Data envelopment analysis (DEA) and financial ratios : a pro-stakeholders’ view of performance measurement for sustainable value creation of the wind energy

Purpose: The purpose of the paper is to explore business performance in a rather sensitive sector that equally combines economic, environmental and social dimensions. The paper investigates the efficiency of wind farm companies, in a framework of pursuing more diverse stakeholders’ interests Design/Methodology/Approach: Ratios and DEA approaches are combined to measure economic efficiency among the DMUs of a sample of wind farms, using data from their financial statements. Findings: Productivity and effectiveness comprise the performance measured by the economic efficiency. We show that by choosing inputs and outputs that are closely related in forming an appropriate financial ratio, it helps to design and explain more fully the impact of a policy intervention aiming at improving economic efficiency. DEA supplements ratios to design, implement and assess a strategy of benchmarking towards bolstering performance, that favors a wider range of stakeholders. Originality/Value: The study provides an in-depth insight into using Data Envelopment Analysis and financial ratios to study economic efficiency. The approach combines economic, social and environmental dimensions (indirectly) of performance, and the composite ratio Return on Total Assets (ROTA). The analysis caters the specific features of the sector renewable energy and their diverse stakeholders.peer-reviewe

Elevating commodity storage with the SALSA host translation layer

To satisfy increasing storage demands in both capacity and performance, industry has turned to multiple storage technologies, including Flash SSDs and SMR disks. These devices employ a translation layer that conceals the idiosyncrasies of their mediums and enables random access. Device translation layers are, however, inherently constrained: resources on the drive are scarce, they cannot be adapted to application requirements, and lack visibility across multiple devices. As a result, performance and durability of many storage devices is severely degraded. In this paper, we present SALSA: a translation layer that executes on the host and allows unmodified applications to better utilize commodity storage. SALSA supports a wide range of single- and multi-device optimizations and, because is implemented in software, can adapt to specific workloads. We describe SALSA's design, and demonstrate its significant benefits using microbenchmarks and case studies based on three applications: MySQL, the Swift object store, and a video server.Comment: Presented at 2018 IEEE 26th International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS

A Stability Approach to Mean-Variance Optimization

I jointly treat two critical issues in the application of mean-variance portfolios, that is, estimation risk and portfolio instability. I find that theory-based portfolio strategies, which are known to outperform naive diversification (inline image) in the absence of transaction costs, heavily underperform it under transaction costs. This is because they are highly unstable over time. I propose a generic method to stabilize any given portfolio strategy while maintaining or improving its efficiency. My empirical analysis confirms that the new method leads to stable and efficient portfolios that offer equal or lower turnover than inline image and larger Sharpe ratio, even under high transaction costs

Observing spin fractionalization in the Kitaev spin liquid via temperature evolution of indirect resonant inelastic x-ray scattering

Motivated by the ongoing effort to search for high-resolution signatures of quantum spin liquids, we investigate the temperature dependence of the indirect resonant inelastic x-ray scattering (RIXS) response for the Kitaev honeycomb model. We find that, as a result of spin fractionalization, the RIXS response changes qualitatively at two well-separated temperature scales, $T_L$ and $T_H$, which correspond to the characteristic energies of the two kinds of fractionalized excitations, $\mathbb{Z}_2$ gauge fluxes and Majorana fermions, respectively. While thermally excited $\mathbb{Z}_2$ gauge fluxes at temperature $T_L$ lead to a general broadening and softening of the response, the thermal proliferation of Majorana fermions at temperature $T_H \sim 10 \, T_L$ results in a significant shift of the spectral weight, both in terms of energy and momentum. Due to its exclusively indirect nature, the RIXS process we consider gives rise to a universal magnetic response and, from an experimental perspective, it directly corresponds to the $K$-edge of Ru$^{3+}$ in the Kitaev candidate material $\alpha$-RuCl$_3$.Comment: 8 pages, 5 figures, published version with infinitesimal change