25 results on '"Saffari, Mohammad"'
Search Results
2. COMMENT ON "OPTIMAL SHELF-SPACE STOCKING POLICY USING STOCHASTIC DOMINANCE UNDER SUPPLY-DRIVEN DEMAND UNCERTAINTY".
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Saffari, Mohammad
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NEWSVENDOR model , *STOCHASTIC dominance , *OPERATIONS research , *CONCAVE functions - Abstract
The paper authored by Amit et al. [Amit, R. K., Mehta, P., & Tripathi, R. R. "Optimal shelf-space stocking policy using stochastic dominance under supply-driven demand uncertainty", European Journal of Operational Research, 246(1), pp. 339-342 (2015)] proposes a newsvendor model in which demand depends on displayed inventory. Under stochastic dominance conditions, they claimed that the profit function is concave at its extremum points. In the present study, it is expressed that this statement is not generally precise. [ABSTRACT FROM AUTHOR]
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- 2021
3. Technical and economic assessment of a hybrid heat pump system as an energy retrofit measure in a residential building.
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Saffari, Mohammad, Keogh, David, De Rosa, Mattia, and Finn, Donal P.
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HEAT pumps , *ELECTRIC pumps , *RESIDENTIAL heating systems , *RETROFITTING , *FUEL switching , *RETROFITTING of buildings - Abstract
Air to water electric heat pumps are one technological solution to achieve energy defossilisation goals for heating of residential building stock. Nevertheless, they may not necessarily be the only solution for all residential building stock. A case in point is where extensive fabric refurbishment is impracticable or where electric heat pumps are installed where low ambient temperatures prevail and/or high water delivery temperatures must be utilised. For such instances, hybrid (gas and electric) heat pumps offer an alternative option by facilitating fuel source switching between electricity and gas, when ambient temperatures are low or high water supply temperatures are required. In the current study, the effectiveness of an air-to-water electric heat pump and hybrid heat pump are examined for different building retrofit scenarios for a residential dwelling located in Ireland. This is achieved by means of a sensitivity study of a validated building simulation model, incorporating both heat pump systems, subject to different building retrofit scenarios. Relative to a conventional oil-fired boiler, for a deep building retrofit scenario, the hybrid and electric heat pumps achieve primary energy reduction of 128 kWh/ m 2 /year (72%) and of 123 kWh/ m 2 /year (70%), respectively. Considering the associated carbon footprints, the reductions were found to be 29.7 g C O 2 e / m 2 /year (74%) for the hybrid heat pump, and 27.6 g C O 2 e / m 2 /year (68%) for the electric heat pump. Finally, the deployment of either an electric heat pump or hybrid heat pump for deep building fabric retrofit achieves approximately half of the heating system capital cost return within 20 years. • Analysis of a hybrid gas-electric heat pump system in a residential building. • Benchmarked against, oil boiler, gas boiler and electric heat pump. • Integrated validated simulation model utilised for retrofit options analysis. • Electric and hybrid heat pumps with deep retrofit are the most economically attractive options. • Electric heat pump and hybrid heat pump systems with deep retrofit exhibit the lowest C O 2 emissions. [ABSTRACT FROM AUTHOR]
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- 2023
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4. A Comparative Study between Supraorbital Keyhole and Pterional Approaches on Anterior Circulation Aneurysms.
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GENESAN, PRAVINNA, HASPANI, MOHAMMAD SAFFARI MOHAMMAD, and NOOR, SAIFUL RAZMAN MOHD
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INTRACRANIAL aneurysm diagnosis , *EYEBROWS , *INTRACRANIAL aneurysm surgery , *AESTHETICS , *BLOOD vessels , *COMPARATIVE studies , *COMPUTED tomography , *COSMETICS , *CRANIOTOMY , *PATIENT satisfaction , *SCARS , *SURGICAL complications , *VISUAL analog scale , *TREATMENT effectiveness , *TREATMENT duration , *SURGERY - Abstract
Background: Many different conventional approaches such as the frontal and pterional approaches are used to access anterior circulation aneurysms. Recently, the supraorbital approach has been widely applied to the treatment of anterior circulation aneurysms. This study was done to evaluate which approach (pterional or supraorbital) has better outcomes in terms of residual neck post-clipping, cosmetic satisfaction, scar tenderness, complications and functional outcomes. Methodology: A total of 123 patients were recruited into this study, comprising 82 patients who underwent a pterional approach and 41 patients who underwent a supraorbital approach. Computed tomography angiograms, the modified Rankin Scale, and the visual analogue scale were administered at 6 months to look for residual aneurysm, functional outcomes, scar tenderness, and cosmetic satisfaction. Complication data were collected from patients' case notes. Results: The mean operating time for the pterional group was 226 min, compared to supraorbital group, which was 192 min (P = 0.07). Cosmetic satisfaction was significantly higher (P = 0.001) in the supraorbital group. There was no significant difference between the supraorbital and pterional groups' scar tenderness (P = 0.719), residual aneurysm (P = 0.719), or functional outcomes (P = 0.137), and there was no significant difference between the groups in terms of intra- operative and post-operative complications. Conclusions: The supraorbital group had better cosmetic outcomes and shorter operating times compared to the pterional group. [ABSTRACT FROM AUTHOR]
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- 2018
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5. Optimized demand side management (DSM) of peak electricity demand by coupling low temperature thermal energy storage (TES) and solar PV.
