Research has been conducted on acoustic metamaterials that control the transmission characteristics of reflected and refracted waves using phase delay by resonators. Using one-dimensional theory, the phase delay equations for the 1/4 wavelength and Helmholtz resonator are presented. These one-dimensional analysis results are compared with the results predicted by three-dimensional FEM. The advantages and disadvantages of 1/4 wavelength and Helmholtz resonator were confirmed in implementing phase delay. An acoustic metamaterial with a refraction angle of 30° was manufactured using multiple tubes and then the sound pressure distribution was measured. A relatively large sound pressure was measured at the target position of 30°, which was compared with the 3D FEM analysis results. Simulations confirmed that a phase delay range closer to 2π was more effective in refraction, but varying the number of resonators was found to have minimal impact on which additional research is needed for generalization.

Fluorine-doped tin oxide (FTO) has been used as a representative transparent conductive oxide (TCO) in various optoelectronic applications, including light emitting diodes, solar cells, photo-detectors, and electrochromic devices. The FTO plays an important role in providing electron transfer between active layers and external circuits while maintaining high transmittance in the devices. Herein, we report the effects of substrate rotation speed on the electrical and optical properties of FTO films during ultrasonic spray pyrolysis deposition (USPD). The substrate rotation speeds were adjusted to 2, 6, 10, and 14 rpm. As the substrate rotation speed increased from 2 to 14 rpm, the FTO films exhibited different film morphologies, including crystallite size, surface roughness, crystal texture, and film thickness. This FTO film engineering can be attributed to the variable nucleation and growth behaviors of FTO crystallites according to substrate rotation speeds during USPD. Among the FTO films with different substrate rotation speeds, the FTO film fabricated at 6 rpm showed the best optimized TCO characteristics when considering both electrical (sheet resistance of 13.73 Ω/□) and optical (average transmittance of 86.76 % at 400~700 nm) properties with a figure of merit (0.018 Ω-1).

췌장낭성병변은 최근 영상기술의 발전으로 우연히 발견되는 비율이 점차 증가하고 있으며, 유병률은 복부컴퓨터단층촬영을 시행한 사람에서 많게는 13.5%까지 보고되었다. 그러나 췌장낭성질환의 정확한 진단은 양성에서 악성 질환까지 다양한 형태로 보일 수 있어 영상학적 진단만으로는 매우 어렵다. 초음파내시경은 췌장낭성병변을 비교적 정확하게 진단하고 치료를 결정하는 데 매우 중요한 도구로 사용된다. 그러나 내시경 초음파는 악성으로 진행 가능한 점액성 췌장낭종과 다른 췌장낭종질환을 구분하는 데 정확도가 65-75%에 불과하다. 인공지능은 대장암, 폐암, 유방암과 같은 여러 종류의 암 진단의 정확도를 향상시키는 데 효과적인 도구로 사용되고 있으며, 최근 연구에서는 췌장낭성병변에서도 점액성 종양과 비점액성 종양을 구분하고 악성으로 진행 위험도를 평가하는 데 도움이 되는 것으로 보고되고 있다. 인공지능의 적용은 영상분석에도 국한되지 않고 최근에는 췌장낭종의 액체 분석, 유전자 분석, confocal laser endomicroscopy 등 다양한 분야에서 활용되고 있으며 기대되는 연구 결과를 발표하고 있다. 인공지능은 의료 분야에서 아직 시작단계에 있어, 임상에 적용하기 위해 적절한 알고리즘을 개발하는 데에는 개발자들의 큰 노력이 필요하다. 그러나 이러한 기술은 앞으로 췌장낭종 병변을 보다 정확하게 진단하고 효과적이고 효율적으로 관리하는 데에 도움을 줄 수 있는 잠재력을 가지고 있다고 하겠다.

3D printing is widely used in product development and prototype manufacturing, and is expected to become universal across various industries with the development of 3D printing-related technologies. However, parts made by Fused Deposition Modeling(FDM) 3D printing using the commonly used stacking manufacturing process, show low tensile strength and hardness. The decreased mechanical properties of these parts limit their use as structural elements. In this study, we aim to investigate the relationship between ultrasonic treatment of PLA parts produced by FDM 3D printing and their mechanical properties. Specifically, we analyze the effects of ultrasonic annealing on the mechanical properties of PLA parts using the tensile test specimen.

