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  • Author: Zhao Liu x
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A Continuous-Time Distributed Algorithm for Solving a Class of Decomposable Nonconvex Quadratic Programming

Abstract

In this paper, a continuous-time distributed algorithm is presented to solve a class of decomposable quadratic programming problems. In the quadratic programming, even if the objective function is nonconvex, the algorithm can still perform well under an extra condition combining with the objective, constraint and coupling matrices. Inspired by recent advances in distributed optimization, the proposed continuous-time algorithm described by multi-agent network with consensus is designed and analyzed. In the network, each agent only accesses the local information of its own and from its neighbors, then all the agents in a connected network cooperatively find the optimal solution with consensus.

Open access
Image Fusion for Travel Time Tomography Inversion

Abstract

The travel time tomography technology had achieved wide application, the hinge of tomography was inversion algorithm, the ray path tracing technology had a great impact on the inversion results. In order to improve the SNR of inversion image, comprehensive utilization of inversion results with different ray tracing can be used. We presented an imaging fusion method based on improved Wilkinson iteration method. Firstly, the shortest path method and the linear travel time interpolation were used for forward calculation; then combined the improved Wilkinson iteration method with super relaxation precondition method to reduce the condition number of matrix and accelerate iterative speed, the precise integration method was used to solve the inverse matrix more precisely in tomography inversion process; finally, use wavelet transform for image fusion, obtain the final image. Therefore, the ill-conditioned linear equations were changed into iterative normal system through two times of treatment and using images with different forward algorithms for image fusion, it reduced the influence effect of measurement error on imaging. Simulation results showed that, this method can eliminate the artifacts in images effectively, it had extensive practical significance.

Open access
Modeling and Analysis of 12-Pulse Inverter in Shipboard or Aircraft

Abstract

With the development of DC distribution system within the isolated power system of a ship or an aircraft, more constant frequency loads will be supplied by inverters connected to DC main bus. In the operating mode conversion process of an isolated power system, inverters will inevitably suffer from serious disturbance and affect the stability of the system. Therefore, it is important to establish a model of the inverter that reflects its dynamic characteristics and based on which to conduct the stability analysis. This paper proposes a 12-pulse inverter model based on the generalized state space averaging (GSSA) method. This model can overcome the limitations of 12-pulse inverter state space averaging (SSA) model in transient analysis with good accuracy and fast analysis ability effectively. Three kinds of models for a 12-pulse aircraft inverter are built in MATLAB, namely GSSA model, SSA model and detail device model. The simulation results show the high accuracy of GSSA model in stability analysis. This study provides an effective analytical tool for stability analysis of 12-pulse inverter and also provides a reference for inverter modeling research of isolated power system such as in aircraft or ship.

Open access
Electronic structure and possible martensitic transformation in Ni2FeIn alloy

Abstract

The electronic structure and magnetic properties of Heusler alloys (Ni2FeIn) have been studied by first principle calculations. The possible tetragonal martensitic transformation has been predicted and the structure optimization was made on cubic austenitic Ni2FeIn in Cu2MnAl type. The equilibrium lattice constant of austenitic Ni2FeIn is 6.03 Å. In tetragonal phase, the global energy minimum occurs at c/a = 1.29. The corresponding equilibrium lattice constants for martensite Ni2FeIn are a = b = 5.5393 Å and c = 7.1457 Å, respectively. In the austenitic phase, E F is located at the peak in the minority DOS for c/a = 0.96 to 1.20, but in the martensitic phase, E F moves to the bottom of the valley in the minority DOS, reducing the value of N(E F) effectively. Both austenitic and martensitic phases are ferromagnetic and the Ni and Fe partial moments contribute mainly to the total moments. Therefore, the martensitic transformation behavior in Ni2FeIn is predicted.

Open access
A Case Report of Bronchobiliary Fistula and Literature Review

Abstract

Bronchobiliary fistula (BBF) is one of the very rare disease. In this report, we described a BBF case. The case was diagnosed by endoscopic retrograde cholangio-pancreatography (ERCP) and percutaneous transhepatic cholangial drainage (PTCD) examinations, and treated properly. From the diagnosis of this BBF case, a patient with cough, biliptysis, fever and pain, should be considered for diagnosis of BBF.