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Saffari, Mohammad, de Gracia, Alvaro, Fernández, Cèsar, Belusko, Martin, Boer, Dieter, and Cabeza, Luisa F.
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ENERGY demand management , *LOW temperatures , *HEAT storage , *ELECTRIC utilities , *ELECTRIC power distribution grids , *COOLING - Abstract
Cooling in the industry sector contributes significantly to the peak demand placed on an electrical utility grid. New electricity tariff structures include high charges for electricity consumption in peak hours which leads to elevated annual electricity costs for high-demanding consumers. Demand side management (DSM) is a promising solution to increase the energy efficiency among customers by reducing their electricity peak demand and consumption. In recent years, researchers have shown an increased interest in utilizing DSM techniques with thermal energy storage (TES) and solar PV technologies for peak demand reduction in industrial and commercial sectors. The main objective of the present study is to address the potential for applying optimization-based time-of-use DSM in the industry sector by using cold thermal energy storage and off-grid solar PV to decrease and shift peak electricity demands and to reduce the annual electricity consumption costs. The results show that when cold thermal energy storage and solar PV are coupled together higher annual electricity cost savings can be achieved compared to using these two technologies independently. Additionally, considerable reductions can be seen in electricity power demands in different tariff periods by coupling thermal energy storage with off-grid solar PV. [ABSTRACT FROM AUTHOR]
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- 2018
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6. Thermal stress reduction in cool roof membranes using phase change materials (PCM).
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Saffari, Mohammad, Piselli, Cristina, de Gracia, Alvaro, Pisello, Anna Laura, Cotana, Franco, and Cabeza, Luisa F.
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THERMAL stresses , *PHASE change materials , *ARTIFICIAL membranes , *ENERGY consumption of buildings , *AIR conditioning , *URBAN heat islands - Abstract
A considerable amount of energy is used in the building sector for air conditioning purposes. Additionally, the building sector contributes to the urban heat island (UHI) phenomenon which causes temperature rise in urban areas. Cool roof is an emerging passive cooling technology that can contribute to reduce the cooling energy use in buildings and to mitigate the UHI effects in the urban area. Cool roofs and reflective coatings, despite of being effective in terms of reducing the cooling thermal loads in buildings and decrease the UHI, can suffer from extreme thermal stress which negatively influences their lifespan and performance. Thermal energy storage (TES) is a promising technology which can be applied together with cool roof technology to decrease the extreme thermal stress due to solar radiation as well as providing thermal inertia to the building. In this study, simulation-based optimization will be used to optimize the PCM melting temperature when integrated into a polyurethane-based cool roof membrane to reduce the thermal stress of the cool roof and also to improve the annual energy performance of the building. The optimization results showed that the application of PCM and cool roof technologies together can reduce the severe thermal stress of the cool roof membrane when the optimization objective is the annual thermal stress of the cool roof. On the other hand, when PCM melting temperature is optimized to reduce the annual energy needs, higher annual energy savings could be achieved with acceptable reductions in the cool roof membrane thermal stress. [ABSTRACT FROM AUTHOR]
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- 2018
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7. Passive cooling of buildings with phase change materials using whole-building energy simulation tools: A review.
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Saffari, Mohammad, De Gracia, Alvaro, Ushak, Svetlana, and Cabeza, Luisa F.
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BUILDINGS & the environment , *THERMAL comfort , *ENERGY consumption of buildings , *COOLING ,ENERGY consumption & climate ,ENVIRONMENTAL aspects - Abstract
Buildings contribute to climate change by consuming a considerable amount of energy to provide thermal comfort for occupants. Cooling energy demands are expected to increase substantially in the world. On this basis, technologies and techniques providing high energy efficiency in buildings such as passive cooling are highly appreciated. Passive cooling by means of phase change materials (PCM) offers high potential to decrease the cooling energy demand and to improve the indoor comfort condition. However, in order to be appropriately characterized and implemented into the building envelope, the PCM use should be numerically analyzed. Whole-building energy simulation tools can enhance the capability of the engineers and designers to analyze the thermal behavior of PCM-enhanced buildings. In this paper, an extensive review has been made, with regard to whole-building energy simulation for passive cooling, addressing the possibilities of applying different PCM-enhanced components into the building envelope and also the feasibility of PCM passive cooling system under different climate conditions. The application of PCM has not always been as energy beneficial as expected, and actually its effectiveness is highly dependent on the climatic condition, on the PCM melting temperature and on the occupants behavior. Therefore, energy simulation of passive PCM systems is found to be a single-objective or multi-objective optimization problem which requires appropriate mathematical models for energy and comfort assessment which should be further investigated. Moreover, further research is required to analyze the influence of natural night ventilation on the cooling performance of PCM. [ABSTRACT FROM AUTHOR]
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- 2017
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8. The Efficacy of Intra-Operative Ultrasound for Tumour Resection Compared to Post-Operative MRI Brain.
