顺向正弦来流条件下圆柱气动力和绕流流场数值模拟研究

为深入了解顺向阵风来流对圆柱气动力和流场特性的影响,开展了雷诺数(Re)为1 000的圆柱绕流三维大涡模拟,研究了不同频率顺向正弦来流对圆柱气动力和流场结构的影响规律,详细分析了升阻力系数、斯特劳哈尔数(St)、回流长度、分离角和尾流结构等参数的变化规律。顺向正弦来流速度为U=U₀+Asin(2πft),其中来流频率f的变化范围为0～0.3 Hz,U₀为平均速度,A为竖向正弦来流的振幅,设为0.15U₀。研究结果表明：圆柱阻力系数卓越频率(即主导频率)与正弦来流频率基本一致,升力系数存在3个明显的频率峰值,分别对应涡脱频率与来流频率之差、涡脱频率、涡脱频率与来流频率之和。随着正弦来流频率f增大,St先减小后增大,在f=0.25 Hz时达到最小值,而回流长度先增大后减小,且在f=0.15 Hz时达到最大值。当f≤St时,分离角不变,而顺流向最小速度逐渐增大;当f>St时,分离角逐渐增大.     

(Ca1-xSrx)[(Li1/3Nb2/3)0.95Zr0.15]3+δ陶瓷微波介电特性

研究了A位Sr2 取代对(Ca1-xSrx)[(Li1/3Nb2/3)0.95Zr0.15]3 δ(0.0≤x≤0.2,CSLNZ)陶瓷的微观结构及微波介电特性的影响.当0≤x≤20%(摩尔分数)时,体系为单一钙钛矿相,随Sr2 含量的增加,介电常数和谐振频率温度系数增大,而品质因素先增大,x=0.05时,开始下降.用键价理论分析了谐振频率温度系数随B位键价的变化关系.当Sr2 含量为5%(摩尔分数)时,陶瓷微波介电性能最佳:εr=32.5,Qf=13500GHz,τf=-2.4×10-6/℃.     

考虑航空战略联盟风险因素的Shapley值收益分配模型

航空联盟已经成为全球航空公司之间重要的合作方式,对航空公司降低成本、提高收入、扩展国际市场等有正向的影响。当航空公司加入航空联盟后,如何对合作后的收益进行合理的分配,将对航空公司的绩效以及航空联盟的稳定性产生重要的影响。为此,本文构建收益最大化为目标的决策模型,分别讨论集中决策和分散决策下两个模型的最优定价和航班频率,以及最优决策下的航空公司和航空联盟的收益。在此基础上,通过模糊综合评价方法评估航空联盟的风险,结合考虑风险的Shapley值方法对联盟的最大化收益进行公平、合理的分配,为加入航空联盟的航空公司提供有效的收益分配解决方案。最后,结合南航的实际情况,将提出的收益分配模型用于制定南航的联盟收益分配方案。     

NdAlO3掺杂对Ba4.2Nd9.2Ti18O54陶瓷微波介电性能的影响

研究了NdAlO3掺杂对Ba4.2Nd9.2Ti18O54(简称BNT)陶瓷材料微观结构及其微波介电性能的影响.采用XRD和场发射扫描电子显微镜分析了掺NdAlO3后的BNT陶瓷材料的微观结构.结果表明,掺入的NdAlO3与Ba4.2Nd9.2Ti18O54形成了固溶体.随着NdAlO3掺入量的增加,材料的介电常数和谐振频率温度系数逐渐减小,Q×f值先增大后减小.当NdAlO3的掺入量为10wt%时,材料的Q×f值达到最大(11400GHz),谐振频率温度系数接近为零(-0.7ppm/℃),此时材料的相对介电常数为66.29(3.5GHz).     

探讨激振频率和容器宽度对颗粒层中对流的影响

竖直振动激励下准二维颗粒层中对流运动受激振频率f和容器宽度L的影响,实验结果表明,对流卷的个数和对流运动的方向强烈地依赖于激振频率而对容器宽度不太敏感。对流运动的强度受激振频率f和容器宽度L的影响都较大,当容器宽度一定时,对流运动的强度随激振频率振荡变化。当频率一定时,容器宽度L存在一个临界值Lc,当LLc时,随着L的增加,对流运动的强度增加;当LLc时,随着L的增加,对流运动的强度反而减小。     

Ca[(Li_(1/3)Nb_(2/3))_(0.8)Sn_(0.2)]O_(3-δ)-xTiO_2陶瓷的微波介电特性

研究了Ca[(Li1/3Nb2/3)0.8Sn0.2]O3-δ-xTiO2(0≤2≤0.2)陶瓷的微观结构及微波介电特性.当0≤x≤10%(摩尔分数,下同)时,体系为单一钙钛矿相.随Ti4+含量的增加,B位1:2有序度下降,品质因素减小,谐振频率温度系数先由-22.6×10-6/℃增加到-11.1×10-6/℃,然后向负值方向移动.当Ti4+含量为10%时,陶瓷微波介电性能最佳:εr=29.3,Qf=2684GHz,τf=-11.1×10-6/℃.     

