low-frequency range with exponential wave attenuation can be generated in the metamaterial. A flat band is obtained that couples two Bragg bandgaps to achieve a wide bandgap in the low-frequency range, where the effective moment of inertia and effective stiffness are both infinite. A zero-frequency bandgap can be achieved by adjusting the structural parameters. Quick attenuation of wave is observed in the zero-frequency ranges with single-negative parameters. Furthermore, an ultrawide-zero-frequency bandgap is obtained by optimizing the structural parameters of the system. In addition, it is easy to switch between the Bragg and locally resonant bandgaps. This new metamaterial can be applied to ultralow-frequency-vibration isolation.
Modified MIT bag Models—part I: Thermodynamic consistency, stability windows and symmetry group
Authors: Lopes Luiz L , Biesdorf Carline , Menezes Débora P
Published: March 2021

In this work we study different variations of the MIT bag model. We start with the so called non-ideal bag model and discuss it in detail. Then we implement a vector interaction in the MIT bag model that simulates a meson exchange interaction and fix the quark-meson coupling constants via symmetry group theory. At the end we propose an original model, inspired by the Boguta-Bodmer models, which allows us to control the repulsion interaction at high densities. For each version of the model we obtain a stability window as predicted by the Bodmer-Witten conjecture and discuss its thermodynamic consistency.
Corrosion behavior of aluminum-Fiber Glass composite fabricated through surface mechanical alloying in alkaline media
Authors: Shehata O S , Mohamed Ebrahim Mohamed Refaat , Abdel Fatah Amr H
Published: March 2021

Dissolution reaction control of aluminum in 2M KOH alkaline media was achieved through surface mechanical alloying SMA with dielectric Fiber glass ‘FG’ powder. A significant decrease corrosion rate from 0.867 for blank Al to 0.0002 mm y−1for SMA Al with FG powder previously etched after 15 min; surface mechanical attrition treatment ‘SMAT’; Formed surface metal matrix Al/FG composites layers on Al anodes have attractive electrical properties. Its analysis obtained using X-Rays Diffraction XRD, scanning electron microscopy SEM. Used three electrochemical techniques EIS, CV and PDP indicate corrosion resistance improvement in 2M KOH correspond to inhibition efficiency reaches 99.81%. Such inhibition encourage for forming efficient and safe air batteries for interesting applications using Al anodes after consecutive SMAT & SMA processing.
Multiple adjustable Fano resonance based on double half ring resonator and its application
Authors: He Qian , Huo Yiping , Guo Yiyuan , Niu Qiqiang , Hao Xiangxiang , Cui Pengfei , Wang Yunyan , Song Meina
Published: March 2021

In this paper, a compact nanostructure is proposed that includes a metal insulator metal (MIM) waveguide with a metal wall and a side-coupled half-ring resonator. The transmission characteristics of the system are studied numerically by using the finite element method (FEM). The simulation results show that double Fano resonances can be produced in the structure, and the two Fano resonances can be controlled independently by two different half rings. The position and intensity of the Fano resonance peaks can be adjusted flexibly and easily by changing the refractive index of the filling medium. The waveguide is sensitive to the refractive index of the filling medium inside the resonator and the maximum sensitivity and figure of merit (FOM) are 1260 nm/RIU and 26,000 respectively. By adding two more half-rings below, four independently adjustable Fano resonances are obtained. The structure of this paper can be used as a sensor which can detect the glucose concentration, so it has a broad application prospect in biomedical and chemical sensing fields.
Cosmological bubble friction in local equilibrium
Authors: Balaji Shyam , Spannowsky Michael , Tamarit Carlos
Published: March 2021

In first-order cosmological phase transitions, the
asymptotic velocity of expanding bubbles is of crucial relevance for
predicting observables like the spectrum of stochastic gravitational
waves, or for establishing the viability of mechanisms explaining
fundamental properties of the universe such as the observed baryon
asymmetry. In these dynamic phase transitions, it is generally
accepted that subluminal bubble expansion requires
out-of-equilibrium interactions with the plasma which are captured
by friction terms in the equations of motion for the scalar
field. This has been disputed in works pointing out subluminal
velocities in local equilibrium arising either from hydrodynamic
effects in deflagrations or from the entropy change across the
bubble wall in general situations. We argue that both effects are
related and can be understood from the conservation of the entropy
of the degrees of freedom in local equilibrium, leading to
subluminal speeds for both deflagrations and detonations. The
friction effect arises from the background field dependence of the
entropy density in the plasma, and can be accounted for by simply
imposing local conservation of stress-energy and including field
dependent thermal contributions to the effective potential. We
illustrate this with explicit calculations of dynamic and static
bubbles for a first-order electroweak transition in a Standard Model
extension with additional scalar fields.
Cascading attack on trusted-relay quantum key distribution networks
Authors: Wang Jian , Liu Xing-tong
Published: March 2021

