含信用等级迁移的公司债券基于双资产 的结构化定价

研究含信用等级迁移风险的公司债券在双资产影响下的定价问题。基于Merton的公司债券结构化定价方法,建立含信用等级迁移风险的公司债券关于流动资产和固定资产的模型假设,分析债券的未来预期收益,给出在信用等级迁移边界处耦合的偏微分方程组,在信用等级迁移边界处添加一阶导数条件或线性组合条件,建立起债券的定价模型。求得了数值解和解析解,最后对模型进行了数值分析。     

担保信用等级变换的利率互换衍生品定价

考虑担保信用等级迁移风险的利率互换合约,在结构化方法的框架下,建立了担保信用等级首次迁移所造成损失的保费定价模型,信用等级依赖于利率并具有高低2个等级.从一个新的角度将低等级下零息票利率互换的价值定义为保费价值的自变量,并利用对冲原理建立保费定价的偏微分方程模型.利用计价单位转换原理对方程进行降维,求出问题的半解析解,然后采用有限差分方法的显式格式对模型进行数值求解.最后,讨论了保费价值关于利率参数的依赖关系.结果表明:保费价值和各参数间存在单调递减的关系.     

基于KMV-CatBoost增强的企业信用债券违约风险评估模型

针对传统预测模型对于企业信用债券违约预测准确率低、拟合效果差的问题,提出了基于Kaufman-Merton-Voss （KMV）-Categorical Boosting （CatBoost）的企业债券违约预测模型. 首先对原始样本数据进行预处理,降低噪声数据对预测模型的影响;然后,利用KMV模型评估借款公司信用违约概率,计算公司资产市场价值与公司资产市场价值的波动率,获得企业资产价值与违约点之间的差额Distance-to-Default（DD）;最后,利用债务偿还期限、短期无风险收益率、公司股权市场价值、公司债务面值计算出的违约距离,将其加入指标中,利用CatBoost算法预测企业信用债券违约风险,通过基于Ordered Boosting方式的CatBoost算法训练模型,得到无偏梯度估计,以减缓预测偏移,从而增强模型的泛化能力. 实验结果表明：基于KMV-CatBoost增强的模型能够提高企业信用债券违约风险识别的准确率,识别正确率约为95.5%.     

基于仿射跳扩散模型的利率衍生品定价

本文考虑短期利率满足一类仿射跳扩散期限结构模型的利率衍生品定价。应用Fourier变换方法和远期测度技术,获到了零息票债券及基于零息票债券为标的资产的欧式债券期权价格的显示解,并将此结果应用于付息债券期权和利率期权的定价。最后,利用数值实例分别分析了债券和零息票债券期权价格受利率模型中各主要参数的影响,以及期权的隐含波动率问题。数值结果表明,跳跃风险参数对利率衍生品价格和隐含波动率有显著作用,这也验证了仿射跳扩散的利率期限结构模型具有较好拟合实际的能力。     

考虑相关性的第三方担保价值评估

在结构化模型的框架下,考虑到担保公司与被担保公司之间存在相关性时,因预付担保债务而导致资不抵债而违约的情况,得到有相关性的第三方担保的公司债券价格所满足的偏微分方程终边值问题.利用数值计算分析了公司资产值、资产相关性、资产波动率、公司回收率和债券发行量等因素对于债券价格的影响.     

小微企业信用等级分类模型研究

以非违约样本与违约样本数量相等的平衡样本为实证样本,采用等分法将全部样本的信用得分分为国际通行的9个等级.计算每个等级内样本客户的违约率,并判断等级分类是否满足信用等级越高、违约率越低的根本要求.如果出现信用等级高而违约率不低的情况时,就动态调整信用等级的信用得分区间,确保调整后的信用等级分类满足信用等级越高、违约率越低这一信用等级分类的根本要求.     

基于信用等级迁移的信用违约互换定价

研究了参考债券具有信用等级结构的信用违约互换(CDS)的定价.考虑债券处于不同的等级,且债券的违约强度和回收率随着债券在等级间的迁移不断变化;基于转移矩阵和回收率向量,构建了常微分方程组(ODE)方程来求解信用违约互换的或有赔付和保费支付的价值,并给出了其解析解,从而确定了CDS保费费率和CDS的价值.最后通过数值分析验证理论结果.     

具有信用等级迁移风险的零息债券定价

建立具有信用等级迁移和违约风险的零息票债券的定价模型.在约化方法下,模型转换为偏微分方程组终值问题.在进一步假设参数为常数下,得出每个等级债券价格的解析解和大小关系.作图展示了其数值解,并分析了参数对债券价格的影响.     

Switch Corridor方差互换定价的蒙特卡罗加速算法

主要研究为对冲跨市场波动率风险而开发的双标的资产的新型方差产品——Switch Corridor方差互换的定价问题。该产品由瑞士信贷(Credit Suisse)于2012年率先推出,逐渐成为了结构性产品市场上最受欢迎的新产品系列之一。使用控制变量Monte Carlo方法研究了双Heston随机波动率模型下Switch Corridor方差互换的定价问题,基于仿射结构理论,得到辅助标的过程下方差产品价格的解析解,构造了问题求解的高效控制变量。进一步地,考察了不同辅助过程波动率的选取对加速效果的影响。通过数值实验可以证明,基于动态波动率选取的辅助过程起到了很好的加速效果。该算法亦可方便地解决其他随机波动率模型下高维方差产品的计算问题。     

马尔可夫调制的跳扩散过程下可分离交易可转换债券的定价

运用测度变换方法和无套利定价原理,得到了风险资产价格满足马尔可夫调制的跳扩散过程及市场利率是随机利率时,可分离交易可转换债券的定价公式.并利用蒙特卡诺方法给出了数值分析,比较了风险资产价格满足不同金融模型下可分离交易可转换债券的价值差别.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with