Risk of COVID-19 Transmission from Infected Outpatients to Healthcare Workers in an Outpatient Clinic

정혜민,Eun Ok Kim,김성한,정지원 대한의학회 2020 Journal of Korean medical science Vol.35 No.50

From January to September 2020, we conducted contact-tracing for confirmed coronavirus disease 2019 (COVID-19) patients who visited our outpatient clinic to evaluate the risk of COVID-19 transmission from infected patients to healthcare workers (HCWs). COVID-19 was diagnosed in 8 outpatients. Per the severe acute respiratory syndrome coronavirus-2 (SARS- CoV-2) polymerase chain reaction test results, none of the 317 HCWs who came in contact had a confirmed COVID-19 diagnosis (0.00%; 95% confidence interval, 0.00%–0.01%). This low rate of transmission from infected outpatients to HCWs suggests that standard precaution such as using surgical mask and hand hygiene protects HCWs from SARS-CoV-2 in a low-risk, outpatient clinic setting.

조현병 환자와 건강한 대조군에서 성별에 따른 뇌파 동시성의 차이

정혜민,이유상,김성수,김성균,정재승,오진석,이승연,김범준,장재승,Jung, Hye Min,Lee, Yu Sang,Kim, Seongsu,Kim, Seongkyun,Jeong, Jaeseung,Oh, Jin-Seok,Lee, Seungyeoun,Kim, Bum Joon,Chang, Jae Seung 대한생물정신의학회 2013 생물정신의학 Vol.20 No.4

Objectives Alteration of epigenetic effects of testosterone during early development was suggested as an ancillary mechanism for the genesis of schizophrenia. EEG coherence was thought to be a marker for cerebral laterality of which important determinant was testosterone during early development. We studied sex-related differences of EEG coherences between patients with schizophrenia and controls to examine the sex effects in the genesis of schizophrenia. Methods EEG was recorded in 35 patients with schizophrenia and 46 healthy controls in the eyes closed resting state. Pair-wise EEG coherences were calculated over delta, theta, alpha, beta and gamma frequency bands. To examine the differences of EEG coherence according to sex in each group, ANCOVA was performed using Statistical Analysis system (SAS, Ver 9.3) and R (Ver 2.15.2). Results Healthy control males showed more increased right intrahemispheric coherences than healthy control females in delta, theta, alpha and beta frequency bands. In patients with schizophrenia, this male dominant pattern in right intrahemispheric coherences was attenuated especially in alpha and beta bands. Healthy control females showed more increased interhemispheric coherences than healthy control males in delta, theta, beta and gamma frequency bands. In patients with schizophrenia, these female dominant patterns in interhemispheric coherences were attenuated especially in delta, theta, and beta bands, which were commonly observed in frontal to central areas. Conclusion Sex differences in resting EEG coherences were attenuated in schizophrenia patients. These results imply that sex-related aberrant cerebral lateralization might exist in patients with schizophrenia, which are partly due to sex hormones via epigenetic mechanisms.

충남 서산 대로리 일대 자연발생석면의 광물학적 특성

정혜민,신주도,김유미,박재봉,노열,Jung, Haemin,Shin, Joodo,Kim, Yumi,Park, Jaebong,Roh, Yul 대한자원환경지질학회 2014 자원환경지질 Vol.47 No.5

