The thermal state of seawater is a fundamental property of the ocean.Extreme changes in the ocean's thermal conditions can significantly impact the marine environment,climate system,ecosystems,and economic activit...The thermal state of seawater is a fundamental property of the ocean.Extreme changes in the ocean's thermal conditions can significantly impact the marine environment,climate system,ecosystems,and economic activities.Marine heatwaves(MHWs)are extreme high-temperature events occurring in the ocean at weather or short-to-medium-term climate scales,representing extreme variations in oceanic conditions(Pearce et al.,2011;Feng et al.,2013;Hobday et al.,2016).展开更多
Workpiece rotational grinding is widely used in the ultra-precision machining of hard and brittle semiconductor materials,including single-crystal silicon,silicon carbide,and gallium arsenide.Surface roughness and sub...Workpiece rotational grinding is widely used in the ultra-precision machining of hard and brittle semiconductor materials,including single-crystal silicon,silicon carbide,and gallium arsenide.Surface roughness and subsurface damage depth(SDD)are crucial indicators for evaluating the surface quality of these materials after grinding.Existing prediction models lack general applicability and do not accurately account for the complex material behavior under grinding conditions.This paper introduces novel models for predicting both surface roughness and SDD in hard and brittle semiconductor materials.The surface roughness model uniquely incorporates the material’s elastic recovery properties,revealing the significant impact of these properties on prediction accuracy.The SDD model is distinguished by its analysis of the interactions between abrasive grits and the workpiece,as well as the mechanisms governing stress-induced damage evolution.The surface roughness model and SDD model both establish a stable relationship with the grit depth of cut(GDC).Additionally,we have developed an analytical relationship between the GDC and grinding process parameters.This,in turn,enables the establishment of an analytical framework for predicting surface roughness and SDD based on grinding process parameters,which cannot be achieved by previous models.The models were validated through systematic experiments on three different semiconductor materials,demonstrating excellent agreement with experimental data,with prediction errors of 6.3%for surface roughness and6.9%for SDD.Additionally,this study identifies variations in elastic recovery and material plasticity as critical factors influencing surface roughness and SDD across different materials.These findings significantly advance the accuracy of predictive models and broaden their applicability for grinding hard and brittle semiconductor materials.展开更多
Background The mulch-free subsurface drip irrigation system demonstrated water-saving potential as an alternative to traditional mulch-based drip irrigation while also eliminating residual film pollution at source.How...Background The mulch-free subsurface drip irrigation system demonstrated water-saving potential as an alternative to traditional mulch-based drip irrigation while also eliminating residual film pollution at source.However,delayed sowing is unavoidable in mulch-free cultivation in ecological regions with a short frost-free period.Intercropping with cumin,which has a shorter growth period,served as an effective strategy to improve land use efficiency during the early growth stages of cotton.Therefore,a two-year field experiment was conducted to study the effects of intercropping cumin at the seeding rate of 2.5(ID1),3.85(ID2),and 5.2(ID3)kg・hm−2 on cotton growth,interspecies competition,fiber quality,and water use efficiency(WUE),as well as system economic benefits under subsurface drip irrigation.Monocropping cotton was used as the control(CK)treatment.Results At the initial flowering(IF)stage(the end of the co-growth period of cotton and cumin),cotton plant height in ID2 and ID3 treatments decreased by 5.93%–16.53%and 10.87%–31.11%,respectively,cotton stem diameter by 11.41%–14.25%and 3.37%–26.49%,respectively,and vegetative biomass by 14.46%–30.65%and 22.59%–49.91%,respectively,compared with CK treatment.With the increase in cumin density,the crop growth rate(CGR)and compensation effect in cotton tended to significantly decrease at the IF stage regardless of organs considered.For the non-co-growth period(after harvesting cumin),cotton reproductive organ biomass in ID2 and ID3 treatments increased by 4.09%‒14.61%at the boll opening stage,crop growth rate in reproductive organs by 20.74%and 74.26%from peak boll to boll opening stages compared with CK treatment,due to an enhancement of 19.09%and 49.30%in the compensation effect.Compared with ID1,the aggressivity treated by ID2 and ID3 decreased by 12.82%–46.34%and 17.95%–31.71%,respectively.However,owing to a greater number of green bolls in the upper canopy at the harvest stages in the ID3 treatment,the system production value(closely related to yield)treated by ID2 was 11.69%–16.89%,6.56%–20.02%,and 16.48%–59.83%greater than that of the ID1,ID3,and CK treatments,respectively.This also led to the highest WUE and net profit under the ID2 treatment.Conclusion Intercropping cumin with medium density improved the cotton biomass accumulation characteristics and increased resources such as land and water utilization efficiency and economic benefits through a stronger compensation effect after harvesting cumin under subsurface drip irrigation without mulch.This study not only provides alternatives to residual film pollution in arid cotton fields but also establishes a sustainable agro-ecological-economic planting paradigm by reducing plastic use and enhancing water and fertilizer use efficiency,holding significant implications for advancing resource-efficient agricultural systems.展开更多
In the gas-coal integrated mining field,the conventional design method of pipeline coal pillars leads to a large amount of coal pillars being unrecovered and overlooks the pipeline's safety requirements.Considerin...In the gas-coal integrated mining field,the conventional design method of pipeline coal pillars leads to a large amount of coal pillars being unrecovered and overlooks the pipeline's safety requirements.Considering the coal pillar recovery rate and pipeline's safety requirements,two new shaped coal pillar design approaches for subsurface pipelines were developed.Firstly,the deformation limitations for measuring pipeline safety are categorized into two:no deformation is permitted,and deformation is acceptable within elastic limits.Subsequently,integrating the key stratum theory(KST)and cave angle,a fishbone-shaped coal pillar design approach that does not permit pipeline deformation is established.Meanwhile,combined with the ground subsidence and the pipeline's elastic deformation limit,a grille-shaped coal pillar design approach that accepts deformation pipelines within elastic limits is established.Those two new approaches clarify parameters including mined width,coal pillar width and mined length.Finally,the case study shows that the designed mined width,coal pillar width and mined length of the fishbone-shaped coal pillar are 90,80,and 130 m,while those of the grille-shaped are 320,370,and640 m.Compared with the conventional method,the fishbone-shaped and grille-shaped coal pillar design approaches recovered coal pillar resources of 2.65×10~6and 5.81×10~6t on the premise of meeting the pipeline safety requirements,and the recovery rates increased by 20.5%and 45.0%,with expenditures representing only 56.46%and 20.02%of the respective benefits.These new approaches provide managers with diverse options for protecting pipeline safety while promoting coal pillar recovery,which is conducive to the harmonic mining of gas-coal resources.展开更多
