Energy Separation Research Articles

Experimental demonstration of rainbow trapping of elastic waves in two-dimensional axisymmetric phononic crystal platesa).

Structures with specific graded geometries or properties can cause spatial separation and local field enhancement of wave energy. This phenomenon is called rainbow trapping, which manifests itself as stopping the propagation of waves at different locations according to their frequencies. In acoustics, most research on rainbow trapping has focused on wave propagation in one dimension. This research examined the elastic wave trapping performance of a two-dimensional (2D) axisymmetric grooved phononic crystal plate structure. The performance of the proposed structure is validated using numerical simulations based on finite element analysis and experimental measurements using a laser Doppler vibrometer. It is found that rainbow trapping within the frequency range of 165-205 kHz is achieved, where elastic waves are trapped at different radial distances in the plate. The results demonstrate that the proposed design is capable of effectively capturing elastic waves across a broad frequency range of interest. This concept could be useful in applications such as filtering and energy harvesting by concentrating wave energy at different locations in the structure.

Optimization of filter structures by evolutionary strategies

The increasing pressure drop of filter media during the capture of solid particles is directly correlated to the energy consumption. It is largely based on the microstructure of the media, especially with regard to the selected porosity gradient. The development of new filter media optimized for separation efficiency and energy consumption is based mainly on experimental work. The use of evolutionary algorithms inspired by nature is of particular interest for the optimization of filter media, as a large number of non-linear influencing factors can be processed. However, a large number of simulations is required for successful application in order to reproduce the natural process of mutation and individual selection. Most numerical simulations of filtration properties are limited due to the high computing power required, making them unsuitable in this context. Therefore, a 1D simulation with low computing power requirements was used in this paper to simulate the loading of a filter medium with particles. This approach enabled the rapid calculation of the loading of different filter media structures, and was coupled with an evolutionary algorithm with the aim of optimizing the porosity gradient. The algorithm was tested on different particle size distributions, which represented different operating conditions. The porosity gradients of the optimized filters was in the form of an inverse square function, leading to a much more homogenous, microscopic loading with particles. Due to the significantly improved utilization of the filter depth compared to a reference medium, a much slower increase in pressure difference could be obtained with a similar filtration efficiency, resulting in increased quality factors of 30% and higher. The optimization of an operating point took about 24 hours on a standard desktop PC and could be extended to other structural parameters of the filter medium apart from the porosity gradient. This shows the potential for a broad application in the selection and optimization of filter media.

Growth of Ni loaded CdS in nanorods structure for photocatalytic and dye degradation applications under solar irradiation

Due to the exponential increase in global energy consumption and the degradation of environmental conditions caused by fossil fuels, it is critical to improve inexhaustible and sustainable resources. Generally, solar energy is one of the clean and environmentally agreeable energy sources. By harvesting solar energy for photocatalysis and considering it as a promising solution for various energy generation applications such as hydrogen production. Herein we are using Cadmium Sulphide and Nickel-doped Cadmium Sulphide in 0.5, 1 and 5 weight percent which act as photocatalyst for water splitting which will eventually produce an enormous amount of Hydrogen (H2). Cadmium sulphide was prepared through the chemical precipitation method and Ni-CdS by hydrothermal technique. The purity and phase formation were examined by the X-ray diffraction (XRD) and validated via Rietveld refinement by using Full Prof software. The surface morphology and the structure of as-synthesized material were evaluated by Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscope (TEM) spectroscopic techniques. Following the results, the Ni-CdS nanocomposite having 1.0 wt% of Ni exhibits the highest H2 evolution rate of 9 mmolg−1 in 5 h with strong photo-stability, which is about 50 times higher than that of CdS. The material was tested to degrade organic dye for its photocatalytic operations. The newly prepared composite materials (CdS-Ni-NiO) were used for the photocatalytic degradation of the methylene blue (MB) dye. Ni(1.0 wt%)-CdS shows an optimal degradation percentage of 95.436 in the presence of artificial solar light in 90 min. Crystal growth mechanism shows the spherical structure of CdS agglomerate to form nanorods structure when doped with Ni metal which is also verified by the TEM images of CdS and Ni-doped CdS. The XPS peaks observed at 854.88 eV and 861.07 eV for Ni2+ with an energy separation of 6.18 eV confirmed the existence of NiO with Ni/CdS. The Raman bands of pure CdS and Ni (1.0 wt%)-CdS nanorods were observed at 300 cm-1 and 293 cm−1 for 1LO phonon and 601 cm−1 and 586 cm−1 for 2LO phonon corresponds. The Ni tuned the CdS band gap from 2.36 to 2.20 eV. The results pave the way for designing multi-component CdS-Ni nano-composites for highly efficient H2 evolution and other environmental applications.

