As a kind of weak-path dependent options, barrier options are an important kind of exotic options. Because the pricing formula for pricing barrier options with discrete observations cannot avoid computing a high dimen...As a kind of weak-path dependent options, barrier options are an important kind of exotic options. Because the pricing formula for pricing barrier options with discrete observations cannot avoid computing a high dimensional integral, numerical calculation is time-consuming. In the current studies, some scholars just obtained theoretical derivation, or gave some simulation calculations. Others impose underlying assets on some strong assumptions, for example, a lot of calculations are based on the Black-Scholes model. This thesis considers Merton jump diffusion model as the basic model to derive the pricing formula of discrete double barrier option;numerical calculation method is used to approximate the continuous convolution by calculating discrete convolution. Then we compare the results of theoretical calculation with simulation results by Monte Carlo method, to verify their efficiency and accuracy. By comparing the results of degeneration constant parameter model with the results of previous models we verified the calculation method is correct indirectly. Compared with the Monte Carlo simulation method, the numerical results are stable. Even if we assume the simulation results are accurate, the time consumed by the numerical method to achieve the same accuracy is much less than the Monte Carlo simulation method.展开更多
To reduce the levelized cost of energy for concentrating solar power(CSP),the outlet temperature of the solar receiver needs to be higher than 700°C in the next-generation CSP.Because of extensive engineering app...To reduce the levelized cost of energy for concentrating solar power(CSP),the outlet temperature of the solar receiver needs to be higher than 700°C in the next-generation CSP.Because of extensive engineering application experience,the liquid-based receiver is an attractive receiver technology for the next-generation CSP.This review is focused on four of the most promising liquid-based receivers,including chloride salts,sodium,lead-bismuth,and tin receivers.The challenges of these receivers and corresponding solutions are comprehensively reviewed and classified.It is concluded that combining salt purification and anti-corrosion receiver materials is promising to tackle the corrosion problems of chloride salts at high temperatures.In addition,reducing energy losses of the receiver from sources and during propagation is the most effective way to improve the receiver efficiency.Moreover,resolving the sodium fire risk and material compatibility issues could promote the potential application of liquid-metal receivers.Furthermore,using multiple heat transfer fluids in one system is also a promising way for the next-generation CSP.For example,the liquid sodium is used as the heat transfer fluid while the molten chloride salt is used as the storage medium.In the end,suggestions for future studies are proposed to bridge the research gaps for>700℃liquid-based receivers.展开更多
This study examined the mechanical properties, springback behavior from three-point bending loading–unloading tests and biocompatibility from human osteoblast cell adhesion and proliferation experiments in Ti-15Mo al...This study examined the mechanical properties, springback behavior from three-point bending loading–unloading tests and biocompatibility from human osteoblast cell adhesion and proliferation experiments in Ti-15Mo alloy with different microstructures. The springback ratio increased after the appearance of deformation microstructures including {332} < 113 > twins and dislocations, due to the increased bending strength and unchanged Young’s modulus. By contrast, the change in springback ratio was dependent on the competing effect of the simultaneous increase in bending strength and Young’s modulus after phase transformation, namely, the isothermal ω-phase formation. Good cell adhesion and proliferation were observed on the alloy surface, and they were not significantly affected by the deformation twins, dislocations and isothermal ω-phase.The diversity of deformation and phase transformation microstructures made it possible to control the springback behavior effectively while keeping the biocompatibility of the alloy as an implant rod used for spinal fixation devices.展开更多
自从《<蒙特利尔议定书>基加利修正案》签订并实施以来,削减当量碳排放、有效延缓全球变暖成为各个行业的热门话题.新能源汽车的快速发展也标志着交通领域的能源结构变革.不过,新能源车目前仍存在安全隐患、里程焦虑、热管理工质...自从《<蒙特利尔议定书>基加利修正案》签订并实施以来,削减当量碳排放、有效延缓全球变暖成为各个行业的热门话题.新能源汽车的快速发展也标志着交通领域的能源结构变革.不过,新能源车目前仍存在安全隐患、里程焦虑、热管理工质温室效应等瓶颈问题,这也从"节能"与"环保"两个方面对车辆热管理行业提出了更高级、更精准的要求.从节能角度来说,本文总结了热管理系统从常规单冷空调技术到热泵空调技术的系统架构转变与实现形式升级,达到了在冬季制热条件下节省大量正温度系数热敏加热器(positive temperature coefficient,PTC)能耗的目的;同时,展示了一体化热管理新概念与各种智能优化控制算法的结合,使乘员舱、电池、电机、电控部分的综合热管理持续向着性能更优、能耗更小的方向演化.另一方面,新能源汽车热管理系统目前仍广泛使用HFC(hydrofluorocarbon)类强温室效应气体(如R134a与R407C)作为制冷剂.从环保角度出发,本文介绍了几种较为热门的环保型制冷剂替代方案,如CO2、R290、R1234yf等.最后,前瞻性地指出新能源汽车热管理技术将朝向"绿色高效化"、"功能一体化"、"结构模块化"、"控制智能化"方向不断前进,以为我国实现碳达峰、碳中和目标作出重要贡献.展开更多
