Modulating the magnetic behavior of Fe(<small>II</small>)–MOF-74 by the high electron affinity of the guest molecule

Han, Sungmin,Kim, Heejin,Kim, Jaehoon,Jung, Yousung The Royal Society of Chemistry 2015 Physical chemistry chemical physics Vol.17 No.26

<P>As a new class of magnetic materials, metal-organic framework (MOF) has received a significant attention due to their functionality and porosity that can provide diverse magnetic phenomena by utilizing host-guest chemistry. For Fe-MOF-74, we here find using density functional calculations that the O-2 and C2H4 adsorptions result in the ferromagnetic (FM) and antiferromagnetic (AFM) orderings along the 1D chain of an hexagonal MOF framework, respectively, while their adsorption energies, pi-complexation, and geometrical changes are all similar upon binding. We reveal that this different magnetism behavior is attributed to the different electronic effects, where the adsorbed O-2 greatly withdraws a minor spin electron from the Fe centers. The latter significant back donation opens a new channel for superexchange interactions that can enhance the FM coupling between Fe centers, where the strength of calculated intrachain FM coupling constrant (J(in)) in O-2 adsorbed Fe-MOF-74 is more than 10 times enhanced compared to bare Fe-MOF-74. This prediction suggests a possibility for the conceptual usage of Fe-MOF-74 as a gas sensor based on its magnetic changes caused by the adsorbed gases. Furthermore, the suggested mechanism might be used to control the magnetic properties of MOFs using the guest molecules, although concrete strategies to enhance such magnetic interactions to be used in practical applications would require further significant investigation.</P>

Ketamine Inhibits Ultrasound Stimulation-Induced Neuromodulation by Blocking Cortical Neuron Activity

Han, Sungmin,Kim, Minkyung,Kim, Hyungmin,Shin, Hyunjoon,Youn, Inchan Elsevier 2018 Ultrasound in medicine & biology Vol.44 No.3

<P><B>Abstract</B></P> <P>Ultrasound (US) can be used to noninvasively stimulate brain activity. However, reproducible motor responses evoked by US are only elicited when the animal is in a light state of anesthesia. The present study investigated the effects of ketamine on US-induced motor responses and cortical neuronal activity. US was applied to the motor cortex of mice, and motor responses were evaluated based on robustness scores. Cortical neuronal activity was observed by fluorescence calcium imaging. US-induced motor responses were inhibited more than 20 min after ketamine injection, and US-triggered Ca<SUP>2+</SUP> transients in cortical neurons were effectively blocked by ketamine. Our results indicate that ketamine suppresses US-triggered Ca<SUP>2+</SUP> transients in cortical neurons and, therefore, inhibits US-induced motor responses in a deep anesthetic state.</P>

An Unsorted Spike-Based Pattern Recognition Method for Real-Time Continuous Sensory Event Detection from Dorsal Root Ganglion Recording

Han, Sungmin,Chu, Jun-Uk,Kim, Hyungmin,Choi, Kuiwon,Park, Jong Woong,Youn, Inchan IEEE 2016 IEEE Transactions on Biomedical Engineering Vol.63 No.6

<P>In functional neuromuscular stimulation systems, sensory information-based closed-loop control can be useful for restoring lost function in patients with hemiplegia or quadriplegia. The goal of this study was to detect sensory events from tactile afferent signals continuously in real time using a novel unsorted spike-based pattern recognition method. The tactile afferent signals were recorded with a 16-channel microelectrode in the dorsal root ganglion, and unsorted spike-based feature vectors were extracted as a novel combination of the time and time-frequency domain features. Principal component analysis was used to reduce the dimensionality of the feature vectors, and a multilayer perceptron classifier was used to detect sensory events. The proposed method showed good performance for classification accuracy, and the processing time delay of sensory event detection was less than 200 ms. These results indicated that the proposed method could be applicable for sensory feedback in closed-loop control systems.</P>

Contributions of Public Investment to Economic Growth and Productivity

HAN, SUNGMIN Korea Development Institute 2017 KDI Journal of Economic Policy (KDI JEP) Vol.39 No.4

Whereas a large variety of previous studies show mixed results regarding the relationship between public investment and economic outcome, several studies have been conducted on related issues in Korea. The present study deals with the effect of public investment in Korea on economic growth and productivity. Using administrative data, it exploits three different methodologies: the total factor productivity approach, production function approach, and stochastic frontier production function approach. The results of this study show that public investment has a statistically significant effect on economic growth. However, it contributes little to enhance productivity. It is explained that there exists inefficiency of production in the Korean economy. These findings indicate that public investment has played a central role in the direct input factor and not in indirect role in Korea. Thus, it is necessary for public investment policies to concentrate on enhancing the efficiency of the Korean economy.

Numerical Approximation of Millimeter-Wave Frequency Sharing between Cellular Systems and Fixed Service Systems

Sungmin Han,Ji-Woong Choi,Joongheon Kim 한국통신학회 2020 Journal of communications and networks Vol.22 No.1

This paper presents numerical analysis and simulationresults in order to study the impact of interference between fixedservice (FS) systems and 5G cellular networks at 28 GHz, 38 GHz,and 60GHz millimeter-wave (mmWave) bands. For this study, twodifferent scenarios were considered, i.e., the aggregation of interferencefrom small cells into an FS receiver from (i) base stations(BSs) to their associated user equipment (UE) (downlink); (ii) fromUEs to their associated BSs (uplink). The simulation results determinedhow much interference rejection is required to protect theoperation of the FS. This study is essential when using mmWavetechnologies in cellular networks, to determine whether the newlydeployed cellular systems can co-exist with pre-deployed FS systemsor not. This paper presents closed-form numerical approximationresults with Taylor series approximation along with intensivesimulation results. Finally, this paper confirmed that thenumerical approximation results were precise, i.e., that here wereonly marginal differences to the intensive simulation results.

