Temperature-related Issues Research Articles

Analyzing the spatio-temporal pattern of urban growth and its influence on urban heat islands in the Sekondi-Takoradi metropolis, Ghana

The rapid urbanization in Sekondi-Takoradi, Ghana has significantly transformed the land cover, resulting in the proliferation of impervious surfaces and a decline in vegetation. However, the influence of this urban growth on the development of urban heat islands (UHIs) in the metropolis remains understudied. This study aimed to fill this research gap by employing Landsat images to explore the influence of urban growth on urban heat islands in the metropolis from 1991 to 2023. The supervised random forest technique was utilized to map the land cover changes. Furthermore, the computed normalized difference built-up index (NDBI), normalized difference vegetation index (NDVI), land surface temperature (LST), and urban thermal field variance index (UTFVI) were used to analyze the influence of urban expansion on UHIs. The findings revealed a 63.07 km2 increase in built-up areas and a 60.99 km2 decrease in vegetation cover during the study period. This dramatic land use change led to a 3.1°C rise in mean LST and a 19.38 km2 expansion of areas affected by the UHI effect. The UTFVI analysis further indicated a 33.63 km2 increase in the worst ecological zone due to the temperature rise. Statistical analysis between LST, NDVI, and NDBI revealed significant variability in explaining the intensity of LST and UHI in the metropolis over the study period. The study equips city authorities and planners with the fundamental knowledge needed to prepare a sustainable development plan that alleviates adverse effects of urban growth and elevated temperature-related issues. Also, the findings contribute to the global efforts in promoting more livable and climate-resilient urban environments.

A semi-analytical approach to wire arc additive manufacturing simulation for deposition sequence optimisation

ABSTRACT Categorised as a directed energy deposition process, wire arc additive manufacturing (WAAM) is a promising technology for fabricating large-scale structures and components across various industries. However, the quality of WAAM parts depends on the tool trajectory, as it affects the temperature distribution. Ideally, temperature-related issues, such as overheating, are minimised by choosing an optimal deposition sequence. Selecting the deposition sequence solely on intuition is an unreliable approach, particularly when dealing with complex and irregular parts. This paper introduces a simplified WAAM simulation (SWS) model, which was embedded into an optimisation procedure for determining the optimal deposition sequence of thin-walled WAAM parts. The proposed method is based on a semi-analytical function, which was calibrated and validated using thermal histories obtained from finite element simulations. The findings showed that the proposed SWS model can reproduce the average thermal history at predefined positions within a sample part with minimal computational effort. Moreover, the optimisation successfully identified optimal deposition sequences for producing the sample part regarding a given optimisation criterion. The outcomes of this research contribute to the tool trajectory planning process for WAAM parts. An optimal deposition sequence improves WAAM part quality, increasing the usability of WAAM technology in the production industry.

Electric Vehicles Under Low Temperatures: A Review on Battery Performance, Charging Needs, and Power Grid Impacts

Electric vehicles (EVs) are gaining mainstream adoption as more countries introduce net-zero carbon targets for the near future. Lithium-ion (Li-ion) batteries, the most commonly used energy storage technology in EVs, are temperature sensitive, and their performance degradates at low operating temperatures due to increased internal resistance. The existing literature on EV-power grid studies assumes that EVs are used under “perfect temperatures" (e.g. 21 Celsius) and temperature-related issues are ignored. In addition, most of the countries/regions with high EV penetration (e.g. Norway, Canada, northern parts of the US and China, etc.) experience harsh cold months, making it extremely critical to understand EV performance and consequently their impacts on the electrical power networks. In this paper, we present a systematic review of the literature that considers the combined investigation of Li-ion battery technology and power networks, with a focus on their operation under suboptimal weather conditions. More specifically, we review: (i) the impact of low temperatures on the electrochemical performance of EV batteries in parking, charging and driving modes, (ii) the challenges experienced by EVs during charging and associated performance degradation, and (iii) the additional impacts of EV charging on the power networks. Our analysis shows that there are serious research gaps in literature and industry applications, which may hinder mass EV adoption and cause delays in charging station roll-out.

Fuzzy-Based Thermal Management Scheme for 3D Chip Multicores with Stacked Caches

By using through-silicon-vias (TSV), three dimension integration technology can stack large memory on the top of cores as a last-level on-chip cache (LLC) to reduce off-chip memory access and enhance system performance. However, the integration of more on-chip caches increases chip power density, which might lead to temperature-related issues in power consumption, reliability, cooling cost, and performance. An effective thermal management scheme is required to ensure the performance and reliability of the system. In this study, a fuzzy-based thermal management scheme (FBTM) is proposed that simultaneously considers cores and stacked caches. The proposed method combines a dynamic cache reconfiguration scheme with a fuzzy-based control policy in a temperature-aware manner. The dynamic cache reconfiguration scheme determines the size of the cache for the processor core according to the application that reaches a substantial amount of power consumption savings. The fuzzy-based control policy is used to change the frequency level of the processor core based on dynamic cache reconfiguration, a process which can further improve the system performance. Experiments show that, compared with other thermal management schemes, the proposed FBTM can achieve, on average, 3 degrees of reduction in temperature and a 41% reduction of leakage energy.