Ab Initio Conformational Analysis of 3,7-Diacetyl-3,7-Diazabicyclo[3.3.1]Nonanes

Introduction: The importance of the conformational behavior comprehension for proper prediction of properties for a certain compound or for a class of compounds is indisputable. For 3,7-diacylbispidines (3,7-diacyl-3,7-diazabicyclo[3.3.1]nonanes), only “double chair” (CC) conformers were prior found experimentally in the condensed phase, which differ only in the acyl groups relative orientation, “parallel,” pa or “antiparallel,” ap. However, 2 other conformer families, “boat-chair,” BC and “double twist,” TT, are known for other bicyclo[3.3.1]nonane derivatives. Features of these conformers would be useful for the accurate prediction of properties and activities of the compounds. Methods: Second-order perturbation theory ab initio techniques (MP2) in the triple-zeta correlation-consistent orbital basis set cc-pVTZ was employed to optimize the electronic energy for structures, to characterize the optimized structures as potential energy surface minima by energy hessian eigenvalue calculations and to calculate zero-point energy corrections for the minima using the “rigid rotor-harmonic oscillator” approximation to model the molecular ensemble thermodynamics. Additionally, the computational chemical thermodynamics benefits much from the concept of the molecular strain and its energy assessed successfully through the bond separation energy formalism. We combine both approaches in our investigation to find and consistently characterize the conformers previously unknown for the compounds under the studies. Results: Six possible conformers were found for the investigated 3,7-diacetyl-3,7-diazabicyclo[3.3.1]nonanes 1-4, formed by combining the skeletal conformation changes with the internal rotation of acyl substituents. The conformational behavior is quite similar for all investigated molecules. In all cases, the CC conformation is optimal for the bicyclic skeleton and ap orientation prevails over pa for 2 acetyl groups. This prevalence is 4-5 kcal mol−1 in CC and less than 1 kcal mol−1 in other skeletal forms, making rotation of 2 acyl groups in BC and TT almost independent. Concerning the skeletal conformations, the common energy sequence CC < BC < TT is found. While the relative BC energy is 6-7 kcal mol−1 over the optimal CC structure, TT forms are all strained by more than 12 kcal mol−1. Conclusions: For the first time, both BC and TT conformers of 3,7-diacetylbispidines were characterized by their strain and conformation energies together with known less strained CC forms. On the basis of our calculations, the relative energies of BC conformers are expected to be close to those of the CC acetyl amide bond rotamers found previously in experiment, therefore, their exclusion from the conformational behavior would look unjustified. On the contrary, TT conformers are found to be much more strained enough to be neglected in the conformational ensemble modeling.

Systematic study of two proton radioactivity within the effective liquid drop model

In this study, we investigated two-proton radioactivity using the effective liquid drop model with varying mass asymmetry shapes and effective inertia coefficients (VMAS-EFF). Gaudin’s expression term for Coulomb potential energy is replaced in the current study’s calculation of potential energy. The VMAS-EFF combination predicts the half-life with the lowest standard deviation ( σ =1.03) compared to other models and previous constant mass asymmetry with Werner-inertial Wheeler’s coefficient combinations. The lowest standard deviation value indicates that the VMAS-EFF combination is suitable for reproducing the experimental data. We extended the half-life predictions to another 54 nuclei and compared them with six theoretical model predictions and two empirical formula predictions. The present work also investigated the decay possibilities using quantum tunnelling by computing the driving potential (V-Q) for various states of angular momentum l = 0, 2, 3, and 4. Found that 6Be, 6B, 8C, 12O,15,16Ne, 19Mg, 22Si, 26S, 30Ar 38,39Ti, 40V, 42Cr, 45Fe, 48,49Ni, 54Zn, 58,59,60Ge and 64Se nuclei have a high chance of emission for two protons, while 7B, 10N, 14F, 17Na, 24P, 28Cl,32K, 34Ca, 36,37Sc, 44Mn, 47Co, 52Cu, 56,57,58Ga, 61,62As nuclei have a lower chance for two proton than one proton decay. The computation of separation energy findings agree well with the driving potential findings.

