• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2006.05a
• /
• pp.36-40
• /
• 2006

An analysis is made of flow and rocket motion during a supersonic separation stage of air-launching rocket(ALR) from the mother plane. Three-dimensional compressible Navier-Stokes equations is numerically solved to analyze the steady/unsteady flow field around the rocket which is being separated from the mother plane configuration(F-4E Phantom). The simulation results clearly demonstrate the effect of shock-expansion wave interaction between the rocket and the mother plane. To predict the behavior of the ALR according to the change of the C.G., three cases of numerical analysis are performed. As a result, a design-guideline of supersonic air-launching rocket for the safe separation is proposed.

• 유체기계공업학회:학술대회논문집
• /
• 2006.08a
• /
• pp.423-426
• /
• 2006

An analysis is made of flow and rocket motion during a supersonic separation stage of air-launching rocket(ALR) from the mother plane. Three-dimensional compressible Navier-Stokes equations is numerically solved to analyze the steady/unsteady flow field around the rocket which is being separated from the mother plane configuration(F-4E Phantom). The simulation results clearly demonstrate the effect of shock-expansion wave interaction between the rocket and the mother plane. To predict the behavior of the ALR according to the change of the C.G., three cases of numerical analysis are performed. As a result, a design-guideline of supersonic air-launching rocket for the safe separation is proposed.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.18 no.2
• /
• pp.17-21
• /
• 2014

Purpose With the recent rise of social issue regarding radiation exposure, attention to medical radiation use has been placed under a great spotlight. During PET-CT examination, generally about 40% more of $^{18}F$-FDG is used than EANM recommendation. While maintaining the diagnostic test result, we hope to find optimal injection dose to minimize the $^{18}F$-FDG in patients by utilizing the latest PET-CT scanner which is equiped with the newest technology. Materials and Methods During this experiment, the Biograph Truepoint 40 (siemens, USA) installed in 2007 and mCT 64 (siemens, USA) installed in 2011 were used and evaluated NECR (noise-equivalent counting rate) by using a scatter phantom. For the image quality evaluation of each scanner, we injected 3.7, 4.44 and 5.18 MBq/kg of $^{18}F$-FDG in NEMA IEC Body Phantom and also evaluated SNR between two scanners by using the data acquired at 60, 70, 80, 90, 100, 110 and 120 sec per bed. For the clinical evaluation, actual data of patients who were injected $^{18}F$-FDG 3.7, 4.44, 5.18 MBq/kg were used to compare SNR and draw a final result. Results As a result, mCT 64 peak NECR value was 1.65e+005, which is 10% higher than Turepoint 40. SNR values using the IEC body phantom was 17.9%, 17.4% and 17.1% higher in $^{18}F$-FDG 3.7 MBq/kg, 4.44 MBq/kg and 5.18 MBq/kg. In clinical patients, SNR values of the image mCT 64 was 16.5, which is 25% higher than Turepoint 40 scanner. Conclusion To draw a conclusion from the test result of this experiment, the same quality of SNR could be attained even with 10% reduced injection dose, if when the duration is extended by 10 sec/bed. This optimal result was possible due to enhanced equipment. The NECR (one of the equipment's performance assessment criteria for the scanner) increased by 10% and the SNR (one of the image quality assessment criteria) also increased by 17.5%. Therefore, we can expect to reduce the injection dose without deterioration of image quality. In consequence, it will also help to decrease the patient's anxiety of the radiation exposure.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.6
• /
• pp.474-482
• /
• 2007

An analysis is made for flow and rocket motion during a supersonic separation stage of an air-launching rocket(ALR) from the mother plane. Three-dimensional compressible Navier-Stokes equations are numerically solved to analyze the steady/unsteady flow fields around the rocket which is being separated from the mother plane configuration(F-4E Phantom). Simulation results clearly demonstrate the effect of shock-expansion wave interaction around both of the rocket and the mother plane. To predict the behavior of the ALR by the change of the center-of-gravity, three cases of numerical analysis are performed. As a result, a design-guideline of supersonic air-launching rockets for safe separation is proposed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2000.04a
• /
• pp.12-12
• /
• 2000

우리 나라는 일본상공의 비행을 피하기 위하여 제주도와 남해안 근해로 발사장 선정이 국한되는 지정학적인 위치로 볼 때 발사장 선택에 제한이 없는 공중발사에 대한 가능성 연구가 필요한 시점에 있다. 본 연구는 우리 나라와 같은 분단 된 특수상황 그리고 지정학적 위치에서의 발사장을 고려한 우주 발사체 개발의 필요성에 따라 F-4에 장착 가능한 3단형 공중발사 로켓을 설계하고 1/3의 축소 모형을 제작하였다. 2kg의 payload를 갖는 발사체의 1단은 LRM ( Lox/kerosene )을 사용하였고 2, 3단은 SRM ( HTPB/AP/Al )을 사용하였으며 발사고도는 11-l2km 상공에서 F-4에 의해서 발사되고 31km지점에서 1단 분리가 이루어지며 62km지점에서 2단 분리와 nose fairing을 분리하게 된다. 전장은 6.85m 이며 전체 무게는 560.6kg 이고 전체 발사체 시스템의 CAD 도면은 아래 그림 1과 같이 주어져 있다. 그림 2에서는 F-4E phantom의 장착성을 검토해 본 결과 장착이 가능함을 알 수 있었으며 추진제 양의 감소로 크기를 대폭 줄일 수 있었다.

