No / The complementary features of various wireless access technologies in heterogeneous wireless networks make it attractive and challenging to offer users an always best connected (ABC) service. To achieve this goal, the dynamic network selection has received many research efforts. However, most of the existing work have focused on the network layer performance and ignored the consideration of energy efficiency. To fill this gap, an energy-efficient network selection scheme is proposed in this paper to improve the energy efficiency of wireless network access in heterogeneous wireless networks environment. The dynamics of network selection is formulated as the process of an evolutionary game. The users in different service areas complete for the data rate from different wireless networks (i.e., WMAN, cellular networks, and WLAN), and the network selection made by a user is based on its payoff that is a function of the data rate and power consumption. The addressed problem is then modelled by the replicator dynamics. Simulation results are presented to demonstrate the significant performance improvement compared to the existing scheme.

Energieffektivisering har länge varit och blir alltmer aktuell, dels för att främja social, ekonomisk och miljömässig hållbarhet, dels för att motverka den rådande energikrisen i Europa. 2014 beslutades det om Lag (2014:266) om energikartläggning i stora företag. Lagen innebär att företag som årligen omsätter mer än 50 miljoner euro och är fler än 250 anställda ska göra en energikartläggning var fjärde år. Foria AB omsätter årligen mer än 50 miljoner euro och blev under 2022 fler än 250 anställda vilket resulterar i att företaget omfattas av Lag (2014:266). Syftet med examensarbetet är identifiera vilka styrkor och svagheter som energikartläggningar har samt att genomföra en energikartläggning över Foria AB:s energikrävande aktiviteter enligt kategorierna transport, verksamhet och byggnader och identifiera energieffektiviserande åtgärder i enlighet med Lag (2014:266). Energikartläggningen är genomförd enligt ISO 50001 standarden vilket bland annat kräver ett kontinuerligt arbete med energifrågan. Ett kontinuerligt arbete med energifrågan har visat sig ha större positiv effekt av företags energieffektivisering i jämförelse med om det är en engångsprocedur. Energikartläggningen är baserad på data om energianvändningen i form av tankad mängd drivmedel, el- och värmefakturor samt schablonberäkningar där data inte är tillgängliga. Resultatet av energikartläggningen visar att Forias transporter utgör den största energiposten med ett energibehov på 22,1 GWh under 2022, följt av byggnader som hade ett energibehov på 0,97 GWh och verksamhet med ett energibehov på 0,51 GWh. Vid utarbetandet av de energieffektiviserande åtgärderna togs beslutet att fokusera på transporter i sin helhet, samt byggnaderna och tillhörande verksamheter vid tre olika platskontor. De energieffektiviserande åtgärder som identifierades inom litteraturen och i samband med intervjuer med Foria AB:s anställda inom transportkategorin är att köra mer sparsamt, installera GPS:er i fordonen för att kunna trafikleda mer effektivt samt att nyttja ett mjukvaruprogram vid trafikledning. Bland dessa energibesparingsåtgärder identifierades överexponeringar och överlappande åtgärder på grund av bristfälliga data, vilka är några av de svagheterna som finns med energikartläggningar. Energieffektiviserande åtgärder inom kategorin byggnader är att behovsanpassa underhållsystem, optimera nyttjandet av lokaler i syfte att minska värme- och ventilationsbehovet samt byta ut och renovera ineffektiva värmesystem. De energibesparande åtgärder som ger störst andel sparad energi är samtliga åtgärder inom transport. Trots att den exakta besparingen inte kunnat fastställas görs bedömningen att det finns potential till energibesparing då både litteraturen och känslighetsanalysen tyder på det. För att få mer exakta resultat av energianvändningen och energibesparingen behöver mer data samlas in. Trots att datainsamlingen delvis är baserad på schablonberäkningar, att svagheter identifierats och de energieffektiviserande åtgärderna är baserade på förväntad andel sparad energi bedöms energikartläggningen ge en tillräckligt representativ bild av energibehovet samt att Foria AB har god potential till energieffektivisering genom att implementera de föreslagna åtgärderna. / To be energy efficiency is increasingly relevant, partly to promote social, economic, and environmental sustainability, and partly to counteract the ongoing energy crisis in Europe. In 2014, the Law (2014:266) on Energy Mapping in Large Companies was enacted. The law stipulates that companies that has an annual turnover of more than 50 million euros and have more than 250 employees must conduct an energy mapping every four years. In 2022, the transportation company Foria AB exceeded 250 employees, had an annual turnover of more than 50 million euros, and is therefore subject to Law (2014:266). The purpose of the thesis is to identify strengths and weaknesses of energy audits and to conduct an energy mapping of Foria AB's energy-intensive activities in the categories of transportation, operations, and buildings, and identify energy efficiency measures in accordance with Law (2014:266).  The energy audit has been conducted according to the ISO 50001 standards, which, among other things, requires ongoing work with the energy related questions. Continuous efforts in addressing energy issues have been found to have a greater impact on a company’s energy efficiency compared to a one-time procedure. The energy audit is based on data regarding fuel consumption, electricity, and heat invoices, as well as default calculations where real data was unavailable. The result of the energy audit revealed that Foria's transportations are the largest energy expenditure, with an energy demand of 22.1 GWh in 2022, followed by buildings with an energy demand of 0.97 GWh and operations with 0.51 GWh. When identifying the energy efficiency measures, the decision was made to focus on transportation, as well as the buildings and associated operations at three different branch offices. The energy efficiency measures were identified in the literature and through interviews with employees at Foria AB. For the transportation category this resulted in driving more efficiently, installing GPS systems in vehicles for more efficient traffic management, and utilizing software programs for traffic control. Energy efficiency measures for buildings include adapting maintenance systems to actual needs, optimizing space utilization to reduce heating and ventilation requirements, and replacing and renovating inefficient heating systems. The energy-saving measures that result in the largest proportion of saved energy are all within transportation. Although the exact savings couldn't be determined, the assessment is that there is potential for energy savings, as both the literature and sensitivity analysis suggest. To obtain more precise results regarding energy consumption and energy savings, more data needs to be collected. Although the data is partly based on default calculations, that weaknesses were identified, and the energy efficiency measures are based on expected energy savings, the energy mapping is deemed to provide a sufficiently representative picture of the energy demand and that Foria AB has good potential for energy efficiency by implementing the proposed measures.

