Oily wastewater poses significant threats to the soil, water, air and human beings because of the hazardous nature of its oil contents. The objective of this review paper is to highlight the current and recently devel...Oily wastewater poses significant threats to the soil, water, air and human beings because of the hazardous nature of its oil contents. The objective of this review paper is to highlight the current and recently developed methods for oily wastewater treatment through which contaminants such as oil, fats, grease, and inorganics can be removed for safe applications.These include electrochemical treatment, membrane filtration, biological treatment,hybrid technologies, use of biosurfactants, treatment via vacuum ultraviolet radiation,and destabilization of emulsions through the use of zeolites and other natural minerals.This review encompasses innovative and novel approaches to oily wastewater treatment and provides scientific background for future work that will be aimed at reducing the adverse impact of the discharge of oily wastewater into the environment. The current challenges affecting the optimal performance of oily wastewater treatment methods and opportunities for future research development in this field are also discussed.展开更多
Presence of fine dust in air causes serious health hazard for mine operators resulting in such serious problems as coal workers’pneumoconiosis and silicosis.Major sources of dust appear of course along the mining fac...Presence of fine dust in air causes serious health hazard for mine operators resulting in such serious problems as coal workers’pneumoconiosis and silicosis.Major sources of dust appear of course along the mining face where the minerals are extracted.Proper control and management are required to ensure safe working environment in the mine.Here,we utilize the computational fluid dynamic(CFD)approach to evaluate various methods used for mitigating dust dispersion from the mining face and for ensuring safe level of dust concentration in the mine tunnel for safety of the operators.The methods used include:application of blowing and exhaust fans,application of brattice and combination of both.The results suggest that among the examined methods,implementation of appropriately located brattice to direct the flow from the main shaft to the mining face is the most effective method to direct dust particles away from the mining face.展开更多
Layered double hydroxide(LDH),a kind of 2D layered materials,has been recognized as the promising anticorrosion materials for metal and its alloy.The microstructure,physical/chemical properties,usage in corrosion inhi...Layered double hydroxide(LDH),a kind of 2D layered materials,has been recognized as the promising anticorrosion materials for metal and its alloy.The microstructure,physical/chemical properties,usage in corrosion inhibition and inhibition performance of LDH have been studied separately in open literature.However,there is a lack of a complete review to summarize the status of LDH technology and the potential R&D opportunities in the field of corrosion inhibition.In addition,the challenges for LDH in corrosion inhibition of metal-based system have not been summarized systematically.Herein,we review recent advances in the rational design of LDH for corrosion inhibition of metal-based system(i.e.Mg alloy,Al alloy,steel and concrete)and high-throughput anticorrosion materials development.By evaluating the physical/chemical properties,usage in metal-based system and the corrosion inhibition mechanism of LDH,we highlight several important factors of LDH for anticorrosion performance and common features of LDH in applying different metal alloys.Finally,we provide our perspective and recommendation in this field,including high-throughput techiniques for combinatorial compositional design and rapid synthesis of anticorrosion alloys,with the goal of accelerating the development and application of LDH in corrosion inhibition of metal-based system.展开更多
Ternary Zn-0.5A1-0.5Mg and quatemary Zn-0.5A1-0.5Mg-xBi （x = 0.1, 0.3 and 0.5） alloys were studied to evaluate the thermal and structural characteristics, mechanical properties, cytotoxicity and in vitro degradation...Ternary Zn-0.5A1-0.5Mg and quatemary Zn-0.5A1-0.5Mg-xBi （x = 0.1, 0.3 and 0.5） alloys were studied to evaluate the thermal and structural characteristics, mechanical properties, cytotoxicity and in vitro degradation behavior. Thermal analysis and microstructural observations showed that Zn-0.5A1-0.5Mg is composed of FCC-A1 ＋ HCP- Zn ＋ Mg2（Zn,A1）ll while a new phase a-Mg3Bi2 appeared after the addition of Bi to the Zn-0.5A1-0.5Mg ternary alloy. The results revealed that the quaternary Zn-A1-Mg-Bi alloys have higher tensile strength, elongation and hardness but slightly lower corrosion resistance than those of the temary Zn-AI-Mg alloy. Based on the MTT assay, the Zn-A1-Mg and Zn-A1-Mg-Bi alloys were found to be biocompatible, and thus, they can be considered for further investigation in an in vivo environment.展开更多
Rockburst is an important phenomenon that has affected many deep underground mines around the world. An understanding of this phenomenon is relevant to the management of such events, which can lead to saving both cost...Rockburst is an important phenomenon that has affected many deep underground mines around the world. An understanding of this phenomenon is relevant to the management of such events, which can lead to saving both costs and lives. Laboratory experiments are one way to obtain a deeper and better understanding of the mechanisms of rockburst. In a previous study by these authors, a database of rockburst laboratory tests was created; in addition, with the use of data mining （DM） techniques, models to predict rockburst maximum stress and rockburst risk indexes were developed. In this paper, we focus on the analysis of a database of in situ cases of rockburst in order to build influence diagrams, list the factors that interact in the occurrence of rockburst, and understand the relationships between these factors. The in situ rockburst database was further analyzed using different DM techniques ranging from artificial neural networks （ANNs） to naive Bayesian classifiers. The aim was to predict the type of rockburst-that is, the rockburst level-based on geologic and construction characteristics of the mine or tunnel. Conclusions are drawn at the end of the paper.展开更多
