For a graph G, let b(G)=max﹛|D|: Dis an edge cut of G﹜ . For graphs G and H, a map Ψ: V(G)→V(H) is a graph homomorphism if for each e=uv∈E(G), Ψ(u)Ψ(v)∈E(H). In 1979, Erd?s proved by probabilistic methods that...For a graph G, let b(G)=max﹛|D|: Dis an edge cut of G﹜ . For graphs G and H, a map Ψ: V(G)→V(H) is a graph homomorphism if for each e=uv∈E(G), Ψ(u)Ψ(v)∈E(H). In 1979, Erd?s proved by probabilistic methods that for p ≥ 2 with if there is a graph homomorphism from G onto Kp then b(G)≥f(p)|E(G)| In this paper, we obtained the best possible lower bounds of b(G) for graphs G with a graph homomorphism onto a Kneser graph or a circulant graph and we characterized the graphs G reaching the lower bounds when G is an edge maximal graph with a graph homomorphism onto a complete graph, or onto an odd cycle.展开更多
In order to analyze the influences of the different tool’s shape and surface conditions (such as different coated and material) and their interaction on the cutting temperature, a coupled thermo-mechanical finite ele...In order to analyze the influences of the different tool’s shape and surface conditions (such as different coated and material) and their interaction on the cutting temperature, a coupled thermo-mechanical finite element analysis (FEA) model of plane-strain orthogonal metal cutting process is constructed, and 16 simulation cases with 16 different types of tools, which cover 4 rake angles, -10°, 0°, 10°, 20°, and 4 friction coefficient values, 0, 0.1, 0.2, 0.3 in the same cutting condition (cutting depth and cutting speed) have been performed. Finally the simulation results are analyzed according to the variance analysis method (VAM) of orthogonal array designs (OADs), the relationships between the rake angle, tool-workpiece interface’s friction coefficient and their interact effect to the maximum temperature value and the temperature field of the chip are obtained. This result has some instructive meaning to analyze the causes of the cutting temperature and to control the maximum temperature value and the overall temperature field in the metal cutting process.展开更多
ith the three criteria for cutting variables proposed by W.W.Gilbert and K.Hitomi,this paper analyzes the reasonable selection of cutting variables,and furth...ith the three criteria for cutting variables proposed by W.W.Gilbert and K.Hitomi,this paper analyzes the reasonable selection of cutting variables,and further states the relations among maximum profit oriented cutting speed,minimum cost oriented cutting speed and maximum productivity oriented cutting speed.It puts forward a mathematical model for the optimization of cutting variables in machining.展开更多
高比例分布式光伏接入引入的不确定性以及雪花型复杂拓扑结构引发的故障传播路径模糊,共同加剧了配电网在复合故障下的脆弱性。传统恢复策略难以兼顾动态负荷需求、分布式电源调度以及信息物理跨域耦合,且受限于静态规则与计算效率瓶颈...高比例分布式光伏接入引入的不确定性以及雪花型复杂拓扑结构引发的故障传播路径模糊,共同加剧了配电网在复合故障下的脆弱性。传统恢复策略难以兼顾动态负荷需求、分布式电源调度以及信息物理跨域耦合,且受限于静态规则与计算效率瓶颈。为此,提出一种信息物理协同的复合故障恢复策略。首先,构建多属性动态决策模型,采用动态的基于准则间相关性的准则重要性(criteria importance through intercriteria correlation,CRITIC)评估法与跨域混合中心性指标,通过滑动时间窗自适应分配权重,捕捉通信时延与受控于通信系统的潮流调节行为之间的时空关联特征。其次,建立双层联合防护规划框架,上层在预算约束下协同优化加固与冗余策略以提升系统韧性,下层动态修正运行安全边界。最后,设计增强型Edmonds-Karp算法,引入势差驱动机制与混合权重割集模型,以最小化隔离代价与最大化恢复流量为目标,输入为信息物理耦合网络状态量,输出为最优割集与恢复路径,有效提升了故障隔离与恢复效率。IEEE算例仿真表明,所提策略显著提升了复合故障场景下的恢复效率与系统韧性。展开更多
文摘For a graph G, let b(G)=max﹛|D|: Dis an edge cut of G﹜ . For graphs G and H, a map Ψ: V(G)→V(H) is a graph homomorphism if for each e=uv∈E(G), Ψ(u)Ψ(v)∈E(H). In 1979, Erd?s proved by probabilistic methods that for p ≥ 2 with if there is a graph homomorphism from G onto Kp then b(G)≥f(p)|E(G)| In this paper, we obtained the best possible lower bounds of b(G) for graphs G with a graph homomorphism onto a Kneser graph or a circulant graph and we characterized the graphs G reaching the lower bounds when G is an edge maximal graph with a graph homomorphism onto a complete graph, or onto an odd cycle.
文摘In order to analyze the influences of the different tool’s shape and surface conditions (such as different coated and material) and their interaction on the cutting temperature, a coupled thermo-mechanical finite element analysis (FEA) model of plane-strain orthogonal metal cutting process is constructed, and 16 simulation cases with 16 different types of tools, which cover 4 rake angles, -10°, 0°, 10°, 20°, and 4 friction coefficient values, 0, 0.1, 0.2, 0.3 in the same cutting condition (cutting depth and cutting speed) have been performed. Finally the simulation results are analyzed according to the variance analysis method (VAM) of orthogonal array designs (OADs), the relationships between the rake angle, tool-workpiece interface’s friction coefficient and their interact effect to the maximum temperature value and the temperature field of the chip are obtained. This result has some instructive meaning to analyze the causes of the cutting temperature and to control the maximum temperature value and the overall temperature field in the metal cutting process.
文摘ith the three criteria for cutting variables proposed by W.W.Gilbert and K.Hitomi,this paper analyzes the reasonable selection of cutting variables,and further states the relations among maximum profit oriented cutting speed,minimum cost oriented cutting speed and maximum productivity oriented cutting speed.It puts forward a mathematical model for the optimization of cutting variables in machining.
文摘高比例分布式光伏接入引入的不确定性以及雪花型复杂拓扑结构引发的故障传播路径模糊,共同加剧了配电网在复合故障下的脆弱性。传统恢复策略难以兼顾动态负荷需求、分布式电源调度以及信息物理跨域耦合,且受限于静态规则与计算效率瓶颈。为此,提出一种信息物理协同的复合故障恢复策略。首先,构建多属性动态决策模型,采用动态的基于准则间相关性的准则重要性(criteria importance through intercriteria correlation,CRITIC)评估法与跨域混合中心性指标,通过滑动时间窗自适应分配权重,捕捉通信时延与受控于通信系统的潮流调节行为之间的时空关联特征。其次,建立双层联合防护规划框架,上层在预算约束下协同优化加固与冗余策略以提升系统韧性,下层动态修正运行安全边界。最后,设计增强型Edmonds-Karp算法,引入势差驱动机制与混合权重割集模型,以最小化隔离代价与最大化恢复流量为目标,输入为信息物理耦合网络状态量,输出为最优割集与恢复路径,有效提升了故障隔离与恢复效率。IEEE算例仿真表明,所提策略显著提升了复合故障场景下的恢复效率与系统韧性。
