• Composites Research
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• 제34권1호
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• pp.23-29
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• 2021

탄소섬유는 단위 중량 당 높은 강도 및 모듈러스를 갖기 때문에 고성능 복합 재료 제조 시 탄소보강재로 많이 사용된다. 그러나 탄소 섬유를 제조하는 공정에서 많은 시간과 높은 에너지를 소모하여 제조비용이 크게 증가하기 때문에 상용화에 어려움을 겪고 있다. 따라서 생산 비용 절감을 위하여 제조 공정에 사용되는 에너지를 대체할 수 있는 고속의 저 에너지원을 적극적으로 찾아 연구할 필요가 높아졌다. 폴리아크릴로니트릴(PAN) 전구체(Precursor)로 상용화 된 탄소 섬유는 180~300℃의 대기 분위기에서 안정화 과정이 이루어지고, 1600℃ 이하의 불활성 가스 분위기에서 탄화하여 탄소 섬유를 생산할 수 있다. 이 두 공정은 많은 시간과 높은 에너지를 사용하지만, 고성능 탄소 섬유를 생산하는 데 필수적이며 중요하다. 따라서 최근에는 공정 시간을 단축하고 에너지 소비를 줄일 수 있는 플라즈마, 전자 빔 및 마이크로파와 같은 다양한 다른 에너지원을 보조적으로 사용 함으로써 저 에너지·고속 안정화 공정 기술이 시도되고 있다. 본 연구에서는 플라즈마 공정과 열처리를 연속적으로 수행하여 PAN 전구체 안정화 공정을 연구하였으며, 모폴로지, 구조적 변화, 열적 및 물리적 특성 변화를 연구하였다.

• Journal of Microbiology and Biotechnology
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• 제32권3호
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• pp.287-293
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• 2022

The hydroxylation of methane (CH₄) is crucial to the field of environmental microbiology, owing to the heat capacity of methane, which is much higher than that of carbon dioxide (CO₂). Soluble methane monooxygenase (sMMO), a member of the bacterial multicomponent monooxygenase (BMM) superfamily, is essential for the hydroxylation of specific substrates, including hydroxylase (MMOH), regulatory component (MMOB), and reductase (MMOR). The diiron active site positioned in the MMOH α-subunit is reduced through the interaction of MMOR in the catalytic cycle. The electron transfer pathway, however, is not yet fully understood due to the absence of complex structures with reductases. A type II methanotroph, Methylosinus sporium 5, successfully expressed sMMO and hydroxylase, which were purified for the study of the mechanisms. Studies on the MMOH-MMOB interaction have demonstrated that Tyr76 and Trp78 induce hydrophobic interactions through π-π stacking. Structural analysis and sequencing of the ferredoxin domain in MMOR (MMOR-Fd) suggested that Tyr93 and Tyr95 could be key residues for electron transfer. Mutational studies of these residues have shown that the concentrations of flavin adenine dinucleotide (FAD) and iron ions are changed. The measurements of dissociation constants (K_ds) between hydroxylase and mutated reductases confirmed that the binding affinities were not significantly changed, although the specific enzyme activities were significantly reduced by MMOR-Y93A. This result shows that Tyr93 could be a crucial residue for the electron transfer route at the interface between hydroxylase and reductase.

• 한국재료학회지
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• 제31권12호
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• pp.665-671
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• 2021

A 1.8 ㎛ thick polycrystalline diamond (PCD) thin film layer is prepared on a Si(100) substrate using hot-filament chemical vapor deposition. Thereafter, its thermal conductivity is measured using the conventional laser flash analysis (LFA) method, a LaserPIT-M2 instrument, and the newly proposed light source thermal analysis (LSTA) method. The LSTA method measures the thermal conductivity of the prepared PCD thin film layer using an ultraviolet (UV) lamp with a wavelength of 395 nm as the heat source and a thermocouple installed at a specific distance. In addition, the microstructure and quality of the prepared PCD thin films are evaluated using an optical microscope, a field emission scanning electron microscope, and a micro-Raman spectroscope. The LFA, LaserPIT-M2, and LSTA determine the thermal conductivities of the PCD thin films, which are 1.7, 1430, and 213.43 W/(m·K), respectively, indicating that the LFA method and LaserPIT-M2 are prone to errors. Considering the grain size of PCD, we conclude that the LSTA method is the most reliable one for determining the thermal conductivity of the fabricated PCD thin film layers. Therefore, the proposed LSTA method presents significant potential for the accurate and reliable measurement of the thermal conductivity of PCD thin films.

