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In order to improve the communications inside and outside the enterprise, efficient utilization of enterprise capitals and make improvements in the services and products of enterprise, many enterprises have turned to use enterprise resource planning (ERP) systems. On the other hand, the more the role of knowledge assets in enterprises grows, the higher the position of knowledge management (KM) in the enterprises becomes and it gradually becomes fundamental to success. The role of knowledge management in today’s knowledge-based world has attracted considerable attention to this topic in industry and academia. The use of ERP and knowledge management in enterprises for the continuation of effective functioning in knowledge-based economy arises the need to study the interactions between ERP and knowledge management and also the possibility of the integration of ERP and KM systems. The mutual relation between knowledge management and enterprise resources planning can be studied from the three perspectives of (A) the effects of knowledge management on the implementation and use of ERP, (B) the ERP effects on improving knowledge management process, and (C) the integration of knowledge management and enterprise resources planning systems. By studying a wide range of academic literature on KM and ERP, this paper aims to review the relation between knowledge management and enterprise resources planning and analyze the opportunities of future research in this area.

Rhabdomyosarcoma (RMS) is the most common pediatric soft-tissue malignant tumor. Treatment of RMS usually includes primary tumor resection along with systemic chemotherapy. Two-dimensional (2D) cell culture systems and animal models have been extensively used for investigating the potential efficacy of new RMS treatments. However, RMS cells behave differently in 2D culture than in vivo, which has recently inspired the adoption of three-dimensional (3D) culture environments. In the current paper, we will describe the detailed methodology we have developed for fabricating a 3D engineered model to study alveolar RMS (ARMS) in vitro. This model consists of a thermally cross-linked collagen disk laden with RMS cells that mimics the structural and bio-chemical aspects of the tumor extracellular matrix (ECM). This process is highly reproducible and produces a 3D engineered model that can be used to analyze the cytotoxicity and autophagy induction of drugs on ARMS cells. The most improtant bullet points are as following:•We fabricated 3D model of ARMS.•The current ARMS 3D model can be used for screening of chemotherapy drugs.•We developed methods to detect apoptosis and autophagy in ARMS 3D model to detect the mechansims of chemotherapy agents., Graphical abstract Rhabdomyosarcoma (RMS) is the most common pediatric soft-tissue malignant tumor. Despite numerous clinical trials that have investigated the efficacy of multidrug chemotherapy regimens, outcomes for high-risk RMS patients are still poor which has inspired research into new targeted therapies that molecularly target malignant RMS cells. In order to evaluate such therapies in vitro in a realistic tumor microenvironment, we have bioengineered a cell-laden 3D tissue-engineered model with uniform geometry and an uncomplicated and reproducible biofabrication process. The transparent collagen-I hydrogel promotes cell attachment and growth and allows for analysis of the cellular response to drugs through brightfield microscopy, immunocytochemistry, and live/dead viability assays.Image, graphical abstract

An integrated guidance and feedback control scheme for steering an underactuated vehicle through desired waypoints in three-dimensional space, is developed here. The underactuated vehicle is modeled as a rigid body with four control inputs. These control inputs actuate the three degrees of freedom of rotational motion and one degree of freedom of translational motion in a vehicle body-fixed coordinate frame. This actuation model is appropriate for a wide range of underactuated vehicles including spacecraft with internal attitude actuators, vertical take-off and landing (VTOL) aircraft, fixed-wing multirotor unmanned aerial vehicles (UAVs), maneuverable robotic vehicles, etc. The guidance problem is developed on the special Euclidean group of rigid body motions, SE(3), in the framework ofgeometric mechanics, which represents the vehicle dynamics globally on this configuration manifold. The integrated guidance and control algorithm selects the desired trajectory for the translational motion that passes through the given waypoints, and the desired trajectory for the attitude based on the desired thrust direction to achieve the translational motion trajectory. A feedback control law is then obtained to steer the underactuated vehicle towards the desired trajectories in translation and rotation. This integrated guidance and control scheme takes into account known bounds on control inputs and generates a trajectory that is continuous and at least twice differentiable, which can be implemented with continuous and bounded control inputs. The integrated guidance and feedback control scheme is applied to an underactuated quadcopter UAV to autonomously generate a trajectory through a series of given waypoints in SE(3) and track the desired trajectory in finite time. The overall stability analysis of the feedback system is addressed. Discrete time models for the dynamics and control schemes of the UAV are obtained in the form of Lie group variational integrators using the discrete Lagrange-d’Alembert principle. Almost global asymptotic stability of the feedback system over its state space is shown analytically and verified through numerical simulations.

