Fertilizer plants are most complex plants in the world (Rashid et al., 2013, Process Safety Progress) and its good opportunity to learn science from operations involved in these plants. Fluid mechanics and heat transf...Fertilizer plants are most complex plants in the world (Rashid et al., 2013, Process Safety Progress) and its good opportunity to learn science from operations involved in these plants. Fluid mechanics and heat transfer operations combination involved in fertilizer complexes are explored in this article.展开更多
It is essential to characterize fluid flow in porous media to have a better understanding of petrophysical properties.Many approaches were developed to determine reservoir permeability among which the integrated analy...It is essential to characterize fluid flow in porous media to have a better understanding of petrophysical properties.Many approaches were developed to determine reservoir permeability among which the integrated analysis of hydraulic flow unit(HFU)and electrofacies(EF)is considered to be useful one.However,the application of HFU and EF analysis has not been totally understood with a limited data to develop correlation for less distance offset wells.In this study,an attempt was made to show the application of integrating HFU and EF for reliable estimation of permeability using core and wireline log data in one of the gas fields in Pakistan.The results obtained indicate that the integrated approach proposed in this study can be used,especially in less distance offset wells when a limited number of data are available for petrophysical characterization.展开更多
To prevent irreversible damage to one’s eyesight,ocular diseases(ODs)need to be recognized and treated immediately.Color fundus imaging(CFI)is a screening technology that is both effective and economical.According to...To prevent irreversible damage to one’s eyesight,ocular diseases(ODs)need to be recognized and treated immediately.Color fundus imaging(CFI)is a screening technology that is both effective and economical.According to CFIs,the early stages of the disease are characterized by a paucity of observable symptoms,which necessitates the prompt creation of automated and robust diagnostic algorithms.The traditional research focuses on image-level diagnostics that attend to the left and right eyes in isolation without making use of pertinent correlation data between the two sets of eyes.In addition,they usually only target one or a few different kinds of eye diseases at the same time.In this study,we design a patient-level multi-label OD(PLML_ODs)classification model that is based on a spatial correlation network(SCNet).This model takes into consideration the relevance of patient-level diagnosis combining bilateral eyes and multi-label ODs classification.PLML_ODs is made up of three parts:a backbone convolutional neural network(CNN)for feature extraction i.e.,DenseNet-169,a SCNet for feature correlation,and a classifier for the development of classification scores.The DenseNet-169 is responsible for retrieving two separate sets of attributes,one from each of the left and right CFI.After then,the SCNet will record the correlations between the two feature sets on a pixel-by-pixel basis.After the attributes have been analyzed,they are integrated to provide a representation at the patient level.Throughout the whole process of ODs categorization,the patient-level representation will be used.The efficacy of the PLML_ODs is examined using a soft margin loss on a dataset that is readily accessible to the public,and the results reveal that the classification performance is significantly improved when compared to several baseline approaches.展开更多
Non-intrusive load monitoring is a method that disaggregates the overall energy consumption of a building to estimate the electric power usage and operating status of each appliance individually.Prior studies have mos...Non-intrusive load monitoring is a method that disaggregates the overall energy consumption of a building to estimate the electric power usage and operating status of each appliance individually.Prior studies have mostly concentrated on the identification of high-power appliances like HVAC systems while overlooking the existence of low-power appliances.Low-power consumer appliances have comparable power consumption patterns,which can complicate the detection task and can be mistaken as noise.This research tackles the problem of classification of low-power appliances and uses turn-on current transients to extract novel features and develop unique appliance signatures.A hybrid feature extraction method based on mono-fractal and multi-fractal analysis is proposed for identifying low-power appliances.Fractal dimension,Hurst exponent,multifractal spectrum and the Hölder exponents of switching current transient signals are extracted to develop various‘turn-on’appliance signatures for classification.Four classifiers,i.e.,deep neural network,support vector machine,decision trees,and K-nearest neighbours have been optimized using Bayesian optimization and trained using the extracted features.The simulated results showed that the proposed method consistently outperforms state-of-the-art feature extraction methods across all optimized classifiers,achieving an accuracy of up to 96%in classifying low-power appliances.展开更多
