scholarly journals Chromate-free chemical conversion coatings for aluminum alloys

2019 ◽  
Vol 37 (4) ◽  
pp. 321-342 ◽  
Author(s):  
Markus Becker
Keyword(s):  
Aluminum Alloys ◽  
Low Cost ◽  
Sol Gel ◽  
Cost Effective ◽  
Chemical Conversion ◽  
Practical Implementation ◽  
Conversion Coatings ◽  
Alternative Technologies ◽  
Advantages And Disadvantages ◽  
Near Term

AbstractCorrosion of metallic components represents a major issue in the aeronautical sector, giving rise to safety concerns and significant financial damages. Conversion coatings (CC) based on hexavalent chromium provide exceptional corrosion protection at relatively low cost. However, environmental issues and health concerns raised a growing interest in the development of alternative technologies. These must not only be cost effective and environmentally friendly but also provide corrosion resistance and adhesion performance comparable to Cr6+-based CCs. Simultaneously fulfilling all of these criteria is a difficult challenge, and an industrial application has so far only been achieved by a small number of systems. This review critically summarizes the recent scientific literature and patents for chromate-free CCs on aluminum alloys and tries to assess their potential regarding the highly demanding aerospace requirements. The bath composition and coating characteristics of the trivalent chromium process, rare earth chemical conversion coatings, transition metal oxyanion additives, Zr/Ti-based chemical conversion coatings, sol-gel coatings, and smart coatings providing stimulus-related inhibitor release are discussed. The advantages and disadvantages of the alternative technologies with regard to their practical implementation are debated, as the aeronautics industry is confronted with the necessity to move away from chromates in the near term.

scholarly journals Indirect Laryngeal Surgery in the Clinical Voice Laboratory: The Renewal of a Lost Art

2000 ◽  
Vol 79 (5) ◽  
pp. 350-361 ◽  
Author(s):  
Norman D. Hogikyan ◽  
Melissa Pynnonen
Keyword(s):  
Cost Effectiveness ◽  
General Anesthesia ◽  
Recent Literature ◽  
Low Cost ◽  
Cost Effective ◽  
Topical Anesthesia ◽  
High Quality ◽  
Advantages And Disadvantages ◽  
Laryngeal Surgery ◽  
Type Of Surgery

Since the advent of precision instruments and safe techniques for direct laryngoscopic surgery under general anesthesia, indirect laryngeal surgery has become very uncommon. A review of the recent literature finds that few authors advocate indirect surgery under topical anesthesia, and many otolaryngologists dismiss this technique as being either of only historical interest or an idiosyncratic method practiced only by a handful of clinicians. The societal mandate for cost-effective healthcare and the availability of relatively low-cost, high-quality endoscopes and video equipment warrant a renewed and broader interest in this type of surgery. In this article, we review a series of 27 indirect surgical procedures performed under topical anesthesia in the clinical voice laboratory. We discuss the indications, outcomes, advantages, and disadvantages of this surgery, and we present a brief analysis of its cost-effectiveness. We conclude that indirect laryngeal surgery in the clinical voice laboratory is an effective, safe, efficient, and less costly alternative to some procedures routinely performed under general anesthesia.

Portable, Low-Cost, Solid-State Luminescence-Based O2 Sensor

1998 ◽  
Vol 52 (5) ◽  
pp. 750-754 ◽  
Author(s):  
A. Neal Watkins ◽  
Brett R. Wenner ◽  
Jeffrey D. Jordan ◽  
Wenying Xu ◽  
James N. Demas ◽  
...  
Keyword(s):  
Solid State ◽  
Response Times ◽  
Ruthenium Complex ◽  
Light Emitting Diode ◽  
Low Cost ◽  
Sol Gel ◽  
Cost Effective ◽  
Fast Response ◽  
Color Filter ◽  
Silicon Photodiode

A novel sensor for quantifying molecular O2 based entirely on solid-state electronics is presented. The sensor is based on the luminescence quenching of tris(4,7-diphenyl-1, 10-phenanthroline)ruthenium(II) ([Ru(dpp)3]2+) by molecular O2. The sensor involves immobilizing the ruthenium complex within a porous sol-gel-processed glass film and casting this film directly onto the surface of a blue quantum-well light-emitting diode (LED). The ruthenium complex is excited by the LED, the [Ru(dpp)3]2+ emission is filtered from the excitation with a low-cost acrylic color filter, and the emission is detected with an inexpensive silicon photodiode. The sensor response to gaseous O2 and dissolved O2 in water is presented. The sensor exhibits fast response times and good reversibility, and detection limits are 0.5%, 0.02%, and 110 ppb, respectively, for O2 in the gaseous (linear Stern–Vobner and multi-site Stern–Volmer analysis) and aqueous phase. This sensor provides a cost-effective alternative to traditional electrochemical-based O2 sensing and also provides a platform for other optically based sensors.

