Production of Two‐Dimensional Nanomaterials via Liquid‐Based Direct Exfoliation

Tremendous efforts have been devoted to the synthesis and application of two‐dimensional (2D) nanomaterials due to their extraordinary and unique properties in electronics, photonics, catalysis, etc., upon exfoliation from their bulk counterparts. One of the greatest challenges that scientists are confronted with is how to produce large quantities of 2D nanomaterials of high quality in a commercially viable way. This review summarizes the state‐of‐the‐art of the production of 2D nanomaterials using liquid‐based direct exfoliation (LBE), a very promising and highly scalable wet approach for synthesizing high quality 2D nanomaterials in mild conditions. LBE is a collection of methods that directly exfoliates bulk layered materials into thin flakes of 2D nanomaterials in liquid media without any, or with a minimum degree of, chemical reactions, so as to maintain the high crystallinity of 2D nanomaterials. Different synthetic methods are categorized in the following, in which material characteristics including dispersion concentration, flake thickness, flake size and some applications are discussed in detail. At the end, we provide an overview of the advantages and disadvantages of such synthetic methods of LBE and propose future perspectives.     

A Probabilistic and Decision Attitude Aggregation Operator for Intuitionistic Fuzzy Environment

In this paper, a new operator for aggregation of uncertain information under intuitionistic fuzzy environment is proposed. A novel approach is proposed for the selection of best alternative action in the face of the imprecise probabilities and the complex attitudinal character of the decision makers (DMs). This approach is distinguished with its capacity to accommodate the linguistic specification of probabilities as provided by human experts directly without the need to determine the fuzzy membership grades. The focus is to compute the net payoff for each alternative in the face of uncertain states of nature and DM's attitude. The proposed operator and the approach are illustrated through two real case studies.     

Statistical Analysis of Long Term Trends of Rainfall During 1901–2002 at Assam,India

Rainfall is a principal element of the hydrological cycle and its variability is important from both the scientific as well as socio-economic point of view. This study presents an analysis based on the precipitation variation in Assam, India over 102 years from 1901 to 2002. Precipitation data from 21 stations have been collected. These data have been analyzed for both annual and seasonal variation. For trend analysis, Mann-Kendell and Sen’s slope estimator test were used. To compare seasonal variations, three seasons of winter, summer and monsoon have been considered. Mean annual precipitation varied from 2,074 mm (at Tinsukia) to 3,538 mm (at North Chahar Hills). The most probable year of change was 1959 in annual precipitation. Time series of the Standardized Precipitation Index (SPI) depict that near normal occurs in about 68 years out 102 years, and in 2.48 years out of 102 years there was an extreme wet. All these findings can help provide rational regulatory and policy in relation to water resources to maintain the health of the various ecosystems that make up Assam, India.     

A technique for generating natural colour images from false colour composite images

Colour is widely used in remote sensing work. In many instances, the use of colour conveys additional information both visually and scientifically. Remote sensing satellites view the earth in different spectral bands, viz. near infrared (NIR), red, green, and blue bands, in a conventional multispectral imaging system. In the absence of a blue channel, colour images can be generated using near infrared, red, and green bands in what is known as a false colour composite (FCC) and does not look natural, like the image we see with the naked eye. For a trained interpreter, this does not pose any problems. However, when the intended use is a fly‐through of a draped terrain, visual interpretation, or a display, meant for the non‐remote sensing professional, this becomes a handicap. To overcome this, there is a requirement to generate natural colour composites (NCC) from the given false colour composite, which demands the simulation of a blue band to be combined with green and red bands. This paper describes a unique method of generating a blue band to form natural colour images from a given false colour image set. We use a spectral transformation method to establish a relationship between the false colour and true colour image pairs provided by a sensor with all the four bands, which has a broader spectral coverage. A transformation function is fitted by selecting radiometric control points along the line of geometric registration to find a set of coefficients to be used for simulating a blue band. This blue band, along with the green and red bands, provides a near true colour or ‘natural colour’ on the display. In this paper, we present a set of adjustable radiometric transformation coefficients to accommodate variation in spatial and dynamic range offered by sensors to generate natural colour. These coefficients seem to work on a large number of images of different seasons, provided similar spectral bands and terrain are used. The proposed ‘natural colour generator’ can be used in changing false colour images to natural colour images with the aim of ‘what you get is what you would have seen’.     

