bluuebunny/crossref_metadata_2025 huggingface dataset:
Jednostki ochrony przeciwpożarowej podczas epidemii COVID-19. Funkcjonowanie i zadania w pierwszych miesiącach aktywności wirusa SARS-CoV-2
Authors: Zwęgliński Tomasz , Radkowski Radosław
Published: December 2020

Abstrakt
Epidemia wirusa SARS-CoV-2 wpisuje się w katalog zagrożeń cywilizacyjno-środowiskowych
globalnego oddziaływania w XXI w. Decyzje i działania dotyczące sposobów przeciwdziałania
temu niebezpieczeństwu podejmowane są w warunkach niepewności. Rzeczywistość, determinowana
warunkami epidemicznymi, stanowi istotne wyzwanie dla władz różnych szczebli
oraz podległych im struktur i systemów bezpieczeństwa (na poziomie międzynarodowym,
krajowym i lokalnym). Jest to realny sprawdzian sprawności i skuteczności ich funkcjonowania
jako całości, jak i poszczególnych elementów systemów bezpieczeństwa.
W niniejszym artykule poddano analizie funkcjonowanie jednostek ochrony przeciwpożarowej
(JOP) w początkowym okresie epidemii. Prowadzone badania i czynione w ich
trakcie obserwacje ogniskowały się wokół wewnętrznych przeobrażeń organizacyjnych oraz
zadań realizowanych w służbie społeczeństwu. Prezentowane w opracowaniu działania
podejmowane przez JOP przedstawione są na tle dynamiki zmian społeczno-gospodarczych
determinowanych przedmiotowym zagrożeniem. Artykuł opracowany został we wrześniu
2020 r., co w sposób naturalny i oczywisty ogranicza teren badań do danych i informacji
aktualnych na ten okres.
W badaniach zastosowano metodę studium przypadku, realizowaną przy udziale innych
metod i technik badawczych, takich jak analiza krytyczna literatury i aktów prawnych, swobodny
wywiad ekspercki, obserwacja, analiza i synteza, a także analogia i abstrahowanie.
Problem badawczy podjęty w artykule sprowadza się do następujących pytań: jakie działania
podejmowane były na poziomie lokalnym przez JOP, a także na jakie elementy funkcjonowania
tych podmiotów warto zwrócić uwagę w przyszłości w kontekście istniejącego stanu epidemii. Celem artykułu jest usystematyzowanie i wstępna analiza działań podjętych przez
JOP w stanie epidemii oraz identyfikacja związanych z nimi problemów.
Wyniki pracy wskazują na potrzebę otwarcia na nieszablonowe rozwiązania, decyzje nieprogramowane,
czasami odbiegające lub nawet z pozoru sprzeczne z wcześniej stosowanymi,
sprawdzonymi praktykami i procedurami wdrażanymi wobec innych zagrożeń. Stan epidemii,
występujący dotychczas niezwykle rzadko, tym bardziej wywołany nowym patogenem,
generuje szereg niepewności, które wymuszają podejmowanie decyzji z zastosowaniem metod
właściwych decyzjom nieprogramowanym, np. heurystycznych i eksperckich.
Multi-Node Localization and Identity Estimation Based Multi-Beacon Searching Algorithm
Authors: Rashid Mofeed Turky , Rashid Abdulmuttalib , Aldair Ammar
Published: December 2020

The accuracy of multi-nodes localization and identity estimation algorithms directly affected the performance of multi-agent systems like WSN, multi-robot, cellular phone and so on. In this paper, a novel algorithm is introduced in order to achieve high accuracy for multi-nodes localization and identity estimation, this algorithm is named multi-beacon searching algorithm. In this algorithm, the concept of the grid is employed for estimating the location and identity of nodes, in which the environment represented by a grid of reference beacons, for each beacon, light-emitting diode (LED) is used. Whereas, each node in the environment is equipped with four LDR sensors which are used to sense the lighting of LEDs according to a proposed searching algorithm. The localization process achieved based on three proposed algorithms: Firstly, a modified binary search algorithm is utilized to estimate the approximate location of the node by a group of neighbor LEDs. Secondly, the accurate localization algorithm is used to find the accurate location of each node by reducing the number of neighbor LEDs. Finaly, two algorithms are introduced to evaluate the location and identification of each node: the centroid algorithm and the minimum bounded circle algorithm. In the minimum bounded circle algorithm, a new faster algorithm called the maxima boundaries convex hull algorithm for polygon convex hull construction is introduced instead of the Chan's algorithm. Several simulation processes have been implemented for testing the proposed algorithms. The obtained results show that the proposed algorithms have very good performance in estimating the accurate localizations of the nodes.
Fractals analysis and control for a kind of three-species ecosystem with symmetrical coupled predatory behavior
Authors: Wang Da , Sun Tianwen , Zhang Yi
Published: December 2020

The Lotka-Volterra model plays an important role in the research area of population biology. This work presents the analysis of dynamical behaviours of a kind of three species GLV systemfrom the viewpoint of fractals. The definition of Julia set which describes the initial distribution of the three species’ densities is introduced. Then a gradient control method which contains both giant parameter and state feedback is applied to realize the control of Julia set. Coupling terms are designed to realize the synchronization of two Julia sets. Numerical examples are included to verify the conclusions
Integrated Embedding Approach for Knowledge Base Completion with CNN
Authors: Chen Samuel , Xie Shengyi , Chen Qingqiang
Published: December 2020

