Hasil untuk "Low temperature engineering. Cryogenic engineering. Refrigeration"

Zhiwen Shen, Xuetong He, Huicai Xie et al.

Magnetic refrigeration at liquid helium temperatures (4.2 K) serves as a critical technology for frontier scientific applications, yet its advancement is constrained by performance limitations of magnetocaloric materials (MCMs). Therefore, it is imperative to develop MCMs with large magnetocaloric effects (MCE) driven by a low magnetic field near liquid helium temperature. In this study, Sr 2+ ‐doped Eu 3 −x Sr x P 2 O 8 ( x  = 0, 1/3, 2/3, and 1) series compounds were synthesized via solid‐state reaction and their magnetization characteristics were investigated. As a result, we demonstrate for the first time that nonmagnetic Sr 2+ substitution in ferromagnetic Eu 3 P 2 O 8 enables effective regulation of the magnetic ordering temperature from 6.4 K to 3.5 K. Remarkably, the maximum magnetic entropy change () remains almost constant between 10.0 and 11.1 J·kg −1 ·K −1 at μ 0 Δ H  = 0–1 T despite the reduced Eu 2+ concentration upon Sr 2+ substitution; the fine‐tuning of the crystal structure and reconstruction of the electronic structure compensate for the negative impact of mere magnetic dilution on magnetocaloric performance. These compounds exhibit giant reversible MCEs near liquid helium temperature, positioning them as promising candidates for helium‐free cryogenic refrigeration. This work establishes a novel paradigm for synergistic optimization of magnetocaloric performance and phase transition temperature through single‐elementsubstituting.

M. Kazem, Ali Khalid Shaker Alsayyab

This study examines the thermodynamic performance of a ternary refrigerant mixture composed of R32, R1234ze (E), and R152a (20/20/60 % by mass fraction) as a low-global warming potential (GWP) alternative to R410A in vapour compression refrigeration systems. The simulation was performed using REFPROP under standard operating conditions linked with an engineering equation solver, including 5 K of superheating and 5 K of subcooling. Under different operating conditions of constant evaporation temperature (Te = 5 °C) with varying condensation temperatures (TC) (40 to 55 °C by step 2.5°C). Key parameters, including cooling capacity (Qₑ), compressor work (Wc), pressure ratio (Pr), discharge temperature (TD), mass flow rate (ṁ), and volumetric efficiency (ηᵥ), were evaluated to assess performance. The mixture’s discharge temperature was slightly lower than that of R410A; this will reduce compressor thermal stress and increase compressor life span. Charts illustrating the effect of Tc on all performance indicators were created. In addition to thermodynamic analysis, safety considerations were reviewed. Despite its mild flammability (A2L), the adopted mixture demonstrated stable operation across various conditions and offers potential for applications where safety measures can be effectively implemented. The results indicate that the new mixture presents an energy-efficient and environmentally sustainable replacement for R410A. Further experimental validation is recommended to confirm these findings in real-world scenarios.

Chao Wang, Quan Zhang, Manchao He et al.

Sonja M. Hyrynsalmi, Grischa Liebel, Ronnie de Souza Santos et al.

The discipline of software engineering (SE) combines social and technological dimensions. It is an interdisciplinary research field. However, interdisciplinary research submitted to software engineering venues may not receive the same level of recognition as more traditional or technical topics such as software testing. For this paper, we conducted an online survey of 73 SE researchers and used a mixed-method data analysis approach to investigate their challenges and recommendations when publishing interdisciplinary research in SE. We found that the challenges of publishing interdisciplinary research in SE can be divided into topic-related and reviewing-related challenges. Furthermore, while our initial focus was on publishing interdisciplinary research, the impact of current reviewing practices on marginalized groups emerged from our data, as we found that marginalized groups are more likely to receive negative feedback. In addition, we found that experienced researchers are less likely to change their research direction due to feedback they receive. To address the identified challenges, our participants emphasize the importance of highlighting the impact and value of interdisciplinary work for SE, collaborating with experienced researchers, and establishing clearer submission guidelines and new interdisciplinary SE publication venues. Our findings contribute to the understanding of the current state of the SE research community and how we could better support interdisciplinary research in our field.

