• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.87-94
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• 2005

This paper investigates the constant-level luffing and time optimal control of jib cranes. The constant-level luffing, which is the sustainment of the load at a constant height during luffing, is achieved by analyzing the kinematic relationship between the angular displacement of a boom and that of the main hoist motor of a jib crane. Under the assumption that the main body of the crane does not rotate, the equations of motion of the boom are derived using Newton's Second Law. The dynamic equations for the crane system are highly nonlinear; therefore, they are linearized under the small angular motion of the load to apply linear control theory. This paper investigates the time optimal control from the perspective of no-sway at a target point. A stepped velocity pattern is used to design the moving path of the jib crane. Simulation results demonstrate the effectiveness of the time optimal control, in terms of anti-sway motion of the load, while luffing the crane.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.10a
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• pp.87-94
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• 2006

In this study we carried out to analyze the effect of wind load on the structural stability of a container crane according to the change of the boom shape using wind tunnel test and provided a container crane designer with data which can be used in a wind resistance design of a container crane assuming that a wind load at 75m/s wind velocity is applied on a container crane. Data acquisition conditions for this experiment were established in accordance with the similarity. The scale of a container crane dimension, wind velocity and time were chosen as 1/200, 1/13.3 and 1/15. And this experiment was implemented in an Eiffel type atmospheric boundary-layer wind tunnel with $11.52m^2$ cross-section area. Each directional drag and overturning moment coefficients were investigated and uplift forces at each supporting point due to the wind load were analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1154-1163
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• 1996

This paper presents a three dimensional modeling and dynamic anlaysis of a hydraulic excavator. An excavator is composed of a ground, an under-frame, two idlers, two spockets, an upper-frame, a boom, an arm, a bucket two yokes, two connecting rods, two boom cylinders, an arm cylinder, and a bucket cylinder. Each cylinder is modeled with two separate bodies which are linked to each other by a translational joint. The three dimensioanl model of the excavator consists of 22 bodies and each body is assumed as rigid. This paper suggested the maximum lifting capability, a critical load and reaction forces at joints form the DADS simulation. It was presumed that the reaction forces due to a critical load are three times bigger than those due to the maximum lifting capacity.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.1
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• pp.87-99
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• 2022

We propoes a study on the dynamic characteristics analysis and position control of 5-degree multi-joint manipulators for untact remote working at construction sites and manufacturing plants. The main frame of freedom multi-joint manipulator consists of five elements, boom cylinder, boom cylinder, arm cylinder, bucket cylinder, and rotation joint and link. In addition, the main purpose of the proposed system is to realize the work of the manufacturing process or construction site by remote control. Motion control of the entire system is a servo valve control method by hydraulic servo cylinders for one to four joints, and a servo motor control method is applied for five joints. The reliability of the proposed method was verified through performance experiments by computer simulation.

• The Journal of Economics, Marketing and Management
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• v.5 no.2
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• pp.33-39
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• 2017

As the aging population geworsened by the a of the low fertility rate in the wake of the birth of the low birth rate, the rapid increase in the retirement age of the baby boomers in the wake of the birth of the Korean War is a significant indication of the separation of the aged and the role of the economically rich and the role of the role of the economically rich. Therefore, this study aims to address issues and countermeasures. The study aims to provide basic data for the future life of the baby boom generation by examining the problems and responses to the economic activity after the retirement activity of the baby boomers. The research suggests that the limit was limited to the retirement age of the baby boomer generation in order to boost the employment of the elderly. Due to the lack of exploration of the exploratory research, the lack of analysis of exploratory facts is the biggest limitation of the analysis. So, further analysis of this will lead to meaningful studies. Looking at the composition of this study, the introduction of the study included the necessity and purpose of the study. The focus on the point was on the concepts and characteristics of the baby boomer, and analyzed the characteristics of the economic activity and analyses and analyses of domestic and international cases. In conclusion, the issue was drawn up and the alternatives were sought.

• Journal of Drive and Control
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• v.19 no.2
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• pp.11-16
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• 2022

It is important to measure the excavator's work productivity that estimates the bucket's payloads on a process. If the bucket isn't filled at every working cycle, the excavator's operator has to drive the machine more to achieve his work quota. If bucket is filled over with the load, the other way around, the transferred object has to spread out on the workplace. That causes additional work to clean the site. This paper proposes a method that can estimate the bucket's payload to improve the excavator's work productivity. This method assumes that the excavator is a lumped mass system. And it uses a 3 points angle (boom link, arm link, swing) and 2 points pressure (boom cylinder's input port and output port) of measurable data. Depending on assumptions, the bucket's payload can be calculated by the payload's motion equation. And this suggested method can be verified by simple experiments.

