Evaluation of formability and fracture of pure titanium in incremental sheet forming

A forming limit diagram (FLD) is commonly used as a useful means for characterizing the formability of sheet metal forming processes. In this study, the Nakajima test was used to construct the forming limit curve at necking (FLCN) and fracture (FLCF). The results of the FLCF are compared with incremental sheet forming (ISF) to evaluate the ability of the Nakajima test to describe the fracture in ISF. Tests were carried to construct the forming limit diagram at necking and fracture to cover the strain states from uniaxial tension to equi-biaxial tension with different stress triaxialities - from 0.33 for uniaxial tension to 0.67 for equi-biaxial tension. Due to the fact that the Gurson–Tvergaard- Needleman (GTN) model can be used to capture fracture occurrence at high stress triaxiality, and the shear modified GTN model (Nahshon-Hutchinson’s shear mechanism) was developed to predict the fracture at zero stress or even negative stress triaxiality, the original GTN model and shear modified GTN model may be not suitable to predict the fracture in all samples of the Nakajima test as some samples are deformed under moderate stress triaxiality. In this study, the fractures are compared using either the original GTN model, shear modified GTN model or Nielsen-Tvergaard model with regard to stress triaxiality. To validate the ability of these models, and to assess which model is more accurate in predicting the fracture with different stress triaxialities, finite element (FE) simulations of the Nakajima test were compared with an experimental results to evaluate the applicability of the Nakajima test to characterise the fracture from ISF. The experimental and FE results showed that the shear modified GTN model could predict the fracture accurately with samples under uniaxial tension condition due to low stress triaxiality and that the original model is suitable for an equi-biaxial strain state (high stress triaxiality), whereas the stress triaxiality modified GTN model should be considered for samples which have moderate stress triaxiality (from plain strain to biaxial strain). The numerical and experimental FLCF of pure titanium from the Nakajima test showed good agreement with the experimental and numerical results of ISF

Efficient Procedures of Sensitivity Analysis for Structural Vibration Systems with Repeated Frequencies

Derivatives of eigenvectors with respect to structural parameters play an important role in structural design, identification, and optimization. Particularly, calculation of eigenvector sensitivity is considered when the eigenvalues are repeated. A relaxation factor embedded in the combined approximations (CA) method makes it effective to the structural response at various modified designs. The proposed method is feasible after overcoming the defection of irreversibility of the characteristic matrix. Numerical examples show that it is easy to implement the computational procedure, and the method presented in this paper is efficient for the general linear vibration damped systems with repeated frequencies

A Comparative Study on Process Potentials for Frictional Stir- and Electric Hot-assisted Incremental Sheet Forming

Abstract Incremental sheet forming (ISF), as an advanced forming technique, has received increasing interest from both academia and industry due to its improved formability, greater process flexibility and reduced energy consumption in its life cycle. However, with the growing application of lightweight alloys with very limited material elongation, conventional ISF inevitably encounters challenges in processing these alloys at room temperature, especially in forming magnesium and titanium alloys. Therefore, heat-assisted ISF techniques have been proposed to further enhance material formability at elevated temperatures. In this work, two heat-assisted ISF approaches, frictional stir- and electric hot- assisted ISF, have been employed to process the hard-to-form materials in terms of the flexibility and local dynamic heating. The temperature evolution and corresponding forming force at different feed rates of these two techniques, is investigated in detail to build up a processing window. In addition, process capabilities are compared by forming different geometrical shapes of magnesium alloy AZ31B of 1.4 mm sheet thickness. The investigation results show the pros and cons of frictional stir- and electric hot- assisted ISF. Frictional stir-assisted ISF is more efficient than electric hot-assisted ISF under current experimental results. However, electric hot-assisted ISF has faster heating rate which makes this technique less dependent on the component geometry

In vitro and in vivo evaluation of folate receptor-targeting amphiphilic copolymer-modified liposomes loaded with docetaxel

