A One-Dimensional Relativistic Shock Model for the Light Curve of Gamma-ray Bursts

We investigate the forming of gamma-ray burst pulses with a simple onedimensional relativistic shock model. The mechanism is that a ＂central engine＂ drives forward the nearby plasma inside the fireball to generate a series of pressure waves. We give a relativistic geometric recurrence formula that connects the time when the pressure waves are produced and the time when the corresponding shocks occurred. This relation enables us to relate the pulse magnitude with the observation time. Our analysis shows that the evolution of the pressure waves leads to a fast rise and an exponential decay pulses. In determining the width of the pulses, the acceleration time is more important than that of the deceleration.

Theoretical Study of Coupling Mechanism between FBG and Shock Waves of Rock Burst

To achieve the monitor of rock burst in coal mine with fiber Bragg grating (FBG) sensing, the coupling mechanism between FBG and shock waves was theoretically analyzed. Based on Housner’s random shock model, the coupling mechanism between shock waves and FBG was theoretically analyzed. The result shows that the wave will change the period Ʌ and effective refractive index n of FBG, and further affect the initial wavelength value. The amplitude, phase and frequency of shock wave are directly related to the wavelength drifts of FBG. The transmitting velocity of shock wave in rock is affected by lithologic characteristics. The Elastic modulus, density and Poisson’s ratio of rock influence the initial wavelength value of FBG. This study provided a theoretical basis and practical application guidance for coal or rock burst monitoring with FBG sensing.

A Detailed Study on the Equal Arrival Time Surface Effect in Gamma-Ray Burst Afterglows

Due to the relativistic motion of gamma-ray burst remnant and its deceleration in the circumburst medium, the equal arrival time surfaces at any moment are not spherical, rather, they are distorted ellipsoids. This will leave some imprints in the afterglows. We study the effect of equal arrival time surfaces numerically for various circumstances, i.e., isotropic fireballs, collimated jets, density jumps and energy injection events. For each case, a direct comparison is made between including and not including the effect. For isotropic fireballs and jets viewed on axis, the effect slightly hardens the spectra and postpones the peak time of the afterglows, but does not change the shapes of the spectra and light curves significantly. In the cases of a density jump or an energy injection, the effect smears out the variations in the afterglows markedly.

Gamma-Ray Bursts: Afterglows and Central Engines

Gamma-ray bursts (GRBs) are the most intense transient gamma-ray events in the sky; this, together with the strong evidence (the isotropic and inhomogeneous distribution of GRBs detected by BASTE) that they are located at cosmological distances, makes them the most energetic events ever known. For example, the observed radiation energies of some GRBs are equivalent to the total convertion into radiation of the mass energy of more than one solar mass. This is thousand times stronger than the energy of a supernova explosion. Some unconventional energy mechanism and extremely high conversion efficiency for these mysterious events are required. The discovery of host galaxies and association with supernovae at cosmological distances by the recently launched satellite of BeppoSAX and ground based radio and optical telescopes in GRB afterglow provides further support to the cosmological origin of GRBs and put strong constraints on their central engine. It is the aim of this article to review the possible central engines, energy mechanisms, dynamical and spectral evolution of GRBs, especially focusing on the afterglows in multi-wavebands.

Afterglow Light Curves of Jetted Gamma-ray Burst Ejecta in Stellar Winds

Optical and radio afterglows arising from shocks by relativistic conical ejecta running into pre-burst massive stellar winds are revisited. Under the homogeneous thin-shell approximation and a realistic treatment for the lateral expansion of jets, our results show that a notable break exists in the optical light curve in most cases we calculated in which the physical parameters are varied within reasonable ranges. For a relatively tenuous wind which cannot decelerate the relativistic jet to cause a light curve break within days, the wind termination shock due to the ram pressure of the surrounding medium occurs at a small radius, namely, a few times 1017 cm. In such a structured wind environment, the jet will pass through the wind within several hours and run into the outer uniform dense medium. The resulting optical light curve flattens with a shallower drop after the jet encounters the uniform medium, and then declines deeply, triggered by runaway lateral expansion.

