bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-weight Balance Design of Portal Crane Boom
Authors: Huang Yi , Zeng Haixia , Chen Yan
Published: June 2021

During the luffing of the portal crane, the height changing of the center of gravity of the boom needs to consume extra energy, which not only wastes energy, but also makes the luffing drive system need to use a larger motor. This paper uses the lever-movable counterweight balance method to design the self-weight balance of the portal crane, and verifies that the designed jib self-weight balance system meets the requirements of the maximum height deviation, unbalanced torque and comprehensive unbalanced torque by evenly taking points. The power and unnecessary energy consumption of the luffing drive mechanism are reduced.
Control system design of an intelligent food delivery robot
Authors: Zeng Haixia , Zhang Ziqing , Hong Yan
Published: June 2021

Contemporary many young people more and more choose to enjoy a variety of food outside, followed by a variety of food service industry emerging in an endless stream of new ideas, new changes. Nowadays, more and more intelligent food delivery robots are appearing in restaurants in many cities, making great contributions to the improvement of the cost and efficiency of food delivery in the catering industry. This paper designs a low-cost, efficient and intelligent food delivery robot, which can receive background instructions, choose the route and order for automatic food delivery, and automatically return after the task. The intelligent food delivery robot adopts a modular design method, mainly including power supply, microprocessor, the keys, drive, positioning, tracking navigation, obstacle avoidance and Wi-Fi communication parts.
A new approach to prepare Polyethylene Glycol Allyl Glycidyl Ether
Authors: Wang Huizhen , Xie Ruiyang , Chen Mingjun , Deng Weihao , Zhang Kaixin , Liu Jiaqin
Published: June 2021

The polyethylene glycol allyl glycidyl ether (PGAGE) is an important intermediate for preparing silicone softener that can be synthesized from allyl alcohol polyoxyethylene ether and epichlorohydrin (ECH). The performance parameters including the concentration of ECH, initial boron trifluoride diethyl etherate (BFEE) as well as CaCl2 quality were investigated respectively. The optimum process parameters which can get high capping and low by-product rate are as follows: the ECH concentration is 2.0 M, the initial BFEE concentration is 1.65mM, and the CaCl2 dosage is 1.65g/L. Under these conditions, the maximal yield can be improved to 91.36%, the percent of capping rate is higher than 98.16%, the residual concentration of F-is only 0.63 mg/L.
Study on the morphology and temperature-sensitivity of poly(N-isopropylacrylamide-co-acrylic acid) microgel by atomic force microscope
Authors: Wang Xiao , Li Yana , Zhang Guoquan , Wang Beihai
Published: June 2021

A group of crosslinked poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AAc)) microgels with different amount of acrylic acid (AAc) were synthesized by surfactant-free emulsion polymerization. The morphology and environmental sensitivity were studied by atomic force microscope (AFM). It was founded that the microgel particles were monodispersed and the diameter of the dried microgel latex particles was about 800nm. Moreover, the volume of the microgel particles decreased as the environmental temperature increased from 15ºC to 50ºC, which revealed the temperature-sensitivity of P(NIPAM-co-AAc)) microgel.
Chiral Pentaphenylpyrrole Derivatives with Aggregation-Induced Emission Enhancement and Aggregation Induced Circular Dichroism and Their Helical Self-assembly
Authors: Wang Yuanyuan , Zhang Longlong , Zhi Junge
Published: June 2021

A pair of enantiomers (S)-P5PdiAM and (R)-P5PdiAM containing two chiral substituents, and their raceme rac-P5PdiAM were synthesized by introducing (R)-/(S)- or racemic 1-phenylethylamine into 1-biphenyl-2,3,4,5-tetraphenylpyrrole. The target compounds all show weak aggregation-induced emission enhancement (AIEE) characteristics in the DMSO/H2O mixed system, indicating that the introduction of chirality hardly affect the photophysical properties of the compound. In addition, the chiral compounds (S)-P5PdiAM and (R)-P5PdiAM show strong circular dichroism (CD) signals in THF/H2O mixed solution with a water fraction of 70%, that is, they exhibit aggregation-induced circular dichroism characteristics (AICD). Because the aggregates of (S)-P5PdiAM and (R)-P5PdiAM emit weakly, there is no circularly polarized luminescence (CPL) signals upon aggregation. The chiral compounds (S)-P5PdiAM and (R)-P5PdiAM can self-assemble to form helical nanofibers in a THF/H2O mixture with a water fraction of 70%, while the racemic rac-P5PdiAM assembled to form nano-particles, indicating that chiral substituents have a great influence on the self-assembly and the morphologies of the nano-aggregates.
Influence of acid environment on Collapsibility of Loess
Authors: Zhang Yao , Jin Cheng , Hu Zaiqiang , Li Ning , Xi Yu
Published: June 2021

