| 1. |
- Boretzky, K., et al.
(author)
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NeuLAND: The high-resolution neutron time-of-flight spectrometer for R 3 B at FAIR
- 2021
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In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 1014
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Journal article (peer-reviewed)abstract
- NeuLAND (New Large-Area Neutron Detector) is the next-generation neutron detector for the R3B (Reactions with Relativistic Radioactive Beams) experiment at FAIR (Facility for Antiproton and Ion Research). NeuLAND detects neutrons with energies from 100 to 1000 MeV, featuring a high detection efficiency, a high spatial and time resolution, and a large multi-neutron reconstruction efficiency. This is achieved by a highly granular design of organic scintillators: 3000 individual submodules with a size of 5 × 5 × 250 cm3 are arranged in 30 double planes with 100 submodules each, providing an active area of 250 × 250 cm2 and a total depth of 3 m. The spatial resolution due to the granularity together with a time resolution of σt≤ 150 ps ensures high-resolution capabilities. In conjunction with calorimetric properties, a multi-neutron reconstruction efficiency of 50% to 70% for four-neutron events will be achieved, depending on both the emission scenario and the boundary conditions allowed for the reconstruction method. We present in this paper the final design of the detector as well as results from test measurements and simulations on which this design is based.
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| 2. |
- Bhowmick, S., et al.
(author)
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Arsenic mobilization in the aquifers of three physiographic settings of West Bengal, India : Understanding geogenic and anthropogenic influences
- 2013
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In: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 262, s. 915-923
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Journal article (peer-reviewed)abstract
- A comparative hydrogeochemical study was carried out in West Bengal, India covering three physiographic regions, Debagram and Chakdaha located in the Bhagirathi-Hooghly alluvial plain and Baruipur in the delta front, to demonstrate the control of geogenic and anthropogenic influences on groundwater arsenic (As) mobilization. Groundwater samples (n=90) from tube wells were analyzed for different physico-chemical parameters. The low redox potential (Eh=-185 to -86mV) and dominant As(III) and Fe(II) concentrations are indicative of anoxic nature of the aquifer. The shallow (<100m) and deeper (>100m) aquifers of Bhagirathi-Hooghly alluvial plains as well as shallow aquifers of delta front are characterized by Ca2+HCO3 - type water, whereas Na+ and Cl- enrichment is found in the deeper aquifer of delta front. The equilibrium of groundwater with respect to carbonate minerals and their precipitation/dissolution seems to be controlling the overall groundwater chemistry. The low SO4 2- and high DOC, PO4 3- and HCO3 - concentrations in groundwater signify ongoing microbial mediated redox processes favoring As mobilization in the aquifer. The As release is influenced by both geogenic (i.e. geomorphology) and anthropogenic (i.e. unsewered sanitation) processes. Multiple geochemical processes, e.g., Fe-oxyhydroxides reduction and carbonate dissolution, are responsible for high As occurrence in groundwaters.
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| 3. |
- Chakraborty, S., et al.
(author)
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Symbolic trajectory evaluation for word-level verification: theory and implementation
- 2017
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In: Formal Methods in System Design. - : Springer Science and Business Media LLC. - 1572-8102 .- 0925-9856. ; 50:2-3, s. 317-352
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Journal article (peer-reviewed)abstract
- Symbolic trajectory evaluation (STE) is a model checking technique that has been successfully used to verify many industrial designs. Existing implementations of STE reason at the level of bits, allowing signals in a circuit to take values from a lattice comprised of three elements: 0, 1, and X. This limits the amount of abstraction that can be achieved, and presents limitations to scaling STE to even larger designs. The main contribution of this paper is to show how much more abstract lattices can be derived automatically from register-transfer level descriptions, and how a model checker for the general theory of STE instantiated with such abstract lattices can be implemented in practice. We discuss several implementation issues, including how word-level circuits can be symbolically simulated using a new encoding for words that allows representing X values of sub-words succinctly. This gives us the first practical word-level STE engine, called STEWord. Experiments on a set of designs similar to those used in industry show that STEWord scales better than bit-level STE, as well as word-level bounded model checking.
