Hongik University
  • Seoul, South Korea
Recent publications
This paper presents our initial research findings on distribution system operator (DSO) functions in South Korea. The project team includes the Korean Electric Power Corporation, which is the only public utility company in South Korea. The planned development is based on a real distribution network and real-world environments. The project encompasses DSO–transmission system operator coordination and management of real-time distribution network congestion; this paper focuses on the latter aspect. For real-time congestion management, algorithms that handle all steps from database analysis to data export, including data preprocessing, topological configuration, power flow calculation, sensitivity analysis, and derivation of solutions to congestion, are developed. The distribution system equipment database of Korean Electric Power Corporation is used to develop a network congestion management system. When examining the database, many gaps between the theoretical and practical environments were found which are introduced in this paper. A practical distribution network database for South Korea is developed to narrow these gaps and to implement practical congestion management techniques. The remaining problems are introduced as future works.
We report a photosynthetic method for producing 2H‐benzo[b][1,4]oxazin‐2‐ones from aryl azides and α‐ketoacids. This method is highly sustainable, requiring only visible light irradiation of the substrates and no external additives. Furthermore, we implemented a continuous‐flow system to achieve efficient light irradiation and rapid mixing, significantly improving reaction efficiency and reducing reaction time compared to the batch process. The flow system enabled gram‐scale synthesis. We also demonstrated the utility of the products, by employing the benzo[1,4]oxazin‐2‐one moiety as a directing group for C−H activation on the 3‐aryl substituent. This green approach highlights the potential for developing environmentally friendly synthetic processes.
Blood cancers, including leukemia, multiple myeloma, and lymphoma, pose significant challenges owing to their heterogeneous nature and the limitations of traditional treatments. Precision medicine has emerged as a transformative approach that offers tailored therapeutic strategies based on individual patient profiles. Ex vivo drug sensitivity analysis is central to this advancement, which enables testing of patient-derived cancer cells against a panel of therapeutic agents to predict clinical responses. This review provides a comprehensive overview of the latest advancements in ex vivo drug sensitivity analyses and their application in blood cancers. We discuss the development of more comprehensive drug response metrics and the evaluation of drug combinations to identify synergistic interactions. Additionally, we present evaluation of the advanced therapeutics such as antibody–drug conjugates using ex vivo assays. This review describes the critical role of ex vivo drug sensitivity analyses in advancing precision medicine by examining technological innovations and clinical applications. Ultimately, these innovations are paving the way for more effective and individualized treatments, improving patient outcomes, and establishing new standards for the management of blood cancers.
Recent advancements in phase‐change memory (PCM) technology have predominantly stemmed from material‐level designs, which have led to fast and durable device performances. However, there remains a pressing need to address the enormous energy consumption through device‐level electrothermal solutions. Thus, the concept of a 3D heater‐all‐around (HAA) PCM fabricated along the vertical nanoscale hole of dielectric/metal/dielectric stacks is proposed. The embedded thin metallic heater completely encircles the phase‐change material, so it promotes highly localized Joule heating with minimal loss. Hence, a low RESET current density of 6–8 MA cm⁻² and operation energy of 150–200 pJ are achieved even for a sizable hole diameter of 300 nm. Beyond the conventional 2D scaling of the bottom electrode contact, it accordingly enhances ≈80% of operational energy efficiency compared to planar PCM with an identical contact area. In addition, reliable memory operations of ≈10⁵ cycles and the 3‐bits‐per‐cell multilevel storage despite ultrathin (<10 nm) sidewall deposition of Ge2Sb2Te5 are optimized. The proposed 3D‐scaled HAA‐PCM architecture holds promise as a universally applicable backbone for emerging phase‐change chalcogenides toward high‐density, ultralow‐power computing units.
In this paper, we introduce an economical technique based on a semi-implicit predictor–corrector scheme for solving fractional Benjamin–Bona–Mahony–Burgers equations, in which the Adams–Moulton schemes are used for predictor and corrector schemes. To resolve a nonlinearity of the given equations in the predictor procedure, the weighted Rubin–Graves linearization scheme is applied to convert the linearized equations at the predictor procedure. Moreover, to alleviate weak regularity at the initial time point, mixed meshes based on uniform grid are used so that it can save the computational costs by not recalculating the coefficients of Adams–Moulton methods for smaller time intervals. The convergence analysis are analytically executed to derive the convergence order and are numerically supported. Several numerical results are provided to show the efficiency of the proposed scheme.
