Empirical Analysis of Indirect Network Effects in the Market for Personal Digital Assistants

We present a framework to measure empirically the size of indirect network effects in high-technology markets with competing incompatible technology standards. These indirect network effects arise due to inter-dependence in demand for hardware and compatible software. By modeling the joint determination of hardware sales and software availability in the market, we are able to describe the nature of demand inter-dependence and to measure the size of the indirect network effects. We apply the model to price and sales data from the industry for personal digital assistants (PDAs) along with the availability of software titles compatible with each PDA hardware standard. Our empirical results indicate significant indirect network effects. By July 2002, the network effect explains roughly 22% of the log-odds ratio of the sales of all Palm O/S compatible PDA-s to Microsoft O/S compatible PDA-s, where the remaining 78% reflects price and model features. We also use our model estimates to study the growth of the installed bases of Palm and Microsoft PDA hardware, with and without the availability of compatible third party software. We find that lack of third party software negatively impacts the evolution of the installed hardware bases of both formats. These results suggest PDA hardware firms would benefit from investing resources in increasing the provision of software for their products. We then compare the benefits of investments in software with investments in the quality of hardware technology. This exercise helps disentangle the potential for incremental hardware sales due to hardware quality improvement from that of positive feedback due to market software provision.     

On the optimal taxation of common-pool resources

Recent research developments in common-pool resource models emphasize the importance of links with ecological systems and the presence of non-linearities, thresholds and multiple steady states. In a recent paper Kossioris et al. (2008) develop a methodology for deriving feedback Nash equilibria for non-linear differential games and apply this methodology to a common-pool resource model of a lake where pollution corresponds to benefits and at the same time affects the ecosystem services. This paper studies the structure of optimal state-dependent taxes that steer the combined economic-ecological system towards the trajectory of optimal management, and provides an algorithm for calculating such taxes.     

浅谈建设工程合同形式对工程造价的影响

不同的合同结构形式对工程造价有不同影响,选择哪种合同结构形式需考虑影响造价的主要因素有,业主自身的管理团队、总包单位的能力、减免税费、项目开办费等。     

数控机床进给伺服系统的典型故障及诊断

数控机床是典型机电一体化产品,故障出现的种类和原因很多,其中进给伺服系统故障所占比重较大,文中主要以典型的进给伺服系统故障为例,总结、分析引起伺服系统故障的原因,并提出解决的思路和办法。     

Does pay affect productivity or react to it?: Examination of U.S. manufacturing

There may be a bi-directional relationship between wages and labor productivity. According to conventional theory, employers reward improvements in productivity by raising pay. It also has been argued that wage increases can provide an incentive to improve productivity. This study applies a technique by Geweke to identify the feedback between pay and productivity in U.S. manufacturing. For the 1949–1998 period, measures of directional feedback indicate that both “pay as reward” and “pay as incentive” behaviors have occurred, but the results vary across manufacturing subsectors.     

Effects of teleconferencing technologies: An exploration of comprehension,feedback, satisfaction and role-related differences

Several theoretical approaches have been put forth to predict and explain the effects of teleconferencing technologies. One approach is to examine the functions of nonverbal signals and to make predictions based on the fact that different teleconferencing technologies allow nonverbal communication to different extents. One of the functions of nonverbal signals is to allow the listener to provide feedback to the speaker in a communication. Prior research has shown that such feedback enhances listener comprehension. In this study, it was hypothesized that different teleconferencing technologies would allow different levels of feedback based on their ability to accommodate nonverbal signals, and this in turn would affect comprehension. An experimental study was conducted to compare comprehension, feedback, and satisfaction in telephone and computer conferencing. The study confirmed that comprehension and speaker satisfaction are related to feedback, but failed to show a relationship between listener satisfaction and feedback. No difference in comprehension, listener, or speaker satisfaction was observed across teleconferencing technologies. Role-related differences were observed between the speaker and the listener. It is suggested that the effects of teleconferencing technologies can be mapped systematically by examining each of the functions of nonverbal signals, one at a time.     

Saying it like it isn't: The pros and cons of 360-degree feedback

In corporate America, the use of 360-degree feedback continues to rise. Is this tool, though, all it purports to be? Used with caution, the feedback process can provide meaningful information for both the organization and the individuals involved. Misuse of the process, however, can lead to hurt feelings, increased anxiety, and even loss of key personnel. This small case study showcases key research findings on best practices for using the 360-design feedback process, especially regarding intended use of feedback, aligning performance measures with organizational goals, and selecting and training participants.     

一种数字丝悬式垂直磁力仪传感器的研制

本文根据我国现有的机械式丝悬垂直磁力仪的结构，提出了将其政装为数字化丝悬式垂直磁力仪的差动式电容传感器的设计方案。样机测试表明，其测量精度可与ＭＰ—４型质子磁力仪相媲美．具有结构简单，易掌握操作，成本低等优点．     

Adding Value to the Teaching and Learning of Design and Technology

It has been argued that design and technology can be used as a vehicle for teaching science and vice versa. In this paper, we report an investigation into Grade 6 students understandings of concepts embodied in the Systems strand of a technology syllabus as they grappled with a unit of work in technology for the first time. The unit of work involved students in the design and construction of simple systems, followed by experiences with more complex systems. Qualitative research methods were used to investigate the activities of the students as they engaged in the design and technology learning experiences for eight weeks. Data sources included student and teacher interviews, video and audio recordings of whole class and small group interactions, students notes, drawings and diagrams, and researchers field notes and reflections. Changes in students ability to identify the individual components and analyse how the components worked together in systems, and evidence of students use of scientific understandings for explanations, were noted as the unit of work progressed. An improvement was observed in students abilities to describe relationships between inputs, processes and outputs, and outline sequences of cause and effect. The technology and science appeared to be complementary as they developed technology specific and action-oriented technology and science language, which may be evidence of the presence of a community of learners. Recommendations are proposed for enhancing the value of both design and technology and science if both subjects are taught together as part of an integrated program in primary schools.     

逆变器并联运行控制策略研究

环流是影响逆变器并联运行性能的一个重要因素,本文介绍了环流产生的原因及环流反馈控制原理,并基于此原理提出了一种双逆变器并联控制策略,并通过仿真验证了所提方法有效抑制环流。