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result(s) for
"Kim, Joo-Young"
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Biased Pressure: Cyclic Reinforcement Learning Model for Intelligent Traffic Signal Control
2022
Existing inefficient traffic signal plans are causing traffic congestions in many urban areas. In recent years, many deep reinforcement learning (RL) methods have been proposed to control traffic signals in real-time by interacting with the environment. However, most of existing state-of-the-art RL methods use complex state definition and reward functions and/or neglect the real-world constraints such as cyclic phase order and minimum/maximum duration for each traffic phase. These issues make existing methods infeasible to implement for real-world applications. In this paper, we propose an RL-based multi-intersection traffic light control model with a simple yet effective combination of state, reward, and action definitions. The proposed model uses a novel pressure method called Biased Pressure (BP). We use a state-of-the-art advantage actor-critic learning mechanism in our model. Due to the decentralized nature of our state, reward, and action definitions, we achieve a scalable model. The performance of the proposed method is compared with related methods using both synthetic and real-world datasets. Experimental results show that our method outperforms the existing cyclic phase control methods with a significant margin in terms of throughput and average travel time. Moreover, we conduct ablation studies to justify the superiority of the BP method over the existing pressure methods.
Journal Article
Grasping through dynamic weaving with entangled closed loops
2023
Pick-and-place is essential in diverse robotic applications for industries including manufacturing, and assembly. Soft grippers offer a cost-effective, and low-maintenance alternative for secure object grasping without complex sensing and control systems. However, their inherent softness normally limits payload capabilities and robustness to external disturbances, constraining their applications and hindering reliable performance. In this study, we propose a weaving-inspired grasping mechanism that substantially increases payload capacity while maintaining the use of soft and flexible materials. Drawing from weaving principles, we designed a flexible continuum structure featuring multiple closed-loop strips and employing a kirigami-inspired approach to enable the instantaneous and reversible creation of a woven configuration. The mechanical stability of the woven configuration offers exceptional loading capacity, while the softness of the gripper material ensures safe and adaptive interactions with objects. Experimental results show that the 130 g·f gripper can support up to 100 kg·f. Outperforming competitors in similar weight and softness domains, this breakthrough, enabled by the weaving principle, will broaden the scope of gripper applications to previously inaccessible or barely accessible fields, such as agriculture and logistics.
Song et al. use the weaving principle to overcome load capacity limitations in soft grippers. The woven structure enables exceptional load capacity, supporting up to 100 kg·f with a 130 g·f gripper, while also offering adaptive interactions with objects.
Journal Article
Programming ultrasensitive threshold response through chemomechanical instability
2021
The ultrasensitive threshold response is ubiquitous in biochemical systems. In contrast, achieving ultrasensitivity in synthetic molecular structures in a controllable way is challenging. Here, we propose a chemomechanical approach inspired by Michell’s instability to realize it. A sudden reconfiguration of topologically constrained rings results when the torsional stress inside reaches a critical value. We use DNA origami to construct molecular rings and then DNA intercalators to induce torsional stress. Michell’s instability is achieved successfully when the critical concentration of intercalators is applied. Both the critical point and sensitivity of this ultrasensitive threshold reconfiguration can be controlled by rationally designing the cross-sectional shape and mechanical properties of DNA rings.
Controlling the threshold response in synthetic molecular structures is challenging. Here, the authors report on the buckling of ring-shaped DNA origami structures into twisted architectures via mechanical instability, induced by DNA intercalators.
Journal Article
Lysosomal Ca2+-mediated TFEB activation modulates mitophagy and functional adaptation of pancreatic β-cells to metabolic stress
2022
Although autophagy is critical for pancreatic β-cell function, the role and mechanism of mitophagy in β-cells are unclear. We studied the role of lysosomal Ca
2+
in TFEB activation by mitochondrial or metabolic stress and that of TFEB-mediated mitophagy in β-cell function. Mitochondrial or metabolic stress induced mitophagy through lysosomal Ca
2+
release, increased cytosolic Ca
2+
and TFEB activation. Lysosomal Ca
2+
replenishment by ER
-
> lysosome Ca
2+
refilling was essential for mitophagy. β-cell-specific
Tfeb
knockout (
Tfeb
Δβ-cell
) abrogated high-fat diet (HFD)-induced mitophagy, accompanied by increased ROS and reduced mitochondrial cytochrome
c
oxidase a
c
tivity or O
2
consumption.
