Compressive test and simulation of cassava stems using ANSYS

Compression tests were conducted on cassava stems with a universal testing machine in order to determine their compressive strength limits, or the points at which the stems began to deform plastically. Based on the test, ANSYS, a universal finite element analysis (FEA) software, was used to construct the mechanical models of the cassava stems and analyze the displacements, stresses, and shear stresses within the stems as they broke under compressive loads

Adaptive virtual guides for compliance control skill teaching in partially known tasks

Compliant manipulation is widely studied in the domain of robotics due to urgent industrial demands of flexible production. In many tasks that require human demonstration of the end-effector’s pose and contact force, cognitive and physical loads on human operators are high. Fortunately, virtual guides (VGs) can effectively assist human users to carry out the corresponding work. This article aims to design an adaptive virtual guides (AVGs) scheme for kinesthetic teaching that can be applied to surface finishing and to reduce human load. For this purpose, the end-effector’s orientation is automatically adjusted according to the workpiece’s 3D model and the end-effector’s position. The force provided by the robot along the end-effector’s z-axis is adjustable, which is used to reduce human’s control effort for contact force demonstration. Our method utilizes the virtual mass-damper system and joint admittance control model for the AVGs design, whose validity is verified on a Sawyer robot in simulation

Structure-Independent Conductance of Thiophene-Based Single-Stacking Junctions.

Intermolecular charge transport is crucial in π-conjugated materials but the experimental investigation remained challenging. Here, we show that charge transport through intermolecular and intramolecular paths in single-molecule and single-stacking thiophene junctions could be investigated using the mechanically controllable break junction (MCBJ) technique. We found that intermolecular charge transport ability through different single-stacking junctions is approximately independent of molecular structures, which contrasts with the strong length dependence of conductance in single-molecule junctions with the same building blocks, and the dominant charge transport path of molecules with two anchors transits from intramolecular to intermolecular paths when the conjugation pattern increased. The increase of conjugation further leads to higher binding probabilities due to the variation in binding energies supported by density functional theory (DFT) calculations. Our results demonstrate that intermolecular charge transport is not only the limiting step but also provides the efficient and dominate charge transport path at the single-molecule scale

Deregulation of DUX4 and ERG in acute lymphoblastic leukemia

Chromosomal rearrangements deregulating hematopoietic transcription factors are common in acute lymphoblastic leukemia (ALL).1,2 Here, we show that deregulation of the homeobox transcription factor gene DUX4 and the ETS transcription factor gene ERG are hallmarks of a subtype of B-progenitor ALL that comprises up to 7% of B-ALL. DUX4 rearrangement and overexpression was present in all cases, and was accompanied by transcriptional deregulation of ERG, expression of a novel ERG isoform, ERGalt, and frequent ERG deletion. ERGalt utilizes a non-canonical first exon whose transcription was initiated by DUX4 binding. ERGalt retains the DNA-binding and transactivating domains of ERG, but inhibits wild-type ERG transcriptional activity and is transforming. These results illustrate a unique paradigm of transcription factor deregulation in leukemia, in which DUX4 deregulation results in loss-of-function of ERG, either by deletion or induction of expression of an isoform that is a dominant negative inhibitor of wild type ERG function

Effect of microwave on formation/decomposition of natural gas hydrate

Natural gas hydrate (NGH) reservoirs have been considered as a substantial future clean energy resource and how to recover gas from these reservoirs feasibly and economically is very important. Microwave heating will be taken as a promising method for gas production from gas hydrates for its advantages of fast heat transfer and flexible application. In this work, we investigate the formation/decomposition behavior of natural gas hydrate with different power of microwave (2450MHZ), preliminarily analyze the impact of microwave on phase equilibrium of gas hydrate,and make calculation based on van der Waals-Platteeuw model. It is found that microwave of a certain amount of power can reduce the induction time and sub-cooling degree of NGH formation, e.g., 20W microwave power can lead to a decrease of about 3A degrees C in sub-cooling degree and the shortening of induction time from 4.5 hours to 1.3 hours. Microwave can make rapid NGH decomposition, and water from NGH decomposition accelerates the decomposition of NGH with the decomposition of NGH. Under the same pressure, microwave can increase NGH phase equilibrium temperature. Different dielectric properties of each composition of NGH may cause a distinct difference in temperature in the process of NGH decomposition. Therefore, NGH decomposition by microwave can be affected by many factors

Experimental Investigation on the Dissociation Behavior of Methane Gas Hydrate in an Unconsolidated Sediment by Microwave Stimulation

The technique of recovery of methane from a hydrate reservoir by microwave stimulation was experimentally verified for a laboratory scale. The stimulation was carried out in the unconsolidated sediment from the South China Sea by applying 2.45 GHz microwave with the average radiation densities ranging from 3 to 19 kW/m(2). We observe that the far-field hydrate layer, which exceeds the microwave penetration depth, dissociated at equilibrium. The hydrate saturation (15.5-54.5%), water saturation (40.7 and 70.4%), freezing and combining with depressurization affect the heating and gas production behaviors, as well as the production efficiency. The formation of ice reduces the gas production efficiency for the frozen sediment but boosts the gas production for the unfrozen sediment combining with depressurization

Static Formation and Dissociation of Methane plus Methylcyclohexane Hydrate for Gas Hydrate Production and Regasification

The formation and decomposition of methane+methylcyclohexane (MCH) hydrate in a static batch reactor, which was also designed as a high-pressure microwave reactor, were investigated. The addition of 300 ppm sodium dodecyl sulfate (SDS) provides continuous formation of CH(4)+MCH hydrate under static conditions. Increasing the initial pressure within the narrow range of 2.7 to 4.6 MPa at 274 K enhances the formation rate by even several times. The gas storage capacity can be largely improved with partial coexisting of sI CH(4) hydrate. Unlike a stirred formation, an increase of nonaqueous MCH inhibits the static formation of sH hydrate. The following regasification by 2.45 GHz microwave heating indicates that the dissociation is rate-controlled by the parallel connection of efficient internal heating and conventional external heating. The multiphase convection characterized by osmotic dehydration and driven by intensified regasification is considered as the dominant mechanism affecting the quiescent dissociation

Path learning by demonstration for iterative human-robot interaction with uncertain time durations

This paper presents a path learning method through physical human-robot interaction (pHRI) based on a stretch compression iterative learning control (ILC) scheme and contouring impedance control. The robot learns a task path desired by the human user through a kinaesthetic interface and provides physical assistance to the human user in repetitive interactions. Due to the uncertainty of the human user’s force and motion, the time duration of each iteration may be different, so a novel ILC scheme based on stretch and compression operation is proposed to update the reference trajectory of the robotic manipulator. By attaching the Frenet-Serret frame to each point on the reference path, the control task is decomposed into impedance control in the tangential direction and position control in the normal or binormal direction constraining the human user on the reference path. Experiments on a 7-DOF Sawyer robot are carried out to show the effectiveness and robustness of the proposed method