김영용 교수

We identify important characteristics of a fading/shadowing channel and present the work of measurement-based channel modeling for packet-level network queueing analysis. Our integration of wireless channel modeling and data queueing analysis at the packet-level provides a unique approach to study the effect of various channel dynamics on high-layer network performance, which otherwise cannot be captured through the traditional bit-level physical-layer channel modeling. In our study, the channel

Poly( N ‐(1‐hexylheptyl)‐ N ′‐(12‐oxydodecyl)perylene‐3,4,9,10‐tetracarboxyldiimide acrylate) (PAcPDI), a perylene diimide (PDI) containing brush polymer, is synthesized, revealing good solubility in organic solvents, excellent thermal stability up to around 340 °C, and two melting transitions over 130−220 °C. The self‐assembly and n‐type memory characteristics of PAcPDI in nanoscale thin films are quantitatively investigated. As‐cast films of PAcPDI are completely amorphous and the PDI units ne

A series of miktoarm star polymers, [poly( n -hexyl isocyanate)(12K)]–[poly(ε-caprolactone) 1–3 (5K)] (PHIC–PCL 1–3 ) (composed of a rigid self-assembling PHIC arm and one to three flexible crystallizable PCL arms), were investigated to examine the polymers’ thermal properties and nanoscale thin film morphologies. The miktoarm polymers were stable up to 180 °C. The PHIC and PCL arm components underwent phase separation during the solution casting, drying, and post toluene-annealing processes, fo

A diblock copolymer of crystalline polyethylene (PE) and amorphous poly(methyl methacrylate) (PMMA), PE 69 - b -PMMA 92, was synthesized; this polymer is thermally stable up to 270 °C. The morphological structures of thermally annealed nanoscale thin films of the copolymer were investigated in detail at various temperatures by using in-situ grazing incidence X-ray scattering (GIXS) with a synchrotron radiation source. Quantitative GIXS analysis found that the PE and PMMA blocks undergo phase sep

The fast fading channel modeling traditionally focuses on physical-level dynamics such as signal strength and bit error rate. We characterize fast fading channel dynamics at the packet-level and analyze the corresponding data queueing performance in various environments. The integration of wireless channel modeling and data queueing analysis provides us a unique way to capture important channel statistics with respect to various wireless network factors such as channel bandwidth, mobile speed an

Here we present the results of a classical ghost imaging experiment accomplished at an XUV free-electron laser (FEL). To perform such experiment at an FEL source each x-ray pulse was transmitted through a moving diffuser, which created a noncorrelated speckled beam. This beam was then split in two identical branches by introducing a beam splitter in the form of a transmission grating. In one of these branches the sample was positioned. We demonstrate the possibility of image formation, a double

A new approach for synthesizing well-defined hollow nanochanneled-silica nanosphere particles is demonstrated, and the structural details of these particles are described for the first time. Positively charged styrene copolymer nanospheres with a clean, smooth surface and a very narrow size distribution are synthesized by surfactant-free emulsion copolymerization and used as a thermal sacrificial core template for the production of core-shell nanoparticles. A surfactant/silica composite shell wi

A Na 2 V 6 O 16 ·2H 2 O cathode, synthesized via Na pre-intercalation using a sonochemical method, enhances Zn-ion storage by improving structural stability. The NaVO//Zn battery delivers 126 mA h g −1 and retains 91.8% of its capacity after 10 000 cycles.

This study proposes a novel approach to achieving highly reliable, low-voltage polarization switching of ferroelectric Hf 0.5 Zr 0.5 O 2 (HZO) thin films using polymorph- and orientation-controlled W electrodes ((111)-textured α-W and (200)-textured β-W) by adjusting the sputtering conditions. We demonstrated the formation of (111) and (002)/(020)-textured HZO films on the (111)-textured α-W and (200)-textured β-W electrodes, respectively. Under a low-voltage pulse of 1.2 V (1.5 MV/cm), α-W/HZO/

This article investigates the formulation of supervisory feedback messages as a function of attributions regarding poor subordinate performance and feedback goals. Theory and research drawn from feedback and attribution literatures were used to develop the research question. Data to investigate the research question were drawn from nurse managers at general hospitals. The results indicate that the goal of supervisors is an important driving force in determining the type of feedback generated, wh

A Hanbury Brown and Twiss interferometry experiment based on second-order correlations was performed at the PAL-XFEL facility. The statistical properties of the X-ray radiation were studied within this experiment. Measurements were performed at the NCI beamline at 10 keV photon energy under various operation conditions: self-amplified spontaneous emission (SASE), SASE with a monochromator, and self-seeding regimes at 120 pC, 180 pC and 200 pC electron bunch charge. Statistical analysis showed sh

High Resolution Image Download MS PowerPoint Slide The crystallographic texture of Hf 0.5 Zr 0.5 O 2 (HZO) thin films plays a crucial role in determining their ferroelectric properties, requiring a deeper understanding of the texture transfer from the substrate. This study investigated the influence of the deposition temperature on the crystallographic texture, residual stress, and ferroelectric properties of HZO thin films. Grazing-incidence wide-angle X-ray scattering analyses confirmed a pron

We demonstrate a fast, simple, and high-resolution absorption spectroscopy approach for high photon energies with free-electron laser sources. The method fosters new possibilities for measurements of absorption spectra in complex samples especially for photo-induced phenomena.