Direct Measurements of the Electron Energy Flux versus Electron Temperature Gradient in Tokamak Discharges

Electron thermal transport is one of the most complex processes in fusionplasmas. It is generally described by a simple thermal diffusivity in transport analyses ofdischarges, but there is evidence of critical gradient effects with moderate stiffness. By analyzingperiodic perturbations to an equilibrium, one canmeasure the variations in electron energy flux andelectron temperature gradient over the perturbation cycle, obtaining the flux as a function ofgradient over the range of parameters generated by the perturbation. Although time-dependenttransport analysis is very sensitive to noise in the input data, averaging over many cycles of aperiodic perturbation can provide data of sufficient quality. The analyses presented here are basedon the ECE temperature data with high spatial and temporal resolution and full profile coverage onDIII-D for sawteeth and modulated ECH heating.

Effects of Finite Aspect Ratio and Noncircular Plasma Flux Surface on Electron Temperature Gradient Driven Modes

A gyrokinetic model with integral eigenmode equations is developed based on the local equilibrium of shaped tokamak plasmas. Effects of main geometric parameters （finite aspect ratio, elongation, triangularity, and Shafranov shift gradient） on the electrostatic electron temper- ature gradient （ETG） driven modes are investigated numerically. It is found that the finite aspect ratio has a general stabilizing effect, while the elongation can be either stabilizing or destabilizing, depending on the poloidal wavelength of the mode and other parameters. It is shown that a low aspect ratio enhances the stabilizing effect of elongation, and weakens its destabilizing effect as well.

Determination of Particulate Matter Emissions from Cattle Feedlots Using Wind-Trax and the Flux-Gradient Technique

Large commercial cattle feedlots are significant sources of particulate matter (PM) emissions. This research compared WindTrax and the flux-gradient technique in estimating emissions of PM with aerodynamic diameter < 10 μm (PM10) from cattle feedlots. Meteorological conditions were measured and PM10 concentrations were profiled vertically (i.e., 2.0 to 7.62 m) at a large commercial beef cattle feedlot in Kansas from May through September 2011. Results show that between the two methods evaluated, WindTrax was least sensitive to changes in heights and number of heights used in the emission estimation, with calculated PM10 emission rates varying by up to 18% only. On the other hand, PM10 emission rates produced by the flux-gradient technique varied by almost 56% when changing either heights and/or number of heights in emission calculation. Both methods were sensitive to height settings, with their respective PM10 emission rates higher when the lowest height setting (2.0 m) was included. Calculating PM10 emission rates with the 7.62-m height led to lower estimates for the flux-gradient technique but no significant change in estimates was observed for WindTrax. As demonstrated in this study, for the flux-gradient technique, settings for the lowest and highest heights were the most critical in emission estimation;exclusion of other heights in between showed only to 2% to 6% change in calculated PM10 emission rates. In general, the higher PM10 emission rates were obtained with the flux-gradient technique. However, eliminating the lowest height (2.0 m) in the calculation and, at the same time, using a specific set of formulations for the flux-gradient technique made its calculated PM10 emission rates slightly lower (but not significantly different) than those from WindTrax.

Near-surface Geothermal Gradient Observation and Geothermal Analyses in the Xianshuihe Fault Zone,Eastern Tibetan Plateau

The Xianshuihe fault（XSHF） zone, characterized by intense tectonic activity, is located at the southwest boundary of the Bayan Har block, where several major earthquakes have occurred, including the 2008 Wenchuan and the 2013 Lushan earthquakes. This study analysed underground temperature sequence data for four years at seven measuring points at different depths（maximum depth： 18.9 m） in the southeastern section of the XSHF zone. High-frequency atmospheric noise was removed from the temperature sequences to obtain relatively stable temperature fields and heat fluxes near the measurement points. Our measurements show that the surrounding bedrock at（the seven stations distributed in the fault zone） had heat flux values range from-41.0 to 206 m W/m^2, with a median value of 54.3 m W/m^2. The results indicate a low heat flux in the northern section of DaofuKangting and a relatively high heat flux in the southern section of Kangting, which is consistent with the temperature distributions of the hot springs near the fault. Furthermore, our results suggest that the heat transfer in this field results primarily from stable underground heat conduction. In addition, the underground hydrothermal activity is also an obvious factor controlling the geothermal gradient.

