bluuebunny/crossref_metadata_2025 huggingface dataset:
Elastic constants of beta tungsten thin films studied by picosecond ultrasonics and density functional theory
Authors: Nagakubo A. , Lee H. T. , Ogi H. , Moriyama T. , Ono T.
Published: January 2020

Tungsten thin films are used for various applications and sometimes exhibit an A15 structure (β-W). They have some superior properties in comparison to the bcc structure (α-W), such as a higher superconducting transition temperature and larger spin Hall angle. However, elastic constants of β-W are unclear, which restricts mechanical applications and reliable density-functional-theory calculations. In this study, we synthesized α-W, β-W, and mixed-phase W films and determined their elastic constants by picosecond ultrasonics. We also calculated the elastic constants based on density functional theory and reveal that β-W has a larger elastic anisotropy and smaller shear modulus. Our calculation further indicates a stable stacking faulted β-W, which leads to a monoclinic structure.
Theoretical model of spintronic device based on tunable anomalous Hall conductivity of monolayer CrI3
Authors: Zhu Mingfeng , Yao Haibo , Jiang Liwei , Zheng Yisong
Published: January 2020

Based on density functional theory, we study the intrinsic anomalous Hall conductivity (AHC) of monolayer (ML) CrI3 in different magnetic configurations. We find that ML CrI3 in both the in-plane and off-plane ferromagnetic (FM) states hosts significant AHC, with quantum plateaus occurring at topologically nontrivial bandgaps. In the in-plane FM state, the AHC of ML CrI3 depends sensitively on the magnetization direction. First, the sign of AHC can be inverted whenever the magnetization angle increases by 60°. Second, the AHC vanishes if the magnetization angle is equal to the odd times of 30°. By doping electrons and applying moderate strain, one can switch the magnetic ground state between the off- and in-plane FM states and manipulate the magnitude and sign of the AHC. Based on these features of AHC of ML CrI3, we propose a theoretical model to realize the functions of spintronic devices such as the reversible spin transport, magnetic sensors, or magnetic read-in head.
Super-resolution photoluminescence lifetime and intensity mapping of interacting CdSe/CdS quantum dots
Authors: Dunlap Megan K. , Ryan Duncan P. , Goodwin Peter M. , Werner James H. , Majumder Somak , Hollingsworth Jennifer A. , Gelfand Martin P. , Van Orden Alan
Published: January 2020

We report an optical imaging method that simultaneously achieves nanometer-scale spatial resolution and records single-photon arrival times with subnanosecond temporal resolution, allowing for visualization of nanoscale photoluminescence dynamics. The technique combines time-correlated single-photon counting with single-molecule localization microscopy by monitoring the emission centroid location with a 2 × 2 array of optical fibers that are coupled to four single-photon counting detectors. We applied this method to image isolated and clustered CdSe/CdS core/shell quantum dots (QDs). Single QDs were localized with ∼5 nm precision using 104 detected photons. Within clusters, emission centroids separated by ∼12 nm were resolved, and spatial mapping of both the emission intensity and lifetime provided evidence of energy transport pathways among the QDs.
Quantum mechanical/molecular mechanical trajectory surface hopping molecular dynamics simulation by spin-flip time-dependent density functional theory
Authors: Minezawa Noriyuki , Nakajima Takahito
Published: January 2020

This paper presents the nonadiabatic molecular dynamics simulation in the solution phase using the spin-flip time-dependent density functional theory (SF-TDDFT). Despite the single-reference level of theory, the SF-TDDFT method can generate the correct topology of S0/S1 crossing points, thus providing a natural S1 → S0 nonadiabatic transition. We extend the gas-phase trajectory surface hopping simulation with the SF-TDDFT [N. Minezawa and T. Nakajima, J. Chem. Phys. 150, 204120 (2019)] to the hybrid quantum mechanical/molecular mechanics (QM/MM) scheme. To this end, we modify the code to evaluate the electrostatic interaction between the QM and MM atoms and to extract the classical MM energy and forces from the MM program package. We apply the proposed method to the photoisomerization reaction of aqueous E-azomethane and anionic green fluorescent protein chromophore in water and compare the results with those of the previous simulation studies based on the multireference methods.
Comparison of time reversal symmetric and asymmetric nano-swimmers oriented with an electric field in soft matter
Authors: Rajonson G. , Poulet D. , Bruneau M. , Teboul V.
Published: January 2020

Using molecular dynamics simulations, we compare the motion of a nanoswimmer based on Purcell’s suggested motor with a time asymmetrical cycle with the motion of the same molecular motor with a time symmetrical cycle. We show that Purcell’s theorem still holds at the nanoscale, despite the local structure and the medium’s fluctuations. Then, with the purpose of both orienting the swimmer’s displacement and increasing the breakdown of the theorem, we study the effect of an electric field on a polarized version of these swimmers. For small and large fields, the time asymmetrical swimmer is more efficient, as suggested by Purcell. However, we find a field range for which Purcell’s theorem is broken for the time symmetric motor. Results suggest that the breakdown of the theorem arises from the competition of the orientation field and Brownian forces, while for larger fields, the field destroys the effect of fluctuations restoring the theorem.
Temperature dependence of tunneling current in Pt/Nb:SrTiO3 Schottky junction
Authors: Kim Yeon Soo , Hwang Sung Moon , Yoon Chansoo , Lee Ji Hye , Jeon Jihoon , Choi Taekjib , Park Bae Ho
Published: January 2020

