FAST ultra-wideband observation of abnormal emission-shift events of PSR B0919+06

PSR B0919+06 is known for its abnormal emission phenomenon, where the pulse emission window occasionally shifts progressively in longitude and returns afterwards. The physical mechanism behind this phenomenon is still under investigation. In this paper, we present our ultra-wideband observation of this pulsar using the Five-hundred-meter Aperture Spherical radio Telescope(FAST), with simultaneous measurements in the frequency ranges 280-780 and 1250-1550 MHz. We have identified three abnormal events, each of which becomes less apparent as the frequency decreases. At 1400 MHz, the averaged profile slightly shifted after the first and third abnormal events, implying a relationship between abnormal event and profile variation. We also found a linear trend in the left-edge position of the averaged profiles between the first and third events as well as after the third event, suggesting the existence of a slow-drifting mode between the two major events. The second event has a comparatively small shift in phase and is thus categorized as a "small flare state". During the third event, a sequence of approximately nine pulses was seen to significantly weaken in all frequency bands, likely associated with the pseudo-nulling observed at 150 MHz.A three-component de-composition analysis of the normal averaged profiles shows that the trailing component is dominant at our observing frequencies, while the centre component has a comparatively steeper spectrum. We found the overall flux density in an abnormal event to slightly differ from that in an ordinary state, and the difference shows a frequency dependence. A comparison of the normal, abnormal and dimmed averaged profile indicates that the leading component is likely to be stable in all states.     

Charged Dirac Particles’ Hawking Radiation via Tunneling of Both Horizons and Thermodynamics Properties of Kerr–Newman–Kasuya–Taub–NUT–AdS Black Holes

We investigate Hawking radiation of electrically and magnetically charged Dirac particles from a dyonic Kerr–Newman–Kasuya–Taub–NUT–Anti-de Sitter (KNKTN–AdS) black hole by considering thermal characters of both the outer and inner horizons. We apply Damour–Ruffini method and membrane method to calculate the temperature and the entropy of the inner horizon of the KNKTN–AdS black hole. The inner horizon admits thermal character with positive temperature and entropy proportional to its area. The inner horizon entropy contributes to the total entropy of the black hole in the context of Nernst theorem. Considering conservation of energy, charges, angular momentum, and the back-reaction of emitting particles to the spacetime, we obtain the emission spectra for both the inner and outer horizons. The total emission rate is obtained as the product of the emission rates of the inner and outer horizons. It deviates from the purely thermal spectrum with the leading term exactly the Boltzman factor and can bring some information out. The result thus can be treated as an explanation to the information loss paradox.     

An analytical study of a doubly clad compressed ellipse optical waveguide

Using an analytical method based on boundary matching technique, the modal behavior and cutoff frequencies of a compressed ellipse doubly clad optical waveguide is studied. The proposed waveguide consists of a core region of higher refractive index with two cladding regions: one is inner cladding and the other is outer cladding. We take appropriate orthogonal coordinates for the proposed structure and impose the boundary conditions to obtain the characteristic equation. The effect of the width of inner cladding layer on the dispersion characteristic is observed. It is found that the width of inner cladding is able to tailor the dispersion characteristic and cutoff condition of the waveguide up to a certain limit.     

The FIGARO II experiment: a general outline of the mission and the principal scientific results

Summary The FIGARO II (French Italian Gamma-Ray Observatory) experiment has been launched successfully three times: in July 1986 from Milo (Trapani), in November 1988 from Charleville (Australia) and in July 1990 again from Milo. In the first flight the observational program was limited to the Crab pulsar PSR0531+21 only because of a telemetry failure: the high sensitivity of FIGARO II allowed an accurate study of the pulse shape as well as a phase-resolved spectroscopy. It was also possible to evaluate the dispersion measure of the Crab pulsar at the flight date from the time delay between gamma-ray and radio pulses. The major results of the second flight were a stringent upper limit to the low-energy gamma-ray flux from PSR 0833-45 (Vela pulsar)—well below the detection claimed by the UCR group —and the observation of a strong emission in the 0.511 MeV annihilation line from the inner region of our Galaxy. The data acquired in the third flight are still under analysis, but preliminary results suggest changes in the shape of the pulse profile. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Charged Particles’ Hawking Radiation via Tunneling of Both Horizons from Reissner-Nordström-Taub-NUT Black Holes

