• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.4
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• pp.282-285
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• 2019

A 100-nm gate-length metamorphic high electron mobility transistor(mHEMT) with a T-shaped gate was fabricated using a two-step gate recess and characterized for DC and microwave performance. The mHEMT device exhibited DC output characteristics having drain current($I_{dss}$), an extrinsic transconductance($g_m$) of 1,090 mS/mm and a threshold voltage($V_{th}$) of -0.65 V. The $f_T$ and $f_{max}$ obtained for the 100-nm mHEMT device were 190 and 260 GHz, respectively. The developed mHEMT will be applied in fabricating W-band monolithic microwave integrated circuits(MMICs).

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.3
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• pp.315-321
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• 2012

In the study, corrosion characteristics of AZ31 magnesium alloy under various environments exposed during machining(immersion in cutting oil, 5 % cutting oil aqueous solution and distilled water & contact with dissimilar metals, SPC4 and A5052-H32) were investigated. A corrosion test was performed AZ31 magnesium alloy was immersed in each electrolyte solution after contacting with each dissimilar metals, and the results were observed by an electron microscope. In immersion tests, corrosion of AZ31 magnesium alloy showed to be in the sequence of distilled water> 5 % cutting oil aqueous solution> cutting oil> air, and in the test of contact with dissimilar metals, corrosion showed to be in the sequence of SPC4> A5052-H32> AZ31. It can be concluded that to prevent corrosion during machining, AZ31 magnesium alloy must prevent contacting water and use magnesium alloy for raw material of Jig & Fixture.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.1
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• pp.66-75
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• 2020

Enemy information has significant value when it comes to the process of military actions in battle field. Our Army now uses Battlefield Management Systems(BMSs) equipped in Ground Fighting Vehicles(GFVs) and we need to make research on what kind of role enemy information can play in such systems. Also, enemy information can be shared among GFVs and target information shall be extracted from it in view of KVMF scheme. Because KVMF becomes requisite standard in modern BMSs, we need to implement target information handling process in KVMF standard. In this article, we will focus on how target information and its sharing process can be managed efficiently without information conflicts. Also, situation map produced by it will be noted.

• The Journal of Korea Robotics Society
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• v.12 no.4
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• pp.385-394
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• 2017

Side scanning sonar (SSS) provides valuable information for robot navigation. However using the side scanning sonar images in the navigation was not fully studied. In this paper, we use range data, and side scanning sonar images from UnderWater Simulator (UWSim) and propose measurement models in a feature based simultaneous localization and mapping (SLAM) framework. The range data is obtained by echosounder and sidescanning sonar images from side scan sonar module for UWSim. For the feature, we used the A-KAZE feature for the SSS image matching and adjusting the relative robot pose by SSS bundle adjustment (BA) with Ceres solver. We use BA for the loop closure constraint of pose-graph SLAM. We used the Incremental Smoothing and Mapping (iSAM) to optimize the graph. The optimized trajectory was compared against the dead reckoning (DR).

• Journal of the Korea Society for Simulation
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• v.24 no.4
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• pp.51-58
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• 2015

Since SBA is regarded as mandatory for DM&S, many M&S frameworks and solutions were developed and applied to military simulation systems. Simulation systems developed based on such framework or solution are consist of simulation control part, scenario generation part and modeling part in common. Although the functions of these parts are similar between another simulation systems, these are developed separately by different implementation, so it causes increase of development cost. In order to solve these problems, we developed a simulation scenario framework which can be reusable regardless of simulation purpose. In this paper, we propose an architecture of simulation scenario framework and its functions.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.389-398
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• 2020

Test cases in the existing weapon system software were created manually by the tester analyzing the test items defined in the software integration test procedure. However, existing test case generation method has two limitations. First, the quality of test cases can vary depending on the tester's ability to analyze the test items. Second, excessive time and cost may be incurred in writing test cases. This paper proposes a method to automatically generate test cases based on the requirements model and specifications to overcome the limitations of the existing weapon system software test case generation. Generate test sequences and test data based on the use case event model, a model representing the requirements of the weapon system software, and the use case specification specifying the requirements. The proposed method was applied to 8 target models constituting the avionics control system, producing 30 test sequences and 8 test data.

• Journal of Korea Society of Industrial Information Systems
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• v.27 no.4
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• pp.11-18
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• 2022

A physically unclonable function (PUF) is a circuit that generates random numbers by exploiting natural variation. Since it utilizes variations, which cannot be fully controlled, it can be used to generate true random numbers, but environment change may distort the output. In this paper, we propose a PUF with a confidence signal. We designed a PUF that exploits the difference of the time constant of the circuit and verified that different PUFs generate distinct outputs and the same PUF keeps generating similar outputs regardless of the temperature change. Compared to the existing technique, which employs an error correction code, the proposed technique offers the same level of reliability at the 700 times smaller overhead.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.4
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• pp.214-224
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• 2021

Recently, as the technology of the supercavitating underwater vehicle is improved, the necessity of research for maneuvering characteristics of the supercavitating underwater vehicle has emerged. In this study, as a preliminary step to analyzing the maneuverability of a supercavitating underwater vehicle, the characteristics of cavity shapes and hydrodynamic forces generated in a supercavitating underwater vehicle with an angle of attack were evaluated numerically. First, the geometry was designed by modifying the shape of the existing supercavitating underwater vehicle. The continuity and the Navier-stokes equations are numerically solved, and turbulent eddy viscosity is solved by the k-ω SST model. The results present the characteristics of cavity shape and the hydrodynamic forces of the designed geometry with an angle of attack.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.4
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• pp.253-261
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• 2021

This paper describes the process of evaluating maneuverability in still water of an unmanned surface vehicle based on data measured by performing sea trials. First, we set up a test scenario that is easy to analyze the maneuverability of the unmanned surface vehicle and to identify and verify the dynamics model. Since the attitude of hull varies according to the speed of the unmanned surface vehicle which has a planing hull shape, the relationship between waterjet RPM, speed and attitude is analyzed by performing straight forward tests at various speeds. The turning tests of the unmanned surface vehicle in which the waterjet angle rotates while turning are performed by changing the waterjet rotation angle under the condition of two representative speeds to analyze turning ability. The turning ability of the unmanned surface vehicle includes speed reduction, yaw rate, heel, and turing diameter at steady turning phase according to the speed and RPM.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.4
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• pp.51-55
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• 2021

The nurses manually carry out the intravenous therapy for the patients. Using an Arduino, the fine flow controlling device was invented to provide an ongoing patient care. The medication is injected through a peristaltic pump, and the amount of the solution is controlled with a RGB color sensor. The power of the device is supplied through the batteries. An amount of the injection is measured with LIG strain sensor fabricated by 355nm UV pulsed laser. This system will provide a better medical service.