Shallow Energy Research Articles

Robust features of off-axis gamma-ray burst afterglow light curves

ABSTRACT The ultra-relativistic outflows powering gamma-ray bursts (GRBs) acquire angular structure through their interaction with external material. They are often characterized by a compact, nearly uniform narrow core (with half-opening angle θc,{ϵ, Γ}) surrounded by material with energy per unit solid angle ($\epsilon =\epsilon _{\rm c}\Theta _{\epsilon }^{-a}$, where $\Theta _{\lbrace \epsilon ,\Gamma \rbrace }=[1+\theta ^2/\theta _{{\rm c},\lbrace \epsilon ,\Gamma \rbrace }^2]^{1/2}$) and initial specific kinetic energy ($\Gamma _0-1=[\Gamma _{\rm c}-1]\Theta _\Gamma ^{-b}$) declining as power laws. Multiwavelength afterglow light curves of off-axis jets (with viewing angle θobs > θc) offer robust ways to constrain a, b, and the external density radial profile (ρ ∝ R−k), even while other burst parameters may remain highly degenerate. We extend our previous work on such afterglows to include more realistic angular structure profiles derived from three-dimensional hydrodynamic simulations of both long and short GRBs (addressing also jets with shallow angular energy profiles, whose emission exhibits unique evolution). We present afterglow light curves based on our parametrized power-law jet angular profiles for different viewing angles θobs and k = {0, 1, 2}. We identify a unique evolutionary power-law phase of the characteristic synchrotron frequencies (νm and νc) that manifests when the light curve is dominated by emission sensitive to the angular structure of the outflow. We calculate the criterion for obtaining single or double peaked light curves in the general case when θc,Γ ≠ θc,ϵ. We emphasize how the shape of the light curve and the temporal evolution of νm and νc can be used to constrain the outflow structure and potentially distinguish between magnetic and hydrodynamic jets.

Chlorinated Conjugated Polymer Based on Chlorine‐ and Cyano‐substituted (E)‐1,2‐Di(thiophen‐2‐yl)ethane for Ambipolar and n‐Type Organic Thin‐film Transistors

Comprehensive SummaryChlorinated conjugated polymers are rarely reported in ambipolar and n‐type organic thin‐film transistors (OTFTs), mainly due to the lack of chlorinated strong electron‐deficient building blocks. Herein, we report three new chlorine (Cl)‐ and cyano (CN)‐ substituted (E)‐1,2‐di(thiophen‐2‐yl)ethane building blocks and their copolymers P2Cl1CNTVT‐DPP, P4Cl1CNTVT‐DPP and P2Cl2CNTVT‐DPP. P2Cl1CNTVT‐DPP and P2Cl2CNTVT‐DPP had nearly planar backbone geometries, mixture of edge‐on and face‐on orientation and deeper energy levels, while P4Cl1CNTVT‐DPP had a twist backbone geometry, face‐on orientation and shallower energy levels. As a result, P2Cl1CNTVT‐DPP exhibited ambipolar characteristic with hole mobility (μh) of 0.70 cm2·V–1·s–1 and electron mobility (μe) of 0.84 cm2·V–1·s–1 and P2Cl2CNTVT‐DPP exhibited n‐type characteristic with μe of 0.64 cm2·V–1·s–1, while P4Cl1CNTVT‐DPP exhibited the lowest μe of 0.36 cm2·V–1·s–1. The devices based on P2Cl2CNTVT‐DPP exhibited good stability after being stored for 10 d in air. The results demonstrate that by rational molecular design, chlorinated polymers with low cost can be applied to high‐performance ambipolar and n‐type OTFTs.

Systematic analysis of performance and cost of two floating offshore wind turbines with significant interactions

Given the depletion of shallow water wind energy resources and maturity of Floating Offshore Wind Turbine (FOWT), offshore wind technology is shifting from bottom fixed to floating. As a consequence, the research has concentrated on the points such as energy production and cost, which affect the commercialization of the wind farm. Researchers have studied the individual factors affecting these points, and used over-simplified methods. In order to provide a systematic and high quality analysis, we conducted a comprehensive study of wind farm based on unsteady Reynolds Average Navier–Stokes simulations two FOWTs and detailed decomposition of cost components. Specifically, under different scenarios, we compare the two FOWT performances, such as the power output, torque and six degrees of freedom motion response. The influences of the relative rotating direction and relative positions are analyzed. More importantly, we extensively discuss the impact of the interaction on the FOWT levelized cost of energy under various scenarios. It is found that tandem layout with a distance of 9.25D is the practical optimal parameter choice. This study is expected to provide guidances and insights for offshore wind researchers and governmental decision makers in future wind farm plannings.