Inter-Tier Process-Variation-Aware Monolithic 3-D NoC Design Space Exploration

Monolithic 3-D (M3D) technology enables high density integration, performance, and energy efficiency by sequentially stacking tiers on top of each other. M3D-based network-on-chip (NoC) architectures can exploit these benefits by adopting tier partitioning for intra-router stages. However, conventional fabrication methods are infeasible for M3D-enabled designs due to temperature-related issues. This has necessitated lower temperature and temperature-resilient techniques for M3D fabrication, leading to inferior performance of transistors in the top tier and interconnects in the bottom tier. The resulting inter-tier process variation leads to the performance degradation of M3D-enabled NoCs. In this article, we demonstrate that without considering inter-tier process variation, an M3D-enabled NoC architecture overestimates the energy-delay-product (EDP) on average by 50.8% for a set of SPLASH-2 and PARSEC benchmarks. As a countermeasure, we adopt a process variation-aware design approach. The proposed design and optimization method distributes the intra-router stages and inter-router links among the tiers to mitigate the adverse effects of process variation. Experimental results show that the NoC architecture under consideration improves the EDP by 27.4% on average across all benchmarks compared to the process-oblivious design.

Microbial community adaptability to altered temperature conditions determines the potential for process optimisation in biogas production

The operating temperature in anaerobic digestion strongly affects biogas yield, process stability and the potential for process optimisation. However, many questions remain on how to manage process operation for optimized microbial community adaptation following temperature changes. A long-term anaerobic digestion experiment was conducted to determine temperature-related issues in operative full-scale biogas plants and to evaluate optimisation potential and links to microbial community structure and responses. Four digesters fed household and slaughterhouse waste were operated in sets of two, at 37 °C or 52 °C, followed by a gradual increase or decrease in temperature in one digester in each set. Stability and flexibility of the digesters were then assessed by step-wise increases in organic loading rate (OLR) from 3 to 7 g VS/(L day), concurrently with decreased hydraulic retention time from 33–40 days to 14–17 days. Transition of operating temperature regime was possible, irrespective of starting temperature. However, slight temporary instability occurred at 42–44 °C and for the thermophilic to mesophilic process a period of adaptation was required to overcome this imbalance. The digesters with constant temperature and the mesophilic-to-thermophilic digester remained stable at the target OLR, demonstrating considerable optimisation potential for the large-scale biogas plants investigated. However, the digester that was changed from thermophilic to mesophilic conditions failed at 6 g VS/(L day). Comparisons of biological and chemical parameters suggested that this failure was caused by a lag in resilience of the acetate and propionate-degrading populations inherited from the community shaped by initial operation in thermophilic conditions. Taken together, these results demonstrate that the existing biogas plants are operating below capacity and that, depending on temperature, the annual energy production could be increased from 26–28 to 59–65 GWh through increasing OLR from 3 to 7 g VS/(L day). However, the results also highlight the importance of careful management and the risks when applying strategies not fully evaluated for the specific system. To our knowledge, this is the first study to demonstrate process performance, optimisation potential and microbial community adaptability to temperature changes in continuously fed anaerobic digesters under both increasing and decreasing operating temperature. The results could be used to guide operation management under temperature changes and increasing OLR in industrial-scale biogas processes.

Effects of thermally modified asphalt concrete on pavement temperature

ABSTRACTThis study investigates the feasibility of mitigating temperature-related issues, such as heat island effect, ice layer formation and thermal distresses of asphalt pavement, by controlling thermal properties of hot mix asphalt (HMA). Expanded polypropylene (EPP) beads and graphite powder are selected as the additives to change the thermal properties of HMA, and their effects on thermal and mechanical properties are evaluated experimentally. The test results show that the EPP modified HMA yields a reduction in thermal conductivity, heat capacity and indirect tensile strength up to 17, 32, and 27%, respectively. Conversely, replacing a part of traditional fillers with graphite powder increases indirect tensile strength and thermal conductivity up to 40 and 43%, respectively. A series of heat transfer analysis was conducted using a finite difference heat transfer model to investigate the effects of the thermally modified HMA on the pavement temperature gradient and surface temperature. The simulation results show that the amplitude of daily surface temperature variation reduces as the HMA thermal conductivity increases. The HMA containing 4.8% graphite by volume of the mixture reduces the daily surface temperature amplitude by 8.1% in the summer simulation and 9.6% in the winter simulation. The graphite modified HMA also has 1.5 °C lower maximum pavement surface temperature than the non-modified HMA in the simulation for a summer day at Texas. This implies that the modified HMA with improved thermal conductivity, such as the graphite modified one, is effective in mitigating thermal cracking, rutting and urban heat island effect. In addition, the improved indirect tensile strength of graphite modified HMA will bring extra extension of pavement service life. The parametric study for wide ranges of thermal conductivity and heat capacity shows that the daily temperature amplitude on a pavement surface can be reduced up to 28.9% by selecting highly conductive aggregates and graphite powder.

