대규모 자유도 문제의 구조해석을 위한 병렬 알고리즘

김민석,이지호,Kim, Min-Seok,Lee, Jee-Ho 한국전산구조공학회 2010 한국전산구조공학회논문집 Vol.23 No.5

본 논문에서는 대규모 자유도 시스템의 병렬처리를 위하여 2단계로 이루어진 영역분할법(Domain Decomposition Method) 기반의 병렬 알고리즘을 제안하였다. 분할된 영역의 내부 및 외부 경계를 상위영역문제로 정의하고 국부영역문제는 변위 경계조건이 모두 주어지는 분할영역에서의 Dirichlet 문제로 구성한다. 상위영역에서는 전체 상위영역에 대한 강성 행렬의 어셈블이 필요없는 반복법을 통하여 변위를 구하고, 이를 바탕으로 국부영역에서 Multi-Frontal Sparse Solver (MFSS)를 이용하여 변위를 계산한다. 상위영역문제의 연산에서 프로세서 간의 데이터 교환을 최소화하여 계산효율을 유지하며, 동시에 해석 가능한 자유도를 증대시키는 병렬 PCG(Preconditioned Conjugate Gradient)법 기반의 알고리즘을 개발하였다. 제안된 알고리즘을 적용하여 수치해석을 수행한 결과, 프로세서 수가 증가할수록 계산성능의 손실없이 해석 가능한 자유도가 비례하여 증가하는 선형 확장성을 관찰할 수 있었으며, 대규모 자유도 문제에 효과적으로 사용 가능함을 확인하였다. In this paper, an efficient two-level parallel domain decomposition algorithm is suggested to solve large-DOF structural problems. Each subdomain is composed of the coarse problem and local problem. In the coarse problem, displacements at coarse nodes are computed by the iterative method that does not need to assemble a stiffness matrix for the whole coarse problem. Then displacements at local nodes are computed by Multi-Frontal Sparse Solver. A parallel version of PCG(Preconditioned Conjugate Gradient Method) is developed to solve the coarse problem iteratively, which minimizes the data communication amount between processors to increase the possible problem DOF size while maintaining the computational efficiency. The test results show that the suggested algorithm provides scalability on computing performance and an efficient approach to solve large-DOF structural problems.

A new approach for blood pressure estimation based on phonocardiogram

Tahar Omari,Fethi Bereksi-Reguig 대한의용생체공학회 2019 Biomedical Engineering Letters (BMEL) Vol.9 No.3

Continuous and non-invasive measurement of blood pressure (BP) is of great importance particularly for patients in criticalstate. To achieve continuous and cuffl ess BP monitoring, pulse transit time (PTT) has been reported as a potential parameter. Nevertheless, this approach remains very sensitive, cumbersome and disagreeable in ambulatory measurement. This paperproposes a new approach to estimate blood pressure through PCG signal by exploring the correlation between PTT anddiastolic duration (S21). In this purpose, an artifi cial neural network was developed using as input data: (systolic duration,diastolic duration, heart rate, sex, height and weight). According to the NN decision, the mean blood pressure was measuredand consequently the systolic and the diastolic pressures were estimated. The proposed method is evaluated on 37 subjects. The obtained results are satisfactory, where, the error in the estimation of the systolic and the diastolic pressures comparedto the commercial blood pressure device was in the order of 6 .48 ± 4.48 mmHg and 3 .91 ± 2.58 mmHg, respectively, whichare very close to the AAMI standard, 5 ± 8 mmHg. This shows the feasibility of estimating of blood pressure using PCG.

NecroX-5 protects mitochondrial oxidative phosphorylation capacity and preserves PGC1α expression levels during hypoxia/reoxygenation injury

Vu, Thi Thu,Kim, Hyoung Kyu,Le, Thanh Long,Nyamaa, Bayalagmaa,Song, In-Sung,To, Thanh Thuy,Nguyen, Quang Huy,Marquez, Jubert,Kim, Soon Ha,Kim, Nari,Ko, Kyung Soo,Rhee, Byoung Doo,Han, Jin The Korean Society of Pharmacology 2016 The Korean Journal of Physiology & Pharmacology Vol.20 No.2

