分流气体对冲排气消声器气流再生噪声模型研究

对分流气体对冲排气消声器气流再生噪声进行了数值计算,通过试验验证了计算方法的准确性。以气流再生噪声总声压级为响应值,使用Design-Expert软件设计了气流再生噪声试验,根据回归分析建立了总声压级与试验因素(内腔直径、对冲孔形状、对冲孔中心距、内腔分流单元锥角、气流速度)之间的数学模型,并检验了模型的显著性。深入分析了不同因素二阶交互作用对气流再生噪声的影响规律。结果表明:随着气流速度的增大气流再生噪声显著增大,斜率都超过了1;对冲孔形状和对冲孔中心距对气流再生噪声影响较显著,且当冲孔形状为矩形、对冲孔中心距为平均值时,气流再生噪声较小;内腔分流单元锥角和内腔直径对气流再生噪声影响较小。以气流再生噪声为优化指标,得到了最佳试验条件。     

对冷冲模具冲裁间隙的商讨

通过冲裁间隙对冲裁断面、冲裁力的影响,提出合理冲裁间隙。     

套期保值案例赏析

套期保值交易的本质是对冲和风险转移,是企业风险把控的最基本工具。长江期货一直在帮助企业对冲风险的同时解决客户没精力或不敢做的问题。在前期通过实地调研给出具体套保方案。企业在套保的过程中,长江期货会与企业进行充分沟通。     

商品互换应用案例赏析

套期保值交易的本质是对冲和风险转移,是企业风险把控的最基本工具。长江期货一直在帮助企业对冲风险的同时解决客户没精力或不敢做的问题。在前期通过实地调研给出具体套保方案。企业在套保的过程中,长江期货会与企业进行充分沟通。     

周期性热流下受限阵列射流沸腾特性的实验研究

以去离子水为工质对恒热流和周期性热流加热下的受限式阵列射流进行了沸腾特性实验,获得了加热面温度分布、沸腾可视化图像以及测试段出口压力波动等数据,综合分析发现:(1)恒热流密度单相换热时,射流对冲区的温度高于滞止区的温度,温差随着热流密度的增加而变大,当对冲区出现稳定沸腾后,温差逐渐减小,并且出现滞止区温度超过对冲区的情况;(2)沸腾时测试段出口压力的频谱分布与气泡在表面的周期性生长和湮灭相对应;(3)周期热流密度时,在高占空比、低频下,沸腾能较快接近稳定沸腾,而在小占空比、高频率下,沸腾无法达到恒热流密度时的沸腾剧烈程度,当热流密度在沸腾起始热流密度附近时,加热结束时对冲区的温度相比于恒热流密度时有较大幅度的增加。     

膜生物反应器处理冲厕海水的试验研究

主要研究了膜生物反应器对冲厕海水中主要污染物的处理效果以及盐度对生物反应器内微生物群落和活性污泥特性的影响.结果表明,微生物经培养驯化后能适应不同的海水盐度,膜生物反应器对冲厕海水中的COD和氨氮的去除率分别达到86%和93%.随着盐度的提高,污泥沉降性能变差.盐度的冲击对膜生物反应器处理效果有一定影响,系统需要较为恒定的盐度条件.     

用统一强度理论求解轴对称混凝土板的冲切强度

本文采用统一强度理论作为混凝土的破坏准则，求解了轴对称混凝土板的冲切破坏强度，利用上限定理求出了一组破坏荷载，得出了强度理论参数 对冲切强度的影响曲线。所得的解可以考虑材料的中间主应力效应对冲切破坏强度的影响, 可以灵活地应用于工程上的各种不同材料, 公式形式简单便于应用, 且与已有结果及试验资料符合较好。     

金属在液固两相流中的冲刷腐蚀

液固两相流体的冲刷腐蚀行为较单相流体更为复杂,在相同液相介质的情况下,其冲刷腐蚀对材料的破坏程度更为严重。综述了国内外对液固两相流的冲刷腐蚀体系开展的研究,对冲刷腐蚀的过程有了进一步的认识,对冲刷腐蚀的影响规律和危害性进行了论述,从而为材料的选用提供一定的参考依据。     

