bluuebunny/crossref_metadata_2025 huggingface dataset:
A review on recent progress in organic photovoltaic devices for indoor applications
Authors: Kumar Gautham , Chen Fang-Chung
Published: May 2023

Organic photovoltaics (OPVs) have shown great potential as a new generation of energy sources because they possess many unique properties, including mechanical flexibility, light weight, semitransparency, and low fabrication costs. In particular, OPV devices exhibit high power conversion efficiencies under indoor and low-level lighting conditions. Therefore, they can function as promising energy sources in low-light or cloudy environments for many applications, including the Internet of Things, wearable electronics, and sensors. In this article, we review recent progress in OPV devices for these special applications. We start with an introduction to the fundamental principles of OPVs. Then, we review the preparation and design principles of the photoactive layers for indoor applications. We also highlight the importance of interlayers in high-performance photovoltaic devices under indoor and/or low-level lighting illumination conditions. Recent efforts to improve the efficiencies of indoor OPV devices using plasmonic nanostructures are also summarized. Finally, we examine the progress in large-area devices and modules for indoor and/or low-level lighting applications. We believe that the rapid progress in indoor OPV cells and modules will trigger the development of low-cost, highly efficient OPV products for indoor applications in the near future.
Black phosphorus/Bi2MoO6 Z-scheme heterojunction for enhanced photocatalytic CO2 reduction
Authors: Su Tongming , Sun Manying , Wu Jing , Chen Liuyun , Ji Hongbing , Qin Zuzeng
Published: May 2023

The photocatalytic CO2 reaction is considered to be an effective way to reduce greenhouse gas emissions. This paper presents how a novel and efficient 2D/2D black phosphorus nanosheets (BPNS)–Bi2MoO6 photocatalyst was synthesized and used for photocatalytic CO2 reduction. Compared to Bi2MoO6, the photocatalytic activity of the BPNS–Bi2MoO6 composite photocatalyst was significantly improved. When the mass ratio of BPNS to Bi2MoO6 was 1:100, the BPNS–Bi2MoO6 photocatalyst exhibited optimal activity for photocatalytic CO2 reduction, and the production of CO reached 72.8 μmol g−1 after reaction for 4 h, which is 1.5 times more than that of Bi2MoO6. Moreover, the BPNS–Bi2MoO6 showed high stability for the photocatalytic CO2 reduction reaction; after reaction for four cycle experiments, the production of CO only reduced by 10%. The enhanced light absortion, enhanced separation of electrons and holes, and the tight 2D/2D heterojunction formed between BPNS and Bi2MoO6 account for the high photocatalytic performance of BPNS/Bi2MoO6.
Electrokinetic cells powered by osmotic gradients: an analytic survey of asymmetric wall potentials and hydrophobic surfaces
Authors: Sánchez G , Méndez F , Ramos E A
Published: May 2023

Nowadays, the fabrication of microelectromechanical systems has given rise to several studies whose main purpose is to obtain the greater benefit of micro-nano scales, putting special interest in the improvement of the design of such devices. One of several applications is harvesting energy due to electrokinetic phenomena, more specifically, streaming potential. Nonetheless, there is a lack of theoretical studies encompassing coupled asymmetries in both slip conditions and electric potentials (these being associated with the chemical and physical characteristics of the surfaces). By virtue of the previous explanation, ideal assumptions based on the symmetry of some variables must be reconsidered, especially when manufacturing symmetric flat surfaces on a tiny scale is quite difficult to achieve. This work presents a theoretical study in power generation, exploiting streaming potentials produced by an asymmetric membrane which in turn prompts a flux inside a microchannel made of two flat parallel surfaces. The driving force in this electrokinetic battery is the osmotic gradient on both sides of the membrane. The model uses the Debye–Hückel approximation together with the appropriate asymmetric boundary conditions for both slips and potentials on the surfaces. The main variables of interest, such as the dimensionless horizontal velocity component, the pressure field, and the average streaming potential, were estimated.
A vision subsampling probsparse self-attention-based informer for bearing remaining useful life prediction
Authors: Li MingLei , Geng Yanfeng , Pan Guangliang , Wang Weiliang , Wang Hongyu
Published: May 2023

Bearing remaining useful life (RUL) prediction has always been a central topic in the industry field, the aim of which is to optimize system safety and sustainability. The validity of prediction models and the accuracy of prediction results are affected by mid-term singularities and terminal mutations, under time-domain bearing vibration information. In this paper, a network structure-cascaded dilated convolution vision informer (CDC-Vii) is put forward to precisely forecast the RUL of bearings, which uses the time–frequency fault features as input. CDC-Vii breaks the limitation of the original Informer, which is only sensitive to time-series information. An adaptive fault frequency band selection algorithm is proposed, which can reduce training time while utilizing rich time–frequency information. Based on the Informer architecture, the attention mechanism is improved to form vision subsampling probsparse self-attention (VSPS). VSPS can precisely assign spatial attention weights and reduce computational complexity. At the same time, a truncated relative position encoding technique is proposed to strengthen the position dependence between attention information. Moreover, cascaded dilated convolution enhances the image contrast of faulty frequency bands while enlarging the use of the receptive field. Experiments on two extensively utilized bearing datasets reveal that CDC-Vii surpasses the advanced RUL prediction models.
Rational engineering NiMoO4 nanosheets or Mn3O4 nanowires on Fe2O3 microdiscs as novel hierarchical anodes for high-performance lithium-ion batteries
Authors: Zeng Xiangbing , Ding Yingyi , Bai Haiyuan , Ding Qian , Lin Xirong , Liu Jinyun , Sun Zhengming
Published: May 2023

