• 비파괴검사학회지
• /
• 제19권3호
• /
• pp.207-216
• /
• 1999

일반적인 하나 또는 두개의 압전소자를 사용하는 트랜스듀서에 비하여 다수의 압전소자를 사용하는 어레이 트랜스듀서는 각 압전소자에 가해지는 펄스의 지연시간을 제어함으로써 초음파 빔을 임의의 지점에 집속시킬 수 있고 기계적 구동없이 임의의 방향으로 조향시켜 실시간 주사를 할 수 있는 장점이 있다. 페이즈드 어레이 트랜스듀서의 설계조건은 압전소자의 수. 압전소자의 크기 그리고 압전소자 사이 간격 등 여러가지가 있으며, 본 연구에서는 그 중에서 압전소자수의 변화에 따른 초음파 빔의 특성을 호이겐스의 원리를 이용한 수평횡파의 시뮬레이션을 통하여 평가하였다. 그 결과 초음파 빔은 조향각이 증가 할수륵 음압이 감소하며, 초음파 빔 특성도 점차적으로 분산됨을 알 수 있었고 또한, 초점거리가 증가할수록 초점에서의 집속효과는 감소하고, 압전소자의 수가 증가되면 집속효과는 향상됨을 알 수 있었다.

• 한방비만학회지
• /
• 제12권2호
• /
• pp.28-43
• /
• 2012

Objectives: The aim of the study was to investigate the efficacy of Boiogito for obesity. We examined the efficacy of Boiogito for obese patients and we expected the reaction of Boiogito would vary according to the single nucleotide polymorphism(SNPs). Methods: 111 subjects(body mass index${\geq}25m/kg^2$) were recruited and randomized to receive Boiogito(n=55) or Placebo(n=56) for 8weeks. Anthropometric factors, serum lipid profile, glucose, blood pressure(BP), pulse rate, resting metabolic rate and Korean version of obesity-related quality of life(KOQOL) scale measured at baseline and 8weeks. SNPs(${\beta}3$-adrenergic receptor(ADRB3), G protein ${\beta}3$(GNB3), peroxisome proliferator activated receptor gamma 2 gene(PPAR-${\gamma}2$), uncoupling protein(UCP2)) were conducted at baseline. Adverse reactions and safety outcome variables were also checked during trials. Results: Both groups showed significant improvement on obesity after treatment. Boiogito group decreased triglyceride than did control group and improved KOQOL. Boiogito showed a significant higher efficacy in C/T and T/T genotype of GNB3 gene / in Trp64 and Arg64 genotype of ADRB3 gene / in D/D genotype of UCP2 gene / in Pro/Pro genotype of PPAR-${\gamma}$ gene. Conclusions: Boiogito promoted obesity indexes without severe adverse reactions and proved its safety. Pharmacogenetical studies of Boiogito on obesity could be a effective method for the individualized treatment and prevention of obesity.

• 인간식물환경학회지
• /
• 제24권5호
• /
• pp.545-550
• /
• 2021

Background and objective: With increasing land use intensity in urban areas, apartment buildings have been recognized as a typical type of urban residence. In this study, the impacts of different views through a window on health-related responses were investigated using psychological and physiological parameters. Methods: Photos of three different types of views taken on low (2-12 m), middle (28-35 m), and high (over 54 m) floors of dense apartment building areas were used as visual stimuli. Twenty-two healthy adults participated in the indoor experiment. Semantic differential methods and profile of mood states were used as psychological tools. Autonomic nervous activity was evaluated using blood pressures, pulse rate and heart rate variability (HRV). Results: Analytic data showed different characteristics of psychological and physiological outcomes in three different apartment views. In the analysis of psychological parameters, significantly negative responses to the views on middle floors were found in the subscales of tension-anxiety and anger-hostility, compared to low floors. Significantly positive scores in the subscale of vigor were found on low floors with abundance of vegetation and high floors with a view of the sky. A significantly increased value of HF was found on low floors (2,294.96 ± 169.79), compared to the middle(1,553.45 ± 84.66) and high (1,523.02 ± 70.49) floors. Despite the high scores in openness and vigor, high floor views showed significantly higher LF/HF values (1.83 ± 0.09), the indicator of the sympathetic nervous system, than low (1.30 ± 0.07) and middle floor views (1.34 ± 0.06), which might be related to the unconscious fear of heights. Conclusion: Views from different heights in an apartment building can affect the psychological states of residents. Green space through the window may have a positive health outcome by reducing physiological stress.