Computational Fluid Dynamics Study on the Decomposition of Ammonia in a Selective Porous Membrane

2008 ◽  
Vol 3 (1) ◽  
Author(s):  
Athanasios Sideridis ◽  
Dimitrios Koutsonikolas ◽  
Dimitrios Missirlis ◽  
Savas Topis ◽  
Sotiris Kaldis ◽  
...  
Keyword(s):  
Flow Field ◽  
Coal Gasification ◽  
Cost Effective ◽  
Porous Membrane ◽  
Fuel Gas ◽  
Environmental Friendliness ◽  
Alternative Technologies ◽  
Advantages And Disadvantages ◽  
Cost Effective Method ◽  
Selective Membrane

The development of alternative technologies for the removal of gas pollutants is an important aspect for the environmental friendliness of energy production. During coal gasification, N2 contained in coal is converted to NH3 and, as much as 50% of the ammonia in the fuel gas can be converted to nitrogen oxides (??x). At these conditions, decomposition seems to be the only applicable solution for the removal of NH3. The application of a high temperature catalytic membrane reactor process appears to offer an efficient and cost effective method of removing the NH3 from coal gasification gas streams.The present work examines the operation of such a selective membrane, used for the decomposition of NH3, under a 2-D axissymetric CFD approach where the flow field, the chemical reactions and the selective porous membrane behavior are being modeled and computed. The main target of this effort was to obtain a more detailed view of the flow field and to investigate the decomposition of ammonia in comparison with a simpler 1-D modeling approach and, thus, to evaluate the advantages and disadvantages of each method.

Reality-check and renewed challenges in earthquake engineering

2012 ◽  
Vol 45 (4) ◽  
pp. 137-160 ◽  
Author(s):  
Stefano Pampanin
Keyword(s):  
Seismic Performance ◽  
Earthquake Engineering ◽  
Design Theory ◽  
Damage Control ◽  
Low Cost ◽  
Modern Society ◽  
Cost Effective ◽  
Practical Implementation ◽  
Reality Check ◽  
General Terms

Earthquake Engineering is facing an extraordinarily challenging era, the ultimate target being set at increasingly higher levels by the demanding expectations of our modern society. The renewed challenge is to be able to provide low-cost, thus more widely affordable, high-seismic-performance structures capable of sustaining a design level earthquake with limited or negligible damage, minimum disruption of business (downtime) or, in more general terms, controllable socio-economical losses. The Canterbury earthquakes sequence in 2010-2011 has represented a tough reality check, confirming the current mismatch between societal expectations over the reality of seismic performance of modern buildings. In general, albeit with some unfortunate exceptions, modern multi-storey buildings performed as expected from a technical point of view, in particular when considering the intensity of the shaking (higher than new code design) they were subjected to. As per capacity design principles, plastic hinges formed in discrete regions, allowing the buildings to sway and stand and people to evacuate. Nevertheless, in many cases, these buildings were deemed too expensive to be repaired and were consequently demolished. Targeting life-safety is arguably not enough for our modern society, at least when dealing with new building construction. A paradigm shift towards damage-control design philosophy and technologies is urgently required. This paper and the associated presentation will discuss motivations, issues and, more importantly, cost-effective engineering solutions to design buildings capable of sustaining low-level of damage and thus limited business interruption after a design level earthquake. Focus will be given to the extensive research and developments in jointed ductile connections based upon controlled rocking & dissipating mechanisms for either reinforced concrete and, more recently, laminated timber structures. An overview of recent on-site applications of such systems, featuring some of the latest technical solutions developed in the laboratory and including proposals for the rebuild of Christchurch, will be provided as successful examples of practical implementation of performance-based seismic design theory and technology.

scholarly journals Manual Borehole Drilling as a Cost-Effective Solution for Drinking Water Access in Low-Income Contexts

