Math modeling for helicopter simulation of low speed, low altitude and steeply descending flight

A math model was formulated to represent some of the aerodynamic effects of low speed, low altitude, and steeply descending flight. The formulation is intended to be consistent with the single rotor real time simulation model at NASA Ames Research Center. The effect of low speed, low altitude flight on main rotor downwash was obtained by assuming a uniform plus first harmonic inflow model and then by using wind tunnel data in the form of hub loads to solve for the inflow coefficients. The result was a set of tables for steady and first harmonic inflow coefficients as functions of ground proximity, angle of attack, and airspeed. The aerodynamics associated with steep descending flight in the vortex ring state were modeled by replacing the steady induced downwash derived from momentum theory with an experimentally derived value and by including a thrust fluctuations effect due to vortex shedding. Tables of the induced downwash and the magnitude of the thrust fluctuations were created as functions of angle of attack and airspeed

Device and method for frictionally testing materials for ignitability

Test apparatus for determining ignition characteristics of various metal in oxidizer environments simulating operating conditions for materials is invented. The test apparatus has a chamber through which the oxidizing agent flows, and means for mounting a stationary test sample therein, a powered, rotating shaft in the chamber rigidly mounts a second test sample. The shaft is axially movable to bring the samples into frictional engagement and heated to the ignition point. Instrumentation connected to the apparatus provides for observation of temperatures, pressures, loads on and speeds of the rotating shaft, and torques whereby components of stressed oxygen systems can be selected which will avoid accidental fires under working conditions

Investigating Automatic Static Analysis Results to Identify Quality Problems: an Inductive Study

Background: Automatic static analysis (ASA) tools examine source code to discover "issues", i.e. code patterns that are symptoms of bad programming practices and that can lead to defective behavior. Studies in the literature have shown that these tools find defects earlier than other verification activities, but they produce a substantial number of false positive warnings. For this reason, an alternative approach is to use the set of ASA issues to identify defect prone files and components rather than focusing on the individual issues. Aim: We conducted an exploratory study to investigate whether ASA issues can be used as early indicators of faulty files and components and, for the first time, whether they point to a decay of specific software quality attributes, such as maintainability or functionality. Our aim is to understand the critical parameters and feasibility of such an approach to feed into future research on more specific quality and defect prediction models. Method: We analyzed an industrial C# web application using the Resharper ASA tool and explored if significant correlations exist in such a data set. Results: We found promising results when predicting defect-prone files. A set of specific Resharper categories are better indicators of faulty files than common software metrics or the collection of issues of all issue categories, and these categories correlate to different software quality attributes. Conclusions: Our advice for future research is to perform analysis on file rather component level and to evaluate the generalizability of categories. We also recommend using larger datasets as we learned that data sparseness can lead to challenges in the proposed analysis proces

Sanitizing the fortress: protection of ant brood and nest material by worker antibiotics

Social groups are at particular risk for parasite infection, which is heightened in eusocial insects by the low genetic diversity of individuals within a colony. To combat this, adult ants have evolved a suite of defenses to protect each other, including the production of antimicrobial secretions. However, it is the brood in a colony that are most vulnerable to parasites because their individual defenses are limited, and the nest material in which ants live is also likely to be prone to colonization by potential parasites. Here, we investigate in two ant species whether adult workers use their antimicrobial secretions not only to protect each other but also to sanitize the vulnerable brood and nest material. We find that, in both leaf-cutting ants and weaver ants, the survival of the brood was reduced and the sporulation of parasitic fungi from them increased, when the workers nursing them lacked functional antimicrobial-producing glands. This was the case for both larvae that were experimentally treated with a fungal parasite (Metarhizium) and control larvae which developed infections of an opportunistic fungal parasite (Aspergillus). Similarly, fungi were more likely to grow on the nest material of both ant species if the glands of attending workers were blocked. The results show that the defense of brood and sanitization of nest material are important functions of the antimicrobial secretions of adult ants and that ubiquitous, opportunistic fungi may be a more important driver of the evolution of these defenses than rarer, specialist parasites

Dynamics of trusses having nonlinear joints

The transient analysis of trusses having nonlinear joints can be accomplished using the residual force technique. The technique was applied a two degree of freedom spring mass system, a four bay planar truss, and an actual ten bay deployable truss. Joints chosen for analysis were the nonlinear gap joints and the linear Voigt joints. Results from the nonlinear gap analyses generally indicate that coupling between the modes can display some interesting effects during free vibration. One particularly interesting effect was that the damping of the structure appeared to be higher than could be accounted for from modal damping alone. Energy transferral from the lower to the higher modes was found to exist as a result of the modal coupling. The apparently increased damping was due to the fact that the energy transferred to the higher modes is inherently dissipated more quickly. Another interesting phenomenon was that the lower modes could drive the higher modes even during free vibration and that these modes could display a rather large quasi-steady state behavior even when modal damping was present. Gaps were also found to increase the amplitude and period of the free vibration response as expected

Philosophy of History, Historical Jesus Studies, and Miracles: Three Roadblocks to Resurrection Research

Jesus’ resurrection is considered by many to be a historical event, but objections are often raised regarding to such inquiry into the past. Philosophy of history is thus an important field in which various roadblocks to resurrection research have been raised. These philosophical questions related to the study of the Jesus’ resurrection have become more prominent recently and seek to undermine the very act of historical inquiry into Jesus’ resurrection specifically and the past more generally. Accordingly, the issues addressed here have implications beyond resurrection research. This work seeks to identify and assess three common roadblocks to such research. The first is the question related to the subjectivity historian and whether or not they can have objective knowledge of the past or whether our knowledge of the past is ultimately a mere construction of the historian. We note that both are possible and that what differentiates objective knowledge of the past or a construction of the past is whether or not virtues or vices have been cultivated by the historian. Second, since we can have knowledge of the past, two ways in which it is possible for one to have this knowledge of the past are then presented. We present the Minimal Facts Approach as one possible avenue and note the application of various historical criteria as a second. These are not the only two methods, but two that we believe to provide secure historical knowledge. Lastly, we argue that historians could, in principle, conclude that a miracle has occurred. After offering some philosophical analysis of the issue of miracles and the historian’s craft, we identify and assess to objections to our conclusion. We ultimately conclude that these are more like bumps in the road rather than actual roadblocks that prevent investigation into the past. They should be considered in historical inquiry, but they certainly do not prevent one from investigating Jesus’ resurrection in particular or the past in general

History and Eschatology by N. T. Wright: A Review

Wright, N. T. History and Eschatology: Jesus and the Promise of Natural Theology. Waco, TX: Baylor University Press, 2019. 365 pp. $34.9

Review of Studies on the Origin of Divine and Resurrection Christology

Review: Studies on the Origin of Divine and Resurrection Christolog

Crucifixion in the Ancient World: A Historical Analysis

Cook, John Granger. Crucifixion in the Mediterranean World. 2nd ed. Vol. 327. Wissenschaftliche Untersuchungen Zum Neuen Testament. Tübingen: Mohr Siebeck, 2019. Pp 549 pp. 79,00 €