A novel correlation approach for prediction of natural gas compressibility factor

Gas compressibility factor （z-Factor） is one of the most important parameters in upstream and downstream calculations of petroleum industries.The importance of z-Factor cannot be overemphasized in oil and gas engineering calculations.The experimental measurements,Equations of State （EoS） and empirical correlations are the most common sources of z-Factor calculations.There are more than twenty correlations available with two variables for calculating the z-Factor from fitting in an EoS or just through fitting techniques.However,these correlations are too complex,which require initial value and more complicated and longer computations or have magnitude error.The purpose of this study is to develop a new accurate correlation to rapidly estimate z-Factor.Result of this correlation is compared with large scale of database and experimental data also.Proposed correlation has 1.660 of Absolute Percent Relative Error （EABS） versus Standing and Katz chart and has also 3.221 of EABS versus experimental data.The output of this correlation can be directly assumed or be used as an initial value of other implicit correlations.This correlation is valid for gas coefficient of isothermal compressibility （cg） calculations also.

知天与顺天:古代农谚中的生态哲学思想

构建生态文明,需要借鉴中华农耕文明中的生态智慧。古代农谚是传统农业生产实践的直观反映,亦是中华农耕文明的重要载体,其中蕴涵着天人合一的生态哲学思想。它是古人知天畏命与顺天而为思想的有机融合,表现了古人在知晓、尊重客观生态规律的基础上,充分发挥人的主观能动性,合理利用自然资源发展农业生产的生态智慧。研究中国古代农谚中天人合一的生态哲学思想,有助于重新审视人与自然生态的互动关系,对缓解当下的生态危机以及建设生态文明,具有一定的借鉴意义。

华北典型针叶混交林林下更新影响因素分析

天然更新在维持森林稳定性与森林群落动态变化方面发挥重要作用,探究其相关影响因素,为促进研究区林下更新提供科学依据。以庞泉沟自然保护区云杉华北落叶松混交林为对象,基于灰色关联度方法从林分结构、立地条件两方面探究影响混交林林下更新的关键因素。结果表明:1)华北落叶松与云杉的混交林中,云杉幼苗351株、幼树172株,华北落叶松仅有幼苗39株、幼树36株,云杉的更新能力较强;2)华北落叶松、云杉混交林天然更新的影响因子关联度排序为树种组成>海拔>大小比>角尺度>林分密度>林龄>坡向>郁闭度>混交度>坡度;整体上看,天然更新对林分结构和立地因子均有显著响应,其中树种组成是影响天然更新的最主要林分非空间结构因子,海拔是影响天然更新的最主要立地因子,大小比、角尺度是影响天然更新的主要林分空间结构因子。因此,在调整未来林分时,可通过优化林分结构来促使云杉、华北落叶松混交林天然更新,从而提高林分稳定性。

目标树抚育间伐对老山林场天然次生林直径分布的影响

研究老山林场天然次生林目标树抚育前后的直径结构特征及动态变化规律,为该地区林分经营提供理论指导。本研究基于实测的31块标准地调查数据,以老山林场5种主要林分类型(杉木纯林、针叶混交林、针阔混交林、硬阔叶混交林、阔叶混交林)为研究对象,采用Weibull、Logistic和Cauchy分布概率密度函数对抚育间伐前后的林分直径分布进行拟合,对比分析林分直径分布及其变化规律。结果表明,(1)抚育后,5种林分类型的平均胸径和平均树高都得到提高,针叶混交林和硬阔叶混交林增加的幅度最大。(2)对比抚育前后的分布函数拟合效果,Weibull分布函数更适合于拟合杉木纯林(R2最大分别为0.85、0.79),Cauchy分布函数则在阔叶混交林中拟合表现较好(R2最大分别为0.96、1.00)。目标树抚育间伐调整了研究区的林分直径结构和树种组成,为老山林场的科学合理经营提供借鉴。

