Intermolecular interactions in the structure of new molecular semiconductor [Pd(dddt)2]2CF3SO3

An X-ray structural investigation of a new molecular semiconductor, [Pd(dddt)₂]₂CF₃SO₃ (1), where dddt²⁻ is 5,6-dihydro-1,4-dithiin-2,3-dithiolate, is made. Crystal data of 1:a = 6.521(7) Å, b = 8.354(4) Å, c = 16.113(6) Å, α = 87.12(4)°, β = 85.51(6)°, γ = 67.94(7)°, V = 811(1) ų, triclinic, space group P. Crystal structure 1 is characterized by layers of [Pd(dddt)₂]^1/2+ radical cations, with [CF₃SO₃]⁻ anions located between them. In these layers, [Pd(dddt)²]^1/2+ cations form dimers with strongly shortened intermolecular contacts Pd…Pd 3.031 (2) Å. The [CF₃SO₃]⁻ anion in the structure of 1 is disordered.     

Theoretical analysis of a CO2–NH3 cascade refrigeration system for cooling applications at low temperatures

As a result of environmental problems related to global warming and depletion of the ozone layer caused by the use of synthetic refrigerants (CFC’s, HCFC’s and HFC’s) experienced over the last decades, the return to the use of natural substances for refrigeration purposes, appears to be the best long-term alternative. In this paper, a cascade refrigeration system with CO₂ and NH₃ as working fluids in the low and high temperature stages, respectively, has been analysed. Results of COP and exergetic efficiency versus operating and design parameters have been obtained. In addition, an optimization study based on the optimum CO₂ condensing temperature has been done. Results show that following both method’s exergy analysis and energy optimization, an optimum value of condensing CO₂ temperature is obtained. The compressor isentropic efficiency influence on the optimum system COP has been demonstrated. A methodology to obtain relevant diagrams and correlations to serve as a guideline for design and optimization of this type of systems has been developed and it is presented in the paper.     

Investigation on Effect of Radial and Extended Fins in PCM Heat Sink for LED Cooling

This work focuses on the efficiency of the LED acting as the heat sink containing Phase Change Material (PCM). Three different heat sink configurations (H-1, H-2, and H-3) are used in this study. Input power and the number of fins are altered to find their effect on junction temperatures, luminous flux, and thermal resistance. The junction temperature of heat sink H-3 with PCM decreased by 3.1 % when compared with heat sink devoid of PCM at 10 W. The thermal resistance of the heat sink H-3 is reduced by 18.2 % when compared to its counterpart devoid of PCM at 10 W. The luminous flux of the PCM filled heat sink H-3 is found to increase by 12.15 % against the PCM not filled heat sink H-1 at 10 W. The H-3 heat sink with PCM showed superior performance because of the enhanced natural convection and conduction in bulk PCM with fins, and with added high latent heat capacity of PCM.     

Adaptive battery aware power management of a computer with self power-managed components

Dynamic power management strategies are generally used to achieve efficient power consumption of battery operated computer systems. Such computer systems usually integrate a number of built-in power-management policies. These policies are generally integrated into device drivers and cannot be changed. This paper addresses the problem of adaptive dynamic power management of a battery operated computer with self-power managed components. The power management task is split into Component Power Manager (CPM) and Global Power Manager (GPM). The CPM is the local-level policy that is pre-defined and can't change. The GPM cannot overwrite the CPM policy. A Service Flow Controller (SFC) is incorporated to control the service request generation for a specific component. The GPM uses model free reinforcement learning to adequately guide SFC actions. Moreover, the GPM implements Reinforcement learning based battery power management aiming at optimizing the battery's State of Charge (SoC) and improving its lifetime. This is performed by letting the GPM adapt the system quality of services to the actual battery SoC. Experiments on measured data traces confirmed the effectiveness of the proposed approach. Up to 57.2% of maximum SoC savings are obtained while good performance levels are maintained. Compared to prior reference studies, the proposed approach is model free, event driven, adapts to non-stationary workloads, considers multiple types of user applications, models the battery nonlinear characteristics, can handle SoC degradation and performance at the same time, and is capable to achieve deep and wide SoC degradation/performance tradeoff curves.     

