万维望远镜平台下基于ASSURE模式的天文教学研究

随着教学手段和教学方法的现代化,信息技术与课程整合正成为教育改革的研究热点。文章以万维望远镜(WWT)平台为教学媒体,以ASSURE模式为教学设计的理论依据,设计并构建用以指导天文教学准备、实施与评价的教学模式,并将该模式应用于“四季星空”的教学案例中,使用基于信息技术的互动分析编码系统和学生课程反馈调查对教学效果进行分析和评价。研究表明,万维望远镜的使用可以降低教师言语比率,改变传统天文教学中以讲授式为主的教学方式。它适合起点能力较高、对新知识和新技能掌握能力较强的学生,能提高其学习兴趣和积极性,激发其探索宇宙的兴趣,有助于培养学生的科学素养。     

Development of efficiently coupled thermo-hydro-mechanical model to predict hydraulic fracture morphology in heavy oil reservoirs

The aim of the study involves examining the effect of heavy oil viscosity on fracture geometry in detail by establishing a heavy oil fracturing model and conventional fracturing model based on thermal–hydraulic–mechanical (THM) coupled theory, Walther viscosity model, and K–D–R temperature model. We consider viscosity and density within the heavy oil fracturing model as functions of pressure and temperature while that as constants within the conventional fracturing model. A heavy oil production well is set as an example to analyze the differences between the two models to account for the thermo-poro-elastic effect. The results show that temperature exhibits the most significant influence on the heavy oil viscosity while the influence of pressure is the least. In addition, a cooling area with a width of 0–1 m and varied length is generated near the fracture. The heavy oil viscosity increases sharply in this area, thereby indicating an area of viscosity increment. The heavy oil viscosity increases faster and is closer to wellbore, and a high viscosity increment reduces the mobility of the heavy oil and prevents the fracturing fluid from entering into the reservoir. The special viscosity distribution results in significant differences in pore pressure, oil saturation, and changing trends between these two models. In the heavy oil reservoir fracturing model, the thermal effect completely exceeds the influence of pore elasticity, and the values of the fracture length, width, and static pressure exceed those calculated in the conventional fracturing model. Thus, a comparison of the measured values indicates that the results obtained by considering viscosity as a function of temperature and pressure are more accurate. Therefore, the results of this study are expected to provide good guidelines for the design of heavy oil fracturing.     

一种飞机空中积冰潜势诊断指数与检验评估

飞机积冰是影响飞行安全的重要危险天气,准确的积冰诊断对民航运行与安全具有重大意义,特别是对国产大飞机适航取证具有重要作用。本文参考改进的CIP(Current Icing Potential)指数,使用垂直速度和云中液态水含量对积冰潜势诊断指数进行优化得到SCIP(Simplified Current Icing Potential)指数,该指数直接基于大气层结资料给出较为准确地飞机积冰潜势,具有命中率高、实用性强的特点。用2021年2月28日至12月31日民航航空器报告对原CIP指数和SCIP指数进行对比验证评估,发现相比于原CIP指数,SCIP指数具有更优异的ROC曲线(Receiver Operating Characteristic Curve)和TSS评分(True Skill Score)。但是对于不同程度的积冰,原CIP指数和SCIP指数均表现出较一致诊断效果,表明SCIP指数对诊断飞机积冰潜势具有重要作用,但无法判断积冰强度。根据2020年3月16日陕西区域飞机结冰个例验证表明增加垂直速度和云中液态水含量的影响对飞机积冰的描述更加细致,对提升积冰潜势诊断效果具有重要意义...     

基于VOSviewer文献计量的互花米草研究进展分析

互花米草(Spartina alterniflora)为美国大西洋沿岸的本地种,在环太平洋沿岸被认为是入侵物种。互花米草作为本地种,被誉为“生态系统工程师”;作为外来物种,其入侵特性亦引起相关领域的高度关注。为加深对互花米草相关研究的认知,探索未来研究重点方向,文章基于文献计量学方法,以Web of Science数据库中发表于1972—2020年的互花米草英文文献为基础数据,使用VOSviewer软件定量分析互花米草的研究进展及发展趋势。研究结果表明：1972—2020年互花米草领域的发文数量与被引频次均不断上升,2004年后呈快速发展态势;研究领域涉及的学科有生态学、环境科学以及海洋与淡水生物等;美洲、亚洲、欧洲与大洋洲等区域发表论文较多,其中美国在该领域的研究实力最强,中国其次;互花米草领域的研究热点集中于其对盐沼湿地生态系统的影响、生物地球化学循环过程以及生理生态和种间相互作用等,未来的研究趋势则集中于其对蓝碳的贡献以及对全球气候变化的响应过程与机制等。     

