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This research analyzed the ventilation effect of the multi-span greenhouse based on the types of greenhouse structure, weather conditions, and locations inside the greenhouse. To compare and analyze the ventilation effects with different types of greenhouse, the uniform environmental conditions should be selected in advance. But these factors are not controlled and require tense many precision facilities and labor forces. Thus, the CFD simulation was used for the air stream to be analyzed qualitatively and quantitatively. In addition, for the ventilation effect analysis, the TGD (Tracer Gas Decay) was used to overcome the shortcomings of the current ventilation measurement method. The calculation error of ventilation rate using TGD was low (10.5%). Thus, the TGD is very effective in calculating the ventilation efficiency. The wind direction of 90 degrees showed the best ventilation effect. The ventilation rate also decreased along the air circulation path, and the rate was the lowest around the outlet. The computed fluid method (CFD) turned out to be a power tool for simulating flow behavior in greenhouse.
송종법(Jong-Beop Song), 최일경(Il-kyung Choi), 정효경(Hyo-kyung Jung), 권순홍(Soon-Hong Kwon), 권순구(Soon-Gu Kwon), 박종민(Jong-Min Park), 김종순(Jong-Soon Kim), 정성원(Sung-Won Jung), 최원식(Won-Sik Choi) 한국산업융합학회 2017 한국산업융합학회 논문집 Vol.20 No.2
Dental implants are required to have biomechanical functions and biostability in order to perform authoring, pronunciation, and aesthetic functions in the oral cavity. In terms of biostability, pure titanium for medical have good biostability and no rejection in the alveolar bone. with appropriate strength in terms of strength as well as biocompatibility. In recent years, various surgical methods and devices have been developed to improve the convenience and safety of the procedure. However, as the number of procedures increases, the screw loosening of the abutment screw connecting the artificial root and the abutment There are many reports of artificial root and abutment fracture. Fig. 1 is an example of a case where the upper part of the abutment screw is arbitrarily modified to remove the abutment by the abutment fracture due to the loosening of the abutment screw. The fundamental cause of abduction of the abutment screw is caused by the slight movement due to the lowering of the retention force of the abutment screw. It is necessary to minimize loosening of the abutment screw to avoid problems such as fracture during the period of using the implant. The purpose of this study is to investigate the structure of the abutment screw to prevent the loosening of the abutment screw by forming 0.5mm slot
The smart irrigation system using ICT technology is crucial for stable production of upland crops. The objective of this study was to develop a smart irrigation system that can control soil water, depending on irrigation methods, in order to improve crop production. In surface irrigation, three irrigation methods (sprinkler irrigation (SI), surface drip irrigation (SDI), and fountain irrigation (FI)) were installed on a crop field. The soil water contents were measured at 10, 20, 30, and 40 cm depth, and an automatic irrigation system controls a valve to maintain the soil water content at 10 cm to be 30%. In subsurface drip irrigation (SSDI), the drip lines were installed at a depth of 20 cm. Controlled drainage system (CDS) was managed with two ground water level (30 cm and 60 cm). The seasonal irrigation amounts were 96.4 ton/10a (SDI), 119.5 ton/10a (FI), and 113 ton/10a (SI), respectively. Since SDI system supplied water near the root zone of plants, the water was saved by 23.9% and 17.3%, compared with FI and SI, respectively. In SSDI, the mean soil water content was 38.8%, which was 10.8% higher than the value at the control treatment. In CDS, the water contents were greatly affected by the ground water level; the water contents at the surface zone with 30 cm ground water level was 9.4% higher than the values with 60 cm ground water level. In conclusion, this smart irrigation system can reduce production costs of upland crops.
Study is an essential part of a human life. It is said, "without study, no life." This is to stress the importance of study in the human life. If a man ceases to study, it can be said that he is no longer alive. To study aims at striving to be human and living as a moral being in a society with others in a situation of mutual understanding and cooperating peace. Acquired studies, such as speaking, reading and writing, work as the basis of embodied studies like body-living and soul-using for becoming a good moral agent in a moral community. Therefore the studies of speaking, reading and writing for trying to win a social success and get a comfortable life are not the whole of but a part of study to a moral agent. To start with honesty in speaking and writing is strongly required to members of a society, especially of an academic world, as moral agents. Academic and religious leaders as well as political and economic leaders should cherish honesty in speaking and writing as the best policy for their performances of a socially given tasks and morally required life. It may not be exaggerating to assert that moral perfection is the end of study. To study is to do a moral act and man should study to be morally human. Man has to study for the aim of becoming a morally good person through all the kinds of studies.
