Introduction Frequency-dependent dielectric response is one of the important properties of ferroelectrics,reflecting the polarization response to high-frequency electric fields.Polarizations are closely related to fer...Introduction Frequency-dependent dielectric response is one of the important properties of ferroelectrics,reflecting the polarization response to high-frequency electric fields.Polarizations are closely related to ferroelectric domain structures,such as single domain,which represents the region with homogeneous polarizations direction.Ferroelectrics usually possess complex domain structures with domain walls(DWs)separating adjacent homogeneously polarized domains.DWs have attracted much attention during the past two decades due to their properties and potential for device designing.The related issues include DW motion,nonvolatile memory,topological defects,enhanced susceptibility,enhanced quality factor,low dielectric loss,and others.(Ba0.8,Sr0.2)TiO3(BST0.8)is a ferroelectric usually with multi-domain structures.Previous work identified two typical types of domain walls(DWs),i.e.,90°DWs and 180°DWs.The enhancement of dielectric response in systems with 90°DWs is now well understood,and the behavior of dielectric response in multi-domain systems with 180°DWs remains unclear.Therefore,gaining insights into how 180°DWs affect the dielectric response can clarify the effects in multidomain systems.Methods We performed molecular dynamics simulations using the ALFE-H code with the first-principles-based effective Hamiltonian method to study the BST0.8 system.All the calculations were performed in the NPT ensemble using the Evans-Hoover thermostat,and periodic boundary condition(PBC)along all three directions.To simulate the substrate,a uniform biaxial strain was fixed to the 1.55%in-plane strain.To analyze the multi-domain with different DWs,the simulations started with a self-constructed initial multi-domain polarization configuration.Subsequent 50 ps MD simulation was performed under chosen strains for structural relaxation.In the initial configuration,the magnitude of non-zero components of soft mode on each site was set to 0.1Å,atomic occupations(alloying)were randomized,and unless otherwise specified,all other mode variables were set to zero.The trajectory of local mode averaged over the supercell during MD simulations was extracted to calculate the dielectric response.The 8 ns MD simulations were performed to obtain an autocorrelation function for any time t ranging from 0 to 1 ns by one step of 10 fs.The fast Fourier transformation(FFT)was performed to calculate the dielectric response.Then two uncoupled damped harmonic oscillators(DHOs)were used to fit the data of dielectric response.Results and discussion The dielectric response of single domain at 300 K with the different electric fields along[110]from 0 to 2 MV/cm was computed.The computational results can be well fitted with the model of two uncoupled DHOs.The real and imaginary parts of the predicted dielectric response at each chosen electric field both exhibit two peaks.As the electric field increases,the low-frequency mode with 300 GHz at zero field in the system gradually disappears,and a high-frequency mode of larger than 8 THz appears when electric field is larger than 1 MV/cm.The high frequencies modes of 3 THz at zero filed and 8 THz under 1 MV/cm shift towards higher frequencies as the electric field increases.In other words,the present simulations reveal that it is possible to manipulate the frequency of peaks in dielectric response via changing the magnitude of the external electric field.The dielectric responses of multi-domain with 90°DWs and 180°DWs are further analyzed.According to the experimental PFM results,the multi-domain structures are simulated and the dielectric response through MD simulations is calculated.The analysis of the dielectric response of single domain structure and multi-domain structures shows that the single domain structures exhibit high-frequency peaks at>300 GHz,whereas the multi-domain structures exhibit low-frequency peaks at 8 GHz and 120 GHz for 180°DWs system and at 10 GHz for 90°DWs system,revealing that there exists a low-frequency mode related to collective oscillation of DWs in multi-domain structures.In addition,the frequencies of peaks in multi-domain with DWs are in a gigahertz range,whereas the single domain structure exhibits peaks in a terahertz range.The contribution of DWs to the dielectric response primarily arises from the timescale of DWs motion,such as sliding or breathing,which differs significantly from the high-frequency vibrations of optical phonon modes.The vibrational frequency of DWs is much lower,with relaxation times in the order of nanoseconds,resulting in a response frequency in GHz range,which is far below the terahertz range of optical phonon modes.Therefore,DWs oscillations dominate the dielectric response at a low frequency.Moreover,multi-domain structure with 180°DWs exhibits a unique low frequency mode at 120 GHz,which is significantly different from single domain and 90°DWs system.In other words,multi-domain structures with 180°DWs and 90°DWs exhibit different dielectric responses.There exists a common low-frequency mode related to the oscillations of DWs in BST0.8.Conclusions It was possible to manipulate the frequency of peaks in dielectric response of single domain through changing the magnitude of the external electric field.Domain walls oscillations dominated the dielectric response in a low frequency gigahertz range,whereas the single domain structures exhibited resonant peaks in a terahertz range.Moreover,multi-domain structures with different domain walls in BST0.8 had different dielectric responses,but the both have a same low-frequency mode at 10 GHz related to the domain walls oscillations.The results of this study indicated the dielectric response behaviors of ferroelectrics induced in an external electric field and internal multi-domain configurations and provided the potential mechanisms and guidance for optimizing application performance.展开更多
Objective:This study aims to identify the prevalence of bullying in the workplace and to examine its association with turnover(TO)intention and secondary traumatic stress(STS)among Jordanian nurses employed in Emergen...Objective:This study aims to identify the prevalence of bullying in the workplace and to examine its association with turnover(TO)intention and secondary traumatic stress(STS)among Jordanian nurses employed in Emergency Departments(EDs)and critical care units(CCUs).Nurses employed in the EDs and CCUs are exposed to high levels of bullying behaviors that may contribute to STS,leading to high rates of TO.Methods:A descriptive cross-sectional design was used.A sample of 150 Jordanian nurses working in CCUs and EDs completed the study.Data collection was performed using the Demographical Questionnaire,the Negative Acts Questionnaire-Revised(NAQ-R),ProQOL scale,and TO scale.The IBM SPSS software was used to analyze data.Results:About 10.7%and 89.3%were categorized as“occasionally bullied”and“victims of workplace bullying”subsequently.Workplace bullying was positively associated with TO intention(r=0.46,P<0.001)and STS(r=0.36,P<0.001).TO was positively associated with STS(r=0.36,P<0.001).Bullying was a unique significant predictor of TO intention(t=4.59,B=0.34,P<0.001)and STS(t=4.15,B=0.34,P<0.001).Conclusions:Bullying behavior has negative adversarial effects on TO and the experience of STS.The prevalence of bullying behavior in the EDs and CCUs remains high despite the increasing awareness of its negative impacts.Healthcare organizations should put systems in place to ensure that zero-tolerance policy are monitored in terms of the effectiveness of its implementation.展开更多
