Turbulent Mixing in Transverse Jets

Turbulent mixing is studied in liquid-phase transverse jets. Jet-fluid concentration fields were measured using laser-induced fluorescence and digital-imaging techniques, for jets in the Reynolds number range 1000 <= Re <= 20,000, at a jet-to-freestream velocity ratio of 10. Analysis of the measured scalar fields indicates that turbulent mixing is Reynolds-number dependent, as manifest in the evolving probability density functions of jet-fluid concentration. Enhanced homogenization is found with increasing Reynolds number. Turbulent mixing is also seen to be flow dependent, based on differences between jets discharging into a crossflow and jets into a quiescent reservoir. A novel technique for whole-field measurement of scalar increments was used to study the distribution of difference (scalar increments) of the scalar field. These scalar increments are found to tend toward exponential-tailed distributions with decreasing separation distance. Finally, the scalar field is found to be anisotropic, particularly at small length scales. This is seen in power spectra, directional scalar microscales, and directional PDFs of scalar increments. The local anisotropy of the scalar field is explained in terms of the global dynamics and large-scale strain field of the transverse jet

Reynolds-number effects and anisotropy in transverse-jet mixing

Experiments are described which measured concentration fields in liquid-phase strong transverse jets over the Reynolds-number range 1.0×10^3 ≤ Rej ≤ 20×10^3. Laser-induced-fluorescence measurements were made of the jet-fluid-concentration fields at a jet-to-freestream velocity ratio of Vr =10. The concentration-field data for far-field (x/dj =50) slices of the jet show that turbulent mixing in the transverse jet is Reynolds number dependent over the range investigated, with a scalar-field PDF that evolves with Reynolds number. A growing peak in the PDF, indicating enhanced spatial homogenization of the jet-fluid concentration field, is found with increasing Reynolds number. Comparisons between transverse jets and jets discharging into quiescent reservoirs show that the transverse jet is an efficient mixer in that it entrains more fluid than the ordinary jet, yet is able to effectively mix and homogenize the additional entrained fluid. Analysis of the structure of the scalar field using distributions of scalar increments shows evidence for well-mixed plateaux separated by sharp cliffs in the jet-fluid concentration field, as previously shown in other flows. Furthermore, the scalar field is found to be anisotropic, even at small length scales. Evidence for local anisotropy is seen in the scalar power spectra, scalar microscales, and PDFs of scalar increments in different directions. The scalar-field anisotropy is shown to be correlated to the vortex-induced large-scale strain field of the transverse jet. These experiments add to the existing evidence that the large and small scales of high-Schmidt-number turbulent mixing flows can be linked, with attendant consequences for the universality of small scales of the scalar field for Reynolds numbers up to at least Re=20×10^4

Family Labor Supply With Taxes

Over the period 1960 - 1983 the proportion of federal tax revenue raised by taxation of labor supply has risen from 57-77 percent. In this paper, we specify and estimate a model of family labor supply which treats both federal and state taxation. Husbands and wives labor supply are treated jointly rather than in aseparate manner as in previous research. A method to calculate the virtual wage for nonworking spouses is used within a utility maximizing framework to treat correctly the joint family labor supply decision. Joint family efforts are found to be important. The efficiency cost (deadweight loss) of labor taxation is estimated to be 29.6% of tax revenue raised. The effect of the new 10% deduction to ease the marriage tax for working spouses leads to a prediction of 3.8% increase in wives labor supply and a .9% decrease in husbands labor supply.Overall taxes paid are predicted to decrease by 3.4%.

Model Counting of Query Expressions: Limitations of Propositional Methods

Query evaluation in tuple-independent probabilistic databases is the problem of computing the probability of an answer to a query given independent probabilities of the individual tuples in a database instance. There are two main approaches to this problem: (1) in `grounded inference' one first obtains the lineage for the query and database instance as a Boolean formula, then performs weighted model counting on the lineage (i.e., computes the probability of the lineage given probabilities of its independent Boolean variables); (2) in methods known as `lifted inference' or `extensional query evaluation', one exploits the high-level structure of the query as a first-order formula. Although it is widely believed that lifted inference is strictly more powerful than grounded inference on the lineage alone, no formal separation has previously been shown for query evaluation. In this paper we show such a formal separation for the first time. We exhibit a class of queries for which model counting can be done in polynomial time using extensional query evaluation, whereas the algorithms used in state-of-the-art exact model counters on their lineages provably require exponential time. Our lower bounds on the running times of these exact model counters follow from new exponential size lower bounds on the kinds of d-DNNF representations of the lineages that these model counters (either explicitly or implicitly) produce. Though some of these queries have been studied before, no non-trivial lower bounds on the sizes of these representations for these queries were previously known.Comment: To appear in International Conference on Database Theory (ICDT) 201

Desorption hysteresis in five ion exchanged montmorillonites

It is generally believed that the formation of recalcitrant (slowly desorbing) fractions of volatile organic compounds (VOCs) in soils is due to diffusion of compounds to sorption sites inaccessible to bulk fluid. The exact nature of these sites, however, is not well understood. In clay minerals, researchers favor two probable areas for the storage of persistent contamination; sites between the clay lamella, or sites with clay particle aggregates. To test the hypothesis that recalcitrant fractions are formed in interlamellar spaces, a Na/Ca Montmorillonite (Smectite) was ion exchanged with five different cations (K+, Na+, Ca+, Mg2+, Fe3+) to form mineralogically similar clays with varying interlamellar environments. These soils were inoculated with an organic compound (toluene), incubated for 24 hours, and the recalcitant fraction quantified for varying desorption times. The results did not show a clear correlation between persistent contamination and the interlamellar environment. Instead, evidence appears to support the conclusion that persistent contamination may be stored in clay particle microaggregates

Plasma, interstitial, and total body water of pigs from birth through six weeks of age with and without iron.

http://www.worldcat.org/oclc/1101375

Frederick Douglass: An American Adult Educator

Throughout his I ife, Frederick Douglass struggled to be something extraordinary. He rose from a life in slavery to become the most prominent African-American of his day and a leading figure in the abolitionist movement. Lost in the discussion of his life are the adult education roles that he played throughout his life and career. Beginning while he was still a slave and extending until his death, he worked to educate adults in order to transfonn individual lives and society as a whole. Douglass was primarily engaged in adult education in the fields of religious adult education, social movements, popular education, and political activism

BUILDING PROFESSIONAL ECONOMIC DEVELOPMENT CAPACITY IN THREE WESTERN UPPER PENINSULA COUNTIES: RESULTS OF A DIAGNOSTIC STUDY AND FOLLOW-UP ACTIVITIES

This paper is a part of a series of reports of the activities conducted under a grant from the Fund for Rural America, U.S. Department of Agriculture. Funds for the three year grant entitled "Enhancing Rural Economies Through Comprehensive Extension, Research & Partnering Approaches Using Multi-County Clusters in Michigan With Application to National Rural Settings" were received by Michigan State University's Department of Agricultural Economics in March, 1998. The major goal of the grant is to increase economic development activity in four clusters of rural counties in Michigan through the utilization of the resources of the Michigan State University Extension Service, Michigan Agricultural Experiment Station, and other resources of Michigan State University. Various local, state, and federal public partners as well as the private sector are to co-sponsor projects. This paper represents the first stages of a continuing project to explore the utilization of retirement community human resources in rural Michigan and to develop Extension programs to meet their needs. Future activities include focus groups, labor supply analysis, a conference, and perhaps a rural academy to be developed by Michigan State University and its partners.Community/Rural/Urban Development,