• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.1
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• pp.84-92
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• 1989

The purpose of this paper is to demonstrate the effect of a FH spread spectrum communication interference in TV channels and frequency compatibility in 30-88 MHz frequency band. To calculate this interferece, the strength of electric field of TV signals is derived as a function of distance between TV transmitter and receiver. An interference model is established based upon thefield strength by using the relation between the transmitted power of FH spread spectrum communications and the distance between the TV image signals, which makes TV screen a cceptble, Simultaneous transmission of FH sprea spectrum signals and TV signals is shown to be feasible, as far as the interference level is lower than the TV image signal level by 23.5dBm. As a result of frequency analysis and experiment, the FH spread spectrum communication can be used together with TV channels.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.273-283
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• 2018

Currently, the dynamic amplification effect of suction is described using the wind vibration coefficient (WVC) of external loads. In other words, it is proposed that the fluctuating characteristics of suction are equivalent to external loads. This is, however, not generally valid. Meanwhile, the effects of the ventilation rate of louver on suction and its WV are considered. To systematically analyze the effects of the ventilation rate of louver on the multi-dimensional WVC of ultra-large cooling towers under suctions, the 210 m ultra-large cooling tower under construction was studied. First, simultaneous rigid pressure measurement wind tunnel tests were executed to obtain the time history of fluctuating wind loads on the external surface and the internal surface of the cooling tower at different ventilation rates (0%, 15%, 30%, and 100%). Based on that, the average values and distributions of fluctuating wind pressures on external and internal surfaces were obtained and compared with each other; a tower/pillar/circular foundation integrated simulation model was developed using the finite element method and complete transient time domain dynamics of external loads and four different suctions of this cooling tower were calculated. Moreover, 1D, 2D, and 3D distributions of WVCs under external loads and suctions at different ventilation rates were obtained and compared with each other. The WVCs of the cooling tower corresponding to four typical response targets (i.e., radial displacement, meridional force, Von Mises stress, and circumferential bending moment) were discussed. Value determination and 2D evaluation of the WVCs of external loads and suctions of this large cooling tower at different ventilation rates were proposed. This study provides references to precise prediction and value determination of WVC of ultra-large cooling towers.

• The Journal of the Petrological Society of Korea
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• v.14 no.1
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• pp.73-81
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• 2005

K-Ar ages have been determined for the submarine basalts dredged from the P2 and P3 segments of the Phoenix Ridge, Drake Passage, Antarctica, for better understanding on the extinction of seafloor spreading. At the P3 segment, the K-Ar ages of the rifted ridge basalts are 3.5-6.4 Ma, and those for the axial seamount basalts are 1.5-3.1 Ma. The K-Ar ages for the basalts at the rifted ridge and axial central high in the P2 segment are 2.1 and 1.4-1.9 Ma, respectively. We suggest that the extinction of seafloor spreading at the P3 and P2 segments occurred at 3.3 and 2.0 Ma, respectively, on the basis of ridge structure and formation time of basalts. This result favors a stepwise extinction model rather than a simultaneous one on the extinction of the Phoenix Ridge.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.2
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• pp.113-121
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• 2010

Recently, as container ships become larger and faster, rudder cavitations are more frequently observed near the gap between the horn and rudder plates of the ships to cause serious damages to the rudder surface of the ship. The authors already have suggested through a series of model experiments and numerical computations that employment of an appropriate blocking device for gap flow may retard the gap cavitation. For examples, a cam device installed near the outer edges of the vertical gap or a water-injection device combined with a pair of half-round bars installed inside the gap can considerably reduce the gap cavitation. However, it is also found that effective blocking of the flow through the vertical gap results in growth of the cavitation near the horizontal gap instead. In the present study, effectiveness of the simultaneous blocking of the flow through the horizontal and vertical gaps of a horn type rudder in minimizing the damage by gap cavitation is studied. Additional blocking disks are inserted inside the horizontal gaps on the top and bottom of the pintle block and numerical computations are carried out to confirm the combined effect of the blocking devices.

