Repair techniques for celion/LARC-160 graphite/polyimide composite structures

The large stiffness-to-weight and strength-to-weight ratios of graphite composite in combination with the 600 F structural capability of the polyimide matrix can reduce the total structure/TPS weight of reusable space vehicles by 20-30 percent. It is inevitable that with planned usage of GR/PI structural components, damage will occur either in the form of intrinsic flaw growth or mechanical damage. Research and development programs were initiated to develop repair processes and techniques specific to Celion/LARC-160 GR/PI structure with emphasis on highly loaded and lightly loaded compression critical structures for factory type repair. Repair processes include cocure and secondary bonding techniques applied under vacuum plus positive autoclave pressure. Viable repair designs and processes are discussed for flat laminates, honeycomb sandwich panels, and hat-stiffened skin-stringer panels. The repair methodology was verified through structural element compression tests at room temperature and 315 C (600 F)

Aberration Corrected Emittance Exchange

Full exploitation of emittance exchange (EEX) requires aberration-free performance of a complex imaging system including active radio-frequency (RF) elements which can add temporal distortions. We investigate the performance of an EEX line where the exchange occurs between two dimensions with normalized emittances which differ by multiple orders of magnitude. The transverse emittance is exchanged into the longitudinal dimension using a double dog-leg emittance exchange setup with a five cell RF deflector cavity. Aberration correction is performed on the four most dominant aberrations. These include temporal aberrations that are corrected with higher order magnetic optical elements located where longitudinal and transverse emittance are coupled. We demonstrate aberration-free performance of an EEX line with emittances differing by four orders of magnitude, \textit{i.e.} an initial transverse emittance of 1~pm-rad is exchanged with a longitudinal emittance of 10~nm-rad

Graphite/Larc-160 technology demonstration segment test results

A structural test program was conducted on a Celion/LARC-160 graphite/polyimide technology demonstration segment (TDS) to verify the technology. The 137 x 152 cm (54 x 60 in.) TDS simulates a full-scale section of the orbiter composite body flap design incorporating three ribs and extending from the forward cove back to the rear spar. The TDS was successfully subjected to mechanical loads and thermal environments (-170 to 316 C) simulating 100 shuttle orbiter missions. Successful completion of the test program verified the design, analysis, and fabrication methodology for bonded Gr/PI honeycomb sandwich structure and demonstration that Gr/PI composite technology readiness is established

Nano-modulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately ten meters. Electron beam simulations from cathode emission through diffraction, acceleration and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties

Ethical dilemmas in clinical social work practice : how are social workers affected and how do we respond?

This mixed-methods exploratory research was undertaken to gain insight into how social workers perceive, are affected by, and respond to situations in which they are not able to enact social work ethics, or are asked to facilitate perceived injustice because of workplace restrictions. Seventy-four social workers responded to my online mixed methods survey. In quantitative responses, Likert scaled responses rated participants’ frequency and level of distress when encountering ethical dilemmas involving structural racism, classism, cultural insensitivity, sexism, heterosexism, protocols prioritizing funding over client care, protocols interfering with the treatment relationship, and protocols interfering with client self-determination. Participants also rated their sense of burnout related to structurally imposed ethical dilemmas. Both descriptive statistics were derived, and correlations were obtained between demographic information and quantitative response re: frequency and distress. Qualitative text boxes allowed descriptions of experiences with ethical dilemmas in more detail – e.g., information about roles and social work settings in which dilemmas took place, and descriptions of participants’ suffering and action in relation to dilemmas. The study opens new avenues for social work as a profession to explore in the interest of preserving its loyalty to the social work code of ethics, and the individual social workers’ well-being and professional satisfaction

New Frontiers in Forestry

I T IS commonly said that forestry in this country really began about the turn of the century. This is true in the sense that building of a profession of foresters, development of the national forest system, and other actual achievements in forestry have been brought about within the last 40 years. These accomplishments would not, however, have been possible without the pioneer work of a small group of leaders during the previous 15 or 20 years. Viewed from the standpoint of the extent and character of work under way today, the high standing of the foresters responsible for it, and the general support of forestry by the general public, the achievements within the past generation are very impressive and may well be a source of gratification and pride to every forester