Jongwon Lee

Electrically tunable mid‐infrared metasurfaces with nanosecond response time and broad tuning range are reported. Electrical tuning is achieved by employing strong polaritonic coupling of electromagnetic modes in metallic nanoresonators with voltage‐tunable inter‐subband transitions in semiconductor heterostructures, tailored for a giant quantum‐confined Stark effect. Experimentally, a 220‐nm‐thick multi‐quantum‐well semiconductor layer is sandwiched between a ground plane and a metal layer patt

Ultrathin metasurfaces with record-high nonlinear optical response of 1.2 × 106 pm V−1 for second harmonic generation are experimentally demonstrated in the mid-infrared spectral range. A second harmonic power conversion efficiency of 0.075% is achieved in a 400-nm-thick (λ/25) metasurface at a pump intensity of only 15 kW cm−2. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized f

Abstract Lithium (Li) metal is regarded as the most attractive anode material for high‐energy Li batteries, but it faces unavoidable challenges—uncontrollable dendritic growth of Li and severe volume changes during Li plating and stripping. Herein, a porous carbon framework (PCF) derived from a metal–organic framework (MOF) is proposed as a dual‐phase Li storage material that enables efficient and reversible Li storage via lithiation and metallization processes. Li is electrochemically stored in

Nonlinear metasurfaces are advancing into a new paradigm of "flat nonlinear optics" owing to the ability to engineer local nonlinear responses in subwavelength-thin films. Recently, attempts have been made to expand the design space of nonlinear metasurfaces through nonlinear chiral responses. However, the development of metasurfaces that display both giant nonlinear circular dichroism and significantly large nonlinear optical response is still an unresolved challenge. Herein, we propose a metho

Abstract Metasurfaces that generate nonlinear optical responses provide new degrees of freedom for applications such as nonlinear holography, wave mixing, and new frequencies generation. To extend the utility of flat nonlinear optics, metasurfaces providing both giant nonlinear response for efficient frequency mixing in subwavelength films and a single‐beam output with a local wavefront control need to be developed. Metasurfaces with giant nonlinear response have recently been realized using the

Soft errors are becoming a critical concern in embedded system designs. Code duplication techniques have been proposed to increase the reliability in multi-issue embedded systems such as VLIW by exploiting empty slots for duplicated instructions. However, they increase code size, another important concern, and ignore vulnerability differences in instructions, causing unnecessary or inefficient protection when selecting instructions to be duplicated under constraints. In this article, we propose

The proton exchange membrane fuel cell (PEMFC) has received a great attention as a clean power generator to convert the chemical energy of hydrogen to electric energy electrochemically. It has major advantages for the portable electronic devices and transportation/stationary power systems such as the high power density and high energy efficiency, rapid start-up, etc. One of the most widely used proton exchange membrane is perfluorosulfonic acid (Nafion, DuPont Co.). It has excellent thermal and

Steam methane reforming has been extensively used in producing syngas, but the H2/CO ratio of the syngas produced by the method is too large to feed to subsequent processes such as the Fischer–Tropsch process. The dry methane reforming process produces a syngas with a small H2/CO ratio. Combining these two processes makes it possible to adjust the H2/CO ratio to provide a syngas with a proper ratio for subsequent processes. Dry reforming is well-known to suffer a severe coke generation problem.

We found that high Ki-67LI, younger age, post-NAC status, higher histologic grade, larger tumor size, and specific morphological attributes were significant factors for predicting successful PDX engraftment of primary breast cancer.

A significant amount of stone sludge is generated as a by-product during the production of crushed stone aggregate, and most of it is disposed of in landfill as waste. In order to recycle this stone sludge, this study evaluated a controlled low-strength material (CLSM) using ultra-rapid-hardening cement and stone sludge for application as backfill and subbase material for road excavation and restoration work. In addition, considering the limited construction time of excavation and restoration wo

Sulfonated poly(fluorinated arylene ether)s (SDF-F)/poly[(N-vinylimidazole)-co-(3-methacryloxypropyl-trimethoxysilane)] (poly(VI-co-MPS))/poly(tetrafluoroethylene) (PTFE) is prepared for a high temperature proton exchange membrane fuel cell (PEMFC). The reaction of the membrane with phosphoric acid forms silicate phosphor, as a chemically bound proton carrier, in the membrane. Thus-formed silicate phosphor, nitrogen in the imidazole ring, and physically bound phosphoric acid act as proton carrie

This paper proposes a linear-time complex-valued eigenvalue solver for solving large-scale on-chip interconnect problems. The fast eigenvalue solution is achieved by eigenvalue clustering, fast system reduction with negligible computational cost, and fast linear-time solution of the reduced system. Numerical and experimental results are presented to demonstrate the accuracy and efficiency of the proposed method.

Intersubband transitions in semiconductor heterostructures offer a way to achieve large and designable nonlinearities with dynamic modulation of intersubband energies through the Stark effect. One promising approach for incorporating these nonlinearities into free space optics is a nonlinear polaritonic metasurface, which derives resonant coupling between intersubband nonlinearities and optical modes in nanocavities. Recent work has shown efficient frequency mixing at low pumping intensities, wi