• 센서학회지
• /
• 제31권6호
• /
• pp.423-427
• /
• 2022

A pressure sensor that mimics the sensing ability of human skin has emerged as high-profile technology because it shows remarkable applications in numerous fields such as robotics, human health monitoring, and artificial prosthetics. Whereas recent pressure sensors have achieved high sensitivity similar to that of human skin, they still show limited detection bandwidth. Moreover, once these e-skin are fabricated, their sensitivity and stiffness are fixed; therefore, they can be used for only limited applications. Our study proposes a new adaptive pressure sensor built with uniform gallium microdroplet-elastomer composite. Based on the phase transition of gallium microdroplets, the proposed sensor undergoes mode transformation, enabling it to have a higher sensitivity and wider detection bandwidth compared with those of human skin. In addition, we succeeded in extending a single adaptive pressure sensor to sensor arrays based on its high uniformity, reproducibility, and large-scale manufacturability. Finally, we designed an adaptive e-skin with the sensor array and demonstrated its applications on health monitoring tasks including blood pulse and body weight measurements.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
• /
• pp.94-100
• /
• 2002

During the last years, great progress has been made in the fields of welding power sources and filler materials for the MIG-welding of magnesium alloys. This advice resulted in a better welding process, md, therefore, in highly improved welding results. Furthermore the gap between short-circuiting- and spray-arc-trunsfer could be closed by the triggered short-circuiting- and the short-circuiting-arc with pulse overlay. A crucial contribution to the welding process is the energy input into the filler material. Many problems result from the physical properties of magnesium, for instance its narrow interval between melting point 600$^{\circ}C$ and vaporization point 1100$^{\circ}C$. The energy input into the filler material has to be regulated in such a way that the wire will melt but not vaporize. For th is reason, special characteristics of power sources hue been examined and optimized with the help of high-speed-photographs of the welding process with particular consideration of the drop detachment. An important improvement of the weld seam profile has been achieved by using filler material of only 1.2 mm in diameter. The experiments hue been made with 2.5 mm thick extruded profiles of AZ31 and AZ6l. The results of tensile testing showed strength values of 80 to 100% of the base metal. B ending angles up to 60$^{\circ}$ have been reached. The fatigue strength under reversed bending of the examined magnesium alloys after welding reaches 50% of the strength of the base metal. When the seam reinforcement is ground of the fatigue strength can be raised up to 75% of the base metal.

• Investigative Magnetic Resonance Imaging
• /
• 제5권1호
• /
• pp.38-42
• /
• 2001

2D TOF혈관조영술에서 presaturation RF펄스를 사용하여 정맥피에서 나오는 MR신호를 제거하고 얻은 동맥 angiogram에는 band형태로 동맥이 끊어져 나타나는 현상이 자주 보인다. 일부 동맥에서 피의 흐름은 한 심장 주기 동안에 3번의 펄스를 갖는데, 이 중 가운데 펄스는 짧은 기간 동안 역류를 한다. 이 역류하는 동맥피는 정맥피와 같은 방향이기 때문에 presaturation RF펄스에 의해 정맥피 처럼 saturation이 되어서 imaging slice로 흘러 들어가게 될 수 있다. 특히 이러한 경우가 phase encoding step의 dc 부근에서 발생하게 되면 그 때의 단면 영상에서 동맥이 강조가 될 수 없게 되어, 결과적으로 angiogram에는 그 단면을 지나는 동맥의 신호가 없어서 band 형태로 핏줄이 끊어져 나타나게 된다. Imaging slice와 saturation band와의 간격을 변화 시켜 가면서 angiogram을 얻어 봄으로서 이러한 현상을 실험적으로 확인하였다 나아가 saturation band를 rectangle형태에서 ramp 형태로 변경함으로써 이러한 artifacts를 제거 할 수 있는 방법을 제시하였다