Cemented connection of loess is an important internal factor of loess collapsibility, which has a direct impact on its collapsibility. In this study, different concentrations of nitric acid were added to the immersion solution of loess collapsibility test, and the collapsibility sensitivity indexes of loess, such as collapsibility coefficient, stability time and collapsibility rate, were tested under acidic environment and different pressures. At the same time, scanning electron microscope was used to observe the changes of pore and structure of soil samples before and after the test. The test results show that in acid solution, the collapsibility coefficient of collapsible loess increases more under low pressure, and the collapsibility stability time of collapsible loess increases under different pressures. Loess has different collapsibility sensitive pressure range in aqueous solution and acidic solution. The structural strength of collapsible loess has an important influence on the depth of collapsible loess.
Temperature-dependent structure of molten eutectic Cu37Sb63
Authors: Ding Guohua , Liang Limeng
Published: June 2021

Quoted measurements of viscosity and our results of electrical resistivity experiments indicate two anomalous changes of physical properties take place in molten eutectic Cu37Sb63. Effective pair inter-ionic potentials evaluated using the hyper-netted chain theory further confirms the presence of two discontinuous structural transitions within the ranges from 1273K to 1073K and from 1073K to 903K, respectively. Moreover, the result of electrical resistivity experiments suggests the two structural transitions for molten Cu37Sb63 are reversible.
Effects of Apple Polyphenol on Fat Metabolism in Mice
Authors: Fu Ruimin , Tang Wei , Zhang Hong , Chang Huiping , Chen Wuling
Published: June 2021

To study the regulation effect of apple polyphenol on fat metabolism in mice. The mice were randomly divided into 5 groups, except the basic control group, the other 4 groups were given high fat diet, body weight was measured once a week, and the obesity model was established. The basal control group and the obesity model group were intragastrically given normal saline (4.2mg/(kgbw.d), The three dose groups were gavaged separately with apple polyphenol 4.2, 8.4, 12.6 mg/(kg bw. d). After 4 consecutive weeks, the body weight of mice, the contents of total cholesterol (TC), total triglyceride (TG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), malondialdehyde (MDA) in serum and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), liver lipase (HL) and lipoprotein lipase (LPL) in serum. should be measured respectively. Apple polyphenol can significantly reduce the body weight, TG, LDL-C, TC and MDA contents, coupled with the atherosclerosis index (AI) of obese mice. It can increase the serum HDL-C content of obese mice, and effectively increase the activities of SOD, GSH-Px, HL and LPL in mice. Apple Polyphenol can reduce blood lipid and prevent atherosclerosis via regulating fat metabolism in mice.
Trait-Based Models of Decomposition with Interspecific and Environmental Interactions
Authors: Liu SiYu , Wang RuiXi , Dong LuYao
Published: June 2021

Most saprotrophic fungi are dominant decomposers, and they play a vital role in the carbon cycle and stability of ecosystem. Previous researchers examined that how traits and environments influence the decomposition rate(DR), but few studies last long enough to scale short-term results up to long-term trends. In this paper, we build several trait-based models of decomposition with interspecific and environmental interactions to describe both short- and long-term trends. First, we build the model of decomposition ratio versus time with covariates – hyphal extension ratio and moisture tolerance for each species. Second, we define Interspecific Interference Ratio (IIR) to reflect interactions between fungi species and rank the relative competitiveness based on Grey System Theory with four evaluation indices: hyphal extension rate, moisture niche width, the hyphal density and thermal niche width. Then, we predict the relative advantages and disadvantages for different species by IIR and analyze the impact of biodiversity. Finally, we perform sensitivity and robustness analysis of our models, which exhibits the wide prospects and a deeper understanding of the role of fungi in the ecosystem.
Research on Copper Indium Gallium Selenide (CIGS) Thin-Film Solar Cells
Authors: Zhou Jixiang , Li Changyu
Published: June 2021

As a new-style solar cell, copper indium gallium selenide (CIGS) thin-film solar cell owns excellent characteristics of solar energy absorption, and it is one of the widely used thin-film solar cells. This paper mainly focuses on the research progress of this type of solar cell. Firstly, its theoretical principles are briefly described. Then, its cell materials, configuration and fabrication procedure are introduced. Subsequently, the remarkable research work about CIGS solar cell are reviewed. Finally, its commercial status is illustrated, followed by the critical issues and future perspectives.
Study on catalytic performance of MnOx nanoparticles for CO oxidation
Authors: Xu Jiayu , Zhang Hongpeng , Yan Chunxiao , Cheng Zhenxing
Published: June 2021

As a kind of toxic gas, carbon monoxide is often found in industrial waste gas, automobile exhaust, confined space such as submarines, etc. In recent years, the purification of carbon monoxide has attracted more and more attention. Catalytic oxidation has become a widely used method for carbon monoxide purification. In this paper, manganese oxide nanoparticles were synthesized by emulsion self-assembly method and characterized by X-ray powder diffraction (PXRD) and high-resolution transmission electron microscope (HRTEM). The activity of the oxide nanoparticle catalysts were evaluated on the fixed bed tubular quartz microreactor at atmospheric pressure. The effects of KMnO4 dosage, flow rate and temperature were investigated and the reaction kinetics range was determined.
Method for improving of activated sludge drying by the appropriate foaming pre-treatment
Authors: Li Xue , Hu Yining , Chen Liang , Song Yuhao , Liu Renguo , Yu Can
Published: June 2021