자연발생석면은 사문석군 석면의 모암인 초염기성암 외에도 탄산염암 및 편암, 염기성암을 모암으로 산출될 수 있다. 하지만 사문석군 석면의 모암인 초염기성암에 비해 탄산염암에서 발생하는 각섬석군 석면의 광물학적 특성에 대한 연구는 미비한 실정이다. 따라서, 이 연구에서는 탄산염암 및 편암을 모암으로 하는 자연발생석면에 대한 광물학적 특성을 연구하고 그 기원에 대해서 고찰하고자 하였다. 연구지역은 충남 서산시 대산읍 대로리 일대로 주된 연구대상은 서산층군 내 석회암 및 편암이며 시대미상의 암맥에 의해 관입되거나 습곡과 단층에 의해 교란되었다. 시료채취는 탄산염암과 편암의 접촉부에서 침상의 결정들이 관찰되는 노두를 선정하여 진행하였다. 광물조성 및 동정을 위해 PLM, XRD, EPMA 및 EDS 분석을 실시하였으며 각섬석의 형태 관찰을 위해 SEM 분석을 실시하였다. 또한 BSEM 이미지 분석을 통해 미세조직을 관찰하였다. XRD와 PLM을 통해 광물동정 한 결과 탄산염암에서는 양기석-투각섬석이 산출되었으며 석면형 결정의 정벽은 치밀하게 얽힌 침상이거나 비석면형의 결정이 벽개면을 따라 석면형으로 발달해가는 것을 확인하였다. EPMA 분석결과 탄산염암에서 산출되는 석면은 양기석-투각섬석으로 총 Fe 함량은 3~17%였다. Fe 함량이 10% 이상인 경우 양기석으로 정의되므로 이는 고용체 관계인 두 종 모두가 산출됨을 의미하며 이는 XRD 분석결과와도 일치했다. BSEM 이미지 분석을 통해 양기석-투각섬석 형성과정에서의 잔류조직을 관찰한 결과 백운석-투각섬석-투휘석으로 이어지는 일련의 전진변성단계의 잔류조직과 투휘석-투각섬석-활석으로 이어지는 후퇴변성단계의 잔류조직이 관찰되었다. 이들 연구 결과를 종합해 볼 때, 탄산염암에서 발생하는 석면은 열수변질작용으로 형성되는 것으로 사료되며 또한 비석면형의 결정이 풍화와 침식을 받는 경우 잠재적으로 석면형으로 발달 가능성이 있으므로 관리가 필요할 것으로 사료된다. Naturally occurring asbestos (NOA) occurs in rocks and soils as a result of natural weathering and human activities. The asbestos have been associated with ultramafic and mafic rocks, and carbonate rock. The previous studies on NOA were mainly limited to ultramafic and mafic rock-hosted asbestos in Korea. But, studies on carbonatehosted asbestos are relatively rare. Therefore, the purposes of this study were to investigate mineralogical characteristics of carbonate-hosted and metapelite-hosted NOA and to examine genesis of NOA occurred in the both rocks. The study area was Daerori, Seosan, Chungnam Province, Korea. The major rock formation consisted of limestone and schist which have been known to contain asbestos. Sampling was performed at outcrop which contained carbonate rock showing acicular asbestos crystals as well as pegmatitic intrusion that contacted with carbonate rock. PLM, XRD, EPMA, and EDS analyses were used to characterize mineral assemblages, mineralogical characteristics, and crystal habits of amphiboles and other minerals. BSEM images were also used to examine the genesis of asbestos minerals. The amphibole group was observed in all of the carbonate rocks, and actinolite and tremolite were identified in all rocks. These mineral habits were mainly micro-acicular crystals or secondary asbestiform minerals on the surface of non-asbestiform minerals appearing split end of columnar crystals produced by weathering. BSEM images showed residual textures of samples. The residual textures of carbonate rocks showed dolomite-tremolite-diopside mineral assemblages that formed during prograde metasomatism stage. Some carbonate rock also showed diopside-tremolite-talc mineral assemblages which were formed during retrograde metasomatism stage, as the residual textures. In result the presence of asbestos actinolite-tremolite in the carbonate rocks were confirmed in the areas where actinolite-tremolite asbestos was influenced by low temperature hydrothermal solution during metasomatism stage. These asbestos minerals showed the acicular asbestiform minerals, but even non-asbestiform minerals, a bundle or columnar shape, could transform to asbestiform minerals as potential NOA by weathering because the end of columnar shape of non-asbestiform minerals appeared as multiple acicular shaped fibers.

