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Polyimides rank among the most heat-resistant polymers and find application in a variety of fields, including transportation, electronics, and membrane technology. The aim of this work is to study the structural, thermal, mechanical, and gas permeation properties of polyimide based nanocomposite membranes in flat sheet configuration. For this purpose, numerous advanced techniques such as atomic force microscopy (AFM), SEM, TEM, TGA, FT-IR, tensile strength, elongation test, and gas permeability measurements were carried out. In particular, BTDA–TDI/MDI (P84) co-polyimide was used as the matrix of the studied membranes, whereas multi-wall carbon nanotubes were employed as filler material at concentrations of up to 5 wt.% All studied films were prepared by the dry-cast process resulting in non-porous films of about 30–50 μm of thickness. An optimum filler concentration of 2 wt.% was estimated. At this concentration, both thermal and mechanical properties of the prepared membranes were improved, and the highest gas permeability values were also obtained. Finally, gas permeability experiments were carried out at 25, 50, and 100 ◦C with seven different pure gases. The results revealed that the uniform carbon nanotubes dispersion lead to enhanced gas permeation properties.
Water security is a major concern for water-scarce cities that face dynamic water challenges due to limited water supply, climate change and increasing water demand. Framing urban water security is challenging due to the complexity and uncertainties of the definitions and assessment frameworks concerning urban water security. Several studies have assessed water security by granting priority indicators equal weight without considering or adapting to the local conditions. This study develops a new urban water security assessment framework with application to the water-scarce city
of Madaba, Jordan. The study applies the new assessment framework on the study area and measures urban water security using the integrated urban water security index (IUWSI) and the analytic hierarchy process (AHP) as a decision management tool to prioritise and distinguish indicators that affect the four dimensions of urban water security: drinking water, ecosystems, climate change and water-related hazards, and socioeconomic aspects (DECS). The integrated urban water security index (IUWSI) highlights the state of water security and intervention strategies in Madaba. The study reveals that urban water security in Madaba is satisfactory to meet basic needs, with shortcomings in some aspects of the DECS. However, Madaba faces poor security in terms of managing climate- and water-related risks. The IUWSI framework assists with a rational and evidence-based decision-making process, which is important for enhancing water resources management in water-scarce cities.
This paper introduces CAAI, a novel cognitive architecture for artificial intelligence in cyber-physical production systems. The goal of the architecture is to reduce the implementation effort for the usage of artificial intelligence algorithms. The core of the CAAI is a cognitive module that processes the user’s declarative goals, selects suitable models and algorithms, and creates a configuration for the execution of a processing pipeline on a big data platform. Constant observation and evaluation against performance criteria assess the performance of pipelines for many and different use cases. Based on these evaluations, the pipelines are automatically adapted if necessary. The modular design with well-defined interfaces enables the reusability and extensibility of pipeline components. A big data platform implements this modular design supported by technologies such as Docker, Kubernetes, and Kafka for virtualization and orchestration of the individual components and their communication. The implementation of the architecture is evaluated using a real-world use case. The prototypic implementation is accessible on GitHub and contains a demonstration.
The use of nematic liquid crystal (LC) mixtures for microwave frequency applicationspresents a fundamental drawback: many of these mixtures have not been properly characterizedat these frequencies, and researchers do not have an a priori clear idea of which behavior they canexpect. This work is focused on developing a new procedure for the extraction of the main parametersof a nematic liquid crystal: dielectric permittivity and loss tangent at 11 GHz under differentpolarization voltages; splay elastic constantK11, which allows calculation of the threshold voltage(Vth); and rotational viscosityγ11, which allows calculating the response time of any arbitrary device.These properties will be calculated by using a resonator-based method, which is implementedwith a new topology of substrate integrated transmission line. The LC molecules should be rotated(polarized) by applying an electric field in order to extract the characteristic parameters; thus,the transmission line needs to have two conductors and low electric losses in order to preserve theintegrity of the measurements. This method was applied to a well-known liquid crystal mixture(GT3-23002 from MERCK) obtaining the permittivity and loss tangent versus bias voltage curves,the splay elastic constant, and the rotational viscosity of the mixture. The results validate the viabilityof the proposed method.
The Enhancement of standard dense phase carbon dioxide (DPCD) pasteurization by additional mechanical effects wasassessed in this work. These effects were induced during pasteurization by the sudden depressurization in a narrow mini-tube. The high flow velocities, moderate pressures (40–80 bar) and low temperatures (25–45°C) lead to intense degasifica-tion and shear stress. The inactivation of the test microorganismEscherichia coliDH5a(E. coliDH5a) was determinedbefore and after depressurization in the minitube, representing entirely chemical DPCD via dissolved CO2and total inacti-vation comprising the effects of dissolved CO2and mechanical effects, respectively. Compared to conventional DPCDpasteurization, which is mostly attributed to chemical effects, the additional mechanical effects increased the inactivationefficiency considerably.