Tfeb
Δβ-cell
mice showed aggravation of HFD-induced glucose intolerance and impaired insulin release. Metabolic or mitochondrial stress induced TFEB-dependent expression of mitophagy receptors including
Ndp52
and
Optn
, contributing to the increased mitophagy. These results suggest crucial roles of lysosomal Ca
2+
release coupled with ER
-
> lysosome Ca
2+
refilling and TFEB activation in mitophagy and maintenance of pancreatic β-cell function during metabolic stress.
Autophagy is important for pancreatic β-cell function, however, the role of mitophagy and mechanism for mitophagy in β-cells are unclear. Here the authors report that in stressed β-cells, lysosomal Ca
2+
release promotes mitophagy via activation of the transcription factor EB (TFEB) and loss of β-cell TFEB aggravates glucose intolerance during high-fat diet.
Journal Article
Intravitreal aflibercept and ranibizumab for pachychoroid neovasculopathy
2019
This retrospective study was to compare the efficacy of intravitreal injection of ranibizumab and aflibercept for patients with pachychoroid neovasculopathy. 54 eyes were initially treated with 3 monthly loading injections of ranibizumab or aflibercept. Treatment switching from ranibizumab to aflibercept, and aflibercept to photodynamic therapy was done at 3 months in case of incomplete fluid absorption. At 3 months, the rate of complete fluid absorption was significantly higher in the aflibercept-treated group than in the ranibizumab-treated group (82.6% vs 51.6%,
p
= 0.018). The mean reduction of subfoveal choroidal thickness was significantly greater in the aflibercept group than in the ranibizumab group (−35 µm vs −9 µm,
p
= 0.013). There was no significant difference between the two groups in terms of visual improvement or decrease in central macular thickness. Complete fluid absorption was achieved after switching from ranibizumab to aflibercept in 13 of 15 eyes (86.7%). Adjunctive photodynamic therapy was required in 6 eyes. In conclusion, treatment mainly with anti-vascular endothelial growth factor effectively improved visual acuity within 12 months (from 20/56 to 20/44 at 3 months and to 20/36 at 12 months). Aflibercept was superior to ranibizumab in achieving dry macula and reducing choroidal thickness at 3 months.
Journal Article
High temperature attenuates the gravitropism of inflorescence stems by inducing SHOOT GRAVITROPISM 5 alternative splicing in Arabidopsis
by
Park, Chung‐Mo
,
Kim, Joo‐Young
,
Ryu, Jae Yong
in
Alternative Splicing
,
Arabidopsis
,
Arabidopsis - genetics
2016
In higher plants, gravitropism proceeds through three sequential steps in the responding organs: perception of gravity signals, signal transduction and asymmetric cell elongation. Light and temperature also influence the gravitropic orientation of plant organs. A series of Arabidopsis shoot gravitropism (sgr) mutants has been shown to exhibit disturbed shoot gravitropism. SGR5 is functionally distinct from other SGR members in that it mediates the early events of gravitropic responses in inflorescence stems. Here, we demonstrated that SGR5 alternative splicing produces two protein variants (SGR5α and SGR5β) in modulating the gravitropic response of inflorescence stems at high temperatures. SGR5β inhibits SGR5α function by forming non‐DNA‐binding heterodimers. Transgenic plants overexpressing SGR5β (35S:SGR5β) exhibit reduced gravitropic growth of inflorescence stems, as observed in the SGR5‐deficient sgr5‐5 mutant. Interestingly, SGR5 alternative splicing is accelerated at high temperatures, resulting in the high‐level accumulation of SGR5β transcripts. When plants were exposed to high temperatures, whereas gravitropic curvature was reduced in Col‐0 inflorescence stems, it was uninfluenced in the inflorescence stems of 35S:SGR5β transgenic plants and sgr5‐5 mutant. We propose that the thermoresponsive alternative splicing of SGR5 provides an adaptation strategy by which plants protect the shoots from hot air under high temperature stress in natural habitats.