• Journal of International Society for Simulation Surgery
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• v.2 no.1
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• pp.1-6
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• 2015

Purpose Bisphophonate-related osteonecrosis of the jaw (BRONJ) is an emerging problem. Extensive osteonecrosis of the jaw needs free flap reconstruction. Free fibular flap is the most useful flap for maxilla-mandibular hard and soft tissue reconstruction. The advantages of fibular free flap are simultaneous soft and hard tissue reconstruction and placing implant in reconstructed mandible and maxilla. In this study, four consecutive BRONJ patients who underwent fibula free flap reconstruction using simulation surgery were reviewed. Materials and Methods Four BRONJ patients who underwent free fibula reconstruction between May 2006 and September 2014 were included in this study. Male to female ratio was 1:3 and average age was 67.3 years old (62-70). All patients need mandibular bone reconstruction. Three patients suffered from osteoporosis and one male patient had multiple myeloma. Postoperative flap survival, functional reconstruction, esthetic results, food taking were evaluated. Results Three osseous flaps and one osteocutaneous flap were used. All the fibular flaps were survived and patients were recovered without complications. Oro-cutaneous fistula was resolved after operation. All patients were satisfied with the esthetic results. Patients reported improved solid food intake after operation with partial denture. One fully edentulous patient had semi-fluid diet after operation. Conclusion Treatment of the BRONJ is difficult due to lack of standard protocol. Fibular free flap using simulation surgery is the workhorse flap for mandibular hard and soft tissue reconstruction, especially in stage III BRONJ patient. In this study, functional and esthetic results were successful in all patients. Normal diet was possible with partial dentures.

• Journal of the Korean housing association
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• v.18 no.6
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• pp.15-23
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• 2007

It was undeniable that rapid development of scientific technology gave us not only convenience and efficiency but troubles for existence of human due to destruction of ecosystem. Especially, rapid and massive expansion of the city deteriorated those phenomenons. Constructing Ecovillage was important and could be an alternative dwelling model in that it was sustainable so that we could cope with the troubles. But now, meaning and purpose of it was being hazy while thoughtless Ecovillage and notions of it were diffused. This study began to derive planning and evaluation index of Ecovillage on the basis of reference studies and suggestion for the notion and purpose of Ecovillage. This study began to suggest more clear notion of Ecovillage with reference study and derive planning and evaluation index of Ecovillage on the basis of the prior study. After Interviewing research and Field study, the derived index was applied to Ansolgi village and an evaluation for the application was made to suggest a direction and ways to develop and activate Ecovillage. The result of evaluation with the indices showed that Ansolgi village had those declined to visible and easy to make planning factors. Therefore, to activate and sustain Ecovillage in KOREA, even, simultaneous and well linked planning and evaluation indices should be developed. At this moment, since ten years have passed from the beginning of Ecovillage in KOREA, a study reflecting dwellers' evaluation is needed. And it is the most important the dwellers' cognition for the problems and will to resolve them and continuous interest and investment of government and others who are interested in sustainable development.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.63-68
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• 1990

The chemical ingredients such as $SiO_2,\;Al_2O_3,\;MgO,\;Fe_2O_3,\;CaO$ and $TiO_2$in silica minerals were determined by X-ray fluorescence spectrometry using a matrix correction method. The synthesized standards mixed with reagent grade oxides and the sample were diluted by fusing with 16 times $Li_2B_4O_7$. The matrix effects correlated among the ingredients were corrected by the empirical coefficient method based on the Lucas-Tooth and Pyne model. The analytical results showed relatively good agreement between the different sets of coefficients but were improved with increasing the number of standard. The accuracy of this method was also examined with the standard reference material of NIST.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1999.11a
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• pp.216-221
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• 1999