The distribution of shear-wave velocities in the subsurface is generally used to assess the potential forseismic liquefaction and soil amplification effects and to classify seismic sites. Newly developeddistributed ac...The distribution of shear-wave velocities in the subsurface is generally used to assess the potential forseismic liquefaction and soil amplification effects and to classify seismic sites. Newly developeddistributed acoustic sensing (DAS) technology enables estimation of the shear-wave distribution as ahigh-density seismic observation system. This technology is characterized by low maintenance costs,high-resolution outputs, and real-time data transmission capabilities, albeit with the challenge ofmanaging massive data generation. Rapid and efficient interpretation of data is the key to advancingapplication of the DAS technology. In this study, field tests were carried out to record ambient noise overa short period using DAS technology, from which the surface-wave dispersion curves were extracted. Inorder to reduce the influence of directional effects on the results, an unsupervised clustering method isused to select appropriate clusters to extract the Green's function. A combination of a genetic algorithmand Monte Carlo (GA-MC) simulation is proposed to invert the subsurface velocity structure. Thestratigraphic profiles obtained by the GA-MC method are in agreement with the borehole profiles.Compared to other methods, the proposed optimization method not only improves the solution qualitybut also reduces the solution time.展开更多
Three-dimensional ocean subsurface temperature and salinity structures(OST/OSS)in the South China Sea(SCS)play crucial roles in oceanic climate research and disaster mitigation.Traditionally,real-time OST and OSS are ...Three-dimensional ocean subsurface temperature and salinity structures(OST/OSS)in the South China Sea(SCS)play crucial roles in oceanic climate research and disaster mitigation.Traditionally,real-time OST and OSS are mainly obtained through in-situ ocean observations and simulation by ocean circulation models,which are usually challenging and costly.Recently,dynamical,statistical,or machine learning models have been proposed to invert the OST/OSS from sea surface information;however,these models mainly focused on the inversion of monthly OST and OSS.To address this issue,we apply clustering algorithms and employ a stacking strategy to ensemble three models(XGBoost,Random Forest,and LightGBM)to invert the real-time OST/OSS based on satellite-derived data and the Argo dataset.Subsequently,a fusion of temperature and salinity is employed to reconstruct OST and OSS.In the validation dataset,the depth-averaged Correlation(Corr)of the estimated OST(OSS)is 0.919(0.83),and the average Root-Mean-Square Error(RMSE)is0.639°C(0.087 psu),with a depth-averaged coefficient of determination(R~2)of 0.84(0.68).Notably,at the thermocline where the base models exhibit their maximum error,the stacking-based fusion model exhibited significant performance enhancement,with a maximum enhancement in OST and OSS inversion exceeding 10%.We further found that the estimated OST and OSS exhibit good agreement with the HYbrid Coordinate Ocean Model(HYCOM)data and BOA_Argo dataset during the passage of a mesoscale eddy.This study shows that the proposed model can effectively invert the real-time OST and OSS,potentially enhancing the understanding of multi-scale oceanic processes in the SCS.展开更多
As a frequently-observed phenomenon in the northern South China Sea(nSCS),subsurface chlorophyll maximum(SCM)evolution from summer to winter remains unclear,neither the associated hydrographic control.In this study,on...As a frequently-observed phenomenon in the northern South China Sea(nSCS),subsurface chlorophyll maximum(SCM)evolution from summer to winter remains unclear,neither the associated hydrographic control.In this study,on the basis of in-situ data of fall-season cruises in 2004–2006,we characterized the depth,thickness and intensity of the SCM in the nSCS using a general Gaussian-function fitting approach,and investigated a linkage to the corresponding ocean vertical buoyance properties.Our results show that the SCM becomes deeper,thicker and less intense offshore-wards in the nSCS during fall seasons.In parallel,a correlation between the SCM variation and mixed layer depth exists in the nSCS,and it becomes pronounced in the shelf region compared to the slope and basin areas in autumn.Physically,once warmer surface ocean and thus stronger thermo-determined stratification,the SCM layer goes deeper and becomes thicker and less intense in the nSCS,especially in the shelf area of the nSCS.Moreover,the impact of water temperatures at deeper layers on the vertical stratification exerts more consequent roles on the spatial variability of SCM,compared to surface temperatures in the nSCS.Specifically,the isotherm line of 22℃ acts as crucial indicator for variations of the SCM in the nSCS during autumns.展开更多
We present an improved angle polishing method in which the end of the cover slice near the glue layer is beveled into a thin,defect-free wedge,the straight edge of which is used as the datum for measuring the depth of...We present an improved angle polishing method in which the end of the cover slice near the glue layer is beveled into a thin,defect-free wedge,the straight edge of which is used as the datum for measuring the depth of subsurface damage. The bevel angle can be calculated from the interference fringes formed in the wedge. The minimum depth of the subsurface damage that can be measured by this method is a few hundred nanometers. Our results show that the method is straightforward, accurate, and convenient.展开更多
Subsurface defects were fluorescently tagged with nanoscale quantum dots and scanned layer by layer using confocal fluorescence microscopy to obtain images at various depths. Subsurface damage depths of fused silica o...Subsurface defects were fluorescently tagged with nanoscale quantum dots and scanned layer by layer using confocal fluorescence microscopy to obtain images at various depths. Subsurface damage depths of fused silica optics were characterized quantitatively by changes in the fluorescence intensity of feature points. The fluorescence intensity vs scan depth revealed that the maximum fluorescence intensity decreases sharply when the scan depth exceeds a critical value. The subsurface damage depth could be determined by the actual embedded depth of the quantum dots. Taper polishing and magnetorheological finishing were performed under the same conditions to verify the effectiveness of the nondestructive fluorescence method. The results indicated that the quantum dots effectively tagged subsurface defects of fused-silica optics, and that the nondestructive detection method could effectively evaluate subsurface damage depths.展开更多
