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41.
纪树立 《计算机光盘软件与应用》2010,(12)
任务驱动教学法是建立在建构主义学习理论基础上的教学模式,将知识的学习放置于具体问题解决上来,通过学生自身或小组协作,来完成任务.在学习计算机编程的课程时,使用任务驱动法教学,可以大大提高教学效果,同时又能培养一种良好的团队精神,体现以学生的全面发展为中心的教育思想. 相似文献
42.
OBJECTIVE: To investigate the relationship among friction, applied torque, and axial push force on cylindrical handles. BACKGROUND: We have earlier demonstrated that participants can exert greater contact force and torque in an "inward" movement of the hand about the long axis of a gripped cylinder (wrist flexion/forearm supination) than they can in an "outward" hand movement. METHOD: Twelve healthy participants exerted anteriorly directed maximum push forces along the long axis of aluminum and rubber handles while applying deliberate inward or outward torques, no torque (straight), and an unspecified (preferred) torque. RESULTS: Axial push force was 12% greater for the rubber handle than for the aluminum handle. Participants exerted mean torques of 1.1, 0.3, 2.5, and -2.0 Nm and axial push forces of 94, 85, 75, and 65 N for the preferred, straight, inward, and outward trials, respectively. Left to decide for themselves, participants tended to apply inward torques, which were associated with increased axial push forces. CONCLUSION: Axial push force was limited by hand-handle coupling--not the whole body's push strength. Participants appeared to intuitively know that the application of an inward torque would improve their maximum axial push force. Axial push forces were least when a deliberate torque was requested, probably because high levels of torque exertions interfered with the push. APPLICATION: A low-friction handle decreases maximum axial push force. It should be anticipated that people will apply inward torque during maximum axial push. 相似文献
43.
On Controllability of Switched Linear Systems 总被引:1,自引:0,他引:1
Zhijian Ji Long Wang Xiaoxia Guo 《Automatic Control, IEEE Transactions on》2008,53(3):796-801
This paper investigates the number of switchings and design of switching sequences for controllability of switched linear systems. Two related results are established. One is a new constructive approach to designing switching sequences. The controllable state set of each switching sequence designed via the approach coincides with the controllable subspace of switched linear systems. The other is a well-estimated value for the minimum number of switchings required for controllability. Each state in the controllable subspace can be steered to origin within this value of switching times. 相似文献
44.
Collapse-free thermal bonding technique for large area microchambers in plastic lab-on-a-chip applications 总被引:1,自引:0,他引:1
Dong Sung Kim Hyun Sup Lee Jungyoup Han Se Hwan Lee Chong H. Ahn Tai Hun Kwon 《Microsystem Technologies》2008,14(2):179-184
Bonding is an essential step to form microchannels or microchambers in lab-on-a-chip applications. In this paper, we present
a novel plastic thermal bonding technique to seal and form large area microchambers (planar characteristic width and length
on the order of 1 mm and characteristic thickness on the order of 10–100 μm) without collapse by introducing a holed pressure
equalizing plate (HPEP) that includes holes of the same size and shape as the microchambers. To demonstrate the proposed technique,
two types of large area microchambers [(1) 20 × 10 mm and 40 μm thick and (2) 12 × 2.5 mm and 120 μm thick] with microchannels
were designed and replicated on plastic substrates by means of hot embossing and injection molding processes with prepared
two nickel mold inserts. The replicated large area microchambers as well as the microchannels in the plastic lab-on-a-chip
were successfully sealed (i.e., no leakage) and formed without any collapse by the proposed thermal bonding technique with
the help of the HPEP. 相似文献
45.
基于新型协调量化容差关系的不完备数据填补方法 总被引:1,自引:0,他引:1
提出一种基于新型协调量化容差关系的不完备数据补齐算法。首先求出属性值不完备对象的容差类,结合属性的重要度,将容差类里面的对象容差关系量化,再根据决策规则独立原则,在尽可能保持系统协调性的前提下对缺失属性值进行补齐。大量实验证明了本算法的有效性。 相似文献
46.
新近出台的数字对讲机国家标准,将这一新型手持通信终端推向了市场前沿.数字对讲机将多采用Soc设计,软件平台成为实现其功能的关键.立足数字对讲设备的应用,按照分步移植与扩展的步骤介绍一种以μC/OS-Ⅱ内核、MiniGUI图形界面与YAFFS文件系统等为基础,兼顾经济性的嵌入式软件平台的组建方法及其关键技术.系统实际运行表明,该方法完全可以满足普通手持通信终端对嵌入式系统的要求. 相似文献
47.
48.
We built and tested one of the key components of a free-space holographically interconnected stored-program optoelectronic computer: a counter. The counter is constructed with 1-ns-latency optoelectronic NOR gates and is interconnected with holographic optical elements. Two synchronization methods were also demonstrated: the gate-and-strobe method and the time-of-flight method. These counters represent prototypical optoelectronic finite-state controllers. They were developed to demonstrate the feasibility of providing optoelectronic controllers for optoelectronic processors. 相似文献
49.
The stable range of PbTiO3 sol and the processing conditions of uniform thin films were investigated using a solution of titanium isopropoxide, three kinds of alkanolamines (monoethanolamine, diethanolamine, triethanolamine), lead acetate trihydrate and isopropanol. Depending on the sol state with various alkanolamine/alkoxide molar ratios, diethanolamine (DEA) was very effective in preparing uniform and dense oxide films through room-temperature reaction, owing to its superior stability during the hydrolysis and condensation reaction. Perovskite PbTiO3 thin films were obtained on oxidized silicon wafer above 550 °C and completely pure films were obtained at 650 °C using DEA as a complexing agent. The dielectric constant and loss tangent of these thin films fired at 650 °C for 30 min were found to be 240 and 0.01 at 1 kHz, respectively. 相似文献
50.
Ruiqi Li Lian Chen Qin Ji Qing Liang Ying Zhu Wei Fu Tianyou Chen Hongwei Duan Wenshan He Zushun Xu Xiaofang Dai Jinghua Ren 《Advanced functional materials》2023,33(37):2213292
Radiotherapy is identified as a crucial treatment for patients with glioblastoma, but recurrence is inevitable. The efficacy of radiotherapy is severely hampered partially due to the tumor evolution. Growing evidence suggests that proneural glioma stem cells can acquire mesenchymal features coupled with increased radioresistance. Thus, a better understanding of mechanisms underlying tumor subclonal evolution may develop new strategies. Herein, data highlighting a positive correlation between the accumulation of macrophage in the glioblastoma microenvironment after irradiation and mesenchymal transdifferentiation in glioblastoma are presented. Mechanistically, elevated production of inflammatory cytokines released by macrophages promotes mesenchymal transition in an NF-κB-dependent manner. Hence, rationally designed macrophage membrane-coated porous mesoporous silica nanoparticles (MMNs) in which therapeutic anti-NF-κB peptides are loaded for enhancing radiotherapy of glioblastoma are constructed. The combination of MMNs and fractionated irradiation results in the blockage of tumor evolution and therapy resistance in glioblastoma-bearing mice. Intriguingly, the macrophage invasion across the blood-brain barrier is inhibited competitively by MMNs, suggesting that these nanoparticles can fundamentally halt the evolution of radioresistant clones. Taken together, the biomimetic MMNs represent a promising strategy that prevents mesenchymal transition and improves therapeutic response to irradiation as well as overall survival in patients with glioblastoma. 相似文献