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The purpose of this paper is to address the problem of polar quantization optimization. Particularly, the aim is to find the method for the optimal resolution‐constrained polar quantizer design.

The new iterative algorithm for determination of the optimal decision and representation magnitude levels and algorithm for optimization of number of phase cells within each magnitude level, is proposed.

At high rates, the new optimal polar quantizer outperforms the optimal polar compander for 0.2 dB, while the more significant gain should be expected at lower rates. In this paper, in order to enable practical implementation of quantizer model, algorithm which transforms real values for the optimal numbers of phase cells within magnitude levels into integer ones is also proposed. Moreover, the approximate closed form of signal‐to‐quantization ratio is derived.

Since circularly symmetric sources and complex presentation of signals arise in numerous applications, it can be concluded that the usage area of the suggested proposal is very wide (audio coding, image coding, spectral phase coding, synthetic aperture radars systems, coding of the discrete Fourier transform).

It should be emphasized that in contrast to earlier work, where models have been designed under high‐rate assumption, the obtained nonuniform unrestricted polar quantizer is optimal for all rates.

The present paper aims to analyse the synergistic effect of pocket orientation and piezo-viscous-polar (PVP) lubrication on the performance of multi-recessed hybrid journal bearing (MHJB) system.

To simulate the behaviour of PVP lubricant in clearance space of the MHJB system, the modified form of Reynolds equation is numerically solved by using finite element method. Galerkin’s method is used to obtain the weak form of the governing equation. The system equation is solved by Gauss–Seidal iterative method to compute the unknown values of nodal oil film pressure. Subsequently, performance characteristics of bearing system are computed.

The simulated results reveal that the location of pressurised lubricant inlets significantly affects the oil film pressure distribution and may cause a significant effect on the characteristics of bearing system. Further, the use of PVP lubricant may significantly enhances the performance of the bearing system, namely.

The present work examines the influence of pocket orientation with respect to loading direction on the characteristics of PVP fluid lubricated MHJB system and provides vital information regarding the design of journal bearing system.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0241/

IN the majority of cases, the performance of a new airscrew design is estimated by making use of other test results, already known, and which are recalculated for the particular case in question by applying the laws of similarity.

With the discovery of oil on Alaska's North Slope, the continued issues regarding the Alaska Native Land Claims Settlement Act, the oil spill of the Exxon Valdez in the Prince William Sound, the controversy over oil exploration in the Arctic National Wildlife Refuge, and the recent announcement by the United States Geological Survey that the Arctic will be the focal point for global change studies, Alaska, once known as “Seward's Follie” and a place that should be given back to Russia, continues to be in the forefront of national and international news.

The purpose of this paper is to present an approach to a polar graph measurement by a flight testing technique and to propose a baseline research method for future tests of UAV polar graphs. The method presented can be used to demonstrate a conceptual and preliminary design process using a scaled, unmanned configuration. This shows how results of experimental flight tests using a scaled flying airframe may be described and analysed before manufacturing the full scale aircraft.

During the research, the flight tests were conducted for two aerodynamic configurations of a small UAV. This allowed the investigation of the influence of winglets and classic vertical stabilizers on the platform stability, performance and therefore polar graphs of a small unmanned aircraft.

A methodology of flight tests for the assessment of a small UAV’s polar graph has been proposed, performed and assessed. Two aerodynamic configurations were tested, and it was found that directional stability had a large influence on the UAV’s performance. A correlation between the speed and inclination of the altitude graph was found – i.e. the higher the flight speed, the steeper the altitude graph (higher descent speed, steeper flight path angle). This could be considered as a basic verification that the recorded data have a physical sense.

The polar graph and therefore glide ratio of the aircraft is a major factor for determining its performance and power required for flight. Using the right flight test procedure can speed-up the process of measuring glide ratio, making it easier, faster, robust, more effective and accurate in future research of novel, especially unorthodox configurations. This paper also can be useful for the proper selection of requirements and preliminary design parameters for making the design process more economically effective.

This paper presents a very efficient method of assessing the design parameters of UAVs, especially the polar graph, in an early stage of the design process. Aircraft designers and producers have been widely performing flight testing for years. However, these procedures and practical customs are usually not wide spread and very often are treated as the company’s “know how”. Results presented in this paper are original, relatively easily be repeated and checked. They may be used either by professionals, highly motivated individuals and representatives of small companies or also by ambitious amateurs.