杉木人工林套种不同树种对林分生长和植物多样性的影响

研究杉木林间伐后,于林下套种香梓楠、华盖木、红豆杉、缅茄4种树种,对比未套种杉木纯林,分析套种后林分的生长状况和植物多样性,为杉木人工林近自然改造与可持续经营提供参考依据。结果表明:香梓楠、华盖木、红豆杉与杉木形成异龄复层混交林,香梓楠胸径、树高生长量及保存率最高,分别达到10.5 cm、9.8 m、82.22%,显著高于其他树种;缅茄胸径、树高生长量及保存率最低,分别为2.4 cm、1.7 m、15.66%。套种缅茄、香梓楠、华盖木对杉木胸径有促进作用,套种缅茄后杉木树高显著提高。5种杉木林分林下植被中共出现33科52属60种植物,草本层出现植物15科25属27种,以禾本科和菊科植物为主;灌木层出现植物18科27属33种,以大戟科、茜草科和桑科植物为主;4种杉木混交林林下出现植物比杉木纯林增加24种。杉木×香梓楠、杉木×华盖木林下植物多样性比杉木×缅茄和杉木纯林显著提高。综合杉木间伐后套种不同树种表现,套种香梓楠对林分生长和植物多样性更具优势,可作为今后杉木近自然改造的参考模式。

天然落叶松林不同演替阶段空间结构参数的多元分布

2023年5月15—30日,在黑龙江省伊春市丰林县汤林林场建立不同演替阶段(中龄林、近熟林)固定监测样地,在森林群落中分别设立15块30 m×30 m的方形样地,将各样地划分为4个15 m×15 m的小样方,对胸径在5.0 cm及以上的乔木进行每木调查、每木检尺,记录样地内林木的树种、胸径、树高;应用RStudio计算中龄林和近熟林的天然落叶松(Larix gmelinii)林分空间结构参数(混交度、大小比数、密集度、角尺度)、统计林分空间结构参数的5种多元分布频率(零元分布、一元分布、二元分布、三元分布、四元分布),系统分析各林分的林分空间结构特征与功能。结果表明:(1)落叶松林的零元分布,两种不同演替程度的林分,整体呈随机分布、混交较好的中庸生长状态,但近熟林比中龄林较密集。(2)落叶松林的一元分布,林分内多数林木处于混交程度、密集程度良好,各大小比数等级占比处于比较相近的随机分布状态。(3)落叶松林的二元分布,两种林分在同一大小比数时的林木多数处于中度混交,同一密集度时的中龄林的密集程度分布相近,近熟林的密集度较集中。(4)落叶松林的三元分布,两种林分中,同一密集度和大小比数的林木,多数处于随机分布。(5)落叶松林的四元分布,两种林分在同一分布格局和生长状态时,相同密集度的林木多数处于中度混交或者混交状态较良好。(6)与比较传统的零元分布、一元分布对林分空间结构进行分析相比,使用多元分布能更加全面、清晰地分析不同演替阶段天然落叶松林的林分内部空间结构特征。

基于Python的中医医案智能收集系统研究

随着数据挖掘技术在中医医案研究中被广泛采用,对医案收集的效率和质量提出更高要求,积极探索中医学与计算机、人工智能等相关学科的交叉融合,实现中医医案的半自动收集,以期为名中医经验传承作出贡献。基于Python编程语言的简洁性、开源性以及丰富的第三方扩展库,使用Python,采用OCR文本识别、自然语言处理Jieba中文分词、Fuzzy-Wuzzy模糊字符串匹配等第三方工具库,编码实现医案智能收集系统。通过与医案手工收集相比,智能收集系统极大地提高了医案收集的工作效率,解放人力,提升医案的可靠性。

不同密度油松天然次生林对林下植被组成和土壤物理性质的影响

以山西省关帝山国有林管理局三道川林场4种不同密度油松天然次生林为研究对象,调查分析了其林下植被组成及土壤物理性质随林分密度的变化规律。结果表明,油松天然次生林林下共出现植物32科64属70种。随着林分密度的增大,林下灌木层和草本层物种组成发生变化,物种数量呈现减少趋势;不同土层的土壤容重均呈现增大趋势,土壤最大持水量、毛管持水量呈现减小趋势。综合来看,为改善油松天然次生林林下植被组成及土壤物理性质,可适当降低林分密度。

