10260970
Pure adaptive search in global optimization
Pure adaptive seach iteratively constructs a sequence of interior points uniformly distributed within the corresponding sequence of nested improving regions of the feasible space. That is, at any iteration, the next point in the sequence is uniformly distributed over the region of feasible space containing all points that are strictly superior in value to the previous points in the sequence. The complexity of this algorithm is measured by the expected number of iterations required to achieve a given accuracy of solution. We show that for global mathematical programs satisfying the Lipschitz condition, its complexity increases at mostlinearly in the dimension of the problem.
17403700
Planning horizons for the deterministic capacity problem
Abstract We consider the problem of determining the optimal timing and sizing of new facility construction under a continuous technology model of possible sizes. The rate of convergence of short to long run optimal policies is established and planning horizon implications are explored. We also present an efficient algorithm for solving such problems for all horizon times by solving a single horizon time problem
17812918
Acquiring and delivering lessons learned for NASA scientists and engineers: a dynamic approach
Web forms are a common mechanism for collecting information online. They pose some limitations which negatively affect ease and flexibility of user interaction. These limitations are more pronounced when collecting information that can not be broken down into well defined and agreed upon structures. Lessons Learned or any kind of 'knowledge' is an example of such information. In this paper we introduce a concept of 'Dynamic Forms' which is aimed at enhancing user interaction while collecting unstructured information, 'Lessons Learned' in particular.
16499745
The Self-4.0 user interface: manifesting a system-wide vision of concreteness, uniformity, and flexibility
Manipulating programs is hard, while manipulating objects in the physical world is often easy. Several attributes of the physical world help make it comprehensible and manipulable: concreteness, uniformity, and flexibility. The Self programming system attempts to apply these attributes to the world within the computer. The semantics of the language, the efficiency and fidelity of its implementation, and the architecture of its user interface conspire to make the experience of constructing programs in Self immediate and tangible. We describe the mechanisms used to achieve this goal, and illustrate those mechanisms within the context of an extended programming task.
5111320
Work rhythms: analyzing visualizations of awareness histories of distributed groups
We examined records of minute-by-minute computer activity coupled with information about the location of the activity, online calendar appointments, and e-mail activity. We present a number of visualizations of the data that exhibit meaningful patterns in users' activities. We demonstrate how the patterns vary between individuals and within individuals according to time of day, location, and day of the week. Some patterns augment the schedule information found in people's online calendars. We discuss applications for group coordination (especially across time zones) plus opportunities for future research. In light of the popularity of instant messaging, this research identifies some of the benefits and privacy risks associated with the uses of online presence and awareness information.
8058532
Perfect secrecy in wireless networks
In a classic paper, among a multitude of other security issues, Claude E. Shannon defined perfect secrecy for a pair of secure computers communicating over an insecure link. The present paper extends Shannon's notion of perfect secrecy to ad hoc wireless networks of computers. All of the wireless transmissions are insecure. This paper assumes a secure base-station communicating wirelessly using symmetric encryption with physically insecure autonomous computers. These wireless communications use a common symmetric encryption algorithm. Each of the computers has a unique fixed key. The base station has a copy of each key. This scenario gives way to a generalization of Shannon's perfect secrecy. This generalizes to t-perfect secrecy which is directly based on t-wise independence. This gives another natural application of t-wise independence to cryptography. Finally, transmission noise, message collisions, and other issues are briefly discussed with respect to this generalization of Shannon's perfect secrecy.
27655269
Unobserved heterogeneity in panel time series models
Recently, the large T panel literature has emphasized unobserved, time-varying heterogeneity that may stem from omitted common variables or global shocks that affect each individual unit differently. These latent common factors induce cross-section dependence and may lead to inconsistent regression coefficient estimates if they are correlated with the explanatory variables. Moreover, if the process underlying these factors is nonstationary, the individual regressions will be spurious but pooling or averaging across individual estimates still permits consistent estimation of a long-run coefficient. The need to tackle both error cross-section dependence and persistent autocorrelation is motivated by the evidence of their pervasiveness found in three well-known, international finance and macroeconomic examples. A range of estimators is surveyed and their finite-sample properties are examined by means of Monte Carlo experiments. These reveal that a mean group version of the common-correlated-effects estimator stands out as the most robust since it is the preferred choice in rather general (non) stationary settings where regressors and errors share common factors and their factor loadings are possibly dependent. Other approaches which perform reasonably well include the two-way fixed effects, demeaned mean group and between estimators but they are less efficient than the common-correlated-effects estimator.