Pseudo Energy Research Articles

Comparative Analysis of Polystyrene versus Zirconia Beads on Breakage Kinetics, Heat Generation, and Amorphous Formation during Wet Bead Milling.

This study determined process conditions under which polystyrene (CPS) and zirconia (YSZ) beads cause similar breakage kinetics and temperature rise during manufacturing of drug nanosuspensions via wet bead milling and explored relative advantages of CPS beads, particularly for stress-sensitive compounds. Besides temperature and particle size measurements, a microhydrodynamic-based kinetic model simulated the conditions for CPS to achieve breakage rates equivalent to those of YSZ. A power law correlation was applied to find conditions conducive to temperature equivalency. The maximum contact pressure and pseudo energy dissipation rate were calculated under these equivalency conditions. When bead loading for CPS was increased to match with YSZ, lower temperature at similar breakage conditions or faster breakage at the same temperature was achieved. Increasing the tip speed did not provide any notable advantages for CPS over YSZ in terms of breakage kinetics or temperature. However, under all conditions investigated, CPS beads exhibited markedly lower maximum contact pressure and pseudo energy dissipation rate, which may correlate with reduced mechanically induced amorphization during milling. A proof-of-concept study demonstrated that a mechanical stress-sensitive drug had lower amorphous generation with CPS compared to YSZ. Therefore, CPS beads are a promising alternative to YSZ beads, especially when used at the highest feasible loading.

Error analysis of positivity-preserving energy stable schemes for the modified phase field crystal model

In this paper, we introduce second-order numerical schemes for the modified phase field crystal (MPFC) model that are decoupled, linear, positivity-preserving, and unconditionally energy-stable. These schemes adopt a positivity-preserving auxiliary variable method to explicitly handle the nonlinear potential function, resulting in decoupled linear systems with constant coefficients at each time step. We rigorously demonstrate that the auxiliary variables remain positive throughout all time steps and prove the unconditionally energy stability of these schemes. The stability pertains to a discrete modified energy, rather than the original free energy or the pseudo energy of the MPFC system. Moreover, a detailed error analysis is provided. A series of numerical experiments are conducted to validate the accuracy and efficiency of our proposed schemes.

A composite indicator-based method to assess the energy security of Nepal and prospects of cross-border electricity sharing in South Asia

Scholars recommend country (or region) specific energy security indices capable of adequately considering local specificities in the absence of a ‘universal’ index. Such an index is not available for Nepal. Hence, this study is the first to develop the Energy Security Composite Index of Nepal (ESCOIN), applying a comprehensive indicator-based approach to quantify energy security (ES) of Nepal. We build upon the notion that a country is able to trade energy when it is energy secure. We quantify Nepal's energy security and qualitatively assess the prospect for regional power trade in South Asia. A long list of 77 indicators is compiled from an extensive review of international literature. Based on the context, applicability to Nepal, data availability and conditions of multi-collinearity, this list of indicators is narrowed down to 21. Principal Component Analysis is then applied to evaluate the importance of the components for ESCOIN. Our results show that Nepal has consistently held a boundary position between “moderate” to “high” classes of ES in the last decade. We identify key reasons for this. First, the country's domestic sector is over-reliant on traditional fuels (dry-dung, firewood and agricultural residues). Second, Nepal faces a problem of suppressed demand in the absence of energy-intensive development activities in all productive sectors of the economy. Third, the growth in the energy demand is met only marginally by domestic hydropower and other renewables, and largely by increasing imports. Hence, we surmise a ‘pseudo energy secure’ state for Nepal. Although efforts are underway, electricity trade with China, Bangladesh and other South Asian Association for Regional Cooperation (SAARC) countries is economically difficult and technically challenging. Hence, cross-border electricity trading, particularly with India, can be seen as an opportunity for Nepal provided considerable infrastructural development occurs, institutional capacity is strengthened, and genuine political commitment and trust are sustained. Moreover, Nepal should focus on achieving self-sufficiency in energy through domestic hydropower and renewable sources and aim to stabilize energy consumption rather than being overly ambitious of exports, at least in the near future.

