Fast iterative solvers for geomechanics in a commercial FE code

There is a pressing need to improve the feasibility of three-dimensional finite element (FE) methods applied to many problems in civil engineering. This is particularly the case for static analyses in geotechnical engineering: ideally, models would be 3D, follow the actual geometry, use non-linear material formulations and allow simulation of construction sequences, and all of this with a reasonable degree of accuracy. One major obstacle to improvements in this regard is the difficulty in solving of the set of (linearised) algebraic equations which arises from a typical discretisation approach. Very large systems become cumbersome for direct techniques to solve economically. This paper describes the incorporation of iterative (rather than direct) solution techniques, developed through University research, into commercial FE software for geotechnics

Feasibility of obtaining hypervelocity acceleration using propellant lined launch tubes Final report, 27 Sep. 1966 - 5 May 1970

Feasibility of explosive lining in launch tube for hypervelocity projectile acceleratio

Practical Seismic Design Considering Non-Linear Soil-Pile-Structure Interaction

A substructure approach is proposed for the seismic analysis considering the soil-pile-structure interaction. Two software packages are available for practical applications, DYNAN program and SAP 2000 program. The nonlinearity of soil is considered approximately using a boundary zone model with non-reflective interface. The validation of model is confirmed with dynamic tests on piles in the field, and the results for a single pile are used to compare with the predictions in this study. The liquefaction for sand soil layer can be accounted for, and a case of liquefaction is discussed. The seismic response of a vacuum tower structure supported on pile foundation is examined in a high seismic zone, including response spectrum analysis and time history analysis. To illustrate the effects of soil-pile-structure interaction on the seismic response of structure, three different base conditions are considered, rigid base, i.e. no deformation of the foundation; linear soil-pile system; and nonlinear soil-pile system. The method and procedure introduced can be applied to the design of tall buildings, bridges, industrial structures and offshore platforms with soil-pile-structure interaction under seismic, blast, sea wave and other dynamic loads

Test results of a Stirling engine utilizing heat exchanger modules with an integral heat pipe

The Heat Pipe Stirling Engine (HP-1000), a free-piston Stirling engine incorporating three heat exchanger modules, each having a sodium filled heat pipe, has been tested at the NASA-Lewis Research Center as part of the Civil Space Technology Initiative (CSTI). The heat exchanger modules were designed to reduce the number of potential flow leak paths in the heat exchanger assembly and incorporate a heat pipe as the link between the heat source and the engine. An existing RE-1000 free-piston Stirling engine was modified to operate using the heat exchanger modules. This paper describes heat exchanger module and engine performance during baseline testing. Condenser temperature profiles, brake power, and efficiency are presented and discussed

Strategic Implications of Data Gathering Activities in Small Firms: A Comparison Between Family and Nonfamily Firms

The empirical research presented in this article examines data gathering activities  and processes of small businesses and compares those activities and processes in family and nonfamily firms. MANOVA and t-test analyses  were  used  in analyzing questionnaire  data from 1245 respondents in 89 small businesses. For these small firms, the results indicated differences in the relative use of types of information gathered and processes used. Further, the study found differences between family and nonfamily firm data gathering activities and processes  used.  Finally, the study indicated that the type of customer to whom a firm sold had an impact on the data gathering activities of a small business and  impacted family  and nonfamily firm  data gathering differentially

Understanding Lifeguard Recruitment and Selection Practices in Victorian Aquatic and Recreation Centers (ARCs)

Extensive research has focused on human resource management (HRM) and recruitment and selection practices across different settings. However, there is a gap in the scholarly literature in ARC settings, including lifeguards. Additionally, the aquatics industry is experiencing unprecedented levels of lifeguard turnover within aquatic facilities. The recruitment and selection process can impact employee turnover. Therefore, an important first step to address lifeguard turnover is to better understand the current recruitment and selection practices of lifeguards. This study focuses on the recruitment and selection practices of ARC management to better understand the recruitment and selection of lifeguards. The analysis is based on 16 semi-structured interviews with ARC managers involved in lifeguard recruitment and selection. Participants included center managers, assistant center managers, and operations managers/coordinators. A deductive analysis was able to effectively explain the current recruitment and selection practices for recruiting lifeguards in Victorian ARCs

