Mobile edge computing （MEC） is a novel technique that can reduce mobiles＇ com- putational burden by tasks offioading, which emerges as a promising paradigm to provide computing capabilities in close proximity to mo...Mobile edge computing （MEC） is a novel technique that can reduce mobiles＇ com- putational burden by tasks offioading, which emerges as a promising paradigm to provide computing capabilities in close proximity to mobile users. In this paper, we will study the scenario where multiple mobiles upload tasks to a MEC server in a sing cell, and allocating the limited server resources and wireless chan- nels between mobiles becomes a challenge. We formulate the optimization problem for the energy saved on mobiles with the tasks being dividable, and utilize a greedy choice to solve the problem. A Select Maximum Saved Energy First （SMSEF） algorithm is proposed to realize the solving process. We examined the saved energy at different number of nodes and channels, and the results show that the proposed scheme can effectively help mobiles to save energy in the MEC system.展开更多
Background Multiple randomized clinical trials have demonstrated that drug eluting stents can significantly reduce the rates of restenosis and subsequent adverse events across lesion and patient. We investigated the m...Background Multiple randomized clinical trials have demonstrated that drug eluting stents can significantly reduce the rates of restenosis and subsequent adverse events across lesion and patient. We investigated the medium term clinical efficacy and safety of Firebird sirolimus eluting stent （SES） in coronary artery disease. Methods The sample was 509 consecutive patients with coronary artery disease （CAD） who were treated by Firebird SES and finished three-year clinical follow-up. The occurrences of major adverse cardiac events （MACE） and Academic Research Consortium defined stent thrombosis （ST） were evaluated in patients with and without diabetes mellitus. Results Three hundred and thirty three patients （65. 4%） were treated by Firebird SES by off label indications. Angiographic success was achieved in 98.3% of the lesions. MACE and target vessel revascularization rates at 6-month, 1 year＇s and 3 years＇ clinical follow-up were 2.4% and 1.4%, 4.1% and 2.8%, 7.9% and 5.1%, respectively. The cumulative 3-year MACE free survival rate was 92.1%. After 3 years, DM patients had significantly higher rates of MACE （13.7% vs 6.4%, P 〈0.05） and TVR （9.8% vs 4.0%, P 〈0.05） and the cumulative MACE free survival rate was very significantly lower in the DM group （86.4% vs 93;6%, P 〈0.05）. ST occurred in 7 patients （1.4%） at the end of 3 years＇ follow-up, 5 of them had definite ST with 4 cases presenting with myocardial reinfarction and 1 with unstable angina, the other 2 with probable ST had reinfarction in the stented coronary territory without angiographic follow-up. There was no difference in occurrence of ST between off label （1.5%） and on label groups （1.1%, P=-0.07）. Conclusions In daily practice, about 2/3 of patients were treated by Firebird SES by off label indications. Medium term clinical follow-up of 3 years indicated CAD patients treated by Firebird SES had a low MACE and acceptable ST rate. DM patients had higher rates of adverse events and than non DM.展开更多
A variation in the classical Turn extremal problem is studied. A simple graph G of order n is said to have property P k if it contains a clique of size k+1 as its subgraph. An n term nonincreasing nonnegative integer ...A variation in the classical Turn extremal problem is studied. A simple graph G of order n is said to have property P k if it contains a clique of size k+1 as its subgraph. An n term nonincreasing nonnegative integer sequence π=(d 1,d 2,...,d n) is said to be graphic if it is the degree sequence of a simple graph G of order n and such a graph G is referred to as a realization of π . A graphic sequence π is said to be potentially P k graphic if it has a realization G having property P k . The problem: determine the smallest positive even number σ(k,n) such that every n term graphic sequence π=(d 1,d 2,...,d n) without zero terms and with degree sum σ(π)=d 1+d 2+...+d n at least σ(k,n) is potentially P k graphic has been proved positive.展开更多
The aircraft antiskid braking system is an important hydraulic system for preventing tire bursts and ensuring safe take-off and landing. The brake system adjusts the force applied on the brake discs by controlling the...The aircraft antiskid braking system is an important hydraulic system for preventing tire bursts and ensuring safe take-off and landing. The brake system adjusts the force applied on the brake discs by controlling the brake pressure. Traditional aircraft antiskid braking systems achieve antiskid performance by controlling the braking pressure with an electrohydraulic servo valve.Because the pilot stage of an electrohydraulic servo valve is easily blocked by carbonized hydraulic oil, the servo valve would become a dangerous weak point for aircraft safety. This paper proposes a new approach that uses an on-off valve array to replace the servo valve for pressure control. Based on this new pressure control component, an efficient antiskid control algorithm that can utilize this discontinuous feature is proposed. Furthermore, the algorithm has the ability to identify the runway circumstances. To overcome the discontinuity in the process of using an on-off valve array, the Filippov framework is introduced. The conditions of convergence of the system are also discussed.The results of the digital simulations and the hardware-in-the-loop(HIL) braking experiments are used to verify the efficiency and stability of the proposed control algorithm. The method also proves that the on-off valve array can replace the servo valve perfectly as a new type of antiskid braking pressure control component.展开更多
Fan blade off（FBO） from a running turbofan rotor will introduce sudden unbalance into the dynamical system,which will lead to the rub-impact,the asymmetry of rotor and a series of interesting dynamic behavior.The pa...Fan blade off（FBO） from a running turbofan rotor will introduce sudden unbalance into the dynamical system,which will lead to the rub-impact,the asymmetry of rotor and a series of interesting dynamic behavior.The paper first presents a theoretical study on the response excited by sudden unbalance.The results reveal that the reaction force of the bearing located near the fan could always reach a very high value which may lead to the crush of ball,journal sticking,high stress on the other components and some other failures to endanger the safety of engine in FBO event.Therefore,the dynamic influence of a safety design named ‘‘fusing＂ is investigated by mechanism analysis.Meantime,an explicit FBO model is established to simulate the FBO event,and evaluate the effectiveness and potential dynamic influence of fusing design.The results show that the fusing design could reduce the vibration amplitude of rotor,the reaction force on most bearings and loads on mounts,but the sudden change of support stiffness induced by fusing could produce an impact effect which will couple with the influence of sudden unbalance.Therefore,the implementation of the design should be considered carefully with optimized parameters in actual aero-engine.展开更多
