Sound transmission analysis of plate structures using the finite element method and elementary radiator approach with radiator error index

Jung, Jaesoon,Kook, Junghwan,Goo, Seongyeol,Wang, Semyung Elsevier 2017 Advances in engineering software Vol.112 No.-

<P><B>Abstract</B></P> <P>In this paper, an accurate and efficient numerical method for sound transmission analysis is presented. As an alternative to conventional numerical methods, such as the Finite Element Method (FEM), Boundary Element Method (BEM) and Statistical Energy Analysis (SEA), the FE-ERA method, which combines the FEM and Elementary Radiator Approach (ERA) is proposed. The FE-ERA method analyzes the vibrational response of the plate structure excited by incident sound using FEM and then computes the transmitted acoustic pressure from the vibrating plate using ERA. In order to improve the accuracy and efficiency of the FE-ERA method, a novel criterion for the optimal number of elementary radiators is proposed. The criterion is based on the radiator error index that is derived to estimate the accuracy of the computation with used number of radiators. Using the proposed criterion a radiator selection method is presented for determining the optimum number of radiators. The presented radiator selection method and the FE-ERA method are combined to improve the computational accuracy and efficiency. Several numerical examples that have been rarely addressed in previous studies, are presented with the proposed method. The accuracy and efficiency of the proposed method are validated by comparison with the results of the three dimensional (3D) FEM structure-acoustic interaction models.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An efficient and accurate numerical method (i.e. FE-ERA method) is proposed to compute the sound transmission loss. </LI> <LI> The FE-ERA method combines the finite element method (FEM) and elementary radiator approach (ERA). </LI> <LI> The radiator error index is derived to estimate the accuracy of the computation using ERA. </LI> <LI> The accuracy and efficiency of the FE-ERA method are further improved using radiator error index. </LI> <LI> The results of several numerical examples validate the accuracy and efficiency of the FE-ERA method. </LI> </UL> </P>

The protective effects of trace elements against side effects induced by ionizing radiation

Seyed Jalal Hosseinimehr,PhD 대한방사선종양학회 2015 Radiation Oncology Journal Vol.33 No.2

Trace elements play crucial role in the maintenance of genome stability in the cells. Many endogenous defense enzymes are containing trace elements such as superoxide dismutase and metalloproteins. These enzymes are contributing in the detoxification of reactive oxidative species (ROS) induced by ionizing radiation in the cells. Zinc, copper, manganese, and selenium are main trace elements that have protective roles against radiation-induced DNA damages. Trace elements in the free salt forms have protective effect against cell toxicity induced by oxidative stress, metal-complex are more active in the attenuation of ROS particularly through superoxide dismutase mimetic activity. Manganese-complexes in protection of normal cell against radiation without any protective effect on cancer cells are more interesting compounds in this topic. The aim of this paper to review the role of trace elements in protection cells against genotoxicity and side effects induced by ionizing radiation.

유한요소/경계요소 연성해석을 통한 수중 구조기인소음 해석

이두호(Dooho Lee),김현실(Hyun-Sil Kim),김봉기(Bong-Ki Kim),이성현(Seong-Hyun Lee) (사)한국CDE학회 2012 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2012 No.2

Radiated noise analysis from ship structure is a challenging topic due to difficulties in accurate calculation of fluid-structure interaction as well as massive degree of freedoms of the problem. To reduce the severity of the problem, a new fluid-structure interaction formulation is proposed in this paper. The complex frequency-dependent added mass and damping matrices are calculated using the high-order Burton-Miller boundary integral equation formulation in order to obtain accurate values over all frequency bands. The calculated fluid-structure interaction effects are added to the structural matrices calculated by commercial finite element software, MSC/NASTRAN. Then, the impedance and underwater radiation noise due to an excitation of structure are calculated. The accuracy of the present formulation is compared with those from the conventional finite element/boundary element formulation. The present formulation enables us to sequentially perform the fluid-structure coupled analysis in fluid and structure parts, which makes the method be implemented in commercial finite element software.

기생소자에 의한 다이폴 배열 안테나의 방사특성 개선에 관한 연구

정진우 대한전자공학회 2019 전자공학회논문지 Vol.56 No.11

The radiation characteristics of an array antenna are affected by the distance between radiating elements. When the distance between radiating elements is increased, the half power beam width is decreased, thus, the directivity of an array antenna is increased. However, when grating lobes(except main lobe) are included in visible region according to increase the distance between radiating elements, the directivity is dereased. Therefore, an array antenna has the threshold for the distance between radiating elements. In this paper, we analyze the radiation characteristics for a dipole antenna with parasitic element, and studied the improving method of the radiation characteristics for a dipole array antenna using parasitic elements in the condition over the threshold. 배열안테나의 방사특성은 방사소자간 간격에 영향을 받는다. 배열된 방사소자간 간격이 증가할수록 배열안테나 주빔의 반치각은 감소하여 지향성이 개선된다. 그러나 만약 방사소자간 간격이 가시영역 내 주빔 이외의 그레이팅 로브가 포함될 때까지 증가하면 지향성은 감소하게 된다. 따라서 배열안테나는 방사소자간 간격에 관한 제약 조건을 갖는다. 본 논문에서는 기생소자에 따른 다이폴 안테나의 방사특성 변화를 분석하였다. 분석 결과를 기반으로 방사소자간 간격에 관한 제약 조건 이상의 구성 조건을 갖는 다이폴 배열 안테나에 있어, 기생소자에 의한 방사특성 개선에 관하여 연구하였다.

