Design of the Parabolic Reflector Antenna with Bended Elliptical Conductor Plate Feed (절곡된 타원형 도체평판 급전부를 갖는 포물선 반사판 안테나 설계)
-
- The Journal of the Korea institute of electronic communication sciences
- /
- v.12 no.6
- /
- pp.989-996
- /
- 2017
The proposed directional pencil beam antenna consists of a waveguide feeder with bended elliptical conductor plate feed and a parabolic curved reflector. Two rectangular apertures located at the broad wall near the end of the feed waveguide inserted from behind the reflector are located at the focus of the reflector and emit electromagnetic energy with bended elliptical conductor plate. This plate is designed to reflect electromagnetic energy primarily and to face the main reflector. The two rectangular apertures located at the waveguide end have inwardly protruding tabs for impedance matching of the antenna system, the shape of the tabs is a truncated oval. The proposed parabolic reflector antenna has a diameter of 400 mm and a focal length of 134.23 mm. The antenna gain is 33.68 dBi at the center frequency of 16.5 GHz, the beam width is
The increase of air traffic volume has brought an increasing amount of issues related to carbon and NOx emissions and noise pollution. Aircraft manufacturers are concentrating their efforts to develop technologies to increase aircraft efficiency and consequently to reduce pollutant discharge and noise emission. Ultra High By-Pass Ratio engine concepts provide reduction of fuel consumption and noise emission thanks to a decrease of the jet velocity exhausting from the engine nozzles. In order to keep same thrust, mass flow and therefore section of fan/nacelle diameter should be increased to compensate velocity reduction. Such feature will lead to close-coupled architectures for engine installation under the wing. A strong jet-wing interaction resulting in a change of turbulent mixing in the aeroacoustic field as well as noise enhancement due to reflection phenomena are therefore expected. On the other hand, pressure fluctuations on the wing as well as on the fuselage represent the forcing loads, which stress panels causing vibrations. Some of these vibrations are re-emitted in the aeroacoustic field as vibration noise, some of them are transmitted in the cockpit as interior noise. In the present work, the interaction between a jet and wing or fuselage is reproduced by a flat surface tangential to an incompressible jet at different radial distances from the nozzle axis. The change in the aerodynamic field due to the presence of the rigid plate was studied by hot wire anemometric measurements, which provided a characterization of mean and fluctuating velocity fields in the jet plume. Pressure fluctuations acting on the flat plate were studied by cavity-mounted microphones which provided point-wise measurements in stream-wise and spanwise directions. Statistical description of velocity and wall pressure fields are determined in terms of Fourier-domain quantities. Scaling laws for pressure auto-spectra and coherence functions are also presented.
The purpose of this paper is to examine the formal characteristics of
In this study, the newly constructed optical measurement system, which was mainly composed of a parametric tunable laser and a near infrared photoelectric multiplier, was introduced to clarify the optical characteristics of wood as discontinuous body with anisotropic cellular structure from the viewpoint of the time-of-flight near infrared spectroscopy (TOF-NIRS). The combined effects of the cellular structure of wood sample, the wavelength of the laser beam λ, and the detection position of transmitted light on the time resolved profiles were investigated in detail. The variation of the attenuance of peak maxima At, the time delay of peak maxima Δt and the variation of full width at half maximum Δw were strongly dependent on the feature of cellular structure of a sample and the wavelength of the laser beam. The substantial optical path length became about 30 to 35 times as long as sample thickness except the absorption band of water. Δt
The characteristics of ship induced waves caused by navigation become widely different from both ship's speed and water depth condition. The ship induced waves specially generated in coastwise routes frequently give rise to call unforeseen danger for swimmers and small boats as well as shoreline erosion or sea wall destruction in coastal zones. The main concern of ship induced wave study until now is either how to reduce ship resistance or how to manoeuvre the ship safely under a constant water depth in the view point of shipbuilding engineers. Moreover, due to the trends for appearance of the high speed ships at the shallow coastal water, we are confronted with the danger of damages from those ship induced waves. Therefore, it is necessary to examine the development of ship induced waves and the influence of their deformation effects according to its propagation ray. In present study, in order to predict the development of the ship induced waves and their propagation under the conditions of complicate and variable shallow water depth with varying ship's speed, we constructed a computer model using Boussinesq equation with a fixed coordinate system and verified the model results by comparison with experimental results. Additionally, the model was applied under the variable water depth based on actual passage and we then confirmed the importance of the variable water depth consideration.
