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This paper discusses the reachable set estimation problem of neural networks with mixed delays. Firstly, by means of the maximal Lyapunov–Krasovskii functional, we obtain a non-ellipsoid form of the reachable set. Further more, when calculating the derivative of the maximum Lyapunov functional, the lower bound lemma and reciprocally convex approach method are used to solve the reciprocally convex combination term, which reduce the related decision variables. Secondly, we extend the results to polytopic uncertainties neural networks and consider the case of uncertain differentiable parameters. Finally, two numerical examples and one application example are listed to show the validity of our methods.

In recent years, Global Navigation Satellite System Reflectometry (GNSS-R) has been studied as a new technique for ocean remote sensing, and the simulation of GNSS-R signals has played a very important role. In this letter, a random model for ocean reflected signal simulation of GNSS-R is presented to provide a useful method for generating reflected signals. The study is conducted by means of a superimposed result of multiple random reflected signals based on a previous fixed model. Reflected signals are randomly selected with different delay bins and different random amplitudes. To generate GNSS-R signals, a software GNSS-R simulator based on the proposed random model is developed. A receiver is also used to process the simulated signals to demonstrate the availability of the proposed model and developed simulator. The analysis shows good agreement between the produced and theoretical delay waveforms with the correlation coefficient of 0.998. To further verify the significance of the random model, the simulated reflected signals are compared with the airborne experimental data collected in Yantai, China. The comparative results show that the random model has better statistical and stochastic characteristics.

Signal is the key to GNSS-R signal simulation. In view of the lack of practical signal model, a method for establishing a model for GNSS signal reflected from ocean surface, is proposed based on the principle of bistatic radar. The scattering region is analyzed, and appropriate reflection units are selected. Then the power of the reflected signal corresponding to the reflection unit is obtained. In addition, the method for increasing the virtual signal is used to compensate the energy of the high frequency part. The correlation power of the simulated reflection signal is compared with the theoretical value of the ZV model. The correlation coefficient of simulation and theoretical values is better than 0.96. The model proposed can simulate the characteristics of the ocean surface well, and is easy to be implemented with less signals.

Polo-like kinase 4 (PLK4) has been identified as an oncogene, which is overexpressed in various types of human cancer; however, its role in colorectal cancer (CRC) development remains unknown. The present study demonstrated that PLK4 protein expression was upregulated in CRC tissues compared with in normal tissues through western blotting. In addition, immunohistochemical analysis of 39 CRC specimens further demonstrated that PLK4 protein expression was upregulated in 64.1% (25/39) of samples. Increased PLK4 expression was closely associated with enhanced tumor size (P=0.031), lymph node metastasis (P=0.016) and TNM stage (P=0.001). Subsequently, cell viability, wound scratch, migration and invasion assays were conducted in vitro, and nude mice CRC xenograft models were generated. The results demonstrated that knockdown of PLK4 in CRC cells resulted in significant decreases in cell viability and proliferation, and decreased the protein expression levels of N-cadherin and snail, which are biomarkers of epithelial-mesenchymal transition. Furthermore, PLK4 knockdown inactivated the Wnt/β-catenin pathway in CRC cells in vitro and in vivo, and suppressed the growth of xenograft tumors in nude mice. In conclusion, these results suggested that PLK4 may promote the carcinogenesis and metastasis of CRC, thus indicating that PLK4 may be considered a molecular target for CRC treatment.

To improve the experience of various network applications, dynamic rate allocation is an essential issue in recent ISP networks. The emergence of software-defined networking (SDN) and the OpenFlow specification makes dynamic rate allocation in ISP networks efficient. The allocation could locally run on a home network gateway (edge switch) under SDN, but such local range of rate allocation reduces the overall fairness and performance in the whole network. However, under a global range, the request of rate allocation from a small number of hosts will cause all switches on the entire network to participate. This is termed as cascading problem, which causes a high cost for re-allocating the rates with the global range of switches. In this paper, we investigate the cascading problem for dynamic rate allocation with SDN, and discuss the tradeoff between the performance and cost for the range of rate allocation. We propose a Rate Allocation algorithm with Limited Range (RALR) in SDN, and discuss it for dynamic rate allocation by the theory of Lyapunov drift. Our intensive simulations verify the performance of the proposed strategy of rate allocation in SDN.

The problem of robust control for space robot collision avoidance maneuver under constant thrust is studied in this paper. Firstly, based on the Clohessy–Wiltshire (C–W) equations and by considering uncertainties and thruster failure in radial direction, the dynamic model for space robot is proposed. Then, based on the established model, a parametric design method of robust controller is given by using the eigenstructure assignment theory and the model reference theory. Next, a new constant thrust switching algorithm is proposed by using the impulse compensation method. Finally, simulation results and performance analysis validate the effectiveness of the proposed approach.

