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Dielectric Response of(Ba,Sr)TiO_(3) Thin Films under Tensile Strain
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作者 YU Zhanbo MA Xingyue +3 位作者 WU Zongshuo GAO Zhihao WU Di YANG Yurong 《硅酸盐学报》 北大核心 2025年第4期800-807,共8页
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
关键词 MULTI-DOMAIN dielectric response effective Hamiltonian method FIRST-PRINCIPLES
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Workplace bullying and its association with secondary traumatic stress and turnover intention among emergency and critical care nurses
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作者 Sandi Mashsha Ahmad Rayan +3 位作者 Manal Hassan Baqeas Suhair Hussni Al-Ghabeesh Yasmeen Abu Sumaqa Nour Ali Assaf Alrida 《Frontiers of Nursing》 2025年第1期79-90,共12页
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
关键词 critical care units emergency department STS turnover intention workplace bullying
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Enhanced Oil Recovery in Sandstone Reservoirs: A Review of Mechanistic Advances and Hydrocarbon Predictive Techniques
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作者 Surajudeen Sikiru Jemilat Yetunde Yusuf +3 位作者 Hassan Soleimani Niraj Kumar Ziaur Rehman Bonnia N N 《Energy Engineering》 2025年第10期3917-3960,共44页
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
关键词 Enhanced oil recovery rock permeability reservoir fluid POROSITY fluid flow
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Unsteady Flow of Hybrid Nanofluid with MagnetohydrodynamicsRadiation-Natural Convection Effects in a U-Shaped Wavy Porous Cavity
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作者 Taher Armaghani Lioua Kolsi +4 位作者 Najiyah Safwa Khashi’ie Ahmed Muhammed Rashad Muhammed Ahmed Mansour Taha Salah Aboulbaba Eladeb 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第12期2225-2251,共27页
In this paper,the unsteady magnetohydrodynamic(MHD)-radiation-natural convection of a hybrid nanofluid within a U-shaped wavy porous cavity is investigated.This problem has relevant applications in optimizing thermal ... In this paper,the unsteady magnetohydrodynamic(MHD)-radiation-natural convection of a hybrid nanofluid within a U-shaped wavy porous cavity is investigated.This problem has relevant applications in optimizing thermal management systems in electronic devices,solar energy collectors,and other industrial applications where efficient heat transfer is very important.The study is based on the application of a numerical approach using the Finite Difference Method(FDM)for the resolution of the governing equations,which incorporates the Rosseland approximation for thermal radiation and the Darcy-Brinkman-Forchheimer model for porous media.It was found that the increase of Hartmann number(Ha)causes a reduction of the average Nusselt number(Nu),with a maximum decrease of 25%observed as Ha increases from 0 to 50.In addition,the influence of the wall’s wave amplitude and the heat source length on the heat transfer rate was quantified,and it was revealed that at high wave amplitude,the average Nu increases by up to 15%.These findings suggest that manipulating magnetic field strength and cavity geometry can significantly enhance thermal performance.The novelty of this is related to the exploration of a U-shaped wavy cavity,which is not covered in previous studies,and to the detailed examination of the combined effects of magnetic fields,radiation,and hybrid nanofluids. 展开更多
关键词 Thermal radiation wavy wall MHD natural convection hybrid-nanofluid porous medium
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Exploring dielectric phenomena in sulflower-like nanostructures via Monte Carlo technique
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作者 N Saber Z Fadil +7 位作者 Hussein Sabbah A Mhirech B Kabouchi L Bahmad Chaitany Jayprakash Raorane Siva Sankar Sana Hassan Fouad Mohamed Hashem 《Communications in Theoretical Physics》 SCIE CAS CSCD 2024年第4期188-198,共11页
This research focuses on the electric behavior of a mixed ferrielectric sulflower-like nanostructure.The structure includes a core with spin S_(i)^(Z)-1 atoms and a shell with spin σ_(j)^(Z)-5/2 atoms.The Blume–Cape... This research focuses on the electric behavior of a mixed ferrielectric sulflower-like nanostructure.The structure includes a core with spin S_(i)^(Z)-1 atoms and a shell with spin σ_(j)^(Z)-5/2 atoms.The Blume–Capel model and the Monte Carlo technique(MCt)with the Metropolis algorithm are employed.Diagrams are established for absolute zero,investigating stable spin configurations correlated with various physical parameters.The MCt method explores phase transition behavior and electric hysteresis cycles under different physical parameters. 展开更多