Spray cooling is an effective tool to dissipate high heat fluxes from hot surfaces. This paper thoroughly investigates the effects of spray parameters on the cooling time and cooling rate under varying inlet pressure ...Spray cooling is an effective tool to dissipate high heat fluxes from hot surfaces. This paper thoroughly investigates the effects of spray parameters on the cooling time and cooling rate under varying inlet pressure using water as the coolant. Cylindrical samples of stainless steel with constant diameter, D = 25 mm, and thickness δ: 8.5 mm, 13 mm, 17.5 mm and 22 mm were investigated. Critical droplet diameter to achieve an ultrafast cooling rate of 300°C/s was estimated by using analytical model for samples of varying thickness. At an inlet pressure of 0.8 MPa, maximum cooling rates of 424.2°C/s, 502.81°C/s and 573.1°C/s were achieved for wall super heat ΔT = 600°C, 700°C and 800°C respectively.展开更多
Many parameters have been indicated crucial for the selection of a saline aquifer as a carbon dioxide(CO_(2))storage site.However,less attention has been given to the impact of heterogeneity on the performance of thes...Many parameters have been indicated crucial for the selection of a saline aquifer as a carbon dioxide(CO_(2))storage site.However,less attention has been given to the impact of heterogeneity on the performance of these storage media.Thus,the heterogeneity effect was evaluated in this paper by adopting a numerical modeling approach and the existing screening criterion developed for the aquifers was updated.The updated criterion for CO_(2)storage purpose would enhance the confidence level during the selection of deep saline aquifer and thus,help to address the climate change issue.The numerical modeling was carried out via CO_(2)STORE module of Eclipse300 Simulator to evaluate the effect of different levels of heterogeneity on CO_(2)storage potential.Different degrees of heterogeneity from homogenous systems to highly heterogeneous systems in the model were incorporated through the Lorenz coefficient.In this way,simulation of nine cases was carried out for three different aquifers with different porosity values.A comparison of these results showed that heterogeneity causes the aquifer to have lower storage capacity.On the trapping potential,dissolution trapping was significant and the amount of free gas in all cases was minimum.In addition,the aquifer with the highest level of heterogeneity(HLH)had a minimum fraction of residual trapping regardless of porosity.It was also found that final pressure at the end of 30 years is the same and high for low-level heterogeneity(LLH)and medium level heterogeneity(MLH)cases and low for HLH,while the injection rate stability duration is least for HLH and maximum for LLH.Based on the results obtained,it can be concluded that low to medium level heterogeneous aquifers with a good porosity can be a suitable choice for CO_(2)storage.展开更多
The particle structure of a complex system has been explored through a unique Evans' s homogenous nonequilibrium molecular dynamics(HNEMD) simulation technique. The crystalline order–disorder structures(OD-struct...The particle structure of a complex system has been explored through a unique Evans' s homogenous nonequilibrium molecular dynamics(HNEMD) simulation technique. The crystalline order–disorder structures(OD-structures) and the corresponding energies of three-dimensional(3 D) nonideal complex systems(NICSs) have been measured over a wide range of plasma states(■, κ) for a body-centered cubic(BCC) structure. The projected technique provides accurate ODstructures with fast convergence and applicable to very small size effect for different temperatures(≡ 1/■) and constant force field(F~*) values. The OD-structure obtained through HNEMD approach is found to be reasonable agreement and more reliable than those earlier identified by simulation approaches and experimental data of NICSs. New simulations of OD-structures show that dusty plasma remains in crystalline(strongly coupled) state at lower temperature and constant F*values, for the whole simulation runs. Our investigations show that the crystalline structure is changed and the particle structure switches from intermediate to disorder(nonideal gaseous) state with an increase of the system's temperature. It has been shown that the long range order shifts toward lower temperature with increasing κ. The presented technique exhibits that the potential energy has a maximum value when the dusty plasma remains in crystalline states(low temperatures),which confirms earlier 3 D simulation results.展开更多