Since current graphite-based lithium-ion battery anode has a low theoretical capacity, the development of high-performance lithium-ion battery is severely restricted. Here, novel hierarchical composites composing of microdisc and the secondarily grown nanosheets and nanowires are developed, taking NiMoO4 nanosheets and Mn3O4 nanowires growing on Fe2O3 microdiscs as demonstrating examples. The growth processes of the hierarchical structures have been investigated by adjusting a series of preparation conditions. The morphologies and structures have been characterized by using scanning electron microscopy, transmission electron microscope and x-ray diffraction. Fe2O3@Mn3O4 composite-based anode displays a capacity of 713 mAh g−1 after 100 cycles at 0.5 A g−1 with a high Coulombic efficiency. A good rate-performance is also achieved. Fe2O3@NiMoO4 anode delivers 539 mAh g−1 after 100 cycles at 0.5 A g−1, which is obviously higher than that of pure Fe2O3. The hierarchical structure is conducive to improve the transport of electrons and ions, and provide numerous active sites, thus significantly enhancing the electrochemical performance. Moreover, the electron transfer performance is investigated by using density functional theory calculations. It is expected the findings presented here and the rational engineering of nanosheets/nanowires on microdiscs would be applicable for developing many other high-performance energy-storage composites.
Focused ion beam lithography for position-controlled nanowire growth
Authors: Mosberg Aleksander B , Ren Dingding , Ahtapodov Lyubomir , Weman Helge , Fimland Bjørn-Ove , van Helvoort Antonius T J
Published: May 2023

To exploit the promising properties of semiconductor nanowires and ensure the uniformity required to achieve device integration, their position on the growth substrate must be controlled. This work demonstrates the direct patterning of a SiO2/Si substrate using focused ion beam (FIB) patterning to control self-catalyzed GaAsSb nanowire growth in molecular beam epitaxy (MBE). Besides position control, FIB patterning parameters influence nanowire yield, composition and structure. Total ion dose per hole is found to be the most important parameter. Yield of single nanowires ranges from ≈34% to ≈83%, with larger holes dominated by multiple nanowires per hole. Areas exposed to low ion beam doses are selectively etched by routine pre-MBE HF cleaning, enabling patterning and nanowire nucleation with minimal damage to the Si substrate. The optical and electronic properties of nanowires are found to depend on the ion dose used during patterning, indicating the potential for FIB patterning to tune nanowire properties. These findings demonstrate the possibility for a FIB lithography protocol which could provide a rapid and direct patterning process for flexible controlled nanowire growth.
Two-dimensional material-based complementary ambipolar field-effect transistors with ohmic-like contacts
Authors: Park Jimin , Son Jangyup , Park Sang Kyu , Lee Dong Su , Jeon Dae-Young
Published: May 2023

Ambipolar field-effect transistors (FETs) possessing both electron and hole carriers enable implementation of novel reconfigurable transistors, artificial synaptic transistors, and output polarity controllable (OPC) amplifiers. Here, we fabricated a two-dimensional (2D) material-based complementary ambipolar FET and investigated its electrical characteristics. Properties of ohmic-like contacts at source/drain sides were verified from output characteristics and temperature-dependent measurements. The symmetry of electron and hole currents can be easily achieved by optimization of the MoS2 or WSe2 channels, different from the conventional ambipolar FET with fundamental issues related to Schottky barriers. In addition, we demonstrated successful operation of a complementary inverter and OPC amplifier, using the fabricated complementary ambipolar FET based on 2D materials.
Formation mechanisms of striations in a filamentary dielectric barrier discharge in atmospheric-pressure argon
Authors: Jovanović Aleksandar P , Hoder Tomáš , Höft Hans , Loffhagen Detlef , Becker Markus M
Published: May 2023

Formation mechanisms of striations along the discharge channel of a single-filament dielectric barrier discharge (DBD) in argon at atmospheric pressure are investigated by means of a time-dependent, spatially two-dimensional fluid-Poisson model. The model is applied to a one-sided DBD arrangement with a 1.5 mm gap using a sinusoidal high voltage at the powered metal electrode. The discharge conditions are chosen to mimic experimental conditions for which striations have been observed. It is found that the striations form in both half-periods during the transient glow phase, which follows the streamer breakdown phase. The modelling results show that the distinct striated structures feature local spatial maxima and minima in charged and excited particle densities, which are more pronounced during the positive polarity. Their formation is explained by a repetitive stepwise ionisation of metastable argon atoms and ionisation of excimers, causing a disturbance of the spatial distribution of charge carriers along the discharge channel. The results emphasise the importance of excited states and stepwise ionisation processes on the formation of repetitive ionisation waves, eventually leading to striations along the discharge channel.
Machine learning for observational cosmology
Authors: Moriwaki Kana , Nishimichi Takahiro , Yoshida Naoki
Published: May 2023

