Performance of MoS2 Coated Gears Exposed to Humid Air During Storage

The purpose of this work was to study the effect of exposure to humid air on the durability of a molybdenum disulfide dry film lubricant applied to spur test gears and subsequently tested in vacuum environment. This study was motivated by the James Webb Space Telescope (JWST) Mission. Some moving mechanical assembles of the JWST have been exposed to humid air during storage as a subassembly and after integration into a higher-level assembly. molybdenum disulfide dry film lubricant was applied to steel spur test gears and subsequently tested in vacuum environment. One-half of the gears had essentially zero time exposure to humid air prior to testing, and the other half were exposed to humid air of 57 percent relative humidity for exposure durations up to 77 days prior to testing. All tests were completed at the same constant torque and speed. On average, the film durability, as measured by the number of pinion revolutions, was shorter for gears exposed to humid air compared to those with zero exposure. For the unexposed gears, the durability ranged from 53,300 to 190,300 pinion revolutions with an average value of 100,200 and a median value of 83,500 revolutions. For the exposed gears, the durability ranged from 21,000 to 84,700 pinion revolutions with an average value of 64,900 and a median value of 68,800 revolutions. Using the unexposed gears as a baseline, the exposure reduced the average durability by 35 percent and the median value of durability by 18 percent. Red-brown coloration was noted on some of the gear teeth that had been exposed to humid air. The colored regions appeared as soon as 17 days after exposure to humid air. SEM inspections showed that at least some of these colored areas included material raised above the surrounding molybdenum disulfide film

Design and Lessons Learned on the Development of a Cryogenic Pupil Select Mechanism Used in the Testing and Calibration of the Integrated Science Instrument Module (ISIM) on the James Webb Space Telescope (JWST)

Calibration and testing of the instruments on the Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST) is being performed by the use of a cryogenic, full-field, optical simulator that was constructed for this purpose. The Pupil Select Mechanism (PSM) assembly is one of several mechanisms and optical elements that compose the Optical Telescope Element SIMulator, or OSIM. The PSM allows for several optical elements to be inserted into the optical plane of OSIM, introducing a variety of aberrations, distortions, obscurations, and other calibration states into the pupil plane. The following discussion focuses on the details of the design evolution, analysis, build, and test of this mechanism along with the challenges associated with creating a sub arc-minute positioning mechanism operating in an extreme cryogenic environment. In addition, difficult challenges in the control system design will be discussed including the incorporation of closed-loop feedback control into a system that was designed to operate in an open-loop fashion

The Design & Development of the Ocean Color Instrument Precision Superduplex Hybrid Bearing Cartridge

A high precision, high-resolution Ocean Color Imaging (OCI) instrument is under development for the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission which requires a pair of medium speed mechanisms to scan the ocean surface continuously. The design of the rotating telescope (RT) mechanism operating at 360 RPM and the half-angle mirror (HAM) mechanism synchronized at 180 RPM was concern for maintaining pointing precision over the required life and continuous operations. An effort was undertaken with the manufacturer to design and analyze a special bearing configuration to minimize axial and radial runout, minimize torque, and maintain nominal contact stresses and stiffness over the operating temperature range and to maximize life. The bearing design, development effort, analysis and testing will be discussed as will the technical challenges that this specific design imposed upon the mechanism engineers. Bearing performance, runout as achieved and verified during encoder installation and operating torque will be described

Dynamic Range of Frontoparietal Functional Modulation is Associated with Working Memory Capacity Limitations in Older Adults

Older adults tend to over-activate regions throughout frontoparietal cortices and exhibit a reduced range of functional modulation during WM task performance compared to younger adults. While recent evidence suggests that reduced functional modulation is associated with poorer task performance, it remains unclear whether reduced range of modulation is indicative of general WM capacity-limitations. In the current study, we examined whether the range of functional modulation observed over multiple levels of WM task difficulty (N-Back) predicts in-scanner task performance and out-of-scanner psychometric estimates of WM capacity. Within our sample (60–77 years of age), age was negatively associated with frontoparietal modulation range. Individuals with greater modulation range exhibited more accurate N-Back performance. In addition, despite a lack of significant relationships between N-Back and complex span task performance, range of frontoparietal modulation during the N-Back significantly predicted domain-general estimates of WM capacity. Consistent with previous cross-sectional findings, older individuals with less modulation range exhibited greater activation at the lowest level of task difficulty but less activation at the highest levels of task difficulty. Our results are largely consistent with existing theories of neurocognitive aging (e.g. CRUNCH) but focus attention on dynamic range of functional modulation as a novel marker of WM capacity-limitations in older adults

Numerical Simulation of Arctic Offshore Structures Interacting with Level Ice and Nonlinear Time-Domain Simulations of Arctic Spar

