6,476 research outputs found
An integrated model for estimating the techno-economic performance of the distributed solar generation system on building facades: Focused on energy demand and supply
No full textThere has been growing interest in the distributed solar generation (DSG) system in accordance with the 'Post-2020 Climate Change Agreement', especially for the reduction of greenhouse gas emissions from buildings. In this respect, this study aimed to develop an integrated model for estimating the techno-economic performance of the DSG system on building fa ades, with a focus on energy demand and supply. The integrated model was developed in five stages: (i) definition of design variables affecting the DSG system on building fa ades; (ii) establishment of a standard database for the DSG system on building fa ades using energy simulation; (iii) technical analysis of the DSG system on building fa ades using the finite element method; (iv) economic analysis of the DSG system on building fa ades through life-cycle cost analysis; and (v) systemization. Detailed analyses were conducted in three aspects: (i) nonlinearity analysis; (ii) validation of the developed model; and (iii) practical application (to the 'S' apartment block in South Korea). With the newly developed integrated model (i-FEM), it was found that the technical performance of the DSG system could be accurately estimated in only 6 s: (i) heating energy demand (1.01%); (ii) cooling energy demand (9.27%); and (iii) building energy supply (3.55%). It is expected that decision-makers (e.g. construction managers or facility managers) can use the newly developed integrated model (i-FEM) to evaluate the potential impact of the DSG system on building facades in a timely and accurate manner.
Self-adaptive MgAl2O4 spinel layer for enhanced corrosion resistance of alumina-forming alloy in molten chloride salts
No full textMolten chloride salts are promising heat-transfer and storage media for next-generation energy systems but pose severe corrosion risks to metallic structural materials. Here, we present a novel corrosion mitigation strategy for FeCrAl alloy by constructively leveraging the molten salt environment to induce a spinel protective layer on the metal surface. Porous alumina is initially engineered through selective anodization of FeCrAl, which facilitates Mg-2(+) incorporation and effectively relieves volumetric expansion stress during molten NaCl-MgCl2 exposure. Consequently, the porous alumina is transformed into a compact and chemically robust MgAl2O4 spinel barrier. Corrosion testing at 700 degrees C for 700 h reveals nearly an order-of-magnitude less chromium depletion in the anodized FeCrAl (similar to 22 mu m) compared with the bare alloy (similar to 171 mu m). Comprehensive characterization, along with measurements of dissolved Cr concentration and mass loss, further support the enhanced corrosion resistance. This scalable strategy offers a viable pathway for long-term materials durability in next-generation nuclear power, concentrated solar power and thermal energy storage systems.
Atomic-Layer-Deposited MoNx Thin Films on Three-Dimensional Ni Foam as Efficient Catalysts for the Electrochemical Hydrogen Evolution Reaction
No full textFuture realization of a hydrogen-based economy requires a high-surface-area, low-cost, and robust electrocatalyst for the hydrogen evolution reaction (HER). In this study, the MoNx thin layer is synthesized on to a high-surface area three-dimensional (3D) nickel foam (NF) substrate using atomic layer deposition (ALD) for HER catalysis. MoNx is grown on NF by the sequential exposure of Mo(CO)(6) and NH3 at 225 degrees C. The thickness of the thin film is controlled by varying the number of ALD cycles to maximize the HER performance of the MoNx/NF composite catalyst. The scanning electron microscopy and transmission electron microscopy (TEM) images of MoNx/NF highlight that ALD facilitates uniform and conformal coating. TEM analysis highlights that the MoNx film is predominantly amorphous with the nanocrystalline MoN grains (4 nm) dispersed throughout it. Moreover, the high-resolution (HR)-TEM analysis shows a rough surface of the MoNx film with an overall composition of Mo0.59N0.41. X-ray photoelectron