Modeling of Twin Screw Extrusion of Polymeric Materials

An issue of modeling of twin-screw extrusion of polymeric materials is reviewed. The paper is written in honor of Prof. James L. White who was a pioneer in studying this issue. A global approach to process modeling is presented which includes solid polymer transport, polymer plasticating, and the flow of molten polymer. The methodology of CFD modeling of twin-screw extrusion is presented as well as the examples of this modeling which show the details of the process. Optimization and scaling of twin-screw extrusion are also covered. And finally, the future prospects of developments and research of twin screw extrusion is discussed.

Where does theory go in military history?

This article presents a critique of Whiggish approaches to military history. It begins with this quotation from Dennis Showalter – ‘military history is arguably the last stronghold of what historiographers call the “Whig interpretation”’ – and notes that Showalter’s assessment was a reflection on both the general absence of theory and the linked poverty of the fallback theoretical basket of the subject, with such staples as War and Society, Face of Battle, and Military Revolutions. Recognizing the shortcomings of numerous approaches to military history, the author identifies the challenge – writing military history that incorporates multiple regions and takes a global approach. As the author concludes, the problem for the historian remains how best to address the complex interactions of, in particular, change and continuity, structure and conjuncture, the West and the wider world, and to do so to produce an account that is able to identify and probe crucial issues and key questions.

The ecology of sustainable tourism

PurposeThis paper questions the present state of the world's tourism industry and advocates the need for an approach where quality assumes greater importance than quantity.Design/methodology/approachThis paper provides an analysis of the tourism industry's recent evolution while trying to identify reasons for its decline which amongst others, include security issues and economic crisis.FindingsIn developing a sustainable tourism industry especially in these economically challenging times, we must learn to appreciate what is precious in our own lives and in our respective communities. This in turn will help us maintain and further explore the uniqueness of our tourist destinations. The greatest threat to leisure and tourism (and to a lesser extent to business travel) is the fact that travel has lost a good deal of its romance and enchantment due to a global approach to its development. In the rush for efficiency and quantitative analysis the travel and tourism industry may have forgotten that each traveller has unique expectations.Originality/valueSustainable tourism is not only about how a tourist location adapts but also about what a city or destination accomplishes when re-discovering its inner essence and then promoting it.

Healthy Knee Kinematic Phenotypes Identification Based on a Clustering Data Analysis

The purpose of this study is to identify healthy phenotypes in knee kinematics based on clustering data analysis. Our analysis uses the 3D knee kinematics curves, namely, flexion/extension, abduction/adduction, and tibial internal/external rotation, measured via a KneeKG™ system during a gait task. We investigated two data representation approaches that are based on the joint analysis of the three dimensions. The first is a global approach that is considered a concatenation of the kinematic data without any dimensionality reduction. The second is a local approach that is considered a set of 69 biomechanical parameters of interest extracted from the 3D kinematic curves. The data representations are followed by a clustering process, based on the BIRCH (balanced iterative reducing and clustering using hierarchies) discriminant model, to separate 3D knee kinematics into homogeneous groups or clusters. Phenotypes were obtained by averaging those groups. We validated the clusters using inter-cluster correlation and statistical hypothesis tests. The simulation results showed that the global approach is more efficient, and it allows the identification of three descriptive 3D kinematic phenotypes within a healthy knee population.

REGULATORY APPROACHES LEADING TO HOLISTIC IMPLEMENTATION IN A FISHING VESSEL FLEET LESS THAN 24 M IN LENGTH

Fishing is a very dangerous sea activity with a high rate of fatalities that is difficult to deal with by Maritime and Fisheries Administrations around the world. Meanwhile the Ocean Governance requires a global approach to sustainability and safety, with overarching principles governing both of them. This paper deals for the first time with the implementation of a complete methodology to assess the safety at sea, by means of a bottom-up goal based standards with safety level approach, encompassing the national regulations and using formal safety assessment as the driver in a fishing vessel fleet below 24 m in length (L). It is concluded that such methodologies are applicable, goal based regulations can be established, flexibility in the design can be provided and have the potential to be later extrapolated to holistic approaches.

Carbon Steel X65QS Pipeline Qualification for Extreme Sour Service a Global Approach: Line Pipe, Welding, Eca Methodology and Diyab Pipeline Case Study

In the wake of failures of large diameter pipelines made from plates using the Thermo-Mechanically Controlled Process (TMCP), the suitability of carbon steel material for sour environments where the H2S partial pressure is largely over 1 bar has been questioned. Understanding that seamless quench and tempered material are not prone to the same phenomenon as large diameter TMCP pipes, it has been decided to ensure the integrity of the DIYAB pipeline by qualification using the actual production environment pH=3.5 at 24°C and 6.84 bar H2S plus 6.84 bar CO2. The global approach includes the qualification to sour service resistance under 6.84bar H2S of the base material and the welds without post weld heat treatment. Fracture toughness tests under 6.84bar H2S were also conducted, and the results fed into an Engineering Criticality Assessment (ECA) to define the Non-Destructive Testing (NDT) acceptance criteria. The NDT tools were selected for their ability to detect the critical flaws and validated. The global approach methodology and results are presented.

An accessible, efficient and global approach for the large-scale sequencing of bacterial genomes

We have developed an efficient and inexpensive pipeline for streamlining large-scale collection and genome sequencing of bacterial isolates. Evaluation of this method involved a worldwide research collaboration focused on the model organism Salmonella enterica, the 10KSG consortium. Following the optimization of a logistics pipeline that involved shipping isolates as thermolysates in ambient conditions, the project assembled a diverse collection of 10,419 isolates from low- and middle-income countries. The genomes were sequenced using the LITE pipeline for library construction, with a total reagent cost of less than USD$10 per genome. Our method can be applied to other large bacterial collections to underpin global collaborations.

Engine Downsizing; Global Approach to Reduce Emissions: A World-Wide Review

Engine downsizing is a promising method to reduce emissions and fuel consumption of internal combustion engines. The main concept is reducing engine displacement volume keeping needed output characteristics unchanged. The issue became one of the most filed of interest in recent years after the International Energy Agency defined a target of 50 % reduction in global average emissions by the year 2030. In this review paper, different aspects of researchers’ efforts on engine downsizing are configured and due to overlaps, categorized into five main areas. Each category is discussed thoroughly and recent works are pointed. The global attention into these categories, countries involved and the trend changed in recent four years are presented in details. Doi: 10.28991/HIJ-2021-02-04-010 Full Text: PDF