Thermal Sensitive Polyurethane Membranes with Desirable Switch Temperatures

Hu Zhou,Jianxian Zeng,Haojun Fan,Yuansen Liu,Jian Zhou 한국고분자학회 2010 Macromolecular Research Vol.18 No.11

Chemical synthesis and physical blending methods were used to prepare thermal sensitive polyurethanes (TSPU) with single or double thermal switches. In the design of the formula, polycaprolactone diol (PCL) with a molecular weight 10,000 and 4,000 and polytetramethylene glycol (PTMG) with a molecular weight 3,000 and 2,000 were used as the soft segments. The effects of the crystallinity and compatibility of the soft segments on the phase transition temperatures of the soft segments of TSPU (defined as switch temperature, Ts) were investigated in detail. To examine the thermal sensitivity of the thermal switch, water vapor permeability (WVP) experiments were performed to investigate the mass transport as a function of temperature. Differential scanning calorimetry (DSC)indicated that all the original TSPUs had a phase separated structure that was independent of the phase transition temperature of the soft and hard segments. The Ts values are determined mostly by the melting temperatures of the soft segments. On the other hand, for their blends, the Ts values are determined by the compatibility of the soft segments and the blending weight ratio. The blends of the PCL-based TSPUs showed good compatibility and single Ts due to the similar structure of the soft segments (just a difference in molecular weight), whereas for the PCL-based and PTMG-based TSPUs (the molecular structure is very different) blends, the Ts two independent values and blending weight ratio-dependent features due to the difference in the structure of the soft segments. Water vapor permeability analysis revealed the mass transport showed switching features to thermal stimuli, i.e. when the temperature reached the Ts, the WVPs of membranes showed rapid changes. On the other hand, the sensitivity of the thermal switch characterized by WVP improvement showed a dependence on the degree of crystallinity of the soft segments,i.e. well-organized soft segment structure is beneficial for improving the thermal sensitivity. Overall, TSPU membranes with a single Ts and different thermal sensitivity can be prepared using different crystalline poly-diols as the soft segments and blending two types of TSPUs with similar soft segments in the molecule structure, whereas TSPU with a double Ts can be achieved easily by blending two types of TSPUs with different soft segments.

Thermal Performance Sensitivity Analysis for Modeling of Spent Fuel Assembly in Transport System

Kun-ho Chun,Joung-yeul Lee,Seong-ki Lee 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

This study is to investigate fuel cladding temperature in a transport system for the purpose of developing a methodology for evaluating the thermal performance of spent fuel. Detailed temperature analysis in the transport system is important because the degradation mechanism of the fuel cladding is generally sensitive to temperature and temperature history. In such a system, the magnitude of the temperature change is determined by examining the temperature sensitivity of fuel assemblies and system components including fuel cladding temperature, considering the material properties, component specifications, component aging mechanism, and heat transfer mechanism. The sensitivity analysis is performed using heat transfer models by computational fluid dynamics for the horizontal transport system. The heat transfer within the system by convection, conduction and thermal radiation is calculated by thermal-hydraulic analysis code FLUENT. The calculation region is divided into a basket cell and a transport cask. The thermal analysis of the basket cell is for predicting the fuel cladding temperature. And the reason for analyzing the transport cask is to provide the boundary condition for the basket cell by reflecting the external environmental conditions. Here, the basket cell containing the spent fuel assembly is modeled on the homogeneous effective thermal conductivity. The purpose of this analysis is to evaluate fuel cladding temperatures for the following four main items. That is the effect of surface emissivity changes in basket due to the oxide layer of the fuel cladding, the effect of degradation of the canister backfill helium gas, the effect of fuel assembly position in basket cell on fuel cladding and basket temperatures in canister, and the effect of using the homogeneous effective thermal conductivity model instead of the fuel assembly in basket cell. As a result of the analysis, the maximum temperatures in basket cells are evaluated for the above four items. Thermal margins for each item are investigated for thermal performance requirements (e.g., peak clad temperature below 400oC).

성별, 비만 및 피하지방이 신체 부위별 온냉감 민감도에 미치는 영향

조영현(Young-Hyun Cho),서여정(Yeo-Jeong Seo),박성열(Sung-Yul Park),성경화(Kyung-Hwa Sung),김정현(Jung-Hyun Kim) 한국생활환경학회 2021 한국생활환경학회지 Vol.28 No.1

The purpose of this study was to determine the effects of gender, obesity, and subcutaneous fat on regional cutaneous warm and cold sensitivity. A total of 52 male and female subjects were recruited and classified into four groups by gender and obesity based on the fat percentage of 25% and 30% for men and women, respectively. Cutaneous warm and cold sensitivity was measured on ten body regions, using a method of limit together with the measurements of regional skinfold thickness. The results indicated no significant interaction between gender and obesity while women exhibiting a higher sensitivity to both cold and warm stimuli than men. However, thermal sensitivity was not significantly associated with skinfold thickness on most regions of the body in men and women. In conclusion, women were more sensitive to both cold and warm stimuli than men. Obesity and local subcutaneous fat appeared not to influence regional thermal sensitivity. Further research is warranted to confirm the effects of obesity and local subcutaneous fat on regional thermal sensitivity.

