巧玩Lava-Lava离线传输

文件能闪电般地传输?对,La- va-Lava的文件传输很出色,不仅传输速度可以达到以兆(M)来计算,而且还可以在外网传输超大文件,即使几百兆也不怕掉线,更何况它还有不限次数的断点续传功能,让人很放心。除此之外,La- va-Lava还有一个绝活,是其他的即时通讯软件所没有的,就是离线传输功能,即使好友不在线,你也可以用离线传输功能将对方所需要的文件发过去。而且当你第二次跟另外一个好友离线发送同样的文件时,只需一秒就可以发给对方了,神奇吧!先不说了,大家跟我一起学如何巧玩离线传输吧。     

Who’s Got the Power? Religious Authority and the Internet

While many themes have been explored in relation to religion online—ritual, identity construction, community—what happens to religious authority and power relationships within online environments is an area in need of more detailed investigation. In order to move discussions of authority from the broad or vague to the specific, this article argues for a more refined identification of the attributes of authority at play in the online context. This involves distinguishing between different layers of authority in terms of hierarchy, structure, ideology, and text. The article also explores how different religious traditions approach questions of authority in relation to the Internet. Through a qualitative analysis of three sets of interviews with Christians, Jews, and Muslims about the Internet, we see how authority is discussed and contextualized differently in each religious tradition in terms of these four layers of authority.     

Double-Averaging Concept for Rough-Bed Open-Channel and Overland Flows: Applications

The paper briefly outlines the double-averaging methodology for studying environmental rough-bed flows. It focuses on the applications of this methodology in environmental hydraulics by providing several examples illustrating advantages of this methodology over conventional approaches. Examples include: (1) identification of specific flow layers and flow types; (2) vertical distribution of the double-averaged velocity between the roughness tops and troughs; (3) vertical distribution of momentum fluxes and sinks for typical roughness types due to turbulence, mean flow heterogeneity, secondary currents, form drag, and viscous drag; (4) estimates of form-induced (dispersive) stresses and evaluation of their structure using quadrant analysis; and (5) closure development for mass-transfer-uptake processes for stream periphyton. These examples illustrate the advantages of the double-averaging methodology over conventional approaches as well as highlight its potential for studying flows over very rough beds, highly mobile beds, permeable beds, and surface–subsurface exchanges of mass, heat, and momentum. This methodology may also significantly improve research tools for studying a wide range of flow–biota interaction phenomena such as those related to aquatic plants, mussel communities, biofilms, and many others.     

Modifying the MRI, elastic stiffness and electrical properties of polyvinyl alcohol cryogel using irradiation

The aim of this work was to study the effect of radiation on the elastic stiffness, electrical and MRI properties of polyvinyl alcohol (PVA)-based cryogel (PVA-C). The PVA-C samples were irradiated with a ⁶⁰C0 γ-source, at 2.18 × 10⁶ Rads. The indentation measurements (an indication of elastic stiffness) reduced by about 14.6% for PVA-3C and 5.7% PVA-6C after irradiation, indicating that the material became harder/stiffer. It was found that MRI relaxation times provide an alternative and non-destructive method to evaluate the radiation effect on PVA-C. The T₁ of PVA-C that had undergone three freeze thaw cycles decreased with irradiation by 10%, 25% and 35% at 1 T, 1.89 T and 3 T respectively. The T₁ of PVA-C that had undergone six freeze thaw cycles decreased with irradiation by 18%, 15% and 11% at 1 T, 1.89 T and 3 T respectively. The T₂ of PVA-C decreased with irradiation only at 1T, however this change is hypothesized to be due to the interaction of two spin pools in the gel. The electrical conductivity (σ) and permittivity constant (ε) of the unirradiated and γ-irradiated PVA-C samples were measured at different frequencies in the range 40 Hz to 1 MHz. The results demonstrated that the conductivity increased with irradiation by 50% for PVA-3C (three freeze thaw cycles) and 75% for PVA-6C (six freeze thaw cycles) at frequencies greater than 1 KHz.The permittivity decreased with irradiation up to 25% for 3C and 35% for 6C at frequencies less than 1 KHz.     

PARO: Supporting Dynamic Power Controlled Routing in Wireless Ad Hoc Networks

This paper introduces PARO, a dynamic power controlled routing scheme that helps to minimize the transmission power needed to forward packets between wireless devices in ad hoc networks. Using PARO, one or more intermediate nodes called redirectors elects to forward packets on behalf of source–destination pairs thus reducing the aggregate transmission power consumed by wireless devices. PARO is applicable to a number of networking environments including wireless sensor networks, home networks and mobile ad hoc networks. In this paper, we present the detailed design of PARO and evaluate the protocol using simulation and experimentation. We show through simulation that PARO is capable of outperforming traditional broadcast-based routing protocols (e.g., MANET routing protocols) due to its energy conserving point-to-point on-demand design. We discuss our experiences from an implementation of the protocol in an experimental wireless testbed using off-the-shelf radio technology. We also evaluate the impact of dynamic power controlled routing on traditional network performance metrics such as end-to-end delay and throughput.     

Synthesis of multistable equilibrium linkage systems using an optimization approach

This paper introduces a methodology for designing multistable equilibrium (MSE) systems. The methodology derives design criteria that relate system equilibrium characteristics to a potential energy curve. These design criteria are then used in a performance index that guides a candidates potential energy to approach the desired potential energy curve. As an example, a four-bar linkage with linear translational springs attached demonstrates the design methodology and the difficulties inherent in synthesizing MSE systems. To solve for the unknown design variables of the example problem a genetic algorithm is used.     

正视网络安全以及网络安全问题一览

在2005年中,伴随着网络技术和计算机技术的发展,网格服务的成熟以及Web service的广泛应用,更多的新技术新应用将融入我们的生活中,而随之而来的,除了便利,还有一些不安。从互联网的兴起开始,越来越多的病毒感染从原本的exe文件感染方式改变为漏洞攻击+驻留+尝试攻击其他机器的模式。不管是Windows也好,Linux也好,Solaris或者其他操作系统也好,软件是人写的,由于效率或考虑不周等因素,常常会在极端测试下造成程序溢出,进而让攻击者取得权限。Windows xp的sp2刚发布没多久,微软的“安全服务”还没喊响之际,就又爆出10多个IE漏洞来,漏洞—…