Wind shear and turbulence simulation

The aviation community is increasing its reliance on flight simulators. This is true both in pilot training and in research and development. In moving research concepts through the development pipeline, there is a sequence of events which take place: analysis, ground based simulation, inflight simulation, and flight testing. Increasing fidelity as progress toward the flight testing arena is accompanied by increasing cost. The question that seems to be posed in relation to the meteorological aspects of flight simulation is, How much fidelity is enough and can it be quantified. As a part of the Langley Simulation Technology Program, there are three principal areas of focus, one being improved simulation of weather hazards. A close liaison with the JAWS project was established because of the Langley Simulation Technology interests regarding reliable simulation of severe convective weather phenomena and their impact on aviation systems. Simulation offers the only feasible approach for examining the utility of new technology and new procedures for coping with severe convective weather phenomena such as wind shear. These simulation concepts are discussed in detail

Sample size and positive false discovery rate control for multiple testing

The positive false discovery rate (pFDR) is a useful overall measure of errors for multiple hypothesis testing, especially when the underlying goal is to attain one or more discoveries. Control of pFDR critically depends on how much evidence is available from data to distinguish between false and true nulls. Oftentimes, as many aspects of the data distributions are unknown, one may not be able to obtain strong enough evidence from the data for pFDR control. This raises the question as to how much data are needed to attain a target pFDR level. We study the asymptotics of the minimum number of observations per null for the pFDR control associated with multiple Studentized tests and $F$ tests, especially when the differences between false nulls and true nulls are small. For Studentized tests, we consider tests on shifts or other parameters associated with normal and general distributions. For $F$ tests, we also take into account the effect of the number of covariates in linear regression. The results show that in determining the minimum sample size per null for pFDR control, higher order statistical properties of data are important, and the number of covariates is important in tests to detect regression effects.Comment: Published at http://dx.doi.org/10.1214/07-EJS045 in the Electronic Journal of Statistics (http://www.i-journals.org/ejs/) by the Institute of Mathematical Statistics (http://www.imstat.org

Cyclic Testing of Reinforced Earthbag Walls

Earthen construction is the most popular building method around the world. One particular building method, using earthbags, has shown promise in performing well against seismic activity. This project undertook the goal of developing a preliminary seismic response modification factor, R, to be used in the design of homes in seismically active areas. Two 4’ wide x 6’ tall x 1’ deep walls were cyclically loaded using a Three-Degree-of-Freedom (TDOF) Test Frame provided by Santa Clara University to determine the in-plane shear capacity of each wall. Testing revealed an average yield force of 419 lbs, an average ultimate force 1058 lbs, and an average R value of 6. Wall design and construction was focused on three aspects of the project that were modeled to replicate common building practices while still being modular enough to test multiple samples. These aspects were the base, bond beam, and wall. Wall bases were designed to withstand up to 3500 lb-ft bending moment during forklift transport, the bond beam was designed to transfer up to 9,000 lbs of shear force into the wall, and, the wall was designed using common building practices used in earthbag construction. Upon completion of the Consortium of Universities for the Research of Earthquake Engineering (CUREE) testing protocol, it was observed that the walls failed in buckling due to compression resulting from the force couple created by the loading arrangement. Despite failure, the walls continued standing even after the pin connection was removed from the tops of wall. This unexpected resiliency and behavior of the walls during testing led the team to believe that earthbag walls are much more ductile a material that was initially anticipated. A deeper understanding is needed to better understand how earthbag buildings behave against seismic forces. This project is encouraging for future research and the development of a more standardized building method

Steganographic checks in digital forensic investigation: A social networking case

Steganography is an ancient art that has received a mega boost in the digital age. Electronic communications are easily accessible by most people and have a wide range of opportunities to embed secret messages in a diverse range of cover objects. Our research questions were: What can an investigator do to check for hidden messages in social media? And, how much searching is enough? The testing was conducted in replicated social networking sites and digital images were selected as the cover objects. The research findings showed that steganography is as easy as sending an email and not much more difficult than downloading and using one of the many steganographic tools available online. Our advice is that investigators do check for hidden messaging in digital media and that the best practice guide developed be used as a minimal baseline

