Low-Power and High-Efficiency Class-D Audio Amplifier Using Composite Interpolation Filter for Digital Modulators

Minchul Kang,Hyungchul Kim,Jehyeon Gu,Wonseob Lim,Junghyun Ham,Hearyun Jung,Youngoo Yang 대한전자공학회 2014 Journal of semiconductor technology and science Vol.14 No.1

This paper presents a high-efficiency digital class-D audio amplifier using a composite interpolation filter for portable audio devices. The proposed audio amplifier is composed of an interpolation filter, a delta-sigma modulator, and a class-D output stage. To reduce power consumption, the designed interpolation filter has an optimized composite structure that uses a direct-form symmetric and Lagrange FIR filters. Compared to the filters with homogeneous structures, the hardware cost and complexity are reduced by about half by the optimization. The coefficients of the digital deltasigma modulator are also optimized for low power consumption. The class-D output stage has gate driver circuits to reduce shoot-through current. The implemented class-D audio amplifier exhibited a high efficiency of 87.8 % with an output power of 57 mW at a load impedance of 16 6 and a power supply voltage of 1.8 V. An outstanding signal-to-noise ratio of 90 dB and a total harmonic distortion plus noise of 0.03 % are achieved for a single-tone input signal with a frequency of 1 kHz.

Antioxidant Activity and Hair Growth Promoting Effect of Mealworm (Tenebrio molitor larvae) Extract

Minchul Seo,Mi-Ae Kim,Eun-Young Yun,Jae-Sam Hwang,Minhee Baek 한국응용곤충학회 2017 한국응용곤충학회 학술대회논문집 Vol.2017 No.10

The insects have been investigated as novel sources for foods and biomaterials in several recent studies. However,its effects on hair growth have not been sufficiently researched. To develop novel and natural materials for preventingalopecia and promoting hair growth, we investigated the antioxidant activity and hair growth promoting effect of Tenebriomolitor larvae extract (TME). As a result, DPPH radical scavenging activity was 81.17%, and nitrite scavenging activitywas 43.69%, which were similar to blueberry extract. And TME promoted the proliferation of human DPCs and NIH3T3cells, concentration dependently. In addition, the TME prevented not only DHT-induced DPCs cytotoxicity but also actionof TBM as a potassium channel blocker in NIH3T3 cells. These results suggest that TME can be used as a functionalmaterial for alopecia therapeutic reagent by preventing hair loss and promoting hair growth.

Opportunistic Source/Destination Cooperation in Cooperative Diversity Networks

MinChul Ju,Il-Min Kim,Dong In Kim IEEE 2010 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.9 No.12

<P>In this paper, we combine opportunistic transmission and source/destination cooperation in a decode-and-forward (DF)-based two-hop cooperative diversity network consisting of multiple source-destination pairs and a single relay. Firstly, we consider a special scenario with two source-destination pairs. For this network, there are two possible strategies in each hop: no-cooperation or cooperation. Considering the combination of the two strategies in two cascaded hops, we investigate four different end-to-end transmission strategies, and we find that the four strategies complement one another depending on channel conditions in terms of outage performance. To maximize the mutual information, we propose an optimum joint selection of source-destination pair and end-to-end transmission strategy. Then we show that the optimum joint selection scheme can be simplified without loss of outage performance, and derive its exact outage probability in closed-form. Secondly, we generalize the proposed transmission strategy into a scenario with multiple source-destination pairs. For this network, we first propose an optimum end-to-end transmission strategy to maximize the mutual information, then a suboptimum end-to-end transmission strategy to reduce the signaling overhead and computational complexity. For the suboptimum strategy, we derive the outage probability and diversity order.</P>

ML performance analysis of the decode-and-forward protocol in cooperative diversity networks

Minchul Ju,Il-Min Kim IEEE 2009 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.8 No.7

<P>We analyze the maximum-likelihood (ML) performance of the decode-and-forward protocol in a cooperative diversity network which consists of a source, a relay, and a destination with a direct path signal, but which is not equipped with cyclicredundancy- check (CRC) codes. In this system, due to a symbol error at the relay, the ML receiver at the destination needs to consider all the possible symbol detection scenarios at the relay as well as at the destination. Therefore, the ML detection metric is given by a linear combination of exponential functions, which prevents the use of the classical minimum Euclidean distance rule. Adopting the max-log approximation, we approximate the ML detection rule which makes the ML performance analysis tractable. In order to facilitate the derivation of decision regions, we simplify the ML detection rule in the two-dimensional real space such that two metric values of two adjacent constellation points are sequentially compared. Then we obtain decision regions in a form without union and intersection. Finally, based on the decision regions, we derive a very accurate closedform BER approximation for M-pulse amplitude modulation (PAM) and M-quadrature amplitude modulation (QAM). The obtained BER expression can serve as the error performance upper-bound of the decode-and-forward protocol in cooperative diversity networks.</P>

Azole Resistance Caused by Increased Drug Efflux in Candida glabrata Isolated from the Urinary Tract of a Dog with Diabetes Mellitus

( Minchul Kim ),( Hyekyung Lee ),( Sun-young Hwang ),( Inhyung Lee ),( Won Hee Jung ) 한국균학회 2017 Mycobiology Vol.45 No.4

A yeast-like organism was isolated from a urine sample of a 6-year-old neutered male miniature poodle dog with urinary tract infection, diabetes ketoacidosis, and acute pancreatitis. We identified the yeast-like organism to be Candida glabrata and found that this fungus was highly resistant to azole antifungal drugs. To understand the mechanism of azole resistance in this isolate, the sequences and expression levels of the genes involved in drug resistance were analyzed. The results of our analysis showed that increased drug efflux, mediated by overexpression of ATP transporter genes CDR1 and PDH1, is the main cause of azole resistance of the C. glabrata isolated here.

