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The cost of software maintenance increases as the continuous iterative development of software.To reduce this cost,automated software refactoring is proven to be an effective solution.One of the most typical automated software refactoring approaches is the search-based refactoring.This approach refactors software according to some predefined objectives.Existing stu-dies show that the selection of objectives plays a decisive role in the search process.Although many quality objectives and non-quality objectives are proposed,there is no research to analyze that in the same evaluation framework which objectives can guide the software refactoring to achieve results that meet developers’ expectations.Meanwhile,whether the combination of quality objectives and non-quality objectives will have better results is not analyzed.To answer these questions,this paper designs a search-based multi-objective software refactoring evaluation framework.Under the framework,this paper investigates the impact of the combination of seven different objectives on software refactoring with six open-source software projects in different scales;the software quality before and after refactoring is evaluated using a variety of indicators,and the effectiveness of different objective combinations is also analyzed.Experimental results show that the combination of quality objectives and non-quality objectives can better improve the effectiveness of software refactoring than using one single type of objectives,and the combination of the ‘qua-lity’ objective and the ‘similarity with recorded code changes’ objective is important to the improvement of software refactoring effectiveness.

Objective: To evaluate value of blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) for early renal hypoxia assessment in chronic kidney disease(CKD). Methods: Fifty-two patients with CKD and 52 age- and sex-matched health volunteers underwent BOLD MRI of the kidneys. Serum creatinine (sCr) levels and estimated GFR (eGFR) were collected. The patients were classified into 5 stages according to the National Kidney Foundation′s Kidney Disease Outcomes Quality Initiative. Difference in R2*s were compared between patients and volunteers and among different stages of CKD. Results: In patients with CKD and volunteers, R2* of renal medulla was higher than that of renal cortex (P0.05). However, medullar R2*s were lower in patients with CKD1 [(16.55 ± 2.12)/s], CKD4 [(16.48 ± 2.95)/s], or CKD5 [(13.99 ± 2.21)/s] than those in volunteers [(18.17± 2.38)/s] (P

To ensure the computational accuracy for the offshore high voltage direct current substation local structure and its large and complex electrical equipment, it is necessary to reduce the modeling complexity and improve the calculation efficiency. Thus, a simplified vibration model with constant key physical parameters was established; the converter valve was used as a test design example and a lower number of samples was used. Finally, the response surface fitting was carried out. Based on the machine learning concept, problems such as the loss of physical meaning of complex system matrices and low iteration efficiency, caused by high-dimensional matrix operations were avoided. In addition, the deterministic screening experiment design greatly reduced the number of samples needed while also ensuring the second-order effect. The fit between the response surface equation and experimental results was good after optimizing the relevant design factors based on the vibration equation. The comparison between the simplified vibration converter valve model and the original complex model has shown that the errors for various physical parameters and the vibration characteristics were below 5% and that the model simplification degree was 95%.

In order to investigate the influence of negative pressure on the interface of T2/Q235 explosive-welded composite plate, low-explosion-velocity diatomite-sensitized powder emulsion explosive with low explosion velocity was used as the welding special explosive, and T2 and Q235 were used as cladding and base plate, respectively. The explosive welding tests were carried out under atmospheric pressured00kPa), 60kPa, and 20kPa ambient pressures, respectively. The morphology and elemental composition of the composite interface were studied by means of metallographic analysis. The mechanism of negative pressure explosive welding was further revealed by numerical simulation. The results show that the charge density of powder emulsion explosive is increased under negative pressure conditions. The detonation velocity of powder emulsion explosive is not changed, and the brisance of powder emulsion explosive under 20kPa is 8.4% higher than that under ambient pressure condition. With decrease of ambient pressure, the interface wave height and wavelength of the composite plate gradually increases. At 20kPa, the wave height and wavelength increase by 49% and 23%, respectively. The oxygen element of T2/Q235 bonding surface under negative pressure is lower than that under ambient pressure. The numerical simulation results show that the T2/Q235 interface wave increases with the increase of explosive density, which is consistent with the experimental results. In the explosion welding process, the impact velocity and pressure of explosives increase by 16.3% and 66. 3% respectively, when the charge density of explosive was 0. 8g/cm³ under negative pressure (20kPa) as compared to 0.711 g/cm³ under normal pressure. The results show that the negative pressure improves the efficiency of explosive energy in explosive welding compared with normal pressure. [ABSTRACT FROM AUTHOR]

As a typical aerospace difficult-to-machine material, tool failure in milling titanium alloy Ti6Al4V will reduce the stability of the milling process and affect the surface quality of the workpiece. Aiming at the fact that cemented carbide tools are prone to wear failure and breakage failure in milling titanium alloy, a safe tool failure boundary map is provided to ensure that the tools will not occur failure with the cutting parameters selected in the safe area during the prediction time. Based on the processing characteristics of Ti6Al4V, the failure boundary map mainly considers three forms of tool failure: flank wear, rake wear, and cutting edge breakage. By revealing the three failure mechanisms, the failure analytical model is established and the failure boundary map is obtained. Compared with the experimental results, it has good consistency, and the research results can provide a reference for the field of titanium alloy cutting process. [ABSTRACT FROM AUTHOR]

In this paper, we study an inverse source problem for the Helmholtz equation from measurements. The purpose of this paper is to reconstruct the salient features of the hidden sources within a body. We propose three stable reconstruction algorithms to detect the number, the location, the size, and the shape of the hidden sources along with compact support from a single measurement of near-field Cauchy data on the external boundary. This problem is nonlinear and ill-posed; thus, we should consider regularization techniques in reconstruction algorithms. We give several numerical experiments to demonstrate the viability of our proposed reconstruction algorithms. [ABSTRACT FROM AUTHOR]