耳蜗结构对低频信号频散特性的影响

耳蜗是人体最为精密的力学元器件,能处理频率从几十到几万赫兹的声信号.实验研究表明,声波进入耳蜗后,沿着基底膜传播,基底膜能够将不同频率的声信号分散到不同的位置,并为位于基底膜上的毛细胞所感知,就像一个天然的Fourier(傅里叶)滤波器.在von Békésy行波理论框架体系下,基于Manoussaki等的三维螺旋基底膜流固耦合耳蜗模型,考虑耳蜗导管高度和基底膜刚度均为纵向梯度变化,推导出基底膜声波传播的频散方程,分别分析了基底膜刚度和耳蜗导管高度对频散特性的影响.发现耳蜗内淋巴液的存在大大提高了耳蜗对低频信号的处理能力,且捕获频率随基底膜刚度和耳蜗导管高度的减小而降低,两者梯度变化在声信号调制中起协同作用.最后,以人、沙鼠和豚鼠的具体耳蜗参数为例,得到3种生物耳蜗频率-点位图,并验证了低频段模型预测的正确性,比较分析了耳蜗频散功能与生物适应性之间的关系.     

默认模式网络与任务正网络之间相互拮抗的神经动力学分析

任务正激活与任务负激活的工作机制是认知功能实现的基本要素.这一拮抗关系的失衡或者受损可能会引发一系列严重的退行性神经疾病，然而到目前为止，尚不清楚这种拮抗现象的神经机制.该文基于默认模式网络与任务正网络在突触层面上相互抑制的假设，并结合多种刺激条件下的工作记忆模型，进行了计算机数值模拟.研究结果表明: 1) 任务正网络与任务负网络之间在神经活动上呈现出拮抗关系； 2) 伴随着工作记忆刺激方向数目的增加，任务负网络神经活动的衰减程度会随之增大； 3) 当工作记忆相关的脑区其神经活动增加时，任务负网络的神经活动减少； 4) 并且随着工作记忆任务难度的增加，任务负网络的神经活动会迅速衰减.这些计算结果都与神经科学实验数据是匹配的.由于任务负激活是默认模式网络的主要特征，因此默认模式网络与任务正网络在突触层面上的相互抑制是这两种不同性质网络之间形成拮抗关系的根本原因.     

奇异齐次非线性系统的H_∞控制

研究了奇异齐次非线性系统的最优控制问题与相关的L2增益问题,基于Hamilton-Jacobi不等式,我们给出了可解性条件,并显式构造出了控制律,在保证内稳定的基础上达到干扰衰减.     

一类非线性参数化时滞系统的鲁棒自适应衰减问题

研究了一类虚拟控制系数未知的非线性参数化时滞系统的自适应衰减问题.利用参数分离技术和backstepping设计方法构造自适应H∞控制器,使闭环系统在L2增益下从干扰输入到系统输出的影响任意小,并且无外部干扰时,系统内稳.     

分子刚度对膜锚定受体-配体结合动力学影响的理论与模拟研究

人体内大部分生物学过程都离不开细胞黏附.细胞黏附行为主要由锚定于细胞膜上的特异性分子（又称受体和配体）的结合动力学关系来决定.已有研究表明，特异性分子的结合关系受外力及细胞膜波动等多种因素影响.然而，特异性分子刚度对细胞膜锚定受体 配体结合关系的影响机制仍不清楚.近期关于新冠病毒强传染力的研究表明，特异性黏附分子刚度对病毒与细胞结合具有重要影响.该文通过建立生物膜黏附的粗粒度模型，借助分子模拟和理论分析来研究分子刚度在黏附中的作用.结果表明，始终存在一个最佳膜间距及最佳分子刚度值，使得黏附分子亲和力和结合动力学参数达到最大值.这项研究不仅能加深人们对细胞黏附的认知，还有助于指导药物设计、疫苗研发等.     

一类非线性高阶Kirchhoff型方程的初边值问题

本文研究了一类具有非线性耗散项的高阶Kirchhoff型方程的初边值问题.通过构造稳定集讨论了此问题整体解的存在性,应用Nakao的差分不等式建立了解能量的衰减估计.在初始能量为正的条件下,证明了解在有限时间内发生blow-up,并且给出了解的生命区间估计.     