Influence of Radiation-Induced Displacement Defect in 1.2 kV SiC Metal-Oxide-Semiconductor Field-Effect Transistors.

The effect of displacement defect on SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) due to radiation is investigated using technology computer-aided design (TCAD) simulation. The position, energy level, and concentration of the displacement defect are considered as variables. The transfer characteristics, breakdown voltage, and energy loss of a double-pulse switching test circuit are analyzed. Compared with the shallow defect energy level, the deepest defect energy level with EC − 1.55 eV exhibits considerable degradation. The on-current decreases by 54% and on-resistance increases by 293% due to the displacement defect generated at the parasitic junction field-effect transistor (JFET) region next to the P-well. Due to the existence of a defect in the drift region, the breakdown voltage increased up to 21 V. In the double-pulse switching test, the impact of displacement defect on the power loss of SiC MOSFETs is negligible.

Computational mechanistic studies on persulfate assisted p-phenylenediamine polymerization.

p-Phenylenediamine (p-PDA) is a monomer of many important polymers such as kevlar, twaron, poly-p-PDA. Most of the noticed polymers formation is initiated by a free-radical, but their polymerization mechanism is not elucidated computationally. The proposed study helps to fully understand the frequently utilized initiator/oxidant, potassium persulfate (K2 S2 O8 ) role in the aromatic diamines polymerization, which support experimental protocols, and a polymer scope. The formation of the poly-p-PDA is studied with the density functional theory (DFT) B3LYP-D3 functional using experimental polymerization parameters (0°C and aqueous media). K2 S2 O8 initiated free-radical polymerization of p-PDA is studied in detail, taking into account sulfate free-radical (SO4 - )· , SFR, persulfate anion (S2 O8 )2- , PA and K2 S2 O8 cluster, PP. The reaction mechanism is calculated as the conversion of p-PDA to free-radical, the p-PDA free-radical attack to the next p-PDA (dimerization), ammonia extrusion from the dimer adduct, the dimer adduct conversion to the free-radical (completion of p-PDA polymerization cycle) for the polymer chain elongation. Calculations show that the dimerization step is the rate-limiting step with a 29.2kcal/mol energy barrier when SFR initiates polymerization. In contrast, the PA-assisted dimerization energy barrier is only 12.7kcal/mol. PP supported polymerization is calculated to have very shallow energy barriers completing the polymerization cycle, i.e., dimerization (TS2K, ∆G‡ = 11.6kcal/mol) and ammonia extrusion (TS3K, ∆G‡ = 6.7kcal/mol).

Inspiratory Muscle Training Strategies in Tracheostomized Critically Ill Individuals.

Inspiratory muscle training (IMT) strategies can reduce ICU length of stay and optimize recovery in critically ill patients. Our objective was to compare IMT combined with spontaneous breathing with T-piece in tracheostomized subjects. Tracheostomized critically ill subjects who were ready to wean were selected and randomly allocated to one of 2 groups: electronically-assisted IMT (EIMT) or spontaneous breathing with T-piece. Electronically assisted IMT was delivered using 30% of maximal inspiratory pressure (manual EIMT or automatically adjusted loads). The following variables were analyzed: ICU length of stay, weaning time, maximal inspiratory pressure, rapid shallow breathing index, pressure (cm H2O), power (W), flow (L/s), volume (L), and energy (J). A total of 132 patients were assessed; 104 subjects were enrolled with EIMT, n = 51 (automatic EIMT, n = 25 and manual EIMT n = 26), or spontaneous breathing with T-piece group, n = 53. The Acute Physiology and Chronic Health Evaluation II score was significantly higher (P = .02) in subjects in the manual EIMT group. Weaning time did not differ significantly between groups (8.55 ± 6.48 d and 10.86 ± 6.48 d, EIMT and spontaneous breathing with T-piece group, respectively; P = .23). Weaning success rates (75%) were lower in the manual EIMT group. Invasive mechanical ventilation time was longer but not significantly different (P = .21) in the spontaneous breathing with T-piece group. Maximal inspiratory pressure was significantly higher in the spontaneous breathing with T-piece and the automatic EIMT groups (P < .001 and P = .007, respectively). Pressure, power, and energy values were significantly higher in the manual EIMT group (P < .001, P = .003, and P = .003, respectively). IMT modalities in this trial had no significant impacts on weaning time or successful weaning rates.

