Active damping in a flexible manipulator

Viewgraphs on active damping in a flexible manipulator are presented. Topics covered include: Shuttle Remote Manipulator System (SRMS); flexible structures; vibration; modeling of a flexible manipulator dynamical structure; designing control law criterion that minimizes vibration; and candidate application of fuzzy logic control law to the problem

Paper Session I-A - Technology Transfer in the Space Sector: Implementation and Issues

Technology transfer is the process of bringing technology from one sector to another in order to satisfy certain demands. Traditionally, technology is developed to address one specific problem. However, it can also be modified and reused for another problem. This paper examines the transferring process of technology: its implementation procedure, the benefit vs. costs, and the technological/managerial obstacles. Examples in the space sector were given in the analysis of technology transfer process

Paper Session I-A - A Historical Perspective of Robotics Development in the Space Station Program

The research field in robotics has grown tremendously in the 80ís because of the technology push from automobile industry and from the space station program. While the automobile industry pushed for implementation of robots to perform repetitive tasks in the assembly line, the space station program pushed for development of either large-scale and light weight tele-operative robots, or intelligent robots for extravehicular activities and exploration of distant planets. Recently, more knowledge of assembly in space became available that it seemed inevitable for a need of intelligent robots in the assembly sequence as well as in operation of the space station. This paper presents a review of the original goal for a space-oriented robotics research program, the historical aspect of robotics development in the space program, and the resulting current robotics technology

The debates and the long-awaited reform

Trung Tran, Phuong-Thao T. Trinh, Thu-Trang Vuong, Hiep-Hung Pham (2019). Chapter 1. The debates and the long-awaited reform. In Quan-Hoang Vuong, Trung Tran (Eds.), The Vietnamese Social Sciences at a Fork in the Road (pp. 17–32). Warsaw, Poland: De Gruyter / Sciendo. DOI:10.2478/9783110686081-006 Online ISBN: 9783110686081 © 2019 De Gruyter / Sciend

UPGRADING OF BIOMASS-DERIVED MOLECULES FOR FUELS VIA HYDRODEOXYGENATION ON SUPPORTED METALS

Biomass-derived molecules such as aldehydes and alcohols have been upgraded to more valuable products via hydrogenation and hydrodeoxygenation on supported metals. For unsaturated aldehydes, the competitive hydrogenation of C=C and C=O may result in an unsaturated alcohol, a saturated aldehyde, or a saturated alcohol. Hydrogenation of 2-methyl-2-pentenal has been studied for supported Pt, Pd and Cu catalysts. The activity follows the order Pt>Pd>Cu. While Pt and Pd primarily catalyzed hydrogenation of the C=C bond to 2-methyl-pentanal, Cu catalyzed hydrogenation of both C=C and C=O but more selective for C=O at low space times, and at high space times forming 2-methyl-pentanol which has good fuel property, compared to ethanol or n-butanol.For coupling reaction to higher carbon chain length, di-methyl-pentyl ethers have been selectively produced from etherification of aldehydes and alcohols on supported Pd catalysts. A yield of 79 % ether with a selectivity of 90% was observed when feeding 2-methyl-pentanal with 2-methyl-pentanol at a molar ratio 1:1 at 125oC. The side product is n-pentane from decarbonylation of the aldehyde. Cross etherification of n-butanol with 2-methyl-pentanal shows a much higher rate than that observed when the alcohol or aldehyde is fed alone. This enhanced activity is consistent with the catalyst requirement for large ensembles that allow surface alkoxide species next to an eta-2 adsorbed aldehyde. The ether yield increases with increased metal loadings and increased reduction temperatures, suggesting etherification is sensitive to metal particle sizes.Bimetallic Pd-Cu catalysts have been studied for the hydrogenation and deoxygenation of 2-methyl-pentanal. Compared to Pd catalysts, Pd-Cu shows a decrease in conversion of 2-methyl-pentanal. At low space time, 5% Pd-2.5% Cu/SiO2 exhibits high selectivity for hydrogenation to 2-methyl-pentanol and substantially reduces decarbonylation activity compared with pure 5% Pd/SiO2. The bimetallic shows that selectivity for etherification is much greater than Pd alone, since the parallel decarbonylation is reduced. The bimetallic maintains good ether selectivity due to its ability to readily hydrogenate the aldehyde to the intermediate alcohol and continue to form the required surface alkoxide in proximity to the remaining eta-2 sites