spectroscopy depth-profile analysis reveals that oxygen contamination is concentrated at the surface because of surface oxidation of the MoN film under ambient conditions. The HER activity of MoNx is evaluated under acidic (0.5 M H2SO4) and alkaline (0.1 M KOH) conditions. In an acidic electrolyte, the sample prepared with 700 ALD cycles exhibits significant HER activity and a low overpotential (eta) of 148 mV at 10 mA cm(-2). Under an alkaline condition, it achieves 10 mA cm(-2) with eta of 125 mV for MoNx/NF (700 cycles). In both electrolytes, the MoNx thin film exhibits enhanced activity and stability because of the uniform and conformal coating on NF. Thus, this study facilitates the development of a large-area 3D freestanding catalyst for efficient electrochemical water-splitting, which may have commercial applicability
A novel real-time method for HVAC system operation to improve indoor environmental quality in meeting rooms
No full textFor indoor environmental quality (IEQ), previous studies only focused on one-sided aspect (e.g. monitoring, diagnostic, or intervention), and have not fully considered excessive pollutants and dew condensation in meeting rooms. Based on a real-time sensor network, this study newly implemented a three-phase cyclic process (i.e. monitoring-diagnostic-intervention process), with which a novel real-time method for HVAC system operation was developed to improve IEQ in meeting rooms. In particular, this study conducted two kinds of analyses and controls: (i) basic analysis and control for excessive pollutants by utilizing temperature and CO2 concentration; and (ii) advanced analysis and control for dew condensation on the diffuser of HVAC system by utilizing temperature, humidity, and CO2 concentration. The main findings were summarized as follows. For the "basic analysis", the CO2 concentration was estimated to exceed 1000 ppm at 14.8% and 3L7% in two meeting rooms. To avoid it, a real-time "basic control" strategy was developed: if the CO2 concentration would exceed 1000 ppm, the ventilation volume of the outdoor air could increase in real time. For the "advanced analysis", dew condensation on the diffuser was estimated to happen at 40.7% and 82.6% in two meeting rooms. To avoid it, a realtime "advanced control" strategy was developed: if the estimated supply air temperature would be lower than the calculated dew-point temperature, the supply-air temperature and ventilation volume of HVAC system could increase. The novel real-time method can be easily applied to HVAC system operation in existing buildings where events are hard to be predicted and recognized.
A novel operation approach for the energy efficiency improvement of the HVAC system in office spaces through real-time big data analytics
No full textSince a traditional centralized control system (e.g., building energy management system) with a fixed schedule and manual control is not appropriate to irregularly occupied rooms, it is expected to have a large amount of energy saving potential in operating the HVAC system. To overcome this challenge, this study aimed to develop a novel operation approach for the energy efficiency improvement of the HVAC system in office spaces. The real-time indoor environmental indicators were collected and analyzed to evaluate the current operation status of the HVAC system as well as to propose a novel control strategy in two ways. The significant findings can be illustrated as follows. First, it could be stated that occupants would tend to establish a lower set-point temperature for a cooler indoor environment. To solve this issue, a basic control strategy was proposed to detect the anomaly detection of the HVAC system and to automatically adjust the indoor temperature within a preferred range. Second, it could be evaluated that the HVAC system would be kept operating since occupants would forget to turn off the HVAC system after the meetings. To solve this issue, an advanced control strategy was proposed to operate the automatic on/off control of the HVAC system by considering the indoor temperature and CO2 concentration in real time. The proposed strategies can contribute to a large amount of energy savings in operating the HVAC system of irregularly occupied spaces.
