Gas-Wall Partitioning of Organic Compounds in a Teflon Film Chamber and Potential Effects on Reaction Product and Aerosol Yield Measurements

Gas-wall partitioning of organic compounds (OC) that included C ₈ –C ₁₆ n-alkanes and 1-alkenes and C ₈ –C ₁₃ 2-alcohols and 2-ketones was investigated in two Teflon FEP chambers whose walls were either untreated, oxidized in sunlight, or previously exposed to secondary organic aerosol (SOA). Partitioning was nearly independent of chamber treatment, reversible, and obeyed Henry's law. The fraction of an OC that partitioned to the walls at equilibrium ranged from 0 to ～ 65%. Values increased with increasing carbon number within an OC class and for OC with similar vapor pressures increased in the order n-alkanes <1-alkenes <2-alcohols <2-ketones. Estimated time constants for achieving partitioning equilibrium ranged from ～ 60 min for n -alkanes to ? 8 min for 2-ketones. The observations are consistent with a sorption mechanism in which OC dissolve into the film but are restricted to the near-surface region by a sharp permeability gradient that develops in response to OC-induced stresses in polymer chains. When the results were analyzed using a model analogous to one commonly employed for gas-particle partitioning, it was estimated that the sorption properties of the chamber walls were equivalent to organic aerosol mass concentrations of 2, 4, 10, and 24 mg m^{– 3} with respect to the partitioning of n -alkanes, 1-alkenes, 2-alcohols, and 2-ketones. These values are up to ～ 4 orders of magnitude larger than concentrations used in most laboratory studies of SOA, which are typically 1–10 ³ μ g m^{– 3} , meaning that if full partitioning equilibrium is established in the chamber then semi-volatile OC will reside overwhelmingly in the chamber walls. Model simulations of gas-particle-wall partitioning were also carried out using the experimental data, and demonstrate quantitatively the large potential effects of Teflon walls on measured yields of gas-phase OC products and SOA.     

Corollaries to two-limit cycle theorems†

A load processor is a system that has a buffer which can receive load and store it while it is waiting to be processed and has a local decision-making policy for determining if portions of its load should be sent to other load processors. A load balancing system is a set of such load processors that are connected in a network so that (i) they can sense the amount of load in the buffers of neighbouring processors and pass load to them, and (ii) so that, via local information and decisions by the individual load processors, the overall load in the entire network can be balanced. Such balancing is important to ensure that certain processors are not overloaded while others are left idle (i.e. load balancing helps avoid underutilization of processing resources). The topology of the network, delays in transporting and sensing load, types of load, and types of local load passing policies all affect the performance of the load balancing system. In this paper, we show how a variety of load balancing systems can be modelled in a discrete event system (DES) theoretic framework, and how balancing properties and performance can be characterized and analysed in a general Lyapunov stability theoretic framework.     

Synthesis of minimum-time control functions with multiple constraints by functional analysis!

This paper presents the functional analysis and iterative procedure for the minimum-time control problem subject to energy and magnitude constraints on the control functions. The necessary change of Swiger's method is described to solve a multi-boundary problem and numerical results are presented for a linear control system.     

The minimal time control of multi-system problems with energy constrained inputs†

This paper presents an. application, of functional analysis to the minimal?time control problem where two or more energy constrained systems of the same order must be taken to an initially unknown common point in state space. Two different types of problems with different forms of the energy constraint are described in detail. The development depends on the fact that the reachable region of a system with an energy constraint on the input vector is an ellipsoid.     

K-order Sampling of N-dimensional Band-limited Functions†

The work of II previous paper, utilizing the gradient in sampling theory, is generalized further to include the sampling of a function and its partial derivatives up to order K ≥ 1. The reconstruction of the sampled function f(t) has the form of a. sum of truncated Taylor series expansions about each of the sample points which lie on a periodic lattice. The single function g(t), of the vector from the sample point to a generic one, which multiplies each series, hag a J+1ourier transform G(r) which must satisfy sets of partial differential equations on the ’ lattice sets ’ of the support of F(r). The necessary and sufficient conditions which insure the validity of the reconstruction demand that the ‘ associated set ’ of each lattice set be among the zeros of n certain kind of polynomial function which in turn can act as u solution for G(r) on the lattice set.     

CHLORINATION KINETICS OF Nb2O5

The reaction of single sintered pellets of α-Nb₂O₅ with chlorine and carbon monoxide was studied in the temperature range from 773 K to 1073 K using a thermogravimetric apparatus. The rate controlling step of the reaction was determined from experiments carried out at variable gas flow rates, gas composition, surface geometry, pellet porosity and temperature. The vapor phase transport reaction can be written as:

Nb₂O₅(s) + 3Cl₂ (g) + 3CO(g) = 2NbOCl₃ (g) + 3CO₂(g).

Up to 60% conversion, the amount of volatilized product was found to be directly proportional to the time of reaction. The external surface area of the pellets remains unchanged up to this stage while the intergranular morphology changes.

These results were compared with reaction rates of commercial pyrochlore concentrate in order to establish the fundamental reaction stages of the process of extraction of Nb₂O₅ from pyrochlore.     

Interactive quality improvement of a process subject to complete inspection

An ongoing production process produces products with quality characteristics following a known probability distribution. Two process states, in-control and out-of-control, are assumed. The process is subject to complete inspection. Whenever the quality characteristic of a product produced exceeds a predetermined action limit, remedial action is taken to restore the process to the in-control state. In addition, the decision maker has a learning opportunity to improve the process by investing resources to identify and eliminate the causes of non-conformance to the target characteristic value. A learning action taken would reduce the probability of shifting from the in-control state to the out-of-control state. A cost model is developed in this paper to determine the optimal number of learning actions to be taken and the optimal action limit. The model gives insight into the tradeoff of cost of quality and cost of prevention.     

Optimal inspection policies in a serial production system including scrap rework and repair: An MILP approach

The allocation of inspection effort problem for aerial systems is formulated as a 0-1 mixed integer linear programming problem. This formulation permits any combination of scrap, rework, or repair at each station and allows the problem to be solved using standard MILP software packages. Moreover electronic spread-sheets may be used to easily calculate the relevant coefficients. An additional advantage of this approach when compared with the traditional dynamic programming approach is the ease with which the basic model may be modified. For example, it is shown how the model may easily be modified to include both a material and a production constraint and to select between various material suppliers. Sensitivity analysis is also easily performed with this approach. This model is then used to show that the optimal inspection policy is dependent on whether a production or a material requirement is used.     

Solid state piezo-resonant crystal motor operating on electrostatic principle†

A new generation of electrostatic high impedance control elements is now becoming available to supplement the current range of electromagnetic, low impedance devices. One of the most representative is tho crystal motor group, e.g. two-phase/one-bridge, two-phase/two-bridge motors operating in piezo-resonant mode. The basic principle of operation is the converse piezoelectric effect, which makes use of the mechanical strain produced in the crystal structure by a controlled electrostatic field.     

Sensitivity analysis of systems involving λ-variation via block-pulse functions

The problem of the sensitivity analysis of systems involving λ-variations may be treated by a new method based on the idea of solving the sensitivity equation of a system using orthogonal functions. Though the presented method is based on the set of block-pulse functions it can also be used for other sets of orthogonal functions. The approach can also be applied for solving other problems of a similar nature (inversion of Laplace transform involving Dirac impulses, analysis of singular perturbed systems etc.).