Following the development of microfluidic systems, there has been a high tendency towards developing lab-on-a-chip devices for biochemical applications. A great deal of effort has been devoted to improve and advance these devices with the goal of performing complete sets of biochemical assays on the device and possibly developing portable platforms for point of care applications. Among the different microfluidic systems used for such a purpose, digital microfluidics (DMF) shows high flexibility and capability of performing multiplex and parallel biochemical operations, and hence, has been considered as a suitable candidate for lab-on-a-chip applications. In this review, we discuss the most recent advances in the DMF platforms, and evaluate the feasibility of developing multifunctional packages for performing complete sets of processes of biochemical assays, particularly for point-of-care applications. The progress in the development of DMF systems is reviewed from eight different aspects, including device fabrication, basic fluidic operations, automation, manipulation of biological samples, advanced operations, detection, biological applications, and finally, packaging and portability of the DMF devices. Success in developing the lab-on-a-chip DMF devices will be concluded based on the advances achieved in each of these aspects.

The delayed feedback stabilization of rigid spacecraft attitude dynamics in the presence of an unknown time-varying delay in the measurement is addressed. The attitude representation is parameterized using minimal attitude coordinates. The time-varying delay and its derivative are assumed to be bounded. By employing a linear state feedback controller via a Lyapunov–Krasovskii functional, a general delay-dependent stability condition is characterized for the closed-loop parameterized system in terms of a linear matrix inequality (LMI) whose solution gives the suitable controller gains. An estimate of the region of attraction of the controlled system is also obtained, inside which the asymptotic stability of parameterized system is guaranteed.

This paper presents an electrohydrodynamic technique for rapid mixing of droplets in open and closed digital microfluidic (DMF) platforms. Mixing is performed by applying a high frequency AC voltage to the coplanar or parallel electrodes, inducing circulation zones inside the droplet which results in rapid mixing of the content. The advantages of the proposed method in comparison to conventional mixing methods that operate based on transporting the droplet back and forth and side to side include 1) a shorter mixing time (as fast as 0.25 s), 2) the use of a fewer number of electrodes, reducing the size of the chip, and 3) the stationary nature of the technique which reduces the chance of cross-contamination and surface biofouling. Mixing using the proposed method is performed to create a uniform mixture after merging a water droplet with another droplet containing either particles or dye. The results show that increasing the frequency, and or the amplitude of the applied voltage, enhances the mixing process. However, actuation with a very high frequency and voltage may result in shedding pico-liter satellite droplets. Therefore, for each frequency there is an effective range of the amplitude which provides rapid mixing and avoids shedding satellite droplets. Also, the increase in the gap height between the two plates (for the closed DMF platforms) significantly enhances the mixing efficiency due to the lower viscous effects. Effects of the addition of salts and DNA to the samples were also studied. The electrothermal effect decreased for these cases, which was solved by increasing the frequency of the applied voltage. To assure the high frequency actuation does not increase the sample temperature excessively, the temperature change was monitored using a thermal imaging camera and it was found that the increase in temperature is negligible.

In the present study a particle focusing technique has been developed for digital microfluidics (DMF) based on cumulative effects of negative dielectrophoretic (nDEP) and gravitational forces. The mechanism of the proposed technique has been studied for different particles, and different magnitudes and frequencies of the applied voltage. Particle focusing using the proposed technique was found to be more efficient for particles with a large diameter and high density. To show a potential application of this method, it was applied to collect particles on one side of a large droplet which was split on a DMF platform into two daughter droplets with very low and very high particle concentrations.