현탁중합에 의한 폴리비닐알코올/점토 나노복합체의 합성 및 특성분석

정혜민,지병철,염정현 한국고분자학회 2006 한국고분자학회 학술대회 연구논문 초록집 Vol.2006 No.4

GAN에서의 점진학습을 위한 잠재벡터 저장 기반 리허설 방법

정혜민,최동완 한국정보과학회 2023 정보과학회논문지 Vol.50 No.4

Unlike humans, sequential learning of multiple tasks is a difficult problem in a deep learning model. This problem is not only for discriminative models, but also for generative models, such as GAN. The Generative Replay method, which is frequently used in GAN continual learning, uses images generated by GAN provided in the previous task together for learning new tasks, but does not generate good images for CIFAR10, which is a relatively challenging task. Therefore, we can consider a rehearsal-based method that stores a portion of the real data, which cannot store a huge amount of images in limited memory because of large dimension of the real image. In this paper, we propose LactoGAN and LactoGAN+, continual learning methods that store latent vectors that are the inputs of GANs rather than storing real images, as the existing rehearsal-based approaches. As a result, more image knowledge can be stored in the same memory; thus, showing better results than the existing GAN continual learning methods. 인간과 달리 딥러닝 모델에게 다수의 태스크에 대한 순차적 학습은 어려운 문제이다. 이는 비단 분류모델뿐만 아니라 GAN과 같은 생성모델도 해당한다. GAN 지속학습 연구에서 주로 사용하는 Generative Replay 방식은 직전 태스크까지 학습된 GAN이 생성한 이미지를 새로운 태스크 학습 시 함께 사용하는데, 비교적 어려운 태스크에 속하는 CIFAR10에 대해서 좋은 품질의 이미지를 생성하지 못한다. 따라서 실제 이미지의 일부를 저장하는 리허설 기반 방법을 고려해볼 수 있는데, 실제 이미지는 큰 차원을 가지기 때문에 제한된 메모리에 많은 양을 저장할 수 없다. 본 논문에서는 기존 리허설 기반 방식에서 이미지를 저장하는 대신에 GAN의 입력이 되는 잠재벡터를 저장하는 지속학습 방법 LactoGAN과 LactoGAN+를 제안한다. 그 결과 같은 메모리에 더 많은 이미지 정보의 저장이 가능하게 되어 기존 GAN 지속학습 방법들에 비해 더 우수한 결과를 보임을 확인하였다.

전문가 설문조사를 통한 국내 성능위주설계 개선 방향설정에 관한 연구

정혜민,홍원화,손종영,전규엽 대한건축학회 2018 대한건축학회논문집 Vol.34 No.2

In recent years, as the development of construction technology and population increase, buildings are becoming more complex and high-rise. These large scale buildings are difficult to secure fire and evacuation safety when fire occurs. So it is necessary to prepare specific measures. According to this situation, in 2011, Republic of Korea officially launched Performance-based Design in 「Fire-fighting system Installationbusiness Act」. But even 6 years passed since the enforcement, there are still faces manifold problems in the course of implementation. In order to examine the necessary improvements, in this study, I conducted interviews and questionnaires with experts, investigated theimprovement items under current laws. And draw up a measures for that items. The subjects of the survey were fire-fighting officer,professional engineer fire fighting, fire protection planner and professor in Daegu. As a result of twice surveys, a total of 19 items arederived. And then compared and analyzed the criteria of overseas countries, and suggested improvement directions for final items. In addition,conducted a third questionnaire survey on the proposed improvement direction to verify the appropriateness of the alternative. The results ofthis study will be used as basic data to deal with the general problems of performance-based design in future, and further study on eachitem will be needed. 최근 건축기술의 발달과 인구의 증가에 따라 건축물이 복합화 및 초고층화 되어가고 있다. 이러한 대규모 건축물은 화재가 발생했을 때 소방 및 피난 안전성의 확보가 어려워 구체적인 대책 마련이 필요한 실정이다. 그에 따라, 대한민국은 2011년부터 정식으로 소방방재청에서 「소방시설등의성능위주설계방법및기준」을 고시하여 성능위주설계를 실시하고 있다. 하지만 실시한 지 6년이 지났음에도, 여전히 시행하는 과정에서 개선이 필요한 사항이 나타나고 있다. 이러한 사항을 조사하기 위해 본 연구에서는 전문가 인터뷰 및 설문조사를 실시하여, 현행 법규 상의 개선항목을 조사하고, 그 항목에 대한 방안을 도출하고자 한다. 설문조사 대상은 대구 소재의 소방 공무원, 소방 기술사 및 설계 관련업체 대표, 교수 등으로 구성하였다. 2차례의 설문조사 결과, 총 19개의 항목이 도출되었다. 해외의 기준을 비교 및 분석하여, 최종 도출된 항목에 대한 개선방향을 제시하였다. 그리고 제시하는 개선방향에 대해 추가적으로 3차 설문조사를 실시하여 해당 대안의 적절성을 검증하였다. 본 연구의 결과는 추후 성능위주설계의 전반적인 문제점을 다루는 기초자료로 쓰일 것이고, 각 항목에 대한 추가적인 자세한 연구가 필요할 것이다.

