Smart Fluorescent Nanoparticles in Water Showing Temperature-Dependent Ratiometric Fluorescence Color Change

Cui, Junjie,Kwon, Ji Eon,Kim, Hyeong-Ju,Whang, Dong Ryeol,Park, Soo Young American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.3

<P>We synthesized two different amphiphilic small molecules 1 and 2 by attaching the same oligo(ethylene glycol) (OEG) unit to the same dicyanodistyrylbenzene (DCS) fluorophore but at different positions. These molecules self-assemble into nanoparticles in water and show lower critical solution temperature (LCST) at 26 and 58 degrees C, respectively. Upon heating, the transition of hydrophilic coils to hydrophobic globules of the OEG unit leads to the change in the stacking structure of the luminescent DCS cores. As a result, it shows significant ratiometric fluorescence color changes from excimeric yellow emission to monomer dominated green emission. Interestingly, the coassembly of 1 and- 2 exhibits single transition temperature between the transition temperatures of the two components. Moreover, it is demonstrated that the transition temperature of the coassembly is delicately tuned over 26-58 degrees C by varying the molar mixing ratio of them.</P>

Development and Application of Polymorphic SSR Markers in Luffa cylindrica

Junjie Cui,Zhen Lv,Tianwen Yang,Jing Wang,Yu Hong 한국원예학회 2022 원예과학기술지 Vol.40 No.5

Two published genomes of Luffa cylindrica, ‘SG2019’ and ‘SO3’, were used to develop polymorphic SSR markers for L. cylindrica by searching and comparing the SSR motifs at the same site in the two genomes. Based on the SSR search conditions and primer design criteria, 2130 polymorphic SSR markers for L. cylindrica were developed. The main motif type was dinucleotide, accounting for 80.28% of the total; the main motif units were AT/AT and AAT/ATT, accounting for 87.80% of the total. Furthermore, 40 polymorphic SSR markers developed in this study were randomly selected and amplified in 24 Luffa samples. According to the results, the 40 polymorphic SSR markers showed an amplification rate of 100% and a polymorphism rate of 80%. Cluster analysis classified the 24 Luffa samples into two main groups, L. cylindrica and L. acutangula. Overall, the polymorphic SSR markers developed in this study display a high polymorphic rate and reliable utilization value.

Analysis of Switching Clamped Oscillations of SiC MOSFETs

Junji Ke,Zhibin Zhao,Zongkui Xie,Changjun Wei,Xiang Cui 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.3

SiC MOSFETs have been used to improve system efficiency in high frequency converters due to their extremely high switching speed. However, this can result in undesirable parasitic oscillations in practical systems. In this paper, models of the key components are introduced first. Then, theoretical formulas are derived to calculate the switching oscillation frequencies after full turn-on and turn-off in clamped inductive circuits. Analysis indicates that the turn-on oscillation frequency depends on the power loop parasitic inductance and parasitic capacitances of the freewheeling diode and load inductor. On the other hand, the turn-off oscillation frequency is found to be determined by the output parasitic capacitance of the SiC MOSFET and power loop parasitic inductance. Moreover, the shifting regularity of the turn-off maximum peak voltage with a varying switching speed is investigated on the basis of time domain simulation. The distortion of the turn-on current is theoretically analyzed. Finally, experimental results verifying the above calculations and analyses are presented.

Influence of Device Parameters Spread on Current Distribution of Paralleled Silicon Carbide MOSFETs

Junji Ke,Zhibin Zhao,Peng Sun,Huazhen Huang,James Abuogo,Xiang Cui 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

This paper systematically investigates the influence of device parameters spread on the current distribution of paralleledsilicon carbide (SiC) MOSFETs. First, a variation coefficient is introduced and used as the evaluating norm for the parametersspread. Then a sample of 30 SiC MOSFET devices from the same batch of a well-known company is selected and tested underthe same conditions as those on datasheet. It is found that there is big difference among parameters spread. Furthermore,comprehensive theoretical and simulation analyses are carried out to study the sensitivity of the current imbalance to variationsof the device parameters. Based on the concept of the control variable method, the influence of each device parameter on thesteady-state and transient current distributions of paralleled SiC MOSFETs are verified separately by experiments. Finally, somescreening suggestions of devices or chips before parallel-connection are provided in terms of different applications and differentdriver configurations.

Favorable Impact Toughness of High Heat Input Coarse-Grained HAZ in an Ultra-Low Carbon High-Strength Microalloyed Steel

Fuhui Cui,Junjie Wang1,Xiangdong Gan,Dawei Yu,Ilya Vladimirovich Okulov,Qinghua Tian,Xueyi Guo 대한금속ᆞ재료학회 2023 METALS AND MATERIALS International Vol.29 No.2

Liquid Mg is capable of quickly eroding the refractory Ni-based superalloy and selectively dissolve Ni, which opens up anew avenue for the recycling of superalloy scraps for comprehensive metal reclamation. This study aims at investigating theunderlining mechanism and kinetics of the selective dissolution of Ni from Inconel 718 (one type of Ni-based superalloy)with liquid Mg, by experimenting at 750, 800, and 850 °C for various amounts of time in an inert atmosphere. This selectivedissolution process is also known as liquid metal dealloying. Results show that a permeable dealloyed layer was formedresulting from the preferential dissolution of Ni over other metallic elements (e.g., Fe, Cr, Nb, Mo, and Ti). At the dealloyingforefront, the grain boundaries of the matrix γ phase were preferentially eroded by liquid Mg. The opposite concentrationgradients of Ni (4–9 wt%) and Mg (12–18 wt%) cross the dealloyed layer suggested their counter diffusion. A higher heatingtemperature substantially increased the dealloying rate.