Due to the high viscosity and stickiness of dehydrated sludge, the combination of foaming pretreatment and drying process is an effective method to improve the drying performance of dehydrated sludge. In this study, alkali and industrial lignin fiber addition followed by mechanical whipping was employed for foaming the dewatered sludge. Using alkali alone as foaming agent, the optimal NaOH addition was found at 2.5 wt%, which was superior to adding CaO. Considering the maximum foaming efficiency, 2% industrial lignin fiber FH-300 collected as a conditioner and 1% NaOH was optimal. The foams in dewatered sludge were highly stable. The total number of bubbles of sludge with different densities had big differences. The diameters of bubbles concentrated on the range of 0.1 mm-0.3 mm.
Lithological body identification and insider description of H12 well area in Beier Sub-sag
Authors: li Guofu , Yan Ming , Liang Guofeng , Xu Weijia , Zhang Bin
Published: June 2021

On the basis of high-resolution seismic data, a high-frequency framework was established for the H12 well area. Combined with drilling analysis and sedimentary facies research, we analyzed favorable lithological development areas. Interpretation of subdivision layers in favorable lithological development areas, optimization of target sand bodies, and multi-attribute analysis techniques, we accurately describe the distribution of lithological bodies. By using spectral decomposition technology to perform insider characterization of lithological bodies, and combine with actual drilling to predict the distribution of effective reservoirs, we have summarized a set of effective methods for identifying such lithological traps.
Kinetics of Impurity Removal in Zinc Hydrometallurgy Based on Parameter Estimation
Authors: Wang Qianqian , Tang Minan , An Aimin , Lu Jiawei , Zhao Yingying
Published: June 2021

Impurity removal is a momentous part of zinc hydrometallurgy process. In this paper, a hybrid modeling method of mechanism modeling and parameter estimation modeling was proposed on the basis of not changing the actual production process of lead-zinc smeltery. Firstly, the overall nonlinear dynamic mechanism model was established, and then the deviation between the theoretical value and the actual detected outlet ion concentration was taken as the objective function to establish the parameter estimation optimization model. The gradient vector and Hessian matrix of the objective function with respect to the parameter vector were derived, and the algorithm based on the steepest descent and Newton method was given. Finally, using the production data of a lead-zinc smeltery in China, the model parameters were inversed. An intensive simulation validation and analysis of the dynamic characteristics shows the accuracy and the potential of the model, also in the perspective of practical implementation, which provides the basis for the optimal control of system output and the guidance for zinc powder addition.
Effect of hexamethylenetetramine on surface smoothness of electroplated copper coating
Authors: Jing Xiang , Wenjing Sheng , Jie Li , Chong Zeng , Yonggang Xu , Wenyao Yang , Jingjie Wang
Published: June 2021

In this paper, hexamethyltetramine is introduced into the electroplating bath to improve the surface morphology of electrodeposited copper. The cyclic voltammetry (CV) and dynamic polarization curves are used to study the effect of Cu(Ⅰ) and hexamethyltetramine on the electrochemical behaviors of electroplating solution. After implementing the electrodeposited copper experiment, scanning electron microscope (SEM) and X-ray diffraction (XRD) are used to explore the influence of Cu(Ⅰ) and hexamethyltetramine on the Surface morphology and crystal plane orientation of the electrodeposited copper. The results show that 5ppm hexamethyltetramine and 7.5ppm hexamethyltetramine can solve the problem of the loose and uneven surface of the electroplated copper layer caused by Cu(Ⅰ).
Study on the collapsibility sensitivity of loess in different acid environment by consolidometer
Authors: Zhang Yao , Jin Cheng , Li Ning , Hu Zaiqiang
Published: June 2021

Cement connection of loess is an important internal factor of loess collapse, which has a direct impact on the sensitivity of the collapse. In this study, different concentrations of nitric acid were added into the immersion water solution of loess collapsibility test. The collapsibility deformation and stability time were measured under different pressure and acid environment. The test results show that: in acid solution, the collapsibility coefficient of collapsible loess increases more under low pressure, and the collapsibility stability time is prolonged under all levels of pressure; Loess has different collapsibility sensitive pressure range in aqueous solution and acidic solution. The structural strength of collapsible loess has an important influence on the depth of collapsible loesr. It is very important to the constructions on the loess area
Hualong-One, le réacteur chinois de troisième génération
Authors: Jacoud Jean-Luc
Published: June 2021

Le Hualong-One est le réacteur développé par les industriels chinois sur la base de transferts technologiques antérieurs. Avec ce réacteur, la Chine ambitionne de développer son parc nucléaire et de s’imposer à l’export. Le 30 janvier 2021, Fuqing-5 est le premier Hualong-One à entrer en opération commerciale et, le 18 mars 2021, le premier des deux réacteurs en construction au Pakistan à être connecté au réseau.
One-Pot Synthetic Approaches for the Construction of Isochroman-4-ones and Benzoxazin-3-ones Using O,P-Acetals
Authors: Maegawa Tomohiro , Nakamura Akira , Yamamoto Kouhei , Murakami Ryo , Kawashita Norihito , Matsumoto Kouichi
Published: June 2021

