Effect of linear carboxylic ester on low temperature performance of LiMn_2O_4-graphite cells

To improve the low-temperature performances of Li-ion cells, three types of linear carboxylic ester-based electrolyte, such as EC/EMC/EA（1：1：2, mass ratio）, EC/EMC/EP（1：1：2, mass ratio） and EC/EMC/EB（1：1：2, mass ratio）, were prepared to substitute for industrial electrolyte（EC/EMC/DMC）. Then, 18650-type Li Mn2O4-graphite cells（nominal capacity of 1150 mA ·h） were assembled and studied. Results show that the cells containing three types of electrolyte are able to undertake 5C discharging current with above 93% capacity retention at-20 °C. Electrochemical impedance spectra show that the discharge capacity fading of Li-ion cells at low temperature is mainly ascribed to the charge transfer resistance increasing with temperature decreasing. In comparison, the cells containing electrolyte of 1.0 mol/L LiPF6 in EC/EMC/EA（1：1：2, mass ratio） have the highest capacity retention of 90% at-40 °C and 44.41% at-60 °C, due to its lowest charge-transfer resistance.

Thin Film Chip Resistors with High Resistance and Low Temperature Coefficient of Resistance

High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than ±15×10-6/℃.Cr-Si-Ta-Al films were prepared with Ar flow rate and sputtering power fixed at 20 standard-state cubic centimeter per minute(sccm) and 100 W,respectively.The experiment shows that the electrical properties of Cr-SiTa-Al deposition films can meet the specification requirements of 0603 ty...

Temperature Compensation Algorithm for Hydraulic System Pressure Control

In this paper the control mechanism of solenoid valve is analyzed,which shows the solenoid valve control is actually the control of coil current.The response characteristic of coil current is related to coil inductance and resistance.The coil resistance is influenced greatly by the ambient temperature and the self-heating of coil,which affects the control precision of coil current.First,considering the heat dissipation mode of coil,the coil temperature model is established from the perspective of heat conduction,and a temperature compensation algorithm for hydraulic system pressure control is put forward.Then the hardware-in-the-loop testbed is set up by using the dSPACE platform,carrying out wheel cylinder pressurization tests with inlet valve fully opened at-40℃ and 20℃,and testing the actual pressure of wheel cylinder with the target pressures at-40℃ and 6 000 kPa/s(pressurization rate).The results show that the pressure control temperature compensation algorithm proposed in this paper accurately corrects the influence of resistance temperature drift on the response accuracy of wheel cylinder pressure.After the correction,the pressure difference is less than 500 kPa,which can meet the control accuracy requirements of solenoid valve,enriching the linear control characteristic of solenoid valve.

Temperature-Irradiance Matrix and Determination of Temperature Coefficients of a Monocrystalline PV Module

Photovoltaic (PV) modules performance testing and energy rating as described in IEC 61853-1 standard depend on electrical performance parameters (short-circuit current, open-circuit voltage, maximum-power) of PV modules as a function of temperature and irradiance. In this work, in order to precisely determine the effects of temperature on the electrical parameters of a monocrystalline PV module, the temperature controlled, xenon light based solar simulator system with irradiance attenuating masks was used. This solar simulator, according to the IEC 60904-9 standard in terms of spectral match, spatial non-uniformity and temporal instability has A+A+A+ classes which are two times better than the standard requirements for a solar simulator to be used in PV module measurements. Moreover, the thermal chamber used in this work is a closed type chamber with fast opening door for not allowing the distortion of temperature uniformity over the surface of PV modules under test. Within about 2 m × 2 m area within 15°C to 75°C temperature interval, the temperature uniformity obtained for this system is less than 1.0°C which is almost two times better than the IEC 60891 standard requirements (±2.0°C). The temperature and irradiance dependent measurements of the electrical performance parameters of a mono-crystalline PV module at various irradiance levels and the evaluation of its temperature coefficients [α (% °C-1), β (% °C-1) and δ (% °C-1)] were done by implementing the interpolation method described in IEC 60891 standard.

Modified 2CLJDQP model and the second virial coefficients for linear molecules

A modified form of 2CLJDQP potential model is proposed to calculate the second virial coefficients of two-center Lennard-Jones molecules. In the presented potential model, the potential parameters σ and ε are considered as the temperature-dependent parameters in the form of hyperbolical temperature function based on the theory of temperaturedependent potential parameters. With this modified model, the second virial coefficients of some homonuclear molecules（such as O2, Cl2, CH3CH3, and CF3CF3） and heteronuclear molecules（such as CO, NO, CH3 F, CH3 Cl, CH3CF3,CH3CHF2, and CF3CH2F） are calculated. Then the Lorentz–Berthelot mixing rule is modified with a temperaturedependent expression, and the second virial coefficients of the heteronuclear molecules（such as CH3 F, CH3 Cl, and CH3CF3） are calculated. Moreover, CO2 and N2O are also studied with the modified 3CLJDQP model. The calculated results from the modified 2CLJDQP model accord better with the experimental data than those from the original model.It is shown that the presented model improves the positive deviation in low temperature range and negative deviation in high temperature range. So the modified 2CLJDQP potential model with the temperature-dependent parameters can be employed satisfactorily in large temperature range.

