共查询到20条相似文献，搜索用时 656 毫秒
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带极电渣堆焊广泛应用于核反应堆压力容器内壁大面积的不锈钢耐蚀层堆焊。文章针对不锈钢耐蚀层带极电渣堆焊时采用冷焊与热焊两种控温方式制备实验试件,分别进行弯曲、金相等项目的性能检验。结果表明:不锈钢耐蚀层采用冷焊与热焊方式均能满足技术条件的要求,但热焊的实验结果更优于冷焊。 相似文献
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利用堆敷合金系统中所添加的相关元素,能够直接在焊接热循环影响中,使得回火期间能够通过弥散碳化的形式来析出。而在这期间,碳化物的析出不仅可以促使堆敷金属得以强化,还能够使得抗磨损能力大幅度提升,最大限度的降低基体组织中所存在的碳物质含量,提高韧性。本篇文章着重对于超高硬度堆焊材料的硬度以及耐磨进行了全面深入的探讨。 相似文献
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铁素体含量作为不锈钢耐蚀堆焊层检验的必检项目,其含量直接影响到堆焊焊接热裂纹的产生。以某加氢反应器手工堆焊焊接工艺评定为依托,通过调整焊接过程中的工艺参数,找出影响熔敷金属铁素体含量的关键因素,最终制定合理的工艺参数,保证堆焊层质量满足规范要求。 相似文献
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犁铲作为田间农业机械关键触土部件,在耕作过程中与土壤相互作用,极易磨损,从而影响作业质量和效率。为解决深松犁铲耐磨性差、失效频繁的问题,文中利用氧-乙炔火焰喷焊技术在65Mn钢基体上制备了镍基碳化钨复合喷焊层,研究了Ni60和不同质量分数WC的复合粉末在预热温度500℃、乙炔流量1000L/h-1、喷焊距离25mm等喷焊参数一定下对喷焊层耐磨性的影响。利用金相显微镜、显微硬度计、往复型磨粒磨损试验机对喷焊层的显微组织结构、显微硬度和耐磨性进行了试验。试验结果表明:在一定范围内随着Ni60复合粉末中WC质量分数的提高,涂层的硬度和耐磨性能增强。 相似文献
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《内蒙古科技与经济》2017,(4)
CSP连铸机连铸辊,母材材质为20Cr13V,堆焊材料采用新型Cr18Ni4Cu3Nb合金系药芯焊丝,匹配高碱度焊剂,堆焊金属中降低了的C、S、P的含量,堆焊后提高了连铸辊的回火温度,降低了堆焊层的硬度,使再制造连铸辊具有抗腐蚀、热裂纹性高、使用寿命长等特点。 相似文献
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Extracellular matrix (ECM) proteins are required for cell culture. In this paper, we report the use of O(2) plasma bonding to fabricate a perfusion culture microchamber array chip with identical-size ECM spots in the isolated microchambers. The chip was fabricated by assembly of two poly(dimethylsiloxane) (PDMS) layers, a microfluidic network layer, and an ECM array layer, which were aligned and then bonded by O(2) plasma oxidation with protection of the ECM microarray with a physical mask made from PDMS. We successfully cultivated Chinese hamster ovary K1 cells in the microchambers with fibronectin. In the fibronectin microchambers, the cells adhered and extended after 12 h of static culture and then grew over the course of 1 d of perfusion culture. 相似文献
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In this paper, we address the problem of output containment control of general linear multi-agent systems (MASs). The MAS under consideration is comprised by multiple followers and multiple leaders, all with heterogeneous dynamics. In particular, the leaders’ dynamics are subject to heterogeneous non-zero (possibly persistent) but bounded inputs, which are not measurable for any follower agent, making the associated distributed control design problem rather challenging. A new distributed observer-based containment control protocol is proposed to overcome associated challenges. It consists of two hierarchical layers including (i) the first layer of adaptive finite-time cooperative observer responsible for estimating the convex-hull signals formed by multiple leaders’ states through inter-agent collaboration; and (ii) the second layer of distributed state-feedback controller