Optical selection rules fundamentally determine the optical transitions between energy states in a variety of physical systems,from hydrogen atoms to bulk crystals such as gallium arsenide.These rules are important fo...Optical selection rules fundamentally determine the optical transitions between energy states in a variety of physical systems,from hydrogen atoms to bulk crystals such as gallium arsenide.These rules are important for optoelectronic applications such as lasers,energy-dispersive X-ray spectroscopy,and quantum computation.Recently,single-layer transition metal dichalcogenides have been found to exhibit valleys in momentum space with nontrivial Berry curvature and excitons with large binding energy.However,there has been little study of how the unique valley degree of freedom combined with the strong excitonic effect influences the nonlinear optical excitation.Here,we report the discovery of nonlinear optical selection rules in monolayer WS2,an important candidate for visible 2D optoelectronics because of its high quantum yield and large direct bandgap.We experimentally demonstrated this principle for second-harmonic generation and two-photon luminescence(TPL).Moreover,the circularly polarized TPL and the study of its dynamics evince a sub-ps interexciton relaxation(2p R 1s).The discovery of this new optical selection rule in a valleytronic 2D system not only considerably enhances knowledge in this area but also establishes a foundation for the control of optical transitions that will be crucial for valley optoelectronic device applications such as 2D valley-polarized THz sources with 2p–1s transitions,optical switches,and coherent control for quantum computing.展开更多
This paper presents a three-dimensional, three-phase compositional model considering CO2 phase equilibrium between water and oil. In this model, CO2 is mutually soluble in aqueous and hydrocarbon phases, while other c...This paper presents a three-dimensional, three-phase compositional model considering CO2 phase equilibrium between water and oil. In this model, CO2 is mutually soluble in aqueous and hydrocarbon phases, while other components, except water,exist in hydrocarbon phase. The Peng–Robinson(PR) equation of state and the Wong–Sandler mixing rule with non-random two-liquid parameters are used to calculate CO2 fugacity in the aqueous phase. One-dimensional and three-dimensional CO2 flooding examples show that a significant amount of injected CO2 is dissolved in water. Our simulation shows 7% of injected CO2 can be dissolved in the aqueous phase, which delays oil recovery by 4%. The gas rate predicted by the model is smaller than the conventional model as long as water is undersaturated by CO2, which can be considered as 'lost' in the aqueous phase. The model also predicts that the delayed oil can be recovered after the gas breakthrough, indicating that delayed oil is hard to recover in field applications. A three-dimensional example reveals that a highly stratified reservoir causes uneven displacement and serious CO2 breakthrough. If mobility control measures like water alternating gas are undertaken, the solubility e ects will be more pronounced than this example.展开更多
The phase equilibrium data of CO2 hydrocarbon binary mixtures are important for the design and operation of CO 2 ood- ing, coal liquefaction, and supercritical extraction processes. Numerous pieces of binary phase equ...The phase equilibrium data of CO2 hydrocarbon binary mixtures are important for the design and operation of CO 2 ood- ing, coal liquefaction, and supercritical extraction processes. Numerous pieces of binary phase equilibrium data have been obtained. Thus, models for the accurate calculation of binary and multicomponent mixtures must be developed on the basis of existing data. In this work, 3578 vapor liquid phase equilibrium data points for 10 CO 2 hydrocarbon binary mixtures, including CO2 butane, CO 2 pentane, CO 2 isopentane, C O 2 hexane, CO 2 benzene, CO 2 heptane, CO 2 octane, C O 2 non- ane, CO 2 decane, and C O 2 undecane, were collected. The PR and PR-BM equations of state (EOS) in combination with relevant mixing rules were used to calculate the phase equilibrium data of the CO 2 hydrocarbon binary mixtures. The binary interaction parameter k ij in the PR EOS was temperature independent, whereas parameters in the PR-BM EOS were functions of temperature. Thus, the