期刊文献+
共找到692篇文章
< 1 2 35 >
每页显示 20 50 100
The present status and prospects in the research of orbital dynamics and control near small celestial bodies
1
作者 Pingyuan Cui Dong Qiao 《Theoretical & Applied Mechanics Letters》 CAS 2014年第1期1-14,共14页
Small celestial body exploration is of great significance to deep space activities. The dynamics and control of orbits around small celestial bodies is of top priority in the exploration research. It includes the mode... Small celestial body exploration is of great significance to deep space activities. The dynamics and control of orbits around small celestial bodies is of top priority in the exploration research. It includes the modeling of dynamics environment and the orbital dynamics mechanism. This paper introduced state-ofthe-art researches, major challenges, and future trends in this field. Three topics are mainly discussed: the gravitational field modeling of irregular-shaped small celestial bodies, natural orbital dynamics and control, and controlled orbital dynamics. Finally, constructive suggestions are made for China’s future space exploration missions. 展开更多
关键词 small celestial body exploration dynamics and control gravitational field of irregular-shaped body natural orbital dynamics controlled orbital dynamics
下载PDF
Water Quality Criteria for Water Bodies in Urban Areas and Accompanying Changes in Surrounding and <i>In-Situ</i>Vegetation: Considerations from the Landscape Aspect of Planning Water Recreational Areas 被引量:1
2
作者 Shigeki Harada Risa Wagatsuma +2 位作者 Tatsunari Koseki Toshiaki Aoki Taisuke Hashimoto 《Journal of Water Resource and Protection》 2013年第2期156-163,共8页
Water bodies in urban areas are important as recreational areas. Thus, management plans that maintain high water quality are quite important. At the Hatadate Water Park adjacent to Miyagi University, water quality par... Water bodies in urban areas are important as recreational areas. Thus, management plans that maintain high water quality are quite important. At the Hatadate Water Park adjacent to Miyagi University, water quality parameters such as visibility, COD, TOC, and TN were monitored at a small pond and the inflowing stream from August to December in 2011, and photographs were taken of these sites. Variations in COD and TOC were highly related to changes in the physical appearance, especially changes in vegetation. These findings suggest: 1) the importance of management of vegetation for water quality control;and 2) the importance of collecting photographic records of sites for research purposes of interpreting data and even as a data point of water quality. Together with the water quality goals for water bodies in urban areas proposed by Sudo et al. [1], these water quality criteria were assessed, and it was notable that COD often exceeded the set goal. These results suggest that the maintenance of vegetation is more important than controlling incoming TN for primary production in the pond. Seasonal variations in COD and TOC were plotted for surface water of Kamafusa and Okura dams, both are important lakes in Miyagi area and the catchments of both lakes are mainly hilly area, using published water quality reports. Similar annual-cycle changing patterns were shown both for the dams, implying that some kinds of ecological factors in the catchments are affecting the water qualities of the dam, even at those larger scale water bodies. Finally, by shifting the focus from only water to upstream features such as small park, or pocket park, with a parking lot for the water body, the importance of landscape including vegetation and tree cover was highlighted. 展开更多
关键词 small WATER Body COD TOC VEGETATION LANDSCAPE
下载PDF
Migration and population structure characteristics of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea 被引量:8
3
