Design and experiment of automatic transplanting device for potted tomato seedlings

In this study, an automatic machine for transplanting potted tomato seedlings was designed, based on the analysis of physical characteristics of the main varieties of tomato seedlings. The machine is composed of a horizontal and vertical seedling supply mechanism, a picking mechanism composed with a gear-rod component, a planting part featured with an eccentric-disk parallelogram duckbilled mechanism, and a control system. The control system included position sensors, stepper motor, variable-frequency motor and program controller. The force condition for successful picking potted tomato seedlings was studied by analyzing the force and motion during the taking procedure with the use of analytical graphic method. Combined with the parameters of physical characteristics of tomato seedlings, the key parameters of the machine was determined, which included L1 = 105 mm as the distance between the point of the gripper needles and the center of rotation, L0 = 18 mm as the initial opening distance between the two gripper needles, and s = 40 mm as the distance between the two gripper needles when they were at the upper hinge point of the clamping hands. The key structure and the parameters of the seedlings-taking part were determined by theoretical calculation according to the position of the seedling during taking and dropping procedure, and the requirement of the motion. The machine was tested by using the potted tomato seedlings. The result showed that the seedling picking rate was 92.35%–86.61%, and the leakage rate was 12.57%–18.03%, when the transplanting speed was between 60 and 90 seedlings per minute. The result demonstrated that the machine was feasible to transplant the potted tomato seedlings efficiently.

Asymmetric dust distribution in an eccentric protoplanetary disk as a signpost of a gas giant planet

The presence of a cavity in a protoplanetary disk revealed by dust continuum emissions is sometimes postulated as a signpost of an embedded gas giant planet. More peculiarly, dust emissions exterior to the cavity are often observed to be asymmetric. We explore the possibility of the asymmetry as a result of the asymmetric distribution of dust in an eccentric protoplanetary disk under the secular gravitational perturbation of an embedded massive gas giant planet. We find that the surface density of the dust well coupled to the disk gas is enhanced around the apocenter of the disk. In addition, the azimuthal distributions of particles of various sizes can deviate significantly due to different coupling to the gas. Overall, the asymmetric structure exhibits a phase correlation between the gas velocity field and dust density distribution. A Doppler map for an eccentric disk is also presented based on Cycle 1 ALMA observations. Our study potentially provides a reality check as to whether an asymmetric disk gap detected at sub-mm and cm wavelengths is a signpost of a massive gas giant planet.

Potential Well Escape of an Eccentric Disk

This paper investigates the dynamic behavior of an eccentric disk rolling on a curve of arbitrary shape and then on a curve defined as a cubic function. Comparisons are made to a disk with no eccentricity and the related point mass approximation. The curve is subject to base excitation, and the system is considered from the perspective of a potential well problem where escape is possible on one side. The equations of motion are derived using a roll-without-slip constraint, and the behavior is investigated by means of simulated frequency and amplitude parameter sweeps and by considering the basins of attraction when initial conditions or forcing parameters are varied.

IR Geminorum: Complex Disk Behavior During Quiescence

We have carried out nearly continuous V-band photometry from Yunnan Observatory (China) and Behlen Observatory (Nebraska, USA) of IR Gem for over six days starting three days after a normal outburst in January 2002. Our observations show that the behavior of this SU UMa star is unexpectedly complicated, and that for IR Gem, quiescence is potentially more interesting than outbursts. We find a photometric modulation with a period of 98.5 min, exactly equal to the spectroscopically determined orbital period. We tentatively attribute this to heating of the secondary. During the first three days a modulation appeared with a period 5% longer than the orbital period. We suggest that this might be a signature of apsidal precession of an eccentric disk. During the middle of our period of observations a modulation with a period 3% shorter than the orbital period appeared. We invoke nodal precession to explain this. A slower modulation we found with a period of about 1.7 d is roughly consistent with the expected period of nodal precession. There is a puzzling 4.3 d period modulation that we suspect may be the result of beating between apsidal and nodal precession frequencies. We also find inexplicable quasi-periodic cycles on timescales drifting from ~ 0.2 to ~ 0.4 days.