Modification of streamer-to-leader transition model based on radial thermal expansion in the sphere-plane gap discharge at high altitude

Historically,streamer-to-leader transition studies mainly focused on the rod-plane gap and low altitude analysis,with limited attention paid to the sphere-plane gap at high altitude analysis.In this work,sphere-plane gap discharge tests were carried out under the gap distance of 5 m at the Qinghai Ultra High Voltage(UHV)test base at an altitude of 2200 m.The experiments measured the physical parameters such as the discharge current,electric field intensity and instantaneous optical power.The duration of the dark period and the critical charge of streamer-toleader transition were obtained at high altitude.Based on radial thermal expansion of the streamer stem,we established a modified streamer-to-leader transition model of the sphere-plane gap discharge at high altitude,and calculated the stem temperature,stem radii and the duration of streamer-to-leader transition.Compared with the measured duration of sphere-plane electrode discharge at an altitude of 2200 m,the error rate of the modified model was 0.94%,while the classical model was 6.97%,demonstrating the effectiveness of the modified model.From the comparisons and analysis,several suggestions are proposed to improve the numerical model for further quantitative investigations of the leader inception.

A hypothesis study on a four-period prevention model for high altitude disease

Background:High altitude disease(HAD)can reduce combat effectiveness and damage the health of soldiers at high altitudes.The objective of this hypothesis study is to build a four-period prevention model for high altitude disease that can be applied at high altitudes of over 3000 m.Presentation of the hypothesis:We divided the time at high altitude into nine periods,with three stages from the ascent preparation to the descent to the plain,and applied a continuous dynamic and systematic four-period prevention model across the nine periods.Each period of three stages has its own different measures and targets high altitude health care services for the prevention of high altitude disease.A standard four-period prevention model for high altitude disease was constructed for the high altitude health services at the population level.Testing the hypothesis:Our hypothesized HAD prevention model represents a continuous dynamic and systematic four-period prevention model across the nine periods.This hypothesis can be tested from three aspects.The first one is assessment of soldiers’operating efficacies.The second is comparison of the long-term high altitude population health basic data and development and utilization of big data.The third is descent population health status comparative study and historical retrospective study on prevention.Implications:As we know,it is necessary to protect soldiers’health through the ascent and descent.Through the standard four-period model,we can protect soldiers’health by preventing high altitude diseases,screening the susceptible population,securely tracking their location and maintaining soldiers’health statuses;we also maintain their operational capabilities,eliminate their psychological fears and ease their family troubles.

Prevalence of Congenital Heart Disease at Extremely High Altitudes in Tibet and the Establishment of a New Free Treatment Model

Background: This study aimed to illustrate the prevalence of CHD by screening children in extremely high-altitudeareas (over 4000 m to even 5000 m above sea level) and explore an aid model for early diagnosis and treatmentfor the Tibetan population. Methods: A total of 2242 students from different schools in Ngamring County,Xigaze City, Tibet from September 2019 to September 2020 were selected for screening. The students were examinedthrough the inquiry of their current medical history and family history, cardiac auscultation and a physicalexamination, in order to screen out the suspected cases of CHD, and then the suspected cases were confirmed bycardiac color ultrasound examinations. After that, positive patients were be transferred to Shandong Province forfree treatment. Results: The prevalence of CHD among children in Ngamring County was 3.70% (83 cases),which is the highest incidence rate ever reported. The most common type of CHD was patent ductus arteriosus(PDA), accounting for 55.42% of the total number of cases screened, followed by atrial septal defect (ASD) andventricular septal defect (VSD), accounting for 28.92% and 12.05%, respectively. The prevalence of CHD in childrenat high altitude was significantly higher than that in children at low altitude. The children with CHD weretransferred to Shandong Province for surgery, the operations were successful and their recoveries went well.Conclusions: The results show that high altitude is closely related to the prevalence of CHD, and the incidencein Ngamring County is much higher than that in previous reports.