作者 XIONG Ying ZHONG Xiaming +1 位作者 TANG Jianhua YANG Jian 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2016年第6期34-41,共8页
Monthly fishery survey data of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea from2003 and 2013 were employed to evaluate the variation in the resource distribution and biological character... Monthly fishery survey data of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea from2003 and 2013 were employed to evaluate the variation in the resource distribution and biological characteristics(especially body length and sex ratio) in the population on a decadal scale.The results indicated that the small yellow croaker migrated from the Shawai fishing ground to the Dasha fishing ground in spring and was mainly distributed in the central and western parts of the Dasha fishing ground in April and May.Larimichthys polyactis in the Dasha fishing ground migrated eastward to offshore wintering grounds in autumn and reached the central Dasha fishing ground in October and November.The small yellow croaker entered the western waters of the Shawai fishing ground in winter.A large number of age 0+ fish occurred in the Shawai and Jiangwai fishing grounds in October of 2003 and 2013.The body lengths of the spawning stock and wintering stock in 2013 were larger than those in 2003,and the monthly sex ratios(female to male) were significantly less than 1 in both years.The monthly distribution of this fish in the southern Yellow Sea was consistent with a previous finding that "the stock migrated between the wintering grounds in the west of Jeju Island and the Lüsi spawning grounds" but tended to move more northward,with the spawning grounds extending outward.In the past decade,body length variation experienced a decline after an increase,rather than a steady decrease.The sex ratio in the single-stick stow net showed a tendency to increase over the decade,but was either less than or more than 1 depending on the fishing gear;therefore,further studies should be conducted to determine the sex structure. 展开更多
关键词 small yellow croaker resource distribution MIGRATION body length sex ratio
下载PDF
Peritonitis with small bowel perforation caused by a fish bone in a healthy patient 被引量:4
4
作者 Yonghoon Choi Gyuwon Kim +2 位作者 Chansup Shim Dongkeun Kim Dongju Kim 《World Journal of Gastroenterology》 SCIE CAS 2014年第6期1626-1629,共4页
Perforation of the gastrointestinal tract by ingested foreign bodies is extremely rare in otherwise healthy patients, accounting for &#x0003c; 1% of cases. Accidentally ingested foreign bodies could cause small bo... Perforation of the gastrointestinal tract by ingested foreign bodies is extremely rare in otherwise healthy patients, accounting for &#x0003c; 1% of cases. Accidentally ingested foreign bodies could cause small bowel perforation through a hernia sac, Meckel&#x02019;s diverticulum, or the appendix, all of which are uncommon. Despite their sharp ends and elongated shape, bowel perforation caused by ingested fish bones is rarely reported, particularly in patients without intestinal disease. We report a case of 57-year-old female who visited the emergency room with periumbilical pain and no history of underlying intestinal disease or intra-abdominal surgery. Abdominal computed tomography and exploratory laparotomy revealed a small bowel micro-perforation with a 2.7-cm fish bone penetrating the jejunal wall. 展开更多
关键词 PERITONITIS small bowel perforation Foreign body Fish bone Japanese red rock fish
下载PDF
Effect of bowel rehabilitative therapy on structural adaptation of remnant small intestine: animal experiment 被引量:14
5
作者 Xin Zhou1 Yuan Xin Li2 +1 位作者 Ning Li2 Jie Shou Li2 1Department of General Surgery, Medical School, Nanjing University, Nanjing 210093. Jiangsu Province. China2Research Institute of General Hospital. Chinese PLA General Hospital of Nanjing Military Area, Nanjing 210002. Jiangsu Province. China 《World Journal of Gastroenterology》 SCIE CAS CSCD 2001年第1期66-73,共8页
