bluuebunny/crossref_metadata_2025 huggingface dataset:
Europa a América: Claudio Sánchez-Albornoz y la fundación de los "Cuadernos de Historia de España"
Authors: RÍOS SALOMA Martín F.
Published: December 2020

En el presente trabajo se reconstruyen trazos poco conocidos de la biografía del medievalista español Claudio Sánchez Albornoz (1893-1984) y se analizan los factores de orden personal y las circunstancias históricas que llevaron a uno de los más destacados historiadores españoles de la primera mitad del siglo XX a emigrar a Buenos Aires y la forma en que dicha experiencia se materializó en la fundación de los Cuadernos de Historia de España que dirigió entre 1944 y 1981, poniendo de relieve la significación intelectual e historiográfica de dicha fundación para el medievalismo hispano.

In this paper we reconstruct little-know aspects about the biography of the Spanish medievalist Claudio Sánchez-Albornoz (1893-1984). At the same time, we analyse the personal causes and the historical circumstances that led one of the most important Spanish historians from the first half of the 20th century to emigrate to Buenos Aires, and in what way that experience resulted in the foundation of the Cuadernos de Historia de España. We highlight the intellectual and historiographic significance of this foundation for Hispanic medievalism.
evolución patrimonial del monasterio de Santa María de la Concepción de la orden de San Jerónimo de Granada (siglos XV-XVII)
Authors: SÁNCHEZ CARRASCO Juan José
Published: December 2020

El objetivo del presente trabajo es estudiar el desarrollo patrimonial del Monasterio de Santa María de la Concepción de la orden de San Jerónimo de Granada. Para la elaboración del ensayo se ha realizado una exhaustiva búsqueda documental en archivos tanto granadinos como nacionales y se han empleado los datos de las publicaciones existentes sobre el monasterio que datan de los años 90 del pasado siglo. Se ha conseguido realizar un estudio completo sobre todas las transacciones que realizó la orden durante los siglos XV-XVI y ubicar sus propiedades mediante Sistemas de Información Geográfica (SIG).

The aim of this work is to study the heritage development of the Monastery of Santa Maria de la Concepción of the Order of Saint Jerome in Granada. For this purpose, an exhaustive data search has been undertaken in both local and national archives, in addition to the use of information contained in the literature published on the topic in the 90s of the twentieth century. It has been possible to achieve a comprehensive study of all the transactions carried out by the Order during the 15th and 16th centuries and locate their properties using geographic information systems (GIS).
Estrategias de enunciación en la literatura del siglo XVI: algunos ejemplos en la caballería literaria
Authors: Gil-Albarellos Pérez-Pedrero Susana
Published: December 2020

Este trabajo muestra una visión de conjunto de las diversas y complejas formas de enunciación utilizadas por los autores de los libros de caballerías durante el siglo XVI, analizando algunos ejemplos representativos de los mismos. La difusión de la materia caballeresca gracias a la expansión de la imprenta, al éxito de las propias obras literarias y a la confusión entre la dualidad historia y ficción favoreció que los autores reales se hicieran pasar por traductores o editores de los textos. Junto a esta circunstancia, otros libros de caballerías aparecieron bajo el anonimato, posiblemente por autoría femenina, y otros, al fin, fueron víctimas de la impostura. En definitiva, el género caballeresco puso enmarcha todo un juego de autores y narradores que anticiparon y abrieron el camino a la consolidación de la novela por parte de Cervantes con el Quijote.
Jacopo Gesiot, «Romanzi tiranni. La prosa iberica di cavalleria nel primo Cinquecento padano», Roma, Aracne, 2018
Authors: Calvo Rigual Cesáreo
Published: December 2020

Ressenya del llibre de Jacopo Gesiot, Romanzi tiranni. La prosa iberica di cavalleria nel primo Cinquecento padano, Roma, Aracne, 2018.
Contributing Factors and Trends in the Usage of IT Outsourcing in Manufacturing and Service Sectors
Authors: Agrawal Vipin K , Agrawal Vijay K , Chau Ngan N , Harms Sherri
Published: December 2020

The study projects long-term trends in the IT outsourcing in the manufacturing and service sectors of the United States. The findings suggest that the respondents perceive that there is approximately an equal usage of IT outsourcing in each of manufacturing and service sectors. Furthermore, the Desired Characteristics of Outsourcing – enabler of organisational flexibility, dynamics, and adaptability, redirection of resources, and increased control of operating costs – are positively related to the change in the requirement of IT outsourcing in the case of manufacturing. Meanwhile for the service sector, the Administrative Motivation for Outsourcing – lack of expertise, promising service offerings to subscribe, shrinkage in system life cycle – are positively associated with growth/no-growth in IT outsourcing.
Relationship Between Sensation Seeking and Attitude on Reckless Riding Behavior in Jabodetabek, Indonesia
Authors: Rahardjo Imanurul Aisha , Kusumawardhani Dianti E.
Published: December 2020