responsible for local tracking control through a modified output regulation technique. Important novelties of the proposed protocol are that (i) it deals with MASs with not only heterogeneous followers but also heterogeneous leaders; (ii) exact output containment control performance can be achieved in the presence of unmeasurable leaders’ inputs and unknown connectivity of communication network; and (iii) associated solvability conditions are formulated as linear matrix inequalities plus linear algebraic equations, which can be tested and solved effectively via efficient semi-definite programming. The developed theoretical results are demonstrated both rigorously using Lyapunov methods and through numerical simulations. 相似文献
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环渤海地区生态脆弱性评价及其空间自相关分析 总被引：14，自引：1，他引：13
基于生态敏感性-生态恢复力-生态压力度概念框架,建立了环渤海地区五省市生态脆弱性评价的指标体系。考虑到指标体系中各评价因子之间可能存在相关性,所以首先在ArcGIS9.2平台上,用主成分分析方法剔除各因子的相关性,并对该区的生态脆弱性进行了评价,然后对脆弱性进行了空间自相关分析。结果表明:生态环境好的、相对不脆弱区主要分布在低山、丘陵等植被状况好、人类活动少的地区;重脆弱区主要分布在农牧交错带、海陆过渡带和城市周围等生态系统不稳定、人类活动剧烈的地区;脆弱区的空间聚集程度呈现出较高的正相关;不同地区之间脆弱性高相关区域主要分布在南部的低脆弱地区,脆弱性低相关区域主要分布在西北部的重脆弱区。 相似文献
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经过各地多部门采取有效措施、积极推进,东北黑土地保护利用取得了显著成效。目前,东北黑土地保护利用已经上升到国家战略,被纳入相关国家规划或纲要中,科学研究取得了重大进展。通过实施东北黑土地保护利用试点项目,黑龙江省、吉林省、辽宁省和内蒙古自治区已经将黑土地保护利用纳入重要工作日程,因地制宜、分区域制定了黑土地保护利用措施,建立了"梨树模式"和"龙江模式";黑土地6个土壤类型耕地地力得到提高,黑土地保护利用工作达到预定目标,社会和民众参与意识明显提升。此外,各级政府通过不断完善相关条例规范,实现黑土地保护利用有章可循,下一步逐步完善国家层面相关法规制度,让黑土地保护利用有法可依。然而,东北黑土地保护利用仍然面临着现有耕作方式能否保持住黑土层厚度、浅薄层黑土能否通过技术创新恢复至中厚层黑土、如何通过低成本投入实现白浆土障碍消减与培肥、黑土区可容忍的风蚀和水蚀量是多少等一系列问题。在未来的工作中,应该加强顶层设计,充分发挥《东北黑土地保护规划纲要(2017—2030年)》和《国家黑土地保护工程实施方案(2021—2025年)》对东北黑土地保护利用的指导作用,在北纬45°以北的黑土带上建立大于4×104km2黑土地保护区,实现中厚层黑土的永续利用;集中力量破解浅薄层黑土耕地地力提升与粮食产能高效的肥沃耕层构建技术瓶颈;建立以长坡为研究对象的水土流失长期观测场,重点攻关坡耕地区域内系统降能排水技术和沟蚀控制技术;设立土壤风蚀监测站点,形成监测网络,进行实时观测,为制定防风蚀技术对策提供重要参考。 相似文献
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《Journal of The Franklin Institute》2019,356(17):10335-10354
This paper is devoted to investigate the designs of the event-based distributed state estimation and fault detection of the nonlinear stochastic systems over wireless sensor networks (WSNs). The nonlinear stochastic systems as well as the filters corresponding to the multiple sensors are represented by interval type-2 Takagi–Sugeno (T–S) fuzzy models. (1) A new type of fuzzy distributed filters based on event-triggered mechanism is established corresponding to the nodes of the WSN. (2) The overall stability and performance, that is mean-square asymptotic stability in H∞ sense, of the event-driven fault detection system is analyzed based on Lyapunov stability theory. (3) New techniques are developed to cope with the problem of parametric matrix decoupling for solving the distributed filter gains. (4) Finally, the desired event-based distributed filter matrices are designed subject to the numbers of the fuzzy rules and a series of matrix inequalities. A simulation case is detailed to show the effectiveness of the presented event-based distributed fault detection filtering scheme. 相似文献