关键词 sulfower-like nanostructure dielectric characteristics Monte Carlo technique phase transition phase diagrams electric hysteresis
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New Asymptotic Results on Fermat-Wiles Theorem
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作者 Kimou Kouadio Prosper Kouakou Kouassi Vincent Tanoé François 《Advances in Pure Mathematics》 2024年第6期421-441,共21页
We analyse the Diophantine equation of Fermat xp yp = zp with p > 2 a prime, x, y, z positive nonzero integers. We consider the hypothetical solution (a, b, c) of previous equation. We use Fermat main divisors, Dio... We analyse the Diophantine equation of Fermat xp yp = zp with p > 2 a prime, x, y, z positive nonzero integers. We consider the hypothetical solution (a, b, c) of previous equation. We use Fermat main divisors, Diophantine remainders of (a, b, c), an asymptotic approach based on Balzano Weierstrass Analysis Theorem as tools. We construct convergent infinite sequences and establish asymptotic results including the following surprising one. If z y = 1 then there exists a tight bound N such that, for all prime exponents p > N , we have xp yp zp. 展开更多
关键词 Fermat’s Last Theorem Fermat-Wiles Theorem Kimou’s Divisors Diophantine Quotient Diophantine Remainders Balzano Weierstrass Analysis Theorem
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The Detrimental Influence of Heavy Metals and Contaminants on Food Production and Consumption
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作者 Olusoji David Alabi Asogan Gounden +2 位作者 Kubendran Kista Naidoo Jason John Mellem Vimla Paul 《Journal of Environmental Protection》 2024年第12期1035-1055,共21页
Contaminated foods with pesticide residues, mycotoxins, and heavy metals pose significant health risks to humans. Fungal mycotoxins, which are organ toxins and cancer-causing agents, can cause long-term diseases like ... Contaminated foods with pesticide residues, mycotoxins, and heavy metals pose significant health risks to humans. Fungal mycotoxins, which are organ toxins and cancer-causing agents, can cause long-term diseases like cancer and acute poisoning. Natural preservatives like essential oils or preservatives were tested for safety. Heavy metals, such as cadmium, lead, and mercury, are the most dangerous pollutants, causing long-term diseases like cancer and acute poisoning. Moreover, extreme weather events increase fungal infestation, thereby increasing the levels of mycotoxins in meals and posing a threat to human life through unsafe food consumption. Bioremediation and phytoremediation techniques use microorganisms and plants to clean water and soil, but have limitations due to applicability limits. Gene modification can solve these limitations. Composted sewage sludge with CuO nanoparticles may improve plant tolerance against metal stress, but high levels may increase As content in crops like rice. Technological advancements have made it easier to detect these pollutants, but strict rules should be in place to limit their presence. Sustainable plant protection methods and biomass-derived materials can be an eco-friendly alternative to conventional pesticides in large-scale farming systems. A holistic approach is needed to address these issues, including comprehensive strategies like quality control measures and mitigation approaches. These should reduce emission rates and monitor pollution levels in food crops grown across different regions. Policymakers should established guidelines to ensure that safe production processes are followed at every stage, from planting to harvesting, processing, and transportation. Failure to follow these steps may lead to more problems than solutions. 展开更多
关键词 CONTAMINATION Heavy Metal MYCOTOXIN Food HARVEST DISEASES Control
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Muscle Strength, Lumbar Curve, Fear of Movement and Functional Disability among Patients with Lumbar Disc Herniation: A Review
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作者 G. M. Jakaria Chua Siew Kuan 《Open Journal of Therapy and Rehabilitation》 2024年第1期28-51,共24页