At the case study of the city of Cologne and the neighbouring Rhein‐Erft‐Kreis (a county), selected resilience aspects of critical infrastructure (CI) and cascading effects are analysed concerning major river floods. Using a Geographic Information System, the applicability of the approach is demonstrated using open source software and data, augmented by manual entries. This study demonstrates the feasibility and limitations of analysing lifeline features of interest for disaster risk and emergency management such as roads, bridges and electricity supply. By highlighting interdependencies of emergency services with CI such as roads, cascading effects of interconnected paths are shown. The findings indicate that in an extreme event flood scenario over 2,000 km of roads and eight bridges will be exposed to floods in the area of the rivers Rhine and Erft. This places huge demands on disaster and emergency management institutions and people affected and limits their resiliency.
The paper presents results of the modelling of heat transfer at film boiling of a liquid in a porous medium on a vertical heated wall bordering with the porous medium. Such processes are observed at cooling of high-temperature surfaces of heat pipes, microstructural radiators etc. Heating conditions at the wall were the constant wall temperature or heat flux. The outer boundary of the vapor film was in contact with moving or stationary liquid inside the porous medium. An analytical solution was obtained for the problem of fluid flow and heat transfer using the porous medium model in the Darcy–Brinkman and Darcy–Brinkman–Forchheimer approximation. It was shown that heat transfer at film boiling in a porous medium was less intensive than in the absence of a porous medium (free fluid flow) and further decreased with the decreasing permeability of the porous medium. Significant differences were observed in frames of both models: 20% for small Darcy numbers at Da < 2 for the Darcy–Brinkman model, and 80% for the Darcy–Brinkman–Forchheimer model. In the Darcy–Brinkman model, depending on the interaction conditions at the vapor–liquid interface (no mechanical interaction or stationary fluid), a sharp decrease in heat transfer was observed for the Darcy numbers lower than five. The analytical predictions of heat transfer coefficients qualitatively agreed with the data of Cheng and Verma (Int J Heat Mass Transf 24:1151–1160, 1981) though demonstrated lower values of heat transfer coefficients for the conditions of the constant wall temperature and constant wall heat flux.
To realize a reliable and cost-effective application of high-temperature superconductive (HTS) equipment at high-voltage (HV) levels, the influence of thermally induced gas bubbles on the dielectric strength of different solid insulating materials in liquid nitrogen (LN2) was investigated. A heatable copper tape electrode arrangement was developed simulating HTS tapes with insulation in between. AC breakdown measurements were performed without and with forced boiling on insulating papers, polypropylene laminated paper (PPLP) and polyimide (PI) films. Under nucleate boiling the influence of bubbles on the dielectric strength of all materials was not significant. However under film boiling the dielectric strength of the insulating papers decreased to a level comparable to their dielectric strength in air, demonstrating the insufficient impregnation of porous materials under film boiling. For PI there was no degradation at all. PPLP retained about 70% of its basic dielectric strength in LN2.
Campylobacter spp. are one of the most important food-borne pathogens, which are quite susceptible to environmental or technological stressors compared to other zoonotic bacteria. This might be due to the lack of many stress response mechanisms described in other bacteria. Nevertheless, Campylobacter is able to survive in the environment and food products. Although some aspects of the heat stress response in Campylobacter jejuni are already known, information about the stress response in other Campylobacter species are still scarce. In this study, the stress response of Campylobacter coli and Campylobacter lari to elevated temperatures (46°C) was investigated by survival assays and whole transcriptome analysis. None of the strains survived at 46°C for more than 8 h and approximately 20% of the genes of C. coli RM2228 and C. lari RM2100 were differentially expressed. The transcriptomic profiles showed enhanced gene expression of several chaperones like dnaK, groES, groEL, and clpB in both strains, indicating a general involvement in the heat stress response within the Campylobacter species. However, the pronounced differences in the expression pattern between C. coli and C. lari suggest that stress response mechanisms described for one Campylobacter species might be not necessarily transferable to other Campylobacter species.
As Digital Twins gain more traction and their adoption in industry increases, there is a need to integrate such technology with machine learning features to enhance functionality and enable decision making tasks. This has lead to the emergence of a concept known as Digital Triplet; an enhancement of Digital Twin technology through the addition of an ’intelligent activity layer’. This is a relatively new technology in Industrie 4.0 and research efforts are geared towards exploring its applicability, development and testing of means for implementation and quick adoption. This paper presents the design and implementation of a Digital Triplet for a three-floor elevator system. It demonstrates the integration of a machine learning (ML) object detection model and the system Digital Twin. This was done to introduce an additional security feature that enabled the system to make a decision, based on objects detected and take preliminary security measures. The virtual model was designed in Siemens NX and programmed via Total Integrated Automation (TIA) portal software. The corresponding physical model was fabricated and controlled using a Programmable Logic Controller (PLC) S7 1200. A control program was developed to mimic the general operations of a typical elevator system used in a commercial building setting. Communication, between the physical and virtual models, was enabled using the OPC-Unified Architecture (OPC-UA) protocol. Object recognition using “You only look once” (YOLOV3) based machine learning algorithm was incorporated. The Digital Triplet’s functionality was tested, ensuring the virtual system duplicated actual operations of the physical counterpart through the use of sensor data. Performance testing was done to determine the impact of the ML module on the real-time functionality aspect of the system. Experiment results showed the object recognition contributed an average of 1.083s to an overall signal travel time of 1.338 s.