• International conference on construction engineering and project management
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• 2022.06a
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• pp.563-570
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• 2022

Industrialized and modular construction is a growing construction technique that can transfer a large portion of the construction process to off-site fabrication yards. This method of construction often involves the fabrication, pre-assembly, and transportation of massive and long volumetric modules. The module weight keeps increasing as the modules become more complete (with infill) to minimize the work at the site and, as higher productivity can be achieved at the fabrication shop. Thus, a volumetric module delivery gets more challenging and risky. Despite its importance, past research paid relatively insufficient attention to the problem related to the lifting of heavy modules. This can be a complex and time-consuming problem with multiple lifting for transportation-and-installation operations both in fabrication yard and jobsite, and require complex crane operations (sometimes, more than one crane) due to crane load capacity and load balance/stability. This study investigates this problem by focusing on the structural perspective of lifting such long volumetric modules through simulation studies. Various scenarios of lifting a weighty module from the top using four lifting cables attached to crane hooks (either a single crane or double crane) are simulated in SAP software. The simulations account for various factors pertaining to structural indices, e.g., bending stress and deflection, to identify a proper method of module lifting from a structural point of view. The method can identify differences in structural indices allowing identification of structural efficiency and safety levels during lifting, which further allows the selection of the number of cranes and location of lifting points.

• Journal of the Korea Society of Computer and Information
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• v.24 no.11
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• pp.171-178
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• 2019

In this paper, we proposed a plan for a indoor air quality management in elderly care hospital by measuring the indoor air quality level of elderly care hospital and conducting a survey the workers' awareness of indoor air quality. The measurement items were Temperature, Humidity, CO2, CO, PM10, VOC and were taken on April 26, 2019. The survey found that the lower the satisfaction level with indoor air quality, the better outdoor air quality and odor items were analyzed to be the lowest among the indoor environmental factors. When the satisfaction level of indoor air quality is high, the satisfaction level of indoor environment factor is high. The result of the multiple response analysis was "lack of ventilation" and the regression analysis was the lower the "relevance of indoor air quality" category. To provide the best indoor air quality environment for elderly care hospital workers the installation of additional ventilation equipment to remove odors, the increase in the number of natural ventilation and the designation of regular ventilation personnel will be necessary. By establishing such a plan, it is possible to provide indoor air quality environment to provide the best services for elderly care hospital workers.

• Journal of the Korean Solar Energy Society
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• v.36 no.5
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• pp.73-89
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• 2016

To assure maximum economic benefits and the energy performance of solar water heating systems, the proper sizing of components and operating conditions need to be optimized. In recent years, a number of studies to design optimally solar water heating systems have been tried. This paper presents a design method for optimizing the various capacity-related and installation-related design variables based on life cycle cost using a genetic algorithm. The design variables considered in this study included the types and numbers of solar collector and auxiliary heaters; the types of storage tanks and heat exchangers; the solar collector slope; mass flow rates of the fluid on the hot and cold sides. The suggested method was applied for optimizing a solar water heating system for an elementary school in Seoul, South Korea. In addition, the effectiveness of the proposed optimization method was assessed by analyzing the obtained optimal solutions of six case studies, each of which was simulated with different solar fractions. It is observed that a trade-off between the equipment cost and the energy cost results in an optimal design that yields the lowest life cycle cost. Therefore, it could be helpful to apply the optimal solar water heating system by comparing the various design solutions obtained by using the optimization method instead of the engineer's experience and intuition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.39-47
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• 2008

Automatic landing performance of UAV can be enhanced by adding Pseudolite(PL) to GPS. However, it is very hard to install and operate PL with confidence because GPS satellites are moving and the landing zone are usually changeable. The coverage and accuracy of combined GPS and PL can be estimated by using simulator and the correct information is very crucial to UAV operation. In this paper, design, implementation and evaluation of GPS/PL simulator for UAV landing are given. A very realistic coverage estimation is obtained using GIS data and ray launching method with considerations of the transmitter power level, altitude of UAV, number and location of PL. The expected accuracy is estimated using DOP and NSP computed using both GPS and PL. The performance of simulator is evaluated by comparing with the results of a real GPS receiver, and the certified simulator shows the required accuracy for UAV landing can be easily met by proper installation of at least 2 PLs.

• Journal of Welding and Joining
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• v.33 no.3
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• pp.62-67
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• 2015

A very large shell-structure built in shipyards like ship hulls or offshore structures are joined by welding through full process. As the welding contains a high thermal cycle at a local area, the welded structures should be distorted unavoidably. Because a distorted ship block should be revised to the designed value before the next stage, the ability to predict and to control the weld distortion is an accuracy level of the yard itself. Despite the ship block size, several present thermal distortion methodologies can deal those sizes, but it is a different story to deal full ship size model. Even a fully constructed ship hull not remaining any welding can have an accuracy issue like outfitting installation problems. Any present thermal distortion methodology cannot accept this size for its recommended element size and the number. The ordinary welding breadth at erection stage is about 20~40 mm. It can hardly be a good choice to make finite element model of these sizes considering human effort and computational environment. The finite element model for structure analysis of a ship hull is prepared at front-end engineering design stage which is the first process of the project. The element size of the model is as fine as the longitudinal space, and it is not proper to obtain a weld distortion at the erection stage. In this study, a methodology is suggested that a weldment can be shrunk at original place instead of using structural finite element model. We cut the original shell elements at erection weld-line and put truss elements between the edges of cut elements for weld shrinkage. Additional truss elements are used to facsimile transverse weld shrinkage which cannot be from the weld-line truss element shrink. They attach to weld-line truss element like twigs from barks. The capacity of developed elements is verified through an accuracy check of erection process of a container vessel at the apt. hull. It can be a useful tool for verifying a centering accuracy after renew and for block-separating planning considering accuracy.

