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Phosphines are commonly employed as ligands for late-transition-metal-catalyzed reactions. While a plethora of ligands with chirality α to the phosphine are used, the P-stereogenic counterparts are less common. This paper is a very nice report on the synthesis of these compounds, which are much more difficult to obtain. The use of (R)-i-Pr-PHOX as the ligand on the ruthenium center gave the best results. Sodium tert-amyloxide was the optimal base, while a variety of benzylic chlorides were shown to be appropriate electrophiles. The use of ethyl bromide gave lower yield and enantioselectivity (70% yield, 57% ee). The products were isolated as the air-stable borane adducts.
While astonishingly successful, Internet is still less reliable than the phone system and supports very limited user choice and control. As many researchers observed, multipath routing is a promising paradigm to address these issues. In this thesis, we argue that multipath routing can indeed go a long way towards these goals as well as lead to a more scalable, extensible, and evolvable Internet. We begin by describing Yet Another Multipath Routing (YAMR) protocol that provably constructs a set of paths resilient to any one interdomain link failure. YAMR uses an efficient scheme to construct the paths and a novel failure hiding technique to further reduce the control plane overhead. Next, we describe Pathlet Routing, a protocol that departs from the path-vector paradigm. Pathlet routing allows ASes to advertise policy-compliant path segments called pathlets, and allows users to stitch them together, thus forming a complete path suitable for the user's particular needs. Pathlet routing greatly reduces the forwarding table size, can efficiently express a wide class of routing policies, and provide an exponential number of paths to the users. Finally, we investigate how pathlet routing can be a basis for an evolvable Internet architecture.
A two-dimensional array of diffusively-coupled nonlinear electronic circuits, Chua's cells, operating in a bistable regime, is used to find the shortest path connecting two points of a given image. Images are previously stored in the system by modulating the diffusion coefficients. Different types of images were considered, from black and white pictures (where 0 means no propagation and 1 propagation), to analog figures (with many intermediate states) and, in all cases, the algorithm used for such calculations succeeded to find the shortest path. The full description of the algorithm is here described and applied to nontrivial cases where the shortest path strongly differs from the straight line.
Wireless communication systems operate in complex time-varying environments. Therefore, selecting the optimal configuration parameters in these systems is a challenging problem. For wireless links, \emph{rate selection} is used to select the optimal data transmission rate that maximizes the link throughput subject to an application-defined latency constraint. We model rate selection as a stochastic multi-armed bandit (MAB) problem, where a finite set of transmission rates are modeled as independent bandit arms. For this setup, we propose Con-TS, a novel constrained version of the Thompson sampling algorithm, where the latency requirement is modeled by a high-probability linear constraint. We show that for Con-TS, the expected number of constraint violations over T transmission intervals is upper bounded by O(\sqrt{KT}), where K is the number of available rates. Further, the expected loss in cumulative throughput compared to the optimal rate selection scheme (i.e., the egret is also upper bounded by O(\sqrt{KT \log K}). Through numerical simulations, we demonstrate that Con-TS significantly outperforms state-of-the-art bandit schemes for rate selection.
ABSTRACT A new technique was developed to obtain reservoir descriptions to aid in the design of enhanced oil recovery (EOR) projects. This technique incorporates the reservoir performance during primary and secondary processes as well as the geological and petrophysical data. The advantage of this technique over statistical techniques is that a more realistic reservoir description can be obtained. The reservoir description when used with an EOR reservoir simulator would yield a more realistic prediction of EOR performance and minimize the risk in an EOR field project. This technique may also be used to validate a reservoir simulator for field scale EOR performance. If the reservoir description is derived independent of EOR performance, the reservoir description is based only on the reservoir heterogeneities. The EOR process variables can then be quantified from the EOR performance without changing the reservoir description (Ader and Stein1). The application of this technique is illustrated for a 250 acre area of interest in a San Andres formation reservoir. The initial reservoir description is formulated based on permeability to porosity ratio plots, injection and production profiles, core data, and pressure transient tests. The initial gas saturations and pressures are obtained based on dimensionless performance curves. The reservoir description is then refined by history matching primary and secondary performance for individual wells using a reservoir simulator. For the example discussed in this paper, an excellent match of performance was achieved using this technique.
A detailed investigation has been carried out of the structure and electrochemical activity of electrodeposited Ni-Fe films for the oxygen evolution reaction (OER) in alkaline electrolytes. Ni-Fe films with a bulk and surface composition of 40% Fe exhibit OER activities that are roughly 2 orders of magnitude higher than that of a freshly deposited Ni film and about 3 orders of magnitude higher than that of an Fe film. The freshly deposited Ni film increases in activity by as much as 20-fold during exposure to the electrolyte (KOH); however, all films containing Fe are stable as deposited. The oxidation of Ni(OH)2 to NiOOH in Ni films occurs at potentials below the onset of the OER. Incorporation of Fe into the film increases the potential at which Ni(OH)2/NiOOH redox occurs and decreases the average oxidation state of Ni in NiOOH. The Tafel slope (40 mV dec(-1)) and reaction order in OH(-) (1) for the mixed Ni-Fe films (containing up to 95% Fe) are the same as those for aged Ni films. In situ Raman spectra acquired in 0.1 M KOH at OER potentials show two bands characteristic of NiOOH. The relative intensities of these bands vary with Fe content, indicating a change in the local environment of Ni-O. Similar changes in the relative intensities of the bands and an increase in OER activity are observed when pure Ni films are aged. These observations suggest that the OER is catalyzed by Ni in Ni-Fe films and that the presence of Fe alters the redox properties of Ni, causing a positive shift in the potential at which Ni(OH)2/NiOOH redox occurs, a decrease in the average oxidation state of the Ni sites, and a concurrent increase in the activity of Ni cations for the OER.
We introduce an intuitive particle-based model of time-symmetric quantum physics that gives a concrete description of what goes on in the time between projective measurements of a quantum system. The time-symmetry in this model means that we ...Physical interpretations of the time-symmetric formulation of quantum mechanics, due to Aharonov, Bergmann, and Lebowitz are discussed in terms of weak values. The most direct, yet somewhat naive, interpretation uses the time-symmetric formulation to ...
Isfahan is one of the largest cities in Iran. In the southern portion of the city, there were some problems with the cathodic protection (CP) of coated gas pipelines buried in soil. The CP levels decreased as the distance from the CP stations increased. Adding new CP stations, repairing anode beds, and applying more CP current produced no significant improvement. During investigations, it was found that the CP designers had not considered factors such as soil resistivity, electrical isolation, and proximity of foreign structures. The design considered only groundbed resistance, and the result was poor distribution of protective current.
An analysis of the application of J integral based elastic-plastic fracture mechanics procedures to fusion structures is carried out. Some limiting flaw-structure geometries are specified along with estimates of upper- and lower-bound service properties of a martensitic stainless steel. Size requirements for J procedures in unconstrained flow geometries and for low strain-hardening conditions result in a small range of valid application even for lower-bound properties. In constrained deformation geometries the range of application is extended for lower-bound properties. Failure of J procedures is shown to coincide with approach to fully-plastic fracture, which can be treated partly with limit-load or net-section stress criteria.