• Design & Manufacturing
• /
• 제17권2호
• /
• pp.55-61
• /
• 2023

With femtosecond (fs) laser pulse irradiation on metals, various types of nano- and micro-scale structures can be naturally induced at the surface through laser-matter interaction. Two notable structures are laser-induced periodic surface structures (LIPSSs) and cone/spike structures, which are known to significantly modify the optical and physical properties of metal surfaces. In this work, we irradiate fs laser pulses onto various types of metals, cold-rolled steel, pickled & oiled steel, Fe-18Cr-8Ni alloy, Zn-Mg-Al alloy coated steel, and pure Cu which can be useful for precise molding and imprinting processes, and adjust the morphological profiles of LIPSSs and cone/spike structures for clear structural coloration and a larger range of surface wettability control, respectively, by changing the fluence of laser and the speed of raster scan. The periods of LIPSSs on metals used in our experiments are nearly independent of laser fluence. Accordingly, the structural coloration of the surface with LIPSSs can be optimized with the morphological profile of LIPSSs, controlled only by the speed of the raster scan once the laser fluence is determined for each metal sample. However, different from LIPSSs, we demonstrate that the morphological profiles of the cone/spike structures, including their size, shape, and density, can be manipulated with both the laser fluence and the raster scan speed to increase a change in the contact angle. By injection molding and imprinting processes, it is expected that fs laser-induced surface structures on metals can be replicated to the plastic surfaces and potentially beneficial to control the optical and wetting properties of the surface of injection molded and imprinted products.

• 열처리공학회지
• /
• 제36권6호
• /
• pp.402-411
• /
• 2023

In order to examine the effect of cementite precipitated on the steel surface on the carburizing rate, the carburizing process was carried out at various boost times to measure the mass gain and carbon flux, phase analysis and carbon concentration analysis were performed on the surface of the carburized specimen. In the case of the only boost type, the longer the boost time, the more the mass gain by the diffused carbon follows the parabolic law and tends to increase. In particular, as the boost time increased, the depth of cementite precipitation and the average size of cementite on the steel surface increased. At a boost time of 7 min, the fraction of cementite precipitated on the surface is 7.32 vol.%, and the carburizing rate of carbon into the surface (surface-carbon flux) is about 17.4% compared to the calculated value because the area of the chemical (catalyst) where the carburization reaction takes place is reduced. The measured carbon concentration profile of the carburized specimen tended to be generally lower than the carbon concentration calculated by the model without considering precipitated cementite. On the other hand, in the pulse type, the mass gain by the diffused carbon increased according to the boost time following a linear law. At a boost time of 7 min, the fraction of cementite precipitated on the surface was 3.62 vol.%, and the surface-carbon flux decreased by about 4.1% compared to the calculated value. As a result, a model for predicting the actual carbon flux was presented by applying the carburization resistace coefficient derived from the surface cementite fraction as a variable.

• 한국의학물리학회지:의학물리
• /
• 제21권1호
• /
• pp.35-41
• /
• 2010

본 연구는 생체 외 $^1H$ 고분해능 매직앵글스핀닝($^1H$ High-Resolution Magic Angle Spinning; $^1H$ HR MAS) 기술을 이용하여 정상군 adult mice의 뇌에서의 부위별 뇌 신경화학 대사물질(brain neurochemical metabolites)을 정량적으로 분석하고, 이를 이용하여 정상군의 뇌 대사물질의 표준 data base를 정립하기 위함이다. 실험에 사용된 adult mice는 C57BL/6J 모델의 체중 25~28 g, 40주령 수컷 10마리를 사용하였으며, 연령과 성별을 일치시켰다. 또한 뇌의 전두엽(frontal cortex), 측두엽(temporal cortex), 해마(hippocampus), 시상(thalamus) 총 4개의 부위를 채취하여 생체 외 $^1H$ 고분해능 매직앵글 스핀닝 실험을 진행 하였다. 생체 조직의 뇌 대사물질의 절대농도를 획득하기 위하여 대표적인 대사물질(Ace, NAA, NAAG, tCr, Cr, tCho, Cho, mIns, GPC+PC, Lac, GABA, Glu, Gln, tau, Ala)을 각 피크의 면적과 대사물질의 프로톤 개수를 계산하였다. 결과적으로 정상 군에서의 mice 뇌의 신경화학 대사물질들을 Acet, NAA, NAAG, Cho, mIns가 부위별로 절대농도차의 유의성을 나타내었으며, 이 외의 대사물질에서는 유의성이 없는 것으로 나타났다. 본 연구 결과를 토대로 $^1H$ HR-MAS을 이용한 생체조직 실험은 뇌조직 내 대사물질의 절대농도를 측정하고 기본적인 지표를 확보하는데 매우 정확하고 정량적인 방법이 될 수 있을 것으로 사료되며, 더 나아가 mice를 이용한 인간질병 모델의 실험동물에서의 뇌 신경화학 대사물질의 표준 자료화 하는데 도움이 될 수 있을 것으로 판단된다.

