基于在线算法的改进指数梯度投资组合策略

弱集成算法是对专家意见进行动态加权平均的在线学习算法。近年来,机器学习和人工智能等方法被用来研究在线投资组合问题。该文从弱集成算法的在线学习及其序列决策性角度出发,设计改进的指数梯度在线投资组合策略,以弥补指数梯度在线投资组合策略不能结合交易费用进行分析的缺陷。首先根据指数梯度在线投资组合策略的更新方法构建代表投资策略的专家意见池,并以此为基础应用弱集成算法加权集成专家意见得到改进的指数梯度在线投资组合策略,证明了该策略可与最优专家策略(基准策略)相媲美。其次将交易费用引入到改进的指数梯度在线投资组合策略中,进一步给出对应的投资策略,重要的是理论上证明了该策略实现的平均累积收益与最优专家策略实现的平均累积收益之间的差值存在渐进式下界,从而提高了指数梯度在线投资组合策略的实用性。最后利用国内外股票市场的历史数据进行实证分析,说明了改进的指数梯度在线投资组合策略的可行性和有效性。     

Intimacy,rapport, and exceptional disclosure: a comparison of in-person and mediated interview contexts

While qualitative researchers increasingly accept online video interviews as a reliable method, many maintain concerns about rapport and data quality. Drawing on two separate interview projects conducted in private in-person settings, public in-person settings, and privately via Skype, we compare interview contexts with regard to rapport, suitability to sensitive topics, interview duration, and scheduling concerns raised by prior research. Analytical comparison of these two corpuses of data suggest, largely in contrast to previous literature, that (1) interviews conducted in private settings (either in-person or via Skype) result in more sharing of deeply personal experiences, and there is little difference in this exceptional disclosure between Skype and in-person private interviews; (2) interviewing via Skype produces neither reduction nor inappropriate excesses of rapport; and (3) Skype interviews are a popular choice among participants, did not result in shorter interview duration, and were not subject to greater rescheduling or cancellation.     

线上线下融合模式下考虑战略顾客行为的供应链协调研究

在移动电商高速发展和移动支付日益便捷的时代,线上线下融合商务模式正日益成为传统零售、电子商务甚至快递物流企业转型升级的重要方向,影响着供应链运营管理及其优化决策。线上线下融合模式下的战略顾客行为不同于传统模式,其对于供应链运营管理及其优化决策的影响也不同于传统模式。基于O2O运作模式特征,运用战略顾客行为理论、供应链优化与协调理论,本文分别构建了"线上下单+线下体验+线下支付+自行提货"O2O模式1、"线上浏览+线下体验+线上购买+线下配送"O2O模式2、纯线下模式和纯线上模式下考虑战略顾客行为的供应链集中决策模型和契约协调模型,并进行了相应的数值分析,在此基础上,提出了相应的管理启示。研究结果表明：（1）无论是"线上下单+线下体验+线下支付+自行提货"O2O模式1还是"线上浏览+线下体验+线上购买+线下配送"O2O模式2,收益分享契约机制可以有效地实现战略顾客行为下的供应链协调。（2）对比两种O2O模式和两种非O2O模式,O2O模式1和O2O模式2能给供应链及其成员带来更多的利润,而纯线上模式和纯线下模式能给战略顾客带来更高的效用。（3）O2O模式下,制定较高的自提补贴和较低的折扣价格,有利于提高供应链及其成员的运营绩效。（4）O2O模式下,增强产品及其相关服务的实际体验效用,有利于提高供应链整体及其成员的运营绩效,有利于提高战略顾客的净效用。     

网络借贷市场参与主体行为策略的演化博弈均衡分析——基于三方博弈的视角

由于监管缺失、信用风险管理缺位,导致网络借贷市场的违约事件持续出现,损害网络借贷市场的参与者利益。本文构建了一个包括网络借贷平台、金融监管机构和投资者的网络借贷市场参与主体的三方行为策略演化博弈模型,从演化博弈的角度分析了网络借贷平台、金融监管机构和投资者的策略选择对网络借贷市场运行的影响,并以拍拍贷平台为案例进行数值模拟分析。研究结果表明：不同初始值的三方博弈结果存在显著差异,网络借贷市场参与主体行为策略的演化博弈不具有稳定中心点、且不存在稳定的均衡点。另外,当金融监管机构采取"严格监管"措施时,惩罚值越高,网络借贷平台越倾向于选择"自律"的行为策略,随着投资者投资额度的增加,网络借贷平台选择"自律"行为策略的概率逐渐降低。最后,提出规范网络借贷市场参与者行为和风险控制的对策建议。     