AIM: To investigate the individual and the combined effects of glutamine, dietary fiber, and growth hormone on the structural adaptation of the remnant small bowel. METHODS: Forty-two adult male Sprague-Dawley rats un... AIM: To investigate the individual and the combined effects of glutamine, dietary fiber, and growth hormone on the structural adaptation of the remnant small bowel. METHODS: Forty-two adult male Sprague-Dawley rats underwent 85% mid-small bowel resection and received total parenteral nutrition (TPN) support during the first three postoperational days.From the 4th postoperational day, animals were randomly assigned to receive 7 different treatments for 8 days: TPNcon group, receiving TPN and enteral 20 g x L(-1) glycine perfusion; TPN+Gln group, receiving TPN and enteral 20 g x L(-1) glutamine perfusion; ENcon group, receiving enteral nutrition (EN) fortified with 20 g x L(-1) glycine; EN+Gln group, enteral nutrition fortified with 20 g x L(-1) glutamine; EN+Fib group, enteral nutrition and 2 g x d(-1) oral soybean fiber; EN+GH group, enteral nutrition and subcutaneous growth hormone (GH) (0.3 IU) injection twice daily; and ENint group, glutamine-enriched EN, oral soybean fiber, and subcutaneous GH injection. RESULTS: Enteral glutamine perfusion during TPN increased the small intestinal villus height (jejunal villus height 250 microm +/- 29 microm in TPNcon vs 330 microm +/- 54 microm in TPN+Gln, ileal villus height 260 microm +/- 28 microm in TPNcon vs 330 microm +/- 22 microm in TPN+Gln, P【0.05) and mucosa thickness (jejunal mucosa thickness 360 microm +/- 32 microm in TPNcon vs 460 microm +/- 65 microm in TPN+Gln, ileal mucosa thickness 400 microm +/- 25 microm in TPNcon vs 490 microm +/- 11 microm in TPN+Gln,P【 0.05) in comparison with the TPNcon group. Either fiber supplementation or GH administration improved body mass gain (end body weight 270 g +/- 3.6g in EN+Fib, 265.7 g +/- 3.3 g in EN+GH, vs 257 g +/- 3.3 g in ENcon, P【 0.05), elevated plasma insulin-like growth factor (IGF-I) level (880 microg x L(-1). 52 microg x L-(-1) in EN+Fib,1200 microg x L(-1). 96 microg x L-(-1) in EN +/- GH, vs 620 microg x L(-1).43 microg x L-(-1) in ENcon, P【 0.05), and increased the villus height (jejunum 560 microm +/- 44 microm in EN +/- Fib, 530 microm +/- 30 microm in EN +/- GH, vs 450 microm +/- 44 microm in ENcon, ileum 400 microm +/- 30 microm in EN+Fib, P【0.05) and the mucosa thickness (jejunum 740 microm +/- 66 microm in EN +/- Fib, 705 microm +/- 27 microm in EN +/- GH, vs 608 microm +/- 58 microm in ENcon, ileum 570 microm +/- 27 microm in EN +/- Fib, 560 microm +/- 56 microm in remnant jejunum and ileum. Glutamine-enriched EN produced little effect in body mass, plasma IGF-I level, and remnant small bowel mucosal structure. The ENint group had greater body mass (280 g +/- 2.2g), plasma IGF-I level (1450 microg x L(-1). 137 microg x L-(-1)), and villus height (jejunum 620 microm +/- 56 microm, ileum 450 microm +/- 31 microm) and mucosal thickness (jejunum 800 microm +/- 52 microm, ileum 633 microm +/- 33 microm) than those in ENcon, EN+Gln (jejunum villus height and mucosa thickness 450 microm +/- 47 microm and 610 +/- 63 microm, ileum villus height and mucosa thickness 330 microm +/- 39 microm and 500 microm +/- 52 microm), EN+GH groups (P【0.05), and than those in EN+Fib group although no statistical significance was attained. CONCLUSION: Both dietary fiber and GH when used separately can enhance the postresectional small bowel structural adaptation. Simultaneous use of these two gut-trophic factors can produce synergistic effects on small bowel structural adaptation. Enteral glutamine perfusion is beneficial in preserving small bowel mucosal structure during TPN, but has little beneficial effect during EN. 展开更多
