How much time is needed for wideband spectrum sensing?

In this paper, we consider a wideband cognitive radio network (CRN) which can simultaneously sense multiple narrowband channels and thus aggregate the perceived available channels for transmission. We study the problem of designing the optimal spectrum sensing time and power allocation schemes so as to maximize the average achievable throughput of the CRN subject to the constraints of probability of detection and the total transmit power. The optimal sensing time and power allocation strategies are developed under two different total power constraints, namely, instantaneous power constraint and average power constraint. Finally, numerical results show that, under both cases, for a CRN with three 6MHz channels, if the frame duration is 100ms and the target probability of detection is 90% for the worst case signal-to-noise ratio of primary users being ?12dB, ?15dB and ?20dB, respectively, the optimal sensing time is around 6ms and it is almost insensitive to the total transmit power.     

How accurate is a commercial monitoring system for photovoltaic plant?

According to uncertainty calculations, the values recorded by means of commercial monitoring systems are expected to be less accurate than those recorded by a system optimized for the measurement of electrical parameters—the so‐called dedicated system (DS). This study aims to verify if a larger expected uncertainty for commercial system (CS) actually turns into a larger spread of the measurements around the true value. In the Airport Bolzano Dolomiti plant, CS and DS are installed on the same photovoltaic arrays. The comparison performed considers the detailed uncertainty budget for the two systems using three performance indicators—energy, yield and performance ratio. Results show that the uncertainty level of the CS is much larger; for example, on performance ratio, it is about four times larger with respect to the optimized one (respectively ±16% and ±4%). Three sources mainly contribute to the uncertainty: measurements of irradiance, current and voltage. The measured values of the electrical parameter are compared in order to verify if the results of the budget calculations turn into a real difference. Results show that the CS is accurate in measuring current and voltage, respectively, ~2% and ~5% of difference from the DS, but not for irradiance—here, the difference is higher than 10%. In particular, the irradiance measured by the CS is systematically smaller; therefore, the performance ratio calculated through the CS is always overestimated and often larger than 100%. Copyright © 2012 John Wiley & Sons, Ltd.     

Employment class arbitration: An oxymoron? Or a matter of contract?

To what extent will courts send employment arbitration cases for class or collective actions? According to Jay W. Waks and William Poorten, of New York, waiving class action arbitrations doesn't impair claimants' substantive rights, and contractual silence means no class actions. The authors analyze the latest case law supporting their positions.     

So you still want judicial review of your arbitration award?

In the wake of the Supreme Court's Hall Street Associates decision rejecting arbitration judicial review, Helena Tavares Erickson, of New York, discusses the option of appellate arbitration.     

How resilient is the open web to the COVID-19 pandemic?

In this paper we refer to the Open Web to the set of services offered freely to Internet users, representing a pillar of modern societies. Despite its importance for society, it is unknown how the COVID-19 pandemic is affecting the Open Web. In this paper, we address this issue, focusing our analysis on Spain, one of the countries which have been most impacted by the pandemic.On the one hand, we study the impact of the pandemic in the financial backbone of the Open Web, the online advertising business. To this end, we leverage concepts from Supply–Demand economic theory to perform a careful analysis of the elasticity in the supply of ad-spaces to the financial shortage of the online advertising business and its subsequent reduction in ad spaces’ price. On the other hand, we analyze the distribution of the Open Web composition across business categories and its evolution during the COVID-19 pandemic. These analyses are conducted between Jan 1st and Dec 31st, 2020, using a reference dataset comprising information from more than 18 billion ad spaces.Our results indicate that the Open Web has experienced a moderate shift in its composition across business categories. However, this change is not produced by the financial shortage of the online advertising business, because as our analysis shows, the Open Web’s supply of ad spaces is inelastic (i.e., insensitive) to the sustained low-price of ad spaces during the pandemic. Instead, existing evidence suggests that the reported shift in the Open Web composition is likely due to the change in the users’ online behavior (e.g., browsing and mobile apps utilization patterns).     

Is digital inclusion a good thing? How can we make sure it is?

Activities directed at including more people in the use of digital technology are predicated on the assumption that such inclusion is invariably a good thing. It appears so, when judged solely by immediate practical convenience. However, if we also judge in terms of human rights, whether digital inclusion is good or bad depends on what kind of digital world we are to be included in. If we wish to work toward digital inclusion as a goal, it behooves us to make sure it is the good kind.     