This study investigates the transport of particles in density-stratified fluids, a prevalent natural phenomenon. In the ocean, particles and marine snow descend through fluids with significant density variations due to salinity and temperature gradients. Such heterogeneity in the background fluid affects the settling or rising rates of particles, often leading to accumulation at transitional density layers. Previous research has primarily focused on spherical particles, examining their isolated motion, pairwise interactions, and collective transport in stratified fluids. This work, however, extends the investigation to the interaction between two spheroidal particles settling in-line in a linearly stratified fluid. This study employs an immersed-boundary technique to perform particle-resolved numerical simulations in a three-dimensional Cartesian domain. The results showcase the effects of varying the stratification strength through the Froude number, the particles’ aspect ratios, and the initial separation distance between the particles on the interaction dynamics between the settling spheroids.
The novel dinuclear Pt(II) complexes, Di‐Pt‐CH3 and Di‐Pt‐CD3 with non‐fluorinated n‐hetero cyclic (NHC) ligands are developed. They exhibit phosphorescent emission in the range of 440–460 nm in film state with ≈60% photoluminescence quantum yield (PLQY) and a shorter lifetime due to a moderate Pt‐Pt distance of 3.21 Å. By suitably combining with blue multiresornance thermally activated delay fluorescence ( MR‐TADF) emitters, t‐DABNA and ν‐DABNA, efficient energy transfer is achieved from the triplet intraligand state (³IL) and triplet metal ligand change transfer (³MLCT) mixed states of Pt(II) complexes to the singlet state of the emitters. Importantly, the delayed triplet lifetime of the TADF emitter is shortened through the fast relaxation of triplet metal‐metal to ligand charge transfer (³MMLCT) states, possessing 0.07 eV lower energy compared to the triplet states of the TADF emitters. Di‐Pt‐CH3 and Di‐Pt‐CD3 are employed in phosphorescent and phosphorescent sensitized TADF (PS‐TADF) blue OLEDs, resulting in high external quantum efficiency (EQE) of 18.8% and 25.4%, respectively. An extremely low roll‐off characteristic of 9.8% is observed in the PS‐TADF OLED. Additionally, deuterium substitution of the methyl group improved phosphorescent device lifetime by 2.6 times. Notably, Di‐Pt‐CD3 resulted in significant lifetime enhancements: 4.7 times in phosphorescent devices and 6.6 times in PS‐TADF devices, compared with Ir(cb)3‐based devices. The mechanism for the increased lifetime is extensively studied through the magneto‐electroluminescence (MEL) and transient electroluminescence (TrEL) measurements.
This paper presents a spatiotemporal spacing policy with decentralized predecessor-following control for heterogeneous vehicle platooning. The spatiotemporal spacing policy is for range control between vehicles with the function of reducing the speed (legitimately) required at hazardous locations. Motivated by many studies on vehicle platoons and the absence of such spacing policies, this paper establishes the basic theory of the spatiotemporal spacing policy and string stability thereof. In addition to theoretical research, computational experiments are conducted to test the proposed spatiotemporal spacing policy and demonstrate its usefulness. An application example verifies that the spatiotemporal spacing policy accomplishes range control between vehicles and speed control required at hazard locations
Three-phase motor current information is essential for vector and torque control of motors. The use of dc-link single shunt has cost and size advantages and can reduce torque ripples caused by offset and scale differences. However, dc-link single shunt can measure the current only when an active voltage vector is applied, which will result in a large immeasurable region. Various current reconstruction schemes have been developed to eliminate immeasurable regions. Conventional solutions are effective only in specific immeasurable regions and limited in their ability to eliminate all the immeasurable regions and require complex calculations. This study proposes an optimal current reconstruction strategy that can be used in all immeasurable regions. The method divides the immeasurable region into three segments and selectively applies various pulsewidth modulation (PWM) techniques, including the proposed edge-aligned PWM method, which requires only simple calculations. The method can reduce the complexity and successfully eliminate all the immeasurable regions. The experiment results confirm the effectiveness and feasibility of the proposed method.