Enhanced SO2 concentrations observed over northern India: role of long-range transport

The combustion of fossil fuels (coal and petroleum products) constitutes a source of continuous release of anthropogenic SO₂ into the atmosphere. Furthermore, natural sources such as volcanoes can inject large amounts of SO₂ directly into the troposphere and sometimes even into the stratosphere. These event-based volcanic eruptions provide solitary opportunities to study the transport and transformation of atmospheric constituents. In this study, we present an episode of high SO₂ concentration over northern India as a result of long-range transport from Africa using multiple satellite observations. Monthly averaged column SO₂ values over the Indo-Gangetic Plain (IGP) were observed in the range of 0.6–0.9 Dobson units (DU) during November 2008 using observations from the Ozone Monitoring Instrument (OMI). These concentrations were conspicuously higher than the background concentrations (<0.3 DU) observed during 2005–2010 over this region. The columnar SO₂ loadings were highest on 6 November over most of the IGP region and even exceeded 6 DU, a factor of 10–20 higher than background levels in some places. These enhanced SO₂ levels were not reciprocated in satellite-derived NO₂ or CO columns, indicating transport from a non-anthropogenic SO₂ source. As most of the local aerosols over the IGP region occur below 3 km, a well-separated layer at 4–5 km was observed from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. Wind fields and back-trajectory analysis revealed a strong flow originating from the Dalaffilla volcanic eruption in Ethiopia during 4–6 November 2008. Although volcanic SO₂ plumes have been extensively studied over many parts of Asia, Europe, and the USA, analysis of such events for the IGP region is being reported for the first time in this study.     

A novel electrical-mobility-based instrument for total number concentration measurements of ultrafine particles

A novel electrical-mobility-based technique to measure total particle number concentration over a selected size range is presented. Charged particles are condensed out onto an electrode that is shaped such that the product of its transfer function and the particle charging efficiency is a constant, independent of particle size. The resulting total current is then proportional to the number concentration of the sampled particles over the collected size range. The theoretical approach for the calculation of the electrode shape function is described. The extension of this technique for measurement of higher moments of the particle size distributions over a desired size range is briefly discussed.This concept is used to design a new instrument, called the tailored electrode concentration sensor (TECS). For validation of the theoretical concept, the collection electrode in the TECS instrument is designed for concentration measurements over a size range of 30–90 nm. In the TECS, the collection section is located downstream of an electrostatic precipitator section, where the sampled flow is split into aerosol and sheath flows, similar to the design of the MEAS [Ranjan, M., & Dhaniyala, S., (2007), Theory and design of a new miniature electrical-mobility aerosol spectrometer, Journal of Aerosol Science, 38(9), 950–963]. This results in a compact, low pressure drop instrument. Experimental results confirm that the response of the optimally-shaped electrode in the TECS system is only proportional to total number concentration over the selected size range.     