Prediction of NbTaTiZr-based high-entropy alloys with high strength or ductility: First-principles calculations

Refractory high-entropy alloys (RHEAs) have a great potential in high-temperature electronics, extensive aerospace and biomedical applications due to their unique strength and ductility. Herein, the effects of alloying elements on the mechanical and electronic properties of NbTaTiZrX (X = V, Mo, Hf, W and Re) RHEAs are investigated by using the density functional theory (DFT) in combination with the special quasi-random structure (SQS) and virtual crystal approximation (VCA) methods. The calculated results show that alloying of Mo, W and Re with high elastic modulus can enhance the strength and the hardness of RHEAs. Among them, NbTaTiZrRe RHEA with the best strengthening effect has a yield strength of exceeds 2 GPa, which is notably higher than other considered high-entropy alloys. For alloying of V and Hf, the ductility of RHEAs is improved, and among which, NbTaTiZrHf RHEA has a relatively best ductility. Compared with other NbTaTiZrX RHEAs, spiral dislocations in NbTaTiZrHf RHEA are more prone to nucleate, and which confirms its excellent ductility. Moreover, the reduction of pseudo energy gaps and the formation of Hf–Hf strong metallic bonds further confirm its metallic ductility from the electronic density of states and charge density. The theoretical predictions in this study are congruent with the existing experimental data, and have certain theoretical guidance relevance for enhancing the mechanical characteristics of NbTaTiZrX (X = V, Mo, Hf, W and Re) RHEAs.

Theoretical study of CDW phases for bulk NbX2 (X = S and Se).

In most two-dimensional transition metal chalcogenides, the superconducting phase coexists with the charge density wave (CDW) phase. There exists at least one case, i.e. bulk 2H-NbS2, that does not conform to this picture. Scientists have shown great interest in trying to experimentally find the CDW phase of bulk NbS2 since 1975. Is there any theoretically more stable thermodynamic state than its higher-temperature metal phase, especially in the case of charge injection? Theoretically more stable CDW bulk configurations (TC for 2H-NbS2 and TTs for 2H-NbSe2) with partial pseudo energy gaps were predicted through the harmonic phonon softening theory and first-principles calculations. The ratios of larger to smaller pseudo gaps around K-H segment in the Brillouin zone for CDW phases are basically equal to those of superconductivity phases for bulk 2H-NbX2 (X = S and Se). The CDW phase should coexist with its superconductor state below the critical temperature rather than the metal phase for bulk 2H-NbS2. The presence of CDW phase should be more easily observed experimentally when the injected charge reaches 0.5e/Nb18S36 for bulk 2H-NbS2. Our calculations of density of state (DOS) indicated that, during Nb atoms contracting to form the CDW phases with symmetry breaking in the in-plane direction, dominant conductive carriers are always of p-type for bulk 2H-NbS2 while the alternation of carrier type from p-type to n-type occurs for bulk 2H-NbSe2. The Fermi level continuously drops and then the M-L segment of the out-of-plane energy band emerges from the Fermi surface, which corresponds to the reversal of p-n type sign. Lifshitz transition of pocket-vanishing types occurs in the out-of-plane direction without symmetry breaking during the geometrical structural phase transition for bulk 2H-NbSe2. Our calculations have theoretically addressed the long-standing coexistence issue of CDW and superconducting phases.

The electronic structures, elastic and thermodynamic properties of alkali earth metal doped Ni3Ti intermetallics

The formation energy, electronic structure, elastic and thermodynamic properties of close–packed hexagonal Ni3Ti intermetallics doped with alkaline earth metals (Be, Mg, Ca, Sr, Ba) have been calculated by first principles method. The influences of pressure and strain on elastic properties are also investigated. It shows that the alkali earth metals tend to occupy the Ti sites preferentially. The formation energy of the doping system increases gradually with the doping concentration increase. The calculated electronic properties indicate the pseudo–energy gap of the system narrows down when the doping atomic radius increases, indicating the proportion of covalent bond decreases gradually with atomic radius increase, resulting in the elastic strength weakened and the ductility enhanced. The Debye temperature and thermal conductivity also decrease with atomic radius increase. The elastic property of Ni12Ti4-xMx (M = Be, Mg, Ca, Ba) is sensitive to strain index except Ni12Ti4-xSrx while the applied strain restrains the elastic anisotropy to some extent.

