Terahertz-frequency optical pulses can resonantly drive selected vibrational modes in solids and deform their crystal structures. In complex oxides, this method has been used to melt electronic ...order, drive insulator-to-metal transitions and induce superconductivity. Strikingly, coherent interlayer transport strongly reminiscent of superconductivity can be transiently induced up to room temperature (300 kelvin) in YBa2Cu3O6+x (refs 9, 10). Here we report the crystal structure of this exotic non-equilibrium state, determined by femtosecond X-ray diffraction and ab initio density functional theory calculations. We find that nonlinear lattice excitation in normal-state YBa2Cu3O6+x at above the transition temperature of 52 kelvin causes a simultaneous increase and decrease in the Cu-O2 intra-bilayer and, respectively, inter-bilayer distances, accompanied by anisotropic changes in the in-plane O-Cu-O bond buckling. Density functional theory calculations indicate that these motions cause drastic changes in the electronic structure. Among these, the enhancement in the character of the in-plane electronic structure is likely to favour superconductivity.
Abstract
Electricity backup systems are needed to address the temporary grid failure, short-term electricity supply at the locations without grids, power surges, and massive blackouts. These power ...backup technologies include a combination of batteries and generators operating mostly on fossil fuels. Concerns regarding instant start capability with generators, noise, and mainly due to carbon emissions have encouraged to look for alternatives with low carbon technologies based on renewable energy sources. Stored electricity from solar, wind and other renewable sources are emerging and cost-competitive alternatives to fossil fuels-based power backup systems. Due to the high energy density, unlimited production source, and easy storage and transportation, hydrogen is emerging as an effective and efficient energy carrier and its applications for an alternative to power supply systems. Hydrogen produced from the electrolysis of water by renewable electricity makes it green and has minimum carbon emissions among the other alternatives and operates in real-time startups with no mechanical noise.
Fuel cell is a growing technology and has the potential to channelize hydrogen energy as an alternative to carbon-intensive power supply systems. In a fuel cell, hydrogen combines with oxygen and produces electricity. The fuel cell is a robust design with several parameters that control its operation and capacity. This paper identifies the parameter-based modeling approach to establish a connection of power demand with hydrogen production. A mathematical model for system sizing of hydrogen production and fuel cell for re-electrification for a reference case is developed.
TEMPORAL SHIFT OF BAGMATI RIVER OVER 25 YEARS USING LANDSAT Subedi, A.; Poudel, P.; Acharya, T. D.
International archives of the photogrammetry, remote sensing and spatial information sciences.,
12/2019, Letnik:
XLII-5/W3
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Bagmati River has been a terrific boon in different aspects like natural, cultural, ecological, etc. However, the river has been in a critical situation with the shift in its quality and quantity ...during these years. Since the changes are slow-growing, actual shifts are barely noticed. While the in-situ analysis and experimentation become costly, the analysis of Landsat images acquired with the application of Remote Sensing (RS) and Geographic Information System (GIS) provides an inexpensive technique in estimating and mapping such temporal shift in the river. Concerning the case, this study modelled the temporal changes of the Bagmati River within 25 years (1991–2016) using the multi-temporal Landsat images. We adopted the Normalized Difference Water Index (NDWI for the unsupervised extraction of the water feature and monitoring the changes. A model was developed in Arc-GIS by discerning the river, and the difference was determined for 25 years. The result indicated a major temporal shift in the river channel with a decreasing trend from 1991 to 2016. Over 25 years, the river loss almost one-third of its original water-flow channel with a severe sweep in the south-western portion of the study area. With this precise information, a field-based study can be undertaken either to analyse the damage caused by the river in those particular portions or to assess the factors affecting the river shift. Hence, we strongly recommend employing the cost-effective methods, RS and GIS, for detecting, analysing and monitoring the shifts and changes in the rivers and lakes over a while.
Abstract
In the present day in the global context, approximately 2 billion internal combustion engines (ICEs) are estimated to be in use. Nearly 7.3 billion metric tons of carbon dioxide (CO2) were ...released into the atmosphere as per the survey on the transportation sector in 2020, making up 41% of all emissions. To solve pollution challenges related to ICEs, recent advancements of alternatives to ICEs have pushed the globe to establish clean energy sources such as hydrogen fuel cells. The conversion of an ICE vehicle to a fuel cell vehicle is able to add further support to its development besides the 30% emission reduction since the old ICE vehicle would not be discarded. FCEVs are seen as a true replacement between BEVs and ICEs since more energy can be stored in less space as compared to BEVs. The objective of this paper is to analyse the energy consumption of a fuel cell-driven motor in the internal combustion engine vehicle chassis of Maruti 800, through mathematical modelling, then compare the specifications with that of an ICE-driven system. The analysis provides details on the optimization of drive system components to maximise the fuel cell energy consumption efficiency based on fuel cell power source requirements for a range of velocities and road gradients. The modifiable specifications of drive system components in the mathematical model ensure reproducibility for any drive cycles and system scenarios.