基于Petri网的微博网络信息传播模型

微博网络中的信息传播模型是分析用户行为,找出传播路径,确定领袖人物,发现舆情热点等研究的基础。虽然多种不同角度的信息传播模型已经得到广泛研究,但缺乏对信息动态传播过程的直观描述。本文基于Petri网的结构和特征,针对微博网络信息传播过程,提出了一种简单直观的描述模型,该模型首先对微博网络的信息动态传播过程中的对象进行结构化描述。本文根据微博网络的用户结构关系,并利用Petri网的相关理论,形式化解释和定义信息传播基本对象,从而更加直接描述了微博网络中的转发、评论、回复等多种用户行为。在此基础上,本文利用Petri网能够描述信息流动问题的特征,结合颜色Petri网和时延Petri网,从Petri网系统的角度表示信息动态传播路径,并研究网络的动态性质和传播条件,使得信息传播模型更加真实地模拟信息传播情况。最后本文分析信息传播算例和新浪微博真实数据实验,验证了模型的有效性和可行性,为舆情态势分析以及用户行为的研究提供帮助和支持,同时也为其它社交网络信息传播的用户行为描述提供了新的思路。     

Strategies and cues adolescents use to assess the age of an online stranger

A common risk among adolescents is sexual solicitation, in which an adolescent is asked to provide sexual information, engage in sexual talk, or in sexual activities. Although scholars increasingly address this topic from an intrapersonal perspective, there is little attention to factors of language use and message content. In two focus group studies, we investigated whether adolescent girls consider themselves capable of assessing whether an online stranger is an adult or a peer, the extent to which adolescent girls actually succeed in making this assessment, the strategies they apply to do so, and the content- and language-related cues focused on. Our findings suggest that most of the adolescent girls are confident in their ability to assess whether the stranger is a peer or an adult with possible sexual intentions. However, we also found that only 43% were able to correctly make this assessment. Most of the adolescents seem to apply the passive strategy of uncertainty reduction: They scan the profile page of the stranger, check contact information, and the profile picture. They may choose to apply the interactive strategy to find out more about the online stranger. Important content-related cues that alarm adolescent girls are: ignoring personal questions, showing an exaggerated amount of interest, acting as a friend, and being sexually oriented. Language cues mentioned related to word usage, abbreviations, sentence length, and tone.     

Comparing Social Work Students’ Perceptions of Risk Using Online Discussion Fora: Lessons Learned from a European Pilot Project

Comparisons of international child welfare systems have identified two basic orientations to practice; a ‘child protection’ orientation and a ‘child welfare’ orientation, which are founded upon fundamentally different values and assumptions regarding the family, the origins of childcare problems, and the proper role of the state in relation to the family. This paper describes a project which sought to compare how undergraduate social work students from three European Universities perceive risk in referrals about the welfare of children and to explore the impact of different cultural, ideological and educational contexts on the way in which risk is constructed by students. Students from Northern Ireland, Germany and Poland examined three vignettes via 10 online discussion fora each of which provided a narrative summary of their discussion. The paper presents some findings from the analysis of the qualitative data emerging from the student discussions and draws out the lessons learned in terms of how the project was designed and implemented using online discussion fora.     

Observational practice in virtual worlds: revisiting and expanding the methodological discussion

Virtual worlds, such as World of Warcraft and Second Life, have seen remarkable mainstream uptake in the last decade. Such environments have grown from hosting niche interest groups to providing sites for leisure, business and education for tens of millions of Internet users. Concurrently, a multi-disciplinary research field exploring the application of such spaces has emerged. This article examines in detail one data collection practice – observation in virtual worlds – that has been applied extensively, but without extensive methodological discussion. By revisiting and extending earlier work on this topic, the article presents four key considerations for those conducting observational research in virtual worlds: defining and delimiting field sites, discerning attention, charting actions and attributing intention. It is concluded that researchers must both ward against flawed assumptions about virtual world observation and consider multi-method strategies to overcome limitations in observational data.     

Network domains in social networking sites: expectations,meanings, and social capital

This paper examines why the use of social networking sites (SNSs) leads to different results in cultivating bridging and bonding social capital for different groups of people. Based on in-depth interviews of 45 university students in Hong Kong, I find that Mainland Chinese students studying in Hong Kong actively use SNSs for seeking practical information about offline matters, and they obtain substantial enacted support from other Mainland students of the same university through SNS use. As a result, they accumulate both bridging and bonding social capital. Local Hong Kong students, however, use SNSs mainly for social information seeking and are only able to accrue limited bridging social capital through SNS use. Drawing on the theory of network domains, I argue that the different offline network structures in which students are located – namely, homogeneous and closed networks versus heterogeneous and open networks – explain this difference. Students with closed offline networks have defined expectations of online ties; they think of their online activities as practical and leading to real changes in their status among peers. Those with open networks have indefinite expectations of their online audience; thus, they interpret online activities differently, thinking of them as recreational, and they are playful in their online behaviour. These different outcomes of online activities consequently lead to diverse results in social capital accrual.     

Lurking Behavior in Online Psychosocial Discussion Forums: Theoretical Perspectives and Implications for Practice

Improving outcomes of telebehavioral psychoeducation requires rethinking program design when delivered wholly or partially for self-directed participation. Discussion forum participation often follows the “90-9-1 Rule” where 90% of participants lurk, rather than contribute content. A theoretical perspective on the behavior can help explain its adaptive functions, as well as the threats that this behavior poses to the lurker. Implications for practice require program redesign that actively links individual skills training and group-based discussion. The proposed linking design can synergize individual and group participation to support the development of mutual aid, as well as greater interaction with psychoeducation content and materials.