bluuebunny/crossref_metadata_2025 huggingface dataset:
Competitions among modes in magnetically insulated transmission line oscillator
Authors: Yang Wen-Yuan , Dong Ye , Sun Hui-Fang , Dong Zhi-Wei ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: November 2020

As a compact and high power microwave source, the competitions among various modes are prone to appear in the initial stage of the development of the radiated electromagnetic field in a magnetically insulated transmission line oscillator (MILO). If the mode competitions are not controlled effectively, the output characteristics of the MILO may decline in the end.

As is well known, the operating mode of MILO is generally designed on the π mode of the TM00 mode and the coaxial disk-loaded waveguide is usually adopted as a slow-wave structure for beam-wave interaction in MILO. Therefore from the dispersion relations between the electron beam and the lower order electromagnetic modes(including TM00, TM01 and HEM11 modes) in the slow-wave structure, the characteristics and possible suppression methods of the three kinds of mode competitions are analyzed simply. The first kind mode competition is between the different axial modes of the fundamental TM00 mode. In this case, the electromagnetic field of the competition mode is also axially symmetric and its frequency is slightly lower than that of the π mode. The second is the competition between the TM00 and higher order TM01 mode. In this case, the competition frequency is rather higher than that of the π mode (TM00). The third is the competitions between the TM00 and low order asymmetric HEM11 modes. In this case, the competition frequency is slightly higher than that of the main mode. Appropriately choosing the radii of the anode vanes, the number of the anode cavity and the load length of the cathode, the corresponding mode competition intensity can be weakened.

Based on the obtained results above and the existing model of the MILO, a compact high output power L-band MILO is proposed. Numerical studies of the mode competitions and output characteristics are carried by using the three dimensional particle-in-cell code. Cold-cavity test shows that in the low frequency range, the easily stimulated electromagnetic modes are the π mode of TM00 and HEM11 modes with frequencies of 1.61 GHz and 1.77 GHz, respectively. The numerical results of hot-cavity verify that the competition in the initial stage comes mainly from the asymmetric HEM11 mode due to the fact that there exists the strut in the output region, the Cartesian coordinates are adopted during the simulation, and totally symmetry cannot be guaranteed. In addition, electron beam emission from the cathode is not ideally even. But stable and high output microwave power is obtained in the end in the L-band MILO by being optimized. The output power and efficiency are 8.1 GW and 18% respectively, and the mode purity reaches about 97%.
Shock vibration characteristics of fluid-structure interaction phononic crystal pipeline
Authors: Hu Bing , Yu Dian-long , Liu Jiang-wei , Zhu Fu-lei , Zhang Zhen-fang ,   Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, Changsha 410073, China,   College of Intelligence Science and Technology, National University of Defense Technology, Changsha 410073, China
Published: November 2020

Fluid-structure interaction pipeline systems are extensively adopted to transfer matter, energy and momentum, which are widely used in various fields. Due to the fluid-structure interaction effect, the pipe wall proves to produce strong vibration and noise under fluid action, which has a serious influence on the safety and concealment of the equipment, even leading to serious damages. Therefore, it is of great significance to study the vibration characteristics of fluid-structure interaction pipeline and methods to reduce the vibration of pipeline both in theory and in practice.

Phononic crystal can suppress the propagation of elastic waves in a specific frequency range by their special band-gap characteristics, which have wide application prospects in the field of vibration and noise reduction. Especially, the band gap characteristics of phononic crystal pipeline used to design fluid-structure interaction pipeline system have been widely studied, thus providing a new technical approach to reducing the vibration and noise of the pipeline.

In this paper, based on the theory of phononic crystal, the vibration transfer characteristics of the Bragg phononic crystal pipeline under fluid-structure interaction are studied. Combining the transfer matrix method and the finite element method, the band structure and band gap characteristics are calculated. Using the finite element method, the vibration characteristics of the phononic crystal pipeline under fluid-structure interaction effect, the shock excitation of pipe wall and the shock excitation of the fluid are considered. The influence of the fluid-structure interaction on the vibration transmission characteristics of the phononic crystal pipeline is also analyzed.

The research results indicate that when the fluid velocity in the fluid-structure interaction pipeline system is small the Bragg phononic crystal pipeline has a good attenuation effect on the shock excitation of pipe wall in the band gap range, and that when the fluid velocity increases the fluid-structure interaction effect becomes significant, the attenuation effect becoming weaker. Bragg phononic crystal pipeline has a certain attenuation effect on the pipe wall vibration caused by the fluid shock excitation near the band gap. The research results are expected to be able to provide a technical reference for the vibration control of pipeline systems under fluid-structure interaction conditions.
Annealing effect on terahertz emission enhancement from ferromagnetic heterostructures
Authors: Gao Yang , Chandan Pandey , Kong De-Yin , Wang Chun , Nie Tian-Xiao , Zhao Wei-Sheng , Miao Jun-Gang , Wang Li , Wu Xiao-Jun ,   School of Electronic and Information Engineering, Beihang University, Beijing 100191, China,   Beijing Advanced Innovation Certer for Big Data and Brain Computing, School of Microelectronics, Beihang University, Beijing 100191, China,   Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China,   School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China,   Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao 266000, China
Published: November 2020

