Blade Envelopes Part I: Concept and Methodology

Blades manufactured through flank and point milling will likely exhibit geometric variability. Gauging the aerodynamic repercussions of such variability, prior to manufacturing a component, is challenging enough, let alone trying to predict what the amplified impact of any in-service degradation will be. While rules of thumb that govern the tolerance band can be devised based on expected boundary layer characteristics at known regions and levels of degradation, it remains a challenge to translate these insights into quantitative bounds for manufacturing. In this work, we tackle this challenge by leveraging ideas from dimension reduction to construct low-dimensional representations of aerodynamic performance metrics. These low-dimensional models can identify a subspace which contains designs that are invariant in performance -- the inactive subspace. By sampling within this subspace, we design techniques for drafting manufacturing tolerances and for quantifying whether a scanned component should be used or scrapped. We introduce the blade envelope as a computational manufacturing guide for a blade. In this paper, the first of two parts, we discuss its underlying concept and detail its computational methodology, assuming one is interested only in the single objective of ensuring that the loss of all manufactured blades remains constant. To demonstrate the utility of our ideas we devise a series of computational experiments with the Von Karman Institute's LS89 turbine blade.

Fatigue strength of steel plate girder railway bridges with butt joints reinforced with one-sided rhomb-shaped cover plates

Due to the long period of service degradation, bridge structures require periodic technical inspections and assessment of the current load capacity. Since the 1970s, this assessment has been carried out according to the Fitness for Purpose criterion. From 2008, the PUK criterion has been replaced with the recommendations of the European Convention on Steel Structures (ECCS). As part of these recommendations, the authors decided to explain the previously obtained unrealistic values of the fatigue class Dsc of the bridge butt joints, covered with one-sided rhomb-shaped cover plates. The computational analysis performed with the FEM method gave excellent results which are briefly presented in the article.

Enhancing the ecological value of tropical agriculture through set-asides

Agricultural expansion across the tropics is the primary driver of biodiversity declines and ecosystem service degradation. However, efforts to mitigate these negative impacts may reduce commodity production. We quantify trade-offs between oil palm cultivation and ecological outcomes (biodiversity, above-ground carbon storage and dung nutrient cycling) across different potential set-aside (uncultivated areas in agricultural landscapes) strategies. We show that all set-aside configurations yield substantial gains in ecological outcomes. The best strategy involves spatially targeted riparian reserves, such as those used in oil palm certification schemes, where species occurrence can be doubled without reducing overall cultivation area. Adopting this strategy throughout the 8 million hectares of plantations in Borneo would lead to extensive improvements in ecological outcomes without losses to production area, and consequently, enhancing agricultural sustainability.

Performance analysis of multi services on container Docker, LXC, and LXD

The emergence of the container in various cloud platforms from Open Stack to Google Cloud Platform has marked the industry interest in opting for container as their cloud service solution. However, the cloud users should aware of performance overheads of different virtualization solutions in order to avoid quality of service degradation because different container platforms delivered different performances. This research evaluated how different container platforms (Docker, LXC, and LXD) impacted in running different TCP services and also measured system performance of each container compared to the native system without any container solution based on overall performance metrics. This research focuses on the three most used PaaS: FTP Server, Web Server, and Mail Server. Related to previous works, our evaluation results show that performance could vary between containers. In terms of system performance, LXD shows better performance while server performance result varies depending on what service is being evaluated.

Review of Geometric Uncertainty Quantification in Gas Turbines

Due to the manufacturing error and in-service degradation of gas turbines, there is always a deviation between the actual geometry and the design geometry. This geometric deviation has a prominent uncertainty characteristic, resulting in a dispersion of the gas turbine performance and thereby reducing the manufacturing qualification rate and service life. As the performance and reliability requirements of gas turbines increase continually, more and more attention has been paid to the quantitative study of the effect of the geometric uncertainty on performance. In this paper, the main sources and features of gas turbine geometric uncertainty are reviewed first. Then, the basic principles, characteristics, and application in gas turbines of different uncertainty quantification (UQ) methods are reviewed. Finally, the progress, challenges, and prospects for correlational research are summarized in the conclusion.

802.11ax

The local wireless environment has been the setting for the co-existence of licensed mobile communications operators and unlicensed WiFi Internet access providers. The IEEE802.11 family of standards, developed for WiFi services in the Institute of Electrical and Electronics Engineers (IEEE), has dominated standards-setting. However, the burgeoning demand for mobile access to the Internet has led to competition for space on the spectrum. Left unaddressed, this co-existence has created practical issues of potential territorial incursion, technical interference, and, ultimately, device underperformance and service degradation. The chapter focuses on the IEEE’s efforts to create a co-existence standard in a crowded and highly contested standards-making space. It shows how alternative standards-making organizational contexts, based on licensed spectrum standards traditions, were able to develop and insert co-existence standards for WiFi ahead of the IEEE initiative. The chapter explains how the IEEE developed its 802.11ax co-existence standard in this environment.