Efficacy of immune-strengthening functional drinks in top-level athletes: a questionnaire survey-based research

( Minchul Lee ),( Jin-Sook Lee ),( Kyunghee Kim ),( Chanju Kim ) 한국운동영양학회 2021 Physical Activity and Nutrition (Phys Act Nutr) Vol.25 No.3

[Purpose] Functional beverages are intended to support those who want to maintain optimal physical condition and improve their quality of life through the enhancement of heart health, immunity, and digestion. The purpose of this study was to investigate the performance of top-level athletes consuming immune- strengthening conditioning nutritional drinks. [Methods] A total of 107 top-level athletes (baseball (56 players), pro volleyball (17), athletics (16), cycling (8), golf (6), and fencing (6)) participated in the experiment. They consumed an immune-enhancing functional beverage once a day for 8 weeks and responded to a survey before, during, and after drinking the beverage. [Results] Three total aspect-based subfactors were drawn from 24 questions in the factor analysis: physical, satisfaction with mental stability, and activity in performance. The physical, mental stability and performance changes of athletes significantly increased in period 2 (4 weeks after intake) and period 3 (after 8 weeks of intake). [Conclusion] We evaluated the efficacy of a new conditioned beverage containing Lactobacillus B240 and protein in improving the performance and physiological utility of top athletes. This functional drink may gain popularity among those seeking health benefits and improved exercise performance.

Central Administration of Tenebrio molitor Larvae Extract Regulates Food Intake and Body Weight in Obesity Mice

Minchul Seo,Joon Ha Lee,Minhee Baek,Hwa Jeong Lee,Jae-Sam Hwang,Mi-Ae Kim 한국응용곤충학회 2017 한국응용곤충학회 학술대회논문집 Vol.2017 No.10

We recently reported the in vitro and in vivo antiobesity effects of Tenebrio molitor larvae, a traditional food in manycountries, but it remains unknown how the larvae affect appetite regulation in mice with diet-induced obesity. We hypothesizedthat the extract of T. molitor larvae mediates appetite by regulating neuropeptide expression. We investigated T. molitorlarvae extract's (TME's) effects on anorexigenesis and endoplasmic reticulum (ER) stress–induced orexigenic neuropeptideexpression in the hypothalami of obese mice. Central administration of TME suppressed feeding by down-regulating theexpression of the orexigenic neuropeptides neuropeptide Y and agouti-related protein. T. molitor larvae extract significantlyreduced the expression of ER stress response genes. These results suggest that TME and its bioactive components arepotential therapeutics for obesity and ER stress–driven disease states.

Cognitive Radio Networks With Secondary Network Selection

MinChul Ju,Kyu-Min Kang IEEE 2016 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.65 No.2

<P>In this paper, we study cognitive radio (CR) networks that consist of multiple secondary TV band device (TVBD) station-user pairs and one primary digital TV (DTV) station-user pair, where each terminal has a single antenna. Specifically, we consider spectrum sharing (SS)-based secondary TVBD networks to effectively utilize limited spectrum resources in the presence of cochannel primary DTV interference. We first present an opportunistic single secondary network selection scheme to maximize the mutual information over all secondary TVBD networks under the constraint of the availability of the primary DTV service. Then, the performance bound of CR networks with the secondary network selection is obtained through the derivation of an exact and closed-form outage probability. It is shown that the derived outage probability is given as a function of transmission power, channel coefficients, and target rates of both the primary DTV network and the secondary TVBD networks.</P>

Genomic Tandem Quadruplication is Associated with Ketoconazole Resistance in Malassezia pachydermatis

( Minchul Kim ),( Yong-joon Cho ),( Minji Park ),( Yoojeong Choi ),( Sun Young Hwang ),( Won Hee Jung ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.11

Malassezia pachydermatis is a commensal yeast found on the skin of dogs. However, M. pachydermatis is also considered an opportunistic pathogen and is associated with various canine skin diseases including otitis externa and atopic dermatitis, which usually require treatment using an azole antifungal drug, such as ketoconazole. In this study, we isolated a ketoconazole-resistant strain of M. pachydermatis, designated “KCTC 27587,” from the external ear canal of a dog with otitis externa and analyzed its resistance mechanism. To understand the mechanism underlying ketoconazole resistance of the clinical isolate M. pachydermatis KCTC 27587, the whole genome of the yeast was sequenced using the PacBio platform and was compared with M. pachydermatis type strain CBS 1879. We found that a ~84-kb region in chromosome 4 of M. pachydermatis KCTC 27587 was tandemly quadruplicated. The quadruplicated region contains 52 protein coding genes, including the homologs of ERG4 and ERG11, whose overexpression is known to be associated with azole resistance. Our data suggest that the quadruplication of the ~84-kb region may be the cause of the ketoconazole resistance in M. pachydermatis KCTC 27587.

GPS-DR Sensor Fusion without coordinates conversion

Minchul Lee,Kichun Jo,Myoungho Sunwoo 한국자동차공학회 2014 한국자동차공학회 학술대회 및 전시회 Vol.2014 No.11