基于NURBS方法的转子表面造型技术

采用双三次NURBS方法对某型号转子进行几何造型,对造型过程中出现的曲面延伸、求交和裁剪等问题进行了研究.根据叶片的形状特征,以曲线的几何形式为基础,提出了一种简单实用的曲线曲面延伸方法,实现了切矢量连续的叶片型面的延伸.对于两相交面分别为自由曲面和解析曲面的求交问题,提出了一种简化的跟踪算法,实现了转子叶片型面和圆台面的准确求交和裁剪,从而实现转子精确的几何造型.     

完全检查下预防维修模型建立及案例分析

为了解决维修间隔期确定的难题,建立了维修间隔期和总停机时间之间关系的目标函数,以及时间延迟维修模型.根据故障记录数据和预防维修活动的检查数据,采用最大似然法估计有关缺陷发生率和时间延迟分布等参数.在所建立目标函数和估计参数的基础上,计算出最优的维修间隔期.     

The Jackknife estimate of covariance of two Kaplan–Meier integrals with covariables

In this paper the Jackknife estimate of covariance of two Kaplan–Meier integrals with covariates is introduced. Its strong consistency is established under mild conditions. Several applications of the estimator are discussed.     

Expanded renal transplantation: a competing risk model approach

Multi-state models (MSMs) are useful to analyze survival data when, besides the event of main interest, one or more intermediate states of the individual are identified. These models take the several existing states and the possible transitions among them into account. At the same time, covariate effects on each transition intensity may be investigated separately and, therefore, MSMs are more flexible than the standard Cox proportional hazards model. In this work, we use MSMs to investigate the impact of the quality of a transplanted kidney for a group of patients at the Hospital Universitario Central de Asturias. Specifically, we use an illness-death model to study the evolution of patients with kidney disease who received a renal transplant after a dialysis period. The intermediate state is defined as the failure of the received organ, while the terminating state is the death of the patient. In order to increase the potential number of organs available for transplant, the standards of quality for the transplanted kidneys were relaxed (the new criteria are labeled expanded criteria), and these ‘expanded kidneys’ were transplanted in appropriate candidates (older patients, with higher prevalence of diabetes mellitus). Results suggest that the expanded kidneys have a minor effect on survival, while both the kidney mortality and the risk of death increase with the patient's age and the serum creatinine and serum hemoglobin levels.     

Small Area Estimation Using Estimated Population Level Auxiliary Data

Unit level linear mixed models are often used in small area estimation (SAE), and the empirical best linear unbiased prediction (EBLUP) is widely used for the estimation of small area means under such models. However, EBLUP requires population level auxiliary data, atleast area specific aggregated values. Sometimes population level auxiliary data is either not available or not consistent with the survey data. We describe a SAE method that uses estimated population auxiliary information. Empirical results show that proposed method for SAE produces an efficient set of small area estimates.     

Ethnicity as a risk indicator for musculoskeletal disease, long consultation times and care utilization A prospective visitor study of 438 consecutive adult consultations of a primary health care centre

This article shows the influence of ethnicity (people born outside Sweden and in Sweden) and social class (socioeconomic class) on the distribution of diagnoses, consultation time and health care utilization in primary health care controlled for sex, age, marital status and educational level. The study was designed as a prospective primary health care utilization study during 7 consecutive weeks. Of a total of 439 adults who lived in the residential area, 290 were born in Sweden and 149 were born elsewhere. The data were analysed unmatched with logistic regression and Poisson regression in main effect models. People born outside Sweden received significantly more diagnoses per consultation than people born in Sweden. The strongest independent risk indicator for musculoskeletal disease was being born outside Sweden, with an estimated odds ratio (OR) of 5.01, 95% confidence interval (CI) = 2.70–8.72. Age over 44 was associated with increased odds for musculoskeletal disease. Respiratory disease, as an indicator of less serious disease, were significantly less common among people born outside Sweden (OR = 0.53, 95% CI = 0.33–0.87). Being born outside Sweden was a risk indicator for consultations longer than 30 minutes (OR = 3.03, 95% CI=1.18–7.43). There were no differences between people born in Sweden and those born elsewhere in health and utilization. Social class was not associated with any of the dependent variables.     

Kernel Density Estimation with Generalized Binning

We propose kernel density estimators based on prebinned data. We use generalized binning schemes based on the quantiles points of a certain auxiliary distribution function. Therein the uniform distribution corresponds to usual binning. The statistical accuracy of the resulting kernel estimators is studied, i.e. we derive mean squared error results for the closeness of these estimators to both the true function and the kernel estimator based on the original data set. Our results show the influence of the choice of the auxiliary density on the binned kernel estimators and they reveal that non-uniform binning can be worthwhile.     

The Problem of Gender Identification in Conditions of Social Instability

Data from the Soviet period is compared with small-scale recent survey research in Chechnya. The author discusses legacy problems of female employment and empowerment in a society emphasizing patriarchal and Muslim values. She argues that outward appearances of religiosity, such as headscarves, do not necessarily equal inner faith. Distortions of gender identifications and social relationships are viewed as magnified in conditions of warfare and social upheaval.