• Design & Manufacturing
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• 제16권1호
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• pp.55-61
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• 2022

As meters become digital and smart, energy data such as electricity, gas, heat, and water can be accurately and efficiently measured with a smart meter, providing consumers with data on energy used, so that real-time demand response and energy management services can be utilized. Although it is developing from a simple metering system to a smart metering industry to create a high value-added industry fused with ICT, illegal counterfeiting of electronic meters is causing problems in intelligent crimes such as manipulation and hacking of SW. The meter not only allows forgery of the meter data through arbitrary manipulation of the SW, but also leaves a fatal error in the metering performance, so that the OIML requires the validation of the SW from the authorized institution. In order to solve this problem, a quantitative confirmation device was developed in order to eradicate the act of cheating the fuel oil quantity through encoder pulse operation and program modulation, etc. In order to prevent the act of deceiving the lubricator, a device capable of checking pulse forgery was developed, manufactured, and verified. In addition, the performance of the device was verified by conducting an experiment on the meter being used in the actual field. It is judged that the developed quantitative confirmation device can be applied to other flow meters other than lubricators, and in this case, accurate measurement can be induced.

• Journal of Veterinary Science
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• 제24권1호
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• pp.11.1-11.14
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• 2023

Background: Peripheral blood mononuclear cells (PBMCs) are commonly used to assess in vitro immune responses. However, PBMC isolation is a time-consuming procedure, introduces technical variability, and requires a relatively large volume of blood. By contrast, whole blood assay (WBA) is faster, cheaper, maintains more physiological conditions, and requires less sample volume, laboratory training, and equipment. Objectives: Herein, this study aimed to develop a porcine WBA for in vitro evaluation of immune responses. Methods: Heparinized whole blood (WB) was diluted (non-diluted, 1/2, 1/8, and 1/16) in RPMI-1640 media, followed by phorbol myristate acetate and ionomycin. After 24 h, cells were stained for interferon (IFN)-γ secreting T-cells followed by flow cytometry, and the supernatant was analyzed for tumor necrosis factor (TNF)-α. In addition, diluted WB was stimulated by lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid (poly I:C), reference strain KCTC3557 (RS), field isolate (FI), of heat-killed (HK) Streptococcus suis, and porcine reproductive and respiratory syndrome virus (PRRSV). Results: The frequency of IFN-γ⁺CD3⁺ T-cells and concentration of TNF-α in the supernatant of WB increased with increasing dilution factor and were optimal at 1/8. WB TNF-α and interleukin (IL)-10 cytokine levels increased significantly following stimulation with LPS or poly I:C. Further, FI and RS induced IL-10 production in WB. Additionally, PRRSV strains increased the frequency of IFN-γ⁺ CD4^-CD8⁺ cells, and IFN-γ was non-significantly induced in the supernatant of re-stimulated samples. Conclusions: We propose that the WBA is a rapid, reliable, and simple method to evaluate immune responses and WB should be diluted to trigger immune cells.

• The Korean Journal of Pain
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• 제36권1호
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• pp.11-50
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• 2023

As the field of interventional pain management (IPM) grows, the risk of surgical site infections (SSIs) is increasing. SSI is defined as an infection of the incision or organ/space that occurs within one month after operation or three months after implantation. It is also common to find patients with suspected infection in an outpatient clinic. The most frequent IPM procedures are performed in the spine. Even though primary pyogenic spondylodiscitis via hematogenous spread is the most common type among spinal infections, secondary spinal infections from direct inoculation should be monitored after IPM procedures. Various preventive guidelines for SSI have been published. Cefazolin, followed by vancomycin, is the most commonly used surgical antibiotic prophylaxis in IPM. Diagnosis of SSI is confirmed by purulent discharge, isolation of causative organisms, pain/tenderness, swelling, redness, or heat, or diagnosis by a surgeon or attending physician. Inflammatory markers include traditional (C-reactive protein, erythrocyte sedimentation rate, and white blood cell count) and novel (procalcitonin, serum amyloid A, and presepsin) markers. Empirical antibiotic therapy is defined as the initial administration of antibiotics within at least 24 hours prior to the results of blood culture and antibiotic susceptibility testing. Definitive antibiotic therapy is initiated based on the above culture and testing. Combination antibiotic therapy for multidrug-resistant Gram-negative bacteria infections appears to be superior to monotherapy in mortality with the risk of increasing antibiotic resistance rates. The never-ending war between bacterial resistance and new antibiotics is continuing. This article reviews prevention, diagnosis, and treatment of infection in pain medicine.

