Competitive Algorithms for Online Leasing Problem in Probabilistic Environments

Abstract. We integrate probability distribution into pure competitive analysis to improve the performance measure of competitive analysis, since input sequences of the leasing problem have simple structure and favorably statistical property. Let input structures be the characteristic of geometric distribution, and we obtain optimal on-line algorithms and their competitive ratios. Moreover, the introducing of interest rate would diminish the uncertainty involved in the process of decision making and put off the optimal purchasing date.

Thermal Stabilization of the HCP Phase in Titanium

We have used a tight-binding model that is fit to first-principles electronic-structure calculations for titanium to calculate quasi-harmonic phonons and the Gibbs free energy of the hexagonal close-packed (hcp) and omega crystal structures. We show that the true zero-temperature ground-state is the omega structure, although this has never been observed experimentally at normal pressure, and that it is the entropy from the thermal population of phonon states which stabilizes the hcp structure at room temperature. We present the first completely theoretical prediction of the temperature- and pressure-dependence of the hcp-omega phase transformation and show that it is in good agreement with experiment. The quasi-harmonic approximation fails to adequately treat the bcc phase because the zero-temperature phonons of this structure are not all stable

The importance of age effects on performance in the assessment of clinical trials

Forty young adult normal subjects, 10 Parkinson's disease patients and their 10 matched normal subjects, and 10 multiple sclerosis patients and their 10 matched normal subjects were evaluated in the Quantitative Examination of Neurological Function to determine age effects and the importance of selecting closely matched normal control groups for assessing the performance of patients. Where there are significant differences among the three normal subject groups, it is the oldest normal subject group that differs from the two younger subject groups. Significant decreases in performance with increasing age were found for the steadiness tests performed in the supported position, the sensation tests, two or five tests in the Neuro-Psychological Examination and tests requiring fine skilled movements primarily with the dominant hand. It was found that older subjects made fewer errors in coordinated tasks.A normalization technique, expressing performance as a percentage of normal function, was introduced. A method was developed to provide quantitative and meaningful indices of neurological function. The measure is obtained by averaging the percentage of normal function scores over several tests that belong to a primary category of neurological function.Young adult normal subjects do not perform significantly better than normal subjects in the age range of multiple sclerosis patients; however, young adult normal subjects do perform significantly better than normal subjects in the age range of Parkinson's disease patients, especially on tasks requiring fine skilled movements of the dominant hand and coordinated activities of the lower extremities. These results indicate that the performance of multiple sclerosis patients can be expressed as a percentage of the function of either age-matched normal controls or young adult normal controls. However, the performance of Parkinson's disease patients should be expressed only as a percentage of the function of age-matched normal controls.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33791/1/0000046.pd

Greedy D-Approximation Algorithm for Covering with Arbitrary Constraints and Submodular Cost

This paper describes a simple greedy D-approximation algorithm for any covering problem whose objective function is submodular and non-decreasing, and whose feasible region can be expressed as the intersection of arbitrary (closed upwards) covering constraints, each of which constrains at most D variables of the problem. (A simple example is Vertex Cover, with D = 2.) The algorithm generalizes previous approximation algorithms for fundamental covering problems and online paging and caching problems

Online Paging for Flash Memory Devices

We propose a variation of online paging in two-level memory systems where pages in the fast cache get modified and therefore have to be explicitly written back to the slow memory upon evictions. For increased performance, up to alpha arbitrary pages can be moved from the cache to the slow memory within a single joint eviction, whereas fetching pages from the slow memory is still performed on a one-by-one basis. The main objective in this new alpha-paging scenario is to bound the number of evictions. After providing experimental evidence that alpha-paging can adequately model flash-memory devices in the context of translation layers we turn to the theoretical connections between alpha-paging and standard paging. We give lower bounds for deterministic and randomized alpha-paging algorithms. For deterministic algorithms, we show that an adaptation of LRU is strongly competitive, while for the randomized case we show that by adapting the classical Mark algorithm we get an algorithm with a competitive ratio larger than the lower bound by a multiplicative factor of approximately 1.7