Transportation needs are increasing along with traffic problems, such as traffic accidents, congestion, and density of motorized vehicles. In Indonesia, especially in its large, crowded cities, accidents involving two-wheeled motorized vehicles are frequent. Human factors such as personality and behavior are a cause of accidents involving careless driving. Additionally, sensation seeking and the attitude toward reckless behavior influence the reckless behavior of motorcyclists in Indonesia, especially in the Jabodetabek area. Methods: data were obtained through a self-report questionnaire. The 69 participants (F:40, M:29) were motorbike riders aged 18–35 years who had an Indonesian driving license type C and had ridden a motorcycle daily for a minimum of 2 years. The questionnaire comprised 17 items that measured sensation seeking and attitudes toward reckless riding. Prerequisite for mediating the relationship among the variables, sensation seeking must correlate with attitudes and reckless riding such that the attitude variable that is a mediator must also correlate with reckless riding. Therefore, in this study, the mediating effect of attitudes in the relation between sensation seeking and reckless riding was tested. Our result demonstrates that’s influence of reckless riding attitude as a partial mediator between sensation seeking and reckless riding.
Pluralismo jurídico estatal: entre conflicto y diálogo. Enseñanzas de un caso colombiano
Authors: López Cuéllar Nelcy
Published: December 2020

Más allá de qué corte tiene la razón en el conocido “choque de trenes” entre las altas cortes colombianas, el libro explora qué tipo de fenómeno jurídico se presenta en este choque. La autora argumenta que el caso colombiano es un claro ejemplo de pluralismo jurídico estatal. Este vívido ejemplo de pluralismo debilita el mito del monismo jurídico dentro del Estado. Igualmente, debido a su relación con el pluralismo jurídico estatal, el texto explora con precisión y cuidado conceptos de uso continuo en la teoría del derecho y ciencia política como: autoridad, obediencia, desobediencia y diálogo interinstitucional. Además, la obra ofrece una mirada nueva a las consecuencias de la implantación del modelo de derecho jerárquico propuesto por Kelsen y sus limitaciones para desarrollar una dinámica de diálogo y colaboración armónica dentro del Estado.
Design and analysis of composite optical receiver for indoor visible light communication
Authors: Wang Yun  , Lan Tian  , Ni Guo-Qiang  ,   Key Laboratory of Photoelectronic Imaging Technology and System, School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

A novel design of optical receiver for visible light communication system in indoor environment is proposed in this study. The compound parabolic concentrator is coupled with a photo-detector as the receiving unit due to its optical properties. The composite optical receiver is composed of seven receiving units inserted in a hyper-hemispherical lens aligned with geometry configuration based on angle diversity. The composite optical receiver has fields of view of 360 in the horizontal direction and 180 in the vertical direction respectively, while the field of view of each receiving unit is 30. Model of indoor visible light communication is built through measurement in a room of a 5 m 5 m 3 m size. The received power and SNR distribution are acquired through MATLAB scripts. The received power of each receiving unit is treated by different algorithms. At a lower data rate, the sum of the received power from all receiving units is the final received power, while at a higher data rate, the final received power is the highest value of power collected by the each unit. The results show that the received powers of the composite receiver by using two different algorithms increase 11.58 and 7.47 dB, respectively, while the gains of the receiver are 15.31 and 5.98, respectively. The mean values of the signaltonoise ratio are 79.17 dB from the sum algorithm and 72.26 dB from maximum algorithm, respectively. It is concluded that signaltonoise ratio is high and the distribution fluctuation is weak. This usually means a good and stable communication performance. It is proved that the composite receiver designed in this study gives high quality communication performance and presents a wide field of view, thereby avoiding the blind area in communication.
Preparation of opal photonic crystal infrared stealth materials
Authors: Zhang Lian-Chao  , Qiu Li-Li  , Lu Wei  , Yu Ying-Jie  , Meng Zi-Hui  , Wang Shu-Shan  , Xue Min  , Liu Wen-Fang  ,   School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China;,   School of Mechatronical Engineering, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