In some recent derivations thermal characters of the inner horizon have been employed; however, the understanding of possible role that may play the inner horizons of black holes in black hole thermodynamics is still somewhat incomplete. Motivated by this problem we investigate Hawking radiation of the Reissner-Nordström-Taub-NUT (RNTN) black hole by considering thermal characters of both the outer and inner horizons. We apply Damour-Ruffini method and the thin film brick wall model to calculate the temperature and the entropy of the inner horizon of the RNTN black hole. The inner horizon admits thermal character with positive temperature and entropy proportional to its area, and it thus may contribute to the total entropy of the black hole in the context of Nernst theorem. Considering conservations of energy and charge and the back-reaction of emitting particles to the spacetime, the emission spectra are obtained for both the inner and outer horizons. The total emission rate is the product of the emission rates of the inner and outer horizons, and it deviates from the purely thermal spectrum and can bring some information out. Thus, the result can be treated as an explanation to the information loss paradox.     

低混杂波驱动电流对等离子体电导率的影响

本文考虑了波驱动通量对磁场位形以及电子密度和温度的空间分布的依赖,应用伴随关系,计算了低混杂波驱动的等离子体电导率的空间分布。结果表明,注入功率谱对电导率空间分布的影响相当敏感,等离子体环外侧的电导率略高于内侧的电导率。但是不论在外侧或内侧,随着离子电荷数增大,波驱动的等离子体电导率降低,而它与斯必泽-亥姆电导率之比却增大。     

夹心式径向复合压电超声换能器

对夹心式径向复合压电换能器径向振动特性进行了研究。该换能器由弹性内芯、预应力金属管及柱面压电陶瓷晶堆径向复合而成.利用机电类比法,得到了换能器的径向振动等效电路及频率方程。探讨了换能器第1、2阶径向共振频率及有效机电耦合系数与其几何尺寸的关系。研究表明,换能器第1阶径向共振频率随其内芯内径及预应力管壁厚度增大而降低;第2阶共振频率随内芯内径增大存在极小值,但随预应力管壁厚度增大单调下降。此外,采用第2阶径向共振模式能获得较高的有效机电耦合系数,并且压电陶瓷处于位移节线时,换能器有效机电耦合系数达极大值。对换能器共振频率的测试与有限元仿真表明。理论与实验及仿真结果符合较好。     

Full-profile fitting of emission spectrum to determine transition intensity parameters of Yb~(3+):GdTaO_4

The Judd-Ofelt theoretic transition intensity parameters A_(tp)~k of luminescence of rare-earth ions in solids are important for the quantitative analysis of luminescence.It is very difficult to determine them with emission or absorption spectra for a long time.A "full profile fitting" method to obtain A_(tp)~k in solids with its emission spectrum is proposed,in which the contribution of a radiative transition to the emission spectrum is expressed as the product of transition probability,line profile function,instrument measurement constant and transition center frequency or wavelength,and the whole experimental emission spectrum is the sum of all transitions.In this way,the emission spectrum is expressed as a function with the independent variables intensity parameters A_(tp)~k,full width at half maximum(FWHM) of profile functions,instrument measurement constant,wavelength,and the Huang-Rhys factor S if the lattice vibronic peaks in the emission spectrum should be considered.The ratios of the experimental to the calculated energy lifetimes are incorporated into the fitting function to remove the arbitrariness during fitting A_(tp)~k and other parameters.Employing this method obviates measurement of the absolute emission spectrum intensity.It also eliminates dependence upon the number of emission transition peaks.Every experiment point in emission spectra,which usually have at least hundreds of data points,is the function with variables A_(tp)~k and other parameters,so it is usually viable to determine A_(tp)~k and other parameters using a large number of experimental values.We applied this method to determine twenty-five A_(tp)~k of Yb~(3+) in GdTaO_4.The calculated and experiment energy lifetimes,experimental and calculated emission spectrum are very consistent,indicating that it is viable to obtain the transition intensity parameters of rare-earth ions in solids by a full profile fitting to the ions' emission spectrum.The calculated emission cross sections of Yb~(3+):GdTaO_4 also indicate that the F-L formula gives larger values in the wavelength range with reabsorption.     