Low energy metallic ions, generated by a Q-switched Nd：YAG laser （1064-nm wavelength, 10-mJ energy, 9-nm 12-ns-pulse width, 1011 W/cm2 intensity） irradiated on a silicon substrate to modify various properties, such...Low energy metallic ions, generated by a Q-switched Nd：YAG laser （1064-nm wavelength, 10-mJ energy, 9-nm 12-ns-pulse width, 1011 W/cm2 intensity） irradiated on a silicon substrate to modify various properties, such as electrical, morphological, and structural modifications. Thomson parabola technique is used to calculate the energy of these metallic ions whereas the electrical conductivity is calculated with the help of Four-point probe. Interestingly circular tracks forming chain like damage trails are produced via these energetic ions which are carefully examined by optical microscopy. It is observed that excitation, ionization, and cascade collisions are responsible for surface modifications of irradiated samples. Four-point probe analysis revealed that the electrical conductivity of substrate has reduced with increasing trend of atomic number of irradiated metallic ions （A1, Ti, Cu, and Au）. The x-ray diffraction analysis elucidated the crystallographic changes leading to reduction of grain size of N-type silicon substrate, which is also associated with the metallic ions used. The decreasing trend of conductivity and grain size is due to thermal stresses, scattering effect, structural imperfections, and non-uniform conduction of energy absorbed by substrate atoms after the ion irradiation.展开更多
Optimization of a manufacturing process results in higher productivity and reduced wastes. Production parameters of a local steel bar manufacturing industry of Pakistan is optimized by using six Sigma-Define, measure,...Optimization of a manufacturing process results in higher productivity and reduced wastes. Production parameters of a local steel bar manufacturing industry of Pakistan is optimized by using six Sigma-Define, measure, analyze, improve, and controlmethodology. Production data is collected and analyzed. After analysis, experimental design result is used to identify significant factors affecting process performance. The significant factors are controlled to optimized level using two-level factorial design method. A regression model is developed that helps in the estimation of response under multi variable input values. Model is tested, verified, and validated by using industrial data collected at a local steel bar manufacturing industry of Peshawar（Khyber Pakhtunkhwa, Pakistan）. The sigma level of the manufacturing process is improved to 4.01 from 3.58. The novelty of the research is the identification of the significant factors along with the optimum levels that affects the process yield, and the methodology to optimize the steel bar manufacturing process.展开更多
Ammonia production is vital in global industries but faces increasing environmental concerns,necessitating a shift towards sustainable methods.This review comprehensively explores diverse hydrogen production approache...Ammonia production is vital in global industries but faces increasing environmental concerns,necessitating a shift towards sustainable methods.This review comprehensively explores diverse hydrogen production approaches and their potential impact on sustainable ammonia synthesis.The primary focus is investigating hydrogen production methods that enhance both efficiency and sustainability in ammonia synthesis,which is crucial for reducing its environmental footprint.Furthermore,the review highlights the pivotal role of catalysts in improving Faradaic efficiency in ammonia synthesis,emphasizing their significance in overall process efficiency.The study identifies innovative technologies that have the potential to revolutionize ammonia production while aligning with global sustainability goals.Through a thorough examination of hydrogen production methods and catalytic advances,this review provides valuable insight into greener and more efficient ammonia production practices.In conclusion,it emphasizes the importance of exploring hydrogen production methods and leveraging catalysts to improve ammonia production sustainability and efficiency.It addresses a critical research gap and paves the way for an environmentally responsible and globally aligned ammonia production industry.展开更多
Excessive emission of greenhouse gases into the atmosphere has resulted in a progressive climate change and global warming in the past decades.There have been many approaches developed to reduce the emission of Carbon...Excessive emission of greenhouse gases into the atmosphere has resulted in a progressive climate change and global warming in the past decades.There have been many approaches developed to reduce the emission of Carbon Dioxide(CO2)into the atmosphere,among which Carbon Capture and Storage(CCS)techniques has been recognized as the most promising method.This paper provides a deeper insight about the CCS technology where CO2 is captured and stored in deep geological formations for stabilization of the earth's temperature.Principles of capturing and storage for a long-term sequestration are also discussed together with the processes,mechanisms and interactions induced by supercritical CO2 upon injection into subsurface geological sites.展开更多