With the development of infrared detection technology, the survival of military target is now under serious threat. Therefore, new infrared stealth technologies and materials are now in an urgent demand. The photonic crystal (PhC) possesses regularly repeating structure which results in band-gap and diffraction satisfying Bragg's law of diffraction. The PhC presents unique optical properties and functionality. The PhC with band-gap located in visible band is used widely as biosensor, chemical sensor, optical filter, reflector, modulator, metasurface and solar cell. The PhC with band-gap located in infrared band can be used to control the propagations of the electromagnetic waves of infrared band, and could be used as a promising material in the infrared stealth technology.
Photonic structure used to tune the infrared radiation usually has a one-dimensional layer-by-layer stack or three-dimensional wood pile structure. However, the poor flexibility, low strength, small area coverage, complicated fabrication process and high cost can prevent this new infrared stealth technology from being applied and developed.
In this report, a simple and cost-effective method of preparing the opal PhC materials is proposed, and this infrared stealth material forbids electromagnetic waves of infrared band to propagate on account of band-gap.In this paper, opal PhCs materials with high quality are assembled from SiO2 colloidal microspheres with micrometer size by using optimized vertical deposition method. We calculate the relation between the diameter of SiO2 colloidal microsphere and the frequency of opal PhCs band-gap in theory and verified in experiment, which operates in the working band of infrared detector. The results show that the diameters of SiO2 colloidal microspheres should be 1.33-2.22 m and 3.56-5.33 m. A series of monodispersed micrometer SiO2 colloidal microspheres is prepared by the modified Stber method, and bigger microspheres are prepared by using the seeded polymerization method. Then, we choose the diameters of 1.5 m and 4.3 m SiO2 microspheres to prepare the opal PhCs materials. The PhCs materials assembled by 1.5 m SiO2 microspheres are prepared in alcohol under 60 ℃ or in acetone under 40 ℃; while the PhCs material assembled by 4.3 m SiO2 microspheres is prepared in alcohol/dibromomethane =3:1 under 60 ℃. Finally, the opal PhC materials with band-gap located in 2.8-3.5 m and 8.0-10.0 m are successfully prepared, and the widths of band-gap are 0.7 m and 1.9 m, respectively. These opal PhCs materials could change the infrared radiation characteristics of the target in infrared waveband, and meet the requirements of wide band-gap for infrared stealth materials.
Experimental investigation on the influence of Mg content on Portevin-Le Chatelier effect in Al-based alloys by using digital image correlation
Authors: Yang Su-Li  , Fu Shi-Hua  , Cai Yu-Long  , Zhang Di  , Zhang Qing-Chuan  ,   CAS Key Laboratory of Mechanical Behavior and Design of Materials, University of Science and Technology of China, Hefei 230027, China;,   State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
Published: December 2020

The Protein-Le Chatelier (PLC) effects are investigated by using digital image correlation at a constant applied strain rate of 5.0010-3 s-1 and room temperature in Al-Mg alloys with Mg content values (wt.%) of 2.30, 4.57, 6.10 and 6.91 respectively in this study. Both the yield strength and the ultimate strength increase with increasing Mg content, which is generally called solution strengthening. Type of PLC band changes from A to B with increasing Mg content. In low Mg content (2.30%) alloy, the serration amplitude almost remains 1 MPa, while in each of high Mg content (4.57%, 6.10%, 6.91%) alloys it linearly increases with the strain increasing. The serration amplitude is found to increase with increasing Mg content and gradually reaches a saturated state. With the increase of Mg content, the period of PLC band for continuous propagation gradually reduces and the time when the PLC band location sudden jumps increases in the process of propagation. When the strain is small, the out-of-band deformation of alloy is inhomogeneous obviously. And the deformation inhomogeneity slightly decreases with increasing Mg content. DIC results indicate that the PLC bandwidth does not change with Mg content, while the maximum strain increment in the PLC band increases with increasing both Mg content and strain. Additionally, special periodic damped serrations are observed in the stress-time curve of the low Mg content (2.30%), the corresponding PLC band shows that the periodic changed serrations in the stress-time curve correspond to the transformation of the PLC band orientation. Besides, the PLC band propagates upward continuously both before and after the shift.
Atomic-scale simulation study of structural changes of Fe-Cu binary system containing Cu clusters embedded in the Fe matrix during heating
Authors: Zheng Zhi-Xiu  , Zhang Lin  ,   School of Material Science and Engineering, Northeastern University, Shenyang 110819, China;,   Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education, Northeastern University, Shenyang 110819, China
Published: December 2020

Nano-size Cu precipitates are the main products of irradiation embrittlement of nuclear reactor pressure vessel steels. Molecular dynamics simulation within the framework of embedded atom method is performed to study atomic packing change in Fe-Cu binary system, where the small Cu clusters are embedded in the crystal body centered cubic (BCC) Fe lattices. As the temperature increases, atomic packing change occurs in the Fe-Cu binary system. The mean square displacement of Cu atom, pair distribution function of the Cu atoms, and the atomic density profile along the radial direction are calculated. The atom packing structures in pure Cu region, Fe-Cu interface region, and pure Fe matrix are analyzed. The simulation results show that the packing structures in the Cu cluster and the Fe matrix are greatly affected by the sizes of these clusters and the volume of the Fe matrix containing these clusters. The structural changes present apparent differences, for the Fe matrixes contain these confined Cu clusters with different atom numbers during heating. As the Fe matrix can only provide small space to accommodate the Cu atoms, packing patterns in many Cu atoms are disordered for the Febulk-Cu135 system. In this binary system, strain region in the Fe matrix is adjacent to the Cu cluster. In the meantime, there are a lot of vacancy defects and strain regions in the matrix. For the Febulk-Cu141 system, although the Cu cluster contains more atoms, the Fe matrix can accommodate Cu atoms in a larger space, and the majority of these Cu atoms are located at the BCC crystal lattices. With increasing the temperature, the changes can be observed that the number of the strain regions decrease, whereas the sizes of some strain regions increase.
Conduction mechanisms of MIM capacitors with ZrO2/SiO2/ZrO2 stacked dielectrics and Ni electrodes
Authors: Liu Qi-Xuan  , Wang Yong-Ping  , Liu Wen-Jun  , Ding Shi-Jin  ,   State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, China
Published: December 2020

