Comparison of a genetic algorithm and simulated annealing in an application to statistical image reconstruction

Genetic algorithms (GAs) are adaptive search techniques designed to find near-optimal solutions of large scale optimization problems with multiple local maxima. Standard versions of the GA are defined for objective functions which depend on a vector of binary variables. The problem of finding the maximum a posteriori (MAP) estimate of a binary image in Bayesian image analysis appears to be well suited to a GA as images have a natural binary representation and the posterior image probability is a multi-modal objective function. We use the numerical optimization problem posed in MAP image estimation as a test-bed on which to compare GAs with simulated annealing (SA), another all-purpose global optimization method. Our conclusions are that the GAs we have applied perform poorly, even after adaptation to this problem. This is somewhat unexpected, given the widespread claims of GAs' effectiveness, but it is in keeping with work by Jennison and Sheehan (1995) which suggests that GAs are not adept at handling problems involving a great many variables of roughly equal influence.We reach more positive conclusions concerning the use of the GA's crossover operation in recombining near-optimal solutions obtained by other methods. We propose a hybrid algorithm in which crossover is used to combine subsections of image reconstructions obtained using SA and we show that this algorithm is more effective and efficient than SA or a GA individually.     

平武山区生态特点及对杂交玉米的要求

分析了地处盆周山区的平武县的地貌、土地、土壤、气候的概况及特点，讨论了山区特殊生态环境条件对玉米生长发育及产量的影响，提出了适应山区环境条件的玉米杂交种应具有的特点。     

杂交水稻新组合江优151高产栽培技术模式

研究表明杂交水稻新组合江优151高产栽培技术模式是：采用水田地膜拱棚覆盖育秧方法，培育矮健多蘖壮秧；栽适龄秧，秧龄不超过45d；栽宽窄行穴植双株，保证基本苗达到180万亩／hm2；施足肥，其施肥量氮氮肥150～172．5kg／hm2，P2O5肥90．0kg／hm2，K2O肥105．0kg／hm2；施肥方法宜采用重底稳中攻穗法，即底肥占60％，苗肥占20％，穗肥占20％。通过示范典型田块的产量结构调查分析，指出增穗、增粒是江优151高产栽培的主攻方向。     

不同不育系所配杂交水稻组合在单、双株寄栽条件下的秧苗素质分析

通过对不同不育系所配杂交水稻组合在单、双株寄裁条件下的秧苗素质研究，结果表明：Ⅱ-32A所配组合的总根数、白根数、白根率和分蘖性能等指标均较优，特别是白根率高，根系活力和分案能力强，但繁茂性稍差。冈46A所配组合其突出特点是叶面积和苗高占优势，繁茂性好，秧田各时期的于物质积累能力较强，但根系活力稍差，白根率较低。二汕A所配组合的特点是在发根力和根系活力上稍占优势，白报率较高。D汕A所配组合无突出特点。寄款方式对秧苗素质影响很大，主要表现在前期和后期的差异大。前期双株秧稍占优势，但在后期刊单株放的优势很明显。因此，在土壤肥沃，水源充足的地方，为培育壮秧，增加秧龄弹性，应提倡单株寄栽。     

平坝区D优63高产栽培综合农艺措施研究

采用五元二次正交旋转组合设计方法,在影响杂交水稻 D 优63产量的诸因素中,选择了五项主要因素,建立五元二次回归模型,在此基础上经电子计算机模拟、筛选,提出 D 优63在平坝区种植条件下,对产量影响较大的因素是秧龄和基本苗,其次是施磷量和施钾量。同时明确了不同产量水平的农艺措施配套方案。     

杂化膜驻极体PVDF／SiO_2的电荷输运特性

通过常温和高温下对ＰＶＤＦ／ＳｉＯ＿２，（ＰＶＤＦ－聚偏氯乙烯）膜的恒压负电晕充电，系统地研究了充电注入的负表面电荷受激脱阱后在电荷层自身内场作用下的输运规律。确定了ＴＳＤ（ＴｈｅｒｍａｌｌｙＳｔｉｍｕｌａｒｅｄＤｉｓｃｈａｒｇｅ）的偶极峰和空间电荷峰对电荷稳定性的明显区另。实验结果表明，高温负电晕充电对该材料的驻极性能有明显的改善。     

A Review of Recent Advances in Benchmark Dose Methodology

In this review, recent methodological developments for the benchmark dose (BMD) methodology are summarized. Specifically, we introduce the advances for the main steps in BMD derivation: selecting the procedure for defining a BMD from a predefined benchmark response (BMR), setting a BMR, selecting a dose–response model, and estimating the corresponding BMD lower limit (BMDL). Although the last decade has shown major progress in the development of BMD methodology, there is still room for improvement. Remaining challenges are the implementation of new statistical methods in user‐friendly software and the lack of consensus about how to derive the BMDL.     

Inference on proportional hazard rate model parameter under Type-I progressively hybrid censoring scheme

ABSTRACT

In this paper, under Type-I progressive hybrid censoring sample, we obtain maximum likelihood estimator of unknown parameter when the parent distribution belongs to proportional hazard rate family. We derive the conditional probability density function of the maximum likelihood estimator using moment-generating function technique. The exact confidence interval is obtained and compared by conducting a Monte Carlo simulation study for burr Type XII distribution. Finally, we obtain the Bayes and posterior regret gamma minimax estimates of the parameter under a precautionary loss function with precautionary index k = 2 and compare their behavior via a Monte Carlo simulation study.     

Inference on progressive-stress model for the exponentiated exponential distribution under type-II progressive hybrid censoring

In this paper, progressive-stress accelerated life tests are applied when the lifetime of a product under design stress follows the exponentiated distribution [G(x)]^α. The baseline distribution, G(x), follows a general class of distributions which includes, among others, Weibull, compound Weibull, power function, Pareto, Gompertz, compound Gompertz, normal and logistic distributions. The scale parameter of G(x) satisfies the inverse power law and the cumulative exposure model holds for the effect of changing stress. A special case for an exponentiated exponential distribution has been discussed. Using type-II progressive hybrid censoring and MCMC algorithm, Bayes estimates of the unknown parameters based on symmetric and asymmetric loss functions are obtained and compared with the maximum likelihood estimates. Normal approximation and bootstrap confidence intervals for the unknown parameters are obtained and compared via a simulation study.     

一维混杂控制系统可生存域计算

讨论了一维混杂控制系统在闭区间里的最大可生存域的计算问题.采用混杂微分包含描述混杂控制系统,针对系统为一维的情况作了合理的简化.将一维混杂控制系统的最大可生存域的计算问题转化为一个优化问题,并给出了具体的例子来说明这一结果.