热Σ-Δ调制技术及在MEMS气体传感器中的应用

微加热器是MEMS气体传感器的重要功能部件,其结构设计与温度控制是MEMS气体传感器设计的重要环节。针对一类典型MEMS气体传感器设计了一款采用热Σ-Δ调制技术的电路,对其微加热器进行闭环温度控制,相比传统的模拟闭环控制电路,该电路结构简单,对元件失配性要求低,在实现温度控制的同时实现了加热器激励信号的数字化。此外,作为调节控制的MOS管工作在开关状态,显著降低其功耗和对功率容量的要求。重点介绍了微加热器的热电等效模型、热Σ-Δ调制控制的基本工作原理、实现电路与测试结果等,实验数据表明微加热器温度控制环路信噪比可达60 dB以上。将其应用于一款可探测挥发性有机物(VOC)的MEMS气体传感器,温度控制稳定性达到0.75%,满足了传感器性能要求。

The Design of TZ-2 High Voltage Pulse Modulator

There are a few assistant heating objects included electron cyclotron resonate heating （ ECRH ）. Two 500 kW gyrotrons introduced from Russia were operated to launch 1 MW energy. So two set of TZ-2 high voltage pulse modulators are needed.

Regulatory Mechanism of Tea Polyphenols on Heat Stress in Animals

Teapolyphenols are the generic term of polyphenols in tea.Tea polyphenols are non-toxic and odorless with high oxidation resistance.Heat stress causes oxidative stress,which impairs the capacity of antioxidant defense system and immunity,thereby seriously affecting the production performance of animals.Teapolyphenols could reduce heatstress response in animals by scavenging harmful free radicals and increasing the activities of antioxidant enzymes.

A Preliminary Evaluation of Global and East Asian Cloud Radiative Effects in Reanalyses

Cloud radiative effects （CREs） at the top of the atmosphere （TOA） in three reanalysis datasets （the Eur- opean Center for Medium-Range Weather Forecasts In- terim Reanalysis （ERA-Interim）, the Japanese 55-yr Re- analysis Project （JRA-55）, and the Modem-Era Retro- spective Analysis for Research and Applications （MERRA）） are evaluated using recent satellite-based observations. The reanalyses can basically capture the spatial pattern of the annual mean shortwave CRE, but the global mean longwave CRE in ERA-interim and JRA55 is weaker than observed, leading to overestimations of the net CRE. Moreover, distinct CRE biases of the reanalyses occur in the Intertropical Convergence Zone （ITCZ）, coastal Pa- cific and Atlantic regions, and East Asia. Quantitative examination further indicates that the spatial correlations of CREs and TOA upward radiation fluxes with corre- sponding observations in ERA-Interim are better than in the other two reanalyses. Although MERRA has certain abilities in producing the magnitudes of global mean CREs, its performance in terms of spatial correlations in winter and summer are worse than for the other two re- analyses. The ability of JRA55 in reflecting CREs lies between the other two datasets. Compared to the global mean results, the spatial correlations of shortwave CRE in East Asia decrease and the biases of regional mean CREs increase in the three reanalyses. This implies that, cur- rently, it is still difficult to reproduce East Asian CREs based on these reanalyses. Relatively, ERA-Interim de- scribes the seasonal variation of East Asian CREs well, albeit weaker than observed. The present study also sug- gests that in-depth exploration of the ability of reanalysis data to describe aspects relating to cloud properties and rad- iation is needed usin~ more comprehensive observations.

Pulse modulated microwave and infrared thermography for superficial hyperthermia

A 3D temperature field distribution of biological tissue for superficial hyperthermia using a pulse modulated microwave （PMMW） was presented. A 3D sliced homogeneous phantom was radiated by the PMMW and an infrared thermal imager was applied to image temperature distribution throughout the phantom. The period of the PMMW is 3 s and the output power is 35 W. The temperature rises by at least 3 ℃ in the phantom when the duty cycle varies from 1/3, 1/2, 2/3 to 1 （denoted by scenarios 1-4）. Both the accumulative temperature-volume histogram and the relative depth-area ratio histogram show that the maximum temperature rise （MTR） is 6.6 and 8 ℃ in scenarios 2 and 3, and they are superior to scenarios 1 and 4. Furthermore, the PMMW can control temperature field distribution of biological tissue. It provides both preliminary basis for thermal volume control and new technology for temperature control and monitor in superficial hyperthermia.

