Internal quantum efficiency drop induced by the heat generation inside of light emitting diodes (LEDs)

The reasons for low output power of AlGalnP Light Emitting Diodes （LEDs） have been analysed. LEDs with AlGaInP material have high internal but low external quantum efficiency and much heat generated inside especially at a large injected current which would reduce both the internal and external quantum efficiencies. Two kinds of LEDs with the same active region but different window layers have been fabricated. The new window layer composed of textured 0.5 μm GaP and thin Indium-Tin-Oxide film has shown that low external quantum efficiency （EQE） has serious impaction on the internal quantum efficiency （IQE）, because the carrier distribution will change with the body temperature increasing due to the heat inside, and the test results have shown the evidence of LEDs with lower output power and bigger wavelength red shift.

Forming technology of boiling structure on evaporation surface of phase-change heat sink for high-power light emitting diode

Boiling structures on evaporation surface of red copper sheet with a diameter （D） of 10 mm and a wall thickness （h） of 1 mm were processed by the ploughing-extrusion （P-E） processing method, which is one part of the phase-change heat sink for high power （HP） light emitting diode （LED）. The experimental results show that two different structures of rectangular- and triangular-shaped micro-grooves are formed in P-E process. When P-E depth （ap）, interval of helical grooves （dp） and rotation speed （n） are 0.12 ram, 0.2 mm and 100 r/min, respectively, the boiling structures of triangular-shaped grooves with the fin height of 0.15 mm that has good evaporation performance are obtained. The shapes of the boiling structures are restricted by dp and ap, and dp is determined by n and amount of feed （f）. The ploughing speed has an important influence on the formation of groove structure in P-E process.

Thermal Analysis of Organic Light Emitting Diodes Based on Basic Heat Transfer Theory

We investigate the thermal characteristics of standard organic light-emitting diodes （OLEDs） using a simple and clear 1D thermal model based on the basic heat transfer theory. The thermal model can accurately estimate the device temperature, which is linearly with electrical input power. The simulation results show that there is almost no temperature gradient within the OLED device working under steady state conditions. Furthermore, thermal analysis simulation results show that the surface properties （convective heat transfer coetficient and surface emissivity） of the substrate or cathode can significantly affect the temperature distribution of the OLED.

Time Dependent Surface Heat Transfer in Light Weight Aggregate Cement Based Materials

Surface temperature changes of building materials affect the calculation of heat flow and thus the energy use in heating and cooling. The surface heat transfer coefficient , limiting the heat flow between material surface and ambient air is normally taken as a constant. In this study we propose a time-dependent function . We estimate from unidirectional heat flow experiments with transient and steady-state conditions. Using temperature measurements and the conservation of energy at the surface including convective and irradiative boundary conditions, the value of was obtained both using Finite Difference and Taylor Polynomials methods. Numerical solutions of temperature distribution as function of time were improved with the obtained -functions compared to with constant . There were no clear difference between on different materials, and the final values observed were in the order of magnitude expected from the literature.

Influence of Artificial Light on Laying Hens Production of Heat, Moisture and Carbon Dioxide in a Floor Housing System

Investigations about laying hens reactions on artificial light conditions were carried out in a climate chamber equipped with a floor housing system for laying hens. The release of moisture increased during light periods probably due to increased activity which increased respiration rate but also on increased scratching which increased evaporation of moisture from bedding material. The daily average was 6.29 g henl h＂l at 4 lux and 5.97 g henl hl, at 93 lux which corresponds to a difference of 5%. The level of light intensity seemed to have little influence on the release of moisture. The total release of heat was slightly higher during light periods compared to dark periods. Explanations can be increased activity but also feed intake increasing the metabolic rate during light periods. The daily average of total heat production was 17.0 W per hen at 4 lux and 14.7 at 93 lux which corresponds to a difference of 16%. The release of carbon dioxide increased during light periods probably due to increased activity and respiration.

