January to August temperature variability since 1776 inferred from tree-ring width of Pinus tabulaeformis in Helan Mountain

Tree-ring standardized chronologies are developed by 78 cores collected from the eastern and western Helan Mountain. Statistical analysis shows that both the STD and RES chronologies correlate negatively with the temperature of different periods of early half year, especially with January to August mean （JA） temperature, which means that JA temperature is one of the predominant limiting factors of tree growth in the Helan Mountain. Based on this analysis, we reconstructed JA temperature, and the explained variance is 43.3% （F=21.422, p〈0.001 ）. The comparatively high temperature periods in the reconstruction were： 1805-1818 1828-1857, 1899-1907, 1919-1931 and 1968-1995; and the comparatively low temperatu re periods happened in 1858-1872, 1883-1895 and 1935-1953. Ten-year moving average curve shows three slow uplifting trends： 1766-1853, 1862-1931 and 1944-1995. Each temperature increase was followed by a sudden temperature decrease about 10 years, that is to say, the JA temperature in the Helan Mountain is characterized by slow increase and sudden decrease. The 70- and 10.77-year periodicities detected in the temperature series correspond to the Gleissberg （80-year） and Schwabe （11-year） periodicities of solar activity respectively, the 2.11-2.62 years cycles are considered to be influenced by QBO （Quasi-Biennial-Oscillation） and the local environmental change.

Dynamics of moisture regime and its reconstruction from a tree-ring width chronology of Pinus sylvestris in the downstream basin of the Selenga River, Russia

Regional tree-ring width chronology of the Scots pine (Pinus sylvestris L.) was constructed from 8 sites in the forest-steppe belt situated in the foothills of the Selenga River basin, Russia. Moisture information contained in tree-ring width chronology was obtained through linear regression reconstruction models of annual August–July precipitation and annual water discharge of the Selenga River during the period 1767–2015. Comparison of the smoothed series allowed estimating long-term variation component of these moisture regime parameters with a high precision. At the same time, regional drought indices are less correlated with pine radial growth, because they have contribution of the other environmental variables, which are much less reflected in the tree-ring of the investigated pine forest stands. Reconstructed dynamic of the moisture regime parameters is supported by documental evident of many socially significant events in the regional history, such as crop failures caused by both droughts and floods, and catastrophic fire in the Irkutsk City in 1879. Also, dependence of the amount of precipitation in the study area on the atmospheric circulation in Central Asia is revealed to have a similar pattern with other regions, i.e., a negative relationship of precipitation with the development of large high atmospheric pressure area within its center in the Altai and Tianshan mountains.

Climatic response of Pinus sylvestris var. mongolica tree-ring width and precipitation reconstruction for the northern Greater Higgnan Mountains, China, since 1720

August-June precipitation has been reconstructed back to AD 1720 for the northern Greater Higgnan Mountains, China, by use ofPinus sylvestris var. mongolica tree-ring width. The reconstruction explains the variance of 39% in observed precipitation from 1973 to 2008. Some extremely dry/wet signals in historical documents and other precipitation reconstructions in previous studies are precisely captured in our reconstruction. Wet periods occurred during the periods of 1730 to 1746, 1789 to 1812, 1844 to 1903, 1920 to 1930, 1942 to 1961, and 1985 to 1998; while periods of 1747 to 1788, 1813 to 1843, 1904 to 1919, 1931 to 1941, and 1962 to 1984 were relatively dry. Power spectral and wavelet analyses demon- strated the existence of significant 24-year, 12-year, and 2-year cycles of variability.

