Fuzzy Logic Path Planning System for Collision Avoidance by an Autonomous Rover Vehicle

Systems already developed at JSC have shown the benefits of applying fuzzy logic control theory to space related operations. Four major issues are addressed that are associated with developing an autonomous collision avoidance subsystem within a path planning system designed for application in a remote, hostile environment that does not lend itself well to remote manipulation of the vehicle involved through Earth-based telecommunication. A good focus for this is unmanned exploration of the surface of Mars. The uncertainties involved indicate that robust approaches such as fuzzy logic control are particularly appropriate. The four major issues addressed are: (1) avoidance of a single fuzzy moving obstacle; (2) back off from a dead end in a static obstacle environment; (3) fusion of sensor data to detect obstacles; and (4) options for adaptive learning in a path planning system

Fuzzy logic control system to provide autonomous collision avoidance for Mars rover vehicle

NASA is currently involved with planning unmanned missions to Mars to investigate the terrain and process soil samples in advance of a manned mission. A key issue involved in unmanned surface exploration on Mars is that of supporting autonomous maneuvering since radio communication involves lengthy delays. It is anticipated that specific target locations will be designated for sample gathering. In maneuvering autonomously from a starting position to a target position, the rover will need to avoid a variety of obstacles such as boulders or troughs that may block the shortest path to the target. The physical integrity of the rover needs to be maintained while minimizing the time and distance required to attain the target position. Fuzzy logic lends itself well to building reliable control systems that function in the presence of uncertainty or ambiguity. The following major issues are discussed: (1) the nature of fuzzy logic control systems and software tools to implement them; (2) collision avoidance in the presence of fuzzy parameters; and (3) techniques for adaptation in fuzzy logic control systems

Implicit and Explicit Sexual Attitude Among United States Baccalaureate Nursing Students

Recognizing sexual minorities continue to experience discrimination and social, institutional, and health disparities, this study explored implicit and explicit sexual attitude among nursing students. Knowledge of these attitudes is an important step to improve the care provided to this vulnerable population. Yet, there remains little research of implicit sexual attitude among nurses and no research among nursing students. This study addressed this gap in the current literature by comparing measurements of implicit and explicit attitude and identifying demographic attributes that predict these attitudes. Critical cosmopolitan theory (Delanty, 2006), informed this non-experimental, descriptive, correlational study. Implicit attitude wasmeasured using the sexuality Implicit Association Test (IAT) (Greenwald, McGhee, & Schwartz, 1998). Explicit attitude of homophobia was measured using the Attitudes Toward Lesbians and Gay Men Scale (ATLG) (Herek, 1988). The IAT had acceptable (α = 0.73) reliability and the ATLG good (α = 0.89) reliability with this study sample. A demographic questionnaire of relevant predictor variables was drawn from the literature attitudes toward sexual minorities. A large sample (n = 1,348) of United States baccalaureate nursing students, drawn from a convenience sample, participated in the study. The majority of participants were female (n = 1,164, 86%), White (n = 990, 73%), self-identified as heterosexual (n = 1,044, 77%), and were enrolled in a registered nurse (RN) to bachelor of science in nursing (BSN) program (n = 790, 59%). The average age of participants was 28 years. Analysis of the results demonstrated a moderate implicit preference favoring heterosexuals over lesbian women and gay men (D-score = 0.22) that was more negative than the general public who took the IAT in 2018 (D-score = 0.15). Explicit attitude results indicated a low level of homophobia (ATLG = 17.52) in contrast to earlier studies, which reported moderate to high levels of this negative explicit attitude. The difference in implicit and explicit scores were found to be statistically significant, consistent with previous research that reported more positive explicit compared to implicit attitude. Among demographic variables, identifying as male, heterosexual, somewhat or very religious, enrolled in a RN to BSN nursing program predicted more negative implicit and explicit attitude. The implications of these findings for nursing education were discussed and recommendations for nursing academic leadership, faculty, and students were presented

Halo gas cross sections and covering fractions of MgII absorption selected galaxies

We examine halo gas cross sections and covering fractions, fc, of intermediate-redshift Mg II absorption selected galaxies. We computed statistical absorber halo radii, Rx, using current values of dN/dz and Schechter luminosity function parameters, and have compared these values to the distribution of impact parameters and luminosities from a sample of 37 galaxies. For equivalent widths Wr(2796) ≥ 0.3 Å, we find 43 ≤ Rx ≤ 88 kpc, depending on the lower luminosity cutoff and the slope, β, of the Holmberg-like luminosity scaling, R ∝ α L^β . The observed distribution of impact parameters, D, are such that several absorbing galaxies lie at D > Rx and several non-absorbing galaxies lie at D ~ 0.5 for our sample. Moreover, the data suggest that halo radii of Mg II absorbing galaxies do not follow a luminosity scaling with β in the range of 0.2–0.28, if fc = 1 as previously reported. However, provided fc ~ 0.5, we find that halo radii can remain consistent with a Holmberg-like luminosity relation with β ≃ 0.2 and R∗ = Rx/√(fc) ~ 110 kpc. No luminosity scaling (β = 0) is also consistent with the observed distribution of impact parameters if fc ≤ 0.37. The data support a scenario in which gaseous halos are patchy and likely have non-symmetric geometric distributions about the galaxies. We suggest that halo gas distributions may not be governed primarily by galaxy mass/luminosity but also by stochastic processes local to the galaxy

Road Sediment Yields from Dispersed Versus Clustered Forest Harvesting Activity: A Case Study

Road sediment yields reaching streams over a twenty year period were modeled under two scenarios for a 4900 ha forest in the foothills of the Oregon Coast Range. In the "clustered" scenario all forest harvesting activity took place in the northern half of the forest. In the "dispersed" scenario the same level of forest harvesting activity was allocated to the full forest estate. Three spatial modeling packages were used: SPECTRUM was used to schedule the harvest settings over a 150 year period, NETWORK 2000 was used to determine which roads would be used during the first 20 years of harvest and how many truck loads would be transported over them, and SEDMODL2 was used to determine the road sediment yields likely to reach a stream. Concentrating the forest harvesting activity on half of the forest estate resulted in a 36% reduction in total road sediment yields when compared with dispersed forest harvesting activity. Fewer roads would generate sediment under the "clustered" scenario but traffic intensities on these roads would be greater, partially negating the sediment yield savings

Reproduction and Growth of Black Drum, Pogonias cromis, in Northeast Florida

Age, growth, and reproduction of black drum, Pogonias cromis, in northeast Florida were investigated between December 1983 and April 1985. Male black drum began maturing at 450-499 mm total length (TL), with 50% of them reaching maturity at about 590 mm (age 4 or 5). Vitellogenesis began at 450-550 mm TL, with 50% of the females reaching maturity at 650-699 mm (age 5 or 6). Spawning occurred during January - April. Thin sections of otoliths displayed distinct opaque bands; the first three or four of these bands were verified by marginal increment analysis as being annuli deposited during March - May. The growth rate was about 100 mm yr-1 for ages 1·3 and gradually slowed to 10·30 mm yr-1 for ages 15-20. Male and female growth rates did not differ significantly, at least through age 4. Length at age was predicted well by the equation mm TL = 1172 mm (1 - exp (- 0.12 (AGE+ 1.3))). The apparent maximum age of black drum is about 50-60 years