BP网络算法在平面运动测量误差补偿中的应用

在航天对接试验平台开发项目中,针对平面运动物体非接触高精度测量的难点,提出一种针对物体三自由度平面运动的创新性测量方法.利用激光测距传感器的并联组合,实现对物体位置和姿态的非接触式测量.以传感器测量值为输入样本,运用BP神经网络算法建立误差模型,通过调整权值因子使建立的网络模型能够拟合出测量误差,从而修正测量的数学模型.基于BP神经网络的误差补偿方法对平面运动物体测量误差的补偿具有明显的效果,能够满足位姿测量的精度要求.     

天然藻类对废水中 COD 的去除效率研究

目前废水中COD的处理问题是我国乃至世界各国普遍关注的问题,找到一种操作简单、成本低且效果好的处理方法是解决问题的关键所在。利用天然藻类中绿藻、硅藻处理不同类型废水,以COD作为检测指标。结果表明,绿藻对废水中COD的去除率最高。同时探讨了不同初始浓度的COD、不同种类废水中COD的去除效率。     

宁夏黄河段水库泥沙淤积对大坝防渗与结构安全影响研究

以宁夏黄河段某水库为例,在对其泥沙淤积原因进行总结分析的基础上,对其淤积情况下大坝渗流分析、结构分析及抗震安全分析进行了有限元计算。研究表明:(1)泥沙淤积情况下大坝渗漏量减小,大坝稳定性增强,抗震安全系数增大;(2)泥沙淤积导致水库有效库容减小,水库建筑物无法正常工作,水库下游生活用水和农业用水无法满足,应采取必要的清淤措施。     

Somatic mutation favors the evolution of diploidy

Explanation of diploidy have focused on advantages gained from masking deleterious mutations that are inherited. Recent theory has shown that these explanations are flawed. Indeed, we still lack any satisfactory explanation of diploidy in species that are asexual or that recombine only rarely. Here I consider a possibility first suggested by Efroimson in 1932, by Muller in 1964 and by Crow and Kimura in 1965: diploidy may provide protection against somatic, not inherited, mutations. I both compare the mean fitness of haploid and diploid populations that are asexual and investigate the invasion of "diploidy" alleles in sexual populations. When deleterious mutations are partially recessive and somatic mutation is sufficiently common, somatic mutation provides a clear advantage to diploidy in both asexual and sexual species.     

Tandem mass spectrometry and nuclear magnetic resonance spectroscopy studies of Candida bombicola sophorolipids and product formed on hydrolysis by cutinase

Natural mixtures of sophorolipids produced by the yeast Candida bombicola have been analyzed by fast atom bombardment (FAB)-MS and collision-induced dissociation (CID)-MS. Some pure components have been analysed by two-dimensional NMR spectroscopy. The presence of acidic, lactonic, and O-acetylated forms and the position of double bonds in the fatty acid part of these glycolipids can be easily inferred from positive and negative ion FAB-mass spectra. Details about position of O-acetylation can be obtained from CID mass spectra of [M+H]+ and [M-H]- ions and from the NMR spectra. Differences in CID fragmentation between protonated and sodiated molecular ions are discussed in detail. Enzymatic hydrolysis of 6',6"-di-O-acetyl sophorolipid lactone by cutinase from Fusarium solani results specifically in the removal of the 6'-O-acetyl group, whereas the 6"-O-acetyl and lactone group are resistant. This specificity is explained from a three-dimensional model of the sophorolipid generated on the basis of the short 1H,1H distances as inferred from the NMR (ROESY) spectra.     

一种新型含硅拒水剂的合成与应用

以甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、γ-甲基丙烯酰氧丙基三(三甲基硅氧烷)硅烷(TRIS)等为主要原料,采用半连续乳液聚合法,合成了具有核壳结构乳胶粒子的阳离子型含硅拒水剂。通过纳米粒度-Zeta电位分析仪、接触角(CA)、红外光谱(FT-IR)、透射电镜(TEM)及热重分析(TG)等手段研究了粒子的核壳形貌结构和固化后树脂的热稳定性等性能,然后考察了不同硅含量和不同浓度拒水剂对织物拒水性的影响。结果表明,有机硅单体参与了聚合,所合成乳胶粒具有明显的核壳结构,平均粒径为100nm。当硅含量最低为2%(占壳单体的质量分数)、有效浓度为2%,整理后的织物对水的接触角可达到135.5°。     

Risk factors for noncompliance with glaucoma follow-up visits in a residents' eye clinic

OBJECTIVE: This study aimed to identify factors associated with compliance with glaucoma follow-up visits. DESIGN: Computer records of a university residents' eye clinic were reviewed to identify a random sample of all persons who had an examination with International Classification of Disease (ICD) 9 coding (ICD9) for glaucoma suspect or glaucoma during a 2-year period (1991-1993) to undergo telephone interview. PARTICIPANTS: Those who were seen at least every 6 months regardless of earlier return instructions were defined as compliant with follow-up (controls, n = 362). Those who had any lapse between visits of longer than 6 months were defined as noncompliant (cases, n = 362). RESULTS: Interviews were completed for 196 cases and 242 controls. Noncompliant persons were significantly more likely to be suspects for glaucoma rather than to have definite glaucoma and to be dissatisfied with waiting time in the clinic (29.1% vs. 17.8%, P < 0.005) and to state that they did not take their glaucoma medications as prescribed (25.4% vs. 13.4%, P < 0.004). They also were less likely to have been prescribed eyedrop medication. A high percentage of both patients and controls knew that glaucoma can lead to blindness (85.2% and 88.4%, respectively). The most common reasons patients gave for not keeping follow-up visits were the perception that their eye problem was "not serious enough," the cost of examinations, and that the doctor did not tell them to come back. CONCLUSION: Compliance with follow-up visits for glaucoma is associated with markers for early disease. Attempts to improve compliance might focus on improved communication of the seriousness of the disease and improvements in clinic waiting time.     

