• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.5
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• pp.410-415
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• 2001

This paper proposes a new control scheme for the power factor improvement of DC power regenerating systems, which can regenerate the excessive DC power from DC bus line to AC supply in substations for traction systems. From the viewpoint of both power capacity and switching losses, the system is designed on the basis of three-phase square-wave inverters and composed of two inverters, zig-zag connected output transformers, and an AC filter. The output voltages of the regenerating system are not sinusoidal. However, regenerated complex power is analyzed on the basis of fundamental components and thus the reactive power produced by harmonics is not considered. Therefore, it is needed a new control scheme capable of controlling the reactive power nearly to zero even for nonsinusoidal cases. To verify the validity of the proposed control scheme, computer simulations are carried out. And the results show that the power factor is theoretically higher than 0.99.

• Journal of Chest Surgery
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• v.30 no.6
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• pp.580-584
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• 1997

To overcome the problems of classical pulmonary banding procedure, we developed a percutaneously adjustable pulmonary artery ba ding device. The banding device consists of banding portion of zig-zag shaped self-expandable stainless steel wire, shaft portion made by a polyvinyl catheter and a screw adjuster which includes a bolt and a nut. As the screw moves, the diameter of banding portion changes. Four Mongrel dogs ranging from 15 kg to 20 kg in weight underwent the banding of the mid portion of descending aorta with this devices through the left thoracotomy. One month after operation, we evaluated the pressure changes by controling the banding with the devices and then the dogs were sacrificed to study the microscopic changes in the aorta. The diameter and circumference of the band could be easily and finely adjustable by the screw control. The pressure recordings . revealed a linear increase and decrease in pressure gradient according to percutaneous ad;ustment of the banding device. Since the banding device can be easily placed and simply adjusted percutaneously, we hope the banding device may be applicab e clinically to improving the safety of pulmonary artery banding and debanding procedures in the future.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.3
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• pp.65-79
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• 1994

In the present paper, An emphasis is laid upon effects of stern bulb on hydrodynamic property and manoeuvring performance. We carried out captive model tests in circulating water channel with two ship models of which the frame lines of aft bodies are different. such as normal stern form and stern form with bulb, but of which the other parts are exactly same. The tests conducted consist of hull resistance test, effective thrust measurement, oblique tow test, and measurements of factors related to rudder force. From the results of model tests, we discussed effects of stern bulb on hull forces and on hull-propeller-rudder interactions, comparing with normal stern form. Furthermore, we also discussed effects of stern bulb on course stability. turning ability. spiral characteristics and zig-zag manoeuvre by computer simulation. As a result, it is clarified that the adoption of stern bulb makes course stability the worse and turning ability the better. The difference of the hydrodynamic derivatives of naked hull between two ship forms cause the worse course stability of the ship with stern bulb. The differences of the effective inflow velocity to rudder and hull forces induced by steered rudder cause the better turning ability of the ship with stern bulb.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.19-26
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• 1995

The assessment of maneuverability of a ship is very important from the view point of safety of human beings and of pollution of ocean. And, it is quite natural that every ship yard wants to have some tools with which they can build a ship with good maneuverability. But, maneuvarability of a ship is very subtle problem, and to calculate the exact maneuvering motion, lots of captive model tests must be carried out. Futhermore, in the initial design stage we can not make the scale model, because the lines of a ship is not fixed. In this paper, some approximate method to calculate the maneuvering motion of a ship, with the principal dimensions of hull, and propeller, rudder characteristics only, is studied. And, proposed approximate method is used to calculate the turning and zig-zag maneuver of several ships. The results of those calculations and the usability of the method are discussed.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.1
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• pp.1-8
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• 2022

To understand physical phenomena of ship maneuvering deeply, a numerical study based on computational fluid dynamics is required. A computational method that can simulate the interaction between the ship hull, propeller, and rudder will provide informative local flows during ship maneuvering tests. The analysis of local flows can be applied to improve a physical model of ship maneuvering that has been widely used in maneuvering simulations. In this study, the numerical program named as WAVIS that has been developed for ship resistance and propulsion problems is extended to simulate ship maneuvering by free-running tests. The six degree-of-freedom of ship motion is implemented based on Euler angles and the overset technique is applied to treat the moving grid of ship hull and rudder. The propulsion force due to a propeller is calculated by a panel method that is based on the lifting-surface theory. The newly extended code is applied to simulate turning and zig-zag tests of KCS and the comparison with the available experimental data has been made.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.1
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• pp.44-54
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• 2023