Research on frequency-temperature compensated sapphire-SrTiO_3 loaded cavity for hydrogen maser

To obtain frequency-temperature compensation in a sapphire loaded cavity for hydrogen maser, a dielectric named SrTiO3 is employed whose temperature coefficient of permittivity is opposite to that of sapphire. Based on theoretical analysis and computer simulation, a TE011 mode of a sapphire loaded cavity associated with two small rings of SrTiO3 with different thickness is solved, and the useful parameters that influence the temperature coefficient of cavity are calculated. Finally an experiment is brought forward and its results are very close to the computing results. When the thickness of SiTiO3 dielectric is 7 mm and the diameter is 17 mm in configuration b, the temperature coefficient of cavity is decreased from -58.8 kHz/K to -8.2 kHz/K and the quality factor is 40248.

A Piecewise-Linear Compensated Bandgap Reference

A bandgap voltage reference is presented with a piecewise linear compensating circuit in order to reduce the temperature coefficient.The basic principle is to divide the whole operating temperature range into some sub ranges.At different temperature sub ranges the bandgap reference can be compensated by different linear functions.Since the temperature sub range is much narrower than the whole range,the compensation error can be reduced significantly.Theoretically,the precision can be improved unlimitedly if the sub ranges are narrow enough.In the given example,with only three temperature sub ranges,the temperature coefficient of a conventional bandgap reference drops from 1 5×10 -5 /℃ to 2×10 -6 /℃ over the -40℃ to 120℃ temperature range.

A Low Voltage,Low Power RF/Analog Front-End Circuit for Passive UHF RFID Tags

This paper presents a low voltage, low power RF/analog front-end circuit for passive ultra high frequency （UHF） radio frequency identification （RFID） tags. Temperature compensation is achieved by a reference generator using sub-threshold techniques. The chip maintains a steady system clock in a temperature range from - 40 to 100℃. Some novel building blocks are developed to save system power consumption,including a zero static current power-on reset circuit and a voltage regulator. The RF/analog front-end circuit is implemented with digital base-band and EEPROM to construct a whole tag chip in 0. 18μm CMOS EEPROM technology without Schottcky diodes. Measured results show that the chip has a minimum supply voltage requirement of 0.75V. At this voltage, the total current consumption of the RF/analog frontend circuit is 4.6μA.

Low remanence temperature coefficient Sm1-xErx(Co,Fe,Cu,Zr)z magnets operating up to 400℃

Er-doped Sm1-xErx(CobalFe0.15Cu0.08Zr0.03)7.8(x=0,0.1,0.2,0.3)magnets with a low remanence temperature coefficient were prepared by powder metallurgy method.The influence of Er content on the remanence and microstructure was investigated.X-ray diffractometer(XRD)analysis showed that the magnets with different Er contents consist of 2:17 R phase and 1:5 H phase.Scanning electron microscopy(SEM)analysis showed that the composition of the matrix is consistent with stoichiometric composition and no obvious precipitated phase appears.With the increase in doped Er amount,the temperature stability of Sm1-xErx(CobalFe0.15Cu0.08Zr0.03)7.8(x=0,0.1,0.2,0.3)is getting better.When x is up to 0.3,the magnets with a low remanence temperature coefficient are obtained and the remanence descends tardily from 0.86 to 0.80 T as the temperature rises from room temperature to 400℃.These results indicate that Er substitution for Sm in SmCobased permanent magnets together with optimal composition and proper heat treatment could achieve a desired magnetic performance combined with high thermal stability.

Excitation of extremely low-frequency chorus emissions: The role of background plasma density

Low-frequency chorus emissions have recently attracted much attention due to the suggestion that they may play important roles in the dynamics of the Van Allen Belts.However, the mechanism(s) generating these low-frequency chorus emissions have not been well understood..In this letter, we report an interesting case in which background plasma density lowered the lower cutoff frequency of chorus emissions from above 0.1 f_(ce)(typical ordinary chorus) to 0.02 f_(ce)(extremely low-frequency chorus).Those extremely low-frequency chorus waves were observed in a rather dense plasma, where the number density N_e was found to be several times larger than has been associated with observations of ordinary chorus waves.For suprathermal electrons whose free energy is supplied by anisotropic temperatures, linear growth rates(calculated using in-situ plasma parameters measured by the Van Allen Probes) show that whistler mode instability can occur at frequencies below 0.1 f_(ce) when the background plasma density N_e increases.Especially when N_e reaches 90 cm–3 or more, the lowest unstable frequency can extend to 0.02 f_(ce) or even less, which is consistent with satellite observations.Therefore, our results demonstrate that a dense background plasma could play an essential role in the excitation of extremely lowfrequency chorus waves by controlling the wave growth rates.

