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关键词： Wet friction clutch   Multiple friction pairs   Engagement characteristics   Torque characteristics  

摘要： A kinematic coupling model of the rotation-axial engagement process of friction elements is established based on the oil film dynamic pressure lubrication and an elastic contact model of the asperities. The engagement characteristics of the multi-disc wet friction clutch are analyzed. The equation for the transmission torque of the clutch is derived by considering the axial movement of the friction elements and the surface morphology of the friction pairs. The influences of the piston pressure and the number of friction pairs on the speed and transmission torque of the clutch during engagement are analyzed considering the viscous torque and the contact torque. Finally, the effects of engagement pressure on the torque and engagement time of the clutch are verified.

关键词： five-axis   cradle type   point-scanning   error modeling  

摘要： There are generally complex features with large curvature or narrow space on surfaces of complicated tiny parts, which makes high-precision measurements of their three-dimensional (3D) overall profiles a long-lasting industrial problem. This paper proposes a feasible measurement solution to this problem, by designing a cradle-type point-scanning five-axis measurement system. All the key technology of this system is also studied from the system construction to the actual measurement process, and the measurement accuracy is improved through error calibration and compensation. Finally, the feasibility is proved by engineering realization. The measurement capability of the system is verified by measuring workpieces such as cross cylinders and microtriangular pyramids.

关键词： Dry clutch vibrations   Mode coupling instability   NVH   Friction  

摘要： Determining the root causes of Noise, Vibration and Harshness (NVH) phenomena in modern automotive drivetrains is a task of critical importance. This research investigates the stability of dry clutch systems vibrational behaviour during engagement. A fully coupled dry clutch numerical model including the influence of friction is presented and validated using vehicle measurements. The clutch component frictional properties are measured using parts that exhibit aggressive NVH behaviour using representative tribometric experiments. The validated numerical tool highlights the occurrence of instabilities which are caused by modal couplings, particularly between the input shaft bending and clutch disc radial motions. Such a validated transient dynamics model of a dry clutch system has not hitherto been presented in the open literature.

关键词： 4-AAQB   cetuximab   KRAS mutation   resistance   colorectal cancer  

摘要： The KRAS mutation is one of the leading driver mutations in colorectal cancer (CRC), and it is usually associated with poor prognosis and drug resistance. Therapies targeting the epidermal growth factor receptor (EFGR) are widely used for end-stage CRC. However, patients with KRAS mutant genes cannot benefit from this therapy because of Ras signaling activation by KRAS mutant genes. Our previous study revealed the anti-proliferative effect of 4-acetyl-antroquinonol B (4-AAQB) on CRC cells, but whether the drug is effective in KRAS-mutant CRC remains unknown. We screened CRC cell lines harboring the KRAS mutation, namely G12A, G12C, G12V and G13D, with one wild type cell line as the control;SW1463 and Caco-2 cell lines were used for further experiments. Sulforhodamine B assays, together with the clonogenicity and invasion assay, revealed that KRAS-mutant SW1463 cells were resistant to cetuximab;however, 4-AAQB treatment effectively resensitized CRC cells to cetuximab through the reduction of colony formation, invasion, and tumorsphere generation and of oncogenic KRAS signaling cascade of CRC cells. Thus, inducing cells with 4-AAQB before cetuximab therapy could resensitize KRAS-mutant, but not wild-type, cells to cetuximab. Therefore, we hypothesized that 4-AAQB can inhibit KRAS. In silico analysis of the publicly available GEO (GSE66548) dataset of KRAS-mutated versus KRAS wild-type CRC patients confirmed that miR-193a-3p was significantly downregulated in the former compared with the latter patient population. Overexpression of miR-193a-3p considerably reduced the oncogenicity of both CRC cells. Furthermore, KRAS is a key target of miR-193a-3p. In vivo treatment with the combination of 4-AAQB and cetuximab significantly reduced the tumor burden of a xenograft mice model through the reduction of the expression of oncogenic markers (EGFR) and p-MEK, p-ERK, and c-RAF/p-c-RAF signaling, with the simultaneous induction of miR-193a-3p expression in the plasma. In summary

关键词： Aerodynamic performance   phi-type vertical axis wind turbine   Pitch motion   IDDES  

摘要： The floating vertical axis wind turbine (VAWT) is considered as a competitive device in the utilization of offshore wind energy. However, the platform pitch motion would affect its aerodynamic behavior. In this paper, the aerodynamic performance of a floating 9-type VAWT under pitch motion is investigated by using the Improved Delayed Detached Eddy Simulation SST k - omega turbulence model. After verifying the feasibility of the numerical model, the effects of pitch motion amplitude and period on the aerodynamic characteristics were evaluated, and the impacts of these observations were elucidated. The results showed that the averaged net power coefficient increment of about 1.5%-15% could be obtained under platform pitch motions, and the fluctuation of aerodynamic loads was found to increase. Besides, the pitch motion pattern could be regarded as the combination of surge and heave motions, which explained the similarity of their effects on the wind turbine aerodynamics. Furthermore, it was found that the frequency of the peak torque coefficient would change under different periods of pitch motion, which should be noticed in the design of floating wind turbine. Finally, it was concluded that the current study provided additional information about the effect of pitch motion on wind turbine aerodynamics. (C) 2021 Elsevier Ltd. All rights reserved.

