• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.3
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• pp.103-108
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• 2019

The results of the measurement of the flow-rate coefficient (Cv-value) and the analysis of a small ball valve are summarized follows. The Cv-values of 1/2-, 3/4- and 1-inch ball valves were measured using a flow-rate measurement test. The manufacturer obtained the Cv-value using a theoretical calculation method. The new experimental measurement and analysis method yielded more reliable results. In addition, the Cv value obtained through numerical analysis was almost identical the value provided by the manufacturer, which was based on experimental results. A Study on Flow Analysis results are all similar appearances as the reliability of the results.

• Tribology and Lubricants
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• v.21 no.2
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• pp.53-62
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• 2005

In this study a general Galerkin FE lubrication analysis method was utilized to analyze the complex lubrication performance of a spiral groove seal having an additional inner circular groove, which was designed for a chemical process mixer operating at a low speed of the maximum 500 rpm. Equilibrium seal clearance analyses under varying outer pressure revealed that the seal maintains a certain levitation seal clearance under the outer pressure of more than about 1.5 bar, regardless of a rotating speed. Also, under the normal outer pressure of 11 bar, the axial stiffness of the seal was predicted to have a high value of more than 7.0 e + 07 N/m, regardless of a rotating speed and thereby, the seal is expected to maintain a stable thickness of lubrication film under a certain external excitation acting. A seal levitation test rig was designed and constructed. Experimental results at 500 rpm agreed well with analytical predictions and the applied lubrication analysis method was verified.

• Steel and Composite Structures
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• v.23 no.2
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• pp.153-160
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• 2017

It is extremely important to be aware of the ballistic performances of engineering materials in order to be able to choose the lightest armor providing full ballistic protection in civil and military applications. Therefore, ballistic tests are an important part of armor design process. In this study, ballistic performance of plates made of carbon steel and cold worked tool steel against 7.62 mm AP (armor-piercing) bullets was examined experimentally and numerically in accordance with NIJ standards. Samples in different sizes were prepared to demonstrate the effect of target thickness on ballistic performance. Some of these samples were coated with titanium nitride using physical vapor deposition (PVD) method. After examining all successful and unsuccessful samples at macro and micro levels, factors affecting ballistic performance were determined. Explicit non-linear analyses were made using Ls-Dyna software in order to confirm physical ballistic test results. It was observed that the ballistic features of steel plates used in simulations comply with actual physical test results.

• Journal of Communications and Networks
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• v.13 no.1
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• pp.70-76
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• 2011

This paper presents the unified user equipment (UE) baseband modulation and demodulation (modem) hardware platform architecture to support multiple radio access technologies. In particular, this platform selectively supports two systems; one is HEDGE system, which is the combination of third generation partnership project (3GPP) Release 7 high speed packet access evolution (HSPA+) and global system for mobile communication (GSM)/general packet radio service (GPRS)/enhanced data rates for GSM evolution (EDGE), while the other is LEDGE system, which is the combination of 3GPP Release 8 long term evolution (LTE) and GSM/GPRS/EDGE. This is done by applying the flexible pin multiplexing scheme to a hardwired pin mapping process. On the other hand, to provide stable connection, high portability, and high debugging ability, the stacking structure is employed. Here, a layered board architecture grouped by functional classifications is applied instead of the conventional one flatten board. Based on this proposed configuration, we provide a framework for the verification step in wireless cellular communications. Also, modem function/scenario test and inter-operability test with various base station equipments are verified by system requirements and scenarios.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.198-200
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• 2017

An Auxiliary Power Unit (APU) is a small gas turbine engine that is mounted on an aircraft and serves to supply energy for ground and air starting of the main engine. APU also supplies emergency and auxiliary power for the aircraft. APU for aircraft is simple and compact in structure, but because it is mounted on manned aircraft, high reliability is required, so it must be proved its reliability through qualification procedure. The Korea Aerospace Research Institute and Hanwha Techwin successfully completed the design / analysis, fabrication, assembly, development test and certification test of APU for helicopter based on accumulated domestic R & D capability and experience from 2007 to 2012. In this paper, the development and certification process of auxiliary power unit for helicopter is summarized.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.1
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• pp.84-94
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• 2016

The warfighting experimentation is the most important for the weapon acquisition process because the warfighting experimentation shall support the operation effectiveness as well as acquisition logicality. Therefore, ROK Navy is starting to set up the next generation warfighting experimentation systems. According to literature studies, there have been many studies regarding the interoperability of Simulators(Virtual) and Exercising models(Constructive), but not for studies regarding interoperability between Simulators(Virtual) and Analysis models(Constructive) that is the core component of next generation maritime warfighting experimentation systems. This study is dealing with the V-C(Analysis model) interoperability test and methodology of interoperation analysis. The purpose of the study is to provide the new analysis methodology through V-C(Analysis model) interoperation, which can be applied for the concept of operations(CONOPS) of next generation maritime warfighting experimentation systems. In addition to that, the study validates the suggested analysis methodology by the case study of a naval operation.

