Black hole entropy,the black hole information paradox,and time travel paradoxes from a new perspective

ABSTRACT

Relatively simple but apparently novel ways are proposed for viewing three related subjects: black hole entropy, the black hole information paradox, and time travel paradoxes. (1) Gibbons and Hawking have completely explained the origin of the entropy of all black holes, including physical black holes – nonextremal and in 3-dimensional space – if one can identify their Euclidean path integral with a true thermodynamic partition function (ultimately based on microstates). An example is provided of a theory containing this feature. (2) There is unitary quantum evolution with no loss of information if the detection of Hawking radiation is regarded as a measurement process within the Everett interpretation of quantum mechanics. (3) The paradoxes of time travel evaporate when exposed to the light of quantum physics (again within the Everett interpretation), with quantum fields properly described by a path integral over a topologically nontrivial but smooth manifold.     

矿井内因火灾的安全评价研究--基于熵值法和突变理论

针对矿井内因火灾的突发性、不确定性和高危害性等特点,提出熵值法和突变理论相结合的矿井内因火灾安全评价方法。选取人、物、环境和管理4个方面的因素建立了4级共20个评价指标的矿井内因火灾安全评价指标体系,运用熵值法判断各个指标的权重,利用突变级数法计算突变级数值,避免了单一熵值法主观人为赋权的弊端。以陕西省红石岩煤矿为例,运用该评价方法对其进行了内因火灾安全评价,其评价结果符合该矿井的安全状况,验证了该评价方法的可行性、实用性。     

基于熵权TOPSIS的工程咨询机构BIM技术应用能力评价

构建工程咨询机构BIM技术应用能力评价的指标体系,提出改进的熵权TOPSIS评价模型,以4个典型的工程咨询单位为例,进行BIM技术运用能力评价。研究表明,BIM行业的整体水平已经有了明显的提升,但是区域间的发展还存在一定差距。     

综合改进奇异谱分解和奇异值分解的齿轮故障特征提取方法

针对齿轮故障特征微弱，在强背景噪声下难以有效提取的问题，提出了一种改进奇异谱分解（ISSD）结合奇异值分解（SVD）的齿轮故障特征提取方法。针对奇异谱分解（SSD）算法中模态参数需凭经验选取的缺陷，基于散布熵优化算法对SSD算法进行了改进，在得到既定的一组奇异谱分量的基础上，根据峭度值最大准则筛选出了最佳奇异谱分量并进行了SVD处理，采用奇异值能量标准谱自适应地确定了信号重构阶数以还原信号和提高降噪效果。最后对信号进行包络解调以提取齿轮故障特征，将所提方法运用到仿真信号和齿轮实测信号中，并同传统包络谱、SSD包络谱以及经验模态分解结合SVD(EMD-SVD)方法进行了对比分析，结果表明，所提方法的降噪和特征提取效果更佳，能够更加有效地实现齿轮故障的判别。     

考虑CEEMDAN样本熵和SVR的短期风速预测

为降低由于风速信号的非线性和非平稳性带来的风速预测难度，提高短期风速预测的准确性，提出一种考虑样本熵的组合分解模式和支持向量回归（SVR）相结合的预测模型。首先采用自适应噪声的完全集合经验模态分解（CEEMDAN）方法分解风速历史数据，并计算各模态分量的样本熵；然后采用变分模态分解（VMD）方法对样本熵最大的模态分量进行二次分解，充分削弱风速分量的非平稳性；接着对分解得到所有模态分量分别建立SVR预测模型；最后将各分量的预测值求和完成最终风速预测。实例分析表明，所提模型对比其他模型的预测误差最小，预测精度最高，可有效预测短期风速。     

考虑不确定性的大坝监测信息异常诊断方法及应用

大坝监测资料分析是一个充满不确定性的复杂非线性问题,常规的分析方法较少考虑监测信息中的不确定性问题,导致分析结果的合理性存疑。因此,基于信息熵理论的重要指标——近似熵研究大坝监测信息中的不确定性问题,利用实际监测数据选取近似熵算法的关键参数,进而评估大坝的运行状态。通过分析混凝土坝坝顶水平位移和土石坝测压管水位,发现近似熵算法能在若干监测信息不确定性条件下较有效地识别大坝监测数据的异常。     