宝鸡市马头滩林区锐齿槲栎天然更新影响因子调查

本研究对宝鸡市马头滩林区主要阔叶树种锐齿槲栎的天然更新状况进行了调查,分析了不同影响因子对该树种天然更新的影响。结果表明:随着锐齿槲栎林分密度的增大,幼苗的更新密度先增大后减小,幼树的更新密度整体上呈减小趋势;阳坡幼苗和幼树的更新密度均最大,阴坡幼苗的更新密度较大;海拔对锐齿槲栎的天然更新影响较大,随着海拔的增高,幼树的更新密度先增大后减小,而幼苗的更新密度整体上呈减小趋势。

Forest structure of a maple old-growth stand: a case study on the Apennines mountains(Southern Italy)

In Europe, very small forest areas can be considered to be old-growth, and they are mainly located in Eastern Europe. The typical structures of old growth forests infrequently occur in Mediterranean mountainous environments, since they have been affected by human activities for centuries. This study focused on a remote and almost pure Italian maple stand located in southern Italy, which has not been managed for long time due to its inaccessibility. The effects of natural evolution on the forest stand were evaluated through the analysis of the spatial and chronological structure and the regeneration patterns, then estimating the amounts and quality of deadwood occurrence. Across the whole stand, all the trees with DBH(diameter at breast height) larger than 50 cm(LLT, large living trees) were measured(DBH and height) and age was also determined through a dendrochronological approach. The diameters observed ranged between 50 and 145 cm with ages of 120 to 250 years. The Latham index calculated for trees within the sample plot highlighted a multilayered canopy with a dominant layer of largeliving trees(age > 120 years). The size-class distribution of stems had a reverse-J shape, and basal area was 52 m^2 ha^(-1). Deadwood was exclusively constituted by standing dead trees and CWD and its volume was on average 31 m^3 ha^(-1). Pure Italian maple forests are generally rare in Europe, and it was unexpected to find a forest stand characterized by a so complex structure with old growth attributes. The study of complex forest stand, even if small, could give precious information on the forest evolution, clarifying also diverse auto-ecological traits of tree species that usually are not common in our forests.

Forest Response to the US 1990 Clean Air Act: The Southern Spruce-Fir Ecosystem

The history of the Black Mountains in North Carolina and the southern Spruce-Fir ecosystem has been fraught with widespread forest decline since the mid 1960’s. Balsam Woolly Adelgid attacks and acidic deposition were two of the most recognized causes of decline. Uncertainty arose about the future of these forests, and projections were made regarding the endangerment or extinction of the endemic Fraser fir ([Pursh] Poiret). This study analyzed data sets from a permanent plot network in the Black Mountains dating 1985, 2002, and 2012. Indications that the Fraser fir population is stabilizing from a “boom-bust” cycle of population growth and has entered the stem exclusion stage of forest stand development are evident. Fir live stem density increased more than 250% from 1985 to 2002, and then declined 40% by 2012 at the highest elevations in the forest. Overall, fir appeared to be more impacted on western facing slopes than eastern ones. The population of red spruce experienced a steady decrease in live stem counts, but an increase in live basal area through all years, and at all elevation classes (1675 m, 1830 m, and 1980 m), indicating a normal progression through stand development. Red spruce was also most negatively impacted on western facing slopes. Live stem density was significantly higher (P 0.001) than eastern plots, but live basal area was similar between the two aspects. Atmospheric deposition concentrations of the four main acidic molecules at Mt. Mitchell all peaked in 1998, but decreased by 2012. These reductions, occurring shortly after tightened regulations in the 1990 amendments to the Clean Air Act may have potential implications for increased forest resilience.

