Growth simulation for 3D surface and through-thickness cracks using SGBEM-FEM alternating method

박재학,Gennadiy P. Nikishkov 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.9

An SGBEM-FEM alternating method had been proposed by Nikishkov, Park and Atluri for the analysis of three-dimensional planar and non-planar cracks and their growth. The proposed method is an effective method for fatigue or stress corrosion crack growth simulation. During crack growth simulation, however, an oscillation phenomenon is observed in crack advance or stress intensity factor distribution. If oscillating amplitude in SIF or crack advance does not decrease during next increment steps, the crack growth simulation fails. In this paper several methods are examined to remove the oscillation phenomenon. As a result, it is found that smoothing in stress intensity factor distribution or in crack front geometry can remove or weaken the oscillation phenomenon. Using the smoothing techniques,stress corrosion crack growth simulation is performed for a semi-elliptical surface crack and a through-thickness crack embedded in a plate. Crack front shape and stress intensity factor distribution are obtained after each increment during the crack growth. And the depth and length of a crack are obtained as a function of time. It is noted that the SGBEM-FEM alternating method is a very effective method for SCC growth simulation for a surface crack and a through-thickness crack.

SGBEM-FEM 교호법을 이용한 관통균열의 해석

박재학(Jai Hak Park),Gennadiy P. Nikishkov 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

A SGBEM-FEM alternating method is extended to analyze a through-thickness crack problem. The effect of shape of boundary element mesh on the accuracy of stress intensity factor is examined. It is noted that the fictitious portion of the boundary element mesh, which is located outside the body, plays an important role in the method. Also the effect of the boundary condition imposed on the edge of boundary element mesh is examined. In order to check the accuracy of the method, we considered a sample problem of a through-thickness crack with unequal surface lengths. The obtained stress intensity factors are compared with the known solutions or the results obtained from finite element method. Using the proposed method stress corrosion crack growth simulation is performed for a through-thickness crack with unequal surface lengths.

Photo- and Cathodoluminescence Studies of ZnO-Filled Opal Nanocomposites

Saidislam S. Kurbanov,Gennadiy N. Panin,김태환,강태원,박영신 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.3

The transmittance, reflectance, photo and cathodoluminescence spectra of a ZnO-filled opal nanocomposite, as well as the spectra of ZnO nanoparticles deposited on sapphire and glass substrates, were investigated. The ZnO nanoparticles have basically a (002) orientation and a regular cone form. They exhibit a strong exciton emission at 380 nm and relatively low green emission at 565 nm. In the ZnO-filled opal nanocomposite a ``red shift'' of the photonic band gap position in comparison with the bare artificial opal and its effect on the photoluminescence spectra are observed. Quenching of the excitonic emission of the ZnO nanoparticles grown in the opal voids is found and it is assigned to an energy transfer from the ZnO nanoparticles to opal matrix defect centers.

The Tartar (Mamiya) Strait Currents

Ponomarev, Vladimir I.,Yurasov, Gennadiy I. 한국해안해양공학회 1994 한국해안해양공학회 논문집 Vol.6 No.4

관측치와 모형 계산결과를 이용하여 Tartar 해협에서의 해류를 흐름 규모별로 분석하였으며, 조석현상과 일반적인 순환특성에 주안점을 두었다. 최대조류의 발생지점은 안정된 경계 흐름지역내에 위치함을 할 수 있었다. 다양한 기상조건 하에서의 흐름의 안정성과 소역에서의 에너지 집중은 바닥이 거친 지역에서 발생하는 조류의 비선형 효과로서 설명될 수 있다. The Tartar Strait currents of different scales are analysed using results of observations and modeling. The paper focuses on tidal phenomena and general circulation features. It is shown that the areas of maximal tidal currents are located in the regions of stable boundary streams. The stability of the streams under different meteorological conditions and energy concentration in the small areas may be explained by non-linear effects of tide over rough bottom topography.