We systematically investigate the influence of annealing effect on terahertz (THz) generation from CoFeB/heavy metal heterostructures driven by femtosecond laser pulses. The THz yield is achieved to increase triply in W/CoFeB through annealing effect, and doubly in Pt/CoFeB. The annealing effect originates from both the decrease of synthetic effect of THz absorption and the increase of hot electron mean free path induced by crystallization, with the latter being dominant, which is experimentally corroborated by THz transmission measurement of time-domain spectrum and four-probe resistivity t. Our observations not only deepen understand the spintronic THz radiation mechanism but also provide a novel platform for high speed spintronic opto-electronic devices.
Baseline correction algorithm for Raman spectra based on median filtering and un-uniform B-spline
Authors: Wang Xin , Kang Zhe-Ming , Liu Long , Fan Xian-Guang ,   Department of Instrumental and Electrical Engineering, Xiamen University, Xiamen 361005, China,   Xiamen Key Laboratory of Optoelectronic Transducer Technology, Fujian Key Laboratory of Universities and Colleges for Transducer Technology, Xiamen 361005, China
Published: November 2020

As one of the key steps for data preprocessing of Raman spectra, baseline correction is an effective method to eliminate fluorescence interference. Traditional algorithms such as polynomial fitting and uniform B-spline fitting are simple and easy to implement, but the uncertain fitting order and internal knots limit their flexibility. In addition, the baseline correction results of traditional algorithms often occur over and under fitting phenomena. Therefore, we propose a baseline correction algorithm for Raman spectra based on median filtering and un-uniform B-spline. Firstly, the trough points of the spectral data are filtered by smoothing preprocess, difference calculation and threshold setting, and the internal knots of the un-uniform B-spline are adaptively selected by the trough positions of the spectral data. Then, the median filtering algorithm is used to process the spectral data so that the un-uniform B-spline has a better baseline fitting effect at the position where the signal changes from peak to smooth band. Finally, the un-uniform B-splines is used to fit the baseline by fitting the baseline iteratively. The proposed algorithm overcomes the shortcoming of traditional B-spline algorithm that the internal knots need to be selected manually based on different Raman spectra, and also avoids influencing the baseline fitting by random noise in the spectral data, and thus further improving the spectral baseline correction effect. The original Raman spectra of polymethyl methacrylate and normal octane are used for experimentally evaluating the baseline correction effect. Compared with the results from polynomial fitting, uniform B-spline and adaptive iteratively reweighted penalized least squares algorithms, the experimental results show that the proposed algorithm can well eliminate the Raman signal baseline drift effectively without over or under fitting phenomena, and it can perform better baseline correction for different baseline drift situations. Therefore, the proposed algorithm can provide more accurate and reliable information for the further analysis of spectral data.
Insight of the doping mechanism of F and Al co-doped ZnO transparent conductive films
Authors: Wang Yan-Feng , Xie Xi-Cheng , Liu Xiao-Jie , Han Bing , Wu Han-Han , Lian Ning-Ning , Yang Fu , Song Qing-Gong , Pei Hai-Lin , Li Jun-Jie ,   Institute of New Energy Science and Technology, College of Science, Hebei North University, Zhangjiakou 075000, China,   College of Science, Civil Aviation University of China, Tianjin 300300, China,   General Courses Department, Army Military Transportation University, Tianjin 300161, China
Published: November 2020

Transparent conductive oxide (TCO) films, as transparent electrodes, are widely used in thin-film solar cells. The performance of TCO film has a significant influence on the conversion efficiency of the film solar cell fabricated byusing it. Although the conductivity can be improved by increasing the carrier concentration, the transmittance in the long wave will be sacrificed. Therefore, the only feasible method is to increase the carrier mobility within a certain carrier concentration range, rather than increase the mobility by reducing carrier concentration. In this paper, the F and Al co-doped ZnO (FAZO) films are deposited on glass substrates (Corning XG) by an RF magnetron sputtering technique with using a small amount of ZnF2 (1 wt.%) and Al2O3 (1 wt.%) dopant. The influences of sputtering pressure on the structure, morphology and photoelectric characteristics of the films are respectively investigated by X-ray diffraction analysis, scanning electron microscope, Hall effect measurement, and ultraviolet–visible–near infrared spectrophotometry. All the thin films show typical wurtzite structure with the c axis preferentially oriented perpendicular to the substrate. With the increase of sputtering pressure, the deposition rate of FAZO film decreases, the crystallization quality is deteriorated, surface topography changes gradually from “crater-like” to co-existent “crater-like” and “granular-like”, and the surface roughness increases. The FAZO film deposited at 0.5 Pa presents the optimal performance with a mobility of 40.03 cm2/V·s, carrier concentration of 3.92 × 1020 cm–3, resistivity of 3.98 × 10–4 Ω·cm, and about 90% average transmittance in a range of 380－1200 nm. The theoretical result shows that the co-doping of F and Al takes the advantages of single F and Al doped ZnO films, and overcomes the shortcoming of metal elements doping, which donates the carriers just from doped metal elements. Furthermore, the co-doping of F and Al not only increases the carriers but also reduces the scatterings caused by the inter-orbital interaction of doped atoms. The doped F 2p electron orbitals repel the O 2p and Zn 4s electron orbitals, making them move down and donate electrons. At the same time, the orbitals of Al 3s and Al 3p also make a contribution to the conductivity. After co-doping of F and Al, both the carrier concentration and conductivity increase significantly.
Terahertz emission generated from Bi2Te3/CoFeB heterostructures grown by magnetron sputtering
Authors: Zhang Fan , Xu Yong , Liu Yang , Cheng Hou-Yi , Zhang Xiao-Qiang , Du Yin-Chang , Wu Xiao-Jun , Zhao Wei-Sheng ,   Beijing Advanced Innovation Center for Big Data and Brain Computing, School of Microelectronics, Beihang University, Beijing 100191, China,   Hefei Innovation Research Institute, Beihang University, Hefei 230012, China,   School of Electronic and Information Engineering, Beihang University, Beijing 100191, China
Published: November 2020