Patterns and driving factors of leaf C,N,and P stoichiometry in two forest types with different stand ages in a mid-subtropical zone

Background:Carbon(C),nitrogen(N),and phosphorus(P)stoichiometry is a key indicator of nutrient utilization in plants,and C/N/P ratios are related to the life histories and adaptation strategies of tree species.However,no consensus has been reached on how leaf stoichiometric characteristics are affected by forest type and stand ages.The relationships between leaf stoichiometry and geographical,meteorological,and soil factors also remain poorly understood.Methods:Leaf and soil were sampled from forest stands of different age groups(young,middle-aged,near-mature,and mature)in two forest types(Chinese fir(Cunninghamia lanceolata)forests and evergreen broadleaved forests).The relationships between leaf C,N,and P stoichiometric parameters and geographical,meteorological,and soil factors were analysed by using redundancy analysis(RDA)and stepwise linear regression analysis.Results:Leaf C concentrations peaked in the near-mature stands with increasing age irrespective of forest type.Leaf N and P concentrations fluctuated with a rising trend in Chinese fir forests,while decreased first and increased later from young to mature phases in natural evergreen broadleaved forests.Chinese fir forests were primarily limited by N and P,while natural evergreen broadleaved forests were more susceptible to P limitation.Leaf C,N,and P stoichiometric characteristics in Chinese fir forests were mainly affected by the soil total P concentration(SP),longitude(LNG),growing season precipitation(GSP)and mean temperature in July(JUT).The leaf C concentration was mainly affected by GSP and JUT;leaf N and P concentrations were both positively correlated with LNG;and leaf P was positively correlated with SP.In evergreen broadleaved forests,however,leaf stoichiometric parameters displayed significant correlations with latitude(LAT)and mean annual precipitation(MAP).Conclusions:Leaf stoichiometry differed among forest stands of different age groups and forest types.Leaf C,N,and P stoichiometry was primarily explained by the combinations of SP,LNG,GSP and JUT in Chinese fir forests.LAT and MAP were the main controlling factors affecting the variations in the leaf C,N,and P status in natural evergreen broadleaved forests,which supports the temperature-plant physiological hypothesis.These findings improve the understanding of the distribution patterns and driving mechanisms of leaf stoichiometry linked with stand age and forest type.

The Nature of Time

Scientists have debated for many years about the nature of time.Why does time seem to flow the past to the future? why does it never flow in the opposite direction-from the

Review of Studies on Structural Features,Regeneration Features and Management of Natural Spruce-Fir Mixed Stand of Coniferous and Broadleaved Trees in China

Natural spruce-fir mixed stand is one of the main forest types in the world,and also has huge ecological,economic and social benefits.According to the structural characteristics and succession laws of natural spruce-fir forest,it is urgent and significant to develop scientific management measures for natural spruce-fir mixed stand in line with local conditions.The article outlined the characteristics of the distribution and structure, regeneration and succession laws of natural spruce-fir forest,and analyzed the current situation and existing problems of natural spruce-fir forest management.The following recommendations were eventually made:1) In no cutting area,all logging activities should be banned.In a restricted cutting area,the cutting intensity should be generally controlled within 15%of the stock volume before cutting.On the commodity forest management area, the appropriate cutting intensity should be determined according to the volume per hectare,determine and classification management should be implemented in accordance with the characteristics of forest,to ensure the scientific selective cutting.2) Closure for afforestation,planting and repair planting should be adopted on vegetation-intensive land,sparse shrubs covered land and harvesting slash,in order to accelerate natural regeneration.3) The in situ conservation should be conducted in nature reserves and scientific experiment stations of rare and endangered species,such as Abies chensiensis,Picea neoveitchii,Abies vuanbaoshanensis,to reduce human destruction.4) It is supposed to collect seeds in time,establish nursery,actively establish forest, expand artificial population and promote natural regeneration.

