814 research outputs found
The long read: 68 years of Indian foreign policy by Raj Verma
No full textAs India becomes an increasingly important player on the global stage scholars have picked over different facets of India’s foreign policy in order to understand past priorities and predict future aspirations. Raj Verma assesses two new studies published this year and their contributions to the growing literature in this area. Indian Foreign Policy: An Overview. Harsh V. Pant. Manchester University Press. 2016. Engaging the World: India’s Foreign Policy Since 1947. Sumit Ganguly. Oxford University Press. 2016
Book review: heading east: security, trade and environment between India and Southeast Asia edited by Karen Stoll Farrell and Sumit Ganguly
No full textIn Heading East, editors Karen Stoll Farrell and Sumit Ganguly explore and evaluate India’s relations and political, economic, diplomatic and security relations and engagement with Southeast Asia from 1991-2015. Raj Verma finds the book a valuable read for academics and non-academics who want to familiarise themselves with India’s engagement in the region and the influence of interest groups, non-state actors and other domestic factors on India’s relations with respect to ASEAN
Book review: deadly impasse: Indo-Pakistani relations at the dawn of a new century by Sumit Ganguly
No full textKashmir has been a thorn in the side of Indo-Pakistani relations since partition and remains a highly contentious issue today. In Deadly Impasse: Indo-Pakistani Relations at the Dawn of a New Century, political scientist Sumit Ganguly traces the conflict from its inception to the fallout from terrorist attacks in the 2000s. Raj Verma writes that the book is an essential read for students at all levels, as well as scholars, policymakers and government officials who want to familiarise themselves with India-Pakistan relations
sj-docx-1-pie-10.1177_09544089221111291 - Supplemental material for Estimation of fatigue crack growth rate in different zones of friction stir welded AA7039
No full textSupplemental material, sj-docx-1-pie-10.1177_09544089221111291 for Estimation of fatigue crack growth rate
in different zones of friction stir welded AA7039 by Chaitanya Sharma, Vijay Verma, Basanthkumar and
Sumit Kumar Sharma, Ajay Tripathi, Sanjay Kumar Singh, Pankaj Sonia in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p
Technoeconomic and mechanistic insights into the electroreduction of carbon dioxide to value added chemicals
No full textAddressing societal needs of improving the standard of living for the rising human population has placed a tremendous stress on the energy supply driving global economic growth. Historically, such increased energy demands have been satisfied by the combustion (burning) of fossil fuels such as coal, oil, and natural gas. However, the increased utilization of fossil fuels has come with a penalty: a rapid rise in the atmospheric carbon dioxide (CO2) levels, especially in the past few decades, with the daily average value crossing and staying above the 400 ppm mark in 2016 for the first time in recorded human history. These increased CO2 levels (along with other greenhouse gases) have been shown to negatively affect the earth’s surface energy balance, leading to an increase in the global mean temperature anomaly (commonly known as global warming) and deleterious climate change effects. Owing to the large scale and growing nature of excess CO2 emissions (currently 4GtC yr–1), a variety of mitigation, adaptation, and utilization approaches need to be implemented together (the stabilization wedges approach), to enable the transition of modern society towards a carbon neutral future.
This dissertation focuses on one such CO2 utilization approach i.e., the renewable electricity driven electroreduction of CO2 to value-added carbon chemicals such as carbon monoxide (CO), formic acid (HCOOH), methane (CH4), methanol (CH3OH), ethylene (C2H4), and ethanol (C2H5OH). These chemicals are currently manufactured on the industrial scale using fossil fuel based methods. The renewable electricity driven electroreduction of CO2 could be a sustainable alternative to such methods.
This dissertation employs a multiscale approach to investigate both the system level technoeconomic and molecular level mechanistic aspects of CO2 electroreduction. Chapter 2 of this dissertation introduces a comprehensive, yet easy to use, gross-margin model to evaluate the technoeconomic prospects of CO2 electroreduction. The model helps answer key questions such as: (i) what products are the best to produce? and (ii) what performance parameters are required to develop an economically viable process? The model shows the commercialization of CO and HCOOH to be viable in the near future. Interestingly, the model also shows that co-producing an economically less viable product (CH3OH, C2H5OH, C2H4) with a more viable product (CO, HCOOH) could be a strategy for offsetting the economic limitations on individual products.