Introduction: Lumbar disc herniation (LDH) refers to the rupture of the fibrous annulus of the intervertebral discs. Lumbar curvature may lead to the occurrence of lumbar disc degeneration. Fear of movement may worsen... Introduction: Lumbar disc herniation (LDH) refers to the rupture of the fibrous annulus of the intervertebral discs. Lumbar curvature may lead to the occurrence of lumbar disc degeneration. Fear of movement may worsen their disc herniation and cause further pain and injury. LDH conditions impact the individuals’ quality of life, to explore the relationship between lumbar curve, muscle strength, fear of movement and functional disability among patients with LDH. Methods: An electronic search was conducted on PubMed, Medline, Science Direct, Springerlink, Google Scholar and a hand search from reference lists was reviewed. Publications were included in human studies, patients 25 - 85 years of age, original studies and published in English language journals from January 2002 to December 2023. Result: In total, 64 articles were researched through the online search engines, and 9 papers were found through manual searches of reference lists. As a result, a total of 11 articles were included for the purpose of this review. The comprehensive analysis revealed the presence of eight cross-sectional studies, two retrospective studies and one experimental study. A minimum of 25 participants and a maximum of 360 participants were included. Ten studies included both genders, only one studies included healthy adults and patients with LDH but these studies didn’t mention gender. Results showed that the factors influencing LDH can be categorized into non-modifiable factors, such as gender, age, height or others. Modifiable factors included increased BMI, DM, smoking, alcohol, employment status, lifestyle and health problems or psychology. Conclusion: Females with greater VASC may be at risk of LDH. The lumbar extensor muscles indicated a localized disc herniation or nerve root pathology in patients with LDH. The fear of movement may lead to psychological consequences and reduce functional disability among patients with LDH. 展开更多
关键词 Lumbar Disc Herniation Fear of Movement Functional Disability Vertical Angle of Spinal Curvature
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Genetic Disposition: Susceptibility of Human Blood Groups and Abo Analysis to Malaria and Typhoid Infections
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作者 Mbeh Ubana Eteng Ekpe Onot Okon +12 位作者 Nyakno Akpan Essien Ugochukwu Iloh Godwin Oju Igile Patrick Ubi Esukwu Richard Undigweundeye Ukpanukpong Ubong Edet Akpan Adaeze Bobchile-Agada Etim Esin Etim John Ojuwu Ojowu Nnennaya Precious Akpa-Onyeabor Ayiku Audu Fanziya Mary Joan Obianuju Ngumah Mcvain Akpam Ugor 《Advances in Infectious Diseases》 CAS 2024年第3期497-510,共14页
Background: Malaria and typhoid have remained major infectious tropical diseases. Clinically, whenever there is severe malaria, cough is always an associating symptom owing to typhoid infection arising from poor hygie... Background: Malaria and typhoid have remained major infectious tropical diseases. Clinically, whenever there is severe malaria, cough is always an associating symptom owing to typhoid infection arising from poor hygiene in respect to drinking water and food. There is a strong association between human blood group and disease. Residual malaria transmission, effect of climate change on malaria vector composition, environmental management targeted at malaria breeding control as an intervention strategy are areas of interest to WHO in malaria control in Sub-saharan Africa. A body of data is been built on susceptibility of human blood groups to malaria, HIV and HBV and presently malaria and typhoid. If climate change warrants a change in composition of vectors and as well resistance to ACT therapy, the susceptibility or vulnerability of the human blood group is also called to question. The link between susceptibility of human blood group to malaria and typhoid has not been previously investigated. Purpose: The present study assesses the genetic disposition (susceptibility of human blood groups and abo analysis) to malaria and typhoid infections. Patients and Methods: One hundred (100) patients were screened for malaria and typhoid infections in a tertiary health facility—His glory hospital Lagos, Nigeria. Blood samples were collected by venu-puncture from 53 females and 47 males adults aged between 15 – 47 years, who were infected either singly or coinfected with malaria and typhoid. Microscopic detection of