Modulation of Tropical Cyclogenesis over the South China Sea by ENSO Modoki During Boreal Summer

This study examines the modulation of tropical cyclogenesis over the South China Sea （SCS） by the E1 Nifio-Southem Oscillation （ENSO） Modoki during the boreal summer. Results reveal that there were more tropical cyclones （TCs） formed over the SCS during central Pacific warming years and less TC frequency during central Pacific cooling years. How different environmental factors （including low-level relative vorticity, mid-level relative humidity, vertical wind shear, and potential intensity） contribute to this influence is investigated, using a genesis potential （GP） index developed by Emanuel and Nolan. Composite anomalies of the GP index are produced for central Pacific warming and cooling years separately, which could account for the changes of TC frequency over the SCS in different ENSO Modoki phases. The degree of contribution by each factor is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. The results suggest that the vertical wind shear and low-level relative vorticity, which are associated with the ENSO Modold-induced anomalous circulations in Matsuno-Gill patterns, make the largest contributions to the ENSO Modoki modulation of tropical cyclogenesis over the SCS as implied by the GP index. These results highlight the important roles of dynamic factors in the modulation of TC fre-quency over the SCS by the ENSO Modold during the boreal summer.

Presence of Contaminants in Refrigerant and Their Effect on Refrigeration Cycle

Refrigerant is a medium used in refrigeration cycle. Until now in thermodynamic models calculations of refrigerant is not considered with lubricant and moist air but as an ideal pure gas （without any contaminants）. This is also the case in refrigeration cycle where the refrigerant is very often considered as an ideal one. Lubricant, air and water vapour are not considered in thermodynamic calculations in spite of their existence. The problems in the existing research are summarized. A further study is suggested on refrigerant systems. This circulation of such calculations is at the origin of a deviation from a theoretical behaviour. This article aims at reviewing the researches of oil-refrigerant, air-refrigerant, moist air-refrigerant or oil-moist air-refrigerant mixtures and focuses particularly on mixture enthalpy calculation. This paper deals with the description of the real mixture of refrigerant and contaminants （lubricant, water, moist air and other remains of refrigerants at elevated pressures and temperatures） which flow in a refrigerating cycle and the main point of this paper is to appoint thermodynamic parameters of such a mixture using the thermodynamic formulas.

Coordinated control strategy for wind power accommodation based on electric heat storage and pumped storage

To solve the severe problem of wind power curtailment in the winter heating period caused by ＂power determined by heat＂ operation constraint of cogeneration units, this paper analyzes thermoelectric load, wind power output distribution and fluctuation characteristics at different time scales, and finally proposes a two level coordinated control strategy based on electric heat storage and pumped storage. The optimization target of the first level coordinated control is the lowest operation cost and the largest wind power utilization rate. Based on prediction of thermoelectric load and wind power, the operation economy of the system and wind power accommodation level are improved with the cooperation of electric heat storage and pumped storage in regulation capacity. The second level coordinated control stabilizes wind power real time fluctuations by cooperating electric heat storage and pumped storage in control speed. The example results of actual wind farms in Jiuquan, Gansu verifies the feasibility and effectiveness of the proposed coordinated control strategy.

Solar air conditioning researches and demonstrations in China

This paper mainly shows the demonstration of solar air conditioning systems in China, which includes LiBr-H2O absorption cooling, silica gel-water adsorption chiller, desiccant cooling and hybrid integrated energy systems for buildings. The match of solar collector types and chiller types have been discussed and suggested.

Modulating a Solar Parabolic Dish to Produce Boiled Water

A two-meter parabolic solar concentration dish has been modulated to produce boiled water over 100℃ for various purposes of central heating services. For an effective performance, the system required both continuous exposure of the dish to sunlight during the day time as well as to an electric control circuit （tracking system）. The amount of the potable water was dependent particularly on the accurate centering of the system which could increase upon preheating. This system has therefore been possible to heat up water at home via increasing the temperature in hot tank by both covering the hot water tank and isolating it from the surroundings using insulators. Applications of a successful parabolic solar concentration has also been designed to provide desalinated water for domestic usage which operates with temperatures higher than other types of the solar radiation for the future.

The Performance of the First Pilot Thermoacoustic Refrigerator

The simple goal of this work is constructing a cheap, demonstrative model of a thermoacoustic refrigerator. To this end, the author succeeded in designing, building and testing the first pilot thermoacoustic refrigeration in Jordan basing on the theory of using sound waves as a coolant. The pilot thermoacoustic refrigerator was built from inexpensive and readily available parts in Mutah University, Jordan. The thermoacoustic refrigerator was operated for several hours. Consequentially, this experiment proved that thermoacoustic refrigerators were technically possible. Additionally, this experiment did yield some findings regarding the efficiency of thermoacoustic refrigeration. On other hand, solid flow CFD software was used to simulate the performance of thermoacoustic refrigerator especially the temperature and velocity inside the refrigerator. In general, very good agreement was deduced.