In this study, the second-order Nomoto's nonlinear expansion model was implemented as a Tagaki-Sugeno fuzzy model based on the heading angular velocity to design the automatic steering system of a ship considering nonlinear elements. A Tagaki-Sugeno fuzzy PID controller was designed using the applied fuzzy membership functions from the Tagaki-Sugeno fuzzy model. The linear models and fuzzy membership functions of each operating point of a given nonlinear expansion model were simultaneously tuned using a genetic algorithm. It was confirmed that the implemented Tagaki-Sugeno fuzzy model could accurately describe the given nonlinear expansion model through the Zig-Zag experiment. The optimal parameters of the sub-PID controller for each operating point of the Tagaki-Sugeno fuzzy model were searched using a genetic algorithm. The evaluation function for searching the optimal parameters considered the route extension due to course deviation and the resistance component of the ship by steering. By adding a penalty function to the evaluation function, the performance of the automatic steering system of the ship could be evaluated to track the set course without overshooting when changing the course. It was confirmed that the sub-PID controller for each operating point followed the set course to minimize the evaluation function without overshoot when changing the course. The outputs of the tuned sub-PID controllers were combined in a weighted average method using the membership functions of the Tagaki-Sugeno fuzzy model. The proposed Tagaki-Sugeno fuzzy PID controller was applied to the second-order Nomoto's nonlinear expansion model. As a result of examining the transient response characteristics for the set course change, it was confirmed that the set course tracking was satisfactorily performed.

• Journal of Intelligence and Information Systems
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• v.25 no.1
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• pp.63-83
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• 2019

Investors prefer to look for trading points based on the graph shown in the chart rather than complex analysis, such as corporate intrinsic value analysis and technical auxiliary index analysis. However, the pattern analysis technique is difficult and computerized less than the needs of users. In recent years, there have been many cases of studying stock price patterns using various machine learning techniques including neural networks in the field of artificial intelligence(AI). In particular, the development of IT technology has made it easier to analyze a huge number of chart data to find patterns that can predict stock prices. Although short-term forecasting power of prices has increased in terms of performance so far, long-term forecasting power is limited and is used in short-term trading rather than long-term investment. Other studies have focused on mechanically and accurately identifying patterns that were not recognized by past technology, but it can be vulnerable in practical areas because it is a separate matter whether the patterns found are suitable for trading. When they find a meaningful pattern, they find a point that matches the pattern. They then measure their performance after n days, assuming that they have bought at that point in time. Since this approach is to calculate virtual revenues, there can be many disparities with reality. The existing research method tries to find a pattern with stock price prediction power, but this study proposes to define the patterns first and to trade when the pattern with high success probability appears. The M & W wave pattern published by Merrill(1980) is simple because we can distinguish it by five turning points. Despite the report that some patterns have price predictability, there were no performance reports used in the actual market. The simplicity of a pattern consisting of five turning points has the advantage of reducing the cost of increasing pattern recognition accuracy. In this study, 16 patterns of up conversion and 16 patterns of down conversion are reclassified into ten groups so that they can be easily implemented by the system. Only one pattern with high success rate per group is selected for trading. Patterns that had a high probability of success in the past are likely to succeed in the future. So we trade when such a pattern occurs. It is a real situation because it is measured assuming that both the buy and sell have been executed. We tested three ways to calculate the turning point. The first method, the minimum change rate zig-zag method, removes price movements below a certain percentage and calculates the vertex. In the second method, high-low line zig-zag, the high price that meets the n-day high price line is calculated at the peak price, and the low price that meets the n-day low price line is calculated at the valley price. In the third method, the swing wave method, the high price in the center higher than n high prices on the left and right is calculated as the peak price. If the central low price is lower than the n low price on the left and right, it is calculated as valley price. The swing wave method was superior to the other methods in the test results. It is interpreted that the transaction after checking the completion of the pattern is more effective than the transaction in the unfinished state of the pattern. Genetic algorithms(GA) were the most suitable solution, although it was virtually impossible to find patterns with high success rates because the number of cases was too large in this simulation. We also performed the simulation using the Walk-forward Analysis(WFA) method, which tests the test section and the application section separately. So we were able to respond appropriately to market changes. In this study, we optimize the stock portfolio because there is a risk of over-optimized if we implement the variable optimality for each individual stock. Therefore, we selected the number of constituent stocks as 20 to increase the effect of diversified investment while avoiding optimization. We tested the KOSPI market by dividing it into six categories. In the results, the portfolio of small cap stock was the most successful and the high vol stock portfolio was the second best. This shows that patterns need to have some price volatility in order for patterns to be shaped, but volatility is not the best.