Energy Efficient Broadcast in Wireless Ad hoc Networks with Hitch-hiking

In this paper, we propose a novel concept called Hitch-hiking in order to reduce the energy consumption of broadcast application for wireless networks. Hitch-hiking takes advantage of the physical layer design that facilitates the combining of partial signals to obtain the complete information. The concept of combining partial signals using maximal ratio combiner [15] has been used to improve the reliability of the communication link but has never been exploited to reduce energy consumption in broadcasting over wireless ad hoc networks. We study the advantage of Hitch-hiking for the scenario when the transmission power level of nodes is fixed as well as the scenario when the nodes can adjust their power level. For both scenarios, we show that Hitch-hiking is advantageous and have proposed algorithms to construct broadcast tree with Hitch-hiking taken into consideration. For fixed transmission power case, we propose and analyze a centralized heuristic algorithm called SPWMH (Single Power Wireless Multicast with Hitch-hiking) to construct a broadcast tree with minimum forwarding nodes. For the latter case, we propose a centralized heuristic algorithm called Wireless Multicast with Hitch-hiking (WMH) to construct an energy efficient tree using Hitch-hiking and also present a distributed version of the heuristic. We also evaluate the proposed heuristics through simulation. Simulation results show that Hitch-hiking can reduce the transmission cost of broadcast by as much as 50%. Further, we propose and evaluate a protocol called Power Saving with Broadcast Tree (PSBT) that reduces energy consumption of broadcast by eliminating redundancy in receive operation. Finally, we propose an algorithm that takes advantage of both Hitch-hiking and PSBT in conserving energy. Manish Agarwal is an engineer at Microsoft, Redmond. He received his Masters degree in Electrical and Computer Engineering from University of Massachusetts, Amherst in 2004. He received his undergraduate degree from Indian Institute of Technology, Guwahati. His research interest lies in the field of mobile ad hoc networks. Lixin Gao is an associate professor of Electrical and Computer Engineering at the University of Masschusetts, Amherst. She received her Ph.D. degree in computer science from the University of Massachusettes at Amherst in 1996. Her research interests include multimedia networking and Internet routing. Between May 1999 and January 2000, she was a visiting researcher at AT&T Research Labs and DIMACS. She is an Alfred P. Sloan Fellow and received an NSF CAREER Award in 1999. She is a member of IEEE, ACM, and Sigma Xi. Joon Ho Cho received the B.S. degree (summa cum laude) in electrical engineering from Seoul National University, Seoul, Korea, in 1995 and the M.S.E.E. and Ph.D. degrees in electrical and computer engineering from Purdue University, West Lafayette, IN, in 1997 and 2001, respectively. From 2001 to 2004, he was with the University of Massachusetts at Amherst as an Assistant Professor. Since July 2004, he has been with Pohang University of Science and Technology (POSTECH), Pohang, Korea, where he is presently an Assistant Professor in the Department of Electronic and Electrical Engineering. His research interests include wideband systems, multiuser communications, adaptive signal processing, packet radio networks, and information theory. Dr. Cho is currently an Associate Editor for the IEEE Transactions on Vehicular Technology. Jie Wu is a Professor at Department of Computer Science and Engineering, Florida Atlantic University. He has published over 300 papers in various journal and conference proceedings. His research interests are in the area of mobile computing, routing protocols, fault-tolerant computing, and interconnection networks. Dr. Wu served as a program vice chair for 2000 International Conference on Parallel Processing (ICPP) and a program vice chair for 2001 IEEE International Conference on Distributed Computing Systems (ICDCS). He is a program co-chair for the IEEE 1st International Conference on Mobile Ad-hoc and Sensor Systems (MASS'04). He was a co-guest-editor of a special issue in IEEE Computer on “Ad Hoc Networks”. He also editored several special issues in Journal of Parallel and Distributing Computing (JPDC) and IEEE Transactions on Parallel and Distributed Systems (TPDS). He is the author of the text “Distributed System Design” published by the CRC press. Currently, Dr. Wu serves as an Associate Editor in IEEE Transactions on Parallel and Distributed Systems and three other international journals. Dr. Wu is a recipient of the 1996–97 and 2001–2002 Researcher of the Year Award at Florida Atlantic University. He served as an IEEE Computer Society Distinguished Visitor. Dr. Wu is a Member of ACM and a Senior Member of IEEE.     

A slow wave structure and its application in bandpass filter design

This paper presents a new slow wave open-loop resonator filters with reduced size and improved stopband characteristics. A comprehensive treatment of different kind of coupling in this structure is demonstrated. Two and four resonator band pass filters at center frequency 2.15 and 2.30 GHz with different bandwidth are designed. The simulated results are verified with the help of two different software packages (IE3D and Sonnet Lite).     

Bench-scale evaluation of seawater desalination by reverse osmosis

In bench-scale tests of seawater reverse osmosis desalination it is important to carefully consider osmotic pressure effects and determine the extent of concentration polarization so that sources of flux variation—whether from fouling, compaction, or osmotic pressure changes—can be properly assessed. Rigorous modeling of concentration polarization is difficult because of the complex geometries and flow regimes in RO modules; typically, concentration polarization must be measured. However, concentration polarization measurement usually requires knowledge of membrane permeability, which can vary from coupon to coupon. In this study a method is presented to determine both the membrane permeability and the concentration polarization regime in a single test. The key to the test is to allow the salt concentration to vary over time in a predictable way and extract parameters from a model fitted to the flux data. The usefulness of this technique is highlighted by evaluating results from several seawater experiments. It was found that specific flux decline in the experiments was caused by changes in osmotic pressure and membrane compaction. RO fouling by seawater organic-matter was not significant for the several seawater samples tested.     

Identification of parameters for embodied energy measurement: A literature review

The building construction industry consumes a large amount of resources and energy and, owing to current global population growth trends, this situation is projected to deteriorate in the near future. Buildings consume approximately 40 percent of total global energy: during the construction phase in the form of embodied energy and during the operation phase as operating energy. Embodied energy is expended in the processes of building material production (mining and manufacture), on-site delivery, construction and assembly on-site, renovation and final demolition. Recent studies have considered the significance of embodied energy inherent in building materials, with a specific focus on this fraction of sequestered energy. Current interpretations of embodied energy are quite unclear and vary greatly, and embodied energy databases suffer from problems of variation and incomparability. Furthermore, there is no reliable template, standard or protocol regarding embodied energy computations that could address these problems in embodied energy inventories. This paper focuses on the analysis of existing literature in order to identify differing parameters so that development of a consistent and comparable database can be facilitated.