We investigate temperature-dependent electrical properties of Pt/Nb:SrTiO3 Schottky junctions by measuring current–voltage and capacitance–voltage curves at various temperatures (20 K–300 K). Interestingly, the Schottky junctions have shown different temperature dependences of resistance according to the polarity of bias voltage: insulating behaviors are displayed in the positive bias branch, while metallic behaviors are observed in the negative bias branch. These behaviors can be ascribed to Schottky barrier modulation that arises from the temperature and field dependences of dielectric permittivity of SrTiO3. The modulation of the barrier profile determines anomalous tunneling current in the negative bias branch as a function of temperature. These comprehensive analyses could not only reveal the rich physics of the Pt/Nb:SrTiO3 Schottky junction but also enhance our understanding for high dielectric materials.
Remarkably enhanced hybrid piezo/triboelectric nanogenerator via rational modulation of piezoelectric and dielectric properties for self-powered electronics
Authors: Wang Weichao , Zhang Jiawei , Zhang Yaju , Chen Fangqi , Wang Heyi , Wu Mengjun , Li Hui , Zhu Quanyong , Zheng Haiwu , Zhang Renyun
Published: January 2020

The hybridization of different materials for energy scavenging techniques based on piezoelectric and triboelectric effects has been studied widely for various applications of nanogenerators. However, there are few reports utilizing the same oxide matrix materials with appropriate doping to simultaneously enhance the piezoelectric and triboelectric outputs. Herein, a hybrid nanogenerator (HG) consisting of a piezoelectric nanogenerator (PENG) and a triboelectric nanogenerator (TENG) was constructed using (Ba0.838Ca0.162)(Ti0.9072Zr0.092)O3 (BCZTO)/polydimethylsiloxane (PDMS) as a piezoelectric layer and Ba(Ti0.8Zr0.2)O3 (BZTO)/PDMS as a triboelectric layer. For the PENG, how the electrical output was related to the BCZTO ratio in the BCZTO/PDMS composite films was systematically investigated. For the TENG, remarkably enhanced output performance is attributed to the ferroelectric polarization and large permittivity of the BZTO/PDMS. The Kelvin probe force microscopy measurements show that the poled BZTO/PDMS composite film with a 20 wt. % mass ratio of BZTO has the highest surface charge potential, in line with the macroscopic electrical outputs of the TENG. Interestingly, the output performance of the PENG in the HG is significantly enhanced compared to the PENG acting alone, which is also verified by COMSOL simulation. After rectification, the HG can produce a maximum output voltage of 390 V and a current density of 47 mA/m2. This work not only provides a feasible solution to enhance the output performance of the HG but also offers an effective approach to develop a small, portable power source with promising application in self-powered electronics.
Flow of wormlike micellar solutions through a long micropore with step expansion and contraction
Authors: Sasmal C.
Published: January 2020

In this study, an extensive numerical investigation has been carried out in order to understand the flow characteristics of a wormlike micellar (WLM) solution through a long micropore with step expansion and contraction. The VCM (Vasquez-Cook-McKinley) [P. A. Vasquez, G. H. McKinley, and P. L. Cook, “A network scission model for wormlike micellar solutions: I. Model formulation and viscometric flow predictions,” J. Non-Newtonian Fluid Mech. 144, 122–139 (2007)] constitutive model has been used for the present WLM solution for predicting its rheological behavior and the governing equations, namely, mass and momentum equations along with the VCM constitutive model equations have been solved using the finite-volume method based open source code OpenFOAM. Within the range of conditions encompassed in this study, different flow regimes have been observed in the pore geometry, for instance, Newtonian like regime, lip vortex formation regime, unsteady and vortex merging regime, etc. In particular, an elastic instability regime has been observed in the pore geometry, and the onset of this regime is accentuated with the increasing values of the Weissenberg number and decreasing values of the nonlinear VCM model parameter ξ. Apart from the flow pattern, a detailed discussion on the distribution of the wormlike micellar concentration, principal stress difference, apparent relative viscosity, etc., is also presented. Finally, a good qualitative agreement (in terms of the flow pattern) has been found between the present simulations and the corresponding experiments.
Orbital localization error of density functional theory in shear properties of vanadium and niobium
Authors: Wang Yi X. , Geng Hua Y. , Wu Q. , Chen Xiang R.
Published: January 2020

It is believed that the density functional theory (DFT) describes most elements with s, p, and d orbitals very well, except some materials that have strongly localized and correlated valence electrons. In this work, we find that the widely employed exchange-correlation (XC) functionals, including local-density approximation (LDA), generalized gradient approximation (GGA), and meta-GGA, underestimate the shear modulus and phase stability of V and Nb greatly. The advanced hybrid functional that is usually better for correlated systems, on the other hand, completely fails in these two simple metals. This striking failure is revealed due to the orbital localization error in GGA, which is further deteriorated by hybrid functionals. This observation is corroborated by a similar failure of DFT+U and van der Waals functionals when applied to V and Nb. To remedy this problem, a semiempirical approach of DFT+J is proposed, which can delocalize electrons by facilitating the on-site exchange. Furthermore, it is observed that including density derivatives slightly improves the performance of the semilocal functionals, with meta-GGA outperforms GGA, and the latter is better than LDA. This discovery indicates the possibility and necessity to include higher-order density derivatives beyond the Laplacian level for the purpose of removing the orbital localization error (mainly from d orbitals) and delocalization error (mainly from s and p orbitals) completely in V and Nb so that a better description of their electronic structures is achieved. The same strategy can be applied to the other d electron system and f electron system.
Evaluation of the spectrum of a quantum system using machine learning based on incomplete information about the wavefunctions
Authors: Burlak Gennadiy
Published: January 2020