Design and Implementation of High Power Factor LED Driver with Hot Swap, Smart Output Voltage Regulation and Dimming Control

In this paper, a high power factor LED driver with hot swap, smart output voltage regulation and dimming control is proposed. The dimming control is used to change LED brightness. During converter is working, the hot swap function supply users to remove and insert LED module. The smart output voltage can regulate quickly and rightly output voltage in different number of LED series connection. The system consists two stages, one is 50 W flyback converter which is used as power factor corrector, it is input source is 110-220 V, PF （power factor） is about 0,994. The other is Boost DC/DC converter, it can offer 35-60 V of output voltage. Finally, a prototype has been built and tested. The simulation and experimental results are shown to verify the feasibility of the proposed method.

Graphene-based thermal modulators

The quest for materials and devices that are capable of controlling heat flux continues to fuel research on thermal controlling devices. In this letter, using molecular dynamics simulations, we demonstrate that a partially clamped singlelayer graphene can serve as a thermal modulator. The mismatch in phonon dispersion between the unclamped and clamped graphene sections results in phonon interface scattering, and the strength of interface scattering is tunable by controlling the clamp-graphene distance via applying the external pressure. Owing to the ultra-thin structure of graphene and its highly sensitive phonon dispersion to external physical interaction, the modulation efficiency--which is defined as the ratio of the highest to lowest heat flux-can reach as high as 150% at a moderate pressure of 50 GPa. This modulation efficiency can be further enhanced by arranging a number of clamps in series along the direction of the heat flux.

Modulation of land-sea thermal contrast on the energy source and sink of tropical cyclone activity and its annual cycle

In general,the tropical cyclone(TC) activity is considered to be influenced by the heat content of underlying ocean,vertical shear of horizontal wind,vorticity in the low troposphere,moisture in the troposphere,and favorable condition for deep convection development.However,these factors by nature merely present the internal factors of either atmosphere or ocean which influence the TC activity.In fact,the energy budget of the Earth system and its variation,modulated by the land-sea thermal contrast,are the intrinsic reasons responsible for the variation of TC activity.Here we investigate the modulation of diabatic heating distribution associated with the land-sea thermal contrast on the distribution of TC activity energy source and sink as well as the seasonality.An accumulated energy increment index(AEI) is defined using the TC best track data,and the energy sources and sinks of TC activity are then diagnosed effectively and practically according to the distribution of AEI.Results show that the thermal contrast of land and ocean is the primary reason for asymmetric distribution of TC activity about the Equator as well as the zonally asymmetric distribution of TC activity.The energy sources of TC activity are dominated by condensation heating of deep convection or double-dominant heating,which includes the condensation heating and cooling of longwave radiation(LO),while the sink areas are dominated by LO.The large scale diabatic heating associated with land-sea thermal contrast results in more favorable conditions for TC activity over the west part of oceans than those over the east parts.Moreover,the intensity of interaction of different diabatic heating over the west and east parts of ocean is also affected by the zonal scale of the oceans,which induces the difference of TC activity over the western North Pacific(WNP) and North Atlantic(ATL).The favorable westerlies and anticyclonic vertical shear associated with the tropical zonally asymmetric diabatic heating also contribute to the most intense TC activity over the WNP.The variation of large scale diabatic heating modulates the annual cycle of TC energy sources and sinks.In particular,the annual cycle over the WNP is the most typical one among the three basins(the WNP,the south Indian Ocean,and western South Pacific) that are characterized by the meridional shift of the energy sources and sinks.However,sources over the eastern North Pacific tend to extend westward and withdraw eastward associated with the variation of LO,while over the ATL,sources always merge from small pieces into a big one as the different diabatic heating over its west and east parts interacts with each other.Over the boreal Indian Ocean,the subcontinental scale land-sea heating contrast modifies the large scale circulation,and consequently contributes to the bimodal annual cycle of TC activity.In summary,TC activities are closely related to the interaction among various components of the climate system more than the atmosphere and ocean.

Ballistic thermal transport in a cylindrical quantum structure modulated with double quantum dots

Ballistic thermal transport properties in a cylindrical quantum structure modulated with double quantum dots(DQDs) are investigated.Results show that the transmission coefficients exhibit the irregular oscillation.Some resonant transmission peaks and stop-frequency gaps can be observed,and the number and positions of these peaks and gaps are sensitive to the sizes of DQDs.With increasing the temperature,the thermal conductance undergoes a transition from the decrease to increase,and can be efficiently tuned by modulating the radius,length of DQDs as well as the interval between DQDs.In addition,at low temperatures,the enhancement of the thermal conductance can be also observed in this case.Some similarities and differences between the cylindrical and rectangular structures are identified.