Statistical Modeling of the High Altitude Platform Dual-Polarized MIMO Propagation Channel

In order to investigate the benefit of multiple-input multiple-output(MIMO) technique applying to the high altitude platform(HAP), a 2×2 MIMO statistical model, which can accurately describe the channel between HAP and high-speed train, is presented. And dual polarization diversity is particularly considered. Based on first-order three-state Markov chain, the single-input single-output(SISO) channel, a subset of the MIMO channel is first established. The ray tracing approach applied to the digital relief model(DRM) which covers the railway between Xi'an and Zhengzhou is used to obtain the state probability vector and matrix of the state transition probability. The proposed model considers both Doppler shift and temporal correlation, and the polarization correlation and spatial correlation statistical properties of large-scale fading and smallscale fading are analyzed. Moreover, useful numerical results on the MIMO HAP channel outage capacity are provided based on which, significant capacity gains with respect to the conventional SISO case are illustrated. Such statistical channel model can be applied to the future wireless communication system between HAP and high-speed train.

A rat model of high altitude polycythemia rapidly established by hypobaric hypoxia exposure

Objective To investigate the effects of simple hypobaric hypoxia on parameters of hematology and blood rheology in order to establish a rat model of simulated high altitude polycythemia(HAPC) for the study of pathophysiologic mechanisms and medical prevention and treatment of HAPC.Methods Fortyeight male Wistar rats were randomly divided into three normal control groups and three hypoxia model groups.Normal control group rats were bred in normoxia conditions,and hypoxia group rats were subjected to hypoxic exposure for 8 hours per day at simulated 5 500 m high altitude in a hypobaric chamber.After hypoxic exposure for 2,4,12 weeks,one group of normal control and hypoxia model rats were killed and blood was collected,respectively.Then parameters of erythrocyte and blood rheology were examined.Results Mucous membrane of hypoxia model rats showed obviously cyanosis after 2 weeks hypoxic exposure.Hemoglobin concentration of hypoxia model rats were beyond 210 g/L after 2 weeks,4 weeks and 12 weeks hypoxia exposure and significantly increased than that of normal control rats respectively.Besides,RBC counts,hematocrit,whole blood viscosity,erythrocyte aggregation index of hypoxia model rats were all notably higher than those of normal control rats respectively.Conclusion A rat model of high altitude polycythemia can be rapidly established by hypobaric hypoxia exposure at simulated 5 500 m high altitude for 8 hours daily.

Industrial Poverty Alleviation Model in Southwestern High-altitude Mountainous Areas of China——A Case Study of Industrial Poverty Alleviation of Xueshan Township in Luquan County of Yunnan Province through Planting Codonopsis pilosula

Due to the severe restrictions of natural conditions and ecological environment,high-altitude mountainous areas usually become the " hard bones" in the battle against poverty. Xueshan Township,Luquan Yi and Miao Autonomous County of Yunnan Province,located in the alpine valley of Jinsha River,is a major township with wide and deep poverty,and the incidence of poverty is up to 45. 00%. In recent years,Xueshan Township has insisted on the battle against poverty,made effort to develop the Codonopsis pilosula industry,and successfully developed a road to poverty alleviation through C. pilosula industry,and formed a unique industrial poverty alleviation model by the end of 2018,the incidence of poverty dropped to 0. 74%. Based on field survey and interview,this paper analyzes and summarizes the specific practices,main results,practical experience and promotion and application measures of the poverty alleviation model of C. pilosula planting industry in Xueshan Township,in the hope of providing certain reference for the targeted poverty alleviation in similar areas in Yunnan Province and other provinces of China.

Research on the distribution characteristics of explosive shock waves at different altitudes

There are great differences in the distribution characteristics of shock waves produced by ammunition explosions at different altitudes.At present,there are many studies on plain explosion shock waves,but there are few studies on the distribution characteristics of plateau explosion shock waves,and there is still a lack of complete analysis and evaluation methods.This paper compares and analyzes shock wave overpressure data at different altitudes,obtains the attenuation effect of different altitudes on the shock wave propagation process and proposes a calculation formula for shock wave overpressure considering the effect of altitude.The data analysis results show that at the same TNT equivalent and the same distance from the measuring point,the shock wave overpressure at high altitude is lower than that at low altitude.With the increase in the explosion center distance of the measuring point,the peak attenuation rate of the shock wave overpressure at high altitudes is smaller than that at low altitudes,and the peak attenuation rate of the shock wave overpressure at high altitudes gradually intensifies with increasing proportional distance.The average error between the shock wave overpressure and measured shock wave overpressure in a high-altitude environment obtained by using the above calculation formula is 11.1389%.Therefore,this method can effectively predict explosion shock wave overpressure in plateau environments and provides an effective calculation method for practical engineering tests.