基于机器学习的锆石成因分类研究

锆石是在自然界中多种温压条件下能够稳定保存,并记录原岩年龄信息的副矿物。锆石微量元素能完整记录地质演化过程信息。通过微量元素分析锆石成因的研究已久,通常利用Th-U图解和La_N-(Sm/La)_N图解等二元图解对锆石进行分类研究。然而,随着锆石研究的深入,以及二元图解无法呈现数据高维度信息的局限性,传统图解已经不能满足对锆石类型进行准确判别,且对已知类型的锆石出现判定偏差。因此,本文将地质大数据与机器学习相结合,训练出高维度锆石成因分类器。文中收集了3 498条不同成因类型的锆石微量元素数据,并通过测试和运用随机森林、支持向量机、人工神经网络和k近邻等4种机器学习算法,最终得出准确率为86.8%的线性支持向量机锆石成因分类器,用于锆石类型的判定与预测。这项工作为锆石分类研究提供了更高维度的判别手段,极大提高了微量元素分析成因结果的精度。将锆石微量元素数据与机器学习方法相结合,是大数据分析与机器学习技术在地球化学研究中的积极探索。     

Quantitative evaluation of weathering degree through Fuzzy-AHP method and petrophysics analysis for sandstone carvings

Natural Hazards - The assessment of weathering degree of sandstone carvings plays an important role in scientific conservation. However, the current state of weathering assessment research cannot...     

NLOS GPS signal detection using a dual-polarisation antenna

The reception of indirect signals, either in the form of non-line-of-sight (NLOS) reception or multipath interference, is a major cause of GNSS position errors in urban environments. We explore the potential of using dual-polarisation antenna technology for detecting and mitigating the reception of NLOS signals and severe multipath interference. The new technique computes the value of the carrier-power-to-noise-density (C/N ₀) measurements from left-hand circular polarised outputs subtracted from the right-hand circular polarised C/N ₀ counterpart. If this quality is negative, NLOS signal reception is assumed. If the C/N ₀ difference is positive, but falls below a threshold based on its lower bound in an open-sky environment, severe multipath interference is assumed. Results from two experiments are presented. Open-field testing was first performed to characterise the antenna behaviour and determine a suitable multipath detection threshold. The techniques were then tested in a dense urban area. Using the new method, two signals in the urban data were identified as NLOS-only reception during the occupation period at one station, while the majority of the remaining signals present were subject to a mixture of NLOS reception and severe multipath interference. The point positioning results were dramatically improved by excluding the detected NLOS measurements. The new technique is suited to a wide range of static ground applications based on our results.     

西宁市老年人口分布与养老资源错位研究

健康中国战略下,积极应对老龄化、建立健全养老和医疗等相关设施,成为许多城市关注的问题。目前相关研究很少关注西北城市的老龄人口的空间分布及养老资源错位的现象。本研究以西宁市主城区为研究区域,基于2010—2018年西宁市公安局各街镇人口数据和兴趣点（POI）数据,选用老年人口系数、赡养率、增长率和地理集中率四个指标,利用综合老龄化指数（CAI）模型、核密度函数模型和空间错位指数模型对西宁市主城区人口老龄化空间分布及养老资源（医疗资源、老年设施）空间错位现象进行探索分析,结果表明：（1）9年间西宁市主城区人口老龄化程度不断加深,已步入老年型社会。（2）通过老龄化综合指数可知：主城区外围街镇人口老龄化增长速度大于城区中心的街道,其中小桥街道、朝阳街道、马坊街道与乐家湾镇人口老龄化最为严重,2018年综合老龄化指数增长速度超过中心城区街道,西宁市主城区人口老龄化严重程度已从中心街道向外围街镇扩散。（3）通过空间错位指数计算可得知：城中区的养老资源数量充足但过于集中,城北区的养老资源分布合理但是数量较少,行政区之间的养老资源与老年人口分布存在较大空间错位问题。     

Comparison of short-term toxicity of 14 common phycotoxins (alone and in combination) to the survival of brine shrimp Artemia salina

Toxic harmful algal blooms(HABs) can cause deleterious effects in marine organisms, threatening the stability of marine ecosystems. It is well known that different strains, natural populations and growth conditions of the same toxic algal species may lead to different amount of phycotoxin production and the ensuing toxicity. To fully assess the ecological risk of toxic HABs, it is of great importance to investigate the toxic effects of phycotoxins in marine organisms. In this study, the short-te...     

Study of double combination evaluation of urban comprehensive disaster risk

Natural Hazards - Aiming at solving the difficult problem of inconsistent single-method evaluation results in comprehensive disaster risk assessment, this paper presents an evaluation method based...