| 1. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 2. |
- Usman, Muhammad, et al.
(författare)
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Use of Gasoline, LPG and LPG-HHO Blend in SI Engine : A Comparative Performance for Emission Control and Sustainable Environment
- 2020
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Ingår i: Processes. - : MDPI. - 2227-9717. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The rising global warming concerns and explosive degradation of the environment requires the mainstream utilization of alternative fuels, such as hydroxy gas (HHO) which presents itself as a viable substitute for extracting the benefits of hydrogen. Therefore, an experimental study of the performance and emission characteristics of alternative fuels in contrast to conventional gasoline was undertaken. For experimentation, a spark ignition engine was run on a multitude of fuels comprising of gasoline, Liquefied petroleum gas (LPG) and hybrid blend of HHO with LPG. The engine was operated at 60% open throttle with engine speed ranging from 1600 rpm to 3400 rpm. Simultaneously, the corresponding performance parameters including brake specific fuel consumption, brake power and brake thermal efficiency were investigated. Emission levels of CO, CO2, HC and NOx were quantified in the specified speed range. To check the suitability of the acquired experimental data, it was subjected to a Weibull distribution fit. Enhanced performance efficiency and reduced emissions were observed with the combustion of the hybrid mixture of LPG with HHO in comparison to LPG: on average, brake power increased by 7% while the brake specific fuel consumption reduced by 15%. On the other hand, emissions relative to LPG decreased by 21%, 9% and 21.8% in cases of CO, CO2, and unburned hydrocarbons respectively. Incorporating alternative fuels would not only imply reduced dependency on conventional fuels but would also contribute to their sustainability for future generations. Simultaneously, the decrease in harmful environmental pollutants would help to mitigate and combat the threats of climate change.
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| 3. |
- Farooq, Muhammad, et al.
(författare)
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Thermodynamic Performance Analysis of Hydrofluoroolefins (HFO) Refrigerants in Commercial Air-Conditioning Systems for Sustainable Environment
- 2020
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Ingår i: Processes. - : MDPI. - 2227-9717. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- Global warming is one of most severe environmental concerns that our planet is facing today. One of its causes is the previous generation of refrigerants that, upon release, remain in the atmosphere for longer periods and contribute towards global warming. This issue could potentially be solved by replacing the previous generation's high global warming potential (GWP) refrigerants with environmentally friendly refrigerants. This scenario requires an analysis of new refrigerants for a comparison of the thermodynamic properties of the previously used refrigerants. In the present research, a numerical study was conducted to analyze the thermodynamic performance of specifically low GWP hydrofluoroolefens (HFO) refrigerants for an actual vapor compression refrigeration cycle (VCRC) with a constant degree of 3 K superheat. The output parameters included the refrigeration effect, compressor work input, the coefficient of performance (COP), and the volumetric refrigeration capacity (VRC), all of which were calculated by varying the condenser pressure from 6 to 12 bars and vapor pressure from 0.7 to 1.9 bars. Results showed that R1234ze(Z) clearly possessed the desired thermodynamic performance. The drop in refrigeration effect for R1234ze(Z) was merely 14.6% less than that of R134a at a 12 bar condenser pressure; this was minimum drop among candidate refrigerants. The drop in the COP was the minimum for R1234ze(Z)-5.1% less than that of R134a at a 9 bar condenser pressure and 4.7% less than that of R134a at a 1.9 bar evaporator pressure, whereas the COP values of the other refrigerants dropped more drastically at higher condenser pressures. R1234ze(Z) possessed favorable thermodynamic characteristics, with a GWP of 7, and it can serve as an alternative refrigerant for refrigeration systems for a sustainable environment.
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| 4. |
- Naqvi, Salman Raza, et al.
(författare)
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Agro-industrial residue gasification feasibility in captive power plants : A South-Asian case study
- 2021
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 214
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is to build knowledge on the potential of agro-industrial residue gasification (AIRG) for use in captive power generation through a comprehensive case study. In order to evaluate the economic viability, key performance indicators, such as net present value (NPV), levelized cost of electricity (LCOE), and operating costs etc. are studied. The major textile industry located in the Raiwind area of Punjab province of Pakistan has been selected. The effect and variations of the capacity factor has also been studied coupled with the levelized cost of electricity. The agricultural residue as feedstock to the gasifier is rice husk that is the abundantly available in South Asia. Furthermore, the impact of government subsidies on natural gas is also under the scope of the study. The agro-industrial residue gasification system is found to be a potential alternative to furnace oil (FO) or gas-based captive power plants (CPPs). The results of residue-based gasification system imply a large potential when comparing the cost of electricity with national grid electricity during the peak hours. Therefore, the proposed gasification system offers economic incentives when the textile industry potentially utilizes gasification-based electricity during peak hours and national grid electricity during off-peak hours. (C) 2020 Elsevier Ltd. All rights reserved.
