Analysis of the shifting behavior of a novel clutchless geared smart transmission

Conventional geared transmissions use some kinds of clutches to control the power flow from an internal combustion engine to the driveline while shifting gears. However, the shifting performance is seriously affected by the clutch engagement and an unavoidable drop in the torque may occur when the clutch is disconnected. Moreover, wear of the clutch, the need for hydraulic equipment, and the load limit may together aggravate the limits of the clutch system. For this reason, as a novel transmission without a clutch, the clutchless geared smart transmission (henceforth CGST) is proposed by our research team. The CGST controls the power flow in a multiple-input gear-train by controlling the electric motor attached to the planetary gear system. However, no CGST has been realized in an actual vehicle thus far, and the performance has been predicted only theoretically. In this research, we analyzed the achievable performance based on a developed CGST dynamic model with a typical CGST structure. In addition, a CGST gear-shifting algorithm is proposed for use with the dynamic model. From the simulation results, the CGST does not show an abrupt drop in its torque or oscillation while shifting gears due to the absence of a discontinuous power flow. The developed dynamic model can serve as a performance reference for the CGST. Moreover, it can be used as a simulation tool for developing a gear-shifting control logic scheme.     

海洋环境下混凝土中钢筋加速锈蚀研究

为研究海洋环境下氯离子渗透导致混凝土中钢筋电化学腐蚀行为、锈胀裂缝发展及锈斑分布情况,同时为青岛地铁高性能混凝土配合比的优化及耐久性能提供试验依据,设计了上置腐蚀溶液槽的钢筋混凝土试件,并针对C40、C50、C50S和C55 4类钢筋混凝土试件开展恒电位加速试验。试验结果表明： 采用本试验方法加速钢筋混凝土锈蚀,靠近混凝土保护层一侧的钢筋锈蚀严重,钢筋出现点蚀现象,与自然环境下钢筋锈蚀情况一致; 依据交流阻抗谱图拟合的钢筋电荷转移电阻随腐蚀时间增加而下降,依据计算的腐蚀电流密度,测试的钢筋电流演变拐点可确定C40、C50、C50S和C55混凝土中钢筋脱钝时间分别为60～70、80～90、90～100、100～110 h,钢筋混凝土锈胀开裂时间分别为120、136、176、264 h; 采用图像处理软件依据灰度值不同可实现锈斑分布的定量计算,混凝土护筋能力排序为C55>C50S>C50>C40。     

主动圆锥齿轮尾部螺纹热处理工艺的研究

为解决热处理后主动圆锥齿轮尾部螺纹硬度达不到技术要求的问题，进行了几种热处理工艺试验。结果表明：采用双重保险工艺处理的主动圆锥齿轮尾部螺纹硬度完全可以达到产品技术要求，质量稳定可靠，但成本较高；采用感应退火工艺，尾部螺纹硬度可以达到技术要求，其特点是节能、生产效率高，但需要定期对尾部螺纹进行力学性能检测。     

基于对称受限玻尔兹曼机的协同过滤算法

协同过滤算法在推荐系统中得到了广泛应用。其中具有代表性的是基于有向图模型的矩阵分解法和基于无向图模型的受限玻尔兹曼机。文中提出了一种基于对称受限玻尔兹曼机的协同过滤算法,该算法充分考虑并利用了推荐系统中用户和物品的对称性,通过对用户和物品分别建立了一个受限玻尔兹曼机,最后,采用回归算法对二者的结果进行融合处理。实验结果显示该方法与其他相关算法相比具有明显的优越性。     

Deep foundation pit excavation procedure optimization considering creep deformation on nearby metro tunnelEI北大核心