Effects of signal spectrum varying on signal processing by parameter-induced stochastic resonance

The effects of signal spectrum varying on signal processing by the method of parameter-induced stochastic resonance (PSR) are investigated. For a binary signal with a smooth power spectral density (PSD), when the PSD curve becomes sharper and narrower, the performance of the nonlinear system via PSR is better. For a multi-frequency signal formed by sine waves with different frequencies, the larger the signal spectral density is, the lower the ability of the PSR system processing signal is. And the signal-to-noise ratio (SNR) gain of the PSR system is increased with the increasing height of the spectral line. Moreover, with the method of PSR, the stochastic signal (the combination of sine waves and noise) improvement is obvious. The results obtained via this method are superior to those with a linear filter.     

The Stability of Some Viable Stars and Electromagnetic Field

We examine the impact of electromagnetic field on the stability of compact stars corresponding' to embedded class one metric using the concept of cracking.For this purpose,we develop the generalized hydrostatic equilibrium equation for charged perfect fluid distribution of compact stars and perturb it by means of local density perturbation scheme to check the stability of inner matter configuration.We investigate the cracking of Her X-1,PSR 1937+21,PSR J 1614-2230,PSR J 0348+0432 and RX J 1856-37.We conclude that PSR J 0348+0432 and RX J 1856-37 exhibit cracking when charge is introduced on these astrophysical objects.     

基于Abel逆变换的激光诱导等离子体辐射特性研究

激光诱导击穿光谱(LIBS)作为一种新型的物质成分测量方法已经在越来越多的领域得到广泛应用，但是与传统的分析方法相比，LIBS技术的分析性能还需进一步提高。LIBS技术的理论基础是激光诱导等离子体，从物理机理上研究等离子体特性，对LIBS系统实验参数的优化具有指导作用，也为提高LIBS技术的检测能力奠定理论基础。激光诱导等离子体是一个与空间相关的非稳态辐射源，空间分辨光谱测量是探究等离子体物理特性的重要手段之一。为研究激光诱导等离子体的辐射特性，采用1 064 nm的Nd∶YAG调Q固体激光器烧蚀合金钢样品产生等离子体，利用空间分辨装置测量二维空间的等离子体辐射光谱信号，通过分析可知实验采集的光谱信号是信号探测器测量路径上的积分光谱强度，由此计算得到的等离子体参数也是观测路径上的平均值。为了深入研究等离子体由内层到外层的辐射规律，首先测量得到等离子体路径积分光谱强度的横向空间分布，然后以等离子体为光学薄和圆柱对称的前提条件，采用三次样条函数算法对路径积分光谱强度进行Abel逆变换，反演得到等离子体由内层到外层谱线辐射率的径向空间分布。选取等离子体辐射光谱中的原子谱线Fe Ⅰ: 374.55 nm和Mn Ⅰ: 403.08 nm为研究对象，分析等离子体辐射光谱的空间分布特征，研究结果表明，等离子体辐射路径积分光谱强度的横向分布呈现出中心位置强度大边缘位置强度小的特征，这是由于等离子体膨胀扩张的结果引起的；通过Abel逆变换得到等离子体光谱辐射率的径向分布，结果表明等离子体从内层到外层谱线的辐射率经过了先增加后减小的变化规律，等离子体中心处出现辐射率的极小值，造成这种现象的主要原因是由于等离子体辐射源中心区域具有较低的电子密度；选取等离子体辐射光谱中Fe元素的11条原子谱线，采用Boltzman法分别由谱线相应的积分光谱强度和辐射率计算等离子体温度，得到等离子体温度的横向空间和径向空间的二维分布，两者具有类似的变化规律；由等离子体温度的横向空间分布可以看出，随着离样品表面距离的增加，等离子体温度呈现单调减小的趋势，等离子体中心到边缘区域等离子体温度逐渐降低，这是由等离子体膨胀扩张以及与环境气体相互作用共同的结果；由等离子体温度的径向空间分布可以看出等离子体由内层到外层等离子体温度逐渐降低，这是由于等离子体膨胀扩张冷却引起的。由此可见，采用Abel逆变换能够实现等离子体由内层到外层的辐射特性分析，为深入理解等离子体产生和演变的物理机理提供实验依据，从而为提高激光诱导击穿光谱技术的分析性能奠定理论基础。     

