Advancements in electronic technology have led to the emergence of portable devices like smartphones and smartwatches. For these devices, low-power supply management systems are crucial. In this ...study, the LDO (low-drop) regulator is implemented with TSMC 0.18 um CMOS high-voltage process. This chip is designed based on multi-current mirror circuits to implement a level-shifting circuit for controlling the error amplifier. The new architecture is achieved using the structure of three low-voltage operational amplifiers. The gate voltage of the power transistor is precisely driven by the level-shifting circuit, eliminating the need for a voltage limiting circuit on the power MOS's
V
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, thus enhancing the response time. This chip incorporates a temperature protection circuit that controls the feedback circuit for high-voltage MOS components. When the temperature exceeds a predefined threshold, the output shuts down immediately. Experimental results demonstrate that this chip can output voltages ranging from 3 to 19 V when the input voltage ranges from 3.5 to 20 V. The chip achieves a maximum output current of 1A and a peak conversion efficiency of 89.94%.
Abstract
We report the development of a nested block-structured adaptive mesh framework to solve multidimensional, time-dependent hyperbolic equations encountered in astrophysics. An approach based ...on a tabular list is used to construct variants of Hilbert space-filling curves in an iterative fashion to maintain the connectivity of locally refined mesh configurations using a doubly linked list. Modifications are made to conventional boundaries of computational blocks to aid the adaptive mesh. We also describe a well-defined, computationally efficient data structure to hold self-similar mesh units for this purpose. The flexibility of this code is demonstrated by the performance of various Riemann solvers implemented in this computational framework.
Abstract
Pseudodisks are dense structures formed perpendicular to the direction of the magnetic field during the gravitational collapse of a molecular cloud core. Numerical simulations of the ...formation of pseudodisks are usually computationally expensive with conventional CPU codes. To demonstrate the proof of concept of a fast computing method for this numerically costly problem, we explore the GPU-powered MHD code Astaroth, a sixth-order finite difference method with low adjustable finite resistivity implemented with sink particles. The formation of pseudodisks is physically and numerically robust and can be achieved with a simple and clean setup for this newly adopted numerical approach for science verification. The method’s potential is illustrated by evidencing the dependence on the initial magnetic field strength of specific physical features accompanying the formation of pseudodisks, e.g., the occurrence of infall shocks and the variable behavior of the mass and magnetic flux accreted on the central object. As a performance test, we measure both weak and strong scaling of our implementation to find the most efficient way to use the code on a multi-GPU system. Once suitable physics and problem-specific implementations are realized, the GPU-accelerated code is an efficient option for 3D magnetized collapse problems.
Large-scale morphology and time evolution are investigated for the unified model of bipolar outflows outlined in Shang et al. (2006), where an outflow forms by a radially directed, wide-angle ...magnetized wind interacting with magnetized isothermal toroids in various quasistatic states. The primary wide-angle wind is toroidally magnetized and maintains a cylindrically stratified density profile, mimicking the asymptotic solution of the cold X-wind model. We explore the interplay between the toroidally magnetized primary wind and the surrounding toroids threaded by poloidal magnetic fields and examine how the jet and shell morphology and fine structures within them vary with the physical parameters. The variation in flatness of the density distribution in the ambient isothermal toroids helps shape the varieties of lobe morphology and collimation. The presence of a stronger ambient poloidal field helps shape the outflow, forming a magnetic cocoon and nested multilayered cavities surrounding the wind-filled lobe, which is most evident in the more open configurations of the ambient toroids. The wind-toroid interface is prone to substantial shear and thus unstable to the Kelvin-Helmholtz instability. Magnetic forces in the compressed toroidally magnetized high-velocity wind can generate vorticity, leading to nonlinear patterns within the extended magnetized mixing layers. Magnetic disturbances generated by the interplay could modulate lobe shapes, density, and velocities, giving rise to visual impressions of thicker and rugged shells and apparent episodic distribution of matter. The system maintains a quasi-self-similar evolution in time, which serves as a proxy for understanding the underlying physical mechanisms driving it.
The formation of rotationally supported protostellar disks is suppressed in ideal MHD in non-turbulent cores with aligned magnetic fields and rotation axes. A promising way to resolve this so-called ..."magnetic braking catastrophe" is through turbulence. The reason for the turbulence-enabled disk formation is usually attributed to the turbulence-induced magnetic reconnection, which is thought to reduce the magnetic flux accumulated in the disk-forming region. We advance an alternative interpretation, based on magnetic decoupling-triggered reconnection of severely pinched field lines close to the central protostar and turbulence-induced warping of the pseudodisk of Galli and Shu. Such reconnection weakens the central split magnetic monopole that lies at the heart of the magnetic braking catastrophe under flux freezing. We show, through idealized numerical experiments, that the pseudodisk can be strongly warped, but not completely destroyed, by a subsonic or sonic turbulence. The warping decreases the rates of angular momentum removal from the pseudodisk by both magnetic torque and outflow, making it easier to form a rotationally supported disk. More importantly, the warping of the pseudodisk out of the disk-forming, equatorial plane greatly reduces the amount of magnetic flux threading the circumstellar, disk-forming region, further promoting disk formation. The beneficial effects of pseudodisk warping can also be achieved by a misalignment between the magnetic field and rotation axis. These two mechanisms of disk formation, enabled by turbulence and field-rotation misalignment respectively, are thus unified. We find that the disks formed in turbulent magnetized cores are rather thick and significantly magnetized. Implications of these findings, particularly for the thick young disk inferred in L1527, are briefly discussed.