涡流空气分级机熵产与分级性能分析

利用热力学第二定律中的熵产理论对涡流空气分级机各不可逆因素引起的熵产进行分析，通过粉料分级试验对其分级性能进行验证，获得了黏性熵产、湍流熵产和壁面熵产分布特点及操作参数对熵产和分级精度的影响规律。熵产分析结果表明，涡流空气分级机内湍流熵产和壁面熵产占总熵产的比例高达56.41%和43.11%，湍流熵产主要产生于转笼叶片间和转笼内部，进风口和细粉出口壁面剪切引起较大壁面熵产；此外，转笼转速和进口风速变化分别仅对转笼区域和切向进风口区域内气流运动熵产影响较大，进口风速-转笼转速处于8.6m/s、 800r/min和18m/s、1200r/min操作工况附近时，涡流空气分级机内总熵产/总能变化率较小，分级流场稳定性较高，对粗、细颗粒分离有利，该工况下分级机的粉料分级试验效果较好，说明熵产理论可用于涡流分级机内流动分析及其操作参数的优化匹配。     

Synthesis and characterization of hydrogenated novel AlCrFeMnNiW high entropy alloy

A novel high entropy alloy (HEA) i.e. AlCrFeMnNiW is synthesized via high-energy planetary ball milling with an average crystallite size of 10.37 nm. The morphology study of hydrogenated and dehydrogenated HEA is carried out through Scanning Electron Microscope (SEM). The HEA is charged with hydrogen using inhouse Sievert's Apparatus which results to be maximum hydrogen storage capacity of 0.615 wt% at atmospheric pressure and temperature. The dehydrogenation of the sample is performed through thermogravimetry (TG) at different scanning rate. The crystalline structure (i.e. lattice parameters) and chemical composition of HEA is studied using X-Ray Diffraction (XRD) and Energy Dispersive X-Ray analysis (EDX) respectively. The unit cell volume of as-prepared alloy is estimated as 0.03131 nm³ whereas the average crystallite size as 10.37 nm. It is observed that the unit cell volume is increased by 0.67% and crystallite size decreased by 10.8% upon hydrogenation whereas it is then decreased by 0.2% and increased by 6.7% respectively upon dehydrogenation. Activation energy during hydrogen desorption is found to be −8.161 kJ/mol. The enthalpy and entropy of the mixing are estimated to be −2.645 kJ/mol and 1.793 R J/mol K.     

基于改进交叉熵算法的电力系统随机生产模拟

蒙特卡洛模拟的计算效率与系统的可靠性密切相关，在其用于高可靠性系统的随机模拟时存在计算效率偏低的问题。为此，提出了一种基于多层交叉熵与对偶变数抽样技术相结合的随机模拟算法。首先使用多层交叉熵构造零方差概率密度函数的近似函数，提高小概率失效事件的抽取概率；其次基于已构造的近似概率函数，采用对偶变数抽样法进行抽样，进一步提高抽样的收敛速度。以IEEE RTS修改系统为例进行了算例分析，算例结果验证了所提出的基于改进交叉熵的电力系统随机生产模拟算法的有效性。     

Influence of Bridgman solidification on microstructures and magnetic behaviors of a non-equiatomic FeCoNiAlSi high-entropy alloy

The non-equiatomic FeCoNiAlSi alloy is prepared by the Bridgman solidification (BS) technique at different withdrawal velocities (V = 30, 100, and 200 μm/s). Various characterization techniques have been used to study the microstructure and crystal orientation. The morphological evolutions accompanying the crystal growth of the alloy prepared at different withdrawal velocities are nearly the same, from equiaxed grains to columnar crystals. The transition of coercivity is closely related to the local microstructure, while the saturation magnetization changes little at different sites. The coercivity can be significantly reduced from the equiaxed grain area to the columnar crystal area when the applied magnetic field direction is parallel to the crystal growth direction, no matter what is the withdrawal velocity. In addition, the alloy possesses magnetic anisotropy when the applied magnetic field is in different directions.