bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermodynamics and its quantum correction of non-commutative Schwarichild black hole
Authors: Shen Jue , Liu Cheng-Zhou , Zhu Ning-Ning , Tong Yi-Nuo , Yan Chen-Cheng , Xue Ke-Lei ,   Department of Physics, Shaoxing University, Shaoxing 312000, China
Published: December 2020

Black hole thermodynamics establishes a deep and satisfying link to gravity, thermodynamics, and quantum theory. And, the thermodynamic property of black hole is essentially a quantum feature of gravity. In this paper, in order to study the influence of the quantum gravity effect on the quantum properties of black hole, we study the thermodynamics and its quantum correction to a non-commutative black hole. First of all, the temperature of the non-commutative Schwarichild black hole is calculated by using three different methods: surface gravity, tunneling effects and the first law of black hole thermodynamics. It is found that the same hole temperature is obtained by means of the surface gravity and tunneling effects. However, by using the first law of black hole thermodynamics, different results are derived from the first two methods. Therefore, we incline to the result obtained by surface gravity and tunneling effects, and the temperature obtained by the thermodynamic law needs modifying. That is, for the non-commutative black hole, there is a contradiction to the first law of thermodynamics. To calculate the temperature and other thermodynamic quantities for the non-commutative Schwarichild black hole, we use the corrected first law of black hole thermodynamics proposed in the literature. It is found that the black hole temperature derived by the corrected first law is the same as the temperature obtained by the surface gravity and the tunneling model, and the black hole entropy still follows Beckenstein-Hawking area law. Also, the heat capacity of the black hole is obtained and analyzed. It is seen that when the horizon radius and non-commutative parameter satisfy the particular conditions, the heat capacity is positive and the non-commutative black holes are thermodynamically stable. This is a different result from that of the usual Schwarichild black hole. Further, by studying the influence of generalized uncertainty principle on non-commutative black hole thermodynamics, the quantum corrections from generalized uncertainty principle for temperature, entropy and heat capacity of the non-commutative Schwarzschild black hole are given. It is found that with considering this quantum gravity effect, the obtained black hole entropy contains the item of are alogarithm. If the effect of the generalized uncertainty principle is neglected, the corrected black hole entropy can return to that in the usual case of Beckenstein-Hawing area law. Similarly, the corrected black hole temperature and heat capacity can also return to their counterparts in the case of usual Schwarzschild black hole when this quantum gravity effect is ignored.
Wavelength-scanned cavity ring down spectroscopy based on Fourier transform
Authors: Wang Zhen , Du Yan-Jun , Ding Yan-Jun , Peng Zhi-Min ,   Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

Continuous wave cavity ring down spectroscopy (CW-CRDS) method with using cavity length scanning is ideal for accurately characterizing the low pressure spectra and measuring the small spectral parameters (such as the Dicke narrowing coefficient and the speed dependent collision broadening coefficient). However, the laser of any wavelength can be coupled to the cavity due to the cavity scan, so the spectral noise caused by the laser wavelength fluctuations cannot be ignored. This noise is non-uniformly distributed in the spectrum (especially on both wings on the spectral line) and is difficult to eliminate even with long-term averaging. Unlike the complex laser frequency locking techniques or the optical frequency combs or the better lasers, in this paper, a simple, easy to operate, fast wavelength-scanned CRDS method is proposed based on Fourier transform. The laser wavelength is continuously tuned across the absorption line to measure the periodic ring-down time. A reconstruction algorithm is developed to precisely recover the absorbance by extracting the characteristic frequencies of the periodic ring-down time after the Fourier transform. An etalon, instead of the wavelength meter, is used to calibrate the relative laser wavelength. This method effectively eliminates the non-uniform spectral noise caused by laser wavelength fluctuation in traditional CW-CRDS and significantly improves the measurement accuracy of spectral line parameters (especially line parameters in complex line shapes, such as speed dependent Voigt line shape) at low pressure. In addition, the measuring system, in which no wavelength meter is used, is simpler, more economical than CW-CRDS. The smaller residuals of the Galatry profile fit to the measured CO transitions at R(5) 6371.299 cm–1 and R(6) 6374.406 cm–1 show that the noise on both wings of the spectra, caused by laser wavelength fluctuation, is effectively reduced and the spectral SNR is then improved. The measured N2 perturbed collision broadening coefficient of the Voigt profile fit for CO is consistent with that from the classical CW-CRDS method and is in good agreement with the HITRAN2016 database. The measured N2 perturbed Dicke narrowing coefficient of the Rautian and Galatry profile and speed dependent collision broadening coefficient of the speed dependent Voigt profile have very good linear relationship with pressure, and have smaller uncertainties than the results from the CW-CRDS method.
Quantum dot refrigerator driven by photon
Authors: Li Wei , Fu Jing , Yang Yun-Yun , He Ji-Zhou ,   Department of Physics, Nanchang University, Nanchang 330031, China
Published: December 2020