关键词 Parenteral Nutrition Total Adaptation Physiological Animals Body Weight Dietary Fiber GLUTAMINE Glycine Growth Hormone Insulin-Like Growth Factor I Intestinal Mucosa Intestine small Male RATS Rats Sprague-Dawley Recovery of Function Research Support Non-U.S. Gov't Short Bowel Syndrome
下载PDF
Stereotactic body radiation therapy for non-small cell lung cancer:A review 被引量:10
6
作者 Kavitha M Prezzano Sung Jun Ma +3 位作者 Gregory M Hermann Charlotte I Rivers Jorge A Gomez-Suescun Anurag K Singh 《World Journal of Clinical Oncology》 CAS 2019年第1期14-27,共14页
Stereotactic body radiation therapy(SBRT) is the treatment of choice for medically inoperable patients with early stage non-small cell lung cancer(NSCLC). A literature search primarily based on PubMed electronic datab... Stereotactic body radiation therapy(SBRT) is the treatment of choice for medically inoperable patients with early stage non-small cell lung cancer(NSCLC). A literature search primarily based on PubMed electronic databases was completed in July 2018. Inclusion and exclusion criteria were determined prior to the search, and only prospective clinical trials were included. Nineteen trials from 2005 to 2018 met the inclusion criteria, reporting the outcomes of 1434 patients with central and peripheral early stage NSCLC. Patient eligibility,prescription dose and delivery, and follow up duration varied widely. Threeyears overall survival ranged from 43% to 95% with loco-regional control of up to 98% at 3 years. Up to 33% of patients failed distantly after SBRT at 3 years. SBRT was generally well tolerated with 10%-30% grade 3-4 toxicities and a few treatment-related deaths. No differences in outcomes were observed between conventionally fractionated radiation therapy and SBRT, central and peripheral lung tumors, or inoperable and operable patients. SBRT remains a reasonable treatment option for medically inoperable and select operable patients with early stage NSCLC. SBRT has shown excellent local and regional control with toxicity rates equivalent to surgery. Decreasing fractionation schedules have been consistently shown to be both safe and effective. Distant failure is common, and chemotherapy may be considered for select patients. However, the survival benefit of additional interventions, such as chemotherapy, for early stage NSCLC treated with SBRT remains unclear. 展开更多
关键词 LUNG CANCER NON-small cell LUNG CANCER STEREOTACTIC body radiation therapy STEREOTACTIC ABLATIVE radiotherapy DISTANT failure
下载PDF
Management of oligometastatic non-small cell lung cancer patients:Current controversies and future directions 被引量:6
7
作者 Felipe Counago Javier Luna +9 位作者 Luis Leonardo Guerrero Blanca Vaquero María Cecilia Guillén-Sacoto Teresa González-Merino Begona Taboada Verónica Díaz Belén Rubio-Viqueira Ana Aurora Díaz-Gavela Francisco JoséMarcos Elia del Cerro 《World Journal of Clinical Oncology》 CAS 2019年第10期318-339,共22页
Oligometastatic non-small cell lung cancer(NSCLC)describes an intermediate stage of NSCLC between localized and widely-disseminated disease.This stage of NSCLC is characterized by a limited number of metastases and a ... Oligometastatic non-small cell lung cancer(NSCLC)describes an intermediate stage of NSCLC between localized and widely-disseminated disease.This stage of NSCLC is characterized by a limited number of metastases and a more indolent tumor biology.Currently,the management of oligometastatic NSCLC involves radical treatment(radiotherapy or surgery)that targets the metastatic lesions and the primary tumor to achieve disease control.This approach offers the potential to achieve prolonged survival in patients who,in the past,would have only received palliative measures.The optimal therapeutic strategies for the different scenarios of oligometastatic disease(intracranial vs extracranial disease,synchronous