Geothermal Energy Extraction Using a Novel Combined Coaxial and U-Shaped Closed-Loop System

In the present study, a novel combined coaxial and U-shaped closed-loop system was proposed to enhance the thermal performance of the U-shaped geothermal system. The proposed geothermal system consists of two separate energy extraction units, called primary and secondary systems. The primary system consists of an insulated U-shaped tube heat exchanger. In order to extract more thermal energy, a coaxial double-pipe heat exchanger was coupled to the primary system as the secondary system. A conjugate heat transfer (CHT) module incorporating a k-ε turbulent model was employed to simulate the heat extraction and fluid flow within the proposed system. Further, the study extended to analyse the effect of various individual parameters on the thermal performance of the proposed closed-loop system. The results depicted that the proposed system can extract up to 42% higher thermal power than that of an insulated U-shaped tube heat exchanger. Further, the coefficient of performance (COP) of the combined system ranges between 1.03 to 1.22 depending upon the operational parameters. Overall, the proposed geothermal system effectively utilized both the heat loss from the hot primary fluid as well as the thermal energy available in the rock surrounding the insulation of U-shaped geothermal heat exchangers. The outcomes of the present study may be productive for researchers and industries interested in the extraction of clean and renewable energy.

Enhanced hydrolytic stability and photocatalytic performance of a uranium‐based organic framework by hybrid carbon nanotubes

Owing to their highly predictable porous structures, facile synthesis, and the presence of functional open metal sites, metal–organic frameworks (MOFs) are extensively employed in various fields, including energy storage, catalysis, adsorption, and separation. Nevertheless, the limited hydrolytic stability exhibited by numerous MOFs poses a significant challenge to their practical application. In the present study, we present the synthesis and characterization of a uranyl organic framework (TCPP‐U1) with a highly porous structure, which is constructed by assembling cobalt, uranyl, and the porphyrin ligand 5,10,15,20‐tetra(4‐carboxyphenyl)porphyrin (TCPP). However, TCPP‐U1 demonstrates poor hydrolytic stability when exposed to water (the structure can be destroyed even after 2 min of exposure to water), greatly impeding its potential applications that would benefit from its high surface area. To address this limitation, we developed a hybrid composite by incorporating acid‐treated multi‐walled carbon nanotubes (CNTs) into the TCPP‐U1 framework via a solvothermal method designated as CNTs@TCPP‐U1. Remarkably, the obtained CNTs@TCPP‐U1 composite possesses an identical crystal structure and morphology to the original TCPP‐U1 yet exhibits significant enhancements in hydrolytic stability (the structure remains stable even after 3 days of immersion in water). Furthermore, CNTs@TCPP‐U1 demonstrates a significant photocatalytic effect on the degradation of tetracycline hydrochloride in aqueous solutions. The reaction rate constant (k) for the pseudo‐first‐order kinetic model is 0.0059 min−1. Our findings present a novel perspective for enhancing the stability and expanding the performance of MOFs materials.