Trusted relays are the main state-of-the-art way to realize quantum key distribution networks. However, it is hard to require that all nodes in the network are fully trusted. In a multipath key-transmission mechanism, the nodes can be weakly trusted because the secret key can be split into many parts and each part is transmitted to the receiver through a different path. However, if the capacity of a node’s quantum key pool is poorly designed, an attacker, Eve may eavesdrop on the communicating parties’ secret message by initiating a redirection attack. In this paper, we show that Eve can trigger a cascading collapse effect by collapsing one of the edges in the network and forcing the communication parties to transmit the message through the nodes controlled by Eve. The influence of the traffic transfer ratio and the control parameters of the edge load on the breakdown probability of the edge are analyzed using a simulation. In order to effectively defend against the cascading attack, it is important for the designer to handle the relationship between the traffic and the capacity of the quantum key pool of each node in the network.
Universal memory based on phase-change materials: From phase-change random access memory to optoelectronic hybrid storage*
Authors: Liu Bo , Wei Tao , Hu Jing , Li Wanfei , Ling Yun , Liu Qianqian , Cheng Miao , Song Zhitang
Published: March 2021

The era of information explosion is coming and information need to be continuously stored and randomly accessed over long-term periods, which constitute an insurmountable challenge for existing data centers. At present, computing devices use the von Neumann architecture with separate computing and memory units, which exposes the shortcomings of “memory bottleneck”. Nonvolatile memristor can realize data storage and in-memory computing at the same time and promises to overcome this bottleneck. Phase-change random access memory (PCRAM) is called one of the best solutions for next generation non-volatile memory. Due to its high speed, good data retention, high density, low power consumption, PCRAM has the broad commercial prospects in the in-memory computing application. In this review, the research progress of phase-change materials and device structures for PCRAM, as well as the most critical performances for a universal memory, such as speed, capacity, and power consumption, are reviewed. By comparing the advantages and disadvantages of phase-change optical disk and PCRAM, a new concept of optoelectronic hybrid storage based on phase-change material is proposed. Furthermore, its feasibility to replace existing memory technologies as a universal memory is also discussed as well.
Thermally induced band hybridization in bilayer-bilayer MoS2/WS2 heterostructure*
Authors: Zhao Yanchong , Bo Tao , Du Luojun , Tian Jinpeng , Li Xiaomei , Watanabe Kenji , Taniguchi Takashi , Yang Rong , Shi Dongxia , Meng Sheng , Yang Wei , Zhang Guangyu
Published: March 2021

Transition metal dichalcogenides (TMDs), being valley selectively, are an ideal system hosting excitons. Stacking TMDs together to form heterostructure offers an exciting platform to engineer new optical and electronic properties in solid-state systems. However, due to the limited accuracy and repetitiveness of sample preparation, the effects of interlayer coupling on the electronic and excitonic properties have not been systematically investigated. In this report, we study the photoluminescence spectra of bilayer-bilayer MoS2/WS2 heterostructure with a type II band alignment. We demonstrate that thermal annealing can increase interlayer coupling in the van der Waals heterostructures, and after thermally induced band hybridization such heterostructure behaves more like an artificial new solid, rather than just the combination of two individual TMD components. We also carry out experimental and theoretical studies of the electric controllable direct and indirect infrared interlayer excitons in such system. Our study reveals the impact of interlayer coupling on interlayer excitons and will shed light on the understanding and engineering of layer-controlled spin-valley configuration in twisted van der Waals heterostructures.
Effect of symmetrical frequency chirp on pair production*
Authors: Wang Kun , Hu Xuehua , Dulat Sayipjamal , Xie Bai-Song
Published: March 2021

By using Dirac–Heisenberg–Wigner formalism we study electron–positron pair production for linear, elliptic, nearly circular, and circular polarizations of electric fields with symmetrical frequency chirp, and we obtain momentum spectra and pair yield. The difference of results among polarized fields is obvious for the small chirp. When the chirp parameter increases, the momentum spectra tend to exhibit the multiphoton pair generation that is characterized by the multi-concentric ring structure. The increase of the number density is also remarkable compared to the case of asymmetrical frequency chirp. Note that the dynamically assisted Schwinger mechanism plays an important role for the enhanced pair production in the symmetrical frequency chirp.
Direct growth of graphene films without catalyst on flexible glass substrates by PECVD*
Authors: Miao Rui-Xia , Zhao Chen-He , Wang Shao-Qing , Ren Wei , Li Yong-Feng , Shu Ti-Kang , Yang Ben
Published: March 2021

A hydrogen-plasma-etching-based plasma-enhanced chemical vapor deposition (PECVD) synthesis route without metal catalyst for preparing the graphene films on flexible glass is developed. The quality of the prepared graphene films is evaluated by scanning electron microscopy, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, ultraviolet-visible spectroscopy, and electrochemical measurements. In a radio frequency (RF) power range of 50 W–300 W, the graphene growth rate increases with RF power increasing, while the intensity ratio of D- to G-Raman peak (I
D/I
G) decreases. When the RF power is higher than 300 W, the I
D/I
G rises again. By optimizing experimental parameters of hydrogen plasma etching and RF power, the properties of as-prepared flexible graphene on glass are modulated to be able to achieve the graphene’s transparency, good electrical conductivity, and better macroscopic uniformity. Direct growth of graphene film without any metal catalyst on flexible glass can be a promising candidate for applications in flexible transparent optoelectronics.
Magnetic shielding property for cylinder with circular, square, and equilateral triangle holes*
Authors: Hao Si-Yuan , Lou Xiao-Ping , Zhu Jing , Chen Guang-Wei , Li Hui-Yu
Published: March 2021

