The Tb3+/Eu3+ doped Y3GaO6 phosphors were prepared using a solid-state method. A comprehensive set of characterization techniques was employed to examine the crystal phase, photoluminescence behavior, thermal stability, quantum efficiency, and electroluminescence properties of the materials. The electronic structure, including the energy band diagram and density of states, was calculated and analyzed. The calculated bandgap is 5.28 eV, which is consistent with the experimental value. Under 266 nm excitation, both red emission from Eu3+ and green emission from Tb3+ were detected. By varying the doping content of Eu3+, efficient energy transfer from Tb3+ to Eu3+, attributed to electric dipole-dipole interactions, enabled continuous tunability of the emission color from green to red. Temperature-dependent photoluminescence measurements demonstrated the phosphor's good thermal stability. The internal quantum efficiency of Y3GaO6:7 %Tb3+,1 %Eu3+ reached 47.02 %. A white LED device fabricated using this phosphor achieved a color rendering index of 82.8 at a driving current of 20 mA. These findings highlight the potential of Tb3+/Eu3+ co-doped Y3GaO6 phosphors for solid-state lighting applications, particularly where multicolor emission via energy transfer is desired.

Mn4+/Tb3+ doped CaAl2Si2O8 (CASO) phosphors were synthesized using high temperature solid-state method. Crystal structure and lattice parameters were acquired through X-ray diffraction technique and Rietveld refinement. Energy band and density of states of CASO host were given by density functional theory calculations. By calculating the bond lengths and total energies of Mn4+ doped CASO, the results show that Mn4+ occupies the Ca2+ site with six coordinating oxygen atoms in the phosphor. The CASO:Mn4+,Tb3+ phosphors exhibit two major emission bands originating from the red emitting of Mn4+ (2Eg -> 4 A 2g ) and the green emitting of Tb3+ (5D4 -> 7 F 5 ). Due to the emitting intensity of Mn4+ and Tb3+ varies differently with temperature, the temperature sensing study was carried out adopting the fluorescence intensity ratio of Tb to Mn. The relative sensitivity of CASO:1.5%Mn4+,6%Tb3+ achieves a peak value of 3.38 % K-1 at 423 K. The repeatability was tested and the result showed that the sample exhibits excellent repeatability. The luminescence color of the employed phosphors transitions from orange to green as the temperature increases. These findings uncover potential applications of CASO:Mn4+,Tb3+ phosphors in temperature sensing and multicolor-tunable emitting.

In this work, the valence states and optical properties of chromium-doped Mg2GeO4 are investigated via first-principles methods. The formation energies and thermal charge transition levels show that the site occupation and valence states of chromium are strongly related to the growth condition: Cr3+ dominates in the Mg sites under Mg-poor conditions, and Cr4+ dominates in the Ge sites under Ge-poor conditions. With the lithium co-doping, the Fermi-level is pinned below the midgap, and the formation energies of chromium-doped Mg sites become the lowest either Mg-poor or Ge-poor conditions, suggesting that the co-doping of lithium ions promotes the chromium to preferentially occupy Mg sites, in good agreement with experiments. Furthermore, the excitation and emission processes of chromium ions are investigated, and our results recommend that the near-infrared emission is related to the 4T2 to 4A2 transition of Cr3+ at the Mg sites and the infrared emission is related to the 3T2-3A2 transition of Cr4+ at the Ge site. Our results help to understand the stability of the valence states of chromium ions doped Mg2GeO4 and the effects of ions co-doping in regulating the chromium valence states, as well as the corresponding optical properties of different types of chromium ions.

文章分析工程机械车辆发动机冷却系统基本原理及主要部件性能,采用AMESim仿真软件搭建冷却系统的仿真模型,基于风洞实验验证模型的准确性;研究环境温度、水泵传动比以及散热器翅片波距对冷却系统的影响,并探讨冷却系统性能的优化路径.结果表明,环境温度过高会使冷却系统性能显著下降,适当提高水泵传动比和降低散热器翅片波距可以提高冷却系统的冷却性能.该文设计的2款散热器通过优化散热器翅片波距提高了冷却系统性能.