An array of large observational programs using ground-based and space-borne telescopes is planned in the next decade. The forthcoming wide-field sky surveys are expected to deliver a sheer volume of data exceeding an exabyte. Processing the large amount of multiplex astronomical data is technically challenging, and fully automated technologies based on machine learning (ML) and artificial intelligence are urgently needed. Maximizing scientific returns from the big data requires community-wide efforts. We summarize recent progress in ML applications in observational cosmology. We also address crucial issues in high-performance computing that are needed for the data processing and statistical analysis.
Undoped vertical dual-bilayer TFET with a super-steep sub-threshold swing: proposal and performance comparative analysis
Authors: Anam Aadil , Amin S Intekhab , Prasad Dinesh , Kumar Naveen , Anand Sunny
Published: May 2023

In this paper, the undoped vertical dual-bilayer tunnel field effect transistor (UV-DBL-TFET) at a low operating voltage (0.5 V) is introduced, and its DC and RF performance parameters are compared with those of the conventional charge plasma-based symmetrical gate electron–hole bilayer TFET (CP-SG-EHBTFET). The charge plasma technique is used in the proposed device to induce the source/drain and electron–hole dual-bilayer channel dopants. Due to the dopingless architecture of the proposed UV-DBL-TFET, its fabrication is simple and efficient, and it does not require an expensive thermal annealing process. Due to its dopingless architecture, the proposed UV-DBL-TFET is immune against random dopant fluctuations. In the study, the quantum confinement effects in the TCAD simulation have been successfully modelled using the Schrodinger approach and the density gradient model. Compared to the conventional CP-SG-EHBTFET, the proposed UV-DBL-TFET has a dual EHB channel, triggers dual line tunnelling, and doubles the band-to-band tunnelling rate and the ON current. Compared to the I
ON of 47.33 μA μm−1 and AVSS of 13.53 of the conventional CP-SG-EHBTFET, the proposed UV-DBL-TFET has almost double the ON current of 93.46 μA μm−1 with a reduced AVSS of 12.3 mV dec−1. The proposed UV-DBL-TFET also gives improved RF/analog performance. Compared to the transconductance (g
m) of 0.337 mS, the cut-off frequency (f
T) of 65.17 GHz, and the gain-bandwidth-product (GBW) of 16.5 GHz of the conventional CP-SG-EHBTFET, the proposed UV-DBL-TFET has a g
m of 0.665 mS, a f
T of 129.0 GHz, and an GBW of 32.6 GHz, an almost doubled improvement. Furthermore, the proposed UV-DBL-TFET-based CMOS inverter has also been comprehensively studied, and perfect complementary inverter action has been obtained, suggesting great potential for future low-power applications.
Quantum information entropy of a particle trapped by the Aharonov–Bohm-type effect
Authors: Lima F C E , Moreira A R P , Almeida C A S , Edet C O , Ali N
Published: May 2023

In this research article, we use the Shannon’s formalism to investigate the quantum information entropy of a particle trapped by the Aharonov–Bohm-type field. For quantum information study, it is necessary to investigate the eigenstates of the quantum system, i.e. the wave functions and energies of the quantum states. We assumed that the particle is in principle, confined in a cylindrical box in the presence of Aharonov–Bohm-type effect due to dislocation defect. Analysis of the quantum information entropy, reveals that the dislocation influences the eigenstates and, consequently, the quantum information of the system.
Theoretical study on the thermal transport and its tunability of a-plane trilayer GaN
Authors: Xu Yaxin , Sun Guoqing , Wan Zijing , Xu Dongwei , Luo Xiaobing
Published: May 2023

Two-dimensional (2D) a-plane gallium nitride, a non-layered 2D material, has promising applications in photoelectric nanodevices due to its direct band bandgap. Herein, employing molecular dynamics simulations, we studied the thermal transport properties of a-plane trilayer GaN, and the temperature, together with strain modulation on the thermal conductivity of the system. The a-plane trilayer GaN shows anisotropic thermal conductivity with 70.22 Wm−1K−1 and 41.81 Wm−1K−1 along zigzag- and armchair- directions respectively at room temperature when extrapolated to infinite size. In addition, the thermal conductivity of trilayer GaN exhibits decreasing trend in response to the increase of temperature. The thermal conductivity decreases monotonically with the increased compressive uniaxial and biaxial strain, while it shows an up-then-down trend under tensile strain. The tunability of thermal conductivity under biaxial strain is much larger than that of uniaxial strain. The phonon density of states is further investigated to understand the behavior of thermal conductivity. The tunability of the system thermal conductivity will expand its applications in thermal management and nanodevices.
Thermodynamics of a quantum ring modified by Lorentz violation
Authors: Araújo Filho A A , Hassanabadi H , Reis J A A S , Lisboa-Santos L
Published: May 2023

In this work, we investigate the consequences of Lorentz-violating terms in the thermodynamic properties of a 1-dimensional quantum ring. In particular, we use the ensemble theory to obtain our results of interest. The thermodynamic functions as well as the spin currents are calculated as a function of the temperature. We observe that parameter ξ, which triggers the Lorentz symmetry breaking, plays a major role in low temperature regime. Finally, depending on the configuration of the system, electrons can rotate in two different directions: clockwise and counterclockwise.
Emission spectrum for a cascade-type three-level atom driven by optical field in photon added coherent state of PHO
Authors: Al-Ghamdi M S , Abdel-Khalek Sayed , Berrada Kamal , Al-Sahafi S D
Published: May 2023