On the Gamma-Ray Bursts Origin

Gamma-ray (GRBs) and X-ray Bursts are millisecond-10 and 1000 seconds-long events of unknown origin. Recent simulations of the merger of binary neutron star systems do not generate a magnetically dominated called funnel nor a relativistic outflow. New models for the detection the afterglow of GRB 121024A, measured 0.15 days after the burst, invoke anisotropy as required to produce the complex microphysics of realistic shocks in relativistic jets. On the other hand the non-thermal gamma-rays are supposed to be produced by a fireball of relativistic e?e+ pairs that are created by annihilation of neutrino-antineutrino pairs in the vicinity of the hot, merged object. It is also known that in a system of a large number of fermions with pairs, gravitational interaction occurs a spontaneous breaking of the vacuum spatial symmetry, accompanied by gravitational mass defect. If spherical symmetry is broken, as in the known case of the merger scenario where a rapidly rotating disk can be formed and material is pulled away from rotation axis by centrifugal forces, then a baryon-free funnel along the rotation axes may allow relativistic beam of γ’s and e?e+ to escape. It might lead to matter ejection with Lorentz factors of ~102 - 103 which are in the right range to enable copious gamma production during shock interaction with ambient interstellar gas. Here we show that the space rays generation mechanism on a method of direct transformation of intergalactic gamma-rays to the proton current on spin shock-waves ensure precise agreement between generated proton currents (spin shock waves theory) with the angular distribution data of Galactic gamma-rays as well as for the individual pulses of gamma-/X-ray bursts. There is a precise confirmation of the generated currents (theory) with the burst radiation data characterized by the standard deviation of ±1% in intensity in relative units within the sensitivity of the equipment. Thus, it was found that the spin angular momentum conservation law (equation of dynamics of spin shock waves) in the X-ray/gamma ranges is fulfilled exactly in real time. The next step involves setting the inverse problem of determining the wave function disturbance on the differential of measured smoothing pulses. In the asymptotic large times the problem is reduced to the solutions of the functional equation with shift of the argument. This will give additional information about the change speed of the wave, as well as on the interaction.

微波热力冲击下硬脆砂岩冲击倾向性演化规律试验研究

冲击地压是深部资源开采的主要灾害类型,冲击倾向性是表征冲击地压风险的重要指标。为了探索微波热力冲击对岩石冲击倾向性的影响,本文对典型强冲击倾向性硬脆砂岩开展了微波热力冲击和单轴压缩试验,分析了微波热力冲击后砂岩的物理力学性质和冲击倾向性指标响应规律。研究结果表明:(1)微波作用后,砂岩表面温度随着热力冲击时间增加持续升高,直至150 s发生热破断;(2)微波热力冲击120 s后,砂岩内部结构发生微破裂,岩石冲击倾向性明显减弱,纵波波速与弹性模量分别下降了15.12%、8%;(3)单轴压缩变形破坏过程各阶段声发射信号密度增大,砂岩最终破坏时的绝对能量最大值下降42.3%;(4)岩石动态破坏时间增长了259%,冲击能量指数减小95%,弹性能量指数下降92%,砂岩由强冲击性岩石变为弱冲击性岩石。研究结果为煤炭深部开采冲击地压防治和深地工程高效破岩具有参考价值。

岩性特征对冲击地压震动波光栅监测影响机理研究

为了得出冲击地压震动波在岩石中传播时岩性特征的影响机理,借助光纤光栅对不同岩石载体中的震动波进行了监测,并从理论上分析了二者之间的耦合关系。以Housner的随机震动模型为基础,对震动波与光纤光栅之间的耦合机理进行了理论分析,结果表明,震动波可以改变光栅的周期Λ和有效折射率n eff,进而影响其初始波长,震动波幅值、相位及频率等参数与波长变化直接相关;震动波在岩石中传播的波速受岩性特征参数的影响,岩石的弹性模量、密度和泊松比以特定的形式影响光纤光栅的初始波长,且与波长变化呈余弦相关;对砂岩、石灰岩及大理石板分别进行了震动波传感监测实验,结果表明,3种岩石的岩性参数I与光纤光栅的初始波长值具有余弦函数对应关系,与理论分析的结果相一致。研究为煤岩冲击地压光纤光栅传感监测提供了理论依据及实践应用指导。

矿震诱发冲击地压机理研究

根据弹性波理论推导出矿震产生的应力波诱发动力扰动的公式,建立冲击地压理论模型从而推导出冲击地压发生的发生理论;并利用ABAQUS数值模拟技术模拟了矿震诱发冲击地压的过程;并探究围岩巷道受到静—动荷载叠加作用时,冲击地压的发生条件;根据现实中某矿矿震引发的冲击地压测得的数据,验证了矿震诱发冲击地压这一理论。模拟结果表明,当围岩巷道受到的地应力静载过大,达到临界塑性区时,微小的矿震会引发围岩巷道出现冲击地压现象。

基于三维负泊松比蜂窝结构的防冲支架性能研究

提出一种应用于支架顶梁上方的吸能缓冲装置,该缓冲装置采用轻质、吸能量高的负泊松比材料,旨在将冲击地压带来的能量快速让位、缓冲吸收。对缓冲装置的构型进行设计并进行准静态压缩仿真;对缓冲装置施加低速、中速、高速进行抗冲击特性研究。结果表明:胞元角度为θ=70°的胞元具有良好的负泊松比效应、更长的压缩行程、更高的吸能量,适宜于做缓冲结构的胞元结构。对缓冲结构施加不同的速度,得到随着冲击速度的增大,缓冲结构的比吸能越大。