본 논문에서는 합성 개구 레이더(SAR: Synthetic Aperture Radar) 영상에서 SAR 보정용으로 설치된 삼각 전파 반사기(TCR: Trihedral Corner Reflector)의 레이더 단면적(RCS: Radar Cross Section)을 정확하게 추출하는 방법을 연구하고, SAR 보정 정확도를 분석한다. TCR의 이론적 RCS를 geometrical optics(GO)와 physical optics(PO) 방법을 이용하여 이론적으로 계산하고, 측정값과 비교하여 정확성을 검증한다. 이때에 단일 반사는 PO로, 이중 반사는 GO-PO로, 삼중 반사는 GO-GO-PO로 계산하고, 모서리 영향은 PTD(Physical Theory of Diffraction) 방법을 이용하여 이론적 RCS를 정확하게 계산한다. 크기가 다른 5개의 TCR를 설치하고, TerraSAR-X로 그 지역에 대한 위성 영상을 취득하여 그 TCR들에 대한 RCS를 추출한다. 레이더 IRF(Impulse Response Function) 특성에 의해 분산된 전력(power spill)을 모두 구하기 위해 정사각형 모양의 면적(window)을 설정하여 정확하게 RCS를 추출하고, 이 RCS를 이론적 RCS와 비교한다. 면적의 크기와 배경의 레이더 후방 산란 계수 크기에 따른 TCR의 RCS 오차를 계산하며, 최소 적분 면적과 최대 배경 산란계수 크기를 제안한다. This paper presents an algorithm for retrieving precise radar cross sections(RCS) of various trihedral corner reflectors (TCR) which are external calibrators of synthetic aperture radar(SAR) systems. The theoretical RCSs of the TCRs are computed based on the physical optics(PO), geometrical optics(GO), and physical theory of diffraction(PTD) techniques; that is, the RCS computation includes the single reflections(PO), double reflections(GO-PO), triple reflections(GO-GOPO), and edge diffractions(PTD) from the TCR. At first, we acquire an SAR image of the area that five TCRs installed in, and then extract the RCS of the TCRs. The RCSs of the TCRs are extracted accurately from the SAR image by adding up the power spill, which is generated due to the radar IRF(Impulse Response Function), using a square window. We compare the extracted RCSs with the theoretical RCSs and analyze the difference between the theoretical and experimental RCSs of the TCR for various window sizes and various backscattering coefficient levels of the adjacent area. Finally, we propose the minimum size of the integration area and the maximum level of the backscattering coefficients for the adjacent area.
본 논문에서는 다양한 종류의 지표면에 대하여 분석하여 산란 특성을 연구하고 SAR 클러터 영상을 제작하고 실제 SAR 클러터 영상과 비교한다. 먼저 지표면의 특성을 분석하기 위해 각각의 지표면에 대해서 입력변수를 측정한다. 측정한 데이터를 이용하여 Oh 모델, PO 모델, radiative transfer model (RTM)을 이용하여 각도 별 산란계수를 구하였다. SAR 영상 생성을 위해 먼저 측정 지역의 DEM (digital elevation map)과 LCM (land cover map)데이터를 제작한다. DEM 데이터의 단일 픽셀(pixel)의 높이 정보를 이용하여 픽셀의 입사각을 계산하고 입사각에 따른 해당 지표면의 산란 계수를 대입한다. LCM 데이터는 해당 지역의 답사를 통해 논, 밭, 산, 길, 인공물 등을 1:5000 지도에 기입하여 SAR 영상 생성에 사용한다. DEM 데이터와 LCM 데이터를 사용하여 입사각과 지표면 종류에 따른 계수를 계산하고 영상잡음(speckle)과 영상질감(texture)을 이용하여 SAR 클러터 영상을 생성하고 실제 영상과 비교한다. In this paper, synthetic aperture radar (SAR) clutter images are simulated based on the extensive analyses for radar backscatter characteristics of various earth surfaces, and the simulated images are compared with measured SAR images. At first, the surface parameters including soil moisture content and surface roughness parameters and other parameters for vegetation canopies are measured for various surfaces. The backscattering coefficients for the surfaces are computed using theoretical and empirical models for surface scattering and the radiative transfer for vegetation-canopy scattering. Then, the digital elevation map (DEM) and land cover map (LCM) are used for the SAR image generation. The SAR impulse response (correlation function) is also employed to simulated reliable SAR images. Finally, the appropriate speckle and texture parameters for various earth surfaces are used for generating the SAR clutter images.