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Kanmani Devi GANISON, Mohammad Saffari MOHAMMAD HASPANI, and Norzaini Rose MOHD ZAIN
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BRAIN tumors , *HOSPITALS , *INTRAOPERATIVE radiotherapy , *LONGITUDINAL method , *MAGNETIC resonance imaging , *PROBABILITY theory , *REGRESSION analysis , *T-test (Statistics) , *TREATMENT effectiveness , *DATA analysis software , *DESCRIPTIVE statistics , *INTRACLASS correlation - Published
- 2017
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9. Simulation-based optimization of PCM melting temperature to improve the energy performance in buildings.
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Saffari, Mohammad, Cabeza, Luisa F., de Gracia, Alvaro, and Fernández, Cèsar
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ELECTRIC power production , *PHASE change materials , *ELECTRIC power consumption , *EMISSIONS (Air pollution) , *HEAT storage - Abstract
Globally, a considerable amount of energy is consumed by the building sector. The building envelope can highly influence the energy consumption in buildings. In this regard, innovative technologies such as thermal energy storage (TES) can help to boost the energy efficiency and to reduce the CO 2 emissions in this sector. The use of phase change materials (PCM), due to its high heat capacity, has been the centre of attention of many researchers. A considerable number of papers have been published on the application of PCM as passive system in building envelopes. Researches have shown that choosing the PCM melting temperature in different climate conditions is a key factor to improve the energy performance in buildings. In the present paper, a simulation-based optimization methodology will be presented by coupling EnergyPlus and GenOpt with an innovative enthalpy-temperature (h-T) function to define the optimum PCM peak melting temperature to enhance the cooling, heating, and the annual total heating and cooling energy performance of a residential building in various climate conditions based on Köppen-Geiger classification. Results show that in a cooling dominant climate the best PCM melting temperature to reduce the annual energy consumption is close to the maximum of 26 °C (melting range of 24–28 °C), whereas in heating dominant climates PCM with lower melting temperature of 20 °C (melting range of 18–22 °C) yields higher annual energy benefits. Moreover, it was found that the proper selection of PCM melting temperature in each climate zone can lead to notable energy savings for cooling energy consumption, heating energy consumption, and total annual energy consumption. [ABSTRACT FROM AUTHOR]
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- 2017
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10. Optimization of roof solar reflectance under different climate conditions, occupancy, building configuration and energy systems.
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Piselli, Cristina, Saffari, Mohammad, De Gracia, Alvaro, Pisello, Anna Laura, Cotana, Franco, and Cabeza, Luisa F.
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SOLAR reflectors , *ROOF design & construction , *ARCHITECTURAL style , *ENERGY consumption of buildings , *DYNAMIC simulation - Abstract
Cool roofs have been widely proved to represent an effective strategy for building thermal-energy performance improvement during the cooling season. However, their effectiveness along the whole year can be affected by building features and other boundary conditions. The present work aims at assessing the energy performance of high solar reflectance roof solutions in different climate zones, when implemented in a variety of building typologies. Therefore, an optimization study was carried out to select the optimum roof solar reflectance able to minimize building annual HVAC energy consumption. In this work, Italian climate zones were considered as case study conditions. The analysis was performed through dynamic simulation of validated standard ASHRAE building reference models. Moreover, the role of (i) type of HVAC system operating, (ii) presence and intensity of internal gains, and (iii) roof thermal insulation level was evaluated on the resulting optimum roof reflectance capability. Results show that the optimum roof solar reflectance varies under different climate conditions, mainly depending on heating or cooling dominated conditions. However, all further analyzed boundary conditions, i.e. building typology, HVAC system, internal gains, and roof insulation level, affect building energy performance and, therefore, the optimum roof reflectance identification. In the hottest climate, the optimum roof solar reflectance resulted to be consistently equal to the maximum considered, i.e. 0.8, also with varying the other parameters. Moreover, the annual HVAC energy need is more sensitive to roof reflectance in the apartment building, showing 17% of energy savings with standard model characteristics. On the other hand, in heating dominated climates, the optimum roof solar reflectance is more variable, ranging over all the considered values, because it is affected by the additional boundary conditions. On the contrary, the variability of HVAC need due to roof solar reflectance variation is generally lower. [ABSTRACT FROM AUTHOR]
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- 2017
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11. Energy savings due to the use of PCM for relocatable lightweight buildings passive heating and cooling in different weather conditions.