Scaling up application performance on single high-end machines is increasingly becoming difficult due to scalability challenges of processor interconnects, cache coherence protocols, and memory bandwidth. Significant prior work has addressed this problem by scaling-out application threads across multiple nodes to exploit resources outside the single machine boundary. Prior works have also leveraged heterogeneous instruction set architecture (ISA) systems to improve application performance as well as energy-efficiency, a major cost driver in datacenters, by augmenting high-end servers with power-efficient embedded boards. Existing works, however, suffer from deployability challenges due to dependencies on the operating system or programming models that require non-trivial application modifications. We introduce CRIU-RTX, a userspace framework to scale-out multi-threaded applications across multiple nodes. Integrated with HetMigrate, a prior work on migrating processes across heterogeneous-ISA systems, CRIU-RTX can suspend a subset of threads in a process and resume their execution on different nodes, including, but not limited to heterogeneous-ISA nodes. CRIU-RTX implements distributed shared memory in userspace, thereby allowing application threads to access distributed memory transparently without any operating system dependency. Our experimental evaluations show 21% to 43% performance gains while scaling-out applications across x86-64 servers, and energy efficiency gains of up to 18% while scaling-out across a cluster of x86-64 server and ARM64 embedded boards. Since CRIU-RTX does not depend on operating system modifications, it can be easily deployed on a diverse set of machines, including, but not limited to ISA-different machines running the stock Linux operating system. / Master of Science / Commonly referred to as "Moore's Law", Gordan Moore predicted that the number of transistors on a chip would double every two years. However, this law no longer holds true, leading to a shift in computer research and development. To meet the increasing demands for faster and cheaper servers, researchers began exploring alternative computer designs. Data centers have started adopting servers with diverse architectures to enhance the cost-to-performance ratio, resulting in heterogeneous environments. Distributed execution refers to the process of running computational tasks or executing software across multiple interconnected systems or nodes. Instead of relying on a single machine or processor, the workload is distributed among a network of computers, allowing for parallel processing and improved performance. Prior works in this direction had difficulty in adoption due to customized hardware or operating system requirements. This thesis introduces CRIU-RTX, a userspace framework to scale-out application threads without operating system dependency. We implemented a distributed shared memory system in userspace to allow application threads running in scaled-out execution to access distributed memory as if they are running on the same machine. Our evaluations of CRIU-RTX show significant improvement in performance and energy-efficiency.