Enhanced oil recovery(EOR)refers to themanymethodologies used to augment the volume of crude oil extracted froman oil reservoir.These approaches are used subsequent to the exhaustion of basic and secondary recovery me...Enhanced oil recovery(EOR)refers to themanymethodologies used to augment the volume of crude oil extracted froman oil reservoir.These approaches are used subsequent to the exhaustion of basic and secondary recovery methods.There are three primary categories of Enhanced Oil Recovery(EOR):thermal,gas injection,and chemical.Enhanced oil recovery methods may be costly and intricate;yet,they facilitate the extraction of supplementary oil that would otherwise remain in the reservoir.Enhanced Oil Recovery(EOR)may prolong the lifespan of an oil field and augment the total output from a specific field.The parameters influencing oil recovery are a significant problem in Enhanced Oil Recovery(EOR)systems,necessitating further examination of the components that impact them.This research examined the impact of permeability fluctuations on fluid dynamics inside a sandstone reservoir and presented a contemporary overview of the three phases of Enhanced Oil Recovery(EOR),including detailed explanations of the methodologies used and the processes facilitating oil recovery.The challenges faced with several common EOR mechanisms were identified,and solutions were suggested.Additionally,the modern trend of incorporating nanotechnology and its synergistic impacts on the stability and efficacy of conventional chemicals for enhanced oil recovery(EOR)was scrutinised and evaluated.Ultimately,laboratory results and field activities were examined.The study looked closely at hownanoparticlesmove through reservoirs and evaluated enhanced oil recovery(EOR),mobility ratio,and fluid displacement efficiency.This study offers comprehensive insights into the use of enhanced oil recovery techniques for sustainable energy generation.展开更多
Objective:To synthesize silver nanopaticles from leaves extract of Eucalyptus chapmaniana(E.chapmaniana)and test the antimicrobial of the nanoparticles against different pathogenic bacteria,yeast and its toxicity agai...Objective:To synthesize silver nanopaticles from leaves extract of Eucalyptus chapmaniana(E.chapmaniana)and test the antimicrobial of the nanoparticles against different pathogenic bacteria,yeast and its toxicity against human acute promyelocytic leukemia(HL-60)cell line.Methods:Ten milliliter of leaves extract was mixed with 90 mL of 0.01 mmol/mL or 0.02 mmol/mL aqueous AgNO_3 and exposed to sun light for 1 h.A change from yellowish to reddish brown color was observed.Characterization using UV-vis spectrophotometery and X-ray diffraction analysis were performed.Antimicrobial activity against six microorganisms was tested using well diffusion method and cytoxicity test using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide,a yellow tetrazole was obtained on the human leukemia cell line(HL-60).Results:UV-vis spectral analysis showed silver surface plasmon resonance band at 413 nm.X-ray diffraction showed that the particles were crystalline in nature with face centered cubic structure of the bulk silver with broad beaks at 38.50°and 44.76°.The synthesized silver nanoparticles efficiently inhibited various pathogenic organisms and reduced viability of the HL-60 cells in a dose-dependent manner.Conclusions:It has been demonstrated that the extract of E.chapmaniana leaves are capable of producing silver nanoparticles extracellularly and the Ag nanoparticles are quite stable in solution.Further studies are needed to fully characterize the toxicity and the mechanisms involved with the antimicrobial and anticancer activity of these particles.展开更多
Ionic liquids ( ILs) based ultrasonic-assisted extract has been applied for the extraction of essential oil from Persicaria minor leaves. The effects of temperature,sonication time,and particle size of the plant mater...Ionic liquids ( ILs) based ultrasonic-assisted extract has been applied for the extraction of essential oil from Persicaria minor leaves. The effects of temperature,sonication time,and particle size of the plant material on the yield of essential oil were investigated. Among the different ILs employed,1-ethyl-3-methyli midazolium acetate was the most effective,providing a 9. 55% yield of the essential oil under optimum conditions( 70 ℃,25 min,IL ∶hexane ratio of 7 ∶10 ( v /v) ,particle size 60-80 mesh) . The performance of 1-ethyl-3-methylimidazolium acetate in the extraction was attributed to its lowviscosity and ability to disintegrate the structural matrix of the plant material. The ability of 1-ethyl-3-methylimidazolium acetate was also confirmed using the conductor like-screening model for realistic solvents. This research proves that ILs can be used to extract essential oils from lignocellulosic biomass.展开更多
In this paper, we use the fractional complex transform and the （G＇/G）-expansion method to study the nonlinear fractional differential equations and find the exact solutions. The fractional complex transform is prop...In this paper, we use the fractional complex transform and the （G＇/G）-expansion method to study the nonlinear fractional differential equations and find the exact solutions. The fractional complex transform is proposed to convert a partial fractional differential equation with Jumarie＇s modified Riemann-Liouville derivative into its ordinary differential equation. It is shown that the considered transform and method are very efficient and powerful in solving wide classes of nonlinear fractional order equations.展开更多
Hedgerows with intercropping systems were established at the ICIMOD test and demonstration site at Godawari to assess the effective- ness of Sloping Agricultural Land Technology （SALT） in reducing run- off water vol...Hedgerows with intercropping systems were established at the ICIMOD test and demonstration site at Godawari to assess the effective- ness of Sloping Agricultural Land Technology （SALT） in reducing run- off water volume, controlling soil loss, increasing crop production, and improving soil fertility in the mid-hills of Nepal. Runoff water volume （1996-2002）, soil loss （1996-2002） and maize yield （1995-2001）, and soil fertility-related parameters were assessed on SALT models with three factors： the type of nitrogen-fixing plant, the farmers＇ practice, and fertilizer use. Results showed a significant effect of Alnus nepalensis and/or Indigofera dosua on runoff water volume, soil loss, crop produc- tion, soil water retention, and soil nutrients （NPK）. Farmers＇ practice and fertilization did not play a significant role in reducing runoff water and soil loss. However, farmers＇ practice significantly increased crop produc- tion. Therefore, integrating soil conservation approaches on SALT sys- tems enhances stable economic output to hills and mountain farmers.展开更多