Stability assessment of tree ring growth of Pinus armandii Franch in response to climate change based on slope directions at the Lubanling in the Funiu Mountains,China

Global warming will affect growth strategies and how trees will adapt.To compare the response of tree radial growth to climate warming in different slope directions,samples of Pinus armandii Franch were collected and tree-ring chronologies developed on northern and western slopes from the Lubanling in the Funiu Mountains.Correlation analyses showed that two chronologies were mainly limited by temperatures in the previous June-August and the com-bination of temperatures and moisture in the current May-July.The difference of the climate response to slopes was small but not negligible.Radial growth of the LBLO1 site on the northern slope was affected by the combined maximum and minimum temperatures,while that of the LBLO2 site was affected by maximum temperatures.With regards to moisture,radial growth of the trees on the north slope was influenced by the relative humidity in the current May-July,while on the western slope,it was affected by the relative humidity in the previous June-August,the current May-July and the precipitation in the current May-July.With the change in climate,the effects of the main limiting factors on growth on different slopes were visible to a certain extent,but the differences in response of trees on different slopes gradually decreased,which might be caused by factors such as different slope directions and the change in diurnal temperature range.These results may provide information for forest protection and ecological construction in this region,and a scientific reference for future climate reconstruction.

Stability assessment of tree ring growth of Pinus armandii Franch in response to climate change based on slope directions at the Lubanling in the Funiu Mountains,China

Global warming will affect growth strategies and how trees will adapt.To compare the response of tree radial growth to climate warming in different slope directions,samples of Pinus armandii Franch were collected and treering chronologies developed on northern and western slopes from the Lubanling in the Funiu Mountains.Correlation analyses showed that two chronologies were mainly limited by temperatures in the previous June–August and the combination of temperatures and moisture in the current May–July.The difference of the climate response to slopes was small but not negligible.Radial growth of the LBL01 site on the northern slope was affected by the combined maximum and minimum temperatures,while that of the LBL02 site was affected by maximum temperatures.With regards to moisture,radial growth of the trees on the north slope was influenced by the relative humidity in the current May–July,while on the western slope,it was affected by the relative humidity in the previous June–August,the current May–July and the precipitation in the current May–July.With the change in climate,the effects of the main limiting factors on growth on different slopes were visible to a certain extent,but the differences in response of trees on different slopes gradually decreased,which might be caused by factors such as different slope directions and the change in diurnal temperature range.These results may provide information for forest protection and ecological construction in this region,and a scientific reference for future climate reconstruction.

Standardization of Qilian Juniper ring-width series in the eastern margin of the Qaidam Basin

Standardization is one of the important procedures in dendroclimatology. We used abundant Qilian juniper （Sabina przewalskii Kom.） tree-ring samples from the eastern margin of the Qaidam Basin to develop a new standardization method, i.e. total growth curve （TGC）. The samples that contained the complete pith and reached to the growing culmination around the 40th-60th year were used to fit TGC, and the generalized negative exponential function was used to fit the curve. Usually, most cores cannot reach the arboreal pith for some reasons and it is difficult to determine the arboreal cambial age. The empirical model of initial radial growth （IRG） was employed to estimate the number of rings missing from the pith by the same data and IRG model explained 90.9% of the variance. When developing the chronology, the cambial ages of cores that contained the complete pith were regarded as beginning from the first year and others were determined by the numbers of missing and included rings in the core. Standardization was accomplished by dividing each tree-ring series by corresponding TGC. The chronologies developed by TGC can retain more low-frequency variational information and TGC helps to develop more reliable tree-ring width chronology.

Pilot Study to Examine Radial Variation in Annual Ring Width, Density and Shrinkage

The annual ring width, density and shrinkage variation from pith to bark in Chinese fir (Cunninghamia lanceolata) and Boka sugi (Cryptomeria japonicd) were studied and compared. The results show that the ring width decreased sharply from pith to bark for Chinese fir. However, the ring width variation pattern for Boka sugi followed a different way, i.e., the ring width decreased to the fifth ring, increased to the tenth ring, decreased again to the fifteenth, and then increased to the twentieth, where it...

