Online pricing for bandwidth provisioning in multi-class networks

We consider the problem of pricing for bandwidth provisioning over a single link, where users arrive according to a known stochastic traffic model. The network administrator controls the resource allocation by setting a price at every epoch, and each user’s response to the price is governed by a demand function. We formulate this problem as a partially observable Markov decision process (POMDP), and explore two novel pricing schemes––reactive pricing and spot pricing––and compare their performance to appropriately tuned flat pricing. We use a gradient-ascent approach in all the three pricing schemes. We provide methods for computing unbiased estimates of the gradient in an online (incremental) fashion. Our simulation results show that our novel schemes take advantage of the known underlying traffic model and significantly outperform the model-free pricing scheme of flat pricing.     

Sensor networks: evolution, opportunities, and challenges

Wireless microsensor networks have been identified as one of the most important technologies for the 21st century. This paper traces the history of research in sensor networks over the past three decades, including two important programs of the Defense Advanced Research Projects Agency (DARPA) spanning this period: the Distributed Sensor Networks (DSN) and the Sensor Information Technology (SensIT) programs. Technology trends that impact the development of sensor networks are reviewed, and new applications such as infrastructure security, habitat monitoring, and traffic control are presented. Technical challenges in sensor network development include network discovery, control and routing, collaborative signal and information processing, tasking and querying, and security. The paper concludes by presenting some recent research results in sensor network algorithms, including localized algorithms and directed diffusion, distributed tracking in wireless ad hoc networks, and distributed classification using local agents.     

反应动力学模型的模糊数学筛选法

运用模糊数学理论,提出了一种新的筛选反应动力学模型的方法。该方法同时考虑了多种因素的影响,建立了诸因素对模型筛选的模糊关系,按其提出的筛选准则:进行筛选,比目前的方法更为有效。     

掺杂Mg2+对钛酸锶薄膜氧敏性能及电阻温度系数的影响

利用溶胶-凝胶的方法制备钛酸锶氧敏薄膜，该薄膜是制造电阻型氧敏传感器的一种潜在材料。在钛酸锶中掺杂不同含量的镁离子，形成SrTil-xMgxO3薄膜，其中Mg的含量，即x值分别为0，0．05，0．10，0．15，0．20，0．25，0．30。镁在钛酸锶中取代钛位，形成受主掺杂。测试不同氧分压(0～10^5Pa)、温度(600～800℃)下薄膜的电阻。发现掺镁的钛酸锶在氧化气氛下是p型半导体。并且当x值（镁的含晨）在0．10～0．15之间、较低氧分压下，薄膜的电阻温度系数接近零。此外，还从缺陷化学反应角度讨论了此现象出现的原因。     

万华集团IT规划案例分析

万华集团为了有效支撑集团管理模式的运作，并同时提升各业务板块的管理水平，提出了在集团范围内进行IT规划的项目，以指导后续的信息化建设。对万华IT规划项目进行总结和分析，介绍了项目背景、方法、内容、意义与关键点，给出了万华集团的信息化蓝图与建设思路。将为类似企业的信息化规划提供经验与参考。     

Isolated sphenoethmoid recess polyps

PURPOSE: The Marshall-Smith Syndrome (MSS) is a rare disease characterized by orofacial dysmorphism, failure to thrive, accelerated osseous maturation and mental retardation. It has anaesthetic implications due to upper airway problems and possible atlanto-axial instability. We present the perioperative problems (difficult intubation, airway obstruction) encountered in a child with MSS who underwent several anaesthetics during his first two years of life. CLINICAL FEATURES: At birth, the child presented with asphyxia due to obstructive apnoea. His trachea was, therefore, intubated immediately. The morphological diagnosis of MSS was confirmed by the pathognomonic radiological appearance of the bones (bone age was eight months at the age of four days). Upper airway difficulty was caused by functional problems at the level of the hypopharynx (inspiratory collapse at the level of the velum palatinum), and was solved by the use of a nasopharyngeal airway (NPA) during the induction of anaesthesia and early postoperative period. CONCLUSION: The use of an NPA during both induction and recovery of anaesthesia may be particularly useful to prevent upper airway problems in children with MSS.     

强激光积分变换镜的光学性能及相关热作用

根据标量衍射理论研究一种常用积分镜，导出任意给定入射光束时在光学系统后不同空间平面上光束的强度分布，给出模拟计算实例，讨论经积分镜变换后光束的热作用。研究结果表明，变换光束带有强烈的干涉及衍射结构，入射光束分布及工作平面位置的选择对变换结果有显著影响。对于导热性能较好的材料，变换光束的干涉和衍射结构的热影响可以忽略，但是，配置与积分镜相应的模拟计算软件是提高使用质量的必要措施。     

Anisotropic thermal expansion of stoichiometric lithium niobate crystals grown along the normal direction of facets

In this paper, a stoichiometric lithium niobate (SLN) crystal with the size up to 20 × 20 × 18 mm³ was grown along the normal direction of the (0 1 2) facet from the 16 mol% K₂O fluxed melt by the top-seeded solution growth method. The anisotropic thermal expansion of the SLN crystal and congruent lithium niobate (CLN) crystal was measured along different directions by using a Shimadzu thermomechanical analyzer. As compared with CLN, the SLN crystal exhibited slightly larger thermal expansion along the Z-axis and slightly smaller expansion along the X-axis. Both the SLN and CLN crystals showed strong anisotropy in the thermal expansion. The thermal expansion coefficient of SLN along the X-axis (16.7 × 10⁻⁶ °C⁻¹ at 300 °C) is much larger than that along the Z-axis (2.5 × 10⁻⁶ °C⁻¹ at 300 °C). Based on the experimental data and polynomial fitting results, we calculated the thermal expansion coefficients for different directions. In the case of growing the SLN crystal along the normal direction of (0 1 2) facet, we studied the radial anisotropic thermal expansion and discussed the cracking problem of the crystal according to its actual growth morphology. It is found that the cracks of SLN can be suppressed by growing the crystal along the W-axis due to its reduced radial anisotropy in the thermal expansion.     

提高水分生产率和农业生产能力是我们追求的目标

我长期从事水稻研究工作,特别是对水稻水管理方面做了许多研究.水稻节水灌溉这个项目的研究意义非常大,因为我们知道水资源短缺使许多国家面临挑战,如何解决水危机,是许多专家和相关国际组织共同关注和探讨的问题.