Correlation between the shape coexistence and stability in Mo and Ru isotopes

In a rapidly changing shape phase region, the presence of shape coexistence and its possible impact on the decay modes and half-lives, has been explored in astrophysically interesting Mo and Ru isotopes, in an extensive study within the microscopic theoretical framework using Nilsson Strutinsky Method and Relativistic Mean Field Model. The isotopic chains of Mo and Ru exhibit rapid shape phase transitions, triaxial γ softness, shape instability along with many coexisting states mostly with oblate and triaxial shapes. Proton and neutron separation energies have been calculated and compared with the available data. Results obtained from both the formalisms are in good agreement with each other as well as the available experimental data. Our computed β-decay half-lives and separation energy for nuclei exhibiting shape coexistence were examined for the decay mode from second minima state of the parent nuclei to the ground or excited state of the daughter nuclei. The second minima state of the coexisting shapes in Mo and Ru isotopes, were seen to impact the structural properties, β-decay half-lives, separation energy and hence the stability of the nuclei.

Many-objective optimization for structural parameters of the fuel cell air compressor based on the Stacking model under multiple operating conditions

As the central element of the cathode air supply system, the centrifugal air compressor is pivotal to the regular and efficient operation of on-board fuel cells. In an attempt to further enhance the overall properties of the air compressor, the computational fluid dynamics (CFD) simulation model and Stacking model are developed and calibrated in this study. On this basis, the Many-Objective Random Walk Gray Wolf Optimizer (MORW-GWO) algorithm is proposed to perform many-objective optimization for compressor structural parameters, and the intrinsic mechanisms of performance improvements are elaborated based on three-dimensional flow analysis. The results indicate that the Stacking model achieves excellent predictive performance and generalization ability through the coupling and mutual error correction of base learners and the meta-learner. The MORW-GWO algorithm demonstrates outstanding many-objective optimization capability, convergence ability and universality. Compared to the original compressor, the optimized air compressor achieves improvements of 2.8%, 2.3%, 9.3% and 16.0% in the pressure ratio, outlet temperature, isentropic efficiency and adiabatic compression work, respectively. Besides, it is found that the internal energy loss, separation loss, friction loss, gas leakage and backflow of the optimized air compressor are reduced through the 3-D flow characteristic analysis. The findings can contribute to the many-objective optimization of compressor structural parameters by giving theoretical guidance, data support and directional evidence.

Research on piezoelectric vibration energy harvester for cutting part of roadheader

At present, coal mine tunneling technology is developing in the direction of intelligence and unmanned. The piezoelectric vibration energy harvester can convert the vibration energy generated by the cutting part of roadheader into electrical energy and realize the energy self-sufficiency of the low-power wireless sensor. In practical applications, the vibration frequency of the cutting part of roadheader is different, and the working condition is complex, resulting in the energy recovery efficiency of the vibration energy harvester is not ideal. In order to improve its adaptability and reliability, a separated excitation broadband piezoelectric vibration energy harvester is proposed in this paper.

AFM signal model for dysarthric speech classification using speech biomarkers.

Neurological disorders include various conditions affecting the brain, spinal cord, and nervous system which results in reduced performance in different organs and muscles throughout the human body. Dysarthia is a neurological disorder that significantly impairs an individual's ability to effectively communicate through speech. Individuals with dysarthria are characterized by muscle weakness that results in slow, slurred, and less intelligible speech production. An efficient identification of speech disorders at the beginning stages helps doctors suggest proper medications. The classification of dysarthric speech assumes a pivotal role as a diagnostic tool, enabling accurate differentiation between healthy speech patterns and those affected by dysarthria. Achieving a clear distinction between dysarthric speech and the speech of healthy individuals is made possible through the application of advanced machine learning techniques. In this work, we conducted feature extraction by utilizing the Amplitude and frequency modulated (AFM) signal model, resulting in the generation of a comprehensive array of unique features. A method involving Fourier-Bessel series expansion is employed to separate various components within a complex speech signal into distinct elements. Subsequently, the Discrete Energy Separation Algorithm is utilized to extract essential parameters, namely the Amplitude envelope and Instantaneous frequency, from each component within the speech signal. To ensure the robustness and applicability of our findings, we harnessed data from various sources, including TORGO, UA Speech, and Parkinson datasets. Furthermore, the classifier's performance was evaluated based on multiple measures such as the area under the curve, F1-Score, sensitivity, and accuracy, encompassing KNN, SVM, LDA, NB, and Boosted Tree. Our analyses resulted in classification accuracies ranging from 85 to 97.8% and the F1-score ranging between 0.90 and 0.97.