Relationships between tree-ring width index and NDVI of grassland in Delingha

Using five well-replicated Qilian juniper (Sabina przewalskii Kom.) tree-ring width index se- ries, monthly normalized difference vegetation index (NDVI) of grassland, and climatic data from 1982 to 2001, the relationships between tree-ring width index, NDVI of grassland, and climatic data were analyzed firstly. Then, the relationship between tree-ring width index and NDVI of grassland was explored. The re- sults showed that: (1) Temperature and precipitation in June influenced tree-ring width index and NDVI of grassland deeply in Delingha. (2) There were sig- nificant relationships between five tree-ring width index series (DLH1-DLH5) and monthly NDVI of grassland from June to September, with the most significant relationship being between tree-ring width index series and NDVI of grassland in August. (3) The PC1 (the first principal component derived from DLH1-DLH5 series) exhibited good agreement with monthly NDVI of grassland in the grass growth sea- son (from June to September) and the averaged NDVI in the growth season, which was attributed to their common responses to water-supply limit in Delingha. This study may allow an increase in studying the past dynamics of grassland in Delingha in that the variation of grassland NDVI during the last millennium has been reconstructed from PC1.

Response of tree-ring width to rainfall gradient along the Tianshan Mountains of northwestern China

By comparing the long-term tree-ring growths at various geographic scales, we can make clear the effects of environmental variations on tree growth, and get an understanding of the responses of forest ecosystems to the possible changes in global and regional climate. Radial tree-ring growth of Picea schrenkiana and its relationship to air temperature and precipitation were investigated across longi- tude transects on the north slopes of the Tianshan Mountains in northwestern China. Tree-ring samples were collected and residual chronologies were developed for three different regions along a gradient of decreasing precipitation from west to east. Response-function analysis was conducted to quantify the relationships between tree-ring chronologies and climate variables, such as monthly mean temperature and monthly precipitation from 1961 to 1998, using the PRECON software program. The statistical characteristics of the chronologies showed that the three chronologies constructed in this study con- tained significant environmental signals and were well suitable to reveal the impacts of climatic change on tree growth and forest productivity. Annual ring-width variations were similar among the three sites, but the variability was greatest in the east. This research showed that the growth trends of Picea schrenkiana in the Tianshan Mountains have not followed a uniform pattern. Response-function analy- sis indicated that there were significant correlations between tree growth and climatic factors in all the three regions, among which precipitation was the principal. With decreasing precipitation, the response of tree-ring widths to increasing temperature changed from a positive to a negative correlation. As for precipitation, the positive relationship to tree-ring width always dominates. It could be expected that with increased temperature and decreased precipitation, the importance of precipitation to tree growth would increase, and the response of tree growth to environmental changes would also increase. This study emphasizes the importance of regional-scale investigations into the biosphere-climate interac- tions. The results of this research indicated a substantial increment of tree-ring radial growth as a re- sult of warmer and wetter climate in the eastern regions. However, climate change will have less effect on forest growth and primary production in the western regions.

Relationship between δ^(13)C and index of ring width

1 Materials and methods THE tree-ring reported here is one of pine discs sampled at 3 200 m a.s.l. in Qongtelian Valley in the Tuomu’er Peak region in 1978. The local geographical and climate condition has been introduced in detail. An index series was obtained after the width of tree-rings on 5 different radii was measured andfitted by linear and negative exponential functional regression. Each annual ring has been separated on the whole to simultaneously measure △14 C and δ13 C of treerings. Cellulose was extracted by the standard chemical method, then oxidized by copper oxide to C02.Carbon isotopic analyses were performed with a Mat-252 mass spectrometer. Results are expressed in thestandard δ notation with respect to the PDB standard with a precision of 0.1‰. 2

A Numerical Investigation on the Influence of the Circular Ring on the Aerodynamic Noise Generated by a Cooling Fan

The influence of the width of the circular ring of a car cooling fan on the aerodynamic noise is investigated numerically through the determination of the overall sound pressure level(OASPL).The results demonstrate that when the circular rings cover near 2/3 of the width of the blade tips of the rotor in the axis direction,the rotor has the lowest OASPL and the related total pressure efficiency and flow mass rate are better than the corresponding values obtained for a reference rotor without a circular ring.With increasing the width of the circular ring in the axis direction,the tip vortex around the trailing edge of the blade tip becomes smaller and finally disappears.Meanwhile,a separated flow field arises gradually and then grows in size around the middle of the junction of the blade tips with the ring.When the circular rings cover nearly 2/3 s of the width of the blade tips of the fan in the axis direction,the extension of the separated flow around the blade’s tip attains a minimum.