The electrical characteristics of Ni electrode-based metal-insulator-metal (MIM) capacitors have been investigated with atomic layer deposited ZrO2/SiO2/ZrO2 symmetric stacked-dielectrics. When the thickness of the stacked-dielectrics is fixed at 14 nm, the resulted capacitance density decreases from 13.1 fF/m2 to 9.3 fF/m2, and the dissipation factor is reduced from 0.025 to 0.02. By comparison of current-voltage (I-V) curves of different MIM capacitors, it is found that the leakage current density in the high voltage region decreases gradually with the increasing thickness of SiO2, and it does not exhibit clear change in the low voltage region. Meanwhile, the capacitors show different conduction behaviors under positive and negative biases with increasing the thickness of SiO2 from 0 to 2 nm. Under the positive bias, different I-V characteristics are demonstrated at high and low electric fields, respectively. However, a single I-V characteristic is dominant under the negative bias. Further, the conduction mechanisms of the capacitors are investigated under the electron bottom and top injection modes, respectively. It is found that the Poole-Frenkel emission and the trap-assisted tunneling are dominant in the high and low field regions, respectively, for the electron bottom injection; however, the trap-assisted tunneling is dominant in the whole field region for the electron top injection. These are attributed to the formation of a thin NiOx interfacial layer between the Ni bottom-electrode and the ZrO2 dielectric layer, as well as the existence of both deep and shallow level traps (0.9 and 2.3 eV) in the ZrO2 dielectric. Therefore, the level trap plays a key role in the electron conduction in the MIM capacitor under different electron injection modes and different electric fields.
Experimental and numerical study of tuneable supercontinuum generation in new kind of highly birefringent photonic crystal fiber
Authors: Xiong Meng-Jie  , Li Jin-Yan  , Luo Xing  , Shen Xiang  , Peng Jing-Gang  , Li Hai-Qing  ,   Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

We report on a new kind of highly birefringent and highly nonlinear photonic crystal fiber with a row of sub-micron air hole in the fiber core. The diameters of air holes in fiber core and cladding are 0.2 μm and 6.6 μ$m respectively. The parameters of birefringence, nonlinear and dispersion coefficient of the fiber are simulated by finite element method. It is found that the birefringence of the fiber can exist at the wavelengths up to 1550 nm, which is one order of magnitude higher than that of the traditional polarization-maintaining fiber. The zero-dispersion wavelengths of the fast axis and slow axis are 1050 nm and 1080 nm respectively. This fiber has a clear advantage over conventional fiber in continuum generation. Firstly, the polarization state of the pulse traveling in the fiber can be sustained along the fiber length and the extinction ratio is more than 20 dB. In addition, the pulses travel at different group velocities along the two polarization directions, which provide a convenient way of tuning the properties of the generated supercontinuum. Using this fiber as a nonlinear medium, an efficient generation of a tunable supercontinuum is demonstrated by pumping with 15 ps pulses of 1040 nm laser radiation, which is located in the normal dispersion region. A half-wave plate is used to vary the input polarization of the light pulse launched into the fiber, and the polarization of output supercontinuum is adjusted by a Glan prism at the same time. It is experimentally found that the polarization of pulse has a significant influence on the generation of the supercontinuum. When the linear polarization of the input pulse matches with the direction of the main axis of the fiber, the supercontinuum can be broadened over wavelength range of 800-1500 nm, and the extinction ratio is 21.2 dB. The polarization direction of the output SC is found to coincide with the pump pulse. When the angle between the polarization of the input pulse and the fast axis is increased to 45 degrees, the output supercontinuum is circularly polarized and becomes narrowest, extending from 900 to 1300 nm. So we can realize the wide tuning of a supercontinuum by only changing the polarization direction of the incident pulse. Under the circumstances, the pulse in optical fiber can be broken into two components along the main axis respectively. If the input polarization direction is away from both principal axis directions, the power along the main axis and the contribution of cross phase modulation are reduced because of the walk-off effect, so the width of the supercontinuum will become narrower. It is suggested that this type of high birefringence photonic crystal fiber could be effectively applied to the generation of the tunable supercontinuum.
Sensitivity-enhanced temperature sensor with fiber optic Fabry-Perot interferometer based on vernier effect
Authors: Yang Yi  , Xu Ben  , Liu Ya-Ming  , Li Ping  , Wang Dong-Ning  , Zhao Chun-Liu  ,   College of Optical and Electronic Technology, China Jiliang University, Hangzhou 310018, China
Published: December 2020

