On characteristic classes of singular hypersurfaces and involutive symmetries of the Chow group

For any algebraic scheme $X$ and every $(n,\mathscr{L})\in \mathbb{Z}\times \text{Pic}(X)$ we define an associated involution of its Chow group $A_*X$, and show that certain characteristic classes of (possibly singular) hypersurfaces in a smooth variety are interchanged via these involutions. For $X=\mathbb{P}^N$ we show that such involutions are induced by involutive correspondences

The topologically twisted index of N=4\mathcal N=4 super-Yang-Mills on T2×S2T^2\times S^2 and the elliptic genus

We examine the topologically twisted index of $\mathcal N=4$ super-Yang-Mills with gauge group $SU(N)$ on $T^2\times S^2$, and demonstrate that it receives contributions from multiple sectors corresponding to the freely acting orbifolds $T^2/\mathbb Z_m\times\mathbb Z_n$ where $N=mn$. After summing over these sectors, the index can be expressed as the elliptic genus of a two-dimensional $\mathcal N=(0,2)$ theory resulting from Kaluza-Klein reduction on $S^2$. This provides an alternate path to the 'high-temperature' limit of the index, and confirms the connection to the right-moving central charge of the $\mathcal N=(0,2)$ theory.Comment: 29 pages, 1 figure; v2: restricted to real chemical potentials in section 4 and added a comment on the index where $c_r(\mathfrak n_a)<0$ in section

Quality assessment technique for ubiquitous software and middleware

The new paradigm of computing or information systems is ubiquitous computing systems. The technology-oriented issues of ubiquitous computing systems have made researchers pay much attention to the feasibility study of the technologies rather than building quality assurance indices or guidelines. In this context, measuring quality is the key to developing high-quality ubiquitous computing products. For this reason, various quality models have been defined, adopted and enhanced over the years, for example, the need for one recognised standard quality model (ISO/IEC 9126) is the result of a consensus for a software quality model on three levels: characteristics, sub-characteristics, and metrics. However, it is very much unlikely that this scheme will be directly applicable to ubiquitous computing environments which are considerably different to conventional software, trailing a big concern which is being given to reformulate existing methods, and especially to elaborate new assessment techniques for ubiquitous computing environments. This paper selects appropriate quality characteristics for the ubiquitous computing environment, which can be used as the quality target for both ubiquitous computing product evaluation processes ad development processes. Further, each of the quality characteristics has been expanded with evaluation questions and metrics, in some cases with measures. In addition, this quality model has been applied to the industrial setting of the ubiquitous computing environment. These have revealed that while the approach was sound, there are some parts to be more developed in the future

New Estimation Strategies for Demand Threshold Models in the Southern United States

This paper estimates demand threshold models using both first generation log-log models and second generation Tobit models to zip code areas in the Southern US. Results of own-place demographic and economic variables were consistent with previous studies but impacts of neighboring zip codes contrasted previous studies.Demand Threshold Analysis, Central Place Theory, Demand and Price Analysis, R120,

The nature of NGO microfinance in Vietnam and stakeholders� perceptions of effectiveness

The microfinance industry in Vietnam, particularly those sponsored by non-government organisations (NGOs), has experienced rapid expansion in recent years. While there have been anecdotal reports alluding to their contribution in alleviating poverty, a systematic analysis of this issue has been lacking. In a bid to help address this shortcoming, this paper reports on data that was obtained during a survey and interview process that incorporated various stakeholders including financial donors, NGO-sponsored microfinance institutions (NMPs), village leaders and NMP members and non-members. Firstly, the nature of NMPs is described - their objectives, target groups and the financial products they offer. Secondly, perceptions of NMPs effectiveness are discussed from the standpoint of various stakeholders. NMPs are found to be at a critical juncture. While their activities are widely perceived to contribute to poverty alleviation, their future viability is clouded by donor requirements that they become financially self-sufficient. At the same time, certain government policies make achieving this goal very difficult.

A geometric characterisation of toric varieties

We prove a conjecture of Shokurov which characterises toric varieties using log pairs.Comment: 40 page

Prediction of remaining life of power transformers based on left truncated and right censored lifetime data

Prediction of the remaining life of high-voltage power transformers is an important issue for energy companies because of the need for planning maintenance and capital expenditures. Lifetime data for such transformers are complicated because transformer lifetimes can extend over many decades and transformer designs and manufacturing practices have evolved. We were asked to develop statistically-based predictions for the lifetimes of an energy company's fleet of high-voltage transmission and distribution transformers. The company's data records begin in 1980, providing information on installation and failure dates of transformers. Although the dataset contains many units that were installed before 1980, there is no information about units that were installed and failed before 1980. Thus, the data are left truncated and right censored. We use a parametric lifetime model to describe the lifetime distribution of individual transformers. We develop a statistical procedure, based on age-adjusted life distributions, for computing a prediction interval for remaining life for individual transformers now in service. We then extend these ideas to provide predictions and prediction intervals for the cumulative number of failures, over a range of time, for the overall fleet of transformers.Comment: Published in at http://dx.doi.org/10.1214/00-AOAS231 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Truncation of Unitary Operads

We introduce truncation ideals of a $\Bbbk$-linear unitary symmetric operad and use them to study ideal structure, growth property and to classify operads of low Gelfand-Kirillov dimension