基于LabVIEW的喷射制冷测控系统的开发

随着能源问题日益引起人们的注意,利用低品位热源驱动的制冷方式-喷射制冷也逐渐引起人们的重视。本实验系统采用电加热来模拟太阳能。本文主要介绍了在LabVIEW平台上开发的喷射制冷测控系统,该系统可以实现数据的实时采集、保存以及数据分析等功能。     

船用低温蒸馏海水淡化装置二级引射器的数值模拟

目前船用蒸馏海水淡化系统中,为减小装置体积并实现系统节能目标,引射器通常需要同时具有抽气和抽水功能,而传统的单级引射器只能形成单一真空度,从而影响淡水产率.文章提出了一种二级双吸口引射器设计方案,通过对引射器的流场特性进行数值模拟,分析结果表明入口流速和压力升高有利于提高真空度,而出口压力升高则会降低真空度.实验结果显示,在流速大于3.5 m/s时,模拟结果与实验数据基本一致,引射器吸口真空度可达到92％和90％,满足了船用引射器性能要求.     

Heating performance of a ground source heat pump system installed in a school building

The heating performance of a water-to-refrigerant type ground source heat pump system is represented in this paper under the actual working conditions of the GSHP(ground source heat pump) system during the winter season of 2008.Ten heat pump equipments with the capacity of 10 HP each and a closed vertical typed-ground heat exchanger with 24 boreholes of 175 m in depth were constructed.We investigated a variety of working conditions,including the outdoor temperature,the ground temperature,and the water tempe...     

换热站并联水泵分布式优化控制

针对现有换热站并联水泵优化算法在集中式架构下控制适应性不足的问题,本文提出了一种改进的分布式并联水泵优化算法.首先,建立了并联水泵的分布式控制系统,并对该优化问题的数学模型进行描述,在目标函数中引入自适应非线性因子;然后,设计了改进的分布式果蝇优化算法,在该算法中每台水泵的控制器仅通过与邻居控制器交互信息即可完成并联水泵的优化;并且,在嗅觉搜索阶段,使用正弦余弦策略替代赋予个体距离与方向的随机策略;最后,以两个实际换热站中不同并联水泵系统为例对算法进行仿真验证,并基于仿真结果进行性能分析.结果表明,相较于传统算法,改进的分布式果蝇优化算法能得到更优的控制策略,有着收敛速度快、稳定性好和鲁棒性强的特点;并且该算法适用于不同系统的并联水泵优化问题,具有可扩展性.在实际工程验证中相较于集中式算法,该算法在总功率和计算时间上分别平均降低了5.47%和29.90%,因此,能够满足实际换热站中对并联水泵热负荷优化分配的需求.     

热泵干制机自动控制系统的研制

分析了自行研制的热泵干制机的结构及工作原理,并研制了以PLC为下位机,计算机为上位机的热泵干制机自动控制系统,可实现对干制时间、风速、干制温度等进行设定和自动控制,并可实时显示干制过程的各种技术参数和曲线图形;使用结果表明:该试验系统设计合理,可方便地进行热泵干制试验,能满足不同农产品在干制过程中的安全性及控制精度的要求.     

Development of a two-band enhanced vegetation index without a blue band

The enhanced vegetation index (EVI) was developed as a standard satellite vegetation product for the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS). EVI provides improved sensitivity in high biomass regions while minimizing soil and atmosphere influences, however, is limited to sensor systems designed with a blue band, in addition to the red and near-infrared bands, making it difficult to generate long-term EVI time series as the normalized difference vegetation index (NDVI) counterpart. The purpose of this study is to develop and evaluate a 2-band EVI (EVI2), without a blue band, which has the best similarity with the 3-band EVI, particularly when atmospheric effects are insignificant and data quality is good. A linearity-adjustment factor β is proposed and coupled with the soil-adjustment factor L used in the soil-adjusted vegetation index (SAVI) to develop EVI2. A global land cover dataset of Terra MODIS data extracted over land community validation and FLUXNET test sites is used to develop the optimal parameter (L, β and G) values in EVI2 equation and achieve the best similarity between EVI and EVI2. The similarity between the two indices is evaluated and demonstrated with temporal profiles of vegetation dynamics at local and global scales. Our results demonstrate that the differences between EVI and EVI2 are insignificant (within ± 0.02) over a very large sample of snow/ice-free land cover types, phenologies, and scales when atmospheric influences are insignificant, enabling EVI2 as an acceptable and accurate substitute of EVI. EVI2 can be used for sensors without a blue band, such as the Advanced Very High Resolution Radiometer (AVHRR), and may reveal different vegetation dynamics in comparison with the current AVHRR NDVI dataset. However, cross-sensor continuity relationships for EVI2 remain to be studied.     