Database management systems (DBMS) are typically tuned for high performance and scalability. Nevertheless, carbon footprint and energy efficiency are also becoming increasing concerns. Unfortunately, existing studies mainly present theoretical contributions but fall short on proposing practical techniques. These could be used by administrators or query optimizers to increase the energy efficiency of the DBMS. Thus, this paper explores the effect of so-called sweet spots, which are energy-efficient CPU frequencies, on the energy required to execute queries. From our findings, we derive the Sweet Spot Technique, which relies on identifying energy-efficient sweet spots and the optimal number of threads that minimizes energy consumption for a query or an entire database workload. The technique is simple and has a practical implementation leading to energy savings of up to 50% compared to using the nominal frequency and maximum number of threads.

No description available.

Wireless sensor network (WSN) technology has gained in importance due to its potential support for a wide range of applications. Most of the WSN applications consist of a large number of distributed nodes that work together to achieve common objectives. Running a large number of nodes requires an efficient mechanism to bring them all together in order to form a multi-hop wireless network that can accomplish specific tasks. Even with the recent developments made in WSN technology, a number of important challenges still create vulnerabilities for WSNs, including: energy waste sources; synchronisation leaks; low network capacity; and self-configuration difficulties. However, energy efficiency perhaps remains both the most challenging and highest priority problem due to the scarce energy resources available in sensor nodes. Synchronization by means of scheduling clusters allows the nodes to cooperate and transmit traffic in a scheduled manner under the duty cycle mechanism. This paper aims to make further advances in this area of work by achieving higher accuracy and precision in time synchronisation through controlling the network topology, self-configuration and estimation of the clock errors between the nodes and finally correcting the nodes’ clock to the estimated value. Furthermore, the target in designing energy efficient protocol relies on synchronized duty cycle mechanism and requires a precise synchronisation algorithm that can schedule a group of nodes to cooperate by communicating together in a scheduled manner. These techniques are considered as parameters in the proposed OLS-MAC algorithm. This algorithm has been designed with the objective of ensuring the schedules of the clusters overlap by introducing a small shift in time between the adjacent clusters’ schedules to compensate for the clock drift. The OLS-MAC algorithm is simulated in NS-2 and compared to some S-MAC derived protocols. The simulation results verified that the proposed algorithm outperforms previous protocols in number of performance criterion.