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1981
Author(s):  
Pedro Martínez-Santos ◽  
Miguel Martín-Loeches ◽  
Silvia Díaz-Alcaide ◽  
Kerstin Danert
Keyword(s):  
Drinking Water ◽  
Low Income ◽  
Rural Areas ◽  
Low Cost ◽  
Cost Effective ◽  
Unconsolidated Sediments ◽  
Low Income Countries ◽  
Water Access ◽  
Middle Income ◽  
Advantages And Disadvantages

Water access remains a challenge in rural areas of low-income countries. Manual drilling technologies have the potential to enhance water access by providing a low cost drinking water alternative for communities in low and middle income countries. This paper provides an overview of the main successes and challenges experienced by manual boreholes in the last two decades. A review of the existing methods is provided, discussing their advantages and disadvantages and comparing their potential against alternatives such as excavated wells and mechanized boreholes. Manual boreholes are found to be a competitive solution in relatively soft rocks, such as unconsolidated sediments and weathered materials, as well as and in hydrogeological settings characterized by moderately shallow water tables. Ensuring professional workmanship, the development of regulatory frameworks, protection against groundwater pollution and standards for quality assurance rank among the main challenges for the future.

Adsorptive Removal of Chromium (VI) Ions Using Cryogel Derived from Oil Palm Fronds’ Lignin

2016 ◽  
Vol 818 ◽  
pp. 242-245 ◽  
Author(s):  
Nur Shahirah Rusli ◽  
Norzita Ngadi
Keyword(s):  
Oil Palm ◽  
Low Cost ◽  
Sol Gel ◽  
Cost Effective ◽  
Supercritical Drying ◽  
Carbon Aerogels ◽  
Oil Palm Fronds ◽  
Chromium Vi ◽  
Cost Effective Treatment ◽  
Palm Fronds

Nowadays, lignin is of special interest since it is the second most abundant biopolymer after cellulose. Given its extremely low cost and phenolic nature, lignin had become one of the leading candidates for preparing aerogels. However, production cost of carbon aerogels are considerably high due to extremely expensive supercritical drying method employed. Thus, carbon cryogels has been introduced by replacing the supercritical drying with freeze drying technique. In this study, lignin was extracted from dried and grinded oil palm fronds to be used as precursor for sol-gel polycondensation. Cryogel derived from oil palm fronds (OPF) was investigated as a suitable adsorbent for the removal of metal ions especially chromium (VI) through adsorption process. In addition, the adsorption amount was greatly increased when this cryogel was prepared with addition of ultrasonic effect instead of normal heating during the sol-gel polycondensation process. This new cryogel seems to be very promising for cost-effective treatment of heavy metals removal since the preparation is easy and being derived from a widely available and low-cost biomass feedstock.

scholarly journals The High Cost of the Low-Cost Polybag System: A Review of Nursery Seedling Production Systems

Land ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 826
Author(s):  
Diane Haase ◽  
Karma Bouzza ◽  
Lucy Emerton ◽  
James Friday ◽  
Becca Lieberg ◽  
...  
Keyword(s):  
Production Systems ◽  
Low Cost ◽  
Field Performance ◽  
Cost Benefit ◽  
Holistic Approach ◽  
Cost Effective ◽  
Cultural Elements ◽  
Advantages And Disadvantages ◽  
Nursery Production ◽  
Survival And Growth

An important strategy for meeting global landscape restoration goals is nursery production of high-quality seedlings. Growing seedlings with attributes that promote post-planting survival and growth can be dramatically influenced by the nursery container system. In many countries, nurseries produce seedlings in polybags filled with excavated soil. These seedlings often develop deformed roots with limited fibrosity which can lead to poor survival and growth after outplanting. Polybags are initially inexpensive but using these single-use plastic containers accrues expenses that are often untracked. Comparisons among nursery production systems must account for factors such as container longevity, labor efficiency, and seedling field performance. A more holistic approach to account for environmental, economic, social, logistic, and cultural elements in the cost–benefit equation that influences nursery production systems is needed. Converting to a modern container system requires concomitant adjustments in nursery scheduling and culturing matched to the new stock type. Doing so provides an opportunity to align nursery production techniques and resulting seedling attributes with anticipated field conditions. This article describes and discusses the advantages and disadvantages of nursery production systems and provides recommendations and case studies to aid nurseries in improving seedling quality toward meeting restoration goals in a cost-effective and timely manner.

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