Privacy preservation is a crucial issue for smart buildings where all kinds of messages, e.g., power usage data, control commands, events, alarms, etc. are transmitted to accomplish the management of power. Without ap...Privacy preservation is a crucial issue for smart buildings where all kinds of messages, e.g., power usage data, control commands, events, alarms, etc. are transmitted to accomplish the management of power. Without appropriate privacy protection schemes, electricity customers are faced with various privacy risks. Meanwhile, the natures of smart grids and smart buildings—such as having limited computation power of smart devices and constraints in communication network capabilities, while requiring being highly reliable—make privacy preservation a challenging task. In this paper, we propose a group key scheme to safeguard multicast privacy with the provisions of availability, fault-tolerance, and efficiency in the context of smart buildings as a part the smart grid. In particular, hybrid architecture accommodating both centralized and contributory modes is constructed in order to achieve both fault-tolerance and efficiency with only one set of group key installed. Key trees are sophisticatedly managed to reduce the number of exponentiation operations. In addition, an individual rekeying scheme is introduced for occasional joining and leaving of member smart meters. Experimental results, on a simulation platform, show that our scheme is able to provide significant performance gains over state-of-the-art methods while effectively preserving the participants’ privacy.展开更多
This study presents the multifunctional characteristics of multi-walled carbon nanotube(MWCNT)/polypropylene random copolymer(PPR) composites enabled via fused filament fabrication(FFF) under monotonic and quasi-stati...This study presents the multifunctional characteristics of multi-walled carbon nanotube(MWCNT)/polypropylene random copolymer(PPR) composites enabled via fused filament fabrication(FFF) under monotonic and quasi-static cyclic compression. Utilizing in-house MWCNT-engineered PPR filament feedstocks, both bulk and cellular composites were realized. The morphological features of nanocomposites were examined via scanning electron microscopy, which reveals that MWCNTs are uniformly dispersed. The uniformly dispersed MWCNTs forms an electrically conductive network within the PPR matrix, and the resulting nanocomposite shows good electrical conductivity(~10^(-1)S/cm), improved mechanical performance(modulus increases by 125% and compressive strength increases by 25% for 8 wt% MWCNT loading) and pronounced piezoresistive response(gauge factor of 27.9-8.5 for bulk samples)under compression. The influence of strain rate on the piezoresistive response of bulk samples(4 wt% of MWCNT) under compression was also measured. Under repeated cyclic compression(2% constant strain amplitude), the nanocomposite exhibited stable piezoresistive performance up to 100 cycles. The piezoresistive response under repeated cyclic loading with increasing strain amplitude of was also assessed.The gauge factor of BCC and FCC cellular composites(4 wt% of MWCNT) with a relative density of 30%was observed to be 46.4 and 30.2 respectively, under compression. The higher sensitivity of the BCC plate-lattice could be attributed to its higher degree of stretching-dominated deformation behavior than the FCC plate-lattice, which exhibits bending-dominated behavior. The 3D printed cellular PPR/MWCNT composites structures were found to show excellent piezoresistive self-sensing characteristics and open new avenues for in situ structural health monitoring in various applications.展开更多
In the United States, emission regulations are enacted at a state level;individual states are allowed to define what methods they will use to mitigate their carbon emissions. The consequence of this is especially inte...In the United States, emission regulations are enacted at a state level;individual states are allowed to define what methods they will use to mitigate their carbon emissions. The consequence of this is especially interesting in the state of Texas where new legislation has created a “deregulated” electricity market in which end-users are capable of choosing their electricity provider and subsequently the type of electricity they wish to consume (generated by fossil fuels or renewable sources). In this paper we analyze the effects of carbon tax on the development of renewable generation capacity at the utility level while taking into account expected adoption of rooftop PV systems by individual consumers using agent based modeling techniques. Monte Carlo simulations show carbon abatement trends and proffer updated renewable portfolio standards at various levels of likelihood.展开更多
Biodiesel production had received a considerable attention as a green, non-toxic and renewable alternative to petroleum diesel. To avoid using vegetable oils, which are expensive and compete with food, as feedstock, w...Biodiesel production had received a considerable attention as a green, non-toxic and renewable alternative to petroleum diesel. To avoid using vegetable oils, which are expensive and compete with food, as feedstock, waste oils have been proposed. However, these waste materials contain a large amount of free fatty acids that complicates the production process. In this work, biodiesel production using an alternative feedstock;namely oils from date-pits, has been investigated. These oils have the same favorable features of straight oils, and at the same time are considered waste, since they are extracted from a waste material. The yield of oils extracted using n-hexane in a Soxhlet apparatus was compared to that of oils extracted using methanol-chloroform solvent mixture. The extracted oils were then converted to biodiesel via transesterification with methanol in presence of Novozym𪥣 or Eversa®Transform. The highest oils extraction yield of 11.7%, per dry weight sample, was obtained using Soxhlet extraction apparatus compared to 8.9% using methanol-chloroform mixture. The highest biodiesel production yield was 30% of the oil used, achieved after 6 hours using Novozym𪥣 at 40°C, 5:1 methanol to oil molar ratio and 10wt% enzyme loading. By using a chemical alkaline catalyst, NaOH, at the same conditions, the yield was 27%.展开更多
