• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.46-51
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• 2012

본 연구에서는 액체로켓엔진 단계식 연소 사이클의 기본 설계 사양을 도출하기 위한 시스템 해석을 수행하였다. 액체산소를 산화제로 하고 액체수소와 RP-1을 각각 연료로 사용하는 엔진에 대해 사이클 해석을 적용하였다. 엔진의 성능지표인 비추력을 기준으로 하여 실제 개발되어있는 엔진과 1% 이내의 차이를 보였다. 사이클 해석을 위해 개발된 프로그램은 압력과 유량 균형, 터보펌프-터빈의 에너지 균형 조건을 만족하며 주어진 추력에 대한 연료 소모와 비추력 및 각 부품의 기본적인 사양을 도출할 수 있다. 추가적인 제한조건들의 조사가 이루어지면 통합 최적화 프로그램으로 발전시킬 수 있을 것으로 판단된다.

• 대한두개안면성형외과학회지
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• 제20권4호
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• pp.274-278
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• 2019

Orbital tuberculosis is a rare form of extrapulmonary tuberculosis, even in endemic areas. It may involve the soft tissue, lacrimal gland, periosteum, or bones of the orbital wall. We present a case of orbital tuberculosis on the lower eyelid. An 18-year-old woman with no underlying disease visited our clinic for evaluation of an oval nodule ($1.5{\times}1.2cm$) on the right lower eyelid. Incision and drainage without biopsy was performed 2 months ago in ophthalmology department, but the periorbital mass had deteriorated, as the patient had erythematous swelling, tenderness, and cervical lymphadenopathy. Visual acuity was normal; there were no signs of proptosis, diplopia, or ophthalmoplegia. Computed tomography revealed a small abscess cavity without bony involvement. We performed an excision and biopsy through a percutaneous incision under local anesthesia. Histological examination revealed a granuloma and was diagnosed as orbital tuberculosis. The patient was additionally treated with anti-tuberculosis therapy for 6 months and recovered without complication or recurrence by 7 months. Orbital tuberculosis occurs in patients with or without associated pulmonary tuberculosis, and should be considered as a differential diagnosis in patients with inflammatory orbital disease and an orbital mass. If recurrence occurs despite adequate initial treatment, we recommend an additional examination and excisional biopsy.

• 대한두개안면성형외과학회지
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• 제20권3호
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• pp.181-185
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• 2019

Intraosseous hemangioma is a rare, slow-growing, benign tumor of blood vessels. Primary hemangioma of the skull is a benign lesion that may appear as a palpable mass or accidentally detected during image evaluation. Simple radiography is the most commonly used technique to localize a lesion and computed tomography (CT) may help determine the effect of a lesion. We report a case of multifocal intraosseous calvarial hemangioma developed in the subgaleal plane of an elderly male patient. Ultrasonography examination revealed hyperechoic striated septae parallel to the skin and discontinuity of the focal cortex, however, the underlying bone cortex appeared relatively intact. No significant flow is observed on Doppler ultrasonography. Based on these evaluations, the mass was interpreted by a radiologist as a subgaleal lipoma. This case highlights the importance of additional CT examination in a patient presenting with a scalloping sign of the underlying calvarium. Clinicians also should be aware of the possibility of intraosseous calvarial hemangiomas in lesion. Furthermore, the proper choice of congenital vascular malformation term is still quite confusing with misconception present in the literature.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1364-1371
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• 2018

An extensive investigation of photon interaction properties has been made for $Zn_xTe_{100-x}$ alloys (where x = 5, 20, 30, 40, 50) to explore its possible use in sensing and shielding gamma radiations. The results show better and stable response of ZnTe alloys for various photon interaction properties over the wide energy range, with an additional benefit of ease in fabrication due to lower melting points of Zn and Te. Mass attenuation coefficient values show strong dependence on photon energy as well as composition. Effective atomic number has maximum value for $Zn_5Te_{95}$ and lowest for $Zn_{50}Te_{50}$ in the entire energy region. The alloy sample with maximum $Z_{eff}$ shows minimal value of $N_e$ and vice versa. Mean free path follows inverse trend as observed for mass attenuation coefficient. The exposure and energy absorption buildup factors depend upon photon energy, penetration thickness and composition (effective atomic number) of $Zn_xTe_{100-x}$ alloys. It finds its application for sensing and shielding from highly energetic and highly penetrating photons at sites where radioactive materials were used and visibility of material is not a big constraint. Further, energy down conversion property of ZnTe alloys with subsequent emission in green band suggests its potential use in sensing gamma photons.