Background CyclinD1 is crucial for cell cycling and can regulate the expression of Dicer, a crucial regulator of microRNA maturation. However, little is known on how CyclinD1 regulates Dicer and miRNA expression, and the progression of intrahepatic cholangiocarcinoma (ICC). Methods The expression of CyclinD1 and Dicer in non-tumor cholangiocytes, ICC cells and tissues as well as their association with clinicopathological characteristics and survival were examined. The potential mechanisms by which CyclinD1 regulates Dicer and relative miRNA expression were determined by immunoprecipitation, ChIP sequence, BSP and luciferase reporter assays following induction of CyclinD1 over-expression or silencing and Dicer silencing. The impact of CyclinD1 and/or Dicer silencing on the growth of ICC was tested in vivo. Results Up-regulated CyclinD1 was associated with down-regulated Dicer expression in ICC tissues and poorer overall survival in patients with ICC. CyclinD1 interacted with the nuclear H3K9me3 and SUV39H1 and bound to the Dicer promoter to increase its CpG island methylation in ICC cells. Functionally, CyclinD1 silencing inhibited the malignancy of ICC cells, which were mitigated partially by Dicer silencing in ICC cells. Dicer silencing down-regulated miR-1914-5p and miR-541-5p expression, which targeted and promoted CyclinD1 and CDK6 expression in ICC cells. Conclusions Our findings uncover that CyclinD1 inhibits Dicer expression by chromatin modification to reduce miR-1914-5p/miR-541-5p expression, which positively-feedback enhances CyclinD1 and CDK6 expression and progression of ICC.

Beijing is a megacity suffering from acute water shortage. The characterization of karst aquifers in Beijing's outlying districts is critical to inform sustainable policies and practices in groundwater development. We captured spring hydrogeochemical dynamics during an intense storm event (721 Storm) by installing a data logger in the weir, which presents an opportunity for defining and characterizing the recharging sources of discharge from Black Dragon (BD) springshed. Multivariate techniques (including PCA, 2D-HCA heat map, and piper diagram) were used to characterize the waters and investigate their geochemical evolution. The results in combination with hydrological evidence suggest BD Spring was dominated by interaction with dolomite host limestone rock during dry season, whereas it was fed by a second water supply (dolomite aquifer) during storm events. The infiltration coefficients were calculated based on the water balance model, and it was found that the 721 Storm has resulted in less infiltration due to the high rainfall intensity. We presented a novel methodology, combining high-frequency data sets and routine manual flow measurements with traditional geochemical sampling techniques. This methodology appears to be very efficient at characterizing a karst aquifer and seems to be potentially applicable to other karst aquifers.

A modified Water-Table Fluctuation (WTF) method is developed to quantitatively characterize the regional groundwater discharge patterns in stressed aquifers caused by intensive agricultural pumping. Two new parameters are defined to express the secondary information in the observed data. One is infiltration efficiency and the other is discharge modulus (recurring head loss due to aquifer discharge). An optimization procedure is involved to estimate these parameters, based on continuous groundwater head measurements and precipitation records. Using the defined parameters and precipitation time series, water level changes are calculated for individual wells with fidelity. The estimated parameters are then used to further address the characterization of infiltration and to better quantify the discharge at the regional scale. The advantage of this method is that it considers recharge and discharge simultaneously, whereas the general WTF methods mostly focus on recharge. In the case study, the infiltration efficiency reveals that the infiltration is regionally controlled by the intrinsic characteristics of the aquifer, and locally distorted by engineered hydraulic structures that alter surface water-groundwater interactions. The seasonality of groundwater discharge is characterized by the monthly discharge modulus. These results from individual wells are clustered into groups that are consistent with the local land use pattern and cropping structures.

Software-Defined Network (SDN) has emerged as an innovation framework with a separated control and data layer running upon Openflow protocol, and simplifies the deployment of the network. Though Software-Defined Network surely solves the specific problems that exist in traditional network, the evaluation on it is necessary. Currently, SDN-enable devices are rare and expensive. Existing simulators show a good performance in several aspects: realism, fidelity, arbitrary topology designing, and tools for debugging. So using software to simulate, monitor, and debug SDN is a relatively better and more economical approach. But the limitations on software are also noticeable when the focus shifts to a large-scale network designing, networks with multiple controllers, load simulation, and flexibility of testbed. Apart from those limitations, the debug information is still far from details expected. All those confine SDN experiments into a tiny space. To solve problems above, in this paper, we propose a scalable testbed framework for SDN simulations with multiple controllers, namely SFMC. Different from existing simulators, SFMC encompasses six modules. It ameliorates many functions as providing a clear structure, supporting several link types (including wireless link), extending the topology scalability into infinitive, enabling multiple controllers, and combining virtual and physical devices. We verify the performance of this testbed and show our experimental results from different scenarios, such as the flow simulation, WiFi environment, and multiple controllers.