设计决定着飞行体验的质量

1952年创办的全日空航空公司（All Nippon Airways Co．，Ltd．下简称为ANA）是亚洲资产规模最大的航空公司。我们拜访了位于东京汐留的全日空总部，发现在如今竞争激烈的航空市场中，飞行服务已经远远不只是把人从一点承载到另一点。当人们开始听说到一个航空公司的名字时，就已经开始对乘坐它的飞机旅行有了一种想象和期望，设计在这里是挑战想象与期望的角色。     

低温烧结(Zr0.8Sn0.2)TiO4陶瓷的晶相组成与微波介电性能

讨论了低温烧结(Zr0.8Sn0.2)TiO4微波介质陶瓷的晶相组成与制备工艺、掺杂离子的关系,结果表明粉体的合成温度对烧结体的晶相构成有很大的影响,进而影响材料的谐振频率温度系数τf,稍高的合成温度有利于提高α-PbO型ZST相的稳定性,使谐振频率温度系数τf由107 ppm/℃降至20.88 ppm/℃.采用Nb5+离子掺杂能更有效地抑制烧结过程中游离氧化物相的析出,当Nb5+达到0.15mol%时,920℃烧结样品的介电常数为25,谐振频率温度系数τf为-2.44 ppm/℃,品质因数Q·f达4868GHz(5GHz).     

Fe73．5Cu1Nb3Si13．5B9纳米晶磁粉芯磁性能研究

用Fe73.5Cu1Nb3Si13.5B9纳米晶粉体,加入一定量的塑化剂,通过模压成型方法制备磁粉芯.实验结果表明,在一定粒度范围内,磁导率μ随粉体粒度增大而增大,品质因数Q,随着粒度的增大而减小,且在一定频率范围内,μ呈现良好的频率稳定性;塑化剂质量百分含量α越大,μ越小.当α=6.5%时,μ达到最大值31.8.0～300kHz范围内,α与Q成反比;300～1000kHz范围内,α与Q成正比例关系;磁导率μ随着成型压力的增加而提高,相反,压力越大,Q值越小;磁导率随着磁粉芯测试温度的提高逐渐减小,0≤f≤700kHz范围内,温度升高,Q降低,700kHz≤f≤1000kHz范围内时,温度升高,Q值升高;随退火温度的增加,μ和Q均呈现先增大后减小的趋势.     

Cesàro平均的带权强求和

设f(x)∈LP(Ωn),1≤P≤2,δ＞(n-1)(1)/(P)-(1)/(2)),σδN(f)(x)表示f(x)在n维球面Ωn上的Cesàro平均.证明了 limN→∞(1)/(N+1) ΣN)/(k=0|σδk(f)(x)-f(x)| 2ak=0 a.e.x∈Ωn 其中权系数ak＞0,满足 1≤(1)/(N+1)ΣN)/(k=0ak≤A (A是一个绝对常数).     

A Stackelberg-Nash model for new product design

Existing conjoint approaches to optimal new product design have focused on the Nash equilibrium concept to model competitive reactions. Whereas these approaches have treated all competing firms equally as Nash players, one firm may have an advantage over its rivals, e.g., more pre-experience on competitors’ behavior and/or a first-mover advantage. This paper proposes a Stackelberg-Nash (leader-followers) model which can accomodate such information for decision making. The optimal product design problem is formulated from the perspective of a profit-maximizing new entrant (the leader) who wants to launch a brand onto an existing product market and acts with foresight by anticipating price-design reactions of the incumbent firms (the Nash followers). In the absence of closed-form solutions, we use a sequential iterative procedure to compute a Stackelberg-Nash equilibrium and to establish its uniqueness. The new conjoint model is illustrated under several competitive scenarios and price, design and profit implications are compared to a simple Nash equilibrium model. We find that a Stackelberg leader strategy may not only yield a much higher profit for the new entrant than a Nash strategy, but may also lead to strong profit asymmetries between competitors with still higher profits for the incumbent firms. In other words, the incumbent firms may also benefit strongly from a new entrant choosing a Stackelberg leader strategy.     