One of the greatest challenges of developing the arctic regions is the harsh environmental conditions caused by the presence of ice. When offshore structures interact with ice, significant structural motion is induced by the ice load, which influences the overall structural robustness. In this study, three different numerical tools are developed to investigate the ice-structure interaction using three scenarios. First, the fixed-type monopile offshore wind turbine in level ice is studied. Because the crushing is the dominant failure mode of level ice against a cylindrical structure, a mechanical ice-crushing model is developed to estimate the ice force on the structure in time domain. The model is further implemented into the wind turbine analysis software, FAST, developed by National Renewable Energy Laboratory (NREL). Second, the floating offshore platform, Artic Spar, in level ice is investigated by employing an analytical method. Artic Spar is characterized by the inverted cone-shaped hull near the waterline so that level ice can fail when bending. The fully coupled floater-riser-mooring dynamic analysis program, CHARM3D, is extended by implementing the analytical ice-bending model. Third, the numerical software for the interaction between level ice and an arbitrary-shaped floating offshore structure is developed by coupling two software programs, LIGGGHTS and CHARM3D. Based on the discrete element method, level ice is modelled as an assembly of multiple spherical particles, and the bonding parallel method is employed to consider the interaction force among the bonded particles. Throughout the newly developed numerical simulation tools, the ice load on different offshore structures is numerically estimated, and the corresponding structural performances are systematically investigated. In addition to these three ice-structure interactions, the nonlinear behavior or Arctic Spar is investigated in time domain. To capture the nonlinearity of platform motions, a nonlinear time-domain simulation tool considering the nonlinear hydro-restoring coefficient and nonlinear Froude-Krylov force is developed by extending CHARM3D with a body-nonlinear method. The heave-to-pitch and heave-to-heave Mathieu instabilities of Arctic Spar are also investigated in both regular and irregular waves

The Infrared Array Camera (IRAC) for the Spitzer Space Telescope

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 microns. Two nearly adjacent 5.2x5.2 arcmin fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four detector arrays in the camera are 256x256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.Comment: 7 pages, 3 figures. Accepted for publication in the ApJS. A higher resolution version is at http://cfa-www.harvard.edu/irac/publication

Cryogenic Optical Position Encoders for Mechanisms in the JWST Optical Telescope Element Simulator (OSIM)

The JWST Optical Telescope Element Simulator (OSIM) is a configurable, cryogenic, optical stimulus for high fidelity ground characterization and calibration of JWST's flight instruments. OSIM and its associated Beam Image Analyzer (BIA) contain several ultra-precise, cryogenic mechanisms that enable OSIM to project point sources into the instruments according to the same optical prescription as the flight telescope images stars - correct in focal surface position and chief ray angle. OSIM's and BIA's fifteen axes of mechanisms navigate according to redundant, cryogenic, absolute, optical encoders - 32 in all operating at or below 100 K. OSIM's encoder subsystem, the engineering challenges met in its development, and the encoders' sub-micron and sub-arcsecond performance are discussed

A cryogenic scan mechanism for use in Fourier transform spectrometers

This paper describes the requirements, design, assembly and testing of the linear Scan Mechanism (SM) of the Composite Infrared Spectrometer (CIRS) Instrument. The mechanism consists of an over constrained flexible structure, an innovative moving magnet actuator, passive eddy current dampers, a Differential Eddy Current (DEC) sensor, Optical Limit Sensors (OLS), and a launch lock. Although all the components of the mechanism are discussed, the flexible structure and the magnetic components are the primary focus. Several problems encountered and solutions implemented during the development of the scan mechanism are also described

A study of the changing complexion of academic governance in New Jersey community colleges

The purpose of this study was to determine the forces of change that will affect community colleges in New Jersey and to capture the attitudes of stakeholders towards the impact of these forces as they relate to the future of the structure of academic governance. The target population of this study was community college administrators and faculty in five community colleges in southern New Jersey (n=90). The study included a random sample of administrators and faculty members, with an overall response rate of 43.5%. In addition to the survey, 12 stakeholders were randomly chosen to participate in interviews, representing a sample of convenience. The survey data were analyzed using the Statistical Package for Social Sciences (SPSS) version 12.0, which calculated frequencies, percentages, means, and standard deviations. Interview data were analyzed by categorizing the comments, predictions, and opinions made by the faculty members and administrators. The research has found that community colleges in New Jersey face many changes that will challenge decision-making processes as autonomy from state control continues to expand, requirements for broader sources of funding for growth and expansion of technologies continue to increase, and internal management continues to migrate to a shared governance structure

Effect of Dilute Acid Pretreatment of Vegetable Waste on Sugar Production and Inhibitor Formation

Vegetable waste is an organic waste with high cellulose and hemicellulose and low lignin content. The cellulose and hemicellulose chains can be broken down by pretreatment using sulfuric acid to obtain reducing sugar. To avoid the formation of degradation products that have the potential as inhibitor compounds, the temperature of the pretreatment operation was carried out at 121 and 125 for 60 minutes with sulfuric acid concentrations varying from 0.5% to 1.5% (v/v). The solid and liquid ratio (S/L) was 5% (w/v). From the experiments, the highest total reducing sugars of 7.068 g/L was obtained by pretreatment conditions at 121 for 60 minutes with a sulfuric acid concentration of 1% (v/v). Meanwhile, the lowest total reducing sugar of 2.764 g/L was produced during the pretreatment operating conditions at 125 for 60 minutes with a sulfuric acid concentration of 1% (v/v). Under the present experimental condition, it was found that only a low level of degradation product was formed, which ensures excellent performance of bacterial growth in the subsequent fermentation process