Maximal concurrent minimal cost flow problems on extended multi-cost multi-commodity networks

The graph is a great mathematical tool, which has been effectively applied to many fields such as economy, informatics, communication, transportation, etc. It can be seen that in an ordinary graph the weights of edges and vertexes are taken into account independently where the length of a path is the sum of weights of the edges and the vertexes on this path. Nevertheless, in many practical problems, weights at vertexes are not equal for all paths going through these vertexes, but are depending on coming and leaving edges. Moreover, on a network, the capacities of edges and vertexes are shared by many goods with different costs. Therefore, it is necessary to study networks with multiple weights. Models of extended multi-cost multi-commodity networks can be applied to modelize many practical problems more exactly and effectively. The presented article studies the maximal concurrent minimal cost flow problems on multi-cost and multi-commodity networks, which are modelized as optimization problems. On the base of the algorithm to find maximal concurrent flow and the algorithm to find maximal concurrent limited cost flow, an effective polynomial approximate procedure is developed to find a good solution.

The first GAEN-based COVID-19 contact tracing app in Norway identifies 80% of close contacts in "real life" scenarios.

The COVID-19 response in most countries depends on testing, isolation, contact tracing, and quarantine, which is labor- and time consuming. Therefore, several countries worldwide launched Bluetooth based apps as supplemental tools. We evaluated the new Norwegian GAEN (Google Apple Exposure Notification) based contact tracing app 'Smittestopp' under two relevant simulated scenarios, namely standing in a queue and riding public transport. We compared two configurations (C1: 58/63 dBm; C2: 58/68 dBm) with multiple weights (1.0-2.5) and time thresholds (10-15 min), by calculating notification rates among close contacts (≤2 meters, ≥15 min) and other non-close contacts. In addition, we estimated the effect of using different operating systems and locations of phone (hand/pocket) using Chi2. C2 resulted in significantly higher notification rates than C1 (p-value 0.05 - 0.005). The optimal setting resulted in notifications among 80% of close contacts and 34% of other contacts, using C2 with weights of 2.0 for the low and 1.5 for the middle bucket with a 13-minutes time threshold. Among other contacts, the notification rate was 67% among those ≤2 meters for <15 minutes compared to 19% among those >2 meters (p=0.004). Significantly (p-values 0.046 - 0.001) lower notification rates were observed when using the iOS operating systems or carrying the phone in the pocket instead of in the hand. This study highlights the importance of testing and optimizing the performance of contact tracing apps under 'real life' conditions to optimized configuration for identifying close contacts.

COMPARATIVE STUDY OF REMOVAL POLLUTANTS ( HEAVY METALS) BY AGRICULTURAL WASTES AND OTHER CHEMICAL FROM THE AQUEOUS SOLUTIONS

This study included the application of some experiments in the chemical treatment of some heavy metals elements by preparing biological surfaces that are adsorbed from natural and other chemical substances, as in preparing activated carbon prepared from charred pistachio shell with concentrated H2SO4 and Nano-Calcium Oxide prepared from CaCL2.2H2O with NaOH . The prepared materials were diagnosed with spectral techniques where the FTIR infrared spectrum proved the formation of carbonyl, hydrogen and oxygenated of the surface in activated charcoal and the hydroxyl and calcium oxide groups in the nano-calcium oxide, as the FE-SEM surface morphology was proven to form on coal blocks The surface is a network of irregular holes and a network of microscopic holes regular on the surface of nano- calcium oxide. As for X-ray diffraction technology, the crystal structures of the surface, its shapes and sizes, are shown, and that activated charcoal consists of that Many types of carbon in the form hexagonally and cuboid and rhomboid with a right angle, while technical proven size of the crystalline calcium oxide nanoscale which ranges between (54.68-67.86nm) cube-shaped. PIAC activated charcoal and n-Calcium oxide were used as sorbents in the removal of, Cd + 2, Pb + 2 ions from aqueous solutions, a study of the effect of pH, contact time, multiple weights for surface and the primary concentration of ions in a horizontal removal method , and the removal of minimal concentrations of ions in large volumes of solutions by the process of preconcentration .

A Generalized Weighted Monte Carlo Calibration Method for Derivative Pricing

The weighted Monte Carlo method is an elegant technique to calibrate asset pricing models to market prices. Unfortunately, the accuracy can drop quite quickly for out-of-sample options as one moves away from the strike range and maturity range of the benchmark options. To improve the accuracy, we propose a generalized version of the weighted Monte Carlo calibration method with two distinguishing features. First, we use a probability distortion scheme to produce a non-uniform prior distribution for the simulated paths. Second, we assign multiple weights per path to fit with the different maturities present in the set of benchmark options. Our tests on S&P500 options data show that the new calibration method proposed here produces a significantly better out-of-sample fit than the original method for two commonly used asset pricing models.