The cross-entropy (CE) method is an adaptive importance sampling procedure that has been successfully applied to a diverse range of complicated simulation problems. However, recent research has shown that in some high-dimensional settings, the likelihood ratio degeneracy problem becomes severe and the importance sampling estimator obtained from the CE algorithm becomes unreliable. We consider a variation of the CE method whose performance does not deteriorate as the dimension of the problem increases. We then illustrate the algorithm via a high-dimensional estimation problem in risk management. 相似文献
Personal ties are generally regarded as important to big business growth in Malaysia, particularly after the New Economic Policy (NEP) in the 1990s. Common types are informal ones established between multi-ethnic big business people and Malay key state and political leaders. Other types of ties, company directorship links and informal ties, are seldom studied especially those between the business people and former state bureaucrats and corporate professionals. Thus, by conceptualising the directorship links and informal personal ties as social networks, the author conducted a sociological analysis of some intra- and inter-ethnic directorship links and ties established by four prominent big businessmen after the NEP in the 1990s. This article reports the main finding on the links and ties becoming a common organisational mechanism of business groups owned and controlled by the businessmen, besides providing access to the state. Therefore, another understanding of inter- and intra-ethnic personal ties in big business growth, especially after the NEP is achieved. 相似文献
Estimation of the time-average variance constant (TAVC) of a stationary process plays a fundamental role in statistical inference for the mean of a stochastic process. Wu (2009) proposed an efficient algorithm to recursively compute the TAVC with \(O(1)\) memory and computational complexity. In this paper, we propose two new recursive TAVC estimators that can compute TAVC estimate with \(O(1)\) computational complexity. One of them is uniformly better than Wu’s estimator in terms of asymptotic mean squared error (MSE) at a cost of slightly higher memory complexity. The other preserves the \(O(1)\) memory complexity and is better then Wu’s estimator in most situations. Moreover, the first estimator is nearly optimal in the sense that its asymptotic MSE is \(2^{10/3}3^{-2} \fallingdotseq 1.12\) times that of the optimal off-line TAVC estimator. 相似文献
High population growth in the tropics is driving urbanisation, removing diverse natural ecosystems. This is causing native species to suffer while introduced synanthropes flourish. City planners are developing urban greenspace networks, in part trying to address this issue. Architects contribute to these greenspace networks by designing elevated and ground level green spaces on large-scale buildings. However, little evidence is available on whether building green spaces support native fauna. This is true for birds in tropical Singapore that support important ecosystem services and have existence value. Therefore, in this study, we conducted bird surveys and statistical analyses to determine, if and how vegetation on three building green space types (ground gardens, roof gardens and green walls) have a positive impact on native or introduced bird species. We found that elevated greenery (roof gardens and green walls) on large-scale buildings supported a higher richness of birds and abundance of urban native birds than control roofs and walls without vegetation. Ground gardens supported similar levels of native species as roof gardens but also a larger proportion of generalist synanthropes. However, we found no tropical forest habitat specialists across any space type. Therefore, we recommend roof gardens and ground gardens as a potential space for urban natives outside of a less competitive ground-level urban environment. Our study also found certain building design elements (height of elevated space, presence of specific plants) supported different species groups. Therefore, we suggest that these ecological requirements for different species groups are considered when designing a building’s green space.
Urban Ecosystems - Anthropogenic noise may mask effective vocal signal transmission by birds, particularly in notes occurring in lower frequencies. Previous studies have shown a correlation of... 相似文献
This study aims at ascertaining how Hong Kong people perceive Hong Kong as a harmonious society. It also identifies the elements
that are most conducive to social harmony in Hong Kong, so that the government could take reference when formulating new policies.
1,062 adults residents were asked to rate their perceived level of social harmony and their satisfaction with 36 items (divided
into three dimensions: public governance, society, and economy, family and work) for which the research team believes would
be influencing the perceived level of social harmony. Results show that the average rating of social harmony was 5.57 (out
of 10), delineating a moderate level of social harmony. Subsequent multivariate factor analysis and regression analysis show
that the four extracted factors (from the three dimensions) had significant impacts on the level of social harmony. These
were, in order of significance: (a) public governance, (b) social solidarity and respect, (c) economy/family/work and, (d)
social tolerance and progressiveness. According to the factor loadings of each significant factor, we identified four core
values which we hope the government would consider when formulating new policies, as follows: (1) A Justice Government with
Sincerity on Communication, (2) Mutual Support and Respect with Integrity and Dedication, (3) Dedication to One’s Job and
Community by Helping the Needed and, (4) Creativity and Progressiveness with Tolerance. Implications for policy making are
discussed.
The study was conducted under the direction and guidance of the Fostering Social Harmony Task Force of the Hong Kong Professionals
and Senior Executives Association (HKPASEA). The authors acknowledge the kind support and assistance provided by the Council
Members of HKPASEA and staff members of the Centre for Corporate Governance and Financial Policy at Hong Kong Baptist University.
We are also grateful to Prof. Alex Michalos and Prof. P. K. Ip for their comments and suggestions given at the International
Conference on National Well-Being held in November 2006 at the National Central University, Taiwan. 相似文献