Some Low Dimensional Evidence for the Weak Gravity Conjecture

We discuss a few examples in 2+1 dimensions and 1+1 dimensions supporting a recent conjecture concerning the relation between the Planck scale and the coupling strength of a non-gravitional interaction, unlike those examples in 3+1 dimensions, we do not have to resort to exotic physics such as small black holes. However, the result concerning these low dimensional examples is a direct consequence of the 3+1 dimensional conjecture.Comment: 7 pages, harvma

Intumescent Flame Retardant Polyamide 11 Nanocomposites

Current polyamide 11 and 12 are lacking in fire retardancy and high strength/high heat resistance characteristics for a plethora of fabricated parts that are desired and required for performance driven applications. The introduction of selected nanoparticles such as surface modified montmorillonite (MMT) clay or carbon nanofibers (CNFs), combined with a conventional intumescent flame retardant (FR) additive into the polyamide 11/polyamide 12 (PA11/PA12) by melt processing conditions has resulted in the preparation of a family of intumescent polyamide nanocomposites. These intumescent polyamide 11 and 12 nanocomposites exhibit enhanced polymer performance characteristics, i.e., fire retardancy, high strength and high heat resistance and are expected to expand the market opportunities for polyamide 11 and polyamide 12 polymer manufacturers. The objective of this research is to develop improved polyamide 11 and 12 polymers with enhanced flame retardancy, thermal, and mechanical properties for selective laser sintering (SLS) rapid manufacturing (RM). In the present study, a nanophase was introduced into the polyamide 11 and combining it with a conventional intumescent FR additive via twin screw extrusion. Arkema RILSAN® polyamide 11 molding polymer pellets were examined with two types of nanoparticles: chemically modified montmorillonite (MMT) organoclays, and carbon nanofibers (CNFs); and Clairant’s Exolit® OP 1230 intumescent FR additive were used to create a family of FR intumescent polyamide 11 nanocomposites. Transmission electron microscopy (TEM) was used to determine the degree of nanoparticles dispersion. Injection molded specimens were fabricated for physical, thermal, and flammability measurements. Thermal stability of these intumescent polyamide 11 nanocomposites was examined by TGA. Flammability properties were obtained using the Cone Calorimeter at an external heat flux of 35 kW/m 2 and UL 94 Test Method. Heat deflection temperatures (HDT) were also measured. TEM micrographs, physical, thermal, and flammability properties are presented. FR intumescent polyamide 11 nanocomposites properties are compared with polyamide 11 baseline polymer. Based on flammability and mechanical material performance, selective polymers including polyamide 11 nanocomposites and control polyamide 11 will be cryogenically ground into fine powders for SLS RM processing. SLS specimens will be fabricated for thermal, flammability, and mechanical properties characterization.Mechanical Engineerin

A Weak Gravity Conjecture for Scalar Field Theories

We show that the recently proposed weak gravity conjecture\cite{AMNV0601} can be extended to a class of scalar field theories. Taking gravity into account, we find an upper bound on the gravity interaction strength, expressed in terms of scalar coupling parameters. This conjecture is supported by some two-dimensional models and noncommutative field theories.Comment: version published in JHE

Interest and barriers to research in obstetric haematology – findings from a national survey in the United Kingdom

Introduction: In 2021, the steering committee members of British Society of Haematology Obstetric Haematology Special Interest Group noted difficulties in opening research studies. This led to the development of a survey to further evaluate this issue. Method: An electronic survey was distributed to all members of the British Society of Haematology Obstetric Haematology Special Interest Group and to relevant specialty leads of the National Institute for Health and Care Research Clinical Research Network for further dissemination within these networks. Results: Responses were received from 65 participants (73% consultant grade); mainly haematologists (52%) or obstetricians (39%). Less than a third of participants reported dedicated time for research in their job plan, with only five participants reporting no challenges in opening research studies in obstetric haematology. Discussion: The survey confirmed significant interest in obstetric haematology research, with barriers to participation. We propose further actions to facilitate increased research