R404A is a widely used medium-temperature refrigerant in low- and medium-temperature refrigeration systems because of its excellent efficiency and ozone-friendly properties. However， its high global warming potential （GWP=3 922） has led to its scheduled phase-out by 2030. R448A has emerged as a key alternative， offering superior thermophysical properties and a significantly lower GWP. This study investigated a refrigeration system in high- and low-temperature test chambers to explore the operating conditions for the case of R404A replaced by R448A. The results showed that the cooling capacity and coefficient of performance （COP） of both systems initially increased and then decreased with increasing refrigerant charge volume. The optimal charge volume for R448A was approximately 9.3% higher than that for R404A， and its cooling capacity and COP improved by over 17%. At the same evaporation temperature， the R448A system was less sensitive to ambient temperature fluctuations. A 10 ℃ increase in ambient temperature resulted in a 16.9% decrease in cooling capacity for R404A， whereas R448A only experienced an 8.6% decrease. Additionally， the maximum COP of the R448A system was approximately 9.9% higher than that of R404A.The return on investment for R448A is approximately one year， and as the system's life cycle progresses， the total annualized cost （TAC） of R448A becomes lower than that of R404A， with annual savings ranging from 0.6% to 6.6%. Replacing R404A with R448A can reduce total carbon emissions by over 32%， with approximately 27% of this reduction attributed to refrigerant leakage during operation and end-of-life recycling.
Heating and ventilation. Air conditioning, Low temperature engineering. Cryogenic engineering. Refrigeration
To investigate the effect of different drying conditions on the efficacy of a closed heat pump clothing-drying system, parametric studies with control variables were carried out on the circulating air volumetric flow rate, expansion valve opening, and air inlet temperature within the drying chamber and their impact on system heat production, heat pump system coefficient of performance (<italic>S</italic><sub>COP</sub>), cooling capacity utilization ratio (<italic>E</italic><sub>R</sub>), and exergy loss. The findings indicated that when the expansion valve was set to 70% opening, the circulating air volumetric flow rate was increased from 500 m<sup>3</sup>/h to 1 000 m<sup>3</sup>/h, and the heat generation of the system increased by 59.73%. In contrast, the <italic>S</italic><sub>COP</sub>, <italic>E</italic><sub>R</sub>, and exergy loss decreased by 31.29%, 56.65%, and 31.31%, respectively. Furthermore, when the circulating air volumetric flow rate of 1 000 m<sup>3</sup>/h was maintained while adjusting the expansion valve opening from 20% to 70%, the heat generation, <italic>S</italic><sub>COP</sub>, and <italic>E</italic><sub>R</sub> of the system increased by 32.58%, 6.51%, and 29.51%, respectively. At the same time, the exergy loss decreased by 12.44%. Finally, under the conditions of a 70% open expansion valve, a circulating air volumetric flow rate of 1 000 m<sup>3</sup>/h, and an increase in the desiccator′s air intake temperature from 40 ℃ to 70 ℃, the heat generation of the system increased by 43.71%, while the <italic>S</italic><sub>COP</sub>, <italic>E</italic><sub>R</sub>, and exergy loss decreased by 11.22%, 60.84%, and 14.17%, respectively. These results emphasize the advantages of reducing the circulating air volumetric flow rate and inlet air temperature within the drying chamber while increasing the expansion valve opening, as these adjustments help to improve the overall performance of the system and promote energy efficiency.
