| 1. |
- Karoly, Janik, et al.
(author)
-
The JCMT BISTRO Survey: Studying the Complex Magnetic Field of L43
- 2023
-
In: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 952:1
-
Journal article (peer-reviewed)abstract
- We present observations of polarized dust emission at 850 mu m from the L43 molecular cloud, which sits in the Ophiuchus cloud complex. The data were taken using SCUBA-2/POL-2 on the James Clerk Maxwell Telescope as a part of the BISTRO large program. L43 is a dense (N-H2 similar to 10(22) - 10(23) cm(-2)) complex molecular cloud with a submillimeter-bright starless core and two protostellar sources. There appears to be an evolutionary gradient along the isolated filament that L43 is embedded within, with the most evolved source closest to the Sco OB2 association. One of the protostars drives a CO outflow that has created a cavity to the southeast. We see a magnetic field that appears to be aligned with the cavity walls of the outflow, suggesting interaction with the outflow. We also find a magnetic field strength of up to similar to 160 +/- 30 mu G in the main starless core and up to similar to 90 +/- 40 mu G in the more diffuse, extended region. These field strengths give magnetically super- and subcritical values, respectively, and both are found to be roughly trans-Alfvenic. We also present a new method of data reduction for these denser but fainter objects like starless cores.
|
|
| 2. |
- Tahani, Mehrnoosh, et al.
(author)
-
JCMT BISTRO Observations: Magnetic Field Morphology of Bubbles Associated with NGC 6334
- 2023
-
In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 944:2
-
Journal article (peer-reviewed)abstract
- We study the Hii regions associated with the NGC 6334 molecular cloud observed in the submillimeter and taken as part of the B-fields In STar-forming Region Observations Survey. In particular, we investigate the polarization patterns and magnetic field morphologies associated with these Hii regions. Through polarization pattern and pressure calculation analyses, several of these bubbles indicate that the gas and magnetic field lines have been pushed away from the bubble, toward an almost tangential (to the bubble) magnetic field morphology. In the densest part of NGC 6334, where the magnetic field morphology is similar to an hourglass, the polarization observations do not exhibit observable impact from Hii regions. We detect two nested radial polarization patterns in a bubble to the south of NGC 6334 that correspond to the previously observed bipolar structure in this bubble. Finally, using the results of this study, we present steps (incorporating computer vision; circular Hough transform) that can be used in future studies to identify bubbles that have physically impacted magnetic field lines.
|
|
| 3. |
- Qian, Chen, 1990-, et al.
(author)
-
How do ideas gain legitimacy in internal crowdsourcing idea development? : Exploring the effects of feedback on idea selection
- 2023
-
In: Innovation. - : Informa UK Limited. - 1447-9338 .- 2204-0226. ; , s. 1-32
-
Journal article (peer-reviewed)abstract
- Internal crowdsourcing offers new opportunities for ideas to gain legitimacy in idea development as not only managers but also experts are able to provide feedback to improve and subsequently accept ideas for further realisation. Given this far limited knowledge about how ideas gain legitimacy in idea development, this paper focuses on the influence of feedback, a main source of idea legitimacy in internal crowdsourcing. More specifically, this study aims to explore how feedback from different feedback providers (i.e., managers and experts) influences idea selection in internal crowdsourcing idea development. Based on text mining methods including sentiment, topic-model, and expert identification analyses, results reveal that feedback sentiment, feedback diversity and feedback amount play key roles in idea legitimisation. Specifically, these aspects of feedback influence idea acceptance in idea selection through the mediating role of idea revision in idea development and that this relationship is moderated by feedback providers. This study extends previous knowledge about the legitimisation process from the perspective of feedback in idea development by offering both a more comprehensive view, including different feedback aspects, and a more granular measurement of these, through the use of text analysis. Based on insights from the study, practical implications are presented for how to gain legitimacy from feedback for idea selection in internal crowdsourcing.
|
|
| 4. |
- Qian, Chen, 1990-, et al.