In this paper, a technique was numerically implemented to generate a frequency shift keying （FSK） radio-over-fiber （RoF） signal in optical domain. Due to the oscillator free generation of FSK signal, this scheme i...In this paper, a technique was numerically implemented to generate a frequency shift keying （FSK） radio-over-fiber （RoF） signal in optical domain. Due to the oscillator free generation of FSK signal, this scheme is highly stable with reduced complexity and extremely cost effective. The remote heterodyne detection method was used to detect the signal, where beating occurs to detect the FSK signal. With this scheme, it is able to efficiently generate FSK signal in the range of 60 and 75 GHz at 8 Gbit/s and effectively transmit it over 80 km link without degrading the signal shape and quality. The nonlinear threshold （NLT） point of the system has also been numerically analyzed to estimate the nonlinear tolerance of the system. Besides, the impact of transmission distance and polarization mode dispersion （PMD） was evaluated. Furthermore, the wavelength reuse for the uplink was implemented in the scheme by reusing the same wave- length for uplink that was used for signal generation at downlink. The whole process was performed in optical domain. Thus this scheme is very cost effective as the overall architecture of RoF system is simplified.展开更多
In this paper,we report on the performance comparison of all-optical signal processing methodologies to compensate fiber transmission impairments,namely chromatic dispersion and nonlinear distortion caused by the Ker...In this paper,we report on the performance comparison of all-optical signal processing methodologies to compensate fiber transmission impairments,namely chromatic dispersion and nonlinear distortion caused by the Kerr effect,in a coherent 112 Gbit∕s dual-polarization 64 bit quadrature amplitude modulation system over 800 km standard single-mode fiber.We numerically compare optical backward propagation(OBP)with optical phase conjugation(OPC)techniques,namely.mid-link spectral inversion,predispersed spectral inversion,and OPC with nonlinearity module.We also evaluate a self-phase-modulation-based optical limiter with an appropriate prechirping to compensate for the intensity fluctuations as a hybrid approach with OBP.The results depict improvement in system performance by a factor of∼4 dB of signal input power by all-optical signal processing methods,which is comparative with ideal digital backward propagation where the high complexity is the intrinsic impediment in the real-time implementation of the technique with coherent receivers.展开更多
Drilling through active shale formations has been a challenging practice in the oil and gas industry for a long period of time,given the complexity of shale structure and its interaction with Water Based Muds(WBMs).Al...Drilling through active shale formations has been a challenging practice in the oil and gas industry for a long period of time,given the complexity of shale structure and its interaction with Water Based Muds(WBMs).Although there have been many additives and methodologies proposed for a safe drilling through shale formations using WBMs,little success has been reported to the application of these methods once tested under different field conditions.In this paper,a new WBM formulated by nanomaterials was proposed to stabilize active shale layers during drilling.A series of rheological,density,filtration loss,bentonite dispersion and shale recovery tests were conducted on the mud samples formulated by nanosilica and Nano Glass Flakes(NGFs).The results indicated that NGF,as a cheap but effective nanomaterial,is able to significantly reduce the flirtation loss without posing any significant impacts on the density and the rheology of WBMs.It also appeared that the bentonite molecules were incapable to either hydrate or disperse in the drilling fluid system in the presence of NGFs.It seems that NGFs can stabilize clay minerals and reduce the filtration loss as remarkably efficient additive,but caution must be taken to ensure that they are properly disperse in the WBMs.展开更多
文摘Fertilizer plants are most complex plants in the world (Rashid et al., 2013, Process Safety Progress) and its good opportunity to learn science from operations involved in these plants. Fluid mechanics and heat transfer operations combination involved in fertilizer complexes are explored in this article.
文摘It is essential to characterize fluid flow in porous media to have a better understanding of petrophysical properties.Many approaches were developed to determine reservoir permeability among which the integrated analysis of hydraulic flow unit(HFU)and electrofacies(EF)is considered to be useful one.However,the application of HFU and EF analysis has not been totally understood with a limited data to develop correlation for less distance offset wells.In this study,an attempt was made to show the application of integrating HFU and EF for reliable estimation of permeability using core and wireline log data in one of the gas fields in Pakistan.The results obtained indicate that the integrated approach proposed in this study can be used,especially in less distance offset wells when a limited number of data are available for petrophysical characterization.