The work-class remotely-operated-underwater-vehicles（ROVs） are mainly driven by hydraulic propulsion system,and the effeciency of hydraulic propulsion system is an important performance index of ROVs.However,the eff...The work-class remotely-operated-underwater-vehicles（ROVs） are mainly driven by hydraulic propulsion system,and the effeciency of hydraulic propulsion system is an important performance index of ROVs.However,the efficiency of traditional hydraulic propulsion system controlled by throttle valves is too low.Therefore,in this paper,for small and medium ROVs,a novel propulsion system with higher efficiency based on high speed on/off valve control hydraulic propeller is proposed.To solve the conflict between large flow rate and high frequency response performance,a two-stage high speed on/off valve-motor unit with large flow rate and high response speed simultaneously is developed.Through theoretical analysis,an effective fluctuation control method and a novel pulse-width-pulse-frequency-modulation（PWPFM） are introduced to solve the conflict among inherently fluctuation,valve dynamic performance and system efficiency.A simulation model is established to evaluate the system performance.To prove the advantage of system in energy saving,and test the dynamic control performance of high speed on/off valve control propeller,a test setup is developed and a series of comparative experiments is completed.The smimulation and experiment results show that the two-stage high speed on/off valve has an excellent dynamic response performance,and can be used to realize high accuracy speed control.The experiment results prove that the new propulsion system has much more advantages than the traditional throttle speed regulation system in energy saving.The lowest efficiency is more than 40%.The application results on a ROV indicate that the high speed on/off valve control propeller system has good dynamic and steady-state control performances.Its transient time is only about 1 s-1.5 s,and steady-state error is less than 5%.Meanwhile,the speed fluctuation is small,and the smooth propeller speed control effect is obtained.On the premise of good propeller speed control performance,the proposed high speed on/off valve control propell展开更多
This article introduces a computer numerical control （CNC）-based open hardware architecture system to realize the special functions of automated tape-laying （ATL） in a numerical control system. It associates a pro...This article introduces a computer numerical control （CNC）-based open hardware architecture system to realize the special functions of automated tape-laying （ATL） in a numerical control system. It associates a programmable multi-axis controller （PMAC） as the motion control unit with programmable numerical controllers （PCL-725, PCL-730） for on-off control. To bring about synchronized movements of the main 5-axis tape-laying head system and the 3-axis ultrasonic tape-cutting sub-system, the tracking-control method associated with time-based mode attributed to PMAC is applied in different cases. In addition, with the goal of realizing real-time tasks in the software system such as synchronizing motion control and on-off control, the real-time Win 2000 system is adopted. As a device driver for PMAC and PCL, a user graphical interface and a numerical control program interpretation module are also designed. This system is helpful to solve complicated problems in designing numerical controls for ATL such as ensuring high requirements for precise machine control and synchronization of motion control and on-off control.展开更多
Walled-off pancreatic necrosis and a pancreatic abscess are the most severe complications of acute pancreatitis. Surgery in such critically ill patients is often associated with significant morbidity and mortality wit...Walled-off pancreatic necrosis and a pancreatic abscess are the most severe complications of acute pancreatitis. Surgery in such critically ill patients is often associated with significant morbidity and mortality within the first few weeks after the onset of symptoms. Minimal invasive approaches with high success and low mortality rates are therefore of considerable interest. Endoscopic therapy has the potential to offer safe and effective alternative treatment. We report here on 3 consecutive patients with infected walled-off pancreatic necrosis and 1 patient with a pancreatic abscess who underwent direct endoscopic necrosectomy 19-21 d after the onset of acute pancreatitis. The infected pancreatic necrosis or abscess was punctured transluminally with a cystostome and, after balloon dilatation, a non-covered self-expanding biliary metal stent was placed into the necrotic cavity. Following stent deployment, a nasobiliary pigtail catheter was placed into the cavity to ensure continuous irrigation. After 5-7 d, the metal stent was removed endoscopically and the necrotic cavity was entered with a therapeutic gastroscope. Endoscopic debridement was performed via the simultaneous application of a high-flow water-jet system; using a flush knife, a Dormia basket, and hot biopsy forceps. The transluminal endotherapy was repeated 2-5 times daily during the next 10 d. Supportive care included parenteral antibiotics and jejunal feeding. All patients improved dramatically and with resolution of their septic conditions; 3 patients were completely cured without any further complications or the need for surgery. One patient died from a complication of prolonged ventilation severe bilateral pneumonia, not related to the endoscopic procedure. No procedure related complications were observed. Transluminal endoscopic necrosectomy with temporary application of a self-expanding metal stent and a high-flow water-jet system shows promise for enhancing the potential of this endoscopic approach in patients with walled-off pancreatic nec展开更多
A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial ten...A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial tension/compression and bending/shearing couplings as well as the mutual reactions of fiber yarns. The method determining microstructure by using woven parameters is described for a typical 3D woven composite material. An analytical cell, constructed by a minimum periodic section of yarn and interlayer matrix, is adopted. Micro stresses in the cell under in-plane tensile loading are obtained by using the proposed beam model and macro modulus is then obtained by the averaging method. Material tests and a 2D micro FEM analysis are made to evaluate this model. Analyses reveal that micro stress caused by tensile/bending coupling effect is not negligible in the stress analysis.展开更多
Alkali and Co^(2+)co-modulation has seldom been investigated as a prospective strategy to achieve high-efficient microwave absorbing(MA)materials.In this work,a new alkali and Co ion exchange co-modulation strategy wa...Alkali and Co^(2+)co-modulation has seldom been investigated as a prospective strategy to achieve high-efficient microwave absorbing(MA)materials.In this work,a new alkali and Co ion exchange co-modulation strategy was first reported,leading to broadband MA capacity through simultaneous manipulating multiple factors,such as composition,micromorphology,and heterogeneous interface.And enhancements in impedance matching and magnetic-dielectric loss were synergistically realized.Consequently,the optimized FeCo alloy@porous carbon(FPC)nanocomposite with the alkali regulation delivered an effective absorption bandwidth(EAB)of 6.72 GHz,making it the merely single FeCo-based metal-organic framework derived FPC absorber with a low filler content of 15 wt.%.Interestingly,the nanocomposites by ion exchange strategy realized the switchable“on/off”states on electromagnetic response.Furthermore,the radar cross-section(RCS)reduction value of the products reached 25.6 dB·m^(2) under the incident angle of 0°.In brief,this work not only offers the special role of alkali and Co^(2+)co-modulation in composition regulation,structure design,and MA capacity,but also provides a reliable strategy to develop smart nano-absorbers to cope with electromagnetic pollution issues.展开更多
