• International Journal of Aeronautical and Space Sciences
• /
• v.15 no.3
• /
• pp.309-319
• /
• 2014

This paper mainly focuses on the conceptual design and stealth performance of the three-surface military aircraft. A three-dimensional (3-D) digital mock-up of the three-surface strike fighter with stealth feature was designed and the schemes of carrying missiles were analyzed in CATIA. Based on physical optics principle and the Method of Equivalent Currents (MEC), a numerical simulation of the RCS feature of the aircraft was carried out with RCSPlus which is a software designed by Beihang University. The paper contributes to the RCS feature analysis of the whole plane and different parts on X-band, S-band and UHF-band and a comparison of RCS feature to Su-37 and T-50 military aircraft is drawn. On X-band, the pitch angle of the incident wave was $0^{\circ}$, and the result shows: (1) Compared with Su-37 aircraft, the forward scattering RCS of the three-surface strike aircraft was reduced to 14.9%, the side scattering RCS to 9.6% and the back scattering RCS to 40.2%. (2) Compared with T-50 aircraft, the forward scattering RCS was reduced to 38.61%, and the side scattering RCS to 67.26%. This paper should be useful for researchers in conceptual design and stealth technology of the military aircraft.

• Journal of the Korean Society for Heat Treatment
• /
• v.27 no.1
• /
• pp.1-9
• /
• 2014

For connector material applications, the influence alloying elements of Mn, Cr, Fe, and Ti and cold rolling reduction on the mechanical property, electrical conductivity and bendiability of Cu-Ni-Si-P alloy was investigated. The hot rolled plates were solution treated at $980^{\circ}C$ for 1.5 h, quenched into water, cold rolled by 10% and 30% reduction in thickness, and then aged at $440{\sim}500^{\circ}C$ for 3, 4, 5 times. respectively. Cu-Ni-Si-P-x alloys cold rolled by 10 reduction before heat treatment have a good bendability compare to cold rolled by 30 reduction. Cu-3.4Ni-0.8Si-0.03P-0.1Ti shows the peak strength value of 759 MPa, an electrical conductivity of 39%IACS, an elongation of 10% and a hardness of 256 Hv aged at $440^{\circ}C$ for 6 hrs. Thus it is suitable for lead frame and connector.

• Journal of computational fluids engineering
• /
• v.19 no.1
• /
• pp.41-46
• /
• 2014

The aerodynamic drag of high-speed train has been calculated and the effect of bogie side fairing on the aerodynamic drag has been investigated. Computational Fluid Dynamics (CFD) simulation based on steady-state 3 dimensional Navier-Stokes equation has been conducted employing FLUENT 12 and the aerodynamic model of HEMU-430x, the Korean next generation high-speed train under development has been built using GAMBIT 2.4.6. Three types of bogie side fairing configuration, the proto-type without fairing, half-covered fairing to avoid the interference with the bogie frame and full-covered fairing have been adopted to the train model to compare the drag reduction effects of the bogie side fairing configurations and the numerical results yields that the bogie side fairing can reduce the aerodynamic drag of the 6-car trainset up to 7.8%. The aerodynamic drag coefficient of each vehicle as well as the flow structures around the bogie system have also been examined to analyze the reason and mechanism of the drag reduction by bogie side fairing.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.33 no.6
• /
• pp.515-520
• /
• 2020

The Ti₃SiC₂ MAX phase was synthesized by arc-melting process under three different processing times. We confirmed that the reaction between the TiC_X phase and Ti-Si liquid phase is important for the synthesis of the Ti₃SiC₂ MAX phase. Results suggest that the Ti₃SiC₂ MAX phase decomposed when the arc-melting time was greater than 80s. Herein, we aim to determine the detailed parameters for the reported arc-melting process, which can provide useful insights on the synthesis of the Ti₃SiC₂ MAX phase by arc-melting process. Furthermore, we compared the electrical characteristics and densities of the three samples.

• Journal of Powder Materials
• /
• v.30 no.6
• /
• pp.493-501
• /
• 2023

This study aimed to develop a solid self-nanoemulsifying drug delivery system (solid-SNEDDS) to enhance the formulation of ketoconazole (KTZ), a BCS Class II drug with poor solubility. Ketoconazole, which is insoluble above pH 3, requires solubilization for effective delivery. This SNEDDS comprises oil, surfactant, and co-surfactant, which spontaneously emulsify in the gastrointestinal tract environment to form nanoemulsions with droplet sizes less than 100 nm. The optimal SNE-vehicle composition of oleic acid, TPGS, and PEG 400 at a 10:80:10 weight ratio was determined based on the smallest droplet size achieved. This composition was used to prepare liquid SNEDDS containing ketoconazole. The droplet size and polydispersity index (PDI) of the resulting liquid SNEDDS were analyzed. Subsequently, solid-SNEDDS was fabricated using a spray-drying method with solidifying carriers such as silicon dioxide, crospovidone, and magnesium alumetasilicate. The physicochemical properties of the solid-SNEDDS were characterized by scanning electron microscopy and powder X-ray diffraction, and its solubility, droplet size, and PDI were evaluated. In particular, the solid-SNEDDS containing ketoconazole and crospovidone in a 2:1 weight ratio exhibited significantly enhanced solubility, highlighting its potential for improved medication adherence and dissolution rates.

