• 대한방사선기술학회지:방사선기술과학
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• 제41권1호
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• pp.33-38
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• 2018

There are limits to check the lesion as inserting a breast implant patients. So the application of BSGI based on Nuclear Medicine examination has increased. In this study, therefore we confirmed the effect of the image applying to breast implants in Breast Specific Gamma Imaging. We utilized Dilon 6800 BSGI scanner and developed the phantom. The self-development phantom was a rectangular shape of $230{\times}190{\times}80mm$ size and had 5 spheres which consisted of diameters of 10, 13, 17, 22, 28 mm in central part. We injected $^{99m}TcO_4$ into the self-development phantom in the proportion of four to one and made each additional phantom filled with 0.9 % sodium chloride, silicon and paraffin. Each additional phantom was placed between detector and self-development phantom. Each image was acquired five times depending on the type and thickness of the additional phantom. Statistical analysis with SPSS ver.18 was applied. In the test of variation according to the thickness of all additional phantoms, as the phantoms which 0.9% sodium chloride, silicon and paraffin increased, the attenuation variation was higher(P<0.005). There was no significant difference in the attenuation variation and the quality of image for type of the additional phantom. Therefore, if the effect of the image applying to breast implants in Breast Specific Gamma Imaging is confirmed, the higher diagnostic value can be achieved.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1633-1637
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• 2019

While considering the photon attenuation coefficient (${\mu}$) and its related parameters for photons shielding, it is necessary to account for its transmitted and reflected photons energy spectra and dose contribution. Monte Carlo simulation was used to study the efficiency of clay ($1.99g\;cm^{-3}$) as a shielding material below 150 keV photon. Am-241 gamma source and an X-ray of 150 kVp were calculated. The calculated value of ${\mu}$ for Am-241 is higher within 5.61% compared to theoretical value for a single-energy photon. The calculated half-value layer (HVL) is 0.9335 cm, which is lower than that of ordinary concrete for X-ray of 150 kVp. A thickness of 2 cm clay was adequate to attenuate 90% and 85% of the incident photons from Am-241 and X-ray of 150 kVp, respectively. The same thickness of 2 cm could shield the gamma source dose rate of Am-241 (1 MBq) down to $0.0528{\mu}Sv/hr$. For X-ray of 150 kVp, photons below 60 keV were significantly decreased with 2 cm clay and a dose rate reduction by ~80%. The contribution of reflected photons and dose from the clay is negligible for both sources.

• International Journal of Naval Architecture and Ocean Engineering
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• 제3권4호
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• pp.242-253
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• 2011

Skin frictional drag reduction efficiency of "stiff" compliant coating was investigated in a wind tunnel experiment. Flat plate compliant coating inserts were installed in a wind tunnel and the measurements of skin frictional drag and velocity field were carried out. The compliant coatings with varying viscoelastic properties had been prepared using different composition. In order to optimize the coating thickness, the most important design parameter, the dynamic viscoelastic properties had been determined experimentally. The aging of the materials (variation of their properties) during half a year was documented as well. A design procedure proposed by Kulik et al. (2008) was applied to get an optimal value for the coating thickness. Along with the drag measurement using the strain balance, velocity and pressure were measured for different coatings. The compliant coatings with the thickness h = 7mm achieved 4~5% drag reduction within a velocity range 30~40 m/s. The drag reduction mechanism of the attenuation of turbulence velocity fluctuations due to the compliant coating was demonstrated. It is envisioned that larger drag reduction effect is obtainable at higher flow velocities for high speed trains and subsonic aircrafts.

• 한국의학물리학회지:의학물리
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• 제18권3호
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• pp.172-178
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• 2007

가로축 방식이 아닌 세로축 방식으로 초음파를 송수신하여 골밀도 측정을 하는 장치를 개발하였다. 반사된 초음파의 시간 차이를 이용하는 speed of sound (SOS) 방식은 주파수 차이를 비교하는 broadband ultrasound attenuation (BUA) 방식에 비하여 더욱 정확한 결과를 얻을 수 있다. 측정부위의 경우 엄지는 초음파 수신율이 좋으나 피부 두께의 변위가 많은 단점을 고려하여 중지를 채택하여 정확성을 높였다. SOS 방식만을 사용하여 측정한 결과 기존의 dual-energy x-ray absorptiometry (DEXA) 방식과 비교하여 거의 동일한 정확도를 얻을 수 있었다.

• 한국자기학회지
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• 제1권2호
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• pp.49-54
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• 1991

본 연구에서는 복합 ferroxplana 전파흠수체의 X-band에서의 재료정수와 전파흡수특성과의 상관관계를 규명하였다. Ferroxplana 분말과 지지재인 고무와의 함량비(F/R)가 증가함에 따라 ${\mu}_{r}'$은 감소하며, ${\mu}_{r}"$은 증가하였다. 전파흡수체의 두께가 증가함에 따라 최대반사감쇠량이 얻어지는 주파수 가 낮은쪽으로 이동하였으며, 흡수체의 두께가 2.6mm인 경우에는 대역폭이 우수하였고, 두께가 3.2mm인 경우에는 반사감쇠량이 우수하였다. 복합 ferroxplana 전파흡수체의 재료 정수를 광대역화에 요구되는 전파흡수체의 재료정수영역에 적용하여 전파흡수특성을 정량적으로 도출하였으며 이러한 재료 정수영역의 설정은 광대역 ferrite 전파흡수체의 설계지침으로 활용이 가능하다.