托卡马克中低模态到高模态转迁模型的混沌运动

利用Melnikov方法详细研究了在托卡马克(Tokamaks)中,等离子区边缘附近低模态到高模态转迁方程的混沌动力学.该转迁方程是一个含外激励和参数激励的系统.对含周期外激励和线性参数激励、三次参数激励的系统分别绘出了用来划分混沌区和非混沌区的临界曲线.得到的结果表明,含有线性或三次参数激励的系统存在不可控区域,在该区域中异宿轨分岔总是导致混沌发生.特别地,三次参数激励系统存在一个"可控频率",施以该频率的激励,不论激励的振幅多大,同宿轨分岔总是不会导致混沌发生.得到了这类系统的一些复杂的动力学行为.     

基于非局部理论的黏弹性纳米杆轴向振动与波传播研究

根据非局部理论和Kelvin黏弹性理论，针对黏弹性纳米杆自由振动和波传播的轴向动力学问题进行研究.首先，推导了黏弹性纳米杆的轴向动力学微分控制方程.然后，通过无量纲化讨论了3种典型边界纳米杆的前三阶振动特性.最后，研究黏弹性纳米杆波的传播问题，导出了圆频率、波速与波数之间的关系.数值结果表明，非局部效应使第一、二阶固有频率持续减小，第三阶频率先增大再减小，出现结构刚度削弱和增强两种趋势.特别地，对于自由端存在集中质量的情形，第二阶频率随着黏性系数增大出现了多值情况，易导致杆件失稳.数值算例还说明了非局部效应的增强可有效降低黏性材料的阻尼效应，产生逃逸频率，使得纵波能够在高波数段传播.另外，黏性系数在低波数段对阻尼比影响可忽略不计，而在高波数段下，黏性系数越大则阻尼比越大.     

复杂网络上耦合神经系统的非聚类相同步

考虑了不同复杂网络结构(小世界、无标度和随机网络)条件下的耦合神经元系统,针对其进入相同步的同步化路径进行了建模与仿真,发现系统呈现出非聚类相同步现象,并对其形成原因进行了定性分析.结果表明:复杂网络上的耦合神经元系统与其在规则网络下有相同的同步行为,系统均不出现通常耦合相振子中的聚类成群现象,而表现为随着耦合强度的增加所有神经元渐进趋于同步.另外,随着放电尖峰的插入与弥合,最终导致系统个体平均频率先增强后衰减的变化.这些结果将丰富对于网络动力学行为(尤其是相同步)的认识,对理解神经认知科学具有一定意义.     

存在内共振的覆冰四分裂导线的非线性舞动

采用非线性有限元方法模拟研究存在内共振的覆冰四分裂导线的非线性舞动.通过稳定风场和随机风场中典型覆冰四分裂线路舞动过程的数值模拟,研究当覆冰四分裂导线的对称面内模态频率与面外模态频率之比接近于2∶1,即存在内共振条件时,导线的舞动特征.结果表明,存在内共振的覆冰四分裂导线在舞动过程中,其能量在竖直面内运动和横向水平面外运动之间不断交换,与不存在内共振线路的舞动特征差别明显.研究结果对舞动耦合机理的理解具有重要的理论意义.     

The influence of stochastic behavior on the human threshold of hearing

The inner hair cells in the cochlea perform the crucial task of transforming mechanical sound signals into electrical activity. The cochlear nerve fibers code this information and convey it to the brain for further processing. This study investigates the performance of the system inner hair cell – primary auditory afferent nerve fibers at the physical limit of the mechano-electrical transduction for the human auditory frequency range. The Brownian motion of the hair cell’s receptive organelle, the hair bundle, does not blunt the sensitivity, but in fact enlarges – especially in frequency regions which are most important for the perception of music and speech – via the mechanism of nonlinear stochastic resonance (SR) the dynamical range of the mechano-electrical transduction by at least one order of magnitude. The coding efficiency of small sinusoidal hair bundle deflections shows basic properties of the human hearing threshold curve for pure tones and corresponds to experimental results of noise-induced tuning curves in mechano-receptors in the rat foot. Furthermore, the model explains how altered coding efficiency contributes to pathological changes in the spiking pattern which arise from morphological changes in the hair bundle structure (e.g., in noise-induced sensorineural hearing loss of cochlear origin).     