Compact and broadband circularly polarized ring antenna with wide beam-width for multiple global navigation satellite systems

A compact and broadband circularly polarized （CP） annular ring antenna with wide beam-width is proposed for multiple global navigation satellite systems （GNSS） in the L1 band. The annular ring is excited by two modified L-probes with quadrature phase difference. It has a 36.3% 10-dB return loss bandwidth and a 13% 3-dB axial ratio bandwidth, because of the orthogonal L-probes with 90° phase difference. The measured peak gain of the antenna is 3.9 dBic. It can detect the satellites at lower elevation as its half power beam-width （HPBW） is 113° in both the x-z and y-z planes, achieving a cross-polarization level of larger than 25 dB. Noticeably, the antenna achieves 89% size reduction compared with the conventional half wavelength patch antennas. It can be used in hand-held navigation devices of multiple GNSS such as COMPASS, Galileo, GPS and GLONASS.

气候因子对云冷杉针叶混交林主要针叶树种径向生长的贡献率分析

【目的】为分析气候变化对针叶树种径向生长的影响,揭示针叶混交林对气候变化的响应规律,在全球气候变暖的背景下,对森林生态系统的适应性经营提供理论支撑。【方法】以金沟岭林场云冷杉针叶混交林中的3个针叶树种为研究对象,建立3个针叶树种的树轮宽度标准化年表,分析3个树种的树轮宽度与气候因子之间的相关关系,明确该地区显著限制其径向生长的气候因子,并用层次分割法量化气候因子对各树种树轮宽度变化的贡献率。【结果】在95%的置信区间下,与气候因子相关分析显示:红松和臭冷杉的径向生长同时受气温和降水的影响,与生长季初期气温正相关;鱼鳞云杉的树轮宽度主要受气温影响,与秋冬季节气温负相关,与降水量的整体相关性较低。3个树种均受到上一年气候因子的影响,有一定的“滞后效应”。滑动相关分析表明,本研究3个主要针叶树种与气候因子的响应关系存在差异,主要表现为负相关性呈增强趋势。3月平均气温对红松的贡献率最高,为34.56%,4月最低气温对臭冷杉的贡献率最高,为22.29%,对鱼鳞云杉的贡献率为60.89%。【结论】层次分割分析法能够有效量化气候因子对各树种树轮生长的贡献率,分析结果可为制定该地区应对未来气候变化的经营管理措施提供理论参考。

两级液环压缩机内流场及外特性

采用数值模拟与试验相结合的方法,以2SY-6两级液环压缩机为研究对象,对多级液环压缩机在不同工况、不同叶轮宽度比下内流场及性能进行对比分析,结果表明:二级叶轮叶片载荷小于一级叶轮,其排气口区域锯齿形气液交界面较一级叶轮更为光滑.一级叶轮吸气口区域回流强度相对于二级叶轮吸气口区域更强,一级叶轮吸气口区域湍动能明显大于二级叶轮.等外径设计的二级叶轮进出口压缩比远小于一级叶轮,二级叶轮的做功能力小于一级叶轮.由于一级叶轮的进出口压缩比较大且均位于效率极值点的右侧,一级叶轮效率随泵的压缩比增大而逐渐下降,而二级叶轮压缩比范围包含极值点,所以其效率先增后减.液环压缩机随着二级叶轮宽度的增大,其吸气能力越强,各个工况下的流量均逐渐增大.低压缩比工况下的效率随k值减小逐渐增大,高压缩比工况下的效率随k值减小先增后减.随首次级叶轮宽度比k值的减小,二级叶轮的压缩比曲线逐渐向上平移,而一级叶轮的压缩比曲线逐渐向下平移.随泵出口压力的增大,首次级叶轮压缩比的比值曲线下降趋于平缓,k值为2.2时两级叶轮压缩比的比值趋于1.1.