정은주(1991)의 연구에서 우리나라 사람의 자산별 수익성 및 안정성에 대한 인식 비교를 보면, 부동산 자산은 수익성도 매우 높고 안정성도 매우 높다고 보고하였다. 지금도 이러한 인식에는 큰 차이가 없어 보인다. 그러나 합리적 시장에서는 재정거래(arbitrage)와 같은 행위로 인해 고수익 저위험 자산은 존재할 수 없다. 본 연구의 목적은 이러한 인식과 실제의 차이의 원인을 설명해보고자 하였고, 특히 부동산과 주식을 비교하는 것에 초점을 맞추어 행동경제학적 이론적 틀을 분석하였다. 다음에, 2001년 이후의 부동산과 주식의 수익성과 안전성에 대한 실제 지표를 분석하였고 나아가 이 지표들을 행동경제학적 관점에서 재해석해 보았다. 현재의 인식을 확인하기 위하여 설문을 통하여 자산별 수익성과 안정성에 대해 조사하였다. 실제 지표, 행동경제학적 해석, 그리고 설문 결과를 비교 분석함으로써 인식과 실제 간의 간극을 살펴보았다. 분석 결과, 실제 월 수익률 평균 측면에서 주식(1.8%)이 부동산(0.98%)에 비하여 높음에도 불구하고, 이를 행동경제학적 인식을 측정하는 가치함수로 전환하는 경우 부동산(1.20%)이 주식(-.2.34%)보다 높게 나타났다. 행동경제학 측면에서는 인간은 손실에 대해서 인지적으로 더욱 강하게 인식하기 때문이다. 나아가, 인식적인 측면에서 주식에 대한 수익률은 마이너스이고 부동산에 대한 수익률은 플러스로 인식하기 때문에 부동산이 주식보다 안정적이라고 인식하는 경향을 갖게 된다. According to Jung(1991), Koreans tend to perceive real estate as a high-return and low-risk asset. This perception has not been changed. However, in a market economy, there is no such high-return low-risk asset due to arbitrage. The purpose of this study is trying to explain this Korean real estate fever from the behavioral economics perspective. Specifically, we compare the return and risk of real estate and stock. We begin with theoretical frame to understand the discrepancy between perception and reality. Next, we investigate the actual return and risk. Then, we re-calculate the actual return and risk using the behavioral economics theory. In addition, we surveyed citizens to comprehend their perception. Finally, we compared this three indicators-actual return and risk, re-calculated numbers, and survey result. As a result, we found that the average monthly gain of stock (1.8%) is actually higher than that of apartment (0.98%). If we re-calculate this number with the value function of the behavioral economics, real estate (1.2%) is higher than stock (-2.34%). Our survey confirms this discrepancy. From the behavioral economics perspective, the discrepancy can occur because loss has 2.25 times more impact on people' perception than gain does.
It is said that the Western Culture has grown in the soil of both the Bible and the Greek myth. The Bible represents the world of monotheism, and the Greek myth shows the world of polytheism The Bible refers largely to Christianity and monotheism, and the Greek myth to Roman culture and polytheism. Often spoken, polytheism tends to admit human beings to have liberty in a large spectrum of human behaviors, while monotheism restricts the autonomy of in many parts of human life. Therefore polytheism tends to be preferred to monotheism among the strong and the confident. The gods of polytheism who worshipped by the Roman empire function only as helpers, not as controllers, according to the view of Siono Nanami who is the writer of Roman Stories which is planned to 15 volumes and published in Japanese, and translated in Korean with 14 volumes by now. Nanarni recognizes that polytheism is the religion of the strong who don't want to be controlled by other persons, even by gods. If so, monotheism has to be the religion of the weak physically, politically or militarily. This point may be a hard problem to Christians, including me, who have their faith in monotheistic Christianity which is not thought to be the religion for only the weak. In the polytheistic world of thought, gods are almost the same as humans in behaviors and morality and their role is largely restricted to the help to human beings, particularly to politically promising elites or militarily winning generals. Considering this point, it is not strange that those who are confident and rich tend to rely on the religion of polytheism If it is true, polytheism must be a humanistic religion which prefers to stand in the side of victorious people or nations, and the religion for the present age, not for the future one. So polytheism was qualified to be the religion of the Roman empire prospering enormously and enlarging outwardly. But the strong is not enduring forever. Though the Roman empire was thought to be eternal among her citizens, their hope was not achieved on account of the decay and collapse of the empire in the middle of 5th century. Some states that the reason to the end of the empire was primarily the emergence of monotheistic Christianity in the world of Roman polytheism. Differing with polytheism, monotheism has one God who provides human beings with the rule of human life and gives the guideline for human behaviors and social relations. Monotheistic thought-world and some doctrines of Christianity may be suffocating people filled with political or economic confidence who refuse to be interfered by others or gods. But Christianity is the religion for the strong as well as the weak. Misunderstanding is characteristic of human beings. A real world of human life is not simple but complicated. It is also true concerning to the attitude to a religion. To most of religious people the thought world of polytheism is intermingled with the thought world of monotheism. People often reveal their duality also in the part of religion. Sometimes they are inclined to rely on polytheism. Sometimes they are to stand in the side of monotheism. Therefore it is not easy to continue to stand in the side of one of two religious world of monotheism and polytheism. Most of the religious are taking their seats in a moving point between the world of monotheism and the world of polytheism. Polytheism politically defeated in struggle with monotheism, particularly with Christianity, in the Western society and Christian churches permeates its humanistic and materialistic belief to the heart of the members of monotheistic Christianity. Polytheistic faith centered on the present age has influenced deeply on the thought world of monotheism. So the more important part of monotheistic faith has been shaken by the shock of polytheistically preferred materialism and Mammonism. Many members of the monotheistic religion of Christianity has been soaked in the religious water of polythei