震源扰动型巷道冲击矿压破坏力能准则及实践

针对震源扰动型巷道冲击矿压破坏机理进行研究,建立了巷道围岩冲击震源扰动型冲击破坏的动力分析模型,推导了巷道围岩承载结构在"静载+动载"组合作用下动力破坏的应力判据和能量准则。基于该力学模型及其机理分析,提出合理设置弱结构消波吸能的防冲理念,并从理论角度分析了弱结构消波吸能的作用机理。最后通过工程实例,应用能量准则进行了冲击煤层巷道的支护设计及其防冲性能核算,理论研究成果初步得到了应用和检验。

炸高对爆炸超压的影响规律

对炸高影响爆炸超压的规律进行了理论分析和实验研究。提出了描述超压与对比炸高和对比距离两个变量的拟合公式。得到了最有利的起爆高度(对比炸高)与对比距离的关系。得出最佳炸高条件下冲击波超压随对比距离的衰减曲线,可近似为一条直线,该曲线上的冲击波超压高于其他条件的超压值。

复合型厚煤层“震-冲”型动力灾害机理、预测与控制

针对软硬分层相间的复合型厚煤层综放工作面发生的动力灾害事故,提出了复合型厚煤层综放工作面"震-冲"型动力灾害的概念.通过理论和实践研究,初步建立了复合型厚煤层"震-冲"型动力灾害的力学模型,研究了其发生的机理,分析了矿震和冲击地压发生的力学条件和相互关系.研究成果在兖州矿业集团公司南屯煤矿得到应用,成功预测了动力灾害发生位置,并做好了预先卸压、监测和防护,实现了"有震无灾"的控制目标.

覆岩关键层运动诱发冲击的规律研究

基于岩层运动关键层理论,研究了覆岩关键层破断规律,从力学机理上分析了覆岩关键层正"O-X"型破断时,矿山压力达到最大值,极易导致强矿震、冲击矿压的发生。利用微震监测系统,对关键层破断诱发冲击矿压进行定位分析,证明了高能量级别的矿震大多数发生在工作面推进过程中覆岩关键层处于正"O-X"型破断位置。研究表明由关键层运动破断诱发冲击矿压前后,微震事件的时空演化规律、前兆信息显著。研究结果为利用岩层运动理论与微震监测相结合的方法预测冲击矿压奠定了基础。

急倾斜特厚煤层水平分段综放开采冲击矿压机理

我国急倾斜特厚煤层开采冲击矿压越发凸显,且灾害显现特殊。为了揭示急倾斜特厚煤层水平分段开采冲击矿压机理,建立覆岩力学模型,分析了覆岩运动、能量释放、煤层应力分布等规律;采用工作面液压支架工作阻力监测数据,分析了工作面支架工作阻力与动载系数分布规律;利用微震监测得到的矿震空间分布,分析了岩层运动和能量释放规律。研究结果表明:急倾斜特厚煤层水平分段开采,顶板倾向破断步距与煤层倾角呈非线性正相关关系,当煤层倾角大于60°时,破断步距出现陡增;覆岩下位坚硬岩层破断后在倾向上可暂时形成平衡结构,随着下位分段开采和放煤,平衡结构可发生破断旋转、断块跌落、结构挤压俯冲等3种类型的失稳冲击过程,对工作面形成动态冲击;在顶底板夹持作用下,工作面煤体靠近顶底板侧将形成非对称倾向支承压力分布,靠近顶板侧为封闭夹持状态,应力集中程度高,靠近底板侧为开放夹持状态,煤体易破坏卸压而处于塑性状态,在非对称支承压力作用下,工作面中部至顶板侧底煤受强烈剪切应力作用,且处于底板弹塑性交界区,易于失稳冲击;急倾斜特厚煤层水平分段综放开采,覆岩破断步距大,顶板破断和失稳冲击的瞬间释放能量强,扰动底煤高应力区诱发冲击矿压显现,揭示了急倾斜特厚煤层水平分段综放开采夹持冲击型冲击矿压机理。工作面液压支架工作阻力监测表明工作面中部至顶板侧动载系数最大达到3.25,表明覆岩形成了悬空式结构失稳;矿震监测结果表明工作面中部至靠近顶板侧底煤容易积聚弹性变形能,底板侧容易释放能量,顶板活动易形成动载扰动。研究结果得到了监测验证。

