Increasing the appropriate seedling density for higher yield in dry direct-seeded rice sown by a multifunctional seeder after wheatstraw return

Dry direct-seeded rice(DDR) sown using a multifunctional seeder that performs synchronous rotary tillage and sowing has received increased attention because it is highly efficient,relatively cheap,and environmentally friendly.However,this method of rice production may produce lower yields in a rice–wheat rotation system because of its poor seedling establishment.To address this problem,we performed field experiments to determine the rice yield at five seedling density levels(B1,B2,B3,B4,and B5=100,190,280,370,and 460 seedlings m-2,respectively) and clarify the physiological basis of yield formation.We selected a representative high-quality rice variety and a multifunctional seeder that used in a typical rice–wheat rotation area in 2016 and 2018.The proportion of main stem panicle increased with increasing seedling density.There was a parabolic relationship between yield and seedling density,and the maximum yield(9.34-9.47 t ha-1) was obtained under B3.The maximum yield was associated with a higher total spikelet number m-2 and greater biomass accumulation from heading to maturity.The higher total spikelet number m-2 under B3 was attributed to an increase in panicle number m-2 compared with B1 and B2.Although the panicle numbers also increased under B4 and B5,these increases were insufficient to compensate for the reduced spikelet numbers per panicle.Lower biomass,smaller leaf area,and lower N uptake per plant from the stem elongation stage to the heading stage were partially responsible for the smaller panicle size at higher seedling density levels such as B5.The higher biomass accumulation under B3 was ascribed to the increases in the photosynthetic rate of the top three leaves m-2 of land,crop growth rate,net assimilation rate,and leaf area index.Furthermore,the B3 rice population was marked by a higher grain–leaf ratio,as well as a lower export ratio and transport ratio of biomass per stem-sheath.A quadratic function predicted that 260-290 seedlings m-2 is the optimum seedling density for achieving maximum yield.Together,these results suggested that appropriately increasing the seedling density,and thereby increasing the proportion of panicles formed by the main stem,is an effective approach for obtaining a higher yield in DDR sown using a multifunctional seeder in a rice–wheat rotation system.

High energy density in ultra-thick and flexible electrodes enabled by designed conductive agent/binder composite

Thick electrodes can increase incorporation of active electrode materials by diminishing the proportion of inactive constituents,improving the overall energy density of batteries.However,thick electrodes fabricated using the conventional slurry casting approach frequently exhibit an exacerbated accumulation of carbon additives and binders on their surfaces,invariably leading to compromised electrochemical properties.In this study,we introduce a designed conductive agent/binder composite synthesized from carbon nanotube and polytetrafluoroethylene.This agent/binder composite facilitates production of dry-process-prepared ultra-thick electrodes endowed with a three-dimensional and uniformly distributed percolative architecture,ensuring superior electronic conductivity and remarkable mechanical resilience.Using this approach,ultra-thick LiCoO_(2)(LCO) electrodes demonstrated superior cycling performance and rate capabilities,registering an impressive loading capacity of up to 101.4 mg/cm^(2),signifying a 242% increase in battery energy density.In another analytical endeavor,time-of-flight secondary ion mass spectroscopy was used to clarify the distribution of cathode electrolyte interphase(CEI) in cycled LCO electrodes.The results provide unprecedented evidence explaining the intricate correlation between CEI generation and carbon distribution,highlighting the intrinsic advantages of the proposed dry-process approach in fine-tu ning the CEI,with excellent cycling performance in batteries equipped with ultra-thick electrodes.