Predicting Enhanced Vegetation Index (EVI) curves for ecosystem modeling applications

Vegetation indices derived from remote sensing data provide information about the variability in stature, growth and vigor of the vegetation across a region, and have been used to model plant processes. For example, the Enhanced Vegetation Index (EVI) provides a measure of greenness of the vegetation that can be used to predict net primary production. However, ecosystem models relying on remote sensing data for EVI or other vegetation indices are limited by the time series of the satellite data record. Our objective was to develop a statistical model to predict EVI in order to extend the time series for modeling applications. To explain the functional behavior of the seasonal EVI curves, a two-stage multiple regression fitting procedure within a semi-parametric mixed effect (SPME) model framework was used. First, a linear mixed effect (LME) model was fitted to the EVI with climate indexes, crop and irrigation information as predictor variables. Second, Penalized B-splines were used to explain the behavior of the smooth residuals, which result from a smooth model fit to the smooth EVI data curve, in order to describe the uncertainty of the EVI curve. Individual models were fit within individual Major Land Resources Areas (MLRAs). Predicted seasonal EVI, derived from our regression equations, showed a strong agreement with the observed EVI and was able to capture the site by site and year by year variation in the EVI curve. Out-of-sample prediction produced excellent results for a majority of the sites, except for sites without clear seasonal patterns, which may have resulted from cloud contamination and/or snow cover. Therefore, given the appropriate climate, crop, and irrigation information, the proposed approach can be used to predict seasonal EVI curves for extending the time series into the past and future.     

并联式太阳能热泵热水器控制系统设计

阐述了并联式太阳热泵热水器是最易受推广使用的太阳能热泵热水器类型;针对23目前并联式太阳能热泵热水器存在的集成化控制问题,分析了并联式太阳热泵热水器控制系统的控制要求,采用水位、温差与时间相结合的控制方法,以ATmega48单片机为核心,研究了控制系统的工作原理、硬件结构及控制数据流程;系统能够根据天气、水温等不同情况自动选择太阳能机组或空气能热泵机组来制取热水,并且具有主要设备的故障自诊断功能、压缩机延时保护功能及智能化霜功能,提高了该热水器的稳定性和低温制热效率;测试结果表明:使用该集成系统后,系统平均能源利用率提高了约23%。     

A comparison of Landsat TM and MODIS vegetation indices for estimating forage phenology in desert bighorn sheep (Ovis canadensis nelsoni) habitat in the Sonoran Desert,USA

Sonoran Desert bighorn sheep (Ovis canadensis mexicana) occupy rugged upland areas that experience irregular periods of vegetation growth associated with precipitation events. These episodic and often spatially limited events provide important forage and preformed water resources that may be important drivers of animal movement and habitat use. Habitat-use models that incorporate forage phenology would broaden our understanding of desert bighorn ecology and have considerable potential to inform conservation efforts for the species. Field-based methods are of limited utility to characterize vegetation phenology across large areas. Vegetation indices (VI) derived from satellite imagery are a viable alternative, but may be confounded by areas of high relief and shadow effects that can degrade VI values. The varying spatial and temporal resolutions of readily available satellite sensors, such as the Landsat thematic mapper (TM) and moderate-resolution imaging spectrometer (MODIS), present additional challenges. In this study, we sought to minimize degrading effects of terrain on TM- and MODIS-based estimates of vegetation phenology. We compared effects of high topographic relief on time series MODIS- and TM-based VI such as the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) using VI departures from average (DA) in shaded and unshaded areas. Sun elevation angle negatively impacted TM-derived NDVI and EVI values in areas of steep terrain. In contrast, MODIS-derived NDVI values were insensitive to sun elevation and terrain effects, whereas MODIS-derived EVI was degraded in areas of steep terrain. Time series MODIS NDVI and EVI DA values differed significantly during months of low sun elevation angle. Average MODIS EVI departure values were ≥20% lower than NDVI under these conditions, confounding time series estimates of plant phenology. Our best results were obtained from MODIS 16-day composited NDVI. These remote-sensing-based VI estimates of seasonal plant phenology and productivity can be used to inform models of habitat use and movements of desert bighorn over large areas.     