To tackle specific problems in knowledge base completion such as computational complexity and complex relations or nodes with high indegree or outdegree, an algorithm called IEAKBC(short for Integrated Embedding Approach for Knowledge Base Completion) is proposed, in which entities and relations from triplets are first mapped into low-dimensional vector spaces, each original triplet represented in the form of 3-column, k dimensional matrix; then features from different relations are integrated into head and tail entities thus forming fused triplet matrices used as another input channel for convolution. In CNN feature maps are extracted by filters, concatenated and weighted for output scores to discern whether the original triplet holds or not. Experiments show that IEAKBC holds certain advantages over other models; when scaling up to relatively larger datasets, signs of superiority of IEAKBC stand out especially on relations with high cardinalities. At last we apply IEAKBC to a personalized search application, comparing its performance with strong baselines to verify its practicality in real environments.
Part-of-Speech Tagging via Deep Neural Networks for Northern-Ethiopic Languages
Authors: Kapočiūtė-Dzikienė Jurgita , Tesfagergish Senait Gebremichael
Published: December 2020

Deep Neural Networks (DNNs) have proven to be especially successful in the area of Natural Language Processing (NLP) and Part-Of-Speech (POS) tagging—which is the process of mapping words to their corresponding POS labels depending on the context. Despite recent development of language technologies, low-resourced languages (such as an East African Tigrinya language), have received too little attention. We investigate the effectiveness of Deep Learning (DL) solutions for the low-resourced Tigrinya language of the Northern-Ethiopic branch. We have selected Tigrinya as the testbed example and have tested state-of-the-art DL approaches seeking to build the most accurate POS tagger. We have evaluated DNN classifiers (Feed Forward Neural Network – FFNN, Long Short-Term Memory method – LSTM, Bidirectional LSTM, and Convolutional Neural Network – CNN) on a top of neural word2vec word embeddings with a small training corpus known as Nagaoka Tigrinya Corpus. To determine the best DNN classifier type, its architecture and hyper-parameter set both manual and automatic hyper-parameter tuning has been performed. BiLSTM method was proved to be the most suitable for our solving task: it achieved the highest accuracy equal to 92% that is 65% above the random baseline.
Deep Learning based Semantic Similarity Detection using Text Data
Authors: Mansoor Muhammad , Rehman Zahoor ur , Shaheen Muhammad , Khan Muhammad Attique , Habib Mohamed
Published: December 2020

Similarity detection in the text is the main task for a number of Natural Language Processing (NLP) applications. As textual data is comparatively large in quantity and huge in volume than the numeric data, therefore measuring textual similarity is one of the important problems. Most of the similarity detection algorithms are based upon word to word matching, sentence/paragraph matching, and matching of the whole document. In this research, a novel approach is proposed using deep learning models, combining Long Short Term Memory network (LSTM) with Convolutional Neural Network (CNN) for measuring semantics similarity between two questions. The proposed model takes sentence pairs as input to measure the similarity between them. The model is tested on publicly available Quora’s dataset. The model in comparison to the existing techniques gave 87.50 % accuracy which is better than the previous approaches.
A New Approach for Missing Data Imputation in Big Data Interface
Authors: Wang Chunzhi , Shakhovska Nataliya , Sachenko Anatoliy , Komar Myroslav
Published: December 2020

The three-stage approach for missing data imputation in Big data interface is proposed in the paper. The first stage includes designing the Big data model in the task of missing data recovery, which enables to process the structured and semistructured data. The next stage is developing the method of missing data recovery based on functional dependencies and association rules. The estimating the algorithm complexity for missing data recovery is provided at the last stage. The proposed method of missing data recovery creates additional data values using a based domain and functional dependencies and adds these values in available training data. The performing the analysis of data different types is possible too. The correctness of the imputed values is verified on the classifier built on the original dataset. The proposed method performs in 12% better than the EM and RF methods for 30% missing data and enables the parallel execution in distributed databases. The acceleration for m=41 attributes is larger in 12.5 times for 20 servers (processors) comparing with the non-parallel modeю
Clinical Features and Prognosis of Invasive Ventilation in Hospitalized Patients with COVID-19: A Retrospective Study
Authors: Rahimzadeh Poupak , Faiz Hamid Reza , Farahmandrad Reza , Hassanlouei Babak , Habibi Azadeh , Hedayati Emami Setareh , Amniati Saied
Published: December 2020

Background: World Health Organization (WHO) declared that the outbreak of COVID-19 constituted a public health emergency of global concern. Objectives: Owing to limited data on critically ill patients admitted to ICU, we aimed to describe the clinical characteristics and prognosis of these patients based on ventilatory variables and clinical features. Methods: In this retrospective study, 45 critically ill patients with laboratory-confirmed COVID-19 who were admitted to Intensive Care Unit (ICU) wards of the hospital from April 8 to May 9, 2020, were enrolled. Medical files of the patients were reviewed, and demographic and clinical characteristics, laboratory data, lung CT scan findings, causes of intubation, and outcomes of the patients were all collected. Results: The median age of the patients was 67 years (range 22 to 91), 64% were men, and hypertension was the most common comorbidity. History of close contact with previously confirmed patients was positive in 62.2% of the patients. The mean time from symptom onset to hospital admission was 5.98 ± 2.93 days. The most common symptoms at the onset of illness were dyspnea (95.6%), and gastrointestinal symptoms (22.2%) were rare. The average length of the intubation was 4.84 ± 3.28 days. The distribution of intubation causes in the deceased patients was significantly more than the recovered patients (P = 0.031). The mean score of lung CT involvement in deaths (370.26 ± 207.50) was significantly higher than the recovered patients (235.71 ± 81.21) (P = 0.042). Length of the intubation had a statistically direct correlation with respiratory rate (P = 0.03). Conclusions: Most of the critically ill patients admitted to ICU were older men and had poor outcomes with a high mortality rate. Furthermore, the score of chest CT involvement and respiratory rate are important prognostic factors in determining the severity of the illness, requiring ventilatory support, and outcome.
The Predictive Value of Initial CT Scan in Patients with COVID-19
Authors: Belice Tahir , Yıldırım Nejla Ozkan , Akan Ozden Yildirim , Yuksel Arif
Published: December 2020