长白落叶松人工林年轮宽度对气候变化的响应

为揭示长白落叶松(Larix olgensis)人工林早材、晚材和全材年轮宽度对气候的响应程度,以东北林业大学帽儿山实验林场27块样地的135株样木树芯为数据源,在建立树木年轮年表的基础上,采用相关性分析量化其早材、晚材和全材年轮宽度与气候要素的关系。结果表明,长白落叶松年轮宽度在时间尺度上可划分为2个明显不同的时间段,其中1974—1985年树木生长主要受春秋两季的温度影响,而1986—2019年则主要受夏季温度的影响。在1974—1985年,冬春季的最高温度和最低温度,特别是上一年和当年的1月和2月以及4月和5月与早材和全材年轮宽度的影响呈负相关的(P<0.05),与晚材年轮宽度的影响呈正相关(P<0.05);上一年和当年春季4、5月的无霜期与早材年轮宽度的影响呈负相关(P<0.05)。在1986—2019年,夏季尤其是上一年和当年6、7月的最高温度以及最低温度与晚材年轮宽度有显著的正相关性(P<0.05);夏季上一年和当年7月的平均温度与晚材年轮宽度的生长有显著的正相关性(P<0.05),但与早材和全材年轮宽度有显著的负相关性(P<0.05)。整体来看,生长季的温度尤其是最低温度和平均温度是限制长白落叶松人工林早材和晚材生长的主要因素,而降水对早材和晚材生长的影响则不显著。

TBM窄刃刀与标准刀现场性能对比测试与分析

极硬岩条件下如何进行刀具选型,使TBM掘进速度和刀具消耗取得综合效益,是有待解决的具有争议性的问题。为此,依托新疆YE工程现场TBM实际掘进,在岩石单轴抗压强度为100~150 MPa的完整Ⅱ类凝灰岩条件下,对比测试刀盘主要区域窄刃刀和标准刀的掘进性能表现以及刀具消耗情况,探索降低滚刀刀圈刃宽,提升TBM贯入度和掘进速度的可行性与合理性。结果表明:1)使用窄刃刀破岩对贯入度和施工速度有着较为明显的提升,且随着围岩抗压强度的增加,窄刃刀对掘进速度的提升效果明显;2)与标准刀相比,窄刃刀消耗数量也有较大增加,但2种滚刀的失效形式占比情况大致相同,对TBM作业利用率影响极小;3)经综合成本估算,窄刃刀通过提升施工速度节省的成本远高于刀具消耗增加的成本。

Reconstruction of hydrological changes based on tree-ring data of the Haba River, northwestern China

