Haptic Assistance for Memorization of 2-D Selection Sequences

Hojin Lee,Gabjong Han,In Lee,Sunghoon Yim,Kyungpyo Hong,Hyeseon Lee,Seungmoon Choi IEEE 2013 IEEE transactions on human-machine systems Vol.43 No.6

<P>This paper investigates the effect of haptic feedback on the learning of a 2-D sequential selection task, used as an abstraction of complex industrial manual assembly tasks. This mnemonic-motor task requires memorization of the selection order of points scattered on a 2-D plane and reproduction of this order using entire arm movements. Four information presentation methods, visual information only, visual information + enactment, visual information + haptic guidance, and visual information + haptic disturbance, are considered. The latter three methods provide different levels of haptic kinesthetic feedback to the trainee. We carried out a user study to assess the quantitative performance differences of the four training methods using a custom-built visuo-haptic training system. Experimental results showed the relative advantages and disadvantages of each information presentation method for both short-term and long-term memorization. In particular, training with only visual information was the best option for short-term memory, while training also with haptic disturbance was the most effective for long-term memory. Our findings have implications to designing a training method that is suitable for given training requirements.</P>

Therapeutic Potential of Stem Cells Strategy for Cardiovascular Diseases

Lee, Chang Youn,Kim, Ran,Ham, Onju,Lee, Jihyun,Kim, Pilseog,Lee, Seokyeon,Oh, Sekyung,Lee, Hojin,Lee, Minyoung,Kim, Jongmin,Chang, Woochul Hindawi Publishing Corporation 2016 Stem cells international Vol.2016 No.-

<P>Despite development of medicine, cardiovascular diseases (CVDs) are still the leading cause of mortality and morbidity worldwide. Over the past 10 years, various stem cells have been utilized in therapeutic strategies for the treatment of CVDs. CVDs are characterized by a broad range of pathological reactions including inflammation, necrosis, hyperplasia, and hypertrophy. However, the causes of CVDs are still unclear. While there is a limit to the currently available target-dependent treatments, the therapeutic potential of stem cells is very attractive for the treatment of CVDs because of their paracrine effects, anti-inflammatory activity, and immunomodulatory capacity. Various studies have recently reported increased therapeutic potential of transplantation of microRNA- (miRNA-) overexpressing stem cells or small-molecule-treated cells. In addition to treatment with drugs or overexpressed miRNA in stem cells, stem cell-derived extracellular vesicles also have therapeutic potential because they can deliver the stem cell-specific RNA and protein into the host cell, thereby improving cell viability. Here, we reported the state of stem cell-based therapy for the treatment of CVDs and the potential for cell-free based therapy.</P>

Serotonergic Signaling in Adipocytes is Critical for Insulin Triggering Adipogenesis

Hojin Lee,Soomin Lee,Jung-Mi Oh,Seoyeong Jung,Hye-Young Joung,Sun Young Park,Sungkun Chun,Jaekwang Lee 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10

5-Hydroxytryptamine (5-HT, serotonin), a monoamine neurotransmitter derived from the amino acid tryptophan, is related to body weight and food intake regulation. Although serotonin signaling is important to develop obesity in the central nervous system, however, it is unclear what the role of serotonin signaling to develop adiposity in peripheral system. In this study, we showed that serotonin was synthesized in adipocytes, regulated adipogenesis by increase of ROS which was produced during serotonin metabolism by monoamine oxidases (MAOs) in adipocyte differentiation. Interestingly, we found that among MAOs, MAO-B was upregulated during differentiation in 3T3L1 and primary adipocytes. In the same line, increased ROS production during adipogenesis was blocked by selegiline, MAO-B inhibitor, in 3T3L1 and primary adipocyte. Moreover, the high-fat diet (HFD) fed mice with the administration of selegiline showed weight loss and reduction of fat size. Consequently, these data suggest that adipocyte is serotonergic cell and adipocytes synthesize serotonin and produce ROS during serotonin degradation by MAO enzymes, specially MAO-B, which could be a therapeutic target for anti-obesity.