Xiang Li1, Xin Tian2, Jing Zhang3, Xu Zhao1, Xiaohui Chen1, Youhong Jiang2, Dongkai Wang1, Weisan Pan11Department of Pharmaceutics, School of Pharmacy, Shenyang Pharmaceutical University, Shenyang; 2The Second Laboratory of Cancer Research Institution, The First Hospital of China Medical University, Shenyang; 3Key Laboratory of Modern Preparation of TCM, Ministry of Education, Jiangxi University of Traditional Chinese Medicine, Nanchang, ChinaBackground: The purpose of this study was to develop folate-poly (PEG-cyanoacrylate-co-cholesteryl cyanoacrylate) (FA-PEG-PCHL)-modified freeze-dried liposomes for targeted chemotherapy using docetaxel as a model drug.Methods: FA-PEG-PCHL was synthesized and its cytotoxicity was evaluated by CCK-8 assay in L929. Docetaxel-loaded liposomes modified by FA-PEG-PCHL were prepared by an organic solvent injection method and lyophilized to obtain freeze-dried FA-PEG-PCHL-docetaxel liposomes (FA-PDCT-L). Two carcinoma cell lines (MCF-7 and A-549 cells) were cultured with docetaxel solution, conventional docetaxel-loaded liposomes, or FA-PDCT-L, and the cytotoxicity and apoptosis was evaluated for each preparation. The uptake of the docetaxel preparations into MCF-7 cells was studied by confocal laser scanning microscopy. Liquid chromatography-mass spectrometry was used to study the pharmacokinetics and tissue distribution characteristics of the preparations.Results: The existence of an enlarged fixed aqueous layer on the surface of the liposomes was affirmed by zeta potential analysis. The entrapment efficiency and particle size distribution were almost the same as those of docetaxel-loaded liposomes. The drug release profile showed that the release rate was faster at higher molecular weight of the polymer. Compared with docetaxel solution and docetaxel-loaded liposomes, FA-PDCT-L demonstrated the strongest cytotoxicity against two carcinoma cell lines, the greatest intracellular uptake especially in the nucleus, as well as the most powerful apoptotic efficacy. In pharmacokinetic studies, the area under the plasma concentration-time curve of FA-PDCT-L was increased 3.82 and 6.23 times in comparison with the values for the docetaxel-loaded liposomes and docetaxel solution, respectively. Meanwhile, a lower concentration of docetaxel was observed for FA-PDCT-L in the liver and spleen, and a significantly higher concentration of FA-PDCT-L in tumors suggested that the presence of FA-PEG-PCHL on the liposomes resulted in greater accumulation of the drug in tumor tissue.Conclusion: Liposomes modified by FA-PEG-PCHL could be one of the promising suspensions for the delivery of antitumor drugs in cancer.Keywords: folate-poly (PEG-cyanoacrylate-co-cholesteryl cyanoacrylate), docetaxel, freeze-dried liposomes, tumor targetin

Sodium aescinate inhibits microglia activation through NF-κB pathway and exerts neuroprotective effect

Background: Microglia are resident immune cells of the central nervous system that sense environmental changes and maintain central nervous system homeostasis. Dysfunctional microglia produce toxic mediators that lead to neuronal death. Recent studies suggest that Sodium Aescinate has a neuroprotective effect. However, it is unclear whether Sodium Aescinate exerts neuroprotective effects by inhibiting activation of microglia.Method: Traumatic brain injury and lipopolysaccharide neuroinflammation model were used to evaluate the microglia activation in vivo. BV2 and primary microglia cells were used to assess the microglia activation in vitro. Molecular docking technique was used to predict the binding energy of Sodium Aescinate to NF-κB signaling pathway proteins.Result: Sodium Aescinate inhibited microglial activation in-vivo and in-vitro. Sodium Aescinate inhibited the activation of microglia in Traumatic brain injury and lipopolysaccharide mouse models. Sodium Aescinate also inhibited the expression of inflammatory proteins in BV2 and primary microglia cells. Western blot experiment showed that SA inhibited the activation of NF-κB pathway in BV2 and primary microglia cells. Molecular docking results also showed that Sodium Aescinate had a better affinity with the core protein of the NF-κB pathway. Western blot identified that SA inhibited activation of NF-κB pathway. In Traumatic brain injury model and conditioned medium experiment, Sodium Aescinate pretreatment inhibited inflammation and protected neuron.Conclusion: Our study confirmed that the protection effects of Sodium Aescinate on neurons by inhibiting microglia activation through NF-κB pathway

An efficient method for thickness prediction in multi-pass incremental sheet forming

Incremental sheet forming (ISF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. In the ISF process, efficient and accurate prediction of part thickness variation is still a challenging task, which is especially true for the multi-pass ISF process. The Sine law equation and the finite element method (FEM) are the two commonly used conventional prediction methods. However, these approaches are either with limited accuracy or very time consuming. For the multi-pass ISF process, the thickness prediction is even more challenging since two or more forming steps are involved. Focusing on the thickness prediction of multi-stage ISF process, this work proposes a thickness prediction model based on the geometrical calculation of intermediate shapes of the formed part and backward tracing of nodal points of the forming tool. By developing this method, the thickness distribution can be calculated through the predicted nodal displacement in the ISF process. To verify the proposed model, four different geometrical shapes, i.e., conic, parabolic conic, non-axisymmetric, and hemispherical parts, are physically formed by using a NC ISF machine. The geometric shapes and the detailed thickness distributions of the formed parts are carefully measured and compared with the prediction model developed. Good agreements between the analytical predictions, and the experimental results are obtained. This indicates the effectiveness and robustness of the developed thickness prediction approach