PVdF 나노섬유와 Graphene Oxide 하이브리드막에 관한 연구

정혜민,진유동,변홍식,양우석 한국막학회 2013 멤브레인 Vol.23 No.3

본 연구는 microfiltration (MF) 적용을 위한 PVdF/GO 하이브리드 나노섬유막(FG) 제조에 관한 것이다. 지지체인 PVdF (polyvinylidene difluoride) 나노섬유막은 N,N-Dimethylacetamide (DMAc)와 아세톤에 PVdF를 녹여 방사용액 제조 후 전기방사법을 이용하여 제조하였다. 본 연구에서 사용된 GO (grapheme oxide) sheets는 Hummer’s 방법에 따라 제조되었으며, PVdF 나노섬유 지지체 위에 에탄올에 분산시킨 GO용액을 분사함으로써, 최종적으로 PVdF/GO 하이브리드 나노섬유막(FG)을 제조하였다. FG막은 SEM, Raman, 접촉각, 기공특성분석장치(Porometer), 만능인장시험기(UTM)를 사용하여 조사하였고, 수투과도 분석은 제작된 셀(Dead-End Cell)을 이용하여 측정하였다. 접촉각 측정 결과로부터 제조된 FG막의 표면이 친수성으로 개질되었음을 확인할 수 있었으며, 수투과도값은 PVdF막에 비해 약 2.5배 향상된 것을 확인할 수 있었다. Recently, many applications with grapheneoxide (GO) have been reported. But GO membrane for water treatment has not been developed. In this study we prepared polyvinylidene difluoride (PVdF) nanofiber/GO hybrid membrane (FG) for the microfiltration application. The PVdF substrate membrane was prepared by using the electrospinning method with a solution of PVdF in N,N-dimethylacetamide (DMAc) and acetone. GO sheets used in this study were prepared by modified Hummer’s method. The PVdF/GO hybrid membrane was finally prepared by spraying the GO solution dispersed in ethanol on the PVdF nanofiber. The successfully prepared FG was thoroughly examined by SEM, Raman, contact angle, porometer and UTM, and water-flux was measured with designed cell (Dead-End Cell). From the contact angle results, it was found that the surface of FG membrane was reformed by hydrophilic property and the water permeability was increased about 2.5 times than that of the nascent PVdF membrane, indicating the possible alternative of the commercial MF membrane.