A molecular dynamics （MD） simulation is carried out to analyze the effect of cutting edge radius,cutdepth, and grinding speed on the depth of subsurface damage layers in monocrystal silicon grinding processes on an ...A molecular dynamics （MD） simulation is carried out to analyze the effect of cutting edge radius,cutdepth, and grinding speed on the depth of subsurface damage layers in monocrystal silicon grinding processes on an atomic scale. The results show that when the cutting edge radius decreases in the nanometric grinding process with the same cut-depth and grinding speed, the depth of the damage layers and the potential energy between the silicon atoms decrease too. Also, when the cut depth increases, both the depth of the damage layers and the potential energy between silicon atoms increase. When the grinding speed is between 20 and 200m/s,the depth of the damage layers does not change much with the increase of the grinding speed under the same cutting edge radius and cut depth conditions. This means that the MD simulation is not sensitive to changes in the grinding speed, and thus increasing the grinding speed properly can shorten the sion,the subsurface damage of monocrystal silicon is silicon atoms, which is verified by the ultra-precision simulation time and enlarge the simulation scale. In conclumainly based on the change of the potential energy between grinding and CMP experiments.展开更多
Various environmental conditions determine soil enzyme activities, which are important indicators for changes of soil microbial activity, soil fertility, and land quality. The effect of subsurface irrigation schedulin...Various environmental conditions determine soil enzyme activities, which are important indicators for changes of soil microbial activity, soil fertility, and land quality. The effect of subsurface irrigation scheduling on activities of three soil enzymes (phosphatase, urease, and catalase) was studied at five depths (0-10, 10-20, 20-30, 30-40, and 40-60 cm) of a tomato greenhouse soil. Irrigation was scheduled when soil water condition reached the maximum allowable depletion (MAD) designed for different treatments (-10, -16,-25,-40, and-63 kPa). Results showed that soil enzyme activities had significant responses to the irrigation scheduling during the period of subsurface irrigation. The neutral phosphatase activity and the catalase activity were found to generally increase with more frequent irrigation (MAD of -10 and -16 kPa). This suggested that a higher level of water content favored an increase in activity of these two enzymes. In contrast, the urease activity decreased under irrigation, with less effect for MAD of -40 and -63 kPa. This implied that relatively wet soil conditions were conducive to retention of urea N, but relatively dry soil conditions could result in increasing loss of urea N. Further, this study revealed that soil enzyme activities could be alternative natural bio-sensors for the effect of irrigation on soil biochemical reactions and could help optimize irrigation management of greenhouse crop production.展开更多
The aims of this research were to compare subsurface drip irrigation scheduling and nitrogen fertilization rates in cucumber, and evaluate yield and quality of cucumber fruit, water （WUE）, irrigation water （IWUE）,...The aims of this research were to compare subsurface drip irrigation scheduling and nitrogen fertilization rates in cucumber, and evaluate yield and quality of cucumber fruit, water （WUE）, irrigation water （IWUE）, and nitrogen use （NUE） efficiencies in the solar greenhouse in Southwest China. The irrigation water amounts were determined based on the 20 cm diameter pan （Ep） placed over the crop canopy, and cucumber plant was subjected to three irrigation water levels （I1, 0.6 Ep; I2, 0.8 Ep; and I3, 1.0 Ep） in interaction with three nitrogen fertilization levels （N1, 300 kg ha-1; N2, 450 kg ha-1; and N3, 600 kg ha-1）. The results showed that the cucumber fruit yield increased with the improvement of irrigation water. Irrigation water increased yields by increasing the mean weight of the fruits, and also by increasing fruit number. But the highest values of IWUE and WUE were obtained from I2 treatment. NUE significantly decreased with the improvement of N application, but increased by irrigating more water. The quality of cucumber fruit decreased with the improvement irrigation water and nitrogen fertilization. In conclusion, the optimum irrigation level and nitrogen fertilizer application level for cucunber under subsurface drip irrigation in the solar greenhouse in Southwest China were 0.8 Ep and 450 and 600 kg ha-1, respectively.展开更多
The operational performance of a full scale subsurface flow constructed wetland, which treated the mixed industrial and domestic wastewater with BOD 5/COD mean ratio of 0 33 at Shatian, Shenzhen City was studied. ...The operational performance of a full scale subsurface flow constructed wetland, which treated the mixed industrial and domestic wastewater with BOD 5/COD mean ratio of 0 33 at Shatian, Shenzhen City was studied. The constructed wetland system consists of screens, sump, pumping station, and primary settling basin, facultative pond, first stage wetland and secondary stage wetland. The designed treatment capacity is 5000 m 3/d, and the actual influent flow is in the range of <2000 to >10000 m 3/d. Under normal operational conditions, the final effluent quality well met the National Integrated Wastewater Discharge Standard(GB 8978\_1996), with the following parameters(mean values): COD 33 90 mg/L, BOD 5 7.65 mg/L, TSS 7.92 mg/L, TN 9.11 mg/L and TP 0 56 mg/L. Seven species of plants were selected to grow in the wetland: Reed, Sweetcane flower Silvergrass, Great Bulrush, Powdery Thalia and Canna of three colours. The growing season is a whole year round. The seasonal discrepancy could be observed and the plants growing in the wetland are vulnerable to lower temperature in winter. The recycling of the effluent in the first stage of the wetland system is an effective measure to improve the performance of the wetland system. The insufficient DO value in the wetland system not only had significant effect on pollutants removal in the wetland, but also was unfavourable to plant growth. The recycling of effluent to the inlet of wetland system and artificial pond to increase DO value of influent to the wetland is key to operate the subsurface constructed wetland steadily and effectively.展开更多
