Solar driven lasers for power satellite applications

The technological feasibility of using multimagawatt lasers for space power transmission is discussed. Candidate lasers include electric discharge lasers, direct optically pumped lasers, and free electron lasers

“Antes éramos de tierra firme”: community perspectives on the past, present, and future of Isla Narganá and Isla Corazón de Jesús, Comarca Guna Yala in the face of a changing climate

The objective of this research was to learn about Isla Narganá and Isla Corazón de Jesús, Comarca Guna Yala residents’ perspectives on climate change and, to learn about what needs to be done to mitigate the effects of climate change on the islands. In April 2022, eighteen semi-structured interviews were conducted in Spanish with residents of the islands. Interviews revealed that flooding caused by sea level rise, intensification of precipitation events, extreme heat, and biodiversity loss were the most reported impacts of climate change on participants’ lives. Poor waste management opportunities were also discussed as a critical environmental issue affecting the communities. In response to said environmental issues, community members reported negative feelings. Participants also reported that there is a lack of discussion related to climate change among the community. In terms of climate mitigation, participants discussed planned relocation to the mainland territory of Guna Yala. Participants also expressed the importance of educating the community, especially children, about climate change and related issues. This paper serves to share the stories, experiences, and ideas of community members on the islands. In the greater academic context of climate research, this paper aims to bring these perspectives into the academic discussion and deepen the understanding of what it means to be a frontline community

Solid Freeform Fabrication of Functional Silicon Nitride Ceramics by Laminated Object Manufacturing 1

The processing of silicon nitride (Si3N4) structural ceramics by Laminated Object Manufacturing (LOM) using ceramic tape preforms was investigated. The key processing stages involved green shape formation (which used the LOM process), followed by the burnout of all organics, and final densification by pressureless sintering. Two material systems were considered. These were a) monolithic Si3N4 and b) a preceramic polymer infiltrated Si3N4. The raw materials for the process were tape preforms of Si3N4, which were fabricated by standard tape casting techniques. Mechanical property data obtained for the LOM processed Si3N4 showed high strength and fracture toughness values. The room temperature and high temperature (1260 o C) flexural strengths were in the range of 700-900 MPa and 360-400 MPa, respectively. The fracture toughness averaged from 5.5-7.5 MPa.m1/2. These strength and fracture toughness values are comparable to those reported for conventionally prepared Si3N4 ceramics. Thus, this research demonstrated that the LOM technique is a viable method for preparing functional Si3N4 ceramics with good physical and mechanical properties.Mechanical Engineerin

South Dakota Grasslands, Their Condition and Management

Statewide surveys of South Dakota grasslands have been made in 1940, 1942, and 1946. The stocking rates presented on the map (center pages) were determined from the 1946 survey, based upon the past ten years\u27 actual use-grazing records from representative farms and ranches. The range and pasture condition method of study was introduced into the 1946 resurvey of South Dakota grassland. The condition approach is much more usable by stockmen and agricultural workers alike than former methods of making grassland inventories. The 1946 inventory of range and pasture condition shows South Dakota grasslands are near the peak of productivity. Above-average rainfall is largely responsible for this condition. When the precipitation cycle becomes less favorable and dry years come and they surely will-then only good management of our grasslands can maintain their productivity and prevent the unfavorable conditions of the mid-thirties. Further studies and follow-up surveys will be made periodically to keep abreast of changes in condition and stocking rates for South Dakota grassland

Dimensional Accuracy in X-Ray Computed Tomography Imaging

X-ray computed tomography (CT) has become an important non-destructive evaluation technique. CT contributes to a wide range of nondestructive evaluation (NDE) applications [1]. These include typical NDE applications (e.g., defect detection and quality control), more advanced NDE applications (e.g., process development and model verification), and the more recent application of CT-based metrology (e.g., geometric inspection and reverse engineering). In the traditional applications of CT, the user is concerned with defect sensitivity, which is a combination of spatial resolution, contrast sensitivity and slice thickness [2]. For CT-based metrology, the term “defect sensitivity” has little meaning; dimensional accuracy of the system becomes paramount

Interseeding Plans for SDSU\u27s New Machine . . . For Better Pasture Production

This bulletin deals with the merits of interseeding, its practice in South Dakota, and the development and use of interseeders by South Dakota State University