A model of quantum dot refrigerator driven by photon, which consists of two two-level quantum dots, a photon reservoir and two leads, is proposed in this paper. Comparing with previous studies, we consider the transitions of electrons between different energy levels in a single quantum dot, which is more practical.Based on the theory of master equation and the assumption of weak coupling, we derive the expression of the cooling rate and the coefficient of performance of the refrigerator and obtain the condition of the tight coupling of the refrigerator operation. Next, we plot numerically the performance characteristic curves between the cooling rate and the coefficient of performance in the case of the tight coupling and in the general case. We find that the curves between the cooling rate and the coefficient of performance are opened loops for tight coupling, but they are closed loops in the general case. And we gain the conclusions that the refrigerator can be reversible under the condition of the tight coupling, while it can be irreversible in the general case. Then the optimally operating range of the refrigerator is determined. Finally, the effect of the temperature of the photon reservoir, transition coefficient, and temperature ratio on the performance of refrigerator under the conditions of the maximum cooling rate are studied, and also the coefficient of performance under the maximum cooling rate, the maximum coefficient of performanceand the cooling rate under the maximum coefficient of performanceare analyzed in detail.
Recent progress of a new type diluted magnetic semiconductors with independent charge and spin doping
Authors: Deng Zheng , Zhao Guo-Qiang , Jin Chang-Qing ,   Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China,   School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China,   Songshan Lake Materials Laboratory, Dongguan 523808, China
Published: December 2020

Due to the potential applications for spintronics devices, diluted ferromagnetic semiconductors (DMS) have received extensive attention for decades. However, in classical Ⅲ–Ⅴ based DMS material, such as (Ga,Mn)As, heterovalent (Ga3+, Mn2+) doping results in lack of individual control of carrier and spin doping, and seriously limited chemical solubility. The two difficulties prevent furtherincrease of the Curie temperature of the Ⅲ–Ⅴ based DMS. To overcome these difficulties, a series of new types of DMS with independent spin and charge doping have been synthesized, such as Ⅰ–Ⅱ–Ⅴ based LiZnAs and Ⅱ–Ⅱ–Ⅴ based (Ba,K)(Zn,Mn)2As2. In these new materials, isovalent (Zn,Mn) substitution is only spin doping, while charge is independently doped by heterovalentsubstitution of non-magnetic elements. As a result (Ba,K)(Zn,Mn)2As2 obtains the reliable record of Curie temperature (230 K) among DMS in which ferromagnetic ordering is mediated by itinerate carriers. In this review, we summarize the recent development of the new DMS materials with following aspects: 1) the discovery and synthesis of several typical new DMS materials; 2) physical properties studies with muon spin relaxation and in-situ high pressure techniques; 3) single crystal growth, Andreev reflection junction based on single crystal and measurements of spin polarization.
Research progress of physical model of full-solid-state magnetic refrigeration system
Authors: Liu Guo-Qiang , Ke Ya-Jiao , Zhang Kong-Bin , He Xiong , Luo Feng , He Bin , Sun Zhi-Gang ,   State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China,   College of Science, Wuhan University of Technology, Wuhan 430070, China
Published: December 2020

Magnetic refrigeration is a kind of energy-saving, environment-friendly and intrinsically-high-efficient refrigeration technology, which has a wide application prospect. At present, the magnetic refrigeration systems based on active magnetic regenerator cycle have been widely studied and many prototypes of refrigerators have been developed. However, fluids and gases are mainly applied to heat exchange in these systems, which brings some problems such as low operating frequency, large regenerative loss, and complicated sub-component design. These problems increase the cost and reduce the efficiency of magnetic refrigerators. In view of the above problems and challenges, researchers try to introduce the solid-state heat transfer enhancement mechanism, and to design and optimize the full-solid-state magnetic refrigeration system model. In this paper, the development process of magnetic refrigeration technology at room temperature is briefly introduced at first. And the reasons for the low operating frequency and efficiency of the magnetic refrigerator, caused by using fluids for heat exchange, are analyzed. Then, two types of solid-state heat exchange media are briefly described, which are thermal diodes (i.e., electric-field-controlled thermal diode and magnetic-field-controlled thermal diode) and high thermal-conductivity material elements. In this paper we review the research progress of the full-solid-state magnetic refrigeration model based on thermal diodes and high thermal-conductivity material elements. Some key items for these models are described in detail, such as the architectural design concept, physical mechanism and working principle, the main performance simulation results of these systems and their physical change rules. Then, the main performances (i.e. operating frequency, specific cooling power, temperature span, and coefficient of performance) of the full-solid-state magnetic refrigeration model and the AMR model are summarized and comparatively analyzed. It shows that the full-solid-state magnetic refrigeration system can work at high frequency and has greater specific-cooling-power. Meanwhile the design of full-solid-state magnetic refrigeration system is more compact and simpler. The characteristics and problems of the two types of solid heat exchange media are also analyzed. Due to the strong thermal transport capability, easy access and integration of thermoelectric elements, the full-solid-state magnetic refrigeration technology based on thermoelectric thermal diodes has greater application potential. Finally, the main research directions and key scientific problems for further studying the full-solid-state magnetic refrigeration field are discussed and analyzed.
Two-stage velocity distribution measurement from multiple projections by tunable diode laser absorption spectrum
Authors: Wang Chuan-Wei , Li Ning , Huang Xiao-Long , Weng Chun-Sheng ,   National Key Laboratory of Transient Physics, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