The role of additives in facilitating the growth of conventional semiconducting thin films is well-established. Apparently, their presence is also decisive in the growth of two-dimensional transition ...metal dichalcogenides (TMDs), yet their role remains ambiguous. In this work, we show that the use of sodium bromide enables synthesis of TMD monolayers via a surfactant-mediated growth mechanism, without introducing liquefaction of metal oxide precursors. We discovered that sodium ions provided by sodium bromide chemically passivate edges of growing molybdenum disulfide crystals, relaxing in-plane strains to suppress 3D islanding and promote monolayer growth. To exploit this growth model, molybdenum disulfide monolayers were directly grown into desired patterns using predeposited sodium bromide as a removable template. The surfactant-mediated growth not only extends the families of metal oxide precursors but also offers a way for lithography-free patterning of TMD monolayers on various surfaces to facilitate fabrication of atomically thin electronic devices.
Stars form in dense cores of molecular clouds that are observed to be significantly magnetized. A dynamically important magnetic field presents a significant obstacle to the formation of protostellar ...disks. Recent studies have shown that magnetic braking is strong enough to suppress the formation of rotationally supported disks in the ideal MHD limit. Whether non-ideal MHD effects can enable disk formation remains unsettled. We carry out a first study on how disk formation in magnetic clouds is modified by the Hall effect, the least explored of the three non-ideal MHD effects in star formation (the other two being ambipolar diffusion and Ohmic dissipation). For illustrative purposes, we consider a simplified problem of a non-self-gravitating, magnetized envelope collapsing onto a central protostar of fixed mass. We find that the Hall effect can spin up the inner part of the collapsing flow to Keplerian speed, producing a rotationally supported disk. The disk is generated through a Hall-induced magnetic torque. Disk formation occurs even when the envelope is initially non-rotating, provided that the Hall coefficient is large enough. When the magnetic field orientation is flipped, the direction of disk rotation is reversed as well. The implication is that the Hall effect can in principle produce both regularly rotating and counter-rotating disks around protostars. The Hall coefficient expected in dense cores is about one order of magnitude smaller than that needed for efficient spin-up in these models. We conclude that the Hall effect is an important factor to consider in studying the angular momentum evolution of magnetized star formation in general and disk formation in particular.
HH 212 is a nearby (400 pc) Class 0 protostellar system showing several components that can be compared with theoretical models of core collapse. We have mapped it in the 350 GHz continuum and ...HCO{sup +} J = 4-3 emission with ALMA at up to ∼0.''4 resolution. A flattened envelope and a compact disk are seen in the continuum around the central source, as seen before. The HCO{sup +} kinematics shows that the flattened envelope is infalling with small rotation (i.e., spiraling) into the central source, and thus can be identified as a pseudodisk in the models of magnetized core collapse. Also, the HCO{sup +} kinematics shows that the disk is rotating and can be rotationally supported. In addition, to account for the missing HCO{sup +} emission at low-redshifted velocity, an extended infalling envelope is required, with its material flowing roughly parallel to the jet axis toward the pseudodisk. This is expected if it is magnetized with an hourglass B-field morphology. We have modeled the continuum and HCO{sup +} emission of the flattened envelope and disk simultaneously. We find that a jump in density is required across the interface between the pseudodisk and the disk. A jet is seen in HCO{sup +} extending out to ∼500 AU away from the central source, with the peaks upstream of those seen before in SiO. The broad velocity range and high HCO{sup +} abundance indicate that the HCO{sup +} emission traces internal shocks in the jet.
The aim of this study was to determine the effect of Coronavirus disease 2019 (COVID-19) pandemic on ophthalmic outpatient numbers and ophthalmic diagnosis distribution in a community hospital ...(Taipei City Hospital Zhongxiao Branch) in Taiwan. The COVID-19 pandemic period in Taiwan was defined as May 1 to July 31, 2021. Demographic data, including age, gender, and top 10 diagnoses from ophthalmic outpatients during this period, were collected. A corresponding control group from the same time in 2020 was also collected. The distribution of different diagnoses was analyzed, and the data of 10 most prominent diagnoses with decreased percentage of case numbers during the COVID-19 pandemic period were obtained. The number of cases during the COVID-19 pandemic decreased by 46.9% compared to the control group. The top three most common diagnoses were dry eye syndrome, glaucoma, and macular diseases. The 10 most prominent diagnoses with decreased number of cases during the COVID-19 pandemic were cataract, refraction & accommodation, macular degeneration, conjunctivitis, retinal detachment, vitreous body disorders, ophthalmic complications of diabetes mellitus, glaucoma, dry eye, and retinal vein occlusion. Identifying and treating these patients as scheduled may yield the highest cost-benefit effect in preventing visual loss during the COVID-19 pandemic.
The strength of Building Information Modeling (BIM) in achieving sustainable buildings is well recognized by the global construction industry. However, current understanding of the state-of-the-art ...green BIM research is still limited. In particular, a focus study on how BIM contribute to green building design through building performance analysis (BPA) is not available. This paper aims to provide systematic and comprehensive insights on current trends and future potentials of green BIM research by analyzing the existing literature with their research features (i.e. research backgrounds, goals, methods and outputs). In total, 80 publications have been collected, analyzed and discussed. The results show that among ten main BPA types, energy & thermal analysis, green building rating analysis, and cost and benefit analysis are the most studied. However, wind & ventilation analysis, acoustic analysis, and water efficiency analysis receive little attention. Moreover, more research focusing on integrated design analysis should be carried out for optimal design outcome. In addition, most of the collected literature research on the capability of data integration and analysis of green BIM tools, while their capability of visualization and documentation has limited examination. Furthermore, most researchers utilized one main software package while utilization of information exchange formats (IEF) is limited. To increase interoperability of green BIM tools, how different BIM authoring tools and IEFs can be utilized for BPA requires further investigation.
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