China
Africa
Explore chapters and articles related to this topic
Mounting Large, Variable-Orientation Mirrors
Published in Paul Yoder, Daniel Vukobratovich, Opto-Mechanical Systems Design, 2017
Another mount design for a 20 in. (50.8 cm) diameter experimental double-arch fused silica primary mirror was described by Iraninejad et al. (1983). As shown in Figure 5.52, the mirror was to be supported by three equally spaced clamp and flexure assemblies oriented so the flexures were compliant in the radial direction, but stiff in all other directions. This allowed the aluminum mounting plate to contract differentially with respect to the mirror as the temperature was reduced to operate at about 10 K. Each mirror clamp was a T-shaped piece made of Invar 36 that engaged a conical hole machined inside the thickest portion of the mirror’s back. The twin flexures were 91 mm (3.6 in.) long × 15 mm (0.6 in.) wide parallel blades with high fundamental frequency. They were to be made of 0.04 in. (l.0 mm) thick 6A1-4V-ELI titanium. The blades would be separated by 25 mm (1.0 in.).
Fatigue of steel bridge infrastructure
Published in Hyun-Moo Koh, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Health Monitoring and Informatics, 2008
Hyun-Moo Koh, Dan M. Frangopol
Ningbo Yongjiang Bridge was designed as a cable-stayed bridge with the span arrangement of 63 m + 132 m + 468 m + 132 m + 63 m shown in Fig. 4 due to the navigational requirement, and twin parallel decks of about 2 � 24 m wide in the feasibility study (ZPHPDI 2007). Aiming at low construction cost in China and high structural damping for dynamic performance, both pylons and bridge deck were proposed to be made by reinforced and prestressed concrete. During preliminary design stage, the further comparison of pylon types and deck sections should be made based on structural performance, in particular dynamic and aerodynamic characteristics. Two types of pylons, including the twin diamond shape in Fig. 5a and the twin H shape in Fig. 5b, and three types of deck sections, including the closed box in Fig. 5a, the twin separated boxes in Fig. 6b and twin side ribs in Fig. 6c, have been numerically compared in structural dynamic characteristics, and the fundamental frequency values of six combinations are listed in Table 5 (Ge et al. 2007).
Simulator Platform Motion—The Need Revisited
Published in Florian Jentsch, Michael Curtis, Eduardo Salas, Simulation in Aviation Training, 2017
Judith Bürki-Cohen, Nancy Ν. Soja, Thomas Longridge
Ryan, Scott, and Browning (1978), on the other hand, used a more diagnostic set of maneuvers to investigate the effect of simulator motion on performance in the airplane, consisting of instrument maneuvers and take-offs and landings with and without engine failures. The asymmetric engine failures create a sudden disturbance that the pilots must recognize and correct in the shortest possible time (Hall, 1989). The participants were first-tour naval aviators that had recently completed multi-engine undergraduate training and possessed "Standard Instrument Cards." They were trained in a P-3 "Operational Flight Trainer" with a narrow-angle television for (modelboard) visual cues and a 6-DOF motion system that was disabled for the no-motion group. All 39 no-motion students and 4 of the motion students transferred to a S-2, a small twin reciprocating-engine airplane. Six motion students transferred to the T-44 twin turboprop airplane. Questionnaires revealed that students and instructors "strongly favor[ed] having motion cues available" (p. 27) but did not indicate any motion sickness associated with either condition. Performance was rated by instructors. These results show that, even with these maneuvers, the results were again the same as in the Jacobs study. That is, the presence of simulator motion improved performance in the simulator but had no bearing on performance in the airplane. A footnote is that the presence of a sudden disturbance did, indeed, increase the diagnosticity of maneuvers—the engine abort on takeoff1 was the only maneuver that demonstrated the motion advantage in the simulator.
A Novel Vertical Axis Parallel Turbines System for In-pipe Hydropower Generation: Conceptual Design and Preliminary Experiment
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Muhammad Fazrin Abdullah, Iswadi Jauhari, Mohd Faizul Mohd Sabri, Nik Nazri Nik Ghazali
In the actual water distribution system, a pressure reducer valve (PRV) is normally used to regulate water flow. The excess pressure available in the pipe might change with water demand. Higher future water demand means the PRV will be further opened making more water flowing thus lowering excess pressure (Dawadi and Ahmad 2013). This is the reason why the prototype in this work is using two turbines instead of one with a larger size. With two turbines, it makes the system more flexible with demand and more cost-effective. Another benefit of using a twin-turbine is making sure power is always available if one of them experiences a problem. This is very critical for most energy-intensive activities (Harrison 2015). It will also dependency on an expensive backup system like energy storage (Wood 2015).