Electrical stimulation inhibits cytosine arabinoside-induced neuronal death by preventing apoptosis in dorsal root ganglion neurons

Han, Sungmin,Kim, Donghwee,Kim, Hyungmin,Park, Jong Woong,Youn, Inchan Wolters Kluwer Health | Lippincott Williams Wilkin 2016 NEUROREPORT - Vol.27 No.16

<P>The current study aimed to investigate whether electrical stimulation could prevent apoptotic neuronal cell death during treatment with cytosine arabinoside (ara-C). From in-vitro experiments, the effects of electrical stimulation were assessed on neurite fragmentation and neuronal cell death in ara-C-treated dorsal root ganglion (DRG) explants. Ara-C treatment increased neurite fragmentation and neuronal cell death in DRG explants and activated caspase-3 by cleaving it, which could induce apoptosis. Electrical stimulation can significantly reduce neurite fragmentation and neuronal cell death compared with nonelectrically stimulated groups. Furthermore, electrical stimulation inhibited caspase-3 activation and reduced apoptotic neuronal death in DRG explants. It was suggested that the neuroprotective effect of electrical stimulation is likely mediated by the inhibition of caspase-3 activation and therefore the inhibition of apoptosis following ara-C treatment.</P>

Implantation of a Matrigel-loaded agarose scaffold promotes functional regeneration of axons after spinal cord injury in rat

Han, Sungmin,Lee, Jee Youn,Heo, Eun Young,Kwon, Il Keun,Yune, Tae Young,Youn, Inchan Academic Press 2018 Biochemical and biophysical research communication Vol.496 No.3

<P><B>Abstract</B></P> <P>An agarose scaffold can be useful for supporting and guiding injured axons after spinal cord injury (SCI), but the electrophysiological signal of regenerated axon in scaffolds has not yet been determined. The current study investigated whether a Matrigel-loaded agarose scaffold would enhance the regeneration of axons after SCI. Moreover, the functional connectivity of regenerated axons within the channels of the scaffold was evaluated by directly recording motor evoked potentials. Our data showed that the agarose scaffold containing Matrigel can support and enhance linearly organized axon regeneration after SCI. Additionally, motor evoked potentials were successfully recorded from regenerated axons. These results demonstrate that an agarose scaffold loaded with Matrigel could promote the regeneration of axons and guide the reconnection of functional axons after SCI.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Spinal cord injury results in axon degeneration, causing the loss of sensory and motor functions. </LI> <LI> Axon regeneration was further improved in agarose scaffold loaded with Matrigel implanted into injured spinal cord. </LI> <LI> Regenerated corticospinal axons in agarose scaffold were connected functionally and anatomically. </LI> </UL> </P>

A 10-Gb/s/lane, 0.5-μm-Pitch, 1-mm-Long Silicon Channel Interface Using 28-nm CMOS for Active Chiplet Interposers

Sungmin Han(한성민),Yoochang Kim(김유창),Young-Ha Hwang(황영하) 대한전자공학회 2023 대한전자공학회 학술대회 Vol.2023 No.6

In the chiplet-based system, it is important to accommodate massively-parallel memory interface in the interposer layer in an area-efficient way. Therefore, the design techniques to maximize the throughput per channel density should be explored. In this work, a silicon channel interface including a 10-Gb/s transmitter with on-chip channels having 0.5-μm pitch and 1-mm length is presented. The proposed channel design technique optimizes the throughput per channel density considering crosstalk, attenuation-to-crosstalk ratio (ACR), and eye diagram. As a result, the proposed interface designed using a 28-nm CMOS process achieves 20 Gb/s/μm, which can be extended to 2 Tb/s in 100-μm width. In the worst case with four aggressors of adjacent channels, the simulated timing margin and eye opening at the victim channel is 0.52 UI and 105 mV at 10 Gb/s, respectively, without any crosstalk cancellation.

Performance Anaysis of 802.15.6 WBAN DPSK System

Sungmin Han,Ji-Woong Choi 한국통신학회 2014 한국통신학회 학술대회논문집 Vol.2014 No.6

Design of the K/Ka band waveguide duplexer with an E-plane T-junction

Sungmin Han,Daeig Chang,Hojin Lee 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7

In this paper, the design and performance of the K/Ka-band (20/30㎓) waveguide duplexer with an Eplane T-junction is described. The waveguide duplexer consists of a transmit band pass filter and a receive band pass filter combined to the antenna port via an E-plane Tjunction. The reason why E-plane T-junction structure was selected which is to reduce PIM (Passive Inter-Modulation) level. The manufactured duplexer has good pass band return loss (>15㏈) and high isolation (>55㏈) for both transmit and receive frequency bands. The duplexer does not need any post fabrication tuning. Those mean the analysis results of the waveguide duplexer are verified through the electrical performance test.