Titanium dichalcogenide-decorated reduced graphene oxide nanocomposite for high-performance photovoltaic cell fabrication

Journal of Materials Science: Materials in Electronics - This study describes the flexible DSSC devices based on efficient TiS2/Reduced Graphene Oxide (TiS2/RGO) hybrid photoanodes that have been...     

Biohydrogen production from seagrass via novel energetically efficient ozone coupled rotor stator homogenization

Biohydrogen production from seagrass (SG) has gained much attention due to their chemical composition (carbohydrate rich biomass). In this study, an attempt was made to enhance the biohydrogen production from sea grass through novel ozone coupled rotor-stator homogenization (ORSH). The efficiency of the homogenization pretreatment was evaluated in terms of seagrass lysis and biohydrogen generation. Initially, sea grass was subjected to rotor-stator homogenization (RSH) to optimize its power input (5.4–19.1 W) and energy spent (0–1285 kJ/kg TS). RSH consumes specific energy of 510 kJ/kg TS to achieve seagrass lysis of 10.45%, whereas ORSH achieved 23.7% of seagrass lysis at less energy (212.4 kJ/kg TS) input. The outcome of the present study reveals ORSH reduced 58.3% of energy input and increased 55.9% of SG lysis when compared with RSH. Hence, a considerable amount of energy could be saved through this combinative pretreatment. Biohydrogenesis was done to evaluate and compare the biohydrogen production potential of ORSH sample. Higher ultimate biohydrogen production was achieved by ORSH (90.7 mL/g COD) than RSH (39.6 mL/g COD). A higher energy ratio of 1.17 could be achieved through ORSH.     

Preparation of SnS quantum dots for solar cells application by an in-situ solution chemical reaction process

SnS quantum dots (QDs) with size of 8 nm were synthesized by an in-situ room temperature solution chemical reaction process. Stannous chloride, as Sn precursor, was coated on the TiO₂ photo-anodes to form a solid precursor film. Ammonium sulfide was dissolved into ethanol to form anionic reaction solution. SnS quantum dots were generated by immersing the Sn-coated TiO₂ photo-anodes into the anionic solution. The structure, morphology and optical absorption properties of the SnS/TiO₂ photoanodes were investigated by means of XRD, SEM, TEM and UV–vis measurements. The photovoltaic properties of the SnS QDs sensitized TiO₂ solar cells were optimized by changing the number of deposition cycles of the SnS QDs. It turns out that the SnS/TiO₂ solar cell with 20 deposition cycles exhibited the best photovoltaic performance with an open-circuit voltage V_oc of 510 mV, a short-circuit current density Jsc of 2.41 mA, a fill factor FF of 0.49 and a power conversion efficiency η of 0.61% under AM 1.5 illumination. This result is interpreted in terms of minimization of the charge transfer resistance. The performance will drop for further deposition because the charge transfer resistance will increase due to QDs agglomeration.     

Design and optimization of a modified Sierpinski fractal antenna for broadband applications

Immense understanding of antenna designers illustrate that a general microstrip antenna demonstrate low efficiency. Various techniques have been adopted to improve the performance characteristics of microstrip antenna. This paper deals with the optimization of Sierpinski fractal antenna structure by utilizing the particle swarm optimization (PSO) and curve fitting method. The required data for optimization and fitting the curve has been obtained by varying different design parameters of the proposed antenna. Electromagnetic solver Ansoft HFSS 13.0 is used for generating the parametric data. The MATLAB curve fitting tool is referred for developing the equations which exhibits the relations between the parameters of proposed antenna design. Particle swarm optimization technique is then applied to find the optimum values of the design parameters for the bandwidth enhancement of proposed antenna. Curve fitting based optimized design represents the remarkable improvement in the bandwidth of conventional microstrip line fed Sierpinski fractal antenna for broadband applications.