A novel approach to using tunable diode laser absorption spectrum (TDLAS) is developed for nonuniform velocity distribution measurement by Doppler effect. An analysis of the energy in direct absorption spectrum at low frequencies is made by Fourier transform, because the TDLAS method offers the advantages in using Beer law to deal with coupling relations between velocity distribution and corresponding length of velocity region. By comparing with traditional TDLAS-Doppler velocity measurement, advantages of this approach to the more exact solution of core flow velocity by signal process without using extra lasers and detectors are explored. Following the published theory, between velocity regions at multiple projections the absorbance about average in frequency offsets and the absorbance about difference in frequency offsets are incorporated into an improved fitting model. A solution to obtaining changes of absorbance energy at low frequencies by Fourier transform is used to demonstrate the ability to recover minor change in absorbance under different conditions, inferring a better method to realize the simultaneous measurement of velocity distribution. The influences of these parameters, such as projection angles and noise during absorption, are investigated by the multiple projection simulations at rovibrational transitions of H2O near 7185.6 cm–1 from three projections. This approach is validated in a two-stage velocity distribution model, demonstrating the ability to exactly measure core flow, with a precision of 0.9% RMS (root mean square). The high velocity in the core flow is less influenced by the random noise in absorption due to nearly linear relationship between the difference in frequency offsets and the ratio of length of velocity region. Some satisfied results can be obtained when larger angles of projection are arranged. The combination of 0°, 30°, and 60° will be a reasonable optic design considering the limitation of spatial resolution. In conclusion, the novel approach to velocity distribution measurement based on TDLAS-Doppler from multiple projections has great potential applications in engine diagnosis and gas dynamic research.
Effect of micro-bubble in ultrasonic field on microstreaming of elastic particle
Authors: Feng Kang-Yi , Wang Cheng-Hui ,   Shaanxi Key Laboratory of  Ultrasonics, Shaanxi Normal University, Xi’an 710119, China
Published: December 2020

In this paper, the interaction between elastic particle and cavitation bubble is considered, the expression of microstreaming velocity and shear stress around the elastic particle are derived by using the theory of acoustic scattering. Taking into account the two predominant modes of elastic particle: n = 0 mode and n = 1 mode, the effects of the distance and the ratio of the radius and the relative position on microstreaming distribution, and the effects of the particle radius and the driving frequency on shear stress distribution are investigated. It is demonstrated that the interaction can increase the amplitude of microstreaming velocity, especially the tangential component of microstreaming velocity, and the shear stress. As the distance between elastic particle and cavitation bubble increases, the interaction weakens and the amplitude of the microstreaming velocity around the elastic particle decreases. When the bubble is in resonance, the microstreaming velocity around the elastic particle is significantly enhanced. The shear stress of the particle is affected by the particle radius and the frequency of sound field. As the particle radius and the frequency of sound field are larger, the external scattering sound becomes stronger and the amplitude of shear stress on the surface of particles turns larger.
Thermoelectric properties of polycrystalline graphene nanoribbons
Authors: Xu Yi , Xu Xiao-Yan , Zhang Wei , Ouyang Tao , Tang Chao ,   School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105, China,   Hunan Key Laboratory for Micro-Nano Energy Materials and Device, Xiangtan University, Xiangtan 411105, China
Published: December 2020