Some variational data assimilation （VDA） problems of time- and space-discrete models with on/off parameterizations can be regarded as non-smooth optimization problems. Same as the sub-gradient type method, intellige...Some variational data assimilation （VDA） problems of time- and space-discrete models with on/off parameterizations can be regarded as non-smooth optimization problems. Same as the sub-gradient type method, intelligent optimization algorithms, which are widely used in engineering optimization, can also be adopted in VDA in virtue of their no requirement of cost function＇s gradient （or sub-gradient） and their capability of global convergence. Two typical intelligent optimization algorithms, genetic algorithm （GA） and particle swarm optimization （PSO）, are introduced to VDA of modified Lorenz equations with on-off parameterizations, then two VDA schemes are proposed, that is, GA based VDA （GA-VDA） and PSO based VDA （PSO-VDA）. After revealing the advantage of GA and PSO over conventional adjoint methods in the ability of global searching at the existence of cost function＇s discontinuity induced by on-off switches, sensitivities of GA-VDA and PSO-VDA to population size, observational noise, model error and observational density are detailedly analyzed. It＇s shown that, in the context of modified Lorenz equations, with proper population size, GA-VDA and PSO-VDA can effectively estimate the global optimal solution, while PSO-VDA consumes much less computational time than GA-VDA with the same population size, and requires a much lower population size with nearly the same results, both methods are not very sensitive to observation noise and model error, while PSO-VDA shows a better performance with observational noise than GA-VDA. It is encouraging that both methods are not sensitive to observational density, especially PSO-VDA, using which almost the same perfect assimilation results can be obtained with comparatively sparse observations.展开更多
The aim of non-intrusive appliance load monitoring （NIALM） is to disaggregate the energy consumption of individual electrical appliances from total power consumption utilizing non-intrusive methods. In this paper, a...The aim of non-intrusive appliance load monitoring （NIALM） is to disaggregate the energy consumption of individual electrical appliances from total power consumption utilizing non-intrusive methods. In this paper, a systematic approach to 0N-0FF event detection and clustering analysis for NIALM were presented. From the aggregate power consumption data set, the data are passed through median filtering to reduce noise and prepared for the event detection algorithm. The event detection algorithm is to determine the switching of ON and OFF status of electrical appliances. The goodness- of-fit （GOF） methodology is the event detection algorithm implemented. After event detection, the events detected were paired into ON-0FF pairing appliances. The results from the ON-OFF pairing algorithm were further clustered in groups utilizing the K-means clustering analysis. The K- means clustering were implemented as an unsupervised learning methodology for the clustering analysis. The novelty of this paper is the determination of the time duration an electrical appliance is turned ON through combination of event detection, ON-OFF pairing and K- means clustering. The results of the algorithm implemen- tation were discussed and ideas on future work were also proposed.展开更多
An interdisciplinary comprehensive survey was conducted in August 2000 with the modern measurement instruments off the Changjiang River. The analysis of the observation data shows that there exist two sources of phyto...An interdisciplinary comprehensive survey was conducted in August 2000 with the modern measurement instruments off the Changjiang River. The analysis of the observation data shows that there exist two sources of phytoplankton blooms off the Changjiang River. The one with wider spatial extent and stronger intensity appears in the surface plume due to photosyn- thesis produced by the eutrophication brought by a huge amount of nutrient load via the Chang- jiang River and well light penetration because of lower turbidity seawater. Photosynthesis pro- duces chlorophyll-a (Chl-a), meanwhile releases oxygen and absorbs carbon dioxide, so the high Chl-a concentration distribution corresponds to the distribution of high dissolved oxygen and pH. The other with smaller spatial extent and weaker intensity exists in the thermocline in the Taiwan Warm Current (TWC), but the high Chl-a concentration does not correspond to the high dissolved oxygen and pH, which may be a result of long distance advection by the TWC. The eutrophica- tion associated with the huge amount of nutrient flowing into the sea via the Changjiang River is the main cause of the red tide bloom in the area off the Changjiang River, the red tide that oc- curred along the Fujian and Zhejiang coast can influence the area off the Changjiang River pos- sibly via the TWC. The distributions of current simulated by a three-dimension numerical model support the above conclusion.展开更多
Since the late 1990s corneal crosslinking(CXL)has been proposed as a new possibility to stop progression of keratoconus or secondary corneal ectasia,with the promising aim to prevent progressive visual loss due to the...Since the late 1990s corneal crosslinking(CXL)has been proposed as a new possibility to stop progression of keratoconus or secondary corneal ectasia,with the promising aim to prevent progressive visual loss due to the evolution of the pathology and to delay or avoid invasive surgical procedures such as corneal transplantation.The possibility of strengthening corneal tissue by means of a photochemical reaction of corneal collagen by the combined action of Riboflavin and ultraviolet A irradiation(UVA),radically modified the conservative management of progressive corneal ectasia.This is a review of the state of the art of CXL,reporting basic and clinical evidence.The paper describes basic principles,advantages and limits of different CXL techniques and possible future evolution of the procedure.展开更多
