塔机主臂杆三维裂纹应力强度因子的计算

采用三维裂纹奇异单元列式方法对含纵向闭合裂纹塔机主臂杆接头部位进行了应力分析和应力强度因子的计算,分析了焊接残余应力对塔机主臂杆母材强度、环向拉应力和应力强度因子的影响。     

《二泉映月》与残缺美

本文就残缺美这样一个久谈不衰的话题,结合《二泉映月》作者的身世及生理残缺,并结合作者当时所处的社会背景,对《二泉映月》的独特演奏手法进行分析与研究。     

A flexible multi-stage design for phase II oncology trials

Phase II trials evaluate whether a new drug or a new therapy is worth further pursuing or certain treatments are feasible or not. A typical phase II is a single arm (open label) trial with a binary clinical endpoint (response to therapy). Although many oncology Phase II clinical trials are designed with a two-stage procedure, multi-stage design for phase II cancer clinical trials are now feasible due to increased capability of data capture. Such design adjusts for multiple analyses and variations in analysis time, and provides greater flexibility such as minimizing the number of patients treated on an ineffective therapy and identifying the minimum number of patients needed to evaluate whether the trial would warrant further development. In most of the NIH sponsored studies, the early stopping rule is determined so that the number of patients treated on an ineffective therapy is minimized. In pharmaceutical trials, it is also of importance to know as early as possible if the trial is highly promising and what is the likelihood the early conclusion can sustain. Although various methods are available to address these issues, practitioners often use disparate methods for addressing different issues and do not realize a single unified method exists. This article shows how to utilize a unified approach via a fully sequential procedure, the sequential conditional probability ratio test, to address the multiple needs of a phase II trial. We show the fully sequential program can be used to derive an optimized efficient multi-stage design for either a low activity or a high activity, to identify the minimum number of patients required to assess whether a new drug warrants further study and to adjust for unplanned interim analyses. In addition, we calculate a probability of discordance that the statistical test will conclude otherwise should the trial continue to the planned end that is usually at the sample size of a fixed sample design. This probability can be used to aid in decision making in a drug development program. All computations are based on exact binomial distribution.     

结构件的高精度抗弯刚度测试方法研究

通过挂质量块来给被测构件施加弯矩测量相应变形是目前结构件抗弯刚度测试的主要方法,针对其测量精度不高、无法实现自动测试等问题, 提出了一种高精度抗弯刚度测试方法。基于抗弯刚度计算理论, 建立了相应的数学计算模型。利用计算转角变形的方法,解决作用力臂精确计算问题。结果表明,相对传统测试方案,不仅能提高被测件的抗弯刚度测试精度,而且实验过程无需人工参与,实现了自动化测试的要求。     

A convenient formula for sample size calculations in clinical trials with multiple co-primary continuous endpoints

The clinical efficacy of a new treatment may often be better evaluated by two or more co-primary endpoints. Recently, in pharmaceutical drug development, there has been increasing discussion regarding establishing statistically significant favorable results on more than one endpoint in comparisons between treatments, which is referred to as a problem of multiple co-primary endpoints. Several methods have been proposed for calculating the sample size required to design a trial with multiple co-primary correlated endpoints. However, because these methods require users to have considerable mathematical sophistication and knowledge of programming techniques, their application and spread may be restricted in practice. To improve the convenience of these methods, in this paper, we provide a useful formula with accompanying numerical tables for sample size calculations to design clinical trials with two treatments, where the efficacy of a new treatment is demonstrated on continuous co-primary endpoints. In addition, we provide some examples to illustrate the sample size calculations made using the formula. Using the formula and the tables, which can be read according to the patterns of correlations and effect size ratios expected in multiple co-primary endpoints, makes it convenient to evaluate the required sample size promptly.     

Data‐driven treatment selection for seamless phase II/III trials incorporating early‐outcome data

Seamless phase II/III clinical trials are conducted in two stages with treatment selection at the first stage. In the first stage, patients are randomized to a control or one of k > 1 experimental treatments. At the end of this stage, interim data are analysed, and a decision is made concerning which experimental treatment should continue to the second stage. If the primary endpoint is observable only after some period of follow‐up, at the interim analysis data may be available on some early outcome on a larger number of patients than those for whom the primary endpoint is available. These early endpoint data can thus be used for treatment selection. For two previously proposed approaches, the power has been shown to be greater for one or other method depending on the true treatment effects and correlations. We propose a new approach that builds on the previously proposed approaches and uses data available at the interim analysis to estimate these parameters and then, on the basis of these estimates, chooses the treatment selection method with the highest probability of correctly selecting the most effective treatment. This method is shown to perform well compared with the two previously described methods for a wide range of true parameter values. In most cases, the performance of the new method is either similar to or, in some cases, better than either of the two previously proposed methods. © 2014 The Authors. Pharmaceutical Statistics published by John Wiley & Sons Ltd.     