phase equilibrium data and other thermodynamic properties of the binary and multicomponent mixtures at di erent temperatures and pressures can be calculated by using the parameters obtained in this work. The PR-BM EOS performed better than the PR EOS, and the average absolute deviations over the temperature range of 255.98 408.15 K calculated by the PR EOS and PR-BM EOS were less than 5.74% and 3.36%, respectively. The results calculated by the two EOS were compared with those calculated by other models, such as PPR78, PR + LCVM + UNIFAC, KIE + PR EOS + HV, and PSRK. The phase equilibrium data of CO 2 butane decane, CO 2 hexane decane, and C O 2 octane decane ternary mixtures were calculated by the two EOS. The average overall deviations for the CO 2 mole fractions calculated by the two EOS were less than 7.66%.展开更多
The first-order resonant Raman spectra of monolayer MoS_(2)are calculated under the circularly polarized photoexcitation.The anomalously nonzero Raman intensity of the in-plane E mode under the Z(σ+σ+)Zor Z(σ−σ−)Z...The first-order resonant Raman spectra of monolayer MoS_(2)are calculated under the circularly polarized photoexcitation.The anomalously nonzero Raman intensity of the in-plane E mode under the Z(σ+σ+)Zor Z(σ−σ−)Zgeometry,which goes against the conventional selection rule,appears under some circum-stances when optical absorption occurs at some special reciprocal points between the zone-center Γ and the zone-edge-center M points.At that moment,the valley selectivity to the circular polarization is lifted.The analysis shows that the anomalous Raman intensity of the E mode for the same circularly polarized incident and scattered light is consistent with the pseudo-angular-momentum conservation law.The cal-culated E Raman tensor of monolayer MoS_(2)is found to vary with laser energy.The two diagonal terms of the Raman tensor change their signs from mutually opposite to the same when the relative intensity of the in-plane E mode to the out-of-plane A'_(1)mode increases,indicating the increasingly important role played by the Frölich-type electron-phonon interaction over the deformation potential.Our study may shed new light on the understanding of the novel electron-photon process and assist in the design of new type of optoelectronic devices.展开更多
[ Objective] The research aimed to study response rule of the M. aeruginosa fluorescence on the biological toxicity of HgCI2. [ Method ] M. aeruginosa as material, fluorescence intensity at its best excitation and emi...[ Objective] The research aimed to study response rule of the M. aeruginosa fluorescence on the biological toxicity of HgCI2. [ Method ] M. aeruginosa as material, fluorescence intensity at its best excitation and emission wavelengths as measured indicator, influence of the HgCI2 at different mass concentrations on fluorescence intensity of the M. aeruginosa was discussed initially. [ Result] HgCI2 at different mass concentrations had different influences on M. aeruginosa. HgCI2 at low concentration （0.002 -0.004 mg/L）could promote photosynthesis of the M. aeruginosa. It showed as fluorescence value of the algae liquid becoming smaller. 0.010 -0.400 mg/L of HgCI2 inhibited photosynthesis of the M. aeruginosa. It showed as fluorescence value of the algae liquid becoming bigger. Moreover, inhibition effect increased as HgCI2 concentration rose, showing a positive correlation between HgCI2 concentration and toxicity （ R 2 = 0.963 5 ）. [ Conclusion ] The research provided new theoretical basis for quickly measuring water toxicity.展开更多
目的探讨手测量法则食物交换份法在社区2型糖尿病(T2DM)患者饮食指导中的应用效果。方法于2013年1月,采用随机数字表法在浙江省舟山市桃湾社区和城隍头社区各抽取确诊为T2DM的患者60例,为避免同村内糖尿病患者之间知识交流,以地理位置...目的探讨手测量法则食物交换份法在社区2型糖尿病(T2DM)患者饮食指导中的应用效果。方法于2013年1月,采用随机数字表法在浙江省舟山市桃湾社区和城隍头社区各抽取确诊为T2DM的患者60例,为避免同村内糖尿病患者之间知识交流,以地理位置为分界线,将城隍头社区的患者作为对照组,桃湾社区的患者作为试验组。对照组采用常规健康教育进行饮食指导,试验组在常规健康教育基础上采用手测量法则食物交换份法进行饮食指导。干预6个月后,分别对两组患者进行饮食知识调查和生化指标检测。结果干预前,两组患者饮食知识调查情况和生化指标检测情况比较,差异无统计学意义(P>0.05);干预后,与对照组比较,试验组患者的体质指数(BMI)、空腹血糖(FPG)、餐后2 h血糖(2 h PG)、糖化血红蛋白(Hb A1c)及血脂水平下降;饮食基本知识、饮食行为习惯及实践操作得分升高,差异有统计学意义(P<0.01)。结论手测量法则食物交换份法为临床医生和糖尿病患者提供了简便的热量计算方法,极大地提高了糖尿病患者的饮食依从性,可以有效地帮助糖尿病患者控制血糖和血脂,延缓其并发症的发生。展开更多
基金This work was supported by the“Light-Material Interactions in Energy Conversion”Energy Frontier Research Center funded by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences under Award Number DE-AC02-05CH11231.