Sensitivity to cutaneous warm stimuli varies greatly in the human head

Kim, Yung-Bin,Jung, Dahee,Park, Joonhee,Lee, Joo-Young Elsevier 2017 Journal of thermal biology Vol.69 No.-

<P><B>Abstract</B></P> <P>The head has been known as the most sensitive area to temperature changes but the values are limited to the face. The purpose of this study was to examine cutaneous warm thresholds on the scalp and face of young males. Eight males participated in this study (24 ± 3 yrs in age, 178.2 ± 5.3cm in height, and 90.0 ± 15.4kg in body mass). All measurements were conducted in an environmental chamber (27 ± 1°C air temperature and 53 ± 1% relative humidity). Cutaneous warm thresholds were measured on nine areas of the following regions: the frontal (two points on the right), parietal (a point on the right and the vertex, respectively), temporal (two points on the right), and occipital region (on the right) along with the forehead using a thermal stimulator (rate of temperature increase 0.1°Cs<SUP>−1</SUP>). Skin temperatures on the nine head regions were monitored during the threshold test. The results showed that 1) no significant differences were found in initial skin temperatures among the nine head regions; 2) cutaneous warm detecting temperatures were significantly greater on the vertex (38.2 ± 3.5°C) than on the forehead (34.8 ± 1.4°C) and the other seven scalp regions (<I>P</I> < 0.05); 3) subjects detected the increase of 1.2 ± 1.0°C on the forehead and 1.5 ± 1.2°C on the occipital region as the first warmth while the vertex was the most insensitive to the increase of temperature (4.0 ± 3.2°C) (<I>P</I> < 0.05). In summary, the scalp region of young males was less sensitive to the temperature change when compared to the forehead, and the vertex was the most insensitive among the eight scalp regions to the temperature increase. We conclude that the entire head should be considered as a binary topography with the face and the scalp in terms of cutaneous thermal sensitivity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cutaneous warm thresholds on the scalp and forehead are demonstrated. </LI> <LI> Increase of 1.2°C (the face) and 4.0°C (the vertex) are perceived as being warmth. </LI> <LI> The vertex is the most insensitive region to detect warmth on the head. </LI> <LI> The head is divided into the scalp and face in terms of thermal sensitivity. </LI> </UL> </P>

열-역학적 연계해석 모델을 이용한 다중 열저장공동 안정성 분석

김현우(Hyunwoo Kim),박도현(Dohyun Park),박의섭(Eui-Seob Park),선우춘(Choon Sunwoo) 한국암반공학회 2014 터널과지하공간 Vol.24 No.4

암반공동을 이용한 열에너지 저장은 대용량 저장이 가능하며 열저장매체를 선택할 수 있는 장점이 있다. 본 연구에서는 사일로 형태의 열저장공동이 지반 내 두 개 이상 배치될 때 공동 사이에 형성되는 암반 필라의 안정성에 대해 3차원 유한차분해석 프로그램인 FLAC3D를 이용하여 분석하였으며, 저장된 열에너지로 인해 암반에 발생하는 열응력을 반영할 수 있도록 열-역학적 연계모델을 사용하였다. 해석 결과, 열에너지 장기 저장으로 인해 암반 필라에 작용하는 최대주응력이 상당량 증가하였으며, 필라 폭이 좁아질수록 근접한 열원 때문에 열응력 증가량도 커짐을 확인하였다. 필라 안정성에 영향을 미치는 주요인자로서 저장공동 간격, 측압계수, 심도를 선정하고 민감도 분석을 실시한 결과, 측압계수, 저장공동 간격, 심도 순서로 영향력이 크게 평가되었다. 저장공동 간격의 경우 동일한 크기의 공동 건설 시 필라 폭을 최소 저장공동 직경 이상 확보해야 할 것으로 판단되었다. 큰 규모의 저장공동 주변에 소규모 수직갱이 설치될 때는 최소한 저장공동 직경의 0.5배 이상 이격함으로써 크기 차이로 인해 수직갱에 응력이 집중되는 현상을 해소할 수 있었다. 또한 최대수평주응력 작용방향과 공동 중심을 잇는 축이 평행하도록 배치하여 저장공동에 의한 방패효과가 발휘될 수 있게 함으로써 현지응력이 공동 사이 암반 필라에 미치는 영향을 최소화할 수 있었다. Cavern Thermal Energy Storage system stores thermal energy in caverns to recover industrial waste heat or avoid the sporadic characteristics of renewable-energy resources, and its advantages include high injectionand-extraction powers and the flexibility in selecting a storage medium. In the present study, the structural stability of rock mass pillar between these silo-type storage caverns was assessed using a coupled thermal-mechanical model in FLAC3D. The results of numerical simulations showed that thermal stresses due to long-term storage depended on pillar width and had significant effect on the pillar stability. A sensitivity analysis of main factors indicated that the influence on the pillar stability increased in the order cavern depth < pillar width < in situ condition. It was suggested that two identical caverns should be separated by at least one diameter of the cavern and small-diameter shaft neighboring the cavern should be separated by more than half of the cavern diameter. Meanwhile, when the line of centers of two caverns was parallel to the direction of maximum horizontal principal stress, the shielding effect of the caverns could minimize an adverse effect caused by a large horizontal stress.