• 대한전자공학회논문지
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• 제18권3호
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• pp.25-34
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• 1981

전하결합소자(charge coupled device)의 제작에 필요한 다중전극구조를 실현하기 위하여 알루미늄양극산화방법을 실험적으로 조사하였다. 양극산화의 전해질용액으로 2% ammonium tartrate를 사용하고, 산화전압을 30∼35 volt로 하여 2시간 정도 산화할 때 형성되는 Al2O3의 두께는 400∼500A이었고 절연파괴전압은 30volt 정도였다. 이와 같은 Al2O3의 성질을 이용하여 CCD transversal 저역여파기를 제작하였다. 17개의 tap coefficient를 갖는 저역파기의 stop band attenuation은 약 22dB 이었으며 사용가능한 주파수 범위는 3 KHz로부터 100KHz까지였다.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1364-1371
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• 2018

An extensive investigation of photon interaction properties has been made for $Zn_xTe_{100-x}$ alloys (where x = 5, 20, 30, 40, 50) to explore its possible use in sensing and shielding gamma radiations. The results show better and stable response of ZnTe alloys for various photon interaction properties over the wide energy range, with an additional benefit of ease in fabrication due to lower melting points of Zn and Te. Mass attenuation coefficient values show strong dependence on photon energy as well as composition. Effective atomic number has maximum value for $Zn_5Te_{95}$ and lowest for $Zn_{50}Te_{50}$ in the entire energy region. The alloy sample with maximum $Z_{eff}$ shows minimal value of $N_e$ and vice versa. Mean free path follows inverse trend as observed for mass attenuation coefficient. The exposure and energy absorption buildup factors depend upon photon energy, penetration thickness and composition (effective atomic number) of $Zn_xTe_{100-x}$ alloys. It finds its application for sensing and shielding from highly energetic and highly penetrating photons at sites where radioactive materials were used and visibility of material is not a big constraint. Further, energy down conversion property of ZnTe alloys with subsequent emission in green band suggests its potential use in sensing gamma photons.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2190-2194
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• 2024

The study investigates the dose-dependent direct X-ray sensing characteristics of Brucinium benzilate (BB) and N-acetylglycine (NAG) organic crystals. BB and NAG were prepared as a slurry and deposited as a thick film on a patterned metal electrode. The X-ray induced photocurrent response was examined for various exposure doses using an intraoral pulsed 70 keV X-ray machine connected to a source meter. Subsequently, the morphological properties and thickness of the thick films were analyzed using scanning electron microscopy (SEM). At a photon energy of 70 keV, the attenuation coefficient values for NAG and BB crystals were determined to be approximately 0.181 and 0.178 cm²/g, respectively. The X-ray stopping power of the crystals was measured using a suniray-2 X-ray imaging system. To evaluate the responsiveness of the sensors, the photocurrent sensitivity and noise equivalent dose rate (NED) were calculated for both thick films. The findings demonstrated a noteworthy capability of sensing low doses (mGy), thereby suggesting the potential application of these organic materials in X-ray sensor development.

• Nuclear Engineering and Technology
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• 제56권7호
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• pp.2570-2575
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• 2024

The study aims to develop a novel, lead-free, flexible and lightweight composite shielding material against ionizing radiation. For this, it was used bismuth oxide (Bi₂O₃) in RTV-2 silicon matrix. The shielding tests were carried out in both diagnostic X-ray energies and intermediate gamma-ray energy range of up to 662 keV to determine the radiation attenuation properties of this material in terms of attenuation ratio, half value layer, tenth value layer, mean free path and lead equivalency of samples in weight of 30%, 40%, 50% in Bi₂O₃. In the diagnostic X-ray energy range, half value layer, tenth value layer and lead equivalency (in mm Pb) of the produced samples were measured at 80 and 100 kVp narrow beam conditions according to the requirements of EN IEC 61331-1 standard. The results show that lead equivalent values of the produced novel sheets was measured to be 0.16 mm Pb, corresponding to a 6 mm thickness of the flexible sample when it contains 30% wt. Bi₂O₃ in RTV matrix. The experimental findings for durability and flexibility also indicated that this new RTV-based flexible, lead -free shielding composite can be used safely for especially for manufacturing aprons, garments and thyroid guards used in mammography, radiology, nuclear medicine and dental applications in practice.

• 한국해양공학회지
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• 제26권3호
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• pp.13-19
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• 2012

Recently, as the importance of the interior noise in a ship cabin has risen, ship builders have becomeconcerned about the use of noise reduction panels to reduce cabin noise. The results of previous researches have been based on analytical and experimental methods using simple sandwich panels. However, panel structures are becoming more complex to improve the transmission loss. Thus, researches that analyze the transmission loss of a panel are reaching the limit of study. This paper reports on research that was performed to determine the sound transmission characteristics of multi-complex panels applicable to high value-added vessels. It presents comparisons between analytical methods and experimental results by using a mini-reverberant chamber with components of sound attenuation panels, including the core and surface materials. The sound transmission loss of multi-complex panels are also analyzed in terms of the influences of the inside perforate plates and air gap thickness on the attenuation. Finally, the multi-complex panel with the highest noise attenuation is proposed based on the analysis results and experimental results in mini-reverberant chamber, which wereverified using a real-size reverberant chamber.