A treatment of the interaction of a multi-photon cascade-type three-level atom in a cavity with a single-mode field initially in the photon added coherent states (PA-CSs) of pseudo-harmonic oscillator (PHO) is presented in this paper. The wavefunction corresponding to the system under consideration and the emission spectrum (ES) are obtained. It is shown that the properties of the ES are affected by the PA-CS of PHO parameters. The influence of the number of added photons to the CS of PHO on the dynamical behavior of the ES is investigated. The results showed that the behavior of the ES is strongly changed according to the CS of PHO parameters and its number of added photons. Symmetric peaks are generated around the vertical axis with increasing influence of some values of the initial field state parameters.
Hierarchy of double-time correlations
Authors: Queisser Friedemann , Schützhold Ralf
Published: May 2023

The hierarchy of correlations is an approximation scheme which permits the study of non-equilibrium phenomena in strongly interacting quantum many-body systems on lattices in higher dimensions (with the underlying idea being somewhat similar to dynamical mean-field theory). So far, this method was restricted to equal-time correlators such as

⟨

A
ˆ

μ

(
t
)

B
ˆ

ν

(
t
)
⟩

. Using the method of complete induction, we generalize this method to double-time correlators such as

⟨

A
ˆ

μ

(
t
)

B
ˆ

ν

(

t

′

)
⟩

. The hierarchical decoupling scheme permits the evaluation of correlation functions in thermal equilibrium as well as in non-equilibrium settings. As an application, we study the equilibrium dynamics of correlation functions and the related light-cone structure of the bosonic Hubbard model in the Mott insulator phase. Furthermore we address the light-cone structure when the system is quenched.
Improved Deep Reinforcement Learning Decision for Integrated Control of Distributed Drive Electric Vehicle Dynamics
Authors: Huang Wenjun , Huang Kaiqi , Huang Maoyun
Published: May 2023

To solve the problem of nonlinear coupling with longitudinal and lateral tire forces in the integrated control of distributed driving electric vehicles, an improved SAC reinforcement learning algorithm is proposed to coordinate the control method of active front steering (AFS) and torque distribution. The coordinated control adopts a layered structure, and the upper layer adopts the LQR controller to determine the additional front wheel rotation angle and yaw moment required for stability control. The three-level reward function is designed with the goal of vehicle stability and state tracking and is determined by the reinforcement learning algorithm. For the weight factors of the two optimization objectives, the SAC reinforcement learning algorithm is used to coordinate the decision-making of the active front wheel steering and the additional yaw moment; the lower controller uses the comprehensive utilization rate of the tire as the objective function to perform the optimal torque distribution. A co-simulation platform is established in MATLAB/Simulink and CarSim software. The results show that compared with AFS control, SAC coordinated control can not only ensure the stability of the vehicle and achieve accurate tracking of the reference state but also effectively reduces the comprehensive utilization rate of tires and the effectiveness of coordinated control.
Modification of Carbon Black by Laser Irradiation
Authors: Milenov T , Dimov D , Kostadinov I , Avdeev G , Russev S , Genkov K , Trifonov D , Zyapkov A , Ivanov K , Kolev S , Valcheva E
Published: May 2023

The effect of modification of Cabot Corporation SPHERON 5000 carbon black suspended in bi-distilled water by laser irradiation (CuBr2 laser with fundamental wavelength of λ = 511nm and 2 kHz repetition rate) has been studied. The carbon black suspensions were prepared by mixing 0.10 g carbon black previously treated with acetone in 100 ml bi-distilled water. Different laser beam fluencies and different irradiation times were used in order to optimize the modification process. The modified suspensions were decanted after sedimentation and dried. The powder fractions obtained were studied by scanning electron microscopy, X-ray diffraction and Raman spectroscopy.
Precise material microprocessing by high-power diffraction limited laser radiation in middle infrared spectral range
Authors: Kostadinov I K , Temelkov K A , Karatodorov S I , Popova L T , Slaveeva S I
Published: May 2023

Diffraction-limited laser radiation with a record-high total average output power exceeding 14 W is obtained in the middle infrared spectral region through a new improved master oscillator – power amplifier system based on the strontium vapor laser. Precise microprocessing of optical grade fused quartz, sapphire, stainless steel, hard biological tissues, and polymers is also accomplished. Using a parabolic mirror for the laser beam focusing, spherical aberrations are overcome and a crater diameter and a channel width of the order of the laser wavelength are achieved.
Some Initial Results on Modification of aC:H Films by Pulsed Laser Irradiation
Authors: Milenov T , Karaivanova D , Dikovska A , Kirilov K , Valcheva E
Published: May 2023