高原脱适应症发生风险预测模型的构建与验证

目的应用不同机器学习算法构建从高原返回平原人群高原脱适应症(high altitude deacclimatization syndrome,HADAS)发病的风险预测模型,并验证其预测效能。方法于2020年11月至2024年2月对结束高原生活返回内地的人群实地或线上发放问卷调查。收集基本资料、慢性高原病(chronic mountain sickness,CMS)情况和脱适应症状等调查资料,经筛选最终纳入1095例作为建模组。阳性事件定义为脱适应症状评分>5分。将建模组按7∶3随机分为训练集(n=766)和内部测试集(n=329),采用最小绝对收缩和选择算子(least absolute shrinkage and selection operator,LASSO)回归筛选自变量,基于多因素Logistic回归(multiple factor logistic regression,LR)、决策树(decision tree,DT)、随机森林(random forest,RF)、极端梯度提升(eXtreme gradient boosting,XGB)、支持向量机(support vector machine,SVM)、K最邻近(K-nearest neighbor,KNN)、轻度梯度提升(light gradient boosting,LGB)、朴素贝叶斯(naïve bayes,NB)8种机器学习方法构建预测模型。采用受试者工作特性曲线(receiver operating characteristic,ROC)、校准曲线和混淆矩阵对模型进行比较并进行内部测试;使用列线图或Shapley加性解释(shapley additive explanations,SHAP)图对最终模型进行展示。于2024年8月收集筛选结束高原生活返回平原132例作为外部验证组,对模型进行外部验证。结果1095例调查人群中有脱适应症者549人(50.14%)。CMS评分、年龄、高原居住时间为LASSO回归筛选出的预测因子。8种机器学习算法建立的HADAS预测模型中,以LR模型最优,ROC的曲线下面积(area under curve,AUC)训练集为0.819(95%CI:0.789~0.850),内部测试集为0.841(95%CI:0.799~0.884),F1评分内部测试集为0.801,内部测试集的AUC、F1得分在8个模型中均为最大;LR模型校准曲线的Spiegelhalter Z检验显示训练集P=0.703、内部测试集P=0.281;LR模型外部验证集AUC为0.867(95%CI:0.765~0.969)。结论以CMS评分、年龄和高原居住时间为预测因子建立的LR模型在内部测试集的综合表现最好,在外部验证集中区分度好,构建的列线图便于应用。

A novel 3-D spatial temporal channel model for high mobility HAPS-based communications scenario

A high altitude platform station （HAPS） based communications scenario for providing Intemet access and broadband multimedia services to the passengers on board of a high speed train （traveling up to 300km/h） is proposed. Regarding the addressed scenario, when the propagation link between HAPS and train is blocked by obstacles, a three-dimensional （3-D） geometrical single cylinder spatial-temporal channel model is presented, in which closed form, mathematically tractable space-time correlation functions are obtained. It shows that the correlation functions determined by the 3-D model are of significant difference with those of the conventional 2-D model. Based on the analysis model, the paper derives a realized simulation model using sum-of-sinusoids approach, and applies method of equal areas （MEA） and modified method of equal areas （MMEA） to determine the model parameters. The fitting performance of the simulation model with the analysis one is evaluated by two means-square error （MSE） performance criteria. Finally, numerical simulation results verify the mathematical analysis conclusion, when N ≥21, simulation model has an excellent fitness with the analysis one.

特高海拔寒区隧道温度场演化规律——以黑恰隧道工程为例

为研究特高海拔寒区隧道温度场的时空分布特征及其变化规律,以青藏高原西北部喀喇昆仑高山区的黑恰隧道为依托工程,首先,在现场建立包括气象要素在内的寒区隧道远程自动监测系统,对特高海拔寒区隧道温度场演化规律进行分析研究;其次,提出考虑湍流对流传热和热传导作用下的隧道三维数值模型,利用现场监测数据验证该模型的准确性;最后,讨论铺设保温层前后隧道温度场的变化特性。研究结果表明:1)在距进口0~270 m隧道受到冻融作用影响,洞内气温与衬砌温度呈线性正相关关系;2)隧道洞内气温对隧道径向温度场的影响主要体现在衬砌和浅层围岩;3)在最冷月平均气温方面,不同类型寒区隧道温度大小关系为特高海拔<高纬度<高海拔,在最大冻结深度方面,不同类型寒区隧道最大冻结深度大小关系为特高海拔>高纬度>高海拔;4)铺设保温隔热层后,保温层对衬砌与围岩起到良好的保温作用。

