The effect of clutch control parameters on the performance of tractor hydraulic systems was investigated in this study to improve the launch quality of the power shuttle tractor under launch conditions. A power shuttle tractor model for launch control was designed as an integrated mechanical, hydraulic, and electric system; a mathematical model was designed for each subsystem, and nonlinear elements were modeled based on the test data. The designed model was validated by comparing the results of the tractor field test with the simulation results. Launch quality was evaluated based on response time and mean jerk. The larger the clutch pressure gradient in the torque phase, the larger is the mean jerk of the tractor. Further, an appropriate fill pulse pressure is desired because excessive fill pulse pressure can cause overfilling and adversely affect launch quality. A smooth launch is required to improve launch quality; however, if the clutch pressure is small, the launch completion time becomes longer, which deteriorates the launch response, and necessitates a compromise.
Trench-structured In-Ga-Zn-O vertical thin-film transistors (T-VTFT) was fabricated with a channel length of 400 nm. T-VTFTs showed channel width-dependent field-effect mobility owing to the back-channel scattering, and the mobility of 24.1 cm2 $/$ Vs was finally obtained with a channel width of $1 ~\mu \text{m}$ . Alternatively, the asymmetric operations of conventional mesa-shaped VTFTs were improved in a symmetrical way owing to the structural benefits of the T-VTFT, leading to excellent immunity against the drain-induced barrier lowering.
HfO 2 (HfO x N y ) thin films for use in gate dielectric were deposited at 300 °C on p-type Si (100) substrates using Hf[OC(CH 3 ) 3 ] 4 as the precursor by plasma enhanced chemical vapor deposition. Compared with HfO 2 , HfO x N y show excellent electrical properties including low leakage current density and good thermal stability. Leakage current density of HfO x N y is approximately one order of magnitude lower than that of HfO 2 for the same EOT.
Highlights This study created a simulation model to predict the ride vibration of a tractor and to optimize its suspension. The parameters of the tractor were obtained from various tests to create a fully validated model. The acceleration measured in a tractor cabin was compared with the simulation model in the time and frequency domains. The ride vibration of a tractor was evaluated under various road conditions with a fully validated model. Abstract . A typical problem with tractors and other agricultural machinery is the excessive ride vibration, which results in an inconvenient working environment and poses a risk to the health of operators. In this study, a simulation model for predicting the ride vibration of a tractor and optimizing the cabin suspension was developed to address this limitation. First, the required parameters used computation tests to create the simulation model. Mode and frequency-response function analyses were then performed to validate the model for ride vibration, from which the natural frequency and mode shape were analyzed. Subsequently, the riding characteristics of an actual tractor on a stepped road surface were simulated using a four-post road simulator, and the acceleration measured in the cab was compared with that of the simulation model in the time and frequency domains. Finally, the parameters of the cabin suspension were optimized using the validated simulation model, and the correlation between the cabin suspension parameters and ride vibration was examined. Following optimization, the vibration value of the tractor cab was found to decrease as the damping coefficient of the cabin suspension decreased for all surface conditions selected in the simulation. Thus, the developed tractor simulation model can be used as a ride vibration simulation when developing the control logic of a tractor’s cabin suspension, as well as a plant model of hardware-in-the-loop simulation to verify the control logic. Keywords: Hydro-pneumatic suspension, Optimization, Ride vibration, Simulation model, Tractor cab, Validation.
ABSTRACT For the realization of reliable nonvolatile phase-change memory operations, it is very important to understand the long-term behaviors of memory states with different resistance values. We investigated the time-dependent behaviors of RESET resistance states (RR) for the fabricated memory devices using Sn-doped GST, in which Sn amounts were varied to control the initial values of RR. It was found that the transient variations of RR showed an increasing trend with time, and that their behaviors were closely related to the microstructure of amorphous phase in the phase-change material.
Composition-modified bilayer channel configuration was introduced for enhancing the device performance of In-Ga-Zn-O (IGZO) thin film transistors (TFTs), which was composed of 3-nmthick In-rich prompt-IGZO and 12-nm-thick prime-IGZO layers for the formation of twodimensional electron gas (2DEG) at interfaces. The cationic compositions of bilayer IGZO channels were designed by modulating the sub-cyclic ratios among the precursors during atomic-layer deposition process. To properly control the effect of modified compositions in bilayer channels, the oxidant for the formation of Al2O3 protection and gate insulator layers were chosen as ozone. The IGZO TFTs fabricated with bilayer channel configurations exhibited the carrier mobility of 45.5 cm2/Vs and the subthreshold swing of 0.24 V/dec, keeping the turnon position at near 0 V of gate bias without performing additional heat treatments including post-annealing process at higher temperatures. From the investigations on the temperaturedependent variations in electrical conductivity and band alignments of bi-layered IGZO channels, composition controls of prime and prompt IGZO layers were found to be crucial for initiating the quantum confinement effect of 2DEG. Thus, the optimum compositions (In:Ga:Zn) of both layers were 1.4:1.0:2.0 and 5.0:1.0:3.4, respectively. The device using optimum bilayer channel composition exhibited excellent positive bias stress (PBS) stability due to the implementation of confinement barrier at interface between the prime and prompt layers, in which the threshold voltage shifts (∆VTH) were estimated to be as low as 1.34 V. Furthermore, it was found that the PBS instability was anomalously compensated even at higher temperature stresses owing to long-term hydrogen diffusion from the ozone-processed gate stacks. The ∆VTH was finally stabilized to 0.22 V at 80oC with a lapse of stress time for 104s.
Silver-rich GeTe solid electrolytes for use in programmable metallization cell (PMC) memory devices were prepared by the in situ diffusion of silver into the GeTe films during the deposition of silver by rf sputtering on GeTe chalcogenide glass films. The concentration of silver in the silver-rich GeTe films was controlled by adjusting the concentration of Te in the GeTe films. A PMC memory device with a Ag(300nm)∕Agx(Ge45Te55)1−x(200nm)∕TiW(100nm) structure and a device diameter of 0.5μm showed reproducible memory characteristics based on resistive switching at low voltage with high Roff∕Ron ratios. The PMC memory device exhibited good switching characteristics up to 100cycles at an amplitude of ±2V and a pulse width of 1μs.
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