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Equations of motion
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
Equation 2.33 is for the beginning of takeoff when the aircraft is stopped and ready for takeoff. At this time, the aircraft is at rest; thus, the lift is zero. Equation 2.34 governs the aircraft’s motion after the aircraft begins to move until the lift is sufficient for liftoff. At this time period, the pilot deflects the elevator and suddenly increases the angle of attack through a rotation about the main gear. At a specific time of takeoff, the lift (plus a vertical component of engine thrust) becomes equal to weight (Equation 2.35); therefore, the aircraft is ready for liftoff. Since the aircraft has acceleration, it continues to speed up and the lift force (plus a vertical component of engine thrust) exceeds the weight of aircraft (Equation 2.36). At this time, first the nose landing gear and then the main gear leave the ground and the aircraft gets airborne. These four equations only govern part of the motion. More details are provided in Chapter 8.
Area-selective atomic layer deposition of Al2O3 using inkjet-printed inhibition patterns and lift-off process
Published in Journal of Information Display, 2023
Jun Ho Yu, Young–In Cho, Jae–Wook Lee, Kyung Hyun Choi, Sang–Ho Lee
To date, there has been no demonstration of AS-ALD using Al2O3 grown by TMA and H2O using inkjet-printed blocking layers on the Si surface. In this study, the inkjet printing process was utilized to form ALD-inhibition patterns with two-layered structures for the AS-ALD process. The ALD-inhibition pattern printing process was developed by using two techniques: overprinting for thickness control and multilayer printing, which are unique advantages of inkjet printing. Al2O3 was chosen as a model metal oxide for selective ALD due to its enormous potential in various fields. FC thin films were inkjet-printed to inhibit Al2O3 nucleation and growth during the ALD process. A thicker photoresist (PR) was inkjet-printed to allow easy removal of ALD-inhibition patterns using a lift-off process. FC, PR, and FC-covered PR (FC/PR) patterns were prepared as ALD-blocking test patterns on Si substrate by inkjet printing. To demonstrate AS-ALD, Al2O3 thin film was deposited via an in-house built system with a multiple-slit gas source. The Al2O3 ALD-inhibition performance of the prepared patterns was evaluated for topological analysis using atomic force microscopy (AFM), surface composition analysis using time of flight secondary ion mass spectrometry (TOF-SIMS) after the lift-off process by O2 plasma, and ultrasonic agitation.
Theoretical and Experimental Study of Transient Behavior of Spiral-Groove Thrust Bearings during Start-Up
Published in Tribology Transactions, 2020
Figure 10b demonstrates the evolution of the minimum oil film thickness and friction torque during the start-up process. Initially, the minimum oil film thickness increased gradually in the mixed lubrication regime. After the lift-off speed was reached, the minimum oil film thickness increased rapidly with rotation speed in the hydrodynamic lubrication regime. The variations in friction torque were similar to those observed in the start-up test as shown in Fig. 9. It should be pointed out that the first period of the start-up process was not involved in the simulation.
Applying augmented feedback in basketball training facilitates improvements in jumping performance
Published in European Journal of Sport Science, 2023
Christian Leukel, Albert Gollhofer
Subjects started with a warm-up (light jogging) of 5–10 minutes. Thereafter, in the pre-test, the experimenter performed a countermovement-jump and a drop-jump to inform the subjects about how the jumps had to be executed. All subjects viewed the same experimenter. Ground reaction forces (AccuGait®, AMTI, Watertown, USA, sampling rate of 1 kHz) were recorded for 10 consecutive countermovement-jumps and 10 consecutive drop-jumps (falling height of 30 cm from a wooden platform) with and without augmented feedback about the jumping height, respectively. Thus, 40 trials were recorded in total in the pre- and post-test. In trials with augmented feedback, subjects received information about the jumping height immediately after completing each jump. Therefore, flight times were analyzed using a computer algorithm (programmed with LabView®, National Instruments®, Austin, Texas) based on ground reaction forces (threshold of 5 N for lift-off and touch-down), and jumping height was calculated by a second LabView-based algorithm accordingly to the formula: 1/8 × g × t2 (g refers the acceleration of gravity and t refers to the duration of the flight phase). The result was displayed on a computer screen in front of the subjects. Display time was 8 seconds. The subjects executed the different types of jumps in a random order, i.e. countermovement-jumps or drop-jumps, with or without augmented feedback. Before recording blocks of 10 countermovement-jumps/drop-jumps, subjects practiced 5 corresponding submaximal warm-up jumps (5 countermovement-jumps/drop-jumps). Subjects were asked to jump as high as possible, and perform short contact times while drop-jumping, but no further advice was provided with regards to knee, ankle and hip angles. The subjects’ hands were placed at the right and left ilium. Subjects wore the same (basketball)shoes in the pre- and post-tests, and the 9 training sessions. Participants had to rest for 10 s between successive jumps and 4 min after 10 jumps were recorded. Figure 1 depicts the experimental design.