Correction: Synergistic photodynamic therapeutic effect of indole-3-acetic acid using a pH sensitive nano-carrier based on poly(aspartic acid-<i>graft</i>-imidazole)-poly(ethylene glycol)
No full textCorrection for ‘Synergistic photodynamic therapeutic effect of indole-3-acetic acid using a pH sensitive nano-carrier based on poly(aspartic acid-graft-imidazole)-poly(ethylene glycol)’ by Taehoon Sim et al., J. Mater. Chem. B, 2017, 5, 8498–8505.</p
Characteristics ofMoSe(2) formation during rapid thermal processing ofMo-coated glass
No full textMulti-layered Mo, prepared using an in-line sputtering system, was selenized by reaction with Se vapor and thermal annealing of bilayer Mo/Se samples. In situ high-temperature X-ray diffraction analysis indicated that the phase evolution of the glass/Mo/Se sample during heat treatment was similar to that of the selenization of glass/Mo with Se vapor, except for crystallization of Se in the glass/Mo/Se sample. However, the MoSe2 layer formed from the selenization of the Mo layer by Se vapor preferentially grew perpendicularly to the Mo surface, whereas MoSe2 formed from the reaction of Mo with Se liquid showed random orientation. The detailed reaction pathways of the double-layer random-MoSe2/vertical-MoSe2 formation from the Mo/Se bilayer sample were suggested on the basis of the several characterization results including X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and selected-area electron diffraction patterns. © 2012 Elsevier B.V.1
Thermodynamic and Transport Properties of H<sub>2</sub>/H<sub>2</sub>O/NaB(OH)<sub>4</sub> Mixtures Using the Delft Force Field (DFF/B(OH)<sub>4</sub><sup>-</sup>)
No full textSodium borohydride (NaBH4) has a high hydrogen (H2 ) gravimetric capacity of 10.7 wt %. NaBH4 releases H2 through a hydrolysis reaction in which aqueous NaB(OH)4 is formed as a byproduct. NaB(OH)4 strongly influences the thermophysical properties of aqueous solutions (i.e., densities, viscosities, and electrical conductivities) and the hydrolysis reaction kinetics and conversion of NaBH4. Here, molecular dynamics (MD) simulations are performed to compute viscosities, electrical conductivities, and self-diffusivities of H2 , Na+, and B(OH)4- for a temperature and concentration range of 298-353 K and 0-5 mol NaB(OH)4/kg water, respectively. Continuous fractional component Monte Carlo (CFCMC) simulations are used to compute the solubilities of H2 and activities of water in aqueous NaB(OH)4 solutions for the same temperature and concentration range. A new force field is developed (Delft force field of B(OH)4-: DFF/B(OH)4-) in which B(OH)4- is modeled as a tetrahedral structure with a scaled charge of −0.85. The OH group in B(OH)4- is modeled as a single interaction site. This force field is based on TIP4P/2005 water and the Madrid-2019 Na+ force field. The MD simulations can accurately capture the densities and viscosities within 2.5% deviation from available experimental data at 298 K up to a concentration of 5 mol NaB(OH)4/kg water. The computed electrical conductivities deviate by ca. 10% from experimental data at 298 K for the same concentration range. Based on the molecular simulations results, engineering equations are developed for shear viscosities, self-diffusivities of H2, Na+, and B(OH)4-, and solubilities of H2, which can be used to design and model NaBH4 hydrolysis reactors.Engineering ThermodynamicsComplex Fluid ProcessingTeam Poulumi De
Oh Holly, The Fish is Dead
No full textFrom Kurt Vonnegut to Stephen King, many novelists use metanarrative techniques to insert fictional versions of themselves in the stories they tell. The function of deploying such techniques is often to draw attention to the liminal space between the fictional constructs inherent in the novel as a form, and the real world from which the constructs draw inspiration, and indeed, are read by an audience. For emerging writers working in short form narratives, however, the structural demands of the short story or flash fiction make the use of similar techniques problematic in the level of depth to which they can be deployed.\ud
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‘Oh Holly, the fish is dead’ is the fourth in a series of short stories that work to overcome the structural limitations of a succinct form by developing a fractured fictional version of the author over a number of pieces and published across a range of sites. The accumulative affect is a richer metanarrative textual arrangement that also allows for the individual short stories to function independently
Continuous Hamiltonian dynamics and area-preserving homeomorphism group of D2
No full textThe main purpose of this paper is to propose a scheme of a proof of the nonsimpleness of the group {\rm Homeo}^\Omega(D^2,\del D^2) of area preserving homeomorphisms of the 2-disc . We first establish the existence of Alexander isotopy in the category of Hamiltonian homeomorphisms. This reduces the question of extendability of the well-known Calabi homomorphism \Cal: {\rm Diff}^\Omega(D^1,\del D^2) \to \R to a homomorphism \overline \Cal: {\rm Hameo(}D^2,\del D^2) \to \R to that of the vanishing of the basic phase function , a Floer theoretic graph selector constructed in \cite{oh:jdg}, that is associated to the graph of the topological Hamiltonian loop and its normalized Hamiltonian on that is obtained via the natural embedding . Here {\rm Hameo(}D^2,\del D^2) is the group of Hamiltonian homeomorphisms introduced by M\"uller and the author \cite{oh:hameo1}. We then provide an evidence of this vanishing conjecture by proving the conjecture for the special class of \emph{weakly graphical} topological Hamiltonian loops on via a study of the associated Hamiton-Jacobi equation.1111Ysciescopuskc
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