A Compact Fourth-Order Finite Difference Scheme for Unsteady Viscous Incompressible Flows

In this paper, we extend a previous work on a compact scheme for the steady Navier–Stokes equations [Li, Tang, and Fornberg (1995), Int. J. Numer. Methods Fluids, 20, 1137–1151] to the unsteady case. By exploiting the coupling relation between the streamfunction and vorticity equations, the Navier–Stokes equations are discretized in space within a 3×3 stencil such that a fourth order accuracy is achieved. The time derivatives are discretized in such a way as to maintain the compactness of the stencil. We explore several known time-stepping approaches including second-order BDF method, fourth-order BDF method and the Crank–Nicolson method. Numerical solutions are obtained for the driven cavity problem and are compared with solutions available in the literature. For large values of the Reynolds number, it is found that high-order time discretizations outperform the low-order ones.     

中国西南易旱地区识别的探讨

利用中国西南地区13个气象站56年以上的长系列月降雨量资料,统计分析了降雨的多年变化、季节变化特征,以及连续少雨时间段事件,探讨了易旱区识别的定性定量分析方法,初步建立了气象易旱区识别指标及标准,将5个地区识别为易旱地区,5个地区识别为较易旱地区,3个地区识别为不易旱地区,将6个地区识别为易发长时间干旱地区,并对识别方法进行了讨论,为进一步的易旱区综合识别研究提出了建议。     

Wafer-level multilayer integration of RF passives with thick BCB/metal interlayer connection in silicon-based SiP

This paper presents an integration technology for RF passives using benzocyclobutene (BCB)/metal multilayer interconnection for system-in-package applications. This technology has been specially developed for RF subsystem packages in which a thick polymer, BCB (more than 15 μm thick), is adopted as dielectric with lossy silicon as substrate for its excellent characteristics. Both dry-etch BCB and photosensitive BCB are applied in this work, and their processes are briefly introduced and compared. An RF power divider, an MIM capacitor, different types of RF inductors as well as a coupled microstrip based band-pass filter are fabricated and measured at wafer level. The results show good electrical performances, and accordingly the passives are well applicable in RF band. Moreover, the subsystem models including monolithic chips connected with passives are presented.     

Spatial and temporal variations in algal blooms in the coastal waters of the western South China Sea

Algal blooms occur frequently in the coastal waters of the western South China Sea (SCS). This paper reports spatial and temporal variations of algal bloom events in these waters from 1993 to 2007. Twenty-five algal bloom events occurred in summer in the coastal waters of South and Central Vietnam where they were associated with wind-induced, coastal, nutrient upwelling and river discharges; a further eight events occurred in the coastal waters of North Vietnam. A greater number of algal bloom events were observed in 1999 and 2002, and were accompanied by several previously unobserved species for the study period. These events may be related to the El Niño events of 1998 and 2002. Furthermore, the bloom-causative species Trichodesmium erythraeum (Cyanophyta) entirely dominated the phytoplankton community of algal blooms during 1993–1999 whereas the species Phaeocystis globosa (Haptophyta) dominated blooms after 2002. This study establishes a basis for further long-term research of algal bloom event variations, and provides a compiled scientific reference that may be used for later prediction of Harmful algal blooms (HABs).     

日本下水污泥处理处置情况介绍

一直以来,日本高度重视污泥的资源化利用,并将考核指标更改为生物质循环利用率,同时对下水道重新定义,这对今后日本污泥处理处置的技术路线产生很大的影响.在介绍日本污泥处理处置现状的基础上,重点介绍在日本广泛应用的回转式污泥干化和焚烧装置.日本污泥处理处置的思路、经验和相关设备对我国污泥处理处置技术路线的选择和干化焚烧设备选择有较好的借鉴意义.     

绿色节能控制器的设计

设计制作基于433.9MHz业余频段的绿色无线节能控制器,实现了通过同步个人电脑(PC)或者服务器的开、关机行为,远程无线控制路由器供电插座的开关,使路由器在不使用的时间处于断电状态.此控制器有发射板与接收板两个部分.控制器的接收部分功耗低于1 W,降低能耗同时减少了空间电磁辐射.发射部分则利用摩托车防盗的电路技术,保证信号稳定性,其有效范围在200m左右.并利用芯片PT2262/2272远程的编码、解码功能屏蔽了干扰.一旦控制器的发射部分接受供电,就能立刻唤醒路由器,在很大程度上节约了电能.     

Preface

Recently, there has been a dramatic increase in research on data mining on social networks and social media. Theubiquitous nature of Web-enabled devices, including desktops,     

The formation of ilmenite FeTiO3 powders by a novel liquid mix and H2/H2O reduction process

FeTiO₃ powder was prepared via a liquid mix and H₂/H₂O reduction process. First, an intermediate compound was synthesized by a liquid mix process. This precursor compound to FeTiO₃ was characterized by thermal analysis (TG/DTA) and Fourier Transform Infrared spectroscopy (FT-IR). Second, the precursor was annealed in the air, H₂/H₂O(g) mixing gas stream, respectively. The obtained powder was characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis spectroscopy (EDAX) and scanning electron microscope (SEM). It was showed that pure and homogenous FeTiO₃ was successfully obtained below 600 °C.