scholarly journals Evaluation of In-Place Asphalt Recycling for Airfield Applications

2021 ◽  
Author(s):  
William D. Carruth
Keyword(s):  
Structural Engineering ◽  
Federal Aviation Administration ◽  
Asphalt Pavements ◽  
Computer Assisted ◽  
Military Aircraft ◽  
Potential Cost ◽  
Design Considerations ◽  
Pavement Structures ◽  
The U.S ◽  
Design Guidance

Over the last few decades, in-place recycling of asphalt pavements has seen increased use by the highway industry, primarily to take a dvantage of potential cost and logistical savings compared to conventional reconstruction. More recently, the U.S. Navy and Federal Aviation Administration have allowed recycling to be used on airfields with lighter traffic. This report contains a discussion of in-place recycling design considerations obtained from a literature review of its use in the highway industry. Observations developed from a review of airfield pavement projects that have utilized recycling is also included. A structural analysis was performed using the Pavement-Transportation Computer Assisted Structural Engineering (PCASE) tool to determine typical stiffness values that recycled layers must achieve to support various types of military aircraft traffic for different pavement structures. Overall, in-place recycling is recommended for consideration as a rehabilitati on technique for military airfield pavements, and further investigation is recommended before it is implemented it into design guidance.

Commercial Aviation, A New Era: summary of the 2017 TQA workshop

2021 ◽  
Vol 263 (3) ◽  
pp. 3896-3899
Author(s):  
gregg fleming
Keyword(s):  
Environmentally Friendly ◽  
Federal Aviation Administration ◽  
Global Leadership ◽  
Aviation Industry ◽  
Engineering Technology ◽  
Commercial Aviation ◽  
New Era ◽  
Government Organizations ◽  
Aircraft Engineering ◽  
The U.S

More environmentally friendly aircraft designs, particularly with regard to noise, was a Technology for a Quieter America (TQA) workshop hosted by the National Academy of Engineering (NAE) held in May 2017. This workshop titled "Commercial Aviation: A New Era", centered on the importance of commercial aviation to the U.S. economy, and what it will take for the U.S. to maintain global leadership in the aviation sector, including a forward-looking topic on more environmentally friendly aircraft designs. A principal focus of the workshop was the necessary step-changes in aircraft engineering technology that must be addressed with the development and testing of flight demonstrators together with significantly increased funding of public-private partnerships. Government agencies which participated included NASA, the Federal Aviation Administration, and the Department of Housing and Urban Development (HUD). There was also substantial participation from the aviation industry, airports, airlines, non-government organizations and academia.

scholarly journals Turbomachinery Design Considerations for the Nuclear HTGR-GT Power Plant

1981 ◽  
Vol 103 (1) ◽  
pp. 65-77 ◽  
Author(s):  
Colin F. McDonald ◽  
Murdo J. Smith
Keyword(s):  
Power Plant ◽  
Gas Turbines ◽  
Mechanical Design ◽  
Primary System ◽  
Design Considerations ◽  
Commercial Plant ◽  
Industrial Gas Turbines ◽  
Plant Configuration ◽  
Turbomachinery Design ◽  
The U.S

For several years, design studies have been underway in the U.S. on a nuclear closed-cycle gas turbine plant (HTGR-GT). This paper presents design aspects of the helium turbo-machine portion of these studies. Gas dynamic and mechanical design considerations are presented for helium turbomachines in the 400 MWe (non-intercooled) and 600 MWe (intercooled) power range. Design of the turbomachine is a key element in the overall power plant program effort, which is currently directed towards the selection of a reference HTGR-GT commercial plant configuration for the U.S. utility market. A conservative design approach has been emphasized to provide for maximum safety and durability. The studies presented for the integrated plant concept outline the necessary close working relationship between the reactor primary system and turbomachine designers. State-of-the-art technology from large industrial gas turbines developed in the U.S., considered directly applicable to the design of a helium turbomachine, particularly in the areas of design methodology, performance, materials, and fabrication methods, is emphasized.

scholarly journals Long-Term Performance of Pavement Structures with Cold In-Place Recycled Base Course