Background: As the pandemic of coronavirus disease 2019 (COVID-19) in Wuhan raised public health concerns, many studies were conducted to reveal the risk factors of the disease and predictive prognostic indicators to plan the treatment strategies and commence therapies earlier. Although specific parameters, including age, gender, chronic diseases, D-dimer, and neutrophil-lymphocyte-ratio play a curial role in COVID-19, the association between mortality and the extent of lung involvement in the initial computerized tomography (CT) scan of patients diagnosed with COVID-19 has not been well documented in the literature. Objectives: We compared two groups (CT-1 and CT-2) in terms of lung involvement in the initial CT of patients admitted to the emergency unit and then hospitallzed with COVID-19. Methods: Using the digital data system of İzmir Bozyaka Training and Research Hospital, Turkey, subjects diagnosed with COVID-19 in April 2020 were retrospectively screened. For each of the 90 patients, the initial CT scans on admission were evaluated for the extent of lung involvement and classified as CT-1 (≤ 5% of lung involvement, n: 45) and CT-2 (> 5% of lung involvement, n: 45). Results: There was not any statistical significance between two different CT groups regarding mortality and length of stay of patients in hospital with COVID-19 (P = 0.72 and P = 0.51, respectively). Neutrophil counts were found to be statistically significant and higher in CT-2 group than the CT-1 (P = 0.02) group. The length of stay in hospital was correlated with age, neutrophil-lymphocyte ratio (NLR), neutrophils, lymphocyte, and only the correlation between length of stay in hospital and age was significant (P = 0.01). Conclusions: The size of involvement is not a predictive indicator for mortality and length of stay in hospital in patients with COVID-19.
Magnetic properties of R(Fe1-xNix)11.3Nb0.7 Compounds
Authors: Wang Jian-Li  , Tang Ning  , Yang Dong  , Shen Yu-Ping  , Wu Guang-Heng  , Yang Fu-Ming  , F.R.de Boer  ,   (1)Van der Waals-Zeeman Institute,University of Amsterdam,1018XE Amsterdam,the Natherlands; (2)中国科学院物理研究所磁学国家重点实验室，北京 100080
Published: December 2020

Structure and magnetic properties of R(Fe1-xNix)11.3Nb0.7 (R=Gd, Tb, Dy, Ho, Er and Y) compounds have been studied by means of X-ray diffraction and magnetic measurements. Substitution of Ni for a fraction of Fe does not change the structure of R Fe11.3Nb0.7, but leads to the contraction of the unit cell volume, the rapidly increasing of the Curie temperature and monotonic decreasing of saturation magnetization. It is notable that introduction of Ni leads to the sharply decline of the easy-axis anisotropy of Fe sublattice and the changes of the spin reorientation temperature Tsr of R Fe11.3Nb0.7 (R=Tb, Dy, Er). A qualitative explanation of the relationship of Tsr and Ni content is given based on the theory of crystal field.
PLASMA DIAGNOSIS OF RF DISCHARGE BY USING IMPEDANCE MEASUREMENT
Authors: YU JIAN-HUA  , HUANG JIAN-JUN
Published: December 2020

It is presented in this paper that the method known from network analysis with home-made probe and experimental setup to measure current, voltage and phase angle of RF discharge in He gas more accurately. The sheath thickness and the real and imaginary parts of the plasma impedance were obtained by using the equivalent circuit model and taking account stray capacitances of the set-up. In addition, making use of Godyak′s RF discharge simple model, the electron density in the discharge was calculated at different pressure and current density.
The influence of tollbooths on highway traffic
Authors: Zhu Liu-Hua  , Chen Shi-Dong  , Kong Ling-Jiang  , Liu Mu-Ren  ,   (1)广西师范大学物理与电子工程学院,桂林 541004; (2)玉林师范学院物理与信息科学系,玉林 537000
Published: December 2020

Based on the Nagel-Schreckenberg traffic flow model，the traffic flow models for electronic and manual toll collection systems are established. The fundamental diagrams of traffic flow are obtained under different parameters via computer simulation. Moreover, the characteristics of electronic and manual toll collection mixed system are analyzed and discussed.
Study on three-dimensional flame temperature distribution reconstruction based on truncated singular value decomposition
Authors: Huang Qun-Xing  , Liu Dong  , Wang Fei  , Yan Jian-Hua  , Chi Yong  , Cen Ke-Fa  ,   浙江大学能源清洁利用国家重点实验室,杭州 310027
Published: December 2020

Three-dimensional flame temperature distribution reconstruction in furnace according to the flame radiative energy images captured by CCD cameras was studied. Temperature reconstruction matrix equation is an ill-posed linear system of equations and the reconstruction problem is an ill-posed problem. Truncated singular value decomposition method (TSVD) was introduced to deal with the ill-posed matrix equation and L-curve method was adopted to choose regularization parameter. Singular value decomposition (SVD) and discrete Picard condition were used to analyze the ill-posed characteristics of the reconstruction problem carefully. The results show that reasonable solutions can be obtained by TSVD and the reconstructed temperature distribution can reproduce the feature of the assumed temperature distribution.
Electronic structure and optical properties of ZnO doped with carbon
Authors: Duan Man-Yi  , Xu Ming  , Zhou Hai-Ping  , Chen Qing-Yun  , Hu Zhi-Gang  , Dong Cheng-Jun  ,   四川师范大学物理与电子工程学院&固体物理研究所低维结构物理实验室,成都  610068
Published: December 2020