Fiber-optic temperature sensors have gained much attention owing to their intrinsic features of light weight, immunity to electromagnetic interference, and capability for distributed measurement. Especially, temperature sensors based on Fabry-Perot interferometers (FPIs) are attractive owing to their advantages of compact size and convenient reflection measurement. However, due to the low thermal expansion or/and thermo-optic coefficient of fiber, the temperature sensitivities of these sensors are normally low (~10 pm/℃ or even lower). In order to improve the temperature sensitivity, a device with dual cascaded FPIs is proposed and demonstrated in this paper, which works on vernier effect and exhibits a much higher temperature sensitivity. The device is fabricated by splicing a short segment of large mode area (LMA) fiber to a short segment of capillary tube fused with a section of single-mode fiber to form an extrinsic Fabry-Perot interferometer with a glass cavity cascaded to an intrinsic FPI with a narrow air cavity. By setting the lengths of capillary tube and LMA fiber to allow similar free spectral ranges to be obtained, and superimposing of the reflection spectra of the two FPIs, the vernier effect can be generated. Firstly, the principle of temperature sensing based on vernier effect of this device is analyzed and simulated theoretically, and it is found that the temperature sensitivity can be improved significantly by using vernier effect compared with that of a single FPI with an air-cavity or glass cavity by directly tracing resonant dips/peaks. Then, the temperature responses of the FPI with single air-cavity and dual cascaded cavities are measured, respectively. Experimental results match well with the theoretical analysis carried out. The temperature sensitivity of the proposed sensor is improved greatly from 0.71 pm/℃ for a single FPI sensor with an air-cavity to 179.30 pm/℃ by employing the vernier effect. Additionally, the sensor exhibits good repeatability in a temperature range of 100-500℃. The proposed sensor has the advantages of compact size (1 mm in dimension) and high sensitivity, which makes it promising for temperature sensing in a variety of industries, such as food inspection, pharmacy, oil/gas exploration, environment, and high-voltage power systems.
A passive range method of broadband impulse source based on matched-mode processing
Authors: Li Xiao-Man  , Zhang Ming-Hui  , Zhang Hai-Gang  , Piao Sheng-Chun  , Liu Ya-Qin  , Zhou Jian-Bo  ,   College of Underwater Acoustic Engeering, Habrbin Engineering Universiy, Harbin 150001, China;,   Acoustic Science and Technology Laboratory, Habrbin Engineering Universiy, Harbin 150001, China
Published: December 2020

Aiming at the passive impulse wideband source range problem in shallow water waveguides, a passive source range method with single hydrophone based on the matched mode processing is presented in this paper, the method is applied to the shallow water waveguide with a bottom of liquid semi-infinite space. Warping transformation is a useful tool to separate the normal modes of the received signals of the impulse source, and the frequency domain signals of each order can be obtained. The seafloor phase shift parameter is an important parameter describing the acoustic parameters of the seafloor, which contains nearly all the information about sea floor, what is more, the seafloor phase shift parameter is also an parameter that can be obtained by some experimental data easily. Each order normal mode can be represented by the expression that contains the phase shift parameter of sea floor. What is more, the influence of sound speed profile of the waveguide on eigenvalue can be approximately eliminated by jointly processing arbitrary two-order normal modes. Sound speed profile has a similar influence on eigenvalue of each order normal mode, therefore, the difference in the eigenvalues between arbitrary two-order normal modes can be approximated represented by the phase shift parameter of the sea-floor, the sea depth and the mean speed in the waveguide. In this way, the phase replica which consists of the eigenvalue difference of each two-order mode can be calculated simply and quickly, and then by constructing cost function and matching normal mode, the underwater impulse source can be located. Compared with the traditional method of processing matched mode and the method of processing matched fields, the method presented in this paper has two advantages: using warping transformation instead of hydrophone arrays to separate the normal modes; the replica can be calculated quickly and easily, depending on a small number of environmental parameters of waveguide. The effectiveness and accuracy of the method are proved by the results of numerical simulation and sea experimental data processing, in which the signals are both received by a single hydrophone. The sea experimental data contain linear frequency modulation impulse source signal and explosion sound source signal, and the mean relative error of range estimation is less than 10%. In the end of this paper, the range estimation error is analyzed, indicating that the error originates mainly from the mode phase parts besides the phase part of Hankel function. Consequently, finding the ways to reduce the range estimation error is an important project in the future.
Shupe effect of fiber sensing coils in multidimensional thermal field
Authors: Zhuo Chao  , Du Jian-Bang  ,   National Key Laboratory of Science and Technology on Aerospace Intelligent Control, Beijing Aerospace Automatic Control Institute, Beijing 100854, China
Published: December 2020