High-performance terahertz emitters, which convert the femtosecond laser pulses into terahertz pulses, are essential for terahertz spectroscopy technology and terahertz wireless communication. Spintronic terahertz emitters based on ferromagnet/nonmagnet bilayers have attracted tremendous attention due to their high efficiency, ultra-broadband, low cost and high flexibility. Here, we systematically investigate the terahertz emission from polycrystalline topological insulator Bi2Te3/ferromagnetic CoFeB heterostructure grown by magnetron sputtering. The Bi2Te3/CoFeB heterostructure exhibits high efficiency of terahertz emission, and the polarization of terahertz waves can be controlled by the external magnetic field direction. The performance of Bi2Te3/CoFeB heterostructure is almost comparable to that of the Pt/CoFeB bilayer. In contrast, no terahertz emission is observed in the pure Bi2Te3 or CoFeB film driven by femtosecond laser pulses, probably because the Bi2Te3 prepared by sputtering is polycrystalline and the thickness of CoFeB is too thin. We also compare the performances of Bi2Te3/CoFeB grown on MgO, glass and high-resistivity silicon substrates, and find that the samples grown on MgO substrates exhibit the best emission performances. The glass substrate absorbs more terahertz waves than MgO substrate, resulting in a slightly weaker terahertz signal emitted from the Bi2Te3/CoFeB grown on the glass substrate. Although the absorption coefficient of high-resistivity silicon to terahertz waves is very small, the residual pump light excites the high-resistivity silicon to generate the photo-generated carriers, which change the conductivity of the high-resistivity silicon and reduce the transmittance of terahertz wave. We attribute the mechanism of the terahertz emission to the spin-charge conversion at the interface of Bi2Te3/CoFeB. The terahertz emission efficiency of our sample is expected to be able to be further improved by optimizing the samples. Moreover, with the sputtering method, it is possible to fabricate large area samples at low cost, which is critical for commercial applications.
Recent progresses of thermal conduction in two-dimensional materials
Authors: Wu Xiang-Shui , Tang Wen-Ting , Xu Xiang-Fan ,   Center for Phononics and Thermal Energy Science, School of Physical Science and Engineering, Tongji University, Shanghai 200092, China
Published: November 2020

The two-dimensional (2D) materials represented by graphene and boron nitride provide an excellent platform for the study of thermal conduction and the interfacial thermal resistance in low-dimensional system. Recent studies recover exotic physics behind the novel thermal transport properties of 2D materials, such as length effect, dimensional effect, isotopic effect, anisotropic effect, etc. In this review, we introduce the recent progress of thermal properties in 2D materials in the last decade. The principle and development of thermal conduction measurement technologies used in 2D materials are introduced, followed by the experimental progress of thermal conduction and interfacial thermal resistance. Special attention is paid to the abnormal thermal transport and relevant physical problems. Finally, we present thermal management and heat dissipation in 2D electronic devices, summarize and point out the problems and bottlenecks, and forecast the future research directions and foregrounds.
Spintronic terahertz emitter: Performance, manipulation, and applications
Authors: Feng Zheng , Wang Da-Cheng , Sun Song , Tan Wei ,   Microsystem and Terahertz Research Center, China Academy of Engineering Physics, Chengdu 610200, China,   Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang 621999, China
Published: November 2020

Spintronic terahertz (THz) emitter, which is based on ultrafast spin-to-charge current conversion in ferromagnetic/nonmagnetic heterostructures, provides excellent advantages such as ultra-broadband, tunable polarization, and ultra-thin structure, thereby attracting increasing interests recently. In this review article, we first introduce the fundamental concepts of THz wave, THz spintronics and spintronic THz emitter. Next, we focus on the recent progress of spintronic THz emitter by closely looking at the performances, manipulations and applications. Performance improvement is presented based on the three fundamental processes: optical excitation, ultrafast spin transport, and THz emission. The active manipulation of polarization and spectral response, as well as the relevant applications such as ultra broadband measurements, magnetic structure detection and imaging, and THz near-field microscopy, are reviewed comprehensively. Finally, a brief summary and outlook are given.
Multi-party quantum key agreement based on d-level GHZ states
Authors: Tang Jie , Shi Lei , Wei Jia-Hua , Yu Hui-Cun , Xue Yang , Wu Tian-Xiong ,   Institute of Information and Navigation, Air Force Engineering University, Xi’an 710077, China
Published: November 2020