Discussion on Calculation Methods of Sensible Heat Flux during GAME/Tibet in 1998

Based on previous research on sensible heat flux, we investigate it from different aspects using GAME/Tibet data measured during 6 June–13 September, 1998. This work consists of the derivation of the surface heat flux equation, analysis on counter-gradient heat transference, comparison between two different methods to compute the sensible heat flux, and investigation on the calculation scheme of sensible heat flux in the Simple Biosphere model 2 (SiB2) with relevant simulation. By improving two previous formulations, an integrated formulation for calculating surface heat flux is given. Secondly, using the measured data, the counter-gradient heat flux is clarified, leading to the fact that buoyancy plays an important role in the sensible heat transfer process. It is concluded that (1) energy imbalance is a common phenomenon resulting from the use of the traditional closure scheme on the heterogeneous underlying surface because the measured ensemble heat fluxes by eddy correlation contain the effect of nonlocal parcel movements; and (2) nonlocal parcel movement deserves more attention in any future heat flux study.

Divergent growth trends and climatic response of Picea obovata along elevational gradient in Western Sayan mountains, Siberia

In mountain ecosystems,plants are sensitive to climate changes,and an entire range of species distribution can be observed in a small area.Therefore,mountains are of great interest for climate–growth relationship analysis.In this study,the Siberian spruce’s(Picea obovata Ledeb.)radial growth and its climatic response were investigated in the Western Sayan Mountains,near the SayanoShushenskoe Reservoir.Sampling was performed at three sites along an elevational gradient:at the lower border of the species range,in the middle,and at the treeline.Divergence of growth trends between individual trees was observed at each site,with microsite landscape-soil conditions as the most probable driver of this phenomenon.Cluster analysis of individual tree-ring width series based on inter-serial correlation was carried out,resulting in two sub-set chronologies being developed for each site.These chronologies appear to have substantial differences in their climatic responses,mainly during the cold season.This response was not constant due to regional climatic change and the local influence of the nearby Sayano-Shushenskoe Reservoir.The main response of spruce to growing season conditions has a typical elevational pattern expected in mountains:impact of temperature shifts with elevation from positive to negative,and impact of precipitation shifts in the opposite direction.Chronologies of trees,growing under more severe micro-conditions,are very sensitive to temperature during September–April and to precipitation during October–December,and they record both inter-annual and long-term climatic variation.Consequently,it would be interesting to test if they indicate the Siberian High anticyclone,which is the main driver of these climatic factors.

Simultaneous Modelling of Gravity and Magnetic Data in a Measured Heat Flux Area to Characterize Geothermal Heat Sources: A Case for Eburru Geothermal Complex, Kenya

Forward modelling of gravity and magnetic data was done simultaneously to show the correlation between gravity and magnetic anomalies on a measured heat flux region. The results were used to characterize the heat source structures in Eburru area. Modelling was done using Oasis montaj geosoft software which is an iteration process where the gravity and magnetic anomalies were calculated and compared to the observed residual anomaly until there was a fit. The start model was constructed based on depths from Euler deconvolution and models constrained using stratigraphy data from the existing wells in the study area. Forward modelling of gravity and magnetic data revealed intrusions within the Earth’s subsurface with depth to the top of the sources ranging from 739 m to 5811 m. The density of the sources ranges between 3.0 g/cm3 and 3.2 g/cm3 while their magnetic susceptibility was zero. This implies that intrusions from the mantle with a magnetic susceptibility of zero have temperatures exceeding the curie temperature of rocks. The density of the intrusions modelled was higher than 2.67 g/cm3, the average crustal density, hence it explains the observed positive gravity anomaly. The results also revealed that areas with high heat flux have shallow heat sources and if the heat sources are deep, then there must be a good heat transfer mechanism to the surface.