Grain-resolving simulations of submerged cohesive granular collapse

We investigate the submerged collapse of weakly polydisperse, loosely packed cohesive granular columns, as a function of aspect ratio and cohesive force strength, via grain-resolving direct numerical simulations. The cohesive forces act to prevent the detachment of individual particles from the main body of the collapsing column, reduce its front velocity, and yield a shorter and thicker final deposit. All of these effects can be captured accurately across a broad range of parameters by piecewise power-law relationships. The cohesive forces reduce significantly the amount of available potential energy released by the particles. For shallow columns, the particle and fluid kinetic energy decreases for stronger cohesion. For tall columns, on the other hand, moderate cohesive forces increase the maximum particle kinetic energy, since they accelerate the initial free-fall of the upper column section. Only for larger cohesive forces does the peak kinetic energy of the particles decrease. Computational particle tracking indicates that the cohesive forces reduce the mixing of particles within the collapsing column, and it identifies the regions of origin of those particles that travel the farthest. The simulations demonstrate that cohesion promotes aggregation and the formation of aggregates. Furthermore, they provide complete information on the temporally and spatially evolving network of cohesive and direct contact force bonds. While the normal contact forces are aligned primarily in the vertical direction, the cohesive bonds adjust their preferred spatial orientation throughout the collapse. They result in a net macroscopic stress that counteracts deformation and slows the spreading of the advancing particle front.

Slow Shallow Energy States as the Origin of Hysteresis in Perovskite Solar Cells

Organic-inorganic metal halide perovskites have attracted a considerable interest in the photovoltaic scientific community demonstrating a rapid and unprecedented increase in conversion efficiency in the last decade. Besides the stunning progress in performance, the understanding of the physical mechanisms and limitations that govern perovskite solar cells are far to be completely unravelled. In this work, we study the origin of their hysteretic behaviour from the standpoint of fundamental semiconductor physics by means of technology computer aided design electrical simulations. Our findings identify that the density of shallow interface defects at the interfaces between perovskite and transport layers plays a key role in hysteresis phenomena. Then, by comparing the defect distributions in both spatial and energetic domains for different bias conditions and using fundamental semiconductor equations, we can identify the driving force of hysteresis in terms of slow recombination processes and charge distributions.

In situ Fe(III)-doped TiO2 mesocrystals catalyzed visible light photo-Fenton system

The difficulty of traditional Fenton reaction is the low conversion of Fe3+/Fe2+. The emergence of the photo-Fenton reaction can greatly improve the oxidation efficiency and Fe2+ utilization rate to a certain extent, but this system is more complicated. Here, we used the in-situ iron (Fe) ions doped titanium dioxide (TiO2) mesocrystals (MST) as a model to study in detail the effect of the catalyst's surface Fe site and oxygen defect on the photo-Fenton reaction. This in-situ doping strategy constructs oxygen vacancies (OVs) on the surface of MST to anchor Fe ions, thereby promoting the circulation of Fe3+/Fe2+. OVs form shallow energy levels in the conduction band of MST, enhancing the separation efficiency of photogenerated electrons and holes. The content of Fe ions can adjust the energy band gap of catalyst, which accelerating the transfer of photogenerated carriers on the surface with visible light. The strong interaction between OVs and Fe ions improves the synergy between photocatalysis and Fenton reaction. Under visible light irradiation, Fex+/MST exhibits efficient degradation of organic pollutants and mineralized intermediates under a wide range of pH conditions. This work provides a potential path to prepare efficient visible light photo-Fenton catalysts.