热泵相变储热器动态特性分析及强化传热研究

热泵相变储热器传输过程具有动态性,提出基于四阶动态响应特性分析的热泵相变储热器动态特性分析及强化传热模型。构建热泵相变储热器的欠阻尼振荡输出特征分析模型,以系统功率突变为控制状态约束对象进行热泵相变储热器动态驱动响应模拟,采用二项单调衰减分量、二项欠阻尼振荡分量作为控制约束变量进行热泵相变储热器动态强化传输控制,建立热泵相变储热器的输出功率调制模型,结合热泵相变储热器动态状态量初始值及变化值进行强化传热过程控制,提高热泵相变储热器的输出性能。仿真结果表明,采用该模型进行热泵相变储热器的输出动态控制能力较好,强化传输的输出增益较高,提高了热泵相变储热器的输出响应能力。     

Sorption characterization and actuation of a gas-gap heat switch

Cryogenic gas-gap heat switches are rendered compact by using a sorption pump as actuating device. The sorption pump adsorbs gas when it is cooled and releases gas when it is heated. Upon desorption, the released gas lies in the gap between two blocks and increases the conduction heat transfer between them; in the reverse case - when the gas is adsorbed - the gap space between the two blocks behaves as an insulator. The temperatures at which there is sufficient desorption and adsorption of gas for actuating the ON an OFF states depend on several parameters of the gas-adsorbent system. The adsorption characteristics of helium gas on several carbon adsorbents were studied at pressures ranging from 50 Pa to 120 kPa and temperatures from 10 to 100 K. One of the carbons was successfully used in a heat switch at 6 K under different configurations in order to access different actuation characteristics. The experimental helium adsorption equilibrium data for each carbon were successfully fitted by a semi-empirical adsorption isotherm model. A thermal model of the heat switch, whose actuation can be tailored upon specifications, was developed based on the adsorption data. The thermal model was validated by reproducing the experimental data for two different configurations of a heat switch prototype.     

邻域自适应粒子群算法求解地源热泵区域 能源系统鲁棒优化调度问题

针对地源热泵区域能源系统中冷热负荷和机组效能的不确定性, 本文提出了一种考虑双重不确定性的鲁棒优化调度方法. 首先, 基于多面体不确定模型描述调度模型中的鲁棒变量. 然后, 针对建筑冷热负荷不确定性, 采用对偶原理将双层优化模型等价为单层优化模型; 对于机组效能不确定性, 采用场景法进行分析. 最后, 采用多目标优化约束处理方法处理鲁棒优化调度模型中的约束条件. 同时, 为更加高效、准确求解所构建的优化调度模型, 提出了一种邻域自适应粒子群优化算法(NAPSO). 实验结果表明, 在制冷和制热工况下, 与经验运行策略相比, 本文所提方法可分别减少7.22%和5.55%的系统运行成本, 是一种解决地源热泵区域能源系统鲁棒优化调度的有效方法.     