It has recently been shown both theoretically and experimentally that a significant modification of the aC:H films is possible using UV irradiation even with a very low irradiation fluence. Some initial results on the modification of aC:H films with thickness of about 40 nm with UV laser irradiation are presented here. The fourth harmonic (λ = 266 nm) of a Nd:YAG laser system (the fundamental wavelength λ = 1064 nm) was used in our experiments. The modified areas of the aC:H films were characterized by optical microscopy, Raman spectroscopy as well as by atomic force microscopy (AFM). A significant modification of aC:H films under certain conditions (laser irradiation fluence and modification modes) to multi-layer graphene accompanied by ablation of a part of the film was established. It was also found that similar aC:H films deposited on 330 nm SiO2/Si substrates did not undergo significant modification under these conditions.
Coherent magneto-optical resonances on the potassium D2 line in Hanle configuration for magnetometry applications
Authors: Tsvetkov S , Andreeva C , Gateva S
Published: May 2023

The coherent magneto-optical resonances on the potassium D2 line are investigated from the point of view of magnetometry applications. The measurements are performed in Hanle configuration with potassium excited by circularly polarized laser beam in cell with dimensions 8 mm and buffer gas 30 Torr Ne. The parameters of the resonances registered in fluorescence and transmission are compared. The capability of the laser system to work with magnetically unshielded cell is demonstrated. The registration of bright and dark magneto-optical resonances detected in fluorescence by controlling the optical thickness of potassium vapor is discussed. The influence of the laser power and transverse magnetic field are considered. The experimental results show the potential of the system for magnetic field sensing and calibration.
Effective application of suitable single pulse of Nd:doped lasers for cleaning of initial carious lesions of human teeth. Experimental study
Authors: Uzunov T , Deneva M , Kazakov V , Uzunova P , Kaimakanova N , Nenchev M
Published: May 2023

We show via detailed experimental investigations that the single pulse from Nd:YAG and Nd:Glass lasers (wavelength 1.06 μm, free lasing operation) are suitable for efficient cleaning initial carious lesions (1 - 3 mm in diameter) on tooth enamel. The cleaning is in combination with tooth preparation for final healing procedures – formation of desired hole and antibacterial cleaning. The measured heating of the tooth chamber is in acceptable limits and crack formation is avoided. The investigation includes laser irradiation with single pulses of energy of ~2 to 5 J, energy density of ~50 to 130 J/cm2 and pulse duration of ~500 ns – 2 ms. In further development of the topic, as a second part of this article, we propose algorithm for application of the discussed cleaning.
PDT and PD of Human Glioblastoma with 5-ALA/PpIX and n-GalLuPc
Authors: Zaharieva L , Angelov I , Genova Ts , Kyurkchiev D , Tumangelova-Yuzeir K , Ivanova-Todorova E , Mantareva V , Karazapryanov P , Minkin K , Avramov L , Borisova E
Published: May 2023

Glioblastoma (GBM) is the most common and severe type of brain tumor. Surgery and subsequent radiotherapy and chemotherapy do not lead to sufficient results in the treatment of this type of malignancy, mostly due to its specific morphology. Only about 6% of the patients of advanced age survive 5 years after being diagnosed with GBM. Therefore, scientists are working on alternative therapies that would lead to more effective and long-term treatment of glioblastoma. Photodynamic therapy (PDT) and photodiagnostics (PD) are such unconventional methods for treating and diagnosing malignant tumors. During our work, more than 20 experiments were carried out with stem cells cultivated from human glioblastoma tumors. We used two types of photosensitizers – delta-aminolevulinic acid (5-ALA) as a precursor of protoporphyrin IX (PpIX) and non-peripherally galactosylated lutetium phthalocyanine (n-GalLuPc). After the irradiation supernatant samples of photosensitizer-treated cell lines were used for evaluation of photosensitizers’ accumulation in the cell lines investigated. The emitting spectra is correlated with the total induced cell death in the treated cells. After considering the overall effectiveness of the two photosensitizers, n-GalLuPc showed higher efficiency. These in vitro results prompted the future investigation of the phthalocyanine for in vivo application in GBM treatments.
Diagnosis of skin lesions through prototype clinical device with diffuse reflectance spectroscopy
Authors: Mircheva V , Borisova E , Genova Ts , Troyanova P , Avramov L , Markovski A
Published: May 2023

Cancerous and precancerous skin conditions occupy one of the leading places in oncology. Early detection of suspects and temporary referrals to a specialist are critical to successful treatment. Numerous optical techniques are used for obtaining a new data from cutaneous neoplasia. Diffuse–reflectance spectroscopy is one of these techniques due to its high sensitivity in detecting subtle tissue alterations. Light scattering events inside the skin tissues change significantly in the development stage of skin lesions. These changes in the tissue scattering properties affect the diffuse reflectance spectrum and provide classification of different skin lesions based on diffuse reflectance measurements. We have investigated diffuse–reflectance spectroscopy for diagnostic of skin lesions and as a result, an optical device for clinical application was developed. The current study shows the obtained results by the prototype device for the reflective ability of pigmented and non-pigmented skin benign, dysplastic, and malignant cutaneous lesions in vivo.
Thermal effects in Nd: YVO4 and Nd: GdVO4 block crystals under diode end-pumped at 914 nm
Authors: Hendaoui N , Boutaka R , Bouadjemine R
Published: May 2023