• Composites Research
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• 제19권4호
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• pp.31-38
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• 2006

본 연구에서는 열탄성 해석과 복합재/알루미늄 링시편 실험을 통해 성형 온도와 자긴 압력이 복합재와 알루미늄 라이너로 구성된 Type 3 극저온 추진제 탱크에 미치는 영향을 살펴보았다. 우선 Type 3 탱크의 온도분포를 구한 뒤 이를 경계조건으로 사용하여 성형온도와 자긴 압력의 영향을 고려한 탄성해석을 수행하였다. 그 결과 복합재의 성형온도가 증가할수록 복합재와 알루미늄 라이너에 각각 잔류압축응력과 잔류인장응력이 증가하였다. 한편 자긴 압력은 극저온 환경에 의해 유발된 잔류열응력의 감소를 초래하였으며 자긴 압력의 크기가 증가할수록 이러한 경향은 두드러졌다. 이러한 성형 온도와 자긴 압력의 영향은 Type 3 극저온 추진제 탱크의 설계 및 제작 단계에 반드시 고려되어야 한다.

• 한국산업융합학회 논문집
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• 제25권2_2호
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• pp.289-297
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• 2022

Deterioration in durability of structures due to the steel corrosion is difficult to determine whether or not corrosion is initiated and how much propagated, and moreover, repair and maintenance are not easy to deal with. Therefore, preventive treatments can be the best option to avoid the deterioration. Various methods for preventing corrosion of steel, such as electrochemical treatments, anti-corrosion agents and steel surface coatings, are being developed, but economic and environmental aspects make it difficult to apply them to in-situ field. Thus, the purpose of this study was to improve corrosion resistance by using CA-based clinker that are relatively simple and expected to be economically profitable Existing CA-based clinkers had problems such as flash setting and low strength development during the initial hydration process, but in order to solve this problem, CA clinker with low initial reactivity were used as binder in this study. The cement paste used in the experiments was replaced with CA₂ clinker for 0%, 10%, 20%, and 30% in OPC. And the mixture used in the chloride binding test for the extraction of water-soluble chloride was intermixed with Cl- 0.5%, 1%, 2%, and 3% by weight of binder content. To evaluate characteristic of hydration heat evolution, calorimetry analysis was performed and simultaneously chloride binding capacity and acid neutralization capacity were carried out. The identification of hydration products with curing ages was verified by X-ray diffraction analysis. The free chloride extraction test showed that the chlorine ion holding ability improved in order OC 10 > OC 30 > OC 20 > OC 0 and the pH drop resistance test showed that the resistance capability in pH 12 was OC 0 > OA 10 > OA 20 > OA 30. The XRD analyses showed that AFm phase, which can affect the ability to hold chlorine ions, tended to increase when CA₂ was mixed, and that in pH12 the content of calcium hydroxide (Ca(OH)₂), which indicates pH-low resistance, decreased as CA₂ was mixed

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.939-946
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• 2023

Comprehensive Research Facility for Fusion Technology (CRAFT) is an integration of different demonstrating or testing facilities, which aim to develop the critical technology or composition system towards the fusion reactor. Due to the importance and challenge of the negative ion based neutral beam injection (NNBI), a NNBI test facility is included in the framework of CRAFT. The initial object of CRAFT NNBI test facility is to obtain a H⁰ beam power of 2 MW at the energy of 200-400 keV for the pulse duration of 100 s. Inside the negative ion accelerator of NNBI system, the interactions of the negative ions with the background gas and electrodes can generate abundant stray electrons. The stray electrons can be further accelerated and dumped on the electrodes or eject from the accelerator. The stray electrons, including the ejecting electrons, cause the unwanted particle and heat flux onto the electrodes and the inner components of beamline (especially the temperature sensitive cryopump). The suppression of the stray electrons from the CRAFT accelerator is carried out via a series of design and simulation works. The paper focuses the influence of different magnetic field configurations on the stray electrons and the character of the ejecting electrons.

• Safety and Health at Work
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• 제14권1호
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• pp.17-30
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• 2023

The human reproductive system can be affected by occupational exposure to many physical and chemical risk factors. This study was carried out to review the studies conducted on the issue of the pathophysiological effects of occupational physical and chemical risk factors on the reproductive system of females and males. In this systematic review, the databases such as "Google Scholar," "Pub-Med," "Scopus," and "Web of Science" were used. Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA 2020), the studies included in our study were published between 2000 and 2021. In order to extract the required data, all sections of the articles were reviewed. Out of 57 articles we reviewed, 34 articles were related to field studies and 23 articles to clinical studies. Among them, 43 studies dealt with the pathophysiological effects of chemical agents, six studies dealt with the pathophysiological effects of physical factors, and 8 studies dealt with the pathophysiological effects of physicochemical factors on the human reproductive system. Physical (noise, heat, and radiofrequency radiation) and chemical (such as carbamate and organophosphate pesticides, benzene, toluene, xylene, formaldehyde, NO2, CS2, manganese, lead, nickel, and n-hexane) risk factors had pathophysiological effects on the human reproductive system. The presence of these risk factors in the workplace caused damage to the human reproductive system. The rate of these negative pathophysiological effects can be reduced by performing appropriate managerial, technical, and engineering measures in work environments.