Run Length Increases Research Articles

Optimizing air distribution in floor and wall burners of an industrial steam cracking firebox: a CFD study

A 3D computational fluid dynamics model for an industrial scale steam cracking firebox is combined with a 1D reactor model for the cracking process within the reactor coil. This framework is validated using industrial tunable diode laser absorption spectroscopy (TDLAS) measurements in a naphtha steam cracking furnace. Industrial O2, H2O, CO and temperature data show good agreement with simulation results at different locations within the firebox. The influence of varying the primary-to-secondary air flow distribution to the floor and wall burners separately is investigated using the validated framework. Altering the primary-to-secondary air flow distribution of the floor burners from 75/25 to 25/75 results in a 66% increase in furnace run length and a 35% decrease in NOx formation. This shift in air ratio ensures a lower rollover height of the flame and a large recirculation zone of the flue gas, spreading the radiative heat flux on the reactor coil more evenly. Altering the primary-to-secondary air flow distribution of the sidewall burners from 50/50 to 100/0 results in a 13% increase in run length and a 30% decrease in NOx formation. More primary air towards the sidewall burners is found to lead to more evenly spread out flames along the wall, resulting in flame interactions between the different burners and a combined flow towards the center of the firebox. These interactions result in a more uniform tube metal temperature profile along the different passes of the coil.

Reconstitution of an active human CENP-E motor.

CENP-E is a large kinesin motor protein which plays pivotal roles in mitosis by facilitating chromosome capture and alignment, and promoting microtubule flux in the spindle. So far, it has not been possible to obtain active human CENP-E to study its molecular properties. Xenopus CENP-E motor has been characterized in vitro and is used as a model motor; however, its protein sequence differs significantly from human CENP-E. Here, we characterize human CENP-E motility in vitro. Full-length CENP-E exhibits an increase in run length and longer residency times on microtubules when compared to CENP-E motor truncations, indicating that the C-terminal microtubule-binding site enhances the processivity when the full-length motor is active. In contrast with constitutively active human CENP-E truncations, full-length human CENP-E has a reduced microtubule landing rate in vitro, suggesting that the non-motor coiled-coil regions self-regulate motor activity. Together, we demonstrate that human CENP-E is a processive motor, providing a useful tool to study the mechanistic basis for how human CENP-E drives chromosome congression and spindle organization during human cell division.

Theory for the Casimir effect and the partitioning of active matter.

Active Brownian particles (ABPs) distribute non-homogeneously near surfaces, and understanding how this depends on system properties-size, shape, activity level, etc.-is essential for predicting and exploiting the behavior of active matter systems. Active particles accumulate at no-flux surfaces owing to their persistent swimming, which depends on their intrinsic swim speed and reorientation time, and are subject to confinement effects when their run or persistence length is comparable to the characteristic size of the confining geometry. It has been observed in simulations that two parallel plates experience a "Casimir effect" and attract each other when placed in a dilute bath of ABPs. In this work, we provide a theoretical model based on the Smoluchowski equation and a macroscopic mechanical momentum balance to analytically predict this attractive force. We extend this method to describe the concentration partitioning of active particles between a confining channel and a reservoir, showing that the ratio of the concentration in the channel to that in the bulk increases as either run length increases or channel height decreases. The theoretical results agree well with Brownian dynamics simulations and finite element calculations.

Technology of Pesticides and Fertilizers Application with Unmanned Aerial Vehicles in Digital Agriculture

Digital agriculture predetermines the development of robotic agricultural technologies for the application of pesticides and fertilizers using unmanned aerial systems, which are based on unmanned aerial vehicles (UAVs) with a certain working load for monitoring agricultural land and applying agrochemicals. ( Research purpose ) To develop a technology for variable-rate application of pesticides and fertilizers using unmanned aerial vehicles in digital agriculture. ( Materials and methods ) In the process of study, the authors used the methodological recommendations on the application of chemicals in the precision farming system (offered by VIM), as well as the normative and technical documentation for unmanned aircraft systems. ( Results and discussion ) It was shown that the developed technology includes the sequential execution of information and technological operations in off-line and on-line modes. It was found that the application rate of the liquid pesticides of 10-20 liters per hectare reduces losses due to drift from the treatment area and ensures the highest productivity of pesticide application using unmanned aerial vehicles. It was determined that the field processing performance increases as the run length increases, and decreases with the increasing flow rate of the liquid chemical. The rational run length was established to equal 0.8-3.2 kilometers. The authors established requirements for the spraying quality of unmanned aerial vehicles. It was proved that to increase the productivity of unmanned aerial vehicles during plant top-dressing, it is necessary to use unmanned aerial vehicles with a larger working load of 300-400 kilograms. ( Conclusions ) The authors have developed a technology for variable-rate application of pesticides and fertilizers using unmanned aerial vehicles, algorithms for preparing them for flight, monitoring agricultural lands, making a field orthophotomap, electronic maps of vegetation indices, the phytosanitary status of crops, and variable-rate application of pesticides and fertilizers.