Nearly Hamiltonian dynamics of laser systems

The Arecchi-Bonifacio (or Maxwell-Bloch) model is the benchmark for the description of active optical media. However, in the presence of a fast relaxation of the atomic polarization, its implementation is a challenging task even in the simple ring-laser configuration, due to the presence of multiple timescales. In this paper we show that the dynamics is nearly Hamiltonian over timescales much longer than those of the cavity losses. More precisely, we prove that it can be represented as a pseudo spatiotemporal pattern generated by a nonlinear wave equation equipped with a Toda potential. The existence of two constants of motion (identified as pseudo energies), thereby elucidates the reason why it is so hard to simplify the original model: the adiabatic elimination of the polarization must be accurate enough to describe the dynamics correctly over unexpectedly long timescales. Finally, since the nonlinear wave equation with Toda potential can be simulated on much longer times than the previous models, this opens up the route to the numerical (and theoretical) investigation of realistic setups.

Unconditionally strong energy stable scheme for Cahn–Hilliard equation with second‐order temporal accuracy

We propose an unconditionally gradient stable scheme for solving the Cahn–Hilliard equation with second‐order accuracy in time using the effective time‐step analysis. The conventional convex splitting scheme is one of the most well‐known methods for solving gradient flows, and it guarantees both energy stability and first‐order accuracy in time. Recently, there are some researches, which are extended to the second‐order accuracy; however, most of results provide the proof of energy stability for a modified (pseudo) energy or in a weak sense. In this paper, we prove the energy stability of the proposed method with respect to the Ginzburg–Landau free energy functional. Moreover, the unique solvability, mass conservation, and accuracy of the proposed scheme are also proven based on the convex splitting approach. The numerical experiments are presented to show convergence rate, mass conservation, energy stability, and phase separation are in good agreement with the theory.

Characterizing thermal fatigue behaviors of asphalt concrete waterproofing layer in high-speed railway using customized overlay test

The novel asphalt concrete waterproofing layer (ACWL) in high-speed railway faced a severe challenge from thermal fatigue cracking, while there was absence of a feasible evaluation method for this unique thermal fatigue mode. In this study, the overlay test (OT) was customized in terms of test temperature and open displacement to simulate the cyclic thermal load on in-service ACWL and characterize the thermal fatigue behaviors of railway asphalt mixtures. Four classical and two dissipated energy-derived indicators, namely maximum tensile load (L0), cracking rate index (CRI), the ratio of transitional tensile load L1 to L0 (L1/L0), pseudo fracture energy (PFE), initial dissipated energy (IDE), and cumulative dissipated energy (CDE), were utilized to evaluate the fatigue characteristics. It was found that the OT at a test temperature of 20 °C and open displacement of 0.6 mm was the most efficient in distinguishing fatigue characteristics, and the CRI, L1/L0, IDE, and PFE were statistically recognized to be feasible and effective. In addition, railway asphalt mixtures could achieve a 10-year fatigue life under moderate conditions while might crack rapidly at a low temperature and a large open displacement. Meanwhile, several indicators, including L0, CRI, L1/L0, PFE, and CDE, demonstrated linear relationships with the fatigue life on a normal or log scale at low temperatures, implying their potential to predict fatigue life. Finally, a Weibull damage model was applied based on load ratio-based damage degree, which had fair linear correlation with actual damage degree, to correlate with the thermal fatigue damage process. As expected, the proposed evaluation method, indicator, and fatigue damage model could fairly characterize the thermal fatigue behaviors of railway asphalt mixtures and further guide the construction and maintenance of ACWL.

Error estimates for the Scalar Auxiliary Variable (SAV) schemes to the modified phase field crystal equation

We design first-order and second-order time-stepping schemes for the modified phase field crystal model based on the scalar auxiliary variable method in this work. The model is a nonlinear sixth-order damped wave equation that includes both elastic interactions and diffusive dynamics. Our schemes are linear and satisfy the unconditional energy stability with respect to pseudo energy. We also rigorously estimate the errors of the numerical schemes. Finally, some numerical tests are presented to validate our theoretical results.