Electronic structure and optical properties of ZnO doped with carbon have been investigated by using density functional theory based on first-principles ultrasoft pseudopotential method. The calculated results show that there is a significant difference in electronic structures between the cases of C substituting O and C substituting Zn in ZnO,which is caused by both the electronic structure of C atom and its interaction with the neighboring atoms. We also find that the optical properties are charged in the low-energy region after doping, while in the high-energy region the optical properties are almost not influenced by doping with C. The changes of optical properties are qualitatively explained in connection with the calculated electronic structure.
Two new methods for construction of Birkhoffian representation
Authors: Ding Guang-Tao
Published: December 2020

Two new methods for the construction of the Birkhoffian representation of first-order systems are presented. The Birkhoffian functions Rμ and B can be computed from the differential equations. An example is given to illustrate the application of the methods.
Chaos tunneling of Bose-Einstein condensates
Authors: Fang Yong-Cui  , Yang Zhi-An
Published: December 2020

Phase transition to chaos of Bose-Einstein condensates in double-well trap with external periodic modulation is investigated in this paper. Particularly, chaos tunneling is studied. It is found that, when resonance between external periodic frequency and natural frequency is established, this system can turn to instability (chaos). The evolutions of Husimi function in quantum condition are discussed. It is found that, when chaos emerges, chaos region and chaos tunneling varies with the interaction between the particles.
Teleportation of the M-particle entangled state by using one entangled state
Authors: Tang You-Liang  , Liu Xiang  , Zhang Xiao-Wei  , Tang Xiao-Fang
Published: December 2020

Respectively in two- and high-dimensional systems, we propose schemes for teleportation of a M-particle entangled state using one entangled state as channel. In this scheme, there are many receivers. By controlling the number of the introduced auxilliary particles, these receivers can arbitrarily adjust the distribution of the teleported entangled state's particles among them and the probability of the success is 1.
Analysis and improvement of multiparty controlled quantum secure direct communication protocol
Authors: Wang Tian-Yin  , Qin Su-Juan  , Wen Qiao-Yan  , Zhun Fu-Chen
Published: December 2020

The security of a multiparty controlled quantum secure direct communication protocol (WCZT protocol) is analyzed and a new attack with teleportation is advanced. Using this attack, the receiver can gain access to the sender's secret message without the permission of any controller; therefore, this protocol is not secure. An improved version of this protocol is proposed and the security analysis shows that the improved protocol can resist the said attack and thus the goal of multiparty controlled quantum secure communication is warranted.
Hawking radiation of black hole
Authors: Zhao Ren  , Zhang Li-Chun  , Li Huai-Fan
Published: December 2020

Taking into consideration the radiation particle reaction with the total energy of spacetime conservation, Hawking radiation from black hole is re-investigated using the Damour-Ruffini method. It is found that the tunneling probability relates to Bekenstein-Hawking entropy, and the radiation spectrum is not exactly thermal. The result is consistent with the works of other researchers， and satisfies the unitary theory of quantum mechanics.
The small parameter expansion solution to Fokker-Planck equation for Brownian motion in a periodic potential with internal time derivative Ornstein-Uhlenbeck noise
Authors: Bai Zhan-Wu  , Meng Gao-Qing
Published: December 2020

By introducing suitable variables, the Brownian particles motion in a periodic potential with internal time derivative Ornstein-Uhlenbeck noise can be described by a high-dimensional Fokker-Planck equation. The equation can not be solved by the usual small parameter expansion method and potential valley expansion method. An alternative small parameter expansion method is proposed to deal with the equation, and the result is applicable for small potential barrier height, intermediate correlation time and in a larger phase space domain, the approximation can be improved systematically.
Synchronizing fractional chaotic systems based on Lyapunov equation
Authors: Hu Jian-Bing  , Han Yan  , Zhao Ling-Dong
Published: December 2020

This paper advances a theory of stability identification based on Lyapunov equation for fractional system whose order is not higher than 1. The theory is successfully applied to synchronize fractional Lorenz chaotic systems with uncertain parameters. Numerical simulation certifies validity of the theory.
Measurement of single-electron transfer cross sections in collisions of C3+ with He, Ne, Ar atoms at low to intermediate velocity
Authors: Liu Hui-Ping  , Chen Xi-Meng  , Liu Zhao-Yuan  , Ding Bao-Wei  , Shao Jian-Xiong  , Cui Ying  , Lu Yan-Xia  , Gao Zhi-Min  , Liu Yu-Wen  , Du Juan  , Sun Guang-Zhi  , Xi Fa-Yuan  , Wang Xing-An  , Lou Feng-Jun
Published: December 2020

Absolute cross sections for single-electron transfer of He， Ne， Ar atoms induced by C3+ at low to intermediate velocity (1.7v0—4.2v0) were measured and calculated using n-body classical trajectory Monte Carlo (nCTMC) method. Though good overall agreements are achieved between experimental and nCTMC results, certain differences are found. Because of the existence of polarization and the nCTMC being unable to calculate the multi-electron correlation capture cross sections, the experimental results are greater than those of nCTMC at low velocities(1.7v0—2.0v0). When the velocity of the projectile is higher(2.2v0—4.2v0), the captured electron’s partial screening of the projectile, the electron-electron dynamic correlation and the effective charge are taken into account in interpreting the qualitative differences between theoretical and experimental results. In addition, the cross section rations of transfer ionization to single electron capture are presented and the mechanism of transfer ionization are discussed.
Generation of squeezed quantum states of a single trapped cold ion
Authors: Zhang Miao  , Jia Huan-Yu  , Ji Xiao-Hui  , Si Kun  , Wei Lian-Fu
Published: December 2020