Effects of Nitrogen Application Rate, Density and Seedling Age on Dry Matter Accumulation of No-tillage Rape in Seedling Stage

[Objective] The aim of the research was to find the optimal nitrogen application rate, density and seedling age for no-tillage rape in seedling stage. [Method] With the D-optimal quadratic regression design for three factors, the 310 scheme was designed to study the effects of nitrogen application rate, density and seedling age on dry matter accumulation of no-tillage rape in seedling stage. [Result] With the increase of nitrogen application rate, density and seedling age, the dry matter content appeared like a parabola, increasing firstly and then declining. The change of nitrogen application rate caused greater influence than that of density and seedling age; the interaction effects between nitrogen application rate and density were greater than that between nitrogen application rate and seedling age as well as between density and seedling age. [Conclusion] Considered comprehensively, the dry matter content of no-tillage rape in seedling stage reached the highest level (4 768.2 kg/hm2) when the nitrogen application rate, the density and the seedling age were 195 kg/hm2, 93 000 plants/hm2 and 33 d, respectively.

Genetic Control of Air-Dried Wood Density, Mechanical Properties and Its Implication for Veneer Timber Breeding of New Triploid Clones in Populus tomentosa Carr

The wood samples of 9 triploid clones of Populus tomentosa Carr. taken from a 9 year old clonal test site were analyzed in order to investigate the genetic variation of wood properties, including air dried wood density and some mechanical properties. The results showed that significant or extremely significant difference in air dried wood density and the mechanical properties existed among the clones, this means these wood properties were under moderate or strong genetic controls and could be improved by genetic manipulations. The radial and vertical variation patterns of air dried wood density were also studied and the results were found to coordinate with other previous research results. The vertical variation patterns of most mechanical properties within the individual tree also conformed to the general wood theories except the modulus of elasticity and cross section hardness. Among the mechanical properties, modulus of elasticity (MOE) and tangent section hardness were under strong genetic control, with the clonal repeatabilities being 0 90 and 0 80, respectively. However, the clonal repeatabilities of other mechanical properties under study were a little lower than above two indexes. Genetic correlation analysis indicated that super clonal selection and breeding for veneer timber could be realized through indirect selection of wood density and form indexes.

Response of leaf carbon metabolism and dry matter accumulation to density and row spacing in two rapeseed(Brassica napus L.)genotypes with differing plant architectures

Biological yield indicates the potential for increasing yield.Leaf carbon metabolism plays an important role in the biomass accumulation of rapeseed(Brassica napus L.).Field experiments with the hybrid HZ62(with a conventional plant architecture)grown in 2016–2017,and HZ62 and accession 1301(with a compact plant architecture)grown in 2017–2018 were conducted to characterize the physiological and proteomic responses of leaf photosynthetic carbon metabolism to density and row spacing configurations.The densities were set at 15×10;ha^(-1)(D1),30×10^(4)ha^(-1)(D2),and 45×10^(4)ha^(-1)(D3)(main plot),with row spacings of 15 cm(R15),25 cm(R25),and 35 cm(R35)(subplot).Individual and plant population biomass accumulation was greatest at R25,R15,and R15 for D1,D2,and D3,respectively,for both genotypes.In comparison with D1 R25,the individual aboveground biomass of HZ62 decreased by60.2%,whereas the population biomass increased by 31.9%,and the individual biomass of genotype1301 decreased by 54.0%and the population biomass increased by 53.9%at D3 R15.Leaf carbon metabolic enzymes varied between genotypes at flowering stage.In contrast to D1 R25,at D3 R15 the activities of ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco)and sucrose phosphate synthase(SPS)and the contents of starch,sucrose and soluble sugars in leaves were significantly decreased in HZ62 and increased in genotype 1301.The activities of fructose-1,6-bisphosphatase(FBPase)decreased,in consistency with the abundance of fructose-bisphosphate aldolase in HZ62.In contrast,sucrose synthase(Su Sy)activity appeared to decrease in both genotypes,but a significant increase in abundance of a protein with sucrose synthase was found in the 1301 genotype by proteomic analysis.With increased density and reduced row spacing,the expression of most key proteins involved in carbon metabolism was elevated,and enzyme activity and carbon assimilate content were increased in 1301,whereas HZ62 showed the opposite trend,indicating that the compact plant type can accumulate more population biomass with denser planting.