Journal Article
Semi-Supervised Domain Adaptation for Multi-Label Classification on Nonintrusive Load Monitoring
by
Lee, Han-Eum
,
Hur, Cheong-Hwan
,
Kim, Young-Joo
in
Adaptation
,
Algorithms
,
appliance usage classification
2022
Nonintrusive load monitoring (NILM) is a technology that analyzes the load consumption and usage of an appliance from the total load. NILM is becoming increasingly important because residential and commercial power consumption account for about 60% of global energy consumption. Deep neural network-based NILM studies have increased rapidly as hardware computation costs have decreased. A significant amount of labeled data is required to train deep neural networks. However, installing smart meters on each appliance of all households for data collection requires the cost of geometric series. Therefore, it is urgent to detect whether the appliance is used from the total load without installing a separate smart meter. In other words, domain adaptation research, which can interpret the huge complexity of data and generalize information from various environments, has become a major challenge for NILM. In this research, we optimize domain adaptation by employing techniques such as robust knowledge distillation based on teacher–student structure, reduced complexity of feature distribution based on gkMMD, TCN-based feature extraction, and pseudo-labeling-based domain stabilization. In the experiments, we down-sample the UK-DALE and REDD datasets as in the real environment, and then verify the proposed model in various cases and discuss the results.
Journal Article
Smart Pack: Online Autonomous Object-Packing System Using RGB-D Sensor Data
by
Hong, Young-Dae
,
Kim, Young-Joo
,
Lee, Ki-Baek
in
3D bin packing problem
,
Automation
,
Deep learning
2020
This paper proposes a novel online object-packing system which can measure the dimensions of every incoming object and calculate its desired position in a given container. Existing object-packing systems have the limitations of requiring the exact information of objects in advance or assuming them as boxes. Thus, this paper is mainly focused on the following two points: (1) Real-time calculation of the dimensions and orientation of an object; (2) Online optimization of the object’s position in a container. The dimensions and orientation of the object are obtained using an RGB-D sensor when the object is picked by a manipulator and moved over a certain position. The optimal position of the object is calculated by recognizing the container’s available space using another RGB-D sensor and minimizing the cost function that is formulated by the available space information and the optimization criteria inspired by the way people place things. The experimental results show that the proposed system successfully places the incoming various shaped objects in their proper positions.
Journal Article
Site Application of Thermally Conductive Concrete Pavement: A Comparison of Its Thermal Effectiveness with Normal Concrete Pavement
2025
In this study, the thermal effectiveness of thermally conductive concrete pavements (TCPs) using silicon carbide (SiC) as a fine aggregate replacement was investigated, compared with that of ordinary Portland cement pavements (OPCPs). The most important purpose of this study is to improve the thermal performance of concrete pavement. Additionally, this study utilized improved thermal properties to enhance the efficiency of pavement heating to prevent icing and snow stacking. Both mixtures met the Korean standards for air content (4.5–6%) and slump (80–150 mm), demonstrating adequate workability. TCP exhibited a higher mechanical performance, with average compressive and flexural strengths of 42.88 MPa and 7.35 MPa, respectively, exceeding the required targets of a 30 MPa compressive strength and a 4.5 MPa flexural strength. The improved strength was mainly attributed to the filler effect and partly due to the van der Waals interactions of the SiC particles. Thermal conductivity tests showed a significant improvement in the TCP (3.20 W/mK), which was approximately twice that of OPCP (1.59 W/mK), indicating an enhanced heat transfer efficiency. In winter field tests, TCP effectively maintained high surface temperatures, overcoming heat loss and outperforming the OPCP. In the site experiment, thermal efficiency was clearly shown in the temperature at the center of the TCP, which was 3.5 °C higher than at the center of the OPCP at the coldest time. These improvements suggest that SiC-reinforced concrete pavements can be practically utilized for effective snow removal and ice mitigation in road systems.
Journal Article
Heterogeneous Impacts of Body Mass Index on Work Hours
2021
This study examined how higher body mass index (BMI) affects the work hours of men and women and how the impact varies by gender and the value of BMI. Using a longitudinal dataset of 1603 British adults (men: n = 775; women: n = 828) and a panel threshold regression model, this study estimated that BMI has significant impacts on work hours but the pattern is different by gender and BMI groups. BMI is positively associated with work hours up to the estimated BMI threshold of 30, which corresponds to the clinical cutoff point of obesity; above this point, additional increases in BMI is associated with reduced work hours. The asymmetric nonlinear relationship between BMI and work hours was more evident among women, particularly female low-skilled workers. The results imply reduced work capacity and lower labor income for women with a higher BMI above an obesity threshold, highlighting a practical role of BMI’s obesity cutoff value. The findings of this study provide a new perspective regarding the economic burden of workplace obesity and point out the need to design gender-specific and BMI-based strategies to tackle productivity loss from obesity.
Journal Article