一个具有多翼吸引子的四维多稳态超混沌系统

构造了一个只有一个平衡点的四维超混沌系统,此系统表现出丰富的多稳态特性,亦具有多翼吸引子。数值分析了系统的动力学特性,仿真了系统的模拟电路和数字电路,探讨了系统的动态复杂度,测试了系统超混沌序列的随机性。分析结果表明,在多组参数值下,系统均存在不同类型的吸引子共存,譬如:两个周期吸引共存,周期与拟周期吸引子共存,双翼混沌与超混沌吸引子共存,两个双翼混沌吸引子共存,双翼与四翼混沌吸引子共存,两个双翼超混沌吸引子共存,两个双翼拟周期吸引子共存,两个双翼超混沌、四翼混沌、四翼超混沌等四个吸引子共存。系统的数字电路和模拟电路的仿真结果均与数值分析结果一致,表明了系统的可实现性。另外,在混沌和超混沌状态下系统复杂度高,且超混沌序列通过了SP800-22 Revla的15项随机测试。     

谐振管几何形状对热声发动机工作性能的影响

谐振管作为热声发动机的重要部件之一,其几何参数的变化对热声系统的工作性能有重大影响,在驻波型热声发动机系统上对锥形谐振管和圆直谐振管进行了初步的实验对比,以探明谐振管的形状对热声发动机系统性能的影响.实验结果表明,在系统的工作频率固定在130 Hz的情况下,无论是压比、输出声功,还是相对卡诺效率,采用锥形管的系统都要比采用圆直管的系统具有更大的优势.     

Modelling a reliability system governed by discrete phase-type distributions

We present an n-system with one online unit and the others in cold standby. There is a repairman. When the online fails it goes to repair, and instantaneously a standby unit becomes the online one. The operational and repair times follow discrete phase-type distributions. Given that any discrete distribution defined on the positive integers is a discrete phase-type distribution, the system can be considered a general one. A model with unlimited number of units is considered for approximating a system with a great number of units. We show that the process that governs the system is a quasi-birth-and-death process. For this system, performance reliability measures; the up and down periods, and the involved costs are calculated in a matrix and algorithmic form. We show that the discrete case is not a trivial case of the continuous one. The results given in this paper have been implemented computationally with Matlab.     

Stability of the unfolding of the predator-prey model

We prove a conjecture of Zeeman that any generic unfolding of the Volterra's original predator-prey model is stable. This well-known two-dimensional model has co-dimension one in the planar Lotka- Volterra system and all its orbits are closed in the region of physical interest. Any generic unfolding of the model locally induces a degenerate Hopf bifurcation, but the presence of a cycle of saddles makes the global stability analysis quite involved. We solve the problem by working in the equivalent replicator system. Our proof of stability uses a family of Lyapunov functions for the unfolding. There are two other co-dimension one bifurcations in the planar replicator (equivalently Lotka- Volterra) system, which involve cycles of saddles and are therefore non-trivial. In one case we prove the stability of the bifurcation and in the other we determine a topologically versa! unfolding of the co-dimension one flow. This then, together with previous work on the subject, completes the study of co-dimension one bifurcations of the system     

冰蓄冷与水源热泵系统设计实例

为了克服冰蓄冷技术和水源热泵技术单独应用时的局限性,真正使二者有机结合起来起到"削峰填谷"的功效,通过对北京大红门服装城空调系统的设计,验证了冰蓄冷技术与水源热泵技术相结合的巨大优势.大红门服装城空调系统的最佳配置为2台1 260 kW三工况水源热泵机组、水源井5口和1套冰蓄冷空调系统,与常规空调系统相比,初期投资有所增加,约56万元,但年运行费用较低,与常规市政热力取暖系统进行比较,每个供暖季可节约212万元.     