Optical fibers have a wide range of applications and constitute the core of fiber-optic gyroscope which is revolutionizing the ancient inertial rotation detection. However, fiber coils in these instruments are susceptible to surrounding physical quantities, which can seriously deteriorate their accuracy. And the thermally induced parasitic effect is one of the most critical factors leading to the bias drift. This drift error is due to the nonreciprocity phase shift in the counter-propagating optical loops when a thermal gradient passes through the fiber coil as described by Shupe. The quadrupole winding patterns along with other coiling schemes have been proposed to reduce the Shupe effect by maintaining fiber parts at equal distances from the coil center beside each other. Many researchers have investigated the thermal effect on this drift on the assumption that the temperature transient propagates only radially along the fiber coil, while little attention has been paid to the case of the multidimensional thermal field. This can hardly satisfy completeness of the theory, and be applied to certain complicated working conditions. In this paper, we develop theoretical models that describe drift signals caused by radially, axially and circumferentially transmitted thermal effects on the quadrupole winding fiber coil. The obtained findings indicate that the bias error excited by the thermal flow in radial and axial directions is proportional to the weighted sum of the difference in temperature changing rate between outer and inner sides of the fiber ring. And the share of the sum linearly grows when approaching to the top surface near the input and output end (I/O end) of the fiber. Thus, it is suggested that it should be avoided to place heat sources in the neighboring area. For the circumferentially distributed temperature field, the drift depends on the symmetry of the thermal gradients on both sides of the centerline connecting the fiber midpoint and the I/O end. This circumferential thermal effect can be dominant, since it tends to cover a larger spatial scale than its counterparts in radial and axial directions. And besides making a good symmetrical design of the temperature distribution with respect to the centerline, it can be suppressed by arranging the nonuniformity of the thermal field in the opposite direction of the fiber coil to the I/O end, which is also beneficial to reducing its sensitivity to the angular change. Our results can help better understand the mechanisms for the thermal error formation and guide us in optimizing and facilitating the thermo-structure design of both fiber gyroscopes and navigation systems.
Evolution characteristic analysis of double-helical vortex wake of high Reynolds number flow
Authors: Li Gao-Hua  , Wang Fu-Xin  ,   School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai 200240, China
Published: December 2020

High Reynolds number helical vortex system possesses a dominant characteristic of helicopter rotor flow field, whose spatiotemporal evolution is one of the most important factors affecting the aerodynamic performance. In such a type of flow field, vortex interaction due to flow unsteadiness and non-linearity possesses the most common characteristic, whose complexity and tightly coupling property make it very hard to understand its physical behaviors. Also, the multi-scale characteristic of the helical vortex evolution poses a severe challenge to the computational fluid dynamics community. In this paper, a hybrid numerical method, blending 5th order weighted essentially non-oscillatory and 6th order cenitral schemes, implemented in a finite volume overset grid framework based on adaptive mesh refinement technique, are adopted to capture the evolution of vortical structure in a high resolution manner. The highly-resolved flow field of Caradonna-Tung rotor with two blades in hover, with a tip Mach number of 0.439 and a tip Reynolds number of 1.92×106, is obtained using delayed detached eddy simulation method. The averaged pressure coefficient distributions at 50%R, 68%R, 80%R, and 96%R stations show good agreement with experiment data, and the vortex trajectories during the stable stage, as well as the instantaneous turbulent kinetic energy distribution in the wake region, and also validate the computed result. In order to reveal the underlying physical mechanism of the helical vortex structure evolution, proper orthogonal decomposition analysis and Lagrangian coherent structures are adopted as a post processing procedure, which brings more details about the unsteady vortex system. The evolution characteristics of the vortex system are revealed as follows. 1) Trailing edge vortex sheet rolling-up and interaction with tip vortex strongly affect vortical stability and downstream nonlinear vortex-vortex behaviors. 2) The vortical system exhibits the spatiotemporal stability at an age less than 720°, and the vorticity decays with age and trajectories by power law, the distribution of circumferential velocity and the evolution of vortex core radius agree well with theoretical models. 3) Results of proper orthogonal decomposition analysis show that the mode of free stream and point vortex combination plays critical roles in the state transition of flow field. 4) Lagrangian coherent structure further gives the evolution process of helical vortex, and reveals the flow characteristics of vortex pairing and co-rotating, showing the effect of trailing edge vortex roll up phenomenon in the vortical system evolution.
Determination of heavy metal content in dust of earth's surface and dust on air conditioner filter by X-ray fluorescence analysis
Authors: Wang Xin  , Kang Ming-Ming  , Liu Jun  , Chen Xiu-Lian  , Qin Xue  ,   College of Physical Science and Technology, Sichuan University, Chengdu 610064, China;,   Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064, China
Published: December 2020