인체 17 부위 피부 온감 역치에서 피부 가온 속도의 영향

정다희,조가영,Andrew Gorski,이주영 한국생활환경학회 2023 한국생활환경학회지 Vol.30 No.1

The purpose of this study was to investigate the effects of heating rate on cutaneous warm thresholds in thermoneutral environments. Fifteen young males participated in this study and their cutaneous thermal thresholds for warmth were measured on 17 body regions using a thermal stimulator at the following three speed conditions: 0.1oC/s, 0.3oC/s, and 0.5oC/s. Subjects pressed the button-switch once they felt ‘warmth’ at first from their neutral-adapting thermal state. The results showed that: (1) among the 17 body regions, only sole temperature at warmth had a significant difference among the three heating rate conditions (31.5 ± 2.0, 32.2 ± 1.4, and 30.8 ± 2.1oC at 0.1oC/s, 0.3oC/s, and 0.5oC/s, respectively; P < 0.05). (2) Noticeable increases in skin temperature to detect the warmth showed significant differences among the three heating rates on the 11 body regions, including the sole (4.0 ± 2.3oC, 4.1 ± 2.4oC, and 5.8 ± 3.2oC at 0.1oC/s, 0.3oC/s, and 0.5oC/s, respectively; P < 0.05), which had increased most rate among the 17 body regions as well (P < 0.01). (3) There were significant differences in the warmth thresholds on the 17 body regions at all the three heating rate conditions. The lower back was the most sensitive to detect warmth while the back calf was the least sensitive (P < 0.05). In summary, the differences between a heating speed of 0.1 and 0.3oC/s did not result in differences in cutaneous warmth thresholds (for the 17 body regions). However, the difference between a heating rate of 0.3 and 0.5oC/s could affect the thermal sensitivity on certain peripheral body regions. These results suggest that differences in heating rate, between 0.1 and 0.5oC/s, had negligible effects on for skin temperature, itself, for the most body regions (except the sole at the 0.5oC/s heating), but increases in skin temperature was affected by the rate of heating speed. Body regional differences, however, rather than heating rate, were more salient features in cutaneous warm sensitivity.

The Influence of Excavation Damaged Zone on the Mechanical and Thermal Behavior of Cement Mortar Block around an Opening

이창수,이동근,전석원 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.6

To investigate the influence of Excavation Damaged Zone (EDZ) on the mechanical and thermal behavior, EDZ was artificially generated around an existing circular hole in a mortar specimen. By applying high compressive stresses on the boundaries of a specimen and repeating loading and unloading cycles, EDZ was generated around the hole. An engineering heater was installed at the hole and the temperature of the heater was maintained at 75°C during the tests. Tangential strains and temperature were monitored at several points around the hole and compared to those measured in the specimen without EDZ. For elliptical and circular damaged zones, the tangential strain in the EDZ increased by as much as 88% and 58%, respectively and temperature in the EDZ decreased by 2.8°C and 0.85°C, respectively. Two-dimensional thermal-mechanical coupled numerical simulation using Particle Flow Code 2D (PFC2D) was carried out to analyze and to demonstrate the experimental results. For the numerical simulation,thermal parameters were determined using the results obtained from sensitivity analyses by a factorial design method. The TMcoupled PFC2D modeling results indicated that significant changes in mechanical and thermal behavior were observed, when the elliptical and circular EDZ was considered. And that the laboratory test results were successfully reproduced.