Monoatomic tantalum induces ordinary-pressure phase transition from graphite to n-type diamond

It is a key challenge to synthesize large-area n-type diamond, which significantly obstacles its application in electronic devices. Here we find that monoatomic tantalum (Ta) lets graphite transform to diamond under normal pressure, subverting the common sense that this transition needs high temperature and high pressure, opening an era for preparing large-area diamond based on large-sized graphite. This phase transition removes non-diamond component in grain boundaries forming closely-packed nanocrystalline diamond films and terminates the grains by Ta, producing high mobility n-type conductivity. First principle calculations reveal that Ta supplies electrons to the adjacent graphene layer, transforming sp2 electronic configuration to sp3 state with energy barrier of −5.38 eV/unit cell. Ta terminated diatomic layer diamond forms a shallow donor energy level of ∼0.4 eV. This supplies important significance in the fabrication of diamond-based electronic devices and gives a way for the sp2/sp3 hybridized matter to realize the phase transition under ordinary pressure.

Assessment of an intermediate working medium and cold energy storage (IWM-CES) system for LNG cold energy utilization under real regasification case

Owing to the fluctuating liquified natural gas (LNG) regasification rates in receiving terminals, LNG cold energy utilization systems face low recovery rate issue. In this work, an intermediate working medium and cold energy storage (IWM-CES) system is proposed to improve the operational flexibility and recovery rate for LNG cold energy utilization under actual regasification case. The proposed system comprises two modules, namely, cold energy recovery module and cold energy storage module. The cold energy recovery module recovers deep and shallow LNG cold energies using intermediate working mediums. The cold energy storage module acts as a buffer to promote stable cooling output. Key results revealed the maximum stable cooling output of conventional system (without cold energy storage) is constrained by the minimum regasification rate, which causes a relatively low recovery rate. On the contrary, the proposed system realizes a larger stable cooling output and enhances the cold recovery rate from 33.2% to 80.3%. Economically, the proposed system requires the injection of additional capital cost but can achieve better lifecycle profit. Environmental benefits are conducted and ultimately evaluated from users' perspective. Compared to the conventional system, the proposed system achieves the improvement of daily CO2 emissions reduction spanning 75.2 tons/day to 453.8 tons/day.

SEM: a shallow energy method for finite deformation hyperelasticity problems

SEM: a shallow energy method for finite deformation hyperelasticity problems

Hydrogen Bonding in the Dimer and Monohydrate of 2-Adamantanol: A Test Case for Dispersion-Corrected Density Functional Methods.

Weakly-bound intermolecular clusters constitute reductionist physical models for non-covalent interactions. Here we report the observation of the monomer, the dimer and the monohydrate of 2-adamantanol, a secondary alcohol with a bulky ten-carbon aliphatic skeleton. The molecular species were generated in a supersonic jet expansion and characterized using broadband chirped-pulse microwave spectroscopy in the 2–8 GHz frequency region. Two different gauche-gauche O-H···O hydrogen-bonded isomers were observed for the dimer of 2-adamantanol, while a single isomer was observed for the monomer and the monohydrate. The experimental rotational parameters were compared with molecular orbital calculations using density functional theory (B3LYP-D3(BJ), B2PLYP-D3(BJ), CAM-B3LYP-D3(BJ), ωB97XD), additionally providing energetic and electron density characterization. The shallow potential energy surface makes the dimer an interesting case study to benchmark dispersion-corrected computational methods and conformational search procedures.

Investigation of XLPE Cable Insulation Using Electrical, Thermal and Mechanical Properties, and Aging Level Adopting Machine Learning Techniques.

