1,039 research outputs found
Operations analysis : method for rating the effectiveness of aircraft warning and control systems with respect to specific enemy raids in the SWPA.
No full textThe complex organization and mechanism of an Aircraft Warning and Control System is for express purpose of giving warning to civilian populations, friendly ground troops, harbor facilities, anti-aircraft ground installations, and to airfields. It must also provide information for control of fighters so enemy raids can be intercepted before they reach the objective and accomplish their mission. To determine the effectiveness of a system it is necessary to analyze its operation during an actual enemy raid
A Survey of Current Operations-Ready Thermospheric Density Models for Drag Modeling in LEO Operations
No full textIn Low Earth Orbit (LEO), atmospheric drag is the largest contributor to trajectory prediction error. The current thermospheric density model used by the Combined Space Operations Center (CSpOC) in operations is the High Accuracy Satellite Drag Model (HASDM). Since HASDM is not available for use outside of the US Government, satellite operators are left to determine what publicly available, open-source density model they should integrate into their internal operational software. This decision is nontrivial due to the number of available density models, each having variable performance dependent on several factors including space weather conditions and orbit altitude. To compound matters, the rapid rise of this solar cycle suggests that the predicted solar maximum between 2024-2027 could be higher than the previous solar maximum, thus causing larger perturbations due to drag from atmospheric density on LEO satellites. Given the evermore challenging nature of operations in LEO, it is imperative for satellite operators to update legacy density models to a state-of-the-art density model to provide improved trajectory predictions for collision risk assessment and vital day-to-day operational decisions. This paper outlines several operations-ready thermospheric density models, describing their performance, computation time, required operational space weather input parameters, and notes for implementation. We define an operations-ready density model as a model that is well-documented, has verified and quantified model performance, and provides publicly available model code for implementation on a user’s own system. Operations-ready models include the Drag Temperature Model (DTM), the Jacchia-Bowman 2008 (JB2008) model, the US Naval Research Laboratory Mass Spectrometer and Incoherent Scatter radar 2.0 (NRLMSIS 2.0) model, and the Thermosphere– Ionosphere–Electrodynamics General Circulation Model (TIE-GCM). US Government operational density models, HASDM and the Whole Atmosphere Model and Ionosphere Plasmasphere Electrodynamics (WAM-IPE) model, are included for comparison in the Analysis section. Models are evaluated against global HASDM density and local Gravity Recovery And Climate Experiment Follow-On (GRACE-FO) satellite accelerometer density data. A propagation analysis is also included in which model performance is compared during quiet and storm conditions and resulting LEO object trajectory prediction errors are quantified at various orbit altitudes. The analysis shows that any of the named operations-ready density models (DTM2020, JB2008, NRLMSIS 2.0, TIE-GCM) are a viable option for satellite operations. In addition to LEO satellite operators, the results from this paper are also informative for the transition of civilian space traffic coordination efforts out of CSpOC and into the Department of Commerce.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Astrodynamics & Space Mission
The general as statesman : exploring the professional need for commanders to support viable political outcomes in peace and stability operations as typified by the UK military approach
Get PDFThe problem of theatre level politico-military arrangements during peace and stability operations is important because the intervening actors, working in complex and often ambiguous circumstances, need to calibrate the application of military and political means as a coherent interdependent whole. This is necessary in order to build peace, secure viable political outcomes and hence strategic successes; however it is not easy in practice. This thesis examines the hypothesis that, beyond their security-related tasks, military commanders should provide direct support to civilian interlocutors in order to facilitate and sustain the local political process. This requires military co-operation with other relevant actors, responsiveness to political direction and the specific shaping of military operations to impact decisively on political outcomes.