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螺旋滚筒是采煤机的重要部件,采煤机通过滚筒截割煤,在工作过程中叶片尾部磨损严重。为解决这一问题,我们决定在叶片尾部基体上堆焊耐磨材料。 相似文献
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We developed an automated laser induced fluorescence system utilizing microfluidic chips for detection and quantification of immunoglobulins. Microchips were fabricated from polydimethysiloxane (PDMS) using the so-called "prepolymerization technique." The microchip structure helped minimize the effects of PDMS autofluorescence and light scattering. Furthermore, a thin and uniform PDMS layer forming the top of the microchip enabled proper focusing and collection of the excitation beam and the emitted fluorescence, respectively. The developed system was tested for the detection of mouse immunoglobulins. The capturing antibodies were immobilized on internal microchannel walls in the form of a polyelectrolyte. We clearly show that this immobilization technique, if correctly realized, gives results with high reproducibility. After sample incubation and washing, secondary antibodies labeled by fluorescein isothiocyanate were introduced into microchannels to build a detectable complex. We show that mouse antibodies can be quantified in a wide concentration range, 0.01-100 μg ml(-1). The lower detection limit was below 0.001 μg ml(-1) (6.7 pM). The developed laser induced fluorescence (LIF) apparatus is relatively cheap and easy to construct. The total cost of the developed LIF detector is lower than a typical price of plate readers. If compared to classical ELISA (enzyme linked immunosorbent assay) plate systems, the detection of immunoglobulins or other proteins in the developed PDMS microfluidic device brings other important benefits such as reduced time demands (10 min incubation) and low reagent consumption (less than 1 μl). The cost of the developed PDMS chips is comparable with the price of commercial ELISA plates. The main troubleshooting related to the apparatus development is also discussed in order to help potential constructors. 相似文献
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基于生态系统服务的生态福祉分类与时空格局——以中国地级及以上城市为例 总被引：2，自引：0，他引：2
基于生态系统服务价值理论,利用生态系统贡献率对生态福祉核算方法进行改进,在此基础上分析中国地级及以上城市人均生态福祉和生态—经济效率时空分异特征,同时提出基于相对公平与效率视角的生态福祉分类模型,通过相对福祉指数与相对效率指数将生态福祉进行分类,并分析2000—2015年中国337个地级及以上城市不同类型的生态福祉时空格局,研究结果可为促进中国生态文明建设提供部分参考。结果表明：①研究时段内中国337个地级及以上城市人均生态福祉与生态—经济效率在胡焕庸线两侧空间分布差异较大,其重心分别位于青海省的玉树藏族自治州和河南省的信阳市,并随时间分别向东北、西南方向移动。②通过双变量空间自相关方法分析得出生态—经济效率与人均生态福祉之间存在空间负相关关系,生态—经济效率与人均生态福祉的高—低聚集区主要分布在上海市以及河北、山东、江苏等省的沿海城市,以及安徽、河南2省的部分地级及以上城市;低—高聚集区主要分布在西部城市;低—低聚集区主要分布在中部地区的山西、河南、安徽3省的部分城市。③运用相对福祉指数与相对效率指数可将研究区划分为4类生态福祉区：高效—低福祉区所在城市主要以河北、山东、山西、河南、江苏5省为主;低效—高福祉区主要分布在西部城市、东北大部分城市与东南部分城市;低效—低福祉区城市主要分布在高效—低福祉区与低效—高福祉区交界处;高效—高福祉区零散分布。因此,全面实现中国各地区的生态文明建设,需要共同提高西部地区生态—经济效率与东部地区人均生态福祉。 相似文献