• Structural Engineering and Mechanics
• /
• 제28권1호
• /
• pp.107-127
• /
• 2008

Wind turbine blades are increasing in magnitude without a proportional increase of stiffness for which reason geometrical and inertial nonlinearities become increasingly important. Often these effects are analysed using a nonlinear truncated expansion in undamped fixed base mode shapes of a blade, modelling geometrical and inertial nonlinear couplings in the fundamental flap and edge direction. The purpose of this article is to examine the applicability of such a reduced-degree-of-freedom model in predicting the nonlinear response and stability of a blade by comparison to a full model based on a nonlinear co-rotating FE formulation. By use of the reduced-degree-of-freedom model it is shown that under strong resonance excitation of the fundamental flap or edge modes, significant energy is transferred to higher modes due to parametric or nonlinear coupling terms, which influence the response and stability conditions. It is demonstrated that the response predicted by such models in some cases becomes instable or chaotic. However, as a consequence of the energy flow the stability is increased and the tendency of chaotic vibrations is reduced as the number of modes are increased. The FE model representing the case of infinitely many included modes, is shown to predict stable and ordered response for all considered parameters. Further, the analysis shows that the reduced-degree-of-freedom model of relatively low order overestimates the response near resonance peaks, which is a consequence of the small number of included modes. The qualitative erratic response and stability prediction of the reduced order models take place at frequencies slightly above normal operation. However, for normal operation of the wind turbine without resonance excitation 4 modes in the reduced-degree-of-freedom model perform acceptable.

• 한국자동차공학회논문집
• /
• 제22권7호
• /
• pp.70-75
• /
• 2014

The experiment was done on traveling at the speed of 20km/h, 60km/h and 100km/h using the performance testing mode for chassis dynamometer. The experimental method were employed to measure the waveform of secondary ignition coil and exhaust emission. In this experiment, the correlation between the secondary waveform coming from ignition coil and exhaust emission were measured in decrepit vehicle. The secondary waveform characterized by the value of effective discharge energy. The following results are obtained by analyzing the data relativity between the effective discharge energy and exhaust emission. The variation rate of effective discharge energy was largest 60km/h, 20km/h, 100km/h velocity in the ordered named. As the vehicle velocity increases, the average variation rate of CO and $NO_X$ decreases and that of HC and $CO_2$ decrease. The value of effective discharge energy, CO, $NO_X$ and fuel consumption is measured badly in case of car with failures in MAP, spark plug and good in case of car with before and after maintenance regardless of vehicle velocities. The value of effective discharge energy is to be nearly parabolic shape as vehicle velocity increases. As the value of effective discharge energy increases, the value of $NO_X$, HC and $CO_2$ decrease, the value of CO increase. The most sensible factors of exhaust emission were CO, $NO_X$, and the small variation factors were HC, $CO_2$.

• 한국정보처리학회논문지
• /
• 제5권8호
• /
• pp.2061-2074
• /
• 1998

패턴 인식의 분야에서 그래프는 복잡한 대상체의 표현 및 인식의 도구로서 많이 사용되지만, 그래프간의 유사성 비교에는 많은 시간이 소요될 뿐아니라 실제 입력되는 영상은 왜곡으로 인해 저장되어 있는 이상적인 영상과 동일함을 기대할 수 없으므로 유사한 정도를 판별하는 기준이 마련되어야만 한다. 이 논문에서는 행렬을 그래프의 표현 수단으로 사용하였다. 행렬은 표현이 간단하며, 정의되어 있는 연산을 통해 순서 배열 및 매칭 과정을 간단히 수행하루 수 있다. 이 때 그래프를 구성하는 노드(node)들을 기하학적 위치에 따라 순서 배열함으로써 그래프를 구성하는 노드들 사이의 대응 관계를 효율적으로 찾을 수 있도록 하였으며, 또한 왜곡으로 인하여 기호를 표현하는 그래프의 노드가 제대로 추출되지 못한 경우는 기호의 구조를 고려하여 보정해 줄 수 있는 분할 과정을 도입하여 해결하였다. 제안한 방법은 악보의 비음표 기호 인식을 통해 실험하였으며, 실험 결과 95% 정도의 인식률을 얻을 수 있었다.