One of the requirements of engine lubricating oil is that it must have a low enough viscosity at low temperatures to assist in cold starting and a high enough viscosity at high temperatures to maintain its load-bearin...One of the requirements of engine lubricating oil is that it must have a low enough viscosity at low temperatures to assist in cold starting and a high enough viscosity at high temperatures to maintain its load-bearing characteristics. Viscosity Index (VI) is one approach used widely in the lubricating field to assess the variation of viscosity with temperature. The VI of both mineral and synthetic base oils can be improved by the addition of polymeric viscosity modifiers (VMs). VI improvement by VMs is widely attributed to the polymer coil size expanding with increasing temperature. However, there is very little physical data supporting this generally accepted mechanism. To address this issue, intrinsic viscosity measurements and Small-Angle Neutron Scattering (SANS) have been used to study the variation of polymer coil size with changing temperature and concentration in a selection of solvents. The results will show that coil size expansion with temperature is not necessary to achieve significant elevation of viscosity index.展开更多
Fluctuating market price of fossil fuel and overwhelming emission of greenhouse gases to the atmosphere have resulted in climate change and have been a global concern in this decade. Hence, biodiesel has become an alt...Fluctuating market price of fossil fuel and overwhelming emission of greenhouse gases to the atmosphere have resulted in climate change and have been a global concern in this decade. Hence, biodiesel has become an alternative option to fossil diesel as it is renewable and environmentally friendly. Nevertheless, this alternative fuel that is usually derived from terrestrial oil crops will cause shortage in food supply and deforestation if mass production is realized. In recent years, cultivation of aquatic microorganism(particularly microalgae) to produce biodiesel is considered as a practical solution due to their high growth rate and ability to synthesize large quantity of lipid within their cell. However, the development of energy and cost-efficiency of microalgae cultivation system are the main issues in producing renewable microalgae biodiesel. Of late, wastewater or organic compost has been used as the cultivation medium as it can provide sufficient nutrients to sustain microalgae growth.Microalgae cultivation method and system are vitally important as these factors undoubtedly affect the final microalgae biomass and lipid yield. In this review, the cultivation system of microalgae, nutrients demanded for microalgae production, cell harvesting and drying, microalgae oil extraction, and utilization of microalgae biomass for biodiesel production are introduced and discussed. It is anticipated to convey clearer perspectives in upstream and downstream processes in microalgae-derived biodiesel production.展开更多
A selective and sensitive competitive enzyme-linked immunosorbent assay(ELISA) method was developed and validated for the quantification of erlotinib in 50 mL of samples of human serum. Anti-erlotinib serum was obtain...A selective and sensitive competitive enzyme-linked immunosorbent assay(ELISA) method was developed and validated for the quantification of erlotinib in 50 mL of samples of human serum. Anti-erlotinib serum was obtained by immunizing mice with an antigen conjugated with bovine serum albumin and 3,4-bis(2-methoxyethoxy)benzoic acid using the N-succinimidyl ester method. Enzyme labeling of erlotinib with horseradish peroxidase was similarly performed using 3,4-bis(2-methoxyethoxy)benzoic acid. A simple competitive ELISA for erlotinib was developed using the principle of direct competition between erlotinib and the enzyme marker for anti-erlotinib antibody, which had been immobilized on the plastic surface of a microtiter plate. Serum erlotinib concentrations lower than 40 ng/mL were reproducibly measurable using the ELISA. This ELISA was specific to erlotinib and showed very slight cross-reactivity(6.7%) with a major metabolite, O-desmethyl erlotinib. Using this assay, drug levels were easily measured in the blood of mice after oral administration of erlotinib at a single dose of 30 mg/kg. ELISA should be used as a valuable tool for therapeutic drug monitoring and in pharmacokinetic studies of erlotinib.展开更多
In the present study, new series of pyridinium carboxylate protic ionic liquids(PILs) were synthesized by pairing pyridinium cation with carboxylate anion from C_1–C_3 forming pyridinium formate([C_5H_6N^+][HCOO^-]),...In the present study, new series of pyridinium carboxylate protic ionic liquids(PILs) were synthesized by pairing pyridinium cation with carboxylate anion from C_1–C_3 forming pyridinium formate([C_5H_6N^+][HCOO^-]),pyridinium acetate([C_5H_6N^+][CH_3COO^-]) and pyridinium propionate([C_5H_6N^+][CH_3CH_2COO^-]) respectively.The physical properties namely, density, viscosity, surface tension(298.15–343.15) K, and refractive index(293.15–323.15) K were measured. Thermal properties namely, glass transition temperature, molar heat capacity, and thermal decomposition temperatures were also determined. The thermal expansivity was calculated using the experimental density data. The effect of increasing the alkyl chain length on the thermophysical properties of the pyridinium carboxylate PILs has been evaluated. As expected the physical properties i.e. density,viscosity, surface tension and refractive index of the investigated pyridinium carboxylates decreased with increasing temperature. In general pyridinium carboxylate PILs possessed low viscosity, high thermal stability and excellent hydrogen bonding capability, and these properties lead them to outperform conventional solvents employed for lignin dissolution.展开更多
Acid mine drainage （AMD） is one of the major problems in high sulfur coal mining areas generating acidic water. The acidic mine water generated contain hazardous elements in varying concentrations. The Northeastern ...Acid mine drainage （AMD） is one of the major problems in high sulfur coal mining areas generating acidic water. The acidic mine water generated contain hazardous elements in varying concentrations. The Northeastern Indian coalfield produces considerable amounts of AMD. The AMD and metal leaching from coal and mine over burden （OB） are the two important naturally occurring processes. In order to know the AMD potential, the aqueous leaching experiment of a few coal and OB samples from the Ledo colliery of the Northeastern coalfield, Mergherita （India）, at different time periods （1, 3, 5, and 8 h） and at different temperatures （25, 45, 65, and 90℃） were performed in the laboratory. The physico- chemical analysis of the aqueous leachates shows the pH, electrical conductivity （EC）, and total dissolved solid （TDS） in the range of 1.62-3.52, 106-2006 μs/cm, and 106-1003 ppm for the raw coal samples respectively. The OB samples produced pH, EC, and TDS in the range of 3.68-6.92, 48.6-480 μs/cm, and 69.5-240 ppm respectively. From the study, it was revealed that the concentrations of major （Si, A1, K, Na, Fe, Ca, Mg）, minor （Mn） and trace/hazardous elements （As, Ba, Cd, Co, Cr, Cu, Hg, Ni, Pb, Se, Zn） considerably change with leaching time as well as with leaching temperature. Out of these elements As, Cd, Hg, Pb, Cr, and Se are of greater environmental importance. Alteration of the physico-chemical structure of the coal and OB samples resulting from leaching was also studied by field emission scanning electron microscope- energy-dispersive X-ray spectroscopy method. The release of the potentially hazardous elements from the raw coal and OB during leaching time periods to the leachates was detected by inductively coupled plasma-atomic emission spectroscopy and ion-chromatographic analyses. The major minerals found in coal and OB are quartz （SiO2）, pyrite （FeS2）, hematite, marcasite, and kaolinite. The association of different functional groups in minerals and their mode of association were studied by Fourier-transform infrared spectroscopy and X-ray diffraction analytical techniques. The present laboratory study will be useful in relating the characteristics of aqueous leaching from coal and mine OB with the natural weathering condition at the coal mine area.展开更多