Continuous-monitoring (CM) of natural phenomenon is one of the major streams of applications in wireless sensor networks (WSNs), where aggregation and clustering techniques are beneficial as correlation dominates in b...Continuous-monitoring (CM) of natural phenomenon is one of the major streams of applications in wireless sensor networks (WSNs), where aggregation and clustering techniques are beneficial as correlation dominates in both spatial and temporal aspects of sensed phenomenon. Conversely, in Event Driven Reporting (EDR), the efficient transmission of sensitive data related to some predefined alarm cases is of major importance. As such, reporting latency is a more important performance parameter. However, in some applications, the transmission of both CM and EDR data is encouraged or even required. For either CM or EDR applications, system performance can be greatly improved when both the number of packets to be transmitted as well as the packet size is reduced. This is especially true for highly dense sensor networks where many nodes detect the same values for the sensed phenomenon. Building on this, this paper focuses on studying and proposing compression techniques to improve the system performance in terms of energy consumption and reporting latency in both CM and EDR applications. Furthermore, we extend our analysis to hybrid networks where CM and EDR are required simultaneously. Specifically, this paper presents a simple aggregation technique named smart aggregation (SAG) for the CM applications and an event driven scheme named compression cluster scheme in spatial correlated region (CC_SCR). The proposed SAG exploits both spatial and temporal correlations where CC_SCR exploits the spatial correlation of such networks by data compression. Rationalizing the developments is attained by simulations that compare energy efficiency of the proposed SAG with k-hop aggregation and CM based event driven reporting (CMEDR) schemes. Results of CC_SCR show that the technique may reduce the energy consumption drastically. In some specific cases the reduction becomes more than 10 times compared to a classical clustering scheme. Two different strategies for the transmission of event reports through the CM infrastructure are incorporated: PER and NPER protocols. Both strategies take advantage of the cluster-based architecture which assigns a TDMA schedule for the CM data transmission while using NP/CSMA for the transmission of the event information. Consequently, no extra energy is consumed for separate event clusters. As such, the number of packets to be transmitted is greatly reduced.展开更多
A first principal modeling of the gasification of a char particle is performed using single step mechanism. The char particle is considered to be spherical in shape and only the physical and chemical properties can ch...A first principal modeling of the gasification of a char particle is performed using single step mechanism. The char particle is considered to be spherical in shape and only the physical and chemical properties can change in the radial direction. The carbon dioxide is used as the gasification agent that reacts with the char and form carbon monoxide. The presence of both solid and gaseous phase species makes the reaction heterogeneous. The char particle is considered with varying porosity that also allows the change in the surface area of the particle. A time invariant temperature and pressure profile is used at which the Arrhenius rate constant and diffusion is calculated. The mass conservation of model results in the form of two coupled partial differential and one ordinary differential equation. The equations are solved with a set of initial and boundary conditions using the bulk species concentration at the particle surface. A second order accurate central differencing scheme is used to discretize space while backward differencing is used to discretize time. Finally, the results are presented for the concentration distribution of CO and CO2 in radial direction with respect to time. It shows that, maximum concentration of CO is present at the center of the particle while the concentration gradient becomes higher near the particle surface. The nonlinear concentration trend due to the diffusion is effectively captured. The results show that, completed conversion of char depend upon the time provided for the reaction which can be reduced by decreasing the size of particle or increasing the reaction temperature. The sensitivity study of temperature and initial porosity also performed and showed that temperature has high impact on char conversion as compare to initial porosity.展开更多
This paper presents a comprehensive overview of the different requirements for applications of solar cells in the built environment, particularly for the MENA （Middle East and North Africa） region. The authors empha...This paper presents a comprehensive overview of the different requirements for applications of solar cells in the built environment, particularly for the MENA （Middle East and North Africa） region. The authors emphasize the assessment of parameters additional to the cost and efficiency of the cells to make a more informed choice of the PV technology to use in specific buildings. They also emphasize the need for the wide use ofphotovoltaics in the built environment to produce electricity in the GCC （Gulf Cooperation Council） region and briefly mention the efforts being made in this regard.展开更多
Biogas fuel is a sustainable and renewable fuel produced from anaerobic digestion of organic matter. The biogas fuel is a flammable mixture of methane and carbon dioxide with low to medium calorific values. Biogas is ...Biogas fuel is a sustainable and renewable fuel produced from anaerobic digestion of organic matter. The biogas fuel is a flammable mixture of methane and carbon dioxide with low to medium calorific values. Biogas is an alternative to conventional fossil fuels and can be used for beating, transportation and power generation. CFD （computational fluid dynamic） analysis of the combustion performance and emissions of biogas fuel in gas turbine engines is presented in this study. The main objective of this study is to understand the impact of the variability in the biogas fuel compositions and lower heating values on the combustion process. Natural gas, biogas from anaerobic digester, landfill biogas, and natural gas/biogas mixture fuels combustion were investigated in this study. The CFD results show lower peak flame temperature and CO mole fractions inside the combustor and lower NOx emissions at the combustor exit for the biogas compared to natural gas fuel. The peak flame temperature decreases by 37% for the biogas landfill （COJCH4 = 0.89） and by 22% for the biogas anaerobic digester （CO2/CH4 = 0.54） compared to natural gas fuel combustion. The peak CO mole fraction inside the combustor decreases from 9.8 × 10-2 for natural gas fuel to 2.22 × 10-4 for biogas anaerobic digester and 1.32 × 10-7 for biogas landfill. The average NOx mole fraction at the combustor exit decreases from 1.13 × 10-5 for natural gas fuel to 0.40 × 10-6 for biogas anaerobic digester and 1.06 × 10-6 for biogas landfill. The presence of non-combustible constituents in the biogas reduces the temperature of the flame and consequently the NOx emissions.展开更多