Analysis of Switching Clamped Oscillations of SiC MOSFETs

Ke, Junji,Zhao, Zhibin,Xie, Zongkui,Wei, Changjun,Cui, Xiang The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.3

SiC MOSFETs have been used to improve system efficiency in high frequency converters due to their extremely high switching speed. However, this can result in undesirable parasitic oscillations in practical systems. In this paper, models of the key components are introduced first. Then, theoretical formulas are derived to calculate the switching oscillation frequencies after full turn-on and turn-off in clamped inductive circuits. Analysis indicates that the turn-on oscillation frequency depends on the power loop parasitic inductance and parasitic capacitances of the freewheeling diode and load inductor. On the other hand, the turn-off oscillation frequency is found to be determined by the output parasitic capacitance of the SiC MOSFET and power loop parasitic inductance. Moreover, the shifting regularity of the turn-off maximum peak voltage with a varying switching speed is investigated on the basis of time domain simulation. The distortion of the turn-on current is theoretically analyzed. Finally, experimental results verifying the above calculations and analyses are presented.

Influence of Device Parameters Spread on Current Distribution of Paralleled Silicon Carbide MOSFETs

Ke, Junji,Zhao, Zhibin,Sun, Peng,Huang, Huazhen,Abuogo, James,Cui, Xiang The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

This paper systematically investigates the influence of device parameters spread on the current distribution of paralleled silicon carbide (SiC) MOSFETs. First, a variation coefficient is introduced and used as the evaluating norm for the parameters spread. Then a sample of 30 SiC MOSFET devices from the same batch of a well-known company is selected and tested under the same conditions as those on datasheet. It is found that there is big difference among parameters spread. Furthermore, comprehensive theoretical and simulation analyses are carried out to study the sensitivity of the current imbalance to variations of the device parameters. Based on the concept of the control variable method, the influence of each device parameter on the steady-state and transient current distributions of paralleled SiC MOSFETs are verified separately by experiments. Finally, some screening suggestions of devices or chips before parallel-connection are provided in terms of different applications and different driver configurations.

Dealloying Superalloy by Liquid Mg for the Selective Extraction of Ni

Fuhui Cui,Junjie Wang,Xiangdong Gan,Dawei Yu,Ilya Vladimirovich Okulov,Qinghua Tian,Xueyi Guo 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.3

Liquid Mg is capable of quickly eroding the refractory Ni-based superalloy and selectively dissolve Ni, which opens up anew avenue for the recycling of superalloy scraps for comprehensive metal reclamation. This study aims at investigating theunderlining mechanism and kinetics of the selective dissolution of Ni from Inconel 718 (one type of Ni-based superalloy)with liquid Mg, by experimenting at 750, 800, and 850 °C for various amounts of time in an inert atmosphere. This selectivedissolution process is also known as liquid metal dealloying. Results show that a permeable dealloyed layer was formedresulting from the preferential dissolution of Ni over other metallic elements (e.g., Fe, Cr, Nb, Mo, and Ti). At the dealloyingforefront, the grain boundaries of the matrix γ phase were preferentially eroded by liquid Mg. The opposite concentrationgradients of Ni (4–9 wt%) and Mg (12–18 wt%) cross the dealloyed layer suggested their counter diffusion. A higher heatingtemperature substantially increased the dealloying rate.

Numerical analysis of stress wave of projectile impact composite laminate

Zhangxin Guo,Weijing Niu,Junjie Cui,Gin Boay Chai,Yongcun Li,Xiaodong Wu 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.87 No.2

The three-dimensional Hashin criterion and user subroutine VUMAT were used to simulate the damage in the composite layer, and the secondary stress criterion was used to simulate the interlayer failure of the cohesive element of the bonding layer and the propagation characteristics under the layer. The results showed that when the shear stress wave (shear wave) propagates on the surface of the laminate, the stress wave attenuation along the fiber strength direction is small, and thus producing a large stress profile. When the compressive stress wave (longitudinal wave) is transmitted between the layers, it is reflected immediately instead of being transmitted immediately. This phenomenon occurs only when the energy has accumulated to a certain degree between the layers. The transmission of longitudinal waves is related to the thickness and the layer orientation. Along the symmetry across the thickness direction, the greater is the stress amplitude along the layer direction. Based on the detailed investigation on the impact on various laminated composites carried out in this paper, the propagation characteristics of stress waves, the damage and the destruction of laminates can be explained from the perspective of stress waves and a reasonable layering sequence of the composite can be designed against damage and failure from low velocity impact.