25 research outputs found

    Bilateral Keratoconus in a Patient with Isolated Foveal Hypoplasia

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    This is a Photo Essay and does not have an abstract

    Optimizing Lifespan of Circular Products: A Generic Dynamic Programming Approach for Energy-Using Products

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    Slowing down replacement cycles to reduce resource depletion and prevent waste generation is a promising path toward a circular economy (CE). However, an obligation to longevity only sometimes makes sense. It could sometimes even backfire if one focuses exclusively on material resource efficiency measures of the production phase and neglects implications on the use phase. The (environmental) lifespan of circular products should, therefore, be optimized, not maximized, considering all life cycle phases. In this paper, a generic method for determining the optimal environmental lifespan (OEL) of energy-using products (EuPs) in a CE is developed, allowing the simultaneous inclusion of various replacement options and lifetime extension processes, like re-manufacturing, in the assessment. A dynamic programming approach is used to minimize the cumulative environmental impact or costs over a specific time horizon, which allows considering an unordered sequence of replacement decisions with various sets of products. The method further accounts for technology improvement as well as efficiency degradation due to usage and a dynamic energy supply over the use phase. To illustrate the application, the OEL of gas heating appliances in Germany is calculated considering newly evolved products and re-manufactured products as replacement options. The case-study results show that with an average heat demand of a dwelling in Germany, the OEL is just 7 years for climate change impacts and 11 years for the aggregated environmental indicator, (Formula presented.). If efficiency degradation during use is considered, the OEL for both environmental impact assessment methods even lowers to 1 year. Products are frequently replaced with re-manufactured products to completely restore efficiency at low investment cost, resulting in higher savings potential. This not only implies that an early replacement before the product breaks down is recommended but also that it is essential to maintain the system and, thus, to prevent potential efficiency degradation. The results for cost optimization, as well as currently observed lifespans, vary considerably from this.ISSN:1996-107

    Optimizing Lifespan of Circular Products: A Generic Dynamic Programming Approach for Energy-Using Products

    No full text
    Slowing down replacement cycles to reduce resource depletion and prevent waste generation is a promising path toward a circular economy (CE). However, an obligation to longevity only sometimes makes sense. It could sometimes even backfire if one focuses exclusively on material resource efficiency measures of the production phase and neglects implications on the use phase. The (environmental) lifespan of circular products should, therefore, be optimized, not maximized, considering all life cycle phases. In this paper, a generic method for determining the optimal environmental lifespan (OEL) of energy-using products (EuPs) in a CE is developed, allowing the simultaneous inclusion of various replacement options and lifetime extension processes, like re-manufacturing, in the assessment. A dynamic programming approach is used to minimize the cumulative environmental impact or costs over a specific time horizon, which allows considering an unordered sequence of replacement decisions with various sets of products. The method further accounts for technology improvement as well as efficiency degradation due to usage and a dynamic energy supply over the use phase. To illustrate the application, the OEL of gas heating appliances in Germany is calculated considering newly evolved products and re-manufactured products as replacement options. The case-study results show that with an average heat demand of a dwelling in Germany, the OEL is just 7 years for climate change impacts and 11 years for the aggregated environmental indicator, ReCiPeendpoint(total). If efficiency degradation during use is considered, the OEL for both environmental impact assessment methods even lowers to 1 year. Products are frequently replaced with re-manufactured products to completely restore efficiency at low investment cost, resulting in higher savings potential. This not only implies that an early replacement before the product breaks down is recommended but also that it is essential to maintain the system and, thus, to prevent potential efficiency degradation. The results for cost optimization, as well as currently observed lifespans, vary considerably from this

    An innovative solar assisted desiccant-based evaporative cooling system for co-production of water and cooling in hot and humid climates

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    Although evaporative coolers consume much lower electricity than the vapor compression systems, they are not applicable in humid climates. Combination of desiccant wheels and evaporative coolers, known as desiccant-based evaporative cooling systems, allows evaporative coolers to be used in humid climates, which provide significant energy and environmental advantages with respect to vapor compression systems. However, one of the main disadvantages of evaporative cooling is the high water. Regarding the global water crisis, a cooling system which saves both water and energy will be an attractive alternative to the current cooling systems. To this aim, this paper presents a novel desiccant-based evaporative cooling system for co-production of water and cooling. In this system, the moisture content of exhaust regeneration air is recycled to cover all of the evaporative cooler water consumption, and also part of the domestic water usage. To evaluate the system performance, dynamic hourly simulation of the proposed system as well as a reference vapor compression system was performed for a typical 60m2 building in hot and humid climate of Bandar Abbas, Iran. The simulation results show that the proposed system is able to provide comfort temperature and relative humidity in a hot and humid climate. Moisture harvesting produce about 590L water during a week, which covers all of the evaporative cooler water consumption, and provides an excess amount of 289L for domestic usage. Monthly integrated results indicate that electricity consumption of the proposed system is 60% lower than the reference system, while its natural gas consumption is 30% higher than VCS, which is due to the high regeneration temperature in some hours. In other worlds, this system replace electricity consumption, a high-exergy and expensive energy carrier, with heat consumption. This system leads to 18.7% saving of CO2 emissions over a month. Economic evaluation proves the economic feasibility of proposed system with a payback period of 3 years. In conclusion, proposed system provide a more environmental friendly cooling system for water, energy and carbon saving