海拔对隧道内列车火灾烟气蔓延特性影响

为探究海拔高度对隧道内列车火灾烟气蔓延的影响,基于已被验证的数值模拟方法,结合三维非定常N-S方程和RNG k-ε湍流模型,采用滑移网格技术模拟了在隧道内匀速运行的列车发生火灾后减速并最终停在隧道内的整个运动过程,并利用动模型试验和缩尺隧道火灾试验数据验证了数值模拟方法的可靠性.结果表明:海拔高度对隧道内列车停车以后的火灾烟气蔓延影响明显;与低海拔隧道相比,同一时刻高海拔隧道拱顶同一位置处的烟气流速更快,烟气逆流至火源上游50 m处的时刻更早;车体周围温度分布也随着海拔高度的不断增加而呈现出逐渐上升的趋势.与0 m海拔隧道相比,5000 m海拔隧道内烟气逆流至火源上游50 m的时刻提前了102 s,同时列车停车360 s时隧道拱顶处的温度峰值增加了216 K,增幅达到42.9%.

无人机低空遥感结合YOLOv7快速评估水稻穗颈瘟抗性

为解决传统水稻稻瘟病抗性评估手段单一、效率低的问题,该研究提出一种无人机低空遥感技术结合YOLOv7模型的水稻穗颈瘟抗性鉴定方法。首先,将标注区域分割成小尺寸图像(≤1 240×1 240像素),将小尺寸图像进行旋转、缩放、平移、剪切和改变对比度处理。经数据清洗,去除分辨率过低的图像,扩充样本数量,以提高数据多样性。然后,将压缩注意力机制(squeeze-excitation attention)和可变形卷积(deformable convolution)引入YOLOv7模型,自适应调整感受野,以提升捕捉穗颈瘟病斑细粒度特征的能力。最后,构建穗颈瘟检测的YOLOv7_Neckblast模型。研究结果表明,YOLOv7_Neckblast能够有效检测穗颈瘟,计算出15个品种的穗颈瘟发病率和病害等级(1、3、5、7和9级的水稻品种分别有4、4、3、2和2个)。在交并比阈值为0.5时,YOLOv7_Neckblast平均精度均值相较于YOLOv7、FCOS和RetinaNet分别提升了4.0、6.4和5.8个百分点,召回率和F1值分别提高了至少4.0和4.0个百分点,且浮点计算数和参数量最低。与育种专家判定的实际抗性水平相比,YOLOv7_Neckblast模型对15个水稻品种的穗颈瘟抗性水平的平均评估准确率为86.67%,能较好地实现不同水稻品种穗颈瘟抗性的区分。无人机低空遥感融合人工智能技术可用于水稻黄熟期育种中穗颈瘟抗性的评估,也可为其他作物优势品种的选育提供参考。

基于D3AR的半球共形阵低空风切变风速估计方法

针对半球共形阵体制下进行低空风切变检测时会受到强地杂波信号的干扰,导致风切变信号难以检测的问题,提出了一种基于空时自回归的直接数据域算法(Space-Time Autoregressive Direct Data Domain,D3AR)的低空风切变风速估计方法。该方法首先将待检测距离单元的数据从空域、时域以及空时域进行信号对消处理;然后将处理后的数据矩阵描述为空时自回归(Autoregression,AR)模型并估计模型参数;再通过构造与杂波子空间正交的空间来实现对杂波的抑制,最后通过提取待检测单元的最大多普勒频率来估计风场速度。根据仿真结果显示,该方法有效地实现了地杂波抑制,并且能够精确估计风速。