A SiC nanofilms have been deposited and investigated on quartz and silicon substrates using pulsed laser deposition technique with the 300 pulses of Nd:YAG laser at two different laser wavelengths of 1064 nm and 532 n...A SiC nanofilms have been deposited and investigated on quartz and silicon substrates using pulsed laser deposition technique with the 300 pulses of Nd:YAG laser at two different laser wavelengths of 1064 nm and 532 nm.The structural,morphological,and optical properties of the deposited nanostructure SiC were prepared and characterized as a function of the wavelengths of the used laser.The structural result shows four different pecks at(111),(200),(220),and(311)planes related to Nano SiC.The transmission result presents that the optical energy gap value for the SiC nanostructure is depended on the wavelength of the used laser and it is found about the range(3.03 eV–3.23 eV).The investigations of the SEM and AFM show that the prepared SiC Nano-films having a grain size range(36.34–48.75)nm and roughness about 4.462 to 3.062 nm.SiC/Si hetero-junction devices show an enhanced performance at 532 nm.展开更多
Since the olden times,infectious diseases have largely affected human existence.The newly emerged infections are excessively caused by viruses that are largely associated with mammal reservoirs.The casualties of these...Since the olden times,infectious diseases have largely affected human existence.The newly emerged infections are excessively caused by viruses that are largely associated with mammal reservoirs.The casualties of these emergencies are significantly influenced by the way human beings interact with the reservoirs,especially the animal ones.In our review we will consider the evolutionary and the ecological scales of such infections and their consequences on the public health,with a focus on the pathogenic influenza A virus.The nutraceutical properties of fungal and plant terpene-like molecules will be linked to their ability to lessen the symptoms of viral infections and shed light on their potential use in the development of new drugs.New challenging methods in antiviral discovery will also be discussed in this review.The authors believe that pharmacognosy is the“wave of future pharmaceuticals”,as it can be continually produced and scaled up under ecofriendly requirements.Further diagnostic methods and strategies however are required to standardise those naturally occurring resources.展开更多
The CCD photometric observations of open star cluster M37(NGC 2099) were carried out up to a limiting magnitude of V ～ 20 in both B and V filters to search for variable stars using a 2k×4k CCD and the 1.3 m tele...The CCD photometric observations of open star cluster M37(NGC 2099) were carried out up to a limiting magnitude of V ～ 20 in both B and V filters to search for variable stars using a 2k×4k CCD and the 1.3 m telescope at the Vainu Bapu Observatory, Kavalur.A total of 314 stars were in the first observing run, out of which 60 were identified as variables.Eight out of the identified 60 variables are classified as W UMa binary stars.For model fitting, we used PHOEBE based on the W-D code to estimate the physical parameters of these newly detected W UMa binaries that theoretically best match the observed light curves.展开更多
The Al-rich waste with aluminium and hydrocarbon as the major contaminant is generated at the wastewater treatment unit of a polymer processing plant. In this research, the heat treatment of this Al-rich waste and its...The Al-rich waste with aluminium and hydrocarbon as the major contaminant is generated at the wastewater treatment unit of a polymer processing plant. In this research, the heat treatment of this Al-rich waste and its use to adjust the silica/alumina ratio of the high calcium fly ash geopolymer were studied. To recycle the raw Al-rich waste, the waste was dried at 110℃ and calcined at 400 to 1000℃. Mineralogical analyses were conducted using X-ray diffraction （XRD） to study the phase change. The increase in calcination temperature to 600, 800, and 1000℃ resulted in the phase transformation. The more active alumina phase of active θ-Al2O3 was obtained with the increase in calcination temperature. The calcined Al-rich waste was then used as an additive to the fly ash geopolymer by mixing with high calcium fly ash, water glass, 10 M sodium hydroxide （NaOH）, and sand. Test results indicated that the calcined Al-rich waste could be used as an aluminium source to adjust the silica/alumina ratio and the strength of geopolymeric materials. The fly ash geopolymer mortar with 2.5wt% of the Al-rich waste calcined at 1000℃ possessed the 7-d compressive strength of 34.2 MPa.展开更多
The Controlled Source Electromagnetic Method (CSEM) is used for offshore hydrocarbon exploration. Hydrocarbon detection in seabed logging (SBL) is a very challenging task for deep hydrocarbon reservoirs. The electroma...The Controlled Source Electromagnetic Method (CSEM) is used for offshore hydrocarbon exploration. Hydrocarbon detection in seabed logging (SBL) is a very challenging task for deep hydrocarbon reservoirs. The electromagnetic field response of an antenna is unable to detect deep hydrocarbon reservoirs due to a weak electromagnetic signal response in the seabed logging environment. This work premise deals with the comparison of the electromagnetic signal strength of a new antenna with a straight antenna and the orientation of an antenna for deep target hydrocarbon exploration. Antenna position and orientation (Tx and Ty) was studied using Computer Simulation Technology software (CST) for deep targets in marine CSEM environments. The model area was assigned as (40 ′ 40 km) to replicate the real seabed environment. From the results, the new dipole antenna shows an 804% and 278% increase in electric and magnetic field strength than the straight antenna. An electric (E) and magnetic (H) field component study was done with and without the presence of a hydrocarbon reservoir. Ex and Hz field component responses with the new antenna at the1 kmtarget were measured in a deep water environment. It was analyzed that the antenna shows 53.10% (Ex) and 83.13% (Hz) field difference in deep water with and without a hydrocarbon reservoir at the30 mantenna position from the sea floor. From the antenna orientation results, it was observed that, the electric field Ex and magnetic field Hz responses decreased from 18% to 12% and 21% to 16%, respectively but was still able to detect the deep target hydrocarbon reservoir at the4 kmtarget depth. This EM antenna may open new frontiers for the oil and gas industry for deep target hydrocarbon detection (HC).展开更多