How is the capacity of ad hoc networks improved with directional antennas?

The capacity of wireless ad hoc networks is constrained by the interference caused by the neighboring nodes. Gupta and Kumar have shown that the throughput for such networks is only Θ bits per second per node in a unit area domain when omnidirectional antennas are used [1]. In this paper we investigate the capacity of ad hoc wireless networks using directional antennas. Using directional antennas reduces the interference area caused by each node, thus increases the capacity of the network. We will give an expression for the capacity gain and we argue that in the limit, when the beam-width goes to zero the wireless network behaves like the wired network. In our analysis we consider both arbitrary networks and random networks where nodes are assumed to be static. We have also analyzed hybrid beamform patterns that are a mix of omnidirectional/directional and a better model of real directional antennas. Simulations are conducted for validation of our analytical results. Su Yi received the B.S. and M.S degrees in automation from Tsinghua University, China, in 1998 and 2001, respectively. She received her Ph.D. degree in electrical engineering from Rensselaer Polytechnic Institute, in December 2005. Her research interests include various topics in wireless ad hoc networks, including capacity of wireless networks, error control coding, and multimedia communications over wireless. Yong Pei is currently a tenure-track assistant professor in the Computer Science and Engineering Department, Wright State University, Dayton, OH. Previously he was a visiting assistant professor in the Electrical and Computer Engineering Department, University of Miami, Coral Gables, FL. He received his B.S. degree in electrical power engineering from Tsinghua University, Beijing, in 1996, and M.S. and Ph.D. degrees in electrical engineering from Rensselaer Polytechnic Institute, Troy, NY, in 1999 and 2002, respectively. His research interests include information theory, wireless communication systems and networks, and image/video compression and communications. He is a member of IEEE and ACM. Shivkumar Kalyanaraman is an Associate Professor at the Department of Electrical, Computer and Systems Engineering at Rensselaer Polytechnic Institute in Troy, NY. He received a B.Tech degree from the Indian institute of Technology, Madras, India in July 1993, followed by M.S. and Ph.D. degrees in computer and Information Sciences at the Ohio State University in 1994 and 1997 respectively. His research interests are in network traffic management topics such as congestion control, reliability, connectionless traffic engineering, quality of service (QoS), last-mile community wireless networks, low-cost free-space-optical networks, automated network management using online simulation, multicast, multimedia networking, and performance analysis. His special interest lies in developing the interdisciplinary connections between network architecture and fields like control theory, economics, scalable simulation technologies, video compression and optoelectronics. He is a member of ACM and IEEE. Babak Azimi-Sadjadi received his B.Sc. from Sharif University of Technology in 1989, his M.Sc. from Tehran University in 1992, and his Ph.D. from the University of Maryland at College Park in 2001 all in Electrical Engineering. He is currently with Intelligent Automation Inc. where he is a Senior Research Scientist He also has a joint appointment with the department of Electrical, Systems, and Computer Engineering of Rensselaer Polytechnic Institute where he is a research assistant professor. His research interests include, nonlinear filtering, networked control systems, and wireless networks.     

Which is a more serious factor to the bandwidth of GI POF:differential mode attenuation or mode coupling?

It is clarified for the first time that the effect of the mode coupling on the bandwidth characteristic is very small in the graded-index polymer optical fiber (GI POF) compared with in the step-index (SI) POF. Although there have been several trials regarding the theoretical prediction of bandwidth characteristics of the GI POF, a disagreement between measured and estimated properties was observed. The origin of disagreement has been generally explained as the mode coupling effect. However, it is clarified in this paper that the effect of the differential mode attenuation is the dominant factor of disagreement between measured and predicted bandwidth characteristics, while the effect of the mode coupling is small. In order to clarify the reason why the calculated bandwidth characteristics of the GI POF show a disagreement with that measured, differential mode delay and differential mode attenuation were investigated. It was found that the highest order mode in the poly methyl methacrylate (PMMA) base GI POF attenuated 17 dB compared with the lowest order mode through 100-m transmission. By taking into account this differential mode attenuation, an excellent agreement is observed between calculated and measured results of both the bandwidth characteristics and group delay, in which no mode coupling was considered     

What is explanation?