Based on the quantum dynamics of laser-ion interaction beyond the Lamd_Dicke limit, we discuss how to superpose a series of vibrational number states of a single trapped ion from the motional ground state. It is shown that, by controlling the durations and phases of the sequentially applied laser pulses, these superposed quantum states could well approach to the various target quantum states, e.g., squeezed coherent states, squeezed odd/even coherent states and squeezed vacuum states, etc.Their experimental realizabilities are also discussed.
Electromagnetically induced left-handedness with vacuum-induced coherence
Authors: Zheng Jun  , Liu Zheng-Dong  , Zeng Fu-Hua  , Fang Hui-Juan
Published: December 2020

The electromagnetically induced left-handedness in a four-level atomic system associated with a pair of upper excited hyperfine levels has been investigated. The properties of left-handedness with vacuum-induced coherence (VIC) arising from the cross coupling spontaneous emission pathways have also been discussed. The theoretical analyses show that the left-handedness of medium will be enhanced with the increase of VIC effect.
Influence of turbulence on the coherent and incoherent combinations of off-axis Gaussian beams
Authors: Ji Xiao-Ling  , Li Xiao-Qing
Published: December 2020

The influence of turbulence on the coherent and incoherent combinations of off-axis Gaussian beams is studied in detail. The analytical propagation equation of the resulting beam in turbulence for the incoherent combination is derived. The mean-squared beam width, the power in the bucket and the β parameter are taken as the characteristic parameters of beam quality to compare the results of coherent and incoherent combinations of off-axis Gaussian beams propagating through atmospheric turbulence, and the reasonable physical explanations are also given. It is shown that, on one hand, both for the incoherent and coherent combinations the turbulence results in a beam spreading and a degradation of the maximum intensity, and the larger the individual beam numbers is, the less sensitive is the resulting beam to the effect of turbulence. On the other hand, the resulting beam for the incoherent combination is less affected by turbulence than that for the coherent combination.
Impact of a stripe waveguide to coupled defect modes of photonic crystals
Authors: Lin Xu-Sheng  , Wu Li-Jun  , Guo Qi  , Hu Wei  , Lan Sheng
Published: December 2020

Coupled defect modes of photonic crystals can be characterized by the transmission spectrum shape that is closely linked to the stripe waveguide connecting the defects. Unlike the direct coupling cases where the phase shift of lightwave depends only on the defect mode frequency, we found that for the waveguide coupling cases the waveguide length and the dispersion relation must be also considered. By changing the waveguide length, the spectrum can exhibit periodically three-peak appearance, two-peak appearance, and flat top appearance. At frequencies close to the defect mode, the results of the coupled mode theory are in good agreement with the simulations using the finite-difference time-domain technique, verifying the validity of the theoretical model even in the complicated cases.
Backward wave propagation in anisotropic metamaterials
Authors: Zhou Jian-Hua  , Liu Hong-Yao  , Luo Hai-Lu  , Wen Shuang-Chun
Published: December 2020

In this paper, we study the backward wave propagation phenomenon in completely anisotropic metamaterials. The formation conditions for backward wave propagation under an arbitrary angle between the metamaterials' intrinsic coordinate axis and transmission axis are obtained. The influences of permittivity and permeability tensors and polarization on the backward wave formation and propagation are analyzed. On this basis, we further analyze the situation of backward wave in anisotropic metamaterials with different dispersion relations, and the angle between wave vector and Poynting vector, and the general conclusion of backward wave propagation are obtained. In addition, we studied the propagation characteristics of backward wave in epsilon-near-zero metamaterials, and discovered that the backward wave in these metamaterials is a perfect backward wave.
First-principle study of electronic structure of Be-doping wurtzite ZnO
Authors: Tang Xin  , Lü Hai-Feng  , Ma Chun-Yu  , Zhao Ji-Jun  , Zhang Qing-Yu
Published: December 2020

Using the density-functional theory combined with the projector augmented wave method, we have investigated the electronic structure of Be-doping wurtzite ZnO. The band structure, total density of states and partial density of states of BexZn1-xO are presented and show that the valence band maximum (VBM) is determined by O 2p electrons and the conduction band minimum (CBM) is occupied by the hybrid Be 2s and Zn 4s electrons. The energies of CBM increase and the energies of VBM decrease with increasing Be-doping concentrations. Both effects lead to broadening of the band gap. Furthermore, it was found that Be-doping can cause compressive strain in the crystal structure, which also widens the band gap.
First-principle study on the electronic structures of intercalation compound Ag1/4TiSe2
Authors: Song Qing-Gong  , Wang Yan-Feng  , Song Qing-Long  , Kang Jian-Hai  , Chu Yong
Published: December 2020

Geometry optimization and total energy computation of Ag1/4TiSe2 and TiSe2 have been completed by means of plane wave pseudopotential method based on the local density approximation to density functional theory. The calculated lattice parameters accords with the experimental results reported and the negative formation energy shows the stability of ordered Ag1/4TiSe2 system. The atomic populations，bond lengths，band structure and density of states indicate that：Ag atoms are bonded with stronger ionicity in Ag1/4TiSe2 than in TiSe2. The intercalation of Ag makes TiSe2 with semimetal property change into Ag1/4TiSe2 with metal property and the conductivity is remarkably improved.
The investigation on the interference phenomenon in electroluminescence spectrum of vertical structured InGaAlN multiple quantum well light-emitting diodes
Authors: Xiong Chuan-Bing  , Jiang Feng-Yi  , Wang Li  , Fang Wen-Qing  , Mo Chun-Lan
Published: December 2020