• Journal of the Mineralogical Society of Korea
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• v.6 no.2
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• pp.116-121
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• 1993

A single crystla of zeolite $Na_{78}Rb_{28}-X$ (approximate composition) was prepared by exposing $Na_{92}-X$ at $350^{\circ}C$ to 0.1 Torr of rubidium vapor, and its structure was determined by single-crystal x-ray diffraction methods in the cubic space group, Fd3, ${\alpha}=25.045(4){\AA}$. The structure was refined to the final error indices $R_1=0.082$ and $R_2=0.084$ with 353 for which I>$3{\sigma}(I)$. Only about 28 of the 92 $Na^+$ ions per unit cell were reduced and only about 14 of the 28 $Na^0$ atoms produced were retained within the zeolite. A $Na_5{^{4+}}$ cluster is present within each sodalite cavity. It is a centered tetrahedron (like $CH_4$) with bond $length=2.80(2){\AA}$ and angle tetrahedral by symmetry, and shows the full symmetry of its site. $T_d$, at the center of the sodalite cavity. Each of the four terminal atoms of the $Na_5{^{4+}}$ cluster bond to three framework oxygens at $2.36(2){\AA}$. At the centers of some double 6-rings are sodium atoms which bridge linearly between $Na_5{^{4+}}$ clusters to form agglomerations such as short zig-zag chains $Na_5{^{4+}}$ clusters. Delocalized electrons, located primarily on the sodiums at centers of the sodalite and (likely) double-six-ring cavities, contribute to the stability of the clusters.

• The Korean Journal of Pesticide Science
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• v.18 no.4
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• pp.429-433
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• 2014

In 2012, a pink mold rot was observed on apple (Malus pumila var. dulcissima Koidz.) at the Wholesale Market for Agricultural Products, Jinju, Korea. The first symptom of pink mold rot on apple fruit is a water-soaked appearance of the affected tissue and surface fruit formed pink mold rot, then became brown and produced a mass of powdery pink conidia spores. Colony was fast growing colonies, pinksh, zonate in diurnal rhythm, powdery from conidia. Optimum temperature for mycelial growth was $25^{\circ}C$. Conidia were hyaline, smooth, two-celled, thick-walled conidia with truncate bases, ellipsoidal to pyriform, and characteristically held together zig-zag chains and $12-26{\times}8-12{\mu}m$ in size. Conidiophore was erect, colorless, unbranched, and $4-5{\mu}m$ wide. On the basis of mycological characteristics, pathogenicity test, and molecular identification with the ITS region, the causal fungus was identified as Trichothecium roseum (Pers.) Link ex Gray.

• The Korean Journal of Physiology
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• v.5 no.2
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• pp.15-27
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• 1971

Physiological analysis of the physical exercise was made on 9 subjects performing mountain climbing. The course between two points (256 and 516 meters altitude) was 1,300 meters in distance and difference of vertical height was 260 meters making the mean grade of 20%. In the field, the heart rates during uphill or downhill walk were recorded by EKG radio-telemetry. In the laboratory, oxygen consumption was obtained by the recorded heart rates, using individual heart rate vs oxygen consumption diagram obtained by treadmill test. the following results were obtained. 1. Uphill walk time was 36.5 minutes, and during this period the mean heart rate was 149.0 heats/min and peak heart rate was 169.2 beats/min. The total heart beats during the uphill walk was 5.433 beats. 2. The ratio of individual mean heart rate during the uphill walk to the maximal heart rate distributed between 66.6% and 98.3%, and the mean of the total group was 83.1%. The ratio of peak heart rate of uphill walk to the maximal heart rate was 94.5% in the group. Thus uphill walk of a 20% grade mountain course was an exhaustive exercise. 3. Oxygen consumption during uphill walk was 2.22 l/min (ranged between 1.79 and 2.70 l/min) and the ratio of this to the resting oxygen consumption was 8.31. The peak value of oxygen consumption during uphill walk was 2.73 l/min and the ratio of this to the resting oxygen consumption was 10.39. 4. Energy expenditure during uphill walk showed a mean of 11.1 kcal/min and the peak expenditure rate was 13.6 kcal/min. The total energy expenditure during 36.5 minutes of uphill walk was 396 kcal. 5. In downhill walk, the time was 31.7 minutes, mean heart rate was 118.4 (ranged between 100.1 and 142.7) beats/min, and the peak heart rate was only 129.4 beats/min. The ratio of mean heart rate to the maximal heart rate was 66.3%. Total heart beats during downhill walk was 3,710 beats. The ratio of downhill oxygen consumption to the resting consumption was 5.70. The rate of energy expenditure was 7.5 kcal/min, and the total onery expenditure during the 31.7 minutes of downhill walk was 228 kcal. 6. The effect of training was manifest in the uphill walk and not in the downhill walk. After training in mountain course walk, i) the uphill time was shortened, ii) mean heart rate increased, iii) time vs heart rate curve became smooth and showed less frequent zig-zag, i.e., the depth of trough on the curve decreased and the magnitude was less than 10 beats. In non-trained subject the depth of trough on the curve was greater than 50 beats and appeared more frequently. 7. Mountain climbing is a good health promotion exercise. For the promotion of health the reasonable amount of uphill mountain walk exercise in a 20% grade course is a walk for 40 or 50 minutes duration once a week.