High-efficiency and accurate temperature control is the key to the application of microfluidic technology in biology, chemistry and medicine fields. At present, gradient temperature control of microfluidic chip in a wide range below room temperature still faces challenges. Based on a microfluidic platform of double emulsion droplets, this study builds a temperature control system and attempts to achieve continuous gradient temperature control on time scale of microfluidics based on thermoelectric cooler. Temperature control unit is designed and relevant control strategies are discussed to achieve accurate temperature control. Meanwhile, the strategy to achieve continuous gradient temperature control of microfluidic chip is mainly explored. Finally, combining with the working characteristics of thermoelectric cooler, continuous gradient temperature control of microfluidic chip is experimentally realized based on adaptive fuzzy PID control, while PID control shows remarkable overshoot, deviation and oscillation. Moreover, small gradient temperature control from 10 & DEG;C down to -15 & DEG;C, -20 & DEG;C and then -25 & DEG;C is precisely realized by using adaptive fuzzy PID control, as well as large gradient temperature control from 20 & DEG;C down to 0 & DEG;C and then -20 & DEG;C. Specifically, the maximum deviation of temperature is 0.192 & DEG;C in small gradient temperature control, and the steady state error is within & PLUSMN;0.07 & DEG;C. In large gradient temperature control, the maximum deviation of temperature is 0.309 & DEG;C, and the steady state error was within & PLUSMN;0.1 & DEG;C. This study provides diversified temperature control in a wide range for microfluidic analysis.

There has been a lot of interest in trivalent chromium ion-doped phosphors for near-infrared (NIR) luminescence in recent years. Here, trivalent chromium-doped NIR emitting SrGa2Si2O8 phosphors were synthesized. The electronic structure was calculated via density functional theory. Although only [SrO7], [SiO4], and [GaO4] polyhedra were found in the host, we still observe broadband luminescence of Cr3+ in the region of 650-950 nm from octahedra site. Due to the doping of Cr3+, a transformation from [GaO4] tetrahedron rearrange into [CrO6] octahedron was produced. The experimental results of X-ray photoelectron spectroscopy and electron para-magnetic resonance spectroscopy demonstrated the presence of Cr3+. A systematic study of the photo-luminescence properties of SrGa2Si2O8:Cr3+ was conducted. The luminescent intensity of SrGa2Si2O8:0.005Cr3+ at 420 K can be retained at 83.42% compared to 300 K, indicating its high thermal stability. The electrolumi-nescence of the prepared light emitting diode (LED) based on SrGa2Si2O8:Cr3+ and blue LED chip was measured under various currents. The application as a NIR LED light source was demonstrated in human hands.

Bi3+/Eu3+ doped Cs3GdGe3O9 luminescent materials were prepared by a solid-state reaction. The energy band and density of states of Cs3GdGe3O9 were calculated by density functional theory. The Cs3GdGe3O9 host presents a broadband emission peaking at 520 nm. Systemic measurement and analysis of luminescence properties were performed to confirm the energy transfer in Cs3GdGe3O9:Bi3+,Eu3+. The multicolor modulated emission from blue (0.1678, 0.1568) to red (0.5931, 0.3251) can be achieved by varying the doping ratio of bismuth to europium. A white light-emitting diode (WLED) was produced by combining the Cs3GdGe3O9:0.05Bi3+,0.1Eu3+ phosphor, a commercial green phosphor, and a 310 nm ultraviolet chip. The color rendering index of the WLED driven by 20 mA bias current is 89.6 with the CIE coordinates of (0.3520, 0.3626). The results reveal that the Cs3GdGe3O9:Bi3+,Eu3+ phosphor is a potential material that can be used in multicolor tunable luminescence and WLEDs.

Tb3+ and Eu3+ doped La4GeO8 multicolor emitting phosphors were synthesized. A systematic investigation was done into the photoluminescence properties of La4GeO8:Tb3+,Eu3+. Energy transfer from trivalent terbium to europium ions in La4GeO8 results from quadrupole-quadrupole interaction. The variable temperature emission spectra ranging from 303 to 513 K were used to demonstrate the thermal stability of La4GeO8:0.07Tb3+,0.01Eu3+ phosphor. The obtained activation energies for trivalent terbium and europium ions were 0.186 eV and 0.187 eV, separately. By altering the content ratio of Eu3+ to Tb3+, the La4GeO8:Tb3+,Eu3+ phosphors can achieve multicolor luminescence and tunable chromaticity from green (0.3416, 0.5423) to red (0.6479, 0.349) under 265 nm light excitation. The findings suggest that La4GeO8:Tb3+,Eu3+ are promising phosphors for solid-state lighting application.