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| 4. |
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| 5. |
- Dwibedi, Debasmita, et al.
(author)
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Ionothermal Synthesis of High-Voltage Alluaudite Na2+2xFe2-x(SO4)(3) Sodium Insertion Compound : Structural, Electronic, and Magnetic Insights
- 2016
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 8:11, s. 6982-6991
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Journal article (peer-reviewed)abstract
- Exploring future cathode materials for sodium-ion batteries, alluaudite class of Na2Fe2II(SO4)(3) has been recently unveiled as a 3.8 V positive insertion candidate (Barpanda et al. Nat. Commun. 2014, 5, 4358). It forms an Fe-based polyanionic compound delivering the highest Fe-redox potential along with excellent rate kinetics and reversibility. However, like all known SO4-based insertion materials, its synthesis is cumbersome that warrants careful processing avoiding any aqueous exposure. Here, an alternate low temperature ionothermal synthesis has been described to produce the alluaudite Na2+2xFe2-xII(SO4)(3). It marks the first demonstration of solvothermal synthesis of alluaudite Na2+2xM2-xII(SO4)(3) (M = 3d metals) family of cathodes. Unlike classical solid-state route, this solvothermal route favors sustainable synthesis of homogeneous nanostructured alluaudite products at only 300 degrees C, the lowest temperature value until date. The current work reports the synthetic aspects of pristine and modified ionothermal synthesis of Na2+2xFe2-xII(SO4)(3) having tunable size (300 nm similar to 5 mu m) and morphology. It shows antiferromagnetic ordering below 12 K. A reversible capacity in excess of 80 mAh/g was obtained with good rate kinetics and cycling stability over 50 cycles. Using a synergistic approach combining experimental and ab initio DFT analysis, the structural, magnetic, electronic, and electrochemical properties and the structural limitation to extract full capacity have been described.
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| 6. |
- Saraf, D., et al.
(author)
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In pursuit of bifunctional catalytic activity in PdS2 pseudo-monolayer through reaction coordinate mapping
- 2018
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In: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 49, s. 283-289
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Journal article (peer-reviewed)abstract
- We have investigated the photocatalytic efficiency and corresponding hydrogen and oxygen evolution reactions (HER and OER) through different functionalization of stable 1T palladium disulfide (PdS2) monolayer. The electronic structure calculations based on Density Functional Theory (DFT) formalism, have been performed along with the corresponding optical properties of functionalized and S-mono-vacancy defected 1T PdS2 monolayer. The optimum band gap required for water splitting makes this two-dimensional material an exciting promise for photocatalysis process. In this work, we have not only envisaged the photocatalytic activity, but also the specific reaction coordinates for HER and OER based on the adsorption energies of the intermediates of the individual reaction. Functionalization of 1T PdS2 monolayer is done by replacing the anion (S) site with P, N and C functionalized atoms and also by creating a mono-vacancy defect at the same site. We have also determined (i) the stability of the functionalized 1T PdS2 monolayer based on the phonon dispersion calculations and (ii) the respective work function of the individual systems. The steady optical response in the visible range is in favour of the photocatalytic activity of the monolayer, while the corresponding reaction coordinates predict the suitability of the functionalized and defected monolayer for HER and OER mechanism. The mono-vacancy defected and N-functionalized PdS2 monolayer have emerged as the most promising systems for OER and HER activities respectively. Overall, we have predicted that the bifunctional catalytic activity can be achieved through functionalization and vacancy defect in PdS2 monolayer.
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| 7. |
- Watcharatharapong, Teeraphat, et al.
