熱點文章

增材製造技術在載人航天工程中的應用與展望

doi:10.13700/j.bh.1001-5965.2022.0455

摘要

近年來，增材製造技術在載人航天工程中的應用迅速發展🚹。對熔融沉積成型技術、激光選區熔化技術、線材電弧增材製造技術🚡、熱噴塗增材技術🍎、月壤增材製造技術等用於載人航天工程的增材製造技術及這些技術的應用領域進行了總結。對增材製造技術在在軌製造飛行器替換件🗜、製造大型桁架等難以在地面製造或發射的部件、製造飛行器復雜部件等應用領域進行了總結。提出未來載人航天工程技術的增材製造中應發展適合載人航天工程的材料體系🤽🏻‍♀️，應研究微重力環境下的增材製造技術🧂，同時未來還應發展相關工藝。

基於Transformer模型的滾動軸承剩余使用壽命預測方法

doi:10.13700/j.bh.1001-5965.2021.0247

摘要

準確的滾動軸承剩余使用壽命(RUL)預測對保證機械安全運行和減小維修損失起著至關重要的作用。為提高滾動軸承RUL預測準確率🥐🪷，提出一種基於Transformer模型的軸承RUL預測方法🥶，充分利用其自註意力機製與編碼器-解碼器結構的優勢，解決軸承RUL預測中序列過長而導致的記憶力退化問題🥂🔮，挖掘出輸入特征與軸承RUL之間復雜映射關系。同時🧖🏿‍♂️，采用三角函數變換與累積變換來修正輸入特征的單調性與趨勢性🤽🏿，使其能更好地表征滾動軸承的退化過程。在PHM2012數據集上的實驗結果表明🕵🏻：所提方法相比於對比方法平均絕對誤差分別降低了9.25%、28.63%、34.14%，平均得分分別提高了2.78%🤙、19.79%🏊‍♂️、29.38%⚠；在XJTU-SY數據集上的實驗結果表明，所提方法相比於對比方法均方根誤差降低了17.4%，平均得分提高了18.6%，進一步證明了其可行性與優越性

熱電復合材料的研究進展

doi:10.13801/j.cnki.fhclxb.20220526.003

摘要

熱障塗層隔熱機理分析及有效性判據

doi:10.13224/j.cnki.jasp.20220309

摘要

建立了一維對流-導熱模型🏋🏻‍♀️👨🏻‍🚀，經理論推導、分析驗證得到了熱障塗層隔熱有效性判據❗️：當塗層熱阻大於無塗層時高溫燃氣側換熱熱阻時🧀，塗層總能使葉片金屬基體外表面溫度降低💇🏼‍♂️，起到隔熱效果；反之，則噴塗熱障塗層（TBC）後外部燃氣側表面傳熱系數存在臨界值👳🏿，只有該表面傳熱系數小於臨界值👳🏿‍♀️，熱障塗層才能起到隔熱效果，否則塗層起不到隔熱效果，甚至會惡化葉片換熱🏃🏻‍♂️‍➡️。熱障塗層自身溫降與有無塗層前後葉片金屬基體外表面溫降成比例關系😀，建立了以葉片金屬基體外表面溫度為基礎的新的塗層隔熱效果評價機製。

In vitro fluidic systems: Applying shear stress on endothelial cells

doi:10.1016/j.medntd.2022.100143

摘要

Endothelial cells (ECs) that reside on the surface of blood vessels are constantly exposed to mechanical stimulation, including shear stress. Fluid shear stress (FSS) controls multiple physiological processes in ECs, regulating various pathways that maintain vascular tone and homeostasis function. The complexity of in vivo biological systems raises a demand for better in vitro techniques, which can generate FSS to closely mimic the cellular microenvironment. Through the rational design and use of flow chamber devices, in vitro fluidic systems are critical for a deeper understanding of endothelial responses to various shear conditions. The paper describes principal types of FSS systems, including functional attributes, development process and recent experiments on ECs. Finally, we prospect their possible contribution in the field of endothelial diseases.

機場跑道水泥混凝土道面板尺寸分析

doi:doi: 10.13700/j.bh.1001-5965.2020.0646

摘要

中國機場通常采用板寬不超過5 m的水泥混凝土道面板，國際上已有機場采用板寬6 m以上的水泥混凝土道面板。相比大尺寸水泥混凝土道面板☎，小尺寸道面板容易產生病害🤼。為了研究道面板尺寸對道面性能的影響，基於彈性層狀理論體系建立道面結構有限元模型👳🏻‍♀️，通過改變水泥混凝土道面板平面尺寸，研究了考慮溫度梯度時飛機荷載作用下道面板內的應力變化。通過某機場實例分析了溫度梯度和飛機荷載共同作用下道面板平面尺寸對道面使用壽命的影響，結果表明🚣🏻‍♀️：道面板內應力受溫度梯度影響較大，常見機型荷載作用下，夏季道面板內拉應力25%以上是由溫度梯度荷載造成🤎；不同尺寸道面板在相同荷載作用下🥷🏻，道面產生的損傷量不同，設計過程中加入道面板溫度應力計算🥍，選擇合適的道面板尺寸🤏🏿，可以顯著提高水泥混凝土道面的預期使用壽命。

Stability characteristics and arworthiness requirements of blended wing body aircraft with podded engines

doi:https://doi.org/10.1016/j.cja.2021.09.002

摘要

Blended-Wing-Body (BWB) aircraft have a relatively short fuselage and no horizontal tail, and they usually adopt podded engines and a V tail instead of a vertical tail. Generally, BWB aircraft have decreased longitudinal and directional static stability and damping. In this paper, the three-axis static and dynamic stability characteristics of an example BWB aircraft with podded engines are studied. According to the differences in flight characteristics of BWB aircraft and conventional aircraft, the different airworthiness requirements for BWB aircraft are analyzed: first, based on current airworthiness regulations and transport aircraft flying quality specification, the relaxation requirement of longitudinal static stability for BWB aircraft is studied; second, the influences of podded engines on longitudinal trim, attitude and trajectory responses and maximum directional control power requirement of BWB aircraft are analyzed; third, the changes in the proportional relationships...

Novel roll effector based on zero-mass-flux dual synthetic jets and its flight test

doi:https://doi.org/10.1016/j.cja.2021.08.015

摘要

​The autonomous and controllable Dual Synthetic Jet Actuator (DSJA) is firstly integrated into the Unmanned Aerial Vehicle (UAV), and flight tests without the deflection of rudders are carried out to verify the viability of DSJA to control the attitudes of UAV during cruising. DSJA is improved into an actuator with two diaphragms and three cavities, which has higher energy levels. Actuators, differentially distributed on both sides of the wings, are installed on the trailing edge close to the wing tips. Flight tests, containing Differential Circulation Control (DCC) using double-side actuators, Positive Circulation Control (PCC) using left-side actuators and Negative Circulation Control (NCC) using right-side actuators, are implemented at cruising speed of 25 m/s. Results show that roll attitude control without rudders could be realized by DSJAs. DCC and NCC can generate the rightward roll and yaw angular velocity...