We report polarization-resolved Raman scattering measurements on single crystals of the pyrochlore compound Eu2Ir2O7 which exhibits a ground state with noncollinear magnetic order, as well as its ...paramagnetic counterpart Pr2Ir2O7. The spectra reveal the six Raman-active optical phonons expected for the pyrochlore lattice symmetry. Combined with density functional calculations, polarization analysis of the Raman intensity allows us to assign all observed peaks to specific vibration patterns. Whereas most phonon profiles are weakly temperature dependent, an Ir-O-Ir bond-bending vibration in Eu2Ir2O7 exhibits a pronounced Fano asymmetry in the paramagnetic state, and marked softening and line-shape anomalies at the magnetic phase transition. These observations indicate strong electron-phonon interactions, which must be considered in models of the electronic properties and phase behavior of the pyrochlore iridates. In addition, a prominent feature appears at 210 cm−1 in the Raman spectrum of Eu2Ir2O7 below the magnetic transition temperature, possibly due to a magnetic excitation.
Background There have been growing interests in the association between vitamin D and depression in recent years. Objective The objective of this study was to find the prevalence of low vitamin D ...level in the patients suffering from depressive episodes. The next objective was to determine whether there are any statistically significant differences between the mean vitamin D levels of different sociodemographic variables and also to find the sociodemographic variables predicting the vitamin D level. Method The patients diagnosed as depressive episodes were selected from the out-patient unit of Department of Psychiatry of Manipal Teaching Hospital, Pokhara. The proforma was used to collect the sociodemographic profile of the patient. The diagnosis of depressive episode was made according to the International Classification of Disease-10 Classification of Mental and Behavioural Disorders: Diagnostic Criteria for Research. The serum vitamin D level of less than 30 ng/ml was considered as low level in this study. Result The prevalence of low vitamin level was found in 81.8%. The mean difference of vitamin D level was statistically significant in gender and marital status of the patients. The low mean vitamin level was found in the socio-demographic variables like in age above 60 years, Newar caste, female gender, separated from the spouse patients and in the patients living in the urban area as compared to other group of patients. The gender of the patients predicted vitamin D level in the depressed patients. Conclusion There is high prevalence of low vitamin D level in the depressed patients. The correction of low vitamin D level would be helpful in the holistic management of patient with depressive episodes.
We have performed low-temperature specific heat and thermal conductivity measurements of the Ni-based superconductor BaNi2As2 (T{c}=0.7 K) in a magnetic field. In a zero field, thermal conductivity ...shows T-linear behavior in the normal state and exhibits a BCS-like exponential decrease below T{c}. The field dependence of the residual thermal conductivity extrapolated to zero temperature is indicative of a fully gapped superconductor. This conclusion is supported by the analysis of the specific heat data, which are well fit by the BCS temperature dependence from T{c} down to the lowest temperature of 0.1 K.
Positioning for subarachnoid block (SAB) in patients with femoral fracture is painful and may remain suboptimal requiring use of large doses of opioids. These patients generally being elderly with ...multiple comorbidities and frailty are likely to have many undesirable effects of opioids including respiratory depression and confusion.
The objective was to compare the feasibility and effectiveness of fascia iliaca compartment block (FICB) and femoral nerve block (FNB) in reducing pain associated with positioning for subarachnoid block in patients undergoing proximal femoral fracture fixation procedures.
Group FICB patients (n=15) received fascia iliaca block with 30 ml of 1.5% lignocaine with adrenaline and group FNB patients (n=15) received femoral nerve block with 15 ml of 1.5% lignocaine with adrenaline. After the study blocks, patients were kept on supine position for at least 20 minutes before shifting them to the operation theatre. Pain was assessed by using visual analog scale values before the block and during the position for subarachnoid block. Time to perform subarachnoid block, quality of positioning and acceptance was recorded.
Visual analog scale values during positioning for SAB were lower in FIB group than in FNB (1.0±1.1 versus 2.1±0.8; P< 0.05). Time to perform SAB was shorter in FIB than in FNB (109.6±28.2 seconds versus 134.8±31.9 seconds; P< 0.05). Quality of patient positioning for SAB was comparable between the groups. Patient acceptance was less in group FNB (P< 0.05).
Fascia iliaca compartment block provides better analgesia than femoral nerve block in terms of facilitating optimal positioning for subarachnoid block in patients undergoing proximal femoral fracture fixation procedure.
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