Trimmable bandgap reference circuit with exponential curvature compensation

This paper proposes an improved exponential curvature-compensated bandgap reference circuit to exploit the exponential relationship between the current gainβof the bipolar junction transistor(BJT)and the temperature as well as reduce the influence of resistance-temperature dependency.Considering the degraded circuit performance caused by the process deviation,the trimmable module of the temperature coefficient(TC)is introduced to improve the circuit stability.The circuit has the advantages of simple structure,high linear stability,high TC accuracy,and trimmable TC.It consumes an area of 0.09 mm^(2)when fabricated by using the 0.25-μm complementary metal-oxide-semiconductor(CMOS)process.The proposed circuit achieves the simulated power supply rejection(PSR)of about-78.7 dB@1 kHz,the measured TC of~4.7 ppm/℃over a wide temperature range from-55℃to 125℃with the 2.5-V single-supply voltage,and the tested line regulation of 0.10 mV/V.Such a high-performance bandgap reference circuit can be widely applied in high-precision and high-reliability electronic systems.

Discovery of the low temperature phase barium metaborate (BBO) and its significance in the search for new type nonlinear optical materials

1 History of discovery of the low temperature phase barium metaborate （BBO）——an excel-lent new-type ultraviolet radiation frequency-doubling crystalline materialTHE first laser excitation in 1960 with ruby （α-Al2O3: Cr） as a laser crystal and the first dou-bling of frequency （347. 15 nm） in 1961 by irradiating quartz crystal （α-SiO2） with a 694. 3nm laser beam have laid the basis for the study of laser and nonlinear optical （NLO） crystals,

低温共烧陶瓷激光测厚系统设计与误差分析

基于提升低温共烧陶瓷(low temperature co-fired ceramic,LTCC)厚度的检测精度、测量效率和可溯源性的需求,设计一套LTCC激光测厚系统。针对测量精度难以满足需求的问题,对存在误差进行分析,采用厚度测量用调整夹具消除同轴度误差和线性度误差,优化设计结构降低倾角误差,循环传感器标定消除重复度误差,通过数据优化和滤波处理降低机械振动误差,提高了系统测量精度。与实际产品厚度数据对比,最终精度误差≤5μm,符合产品的应用要求,具有广阔的应用市场。

一种低温度系数高阶补偿基准电压电路设计

基准电压对模拟系统的性能与精度有着至关重要的影响.一般的曲率补偿仅能消除与温度相关的二阶项,难以满足某些电路对高精度的要求.现有的电路存在温度系数较高的问题,亟须对更高阶进行补偿.本文提出了一种新的高阶曲率补偿方法,通过利用CMOS晶体管亚阈值特性设计,成功实现了一种低温度系数电压基准电路.该方法首先利用两个不同温度系数的电流流过相同的亚阈值区CMOS晶体管,产生两个具有不同温度特性的栅源电压.然后,通过对这两个不同温度特性的栅源电压进行相减,产生对数电压,并与一阶补偿电压进行加权叠加,从而实现高阶补偿.为了提高电源抑制比(PSRR),该电路采用了高增益负反馈回路,避免了传统电压基准电路中放大器的使用,进一步地降低了功耗.本设计基于0.18μm CMOS工艺,在Cadence软件下完成电路设计、版图设计与仿真验证.仿真结果显示,该电路正常工作电压范围为1.6~3 V,在2 V的工作电压下,基准电压输出295 mV,在-45~125℃范围内温度系数为1.26 ppm/℃,PSRR为51.1 dB@1 kHz,最大静态电流为8.9μA.结果表明,该基准电压电路能够满足高精度集成电路系统的需求.

一种低温漂低功耗的带隙基准电压源设计

为了提高DC-DC转换器的性能,提出了一种电压带隙基准。通过调节参数抵消掉两路电流的一阶温度项,得到了只具有常数项和高阶温度项的电流,从而在输出电阻上转化为电压补偿三极管的高阶温度项,进而使得带隙具有较低的温度系数。之后在输出端加上RC滤波器,使得高频段的电源抑制比得到提升。同时为了探索带隙在低功耗下的工作特性,几乎将所有MOS管置于亚阈值区,达到降低静态电流的效果。基于TSMC 0.18μm CMOS工艺完成了电路的设计与仿真,结果表明,在1.8 V的电源电压下,带隙输出为1.256 V;在-40~140℃的变化范围内,温度系数为6.3×10^(-6)℃^(-1);通过增加RC滤波器,高频电源抑制比为-65 dB@10 MHz;而且整个带隙的静态电流仅有6.2μA。