THE SENSITIVITY TEST STUDY OF AIR-SEA SURFACE FLUX MODEL

In this article, a sensitivity test of air-sea surface flux model was carried out with the field observation data of Project “South China Sea Air-Sea Flux Measurement in 2000”. The results show that sensible heat fluxes are sensitive to observation errors, increasing the error of model calculation; In contrast, the latent heat flux and momentum flux are not as sensitive to observation errors as the sensible heat, and their calculated results are reliable. The test result also verifies the rationality of the surface flux values calculated and the conclusions can be used to detect errors in observed data.

Improvement of surface flux calculation:A study based on measurements over alpine meadow in the eastern Tibet Plateau in summer

An improved flux-gradient relationship between momentum φm（ζ） and sensible heat φh（ζ） is obtained by the use of the observational data over an alpine meadow in the eastern Tibet Plateau, in Maqu of China during the period June to August, 2010. The empirical coefficients of Businger-Dyer type function for the cases of unstable and stable stratification are modified. Non-dimensional vertical gradients of wind and potential temperature are calculated by three fitting func- tions; that is, the log-linear, log-square, and log--cubic functions, respectively. It is found that the von Karman constant approaches 0.4025 and the Prandtl number is about 1.10 based on the measurements in near-neutral conditions, which are within reasonable range proposed in previous studies. The revised flux-gradient profile functions of -1/5 power law for momentum and - 1/3 power law for sensible heat are best fitted in unstable stratification conditions. Meanwhile, 2/5 power law, instead of linear functions, is more appropriate in stable stratification cases for momentum and sensible heat. Com- pared with results from previous studies in which traditional functions are used, the momentum and sensible heat fluxes estimated by the revised profile functions in the current study are much closer to the observations for the unstable and stable stratification conditions.

Deduction of the Sensible Heat Flux from SODAR Data

A new method for deduction of the sensible heat flux is validated with three sets of published SODAR （sound detection and ranging） data. Although the related expressions have previously been confirmed by the author with surface layer data, they have not yet been validated with observations from the boundary layer before this work. In the study, selected SODAR data are used to test the method for the convective boundary layer. The sensible heat flux （SHF） retrieved from SODAR data is found to decrease linearly with height in the mixed layer. The surface sensible heat fluxes derived from the deduced sensible heat flux profiles under convective conditions agree well with those measured by the eddy correlation method. The characteristics of SHF profiles deduced from SODAR data in different places reflect the background meteorology and terrain. The upper part of the SHF profile （SHFP） for a complicated terrain is found to have a different slope from the lower part. It is suggested that the former reflects the advective characteristic of turbulence in upwind topography. A similarity relationship for the estimation of SHFP in a well mixed layer with surface SHF and zero-heat-flux layer height is presented.

Reflection and transmission of elastic waves at five types of possible interfaces between two dipolar gradient elastic half-spaces

Reflection and transmission of an incident plane wave at five types of possible interfaces between two dipolar gradient elastic solids are studied in this paper. First, the explicit expressions of monopolar tractions and dipolar tractions are derived from the postulated function of strain energy density. Then, the displacements, the normal derivative of displacements, monopolar tractions, and dipolar tractions are used to create the nontraditional interface conditions. There are five types of possible interfaces based on all possible combinations of the displacements and the normal derivative of displacements. These interfacial conditions with consideration of microstructure effects are used to determine the amplitude ratio of the reflection and transmission waves with respect to the incident wave. Further, the energy ratios of the reflection and transmission waves with respect to the incident wave are calculated. Some numerical results of the reflection and transmission coefficients are given in terms of energy flux ratio for five types of possible interfaces. The influences of the five types of possible interfaces on the energy partition between the refection waves and the transmission waves are discussed, and the concept of double channels of energy transfer is first proposed to explain the different influences of five types of interfaces.

Blow-up rate estimate for degenerate parabolic equation with nonlinear gradient term

Abstract In this paper, the blow-up rate is obtained for a porous medium equation with a nonlinear gradient term and a nonlinear boundary flux. By using a scaling method and regularity estimates of parabolic equations, the blow-up rate determined by the interaction between the diffusion and the boundary flux is obtained. Compared with previous results, the gradient term, whose exponent does not exceed two, does not affect the blow-up rate of the solutions.