Although the antioxidant and cardioprotective effects of NecroX-5 on various in vitro and in vivo models have been demonstrated, the action of this compound on the mitochondrial oxidative phosphorylation system remains unclear. Here we verify the role of NecroX-5 in protecting mitochondrial oxidative phosphorylation capacity during hypoxia-reoxygenation (HR). Necrox-5 treatment ($10{\mu}M$) and non-treatment were employed on isolated rat hearts during hypoxia/reoxygenation treatment using an ex vivo Langendorff system. Proteomic analysis was performed using liquid chromatography-mass spectrometry (LC-MS) and non-labeling peptide count protein quantification. Real-time PCR, western blot, citrate synthases and mitochondrial complex activity assays were then performed to assess heart function. Treatment with NecroX-5 during hypoxia significantly preserved electron transport chain proteins involved in oxidative phosphorylation and metabolic functions. NecroX-5 also improved mitochondrial complex I, II, and V function. Additionally, markedly higher peroxisome proliferator-activated receptor-gamma coactivator-$1{\alpha}$ ($PGC1{\alpha}$) expression levels were observed in NecroX-5-treated rat hearts. These novel results provide convincing evidence for the role of NecroX-5 in protecting mitochondrial oxidative phosphorylation capacity and in preserving $PGC1{\alpha}$ during cardiac HR injuries.

The regulatory role of c-MYC on HDAC2 and PcG expression in human multipotent stem cells

Bhandari, Dilli Ram,Seo, Kwang-Won,Jung, Ji-Won,Kim, Hyung-Sik,Yang, Se-Ran,Kang, Kyung-Sun Blackwell Publishing Ltd 2011 JOURNAL OF CELLULAR AND MOLECULAR MEDICINE Vol.15 No.7

<P><B>Abstract</B></P><P>Myelocytomatosis oncogene (c-MYC) is a well-known nuclear oncoprotein having multiple functions in cell proliferation, apoptosis and cellular transformation. Chromosomal modification is also important to the differentiation and growth of stem cells. Histone deacethylase (HDAC) and polycomb group (PcG) family genes are well-known chromosomal modification genes. The aim of this study was to elucidate the role of c-MYC in the expression of chromosomal modification <I>via</I> the HDAC family genes in human mesenchymal stem cells (hMSCs). To achieve this goal, c-MYC expression was modified by gene knockdown and overexpression <I>via</I> lentivirus vector. Using the modified c-MYC expression, our study was focused on cell proliferation, differentiation and cell cycle. Furthermore, the relationship of c-MYC with HDAC2 and PcG genes was also examined. The cell proliferation and differentiation were checked and shown to be dramatically decreased in c-MYC knocked-down human umbilical cord blood-derived MSCs, whereas they were increased in c-MYC overexpressing cells. Similarly, RT-PCR and Western blotting results revealed that HDAC2 expression was decreased in c-MYC knocked-down and increased in c-MYC overexpressing hMSCs. Database indicates presence of c-MYC binding motif in HDAC2 promoter region, which was confirmed by chromatin immunoprecipitation assay. The influence of c-MYC and HDAC2 on PcG expression was confirmed. This might indicate the regulatory role of c-MYC over HDAC2 and PcG genes. c-MYCs’ regulatory role over HDAC2 was also confirmed in human adipose tissue-derived MSCs and bone-marrow derived MSCs. From this finding, it can be concluded that c-MYC plays a vital role in cell proliferation and differentiation <I>via</I> chromosomal modification.</P>

PERFORMANCE OF G-PCG METHOD FOR IMAGE DENOISING PROBLEMS

윤재헌 한국전산응용수학회 2017 Journal of applied mathematics & informatics Vol.35 No.3

We first provide the linear operator equations corresponding to the Tikhonov regularization image denoising problems with different regularization terms, and then we propose how to choose Kronecker product preconditioners which are required for accelerating the G『-PCG method. Next, we provide how to apply the G『-PCG method with Kronecker product preconditioner to the linear operator equations. Lastly, we provide numerical experiments for image denoisng problems to evaluate the effectiveness of the G『-PCG with Kronecker product preconditioner.