The electroluminescence (EL) spectrum of vertical structured InGaN multiple-quantum-well light-emitting diodes were obtained at different space angles. It was found that the multiple EL peak pattern was caused by the interference phenomenon and the distance between the peaks could indicate the thickness uniformity of the p-type layer. The intensity difference between the wave crest and the wave trough of the peak pattern indicates the reflectance ratio of p-type ohmic contact layer. The integral EL intensity in the normal direction of the chip was not so strong， while in the directions of 80° and 75° the intensities were the largest and the interference phenomenon was the sharpest. The intensity of the EL and the interference phenomenon of the side face of the chip was the weakest.
Determination of the optical constants of sol-gel derived ZrO2 films simply form the transmission spectra
Authors: Liang Li-Ping  , Hao Jian-Ying  , Qin Mei  , Zheng Jian-Jun
Published: December 2020

By combining Swanepoels theory and the Wemple-DiDomenico dispersion model， a simple method was established to determine the optical constants of the sol-gel derived ZrO2 films directly from the corresponding transmission spectra. The results showed that the sol-gel ZrO2 films exhibite the optical characteristics of high refractive index of 1.63—1.93 (at 632.8nm)， negligible absorption in spectral region of 400—1200nm， as well as the direct band gap of about 4.97—5.63eV. And the specific values of the optical constants strongly depend on the annealing temperature, which is one of the important technologicalparameters for the sol-gel preparation of ZrO2 films. Moreover， in the weakand medium absorption spectral regions， the calculated values of refractive indices are in satisfactory agreement with the results derived from the high-resolution Tek 3000 film-characterization system， indicating the reliability and feasibility of the method in determining the optical constants of ZrO2 films.
Resonant diffusion of radiation belt energetic electrons by field-aligned propagation whistler-mode chorus waves
Authors: Ni Bin-Bin  , Zhao Zheng-Yu  , Gu Xu-Dong  , Wang Feng
Published: December 2020

Adopting the dipole geomagnetic field， Gaussian spectral density for the waves， and semi-empirical latitudinal electron density models obtained from available in situ data， this paper has calculated the local and bounce-averaged quasi-linear resonant electron diffusion coefficients due to chorus and then determined the timescales for electron precipitation loss and stochastic acceleration， in the range of 4≤L≤7 outside the plasmapause. The results indicate that the spatial extent where gyroresonance occurs depends on electron energy， equatorial pitch angle， wave spectrum， and the local electron number density and magnetic field. Besides these five parameters， the actual values of resonant frequency rely on magnetic latitude where resonance occurs. The acceleration of radiation belt energetic electrons occurs predominantly due to equatorial chorus， and the mid-latitude chorus preferably contributes to the precipitation loss of relativistic electrons. The timescales for both electron loss and acceleration due to chorus-driven diffusion have been evaluated to be of hours for lower-energy electrons (about 200keV) and of days for higher-energy electrons (about 1MeV). It is also found that variation of latitudinal density distributions contributes importantly to chorus-driven electron resonant diffusion. In general， an increasing latitudinal electron density increases the loss timescales for untrapped electrons with small equatorial pitch angles， but has negligible effect on the acceleration of trapped electrons with large equatorial pitch angles. The variations of chorus wave amplitude and wave spectrum with magnetic latitude and L-shell also make important contributions to the lifetime and acceleration of radiation belt electrons， which are generally greater than the effects of varying latitudinal distribution of cold plasma density.
Investigation on the surface damage to solar cells by impacts of space micro-debris on low earth orbit
Authors: Huang Jian-Guo  , Han Jian-Wei  , Li Hong-Wei  , Cai Ming-Hui  , Li Xiao-Yin
Published: December 2020

Cumulative damage to the exposed spacecraft materials by the micro-debris on low earth orbit， where the debris is densely populated， is one of the crucial problems calling for due consideration in designing of spacecrafts. The flux of micro-debris encountered by a typical sun-synchronous vehicle was calculated， the associated hypervelocity impact simulation experiment was carried out， and the damage equation was established. Based on the flux result and the damage equation， the surface damage ratio of the solar cell due to micro-impacts was calculated， and the associated optical transmittance decrease of the cell was evaluated according to optical measurement and theoretical model. The result showed that the surface damage ratio of solar cell after 10 a cumulative micro-impacts reaches 0.61% on average， and up to 2.3% in the worst case. The optical transmittance decreases by 0.5% on average， and up to 1.5% in the worst case. In this paper， a quantitative method of evaluation for the issue of solar cells surface damage due to micro-impacts was demonstrated through a concrete example.
Self-similarity model of nonsingular perfect gas universe
Authors: Lai Xiao-Ming  , Bian Bao-Min  , Yang Ling  , Yang Juan  , Bian Niu  , Li Zhen-Hua  , He An-Zhi
Published: December 2020

The present paper investigates the dimensionless dynamical continuity equation of perfect gas motion in gravitational field. Based on Π axiom of dimensional theory， self-similarity of perfect gas universe with gravity and a series of exact solutions of R(t) are deduced. Based on R(t)，a non-Euclidean homogeneous space-time coordinate system S(t,ξ，θ，φ) can be established. A perfect gas universe solution can be worked out， in which there is a constant density ρ， the velocity u value being zero， and there is a nonzero pressure p. In this solution， the red shift z represents the propagating distance r. When z is much less than 1， it is proportional to r (Hubbles law). The Robertson-Walker (k=-1) metric of normal universe model is obtained from homogeneous expanding coordinates， and the ratio of expanding rate HF to the Hubble constant H0 decreases notably as the value of z rises. It corresponds to the “universal accelerated expansion” observed in the spectrum of a high-red-shift supernova.
Structural and thermodynamic properties of Fe based compounds with NaZn13-type
Authors: Chen Yi  , Shen Jiang  ,   北京科技大学应用物理研究所,北京  100083
Published: December 2020