CO_2 CONCENTRATION AND FLUX NEAR GROUND IN MARSH OF THE SANJIANG PLAIN OF NORTHEAST CHINA

There is limited information available on CO2 concentration and flux over marsh. The objective of this work was to characterize CO2 concentration and flux within and above marsh plant (Cares lasiocarpa Ehrh. and C. pseudoucuaica F. Schm) canopy at heights 0. 5, 1. 0 and 1. 5 m.CO2 concentration was measured sequentially every 3 bars by using an infrared gas analyzer. Soil and air temperature, wind speed, net radiation and soil heat flux were also measured simultaneously. Extremely drily minimum and maximum CO2 concentration rangal from 250 to 754 μmd/mol for the 4-year work. The typical minimum and maximum values ranged from 314 to 464 μmol/mol at the height of marsh plant (about 0. 5 m) during the fruiting perioed and mature date. The seasonal changes in CO2 concentration show that the minimum CO2 concentration occurred in the fruiting period and mature date, and both of their minimum values were 314 μmol/mol. This illustrates that CO2 consumed by photosynthesis was stable during the period. The flux of CO2 can be thought as a turbulent diffusion phenomenon. By micrometeorological methods, the diurnal CO2 fluxes were measured in the flowering peried, fruiting period, early mature date, late mature date and yellow-ripe stage. Their values were -0. 18, 38. 15,24. 13, 10. 9 and 4. 91 μmol/mol respectively.

Unexpected Increase in Arterial to End-Tidal CO₂Gradient in a Child Undergoing Embolization of MAPCAs

A 17-month-old infant with multiple aorto-pulmonary collateral arteries (MAPCAs) and pulmonary hypertension presented for diagnostic catheterization. On the day of the procedure, the infant was asymptomatic with oxygen saturation in the 90’s on 1.0 L/min O2 nasal cannula. His parents denied any recent illness. During the procedure, one coil was inadvertently embolized into the right lung resulting in markedly increased pulmonary artery pressures. The Pa-etCO2 gradient increased to 25 mmHg from a baseline of 2 mmHg. Therapy was initiated to reduce the PaCO2. The patient could not be weaned from mechanical ventilation due to elevated PA pressures.

季风降雨前后深圳地区地表通量差异分析

为进一步认识夏季西南季风对深圳地区地表通量的影响,采用深圳气象梯度塔的辐射和涡动协方差系统观测资料,研究该地区季风强降水过程中地表通量的变化特征。结果显示:在季风降水期间和降水后,深圳地区近地面太阳辐射明显减弱,同时反照率减小。在降水期间,深圳地区地表感热和潜热通量均明显低于降水前和降水后,而且由碳汇转为碳源。

职住地建成环境对轨道交通通勤行为的非线性影响机制研究——以武汉市为例

改革开放以来中国大城市快速蔓延导致了职住分离及交通拥堵等问题,倡导轨道交通等绿色交通方式出行成为大城市缓解通勤压力的重要手段。当前研究主要以居住地作为地理背景考察建成环境对轨道交通通勤的作用,但较少探索就业地建成环境的影响。本研究以武汉市为例,通过189个轨道站点的刷卡数据识别轨道交通通勤人员并构建通勤出行链,通过梯度提升决策树(GBDT)解析职住地涉及建成环境和轨道站点的30个特征因素对通勤客流量和通勤时间的非线性影响机制。研究发现:①居住地通勤客流量表现为较集中的点状分布,就业地通勤客流量则呈现显著的“中心-外围”结构,职住地两端通勤时间的空间格局均呈中间低、外围高的分布特征;②职住地周边建成环境因素对轨道交通通勤客流量和通勤时间普遍存在非线性影响及阈值效应,整体而言居住地建成环境的相对影响程度高于就业地,但就业地“公司企业数”是影响通勤客流最重要的要素,就业地“与城市中心距离”则是影响通勤时间的首要因素;③职住地周边同一建成环境因素,对于通勤客流量和通勤时间的影响可能截然相反,这与城市轨道交通网络建设和社会实际发展状况相关。研究结果可以更好地理解职住地建成环境与轨道交通通勤行为的关联,有助于促进城市轨道交通和城市职住空间的协调发展。