We propose an effective approach for rapid estimation of the energy spectrum of quantum systems with the use of the machine learning (ML) algorithm. In the ML approach (backpropagation), the wavefunction data obtained from experiments are interpreted as the attribute class (input data), while the spectrum of quantum numbers establishes the label class (output data). To evaluate this approach, we employ two exactly solvable models with the random modulated wavefunction amplitude. The random factor allows modeling the incompleteness of information about the state of quantum system. The trial wave functions are fed into the neural network, with the goal of making prediction about the spectrum of quantum numbers. We found that in such a configuration, the training process occurs with rapid convergence if the number of analyzed quantum states is not too large. The two qubit entanglement is studied as well. The accuracy of the test prediction (after training) reached 98%. It is considered that the ML approach opens up important perspectives to plane the quantum measurements and optimal monitoring of complex quantum objects.
Ultrafast excited-state proton transfer dynamics in dihalogenated non-fluorescent and fluorescent GFP chromophores
Authors: Chen Cheng , Zhu Liangdong , Boulanger Sean A. , Baleeva Nadezhda S. , Myasnyanko Ivan N. , Baranov Mikhail S. , Fang Chong
Published: January 2020

Green fluorescent protein (GFP) has enabled a myriad of bioimaging advances due to its photophysical and photochemical properties. To deepen the mechanistic understanding of such light-induced processes, novel derivatives of GFP chromophore p-HBDI were engineered by fluorination or bromination of the phenolic moiety into superphotoacids, which efficiently undergo excited-state proton transfer (ESPT) in aqueous solution within the short lifetime of the excited state, as opposed to p-HBDI where efficient ESPT is not observed. In addition, we tuned the excited-state lifetime from picoseconds to nanoseconds by conformational locking of the p-HBDI backbone, essentially transforming the nonfluorescent chromophores into highly fluorescent ones. The unlocked superphotoacids undergo a barrierless ESPT without much solvent activity, whereas the locked counterparts exhibit two distinct solvent-involved ESPT pathways. Comparative analysis of femtosecond transient absorption spectra of these unlocked and locked superphotoacids reveals that the ESPT rates adopt an “inverted” kinetic behavior as the thermodynamic driving force increases upon locking the backbone. Further experimental and theoretical investigations are expected to shed more light on the interplay between the modified electronic structure (mainly by dihalogenation) and nuclear motions (by conformational locking) of the functionalized GFP derivatives (e.g., fluorescence on and off).
Spin-valve Josephson junctions with perpendicular magnetic anisotropy for cryogenic memory
Authors: Satchell N. , Shepley P. M. , Algarni M. , Vaughan M. , Darwin E. , Ali M. , Rosamond M. C. , Chen L. , Linfield E. H. , Hickey B. J. , Burnell G.
Published: January 2020

We demonstrate a Josephson junction with a weak link containing two ferromagnets with perpendicular magnetic anisotropy and independent switching fields in which the critical current can be set by the mutual orientation of the two layers. Such pseudospin-valve Josephson junctions are a candidate cryogenic memory in an all superconducting computational scheme. Here, we use Pt/Co/Pt/CoB/Pt as the weak link of the junction with dCo=0.6 nm, dCoB=0.3 nm, and dPt=5 nm and obtain a 60% change in the critical current for the two magnetization configurations of the pseudospin-valve. Ferromagnets with perpendicular magnetic anisotropy have advantages over magnetization in-plane systems, which have been exclusively considered at this point, as, in principle, the magnetization and magnetic switching of layers in the junction should not affect the in-plane magnetic flux.
Molecular orientation of disk-shaped small molecules exhibiting thermally activated delayed fluorescence in host–guest films
Authors: Tanaka Masaki , Noda Hiroki , Nakanotani Hajime , Adachi Chihaya
Published: January 2020

Control of the molecular orientation in a glassy film is a crucial issue, not only for an understanding of the fundamental processes of organic amorphous film formation but also for enhancement of the performance of organic light-emitting diodes (OLEDs) by increasing their light-outcoupling efficiency. In this study, the molecular orientation in codeposited films composed of a host molecule and a disk-shaped emitter that exhibits thermally activated delayed fluorescence is investigated systematically. It is found that the orientation of the transition dipole moment (TDM) of the disk-shaped emitters is strongly dependent on the glass transition temperature and the polarization of the host molecules, and almost perfectly horizontal orientation of the TDM of the disk-shaped emitters can be realized. Our findings clarify the role of the host–guest dipole–dipole interaction in the molecular orientation, and it will enable the expansion of both the molecular design and the material combination rules for high-performance OLEDs.
Effects of palmitic acid (16:0), hexacosanoic acid (26:0), ethephon and methyl jasmonate on the cuticular wax composition, structure and expression of key gene in the fruits of three pear cultivars
Authors: Wu Xiao , Chen Yangyang , Shi Xinjie , Qi Kaijie , Cao Peng , Liu Xueying , Yin Hao , Zhang Shaoling
Published: January 2020

