Search

Colon-targeted drug delivery is gradually attracting attention because it can effectively treat colon diseases. Furthermore, electrospun fibers have great potential application value in the field of drug delivery because of their unique external shape and internal structure. In this study, a core layer of hydrophilic polyethylene oxide (PEO) and the anti-colon-cancer drug curcumin (CUR), a middle layer of ethanol, and a sheath layer of the natural pH-sensitive biomaterial shellac were used in a modified triaxial electrospinning process to prepare beads-on-the-string (BOTS) microfibers. A series of characterizations were carried out on the obtained fibers to verify the process–shape/structure–application relationship. The results of scanning electron microscopy and transmission electron microscopy indicated a BOTS shape and core–sheath structure. X-ray diffraction results indicated that the drug in the fibers was in an amorphous form. Infrared spectroscopy revealed the good compatibility of the components in the fibers. In vitro drug release revealed that the BOTS microfibers provide colon-targeted drug delivery and zero-order drug release. Compared to linear cylindrical microfibers, the obtained BOTS microfibers can prevent the leakage of drugs in simulated gastric fluid, and they provide zero-order release in simulated intestinal fluid because the beads in BOTS microfibers can act as drug reservoirs. [ABSTRACT FROM AUTHOR]

High-quality maps are pertinent to performing tasks requiring precision interaction with the environment. Current challenges with creating a high-precision map come from the need for both high pose accuracy and scan accuracy, and the goal of reliable autonomous performance of the task. In this paper, we propose a multistage framework to create a high-precision map of an environment which satisfies the targeted resolution and local accuracy by an autonomous mobile robot. The proposed framework consists of three steps. Each step is intended to aid in resolving the challenges faced by conventional approaches. In order to ensure the pose estimation is performed with high accuracy, a globally accurate coarse map of the environment is created using a conventional technique such as simultaneous localization and mapping or structure from motion with bundle adjustment. The high scan accuracy is ensured by planning a path for the robot to revisit the environment while maintaining a desired distance to all occupied regions. Since the map is to be created with targeted metrics, an online path replanning and pose refinement technique is proposed to autonomously achieve the metrics without compromising the pose and scan accuracy. The proposed framework was first validated on the ability to address the current challenges associated with accuracy through parametric studies of the proposed steps. The autonomous capability of the proposed framework was been demonstrated successfully in its use for a practical mission. [ABSTRACT FROM AUTHOR]

The existing MDOE methods based on the parametric model cannot meet the tunnel test requirements of advanced vehicle because of strong nonlinear aerodynamic behaviors. It is necessary to develop the MDOE method based on the non-parametric model instead. The formal design of experiments method of MDOE for wind tunnel tests is researched in this paper. The applicability of Latin Hypercube Sampling and Uniform Design in wind tunnel tests is compared through virtual experiments. And several optimizing methods based on Uniform Design are developed, which can improve the quality of design results to meet the requirement of wind tunnel tests. Studies show that, Uniform Design is more robust and uniform than Latin Hypercube Sampling for the MDOE method based on the non-parametric model, the optimization including boundary complement, density adjustment of sampling points and repetition points design can utilize the priori information to the design, the formal design of experiments method developed in the paper requires less sampling points than the OFAT, which are only 66.7% in the demonstration, and samples the intensive non-linear changing law adequately and exactly. The studies on the formal design of experiments method of MDOE in wind tunnel tests laid the foundation for further study of the MDOE method based on the non-parametric model. [ABSTRACT FROM AUTHOR]

longitudinal and lateral aerodynamic characteristics of the low aspect ratio flying wing calibration model are investigated in a low speed wind tunnel. Normal force measuring experiment is conducted to gain the longitudinal aerodynamic characteristics and yaw control characteristics, and the PIV test is also conducted to investigate the flow mechanism of the low aspect ratio flying wing. The results indicate that the leading-edge separation vortex appears on the wing's spine surface when the attack angle is at 6 degree. The vortex intensity increases and the vortex core shifts to the symmetric plane of flying wing with the increase of attack angle. Increasing the attack angle further, the vortex core becomes unsteady and begins to oscillate, finally break entirely. The broken position shifts from the ending edge to the leading edge. Yaw control characteristics of low aspect ratio flying wing is also studied in this paper. The results indicate that the flying wing is static stabile at the test attack angle. When the attack angle is less than 6 degree, it is controllable in yaw direction. And when attack angle is more than 6 degree, the yaw control ability decreases because the control surface may lays in the wake region of broken leading-edge vortex. [ABSTRACT FROM AUTHOR]