一种新型带曲率补偿的带隙基准

针对传统带隙基准存在温度漂移大以及电源抑制比低的问题,提出了一种新型的带曲率补偿的带隙基准电压源。采用基极电流补偿以及曲率补偿技术对传统带隙基准结构进行改进。设计了低失配改进电路、低温漂改进以及启动电路等。利用共源共栅电流镜技术和负反馈网络保证带隙基准输出电压,极大程度降低了运放失调电压对带隙基准电压的干扰,实现了低温漂特性。基于东部高科0.18μm BCD工艺,在Cadence Spectre下进行仿真。仿真结果表明:该带隙基准电路在-40~150℃温度范围内,输入电压为5 V,输出电压稳定在1.192 V;温度系数为4.84×10^(-6)/℃;在低频时电源抑制比为-78 dB。

基于低居里点PTC材料的风机叶片防冰数值模拟及试验验证

叶片覆冰会严重影响风机的安全稳定运行。目前,电热防冰是最高效可靠的风机叶片防冰方法,但存在防冰区域受热不均匀、局部覆冰以及过多分区导致防冰系统过于复杂等问题。为此提出采用正温度系数(positive temperature coefficient,PTC)材料进行风机叶片自适应电加热防冰的创新方法,通过原位聚合法成功制备了一种低居里点PTC材料,其居里温度点为1℃。随后,基于该材料的阻-温特性,建立了风机叶片的电加热防冰模型,并进行数值模拟。研究结果显示,当采用低居里点PTC材料进行风机叶片电加热防冰时,无需进行防冰区域的分区,就能使得防冰区域受热更加均匀。在一定的工作电压下,低居里点PTC材料在不同环境温度和风速下展现出自适应调节加热功率的能力,并且经过100次循环阻-温测试后,材料仍具有极强的自适应调节能力。最后,通过试验验证了材料的这种自适应调节能力。该研究结果为后续基于低居里点PTC材料的风机叶片防冰系统的研究奠定了坚实基础。

基于磁性传感器的低失调温度补偿接口电路设计

面向磁性传感器在物联网(IoT)技术中的广泛应用,该文基于180 nm CMOS工艺设计了一种具有低失调电压,低温度漂移特性的霍尔传感器接口电路。针对霍尔传感器灵敏度的温度漂移特性,该文设计了一种感温电路并与查表法相结合,调节可编程增益放大器(PGA)的增益有效地降低了霍尔传感器的温度系数(TC)。在此基础上,通过在信号主通路中使用相关双采样(CDS)技术,极大程度上消除了霍尔传感器的失调电压。仿真结果表明,在–40°C~125°C温度范围内,霍尔传感器的TC从966.4 ppm/°C减小到了58.1 ppm/°C。信号主通路的流片结果表明,霍尔传感器的失调电压从25 mV左右减小到了4 mV左右,霍尔传感器的非线性误差为0.50%。芯片的总面积为0.69 mm^(2)。

一种高PSRR低温漂无运放带隙基准

针对无运放带隙基准电压源温度特性及电源抑制比差的问题,设计一种高电源抑制比、低温漂的无运放带隙基准电路。该电路通过电流镜进行钳位,避免运算放大器失调电压对输出基准的影响,利用晶体管栅极与三极管基极生成稳定的补偿电流,以降低基准电压的高阶温度系数,输出端采用共源共栅结构提高电源抑制比。基于SMIC 0.18μm BCD工艺在Cadence环境下对电路进行仿真,仿真结果表明:在-40~125℃范围内,电路的温度系数为3.187×10^(-6)/℃,10 Hz时电源抑制比为-88.6 dB,1 MHz时电源抑制比为-50.2 dB。在考虑启动电路影响的情况下,电路在5 V电源下的静态电流为3.78μA,带隙基准的版图面积为160μm×183μm。可实现对基准电压高阶温度项的补偿,降低温度系数,并在没有滤波电容的条件下提高带隙基准的PSRR。

MEMS加速度计全温性能优化方法

针对微机电系统(MEMS)加速度计全温性能低的问题,提出锚区应力对消方法、低应力粘接工艺和温度补偿方法。首先,通过调整两个键合的锚区面积大小实现锚区应力对消,使得加速度计的温度性能得到改善;然后,建立加速度计堆叠封装模型并对专用集成电路(ASIC)粘接参数、加速度计敏感结构点胶方式与点胶参数进行仿真分析,从而确定了加速度计的低应力粘接形式和粘接工艺;最后,对加速度计零偏和标度因数设计了三阶温度补偿方法并进行了实验测试。实验结果表明,加速度计全温零偏稳定性达到47.3μg(1σ)、全温标度因数稳定性达到43.6 ppm(1σ),提高了加速度计的全温性能。