Four depth treatments of subsurface drip irrigation pipes were designated as 1) at 20,2) 30 and 3) 40 cm depths all with a drip-proof flumes underneath,and 4) at 30 cm without a drip-proof flume to investigate the res...Four depth treatments of subsurface drip irrigation pipes were designated as 1) at 20,2) 30 and 3) 40 cm depths all with a drip-proof flumes underneath,and 4) at 30 cm without a drip-proof flume to investigate the responses of a tomato root system to different technical parameters of subsurface drip irrigation in a glass greenhouse,to evaluate tomato growth as affected by subsurface drip irrigation,and to develop an integrated subsurface drip irrigation method for optimal tomato yield and water use in a glass greenhouse. Tomato seedlings were planted above the subsurface drip irrigation pipe. Most of the tomato roots in treatment 1 were found in the top 0-20 cm soil depth with weak root activity but with yield and water use efficiency (WUE) significantly less (P ---- 0.05) than treatment 2; root activity and tomato yield were significantly higher (P = 0.05) with treatment 3 compared to treatment 1; and with treatment 2 the tomato roots and shoots grew harmoniously with root activity,nutrient uptake,tomato yield and WUE significantly higher (P= 0.05) or as high as the other treatments. These findings suggested that subsurface drip irrigation with pipes at 30 cm depth with a drip-proof flume placed underneath was best for tomato production in greenhouses. In addition,the irrigation interval should be about 7-8 days and the irrigation rate should be set to 225 m3 ha-1 per event.展开更多
A subsurface flow wetland(SSFW)was simulated using a commercial computational fluid dynamic(CFD)code.The constructed media was simulated using porous media and the liquid resident time distribution(RTD)in the SSFW was...A subsurface flow wetland(SSFW)was simulated using a commercial computational fluid dynamic(CFD)code.The constructed media was simulated using porous media and the liquid resident time distribution(RTD)in the SSFW was obtained using the particle trajectory model.The effect of wetland configuration and operating conditions on the hydraulic performance of the SSFW were investigated.The results indicated that the hydraulic performance of the SSFW was predominantly affected by the wetland configuration.The hydr...展开更多
Subsurface damage is easily induced in machining of hard and brittle materials because of their particular mechani?cal and physical properties. It is detrimental to the strength,performance and lifetime of a machined ...Subsurface damage is easily induced in machining of hard and brittle materials because of their particular mechani?cal and physical properties. It is detrimental to the strength,performance and lifetime of a machined part. To manu?facture a high quality part,it is necessary to detect and remove the machining induced subsurface damage by the subsequent processes. However,subsurface damage is often covered with a smearing layer generated in a machining process,it is rather di cult to directly observe and detect by optical microscopy. An e cient detection of subsur?face damage directly leads to quality improvement and time saving for machining of hard and brittle materials. This paper presents a review of the methods for detection of subsurface damage,both destructive and non?destructive. Although more reliable,destructive methods are typically time?consuming and confined to local damage infor?mation. Non?destructive methods usually su er from uncertainty factors,but may provide global information on subsurface damage distribution. These methods are promising because they can provide a capacity of rapid scan and detection of subsurface damage in spatial distribution.展开更多
In order to enhance the hydraulic loading rate （HLR） of a subsurface wastewater infiltration system （SWIS） used in treating domestic sewage, the intermittent operation mode was employed in the SWIS. The results sh...In order to enhance the hydraulic loading rate （HLR） of a subsurface wastewater infiltration system （SWIS） used in treating domestic sewage, the intermittent operation mode was employed in the SWIS. The results show that the intermittent operation mode contributes to the improvement of the HLR and the pollutant removal rate. When the wetting-drying ratio （RwD） was 1.0, the pollutant removal rate increased by （13.6 ± 0.3）% for NH3-N, （20.7 ± 1.1）% for TN, （18.6± 0.4）% for TP, （12.2 ± 0.5）% for BOD, （10.1 ± 0.3）% for COD, and （36.2 ± 1.2）% for SS, compared with pollutant removal rates under the continuous operation mode. The pollutant removal rate declined with the increase of the HLR. The effluent quality met The Reuse of Urban Recycling Water - Water Quality Standard for Scenic Environment Use （GB/T 18921-2002） even when the HLR was as high as 10 cm/d. Hydraulic conductivity, oxidation reduction potential （ORP）, the quantity of nitrifying bacteria, and the pollutant removal rate of NH3-N increased with the decrease of the RWD. For the pollutant removal rates of TP, BOD, and COD, there were no significant difference （p 〈 0.05） under different RwDS. The suggested RWD was 1.0. Relative contribution of the pretreatment and SWlS to the pollutant removal was examined, and more than 80% removal of NH3-N, TN, TP, COD, and BOD occurred in the SWIS.展开更多
CHEMTAX analysis of high-performance liquid chromatography （HPLC） pigment was conducted to study phytoplankton community structure in the northern Bering Sea shelf, where a seasonal subsurface cold pool emerges. The...CHEMTAX analysis of high-performance liquid chromatography （HPLC） pigment was conducted to study phytoplankton community structure in the northern Bering Sea shelf, where a seasonal subsurface cold pool emerges. The results showed that fucoxanthin （Fuco） and chlorophyll a （Chl a） were the most abundant diagnostic pigments, with the integrated water column values ranging from 141 to 2160 μg/m2 and 477 to 5 535 μg/m2, respectively. Moreover, a diatom bloom was identified at Sta. BB06 with the standing stock of Fuco up to 9214 μg/m3. The results of CHEMTAX suggested that the phytoplankton community in the northern Bering Sea shelf was dominated by diatoms and chrysophytes with an average relative contribu- tion to Chl a of 80% and 12%, respectively, followed by chlorophytes, dinoflagellates, and cryptophytes. Dia- toms were the absolutely dominant algae in the subsurface cold pool with a relative contribution exceeding 90%, while the contribution of chrysophytes was generally higher in oligotrophic upper water. Additionally, the presence of a cold pool would tend to favor accumulation of diatom biomass and a bloom that occurred beneath the halocline would be beneficial to organic matter sinks, which suggests that a large part of the phytoplankton biomass would settle to the seabed and support a rich benthic biomass.展开更多
China's Mars probe,named Tianwen-1,including an orbiter and a landing rover,will be launched during the July-August 2020 Mars launch windows.Selected to be among the rover payloads is a Subsurface Penetrating Rada...China's Mars probe,named Tianwen-1,including an orbiter and a landing rover,will be launched during the July-August 2020 Mars launch windows.Selected to be among the rover payloads is a Subsurface Penetrating Radar module(RoSPR).The main scientific objective of the RoSPR is to characterize the thickness and sub-layer distribution of the Martian soil.The RoSPR consists of two channels.The low frequency channel of the RoSPR will penetrate the Martian soil to depths of 10 to 100 m with a resolution of a few meters.The higher frequency channel will penetrate to a depth of 3 to 10 m with a resolution of a few centimeters.This paper describes the design of the instrument and some results of field experiments.展开更多