Root-associated microbes are critical for plant growth and nutrient acquisition. However, scant information exists on optimizing communities of beneficial root-associated microbes or the mechanisms underlying their in...Root-associated microbes are critical for plant growth and nutrient acquisition. However, scant information exists on optimizing communities of beneficial root-associated microbes or the mechanisms underlying their interactions with host plants. In this report, we demonstrate that rootassociated microbes are critical influencers of host plant growth and nutrient acquisition. Three synthetic communities(SynComs) were constructed based on functional screening of 1,893 microbial strains isolated from root-associated compartments of soybean plants. Functional assemblage of SynComs promoted significant plant growth and nutrient acquisition under both N/P nutrient deficiency and sufficiency conditions.Field trials further revealed that application of SynComs stably and significantly promoted plant growth, facilitated N and P acquisition, and subsequently increased soybean yield. Among the tested communities, SynCom1 exhibited the greatest promotion effect, with yield increases of up to 36.1% observed in two field sites. Further RNA-seq implied that SynCom application systemically regulates N and P signaling networks at the transcriptional level, which leads to increased representation of important growth pathways, especially those related to auxin responses. Overall,this study details a promising strategy for constructing SynComs based on functional screening,which are capable of enhancing nutrient acquisition and crop yield through the activities of beneficial root-associated microbes.展开更多
文摘As a kind of weak-path dependent options, barrier options are an important kind of exotic options. Because the pricing formula for pricing barrier options with discrete observations cannot avoid computing a high dimensional integral, numerical calculation is time-consuming. In the current studies, some scholars just obtained theoretical derivation, or gave some simulation calculations. Others impose underlying assets on some strong assumptions, for example, a lot of calculations are based on the Black-Scholes model. This thesis considers Merton jump diffusion model as the basic model to derive the pricing formula of discrete double barrier option;numerical calculation method is used to approximate the continuous convolution by calculating discrete convolution. Then we compare the results of theoretical calculation with simulation results by Monte Carlo method, to verify their efficiency and accuracy. By comparing the results of degeneration constant parameter model with the results of previous models we verified the calculation method is correct indirectly. Compared with the Monte Carlo simulation method, the numerical results are stable. Even if we assume the simulation results are accurate, the time consumed by the numerical method to achieve the same accuracy is much less than the Monte Carlo simulation method.
基金the National Natural Science Foundation of China(Grant Nos.51721004 and 51888103)the Research Plan of Shaanxi Province(Nos.2022GXLH-01-04 and 2019JCW-09).
文摘To reduce the levelized cost of energy for concentrating solar power(CSP),the outlet temperature of the solar receiver needs to be higher than 700°C in the next-generation CSP.Because of extensive engineering application experience,the liquid-based receiver is an attractive receiver technology for the next-generation CSP.This review is focused on four of the most promising liquid-based receivers,including chloride salts,sodium,lead-bismuth,and tin receivers.The challenges of these receivers and corresponding solutions are comprehensively reviewed and classified.It is concluded that combining salt purification and anti-corrosion receiver materials is promising to tackle the corrosion problems of chloride salts at high temperatures.In addition,reducing energy losses of the receiver from sources and during propagation is the most effective way to improve the receiver efficiency.Moreover,resolving the sodium fire risk and material compatibility issues could promote the potential application of liquid-metal receivers.Furthermore,using multiple heat transfer fluids in one system is also a promising way for the next-generation CSP.For example,the liquid sodium is used as the heat transfer fluid while the molten chloride salt is used as the storage medium.In the end,suggestions for future studies are proposed to bridge the research gaps for>700℃liquid-based receivers.
