• Journal of Radiation Industry
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• v.9 no.3
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• pp.143-151
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• 2015

A PET-MR system is particularly useful in diagnosing brain diseases. We have developed a prototype positron emission tomography (PET) system which can be inserted into the bore of a whole-body magnetic resonance imaging (MRI) system that enables us to obtain PET and MRI images simultaneously with a reduced cost. Silicon photomultipliers (SiPM) are appropriated as a PET detector at PET/MR system because detectors have a high gain and are insensitive to magnetic fields. Despite of its improved performance compared to that of PMT-based detectors, there is a problem of the photo-peak channel shift which is due to the increase of the temperature inside the ring detector. This problem will occur decreasing sensitivity of the PET and image distortion. In this paper, I quantitative analyze parameters of the KAIST SiPM depending on temperature by experiments. And I designed cooling methods in consideration of the degradation of sensors for correction of the temperature in the PET gantry. According to this research, we expect that distortive images and degradation of the sensitivity will not be occurred with using the above idea to reduce heat even if the PET system operates for a long time.

• Steel and Composite Structures
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• v.45 no.1
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• pp.147-157
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• 2022

This study assessed the compressive and tensile strengths and modulus of elasticity of waste polyethylene terephthalate (PET) using the ASTM standard tests. In addition, short carbon and glass fibers were mixed with waste PET to examine the improvements in ductility and strength during compression. The bonding was examined via field-emission scanning electron microscopy. The strength degradation of the waste PET tested under UV was 40-50%. However, it had a compressive strength of 32.37 MPa (equivalent to that of concrete), tensile strength of 31.83 MPa (approximately ten times that of concrete), and a unit weight of 12-13 kN/m3 (approximately half that of concrete). A finite element analysis showed that, compared with concrete, a waste PET pile foundation can support approximately 1.3 times greater loads. Mixing reinforcing fibers with waste PET further mitigated this, thereby extending ductility. Waste PET holds excellent potential for use in foundation piles, especially while mitigating brittleness using short reinforcing fibers and avoiding UV degradation.

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.351-354
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• 2001

Poly(ethylene terephthalate) (PET)는 물리적, 기계적 성질이 우수한 엔지니어링 플라스틱의 하나로 섬유, 필름, 및 여러 가지 용도로 다양하게 사용되고 있다. PET는 DMT(dimethyl terephthalate) 또는 TPA(terephthalic acid)와 EG(ethylene glycol)를 축합 중합하여 제조한다. (중략)

• Polymer(Korea)
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• v.30 no.2
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• pp.118-123
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• 2006

The effect of transesterification on the rheological properties in the melt reactive blending of poly(butylene terephthalate)(PBT) with poly(ethylene terephthalate)(PET) has been studied. The melt viscosity depression in PBT was found in PBT/PET blends due to the intrinsic low melt viscosity of PET compared to PBT. In addition, the thermal degradation in the melt blending and transesterification between two polyesters were considered as other factors fer the lowering of the melt viscosity in the blends. In the PBT/PET blends, calcium stearate was less effective than in PBT as a lubricant, however it accelerated both the thermal degradation and transesterification during melt blending. As a result, further melt viscosity drop was obtained in the reactive melt blending of PBT/PET.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.251-254
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• 2003

자동차에 장착되어 폐차시까지 사용되는 안전벨트용 웨빙은 일정 수준이상의 인장강도를 지속적으로 유지하여 착용자를 사고로부터 보호하는 중요한 역할을 하는 섬유 제품이다. 그러나 차량에 처음 장착되었을 때의 초기 인장강도가 사용 기간 증가에 따라 점차 저하된다. 웨빙의 사용 시간 증가에 따른 인장강도 저하의 주요 원인을 구성 PET 필라멘트의 취화로 생각할 수 있다. 따라서 웨빙의 구성 소재인 PET 필라멘트가 환경 요인에 의하여 취화되는 과정을 확인하고자 온도와 UV-B 자외선 조사에 의한 가속실험을 실시하였다. (중략)

• Polymer(Korea)
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• v.33 no.3
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• pp.198-202
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• 2009

