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Estimation of a Shear-wave Velocity Structure and Topographic Ground Motion Amplifications in the Pohang Basin, South Korea
No full textDepartment of Urban and Environmental Engineering (Disaster Management Engineering)clos
Exploring Wheel-Based Mobile Motion as an Emotional Expression Modality in Socially Interactive Robots
No full textDepartment of Designclos
Toward Zero-Calibration for Day-to-Day Use of Brain-Compute Interface
No full textDepartment of Biomedical EngineeringTo forward daily life out of the laboratory, the P300-based BCI system had several issues to solve. One of them is the time-consumed issues related to the need for re-calibration sessions. Without recalibration in using the P300-based BCI system, a deterioration in performance could occur. This problem would be more emphasized in routine life which is daily repeatedly performed the uses of the P300-based BCI system. Because a wave pattern of the P300 component, appearing during using the P300-based BCI system and being a useful marker for detecting users??? intent, seem to be changed by the physiological or habitual effect in daily uses of its system.
Therefore, in this paper, we first verified appearing the deterioration of performance in using the P300-based BCI system without the calibration session on a different day. The task was performed by subjects for 5 days, and a break before doing the task on the last day. The performance comparison was conducted with or without the calibration, which is a session obtaining the information of brain signals to train the discriminator for the user's intent in the BCI systems. As a result of the performance decreasing without the calibration session significantly on days 13-15 (p < 0.05) in the P300-based BCI system, the factor causing the deterioration of the performance was investigated. Positively signed area amplitude in the time ranges from 275 to 450ms was obtained for comparing the amplitude of the P300 component between days. Regarding that, the characteristics of the P300 component decreased mainly in the central brain area on day 13-15 (p<0.05) relative to the characteristic of that on day 1. Thus, daily uses of the P300-based BCI could attribute to making a change in the signal amplitude of the P300 component.
To solve the issues without re-calibration of the performance decreasing for the P300-based BCI system, an approach as a solution was applied, which approach is the separation of the common signals between days from the variable signals. The sparse dictionary learning methods were applied as one method for this approach, and it recovered the performance especially on day 13-15 without performing the calibration session for the new day. Our proposed methods in which performance less worsen expect to contribute to the use of the P300-based BCI system without an additional re calibration for a new day.
In relation to that, we described how daily repetitive usage altered the P300-based BCI system and a task-related brain signal. In fact, it was given instructions on how to address problems with the amount of time re-calibration sessions took during the day. As a result, it is anticipated that this research will aid in the commercialization of the P300-based BCI system's everyday uses.clos
FISH ??? CRISPR ?????? ???????????? ????????? ????????? ????????? ??????
No full textDepartment of Biomedical EngineeringThe function of nucleic acids has so far been interpreted usually based on the sequence information. Recently, many studies have suggested that structural changes and dynamics of chromatin are also related to DNA replication, gene regulation, and repair. Therefore, it is becoming important to develop efficient experimental techniques to visually check the structural changes and dynamics of chromatin. In this study, the advantages and disadvantages of current FISH and CRISPR-based chromatin labeling techniques are compared by observing GGAAT repeat sequences highly concentrated in the pericentromeric region of chromosome 9. First, lambda exonuclease technique was applied to improve DNA FISH probe preparation. It was found that it can successfully reduce cost and preparation process, but background problem needs to be solved. Second, two representative current chromatin imaging techniques, DNA FISH and CASFISH, were evaluated. It was observed that, unlike DNA FISH, CASFISH can be finished in a relatively short time and could detect large foci and even smaller foci. By analyzing repeat sequence distribution in the whole genome sequence, lots of GGAAT repeats were found in other chromosomes as well as chromosome 9, so smaller foci detected by CASFISH may come from these repeat regions. Therefore, it could be suggested that the CASFISH technique may be sensitive enough to detect these smaller foci. Third, this study tried to address the cause for several unique phenomena, i.e., chromatin expansions, fibers(extensions), and islands(fragments), created during CRISPR-based chromatin labeling, a powerful method for observing the structural changes and dynamic movements of chromatin with deactivated Cas9 (dCas9) which has no cutting function but binds and labels specific DNA sequences. In order to determine whether these specific structures are caused by CRISPR-associated DNA damage and its repair response, chromatin structural changes were observed by applying additional Cas9, expecting greater damage and more severe structures. However, by increasing Cas9 ratios, specific structures were reduced rather than increased. This means that the cause of these specific structures may not just be DNA double-strand break, rather it might be related to other possibilities, including the stalling that occurs during DNA replication.clos
Environmental motion presented ahead of self-motion modulates the heading direction estimation
Get PDFDepartment of Biomedical Engineering (Human Factors Engineering)Safely navigating through an environment requires an accurate estimation of self-motion. This accuracy can be relatively easily achieved when the observer is moving in a stationary environment because perceived retinal motion is only generated from self-motion. However, when the observer moves in a moving environment, this individually moving environment may be wrongly attributed to be caused by self-motion. Studies have shown that when object motion was presented during self-motion. The heading deviated from the true heading direction. This is explained by the visual-vestibular integration in heading estimation.