광효율 향상을 위해 유기발광 소자에 적용된 고굴절 산란층에 대한 연구

정혜민,곽진석 한국물리학회 2016 새물리 Vol.66 No.5

In this paper, we propose an organic light-emitting diode (OLED) structure with a high-refractive-index scattering layer to improve the OLED's external light efficiency. The light generated from the emitting layer is trapped partially in the hole transport layer (HTL) by total reflection, and the remaining light passes through the glass substrate and meets an air layer, where more light undergoes total reflection. Owing to these, OLED's efficiency is reduced by more than 50%. In order to decrease the reduction in the efficiency caused by the total reflection, we change the path of light to the air layer to a more normal direction. To change the light path, we use micro-sized SiO$_{2}$ particles which play the role of a kind of lens. Furthermore, so as to change more clearly the path of the light, we use a high-refractive-index material (TiO$_{2}$) around the SiO$_{2}$ particles. When the efficiency of a conventional OLED is compared to that of the OLED with a high-refractive-index scattering layer for which the ratio of SiO$_{2}$ particle to the high-refractive-index material (TiO$_{2}$) is 1 : 3, the efficiency of the latter is found to be increased by about 24.12%. 본 연구는 유기발광 소자의 낮은 외부 광 효율을 향상시키기 위해 굴절 산란 층이 적용된 유기 발광 소자 구조를 제안한다. 일반적으로 유기 발광 층에서 발생된 빛은 정공수송층에서 굴절률의 차이로 일부 전반사가 일어나게 되고 나머지 유리기판을 지나가는 빛은 공기층에서 많은 전반사를 겪게 된다. 이로 인해 유기발광 소자는 필연적으로 50% 이상의 효율의 감소를 수반하게 된다. 이런 전반사로 인한 손실을 줄이기 위해 공기층으로 나가는 빛의 경로를 바꾸어 줄 필요성이 제기되는데 본 연구에서는 공기층으로 나가는 빛의 경로를 변경시키기 위해 렌즈작용을 하는 마이크로 크기의 SiO$_{2}$ 산란입자를 사용하였고 보다 확실한 경로 변경을 할 수 있도록 SiO$_{2}$ ($n$ = 1.5) 산란입자 주변을 고굴절 물질인 TiO$_{2}$로 도포하여 광효율 향상을 최대화하였다. 기존의 구조와 고굴절-산란층이 삽입된 광소자 구조를 실험으로 측정 비교해본 결과 기존구조에선 전압 16 cd/cm$^{2}$일 때 휘도가 4.95 lm/W인 반면 고굴절-산란층이 도입된 소자인 경우 6.14 lm/W를 가져 24.12%의 효율이 향상되었음을 확인하였다.

The Impact of an Emergency Fee Increase on the Composition of Patients Visiting Emergency Departments

정혜민,도영경,김윤,노준수 대한예방의학회 2014 Journal of Preventive Medicine and Public Health Vol.47 No.6

Objectives: This study aimed to test our hypothesis that a raise in the emergency fee implemented on March 1, 2013 has increased the proportion of patients with emergent symptoms by discouraging non-urgent emergency department visits. Methods: We conducted an analysis of 728 736 patients registered in the National Emergency Department Information System who visited level 1 and level 2 emergency medical institutes in the two-month time period from February 1, 2013, one month before the raise in the emergency fee, to March 31, 2013, one month after the raise. A difference-in-difference method was used to estimate the net effects of a raise in the emergency fee on the probability that an emergency visit is for urgent conditions. Results: The percentage of emergency department visits in urgent or equivalent patients increased by 2.4% points, from 74.2% beforeto 76.6% after the policy implementation. In a group of patients transferred using public transport or ambulance, who were assumedto be least conscious of cost, the change in the proportion of urgent patients was not statistically significant. On the other hand, the probability that a group of patients directly presenting to the emergency department by private transport, assumed to be most conscious of cost, showed a 2.4% point increase in urgent conditions (p<0.001). This trend appeared to be consistent across the level 1 and level 2 emergency medical institutes. Conclusions: A raise in the emergency fee implemented on March 1, 2013 increased the propoEmergency fee, Hospital emergency service, Overcrowding, Difference-in-differencertion of urgent patients in the total emergency visits by reducing emergency department visits by non-urgent patients. Objectives: This study aimed to test our hypothesis that a raise in the emergency fee implemented on March 1, 2013 has increased the proportion of patients with emergent symptoms by discouraging non-urgent emergency department visits. Methods: We conducted an analysis of 728 736 patients registered in the National Emergency Department Information System who visited level 1 and level 2 emergency medical institutes in the two-month time period from February 1, 2013, one month before the raise in the emergency fee, to March 31, 2013, one month after the raise. A difference-in-difference method was used to estimate the net effects of a raise in the emergency fee on the probability that an emergency visit is for urgent conditions. Results: The percentage of emergency department visits in urgent or equivalent patients increased by 2.4% points, from 74.2% beforeto 76.6% after the policy implementation. In a group of patients transferred using public transport or ambulance, who were assumedto be least conscious of cost, the change in the proportion of urgent patients was not statistically significant. On the other hand, the probability that a group of patients directly presenting to the emergency department by private transport, assumed to be most conscious of cost, showed a 2.4% point increase in urgent conditions (p<0.001). This trend appeared to be consistent across the level 1 and level 2 emergency medical institutes. Conclusions: A raise in the emergency fee implemented on March 1, 2013 increased the proportion of urgent patients in the total emergency visits by reducing emergency department visits by non-urgent patients.