The single family housing sector currently accounts for approximately 15% (US DOE 2002) of the total national energy consumption with the majority of the energy use associated with the HVAC system to provide comfort for the residents. In response to recent concern over the unpredictability of the energy supply and the pollution associated with its consumption, new methods are constantly being developed to improve the energy efficiency of homes. A variety of concrete wall systems including Multi-functional Precast Panel (MPP) systems and Insulating Concrete Form (ICF) systems have been proposed to not only improve the building envelope thermal performance but other important residential characteristics such as durability and disaster and fire resistance. MPPs consist of Precast Concrete Panels (PCPs) that incorporate structural elements, interior and exterior finishes, insulation, and even heating/cooling systems into a single manufactured building panel. The ICF system is a cast-in-place concrete panel system that does not offer the level of integration found in the MPP system but has become increasingly accepted in the building construction industry. This research evaluates the thermal performance benefits of concrete wall systems in detached, single family home applications. The thermal performance benefits of two MPP systems and an ICF system are analyzed within the context of a representative or prototypical home in the U.S. and are compared to two wood frame systems; one representing a typical configuration and the other an energy efficient configuration. A whole wall approach is used to incorporate the two and three dimensional conduction and transient characteristics of the entire wall assembly, including the clear wall and wall detail regions, into a whole building simulation of the prototypical house. The prototypical house heating and cooling energy consumption associated with each wall system is determined for six representative climates throughout the U.S. to evaluate the effect of various ambient conditions on the relative energy savings. For each wall system, the effect of thermal bridging on overall R value, the effect of thermal capacitance, and the role of infiltration on energy use are investigated. The results of the research include a comparison of the prototypical house energy savings associated with each of the wall systems; an assessment of the relative importance of the increased insulation, thermal mass, and improved air tightness on the overall energy load; and a comparison of the cost of ownership for the various wall systems. The results indicate that properly designed concrete wall systems can reduce annual heating and cooling costs. In addition, the results show that the most significant impacts of improved wall systems are, from greatest to least: infiltration reduction, improved insulation configuration, and thermal capacitance. Finally, the results show that while there are energy savings associated with concrete wall systems, economic justification of these systems must also rely on the other attractive features of concrete systems such as greater durability and disaster resistance. / Master of Science

Multimodal micron-sized spherical aluminum powders were subjected to the detonation products of a gaseous oxyacetylene mixture. The objective was to analyze the blast enhancement from the combustion of non-uniform-sized aluminum particles. These multimodal aluminum powders consisted of a 50/50 mixture by mass of larger (~30 μm) and smaller (~1-10 μm) particles. Experiments were conducted at the large-scale Virginia Tech Shock Tube Research Facility to measure blast pressure, impulse, and heat release efficiency during combustion in these detonations. These results were compared against oxyacetylene detonations conducted with the addition of unimodal aluminum particles approximately 1, 10, 30, and 95 μm in diameter. These experiments were controlled by maintaining a particle mass concentration of 200 g/m3, a constant volume of air for particle dispersion, and a consistent size for the gaseous oxyacetylene explosive charge of 0.11 m3. This approach ensured that any variations in explosive output were due to the characteristics of the aluminum powder. For unimodal aluminum, the combustion of 1 μm aluminum powder yielded the highest increase in blast pressure, impulse, and heat of combustion efficiency whereas H-95 provided the least amount of blast enhancement. These results showed an inverse relationship where decreasing aluminum particle size resulted in increased blast output, a phenomenon driven by the shorter combustion times of smaller particles. For multimodal aluminum combustion, the performance of these powders exceeded the pressure and impulse performance of their unimodal counterparts. The heat of combustion efficiency—defined as the ratio of energy driving the shock wave to the total energy available—was estimated using a two-part blast scaling methodology. The first step in this process used Sachs' blast scaling laws to infer time-dependent energy release contributing initially to blast pressure and impulse. The second step introduced a new modified Sachs scaling technique to account for late-time energy release contributing solely to blast impulse. This scaling approach addressed the previously neglected impact of delayed aluminum combustion on blast behavior. This two-part scaling approach revealed that the combustion of multimodal aluminum powders in oxyacetylene detonations resulted in 75.1%-85.3% of the available heat of combustion contributing to blast pressure and impulse compared to the 30.8%-74.6% provided by unimodal aluminum powders. These results suggest that the combustion of multimodal aluminum powder results in more powerful and efficient detonations, providing a technique to improve and optimize energetic performance. / Master of Science / Micron-sized spherical aluminum powders serve as additives to enhance the performance of propellants, pyrotechnics, and explosives. Previous laboratory-scale research has shown that aluminum's ignition and combustion characteristics are influenced by particle size, with smaller particles tending to ignite more quickly and release more energy than larger ones. However, little research has been directed at understanding the impact of particle size distribution on aluminum combustion, and whether combining smaller particles with larger ones can enhance the overall combustion reactivity and efficiency. This work investigated the impact of mixed (multimodal) aluminum combustion on the blast pressure, impulse, and overall heat of combustion efficiency of oxyacetylene detonations. To achieve this, the experimental procedure consisted of three testing series: (i) oxyacetylene detonations without aluminum powder; (ii) unimodal aluminum combustion in oxyacetylene detonations; and (iii) multimodal aluminum combustion in oxyacetylene detonations. These blast experiments were conducted using the large-scale Virginia Tech Shock Tube Research Facility. This detonation-driven shock tube maintained a constant aluminum particle mass concentration of 200 g/m3, a constant volume of air for particle dispersion, and a consistent size for the gaseous oxyacetylene explosive charge of 0.11 m3. This experimental design ensured that any variations in explosive output were due to the explosive charge size and particle characteristics of the aluminum powder. Results showed that introducing unimodal aluminum powder into oxyacetylene detonations significantly enhanced blast pressure, impulse, and energy efficiency compared to the control case of pure oxyacetylene. Furthermore, a reduction in the mean particle size of aluminum powder resulted in greater blast output, revealing an inverse relationship where smaller particle sizes led to higher blast performance due to their faster reaction rates. For multimodal aluminum powders, the use of mixed particle sizes produced even greater blast pressure, impulse, and energy efficiency than their unimodal counterparts. These findings indicate that the combustion of multimodal aluminum powder produces more powerful and efficient detonations, providing an approach to enhance and optimize energetic performance.