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| 5. |
- Naqvi, Salman Raza, et al.
(författare)
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Potential of biomass for bioenergy in Pakistan based on present case and future perspectives
- 2018
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 81:1, s. 1247-1258
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Forskningsöversikt (refereegranskat)abstract
- Future energy security and environmental issues are major driving forces for increased biomass utilization globally and especially in developing countries like Pakistan. For efficient utilization of indigenous biomass resources in the future energy mix, it is important to gain knowledge of current energy system in various sectors. Some of the technologies and initiatives are under development to achieve transition from non-renewable resources to renewable resources, and reducing fossil fuel dependency and greenhouse gas emissions. Recently, number of proposals has been presented for the development of sustainable biofuels production methods for promise for accelerating a shift away from an unsustainable approach to possible sustainable production practices or a sustainable social, economic and environment. This article presents an extensive literature review of the biomass-based renewable energy potential in Pakistan based on current energy scenario and future perspectives. It also highlights the availability of the indigenous and local biomass resources and potential biomass conversion technologies to convert such resources to bioenergy. The drivers for utilization of indigenous biomass resources in future energy mix and challenges regarding awareness among stakeholders and R & D to fill knowledge gaps are economically restraints. The article concludes with suggestions on future directions and policies for effective implementation of biomass based renewable energy production.
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| 6. |
- Arslan, Muhammad, et al.
(författare)
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Impact of Varying Load Conditions and Cooling Energy Comparison of a Double-Inlet Pulse Tube Refrigerator
- 2020
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Ingår i: Processes. - : MDPI. - 2227-9717. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- Modeling and optimization of a double-inlet pulse tube refrigerator (DIPTR) is very difficult due to its geometry and nature. The objective of this paper was to optimize-DIPTR through experiments with the cold heat exchanger (CHX) along the comparison of cooling load with experimental data using different boundary conditions. To predict its performance, a detailed two-dimensional DIPTR model was developed. A double-drop pulse pipe cooler was used for solving continuity, dynamic and power calculations. External conditions for applicable boundaries include sinusoidal pressure from an end of the tube from a user-defined function and constant temperature or limitations of thermal flux within the outer walls of exchanger walls under colder conditions. The results of the system's cooling behavior were reported, along with the connection between the mass flow rates, heat distribution along pulse tube and cold-end pressure, the cooler load's wall temp profile and cooler loads with varied boundary conditions i.e. opening of 20% double-inlet and 40-60% orifice valves, respectively. Different loading conditions of 1 and 5W were applied on the CHX. At 150 K temperature of the cold-end heat exchanger, a maximum load of 3.7 W was achieved. The results also reveal a strong correlation between computational fluid dynamics modeling results and experimental results of the DIPTR.
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| 7. |
- Naqvi, Salman Raza, et al.
(författare)
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Recent developments on sewage sludge pyrolysis and its kinetics : Resources recovery, thermogravimetric platforms, and innovative prospects
- 2021
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Ingår i: Computers and Chemical Engineering. - : Elsevier. - 0098-1354 .- 1873-4375. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- Sewage sludge is a by-product of the wastewater treatment process, which has the potential to be a source of transport fuels, heat, and power using the pyrolysis process. Considering the prevalence and disposal issues associated with sewage sludge, the objective of this study is to critically review the recent advancements in sewage sludge pyrolysis and its kinetics obtained using the thermogravimetric techniques, and other associated different kinetic models documented in the literature. The study will identify optimum operating conditions and design parameters to obtain high yields. The state-of-the-art perspectives and the challenges associated with full-scale implementation are highlighted for biofuels and resource recovery from the sewage sludge. Furthermore, machine-learning approaches in thermal kinetics of pyrolysis are presented and discussed in terms of their effectiveness in predicting thermal kinetics data. Finally, the challenges for a successful implementation and commercial viability of sewage sludge pyrolysis are discussed.