In this work, an experimental study combined with numerical simulation was conducted to investigate the potential of chemically enhanced water alternating gas （CWAG） injection as a new enhanced oil recovery method. ...In this work, an experimental study combined with numerical simulation was conducted to investigate the potential of chemically enhanced water alternating gas （CWAG） injection as a new enhanced oil recovery method. The unique feature of this new method is that it uses alkaline, surfactant, and polymer additives as a chemical slug which is injected during the water alternating gas （WAG） process to reduce the interfacial tension （IFT） and simultaneously improve the mobility ratio. In essence, the proposed CWAG process involves a combination of chemical flooding and immiscible carbon dioxide （CO2） injection and helps in IFT reduction, water blocking reduction, mobility control, oil swelling, and oil viscosity reduction due to CO2 dissolution. Its performance was compared with the conventional immiscible water alter- nating gas （I-WAG） flooding. Oil recovery utilizing CWAG was better by 26 % of the remaining oil in place after waterflooding compared to the recovery using WAG conducted under similar conditions. The coreflood data （cumulative oil and water production） were history mat- ched via a commercial simulator by adjusting the relative permeability curves and assigning the values of the rock and fluid properties such as porosity, permeability, and the experimentally determined IFT data. History matching ofthe coreflood model helped us optimize the experiments and was useful in determining the importance of the parameters influencing sweep efficiency in the CWAG process. The effectiveness of the CWAG process in pro- viding enhancement of displacement efficiency is evident in the oil recovery and pressure response observed in the coreflood. The results of sensitivity analysis on CWAG slug patterns show that the alkaline-surfactant-polymer injection is more beneficial after CO2 slug injection due to oil swelling and viscosity reduction. The CO2 slug size analysis shows that there is an optimum CO2 slug size, around 25 % pore volume which leads to a maximum oil recovery in the CWAG process. This study shows that the ultralow IFT system, i.e., IFT equaling 10 2 or 10 3 mN/ m, is a very important parameter in CWAG process since the water blocking effect can be minimized.展开更多
文摘Introduction Frequency-dependent dielectric response is one of the important properties of ferroelectrics,reflecting the polarization response to high-frequency electric fields.Polarizations are closely related to ferroelectric domain structures,such as single domain,which represents the region with homogeneous polarizations direction.Ferroelectrics usually possess complex domain structures with domain walls(DWs)separating adjacent homogeneously polarized domains.DWs have attracted much attention during the past two decades due to their properties and potential for device designing.The related issues include DW motion,nonvolatile memory,topological defects,enhanced susceptibility,enhanced quality factor,low dielectric loss,and others.(Ba0.8,Sr0.2)TiO3(BST0.8)is a ferroelectric usually with multi-domain structures.Previous work identified two typical types of domain walls(DWs),i.e.,90°DWs and 180°DWs.The enhancement of dielectric response in systems with 90°DWs is now well understood,and the behavior of dielectric response in multi-domain systems with 180°DWs remains unclear.Therefore,gaining insights into how 180°DWs affect the dielectric response can clarify the effects in multidomain systems.Methods We performed molecular dynamics simulations using the ALFE-H code with the first-principles-based effective Hamiltonian method to study the BST0.8 system.All the calculations were performed in the NPT ensemble using the Evans-Hoover thermostat,and periodic boundary condition(PBC)along all three directions.To simulate the substrate,a uniform biaxial strain was fixed to the 1.55%in-plane strain.To analyze the multi-domain with different DWs,the simulations started with a self-constructed initial multi-domain polarization configuration.Subsequent 50 ps MD simulation was performed under chosen strains for structural relaxation.In the initial configuration,the magnitude of non-zero components of soft mode on each site was set to 0.1Å,atomic occupations(alloying)were randomized,and unless otherwise specified,all other mode variables were set to zero.The trajectory of local mode averaged over the supercell during MD simulations was extracted to calculate the dielectric response.The 8 ns MD simulations were performed to obtain an autocorrelation function for any time t ranging from 0 to 1 ns by one step of 10 fs.The fast Fourier transformation(FFT)was performed to calculate the dielectric response.Then two uncoupled damped harmonic oscillators(DHOs)were used to fit the data of dielectric response.Results and discussion The dielectric response of single domain at 300 K with the different electric fields along[110]from 0 to 2 MV/cm was computed.The computational results can be well fitted with the model of two uncoupled DHOs.The real and imaginary parts of the predicted dielectric response at each chosen electric field both exhibit two peaks.As the electric field increases,the low-frequency mode with 300 GHz at zero field in the system gradually disappears,and a high-frequency mode of larger than 8 THz appears when electric field is larger than 1 MV/cm.The high frequencies modes of 3 THz at zero filed and 8 THz under 1 MV/cm shift towards higher frequencies as the electric field increases.In other words,the present simulations reveal that it is possible to manipulate the frequency of peaks in dielectric response via changing the magnitude of the external electric field.The dielectric responses of multi-domain with 90°DWs and 180°DWs are further analyzed.According to the experimental PFM results,the multi-domain structures are simulated and the dielectric response through MD simulations is calculated.The analysis of the dielectric response of single domain structure and multi-domain structures shows that the single domain structures exhibit high-frequency peaks at>300 GHz,whereas the multi-domain structures exhibit low-frequency peaks at 8 GHz and 120 GHz for 180°DWs system and at 10 GHz for 90°DWs system,revealing that there exists a low-frequency mode related to collective oscillation of DWs in multi-domain structures.In addition,the frequencies of peaks in multi-domain with DWs are in a gigahertz range,whereas the single domain structure exhibits peaks in a terahertz range.The contribution of DWs to the dielectric response primarily arises from the timescale of DWs motion,such as sliding or breathing,which differs significantly from the high-frequency vibrations of optical phonon modes.The vibrational frequency of DWs is much lower,with relaxation times in the order of nanoseconds,resulting in a response frequency in GHz range,which is far below the terahertz range of optical phonon modes.Therefore,DWs oscillations dominate the dielectric response at a low frequency.Moreover,multi-domain structure with 180°DWs exhibits a unique low frequency mode at 120 GHz,which is significantly different from single domain and 90°DWs system.In other words,multi-domain structures with 180°DWs and 90°DWs exhibit different dielectric responses.There exists a common low-frequency mode related to the oscillations of DWs in BST0.8.Conclusions It was possible to manipulate the frequency of peaks in dielectric response of single domain through changing the magnitude of the external electric field.Domain walls oscillations dominated the dielectric response in a low frequency gigahertz range,whereas the single domain structures exhibited resonant peaks in a terahertz range.Moreover,multi-domain structures with different domain walls in BST0.8 had different dielectric responses,but the both have a same low-frequency mode at 10 GHz related to the domain walls oscillations.The results of this study indicated the dielectric response behaviors of ferroelectrics induced in an external electric field and internal multi-domain configurations and provided the potential mechanisms and guidance for optimizing application performance.