祁门浙江楠天然林树种组成与空间结构特征分析

以安徽省祁门县浙江楠(Phoebe chekiangensis)天然林为研究对象,探究其树种组成及空间结构特征,为该地区浙江楠的林分结构优化和保护提供理论依据。设置10个20 m×25 m的调查样地,进行每木检尺调查,基于树种组成、林分直径结构及角尺度、混交度、大小比数等林分空间结构参数进行分析研究。结果表明:浙江楠天然林的径级(≥5 cm)分布主要表现为近似正态分布;浙江楠是优势种,苦槠、枫香、香樟为亚优势种,与其他乔木共同构成了以浙江楠为主的群落;浙江楠天然林林分以中度混交(0.45)为主,处于中庸生长状态,林分内个体大小分化严重,存在较强的种间竞争。优势种浙江楠空间隔离差,面临激烈的种内竞争;浙江楠种群中处于随机分布格局的个体数占48%;平均大小比数为0.43。祁门县浙江楠种群状态相对稳定,更新良好,实践中可依据以上结果和各树种现状,采取择伐、补植等人为干扰措施,优化其种群组成及空间结构,促使群落更新演替成顶级群落。

目标树经营对松栎混交林天然更新的影响

揭示马尾松栓皮栎混交林目标树经营不同间伐强度和环境因子对天然更新的影响,为培育近自然多功能森林提供科学依据。该研究根据不同间伐强度(弱度(WT)(7.6%)、轻度(LT)(15.3%)、中度(MT)(24.3%)和对照),设置28块5 m×5 m样方,记录伐后3 a的天然更新数据,分析不同间伐强度不同年份更新物种丰富度、物种多样性、更新密度、更新频度、生长差异以及环境和林分因子对天然更新的影响。研究结果表明,3 a共调查到天然更新物种33种,隶属23科31属,以阔叶树种为主;不同间伐强度天然更新物种丰富度均高于CK;间伐后的3 a中,天然更新物种的本质多样性大小为MT>LT>WT>CK。中度间伐MT与CK的更新密度在伐后不同年份存在显著和极显著差异(P<0.05和P<0.01);3 a中不同间伐强度下更新频度均值高于CK。各间伐强度天然更新苗高均高于CK,增大间伐强度可促进苗高生长。更新组和环境组间典型相关分析表明,间伐强度越大,坡度越小,天然更新密度越大且物种丰富度越高。此研究表明增大间伐强度可促进物种丰富度,提高物种多样性、更新密度和更新频度,以MT最优,坡度和坡向的协同负效应可能会在一定程度上抵消由间伐强度增大给天然更新带来的正效应,其相应经营对策应在实践中进一步加以研究。

海南热带雨林国家公园3种半天然林特征

为揭示海南热带雨林国家公园32年生杉木、34年生加勒比松和27年生马占相思3种半天然林特征,采用主要测树因子分析林分生长特征,运用重要值与生物多样性指标分析树种组成与多样性特征。结果表明:3种半天然林整体上均已是充分郁闭林分,乔木层均已经明显分异出2个亚层,直径分布均已表现为异龄林结构,林分密度分别为3600、2472和1540株·hm^(-2);灌木层林分密度分别高达8374、6828和9776株·hm^(-2);2500 m^(2)样地面积的乔木层树种丰富度分别为79、61和49,Shannon-Wiener指数分别为3.12、3.83和3.98;虽然乔木层优势种仍然为人工造林树种,但天然更新乡土树种重要值合计分别高达46.3%、54.0%和65.1%,其中乔木树种重要值占比分别高达87.1%、81.1%和93.1%;灌木层均为乡土树种天然更新林木,树种丰富度分别为137、113和91,Shannon-Wiener指数分别为4.66、5.25和3.89,其中乔木树种重要值占比分别为49.4%、54.8%和70.2%。3种半天然林都已是乔木层分异明显、乡土树种多样性异常丰富、异龄林结构特征明显的复层混交异龄林,天然更新乡土树种(80%以上为乔木树种)重要值合计已接近甚至是人工造林树种的2倍,其树种多样性高于30年生海南山地雨林皆伐伐后林和海南低地雨林残次林,乔木层和灌木层中均有不少珍贵或高价值乡土树种。