文摘To prevent irreversible damage to one’s eyesight,ocular diseases(ODs)need to be recognized and treated immediately.Color fundus imaging(CFI)is a screening technology that is both effective and economical.According to CFIs,the early stages of the disease are characterized by a paucity of observable symptoms,which necessitates the prompt creation of automated and robust diagnostic algorithms.The traditional research focuses on image-level diagnostics that attend to the left and right eyes in isolation without making use of pertinent correlation data between the two sets of eyes.In addition,they usually only target one or a few different kinds of eye diseases at the same time.In this study,we design a patient-level multi-label OD(PLML_ODs)classification model that is based on a spatial correlation network(SCNet).This model takes into consideration the relevance of patient-level diagnosis combining bilateral eyes and multi-label ODs classification.PLML_ODs is made up of three parts:a backbone convolutional neural network(CNN)for feature extraction i.e.,DenseNet-169,a SCNet for feature correlation,and a classifier for the development of classification scores.The DenseNet-169 is responsible for retrieving two separate sets of attributes,one from each of the left and right CFI.After then,the SCNet will record the correlations between the two feature sets on a pixel-by-pixel basis.After the attributes have been analyzed,they are integrated to provide a representation at the patient level.Throughout the whole process of ODs categorization,the patient-level representation will be used.The efficacy of the PLML_ODs is examined using a soft margin loss on a dataset that is readily accessible to the public,and the results reveal that the classification performance is significantly improved when compared to several baseline approaches.
文摘Non-intrusive load monitoring is a method that disaggregates the overall energy consumption of a building to estimate the electric power usage and operating status of each appliance individually.Prior studies have mostly concentrated on the identification of high-power appliances like HVAC systems while overlooking the existence of low-power appliances.Low-power consumer appliances have comparable power consumption patterns,which can complicate the detection task and can be mistaken as noise.This research tackles the problem of classification of low-power appliances and uses turn-on current transients to extract novel features and develop unique appliance signatures.A hybrid feature extraction method based on mono-fractal and multi-fractal analysis is proposed for identifying low-power appliances.Fractal dimension,Hurst exponent,multifractal spectrum and the Hölder exponents of switching current transient signals are extracted to develop various‘turn-on’appliance signatures for classification.Four classifiers,i.e.,deep neural network,support vector machine,decision trees,and K-nearest neighbours have been optimized using Bayesian optimization and trained using the extracted features.The simulated results showed that the proposed method consistently outperforms state-of-the-art feature extraction methods across all optimized classifiers,achieving an accuracy of up to 96%in classifying low-power appliances.
文摘Spray cooling is an effective tool to dissipate high heat fluxes from hot surfaces. This paper thoroughly investigates the effects of spray parameters on the cooling time and cooling rate under varying inlet pressure using water as the coolant. Cylindrical samples of stainless steel with constant diameter, D = 25 mm, and thickness δ: 8.5 mm, 13 mm, 17.5 mm and 22 mm were investigated. Critical droplet diameter to achieve an ultrafast cooling rate of 300°C/s was estimated by using analytical model for samples of varying thickness. At an inlet pressure of 0.8 MPa, maximum cooling rates of 424.2°C/s, 502.81°C/s and 573.1°C/s were achieved for wall super heat ΔT = 600°C, 700°C and 800°C respectively.
