Harvest and extinction in multi-species ecosystems

A potential cost of harvesting in multi-species ecosystems is the extinction of nonharvested species that are at the same trophic level as the harvested species. Existing analytical models are not well-suited for studying this harvest externality because they focus on species interactions across trophic levels instead of within them. We identify the conditions under which the harvesting of a single species causes at least one extinction of nonharvested species at the same trophic level. We compare two harvest regimes: uniform management, in which a privately optimal harvest rate is applied to the entire ecosystem; and specialized management, in which a portion of the ecosystem is intensively managed for the harvested species and the rest is left unharvested. Which regime is more likely to result in extinction depends on the discount rate and on the harvested species' competitive ability and colonization rate compared to those of the other species.     

Trustee decision making in small UK charities

Management theory suggests that increasing the quantity and quality of management information available to key members in organisations will lead to improvements in their decision making. However, judgements as to what counts as ‘management information’, and in what its quality consists may vary according to organisational location, size and purpose. Where those ‘key members’ are volunteers, as with charity trustees, perceptions of management information need, amount and value, may vary further. This paper explores aspects of this theory, with particular reference to trustees of small charities in the United Kingdom. It outlines a research programme drawing on trustees in organisations working for children and for people with disabilities. A range of findings is presented, recording trustee experiences of and responses to management information, as this affects their charities' performance. Following from three in-depth case studies in small charities, findings show that informal systems are in operation, whereby trustees devolve much of the responsibility for management information to their chief officers, who are then monitored by their chairs. While this system is viewed by participants as an effective and practical means of enabling decision making, certain questions are raised regarding trustee liability and accountability.     

Continued usage of e‐learning communication tools: a study from the learners' perspective in Hong Kong

In line with the mainstream research on e‐learning, we propose a model of the continued usage of e‐learning communication tools by learners. We observe in particular that there are two less studied but potentially very important factors, learning self‐efficacy and compatibility of values and beliefs with learning tools, which may contribute significantly to the continued usage of e‐learning communication tools. We carried out a study of 682 e‐learners and the results support our propositions.     

剖析住房市场崩溃根源

【美国《华尔街日报》7月24日】美国现已开始探寻住房市场崩溃的根源。国会两位重要领袖宣称已经找到了一些主要原因，但他们对此给出的解释却并不完整。     

Management Information Needs and Perceptions in Smaller Charities: An Exploratory Study

This article explores the extent and nature of management information needs of trustees, as perceived by selected trustees of smaller charities. It links these perceptions to questions concerning charity performance, drawing on assumptions in the literature (often implicit) that the quality of management information can be gauged. Also, that there is a corresponding link between meeting management information needs and improving organisational performance. The research methodology comprised a general pilot study and trustee survey, followed by accounts analysis and in-depth interviews in selected charities. From this, vignettes of trustees' perceptions were drawn up and case study accounts of three charities' approach to trusteeship, management information handling strategies, and self-assessment of performance were developed. The study discovered the existence of an 'expectations gap'between what charity trustees are supposed to do and what they can actually achieve.     

User experience on mobile video appreciation: How to engross users and to enhance their enjoyment in watching mobile video clips

In the past few years consumers have enjoyed consuming video content on a growing number of devices including the traditional television, personal computers, mobile phone and tablets. Each device has its own technical attributes and associated consumption characteristics. This research examines the differential effects of user experience on engagement during video consumption in the mobile and desktop environments. We have experimented with different situations related to the genre, the sequence of playing, the extent of interruption, the timing of the interruption, and length of the video clips. Our model was quantitatively tested, with 270 users taking part in a between subject experiment.In the mobile environment, our results provide evidence that sensory experience is a significant factor for enjoyment and engagement with the video, while emotional response is not. The reverse is true for the desktop environment. Learning curve factors work differently in the two environments. User enjoyment and engagement are significantly moderated by learning curve factors in the mobile environment only. The result is robust as it is true for both previous learning (usage experience with the device), and on-the-go experience (sequencing of video clips). Attention span only affects engagement and enjoyment in the desktop environment. Outside interruption only affects engagement and enjoyment in the mobile environment.Our findings can inform commercial practices on the video design and user interface, and also enhance our understanding of the contextual dependency of the theoretical concept of engagement in mobile entertainment.     

NET ACCUMULATION OF TIMBER RESOURCES

National accounting issues related to forest resources have attracted much attention recently. The net-depletion method, the most popular method for estimating aggregate changes in the value of timber stocks, tends to overstate both the depreciation of mature forests due to harvests and the appreciation of immature forests due to growth. Alternative, correct methods, which I term the net-price and El Serafy variations, can be derived from an asset valuation model that takes forest age into account. An empirical example indicates that estimates from the net-depletion method can deviate from actual values by up to 40 percent for some age classes.