SiO_(x)is commonly used in lithium-ion batteries because of its capacity and affordability,but it has issues with volume expansion and conductivity.Synthetic methods are crucial for achieving the desired microstructur...SiO_(x)is commonly used in lithium-ion batteries because of its capacity and affordability,but it has issues with volume expansion and conductivity.Synthetic methods are crucial for achieving the desired microstructure and material properties.This study introduces a new technique,fluidized bed granulation,to produce SiO_(x)@GNs composites.These composites have a core-shell structure with SiO_(x)particles coated in graphene sheets,and high-energy vibration is used to create a SiO_(x)-Fe structure on the surface.The graphene coating prevents volume expansion and enhances electron transfer.Real-time confocal imaging shows the charging and discharging process.Experiment results show that the SiO_(x)@GNs electrode has a lower expansion rate of 53.60%compared to 73.04%for the SiO electrode,indicating improved electrochemical properties with the graphene coating.After 100 cycles at 2 C,SiO_(x)@GNs demonstrate a reversible capacity of 1265.8 mA,h·g^(-1)and discharge capability at 7 C with a capacity of 1050 mA,h·g^(-1).The battery retains 90.21%of its capacity after 500 cycles at 0.5 C,showing potential as a LIB anode alternative with a unique structure for different energy storage materials.Fluidized bed granulation can aid in scaling up the use of SiO_(x)anodes in lithium-ion batteries.展开更多
A better understanding of the bonding and aggregation processes occurring between carbon nanomaterials and metal oxide particles in aqueous solutions is important in the development of novel nanosolids for application...A better understanding of the bonding and aggregation processes occurring between carbon nanomaterials and metal oxide particles in aqueous solutions is important in the development of novel nanosolids for applications in the areas of sensor development,highly conductive paint,nanotube alignment,polymer composites,Li-ion batteries,and many other areas.The current investigation reviews these processes and presents a detailed description of the aggregation processes occurring between carbon nanomaterials and metal oxide particles(metals)in various aqueous solutions.The results indicate that the charge attraction between the particles results in a strong homogeneous bonding that occurs within the aqueous solution and for the first time demonstrate and describe the aggregation process of these nanoparticles.The relative importance of many parameters that impact the aggregation process is identified and discussed,and guidelines for controlling the aggregation process are presented.This is a simple and cost-effective process to manufacture a novel nano-solid based on carbon nanomaterial and metal oxide.In addition,the process is easy to scale up and optimize.The methodology could lead to many significant applications as well as commercialization.展开更多
We formulate an age-structured model based on a system of nonlinear partial differen- tial equations to assist the early and catch up female vaccination programs for human papillomavirus （HPV） types 6 and 11. Since ...We formulate an age-structured model based on a system of nonlinear partial differen- tial equations to assist the early and catch up female vaccination programs for human papillomavirus （HPV） types 6 and 11. Since these HPV types do not induce permanent immunity, the model, which stratifies the population based on age and gender, has a susceptible-infectious-susceptible （SIS） structure. We calculate the effective reproduction number Rv for the model and describe the local-asymptotic stability of the disease-free equilibrium using Rv. We prove the existence of an endemic equilibrium for Rv 〉 1 for the no vaccine case. However, analysis of the model for the vaccine case reveals that it undergoes the phenomenon of backward bifurcation. To support our theoretical results, we estimate the age and time solution with the given data for Toronto population, when an early and catch up female vaccine program is adopted, and when there is no vaccine. We show that early and catch up female vaccine program eliminates the infection in both male and female populations over a period of 30 years. Finally, we introduce the optimal control to an age-dependent model based on ordinary differential equations and solve it numerically to obtain the most cost-effective method for introducing the catch up vaccine into the population.展开更多
An optically enabled z-axis micro-disk inertia sensor is presented, which consists of a disk-shaped proof mass integrated on top of an optical waveguide. Numerical simulations show that the optical power of laser beam...An optically enabled z-axis micro-disk inertia sensor is presented, which consists of a disk-shaped proof mass integrated on top of an optical waveguide. Numerical simulations show that the optical power of laser beam propagating in a narrow silicon nitride （Si3N4） waveguide located under the disk is attenuated in response to the vertical movement of the micro-disk. The high leakage power of the TM mode can effectively be used to detect a dynamic range of 1 g - 10g （g=9.8 rn/s ）. At lest, the waveguide is kept at a nominal gap of 1 μm from the proof mass. It is adiabatically tapered to a narrow dimension of W×H = 350×220nm2 in a region where the optical mode is intended to interact with the proof mass. Furthermore, the bottom cladding is completely etched away to suspend the waveguide and improve the optical interaction with the proof mass. The proposed optical inertia sensor has a high sensitivity of 3 dB/g when a 50μm-long waveguide is used （normalized sensitivity 0.5 dB/μm2） for the vertical movement detection.展开更多
文摘Oily wastewater poses significant threats to the soil, water, air and human beings because of the hazardous nature of its oil contents. The objective of this review paper is to highlight the current and recently developed methods for oily wastewater treatment through which contaminants such as oil, fats, grease, and inorganics can be removed for safe applications.These include electrochemical treatment, membrane filtration, biological treatment,hybrid technologies, use of biosurfactants, treatment via vacuum ultraviolet radiation,and destabilization of emulsions through the use of zeolites and other natural minerals.This review encompasses innovative and novel approaches to oily wastewater treatment and provides scientific background for future work that will be aimed at reducing the adverse impact of the discharge of oily wastewater into the environment. The current challenges affecting the optimal performance of oily wastewater treatment methods and opportunities for future research development in this field are also discussed.