Thermoelectric materials, which can convert heat energy into electric energy and also from electric energy into heat energy, have aroused widespread interest of both theoretical and technological researches recently. Graphene is a typical two-dimensional carbon nanomaterial and regarded as a competitive candidate for the next-generation micro/nano-devices. Unfortunately, graphene is an inefficient thermoelectric material due to the extremely high thermal conductivity. To overcome this drawback, exploring an effective way to improve the thermoelectric performance is of critical importance. In this paper, using the nonequilibrium Green’s function approach, we systematically investigate the effects of grain boundary on the thermoelectric properties of graphene nanoribbons. The results show that owing to the existence of grain boundary, the phonons and electrons encounter great scatterings when they transmit through the polycrystalline graphene nanoribbons. These scatterings cause the phononic and electronic transmission coefficient to decrease dramatically, and thus leading the thermal conductance (including both electron and phonon parts) of graphene nanoribbons to be evidently suppressed. Meanwhile, such scatterings induce more intense transmission peaks and pits in the electronic transmission spectrum of polycrystalline graphene nanoribbons. Generally, the Seebeck coefficient depends on the derivative of electronic transmission coefficient. The larger the logarithmic derivative of transmission, the higher the Seebeck coefficient can be obtained. Therefore Seebeck coefficient is improved obviously in the polycrystalline graphene nanoribbons. Based on such two positive effects, the thermoelectric performance of polycrystalline graphene nanoribbons is significantly enhanced. At room temperature, the thermoelectric figure of merit of polycrystalline graphene nanoribbons can approach to 0.3, which is about 6 times larger than that of pristine graphene nanoribbon (figure of merit is about 0.05). It is also found that the quantity of grain boundaries and length of system can further improve the thermoelectric properties of the polycrystalline graphene nanoribbons, while the width of system has a limited influence on it. This is because the quantity of grain boundaries and length of polycrystalline graphene nanoribbons can give rise to more intense phonon and electron scatterings and further decreasing of thermal conductance and enhancement of Seebeck coefficient. The results presented in this paper demonstrate that polycrystalline structure is indeed an effective way to improve the thermoelectric conversion efficiency of graphene nanoribbons, and provide a theoretical guideline for designing and preparing thermoelectric devices based on graphene nanoribbons.
Multiple-image encryption method based on spatial angle multiplexing and double random phase encoding
Authors: Wang Xue-Guang , Li Ming , Yu Na-Na , Xi Si-Xing , Wang Xiao-Lei , Lang Li-Ying ,   School of Information and Control Engineering, China University of Mining and Technology, Xuzhou 221116, China,   School of Mathematics and Physics, Hebei University of Engineering, Handan 056038, China,   Institute of Modern Optics, Nankai University, Tianjin 300350, China,   Hebei University of Technology, Tianjin 300401, China
Published: December 2020

An optical encryption method of multiple-image based on spatial angle multiplexing and double random phase encoding is proposed in this paper. In the encryption process, firstly the original images are modulated by random phase in Fresnel transform with different diffraction distances. Secondly, the modulated images are coherently superposed with reference beams which have different spatial angles and random phases, to generate interference fringes. Finally, the interference fringes from different directions are superposed to form a compound encrypted image. In the decryption process, the compound image is placed in a spatial filtering and Fresnel diffraction system, and the decrypted images are obtained after implementing the different phase keys’ demodulation and Fresnel diffraction with correct distance. This method encrypts multiple images into a single gray-scale image, which is easy to save and transmit. The double random phases are placed in object light and reference light respectively, which reduces the complexity of the encryption system and overcomes the difficulty of pixel-by-pixel alignment of random phase keys in traditional decryption experiment. At the same time, the multiplexing capacity of the proposed encryption system is analyzed, and the result shows that the system has sufficient encryption capacity. So the proposed method possesses the characteristics of high storage efficiency, simple calculation and strong anti-noise ability, and thus can encrypt multiple images simultaneously. In this paper, the encryption effect is evaluated by correlation coefficient, while the effectiveness and security are verified by simulation experiment.
Research progress of topological photonics
Authors: Wang Hong-Fei , Xie Bi-Ye , Zhan Peng , Lu Ming-Hui , Chen Yan-Feng ,   National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China,   School of Physics, Nanjing University, Nanjing 210093, China,   Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China,   Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing 210093, China
Published: December 2020

Inspired by topological phases and phase transitions in condensed matter, a new research field based on topological band theory, topological photonics, has emerged. It breaks through the traditional idea of light regulation by optical superposition principle of real space and energy band theory of solids of reciprocal space, providing a novel mechanism of optical regulation and rich properties of transport and light manipulation. Such as transmission properties of against backscattering and rubout to defects and disorders, selective transports dependent on spin-orbit coupling, and high dimensional manipulation of light. This review paper classifies different topological photonic systems by dimensions, briefly introducing the topological model, the novel physical phenomena, and the corresponding physical picture, such as SSH models, photonic quantum Hall effects, photonic quantum spin Hall effects, photonic Floquet topological insulator, and photonic three-dimensional topological insulator; other advanced platforms such as higher-order, non-Hermitian, and nonlinear topological platforms are also involved; a summary and outlook about the current development, advantages, and challenges of this field are present in the end.
Research progress of low-dimensional semiconductor materials in field of nonlinear optics
Authors: Bai Rui-Xue , Yang Jue-Han , Wei Da-Hai , Wei Zhong-Ming ,   State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China,   College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Since the first ruby laser was invented, researchers have focused their attention on how to achieve a strong laser light source, which cannot be produced by the ordinary light sources. Since then, the rich and colorful characteristics of nonlinear optical materials have been discovered, such as the saturation absorption, reverse saturation absorption and nonlinear refraction. They are applied to optoelectronic devices, optical switching devices and optical communication. At the same time, with the increase of the requirements for device integration performance in industrial production, ordinary three-dimensional devices are difficult to meet the production requirements, and the advent of low-dimensional semiconductor devices effectively solves this problem. Therefore, the combination of nonlinear optics and low-dimensional semiconductor materials is a general trend. The emergence of quantum dots, quantum wire lasers, and amplifiers confirms this. In this paper, we summarize the frontier work on nonlinear optics by selecting several special low-dimensional structures and several materials, providing some references for future research. However, due to the fact that the instability and low filling ratio of low-dimensional materials remain to be improved, further relevant research is still required.
Domains in ferroelectrics: formation, structure, mobility and related properties
Authors: Lu Xiao-Mei , Huang Feng-Zhen , Zhu Jin-Song ,   National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
Published: December 2020