考虑信息泄露的供应链成员行为

为了研究供应链中纵向成员信息共享及横向成员之间的需求信息泄露行为发生机理,针对服从伯川德竞争的替代产品,建立了由一个批发商与两个竞争型零售商（在位零售商和跟随零售商）组成的基本模型,探讨了批发商泄露与不泄露在位零售商产品定价信息时两个零售商的产品差别定价策略,分析了批发商的泄露行为选择机理。研究表明：当批发商泄露在位零售商定价信息时,零售商一定进行分离均衡定价;当在位零售商定价高于分离均衡高价格时,跟随零售商判断市场为高需求状态,反之为低;当在位零售商的产品定价位于最小泄露区间时,批发商一定泄露在位零售商的定价信息。     

Technology investment strategy in the presence of competitor entry: Broadband deployment in the US telecommunications industry

We evaluated the broadband deployment strategy of incumbent firms in the local exchange sector of the US telecommunications industry (1994–1998), each of which must devise strategies for dealing with new firms entering their markets. We found that incumbents consistently under-invested in fiber optics that would have enabled them to upgrade their broadband infrastructure in the face of competitive entrants. Contrary to theories of entry deterrence, this behavior did not signal accommodation by monopolistic incumbents. Rather, it was consistent with an entrapment strategy: when a new firm entered and invested in capacity, the incumbents used their monopoly power to deny access or to provide poor-quality access, thereby making the competitors’ product quality worse than the incumbent's, leading to customer dissatisfaction and revenue losses that could eventually weaken the rival.Yet, such a strategy was dysfunctional. A strategy of investment would have been best for the incumbents since the gains from triggering network externalities would have been substantial. As new competitors entered the incumbents’ markets, the best strategy for the incumbents would have been to reciprocate positively, invest in fiber capacity, and then play tit for tat. If the incumbents had invested in broadband and even more competitive entrants followed, which in turn caused greater broadband investment, and so on, the wiring of the entire United States by new entrants and incumbents with broadband technology would today be complete.     

Impact of the implementation of rest days in live bird markets on the dynamics of H5N1 highly pathogenic avian influenza

Live bird markets (LBMs) act as a network ‘hub’ and potential reservoir of infection for domestic poultry. They may therefore be responsible for sustaining H5N1 highly pathogenic avian influenza (HPAI) virus circulation within the poultry sector, and thus a suitable target for implementing control strategies. We developed a stochastic transmission model to understand how market functioning impacts on the transmission dynamics. We then investigated the potential for rest days—periods during which markets are emptied and disinfected—to modulate the dynamics of H5N1 HPAI within the poultry sector using a stochastic meta-population model. Our results suggest that under plausible parameter scenarios, HPAI H5N1 could be sustained silently within LBMs with the time spent by poultry in markets and the frequency of introduction of new susceptible birds'' dominant factors determining sustained silent spread. Compared with interventions applied in farms (i.e. stamping out, vaccination), our model shows that frequent rest days are an effective means to reduce HPAI transmission. Furthermore, our model predicts that full market closure would be only slightly more effective than rest days to reduce transmission. Strategies applied within markets could thus help to control transmission of the disease.     

An Exploratory Study on the Transition from OEM to OBM: Case Studies of SMEs in Korea

This study investigates how the transformation of latecomer small- and medium-sized enterprises (SMEs) in emerging economies from dependent or subcontracting original equipment manufacturing (OEM) firms into independent or original brand manufacturing (OBM) firms is possible to achieve a significant catch-up in their share of regional or global markets. Given that SMEs are rarely able to make such a transition, we elaborate this dynamic process by performing case studies on eight Korean SMEs. These SMEs created their own paths instead of following their forerunners. These paths are neither entirely new nor take the form of leapfrogging, but are characterized by new combinations of existing paths. We identify several risk factors, such as counterattacks and intellectual property lawsuits, that latecomer SMEs face from incumbent SMEs. In addition, we emphasize the importance of cultivating firm-specific knowledge by engaging in a continuing process of trial and error type in-house experiments.     