This paper studies the effect of the electrode aspect ratio on droplet splitting in a digital microfluidics (DMF) chip including an array of 3 electrodes in which the middle electrode is kept square while the two side electrodes have different aspect ratios. The aspect ratio is changed from 0.9 to 1.3 while the surface area of the electrodes is kept constant for all cases. Results show that changing the aspect ratio can severely change the required voltage for splitting with a nonlinear behavior. It is also shown that for a constant gap between the top and bottom plates and a constant volume of the droplet, the relation between the threshold voltage and the aspect ratio is parabolic, for which there is an aspect ratio with a minimum threshold voltage. Changing the volume of the droplet changes the threshold voltage and hence the aspect ratio corresponding to the minimum threshold voltage required for splitting.Copyright © 2014 by ASME

In the present study, unequal droplet splitting is performed simply by modifying the electrode geometry: an electrode is divided into four small squares or four narrow sub-electrodes which are surrounded by regular spatial electrodes. Two possible configurations are studied for the narrower modified electrodes in which the narrow sub-electrodes are i) parallel, and ii) perpendicular to the flow direction. By actuating one (or more) sub-electrodes on one side and a spatial electrode on the other side of the droplet reproducible unequal splitting was achieved without a need for a complicated control system. In addition to reproducibility, the proposed approach offers a great deal of flexibility by splitting the droplet (or dispense a droplet) to different volumes based on the number of the actuated sub-electrodes.Copyright © 2013 by ASME

Observer-based attitude controllers for single- and multi-actuator maneuvers are developed from the delayed state feedback control laws obtained by the Lyapunov-Krasovskii functional and inverse dynamics approaches, respectively. The TRIAD algorithm is employed to process the observations. The observer gain is selected based on the extended Kalman-Bucy (EKB) filter, and a novel delay estimation approach is used to provide the estimates of the delay. The observer-based delayed feedback control laws are shown to be capable of accurate control of spacecraft attitude from noise-corrupted attitude measurements.

The present study is intended to investigate and compare the hemodynamics in two different sizes of hemodialysis arteriovenous grafts for upper arm hemodialysis vascular access: 8-mm tapered to 6-mm at the arterial side and straight 6 mm. A computational simulation approach is presented for this study, which is validated against the available experimental and numerical pressure measurements in the literature. The imposed boundary conditions at the arterial inlet and venous outlet boundaries of the models are physiological velocity and pressure waveforms, respectively. Blood flow fields and distribution patterns of the hemodynamic indices including wall shear stress (WSS) as one of the major hemodynamic parameters of the cardiovascular system and spatial wall shear stress gradient (SWSSG) as an indicator of disturbed flow patterns and hence susceptible sites of lesion developments are analyzed and compared between the two grafts. The tapered 6- to 8-mm graft seemingly is associated with less disturbed flow patterns within the venous anastomosis (VA) and the vein downstream while benefiting from higher blood flow rates within. Also, it shows a definitive advantage in terms of WSS and SWSSG distribution patterns around the VA and throughout the vein downstream with significantly lower values, which reduce the risk of thrombosis formation and stenotic lesion developments. The only disadvantage encountered in using 6- to 8-mm tapered graft is higher values of hemodynamic parameters at the arterial junction attributable to its significantly higher mean blood flow rate within. The results clearly indicate that the tapered 6- to 8-mm graft entirely outperforms straight 6-mm graft hemodynamically as an upper arm hemodialysis vascular access graft and confirms clinical data in the literature, which suggests advantageous use of tapered 6- to 8-mm grafts in the creation of upper arm brachioaxillary hemodialysis vascular access grafts in selected groups of patients with expectably higher patency rates and lower complications.

Hemodialysis vascular access dysfunction is still considered as a major cause of morbidity and mortality in hemodialysis patients. The most common cause of this vascular access dysfunction is venous stenosis secondary to the progression of venous intimal hyperplasia at the graft-vein junction or in the draining vein. The geometry of the vessels and the local hemodynamics are believed to be contributory factors in the development of intimal hyperplasia. In the present study, the hemodynamic parameters in two types of vascular access grafts of different diameters: 6 mm and 8 mm tapered to 6 mm at the arterial site were compared. A three-dimensional CFD model was developed to simulate blood flow in the two graft types. The boundary conditions applied were a pulsatile velocity waveform at the arterial inlet and a pulsatile pressure waveform at the venous outlet. Computational fluid dynamics software was used to solve the time dependent Navier-Stokes equations under physiological conditions in both graft types. Since the cross section area and the diameter of the venous side of the tapered graft are larger than those of the straight one, the flow aligns well with the vein downstream of the graft and hence the smaller vortices are generated. Comparing the parameters at the two venous anastomosis regions also indicates that in spite of the higher flow rate in 6–8 mm tapered graft, the velocity and the wall shear stress values are lower than the values of the 6 mm straight graft.Copyright © 2010 by ASME