Study on the thermal sensitivity of β-NaYF4: Yb3+-Er3+ nano-thermometers based on luminescence ratiometric technology

Leipeng Li,Feng Qin,Yuan Zhou,Yangdong Zheng,Hua Zhao,Zhiguo Zhang 한국물리학회 2019 Current Applied Physics Vol.19 No.4

It is demonstrated here that relative sensitivity should gain more concern than absolute sensitivity when designing a new type of nano-thermometer based on luminescence ratiometric technology. Following the NIR excitation by a 980 nm laser diode, the 520/527 and 540/547 nm upconversion luminescence bands, which are respectively ascribed to the 2H11/2–4I15/2 and 4S3/2–4I15/2 transitions of Er3+ ions embedded in NaYF4 nanocrystals, are investigated as a function of temperature between 303 and 483 K. It is found that the 520/540, 520/ 547, 527/540 and 527/547 nm emission lines can constitute four pairs of thermally coupled energy levels. These four pairs of lines own the different absolute sensitivities. However, the relative sensitivities for them are identical at the same temperature. A third parameter, that is, temperature resolution, is then introduced to identify the difference between the two sensitivities. It is found that these four pairs of lines own the same temperature resolution, suggesting that absolute sensitivity is an intermediate parameter and relative sensitivity reflects the fundamental nature of sensors.

Molecular design of sensitizer to suppress efficiency loss mechanism in hyper-fluorescent organic light-emitting diodes

Jang, Ji Seon,Han, Si Hyun,Choi, Hye Won,Yook, Kyoung Soo,Lee, Jun Yeob Elsevier 2018 ORGANIC ELECTRONICS Vol.59 No.-

<P><B>Abstract</B></P> <P>Efficiency loss mechanism of hyper-fluorescent organic light-emitting diodes was studied by comparing two sensitizers with different molecular structures and a design strategy of the sensitizer was suggested. Examination of two sensitizers with a 3,6-dimethylcarbazole or 3,6-di (<I>tert</I>-butyl)carbazole donor proposed that the 3,6-dimethylcarbazole donor could not suppress efficiency loss by fluorescent emitter doping, but the 3,6-di(<I>tert</I>-butyl)carbazole donor effectively suppressed the efficiency loss. There was little decrease of the efficiency of the hyper-fluorescent device built on the 3,6-di(<I>tert</I>-butyl)carbazole based TADF sensitizer according to fluorescent emitter doping concentration. It was proven from this work that the <I>tert</I>-butyl carbazole modified TADF molecules are effective as the sensitizers of the hyper-fluorescent devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Molecular design principle of sensitizer for high quantum efficiency in hyperfluorescence device. </LI> <LI> Suppressed Dexter energy transfer by <I>t</I>-butyl modified sensitizer. </LI> <LI> Constant external quantum efficiency irrespective of fluorescent dopant doping concentration. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Characteristic Changes Observation of N-isopropylacrylamide Phantom by Repeated Ultrasound Irradiation

김주영(Ju Young Kim),김재영(Jae Young Kim),노시철(Si Cheol Noh),최흥호(Heung Ho Choi) 한국방사선학회 2015 한국방사선학회 논문지 Vol.9 No.7

본 연구에서는 재사용이 가능한 NIPAM 팬텀의 열적 민감도를 측정하여 조직유사 팬텀의 열변성 특성을 평가하였으며, 초음파 재사용 횟수와 재사용 기간에 따른 음향학적 특성 및 열 변성 형태 특성을 관찰하였다. 측정 결과조사 횟수가 증가함에 따라 NIPAM 팬텀의 음속은 100 m/s 정도 감소하고 감쇠계수는 조금 증가하는 경향을 보였다. 반면에 재사용 기간에 따른 변화는 관찰되지 않았다. 초음파 조사에 따른 열변성의 형태 및 크기는 유효할 정도의 변화는 확인되지 않았다. 본 연구를 통하여 NIPAM 팬텀이 반복 조사를 통한 초음파 치료 평가에도 적합한 것으로 판단되었다. In this study, we evaluated the thermal denaturation characteristics of reusable NIPAM tissue mimicking (TM) Phantom by measuring the thermal sensitivity. And the changes of acoustic characteristic and thermal denaturation shape in NIPAM TM phantom according to the number of re-use time and re-use period were observed. With the result, as the sonication time is increased, the sound velocity of NIPAM phantom was decreased by 100 m/s and the attenuation was increased slightly. However, the changes according to the re-use period was not observed. In the thermal denaturation shape and size observation by ultrasound sonicaton, the remarkable changes have not been confirmed. With the result of this study, NIPAM Phantom was considered appropriate to evaluate and predict the effect of therapeutic ultrasound by in repeated sonication test.