COMPETITIVENESS ASSESSMENT WITH THE IMPLEMENTATION OF AN ENERGY CAPACITY MARKET IN BRAZIL

Purpose: This article investigates issues related to the need to implement a capacity market in the Brazilian electricity sector to add security to the system and increase market competitiveness to benefit its energy consumers, as well as attract investments to the supply segments of this industry. Theoretical Framework: This research focuses on the Market Design Theory and the transition to the capacity market, detailing its principles and relevance in the current context. Through it, we seek to understand the mechanisms that shape the contemporary market. Design/Methodology/Approach: This research adopts an applied research approach. It is structured as a case study, where Brazil is analyzed in the context of implementing a capacity market. Techniques such as interviews, and documentary research were used to collect data. Findings: The study delves into the intricacies of establishing a capacity market in a competitive environment. The central findings encompass distinctions between the separation of backing and energy versus the capacity market; the blueprint of the auction and regulation of contracting; shaping the long-term market perspective; and the methodology for deducing the capacity market demand. Research, Practical & Social Implications: This article contributes to the literature by surveying cases on capacity market development in developed countries. Furthermore, as a practical contribution, it details the benefit of implementing a capacity market in the Brazilian case. Originality/Value: This research provides innovative solutions for Brazil, drawing from global benchmarks and tailoring them to Brazil's unique challenges and recent legal changes.

Surface oxide ion conduction of BaCe0.5Pr0.3Y0.2O3−δ thin film with complex mixed valence states

Solid oxide fuel cells (SOFCs), which operate in the medium temperature range from 300 °C to 500 °C, are effective in shortening startup time and reducing fuel gas. In order to realize a practical electrolyte with high oxide ion conductivity, we have investigated the ionic conductivity of c-axis oriented BaCe0.5Pr0.3Y0.2O3−δ (BCPY) thin films with complex mixed valence states prepared on Al2O3 (0001) substrates by RF magnetron sputtering. The amount of oxygen vacancies on the surface in the as-deposited BCPY thin film was evaluated to be ∼6.7% by X-ray absorption spectroscopy and defect chemical analysis. The as-deposited film exhibited relatively high ionic conductivity (σT) of more than 10−1 S·K cm−1 and activation energy (E A) of ∼0.57 eV in the medium temperature range by thermal activation process on the surface. The energy separation between the top of the VB and the Fermi level was much larger than E A, indicating that the BCPY thin film is a pure oxide ion conductor without the contribution of electron or hole carriers. These results indicate that the c-axis oriented BCPY thin film can be applied to electrolyte of SOFC operating in the medium temperature range.

Observation of plaid-like spin splitting in a noncoplanar antiferromagnet.

Spatial, momentum and energy separation of electronic spins in condensed-matter systems guides the development of new devices in which spin-polarized current is generated and manipulated1-3. Recent attention on a set of previously overlooked symmetry operations in magnetic materials4 leads to the emergence of a new type of spin splitting, enabling giant and momentum-dependent spin polarization of energy bands on selected antiferromagnets5-10. Despite the ever-growing theoretical predictions, the direct spectroscopic proof of such spin splitting is still lacking. Here we provide solid spectroscopic and computational evidence for the existence of such materials. In the noncoplanar antiferromagnet manganese ditelluride (MnTe2), the in-plane components of spin are found to be antisymmetric about the high-symmetry planes of the Brillouin zone, comprising a plaid-like spin texture in the antiferromagnetic (AFM) ground state. Such an unconventional spin pattern, further found to diminish at the high-temperature paramagnetic state, originates from the intrinsic AFM order instead of spin-orbit coupling (SOC). Our finding demonstrates a new type of quadratic spin texture induced by time-reversal breaking, placing AFM spintronics on a firm basis and paving the way for studying exotic quantum phenomena in related materials.