Modes of the tectorial membrane, transversal eigenfunctions, and the origin of the outer hair cell oscillations

The tectorial membrane (TM) of the mammalian inner ear is considered as a system of weakly bent beams and is modeled by a long flat anisotropic plate with one edge supported by the immovable “limbus,” while the opposite edge rests on top of the outer hair cells (OHC). The cross-sectional eigenfunctions of the tectorial membrane isolated from Corti's organ are calculated. It is shown that, under the condition that the limbal edge is supported, the first eigenfunction has an immovable nodal point near the free edge. If the corresponding eigenfrequency of the tectorial membrane coincides with the fundamental eigenfrequency of the cross section, the middle part of the tectorial membrane moves in phase with the basilar membrane, while its marginal edge moves in the opposite direction. As a consequence, the outer hair cells, connecting the middle line of the basilar membrane with its marginal edge, are subject to altering compressive and stretching forces. Thus, the oscillations of the outer hair cells seem to be merely a forced, “passive” mechanical movement rather than an “active” biological process. Taking into account the shapes of the graphs of the tectorial membrane cross-sectional eigenfunctions provides a possibility of explaining a great deal of various experimental data in a simple and natural way without conjecturing negative damping. Bibliography: 25 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 218, 1994, pp. 138–148. This work was supported by the Russian Foundation of Fundamental Research (Grant 93-011-16148). Translated by S. M. Novoselova.     

基于峰谷分时电价机制的节能发电调度优化模型

为减少能源消耗,电力工业在发电侧推行节能发电调度,而在用电侧则施行需求侧管理。事实上,发电侧与用电侧可以通过联合优化实现更好的节能效果。峰谷分时电价将改变原有系统负荷的分布,发电侧机组发电调度的安排将随之改变,发电煤耗水平也将相应地变动。有鉴于此,首先分别构建了需求侧峰谷分时电价响应分析模型以及发电侧节能发电调度的机组组合模型;其次,为了实现分时电价响应向机组煤耗效益的传递,以机组发电煤耗与启停煤耗最少为目标构建了需求侧与发电侧的联合优化模型;最后,通过算例分析发掘模型的节能效益,借助GAMS求解上述模型,优化结果表明分时电价的优化将有助于改进发电侧的节能调度效果,同时将实现一定的环境效益。     

Green overhead and underground multiple-input multiple-output medium voltage broadband over power lines networks: energy-efficient power control

The broadband potential of overhead and underground medium-voltage/broadband over power lines (MV/BPL) systems associated with multiple-input multiple-output (MIMO) transmission technology and energy efficient (EE) or green policies is examined analytically. The contribution of this paper is threefold. First, various overhead and underground MIMO/MV/BPL topologies have been studied with regard to appropriate transmission measures and spectral efficient (SE)/EE metrics such as channel attenuation, subchannel efficiency, EE subchannel efficiency, capacity, EE capacity, and power consumption. It is found that the above metrics depend drastically on the frequency, power constraints imposed to suppress electromagnetic interference (EMI) to other services, EE policies adopted to regulate power consumption, power grid type (either overhead or underground), MIMO scheme properties, MTL configuration, the physical properties of the cables used, and other topological characteristics. Second, further insights regarding the transmission and SE/EE capacity properties of various MIMO/MV/BPL systems reveal the similar behavior among single-input multiple-output, multiple-input single-output, and single-input single-output MV/BPL systems due to specific MIMO/MV/BPL channel characteristics. Third, using suitable SE/EE metrics, significant trade-off curves between capacity performance and power consumption described through dynamic quasiconcave curves are disclosed. The definition of proper injected power spectral density mask limits combined with the use of continuous/adaptive EE policies provide both EMI protection and EE-oriented high-bitrate MIMO/MV/BPL system design aiding towards sustainable BPL technology satisfying both Quality of Service requirements and ecological awareness (green technology initiatives).     