An Improved Back-Projection Algorithm for GNSS-R BSAR Imaging Based on CPU and GPU Platform

Global Navigation Satellite System Reflectometry Bistatic Synthetic Aperture Radar (GNSS-R BSAR) is becoming more and more important in remote sensing because of its low power, low mass, low cost, and real-time global coverage capability. The Back Projection Algorithm (BPA) was usually selected as the GNSS-R BSAR imaging algorithm because it can process echo signals of complex geometric configurations. However, the huge computational cost is a challenge for its application in GNSS-R BSAR. Graphics Processing Units (GPU) provides an efficient computing platform for GNSS-R BSAR processing. In this paper, a solution accelerating the BPA of GNSS-R BSAR using GPU is proposed to improve imaging efficiency, and a matching pre-processing program was proposed to synchronize direct and echo signals to improve imaging quality. To process hundreds of gigabytes of data collected by a long-time synthetic aperture in fixed station mode, a stream processing structure was used to process such a large amount of data to solve the problem of limited GPU memory. In the improvement of the imaging efficiency, the imaging task is divided into pre-processing and BPA, which are performed in the Central Processing Unit (CPU) and GPU, respectively, and a pixel-oriented parallel processing method in back projection is adopted to avoid memory access conflicts caused by excessive data volume. The improved BPA with the long synthetic aperture time is verified through the simulation of and experimenting on the GPS-L5 signal. The results show that the proposed accelerating solution is capable of taking approximately 128.04 s, which is 156 times lower than pure CPU framework for producing a size of 600 m × 600 m image with 1800 s synthetic aperture time; in addition, the same imaging quality with the existing processing solution can be retained

TEST AND EVALUATION OF GPS/DR APPLICATION FOR CAR NAVIGATION SYSTEM

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, NevadaGlobal Positioning System (GPS) was analyzed in terms of its repeatable accuracy, UTM projection for 2D plane coordinate system, satellite visibility performance and the horizontal dilution of positioning (HDOP). The principle of Dead Reckoning together with body coordinate system transformation was introduced. The complementary performance of GPS and DR, and GPS/DR integration using gyroscope and accelerometer were given. Test results were demonstrated that the repeatable accuracy of GPS alone is about 10 meters in open air, and DR can provide continuous positioning output within sufficient accuracy when GPS signal is outage.International Foundation for TelemeteringProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection

The perinatal outcomes of frozen-thawed blastocyst transfer are better than fresh blastocyst transfer: a systematic review and meta-analysis

Objectives: Transfer of cryopreserved-warmed blastocysts is common in the practice of in vitro fertilization. The purpose of the study is to examine the available evidence and determine whether cryopreservation of blastocysts and subsequent frozen blastocyst transfer (BT) result in better outcomes than fresh BT. Material and methods: Related studies comparing outcomes of in vitro fertilization (IVF) cycles between fresh and frozen BTs were retrieved from Medline, Cochrane Central Register of Clinical Trials, EMBASE, DARE, and CINAHL through March 2020. The outcomes of interest were preterm birth, extremely preterm birth, small for gestational age, large for gestational age, low birth weight, extremely low birth weight, caesarean section, perinatal mortality and preeclampsia. The analysis was performed using Rev Man 5.1 software. Risk ratios (RRs) and risk differences were calculated with 95% confidence intervals, to evaluate the results of each outcome. The quality of the referenced studies was assessed using the Newcastle-Ottawa scale (NOS) checklists. Results: Nine studies with 42,342 women incorporated in this meta-analysis. The incidence of preterm birth (RR = 0.89, 95% CI: 0.82, 0.97) and small for gestational age (RR = 0.55, 95% CI 0.41–0.74) was low in frozen BT group. There was no significant difference in the risk of low birth weight (RR = 0.89, 95% CI: 0.67, 1.19) and perinatal mortality (RR = 1.47, 95% CI: 0.85, 2.55) between frozen-thawed and fresh BT. Singleton pregnancy after frozen BT was associated with higher large for gestational age (RR = 1.47, 95% CI: 1.37, 1.57), caesarean section rates (RR = 1.24, 95% CI: 1.13, 1.36) and preeclampsia compared with fresh BT (RR = 1.85, 95% CI: 1.22, 2.82). Conclusions: The frozen BT results in better perinatal outcomes compared with that of fresh BT. Furthermore, comprehensive randomized clinical trials comparing freeze-all with fresh BT cycles are needed to draw sound conclusions