Vegetation cover density and disturbance affected arbuscular mycorrhiza fungi spore density and root colonization in a dry Afromontane forest, northern Ethiopia

Arbuscular mycorrhiza fungi(AMF) are vital in the regeneration of vegetation in disturbed ecosystems due to their numerous ecological advantages and therefore are good indicators of soil and ecosystem health at large. This study was aimed at determining how the seasonal, vegetation cover density, edaphic and anthropogenic factors affect AMF root colonization(RC) and spore density(SD)in Desa’a dry Afromontane forest. AMF RC and SD in the rhizosphere of five dominant woody species, Juniperus procera, Olea europaea, Maytenus arbutifolia, Carissa spinarum and Dodonaea angustifolia growing in Desa’a forest were studied during the rainy and the dry seasons in three permanent study vegetation cover density plots(dense, medium, and poor). Each plot(160 x40 m2) has two management practices(fenced and unfenced plots) of area. A 100 g sample of rhizosphere soil from moisturefree composite soil was used to determine spore density.Spore density ranged from 50 to 4467 spores/100 g soil,and all species were colonized by AMF within a range of 4–95%. Glomus was the dominant genus in the rhizosphere of all species. Vegetation cover density strongly affected SD and RC. The SD was significantly higher(p < 0.05) in the poor vegetation cover density than in the other two and lowest in the dense cover; root colonization showed the reverse trend. Management practices significantly(p <0.05) influenced AMF SD and RC, with the fenced plots being more favoured. Seasons significantly(p < 0.05) affected RC and SD. More RC and SD were observed in the wet period than the dry period. Correlating AMF SD and RC with soil physical and chemical properties showed no significant difference(p> 0.05) except for total nitrogen. Disturbance, vegetation cover density, season and total nitrogen are significant factors that control the dynamics and management interventions to maintain the forest health of dry Afromontane forests.

Effect of dry density on the liquefaction behaviour of Quaternary silt

Quaternary silt is widely distributed in China and easily liquefies during earthquakes. To identify the influence of the dry density on the liquefaction behaviour of Quaternary silt, 40 cyclic triaxial liquefaction tests were performed on loose silt(dry density rd=1.460 g/cm^3) and dense silt(rd=1.586 g/cm^3) under different cyclic stress ratios(CSRs) to obtain liquefaction assessment criteria, determine the liquefaction resistance, improve the excess pore water pressure(EPWP) growth model and clarify the relationship between the shear modulus and damping ratio. The results indicate that the initial liquefaction assessment criteria for the loose and dense silts are a double-amplitude axial strain of 5% and an EPWP ratio of 1. The increase in the anti-liquefaction ability for the dense silt is more significant under lower confining pressures. The CSR of loose silt falls well within the results of the sandy silt and Fraser River silt, and the dense silt exhibits a higher liquefaction resistance than the sand-silt mixture. The relationships between the CSR and loading cycles were obtained at a failure strain of 1%. The EPWP development in the dense and loose silts complies with the "fast-stable" and "fast-gentle-sharp" growth modes, respectively. The power function model can effectively describe the EPWP growth characteristics of the dense silt. Finally, based on the liquefaction behaviour of silt, a suggestion for reinforcing silt slopes or foundations is proposed.

Effect of reduced energy density of close-up diets on dry matter intake,lactation performance and energy balance in multiparous Holstein cows

