Experiences with and interpretation of standard test methods of building energy analysis tools

The authors separately apply ANSI/ASHRAE Standard 140-2001 to the simulation program TRNSYS, comparing not only their results but the differences in their simulation assumptions and in their interpretations of the Standard's test cases. Results of the application are presented for all three authors, showing that there is a significant amount of leeway within a complex simulation tool such asTRNSYS for users of different backgrounds to apply their own common simulating practices and still fall comfortably within the range of acceptability specified by such Standards. Included in the application results are results of sensitivity tests that demonstrate the relative importance of assumption differences

Converging on a recommended set of interpretations and assumptions in applying standard tests to energy analysis tools

The authors, having individually applied ANSI/ASHRAE Standard 140-2001 to the simulation program TRNSYS in a previous project, compare their results, simulation assumptions, and interpretations of the Standard's test cases to arrive at a conformed set of recommended practices. Sensitivities to individual assumptions are investigated and results of applying the conformed set of assumptions are presented

Combining different validation techniques for continuous software improvement - Implications in the development of TRNSYS 16

Validation using published, high quality test suites can serve to identify different problems in simulation software: modeling and coding errors, missing features, frequent sources of user confusion. This paper discusses the application of different published validation procedures during the development of a new TRNSYS version: BESTEST/ASHRAE 140 (Building envelope), HVAC BESTEST (mechanical systems) and IEA ECBCS Annex 21 / SHC Task 12 empirical validation (performance of a test cell with a very simple mechanical system). It is shown that each validation suite has allowed to identify different types of problems. Those validation tools were also used to diagnose and fix some of the identified problems, and to assess the influence of code modifications. The paper also discusses some limitations of the selected validation tools

An investigation of messy genetic algorithms

Genetic algorithms (GAs) are search procedures based on the mechanics of natural selection and natural genetics. They combine the use of string codings or artificial chromosomes and populations with the selective and juxtapositional power of reproduction and recombination to motivate a surprisingly powerful search heuristic in many problems. Despite their empirical success, there has been a long standing objection to the use of GAs in arbitrarily difficult problems. A new approach was launched. Results to a 30-bit, order-three-deception problem were obtained using a new type of genetic algorithm called a messy genetic algorithm (mGAs). Messy genetic algorithms combine the use of variable-length strings, a two-phase selection scheme, and messy genetic operators to effect a solution to the fixed-coding problem of standard simple GAs. The results of the study of mGAs in problems with nonuniform subfunction scale and size are presented. The mGA approach is summarized, both its operation and the theory of its use. Experiments on problems of varying scale, varying building-block size, and combined varying scale and size are presented

Simulation synergy : expanding TRNSYS capabilities and usability

Developers of simulation packages are now able to take advantage of the increase in available desktop computing power to expand the capabilities and usability of their programs. This paper will illustrate these opportunities by discussing the different techniques the developers of the TRNSYS software package have used to try and create a synergy between TRNSYS and external programs and between the developers and users of the program

Redshifts and Luminosities for 112 Gamma Ray Bursts

Two different luminosity indicators have recently been proposed for Gamma Ray Bursts that use gamma-ray observations alone. They relate the burst luminosity (L) with the time lag between peaks in hard and soft energies, and the spikiness or variability of the burst's light curve (V). These relations are currently justified and calibrated with only 6 or 7 bursts with known red shifts. We have examined BATSE data for the lag and V for 112 bursts. (1) A strong correlation between the lag and V exists, and it is exactly as predicted from the two proposed relations. This is proof that both luminosity indicators are reliable. (2) GRB830801 is the all-time brightest burst, yet with a small V and a large lag, and hence is likely the closest known event being perhaps as close as 3.2 Mpc. (3) We have combined the luminosities as derived from both indicators as a means to improve the statistical and systematic accuracy when compared with the accuracy from either method alone. The result is a list of 112 bursts with good luminosities and hence red shifts. (4) The burst averaged hardness ratio rises strongly with the luminosity of the burst. (5) The burst luminosity function is a broken power law, with the break at L = 2x10^{52} erg/s. The luminosity function has power law indices of -2.8+-0.2 above the break and -1.7+-0.1 below the break. (6) The number density of GRBs varies with red shift roughly as (1+z)^(2.5+-0.3) between 0.2<z<5. Excitingly, this result also provides a measure of the star formation rate out to z~5 with no effects from reddening, and the rate is rising uniformly for red shifts above 2.Comment: 13 pages, 4 figures, submitted to ApJLet

Species Limits and Phylogeography of North American Cricket Frogs (Acris: Hylidae)

Cricket frogs are widely distributed across the eastern United States and two species, the northern cricket frog (Acris crepitans) and the southern cricket frog (A. gryllus) are currently recognized. We generated a phylogenetic hypothesis for Acris using fragments of nuclear and mitochondrial genes in separate and combined phylogenetic analyses. We also used distance methods and fixation indices to evaluate species limits within the genus and the validity of currently recognized subspecies of A. crepitans. The distributions of existing A. crepitans subspecies, defined by morphology and call types, do not match the distributions of evolutionary lineages recovered using our genetic data. We discuss a scenario of call evolution to explain this disparity. We also recovered distinct phylogeographic groups within A. crepitans and A. gryllus that are congruent with other codistributed taxa. Under a lineage-based species concept, we recognize Acris blanchardi as a distinct species. The importance of this revised taxonomy is discussed in light of the dramatic declines in A. blanchardi across the northern and western portions of its range

The Effect of Particle Strength on the Ballistic Resistance of Shear Thickening Fluids

The response of shear thickening fluids (STFs) under ballistic impact has received considerable attention due to its field-responsive nature. While efforts have primarily focused on the response of traditional ballistic fabrics impregnated with fluids, the response of pure STFs to penetration has received limited attention. In the present study, the ballistic response of pure STFs is investigated and the effect of fluid density and particle strength on ballistic performance is isolated. The loss of ballistic resistance of STFs at higher impact velocities is governed by particle strength, indicating the range of velocities over which they may provide effective armor solutions.Comment: 4 pages, 4 figure