A method for synthesizing six-membered heterocyclic compounds was developed based on the features of O,P-acetals. Sequential reactions of intramolecular cyclization between the methylene carbon atom of O,P-acetal and its electrophilic functional group (ester or protected carbamate) was followed by Horner–Wadsworth–Emmons (HWE) olefination with various aldehydes. The developed one-pot method yielded isochroman-4-one and benzoxazin-3-one derivatives with an alkylidene moiety.
Synthesis of a Glycosylphosphatidylinositol (GPI) Fragment as a Potential Substrate for Mannoprotein Transglycosidases
Authors: Belz Tyson F.
Published: June 2021

A glycophosphatidylinositol tetrasaccharide fragment was synthesized to mimic the core features of primary model, that of Saccharomyces cerevisiae. The salient feature of this approach is centered on the quick access to various α-1,2- and α-1,6-mannosyl and α-1,4-glycosyl linkages by using simple glycosylation and protective-group techniques. 1D and 2D-J-resolved NMR spectroscopy was used to verify the α-configuration of the new linkages. The tetrasaccharides obtained in this work are useful for examining fungal cell-wall glycoprotein cross-linking by transglycosidase enzymes for antifungal drug development.
Percutaneous Transhepatic and Translumbar Sclerotherapy of a Thoracic Duct Cyst: A Case Report
Authors: Alrashidi Ibrahim , Shin Ji Hoon
Published: June 2021

A 58-year-old male presented with chronic abdominal pain lasting 5 years and a 15 × 6-cm multicystic thoracic duct cyst with three compartments, located in the right retrocrural and retrocardiac regions from T5/T6 to T12/L1. A transhepatic route was selected to sclerose the middle and lower compartments. Subsequent contrast injection showed minimal contrast passage into the upper compartment through a narrow neck, but the guidewire could not pass into this compartment. The contrast-filled upper compartment was punctured with a 22-g Chiba needle using a translumbar approach under cone-beam computed tomography (CT) guidance and ethanol sclerotherapy was performed. Six-month follow-up CT revealed decreased thoracic duct cyst size (5×3 cm) and no pain. This case illustrates successful percutaneous transhepatic and translumbar sclerotherapy for retrocardiac and retrocrural thoracic duct cysts, which are very difficult to remove surgically.
Perception of Interventional Radiology among Jazan Medical Students: Assessment of Knowledge and Career Intentions
Authors: Bahkali Salha Al , Harbi Ali Al , Kamili Fatimah , Rashidi Ibrahim Al
Published: June 2021

Context Lack of awareness among the students in the medical field is the greatest challenge to overcome in the emergence of contemporary interventional radiology (IR).

Objectives We aimed to conduct a survey among medical students of Jazan University to explore their knowledge about IR, interest in IR as a future career, and preferred methods of training in IR.

Materials and Methods This was a cross-sectional, self-directed questionnaire study. The target population was all medical students at Jazan University. Surveys were sent to 600 students. The questionnaire consisted of 11 closed and open-ended questions.

Statistical Analysis We calculated the size of the sample using the Raosoft Sample Size Calculator Web site. Data analysis was performed using SPSS statistics.

Results A total of 270 students responded (45%); more than half of the respondents (58.5%) were in the preclinical stage, while the rest were in the clinical stage. About 62.5% of clinical students and 66.4% preclinical students reported that their perception regarding the terminology of IR was good or excellent. Regarding the identification of interventional radiologists, 50.9% from the clinical students thought them to be radiologists and 50% from preclinical students also identified them as such.

About 29.5% from the clinical students and 27.8% from the preclinical students thought them special surgeons, and 31.3% clinical students compared with 30.4% preclinical students believed they are vascular surgeons working with X-rays. About 19.6% clinical students compared with 17.7% preclinical students said they are general surgeons working with X-rays, and 48.2% clinical students compared with 45.6% preclinical students said they are special radiologists who work with percutaneous techniques. There was a significant difference (p = 0.041) in the responses between preclinical and clinical students regarding knowledge about what this medical specialty does. About 60.8% of clinical students reported that their knowledge and information regarding IR are efficient in comparison to 39.2% of preclinical students.

Conclusion This study demonstrated that the basic knowledge among Jazan medical students is poor. About half of the respondents were clinical students who understood the radiology specialty, compared with one-third of preclinical students. This could impact the student’s decision toward IR as a future career.
The epistemic foundations of injustice: lessons from the Young Marx
Authors: Casuso Gianfranco
Published: June 2021

This article intends to show to what extent the early Marxian categories of alienation, ideology and proletariat can serve to better understand current forms of epistemic injustice, as well as, conversely, how the latter can illuminate some unclear aspects of such concepts. In the first part, it will be explained the extent to which Marx’s concept of alienation accounts for the experience of an individual in a world to whose norms she is subject, but which she cannot recognise as her own. It will be shown that Marx finds the answer in a form of emancipatory praxis linked to a transformative appropriation of social reality. In order to deepen the understanding of this idea of emancipation, the second part will analyse the Marxian concept of the proletariat. It will be argued that taking up some considerations about the Hegelian figure of the rabble, Marx distinguishes a “liberal” from a “human” form of emancipation. In the third part, a contemporary example will be used to show the usefulness of the young Marx’s analyses concerning this dimension of emancipation struggles. In the fourth part, these ideas will be developed further through the concept of epistemic injustice, which has gained great importance in the recent studies that Critical Theory carries out of the different socio-epistemic blocks of an ideological nature that prevent articulating, communicating and overcoming negative experiences that hinder individual self-realisation. In this sense, it will be shown the importance of the Marxian categories of alienation and ideology to theoretically address current forms of epistemic injustice, and, in relation to this, it will be explained the transformative and constitutive function of the excluded in the creation of new sectors of reality through which their demands can be met.
UV-coated optical filters for space based optical systems to study space-based processes
Authors: McConnon Aili
Published: June 2021

