• Korean Chemical Engineering Research
• /
• 제61권1호
• /
• pp.155-161
• /
• 2023

이온 농도 분극 현상은 전기투석, 전기화학 전지에서 일어나는 기초 이동 현상일 뿐만 아니라, 생체 물질 전처리용 농축 장치의 핵심 기작으로 활용된다. 외부 인가 전압에 의해 발생한 이온 농도 분극 현상은 분석 물질의 농축에 필요한 국소적으로 증폭된 전기장을 통해 물질의 농축을 가능케 한다. 그러나 기존의 농축 기작은 농축의 평형 지점이 불분명하며, 농축 플러그의 유체역학적 불안정성의 두가지 문제점을 가지고 있다. 본 연구에서는, 이온 농도 분극 기반의 농축 기작의 한계점을 해결하기 위해 막다른 미세유로와 양이온 교환막을 사용한 농축 방법을 연구하였다. 막다른 미세유로의 공간 제약적 구조를 통해 유체역학적 안정성을 확보할 수 있으며, 분석 물질의 농축 지점이 이온 공핍 영역의 충격 전단과 일치함을 수치적으로 확인하였다. 또한 농축 공정의 핵심 인자로써 인가 전압과 미세유로의 체적 전하 농도를 변화시켜가며, 농축 물질의 전기동역학적 거동을 연구하였다. 본 연구의 결과는 현장 진단 검사(point-of-care)와 같은 초단시간의 농축을 필요로 하는 미세유체역학 장치에 유효한 기작으로 사용될 수 있을 것이다.

• Composites Research
• /
• 제20권3호
• /
• pp.43-49
• /
• 2007

회전원판의 동적 불안정성은 회전속도를 제한하는 가장 중요한 요인이다. 복합재료를 회전원판에 적용시킬 경우 동적 안정성을 증가시킬 수 있어 경량화와 고속화를 동시에 이룰 수 있다. 티모쉔코 효과라고 불리는 횡전단변형과 회전관성이 판 구조물의 동적거동에 미치는 영향은 많은 연구가 진행되어왔으나 원판의 회전이 이 효과에 미치는 영향에 대한 연구는 극히 제한적이며 복합재료 원판의 경우는 전무한 실정이다. 본 연구에서는 티모쉔코 효과를 고려한 직교이방성 회전원판의 동적 방정식을 유도하였으며 상용 유한요소 프로그램인 MSC/NASTRAN을 이용하여 진동해석을 수행하였다. 해석결과에 따르면 특정 모드에서는 일반적으로 알려진 바와는 달리 회전수의 증가에 따라 티모쉔코 효과가 감소하다 증가하는 현상을 보였다. 또한 데이터만을 기초로 회전증가에 따른 티모쉔코 효과의 감소는 두께비가 작아질수록 증가하고, 반경비, 탄성계수 대 전단계수 비, 진동 모드 수가 커질수록 증가하는 것으로 결론지을 수 있다.

• Parasites, Hosts and Diseases
• /
• 제61권2호
• /
• pp.183-193
• /
• 2023

Balamuthia mandrillaris amebic encephalitis (BAE) can cause a fatal condition if diagnosis is delayed or effective treatment is lacking. Patients with BAE have been previously reported in 12 provinces of China, with skin lesions being the primary symptom and encephalitis developing after several years. However, a significantly lower number of cases has been reported in Southwest China. Here we report an aggressive BAE case of a 64-year-old woman farmer with a history of skin lesions on her left hand. She was admitted to our hospital due to symptoms of dizziness, headache, cough, vomiting, and gait instability. She was initially diagnosed with syphilitic meningoencephalitis and received a variety of empirical treatment that failed to improve her symptoms. Finally, she was diagnosed with BAE combined with amebic pneumonia using next-generation sequencing (NGS), qRT-PCR, sequence analysis, and imaging studies. She died approximately 3 weeks after the onset. This case highlights that the rapid development of encephalitis can be a prominent clinical manifestation of Balamuthia mandrillaris infection.