2021 ◽  
Vol 16 (2) ◽  
pp. 48-65
Author(s):  
Audrius Vaitkus ◽  
Judita Gražulytė ◽  
Andrius Baltrušaitis ◽  
Jurgita Židanavičiūtė ◽  
Donatas Čygas
Keyword(s):  
Asphalt Pavement ◽  
Asphalt Mixture ◽  
Asphalt Pavements ◽  
Recycled Asphalt ◽  
Binding Agents ◽  
Pavement Structure ◽  
Pavement Structures ◽  
Base Course ◽  
Surface Distress ◽  
Foamed Bitumen

Properly designed and maintained asphalt pavements operate for ten to twenty-five years and have to be rehabilitated after that period. Cold in-place recycling has priority over all other rehabilitation methods since it is done without preheating and transportation of reclaimed asphalt pavement. Multiple researches on the performance of cold recycled mixtures have been done; however, it is unclear how the entire pavement structure (cold recycled asphalt pavement overlaid with asphalt mixture) performs depending on binding agents. The main objective of this research was to evaluate the performance of cold in-place recycled asphalt pavements considering binding agents (foamed bitumen in combination with cement or only cement) and figure out which binder leads to the best pavement performance. Three road sections rehabilitated in 2000, 2003, and 2005 were analysed. The performance of the entire pavement structure was evaluated in terms of the International Roughness Index, rut depth, and pavement surface distress in 2013 and 2017.

scholarly journals Aerospace Titanium Alloy Melt Process Quality Improvements

2020 ◽  
Vol 321 ◽  
pp. 04008
Author(s):  
Andrew Woodfield ◽  
Gérard Lemaitre
Keyword(s):  
Titanium Alloy ◽  
Aircraft Engine ◽  
Federal Aviation Administration ◽  
High Density ◽  
Vacuum Arc ◽  
Quality Improvements ◽  
Jet Engine ◽  
Aircraft Accident ◽  
The U.S

This Jet Engine Titanium Quality Committee (JETQC) paper describes industry quality improvements since 1990. Quality refers to freedom from melt-related hard-alpha and high-density inclusions (HDI). JETQC, formed under the auspices of the U.S. Federal Aviation Administration (FAA) following the Sioux City aircraft accident in 1989, is comprised of U.S., E.U. and Japanese aircraft engine manufacturers to address the quality of premium / rotor quality titanium alloy production. Titanium suppliers provide melt-related inclusion data. JETQC focuses on hard-alpha and HDI inclusion rates in premium quality (PQ) titanium alloy products for critical rotating aircraft engine applications. PQ materials typically are produced via triple vacuum arc re-melt (3XVAR) or hearth melt VAR (HMVAR) processes, but more recently, the Skull plus VAR (SVAR) process has been introduced. Hard-alpha rates have continued to decline over the last decade primarily for the HMVAR process. HDI rates declined in the early 90’s, but more recently the overall rate has stayed approximately constant with inclusions confined to the 3XVAR process. Combining the trends for both hard-alpha and HDIs, the HMVAR process has demonstrated in recent years to be higher quality compared with the 3XVAR process.

An Optimization Model for Selecting Sample Days

2021 ◽  
pp. 2050052
Author(s):  
Tao Li
Keyword(s):  
North Atlantic ◽  
Optimization Model ◽  
Federal Aviation Administration ◽  
Selection Method ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
Managerial Decisions ◽  
The North ◽  
The North Atlantic ◽  
The U.S

Sample day selection method plays an important role in managerial decisions which require analyses that are prohibitively expensive to apply to a large number of days. We develop a general sample day selection model that selects sample days based on the cumulative distributions of airspace conditions and characteristics (C&C) by considering factors such as sampling targets, degree of diversity and coverage of the selected days. We introduce indicators that capture the airspace C&C of the North Atlantic region (NAT) and apply the model to select sample days for the NAT. The results show that the model outperforms the methods used by the U.S. Federal Aviation Administration.