Some practical considerations in three‐arm non‐inferiority trial design

Non‐inferiority trials aim to demonstrate whether an experimental therapy is not unacceptably worse than an active reference therapy already in use. When applicable, a three‐arm non‐inferiority trial, including an experiment therapy, an active reference therapy, and a placebo, is often recommended to assess assay sensitivity and internal validity of a trial. In this paper, we share some practical considerations based on our experience from a phase III three‐arm non‐inferiority trial. First, we discuss the determination of the total sample size and its optimal allocation based on the overall power of the non‐inferiority testing procedure and provide ready‐to‐use R code for implementation. Second, we consider the non‐inferiority goal of ‘capturing all possibilities’ and show that it naturally corresponds to a simple two‐step testing procedure. Finally, using this two‐step non‐inferiority testing procedure as an example, we compare extensively commonly used frequentist p ‐value methods with the Bayesian posterior probability approach. Copyright © 2016 John Wiley & Sons, Ltd.     

Do single‐arm trials have a role in drug development plans incorporating randomised trials?

Often, single‐arm trials are used in phase II to gather the first evidence of an oncological drug's efficacy, with drug activity determined through tumour response using the RECIST criterion. Provided the null hypothesis of ‘insufficient drug activity’ is rejected, the next step could be a randomised two‐arm trial. However, single‐arm trials may provide a biased treatment effect because of patient selection, and thus, this development plan may not be an efficient use of resources. Therefore, we compare the performance of development plans consisting of single‐arm trials followed by randomised two‐arm trials with stand‐alone single‐stage or group sequential randomised two‐arm trials. Through this, we are able to investigate the utility of single‐arm trials and determine the most efficient drug development plans, setting our work in the context of a published single‐arm non‐small‐cell lung cancer trial. Reference priors, reflecting the opinions of ‘sceptical’ and ‘enthusiastic’ investigators, are used to quantify and guide the suitability of single‐arm trials in this setting. We observe that the explored development plans incorporating single‐arm trials are often non‐optimal. Moreover, even the most pessimistic reference priors have a considerable probability in favour of alternative plans. Analysis suggests expected sample size savings of up to 25% could have been made, and the issues associated with single‐arm trials avoided, for the non‐small‐cell lung cancer treatment through direct progression to a group sequential randomised two‐arm trial. Careful consideration should thus be given to the use of single‐arm trials in oncological drug development when a randomised trial will follow. Copyright © 2015 The Authors. Pharmaceutical Statistics published by JohnWiley & Sons Ltd.     

固定电机驱动的平面关节型机器人无参数运动学标定

针对传统平面关节型机器人（简称SCARA）运动臂质量大的缺点,设计一种固定电机驱动的SCARA。为提高其 精度用无参数化标定的方法进行运动学标定,根据D-H方法,在空间坐标转换的基础上建立了该SCARA的数学模型, 得到杆件间相对位置关系;通过外部测量设备测出末端执行器的位姿,利用运动学正逆解解出实际位姿与理论位姿之间 驱动输入的差值,补偿到理论的输入中,得到补偿后的动平台位姿。通过计算机仿真表明该标定方法能极大提高末端执 行器的位置精度,证明了无参数化标定方法的有效性和可靠性。     

Fit for purpose: issues from practice placements,practice teaching and the assessment of students' practice

This paper explores a number of significant issues regarding the delivery of practice based learning for qualifying social workers, in the context of plans for the new social work degree. We also discuss four particular issues: 1. the definition and measurement of ‘good enough’ practice;

2. the determination of students' suitability for social work;

3. the role of practice teachers in responding to sensitive information and students facing personal crises; and

4. specialist and ‘long‐arm’ practice teaching.

In doing so, we draw on both our own direct experience and on discussions between over 70 practice teachers, tutors and placement co‐ordinators attending a Mid‐Yorkshire Social Work Education and Training Planning Group (MYSWETPG) conference hosted by Bradford College in March 2001.

We conclude that, given the current difficulties in the field of qualifying training and education for social workers, any significant improvements following from the new degree will remain dependent on the provision of adequate funding for practice learning, in general, and for the training, structured support and affirmation of practice teachers, in particular.