Cones with a dual structure formed on Ar+-bombarded Si surfaces

Transmission electron microscopy disclosed that cones formed on crystalline Si surfaces bombarded with a few keV Ar⁺ ions were of a dual structure inexplicable by the existing models of cone formation. The outer region of the cones was composed of unoriented crystallites of Si, whereas the inner region was a single crystal oriented in the 〈111〉 direction. The polycrystalline region was too thick to explain its formation in terms of ion-induced disordering of the monocrystalline phase, suggesting that the redeposition of sputtered Si atoms was deeply concerned in evolving the cones. It is supposed that the present cone evolution involved particle supply processes underlying the growth of Si whiskers from the vapor phase.     

New classes of anisotropic models with generalized polytropic equation of state

In this paper, we investigate the gravitational behavior of compact objects with the help of generalized polytropic equation of state in isotropic coordinates. We found three exact solutions of Einstein field equations by taking into account the different values of polytropic index with spherically symmetric anisotropic inner fluid distribution. We have regained the masses of PSR \(\hbox {J}1614-2230\), Vela X-1, Vela 4U, PSR J1903+327 and 4U 1820-30. Speed of sound has been used to analyze the stability of models. The comprehensive analysis indicates that all the models are physically viable and well behaved.     

Observation of inner electron ionization from radial rydberg wave packets in two-electron atoms

We have observed multiphoton ionization of the 5s core electron from a 5snd radial Rydberg wave packet of Sr atoms using a short optical pulse. When the outer nd electron is at its outer turning point the inner 5s electron is removed from the atom, and the outer electron is left in a Sr+ Rydberg state, but when the outer electron is at the inner turning point this does not occur. Analysis of the final Sr+ Rydberg states shows that the two electrons interact as the inner electron leaves, so that the outer electron is not simply projected onto the Sr+ Rydberg states.     

On the Non-Adaptive Zero-Error Capacity of the Discrete Memoryless Two-Way Channel

We study the problem of communicating over a discrete memoryless two-way channel using non-adaptive schemes, under a zero probability of error criterion. We derive single-letter inner and outer bounds for the zero-error capacity region, based on random coding, linear programming, linear codes, and the asymptotic spectrum of graphs. Among others, we provide a single-letter outer bound based on a combination of Shannon’s vanishing-error capacity region and a two-way analogue of the linear programming bound for point-to-point channels, which, in contrast to the one-way case, is generally better than both. Moreover, we establish an outer bound for the zero-error capacity region of a two-way channel via the asymptotic spectrum of graphs, and show that this bound can be achieved in certain cases.     