A series of Fe based compounds with NaZn13-type structure is studied by using inversed interatomic potentials. Calculated results show that Si atoms and Co atoms are preferentially substituted for Fe atoms at 96i site. The addition of Si or Co makes the cohesive energy decrease. It is found that the lattice constants of LaFe13-x-yCoySix and NdFe13-x-yCoy Six decrease with the increase of Co content. The investigation on the phonon density of states indicates that the lower frequency modes are mostly excited by the rare-earth atoms, and the higher frequency modes are mostly excited by Si atoms. Moreover, the addition of Co atoms makes the Debye temperature of LaFe11.5-yCoySi1.5 compounds increase.
Influences of deposition rate and oxygen partial pressure on residual stress of HfO2 films
Authors: Cen Min  , Zhang Yue-Guang  , Chen Wei-Lan  , Gu Pei-Fu  ,   (1)复旦大学电光源与照明工程学系，上海  200433; (2)浙江大学现代光学仪器国家重点实验室，杭州  310027
Published: December 2020

HfO2 films were prepared by electron beam evaporation on K9 glass. The residual stresse was measured by viewing the substrate deflection using ZYGO interferometer. The influences of deposition rate and oxygen partial pressure on the residual stress were studied. The results show that all the residual stresses are tensile stresses. The packing density of films increases while the residual stress decreases with the increasing deposition rates and the decreasing oxygen partial pressure. The microstructure of the HfO2 films was inspected by X-ray diffraction （XRD）. The relationship between the stress and the microstructure was also discussed.
The first-principles study on the elasticity of V-based solid solution hydrogen storage materials
Authors: Zhou Jing-Jing  , Chen Yun-Gui  , Wu Chao-Ling  , Pang Li-Juan  , Zheng Xin  , Gao Tao  ,   四川大学材料科学与工程学院，成都  610065
Published: December 2020

The lattice parameters， elastic properties and electronic density of state of the （59Cr-41Ti）100－xVx（x=5， 15， 30， 60， 80， 100） V-based solid solution hydrogen storage alloys were calculated using the first-principles plane-wave pseudo-potential method based on the density functional theory， and the calculated results were in agreement with the experimental results. It was found that the V-based alloy x=60 showing better elastic properties， with the Young modulus Yzz=14930 GPa， shear modulus Ct=5442 GPa and bulk elastic modulus B=19396 GPa. By combining the experimental cyclic durability performance， we found plastic deformations occurred in the alloys. Thus， we concluded that the elastic properties were not the primary factor that determines the cyclic durability of the V-based hydrogen storage alloys. The micromechanism of the elastic properties of the impure alloys were also explained with the electronic density of state.
Measurement of anisotropy thermopower of decagonal AlCuCo quasicrystal
Authors: Fan Zhen-Jun  , Geng Xue-Wen  , Kong Wen-Jie  , Jin Yi-Rong  ,   (1)广西师范大学物理与电子工程学院，桂林  541004; (2)中国地质大学（北京）材料科学与工程学院，北京  100083; (3)中国地质大学（北京）材料科学与工程学院，北京  100083；中国科学院物理研究所，北京  100190; (4)中国科学院物理研究所，北京  100190
Published: December 2020

The thermopower of decagonal AlCuCo quasicrystal was measured in the periodic and quasiperiodic direction by laser heating alternating current measurement method in the temperature range of from 300 K to 1200 K. We found that the thermopower is negative in the periodic direction and positive in the quasiperiodic direction. The thermopower hopps at 1123 K （850 ℃） along the periodic direction. The change of the thermopower is not monotonic at high temperature. The measurement method we used is sensitive to the phase transition point.
A compact interconnect temperature distribution model considering the via effect and the heat fringing effect
Authors: Zhu Zhang-Ming  , Hao Bao-Tian  , Qian Li-Bo  , Zhong Bo  , Yang Yin-Tang  ,   西安电子科技大学微电子研究所，西安  710071
Published: December 2020

Considering the via effect and the heat fringing effect simultaneously，we proposed a compact interconnect temperature distribution model that can be applied for single interconnect and multilevel interconnects. Based on the 65 nm complementary metal-oxide semiconcluctor （CMOS） interconnect and material parameter，the temperature distribution of multilevel interconnects and single interconnect with different lengths was calculated. The results show that the temperature rise of global interconnect is still large when the via effect is considered，while the temperature rise of intermediate line and local line is quite small. For multilevel interconnects，the temperature rise in the uppermost layer interconnect is the largest. The temperature rise is approximately proportional to the thickness of insulator，and will rise higher if the thermal conductivity of dielectric materials becomes smaller. The proposed interconnect temperature distribution model can be used in nanometer CMOS computer-aided design.
First-principles study of Co doped BiFeO3
Authors: Zhang Hui  , Liu Yong-Jun  , Pan Li-Hua  , Zhang Yu  ,   扬州大学物理科学与技术学院，扬州  225002
Published: December 2020