基金financially supported by the Singapore Economic Development Board (EDB) through Minerals Metals and Materials Technology Centre (M3TC) (No.R261501013414)
文摘Presence of fine dust in air causes serious health hazard for mine operators resulting in such serious problems as coal workers’pneumoconiosis and silicosis.Major sources of dust appear of course along the mining face where the minerals are extracted.Proper control and management are required to ensure safe working environment in the mine.Here,we utilize the computational fluid dynamic(CFD)approach to evaluate various methods used for mitigating dust dispersion from the mining face and for ensuring safe level of dust concentration in the mine tunnel for safety of the operators.The methods used include:application of blowing and exhaust fans,application of brattice and combination of both.The results suggest that among the examined methods,implementation of appropriately located brattice to direct the flow from the main shaft to the mining face is the most effective method to direct dust particles away from the mining face.
基金the Graduate Research and innovation of Chongqing,China(Grant No.CYB20005)the project of Technological Innovation and Application Development in Chongqing(cstc2019jscxmsxm0378)+8 种基金the National Natural Science Foundation of China(Grant Nos.51908092)the Joint Funds of the National Natural Science Foundation of China-Guangdong(Grant No.U1801254)the project funded by Chongqing Special Postdoctoral Science Foundation(XmT2018043)Natural Science Foundation Project of Chongqing for Post-doctor(cstc2019jcyjbsh0079)Technological projects of Chongqing Municipal Education Commission(KJZDK201800801)Projects(No.2020CDJXZ001,2020CDCGJ006 and 2020CDCGCL004)the Fundamental Research Funds for the Central Universitiesthe Innovative Research Team of Chongqing(CXTDG201602014)the Innovative technology of New materials and metallurgy(2019CDXYCL0031).
文摘Layered double hydroxide(LDH),a kind of 2D layered materials,has been recognized as the promising anticorrosion materials for metal and its alloy.The microstructure,physical/chemical properties,usage in corrosion inhibition and inhibition performance of LDH have been studied separately in open literature.However,there is a lack of a complete review to summarize the status of LDH technology and the potential R&D opportunities in the field of corrosion inhibition.In addition,the challenges for LDH in corrosion inhibition of metal-based system have not been summarized systematically.Herein,we review recent advances in the rational design of LDH for corrosion inhibition of metal-based system(i.e.Mg alloy,Al alloy,steel and concrete)and high-throughput anticorrosion materials development.By evaluating the physical/chemical properties,usage in metal-based system and the corrosion inhibition mechanism of LDH,we highlight several important factors of LDH for anticorrosion performance and common features of LDH in applying different metal alloys.Finally,we provide our perspective and recommendation in this field,including high-throughput techiniques for combinatorial compositional design and rapid synthesis of anticorrosion alloys,with the goal of accelerating the development and application of LDH in corrosion inhibition of metal-based system.
文摘Ternary Zn-0.5A1-0.5Mg and quatemary Zn-0.5A1-0.5Mg-xBi （x = 0.1, 0.3 and 0.5） alloys were studied to evaluate the thermal and structural characteristics, mechanical properties, cytotoxicity and in vitro degradation behavior. Thermal analysis and microstructural observations showed that Zn-0.5A1-0.5Mg is composed of FCC-A1 ＋ HCP- Zn ＋ Mg2（Zn,A1）ll while a new phase a-Mg3Bi2 appeared after the addition of Bi to the Zn-0.5A1-0.5Mg ternary alloy. The results revealed that the quaternary Zn-A1-Mg-Bi alloys have higher tensile strength, elongation and hardness but slightly lower corrosion resistance than those of the temary Zn-AI-Mg alloy. Based on the MTT assay, the Zn-A1-Mg and Zn-A1-Mg-Bi alloys were found to be biocompatible, and thus, they can be considered for further investigation in an in vivo environment.