The dust of earth's surface and the dust on air conditioner filters reflect a certain area of air pollution in a period of time. In the present study, we investigate the dust collected from the Wangjiang campus of Sichuan University on March, 2017. The dust is divided into 9 groups according to their diameters. The dust is made into the samples by mixing the dust and analytically pure starch at a ratio of 1:2, and pressing it into slices of 1.5 cm in radius and 6 mm in thickness through using a powder compressor. Likewise, the salts (MnSO4H2O, Fe(NO3)39H2O, CuSO45H2O, ZnSO47H2O, Pb(NO3)2), are also made into standard samples of different elements (Mn, Fe, Cu, Zn, and Pb). X-ray fluorescence analyzer is used to measure the element content in each of the samples according to calibration curves measured from the standard samples. The results show that the content of each element in the earth's surface dust is lower than that in the dust on the air conditioner filter. The values of Cu, Zn, and Pb content in the dust are higher than the average content of the topsoil in Sichuan Province, China. These elements possibly originate from motor vehicle exhaust.
Based on the theoretical model for the gaseous elements to change into the fine particulate matter, the change of the trace element content with the particle size can be expressed as Ci kiDn, where Ci is the content of the metal element i in the dust, ki is a scale factor, D is the diameter of the dust particle, and n is the distribution index. From the results it is concluded that the distribution indexes corresponding to various elements are approximately the same in the size range of interest to us (32.5-230 m). A recommended value of n is -0.430.06.
Atomistic simulation of microvoid formation and its influence on crack nucleation in hexagonal titanium
Authors: He Yan  , Zhou Gang  , Liu Yan-Xia  , Wang Hao  , Xu Dong-Sheng  , Yang Rui  ,   Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;,   University of Chinese Academy of Science, Beijing 100864, China;,   College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, China;,   School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China;,   School of Physics, Liaoning University, Shenyang 110036, China
Published: December 2020

During the plastic deformation of hexagonal metals, it is easy to generate the point defect clusters with complex shapes and configurations due to their anisotropic properties. The interactions among these clusters and between these clusters and moving dislocations significantly influence the physical and mechanical properties of hexagonal materials. However, none of these issues in particular concerning the evolutions of vacancy clusters, the formation of microvoids, and the crack nucleation and propagation, is comprehensively understood on an atomic scale. In the present work, we first employ the activation-relaxation technique, in combination with ab initio and interatomic potential calculations, to systematically investigate vacancy cluster configurations in titanium and the transformation between these clusters. The results indicate the stable and metastable configurations of vacancy clusters at various sizes and activation energies of their dissociation, combination and migration. It is found that the formation and migration energies decrease with the size of vacancy cluster increasing. Small vacancy clusters stabilize at configurations with special symmetry, while large clusters transform into microvoids or microcracks. High-throughput molecular dynamics simulations are subsequently employed to investigate the influences of these clusters on plastic deformation under tensile loading. The clusters are found to facilitate the crack nucleation by providing lower critical stress, which decreases with the size of the vacancy clusters increasing. Under tensile loading, cracks are first nucleated at small clusters and then grow up, while large clusters form microvoids and cracks directly grow up.
Quantum vortex phenomenon of many sub-Bose-Einstein condensations formed by expansion and superposition
Authors: Dong Bi-Yuan  , Xu Zhi-Jun  ,   Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310032, China
Published: December 2020

Based on the two-dimensional model, the formation mechanism of quantum vortex by the expansions and superpositions of the many sub-Bose-Einstein condensations (BECs) in the weak harmonic trap is studied. In the harmonic approximation, the initial wave function of the sub-BEC is Gaussian function. Once the initial wave function is known, by using the propagation method, the time evolution of the wave function for the sub-BECs could be obtained. The physical processes of the macroscopic quantum vortex formed by the symmetric distribution of the three sub-BEC expansions and superpositions are analyzed, and the law of quantum vortex with time evolution is obtained. It is found that the vortex distribution is oscillatory in the harmonic trap, and vortex and anti-vortex are mutually transformed in time. At the same time of evolution, the vortex direction is always opposite to that of the neighbor vortex, and at different evolutionary times t and t', which satisfy a relation of t+t'=T (period of harmonic trap), the position of vortex nucleus is unchanged, but the vortex is transformed into the anti-vortex. These basic phenomena of quantum vortex are explained and discussed. In particular, in this paper we also introduce the particle flow density, calculate the flow circulation of our system, and analyze the mechanism of vortex formation. The research ideas and methods in this paper are easily to be extended to the study about the vortex formed by more than three sub-BEC expansions and superpositions, and they can also be used to discuss the effects of sub-BECs with different initial phase differences. This model is also easier to implement in experiment. Therefore, the research of this paper also has enlightenment to the experimental work.
Numerical experiment studies of clogging during the discharge of granular matter in a three-dimensional hopper
Authors: Ma Li-Dong  , Yang Guang-Hui  , Zhang Sheng  , Lin Ping  , Tian Yuan  , Yang Lei  ,   Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China;,   School of Physical Science, University of Chinese Academy of Sciences, Beijing 100049, China;,   School of Infomation Technology and Engineering, Lanzhou University, Lanzhou 730000, China
Published: December 2020