砂质黏土中不同深度爆炸自由场地冲击参数预计方法研究

根据爆炸地冲击试验的主要影响因素,运用量纲分析方法推导出爆炸地冲击参数的经验表达式。由砂质黏土中不同深度爆炸地冲击试验所得的地冲击应力峰值衰减曲线可以看出,装药比例埋深变化范围为-0.2～1.0 m/kg1/3,装药比例埋深对地冲击应力峰值的大小有较大影响,但应力峰值的衰减规律是一致的,即应力峰值经验公式的衰减指数大致相同,只是衰减系数随装药比例埋深的增加而增大。当装药比例埋深达到0.80 m/kg1/3以后,地冲击应力峰值衰减曲线之间的间距已经很小,这说明装药到此比例埋深以后装药比例埋深对爆炸地冲击参数的影响不再明显。在上述砂质黏土中不同深度爆炸自由场地冲击衰减规律的基础上,以"等效当量埋深系数"定义同一介质在相同比例距离上产生相同地冲击强度的2种不同深度爆炸装药量之间的关系,并运用此系数给出砂质黏土中不同深度爆炸自由场地冲击参数的预计方法,为地下工程抗爆研究与结构设计提供荷载依据。

煤岩“震-冲”动力系统冲击失稳致灾机制研究

为有效防治"震-冲"型冲击地压,根据矿震与冲击地压的关系建立煤岩"震-冲"动力系统模型。以此作为研究的基本模型,探讨"震-冲"型冲击地压的发生机制和判据。采用数值模拟方法研究强矿震在工作面附近产生的动力效应。提出"震-冲"型冲击地压的防治对策。结果表明,"震-冲"型冲击地压的发生机制是在矿震扰动下,煤岩应力瞬间进入塑性软化阶段,煤岩体积聚能量与破坏消耗能量的差能增大,在满足冲击破坏的刚度条件时,发生强烈的冲击地压事故。分别控制矿震震动源区、矿震震能传播路径和冲击源区,能大大减弱或消除发生"震-冲"型冲击地压的危险性。

空中强爆炸冲击波地面反射规律数值模拟研究

为准确预测空中强爆炸产生的冲击波载荷分布,基于欧拉坐标系建立了能够模拟具有高密度比、高压力比的强激波问题的二维多介质流体数值方法。结合网格自适应技术,对1 kt TNT当量的空中强爆炸在不同爆炸高度下的冲击波地面反射过程进行了数值模拟,并考虑了真实气体状态方程和空气随高度不均匀分布的影响。计算得到了地面上距爆心投影点大尺度范围内的反射超压和冲量等冲击波载荷分布,并给出了冲击波载荷随爆高的变化规律。

太阳米波和分米波Ⅱ型、Ⅲ型射电暴及其精细结构观测研究进展

太阳米波和分米波的射电观测是对太阳爆发过程中耀斑和日冕物质抛射现象研究的重要观测手段。米波和分米波的太阳射电暴以相干等离子体辐射为主导,表现出在时域和频域的多样性和复杂性。其中Ⅱ型射电暴是激波在日冕中运动引起电磁波辐射的结果。在Ⅱ型射电暴方面,首先对米波Ⅱ型射电暴的激波起源问题和米波Ⅱ型射电暴与行星际Ⅱ型射电暴的关系问题进行了讨论;其次,结合Lin-Forbes太阳爆发理论模型对Ⅱ型射电暴的开始时间和起始频率进行讨论:最后,对Ⅱ型射电暴信号中包含的两种射电精细结构,Herringbone结构(即鱼骨结构)和与激波相关的Ⅲ型射电暴也分别进行了讨论。Ⅲ型射电暴是高能电子束在日冕中运动产生电磁波辐射的结果。在Ⅲ型射电暴方面,首先介绍了利用Ⅲ型射电暴对日冕磁场位形和等离子体密度进行研究的具体方法;其次,对利用Ⅲ型射电暴测量日冕温度的最新理论进行介绍;最后,对Ⅲ型射电暴和Ⅱ型射电暴的时间关系、Ⅲ型射电暴和粒子加速以及Ⅲ型射电暴信号中包含的射电精细结构(例如斑马纹、纤维爆发及尖峰辐射)等问题进行讨论并介绍有关的最新研究进展。

巷道超前支护装备的防冲击控制策略研究

针对冲击地压会对巷道超前支护装备产生冲击等不利影响,提出一种基于改进型扰动观测器的控制方法。该方法在常规扰动观测器基础上,增加两个控制器,对理想模型控制器的输出进行动态补偿。使控制器不仅能够对频率较低的外界扰动进行抑制,同时能够对高频的测量噪声干扰进行消除。对其进行数值仿真与模拟实验,结果表明改进后控制方法能够有效降低冲击地压对超前支护装备产生的不利影响。