• Journal of the Korean Society of Systems Engineering
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• v.18 no.2
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• pp.1-10
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• 2022

In general, similar or previous projects are mainly referred to in order to derive operational test and evaluation(OT&E) items after acquiring weapon system. The idea that a more systematic method is needed is spreading because some of OT&E items derived in this process are redundant or unnecessary. Therefore, in this topic, we plan to use WBS, a tool that classifies components into a hierarchical structure and manages development easily to achieve the weapon system development goal. In addition, the WBS tool is applied to the medium-sized standard vehicle project, which is currently being research and developed, to effectively derive OT&E items. As a result of deriving OT&E items by applying WBS to the vehicle development field and electric devices of the medium-sized standard vehicle project, the operability and relationship were judged early, and then contents of the evaluation items could be written substantially while working on environmental adaptability. In the future, it is judged that the efficiency will be increased if the method discussed in this paper is applied when deriving the OT&E items from the R&D development project.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.3
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• pp.31-36
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• 2022

Recently, drones are being used in various fields, and drone technology is also developing. The risks of drones are increasing, then technology to detect drones is important. However, it is extremely difficult to detect and recognize drones due to the low level radar cross section of the commercial drones. In this paper, a signal processor structure that was mounted the miniaturized and light-weighted was designed. in order to process large amounts of data in real time, parallel processing was performed for each channel and an algorithm was applied to shorten the operation time in each step. As a test of verifing the detection performance through test, it was confirmed that the structure design works in real time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.147-154
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• 2018

This paper focuses on the development of a support system that can rapidly generate the design data of a hot-form die with cooling channels, commonly known as hot stamping technology. We propose a new process for designing hot-form dies based on our (automated) system, whose main features are derived from the analysis of the design requirements and design process in the current industry. Our design support system consists of two modules, which allow for the generation of a 3D geometry model and its 2D drawings. The module for 3D modeling automation is implemented as a type of CATIA template model based on CATIA V5 Knowledgeware. This module automatically creates a 3D model of a hot-form die, including the cooling channels, that depends on the shape of the forming surface and the number of STEELs (subsets of die product) and cooling channels. It also allows for both the editing of the positions and orientations of the cooling channels and testing for the purpose of satisfying the constraints on the distance between the forming surface and cooling channels. Another module for the auto-generation of the 2D drawings is being developed as a plug-in using CAA (CATIA SDK) and Visual C++. Our system was evaluated using the S/W test based on a user defined scenario. As a result, it was shown that it can generate a 3D model of a hot form die and its 2D drawings with hole tables about 29 times faster than the conventional manual method without any design errors.

• Composites Research
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• v.37 no.3
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• pp.219-225
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• 2024

It is essential to develop a light-weight, high-performance structure for the deployable reflector antenna, which is the payload of a reconnaissance satellite, considering launch and orbital operation performance. Among them, the composite main reflector is a key component that constitutes a deployable reflector antenna. In particular, the development of a high-performance main reflector is required to acquire high-quality satellite images after agile attitude control maneuvers during satellite missions. To develop main reflector, the initial design of the main reflector was confirmed considering the structural performance according to the laminate stacking design and material properties of the composite main reflector that constitutes the deployable reflector antenna. Based on the initial design, four types of composite main reflectors were manufactured with the variable for manufacturing process. As variables for manufacturing process, the curing process of the composite structure, the application of adhesive film between the carbon fiber composite sheet and the honeycomb core, and the venting path inside the sandwich composite were selected. After manufacture main reflector, weight measurement, non-destructive testing(NDT), surface error measurement, and modal test were performed on the four types of main reflectors produced. By selecting a manufacturing process that does not apply adhesive film and includes venting path, for a composite main reflector with light weight and structural performance, we developed and verified a main reflector that can be applied to the SAR(Synthetic Aperture Rader) satellite.