非等高双重抗侧力体系的稳定性

该文研究了非等高的双重抗侧力体系的稳定性。首先, 分析了弯曲型高-剪切型低的双重抗侧力体系, 提出了该结构体系的屈曲方程及稳定临界荷载解析解。通过分析弯曲型高-剪切型低的双重抗侧力体系的上下两部分存在相互支援作用, 给出了求解该体系稳定临界荷载的近似公式, 通过算例对比, 发现与解析解相比, 近似解具有很好的精度;同时, 近似法便于实际应用。其次, 研究了剪切型高-弯曲型低的双重抗侧力体系稳定性, 研究发现由于轴压力分布的不同, 此类体系将出现两种不同形式的失稳模式, 分别为结构上部发生纯剪切型失稳的局部失稳模式以及结构下部发生整体有侧移失稳模式。提出了判别结构在某一特定形式的荷载作用下, 发生哪一种失稳模式的准则, 以及相应的临界荷载计算公式。     

Impact of customer impatience on a production service system

In this paper, we explore the impact of customer impatience on the performance of a production service system that consists of one production inventory subsystem and one service subsystem. It is inevitable that the un-storability of service makes customers wait in the production service system. Waiting for service easily leads to impatient behaviors. The impact of two kinds of impatient behaviors balk and reneging on the production service system performance is examined. The problem is formulated as a Markov system, then the stationary probability of the system is derived to conduct the performance evaluation. The results show that customer impatience has the different impact patterns on the two subsystems (i.e. production inventory subsystem and service subsystem) of the production service system. Specifically, customer impatience leads to the performance improvement of one subsystem along with the performance deterioration of the other subsystem. Meanwhile, service capacity plays an important role in the influence extent of customer impatience on the system performance. In addition, lower customer impatience does not necessarily improve system profit. Therefore, the management of the production service system with impatient customers will be more intractable. Some managerial insights and suggestions are proposed.     

Dynamics of Uniaxial Tension of a Viscoelastic Strain-Hardening Body in a System with One Degree of Freedom. Part 4. Action of an External Force on a Compound Body

A rheological model and the dynamics of an open mechanical system, comprising an elastic machine element and a compound body consisting of two irreversibly deformable bodies connected in series with one degree of freedom under the action of an external force are considered. If the system is subjected to a load below the elastic limit of both bodies, the motion of the mechanical system is described by a classical second-order dynamic system. If the system is subjected to a load above the elastic limit of one of the bodies, the motion of the mechanical system is described by a third-order dynamic system, and when it is loaded above the elastic limit of both bodies, the motion is described by a dynamic system of two third-order differential equations. The solutions of this dynamic system are damped oscillations in character, with the damping factor increasing with the ratios of the elastic stiffness and strain hardening values to the value of viscous resistance of deformable bodies.     

一种被动TMA的可测性问题分析

本文讨论了声纳被动定位中,一般非线性动态系统在基于目标方位测量情形下ＴＭＡ的可测性问题。虽然这是个非线性系统,结果证明它是一个可测的动态系统。     

新型分布式布喇格光纤光栅传感系统的研究

提出了一种新型分布式布喇格光纤光栅(FBG)传感系统.为了满足一个大型工程同时监测上百个不同位置的要求,将这一百个点分成若干组,每组构成一个小区域,每个小区域由四个波长相同的光栅组成,这样就满足了在一条光纤上刻一百个光栅的要求.当某点温度发生变化时,该区域的最高温度可测得;若此最高温度超过警戒温度,则系统发出报警信号,进而对这个小区域进行整体降温处理.在理论分析的基础上,对多组不同波长的光纤光栅进行了温控对比实验,在10～110℃的温度范围内,FBG的中心波长随温度变化呈良好的线性,线性度达到99.6%以上.实验表明该系统具有精度高、适用于分布式多点测量的特点.     

“柔性桩”公共自行车系统管理模式设计与应用

目的针对当下各种类型的公共性自行车管理系统所存在的问题和潜在需求,提出新的有效的解决方案。方法通过对现有"一车一桩"公共自行车系统和共享单车无桩化管理模式的问题分析,从公共空间的合理运用和规范管理入手,提出一种新型"柔性桩"公共自行车交通系统,将原有的一车一桩改为中控柱与多车串联模式。通过在每个公共自行车网点设立一根或多根接通市电的带锁头的"中控柱",在头车与锁头连接后,后车则采用与前车串联的方式依次停放并锁车。结论 "柔性桩"的应用较好地解决了公共自行车系统用车的"潮汐现象",降低项目建设和维护成本,更适于特定区域的管理需求,且有助于实现交通信息网络的交通数据互联。     