The chemical composition, crystal morphology and expression levels of associated genes involved in the cuticular wax of three pear cultivars ‘Housui’, ‘Cuiguan’ and ‘Yuluxiang’ after treatment with palmitic acid (PA), hexacosanoic acid (HA), ethephon and methyl jasmonate (Meja) were determined. A total of 59 cuticular wax compounds were detected across all samples. The wax coverage of ‘Housui’ fruits increased by 71.74, 93.48 and 89.13% after treatment with PA, ethephon and Meja, respectively, and treatment with PA, HA and Meja also increased the wax coverage in ‘Cuiguan’ (65.33, 20.00 and 21.33% respectively) and in ‘Yuluxiang’ (38.60, 63.16 and 42.11% respectively) fruits. Heatmap clustering analysis and partial least-squares-discriminate analysis (PLS-DA) also revealed that the different treatments exerted various influences on cuticular wax among the different cultivars. In addition, the wax component coverage and wax crystal structures showed variations among the different cultivars as well as different treatments. Gene expression analysis revealed 11 genes likely to be involved in pear fruit wax synthesis, transport and regulation. Taken together, the results of this study demonstrate that the differences in the cuticular waxes of the fruits of different cultivars after treatment with PA, HA, ethephon or Meja might lead to a better understanding of the regulatory effect of a substrate or elicitor on the composition and deposition of cuticular waxes.
The interactive effects of soil disturbance and residue quality on soil nitrogen mineralisation in a tropical sandy soil
Authors: Butnan Somchai , Vityakon Patma
Published: January 2020

Soil conservation practices, such as reduced and no tillage, have been found to enhance soil nitrogen (N) sequestration through decreasing the rate of N mineralisation of added organic materials. Nitrogen mineralisation is not only affected by tillage, but also by the quality (chemical composition) of the organic residues. This study evaluated the interaction of residue quality and soil disturbance on N mineralisation in a sandy soil. A 112-day incubation experiment was conducted with two levels of soil disturbance (undisturbed and disturbed conditions) and five plant residue amendments of contrasting quality. The contrasting quality (N, lignin (L), and polyphenols (Pp)) (in g kg–1) amendments follow: (i) unamended; (ii) Sesbania grandiflora (N 44, L 173, Pp 9.2); (iii) Indigofera hirsuta (N 41, L 177, Pp 30); (iv) Dipterocarpus tuberculatus (N 8.2, L 203, Pp 71); and (v) Eucalyptus camaldulensis (N 9.7, L 126, Pp 110). Residues (ii) and (iii) were fresh legume leaves, while (iv) and (v) were non-legume leaf litter. Disturbance only significantly increased N mineralisation rates in the legume-residue treated soils (increases of 18.8% for S. grandiflora and 27.1% for I. hirsuta) during the early stage of decomposition (first 14 days). In the legume treatment, disturbance significantly increased the ammonification, but decreased nitrification in soil relative to undisturbed soils. The difference in patterns of ammonification and nitrification was more pronounced in the early than in the later period of decomposition. This indicated an inhibitory effect of soil disturbance on nitrification, which was particularly pronounced in the legume-treated soils. The Pp content of residues was the major quality parameter regulating the soil ammonium-N and nitrate-N concentrations. Minimum soil disturbance should be adopted under legume soil organic amendment so that both ammonification and nitrification components of N mineralisation process can occur normally, and nitrate-loving crops can take up N in the form of nitrate-N which will enhance their yields. Moreover, undisturbed conditions under legume organic amendments reduced N mineralisation, resulting in enhancing soil N sequestration.
Low seasonal nitrous oxide emissions in tea tree farming systems following nitrogen fertilisation using poultry litter application or green manure legumes
Authors: Rose Terry J. , Kearney Lee J. , Morris Stephen , Van Zwieten Lukas
Published: January 2020

The integration of legumes into coppiced tree crop systems to replace some or all of the external nitrogen (N) fertiliser requirements may be one means to lower seasonal nitrous oxide (N2O) emissions. We investigated soil N2O emissions using static chamber methodology in field trials located within two commercial tea tree (Melaleuca alternifolia) plantations (Casino and Tweed Heads) where N (116 and 132 kg N ha–1 respectively) was supplied via poultry litter application (5 t wet ha–1) or by termination of annual legumes (soybean or mung bean) grown in the inter-row. While there was no treatment effect at the Tweed Heads site, both legume treatments had significantly (P = 0.01) lower cumulative N2O emissions (0.33 and 0.30 kg N2O-N ha–1 season–1 for soybean and mung beans respectively) than the poultry litter treatment (0.66 kg N2O-N ha–1 season–1) at the Casino site. However, the amount of N added to soils in each treatment was not identical owing to an inability to accurately predict N inputs by legume crops, and thus differences could not be attributed to the N source. A third site was thus established at Leeville comparing N2O emissions from poultry litter amendment (5 t wet ha–1 contributing 161 kg N ha–1) to an inter-row faba bean crop (contributing 92 kg N ha–1) and a nil-N control. Cumulative seasonal N2O emissions were significantly (P < 0.05) lower in the faba bean treatment than the poultry litter treatment (0.08 and 0.23 kg N2O-N ha–1 season–1 respectively), but owing to different N inputs and generally low emissions, it was not possible to draw definitive conclusions on whether green manure legume crops can lower N2O emissions. Overall, soil N2O emissions in coppiced tea tree systems under current management practices were very low, offering limited potential to reduce seasonal N2O emissions through management practice change.
The use of language and religion from a sociolinguistic perspective
Authors: Alsaawi Ali
Published: January 2020

