检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

力学性能可调的高氧钛原位电弧增材制造

Transactions of Nonferrous Metals Society of China 2024年第1期34卷 171-183页

作者：李昌远刘长猛鲁涛郭跃岭刘彬北京理工大学机械与车辆学院北京100081 中国运载火箭技术研究院北京宇航系统工程研究所北京100076

通过电弧增材制造原位制备高氧钛,并对高氧钛的成分偏析、显微组织和力学性能进行研究。结果表明,高氧钛试样的显微组织主要呈现为针状α相集束。随着氧含量的增加,试样针状α相逐渐变宽,集束尺寸变大。受氧的强化作用以及晶粒尺寸效应... 详细信息

通过电弧增材制造原位制备高氧钛,并对高氧钛的成分偏析、显微组织和力学性能进行研究。结果表明,高氧钛试样的显微组织主要呈现为针状α相集束。随着氧含量的增加,试样针状α相逐渐变宽,集束尺寸变大。受氧的强化作用以及晶粒尺寸效应共同影响,试样的强度先提高后下降,伸长率显著下降,断裂形式由塑性断裂向解理断裂过渡。当氧含量达到0.37%(质量分数)时,伸长率约为7%,试样抗拉强度超过730 MPa,约为商业纯钛的2倍。

关键词：电弧增材制造纯钛高氧含量显微组织力学性能

Cone-beam computed tomography noise reduction method based on U-Net with convolutional block attention module in proton therapy

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第7期35卷 89-100页

作者： Xing-yue Ruan Xiu-Fang Li Meng-Ya guo Mei Chen Ming Lv Rui Li Zhi-ling Chen Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai201800China University of Chinese Academy of Sciences Beijing100049China Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai201210China Department of Radiation Oncology Ruijin HospitalShanghai Jiao Tong University School of MedicineShanghai200025China Shanghai Key Laboratory of Proton therapy Shanghai201801China

Cone-beam computed tomography(CBCT) is mostly used for position verification during the treatment process. However,severe image artifacts in CBCT hinder its direct use in dose calculation and adaptive radiation therapy re-planning for proton therapy. In this study, an improved U-Net neural network named CBAM-U-Net was proposed for CBCT noise reduction in proton therapy, which is a CBCT denoised U-Net network with convolutional block attention modules. The datasets contained 20 groups of head and neck images. The CT images were registered to CBCT images as ground truth. The original CBCT denoised U-Net network, sCTU-Net, was trained for model performance comparison. The synthetic CT(SCT) images generated by CBAM-U-Net and the original sCTU-Net are called CBAM-SCT and U-Net-SCT images, respectively. The HU accuracies of the CT, CBCT, and SCT images were compared using four metrics: mean absolute error(MAE), root mean square error(RMSE), peak signal-to-noise ratio(PSNR), and structure similarity index measure(SSIM). The mean values of the MAE, RMSE, PSNR, and SSIM of CBAM-SCT images were 23.80 HU, 64.63 HU, 52.27 dB, and 0.9919, respectively,which were superior to those of the U-Net-SCT images. To evaluate dosimetric accuracy, the range accuracy was compared for a single-energy proton beam. The γ-index pass rates of a 4 cm × 4 cm scanned field and simple plan were calculated to compare the effects of the noise reduction capabilities of the original U-Net and CBAM-U-Net on the dose calculation results. CBAM-U-Net reduced noise more effectively than sCTU-Net, particularly in high-density tissues. We proposed a CBAM-U-Net model for CBCT noise reduction in proton therapy. Owing to the excellent noise reduction capabilities of CBAM-U-Net, the proposed model provided relatively explicit information regarding patient tissues. Moreover, it maybe be used in dose calculation and adaptive treatment planning in the future.