基于GBDT的望奎县农田土壤有机碳主控因子研究

利用多源公开数据,针对于2012年搜集到的农田土壤有机碳(SOC)数据,通过梯度增强决策树(GBDT)探究SOC的主控因子,揭示SOC空间分异机理.选择国家商品粮食生产基地县和全国产量大县-望奎县作为研究区域,结果表明,GBDT模型相较于一元线性回归模型在所有的自变量上均具有更好的预测效果,总体的R^(2)为0.958,表明该模型能够很好地解释目标变量的变异;碱解氮、有效磷、气温、土壤微生物多样性、速效钾、土壤pH和降水量依次是影响有机碳含量最为显著的几个因素,其中碱解氮以33.85%的影响权重位居最高;7个环境协变量均观察到对SOC的阈值效应,且均具有两个阈值.研究发现任意两个变量都不是独立的,均存在相互作用的负值效应.表明环境变量对SOC含量的影响是一个复杂的交互作用,而不是简单的叠加.侧面证明了过度施肥并不会达到增加土壤肥力的作用,而会造成资源浪费和农田生态污染问题.

梯度纳米纤维膜在纯生啤酒中的除菌过滤研究

针对目前商业化纯生啤酒用除菌滤膜存在孔径分布宽、抗污性差、膜孔易堵塞、可重复使用性差等问题,利用熔融挤出相分离法制备了不同直径大小的乙烯-乙烯醇共聚物(EVOH),通过将粗、细纳米纤维在上、下层的先后排列构筑了一种梯度结构纳米纤维膜。通过对梯度纳米纤维膜过滤性能、抗污性及可重复使用性等进行研究,发现梯度纳米纤维膜对10 g/L的酵母浸膏发酵液重复过滤后,稳定后的通量为22660 L m^(-2)h^(-1),远高于Pall®商业膜(4840 L m^(-2)h^(-1))。经高温蒸汽灭菌处理后的梯度纳米纤维膜的稳定通量为6600 L m^(-2)h^(-1),而商业膜仅为1760 L m^(-2)h^(-1),表现出优异的耐高温水蒸气性能。此外,污染后的梯度纳米纤维膜经80℃水清洗后的通量恢复率可达43%,而商业膜的通量恢复率仅为32%,表明梯度纳米纤维膜显示了优异的可重复使用性。为纯生啤酒用除菌滤膜的国产化替代提供了一种新的途径。

三芯电缆中间接头压接缺陷多物理场及温度梯度场分析

为解决传统电缆中间接头压接缺陷识别温度敏感性差、环境影响因素多、设备检测精度低等问题,提出了一种基于温度梯度矢量分析的电缆中间接头缺陷识别方法。通过对10 kV三芯电缆开展多场耦合计算,采用矢量分析方法获得了电缆中间接头的温度梯度场和热流密度分布矢量图,形成了电缆中间接头温度梯度场分布规律。结果表明:电缆中间接头表面温度梯度主要受x方向(电缆径向)温度梯度的影响;正常接头表面温度变化率不超过16.6%,其表面温度梯度变化率达49.8%;缺陷接头表面温度变化率不超过21.8%,其表面温度梯度变化率达57.8%,温度梯度场相较温度场有更高的检测灵敏度。开展电缆中间接头温度梯度场分析研究,对电缆接头致热型缺陷运维效率提升有积极意义。

梯度投影法实现永磁同步电机最优曲线跟踪

针对永磁同步电机弱磁控制在线计算复杂度高、计算负担较重的问题,提出一种高效的弱磁曲线跟踪方法,以实现永磁同步电机的运动控制,通过一种更优化的投影与迭代结合的方法实现在一定的电流、电压约束下,电机最优运行状态的在线跟踪。同时,提出了针对ADADELTA梯度下降法的一种简化方法,优化了梯度下降法的计算流程,减少了迭代次数,提高了运算性能。该方法避免了不同运行区域的算法切换,有效地发挥了电机潜能,保证电机高功率输出。最后通过电机对拖实验,验证了此算法的合理性。