This research proposes to simplify the energy consumption assessment for residential homes while building the foundation towards the development of prediction tools that can achieve a credible level of accuracy for confident decision making. The energy consumption assessment is based on simplified energy consumption models. The energy consumption analysis uses a reduced number of energy model equations utilizing a critical, limited set of parameters. The results of the analysis are used to develop the minimum set of consumption influence parameters with predicted effects for each energy consumption domain. During this research study, multiple modeling approaches and occupancy scenarios were utilized according to climate conditions in Blacksburg, Virginia. As a part of the analysis process, a parameter study was conducted to: develop a comprehensive set of energy consumption influence parameters, identify the inter-relationships among parameters, determine the impact of energy consumption influence parameters in energy consumption models, and classify energy consumption influence parameters under identified energy consumption domains. Based on the results of the parameter study, a minimum set of parameters and energy consumption influence matrices were developed. This research suggests the minimum set of parameters with predicted effects to be used during the development of the simplified baseline energy consumption model. / Ph. D.

This study focuses on conducting a benchmarking analysis for light wheeled and tracked robotic vehicles. Vehicle mobility has long been a key aspect of research for many organizations. According to the Department of Defense vehicle mobility is defined as, "the overall capacity to move from place to place while retaining its ability to perform its primary mission"[1]. Until recently this definition has been applied exclusively to large scale wheeled and tracked vehicles. With new development lightweight ground vehicles designed for military and space exploration applications, the meaning of vehicle mobility must be revised and the tools at our disposal for evaluating mobility must also be expanded. In this context a significant gap in research is present and the main goal of this thesis is to help fill the void in knowledge regarding small robotic vehicle mobility assessment. Another important aspect of any vehicle is energy efficiency. Thus, another aim of this study is to compare the energy needs for a wheeled versus tracked robot, while performing similar tasks. The first stage of the research is a comprehensive review of the state-of-the-art in vehicle mobility assessment. From this review, a mobility assessment criterion for light robots will be developed. The second stage will be outfitting a light robotic vehicle with a sensor suite capable of capturing relevant mobility criteria. The third stage of this study will be an experimental investigation of the mobility capability of the vehicle. Finally the fourth stage will include quantitative and qualitative evaluation of the benchmarking study. / Master of Science