A variant constrained genetic algorithm （VCGA） for effective tracking of conditional nonlinear optimal perturbations （CNOPs） is presented. Compared with traditional constraint handling methods, the treatment of th...A variant constrained genetic algorithm （VCGA） for effective tracking of conditional nonlinear optimal perturbations （CNOPs） is presented. Compared with traditional constraint handling methods, the treatment of the constraint condition in VCGA is relatively easy to implement. Moreover, it does not require adjustments to indefinite pararneters. Using a hybrid crossover operator and the newly developed multi-ply mutation operator, VCGA improves the performance of GAs. To demonstrate the capability of VCGA to catch CNOPS in non-smooth cases, a partial differential equation, which has ＂on off＂ switches in its forcing term, is employed as the nonlinear model. To search global CNOPs of the nonlinear model, numerical experiments using VCGA, the traditional gradient descent algorithm based on the adjoint method （ADJ）, and a GA using tournament selection operation and the niching technique （GA-DEB） were performed. The results with various initial reference states showed that, in smooth cases, all three optimization methods are able to catch global CNOPs. Nevertheless, in non-smooth situations, a large proportion of CNOPs captured by the ADJ are local. Compared with ADJ, the performance of GA-DEB shows considerable improvement, but it is far below VCGA. Further, the impacts of population sizes on both VCGA and GA-DEB were investigated. The results were used to estimate the computation time of ~CGA and GA-DEB in obtaining CNOPs. The computational costs for VCGA, GA-DEB and ADJ to catch CNOPs of the nonlinear model are also compared.展开更多
The sedimentary record of mud areas is an important carrier of information on the Holocene evolution of marine environments. Based on fine interpretations of the shallow stratigraphic section data, a small mud deposit...The sedimentary record of mud areas is an important carrier of information on the Holocene evolution of marine environments. Based on fine interpretations of the shallow stratigraphic section data, a small mud deposit area has been found in the southern coastal waters off Shandong Peninsula. This mud area is mainly distributed in coastal waters north of Laoshantou to the vicinity of Rushan Estuary. Overall, it is parallel to the coastline and spreads in a banded pattern, gradually thinning from offshore to the sea. The isopach map of depth distribution is parallel with the shoreline, and the depocenter lies in coastal waters of the Aoshan Bay where the maximum thickness is up to 22.5 m. Accelerator mass spectrometry（AMS） ^（14）C dating shows that the mud area was formed in the Holocene. The test data of surface sediments from the mud area, including particle size, mineral characteristics, and rare earth element contents, are used in comparisons with the composition of materials from the major surrounding medium and small rivers flowing into the sea and the Huanghe（Yellow） River. In this paper, the sedimentary characteristics and provenance of the mud deposit area are discussed. The results show that the formation of this mud area resulted from the joint action of the Huanghe River and surrounding rivers flowing into the sea.展开更多
Global vegetation photosynthesis and productivity have increased substantially since the 1980s,but this trend is heterogeneous in both time and space.Here,we categorize the secular trend in global vegetation greenness...Global vegetation photosynthesis and productivity have increased substantially since the 1980s,but this trend is heterogeneous in both time and space.Here,we categorize the secular trend in global vegetation greenness into sustained greening,sustained browning and greening-to-browning.We found that by 2016,increased global vegetation greenness had begun to level off,with the area of browning increasing in the last decade,reaching 39.0 million km^(2)(35.9%of the world’s vegetated area).This area is larger than the area with sustained increasing growth(27.8 million km^(2),26.4%);thus,12.0%±3.1%(0.019±0.004 NDVI a^(-1))of the previous earlier increase has been offset since 2010(2010–2016,P<0.05).Global gross primary production also leveled off,following the trend in vegetation greenness in time and space.This leveling off was caused by increasing soil water limitations due to the spatial expansion of drought,whose impact dominated over the impacts of temperature and solar radiation.This response of global gross primary production to soil water limitation was not identified by land submodels within Earth system models.Our results provide empirical evidence that global vegetation greenness and primary production are offset by water stress and suggest that as global warming continues,land submodels may overestimate the world’s capacity to take up carbon with global vegetation greening.展开更多
There is a relatively complex flow state inside the high speed on-off valve,which often produces low pressure area and oil reflux in the high-speed opening and closing process of the spool,causing cavitation and vorte...There is a relatively complex flow state inside the high speed on-off valve,which often produces low pressure area and oil reflux in the high-speed opening and closing process of the spool,causing cavitation and vortex and other phenomena.These phenomena will affect the stability of the internal flow field of the plate valve and the flow characteristics of the high speed on-off valve.Aiming at the problems of small flow rate and instability of internal flow field,a new spool structure was designed.The flow field models of two-hole and three-hole plate spools with different openings were established,and software ANSYS Workbench was chosen to mesh the model.The standard k−εturbulence model was selected for numerical simulation using FLUENT software.The pressure distribution and velocity distribution under the same pressure and different opening degree were obtained.The structure and parameters of the optimization model were also obtained.The stability analysis of flow field under different pressure was carried out.The results demonstrate that the three-hole spool has a similar flow field change with the two-hole spool,but it does not create a low pressure zone,and the three-hole spool can work stably at 2 MPa or less.This method improves the appearance of low pressure area and oil backflow in the process of high speed opening and closing of spool.The stability of flow field and the flow rate of high speed switch valve are improved.Finally,the products designed in this paper are compared with existing hydraulic valve products.The results show that the three-hole plate type high speed on-off valve designed in this paper maintains the stability of the internal flow field under the condition of 200 Hz and large opening degree,and realizes the increase of flow rate.展开更多
基金supported by NSFC(No. 61571055)fund of SKL of MMW (No. K201815)Important National Science & Technology Specific Projects(2017ZX03001028)
文摘Mobile edge computing （MEC） is a novel technique that can reduce mobiles＇ com- putational burden by tasks offioading, which emerges as a promising paradigm to provide computing capabilities in close proximity to mobile users. In this paper, we will study the scenario where multiple mobiles upload tasks to a MEC server in a sing cell, and allocating the limited server resources and wireless chan- nels between mobiles becomes a challenge. We formulate the optimization problem for the energy saved on mobiles with the tasks being dividable, and utilize a greedy choice to solve the problem. A Select Maximum Saved Energy First （SMSEF） algorithm is proposed to realize the solving process. We examined the saved energy at different number of nodes and channels, and the results show that the proposed scheme can effectively help mobiles to save energy in the MEC system.
