卫星伸展机构的图示评审技术应用

目的解决卫星伸展机构参数表现形式多样且不确定的问题。方法运用图示评审技术,构建MU-GERT网络模型,并将参数统一用广义灰数表征。考虑解析算法的复杂性,提出针对该网络模型的矩阵式表征方法,并设计出矩阵式求解算法,便于运用计算机编程进行准确快速的求解。结果用MU-GERT网络模型计算概率不确定时制作一个合格卫星伸展机构需要的时间,仿真模拟出制作出一个合格卫星伸展机构的期望与机会。结论为图示评审技术在卫星伸展机构研制中的应用提供了研究思路和经验借鉴。     

东北地区林业产业结构变动对林业经济增长的贡献

运用数学模型对东北地区林业产业结构变动对林业经济增长的贡献进行了定量测度.基于多部门经济模型,研究1996年以来东北地区及其黑龙江、吉林和辽宁三省林业产业结构对经济增长贡献(Z值)的变化趋势得出:Z值在长期波动中呈下降趋势,产业结构稳定性增强;基于偏离—份额分析方法分解1996-2009年Z值的地域差异构成,得出黑龙江、吉林和辽宁林业产业结构变动对当地林业经济增长的贡献地域差异明显,对各省今后林业产业结构调整和林业产业发展的方向、可行措施提出了相应的对策建议.     

冬季采暖期气象条件对PM2.5等空气质量要素的影响——以咸阳市为例

以汾渭平原典型城市——咸阳为研究区域,利用地面空气质量监测数据和欧洲中期天气预报中心（ECMWF）发布的第五代全球气候再分析资料数据集（ERA5）,分析了咸阳市2018—2020年3 a采暖期污染物浓度变化特征和不同污染程度下的气象条件,采用统计学方法分析各项污染物浓度与气象因素间的相关性,使用多元线性回归模型评价各气象因素对PM_2.5浓度的影响程度,使用二元Logistic回归分析气象因素对PM_2.5超标风险的影响。咸阳市采暖期首要污染物以细颗粒物（PM_2.5）和可吸入颗粒物（PM₁₀）为主,采暖期超标最多的污染物为PM_2.5,超标天数逐年递减;PM₁₀的日变化呈“双峰双谷”型,PM_2.5的谷值出现在17∶00且夜晚浓度较高。颗粒物浓度与相对湿度呈正相关,与风速、边界层高度、温度、气压呈负相关。多元线性回归预测模型显示PM_2.5浓度预测值与实测值变化趋势保持一致,预测值的波动频率比实测值大,预测准确率为51.54%;二元Logistic回归模型显示：除相对湿度外,其他气象因素对PM_2.5超标情况都是保护因素,边界层高度每增高1 m,日均浓度超标风险降低0.7%;相对湿度每升高1%,日均浓度超标风险升高5.3%;温度每升高1℃,日均浓度超标风险降低19.8%;气压每升高1 hPa,日均浓度超标风险降低9.7%。以上研究结果揭示了咸阳市采暖期主要气象因素对空气污染的影响程度,为我国北方城市今后的空气污染治理提供科学依据,为相关政策制定提供理论参考。     

典型重化工园区产能增加对城市O3浓度影响

重化工园区产能增加将加大园区挥发性有机物(VOCs)排放总量,进而影响本地及周边城市O₃浓度.珠三角实施的“VOCs倍量替代”政策可在城市层面有效抵消重化工园区VOCs排放量上升的不利影响,还可进一步降低城市VOCs排放总量,实现区域O₃浓度下降.以惠州市某大型重化工园区为例,编制2018—2020年重化工园区产能增加以及实施“VOCs倍量替代”政策的污染物排放清单,基于WRF-CMAQ模拟体系,定量分析多种情景下园区在基准年(2017年)7—10月气象条件下对惠州市及周边城市O₃影响程度.研究表明,重化工园区增产而增加VOCs排放4101.96 t,“VOCs倍量替代”综合减排余量7298.97 t;“VOCs倍量替代”政策可有效解决重化工园区增产对O₃浓度的不利影响,其中7月最为显著,主导东南风下风向的深圳市及惠州市大亚湾管委会站点O₃浓度降幅最大,分别为3.9μg·m^-3(下降率2.97%)和7μg·m^-3(下降率4.95%);...     

佛山臭氧浓度预报方程的建立与应用

臭氧作为大气中的二次污染物,其形成和变化复杂,臭氧预报更是当下空气污染治理的难题之一.通过分析2014~2017年佛山地区近地面O₃浓度与高低层气象要素的关系,建立了佛山O₃浓度预报方程,并进行了检验和应用.结果表明,佛山近地面O₃的变化与高低层气象要素关系密切,气温和日照时数等气象要素与O₃浓度呈显著正相关,相对湿度、总（低）云量和风速等与其呈负相关;高浓度O₃污染发生的气象条件为小风速、晴间少云、低相对湿度、较长的日照时间和较高的温度,高浓度O₃潜势指数（HOPI）和风向指数（WDI）的定义可以较好地衡量O₃污染气象条件的好坏;综合考虑HOPI和不同高度WDI等13种气象要素,采用多指标叠套和多元逐步回归建立了佛山地区臭氧浓度预报方程;利用2018年资料检验发现,模拟值与实测值二者的相关系数R可达0.82,预报方程具有良好的拟合效果和可预报性.     