• Korean Chemical Engineering Research
• /
• 제56권5호
• /
• pp.655-662
• /
• 2018

신 기후체제 출범에 따른 기후변화의 효율적 대응을 위해 정부는 분산형 전원의 확대를 모색하고 있다. 이 중 가스열병합발전(CHP)을 중심으로 하는 집단에너지 시스템이 가장 현실적인 대안으로써 받아들여지고 있다. 한편 최근 발표된 8차 전력수급 기본계획을 통해 정부는 기저 발전 중심에서 친환경 발전 위주로 에너지 패러다임의 변화를 공표하였다. 본 연구에서는 이러한 에너지 패러다임의 변화가 CHP의 열 생산 패턴을 변화시켜 집단에너지 공헌이익에 미칠 수 있는 정량적인 손익 효과를 분석하는 연구를 수행하였다. 이를 위해 먼저 상용화된 전력시장 종합분석 프로그램을 활용하여 7,8차 수급계획별 전력시장 장기 시뮬레이션을 수행하였다. 또한 현재 수도권에서 830 MW급 CHP를 운영 중인 사업자의 실적을 활용하여 CHP 운전 Mode별로 전력생산량과 열 생산량을 산정할 수 있는 CHP 운영모델을 구성하였다. 이를 바탕으로 상용화된 집단에너지 최적운영 프로그램을 통해 CHP의 Life-Cycle 동안의 최대의 운영수익을 실현할 수 있는 운전 최적화를 수행하였다. 그 결과 정부의 에너지 패러다임의 변화는 CHP의 급전지시량을 증가시키고 이로 인해 열 생산원가가 하락하여 사업자의 공헌이익이 30년 동안 909억 증가함을 확인할 수 있었다.

• 복식
• /
• 제35권
• /
• pp.17-44
• /
• 1997

Medieval European practical art and style of costume is studied through referring to the literatures. The type of clothing that was seen on tapestries arts and crafts paintings and wall paintings and appeared in the architecture such as church. There were symbolic aspects of color motifs at this period and some restraints for clothing according to the social class, It was a period that draped garments due to the War of Crusades is appeared. Be-cause the medieval taste and decorative character is not only 'formative art' but also the taste beyoud 'mode' and atomsphere of that times it could be seen the strong reflec-tion of customs in the clothing of that times which is shown in works of art. 1) The purpose of Christian art which was found in mosaics stained glasses wall pain-tings and statues of architecture was not just the revival of natural phenomena but visuali-zation of sacred and invisible things. It was valuable to understandin of the spiritual through the sense organ It was a monumental art that was combined with decorative func-tion and role of the Bible. It revealed what was about the religious spiritual miracle, 2) In the medieval European painting characteristic and beautiful creativity was the basis of an argument. Both "Worship of East-ern" that is painted ion a parchment and "Cor-onation of Charles VI" were described decor-ation motifs on the edge of buildings geo-metric patterns and others with outstanding skill. there were precise technologic skill of architect and glassmen and lots of patience of craftsmen. " The Labour of the Months" and the scene of"A Trial at the Court" is also de-scribed elaborately. 3) Tapestry was developed in France Ger-many Swiss at the 14th century. Religionary and historical themes unicorn lady bird flowering plants and others were major motifs. It was very important as decorative wall coverings and as practical door arch and bed hangings. It was made through patient hard work with simple technique and it was con-sidered as an art for practical use. Tapestry was what everyone wish to have. It is reckoned for the item of the best gift. The royalty and nobility ordered and used custom-made tapestries. Sometimes the subject of motifs consisted of series which were deeply related to living 4) Decorative arts and crafts was the art that used materials such as precious metals jewels and others and that accorded with the luxurious and gorgeous taste of the royalty and nobility. Christian considered splendid and beautiful color of light as a symbol of glory. They used also for church appliances, There were metal crafts wood crafts textile crafts and others, As was stated above the costume appeared on the arts and crafts for living revealed the process of changes saw how the politic econ-omic and social organizations were developed.and social organizations were developed.