A bottom-up assessment of recent (2016–20) energy use by the global iron and steel industry constrained to match a top-down (International Energy Agency) assessment

This paper presents the first estimates, at the global scale, of energy use by energy type associated with individual steps in the production of fabricated steel products. Estimates are averaged over the period 2016–20, based on a synthesis of literature regarding energy use for (i) preparation of iron ore; (ii) production of iron in a blast furnace (BF) and as direct reduced iron; (iii) production of refined steel in the basic oxygen furnace or electric arc furnace; (iv) steel casting, hot and cold rolling, and coating; (v) fabrication of intermediate steel products; and (vi) processing of scrap. The International Energy Agency provides separate global energy use for coking, transformation energy use by BF, and by the remainder of the iron and steel industry (rISI) including the remaining BF energy use. With re-allocation of the BF portion of rISI back to BF, and a 9% increase in literature-based estimates of energy intensity across all production steps except coking, bottom-up and IEA estimates of total energy use agree. The resulting mean cumulative energy intensity of fabricated steel products is 24.1 GJ/t. The energy content of the lost iron equals about 10% of the total energy used in producing finished steel products.

Feasibility of bone marrow edema detection using dual-energy cone-beam computed tomography.

Dual-energy (DE) detection of bone marrow edema (BME) would be a valuable new diagnostic capability for the emerging orthopedic cone-beam computed tomography (CBCT) systems. However, this imaging task is inherently challenging because of the narrow energy separation between water (edematous fluid) and fat (health yellow marrow), requiring precise artifact correction and dedicated material decomposition approaches. We investigate the feasibility of BME assessment using kV-switching DE CBCT with a comprehensive CBCT artifact correction framework and a two-stage projection- and image-domain three-material decomposition algorithm. DE CBCT projections of quantitative BME phantoms (water containers 100-165mm in size with inserts presenting various degrees of edema) and an animal cadaver model of BME were acquired on a CBCT test bench emulating the standard wrist imaging configuration of a Multitom Rax twin robotic x-ray system. The slow kV-switching scan protocol involved a 60kV low energy (LE) beam and a 120kV high energy (HE) beam switched every 0.5° over a 200° angular span. The DE CBCT data preprocessing and artifact correction framework consisted of (i) projection interpolation onto matched LE and HE projections views, (ii) lag and glare deconvolutions, and (iii) efficient Monte Carlo (MC)-based scatter correction. Virtual non-calcium (VNCa) images for BME detection were then generated by projection-domain decomposition into an Aluminium (Al) and polyethylene basis set (to remove beam hardening) followed by three-material image-domain decomposition into water, Ca, and fat. Feasibility of BME detection was quantified in terms of VNCa image contrast and receiver operating characteristic (ROC) curves. Robustness to object size, position in the field of view (FOV) and beam collimation (varied 20-160mm) was investigated. The MC-based scatter correction delivered>69% reduction of cupping artifacts for moderate to wide collimations (>80mm beam width), which was essential to achieve accurate DE material decomposition. In a forearm-sized object, a 20% increase in water concentration (edema) of a trabecular bone-mimicking mixture presented as ∼15 HU VNCa contrast using 80-160mm beam collimations. The variability with respect to object position in the FOV was modest (<15% coefficient of variation). The areas under the ROC curve were>0.9. A femur-sized object presented a somewhat more challenging task, resulting in increased sensitivity to object positioning at 160mm collimation. In animal cadaver specimens, areas of VNCa enhancement consistent with BME were observed in DE CBCT images in regions of MRI-confirmed edema. Our results indicate that the proposed artifact correction and material decomposition pipeline can overcome the challenges of scatter and limited spectral separation to achieve relatively accurate and sensitive BME detection in DE CBCT. This study provides an important baseline for clinical translation of musculoskeletal DE CBCT to quantitative, point-of-care bone health assessment.

