Effects of hydrostatic pressure on the mechanical behavior of body centered cubic refractory metals and alloys

Hydrostatic pressure on mechanical behavior of body centered cubic refractory metals and alloy

Evaluation of Poroton Masonry and Suggestion for Quick Design Procedure

Poroton masonry units are highly cored extruded clay units with numerous thin webs. They have ground surfaces and are laid on a thin fluid mortar bed, with no mortar in the head joints. They offer the advantages of quick construction, which can be performed by a general labor force. This thesis describes the results of component and prism testing of Poroton masonry. Compressive strength tests occurred on individual units and on prisms constructed with two units in accordance with the manufacturer’s directions. The average unit compressive strength was approximately 2900 psi. The average prism compressive strength was about 900 psi. In addition to compressive testing on the two unit prisms, flexural strength testing was conducted on the prisms. During flexural strength testing, modifications to the flexural testing device, also known as the “Bond Wrench,” were made. These changes allowed a pure moment to be applied during flexural tension testing. The average flexural tensile strength for Poroton masonry was 65 psi. With the strength properties now defined, a review of unreinforced and reinforced design methods applicable to the Poroton units have been made. For unreinforced design, conventional procedures can be used for Poroton construction. However, section properties can be approximately determined based on net moment of inertia of 60% of the gross moment of inertia. For reinforced design, an approximate method was developed. The approximate method is based on a simplified “T-beam” design that is commonly used for partially grouted walls. The distance from extreme compression fiber to the neutral axis was slightly modified to account for the unusual crosssectional geometry. This approximate reinforced design method tended to be slightly conservative when compared to an exact design method

Surveyor nose fairing mode survey

Shell mode frequencies, shapes, and damping values for Surveyor nose fairing under simulated flight delta pressure and nose cone tip rotation during pressure simulatio

Adjusting process count on demand for petascale global optimization⋆

There are many challenges that need to be met before efficient and reliable computation at the petascale is possible. Many scientific and engineering codes running at the petascale are likely to be memory intensive, which makes thrashing a serious problem for many petascale applications. One way to overcome this challenge is to use a dynamic number of processes, so that the total amount of memory available for the computation can be increased on demand. This paper describes modifications made to the massively parallel global optimization code pVTdirect in order to allow for a dynamic number of processes. In particular, the modified version of the code monitors memory use and spawns new processes if the amount of available memory is determined to be insufficient. The primary design challenges are discussed, and performance results are presented and analyzed

The role of clinical parapapillary atrophy evaluation in the diagnosis of open angle glaucoma

Joshua R Ehrlich, Nathan M RadcliffeDepartment of Ophthalmology, Weill Cornell Medical College, New York, NY, USAPurpose: To determine if clinical evaluation of parapapillary atrophy (PPA) significantly improves the ability to distinguish open-angle glaucoma (OAG) patients from glaucoma suspects.Methods: Patients in this study were under evaluation for glaucoma and had open angles, at least one reliable 24-2 SITA-standard automatic perimetry, and digital stereophotographs of the optic disc. PPA was identified clinically as a parapapillary region of absent (βPPA) or hyper/hypopigmented (αPPA) retinal pigment epithelium. A single masked observer evaluated photos for: vertical cup-to-disc ratio (CDR), clock hours of total and βPPA, βPPA as percentage width of the optic disc, presence or absence of βPPA at each disc quadrant, and ordinal rating of total PPA. Generalized linear models were used to determine odds of an abnormal or borderline glaucoma hemifield test (GHT) as a function of PPA variables and covariates; model fit was assessed using the log-likelihood ratio test.Results: Of 410 consecutive patients, 540 eyes (of 294 patients) met inclusion criteria. Mean age was greater among patients with abnormal compared with normal GHT (P < 0.001), but sex and race/ethnicity did not differ between groups (P ≥ 0.22). Age, central corneal thickness (CCT) and CDR (P ≤ 0.006), but not intraocular pressure (IOP) (P = 0.71), were significant univariable predictors of the odds of an abnormal GHT. All PPA parameters significantly ­predicted GHT (P ≤ 0.03), except presence of temporal βPPA (P = 0.25). Adjustment for age, CCT, IOP, and CDR reduced the association between PPA and GHT, and model fit was not greatly improved by addition of PPA variables.Conclusions: Addition of most PPA parameters to a model already containing commonly assessed variables including age, CCT, IOP, and CDR does not significantly improve the ability to distinguish OAG patients from glaucoma suspects.Keywords: glaucoma, visual fields, parapapillary atrophy, optic nerv

Simulation of fluid flows during growth of organic crystals in microgravity

Several counter diffusion type crystal growth experiments were conducted in space. Improvements in crystal size and quality are attributed to reduced natural convection in the microgravity environment. One series of experiments called DMOS (Diffusive Mixing of Organic Solutions) was designed and conducted by researchers at the 3M Corporation and flown by NASA on the space shuttle. Since only limited information about the mixing process is available from the space experiments, a series of ground based experiments was conducted to further investigate the fluid dynamics within the DMOS crystal growth cell. Solutions with density differences in the range of 10 to the -7 to 10 to the -4 power g/cc were used to simulate microgravity conditions. The small density differences were obtained by mixing D2O and H2O. Methylene blue dye was used to enhance flow visualization. The extent of mixing was measured photometrically using the 662 nm absorbance peak of the dye. Results indicate that extensive mixing by natural convection can occur even under microgravity conditions. This is qualitatively consistent with results of a simple scaling analysis. Quantitave results are in close agreement with ongoing computational modeling analysis

JOINT DISPLACEMENTS AND PEAK ACHILLES TENDON FORCE DURING IRISH DANCING-SPECIFIC LANDING TASKS

Achilles tendinopathy is prevalent among Irish dancers, thought to be due to the high impact, stiff-style landing tasks associated with the sport. This study aimed to investigate the relationship between sagittal plane joint displacements, at the ankle, knee, hip and thorax segment, and peak Achilles tendon force during an Irish dancing ‘leap over’ landing task. Kinetic and kinematic data were collected for 12 participants performing the ‘leap over’, and used to calculate peak Achilles tendon force and joint displacements. Results of the study found a statistically significant positive correlation between ankle dorsiflexion and peak Achilles tendon force during the ‘leap over’. These findings can be used to inform future research into the effect of joint displacement on peak Achilles tendon force, and to develop strategies to help dancers reduce their risk of developing Achilles tendinopathy