Ferroelectric materials with domains being the basic microstructures, have been investigated for about 100 years. With the development of the material fabrication method and the characterization technique, the important influence of domain configuration on the physical properties of ferroelectrics becomes more and more prominent. Recent researches even reveal that the domains and domain walls can act as individual functional units of micro-nano electronic devices, possessing wide potentials in the areas of information storage, energy transformation, electro-mechanical drive, quantum computation, etc. In this paper, starting from group theory analysis of domain structures, we introduce first the formation and the structures of ferroelectric domains, and then the macroscopic mechanical spectra as well as the electrical properties of the ferroelectric materials. Finally, the recent research progress of polarization switching and domain characterization by piezoresponse force microscopy are also reviewed.
Design of subwavelength broadband hybrid sound absorption structure based on micro-perforated plate and coiled channels
Authors: Wu Fei , Huang Wei , Chen Wen-Yuan , Xiao Yong , Yu Dian-Long , Wen Ji-Hong ,   Laboratory of Science and Technology on Integrated Logistics Support, College of Intelligence Science and Technology, National University of Defense Science and technology, Changsha 410073, China,   College of Engineering and Technology, Southwest university, Chongqing 400715, China
Published: December 2020

In this paper, we propose a hybrid subwavelength broadband sound absorber based on micro perforated plate and multiple coiled channels. And the mechanism of low frequency broadband sound absorption of the hybrid sound absorber is analyzed in detail. Based on this, the theoretical analysis model and the finite element numerical analysis model are established, and the mutual verification of theoretical and numerical solutions is completed. The structure can theoretically achieve the low-frequency and high-efficiency sound absorption with an average absorption coefficient of 0.8 in a frequency band of 200–500 Hz when the overall thickness of the sound absorbing structure is 60 mm. At the same time when the overall thickness is 90 mm, quasi-perfect sound absorption with peaks up to 0.95 in a frequency range of 180–350 Hz is realized theoretically. The composite sound absorption structure has a certain application prospect in engineering low frequency noise in future.
Nonlinear propagation and anomalous absorption of ultrasound in liquid
Authors: Chen Hai-Xia , Lin Shu-Yu ,   School of Physics & Information Technology, Shaanxi Key Laboratory of Ultrasonic, Shaanxi Normal University, Xi’an 710062, China
Published: December 2020

Recent work has rendered possible the formulation for the nonlinear propagation of pressure waves in liquids by using the generalized Navier - Stokes equations and the modified equations of state, with the heat transfer and fluid viscidity taken into consideration. And the nonlinear approximation solution of the second order term is obtained. The conclusion concerns the acoustic pressure, phase speed, attenuation, and velocity distribution function. When the amplitude of driving acoustic pressure is higher than the cavitation threshold of the host liquid, the cavitation occurs. The cavitation bubbles will prevent the sound field from spreading in the liquid, and the acoustic energy accumulates near the cavitation zone. So when studying the transmission characteristics of acoustic wave in the liquid, the cavitation attenuation must be considered. Note that the particularity of cavitation bubble movement, cavitation bubble vibration and viscous force are simulated under the initial driving sound. Through the analysis, it is found that the transmission of sound is influenced by the viscosity of the fluid, heat transfer, driving sound pressure (amplitude, frequency, duration) and cavitation bubble in liquid. The physical mechanism is that the higher driving pressure causes the cavitation to turn stronger, the acoustic loss to be faster, the sound propagation distance to be smalletr and the vibration of bubbles to transfer energy from the fundamental wave to harmonics. As a result, the stronger absorption from the liquid causes abnormal phenomena, and the output sound is lower finally. It shows that the nonlinear radial motion of cavitation bubble is mainly responsible for the sound intensity attenuation.
Recent progress on stretchable conductors
Authors: He Wen-Qian , Zhou Xiang , Liu Zun-Feng ,   Key Laboratory of Functional Polymer Materials, Ministry of Education, State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, College of Pharmacy, Nankai University, Tianjin 300071, China,   Jiangsu Key Laboratory of Bioactive Natural Product Research, State Key Laboratory of Natural Medicines, Pharmaceutical University, Nanjing 210009, China
Published: December 2020