基于MSISE-90研究高海拔宇宙线观测站处的大气深度廓线模型

高海拔宇宙线观测站(LHAASO)位于四川省稻城县海子山,它的广角切伦科夫望远镜阵(WFCTA)主要是通过观测广延大气簇射过程中产生的切伦科夫光信号对宇宙线进行研究.WFCTA的标定、模拟和重建都和大气深度有关,目前使用的大气深度模型是美国标准大气深度廓线模型.本研究中将美国标准大气深度廓线模型与卫星TIMED搭载的红外辐射计SABER记录到的LHAASO处14-50 km处的大气深度廓线进行比较,同时也与LHAASO处地面气象站记录的大气深度进行比较,美国标准大气模型的大气深度均偏小.MSISE-90大气模型描述了地球大气中从地面到热层的中性温度和密度,进一步研究发现MSISE-90大气模型与TIMED/SABER和LHAASO处地面标准气象站记录的大气深度的一致性较好.根据MSISE-90大气模型计算得到LHAASO处的大气深度均值廓线在1月最低,其次是2月、3月、4月、11月和12月,这也是WFCTA运行的最佳观测月份.4月份的大气边界层最高,其大气深度存在约2%的日变化.利用美国标准大气模型的函数形式,拟合每月的4.4-100 km处的大气深度廓线,得到了LHAASO处的每月的大气深度廓线模型,并比较了30°天顶角入射的100 TeV的宇宙线质子在MSISE-90大气模型和美国标准大气模型中产生的切伦科夫光的横分布的差异,二者最大差异约可以达到20%.

基于颜色–耳标参数映射的时空信息可听化方法

随着时空信息的爆炸式增长,如何在保留地图可视化传统优势的基础上实现时空信息可听化是一个值得研究的方向。因此,首先以2022年纽约市PM_(2.5)污染情况为例,采用通用克里金法对PM_(2.5)污染浓度数据进行插值,得到纽约市2022年365幅PM_(2.5)浓度专题地图;其次,提取每张专题地图的色相、饱和度、明度平均值,并将它们与PM_(2.5)浓度数据的标准差分别映射为音色、音高、音强、音长四个维度的耳标参数,使用Sibelius编排创建乐曲,实现纽约市2022年PM_(2.5)数据的可听化;最后,对可听化的污染意象信息传递效果进行评估。结果显示:(1)污染浓度最严重比最不严重和不严重信息的传递效果好;(2)污染浓度变化最大和变化较大比变化最小信息的传递效果好;(3)污染浓度地域差异变化最大比变化最小信息的传递效果好;(4)音强和音高传递污染浓度信息的效果最佳,被试者的认可度也最高,而音长传递污染地域差异的效果最差;(5)被试者对于使用以上可听化形式来传递污染信息的态度持中立到同意的态度,但在理解上存在一定难度。实验拓展了时空信息可听化的研究内容,丰富了对于地图可听化技术的探索。

康北高原慢性阻塞性肺疾病急性加重患者发生静脉血栓栓塞症风险预测模型的构建及预测效能

目的筛选康北高原慢性阻塞性肺疾病急性加重患者发生静脉血栓栓塞症风险的预测因素,建立AECOPD发生VTE风险的联合预测模型并分析其预测效能。方法选择2018年1月-2022年9月因慢性阻塞性肺疾病急性加重在甘孜县人民医院住院治疗的患者71例,根据是否发生VTE分为血栓组35例,对照组36例。收集患者的基本资料和检查、检验资料等相关参数数据,选出两组之间具有显著差异的指标。将上述单因素分析中有显著差异的指标纳入多因素分析,筛选出AECOPD发生VTE风险的独立影响因素,并构建预测模型。利用受试者工作特征(receiver operating characteristic,ROC)曲线评价各独立因素及预测模型的应用价值,计算曲线下面积及其敏感度与特异度,分析其预测效能,霍斯默-莱梅肖检验评价拟合度。结果单因素分析显示血栓组PPS评分、乳酸脱氢酶(LDH)、D-二聚体、降钙素原(PCT)均高于对照组(均P<0.05)。Logistic回归分析显示PPS评分、乳酸脱氢酶(LDH)、D-二聚体为AECOPD发生VTE的独立预测因素。三者联合构建的预测模型曲线下面积(area under curve,AUC)为0.944(95%CI:0.893~0.996),灵敏度、特异度均明显优于各单一指标(灵敏度为94.3%、特异度为83.3%),霍斯默-莱梅肖检验拟合度好(χ^(2)=11.915,P=0.155)。结论PPS评分、乳酸脱氢酶(LDH)、D-二聚体可能是预测康北高原AECOPD发生VTE的因素,且三者联合构建的预测模型对VTE风险预测具有很好效能,可为预测AECOPD发生VTE的风险提供参考。

