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101.
We consider a class of cure rate frailty models for multivariate failure time data with a survival fraction. This class is formulated through a transformation on the unknown population survival function. It incorporates random effects to account for the underlying correlation, and includes the mixture cure model and the proportional hazards cure model as two special cases. We develop efficient likelihood-based estimation and inference procedures. We show that the nonparametric maximum likelihood estimators for the parameters of these models are consistent and asymptotically normal, and that the limiting variances achieve the semiparametric efficiency bounds. Simulation studies demonstrate that the proposed methods perform well in finite samples. We provide an application of the proposed methods to the data of the age at onset of alcohol dependence, from the Collaborative Study on the Genetics of Alcoholism. 相似文献
102.
Networks of topologically linked minicircle polymers are found in diverse natural systems and are a subject of intense research
in nanotechonology. In a recent report the authors introduced a new theoretical model to study the effects of polymer density
on the formation and on the topological properties of minicircle networks. Three key topological characteristics were identified
in the formation and characterization of a network: the critical percolation density, the average saturation density and the
mean valence of the network. In this work we report how these characteristics change when an orientation bias is imposed on
the minicircles forming the network. We observe that such restrictions have significant effects on the key topological characteristics
of the network. In particular while the effects of restriction of the tilting angle can be predicted we find that those of
the azimuthal angle can have somewhat unexpected results. 相似文献
103.
By employing the dissociation energy and the equilibrium bond length for a diatomic molecule as explicit parameters, we generate improved expressions for the well-known Rosen-Morse, Manning-Rosen, Tietz, and Frost-Musulin potential energy functions. It is found that the well-known Tietz potential function that is conventionally defined in terms of five parameters [T. Tietz, J. Chem. Phys. 38, 3036 (1963)] actually only has four independent parameters. It is shown exactly that the Wei [Phys. Rev. A 42, 2524 (1990)] and the well-known Tietz potential functions are the same solvable empirical function. When the parameter h in the Tietz potential function has the values 0, +1, and -1, the Tietz potential becomes the standard Morse, Rosen-Morse, and Manning-Rosen potentials, respectively. 相似文献
104.
The thermodynamical behaviors of E′ centers in 8 quartz samples from core XJ33-2-1 recovered in the Zhujiang Mouth Basin were measured by electron spin resonance (ESR) technique. The E′ ESR spectral intensity of samples before any laboratory treatment was measured and expressed asI 1. The samples were then annealed at 300°C or 350°C for 60 min. The E′ ESR spectral intensity measured after this procedure is expressed asI 2. The ratios ofI 1, toI 2 for the samples increase with the sample depth (from 320 to 3972 m), showing that there is a correlation between this ratio and the storage temperature of samples. Therefore the ratio ofI 1/I 2 can be used as an ESR paleothermometer. Besides the temperature, we must take into account the period of time for which the samples have been buried since their deposition, because we find that the ratiosI 1/I 2 (from 0.293 to 0.941) are closely related to the sediment ages (from 1.5 to 27.5 Ma), with a correlation coefficient of 0.98 or 0.99 obtained by linear or exponential regression, respectively. This relation can be explained by the increase of E′ center concentration in quartz samples with the sedimentation age. 相似文献
105.
Chang Ying ZHU* Xiao Di KOU Zhi Qiang ZHANG Ying Cai YOU Diao Hu Xin Department of chemistry Nankai University Department of Micro-organism Nankai University Tianjin 《中国化学快报》2001,(7)
With the increasing use of one-off plastic products, the environmental pollution resulted from the plastic waste has become more and more serious. So many scientists have focused their attention on developing biodegradable polymers to substitute the traditional unbiodegradable polymers in the manufacture of disposable products. Thus the plastic waste can be treated by landfill or composting technique. It has been found that aliphatic polyesters possess better biodegradability compared with oth… 相似文献
106.
107.
Hanbin Liu Guangqiu Shen Xiaoqing Wang Jingzhi Wei Dezhong Shen 《Progress in Crystal Growth and Characterization of Materials》2000,40(1-4):235-241
The high viscosity in melts of the Li2O---B2O3 system makes it very difficult to grow large crystals of lithium triborate. The viscosity and IR characteristics of molten li2O---B2O3 system are reported in this paper. When the temperature increases the viscosity of li2O---B2O3 system decreases and follows an Arrhenius-type relationship. With an increasing 13203 ratio in Li2O---B2O3 melts, the viscosity rises gradually to a maximum with a composition Li2O: 3.513203 then it falls rapidly. In order to find active agents to reduce the viscosity, Na2O, NaCl, LiF, P205, M003, W03 etc oxides were added to Li2O---B2O3 samples respectively and investigated using the orthogonal method. The experimental results show that the addition of acidic oxides can significantly decrease the viscosity in the Li2O---B2O3 system. For Li2O: 4.513203, an ideal additive agent is 20wt% Li2O:: 2MoO3. Near the composition for crystal growth, the percentage reduction of viscosity is 62.2%. The IR spectra of Li2O---B2O3 system revealed that the BO4−/NO3− ratio is reduced in the melt using Li2O: 2MoO3 as an additive. It is proposed that the M003 reduced the concentration of bridging oxygen atoms of BO4−. The change of structure explains the decline in the viscosity. In the crystal structures of lithium triborate, the matrix spaces are so small that larger other cations than Li+ are very difficult to enter the crystal matrix. So the use of additive agents to reduce the viscosity is a possible method if no new phase appears. 相似文献
108.
在对不同晶相比硅薄膜的实验研究的基础上,利用有效介质理论估算了这种两相材料的光吸 收系数、迁移率寿命乘积及带隙宽度等参量,计算机模拟了不同结晶比硅薄膜电池的伏安特 性及光谱响应;结果为随着本征层微晶成分的增多,电池的开路电压逐渐减小,短路电流逐 渐增大,本征层的最佳厚度逐渐增大,填充因子有降低的趋势,电池的效率随晶相比的增大 而减小. 电池的光谱响应曲线表明,随晶相比的增大电池的长波响应明显提高. 根据这些模 拟结果,分析讨论了在考虑Lambertian背反射的情况下,非晶/微晶叠层电池的底电池采用 晶相比为40%—50%的两相硅薄膜材料做本征层是最佳选择.
关键词:
两相硅薄膜
太阳能电池
计算机模拟 相似文献
109.
首先制备了不同周期的染料掺杂全息液晶/聚合物光栅并进行激光抽运实验, 得到了激光器的调谐曲线,确定了激光器在574 nm到685 nm的谱带里均可以实现激光输出, 即激光器具有110 nm左右的可调谐范围. 之后, 通过温控仪控制样品的温度, 对周期为610 nm的染料掺杂全息液晶/聚合物光栅进行激光抽运, 探测不同温度下的输出激光光谱, 观察到随着温度由20℃升高到65℃, 激光器的中心波长由627.9 nm减小到623 nm, 产生了4.9 nm的波长蓝移. 相似文献
110.