Hybrid Adsorbent Based on Zeolite NaX Modified with Hyperbranched Polyester Poly(N-benzoylthiocarbamate)

Aleksei Maksimov,Alina Vagapova,Marianna Kutyreva,Gennadiy Kutyrev 한국고분자학회 2022 Macromolecular Research Vol.30 No.1

A new hybrid adsorbent has been synthesized by covalent linking of activated zeolite with hyperbranched polyester containing 8 terminal N-benzoylthiocarbamate groups. The structure of the polymer ligand was defined by IR, 1H and 13C NMR spectroscopy. The complexing properties of the adsorbent have been studied using the example of complexes with Cu(II) and Co(II) ions. It was proved by IR spectroscopy that N-benzoylthiocarbamate and toluylenecarbamate groups participate in complexation with metal ions. According to electron microscopy and porometry data, the average particle diameter of the adsorbent is 34.56 μm and the mesopore diameter is 4.19 nm. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) have shown that the hybrid adsorbent is thermally stable up to 150℃. The sorption capacities of the adsorbent for Cu(II) and Co(II) ions are 31.92 and 17.7 g/kg. It was shown that the desorption process of metal ions from the complexes occurs in an acidic medium at pH 4 with the regeneration of the original adsorbent.

Poster Session : PS 0024 ; Cardiology : Plasma Levels of Matrix Metalloproteinase 9 and Tissue Inhibitor of Matrix Metalloproteinases Type 1 in Aortic Valve Calcifi cation

( Elena Shcheglova ),( Olga Boeva ),( Zarema Chotchaeva ),( Gennadiy Khait ),( Alexander Yagoda ),( Madina Baikulova ),( Asiyat Laipanova ) 대한내과학회 2014 대한내과학회 추계학술대회 Vol.2014 No.1

Background: The purpose of the study was to investigate the plasma levels of matrix metalloproteinase 9 (MMP9) and tissue inhibitor of matrix metalloproteinases (TIMP1) in patients with calcifi cation of aortic valve (AV). Methods: Objects were 70 patients with AV calcifi cation (AVC); median age 72,5±7,5; 48,5% - males. 32,4% demonstrated no signs of calcifi c aortic stenosis (CAS), 44,1% had mild signs of that, 7,4% - moderate and another 16,2% had severe CAS. The control group included 36 patients with intact AVs comparable with the main group on their clinical and anamnestic data. Serum levels of MMP 9 and TIMP 1 were detected by ELISA. Statistical analysis was performed using IBM SPSS Statistics 21 for Windows (IBM SPSS Inc., USA). Results: The serum levels of MMP9 in patients with AVC (16,7 (14,1-19,0) μg/l) were not higher than in controls (17,1 (14,4-19,3) μg/l, р>0,05). The TIMP1 levels in the main group (257,5 (151.5-325.9) μg/l) occurred to be significantly higher than in controls (129,7 (86,2-229,0) μg/l, p<0,05). The MMP9/TIMP1 ratio also differed significantly: 0,069 (0,047-0,1) in AVC vs. 0,14 (0,06-0,2) in controls, р<0,01. The patients with AVC were divided into two subgroups according to the degree of aortic stenosis. Those who had moderate and severe CAS demonstrated higher TIMP1 levels (304,1 (215,0-413,1) μg/l vs. 249,9 (144,4-305,5) μg/l, р<0,05) than patients without stenosis or mild CAS. MMP9 and MMP9/TIMP1 levels showed no similar dependence. Conclusions: There has been an association detected between TIMP1 levels and the presence AVC as well as the severity of CAS. This might be a sign of TIMP1 role in the pathogenesis of the disease. No association has been found between the MMP9 levels, AVC and CAS.

Modeling of Hydrodynamic Processes at a Large Leak of Water into Sodium in the Fast Reactor Coolant Circuit

Sergey Perevoznikov,Yuriy Shvetsov,Aleksey Kamayev,Ilia Pakhomov,Viacheslav Borisov,Gennadiy Pazin,Oleg Mirzeabasov,Olga Korzun 한국원자력학회 2016 Nuclear Engineering and Technology Vol.48 No.5

In this paper, we describe a physicomathematical model of the processes that occur in a sodium circuit with a variable flow cross-section in the case of a water leak into sodium. The application area for this technique includes the possibility of analyzing consequences of this leak as applied to sodiumewater steam generators in fast neutron reactors. Hydrodynamic processes that occur in sodium circuits in the event of a water leak are described within the framework of a one-dimensional thermally nonequilibrium threecomponent gaseliquid flow model (sodiumehydrogenesodium hydroxide). Consideration is given to the results of a mathematical modeling of experiments involving steam injection into the sodium loop of a circulation test facility. That was done by means of the computer code in which the proposed model had been implemented.