• 대한교통학회지
• /
• 제33권6호
• /
• pp.584-597
• /
• 2015

보행로 서비스 수준 평가에 활용된 기존 지표는 보행의 양적인 측면에만 집중한다는 점에서 서비스 수준을 올바르게 평가하지 못하는 한계점을 갖고 있다. 이를 극복하기 위해 본 연구는 평가를 위한 효과척도로 접근성 지표를 제안하였다. 특히 대중교통수단과 보행로간의 접근성에 주목하여 변수를 구축하였다. 본 연구는 3단계로 구성된다. 1단계에서는 버스와 지하철 등의 대중교통 지표를 활용해 접근성 변수를 수단별로 정의하였다. 2단계에서는 접근성 변수와 보행류율간의 상관관계를 검토하였다. 3단계에서는 접근성 변수를 포함한 보행로 서비스 수준의 영향요인을 규명하는 모형을 개발하였다. 개발 결과, 접근성, 보행로 기하구조, 주거와 상업 등의 토지이용 용도 등이 보행로 서비스 수준에 영향을 끼치는 것으로 나타났다. 특히 접근성, 상업용도 면적 비율은 보행 활동을 유인하여 서비스 수준을 떨어트리는 것으로 밝혀졌다. 이와 함께 지장물과 버스 정류장이 입지하는 경우에도 서비스 수준은 하락하였다. 그러나 주거면적 비율이 높거나 유효보도폭이 넓을수록 서비스 수준은 향상되는 것으로 분석되었다. 이러한 결과는 보행로 서비스 수준 산정, 유효보도폭 결정 등의 분야에 활용될 수 있다.

• 핵의학기술
• /
• 제27권2호
• /
• pp.111-127
• /
• 2023

Purpose: Gallium-68 (⁶⁸Ga) is increasingly used in nuclear medicine imaging for various conditions such as lymphoma and neuroendocrine tumors by labeling tracers like Prostate Specific Membrane Antigen (PSMA) and DOTA-TOC. However, compared to Fluorine-18 (¹⁸F) used in conventional nuclear medicine imaging, ⁶⁸Ga has lower spatial resolution and relatively higher Signal to Background Ratio (SBR). Therefore, this study aimed to investigate the optimized parameters and reconstruction methods for PET/CT imaging using the ⁶⁸Ga radiotracer through model-based image evaluation. Materials and Methods: Based on clinical images of ⁶⁸Ga-PSMA PET/CT, a NEMA/IEC 2008 PET phantom model was prepared with a Hot vs Background (H/B) ratio of 10:1. Images were acquired for 9 minutes in list mode using DMIDR (GE, Milwaukee WI, USA). Subsequently, reconstructions were performed for 1 to 8 minutes using OS-EM (Ordered Subset Expectation Maximization) + TOF (Time of Flight) + Sharp IR (VPFX-S), and BSREM (Block Sequential Regularized Expectation Maximization) + TOF + Sharp IR (QCFX-S-400), followed by comparative evaluation. Based on the previous experimental results, images were reconstructed for BSREM + TOF + Sharp IR / 2 minutes (QCFX-S-2min) with varying β-strength values from 100 to 700. The image quality was evaluated using AMIDE (freeware, Ver.1.0.1) and Advanced Workstation (GE, USA). Results: Images reconstructed with QCFX-S-400 showed relatively higher values for SNR (Signal to Noise Ratio), CNR (Contrast to Noise Ratio), count, RC (Recovery Coefficient), and SUV (Standardized Uptake Value) compared to VPFX-S. SNR, CNR, and SUV exhibited the highest values at 2 minutes/bed acquisition time. RC showed the highest values for a 10 mm sphere at 2 minutes/bed acquisition time. For small spheres of 10 mm and 13 mm, an inverse relationship between β-strength increase and count was observed. SNR and CNR peaked at β-strength 400 and then decreased, while SUV and RC exhibited a normal distribution based on sphere size for β-strength values of 400 and above. Conclusion: Based on the experiments, PET/CT imaging using the ⁶⁸Ga radiotracer yielded the most favorable quantitative and qualitative results with a 2 minutes/bed acquisition time and BSREM reconstruction, particularly when applying β-strength 400. The application of BSREM can enhance accurate quantification and image quality in ⁶⁸Ga PET/CT imaging, and an optimization process tailored to each institution's imaging objectives appears necessary.