This paper proposes a cost-effective and reliable circuit configuration for active power decoupling in dual-inverter-fed open-end winding motor systems. Compared to separately installed active power decoupling circuits, the proposed configuration and control method that utilizes mode switches minimizes the number of components and prevents lifetime imbalance of the inverters by alternating their use every cycle while maintaining low voltage ripple. Junction temperature analysis of the power devices further indicates this approach can prevent lifetime imbalance and rapid aging of the dual-inverter system, resulting in enhanced overall system reliability. The effectiveness of the proposed configuration and control method is validated through a MATLAB/Simulink model and experimental tests using a digital signal processor.
PURPOSE Fatigue is a highly prevalent and disabling symptom for patients with metastatic breast cancer (MBC). Evidence-based interventions for managing fatigue in advanced cancer populations are lacking. This phase II randomized controlled trial tested the effect of acceptance and commitment therapy (ACT) on fatigue interference with functioning in patients with MBC. METHODS Eligible patients were women with stage IV breast cancer who had moderate to severe fatigue interference. Patients completed a baseline assessment that included self-report measures of fatigue interference with activities, mood, and cognition (primary outcome) and sleep interference with functioning, engagement in daily activities, and quality of life (QOL; secondary outcomes). Then patients were randomly assigned to six weekly telephone-delivered sessions of either ACT (n = 116) or education/support (n = 120). Follow-up assessments occurred at 2 weeks, 3 months, and 6 months postintervention (means, 9.69, 20.51, and 33.59 weeks postbaseline, respectively). RESULTS Linear mixed model analyses showed that compared with patients in the education/support condition, patients in the ACT condition reported significantly less fatigue interference ( P = .018). These results were significant at 2 weeks and 6 months postintervention. ACT's effect on sleep interference was not statistically significant after the Sidak adjustment for multiple comparisons ( P = .037). ACT patients showed a steady decline in sleep interference, a trend that was not found for education/support patients. Engagement in daily activities and QOL did not significantly differ between study groups, except for functional QOL ( P = .006). Compared with education/support patients, ACT patients showed significantly better functional QOL at 2 weeks and 6 months postintervention. CONCLUSION Results suggest that a brief, telephone-delivered ACT intervention can reduce fatigue interference with functioning in patients with MBC.
Traffic speed prediction is an important topic in Intelligent Transport Systems (ITS). Although traffic speed prediction for real-life applications is burgeoning, the study of explaining and interpreting AI-based speed prediction is still in its initial stage. In this paper, we applied multiple advanced regression techniques, such as XGBoost and CatBoost optimized gradient boosting, Random Forest, and LASSO to predict traffic speed more accurately in the subsequent time windows. The experiment with prediction methods was conducted using the traffic speed data of the Seoul metropolitan road network. Each road segment represented as a node in the network is associated with neighboring roads within a configurable range. We picked heavily congested nodes as prediction targets. Then, we evaluated nearby road influences to determine critical contributions to the situation of the target nodes. We interpreted the model’s output and extracted the topmost influential neighboring nodes by using an ensemble of explainable artificial intelligence (XAI) techniques such as feature importance assessment using the GINI entropy function, Recursive Feature Elimination, Shapely Additive Explanation, and a method of measuring the impact of masked nodes. We validated the XAI interpretations through traffic flow simulation by tuning the topmost influential nearby roads’ speed and observing the effect on the roads’ traffic congestion relief correspondingly. We also proved our solution through local explanation techniques such as Local Interpretable Model-Agnostic Explanations. Our methods are applicable to any transport network and open the door to new strategies for controlling the specific nearby roads for effective congestion relief.
https://www.tandfonline.com/eprint/JYTJ9IDEUKUCSQHYHSAU/full?target=10.1080/00309230.2024.2413152
Due to interest in thin films of oxides and nitrides of group 13 elements (Al, Ga, and In) and their multicomponent combinations, their atomic layer deposition (ALD) processes are being actively investigated. However, often in ALD of multicomponent thin films, the composition of the injected precursor species and atomic percentage in the deposited film show significant discrepancies. In this study, exchange reactions of the group 13 element atoms with other group 13 precursors are suggested as a factor affecting the composition of the ternary oxides and nitrides during ALD. Density functional theory calculations are performed to investigate the surface chemistry of the group 13 oxides and nitrides. After the initial adsorption of the first precursor on the substrate, sequential adsorption of the secondary injected precursor with a different metal element is contemplated. By estimating the kinetic and thermodynamic factors of the exchange reactions, the reactivity trend of the group 13 elements is found to follow the trend Al > Ga ∼ In, allowing the more active Al to undergo exchange with Ga and In on each surface, thereby making the deposited films richer in Al. These findings can contribute to the advancement of thin film fabrication for next-generation semiconductor or display devices.