Flexible stretchable conductors have attracted wide attention due to their promising applications in information, energy, medical, national defense and other fields, where elastic conductors undergo large deformation and form intimate contact with three-dimensional irregular surfaces. Many conductive nanomaterials with excellent properties have been developed over the past decades, such as metal nanowires, carbon nanotubes, graphene and conductive polymers. One efficient method to prepare stretchable conductor is to disperse conductive materials into elastic matrix to form a conductive network, showing stretchability and conductivity. As an alternative way, elastic conductors show stable resistance change during stretch by use of buckled or serpentine structural design for rigid conductors. This review summarizes recent advances in flexible elastic conductors in the past five years. In addition, some flexible electronic devices such as light-emitting diodes, sensors, heaters, etc. are also discussed and the development direction in the field of flexible electronic devices is also suggested.
Interaction between bubble and particle in spherical liquid cavity surround by an elastic medium
Authors: Zhang Tao-Ran , Mo Run-Yang , Hu Jing , Chen Shi , Wang Cheng-Hui , Guo Jian-Zhong ,   Shaanxi Key Laboratory of Ultrasonics, Shaanxi Normal University, Xi’an 710062, China
Published: December 2020

A theory is developed to model the dynamic of bubble and particle inside a spherical liquid-filled cavity surrounded by an elastic medium. The aim of this work is to study how the outer elastic medium affects the interaction between bubble and particle. Starting from the theory of velocity potential distribution, combined with Lagrangian equations, the motion equations of bubbles and particles in the cavity are obtained. The resonance frequency of the bubbles and influence of the interaction between particle and bubble on the translational behavior under the action of sound waves are analyzed. The results show that the properties of medium elasticity and density can change the resonance frequency of the bubble in the cavity. As the radius of the spherical cavity increases, the resonance frequency of the bubble has a tendency to first decrease and then increase, and gradually tends to the resonance frequency of a single bubble in an unbounded liquid. The translation of bubble and particle in the spherical liquid cavity is affected by factors such as acoustic field parameters, the characteristics of the outer elastic medium, and the characteristics of the bubble and particle themselves. The overall characteristic is that the particle has a tendency to move to the cavity wall, and the translation of bubble is closely related to the interaction characteristics between bubble and particle.
Methodology of improving sensitivity of silicon vacancy spin-based sensors based on double spiral coil RF resonance structure
Authors: Zhang Wen-Jie , Liu Yu-Song , Guo Hao , Han Xing-Cheng , Cai An-Jiang , Li Sheng-Kun , Zhao Peng-Fei , Liu Jun ,   Key Laboratory of Instrumentation Science and Dynamic Measurement, Ministry of Education, North University of China, Taiyuan 030051, China,   School of Mechanical and Electrical Engineering, Xi’an University of Architecture and Technology, Xi’an 710311, China,   Shaanxi Key Laboratory of Nanomaterials and Technology, Xi’an 710311, China
Published: December 2020

 Due to the power instability and field non-uniformity of radio frequency (RF), microwave (MW) and laser signals, inhomogeneous broadening of spin magnetic resonance line causes the absorption to decrease in a nuclear resonance system, which can reduce the sensitivity of spin-based sensing and testing technology. In this paper, we propose and design a double solenoid coil RF resonance antenna structure. The nearly uniform RF field density is produced by the two solenoid coil antenna structures that are parallel to the symmetry axis. The size of the uniformity in the center region of double solenoid coil RF resonance antenna structure is about π×375 mm2 × 10 mm. And the non-uniformity is less than 0.9%. Comparing with a single straight wire antenna and the single solenoid coil RF resonance antenna structure, the uniformity is improved by about 56.889 times and 42.889 times, respectively. At the same time, based on the near-field mutual inductance coupled resonance effect, the intensities of RF field in the center region of the two-solenoid coil antenna structure is enhanced. Comparing with the single solenoid coil antenna structures, it is enhanced by about 1.587 times. And the equivalent sensitivity of the silicon vacancy color center spin based sensor is enhanced by about 4.833 times.

 In the experiment, an optical detection magnetic resonance measurement system based on the spin magnetic resonance effect of silicon vacancy color center in single crystal SiC is built. Comparing with the single straight wire antenna and the single solenoid coil RF resonance antenna structure, the contrast of the silicon vacancy color center spin magnetic resonance signals of the double solenoid coil RF resonance antenna structure increases about 6 times and 2.4 times, respectively. The sensitivity of the spin-based sensor is increased by 4.833 times and 2.071 times through using the modulation and demodulation method, and the noise decreases by 8 times and twice. Hence, based on this double solenoid coil RF resonance antenna structure, the sensitivity of the silicon vacancy spin sensor can be improved. Combined with chip manufacturing technology of SiC wafer, it proves to be a potential approach to developing the high precision, chip scale spin sensor devices and measurement technology.
Analysis of stability catastrophe of confocal cavity
Authors: Hu Yue , Cao Feng-Zhao , Dong Ren-Jing , Hao Chen-Yue , Liu Da-He , Shi Jin-Wei ,   Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
Published: December 2020