However, the existing literature has predominantly focused on visual and vestibular processing during self-motion, neglecting the investigation of visual motion stimuli preceding self-motion. In real-world scenarios, we often observe visual motion before initiating our movements, which could provide valuable information for interpreting retinal motion during self-motion.
The main objective of this thesis is to explore the role of visual motion observed before self-motion in interpreting visual motion generated by the environment and self-motion during self-motion. Participants were passively moved in a motion platform and they were asked to report their heading estimation by adjusting a probe presented after they moved. Self-motion was paired with visual motion that occurred before and during the self-motion. The results indicate that the duration of visual motion presented before self-motion affects heading bias, with longer presentations leading to reduced bias. This suggests that our perceptual system subtracts visual motion observed before self-motion from the perceived retinal motion during self-motion, resulting in the cancellation of the world motion component. However, even with longer durations of visual motion before self-motion, a bias was still observed, indicating that the system does not completely subtract the entire visual motion speed preceding self-motion.
We propose that this residual bias may be attributed to a slow-speed bias, where visual motion is perceived as slower than its actual speed. This bias can occur due to the observer's strong prior knowledge that the world is predominantly stationary, and judgments are based on noisy measurements. To test the accountability of the slow-speed bias in our observed data, we fit a linear model that incorporates a slow-speed bias coefficient in the optimal cue integration of visual and vestibular signals for heading estimation. The results of our analysis demonstrate agreement between the observed data and the estimates from our linear model, supporting the hypothesis that visual motion observed before self-motion is subtracted during heading estimation, and this visual motion is scaled by the slow-speed bias.
The thesis begins with a comprehensive literature review that explores the intricate relationship between visual function and postural balance, encompassing crucial aspects such as visual acuity, contrast sensitivity, and visual motion perception. Building upon this foundation, Chapter 2 delves deeper into the intricate link between visual motion perception and balance control. To further unravel the impact of visual motion on self-motion perception, Chapter 3 presents a study where observers were asked to report their heading direction while being passively moved on a motion platform and simultaneously exposed to visual motion stimuli. By manipulating the temporal delay between visual and self-motion, we aimed to assess the influence of visual motion on self-motion perception.
Chapter 4 delves into the fascinating realm of processing visual motion stimuli preceding self-motion and its profound influence on heading estimation. By skillfully manipulating the onset of visual motion relative to self-motion, we gain control over the duration of the presentation of visual motion before self-motion. Despite our initial expectation of observing no bias with the longest duration of visual motion before self-motion, intriguingly, we still detected heading bias, suggesting the presence of sub-optimal subtraction processes. A plausible explanation for this phenomenon lies in the influence of slow-speed bias in visual motion perception, which affects the accurate estimation of motion speed.
To comprehensively investigate the contribution of slow-speed bias and its impact on heading estimation, Chapter 5 introduces three distinct conditions of visual motion before self-motion while maintaining constant visual motion during self-motion across all conditions. Through strategic manipulation of the speed of visual motion before self-motion, any variations in heading estimation are likely attributable to the visual motion information observed before the observer's movement. To validate and explain these results, we employ an optimal cue integration model that incorporates the constant slow-speed bias and visual motion before self-motion.
Overall, the findings presented in this thesis provide profound insights into the intricate processing of visual motion before self-motion and its far-reaching implications for accurate heading estimation in real-world scenarios. By unraveling this complex relationship, we gain a deeper understanding of the challenges inherent in estimating heading direction in dynamic environments.clos
Targeting PARP1-Deficient Tumors with Novel Small Molecules through Nucleobase Alkylation and BRD4 Inhibition
No full textDepartment of Biological Sciencesclos
Advanced Analysis for Relaxor-PbTiO3 Single Crystals
No full textDepartment of Materials Science and Engineeringclos
Secondary Effects of Alkylammonium Cations on Perovskite Solar Cells
No full textSchool of Energy and Chemical Engineering (Energy Engineering)???????????? ??????????????? ?????? ?????? ???????????? ????????? ??????????????? ????????? ?????? ????????? ?????? ??????????????????. ?????? ????????? ???????????? ????????? ?????????, ?????? ?????? ????????? ????????????, ?????? ?????? ????????? ????????? ????????? ?????? ????????? ????????? ???????????? ?????? ??? ???????????? ????????? ????????? ??????????????? ?????? ???????????????. ?????? ?????? ??????????????? ?????? ????????? ??????????????? ????????? ?????????, ?????? ???????????? ?????? ????????? ???????????? ????????????. ????????????????????? ????????????(PSC)??? 26% ????????? ????????? ????????? ?????? ???????????? ????????? ???????????? ???????????? ???????????? ?????? ????????? ??????????????? ??????????????????. ????????? ????????? ????????? ?????? ??????????????? ?????? ?????? ???????????? ?????? ???????????? ???????????? ?????? ????????????.