Using atomic layer deposition to create high-precision, multilayer, UV-based optical systems to study star formation in galaxies
Coupled time resolved and high frequency modulated photoluminescence probing surface passivation of highly doped n-type InP samples
Authors: Zhao Wei , Bérenguier Baptiste , Rakotoarimanana Cendra , Gonçalves Anne-Marie , Etcheberry Arnaud , Frégnaux Mathieu , Lombez Laurent , Guillemoles Jean-François
Published: June 2021

Electronic passivation of III–V surfaces is essential for applications in optoelectronic devices. A key aspect is the measurement of the surface recombination properties, which can be done by various techniques including transient photoluminescence (TRPL) or luminescence quantum yield. These measurement techniques are always indirect since they suppose postulating a mathematical model for the data interpretation. Most common models use the notion of surface recombination velocity to quantify the surface recombination. In this paper, we demonstrate on the InP substrate that this notion is not always sufficient to represent the injection dependence of the surface phenomena. The study of power dependence of TRPL decays coupled with modulated photoluminescence (MPL) spectra on four samples from the same wafer with different surface treatments (epi-ready, freshly cleaned, after air exposure, and with poly-phosphazen passivation) allows us to discriminate between bulk and surface properties. We introduce surface defect trapping as an alternative to explain TRPL decays and MPL phase excitation power dependences of the three non-passivated samples. Surface trap parameters such as capture cross section and defect density are extracted. The passivated sample exhibits an invariant response shape on eight orders of magnitude of illumination. The stability of the PL response at high flux is in agreement with the perfect stability of the passivation layer, which is able to protect the InP surface without chemical changes over more than one year. They are linked to the nature of the passivation layer/InP interface. Other surface treatments were found to have an injection dependent response at high flux corresponding to different surface defect distributions but also possibly to surface chemical changes for the freshly cleaned sample.
The onset of uninhibited heat conduction and non-local absorption in flux-limited laser-plasma ablation
Authors: Ben Dov M. , Sapir N. , Pomerantz I.
Published: June 2021

We study the developing temperature profile in planar laser-ablation in the limit of a completely ionized low-Z plasma. The problem is analyzed both analytically and numerically, assuming complete laser absorption by near-critical absorption and inverse bremsstrahlung absorption, and heat conduction by flux-limited diffusion. We show through dimensional analysis that the temperature in the resulting corona and conduction zones is characterized by scaling relations expressed through three dimensional parameters and depends on two dimensionless parameters. Our results form a phase diagram for the behaviors of the maximal temperature as a function of time at different phases of the flow. The phase boundaries curve describes the transition times as a function of the flux limiter. We show that for low values of the flux-limiter the flow behavior is highly dependent on local details of the laser absorption at the critical surface. Measured experimentally, the identified transition times between the different phases can be used to infer the characteristic value of the flux-limiter.
On the pulsed–pulseless mode transition of negative DC corona in atmospheric nitrogen
Authors: Zhang Xing , Guo Yulin , Sun Anbang , Li Yanru , Zhang Guanjun , Yuan Xuchu , Abbas Muhammad Farasat
Published: June 2021

Pulsed mode as a common phenomenon appears in many kinds of DC corona discharge, whose characteristics can be affected by some specific factors. In this paper, an important research field of pulsed mode, pulsed–pulseless mode transition, is investigated in needle–plate electrodes in nitrogen at atmospheric pressure, and we discuss the effect of external circuit, gas temperature, and associative ionization on mode transition by experiment and simulation. The external circuit coupling with plasma can make the pulseless mode be achieved when there is a balance of charge between loss by discharge and gain by source before discharge quenches. The time-averaged gas temperature remains at 700 K which is regardless of source voltage and discharge mode, so gas heating is not a critical factor for mode transition. We investigate the effect of the associative ionization involving metastable particles by comparing the results with and without associative ionization reactions in the simulation; we find that the associative ionization is vital to determine the cathode voltage, discharge current, and the concentrative shape of discharge in the pulseless mode. Finally, we compare the pulsed–pulseless mode transition in nitrogen and air to clarify the effect of specific factors that depend on electronegativity of gas.
Ignition and propagation of nanosecond pulsed plasmas in distilled water—Negative vs positive polarity applied to a pin electrode
Authors: Grosse K. , Falke M. , von Keudell A.
Published: June 2021

