Computer Modeling of Radiofrequency Cardiac Ablation including Heartbeat-Induced Electrode Displacement

Background: The state of the art in computer modeling of radiofrequency catheter ablation (RFCA) only considers a static model, i.e. it does not allow modeling ablation electrode displacements induced by tissue movement due to heartbeats. This feature is theoretically required, since heartbeat-induced changes in contact force can be detected during this clinical procedure. Methods: We built a 2D RFCA model coupling electrical, thermal and mechanical problems and simulated a standard energy setting (25 W - 30 s). The mechanical interaction between the ablation electrode and tissue was dynamically modeled to reproduce heartbeat-induced changes in the electrode insertion depth from 0.86 to 2.05 mm, which corresponded with contact forces between 10 and 30 g when cardiac tissue was modeled by a hyperelastic Neo-Hookean model with a Young's modulus of 75 kPa and Poisson's ratio of 0.49. Results: The dynamic model computed a lesion depth of 5.86 mm, which is within the range of previous experimental results based on a beating heart for a similar energy setting and contact force (5.6-6.7 mm). Lesion size was practically identical (differences less than 0.02 mm) to that using a static model with the electrode inserted to an average depth (1.46 mm, equivalent to 20 g contact force). Conclusions: The RFCA dynamic model including heartbeat-induced electrode displacement predicts lesion depth reasonably well compared to previous experimental results based on a beating heart model, however this is true only at a standard energy setting and moderate contact force.

Uncertainty analysis of climate change potential assessments of five building energy renovation measures in Sweden

The aim of this study is to assess the impact of the uncertainties of life cycle inventory (LCI) data for energy use and materials in life cycle assessments of standard energy renovation measures carried out in multi-family buildings in Sweden. Five energy renovation measures were assessed with regard to their climate change potential. Modules A1–A3 and module B6 were included in the assessment and the functional unit, 1 m2 heated floor area of a renovated building fulfilling the Swedish building regulations and with a calculation period of 20 years, was used. The uncertainty of LCI data for materials and energy were assessed using the Ecoinvent data quality system. This study shows that with two different energy mixes, all renovation measures result in a decrease in the climate change potential. The five renovation measures used in the simulations, with and without consideration to uncertainties, show a lower climate change potential when carried out than when not carried out. It is also shown in this study that the inclusion of the uncertainties of the input data did not have any impact on the overall decisions to renovate or not to renovate. However, this should not be regarded as a general conclusion. If a renovation measure were to have a higher level of material use, or if the “Future energy mix” were to be improved, uncertainty considerations could become much more important from a climate change perspective. Article Highlights All assessed energy renovation measures show a decrease in their climate change potential when carried out. The energy renovation measures with the largest decreases of climate change potential are also the measures with largest energy saving potential. When uncertainties are considered, there are no overlaps in the results when carrying out or not carrying out a renovation measure.

Assessing Global Long-Term EROI of Gas: A Net-Energy Perspective on the Energy Transition

Natural gas is expected to play an important role in the coming low-carbon energy transition. However, conventional gas resources are gradually being replaced by unconventional ones and a question remains: to what extent is net-energy production impacted by the use of lower-quality energy sources? This aspect of the energy transition was only partially explored in previous discussions. To fill this gap, this paper incorporates standard energy-return-on-investment (EROI) estimates and dynamic functions into the GlobalShift bottom-up model at a global level. We find that the energy necessary to produce gas (including direct and indirect energy and material costs) corresponds to 6.7% of the gross energy produced at present, and is growing at an exponential rate: by 2050, it will reach 23.7%. Our results highlight the necessity of viewing the energy transition through the net-energy prism and call for a greater number of EROI studies.

A Centralized Power Flow Control Scheme of EV-Connected DC Microgrid to Satisfy Multi-Objective Problems under Several Constraints

Integrating electric vehicles (EVs) into a microgrid improves the efficiency, flexibility, and robustness of microgrids. Unfortunately, the uncertainties of EVs, in terms of their connection/disconnection times and their initial SOC values, make integrating EVs into microgrids a more challenging issue. Contrary to the standard energy management system (EMS), integrating EVs into microgrids raises several multi-objective problems that need to be solved. In this study, a centralized power flow control scheme for an EV-connected DC microgrid (DCMG) is proposed to satisfy these multi-objective problems under several constraints. Two prime objective functions of the DCMG are presented to demonstrate the benefits to both the DCMG system and EV owners. Then, a reliable and optimized DCMG system is constructed to satisfy the selected prime objective function. The operating modes of each agent in the DCMG are defined based on information regarding the EV connection/disconnection status, the initial EV SOC values, the generation power of the wind power agent, the battery SOC levels, and the grid availability. The effectiveness and robustness of the proposed scheme have been validated by in-depth simulations and experimental tests under the uncertainties of DG power, grid availability, electricity price conditions, and EV connections. In addition, the proposed scheme reliably regulates the DC-link voltage without severe transience, even if these uncertainties cause the task of controlling the DC-link voltage to be transferred from one agent to another.