关键词： Proton therapy Cone-beam CT CBAM-U-Net γ-index

Evaluation of the efficacy and safety of endoscopic band ligation in the treatment of bleeding from mild to moderate gastric varices type 1

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2024年第5期30卷 440-449页

作者： yue Deng Ya Jiang Tong Jiang ling Chen Hai-Jun Mou Bi-Guang Tuo guo-Qing Shi Department of Gastroenterology Digestive Disease HospitalThe Affiliated Hospital of Zunyi Medical UniversityZunyi 563000Guizhou ProvinceChina Department of Gastroenterology Guizhou Hospital of the First Affiliated HospitalSun Yat-sen UniversityGuiyang 550000Guizhou ProvinceChina Department of Gastroenterology Yinjiang Autonomous County People’s HospitalTongren 554300Guizhou ProvinceChina

BACKGROUND According to practice guidelines,endoscopic band ligation(EBL)and endoscopic tissue adhesive injection(TAI)are recommended for treating bleeding from esophagogastric ***,EBL and TAI are known to cause serious complications,such as hemorrhage from dislodged ligature rings caused by EBL and hemorrhage from operation-related ulcers resulting from ***,the optimal therapy for mild to moderate type 1 gastric variceal hemorrhage(GOV1)has not been ***,the aim of this study was to discover an individualized treatment for mild to moderate *** To compare the efficacy,safety and costs of EBL and TAI for the treatment of mild and moderate *** A clinical analysis of the data retrieved from patients with mild or moderate GOV1 gastric varices who were treated under endoscopy was also *** were allocated to an EBL group or an endoscopic TAI *** differences in the incidence of varicose relief,operative time,operation success rate,mortality rate within 6 wk,rebleeding rate,6-wk operation-related ulcer healing rate,complication rate and average operation cost were compared between the two groups of *** The total effective rate of the two treatments was similar,but the efficacy of EBL(66.7%)was markedly better than that of TAI(39.2%)(Pling rate of operation-related ulcers in the EBL group was 80.4%,which was significantly greater than that in the TAI group(35.3%)(P<0.01).The incidence of postoperative complications in the two groups was *** average cost and other related economic factors were g

关键词： Gastric varices Type 1 gastric variceal hemorrhage Endoscopic band ligation Tissue adhesive injection

Energy Density Dependence of Bonding Characteristics of Selective Laser-Melted Nb–Si-Based Alloy on Titanium Substrate

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2018年第5期31卷 477-486页

作者： yue-ling guo Li-Na Jia Bin Kong Yong-Lin Huang Hu Zhang School of Materials Science and Engineering Beihang University

Spherical Nb–20Si–24Ti–2Cr–2Al pre-alloyed powders were processed by selective laser melting（SLM） on Ti6Al4V substrates with different energy densities. A series of single tracks and single layers were produced using different processing parameters, including powder size, laser power, scanning speed and hatch distance. Results showed that the pre-alloyed powders ranging from 45 to 75 lm were more applicable to SLM with less balling tendency, in comparison with those between 75 and 180 lm. The increase in linear energy density（LED） resulted in the decrease in contact angle and the increase in the width of single track as well as its penetration depth into the substrate. Smaller hatch distance leaded to a larger remelted part of the former track and a higher volumetric laser energy density. With a thickness of 75.6 lm, an interfacial intermediate layer, enriched in Ti and depleted in Nb, Si, Cr and Al, was formed between the SLM part and the Ti6Al4V substrate. The mechanisms of the elimination of balling phenomenon by employing a higher LED and the interfacial bonding characteristics between Nb–Si-based alloys via SLM and the Ti6Al4V substrate were discussed.

关键词： Nb-Si alloys Selective laser melting Additive manufacture Bonding character Microstructure

Enhanced bright green luminescence from GdOF:Ho^(3+) up-conversion phosphor via Yb^(3+) doping

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第2期42卷 263-269,I0002页

作者： Linjun Qin yue guo Jing Xu Lixi Wang Qitu Zhang College of Materials Science and Engineering Nanjing Tech UniversityNanjing211816China