• Journal of Radiation Protection and Research
• /
• v.24 no.4
• /
• pp.205-213
• /
• 1999

Effective dose conversion coefficients from unit activity radionuclides contaminated on the ground surface were calculated by using MCNP4A rode and male/female anthropomorphic phantoms. The simulation calculations were made for 19 energy points in the range of 40 keV to 10 MeV. The effective doses E resulting from unit source intensity for different energy were compared to the effective dose equivalent $H_E$ of previous studies. Our E values are lower by 30% at low energy than the $H_E$ values given in the Federal Guidance Report of USEPA. The effective dose response functions derived by polynomial fitting of the energy-effective dose relationship are as follows: $f({\varepsilon})[fSv\;m^2]=\;0.0634\;+\;0.727{\varepsilon}-0.0520{\varepsilon}^2+0.00247{\varepsilon}^3,\;where\;{\varepsilon}$ is the gamma energy in MeV. Using the response function and the radionuclide decay data given in ICRP 38, the effective dose conversion coefficients for unit activity contamination on the ground surface were calculated with addition of the skin dose contribution of beta particles determined by use of the DOSEFACTOR code. The conversion coefficients for 90 important radionuclides were evaluated and tabulated. Comparison with the existing data showed that a significant underestimates could be resulted when the old conversion coefficients were used, especially for the nuclides emitting low energy photons or high energy beta particles.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.20 no.2
• /
• pp.21-26
• /
• 2016

Purpose Because of many advantages, PET-CT Scanners generally use CT Data for attenuation correction. By using CT based attenuation correction, we can get anatomical information, reduce scan time and make more accurate correction of attenuation. However in case metal artifact occurred during CT scan, CT-based attenuation correction can induce artifacts and quantitative errors that can affect the PET images. Therefore this study infers true SUV of metal artifact region from attenuation corrected image count -to- non attenuation corrected image count ratio. Materials and Methods Micro phantom inserted $^{18}F-FDG$ 4mCi was used for phantom test and Biograph mCT S(40) is used for medical test equipment. We generated metal artifact in micro phantom by using metal. Then we acquired both metal artifact region of correction factor and non metal artifact region of correction factor by using attenuation correction image count -to- non attenuation correction image count ratio. In case of clinical image, we reconstructed both attenuation corrected images and non attenuation corrected images of 10 normal patient($66{\pm}15age$) who examined PET-CT scan in SNUH. After that, we standardize several organs of correction factor by using attenuation corrected image count -to- non attenuation corrected count ratio. Then we figured out metal artifact region of correction factor by using metal artifact region of attenuation corrected image count -to- non attenuation corrected count ratio And we compared standard organs correction factor with metal artifact region correction factor. Results according to phantom test results, metal artifact induce overestimation of correction factor so metal artifact region of correction factors are 12% bigger than the non metal artifact region of correction factors. in case of clinical test, correction factor of organs with high CT number(>1000) is $8{\pm}0.5%$, correction factor of organs with CT number similar to soft tissue is $6{\pm}2%$ and correction factor of organs with low CT number(-100>) is $3{\pm}1%$. Also metal artifact correction factors are 20% bigger than soft tissue correction factors which didn't happened metal artifact. Conclusion metal artifact lead to overestimation of attenuation coefficient. because of that, SUV of metal artifact region is overestimated. Thus for more accurate quantitative evaluation, using attenuation correction image count -to-non attenuation correction image count ratio is one of the methods to reduce metal artifact affect.

• 한국전산유체공학회:학술대회논문집
• /
• 2005.10a
• /
• pp.255-259
• /
• 2005

An analysis is made of flow and rocket motion during a supersonic separation stage of air-launching rocket from the mother plane. Three-dimensional Euler and Navier-Stokes equations are numerically solved to analyze the steady/unsteady flow field around the rocket which is being separated from two cases of mother plane configuration: one is an idealized ogive-cylinder body and the other is a real F-4E Phantom. The simulation results clearly demonstrate the effect of shock-expansion wave interaction between the rocket and the mother plane. As a result, a design-guideline of supersonic air-launching rocket for the safe separation is proposed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2003.10a
• /
• pp.20-24
• /
• 2003

The feasibility of hybrid motor as a first stage of the air launch vehicle is investigated, and the result shows the hybrid motor can replace the solid motor. Optimal design study has been performed for the hybrid motor as a first stage of nanosat air launch vehicle. The first stage hybrid motor of the nanosat air launch vehicle, which uses the F-4E Phantom as a mother plane is designed for given mission requirements. Selected design variables are the number of ports, the initial oxidizer flux, the combustion chamber pressure, and the nozzle expansion ratio. The design results show that a hybrid motor can be successfully applicable to very small air launch vehicles which have severe physical constraints of length and diameter imposed by the mother plane.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.32 no.4
• /
• pp.53-60
• /
• 2004

Optimal design of the hybrid motor has been performed for the first stage of nanosat air launch vehicle using F-4E Phantom as mother plane. Selected design variables are number of ports, the initial oxidizer flux, the combustion chamber pressure, and the nozzle expansion ratio. GBM(Gradient Based Method) and GA(Genetic Algorithm) are simultaneously used to compare the versatility of each algorithm for optimal design in this problem. Also, two objective functions of motor weight, and length are treated separatedly in the optimization to study how the objective function can affect the optimal design. The design results show that the optimal design can be successfully achieved either using GBM or GA regardless of the choice of the objective function; motor weight or length. And nanosat air launch vehicle which has total mass of 704.74kg, and length of first stage 3.74m is designed.