双层分流对冲穿孔管结构消声特性研究

发动机排气系统中的噪声特性为高频、宽频带，以及排气气流作用下产生的再生噪声，传统的消声结构不能有效地解决该噪声问题。因此，提出通过将锥形分流单元与双层穿孔管相结合的消声方法。首先通过一个锥形分流单元对进入消声器的气流进行分流，分流后的气流在第一层穿孔管外腔得到充分的减速，再经过第一层穿孔管进行初次消声，然后通过第二层穿孔管进行二次消声，最后通过第二层穿孔管上的小孔进入到对冲腔，使气流在对冲腔发生对冲，气流在对冲的过程中速度逐渐降低，再生噪声减小消声效果增强。通过对双层穿孔管结构的传递损失进行推导，分析结构参数对消声性能的影响，得到传递损失的影响因素与变化特性，并进行实验验证。实验结果表明：提出的消声方法能够在高频入射声波的情况下维持较高的传递损失和较宽的消声频带。     

柴油机分流气体对冲耦合消声器压力损失研究

消声器设计中消声量与排气背压之间是相互矛盾且需要反复权衡的关系，同时消声器消声量、排气背压、气流通过性等性能评价指标与其内部气流速度有直接关系即内部气流速度越大，总体性能参数越差。以降低消声器内部气流速度为出发点，基于分流气体对冲降速原理，结合传统消声单元获得新型耦合结构消声器，并对其压力损失进行研究。采用理论分析、数值仿真和测试试验的方法，分析分流气体对冲结构的降速原理，并对新型耦合结构消声器压力损失进行研究。结果表明：气体经过对冲腔前后速度从57.6 m/s 降为28.7 m/s，对冲腔压力较原装消声器降低1.67 kPa，消声器内部湍动能场强度小于原装消声器，试验结果表明新型耦合结构消声器压力损失和出口气流速度比原装消声器均降低20 %以上。该新型耦合结构消声器的气流通过性能、压力损失、出口气流速度均优于原装消声器。     

R-藤Pair Copula模型下的投资组合最优套期保值比例研究

目前我国证券市场尚未成熟,风险对冲手段单一,因此构建一个期货对多资产进行套期保值策略对于投资组合的风险管理尤为重要．本文构建了基于线性规划的最小CVaR（Conditional Value at Risk）套期保值模型,同时运用R-藤Pair Copula-GARCH模型结合蒙特卡洛模拟生成投资组合中各资产收益率的情景和概率,将结果用于基于线性规划的最小CVaR套期保值模型,可确定投资组合的最优套期保值比例．针对沪深300指数和5支沪深300成分股的实证研究表明,相对改良后的正态假定模型,经本文模型套期保值后的投资组合在风险和收益上均有更好的表现．     

Management of price uncertainty in short-term generation planning

Price uncertainty is faced by gencos in the scheduling of their units in competitive power markets. the proper way to deal with the uncertainty depends on the risk preference of the genco. two important means to manage the price uncertainty are (i) suitable flexible bids and (ii) the use of hedging tools such as forward contracts. the influence of these factors in the genco's short-term generation planning and the corresponding profit performances is studied. the market price is represented by lognormal distribution, genco risk behaviour is represented by exponential utility functions, the bid functions are taken to be flexible and simple contracts for hedging are assumed available. the unit commitment problem is combined with the hedging problem to obtain the optimal solution. formulation of the problem to maximise profit in the spot market and its extension to incorporate the risk behaviour of the gencos and the forward contacts for hedging is presented. solution method based on genetic algorithms is implemented in matlab. it is observed through numerical examples that the flexible outputs and the forward contracts can be used to hedge against price risks to achieve desired profit performance according to gencos' risk behaviour.     

Change of claim structures of market leaders’ Japanese published unexamined patent applications according to the degree of technology maturity

This paper analyses claim structures of Japanese published unexamined patent applications on digital camera filed by firms participating in the Japanese market of digital camera for each of the stages from the innovator stage to the late majority stage and investigates the contribution of claim structures to capture of market share for each stage. A main finding is that claim structures reflect the life-cycle stages of a product. The market leader of the early adopter stage filed patent applications having more independent claims of which the claim category is ‘digital camera’ or the like compared to the rest of the participating firms, while the market leader of the late majority stage has more dependent claims. This indicates that it is critical to cover a maximal scope of the invention by plural independent claims in the early adopter stage, while, in the late majority stage in which the technologies are highly matured, the total number of dependent claims are increased to protect the market leader’s technologies against competitors and as a means of fallback options.     