A robust constant thrust rendezvous approach under thrust failure is proposed based on the relative motion dynamic model. Firstly, the design problem is cast into a convex optimization problem by introducing a Lyapunov function subject to linear matrix inequalities. Secondly, the robust controllers satisfying the requirements can be designed by solving this optimization problem. Then, a new algorithm of constant thrust fitting is proposed through the impulse compensation and the fuel consumption under the theoretical continuous thrust and the actual constant thrust is calculated and compared by using the method proposed in this paper. Finally, the proposed method having the advantage of saving fuel is proved and the actual constant thrust switch control laws are obtained through the isochronous interpolation method, meanwhile, an illustrative example is provided to show the effectiveness of the proposed control design method.

Global Navigation Satellite System-Reflection (GNSS-R) technology has attracted more and more attention in remote sensing and navigation field, especially in the ocean remote sensing. A feasible GNSS-R model based on reverse thinking method was proposed in our previous work. In this paper, in order to make the model applicable to the case of higher wind speed, we presented an improved GNSS-R model by expanding the range of time delay from 5 to 9 chips. A mathematical derivation was built to guide the design of the model. The number of reflected signals was 30 and the delay interval was 0.3 chip in the newly built model by optimizing the accuracy and computation of the model. Moreover, a GNSS-R software simulator was designed based on the improved GNSS-R model. The simulation reflected signals were compared with the experimental data collected in Yantai, Shandong province. Good agreement was found in the simulation results and experimental data, and the correlation coefficient between two correlation power curves was 0.9964, with the error in retrieving wind speed of 0.8 m/s. These results proved that the improved GNSS-R model and the simulator design can be applied in simulation of GNSS ocean reflected signals.

INTRODUCTION Hepatic haemangiomas are the most common benign liver tumours. They can be treated with surgical resection such as enucleation or hepatectomy if necessary. However, controversy remains over the clinical outcome and safety of these two methods. In this study, we performed a comprehensive meta-analysis to compare the efficacy of liver resection with enucleation for giant haemangiomas. METHODS The online databases PubMed, Embase and CNKI (China National Knowledge Infrastructure) were searched for relevant original articles. We compared operation time, blood loss, transfusion requirements, inflow occlusion time and postoperative complications between enucleation and hepatectomy. RESULTS Seven controlled clinical trials met the predefined inclusion criteria. Analysis indicated that the enucleation group had significantly shorter operation time (weighted mean difference, WMD –28.22, 95% confidence interval, CI, –54.82 to –1.62), less blood loss (WMD –395.92, 95% CI –521.25 to –270.58) and fewer complications (odds ratio, OR, 0.47, 95 % CI 0.34 to 0.65). There were no significant differences between enucleation and hepatectomy with regard to transfusion requirements (OR 0.61, 95% CI 0.22 to 1.68) and inflow occlusion time (WMD 7.91, 95% CI –5.62 to 21.44). CONCLUSIONS Enucleation has advantages over hepatectomy in relation to operation time, blood loss and complications. Enucleation is a safe and effective treatment for giant hepatic haemangioma.

INTRODUCTION Benign and malignant primary retroperitoneal tumours (PRT) have different clinical manifestations and pathological characteristics. We explore the characteristics and evaluate the value of computed tomography (CT) for PRT. METHODS Fifty-six benign and fifty-seven malignant PRT with clinical, radiographic and surgical data were retrospectively investigated. Statistical analysis was carried out using SPSS software. RESULTS We found that mean size of benign tumours was 12.4 ± 7.7cm but 20.7 ± 11.6cm in malignant cases (P < 0.05). The accuracy of CT localisation was approximately 70%. The sensitivity and specificity of CT diagnosis for benign tumours were 96% and 85%, respectively; 51 (91%) underwent complete resection among benign cases but 42 (74%) in malignant cases (P < 0.05). Sensitivity of CT evaluation for invaded organs and vessels was 50% and 65%, respectively, and specificity was 88% and 81%, respectively. CONCLUSIONS Large size, no capsule, irregular margin, heterogeneous density and specific enhancement pattern on CT are highly suggestive of malignancy. CT is the most useful tool in assessing the size and characteristics of PRT but it does not have the sensitivity to assess the involvement of organs and vessels.

