28,153 research outputs found
Improving the performance of bubble sort using a modified diminishing increment sorting
Sorting involves rearranging information into either ascending or descending order. There are many
sorting algorithms, among which is Bubble Sort. Bubble Sort is not known to be a very good sorting
algorithm because it is beset with redundant comparisons. However, efforts have been made to
improve the performance of the algorithm. With Bidirectional Bubble Sort, the average number of
comparisons is slightly reduced and Batcher’s Sort similar to Shellsort also performs significantly
better than Bidirectional Bubble Sort by carrying out comparisons in a novel way so that no
propagation of exchanges is necessary. Bitonic Sort was also presented by Batcher and the strong
point of this sorting procedure is that it is very suitable for a hard-wired implementation using a sorting
network. This paper presents a meta algorithm called Oyelami’s Sort that combines the technique of
Bidirectional Bubble Sort with a modified diminishing increment sorting. The results from the
implementation of the algorithm compared with Batcher’s Odd-Even Sort and Batcher’s Bitonic Sort
showed that the algorithm performed better than the two in the worst case scenario. The implication is
that the algorithm is faster
Bringing Back Subprime? The Hazards of Restructuring the GSEs
There have been a number of proposals for replacing the government-sponsored enterprises (GSEs), Fannie Mae and Freddie Mac, with a system under which private financial institutions would issue mortgage-backed securities (MBS) that carry a government guarantee. This paper raises a number of questions about the merits of such a system. It points out that both the gains to low-income families seeking to become homeowners from such a system and interest rate savings are likely to be relatively modest, and that there are few obvious safeguards that would make this new system sounder than the system of privately-issued mortgage-backed securities in the bubble years
Spin-the-bottle Sort and Annealing Sort: Oblivious Sorting via Round-robin Random Comparisons
We study sorting algorithms based on randomized round-robin comparisons.
Specifically, we study Spin-the-bottle sort, where comparisons are
unrestricted, and Annealing sort, where comparisons are restricted to a
distance bounded by a \emph{temperature} parameter. Both algorithms are simple,
randomized, data-oblivious sorting algorithms, which are useful in
privacy-preserving computations, but, as we show, Annealing sort is much more
efficient. We show that there is an input permutation that causes
Spin-the-bottle sort to require expected time in order to
succeed, and that in time this algorithm succeeds with high
probability for any input. We also show there is an implementation of Annealing
sort that runs in time and succeeds with very high probability.Comment: Full version of a paper appearing in ANALCO 2011, in conjunction with
SODA 201
Are Exchange Rates Excessively Variable?
"Unnecessary variation" is defined as variation not attributable to variation in fundamentals. In the absence of a good model of macroeconomic fundamentals, the question "are exchange rates excessively variable?" cannot be answered by comparing the variance of the actual exchange rate to the variance of a set of fundamentals. This paper notes the failure of regression equations to explain exchange rate movements even using contemporaneous macroeconomic variables. It notes as well the statistical rejections of the unbiasedness of the forward exchange rate as a predictor of the spot rate. It then argues that, given these results, there is not much to be learned from the variance-bounds tests and bubbles tests. The paper also discusses recent results on variation in the exchange risk premiums arising from variation in conditional variances, both as a source of the bias in the forward rate tests and as a source of variation in the spot rate. It finishes with a discussion of whether speculators' expectations are stabilizing or destabilizing, as measured by survey data. The paper concludes that it is possible that exchange rates have been excessively variable -- as, for example, when there are speculative bubbles -- but that if policy-makers try systematically to exploit their credibility in order to stabilize exchange rates, they may see their current credibility vanish.
Organic rankine cycle with positive displacement expander and variable working fluid composition
Organic Rankine Cycles are often used in the exploitation of low-temperature heat sources. The relatively small temperature differential available to these projects makes them particularly vulnerable to changing ambient conditions, especially if an air-cooled condenser is used. The authors have recently demonstrated that a dynamic ORC with a variable working fluid composition, tuned to match the condensing temperature with the heat sink, can be used to achieve a considerable increase in year-round power generation under such conditions [1]. However, this assumed the expander was a turbine capable of operating at multiple pressure ratios for large scale applications. This paper will investigate if small scale ORC systems that use positive-displacement expanders with fixed expansion ratios could also benefit from this new concept. In this paper, a numerical model was firstly developed. A comprehensive analysis was then conducted for a case study. The results showed that the dynamic Organic Rankine Cycle concept can be applied to lower-power applications that use that use positive-displacement expanders with fixed expansion ratios and still result in improvements in year-round energy generation
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