Chapter 3 of this dissertation utilizes some of the technoeconomic insights gained in Chapter 2 to develop an alternative CO2 electroreduction approach i.e., the co-electrolysis of CO2 and glycerol. Thermodynamic analysis of the conventional CO2 electroreduction approach (i.e., CO2 reduction at the cathode coupled to the oxygen evolution reaction (OER) at the anode) indicates the OER (and not the CO2 reduction) to be the energetically intense step, consuming nearly 90% of the electricity input. Hence, identifying and utilizing anode reactions with lower energy requirements than the OER could result in a radical lowering (i.e., a step change) in the electricity consumption. The results in Chapter 3 show that several alternate anode reactions can be utilized. In particular, the anodic oxidation of glycerol (waste byproduct of biodiesel production) in combination with the cathodic reduction of CO2 (co-electrolysis of CO2 and glycerol) seems promising, with the resulting system requiring 37-53% less electricity than the conventional CO2 electroreduction process with the OER at the anode, thus drastically improving the techno-economic prospects of CO2 electroreduction.
Chapters 4 and 5 of this dissertation focuses on analyzing the effect of electrolytes and developing better electrocatalytic systems for the electroreduction of CO2 to CO. In Chapter 4, the effect of electrolyte concentration and the role of anions on the electroreduction of CO2 on a silver coated gas diffusion layer (GDL) electrode is studied using aqueous solutions of KOH, KCl, and KHCO3. Multiple fold improvement in the activity for CO was obtained on increasing the electrolyte concentration from 0.5 to 3.0 M with a maximum current density of 440 mA cm–2 (one of the highest values reported to date) being obtained at an energy efficiency of 42% when using 3.0 M KOH as the electrolyte. The electrolyte anions were found to play an important role in the process as well, with the onset potential of CO changing in the order OH– (–0.13 V vs. RHE) < HCO3– (–0.46 V vs. RHE) < Cl– (–0.60 V vs. RHE). In Chapter 5, sub 5-nm gold nanoparticles supported on polybenzimidazole wrapped carbon nanotubes are reported as catalysts for the electroreduction of CO2 in a GDL electrode based alkaline flow electrolyzer. An onset cell potential of just –1.50 V and an onset cathode potential of just –0.02 V vs. RHE was observed for CO production. Additionally, activity levels as high as 99 and 158 mA cm–2 were obtained at cell overpotentials of just –0.7 and –0.94 V, respectively, corresponding to energetic efficiencies of 63.8 and 49.3%. These results represent the lowest onset cell and cathode potential as well as the highest activity for CO production at high energetic efficiency reported in the literature. This electrochemical system was further used to interrogate the mechanism of CO2 electroreduction under alkaline conditions. Combinations of the onset cathode potential data, Tafel slopes, and kinetic isotope effect demonstrated the rate determining step for CO production to be the pH independent single electron transfer step instead of the commonly assumed concerted proton electron transfer step, resulting in an intrinsic lowering of the overpotentials at high pH.
Overall, the studies reported in this dissertation provide both system and molecular level insights into the design of electrochemical processes, electrolytes, and catalysts for the electroreduction of CO2 at high levels of activity while minimizing the energy requirements. Such insights will help guide the design of even better CO2 electroreduction systems in the future.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2020-05-01The student, Sumit Verma, accepted the attached license on 2018-03-12 at 08:18.The student, Sumit Verma, submitted this Dissertation for approval on 2018-03-12 at 08:33.This Dissertation was approved for publication on 2018-03-14 at 09:31.DSpace SAF Submission Ingestion Package generated from Vireo submission #12060 on 2018-08-31 at 17:17:15Made available in DSpace on 2018-09-04T20:33:51Z (GMT). No. of bitstreams: 12
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Previous issue date: 2018-03-14Embargo set by: Seth Robbins for item 107204
Lift date: 2020-09-04T20:34:13Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 107204
Lift date: 2020-09-04T20:37:00Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 107204
Lift date: 2020-09-04T20:42:08Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 107204 on 2020-09-05T09:15:26Z
Performance analysis of the WiNC2R platform:
No full textA Cognitive Radio (CR) is an intelligent transceiver device, able to support multiple technologies, dynamic re-configurability, ease of programming and collaboration with other CR devices to improve the communication efficiency. The two key requirements for an efficient CR implementation are flexibility in operation/programming and speed.