文摘Background Multiple randomized clinical trials have demonstrated that drug eluting stents can significantly reduce the rates of restenosis and subsequent adverse events across lesion and patient. We investigated the medium term clinical efficacy and safety of Firebird sirolimus eluting stent （SES） in coronary artery disease. Methods The sample was 509 consecutive patients with coronary artery disease （CAD） who were treated by Firebird SES and finished three-year clinical follow-up. The occurrences of major adverse cardiac events （MACE） and Academic Research Consortium defined stent thrombosis （ST） were evaluated in patients with and without diabetes mellitus. Results Three hundred and thirty three patients （65. 4%） were treated by Firebird SES by off label indications. Angiographic success was achieved in 98.3% of the lesions. MACE and target vessel revascularization rates at 6-month, 1 year＇s and 3 years＇ clinical follow-up were 2.4% and 1.4%, 4.1% and 2.8%, 7.9% and 5.1%, respectively. The cumulative 3-year MACE free survival rate was 92.1%. After 3 years, DM patients had significantly higher rates of MACE （13.7% vs 6.4%, P 〈0.05） and TVR （9.8% vs 4.0%, P 〈0.05） and the cumulative MACE free survival rate was very significantly lower in the DM group （86.4% vs 93;6%, P 〈0.05）. ST occurred in 7 patients （1.4%） at the end of 3 years＇ follow-up, 5 of them had definite ST with 4 cases presenting with myocardial reinfarction and 1 with unstable angina, the other 2 with probable ST had reinfarction in the stented coronary territory without angiographic follow-up. There was no difference in occurrence of ST between off label （1.5%） and on label groups （1.1%, P=-0.07）. Conclusions In daily practice, about 2/3 of patients were treated by Firebird SES by off label indications. Medium term clinical follow-up of 3 years indicated CAD patients treated by Firebird SES had a low MACE and acceptable ST rate. DM patients had higher rates of adverse events and than non DM.
文摘A variation in the classical Turn extremal problem is studied. A simple graph G of order n is said to have property P k if it contains a clique of size k+1 as its subgraph. An n term nonincreasing nonnegative integer sequence π=(d 1,d 2,...,d n) is said to be graphic if it is the degree sequence of a simple graph G of order n and such a graph G is referred to as a realization of π . A graphic sequence π is said to be potentially P k graphic if it has a realization G having property P k . The problem: determine the smallest positive even number σ(k,n) such that every n term graphic sequence π=(d 1,d 2,...,d n) without zero terms and with degree sum σ(π)=d 1+d 2+...+d n at least σ(k,n) is potentially P k graphic has been proved positive.
基金the Science and Technology on Aircraft Control Laboratorythe National Nature Science Foundation of China (Nos. 51775014 and 51890882)
文摘The aircraft antiskid braking system is an important hydraulic system for preventing tire bursts and ensuring safe take-off and landing. The brake system adjusts the force applied on the brake discs by controlling the brake pressure. Traditional aircraft antiskid braking systems achieve antiskid performance by controlling the braking pressure with an electrohydraulic servo valve.Because the pilot stage of an electrohydraulic servo valve is easily blocked by carbonized hydraulic oil, the servo valve would become a dangerous weak point for aircraft safety. This paper proposes a new approach that uses an on-off valve array to replace the servo valve for pressure control. Based on this new pressure control component, an efficient antiskid control algorithm that can utilize this discontinuous feature is proposed. Furthermore, the algorithm has the ability to identify the runway circumstances. To overcome the discontinuity in the process of using an on-off valve array, the Filippov framework is introduced. The conditions of convergence of the system are also discussed.The results of the digital simulations and the hardware-in-the-loop(HIL) braking experiments are used to verify the efficiency and stability of the proposed control algorithm. The method also proves that the on-off valve array can replace the servo valve perfectly as a new type of antiskid braking pressure control component.