In this paper, we report a numerical study of the thermal effects within both a-cut crystals Nd: YVO4 (1.5 at.%) and Nd: GdVO4 (1.5 at.%) end-pumped by a diode laser emitting at 914 nm. The temperature, stresses distributions and thermal lensing parameters were calculated by finite element method using LASCAD© software. The obtained results show that the Nd:GdVO4 is the best candidate for high power diode laser end-pumped solid-state lasers because of its lower thermal effects.
Impact of annealing and soft template concentration on optical and sensing properties of wet-deposited SiO2 thin films
Authors: Chorbadzhiyska Y , Georgiev R , Georgieva B , Babeva T
Published: May 2023

The present study demonstrates deposition of porous SiO2 thin films using combination of sol-gel, soft-templating and spin-coating methods. The recipe for Si-sol using TEOS (tetraethylorthosilicate) as a precursor was optimized in order transparent and stable sol to be obtained. Commercially available triblock co-polymer Pluronic 123 was considered as a soft template and its concentration and volume fraction to sol were varied. For achieving the final composition of silica films, different stepwise annealing regimes were implemented where the temperatures and duration of each step were optimized. Optical properties of films were calculated using nonlinear curve fitting of measured reflectance spectra in UV-VIS spectral range. Surface morphology and structure of the films were characterized by Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED). The porosity and optical sensing ability of the films were tested by measurement of their reflectance spectra prior to and during exposure to acetone vapors which served as probe molecules. The influence of soft template composition and annealing regimes on SiO2 properties were revealed and application of studied films as sensitive media for opto-chemical sensing was discussed.
Surface modification of Ti6Al4V alloy by continuous electron beam
Authors: Ormanova M , Kotlarski G , Stoyanov B , Valkov S
Published: May 2023

In this work, Ti6Al4V alloy was surface modified by a scanning electron beam. During the modification procedure, the current of the electron beam was 25 mA, the frequency of scanning of the e-beam was 200 Hz, the accelerating voltage was 60 kV, the velocity movement of the sample was 5 mm/s and 10 mm/s. The samples were modified using a continuous electron beam, where the geometry of the beam deflection was in the form of a Lissajous curve. The phase composition of the obtained samples was investigated by X-ray diffraction. The microstructure was studied by optical microscopy. The microhardness was also investigated. The results showed that the treatment process causes the formation of a single-phase structure of α’ martensite, where the velocity of the specimen during the modification procedure does not affect the phase composition of the modified surfaces. The hardness values at the sample treated with 5 mm/s speed motion are lower than that treated at speed of sample movement of 10 mm/s.
Investigation of the change in wettability properties and corrosion behavior of AISI 304 after laser surface texturing
Authors: Adijāns I , Lazov L , Ilieva M , Nikolova M P
Published: May 2023

Stainless steel is a widely used material in industry, architecture, and medical instruments. However, after various thermal processing of stainless steels, chromium carbides can be formed, which locally depletes the chromium available to form a passive film and reduces the corrosion performance. Laser surface treatment can change the surface chemistry of the steel and improve some electrochemical characteristics. However, these characteristics are influenced by the laser power, pulse width, distance between the lines, scanning speed, etc., which all change the surface chemistry and characteristics of laser surface texturing. Simultaneously, the ability to repel liquids that cause corrosion actions could combine to enhance corrosion performance. Since the wettability of a solid surface depends both on its topography and chemical nature, the micro structuring of an austenitic steel surface is an effective way of fabricating hydrophobic or super hydrophobic corrosion-resistant surfaces. For this reason, this study discusses the effect of laser power in the impact zone and the distance between raster lines on the microstructure, wettability, and corrosion resistance of austenitic steel (AISI 304) when exposed to nanosecond fiber laser radiation. The results indicate that parameter-controlled micro structuring can be used to form both hydrophilic and hydrophobic surfaces with different electrochemical performances.
Investigation of the influence of the processing speed and the linear pulse density of the laser surface texturing process
Authors: Adijāns I , Lazov L , Ilieva M , Nikolova M P
Published: May 2023

Fine-tuning laser parameters is necessary to achieve the desired quality of the process of laser surface texturing. This requires a set of experiments to assess the influence of the main process parameters on the quality of the surface of a treated alloy. By varying the laser parameters, different laser-material interactions, such as heating, melting, or evaporation can be observed. This study analyzes the influence of two interrelated processing parameters in laser surface texturing – the speed of beam motion on the surface on the one hand, and, on the other, the linear pulse density. They ultimately have a direct impact on the resulting microstructure, hydrophilicity, and electrochemical properties of austenitic steel (AISI 304). By adjusting the pulse repetition rate of a 1064-nm fiber laser from 500 kHz to 1000 kHz at a constant speed of 100 mm/s, the surface wettability changes from hydrophobicity to hydrophilicity. All surfaces treated with laser scanning speeds varying from 20 mm/s to 200 mm/s at a constant rate of 500 kHz are hydrophobic. As a result, the changed ability to repel liquids alters the corrosion properties of the steel in a 0.5 M H2SO4 solution. The results allow one to distinguish ranges of laser-beam parameters that could be useful in selecting certain properties of the stainless-steel surface layer.
Thermal runaway difference between fresh and retired lithium iron phosphate batteries under overheating
Authors: Wang Cong-jie , Wang Shu-ping , Gao Fei , Li Chang-hao , Zhu Yan-li
Published: May 2023