vs metachronous)remain undefined.Given the lack of head-to-head studies comparing radiotherapy to surgery in these patients,the decision to apply surgery or radiotherapy(with or without systemic treatment)must be based on prognostic factors that allow us to classify patients.This classification will allow us to select the most appropriate therapeutic strategy on an individualized basis.In the future,the molecular or microRNA profiles will likely improve the treatment selection process.The objective of the present article is to review the most relevant scientific evidence on the management of patients with oligometastatic NSCLC,focusing on the role of radiotherapy and surgery.We also discuss areas of controversy and future directions. 展开更多
关键词 NON-small cell lung cancer METASTASECTOMY OLIGOMETASTASES STEREOTACTIC ablative radiotherapy STEREOTACTIC body radiation therapy RADIOSURGERY
下载PDF
Incorporation of circulating tumor cells and whole-body metabolic tumor volume of 18F-FDG PET/CT improves prediction of outcome inⅢB stage small-cell lung cancer 被引量:3
8
作者 Lei Fu Ying Zhu +3 位作者 Wang Jing Dong Guo Li Kong Jinming Yu 《Chinese Journal of Cancer Research》 SCIE CAS CSCD 2018年第6期596-604,共9页
Objective: We investigated the correlation between the number of circulating tumor cells(CTCs) and wholebody metabolic tumor volume(WBMTV) measured by 18 F-fluorodeoxyglucose(FDG) positron emission tomography/computed... Objective: We investigated the correlation between the number of circulating tumor cells(CTCs) and wholebody metabolic tumor volume(WBMTV) measured by 18 F-fluorodeoxyglucose(FDG) positron emission tomography/computed tomography(PET/CT).The aim was to evaluate the value of the incorporation of CTC number and WBMTV in the prognostic prediction of stage III small-cell lung cancer(SCLC).Methods: One hundred and twenty-nine patients were enrolled in this study.All patients were treated with four cycles of a platinum-based regimen and concurrent chest irradiation,followed by prophylactic cranial irradiation.Blood samples for CTC analysis were obtained from 112 patients before the initiation of chemotherapy(as a baseline),after cycle 1 and after cycle 4.CTCs were measured using the CELLSEARCH? system.The patients underwent pretreatment FDG PET/CT WBMTV,which included all malignant lesions.The Spearman rank test was used to determine the correlation among CTC counts,WBMTV and disease stage.Overall survival(OS) and progression-free survival(PFS) curves were produced using the Kaplan-Meier method,and survival differences between groups were assessed by the log-rank test.Results: The number of CTCs at baseline did not correlate with WBMTV before the initiation of therapy(P=0.241).The number of CTCs at baseline and the WBMTV before the initiation of therapy were independent relevant factors for PFS and OS.The subgroup analysis(Group A: CTC count >19.5 and a WBMTV >266.5cm~3;Group B: CTC count >19.5 and a WBMTV ≤266.5cm~3; Group C: CTC count ≤19.5 and a WBMTV >266.5cm~3;Group D: CTC count ≤19.5 and a WBMTV ≤266.5cm~3) showed that the differences were statistically significant in the median PFS(Group A vs.D,P<0.001; Group B vs.D,P=0.018; Group C vs.D,P=0.029) and in the median OS(Group A vs.D,P<0.001; Group B vs.D,P=0.012).Conclusions: CTC number and WBMTV are related to progression and death in patients with SCLC.The incorporation of CTC number and WBMTV scans can provide a detailed prognostic prediction for SCLC. 展开更多
关键词 small-cell lung cancer circulating tumor cell PET-CT whole-body metabolic tumor volume PROGNOSIS
下载PDF
Autonomous orbit determination for the probe around small body
9
作者 黄翔宇 崔祜涛 +1 位作者 崔平远 栾恩杰 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2004年第3期327-332,共6页