A multi-party quantum key agreement protocol based on d-level multi-particle GHZ states is proposed. The “d-level” is common in other quantum cryptographic protocols, but there are few researches in the field of quantum key agreement. In our scheme, we introduce two indistinguishable orthogonal bases, i.e. the quantum Fourier transform and shift operation, into a d-level quantum system. In addition, we make full use of shift operation to encode the key into the sequence of quantum states, and the key can be measured by the d-level Z-basis. By decoding and calculating, each participant can equally extract other participants’ key and obtain the final shared key \begin{document}$ K = {K_0} \oplus {K_1} \oplus \cdots \oplus {K_{k - 1}}$\end{document}. The protocol resists external eavesdropping by inserting decoy states and conducting two security checks. Furthermore, we present an example by assigning certain values to parameters for illustrative purpose. Finally, QKA protocol mainly involves two types of attacks: participant attack and external attack. The external attack can be divided into Trojan attack, intercept-resend attack, and entangle-measure attack. To demonstrate the security of the scheme, we analyze the two types of attacks. The results show that the scheme can effectively resist the attack from internal participants and external eavesdroppers. However, the premise of our protocol is based on the ideal quantum channel. In practical applications, particles are usually affected by noise in the process of quantum channel transmission. Therefore, how the agreement adapts itself to a more complicated environment is our main work in the future.
Stepwise strand exchange during RecA-induced homologous recombination
Authors: Huang Xing-Yuan , Sui Ming-Yu , Hou Wen-Qing , Li Ming , Lu Ying , Xu Chun-Hua ,   Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China,   University of Chinese Academy of Sciences, Beijing 100049, China,   School of Physical Science and Technology, University of Lanzhou, Lanzhou 730000, China
Published: November 2020

Homologous recombination (HR) which is important for maintaining the genetic stability of the cell is mainly mediated by recombinase. As a critical recombinase exists in prokaryotic organism, RecA has been widely studied. RecA could bind single strand DNA to form a filament structure to perform strand invasion and exchange with homologous DNA. The basic strand exchange step is a pathway to investigating the mechanism of strand exchange process. However, the specific step length is still controversial. The mainstream view is to regard the basic step as 3 bp, which sounds reasonable because the basic unit of RecA filament is a RecA monomer which binds 3 base pairs, but our previous study found that the most probable basic strand exchange step is 9 bp. In this research, we set up a series of experiments to demonstrate that the basic strand exchange step is 9 bp and how the mismatch base pairs in 9 bp affect the strand exchange process. We ues digestion protection to confirm whether the strand exchange process is completed and we employ a magnetic tweezer to measure how many base pairs are exchanged by strand exchange process. The digestion protection experiments show the strand exchange cannot overcome 33% mismatch sequence, but according to the result that strand exchange could overcome a single mismatch base pair, so that the step is not 3 bp. According to strand exchange length of 33% mismatch sequence, we find a 9 bp interval between the main peaks, which implies that the strand exchange step should be 9 bp rather than 3 bp. We also use continuous mismatch base pairs instead of periodic mismatch sequence to see whether the strand exchange process can be overcome. We find that the more the mismatch base pairs, the harder the strand exchange process passes across. Homology degree and its distribution both affect the strand exchange process. In general, the results suggest that the strand exchange step mediated by RecA is 9 bp, and the number of mismatched base pairs and their distribution influence the strand exchange process. The combination of digestion protection assay and magnetic tweezers can further take advantage of single molecule techniques to investigate mechanism of HR.
Molecular junction stretching and interface recognition: Decode the mystery of high/low conductance switching in stretching process of 4, 4′-bipyridine molecular junction
Authors: Suo Yu-Qing , Liu Ran , Sun Feng , Niu Le-Le , Wang Shuang-Shuang , Liu Lin , Li Zong-Liang ,   School of Physics and Electronics, Shandong Normal University, Jinan 250358, China
Published: November 2020

The high/low conductance switching in stretching process of 4,4′-bipyridine molecular junction is a distinctive phenomenon in molecular electronics, which is still a mystery and has been unsolved for more than one decade. Based on the techniques and processes of experimental measurement, the ab initio-based adiabatic molecule-junction-stretch simulation (AMJSS) method is developed, by which the stretching processes of 4,4′-bipyridine molecular junctions are calculated. The conductance traces of the molecular systems in the stretching processes are studied and the mystery of high/low conductance switching in the stretching processes of 4,4′-bipyridine molecular junction is decoded by using the one-dimensional transmission combined with the three-dimensional correction approximation (OTCTCA) method. The numerical results show that, in the stretching process of 4,4′-bipyridine molecular junction, the upper terminal nitrogen atom in the pyridine ring is easy to vertically adsorb on the second gold layer of the probe electrode. At the same time, the molecule produces unique lateral-pushing force to push the tip atoms of the probe electrode aside. Thus, the high conductance plateau arises. With the molecular junction further stretched, the upper terminal nitrogen atom of the molecule shifts from the second gold layer to the tip gold atom of the probe electrode with the tip gold atom moving back to the original lattice position. Consequently, the conductance value decreases by about 5–8 times, and the low conductance plateau is presented. According to our calculations, the phenomenon of high/low conductance switching in the stretching process of 4,4′-bipyridine molecular junction also indicates that, single surface gold atom often lies on the surface of substrate electrode. Moreover, the phenomenon of high/low conductance switching can only be found when the molecule is adsorbed on the surface gold atom of the substrate electrode. Thus, using conductance traces measured in the stretching processes of molecular junction and with the help of theoretical calculations, the interface structures of molecular junctions can be recognized efficiently. Our study not only decodes the physical process and intrinsic mechanism of the high/low conductance switching phenomenon of 4,4′-bipyridine molecular junction, but also provides significant technique information for using pyridine-based molecule to construct functional molecular devices, such as molecular switch, molecule memory, molecular sensor, etc.
A STUDY OF THE IONOSPHERIC DATA OBTAINED AT WUCHANG-SEPT. 1946 THRU. DEC. 1947
Authors: P. H. LIANG  , H. L. LUNG  , S. WANG  ,   Ionosphere Laboratory,National Wuhan University,Wuchang
Published: November 2020