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Marin, Paula, Saffari, Mohammad, de Gracia, Alvaro, Zhu, Xibingyan, Farid, Mohammed M., Cabeza, Luisa F., and Ushak, Svetlana
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ENERGY consumption of buildings , *PHASE change materials , *ENERGY conservation in buildings , *HEATING , *COOLING , *HEAT storage - Abstract
Relocatable, transportable or off-site constructed lightweight buildings typically undergo sharp indoor temperature fluctuations in the heating and cooling seasons due to the lack of sufficient thermal mass in their envelopes, resulting in high energy consumption to provide the zone with comfort temperature. The application of phase change materials has been suggested as a promising solution to control the indoor thermal condition in buildings. This work is an attempt to support the application of PCM technology in lightweight relocatable buildings as a passive alternative to save energy under different weather conditions. The numerical results highlighted the potential of using PCM-enhanced gypsum boards in lightweight buildings to increase the energy performance during both heating and cooling seasons in arid and warm temperate main climate areas. [ABSTRACT FROM AUTHOR]
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- 2016
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12. Economic impact of integrating PCM as passive system in buildings using Fanger comfort model.
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Saffari, Mohammad, de Gracia, Alvaro, Ushak, Svetlana, and Cabeza, Luisa F.
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ENERGY consumption of buildings , *HEATING , *VENTILATION , *THERMAL comfort , *PHASE change materials , *SIMULATION software - Abstract
In buildings, HVAC systems consume a high amount of energy to provide thermal comfort for occupants. A methodology is presented in this paper to control thermostat operation of the buildings considering the effects of indoor and outdoor boundary conditions and phase change material (PCM) characteristics. EnergyPlus v8.1 building energy simulation software was used to analyze the energy performance of the PCM incorporated building models and to implement Fanger model to control HVAC thermostat operation according to BS EN 15251:2007 thermal comfort categories. Three types of building HVAC schedule, PCM with different melting points and layer thicknesses were studied for Madrid climate zone. Moreover, the impact of occupants clothing on the energy consumption was investigated. Furthermore, payback analysis was conducted to find out the economic benefits of PCM integration into the building envelopes. Application of PCM improved the cooling and heating energy performances except for the office model in winter (heating period). Additionally, higher energy savings and lower payback periods were observed when PCM with higher melting point was applied to the buildings. Eventually, energy savings in PCM incorporated models were found to improve further when occupants changed their clothing behavior in winter. [ABSTRACT FROM AUTHOR]
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- 2016
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13. Home energy retrofit: Reviewing its depth, scale of delivery, and sustainability.
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Saffari, Mohammad and Beagon, Paul
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SUSTAINABILITY , *RETROFITTING , *CLIMATE change mitigation , *GREENHOUSE gas mitigation , *POWER resources , *CARBON dioxide mitigation - Abstract
• Relative and absolute home retrofit targets are reviewed and discussed. • Retrofit depth is determined by policy targets or practical cost-effectiveness. • Research studies find feasible energy savings of around 60% maximum. • Neighbourhood is optimal spatial scale to large-scale deliver home energy retrofit. • Future retrofits to be phased instead of one-off, and less primacy of fabric first. Home energy retrofit has been a publicly-funded policy in many countries since the 1990s. Government motivations have spanned from combating energy poverty to climate action and sustainability. Given the ambition of public policy, this paper reviews the targets, spatial scales and metrics used to deliver and evaluate home energy retrofit. Large-scale retrofit projects do differ: by spatial area, by retrofit depth and in evaluation metrics (if used). This review surveys first, the quantities of homes and inhabitants in intermediate spatial scales used to plan retrofit programmes. Second, the optimal spatial scale and retrofit depth to deliver large-scale home retrofit. Third, the quantitative metrics to evaluate retrofits, and future trends in occupant-based metrics. Neighbourhood is found to be the optimal spatial scale for home energy retrofit. Deep retrofit is described as 60% energy savings that, in synergy with energy supply decarbonisation, promises to deliver 80% or higher emission reductions. Recent evidence shows a shifting primacy from fabric-first retrofit to decarbonisation of heat generation and occupant health and well-being. [ABSTRACT FROM AUTHOR]
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- 2022
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14. The M/M/1 queue with inventory, lost sale, and general lead times.
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Saffari, Mohammad, Asmussen, Søren, and Haji, Rasoul
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QUEUEING networks , *POISSON processes , *LEAD time (Supply chain management) , *RANDOM variables , *BACK orders - Abstract
We consider an M/M/1 queueing system with inventory under the $$(r,Q)$$ policy and with lost sales, in which demands occur according to a Poisson process and service times are exponentially distributed. All arriving customers during stockout are lost. We derive the stationary distributions of the joint queue length (number of customers in the system) and on-hand inventory when lead times are random variables and can take various distributions. The derived stationary distributions are used to formulate long-run average performance measures and cost functions in some numerical examples. [ABSTRACT FROM AUTHOR]
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- 2013
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15. Applying Iranian Gum Tragacanth to Improve Textural Properties of Maltodextrin Microcapsules.