Influence of Cracking Damage on Deflection Basin Test Data of FWD

2014 ◽  
Vol 620 ◽  
pp. 55-60 ◽  
Author(s):  
Xin Qiu ◽  
Xiao Hua Luo ◽  
Qing Yang
Keyword(s):  
Probabilistic Approach ◽  
Asphalt Pavements ◽  
Falling Weight Deflectometer ◽  
Layer System ◽  
Linear Elastic ◽  
Distribution Features ◽  
Pavement Structures ◽  
And Performance ◽  
Falling Weight ◽  
Non Destructive

With the popularization of falling weight deflectometer (FWD) to calculate the stiffness related parameters of the pavement structures, non-destructive evaluation of physical properties and performance of pavements has taken a new direction. FWD backcalculation is mathematically an inverse problem that could be solved either by deterministic or by probabilistic approach. A review of the currently used backcalculation procedures indicates that the calculation is generally based on a homogeneous, continuous, and linear elastic multi-layer system. Identifying effective data of dynamic deflection basins seems to be an important task for performing modulus backcalculation. Therefore, the main objective of this paper was to discuss the distribution features of dynamic deflection basins of asphalt pavements with crack distresses, and present the reasonable criteria to filter the testing data of FWD deflection basins. Finally, the study aims to validate the established criteria by conducting in-situ case study.

Implementing ICAO language proficiency requirements in the Versant Aviation English test

2009 ◽  
Vol 32 (3) ◽  
pp. 27.1-27.17
Author(s):  
Alistair Van Moere ◽  
Masanori Suzuki ◽  
Ryan Downey ◽  
Jian Cheng
Keyword(s):  
Language Proficiency ◽  
Information Exchange ◽  
Federal Aviation Administration ◽  
Computerized Testing ◽  
Civil Aviation ◽  
Automated Scoring ◽  
International Civil Aviation Organization ◽  
Valid Assessment ◽  
The U.S ◽  
Aviation English

This paper discusses the development of an assessment to satisfy the International Civil Aviation Organization (ICAO) Language Proficiency Requirements. The Versant Aviation English Test utilizes speech recognition technology and a computerized testing platform, such that test administration and scoring are fully automated. Developed in collaboration with the U.S. Federal Aviation Administration, this 25-minute test is delivered via a telephone or computer. Two issues of interest are discussed. The first concerns the practicalities of assessing candidates in each of six separate dimensions of spoken proficiency: Pronunciation, Structure, Vocabulary, Fluency, Comprehension, and Interactions. Although an automated scoring system can objectively segregate these skills, we question whether human raters have the capacity to do this in oral interviews. The second issue discussed is how an automated test can provide a valid assessment of spoken interactions. Tasks were designed to simulate the information exchange between pilots and controllers on which candidates’ proficiency in ‘Interactions’ could be measured, for example, by eliciting functions such as correcting miscommunications and providing clarification. It is argued that candidate ability can be probed and estimated in a fair and standardized way by presenting a series of independent items which are targeted in difficulty at the various ICAO levels.

The Impact of Computer Assistance on District Office Operations

1979 ◽  
Vol 23 (1) ◽  
pp. 586-590
Author(s):  
L. Dan Massey ◽  
Jerry T. Lawler
Keyword(s):  
Cost Effectiveness ◽  
Response Time ◽  
Capital Investment ◽  
System Response ◽  
Computer Assisted ◽  
Social Security Administration ◽  
Potential Cost ◽  
Computer Assistance ◽  
System Response Time ◽  
The Impact

To predict the potential cost effectiveness of computer assisted information processing in the District Offices (DOs) of the Social Security Administration (SSA), we developed a model of manpower allocation in present DO operations. We adapted existing SSA management data sources to quantify this baseline model. We also constructed a description of the changes in manpower requirements expected to occur on introduction of a hypothetical computer assisted system. We used analyses of user functional requirements to determine overall system capabilities. We used the results of user performance trials on a simulated system to quantify this change model. Significant reductions in manpower for processing of individual claims in the DO appear to be attainable. Computer system response time was identified as a controllable design characteristic with a strong effect on manpower requirements. Introduction of computer assistance to the DO could free manpower from mechanical clerical activities for application to more creative and professional functions. This manpower could be applied to expansion of SSA services and to improvement of DO service quality. An overall increase of 25% to 33% in workload processing capacity appears potentially attainable with computer assistance at current DO manpower levels. Suitable workstations might be based on use of individual personal computers or on sharing the resources of a single larger machine among a number of users. Consideration of relative costs and benefits suggests that the personal computer approach, while initially more costly, offers better control over system response time, which can have a major effect on system acceptance and cost effectiveness. It is likely that computer assistance for DOs will be deployed through workstations based on individual personal machines. Full recovery of capital investment can potentially be achieved in two years of actual operation.

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