In this paper,a series of GdOF-based green phosphors doped with Ho^(3+) and Yb^(3+) ions was prepared by a simple co-precipitation *** crystal structure s and optical prope rties were investigated in *** intensity of the emission of GdOF:Yb^(3+),Ho^(3+) phosphors is enhanced by the effective energy transfer from Yb^(3+) to Ho^(3+),and the optimal luminescence is achieved with the Ho^(3+)doping amount of 0.1 mol%as well as Yb^(3+) doping amount of 5 mol%.Tunable UC emission of samples is achieved by adjusting the doping concentration of Ho^(3+) or Yb^(3+).The purity of the green UC emission is further improved by enhancing the excitation pumping *** addition,logarithmic functions of green,red and nearinfrared radiation intensities were calculated versus logarithmic function of pump power for further study.A possible UC luminescence mechanism between Yb^(3+) and Ho^(3+) is discussed based on powerdependent UC luminescence spectrum and decay *** results suggest that GdOF:Yb^(3+),Ho^(3+)phosphors with bright and high-purity green UC emission have potential applications in the fields of bioimaging,display and illumination.

关键词： Up-conversion GdOF Lanthanide ions Rare earths

Heat transfer and temperature evolution in underground mininginduced overburden fracture and ground fissures: Optimal time window of UAV infrared monitoring

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2024年第1期34卷 31-50页

作者： Yixin Zhao Kangning Zhang Bo Sun Chunwei ling Jihong guo Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources China University of Mining and Technology-BeijingBeijing 100083China School of Energy&Mining Engineering China University of Mining and Technology-BeijingBeijing 100083China State Key Laboratory of Coal Resources and Safe Mining China University of Mining and Technology-BeijingBeijing 100083China

Heat transfer and temperature evolution in overburden fracture and ground fissures are one of the essential topics for the identification of ground fissures via unmanned aerial vehicle(UAV) infrared imager. In this study, discrete element software UDEC was employed to investigate the overburden fracture field under different mining conditions. Multiphysics software COMSOL were employed to investigate heat transfer and temperature evolution of overburden fracture and ground fissures under the influence of mining condition, fissure depth, fissure width, and month alternation. The UAV infrared field measurements also provided a calibration for numerical simulation. The results showed that for ground fissures connected to underground goaf(Fissure Ⅰ), the temperature difference increased with larger mining height and shallow buried depth. In addition, Fissure Ⅰ located in the boundary of the goaf have a greater temperature difference and is easier to be identified than fissures located above the mining goaf. For ground fissures having no connection to underground goaf(Fissure Ⅱ), the heat transfer is affected by the internal resistance of the overlying strata fracture when the depth of Fissure Ⅱ is greater than10 m, the temperature of Fissure Ⅱ gradually equals to the ground temperature as the fissures’ depth increases, and the fissures are difficult to be identified. The identification effect is most obvious for fissures larger than 16 cm under the same depth. In spring and summer, UAV infrared identification of mining fissures should be carried out during nighttime. This study provides the basis for the optimal time and season for the UAV infrared identification of different types of mining ground fissures.

关键词： Heat transfer Overburden fracture Ground fissures Infrared thermal imaging Unmanned aerial vehicle(UAV) COMSOL simulation

Recent Advances in Mechanistic Understanding of Metal-Free Carbon Thermocatalysis and Electrocatalysis with Model Molecules

在线全文

学校读者我要写书评

暂无评论

Nano-Micro Letters 2024年第7期16卷 74-97页

作者： Wei guo Linhui Yu ling Tang Yan Wan Yangming Lin CAS Key Laboratory of Design and Assembly of Functional Nanostructures Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002People’s Republic of China Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials Xiamen Institute of Rare Earth MaterialsHaixi InstituteChinese Academy of SciencesXiamen 361021People’s Republic of China State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002People’s Republic of China Institute of Urban Environment Chinese Academy of SciencesXiamen 361021People’s Republic of China

