222 research outputs found
Ground or Excited State: a State-Specific Variational Quantum Eigensolver for Them All
Variational Quantum Eigensolver (VQE) provides a lucrative platform to
determine molecular energetics in near-term quantum devices. While the VQE is
traditionally tailored to determine the ground state wavefunction with the
underlying Rayleigh-Ritz principle, the access to specific symmetry-adapted
excited states remains elusive. This often requires high depth circuit or
additional ancilla qubits along with prior knowledge of the ground state
wavefunction. We propose a unified VQE framework that treats the ground and
excited states in the same footings. With the knowledge of the irreducible
representations of the spinorbitals, we construct a multi-determinantal
reference that is adapted to a given spatial symmetry where additionally, the
determinants are entangled through appropriate Clebsch-Gordan coefficients to
ensure the desired spin-multiplicity. We introduce the notion of totally
symmetric, spin-scalar unitary which maintains the purity of the reference at
each step of the optimization. The state-selectivity safeguards the method
against any variational collapse while leading to any targeted low-lying
eigenroot of arbitrary symmetry. The direct access to the excited states
shields our approach from the cumulative error that plagues excited state
calculations in a quantum computer and with few parameter count, it is expected
to be realized in near-term quantum devices.Comment: 12 pages, 5 figure
Biochar production though combined solar drying & single chamber pyrolysis
In this study, the challenging management of fibrous organic wastes (FOW) and dewatered municipal sewage sludge (MSS) in urban areas of Asia’s newly industrialised countries is presented with high energy efficiency, negative CO2 balance and biochar generation. This study investigates the feasibility and benefits of a combined treatment approach for both of the substrates, comprising solar drying (SD) and pyrolysis process (PYR). Based on material investigations, a calculation model is developed to project the material and energy flows of this process combination on the example of Chennai, India.
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Biochar from co-pyrolysis of urban organic wastes : Investigation of carbon sink potential using ATR-FTIR and TGA
Urban organic wastes (UOW) strain the infrastructures for solid waste treatment (SWT) in emerging economies. This study investigated biochar gained from three major UOW sources in India—banana peduncles (BP), a fibrous waste, from fruit markets; sewage sludge (SS) from wastewater treatment plants; and anaerobic digestate (AD) from food and market waste processing facilities—in terms of its potential to sequester and become long-term carbon sink in soils. Herein, the chemical properties (using ATR-FTIR) and thermal oxidative stability (using TGA) of biochars derived from these UOW and their three blends were examined. Biochar from SS and AD and the blends were found to possess more ash content, Cl, and alkali and alkaline earth metals (AAEM) than that from BP. The conventional recalcitrance index (R50) could not quantify and compare the stability of these mineral- and ash-rich biochars. Hence, a modified thermal oxidative recalcitrance index (TORi) is proposed. All the biochar from blends prepared at highest treatment temperature of 650 °C shows similar aromaticity. However, biochar from blend of 50% SS, 30%BP, and 20% AD exhibits the highest recalcitrance (TORi = 0.193) to become a long-term carbon sink in soil. More than aromaticity, the influence of Si, Fe, and AAEM on the biochar matrix affects its recalcitrance. Variations in the structural properties and recalcitrance of biochars from blends are attributable to the synergy among their constituents SS, AD, and BP. The determined TORi confirms the potential of biochar from the blends of UOW as a long-term carbon sink. © 2020, The Author(s)
Biochar Synthesis from Mineral- and Ash-Rich Waste Biomass, Part 1: Investigation of Thermal Decomposition Mechanism during Slow Pyrolysis
Synthesizing biochar from mineral- and ash-rich waste biomass (MWB), a by-product of human activities in urban areas, can result in renewable and versatile multi-functional materials, which can also cater to the need of solid waste management. Hybridizing biochar with minerals, silicates, and metals is widely investigated to improve parent functionalities. MWB intrinsically possesses such foreign materials. The pyrolysis of such MWB is kinetically complex and requires detailed investigation. Using TGA-FTIR, this study investigates and compares the kinetics and decomposition mechanism during pyrolysis of three types of MWB: (i) mineral-rich banana peduncle (BP), (ii) ash-rich sewage sludge (SS), and (iii) mineral and ash-rich anaerobic digestate (AD). The results show that the pyrolysis of BP, SS, and AD is exothermic, catalyzed by its mineral content, with heat of pyrolysis 5480, 4066, and 1286 kJ/kg, respectively. The pyrolysis favors char formation kinetics mainly releasing CO2 and H2O. The secondary tar reactions initiate from ≈318 °C (BP), 481 °C (SS), and 376 °C (AD). Moreover, negative apparent activation energies are intrinsic to their kinetics after 313 °C (BP), 448 °C (SS), and 339 °C (AD). The results can support in tailoring and controlling sustainable biochar synthesis from slow pyrolysis of MWB
Gauche and staggered forms of diethylamine in solvates of 1,5-dichloro-cis-9,10-diethynyl-9,10-dihydroanthracene-9,10-diol. A case of conformational pseudopolymorphism?