Annual Total Gross Primary Production Estimation based on Vegetation Indices Seasonal Variation Curve

For the estimation of annual Gross Primary Productivity(GPP),it is proposed an estimation method with simple parameters and small errors.By taking each type of vegetation in the area of Three-North Shelterbelt Program(TNSP) as the research subject,the MODIS vegetation indices were obtained,and the seasonal variation curve of vegetation indices were built.Then,the fitting relation between the integral of time series vegetation indices(ΣVIs) and GPP products of MODIS was established,so as to realize a simple GPP estimation method and study the applicable ΣVIs for estimating the GPP of all vegetation types.The results show that：(1) ΣVIs is suitable for estimating the annual total GPP in research area and significantly correlated with MODIS GPP at the confidence level of p<0.01;(2) ΣEVI2 is applicable to estimate the GPP of evergreen needleleaf forest,decidious needleleaf forest,decidious broadleaf forest,mixed forest,woody savannas,savannas,permanent wetlands,croplands,croplands/natural vegetation mosaic,while the effect of ΣNDVI for estimating the GPP of closed shrublands,open shrublands,grasslands,croplands,and barren or sparsely vegetated is superior to ΣEVI andΣEVI2;(3) Since the NDVI itself is saturated in the area of high Leaf Area Index(LAI),the error of estimating the GPP of high LAI vegetation type by ΣNDVI is larger,while using ΣEVI and ΣEVI2 to estimate them has better accuracy,and the limitation from blue band of EVI2 reduces compared with EVI,which can be applied to the GPP research of long time series better.     

Seasonal and inter-annual variation in view angle effects on MODIS vegetation indices at three forest sites

The bi-directional reflectance distribution function (BRDF) has been widely studied across different vegetation types. However, these studies generally report values for only one point in time. We were interested in the potential for seasonal and inter-annual variation in BRDF parameters. NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on board the EOS satellites has now been collecting data for 10 years. Since BRDF parameters are reported for the individual spectral bands, these data can be used to examine intra-annual variation. However, MODIS BRDF parameters are not calculated for the various vegetation indices which are derived from the spectral bands. Our objective in this study was to use the 10 years of MODIS data now available to examine seasonal and inter-annual variation in the view angle sensitivity of three vegetation indices; the normalized difference vegetation index (NDVI), the enhanced vegetation index (EVI), and the photochemical reflectance index (PRI) at 3 flux tower sites (Harvard Forest, Howland Forest and Morgan Monroe State Forest). For these 3 sites, only EVI was significantly affected by view angle. There was also a substantial variation in the view angle sensitivity of EVI across seasons and this variation was different for backscatter vs. forward scatter data. It is possible that differences in the scattering of radiation between the spring and the fall are responsible for the seasonal difference in view angle sensitivity. There were also complimentary variations in forward and backscatter view angle sensitivity of EVI across years. The greater view angle sensitivity of EVI, as opposed to NDVI, suggests that greater care must be taken to correct for BRDF effects when using this vegetation index.     

On-Demand DNA Synthesis on Solid Surface by Four Directional Ejectors on a Chip

This paper presents a synthesis technique for any random deoxyribonucleic acid (DNA) sequences on different substrates such as glass, plastic or silicon by an array of directional droplet ejectors. Any DNA sequence can be synthesized by ejecting droplets of DNA bases by an ultrasonic transducer having lens with air-reflectors (LWARs) that requires no nozzle. The LWAR is capable of ejecting liquid droplets around 80 mum in diameter, and reduces the amount of reagents needed for the synthesis from most of conventional microarray techniques. One major advantage of the nozzleless ejector is that it can eject droplets in any direction, so that a spot can be inked by four ejectors (carrying four DNA bases) without moving the ejector. The directional ejection of the droplets removes the need for aligning the substrate with the ejector, and minimizes the automation and control circuitry. To demonstrate the DNA synthesis capability of the directional droplet ejectors, four LWAR ejectors were used to synthesize a 15-mer 5'-CGCCAAGCAGTTCGT-3' on a substrate surface. This paper describes the concept and scheme of the on-demand DNA synthesis (with MEMS ejector integrated with microfluidic components) along with experimental results of an actual DNA synthesis by four directional droplet ejectors.     

Film transfer and bonding techniques for covering single-chip ejector array with microchannels and reservoirs

This paper describes a novel covering technique for an MEMS ejector array that is integrated with liquid reservoirs and microchannels on a single chip. The covering technique is based on wicking of a low viscous epoxy through the gap between the ejector wafer and a plate containing a parylene film, and allows the integrated ejector array to be fully covered by the parylene film with excellent uniformity, repeatability and yield. The technique is batch-processible and is suitable to cover many microfluidic systems with a thin film. The parylene film is tightly attached to the ejector array chip (with excellent bonding strength owing to the epoxy), so that liquid is automatically brought into the ejectors from the reservoirs through the microchannels (due to capillary force), as the ejectors shoot out liquid droplets. This automatic liquid supply makes the liquid level (in the ejector) be maintained constant throughout the entire ejection process until more than 90% of the liquid stored in the reservoir is delivered to the ejector through the microchannel. This paper describes also a number of other covering methods that we have experimentally tried, and compares those with the new covering technique. [1459].     