摘要： Evaluative stances are common in narrative and realized at all levels of linguistic structure. In film reviews, evaluation has been recognized as one of the most important stages alongside description (Taboada, 2011). Following Martin & White's Appraisal Theory of Evaluation, the present comparative study focuses on two sub-systems of Appraisal, namely Appreciation and Engagement. The purpose of this paper is two-fold: a) to compare the way in which film critics use evaluative, axiological adjectives to evaluate two different film types and b) to study how professional film critics use of two types of engagement devices, namely epistemic and opinion devices, to position their own claims towards other potential viewpoints. The study is also influenced by two previous claims: Holbrook's claim that, in contrast to consumers who seem to prefer American-made, commercial films, expert critics usually appreciate complex cinematography and culturally diverse films; and Carretero's claim that in professional film reviews opinion devices are an almost absent feature, since these tend to be replaced by epistemic devices. To further explore these claims, this comparative, corpus- based study focuses on the frequency of evaluation adjectives and engagement devices used by expert film critics for the positive or negative evaluation of two different films: the 2020 box office hit "Bad Boys for Life" and the 2018 art film "Cold War". The study used a mixed-method design, first subjecting the realizations of Appreciation and Engagement to a quantitative analysis and following this with a qualitative discussion of results. The results indicate: a) that in the case of both films positive evaluations clearly surpass negative evaluations; however, individual examples seem to express a mildly deprecatory attitude towards commercial cinematography and b) that although the number of epistemic devices in the reviews clearly surpasses that of opinion devices, the frequencies of opinion devic

关键词： 电动汽车   无动力中断两挡变速器   离合器半结合点   自学习算法  

摘要： 两挡电控机械自动变速器(automatic mechanical transmission,AMT)可以优化电动汽车的驱动电机工作区间,改善整车的动力性和经济性,但在工作过程中,离合器的半结合点准确辨识对换挡性能影响很大。当离合器摩擦片磨损或膜片弹簧疲劳状态下,离合器实际工作位置发生偏移,需要通过自学习方式来准确辨识离合器半结合点位置,以保证变速器高质量换挡控制性能。以一种新型的电动汽车无动力中断两挡变速器I-AMT(Inverse AMT)为研究对象,针对其干式离合器磨损后半结合点位置发生变化等问题,提出一种离合器半结合点位置自学习策略,使得在离合器缓慢分离的同时,通过检测与离合器主动端相连的驱动电机转速编码器变化趋势,实现离合器半结合点位置准确辨识。试验表明,在离合器存在磨损的情况下,该策略能够准确识别离合器半结合点位置,从而自适应调整变速器工作状态,以保证I-AMT高质量无动力中断换挡。

关键词： 齿轮传动   可靠性   优化模型   遗传算法  

摘要： 以可靠性理论为基础,将齿轮的应力与强度视为服从正态分布的随机变量,通过建立以最小体积为目标,以强度、可靠性为约束的优化模型,对齿轮传动的主要结构参数进行优化设计。以某轿车减速器齿轮传动为例,建立优化模型,利用MATLAB遗传算法求解模型。与原始设计相比,经优化后齿轮分度圆体积之和减小16.4%,齿轮结构更加紧凑,实现了节省材料、降低成本的目的。

关键词： 自动同步离合器   磨损   故障分析   静态调试  

摘要： SSS离合器运用范围非常广泛,装配要求也非常严格。近年来有部分项目在离合器切换过程中出现过磨损现象,给机组运行的经济性和安全性都带来了隐患。文章对离合器的常见问题进行了解析,并提出处理建议,为工程应用及故障判断提供了参考价值。

关键词： 内转子   永磁电机   桥门式起重机   结构  

摘要： 随着具有快速电流跟踪功能的变频装置、DSP信号处理器以及高性能钕铁硼永磁材料的出现永磁同步电动机及其控制技术发展迅速,其易用于低速直接驱动,可省去齿轮减速装置,永磁同步电动机无齿轮传动已成为桥门式起重机械趋势。采用永磁同步电机来驱动桥门式起重机的机构简化了机械结构,而且低碳环保、高效节能。永磁同步电机的应用,将使桥门式起重机行业更新换代,物料搬运更加节能高效。