Hydrothermal and chemical aging tests on a 230 kV cross-linked polyethylene (XLPE) insulation cable were carried out in the present study to evaluate the degradation and aging levels qualitatively. The samples were subjected to water aging at a temperature of 80 °C, and in an aqueous ionic solution of CuSO4 at room temperature. The diffusion coefficient results indicated that the ion migration was not at the same rate in the aging conditions. The diffusion coefficient–D–of the sample immersed in an aqueous CuSO4 solution was lower than the hydrothermally aged specimens. The hydrophobicity of aged specimens decreased considerably compared to unaged samples. The distribution of trapped charges was quantitatively characterized. The presence of shallow trap energy states were observed in unaged XLPE, whereas the deep trap sites were noticed in aged specimens. In addition, the charge trap characteristics were different for positive and negative charge deposition. Various material characterization techniques, viz. dynamic mechanical analysis (DMA), tensile, contact angle, and LIBS, were further employed on the aged and virgin specimens. The tensile behavior of the hydrothermally aged specimen was degraded due to the oxidised regions, which had formed a weak spot against the mechanical stress. Reduced glass transition temperature and increased loss tangent measurements were noticed for aged specimens over their unaged counterparts. Machine learning techniques, such as the principal component analysis (PCA) and the artificial neural network (ANN) analysis, were performed on LIBS spectral data of the samples to classify the aging mechanisms qualitatively.

Global Status, Development and Prospects of Shallow and Deep Geothermal Energy

Geothermal heat pump systems (GHP), producing from shallow resources, are the spearhead of geothermal achievement and development. Global heat delivery grew exponentially to 600 PJ in 2020. GHP is the fastest growing segment in geothermal technology and one of the fastest growing application of renewable energy technologies worldwide. Other, various direct-use applications like space heating, bathing and swimming/wellness, industrial, agricultural (especially greenhouses) and aquacultural applications are based on deep, hydrothermal resources. These varieties produced worldwide 420 PJ heat in 2020; the average linear growth was, from 1995 on, about 10 % per year. It can be expected that this trend continues. Power generation, also from deep, hydrothermal resources, develops slowly but steadily, with an average growth-rate of 5 % per year, producing 95.0 TWh in 2020 in 30 countries. When comparing with other renewable power plant technologies (hydro, biomass, solar PV, wind), geothermal falls far behind – both in installed capacity (GWe) and in production (TWh). Only the annual availability of geothermal electricity is the highest among the renewables (60 %). Low geothermal productivity and growth-rate is due to extensive investments for solar PV and wind, which are by orders of magnitude higher than for geothermal power. The technology of Enhanced Geothermal Systems (EGS), based on deep, petrothermal resources, could be a game-changer. Requirements, problems and research goals to find solutions are presented.

Nonfused Ring Electron Acceptors for Efficient Organic Solar Cells Enabled by Multiple Intramolecular Conformational Locks

Nonfused ring electron acceptors (NFREAs) have become a research hotspot of organic solar cells (OSCs) due to their facile synthesis. However, efficient NFREAs not only need to maintain the advantages of FREAs but also need to optimize the molecular structure of the conjugate backbone to achieve good planarity. Therefore, choosing the appropriate building blocks is a prerequisite for achieving efficient OSCs. Here, two simple NFREAs 2T2CSi-4F and 4T2CSi-4F, based on diester-thieno[3,2-b]thiophene (2T2C) as the central core unit and 4,4-di-2-ethylhexyl-dithieno[3,2-b:2′,3′-d]silole (DTSi) or thieno[3,2-b]thiophene (TT) as the conjugated linking unit, were designed and synthesized. The density function theory results manifest that the oxygen atom of the thiophene ester group can form O···S interaction with the sulfur atom. Introducing noncovalent interactions can form multiple intramolecular conformational locks, which greatly enhance the molecular planarity. In addition, 2T2CSi-4F with a symmetrical structure exhibits red-shifted absorption, shallower lowest unoccupied molecular orbital energy levels, and stronger crystallinity than 4T2CSi-4F. Therefore, the PBDB-T:2T2CSi-4F device with favorable molecular packing and morphology achieves a higher power conversion efficiency of 10.04%. Our work demonstrates that the 2T2C unit and multimolecular conformational lock strategy are conducive to the development of efficient NFREAs.