Open access
Risk factors of community-associated infections in Chinese patients with diabetes: A meta-analysis

Abstract

Objective: To identify the common sites and risk factors of community-associated infections in Chinese patients with diabetes. Materials and Methods: The Wanfang, CNKI, PUBMED and VIP databases restricting to Chinese patients with diabetes were queried without restriction to time period. Randomized controlled trials (RCTs) on the risk factors of community-associated infections in Chinese patients with diabetes were considered. Polled odd ratios (OR) and 95% confidence intervals (95% CI) were used for each factor in fixed or random-effect metaanalyses. Results: Twelve studies were identified that investigated seven risk factors of community-associated infections in Chinese patients with diabetes. The average infection incidence was 39.55%. The respiratory tract and urology tract were the predilection sites. Meta-analysis results are as follows: Diabetic patients with chronic complications (OR: 1.63; 95% CI 1.45-1.82), advanced age (OR: 1.30; 95% CI 1.19-1.42), longer duration (OR: 1.47; 95% CI 1.35-1.61) or ketoacidosis (OR: 1.37; 95% CI 1.13-1.66) were more prone to suffer from infections. Those with better glycemic control (OR: 0.68; 95% CI 0.61-0.76) or males (OR: 0.69; 95% CI 0.64-0.75) were less prone to suffer from infections. Conclusion: Chinese patients with diabetes had a high incidence of community-associated infections. We should highlight the risk factors that might provide a reference for the same.

Open access
Delayed cerebral ischemia after clipping of middle cerebral artery aneurysms

Abstract

Background: Delayed cerebral ischemia (DCI) that occurs more than 14 days after clipping of middle cerebral artery (MCA) aneurysms is rare.

Objective:To investigate whether multiple treatments that prevent vasospasms and microthrombosis may achieve a better outcome for DCI.

Method: We present three cases of subarachnoid hemorrhage (SAH) in patients who experienced DCI before and after MCA aneurysmal clipping. Their clinical manifestations, neuroradiological aspects, treatment, and outcomes are presented. Digital subtraction angiograms and computed tomographic angiography were performed to confirm the MCA aneurysms. Aneurysmal clippings were implemented via a pterional approach within 3 days of the onset of SAH. Triple-H therapy was conducted, and nimodipine was administered intravenously. The three patients were released with intact neurological status within 14 days to 17 days of clipping.

Results: The three patients were readmitted within 7 days after discharge because of cerebral ischemia in the corresponding MCA area. Antiplatelet drugs were administered with resolution of clinical symptoms within a few days.

Conclusion: The occurrence of this kind of DCI is rare. The pathogenesis of DCI is unknown and may be complex. Multiple treatments that prevent vasospasms as well as microthrombosis may achieve a better outcome.

Open access
The Cavitation Nuclei Transient Characteristics of Lennard-Jones Fluid in Cavitation Inception

Abstract

In the field of ocean engineering, cavitation is widespread, for the study of cavitation nuclei transient characteristics in cavitation inception, we applied theoretical analysis and molecular dynamics (MD) simulation to study Lennard-Jones (L-J) fluid with different initial cavitation nuclei under the NVT-constant ensemble in this manuscript. The results showed that in cavitation inception, due to the decrease of liquid local pressure, the liquid molecules would enter the cavitation nuclei, which contributed to the growth of cavitation nuclei. By using molecular potential energy, it was found that the molecular potential energy was higher in cavitation nuclei part, while the liquid molecular potential energy changes greatly at the beginning of the cavitation nuclei growth. The density of the liquid and the surface layer changes more obvious, but density of vapor in the bubble changes inconspicuously. With the growth of cavitation nuclei, the RDF peak intensity increased, the peak width narrowed and the first valley moved inner. When cavitation nuclei initial size reduced, the peak intensity reduced, the corresponding rbin increased. With the decrease of the initial cavitation nuclei, the system pressure and total energy achieved a balance longer, and correspondingly, they were smaller. In addition, at the beginning of the cavitation nuclei growth, the total energy and system pressure changed greatly.

Open access