Impact of Temperature Variation on Performance of Carbon Nanotube Field-Effect Transistor—Based on Chaotic Oscillator: A Quantum Simulation Study**Supported by the Basic Science Research Program through the National Research Foundation of Korea Funded by the Ministry of Education, Science and Technology under Grant No 2012-0002777.

We evaluate the impact of temperature on the output behavior of a carbon nanotube field effect transistor (CNFET) based chaotic generator. The sources cause the variations in both current-voltage characteristics of the CNFET device and an overall chaotic circuit is pointed out. To verify the effect of temperature variation on the output dynamics of the chaotic circuit, a simulation is performed by employing the CNFET compact model of Wong et al. in HSPICE with a temperature range from −100°C to 100°C. The obtained results with time series, frequency spectra, and bifurcation diagram from the simulation demonstrate that temperature plays a significant role in the output dynamics of the CNFET-based chaotic circuit. Thus, temperature-related issues should be taken into account while designing a high-quality chaotic generator with high stability.

Future projections of temperature-related climate change impacts on the railway network of Great Britain

Great Britain’s main line railway network is known to experience various temperature-related impacts, e.g. track buckling and overhead power line sag at high ambient temperatures. Climate change could alter the frequency of occurrence of these impacts. We have therefore investigated the climate change impact on various temperature-related issues, identified during workshops with rail industry specialists, using a perturbed physics ensemble (PPE) of the Met Office’s regional climate model (RCM), HadRM3. We have developed novel approaches to combine RCM data with railway industry knowledge, typically by identifying key meteorological thresholds of interest and analysing exceedance of these out to the 2040s. We performed a statistical analysis of the projected changes for each issue, via bootstrapping of the unperturbed PPE member. Although neither the PPE nor the bootstrapping analysis samples the full range of uncertainty in the projections, they nonetheless provide complementary perspectives on the suitability of the projections for use in decision-making. Our main findings include projected increases in the summertime occurrence of temperature conditions associated with (i) track buckling, (ii) overhead power line sag, (iii) exposure of outdoor workers to heat stress, and (iv) heat-related delays to track maintenance; and (v) projected decreases in the wintertime occurrence of temperatures conditions associated with freight train failure owing to brake problems. For (i), the statistical significance varied with track condition and location; for (ii) and (iii), with location; and for (iv) and (v), projected changes were significant across Great Britain. As well as assessing the changes in climate-related hazard, information about the vulnerability of the network to past temperature-related incidents has been summarised. Combining the hazard and vulnerability elements will eventually support a climate risk assessment for the industry.

Performance Analysis of Temperature Management Approaches in Networks-on-Chip

With the progress of deep submicron technology, power consumption and temperature related issues have become dominant factors for chip design. Therefore, very large-scale integrated systems like Systems-on-Chip (SoCs) are exposed to an increasing thermal stress. On the one hand, this necessitates effective mechanisms for thermal management. On the other hand, application of thermal management is accompanied by disturbance of system integrity and degradation of system performance. In this paper the authors propose to precompute and proactively manage on-chip temperature of systems based on Networks-on-Chip (NoCs). Thereby, traditional reactive approaches, utilizing the NoC infrastructure to perform thermal management, can be replaced. This results not only in shorter response times for application of management measures and a reduction of temperature and thermal imbalances, but also in less impairment of system integrity and performance. The systematic analysis of simulations conducted for NoC sizes ranging from 2x2 to 4x4 proves that under certain conditions the proactive approach is able to mitigate the negative impact of thermal management on system performance while still improving the on-chip temperature profile.

Recent thermal management techniques for microprocessors

Microprocessor design has recently encountered many constraints such as power, energy, reliability, and temperature. Among these challenging issues, temperature-related issues have become especially important within the past several years. We summarize recent thermal management techniques for microprocessors, focusing on those that affect or rely on the microarchitecture. We categorize thermal management techniques into six main categories: temperature monitoring, microarchitectural techniques, floorplanning, OS/compiler techniques, liquid cooling techniques, and thermal reliability/security. Temperature monitoring, a requirement for Dynamic Thermal Management (DTM), includes temperature estimation and sensor placement techniques for accurate temperature measurement or estimation. Microarchitectural techniques include both static and dynamic thermal management techniques that control hardware structures. Floorplanning covers a range of thermal-aware floorplanning techniques for 2D and 3D microprocessors. OS/compiler techniques include thermal-aware task scheduling and instruction scheduling techniques. Liquid cooling techniques are higher-capacity alternatives to conventional air cooling techniques. Thermal reliability/security issues cover temperature-dependent reliability modeling, Dynamic Reliability Management (DRM), and malicious codes that specifically cause overheating. Temperature-related issues will only become more challenging as process technology continues to evolve and transistor densities scale up faster than power per transistor scales down. The overall objective of this survey is to give microprocessor designers a broad perspective on various aspects of designing thermal-aware microprocessors and to guide future thermal management studies.