Trivalent bismuth and trivalent terbium ions doped CaYGaO4 were prepared. The crystal structure, phase purity, photoluminescence, decay curves, and emission spectra under various temperatures were investigated. The six-coordinate Ca2+ and Y3+ ions are occupied by Bi3+ ions, while Tb3+ ions take up the six-coordinate Y3+ ions in the CaYGaO4:Bi3+,Tb3+ phosphor. The emissions of trivalent bismuth (3P1 & RARR; 1S0) and trivalent terbium ions (5D4 & RARR; 7F5) excited by 320 nm were observed. The analysis of spectra and decay curves demonstrated that Bi3+ could transfer energy to Tb3+ via electric dipole-quadrupole interaction. By altering the concentration of trivalent terbium ions, the emitting color of phosphor was tuned from blue to green. The temperature sensing property of CaYGaO4:Bi3+,Tb3+ was described, and its relative sensitivity at 303 K achieves a maximum of 0.61% K-1. According to the results, CaYGaO4:Bi3+,Tb3+ is a potential material for color tunable emission and temperature sensing.

文章以热泵系统来代替露点蒸发海水淡化系统中的二级淡化系统,通过对普通淡化系统和热泵辅助淡化系统的模型建立,对2种系统在不同操作条件下淡水产量和造水比的变化规律进行仿真和对比.仿真结果显示,热泵辅助淡化系统的性能优于普通淡化系统,当海水流量增加时,热泵辅助淡化系统的淡水产量比普通淡化系统的淡水产量高6.6kg/h,造水比高1.10～1.30;当海水进口温度增加时,热泵辅助淡化系统的淡水产量比普通淡化系统的淡水产量最多高10.4 kg/h,造水比高0.67～1.15.

文章针对结构因素和非结构因素影响文丘里分流器分流效果的问题,首先对两相分配器仿真,将仿真结果与已有的实验结果进行对比,验证仿真计算模型的可靠性;然后通过计算流体动力学(computational fluid dynamics,CFD)模拟研究各因素对文丘里分流器分流效果的影响.研究结果表明:对于文丘里分流器,收缩段型线采用直线且各出口管与中心线采用60°的夹角可以使分流不均匀度更低,改进后的分流器不均匀度约降低28％;且随着入口制冷剂质量流量的增加和干度的降低,该分流器分流均匀性的效果更好.

Regulation of solar transmission through windows offers the potential to reduce energy consumption in buildings. Recently, the daylighting control characteristic of optical concentrators have drawn considerable research attentions owing to their variable transmittance in response to sun motion. In this research, we aim to propose and validate a novel way to smartly regulate the indoor daylighting environment while generating renewable electricity generation at the same time through the concentrating photovoltaic/Daylighting (TLWCPC-PV/D) skylight. This research particularly focuses on the evaluation of smart daylighting control (SDC) performance of it. The optical model of the TLWCPC-PV/D skylight was built with using ray-tracing simulation technique, which is also validated by experiment results. Because of the variable optical concentration process, the TLWCPC shows obvious SDC characteristic: when -32 degrees<theta<32 degrees, average daylighting efficiency is 11.15% while when 43 degrees <=theta <=-32 degrees and 32 degrees <= theta <= 43 degrees, average daylighting efficiency is 58.89%. Five cities with different latitudes are selected to perform the yearly daylighting control analysis. The comparative results indicated that orientation direction has an essential impact on SDC characteristic of the TLWCPC-PV/D skylight and the system in the North-South orientation shows excellent SDC ability i.e. it shows larger daylighting efficiency during the early morning and later afternoon periods while maintains lower daylighting efficiency during the noon period. Compared with other complex and expensive energy-saving glasses, the TLWCPC-PV/D skylight smartly adjusts the solar transmission through the optical concentration process according to sun motion and offers a new strategy of easy fabrication and multi-energy use that opens avenues for both static solar concentrator design and SDC mechanism in energy-saving buildings.Y