    Comparison of the effect of Propofol, Etomidate and Thiopental on Seizure duration following electro convulsion therapy:A clinical trial study

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    Background and Objective: Electro convulsion therapy (ECT) is one of the most common ways for treatment of psychiatric disorders. The aim of this study was to compare the effect of Propofol, Etomidate, and Thiopental on seizure and recovery duration following ECT. Methods: In this clinical trial study, 90 patients diagnosed with a psychiatric disorder by a psychiatrist, who need to be treated by ECT in 5 Azar hospital, Gorgan, north Iran. The patients were randomly divided into the three groups by simple random allocation method. Interventions included standard monitoring and pre-oxygenation with 100% FiO2 for 3 minutes for all patients in three groups. Anesthesia of the patients in the first, second, and third group was done with Thiopental (1.5 mg/kg), Propofol (0.6 mg/kg), and Etomidate (0.1 mg/kg), respectively. Administration of Succinyl Colin (0.5 mg/kg) as muscle relaxant and Atropine for prevention of bradycardia was uesd in all patients. Duration of seizure and recovery; changes in hemodynamic status including heart rate (HR) and mean arterial pressure (MAP); and amount of charge for ECT were recorded for each subject. Results: Mean of seizure duration in Thiopental, Propofol, and Etomidate groups were 43.72±11.81, 35.74±10.58 and 45.81±17.26 seconds, respectively (P<0.05). Amount of charge for ECT in 3 sessions of treatment and changes of HR were not different between the 3 groups. Changes of MAP in the Propofol group was significantly less than other two groups (P<0.05). Recovery time following ECT was the least in Etomidate group in comparison with Thiopental and Propofol (P<0.05). Conclusion: Ethomidate and Thiopental had the same effect on increasing seizure duration. However, due to the significant reduction in recovery time compared with Thiopental, Ethomidate may be considered as the best choice

    Mapping Local Synergies: Spatio-Temporal Analysis of Switzerland’s Waste Heat Potentials vs. Heat Demand

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    As nations transition to renewable energy, making use of waste heat becomes crucial to combat climate change. This study focused on quantifying Switzerland’s waste heat potential from industrial processes and waste-to-energy facilities, using diverse methodologies tailored to facility characteristics and data availability. We assessed potential waste heat utilization by comparing local heat supply and demand, creating comprehensive heat-balance maps considering different temperature levels and seasonal fluctuations. Results revealed a substantial annual waste heat potential of 37 TWh, with almost half (17 TWh) below 45 °C, primarily from wastewater. Heat between 45 °C and 70 °C, ideal, e.g., for greenhouse heating, is mainly available from solid waste incineration plants, while industries contributed to waste heat supply exceeding 150 °C. In contrast to heat demand, seasonal variations in heat supply were small, with a 12% winter decrease. Analyzing heat demand versus supply unveiled local and seasonal disparities. Most municipalities had a net excess heat demand (totaling 89 TWh). Additionally, waste heat could not satisfy 8 TWh of industrial process heat demand exceeding 400 °C, emphasizing reliance on primary energy sources for higher-temperature heat. Targeted strategies are essential for effective waste heat utilization, especially tapping into low-temperature sources. Integrating these sources with low-carbon technologies can pave the way to a sustainable energy future.ISSN:1996-107

    Implementing conceptual model using renewable energies in rural area of Iran

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    In a glance, more than three billion people live in the rural areas of low and middle income countries. In most cases, rural households have many unmet energy needs including cooking, lighting, heating, transportation and telecommunication needs. The main goal of this study is Implementing Conceptual Model Using Renewable Energies in Rural Area of Iran. In this study, the Weibull and Angestrom distribution methods were used to assess the potential of wind and solar energy range in Chaharmahal va Bakhtiari province of Iran (The Case study). After determining the values calculated based on meteorological stations' data, the IDW interpolation method in GIS software was used for the entire geographic range of the province. After reviewing multiple regions and identifying potential classes, a village which has the potential to be enough sun and wind energy was selected (Kahkesh village) and then a field survey based on biomass resources was accomplished. The needs of rural residents and rural renewable energy potential was evaluated by study conceptual frameworks during one year. By dividing the value of frameworks energies the amount of energy saving can be calculated. Finally, it recommended that for utilizing the renewable energies in rural areas, as will be discussed in the present work and particularly using the conceptual frameworks, is performed
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