Routine hourly observations of ionospheric characteristics have been taken at Wuchang since August 20. 1946. In this paper a general analysis of the data obtained from September 1946 through December 1947 is attempted. The diurnal and seasonal variations of ionization density and virtual height for all regular layers (E, F-l, F-2) are plotted in diagrams and briefly explained. Deviations from the normally recognized characteristics are discussed in more detail.Besides the normal characteristics, some special phenomena such as the occurrence of E2 near Sunrise and two major ionospheric storms are briefly described. Comparatively detailed study is made on the sporadic E ionization, with the conclusion that its percentage time of occurrence before mid-night is more than that after mid-night and that it is more prevalent in autumn than in any other season. Abnormally high E3 ionization was observed on October 10, 1946 when the Giacobini-Zinner comet was nearest the Earth. These facts indicate that metenrs are probably important agents in producing sporadic E jouization.
THERMODYNAMICS OF EQUILIBRIUM AND STABILITY
Authors: J. S. WANG  ,   Department of Physics,National Tsing Hua University.
Published: November 2020

The dependence of the entropy of a homogeneous system on the composition is investigated with the help of a reversible adiabatic process which allows the change of composition by means of a semipermeable wall. The conditions of equilibrinm for phase transition and for homogeneous chemical reaction are derived in a new way. Next the criterion of minimum energy for constant entropy and volume is derived from the principle of increase of entropy. This criterion is then applied to obtain the conditions of equilibrium and stability with the help of Lagrange's multipliers. The conditions of stability are expressed in several alternative forms. Next the equilibrium properties of a binary system arc considered, and some types of phase diagram are explained by means of equations. The theory is extended to the general heterogeneous equilibrium of a system consisting of any number of independent components. A system of equations for the change of temperature, pressure, and composition are obtained and are solved by means of determinants. Next Planck's theory of a binary solution is extended to a solution consisting of several solnte components, with the same conclusion regarding the lowering of freezing point as for a binary solution. Finally Planck's theory on the number of coexisting phases for aone-component system is extended to a system consisting of k components with the result that a state with, σ coexisting phases is more stable than one with σ-1 phases: where σ is an integer not greater than k + 2.
ON THE ABSORPTION COEFFICIENTS OF β- RAYS
Authors: Tcheng Da-Tchang  , Yang Jeng-Tsong  ,   北平研究院镭学研究所
Published: November 2020

The absorption coefficients of β-rays from UX2 and RaE were completely studied. Two outstanding features have been found by the authors: (1) The complete logarithmic absorption curve of β-rays is not a really straight line but a broken one consisting of several segments of straight lines which intersected at a certain point. The slopes of the segments are greater as the absorbing screens are thicker. (2) The values of the absorp-tion coefficients are not constant but can be varied according to the surrounding conditions of measurement. Among the conditions, the substance beneath the preparation Or the reflector, the substance encircles the preparation or the screen support, and the distance between the active preparation and the ionisation chamber window are the three main determinating tactors which influence the variation of the coefficient.
DISCUSSION ON THE BEHAVIOR OF AN ELECTRON ENCLOSED IN A SPHERE
Authors: T. T. KOU  ,   Department of Physics,National Central University,Nanking
Published: November 2020

The quantized energy values of an electron enclosed in a spherical box are calculated by solving Schrodinger's wave equation. The energy levels are very close together if the sphere is of ordinary dimensions. But as the radius of the sphere decreases toward atomic dimensions, the value of every energy level increases and the spread between the levels also increases.
PHASE COMPENSATION IN POWER OSCILLATORS
Authors: PING-CHUAN FENG  , PENG-FEI HSU  ,   岭南大学物理学系
Published: November 2020

Conditions for correct phase angle are examined for several types of power oscillators. Several phase compensating circuits are discussed. Experimental results show reasonable agreement with theoretical analysis.
FACTORS AFFECTING THE FREQUENCY DEVIATION IN REACTANCE-TUBE FREQUENCY MODULATION CIRCUITS
Authors: Chai Yeh  , Y. K. Tzu  ,   清华大学电机系物理系
Published: November 2020