아끼바레 및 밀양 23호 쌀전분의 이화학적 성질비교

정혜민,안승요,김성곤 한국응용생명화학회 1982 Applied Biological Chemistry (Appl Biol Chem) Vol.25 No.2

아끼바레 및 밀양 23호 쌀 전분의 이화학적 성질, 전분 gel의 노화 및 음이온에 의한 호화양상을 조사하였다. 두 전분입자의 성상은 다각형이며 입자의 크기는 3~6㎛정도였으며, 아끼바레가 밀양 23호 보다 다소 작았다. 두 전분의 X-ray 회절도는 A형으로 peak 형태와 강도에서 약간의 차이를 보였다. 아끼바레 및 밀양 23호 쌀 전분의 아밀로스 함량은 각각 18.5 및 19.5%이었고 물 결합능력은 106 및 100%이었다. 팽화력은 50℃까지는 큰 변화가 없었으나 이후에 급격히 증가하였고 밀양 23호 쌀 전분의 팽화력이 더 컸다. 전분 현탁액(0.1%)의 광투과도는 두 전분 모두 60℃ 이후에서 급격히 증가하였으며 밀양 23호 쌀 전분이 더 큰 광투과도를 보였다. 음이온에 의한 아밀로그람 pattern은 NaCl과 NaF는 동일하였고, NaSCN과 NaI는 유사였다. 호화온도 및 최고점도시의 온도는 SCN^(-)<I^(-)<Cl^(-)<F^(-)<SO₄^(=)의 순으로 증가하였고 SCN^(-) 및 I^(-)이온은 최고 점도를 증가시켰으나 NaCl은 감소시켰다. SO₄^(=)이온을 첨가한 경우 점도는 계속 증가하였고 최고점도에 도달하지 않았다. 아끼바레 및 밀양 23호 전분 gel율 21℃에서 저장한 경우 시간 상수가 각각 6.72 및 6.42일이었다. Morphology, pbysicochemical properties, pasting properties in the presence of various anionic ions and aging of gels of Akibare (Japoica type) and Milyang 39 (Indica type)rice starch were studied Both starches. were polygonal with length in the range of 3~6㎛. Starch granules of Akibare were somewhat smaller than those of Milyang 23. X-ray diffraction study demonstrated that peak shape and intensity were significantly different between the two starches. Akibare and Milyang 23 rice starch had amylose content of 18.5 and 19,5% and water binding capacity of 106 and 100%, respectively. Milyang 23 rice starch had a higher swelling power than Akibare starch. A relationship between percent solubility and swelling power implied that bonding forces within the granules of the both starches were different. The optical transmittance of 0.1% suspension of the two starches increased rapidly from 60℃. In the range of 60~90℃, the two starches showed a single gelatinization pattern. Amylograms of the two starches in the presence of various anionic ions showed that pasting temperature and peak temperature were progressively increased in the order of SCN-<I-<CI-<F-<SO₄=. SCN- and I- ions increased the peak height of Akibare rice starch white only SCN- ion was effective for Milyang 23 rice starch. There were no differences in the rates of retrogradation of 45% gels of the two starches stored at 21℃.