Numerical Simulation Study of Energy Separation in Jet Shear Layer

In order to investigate the rational utilization of energy in the fluid jet process, a free dual jet of parallel air is used as a research object. Simulation of turbulence was carried out based on the realizable k-epsilon equations with pressure-velocity coupling, PISO method, discrete method with second-order windward format, and first-order implicit transient solution. The energy separation phenomenon within the jet shear layer and its influencing factors were investigated under dual-jet Reynolds number differences of 12,800, 19,200, 25,600, 32,000, 41,500, and 51,100, respectively. The simulation is in transient format and the jet inlet velocity is given by udf. Calculations show that the pressure perturbation in the air shear layer, which gives rise to the pressure work exchange between the jet and the surroundings, is the main reason for the coexistence of high- and low-temperature regions formed within the jet shear layer, and the larger the Reynolds number, the stronger the energy separation effect. The center streamline path of a parallel air free dual jet can be fitted by a circular arc, whose radius of curvature increases with the Reynolds number, and the curvilinear development path of the dual jet can offset the energy separation effect to some extent. This paper confirms the existence of energy separation in the shear layer of a parallel air free double jet, reveals the mechanism of energy separation in the fluid domain, and explores the flow characteristics of two parallel jets.

Performance evaluation of quantitative material decomposition in slow kVp switching dual-energy CT.

Slow kVp switching technique is an important approach to realize dual-energy CT (DECT) imaging, but its performance has not been thoroughly investigated yet. This study aims at comparing and evaluating the DECT imaging performance of different slow kVp switching protocols, and thus helps determining the optimal system settings. To investigate the impact of energy separation, two different beam filtration schemes are compared: the stationary beam filtration and dynamic beam filtration. Moreover, uniform tube voltage modulation and weighted tube voltage modulation are compared along with various modulation frequencies. A model-based direct decomposition algorithm is employed to generate the water and iodine material bases. Both numerical and physical experiments are conducted to verify the slow kVp switching DECT imaging performance. Numerical and experimental results demonstrate that the material decomposition is less sensitive to beam filtration, voltage modulation type and modulation frequency. As a result, robust material-specific quantitative decomposition can be achieved in slow kVp switching DECT imaging. Quantitative DECT imaging can be implemented with slow kVp switching under a variety of system settings.

Green Synthesis of Silver/Silver Chloride Nanoparticles using Shallot Peel Extract as Reducing Agent

Precious metal nanoparticles, especially silver, can be an alternative antibacterial agent that is more promising than antibiotics, which tends to induce resistance over time. Unfortunately, most Silver nanoparticle (AgNP) manufacturing methods involve hazardous substances, extreme conditions, high energy, and complicated separations. Reduction of AgNO3 solution with plant extracts can serve as a ‘green’ synthesis pathway, especially if using food processing waste or other biological materials. Reducing substances that are commonly found in plant extracts, such as flavonoids, are widely contained in shallots (Allium cepa L. var. aggregatum) which are commonly used as food ingredients in Indonesia, but the processing waste is still not widely used. This paper describes the synthesis of silver nanoparticles (AgNP) with the AgNO3 solution reduction method, using onion peel waste extract as a reducing agent. Experiments were carried out with variations in the ratio of AgNO3 solution to onion peel extract. The resulting AgNPs were characterized by TEM and UV-vis.

Manipulating the Spin State of Co Sites in Metal-Organic Frameworks for Boosting CO2 Photoreduction.

Photocatalytic CO2 reduction holds great potential for alleviating global energy and environmental issues, where the electronic structure of the catalytic center plays a crucial role. However, the spin state, a key descriptor of electronic properties, is largely overlooked. Herein, we present a simple strategy to regulate the spin states of catalytic Co centers by changing their coordination environment by exchanging the Co species into a stable Zn-based metal-organic framework (MOF) to afford Co-OAc, Co-Br, and Co-CN for CO2 photoreduction. Experimental and DFT calculation results suggest that the distinct spin states of the Co sites give rise to different charge separation abilities and energy barriers for CO2 adsorption/activation in photocatalysis. Consequently, the optimized Co-OAc with the highest spin-state Co sites presents an excellent photocatalytic CO2 activity of 2325.7 μmol·g-1·h-1 and selectivity of 99.1% to CO, which are among the best in all reported MOF photocatalysts, in the absence of a noble metal and additional photosensitizer. This work underlines the potential of MOFs as an ideal platform for spin-state manipulation toward improved photocatalysis.