Hemodialysis vascular access failure considered as a primary cause of morbidity and hospital admissions for chronic hemodialysis patients. Clearly the hemodynamics within a vascular access graft and also the anastomotic geometry induced disturbed flow patterns have a substantial influence on the initiation and development of “intimal hyperplasia” the most common cause of vascular access failures. The present study is intended to investigate and compare the hemodynamics in two types of hemodialysis vascular access grafts of different diameters: 6 mm straight versus 8 mm tapered to 6 mm at the arterial site in an upper arm brachio-axillary prosthetic graft in straight configuration. Using a three-dimensional CFD model of an upper arm straight vascular access graft the two graft types have been compared in terms of overall flow pattern, wall shear stress distribution and other hemodynamic parameters. The boundary conditions applied are a physiological pulsatile velocity waveform at the arterial inlet and a pulsatile pressure waveform at the venous outlet. Results show higher values of wall shear stresses at the arterial amastomosis region of the 6-8 mm tapered graft over its 6 mm straight graft counterpart. Comparing the parameters at the two venous anastomosis regions indicates that in spite of the higher flow rate in 6-8 mm tapered graft, the velocity and the wall shear stress values are lower than the values of the 6 mm straight graft. The larger diameter and hence the larger venous anastomotic length of the tapered 6-8 mm graft let the flow align well with the vein downstream of the graft with less perturbation and thereby smaller the vortices generated and lower the wall shear stress values at the vein floor opposite to the graft outflow in comparison with the straight 6 mm graft.

This paper presents the thorough analysis of a new operator developed for unequal droplet splitting by geometrical modification of a conventional electrode in digital microfluidic (DMF) platforms. This operator functions in an area as small as the size of a conventional electrode divided into several smaller sub-electrodes addressable independently. Using this operator, droplets can be precisely split unequally with a high volume ratio, as well as being dispensed with a wide range of sizes from a reservoir. This operator functions without complications in the fabrication process and the need for additional external modules such as feedback control systems. To characterize the range of the applicability of this operator, the effects of the applied voltage, the gap height between the two plates, and the sub-electrode geometry on the splitting performance are studied. For high applied voltages, splitting is performed with an error close to 5% (similar to the splitting precision obtained in conventional DMF devices); whereas, for voltages close to the threshold value, the error is less than 1%. In this way the droplet size becomes fairly independent of the geometry and the gap height. The threshold splitting voltage versus gap height has also been studied and shows a linear behavior, facilitating the selection of proper voltages for high precision splitting. For the three sub-electrode patterns studied here (i.e. square, horizontal stripe, and vertical stripe), the results show that the square sub-electrodes provide higher reliability and a wider range of sizes for the split droplet as compared to the other patterns. The final part of the study illustrates that there is a linear relation between the area of the split droplets and the number of actuated sub-electrodes. This linear behavior allows for the selection of an appropriate number of the sub-electrodes to be actuated based on the desired volume of the droplet.

Autonomous proximity operations to explore small solar system bodies (asteroids and comets), servicing of aerospace vehicles, and active space debris removal, are likely to increase in the future with NASA’s Asteroid Redirect Mission and Grand Challenge, and planned activities in autonomous rendezvous/proximity operations (ARPO) and active debris removal. Autonomous navigation is essential for these applications. The concept proposed here is to have a single stable estimator for the naturally coupled translational and rotational motion of an observed object from only vision-based, infra-red or lidar measurements, without needing a dynamics model for this object, during proximity operations. This estimator can also be used to improve an existing dynamics model. This avoids the need for measurements from external sources, like GPS, which is anyway not available for proximity operations near asteroids or comets. It also avoids mishaps due to changes in sensors and estimation schemes used during close proximity operations between spacecraft, as witnessed during the DART and Orbital Express missions. Attitude and translational motion of spacecraft, asteroids and comets are dynamically coupled through natural effects like gravity as well as control forces and torques for spacecraft. This coupling can also be used to estimate the mass and gravity parameters of the asteroid/comet.