Heating and ventilation. Air conditioning, Low temperature engineering. Cryogenic engineering. Refrigeration
Within the project management context, project scheduling serves as an indispensable component, functioning as a fundamental tool for planning, monitoring, controlling, and managing projects more broadly. Although the resource-constrained project scheduling problem (RCPSP) lies at the core of project management activities, it remains largely disconnected from the broader literature on model-based systems engineering (MBSE), thereby limiting its integration into the design and management of complex systems. The original contribution of this paper is twofold. First, the paper seeks to reconcile the RCPSP with the broader literature and vocabulary of model-based systems engineering and hetero-functional graph theory (HFGT). A concrete translation pipeline from an activity-on-node network to a SysML activity diagram, and then to an operand net is constructed. Using this representation, it specializes the hetero-functional network minimum-cost flow (HFNMCF) formulation to the RCPSP context as a systematic means of HFGT for quantitative analysis and proves that the RCPSP is recoverable as a special case of a broader model. Secondly, on an illustrative instance with renewable and non-renewable operands, the specialized HFNMCF, while producing similar schedules, yields explicit explanations of the project states that enable richer monitoring and control. Overall, the framework preserves the strengths of the classical RCPSP while accommodating real-world constraints and enterprise-level decision processes encountered in large, complex megaprojects.
Context: Autism spectrum disorder (ASD) leads to various issues in the everyday life of autistic individuals, often resulting in unemployment and mental health problems. To improve the inclusion of autistic adults, existing studies have highlighted the strengths these individuals possess in comparison to non-autistic individuals, e.g., high attention to detail or excellent logical reasoning skills. If fostered, these strengths could be valuable in software engineering activities, such for identifying specific kinds of bugs in code. However, existing work in SE has primarily studied the challenges of autistic individuals and possible accommodations, with little attention their strengths. Objective: Our goal is to analyse the experiences of autistic individuals in software engineering activities, such as code reviews, with a particular emphasis on strengths. Methods: This study combines Social-Technical Grounded Theory through semi-structured interviews with 16 autistic software engineers and a survey with 49 respondents, including 5 autistic participants. We compare the emerging themes with the theory by Gama et al. on the Effect of Neurodivergent Cognitive Dysfunctions in Software Engineering Performance. Results: Our results suggest that autistic software engineers are often skilled in logical thinking, attention to detail, and hyperfocus in programming; and they enjoy learning new programming languages and programming-related technologies. Confirming previous work, they tend to prefer written communication and remote work. Finally, we report a high comfort level in interacting with AI-based systems. Conclusions: Our findings extend existing work by providing further evidence on the strengths of autistic software engineers.
Digital Engineering currently relies on costly and often bespoke integration of disparate software products to assemble the authoritative source of truth of the system-of-interest. Tools not originally designed to work together become an acknowledged system-of-systems, with their own separate feature roadmaps, deprecation, and support timelines. The resulting brittleness and conglomeration of disparate interfaces in the Digital Engineering Ecosystem of an organization drains resources and impairs efficiency and efficacy. If Model-Based Systems Engineering were applied to this problem, a complete system architecture model would be defined, and a purpose-built computing system-of-systems would be constructed to satisfy stakeholder needs. We have decades of research in computer science, cybersecurity, software and systems engineering, and human-computer interaction from which to draw that informs the design of a Seamless Digital Engineering tooling system, but it would require starting from a clean slate while carefully adopting existing standards. In this paper, this problem space and solution space are characterized, defining and identifying Seamless Digital Engineering as a grand challenge in Digital Engineering research.
Lyle Regenwetter, Cyril Picard, Amin Heyrani Nobari
et al.
The field of engineering is shaped by the tools and methods used to solve problems. Optimization is one such class of powerful, robust, and effective engineering tools proven over decades of use. Within just a few years, generative artificial intelligence (GenAI) has risen as another promising tool for general-purpose problem-solving. While optimization shines at precisely identifying highly-optimal solutions, GenAI excels at inferring problem requirements, bridging solution domains, handling mixed data modalities, and rapidly generating copious numbers of solutions. These differing attributes also make the two frameworks complementary. Hybrid `generative optimization' algorithms have gained traction across a few engineering applications and now comprise an emerging paradigm for engineering problem-solving. We expect significant developments in the near future around generative optimization, leading to changes in how engineers solve problems using computational tools. We offer our perspective on existing methods, areas of promise, and key research questions.
Duncan V. Mifsud, Sándor Góbi, Péter Herczku
et al.