This study empirically examines how employee compassion relates to job performance. Specifically, this study is a constructive replication and expansion of a previous study on the relationship between compassion and job performance using multiple sources of measurement. It investigates unexplored pathways within the public art sector in South Korea. Focusing on the mediating roles of positive work-related identity (PWRI) and positive psychological capital, we collected data from public art institutions in Korea, including galleries and museums, using a survey method. We tested the hypotheses using structural equation modeling and the PROCESS bootstrapping method. Our findings demonstrate a positive association between compassion and job performance, serially mediated by PWRI and positive psychological capital. Theoretically, by constructively replicating and expanding the previous findings, our study contributes to a robust understanding of how compassion could enhance employee performance. Practically, this study reinforces the value of fostering compassion and positive psychological resources to improve job performance, particularly within the public art sector.
Amorphous indium-gallium-zinc-oxide (a-IGZO) has been attracting great attention as a channel material for dynamic random access memory (DRAM) cell transistors due to its superior characteristics including low leakage current, large area deposition, and back-end-of-line (BEOL) compatibility. It should be clearly taken into account that DRAM will also be used in harsh environments such as military surveillance, aerospace, and nuclear power plants. Especially, these situations can cause inevitable and persistent degradation in long-term operations. When the a-IGZO thin film transistors (TFTs) were irradiated by gamma-ray with total doses of 500 Gy, threshold voltage (VT) was negatively shifted and hysteresis(delta of VT between forward and backward sweeps) was increased by creating a positive charge in gate insulator. The extracted density-of-states (DOS) and fitted model were employed to investigate the behavior of oxygen vacancy (VO) in a-IGZO thin film. Electrical performance degraded by gamma-ray irradiation such as changes in VT, border trap, tail acceptor-like states (gTA(E)), and shallow donor-like states (gSD(E)) were recovered through rapid thermal annealing (RTA) under the O2 ambient.
This paper focuses on the methodology for evaluating the degree of total curling in concrete pavement using machine learning. Deflection induced by falling weight deflectometer (FWD) testing is known as a direct correlation to total curling including built-in and daily curling. However, deflection measurement in the in-service road is also affected by others, such as environmental conditions, pavement geometry, subgrade stiffness, and mixture design. Thus, it is challenging to determine the level of curling from FWD data due to the complexity of influencing parameters. To navigate this complexity, prominent machine learning models are exploited to identify a non-linear relationship between curling and FWD deflections. A finite-element simulation of FWD is conducted to generate a vast data set, and a robust regression model is trained to estimate the total effective temperature difference (TETD) to quantify the effects of curling. Since input parameters for testing pavements can be measurable in the field, curling from TETD can be readily obtained using the proposed methodology. Comparative simulations highlight that the proposed models, with an MAE less than 0.5 °C significantly outperform the multiple regression performance, which registers an MAE of 3.45 °C in TETD, particularly in offering cost-effective and noise-tolerant prediction.
Institution pages aggregate content on ResearchGate related to an institution. The members listed on this page have self-identified as being affiliated with this institution. Publications listed on this page were identified by our algorithms as relating to this institution. This page was not created or approved by the institution. If you represent an institution and have questions about these pages or wish to report inaccurate content, you can contact us here.
1,376 members
Jeryang Park
  • Department of Civil & Environmental Engineering
Haeyoung Lee
  • Department of Computer Engineering
Jong Chang Yi
  • Department of Electronic and Electrical Engineering
Jae-Sang Ro
  • Department of Materials Science and Engineering
Seung Oh Lee
  • Department of Civil and Environmental Engineering
Information
Address
Seoul, South Korea