??? ??????????????? ????????? ?????? ????????? FAPbI3 ?????? ????????? ????????? ????????? A ???????????? ???????????????????????? ????????? ????????? ?????? PSC??? ???????????? ????????? ????????? ??? ?????? ????????? ???????????????. ?????? ????????? ?????? ????????????????????? ????????? ???????????? ????????? ?????? ????????? ???????????????. ???????????? ?????? ??????????????? ????????? ???????????? ?????? ?????? ??? ?????? ????????? PSC??? ????????? ????????? ????????? ???????????????.
3???????????? ????????? ?????? ????????? PSC??? ????????? ???????????? ????????? ????????? ???????????? ????????? ???????????? FAPbI3 ???????????????????????? ????????? ?????? ???????????????. ????????? ????????? ?????? ?????? ????????? ????????????, ????????? ???????????? ????????????????????? ?????? ????????? ????????? ???????????????????????? ?????????(iPAmH+)??? ???????????? ????????? ???????????????. ?????? ????????? ?????? ?????? ???????????? ?????????????????????????????????(iPAmHCl)??? FAPbI3 ????????? ????????? ???????????? PSC??? ???????????? ????????? ???????????? ???????????????.
4???????????? ????????????????????????(DMA)??? ?????????(EtOH)??? 1:1??? ???????????? ?????????????????????(RNH3Cl)??? ???????????? ?????? ????????? ???????????? ????????? ????????? PSC??? ????????? ??? ?????? ???????????? ????????? ???????????? ????????? PSC??? ???????????? ??????????????? ????????? ???????????????.
5???????????? MAPbI3??? ?????? ?????? ????????? ???????????? MAPbI3??? ??????????????? ????????? ????????????(MA) ????????? ??????????????? ?????? PSC??? ???????????? ????????? ???????????? ???????????????. ???????????? ????????? ????????? MAPbI3??? ?????? ????????? ???????????? ??? ????????? ?????????. ?????? ?????? ????????? ?????? ????????? TCO??? ??????????????? ?????? ?????? ??????????????? ???????????? ?????? PSC??? ????????? ??? ????????????. ?????? MAPbI3??? ???????????? ????????? ????????? 19%??? ????????????, ?????? ???????????? ?????? CTL??? ???????????? ?????? ????????? ????????? ???????????????.The rapid increase in fossil fuel usage during the onset of industrialization has led to a significant rise in the Earth's average temperature. The Paris Agreement underscores the urgent need for global collaboration to reduce greenhouse gas emissions, achieve net-zero carbon emissions, and mitigate the impacts of climate change, including the growing prevalence of climate-related disasters. As a result, researchers have been exploring renewable energy sources, focusing on solar cells as a major alternative. Perovskite solar cells (PSCs) have emerged as a promising solution due to their low-cost, lightweight, flexible, and translucent properties, along with a laboratory efficiency of over 26%. However, their commercialization is hindered by stability issues and environmentally unfriendly manufacturing methods.
In this study, we investigate methods to improve the stability and efficiency of PSCs, focusing on the effects of different manufacturing techniques on FAPbI3 film characteristics and the role of alkylammonium chloride in the A site. Additionally, an eco-friendly manufacturing process using ethanol-based perovskite solutions is proposed. A novel method for creating bifacial PSCs that can receive light from both sides is also introduced, utilizing methylamine with volatile properties.
Chapter 3 discusses the application of FAPbI3 perovskite in solar devices, examining the impact of different preparation methods on the performance and stability of PSCs. The one-pot and sequential spin-coating methods are compared, and the incorporation of isopropylammonium cations (iPAmH+) at the perovskite layer's grain boundaries in the sequential process is proposed. Model experiments demonstrate that adding isopropylammonium chloride (iPAmHCl) to the FAPbI3 precursor solution in the one-pot process enhances the stability and efficiency of PSCs.
Chapter 4 explores eco-friendly methods for producing large-area PSCs, focusing on an innovative technique using a 1:1 mixture of dimethylacetamide (DMA) and ethanol (EtOH) with added alkylammonium chloride (RNH3Cl) to create a stable FAPbI3 perovskite precursor solution, enabling the formation of high-efficiency PSCs without the use of toxic solvents.
In Chapter 5, a new approach for creating bifacial PSCs is proposed, utilizing the self-healing phenomenon of MAPbI3 and recycling the methylamine (MA) gas generated from the thermal decomposition of MAPbI3. The gas produced at the interface aids in merging the MAPbI3 into a single layer. This allows to produce double-sided PSCs using only inorganic charge transport layers while using TCO for both anode and cathode. The efficiency achieved using pure MAPbI3 is close to 19%, comparable to conventional structures employing noble metals and organic CTL.clos
???????????? ??????????????? ??????????????? ?????? ????????? ?????? ????????? ???????????? ??????????????? ?????? ??????
No full textSchool of Energy and Chemical Engineering (Energy Engineering)clos