文摘Rockburst is an important phenomenon that has affected many deep underground mines around the world. An understanding of this phenomenon is relevant to the management of such events, which can lead to saving both costs and lives. Laboratory experiments are one way to obtain a deeper and better understanding of the mechanisms of rockburst. In a previous study by these authors, a database of rockburst laboratory tests was created; in addition, with the use of data mining （DM） techniques, models to predict rockburst maximum stress and rockburst risk indexes were developed. In this paper, we focus on the analysis of a database of in situ cases of rockburst in order to build influence diagrams, list the factors that interact in the occurrence of rockburst, and understand the relationships between these factors. The in situ rockburst database was further analyzed using different DM techniques ranging from artificial neural networks （ANNs） to naive Bayesian classifiers. The aim was to predict the type of rockburst-that is, the rockburst level-based on geologic and construction characteristics of the mine or tunnel. Conclusions are drawn at the end of the paper.
文摘Privacy preservation is a crucial issue for smart buildings where all kinds of messages, e.g., power usage data, control commands, events, alarms, etc. are transmitted to accomplish the management of power. Without appropriate privacy protection schemes, electricity customers are faced with various privacy risks. Meanwhile, the natures of smart grids and smart buildings—such as having limited computation power of smart devices and constraints in communication network capabilities, while requiring being highly reliable—make privacy preservation a challenging task. In this paper, we propose a group key scheme to safeguard multicast privacy with the provisions of availability, fault-tolerance, and efficiency in the context of smart buildings as a part the smart grid. In particular, hybrid architecture accommodating both centralized and contributory modes is constructed in order to achieve both fault-tolerance and efficiency with only one set of group key installed. Key trees are sophisticatedly managed to reduce the number of exponentiation operations. In addition, an individual rekeying scheme is introduced for occasional joining and leaving of member smart meters. Experimental results, on a simulation platform, show that our scheme is able to provide significant performance gains over state-of-the-art methods while effectively preserving the participants’ privacy.
基金financial support from the Abu Dhabi National Oil Company (ADNOC), United Arab Emirates under Award No: EX2016-000010。
文摘This study presents the multifunctional characteristics of multi-walled carbon nanotube(MWCNT)/polypropylene random copolymer(PPR) composites enabled via fused filament fabrication(FFF) under monotonic and quasi-static cyclic compression. Utilizing in-house MWCNT-engineered PPR filament feedstocks, both bulk and cellular composites were realized. The morphological features of nanocomposites were examined via scanning electron microscopy, which reveals that MWCNTs are uniformly dispersed. The uniformly dispersed MWCNTs forms an electrically conductive network within the PPR matrix, and the resulting nanocomposite shows good electrical conductivity(~10^(-1)S/cm), improved mechanical performance(modulus increases by 125% and compressive strength increases by 25% for 8 wt% MWCNT loading) and pronounced piezoresistive response(gauge factor of 27.9-8.5 for bulk samples)under compression. The influence of strain rate on the piezoresistive response of bulk samples(4 wt% of MWCNT) under compression was also measured. Under repeated cyclic compression(2% constant strain amplitude), the nanocomposite exhibited stable piezoresistive performance up to 100 cycles. The piezoresistive response under repeated cyclic loading with increasing strain amplitude of was also assessed.The gauge factor of BCC and FCC cellular composites(4 wt% of MWCNT) with a relative density of 30%was observed to be 46.4 and 30.2 respectively, under compression. The higher sensitivity of the BCC plate-lattice could be attributed to its higher degree of stretching-dominated deformation behavior than the FCC plate-lattice, which exhibits bending-dominated behavior. The 3D printed cellular PPR/MWCNT composites structures were found to show excellent piezoresistive self-sensing characteristics and open new avenues for in situ structural health monitoring in various applications.
文摘In the United States, emission regulations are enacted at a state level;individual states are allowed to define what methods they will use to mitigate their carbon emissions. The consequence of this is especially interesting in the state of Texas where new legislation has created a “deregulated” electricity market in which end-users are capable of choosing their electricity provider and subsequently the type of electricity they wish to consume (generated by fossil fuels or renewable sources). In this paper we analyze the effects of carbon tax on the development of renewable generation capacity at the utility level while taking into account expected adoption of rooftop PV systems by individual consumers using agent based modeling techniques. Monte Carlo simulations show carbon abatement trends and proffer updated renewable portfolio standards at various levels of likelihood.
文摘Biodiesel production had received a considerable attention as a green, non-toxic and renewable alternative to petroleum diesel. To avoid using vegetable oils, which are expensive and compete with food, as feedstock, waste oils have been proposed. However, these waste materials contain a large amount of free fatty acids that complicates the production process. In this work, biodiesel production using an alternative feedstock;namely oils from date-pits, has been investigated. These oils have the same favorable features of straight oils, and at the same time are considered waste, since they are extracted from a waste material. The yield of oils extracted using n-hexane in a Soxhlet apparatus was compared to that of oils extracted using methanol-chloroform solvent mixture. The extracted oils were then converted to biodiesel via transesterification with methanol in presence of Novozym𪥣 or Eversa®Transform. The highest oils extraction yield of 11.7%, per dry weight sample, was obtained using Soxhlet extraction apparatus compared to 8.9% using methanol-chloroform mixture. The highest biodiesel production yield was 30% of the oil used, achieved after 6 hours using Novozym𪥣 at 40°C, 5:1 methanol to oil molar ratio and 10wt% enzyme loading. By using a chemical alkaline catalyst, NaOH, at the same conditions, the yield was 27%.