The shielding property of cylinder with circular, square, and equilateral triangle holes was investigated by finite element analysis (FEA). The hole area (S
hole) plays an important role in magnetic circuit on the surface of cylinder. When S
hole is less than the critical area (S
H), cylinder with three shapes of holes obtained the same remanent magnetization inside, indicating that the shielding property is unaffected by the shape of the hole. Hence, high-permeability material is the major path of the magnetic field. On the condition of S
hole > S
H, the sequence of the shielding property is equilateral triangle > square > circular, resulting from magnetoresistance of leakage flux in air dielectric. Besides, the anisotropy of shielding property caused by hole structural differences of the cylinder is evaluated. We find that a good shielding effectiveness is gained in the radial direction, compared with the axis direction. This research focuses on providing a theoretical support for the design of magnetic shield and improvement on the magnetic shielding ability.
Low temperature ferromagnetism in CaCu3Ti4O12
*
Authors: Yang Song , Luo Xiao-Jing , Shen Zhi-Ming , Gao Tian , Liu Yong-Sheng , Tang Shao-Long
Published: March 2021

The low-temperature magnetic order behaviors of perovskite oxide CaCu3Ti4O12 (CCTO) ceramics prepared by different methods are discussed. X-ray diffraction, scanning electron microscope, x-ray photoelectron spectroscopy, and direct current (DC) magnetization are used to characterize the structures, microscopic morphologies, valence states, and magnetic properties of the samples. The results show that the magnetic behaviors of CCTO ceramics are very sensitive to the preparation process. The quenched CCTO ceramic and CCTO powders grown in a molten salt crystal, which contain much more oxygen vacancies and Ti3+, show the coexistence of weak ferromagnetic order and antiferromagnetic order below the Neel temperature. It suggests that the bound magnetopolaron formed by oxygen vacancies and Ti3+ ion composite defects are responsible for the weak ferromagnetic order at low temperature.
Quantum multicast schemes of different quantum states via non-maximally entangled channels with multiparty involvement*
Authors: Yu Yan , Zhao Nan , Pei Chang-Xing , Li Wei
Published: March 2021

Due to the unavoidable interaction between the quantum channel and its ambient environment, it is difficult to generate and maintain the maximally entanglement. Thus, the research on multiparty information transmission via non-maximally entangled channels is of academic value and general application. Here, we utilize the non-maximally entangled channels to implement two multiparty remote state preparation schemes for transmitting different quantum information from one sender to two receivers synchronously. The first scheme is adopted to transmit two different four-qubit cluster-type entangled states to two receivers with a certain probability. In order to improve success probabilities of such multicast remote state preparation using non-maximally entangled channels, we put forward the second scheme, which deals with the situation that is a synchronous transfer of an arbitrary single-qubit state and an arbitrary two-qubit state from one sender to two receivers. In particular, its success probability can reach 100% in principle, and independent of the entanglement degree of the shared non-maximally entangled channel. Notably, in the second scheme, the auxiliary particle is not required.
Numerical and Experimental Analysis in the Production of a Solar Still
Authors: Chávez S , Terres H , Lizardi A , López R , Lara A , Vaca M
Published: March 2021

In this work, a numerical and experimental study is shown for a single slope solar still with internal reflectors and a finned system at the absorber plate, in it 30 experimental tests were made with 3 L of water, for which temperature measurements were obtained, mainly at the glass cover, the absorber plate, fluid and at the environment, as well as the incident solar radiation, the experimental information was obtained through ADAMS modules, type K thermocouples and a pyranometer, besides the distillate volume was measured with measuring cylinders. From the experimental data, a model was constructed to understand the effect of solar radiation and fluid temperature on distillate production. As a result, for this experiment a cubic function that describes de distillate volume behaviour was found, which only depends on the solar radiation and the official time, this equation has at least a 6% error on average regarding to the experimental distillate volume.
Speed PID controller simulation of a reaction wheel for CubeSat orientation applications
Authors: Medina I , Santiago L , Hernández-Gómez J J , Castillo R , Couder-Castañeda C
Published: March 2021

CubeSat technology is a low-cost alternative for space research in universities worldwide, promoting research areas in tele-detection, Earth and space observation, telecommunications, meteorology, etc. In this sense, Attitude and Determination Control Subsystem (ADCS) plays a key role in order to achieve a fast and precise orientation of the satellite, aiding the system by acquiring the specific and critical angles they require to accomplish the space mission. Therefore, choosing adequate actuators is key for the correct manipulation of the CubeSat, and it must consider size, weight and electrical power usage limitations of the CubeSat Standard. ADCS actuators must generate a quick response to generate an active momentum that modifies the satellite attitude. This work proposes a speed PID controller for a reaction wheel using low-cost materials for its implementation in 1U CubeSats.