The magnetic structure，energy band structure and electronic structure of BiFeO3 and BiFe075Co025O3 are investigated by using density functional theory combined with the projector augumented wave （PAW） method. Our numerical results show that the doping of Co does not destroy its perovskite structure and BiFe075Co025O3 keeps the obvious ferroelectricity. The ferromagnetism can be significantly improved since the doping of Co changes the G-type antiferromagnetic order into ferromagneti cone. However，the doping of impurity Co degrades the insulativity.
Numerical calculation of Mueller matrices of randomly distributed soot cluster agglomerates
Authors: Lei Cheng-Xin  , Zhang Hua-Fu  , Liu Han-Fa  ,   山东理工大学理学院，淄博  255049
Published: December 2020

Cluster-cluster aggregation model based on Monte Carlo method is used to simulate the structure of the fractal-like soot cluster agglomerates consisting of spherical primary particles，and Mueller-matrix elements of fractal-like soot cluster agglomerates are calculated based on the discrete dipole approximation method. The numerical relations between the Mueller-matrix elements and the total number and the diameter of the primary sphere in agglomerate are discussed for different incident wavelengths，which provides an effective theoretical method for studing the formation mechanism，structural characteristics and scattering characteristics of randomly distributed cluster agglomerates.
Thermal effect in current induced magnetic switching
Authors: Dong Hao  , Ren Min  , Zhang Lei  , Deng Ning  , Chen Pei-Yi  ,   清华大学微电子学研究所，清华信息科学与技术国家实验室（筹），北京  100084
Published: December 2020

Based on the Neel-Brown relaxation time theory and the effective temperature model proposed by Li et al.，the thermal effect in current induced magnetic spin torque switching is theoretically studied. On the basis of Landau-Lifshitz-Gilbert equation and Fokker-Planck equation，through analyzing the current induced magnetic switching and potential change，a new model to explain the potential barrier reducing is proposed. Different from Lis model，this model is nonlinear. The model is used to discuss the relation between temperature，switching time and critical current. For the current induced temperature rise，our model does accord with the experiment well. The method for determining the intrinsic switch electric current，testing time and intrinsic potential barrier in magnetic switching is also proposed.
Non-Gaussianity of noise in n-type metal oxide semiconductor field effect transistor
Authors: Li Wei-Hua  , Zhuang Yi-Qi  , Du Lei  , Bao Jun-Lin  ,   (1)西安电子科技大学技术物理学院，西安  710071; (2)西安电子科技大学微电子学院，宽禁带半导体材料与器件教育部重点实验室，西安  710071
Published: December 2020

On the basis of the number fluctuation model of n-type metal oxide semiconductor field effect transistor （nMOSFET），non-Gaussianity of noise in nMOSFET was studied by the quadratic sum of the bicoherence，which belongs to higher order statistics. Comparing nMOSFETs test noise with Monte Carlo simulative noise，we proved that there is non-Gaussianity in nMOSFTs noise, that the noises non-Gaussian degree in small size devices is stronger than that in large size devices, and that the non-Gaussian degree of nMOSFTs noise in strong inversion and linear regime increase with the drain-source voltage. The physical mechanism of nMOSFET noise is discussed from Monte Carlo simulation and the central limit theorem.
Dynamic characteristics of Tl-2212 bicrystal Josephson junctions on SrTiO3 substrates and the effect of noise on it
Authors: Wang Zheng  , Yue Hong-Wei  , Zhou Tie-Ge  , Zhao Xin-Jie  , He Ming  , Xie Qing-Lian  , Fang Lan  , Yan Shao-Lin  ,   (1)南开大学信息技术科学学院电子系，天津  300071; (2)南开大学信息技术科学学院电子系，天津  300071；广西师范学院物理与电子信息科学系，南宁  530001
Published: December 2020

Tl-2212 bicrystal Josephson junctions on SrTiO3 substrates have been fabricated. The I-V characteristic of a Josephson junction under microwave radiation were measured，and microwave induced steps were observed in accordance with the Josephson frequency-voltage relationship. The RCSJ model including noise of bicrystal Josephson junction was constructed through numerical simulation，and the results of simulation were in good agreement with the experimental data. Using the RCSJ model，we investigated the effect of noise on the dynamic characteristics of Josephson junction through simulation，and explained the phenomenon of reduced height and increased breadth of the minima of microwave induced steps. We proposed that the effective noise temperature should be the sum of operational temperature and equivalent temperature of the external noise.
Structure and magnetic properties of Sm2Fe17-xCrxcompound prepared by arc melting
Authors: Hao Yan-Ming  , Wang Ling-Ling  , Yan Da-Li  , An Li-Qun  ,   (1)天津科技大学理学院物理部，天津  300222; (2)天津师范大学物理系，天津  300384
Published: December 2020

The structural and magnetic properties of Sm2Fe17-xCrx compound have been investigated by means of x-ray diffraction and magnetization measurements. The results show that the Sm2Fe17-xCrx （x=1—3） compounds annealed at 1050 ℃ for 5 days have a rhomhedral Th2Zn17-type structure，and the Sm2Fe17-xCrx（x=25, 30） compounds annealed at 1050 ℃ for 7 days have a monoclinic Nd3（Fe，Ti）29-type structure. Long annealing time and high content of Cr can make the Sm-Fe-Cr compound with a Nd3（Fe，Ti）29-type structure become very stable. This is quiet different from the R2Fe17-xCrx compound （R is a heavy rare earth element）. The analysis of unit-cell volume and unit-cell parameters show that there exists a strong anisotropic magneto-volume effect in Sm2Fe17-xCrx compounds. The result of magnetization measurement shows that the effects of the substituting Cr for Fe at dumbbell sites on the Curie temperature and the magneto-crystalline anisotropy of the compound with Th2Ni17-type structure are greater than that of the compound with Th2Zn17-type structure.