The radiation chemistry and physics of solid N2O have been increasingly studied due to its potential presence on the surfaces of cold, outer Solar System bodies. However, to date, no study has investigated systematically the influence of temperature on this chemistry and physics. In this present study, crystalline N2O ices were irradiated using 2 keV electrons at five different temperatures in the 20-60 K range and the radiolytic dissociation of the molecular solid (as well as the radiolytic formation of seven product molecules) was quantified through the G-value. Our results indicate that temperature does indeed play a role in the radiolytic destruction of crystalline N2O, with higher temperatures being associated with higher destruction G-values. The formation G-values of NO, NO2, N2O2, N2O3, N2O4, N2O5, and O3 were also noted to vary with temperature, with each product molecule exhibiting a distinct trend. The applications of our experimental results to further understanding solid-phase radiation chemistry in the outer Solar System are discussed.
Eriks Klotins, Michael Unterkalmsteiner, Tony Gorschek
Context: Start-up companies have become an important supplier of innovation and software-intensive products. The flexibility and reactiveness of start-ups enables fast development and launch of innovative products. However, a majority of software start-up companies fail before achieving any success. Among other factors, poor software engineering could be a significant contributor to the challenges experienced by start-ups. However, the state-of-practice of software engineering in start-ups, as well as the utilization of state-of-the-art is largely an unexplored area. Objective: In this study we investigate how software engineering is applied in start-up context with a focus to identify key knowledge areas and opportunities for further research. Method: We perform a multi-vocal exploratory study of 88 start-up experience reports. We develop a custom taxonomy to categorize the reported software engineering practices and their interrelation with business aspects, and apply qualitative data analysis to explore influences and dependencies between the knowledge areas. Results: We identify the most frequently reported software engineering (requirements engineering, software design and quality) and business aspect (vision and strategy development) knowledge areas, and illustrate their relationships. We also present a summary of how relevant software engineering knowledge areas are implemented in start-ups and identify potentially useful practices for adoption in start-ups. Conclusions: The results enable a more focused research on engineering practices in start-ups. We conclude that most engineering challenges in start-ups stem from inadequacies in requirements engineering. Many promising practices to address specific engineering challenges exists, however more research on adaptation of established practices, and validation of new start-up specific practices is needed.
Vinicius Soares Silva Marques, Laurence Rodrigues do Amaral
Documentation is one of the most neglected activities in Software Engineering, although it is an important method of assuring quality and understanding. Bioinformatics software is generally written by researchers from fields other than Computer Science who usually do not provide documentation. Documenting bioinformatics software may ease its adoption in multidisciplinary teams and expand its impact on the community. In this paper, we highlight how one can document software that is already finished, using reverse engineering and thinking of the end-user.
In the ever-evolving realm of cybersecurity, the rise of generative AI models like ChatGPT, FraudGPT, and WormGPT has introduced both innovative solutions and unprecedented challenges. This research delves into the multifaceted applications of generative AI in social engineering attacks, offering insights into the evolving threat landscape using the blog mining technique. Generative AI models have revolutionized the field of cyberattacks, empowering malicious actors to craft convincing and personalized phishing lures, manipulate public opinion through deepfakes, and exploit human cognitive biases. These models, ChatGPT, FraudGPT, and WormGPT, have augmented existing threats and ushered in new dimensions of risk. From phishing campaigns that mimic trusted organizations to deepfake technology impersonating authoritative figures, we explore how generative AI amplifies the arsenal of cybercriminals. Furthermore, we shed light on the vulnerabilities that AI-driven social engineering exploits, including psychological manipulation, targeted phishing, and the crisis of authenticity. To counter these threats, we outline a range of strategies, including traditional security measures, AI-powered security solutions, and collaborative approaches in cybersecurity. We emphasize the importance of staying vigilant, fostering awareness, and strengthening regulations in the battle against AI-enhanced social engineering attacks. In an environment characterized by the rapid evolution of AI models and a lack of training data, defending against generative AI threats requires constant adaptation and the collective efforts of individuals, organizations, and governments. This research seeks to provide a comprehensive understanding of the dynamic interplay between generative AI and social engineering attacks, equipping stakeholders with the knowledge to navigate this intricate cybersecurity landscape.