POMY: 햅틱 피드백을 적용한 몰입형 영어 학습 시스템

이재봉(Jaebong Lee),이규송(Kyusong Lee),Hoang Minh Phuong,이호진(Hojin Lee),이근배(Gary Geunbae Lee),최승문(Seungmoon Choi) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.8

In this paper, we propose a novel CALL (Computer-Assisted Language Learning) system, which is called POMY (POSTECH Immersive English Study). In our system, students can study English while talking to characters in a computer-generated virtual environment. POMY also supports haptic feedback, so students can study English in a more interesting manner. Haptic feedback is provided by two platforms, a haptic chair and a force-feedback device. The haptic chair, which is equipped with an array of vibrotactile actuators, delivers directional information to the student. The force-feedback device enables the student to feel the physical properties of an object. These haptic systems help the student better understand English conversations and focus on studying. We conducted a user experiment and its results showed that our haptic-enabled English study contributes to better learning of English.

Alternative new mesenchymal stem cell source exerts tumor tropism through ALCAM and N-cadherin via regulation of microRNA-192 and -218

Kim, Ran,Park, Sang In,Lee, Chang Youn,Lee, Jihyun,Kim, Pilseog,Oh, Sekyung,Lee, Hojin,Lee, Min Young,Kim, Jongmin,Chung, Yong-An,Hwang, Ki-Chul,Maeng, Lee-So,Chang, Woochul Springer US 2017 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.427 No.1

<P>Gliomas are the most common type of malignant primary brain tumors. Some treatments of gliomas exist, but they are rarely curative. Mesenchymal stem cells (MSCs) are emerging as potential modes of targeted cancer therapy owing to their capacity for homing toward tumor sites. It has been proposed that MSCs derived from various sources, such as bone marrow, adipose tissue and umbilical cord blood, can be used as cell-based therapy for brain tumors. Here, MSCs obtained from the synovial fluid of osteoarthritis or rheumatoid arthritis patients were investigated as therapeutic candidates. Specifically, we compared migratory and adhesive abilities, as well as expression levels of related genes and microRNA in bone marrow derived-MSCs (BMMSCs), adipose derived-MSCs (ADMSCs), and synovial fluid derived-MSCs (SFMSCs) after treatment with conditioned medium from gliomas. Migration and adhesion of SFMSCs increased through upregulation of the activated lymphocyte cell adhesion molecule (ALCAM) and N-cadherin by microRNA-192 and -218 downregulation, similar to BMMSCs and ADMSCs. Migratory capacities of all types of MSCs were evaluated in vivo, and SFMSCs migrated intensively toward gliomas. These results suggest that SFMSCs have potential for use in cell-based antitumor therapies.</P>

Nonparametric Modeling of Conditional Heterogeneity and Non-Normality of Stock Returns

( Hojin Lee ) 한국재무관리학회 2016 財務管理硏究 Vol.33 No.1

Discrete- and continuous-time stochastic volatility (SV) models are introduced to explain conditional heterogeneity and dependence along with conditional leptokurtosis found in higher order moments of two stock market index return processes. We use the efficient method of moments (EMM) procedure combined with the seminonparametric (SNP) model as the score generator to estimate SV models. The EMM is applicable to a variety of asset pricing models where the moment restrictions contain unobservable state vector and improves efficiency of the estimator without resorting to the likelihood approach. By employing EMM in estimating two SV models with SNP auxiliary models, we aim to evaluate the performance of the SNP conditional density function and the SV models in characterizing non-Gaussianity of the conditional volatility process. As seen from the empirical results, the SV models fail to fit the various scores considered in the EMM estimation. The SV models are not appropriate for capturing the characteristics of non-Gaussianity, fat-tailed behavior and conditional heterogeneity of the observed data. We also find that the SNP models are more appropriate in modeling non-Gaussianity and non-linear dynamics along with conditional heterogeneity of the conditional distribution in the index return process.