帽儿山天然软阔叶次生林林分结构动态变化

以帽儿山天然软阔叶次生林为研究对象,通过对其前后4期13 a的数据进行分析,探索帽儿山林分结构动态变化规律,为帽儿山天然次生林科学经营管理提供参考依据。结果表明:2007-2020年间直径分布都近似反J形分布,Weibull模型的R2为0.889~0.917,Logistic分布模型的R2为0.982~0.989,拟合效果均较好。林分径阶分布均匀,树种组成复杂,非空间结构指标中除林分密度(24.18~26.54)增加外,树种多样性(0.809~0.755)、林分稳定性(0.96~1.12)、株数密度均为下降。空间结构在13 a期间变化不明显,林分水平分布格局(0.525~0.518)呈现聚集分布、林木竞争为中庸状态(0.504~0.499)、林分混交程度整体为中度混交(0.615~0.640)、林分垂直复杂度下降(0.542~0.526)、林分空间综合指数变化稳定。综上所述,帽儿山天然软阔叶次生林林分结构保持相对稳定且呈现正向演替趋势,未来需对林分进行适当间伐,扩大生长空间,改善生境条件,同时适当补植红松等珍贵树种,提高经济价值,改善林分格局。

格氏栲天然林更新特征及影响因子

为明确格氏栲天然林更新现状及其主导因子,对该树种的保护和恢复提供参考,在结合格氏栲天然林林分现状、林龄结构以及更新树种重要值的基础上,采用逐步多元回归的方法探究了环境因子、林分结构因子对格氏栲林天然林不同等级更新密度的影响。结果表明:群落更新状况属于中等水平,总更新密度为2443.75株·hm^(-2)。格氏栲的更新状况不良,总更新密度为343.75株·hm^(-2),林龄多数集中在Ⅱ、Ⅲ、Ⅻ龄级,生长状态基本稳定,但更新幼苗与小苗数量极少,更新潜力不足。更新数量最多的是润楠,且重要值最大,格氏栲的重要值位于第4位。多元回归结果表明:更新密度同时受到环境因子与林分结构的共同作用,坡度在18°~25°之间时,坡度稍大且位于下坡位的阳坡区域更新密度较大。乔木层冠幅、土壤含水率和全氮质量分数是影响格氏栲群落更新密度的主导因子;土壤有效磷、有机质质量分数是影响格氏栲种群更新密度的主导因子。为促进格氏栲天然林的恢复和更新,应加强自然区的经营管理,有针对性的进行调整林分结构与土壤元素质量分数,合理利用林内空间,提高土壤肥力。

落叶松天然林灌草多样性对林分乔木特征的响应

生物多样性是生态系统结构和功能稳定性的重要基础。本研究以华北落叶松天然次生林为研究对象,2021年7月,在山西省庞泉沟国家级自然保护区设置有代表性的固定样地共27块,样地规格为20 m×20 m。在每块样地的对角线位置分别设置3个5 m×5 m的灌木样方,每个灌木样方的中心再分别设置1个1 m×1 m的样方进行草本调查。本研究主要采用物种丰富度指数(D)、Simpson多样性指数(H’)、Shannon-Wiener多样性指数(H)、Pielou物种均匀度指数(Jsw)、重要值等指标分别统计描述林下灌木层、草本层的物种特征,采用SPSS软件对林分乔木特征因子与灌木层、草本层多样性指数进行相关性分析,以探究林下植被物种多样性对林分乔木特征的响应。结果表明:本研究共记录林下植物25种,其中灌木5科9属9种,草本12科16属16种。影响林下灌木层的主要林分乔木因子为林分密度和平均冠幅。草本层的优势物种的丰富度指数、Shannon-Wiener多样性指数和Simpson多样性指数在各密度等级样地间存在显著性差异(P<0.05)。影响林下草本层生物多样性的主要林分特征因子为林分平均胸径和平均活枝下高。平均胸径、平均活枝下高、林分密度和平均冠幅是影响华北落叶松天然次生林林下植被多样性的主要乔木特征因子。