Heat-Resistant Properties of a SiO₂-Coated PET Film Prepared by Irradiating a Polysilazane-Coated Film with Excimer Light

Flexible electronics have been recently paid much attention. A flexible substrate (Organic resin film) is indispensable component for flexible devices. Though PET film is low-cost organic film, low heat-resistance of PET film limits its application as a flexible device substrate. We have developed heat-resistant PET which does not deteriorate even at 190°C heat treatment for one hour. An excimer light was irradiated onto a polysi-lazane (PHPS: perhydropolysilane)-coated film to form a dense silicon-dioxide (SiO2) layer on a PET film, and the heat-resistance property of the formed film was examined. Changes of surface state and cross-sectional structure of the formed film due to heat treatment were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). Compared to normal PET, which is deteriorated and whitened by heat treatment of about 110°C - 120°C, the SiO2-coated PET film maintains transparency and does not deteriorate after heat treatment at 180°C - 190°C for one hour. This high heat resistance is due to a dense SiO2 film formed on the surface that prevents surface precipitation and crystallization of low-molecular-weight oligomers (which are the cause of thermal degradation of PET). It is expected that enhancing the heat resistance of PET—which has high versatility and low cost—to about 180°C to 190°C will allow SiO2-film-coated PET to be developed as a film substrate for flexible devices.

温差发电协同储能元件驱动LED车灯的响应特性

为实现低品位能源的高效利用,构建了基于温差发电的余热回收系统将余热转化为电能,用以驱动发光二极管(light emitting diodes,LED)车灯点亮.利用恒温加热炉模拟热源,探究了余热回收系统在不同阶段能量转化和驱动LED车灯的响应特性.在实际应用中,研究了储能元件独立驱动LED车灯时光输出特性的变化规律.结果表明:储能元件可以存储回收余热所转化的电能,并独立驱动LED车灯工作,还能缓冲温度变化引起的电压波动;锂电池的能量密度高,可储存更多电能,独立驱动LED车灯时冷启动速度快,点亮时间更长,但充满电所需时间也较长;超级电容冷启动速度慢,但充放电速度较快,有助于余热回收系统短时间工作时缓解LED车灯的驱动电压波动.

基于纳米复合PCM集蓄热构件的建筑太阳能供暖特性研究

设计一种基于吸光型纳米复合相变材料(PCM)模块化集蓄热构件,将其应用于建筑太阳能采暖,以降低能耗和碳排放。开展石墨烯-石蜡复合相变材料的制备和物性测试,建立PCM集蓄热数学模型,并结合典型气候工况进行供热特性的数值模拟,研究定风量情况下蓄热层厚度和空气流道宽度对供暖特性的影响,分析通风速度对送风温度、日供热量以及太阳能供暖保证率的影响。研究结果表明:添加石墨烯后的纳米复合PCM相对于纯石蜡的集热效率约提升了60%;对于具有18 m^(2)采光面积的集蓄热构件,当通风速度为1.0 m/s时,太阳能集蓄热墙具有较为优异的供暖性能,此时供给室内的日供热量、日平均热效率和供暖保证率分别为112.5 MJ、67.6%和90.0%,室内能够达到20℃的设定温度的时间为13 h。

Fabrication and testing of phase change heat sink for high power LED

A novel phase change heat sink was fabricated for packaging cooling of high power light emitting diode （LED）. 3D structures as enhanced boiling structure in the evaporation surface were composed of a spiral micro-groove along circumferential direction and radial micro-grooves which were processed by ploughing-extrusion （P-E） and stamping, respectively. Meanwhile, the cycle power of refrigerant was supplied by wick of sintered copper powder on internal surface of phase change heat sink. Operational characteristics were tested under different heat loads and refrigerants. The experimental results show that phase change heat sink is provided with a good heat transfer capability and the temperature of phase change heat sink reaches 86.8 ℃ under input power of 10 W LED at ambient temperature of 20 ℃.