文摘Continuous-monitoring (CM) of natural phenomenon is one of the major streams of applications in wireless sensor networks (WSNs), where aggregation and clustering techniques are beneficial as correlation dominates in both spatial and temporal aspects of sensed phenomenon. Conversely, in Event Driven Reporting (EDR), the efficient transmission of sensitive data related to some predefined alarm cases is of major importance. As such, reporting latency is a more important performance parameter. However, in some applications, the transmission of both CM and EDR data is encouraged or even required. For either CM or EDR applications, system performance can be greatly improved when both the number of packets to be transmitted as well as the packet size is reduced. This is especially true for highly dense sensor networks where many nodes detect the same values for the sensed phenomenon. Building on this, this paper focuses on studying and proposing compression techniques to improve the system performance in terms of energy consumption and reporting latency in both CM and EDR applications. Furthermore, we extend our analysis to hybrid networks where CM and EDR are required simultaneously. Specifically, this paper presents a simple aggregation technique named smart aggregation (SAG) for the CM applications and an event driven scheme named compression cluster scheme in spatial correlated region (CC_SCR). The proposed SAG exploits both spatial and temporal correlations where CC_SCR exploits the spatial correlation of such networks by data compression. Rationalizing the developments is attained by simulations that compare energy efficiency of the proposed SAG with k-hop aggregation and CM based event driven reporting (CMEDR) schemes. Results of CC_SCR show that the technique may reduce the energy consumption drastically. In some specific cases the reduction becomes more than 10 times compared to a classical clustering scheme. Two different strategies for the transmission of event reports through the CM infrastructure are incorporated: PER and NPER protocols. Both strategies take advantage of the cluster-based architecture which assigns a TDMA schedule for the CM data transmission while using NP/CSMA for the transmission of the event information. Consequently, no extra energy is consumed for separate event clusters. As such, the number of packets to be transmitted is greatly reduced.
文摘A first principal modeling of the gasification of a char particle is performed using single step mechanism. The char particle is considered to be spherical in shape and only the physical and chemical properties can change in the radial direction. The carbon dioxide is used as the gasification agent that reacts with the char and form carbon monoxide. The presence of both solid and gaseous phase species makes the reaction heterogeneous. The char particle is considered with varying porosity that also allows the change in the surface area of the particle. A time invariant temperature and pressure profile is used at which the Arrhenius rate constant and diffusion is calculated. The mass conservation of model results in the form of two coupled partial differential and one ordinary differential equation. The equations are solved with a set of initial and boundary conditions using the bulk species concentration at the particle surface. A second order accurate central differencing scheme is used to discretize space while backward differencing is used to discretize time. Finally, the results are presented for the concentration distribution of CO and CO2 in radial direction with respect to time. It shows that, maximum concentration of CO is present at the center of the particle while the concentration gradient becomes higher near the particle surface. The nonlinear concentration trend due to the diffusion is effectively captured. The results show that, completed conversion of char depend upon the time provided for the reaction which can be reduced by decreasing the size of particle or increasing the reaction temperature. The sensitivity study of temperature and initial porosity also performed and showed that temperature has high impact on char conversion as compare to initial porosity.
文摘This paper presents a comprehensive overview of the different requirements for applications of solar cells in the built environment, particularly for the MENA （Middle East and North Africa） region. The authors emphasize the assessment of parameters additional to the cost and efficiency of the cells to make a more informed choice of the PV technology to use in specific buildings. They also emphasize the need for the wide use ofphotovoltaics in the built environment to produce electricity in the GCC （Gulf Cooperation Council） region and briefly mention the efforts being made in this regard.
文摘Biogas fuel is a sustainable and renewable fuel produced from anaerobic digestion of organic matter. The biogas fuel is a flammable mixture of methane and carbon dioxide with low to medium calorific values. Biogas is an alternative to conventional fossil fuels and can be used for beating, transportation and power generation. CFD （computational fluid dynamic） analysis of the combustion performance and emissions of biogas fuel in gas turbine engines is presented in this study. The main objective of this study is to understand the impact of the variability in the biogas fuel compositions and lower heating values on the combustion process. Natural gas, biogas from anaerobic digester, landfill biogas, and natural gas/biogas mixture fuels combustion were investigated in this study. The CFD results show lower peak flame temperature and CO mole fractions inside the combustor and lower NOx emissions at the combustor exit for the biogas compared to natural gas fuel. The peak flame temperature decreases by 37% for the biogas landfill （COJCH4 = 0.89） and by 22% for the biogas anaerobic digester （CO2/CH4 = 0.54） compared to natural gas fuel combustion. The peak CO mole fraction inside the combustor decreases from 9.8 × 10-2 for natural gas fuel to 2.22 × 10-4 for biogas anaerobic digester and 1.32 × 10-7 for biogas landfill. The average NOx mole fraction at the combustor exit decreases from 1.13 × 10-5 for natural gas fuel to 0.40 × 10-6 for biogas anaerobic digester and 1.06 × 10-6 for biogas landfill. The presence of non-combustible constituents in the biogas reduces the temperature of the flame and consequently the NOx emissions.