Single-crystal silicon is an important material in the semiconductor and optical industries.However,being hard and brittle,a silicon wafer is vulnerable to subsurface cracks(SSCs)during grinding,which is detrimental t...Single-crystal silicon is an important material in the semiconductor and optical industries.However,being hard and brittle,a silicon wafer is vulnerable to subsurface cracks(SSCs)during grinding,which is detrimental to the performance and lifetime of a wafer product.Therefore,studying the formation of SSCs is important for optimizing SSC-removal processes and thus improving surface integrity.In this study,a statistical method is used to study the formation of SSCs induced during grinding of silicon wafers.The statistical results show that grinding-induced SSCs are not stochastic but anisotropic in their distributions.Generally,when grinding with coarse abrasive grains,SSCs form along the cleavage planes,primarily the{111}planes.However,when grinding with finer abrasive grains,SSCs tend to form along planes with a fracture-surface energy higher than that of the cleavage planes.These findings provide a guidance for the accurate detection of SSCs in ground silicon wafers.展开更多
基金Supported by the National Natural Science Foundation of China(No.42476016)the Laoshan Laboratory(No.LSKJ202202702)the Indo-Pacific Ocean and Climate Laboratory Project(No.424530)from Hohai University。
文摘The thermal state of seawater is a fundamental property of the ocean.Extreme changes in the ocean's thermal conditions can significantly impact the marine environment,climate system,ecosystems,and economic activities.Marine heatwaves(MHWs)are extreme high-temperature events occurring in the ocean at weather or short-to-medium-term climate scales,representing extreme variations in oceanic conditions(Pearce et al.,2011;Feng et al.,2013;Hobday et al.,2016).
基金supported by the National Key Research and Development Program of China(2022YFB3605902)the National Natural Science Foundation of China(52375411,52293402)。
文摘Workpiece rotational grinding is widely used in the ultra-precision machining of hard and brittle semiconductor materials,including single-crystal silicon,silicon carbide,and gallium arsenide.Surface roughness and subsurface damage depth(SDD)are crucial indicators for evaluating the surface quality of these materials after grinding.Existing prediction models lack general applicability and do not accurately account for the complex material behavior under grinding conditions.This paper introduces novel models for predicting both surface roughness and SDD in hard and brittle semiconductor materials.The surface roughness model uniquely incorporates the material’s elastic recovery properties,revealing the significant impact of these properties on prediction accuracy.The SDD model is distinguished by its analysis of the interactions between abrasive grits and the workpiece,as well as the mechanisms governing stress-induced damage evolution.The surface roughness model and SDD model both establish a stable relationship with the grit depth of cut(GDC).Additionally,we have developed an analytical relationship between the GDC and grinding process parameters.This,in turn,enables the establishment of an analytical framework for predicting surface roughness and SDD based on grinding process parameters,which cannot be achieved by previous models.The models were validated through systematic experiments on three different semiconductor materials,demonstrating excellent agreement with experimental data,with prediction errors of 6.3%for surface roughness and6.9%for SDD.Additionally,this study identifies variations in elastic recovery and material plasticity as critical factors influencing surface roughness and SDD across different materials.These findings significantly advance the accuracy of predictive models and broaden their applicability for grinding hard and brittle semiconductor materials.
基金supported by the National Natural Science Foundation of China(31250512).
文摘Background The mulch-free subsurface drip irrigation system demonstrated water-saving potential as an alternative to traditional mulch-based drip irrigation while also eliminating residual film pollution at source.However,delayed sowing is unavoidable in mulch-free cultivation in ecological regions with a short frost-free period.Intercropping with cumin,which has a shorter growth period,served as an effective strategy to improve land use efficiency during the early growth stages of cotton.Therefore,a two-year field experiment was conducted to study the effects of intercropping cumin at the seeding rate of 2.5(ID1),3.85(ID2),and 5.2(ID3)kg・hm−2 on cotton growth,interspecies competition,fiber quality,and water use efficiency(WUE),as well as system economic benefits under subsurface drip irrigation.Monocropping cotton was used as the control(CK)treatment.Results At the initial flowering(IF)stage(the end of the co-growth period of cotton and cumin),cotton plant height in ID2 and ID3 treatments decreased by 5.93%–16.53%and 10.87%–31.11%,respectively,cotton stem diameter by 11.41%–14.25%and 3.37%–26.49%,respectively,and vegetative biomass by 14.46%–30.65%and 22.59%–49.91%,respectively,compared with CK treatment.With the increase in cumin density,the crop growth rate(CGR)and compensation effect in cotton tended to significantly decrease at the IF stage regardless of organs considered.For the non-co-growth period(after harvesting cumin),cotton reproductive organ biomass in ID2 and ID3 treatments increased by 4.09%‒14.61%at the boll opening stage,crop growth rate in reproductive organs by 20.74%and 74.26%from peak boll to boll opening stages compared with CK treatment,due to an enhancement of 19.09%and 49.30%in the compensation effect.Compared with ID1,the aggressivity treated by ID2 and ID3 decreased by 12.82%–46.34%and 17.95%–31.71%,respectively.However,owing to a greater number of green bolls in the upper canopy at the harvest stages in the ID3 treatment,the system production value(closely related to yield)treated by ID2 was 11.69%–16.89%,6.56%–20.02%,and 16.48%–59.83%greater than that of the ID1,ID3,and CK treatments,respectively.This also led to the highest WUE and net profit under the ID2 treatment.Conclusion Intercropping cumin with medium density improved the cotton biomass accumulation characteristics and increased resources such as land and water utilization efficiency and economic benefits through a stronger compensation effect after harvesting cumin under subsurface drip irrigation without mulch.This study not only provides alternatives to residual film pollution in arid cotton fields but also establishes a sustainable agro-ecological-economic planting paradigm by reducing plastic use and enhancing water and fertilizer use efficiency,holding significant implications for advancing resource-efficient agricultural systems.
