一类不完全市场期权定价的超复制

对于一类不完全市场期权定价的离散模型 ,运用凸分析和随机控制的方法给出了期权定价的超复制 。

市场监管对伴有内部信息的欧式期权超复制定价的影响

研究一类具有内部信息、交易成本和市场监管的欧式期权超复制定价问题,其中市场监管以一定的概率发现内部交易并给予一定的处罚。通过滤子扩张方法,证明了当交易时段趋于零时,超复制价格存在尺度极限,并给出了其表达式,从而得到当投资者几乎知晓未来全部信息时的超复制尺度极限。研究表明:若市场监管者发现内部交易的概率越大,超复制价格的尺度极限也越大,内部交易成本增加,因而更大的内部交易发现概率有助于减少内部交易行为。

杠杆交易限制下可转债的交换期权定价模型

不同于标准期权,可转债转股条款的实质是一份交换期权。考虑了市场中的杠杆交易限制,利用远期风险中性测度原理和超复制方法,重新构建了一个可转债交换期权模型。结合2015年2月至2015年10月的可转债市场数据,通过比较基于套利限制的交换期权定价方法与基于无套利原理的标准期权定价方法的计算结果,发现前者能够为可转债的真实价值确定一个参考区间,而后者仅仅是前者的一个特例,且后者大致相当于价值参考区间的下界。通过调整杠杆交易限制的参数,发现:一方面,随着市场杠杆交易限制的增加,转股权(从而转债)的价值会由于其复制成本的上升而增加;另一方面,当转股权处于深度虚值或深度实值状态时,转股权(从而转债)的理论价值区间会缩小。这就为杠杆交易限制与转债价格无套利区间之间所存在的正向关系,以及转股权实/虚值程度与转债价格无套利区间之间所存在的反向关系提供了理论上的依据。

组合受“矩形”约束下的BLACK-SCHOLES定价公式

BROADIE,CIVITANIC AND SONER[2]研究了投资组合受凸约束下的BLACK-SCHOLES期权定价模型,获得了期权超价格的显式刻画结果,并且证明在一些技术性条件下期权超价格与相应的偏微分方程的解相对应．研究了投资组合受“矩形”约束的BLACK-SCHOLES期权定价模型,利用 BROADIE,CIVITANIC AND SONER[2]期权超价格的显式刻画结果和风险中性定价方法获得了投资组合受“矩形”约束下BLACK-SCHOLES期权超价格的解析解．

新型智能电化学微加工系统的研究

约束刻蚀剂层技术是三维超微图形复制加工的新型技术。本文根据约束刻蚀剂层技术的工艺特点 ,介绍了约束刻蚀剂层电化学微加工仪器的组成 ,讨论了具有微力传感的纳米级微定位系统的研究与开发。利用研制的加工仪器 ,在半导体GaAs进行刻蚀加工 ,复制出微孔阵列 ,其排列周期与模板的微锥阵列的排列周期吻合得很好 。

Microstructural development and its effects on mechanical properties of Al/Cu laminated composite

The microstructural development and its effect on the mechanical properties of Al/Cu laminated composite produced by asymmetrical roll bonding and annealing were studied. The composite characterizations were conducted by transmission electron microscope（TEM）, scanning electron microscope（SEM）, peeling tests and tensile tests. It is found that the ultra-fine grained laminated composites with tight bonding interface are prepared by the roll bonding technique. The annealing prompts the atomic diffusion in the interface between dissimilar matrixes, and even causes the formation of intermetallic compounds. The interfacial bonding strength increases to the maximum value owing to the interfacial solution strengthening at 300 °C annealing, but sharply decreases by the damage effect of intermetallic compounds at elevated temperatures. The composites obtain high tensile strength due to the Al crystallization grains and Cu twins at 300 °C. At 350 °C annealing, however, the composites get high elongation by the interfacial interlayer with submicron thickness.

