Traditional Solution Approaches Research Articles

Solution mediated halide exchange engineering for the fabrication of a thick CsPbCl3 film and its application in photovoltaics with outstanding performance.

It is a big challenge to prepare thick CsPbCl3 films using traditional solution processed approaches owing to the low solubility of precursors of PbCl2 and CsCl in common solvents. Here, we propose an indirect solution process to prepare thick CsPbCl3 films. In this new approach, a mother film of CsPbBr3 is first prepared through a solution process, and then it is dipped into a diluted HCl/methanol solution. During the dipping process, it triggers a halide exchange reaction between Br- and Cl-, and it eventually produces a thick CsPbCl3 film (∼400 nm) with high quality and purity. Afterwards, a carbon based hole transportation layer (HTL) free solar cell with a configuration of FTO/TiO2/CsPbCl3/carbon is constructed, and it delivers an average PCE of 1.23% and an outstanding PCE of 1.39% in a batch of PSCs. Meanwhile, the solar cell maintains its 82% initial PCE after storage in open air for 31 days. This work overcomes the obstacle of the traditional solution approach for the preparation of CsPbCl3 films, which makes it promising for preparing various CsPbCl3 film-based devices via a solution process.

Algorithms and Data Structures for Matrix-Free Finite Element Operators with MPI-Parallel Sparse Multi-Vectors

Traditional solution approaches for problems in quantum mechanics scale as O ( M 3 ), where M is the number of electrons. Various methods have been proposed to address this issue and obtain a linear scaling O ( M ). One promising formulation is the direct minimization of energy. Such methods take advantage of physical localization of the solution, allowing users to seek it in terms of non-orthogonal orbitals with local support. This work proposes a numerically efficient implementation of sparse parallel vectors within the open-source finite element library deal.II. The main algorithmic ingredient is the matrix-free evaluation of the Hamiltonian operator by cell-wise quadrature. Based on an a-priori chosen support for each vector, we develop algorithms and data structures to perform (i) matrix-free sparse matrix multivector products (SpMM), (ii) the projection of an operator onto a sparse sub-space (inner products), and (iii) post-multiplication of a sparse multivector with a square matrix. The node-level performance is analyzed using a roofline model. Our matrix-free implementation of finite element operators with sparse multivectors achieves a performance of 157 GFlop/s on an Intel Cascade Lake processor with 20 cores. Strong and weak scaling results are reported for a representative benchmark problem using quadratic and quartic finite element bases.

Integrating slacks-based measure of efficiency and super-efficiency in data envelopment analysis

In this paper, we develop an integrated model for slacks-based measure (SBM) simultaneously of both the efficiency and the super-efficiency for decision-making units (DMUs) in data envelopment analysis (DEA). Unlike the traditional solution approaches in which we need to identify the efficient DMUs by the SBM model of Tone (2001) [20] before applying the super SBM model of Tone (2002) [21] for the DMUs to achieve their super-efficiency scores, our integration can obtain the efficiency scores of the inefficient DMUs and the super-efficiency scores of the efficient DMUs by solving simultaneously these two models by an one-stage approach. Therefore, it may save computational time for large-scale practical applications. Due to the non-linearity in the objective function of this integrated model, we develop a linearisation technique to deal with the non-linear model. The numerical experiments, carried out on several examples in the literature and a case study, have demonstrated the accuracy and the computational time effectiveness of our proposed model as compared with the traditional solution approaches.

Computer Simulation of the Ternary Problem – Technical Aspects and Possibilities

Interaction between groundwater contaminants (e.g. radioactive elements), soil and humic matter plays a crucial role in transport prognoses. This type of interaction, denoted as the ternary problem, may speed up propagation of a contaminant in comparison with the case in the absence of humic compounds. It is very difficult (almost impossible) to find a simple description of the ternary problem in the form of chemical equations. This difficulty is caused by the complex nature of humic substances. Rather than with particular chemical equations, the ternary problem is commonly described by schematic expressions which consider groups of species. The usual approach for the problem formulation is grouping of species resulting in a system of differential and algebraic equations (DAE). This article introduces a different approach allowing a semi-automatic formulation of a system of ordinary differential equations (ODE) for the same problem. The proposed method enables to avoid an operator-splitting already during the model formulation process. The approach for the model formulation and its solution has been implemented using two different open-source software packages. The results have been compared with reference results of a traditional solution approach using DAE systems. The implementation in Python verified the possibility of automation of the formulation and solution. A sensitivity analysis has been performed to evaluate the behaviour of the system with respect to parameter variation.

Radial structure of the constricted positive column: Modeling and experiment.