Compared with the PV electricity generation alone system, the hybrid photovoltaic/daylighting system is more efficient and more economical for the building application. In this paper, a novel self-regulating concentrating photovoltaic/daylighting system is proposed. Because the concentrator is made of the transparent material, the daylighting function can be efficiently incorporated without decreasing its optical efficiency. The transmittance characteristic of the concentrating photovoltaic/daylighting system is a vital parameter that is related to the electrical and daylighting performance of it, which also has a significant impact on the building’s energy consumption behavior. To address this issue, the experimental investigation of this new system towards the visible light transmittance in different seasons and under different weather conditions is presented for the first time. The transmittance evaluation method based on the integrating box is adopted for the experimental test. The experiments are conducted on four different days that are corresponding to different seasons and different weather conditions. The conversion factor of the integrating box is first experimentally calibrated. The internal illuminance on four walls of the integrating box and the external illuminance are obtained, based on results of which, the transmittance of the concentrating photovoltaic/daylighting system is determined. It's found through experimental results that under the sunny weather condition in the summer, autumn, and winter seasons, the daily average tested transmittance of the concentrating photovoltaic/daylighting system is 8.57%, 6.78%, and 7.43% respectively. The experimental results under the overcast weather condition indicate that the transmittance of the concentrating photovoltaic/daylighting system for the diffuse solar irradiance is 7.22%.

A series of Bi3+ based blue long afterglow phosphor Ca14Ga10Zn6O35:Bi3+ were successfully synthesized via solid state reaction method. Under ultraviolet excitation of the samples, a blue emission originated from 3P1 -> 1S0 transition of Bi3+engendered a broadband from 380 to 600 nm with peak at around 432 nm. The peak positions of the emission curves have experienced a slight red shift from 432 to 442 nm when the concentrations of Bi3+ were increased from 0.1 % to 1.5 %. After excitation stopped, the persistent luminescence from Bi3+ ions could last more than half an hour. The afterglow duration times were shortened remarkably with the increasing concentration of Bi3+, from several thousand seconds to several hundred seconds, along with decreased afterglow intensity. With the alkaline metals Li+ and Na+ co-doped to provide charge compensation, the emission intensity of Bi3+ ions was increased, together with compensated by the shortened persistent time. A series of thermoluminescence glow curves of 0.1 % Bi3+ doped sample were measured with different delay times to detect the population dynamics of traps. With the systematical experimental results, a reasonable model was proposed to illuminate the mechanism of the emission and persistent phenomenon of this promising novel Bi3+ based blue long afterglow phosphor.

Temperature sensing performance of GdVO4: Eu3+ phosphors have been studied using a method based on thermal coupling of the low-lying levels (7FJ: J = 0, 1, 2) of Eu3+. GdVO4: Eu3+ phosphors exhibit the outstanding luminescence characteristics with temperature and high detection sensitivity. Luminescence intensity ratio has been investigated between the 5D0 -> 7F4 emission intensities when 5D0 excited from thermally populated lowlying excited states 7F1 and 7F2 with respect to 7F0 level. The luminescence intensity ratio monotonously increases with rising of temperature from 133 K to physiological temperature of 313 K. Specifically, the maximum value of relative sensitivity SR reach to 6.73% K-1 for first scheme and 2.87% K-1 for second scheme. The GdVO4:Eu3+ phosphor shows the excellent relative sensitivity of 1.23% K-1 in physiological temperature range (310 K), recommending its potential for applications in bio-medical field.

Developing a feasible scheme for solid-state lighting with high-quality white light remains a significant challenge. Particularly, tunable luminescence with single-component white emission have been widely studied to improve the luminescence performance of phosphor-converted white light-emitting diodes (pc-WLEDs) phosphors. In this work, a novel spontaneous reduction phenomenon was first found in Eu-activated apatite-type Ba-5(PO4)(3)Cl phosphors prepared by a solid-phase reaction in air. Under 362 nm excitation, the luminescence results showed that a broad blue Eu2+ emission band with a peak at 437 nm appears unexpectedly in addition to the usual sharp orange-red emission of Eu3+. The mixed-valence fact of Eu2+/Eu3+ was further confirmed by X-ray photoelectron spectra and time-resolved spectroscopy techniques. The underlying mechanism could be explained by a charge compensation model. Accordingly, the local crystal-site engineering control of the luminescence in Ba5-yCay(PO4)(3)Cl:Eu2+/Eu3+ had been studied in detail by the introduction of Ca2+. It is found that the Ca2+ substitution of Ba2+ will lead to new splitting peaks of Eu3+ emission and a red-shift followed by a blue-shift of Eu2+ emission respectively, which could eventually adjust the luminescence of phosphors to the proper white light region. These phenomena are mainly ascribed to the introduction of Ca2+ to the structure modification of activator coordination environment. Finally, based on the thermal quenching results indicate that the potential application of the single-doped mixed-valence phosphor system in pc-WLEDs. (C) 2021 Elsevier B.V. All rights reserved.