Energy intake prepartum is critically important to health, milk performance, and profitability of dairy cows. The objective of this study was to determine the effect of reduced energy density of dose-up diets on dry matter intake （DMI）, lactation performance and energy balance （EB） in multiparous Holstein cows which were housed in a free-stall barn and fed for ad libitum intake. Thirty-nine dry cows were blocked and assigned randomly to three groups fed a high energy density diet [HD, n = 13; 6.8 MJ of net energy for lactation （NEL）/kg; 14.0% crude protein （CP） ], or a middle energy density diet （MD, n = 13; 6.2 MJ NEh/kg; 14.0% CP）, or a low energy density diet （LD, n = 13; 5.4 MJ NEh/kg; 14.0% CP） from d 21 before expected day of calving. After parturition, all cows were fed the same lactation diet to d 70 in milk （DIM）. The DMI and NEE intake prepartum were decreased by the reduced energy density diets （P 〈 0.05）. The LD group consumed 1.3 last 24 h before calving. The milk yield and the postpartum kg/d （DM） more diet compared with HD group in the DMI were increased by the reduced energy density diet prepartum （P 〈 0.05）. The changes in BCS and BW prepartum and postpartum were not affected by prepartum diets HD group had higher milk fat content and lower lactose content compared with LD group during the first 3 wk of lactation （P 〈 0.05）. The energy consumption for HD, MD and LD groups were 149.8%, 126.2% and 101.1 % of their calculated energy requirements prepartum （P 〈 0.05）, and 72.7%, 73.1% and 7.5.2% during the first 4 wk postpartum, respectively. In conclusion, the low energy density prepartum diet was effective in controlling NF_L intake prepartum, and was beneficial in increasing DMI and milk yield, and alleviating negative EB postpartum.

EFFECTS OF SEEDING DENSITY AND BASIC MANURE ON THE GROWTH OF DRY NURSERY SEEDLINGS IN LATE DOUBLE CROPPING RICE IN SOUTH CHINA

During the period of dry nursery seedling raising of late double cropping indica rice in South China, both chemical fertilizer and farmyard manure did not show obvious effect on the growth of shoot and root in young seedlings at 4-leaf stage （18-day-old seedling）, but had significant effects on root growth in old seedlings with 6-7 leaves （27-day-old seedling） at suitable seeding densities (65-125g m-2). There were satistically significant differences （at 0.01 or 0.05 levels）between treatments in root number and rooting ability of root-pruned seedlings.

Influence of Dry Density on Soil-Water Retention Curve of Unsaturated Soils and Its Mechanism Based on Mercury Intrusion Porosimetry

The soil-water retention curve(SWRC)can be used to evaluate the ability of unsaturated soils to attract water at various water contents and suctions. In this study, drying SWRCs for a kind of sandy soil were obtained in the laboratory by using self-modified SWRC apparatus. In addition, the porosity and the pore size distribution of the samples were investigated by a mercury porosimetry test in order to analyze the effect of dry density. Results showed that the soil-water retention of the soil specimens was strongly dependent on the dry density. Under zero suction, soil specimens with a higher dry density exhibited lower initial volumetric water content. The higher the dry density of soil, the more slowly the volumetric water content decreased with the increase of suction. There was a general and consistent trend for a soil specimen to possess a larger air-entry value and residual suction, while smaller slope of SWRC when it had a higher density. This was probably attributed to the presence of smaller interconnected pores in the soil specimen with a higher dry density. The proportion of large diameter pores decreased in comparison to pores with small diameters in the soil tested. The measured total pore volume of the soil specimen, which had a larger dry density, was lower than that of the relatively loose specimens.

Dry Matter Partitioning, Nodulation and Seed Traits of Medium and Late Maturing Soybean Varieties as Affected by Planting Pattern and Plant Density

An experiment was conducted on Fluvisols of Awassa for two consecutive years （2005-2006） to determine effects of planting pattern and plant density on dry matter accumulation, nodulation, protein and oil content in early and late maturing soybean varieties. Results indicated that Awassa-95 variety produced significantly higher （P 〈 0.05） number of nodules/plant （NDN）, nodule dry matter （NDM） and leaf dry matter （LDM at R2 （mid flowering） stage of soybean growth than that of variety Belessa-95）. Similarly, variety Awassa-95 （45%） produced significantly higher protein content than variety Belessa-95 （40%）. However, variety Belessa-95 accumulated significantly higher （P 〈 0.01） dry matter in straw, grain and total biomass at R7 （physiological maturity） stage of soybean growth than variety Awassa-95. Similarly, oil content of variety Belessa-95 （18.1%） was significantly （P 〈 0.05） higher than that of variety Awassa-95 （15.9%）. Equidistant rows produced significantly higher （P 〈 0.05） NDM than either rectangular or paired rows. Moreover, soybean plants grown in both rectangular and equidistant rows produced significantly higher （P 〈 0.01） straw dry matter than those grown in paired rows; but, grain dry matter/plant （GDM） was significantly higher （P 〈 0.01） paired and rectangular rows compared to equidistant rows. Plant density also affected the per plant GDM production as it was significantly higher （P 〈 0.01） in 20 and 30 plants/m2 than higher plant densities （40 and 50 plants/m2）. However, dry matter and yield components had strong negative association with protein content. In fact, strong positive correlation （R 〉 0.600） occurred between grain yield and its components with dry matter components at R2 （stem dry matter （SDM）, leaf dry matter （LDM） and stem ＋ nodule ＋ leaf dry matter together known as TDM） and straw dry matter at R7 in both varieties. This study depicted that soybean plants that produce higher dry matter components at R2 would probably produce more straw dry matter, greater grain yield components and higher grain yield dry matter at later stages.