인공위성 열해석을 위한 유한요소 열복사해석의 복사전달행렬 구성 방법 연구

김민기 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4

한국항공우주연구원에서 개발 중인 인공위성 종합설계 소프트웨어에 복사가 포함된 열해석을 위한 유한요소법 기반 열해석기가 탑재되어 있다. 해당 소프트웨어의 복사가 포함된 유한요소 열해석 코드는 전도만 포함된 열해석에 비해 복사열전달의 해의 효율성을 높이기 위한 특별한 수치적 기법이 필요하다. 유한요소 열해석의 온도장의 이산화에 사용되는 Galerkin법을 복사열전달에 그대로 적용하면 같은 평면 내의 요소들에 대해서도 복사열전달이 일어날 수 있으며, 이는 실제 물리 현상과 일치하지 않는다. 이를 극복하기 위해 본 연구에서는 복사열교환 행렬의 구성에 있어 서로 다른 요소 간 열교환을 위한 절점에 집중화된 새로운 복사열교환 행렬 구성법을 제시하였으며, 이를 통한 해석 결과는 기존의 방법으로는 구할 수 없었던 열해석 결과를 합리적으로 산출할 수 있음을 확인하였다. KARI Satelllite Design Software being developed by KARI has finite element thermal analysis solver including radiational heat transfer. It is required to implement special technique in the finite element thermal analysis solver for the radiative heat transfer. Generally, using standard Galerkin discretization of radiational heat exchange causes radiational heat transfer between nodes in a common element, which is not appropriate in the real physical world. To overcome this, this paper introduces new way of assembling radiation exchange matrix lumped into nodes between two distinguished radiation elements. Proposed method shows better results that cannot be represented by previous algorithm.

The protective effects of trace elements against side effects induced by ionizing radiation

Hosseinimehr, Seyed Jalal The Korean Society for Radiation Oncology 2015 Radiation Oncology Journal Vol.33 No.2

Trace elements play crucial role in the maintenance of genome stability in the cells. Many endogenous defense enzymes are containing trace elements such as superoxide dismutase and metalloproteins. These enzymes are contributing in the detoxification of reactive oxidative species (ROS) induced by ionizing radiation in the cells. Zinc, copper, manganese, and selenium are main trace elements that have protective roles against radiation-induced DNA damages. Trace elements in the free salt forms have protective effect against cell toxicity induced by oxidative stress, metal-complex are more active in the attenuation of ROS particularly through superoxide dismutase mimetic activity. Manganese-complexes in protection of normal cell against radiation without any protective effect on cancer cells are more interesting compounds in this topic. The aim of this paper to review the role of trace elements in protection cells against genotoxicity and side effects induced by ionizing radiation.

우주방사선의 인체영향 연구 동향

김미숙,정성철,이희령,김미영 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4

우주개발에 따라 우주왕복선, 우주정거장 체류, 민간 우주여행 등 다양한 형태로 유인 우주여행이 이루어지고 있다. 그러나 우주여행은 고에너지 입자방사선과 양성자, 중성자 등 우주방사선 노출 위험을 피할 수 없다. 우주방사선의 생물학적 영향에 대한 규명과 우주방사선 노출에 대한 리스크 관리는 향후 우주개발에서 풀어야할 숙제다. 미국 항공우주국(NASA)는 우주방사선 프로그램을 통해 우주방사선생물학을 연구해오고 있고, 미국 내의 대학 및 의료기관들과 다양한 연구 프로젝트를 추진하고 있다. 유럽연합과 일본도 우주방사선의 인체영향에 대한 연구를 추진하고 있으나, 한국은 아직 우주방사선의 인체영향에 대한 연구가 활성화되어 있지 않다. 우주인 배출, 나로호 발사 이후 국민적 관심과 함께 정부에서도 우주개발에 박차를 가하고 있는 바, 우주방사선의 인체영향에 대한 체계적인 연구가 필요하다. As humans have explored space, manned space travel such as space shuttle, International Space Station, private space tourism has been enabled. However, it is accompanied by exposure to the high energy charged particles of galactic cosmic rays and solar particle events, and secondary protons and neutrons. The effects of space radiation on the human body and the risk assessment are to be addressed in the future. NASA established Space Radiation Program Element and has conducted researches on space radiobiology in collaboration with universities and medical centers. EU and Japan have also conducted researches on the biological effects of space radiation. However, Korea has not established any space radiation research program yet. Along with growing public attention after the Korean Astronaut Program and successful launch of the Korea Space Launch Vehicle-1(the NARO), the Korean government is accelerating the space development which increases the necessity of space radiation research program.

