• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.5
• /
• pp.600-607
• /
• 2011

Recently, high carbon steel has become essential not only for shipbuilding parts, but also mass production. Its surface has been treated by carburizing, nitriding and induction hardening, but these existing treatments cause considerable deformation and increase the expense of postprocessing after treatment; furthermore, these treatments cannot be easily applied to parts that requiring the hardening of only a certain section. This is because the treatment cannot heat the material homogeneously, nor can it heat all of it. Laser surface treatment was developed to overcome these disadvantages, and when the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate, microstructural changes and hardness characteristics of two parts (the surface treatment part, and parental material) are observed with the change of laser beam speed and surface temperature.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.6
• /
• pp.761-769
• /
• 1999

In this paper the effect of aging heat treatment to the Corrosion behavior for the Nimonic 80A superalloy was studied by AC Impedance methods. Tested solution was 3.5% with tempera-ture $25^{\circ}C$ Electro-chemical corrosion test were carried out for the Nimonic 80A super-alloy which solution heat treated at $1080^{\circ}C$ for 8 hours followed by aging heat treated at $650^{\circ}C,\;700^{\circ}C,\;750^{\circ}C\;800^{\circ}C$ and $850^{\circ}C$ with 16hours under vacuum environment. The obtained results were as follows; 1. Base metal and solution-treated materials were exhibited similar corrosion tendency as Ran-dle equivalent cell. The value of passive film resistance was 579 ohms for the base metal and 124,770 ohms for the solutionized metal such a difference was arose by the ${{\gamma}_^'}$ precipitate on the metal surface during heat treatment. 2. The measure value of $R_p$ for heat-treated at $650^{\circ}C,\;700^{\circ}C,\;800^{\circ}C$and $850^{\circ}C$ were 97,943, 93, 111, 26,961, 15,798 and 11,780ohm respectively. Which indicated that the passive film resistance Rp was reduced as aging temperature increased due to the growth of grain size and sensitization at the grain boundary. 3. The similar tendency was exhibited for corrosion behavior of the electro-chemical corrosion polarization method and AC impedance method and confirmed that AC impedance method was useful tool for corrosion research.

• Journal of Advanced Marine Engineering and Technology
• /
• v.24 no.6
• /
• pp.70-77
• /
• 2000

In this paper, the effect of solution and age heat treatment to the corrosion behavior for the Ti-6Al-4V alloy were studied by cyclic polarization methods. Ti-6Al-4V was solution heat treated at $1,066^{\circ}C$ and $966^{\circ}C$ for 5 hours, and followed by age heat treated at $650^{\circ}C$, $600^{\circ}C$ and $550^{\circ}C$ with 1, 2, 4, 8 and 16 hours under vacuum environment. Test solution was 3.5% NaCl with temperature $25^{\circ}C$. The obtained results were as follows: 1. Base metal was exhibited higher electrical charge than that of solution and aged material. With decrease of solution-treatment temperature from 1066 to $966^{\circ}C$, the electrical charge was increased due to softening of micro structure. 2. The corrosion resistance of specimen that solution treated at $966^{\circ}C$ for 5 hours and age heat treated at 650, 660 and $550^{\circ}C$ were increased with increase of aging time to 4, 8 and 16 hours respectively, and then decreased. 3. In case of 316L stainless steel, measured charge and corrosion potential was 0.0627 coulomb and -614 mV respectively. Corrosion resistance of Ti-6Al-4V was higher than that of 316L.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.2
• /
• pp.135-143
• /
• 2013

Friction Stir Welding (FSW) was developed, it is successfully commercialized in the field of transportation vehicles. In this study, we analyzed the defects of A2024-T4 alloy using non-destructive test of radiograph, ultrasonic, electrical conductivity and destructive test of microstructure observation, tensile strength. As the results of experiment, mapping of defects was obtained. Fine defects which were not detected in radiograph test were detected in ultrasonic test, and it enabled efficient detection of defects by difference of sound pressure and color. The values of electrical conductivity was decreased as amount of defects was increasing. Joint efficient of defect-free weldment that found by non-destructive and destructive test was 91%. Therefore it was considered that non-destructive test of friction stir welded A2024-T4 Alloy was an efficient method.

• Korean Journal of Construction Engineering and Management
• /
• v.23 no.1
• /
• pp.28-36
• /
• 2022

Since the establishment of a large-scale public experience facility in Korea, the construction project of public experience facilities has recently changed to a form where local governments or local education offices place delivery alone or agreements. In particular, due to the low frequency of delivery and the nature of delivery organization that do not have specialized organizations specializing in Delivery Framework, the role of enhanced Public Owner is needed. In response, this study investigated the current status and operation status of public experience facility construction projects in Korea and derived problems and directions for improvement of the current role of Public Owner. In addition, the study proposed the improvement of the role of public Owner in public experience facilities, which are composed of the promotion stage and functions reflecting the factors and attribute information of the business characteristics.

• Korean Journal of Construction Engineering and Management
• /
• v.24 no.3
• /
• pp.31-41
• /
• 2023

This study is a study to develop a configuration management methodology for efficient and systematic management in the event of configuration changes such as deformation, explosion, and remodeling of launch vehicle development test facilities, which are emerging as important national facilities in the era of full-scale space competition. Through the analysis of international standards for configuration management, a configuration management process framework to be applied to launch vehicle development test facilities is extracted, a survey was conducted on experts who performed life cycle engineering of launch vehicle development test facilities, and a configuration management methodology optimized for operation/management of domestic launch vehicle development test facilities was proposed. Identify the configuration for launch vehicle development test facilities, the configuration management manager, configuration management organization, and configuration management board approve/process the configuration changes, and after construction is completed according to design requirements, launch vehicle development test facilities try to manage the configuration in a controlled state.

