论摄影审美方式的独特性

摄影艺术中，审美方式的独特性有四个方面：在发现选择中实现平凡美的升华；在观察取舍中体现光影美的追求；在等待捕捉中完成瞬间美的凝聚；在构思导演中进行摄影美的再造。     

二维守恒律方程四块常数的黎曼问题Guckenheimer解

1 Introduction Consider scalar conservation laws in two spacedi mensionsut f(u)x g(u)y=0 , (1)wheref(u) ,g(u) satisfies the conditions (1)f(u) ,g(u)∈C3(R) ; (2)f″(u)≠0 ,(u-u0)g″(u) >0 ; (3)gf″″((uu))′≠0 ,and the Riemann problemu(0 ,x,y) =u0(θ) ,0≤θ≤2π, (2)whereθis a polar angle in the (x,y)-plane andu0(θ) is a piecewise constant function. For the sakeof definiteness and si mplicity, we might assumef(u) ,g(u)∈C3(R1) ,f″(u) >0 , ug″(u) >0 ,fg″″((uu))′>0 (H)as well .The exi…     

二维离散型随机变量独立性证明的矩阵形式

目的：为了简化二维离散型随机变量的独立性证明过程.方法：引进二维离散型随机变量概率分布的矩阵形式A,用矩阵形式来判断独立性,再利用Matlab软件求解.结果：独立性判定的条件pij=pi.p.j转化为A=AIX.IYA.结论：二维离散型随机变量的独立性判断过程大大简化了.     

基于3G网络与二维码的产品追溯防伪技术及应用

随着3G网络技术发展,网络通信质量的不断提高,为越来越多的手机网络应用提供了基础平台。提出基于3G网络与二维条码的产品追溯防伪技术,解决武夷岩茶防伪验证的技术难题,降低政府与企业的打假成本,提高武夷岩茶品牌保护力度,在消费者查询验证产品的同时二维条码能为政府、企业提供更多机会进行知识普及、企业自身形象、产品宣传。     

科技期刊二维码的应用情况分析

二维码的应用分为主读和被读2类。从这2个方面分析二维码在科技期刊中的应用情况,并从编辑、作者、读者以及技术、标准的制订等方面指出二维码应用中存在的问题,提出解决问题的途径。     

新生报到系统移动客户端的研究与设计

通过对android开发系统平台和二维条形码的信息存储和识别设备的深入探索和实践,结合高等院校的实际需要,开发出的移动客户端可以更加方便进行新生的管理,包括新生的缴费问题、宿舍分配问题等工作。     

一个二维离散系统的分岔分析

应用动力系统的局部分支理论,研究一个二维离散动力系统当参数变化时产生的复杂动力学性质。我们应用中心流形定理和分岔理论证明了这个二维离散动力系统存在叉型分岔、倍周期分岔和Hopf分岔。     

Graphdiyne-based metal atomic catalysts for synthesizing ammonia

Development of novel catalysts for nitrogen reduction at ambient pressures and temperatures with ultrahigh ammonia (NH₃) yield and selectivity is challenging. In this work, an atomic catalyst with separated Pd atoms on graphdiyne (Pd-GDY) was synthesized, which shows fascinating electrocatalytic properties for nitrogen reduction. The catalyst has the highest average NH₃ yield of 4.45 ± 0.30 mg_NH3 mg_Pd⁻¹ h⁻¹, almost tens of orders larger than for previously reported catalysts, and 100% reaction selectivity in neutral media. Pd-GDY exhibits almost no decreases in NH₃ yield and Faradaic efficiency. Density functional theory calculations show that the reaction pathway prefers to perform at the (Pd, C1, C2) active area because of the strongly coupled (Pd, C1, C2), which elevates the selectivity via enhanced electron transfer. By adjusting the p–d coupling accurately, reduction of self-activated nitrogen is promoted by anchoring atom selection, and side effects are minimized.     

基于二维模式的供应链冲突处理策略探析

供应链是由通过协同合作来共同制定战略定位和提高运作效率的一些相互关联的企业组成。供应链管理则是利用计算机网络技术全面规划供应链中的商流、物流、知识流、信息流和资金流等管理的过程。现实中,由于很多企业都跨供应链,致使供应链的整合和跨供应链管理存在很多问题和隐患。将二维模式引入供应链企业间冲突问题的解决中来,提出供应链企业间冲突解决的五种策略,一定程度上丰富和充实了供应链理论研究,为现实中企业解决实际问题提供了借鉴。     

Giant magnetic field from moiré induced Berry phase in homobilayer semiconductors

When quasiparticles move in condensed matters, the texture of their internal quantum structure as a function of position and momentum can give rise to Berry phases that have profound effects on the material’s properties. Seminal examples include the anomalous Hall and spin Hall effects from the momentum-space Berry phases in homogeneous crystals. Here, we explore a conjugate form of the electron Berry phase arising from the moiré pattern: the texture of atomic configurations in real space. In homobilayer transition metal dichalcogenides, we show that the real-space Berry phase from moiré patterns manifests as a periodic magnetic field with magnitudes of up to hundreds of Tesla. This quantity distinguishes moiré patterns from different origins, which can have an identical potential landscape, but opposite quantized magnetic flux per supercell. For low-energy carriers, the homobilayer moirés realize topological flux lattices for the quantum-spin Hall effect. An interlayer bias can continuously tune the spatial profile of the moiré magnetic field, whereas the flux per supercell is a topological quantity that can only have a quantized jump observable at a moderate bias. We also reveal the important role of the non-Abelian Berry phase in shaping the energy landscape in small moiré patterns. Our work points to new possibilities to access ultra-high magnetic fields that can be tailored to the nanoscale by electrical and mechanical controls.