P. falciparum, widal serological technique for salmonella antibody presence and genotypic determination were all done using standard WHO methods. Human material or data were analyzed or performed in accordance with the declaration of Helsinki (2000). Ethical clearance was obtained from the ethic and research committee of the Ministry of Health via the Faculty of the Basic Medical Sciences, University of Calabar (Ethical Certificate number CRS/MOH/HRP/2023/396). Results: The results obtained expressed in percentage frequency show that genotype AA were more susceptible to typhoid and malaria infections compared to AS and SS, also blood group O was more susceptible to malaria and typhoid infection compared to blood groups A, AB and B, although, there is no significant difference between male and female gender, susceptibility to malaria infection, the female gender is more susceptible to typhoid than the male. The finding may be relevant to malaria susceptibility and genetics and thus provide baseline information on management of the scourge. Conclusion: We conclude that genotype AA and blood group 0+ are more susceptible to malaria and typhoid infection in humans. 展开更多
关键词 MALARIA Plasmodium Falciparium GENOTYPE Genetig Disposition
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The impact of tobacco use and nicotine addiction on health: A literature review of nursing interventions for smoking cessation
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作者 Raghad ABDELKADER Roqia Saleem MAABREH +9 位作者 Riyad AL-DGHEIM Naif Salem ALTARAWNEH Mahmoud HALRABAB’A Hala ZAITON Amaal Samir ABDELMAKSOUD Wesam T.ALMAGHARBEH Khaldoon Aied ALNAWAFLEH Hazem A.ALFANASH Zyad T.SALEH Rami Azmi ELSHATARAT 《Journal of Integrative Nursing》 2024年第4期218-230,共13页
Tobacco use remains one of the leading preventable causes of morbidity and mortality globally,with nicotine addiction significantly impacting health outcomes.This literature review explores the multifaceted nature of ... Tobacco use remains one of the leading preventable causes of morbidity and mortality globally,with nicotine addiction significantly impacting health outcomes.This literature review explores the multifaceted nature of tobacco use and its health implications,emphasizing the role of nursing interventions in smoking cessation.The review highlights various strategies employed by nurses,including assessment,counseling,pharmacotherapy support,and behavioral interventions,which are essential for effective tobacco cessation.By analyzing current evidence-based practices,the study underscores the importance of comprehensive assessments and personalized care plans tailored to individual patient needs.It also addresses the significance of motivational interviewing and the 5 A’s framework in facilitating successful quit attempts.In addition,the review discusses the integration of cognitive-behavioral therapy and stress management techniques as vital components of behavioral interventions.Recommendations for improving tobacco cessation efforts include enhanced training for healthcare professionals,the establishment of community-based support groups,and advocacy for robust tobacco control policies.The findings underscore the critical need for ongoing research into the long-term effectiveness of cessation interventions across diverse populations.This study aims to inform nursing practice and public health policy,ultimately contributing to the reduction of tobacco-related health issues and promoting healthier communities. 展开更多
关键词 ADDICTION clinical interventions health hazards policy advocacy public health secondhand smoke smoking cessation tobacco use
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旋转控制头胶芯性能的影响因素分析 被引量:1
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作者 何宇航 吴霁薇 +3 位作者 郑立伟 侯作富 夏成宇 钱利勤 《石油机械》 北大核心 2020年第8期16-22,共7页
为了研究旋转控制头胶芯配方及胶芯的使用和储存温度对其密封性能的影响,基于虚功原理应用橡胶单轴压缩试验确立了胶芯变形过程中Yeoh本构模型,利用ABAQUS软件建立了旋转控制头胶芯动态密封仿真模型,讨论了摩擦因数、材料配方及温度对... 为了研究旋转控制头胶芯配方及胶芯的使用和储存温度对其密封性能的影响,基于虚功原理应用橡胶单轴压缩试验确立了胶芯变形过程中Yeoh本构模型,利用ABAQUS软件建立了旋转控制头胶芯动态密封仿真模型,讨论了摩擦因数、材料配方及温度对旋转控制头胶芯密封性能的影响。分析结果表明:采用Yeoh本构模型能够较好地拟合胶芯材料的大变形现象;胶芯的密封性能随着摩擦因数的增大而增强,但摩擦因数过大会加速胶芯失效,推荐胶芯材料摩擦因数为0.40;低温储存和运输过程对旋转控制头胶芯的力学性能影响不大,但在使用前需做充分预热处理;高温环境下,胶芯材料的拉伸强度随温度的升高先降低后增加,在65℃左右降到最低。所得结果可为提高国产旋转控制头胶芯的性能提供参考。 展开更多
关键词 旋转控制头 胶芯 Yeoh本构模型 橡胶材料 有限元
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井下水力增压器设计与仿真分析 被引量:1
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作者 黄壮 夏成宇 +3 位作者 何宇航 郭良林 冯超 吴霁薇 《石油机械》 北大核心 2021年第10期99-107,共9页