For a granular flow in hopper in engineering and experimental applications, it is necessary to guarantee the discharge continuously and steadily. The clogging will easily happen if the outlet size is small enough via formation of the arch above the outlet. The clogging phenomenon is also important for studying traffic or evacuation problems. In previous numerical and experimental study, to expedite the experiments or simulations, the perturbations, such as a jet of pressurized air or the vibration of the wall of the hopper, were induced to break the clogging and restart the flow. But these perturbations are hardly normalized and described in modeling the process. In this paper, we present a series of numerical experiments of clogging in the discharge of particles from a three-dimensional hopper through a circular opening. We employ our discrete element method simulation code for large scale dense granular flow based on the graphic processing unit to expedite this simulation. In contrast to pervious studies, here we study the first clogging after opening the outlet of hopper, thus the above perturbations are avoided. From simulating granular flow in hopper in a wide range of outlet size and cone angle, we obtain the size of distribution of avalanche, which is defined as the number of particles that fall through the opening from the outlet opening to the first clogging. The effects of the outlet size and cone angle of hopper on avalanche size are investigated and discussed. The results show that the previous conclusion of the distribution of possibility of avalanche size is also valid in this study. There is a peak in the distribution of possibility of avalanche size, and the distribution can be divided into two regions, which can be fitted with a power-law and an exponential function respectively. The exponential part can be explained by a possibility model which is suggested by Janda et al. From the fitting we find that it has a critical value for the outlet size above which no clogging will occur and the value in this work (4.75d) is slightly lower than in Zuriguel et al.'s experiment (4.94d). Moreover, there is also a critical value for the cone angle of hopper, which supports the inference in previous study and the value in this paper (77) is closed to the predicted one (75) in To et al.'s work.
Theoretical study on the structure and stability of neutral and cationic butanone clusters
Authors: Yang Xue  , Ding Da-Jun  , Hu Zhan  , Zhao Guo-Ming  ,   College of Science, Jilin Institute of Chemical Technology, Jilin 132022, China;,   Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
Published: December 2020

The molecular clusters have attracted increasing attention in recent years due to their applications in areas of laser, synchrotron radiation, molecular beam and time-of-flight mass spectrometry. The cluster structures can be speculated by the mass spectrum measurement and predicted by the quantum chemical methods. It is very important for understanding the solvation kinetics and nucleation to explore the formation and growth of clusters. Meanwhile, it is also beneficial to understanding the atomic or intermolecular interactions in the clusters.
The molecular clusters have been studied in our previous work. The acetone clusters (CH3COCH3)n (n 12) were observed by 355 nm pumping laser. The structures of (CH3COCH3)n with n=2-7 were calculated by density functional theory, and some structures of clusters with low energy were given. Subsequently, several butanone cluster fragment ions and protonated butanone (CH3COC2H5, which is formed by taking a methyl change into ethyl from acetone CH3COCH3) clusters were observed by measuring the mass spectra under the irradiations of 355 nm and 118 nm laser lights, respectively.
It is important to determine the stable cluster structures and explain the dynamics of the clusters by theoretical calculation. The stable geometric structures of neutral and cationic butanone clusters are optimized at B3LYP/6-31G* and B3LYP/6-311+G** levels based on the density functional theory. The structural characteristics and stabilities of butanone clusters with various sizes are also analyzed. The average binding energy, first-order difference energy, HOMO-LUMO gap and ionized energy are further discussed systematically in the present work. The results show that the structures of (CH3COC2H5)n and (CH3COC2H5)n+ have similar characteristics, single-ring structure is the most stable for them when n=3-7, and the structures also occur in some hydrogen bonded clusters, such as (H2O)n (n=3-6), (NH3)n (n=3-6), (CH3OH)n (n=3-6), and (HCHO)n (n=3-8). Moreover, the stability of double ring structure rises with cluster size increasing. The (CH3COC2H5)3 has the best stability in neutral clusters (CH3COC2H5)n with n=2-7, and it corresponds to the strongest peak in experiment. In addition, the (CH3COC2H5)4+ is the most stable in the cationic clusters with corresponding sizes. Furthermore, the vertical ionization energy of butanone molecule is 9.535 eV via theoretical calculation, which is in agreement with the experimental data. At the same time, the structures of (CH3COC2H5)2+ and (CH3COC2H5)2 are proved to be different by the ionization energy. The results provide a theoretical basis for the formation mechanism of butanone cluster fragment ions in experiment, and it is beneficial to the further study of growing the ketone clusters.