The properties of porous silicon as a therapeutic agent <i>via</i> the new photodynamic therapy

Lee, Chongmu,Kim, Hojin,Cho, Youngjoon,Lee, Wan In Royal Society of Chemistry 2007 Journal of materials chemistry Vol.17 No.25

<P>Photodynamic therapy (PDT) is a very useful approach for cancer treatment, but it has a few short-term and long-term side effects arising from reactive oxygen species (ROS) generation. Recently a new photodynamic therapy (PDT) based not on the ROS generation capability of photosensitizers but on the heat generation capability of carbon nanotubes (CNT) combined with a near-infrared (NIR) light irradiation technique has received significant attention. Our experimental results show that PSi can also be utilized as a therapeutic agent that generates sufficient heat to kill cancer cells without toxicity. The surface temperature of PSi increases as high and as quickly as that of CNT, but PSi was found to produce a smaller amount of ROS than CNT during NIR light irradiation. In addition, we developed a new method to effectively measure the amount of the ROS produced by nanomaterial photosensitizers including porous silicon (PSi) and CNT. The analysis results show that this method is reliable and reproducible.</P> <P>Graphic Abstract</P><P>Porous silicon can be utilized as a therapeutic agent that generates sufficient heat to kill cancer cells with minimal reactive oxygen species generation upon exposure to near-infrared light. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b700892a'> </P>

The Effect of interest in COVID-19 on intention to practice preventive behavior in restaurants

Hojin Lee,Jin-Yi Jeong 한국관광레저학회 2021 한국관광레저학회 학술발표대회 Vol.2021 No.12

A Study on Dynamic Asset Allocation Strategy for Optimal Portfolio Selection

Lee, Hojin Korea Institute for International Economic Policy 2021 East Asian Economic Review Vol.25 No.3

We use iterative numerical procedures combined with analytical methods due to Rapach and Wohar (2009) to solve for the dynamic asset allocation strategy for optimal portfolio demand. We compare different optimal portfolio demands when investors in each country have different access to overseas and domestic investment opportunities. The optimal dynamic asset allocation strategy without foreign investment opportunities leads domestic investors in Korea, Hong Kong, and Singapore to allocate more funds to domestic bonds than to domestic stocks. However, the U.S. investors allocate more wealth to domestic stocks than to domestic bonds. Investors in all countries short bills at a low level of risk aversion. Next, we investigate dynamic asset allocation strategy when domestic investors in Korea have access to foreign markets. The optimal portfolio demand leads investors in Korea to allocate most resources to domestic bonds and foreign stocks. On the other hand, the portfolio weights on foreign bonds and domestic stocks are relatively low. We also analyze dynamic asset allocation strategy for the investors in the U.S., Hong Kong, and Singapore when they have access to the Korean markets as overseas investment opportunities. Compared to the results when the investors only have access to domestic markets, the investors in the U.S. and Singapore increase the portfolio weights on domestic stocks in spite of the overseas investment opportunities in the Korean markets. The investors in the U.S., Hong Kong, and Singapore short domestic bills to invest more than initial funds in risky assets with a varying degree of relative risk aversion coefficients without exception.

Output Feedback Control Methods Using Linear Transformation For Rotational Inverted Pendulum

Hojin Lee,Junghwan Gil,Sesun You,Wonhee Kim 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10

We propose a control method for disturbance compensation by using linear transformation(LT) of the linearized dynamic system of rotational pendulum in DC motor. Because input is applied to 2 states, it is hard to consider both states that designing controller which compensates input disturbance by using conventional control methods. We propose linear transformation of the linearized state space equation. By transforming the system, we can reduce extra input term so that design single control input. Because transformed state space equation has single input, estimated disturbance can be compensated to input easily. At conclusion section, we compare and analysis the performance of each controllers.