Background: Pulse wave velocity (PWV), which is inversely related to the distensibility of an arterial wall, offers a simple and potentially useful approach for an evaluation of cardiovascular diseases. In spite of the clinical importance and widespread use of PWV, there exist no standard either for pulse sensors or for system requirements for accurate pulse wave measurement. Objective of this study was to assess the reproducibility of PWV values using a newly developed PWV measurement system in healthy subjects prior to a large-scale clinical study. Methods: System used for the study was the PP-1000 (Hanbyul Meditech Co., Korea), which provides regional PWV values based on the measurements of electrocardiography (ECG), phonocardiography (PCG), and pulse waves from four different sites of arteries (carotid, femoral, radial, and dorsalis pedis) simultaneously. Seventeen healthy male subjects with a mean age of 33 years (ranges 22 to 52 years) without any cardiovascular disease were participated for the experiment. Two observers (observer A and B) performed two consecutive measurements from the same subject in a random order. For an evaluation of system reproducibility, two analyses (within-observer and between-observer) were performed, and expressed in terms of mean difference
The purpose of this study is to examine the actual cases of crane breeding at private homes in the Joseon Dynasty period, thereby identifying the universal meaning and characteristics of this act reflected in these cases. This study is likely to help understand the true nature of garden culture during the period. The study' temporal and spatial scope was limited to the Joseon Dynasty and private homes. As references for the study, translated versions of classical literature were selected from the Database of Korean Classics(http://db.itkc.or.kr). To complement for the data, related researchers' translated materials were also used in part. The study's results are summed up as follows: First, Individuals from various social classes including royal families, noblemen, noble families in countryside, and commoners kept cranes at their homes. These crane breeders included those who left a significant mark in the Joseon Dynasty politically and academically as well as 'cheosa(處士)' that refers to scholars living in seclusion without entering the government throughout their lifetime. Second, Crane breeders were spread all over the country. Notably, various cases of crane breeding were found within the Hanyang Wall and its vicinity. Third, The act of crane breeding was highly associated with blood ties and academic lineages such as friendships and teacher-student relations. In this regard, crane breeding was not just a simple taste or appreciation for the arts, but rather reflective of a person's life attitude and orientation. Forth, The consciousness of Confucian origins based on an ancient story of Limpo (林逋) appears to have a large impact on the act of crane breeding. In addition, some cases exhibited the reflection of Taoistic tastes. Fifth, Some individuals tamed cranes for a living. This proves the presence of steady demand for cranes in this period. The present study's limitation is its reliance on translated materials, which hindered research into various cases. Therefore, the future discovery of additional data and the accumulation of their translations will enable the investigation of a wealth of cases.
"Nectar of Immortality", also known as Suryukwha, is a painting which is hung on the wall during Suryukjae, a rite to console the spirits residing on both land and water. The Suryukwha at Bonyung Temple in the Ming Dynasty consisted of 139 scrolls depicting separate scenes. In Korea, however, Nectar of Immortality combines all the scenes into one large painting. The lower part of Nectar of Immortality describes pain, disasters, and the frailty of human life in this world. This is intended to inspire people to embrace Buddhism and be delivered from their worldly existence. However, it reflects the social realities of that time as well. The scenes at the bottom of the painting of nomadic troupes of entertainers and their performances are part of this reflection. In this section, various scenes of traditional Korean performance are illustrated, such as double and single tightrope walking, Sotdaetagi (performing atop a pole), Ssangjulbaegi (one form of Sotdaetagi), tumbling, bell juggling, mask dramas, dish spinning, puppet shows, the dance of Sadang, and sword dancing. Among these performances, some, such as Sotdaetagi, Ssangjulbaegi, double tightrope walking, bell juggling and sword dancing (Punggakjaengipae), have since ceased to exist. The troupes of entertainers depicted in Nectar of Immortality are Sadangpae, Namsadangpae, Sotdaejaengipae, Choranipae, Punggakjaenipae, Gutjungpae, and circus troupes. When, after itinerant lives, these entertainers die, they become forlorn wandering spirits with no descendants to perform their memorial services. The entertainers in the performance scenes are the embodiment of souls who are the subjects of salvation through Suryukjae. Among these entertainers, Sotdaejaengipae, Sadangpae, Choranipae, Punggakjaenipae and Gutjungpae no longer exist. In sum, Nectar of Immortality provides insight into the vanished content of numerous historic forms of performance and the activities of nomadic troupes of entertainers.
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70