We present a detailed self-consistent model of a positive column in argon glow discharge at moderate pressures and currents. This model describes the discharge transition between diffuse and constricted states. The model includes an extensive set of plasma chemical reactions and equation for inhomogeneous gas heating. The nonequilibrium behavior of an electron distribution function is also considered. One of the main features of the model is an accurate treatment of radiation trapping by solving the Holstein-Biberman equation directly. Influence of the radiation trapping on macroscopic parameters of the constricted positive column is studied. We propose a method for solving a boundary-value problem, including particle and energy balance equations for electrons, ground state atoms, atomic and molecular ions, and excited species. Unlike traditional solution approaches for similar systems, the method provides continuous Z- and S-shaped characteristics of discharge parameters, describing hysteresis in transition between diffuse and constricted discharge regimes. Performed experiments include measurements of volt-ampere characteristics and spectroscopic study of radial density profiles of excited atoms by measuring line emission and absorption, and electrons by measuring bremsstrahlung intensity. The role of resonance radiation trapping in spatial redistribution of 1s and 2pstates of argon is demonstrated. Results of modeling are compared to the experimental data.

An Investment Evaluation of a RFID-Enabled Meat Supply Chain: A Multi-Criteria Approach

In recent years, consumers have become increasingly concerned about the safety and quality of meat they purchase from supermarkets. A study by Mohammed [1] proposed a RFID (Radio Frequency Identification)-enabled monitoring system for meat supply chains to improve the traceability of meat products throughout their entire supply chain with the aim of maintaining product safety. This paper extends that work to examine the economic feasibility for the proposed RFID-enabled monitoring system. To this aim, a multi-criteria optimization model was developed. The considered criteria were minimizing the total cost, maximizing consumer satisfaction, maximizing product freshness and maximizing profits. In order to obtain Pareto solutions from the developed model, a new solution approach was developed and its results were compared to two traditional solution approaches. A case study was applied conducive to an examination for the applicability of the developed model and the performance of the proposed solution approaches. Results have proved the feasibility of the proposed RFID-enabled monitoring system in terms of economic costs in addition to the capability of the developed optimization model in obtaining a trade-off among the considered criteria.

Warehouse location and two-echelon inventory management with concave operating cost

In this paper, we study a location–inventory network design problem which jointly optimises the warehouse location, the warehouse–retailer assignments, the warehouse–retailer echelon inventory replenishment and the safety stock-level decisions over an infinite planning horizon. The consideration of the facility operating cost, the safety stock cost and the two-echelon inventory cost results in an MIP model with several nonlinear terms. Due to the complex trade-offs among the various costs and multiple nonlinear terms in the model, traditional solution approaches no longer work for this problem. We outline a polymatroid cutting-plane approach based on the submodular property of the cost terms to address this problem. Computational results demonstrate that the cutting-plane method based on polymatroid inequalities can efficiently solve randomly generated instances with moderate sizes.

An efficient local search heuristic for the double row layout problem with asymmetric material flow

The double row layout problem (DRLP) consists of arranging a number of rectangular machines of varying widths on either side of a corridor to minimize the total cost of material handling for products that move between these machines. This problem arises in the context of many production environments, most notably semiconductor manufacturing. Because the DRLP contains both combinatorial and continuous aspects, traditional solution approaches are not well suited to obtain solutions within a reasonable time. Moreover, previous approaches to this problem did not consider asymmetric flows. In this paper, an effective local search procedure featuring linear programming is proposed for solving the DRLP with asymmetric flows (symmetric flows being a special case). This approach is compared against several constructive heuristics and solutions obtained by a commercial mixed integer linear programming solver to evaluate its performance. Computational results show that the proposed heuristic is an effective approach, both in terms of solution quality and computational effort.

Reading between the lines: Subtle stereotype threat cues can motivate performance

This research examined the impact of subtle stereotype threat cues (i.e., no mention of group differences) on motivation. Recent research suggests that blatant manipulations of threat motivate targets to attempt to disprove relevant stereotypes, but this motivation can, in turn, undermine performance. On the other hand, research suggests that subtle cues lead individuals to expend resources so as to reduce uncertainty about the presence of bias. We tested the possibility that subtle threat could also motivate individuals to try to disprove stereotypes. The results indicate that similar to blatant threat, subtle threat cues motivated participants, and this motivation directly led to worse performance in this research because of an over-reliance on traditional solution approaches and a lack of flexibility (i.e., inflexible perseverance).

