基于多元回归模型的燃气热泵系统制热性能分析

基于实测数据构建燃气热泵系统中天然气发动机的多元回归模型和开式涡旋压缩机的计算模型,采用EES软件对燃气热泵系统进行性能计算,分析出口水温(t_out)、发动机转速(N_eng)、环境温度(t_amb)及余热回收量对系统制热性能系数COP与一次能源利用率PER的影响。模拟研究表明：在同等条件下,不开启余热回收系统时,COP与PER随t_out增加线性降低,模拟值与实测值的最大误差分别为1.62%与3.06%;同时,t_amb对COP的影响较大,当N_eng为1 500 r/min时,随着t_amb从-15℃变化到24℃时,COP上升了225.87%,PER上升了217.26%;开启余热回收系统后,同等条件下的COP与PER分别提升了24.65%和24.67%,且COP,PER变化的趋势发生了明显变化。     

基于R410A制冷剂的空气源燃气热泵系统制冷特性

该文搭建了使用R410A制冷剂涡旋式压缩机的高能效空气源燃气热泵实验平台。在实验台上进行不同进水温度t_w,in(8.8～18.8℃)、发动机转速N_eng(1400～2400 r/min)、环境温度T_amb(24～43℃)、进水流量G_w(9.16～18.32 m³/h)影响下的制冷特性研究，得到制冷量(Q·_c)、耗气功率(P_gas)、压缩机功率(P_comp)、一次能源利用率(R_PER)、总一次能源利用率(R_PER,all)及性能系数(R_COP)的变化规律。结果表明，R_PER受R_COP与发动机热效率η_eng的双重影响，制冷运行时R_PER、R_PER,all与η_eng分别处于0.935～1.224、1.388～1.720与27...     

General energy decay rates for a weakly damped Timoshenko system

In this paper, we consider the following Timoshenko-type system:

Rolling of manifolds without spinning

The control model of rolling of a Riemannian manifold (M; g) onto another one $ \left( {\hat{M},\hat{g}} \right) $ consists of a state space Q of relative orientations (isometric linear maps) between their tangent spaces equipped with a so-called rolling distribution $ {\mathcal D} $ _R, which models the natural constraints of no-spinning and no-slipping of the rolling motion. It turns out that the distribution $ {\mathcal D} $ _R can be built as a sub-distribution of a so-called no-spinning distribution $ {{\mathcal{D}}_{\overline{\nabla}}} $ on Q that models only the no-spinning constraint of the rolling motion. One is thus motivated to study the control problem associated to $ {{\mathcal{D}}_{\overline{\nabla}}} $ and, in particular, the geometry of $ {{\mathcal{D}}_{\overline{\nabla}}} $ -orbits. Moreover, the definition of $ {{\mathcal{D}}_{\overline{\nabla}}} $ (contrary to the definition of $ {\mathcal D} $ _R) makes sense in the general context of vector bundles equipped with linear connections. The purpose of this paper is to study the distribution $ {{\mathcal{D}}_{\overline{\nabla}}} $ determined by the product connection $ \nabla \times \hat{\nabla} $ on a tensor bundle $ {E^{*}}\otimes \hat{E}\to M\times \hat{M} $ induced by linear connections ?, $ \hat{\nabla} $ on vector bundles $ E\to M,\,\,\,\hat{E}\to \hat{M} $ . We describe completely the orbit structure of $ {{\mathcal{D}}_{\overline{\nabla}}} $ in terms of the holonomy groups of ?, $ \hat{\nabla} $ and characterize the integral manifolds of it. Moreover, we describe the general formulas for the Lie brackets of vector elds in $ {E^{*}}\otimes \hat{E} $ in terms of $ {{\mathcal{D}}_{\overline{\nabla}}} $ and the vertical tangent distribution of $ {E^{*}}\otimes \hat{E}\to M\times \hat{M} $ . In the particular case of tangent bundles $ TM\to M,\,\,\,T\hat{M}\to \hat{M} $ and Levi-Civita connections, we describe in more detail how $ {{\mathcal{D}}_{\overline{\nabla}}} $ is related to the above mentioned rolling model, where these Lie brackets formulas provide an important tool for the study of controllability of the related control system.     

