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101.
针对翼伞–火箭一子级柔性结构系统的控制难题,提出了一种采用固定时间观测器的改进矢量场轨迹跟踪控制方法.首先,设计了在线风场估计方法对未知风场进行了估计;其次,为了保证该控制系统在气动参数不确定、子系统铰连耦合等因素影响下的快速稳定性,提出了一种固定时间干扰观测器用来估计无需知道干扰上边界的复合干扰,并用于补偿控制系统的输入;然后,设计了一个同时保证侧偏距、偏航角以及偏航角速率稳定的横侧向控制器,并利用Lyapunov理论证明了闭环翼伞控制系统的收敛特性.最后,通过数值仿真及硬件在环实验验证了所提出方法的有效性及应用价值. 相似文献
102.
结合注意力机制的循环神经网络(RNN)模型是目前主流的生成式文本摘要方法,采用基于深度学习的序列到序列框架,但存在并行能力不足或效率低的缺陷,并且在生成摘要的过程中存在准确率低和重复率高的问题.为解决上述问题,提出一种融合BERT预训练模型和卷积门控单元的生成式摘要方法.该方法基于改进Transformer模型,在编码器阶段充分利用BERT预先训练的大规模语料,代替RNN提取文本的上下文表征,结合卷积门控单元对编码器输出进行信息筛选,筛选出源文本的关键内容;在解码器阶段,设计3种不同的Transformer,旨在探讨BERT预训练模型和卷积门控单元更为有效的融合方式,以此提升文本摘要生成性能.实验采用ROUGE值作为评价指标,在LCSTS中文数据集和CNN/Daily Mail英文数据集上与目前主流的生成式摘要方法进行对比的实验,结果表明所提出方法能够提高摘要的准确性和可读性. 相似文献
103.
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°。 相似文献
104.
目的 针对一款吹塑成型的牛奶包装HDPE瓶易瘪瓶的问题,研究瓶体不同部位的厚度比对HDPE瓶顶部负载的影响,并轻量化设计HDPE瓶。方法 通过3D扫描获得HDPE瓶的3D实体模型,测量瓶体厚度,并在ABAQUS中构建不等壁厚的HDPE瓶壳体有限元模型,通过静压试验验证有限元模型的准确性。仿真分析厚度比对整瓶顶部负载能力的影响,并拓扑优化HDPE瓶材料分布。结果 顶部负载时,有限元模型仿真分析和实验得到的临界载荷和临界位移误差分别为2.49%和5.11%;结合厚度比优化与轻量化分析可知,HDPE瓶单瓶材料用量减少了12 g。结论 考虑了瓶体实际厚度的HDPE瓶有限元模型具有较高的准确度。在设计HDPE瓶时,应关注瓶体各部位的厚度组成,以获得更好的瓶体力学性能。 相似文献
105.
O Kosoko HA Quigley S Vitale C Enger L Kerrigan JM Tielsch 《Canadian Metallurgical Quarterly》1998,105(11):2105-2111
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. 相似文献
106.
SV Singh PJ Benson X Hu A Pal H Xia SK Srivastava S Awasthi HA Zaren JL Orchard YC Awasthi 《Canadian Metallurgical Quarterly》1998,128(2):197-204
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. 相似文献
107.
A van Teunenbroek SM de Muinck Keizer-Schrama T Stijnen M Jansen BJ Otten HA Delemarre-van de Waal T Vulsma JM Wit CW Rouwé HM Reeser JJ Gosen C Rongen-Westerlaken SL Drop 《Canadian Metallurgical Quarterly》1996,81(11):4013-4021
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. 相似文献
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