• Journal of Chest Surgery
• /
• 제37권3호
• /
• pp.201-209
• /
• 2004

생명구조장치(ECLS)는 호흡부전 및 심부전에 적용하는 장치로 세계적으로 많은 연구개발과 임상시도가 계속되고 있다. 현재까지 생명구조장치의 혈류펌프로는 비박동형 구동장치가 표준으로 사용되고 있으며, 박동형 구동장치는 생리적인 측면에서 유리하지만 급격한 회로압 상승과 그에 따른 혈구손상에 대한 우려가 있고 특히 막형산화기를 사용하는 인공폐 회로에서 기피되어 왔다. 본 연구는 인공폐 실험모델에서 단일 박동형 구동펌프와 막형 산화기 사이에 압력완충장치를 설치함으로써 언급한 부작용을 최소화시키면서 생리적인 박동혈류를 유도할 수 있을 것이라는 가능성을 검증하였다. 실험대상은 올레익산으로 급성 호흡부전증이 유발된 잡견(N=16)을 사용하였다. 실험군은 사용된 구동펌프의 종류와 압력완충장치의 유무에 따라 3개 군으로 분류하였다. 제1군(n=6)은 대조군으로 원심펌프를 이용하였고, 제2군(n=4)은 단일 박동형 구동펌프를 사용하였으며, 제3군(n=6)은 단일 박동형 구동펌프에 압력완충장치를 설치하였다. 실험모델은 흉강 절개 후 우심방-대동맥을 우회시키는 부분 체외순환 형태로, 1.8～2 L/min의 펌프박출량에서 2시간을 구동하였다. 관찰지표는 주로 혈역학 변화, 회로압, 혈액검사 및 혈구세포에 미치는 영향 등에 한정하였다. 맥동압(pulse pressure)은 박동형 구동펌프를 이용한 2군(47$\pm$10 mmHg)과 3군(41$\pm$9 mmHg)에서 비박동형 원심펌프를 이용한 1군(17$\pm$7 mmHg)에 비해 유의하게 높았다(p<0.001). 막형산화기에 걸리는 회로압은 1 군의 경우 222$\pm$8mmHg, 2군의 경우 739 $\pm$ 35 mmHg, 3군의 경우 470$\pm$ 17 mmHg였다(p<0.001). 순환 2시간째의 동맥혈 산소분압은 1군에 비해 박동혈류를 사용하는 2군과 3군에서 현저하게 높았다(77$\pm$41, 96$\pm$48, 97$\pm$25 mmHg; p<0.05). 혈구손상지표인 혈장 유리 헤모글로빈치는 1군에서 가장 낮았고, 2군에서 가장 높았으며, 3군에서 유의하게 감소하였다(55.7$\pm$43.3, 162.8$\pm$113.6, 82.5$\pm$25.1 mg%; p<0.05). 기타 혈액검사치는 특별한 차이가 없었다. 이상의 결과에서 단일 박동형 구동펌프는 비박동형 원심펌프에 비해 막형산화기의 산소교환에 유리한 반면, 회로압과 혈구세포 손상 측면에서 불리하다는 것을 알 수 있었다. 그러나 단일 박동형 구동펌프와 막형 산화기 사이에 압력완충장치를 설치하는 경우, 회로압 상승과 혈구세포손상을 유의하게 감소시킬 수 있었다.