Homogenizing spatially variable Young modulus using pseudo incremental energy method

Homogenization is the process of representing a spatially variable property by an equivalent (or effective) homogenous property. The second and fifth authors proposed the pseudo incremental energy (PIE) method to represent a spatially variable Young’s modulus by an effective Young’s modulus for a rigid footing problem, the overall Young’s modulus actually “felt” by the footing. The effective Young’s modulus is based on a non-uniform geometric average with weights provided by PIE. It performs better than the conventional uniform geometric average at a cost of computing PIE weights from one deterministic finite element analysis. The current paper extends the previous work on PIE in four respects. First, a new PIE procedure is developed to address a known issue in the previous PIE. Second, the applicability of the new PIE is verified for a wide variety of two-dimensional (2D) and three-dimensional (3D) geotechnical problems, including 2D retaining wall, 2D & 3D axially loaded pile, 2D & 3D laterally loaded pile, and 2D & 3D base heave. Third, the new PIE is extended to problems with layered soils, where each layer is modeled by a separate random field. Finally, the new PIE is implemented to a real case study of a 3D rigid footing. The new PIE method can approximately match the results from a random finite element analysis (RFEA) at the realization level (not ensemble statistics level) at an acceptable cost of one deterministic finite element analysis. It is much cheaper than RFEA that requires hundreds of thousands of deterministic analyses. It is slightly more costly than the original PIE.

NMR-Based Configurational Assignments of Natural Products: Gibbs Sampling and Bayesian Inference Using Floating Chirality Distance Geometry Calculations.

Floating chirality restrained distance geometry (fc-rDG) calculations are used to directly evolve structures from NMR data such as NOE-derived intramolecular distances or anisotropic residual dipolar couplings (RDCs). In contrast to evaluating pre-calculated structures against NMR restraints, multiple configurations (diastereomers) and conformations are generated automatically within the experimental limits. In this report, we show that the “unphysical” rDG pseudo energies defined from NMR violations bear statistical significance, which allows assigning probabilities to configurational assignments made that are fully compatible with the method of Bayesian inference. These “diastereomeric differentiabilities” then even become almost independent of the actual values of the force constants used to model the restraints originating from NOE or RDC data.

Efficient linear and unconditionally energy stable schemes for the modified phase field crystal equation

In this paper, we construct efficient schemes based on the scalar auxiliary variable (SAV) block-centered finite difference method for the modified phase field crystal (MPFC) equation, which is a sixth-order nonlinear damped wave equation. The schemes are linear, conserve mass and unconditionally dissipate a pseudo energy. We prove rigorously second-order error estimates in both time and space for the phase field variable in discrete norms. We also present some numerical experiments to verify our theoretical results and demonstrate the robustness and accuracy.

Effect of sputtering power on the first order magnetization reversal, reversible and irreversible process in Fe71Ga29 thin films

We report on the first-order reversal curves (FORC) of magnetization and effect of defects on magnetization process in Fe71Ga29 thin films with different values of sputtering power (50 – 120 W). Phase purity of the thin films was confirmed by grazing incidence X– ray diffraction (GI-XRD). The reversible and irreversible contributions to the magnetization are evidenced through the minor loop parameter such as pseudo hysteresis loss (WF*) and energy loss coefficient (WF0). In particular, the energy loss coefficient is found to decrease from 28 × 106 (A/m. mT) at 50 W to 21 × 106 (A/m. mT) at 120 W, which signifies a decrease in domain wall resistance. FORC infers narrow switching, which leads to low coercivity distribution at 120 W as a result of less defects.

Low Recombination Firing-Through Al Paste for N-Type Solar Cell with Boron Emitter

A kind of low recombination firing-through screen-printing aluminum (Al) paste is proposed in this work to be used for a boron-diffused N-type solar cell front side metallization. A front side fire-through contact (FTC) approach has been carried out for the formation of local contacts for a front surface passivated solar cell. With a low contact resistivity (ρc) of 1.0 mΩ·cm2, good ohmic contact between the boron-doped front surface of the silicon sample and the Al paste was realized. To obtain a good energy conversion efficiency, a balance can be achieved between the open circuit voltage (Voc) and contact resistivity (ρc) of the cell by combining suitable Al powders and appropriate additives. The detailed micro-contact difference in Si/metallization between the firing-through Al paste and silver-aluminum (Ag-Al) paste was analyzed. The dark saturation current density beneath the metal contact (J0, metal) of the Si/metallization region using our firing-through Al paste was discussed, which was proven to be 61% lower than using Ag-Al paste. The pseudo energy conversion efficiency of the cell using Al paste measured by Suns-VOC was also higher than using Ag-Al paste. The role of Al paste in low surface metal recombination is discussed. The utilization of this new kind of Al paste was much cheaper and more convenient, compared to the traditional process using Ag or Ag-Al paste.