Oligo(ethylene terephthalate)(OET), oligo(ethylene succinate-co-terephthalate)(OEST) and oligo(butylene succinate-co-terephthalate)(OBST), which are part of the poly(ethylene terephthalate)(PET) oligomer, were synthesized. Degradation test of oligomers carried out by the presence of lipase PS. There were two objectives in the experiment: first, to measure the weight remaining of the PET oligomer as increasing degradation time, and second to examine the degradation mechanism by analyzing the resulting degraded product. In the synthesis of OEST and OBST, by controlling the feed ratio of both OEST and OBST, we were able to obtain oligomer of different composition ratios. The various composition ratios resulted in oligomer of vastly different thermal properties. We observed that both OEST and OBST were degraded using lipase PS, but as the composition of terephthalic acid was increased, the lipase PS became less effective. We confirmed that the lipase PS easily decomposed polyester of the aliphatic compound.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2230-2234
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• 2010

This paper deals with the change of surface potential decay, surface resistivity, contact angle and XPS of ultraviolet-treated PET films. From the experimental results on the surface potential decay of UV degraded-samples, it was found that the accumulation of charge is decreased and the surface potential decay time is shortened. Also, from the result of XPS, it was found that the changes affected by the surface degradation of PET film were caused by the generation of carboxyl groups through the chain decomposition and recombination with oxygen molecules in the air.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.404-409
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• 2018

The integration of organic and inorganic building blocks into hierarchical porous architectures makes potentially desirable catalytic material in many catalytic applications due to their combination of dissimilar components and well-constructed reactant transport path. In this study, we prepared the hierarchical porous $Co_3O_4@graphene$ 3D gel by hydrothermal method to achieve high catalytic performance in PET glycolysis reaction. Obtained $Co_3O_4@graphene$ 3D gel consisted of interconnected networks of $Co_3O_4$ and graphene sheets, providing large number of accessible active sites for efficient catalytic reaction. These structural merits from synergistic effect of $Co_3O_4$ and graphene gave a high performance in the PET degradation reaction giving high conversion yield of BHET, fast degradation rate of PET, and remarkable stability.

• Textile Coloration and Finishing
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• v.26 no.2
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• pp.88-98
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• 2014

This study is to assess the photocatalytic degradation of PET and Nylon 6 films containing nano-sized $TiO_2$ powders of anatase and rutile types. The PET and Nylon 6 films containing six kinds of the nanoparticles were prepared by melt casting method using a heating press machine. Reflectance in visible region and water contact angles of the irradiated PET and Nylon 6 composite films decreased with increasing UV/$O_3$ irradiation. Also the enhanced hydrophilicity has a close relationship with the increase in the Lewis base parameter, which indicates more oxidized polymer surfaces. The photocatalytic degradation of the nanocomposite films increased with increasing $TiO_2$ content and UV energy, which is more significant with the anatase types rather than the rutile types. The amide linkages in the Nylon 6 seemed to be more susceptible to the UV light compared to the ester groups in the PET, particularly in the presence of the $TiO_2$ photocatalysts. The photoscission and photodegradation of the polymers in the composites produced more degraded structure assisted by the photocatalytic activity of the $TiO_2$ nanoparticles. Also the composite films can bleach the methylene blue dyes more easily under the UV/$O_3$ irradiation, suggesting the photobleaching activity of the $TiO_2$ nanoparticles.

• Nuclear Medicine and Molecular Imaging
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• v.42 no.2
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• pp.172-180
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• 2008

PET/CT fused image with anatomical and functional information have improved medical diagnosis and interpretation. This fusion has resulted in more precise localization and characterization of sites of radio-tracer uptake. However, a motion during whole-body imaging has been recognized as a source of image quality degradation and reduced the quantitative accuracy of PET/CT study. The respiratory motion problem is more challenging in combined PET/CT imaging. In combined PET/CT, CT is used to localize tumors and to correct for attenuation in the PET images. An accurate spatial registration of PET and CT image sets is a prerequisite for accurate diagnosis and SUV measurement. Correcting for the spatial mismatch caused by motion represents a particular challenge for the requisite registration accuracy as a result of differences in PET/CT image. This paper provides a brief summary of the materials and methods involved in multiple investigations of the correction for respiratory motion in PET/CT imaging, with the goal of improving image quality and quantitative accuracy.