In reactance-tube frequency modulation circuits, the fractional frequency deviation is expected to vary with the phase shift constants of the modulator and the Lf/Cf ratio of the tank-circuit of the oscillator. The way in which the frequency deviation is affected by these factors is discussed theoretically. Experimental checks are made, Two types of circuits are studied, the inductive and the capacitive reactance-tube circuits. It is found that within the straight portion, of the operating characteristic of the tube, the agreement is fairly satisfactory.
STUDY OF FREQUENCY STABILITY OF ELECTRON- COUPLED OSCILLATORS
Authors: PENG-FEI HSU  , PING-CHUAN FENG  ,   岭南大学物理学系
Published: November 2020

This paper points out that: (1) an electron-coupled oscillator has a sluggish loop characteristic with respect to supply voltage, (2) the most commonly used electron-coupled oscillator circuit is an incomplete electron-coupling circuit and has rather poor frequency characteristics, (3) the frequency stability can be greatly improved by applying phase compensation, (4) the best e.c.o. circuit is a modified Colpitts oscillator with grounded cathode.
THE FOURIER AND THE NEW POINT DIAGRAM SYNTHESES IN X- RAY CRYSTALLOGRAPHY
Authors: S. H. Yu  ,   国立清华大学
Published: November 2020

A newly developed synthesis of X-ray data for crystal analysis, called the point diagram synthesis, is compared with the classical Fouriers. The fundamental assumption in the method s first explained. A correlation matrix of index 10 is then quoted. Some mathematical properties of the correlation matrices, that is, the absolute convergence, and the h- and μ-summation rules are described and illustrated. The method is next applied in parallel with the Fouriers to an arbitrary structure along with its two component structures. The crystal NaCl is next studied, using the actual experimental data. It is shown that on the basis of exactly the same experimental data the inormation given by the two types of syntheses are entirely different. Conclusions about the method drawn in the previous articles are then discussed in the light of the new studies and approved once more.
OF THE BINDING ENERGIES OF THE NUCLEI 6Li AND 7Li——PART Ⅲ. NUMERICAL CALCULATION FOR 7Li (Contributions from Institute of Modern Physics, Academia Sinica, No. 5)
Authors: KING SING-NAN  ,   中国科学院近代物理研究所
Published: November 2020

By using the formulae obtained in Part I for the calculation of the binding energy of 7Li a numerical estimate of the binding energy of 7Li is made in accordance with the variational method, the wave function being chosen rather roughly. The results here are also in favour of the two range potential considered previously by Peng and Chang, and in particular the results indicate that the ratio of the two ranges of the nuclear potential may be not less than 3, as in the case for 6Li treated above, Part II.
RELATIVISTIC HAMILTONIAN SYSTEM OF A PARTICLE AND RELATIVISTIC HEISENBERG'S EQUATION
Authors: K. H. Tzou  ,   浙江大学物理系
Published: November 2020

In this paper, as suggested by the classical canonical equations, a new set of the corresponding relativistic equations is set up. Therefrom a relativistic form of Heisenberg's equation is deduced. The rclalivistic Hamiltonian system of a particle according to the formulation here established has been fully discussed and by following it, however, Diracs equation appears naturally as a necessary form of relativistic wave equation tor electron in quantum mechanics. The process of taking square root in Dirac's theory is seen to have its classical analogy. Finally, some applications of the relativistic Heisenberg's equation to Dirac's theory have been discussed and it has thereby been pointed out that this equation brings some quantities to being more symmetrical in the relativity sense and also some more general than those the non-relativistic equation can introduce.
INTERNAL FRICTION AND GRAIN BOUNDARY PRECIPITATION DURING THE AGING OF AN AL-CU ALLOY
Authors: T. S. KE  ,   清华大学物理系,中国科学院应用物理研究所
Published: November 2020

The precipitation at the grain boundaries during aging at 200℃ of an Al-4% Cu alloy was studied by measurements of the internal friction associated with the viscous behavior of grain boundaries. This internal friction was measured also at 200℃ with a torsion pendulum having a frequency of about one cycle per second. The results showed that the internal friction first decreases with aging but starts to rise after an aging of 6 1/2 hours. At very long aging times, the internal friction decreases again as the aging proceeds. Such a change of internal friction indicates a corresponding change in the nature of the "precipitates" at the grain boundaries during aging. This is in conformity with the results of metallographic examinations. A preliminary understanding toward the nature of these "precipitates" was obtained on comparing the results of internal friction measurements with those of metallographic examination.
RELATIVISTIC NATURE OF COULOMBIAN INTERACTIONS
Authors: T. S. CHANG  ,   北京大学物理系,中国科学院数学研究所
Published: November 2020

Longitudinal waves arc eliminated from the operators Dμν Dρ in quantum electrodynamics, which govcrn the change of the wave functional as we change from one Lorentz observer to another, and the resulting operators are found to satisfy the same set of commutation relations as before. This reveals that a theory with explicit Coulombian interactions may be relativistic, contrary to the usual belief.
NOTE ON THE PHOTO-DISINTEGRATION OF THE DEUTRON
Authors: TENG CHIA-HSIEN  ,   中国科学院近代物理研究所
Published: November 2020