考虑多约束因素的物流无人机网络高精度风险分析模型

物流无人机为全球快递物流业的扩张带来了新的机遇,有效克服了地面运输方式的不足。当前物流无人机仍处于起步阶段,因此有必要分析其运行过程中的碰撞风险。本文采用冲突区碰撞建模理论,根据物流无人机的特点和局限性,研究了其在特定空域飞行内的安全隐患。首先,为了衡量可靠性和故障率等多种因素对物流无人机在特定空域安全运行的影响,建立了物流无人机与其他无人机在特定空域的碰撞风险分析模型。然后,通过分析影响物流无人机安全运行的因素,包括空域条件、人机系统、环境条件和管理条件,建立了在特定空域运行的物流无人机与民用飞机碰撞风险分析模型。为了验证所提出模型的准确性,本研究对这两种情况下的模型进行了求解,并与国际民航组织制定的安全性标准进行了比较。

区块链增强的低空智联网可信协作架构及集群构建策略

低空生态的繁荣不断推动智能网络服务由平面向低空三维立体方向转变,低空业务呈现出规模化、协同化和智能化等演进态势,对低空智联网跨域设备协作能力、任务处理效率、数据安全性及操作可信性等提出了较严苛要求。集群式多设备联合计算协作可提升低空智联网中复杂化大规模任务的处理效率,然而现有模式仍存在跨域设备协作困难、安全可信性缺乏保障以及资源调度灵活性不足等问题。区块链具有数据及操作不可篡改、公开透明和集体维护等特性,尤为适合在多方参与的低空智联环境中建立高效协作信任。本文提出区块链增强的低空智联网可信协作架构,为低空多源异构智联设备提供链上跨域协作计算与状态同步渠道,并设计深度融合集群任务处理流程的多级共识协议,保障低空智联网协作集群式计算服务的安全性与可信性。针对低空智联网中协作集群链上同步状态的时效性开展分析,并据此提出一种基于排队模型的低空智联协作节点链上状态修正算法与高效集群构建策略,保障链上协作任务处理效率。仿真结果表明所提架构及方案可有效提升低空智联网中协作任务处理效率和资源利用率等性能。

海拔高度对化爆冲击波压力分布规律影响分析

海拔高度会引起空气密度及气压的变化,直接影响冲击波压力在空气介质中的传播分布规律。该项研究采用AUTODYN建立了0、1 000、2 000、3 000、4 500 m等5种海拔高度下爆炸冲击波压力传播规律的有限元数值仿真模型,开展了等效TNT当量为10、30、50 kg工况下的数值仿真分析,并对获取的冲击波压力分布规律进行了分析。分析结果表明:海拔高度对冲击波压力具有显著的影响作用,具体表现为在同一等效TNT当量下,随海拔高度的增加,冲击波超压峰值、比冲量都逐渐减小,峰值到达时刻随测点距离增大逐渐提前;并且随等效TNT当量的增加,爆炸冲击波压力峰值和比冲量都逐渐增大,峰值到达时间逐步提前。数值仿真结果与试验结果具有较高的吻合度,该项研究揭示了海拔高度对爆炸冲击波传播分布规律的影响作用,为实际工程测试提供了理论支撑。

高海拔下ZGB空化模型的修正及其对水翼空化的影响

空化模型在流体机械的研究和设计中必不可少,但目前缺乏对适用于高海拔工况的空化数值模型的研究。首先基于Zwart-Gerbera-Belamri空化模型,分析和推导了气泡初始半径、气核体积分数等模型中关键参数关于海拔高度的关系式,使模型适用于高海拔环境。然后将数值计算结果与相应实验数据进行了对比,验证了模型的适用性。最后针对NACA0009水翼,在0~5 km海拔高度下,使用修正后的空化模型进行了数值计算。结果表明:相同工况设置下,随着海拔高度的增加,环境气压降低、气核体积分数降低、气泡初始半径增加、压力面最大压力系数基本不变、吸力面最小压力系数略微增加、空穴长度显著增加,当海拔为5 km时,空穴长度增加到约弦长的81%,空穴长度增长率随海拔高度的增加而增加,在4 km处达到峰值0.17后开始降低。