The compressor is the core equipment of a vapor compression system, which significantly affects the energy consumption and stability of the system. An experimental system was built for the vapor compression system driven by the roots compressor, in which the evaporation temperature, evaporation pressure, compressor pressure, and evaporation capacity were 80–100 °C, 46.60–101.64 kPa, 17.86–36.03 kPa and 125.72–424.85 kg/h, respecitvely. The suction flow rate, compression specific power, volumetric efficiency, and isentropic efficiency of the root water vapor compressor with varying evaporation temperatures were studied experimentally. The results show that the suction flow rate (7.10–11.74 m3/min) gradually increased, and the compression specific power (310.69–158.54 kJ/kg) gradually decreased with the increase in evaporation temperature. Both the volumetric efficiency (52.21%–71.54%) and isentropic efficiency (16.48%–36.15%) increased with the increase in evaporation temperature. Increasing the frequency can enhance the efficiency of the compressor, and the measured volumetric efficiency and compression specific power were consistent with the data in previous studies. There was a difference between the experimental and theoretical values of the volumetric efficiency and the isentropic efficiency of the compressor, but this difference decreased with an increase in the evaporation temperature, and the root water vapor compressor was more stable and highly efficient in the range of evaporation temperature of 90–100 °C.
Heating and ventilation. Air conditioning, Low temperature engineering. Cryogenic engineering. Refrigeration
Latent heat thermal energy storage technology is applied to air-source heat pump systems in cold regions to improve their adaptability. Heat is stored during the day and released at night. A simulation is conducted in this study to further investigate the heat storage and discharge characteristics of the system and the effect of applying multistage PCMs (phase-change materials). The results show that the heat storage capacity varies linearly with the charging time, where 18.94 kW?h is achieved at 380 min, and the average COP is 2.51. The heat discharge capacity first increases linearly and then reaches 13.58 kW?h at 180 min. When the inlet water temperature is 35 °C, the system stabilized after six continuous cycles, and its energy storage efficiency is 99.06%. The charging time of the three-stage PCM is reduced by 9.60%; its COP is increased by 3.97%; its total exergy efficiency is increased by 4.84% compared with those of a single-stage PCM. Reducing the melting point of the PCM in the subcooled zone is key to improving the system performance.
Heating and ventilation. Air conditioning, Low temperature engineering. Cryogenic engineering. Refrigeration
Wolfgang Mauerer, Stefan Klessinger, Stefanie Scherzinger
Ascertaining reproducibility of scientific experiments is receiving increased attention across disciplines. We argue that the necessary skills are important beyond pure scientific utility, and that they should be taught as part of software engineering (SWE) education. They serve a dual purpose: Apart from acquiring the coveted badges assigned to reproducible research, reproducibility engineering is a lifetime skill for a professional industrial career in computer science. SWE curricula seem an ideal fit for conveying such capabilities, yet they require some extensions, especially given that even at flagship conferences like ICSE, only slightly more than one-third of the technical papers (at the 2021 edition) receive recognition for artefact reusability. Knowledge and capabilities in setting up engineering environments that allow for reproducing artefacts and results over decades (a standard requirement in many traditional engineering disciplines), writing semi-literate commit messages that document crucial steps of a decision-making process and that are tightly coupled with code, or sustainably taming dynamic, quickly changing software dependencies, to name a few: They all contribute to solving the scientific reproducibility crisis, and enable software engineers to build sustainable, long-term maintainable, software-intensive, industrial systems. We propose to teach these skills at the undergraduate level, on par with traditional SWE topics.