Safety is an important factor restricting the cascade utilization of lithium-ion batteries (LIBs). In this paper, the safety characteristics of fresh and retired lithium iron phosphate batteries are investigated by means of a heating-triggered thermal runaway (TR). The results show that under the heating condition of 200 W, the internal short circuit (ISC) can directly cause the TR of a new battery and lead to an explosion with an overpressure of 98.9 kPa. However, there is still a buffer time of 13.1-22.3 min between the ISC and TR for the retired battery with states of health (SOHs) of 80% - 60%, and the retired battery cannot explode. The large-scale ISC onset time, TR onset time, and TR onset temperature of the 70% SOH battery are 27.4 min, 40.5 min, and 179.9 °C, respectively, which are the smallest among retired batteries, indicating that the 70% SOH battery may be more likely to trigger TR. The findings can provide guidance for the safe application of retired batteries.
Study on Dynamic Line Rating of Overhead Transmission Line Based on Large-Scale New Energy Power Grid Connection
Authors: Peng Zhengwei , Shi Jinzhi , Li Yanyan , Huang Junhan , Zhao Jinquan
Published: May 2023

With increasing new energy power grid connections and increasingly complex user loads, higher ampacity is required during peak power demand. Construction of new transmission lines can cost a lot and is limited by the environment and the shortage of land resources. Considering the intermittency of new energy power generation, dynamic line rating can increase the power transmission capacity of existing lines by exploiting their potential capacity. In this paper, the ampacity of transmission lines is calculated accurately, and influencing factors of ampacity are studied. Additionally, temperature change patterns and field distribution of the lines are studied. The results show that wind speed, ambient temperature, and sunshine intensity are the three main factors affecting the ampacity. Wind speed is proportional to ampacity, while ambient temperature and sunshine intensity are opposite. Then, it is found that the thermal inertia effect of transmission lines that temperature change lags behind current change can be utilized for ampacity enhancement. Furthermore, the radial temperature difference is found in the lines, and excessive temperature differences may accompany the risk of strand breakage. It is of great significance to study the temperature field of the lines for dynamic line rating based on large-scale new energy power grid connections.
Effect of TiO2-SiO2 composite films on the performance of perovskite solar cells
Authors: Wang Renbao
Published: May 2023

Nano-TiO2 semiconductor film has the characteristics of high porosity and large specific surface area. However, there is much surface state in the TiO2 semiconductor film, and its energy level is in the band gap, which forms a local state with traps, restricts the movement of electrons in the film, and causes serious electron recombination. In this paper, the TiO2 surface is covered with a wide band gap semiconductor SiO2 in the electron transport layer of the perovskite solar cell. A core-shell electrode is formed to inhibit electron recombination and improve efficiency of perovskite solar cells.
Research on Calculation Method of Energy Storage Capacity Configuration for Primary Frequency Control of Photovoltaic Power Station
Authors: Zhang Ning-yu , Zhu Xin-yao , Liu Jian
Published: May 2023

An energy storage capacity allocation method is proposed to support primary frequency control of photovoltaic power station, which is difficult to achieve safe and stable operation after a high proportion of photovoltaic connected to public power grid. In this paper, by taking the photovoltaic power plant containing energy storage as an example, and based on the fluctuation characteristics of photovoltaic power output and the performance requirements of primary frequency control response, the required battery storage capacity of photovoltaic power station for primary frequency control is calculated without considering the power abandonment and power limitation conditions, and the typical case is established based on power system simulation software to verify the reasonableness and effectiveness.
Analysis of Intergranular Corrosion Cracking of Austenitic Stainless Steel Tubes for Utility Boilers
Authors: Sun Yunfei , Tan Xiaomeng , Liu Jun , Yun Feng
Published: May 2023

The cracking failure accidents of austenitic stainless steel pipes of utility boilers often occur. The intergranular corrosion cracking caused by improper control of welding, heat treatment and cold working processes is an important reason for its failure. Through the analysis of typical cases, this paper expounds on the influence of welding, heat treatment and cold working processes on the service safety of austenitic stainless steel pipes and puts forward protective measures.
Optimal Scheduling of Pumped Storage Power Station Based on Immune Ant Colony Algorithm
Authors: Chen Xin , Xiao Renjun , Ma Jiankai
Published: May 2023

At present, in the application of hydropower for multi-energy complementary, the utilization of large hydropower stations and pumped storage power stations is mainly considered. The utilization of small hydropower stations is relatively scarce. The use of small hydropower can implement complementary regulation of distributed energy nearby, which is very conducive to distributed power consumption. This paper proposes an improved genetic immune ant colony optimization algorithm to find the optimal solution. To solve the shortcomings of the ant colony algorithm in the early stage, such as the weak ability to traverse all paths, easy falling into a premature and local optimum, and slow convergence speed, a genetic algorithm is applied to initialize the genetic factor. It can dynamically adjust the step factor and introduce the genetic immune ant colony with a momentum coefficient when updating the position to search for the optimal solution. The penalty function is adopted to solve the model, and the specific steps are given. Through the comparative test of the algorithm, it is verified that the algorithm proposed has a better effect on the optimal solution, the shortest occupied time, good reliability, and strong optimization ability. It is of great practical significance to the scientific evaluation of the water resource’s eco-economic system.
An Efficiency Optimization Strategy for Electric Vehicle Wireless Energy Transmission System
Authors: Wang Runhua , Shi Yuefeng , Wang Jihui , Wang Yawei
Published: May 2023