Diethylamine has been trapped in its less stable gauche conformation in a solvate of the title diol; the staggered conformation, which is ca. 4 kJ mol-1 more stable, is found in another solvate of the same host
A comparison of the impacts of CMEs and CIRs on the Martian dayside and nightside ionospheric species
Measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN)
spacecraft, orbiting Mars are used for investigating the impact of coronal mass
ejections (CMEs) and corotating interaction regions (CIRs) on Martian
ionospheric species. We have chosen 15 CME and 15 CIR events at Mars from the
existing catalogs. We have extensively analyzed Martian dayside and nightside
profiles of ionospheric species during each of the CME and CIR events. We have
selected the disturbed orbit plasma density profiles which are beyond the quiet
time mean profile during each event. The primary focus of this paper is to
provide a comparative average scenario of the variation of Martian ionospheric
species during CME and CIR events between 150-500 km altitudes. A significant
difference can be observed in the profiles of Martian dayside and nightside
ionospheric species (O+, O2+, CO2+, NO+, C+, N+, & OH+) during CMEs and CIRs.
The difference is more prominent on the nightside in comparison to the dayside
ionosphere. We have observed that the plasma densities were lower during CIRs
compared to CMEs. During CIRs, the nightside ion density is one order of
magnitude less (above 250 km) in comparison to CMEs. The mean peak altitude and
density of the lighter ions (O+, C+, N+, & OH+) were at lower altitudes during
the CIRs compared to CMEs. Therefore, this study suggests that the impact of
CIRs on the Martian ionospheric species is more prominent compared to CMEs
Structure-Property Correlation of Hypoeutectic Al-7.6Si Alloys with and without Al-5Ti-1B Grain Refiner
696-700Hypoeutectic Al-7.6Si alloy has been developed with and without Al-5Ti-1B grain refiner through the gravity casting method. Effects of 2, 4, and 6 wt % master alloy (Al-5Ti-1B) addition on the microstructural morphology, mechanical properties (percentage elongation (%El) and ultimate tensile strength (UTS)), hardness and fracture behaviour of the Al-7.6Si alloy have been investigated. Unmodified hypoeutectic Al-7.6Si alloy consists of needle and rod-like eutectic Si ((Si)E) particles with sharp corners inside the Alα phase. In the grain refined Al-7.6Si alloy, TiB2 is formed and these TiB2 acts as a potential site for nucleation of Alα grains. Therefore, the grain refined alloys have fine globular Alα grains and fibrous (Si)E phase. The bulk hardness, UTS and elongation (%) are increased in the grain refined alloys. Further, fractography show that the cleavage fracture is reduced in the modified alloy and fine dimple formation is increased
Structure-Property Correlation of Hypoeutectic Al-7.6Si Alloys with and without Al-5Ti-1B Grain Refiner
Hypoeutectic Al-7.6Si alloy has been developed with and without Al-5Ti-1B grain refiner through the gravity casting method. Effects of 2, 4, and 6 wt % master alloy (Al-5Ti-1B) addition on the microstructural morphology, mechanical properties (percentage elongation (%El) and ultimate tensile strength (UTS)), hardness and fracture behaviour of the Al-7.6Si alloy have been investigated. Unmodified hypoeutectic Al-7.6Si alloy consists of needle and rod-like eutectic Si ((Si)E) particles with sharp corners inside the Alα phase. In the grain refined Al-7.6Si alloy, TiB2 is formed and these TiB2 acts as a potential site for nucleation of Alα grains. Therefore, the grain refined alloys have fine globular Alα grains and fibrous (Si)E phase. The bulk hardness, UTS and elongation (%) are increased in the grain refined alloys. Further, fractography show that the cleavage fracture is reduced in the modified alloy and fine dimple formation is increased
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