基金the financial support from the National Natural Science Foundation of China(Nos.51575022 and 51475021)
文摘Fan blade off（FBO） from a running turbofan rotor will introduce sudden unbalance into the dynamical system,which will lead to the rub-impact,the asymmetry of rotor and a series of interesting dynamic behavior.The paper first presents a theoretical study on the response excited by sudden unbalance.The results reveal that the reaction force of the bearing located near the fan could always reach a very high value which may lead to the crush of ball,journal sticking,high stress on the other components and some other failures to endanger the safety of engine in FBO event.Therefore,the dynamic influence of a safety design named ‘‘fusing＂ is investigated by mechanism analysis.Meantime,an explicit FBO model is established to simulate the FBO event,and evaluate the effectiveness and potential dynamic influence of fusing design.The results show that the fusing design could reduce the vibration amplitude of rotor,the reaction force on most bearings and loads on mounts,but the sudden change of support stiffness induced by fusing could produce an impact effect which will couple with the influence of sudden unbalance.Therefore,the implementation of the design should be considered carefully with optimized parameters in actual aero-engine.
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No.2006AA09Z215)
文摘The work-class remotely-operated-underwater-vehicles（ROVs） are mainly driven by hydraulic propulsion system,and the effeciency of hydraulic propulsion system is an important performance index of ROVs.However,the efficiency of traditional hydraulic propulsion system controlled by throttle valves is too low.Therefore,in this paper,for small and medium ROVs,a novel propulsion system with higher efficiency based on high speed on/off valve control hydraulic propeller is proposed.To solve the conflict between large flow rate and high frequency response performance,a two-stage high speed on/off valve-motor unit with large flow rate and high response speed simultaneously is developed.Through theoretical analysis,an effective fluctuation control method and a novel pulse-width-pulse-frequency-modulation（PWPFM） are introduced to solve the conflict among inherently fluctuation,valve dynamic performance and system efficiency.A simulation model is established to evaluate the system performance.To prove the advantage of system in energy saving,and test the dynamic control performance of high speed on/off valve control propeller,a test setup is developed and a series of comparative experiments is completed.The smimulation and experiment results show that the two-stage high speed on/off valve has an excellent dynamic response performance,and can be used to realize high accuracy speed control.The experiment results prove that the new propulsion system has much more advantages than the traditional throttle speed regulation system in energy saving.The lowest efficiency is more than 40%.The application results on a ROV indicate that the high speed on/off valve control propeller system has good dynamic and steady-state control performances.Its transient time is only about 1 s-1.5 s,and steady-state error is less than 5%.Meanwhile,the speed fluctuation is small,and the smooth propeller speed control effect is obtained.On the premise of good propeller speed control performance,the proposed high speed on/off valve control propell
基金National High-Tech Research and Development Program Special Foundation of China(2002AA334130)
文摘This article introduces a computer numerical control （CNC）-based open hardware architecture system to realize the special functions of automated tape-laying （ATL） in a numerical control system. It associates a programmable multi-axis controller （PMAC） as the motion control unit with programmable numerical controllers （PCL-725, PCL-730） for on-off control. To bring about synchronized movements of the main 5-axis tape-laying head system and the 3-axis ultrasonic tape-cutting sub-system, the tracking-control method associated with time-based mode attributed to PMAC is applied in different cases. In addition, with the goal of realizing real-time tasks in the software system such as synchronizing motion control and on-off control, the real-time Win 2000 system is adopted. As a device driver for PMAC and PCL, a user graphical interface and a numerical control program interpretation module are also designed. This system is helpful to solve complicated problems in designing numerical controls for ATL such as ensuring high requirements for precise machine control and synchronization of motion control and on-off control.
文摘Walled-off pancreatic necrosis and a pancreatic abscess are the most severe complications of acute pancreatitis. Surgery in such critically ill patients is often associated with significant morbidity and mortality within the first few weeks after the onset of symptoms. Minimal invasive approaches with high success and low mortality rates are therefore of considerable interest. Endoscopic therapy has the potential to offer safe and effective alternative treatment. We report here on 3 consecutive patients with infected walled-off pancreatic necrosis and 1 patient with a pancreatic abscess who underwent direct endoscopic necrosectomy 19-21 d after the onset of acute pancreatitis. The infected pancreatic necrosis or abscess was punctured transluminally with a cystostome and, after balloon dilatation, a non-covered self-expanding biliary metal stent was placed into the necrotic cavity. Following stent deployment, a nasobiliary pigtail catheter was placed into the cavity to ensure continuous irrigation. After 5-7 d, the metal stent was removed endoscopically and the necrotic cavity was entered with a therapeutic gastroscope. Endoscopic debridement was performed via the simultaneous application of a high-flow water-jet system; using a flush knife, a Dormia basket, and hot biopsy forceps. The transluminal endotherapy was repeated 2-5 times daily during the next 10 d. Supportive care included parenteral antibiotics and jejunal feeding. All patients improved dramatically and with resolution of their septic conditions; 3 patients were completely cured without any further complications or the need for surgery. One patient died from a complication of prolonged ventilation severe bilateral pneumonia, not related to the endoscopic procedure. No procedure related complications were observed. Transluminal endoscopic necrosectomy with temporary application of a self-expanding metal stent and a high-flow water-jet system shows promise for enhancing the potential of this endoscopic approach in patients with walled-off pancreatic nec
文摘A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial tension/compression and bending/shearing couplings as well as the mutual reactions of fiber yarns. The method determining microstructure by using woven parameters is described for a typical 3D woven composite material. An analytical cell, constructed by a minimum periodic section of yarn and interlayer matrix, is adopted. Micro stresses in the cell under in-plane tensile loading are obtained by using the proposed beam model and macro modulus is then obtained by the averaging method. Material tests and a 2D micro FEM analysis are made to evaluate this model. Analyses reveal that micro stress caused by tensile/bending coupling effect is not negligible in the stress analysis.
基金We are thankful for financial support from the National Nature Science Foundation of China(Nos.51971111 and 52273247)the Fund of Prospective Layout of Scientific Research for NUAA(Nanjing University of Aeronautics and Astronautics)(No.ILA220461A22)the facilities in the Center for Microscopy and Analysis at Nanjing University of Aeronautics and Astronautics.
