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금속폼 DPF의 Clean Filter 성능에 관한 연구
Khai Nguyen(Khai Nguyen),권오채(Oh Chae Kwon),성낙원(Nakwon Sung),조규백(Gyubaek Cho),오권오(Kwonoh Oh),이의성(Euisung Lee) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
Pressure drops in metallic foam diesel particulate filters (DPFs) were experimentally and computationally studied in order to understand effects of various design parameters on the fundamental clean filter performance. Axial type filters of Nickel-based super alloy (Inconel) foam, which is a new valuable medium for DPFs due to lower cost, higher temperature corrosion, light-weight. ductility and design flexibility compared to conventional honeycomb wall-flow monoliths, were considered for volume flow rates of 500 to 3000 1/min, filter thickness of 25 to 50 ㎜, pore size of 450 to 600 ㎛, and inlet cone angles of 0 to 50. Predicted and measured pressure drops for the various conditions agreed well each other, indicating that the present modeling using a 3-dimensional CFD code combined with a porous media model can provide reliable predictions.
Leaking Thoracic Aorta Aneurysm Causing Pleural Effusion: A Potential Disaster
( Khai Lip Ng ),( Hema Yamini Devi A ),( P Yamarmuty ),( Kunji Kannan A/l Sivaraman Kannan ) 대한결핵 및 호흡기학회 2021 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.129 No.-
Introduction Thoracentesis is the first step in diagnosing a unilateral pleural effusion. Although malignancy remains the most common cause of a hemoserous effusion, we must be aware of other causes such as uremia, pulmonary infarction, post cardiac injury syndrome etc. We report a rare case of leaking thoracic aortic aneurysm masquerading as a unilateral hemoserous pleural effusion. Case Report A 79-year-old female with underlying hypertension, dyslipidemia and chronic kidney disease presented with a 2-weeks history of cough and dyspnea. She also reported a weight loss of 5 kilograms in 1 month. A Chest X-Ray (CXR) on presentation revealed a large left pleural effusion. She has exudative effusion based on Light's criteria. pleural fluid culture and cytology was negative. As her main differential diagnosis was malignancy, she was subjected to pleuroscopy to obtain a tissue diagnosis. During pleuroscopy, 1 liter of hemoserous fluid was drained. Apart from thickened parietal pleura, a large cystic mass was seen adhered to the parietal pleura posteriorly. Biopsies were taken from the parietal pleura and decision was made not to biopsy or aspirate the cystic mass during pleuroscopy. Computed tomography of the thorax done few weeks later showed a large thoracic aorta aneurysm with multiple penetrating atherosclerotic ulcers and mural thrombus. There was no pleural or lung mass detected. Patient was counseled for surgical repair but opted for conservative management. Discussion and conclusion Leaking thoracic aneurysm is an uncommon but potentially dangerous cause of hemoserous pleural effusion. A blind thoracentesis or biopsy of the cystic mass during pleuroscopy would have led to rupture of the aneurysm. Depending on the clinical context, it is safer to obtain a CT thorax prior to pleuroscopy when dealing with undiagnosed pleural effusion.
Khai, Tran Van,Prachuporn, Maneeratanasarn,Shim, Kwang-Bo The Korea Association of Crystal Growth 2012 韓國結晶成長學會誌 Vol.22 No.2
Single and few-layer graphene nanosheets (GNs) have successfully synthesized by a modified Hummer's method followed by chemical reduction of exfoliated graphene oxide (GO) in the presence of hydrazine monohydrate. GO and GNs were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffractions (XRD), Raman spectroscopy, Transmission electron microscopy (TEM), Atomic force microscopy (AFM), Optical microscopy (OM) and by electrical conductivity measurements. The result showed that electrical conductivity of GNs was significantly improved, from $4.2{\times}10^{-4}$ S/m for GO to 12 S/m for GNs, possibly due to the removal of oxygen-containing functional group during chemical reduction. In addition, the $NO_2$ gas sensing characteristics of GNs are also discussed.