The pleiohomeotic gene is required for maintaining expression of genes functioning in ventral appendage formation in Drosophila melanogaster

Kim, S.N.,Jung, K.I.,Chung, H.M.,Kim, S.H.,Jeon, S.H. Academic Press 2008 Developmental biology Vol.319 No.1

Polycomb group (PcG) proteins are negative regulators that maintain the expression of homeotic genes and affect cell proliferation. Pleiohomeotic (Pho) is a unique PcG member with a DNA-binding zinc finger motif and was proposed to recruit other PcG proteins to form a complex. The pho null mutants exhibited several mutant phenotypes such as the transformation of antennae to mesothoracic legs. We examined the effects of pho on the identification of ventral appendages and proximo-distal axis formation during postembryogenesis. In the antennal disc of the pho mutant, Antennapedia (Antp), which is a selector gene in determining leg identity, was ectopically expressed. The homothorax (hth), dachshund (dac) and Distal-less (Dll) genes involved in proximo-distal axis formation were also abnormally expressed in both the antennal and leg discs of the pho mutant. The engrailed (en) gene, which affects the formation of the anterior-posterior axis, was also misexpressed in the anterior compartment of antennal and leg discs. These mutant phenotypes were enhanced in the mutant background of Posterior sex combs (Psc) and pleiohomeotic-like (phol), which are another PcG genes. These results suggest that pho functions in maintaining expression of genes involved in the formation of ventral appendages and the proximo-distal axis.

PERFORMANCE OF Gℓ-PCG METHOD FOR IMAGE DENOISING PROBLEMS

YUN, JAE HEON The Korean Society for Computational and Applied M 2017 Journal of applied mathematics & informatics Vol.35 No.3

We first provide the linear operator equations corresponding to the Tikhonov regularization image denoising problems with different regularization terms, and then we propose how to choose Kronecker product preconditioners which are required for accelerating the $G{\ell}$-PCG method. Next, we provide how to apply the $G{\ell}$-PCG method with Kronecker product preconditioner to the linear operator equations. Lastly, we provide numerical experiments for image denoisng problems to evaluate the effectiveness of the $G{\ell}$-PCG with Kronecker product preconditioner.

PARALLEL PERFORMANCE OF THE G`-PCG METHOD FOR IMAGE DEBLURRING PROBLEMS

윤재헌 한국전산응용수학회 2018 Journal of applied mathematics & informatics Vol.36 No.3

We rst provide how to apply the global preconditioned conju- gate gradient (G`-PCG) method with Kronecker product preconditioners to image deblurring problems with nearly separable point spread functions. We next provide a coarse-grained parallel image deblurring algorithm using the G`-PCG. Lastly, we provide numerical experiments for image deblur- ring problems to evaluate the eectiveness of the G`-PCG with Kronecker product preconditioner by comparing its performance with those of the G`-CG, CGLS and preconditioned CGLS (PCGLS) methods.

Effects of pleiohomeotic Mutation on the Drosophila Nervous System Development

Jeon, Sang-Hak 한국유전학회 2002 Genes & Genomics Vol.24 No.2

The homeotic genes are expressed in epidermis, central nervous system and visceral mesoderm during embryogenesis. Its expression is initiated by the segmentation genes and maintained by the cross-regulation of the homeotic genes, the positive regulation of the trithorax group and the negative regulation of the polycomb group (PcG) genes. The PcG mutation causes the strong ectopic expression of the homeotic genes in the central nervous system so that we investigated the effect of pho, which is one of PcG genes, on the development of the nervous system. We report that the nervous system was very abnormal in the pho maternal effect mutation, but not in the zygotic one. The nervous system of the mutant embryos showed a distorted ladder shape, no expression signal in some segments, or only head development. Based on these findings, unlike other PcG mutations, pho has strong effects on CNS and PNS development.

PARALLEL PERFORMANCE OF THE Gℓ-PCG METHOD FOR IMAGE DEBLURRING PROBLEMS

YUN, JAE HEON The Korean Society for Computational and Applied M 2018 Journal of applied mathematics & informatics Vol.36 No.3

We first provide how to apply the global preconditioned conjugate gradient ($G{\ell}-PCG$) method with Kronecker product preconditioners to image deblurring problems with nearly separable point spread functions. We next provide a coarse-grained parallel image deblurring algorithm using the $G{\ell}-PCG$. Lastly, we provide numerical experiments for image deblurring problems to evaluate the effectiveness of the $G{\ell}-PCG$ with Kronecker product preconditioner by comparing its performance with those of the $G{\ell}-CG$, CGLS and preconditioned CGLS (PCGLS) methods.