Nanosecond plasmas in liquids are being used for water treatment, electrolysis, or biomedical applications. The exact nature of these very dynamic plasmas and, most importantly, their ignition physics are strongly debated. The ignition itself may be explained by two competing hypotheses: ignition in water may occur (i) via field effects at the tip of the electrode followed by tunneling of electrons in between water molecules causing field ionization or (ii) via gaseous processes of electron multiplication in nanovoids that are created from liquid ruptures due to the strong electric field gradients. Both hypotheses are supported by theory, but experimental data are very sparse due to the difficulty in monitoring the very fast processes in space and time. In this paper, we analyze nanosecond plasmas in water that are created by applying a positive and a negative polarity to a sharp tungsten electrode. The main diagnostics are fast camera measurements and fast emission spectroscopy. It is shown that plasma ignition is dominated by field effects at the electrode–liquid interface either as field ionization for positive polarity or as field emission for negative polarity. This leads to a hot tungsten surface at a temperature of 7000 K for positive polarity, whereas the surface temperature is much lower for negative polarity. At ignition, the electron density reaches 4×1025 m−3 for the positive and 2×1025 m−3 for the negative polarity. At the same time, the emission of the Hα light for the positive polarity is four times higher than that for the negative polarity. During plasma propagation, the electron densities are almost identical of the order of 1–2×1025 m−3 followed by a decay after the end of the pulse over 15 ns. It is concluded that plasma propagation is governed by field effects in a low density region that is created either by nanovoids or by density fluctuations in supercritical water surrounding the electrode that is created by the pressure and temperature at the moment of plasma ignition.
Effective anisotropy of periodic acoustic and elastic composites
Authors: Laude Vincent , Iglesias Martínez Julio Andrés , Wang Yan-Feng , Kadic Muamer
Published: June 2021

The propagation of acoustic or elastic waves in artificial crystals, including the case of phononic and sonic crystals, is inherently anisotropic. As is known from the theory of periodic composites, anisotropy is directly dictated by the space group of the unit cell of the crystal and the rank of the elastic tensor. Here, we examine effective velocities in the long wavelength limit of periodic acoustic and elastic composites as a function of the direction of propagation. We derive explicit and efficient formulas for estimating the effective velocity surfaces based on the second-order perturbation theory, generalizing the Christoffel equation for elastic waves in solids. We identify strongly anisotropic sonic crystals for scalar acoustic waves and strongly anisotropic phononic crystals for vector elastic waves. Furthermore, we observe that under specific conditions, quasi-longitudinal waves can be made much slower than shear waves propagating in the same direction.
Effective plasma frequency in tunable THz reflectors based on graphene and phosphorene
Authors: Tepanecatl Fuentes L. A. , Fuentecilla-Carcamo I. , Gutierrez-Villarreal J. M. , Gaspar-Armenta Jorge A. , Palomino-Ovando M. A. , Hernández-Cocoletzi G.
Published: June 2021

In this work, we show that a THz reflector made of a phosphorene (graphene)–dielectric multilayer can be analyzed through a simple effective plasma frequency model. We obtain the cutoff frequency, marking the beginning of the transmission region in terms of the effective plasma frequency, which depends on structural parameters of the multilayer and, more importantly, on the carrier density of phosphorene (graphene) layers. This implies that the cutoff frequency can be varied when considering carrier density tuning. We also show that the frequency regime, where cutoff frequency is obtained by carrier density tuning, goes through a wide range in the THz domain (3–25 THz), making the design of tunable reflectors in these frequencies possible through electrical doping. We numerically analyze the cutoff frequency as a function of carrier density and optical thickness of the multilayer, finding that the cutoff frequency and carrier density of phosphorene (graphene) have a very simple quadratic (quartic) relation. Our analysis allows us to obtain ranges where the effective analytical model fits better with the cutoff frequency computed from photonic bands for the multilayer periodic structure.
An ultraviolet-ozone post-treatment to remove the inherent impurities in all-ambient solution-processed CsPbBr3 perovskite films
Authors: Li Jincheng , Feng Jianyong , Huang Huiting , Zhu Zhi , Han Xiaopeng , Yu Tao , Li Zhaosheng , Zou Zhigang
Published: June 2021

It is very important to exclude impurities during the material preparation process for the production of high-quality optoelectronic devices. For the all-ambient solution-processed CsPbBr3 films, unexpected inherent impurities could be inadvertently introduced, which would induce electronic trap states and impede carrier transport in the as-derived CsPbBr3-based optoelectronic devices, such as all-inorganic perovskite solar cells (PSCs). Herein, it is found that ultraviolet-ozone (UVO) post-treatment, which is usually applied for cleaning substrates, has the ability to remove these harmful impurities in all-ambient solution-processed CsPbBr3 films. Upon proper UVO post-treatment, the assembled PSC with the architecture of fluorine-doped tin oxide/compact TiO2 (c-TiO2)/CsPbBr3/carbon exhibits an improved power conversion efficiency of 7.82% from 7.37%. X-ray photoelectron spectroscopy measurements demonstrate that the undesirable inherent impurities in all-ambient solution-processed CsPbBr3 films may be related to organic solvents and adsorbates, which can be removed effectively by UVO post-treatment. After UVO post-treatment, photoluminescence and space-charge-limited current measurements reveal that CsPbBr3 films possess reduced trap states. Meanwhile, due to the enhanced contact between the CsPbBr3 film and the subsequently deposited carbon electrode, the charge collection at the interface is effectively promoted. Our work not only finds the influence of the inherent impurities residual in all-ambient solution process, but also proposes a simple and effective strategy to remove these impurities.
Numerical study of light emission from a micro-hollow cathode discharge; the effects of different working gases
Authors: Namvar L. , Foroutan G. , Foroutan V.
Published: June 2021