Reconstructing the hydrological change based on dendrohydrological data has important implications for understanding the dynamic distribution and evolution pattern of a given river. The widespread, long-living coniferous forests on the Altay Mountains provide a good example for carrying out the dendrohydrological studies. In this study, a regional composite tree-ring width chronology developed by Lariat sibirica Ledeb. and Picea obovata Ledeb. was used to reconstruct a 301-year annual （from preceding July to succeeding June） streamflow for the Haba River, which originates in the southern Altay Mountains, Xinjiang, China. Results indicated that the reconstructed streamflow series and the observations were fitting well, and explained 47.5% of the variation in the observed streamflow of 1957-2008. Moreover, floods and droughts in 1949-2000 were precisely captured by the streamflow reconstruction. Based on the frequencies of the wettest/driest years and decades, we identified the 19th century as the century with the largest occurrence of hydrological fluctuations for the last 300 years. After applying a 21-year moving average, we found five wet （1724-1758, 1780-1810, 1822-1853, 1931-1967, and 1986-2004） and four dry （1759-1779, 1811-1821, 1854-1930, and 1968-1985） periods in the streamflow reconstruction. Furthermore, four periods （1770-1796, 1816-1836, 1884-1949, and 1973-1997） identified by the streamflow series had an obvious increasing trend. The increasing trend of streamflow since the 1970s was the biggest in the last 300 years and coincided with the recent warming-wetting trend in northwestern China. A significant correlation between streamflow and precipitation in the Altay Mountains indicated that the streamflow reconstruction contained not only local, but also broad-scale, hydro-climatic signals. The 24-year, 12-year, and 2.2-4.5-year cycles of the reconstruction revealed that the streamflow variability of the Haba River may be influenced by solar activity and the atmosphere-ocean system.

Tree-ring response of Larix chinensis on regional climate and sea-surface temperature variations in alpine timberline in the Qinling Mountains

Tree-ring width chronologies of Larix chinensis were developed from the northern and southern slopes of the Qinling Mountains in Shaanxi Province,and climatic factors affecting the tree-ring widths of L.chinensis were examined.Correlation analysis showed that similar correlations between tree-ring width chronologies and climatic factors demonstrated that radial growth responded to climate change on both slopes.The radial growth of L.chinensis was mainly limited by temperature,especially the growing season.In contrast,both chronologies were negatively correlated with precipitation in May of the previous year and April of the current year.Spatial climate-correlation analyses with gridded land-surface climate data revealed that our tree-ring width chronologies contained a strong regional temperature signal over much of northcentral and eastern China.Spatial correlation with seasurface temperature fields highlights the influence of the Pacific Ocean,Indian Ocean,and North Atlantic Ocean.Wavelet coherence analysis indicated the existence of some decadal and interannual cycles in the two tree-ring width chronologies.This may suggest the influences of El Nin˜o-Southern Oscillation and solar activity on tree growth in the Qinling Mountains.These findings will help us understand the growth response of L.chinensis to climate change in the Qinling region,and they provide critical information for future climate reconstructions based on this species in semi-humid regions.

Tree ring based drought variability in Northwest Tajikistan since 1895 AD

Determining the mechanisms controlling the changes of wet and dry conditions will improve our understanding of climate change over the past hundred years,which is of great significance to the study of climate and environmental changes in the arid regions of Central Asia.Forest trees are ecologically significant in the local environment,and therefore the tree ring analysis can provide a clear record of regional historical climate.This study analyzed the correlation between the tree ring width chronology of Juniperus turkestanica Komarov and the standardized precipitation evapotranspiration index(SPEI)in Northwest Tajikistan,based on 56 tree ring samples collected from Shahristan in the Pamir region.Climate data including precipitation,temperature and the SPEI were downloaded from the Climate Research Unit(CRU)TS 4.00.The COFECHA program was used for cross-dating,and the ARSTAN program was used to remove the growth trend of the tree itself and the influence of non-climatic factors on the growth of the trees.A significant correlation was found between the radial growth of J.turkestanica trees and the monthly mean SPEI of February–April.The monthly mean SPEI sequence of February–April during the period of 1895–2016 was reconstructed,and the reconstruction equation explained 42.5%of the variance.During the past 122 a(1895–2016),the study area has experienced three wetter periods(precipitation above average):1901–1919,1945–1983 and 1995–2010,and four drier periods(precipitation below average):1895–1900,1920–1944,1984–1994 and 2011–2016.The spatial correlation analysis revealed that the monthly mean SPEI reconstruction sequence of February–April could be used to characterize the large-scale dry-wet variations in Northwest Tajikistan during the period of 1895–2016.This study could provide comparative data for validating the projections of climate models and scientific basis for managing water resources in Tajikistan in the context of climate change.