文摘Alkali and Co^(2+)co-modulation has seldom been investigated as a prospective strategy to achieve high-efficient microwave absorbing(MA)materials.In this work,a new alkali and Co ion exchange co-modulation strategy was first reported,leading to broadband MA capacity through simultaneous manipulating multiple factors,such as composition,micromorphology,and heterogeneous interface.And enhancements in impedance matching and magnetic-dielectric loss were synergistically realized.Consequently,the optimized FeCo alloy@porous carbon(FPC)nanocomposite with the alkali regulation delivered an effective absorption bandwidth(EAB)of 6.72 GHz,making it the merely single FeCo-based metal-organic framework derived FPC absorber with a low filler content of 15 wt.%.Interestingly,the nanocomposites by ion exchange strategy realized the switchable“on/off”states on electromagnetic response.Furthermore,the radar cross-section(RCS)reduction value of the products reached 25.6 dB·m^(2) under the incident angle of 0°.In brief,this work not only offers the special role of alkali and Co^(2+)co-modulation in composition regulation,structure design,and MA capacity,but also provides a reliable strategy to develop smart nano-absorbers to cope with electromagnetic pollution issues.
基金funded by the National Natural Science Foundation of China(Grant No.40830955)
文摘Some variational data assimilation （VDA） problems of time- and space-discrete models with on/off parameterizations can be regarded as non-smooth optimization problems. Same as the sub-gradient type method, intelligent optimization algorithms, which are widely used in engineering optimization, can also be adopted in VDA in virtue of their no requirement of cost function＇s gradient （or sub-gradient） and their capability of global convergence. Two typical intelligent optimization algorithms, genetic algorithm （GA） and particle swarm optimization （PSO）, are introduced to VDA of modified Lorenz equations with on-off parameterizations, then two VDA schemes are proposed, that is, GA based VDA （GA-VDA） and PSO based VDA （PSO-VDA）. After revealing the advantage of GA and PSO over conventional adjoint methods in the ability of global searching at the existence of cost function＇s discontinuity induced by on-off switches, sensitivities of GA-VDA and PSO-VDA to population size, observational noise, model error and observational density are detailedly analyzed. It＇s shown that, in the context of modified Lorenz equations, with proper population size, GA-VDA and PSO-VDA can effectively estimate the global optimal solution, while PSO-VDA consumes much less computational time than GA-VDA with the same population size, and requires a much lower population size with nearly the same results, both methods are not very sensitive to observation noise and model error, while PSO-VDA shows a better performance with observational noise than GA-VDA. It is encouraging that both methods are not sensitive to observational density, especially PSO-VDA, using which almost the same perfect assimilation results can be obtained with comparatively sparse observations.
文摘The aim of non-intrusive appliance load monitoring （NIALM） is to disaggregate the energy consumption of individual electrical appliances from total power consumption utilizing non-intrusive methods. In this paper, a systematic approach to 0N-0FF event detection and clustering analysis for NIALM were presented. From the aggregate power consumption data set, the data are passed through median filtering to reduce noise and prepared for the event detection algorithm. The event detection algorithm is to determine the switching of ON and OFF status of electrical appliances. The goodness- of-fit （GOF） methodology is the event detection algorithm implemented. After event detection, the events detected were paired into ON-0FF pairing appliances. The results from the ON-OFF pairing algorithm were further clustered in groups utilizing the K-means clustering analysis. The K- means clustering were implemented as an unsupervised learning methodology for the clustering analysis. The novelty of this paper is the determination of the time duration an electrical appliance is turned ON through combination of event detection, ON-OFF pairing and K- means clustering. The results of the algorithm implemen- tation were discussed and ideas on future work were also proposed.
文摘An interdisciplinary comprehensive survey was conducted in August 2000 with the modern measurement instruments off the Changjiang River. The analysis of the observation data shows that there exist two sources of phytoplankton blooms off the Changjiang River. The one with wider spatial extent and stronger intensity appears in the surface plume due to photosyn- thesis produced by the eutrophication brought by a huge amount of nutrient load via the Chang- jiang River and well light penetration because of lower turbidity seawater. Photosynthesis pro- duces chlorophyll-a (Chl-a), meanwhile releases oxygen and absorbs carbon dioxide, so the high Chl-a concentration distribution corresponds to the distribution of high dissolved oxygen and pH. The other with smaller spatial extent and weaker intensity exists in the thermocline in the Taiwan Warm Current (TWC), but the high Chl-a concentration does not correspond to the high dissolved oxygen and pH, which may be a result of long distance advection by the TWC. The eutrophica- tion associated with the huge amount of nutrient flowing into the sea via the Changjiang River is the main cause of the red tide bloom in the area off the Changjiang River, the red tide that oc- curred along the Fujian and Zhejiang coast can influence the area off the Changjiang River pos- sibly via the TWC. The distributions of current simulated by a three-dimension numerical model support the above conclusion.
文摘Since the late 1990s corneal crosslinking(CXL)has been proposed as a new possibility to stop progression of keratoconus or secondary corneal ectasia,with the promising aim to prevent progressive visual loss due to the evolution of the pathology and to delay or avoid invasive surgical procedures such as corneal transplantation.The possibility of strengthening corneal tissue by means of a photochemical reaction of corneal collagen by the combined action of Riboflavin and ultraviolet A irradiation(UVA),radically modified the conservative management of progressive corneal ectasia.This is a review of the state of the art of CXL,reporting basic and clinical evidence.The paper describes basic principles,advantages and limits of different CXL techniques and possible future evolution of the procedure.