• 천문학회보
• /
• 제46권2호
• /
• pp.70.2-71
• /
• 2021

We examine gas kinematics and star formation activities of NGC 6822, a gas-rich dwarf irregular galaxy in the Local Group at a distance of ~490 kpc. We perform profile decomposition of all the line-of-sight (LOS) HI velocity profiles of the high-resolution (42.4" × 12" spatial; 1.6 km/s spectral) HI data cube of the galaxy, taken with the Australian Telescope Compact Array (ATCA). To this end, we use a novel tool based on Bayesian Markov Chain Monte Carlo (MCMC) techniques, the so-called BAYGAUD, which allows us to decompose a velocity profile into an optimal number of Gaussian components in a quantitative manner. We group all the decomposed components into bulk-narrow, bulk-broad, and non-bulk gas components classified with respect to their velocity dispersions and the amounts of velocity offset from the global kinematics, respectively. Using the surface densities and velocity dispersions of the kinematically decomposed HI gas maps together with the rotation curve of NGC 6822, we derive Toomre-Q parameters for individual regions of the galaxy which quantify the level of local gravitational instability of the gaseous disk. We also measure the local star formation rate (SFR) of the corresponding regions in the galaxy by combining GALEX Far-ultraviolet (FUV) and WISE 22㎛ images. We then relate the gas and SFR surface densities in order to investigate the local Kennicutt-Schmidt (K-S) law of gravitationally unstable regions which are selected from the Toomre Q analysis. Of the three groups, the bulk-narrow, bulk-broad and non-bulk gas components, we find that the lower Toomre-Q values the bulk-narrow gas components have, the more consistent with the linear extension of the K-S law derived from molecular hydrogen (H2) observations.

• 천문학회보
• /
• 제46권1호
• /
• pp.34.4-35
• /
• 2021

We present the TESS photometry and our high-resolution spectra of the semi-detached Algol EW Boo. For an orbital period study, we collected all available times of minima including ours for the last 30 years. It is found that the eclipse timing variation of the system can be represented by a periodic oscillation of 18.5±1.0 yr plus a secular period increase with a rate of [dP/dt]_orb=-6(±3)×10^-8 d yr^-1. From our observed spectra, the effective temperature of the primary star was determined to be T_eff,1=8560±118 K. From a simultaneous analysis of the TESS light and our double-lined radial velocity curves, the absolute masses, radii, and luminosities are M₁=2.30±0.07M_⊙, M₂=0.38±0.01M_⊙, R₁=1.92±0.02 R_⊙, R₂=1.27±0.01 R_⊙, L₁=1.92±0.02 L_⊙, and L₂=0.752±0.007 L_⊙, respectively. Multiple frequency analyses were carried out for the light residuals after subtracting the binary star model. We detected a total of 75 frequencies in the region of 16.50-104.8 day-1. Our results demonstrate that the more hotter primary star of EW Boo is a δ Sct pulsator by considering its position in the δ Scuti region of the Cepheid instability strip and pulsational characteristics.

• 천문학회보
• /
• 제45권1호
• /
• pp.59.2-59.2
• /
• 2020

Disks around protostars are the birthplace of planets. The first step toward planet formation is grain growth from ㎛-sized grains to mm/cm-sized grains in a disk, particularly in dense regions. In order to study whether grains grow and segregate at the protostellar stage, we investigate the ALMA Band 3 (3.1 mm) and 7 (0.87 mm) dust continuum observations of the protostellar disk WL 17 in ρ Ophiuchus L1688 cloud. As reported in a previous study, the Band 3 image shows substructures: a narrow ring and a large central hole. On the other hand, the Band 7 image shows different substructures: a non-axisymmetric ring and an off-center hole. The two-band observations provide a mean spectral index of 2.3, which suggests the presence of mm/cm-sized large grains. Its non-axisymmetric distribution may imply dust segregation between small and large grains. We perform radiative transfer modeling to examine the size and spatial distributions of dust grains in the WL 17 disk. The best-fit model suggests that large grains (>1 cm) exist in the disk, settling down toward the midplane, whereas small grains (~10 ㎛) well mixed with gas are distributed off-center and non-axisymmetrically in a thick layer. The low spectral index and the modeling results suggest that grains rapidly grow at the protostellar stage and that grains differently distribute depending on sizes, resulting in substructures varying with observed wavelengths. To understand the differential grain distributions and substructures, we discuss the effects of the protoplanet(s) expected inside the large hole and the possibility of gravitational instability.

• 대한토목학회논문집
• /
• 제29권5C호
• /
• pp.191-198
• /
• 2009

국내 풍화사면에서의 표면파괴는 주로 강우에 의한 침투로 인하여 발생한다고 알려져 있다. 이러한 파괴는 표면토사부에 강우로 인한 하향 침투수에 흡수력의 감소와 습윤대의 증가에 의하여 야기된다. 따라서 국내에 흔히 존재하는 편마계열 풍화사면토를 대상으로 강우로 인한 습윤 경로 및 그 추이를 현상학적인 접근법으로 살펴볼 필요가 있다. 이에 본 논문에서는 풍화토를 대상으로 습윤 함수특성곡선에 대한 실내실험을 수행하고 결과를 활용하여 강우시 불포화 사면안정해석을 실시하였다. 기존 문헌의 자료에서 현장의 함수특성이 실내시험에서의 습윤경로에서 잘 반영하고 있어 상계 조건으로 실내시험에서 구한 습윤경로 함수특성곡선을 사면해석에 활용하는 것도 합리적임을 알 수 있다.