Using models for requirements engineering (RE) is uncommon in systems engineering, despite the widespread use of model-based engineering in general. One reason for this lack of use is that formal models do not match well the trend to move towards agile developing methods. While there exists work that investigates challenges in the adoption of requirements modeling and agile methods in systems engineering, there is a lack of work studying successful approaches of using requirements modelling in agile systems engineering. To address this gap, we conducted a case study investigating the application of requirements models at Ericsson AB, a Swedish telecommunications company. We studied a department using requirements models to bridge agile development and plan-driven development aspects. We find that models are used to understand how requirements relate to each other, and to keep track with the product's evolution. To cope with the effort to maintain models over time, study participants suggest to rely on text-based notations that bring the models closer to developers and allow integration into existing software development workflows. This results in tool trade-offs, e.g., losing the possibility to control diagram layout.
Emad Shihab, Stefan Wagner, Marco A. Gerosa
et al.
We are witnessing a massive adoption of software engineering bots, applications that react to events triggered by tools and messages posted by users and run automated tasks in response, in a variety of domains. This thematic issues describes experiences and challenges with these bots.
This study investigated the optimal design of a capillary heat exchanger device for the heat pump system and its innovative engineering application in a building. The overall aim was to use a capillary heat exchanger to obtain energy in coastal areas for promoting renewable energy in low-carbon building design. Initially, the main factors affecting the efficiency of the capillary heat exchanger were identified, a mathematical model was then established to analyse the heat transfer process. The analysis showed the flow rate and the capillary length are the key factors affecting the efficiency of the capillary heat exchanger. Secondly, to optimize the structural design of the capillary heat exchanger, the heat energy transfer is calculated with different lengths of the capillary under various flow rates in summer and winter conditions, respectively. Thirdly, a typical building is selected to analyse the application of the capillary heat exchanger for extracting energy in the coastal area. The results show the performance of the selected capillary heat exchanger heat pump system, in winter, the heat energy transfer rate is 60 W/m2 when the seawater temperature is 3.7 °C; in summer, the heat energy transfer rate is 150 W/m2 when the seawater temperature is 24.6 °C. Finally, the above field test results were examined using a numerical simulation model, the test and simulation results agree with each other quite well. This paper is conducive in promoting the development of the capillary heat exchanger heat pump as an innovative sustainable technology for net-zero energy and low carbon buildings using renewable energy in coastal areas. Practical application: A recently proposed capillary heat exchanger is used as an energy extraction and utilisation device to obtain energy in coastal areas for promoting renewable energy in low-carbon building design. This paper explores the application of a capillary heat exchanger as both cold and heat sources for application in typical low-rise buildings. The analysis of the heat energy transfer rate of a typical low-rise building located in a coastal area in summer and winter provides guidance for the application of capillary heat exchangers.
The concrete transition zone plays an important role in bridge expansion joint structure, which provides a good connection between the expansion joint installation and bridge decks. However, the premature deteriorations of concrete transition zone are found to be the major diseases of expansion joint during service life. Therefore, a material with high ductility, superior durability, and low modulus/stiffness is highly desired for transition zone. Engineering cementitious composites (ECC), a kind of high-performance concrete featuring the prominent ductility and durability, are a promising material for transition zone of expansion joint. This paper introduces a specific ECC material for transition zone, which is modified by emulsified asphalt (EA-ECC), and has the high deformation ability and low modulus/stiffness. The flexural mechanical properties including flexural stress-load displacement relation, flexural secant stiffness, and elastic modulus of the EA-ECC’s matrix were investigated experimentally. The microstructures of EA-ECC were observed via scanning electron microscope (SEM) imaging. Additionally, the influence of test temperature on flexural mechanical properties of EA-ECC was also investigated. It is found that the ultimate flexural stress of EA-ECC reduces gradually with increasing EA content. Conversely, the flexural deformation capacity shows an increasing trend with EA content. Additionally, incorporating EA significantly reduces the flexural secant stiffness and elastic modulus of EA-ECCs. The research results concluded that incorporating EA in ECC can significantly improve the flexural deformation ability accompanied by relatively lower modulus, which is likely to reduce the impact load on transition zone caused by vehicle bumping and prolong the service life of the whole bridge expansion joint structure.