Yining Hong, Christopher S. Timperley, Christian Kästner

Machine learning (ML) components are increasingly integrated into software products, yet their complexity and inherent uncertainty often lead to unintended and hazardous consequences, both for individuals and society at large. Despite these risks, practitioners seldom adopt proactive approaches to anticipate and mitigate hazards before they occur. Traditional safety engineering approaches, such as Failure Mode and Effects Analysis (FMEA) and System Theoretic Process Analysis (STPA), offer systematic frameworks for early risk identification but are rarely adopted. This position paper advocates for integrating hazard analysis into the development of any ML-powered software product and calls for greater support to make this process accessible to developers. By using large language models (LLMs) to partially automate a modified STPA process with human oversight at critical steps, we expect to address two key challenges: the heavy dependency on highly experienced safety engineering experts, and the time-consuming, labor-intensive nature of traditional hazard analysis, which often impedes its integration into real-world development workflows. We illustrate our approach with a running example, demonstrating that many seemingly unanticipated issues can, in fact, be anticipated.

Hashini Gunatilake, John Grundy, Rashina Hoda et al.

Empathy, defined as the ability to understand and share others' perspectives and emotions, is essential in software engineering (SE), where developers often collaborate with diverse stakeholders. It is also considered as a vital competency in many professional fields such as medicine, healthcare, nursing, animal science, education, marketing, and project management. Despite its importance, empathy remains under-researched in SE. To further explore this, we conducted a socio-technical grounded theory (STGT) study through in-depth semi-structured interviews with 22 software developers and stakeholders. Our study explored the role of empathy in SE and how SE activities and processes can be improved by considering empathy. Through applying the systematic steps of STGT data analysis and theory development, we developed a theory that explains the role of empathy in SE. Our theory details the contexts in which empathy arises, the conditions that shape it, the causes and consequences of its presence and absence. We also identified contingencies for enhancing empathy or overcoming barriers to its expression. Our findings provide practical implications for SE practitioners and researchers, offering a deeper understanding of how to effectively integrate empathy into SE processes.

Qi Guo, Daxton Everage, Qinhe Zhang

Thermodynamics is a fundamental subject in engineering education, yet it often poses challenges for students due to its abstract nature and complex concepts. One particularly difficult topic within thermodynamics is refrigeration cycles, which require a deep understanding of thermodynamic principles and their practical applications. This paper explores the implementation and impact of hands-on refrigeration labs in an engineering curriculum to enhance students’ understanding of thermodynamics, specifically focusing on refrigeration systems. The hands-on labs utilize a refrigeration cycle hands-on trainer, providing students with practical experience in measuring temperature and pressure, analyzing heat transfer and thermodynamic work with enthalpy and entropy data, computing refrigerant mass flow rate and Coefficient of Performance (COP), and applying thermodynamic principles to real-world scenarios. By conducting these labs, students not only deepen their theoretical knowledge but also develop critical skills such as problem-solving, critical thinking, and practical application of engineering principles. The hands-on refrigeration labs demonstrate the effectiveness of experiential learning methodologies in enhancing students’ understanding of thermodynamics. Through the lab activities, many students expressed that the labs significantly improved their understanding of refrigeration systems and their ability to apply thermodynamic concepts in engineering practice. This experiential learning approach bridges the gap between theory and practice, preparing students for future engineering challenges and enhancing their readiness for the workforce.

Sayan Chatterjee, Ching Louis Liu, Gareth Rowland et al.

The increasing popularity of AI, particularly Large Language Models (LLMs), has significantly impacted various domains, including Software Engineering. This study explores the integration of AI tools in software engineering practices within a large organization. We focus on ANZ Bank, which employs over 5000 engineers covering all aspects of the software development life cycle. This paper details an experiment conducted using GitHub Copilot, a notable AI tool, within a controlled environment to evaluate its effectiveness in real-world engineering tasks. Additionally, this paper shares initial findings on the productivity improvements observed after GitHub Copilot was adopted on a large scale, with about 1000 engineers using it. ANZ Bank's six-week experiment with GitHub Copilot included two weeks of preparation and four weeks of active testing. The study evaluated participant sentiment and the tool's impact on productivity, code quality, and security. Initially, participants used GitHub Copilot for proposed use-cases, with their feedback gathered through regular surveys. In the second phase, they were divided into Control and Copilot groups, each tackling the same Python challenges, and their experiences were again surveyed. Results showed a notable boost in productivity and code quality with GitHub Copilot, though its impact on code security remained inconclusive. Participant responses were overall positive, confirming GitHub Copilot's effectiveness in large-scale software engineering environments. Early data from 1000 engineers also indicated a significant increase in productivity and job satisfaction.