文摘Many parameters have been indicated crucial for the selection of a saline aquifer as a carbon dioxide(CO_(2))storage site.However,less attention has been given to the impact of heterogeneity on the performance of these storage media.Thus,the heterogeneity effect was evaluated in this paper by adopting a numerical modeling approach and the existing screening criterion developed for the aquifers was updated.The updated criterion for CO_(2)storage purpose would enhance the confidence level during the selection of deep saline aquifer and thus,help to address the climate change issue.The numerical modeling was carried out via CO_(2)STORE module of Eclipse300 Simulator to evaluate the effect of different levels of heterogeneity on CO_(2)storage potential.Different degrees of heterogeneity from homogenous systems to highly heterogeneous systems in the model were incorporated through the Lorenz coefficient.In this way,simulation of nine cases was carried out for three different aquifers with different porosity values.A comparison of these results showed that heterogeneity causes the aquifer to have lower storage capacity.On the trapping potential,dissolution trapping was significant and the amount of free gas in all cases was minimum.In addition,the aquifer with the highest level of heterogeneity(HLH)had a minimum fraction of residual trapping regardless of porosity.It was also found that final pressure at the end of 30 years is the same and high for low-level heterogeneity(LLH)and medium level heterogeneity(MLH)cases and low for HLH,while the injection rate stability duration is least for HLH and maximum for LLH.Based on the results obtained,it can be concluded that low to medium level heterogeneous aquifers with a good porosity can be a suitable choice for CO_(2)storage.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11505286 and 11805272)
文摘The particle structure of a complex system has been explored through a unique Evans' s homogenous nonequilibrium molecular dynamics(HNEMD) simulation technique. The crystalline order–disorder structures(OD-structures) and the corresponding energies of three-dimensional(3 D) nonideal complex systems(NICSs) have been measured over a wide range of plasma states(■, κ) for a body-centered cubic(BCC) structure. The projected technique provides accurate ODstructures with fast convergence and applicable to very small size effect for different temperatures(≡ 1/■) and constant force field(F~*) values. The OD-structure obtained through HNEMD approach is found to be reasonable agreement and more reliable than those earlier identified by simulation approaches and experimental data of NICSs. New simulations of OD-structures show that dusty plasma remains in crystalline(strongly coupled) state at lower temperature and constant F*values, for the whole simulation runs. Our investigations show that the crystalline structure is changed and the particle structure switches from intermediate to disorder(nonideal gaseous) state with an increase of the system's temperature. It has been shown that the long range order shifts toward lower temperature with increasing κ. The presented technique exhibits that the potential energy has a maximum value when the dusty plasma remains in crystalline states(low temperatures),which confirms earlier 3 D simulation results.
文摘Low energy metallic ions, generated by a Q-switched Nd：YAG laser （1064-nm wavelength, 10-mJ energy, 9-nm 12-ns-pulse width, 1011 W/cm2 intensity） irradiated on a silicon substrate to modify various properties, such as electrical, morphological, and structural modifications. Thomson parabola technique is used to calculate the energy of these metallic ions whereas the electrical conductivity is calculated with the help of Four-point probe. Interestingly circular tracks forming chain like damage trails are produced via these energetic ions which are carefully examined by optical microscopy. It is observed that excitation, ionization, and cascade collisions are responsible for surface modifications of irradiated samples. Four-point probe analysis revealed that the electrical conductivity of substrate has reduced with increasing trend of atomic number of irradiated metallic ions （A1, Ti, Cu, and Au）. The x-ray diffraction analysis elucidated the crystallographic changes leading to reduction of grain size of N-type silicon substrate, which is also associated with the metallic ions used. The decreasing trend of conductivity and grain size is due to thermal stresses, scattering effect, structural imperfections, and non-uniform conduction of energy absorbed by substrate atoms after the ion irradiation.
文摘Optimization of a manufacturing process results in higher productivity and reduced wastes. Production parameters of a local steel bar manufacturing industry of Pakistan is optimized by using six Sigma-Define, measure, analyze, improve, and controlmethodology. Production data is collected and analyzed. After analysis, experimental design result is used to identify significant factors affecting process performance. The significant factors are controlled to optimized level using two-level factorial design method. A regression model is developed that helps in the estimation of response under multi variable input values. Model is tested, verified, and validated by using industrial data collected at a local steel bar manufacturing industry of Peshawar（Khyber Pakhtunkhwa, Pakistan）. The sigma level of the manufacturing process is improved to 4.01 from 3.58. The novelty of the research is the identification of the significant factors along with the optimum levels that affects the process yield, and the methodology to optimize the steel bar manufacturing process.
