Force instrumentation for cryogenic wind tunnels using one-piece strain-gage balances

The use of cryogenic temperatures in wind tunnels to achieve high Reynolds numbers has imposed a harsh operating environment on the force balance. Laboratory tests were conducted to study the effect cryogenic temperatures have on balance materials, gages, wiring, solder, adhesives, and moisture proofing. Wind tunnel tests were conducted using a one piece three component balance to verify laboratory results. These initial studies indicate that satisfactory force data can be obtained under steady state conditions

Strain gage balances and buffet gages

One-piece strain gage force balances were developed for use in the National Transonic Facility (NTF). This was accomplished by studying the effects of the cryogenic environment on materials, strain gages, cements, solders, and moisture proofing agents, and selecting those that minimized strain gage output changes due to temperature. In addition, because of the higher loads that may be imposed by the NTF, these balances are designed to carry a larger load for a given diameter than conventional balances. Full cryogenic calibrations were accomplished, and wind tunnel results that were obtained from the Langley 0-3-Meter Transonic Cryogenic Tunnel were used to verify laboratory test results

Aerodynamic force measurements with a strain-gage balance in a cryogenic wind tunnel

Aerodynamic force measurements on a generalized 75 deg delta wing model with sharp leading edges were made with a three component internal strain gage balance in a cryogenic wind tunnel at stagnation temperatures of 300 K, 200 K, and 110 K. The feasibility of using a strain gage balance without thermal control in a cryogenic environment as well as the use of electrical resistance heaters, an insulator between the model and the balance, and a convection shield on the balance was investigated. Force and moment data on the delta wing model as measured by the balance are compared at the different temperatures while holding constant either the Reynolds number or the tunnel stagnation pressure. Tests were made at Mach numbers of 0.3 and 0.5 and at angles of attack up to 29 deg. The results indicate that it is feasible to acquire accurate force and moment data while operating at steady state thermal conditions in a cryogenic wind tunnel, either with or without electrical heaters on the balance. Within the limits of the balance accuracy, there were no apparent Reynolds number effects on the aerodynamic results for the delta wind model

Strain Gauge Balance Calibration and Data Reduction at NASA Langley Research Center

This paper will cover the standard force balance calibration and data reduction techniques used at Langley Research Center. It will cover balance axes definition, balance type, calibration instrumentation, traceability of standards to NIST, calibration loading procedures, balance calibration mathematical model, calibration data reduction techniques, balance accuracy reporting, and calibration frequency

A biophysical model of prokaryotic diversity in geothermal hot springs

Recent field investigations of photosynthetic bacteria living in geothermal hot spring environments have revealed surprisingly complex ecosystems, with an unexpected level of genetic diversity. One case of particular interest involves the distribution along hot spring thermal gradients of genetically distinct bacterial strains that differ in their preferred temperatures for reproduction and photosynthesis. In such systems, a single variable, temperature, defines the relevant environmental variation. In spite of this, each region along the thermal gradient exhibits multiple strains of photosynthetic bacteria adapted to several distinct thermal optima, rather than the expected single thermal strain adapted to the local environmental temperature. Here we analyze microbiology data from several ecological studies to show that the thermal distribution field data exhibit several universal features independent of location and specific bacterial strain. These include the distribution of optimal temperatures of different thermal strains and the functional dependence of the net population density on temperature. Further, we present a simple population dynamics model of these systems that is highly constrained by biophysical data and by physical features of the environment. This model can explain in detail the observed diversity of different strains of the photosynthetic bacteria. It also reproduces the observed thermal population distributions, as well as certain features of population dynamics observed in laboratory studies of the same organisms

Resident macrophages of pancreatic islets have a seminal role in the initiation of autoimmune diabetes of NOD mice

Significance Our studies indicate that the resident macrophages of the pancreatic islets of Langerhans have a seminal role in the initiation and progression of autoimmune diabetes in NOD mice. In this study, islet macrophages were depleted by administration of a monoclonal antibody to the CSF-1 receptor. Macrophage depletion, either at the start of the autoimmune process or when diabetogenesis is active, leads to a significant reduction in diabetes incidence. Depletion of the islet macrophages reduces the entrance of T cells into islets and results in the absence of antigen presentation. Concordantly, a regulatory pathway develops that controls diabetes progression. We conclude that treatments that target the islet macrophages may have important clinical relevance for the control of autoimmune type 1 diabetes.</jats:p