Sergio Rico

Case studies are a popular and noteworthy type of research study in software engineering, offering significant potential to impact industry practices by investigating phenomena in their natural contexts. This potential to reach a broad audience beyond the academic community is often undermined by deficiencies in reporting, particularly in the context description, study classification, generalizability, and the handling of validity threats. This paper presents a reflective analysis aiming to share insights that can enhance the quality and impact of case study reporting. We emphasize the need to follow established guidelines, accurate classification, and detailed context descriptions in case studies. Additionally, particular focus is placed on articulating generalizable findings and thoroughly discussing generalizability threats. We aim to encourage researchers to adopt more rigorous and communicative strategies, ensuring that case studies are methodologically sound, resonate with, and apply to software engineering practitioners and the broader academic community. The reflections and recommendations offered in this paper aim to ensure that insights from case studies are transparent, understandable, and tailored to meet the needs of both academic researchers and industry practitioners. In doing so, we seek to enhance the real-world applicability of academic research, bridging the gap between theoretical research and practical implementation in industry.

R. Saligram, A. Gaidhane, Yu Cao et al.

Cryogenic CMOS is a promising technology for high performance computing due to its improvement in subthreshold slope, carrier mobilities and reduced wire resistance. The threshold voltage (Vth) increase at 77K can be mitigated by metal gate work function (PHIG) engineering to achieve matched off current (Ioff) further enhancing the device performance allowing us to operate at very low supply voltage thereby reducing the Energy Delay Product (EDP). However, the effect of variation on noise margins of static random access memories (SRAM) deploying these matched Ioff devices is very prominent especially at low supply voltages (Vdd) limiting its scaling. In this work, we propose a framework to perform Vth retargeting for cryogenic SRAM for improving noise margins in high performance cryogenic SRAM cells under variation. The proposed framework comprises of a Monte-Carlo engine which performs statistical analysis and DC characterization and a backend processing engine to analyze noise margins and tune the PHIG. To demonstrate the framework, we use calibrated 14nm FinFET models at 300K and 77K. First, we analyze the logic blocks using iso-Ioff devices, which yield up to 3x improvement in delay at iso-energy and a 4.5x reduction in energy at iso-delay. Next, we study the effect of Vth variation on the device currents. Finally, the framework is deployed to tune PHIG, and results show that it can enhance the noise margins by 23%, 31% and 19% for hold, read and write operations respectively at 77K compared to iso-Ioff devices. Further, a 1kb SRAM array has been simulated using iso-Ioff tuned peripherals and framework tuned SRAM cells, and it shows 5.4x reduction in read/write energies along with 1.2x delay reduction and better noise margins at 77K compared to 300K.

R. Mishra, Ansh Agarwal, J. Dixit et al.

Tetrafluoroethane (CF3CH2F), an HFC refrigerant, is also known as R134a. It is safe for normal handling because it is neither poisonous, flammable, nor corrosive. After it was discovered recently that R-134a contributes to global warming, the European Union forbade its use in brand-new automobiles starting in 2011. Worked on a vapour compression-based refrigeration system, utilised hydrocarbon (HC) refrigerants which were examined for their energetic and exergetic performance. In this investigation, pure Tetrafluoroethane (CF3CH2F) from the R134a family of HFCs was used for a theoretical analysis, along with other refrigerants which were eco-friendly and had a lower environmental impact( low Global Warming Potential and Ozone Depletion Potential) :trans-1,3,3,3- Tetrafluoroprop -1-ene( R1234 ze (Z), R1234ze (E), (Z)-1-Chloro-2,3,3,3-Tetrafluoropropane (R1224YD (Z)), Fluoroethene (R1141),3,3,3-Trifluoroprop-1-ene (R1243 ZF).The thermodynamic equations of the refrigerants were solved for analysis using the Engineering equation solver application. It was concluded that R1234ZE (Z) is the most effective refrigerant.