Experimental research on the mixed sand ratio and initial dry density of weathered sand improved expansive soil free load swelling rate

In this paper, through the indoor free load swelling rate test, expansive soil in a section of a first- class highway reconstruction project in Yichang City was studied. It emphatically analyzed the interrelations among free load swelling rate, non-load time, the proportion of mixed sand and initial dry density. Experimen- tal studies have shown that： Free load swelling deformation is mainly divided into three stages of rapid expan- sion, slow expansion and final stability; when the initial dry density is constant, free load swelling rate of the weathered sand modified soil will reduce rapidly before they slow down with the increase of sand proportion, and weathered sand modified soil free load swelling rate is not sensitive to the large amount of sand mixed; in the same mixed sand ratio, weathered sand modified soil free load swelling rate increases rapidly with the in- crease of initial dry density, there is a good linear correlation between them. To take appropriate control of the initial dry density during the expansive soil subgrade construction helps to reduce its swelling deformation and ensures the stability of the embankment.

Effects of Different Planting Densities on the Yield of Rice Developed from Seedlings Dry Raised in Plug Trays

[Objectives]This study was conducted to investigate the effects of different planting densities on rice tillering dynamics and yield. [Methods]The effects of different planting densities on rice yield were studied based on seedlings dry raised in plug trays. [Results]Planting density had obvious effects on tillering dynamics,number of panicles per unit area,number of grains per panicle and rice yield under the condition of seedlings dry raised in plug trays. Comprehensive analysis showed that the row spacing × hill spacing = 25 cm × 14 cm,that is,the planting density of 2. 85 × 10~5 hills/hm^2,achieved the highest yield,at 9 960 kg/hm^2. [Conclusions]This study provides a scientific basis for optimizing rice cultivation techniques and achieving high yield and high efficiency in rice production.

Comparative Study between Dielectric Properties and Compaction Parameters: Case Study on Three Laterite Quarries

This work studies the variability of the relationship between relative permittivity and compaction parameters as a function of certain geotechnical properties for different laterite types. This study allows to purpose the dielectric permittivity as a third compaction parameter allowing to obtain a non destructive control méthod. Preliminary studies on Diack laterite had shown a good correlation. Additional investigations are carried out to verify the possibility of generalizing this correlation to three new laterite careers: Ngoudiane, Yéba and Fandene. To proceed, particle size analysis, Atterberg limits, specific weight tests and compaction according to the modified Proctor test were performed on laterite samples. Using the radar method, experimental permittivities are determined for laterite samples by the point method of propagation times and confirmed by the diffraction hyperbole method. The geotechnical and radar data obtained allowed correlations between permittivity and water content on the one hand and between permittivity and dry density on the other. The results show that the maximum dry density as a function of permittivity corresponds with the optimum Proctor, which confirms the results previously obtained on Diack laterite.