北京气候与档案保护

档案是历史记录,是有永久保存价值的文件。然而,档案的寿命又是有限的。这是一对尖锐的矛盾,如何解决?办法只有一条,就是根据档案制成材料的损坏规律,寻求科学保护档案的技术方法,以求最大限度地延长档案寿命。而自然气候与档案保护具有密切关系,搞好北京地区档案保护。

Fabrication of cast carbon steel with ultrafine TiC particles

The carbon steels dispersed with ultrafine TiC particles were fabricated by conventional casting method. The casting process is more economical than other available routes for metal matrix composite production, and the large sized components to be fabricated in short processing time. However, it is extremely difficult to obtain uniform dispersion of ultrafine ceramic particles in liquid metals due to the poor wettability and the specific gravity difference between the ceramic particle and metal matrix. In order to solve these problems, the mechanical milling (MM) and surface-active processes were introduced. As a result, Cu coated ultrafine TiC powders made by MM process using high energy ball milling machine were mixed with Sn powders as a surfactant to get better wettability by lowering the surface tension of carbon steel melt. The microstructural investigations by OM show that ultrafine TiC particles are distributed uniformly in carbon steel matrix. The grain sizes of the cast matrix with ultrafine TiC particles are much smaller than those without ultrafine TiC particles. This is probably due to the fact that TiC particles act as nucleation sites during solidification. The wear resistance of cast carbon steel composites added with MMed TiC/Cu-Sn powders is improved due to grain size refinement.

Strengthening contributions in ultra-high strength cryorolled Al-4%Cu-3%TiB_2 in situ composite

Ultra-high strength Al alloy system was developed by cryorolling and the contribution of various strengthening mechanisms to the overall yield strength of the system was evaluated. Cryorolling of Al-4%Cu-3%TiB2 in situ composite followed by short annealing at 175 ℃ and ageing at 125℃ resulted in an ultra-high yield strength of about 800 MPa with 9%total elongation. The strengthening contributions form solid solution strengthening, grain refinement, dislocation strengthening, precipitation hardening and dispersion strengthening were evaluated using standard equations. It was estimated that the maximum contribution was from grain refinement due to cryorolling followed by precipitation and dispersion strengthening.

In situ(Mg_2Si+MgO)/Mg composites fabricated from AZ91-Al_2(SiO_3)_3 with assistance of high-energy ultrasonic field

In situ （Mg2Si＋MgO）/Mg composites fabricated from AZ91-A12（SiO3）3 under high-energy ultrasonic field were investigated by XRD, DSC and SEM. The results indicate that the size, morphology and distribution of the in situ Mg2Si particles are greatly optimized with the assistance of the high-energy ultrasonic field. The amounts of the in situ Mg2Si particles are increased, the sizes are refined, the distributions become uniform, and the morphologies are changed to smooth olive-shape or spherical shape. The amounts of brittle fl-Mgl7All2 phases are decreased and the morphologies are granulated. The values of the tensile strength ab and HB hardness are increased. These are due to the cavitation effects and acoustic streaming effects induced by the high-energy ultrasonic field.

Preparation of ultrafine WC-10Co composite powders by reduction and carbonization

A solid state synthesis of ultrafine/nanocrystalline WC-10Co composite powders was reported from WO3 , Co3O4 and carbon powders after reduction and carburization at relatively low temperatures in a short time under pure H2 atmosphere. The effects of ball milling time and reaction temperature on the preparation of ultrafine/nanocrystalline WC-Co composite powders were studied using X-ray diffraction and scanning electron microscope (SEM). The results show that fine mixed oxide powders (WO3 , Co3O4 and carbon powders) can be obtained by long time ball milling. Increasing the reaction temperature can decrease the formation of Co3W3C and graphite phases and increase the WC crystallite size. Long-time ball milling and high reaction temperature are favorable to obtain fine and pure composite powders consisting of nanocrystalline WC from WO3 , Co3O4 and carbon powders.

Fabrication of carbon nanotubes reinforced AZ91D composites by ultrasonic processing

Magnesium matrix nanocomposite reinforced with carbon nanotubes(CNTs/AZ91D) was fabricated by mechanical stirring and high intensity ultrasonic dispersion processing.The microstructures and mechanical properties of the nanocomposite were investigated.The results show that CNTs are well dispersed in the matrix and combined with the matrix very well.As compared with AZ91D magnesium alloy matrix,the tensile strength,yield strength and elongation of the 1.5%CNTs/AZ91D nanocomposite are improved by 22%,21%and 42%respectively in permanent mold casting.The strength and ductility of the nanocomposite are improved simultaneously.The tensile fracture analysis shows that the damage mechanism of nanocomposite is still brittle fracture.But the CNTs can prevent the local crack propagation to some extent.