Since the development of endoscopic ultrasound (EUS), the importance in the using EUS in pancreas and biliary tree has gradually increased. In order to properly observe the pancreas and biliary tree in EUS, it is necessary to learn landmark structures at each location, such as the stomach and duodenum, and to learn the positional relationship between them and normal structures. In this article, we will deal with the examination method at each position of the linear and radial EUS and reveal the normal EUS image.

Lithium lanthanum titanium oxide (LLTO) is a promising ceramic electrolyte because of its high ionic conductivity at room temperature, low electrical conductivity, and outstanding physical properties. Several routes for the synthesis of bulk LLTO are known, in particular, solid-state synthesis and sol-gel method. However, the extremely low ionic conductivity of LLTO at grain boundaries is one of the major problems for practical applications. To diminish the grain boundary effect, the structure of LLTO is tuned to nanoscale morphology with structures of different dimensionalities (0D spheres, and 1D tubes and wires); this strategy has great potential to enhance the ion conduction by intensifying Li diffusion and minimizing the grain boundary resistance. Therefore, in this work, 0D spherical LLTO is synthesized using ultrasonic spray pyrolysis (USP). The USP method primarily yields spherical particles from the droplets generated by ultrasonic waves passed through several heating zones. LLTO is synthesized using USP, and the effects of each precursor and their mechanisms as well as synthesis parameters are analyzed and discussed to optimize the synthesis. The phase structure of the obtained materials is analyzed using X-ray diffraction, and their morphology and particle size are analyzed using field-emission scanning electron microscopy.

강풍, 폭우 등 이상기후의 대형화와 빈도 증가로 인해 나무가 부러지거나 쓰러지는 훼손이 증가하고 있으나 나무 내부의 공동, 부후 등 구조적 결함은 육안조사로 판별이 어렵기 때문에 예측을 통한 사전대응에 한계가 있다. 비파괴 음파단층촬영은 나무에 미치는 물리적 훼손을 최소화하면서 내부결함을 추정하는 방법으로 내부결함 진단에 효율적이 나 수종별 정확도에 차이가 발생하기 때문에 현장적용 전 측정결과의 신뢰성 분석이 선행되어야 한다. 이번 연구는 우리나라 대표 수종인 소나무와 은행나무 노거수를 대상으로 음파단층촬영의 신뢰성 검증을 위해 침입성 드릴저항 측정을 교차 적용하여 목재 내부결함을 측정하고 평가결과를 비교하였다. 두 집단 간 결함부 측정 평균값에 대한 t검정 결과 소나무는 통계적으로 유의한 차이가 없는 반면, 은행나무는 유의성에 차이가 있었다. 선형회귀분석 결과 두 수종 모두 드릴저항그래프의 결함이 증가할 때 음파단층영상 결함이 증가하는 양의 상관관계를 보였다.

담낭암은 드물지만 치명적인 악성 종양으로 초기에는 증상이 없어 대부분의 담낭암이 늦게 진단되고, 급속하게 인접 장기로 전이되기 때문에 예후가 불량하다. 따라서 담낭암을 조기에 발견하는 경우는 드물고, 담낭담석이나 용종으로 수술적 절제를 시행한 후 우연히 발견되는 때가 대부분이다. 저자들은 급성 무결석 담낭염 환자에서 초음파 내시경을 통해 비교적 조기에 담낭관암을 발견하여 성공적으로 치료할 수 있었던 증례를 경험하였다. 이에 문헌고찰과 함께 보고한다.

This study demonstrates the effect of the compaction pressure on the microstructure and properties of pressureless-sintered W bodies. W powders are synthesized by ultrasonic spray pyrolysis and hydrogen reduction using ammonium metatungstate hydrate as a precursor. Microstructural investigation reveals that a spherical powder in the form of agglomerated nanosized W particles is successfully synthesized. The W powder synthesized by ultrasonic spray pyrolysis exhibits a relative density of approximately 94% regardless of the compaction pressure, whereas the commercial powder exhibits a relative density of 64% under the same sintering conditions. This change in the relative density of the sintered compact can be explained by the difference in the sizes of the raw powder and the densities of the compacted green body. The grain size increases as the compaction pressure increases, and the sintered compact uniaxially pressed to 50 MPa and then isostatically pressed to 300 MPa exhibits a size of 0.71 m. The Vickers hardness of the sintered W exhibits a high value of 4.7 GPa, mainly due to grain refinement.