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Saffari, Mohammad Mahdi, Farzi, Mina, Emam‐Djomeh, Zahra, Moini, Sohrab, and Mohammadifar, Mohammad Amin
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FOOD texture , *MALTODEXTRIN , *MICROENCAPSULATION , *LEGUMES , *BUTYL acetate - Abstract
The effects of adding one of the species of Iranian gum tragacanth, Astragalus compactus, to maltodextrin solutions used for microencapsulation of 2-methylbutyl acetate (water-soluble flavoring compound of strawberry) were studied. Initial emulsions were evaluated regarding rheological behavior and particle size distribution. The resulted microcapsules were also analyzed for particle size distributions, glass transition temperature Tg, the morphology of the capsules and the rate of release from them. The results showed that addition of 0.5% w/w A. compactus gum to maltodextrin solutions (14.5% w/w) can increase the viscosity and Tg to an optimum level and can prevent stickiness. Also this species of gum tragacanth had an interesting effect in reducing physical defects of microcapsules and eliminated ruptures significantly. It was also showed that the rate of release of 2-methylbutyl acetate decreased by incorporating gum tragacanth in the wall material. Practical Applications Microencapsulation is of great interest in preservation of flavoring compounds. One of the most important wall materials is maltodextrin, which has several defects to protect flavorings. This study proposes the use of a new material, Iranian gum tragacanth from Astragalus compactus, to overcome these defects. It was found that new microcapsules did not undergo rupture and could retain the flavoring well. [ABSTRACT FROM AUTHOR]
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- 2013
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16. A queueing system with inventory and mixed exponentially distributed lead times.
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Saffari, Mohammad, Haji, Rasoul, and Hassanzadeh, Farhad
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QUEUING theory , *INVENTORIES , *LEAD time (Project management) , *NUMERICAL analysis , *DISTRIBUTION (Probability theory) , *ECONOMIC demand - Abstract
We consider M/M/1/∞ systems with inventory in which completing each service in the queueing system requires an on-hand inventory. Continuous review (r, Q) policy is considered for the inventory system, and lead times are assumed to be mixed exponentially distributed. During stockout, arriving demands get rejected from the queue and become lost (lost sale situation). We derive stationary distribution of product form of joint queue length and on-hand inventory. The resulting distribution is employed to compute performance measures which can be used to derive the optimal policy. Optimal order size for predetermined reorder policy is initially determined and finally, optimal reorder point and corresponding optimal order size are simultaneously computed for several numerical examples. [ABSTRACT FROM AUTHOR]
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- 2011
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17. Effect of ultrasonic treatment on the rheological properties and particle size of gum tragacanth dispersions from different species.
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Farzi, Mina, Saffari, Mohammad Mahdi, Emam-Djomeh, Zahra, and Mohammadifar, Mohammad Amin
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ULTRASONIC therapy , *RHEOLOGY , *PARTICLE size distribution , *SONICATION , *VISCOSITY , *CLUSTERING of particles , *SOUND waves - Abstract
Dispersions of different species of gum tragacanth were sonicated at a frequency of 24 kHz with a total nominal output power of 200 W for different time intervals (0, 7, 15, 45 and 90 s). Various species behave differently under sonication, which is related to structural differences in these species. In the case of Astragaslus compactus and A. rahensus dispersions, as the sonication time increased, the viscosity and particle size of the dispersions decreased, just as in gum Arabic solutions. However, A. gossypinus gum behaved differently compared to the other species. At early stages of sonication (up to 15 s), the viscosity of the dispersions increased sharply and reached its maximum value (106.04 mPa s) as the particle size increased slightly to 275.69 μm. Continuing sonication led to a decrease in the viscosity of the dispersions, though the particle size did not show any changes. This behaviour is thought to be due to the rupture and aggregation of particles. [ABSTRACT FROM AUTHOR]
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- 2011
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18. A fundamental unified framework to quantify and characterise energy flexibility of residential buildings with multiple electrical and thermal energy systems.
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Bampoulas, Adamantios, Saffari, Mohammad, Pallonetto, Fabiano, Mangina, Eleni, and Finn, Donal P.