Fabrication of SPES/Nano-TiO_2 Composite Ultrafiltration Membrane and Its Anti-fouling Mechanism

Membrane fouling is one of the major obstacles for reaching a high flux over a prolonged period of ultrafiltration（UF）process.In this study,a sulfonated-polyethersulfone（SPES）/nano-TiO2 composite UF membrane with good anti-fouling performance was fabricated by phase inversion and self-assembly methods.The TiO2 nanoparticle self-assembly on the SPES membrane surface was confirmed by X-ray photoelectron spectroscopy （XPS）and FT-IR spectrometer.The morphology and hydrophilicity were characterized by scanning electron microscopy（SEM）,atomic force microscopy（AFM）and contact angle goniometer,respectively.The anti-fouling mechanism of composite UF membrane was discussed through the analysis of the micro-structure and component of UF membrane surface.The results showed that the TiO2 content and the micro-structure of the composite UF membrane surface had great influence on the separation and anti-fouling performance.

Radiation induced graft polymerization of multi-walled carbon nanotubes for superhydrophobic composite membrane preparation

Highly soluble multi-walled carbon nanotubes （MWNTs） were prepared by radiation-induced free radical graft polymerization of vinyl acetate （VAc） onto pristine MWNT surfaces. High resolution transmission electron microscopy （HR-TEM）, Fourier transform infrared （FT1R） spectroscopy, and micro-Raman spectroscopy were used to confirm that poly（vinyl acetate） （PVAc） had been successfully grafted onto the surface of the MWNTs. The effects of experimental parameters on the degree of graft- ing （DG） of PVAc were also investigated, including adsorbed dose, dose rate, initial monomer concentration, and solvents. The grafted MWNTs （MWNTs-g-PVAc） exhibited good solubility in common organic solvents at high mass fraction. In addition, a superhydrophobic composite membrane could be readily fabricated by vacuum filtration of MWNTs-g-PVAc onto a support- ing membrane, as was confirmed by water contact angle testing and visualization by scanning electron microscopy.

Mesoporous polypyrrole-based graphene nanosheets anchoring redox polyoxometalate for all-solid-state micro-supercapacitors with enhanced volumetric capacitance

Micro-supercapacitors（MSCs） have emerged as one competitive candidate of high-performance, flexible, safe,portable and wearable energy storage devices. However, improving their electrochemical performance from electrode materials to assembled devices still remains huge challenges.Here, we for the first time synthesized two-dimensional（2D）,ultrathin, mesoporous polypyrrole-based graphene nanosheets uniformly anchored with redox polyoxometalate（mPPy@rGO-POM） by soft template approach. Further, using a layer-by-layer deposition and mask-assisted technique, the compactly stacked and sandwich-like hybrid film（mPGM）based on pseudocapacitive mPPy@rGO-POM nano sheets and electrochemically exfoliated graphene was directly fabricated as binder-and additive-free interdigital electrodes for all-solid-state planar micro-supercapacitors（mPGM-MSCs）. Notably, the resulted mPGM-MSCs exhibited outstanding areal capacitance（115 mF cm^-2）, remarkably enhanced volumetric capacitance（137 F cm^-3 at 1 mV s^-1） in comparison with MSCs based on the films of mPPy@rGO without POM anchoring（95 F cm^-3）, and non-porous polypyrrole-graphene（68 F cm^-3）.Further, mPGM-MSCs disclosed robust mechanical flexibility with ～96% of capacitance retention at a highly bending angle of 180°, and impressive parallel or serial interconnection for boosting capacitance or voltage output. As a consequence, our proposed strategy of filling the redox species into mesoporous graphene and other 2D nanosheets will open up new ways to manufacture high-compact and flexible energy storage devices ranging from supercapacitors to batteries.

Rapid progress of DNA replication studies in Archaea,the third domain of life

Archaea,the third domain of life,are interesting organisms to study from the aspects of molecular and evolutionary biology.Archaeal cells have a unicellular ultrastructure without a nucleus,resembling bacterial cells,but the proteins involved in genetic information processing pathways,including DNA replication,transcription,and translation,share strong similarities with those of Eukaryota.Therefore,archaea provide useful model systems to understand the more complex mechanisms of genetic information processing in eukaryotic cells.Moreover,the hyperthermophilic archaea provide very stable proteins,which are especially useful for the isolation of replisomal multicomplexes,to analyze their structures and functions.This review focuses on the history,current status,and future directions of archaeal DNA replication studies.