Religion plays a pivotal role in some societies, but the interaction between language and religion as a
sociolinguistic field of study has not fully been explored. The overlap between the two has recently been considered by Omoniyi and Fishman (2006). Many studies have been conducted regarding language use
within institutional settings, such as schools, universities, workplaces and courtrooms. However, less attention has been paid to
language use outside of these settings, such as within religious contexts, although mosques are viewed as institutional in nature.
In particular, imams may switch between languages in their sermons in the mosque. To explore this phenomenon, a qualitative study
was undertaken by means of simulated recall interviews and non-participant observation with imams (n = 10) and
mosque audiences (n = 7) where the participants are of Asian pacific origins (Pakistan, India & Indonesia).
The study reveals that employing more than one language in one-way religious speech is a means of increasing historical
authenticity, exposing audiences to Arabic, overcoming a lack of easy equivalents in English, emphasizing religious authority,
assuming audiences’ knowledge of some Arabic features, or accommodating the diverse backgrounds of the audience, some member of
whom have knowledge of Arabic. This has been described as having spiritual, historical and emotional significance, invoking
religious links associated between Arabic and Islam. Stakeholders, especially audiences, claim benefits beyond the language used
in the sermons themselves. Imams, in addition, tend to see the use of both English and Arabic as socially and culturally salient,
a means of uniting people in an otherwise often fractured world, or one frequently presented as such in the media.
Lie sphere geometry in lattice cosmology
Authors: Fennen Michael , Giulini Domenico
Published: January 2020

In this paper we propose to use Lie sphere geometry as a new tool to systematically construct time-symmetric initial data for a wide variety of generalised black-hole configurations in lattice cosmology. These configurations are iteratively constructed analytically and may have any degree of geometric irregularity. We show that for negligible amounts of dust these solutions are similar to the swiss-cheese models at the moment of maximal expansion. As Lie sphere geometry has so far not received much attention in cosmology, we will devote a large part of this paper to explain its geometric background in a language familiar to general relativists.
Schemes for nondestructive quantum gas microscopy of single atoms in an optical lattice
Authors: Okuno Daichi , Amano Yoshiki , Enomoto Katsunari , Takei Nobuyuki , Takahashi Yoshiro
Published: January 2020

We propose a quantum gas microscope for ultracold atoms that enables nondestructive atom detection, thus evading higher-band excitation and change of the internal degrees of freedom. We show that photon absorption of a probe beam cannot be ignored even in dispersive detection to obtain a signal-to-noise ratio greater than unity because of the shot noise of the probe beam under a standard measurement condition. The first scheme we consider for the nondestructive detection, applicable to an atom that has an electronic ground state without spin degrees of freedom, is to utilize a magic-wavelength condition of the optical lattice for the transition for probing. The second is based on the dispersive Faraday effect and squeezed quantum noise and is applicable to an atom with spins in the ground state. In this second scheme, a scanning microscope is adopted to exploit the squeezed state and reduce the effective losses. Application to ultracold ytterbium atoms is discussed.
Boron-doped III–V semiconductors for Si-based optoelectronic devices
Authors: Zhao Chao , Xu Bo , Wang Zhijie , Wang Zhanguo
Published: January 2020

Optoelectronic devices on silicon substrates are essential not only to the optoelectronic integrated circuit but also to low-cost lasers, large-area detectors, and so forth. Although heterogeneous integration of III–V semiconductors on Si has been well-developed, the thermal dissipation issue and the complicated fabrication process still hinders the development of these devices. The monolithic growth of III–V materials on Si has also been demonstrated by applying complicated buffer layers or interlayers. On the other hand, the growth of lattice-matched B-doped group-III–V materials is an attractive area of research. However, due to the difficulty in growth, the development is still relatively slow. Herein, we present a comprehensive review of the recent achievements in this field. We summarize and discuss the conditions and mechanisms involved in growing B-doped group-III–V materials. The unique surface morphology, crystallinity, and optical properties of the epitaxy correlating with their growth conditions are discussed, along with their respective optoelectronic applications. Finally, we detail the obstacles and challenges to exploit the potential for such practical applications fully.
The application of perovskite materials in solar water splitting
Authors: Huang Yanbin , Liu Jun , Deng Yanchun , Qian Yuanyuan , Jia Xiaohao , Ma Mengmeng , Yang Cheng , Liu Kong , Wang Zhijie , Qu Shengchun , Wang Zhanguo
Published: January 2020