Synthesis of SnO<sub>2</sub> nanowires on one-dimensional carbonization cotton fabric
Khai, Tran Van,Shim, Kwang-Bo The Korea Association of Crystal Growth 2012 韓國結晶成長學會誌 Vol.22 No.1
Tin-oxide ($SnO_2$) nanowires have been synthesized on one-dimensional (1D) carbonization cotton fabric using chemical vapour deposition method. One-dimensional (1D) carbonization cotton fabric has been synthesized from cotton fabric using annealing process in nitrogen gas at $1000^{\circ}C$. The $SnO_2$ nanowires are single-crystalline rutile structures with 20 nm in diameter and 10 ${\mu}m$ in length. Scanning electron microscopy (SEM), x-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy and photoluminescence (PL) spectroscopy were utilized to characterize the as-synthesized products.
Khai, Lam Duc,Tien, Tran Van The Korea Institute of Information and Commucation 2020 Journal of information and communication convergen Vol.18 No.1
This paper proposes a fast-processing and low-cost hardware multiple input multiple output (MIMO) channel emulator. The channel emulator is an important component of hardware-based simulation systems. The novelty of this work is the use of sharing and pipelining functions to reduce hardware resource utilization while maintaining a high sample rate. In our proposed emulator, the samples are created sequentially and interpolated to ensure the sample rate is equal to the base band rate. The proposed 4 × 4 MIMO requires low-cost hardware resource so that it can be implemented on a single field-programmable gate array (FPGA) chip. An implementation on Xilinx Virtex-7 VX980T was found to occupy 10.47% of the available configurable slice registers and 12.58% of the FPGA's slice lookup tables. The maximum frequency of the proposed emulator is 758.064 MHz, so up to 560 different paths can be processed simultaneously to generate 560 × 758 million × 2 × 32 bit complex-valued fading samples per second.
Khai Ngoc Nguyen,김윤아,Sawarot Maibunkaew,박지수,Mien Thi Nguyen,오두병,권오석 한국생물공학회 2021 Biotechnology and Bioprocess Engineering Vol.26 No.2
1-Deoxynojirimycin (DNJ) is a potent inhibitor of α-glucosidase having antidiabetic and antiviral activities. In the present study, DNJ production by Bacillus subtilis subsp. inaquosorum KCTC 13429 (B. subtilis IWT) was confirmed and a mutant B. subtilis I.247 strain showing 52% increased DNJ production than wild-type strain after cultivation in 5% defatted soybean meal (DFS) for five days was isolated by UV random mutagenesis. The optimum culture conditions to maximize DNJ production by B. subtilis I.247 was predicted using response surface methodology to cultivate in medium containing 3.4% sorbitol and 2.4% yeast extract as carbon and nitrogen sources, respectively, at a temperature of 32ºC. Under these conditions B. subtilis I.247 was able to produce 359 mg/L after five days of cultivation. Furthermore, when the B. subtilis I.247 transformant harboring a vector expressing a gabT1-yktc1- gutB1 DNJ biosynthetic gene cluster was cultured under the optimized condition, DNJ production was increased to 773 mg/L, representing a level 6.2-fold higher than that of the wild-type strain cultured in 5% DFS for five days.
Low-Complexity Block Diagonalization Precoder Hardware Implementation for MU-MIMO 4×4
Khai, Lam Duc The Korea Institute of Information and Commucation 2019 Journal of information and communication convergen Vol.17 No.1
In this paper, we present the block diagonalization (BD) algorithm for the multiple-user multiple input multiple output (MU-MIMO) $4{\times}4$ system using specific purpose processor (SPP) hardware. Our objective is to improve the single-user MIMO (SU-MIMO) system using the MU-MIMO technology, which is remarkably fast and allows more users to connect simultaneously. To that end, our MU-MIMO precoder uses the BD algorithm to ensure signal integrity when connecting multiple users; but remains accurate and stable. However, a precoder that uses the BD algorithm is computationally complex; therefore, we use an SPP with special functions designed to compute the BD algorithm. The implementation test results show that our SPP computes the BD algorithm faster than the software solution.