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HEAT , *GROUND source heat pump systems , *ELECTRICAL energy , *DAYLIGHT , *DWELLINGS , *ELECTRIC power consumption , *HOME energy use , *HEAT storage - Abstract
To date, the energy flexibility assessment of multicomponent electrical and thermal systems in residential buildings is hindered by the lack of adequate indicators due to the different interpretations, properties, and requirements that characterise an energy flexible building. This paper addresses this knowledge gap by presenting a fundamental energy flexibility quantification framework applicable to various energy systems commonly found in residential buildings (i.e., heat pumps, renewables, thermal and electrical storage systems). Using this framework, the interactions between these systems are analysed, as well as assessing the net energy cost of providing flexibility arising from demand response actions where onsite electricity production is present. A calibrated white-box model of a residential building developed using EnergyPlus (including inter alia a ground source heat pump, a battery storage system, and an electric vehicle) is utilised. To acquire daily energy flexibility mappings, hourly independent, and consecutive demand response actions are imposed for each energy system, using the proposed indicators. The obtained flexibility maps give insights into both the energy volumes associated with demand response actions and qualitative characteristics of the modulated electricity consumption curves. The flexibility potential of each studied energy system is determined by weather and occupant thermal comfort preferences as well as the use of appliances, lighting, etc. Finally, simulations show that zone and water tank thermostat modulations can be suitably combined to shift rebound occurrences away from peak demand periods. These insights can be used by electricity aggregators to evaluate a portfolio of buildings or optimally harness the flexibility of each energy system to shift peak demand consumption to off-peak periods or periods of excess onsite electricity generation. • Few studies evaluate energy flexibility from an integrated energy systems perspective. • A novel unified framework is proposed for capturing the DR potential of thermal and electrical systems. • A series of novel indicators are introduced to acquire daily energy flexibility mappings. • Flexibility maps are used to quantify energy flexibility concisely and consistently. • Weather, occupant schedules and use of appliances shape the flexibility potential of each system. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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19. Improving the energy efficiency of passive PCM system using controlled natural ventilation.
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Prabhakar, Mohit, Saffari, Mohammad, de Gracia, Alvaro, and Cabeza, Luisa F.
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NATURAL ventilation , *HEAT storage , *ENERGY consumption , *SPACE heaters , *VENTILATION , *ENERGY consumption of buildings - Abstract
• PCM passive system was coupled with natural ventilation. • PCM melting temperature was optimized in different climate zones. • Airflow rates were numerically calculated based on the wind and buoyancy effects. • Two control strategies were implemented to maximize the utilization of ventilation. In recent years, the building sector has been responsible for continuous increase in energy consumption in the world. Space heating and cooling accounts for 34% of this energy consumption in buildings. In this context, using thermal energy storage (TES) can reduce energy consumption for space air conditioning. The use of phase change materials (PCM) as latent heat thermal energy storage (LHTES) system in the building envelope has been of great interest for passive cooling applications due to the high energy storage capacity of this technology. However, in order to utilize the full potential of a PCM, it needs to be fully charged at each cycle. Ventilation during the night is an effective method which can be used in PCM-enhanced office buildings with the aim of charging the PCM every required cycle. In the present study, PCM melting temperature of office building in various climate conditions was optimized using a simulation-based optimization and coupled with free cooling operation. Ventilation control strategies were used to improve the cooling energy performance of the PCM enhanced building integrated into envelopes. It was found that charging PCM with night ventilation, especially when using some specific control strategies of natural ventilation operated by external windows opening results in considerable cooling energy savings. The study was conducted for 15 different cities around the world. It was found that, in hot arid conditions, PCM passive cooling system was ineffective. Although, the energy savings were improved by coupling PCM and natural ventilation in these climate conditions. But the benefits were more or less similar to using natural ventilation only. On the other hand, in temperate condition, the effectiveness of PCM was increased from 3.32% to 25.62% by coupling a PCM passive system with night ventilation. It was further improved to 40% when using PCM with temperature-controlled ventilation. Moreover, it can be said that smart control of ventilation can lead to considerable energy savings. [ABSTRACT FROM AUTHOR]
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- 2020
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20. Providing a four-layer method based on deep belief network to improve emotion recognition in electroencephalography in brain signals.
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Mousavinasr, Seyed, Pourmohammad, Ali, and Saffari, Mohammad
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EMOTION recognition , *EMOTIONAL conditioning , *BRAIN-computer interfaces , *FILTER banks , *FEATURE extraction , *NEURAL circuitry , *INDEPENDENT component analysis - Abstract
Background: One of the fields of research in recent years that has been under focused is emotion recognition in electroencephalography (EEG) signals. This study provides a four-layer method to improve people's emotion recognition through these signals and deep belief neural networks. Methods: In this study, using DEAP dataset, a four-layer method is established, which includes (1) preprocessing, (2) extracting features, (3) dimension reduction, and (4) emotion identification and estimation. To find the optimal choice in some of the steps of these layers, three different tests have been conducted. The first is finding the perfect window in feature extraction section that resulted in superiority of Hamming window to the other windows. The second is choosing the most appropriate number of filter bank and the best result was 26. The third test was also emotion recognition that its accuracy was 92.93 for arousal dimension, 92.64 for valence dimension, 93.14 for dominance dimension in two-class experiment and 76.28 for the arousal, 74.83 for the valence, and 75.64 for dominance in three-class experiment. Results: The results of this method show an improvement of 12.34% and 7.74% in two- and three-class levels in the arousal dimension. This improvement in the valence is 12.77 and 8.52, respectively. Conclusion: The results show that the proposed method can be used to improve the accuracy of emotion recognition. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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21. Closing the gap between simulation and measured energy use in home archetypes.