This work addresses the ultraviolet, infrared, and visible light emissions from a micro-hollow cathode discharge operating at the self-pulsing regime. Three different gas mixtures, i.e., He–Xe, Ne–Xe, and He–Ne–Xe, are investigated. A volume-averaged approach with a comprehensive chemistry model is used to simulate the discharge. The effects of different gas mixtures, the total gas pressure, and the concentration of xenon atoms on the generation of different species, as well as on the light emissions, are carefully studied. The results show that the infrared efficiency of the micro-hollow cathode discharge is dramatically low (less than 0.001%), but its ultraviolet efficiency, with a maximum of 38% for a pure Xe discharge, is even higher than that of plasma display panels, which have a maximum of 35%. The ultraviolet efficiency of the Ne–Xe discharge is higher than that of the He–Xe at low xenon concentrations, whereas the reverse is true at higher concentrations. It is also found that there is an optimum pressure that maximizes the excimers’ densities and consequently the amount of ultraviolet radiation. The optimum pressure depends on the hole diameter of the hollow cathode structure. A comparison between different gas mixtures revealed that the ultraviolet efficiency of the He–Ne–Xe mixture at certain mixing ratios, e.g., 0.45He–0.45Ne–0.1Xe, can be much higher than those of He–Xe and Ne–Xe mixtures.
Study on the reaction rate model for shock initiation of aluminized hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) explosive under shock waves
Authors: Wang Hongfu , Liu Yan , Bai Fan , Huang Fenglei
Published: June 2021

To investigate the influence of the aluminum (Al) powder sizes on shock initiation of aluminized hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), shock initiation experiments were carried out. The experimental results show that as the Al constituent size decreases, a rapid increase in the propagation velocity of the precursory shock waves enhances the peak pressures, shortens the time intervals between the peak pressures and the arrival times of precursory shock waves, and improves the shock sensitivity of the aluminized RDX. Consequently, to predict and evaluate the stability of aluminized RDX with small-size Al powder, a microscopic reaction rate model for shock initiation was established. This model includes the pore collapse model of a double-layered spherical shell structure composed of an RDX spherical shell and a mixture (of Al powder and binders) spherical shell and the reaction model of Al powder in RDX decomposition products under the effect of shock waves and thermal energy released by RDX. The simulation results show that when the diameter of the Al powder is about 1/5 or less of the size of the base explosive (RDX) particles, the microscopic reaction rate model can accurately simulate the shock initiation process of aluminized RDX. As the Al powder size decreases, the reaction rate and the proportion of the Al involved in the initiation reaction for aluminized RDX increase.
Effect of liquid–air interface on particle cloud dynamics in viscous liquids
Authors: Harikrishnan S , Mahapatra Pallab Sinha
Published: June 2021

Three-dimensional numerical investigations have been performed to study the effect of liquid–air interface on particle cloud evolution in the stagnant pool of viscous liquid. Computations have been carried out using open-source computational fluid dynamics package open-source field operation and manipulation under different operating conditions. A hybrid multifluid–volume-of-fluid-based solver is used to identify the influence of liquid–air interface on particle cloud dynamics. Mainly, two different operating conditions have been considered in the present study, viz., falling particle cloud within the liquid and falling from the liquid–air interface. The effect of particle Reynolds number (Re) on cloud evolution has also been considered in the present study. The effect of the liquid–air interface on particle cloud dynamics has been qualitatively explained with the help of particle volume fraction iso-surface, liquid velocity vectors, and iso-Q-surface, and quantitatively explained with the help of average particle cloud velocity, penetration depth, plume half-width, and particle cloud mass. Proper orthogonal decomposition-based analysis has been used to explain the vortex structures generated in the viscous fluid for different cases. Releasing particle cloud from liquid–air interface decreases radial spreading as compared to the case of particle release within the liquid. Particle cloud evolution pattern is found to depend on particle Reynolds number only for the case with the liquid–air interface. The liquid–air interface's downward movement enhances and upward movement suppresses the spreading of the particle cloud, which subsequently alters the particle dispersion mechanisms in the later stages.
Thermal conductance of nanostructured interfaces from Monte Carlo simulations with ab initio-based phonon properties
Authors: Zhao Xinpeng , Qian Xin , Li Xiaobo , Yang Ronggui
Published: June 2021