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利用MEC和LSC耦合的程序研究了EAST天线不同的相位差 对功率谱的影响及对功率沉积位置和电流分布的影响。通过计算发现,随着 的增大,功率谱的结构发生了改变,当 >200°后功率沉积和电流密度分布由原先的向外层移动变为向内层移动; =200°时形成一个离轴最远的驱动电流, =120°、 =260°时分别得到电流强度最小和最大的驱动电流。因此可以通过选取合适的天线相位差 ,实现对低杂波功率沉积和驱动电流剖面的控制。     

间接驱动内爆靶丸示踪元素Ar发射X光谱线的理论模拟研究

惯性约束聚变内爆物理研究中, 示踪元素X光谱线诊断方法是推测内爆压缩温度、密度以及燃料混合的有效办法, 因此, 对示踪元素X光发射的规律及其与内爆过程的关系的研究非常必要, 有助于通过谱线发射特征诊断内爆状态. 以SGIII原型装置的实验条件下的内爆过程为例, 对内爆靶丸示踪元素Ar发射X光谱线进行了理论模拟. 研究了谱线自吸收效应、Ar掺杂浓度、等离子体空间分布不均匀等对Ar发射的X光谱线分布的影响. 还对Ar发射X光谱线强度的时间演化及其与内爆过程的关系进行了研究. 结果表明, 增加掺杂浓度, 谱线强度增强, 但是谱线自吸收效应的影响也明显增强. 示踪元素Ar发射的X光谱线强度的峰值时刻与中子产生速率的峰值时刻接近(前者延迟约15 ps). 高温、高密度及合适的电离度是谱线发射的3个条件, 在X光谱线发射的峰值时刻, 由于燃料芯部Ar等离子体过电离, Ar等离子体发射的X光谱线的空间峰值区域靠近燃料边界区域, 占燃料总体积56%的薄壳(厚度～4 μm), 其发射的X光谱线强度约为总强度的72%. 因此, 对发射谱线分布拟合得到的空间平均的等离子体温度、密度主要反映这一区域的等离子体状态.     

A study on waviness induced vibration of ball bearings based on signal coherence theory

This paper focuses on the effects of waviness on vibration of ball bearings. An experimental analysis method is developed by adopting signal coherence theory of multiple-inputs/single-output (MISO) system. The inputs are waviness excitations of the inner and outer races, and the output is vibration response of the outer ring. Waviness excitation signals are first derived from the manufacturing deviations, and found to be strongly coherent in low frequency range. Virtual input signals are then introduced by the method of orthogonalization. In both cases of vibration acceleration and speed responses, the cumulated virtual input–output coherence function verifies that the first peak region of vibration spectrum is mainly induced by the waviness excitations. In order to distinguish the contributions of the inner and outer races, coherence functions of the virtual inputs with real inputs are calculated, and the results indicate that the outer race waviness contributes more to vibration than the inner race waviness does in the example. Further, a multi-body dynamic model is constructed and employed to frequency response analyses. It is discovered that the waviness induced spectral peak frequency is close to the natural frequency of bearing.     

W-型单模单偏振光纤截止基模的能量损耗

给出了一种新的数值计算W型单模单偏振光纤截止基模能量损耗的方法－－区域模场边界条件匹配法。用这种方法分析了截止基模能量损耗与光张结构参数的关系。得出了截止基模能量损耗随椭圆内包层长半轴、短半轴或内包层折射率深度的增加而迅速减小，以及高椭圆度内包层情形下截止基模能量损耗仅由内包层短半轴、内包层折射度和纤芯－外包层相对经差确定的结论；同时得出了截止基模能量损耗与纤芯－外包层相对折射率差的平方根成正比的解析结果。最后将数值计算和实验进行了比较，两者较为一致。     

Angular distribution of electrons in the field of a short laser pulse of relativistic intensity

Based on the dynamics of the electron in the field of a laser pulse of relativistic intensity, the electron emission angles with respect to the laser pulse propagation axis are calculated. The angular distribution of accelerated electrons is analyzed together with their energy spectrum. It is shown that fast electrons forming the high-energy spectral region are emitted into a fixed angular cone.