Kapil Jain, B. K. Chourasia

Abstract: This study employs Response Surface Methodology (RSM) with a Box-Behnken design to optimize the Coefficient of Performance (COP) in a Single-Effect Vapor Absorption System. The thermodynamic model considers a 1-ton refrigeration (TR) system utilizing Lithium bromide-water as the refrigerant, and simulations are conducted using the Engineering Equation Solver (EES). The optimization process identifies optimal values for the generator, absorber, condenser, and evaporator temperatures, set at 90°C, 33°C, 33°C, and -5°C, respectively, resulting in an achieved optimum COP of 0.716. Statistical analysis through ANOVA of the quadratic regression model reveals a significant F-value of 110.62, with a low probability value (p=0.0003), attesting to the model's robustness. Key statistical metrics for the model encompass a standard deviation (Std. Dev.) of 0.0059, a mean of 0.8956, a coefficient of variation (C.V. %) of 0.6559, an R² of 0.9901, an adjusted R² of 0.9811, a predicted R² of 0.9159, and an adequate precision of 38.2967. This research offers crucial insights into enhancing the performance of a Single-Effect Vapor Absorption System, thereby contributing to the advancement of energy-efficient refrigeration technologies

Christopher Nkansah

Cryogenic distillation remains a cornerstone technology for the high-purity separation of industrial gases such as oxygen, nitrogen, and argon. Despite its widespread application across critical sectors including pharmaceuticals, semiconductors, aerospace, and energy numerous technical and regulatory challenges continue to constrain operational efficiency and product compliance. This study critically examines the multifaceted issues facing cryogenic distillation systems, including thermodynamic limitations, material degradation at ultra-low temperatures, complex process control requirements, and evolving regulatory expectations. Drawing from recent advances in process engineering, the paper explores innovative solutions such as digital twin modeling, AI-driven control systems, and sustainable design integration. Through case studies and comparative industry analyses, the research highlights best practices for aligning distillation processes with stringent compliance benchmarks while optimizing energy and cost performance. The findings underscore the need for a cross-disciplinary approach that combines engineering innovation with regulatory foresight, paving the way for a new generation of high-fidelity cryogenic separation systems.

Khemraj Deshmukh, Arindam Bit

The analysis of degradation in the presence of cell death and migration is a critical aspect of research in various biological fields, such as tissue engineering, regenerative medicine, and disease pathology. In present study, numerical study of degradation of scaffold were performed in present of cells, cell apoptosis and cell migration. A poly electrolyte complex (PEC) silk fibroin scaffold was used for degradation study. Degradation study in the presence of cells and migration were performed at fixed pH concentration 7.2. Similarly, degradation study of scaffold were performed at different pH cell apoptosis. A transient analysis of scaffold was evaluated in COMSOL 5.5 in presence of cryogenic temperature at different temperature gradient. The parameters; temperature, stress, strain tensor and deformation gradient associated with the degradation of polyelectrolyte complex scaffold were evaluated. Result shows that in both geometries minimum temperature had been achieved as 230.051 K at point P4 in series view and parallel view and at a point P3 for cell migration study for −5 k min−1 and −1 k min−1, respectively. The maximum stress had been generated for 5.57 × 107 N m−2 for the temperature gradient of −2 K min−1 at T cycle in the case of cell migration study. In contrast in series view the maximum stress 2.9 × 107 N m−2 were observed at P4 which was higher as compare to P3. Similarly, for a parallel view, maximum stress (3.93 × 107 N m−2) was obtained for point P3. It had been observed that the maximum strain tensor 5.21 × 10−3, 5.15 × 10−3 and 5.26 × 10−3 was generated in series view at 230 k on a point P3 for − 1, −2 and −5 K min−1, respectively. Similarly, the maximum strain tensor 8.16 × 10−3, 8.09 × 10−3 and 8.09 × 10−3 was generated in parallel view at 230 k on a point P3 for −1, −2 and −5 K min−1, respectively. In the presence of cells, at a point P4 for temperature gradient of −1 and −2 K min−1, it had been closed to the scaffold wall, which had a different temperature profile than the point P3 and scaffold comes to the contact with the cells. The analysis of PEC scaffold degradation in the presence of cells, including cell apoptosis and migration, offers significant insights into the relationship between scaffold properties, cell behaviour, and tissue regeneration.