Inertia–Gravity Waves Breaking in the Middle Atmosphere at High Latitudes: Energy Transfer and Dissipation Tensor Anisotropy

Abstract We present direct numerical simulations of inertia–gravity waves breaking in the middle–upper mesosphere. We consider two different altitudes, which correspond to the Reynolds number of 28 647 and 114 591 based on wavelength and buoyancy period. While the former was studied by Remmler et al., it is here repeated at a higher resolution and serves as a baseline for comparison with the high-Reynolds-number case. The simulations are designed based on the study of Fruman et al., and are initialized by superimposing primary and secondary perturbations to the convectively unstable base wave. Transient growth leads to an almost instantaneous wave breaking and secondary bursts of turbulence. We show that this process is characterized by the formation of fine flow structures that are predominantly located in the vicinity of the wave’s least stable point. During the wave breakdown, the energy dissipation rate tends to be an isotropic tensor, whereas it is strongly anisotropic in between the breaking events. We find that the vertical kinetic energy spectra exhibit a clear 5/3 scaling law at instants of intense energy dissipation rate and a cubic power law at calmer periods. The term-by-term energy budget reveals that the pressure term is the most important contributor to the global energy budget, as it couples the vertical and the horizontal kinetic energy. During the breaking events, the local energy transfer is predominantly from the mean to the fluctuating field and the kinetic energy production is in balance with the pseudo kinetic energy dissipation rate.

A ductile phase-field model based on degrading the fracture toughness: Theory and implementation at small strain

A reliable prediction of structural failure is extremely important in industrial applications. The promising phase-field model has been intensively studied in fracture simulation and been validated by experiments to effectively predict crack initiation, propagation as well as branching. Experimentally motivated, a variety of phase-field models have been proposed for ductile fracture, which redefine either the fracture driving force H consisting of both the elastic energy and the pseudo plastic energy or modify the degradation function g(d) of the fracture driving force H. Different from the existing approaches, this work formulates a novel ductile phase-field model by defining the fracture toughness Gc depending on the accumulated plastic strain, i.e. the local fracture toughness decreases due to increased plastic deformation. The phase-field driving force H is still defined only consisting of the elastic strain potential based on the definition of Griffith-type fracture. As a result, the locally increasing H and the locally decreasing Gc govern the ductile fracture evolution simultaneously. This approach is formulated for small strain by coupling the classical Von Mises plasticity and, subsequently, is implemented into the context of the Finite Element (FE) framework. Several representative examples are evaluated to demonstrate the capabilities of the model, and corresponding findings and perspectives are consequently summarized.

Spacetimes with different forms of energy–momentum tensor

The object of the present paper is to characterize spacetimes with different types of energy–momentum tensor. At first we consider spacetimes with pseudo symmetric energy–momentum tensor T. We obtain a necessary and sufficient condition for a spacetime with pseudo symmetric energy–momentum tensor to be a pseudo Ricci symmetric spacetime. Next we consider the spacetimes with Codazzi type of energy–momentum tensor and several interesting results are pointed out. Moreover, some results related to perfect fluid spacetimes with different forms of energy–momentum tensors have been obtained. We study spacetimes with quadratic Killing energy–momentum tensor T and show that a GRW spacetime with quadratic Killing energy–momentum tensor is an Einstein space. Finally, we have considered general relativistic spacetimes with semisymmetric energy–momentum tensor and obtained some important results.

Propose Image Analysis Tools to Improve Radiology Interpretation

There are many image analysis tools and enhancement techniques that can improve image interpretation. In ports around the world, customs agencies use many x-ray machines to scan cars, trucks, luggages, and containers [1] . Many of these systems use imaging adjustment techniques which are not being used in medical radiology departments. This paper is purpose using of these image adjustment tools in the radiology field which may help in improving image recognition. As well, this paper will explain in details the uses of these image adjustment tools and what they can be used for in radiology departments. This paper will take rapiscan systems as an example of the companies that produces x-ray machines that used by customs agencies to scan cars, trucks, luggages, containers, etc. The tools and techniques that will be discussed in this paper including the following; pseudo color, quick enhancement (Q), crystal clear (CC), atomic number (Z), invert option (INT), energy option (HI and LO), histogram option, edge enhancement (E and E 2 ), and enhancement tools (log 1, 2, 3, and 4).

Visualization of the macroscopic physical properties through the pseudo energy landscape

Visualization of the macroscopic physical properties through the pseudo energy landscape