Effect of pin generatrix on the elastohydrodynamic lubrication performance of pin-bush pair in industrial roller chains

For industrial roller or bush chains, the bush swings relative to the pin at working condition. If proper lubrication is maintained, an elastohydrodynamic lubrication contact is formed between the pin and the bush. In this study, a custom-made pin was used to replace the steel ball of a ball-disk test rig and optical interferometric experiments were carried out to study the effect of pin generatrix on the lubrication performance. The effects of generatrix shape, stroke length and oil supply condition on the lubrication state were explored. It is found that the change of the generatrix has an important influence on the oil film thickness, especially under rare oil supply condition.

Effect of Sediment Supply on Morphodynamics of Free Alternate Bars: Insights from Hydrograph Boundary Layer

Sediment supply plays an essential role in river morphology. However, the specific impact of sediment supply on river morphology is not apparent. According to the hydrograph boundary layer (HBL) concept, upstream riverbed changes caused by the imbalance between sediment supply and the capacity can propagate only a limited length and have a negligible effect on the riverbed beyond such a short length. We performed a two-dimensional morphodynamic calculation to test the concept of HBL, which was proposed under a one-dimensional simulation, meaning that the concept of HBL is still valid for plane changes in river morphology. We employed an unsteady flow with equilibrium or constant sediment supply in a straight, modeled gravel-bedded channel with an unerodible bank to simulate alternate bar morphodynamics. The results show that regardless of the sediment supply condition, the alternate bar features formed downstream of the HBL are considerably similar. This suggests that sediment disturbance at the upstream end has a negligible effect on the mobile-bed dynamic processes, including alternate bar formation and development downstream of the HBL.

Measurements to Quantify the Effect of a Reduced Flow Rate On the Performance of a Tilting Pad Journal Bearing (LBP) with Flooded Ends

Operation of tilting pad journal bearings (TPJBs) with a reduced flow improves system energy efficiency by reducing drag power losses, albeit the temperature rise in both the bearing pads and the lubricating oil become a concern. This paper presents measurements of the static and dynamic load performance of a flooded ends TPJB with flowrates ranging from 150% to ~5% of a nominal supply condition. The test bearing is a four-pad, 102 mm diameter, center pivot, with single orifice feeds, and configured with end seals. Experiments include operation at two shaft speeds = 6 krpm and 12 krpm and under three specific loads = 0.345 MPa, 1.03 MPa and 2.07 MPa applied in between pads (LBP). The measurements show the bearing drag power loss decreases by nearly 20% when flow rate drops to 50% of nominal. However, halving the flow produces a raise in pad subsurface temperatures, ~7 °C for operation at 12 krpm. Flow reduction below 50% results in substantial power savings; however, it also produces too hot pad temperatures that approach a known limit for Babbitt material safe operation. Damping coefficients decrease by ~30% as the flow rate decreases from 150% to just a few % of nominal flow. The experimental results are first to quantify operation of a TPJB supplied with minute amounts of lubricant flow. A test with a very low flow rate at ~2% of nominal and under a light load produced the emergence of a broadband subsynchronous vibration frequency, albeit with very small amplitude.

Effects of bearing lubrication conditions on rotor dynamic behavior

Usually, rotor dynamic analyses do not consider the effects of the lubricant supply condition, although this is an important aspect of journal bearing performance. Therefore, this work has implemented a mass-conserving model to realistically describe the oil feeding condition and evaluate its influence on rotor dynamics. This analysis was carried out by varying feeding pressure and groove position and the results indicate that the oil supply conditions significantly influence the bearing performance and affect the dynamic behavior of the entire rotor. In general, lower flow rates lead to a bearing with a greater stability region, as observed mainly in the bearing with a groove at 270° and, on the other hand, the increase in feeding pressure reduces the instability threshold.

The Path Direction Control System for Lanange Jagad Dance Robot Using the MPU6050 Gyroscope Sensor

The ability to walk straight on a dance robot is very important considering that in competitions, dance robots are required to be able to walk through several zones starting from the starting zone and ending with the closed zone. Therefore, a control system is needed in the Lanange Jagad dance robot so that the robot can control the direction of its walking motion and reduce errors in dance motion while walking on the dance robot. This control system uses a reading value based on the orientation of the rotating motion on the yaw angle axis on the MPU6050 gyroscope sensor which will later be used as a corrector for dance robots when performing various dance movements while walking in the competition arena. From the results of the overall test of the Lanange Jagad dance robot after adding the road direction control system, the percentage of the success rate in the battery power supply condition is 12 volts to 12.6 volts by 100% with the greater the battery power supply, the error in the robot's final angle average to The starting angle of the robot is getting smaller and the percentage of the success rate at the slope of the 0o to 4o race arena is 93.3%. With the tilted race arena, the error in the mean error of the robot's final angle to the starting angle of the robot is also greater, so it can be concluded that the robot can be controlled direction of walking and can walk straight to the finish in the closed zone.

