This work deals with the study of the reflection and transmission properties of plane periodic structures composed of N periods (1 ≤ N ≤ 3) in the MHz frequency range. The period consists of two bounded plates prese...This work deals with the study of the reflection and transmission properties of plane periodic structures composed of N periods (1 ≤ N ≤ 3) in the MHz frequency range. The period consists of two bounded plates presenting a high acoustic impedance contrast one of which is in aluminum, the other is in polyethylene. The longitudinal and transversal attenuations are considered in polyethylene and neglected in aluminum. We take into account the case of emerging holes in the polyethylene layer. Simulations are based on the stiffness matrix method (SMM) developed by Rokhlin. When attenuation is considered in polyethylene, the reflection coefficients are different depending on the insonification side. The comparison of results without or with holes configurations are performed and showed that throughout holes allow the rapid observation of forbidden bands. The attenuation of the whole multilayer is also determined.展开更多
企业与金字塔底层(Bottom of the Pyramid,BOP)群体经济关系的建立是开展包容性创新的重要前提。从BOP群体与企业的关系视角出发,认为二者之间存在"结构洞"现象,即政策制度和配套设施短缺导致的"市场洞",融资困难...企业与金字塔底层(Bottom of the Pyramid,BOP)群体经济关系的建立是开展包容性创新的重要前提。从BOP群体与企业的关系视角出发,认为二者之间存在"结构洞"现象,即政策制度和配套设施短缺导致的"市场洞",融资困难、知识和技能不足导致的"资源洞",信息获取、传播和扩散困难导致的"信息洞"。引入小微企业作为第三方,搭建大企业与BOP群体之间的连接桥。提出在包容性创新情境下,利用小微企业的定位优势、资源优势以及协调优势来实现"结构洞"的跨越,并在从企业能力提升和外部环境两方面提出建议。展开更多
文摘This work deals with the study of the reflection and transmission properties of plane periodic structures composed of N periods (1 ≤ N ≤ 3) in the MHz frequency range. The period consists of two bounded plates presenting a high acoustic impedance contrast one of which is in aluminum, the other is in polyethylene. The longitudinal and transversal attenuations are considered in polyethylene and neglected in aluminum. We take into account the case of emerging holes in the polyethylene layer. Simulations are based on the stiffness matrix method (SMM) developed by Rokhlin. When attenuation is considered in polyethylene, the reflection coefficients are different depending on the insonification side. The comparison of results without or with holes configurations are performed and showed that throughout holes allow the rapid observation of forbidden bands. The attenuation of the whole multilayer is also determined.
文摘企业与金字塔底层(Bottom of the Pyramid,BOP)群体经济关系的建立是开展包容性创新的重要前提。从BOP群体与企业的关系视角出发,认为二者之间存在"结构洞"现象,即政策制度和配套设施短缺导致的"市场洞",融资困难、知识和技能不足导致的"资源洞",信息获取、传播和扩散困难导致的"信息洞"。引入小微企业作为第三方,搭建大企业与BOP群体之间的连接桥。提出在包容性创新情境下,利用小微企业的定位优势、资源优势以及协调优势来实现"结构洞"的跨越,并在从企业能力提升和外部环境两方面提出建议。