基于PCA-VMD-CNN的输电线路覆冰重量预测模型*

为防止覆冰灾害危及电路安全,提出1种输电线路覆冰重量预测模型。首先对多个气象因素进行主成分分析提取气象因素中的有效信息,再对覆冰历史数据进行变分模态分解,获得具有不同特性的本征模态分量;然后基于卷积神经网络,对具有不同时间尺度（周期性、波动性不同）的各个分量进行训练及预测,并将每个分量的预测结果相加。研究结果表明:通过对某覆冰区域的输电线路监测数据进行实验仿真,研究所提出的覆冰重量预测模型有更高精度。     

Neural tube defects in the sample of genetic counselling

Objective This study was conducted to evaluate the major demographic details, diagnostical and clinical features, as well as the risk of recurrence of cases with the major types of neural tube defects (NTD). We also examined the efficiency of ultrasonography based on autopsy examinations during 26 years. Methods The investigations were made into the sample of 743 NTD diagnosed between 1 January 1976 and 31 December 2002. A computerized database was used to sum up the available information about the individual cases; in addition to surveying the couples' major demographic details, we also had the opportunity to collect detailed information about the history, diagnostics (ultrasound) and outcome of the pregnancies as well as the results of the autopsies during the investigation. Results In the 743 cases of NTD, maternal and paternal median ages turned out to be 23.7 years (±5.22 years) and 28.7 years (±5.81 years), respectively. The male:female ratio was 0.78. Comparable samples of anencephaly and spina bifida allowed for the conclusion that a positive genetic history was equally often found while a positive obstetrical history was almost twice as common in anencephaly. The sensitivity of the maternal serum-alpha fetoprotein (AFP) screening test is the highest in anencephaly and lowest in encephalocele. While the majority of cases of anencephaly were diagnosed before the 24th gestational week, examples of diagnosing spina bifida and encephalocele at a later time could also be found. Among the associated malformations other than those of the central nervous system special mentioning should be made of fetal pyelectasia, cleft palate as well as diaphragmatic herniation. No pathological karyotypes were found in association with encephalocele or spina bifida, but anencephaly was accompanied with trisomy 21 and trisomy 18 in one case each. Anencephaly was found to have the highest risk of recurrence in both nervous system malformations and malformations other than those of the nervous system. Sonography proved to be the most reliable method in cases of enecephalocele. Conclusion The respective median values of maternal and paternal age show that aetas has no role in the occurrence of NTDs. NTDs are more common among girls. Positive genetic, obstetrical and medical findings are of great importance in the incidence of NTDs. Although reliable to only a limited extent, maternal serum-AFP tests are considered to be useful and necessary in screening NTDs, while sonography is the gold standard method in recognizing these frequent malformations. The knowledge of the eventual associated malformations is mainly important in certain cases of spina bifida, which may also yield a good post-natal prognosis. Our data obtained from the sample of 26 years also confirm that the periconceptional administration of folic acid reduces the incidence and risk of recurrence of NTDs. Copyright © 2007 John Wiley & Sons, Ltd.     

Invasive diagnostic procedures in twin pregnancies

The rising rate of multiple pregnancies and its association with advanced maternal age has expanded the need for prenatal diagnosis in twins and higher order gestations. The complexity of the invasive diagnostic procedures and the risk of loss of an unaffected twin raise significant clinical, technical and ethical issues. In this review we discuss the specific issues of early scanning, counseling and determination of chorionicity prior to invasive procedures in twins. We present the available data describing the risk associated with these procedures in twins and compare data of fetal loss rate from different studies. We also discuss the issues of fetal blood sampling and late karyotyping in twin pregnancies. Copyright © 2005 John Wiley & Sons, Ltd.     

Detection of Jarcho–Levin syndrome at 12 weeks' gestation by nuchal translucency screening and three-dimensional ultrasound

Jarcho–Levin syndrome (JLS) or spondylothoracic dysotosis causes early newborn death from respiratory insufficiency. Prenatal diagnosis is possible using fetal ultrasound, but requires a high level of suspicion and definitive diagnosis may be delayed well into the second trimester. We present a case in which a combination of three-dimensional ultrasound and measurement of nuchal translucency thickness allowed successful detection of recurrent JLS at 12 weeks' gestation. Copyright © 2001 John Wiley & Sons, Ltd.