中国造船工业供应商评价指标体系与管理体制构建

对于中国造船企业，构建完整的供应商管理体系是其从分散型采购体系向一体化采购体系整合的关键步骤之一。本文主要针对中国造船工业供应商管理的特点以及所存在的不足，将质量、交付能力、价格、服务能力和持续改进这5个定量评价指标与供货商关系指标和供货商管理能力指标这2个定性评价指标相结合，运用AHP法，构建了造船行业的供应商评价指标体系，并依据这一指标体系，构建了与造船行业集中化采购体系相适应的供应商管理体制。     

多共振消声器串联系统声学特性分析及应用

针对内燃机进气系统需良好的低频消声效果而可用空间有限的问题,研究多个消声器串联后的声学特性。基于共振消声器集中参数模型,推导消声器串联后系统主消声频率公式并验证。结果表明,双共振消声器串联系统有两主消声频率,即小于、大于下端消声器的偏频;增加体积比时较小的接近偏频,较大的远离偏频;长度比等于1、面积比小于等于1时串联系统所需体积小。串联系统消声器结构参数均相同时主消声频率个数与消声器个数相同。基于此,对某商用车进气系统进行降噪设计,使200 Hz以内的传声损失整体提高约5 dB。     

用于离心式高温热泵机组研发的模拟模型

为了对所设计的高温热泵机组中各设备进行合理匹配,建立其稳态模拟模型。该模型包括关键部件的子模型:带有经济器的双级离心式压缩机、卧式壳管式冷凝器、浮球膨胀阀、满液式蒸发器和回热器。在模拟算法的设计中,将模块化方法与二分法相结合,所需输入参数易于为设计者所获得,且不会限制系统的运行。利用该模型,对高温热泵进行初步设计;经过多方案比较,确定各换热器的结构参数,并预测该系统的性能和运行参数。     

Reliability-based optimization of fibrous laminated composites

This paper is concerned with the optimum design of multiaxial fiber reinforced laminate systems under probabilistic conditions of loads and material properties. A multiaxially laminated composite is treated as a structural system with each ply contained in the composite as one element. The Tsai-Wu failure criterion is adopted as the limit state function of a unidirectional ply. It is assumed that the system failure occurs when any one of the plies in a laminate system fails. The multiple-check-point method is successfully applied to evaluate the system reliabilities of multiaxial laminates under probabilistic in-plane stresses. An optimization problem is defined to find the optimal number of fiber orientation axes, optimum orientation angles, and optimum ply ratios which yield the highest system reliability.     

Large-scale simulations of crack–void and void–void plasticity in metallic fcc crystals under high strain rates

We have simulated the failure of three-dimensional fcc solids containing voids under mode one tension using molecular dynamics, simple interatomic potentials and a system comprising 15 million atoms. When a linear brittle crack front approaches a void, the void acts to impede the progress of the front by causing dislocation emission, thereby rendering the system ductile. When two voids are alone in the system, failure is via ductility with, first, dislocation loops being emitted from the void surfaces and, then, these loops interacting with one another to form.     

A Crack in the Homogeneous Half Plane Interacting with a Crack at the Interface Between the Nonhomogeneous Coating and the Homogeneous Half-Plane

A fundamental solution is established for a crack in a homogeneous half-plane interacting with a crack at the interface between the homogeneous elastic half-plane and the nonhomogeneous elastic coating in which the shear modulus varies exponentially with one coordinate. The problem is solved under plane strain or generalized plane stress conditions using the Fourier integral transform method. The stress field in the homogeneous half plane is evaluated by the superposition of two states of stresses, one of which is associated with a local coordinate system in the infinite fractured plate, while the other one in the infinite half plane defined in a structural coordinate system.     

某会所的空调节能系统设计

本文介绍了某小区会所的空调节能系统设计,包括恒温泳池的三集一体系统、带热回收的变冷媒空调系统和新风全热回收系统。     

空间遥控机械手的声控识别与应答系统

描述了用自然语言控制空间遥控机械手执行远程操作的自然语言接口系统。该系统以孤立词语音识别为核心,着重于系统的可靠性和实用性。为此,在系统的开发过程中,考虑了人类语音交互的听觉感知特点、汉语的一字一音节特点、具体识识时语音的声学模型不必与其语言学模型严格一致的特点以及环境噪声对系统性能的影响等,提出以过渡段＋韵母段作为识别基元,采取多层识别策略进行识别。识别实验与仿真实验结果表明,系统达到了预期性能