The algorithm of autonomous orbit determination for the probe around small body is studied. In the algorithm, first, the observed images of the body are compared with its pre-computed model of the body to obtain the l... The algorithm of autonomous orbit determination for the probe around small body is studied. In the algorithm, first, the observed images of the body are compared with its pre-computed model of the body to obtain the location of the limb features of the body in the inertial coordinate. Second, the information of the images and features in utilized to obtain the position of the probe using the Levenberg-Marquardt algorithm. The position is then input to an extended Kalman filter which determines the real time orbit of the probe. Finally, considering the effective of the irregular small body shape perturbation and the small body model parameter error on the orbit determination precise, the procedure of autonomous orbit determination is validated using digital simulation. 展开更多
关键词 autonomous orbit determination probe around small body Levenberg-Marquardt algorithm extended Kalman filter
下载PDF
Spacecraft motion analysis about rapid rotating small body
10
作者 史雪岩 崔祜涛 +1 位作者 崔平远 栾恩杰 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2003年第4期363-366,共4页
The orbital dynamics equation of a spacecraft around an irregular sphere small body is established based on the small body’s gravitational potential approximated with a tri-axial ellipsoid. According to the Jacobi in... The orbital dynamics equation of a spacecraft around an irregular sphere small body is established based on the small body’s gravitational potential approximated with a tri-axial ellipsoid. According to the Jacobi integral constant, the spacecraft zero-velocity curves in the vicinity of the small body is described and feasible motion region is analyzed. The limited condition and the periapsis radius corresponding to different eccentricity against impact surface are presented. The stability of direct and retrograde equator orbits is analyzed based on the perturbation solutions of mean orbit elements. 展开更多
关键词 SPACECRAFT orbital dynamics small body
下载PDF
New perspectives in the management of small cell lung cancer
11
作者 Cristina Pangua Jacobo Rogado +7 位作者 Gloria Serrano-Montero JoséBelda-Sanchís BeatrizÁlvarez Rodríguez Laura Torrado Nuria Rodríguez De Dios Xabier Mielgo-Rubio Juan Carlos Trujillo Felipe Couñago 《World Journal of Clinical Oncology》 CAS 2022年第6期429-447,共19页
The treatment of small cell lung cancer(SCLC)is a challenge for all specialists involved.New treatments have been added to the therapeutic armamentarium in recent months,but efforts must continue to improve both survi... The treatment of small cell lung cancer(SCLC)is a challenge for all specialists involved.New treatments have been added to the therapeutic armamentarium in recent months,but efforts must continue to improve both survival and quality of life.Advances in surgery and radiotherapy have resulted in prolonged survival times and fewer complications,while more careful patient selection has led to increased staging accuracy.Developments in the field of systemic therapy have resulted in changes to clinical guidelines and the management of patients with advanced disease,mainly with the introduction of immunotherapy.In this article,we describe recent improvements in the management of patients with SCLC,review current treatments,and discuss future lines of research. 展开更多
关键词 small cell lung cancer Whole-brain radiotherapy Prophylactic cranial irradiation Stereotactic body radiotherapy IMMUNOTHERAPY Atezolizumab Durvalumab
下载PDF
Survey of Stereotactic Body Radiation Oncology for Early Staged Non-Small Cell Lung Cancer in China
12
作者 Ligang Xing Yong Yin +1 位作者 Spring Kong Jinming Yu 《International Journal of Medical Physics, Clinical Engineering and Radiation Oncology》 2014年第1期56-59,共4页