Solar water splitting is a promising strategy for sustainable production of renewable hydrogen, and solving the crisis of energy and environment in the world. However, large-scale application of this method is hampered by the efficiency and the expense of the solar water splitting systems. Searching for non-toxic, low-cost, efficient and stable photocatalysts is an important way for solar water splitting. Due to the simplicity of structure and the flexibility of composition, perovskite based photocatalysts have recently attracted widespread attention for application in solar water splitting. In this review, the recent developments of perovskite based photocatalysts for water splitting are summarized. An introduction including the structures and properties of perovskite materials, and the fundamentals of solar water splitting is first provided. Then, it specifically focuses on the strategies for designing and modulating perovskite materials to improve their photocatalytic performance for solar water splitting. The current challenges and perspectives of perovskite materials in solar water splitting are also reviewed. The aim of this review is to summarize recent findings and developments of perovskite based photocatalysts and provide some useful guidance for the future research on the design and development of highly efficient perovskite based photocatalysts and the relevant systems for water splitting.
Quantum cascade superluminescent light emitters with high power and compact structure
Authors: Sun Jialin , Hou Chuncai , Chen Hongmei , Zhang Jinchuan , Zhuo Ning , Ning Jiqiang , Zheng Changcheng , Wang Zhanguo , Liu Fengqi , Zhang Ziyang
Published: January 2020

Quantum cascade (QC) superluminescent light emitters (SLEs) have emerged as desirable broadband mid-infrared (MIR) light sources for growing number of applications in areas like medical imaging, gas sensing and national defense. However, it is challenging to obtain a practical high-power device due to the very low efficiency of spontaneous emission in the intersubband transitions in QC structures. Herein a design of ~5 μm SLEs is demonstrated with a two-phonon resonance-based QC active structure coupled with a compact combinatorial waveguide structure which comprises a short straight part adjacent to a tilted stripe and to a J-shaped waveguide. The as-fabricated SLEs achieve a high output power of 1.8 mW, exhibiting the potential to be integrated into array devices without taking up too much chip space. These results may facilitate the realization of SLE arrays to attain larger output power and pave the pathway towards the practical applications of broadband MIR light sources.
Bioclimatic design and low energy cooling systems at IER-UNAM
Authors: Rojas J , Huelsz G , Barrios G , Tovar R
Published: January 2020

This article presents some strategies of bioclimatic design for hot-subhumid climate and of low energy cooling systems and how they have been implemented at the IER-UNAM buildings since 1985. Some of the experimental and numerical simulation projects carried out by the Energy in Buildings Group (GEE) are commented. Finally, the project for a new building for undergraduate students is presented, where passive and low energy strategies as night ventilation, evaporative cooling, radiative cooling and earth tube cooling are been evaluated.
Design of a “Test Cell” to be located at 4500 masl in a high Andean region of Peru and dynamic simulation of the thermal performance of housing wall materials
Authors: Molina J O , Horn M J , Gómez M M
Published: January 2020

The objective of the present study is to select appropriate wall materials for houses in high Andean regions based on the measurements of the thermal behavior of construction materials using a “Test Cell” under real environmental conditions. It will be the first “Test Cell” to be installed in Peru, in Imata-Arequipa, at 4500 masl. The design and thermal analysis of the “Test Cell” are presented using dynamic simulations with the EnergyPlus program. Initially, the thermal performance of adobe, a traditional construction material in rural regions of Peru, is simulated using real meteorological data recorded in Imata between August 18 and 24, 2018, a period with low temperatures (-12.6 °C).
Thermal characterization of materials used in rural housing constructions in Ayacucho, Peru
Authors: Janampa K , Cerón O , Morales O , Oré J
Published: January 2020

The thermal conductivity of construction materials used in rural areas of Ayacucho has been measured. For this purpose, a thermal conductivity meter for material sample plates of a size of 12 cm x 12 cm has been designed and built, based on “ASTM C177 - Standard Test Method for Steady-State Heat Flux”. The effect of the thickness of the samples and of the heating power of the central plate on the measurement results was evaluated, resulting that best results were obtained with samples less than 2 cm thick and heating powers of less than 3 W. The thermal conductivities obtained vary between 0.148± 0.005 W.m-1.K-1 for “tornillo” wood, and 0.663 ± 0.010 W.m-1.K-1 for red clay from Quinua.
A low-cost measurement device for recording perceptions of thermal comfort
Authors: Molina J R , Nakama V L , Lefebvre G
Published: January 2020

In this article, we describe the implementation of a low-cost device that registers perceptions of thermal comfort. The parameters of relative humidity (RH), temperature, thermal sensation (cold, cool, neutral, warn, hot) and clothing worn by people are collected. The design and validation of the device in an indoor environment are explained, and the calibration curves of the temperature and relative humidity sensors are obtained. The measurement results for the device from 10 people are shown. The study was carried out in the village of Imata (high Andean zone), at 4700 masl in the south of Peru.
Capacitance voltage curve simulations for different passivation parameters of dielectric layers on silicon
Authors: Sevillano-Bendezú M A , Dulanto J A , Conde L A , Grieseler R , Guerra J A , Töfflinger J A
Published: January 2020