(author)
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Effect of Transition Metal Cations on Stability Enhancement for Molybdate-Based Hybrid Supercapacitor
- 2017
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In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 9:21, s. 17977-17991
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Journal article (peer-reviewed)abstract
- The race for better electrochemical energy storage systems has prompted examination of the stability in the molybdate framework (MMoO4; M = Mn, Co, or Ni), based on a range of transition metal cations from both computational and experimental approaches. Molybdate materials synthesized:with controlled nano scale morphologies (such as nanorods, agglomerated nanostructures, and nanoneedles for Mn, Co, and Ni elements, respectively) have been used as a cathode in hybrid energy storage systems. The computational and experimental data confirms that the MnMoO4 crystallized in beta-form with alpha-MnMoO4 type whereas Co and Ni cations crystallized in alpha-form with alpha-CoMoO4 type structure. Among the various transition metal Cations studied, hybrid device comprising NiMoO4 vs activated carbon exhibited excellent electrochemical performance having the specific capacitance 82 F g(-1) at a current density of 0.1 A g(-1) but the cycling Stability, needed to be significantly improved. The specific capacitance of the NiMoO4 electrode material is shown to be directly related to the surface area of the electrode/electrolyte interface, but the CoMoO4 and MnMoO4 favored a bulk formation that could be suitable for structural stability. The useful insights from the electronic structure analysis and effective mass have been provided to: demonstrate the role of cations in the molybdate structure and its influence in electrochemical energy storage. With improved cycling stability, NiMoO4 can be suitable for renewable energy storage. Overall, this study will enable the development of next generation molybdate materials with multiple cation substitution resulting,in better cycling stability and higher specific capacitance.
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| 8. |
- Chakraborty, M., et al.
(author)
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QoS support in TLMM : Three level mobility model for IP-based networks
- 2004
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In: DISTRIBUTED COMPUTING. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 3540240764 ; , s. 192-197
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Conference paper (peer-reviewed)abstract
- TLMM, a three level mobility model for IP-based mobility management has been recently proposed as an architecture for managing global mobility in an IP-based network. This paper evaluates the performance of TLMM's Quality of Service (QoS) framework using a combination of DiffServ and Int-Serv architectures with the concept of Bandwidth Broker for admission control and resource reservation for different service classes. The most important contribution in this paper is a dynamic handoff policy using the concept of Boundary Location Area, for performing location updates for inter-domain roaming of mobile nodes, which helps in maintaining proper QoS. The performance evaluation of the proposed protocol is provided by simulation results using Network Simulator (ns-2).
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| 9. |
- Saha, D., et al.
(author)
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Mobility support in IP : A survey of related protocols
- 2004
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In: IEEE Network. - 0890-8044 .- 1558-156X. ; 18:6, s. 34-40
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Journal article (peer-reviewed)abstract
- This article presents an overview of a set of IP-based mobility protocols - Mobile IP, HAWAII, Cellular IP, Hierarchical MIP, TeleMIP, Dynamic Mobility Agent, and Terminal Independent MIP - that will play an important role in the forthcoming convergence of IP and legacy wireless networks. A comparative analysis with respect to system parameters such as location update, handoff latency and signaling overhead exposes their ability in managing micro/macro/global-level mobility. We use this observation to relate their features against a number of key design issues identified for seamless IP-based mobility as envisioned for future 4G networks.
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| 10. |
- Thanos, George A., et al.
(author)
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Evaluating demand response programs by means of key performance indicators
- 2013
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In: 5th International Conference on Communication Systems and Networks, COMSNETS 2013. - Piscataway, NJ : IEEE Communications Society. - 9781467354943
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Conference paper (peer-reviewed)abstract
- Demand response (DR) has received significant attention in recent years and several DR programs are being deployed and evaluated worldwide. DR systems provide a wide range of economic and operational benefits to different stakeholders of the electrical power system including consumers, generators and distributors. DR can be achieved through a number of different mechanisms such as direct-load-control, incentives, pricing signals, or a combination of these schemes. Due to the remarkable variation in demand response systems, it becomes a challenge to evaluate and compare the effectiveness of different DR programs holistically. In this work, we define a number of different performance metrics that could be used to evaluate DR programs based on peak reduction, demand variation and reshaping, and economic benefits
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