对于螺杆式压缩制冷机组,润滑油的冷却是机组稳定、可靠运行的保证,而在几种冷却方式中,分相式热虹吸油冷却系统最适用于螺杆式压缩制冷机组.建立了分相式热虹吸油冷却系统的数学模型,研究了螺杆式压缩制冷机组的冷凝温度、液位高度差和连接管管径对系统换热性能的影响.结果表明:油冷却系统的换热量先随着液位高度差的增大而增大,然后保持稳定;连接管管径从32 mm变化至42 mm,油冷却系统的换热量提高12.2％～19.7％;冷凝温度升高会导致油冷却器内制冷剂的蒸发温度升高,削弱制冷剂和润滑油之间的换热能力,导致换热量降低.

The droplet suspension technology is used to study the effects of ambient temperatures (from 673 to 873 K) and gasoline blending ratios (from 0% to 20%) on evaporation and combustion characteristics of lubricating oil (LO), used lubricating oil (ULO) and the mixture of lubricating oil and gasoline (LO/gasoline and ULO/gasoline). The experimental results show that the evaporation process of LO80G20 (the blend of 80% LO and 20% gasoline by volume fraction) contains a transient heating period, a fluctuation evaporation period and a slow evaporation period at 673 K. The combustion process at high temperatures (from 723 to 873 K) includes an auto-ignition delay period, a combustion period and an extinction period. At the same ambient temperature, both the auto-ignition delay and lifetime of ULO are shorter than those of new LO. The occurrence time and intensity of puffing for ULO are earlier and stronger than those of new LO. For the mixture of lubricating oil and gasoline (LO/gasoline and ULO/gasoline), the auto-ignition delay, droplet lifetime and the occurrence time of puffing decrease with the increase of gasoline component.

Micro-thermoelectric coolers have great potential in the thermal management of highly integrated electronic devices, especially the local cooling. This paper develops a numerical model to explore the influence of Thomson effect on the cooling performance of micro-thermoelectric coolers, capturing interfacial and size effects. The presented model is validated with a commercial micro-thermoelectric cooler. And, analyses are carried out with respect to micro-thermoelectric coolers of different sizes, under different temperatures and cooling loads. The results indicate that a positive Thomson coefficient can improve the cooling capacity, and higher current and thickness correspond to greater impact of Thomson effect. In addition, the decrease of minimum cooling temperature caused by Thomson effect is even more obvious under higher cooling load. The results also show that the influence of Thomson effect on the maximum cooling temperature difference gradually becomes weaker as the cross area to thickness ratio increases. For heat fluxes of 100 W/cm(2) and 200 W/cm(2), the minimum cooling temperature can be respectively reduced by 2.1 K and 4.1 K, considering Thomson effect. In addition, for the thickness of 10 mu m, the increment of maximum cooling temperature difference gradually declines from 2.2 K to 1.1K as the cross area to thickness ratio increases. (C) 2020 Elsevier Ltd. All rights reserved.

A R134 a/CO2 cascade heat pump system was introduced, and the mathematical model of the system and each parameter was established. The trend of heat pump system performance was studied under different condensing temperature and evaporating temperature of low temperature stage, condensing temperature of high temperature stage, intermediate heat transfer temperature difference and the mass flow ratio of two stages. The result shows that the coefficient of performance（COP） of the cascade heat pump system increases with the rise of the evaporating temperature of low temperature stage and the drop of the condensing temperature of high temperature stage, and decreases with the rise of intermediate heat transfer temperature difference, while the trend of the mass flow ratio of high and low temperature stages is opposite. Meanwhile, there exists an optimal intermediate temperature which makes the COP of the system maximum.