干旱对灌溉和雨养农田生态系统生产力的影响对比分析

灌溉是农作物应对干旱等极端气候条件的有效调节机制,在全球气候变化的背景下,未来干旱等极端气候事件发生的频率和严重程度预估会增加,定量分析灌溉和雨养条件下干旱对农田生态系统农作物生长的影响有助于更好地评估人类应对极端气候事件对生态系统的消极影响的能力,为制定合理有效的生态系统保护措施提供依据.以中国北方干旱区为研究区,基...     

Intelligent computer-aided design optimization of heat pumps

The Rankine vapor cycle plays a very important role in heat pump design and analysis. The vapor heat pump cycle design process can be long and tedious. The designer must obtain various cycle performance parameters, including compressor work, heat added, cooling load, and coefficient of performance (COP), both quickly and accurately. This paper describes the use of an intelligent computer-aided software program in design and possible refinements of vapor heat pump technology. Several different arrangements of Rankine heat pump cycles are demonstrated. Objectives for improvements, constraints, and design optimization, which cannot be easily accomplished using conventional hand calculations, are emphasized. Using the featured software increases the engineer's efficiency and abilities in analyzing vapor heat pump designs.     

Land Use Intensity and Radiation Feedback in Beijing from 2000 to 2015

Many current studies focus on urban expansion and its heat island effect, but the impact of different land use intensity on radiant energy needs further analysis. Based on the land use data of 2000 and 2015 in Beijing, this study divided the land use of Beijing into five types according to the influence degree of human activities and vegetation resilience, namely, the old urban areas, urban expansion areas, unchanged cropland areas, mixed pixel areas with changed gridcells, and unchanged pure pixel areas. On this basis, we calculated Radiative Forcing (RF) due to the change of surface albedo and explored the relationship between RF and vegetation cover. The results showed that: (1) In pure pixel areas, natural vegetation had a lower albedo, and the corresponding RF was larger than the other four land use type areas. However, under the influence of human activities, RF in the four land use type areas showed an obvious increasing trend during the research period, and the increment was also larger than RF in PP areas. (2) Comparing with unchanged pure pixel, the EVI within the other four human-affected land type areas (old urban areas, urban expansion areas, mixed pixel, and unchanged cropland) decreased but the LOS extended. The combined effect of LOS and EVI contributed to the decreasing trend of surface albedo, which prompted the increase of RF. Our finding highlights that human activities often enhances RF by affecting the intensity of land use. This study has important reference value for analyzing the climate feedback of land use change from physical mechanism.     

2000~2015年北京市土地利用强度及其辐射反馈评估

当前很多研究关注城市扩展及其热岛效应,但不同土地利用强度对辐射能量的影响尚有待进一步的分析。以北京市为例,基于2000和2015年的土地利用数据,按照人为活动对土地的利用程度,将北京市的土地利用变化划分为5类：即老城区、城市扩展区、混合变化区、耕地及自然纯像元区。在此基础上,在反照率和太阳辐射遥感反演数据的支持下,分析2000~2015年由地表反照率引起的辐射强迫(RF, Radiative Forcing),并探讨了RF与植被的关系。结果表明：相比自然纯像元区域,老城区、城市扩展区、混合变化区及耕地的RF在研究时段内均明显增加,后三年的RF均值比前三年增加了0.78 W/m²以上,远大于自然纯像元区的RF增量(0.19 W/m²)。本研究同时发现,植被绿度随土地利用强度的增加而逐年下降,但植被生长期长度却有所延长,两者综合作用于地表反照率,促使了RF的增加,说明单纯从辐射平衡来讲,北京市的土地利用变化在一定程度上增强了RF。