Optical cavity is a fundamental device of modern optics and has a wide range of applications in the fields of laser generation, nonlinear optical conversion, and optical sensors. A major aspect of the properties of optical cavity is the stability analysis. According to different geometric losses, these optical cavities can be divided into three types: stable cavity, critical cavity, and unstable cavity. The determination of the stability of the optical cavity is the basic problem of a classic system, but the research and analysis of this point have been much insufficient in the past. In this paper, by extending the definition domain of the inverse trigonometric function, the propagation matrices of the symmetric confocal cavity and the asymmetric confocal cavity are solved. The sudden change of stability with the change of geometric parameters is explained by algebraic analysis and optical ray topology.The mathematical analysis shows that the stability catastrophe of confocal cavity is due to the sudden change in the value of inverse cosine function at the critical point of the traditional domain of definition. From the perspective of geometric topology, we define the topological charge of the cavities according to the geometric propagation path of light in the cavity. Only the cavities with zero topological charge are found to be stable, and the change of topological charge is quantized, which explains the sudden change of confocal cavity stability. Finally, we build a coupled stable cavity consisting of two unstable cavities with the same parameters. The quality factors of the coupled stable cavity and the unstable cavity are analyzed by the finite difference time domain method, which further verifies the origin of the sudden change in the stability of the confocal cavity. We propose that the coupled unstable dual cavities with opposite topological charges are able to be stable, and we also find that there are new modes in the coupled cavities which are not found in the corresponding single cavity. These findings suggest a new method for controlling microcavity loss, which has a certain value for studying the new micro-nano lasers, on-chip nonlinear devices, and non-Hermitian optical sensors.
Recent advances in silk-based wearable sensors
Authors: Li Sheng-You , Liu Jia-Rong , Wen Hao , Liu Xiang-Yang , Guo Wen-Xi ,   Research Institute for Biomimetics and Soft Matter, College of Physical Science and Technology, Xiamen University, Xiamen 361005, China,   Faculty of Science, National University of Singapore, Singapore 119077, Singapore
Published: December 2020

In recent years, wearable electronics has received extensive attention, providing new opportunities for implementing health monitoring, human disease diagnosis and treatment, and intelligent robotics. Sensor is one of the key components of wearable electronics. Silk (Bombyx Mori) material shows unique features including high yield, excellent tensile strength (0.5–1.3 GPa) and toughness ((6–16) × 104 J/kg), good biocompatibility, programmable/controllable biodegradability, novel dielectric properties, and various material formats. With the rapid development of biomaterials and related manufacturing technologies, advanced silk-based materials have been studied and applied to wearable sensors. Here, we firstly introduce the five-level structure of silk fibroin from bottom to top and characteristics of silk-based advanced materials, and then review the research progress of silk-based advanced materials in wearable sensors in recent years, including mechanical sensors, electrophysiological sensors, temperature sensors and humidity sensors. The working mechanism, structure and performance of different sensors, the role of silk proteins in them, and their applications in health monitoring are discussed and summarized. Finally, the challenges and future prospects of silk-based wearable sensors in practical applications are put forward.
Stretchable supercapacitors: Electrodes, electrolytes, and devices
Authors: Shao Guang-Wei , Guo Shan-Shan , Yu Rui , Chen Nan-Liang , Ye Mei-Dan , Liu Xiang-Yang ,   Shanghai Collaborative Innovation Center for High Performance fiber composites, Engineering Research Center of Technical Textile, Ministry of Education, College of Textiles, Donghua University, Shanghai 201620, China,   Research Institute for Biomimetics and Soft Matter, College of Physical Science andTechnology, Xiamen University, Xiamen 361005, China,   Faculty of Science, National University of Singapore, Singapore 119077, Singapore
Published: December 2020

Stretchable supercapacitors have received more and more attention due to their potential applications in wearable electronics and health monitoring. The stretchable supercapacitors have not only the advantages of high power density, long cycle life, safety and low cost of ordinary supercapacitor, but also good flexibility and stretchability to integrate well with wearable system. In this review, according to the structures of supercapacitors, the methods of preparing stretchable electrodes/devices reported in the literature are categorized and analyzed. We particularly highlight the key findings of creating stretchable electrodes/devices, which include elastic polymer substrates, tensile structure design and elastic polymer + tensile structure. In addition, the research progress of multi-functional stretchable supercapacitors and high elastic gel electrolytes are discussed. Finally, the challenges to the future development of the stretchable supercapacitors are analyzed and summarized. We expect to stimulate more research in creating stretchable supercapacitors for wide practical applications.
Design of optical parametric cavity for broadband squeezed light field
Authors: Wang Jun-Ping , Zhang Wen-Hui , Li Rui-Xin , Tian Long , Wang Ya-Jun , Zheng Yao-Hui ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China,   Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
Published: December 2020