基金supported by the National Natural Science Foundation of China(No.52071051)。
文摘This study examined the mechanical properties, springback behavior from three-point bending loading–unloading tests and biocompatibility from human osteoblast cell adhesion and proliferation experiments in Ti-15Mo alloy with different microstructures. The springback ratio increased after the appearance of deformation microstructures including {332} < 113 > twins and dislocations, due to the increased bending strength and unchanged Young’s modulus. By contrast, the change in springback ratio was dependent on the competing effect of the simultaneous increase in bending strength and Young’s modulus after phase transformation, namely, the isothermal ω-phase formation. Good cell adhesion and proliferation were observed on the alloy surface, and they were not significantly affected by the deformation twins, dislocations and isothermal ω-phase.The diversity of deformation and phase transformation microstructures made it possible to control the springback behavior effectively while keeping the biocompatibility of the alloy as an implant rod used for spinal fixation devices.
文摘自从《<蒙特利尔议定书>基加利修正案》签订并实施以来,削减当量碳排放、有效延缓全球变暖成为各个行业的热门话题.新能源汽车的快速发展也标志着交通领域的能源结构变革.不过,新能源车目前仍存在安全隐患、里程焦虑、热管理工质温室效应等瓶颈问题,这也从"节能"与"环保"两个方面对车辆热管理行业提出了更高级、更精准的要求.从节能角度来说,本文总结了热管理系统从常规单冷空调技术到热泵空调技术的系统架构转变与实现形式升级,达到了在冬季制热条件下节省大量正温度系数热敏加热器(positive temperature coefficient,PTC)能耗的目的;同时,展示了一体化热管理新概念与各种智能优化控制算法的结合,使乘员舱、电池、电机、电控部分的综合热管理持续向着性能更优、能耗更小的方向演化.另一方面,新能源汽车热管理系统目前仍广泛使用HFC(hydrofluorocarbon)类强温室效应气体(如R134a与R407C)作为制冷剂.从环保角度出发,本文介绍了几种较为热门的环保型制冷剂替代方案,如CO2、R290、R1234yf等.最后,前瞻性地指出新能源汽车热管理技术将朝向"绿色高效化"、"功能一体化"、"结构模块化"、"控制智能化"方向不断前进,以为我国实现碳达峰、碳中和目标作出重要贡献.
基金supported by the by National Natural Science Foundation of China(No.31830083)China National Key Program for Research and Development(No.2016YFD0100700)。
文摘Root-associated microbes are critical for plant growth and nutrient acquisition. However, scant information exists on optimizing communities of beneficial root-associated microbes or the mechanisms underlying their interactions with host plants. In this report, we demonstrate that rootassociated microbes are critical influencers of host plant growth and nutrient acquisition. Three synthetic communities(SynComs) were constructed based on functional screening of 1,893 microbial strains isolated from root-associated compartments of soybean plants. Functional assemblage of SynComs promoted significant plant growth and nutrient acquisition under both N/P nutrient deficiency and sufficiency conditions.Field trials further revealed that application of SynComs stably and significantly promoted plant growth, facilitated N and P acquisition, and subsequently increased soybean yield. Among the tested communities, SynCom1 exhibited the greatest promotion effect, with yield increases of up to 36.1% observed in two field sites. Further RNA-seq implied that SynCom application systemically regulates N and P signaling networks at the transcriptional level, which leads to increased representation of important growth pathways, especially those related to auxin responses. Overall,this study details a promising strategy for constructing SynComs based on functional screening,which are capable of enhancing nutrient acquisition and crop yield through the activities of beneficial root-associated microbes.