(author)
-
Selection bias of ideas for sustainability-oriented innovation in internal crowdsourcing
- 2023
-
In: Technovation. - : Elsevier BV. - 0166-4972 .- 1879-2383. ; 124, s. 102761-102761
-
Journal article (peer-reviewed)abstract
- Decision biases reinforce firms’ tendency to develop innovations based on narrow economic motivations. Consequently, sustainability-oriented ideas explicitly targeting social and environmental issues are easily discarded in idea selection when trade-offs between economic and sustainability values are faced. Given the so far limited knowledge about how sustainability-oriented ideas are developed and selected in organizations today, this research aims to explore how managerial biases affect selection of sustainability-oriented ideas in internal crowdsourcing. It does so through an empirical study drawing on data collected from a Swedish multinational company using internal crowdsourcing for different types of innovation ideas. The empirical study explicitly identifies sustainability-oriented ideas based on machine learning and captures managerial biases for ideas based on sentiment analysis. Regression analyses reveal that managerial biases potentially affect the selection of sustainability-oriented ideas through the mediating role of managerial attention in idea development. Furthermore, this mediating relationship is moderated by search pattern in terms of directed search. The study contributes to the literature on both innovation and sustainability, shedding new light on the effects of managerial bias, managerial attention, and innovation search for decision making and provides managerial implications enabling a fruitful adoption of sustainability-oriented innovation ideas.
|
|
| 5. |
- Qin, Haihong, et al.
(author)
-
Evaluation and Suppression Method of Turn-off Current Spike for SiC/Si Hybrid Switch
- 2023
-
In: IEEE Access. - 2169-3536 .- 2169-3536. ; 11, s. 26832-26842
-
Journal article (peer-reviewed)abstract
- SiC MOSFET/Si IGBT (SiC/Si) hybrid switch usually selects the gate control pattern that SiC MOSFET turns on earlier and turns off later than Si IGBT, with the aim of making the hybrid switch show excellent switching characteristics of SiC MOSFET and reduce switching loss. However, when SiC MOSFET turns off, the fast slew rate of drain source voltage causes the current spike in Si IGBT due to the effects of parasitic capacitance charging and carrier recombination, which will produce additional turn-off loss, thus affecting the overall efficiency and temperature rise of the converter. Based on the double pulse test circuit of SiC/Si hybrid switch, the mathematical model of the turn-off transient process is established. The effects of the remnant carrier recombination degree of Si IGBT, the turn-off speed of SiC MOSFET and the working conditions on the turn-off current spike of hybrid switch are evaluated. Although adjusting these parameters can reduce the turn-off current spike somewhat, additional losses will be introduced. Therefore, a new method to suppress the turn-off current spike is proposed to balance the power loss and current stress.
|
|
| 6. |
- Qin, Haihong, et al.
(author)
-
Evaluation of antiparallel SiC Schottky diode in SiC MOSFET phase-leg configuration of synchronous rectifier
- 2023
-
In: Energy Reports. - 2352-4847. ; 9, s. 337-342
-
Journal article (peer-reviewed)abstract
- The MOSFET synchronous rectification (SR) is widely used to reduce the conduction loss during the freewheeling period. Due to the wide band gap of silicon carbide (SiC), the intrinsic body diode of SiC MOSFET exhibits a high voltage drop. Therefore, SiC Schottky diodes (SBD) and SiC MOSFETs are usually used in reverse parallel to reduce power loss. However, the increase of equivalent junction capacitance due to the addition of an external SiC SBD could bring larger turn-on current on opposite power transistor of the phase-leg. Furthermore, as the parasitic inductance associated with layout hinders the prompt transfer of current between SiC SBD and body diode, the external SiC SBD cannot be fully utilized, and it may deteriorate the overall performance, especially at heavy load. We comprehensively compare power losses when SiC SBD are antiparallel or not, at different working conditions, including different layout compactness, load current and dead time. It's hard to get the effect of loss reduction loss when add antiparallel SiC SBD due to the parasitic inductance induced by the layout. The results can provide a guidance to properly select SiC SBD in a phase-leg configuration under SR mode for freewheeling during the dead time.
|
|
| 7. |
- Qin, Haihong, et al.
(author)
-
Parameters Design and Optimization of SiC MOSFET Driving Circuit with Consideration of Comprehensive Loss and Voltage Stress
- 2023
-
In: Micromachines. - : MDPI AG. - 2072-666X. ; 14:3
-
Journal article (peer-reviewed)abstract
- In conventional parameters design, the driving circuit is usually simplified as an RLC second-order circuit, and the switching characteristics are optimized by selecting parameters, but the influence of switching characteristics on the driving circuit is not considered. In this paper, the insight mechanism for the gate-source voltage changed by overshoot and ringing caused by the high switching speed of SiC MOSFET is highlighted, and we propose an optimized design method to obtain optimal parameters of the SiC MOSFET driving circuit with consideration of parasitic parameters. Based on the double-pulse circuit, we evaluated the influence of main parameters on the gate-source voltage, including driving voltage, driving resistance, gate parasitic inductance, and stray inductance of the power circuit. A SiC-based boost PFC is constructed and tested. The test results show that the switching loss can be reduced by 7.282 W by using the proposed parameter optimization method, and the over-voltage stress of SiC MOSFET is avoided.
|
|
