CFD and Experimental Study of Gas Flow Inside the Steel Pipe Fitted in Reciprocating Hydrogen Compression System

라흐만(Mohammad-Shiddiqur Rahman),이경환(Gyeong-Hwan Lee),이광성(Kwang-Sung Lee),정한식(Han-Shik Chung),정효민(Hyo-Min Jeong) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-

Renewability and pollutant free energy source makes hydrogen energy popular rapidly. Hydrogen gas pressure which is after passing through reciprocating compressor part has high pulsation wave form. A unit, snubber is used as compressor components to reduce the harmful pulsation waveform and to remove the impurities in the hydrogen gas. An experiment has been conducted to investigate the pulsation reduction performance of a steel pipe used in snubber system. The amplitude of pressure reduction were varied from 0.054 ~ 0.321 ㎪ for 10 hz to 60 hz motor speed. Compressor operation by motor with 10 to 60 hz were resulted in reduction of pressure pulsation from 16.415% to 35.151%. Pressure losses were varied from 0.001% ~ 0.759%, and pressure drop per centimeter of the steel pipe were varied from 0.0160 ~ 16.031 ㎩.

Surface treatment of silver-paste electrode by atmospheric-pressure plasma-jet

라흐만 셰이크 압둘,칸 세나와르 알리,양윤석,김우영 한국응용과학기술학회 2023 한국응용과학기술학회지 Vol.40 No.1

Silver paste is a valuable electrode material for electronic device applications because it is easy to handle with relatively low heat treatment. This study treated the electrode surface using an atmospheric-pressure plasma jet on the silver-paste electrode. This plasma jet was generated in an argon atmosphere using a high voltage of 5.5 to 6.5 kV with an operating frequency of 11.5 kHz. Plasma-jet may be more beneficial to the printing process by performing it at atmospheric pressure. The electrode surface becomes hydrophilic quickly and contact angle variation is observed on the electrode surface as a function of plasma treatment time, applied voltage, and gas flow rate. Also, there was no deviation in the contact angle after the plasma treatment in the large-area sample, that means a uniform result could be obtained regardless of the substrate size. The outcomes of this study are expected to be very useful in forming a stacked structure in the manufacture of large-area electronic devices and future applications.

Plazomicin—a New Aminoglycoside—for Treating Complicated Urinary Tract Infections

라흐만 모하마드 세이더,Gazi Mohammad Al Amin,Shah Mohammad Anwar,Mohammad Ferdaus Azam,Fatema Akhter,Mohammad Rabiul Islam,고영상 대한미생물학회 2023 Journal of Bacteriology and Virology Vol.53 No.1

Plazomicin belongs to a new class of semisynthetic aminoglycosides that suppress bacterial protein synthesis. The US Food and Drug Administration has approved this antibacterial drug for use in adult patients with complicated urinary tract infections (cUTIs), such as pyelonephritis. The worldwide emergence of multidrug- resistant (MDR) organisms has become a significant health issue. It is a promising alternative to carbapenems or β-lactam/β-lactamase inhibitors for treating cUTIs caused by MDR Enterobacterales. Plazomicin is primarily designed to overcome the common resistance mechanisms of pathogens. It has also demonstrated good in vitro efficacy against various resistant gram-negative pathogens. Plazomicin inhibits bacterial protein synthesis and exhibits rapid bactericidal efficacy against numerous extended-spectrum beta-lactamase (ESBL) producing, aminoglycoside- resistant, and carbapenem-resistant bacterial isolates. Similar to other amin- oglycosides, plazomicin inhibits bacterial protein synthesis by attaching to the 30S ribosomal subunit of bacteria. Plazomicin also demonstrated a favorable minimum inhibitory concentration value compared to other aminoglycosides such as gentamicin, amikacin, and tobramycin. The commonly observed adverse effects of plazomicin include headache, hypertension, nausea, diarrhea, vomiting, and hypotension. In this review, we discuss the likelihood of using plazomicin to treat bacterial infections, focusing on its chemistry, mode of action pharmacokinetics, indications for treatment, adverse reactions, and safety profile.

Sustainable Natural Textile Dyeing Using Chitosan and Its Derivatives

라흐만 엠디 모르쉐둘,조용균,오사랑,고준석 한국섬유공학회 2023 한국섬유공학회지 Vol.60 No.5

In recent years, natural dyes are gaining more attention as a sustainable and ecofriendly alternative to synthetic dyes. However, the use of toxic metal mordants make the natural dyeing process unsustainable. In order to make natural dyeing process truly sustainable, it is challenging to find alternative sources of mordant-like materials that are sustainable and ecofriendly. Chitosan, a natural resource, and a cost-effective cationic biopolymer could be a sustainable alternative to metal mordants. This paper provides an in-depth review of chitosan and its derivatives and discuss their potential role as a biomordant in natural dyeing of textiles. This review will help the academic readers to understand the basic mordanting mechanism of chitosan and its efficient application technique. Furthermore, the prospects and challenges of chitosan mordant in natural dyeing are also discussed.