基金supported by Guangdong Key R&D Program of China(2019B090908001)National Natural Science Foundation of China(U22B2069)+2 种基金Shanghai Rising Star Program(No.22QA1406400)National Key R&D Program of China(2022YFB3305400)Science and Technology lnnovation Action Plan of the Science and Technology Commission of Shanghai Municipality(No.23DZ1200800)。
文摘SiO_(x)is commonly used in lithium-ion batteries because of its capacity and affordability,but it has issues with volume expansion and conductivity.Synthetic methods are crucial for achieving the desired microstructure and material properties.This study introduces a new technique,fluidized bed granulation,to produce SiO_(x)@GNs composites.These composites have a core-shell structure with SiO_(x)particles coated in graphene sheets,and high-energy vibration is used to create a SiO_(x)-Fe structure on the surface.The graphene coating prevents volume expansion and enhances electron transfer.Real-time confocal imaging shows the charging and discharging process.Experiment results show that the SiO_(x)@GNs electrode has a lower expansion rate of 53.60%compared to 73.04%for the SiO electrode,indicating improved electrochemical properties with the graphene coating.After 100 cycles at 2 C,SiO_(x)@GNs demonstrate a reversible capacity of 1265.8 mA,h·g^(-1)and discharge capability at 7 C with a capacity of 1050 mA,h·g^(-1).The battery retains 90.21%of its capacity after 500 cycles at 0.5 C,showing potential as a LIB anode alternative with a unique structure for different energy storage materials.Fluidized bed granulation can aid in scaling up the use of SiO_(x)anodes in lithium-ion batteries.
基金This research was funded by Army Research Lab(Cooperative agreement W91INF 15-2-0034-S)Georgia Tech IRAD funds(DE00005346).
文摘A better understanding of the bonding and aggregation processes occurring between carbon nanomaterials and metal oxide particles in aqueous solutions is important in the development of novel nanosolids for applications in the areas of sensor development,highly conductive paint,nanotube alignment,polymer composites,Li-ion batteries,and many other areas.The current investigation reviews these processes and presents a detailed description of the aggregation processes occurring between carbon nanomaterials and metal oxide particles(metals)in various aqueous solutions.The results indicate that the charge attraction between the particles results in a strong homogeneous bonding that occurs within the aqueous solution and for the first time demonstrate and describe the aggregation process of these nanoparticles.The relative importance of many parameters that impact the aggregation process is identified and discussed,and guidelines for controlling the aggregation process are presented.This is a simple and cost-effective process to manufacture a novel nano-solid based on carbon nanomaterial and metal oxide.In addition,the process is easy to scale up and optimize.The methodology could lead to many significant applications as well as commercialization.
文摘We formulate an age-structured model based on a system of nonlinear partial differen- tial equations to assist the early and catch up female vaccination programs for human papillomavirus （HPV） types 6 and 11. Since these HPV types do not induce permanent immunity, the model, which stratifies the population based on age and gender, has a susceptible-infectious-susceptible （SIS） structure. We calculate the effective reproduction number Rv for the model and describe the local-asymptotic stability of the disease-free equilibrium using Rv. We prove the existence of an endemic equilibrium for Rv 〉 1 for the no vaccine case. However, analysis of the model for the vaccine case reveals that it undergoes the phenomenon of backward bifurcation. To support our theoretical results, we estimate the age and time solution with the given data for Toronto population, when an early and catch up female vaccine program is adopted, and when there is no vaccine. We show that early and catch up female vaccine program eliminates the infection in both male and female populations over a period of 30 years. Finally, we introduce the optimal control to an age-dependent model based on ordinary differential equations and solve it numerically to obtain the most cost-effective method for introducing the catch up vaccine into the population.
文摘An optically enabled z-axis micro-disk inertia sensor is presented, which consists of a disk-shaped proof mass integrated on top of an optical waveguide. Numerical simulations show that the optical power of laser beam propagating in a narrow silicon nitride （Si3N4） waveguide located under the disk is attenuated in response to the vertical movement of the micro-disk. The high leakage power of the TM mode can effectively be used to detect a dynamic range of 1 g - 10g （g=9.8 rn/s ）. At lest, the waveguide is kept at a nominal gap of 1 μm from the proof mass. It is adiabatically tapered to a narrow dimension of W×H = 350×220nm2 in a region where the optical mode is intended to interact with the proof mass. Furthermore, the bottom cladding is completely etched away to suspend the waveguide and improve the optical interaction with the proof mass. The proposed optical inertia sensor has a high sensitivity of 3 dB/g when a 50μm-long waveguide is used （normalized sensitivity 0.5 dB/μm2） for the vertical movement detection.