• Information and Communications Magazine
• /
• v.34 no.6
• /
• pp.27-33
• /
• 2017

차량사물통신은 차량이 다양한 대상과 유무선 망을 이용해 정보를 주고 받는 기술을 의미한다. 차량사물통신을 이용하면 실시간으로 변화하는 교통 상황에 대해 개별 차량의 안정성을 크게 향상시킬 수 있다. 차량사물통신을 실현하기 위해서는 고도화 된 통신 기술들이 집약적으로 활용되어야 하며, 이러한 차량사물통신은 차세대 통신 시스템에서 각광받는 주요 기술이다. 본고는 차량사물통신을 위한 통신 기술 중 특별히 5G 통신에 관련된 세부 기술들을 소개한다. 먼저 차량사물통신을 위한 무선 통신에서 요구되는 기술적인 어려움에 대해 논의하고, 이를 바탕으로 차량사물통신에 대한 5G 통신 기술의 필요성에 관해 논의한다. 다음으로 차량사물통신을 위한 5G 통신의 세부기술들을 소개하고, 각 기술에 대한 기술적인 과제와 적용 시나리오에 대해 알아본다.

• International Journal of Aeronautical and Space Sciences
• /
• v.9 no.1
• /
• pp.76-84
• /
• 2008

This paper is mainly concerned with the vision-based attitude stabilization of a quad-rotor UAV. The methods for attitude control rely on computing the roll and pitch angles of the vehicle from a two-camera vision system. One camera is attached to the body-fixed x-axis and the other to the body-fixed y-axis. The attitude computation for the quad-rotor UAV is performed by image processing consisting of Canny edge and Hough line detection. A proportional and integral controller is employed for the attitude hold autopilot. In this paper, the quad-rotor UAV is modeled by 6-DOF nonlinear equations of motion that includes rotor aerodynamics with blade element theory. The performance of the proposed method is evaluated through 3D environmental numerical simulations.

• Journal of Surface Science and Engineering
• /
• v.56 no.6
• /
• pp.451-456
• /
• 2023

Transparent conducting films having a three layered structure of ZnO/Cu/ZnO (ZCZ) were deposited onto the glass substrates by using RF and DC magnetron sputtering at room temperature. The emissivity and opto-electrical properties of the films were investigated with a varying thickness(5, 10, 15 nm) of the Cu interlayer. With increasing the Cu thickness to 15 nm, the films showed a enhanced electrical properties. Although ZnO 30/Cu 15/ZnO 30 nm film shows a lower resistivity of 5.2×10^-5 Ωcm, it's visible transmittance is deteriorated by increased optical absorbtion of the films. In addition, X-ray diffraction patterns indicated that the insertion of Cu interlayer improve the grain size of ZnO films, which is favor for the electrical and optical properties of transparent conducting films. From the observed low emissivity of the films, it is concluded that the ZCZ thin films with optimal thickness of Cu interlayer can be applied effectively for the car's window coating materials.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.3 no.3
• /
• pp.1-11
• /
• 2000

This study was analysed the characteristis of traveling vehicles using the collected data by DGPS receiver. These data were checked the vehicle position in every 2 seconds and compared with GIS digital map after correcting the errors. These are compared travel speed and running speed overall and analysed the stopping vehicle in the middle of travelling. The stopping frequency, stopping time and stopping factor was analysed. The X, Y coordinates positioning of DGPS received data about stopping vehicle was analysed. DGPS receiver didn't position at first but positioned it exactly as time went. This study carried out the basic study about travel characteristics with digital map and DGPS received data. Few studies which applied advanced technology like GIS & DGPS have been executed. I hope that the more study will be executed in this traffic field.

• The Korean Journal of Emergency Medical Services
• /
• v.3 no.1
• /
• pp.20-32
• /
• 1999

The purpose of this retrospective research of 603 patients who were transferred to the emergency medical center of university hospital from 1 Jan, 1998 to 31 Jan, 1998 was making of basic data for emergency medical transfer system improvement countermeasure and the point at issue of overlapping reexamination ststus of patients transfered to emergency medical center of university hospital from 1,2 level hospital. The data analysis was done by SPSS, t-test, ANOVA, Pearson correlation. The results were as follows: 1. Male to female ratio was 1.7:1 and peak age group was patients over forties and under nine years of age(70.5%) 2. Traumatic patients were 17.8%, motor vehicle accident patients were 16.7% and Non-traumatic patients were 65.3%. Transferring hospital was divided into 2groups: primary hospital, secondary hospital. The majority was secondary hospital(73.3%). The result of symptom severity classification of patients transferred to 3rd emergency medical center was urgent patients 32.5%, emergency patients 33.58%, non-emergency patients 34.0% 3. Most highest score items amoung overlapping reexamination of patients transfered to emergency medical center of university hospital from 1,2 level hospital were CBC test, simple X-ray (0.93점), CBC test(0.97점), urin test(0.88점), chemistry test(0.94점), simple X-ray(0.98점), CT(0.42점), EKG(0.89점) amoung overlapping reexamination of motor vehicle accident patients were more higher reexamination score than traumatic patients and non-traumatic patients 4. CBC test(P<0.001), urin test(P<0.001), chemistry test(P<0.001), simple X-ray(P<0.001), CT(P<0.01), EKG(P<0.001) amoung overlapping reexamination of patients in 2 level hospital were more higher reexamination score than 1 level hospital patients 5. About symptom severity classification of patients transferred to 3rd emergency medical center, CBC test(P<0.001), urin test(P<0.001), chemistry test(P<0.001), simple X-ray(P<0.01), CT(P<0.001), EKG(P<0.001) amoung overlapping reexamination items in urgent patients were more higher reexamination score than other patients 6. Influencing variation for overlapping reexamination in hospital was CBC test(P<0.001), CT (P<0.001), MRI (P<0.05).