DRIS法在金花茶和山茶营养诊断上的应用研究

【目的】根据研究结果及植物营养与肥料的关系进行平衡施肥,提高八角林下金花茶和山茶的生产能力和肥料利用率,为林下种植金花茶和山茶的栽培养护提供理论依据。【方法】以金花茶(Camellia nitidissima Chi)和山茶(C.japonica L)为试验材料,测定4种不同郁闭度下的金花茶和山茶的N、P、K元素含量,同时用DRIS法分析金花茶和山茶在不同郁闭度的八角林下的营养指标和养分情况。【结果】金花茶叶片的全N、全P含量均随着郁闭度的增加呈"增加-减小"趋势,均在郁闭度0.7下最大;金花茶叶片的全K和山茶叶片的全N、P、K含量均随着郁闭度的增加呈现增加趋势,且均在郁闭度0.9下最大。根据诊断施肥综合法(DRIS)分析发现,不同郁闭度下两种植物的需肥顺序各不相同;金花茶在全光照、郁闭度0.5、郁闭度0.7、郁闭度0.9下的需肥顺序为K>P>N、N>P>K、K>N>P、P>N>K;山茶在全光照、郁闭度0.5、郁闭度0.7、郁闭度0.9下的需肥顺序为N>P>K、K>P>N、K>N>P、P>K>N;金花茶的NII(营养不平衡指数)大小表现为郁闭度0.9>CK>郁闭度0.7>郁闭度0.5,山茶表现为CK>郁闭度0.9>郁闭度0.5>郁闭度0.7。【结论】根据两种植物的NII值大小可以得出,金花茶在郁闭度0.5下、山茶在郁闭度0.7下的营养最平衡,比较适宜两种植物的生长,但不同郁闭度下两种植物土壤养分状况、需肥情况存在一定差异,在生产上要根据实际郁闭度进行合理施肥。

Progress in developments of dry coal beneficiation

China’s energy supply heavily relies on coal and China’s coal resource and water resource has a reverse distribution.The problem of water shortages restricts the applications of wet coal beneficiation technologies in drought regions.The present situation highlights the significance and urgency of developing dry beneficiation technologies of coal.Besides,other countries that produce large amounts of coal also encounter serious problem of lack of water for coal beneficiation,such as American,Australia,Canada,South Africa,Turkey and India.Thus,dry coal beneficiation becomes the research hot-points in the field of coal cleaning worldwide in recent years.This paper systematically reviewed the promising research efforts on dry coal beneficiation reported in literature in last 5 years and discussed the progress in developments of dry coal beneficiation worldwide.Finally,we also elaborated the prospects and the challenges of the development of dry coal beneficiation.

Weed growth, herbicide efficacy, and rice productivity in dry seeded paddy field under different wheat stubble management methods

To ascertain the influence of wheat stubble management options and chemical weed control methods on weed growth and productivity of dry direct-seeded fine rice, a two years' field study was undertaken at the Agronomic Research Farm, University of Agriculture, Faisalabad, Pakistan in 2013 and 2014. Different wheat stubble management methods, viz., incorporation, burning and retention were executed during seed-bed preparation. While, herbicide treatments comprised of a weed check, weed free, pendimethalin followed by tank mixture of fenoxaprop p-ethyl+ethoxysulfuron ethyl, and bispyribac sodium followed by tank mixture of fenoxaprop p-ethyl+ethoxysulfuron ethyl. Results revealed that weed control efficacy of both herbicide treatments ranged from 84 to 94%. Herbicide treatments significantly reduced weed density(88–90%) and dry weight(86–88%), while improved the rice growth attributes compared with weed check. Application of bispyribac sodium followed by tank mixture of fenoxaprop p-ethyl+ethoxysulfuron ethyl in stubble retention recorded 226 and 273% increase in kernel yield over weedy check in 2013 and 2014, respectively. In stubble incorporation, pendimethalin followed by tank mixture of fenoxaprop p-ethyl+ethoxysulfuron ethyl was more effective in increasing(256–293%) rice yields over weedy check. Among different treatment combinations, the maximum net benefits(1 397.49^(–1) 472.22 USD ha^(–1)), net returns(636–700 USD ha^(–1)), benefit cost ratio(1.77^(–1).83) and marginal rate of return(2 187–2 330%) were recorded with the application of bispyribac sodium followed by fenoxaprop p-ethyl+ethoxysulfuron ethyl in stubble retention. In crux, application of bispyribac sodium followed by tank mixture of fenoxaprop p-ethyl+ethoxysulfuron ethyl in stubble retention is efficient approach to control weeds, and get maximum rice productivity and net economic returns under dry seeded system.