现有研究采用简化处理增压腔模型或只利用数值模拟仿真水力增压器增压性能,可能导致计算结果不可靠。为此,基于实际钻井工艺要求,设计了利用井下水力能量增压的井下水力增压器。根据增压器的结构和工作原理,建立了增压腔的数学模型和流... 现有研究采用简化处理增压腔模型或只利用数值模拟仿真水力增压器增压性能,可能导致计算结果不可靠。为此,基于实际钻井工艺要求,设计了利用井下水力能量增压的井下水力增压器。根据增压器的结构和工作原理,建立了增压腔的数学模型和流体域模型,采用Matlab数值模拟和Fluent动网格技术仿真对增压腔的增压特性进行研究,并将两者结果进行对比分析,以验证研究结果的正确性。研究结果表明:增压过程中,活塞运动速度、流体出射速度及有杆增压腔流体压力均随时间延长呈现出先增大后逐渐趋于稳定的规律;随着高压出口直径的减小和低压腔与有杆增压腔有效作用面积比的增大,有杆增压腔内流体压力增大,高压出口处流体出射速度增大,增压器的增压效果越明显;对增压腔结构参数进行优选,当高压出口直径不大于8 mm、低压腔与有杆增压腔的有效作用面积比不小于3.5时,可增强增压器增压效果。研究结果可为增压器的优化设计提供理论支持。 展开更多
关键词 井下增压器 增压腔 高压射流 活塞速度 MATLAB Fluent动网格技术
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基于离子液的超声辅助萃取小蓼叶中的精油及真实溶剂似导体屏蔽模型研究 被引量:4
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作者 Habib ULLAH Cecilia D WILFRED Maizatul S SHAHARUN 《色谱》 CAS CSCD 北大核心 2017年第6期656-664,共9页
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
关键词 gas chromatography mass spectrometry(GC-MS) IONIC liquid(IL) ultrasonication optimization Persicaria MINOR essential oil
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Green synthesis,antimicrobial and cytotoxic effects of silver nanoparticles using Eucalyptus chapmaniana leaves extract 被引量:4
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作者 Ghassan Mohammad Sulaiman Wasnaa Hatif Mohammed +3 位作者 Thorria Radam Marzoog Ahmed Abdul Amir Al-Amiery Abdul Amir H.Kadhum Abu Bakar Mohamad 《Asian Pacific Journal of Tropical Biomedicine》 SCIE CAS 2013年第1期58-63,共6页
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
关键词 EUCALYPTUS chapmaniana Silver nanoparticles ANTIMICROBIAL activity CYTOTOXIC effect
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Exact solutions of nonlinear fractional differential equations by (G'/G)-expansion method 被引量:6
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作者 Ahmet Bekir zkan Güner 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第11期140-145,共6页
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
关键词 (G'/G)-expansion method time-fractional Burgers equation fractional-order biological popula-tion model space-time fractional Whitham-Broer-Kaup equations
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Effectiveness of sloping agricultural land technology on soil fertility status of mid-hills in Nepal 被引量:3
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作者 Kiran Lamichhane 《Journal of Forestry Research》 SCIE CAS CSCD 2013年第4期767-775,共9页
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
关键词 Sloping Agricultural Land Technology HEDGEROWS AGROFORESTRY mountain fanning system soil erosion soil nutrient
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How Polymers Behave as Viscosity Index Improvers in Lubricating Oils 被引量:5
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作者 Michael J. Covitch Kieran J. Trickett 《Advances in Chemical Engineering and Science》 2015年第2期134-151,共18页
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
关键词 VISCOSITY Index IMPROVER VISCOSITY MODIFIER Polymer SMALL-ANGLE NEUTRON Scattering RHEOLOGY
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Cultivation of microalgae for biodiesel production:A review on upstream and downstream processing 被引量:8
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作者 Xin Bei Tan Man Kee Lam +3 位作者 Yoshimitsu Uemura Jun Wei Lim Chung Yiin Wong Keat Teong Lee 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2018年第1期17-30,共14页
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
关键词 Microalgae Cultivation Lipid Biodiesel Harvesting
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Quantitative determination of erlotinib in human serum using competitive enzyme-linked immunosorbent assay 被引量:1
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作者 Yuta Yamamoto Tetsuya Saita +1 位作者 Yutaro Yamamoto Masashi Shin 《Journal of Pharmaceutical Analysis》 SCIE CAS CSCD 2018年第2期119-123,共5页
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
关键词 ERLOTINIB Enzyme-linked IMMUNOSORBENT ASSAY O-desmethyl ERLOTINIB TYROSINE-KINASE INHIBITOR
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Effect of alkyl chain length on the thermophysical properties of pyridinium carboxylates 被引量:1
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作者 Tazien Rashid Chong Fai Kait Thanabalan Murugesan 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2017年第9期1266-1272,共7页
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
关键词 Protic ionic liquids PYRIDINE Carboxylic acids ANION Physicochemical properties
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