基金funded by the National Natural Science Foundation of China (No.52225402)Inner Mongolia Research Institute,China University of Mining and Technology-Beijing (IMRI23003)。
文摘In the gas-coal integrated mining field,the conventional design method of pipeline coal pillars leads to a large amount of coal pillars being unrecovered and overlooks the pipeline's safety requirements.Considering the coal pillar recovery rate and pipeline's safety requirements,two new shaped coal pillar design approaches for subsurface pipelines were developed.Firstly,the deformation limitations for measuring pipeline safety are categorized into two:no deformation is permitted,and deformation is acceptable within elastic limits.Subsequently,integrating the key stratum theory(KST)and cave angle,a fishbone-shaped coal pillar design approach that does not permit pipeline deformation is established.Meanwhile,combined with the ground subsidence and the pipeline's elastic deformation limit,a grille-shaped coal pillar design approach that accepts deformation pipelines within elastic limits is established.Those two new approaches clarify parameters including mined width,coal pillar width and mined length.Finally,the case study shows that the designed mined width,coal pillar width and mined length of the fishbone-shaped coal pillar are 90,80,and 130 m,while those of the grille-shaped are 320,370,and640 m.Compared with the conventional method,the fishbone-shaped and grille-shaped coal pillar design approaches recovered coal pillar resources of 2.65×10~6and 5.81×10~6t on the premise of meeting the pipeline safety requirements,and the recovery rates increased by 20.5%and 45.0%,with expenditures representing only 56.46%and 20.02%of the respective benefits.These new approaches provide managers with diverse options for protecting pipeline safety while promoting coal pillar recovery,which is conducive to the harmonic mining of gas-coal resources.
基金supported by the National Natural Science Foundation of China(Grant Nos.42225702 and 42077235)the Natural Science Foundation of Jiangsu Province(Grant No.BK20211086)the open fund of the Key Laboratory of Earth Fissures Geological Disaster,Ministry of Natural Resources.
文摘The distribution of shear-wave velocities in the subsurface is generally used to assess the potential forseismic liquefaction and soil amplification effects and to classify seismic sites. Newly developeddistributed acoustic sensing (DAS) technology enables estimation of the shear-wave distribution as ahigh-density seismic observation system. This technology is characterized by low maintenance costs,high-resolution outputs, and real-time data transmission capabilities, albeit with the challenge ofmanaging massive data generation. Rapid and efficient interpretation of data is the key to advancingapplication of the DAS technology. In this study, field tests were carried out to record ambient noise overa short period using DAS technology, from which the surface-wave dispersion curves were extracted. Inorder to reduce the influence of directional effects on the results, an unsupervised clustering method isused to select appropriate clusters to extract the Green's function. A combination of a genetic algorithmand Monte Carlo (GA-MC) simulation is proposed to invert the subsurface velocity structure. Thestratigraphic profiles obtained by the GA-MC method are in agreement with the borehole profiles.Compared to other methods, the proposed optimization method not only improves the solution qualitybut also reduces the solution time.
基金jointly supported by the National Key Research and Development Program of China(2022YFC3104304)the National Natural Science Foundation of China(Grant No.41876011)+1 种基金the 2022 Research Program of Sanya Yazhou Bay Science and Technology City(SKJC-2022-01-001)the Hainan Province Science and Technology Special Fund(ZDYF2021SHFZ265)。
文摘Three-dimensional ocean subsurface temperature and salinity structures(OST/OSS)in the South China Sea(SCS)play crucial roles in oceanic climate research and disaster mitigation.Traditionally,real-time OST and OSS are mainly obtained through in-situ ocean observations and simulation by ocean circulation models,which are usually challenging and costly.Recently,dynamical,statistical,or machine learning models have been proposed to invert the OST/OSS from sea surface information;however,these models mainly focused on the inversion of monthly OST and OSS.To address this issue,we apply clustering algorithms and employ a stacking strategy to ensemble three models(XGBoost,Random Forest,and LightGBM)to invert the real-time OST/OSS based on satellite-derived data and the Argo dataset.Subsequently,a fusion of temperature and salinity is employed to reconstruct OST and OSS.In the validation dataset,the depth-averaged Correlation(Corr)of the estimated OST(OSS)is 0.919(0.83),and the average Root-Mean-Square Error(RMSE)is0.639°C(0.087 psu),with a depth-averaged coefficient of determination(R~2)of 0.84(0.68).Notably,at the thermocline where the base models exhibit their maximum error,the stacking-based fusion model exhibited significant performance enhancement,with a maximum enhancement in OST and OSS inversion exceeding 10%.We further found that the estimated OST and OSS exhibit good agreement with the HYbrid Coordinate Ocean Model(HYCOM)data and BOA_Argo dataset during the passage of a mesoscale eddy.This study shows that the proposed model can effectively invert the real-time OST and OSS,potentially enhancing the understanding of multi-scale oceanic processes in the SCS.
