Simulation of Single Gimbal Control Moment Gyroscopes (SGCMG) Cluster for Microsatellite Maritime Surveillance Mission

The potential for agile missions for small satellites exists through development of single gimbal control moment gyroscopes (SGCMG). An SGCMG cluster comes with additional complexity and volume requirements, but efforts in their development have reduced their overall size while providing higher torque over similarly sized reaction wheels. In this paper, we present a feasibility study of a small satellite using a small volume pyramid SGCMG cluster for coastline monitoring through Simulink. Two realistic torque profiles for sweeping capture of complex coastlines within one minute were generated using STK, requiring maximum torques of 0.190 and 0.218 Nm and rapid slew rate. The torques are beyond the capabilities of a similarly sized reaction wheel, which can only output maximum torques of 0.020 Nm. The torque profiles were replicated using simulated SGCMG cluster using modelled SGCMG scaled for small satellites. Results show that the SGCMG pyramid cluster meets the required torque profiles with less than 0.3 degrees of pointing error throughout the maneuver. A novel SGCMG hardware is currently under development and preliminary analysis indicates sufficient torque for agile missions such as coastal monitoring presented in this paper. The viability of SGCMG cluster provide promising alternative for ACS design of small satellites where agility have been limited by existing attitude actuators

Preliminary Study on the Fabrication of Particulate Fuel through Pressureless Sintering Process

U-10wt%Zr spherical particles for use as particulate fuel were prepared by centrifugal atomization and subjected to pressureless sintering, which is one of the simplest powder processing techniques. At sintering temperature of 1100°C for 30 or 60 min, all samples ranging from +50 to −325 mesh showed no apparent bonding between the particles. However, at 1150°C (80 min), all samples formed a bulk body and the microstructures showed apparent sintering stages. Particularly, sample B (50–70 mesh) and sample C (70–100 mesh) showed pore characteristics suitable for a particulate fuel. The results suggest that pressureless sinterability for U-10Zr particulate fuel can be improved by adding small-size (–325 mesh) particles

Role of G{alpha}12 and G{alpha}13 as Novel Switches for the Activity of Nrf2, a Key Antioxidative Transcription Factor

G{alpha}12 and G{alpha}13 function as molecular regulators responding to extracellular stimuli. NF-E2-related factor 2 (Nrf2) is involved in a protective adaptive response to oxidative stress. This study investigated the regulation of Nrf2 by G{alpha}12 and G{alpha}13. A deficiency of G{alpha}12, but not of G{alpha}13, enhanced Nrf2 activity and target gene transactivation in embryo fibroblasts. In mice, G{alpha}12 knockout activated Nrf2 and thereby facilitated heme catabolism to bilirubin and its glucuronosyl conjugations. An oligonucleotide microarray demonstrated the transactivation of Nrf2 target genes by G{alpha}12 gene knockout. G{alpha}12 deficiency reduced Jun N-terminal protein kinase (JNK)-dependent Nrf2 ubiquitination required for proteasomal degradation, and so did G{alpha}13 deficiency. The absence of G{alpha}12, but not of G{alpha}13, increased protein kinase C {delta} (PKC {delta}) activation and the PKC {delta}-mediated serine phosphorylation of Nrf2. G{alpha}13 gene knockout or knockdown abrogated the Nrf2 phosphorylation induced by G{alpha}12 deficiency, suggesting that relief from G{alpha}12 repression leads to the G{alpha}13-mediated activation of Nrf2. Constitutive activation of G{alpha}13 promoted Nrf2 activity and target gene induction via Rho-mediated PKC {delta} activation, corroborating positive regulation by G{alpha}13. In summary, G{alpha}12 and G{alpha}13 transmit a JNK-dependent signal for Nrf2 ubiquitination, whereas G{alpha}13 regulates Rho-PKC {delta}-mediated Nrf2 phosphorylation, which is negatively balanced by G{alpha}12

(7-Dimethylamino-1-hydroxy-3-naphthyl)(morpholino)methanone

In the title compound, C17H20N2O3, the morpholine ring is in a slightly distorted chair form. The crystal structure is stabilized by an inter­molecular O—H⋯O hydrogen bond between the H atom of the hydroxyl group and the O atom of a neighbouring carbonyl group. A weak inter­molecular C—H⋯π inter­action is also present

An efficient downlink beamforming scheme for FDD/SDMA systems

Without channel information of the downlink, the base station can generate downlink beam pattern using the weight vector used for the uplink. In the frequency division duplex system, however, it may result in significant performance degradation due to the carrier frequency offset between the uplink and downlink. To resolve this problem, we propose an efficient downlink beamforming algorithm based on a least square method with constraints. We also consider the control of null depth to obtain a desired signal to interference power ratio. Simulation results show that the proposed scheme can sufficiently reduce the interference from other users, improving the BER performance in the downlink

Determination of Cutting Date and Interval on Native Grass Management of Agricultural Waterways in South Korea

Agricultural waterways provide a buffer zone between crop fields and adjacent rivers or streams. Waterways are important resource for agriculture water management, water quality and biodiversity conservation. The total linear distance of waterway in Korea is about 180,000 km, and about 40% are concrete and about 60% are grassed waterways. At present, the percentage of concrete waterways is increasing because of their water management efficiency. Some argue that continued expansion of concrete waterways is not sustainable because it leads to potential-degradation of the earth\u27s environment. This concern has led to renewed efforts to use grassed waterways as an alternative to concrete. In addition, grassed waterways enhance the environment-friendly image of agriculture that Korea farmers want to promote. The objective of this experiment was to determine the effect of cutting date and interval of native grasses for water management efficiency of agricultural waterway

Enhanced black state induced by spatial silver nanoparticles in an electrochromic device

The use of three-dimensional (3D) hierarchical indium tin oxide (ITO) branches of electrochromic devices (ECDs) is an effective approach for increasing the optical properties via localized surface plasmon resonance compared with two- dimensional nanostructured electrodes. ECDs with 3D branches were designed to operate in transparent, mirror and black states. Finite- difference time- domain simulation was used to find the electrical field distributions in three types of ECD: glass/ITO with Ag film, glass/ITO branches and glass/ITO branches with Ag nanoparticles. The ECDs had an optical transmittance of 73.76% in the transparent state, a reflectance of 79.77% in the mirror state and a reflectance of 8.78% in the black state. We achieved an ECD with high stability that can show similar to 10 000 switching cycles among the three states.113Ysciescopu