• Journal of Drive and Control
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• v.20 no.4
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• pp.9-16
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• 2023

This paper analyzed a drainage tower used to drain water in flooded areas. Multi-body dynamics simulation was used to analyze the dynamic behavior of the drainage tower. Structural analysis, flexible-body dynamic analysis, and rigid body dynamic analysis were done to study the maximum Von-Mises stress of the drainage tower. The results showed that the maximum Von-Mises stress occurs at the turn table, and it decreases when the angle of the boom is increased. Also, the rate of the change of angle affects the maximum stress so that the maximum stress changes more when the angular velocity of the boom increases. Based on the rigid body dynamic analysis and the theoretical analysis results, the centrifugal force from the angular velocity makes the difference in the maximum stress at the turn table because of the difference in their direction. Consequently, it was concluded that the centrifugal force should be considered when designing construction machinerythat can rotate.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.15 no.2
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• pp.95-100
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• 1979

In fishing with the anchovy boat seine, it is required to haul up the bag net without injuring anchovy body. Not to injure anchovy body, the bag net is operated with 30 to 34 crews in the traditional method. With a view point of decreasing crews, the authors tried to operate the bag net with side drum winch and derrick boom. Side drum winch was installed beside the engine casing and it was operated by the main engine through the belt, pulley and bevel gear. The derrick boom, 7 meters long, was installed above the working deck which is located in the stern of the common boat seiner. Three single blocks are attached to the boom, each 2 meters apart from the top. A hook was attached to the free end of the block line for hooking up the bolch line which attached inside the bag net especially prepared for the purpose. The hauling end of the block line was induced to the side drum winch for hauling up the bag net. By using this mechanism, the bag net was hauled up with peeling the bag net just like in the traditional method. So the following results are found. (1) No injury of anchovy body was found in the process of hauling up. (2) The bag net can be operated by mere 14 crews. (3) Duration, spent in hauling up the bag net, was almost the same when the catch are a little amount, and less duration was needed by the experimented method than the traditional one when the catch are a large amount. the bag net. By using this mechanism, the bag net was hauled up with peeling the bag net just like in the traditional method. So the following results are found. (1) No injury of anchovy body was found in the process of hauling up. (2) The bag net can be operated by mere 14 crews. (3) Duration, spent in hauling up the bag net, was almost the same when the catch are a little amount, and less duration was needed by the experimented method than the traditional one when the catch are a large amount.

• Journal of the Korea Fashion and Costume Design Association
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• v.17 no.3
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• pp.85-98
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• 2015

Modern fashion shows the trend of various styles and the period focusing on only product functions is changed to the period focusing on consumer's sensibility. Consumers show different sensitivities and preference by individual at the stage cognizing and recognizing the stimulation of given image and the method of objective measurement based on the fashion sensible vocabularies is necessary to measure fashion sensibility. Therefore, this research is significant to examine differences of preference to classic fashion by generation and awareness for sensible vocabularies and suggest methodology of design sensible evaluation research through the quantitative evaluation objectifying subjective sensibility. For the method of research, precedent theses related to classic, concept and characteristics of classic in books and definition and characteristics by generation were examined, the best 3 domestic portal sites were selected and adjective vocabularies and images related to classic were collected from 2010 to 2014. Among the 206 adjectives collected, vocabularies whose average is more than 3.5 were drawn by 5-point Likert scale for fashion expert group. And, among the total 306 images collected, 21 representative images were selected by preliminary investigation of fashion expert group. For the classic images and vocabularies selected, frequency analysis, factor analysis and variance analysis were conducted by SPSS 19.0. The results of analysis are as follows. Preference to classic fashion image by generation was analyzed. As a result, both of two generations selected classic fashion as the most classic one. The images of the next orders were analyzed. As a result, Y generation selected basic classic fashion image which is casual with high activity as a classic one. Baby boom generation selected ancient classic fashion image, so there were differences in preference for classic by generation. As a factor analysis on classic adjective vocabularies, they could be divided into 5 factors such as basic form, attractive form, traditional form, vintage form and active form and they verified that credibility of all measuring variables for classic sensible vocabularies was achieved. Differences of classic sensible vocabularies by classic fashion image and generation were examined. As a result, generation and classic fashion image made a significant effect on five factors. Therefore, there were differences of the awareness on classic fashion images and sensible vocabularies among the generations and this thesis can be a fundamental material which objectifies subjective sensibility and suggests the methodology of new research.

• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.299-306
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• 2000

Korea IS one of countries to be predicted short of water in the 21st century. The government has been investigating various alternatives to resolve the problems including construction of reservoirs. Freshwater retention techniques using boom and skirt system is one of them. It is very difficult to intake water in the estuaries of south and west coast of Korea because a big tide penetrates into an upstream river. Thus, means or retaining and keeping separate freshwater from seawater could potentially be helpful in solving the water supply problems. In this study, the proposed means to achieve freshwater retention is by use of floating boom and skirt systems. The hydraulic viability of these systems in taking advantage of natural stratification tendencies between the fresh and seawaters has been investigated through hydraulic experiments. It is found that freshwater retention capacity depends on skirt length and the opening beneath the skirt. The choice of skirt length IS very important to optimize freshwater storage because longer skirt lengths cause faster mixing and shorter lengths retain less volume. Results show that the freshwater retention volume generally increases as the length of the skirt increases. However, they show that water storage might be insufficient if skirts were either too long or too short.