文摘Optical selection rules fundamentally determine the optical transitions between energy states in a variety of physical systems,from hydrogen atoms to bulk crystals such as gallium arsenide.These rules are important for optoelectronic applications such as lasers,energy-dispersive X-ray spectroscopy,and quantum computation.Recently,single-layer transition metal dichalcogenides have been found to exhibit valleys in momentum space with nontrivial Berry curvature and excitons with large binding energy.However,there has been little study of how the unique valley degree of freedom combined with the strong excitonic effect influences the nonlinear optical excitation.Here,we report the discovery of nonlinear optical selection rules in monolayer WS2,an important candidate for visible 2D optoelectronics because of its high quantum yield and large direct bandgap.We experimentally demonstrated this principle for second-harmonic generation and two-photon luminescence(TPL).Moreover,the circularly polarized TPL and the study of its dynamics evince a sub-ps interexciton relaxation(2p R 1s).The discovery of this new optical selection rule in a valleytronic 2D system not only considerably enhances knowledge in this area but also establishes a foundation for the control of optical transitions that will be crucial for valley optoelectronic device applications such as 2D valley-polarized THz sources with 2p–1s transitions,optical switches,and coherent control for quantum computing.
基金financially supported by National Natural Science Foundation of China(U1762101)National Science and Technology Major Projects(2017ZX05069)
文摘This paper presents a three-dimensional, three-phase compositional model considering CO2 phase equilibrium between water and oil. In this model, CO2 is mutually soluble in aqueous and hydrocarbon phases, while other components, except water,exist in hydrocarbon phase. The Peng–Robinson(PR) equation of state and the Wong–Sandler mixing rule with non-random two-liquid parameters are used to calculate CO2 fugacity in the aqueous phase. One-dimensional and three-dimensional CO2 flooding examples show that a significant amount of injected CO2 is dissolved in water. Our simulation shows 7% of injected CO2 can be dissolved in the aqueous phase, which delays oil recovery by 4%. The gas rate predicted by the model is smaller than the conventional model as long as water is undersaturated by CO2, which can be considered as 'lost' in the aqueous phase. The model also predicts that the delayed oil can be recovered after the gas breakthrough, indicating that delayed oil is hard to recover in field applications. A three-dimensional example reveals that a highly stratified reservoir causes uneven displacement and serious CO2 breakthrough. If mobility control measures like water alternating gas are undertaken, the solubility e ects will be more pronounced than this example.
基金supported by the National Key Research and Development Program of China (2016YFB0600804-3)Shandong Natural Science Foundation (ZR2017BB076)
文摘The phase equilibrium data of CO2 hydrocarbon binary mixtures are important for the design and operation of CO 2 ood- ing, coal liquefaction, and supercritical extraction processes. Numerous pieces of binary phase equilibrium data have been obtained. Thus, models for the accurate calculation of binary and multicomponent mixtures must be developed on the basis of existing data. In this work, 3578 vapor liquid phase equilibrium data points for 10 CO 2 hydrocarbon binary mixtures, including CO2 butane, CO 2 pentane, CO 2 isopentane, C O 2 hexane, CO 2 benzene, CO 2 heptane, CO 2 octane, C O 2 non- ane, CO 2 decane, and C O 2 undecane, were collected. The PR and PR-BM equations of state (EOS) in combination with relevant mixing rules were used to calculate the phase equilibrium data of the CO 2 hydrocarbon binary mixtures. The binary interaction parameter k ij in the PR EOS was temperature independent, whereas parameters in the PR-BM EOS were functions of temperature. Thus, the phase equilibrium data and other thermodynamic properties of the binary and multicomponent mixtures at di erent temperatures and pressures can be calculated by using the parameters obtained in this work. The PR-BM EOS performed better than the PR EOS, and the average absolute deviations over the temperature range of 255.98 408.15 K calculated by the PR EOS and PR-BM EOS were less than 5.74% and 3.36%, respectively. The results calculated by the two EOS were compared with those calculated by other models, such as PPR78, PR + LCVM + UNIFAC, KIE + PR EOS + HV, and PSRK. The phase equilibrium data of CO 2 butane decane, CO 2 hexane decane, and C O 2 octane decane ternary mixtures were calculated by the two EOS. The average overall deviations for the CO 2 mole fractions calculated by the two EOS were less than 7.66%.