This paper reports on the successful introduction of a sophisticated online catalogue system at the library of the Scott Polar Research Institute, Cambridge, using the Muscat program package. The system provides to both end‐users and library staff a choice between boolean searching on keywords and access using relevance feedback based on free text in English, mixed with UDC classification numbers. The system is implemented on an IBM 3084 computer. Significant benefits from the application of relevance feedback are reported with 10,000 records on file.

The purpose of this work is to study heat and mass transfer from mixed convection flow of polar fluid along a plate in porous media with chemical reaction.

The governing equations for this problem are solved numerically.

Polar fluids behave very differently from Newtonian fluids.

This work is original as little work has been reported for polar fluids.

The purpose of this paper is to provide a conceptual framework for using citizen science – defined as a data collection method through which non-professionals engage in contributing to authentic scientific inquiry – within the expedition cruise industry to contribute significantly to the collection of environmental data from hard-to-access Arctic areas.

The authors review trends in Arctic expedition cruise tourism and current needs in Arctic research and monitoring, and clarify where the expedition cruise tourism industry could have the most impact by providing data to the scientific community. The authors also compare the regulatory context in the Antarctic to that in the Arctic and discuss how these differences could affect the widespread use of citizen science. At last, the authors describe some general principles for designing citizen science programs to be successful on board, and highlight several existing programs that are being recognized for their contributions to a greater scientific understanding of the Arctic.

The authors find that citizen science data from the expedition cruise industry are underutilized as a tool for monitoring Arctic change. Numerous examples illustrate how citizen science programs on-board expedition ships can successfully collect robust scientific data and contribute to enhancing the knowledge and stewardship capacity of cruise passengers. Inclusion of citizen science data from the expedition cruise industry should be considered a critical part of international Arctic observing networks and systems.

Active participation in Arctic citizen science by tourists on expedition cruise ships has many potential benefits beyond the collection of high quality data, from increasing passengers’ knowledge and understanding of the Arctic while on board, to affecting their attitudes and behaviors after they return home.

The potential for tourism to contribute to Arctic observing systems has been discussed previously in the scientific literature; the authors narrow the focus to citizen science programs in the expedition cruise industry, and provide concrete examples, in the hope that this will streamline acceptance and implementation of these ideas by researchers and tourism practitioners.

The purpose of this study is to evaluate the effect of the four tautomeric forms of 2-amino-5-mercatpo-1,3,4-thiadizole (AMT) absorbed on copper surface by the polar or non-polar groups. Polar group of AMT is mostly electronegative with larger N and S atoms as central atoms. 5-amino-1,3,4-thiadiazole-2(3H)-thion (AMT-c) has the highest adsorption energy and is easy to react with copper. The interaction between AMT-c and copper conforms to chemisorption, which is to be further verified by the experiment on the weight loss measurement.

Adsorption behavior of AMT as corrosion inhibitor on copper surface in oil field was studied by weight loss measurement, and the corrosion inhibition mechanism was analyzed. Reactive sites and distributions of tautomeric forms of AMT as inhibitor on Cu(100) crystal plane were calculated by density functional theory.

All atoms of AMT are in the same plane, and AMT is an aromatic ring structure by large p-chain adsorbed on the metal surface by a plane configuration. AMT-c has the highest adsorption energy and also the most stable isomerized product. The determinate locations of AMT on the Cu(100) surface are the bridge and the hollow sites using molecular dynamics. Corrosion of copper can be effectively inhibited by AMT, which is a kind of excellent corrosion inhibitor, and this property is attributed to the polar groups and non-polar groups of AMT that play a role as absorption and shielding on copper surface, respectively. Inhibition efficiency is increased with the increase in the concentration of the inhibitor. The maximum efficiency of 92 per cent is obtained for 50 ppm AMT concentration at 373 K, which is attributed to the presence of extensively delocalized electrons of the phenyl rings, planarity and the presence of lone pair of electrons on N and S atoms, which favored a greater adsorption of inhibitors on copper surface.

Corrosion of copper can be effectively inhibited by AMT, which is a kind of excellent corrosion inhibitor, and this property is attributed to the polar groups and non-polar groups of AMT that play a role as absorption and shielding on copper surface, respectively. Adsorption of AMT as corrosion inhibitor on copper surface obeys Langmuir isotherm. The interaction between AMT and copper conforms to chemisorption, which is to be further verified by the experiment on the weight loss measurement.