A brief derivation of the formulae for the cross-sections and angular distribution for the photo-disintegration of the deuteron is given here by treating protons and neutrons as identical paricles.Wave functions obtained by Hulthén's variational method are used to calculate the matrix elemcntsfor various transitions.
INVESTIGATION ON HEAVY NUCLEI BY PHOTOGRAPHIC METHOD
Authors: HOANG TCHANG-FONG  ,   上海交通大学物理系
Published: November 2020

An improved δ-ray method for determining the nature of heavy nudei is obtaincl img application of a seini-empirical formula giing;; the δ-ray density per 100 μ of the track in function of the remaining range R; N=C ZpR-b with p=1.54. b=0.46 and C depending on the nature of the emulsion and the conditions of measurement.Discussions arc given on the "thin-down effect" and the relation between the ihin-down length and the atomic charge.
THE F-2 REGION OF THE IONOSPHERE AT WUCHANG DURING THE SOLAR ECLIPSE OF MAY 9, 1948
Authors: C. T. KWEI  , P. H. LIANG  , J. H. MOH  , W. CHOW  ,   (1)武汉大学游离层实验室; (2)武汉大学游离层实验室,中国科学院地球物理研究所
Published: November 2020

From data obtained during the eclipse and on control days, the effective coefficient of recombination for F-2 layer is found to be 4×10-10 cm3/electron per sec. The magnitude of a is apparently a function of the height of the layer which becomes lower with increasing latitude. Solar eruptions may be associated with two of the discontinuities of the eclipse curve. The thickness of the F-2 layer became compressed and dropped as a whole during the eclipse, possibly due to air movement caused by lowering of temperature. The sporadic E layer was not influenced by the change of solar radiation, and must be due to other causes.
ON THE THEORY OF BETA-DISINTEGRATION
Authors: NING HU  , MIN YU  ,   (1)北京大学物理系; (2)中国科学院近代物理研究所
Published: November 2020

It is pointed out that the divergence in Yukawa's theory of βdisintegration can be removed by charge and mass renormalizations, whereas in conventional Fermi's theory this is not the case. From the known interaction constants for nuclear β-decay, for μ-e decay and for the interaction of μ-mesons with nucleons, it is found that the life time of the intermediary meson should be of the order 10-16 sec. We can therefore consider this intermediary meson as a new particle which has not been observed experimentally owing to its extremely short life time. Best agreement with experiment is obtained if the intermdiary meson is pseudo-vector in nature and under pseudo-vector interaction with the Fermi fields, those types of interactions being excluded which lead to divergent results for observable effects.
THE S-MATRIX IN MESON THEORY
Authors: NING HU  ,   北京大学物理系
Published: November 2020

It is shown that the divergence in the cases of pseudo-scalar mesons with pscudo-vector conpling and the charged pscudo-vector mesons with pscudo-vector coupling can be reduced to the same type as that in electrodynamics. Other types of meson theories having stronger divergence than quantum electrodynamics are also investigated. Our program of reduction is less-successful in these cases.
ON THE THREE-DIMENSIONAL PROBLEMS OF THE THEORY OF ELASTICITY OF A TRANSVERSELY ISOTROPIC BODY
Authors: HU HAI-CHANG  ,   中国科学院数学研究所
Published: November 2020

In this paper, we follow S. G. Lehnitzky in the study of the three-dimensional problems of a transversely isotropic body depending on three variables. We give up the restriction of S. G. Lehnitzky about deformation and reserve only the assumption about the elastic property of the body. The results of this paper give a wide possibility for the solution of special problems.
THEORY OF ATTENUATION OF SOUND IN FOGGY AIR DUE TO EVAPORATION AND CONDESATION PROCESSES
Authors: WEI YUNG-CHIO  ,   南京大学物理系
Published: November 2020

As sound waves traverse in clouds or foggy air the temperature change, which accompanies the pressure variation, would make the water molecules at the droplet's surface to evaporate or those in its close surroundings to condense according as there is condensation or rarefaction respectively. In general, the pressure waves always pro-pagate ahead of the density waives since a finite time is required for this process to take place. However at very high frequencies, the periodic pressure varies too fast for this process to follow, the situation is essentially "dry adiabatic". Only at very low frequencies is the term "relaxation time" of any significance, so the "dispersion" and "absorption".This problem has been handled, in the present paper, in some respect in an analogous way to that in the collision theory of molecular absorption of sound. The previous calculations due to Oswatitsch have been found to be erroneus, and special attention has been given to each of the following:(1) Relation between air density and particle concentration;(2) Relation between the change of the amount of liquid water and the amount of vapor;(3) Derivation of the equation of growth of droplet; and(4) Diffusion and heat conduction coefficients.
ELECTRIC CIRCUIT ANALYSIS BY THE NETHOD OF DIFFERENCE EQUATION
Authors: YEH KAI-YUAN  ,   北京大学力学专业
Published: November 2020