势阱深度对双稳态电磁发电系统发电性能的影响研究

电磁式振动能量捕获技术从单稳态系统发展到多稳态系统,拓宽了响应频带,增大了输出电压,能够获得较好的发电性能.以附加线性振子的双稳态电磁式振动能量捕获器为研究对象,主要研究了势阱深度对双稳态系统发电性能的影响,并基于最优发电性能下的势阱深度,研究了双稳态系统结构参数中质量比与调频比对系统发电性能的影响.通过数值仿真结果说明,在外部激励频率为低频时:势阱深度较大时,双稳态系统的振子只能在一个阱内发生小幅振动运动;当势阱深度小到一定程度时,双稳态系统的振子跨过势垒在两个阱间内发生大幅混沌运动或周期运动,其优于小幅振动运动时的平均输出功率.通过数值模拟,得到双稳态系统具有较高的发电性能下的最优质量比、调频比以及阻尼比参数.     

Power Aspects of Rheonomic Multibody Systems

Flexible manufacturing systems are characterized by machines with some or all mechanical degrees of freedom actively controlled resulting in the necessary prescribed motion of the production process or rheonomic constraints, respectively. Due to the high nonlinearity of large displacement motions inverse dynamics is a standard control concept well established in robotics and walking machines. It is shown that inverse dynamics results in high energy consumption and requires large power supply. For autonomous robots and walking machines the power supply adds to the weight, and additional weight needs more power again. Finally, actively controlled walking machines are very heavy devices not comparable to the lightweight design of passive walking mechanisms. It is proposed to use local energy storage by springs to overcome the drawback of inverse dynamics. The design principles for reduced energy consumption are outlined with simple mechanical models and will include nonlinear characteristics of the springs to improve further the local energy storage capacity.     

中国城镇居民生活用能影响因素定量研究

利用面板数据对中国城镇居民生活用能影响因素进行了实证分析.结果表明,能源消费总量对人均可支配收入的弹性最大,人口对城镇居民用能具有广义的规模效应,居民用能对能源价格很敏感.此外,夏季与冬季的温差每上升一摄氏度,城镇居民生活用能总量会上升3%.如果一个地区有集体供暖,其城镇居民部门能源消费总量会比没有集体供暖时减少19%.     

坑口电厂低碳经济发展系统动力学仿真研究

通过分析坑口电厂低碳经济系统的复杂结构特征和动态反馈机制,建立了坑口电厂低碳经济系统动力学模型,描述系统内部各要素之间的相互关系,并以平煤集团坑口电厂为例,对不同发展方案下的坑口电厂低碳经济系统进行仿真模拟.结果表明:科技投资、环保投资、能源利用率、能源消费结构等因素是影响坑口电厂低碳经济发展的关键因素;可以通过优化能源消费结构,提高煤矸石消耗比例;增加科技投资和环保投资,提高能源利用和转换效率,降低污染物和二氧化碳排放量,从而达到高效率、低能耗、低排放的低碳经济发展模式.     

电力零售商引导下智能电网多方利益均衡策略

文提出以电力零售商为主导的智能电网系统运行策略,电力零售商根据发电商供电价和发电量以收益最大化为目标输出用户实时电价。在供能侧对不同类型供电商上网顺序进行优化,考虑风电光伏能源出力不确定的鲁棒性分析,在维持平衡供需的基础上优化供电商利益。在需求侧根据用电规模对用户进行分类,按供电重要性进行二次分类,使用粒子群算法求解用户最优用电量。仿真结果显示电力零售商在电力系统中维护各方利益均衡,对供电商和用户都存在潜在的好处。     

Productive efficiency and energy use: An historical perspective

The paper discusses long-term trends in relationships between energy use and the overall productive efficiency of the American economy. While total energy consumption grew strongly during the twentieth century, the intensity of energy use (i.e. the energy/GNP ratio) fell persistently much of the time. Thus, there were simultaneous long-term improvements in labor productivity, total factor productivity,and energy productivity. The historical record appears to be at odds with conventional beliefs that gains in productive efficiency depend upon the rising intensity of energy use in production processes. A key role in bringing about these counter-intuitive results is assigned to what is referred to as the energy-technology-productivity nexus, in which the quality of particular energy forms such as electricity and liquid fuels (along with closely linked changes in energy-using technologies) played a critical part in leveraging the overall efficiency of production. As a result of these energy form-dependent improvements in productive efficiency, outputs grew more rapidly than all inputs, including the inputs of energy. The more recent past stands in sharp contrast to the long-term record. While energy efficiency (as measured by energy/GNP) showed strong gains during the late 1970's and early 1980's, the growth in overall productive efficiency was severely retarded. Implications for the future of suggested linkages between the quality of particular energy forms and technological progress are considered.