Purpose: To evaluate the current status of stereotactic body radiotherapy (SBRT) for early staged non-small cell lung cancer (NSCLC) at main cancer hospitals in China. Methods and Materials: The questionnaire was sent... Purpose: To evaluate the current status of stereotactic body radiotherapy (SBRT) for early staged non-small cell lung cancer (NSCLC) at main cancer hospitals in China. Methods and Materials: The questionnaire was sent by mail and email to 21 hospitals, which include the patient enrollment, treatment technique, dose and fractionation, quality control, disease control and side effects. Results: Nineteen hospitals responded. It was found that SBRT has been used for early staged NSCLC in most of the hospitals participating in the survey. The patient characteristics and techniques were relatively consistent, but there were many controversies regarding dose fractionation and quality control. Conclusions: SBRT for early staged NSCLC has been applied at main cancer hospitals in China. However, considerable variation exists. The establishment of clinical guidelines and standardized quality control are crucial for further improvement. 展开更多
关键词 NON-small Cell Lung Cancer STEREOTACTIC BODY RADIOTHERAPY SURVEY
下载PDF
Shear Stress in MR Fluid with Small Shear Deformation in Bctlattic Structure
13
作者 LIU Lisheng RUAN Zhongwei ZHAI Pengcheng ZHANG Qingjie 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2008年第4期532-535,共4页
A theoretical model based on BCT lattice structure was developed. Resultant force in the BCT lattice structure was deduced, following the interaction force of two kinds of magnetic particles. According to empirical Fr... A theoretical model based on BCT lattice structure was developed. Resultant force in the BCT lattice structure was deduced, following the interaction force of two kinds of magnetic particles. According to empirical FroHlich-Kermelly law, the relationship between the magnetic induction and the magnetic field was discussed, and a predictive formula of shear stresses of the BCT lattice structure model was established for the case of small shear deformation. Compared with the experimental data for different particle volume fractions, the theoretical results of the shear stress indicate the effects of the saturation magnetization and the external magnetic field on the shear stress. 展开更多
关键词 magnetorheological fluids (MR fluids) body-centered-tetragonal(BCT) interaction force shear stress small deformation
下载PDF
基于机器学习的寒区渠道冰情的遥感监测方法 被引量:1
14
作者 管光华 熊发京 《农业工程学报》 EI CAS CSCD 北大核心 2024年第4期194-203,共10页
寒区渠道冬季运行时常出现冰情,控制平封的封冻过程会大幅降低渠道输水能力,调控不当甚至可能产生冰塞、冰坝等灾害。国内外开展了大量渠道冰情研究,以期提升渠道冰期输水能力,但受限于观测资料的时空密度,数值模拟结果难以验证,调度决... 寒区渠道冬季运行时常出现冰情,控制平封的封冻过程会大幅降低渠道输水能力,调控不当甚至可能产生冰塞、冰坝等灾害。国内外开展了大量渠道冰情研究,以期提升渠道冰期输水能力,但受限于观测资料的时空密度,数值模拟结果难以验证,调度决策缺少依据。遥感技术因其具有监测范围大、时效性高的特性,在渠道冰情监测中具有较大的应用潜力。为探索适用于寒区渠道冰情遥感监测的方法,该研究以南水北调中线京石段明渠段为研究区,基于Sentinel-2影像的11个波段反射率构建了完全特征、优选特征和组合特征3类特征空间数据集,作为支持向量机(support vector machine,SVM)、最大似然估计(maximum likelihood estimation,MLE)、随机森林(random forest,RF)分类算法输入,训练得到了9个地物分类器,用于渠道结冰范围识别,并采用北拒马闸前影像渠道结冰范围提取试验,对比不同分类算法和输入特征组合下的分类性能。结果表明:在渠道结冰范围识别中,近红外、可见光和短波红外是关键波段。在样本数量有限的条件下,SVM算法结冰范围识别精度最高,不同特征输入下制图精度(producer’s accuracy,PA)可达85.10%~87.91%,错分误差(commission error,CE)为10.84%~16.08%;RF算法在完全特征和优选特征输入下分类精度与SVM接近,PA为84.67%~86.61%,CE为13.76%~14.41%,但其在组合特征下分类结果严重偏离实际;MLE算法在3类特征下的分类精度均较低,不适宜作为渠道结冰范围识别算法。综合来看,SVM算法对特征空间敏感性较低,在不同的特征输入下均能实现渠道结冰范围的高精度提取;RF算法对特征空间敏感性较高,当输入特征发生变化时,结冰范围识别精度不稳定。最后以完全特征下的SVM算法为例,进行了分类器的时空泛化性验证,结果表明模型在不同时间、不同渠段下,制图精度不低于82.09%,错分误差不高于13.82%,分类模型精度均较好,能有效识别渠道结冰范围。该研究方法可为寒区输水工程冰情监测提供新思路,亦可为类似工作提供参考。 展开更多
关键词 遥感 寒区渠道 机器学习 细小水体 Sentinel-2
下载PDF
贵东复式岩体中东部晚期花岗质小岩体的SHRIMP锆石U-Pb年龄及其地质意义
15
作者 吴佳 巫建华 +2 位作者 刘晓东 王凯兴 刘帅 《高校地质学报》 CAS CSCD 北大核心 2024年第1期56-71,共16页