Gender-related differences in susceptibility of A/J mouse to benzo[a]pyrene-induced pulmonary and forestomach tumorigenesis

A commercial patient dose verification system utilizing non-invasive metal oxide semiconductor field effect transistor (MOSFET) dosimeters originally designed for radiotherapy applications has been evaluated for use at diagnostic energy levels. The system features multiple dosimeters that may be used to monitor entrance or exit skin dose and intracavity doses in phantoms in real time. We have characterized both the standard MOSFET dosimeter designed for radiotherapy dose verification and a newly developed "high sensitivity" MOSFET dosimeter designed for lower dose measurements. The sensitivity, linearity, angular response, post-exposure response, and physical characteristics were evaluated. The average sensitivity (free in air, including backscatter) of the radiotherapy MOSFET dosimeters ranged from 3.55 x 10(4) mV per C kg(-1) (9.2 mV R(-1)) to 4.87 x 10(4) mV per C kg(-1) (12.6 mV R(-1)) depending on the energy of the x-ray field. The sensitivity of the "high sensitivity" MOSFET dosimeters ranged from 1.15 x 10(5) mV per C kg(-1) (29.7 mV R(-1)) to 1.38 x 10(5) mV per C kg(-1) (35.7 mV R(-1)) depending on the energy of the x-ray field. The high sensitivity dosimeters demonstrated excellent linearity at high energies (90 and 120 kVp) and acceptable linearity at lower energies (60 kVp). The angular response was significant for free-in-air exposures, as illustrated by the sensitivity differences between the two sides of the dosimeter, but was excellent for measurements within a tissue equivalent cylinder. The post-exposure drift response is a complicated but reproducible function of time. Real-time monitoring requires little if any corrections for the post-exposure drift response. The MOSFET dosimeter system brings some unique capabilities to diagnostic radiology dosimetry including small size, real-time capabilities, nondestructive measurement, good linearity, and a predictable angular response.     

Yearly stepwise increments of the growth hormone dose results in a better growth response after four years in girls with Turner syndrome. Dutch Working Group on Growth Hormone

To optimize the growth promoting effect of growth hormone (GH), 65 previously untreated girls with Turner syndrome (TS), chronological age (CA) 2-11 yr, were randomized into 3 dosage regimen groups: A, B, and C, with a daily recombinant-human GH dose during 4 study years of 4-4-4-4, 4-6-6-6, and 4-6-8-8 IU/m2 b.s. The first GH dosage increase in groups B and C resulted in a significantly higher mean height velocity (HV) compared with constant dose group A. During the third year, when the dose was raised again only in group C, mean HV was significantly higher in groups B and C than in group A, and in group C compared with group B. In year 4 only group C mean HV remained significantly higher than group A. The pattern of change in HSDSCA (Dutch-Swedish-Danish Turner references) was identical; however, in year 4 mean delta HSDSCA in group B also remained significantly higher than group A. After 4 yr GH treatment, the following was determined. 1) The mean delta HSDSCA was significantly higher for groups B and C compared with group A, but not significantly different between groups B and C. 2) Although significantly higher compared with estimated values for untreated Dutch girls with TS, bone maturation of the GH treated girls was not significantly different between groups. 3) It was positively related with the degree of bone age (BA) retardation at start of study and negatively with baseline CA. 4) Both the modified Index of Potential Height (mIPHRUS) and a recently developed Turner-specific final height (FH) prediction method (PTSRUS), based on regression coefficients for H, CA, and bone age, showed significant increases in mean FH prediction, without significant differences between groups. PTSRUS values were markedly higher than the mIPHRUS values. Dose dependency could be shown for the area under the curve (AUC) for GH, but delta HSDSCA was not linearly related with AUC. Baseline GH binding protein (BP) levels were in 84% of the cases within the normal age range; the decrease in mean levels after 6 months GH was not significant. Mean insulin-like growth factor I (IGF-I) and IGFBP-3 plasma levels increased significantly, without significant differences between groups. delta HSDSCA during GH was dependent on IGF-I plasma levels at baseline and during the study period, beta-0.002 and beta-0.0004. Thus, a stepwise GH-dosing approach reduced the "waning" effect of the growth response after 4 yr treatment without undue bone maturation. FH prediction was not significantly different between treatment groups. Irrespective of the GH dose used, initiation of GH treatment at a younger age was beneficial after 4 yr GH when expressed as actual cm gained or as gain in FH prediction, but was not statistically significant when expressed as delta HSDSCA over the study period.     

基于C8051F410单片机的钨灯电源设计

针对光谱测试系统对光源稳定性越来越高的要求,介绍了一种以单片机为核心的高稳定性的钨灯电源系统.它以C8051F410单片机为核心,采用增量式PID控制算法,通过控制单片机的D/A输出来调整MOS场效应管的导通情况,从而达到稳定钨灯工作电流的目的,保证钨灯的发光稳定.通过实验验证,新设计的电源具有控制精度高、稳定性好、性能可靠等优点,可应用于光谱测试系统中.