Magnetic coupling resonant wireless energy transmission technology has become an important research direction for electric vehicle wireless charging systems. This paper proposes an efficiency optimization strategy for the electric vehicle wireless energy transmission system based on LCL-S topology to improve the efficiency of electric vehicle magnetic coupling resonant wireless charging. This paper analyzes the optimization method of system efficiency based on LCL-S topology, establishes an experimental model in MATLAB/Simulink simulation software, and verifies it with the control variable method. The experiment shows that the efficiency optimization strategy based on the LCL-S topology proposed in this paper can effectively improve the system transmission efficiency and stabilize the transmission efficiency at a higher level faster.
Study of Temperature Rise Characteristics and Voltammetry Characteristics of ZnO Varistor under 10/350μs Pulse Current
Authors: Xiong Fuzhi
Published: May 2023

To study the effect of 10/350μs pulse current on the electrical performance of ZnO varistor, a high-current impulse experimental study was conducted in this paper. Firstly, the varistor was subjected to different amplitude impulse discharge experiments, and the temperature change of the varistor after the impulse was recorded. Then, the temperature of the varistor at the moment of 1 second after the pulse impulse was suffered by the Asymptotic function, and the Levenberg-Marquardt optimization algorithm was calculated to compare the temperature rise of the varistor under different current amplitudes. Finally, the upward shift of voltammetry characteristics in the high-current region after the impulse was explained according to the double Schottky barrier model and the linear chain aging theory. The results show that the higher the pulse current amplitude is, the higher the temperature rise of the varistor is at the 1s moment. The highest voltammetry characteristic upshift is caused by the 6.4kA pulse current. The temperature rise and the voltammetry characteristic drift in the high-current region are positively correlated. The results of the study can provide a reference for manufacturers to produce ZnO varistors for direct lightning protection of buildings.
Research on fault causes and treatment methods of squirrel-cage asynchronous wind turbine
Authors: Zhang Xiuqi , Gao Huifang , Cao Bin
Published: May 2023

Renewable energy development is conducive to alleviating the climate problem, and it is an important measure to fulfill China’s double-carbon commitment. This paper first introduces the current situation of wind power generation and the working principle of a squirrel-cage asynchronous wind turbine, then counts the fault data of squirrel-cage asynchronous wind turbine, sorts out its common faults, and deeply analyzes the causes of the faults. Finally, it puts forward corresponding treatment methods for different kinds of faults, as well as suggestions for further improving the reliability of the squirrel-cage asynchronous wind turbine.
Modelling of Large-Scale Photovoltaic Power Generation System Based on PSCAD and Analysis of Its Stability
Authors: Chen Xiaoke , Li Yanyan , Shi Jinzhi , Zhao Jinquan , Huang Junhan
Published: May 2023

In this paper, based on the study of PV power generation principles and mathematical models of PV cells, PSCAD simulation modelling is performed for a large-scale PV plant with required output over 100 MW, and its operational characteristics are analysed. An improved Newton iteration, conductance increment method and semi-aggregate equivalent control algorithm are used to achieve maximum power point tracking (MPPT) for large-sized photovoltaic electricity plant. Finally, the simulation analysis of the large-scale photovoltaic electricity generation system under normal operation and light disturbance is conducted to validate the validity and stability of the model.
Skeleton-Based Human Activity Recognition of Low-voltage Distribution Room Based on MQTT Protocol and Wireless Sensor Network
Authors: Chen Deying , Chen Jing , Tong Yixuan , Zheng Shaocong
Published: May 2023

For the activity recognition of operators in low-voltage distribution rooms, a human activity recognition system based on the bidirectional gated recurrent unit model (BiGRU) is proposed to realize the skeleton information acquisition by the WiFi Channel State Information (CSI) sensor. The CSI sensor is used to collect the activity data and the Kinect v2 camera is used to capture the skeleton of the human body as annotations of the CSI data. The BiGRU model is employed to effectively extract the characteristics of the data. Aiming at the problem of poor remote communication, the MQTT connection can be established by using Message Queuing Telemetry Transport (MQTT) protocol combined with ESP8266 WiFi serial port communication module is proposed to improve the poor communication situation and carry out better data communication. The system achieves remote intelligent monitoring of the activities of the operator in the low-voltage distribution room.
Research on Processing the Feature Model of Converter Station Based on Machine Learning
Authors: Zhu Liu , Wang Kang , Sun Fei , Wang Weijia
Published: May 2023

The current traditional converter station feature model processing method uses switching functions to model converter station equipment, which leads to poor processing results because it ignores the dynamic coupling characteristics between the second harmonics inside the converter station. In this regard, a machine-learning-based switching station feature model processing method is proposed. By combining different terminals to determine their port parameters, constructing the characteristic impedance model of the converter station, using time-domain recursive convolution to calculate the voltage levels at each key point of the AC system, and finally calculating the magnitude as well as the phase angle constants, the time-varying model of the multi-harmonic converter can be fixed. In the experiments, the computational accuracy of the proposed method is verified. The analysis of the experimental results shows that the proposed method has a high component amplitude and excellent computational performance when the characteristic model of the converter station is processed.