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Beagon, Paul, Boland, Fiona, and Saffari, Mohammad
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HOME energy use , *ENERGY consumption , *ARCHETYPES , *HEAT , *HEAT pumps , *MINE ventilation - Abstract
• TABULA home archetypes are white-box modelled with realistic occupant variables. • Model parameters narrow the gap between calculated and measured energy use to 5–10%. • In temperate climates, measured heat energy is 22–32% below steady-state simulation. • Deep retrofit of an old home with modern boiler achieves up to 60% energy savings. • Shallow retrofit of a modern home achieves climate action target with heat pump only. Recent climate action plans set ambitious targets for large-scale home energy retrofit. These retrofit targets also recommend switching from oil boilers to electrical heat pumps. One area-based approach to retrofit is neighbourhood scale. Ideally with local community participation, neighbourhood retrofit improves a group of structurally similar homes, of the same archetype. Defined home archetypes already exist for 20 European countries thanks to previous research. That same research attempted steady-state calculations of space heating energy using the ISO 13790 Seasonal Method. Those calculations diverged from measured energy use by a large gap. Taking example home archetypes from Ireland, this study narrowed this energy-use gap by incorporating realistic parameters and schedules. Physical white-box models were constructed in DesignBuilder, and simulated by EnergyPlus with local weather data. The simulations combined realistic heating schedules, internal gains, infiltration and ventilation; converging simulation energy use with typical measurements and mostly achieved model calibration indices. Therefore, the resultant energy-use data was capable of tuning future grey-box models to investigate home energy use across ranges of heating patterns and heating setpoints. The aims of this study are threefold. First, devise a repeatable method to produce heat energy-use values by simulating white-box models of home archetypes, that enable tuning of future grey-box models. Second, specify the heating variables that result in acceptable energy-use gaps between simulation of home archetype models and their typical measurements. Third, test if the retrofits of three Irish home archetypes under a typical occupant schedule, achieve national climate action targets. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
22. Optimal control of natural ventilation as passive cooling strategy for improving the energy performance of building envelope with PCM integration.
- Author
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Piselli, Cristina, Prabhakar, Mohit, de Gracia, Alvaro, Saffari, Mohammad, Pisello, Anna Laura, and Cabeza, Luisa F.
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NATURAL ventilation , *BUILDING performance , *BUILDING envelopes , *PHASE transitions , *HEAT storage , *BUILDING-integrated photovoltaic systems , *MINE ventilation - Abstract
Phase Change Materials have been acknowledged for their potential to be used as passive strategy for improving energy efficiency and occupants' thermal comfort in buildings. However, their performance still needs to be enhanced to have them effectively used. In this view, this study investigates the potential improvement of PCMs performance for passive cooling application by efficient natural ventilation in residential building stock. Therefore, coupled dynamic simulation and optimization analysis is performed to explore the optimum melting temperature of PCM integrated in the external building envelope to minimize cooling loads in different Italian climate zones. Moreover, various natural ventilation control strategies are implemented to assess their influence on the process of PCM charge-discharge cycle. Results show that PCM inclusion in the building envelope provides significant cooling savings, up to about 300 kWh/year in mild climates. Furthermore, both night and temperature controlled natural ventilation are able to enhance the efficiency of PCMs thermal energy storage charge-discharge cycle. However, the optimum performance is obtained by coupling PCMs with natural ventilation controlled by indoor/outdoor temperature difference in all considered climate contexts. Accordingly, considerable building cooling energy need reduction is achievable through the optimum combination of PCMs and natural ventilation control, especially in milder climates. • PCM passive cooling performance coupled with natural ventilation control is studied. • Summer optimum PCM melting temperature is explored via optimized dynamic simulation. • PCM is included in the building envelope in various Italian climate zones. • PCMs provide significant passive cooling contribution, especially in mild climates. • PCM coupled to T-controlled natural ventilation further improves energy saving. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