Metal-free carbon,as the most representative heterogeneous metal-free catalysts,have received considerable interests in electro-and thermo-catalytic reac-tions due to their impressive performance and *** the past decade,well-designed carbon catalysts with tunable structures and heteroatom groups coupled with various characterization techniques have proposed numerous reaction ***,active sites,key intermediate species,precise structure-activity relationships and dynamic evolution processes of carbon catalysts are still rife with controversies due to the monotony and limitation of used experimental *** this Review,we sum-marize the extensive efforts on model catalysts since the 2000s,particularly in the past decade,to overcome the influences of material and structure limitations in metal-free carbon *** both nanomolecule model and bulk model,the real contribution of each alien species,defect and edge configuration to a series of fundamentally important reactions,such as thermocatalytic reactions,electrocatalytic reactions,were systematically *** with in situ techniques,isotope labeling and size control,the detailed reaction mechanisms,the precise 2D structure-activity relationships and the rate-determining steps were revealed at a molecular ***,the outlook of model carbon catalysis has also been proposed in this work.

关键词： Metal-free carbon catalysts Model catalyst Electrocatalysis Active site Reaction mechanisms

Ramsey Numbers of Trees Versus Multiple Copies of Books

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2024年第3期40卷 600-612页

作者： Xiao-bing guo Si-nan HU yue-jian PENG School of Mathematical Sciences Luoyang Normal UniversityLuoyang 471934China School of Mathematics Hunan UniversityChangsha 410082China

Given two graphs G and H,the Ramsey number R(G,H) is the minimum integer N such that any two-coloring of the edges of K_(N) in red or blue yields a red G or a blue *** v(G) be the number of vertices of G and χ(G) be the chromatic number of *** s(G) denote the chromatic surplus of G,the number of vertices in a minimum color class among all proper χ(G)-colorings of *** showed that R(G,H)≥(v(G)-1)(χ(H)-1)+s(H) if G is connected and v(G)≥s(H).A connected graph G is H-good if R(G,H)=(v(G)-1)(χ(H)-1)+s(H).Let tH denote the disjoint union of t copies of graph H,and let G∨H denote the join of G and *** a complete graph on n vertices by K_(n),and a tree on n vertices by T_(n).Denote a book with n pages by B_(n),i.e.,the join K_(2) ∨■.Erd?s,Faudree,Rousseau and Schelp proved that T_(n) is B_(m)-good if n≥*** this paper,we obtain the exact Ramsey number of T_(n) versus 2B_(2).Our result implies that T_(n) is 2B_(2)-good if n≥5.

关键词： ramsey number ramsey goodness tree book

High-temperature oxidation behavior of Nb-Si-based alloy with separate vanadium,tantalum,tungsten and zirconium addition

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2021年第3期40卷 607-615页

作者： Sheng-Nan Zhang Li-Na Jia yue-ling guo Bin Kong Feng-Xiang Zhang Hu Zhang School of Materials Science and Engineering Beihang UniversityBeijing 100191China

The microstructure and oxidation behavior of directionally solidified(DS) Nb-15 Si-24 Ti-4 Cr-2 Al-2 Hf alloys with separate vanadium,tantalum,tungsten and zirconium additions were investigated by X-ray diffraction(XRD),electron probe microanalyzer(EPMA) equipped with wave-dispersive spectroscopy(WDS),scanning electron microscopy(SEM) and transmission electron microscopy(TEM) equipped with an energy-dispersive spectroscopy(EDS).Results show that the five alloys are all composed of primary(Nb,Ti) solid solution((Nb,Ti)ss)phase and eutectic(Nb,Ti)ss/(Nb,Ti)_(5) S_(3) *** oxidation at 1250℃ for 100 h in air,the surfaces of the five alloys are covered by the oxides of Nb_(2)O_(5),TiNb_(2) O_(7),Ti_(2) Nb10O29,TiO_(2) and amorphous SiO_(2).It is found that the alloying elements of V and W are detrimental for oxidation resistance and the addition of Ta has no obvious *** addition obviously benefits the oxidation resistance at high temperature,by decreasing the weight gain from 242.75 to184.83 mg·cm^(-2).The oxidation mechanism of Nb-Sibased alloys and the effects of different alloying elements on the oxidation resistance of Nb-Si-based alloys were discussed.

关键词： Nb-Si-based alloys Directional solidification Microstructure Oxidation