This work establishes that Western and United Nations doctrinal guidance extols political primacy and civil-military cooperation but does not fully explain the central importance of the political process, nor does it capture the potential peace building role of the military component. Analysis of practice in Kosovo, Iraq and Afghanistan, suggests that military commanders retain a uniquely influential position and have generally used their military means to positively influence political progress and help coordinate multi-dimensional plans. On occasion, to secure momentum and fill a void, commanders have quietly assumed a political function. Doctrine now needs to be refreshed to reflect practice. It should explain the military role in supporting the political process, elaborate the politico-military relationship as the inner core of a comprehensive approach to peace building and provide candid guidance on the difficulties to be expected where politico-military and coordination arrangements are incoherent. Moreover further work is needed on the wider application of this doctrine by the United Nations and the preparation of civilian leaders for politico-military relationships
Efficiency of inland waterway container terminals: Stochastic frontier and data envelopment analysis to analyze the capacity design- and throughput efficiency
Get PDFAlthough terminal efficiency has been thoroughly studied for deep-sea container ports and terminals, up till now, there has been little scientific literature on the efficiency of inland waterway container terminals (IWTs). This paper therefore focuses on determining and analyzing terminal characteristics that influence efficiency. Our analysis led to a number of conclusions. First, there exist important differences between IWTs and maritime terminals in terms of design capacity and thus also in operations. Different combinations of inputs and output have been tested with the SFA and DEA methodologies. Important terminal inputs turned out to be yard and crane, but also terminal operating hours and terminal area are important. When capacity is excluded as an input it turns out that the importance of inputs becomes more diverse under SFA. Furthermore, when the inputs and output are varied it shows that this leads to a variation in best and worst performers (the efficiency depends on defined inputs and output). Finally, terminal operating hours are an important input for IWTs which is an important difference with maritime terminals which are open 24/7. In terms of how efficiency is defined, there arises a considerable difference between design efficiency (capacity) and the operational efficiency (terminal throughput).Transport and Plannin
A study of the strategic environment of an R&D section within a larger organisation
Get PDFThis work addresses the problem of how an R&D section should decide on a strategy to guide its work when there is no strategic direction supplied from above by the company. The work includes a participant observer case study carried out over five years in a single R&D section, an analysis of research papers on the subject of management of section level R&D, and a review of textbooks on strategy, management and organisational behaviour.
From the case study it was concluded that the company itself formed the strategic environment which the strategy of the R&D section had to address, and that the section’s strategic environment was chaotic in the mathematical sense. From the review of management textbooks it was concluded that standard theories do not give usable guidelines for the manager in this situation. A theory was developed that R&D strategy can be thought about in four distinctly different ways. Publications concentrate on two of these, while the case study and surveys of practising managers revealed that the other two were more pertinent in practice.
The analysis of research papers was carried out using a newly developed technique, which showed that this body of literature is in a pre-paradigm state. The new technique was also used to show that the four different ways of thinking about R&D are present in the papers. The new literature analysis technique and the theory that R&D strategy can be thought about in four different way were tested by means of questionnaires filled in by authors of papers and by groups of R&D practitioners
A comparative analysis of the demand for higher education: results from a meta-analysis of elasticities
Get PDFStudies of the demand for higher education have produced numerous estimates of the tuition and income elasticities. Because of widespread variation in the models estimated, this paper performs a meta-analysis of the literature to uncover the extent to which study characteristics influence elasticities. In addition to being more inelastic in the short-run, the results reveal that demand is least responsive to tuition and income in the United States. Also, the measure of quantity and price, coupled with the method of estimation, have important effects on the tuition elasticity. Nonetheless, there are many study characteristics that have little impact on elasticity estimates.
Cutting data for automated turning tool selection in industry
Get PDFThis thesis is concerned with the determination of cutting parameters (cutting speed, feed rate and depth of cut) in turning operations within an industrial environment. The parameters are required for the purposes of tool selection, working with a variety of batches of different materials. Previous work of this nature, little of which has been transferred into industry, has concentrated primarily on deriving optimum cutting conditions, based on a variety of deterministic and non- deterministic approaches, with a general reliance on experimentally-derived input variables. However, this work is only suited to tool selection for a single material. Under industrial conditions tools will frequently need to be selected for more than one material, in tool/material combinations not recommended by tool makers. Consequently, the objective of the research described in this thesis was to employ existing cutting data technology and to use it as the basis for a cutting data system, suitable for multi-batch tool selection. Two companies collaborated in this work, by making available suitable personnel and the provision of shop floor facilities on their premises. The initial work concentrated on the development of an algorithmic model, based on established theory. This was then tested industrially, using the concept of shop floor approved data as a substitute for optimum cutting data. The model was found to work reasonably, but required further development to make it suitable for multi- batch tool selection. This development took three main forms: a) a reduction of input data, particularly in the number of experimentally-derived variables, b) the removal of the tool/material-specific constraints traditionally used in cutting data optimisation, c) a method of data correction based on adjustment of the mean and standard deviation of the data. Further industrial testing was carried out using the resulting system. It was demonstrated that it was possible for a relaxed system with reduced input variables and appropriate data correction to function within an industrial environment