The field of squeezed state is an important quantum resource in the study of quantum optics. In the application of quantum information, the spectrum bandwidth of the squeezed light field is an important index to limit the information transmission capacity. Currently, the optical parametric oscillator (OPO) is one of the most efficient ways to generate high squeezed non-classical optical fields. In this paper, the degenerate singly-resonant and doubly-resonant OPO structures are introduced. Both OPOs are composed of concave mirrors and periodically poled potassium titanyl phosphate crystals (PPKTP). The length of PPKTP crystal is 10 mm. The curvature radius of the curved surface is 12 mm, and it has high reflectivity at 1550 nm and 775 nm. The plane surface is coated with anti-reflection coating. The air gap length is 21 mm. The concave mirror is an output coupling mirror, and its radius of curvature is 25 mm. In the singly-resonant OPO, only the signal light resonates in the cavity, and the pump light passes through the nonlinear crystal twice and then outputs out of the cavity. The reflectivity of OPO output coupling mirror to the wavelength of 1550 nm is 88%. The linewidth of the corresponding fundamental frequency wave is 77.4 MHz. For doubly-resonant OPO, both the signal light and the pump light resonate simultaneously in the cavity. The reflectivity of OPO output coupling mirror to 1550 nm and 775 nm is 85% and 97.5%, respectively. The linewidth of the corresponding fundamental frequency wave and harmonic is 97.1 MHz and 15.6 MHz, respectively. Then the threshold of OPO is calculated. The threshold pump power of OPO increases with signal light transmittance increasing, but the threshold value of doubly-resonant OPO is obviously smaller than that of singly-resonant OPO. After that, the variation of the squeezing bandwidth of the squeezed light field generated by OPO with the transmittance of the signal is analyzed. Finally, we complete the design of quantum squeezer with low threshold (18 mW), broadband (84.2 MHz) and high stability (the standard deviation of locking baseline is 0.32 MHz) experimentally. The results show that compared with the singly-resonant optical parametric oscillator, the doubly-resonant cavity has the characteristics of low threshold and high stability, which is more suitable for the preparation and practical application of broadband squeezed light field.
Interface modification and energy storage properties of barium titanate-based/ polyvinylidene fluoride composite
Authors: Wang Jiao , Liu Shao-Hui , Chen Chang-Qing , Hao Hao-Shan , Zhai Ji-Wei ,   School of Science, Henan Institute of Engineering, Zhengzhou 451191, China,   School of Materials Science and Engineering, Tongji University, Shanghai 201804, China
Published: December 2020

With the development of power electronic device equipment towards miniaturization and high performance, the dielectric materials with high energy storage density, high charge and discharge efficiency, easy processing and molding, and stable performance are urgently needed. At present, Barium titanate-based dielectric ceramics have a high dielectric constant, but low breakdown field strength and poor flexibility. Polymer-based dielectric materials have ultra-high functional density, ultra-fast charge and discharge response time, good flexibility, high breakdown field strength, light weight and other advantages, but low dielectric constant and low polarization strength. Their energy storage density is low, which limits the power capacitor component size and application scope. In order to obtain material with high energy storage performance, it was proposed to add high dielectric constant inorganic ceramic fillers to the polymer through a composite method to improve the energy storage performance of the material. The interface plays a vital role in the performance of the composite material. In this article, we review the latest research advance in the interface design and control of barium titanate/polyvinylidene fluoride composite dielectric materials. The effects of interface modification methods such as organic surface modification, inorganic functionalization and organic-inorganic synergistic modification on the polarization and energy storage performance of composite materials are summarized. The existing interface models and theoretical research methods are discussed, and the existing challenges and practical limitations, and the future research directions are prospected.
Charge-mediated magnetoelectricity: from ferroelectric field effect to charge-ordering ferroelectrics
Authors: An Ming , Dong Shuai ,   School of Physics, Southeast University, Nanjing 211189, China
Published: December 2020

Magnetoelectricity is an emerging topic and a frontier issue of the field of ferroelectricity. Multiferroics containing more than one ferroic order is an ideal system to pursuit intrinsic and robust magnetoelectric coupling, which holds rich physics and great potential applications. As a branch of the correlated electron family, multiferroic also has multiple degrees of freedom, including the charge, spin, orbital, and lattice. Among them, the charge degree of freedom has been mostly overlooked in the past researches and actually it may play an important role in magnetoelectricity. In this topical review, the charge-mediated magnetoelectricity is introduced, including the ferroelectric field effect in heterostructures and the charge ordering in single-phase multiferroics. The physical mechanisms will be revealed, together with several examples we given in recent years. We hope that this topical review can provide a reference for the researches in this vigorous filed.