光/热双重固化树脂的制备及性能研究

以环氧丙烯酸酯和环氧树脂的混合体系作为基体树脂,加入光引发剂、活性稀释剂、高温热固化剂、促进剂,制备了体积收缩率小、固化速度快、力学性能优良的光/热双重固化树脂,研究了光固化树脂和热固化树脂质量比、热固化时间、热固化温度对光/热双重固化树脂性能的影响。结果表明,光固化树脂和热固化树脂质量比为5∶5、热固化温度为100℃、热固化时间为3h时,光/热双重固化树脂性能最佳,拉伸强度为18.82MPa,冲击强度为85.76J/m^(2),体积收缩率为2.48%。

红外与可见光双模导引头光学系统设计

为了提升导弹在复杂环境下的寻的制导能力,设计了一种红外与可见光双模式导引头光学系统。该方案中采用分光镜透射红外光反射可见光,使结构布局更加紧凑,实现红外与可见光共口径,同时配合红外材料选取,实现光学被动消热差设计。中红外模式视场角3°×2.3°,可见光模式视场角5°×4°,工作温度20℃条件下,双模式在截止频率处,MTF(Modulation Transfer Function)值均大于0.4。红外与可见光双模式光学系统适合应用于复杂环境的导弹制导,对温度有良好的适应性,具有较好的成像质量,满足系统的性能要求。

菲涅尔定向传光装置多因素交互作用研究

搭建菲涅尔定向传光装置实验平台,对菲涅尔定向传光装置集热性能进行实验探究,研究菲涅尔定向传光装置抛物反射面焦准距p、反射率ρ、传光距离L、几何聚光比Cg和接收表面吸收率α这5个结构参数及其交互作用对菲涅尔定向传光装置光学效率的相对影响程度,并利用光学软件TracePro对菲涅尔定向传光装置的光学性能进行仿真研究。研究结果表明:焦准距和传光距离这2个因素之间的交互作用对菲涅尔定向传光装置的光学效率具有显著影响,传光距离对菲涅尔定向传光装置的光学效率的影响最显著;正北侧全年平均光学效率最高为81.31%,正南侧全年平均光学效率最高为62.26%。

改性轻烧氧化镁细粉的抗水化性能

为解决MgO的易水化问题,以乙二醇和聚异丁烯顺丁烯酸酐共聚物(ISOBAM-104)为改性剂,经混合、研磨、热处理对轻烧MgO细粉进行了改性处理,研究了ISOBAM-104的加入量(分别加入MgO细粉质量的0、1%、3%、5%、7%、9%)和热处理温度(200、250、300℃保温1 h)对改性后轻烧MgO的物相组成、显微结构及抗水化性的影响。结果表明:当ISOBAM-104的加入量为MgO细粉质量的7%时,经250℃保温1 h热处理后改性轻烧MgO的水化质量增加率最低,为2.2%。ISOBAM-104/乙二醇改性轻烧MgO细粉抗水化性能提高的主要原因是其表面生成了醇镁化合物及疏水性亚酰胺基团。

纳米纤维素/MXene多功能电磁干扰屏蔽复合材料的研究进展

电磁干扰(EMI)屏蔽材料在日益密集的电磁环境中显得尤为重要。纳米纤维素具有低密度、优异的力学性能、高度的结构稳定性和热稳定性等特点;MXene具有类金属的高电导率、大纵横比、高比表面积及优良的电化学特性等优点。因此,将纳米纤维素与MXene复合能够制备高性能EMI屏蔽复合材料。本文对不同维度纳米纤维素/MXene EMI屏蔽复合材料的制备方法进行综述,包括宏观复合纤维、薄膜和气凝胶复合材料,重点总结了纳米纤维素/MXene EMI屏蔽复合材料的多功能性应用,包括光热转化、储能和柔性传感等,并对其发展进行了展望。

