共查询到20条相似文献，搜索用时 78 毫秒
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采用有限体积流固耦合计算方法、非线性有限元热结构耦合分析方法和局部应变法研究大面积比铣槽喷管三维再生冷却槽道在循环工作条件下的热结构变形与低周疲劳寿命,并对比分析了冷却剂质量流量与入口温度对铣槽喷管疲劳使用寿命的影响。计算结果表明,铣槽喷管热结构响应呈现复杂的三维效应,应变较大位置主要分布在与肋连接的内衬区域,喷管中部的残余应变量最大;冷却槽道低周疲劳寿命分布和热结构响应基本一致,最小寿命位于喷管中部与肋相连的内衬区域燃气侧;随冷却剂质量流量增加,铣槽喷管低周疲劳寿命不断提高;随冷却剂入口温度增加喷管尾部低周疲劳寿命值不断降低,而喷管中前部的低周疲劳寿命值却不断提高,当冷却剂入口温度为280K左右时,本文的铣槽喷管总体使用寿命达到最大。 相似文献
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目的:超临界航空煤油在换热过程中会出现传热恶化的现象。本文旨在研究该现象产生的原因及质量流量、壁面热流、入口温度和压力对此现象的影响。创新点:1.分析超临界航空煤油的传热恶化现象;2.揭示超临界航空煤油传热过程中传热恶化现象与质量流量、壁面热流、入口温度及压力的关系。方法:利用数值模拟的方法,模拟超临界航空煤油在管内的流动换热情况,分析其换热特性,并探讨传热恶化产生的原因及影响因素。结论:1.传热恶化是在壁面温度达到拟临界温度或流体平均温度达到临界温度时产生的;2.换热系数随质量流量的增加或壁面热流的降低而增大;3.通过提高煤油的压力可以显著降低恶化现象。 相似文献
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《实验室研究与探索》2017,(7)
为降低采暖能耗,解决室内污染物排放超标的问题,将金属纤维红外燃烧技术与辐射采暖技术相结合,设计了一种金属纤维红外辐射采暖器,该系统主要包括燃烧控制器、风机、燃气电磁阀、燃气调节阀、空气-燃气混合器、点火针、金属纤维等部件。通过对该辐射传热模型的理论分析给出了采暖器安装高度的计算方法,并利用实验手段研究该采暖器的各项工作性能。结果表明,该采暖器工作120min后,房内温度15~22℃,平均18~19℃(目标17℃),已达到采暖要求;实验房间内0~20 min温度上升速度较快,20 min后温度上升较缓慢,采暖器工作120min后,物体温度约高于空气温度2.8℃。当空燃比介于1.1~1.5时,CO与NOx的排放量均低于50×10-6,已达到污染物排放标准;随空燃比增加,CO与NOx的排放量降低,且CO排放量降低更为显著。通过对系统的辐射传热模型理论分析,给出安装高度与功率、辐射表面尺寸定量关系。 相似文献
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以五种常见食用油脂为研究对象, 采用微波加热的处理方法, 探讨了不同微波辐射强度、辐射时间对食用油脂的酸值(AV) 和过氧化值(POV) 的影响及其变化规律; 对微波处理前后油脂的组成进行红外光谱图的分析。结果表明, 油脂的酸值随微波辐射强度增大和加热时间的延长不断增大, 但变化缓慢, 而过氧化值随加热时间的延长先增大后减少再增大, 呈现曲折变化。但五种油脂的酸值和过氧化值经微波处理后均没有超过国家规定的指标, 红外光谱也表明微波加热一定时间后油脂组成未发生明显变化, 因此采用微波加热油脂是一种良好的加热方式, 为微波在油脂业中的应用提供了必要的科学依据。 相似文献
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《滨州学院学报》2020,(6):24-30
超燃冲压发动机喷管是发动机提供推力和升力的主要部件,因此对该流场流向涡特性的研究具有重要意义。采用计算流体力学软件运用数值模拟的方法对超燃冲压发动机喷管的三维流场做定常计算,得到了流场各个截面的流线图。结果表明:外喷管流场中的流向涡起源于喷管下壁面两侧,流向涡随着流动的发展涡的强度会逐渐减弱,且发现外喷管流场中上壁面两侧边缘附近流线开始出现弯折。这是由于此处存在边界层分离现象,该处流场的扰动会向下游传递,并在尾流中形成流向涡;尾流流场流向涡起源于上壁面尾部两侧,随着流动的发展流向涡的尺度逐渐增大,并且涡核有明显靠近的趋势,当两个流向涡边界发生接触时,涡核位置的变化不再明显。同时由于涡尺度的增大流向涡之间会发生挤压变形,但在一定长度内的尾流流场中流向涡不会发生相互卷并。 相似文献
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利用溶剂热法合成Er~(3+)/Yb~(3+)/Ce~(3+)共掺杂的K_2YF_5微晶.在980 nm红外激光激发下,微晶产生有效的可见上转换辐射及1.5μm近红外辐射.随着Ce~(3+)掺杂量的增加,上转换荧光逐渐减弱,而1.5μm红外光随Ce~(3+)掺杂浓度的增加先增加而后减弱,当Ce~(3+)掺杂浓度为4%时,1.5μm近红外辐射最强,约为不掺杂Ce~(3+)样品辐射强度的4倍.微晶发光性能的变化被归因于Er~(3+)、Ce~(3+)之间的能量交叉弛豫.结合掺杂离子的能级结构,对微晶的发光机理进行详细的讨论. 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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Rachel Zupek 《海外英语》2007,(11):40-41
我们绝大部分人都同意一件事情——我们喜欢金钱。但是你对金钱的喜欢之情足够到让你创立一份事业么?.财富通常被人忽视,主要在于人们不能真正了 相似文献
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陈美曦 《山东教育学院学报》2008,23(2):103-107
Different nations have different social cultures, and the social culture of every nation is developing with the development of the nation, language is greatly influenced by social culture, which enables language to possess national and historical characteristics. Word is the smallest, independent, meaningful linguistic unit of language. It can well reflect the national and historical characteristics. From synchronic aspect, the social and cultural influence on word meaning is mainly embodied in conceptual and associative meanings of word. The incorrespondence of word meaning is a phenomenon that exists in both conceptual and associative meanings of word among different languages. From diachronic aspect, the development of social culture causes some changes of word meaning to some extent. Therefore, social culture plays a key role in vocabulary learning and mastery of a language. 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献