Why do major chemical accidents still happen in China: Analysis from a process safety management perspective
No full textAs an important consideration in the chemical industry, chemical process safety has received notable attention in China. However, catastrophic chemical accidents still occur. To better understand why accidents continue to occur, this paper presented a diagnostic analysis of 14 major chemical accidents in China from 2012 to 2022 based on VOSviewer software. The authors analysed the correlation between the accident causation and their relationship with the safety management elements. The study observed that inferior process safety culture, intentional violation (rule-breaking) of procedure, inadequate safety training, and illegal operations were the most frequent causes of accidents. These causes highlighted the prominent gaps in PSM in China in the process safety culture, compliance with standards, the conduct of operations, process safety competency, and training & performance assurance. The results based on co-occurrence analysis indicated a strong correlation between these gaps in PSM. Enterprises should pay attention to collaborative management among them. These deficiencies in the enterprise's PSM system showed that the essential defects in China's chemical industry are a poor safety culture, inadequate accident investigation, inadequate training, and a lack of chemical safety personnel. The study recommended that the chemical industry establish superior process safety culture and competency for all personnel, monitor leading and lagging process safety indicators, apply inherent safety, and practice advanced safety management concepts. We hope that the findings can provide China's perspectives and strengths for global chemical safety.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Safety and Security Scienc
On the derivation and analysis of decision architectures for unmanned aircraft systems
No full text©Cranfield University © BAE SystemsOperation of Unmanned Air Vehicles (UAVs) has increased significantly over the past few years. However, routine operation in non-segregated airspace remains a challenge, primarily due to nature of the environment and restrictions and challenges that accompany this. Currently, tight human control is envisaged as a means to achieve the oft quoted requirements of transparency , equivalence and safety. However, the problems of high cost of human operation, potential communication losses and operator remoteness remain as obstacles. One means of overcoming these obstacles is to devolve authority, from the ground controller to an on-board system able to understand its situation and make appropriate decisions when authorised. Such an on-board system is known as an Autonomous System. The nature of the autonomous system, how it should be designed, when and how authority should be transferred and in what context can they be allowed to control the vehicle are the general motivation for this study. To do this, the system must overcome the negative aspects of differentiators that exist between UASs and manned aircraft and introduce methods to achieve required increases in the levels of versatility, cost, safety and performance. The general thesis of this work is that the role and responsibility of an airborne autonomous system are sufficiently different from those of other conventionally controlled manned and unmanned systems to require a different architectural approach. Such a different architecture will also have additional requirements placed upon it in order to demonstrate acceptable levels of Transparency, Equivalence and Safety. The architecture for the system is developed from an analysis of the basic requirements and adapted from a consideration of other, suitable candidates for effective control of the vehicle under devolved authority. The best practices for airborne systems in general are identified and amalgamated with established principles and approaches of robotics and intelligent agents. From this, a decision architecture, capable of interacting with external human agencies such as the UAS Commander and Air Traffic Controllers, is proposed in detail. This architecture has been implemented and a number of further lessons can be drawn from this. In order to understand in detail the system safety requirements, an analysis of manned and unmanned aircraft accidents is made. Particular interest is given to the type of control moding of current unmanned aircraft in order to make a comparison, and prediction, with accidents likely to be caused by autonomously controlled vehicles. The effect of pilot remoteness on the accident rate is studied and a new classification of this remoteness is identified as a major contributor to accidents A preliminary Bayesian model for unmanned aircraft accidents is developed and results and predictions are made as an output of this model. From the accident analysis and modelling, strategies to improve UAS safety are identified. Detailed implementations within these strategies are analysed and a proposal for more advanced Human-Machine Interaction made. In particular, detailed analysis is given on exemplar scenarios that a UAS may encounter. These are: Sense and Avoid , Mission Management Failure, Take Off/Landing, and Lost Link procedures and Communications Failure. These analyses identify the nature of autonomous, as opposed to automatic, operation and clearly show the benefits to safety of autonomous air vehicle operation, with an identifiable decision architecture, and its relationship with the human controller. From the strategies and detailed analysis of the exemplar scenarios, proposals are made for the improvement of unmanned vehicle safety The incorporation of these proposals into the suggested decision architecture are accompanied by analysis of the levels of benefit that may be expected. These suggest that a level approaching that of conventional manned aircraft is achievable using currently available technologies but with substantial architectural design methodologies than currently fielded
- …