Effect of Ultraviolet Radiation on Hsp70 Protein Expression in HaCaT Cells

Ultraviolet radiation by its wavelength is divided into: UVA, UVB and UVC. Only UVA and UVB manage to penetrate the ozone layer, but due to anthropological activities, all of them are capable of interacting with humans to a greater or lesser extent, and can generate adverse effects such as cellular stress when interacting with intra-and extracellular biomolecules. The skin is the first organ in contact with UV radiation, and the stress it generates can be analyzed by the expression of a bioindicator of cellular damage such as Hsp70. Therefore, the objective of the project was: to determine the effect of UVA, UVB and UVC radiation on HaCaT epithelial cells, by analyzing the expression of Hsp70. Materials and methods: HaCaT cells were cultured in vitro, which were irradiated with UVA, UVB and UVC light at different doses, to subsequently determine the degree of Hsp70 expression by Immunodetection by PAGE-SDS and Western Blot. Results: Basal expression of Hsp70 was observed in no irradiated HaCaT cells. When HaCaT cells were irradiated with UVA, UVB, UVC, an increase in this Hsp70 protein was observed. With UVA, a higher degree of expression was observed at a time of 30 minutes of irradiation. With UVB the highest expression shifted to a time of 20 minutes. With UVC, overexpression was observed after 10 minutes. Conclusion: UV radiation generates cellular stress on HaCaT cells, evaluated by the stress bioindicator Hsp70. According to the wavelength of UV radiation, those that have a shorter wavelength have a greater potential for cellular damage, such as UVC.

热敏灸联合毫火针及308 nm准分子光治疗稳定期局限性白癜风临床观察

目的 研究用热敏灸联合毫火针及308 nm准分子光治疗稳定期局限性白癜风的临床效果。方法 按照随机对照原则,选取2021年1月—2021年8月于枣庄市中医医院皮肤科治疗的稳定期局限性白癜风患者60例。对照组采用毫火针联合308 nm准分子光治疗,治疗组在对照组基础上加用热敏灸。比较2组患者白斑处治疗前后的面积变化、复色率及临床效果。结果 治疗前,2组白斑面积比较差异无统计学意义(P>0.05);治疗12周、24周后,治疗组的白斑面积均显著小于对照组,复色率均大于对照组(P<0.05)。治疗后,治疗组白斑处愈显率为86.7%(26/30),高于对照组的76.7%(23/30);治疗组总有效率为96.7%(29/30),高于对照组的90.0%(27/30),差异均有统计学意义(P<0.05)。结论 热敏灸联合毫火针及308 nm准分子光疗法治疗稳定期局限性白癜风的临床效果明确,明显优于毫火针联合308 nm准分子光疗法。治疗过程中未见明显不良反应,安全性高,患者乐于接受,亦方便推广应用。

激光照明应用MgO-La_(3)Si_(6)N_(11)∶Ce^(3+)复合荧光玻璃的制备及性能优化

荧光玻璃材料在激光照明领域具有良好的应用潜力,然而玻璃基质的低热导率特性导致其在工作条件下容易出现严重的热猝灭问题,进而降低发光性能。为了提升荧光玻璃的散热性能,本研究将高热导率MgO颗粒引入到了La_(3)Si_(6)N_(11)∶Ce^(3+)(LSN∶Ce^(3+))氮化物荧光玻璃中,制备获得了MgO-LSN∶Ce^(3+)复合荧光玻璃材料。通过优化制备工艺、MgO含量以及玻璃厚度,具有最优综合性能的复合荧光玻璃在激光激发下的发光饱和阈值达到了2.08 W/mm^(2),比无MgO荧光玻璃样品(1.5 W/mm^(2))提高了38.7%,最高光通量也相应地提升了44.6%,从383 lm提高到了554 lm。同时,由于散射性能的提升,MgO-LSN∶Ce^(3+)复合荧光玻璃的发光均匀性也得到显著优化。最后,通过进一步在复合荧光玻璃中引入红色发光的CaAlSiN_(3)∶Eu^(2+)(CASN∶Eu^(2+))荧光粉,并调节LSN∶Ce^(3+)和CASN∶Eu^(2+)之间的比例,可实现显色指数(Ra)达到85.5的高品质激光驱动白光光源。

