Hanyang University

About: Hanyang University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Thin film & Population. The organization has 29387 authors who have published 58815 publications receiving 1190144 citations. The organization is also known as: Hanyang Taehakkyo.

Surface modification of cathode materials from nano- to microscale for rechargeable lithium-ion batteries

Abstract: The present concern with global warming urgently requires a large increase in the energy share provided by green, renewable energy sources, as well as massive commercialization of sustainable vehicles The widespread availability of reliable energy storage systems and highly efficient lithium batteries can, in principle, meet this need For example, many individuals already own at least one lithium-ion battery portable device, such as a cellular phone, MP3 player, digital camera, or laptop computer Hybrid electric vehicles and full electric vehicles will sooner or later be marketed with lithium-ion batteries However, to acquire an established role in the commercial sector, lithium-ion batteries must be improved with regard to energy density, cost, and particularly, safety Further development of electrode materials, especially the cathode active materials, is important to satisfy the above requirements The easiest route to cathode improvement is to modify the cathode surface This article describes recent advances in cathode active materials with surface modification from the nano- to microscale

Scheduling algorithm of data sampling times in the integrated communication and control systems

Abstract: Integrated communication and control systems (ICCS) consist of several distributed control processes which share a network medium. Performance of several feedback control loops in the ICCS is subject to the network-induced delays from sensor to controller and from controller to actuator. The network-induced delays are directly dependent upon the data sampling times of the control components which share a network medium. In this study, a scheduling algorithm of determining data sampling times is developed using the window concept, where the sampled data from the control components in the ICCS share a limited number of windows, so that the performance requirement of each control loop is satisfied as well as the utilization of network resources is considerably increased. The scheduling algorithm is verified by discrete-event/continuous-time simulation model of an example of ICCS. >

Li–O2 cells with LiBr as an electrolyte and a redox mediator

Abstract: After many years of successful and disappointing results, the field of Li–O2 research seems to have reached an equilibrium state. The extensive knowledge that has accrued through advanced analytical studies enables us to delineate the weaknesses of the Li–O2 battery. It is now clear that the instability of the cell components toward extreme conditions existing during cell operation leads to early cell failure as well. One serious challenge is the high oxidation potential applied during the charge process. Redox-mediators may reduce the over-potential and, therefore, improve the efficiency and cyclability of Li–O2 cells. Their use in Li–O2 cells is mandatory. We have previously shown that LiI can indeed behave in such a manner; however, it also promotes the formation of side products during cell operation. We have, therefore, embarked on a comprehensive study of lithium halide salts as electrolytes for use in Li–O2 cells. We examine herein the effect of other components in the cell, such as solvents and contaminants, on the lithium halide salt activity. Based on the electrochemical behavior and the identity of the final cell products under various conditions, we can glean substantial information regarding the detailed operation mechanisms for each specific case. We have concluded that low concentration of LiBr in diglyme solution can improve the cell performance with fewer side effects than LiI. With LiBr, only the desired Li2O2 is formed during discharge. During charge, the bromine redox couple (Br−/Br3−) can reduce the oxidation potential to only 3.5 V. Higher efficiency and better cyclability of cells containing LiBr demonstrate that the electrolyte solution is the key to a successful Li–O2 battery.

All-solid-state spatial light modulator with independent phase and amplitude control for three-dimensional LiDAR applications

Abstract: Spatial light modulators are essential optical elements in applications that require the ability to regulate the amplitude, phase and polarization of light, such as digital holography, optical communications and biomedical imaging. With the push towards miniaturization of optical components, static metasurfaces are used as competent alternatives. These evolved to active metasurfaces in which light-wavefront manipulation can be done in a time-dependent fashion. The active metasurfaces reported so far, however, still show incomplete phase modulation (below 360°). Here we present an all-solid-state, electrically tunable and reflective metasurface array that can generate a specific phase or a continuous sweep between 0 and 360° at an estimated rate of 5.4 MHz while independently adjusting the amplitude. The metasurface features 550 individually addressable nanoresonators in a 250 × 250 μm2 area with no micromechanical elements or liquid crystals. A key feature of our design is the presence of two independent control parameters (top and bottom gate voltages) in each nanoresonator, which are used to adjust the real and imaginary parts of the reflection coefficient independently. To demonstrate this array’s use in light detection and ranging, we performed a three-dimensional depth scan of an emulated street scene that consisted of a model car and a human figure up to a distance of 4.7 m. By controlling two voltage gates separately from one another, a spatial light modulator has been made that can continuously vary the phase of 360 degrees while independently adjusting the amplitude.