Is "No test is better than a bad test"? Impact of diagnostic uncertainty in mass testing on the spread of Covid-19

Testing is viewed as a critical aspect of any strategy to tackle epidemics. Much of the dialogue around testing has concentrated on how countries can scale up capacity, but the uncertainty in testing has not received nearly as much attention beyond asking if a test is accurate enough to be used. Even for highly accurate tests, false positives and false negatives will accumulate as mass testing strategies are employed under pressure, and these misdiagnoses could have major implications on the ability of governments to suppress the virus. The present analysis uses a modified SIR model to understand the implication and magnitude of misdiagnosis in the context of ending lockdown measures. The results indicate that increased testing capacity alone will not provide a solution to lockdown measures. The progression of the epidemic and peak infections is shown to depend heavily on test characteristics, test targeting, and prevalence of the infection. Antibody based immunity passports are rejected as a solution to ending lockdown, as they can put the population at risk if poorly targeted. Similarly, mass screening for active viral infection may only be beneficial if it can be sufficiently well targeted, otherwise reliance on this approach for protection of the population can again put them at risk. A well targeted active viral test combined with a slow release rate is a viable strategy for continuous suppression of the virus.</jats:p

Design of developmental test programs for one-shot systems with two state reliability

This dissertation considers efficient developmental testing for one-shot systems (for example, missiles) that are destroyed in testing or first normal use, where there is the possibility of reliability growth of the basic system design as a result of redesigns following failed developmental tests. We consider situations where the cost of redesign is negligible and there is a fixed procurement budget covering both system development and purchase, each developmental test produces either a binary (success-failure) or a continuous outcome. The analysis offered here is intended as an answer to the question How much testing is enough? posed by Seglie (1992) in the context of the procurement of military weapons systems. For a particular two-state model of system reliability, dynamic programming is used to identify testing plans/stopping rules that are optimal in the sense of maximizing the expected number of effective systems (of the final design) that can be purchased with the remaining budget when developmental testing is terminated. Several reasonable and easily implemented sub-optimal rules are also considered, and their performances are compared to that of the optimal rule for a variety of combinations of model parameters

Steganographic Checks In Digital Forensic Investigation: A Social Networking Case

Steganography is an ancient art that has received a mega boost in the digital age. Electronic communications are easily accessible by most people and have a wide range of opportunities to embed secret messages in a diverse range of cover objects. Our research questions were: What can an investigator do to check for hidden messages in social media? And, how much searching is enough? The testing was conducted in replicated social networking sites and digital images were selected as the cover objects. The research findings showed that steganography is as easy as sending an email and not much more difficult than downloading and using one of the many steganographic tools available online. Our advice is that investigators do check for hidden messaging in digital media and that the best practice guide developed be used as a minimal baseline

Operationally-relevant test lengths : a decision-analysis approach.

This thesis approaches the question of How much testing is enough? by formulating a model for the combat situation in which the weapon (e.g., missile) will be used. Methods of Bayesian statistics are employed to allow the decision maker to benefit from prior information gained in the testing of similar systems by forecasting the operational gain from acceptance. A Microsoft Excel V7.0 spreadsheet serves as the user interface, and Visual Basic for Applications, Excel's built in macro-language, is the language used to produce the source code. The methodology accommodates two different tactical usages for the missile: a single shot, or a salvo of two shots. The missile might be acceptable if used in the two-shot salvo mode, but not in the single shot mode, and this would imply a greater cost per mission. In the end the missile might not be judged cost effective as compared to a competitive system. If the model proposed is (or can become) adequate much can be calculated/estimated before any operational tests are made. This could assist in economizing on operational testinghttp://archive.org/details/operationallyrel00gormApproved for public release; distribution is unlimited