Chromatographic and Traditional Albumin Isotherms on Cellulose: A Model for Wound Protein Adsorption on Modified Cotton

Albumin is the most abundant protein found in healing wounds. Traditional and chromatographic protein isotherms of albumin binding on modified cotton fibers are useful in understanding albumin binding to cellulose wound dressings. An important consideration in the design of cellulosic wound dressings is adsorption and accumulation of proteins like albumin at the solid-liquid interface of the biological fluid and wound dressing fiber. To better understand the effect of fiber charge and molecular modifications in cellulose-containing fibers on the binding of serum albumin as observed in protease sequestrant dressings, albumin binding to modified cotton fibers was compared with traditional and chromatographic isotherms. Modified cotton including carboxymethylated, citrate-crosslinked, dialdehyde and phosphorylated cotton, which sequester elastase and collagenase, were compared for their albumin binding isotherms. Albumin isotherms on citrate-cellulose, cross-linked cotton demonstrated a two-fold increased binding affinity over untreated cotton. A comparison of albumin binding between traditional, solution isotherms and chromatographic isotherms on modified cellulose yielded similar equilibrium constants. Application of the binding affinity of albumin obtained in the in vitro protein isotherm to the in vivo wound dressing uptake of the protein is discussed. The chromatographic approach to assessment of albumin isotherms on modified cellulose offers a more rapid approach to evaluating protein binding on modified cellulose over traditional solution approaches.

Practical solution techniques for first-order MDPs

Many traditional solution approaches to relationally specified decision-theoretic planning problems (e.g., those stated in the probabilistic planning domain description language, or PPDDL) ground the specification with respect to a specific instantiation of domain objects and apply a solution approach directly to the resulting ground Markov decision process (MDP). Unfortunately, the space and time complexity of these grounded solution approaches are polynomial in the number of domain objects and exponential in the predicate arity and the number of nested quantifiers in the relational problem specification. An alternative to grounding a relational planning problem is to tackle the problem directly at the relational level. In this article, we propose one such approach that translates an expressive subset of the PPDDL representation to a first-order MDP (FOMDP) specification and then derives a domain-independent policy without grounding at any intermediate step. However, such generality does not come without its own set of challenges—the purpose of this article is to explore practical solution techniques for solving FOMDPs. To demonstrate the applicability of our techniques, we present proof-of-concept results of our first-order approximate linear programming (FOALP) planner on problems from the probabilistic track of the ICAPS 2004 and 2006 International Planning Competitions.

A PDE based Implementation of the Hull&White Model for Cashflow Derivatives

A new implementation for the one-dimensional Hull&White model is developed. It is motivated by a geometrical approach to construct an invariant manifold for the future dynamics of forward zero coupon bond prices under a forward martingale measure. This reduces the option-pricing problem for cashflow derivatives to the solution of a series of heat equations. The heat equation is solved by a standard Crank-Nicolson scheme. The new method avoids the calibration used in traditional solution approaches. The computation of prices for European and Bermudan swaptions shows the convergence behavior of our new implementation. We also demonstrate the efficiency of our new approach resulting in a speed improvement by one order of magnitude compared to traditional trinomial tree implementations.

Sequential quadratic programming and the ASTROS structural optimization system

The NLPQL sequential quadratic programming algorithm of Schittkowski is integrated with the Automated Structural Optimization System (ASTROS) and tested on three largescale optimization problems, including one with constraints from multiple disciplines. Furthermore, the traditional solution approach, which involves the formulation and solution of an explicitly defined approximate problem during each iteration, is replaced by a simpler approach, in which the approximate problem is eliminated, and each finite element analysis is followed by one iteration of the optimizer. To compensate for the cost of additional analyses, a much more restrictive active set strategy is used. Although not much computational efficiency is gained, the alternative approach gives accurate solutions. The largest test problem, which had 1527 design variables and 6124 constraints was solved with ASTROS for the first time using a direct method. The resulting design represents the lowest weight feasible design recorded to date.

Stabilization of critical temperature with respect to repulsion in strong-coupled superconductors.

It is shown that the Eliashberg's equations (EE) have two kinds of solutions for the critical temperature ${\mathit{T}}_{\mathit{c}}$. The solution of the first kind leads to the traditional smooth dependence of ${\mathit{T}}_{\mathit{c}}$ on the value of the Coulomb pseudopotential ${\mathrm{\ensuremath{\mu}}}^{\mathrm{*}}$. This dependence has been extensively studied in literature. The second kind of solutions manifests as quantized critical temperatures appearing at finite values of ${\mathrm{\ensuremath{\mu}}}^{\mathrm{*}}$ but not depending on its magnitude. Such solutions are only possible for strong-coupled superconductors. Thus, the dependence ${\mathit{T}}_{\mathit{c}}$(${\mathrm{\ensuremath{\mu}}}^{\mathrm{*}}$) in the mean-field approximation is a many-valued function. In the vicinity where the traditional solution approaches a quantized solution the mean-field approximation fails and the system fluctuationally switches to another stable mean-field branch. This process results in appearance of flat regions in the ${\mathit{T}}_{\mathit{c}}$(${\mathrm{\ensuremath{\mu}}}^{\mathrm{*}}$) dependence.