Explanation is the bread-and-butter activity of any technical communicator. We explain things for a living, but how well can any of us explain the nature of explanation itself? What makes technical explanation different from persuasion or narration? Web-based instructional systems have pushed us away from traditional kinds of paper-bound explanation. In these new realms, anything better than hit-and-miss success requires a clear sense of basic principles. With that in mind, I discuss the basic logic of explanation first proposed by the philosopher C.S. Peirce in the 1870s, and more recently extended by J. Hintikka (1998)     

What is engineering management?

The question, “what is engineering management?” has certainly been addressed before in both professional articles and textbooks. However, it seems appropriate to again address this question because of the renewed interest in engineering management. This renewed interest comes in many forms, but two stand out. The first is the increasing trend to give engineering management assignments earlier and earlier in a new engineering graduate's career. The second is the emphasis of engineering management skills in ABET 2000 in the undergraduate engineering program. Both of these initiatives seem to be led by industry and may be a direct result of industry's interest in engineering management skills as a competitive advantage as well as their downsizing practices, which have resulted in the more experienced engineers retiring early and their responsibilities being pushed down to the more junior engineers. If you believe, as does this author, that before you can become a good engineering manager you should first be a good engineer, then the trend of giving management assignments before engineers have had an opportunity to become well grounded in their engineering disciplines should be disturbing. This could eventually affect a company's ability to continue to play a leadership role in introducing new technologies. Hence, the question “what is engineering management?” is an important question. This article attempts to answer the question by addressing when engineering management skills are needed in an engineer's career     

How篇·怎样买?

怎样去买电脑?其实,买电脑和买菜本质上没有什么区别,都是用钞票换东西,差别也就在于用的钞票多一些,买的东西大一些。还有什么可说的?大道理都是多余的,下面我们来说说买电脑的注意事项吧。     

How informed are messaging app users about politics? A linkage of messaging app use and political knowledge and participation

Mobile messaging apps, such as Snapchat, Facebook Messenger, and WhatsApp, were unique campaign and information platforms in the 2016 U.S. presidential election. This study assesses how using such apps for campaign information is related to political knowledge and participation. Data from an online survey conducted prior to the election indicate that using messaging apps for news is positively related to knowledge miscalibration. Knowledge miscalibration is positively related to offline and online political participation. Findings are discussed in terms of the role of messaging apps in the political process.     

HowⅡ·怎样用?

电脑回到家了,怎么用也是一个关键的问题,相信没有人愿意花几千元买的是摆设。     

How Many CPU Cores is an FPGA Worth? Lessons Learned from Accelerating String Sorting on a CPU-FPGA System

Journal of Signal Processing Systems - String sorting is a fundamental kernel of string matching and database index construction; yet, it has not been studied as extensively as fixed-length keys...     

What's all this talk about ‘MEMS’?

When one whispers “MEMS' the word” the obvious pun appears to be in jest. It isn't. The word on the busy streets of San Francisco at SEMICON/West, and at over 40 annual conferences this year, is that the MEMS-based ‘microsystem,’ or ‘micromachine’ business indeed has the potential of transforming our society.     

How crucial is back gate misalignment/oversize in double gate MOSFETs for ultra-low-voltage analog/rf applications?

In the present work, by investigating the influence of source/drain (S/D) extension region engineering (also known as gate-underlap architecture) in planar Double Gate (DG) SOI MOSFETs, we offer new design insights to achieve high tolerance to gate misalignment/oversize in nanoscale devices for ultra-low-voltage (ULV) analog/rf applications. Our results show that (i) misaligned gate-underlap devices perform significantly better than DG devices with abrupt source/drain junctions with identical misalignment, (ii) misaligned gate underlap performance (with S/D optimization) exceeds perfectly aligned DG devices with abrupt S/D regions and (iii) 25% back gate misalignment can be tolerated without any significant degradation in cut–off frequency (f_T) and intrinsic voltage gain (A_VO). Gate-underlap DG devices designed with spacer-to-straggle ratio lying within the range 2.5 to 3.0 show best tolerance to misaligned/oversize back gate and indeed are better than self-aligned DG MOSFETs with non-underlap (abrupt) S/D regions. Impact of gate length and silicon film thickness scaling is also discussed. These results are very significant as the tolerable limit of misaligned/oversized back gate is considerably extended and the stringent process control requirements to achieve self-alignment can be relaxed for nanoscale planar ULV DG MOSFETs operating in weak-inversion region. The present work provides new opportunities for realizing future ULV analog/rf design with nanoscale gate–underlap DG MOSFETs.