2,030 research outputs found
The Computational Power of Optimization in Online Learning
We consider the fundamental problem of prediction with expert advice where
the experts are "optimizable": there is a black-box optimization oracle that
can be used to compute, in constant time, the leading expert in retrospect at
any point in time. In this setting, we give a novel online algorithm that
attains vanishing regret with respect to experts in total
computation time. We also give a lower bound showing
that this running time cannot be improved (up to log factors) in the oracle
model, thereby exhibiting a quadratic speedup as compared to the standard,
oracle-free setting where the required time for vanishing regret is
. These results demonstrate an exponential gap between
the power of optimization in online learning and its power in statistical
learning: in the latter, an optimization oracle---i.e., an efficient empirical
risk minimizer---allows to learn a finite hypothesis class of size in time
. We also study the implications of our results to learning in
repeated zero-sum games, in a setting where the players have access to oracles
that compute, in constant time, their best-response to any mixed strategy of
their opponent. We show that the runtime required for approximating the minimax
value of the game in this setting is , yielding
again a quadratic improvement upon the oracle-free setting, where
is known to be tight
Studi Aplikasi Keramik Znbico Sebagai Termistor Ntc
STUDY ON THE APPLICA TION OF ZnBiCo CERAMICS AS NTC THERMISTORS. A study onthe application ofZnO-Bi203-CoO (ZnBiCo) ceramicsfor NTC thermistors had been carried out. The aim ofthisstudywas tofind alternative NTCthermistors. The studywas done as follow. Powder ofZnO, CoO andBi203 with concentration of Bi203 of 0, 0.25, 0.5, and 0.75 mole % and of CoO of 2 mole % werehomogeneously mixed. The mixedpowder was pressed with pressure of3.9ton/cm2 into pellets and sinteredat HOCfC in airfor 1 hour. The sintered pellets were evaluated using x-ray diffraction (XRD), opticalmicroscope andSEM(Scanningelectron microscope). Resistivity-temperature characteristic (p-Tcurve) wasdetermined through measurement of resistivity at various temperatures from room temperature to WCfC.XRD andmicrostructure datashowed thatmostofCoOformed a solid solution withZnOmatrix while Bi203was segregated at grain boundaries as ZnO,24Bi203 second phase. It was known that the all ceramicsproducedin this studyhad the same structure i.e. hexagonal. It was known also that the addition ofBi203increased the average grain size of the ZnBiCo ceramics. Electrical data showed that Bi203 increased theroom temperature resistivity (ps^) and the thermistor constant (B) of the ZnBiCo ceramic thermistors. Thethermistor constant and sensitivity (a) of the thermistor ceramics in this study were relatively high (largerthan 200(fKfor Band larger than 2.2 (°K)~lfor a)andsuitableforcommercial application
Equidistribution of expanding translates of curves and Dirichlet's theorem on Diophantine approximation
We show that for almost all points on any analytic curve on R^{k} which is
not contained in a proper affine subspace, the Dirichlet's theorem on
simultaneous approximation, as well as its dual result for simultaneous
approximation of linear forms, cannot be improved. The result is obtained by
proving asymptotic equidistribution of evolution of a curve on a strongly
unstable leaf under certain partially hyperbolic flow on the space of
unimodular lattices in R^{k+1}. The proof involves ergodic properties of
unipotent flows on homogeneous spaces.Comment: 26 page
Interaction Between Active Compounds From Aegle Marmelos Correa as Anti Inflammation Agent with Cox-1 and Cox-2 Receptor
The compounds in Aegle marmelos have an activity as anti inflammation. The objective of this study is to evaluate six active compounds in Aegle marmelos Correa, (E,R)- Marmin, skimmianine, (S)-aegeline, aurapten, zeorin, and dustanin as anti inflammation to the COX-1 and COX-2 as target receptors. Method: Molecular docking was done with PLANTS. Ligand preparation used MarvinSketch, and protein preparation was done by using YASARA. The result was marmin, skimmianine, aegeline, aurapten, zeorin, and dustanin have interaction with Arg120, tyr 355, and Ile 523 in COX-1 and Ser353, Arg 513, and Ser 530 in COX-2. Based on the result of molecular docking, active compounds in Aegle marmelos Correa have potency as anti inflammation agent
Discovering Valuable Items from Massive Data
Suppose there is a large collection of items, each with an associated cost
and an inherent utility that is revealed only once we commit to selecting it.
Given a budget on the cumulative cost of the selected items, how can we pick a
subset of maximal value? This task generalizes several important problems such
as multi-arm bandits, active search and the knapsack problem. We present an
algorithm, GP-Select, which utilizes prior knowledge about similarity be- tween
items, expressed as a kernel function. GP-Select uses Gaussian process
prediction to balance exploration (estimating the unknown value of items) and
exploitation (selecting items of high value). We extend GP-Select to be able to
discover sets that simultaneously have high utility and are diverse. Our
preference for diversity can be specified as an arbitrary monotone submodular
function that quantifies the diminishing returns obtained when selecting
similar items. Furthermore, we exploit the structure of the model updates to
achieve an order of magnitude (up to 40X) speedup in our experiments without
resorting to approximations. We provide strong guarantees on the performance of
GP-Select and apply it to three real-world case studies of industrial
relevance: (1) Refreshing a repository of prices in a Global Distribution
System for the travel industry, (2) Identifying diverse, binding-affine
peptides in a vaccine de- sign task and (3) Maximizing clicks in a web-scale
recommender system by recommending items to users
Delirium, frailty and mortality:interactions in a prospective study of hospitalized older people
AbstractBackgroundIt is unknown if the association between delirium and mortality is consistent for individuals across the whole range of health states. A bimodal relationship has been proposed, where delirium is particularly adverse for those with underlying frailty, but may have a smaller effect (perhaps even protective) if it is an early indicator of acute illness in fitter people. We investigated the impact of delirium on mortality in a cohort simultaneously evaluated for frailty.MethodsWe undertook an exploratory analysis of a cohort of consecutive acute medical admissions aged ≥70. Delirium on admission was ascertained by psychiatrists. A Frailty Index (FI) was derived according to a standard approach. Deaths were notified from linked national mortality statistics. Cox regression was used to estimate associations between delirium, frailty and their interactions on mortality.ResultsThe sample consisted of 710 individuals. Both delirium and frailty were independently associated with increased mortality rates (delirium: HR 2.4, 95%CI 1.8-3.3, p<0.01; frailty (per SD): HR 3.5, 95%CI 1.2-9.9, p=0.02). Estimating the effect of delirium in tertiles of FI, mortality was greatest in the lowest tertile: tertile 1 HR 3.4 (95%CI 2.1-5.6); tertile 2 HR 2.7 (95%CI 1.5-4.6); tertile 3 HR 1.9 (95% CI 1.2-3.0).ConclusionWhile delirium and frailty contribute to mortality, the overall impact of delirium on admission appears to be greater at lower levels of frailty. In contrast to the hypothesis that there is a bimodal distribution for mortality, delirium appears to be particularly adverse when precipitated in fitter individuals.</jats:sec
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