• Convergence Security Journal
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• v.12 no.6
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• pp.61-67
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• 2012

Accordingly the number of smart-phone-based malicious codes is also increasing and their techniques for malicio us purpose are getting more clever and evolved. Among them, the malicious codes related to Android take the major portion and it can be estimated that they are based on open source so that the access to the system is easy. Intent is a technique to support the communication between application's components by transmitting message subjects in Android. Intent provides convenience to developers, but it can be utilized as security vulnerability that allows the developer with a malicious purpose to control the system as intended. The vulnerability of intent security is that personal information can be accessed using discretionally its proper function given to application and smart phone's functions can be maliciously controlled. This paper improves with the Intent security vulnerability caused by the smart phone users' discretional use of custom kernel. Lastly, it verifies the malicious behaviors in the process of installing an application and suggests a technique to watch the Intent security vulnerability in realtime after its installation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.108-116
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• 2014

The proper stress history measurement should be conducted in order to examine the accurate cause of fatigue cracks or the fatigue safety in the steel bridge. Only one strain gauge is generally installed in the field for the stress history examination because of the field circumstances, economic feasibility, workability, and so on. However, this method may not consider the actual size of the specific structure, the gauge length, and the affect of stress concentration in the welded joint. In addition, it is difficult to apply for the stress analysis. Therefore, this study suggests improvements that are a great number of gauge installations, the gauge location adjustment, and the use of the minimum length gauge. It is drived the correlative equation of strain for the distance between the welding toe and the strain gauge installation, and compare correlative equation with equation of IIW. Also, this study could estimate the remaining life and fatigue damage of bridge in service by selecting the suitable stress category. In conclusion, it is possible to understand the member which is high in the fatigue cracks, and the quantitative relations between the welding toe and the strain gauge installation distances. The proposed approach in this study can make an more accurate fatigue damage and a remaining life prediction so that the improved method should be applied in measuring the strain of bridges from now on.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1095-1104
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• 2013

The number of vehicles registered in Korea is rapidly increasing and will reach 18.26 million as of June 2011. The rapid increase of large-size passenger cars and RVs among this number is causing damage to other vehicles when parked in currently installed parking lots, increased civil complaints from the damage, and inconveniences to people trying to pass through parking lots as well. In particular, the car-stoppers indiscriminately installed at the parking lots are also causing accidents and adding to parking problems, causing economic losses. Accordingly, there should be new regulations for the amount of parking space per vehicle and for locations to install the car-stoppers. The research has first reviewed the distribution ratio of vehicle models from home and abroad for the width and length of the vehicles by each model, parking space per vehicle where the car-stoppers are installed and examples of changes in distribution ratio. In addition, the amount of parking space per vehicle was calculated with consideration for various specifications by each car model. As a result, margin width of full sized car is decreased by 18~21mm on the existing width. This is judged decreases accident of parking lot, because length of the front of car is not deviate parking Space Section. In conclusion, presented improvement ideas for parking plans with enhanced convenience and safety from the aspect of the drivers. Parking lot relevant businesses will also be maximized in terms of cost and efficiency when the criteria for the structure of parking lots and their installation is established and the improved parking plan is applied in the future.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.3
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• pp.20-33
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• 2021

Modern society is steadily implementing policies to encourage public transportation to cope with the growing traffic demand on limited roads. The expectation is rising for transit signal priority to ensure the speed of buses as the installation of the bus rapid transit(BRT) expands nationwide to secure the competitiveness of buses. On the other hand, the form of BRT stops without considering some aspects of bus operation may increase the number of stops on the bus, thereby reducing the effectiveness of bus signal priority applications. This study suggests the type of bus stop to increase the operation efficiency of buses by analyzing the bus signal priority effect according to the BRT station type using Hannuri-daero, Sejong. The bus signal priority is used to maximize the two-way bandwidth of passenger cars and buses. As a result of the application, the effectiveness of the bus signal priority at the stop causing the double stop of the bus was reduced drastically, and the efficiency of the bus signal priority was increased significantly after improvement. These results are expected to be used as basic data in the form of proper bus stops considering the aspects of traffic operation when designing BRT stops in new towns in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.3
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• pp.607-616
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• 2015

The demand for cars has been so steadily increasing based on the economic growth that the number of registered cars reached 18,870,000 as of the end of December, 2012. Due to this, the demand for the parking lots also rises continuously. Because of the limited ground space, the buildings ever becoming larger, and the trend of underground parking spaces, recent parking spaces are generally constructed underground. Accordingly, the parking lot ramps slope is limited to less than 17% by relevant laws to ensure the driver safety. However, when a driver enters a parking lot ramps whose slope is slightly steep, he frequently experiences his car body colliding with ramp brackets and often sees the scratches on ramp floor. Thus, this study is intended to prevent any damage to a structure and to contribute to ensuring the riding comfort and safety of drivers and passengers by presenting the details of proper vertical curve to prevent the collision of vehicles with ramp brackets through a vertical analysis of the first and last parts of a parking lot ramps. Because it is necessary to decide the appropriate and suitable vertical slope of a parking lot ramps, this study first identified the problems through site inspection, targeting the parking lot ramps of large buildings frequently that are used by many random people. Next, the possibility of mutual collision was assessed through a theoretical analysis of the first and last parts of a parking lot ramps. Lastly, the vertical curve of a parking ramp was analyzed to estimate its details, which was presented in this study. In conclusion, if the vertical curve presented through this study is used, it will help prevent any damage to the cars and structures, ensure the riding comfort and safety of the drivers, and further reestablish the criteria for vertical installation of a parking lot ramps.