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| 8. |
- Ali, Imtiaz, et al.
(författare)
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Kinetic and thermodynamic analyses of dried oily sludge pyrolysis
- 2021
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Ingår i: Journal of the Energy Institute. - : Elsevier. - 1743-9671 .- 1746-0220. ; 95, s. 30-40
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Tidskriftsartikel (refereegranskat)abstract
- Oily sludge has the potential to utilize in pyrolysis process effectively because of higher product recovery and lower harmful emissions. Due to the complex nature of reactions, it is necessary to evaluate the thermo-kinetic behavior of the process to make it commercially feasible. This study includes thermal degradation behavior, the kinetic and thermodynamic analysis of dry oily sludge by applying Friedman and Vyazovkin method (model-free approach), and Coats-Redfern method (model-fitting approach) with the help of thermogravimetric analysis TGA at different heating rates (5, 20, 40 °C/min). The active region was from 20 to 60% conversion range because the maximum conversion occurs in this region. The overall activation energy decreases as the conversion increases from a lower range (60%) to a higher range (80%) for all satisfied models. The estimated range of pre-exponential coefficient for each model was to 4.91E+15 to 2.30E-01min−1 in the conversion range of 20–60% and 9.80E+02 to 4.89E-04min−1 in the conversion range 60–80%. The overall value of the change in enthalpy ΔH and change in Gibbs free energy ΔG decrease as the conversion increases from the lower range to the higher range.
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| 9. |
- Anees, Hafiz Muhammad, et al.
(författare)
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A mathematical model-based approach for DC multi-microgrid performance evaluations considering intermittent distributed energy resources, energy storage, multiple load classes, and system components variations
- 2021
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Ingår i: Energy Science & Engineering. - : John Wiley & Sons. - 2050-0505. ; 9, s. 1919-1934
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Tidskriftsartikel (refereegranskat)abstract
- The efficiency of DC microgrid needs investigation from a smart grid perspective, since their spread has expected to prevail in comparison with AC counterparts. Furthermore, there is a need to address the limitations (majorly to cater the intermittency of distributed energy resources (DERs) as well as the time dependency of systematic parameters etc.) in previous model and propose a new mathematical model to evaluate system efficiency for given parameters and scenarios. The core focus of current study aims at formulation of an improved (composite) mathematical model, that is capable of bridging issues and serve as a tool to address requirements of future DC systems including microgrids (MGs) and multi-microgrids (MMGs). This research work offers such a mathematical model that consists of 3D matrices based on newly derived set of discrete time dependent equations, which evaluates the system efficiency of residential DC-MMGs. Each DC-MG is embedded with intermittent DERs, storage, components (with efficiency variations), and multi-class load (with discrete time dependency), for evaluation across worst, normal, and best scenarios. A comprehensive sensitivity analysis across various cases and respective scenarios are also presented to evaluate overall system performance. Also, the impacts of system parameters on various system variables, states, and overall system efficiency have presented in this paper.
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| 10. |
- Danish, Muhammad, et al.
(författare)
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Characterization of South Asian agricultural residues for potential utilization in future 'energy mix'
- 2015
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Ingår i: Energy Procedia. - : Elsevier. ; 75, s. 2974-2980
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Konferensbidrag (refereegranskat)abstract
- This paper characterizes various locally available agricultural residues in South Asian region to evaluate their potential as feedstock for renewable energy production and contributing toward solving energy crisis and environmental issues. The thermo-chemical characterization has been performed in order to determine if the residues have potential to be used in biomass conversion technologies producing combined heat and power. The characterization methods for comparing different agricultural residues include proximate and ultimate analysis, heating value, ash content, thermo gravimetric analysis (TGA) and structural composition analysis (SCA). Widely available agricultural wastes in South Asian region were selected for the characterization i.e. bagasse, almond shell, corn cob, cotton stalks, wheat straw, sawdust, corn leaf, rice husk, rice straw, and corn straw. The analysis showed that the corn cob had the highest moisture content that will result in low energy efficiency of the thermal conversion technology due to energy requirement for drying. Whereas almond shell had the lowest moisture content. Ash and volatile contents were found to be highest in rice straw and almond shell respectively. The thermo gravimetric analysis showed that most of the agricultural residues can be easily decomposed and represent potential feedstock for biomass flexible combined heat and power systems through pyrolysis or gasification.
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