In conventional force measure wind tunnel test, the balance can get the aerodynamic force of the aircraft and also the directly moment. It is while the pressure center is usually considered as the intersection point between aerocraft's longitudinal axis and its aerodynamic force, which is not the virtually real value of the pressure center of the aircraft. How to obtain the pressure center of re-entry aerocraft accurately with the general method in wind tunnel test remains a difficult problem. In this paper, the position of re-entry vehicle's pressure center was obtained through the technique of attack angle continuous change and real-time data acquisition. Also the pressure center of re-entry module change rule with the change of attack angle was obtained. Experiments demonstrated the feasibility of the proposed method. With the increasing of negatives attack angle, the contribution of axial force to pitch moment becomes great, while the influence of normal force is just the contrary, which results in thickcreased gap between the conventional measured value and the real value of vehicle's center of pressure. The vertical position of re-entry aircraft's load center is relatively small in the test. The final CA-Cm curve shows that the axial force should not be neglected or simplified in wind tunnel test. [ABSTRACT FROM AUTHOR]

Abstract: Energy efficiency and load balance are two important factors to prolong network lifetime in wireless sensor networks (WSNs). In this paper, we propose a joint energy-balanced organizing scheme, which combines energy-balanced LEACH (EB-LEACH) protocol and cooperative MIMO. We name it as EB-LEACH-MIMO scheme. EB-LEACH is designed to be an improved LEACH algorithm, in which the monitored region is plotted into hexagons for avoiding the non-uniformity distribution of cluster heads. In EB-LEACH-MIMO scheme, the location and the residual energy of each node are considered when we choose the cluster heads for clustering and cooperative nodes for MIMO system. The simulation results show that the hexagonal network partition contributes to the energy balance among clusters while the cooperative MIMO benefits for the energy balance among nodes in a cluster. Consequently, EBLEACH-MIMO scheme can well-balance the network load, save network energy and prolong the network lifetime. [Copyright &y& Elsevier]

This paper presents a new approach for estimating the motion state of a target that is maneuvered by an unknown human from observations. To improve the estimation accuracy, the proposed approach associates the recurring motion behaviors with human intentions, and models the association as an intention-pattern model. The human intentions relate to labels of continuous states; the motion patterns characterize the change of continuous states. In the preprocessing, an Interacting Multiple Model (IMM) estimation technique is used to infer the intentions and extract motions, which eventually construct the intention-pattern model. Once the intention-pattern model has been constructed, the proposed approach incorporate the intention-pattern model to estimation using any state estimator including Kalman filter. The proposed approach not only estimates the mean using the human intention more accurately but also updates the covariance using the human intention more precisely. The performance of the proposed approach was investigated through the estimation of a human-maneuvered multirotor. The result of the application has first indicated the effectiveness of the proposed approach for constructing the intention-pattern model. The ability of the proposed approach in state estimation over the conventional technique without intention incorporation has then been demonstrated. [ABSTRACT FROM AUTHOR]

Changing the model attitude with the coupled angle of attack and roll is an important mode for the lateral test. Although the lateral flexible angle is offered in this kind of test, the data of lateral flexible angle is often neglected, which leads to the inaccuracy of the relation between the aerodynamic loads and the model attitude. Lateral flexible angle is generated from the lateral force and the yawing moment, and the effect of the lateral flexible angle will be notable when the values of the lateral force and the yawing moment are large in the test, for example, the yaw steerage test. The effect of the lateral flexible angle is analyzed, offers a data processing method of the lateral flexible angle. Calculative and experimental results show that the method can increase the accuracy of the application data. [ABSTRACT FROM AUTHOR]

Both spike and forward-facing jet can reduce the shock wave drag acted on a blunt head hypersonic vehicle significantly. However, they are not be adopted widely because of some shortages. The combination of spike and forward-facing jet takes advantages of both of them, while more complex aerodynamical phenomena and parameter optimization issue are involved. In this paper, the parametric optimization of combination of spike and forward-facing jet is carried out by response surface methodology. The objective of the optimization is to minimize the drag and the jet flux. The optimized parameters are the length of the spike, total pressure of the jet and the diameter of the jet out let. The response surface model is involved to feedback the relationship between the response and the designing parameters. IV-optimal is used to design the sample points, of which the response values are achieved through numerical simulation. The desirability value is used to estimate the benefits. The principal conclusions are as following: The function of drag and design parameters is supposed to be 2nd or 3rd order non-linear polynomial, and the coupling effects among design parameters are evident, especially between the diameter of jet outlet and the total pressure of jet. Response surface model speculated from sample points simulations reveals the relationship between the drag and the design parameters, from which the drag prediction interval of arbitrary parameters combination in design space can be obtained. The optimal parameters of minimum drag and jet mass flow are acquired, where the drag is predicted in a good precision. The study shows that response surface methodology in parameters optimization has high reliability and practicality with less computation requirement, and has good prospect of application in aircraft design. [ABSTRACT FROM AUTHOR]