Digital transformation of incumbent firms from the perspective of portfolios of innovation

Digital technology has created new elements of innovation types and given incumbent firms new portfolios of innovation. The portfolio of innovation used during a digital transformation allows it to be successfully implemented and gives a competitive advantage to incumbent firms. We present two propositions for the portfolio of innovation and its shift during the process of digital transformation. Based on an emergent innovation matrix, we conducted a multi-case study on three Chinese firms from different industries, in order to identify the novel innovation types that appear when these firms undergo digital transformation. The research suggests that incumbent firms innovate in various ways simultaneously to implement a digital transformation when faced with market and technology change, and the portfolio of innovation shifts during the digital transformation process.     

Anchor,incumbent and late entry MNEs as propellents of technology cluster evolution

This paper reports on a longitudinal qualitative study on the role of MNEs (multinational enterprises), as conduits of knowledge flows, in the evolution of a technology cluster. Previous studies illustrated how MNEs were attracted to existent clusters and their modes of entry into the cluster. This study however sets out not only how MNEs originated this cluster, but also how incumbent and later entrant MNEs propelled the cluster onwards in related and unrelated technology branches through both shaping knowledge density in the cluster and spreading knowledge breadth across the cluster. This facilitated simultaneous cluster specialisation, diversification and connectivity into the global system, thereby reducing vulnerability to technological disruption.     

Rethinking the Institutional Contexts of Emerging Markets Through Metaphor Analysis

• Recent literature recommends greater analysis of institutional contexts in order to better adapt strategies in emerging market economies. This paper explores cognitive challenges in understanding institutional contexts, and reveals an outdated vernacular around emerging markets. Unwittingly, we may be crafting strategies based on how we would like emerging markets to be, rather than on how emerging markets actually are.
• Institutional context is investigated through metaphor analysis. As conceptual constructions that link the abstract to the concrete, metaphors can yield rich insights when analyzed. The metaphor analysis performed finds powerful cognitive simplifications and preconceptions of emerging markets.
• Eliciting novel metaphors around the labels ??emerging markets??, ??developing countries??, and ??third world?? uncovers a fragmented rather than holistic view of institutional context. Strategies unresponsive to emerging markets may flow from a fragmented view of institutional context.
• In terms of theory, the use of metaphor analysis highlights the importance of considering subjective and even messy elements of institutional context. Prevailing discussions in the international business literature often focus on streamlined, objective measures of institutional context. This paper emphasizes that a complex process of institutionalization is being observed rather than a steady state of objective outcomes.

     

Born-Globals and Culturally Proximate Markets

• In this paper we focus on the differences between born-globals and older firms. We compare whether cultural proximity is important for born-globals and older firms and whether international or technological knowledge drives their internationalisation. In addition, we compare whether born-globals and older firms are proactive or reactive in their choice of culturally proximate markets.
• Our research suggests that born-globals tend to internationalise rapidly into markets ready to adopt their technology. This is driven by the need to establish a revenue stream (cash flow) as quickly as possible. These born-globals usually seek larger advanced economies, which are often culturally similar (proximate) and offer economies of scale; reducing risk for inexperienced firms. Indeed, born-global firms are more willing than older firms to move from culturally proximate to culturally non-proximate markets very quickly.
• Utilising an abductive approach based on case studies, our findings show that born-globals use their technological knowledge and networks and are proactive when they enter culturally non-proximate markets. Born-globals must assess a new market for its ability to provide a revenue stream very soon after entry. If the culturally proximate market does not offer this, then they will leverage technological knowledge and networks to move rapidly into nearby non-proximate markets where they perceive better opportunities for building a customer base or new funding alternatives to sustain the firm in their early foreign market forays.
• Our research significantly extends theory in highlighting that born-globals rely more on technological experience and display proactive behaviour more than older firms which can draw on previous international experience.

     

Exploring the validity of patent applications as an indicator of Chinese competitiveness and market structure

An increasing number of studies are using either worldwide Chinese patent applications as an indicator to assess the country’s international competitiveness or applications at the Chinese SIPO as an indicator of the internal structure of innovative activities on its domestic market. Whenever such macro level studies are presented, however, many practitioners tend to express disbelief regarding the validity of patent indicators in this emerging market, where IPR protection is perceived to play a role that differs strongly from that in other economies. This paper, therefore, compares the structure of both patent applications at the Chinese national office and global applications by Chinese inventors. Moreover, it contrasts Chinese application activities with those of other nations. On this basis, it analyses if there is evidence of different underlying motivations for and logics of application that would substantiate such doubts. It concludes that, following WTO accession, the Chinese technology market is finding its specific equilibrium but retains certain persistent particularities. Global filings of Chinese applicants, in contrast, remain biased towards the few major firms that can compete at the world markets for technology.