Dispersion Behavior of Al₂O₃-H₂O Nanofluids with Dependence of Time

하피줘 라흐만(Hafizur Rehman),여철모(Chul-Mo Yeo),정현권(Hyun-Gweon Jeong),정효민(Hyomin Jeong),정한식(Hanshik Chung) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7

Nanofluids are kind of engineering material, with a new challenge for thermal sciences provided by nanotechnology. Nanofluids are being investigated for numerous applications, including cooling process, manufacturing process, chemical process pharmaceutical process and medical treatment process etc. Nanofluids are basically the suspension of solid nanoparticles with size typically 1- 100 ㎚ in base fluid. In current research, Alumina size less than 50㎚ has been used. The tested fluids have been prepared by dispersing Al₂O₃ into DI water at three different conditions by using 1%wt, 3%wt. and 5%wt. concentrations of alumina without using any surfactant. To ensure the best dispersion and stability of alumina nanoparticles in DI water ultrasonicator with 47㎑ frequency and dispersion time until 3hrs has been used. Particles sedimentation test of these different condition nanofluid samples has been critically observed until 30days. As per result, after 30 days approximately 28% particles sedimentation of Al₂O₃ nanofluid with ultrasonicator dispersion time 3hrs recorded in 3%wt and 21% recorded in 5%wt concentration. Also particle size system (PSS) result of 3%wt and 5%wt concentration of Al₂O₃ nanofluid with dispersion time 3hrs achieved as 46nm and 60nm respectively. The present research will be helpful to investigate the dispersion behavior of water-based Al₂O₃ nanofluid with changing rate of time and also helpful to select different conditions for making Al₂O₃ nanofluid without using surfactants or any other surface additives to use further in heat transfer processes.

هل كان أبو العلاء المعري نحالاً؟ دراسة في النقد وتاريخ الأدب

압둘 라흐만 발로 한국아랍어아랍문학회 2023 아랍어와 아랍문학 Vol.27 No.3

النحل هو نسبة الشعر لغير قائله لغرض معين في نفس "الناحل"، وقد يعمد بعض الناحلين إلى خلق شخصية معينة ينسبها إلى "ملة" أو "نحلة" أو "قبيلة" ما ليحقق هدفا معينا. وهي ظاهرة معروفة في الأدب العربي القديم. درسها مؤرخو الأدب منذ أيام ابن سلام الجمحي وازدادت وتيرتها في ق20. ومن أكثر الشعراء إشادة بالصدق وشهرةً به وبالزهد في المديح والرياء أبو العلاء المعري 368-449هـ مما يجعله بعيدا -لأول وهلة- عن شُبهة "النحل" لأن النَّحل نوع من الاختلاق المُخل بالعدالة وهو أدنى من مجرَّد الكذب درَكةً لأن فيه إنتاج فعل إضافي فيدخل بذلك في التزوير والبهتان. وهذا الفعل لا يُمكن بسهولة تصديق صدوره عن مبدئيٍّ اشتهر بالرحمة والرأفة واللطف. يحاول هذا البحث أن يُبحر ضد التيار فيتتبع المواضع التي من الممكن، بل من المحتمل جدا أن يكون المعري قد نحَل فيها بعض الشخصيات التاريخية أشعاراً لم يقولوها هم، بل قوّلهم إياها المعرّي نفسه دون أن يُصرِّح لأحد بذلك. وقد توصل البحث إلى "ترجيح" أو "إثبات" صدور مثل هذا الفعل من الشاعر الكبير وحاول حدس الدوافع والزمن لذلك. اعتمد البحث كتب المعري بالأساس ثم الدراسات الجمة عنه منذ عصره ثم تاريخ ذات الصلة. اتبعنا المنهج التاريخي التتبعي واستفدنا من مدونة إلكترونية كبيرة لكتب الأدب العربي Abū Al-ʿAlāʿ-Maʿarrī (368-449 AH, 1057 CE), celebrated for truthfulness and asceticism, undergoes scrutiny in this research for a potential act of fabricating poems. Despite a reputation for self-restraint, the study delves into the possibility that he crafted verses attributed to historical or fictional figures without explicit disclosure. This includes constructing verses for fictional characters, forming a persona, and attributing verses to historical figures, raising questions about his engagement in fabricating poems. The research leans toward suggesting or proving such acts, speculating on motives, and timing during his youth, maturity, or old age. Drawing on Abū Al-ʿAlāʿ-Maʿarrī's writings, historical context, and a digital corpus of Arabic literature, the study employs a historical and chronological approach to navigate this complex investigation.