The Deligne–Simpson Problem and the Connectedness of some Varieties

The Deligne–Simpson problem is formulated as follows: give necessary and sufficient conditions for the choice of the conjugacy classes or so that there exist irreducible (p+1)-tuples of matrices M _j ∈ C _j or A _j ∈ c _j satisfying the equality M ₁ ⋯ M _p+1 = I or A ₁ + ⋯ + A _p+1 = 0. The matrices M _j and A _j are interpreted as monodromy operators of regular linear systems and as matrices-residues of Fuchsian ones on the Riemann sphere. We prove that in the so-called simple case the subset or of the variety or consisting of all irreducible (p+1)-tuples (if nonempty) is connected. “Simple” means that the greatest common divisor of all quantities of Jordan blocks of a given size, of a given matrix M _j or A _j , and with a given eigenvalue is 1. To the memory of my mother     

Regions Where the Exponential Map at Regular Points of Sub-Riemannian Manifolds is a Local Diffeomorphism

For a k-step sub-Riemannian manifold which admits a bracket generating vector at a point, we describe a region near the point where the exponential map is a local diffeomorphism. This is proved by taking the Taylor series of the exponential map and calculating the first nonzero term, which has order , where n is the topological dimension and is the Hausdorff dimension of the metric space associated to the sub-Riemannian manifold.      

Foliation Admitting Recurrent Leaves of Infinite Depth on Compact Two-Manifolds

Let be a foliation on a two-manifold M. Denote the topology closure of each leaf L of by . A sequence of proper inclusions , where each L _i is a recurrent leaf of , is called a nest of length k. The maximal length of various nests is known as the depth of the foliations . It is well known that if is orientable and M is compact, the depth of is at most one. In this paper, we show that on any orientable, compact two-manifold, there exist nonorientable foliations of infinite depth. This work negatively answers the Aranson conjecture [1]. This work was partially supported by FAPESP-Proj. Tematico No. 03/03107-9.     

An Estimate for the Entropy of Hamiltonian Flows

In this paper, we present a generalization to Hamiltonian flows on symplectic manifolds of the estimate proved by Ballmann and Wojtkovski in [4] for the dynamical entropy of the geodesic flow on a compact Riemannian manifold of nonpositive sectional curvature. Given such a Riemannian manifold M, Ballmann and Wojtkovski proved that the dynamical entropy h _μ of the geodesic flow on M satisfies the inequalitywhere v is a unit vector in T _p M if p is a point in M, SM is the unit tangent bundle on M, K(v) is defined as , where is the Riemannian curvature of M, and μ is the normalized Liouville measure on SM. We consider a symplectic manifold M of dimension 2n, and a compact submanifold N of M, given by the regular level set of a Hamiltonian function on M; moreover, we consider a smooth Lagrangian distribution on N, and we assume that the reduced curvature of the Hamiltonian vector field with respect to the distribution is non-positive. Then we prove that under these assumptions, the dynamical entropy h _μ of the Hamiltonian flow with respect to the normalized Liouville measure on N satisfies      

Controllability of control systems on complex simple lie groups and the topology of flag manifolds

Let S be a subsemigroup with nonempty interior of a connected complex simple Lie group G. It is proved that S = G if S contains a subgroup G(α) ≈ Sl (2, $ \mathbb{C} $ ) generated by the exp $ {{\mathfrak{g}}_{{\pm \alpha }}} $ , where $ {{\mathfrak{g}}_{\alpha }} $ is the root space of the root α. The proof uses the fact, proved before, that the invariant control set of S is contractible in some flag manifold if S is proper, and exploits the fact that several orbits of G(α) are 2-spheres not null homotopic. The result is applied to revisit a controllability theorem and get some improvements.     

Multiple positive solutions of singular dirichlet second-order boundary-value problems with derivative dependence

The existence of multiple positive solutions for the singular Dirichlet boundary-value problem

Limit Cycles for a Class of Three-Dimensional Polynomial Differential Systems

Perturbing the system inside the family of polynomial differential systems of degree n in , we obtain at most n ² limit cycles using the first-order averaging theory. Moreover, there exist such perturbed systems having at least n ² limit cycles.      

On Topological Equivalence of Linear Lows with Applications to Bilinear Control Systems

This paper classifies continuous linear flows using concepts and techniques from topological dynamics. Specifically, the concepts of equivalence and conjugacy are adapted to flows on vector bundles, and the Lyapunov decomposition is characterized using the induced flows on the Grassmann and the flag bundles. These results are then applied to bilinear control systems, for which their behavior in , on the projective space , and on the Grassmannians is characterized. This research was partially supported by Proyecto FONDECYT No. 1060981 and Proyecto FONDECYT de Incentivo a la Cooperación Internacional No. 7020439.