系统频率电磁调谐的双层薄膜声学超材料

为了拓宽声学超材料对低频声波的隔声带宽,设计了1种系统频率电磁调谐的双层薄膜声学超材料,该超材料由双层硅橡胶薄膜、薄膜之间的羰基铁粉、附加铅质质量块、铝质框架和电磁场加载装置等组成.运用COMSOL Multiphysics 5.5仿真和试验等方法,对声学超材料的声学性能进行了研究.研究结果表明:该声学超材料在低频范围内可实现良好的隔声效果;通过输入不同电流改变磁场强度,可以实现声学超材料固有频率的定向调节;与被动声学超材料相比,主动声学超材料实现了声学超材料隔声性能的非接触主动调谐,拓宽了声学超材料的声波控制带宽;在此基础上,通过进一步探讨材料参数对声学超材料声学性能的影响,发现双层薄膜的厚度越厚,杨氏模量越大,声学超材料将获得更宽的隔声带宽.     

江西赣江源自然保护区森林固碳释氧及转化太阳能的价值核算

赣江源自然保护区是以保护中亚热带常绿阔叶林生态系统为主的自然保护区,涵盖江西的石城、瑞金二县市.流域面积161.008 5 km<'2>.赣江是江西省的母亲河,流域面积83 500 km<'2>,占全省国土面积的48%,保护赣江源区的森林环境资源,对江西经济社会的发展,具有重要的战略和现实意义.     

C&R Tree算法在车险费率厘定中的应用

提出基于C&R Tree算法的车险理赔风险模型。现有研究方法对变量多、数据类型复杂和数据量大的数据不能准确进行分析,导致对车险客户的理赔风险出现误判,从而不能准确制定车险费率,为了解决上述问题,提出C&R Tree算法。C&R Tree算法通过检测输入字段,通过度量各个划分产生的异质性的减少程度,找到最佳的一个划分,将C&R Tree算法应用到车险理赔数据中,实验证明:所得理赔风险模型不依赖于经验知识,其模型易于理解,且具有较高的准确率,能够满足评价的要求。     

儿童绘本的教育功能探析

儿童绘本具有简洁的文字、精美的画面、灵活的版式,符合儿童早期阅读的特点和习惯。绘本阅读能够发展儿童的语言能力,培养想象力、观察力和思维能力,增强审美意识,培养丰富情感。为更好地发挥儿童绘本阅读在儿童教育中的作用,既要为儿童选择适合其需要的绘本,也要家长和教师在阅读中加以引导,更要注重家庭教育和学校教育相结合。     

杂文的批评意识刍议

批评意识,是杂文与生俱来的文体特质。但杂文批评的文体特质,从文体确立至今,很多人也还有着这样那样的误解。有人把杂文批评等同于政治批评,或把杂文的批评性与建设性割裂开来,从而导致了历史上屡见不鲜的杂文悲剧,也妨碍了杂文创作的发展。     

带非线性观测器的欠驱动船舶自适应动态面输出反馈轨迹跟踪控制

针对船速与艏摇角速度均不可测的三自由度欠驱动船舶轨迹跟踪问题,考虑在海洋环境扰动未知,提出一种带非线性观测器的动态面自适应输出反馈控制方法。该方法通过对系统模型进行坐标变换,设计非线性观测器估计船舶的速度向量;采用动态面技术可处理反演法对虚拟控制量求导导致的“微分膨胀”问题,减少计算量;同时采用自适应律估计海洋环境干扰的界值,从而防止参数漂移。利用Lyapunov函数证明该控制律可保证船舶轨迹跟踪误差的一致最终有界性,仿真结果证明了所提出控制方法的有效性。     

基于云计算的唐山市信息资源共享模式设计

针对唐山市信息资源及信息服务现状,对由于管理体制条块分割、资金短缺、资源重复浪费严重、标准化进程缓慢等影响唐山市信息资源共享的因素进行分析,探讨基于云计算创建唐山市信息资源共享模式的方法途径,为制定我国区域信息资源共享的发展方略、开发利用区域信息资源、提升区域竞争力提供支撑,为云计算在区域地方资源共建共享中的应用提供参考.     

基于Excel的模糊聚类分析在区域产业发展评价中的应用

简要概括了模糊聚类分析方法的基本思想和基本步骤,选取2010年广西各地市第三产业发展数据作为研究对象,探讨了模糊聚类分析方法在Excel计算平台上的创新实践。     

Birds of the desert region of Uintah County, Utah

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} The Common Loon, White Pelican, Double-crested Cormorant, recurvirostrids, and most grebes, waterfowl, gulls, and terns have become more abundant in Uintah County, Utah, since 1937 (Twomey 1942) due to the establishment of Pelican Lake and adjacent water bodies and the ponds and marshes at Ouray National Wildlife Refuge and Pariette Wetlands Wildlife Management Area. The incidence of herons, egrets, thrushes, nuthatches, and icterids has generally remained about the same since 1937. Diurnal raptors have largely declined in abundance in the desert region of Uintah County since Twomey&rsquo;s (1942) study. Plovers, sandpipers, phalaropes, and the White-faced Ibis were generally less common in 1977&ndash;1982 than in 1937, perhaps chiefly due to their displacement from wintering grounds by human population expansion and agricultural and industrial development. The incidence of owl species remains constant. Most flycatchers, swallows, warblers, vireos, orioles, and emberizids have diminished in number since 1937, probably because of the shrinkage of their winter habitats in Latin America and the southwestern U.S. The Blue Grosbeak and Black-throated Sparrow were not recorded in Uintah County in 1937 but were found there during this study and may represent a range extension northward since 1937. The Blue-gray Gnatcatcher is more common now than in 1937 due to the northward extension of its range. The Starling and Rock Dove and, more recently, the Common Grackle, Great-tailed Grackle, and Cattle Egret have invaded Uintah County due to the expansion of their ranges. It is not clear why the Pine Siskin, House Finch, and most corvids are presently less common than in 1937. &nbsp;&nbsp;