Proceedings of the Third Cryocooler Conference

Mechanical and non-mechanical types of small cryocoolers in the temperature range of 4 to 80 K are discussed. Applications of these small cryocoolers include the cooling of infrared detectors, cryopumps, small superconducting devices and magnets, and electronic devices

Open-Loop Spatial Multiplexing and Diversity Communications in Ad Hoc Networks

This paper investigates the performance of open-loop multi-antenna point-to-point links in ad hoc networks with slotted ALOHA medium access control (MAC). We consider spatial multiplexing transmission with linear maximum ratio combining and zero forcing receivers, as well as orthogonal space time block coded transmission. New closed-form expressions are derived for the outage probability, throughput and transmission capacity. Our results demonstrate that both the best performing scheme and the optimum number of transmit antennas depend on different network parameters, such as the node intensity and the signal-to-interference-and-noise ratio operating value. We then compare the performance to a network consisting of single-antenna devices and an idealized fully centrally coordinated MAC. These results show that multi-antenna schemes with a simple decentralized slotted ALOHA MAC can outperform even idealized single-antenna networks in various practical scenarios.Comment: 51 pages, 19 figures, submitted to IEEE Transactions on Information Theor

Cryogenic Propellant Scavenging

A detailed description of a computer model that has been developed for assessing the feasibility of low g cryogen propellant scavenging from the space shuttle External Tank (ET) is given. Either pump-assisted or pressure-induced propellant transfer may be selected. The program will accept a wide range of input variables, including the fuel to be transferred (LOX or LH2), heat leaks, tank temperatures, and piping and equipment specifications. The model has been parametrically analyzed to determine initial design specification for the system

Defect-induced modification of low-lying excitons and valley selectivity in monolayer transition metal dichalcogenides

We study the effect of point-defect chalcogen vacancies on the optical properties of monolayer transition metal dichalcogenides using ab initio GW and Bethe-Salpeter equation calculations. We find that chalcogen vacancies introduce unoccupied in-gap states and occupied resonant defect states within the quasiparticle continuum of the valence band. These defect states give rise to a number of strongly-bound defect excitons and hybridize with excitons of the pristine system, reducing the valley-selective circular dichroism. Our results suggest a pathway to tune spin-valley polarization and other optical properties through defect engineering

Development and Experimental Investigation of Modular Crates for Industrial Packaging Applications

For the increased product varieties, engineered plywood crate production technique could not facilitate box size optimization. This paper investigates the implementation of modularity function onto the plywood crate to resize the pack cube volume on customer requirement and to reduce space wastage inside the box. This is achieved by using a new joint technique called “Flat- Post Tongue Joint”. The full-sized experimental work is carried out comprising Flexural test analysis on Flat-Post Tongue joint, Tensile test analysis on tongue joint and Box Compression Test analysis on the two developed models of modular crates namely Modifiable Reinforced Plywood Crate (MRPC) and Modifiable Plywood Crate (MPC). The test results exhibited an improved flexural strength and box compression strength in comparison to the conventional plywood crates. The findings of the research work indicates that the modular plywood crate is a performance efficient method to reduce space wastage and source material by weight and volume when accommodating variable product sizes in a product family

A Dynamic Programming Approach to Determine Optimum Modularity Level in Industrial Packaging

Modular packaging facilitate customization for accommodating variable product sizes in a product family. When determining package sizes for product variability, packaging engineers does not find difficulty to determine package dimension for less product variety whereas if the product variety is more, then determining the dimension of modular package involves complex decision-making and time-consuming process to find the optimal solution. This in turn directly impacts the overall lead time of the supply chain. Thus, in this paper a dynamic programming is developed to determine the quantity and dimension of modular packages for every demand of assorted products sizes. The program helps in finding the optimum modularity level of the modular packaging by identifying the midpoint between reduced space wastage and minimum production quantity. Four different case studies are employed in this research to illustrate how the levels of modularity has the effect on reducing the source material wastage by volume. From the results of the case studies, the percentage improved in the container space utilization is represented