基金Supported by the Ministry of Science and Technology of the People’s Republic of China(No.2019 YFE 0125000)the National Natural Science Foundation of China-Shandong Joint Fund(No.U 1906215)+1 种基金the National Natural Science Foundation of China(No.41406010)partially by the Key Laboratory of Coastal Environmental Processes and Ecological Remediation,Chinese Academy of Sciences Opening Fund(No.2020 KFJJ 04)。
文摘As a frequently-observed phenomenon in the northern South China Sea(nSCS),subsurface chlorophyll maximum(SCM)evolution from summer to winter remains unclear,neither the associated hydrographic control.In this study,on the basis of in-situ data of fall-season cruises in 2004–2006,we characterized the depth,thickness and intensity of the SCM in the nSCS using a general Gaussian-function fitting approach,and investigated a linkage to the corresponding ocean vertical buoyance properties.Our results show that the SCM becomes deeper,thicker and less intense offshore-wards in the nSCS during fall seasons.In parallel,a correlation between the SCM variation and mixed layer depth exists in the nSCS,and it becomes pronounced in the shelf region compared to the slope and basin areas in autumn.Physically,once warmer surface ocean and thus stronger thermo-determined stratification,the SCM layer goes deeper and becomes thicker and less intense in the nSCS,especially in the shelf area of the nSCS.Moreover,the impact of water temperatures at deeper layers on the vertical stratification exerts more consequent roles on the spatial variability of SCM,compared to surface temperatures in the nSCS.Specifically,the isotherm line of 22℃ acts as crucial indicator for variations of the SCM in the nSCS during autumns.
文摘We present an improved angle polishing method in which the end of the cover slice near the glue layer is beveled into a thin,defect-free wedge,the straight edge of which is used as the datum for measuring the depth of subsurface damage. The bevel angle can be calculated from the interference fringes formed in the wedge. The minimum depth of the subsurface damage that can be measured by this method is a few hundred nanometers. Our results show that the method is straightforward, accurate, and convenient.
基金Project(JCKY2016212A506-0503) supported by the Science Challenge Project of ChinaProject(51475106) supported by the National Natural Science Foundation of China
文摘Subsurface defects were fluorescently tagged with nanoscale quantum dots and scanned layer by layer using confocal fluorescence microscopy to obtain images at various depths. Subsurface damage depths of fused silica optics were characterized quantitatively by changes in the fluorescence intensity of feature points. The fluorescence intensity vs scan depth revealed that the maximum fluorescence intensity decreases sharply when the scan depth exceeds a critical value. The subsurface damage depth could be determined by the actual embedded depth of the quantum dots. Taper polishing and magnetorheological finishing were performed under the same conditions to verify the effectiveness of the nondestructive fluorescence method. The results indicated that the quantum dots effectively tagged subsurface defects of fused-silica optics, and that the nondestructive detection method could effectively evaluate subsurface damage depths.
文摘A molecular dynamics （MD） simulation is carried out to analyze the effect of cutting edge radius,cutdepth, and grinding speed on the depth of subsurface damage layers in monocrystal silicon grinding processes on an atomic scale. The results show that when the cutting edge radius decreases in the nanometric grinding process with the same cut-depth and grinding speed, the depth of the damage layers and the potential energy between the silicon atoms decrease too. Also, when the cut depth increases, both the depth of the damage layers and the potential energy between silicon atoms increase. When the grinding speed is between 20 and 200m/s,the depth of the damage layers does not change much with the increase of the grinding speed under the same cutting edge radius and cut depth conditions. This means that the MD simulation is not sensitive to changes in the grinding speed, and thus increasing the grinding speed properly can shorten the sion,the subsurface damage of monocrystal silicon is silicon atoms, which is verified by the ultra-precision simulation time and enlarge the simulation scale. In conclumainly based on the change of the potential energy between grinding and CMP experiments.
基金Project supported by the National High Technology Research and Development Program of China (863 Program) (No. 2002AA2Z4321) and the Key Project of Water-Saving Irrigation and Cultivation Techniques of Liaoning Province of China (No. 2001212001).
文摘Various environmental conditions determine soil enzyme activities, which are important indicators for changes of soil microbial activity, soil fertility, and land quality. The effect of subsurface irrigation scheduling on activities of three soil enzymes (phosphatase, urease, and catalase) was studied at five depths (0-10, 10-20, 20-30, 30-40, and 40-60 cm) of a tomato greenhouse soil. Irrigation was scheduled when soil water condition reached the maximum allowable depletion (MAD) designed for different treatments (-10, -16,-25,-40, and-63 kPa). Results showed that soil enzyme activities had significant responses to the irrigation scheduling during the period of subsurface irrigation. The neutral phosphatase activity and the catalase activity were found to generally increase with more frequent irrigation (MAD of -10 and -16 kPa). This suggested that a higher level of water content favored an increase in activity of these two enzymes. In contrast, the urease activity decreased under irrigation, with less effect for MAD of -40 and -63 kPa. This implied that relatively wet soil conditions were conducive to retention of urea N, but relatively dry soil conditions could result in increasing loss of urea N. Further, this study revealed that soil enzyme activities could be alternative natural bio-sensors for the effect of irrigation on soil biochemical reactions and could help optimize irrigation management of greenhouse crop production.
基金supported by the Innovation Capability Special Fund in Guizhou Province, China (KY-2010N-004)
文摘The aims of this research were to compare subsurface drip irrigation scheduling and nitrogen fertilization rates in cucumber, and evaluate yield and quality of cucumber fruit, water （WUE）, irrigation water （IWUE）, and nitrogen use （NUE） efficiencies in the solar greenhouse in Southwest China. The irrigation water amounts were determined based on the 20 cm diameter pan （Ep） placed over the crop canopy, and cucumber plant was subjected to three irrigation water levels （I1, 0.6 Ep; I2, 0.8 Ep; and I3, 1.0 Ep） in interaction with three nitrogen fertilization levels （N1, 300 kg ha-1; N2, 450 kg ha-1; and N3, 600 kg ha-1）. The results showed that the cucumber fruit yield increased with the improvement of irrigation water. Irrigation water increased yields by increasing the mean weight of the fruits, and also by increasing fruit number. But the highest values of IWUE and WUE were obtained from I2 treatment. NUE significantly decreased with the improvement of N application, but increased by irrigating more water. The quality of cucumber fruit decreased with the improvement irrigation water and nitrogen fertilization. In conclusion, the optimum irrigation level and nitrogen fertilizer application level for cucunber under subsurface drip irrigation in the solar greenhouse in Southwest China were 0.8 Ep and 450 and 600 kg ha-1, respectively.