Research purposes: The existing researches about excavating procedures of deep foundation pit on nearby metro tunnel in soft formation are lack of systematicness, and creep characteristics of soft clay are not usually taken into consideration. This paper takes Qianhaiwan station of Metro Line 11 in Shengzhen as engineering background and considers creep characteristics in sludge formation. The influence of step excavation in the transversal, longitudinal and vertical directions on the deformation of foundation pit and nearby subway tunnel are simulated, which may be expected to provide theoretical basis for choosing foundation pit excavation procedure of Qianhaiwan station. Research conclusions: (1) The segment far away from tunnel should be excavated firstly when only transversal step excavation was undertaken along the horizontal direction of foundation pit. (2) The maximum horizontal displacement of the piles show exponential relations with the number of segments when step excavation of foundation pit was undertaken in vertical and transversal or longitudinal. If thickness of every step excavation was limited in 1.5~2 m, the horizontal displacement of the pile near tunnel can be reduced about 9 percent when there is no horizontal step excavation. (3) Transversal step excavation with segments far from tunnel excavated firstly was found to be the best step excavation method under the same condition of step number and support, and longitudinal and transversal step excavation followed while longitudinal step excavation was the last. (4) The research results have guiding significance for foundation pit of Qianhaiwan station and similar projects.     

线控转向系统对汽车操纵稳定性的影响

基于MATLAB/Simulink软件建立线控转向系统的动力学模型,分析线控转向系统关键部件——转向电机的转动惯量、阻尼系数、刚度等对汽车操纵稳定性的影响。合理设计线控转向系统转向电机的结构参数,可提高汽车的操纵稳定性。     

水下光通信LED阵列光源方法与实现

为了设计一种新的用于水下通信的光源,分析了LED光源用于水下通信的优势,介绍了水下光通信系统选择光源的条件,进行了具体的LED光源阵列及其光学系统设计,最后进行了水下光通信实验。实验结果表明：LED阵列光源应用于水下光通信,体积小,重量轻,结构简单,能较好、较快地实现水下光通信。     

南海奋进FPSO单点液压缸拆卸分析

中海石油(湛江)有限公司文昌作业公司所属的南海奋进FPSO在坞修期间,用于单点液压大钳锁定装置的液压缸需要运输到车间进行拆卸检修及更换密封垫圈。针对单点液压缸在拆卸中出现的问题,制定新的拆卸方案,改进专用工具,收到良好的效果。     

飞机降落冲击荷载作用下高铁隧道动力响应及疲劳损伤研究北大核心CSCD

针对运营期高铁隧道衬砌结构在飞机降落冲击荷载作用下的动力响应规律及疲劳损伤问题,以成自高铁下穿天府机场东二跑道区间隧道为工程背景,采用有限元分析的方法研究隧道动力响应及疲劳损伤规律。结果表明:B747-400型飞机在粗暴着陆后0.05 s时刻动力载荷达到最大值,约为500 kN;在单次粗暴着陆工况下,拱顶位移和受力最大,位移最大峰值为1.58 mm,拉应力最大峰值为437.79 kPa,压应力最大峰值为556.24 kPa,衬砌结构未出现塑性损伤;飞机荷载长期作用下,随着循环次数的增加,结构损伤部位和程度也随之增加,拱顶损伤最突出,其次为边墙,隧道衬砌在上方飞机长期粗暴着陆作用下的疲劳寿命大致为25 a。     

Analysis of travel activity determinants using robust statistics

This study investigates travel behavior determinants based on a multiday travel survey conducted in the region of Ghent, Belgium. Due to the limited data reliability of the data sample and the influence of outliers exerted on classical principal component analysis, robust principal component analysis (ROBPCA) is employed in order to reveal the explanatory variables responsible for most of the variability. Interpretation of the results is eased by utilizing ROSPCA. The application of ROSPCA reveals six distinct principal components where each is determined by a few variables. Among others, our results suggest a key role of variable categories such as journey purpose-related impedance and journey inherent constraints. Surprisingly, the variables associated with journey timing turn out to be less important. Finally, our findings reveal the critical role of outliers in travel behavior analysis. This suggests that a systematic understanding of how outliers contribute to observed mobility behavior patterns, as derived from travel surveys, is needed. In this regard, the proposed methods serve for processing raw data typically used in activity-based modelling.