Azoospermic men with isolated elevation of follicle-stimulating hormone represent a specific subpopulation of patients with poor reproductive outcomes

Gamidov, Safar,Shatylko, Taras,Popova, Alina,Gasanov, Natig,Sukhikh, Gennadiy The Korean Society for Reproductive Medicine 2022 Clinical and Experimental Reproductive Medicine Vol.49 No.1

Objective: This study aimed to describe a distinct subpopulation of azoospermic patients with isolated elevation of follicle-stimulating hormone (iFSH) and poor outcomes of microdissection testicular sperm extraction (microTESE). Methods: A retrospective analysis of microTESE outcomes was conducted among 565 patients with non-obstructive azoospermia (NOA). Testicular pathology was assessed by the dominant histological pattern and Bergmann-Kliesch score (BKS). Descriptive statistics were presented for the iFSH subgroup. Inhibin B levels, the sperm retrieval rate (SRR), and BKS were compared in iFSH patients and other NOA patients. Results: The overall SRR was 33.3% per microTESE attempt. The median BKS was 0.6 (interquartile range, 0-2). Of all NOA patients, 132 had iFSH, and microTESE was successful only in 11 of those cases, with an SRR of 8.3%, while the total SRR in other NOA patients was 38.1% (p<0.001). iFSH had a sensitivity of 32.1% (95% confidence interval [CI], 27.4%-36.8%) and specificity of 94.1% (95% CI, 90.8-97.5%) as a predictor of negative microTESE outcomes. Conclusion: Patients with iFSH may harbor a distinct testicular phenotype with total loss of the germ cell population and poor outcomes of surgical sperm retrieval.

위성 통신용 다대역 안테나

정치현(Chi-Hyun Cheong),정혜미(Hye-Mi Jeong),김건우(Kun-Woo Kim),배기형(Ki-Hyoung Bae),태현식(Hyun-Sik Tae),엡츄시킨겐나디(Evtyushkin Gennadiy) 한국항공우주학회 2010 韓國航空宇宙學會誌 Vol.38 No.12

본 논문에서 소개하는 위성 통신 안테나는 대용량 데이터 전송을 위한 위성 송수신 시스템에 응용되어 추가적인 급전부 교체나 다른 기구 형상 변경 없이 X, Ku와 Ka 3중 대역의 전파 신호를 통시에 송수신할 수 있다. 설계된 안테나는 오프셋 파라볼라 안테나 형태로 2중 대역(X/Ka 대역) 급전혼, 단일대역(Ku 대역) 급전혼, 주파수 선택막(FSS : frequency selective surface) 특성을 갖는 부반사판 및 파라볼라 주반사판으로 구성되어 있다. 주반사판의 초점에는 2중 대역 급전혼이 위치하며, FSS 부반사판으로 이미지 초점을 만들어 단일 대역 급전혼이 설치되어 운용된다. 본 안테나는 전기적 특성이 국내 위성 환경에 부합되도록 3차원 EM 시뮬레이터를 이용하여 설계하였고, 측정결과 X/Ku/Ka 대역에서 안테나 이득이 각각 31.6 dBi, 36.8 dBi, 40.8 dBi 이상, 교차편파는 각각 21.7 ㏈, 26.6 ㏈, 그리고 25.2 ㏈ 이상의 특성으로 목표 성능을 만족함을 확인하였다. The design is presented for a SATCOM antenna capable of simultaneous multi-band (X/Ku/Ka-Band) communications without replacement of feed horns or change of other parts in the application as a ground satellite terminal for large data transfer. The antenna is the offset configuration and consists of a dual-band(X/Ka-band) feed horn, a single-band(Ku-band) feed horn, a frequency selective surface(FSS) sub-reflector and a parabolic main-reflector. The antenna has a main reflector defining a prime focus and a frequency selective surface sub-reflector defining an image focus. A dual-band feed and a single-band feed are provided at each of the prime focus and image focus. The antenna is designed using 3D EM simulator and the gains measured in X/KulKa-band of the complete antenna assembly is more than 31.6dBi, 36.8dBi, 40.8dBi, and the cross polarization is 2l.7㏈, 26.6㏈, 25.2㏈, respectively.