• Steel and Composite Structures
• /
• 제49권4호
• /
• pp.381-392
• /
• 2023

This study experimentally investigates the flexural behavior of steel-UHPC composite slabs composed of an innovative negative Poisson's ratio (NPR) steel plate and Ultra High Performance Concrete (UHPC) slab connected via demountable high-strength bolt shear connectors. Eight demountable composite slab specimens were fabricated and tested under traditional four-point bending method. The effects of loading histories (positive and negative bending moment), types of steel plate (NPR steel plate and Q355 steel plate) and spacings of high-strength bolts (150 mm, 200 mm and 250 mm) on the flexural behavior of demountable composite slab, including failure mode, load-deflection curve, interface relative slip, crack width and sectional strain distribution, were evaluated. The results revealed that under positive bending moment, the failure mode of composite slabs employing NPR steel plate was distinct from that with Q355 steel plate, which exhibited that part of high-strength bolts was cut off, part of pre-embedded padded extension nuts was pulled out, and UHPC collapsed due to instantaneous instability and etc. Besides, under the same spacing of high-strength bolts, NPR steel plate availably delayed and restrained the relative slip between steel plate and UHPC plate, thus significantly enhanced the cooperative deformation capacity, flexural stiffness and load capacity for composite slabs further. While under negative bending moment, NPR steel plate effectively improved the flexural capacity and deformation characteristics of composite slabs, but it has no obvious effect on the initial flexural stiffness of composite slabs. Meanwhile, the excellent crack-width control ability for UHPC endowed composite members with better durability. Furthermore, according to the sectional strain distribution analysis, due to the negative Poisson's ratio effect and high yield strength of NPR steel plate, the tensile strain between NPR steel plate and UHPC layer held strain compatibility during the whole loading process, and the magnitude of upward movement for sectional plastic neutral axis could be ignored with the increase of positive bending moment.

• 중환자간호학회지
• /
• 제16권3호
• /
• pp.1-10
• /
• 2023

Purpose : This study explores the professional status of Advanced Practice Nurses (APNs) in Korea, who, despite being legally certified, face instability in their professional standing, including their scope of practice and compensation. Method : The study uses Flexner's professional characteristics as a framework to analyze and project the future trajectory of Korean APNs. Results : First, to ensure social accountability, professional bodies need to establish uniform nursing policies related to job roles, and healthcare institutions must adhere to these policies. Second, nursing leaders should spearhead the creation of nursing knowledge essential for the profession's advancement, aiming to establish it as the foundation for nursing practice through a consensus process within the nursing community. Third, the curriculum for APNs should enhance the quantitative and qualitative aspects of practice in response to societal needs. Fourth, professional bodies should formulate consistent nursing policies based on a thorough analysis of the healthcare environment and legal considerations, and guide their implementation in clinical practice through a consensus process within the nursing community. Lastly, guidelines should be established for professional standards suitable for the Korean context. Conclusion : Based on this review, it is recommended that all APNs adhere to the professional standards set by their respective organizations, actively participate in personal quality improvement initiatives, and fulfill their duties and roles as members of these professional bodies. Furthermore, these organizations should devise practical strategies to solidify the APN system and should spearhead a systematic consensus process that garners the agreement of all members within the nursing community.

• 한국환경과학회지
• /
• 제33권4호
• /
• pp.279-282
• /
• 2024

This study aimed to verify the results of emotional analysis with respect to canine behavior as reported in the existing animal behavior field based on the dog vestibular emotional reflex (VER) principle, and to evaluate humans and animals based on empathy gained through true communication rather than human-centered interpretation. A total of 200 canines were divided into non-daily and daily situation groups (n=100 each). To assess the psychological and emotional state of each group, these changes were applied to the principle of VER, and six measurement values were selected: positive emotion (balance and energy), negative emotion (tension/anxiety and stress), and body condition (inhibition and neuroticism). The results showed a statistically significant difference (p<0.05) in positive emotions, negative emotions, and body conditions between the two groups. In addition, balance, energy, tension/anxiety, inhibition, and neuroticism were higher in the non-daily situation group than in the daily situation group, with an exception for stress. Compared with the canine daily situation groups, canine in the non-daily situation groups instinctively observed their surroundings to cope with possible threats, had decreased concentration, and elevated vitals due to high-intensity anxiety. This can be perceived as a state of immediate reaction to possible situations/threats. In conclusion, it was confirmed through Vibra Image technology that canine instability mainly affects three factors: positive emotion, negative emotion, and physical condition.