Review of highway runoff characteristics: Comparative analysis and universal implications

This review interprets highway runoff characterization studies performed on different continents. The results are synthesized to discuss the historical trends, first flush effects of pollutants, pollutant form as dissolved vs. particulate, and to identify surrogate water quality parameters. The information presented in this review showed that: (1) variability has been observed in all quality parameters from each continent and among continents; (2) with a few exceptions the variability seems to be within the expected range; (3) inconsistent monitoring data as well as inconsistent quality assurance and quality control measures were reported among studies, which may be partially responsible for variability of water quality results; (4) compared with historic data, the concentration of total Pb decreased exponentially, which can mostly be credited to leaded gasoline phase-out regulation; (5) first flush effects of pollutants based on concentration have been reported consistently (however, mass first flush effects for pollutants have been reported inconsistently compared with concentration first flush effect); (6) most metal pollutants and phosphorus are present in both the particulate and dissolved forms; and (7) strong correlations were observed between TSS, TDS, TOC and iron (Fe) and 13 other constituents and water quality parameters (turbidity, O&G, TPH, DOC, TKN, EC, Cl, Cd, Cr, Cu, Ni, Pb, Zn).     

Determination of robotic melon harvesting efficiency: a probabilistic approach

To automate the harvesting of melons, a mobile Cartesian robot is developed that traverses at a constant velocity over a row of precut melons whose global coordinates are known. The motion planner is programmed to have the robot harvest as many melons as possible. Numerous simulations of the robot over a field with different sets of randomly distributed melons resulted in nearly identical percentages of melons harvested. This result holds true over a wide range of robot dimensions, motor capabilities, velocities and melon distributions. Using probabilistic methods, we derive these results by modelling the robotic harvesting procedure as a stochastic process. In this simplified model, a harvest ratio is predicted analytically using Poisson and geometric distributions. Further analysis demonstrates that this model of robotic harvesting is an example of an infinite length Markov chain. Applying the mathematical tools of Markov processes to our model yields a formula for the harvest percentage that is in strong agreement with the results of the simulation. The significance of the approach is demonstrated in two of its applications: to select the most efficient actuators for maximal melon harvesting and determine the set of optimal velocities along a row of melons of varying densities.     

ARMA spectral estimation based on partial autocorrelations

This paper presents a new method for estimating the coefficients of autoregressive moving-average parameters of stationary time series. The method is based on computing the sample autocorrelations of the given time series and fitting an ARMA model so as to approximate the partial autocorrelations in a least-squares sense. When the given time series are characterized by spectral zeroes near the unit circle, they tend to have relatively long sequences of nonzero partial autocorrelations; hence the new method is especially effective in such cases. This paper contains a derivation of all necessary mathematical details, as well as several numerical examples illustrating the performance.     

Autofrettage—Stress distribution under load and retained stresses after depressurization

There is a long-standing interest in developing a capability to predict the distribution of retained stresses in thick-walled tubes after the removal of an internal pressure—post-autofrettage. In this paper, four different methods of calculating such stresses are presented and compared. The methods presented are based on the following assumed yield criteria and deformation conditions: (1) Tresca's yield criterion, (2) Tresca's yield criterion × 2/√3, (3) Mises' yield criterion in plane-stress, and (4) Mises' yield criterion in plane-strain.     

"Speed of scanning in primary memory in persons with dementia of the Alzheimer type": Correction.

Reports editorial errors in the original article by T. L. Boaz and D. R. Denney (Psychology and Aging, 1993[Jun], Vol 8[2], 294–300). A short segment of text was misplaced in the Results section; the corrected text is included. (The following abstract of this article originally appeared in record 1993-42036-001.) The nature of the search of primary memory by persons with a presumptive diagnosis of mild Alzheimer's disease (dementia of the Alzheimer type [DAT]) was compared with that of normal elderly and young persons using the S. Sternberg (1966) paradigm. DAT Ss evidenced a substantial deficit in the speed of scanning in primary memory and a deficit in at least one other stage of processing. These findings are consistent with the hypothesis that the decline in memory performance evidenced by persons with DAT may be attributable to an increase in the time requirements of mnemonic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A field study of employees' attitudes and behaviors after promotion decisions.