FEATURES OF PRESSURES IN THE PIPE FITTED BETWEEN TWO SNUBBERS IN HYDROGEN COMPRESSING SYSTEM

Mohammad Rahman(라흐만),Kyeonghwan Lee(이경환),Suprianto Wobowo(위보워),Jusik Woo(우주식),Hanshik Chung(정효민),i Hk Chung(정한식) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

Compressing system is one of the most important processes in hydrogen gas handling: production, storage, distribution until using. High pulsation waveforms produced during hydrogen compression can be reduced by employing snubber in the system. There are some pipes to flow hydrogen between two snubbers. An experiment has been conducted to investigate the features of pressure in the pipe placed between snubbers in reciprocating compression system. In measuring amplitude FFT was done and pressure RMS values at input and output of one the pipe using data for 10, 20, 30, 50 and 60 ㎐ motor frequency of compressor operation. The pressure pulsation reductions are varied from 16.415~35.151% and corresponding pressure losses 0.007~0.759%.

이미지를 사용한 가상의상착용을 위한 개선된 알고리즘

미나르 마드올 라흐만(Matiur Rahman Minar),따이 트안 투안(Thai Thanh Tuan),안희준(Heejune Ahn) 한국산업정보학회 2020 한국산업정보학회논문지 Vol.25 No.2

최근 이미지를 사용한 가상착용기술 (Virtual try-on: VTON)에 대한 일련의 연구들이 발표되었다. 이에 의상과 사용자 이미지를 사용한 대표적 방식 (SCMM 기반의 비-딥러닝 방식, 딥러닝 기반 VITON 과 CP-VITON)에 대해 인물의 자세 및 체형, 의상의 가려짐 정도, 의상의 특성 등에 따라 분석한 연구가 보고되었다. 본 논문에서는 이중 가장 좋은 성능을 보이는 CP-VTON의 문제점을 살펴보고 이에 따른 해결책을 제시한다. 구체적으로 대상인물의 분할 표현 문제, 교체 대상이 아닌 영역이 유지되지 못하는 문제, 합성 마스크 생성네트워크의 학습에 사용되는 비용함수 문제, 합성 네트워크의 마스크 문제를 지적하고 이를 개선하는 알고리즘을 제안하였다. 그 결과 SSIM 등에서 5%내외의 주관적으로는 상당한 개선을 보였다. Recently, a series of studies on virtual try-on (VTON) using images have been published. A comparison study analyzed representative methods, SCMM-based non-deep learning method, deep learning based VITON and CP-VITON, using costumes and user images according to the posture and body type of the person, the degree of occlusion of the clothes, and the characteristics of the clothes. In this paper, we tackle the problems observed in the best performing CP-VTON. The issues tackled are the problem of segmentation of the subject, pixel generation of un-intended area, missing warped cloth mask and the cost function used in the learning, and limited the algorithm to improve it. The results show some improvement in SSIM, and significantly in subjective evaluation.

Pressure Features in 3_arm steel pipe in Reciprocating Hydrogen Compression System

M. Sq. Rahaman(라흐만),G. H. Lee(이경환),S. Wibowo(위보워),J. S. Woo(우주식),H. M Jeong(정효민),H. S. Chung(정한식) 한국마린엔지니어링학회 2009 한국마린엔지니어링학회 학술대회 논문집 Vol.2009 No.-

Compressing system is essential parts of hydrogen economy. High pulsation waveforms produced during hydrogen compression can be reduced by employing snubber in the system. There aresome pipes to flow hydrogen between snubbers. An experiment has been conducted to investigate the features of pressure in the pipe placed between snubbers in reciprocating compression system. The 32.6970 ~ 53.1210% pressure pulsation reductions are found with pressure losses 0.1092 ~ 1.4413% by experiment and detail of pressure are obtained by CFD analysis.

Influence of Pressure Variation Inside the Snubber on Reciprocating Hydrogen Compression System

M. Sq. Rahman(라흐만),G. H. Lee(이경환),J. S. Woo(우주식),T. S. Utomo(토니),H. S. Chung(정한식),H. M. Jeong(정효민) 한국동력기계공학회 2009 동력시스템공학회지 Vol.13 No.2