贵东复式岩体由多期次、多类型的岩体组成,且东部盛产铀矿床,因此精确厘定该复式岩体的时代及其时序,查明复式岩体东部与中西部岩浆活动的差异性及其与铀成矿的关系,不仅有利于深入研究区域岩浆活动,而且有利于深刻认识铀的成矿规律。... 贵东复式岩体由多期次、多类型的岩体组成,且东部盛产铀矿床,因此精确厘定该复式岩体的时代及其时序,查明复式岩体东部与中西部岩浆活动的差异性及其与铀成矿的关系,不仅有利于深入研究区域岩浆活动,而且有利于深刻认识铀的成矿规律。现有研究认为,以龟尾山断裂带为界,贵东复式岩体中西部岩基属燕山早期、东部岩基属印支早期,东部广泛发育的燕山期中基性脉岩与铀成矿关系密切。但对复式岩体中东部呈岩枝、岩株广泛出露的晚期花岗质小岩体的成岩地质时代及其分布规律尚存在争议,也有待进一步查明花岗质小岩体与铀矿床的时空关系。文章选择贵东复式岩体中东部晚期花岗质小岩体为研究对象,采用SHRIMP锆石U-Pb法厘定其成岩时代,并分析它们的时空分布及其与铀成矿的关系。测试结果显示,贵东复式岩体中东部晚期花岗质小岩体普遍存在高铀锆石,这可能是对同一岩体不同学者所获得的^(206)Pb/^(238)U加权平均年龄差别较大的主要原因。剔除高铀锆石的年龄数据,龟尾山断裂带以西的隘子、司前、陈洞岩体锆石^(206)Pb/^(238)U加权平均年龄分别为163.0±1.6 Ma、163.1±1.6 Ma、160.7±1.9 Ma,属燕山早期岩浆活动的产物;而以东的帽峰、分水坳、龟尾山岩体锆石^(206)Pb/^(238)U加权平均年龄分别为230.0±2.7 Ma、225.9±2.9 Ma和232.6±3.1 Ma,属印支期岩浆活动的产物。所以,龟尾山断裂以西和以东晚期花岗质小岩体的时代不同。且龟尾山断裂带以东的印支期花岗质小岩体空间上与铀矿化、尤其是与燕山早期的绢英岩化型等中高温热液铀矿化关系密切,是主要的储矿围岩;结合元素地球化学研究结果,该区产出的印支期花岗质小岩体也可为铀成矿提供铀源。 展开更多
关键词 贵东复式岩体 花岗质小岩体 SHRIMP锆石U-PB年龄 铀成矿
下载PDF
弱引力小天体的自主捕获与相对导航方法
16
作者 刘一武 胡锦昌 +3 位作者 梁潇 田启航 张辉 尹芳 《中国空间科学技术(中英文)》 CSCD 北大核心 2024年第4期50-58,共9页
远距离自主捕获与近距离高精度自主相对导航是小天体探测任务中的关键问题,并且目标尺寸越小,问题越突出。首先,针对数万千米到数千千米远距离范围内的星空背景暗弱目标难以识别的问题,提出综合利用运动学和亮度的全自主捕获和识别方法... 远距离自主捕获与近距离高精度自主相对导航是小天体探测任务中的关键问题,并且目标尺寸越小,问题越突出。首先,针对数万千米到数千千米远距离范围内的星空背景暗弱目标难以识别的问题,提出综合利用运动学和亮度的全自主捕获和识别方法,可以实现距离大范围变化的快速准确捕获,具备了3万千米以远捕获10等星暗弱目标的能力;其次,针对数千到数十千米范围交会段视线测量可观性不足的问题,提出基于视线和轨迹机动一体化设计的相对导航方法,在考虑燃料消耗的前提下有效地提高了轨迹可观性,实现了交会段优于5%精度的相对位置导航;最后,针对近距离不规则小天体表面附近的相对导航问题,提出基于图像陆标和点云特征相结合的光学导航方法,可同时适应阳照区和阴影区的探测需求,并结合基于多源数据融合的弱引力小天体重力场反演方法,进一步提高近距相对导航的精度,近距采样相对位置优于1 m,相对速度优于1 cm/s。对所提出的方法进行了数学和物理的仿真验证。提出的方法有效解决了小天体探测中的高精度相对导航问题,也能适用于数十米量级直径大小和明暗快速交替变化的小天体着陆探测任务。 展开更多
关键词 小天体探测 接近与附着 自主捕获 相对导航 图像导航
下载PDF
弱引力环境四足机器人的强化学习姿态机动控制
17
作者 高海波 齐骥 +3 位作者 苏桓立 霍明英 于海涛 邓宗全 《宇航学报》 EI CAS CSCD 北大核心 2024年第10期1676-1684,共9页
针对四足机器人在小天体表面跳跃巡游探测过程中的空中姿态控制问题,提出了一种基于强化学习的无模型控制方案。在小天体的弱引力环境下,机器人单次跳跃的滞空时间很长,机器人需要利用这段时间修正起跳带来的姿态偏差以实现安全着陆,或... 针对四足机器人在小天体表面跳跃巡游探测过程中的空中姿态控制问题,提出了一种基于强化学习的无模型控制方案。在小天体的弱引力环境下,机器人单次跳跃的滞空时间很长,机器人需要利用这段时间修正起跳带来的姿态偏差以实现安全着陆,或改变偏航角以改变未来行进方向。提出的基于近端策略优化(PPO)算法训练的控制器以猫落反射为启发,无需引入额外的姿态控制执行器。仿真结果表明,训练得到的控制器可通过控制四足机器人摆动腿部关节实现三轴姿态机动。设计并搭建了四足机器人气浮微重力模拟试验平台,通过样机试验,控制策略模型的有效性得到了验证。 展开更多
关键词 星球探测机器人 小天体探测 强化学习 微低重力模拟
下载PDF
体重指数对Ⅲ/Ⅳ期非小细胞肺癌患者冷冻消融术后生存期的影响
18
作者 冯瑞 郭鹏德 +1 位作者 李胜鳌 胡凯文 《中国CT和MRI杂志》 2024年第2期67-69,共3页
目的探讨体重指数(BMI)与接受冷冻消融治疗的Ⅲ/Ⅳ期非小细胞肺癌(NSCLC)患者的生存期关系。方法回顾性分析49例接受CT引导下冷冻消融治疗的Ⅲ/Ⅳ期NSCLC患者的临床资料。对BMI与消融术后生存期(COS)进行了相关性分析。结果49例患者中,... 目的探讨体重指数(BMI)与接受冷冻消融治疗的Ⅲ/Ⅳ期非小细胞肺癌(NSCLC)患者的生存期关系。方法回顾性分析49例接受CT引导下冷冻消融治疗的Ⅲ/Ⅳ期NSCLC患者的临床资料。对BMI与消融术后生存期(COS)进行了相关性分析。结果49例患者中,体重不足者3例,正常体重者33例,超重者13例,肥胖者0例。体重不足组、正常体重组、超重组平均COS分别为11.00月、10.79月,17.08月。LSD法两两比较,正常体重组与超重组COS差异有统计学意义,P=0.013<0.05。Spearman相关分析示,分期(r=-0.355,P=0.015<0.05)、BMI(r=0.399,P=0.006<0.05)与患者消融后生存期有相关关系;控制分期后行偏相关分析,BMI仍与COS存在相关(r=0.327,P=0.028<0.05)。结论BMI与冷冻消融治疗Ⅲ/Ⅳ期NSCLC患者的生存期独立相关,高BMI的患者COS更长。 展开更多
关键词 非小细胞肺癌 体重指数 冷冻消融术 计算机断层扫描 总生存期
下载PDF
解毒抑瘤汤联合西医标准方案治疗基因突变阴性晚期非小细胞肺癌的疗效观察
19
作者 杨万全 王恳 +1 位作者 王红 龙文玲 《四川中医》 2024年第3期112-116,共5页
目的:观察基于“癌毒-气血津液”病机理论组方的解毒抑瘤汤联合西医标准方案治疗基因突变阴性晚期非小细胞肺癌(Non-small cell lung cancer,NSCLC)的疗效及毒副反应。方法:收集基因突变阴性晚期NSCLC病例共48例,采用随机数字表法分为... 目的:观察基于“癌毒-气血津液”病机理论组方的解毒抑瘤汤联合西医标准方案治疗基因突变阴性晚期非小细胞肺癌(Non-small cell lung cancer,NSCLC)的疗效及毒副反应。方法:收集基因突变阴性晚期NSCLC病例共48例,采用随机数字表法分为治疗组与对照组,每组各24例,对照组采用西医标准方案治疗,治疗组在对照组基础上给予中药汤剂解毒抑瘤汤加减,以21天为1个周期,连续治疗2个周期后评价两组患者的近期疗效、中医证候疗效、生活质量、中位无进展生存期及毒副反应。结果:治疗组vs对照组:治疗有效率:54.2%vs 45.8%;疾病控制率:83.3%vs 70.8%;中医证候疗效:87.5%vs 70.8%;KPS评分:78.49±12.81分vs 69.32±13.94分;中位无进展生存期:9.8月vs 6.2月。治疗组在治疗有效率、疾病控制率、中医证候疗效、KPS评分及中位无进展生存期方面均优于对照组(P<0.05)。治疗组的恶心呕吐、便秘、纳差乏力发生率低于对照组(P<0.05),治疗组的骨髓抑制和肝肾损害发生率与对照组相比无统计学差异(P>0.05)。结论:解毒抑瘤汤能提高西医标准方案治疗基因突变阴性晚期NSCLC的近期疗效,延长患者生存时间,改善患者中医证候和生活质量,同时能减轻化疗相关部分副反应,且安全性好。 展开更多
关键词 解毒抑瘤汤 癌毒 气血津液 病机 疗效 非小细胞肺癌
下载PDF
面向中小猪场的生猪体温监测智能耳标研究现状及优化对策
20
作者 谢红 冉涌 陈晓琴 《现代畜牧科技》 2024年第9期134-136,共3页
生猪是我国农业重要基础产业之一,生猪体温监测在疫病防治中具有重要作用。针对中小规模养猪场生猪个体信息监控信息化水平不高,以及提高其性价比为目的,结合重庆农村中小规模养猪场实际情况,比较分析传统的生猪体温监测方式及存在的主... 生猪是我国农业重要基础产业之一,生猪体温监测在疫病防治中具有重要作用。针对中小规模养猪场生猪个体信息监控信息化水平不高,以及提高其性价比为目的,结合重庆农村中小规模养猪场实际情况,比较分析传统的生猪体温监测方式及存在的主要问题,提出适用于中小养猪场体温监测的智能电子耳标设计方案。 展开更多
关键词 体温监测 智能耳标 中小猪场 传感器
下载PDF
上一页 1 2 35 下一页 到第
使用帮助 返回顶部