文摘Objective:This study aims to identify the prevalence of bullying in the workplace and to examine its association with turnover(TO)intention and secondary traumatic stress(STS)among Jordanian nurses employed in Emergency Departments(EDs)and critical care units(CCUs).Nurses employed in the EDs and CCUs are exposed to high levels of bullying behaviors that may contribute to STS,leading to high rates of TO.Methods:A descriptive cross-sectional design was used.A sample of 150 Jordanian nurses working in CCUs and EDs completed the study.Data collection was performed using the Demographical Questionnaire,the Negative Acts Questionnaire-Revised(NAQ-R),ProQOL scale,and TO scale.The IBM SPSS software was used to analyze data.Results:About 10.7%and 89.3%were categorized as“occasionally bullied”and“victims of workplace bullying”subsequently.Workplace bullying was positively associated with TO intention(r=0.46,P<0.001)and STS(r=0.36,P<0.001).TO was positively associated with STS(r=0.36,P<0.001).Bullying was a unique significant predictor of TO intention(t=4.59,B=0.34,P<0.001)and STS(t=4.15,B=0.34,P<0.001).Conclusions:Bullying behavior has negative adversarial effects on TO and the experience of STS.The prevalence of bullying behavior in the EDs and CCUs remains high despite the increasing awareness of its negative impacts.Healthcare organizations should put systems in place to ensure that zero-tolerance policy are monitored in terms of the effectiveness of its implementation.
文摘Enhanced oil recovery(EOR)refers to themanymethodologies used to augment the volume of crude oil extracted froman oil reservoir.These approaches are used subsequent to the exhaustion of basic and secondary recovery methods.There are three primary categories of Enhanced Oil Recovery(EOR):thermal,gas injection,and chemical.Enhanced oil recovery methods may be costly and intricate;yet,they facilitate the extraction of supplementary oil that would otherwise remain in the reservoir.Enhanced Oil Recovery(EOR)may prolong the lifespan of an oil field and augment the total output from a specific field.The parameters influencing oil recovery are a significant problem in Enhanced Oil Recovery(EOR)systems,necessitating further examination of the components that impact them.This research examined the impact of permeability fluctuations on fluid dynamics inside a sandstone reservoir and presented a contemporary overview of the three phases of Enhanced Oil Recovery(EOR),including detailed explanations of the methodologies used and the processes facilitating oil recovery.The challenges faced with several common EOR mechanisms were identified,and solutions were suggested.Additionally,the modern trend of incorporating nanotechnology and its synergistic impacts on the stability and efficacy of conventional chemicals for enhanced oil recovery(EOR)was scrutinised and evaluated.Ultimately,laboratory results and field activities were examined.The study looked closely at hownanoparticlesmove through reservoirs and evaluated enhanced oil recovery(EOR),mobility ratio,and fluid displacement efficiency.This study offers comprehensive insights into the use of enhanced oil recovery techniques for sustainable energy generation.
基金Supported by University of Technology.Baghdad.Iraq and Universiti Kebangsaan Malaysia(Grant No.DIP-2012-02)
文摘Objective:To synthesize silver nanopaticles from leaves extract of Eucalyptus chapmaniana(E.chapmaniana)and test the antimicrobial of the nanoparticles against different pathogenic bacteria,yeast and its toxicity against human acute promyelocytic leukemia(HL-60)cell line.Methods:Ten milliliter of leaves extract was mixed with 90 mL of 0.01 mmol/mL or 0.02 mmol/mL aqueous AgNO_3 and exposed to sun light for 1 h.A change from yellowish to reddish brown color was observed.Characterization using UV-vis spectrophotometery and X-ray diffraction analysis were performed.Antimicrobial activity against six microorganisms was tested using well diffusion method and cytoxicity test using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide,a yellow tetrazole was obtained on the human leukemia cell line(HL-60).Results:UV-vis spectral analysis showed silver surface plasmon resonance band at 413 nm.X-ray diffraction showed that the particles were crystalline in nature with face centered cubic structure of the bulk silver with broad beaks at 38.50°and 44.76°.The synthesized silver nanoparticles efficiently inhibited various pathogenic organisms and reduced viability of the HL-60 cells in a dose-dependent manner.Conclusions:It has been demonstrated that the extract of E.chapmaniana leaves are capable of producing silver nanoparticles extracellularly and the Ag nanoparticles are quite stable in solution.Further studies are needed to fully characterize the toxicity and the mechanisms involved with the antimicrobial and anticancer activity of these particles.
文摘Ionic liquids ( ILs) based ultrasonic-assisted extract has been applied for the extraction of essential oil from Persicaria minor leaves. The effects of temperature,sonication time,and particle size of the plant material on the yield of essential oil were investigated. Among the different ILs employed,1-ethyl-3-methyli midazolium acetate was the most effective,providing a 9. 55% yield of the essential oil under optimum conditions( 70 ℃,25 min,IL ∶hexane ratio of 7 ∶10 ( v /v) ,particle size 60-80 mesh) . The performance of 1-ethyl-3-methylimidazolium acetate in the extraction was attributed to its lowviscosity and ability to disintegrate the structural matrix of the plant material. The ability of 1-ethyl-3-methylimidazolium acetate was also confirmed using the conductor like-screening model for realistic solvents. This research proves that ILs can be used to extract essential oils from lignocellulosic biomass.
文摘In this paper, we use the fractional complex transform and the （G＇/G）-expansion method to study the nonlinear fractional differential equations and find the exact solutions. The fractional complex transform is proposed to convert a partial fractional differential equation with Jumarie＇s modified Riemann-Liouville derivative into its ordinary differential equation. It is shown that the considered transform and method are very efficient and powerful in solving wide classes of nonlinear fractional order equations.
基金supported in part by the Nepal Academy of Science and Technology(NAST)
文摘Hedgerows with intercropping systems were established at the ICIMOD test and demonstration site at Godawari to assess the effective- ness of Sloping Agricultural Land Technology （SALT） in reducing run- off water volume, controlling soil loss, increasing crop production, and improving soil fertility in the mid-hills of Nepal. Runoff water volume （1996-2002）, soil loss （1996-2002） and maize yield （1995-2001）, and soil fertility-related parameters were assessed on SALT models with three factors： the type of nitrogen-fixing plant, the farmers＇ practice, and fertilizer use. Results showed a significant effect of Alnus nepalensis and/or Indigofera dosua on runoff water volume, soil loss, crop produc- tion, soil water retention, and soil nutrients （NPK）. Farmers＇ practice and fertilization did not play a significant role in reducing runoff water and soil loss. However, farmers＇ practice significantly increased crop produc- tion. Therefore, integrating soil conservation approaches on SALT sys- tems enhances stable economic output to hills and mountain farmers.