23. Data analytics for sustainable global supply chains.
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Mangina, Eleni, Narasimhan, Pranav Kashyap, Saffari, Mohammad, and Vlachos, Ilias
- Subjects
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SUPPLY chains , *ECOLOGICAL impact , *DATA analysis - Abstract
Based on the key metrics to monitor energy sector improvements from the International Energy Agency (IEA), transport emissions must decrease 43% by 2030. Freight logistics operations in Europe are struggling with ways to reduce their carbon footprints in order to adhere to regulations on governing logistics, while providing the increasing demand for sustainable products from the customers. This study investigates the anonymised microdata from the European Road Freight Transport Survey (2011–2014) to acquire patterns in logistic operations based on over 11 million journeys within 27 EU and EFTA countries involved. Different algorithms were implemented (Horizontal Cooperation, Pooling and Physical Internet) to analyse efficiency, in terms of vehicle utilisation, degree of vehicles' loading during each journey and sustainability in terms of the amount of C O 2 emissions per journey. This study shows that existing data can provide invaluable information on the efficiency of logistics operations and the positive effects data analytics can provide. Physical Internet algorithm has performed better in terms of reducing emissions and improving the logistics' efficiency, especially when the sample sizes are large, but this would require a shift to an open global supply web. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
24. Cool Roof Impact on Building Energy Need: The Role of Thermal Insulation with Varying Climate Conditions.
- Author
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Piselli, Cristina, Pisello, Anna Laura, Saffari, Mohammad, de Gracia, Alvaro, Cotana, Franco, and Cabeza, Luisa F.
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OFFICE buildings , *THERMAL insulation , *ENERGY consumption of buildings , *ROOFS , *ENGINEERING standards , *BUILDING performance - Abstract
Cool roof effectiveness in improving building thermal-energy performance is affected by different variables. In particular, roof insulation level and climate conditions are key parameters influencing cool roofs benefits and whole building energy performance. This work aims at assessing the role of cool roof in the optimum roof configuration, i.e., combination of solar reflectance capability and thermal insulation level, in terms of building energy performance in different climate conditions worldwide. To this aim, coupled dynamic thermal-energy simulation and optimization analysis is carried out. In detail, multi-dimensional optimization of combined building roof thermal insulation and solar reflectance is developed to minimize building annual energy consumption for heating–cooling. Results highlight how a high reflectance roof minimizes annual energy need for a small standard office building in the majority of considered climates. Moreover, building energy performance is more sensitive to roof solar reflectance than thermal insulation level, except for the coldest conditions. Therefore, for the selected building, the optimum roof typology presents high solar reflectance capability (0.8) and no/low insulation level (0.00–0.03 m), except for extremely hot or cold climate zones. Accordingly, this research shows how the classic approach of super-insulated buildings should be reframed for the office case toward truly environmentally friendly buildings. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
25. Prevalence of Shunt Dependency and Clinical Outcome in Patients with Massive Intraventricular Haemorrhage Treated with Endoscopic Washout and External Ventricular Drainage.
- Author
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Jason Raj Johnson, Zamzuri Idris, Jafri Malin Abdullah, Azmi Alias, and Mohammad Saffari Mohammad Haspani
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BRAIN , *RADIOGRAPHY , *TREATMENT effectiveness , *CEREBRAL hemorrhage , *CEREBROSPINAL fluid shunts , *COMPUTED tomography , *ENDOSCOPY , *IRRIGATION (Medicine) , *STATISTICAL sampling , *RANDOMIZED controlled trials , *GLASGOW Coma Scale , *MEDICAL drainage - Abstract
Background: Intraventricular haemorrhage (IVH) causes blockage of ventricular conduits leading to hydrocephalus, increased intracranial pressure (ICP), and a reduced level of consciousness. The current standard management of IVH is insertion of an external ventricular drainage (EVD) catheter. However, this procedure addresses only the problems of acute hydrocephalus and raised ICP. Endoscopic washout allows for a more complete removal of the intraventricular clot. This study compared these two types of treatment in terms of shunt dependency and relevant clinical outcomes. Methods: Patients who were 10-80 years old and presented with a Graeb score of more than six were randomised into endoscopic washout and EVD treatment groups. A CT brain was repeated on each patient within 24 hours after surgery, and if a patient's Graeb score was still more than six, a repeat endoscopic washout was performed to clear the remaining clots. All patients were monitored for shunt dependency at two weeks and three months, and clinical outcomes were measured at six months after the procedure. Results: A total of 39 patients were recruited; 19 patients were randomised into the endoscopic washout group, and 20 were randomised into the EVD group. However, three patients in the endoscopic group refused that treatment and opted for EVD insertion. Patients treated with endoscopic washout had significantly less drainage dependency at two weeks (P < 0.005) and at three months (P < 0.004) as compared to patients in the external ventricular drainage group. The reduction in Graeb scores was also significantly greater in the endoscopic washout group (P < 0.001). However, the functional outcome at six months measured via a modified Rankin scale score was no different in the two groups of patients. The difference in the functional outcome of the patients was mainly dependent on the initial pathology, with those presenting with a thalamic bleed with IVH showing a poor functional outcome. This parameter was also influenced by the Glasgow Coma Scale (GCS) score on admission, with those patients with a score of 12 or less having a poor functional outcome (MRS 5-6) at three and six months after the surgery. Conclusions: The use of neuroendoscopy in patients with a massive IVH significantly reduced drainage dependency. However, it did not alter the final functional outcome. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
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