In the application of GNSS-R technology, the reflection signal source is needed to test the receiver in order to reduce costs. The signal model is the core of GNSS-R signal source. In this paper, GPS reflection signal from sea surface is taken as the research object. Firstly, the appropriate signal phases are selected according to the correlation power distribution of the reflection signal in the ZV model. Then the equations are solved. And the result curve of the equations is approximated by numerical fitting method, so as to obtain the normalized amplitude corresponding to different phases. Finally, the time delay and doppler frequency offset of the specular point signal, with respect to the direct signal, are calculated. Thereby, three-dimensional parameters of the 100 reflection signals, namely the pseudo-code delay, Doppler frequency and amplitude, could be obtained. And it is verified by the correlation processing, which show the effectiveness of the method.

Heterochromatin protein 1α (HP1α) is a gene that mediates chromatin conformation, gene silencing and cancer progression. However, little is known regarding the impact of HP1α in the pathogenesis of cholangiocarcinoma (CCA). In the present study, we demonstrate that HP1α is significantly upregulated in CCA tissues and cell lines, while downregulation of HP1α leads to suppression of cell proliferation. Then we find that downregulation of HP1α can decrease H3K9me3 enrichment and DNA methylation rate of secreted frizzled-related protein 1 (SFRP1) promoter, resulting in restoring the expression of SFRP1. Moreover, restoration of SFRP1 expression can suppress CCA cells proliferation. These results provide a mechanistic understanding of the role of HP1α in the pathogenesis of CCA and may offer a novel therapeutic target in this disease.

In this paper, the relative position parameters of the chaser are obtained by using the vision measurement and the target departure manoeuvre positions are calculated through the isochronous interpolation method. A guidance algorithm for -V-bar constant thrust departure with consideration of the constraints of field of view and safety distance is investigated. New switching control laws under constant thrust are designed for departure manoeuvres of the chaser. The switching control laws are obtained based on the acceleration sequences and the on time of thrusters in three axes which can be respectively computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the on time of thrusters. On the basis of the toolbox of matlab, practical examples for simulation and application are given. The simulation results show that the proposed guidance algorithm can well satisfy the conditions for the constraints and can make sure the chaser departures from the target spacecraft safely.

In this paper, constant thrust rendezvous is studied and the optimal rendezvous time is calculated by using continuous genetic algorithm. Firstly, the relative position parameters of the target spacecraft are obtained by using the vision measurement and the target maneuver positions are calculated through the isochronous interpolation method. Then, the results of the calculation of constant thrust rendezvous is founded by processing with multivariate linear regression method. Next, a new switching control law is designed based on the thrust acceleration sequence and the on time of thrusters which can be computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the on time of thrusters. At last, a monte carlo analysis is performed to calculate the relative velocities at which the rendezvous maneuvers can be carried out and simulation examples are given to illustrate the validity of the method presented in this paper. The simulation results show that with the switching control law can ensure the success of the rendezvous.

In this paper, the collision avoidance maneuver under the chaser’s thruster failure in radial direction is investigated. First, based on the vision measurement, the relative position parameters of the target spacecraft are obtained and the target maneuvre positions are calculated through the isochronous interpolation method. Then, by using coupling effects, the thrusters working time intervals can be computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the thrusters working time intervals. Next, the switching control law under constant thrust is designed for active collision avoidance maneuvres along a specified trajectory. At last, a monte carlo analysis is performed to calculate the relative velocities at which there are the possibility of collision. The simulation results show that with the switching control law, the chaser will maneuver along the specified trajectory and the goal of the collision avoidance can be achieved.

In this paper, the relative position parameters of the target spacecraft are obtained by using the vision measurement and the target manoeuvre positions are calculated through the equidistant interpolation method. Furthermore, new switch control laws under constant thrust are designed for active collision avoidance manoeuvre of the chaser along a designated trajectory. The switch control laws are obtained based on the acceleration sequences and the working times of thrusters in three axes which can be, respectively, computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the working times. The simulation results show that, with the switch control laws, the chaser will manoeuvre along the designated trajectory when there is a possibility of collision.

A new switching control algorithm under constant thrust is designed for the chaser fast flying around the target spacecraft along a specified fly-around trajectory. The switching control laws are obtained based on the acceleration sequences and the on time of thrusters which can be computed by the time series analysis method. The perturbations and fuel consumptions are addressed during the computation of the on time of thrusters. Furthermore, the relative position parameters of the target spacecraft are obtained by using the vision measurement and the target fly-around positions are calculated through the isochronous interpolation method. The change of the relative position and the relative velocity of the chaser during the constant thrust fast fly-around are presented through simulation example. It is proved that, with the switching control laws, the chaser will fast fly around the target spacecraft along the specified fly-around trajectory.