김영하 교수

Abstract. The Stratosphere–troposphere Processes And their Role in Climate (SPARC) Quasi-Biennial Oscillation initiative (QBOi) aims to improve the fidelity of tropical stratospheric variability in general circulation and Earth system models by conducting coordinated numerical experiments and analysis. In the equatorial stratosphere, the QBO is the most conspicuous mode of variability. Five coordinated experiments have therefore been designed to (i) evaluate and compare the verisimilitude of mod

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Abstract. The momentum forcing of the QBO (quasi-biennial oscillation) by equatorial waves is estimated using recent reanalyses. Based on the estimation using the conventional pressure-level data sets, the forcing by the Kelvin waves (3–9 m s−1 month−1) dominates the net forcing by all equatorial wave modes (3–11 m s−1 month−1) in the easterly-to-westerly transition phase at 30 hPa. In the opposite phase, the net forcing by equatorial wave modes is small (1–5 m s−1 month−1). By comparing the res

A novel design strategy is presented for a dual-stage actuator servo system in magnetic disk drives. Based on the existing decoupled-design strategy, we adopt the idea of the well-known zero-phase error tracking controller to minimize destructive effect resulting when two control loops are combined. Since the zero-phase tracking control requires previews of signals in a feedback loop, a kind of estimation scheme is suggested based on the actuators' dynamic model. The best practical advantage is

Abstract In a companion paper, the Multiscale Gravity Wave Model (MS-GWaM) has been introduced and its application to a global model as a transient subgrid-scale parameterization has been described. This paper focuses on the examination of intermittency of gravity waves (GWs) modeled by MS-GWaM. To introduce the variability and intermittency in wave sources, convective GW sources are formulated, using diabatic heating diagnosed by the convection parameterization, and they are coupled to MS-GWaM

The adhesion behavior of Ti thin films to several oxide substrates has been studied. Ti was electron beam deposited onto single-crystal sapphire, magnesia, quartz, and fused silica substrates. Adhesion was measured by the peel test. Ti adhesion to sapphire was the highest, followed by magnesia, quartz, and fused silica, respectively. In situ x-ray photoelectron spectroscopy (XPS) studies demonstrate that the chemical effect is not a major factor in the adhesion strength in the systems investigat

A novel library of amino-substituted 2-pyridones has been constructed through a two-step sequence of microwave-promoted Buchwald-Hartwig amination of 2-benzyloxy halopyridines followed by debenzylation. Microwave-promoted amination of 3- or 4-halopyridine in the presence of a suitable palladium catalyst and ligand system provided amino-substituted 2-benzyloxypyridines in excellent yields. Then, debenzylation of 2- benzyloxypyridines afforded the corresponding 2-pyridones with high efficiency.

본 연구는 국화과에 속하는 유럽 원산의 외래잡초인 가시상추(Lactuca scariola)의 분포와 생육지 유형별 특성을 조사하여 관리 계획에 필요한 기초적인 자료를 제공하고자 하였다. 가시상추는 전국의 211개 지점에서 분포가 확인되었고, 생육지 유형은 크게 나지, 도로변, 항구 및 항만 주변과 하천변 등 4가지로 구분되었다. 종순위-우점도 곡선을 이용한 종다양성 지수는 도로변에서 가장 높았고, 항구 및 항만주변, 나지, 도로변의 순서였다. 생육지 유형별로 총 32개 조사지역에서 공통 출현한 식물의 빈도는, 달맞이꽃이 24회로 가장 높았고, 돼지풀 17회, 쑥 16회 등이 조사되었다. 또한, 가시상추 생육지에서의 식물상은 총 26과 77속 89종 7변종 1품종으로 총 97분류군이 확인되었는데, 외래식물은 44종으로 전체의 45.4%를 차지하였다. 생활형을 분석한 결과, Th-D4-R5-e로 1년생 식물(Th)이 가장 높은 빈도를 차지하여 가시상추의 생육지가 인간 활동으로 인하여 교

Abstract. ​​​​​​​In climate modelling, the reality of simulated flows in the middle atmosphere is largely affected by the model's representation of gravity wave processes that are unresolved, while these processes are usually simplified to facilitate computations. The simplification commonly applied in existing climate models is to neglect wave propagation in horizontal direction and time. Here we use a model that fully represents the propagation of unresolved waves in all directions, thereby el

Abstract. For a case study of Typhoon Ewiniar performed with a mesoscale model, we compare stratospheric gravity wave (GW) momentum flux determined from temperature variances by applying GW polarization relations and by assuming upward propagating waves, with GW momentum flux calculated from model winds which is considered as a reference. The temperature-based momentum-flux profile exhibits positive biases relative to the reference, which fluctuate significantly with altitude. The vertically-ave

We investigate the effects of planetary rotation on the exospheres of the earth and Mars with simple collisionless models. We develope a numerical code that computes exospheric densities by integrating velocity functions at the exobase with a 10 point Gauss method. It is assumed in the model that atoms above the exobase altitude move collisionlessly on an orbit under the planet's gravity. Temperatures and densities at the exobase over the globe are adopted from MSIS-86 for the earth and from Bou

Immune cells express toll-like receptors (TLRs) and respond to molecular patterns of various pathogens. CpG motif in bacterial DNA activates innate and acquired immune systems through binding to TLR9 of immune cells. Several studies reported that CpG can directly regulate B cell activation, differentiation, and Ig production. However, the role of CpG in B cell growth and Ig production is not fully understood. In this study, we analyzed the effect of CpG on the kinetics of mouse B cell viability,