Physiological and Transcriptomic Responses of Antioxidant System and Nitrogen Metabolism in Tomato Roots Treated With Nitrogen Starvation and Re-Supply

Nitrogen (N) is one of the essential macronutrients that plays important roles in plant growth and development. To better understand the response of antioxidant system and N metabolism under N starvation and re-supply condition, physiological and transcriptomic analysis were performed in tomato roots. The malondialdehyde (MDA) and reactive oxygen species (ROS) contents increased significantly in tomato seedlings after N starvation for 24 h. The activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR), the ratio of ASA/DHA and GSH/GSSG, the NO3- contents, nitrate reductase (NR) activity were decreased after N starvation treatment and increased after N re-supply for 24 h. Compared with the control, 1766 genes were up-regulated and 2244 genes were down-regulated after N starvation in tomato. These differentially expressed genes (DEGs) are mainly enriched in functional items such as cellular process, metabolic process and catalytic activity. The KEGG pathways revealed that the DEGs were mainly involved in phenpropane biosynthesis, amino sugar and nucleotide sugar metabolism, and N metabolism. The expression patterns of tomato SlSOD, SlCAT, SlAPX, SlMDHAR, thioredoxin (SlTrxh), peroxiredoxin (SlPrx) and glutaredoxin (SlGrx) genes, and nitrate transporter SlNRT2.4, SlNR, glutamine synthetase (SlGS2), nitrite reductase (SlNiR) decreased after N starvation and increased after N re-supply, which were validated by qRT-PCR. Our results provide a basis for understanding the response of tomato to N deficiency and re-supply and a theoretical reference for cultivation regulation.

STUDY ON THE OPTIMIZATION FOR THE SIZE OF FUEL CELL FLOW FIELD UNDER INADEQUATE AIR SUPPLY CONDITION

In this paper, the influence of the optimization for flow field size on the proton exchange membrane fuel cell (PEMFC) performance under the inadequate air supply of cathode was studied based on the three-dimensional, steady-state, and constant temperature PEMFC monomer model. Additionally, the effect of the optimization for hybrid factors, including length, width, depth and width-depth, on the PEMFC performance was also investigated. The results showed that the optimization of the flow field size can improve the performance of the PEMFC and ensure that it is close to the level under the normal gas supply.

Study on temperature field of entrance section at high altitude tunnel considering water supply from snowmelt

To explore the influence of snowmelt supply at the entrance section at high altitude tunnel on tunnel engineering, several indoor model tests were carried out by setting a water-supply system above the model device for simulating the actual snowmelt supply environment. The model tests were based on a project at high altitude tunnel in Qinghai. The varied characteristics of temperature field in typical cross-sections of tunnel entrances with and without water-supply condition under freeze-thaw cycles were analyzed accurately by the model. This study shows that the external water supply has a great influence on the tunnel entrance. When the surrounding rock freezes at the tunnel entrance, it first freezes from the arch, then develops to the side wall, and then spreads to the inverted arch to form a freezing circle. The faster the freezing development rate is, the greater the thickness of the freezing ring is under the water-supply condition. The development of temperature field under water-supply condition is obviously faster than that under normal condition. The distribution characteristics of freezing depth in both conditions are the arch is the largest, the side wall is the second, and the inverted arch is the smallest. This study can provide a reference for analyzing the process of freezing injury caused by high altitude snowmelt water supply into tunnel entrances in western Sichuan.

Water reuse: dairy effluent treated by a hybrid anaerobic biofilm baffled reactor and its application in lettuce irrigation

There is a synergy between the large quantities of organics-rich effluents generated by the dairy industry and the continually increasing water needs for crop irrigation. In this sense, this study aimed at evaluating the effect of decreasing the hydraulic retention time (HRT) on the stability and efficiency of a hybrid anaerobic biofilm baffled reactor (HABBR) treating simulated fat- and salt-rich dairy wastewater, followed by its agricultural reuse. The reactor was monitored over 328 days, during which 72, 24, and 12 h were the hydraulic detention times. After achieving steady-state, the reactor presented organic matter removal greater than 90% and produced biogas with 41 ± 23%, 53 ± 3%, and 64 ± 12% of methane for HRTs of 72, 24, and 12 h, respectively. The best process performance was observed for an HRT of 24 h, and thus, a lettuce culture was irrigated with the treated effluent. The irrigation was performed in five different treatments, for which the amount of treated effluent added to tap water varied from 0 to 100%. Both the effluent and the harvested vegetables were evaluated for microbial contamination. Apart from the 75% effluent supply condition, there were no losses in leaf mass or area observed; instead, there was an increase of these parameters for the 25% and 50% effluent supply treatment. The use of dairy effluent treated by the HABBR allowed for microbiologically safe food production. Therefore, the process offered both potential cost reduction for fertilizers, preservation of water resources, and a renewable energy source.