Although uncertainty is rife in many project management contexts, little is known about adaptively optimizing project schedules. We formulate the problem of adaptively optimizing the expected present value of a project’s cash flow, and we show that it is practical to perform the optimization. The formulation includes randomness in activity durations, costs, and revenues, so the optimization leads to a recursion with a large state space even if the durations are exponentially distributed. We present an algorithm that partially exercises the “curse of dimensionality” as computational results demonstrate. Most of the paper is restricted to exponentially distributed task durations, but we sketch the adaptation of the algorithm to approximate any probability distribution of task duration. 相似文献
Electronic effects in the design of new types of phosphocontaining cavity systems were considered. The matter of this phenomenon consists in supramolecular interaction of the organic radicals of substrates with the cyclophosphorylating reagents. 相似文献
In the present paper we study the well-posedness using the Galerkin method and the stabilization considering multiplier techniques for a fourth-order nonlinear Schrödinger equation in domains with moving boundaries. We consider two situations for the stabilization: the conservative case and the dissipative case. 相似文献
In recent years, capillary electrophoresis coupled to mass spectrometry (CE-MS) has been increasingly applied in clinical research especially in the context of chronic and age-associated diseases, such as chronic kidney disease, heart failure and cancer. Biomarkers identified using this technique are already used for diagnosis, prognosis and monitoring of these complex diseases, as well as patient stratification in clinical trials. CE-MS allows for a comprehensive assessment of small molecular weight proteins and peptides (<20 kDa) through the combination of the high resolution and reproducibility of CE and the distinct sensitivity of MS, in a high-throughput system. In this study we assessed CE-MS analytical performance with regards to its inter- and intra-day reproducibility, variability and efficiency in peptide detection, along with a characterization of the urinary peptidome content. To this end, CE-MS performance was evaluated based on 72 measurements of a standard urine sample (60 for inter- and 12 for intra-day assessment) analyzed during the second quarter of 2021. Analysis was performed per run, per peptide, as well as at the level of biomarker panels. The obtained datasets showed high correlation between the different runs, low variation of the ten highest average individual log2 signal intensities (coefficient of variation, CV < 10%) and very low variation of biomarker panels applied (CV close to 1%). The findings of the study support the analytical performance of CE-MS, underlining its value for clinical application. 相似文献
A new biomimetic approach for performing CaCO3 synthesis exclusively inside micron‐sized polyelectrolyte capsules, based on the fermentative formation of a precipitative agent (CO32− anion) by urease‐catalyzed urea hydrolysis, was developed. Precipitated CaCO3 completely fills the interior capsule volume and has a metastable vaterite phase.
Pumice from the “Minoan eruption” on Thera (Cyclades, Greece) was investigated to reveal the differences between the composition
of the bulk material, which contains a certain percentage of crystallites, and the pure glass phase. This is important for
the identification of vitric tephra layers found in the Eastern Mediterranean region in archaeological context and in deep
sea drilling cores. Eruption products, deposited at some distance, have usually lost their crystalline fraction due to gravity
separation and consist only of glass shards. Only major element distributions in such layers and in pumiceous glass phases
have been published up to now, but these data are not sufficient for a reliable identification of the volcanic source, as
several other eruptions are known to have produced chemically very similar layers in this region (Milos, Nisyros, Yali, Kos).
Therefore, a technique has been developed to separate the glass phase from the primary pumice to reveal differences in the
trace element distributions obtained by instrumental neutron activation analysis (INAA). X-ray diffractometry and microscopical
techniques were applied to check the purity of this fraction. The concentrations of the major constituents, in particular
Al, Ca, Fe, K, Mg, Mn, Na, Si, and Ti were determined by X-ray fluorescence (XRF) and electron probe microanalysis (EPMA),
those of Al, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Ti, Th, U, Yb and Zr by instrumental
neutron activation analysis and partly also by X-ray fluorescence. Subtle differences between the compositions of the glass
phase and the bulk material are explained by differentiation during partial crystallization and their applicability to the
classification of tephra layers is demonstrated. 相似文献
A conic linear system is a system of the form?P(d): find x that solves b - Ax∈CY, x∈CX,? where CX and CY are closed convex cones, and the data for the system is d=(A,b). This system is“well-posed” to the extent that (small) changes in the data (A,b) do not alter the status of the system (the system remains solvable or not). Renegar defined the “distance to ill-posedness”,
ρ(d), to be the smallest change in the data Δd=(ΔA,Δb) for which the system P(d+Δd) is “ill-posed”, i.e., d+Δd is in the intersection of the closure of feasible and infeasible instances d’=(A’,b’) of P(·). Renegar also defined the “condition measure” of the data instance d as C(d):=∥d∥/ρ(d), and showed that this measure is a natural extension of the familiar condition measure associated with systems of linear
equations. This study presents two categories of results related to ρ(d), the distance to ill-posedness, and C(d), the condition measure of d. The first category of results involves the approximation of ρ(d) as the optimal value of certain mathematical programs. We present ten different mathematical programs each of whose optimal
values provides an approximation of ρ(d) to within certain constants, depending on whether P(d) is feasible or not, and where the constants depend on properties of the cones and the norms used. The second category of
results involves the existence of certain inscribed and intersecting balls involving the feasible region of P(d) or the feasible region of its alternative system, in the spirit of the ellipsoid algorithm. These results roughly state that
the feasible region of P(d) (or its alternative system when P(d) is not feasible) will contain a ball of radius r that is itself no more than a distance R from the origin, where the ratio R/r satisfies R/r≤c1C(d), and such that r≥ and R≤c3C(d), where c1,c2,c3 are constants that depend only on properties of the cones and the norms used. Therefore the condition measure C(d) is a relevant tool in proving the existence of an inscribed ball in the feasible region of P(d) that is not too far from the origin and whose radius is not too small.
Received November 2, 1995 / Revised version received June 26, 1998?Published online May 12, 1999 相似文献
Titania was prepared by the sol-gel method from titanium alkoxide. Depending on the pH of the gelling solution, specific surface areas between 88 and 10 m2/g were obtained. The band gap (Eg) of the samples was found between 3.05 and 3.32 eV. In samples gelled at pH5 and 9 and calcined at 400°C only anatase phase is observed, while for pH3 and pH7 brookite, anatase and rutile or anatase-rutile phases coexist. It was found that the photoactivity in the 2,4-dinitroanailine decomposition depends on the Eg and on the crystalline phases. The highest activity corresponds to the catalysts having the lowest Eg and more than one crystalline phases co-existing. 相似文献