文摘Ammonia production is vital in global industries but faces increasing environmental concerns,necessitating a shift towards sustainable methods.This review comprehensively explores diverse hydrogen production approaches and their potential impact on sustainable ammonia synthesis.The primary focus is investigating hydrogen production methods that enhance both efficiency and sustainability in ammonia synthesis,which is crucial for reducing its environmental footprint.Furthermore,the review highlights the pivotal role of catalysts in improving Faradaic efficiency in ammonia synthesis,emphasizing their significance in overall process efficiency.The study identifies innovative technologies that have the potential to revolutionize ammonia production while aligning with global sustainability goals.Through a thorough examination of hydrogen production methods and catalytic advances,this review provides valuable insight into greener and more efficient ammonia production practices.In conclusion,it emphasizes the importance of exploring hydrogen production methods and leveraging catalysts to improve ammonia production sustainability and efficiency.It addresses a critical research gap and paves the way for an environmentally responsible and globally aligned ammonia production industry.
文摘Excessive emission of greenhouse gases into the atmosphere has resulted in a progressive climate change and global warming in the past decades.There have been many approaches developed to reduce the emission of Carbon Dioxide(CO2)into the atmosphere,among which Carbon Capture and Storage(CCS)techniques has been recognized as the most promising method.This paper provides a deeper insight about the CCS technology where CO2 is captured and stored in deep geological formations for stabilization of the earth's temperature.Principles of capturing and storage for a long-term sequestration are also discussed together with the processes,mechanisms and interactions induced by supercritical CO2 upon injection into subsurface geological sites.
文摘In this paper, a technique was numerically implemented to generate a frequency shift keying （FSK） radio-over-fiber （RoF） signal in optical domain. Due to the oscillator free generation of FSK signal, this scheme is highly stable with reduced complexity and extremely cost effective. The remote heterodyne detection method was used to detect the signal, where beating occurs to detect the FSK signal. With this scheme, it is able to efficiently generate FSK signal in the range of 60 and 75 GHz at 8 Gbit/s and effectively transmit it over 80 km link without degrading the signal shape and quality. The nonlinear threshold （NLT） point of the system has also been numerically analyzed to estimate the nonlinear tolerance of the system. Besides, the impact of transmission distance and polarization mode dispersion （PMD） was evaluated. Furthermore, the wavelength reuse for the uplink was implemented in the scheme by reusing the same wave- length for uplink that was used for signal generation at downlink. The whole process was performed in optical domain. Thus this scheme is very cost effective as the overall architecture of RoF system is simplified.
文摘In this paper,we report on the performance comparison of all-optical signal processing methodologies to compensate fiber transmission impairments,namely chromatic dispersion and nonlinear distortion caused by the Kerr effect,in a coherent 112 Gbit∕s dual-polarization 64 bit quadrature amplitude modulation system over 800 km standard single-mode fiber.We numerically compare optical backward propagation(OBP)with optical phase conjugation(OPC)techniques,namely.mid-link spectral inversion,predispersed spectral inversion,and OPC with nonlinearity module.We also evaluate a self-phase-modulation-based optical limiter with an appropriate prechirping to compensate for the intensity fluctuations as a hybrid approach with OBP.The results depict improvement in system performance by a factor of∼4 dB of signal input power by all-optical signal processing methods,which is comparative with ideal digital backward propagation where the high complexity is the intrinsic impediment in the real-time implementation of the technique with coherent receivers.
文摘Drilling through active shale formations has been a challenging practice in the oil and gas industry for a long period of time,given the complexity of shale structure and its interaction with Water Based Muds(WBMs).Although there have been many additives and methodologies proposed for a safe drilling through shale formations using WBMs,little success has been reported to the application of these methods once tested under different field conditions.In this paper,a new WBM formulated by nanomaterials was proposed to stabilize active shale layers during drilling.A series of rheological,density,filtration loss,bentonite dispersion and shale recovery tests were conducted on the mud samples formulated by nanosilica and Nano Glass Flakes(NGFs).The results indicated that NGF,as a cheap but effective nanomaterial,is able to significantly reduce the flirtation loss without posing any significant impacts on the density and the rheology of WBMs.It also appeared that the bentonite molecules were incapable to either hydrate or disperse in the drilling fluid system in the presence of NGFs.It seems that NGFs can stabilize clay minerals and reduce the filtration loss as remarkably efficient additive,but caution must be taken to ensure that they are properly disperse in the WBMs.