능동 소자 패턴을 고려한 위상배열 안테나의 빔조향 효율 최적화

김창성,박슬기,박영미,이철수 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.8

This paper proposes a novel method to optimize the beam-steering efficiency considering the active element pattern for phased array antennas. Phase excitations by the steering angle were calculated assuming that the radiation pattern of all elements is the same in a conventional beam-steering algorithm. On the other hand, the radiation pattern of elements was different because of mutual coupling and edge effects, so that the beam-steering efficiency decreases. Therefore, the method to calculate the phase and amplitude weighting considering the active element pattern is suggested. The active element pattern, including coupling and structural features, was simulated using CST-MWS. The improvement of beam-steering efficiency was confirmed by comparing the conventional algorithm with the proposed method. The suggested optimization algorithm is useful for beam-shaping technology in the case of phased array antennas, which have many elements. 본 논문에서는 위상배열 안테나의 능동 소자 패턴을 고려하여 빔조향 효율을 최적화하는 방법을 제안한다. 기존의 빔조향 알고리즘에서 지향 각도별 인가 위상은 각 배열 소자의 방사 패턴이 모두 동일하다는 조건에서 계산된다. 하지만 실제 배열 소자의 방사 패턴은 상호 커플링 및 모서리 효과로 인해 상이하고, 이로 인해 빔조향 효율이 감소한다. 그러므로 본 최적화 방법에서는 각 배열 소자의 능동 소자 패턴이 고려된 소자별 위상 가중치와 진폭 가중치를 계산하는 방법을 제시한다. 배열 소자의 능동 소자 패턴은 CST(Computer Simulation Technology) - MWS(MicroWave Studio)로 시뮬레이션 되었다. 최적화된 위상 가중치와 진폭 가중치 적용 전후의 안테나 이득 및 투과 전력을 비교하여 빔조향 효율이 개선됨을 입증하였다. 본 최적화 알고리즘을 적용하면, 수백 개 이상의 소자를 가진 위상배열 안테나의 빔 형성 기술에 있어서 활용도가 높을 것으로 판단된다.

Biological changes of transposable elements by radiation: recent progress

배진한,어정우,김태오,이주미 한국유전학회 2015 Genes & Genomics Vol.37 No.2

Mobile genetic elements within genomes havebeen known to drive genome evolution in diverse ways. Since developing high-technology for whole-genomesequencing, many researchers have focused on not onlyhow mobile genetic elements have affected the evolution ofgenes and their function, particularly of human and mammals,but also how these elements involve in gene activationor inactivation associated with a number of humandiseases. Here we describe what kind of biological changesby mobile genetic elements contribute to disease, especiallycancer and present an overview of what is knownabout this large, and largely unexplored, segment of thegenome. Finally, we discuss understanding the genomicchanges or cellular responses to genotoxic stress such asradiation may permit to implicate for potential clinicalapplication.

Protective Effect of Administered Rolipram against Radiation-Induced Testicular Injury in Mice

김중선,Wan Lee,손영훈,Hyosun Jang,Min Ji Bae,Jungki Kim,Dongil Kang 대한남성과학회 2015 The World Journal of Men's Health Vol.33 No.1

Purpose: Pelvic irradiation for the treatment of cancer can affect normal cells, such as the rapidly proliferating spermatogenic cells of the testis, leading to infertility, a common post-irradiation problem. The present study investigated the radioprotective effect of rolipram, a specific phosphodiesterase type-IV inhibitor known to increase the expression and phosphorylation of the cyclic adenosine monophosphate response element-binding protein (CREB), a key factor for spermatogenesis, with the testicular system against pelvic irradiation.Materials and Methods: Male C57BL/6 mice were treated with pelvic irradiation (2 Gy) and rolipram, alone or in combination, and were sacrificed at 12 hours and 35 days after irradiation.Results: Rolipram protected germ cells from radiation-induced apoptosis at 12 hours after irradiation and significantly increased testis weight compared with irradiation controls at 35 days. Rolipram also ameliorated radiation-induced testicular morphological changes, such as changes in seminiferous tubular diameter and epithelial height. Additionally, seminiferous tubule repopulation and stem cell survival indices were higher in the rolipram-treated group than in the radiation group. Moreover, rolipram treatment counteracted the radiation-mediated decrease in the sperm count and mobility in the epididymis.Conclusions: These protective effects of rolipram treatment prior to irradiation may be mediated by the increase in pCREB levels at 12 hours post-irradiation and the attenuated decrease in pCREB levels in the testis at 35 days post-irradiation in the rolipram-treated group. These findings suggest that activation of CREB signaling by rolipram treatment ameliorates the detrimental effects of acute irradiation on testicular dysfunction and the related male reproductive functions in mice.