随机利率下的均值-方差最小套期保值

均值-方差套期保值是套期保值的主要方法之一。不连续资产价格的均值-方差套期保值策略通常是在利率为非随机的情况下获得的。本文考虑在随机利率下,资产价格为特殊半鞅的均值-方差套期保值问题。通过适当的概率测度变换,将具有随机利率的情形简化为非随机利率情形,再利用Galtchouk-Kunita-Watanabe分解,获得了资产价格为一般的特殊半鞅,具有随机利率的的均值-方差套期保值策略。     

Optimal policy in a hybrid manufacturing/remanufacturing system with financial hedging

This paper proposes a hybrid manufacturing/remanufacturing model with the financial hedging in the case where the randomness in demand is correlated with the financial markets. The provided models are mainly for those risk-averse remanufacturers who faced with random demand and yield. The aim of this paper is to maximise remanufacturer utility by purchasing financial instruments and producing new and remanufactured products. A hybrid manufacturing/remanufacturing system production planning model is first built under mean-variance framework, and then the financial hedging is integrated into the hybrid production system. There are three main findings. First, the variance of profit with financial hedging is always less than the variance of the model without financial hedging. Second, the remanufacturer with high (low) risk aversion is more likely to produce new (remanufactured) products. Third, the model without (with) financial hedging tends to produce new (remanufactured) products unless remanufacturing cost is low (high) enough. All those findings proved that financial hedging can reduce the operational uncertainty effectively and increase the proportion of remanufacturing, which will make remanufacturing firms more economical and environmentally friendly. Therefore, remanufacturing firms can consider using financial hedging to reduce operational uncertainty.     

限制市场中不定权益的定价

通过构造一族辅助风险溢价来确定不定权益的无套利价格，用这种方法 讨论了存在交易限制时欧式不定权益的定价问题，其结果与Davis的公平价格一致.     

Two-level hedging point control of a manufacturing system with multiple product-types and uncertain demands

This research is motivated by the co-operative production process of networked manufacturing systems (NMS). Manufacturing resource sharing and flexible production scheduling are two features of NMS. For an individual manufacturing system in an NMS, ‘flexible production scheduling’ means that it can produce multiple product-types and the switching of products is quick enough to respond to the demand fluctuation. ‘Manufacturing resource sharing’ means the utilisation of extra production capacity from other manufacturing systems in the NMS. Of course, that will bring extra cost. This paper focuses on the optimal production control problem of such a situation: one manufacturing system, multiple product-types, and uncertain demands. Here, it is assumed that there are two demand-levels for each product-type: the lower one and the higher one. The total normal production capacity is larger than the total lower demands and smaller than the total higher demands. If the total demands cannot be satisfied and the work-in-process (WIP) of all product-types decrease to a certain level, e.g. zero WIP, the extra production capacity may be utilised. For such a system, a new two-level hedging point policy is proposed, in which two hedging points (a higher one and a lower one) are given for each product-type. Different from the prioritised hedging point (PHP) policy which is usually applied to one-machine and multiple part-type systems, our control policy considers all part-types at the same prioritised level and keeps the work-in-process states of all product-types on a straight line in the state space. Thus, the total costs for WIP inventory and the occupation of extra capacity can be obtained in a closed form, which is a function with respect to the hedging points. Then the method for optimising the hedging points is proposed and the special structure of the optimal hedging point is obtained. Numerical experiments verify the optimality and the special structure of the hedging point obtained by our method.     

Bundled automobile insurance coverage and accidents

This paper investigates the characteristics of automobile accidents by taking into account two types of automobile insurance coverage: comprehensive vehicle physical damage insurance and voluntary third-party liability insurance. By using a unique data set in the Taiwanese automobile insurance market, we explore the bundled automobile insurance coverage and the occurrence of claims. It is shown that vehicle physical damage insurance is the major automobile coverage and affects the decision to purchase voluntary liability insurance coverage as a complement. Moreover, policyholders with high vehicle physical damage insurance coverage have a significantly higher probability of filing vehicle damage claims, and if they additionally purchase low voluntary liability insurance coverage, their accident claims probability is higher than those who purchase high voluntary liability insurance coverage. Our empirical results reveal that additional automobile insurance coverage information can capture more driver characteristics and driving behaviors to provide useful information for insurers’ underwriting policies and to help analyze the occurrence of automobile accidents.     

外汇期权的多维Black-Scholes模型

建立了多维Black-Scholes模型，利用倒向随机微分方程和鞅方法，讨论外汇欧式未定权益的一般定价问题，获得了一般定价公式及套期保值策略，由此给出了欧式看涨期权与看跌期权定价和套期保值的解析表达式。     

标的资产由分数维布朗运动驱动的亚式期权定价及套期保值

在标的资产价格由分数维布朗运动驱动的假设下,文章研究了一种亚式期权的定价.我们利用Numeraire变换与复制首先将亚式期权定价转变为类似的欧式期权定价,然后运用Merton对冲风险的思想得到亚式期权的定价,最后运用Malliavin分析与一般地Clark公式给出亚式期权的套期保值策略.