• Journal of Chest Surgery
• /
• v.43 no.6
• /
• pp.602-613
• /
• 2010

Background: As life expectancy has been increased, the cardiac valve disease has been increased. In past, mechanical valve for valve replacement surgery was used widely, but it has many weaknesses, such as hemorrhage, teratogenic effect caused by warfarin, acute mechanical failure, taking warfarin during life, etc. So, the tissue valve is used widely and researches for durability of tissue valve are in progress. Tissue valves being used are all imported in Korea, and there is a lack of information on its geometry and design. So, we studied the geometry of porcine aortic and pulmonary valve, and tried to suggest theoretical basis for making the aortic and pulmonary valve. Material and Method: We harvested aortic and pulmonary valves of 25 pigs and measured the geometry of valve at fresh and glutaraldehyde (GA) fixed state. In each group, we measured the diameter of the base, diameter of commissure, valve height, commissural height, etc. Also, for making implantable porcine and bovine pericardial valve, we designed the valve stent form, thickness, height, and leaflet size, form, thickness by different size of valve. Result: The aortic and pulmonary valve geometry and ratio were measured in each group. The right coronary cusp of aortic valve and right facing cusp of pulmonary valve was bigger than other cusps and non coronary cusp was smaller than others (RCC: NCC : LCC=1 : 0.88 : 1). Valve height was correlated to the leaflet size. We designed the outer diameter of stented porcine aortic valve from 19 mm to 33 mm and designed stent height and width, using previous measured ratio of each structure, stent thickness, working thickness (for making valve). Also, we designed the size of stent and form for stented bovine pericardial valve, considering diameter of valve, leaflet length, height and leaflet minimum coaptation area. Conclusion: By measuring of 25 pig's aortic and pulmonary valve geometry and ratio, we can make theoretical basis for making implantable stented porcine valve and bovine pericardial valve in various size. After making implantable valve using these data, it is necessary to do in vivo and in vitro researches, furthermore.

• Archives of design research
• /
• v.12 no.3
• /
• pp.227-234
• /
• 1999

We paid attention to the fact that a project will always tend to increase in size even if its scope is narrowing. The complexities and multidisciplinary aspects of projects require that the many parts should be put together so that the prime objectives- performance, time, and cost- are met. These aspects lead to the use of teams to solve problems that used to be solved by individuals. Firstly, We surveyed the design companies and their clients on the design projects, and categorized the design task into 5 phases, that are marketing, planning, idea development, presentation, and follow-up. Among the phases, the presentation has the most difficult task, longest processing time, and highest cost, whereas idea development phase has relatively low cost, longer processing time, and more difficult task. Most of the companies used to be faced several bottlenecks on their design projects - time control, budget control, and resource control. Secondly, for improving the project managing process, we adopted that dividing and analyzing the sub critical paths may help in the effective managing.(Badiru, Adedeji B., 1995) Some critical paths require almost as much attention as the critical path since they have a high potential of becoming critical when changes occur in the network. Therefrom we suggest the Total task weight(Gt) as a management formula for the design project management.${Gt=\mathrm{T}\ast\leftthreetimes\ast1/100}$<\TEX> ( Gt = Total task weight, mathrm{T} = Task Weight, \leftthreetimes= Criticality ) Thirdly, In order to support to managing for the design projects, we set up an application system, which is graphically planning and implementing a complex undertaking. It is helpful to make the control of a project easy. The DPMS(Design Project Management System), which has two sub system. One is Project Screening System(PSS), and another Project Managing System(PMS). In PMS, we divided the design project into three modules; Project Planning, Project Implementation, and Project Evaluation. As a result, the DPMS will contribute to supply the control of a project easily and effectively. Also teams are used for making decisions and taking action with the DPMS. But we need to get further studies on the relationships between the whole project and its tasks.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.8
• /
• pp.877-885
• /
• 2013

A seawater pipe of the engine room in the ships is being surrounded with severely corrosive environments caused by fast flowing of the seawater, containing aggressive chloride ion and high conductivity etc.. Therefore, the leakage of the seawater from its pipe have been often occurred due to its local corrosion by aggressive chloride ions. Subsequently, its leakage area is usually welded by AC shielded metal arc welding with various electrodes. In this study, when the sea water pipe is welded with several types of electrodes such as E4301, E4311, E4313 and E4316, a difference of the corrosion resistance on the welding metal zones was investigated using an electrochemical method, observing microstructure, measuring polarization behaviors and hardness. The weld metal zone welded with E4313 electrode exhibited the lowest value of hardness compared to other weld metal zones. In addition, its zone indicated also the best corrosion resistance than those of other weld metal zones. Furthermore, all of the weld metal zones revealed a relatively better corrosion resistance than those of the base metal zones. and also showed higher hardness than the base metal zones.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.1
• /
• pp.70-80
• /
• 2020

This study examined the effects of the R&D project managers' leadership on the product development performance. A survey was carried out empirically on a group of 175 experts associated with project management R&D operations in the field of manufacturing, construction engineering, shipbuilding, plant, and IT. The survey results showed that the effects of the R&D project managers' leadership on the product development performance were not significant, and the mediating effects of the project sponsor roles were significant. This means that the leadership of leaders, which requires efficient control and management based on complicated intergroup relationships and roles, is important in a project involving experts from the professional field. This suggests that the efficient leadership of leaders can improve the performance through the cooperation of members in the organization and aggregation of their core competencies in a limited time. Overall, the key results of this study mean that project leaders should play an active mediating role to maximize their leadership and enhance the role of project sponsors. In addition, the mediating role of project sponsors has an effect on the leadership of project managers, affecting the project performance quality.