Search

Additional file 1.

Background Acinetobacter baumannii (A. baumannii) is an important nosocomial pathogen in hospital-acquired infections, and the resistance to carbapenems has been observed increasingly worldwide. Oxacillinase produced by blaOXA-23 is one of the predominant carbapenem resistance mechanisms in A. baumannii, which is highly prevalent worldwide, especially in China. The rapid identification of blaOXA-23 may give a valuable hint for the administration of directed antimicrobial therapy. Method In this study, we aimed to develop a LAMP-based detection for the blaOXA-23 gene; clinical samples of A. baumannii were used to determine the sensitivity and specificity of this method compared to phenotypic antimicrobial susceptibility testing and traditional PCR method. MLST was performed to investigate the epidemiology of A. baumannii bacterial population. Results Compared to the antimicrobial susceptibility testing, the sensitivity and specificity of LAMP in detecting blaOXA-23 was 88.4% and 97.7%, respectively. However, the LAMP method was found to be much simpler and the result could be available in a shorter period (within 60 minutes) when compared to conventional PCR and phenotypic susceptibility testing. The 113 isolates could be clustered into 30 sequence types (STs), and majority (83/113) of these strains belong to clonal complex 92 (CC92), which is also the dominant CC in the China. Conclusion The LAMP-based method detected blaOXA-23 in a much simpler way, by which could provide timelier results for differentiating the carbapenem-resistant Acinetobacter baumannii than conventional methods. Consequently, blaOXA-23 may potentially serving as surrogate marker for the presence of CRAB in patients with serious infections in clinic.

In order to improve the stability of the GaN FET power driven integrated circuit, the integrated circuits usually design corresponding protective circuit modules, such as overcurrent, over temperature, under-voltage protection circuit, etc. In this paper, combined with the characteristics of GaN FET, based on the 0.18 m BiCMOS technique, a novel UVLO circuit used in GaN FET power driven integrated circuits is designed. The average temperature drift of turn on circuit voltage threshold(VDDTH+) is 0.12V, the maximum temperature drift is 0.481V, the average temperature drift of turn off threshold voltage(VDDTH-) is 0.03V, the maximum temperature drift is 0.142V; the VDDTH+ and VDDTH-are 4.241v and 3.885v; The hysteresis voltage is 356mv between VDDTH+ and VDDTH-, improved the circuit anti interference ability. The simulation results show that the circuit can output low voltage logic signals in under-voltage, and has low temperature drift and voltage hysteresis function, which has important significance for improving the performance of GaN FET power drive integrated circuit.

The reliability of GaN-based high electron mobility transistors (HEMTs) is of great importance due to the special characteristics of AlGaN/GaN heterostructure such as intense polarization effect, high material defect density, strong electric field working condition, complicated process etc. Failure analysis is the premise and foundation to improve reliability of semiconductor devices. However, there is less research on failure analysis method about HEMTs at present. In this paper, an effective method of failure analysis of HEMT is presented to analyze the failure reason of electrical stress on many occasions, and a corresponding case analysis of HEMT is carried out. Following the unique complementary detection process of electrical testing, thermal radiation and photon emission, device failure position can be determined rapidly and failure mode and mechanism can be analyzed by this method. A 4-finger GaN-based HEMT with a operating voltage of 28V and a gate width of 1.25mm are analyzed according to this failure analysis method. Two failure positions were localized and the failure mode and mechanism were determined by comprehensive analysis of testing images and data. Finally, several improvements in design and process of GaN-based HEMTs are proposed, which is a valuable reference on the failure analysis and reliability enhancement of HEMT devices.

Compared to traditional silicon based semiconductors, wide band gap semiconductors (e.g. GaN and SiC) have been widely used in high power electronics with their advantages of higher thermal conductivity, higher breakdown field strength, higher operating temperature and lower power loss. The SiC power diode packages, including Schottky Barrier Diode (SBD) and Junction Barrier Schottky (JBS), are usually manufactured with the SiC die as a function chip and aluminum wires as interconnections. Since aluminum wires are usually operated under the condition of high temperature and high power cycling, their fatigue damage is considered as one of great failures happened in package level. Because of the mismatch of coefficient of thermal expansions (CTEs) between the interconnections, aluminum wires are highly stressed under a multiple electrical-thermo-mechanical condition. This paper assesses the reliability of wire bonds in a SiC SBD package under an accelerated operation test condition with higher currents. And the fatigue damage of the wire bond was predicted by using a multi-physics finite element (FE) simulation method. In details, the strain-based and stress-based 3D finite element simulation models, which will be afforded to the traditional strain-based Coffin-Manson model and stress-based Basquin's equation for fatigue life prediction, were chosen to simulate the stress/strain density distribution of the wire bond in the SiC SBD package. Finally, the effects of the high current conditions on the the stress/strain density distribution of the wire bond were analyzed based on the simulation results.

In this paper, a general dynamic model is presented for studying the dynamic properties of rotor system supported by ball bearings under the effects of both internal clearance and bearing running surface waviness. The ball bearing model includes the high-speed effects of ball centrifugal force and gyroscopic moment. The cage speed is considered a time-variation parameter related with the orbital speed of balls. Numerical results of this research are in good agreement with prior authors’ experimental researches and already existing models. Then the model is employed to investigate the effects of clearance, waviness, preload and radial force on the nonlinear stability and vibration behavior of a rotor bearing system at high speed. It is shown that the clearance, axial preload and radial force play a significant role in affecting the system stability. The effect of outer race waviness on cage speed variation is more considerable than that of inner race and ball waviness.