Research on Freeze Drying and High-temperature Molding in Medium-temperature Fluorocarbon Board

A research and test system for the carbon anode plate preparation technology was established to optimize the physical and chemical indicators of carbon anode plates,such as bulk density,resistivity,and compressive strength,and improve the operating cycle.In this study,a carbon plate was prepared via a combination of high-temperature molding and freeze drying using a formulation with asphalt content much lower than the industry standard.The experimental results show that the density of the carbon plate is increased by 0.02-0.04 g/cm^(3) by improving the drying method.The carbon plate prepared in the laboratory has a bulk density of 1.814 g/cm^(3),resistivity of 29.8μΩ·m,and compressive strength of 89.27 MPa.The bulk density,room-temperature resistivity,compressive strength,graphitization,and other key indices of the carbon plates made in the laboratory and those procured from a factory in Shanxi,Datong,were tested.Additionally,the specimens were analyzed using thermogravimetry-differential scanning calorimetry,scanning electron microscopy,and X-ray fluorescence.The laboratory-made carbon plates were superior to the factory specimens in terms of all the indicators tested.The process in this study improves the performance of the carbon anode plate and is used to provide technical support for electrolytic fluorine production in enterprises.The carbon plates prepared in the laboratory fully meet the process requirements of a medium-temperature electrolytic fluorine production line,which indicates the possibility of its use in the stable production of fluorine gas.

基于Pilodyn的楠木木材密度预测模型的建立

木材密度是决定用材树种木材质量的重要性状。以12~96年生楠木为对象,采用Pilodyn方法对活立木胸径处南北向木材进行探测,结合实测值构建楠木木材材性指标预测模型,以实现楠木活立木材性的快速、可靠评价。结果表明,楠木木材纤维长度、纤维宽度和纤维长宽比分别在629.90~1238.76、13.78~23.95μm和29.83~80.35。纤维长度和长宽比随树龄增加而增加,纤维宽度随树龄增加而降低,而气干密度与树龄无相关性。木材外侧、内侧和整株木材气干密度分别在0.40~0.698、0.13~0.66和0.40~0.57。采用不同回归方程模型构建木材气干密度预测模型,结果显示,Pilodyn测定值与气干密度的指数函数方程的拟合效果最佳,Pilodyn测定值与各木材气干密度间均呈极显著负相关关系(P<0.0001),决定系数R(-0.3002~-0.5184)。虽然pilodyn测定值与纤维长度与宽度呈现出显著的负相关关系,但决定系数均较低(R<0.15),无法保证预测模型结果的准确性。最后,分别构建楠木木材外侧(y=2.4782x^(-0.539))和整株气干密度预测模型(y=0.9538 x^(-0.24)),该预测模型的建立为今后快速无损评估楠木活立木木材密度提供新的思路和方法。

Relative Dielectric Permittivity Variations during Compaction as a Mean of Compaction Quality Control: Case Study on Laterite Samples from Senegal

This study explores an alternative to the classical use of direct methods, as water content and dry density measurements, for compaction quality control. For this purpose, the dielectric properties of lateritic materials are determined by radar method and are compared with the permittivity determined from the Topp formula and from the CRIM model. This approach allowed to establish a relationship between the geotechnical properties determined during compaction such as dry density, water content or porosity with dielectric permittivity. The obtained results made it possible to determine an optimum dielectric permittivity corresponding to the optimum dry density and the optimum water content that could be used for non-destructive in situ compaction testing. Such an approach should improve the implementation and effectiveness of in situ compaction quality control of geotechnical infrastructures.