WiNC2R (Winlab Network Centric Cognitive Radio) achieves high speed of operation using its hardware platform and flexibility using its software-configurable architecture. The current WiNC2R architecture implements an 802.11a-like OFDM flow. We evaluate the WiNC2R hardware architecture to see the modularity in the architecture, separation of data and control flow and the performance in terms of latency and throughput. To test the system, the Xilinx Bus Functional Model environment, which is designed to test the IBM standard bus-architecture-based hardware systems, is used. We use a simple ALOHA protocol in the MAC layer to communicate between two WiNC2R nodes and evaluate the performance under the best-case scenario, where the performance is only hindered by the architecture itself rather than external conditions like channel state.
The results of our basic experiments showed that for a single OFDM 802.11a-like flow, the Unit Control Modules (UCM) were idle for almost 80% of the total processing time.
We then tested the WiNC2R system to study the effects of changing the frame size. It was seen that the latencies in the WiNC2R transmitter are frame-size dependent while those in the receiver mainly depend on the size of the data in the last chunk rather than the size of the whole frame. We suggest that chunk size should be 2 OFDM symbols, and chunking be moved to MAC layer for better performance. We give analytical estimates of resulting performance improvement. In the next experiment, we describe virtualization in the WiNC2R by adding more flows. We describe the steps to implement the additional flows and estimate maximum number of concurrent flows possible.
In the last analysis, we show the effect of operating clock frequency on the performance. We prove that at 250 MHz operating frequency and 2 OFDM symbols per chunk, the current WiNC2R implementation will be able to satisfy the SIFS criterion.M.S.Includes bibliographical references (p. 72-73)by Sumit Satarka
Revealing channelized features through multi-scale workflows in a mixed carbonate siliciclastic setting, Grayburg and San Andres formations, Midland Basin, TX
No full textChannelized systems in mixed carbonate-siliciclastic settings are challenging to characterize from the geological standpoint as facies variability is expected to be high (e.g., siliciclastic porous channel fills, carbonate cemented channel fills or even carbonate channel fills). Determining the lithological composition is crucial for not only understanding the basin evolution but also is required for drilling plans either if the channels serve as reservoirs or drilling hazards.
An example of one such compositionally mixed channel system is identified in the San Andres and Grayburg formations in the Midland Basin, TX. For this specific example, channels are presumably siliciclastic infilled while the shelf the channels cut across is dominantly carbonate. An integrated study of core, well-log, and seismic data is conducted to analyze the facies variability of the channelized interval and understand its geomorphological evolution. Seismic attributes such as coherent energy, sweetness and spectral components (CWT) prove to be the most efficient at enhancing the contrast between the clastic vs carbonate elements; demonstrating that it is feasible to depict the lithological heterogeneity between the channel infills and the shelf at a seismic scale. Additionally, conventional seismic interpretation and geometric attributes (e.g., apparent dip, dip azimuth and magnitude, etc.) suggests two categories of channel incisions: type I, characterized by V-shaped bases, straight and mostly oriented in a NE-SW direction; and a type II, that tend to be U-shaped, slightly sinuous, and oriented in a NW-SE trend. Well-log based litho-density techniques such as ρmaa-Umaa and core descriptions support the seismic observations by illustrating the vertical and horizontal heterogeneity and how the channel infills are dominantly siliciclastic in nature. A 3D lithology model constrained to the previous analyses illustrates a dominance of siliciclastics in the Lower San Andres while the Upper San Andres and Grayburg are limestone-rich with episodic siliciclastic events (i.e., related to the channel incisions) and dolostone (in the Upper Grayburg). Lithologies and morphological changes are directly related to changes in the sea level and source rock composition. This study is pioneering in its understanding of the siliciclastic deposition in the middle Guadalupian units in this portion of the Midland Basin, which are referred in literature as the Midland sands and identified as analogs of the Brushy and Cherry Canyon formations in the Delaware Basin
