Reasoning about action and change

Reasoning about change is a central issue in research on human and robot planning. We study an approach to reasoning about action and change in a dynamic logic setting and provide a solution to problems which are related to the <i>Frame problem</i>. Unlike most work on the frame problem the logic described in this paper is <i>monotonic</i>. It (implicitly) allows for the occurrence of actions of multiple agents by introducing non-stationary notions of waiting and test. The need to state a large number of <img src="/content/l60251587l77405x/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">frame axioms<img src="/content/l60251587l77405x/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> is alleviated by introducing a concept of <i>chronological preservation</i> to dynamic logic. As a side effect, this concept permits the encoding of <i>temporal</i> properties in a natural way. We compare the relative merits of our approach and non-monotonic approaches as regards different aspects of the frame problem. Technically, we show that the resulting extended systems of propositional dynamic logic preserve (weak) completeness, finite model property and decidability.     

On l∞ and l2 robustness of spatially invariant systems

We consider spatiotemporal systems and study their <i>l</i><sub>∞</sub> and <i>l</i><sub>2</sub> robustness properties in the presence of spatiotemporal perturbations. In particular, we consider spatially invariant nominal models and provide necessary and sufficient conditions for system robustness for the cases when the underlying perturbations are linear spatiotemporal varying, and nonlinear spatiotemporal invariant, unstructured or structured. It turns out that these conditions are analogous to the scaled small gain condition (which is equivalent to a spectral radius condition and a linear matrix inequality for the <i>l</i><sub>∞</sub> and <i>l</i><sub>2</sub> cases, respectively) derived for standard linear time‐invariant models subject to time‐varying linear and time‐invariant nonlinear perturbations. Copyright © 2009 John Wiley & Sons, Ltd.     

基于奇异值分解的稀疏重构近场声源定位*

针对近场声源定位问题,提出一种基于奇异值分解的稀疏重构定位方法。该方法通过奇异值分解得到信号子空间,然后在信号子空间约束l<sub>1</sub>范数求解优化问题实现声源的定位。与直接对接收信号进行稀疏重构相比,该方法通过奇异值分解降低了计算量,有效抑制了噪声。仿真结果表明,与子空间方法相比,提高了定位的抗噪声性能和分辨率。     

新型力解耦和各向同性机器人六维力传感器

介绍了基于并联 6 -SPS结构的新型机器人六维力与力矩传感器的结构特点 ,并分析计算了其力与应变之间的转换关系及其力各向同性 ,为该六维力与力矩传感器的设计和使用提供了理论依据。分析计算结果表明该传感器是力与力矩解耦和各向同性的。该传感器采用弹性铰链替代球铰 ,具有结构灵巧、工艺性好等优点 ,可应用到机器人手腕、手指和其它使用多维力与力矩传感器的场合。     

Co-Mg-NiO系氧敏材料的研究

研究了Co -Mg -NiO系氧敏材料在氧分压为 1～ 10 -2 3 atm(1atm =10 1.32 5kPa) ,温度为 70 0～10 0 0℃范围内的电导率与氧分压及温度的关系 ,讨论了材料的氧敏特性、导电机理 ,得出高温下材料中的缺陷类型随氧分压的降低主要是单电离和双电离的金属缺位 ,并得到了材料的某些参数。     

Convergence analysis of geometrical multigrid methods for solving data-sparse boundary element equations

The convergence analysis of multigrid methods for boundary element equations arising from negative-order pseudo-differential operators is quite different from the usual finite element multigrid analysis for elliptic partial differential equations. In this paper, we study the convergence of geometrical multigrid methods for solving large-scale, data-sparse boundary element equations. In particular, we investigate multigrid methods for <span class="InlineEquation" id="IEq2">\(\mathcal{H}\)</span>-matrices arising from the adaptive cross approximation to the single layer potential operator.     