Chronic Intake of Energy Drinks and Their Sugar Free Substitution Similarly Promotes Metabolic Syndrome

Energy drinks containing significant quantities of caffeine, taurine and sugar are increasingly consumed, particularly by adolescents and young adults. The putative effects of chronic ingestion of either standard energy drink, MotherTM (ED), or its sugar-free formulation (sfED) on metabolic syndrome were determined in wild-type C57BL/6J mice, in comparison to a soft drink, Coca-Cola (SD), a Western-styled diet enriched in saturated fatty acids (SFA), and a combination of SFA + ED. Following 13 weeks of intervention, mice treated with ED were hyperglycaemic and hypertriglyceridaemic, indicating higher triglyceride glucose index, which was similar to the mice maintained on SD. Surprisingly, the mice maintained on sfED also showed signs of insulin resistance with hyperglycaemia, hypertriglyceridaemia, and greater triglyceride glucose index, comparable to the ED group mice. In addition, the ED mice had greater adiposity primarily due to the increase in white adipose tissue, although the body weight was comparable to the control mice receiving only water. The mice maintained on SFA diet exhibited significantly greater weight gain, body fat, cholesterol and insulin, whilst blood glucose and triglyceride concentrations remained comparable to the control mice. Collectively, these data suggest that the consumption of both standard and sugar-free forms of energy drinks induces metabolic syndrome, particularly insulin resistance.

Enhanced piezoelectric energy harvesting power with thermoelectric energy assistance

The demand for life-time power supply in Internet of Things (IoT) nodes is a challenge issue. Piezoelectric energy harvesting (PEH) is expected to meet the demand by harvesting vibration energy and converting it into electricity for the IoT nodes. This article presents a novel PEH power improvement circuit with thermoelectric energy assistance. The proposed circuit can extract energy from thermoelectric generator (TEG) to assist the PEH. Simulation and experimental platforms are built for testing the power generation performance of the proposed circuit. With the thermoelectric assistance of 0.1 V and 0.2 V, the harvested power can reach 3.4 times and 4 times that of the standard energy harvesting (SEH) circuit when the piezoelectric transducer (PZT) original open circuit voltage Voc,org = 8 V, respectively. The harvested power can be increased by 13.3% and 33.3% with the thermoelectric assistance of 0.1 V and 0.2 V, respectively.

A methodological approach for a home occupants centred web tool to support buildings energy retrofitting process

This paper presents a methodological approach to develop a user-oriented web tool to support the early stage of the decision making process for energy retrofitting of residential real estates. The tool mixes a simple analytical Urban Building Energy Model (UBEM) to user-oriented feedback interfaces to simulate the retrofitting potential of the residential units. The AUREE tool will be based on a Web – GIS GeoBlog portal with customized interfaces aimed to share the knowledge on urban building heritage and promote participation of stakeholders of the urban community. There are many literature exempla of guidelines or quality protocols on the topic of energy efficiency specified to particular types of buildings or focused on a territorial area, but these are generally not integrated into a geographically based tool. Moreover, the AUREE methodology aims to set interfaces that could use the portal users’ feedback to update the content of the portal itself. After touch on the theoretical context, a summary of the AUREE project is presented, and then the paper focuses on the structures of algorithms and tools adopted on the residential users’ interfaces. The interface mixes the results of an engineering Urban Building Energy Model based on local archetypal approach and standard energy calculation (series UNI 11300 - TS), with participative data provided via user-interactive interfaces to obtain customized retrofitting scenarios and suggestions. At the end of the paper, the main critical aspects and the further step of the research project are pointed

The Selection of Green Technology Innovations under Dual-Credit Policy

In the pressure of excessive resource consumption and serious environmental pollution, government in China proposed a dual-credit policy to promote the production of green vehicles, such as energy-saving fuel vehicle (FV) and electric vehicle (EV). This study explores the firm’s selection of green technology innovations (GTIs) under dual-credit policy, including the energy-saving technology for FV and the technology for producing EV. We found that the firm’s technology capacity of improving the energy-saving level of FV plays an important role in affecting the firm’s selections of GTIs. Specifically, when the technology capacity is moderate, the firm chooses both types of GTIs to produce both EV and energy-saving FV, otherwise he will choose one type only. Moreover, no matter which GTI is selected by the firm, its pricing and environmental efforts decisions keep the same. With the dual-credit policy, we found that it could encourage the production of the EV under certain conditions. Besides this, increasing the green credit of EV can align the economic and environmental interests while increasing standard energy consumption has conflicts in both interests. In particular, when the firm offers FV only or both EV and FV, increasing the price of credit has conflicting interests in economy and environment. However, when the firm offers EV only, increasing the price of credit could improve the firm’s profit without hurting the environment.