The method of difference equation recently employed by Prof. Chien Wei-zang in his treatment of continuous beams is applied here to the solution of electric circuit problem. The superiority of this method over the customary ones-viz. (1) classical method, (2) Heaviside transformation, (3) Fourier transformation, and (4) Laplace transformation,-lies in the fact that the tedious work of solving a large number of simultaneous equations in the customary methods is avoided. The present paper is confined to the problem of the continuous network. The investigation is divided into two parts: (1) the continuous net-work in steady state, (2) in transient state. In the first part, the chief result is
TORSION OF PRISMS BOUNDED BY TWO INTERSECTING CIRCULAR CYLINDERS
Authors: HU HAI-CHANG  ,   中国科学院数学研究所
Published: November 2020

In this paper, the problem of torsion of prisms bounded by two intersecting circular cylinders is solved by means of Fourier's integrals. It is found that when the angle of intersection of these two circular cylinders is commensurable with π the stress function and the torsional rigidity of the prism can be expressed in closed form in terms of circular and hyperbolic sines and cosines.
APPROXIMATE SOLUTION OF A ROTATING RECTANGULAR PLATE
Authors: ZHANG FU-FAN  ,   清华大学
Published: November 2020

The analysis of a rotating circular plate is an easy problem because of circular symmetry. However, for the boundary other than circular, the problem will become much more complicated. For example, we may be theoretically interested in the stresses in a rectangular plate, which rotates with respect to its geometric center. If die thickness of he plate is small when compared with its length and width, the variation of stresses throughout the thickness can be neglected. Consequently, we shall have a two dimensional problem with body force acting. To solve a two dimensional problem with rectangular boundary is not always feasible. By using trigonometric series, we can only satisfy the conditions on the two sides of the plate. Accordingly the result can only be of value when the length of the plate is much larger than its width. If both dimensions of the plate are of the same order, the boundary conditions on the four sides must be considered. In the solution of the problem of this kind the principle of minimum strain energy may be successfully applied.
Gamma activity accelerates during prefrontal development
Authors: Bitzenhofer Sebastian H , Pöpplau Jastyn A , Hanganu-Opatz Ileana
Published: November 2020

Gamma oscillations are a prominent activity pattern in the cerebral cortex. While gamma rhythms have been extensively studied in the adult prefrontal cortex in the context of cognitive (dys)functions, little is known about their development. We addressed this issue by using extracellular recordings and optogenetic stimulations in mice across postnatal development. We show that fast rhythmic activity in the prefrontal cortex becomes prominent during the second postnatal week. While initially at about 15 Hz, fast oscillatory activity progressively accelerates with age and stabilizes within gamma frequency range (30–80 Hz) during the fourth postnatal week. Activation of layer 2/3 pyramidal neurons drives fast oscillations throughout development, yet the acceleration of their frequency follows similar temporal dynamics as the maturation of fast-spiking interneurons. These findings uncover the development of prefrontal gamma activity and provide a framework to examine the origin of abnormal gamma activity in neurodevelopmental disorders.
Robo functions as an attractive cue for glial migration through SYG-1/Neph
Authors: Qu Zhongwei , Zhang Albert , Yan Dong
Published: November 2020

As one of the most-studied receptors, Robo plays functions in many biological processes, and its functions highly depend on Slit, the ligand of Robo. Here we uncover a Slit-independent role of Robo in glial migration and show that neurons can release an extracellular fragment of Robo upon cleavage to attract glia during migration inCaenorhabditis elegans. Furthermore, we identified the conserved cell adhesion molecule SYG-1/Neph as a receptor for the cleaved extracellular Robo fragment to mediate glial migration and SYG-1/Neph functions through regulation of the WAVE complex. Our studies reveal a previously unknown Slit-independent function and regulatory mechanism of Robo and show that the cleaved extracellular fragment of Robo can function as a ligand for SYG-1/Neph to guide glial migration. As Robo, the cleaved region of Robo, and SYG-1/Neph are all highly conserved across the animal kingdom, our findings may present a conserved Slit-independent Robo mechanism during brain development.
High-resolution transcriptional and morphogenetic profiling of cells from micropatterned human ESC gastruloid cultures
Authors: Minn Kyaw Thu , Fu Yuheng C , He Shenghua , Dietmann Sabine , George Steven C , Anastasio Mark A , Morris Samantha A , Solnica-Krezel Lilianna
Published: November 2020

During mammalian gastrulation, germ layers arise and are shaped into the body plan while extraembryonic layers sustain the embryo. Human embryonic stem cells, cultured with BMP4 on extracellular matrix micro-discs, reproducibly differentiate into gastruloids, expressing markers of germ layers and extraembryonic cells in radial arrangement. Using single-cell RNA sequencing and cross-species comparisons with mouse, cynomolgus monkey gastrulae, and post-implantation human embryos, we reveal that gastruloids contain cells transcriptionally similar to epiblast, ectoderm, mesoderm, endoderm, primordial germ cells, trophectoderm, and amnion. Upon gastruloid dissociation, single cells reseeded onto micro-discs were motile and aggregated with the same but segregated from distinct cell types. Ectodermal cells segregated from endodermal and extraembryonic but mixed with mesodermal cells. Our work demonstrates that the gastruloid system models primate-specific features of embryogenesis, and that gastruloid cells exhibit evolutionarily conserved sorting behaviors. This work generates a resource for transcriptomes of human extraembryonic and embryonic germ layers differentiated in a stereotyped arrangement.