Enhanced Photocatalytic Activity in Strain Engineered Janus WSSe Monolayers
No full textThe relevant fundamental properties of Janus WSSe monolayers to photocatalytic water-splitting performance are presented here and investigated using density functional theory. The Janus WSSe monolayer with a direct band gap of 1.75 eV is subjected to biaxial strain, and related optoelectronic properties are investigated. The effect of strain is reflected in band gap change from direct to indirect. Hydrogen evolution reaction (HER) is active all over, whereas oxygen evolution reaction (OER) is active only at 4% and 6% compressive strains. The red- and blue-shifts under tensile and compressive strains, respectively, substantiate possible control over exciton-phonon interaction making it suitable for the water-splitting application. Graphic Abstract: Upon being irradiated by sunlight with sufficient energy, the biaxially strained Janus WSSe monolayer complying with HER/OER requirement produces hydrogen gas along with oxygen as a secondary product.[Figure not available: see fulltext.].Author Ambesh Dixit acknowledges the funding agency Science & Engineering Research Board (SERB), Department of Science and Technology, Government of India, through project # CRG/2020/004023 for carrying out this work. Hemant Verma acknowledges HPC facilities at IIT Jodhpur and Mr. Ram Milan Sahani, Mr. Sumit Kukreti, Ms. Surbhi Ramawat, Ms. Priyambada Sahoo, Mr. Ram Niwas Kumhar, and Mr. Harsh Jain for their fruitful discussion during the work
GEOPHYSICAL CHARACTERIZATION OF RESOURCE PLAYS
No full textThe shale exploration and production in the United States have changed the dynamics of the oil and gas business in the world. The production heterogeneity associated with shale resource plays demands recording different kinds of data during the lifecycle of a shale reservoir. Surface seismic, microseismic, well logs, vertical seismic profile (VSP), and core data are some of the most common data acquired for subsurface characterization. Due to the large number of wells drilled in some of the most prolific basins such as Anadarko and Permian Basins, geoscientist resort to well correlations and statistical analysis to plan optimum well locations and the surface seismic data is considered unsought. Well planning with well log correlation entails high uncertainty due to high inherent rock heterogeneity. In this dissertation, I show how incorporating the surface seismic data with log/core data can decrease the uncertainty of mapping producible rock types, and aid in avoiding perilous drilling location such as those that can cause induced earthquakes.
In this dissertation, I show a methodology that combines core and seismic data to delineate petrophysically defined rock types away from the cored well. In the case study presented in the dissertation, the rock types were delineated over an area of 477 square miles from measurements conducted on one cored well. The rock types were defined using porosity and permeability values and estimated away from the well by combining elastic measurements from seismic and core samples. The seismic elastic properties P-impedance (ZP), S-impedance (ZS), and density (ρ) were estimated by simultaneous prestack inversion. One of the limitations of estimating elastic parameters from prestack data is ZS, and ρ experiencing a decrease in resolution compared to ZP due stretching of the non-zero offset data caused by NMO corrections. Hence, we propose a method to compensate for the NMO stretch that balances the spectrum across the reflector, increasing the resolution of ZS and ρ after prestack inversion.
In the final chapter of the dissertation, I propose methodologies to image seismogenic faults. The strike-slip faulting is the dominant deformation style in Anadarko Basin, and the faults get unrecognized due to their low offset in the sedimentary formation while planning water injection or hydrocarbon production well. These faults might act seismogenic to injection or production activities based on their orientation and regional stress conditions. I propose a new method called band-limited multispectral coherence to image the strike-slip faults in basins with similar deformation style as Anadarko Basin and with a record of active induced seismicity. In Anadarko Basin, the strong visual correlation between recorded earthquakes and the faults delineated by the proposed methodology signals the seismogenic nature of the faults. The faults with no associated induced seismicity, geomechanical modeling is proposed to investigate their reactivation potential
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