Vibration analysis of new drill string system with hydro-oscillator in horizontal well

With the growth of oil and gas resource demand, the hydro-oscillator is widely used to enhance the Rate of penetration (ROP) and improve the efficacy in drilling various wells. The vibration model is the key issue of dynamics analysis and optimization of downhole tools. For the vibration analysis of the new drill string system with hydro-oscillator in the horizontal well, based on the design of the new hydro- oscillator and its operation conditions, the kinematics expressions are presented. Combined with the vibration force calculation results of the hydro-oscillator, the dynamics model of the new drill string system is established. Furthermore, the important features of vibration frequency, displacement, velocity and acceleration are discussed in the numerical example calculation results. By comparing the results of the calculation and experiment test, we can verify the correctness of the analysis model. With the hydro-oscillator vibration effect, the static friction between the drill string and wellbore is changed to the dynamic friction, so it can result in a significant increase in run length. At the same time, the ROP can be enhanced with the vibration effect. Moreover, with the parameters’ adjustment according to the operation conditions, the analysis method and model can also provide references to the study of similar downhole tools dynamics or mechanical properties.

Age-related differences in dynamic balance control during stair descent and effect of varying step geometry

The incidence of stairway falls and related injuries remains persistently high; however, the risk of stair injuries could be reduced through improved stairway design. The current study investigated dynamic balance control during stair descent and the effects of varying the step geometry. Data were collected from 20 healthy young and 20 older adults as they descended three staircases (riser heights of 7, 7.5 and 8 inches (178, 190 and 203 mm, respectively)). At each riser height, the tread run length was varied between 8 and 14 inches (203 mm and 356 mm) in one-inch (25 mm) increments. Kinematic data provided measures of segmental and whole-body dynamic control. Results demonstrated that older adults had greater lateral tilt of the upper body than young adults, but actually had larger margins of stability than the young in the antero-posterior direction as a result of their slower cadence. Nonetheless, for both age groups, the longer run lengths were found to provide the largest margins of stability. In addition, increase in run length and decrease in riser height tended to reduce forward upper body tilt. These results help to explain the underlying biomechanical factors associated with increased risk of falls and the relationship with step geometry. Considering the importance of stair ambulation in maintaining independence and activity in the community, this study highlights the definite need for safer stair design standards to minimize the risk of falls and increase stair safety across the lifespan.

Opposing microtubule motors control motility, morphology and cargo segregation during ER-to-Golgi transport

ABSTRACTWe recently demonstrated that dynein and kinesin motors drive multiple aspects of endosomal function in mammalian cells. These functions include driving motility, maintaining morphology (notably through providing longitudinal tension to support vesicle fission), and driving cargo sorting. Microtubule motors drive bidirectional motility during traffic between the endoplasmic reticulum (ER) and Golgi. Here, we have examined the role of microtubule motors in transport carrier motility, morphology, and domain organization during ER-to-Golgi transport. We show that, consistent with our findings for endosomal dynamics, microtubule motor function during ER-to-Golgi transport of secretory cargo is required for motility, morphology, and cargo sorting within vesicular tubular carriers en route to the Golgi. Our data are consistent with previous findings that defined roles for dynein-1, kinesin-1 (KIF5B) and kinesin-2 in this trafficking step. Our high resolution tracking data identify some intriguing aspects. Depletion of kinesin-1 reduces the number of motile structures seen, which is in line with other findings relating to the role of kinesin-1 in ER export. However, those transport carriers that were produced had a much greater run length suggesting that this motor can act as a brake on anterograde motility. Kinesin-2 depletion did not significantly reduce the number of motile transport carriers but did cause a similar increase in run length. These data suggest that kinesins act as negative regulators of ER-to-Golgi transport. Depletion of dynein not only reduced the number of motile carriers formed but also caused tubulation of carriers similar to that seen for sorting nexin-coated early endosomes. Our data indicated that the previously observed anterograde–retrograde polarity of transport carriers in transit to the Golgi from the ER is maintained by microtubule motor function.

Performance of folded variance estimators for simulation

We extend and analyze a new class of estimators for the variance parameter of a steady-state simulation output process. These estimators are based on “folded” versions of the standardized time series (STS) of the process, and are analogous to the area and Cramér--von Mises estimators calculated from the original STS. In fact, one can apply the folding mechanism more than once to produce an entire class of estimators, all of which reuse the same underlying data stream. We show that these folded estimators share many of the same properties as their nonfolded counterparts, with the added bonus that they are often nearly independent of the nonfolded versions. In particular, we derive the asymptotic distributional properties of the various estimators as the run length increases, as well as their bias, variance, and mean squared error. We also study linear combinations of these estimators, and we show that such combinations yield estimators with lower variance than their constituents. Finally, we consider the consequences of batching, and we see that the batched versions of the new estimators compare favorably to benchmark estimators such as the nonoverlapping batch means estimator.

Estimating the asymptotic variance with batch means

We show that there is no batch-means estimation procedure for consistently estimating the asymptotic variance when the number of batches is held fixed as the run length increases. This result suggests that the number of batches should increase as the run length increases for sequential stopping rules based on batch means.