Surface passivation is a widely used technique to reduce the recombination losses at the semiconductor surface. The passivating layer performance can be mainly characterized by two parameters: The fixed charge density (Q
ox) and the interface trap density (D
it) which can be extracted from Capacitance-Voltage measurements (CV). In this paper, simulations of High-Frequency Capacitance-Voltage (HF-CV) curves were developed using simulated passivation parameters in order to examine the reliability of measured results. The D
it was modelled by two different sets of functions: First, the sum of Gaussian functions representing different dangling bond types and exponential tails for strained bonds. Second, a simpler U-shape model represented by the sum of exponential tails and a constant value function was employed. These simulations were validated using experimental measurements of a reference sample based on silicon dioxide on crystalline silicon (SiO2/c-Si). Additionally, a fitting process of HF-CV curves was proposed using the simple U-shape D
it model. A relative error of less than 0.4% was found comparing the average values between the approximated and the experimentally extracted D
it’s. The constant function of the approximated D
it represents an average of the experimentally extracted D
it for values around the midgap energy where the recombination efficiency is highest.
Low-cost data logging device to measure irradiance based on a Peltier cell and artificial neural networks
Authors: Palo-Tejada E , Campos-Falcon V , Merma M , Huanca E
Published: January 2020

The measurement of solar irradiance is one of the most important variables for ensuring working conditions at maximum power (MPPT) in a photovoltaic system (PV). In this work, a pyranometer is constructed to measure solar irradiance using a Peltier cell as a thermoelectric generator (TEG), an absolute temperature sensor and a feedforward neural network. The instrument is a low-cost data logger that runs on 3 AAA batteries, has an autonomy of up to 1 year and can record up to 65 000 irradiation data points at programmable time intervals.
Carbon-based perovskite solar cells by screen printing with preheating
Authors: Martinez V C , Xie H , Mingorance A , Pereyra C , Narymany A , Gómez M M
Published: January 2020

Carbon-based perovskite solar cells were manufactured by the screen-printing method using a triple mesoscopic layer of TiO2, ZrO2 and carbon. The perovskite solution was infiltrated at the TiO2/ZrO2 porous interface through the printed carbon layer on top of the ZrO2. Using a simple preheating of the substrates and the perovskite solution, a film deposited in air can be obtained. Using this method, an air-processed CPSC made under a humid atmosphere with 55% RH achieved a PCE of 10.35%.
The CuO/ZnO and CuO/ZnO/biochar materials for water treatment
Authors: Lang J , G J F , Cruz  , Solis J L
Published: January 2020

The research of new materials and methods for water treatment is necessary. Two sets of materials were prepared. The one set is composed from CuO/ZnO oxides with variable content of CuO and the second set consists of its biochar impregnated counterparts. The structure and phase composition was determined using X-ray diffraction method and morphology of the materials was studied using scanning electron microscopy. The photodegradation activity and adsorption properties were tested on model pollutant – Methylene blue (MB) dye solution. The experimental kinetic of the data was analyzed using pseudo-first-order and pseudo-second-order kinetic models and the equilibrium data was evaluated using Langmuir, Freundlich and Dubinin-Radushkievic models. It was found that optimal material for photodegradation of MB is 1% CuO/ZnO oxide and for the adsorption of MB is the best material raw corn cob biochar.
Efficacy of copper-silver ionization for the disinfection of drinking water in Tumbes, Peru
Authors: Solis-Castro R L , Silva L , Costa A , Gebhardt K , Cruz G J F
Published: January 2020

High quality is recommended for drinking water to prevent the transportation of pathogenic bacteria. To ensure its quality, different technologies are applied, and copper-silver ionization is used to maintain the microbiological quality. However, considering that the characteristics of this source vary in different scenarios, it was proposed to evaluate the efficacy of copper-silver ionization for the disinfection of drinking water in Tumbes, Peru. For this evaluation, the physicochemical and microbiological parameters of drinking water were tested at different lengths of copper-silver ionization treatment (10, 20 and 30 minutes). Water samples were collected from 20 houses located in urban areas of Tumbes city where Cu-Ag ionizers (Necon GmbH) were installed. The application of Cu-Ag ionization reduced the microbiological load in the water samples, keeping them below the Peruvian permissible limits (mesophilic bacteria < 500 CFU/100 mL and coliforms < 0 CFU/100 mL). However, in samples with a high microbial load and high electrical conductivity, the microbial load was not completely diminished. Cu-Ag ionization considerably improved the microbiological quality of the water, but some physical parameters, such as pH and electrical conductivity, must be taken into account to further improve the results.
Particle dynamics in a magnetic field: symplectic reduction and classification of singular trajectories
Authors: Boldyreva M N , Magazev A A
Published: January 2020

The paper studies the dynamics of a classical non-relativistic charged particle moving in a superposition of force-free and constant magnetic fields. Using the first integrals of the problem, a symplectic reduction of the corresponding Newton-Lorentz equations to an auxiliary two-dimensional Hamiltonian system is performed. By the linearisation method, the types of singular points of the reduced Hamiltonian system are classified. The results obtained are applied to the problem of studying the trajectories of the original Hamiltonian system that are close to singular trajectories.
Influence of ION-plasma spraying regimes on the formation and properties of multi-element coatings
Authors: Eremin E N , Yurov V M , Laurynas V Ch
Published: January 2020