文摘One of the requirements of engine lubricating oil is that it must have a low enough viscosity at low temperatures to assist in cold starting and a high enough viscosity at high temperatures to maintain its load-bearing characteristics. Viscosity Index (VI) is one approach used widely in the lubricating field to assess the variation of viscosity with temperature. The VI of both mineral and synthetic base oils can be improved by the addition of polymeric viscosity modifiers (VMs). VI improvement by VMs is widely attributed to the polymer coil size expanding with increasing temperature. However, there is very little physical data supporting this generally accepted mechanism. To address this issue, intrinsic viscosity measurements and Small-Angle Neutron Scattering (SANS) have been used to study the variation of polymer coil size with changing temperature and concentration in a selection of solvents. The results will show that coil size expansion with temperature is not necessary to achieve significant elevation of viscosity index.
基金Supported by the Ministry of Higher Education,Malaysia(FRGS with cost center015AB-L25)Universiti Teknologi PETRONAS(YUTP-FRG with cost center 0153AAH46)
文摘Fluctuating market price of fossil fuel and overwhelming emission of greenhouse gases to the atmosphere have resulted in climate change and have been a global concern in this decade. Hence, biodiesel has become an alternative option to fossil diesel as it is renewable and environmentally friendly. Nevertheless, this alternative fuel that is usually derived from terrestrial oil crops will cause shortage in food supply and deforestation if mass production is realized. In recent years, cultivation of aquatic microorganism(particularly microalgae) to produce biodiesel is considered as a practical solution due to their high growth rate and ability to synthesize large quantity of lipid within their cell. However, the development of energy and cost-efficiency of microalgae cultivation system are the main issues in producing renewable microalgae biodiesel. Of late, wastewater or organic compost has been used as the cultivation medium as it can provide sufficient nutrients to sustain microalgae growth.Microalgae cultivation method and system are vitally important as these factors undoubtedly affect the final microalgae biomass and lipid yield. In this review, the cultivation system of microalgae, nutrients demanded for microalgae production, cell harvesting and drying, microalgae oil extraction, and utilization of microalgae biomass for biodiesel production are introduced and discussed. It is anticipated to convey clearer perspectives in upstream and downstream processes in microalgae-derived biodiesel production.
文摘A selective and sensitive competitive enzyme-linked immunosorbent assay(ELISA) method was developed and validated for the quantification of erlotinib in 50 mL of samples of human serum. Anti-erlotinib serum was obtained by immunizing mice with an antigen conjugated with bovine serum albumin and 3,4-bis(2-methoxyethoxy)benzoic acid using the N-succinimidyl ester method. Enzyme labeling of erlotinib with horseradish peroxidase was similarly performed using 3,4-bis(2-methoxyethoxy)benzoic acid. A simple competitive ELISA for erlotinib was developed using the principle of direct competition between erlotinib and the enzyme marker for anti-erlotinib antibody, which had been immobilized on the plastic surface of a microtiter plate. Serum erlotinib concentrations lower than 40 ng/mL were reproducibly measurable using the ELISA. This ELISA was specific to erlotinib and showed very slight cross-reactivity(6.7%) with a major metabolite, O-desmethyl erlotinib. Using this assay, drug levels were easily measured in the blood of mice after oral administration of erlotinib at a single dose of 30 mg/kg. ELISA should be used as a valuable tool for therapeutic drug monitoring and in pharmacokinetic studies of erlotinib.
文摘In the present study, new series of pyridinium carboxylate protic ionic liquids(PILs) were synthesized by pairing pyridinium cation with carboxylate anion from C_1–C_3 forming pyridinium formate([C_5H_6N^+][HCOO^-]),pyridinium acetate([C_5H_6N^+][CH_3COO^-]) and pyridinium propionate([C_5H_6N^+][CH_3CH_2COO^-]) respectively.The physical properties namely, density, viscosity, surface tension(298.15–343.15) K, and refractive index(293.15–323.15) K were measured. Thermal properties namely, glass transition temperature, molar heat capacity, and thermal decomposition temperatures were also determined. The thermal expansivity was calculated using the experimental density data. The effect of increasing the alkyl chain length on the thermophysical properties of the pyridinium carboxylate PILs has been evaluated. As expected the physical properties i.e. density,viscosity, surface tension and refractive index of the investigated pyridinium carboxylates decreased with increasing temperature. In general pyridinium carboxylate PILs possessed low viscosity, high thermal stability and excellent hydrogen bonding capability, and these properties lead them to outperform conventional solvents employed for lignin dissolution.
文摘Acid mine drainage （AMD） is one of the major problems in high sulfur coal mining areas generating acidic water. The acidic mine water generated contain hazardous elements in varying concentrations. The Northeastern Indian coalfield produces considerable amounts of AMD. The AMD and metal leaching from coal and mine over burden （OB） are the two important naturally occurring processes. In order to know the AMD potential, the aqueous leaching experiment of a few coal and OB samples from the Ledo colliery of the Northeastern coalfield, Mergherita （India）, at different time periods （1, 3, 5, and 8 h） and at different temperatures （25, 45, 65, and 90℃） were performed in the laboratory. The physico- chemical analysis of the aqueous leachates shows the pH, electrical conductivity （EC）, and total dissolved solid （TDS） in the range of 1.62-3.52, 106-2006 μs/cm, and 106-1003 ppm for the raw coal samples respectively. The OB samples produced pH, EC, and TDS in the range of 3.68-6.92, 48.6-480 μs/cm, and 69.5-240 ppm respectively. From the study, it was revealed that the concentrations of major （Si, A1, K, Na, Fe, Ca, Mg）, minor （Mn） and trace/hazardous elements （As, Ba, Cd, Co, Cr, Cu, Hg, Ni, Pb, Se, Zn） considerably change with leaching time as well as with leaching temperature. Out of these elements As, Cd, Hg, Pb, Cr, and Se are of greater environmental importance. Alteration of the physico-chemical structure of the coal and OB samples resulting from leaching was also studied by field emission scanning electron microscope- energy-dispersive X-ray spectroscopy method. The release of the potentially hazardous elements from the raw coal and OB during leaching time periods to the leachates was detected by inductively coupled plasma-atomic emission spectroscopy and ion-chromatographic analyses. The major minerals found in coal and OB are quartz （SiO2）, pyrite （FeS2）, hematite, marcasite, and kaolinite. The association of different functional groups in minerals and their mode of association were studied by Fourier-transform infrared spectroscopy and X-ray diffraction analytical techniques. The present laboratory study will be useful in relating the characteristics of aqueous leaching from coal and mine OB with the natural weathering condition at the coal mine area.
文摘A SiC nanofilms have been deposited and investigated on quartz and silicon substrates using pulsed laser deposition technique with the 300 pulses of Nd:YAG laser at two different laser wavelengths of 1064 nm and 532 nm.The structural,morphological,and optical properties of the deposited nanostructure SiC were prepared and characterized as a function of the wavelengths of the used laser.The structural result shows four different pecks at(111),(200),(220),and(311)planes related to Nano SiC.The transmission result presents that the optical energy gap value for the SiC nanostructure is depended on the wavelength of the used laser and it is found about the range(3.03 eV–3.23 eV).The investigations of the SEM and AFM show that the prepared SiC Nano-films having a grain size range(36.34–48.75)nm and roughness about 4.462 to 3.062 nm.SiC/Si hetero-junction devices show an enhanced performance at 532 nm.