Premelting transition in uranium dioxide

Thermal analysis of the cooling curves of small samples of UO<sub>2±<i>x</i> </sub>—initially laser heated (in a high-pressure autoclave to inhibit evaporation) on a subsecond time scale to temperatures just below their melting points [<i>T</i> <sub>m</sub>(<i>x</i>)]—reveals, in the case of nominally stoichiometric UO<sub>2.00</sub>, a significant, <i><img src="/content/klx31427l5735415/xxlarge955.gif" alt="lambda" align="BASELINE" BORDER="0"></i>-like, heat capacity [<i>C</i> <sub>p</sub>(<i>T</i>)] peak near 2670 K; the cooling curves of samples exposed to a reducing environment, on the other hand, exhibit <i>undercooling</i>, characteristic of a first-order phase transition, while under oxidizing conditions it is found that the premelting transition readily disappears. These findings confirm Bredig's original prediction of a premelting transition in this material, in common with that found in other (nonactinide) fluorites near 0.85<i>T</i> <sub>m</sub>. A simple model is presented in terms of which the observed behavior can be rationalized. The model is based on the hypothesis that the premelting transition is due to Frenkel disordering of the oxygen sublattice—a process which is rendered <i>cooperative</i> by <i>attractive</i> interactions between complementary Frenkel defects (oxygen interstitials and vacancies); these interactions are treated in a <img src="/content/klx31427l5735415/xxlarge8220.gif" alt="ldquo" align="MIDDLE" BORDER="0">mean-field<img src="/content/klx31427l5735415/xxlarge8221.gif" alt="rdquo" align="MIDDLE" BORDER="0"> approximation. The quantitative degree of maximum disorder (realized just above the transition) is, on the other hand, controlled by <i>repulsive</i> interactions between <i>like</i> defects—the inclusion of which, solely through their effect on the configurational entropy, satisfactorily reproduces the values inferred from recent high-temperature neutron diffraction experiments. Assuming that the phase transition in stoichiometric UO<sub>2.00</sub> is of second order, the model predicts a divergent heat capacity, <i>C</i> <sub>v</sub>, which approximates well to the experimental (<i><img src="/content/klx31427l5735415/xxlarge955.gif" alt="lambda" align="BASELINE" BORDER="0"></i>-like) <i>C</i> <sub>p</sub> peak. Crucial to reproducing the observed behavior <i>away</i> from stoichiometry is the introduction of a (linear) dependence of the nonconfigurational partial entropy of formation on the prevailing concentration of intrinsic Frenkel defects in UO<sub>2±x</sub>; interestingly, it is found that the line of calculated (but unrealized) second-order transitions in UO<sub>2+x</sub> intersects the U<sub>4</sub>O<sub>9</sub> phase boundary near to where a high-temperature diffuse order-disorder transition has been observed in the oxygen superlattice, suggesting that the second-order, <i><img src="/content/klx31427l5735415/xxlarge955.gif" alt="lambda" align="BASELINE" BORDER="0"></i>-transition in UO<sub>2.00</sub> is the stoichiometric counterpart of this transition in U<sub>4</sub>O<sub>9</sub>.     

低渗透中等偏强水敏油层储层保护技术的研究——以辽河油田强1块为例

强1块本身储层物性差,属于低孔、低一特低渗储层,粘土含量高,水敏表现为中等偏强。对于这种低渗区块进行注水开发时,储层的保护措施尤其关键。针对上述特点,确定各种工作液注入时相关临界值参数,同时开展防膨剂优选和注入水质的研究,采用离心法和X衍射法筛选了12种防膨剂的防膨效果,并进一步优化防膨剂的注入方式和注入浓度。结果表明,6#防膨剂效果好,现场可以先期采用注入质量分数为1％段塞,之后采用防膨剂质量分数为0．5％连续注入;从而实现该块自实施注水以来,注水压力稳定,且达到日配注量的要求,成功实施注水开发。     

一种基于l1范数的欠定盲源分离算法

提出了一种基于两步法的欠定盲源分离新算法.在混叠矩阵估计阶段,采用基于势函数的聚类方法,在源信号恢复阶段,提出一种快速的稀疏信号重构算法.系统方程As(t)=x(t)的任一解,由它的一个特解与其相对应的齐次线性方程组的一组基的线性组合之和表示,从而使原来直接估计有n个独立变量的源信号s(t)转化为估计只有n-m个独立变量的系数向量z.再借助稀疏表示实现盲源信号的分离.仿真实验验证了新算法容易实现,分离速度快,能够很好地满足盲分离对速度的要求.     

基于旋转扩展和稀疏表示的鲁棒遥感图像目标识别

针对含有残缺图像的遥感图像目标识别问题,提出一种基于旋转扩展和稀疏表示的目标识别方法.首先对训练集进行旋转扩展,使得测试图像能近似用训练集稀疏表示,然后通过求解一个l1范数最小化问题得到测试图像相对于训练集的一个稀疏表示,进而根据不同类对应的稀疏表示对测试图像的近似程度进行识别.与代表性的方法进行比较,实验结果与分析表明,该方法识别率优于已有方法,对残缺图像的识别有较好的鲁棒性,且在小样本、低采样率情况下也能保持较好的识别性能.