The technological parameters of deposition of high-entropy ion-plasma coatings based on 12Kh18N10T alloyed steel by zirconium, copper and aluminum were studied. It has been established that with increasing evaporator arc current, the surface energy of the coating decreases, which is explained by a rapid increase in its thickness, leading to an increase in the dislocation density in the coating being formed. The optimal value of the arc current is 90-110 A. Coatings obtained at a nitrogen pressure of P=10−3 mm Hg. and the substrate temperature of 400 °C, have the most evenly distributed fine dense structure, the minimum content of the droplet phase, pores, influx, detachments, the highest values of surface energy and an increase in microhardness by 30%.
Semiconductor heterosystem InAs-ZnS. Physical and chemical properties
Authors: Kirovskaya I A , Mironova E V , Umanskiy I Yu , Ekkert A O , Ekkert R V , Kopylova E N , Blesman A I , Polonyankin D A , Goncharov V B
Published: January 2020

According to the developed methodology based on isothermal diffusion of the initial binary compounds (InAs, ZnS) in the light of their known bulk properties, the InAs-ZnS system solid solutions have been obtained. Pursuant to the results of the X-ray investigation, they have been certified as substitutional solid solutions with the cubic sphalerite structure.

The surface (acid-base) properties of the InAs-ZnS system components corresponding to the weak acidic area have been studied.

Consistent patterns in changes with the composition of the studied properties have been established, which are both statistical (smooth) and extreme. Correlations between the consistent patterns and, respectively, the link between surface and bulk properties, which allow predicting the desired materials for the semiconductor gas analysis have been found.
Peculiarities of wear of nanostructured topocomposites on the hard-alloy basis
Authors: Korotaev D N , Poleschenko K N , Orlov P V , Eremin E N , Tarasov E E , Ivanova E V
Published: January 2020

The article considers the wear resistance and wear peculiarities of nanostructured topocomposites with the clustered gradient architecture. The authors regard the specificity of the impact of the cluster morphology on the contact interaction under microcutting conditions. They study the causes of persistence of the high wear resistance for the given class of nanostructured topocomposites. The mechanisms of energy dissipation from the tribocontact zone due to their nanogeometry and the structural-phase structure are analyzed. The contribution of triboactivated diffusion and deformation processes to providing the increased wear resistance of topocomposites on the hard-alloy basis is differentiated. Their approbation in the conditions of edge cutting processing of heat-resistant titanium alloy is carried out.
The structure of composite coatings based on titanium nitride, formed using condensation with ion bombardment
Authors: Korusenko P M , Nesov S N , Povoroznyuk S N , Poleshenko K N , Orlov P V , Korotaev D N , Suleymenova D A
Published: January 2020

The main aim of this work was to study the morphology, elemental and quantitative composition, as well as the chemical state of titanium nitride coatings obtained by condensation with ion bombardment on substrates of sintered hard alloy (VK8: WC – 92%, Co – 8%) and Hadfield steel (110G13L: Mn – 11-14.5%, C – 0.9-1.3%). Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were used to analyze the structure and composition of the coatings. It was established that the composition of coatings formed on different substrates at the same deposition time is almost identical and consists of TiN, TiNO, and TiC. This indicates that coating formation conditions are reproducible. At the same time, it was shown that in the coating formed on 110G13L steel, an increase in the amount of titanium oxy nitrides is observed, associated with the peculiarity of the occurrence of nonequilibrium processes in the preparation of coatings. It was shown that the application of the approach based on the use of XPS and EDX data obtained from various depths makes it possible to correctly study the composition of coatings based on titanium nitride and future control their composition by changing the parameters of coating formation.
The assessment of technical and economic indicators of gas cleaning systems working on various types of coal
Authors: Batrakov P A , Yakovleva E V , Mrakin A N , Selivanov A A , Mingaleeva G R , Afanaseva O V
Published: January 2020

The object of the study is a set of activities to reduce the concentration of sulfur and nitrogen oxides in the combustion products of boiler units, by equipping them with a gas purification system. Improving the environmental parameters of the power facility is achieved through the installation of devices for cleaning combustion products: an absorber for cleaning sulfur oxides and a neutralizer for cleaning combustion products from nitrogen oxides. In this work the definition of technical and economic indicators is carried out and a comparative analysis of various types of fuels in order to increase the economic and environmental parameters of the installation are presented. The technical and economic indicators for each type of the fuel are determined.
Information and analytical platform for evaluating the effectiveness and choosing directions for improving the energy and water supply systems of oil and gas chemical complexes
Authors: Dolotovsky I V , Semenov B A
Published: January 2020

The paper presents the structure and content of a specialized enterprise information system that can be used to calculate the parameters of energy generation process and complex structure and to study and develop specific equipment for individual plants and create autonomous energy and water supply systems for oil and gas chemical complexes. The paper proposes a three-dimensional hierarchical model with orthogonal connections that includes the object of study, the problems of increasing energy performance of such object and potential methods of solving these problems. The paper presents calculation algorithms and the results of numerical modeling of energy supply systems operating within the conditions of dynamically developing oil and gas chemical complexes. Schematic solutions of the developed optimal resource-efficient energy supply systems for various technological processes are also provided. The paper discusses the potential beneficial modifications of energy supply system structure of raw hydrocarbon processing facilities; these modifications are based on the principles of polygeneration and further integration between energy supply system and processing units.