基金financially supported by the National Natural Science Foundation of China(Nos.52031014 and 51702146)the National Key R&D Program of China(No.2017YFA0206301)。
文摘The first-order resonant Raman spectra of monolayer MoS_(2)are calculated under the circularly polarized photoexcitation.The anomalously nonzero Raman intensity of the in-plane E mode under the Z(σ+σ+)Zor Z(σ−σ−)Zgeometry,which goes against the conventional selection rule,appears under some circum-stances when optical absorption occurs at some special reciprocal points between the zone-center Γ and the zone-edge-center M points.At that moment,the valley selectivity to the circular polarization is lifted.The analysis shows that the anomalous Raman intensity of the E mode for the same circularly polarized incident and scattered light is consistent with the pseudo-angular-momentum conservation law.The cal-culated E Raman tensor of monolayer MoS_(2)is found to vary with laser energy.The two diagonal terms of the Raman tensor change their signs from mutually opposite to the same when the relative intensity of the in-plane E mode to the out-of-plane A'_(1)mode increases,indicating the increasingly important role played by the Frölich-type electron-phonon interaction over the deformation potential.Our study may shed new light on the understanding of the novel electron-photon process and assist in the design of new type of optoelectronic devices.
基金Supported by National 863 Item,China (2007AA092201)
文摘[ Objective] The research aimed to study response rule of the M. aeruginosa fluorescence on the biological toxicity of HgCI2. [ Method ] M. aeruginosa as material, fluorescence intensity at its best excitation and emission wavelengths as measured indicator, influence of the HgCI2 at different mass concentrations on fluorescence intensity of the M. aeruginosa was discussed initially. [ Result] HgCI2 at different mass concentrations had different influences on M. aeruginosa. HgCI2 at low concentration （0.002 -0.004 mg/L）could promote photosynthesis of the M. aeruginosa. It showed as fluorescence value of the algae liquid becoming smaller. 0.010 -0.400 mg/L of HgCI2 inhibited photosynthesis of the M. aeruginosa. It showed as fluorescence value of the algae liquid becoming bigger. Moreover, inhibition effect increased as HgCI2 concentration rose, showing a positive correlation between HgCI2 concentration and toxicity （ R 2 = 0.963 5 ）. [ Conclusion ] The research provided new theoretical basis for quickly measuring water toxicity.
文摘目的探讨手测量法则食物交换份法在社区2型糖尿病(T2DM)患者饮食指导中的应用效果。方法于2013年1月,采用随机数字表法在浙江省舟山市桃湾社区和城隍头社区各抽取确诊为T2DM的患者60例,为避免同村内糖尿病患者之间知识交流,以地理位置为分界线,将城隍头社区的患者作为对照组,桃湾社区的患者作为试验组。对照组采用常规健康教育进行饮食指导,试验组在常规健康教育基础上采用手测量法则食物交换份法进行饮食指导。干预6个月后,分别对两组患者进行饮食知识调查和生化指标检测。结果干预前,两组患者饮食知识调查情况和生化指标检测情况比较,差异无统计学意义(P>0.05);干预后,与对照组比较,试验组患者的体质指数(BMI)、空腹血糖(FPG)、餐后2 h血糖(2 h PG)、糖化血红蛋白(Hb A1c)及血脂水平下降;饮食基本知识、饮食行为习惯及实践操作得分升高,差异有统计学意义(P<0.01)。结论手测量法则食物交换份法为临床医生和糖尿病患者提供了简便的热量计算方法,极大地提高了糖尿病患者的饮食依从性,可以有效地帮助糖尿病患者控制血糖和血脂,延缓其并发症的发生。