Impact of slurry application method on phosphorus loss in runoff from grassland soils during periods of high soil moisture content

Abstract Previous studies have reported that the trailing shoe application technique reduces phosphorus (P) in the runoff postslurry application when compared to the traditional splash-plate application technique. However, the effectiveness of the trailing-shoe technique as a means of reducing P losses has not been evaluated when slurry is applied during periods of high soil moisture levels and lower herbage covers. To address this issue, three treatments were examined in a 3 × 4 factorial design split-plot experiment, with treatments comprising three slurry treatments: control (no slurry), splashplate and trailing-shoe, and four slurry application dates: 7 December, 18 January, 1 March and 10 April. Dairy cow slurry was applied at a rate of 20 m3/ha, while simulated runoff was generated 2, 9 and 16 days later and analysed for a range of P fractions. Dissolved reactive P concentrations in runoff at day two was 41% lower when slurry was applied using the trailing-shoe technique, compared to the splash-plate technique (P &lt; 0.05). In addition, P concentrations in runoff were higher (P &lt; 0.05) from slurry applied in December and March compared to slurry applied in January or April, coinciding with periods of higher soil moisture contents. While the latter highlights that ‘calendar’-based non-spreading periods might not always achieve the desired consequences, the study demonstrated that further field-scale investigations into the trailing shoe as a mitigation measure to reduced P loss from agricultural soils is warranted.</jats:p

Apparent-Strain Correction for Combined Thermal and Mechanical Testing

Combined thermal and mechanical testing requires that the total strain be corrected for the coefficient of thermal expansion mismatch between the strain gage and the specimen or apparent strain when the temperature varies while a mechanical load is being applied. Collecting data for an apparent strain test becomes problematic as the specimen size increases. If the test specimen cannot be placed in a variable temperature test chamber to generate apparent strain data with no mechanical loads, coupons can be used to generate the required data. The coupons, however, must have the same strain gage type, coefficient of thermal expansion, and constraints as the specimen to be useful. Obtaining apparent-strain data at temperatures lower than -320 F is challenging due to the difficulty to maintain steady-state and uniform temperatures on a given specimen. Equations to correct for apparent strain in a real-time fashion and data from apparent-strain tests for composite and metallic specimens over a temperature range from -450 F to +250 F are presented in this paper. Three approaches to extrapolate apparent-strain data from -320 F to -430 F are presented and compared to the measured apparent-strain data. The first two approaches use a subset of the apparent-strain curves between -320 F and 100 F to extrapolate to -430 F, while the third approach extrapolates the apparent-strain curve over the temperature range of -320 F to +250 F to -430 F. The first two approaches are superior to the third approach but the use of either of the first two approaches is contingent upon the degree of non-linearity of the apparent-strain curve

DEMONSTRATION OF THE ZIRFLEX PROCESS ON IRRADIATED PWR BLANKET FUEL

Fifteen PWR blanket fuel specimens varying in burnup from 80 to 1100 Mwd/ T, were declad with boiling 6 M NH/sub 4/F-1.0 M NH/sub 4/NO/sub 3/ before the UO/ sub 2/ core was dissolved in 10 M HNO/sub 3/. Uranium and plutonium losses to the decladding solution were less than 0.2% in nearly all runs. While these ments with unirradiated fuel, they are of the same order of magnitude as those obtained in the testing of the hot cell HF was used as the decladding reagent, the uranium and plutonium losses averaged 1.0 and 0.4%, respectively. (auth

Leader Behaviors as Mediators of the Leader Characteristics - Follower Satisfaction Relationship

This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this record.This study examined two potential mediators through which leaders transmit their position power into an effectiveness outcome. Drawing upon recent work integrating trait, situational, and behavioral theories of leadership effectiveness, we hypothesized and tested a model specifying that the interactive effects of leader position power and leader political skill on follower satisfaction would be mediated by followers’ perceptions of leaders’ initiating structure and consideration behaviors. Specifically, this model indicates that leaders who are both in powerful positions and politically skilled are perceived to initiate more structure and demonstrate more consideration for their followers than their nonpolitically skilled counterparts, which, in turn, positively impacts followers’ satisfaction (i.e., an indication of subjective leadership effectiveness). Utilizing 190 leaders and 476 followers, we found support for the hypothesized model. Contributions to various literatures, strengths, limitations, and practical implications are discussed