There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

/pdf/light-emitting-diodes-ubzde6g9qc.pdf

Light-emitting diodes

Lifetime of aluminum electrolytic capacitors is of paramount importance, since in many power electronic voltage source converter systems this capacitor type is used in the DC-link. Thermal stress is one of the most critical stressors for electrolytic capacitors leading to wear-out and failures. Therefore, methods to perform online monitoring of the hotspot temperature of capacitors would lead to beneficial information, which could be used for protection or lifetime prediction purposes. This paper proposes a hotspot temperature estimation method based on the linear dependence between capacitance and temperature of electrolytic capacitors. For this, a set of nine samples of the same aluminum capacitor type is characterized by means of capacitance measurements at different hotspot temperatures. The obtained linear correlation is used to calibrate hotspot temperature estimation for the investigated electrolytic capacitor type. It is verified experimentally that the temperature estimation error of the proposed method is well below 5 K. Thus, the proposed procedure can be used as a basis for future research on improving condition monitoring of electrolytic capacitors.

A method for hotspot temperature estimation of aluminum electrolytic capacitors

This paper proposes an ac resistance optimization method applicable for both inductor and transformer windings with full layers sand partial layers. The proposed method treats the number of layers of the windings as a design variable instead of as a predefined parameter, compared to existing methods. The window height and width of magnetic cores and the insulation requirements are introduced as boundary conditions in the optimization process. The optimization can be realized simply by mathematical design map analyses instead of iteration programs. Moreover, a corresponding closed form expression of ac resistance of windings with partial layers is proposed. The developed analytical equation is verified by both Finite Element Method (FEM) simulations and experimental results from two transformer prototypes. A case study of a transformer design with partial layer windings for a LCC resonant circuit is presented with experimental verifications to demonstrate the optimization method.

/pdf/an-ac-resistance-optimization-method-applicable-for-inductor-ob6qjahq9n.pdf

An AC resistance optimization method applicable for inductor and transformer windings with full layers and partial layers

Synchronous interleaved boost converters (SIBCs) result in lower ripple currents and bidirectional power flow. The boost topology has a non-minimum phase characteristic, producing instability problems when a large bandwidth is required. Linear controllers inherently limit the boost controller bandwidth, resulting in a slow response. In this paper, state-trajectory control of the SIBC based on boundary control is proposed to provide an outstanding dynamic response during start-up and sudden load changes, close to the physical limit of the system. The proposed controller and derivation provides a rigorous framework that deals with four switching states, and three state equations, resulting in a simple control law with very fast dynamic response. The normalized trajectories for the SIBC are determined in the geometric domain along with the control law. The exact trajectories are used for fast transients, and approximate trajectories are employed for constant frequency in steady-state. Simulation and experimental results are provided to validate the proposed procedures.

/pdf/introducing-state-trajectory-control-for-the-synchronous-4coaxveo92.pdf

Introducing state-trajectory control for the synchronous interleaved boost converter

Coxsackie virus B3 (CVB3), an enterovirus, is the main pathogen causing viral myocarditis, pericarditis, hepatitis and other inflammation-related diseases. Non-coding RNAs with a closed loop molecular structure, called circular RNAs (circRNAs), have been shown to be involved in multiple virus-related processes, but roles and mechanisms in CVB3 infection have not been systematically studied. In this study, when HeLa cells were infected with CVB3, the expression of hsa_circ_0000367 (circSIAE) was significantly decreased as demonstrated by real-time quantitative PCR assays. We found that circSIAE downregulated the expression of miR-331-3p through direct binding and inhibited the replication of CVB3 in HeLa and 293T cells. The analysis of signals downstream of miR-331-3p suggested that miR-331-3p promotes CVB3 replication, viral plaque formation and fluorescent virus cell production through interactions with the gene coding for thousand and one amino-acid kinase 2 (TAOK2). In conclusion, this study found that circSIAE can target TAOK2 through sponge adsorption of miR-331-3p to inhibit the replication and proliferation of CVB3 virus, providing an early molecular target for the diagnosis of CVB3 infection.

/pdf/the-circrna-circsiae-inhibits-replication-of-coxsackie-virus-93mfmo5e.pdf

The circRNA circSIAE Inhibits Replication of Coxsackie Virus B3 by Targeting miR-331-3p and Thousand and One Amino-Acid Kinase 2

This paper investigates the short circuit performance of commercial 1.7 kV / 1 kA IGBT power modules by means of a 6 kA Non-Destructive-Tester. A mismatched current distribution among the parallel chips has been observed, which can reduce the short circuit capability of the IGBT power module under short circuit conditions. Further Spice simulations reveal that the stray parameters inside the module play an important role in contributing to such a phenomenon.

/pdf/a-comprehensive-investigation-on-the-short-circuit-2whvmaagat.pdf

Huai Wang

Papers

A method for hotspot temperature estimation of aluminum electrolytic capacitors

An AC resistance optimization method applicable for inductor and transformer windings with full layers and partial layers

Introducing state-trajectory control for the synchronous interleaved boost converter

The circRNA circSIAE Inhibits Replication of Coxsackie Virus B3 by Targeting miR-331-3p and Thousand and One Amino-Acid Kinase 2

A comprehensive investigation on the short circuit performance of MW-level IGBT power modules