凉血清肺汤辅助窄谱强脉冲光治疗寻常痤疮肺胃热盛证的疗效

目的观察凉血清肺汤辅助窄谱强脉冲光治疗寻常痤疮肺胃热盛证的疗效。方法前瞻性选取2022年1月至2023年3月北京中医药大学东直门医院收治的82例辩证为肺胃热盛证的寻常痤疮患者为研究对象,按照随机数字表法将其分为脉冲光组和凉血清肺组,每组各41例。脉冲光组给予窄谱强脉冲光治疗,凉血清肺组在窄谱强脉冲光基础上给予凉血清肺汤辅助治疗。检测两组治疗前、治疗3个月后的皮肤生理指标[皮脂分泌率(SER)、皮肤经皮水丢失(TEWL)及pH值]的差异,评估两组治疗前、治疗3个月后的中医症状评分变化,统计两组总有效率和不良反应发生情况。结果治疗3个月后,两组SER、TEWL及pH值均较治疗前降低,且凉血清肺组治疗3个月后SER、TEWL及pH值分别为(1.23±0.25)μg/(cm^(2)·min)、(14.02±2.65)g/(h·m^(2))、4.31±0.42,均低于凉血清肺组[(1.54±0.31)μg/(cm^(2)·min)、(17.25±3.14)g/(h·m^(2))、5.06±0.47],差异均有统计学意义(P<0.05)。治疗3个月后,两组丘疹脓包、面部潮红、瘙痒肿痛、口干黏苦、口臭、大便秘结、小便黄及总分均较治疗前降低,且凉血清肺组治疗3个月后中医症状评分均低于凉血清肺组,差异均有统计学意义(P<0.05)。凉血清肺组总有效率为92.68%,明显高于脉冲光组(75.61%),差异有统计学意义(P<0.05)。脉冲光组发生皮肤刺痛1例,发生皮肤肿胀3例,皮肤干燥2例。凉血清肺组发生胃肠道反应2例,皮肤干燥和皮肤刺痛各1例。两组不良反应发生率比较,差异无统计学意义(P>0.05)。结论凉血清肺汤辅助窄谱强脉冲光治疗寻常痤疮肺胃热盛证可改善皮肤生理状态指标,减轻症状,提高疗效。

吸光发热涤纶的性能研究

采用扫描电镜法、傅里叶红外光谱法、差示扫描量热法、X射线衍射法、纤维强伸度测试法及紫外可见近红外光谱法,研究吸光发热涤纶和普通涤纶的表面形态、特征结构和官能团、热学性能、晶体结构、力学性能及吸光性能,探究两者性能上的差异。结果表明:2种纤维纵向形态一致,只是吸光发热涤纶纤维表面有细小颗粒附着;与普通涤纶相比,吸光发热涤纶结晶度减小,熔融温度、断裂强度及初始模量略低,断裂伸长率稍高;吸光发热涤纶在全光谱波段具有更优良的吸光能力。

大型铁路客站站房外遮阳节能潜力分析及调控阈值优化

大窗墙比、大天窗比的透明围护结构是大型铁路场站冷负荷大、环控能耗高的重要原因之一,外遮阳设置是缓解该现象的有效手段,但其应用还需合理平衡对自然采光的影响。以某大型铁路客站站房为对象,建立其光热环境数值分析模型并进行验证;在此基础上,以空调照明综合能耗为指标,选取卷帘外遮阳为代表,分析建筑外遮阳在不同气候区铁路客站应用的综合节能潜力,并确定了适宜外遮阳应用的热工气候分区;在保证室内光热环境水平的前提下,分析空调照明综合能耗随外遮阳调控阈值(以太阳辐射投射强度为依据)的变化情况,并总结不同气候区的最佳调控阈值。该研究成果完善了交通基础设施的被动式技术体系,可为外遮阳技术在大型铁路客站站房的设计和调控提供理论依据。