基金supported by the National Natural Science Foundation of China(Grant No.40975063)the National Natural Science Foundation of China(Grant No.41331174)
文摘A variant constrained genetic algorithm （VCGA） for effective tracking of conditional nonlinear optimal perturbations （CNOPs） is presented. Compared with traditional constraint handling methods, the treatment of the constraint condition in VCGA is relatively easy to implement. Moreover, it does not require adjustments to indefinite pararneters. Using a hybrid crossover operator and the newly developed multi-ply mutation operator, VCGA improves the performance of GAs. To demonstrate the capability of VCGA to catch CNOPS in non-smooth cases, a partial differential equation, which has ＂on off＂ switches in its forcing term, is employed as the nonlinear model. To search global CNOPs of the nonlinear model, numerical experiments using VCGA, the traditional gradient descent algorithm based on the adjoint method （ADJ）, and a GA using tournament selection operation and the niching technique （GA-DEB） were performed. The results with various initial reference states showed that, in smooth cases, all three optimization methods are able to catch global CNOPs. Nevertheless, in non-smooth situations, a large proportion of CNOPs captured by the ADJ are local. Compared with ADJ, the performance of GA-DEB shows considerable improvement, but it is far below VCGA. Further, the impacts of population sizes on both VCGA and GA-DEB were investigated. The results were used to estimate the computation time of ~CGA and GA-DEB in obtaining CNOPs. The computational costs for VCGA, GA-DEB and ADJ to catch CNOPs of the nonlinear model are also compared.
基金The National Natural Science Foundation of China(NSFC)under contract Nos 41376079 and 41276060the Marine Geology Survey Project under contract Nos GZH200900501 and GZH201400204the Foundation of the Shandong Provincial Key Laboratory of Marine Ecology and Environment&Disaster Prevention under contract No.201304
文摘The sedimentary record of mud areas is an important carrier of information on the Holocene evolution of marine environments. Based on fine interpretations of the shallow stratigraphic section data, a small mud deposit area has been found in the southern coastal waters off Shandong Peninsula. This mud area is mainly distributed in coastal waters north of Laoshantou to the vicinity of Rushan Estuary. Overall, it is parallel to the coastline and spreads in a banded pattern, gradually thinning from offshore to the sea. The isopach map of depth distribution is parallel with the shoreline, and the depocenter lies in coastal waters of the Aoshan Bay where the maximum thickness is up to 22.5 m. Accelerator mass spectrometry（AMS） ^（14）C dating shows that the mud area was formed in the Holocene. The test data of surface sediments from the mud area, including particle size, mineral characteristics, and rare earth element contents, are used in comparisons with the composition of materials from the major surrounding medium and small rivers flowing into the sea and the Huanghe（Yellow） River. In this paper, the sedimentary characteristics and provenance of the mud deposit area are discussed. The results show that the formation of this mud area resulted from the joint action of the Huanghe River and surrounding rivers flowing into the sea.
基金the National Key Research and Development Program of China(2017YFA0604700)the National Natural Science Foundation of China(41722104)+3 种基金the Key Research Project of Chinese Academy of Sciences(QYZDY-SSWDQC025 and 2019DC0027)supported by the European Research Council Synergy(ERC-2013-Sy G-610028 IMBALANCE-P)the Spanish Government(CGL2016-79835)the Catalan Government(SGR 2017-1005)。
文摘Global vegetation photosynthesis and productivity have increased substantially since the 1980s,but this trend is heterogeneous in both time and space.Here,we categorize the secular trend in global vegetation greenness into sustained greening,sustained browning and greening-to-browning.We found that by 2016,increased global vegetation greenness had begun to level off,with the area of browning increasing in the last decade,reaching 39.0 million km^(2)(35.9%of the world’s vegetated area).This area is larger than the area with sustained increasing growth(27.8 million km^(2),26.4%);thus,12.0%±3.1%(0.019±0.004 NDVI a^(-1))of the previous earlier increase has been offset since 2010(2010–2016,P<0.05).Global gross primary production also leveled off,following the trend in vegetation greenness in time and space.This leveling off was caused by increasing soil water limitations due to the spatial expansion of drought,whose impact dominated over the impacts of temperature and solar radiation.This response of global gross primary production to soil water limitation was not identified by land submodels within Earth system models.Our results provide empirical evidence that global vegetation greenness and primary production are offset by water stress and suggest that as global warming continues,land submodels may overestimate the world’s capacity to take up carbon with global vegetation greening.
基金Project(51975164)supported by the National Natural Science Foundation of ChinaProject(201908230358)supported by the China Scholarship CouncilProject supported by the Fundamental Research Foundation for Universities of Heilongjiang Province,China。
文摘There is a relatively complex flow state inside the high speed on-off valve,which often produces low pressure area and oil reflux in the high-speed opening and closing process of the spool,causing cavitation and vortex and other phenomena.These phenomena will affect the stability of the internal flow field of the plate valve and the flow characteristics of the high speed on-off valve.Aiming at the problems of small flow rate and instability of internal flow field,a new spool structure was designed.The flow field models of two-hole and three-hole plate spools with different openings were established,and software ANSYS Workbench was chosen to mesh the model.The standard k−εturbulence model was selected for numerical simulation using FLUENT software.The pressure distribution and velocity distribution under the same pressure and different opening degree were obtained.The structure and parameters of the optimization model were also obtained.The stability analysis of flow field under different pressure was carried out.The results demonstrate that the three-hole spool has a similar flow field change with the two-hole spool,but it does not create a low pressure zone,and the three-hole spool can work stably at 2 MPa or less.This method improves the appearance of low pressure area and oil backflow in the process of high speed opening and closing of spool.The stability of flow field and the flow rate of high speed switch valve are improved.Finally,the products designed in this paper are compared with existing hydraulic valve products.The results show that the three-hole plate type high speed on-off valve designed in this paper maintains the stability of the internal flow field under the condition of 200 Hz and large opening degree,and realizes the increase of flow rate.