Interfaces are ubiquitous in electronics, photonics, and advanced materials. Interface engineering has become an essential strategy for developing functional materials with low thermal conductivities such as thermoelectric materials and thermal barrier coatings. On the other hand, interfaces are becoming a bottleneck for thermal management in electronic devices. Recent experiments have shown that a fin-like nanostructured interface with a size of 30–100 nm could enhance thermal transport across interfaces. Since phonon mean free paths span from several nanometers to dozens of micrometers, depending on the material, the size of the interface features may significantly affect the phonon transport regime and interface conductance. Here, the Monte Carlo simulation, with ab initio-based phonon properties as input parameters, was developed to study thermal conductance of a fin-like nanostructured interface. Simulated results indicate that the nanofin size (i.e., width, spacing, and height) significantly affects interface thermal conductance. Interface conductance is found to first increase and then decrease with increasing width of the nanofin when its height is 100 nm. This phenomenon is attributed to competition between the enlarged interface area and increased backscattering of transmitted phonons. This study demonstrates the existence of an optimal nanofin size for maximizing interface conductance, which could be important for thermal management of high-power electronics using nanostructured interfaces.
On quasineutral plasma flow in the magnetic nozzle
Authors: Smolyakov A. I. , Sabo A. , Yushmanov P. , Putvinskii S.
Published: June 2021

Exact solutions for quasineutral plasma acceleration of magnetized plasma in the paraxial magnetic nozzle are obtained. It is shown that the non-monotonic magnetic field with a local maximum of the magnetic field is a necessary condition for the formation of the quasineutral accelerating potential structure. A global nature of the accelerating potential that occurs as a result of the constraint due to the regularity condition at the sonic point is emphasized, and properties of such solutions are discussed for the case of general polytropic equation of state for electrons.
Mechanically induced Shapiro steps: Enormous effect of vibrations on the charge-density wave transport
Authors: Nikitin M. V. , Zybtsev S. G. , Pokrovskii V. Ya. , Loginov B. A.
Published: June 2021

Charge-density wave (CDW) transport is studied in the whiskers of orthorhombic TaS3 suspended between piezoelectric actuators. It is found that when the frequency of rf voltage applied to the actuators coincides with a vibration resonance of the whisker, the I–V curves show Shapiro-step-like features, similar with those under rf voltage applied directly to the sample. We provide evidence that the features observed are coupled with the periodic lattice deformation. The effect of vibrations appears surprisingly strong: a time-dependent strain not exceeding 10−4 results in a periodic stop of the CDW. The result suggests an area of electromechanical effects inherent to sliding CDWs.
Low lattice thermal conductivity of pentadiamond
Authors: Chen Yanyan , Sun Jie , Li Tingwei , Wang Qian
Published: June 2021

The lattice thermal conductivity of carbon materials is particularly interesting because it can vary within a range spanning five orders of magnitude depending on the atomic configuration. Herein, we systematically study the lattice thermal conductivity and phonon transport properties of pentadiamond, a new three-dimensional carbon allotrope consisting of pentagonal carbon rings. Based on first-principles calculations and an iterative solution to the linearized Boltzmann transport equation, the intrinsic lattice thermal conductivity (kl) is found to be 490.88 W/mK at room temperature, much lower than 2664.93 W/mK of diamond. A detailed analysis of both harmonic and anharmonic properties reveals that the low kl of pentadiamond essentially originates from its large phonon phase space, short phonon relaxation time resulting from strong overlap between the acoustic and low-lying optical phonon branches, and the low phonon group velocity. The distinct thermal transport behavior exhibited in pentadiamond further shows the diversity and complexity in lattice thermal conductivity of carbon allotropes.
Exact solutions of Stokes' second problem for hybrid nanofluid flow with a heat source
Authors: Roy Nepal Chandra , Pop Ioan
Published: June 2021

In this study, Stokes' second problem for Cu-Al2O3/water hybrid nanofluid is considered along with the effects of buoyancy force and a heat source. Using Laplace transforms, transient velocity, skin friction coefficient, and local Nusselt number are established in closed forms involving exponentials and error functions. The exact solutions have been compared with the numerical solutions as well as with available exact solutions, which show excellent agreement. It is found that the temperature, skin friction coefficient, and local Nusselt number are strongly affected and increased owing to the increase in the volume fractions of copper and alumina nanoparticles and heat source parameter. On the other hand, the mixed convection parameter noticeably enhances the flow velocity. When the heat source is absent, the skin friction coefficients are oscillating and the heat transfer approaches an asymptotic value. However, for a higher heat source parameter, when time increases, the amplitude of oscillation of the skin friction coefficients gradually increases and the magnitude of heat transfer exponentially increases. Both eventually go to infinity after a long period of time.
Visualization of β-adrenergic receptor dynamics and differential localization in cardiomyocytes
Authors: Bathe-Peters Marc , Gmach Philipp , Boltz Horst-Holger , Einsiedel Jürgen , Gotthardt Michael , Hübner Harald , Gmeiner Peter , Lohse Martin J. , Annibale Paolo
Published: June 2021

Significance

We custom synthesize a fluorescent ligand and use highly sensitive microscopy methods to show that receptors may be targeted to distinct sites of a cell. We provide microscopic images of the localization of β
1
‐adrenergic receptors (β
1
-ARs) and β
2
‐adrenergic receptors (β
2
‐ARs), main drivers of the contractility of the heart, in heart muscle cells. We show that β
2
‐ARs are exclusively targeted to specific structures in these cells, the T-tubules, while β
1
-ARs are found at the entire cell surface and in T-tubules. Such differential localization may explain their different physiological functions, even though they trigger the same biochemical signal, i.e. an increase in cyclic adenosine monophosphate (cAMP). Thus, receptor function may be determined not only by their biochemical signals, but also by their specific cellular localization.