基金the Leverhulme Trust(ECF-2018-691)the University of Warwick through an Early Career Fellowship.
文摘Since the olden times,infectious diseases have largely affected human existence.The newly emerged infections are excessively caused by viruses that are largely associated with mammal reservoirs.The casualties of these emergencies are significantly influenced by the way human beings interact with the reservoirs,especially the animal ones.In our review we will consider the evolutionary and the ecological scales of such infections and their consequences on the public health,with a focus on the pathogenic influenza A virus.The nutraceutical properties of fungal and plant terpene-like molecules will be linked to their ability to lessen the symptoms of viral infections and shed light on their potential use in the development of new drugs.New challenging methods in antiviral discovery will also be discussed in this review.The authors believe that pharmacognosy is the“wave of future pharmaceuticals”,as it can be continually produced and scaled up under ecofriendly requirements.Further diagnostic methods and strategies however are required to standardise those naturally occurring resources.
文摘The CCD photometric observations of open star cluster M37(NGC 2099) were carried out up to a limiting magnitude of V ～ 20 in both B and V filters to search for variable stars using a 2k×4k CCD and the 1.3 m telescope at the Vainu Bapu Observatory, Kavalur.A total of 314 stars were in the first observing run, out of which 60 were identified as variables.Eight out of the identified 60 variables are classified as W UMa binary stars.For model fitting, we used PHOEBE based on the W-D code to estimate the physical parameters of these newly detected W UMa binaries that theoretically best match the observed light curves.
基金supported by the Higher Education Research Promotion and National Research University Project of Thailand,Office of the Higher Education Commission, through the Advanced Functional Materials Cluster of Khon Kaen Universitythe Thailand Research Fund (TRF) under TRF Senior Research Scholar contract No.RTA5480004
文摘The Al-rich waste with aluminium and hydrocarbon as the major contaminant is generated at the wastewater treatment unit of a polymer processing plant. In this research, the heat treatment of this Al-rich waste and its use to adjust the silica/alumina ratio of the high calcium fly ash geopolymer were studied. To recycle the raw Al-rich waste, the waste was dried at 110℃ and calcined at 400 to 1000℃. Mineralogical analyses were conducted using X-ray diffraction （XRD） to study the phase change. The increase in calcination temperature to 600, 800, and 1000℃ resulted in the phase transformation. The more active alumina phase of active θ-Al2O3 was obtained with the increase in calcination temperature. The calcined Al-rich waste was then used as an additive to the fly ash geopolymer by mixing with high calcium fly ash, water glass, 10 M sodium hydroxide （NaOH）, and sand. Test results indicated that the calcined Al-rich waste could be used as an aluminium source to adjust the silica/alumina ratio and the strength of geopolymeric materials. The fly ash geopolymer mortar with 2.5wt% of the Al-rich waste calcined at 1000℃ possessed the 7-d compressive strength of 34.2 MPa.
文摘The Controlled Source Electromagnetic Method (CSEM) is used for offshore hydrocarbon exploration. Hydrocarbon detection in seabed logging (SBL) is a very challenging task for deep hydrocarbon reservoirs. The electromagnetic field response of an antenna is unable to detect deep hydrocarbon reservoirs due to a weak electromagnetic signal response in the seabed logging environment. This work premise deals with the comparison of the electromagnetic signal strength of a new antenna with a straight antenna and the orientation of an antenna for deep target hydrocarbon exploration. Antenna position and orientation (Tx and Ty) was studied using Computer Simulation Technology software (CST) for deep targets in marine CSEM environments. The model area was assigned as (40 ′ 40 km) to replicate the real seabed environment. From the results, the new dipole antenna shows an 804% and 278% increase in electric and magnetic field strength than the straight antenna. An electric (E) and magnetic (H) field component study was done with and without the presence of a hydrocarbon reservoir. Ex and Hz field component responses with the new antenna at the1 kmtarget were measured in a deep water environment. It was analyzed that the antenna shows 53.10% (Ex) and 83.13% (Hz) field difference in deep water with and without a hydrocarbon reservoir at the30 mantenna position from the sea floor. From the antenna orientation results, it was observed that, the electric field Ex and magnetic field Hz responses decreased from 18% to 12% and 21% to 16%, respectively but was still able to detect the deep target hydrocarbon reservoir at the4 kmtarget depth. This EM antenna may open new frontiers for the oil and gas industry for deep target hydrocarbon detection (HC).
基金the EOR Center at University Technology Petronas for providing financial support
文摘In this work, an experimental study combined with numerical simulation was conducted to investigate the potential of chemically enhanced water alternating gas （CWAG） injection as a new enhanced oil recovery method. The unique feature of this new method is that it uses alkaline, surfactant, and polymer additives as a chemical slug which is injected during the water alternating gas （WAG） process to reduce the interfacial tension （IFT） and simultaneously improve the mobility ratio. In essence, the proposed CWAG process involves a combination of chemical flooding and immiscible carbon dioxide （CO2） injection and helps in IFT reduction, water blocking reduction, mobility control, oil swelling, and oil viscosity reduction due to CO2 dissolution. Its performance was compared with the conventional immiscible water alter- nating gas （I-WAG） flooding. Oil recovery utilizing CWAG was better by 26 % of the remaining oil in place after waterflooding compared to the recovery using WAG conducted under similar conditions. The coreflood data （cumulative oil and water production） were history mat- ched via a commercial simulator by adjusting the relative permeability curves and assigning the values of the rock and fluid properties such as porosity, permeability, and the experimentally determined IFT data. History matching ofthe coreflood model helped us optimize the experiments and was useful in determining the importance of the parameters influencing sweep efficiency in the CWAG process. The effectiveness of the CWAG process in pro- viding enhancement of displacement efficiency is evident in the oil recovery and pressure response observed in the coreflood. The results of sensitivity analysis on CWAG slug patterns show that the alkaline-surfactant-polymer injection is more beneficial after CO2 slug injection due to oil swelling and viscosity reduction. The CO2 slug size analysis shows that there is an optimum CO2 slug size, around 25 % pore volume which leads to a maximum oil recovery in the CWAG process. This study shows that the ultralow IFT system, i.e., IFT equaling 10 2 or 10 3 mN/ m, is a very important parameter in CWAG process since the water blocking effect can be minimized.