Secrecy performance of TAS/SC-based multi-hop harvest-to-transmit cognitive WSNs under joint constraint of interference and hardware imperfection

In this paper, we evaluate the secrecy performance of multi-hop cognitive wireless sensor networks (WSNs). In the secondary network, a source transmits its data to a destination via the multi-hop relaying model using the transmit antenna selection (TAS)/selection combining (SC) technique at each hop, in the presence of an eavesdropper who wants to receive the data illegally. The secondary transmitters, including the source and intermediate relays, have to harvest energy from radio-frequency signals of a power beacon for transmitting the source data. Moreover, their transmit power must be adjusted to satisfy the quality of service (QoS) of the primary network. Under the joint impact of hardware imperfection and interference constraint, expressions for the transmit power for the secondary transmitters are derived. We also derive exact and asymptotic expressions of secrecy outage probability (SOP) and probability of non-zero secrecy capacity (PNSC) for the proposed protocol over Rayleigh fading channel. The derivations are then verified by Monte Carlo simulations.Web of Science195art. no. 116

Effects of foundation mass on dynamic responses of beams subjected to moving oscillators

This paper aims at the effects of foundation mass on the dynamic responses of beams subjected to moving oscillators. To achieve this aim, experiments were performed for a beam resting on the foundation considering effects of the foundation model including linear elastic spring, shear layer, viscous damping. In addition, special effects of mass density of foundation during vibration were established to obtain the characteristic parameter of the influence of foundation mass based on natural circular frequency of the structure system determined from FFT plots of the time history of acceleration data. Furthermore, the experimental parameters were used to analyze the influence of the foundation mass on the dynamic response of the beam subjected to moving oscillator. Comparisons between experimental and simulated results showed that the foundation mass showed significant effects on the dynamic characteristic response of the beam system. It increased the general vibrating mass of the structure system. Hence, it decreased of the natural frequency of the structural system and caused a significant increase on the dynamic response of the beam when compared with the case without considering the foundation mass. Finally, the relationships between the foundation properties and the parameters of foundation mass were derived and discussed

Experimental Evaluation of Geopolymer Concrete Strength Using Sea Sand and Sea Water in Mixture

This paper presents the experimental strength evaluation of geopolymer concrete and ordinary concrete using sea sand and seawater in the mixture. A series of 30 cubic samples with a 150 mm side length and 12 rectangular specimens with a dimension of 100 × 100 × 400 mm (width × thickness × length) were cast and tested in this study. Specimens were divided equally into two groups. The first group of specimens was cast using geopolymer as the main binder (GPC), while the second group of samples was made using ordinary Portland Cement (OPC). While the compression tests were performed for specimens in two groups at the ages of 3, 7, 28, 60, and 120 days, the tensile tests were only performed for specimens at 7 and 28 days. The testing results revealed that the compression strength of GPC specimens using sea sand and seawater was significantly higher than that of OPC samples using the same type of salted sand and water. Besides, the use of sea sand and seawater for replacing river sand and fresh water in the production of GPC is feasible in terms of compressive strength since GPC produces a higher compressive strength than that of conventional concrete. Doi: 10.28991/CEJ-2022-08-08-03 Full Text: PD

The influence of foundation mass on dynamic response of track-vehicle interaction

The influence of foundation mass on the dynamic response of track-vehicle interaction is studied in this paper. The moving vehicle is modeled as a two-axle mass-spring-damper four-degrees-of-freedom system. A new dynamic foundation model, called "Dynamic foundation model" including linear elastic spring, shear layer, viscous damping and foundation mass parameter, is used to analyze the dynamic response of the track-vehicle interaction. The railway track on the new dynamic foundation model subjected to a moving vehicle is regarded as an integrated system. By means of the finite element method and dynamic balance principle, the governing equation of motion for railway track-vehicle-foundation interaction is derived and solved by the step-by-step integration method. The accuracy of the algorithm is verified by comparing the numerical results with the other numerical results in the literature. The influence of foundation mass parameter on the dynamic response of railway track-vehicle interaction is investigated. The numerical results show that with the new dynamic foundation model the foundation mass effects more significantly on the dynamic response of track-vehicle interaction. The study shows that the new dynamic foundation model describes the true behavior of soil in the analysis of dynamic response of structures on the foundation