The impact of promotion decisions on equity, commitment, and behavioral outcomes was examined in a field setting. Workers in a service company who submitted their candidacy for promotion to either department or division heads were compared with their noncandidate counterparts (total N?=?191). Ss completed surveys after promotion decisions were made. In addition, measures of the Ss' lateness and absence before and after the promotion were available. Data analyzed by level of position (department vs division) and promotion decision (promoted, not promoted, and control) indicated that promotions resulting from self-initiated candidacies might actually produce undesirable outcomes. Failure to get a promotion was associated with feelings of inequity, a decrease in commitment, and an increase in absenteeism; positive promotion decisions increased commitment. Theoretical and organizational implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Internal union dynamics during a strike: A quasi-experimental study.

Hypothesized that union members on strike will (a) give a higher evaluation of the union and of the leadership, (b) evaluate the benefit package more highly after the strike, (c) become more militant against the employer during the strike, (d) report more willingness to participate in union activities, and (e) show more intraunion cohesion during the strike. Random samples of members of 9 local unions (3 each from Ford, General Motors, and Chrysler) were surveyed on 4 occasions: before the 1976 bargaining, during the strike at Ford, after settlement of the national contract, and 7 mo after the strike ended. Usable responses from a questionnaire totaled 1,182 (405 strikers, 777 nonstrikers). With the exception of greater intraunion cohesion during the strike, all hypotheses were confirmed. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distributed MST for constant diameter graphs

This paper considers the problem of distributively constructing a minimum-weight spanning tree (MST) for graphs of constant diameter in the bounded-messages model, where each message can contain at most B bits for some parameter B. It is shown that the number of communication rounds necessary to compute an MST for graphs of diameter 4 or 3 can be as high as and , respectively. The asymptotic lower bounds hold for randomized algorithms as well. On the other hand, we observe that O(log n) communication rounds always suffice to compute an MST deterministically for graphs with diameter 2, when B = O(log n). These results complement a previously known lower bound of for graphs of diameter Ω(log n). An extended abstract of this work appears in Proceedings of 20th ACM Symposium on Principles of Distributed Computing, August 2001.     

On the complexity of distributed stable matching with small messages

We consider the distributed complexity of the stable matching problem (a.k.a. “stable marriage”). In this problem, the communication graph is undirected and bipartite, and each node ranks its neighbors. Given a matching of the nodes, a pair of unmatched nodes is called blocking if they prefer each other to their assigned match. A matching is called stable if it does not induce any blocking pair. In the distributed model, nodes exchange messages in each round over the communication links, until they find a stable matching. We show that if messages may contain at most B bits each, then any distributed algorithm that solves the stable matching problem requires ${\Omega(\sqrt{n/B\log n})}We consider the distributed complexity of the stable matching problem (a.k.a. “stable marriage”). In this problem, the communication graph is undirected and bipartite, and each node ranks its neighbors. Given a matching of the nodes, a pair of unmatched nodes is called blocking if they prefer each other to their assigned match. A matching is called stable if it does not induce any blocking pair. In the distributed model, nodes exchange messages in each round over the communication links, until they find a stable matching. We show that if messages may contain at most B bits each, then any distributed algorithm that solves the stable matching problem requires W(?{n/Blogn}){\Omega(\sqrt{n/B\log n})} communication rounds in the worst case, even for graphs of diameter O(log n), where n is the number of nodes in the graph. Furthermore, the lower bound holds even if we allow the output to contain O(?n){O(\sqrt n)} blocking pairs, and if a pair is considered blocking only if they like each other much more then their assigned match.