Gamma自适应滤波器及其最小均方误差训练方法

本文提出了一种新的自适应滤波器－Ｇａｍｍａ滤波器及其基于最小均方程误差准则的训练方法，首先建立了最小均方误差准则下Ｇａｍｍａ滤波器的Ｗｉｅｎｅｒ－Ｈｏｐｆ方程，然后分别提出了３种训练算法：（１）新斯－牛顿算法；（２）确定性梯度算法；（３）ＬＭＳ算法。最后给出Ｇａｍｍａ滤波器在随机信号预测中的应用和仿真结果。     

Gamma（TiAl）Alloy Technology2012在北京举行

2012年6月5～9日，“Gamma（TiAl）Alloy Technology2012”在北京稻香湖景酒店隆重举行。此次会议由北京科技大学林均品教授和国际TiAl合金界权威人士Y．W．Kim博士共同组织，北京科技大学新金属材料国家重点实验室承办。会议主要围绕Gamma（TiAl）金属间化合物合金最新研究的重大进展、工艺技术突破，分享和交流近些年积累的知识基础和经验，研究、论讨目前该合金工业应用中出现的问题，提出优化的解决方案，把握当今Gamma（TiAl）合金的发展方向，是该领域最高规格的学术会议，同时该会议也是首次在中国举行。     

A Metallic Magnetic Calorimeter for Hard X-Ray and Gamma Ray Spectrometry

The CEA/LNHB is responsible for the determination and publication of atomic and nuclear data such as X-ray and gamma ray emission probabilities. In order to reduce uncertainties on the determination of these data, a high energy resolution associated with a good intrinsic detection efficiency is required. Hence taking into account these two aspects, we are developing cryogenic detectors, especially metallic magnetic calorimeters (MMCs) for photon spectrometry from few keV up to 200 keV. A MMC using a meander pick-up coil made of niobium thin films has been optimized. The gold absorber (diameter: 1.1 mm, thickness: 335 μm) has an intrinsic detection efficiency larger than 70% for photons from few keV up to 100 keV. From an energy spectrum obtained with a ¹³³Ba multi-gamma source, we have characterized this first detector. The energy resolution is 320 eV and 560 eV respectively at 30 keV and 357 keV. Possible improvements of the performance of the detector are discussed.     

基于Gamma退化过程的直升机主减速器行星架剩余寿命预测模型

鉴于Gamma过程具有平稳、独立增量等退化建模所需的属性,将其用于描述设备退化过程,并针对缺乏故障数据时难以进行剩余寿命预测的问题,利用设备运行中采集的表征其退化状态的大量间接状态参数和少量直接状态参数,建立了基于Gamma退化过程的剩余寿命预测模型;针对经验最大化算法中似然函数难以解析求解的问题,引入粒子滤波算法实现了模型参数估计;最后将模型应用于直升机主减速器行星架的剩余寿命预测,得到了不同时刻的预测结果及95%置信区间,验证了预测模型的有效性和准确性。     

q-对称熵损失函数下Gamma分布的尺度参数的估计

本文在对称熵损失函数的基础上定义了q-对称熵损失函数,并用参数估计的方法研究了在q-对称熵损失函数下Gamma分布的尺度参数的最小风险同变估计(MRE)、贝叶斯(Bayes)估计、最小最大(Mininax)估计等。我们还对这些估计量的可容许性和不可容许性进行了讨论,最后分别对指数分布和Gamma分布在两种损失函数下的估计结果进行了数值比较。     

Calculations of the Passage of Gamma‐Quanta through a Polymer Radiation‐Protective Composite

We have investigated the radiationprotective characteristics of a thermoplastic polystyrene composite material filled with a highdispersion modified lead oxide as well as the dependences of the energy (flux) buildup and transmission factors and albedos on the energy and protectiveshield thickness. Calculations of the integral characteristics of the radiationprotective properties of materials have been done.     

Effects of Microstructure on the Tensile, Fracture Toughness and Fatigue Behaviour of Gamma Titanium Aluminides

The effects of microstructure on the deformation and fracture behaviour of two-phase TiAl alloys were investjgated under monotonic and cyclical loading conditions, over a range of temperatu res.The tensile behaviour is analyzed for deformation temperatures between RT and 950℃, Fracture resistance behaviour and toughening mechanisms at RT and 800℃ are analyzed. and the inverse relationship botween ductility and toughness is explained using the crack initiation toughness. The preliminary results of load-controlled fatigue behaviour at 800℃ are interpreted using the tensile behaviour because deformation structure and fracture modes are similar under these two loading conditions     

Assessing the actual Gamma process quality – a curve-fitting approach for modifying the non-normal flexible index

Process capability indices (PCIs) have been widely adopted for quality assurance activities. By analysing PCIs, a production department can trace and improve a poor process to enhance product quality level and satisfy customer requirements. Among these indices, C_pk remains the most prevalent for facilitating managerial decisions because it can provide bounds on the process yield for normally distributed processes. However, processes are often non-normal in practice, and C_pk may quite likely misrepresent the actual product quality. Hence, the flexible index C_jkp, which considers possible differences in the variability above and below the target value, has been developed for practical use. However, C_jkp continues to suffer from serious bias in assessing actual capability, especially when the process distribution is highly skewed. In this paper, we modify C_jkp for assessing the actual process quality of a Gamma process. A correction factor is obtained by the curve-fitting method. The results show that our proposed method can significantly reduce the bias for calculation of actual nonconformities. Moreover, we introduce a sample estimator for our modified index. The ratio of this estimator’s average value and the modified index is approximately 1. This implies that our proposed estimator can provide an appropriate estimation for assessing the actual Gamma process quality.     

Effect of Gamma Irradiation on the Piezoelectric Properties of K2Sr4Nb10O30–K6Li4Nb10O30 Solid Solutions

The effect of gamma irradiation on the dielectric ( ₃₃/₀, tan) and piezoelectric (d ₃₁, g ₃₁, K _p, Q _m) properties of ₂Sr₄Nb₁₀O₃₀–K₆Li₄Nb₁₀O₃₀ solid solutions (tetragonal tungsten bronze structure) was studied as a function of K₆Li₄Nb₁₀O₃₀ content. The results demonstrate that increasing the gamma dose to 9 × 10⁵ Gy reduces ₃₃/₀ and tan. With increasing Li⁺ content (filling of triangular channels), d ₃₁, g ₃₁, K _p, and Q _m increase. The results are interpreted in terms of the generation of stable defects and effective redistribution of the energy of gamma radiation over the ceramic sample.     

Effect of Gamma Irradiation on the Dielectric Properties of (CH3)2NH2Ga(SO4)2 · 6H2O Crystals in the Vicinity of the Ferroelectric Transition

The effect of gamma irradiation on the dielectric permittivity and loss tangent of (CH₃)₂NH₂Ga(SO₄)₂ · 6H₂O crystals was studied near the ferroelectric transition at different frequencies. Irradiation was found to sharply reduce and tan at gamma doses below 5 × 10⁷ R. At higher doses, and tan level off. With increasing gamma dose, the ferroelectric transition shifts to lower temperatures, irrespective of frequency.