Nanocrystalline gadolinium doped ZnO: An excellent photoluminescent material and efficient photocatalyst towards optoelectronic and environment remedial applications

Simple wet-chemical method of synthesis was adopted for the preparation of Gd doped ZnO nanoparticles along with pristine ZnO aiming towards the improvisation of photoluminescence (PL) and photocatalytic (PC) properties of ZnO by rare earth doping. X-ray diffraction measurement reveals the formation of wurtzite ZnO without any impurity phases related to the Gd dopants. Effective increase in the crystallite size of ZnO has been observed with Gd doping along with microstrain increment as obtained from the XRD results. A notable change in the particle morphology of ZnO is also noticed from FESEM study as Gd ions are incorporated into ZnO lattice. FTIR spectra indicate the formation new bands linked with Gd–O in the doped samples along with Zn–O bonds. Absorbance study in UV–Vis region exhibits a decrease in ZnO band gap as Gd ions are incorporated. Gd doping introduces shallow energy levels in the band gap resulting the shrinking of band gap. PL measurement shows an enhancement in the blue emission band with the introduction of new orange-red emission initiated by Gd doping. Photocatalytic measurement shows that the Gd-ZnO sample demonstrates better degradation efficiency in degrading organic dyes like methyl orange and methylene blue as compared to pure ZnO. Doping of Gd ions results in a better charge separation efficiency and suppression in carrier recombination which leads to such enhanced photodegradation efficiency. Gd-ZnO samples display the quality of being highly stable after fourth cycle of degradation hence can be used for treating industrial waste materials in an effective manner.

P-type ZnO for photocatalytic water splitting

Global environmental pollution and energy crisis have been regarded as important issues in recent years, making people aware of the need to develop environmentally friendly energy sources. ZnO photocatalysts play a key role in the development of hydrogen generation from water splitting via a photocatalytic strategy. ZnO generally exhibits n-type conductivity, and the difficulty in preparing p-type for forming stable p–n junctions limits its large-scale application. The doping of related elements into ZnO can introduce new shallow acceptor energy levels to achieve p-type conductivity and also overcome the barrier of the wide bandgap to accomplish higher light absorption efficiency. Meanwhile, the realization of p-type ZnO can facilitate the construction of ZnO-based homojunctions and heterojunctions, which will accelerate the photoinduced charge separation and then enhance the photocatalytic water splitting performance. In this Perspective, we discuss recent advances in the fabrication of p-type ZnO by different dopants and describe the benefits of p-type ZnO compared to n-type ZnO for photocatalytic applications. Finally, we analyze the difficulties and challenges of p-type ZnO employed in photocatalytic water splitting and consider the future advancement of p-type ZnO in an emerging area.

Comparison of Total Ionizing Dose Effects in SOI FinFETs Between Room and High Temperature

The synergetic effects of total ionization dose and high-temperature stress of SOI FinFETs are investigated under ON-state bias condition. The experiments and TCAD simulations are employed to analyze the influence of different trapped-charges in the gate and buried oxide on the threshold voltage and mobility variations on the ON-state current of the devices. Results show that the threshold voltage degradation worsens for n-SOI FinFETs but weakens for the p-SOI FinFETs. Also, the ON-state current of n-SOI FinFETs is significantly enhanced while the change of p-SOI FinFETs is weak under the synergetic effects. The threshold voltage degradation induced by synergetic effects for both n- and p-type SOI FinFETs can exceed the linear superposition of the two types of stresses, which may be related to the thermal release of trapped charges in the gate oxide. The enhanced degradation in the n-SOI FinFETs compared with the p-SOI FinFETs may result from the shallow energy level electron traps in HfO2. Besides, for both n- and p-type SOI FinFETs, the ON-state current variations under the synergetic effects depend on the competitive process of threshold voltage variation and the mobility fluctuation.

Ostracoda (Crustacea) from the Lower Jurassic of northeastern Thailand: stratigraphic and paleoenvironmental implications

Freshwater ostracods were recovered from limestone strata belonging to the Nam Phong Formation exposed at Ban Non Tum section in Chaiyaphum Province, northeastern Thailand. The examined rocks were collected above the oldest known dinosaur footprints site in Thailand. All recovered ostracods belong to the Superfamily Darwinuloidea and were attributed to three species: Suchonellina sarytirmensis (Sharapova) in Mandelstam, 1947, Suchonellina. sp. A and Suchonellina sp. B. The ostracods represent the first known record of Jurassic darwinuloideans in Southeast Asia. The ostracod assemblage and microfacies are indicative of deposition in a shallow and low energy fluvio-lacustrine regime.