• 한국응급구조학회지
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• 제24권3호
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• pp.147-154
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• 2020

Purpose: The purpose of the study was to investigate traumatic urethral injury in a 63-year-old patient with hematuria. Methods: A hematuria patient was transferred by paramedics. At the time of the visit, the patient's blood pressure (151/91mmHg), pulse rate (86/min), body temperature (37.1℃), and other vital signs were stable. Their KTAS (Korean Triage and Acuity Scale) was Level 4. The patient had no damage to the injured area, but a large contrast defect was observed between the prostate urethra and the bladder in urethral angiography performed due to persistent hematuria and pain in the injured area. Results: Following radiological evaluation of a suspected liposarcoma or neuroma mass of the prostate urethra, the mass was removed through urethral tumor resection. The result of histologic evaluation provided a diagnosis of highly differentiated invasive urethral cell carcinoma that had invaded the muscle layer. The patient was given additional treatment for urethral cancer but was rejected and is currently being followed. Conclusion: The prognosis for urinary tract cancer has distinct differences for patients with lymph node metastasis and tumor characteristics. The presence or absence of urethral cancer should be confirmed through angiography, CT, MRI, and cystoscopy.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3962-3973
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• 2022

Several critical heat flux (CHF) correlations including the look-up table in the MARS code have been assessed for the prediction of CHF in a downward-flow narrow rectangular channel. For the assessment, we built an experiment database that covers pressures between 1.01 and 39.0 bar, gap sizes between 1.09 and 6.53 mm, mass fluxes up to 25,772 kg/m²s, and under one-sided and two-sided heating conditions. The results of the assessment showed that the Kaminaga correlation has the best overall prediction compared to others. However, because the correlation uses global variables, such as inlet and outlet subcooling and total heat transfer area, it is difficult to use in a system code. A new CHF correlation is then proposed by replacing the global variables in the Kaminaga correlation with local ones and adding correction factors to consider the effect of gap size, mass flux, and the number of heating walls. Additional correction factor is added to consider the effect of inlet subcooling. It is shown that the new one is better than the Kaminaga correlation and it is easy to implement to any system code.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3918-3929
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• 2021

In this study, we experimentally investigate of a two-phase natural circulation loop that functions as a passive containment cooling system (PCCS). The experimental apparatus comprises two loops: a hot loop, for simulating containment under severe accidents, and a natural circulation loop, for simulating the PCCS. The experiment is conducted by controlling the pressure and inlet temperature of the hot loop in the range of 0.59-0.69 MPa (abs) and 119.6-158.8 ℃, respectively. The heat balance of the hot loop is established and compared with a natural circulation loop to assess the thermal reliability of the experimental apparatus, and an additional system is installed to measure the vapor mass flow rate. Furthermore, the thermal-hydraulic characteristics are considered in terms of a temperature, mass flow rate, heat transfer coefficient (HTC), etc. The flow rate of the natural circulation loop is induced primarily by flashing, and a distortion is observed in the local HTC because of the fully develop as well as subcooled boiling. As a result, we present the amount of heat capacity that the PCCS can passively remove according to the experimental conditions and compared the heat transfer performance using Chen's and Dittus-Boelter correlation.

• Smart Structures and Systems
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• 제29권3호
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• pp.457-473
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• 2022

A high-frequency vibration control method is proposed in this paper for Pumped Storage Power Plants (PSPPs) using Eddy Current Tuned Mass Damper (EC-TMD), based on which a new type of EC-TMD device is designed. The eddy current damper parameters are optimized by numerical simulation. On this basis, physical simulation model tests are conducted to compare and study the effect of structural performance with and without damping, different control strategies, and different arrangement positions of TMD. The test results show that EC-TMD can effectively reduce the control effect under high-frequency vibration of the plant structure, and after the additional damping device forms EC-TMD, the energy dissipation is further realized due to the intervention of eddy current damping, and the control effect is subsequently improved. The Multi-Tuned Mass Damper (MTMD) control strategy broadens the tuning band to improve the robustness of the system, and the vibration advantage is more obvious. Also, some suggestions are made for the placement of the dampers to promote their application.

• Advances in concrete construction
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• 제15권4호
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• pp.215-228
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• 2023

The vibrational behavior of nanoelements is critical in determining how a nanostructure behaves. However, combining vibrational analysis with stability analysis allows for a more comprehensive knowledge of a structure's behavior. As a result, the goal of this research is to characterize the behavior of nonlocal nanocyndrical beams with uniform and nonuniform cross sections. The nonuniformity of the beams is determined by three distinct section functions, namely linear, convex, and exponential functions, with the length and mass of the beams being identical. For completely clamped, fully pinned, and cantilever boundary conditions, Eringen's nonlocal theory is combined with the Timoshenko beam model. The extended differential quadrature technique was used to solve the governing equations in this research. In contrast to the other boundary conditions, the findings of this research reveal that the nonlocal impact has the opposite effect on the frequency of the uniform cantilever nanobeam. Furthermore, since the mass of the materials employed in these nanobeams is designed to remain the same, the findings may be utilized to help improve the frequency and buckling stress of a resonator without requiring additional material, which is a cost-effective benefit.

• 한국지하수토양환경학회지:지하수토양환경
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• 제29권2호
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• pp.1-10
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• 2024

With industrial development, the inevitable increase in both organic and inorganic waste necessitates the exploration of waste treatment and utilization methods. This study focuses on co-pyrolyzing lignin and red mud to generate metalbiochar, aiming to demonstrate their potential as effective adsorbents for water pollutant removal. Thermogravimetric analysis revealed mass loss of lignin below 660℃, with additional mass loss occurring (>660℃) due to the phase change of metals (i.e., Fe) in red mud. Characterization of the metal-biochar indicated porous structure embedded with zero-valent iron/magnetite and specific functional groups. The adsorption experiments with 2,4-dichlorophenol and Cd(II) revealed the removal efficiency of the two pollutants reached its maximum at the initial pH of 2.8. These findings suggest that copyrolysis of lignin and red mud can transform waste into valuable materials, serving as effective adsorbents for diverse water pollutants.