High-quality ZnO nanowire arrays directly synthesized from Zn vapor deposition without catalyst
Khai, Tran Van,Prachuporn, Maneeratanasarn,Choi, Bong-Geun,Kim, Hyoun-Woo,So, Dae-Sup,Lee, Joon-Woo,Park, No-Hyung,Huh, Hoon,Tung, Ngo Trinh,Ham, Heon,Shim, Kwang-Bo The Korea Association of Crystal Growth 2011 韓國結晶成長學會誌 Vol.21 No.4
Vertically well-aligned ZnO nanowire (NW) arrays were synthesized directly on GaN/sapphire and Si substrate from Zn vapor deposition without catalysts. Experimental results showed that the number density, diameter, crystallinity and degree of the alignment of ZnO NWs depended strongly on both the substrate position and kind of the substrates used for the growth. The photoluminescence (PL) characteristics of the grown ZnO NW arrays exhibit a strong and sharp ultraviolet (UV) emission at 379 nm and a broad weak emission in the visible range, indicating that the obtained ZnO NWs have a high crystal quality with excellent optical properties. The as-grown ZnO NWs were characterized by using scanning electron microscopy (SEM), high resolution transmission electronic microscopy (HR-TEM), and X-ray diffraction (XRD).
Khai, Tran Van,Sub Kwak, Dong,Jung Kwon, Yong,Bo Shim, Kwang,Woo Kim, Hyoun WILEY‐VCH Verlag 2013 Crystal research and technology Vol.48 No.2
<P><B>Abstract</B></P><P>Vertically well‐aligned zinc oxide nanowires (NWs) with high density were successfully synthesized on Si, sapphire and GaN/sapphire substrates by thermal evaporation of zinc powders without catalysts or additives. The growth behavior of ZnO NWs was strongly dependent on the substrate materials. The effects of the substrate position on the structures and properties of ZnO NWs were primarily discussed. The morphology and crystallinity of the resultant NWs were studied by scanning electron microscope, transmission electronic microscope and X‐ray diffraction. The photoluminescence (PL) characteristics of the ZnO NWs on the different substrates were studied. The results showed that the as‐grown ZnO NWs exhibit a sharp and strong ultraviolet emission at 3.27 eV and a very weak green emission at around 2.48 eV, indicating that the a‐synthesized NWs have excellent PL properties with good crystalline quality and can be an ideal candidate for making luminescent devices. By comparison of PL spectra, we revealed that the green‐to‐UV emission intensity ratios were considerably dependent on the substrate materials, which was explained by the difference in the structural morphology of the produced nanowires.</P>
( Khai Lip Ng ),( Nai-chien Huan ),( Ummi Nadira Daut ),( Sanusi Zulkifli ),( Noorul Afidza Muhammad ),( Mona Zaria Nasaruddin ),( Jamalul Azizi Abdul Rahaman ) 대한결핵 및 호흡기학회 2020 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.128 No.-
Introduction Pulmonary murcomycosis is an uncommon fungal infection that typically affects immunocompromised patients. Rarely, it can affect immunocompetent patients, presenting as endobronchial lesions mimicking lung malignancy. Herein we report a patient with pulmonary murcomycosis with favourable treatment outcome via a multimodality approach utilizing antifungal agents and endobronchial intervention. Case Report A 31-year-old lady with no prior medical condition presented with a 3-month history of cough associated with weight loss of more than 5 kilograms and occasional haemoptysis (blood streaks in sputum). Chest radiograph and computed tomography demonstrated mediastinal lymphadenopathy and left hilar mass with infiltration into left main bronchus. Flexible bronchoscopy revealed presence of an endobronchial mass occluding the left main bronchus. Her tuberculosis workup, diabetes screening and retroviral tests were all negative but she was found to be pregnant at 6weeks. She was subsequently scheduled for rigid bronchoscopy and debulking of endobronchial mass. To our surprise, histopathological examination revealed inflamed tissue with presence of fungal organism which was subsequently confirmed to be Rhizopus microspores via fungal polymerase-chain-reaction. With the diagnosis in mind, she was promptly treated with intravenous amphotericin-B for a total of 2 weeks in duration, which was accompanied by clinical improvements and total radiological resolution. Amphotericin-B was chosen instead of other anti-fungal agents after taking into account of her pregnancy status. Conclusion Murcomycosis should be considered among young patients who presented with endobronchial lesion. Rapidly progressing nature of the disease warrants early diagnosis and treatment to ensure a better clinical outcome.