Lizhan Zhang, Yina Lin, Xueqing Yi et al.

Halophilic Halomonas bluephagenesis has been engineered to produce various added-value bio-compounds with reduced costs. However, the salt-stress regulatory mechanism remained unclear. H. bluephagenesis was randomly mutated to obtain low-salt growing mutants via atmospheric and room temperature plasma (ARTP). The resulted H. bluephagenesis TDH4A1B5 was constructed with the chromosomal integration of polyhydroxyalkanoates (PHA) synthesis operon phaCAB and deletion of phaP1 gene encoding PHA synthesis associated protein phasin, forming H. bluephagenesis TDH4A1B5P, which led to increased production of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-4-hydrobutyrate) (P34HB) by over 1.4-fold. H. bluephagenesis TDH4A1B5P also enhanced production of ectoine and threonine by 50% and 77%, respectively. A total 101 genes related to salinity tolerance was identified and verified via comparative genomic analysis among four ARTP mutated H. bluephagenesis strains. Recombinant H. bluephagenesis TDH4A1B5P was further engineered for PHA production utilizing sodium acetate or gluconate as sole carbon source. Over 33% cost reduction of PHA production could be achieved using recombinant H. bluephagenesis TDH4A1B5P. This study successfully developed a low-salt tolerant chassis H. bluephagenesis TDH4A1B5P and revealed salt-stress related genes of halophilic host strains.

Taolue Yang, Shi Liu, Yi Yang et al.

Wang Jiaxuan, Song Xia, Gao Tianyuan et al.

Aviation applications are facing the challenges of cooling high-power and high-heat-flux electronic equipment. Traditional cooling methods cannot cope with thermal requirements greater than a heat flux of 100 W/cm2. In this study, the ground test bench of a pump-driven two-phase cooling loop (MPCL) system is constructed, and the control strategy of the system is designed. The cooling ability and resistance characteristics of the system are tested, and the mathematical model is developed. The results show that the mechanical pump drives the two-phase cooling system with good thermal performance. The designed copper cold plate is able to effectively handle 6 kW concentrated heat sources with a heat flux of 120 W/cm2. A 10 kW heat source can be effectively cooled by the MPCL system using 70% less working fluid than single-phase cooling under designed working conditions. The surface temperature of the heating element can be stabilized at 63–70 °C, which meets the temperature requirements of the chip. Additionally, the temperature is uniform between the evaporator branches, with a temperature difference below 5 ℃. The pressure drop of the phase-change segment is below 400 kPa, and the resistance characteristics can be described by the Kim and Mudawar models.

Sehrish Malik, Moeen Ali Naqvi, Leon Moonen

There is an increasing need to assess the correct behavior of self-adaptive and self-healing systems due to their adoption in critical and highly dynamic environments. However, there is a lack of systematic evaluation methods for self-adaptive and self-healing systems. We proposed CHESS, a novel approach to address this gap by evaluating self-adaptive and self-healing systems through fault injection based on chaos engineering (CE) [ arXiv:2208.13227 ]. The artifact presented in this paper provides an extensive overview of the use of CHESS through two microservice-based case studies: a smart office case study and an existing demo application called Yelb. It comes with a managing system service, a self-monitoring service, as well as five fault injection scenarios covering infrastructure faults and functional faults. Each of these components can be easily extended or replaced to adopt the CHESS approach to a new case study, help explore its promises and limitations, and identify directions for future research. Keywords: self-healing, resilience, chaos engineering, evaluation, artifact

M. Mehrpooya, S. Mousavi, Majid Asadnia et al.

M. Fallah, S. Mahmoudi, M. Yari et al.