A mental task combined with noise background is an effective model of laboratory stress for study of psychophysiology of the autonomic nervous system (ANS). The intensity of the background noise significantly affects both a subjective evaluation of experienced stress level during test and the physiological responses associated with mental load in noisy environments. Providing tests of similar difficulties we manipulated the background noise intensity as a main factor influencing a psychophysiological outcome and the analyzed reactivity along withe the noise intensity dimension. The goal of this study was to identify the patterns of ANS responses and the relevant subjective stress scores during performance of word recognition tasks on the background of white noise (WN) of the different intensities (55, 70 and 85 dB). Subjects were 27 college students (19-24 years old). BIOPAC, Grass Neurodata System and AcqKnowlwdge 3.5 software were used to record ECG, PPG, SCL, skin temperature, and respiration. Experimental manipulations were effective in producing subjective and physiological responses usually associated with stress. The results suggested that the following potential autonomic mechanisms might be involved in the mediation of the observed physiological responses: A sympathetic activation with parasympathetic withdrawal during mild 55 and 70dB noise (featured by similar profiles) and simultaneous activation of sympathetic and parasympathetic systems during intense 85dB WN. The parasympathetic activation in this case might be a compensatory effect directed to prevent sympathetic domination and to maintain optimal arousal state for the successful performance on mental stress task. It should be mentioned that obtained results partially support Gellhorn's (1960; 1970) "tuning phenomenon" as a possible mechanism underlying stress response.

• Journal of Microbiology and Biotechnology
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• v.22 no.12
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• pp.1613-1620
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• 2012

Bacterial wilt caused by Ralstonia solanacearum is a devastating disease of many economically important crops. Since there is no promising control strategy for bacterial wilt, phage therapy could be adopted using virulent phages. We used phage PE204 as a model lytic bacteriophage to investigate its biocontrol potential for bacterial wilt on tomato plants. The phage PE204 has a short-tailed icosahedral structure and double-stranded DNA genome similar to that of the members of Podoviridae. PE204 is stable under a wide range of temperature and pH, and is also stable in the presence of the surfactant Silwet L-77. An artificial soil microcosm (ASM) to study phage stability in soil was adopted to investigate phage viability under a controlled system. Whereas phage showed less stability under elevated temperature in the ASM, the presence of host bacteria helped to maintain a stable phage population. Simultaneous treatment of phage PE204 at $10^8$ PFU/ml with R. solanacearum on tomato rhizosphere completely inhibited bacterial wilt occurrence, and amendment of Silwet L-77 at 0.1% to the phage suspension did not impair the disease control activity of PE204. The biocontrol activities of phage PE204 application onto tomato rhizosphere before or after R. solanacearum inoculation were also investigated. Whereas pretreatment with the phage was not effective in the control of bacterial wilt, post-treatment of PE204 delayed bacterial wilt development. Our results suggested that appropriate application of lytic phages to the plant root system with a surfactant such as Silwet L-77 could be used to control the bacterial wilt of crops.

• Journal of Korea Foundry Society
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• v.17 no.5
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• pp.465-471
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• 1997

An integrated computer program consisting of a pre-processor, main solver, and post-processor was developed for the design of large steel castings. The pre-processor, based on the AutoCAD, enables the user to produce approval drawings, casting design drawings and mesh diagrams in sequence using a personal computer. In the main solver, two numerical models were employed; one models the fluid flow during mold filling, and the other models the heat transfer and solidification. The post-processor can be used to present simulation results such as flow pattern, mold filling sequences, solidification times, temperature gradients and location of shrinkage defects by color graphics. In order to validate the applicability of the present integrated program, a series of experiments on simple-shaped steel castings were carried out. After the validation of the present model, it was applied to the casting design of the large steel anchor of an SC42 alloy. Various solidification parameters such as a temperature distribution and a solidification time in the casting and the mold were compared with those obtained experimentally. Simulated results predicting shrinkage defects were in good agreement with those obtained experimentally. It was found that the present method can be successfully applied to the quantitative casting design for complex-shaped large steel castings.