Hyungjin Park

Jinkwan Jang, Hyunbin Jin, Hyungjin Park et al.

Time series forecasting is critical to real-world decision making, yet most existing approaches remain unimodal and rely on extrapolating historical patterns. While recent progress in large language models (LLMs) highlights the potential for multimodal forecasting, existing benchmarks largely provide retrospective or misaligned raw context, making it unclear whether such models meaningfully leverage textual inputs. In practice, human experts incorporate what-if scenarios with historical evidence, often producing distinct forecasts from the same observations under different scenarios. Inspired by this, we introduce What If TSF (WIT), a multimodal forecasting benchmark designed to evaluate whether models can condition their forecasts on contextual text, especially future scenarios. By providing expert-crafted plausible or counterfactual scenarios, WIT offers a rigorous testbed for scenario-guided multimodal forecasting. The benchmark is available at https://github.com/jinkwan1115/WhatIfTSF.

Jinkwan Jang, Hyungjin Park, Jinmyeong Choi et al.

Real-world time series data are inherently multivariate, often exhibiting complex inter-channel dependencies. Each channel is typically sampled at its own period and is prone to missing values due to various practical and operational constraints. These characteristics pose three fundamental challenges involving channel dependency, sampling asynchrony, and missingness, all of which must be addressed simultaneously to enable robust and reliable forecasting in practical settings. However, existing architectures typically address only parts of these challenges in isolation and still rely on simplifying assumptions, leaving unresolved the combined challenges of asynchronous channel sampling, test-time missing blocks, and intricate inter-channel dependencies. To bridge this gap, we propose ChannelTokenFormer, a Transformer-based forecasting framework with a flexible architecture designed to explicitly capture cross-channel interactions, accommodate channel-wise asynchronous sampling, and effectively handle missing values. Extensive experiments on public benchmark datasets reflecting practical settings, along with one private real-world industrial dataset, demonstrate the superior robustness and accuracy of ChannelTokenFormer under challenging real-world conditions.

Gihoon Kim, Hyungjin Park, Taesup Kim

Personalization using text-to-image diffusion models involves adapting a pretrained model to novel subjects with only a few image examples. This task presents a fundamental challenge, as the model must not only learn the new subject effectively but also preserve its ability to generate diverse and coherent outputs across a wide range of prompts. In other words, successful personalization requires integrating new concepts without forgetting previously learned generative capabilities. Forgetting denotes unintended distributional drift, where the model's output distribution deviates from that of the original pretrained model. In this paper, we provide an analysis of this issue and identify a mismatch between standard training objectives and the goals of personalization. To address this, we propose a new training objective based on a Lipschitz-bounded formulation that explicitly constrains deviation from the pretrained distribution. Our method provides improved control over distributional drift and performs well even in data-scarce scenarios. Experimental results demonstrate that our approach consistently outperforms existing personalization methods, achieving higher CLIP-T, CLIP-I, and DINO scores.