文摘The operational performance of a full scale subsurface flow constructed wetland, which treated the mixed industrial and domestic wastewater with BOD 5/COD mean ratio of 0 33 at Shatian, Shenzhen City was studied. The constructed wetland system consists of screens, sump, pumping station, and primary settling basin, facultative pond, first stage wetland and secondary stage wetland. The designed treatment capacity is 5000 m 3/d, and the actual influent flow is in the range of <2000 to >10000 m 3/d. Under normal operational conditions, the final effluent quality well met the National Integrated Wastewater Discharge Standard(GB 8978\_1996), with the following parameters(mean values): COD 33 90 mg/L, BOD 5 7.65 mg/L, TSS 7.92 mg/L, TN 9.11 mg/L and TP 0 56 mg/L. Seven species of plants were selected to grow in the wetland: Reed, Sweetcane flower Silvergrass, Great Bulrush, Powdery Thalia and Canna of three colours. The growing season is a whole year round. The seasonal discrepancy could be observed and the plants growing in the wetland are vulnerable to lower temperature in winter. The recycling of the effluent in the first stage of the wetland system is an effective measure to improve the performance of the wetland system. The insufficient DO value in the wetland system not only had significant effect on pollutants removal in the wetland, but also was unfavourable to plant growth. The recycling of effluent to the inlet of wetland system and artificial pond to increase DO value of influent to the wetland is key to operate the subsurface constructed wetland steadily and effectively.
基金Project supported by the Chinese Academy of Sciences (CAS) (No. KZCX-SW-416-02), and the K. C. Wong Post Doctoral Research Award Fund of CAS (No. 29, 2002).
文摘Four depth treatments of subsurface drip irrigation pipes were designated as 1) at 20,2) 30 and 3) 40 cm depths all with a drip-proof flumes underneath,and 4) at 30 cm without a drip-proof flume to investigate the responses of a tomato root system to different technical parameters of subsurface drip irrigation in a glass greenhouse,to evaluate tomato growth as affected by subsurface drip irrigation,and to develop an integrated subsurface drip irrigation method for optimal tomato yield and water use in a glass greenhouse. Tomato seedlings were planted above the subsurface drip irrigation pipe. Most of the tomato roots in treatment 1 were found in the top 0-20 cm soil depth with weak root activity but with yield and water use efficiency (WUE) significantly less (P ---- 0.05) than treatment 2; root activity and tomato yield were significantly higher (P = 0.05) with treatment 3 compared to treatment 1; and with treatment 2 the tomato roots and shoots grew harmoniously with root activity,nutrient uptake,tomato yield and WUE significantly higher (P= 0.05) or as high as the other treatments. These findings suggested that subsurface drip irrigation with pipes at 30 cm depth with a drip-proof flume placed underneath was best for tomato production in greenhouses. In addition,the irrigation interval should be about 7-8 days and the irrigation rate should be set to 225 m3 ha-1 per event.
基金The authors are grateful to"Chemical Grid Project"of Beijing University of Chemical Technology for providingthe computer facilities.
文摘A subsurface flow wetland(SSFW)was simulated using a commercial computational fluid dynamic(CFD)code.The constructed media was simulated using porous media and the liquid resident time distribution(RTD)in the SSFW was obtained using the particle trajectory model.The effect of wetland configuration and operating conditions on the hydraulic performance of the SSFW were investigated.The results indicated that the hydraulic performance of the SSFW was predominantly affected by the wetland configuration.The hydr...
基金Supported by National Natural Science Foundation of China(Grant No.51575084)the Science Fund for Creative Research Groups of NSFC(Grant No.51621064)the Science Challenge Project(Grant No.JCKY2016212A506–0101)
文摘Subsurface damage is easily induced in machining of hard and brittle materials because of their particular mechani?cal and physical properties. It is detrimental to the strength,performance and lifetime of a machined part. To manu?facture a high quality part,it is necessary to detect and remove the machining induced subsurface damage by the subsequent processes. However,subsurface damage is often covered with a smearing layer generated in a machining process,it is rather di cult to directly observe and detect by optical microscopy. An e cient detection of subsur?face damage directly leads to quality improvement and time saving for machining of hard and brittle materials. This paper presents a review of the methods for detection of subsurface damage,both destructive and non?destructive. Although more reliable,destructive methods are typically time?consuming and confined to local damage infor?mation. Non?destructive methods usually su er from uncertainty factors,but may provide global information on subsurface damage distribution. These methods are promising because they can provide a capacity of rapid scan and detection of subsurface damage in spatial distribution.
基金supported by the National Natural Science Foundation of China(Grant No.51108275)the Program for Liaoning Excellent Talents in Universities(LNET)(Grant No.LJQ2012101)+2 种基金the Program for New Century Excellent Talents in Universities(Grant No.NCET-11-1012)the Science and Technology Program of Liaoning Province(Grants No.2011229002 and2013229012)the Basic Science Research Fund in Northeastern University(Grants No.N130501001 and N140105003)
文摘In order to enhance the hydraulic loading rate （HLR） of a subsurface wastewater infiltration system （SWIS） used in treating domestic sewage, the intermittent operation mode was employed in the SWIS. The results show that the intermittent operation mode contributes to the improvement of the HLR and the pollutant removal rate. When the wetting-drying ratio （RwD） was 1.0, the pollutant removal rate increased by （13.6 ± 0.3）% for NH3-N, （20.7 ± 1.1）% for TN, （18.6± 0.4）% for TP, （12.2 ± 0.5）% for BOD, （10.1 ± 0.3）% for COD, and （36.2 ± 1.2）% for SS, compared with pollutant removal rates under the continuous operation mode. The pollutant removal rate declined with the increase of the HLR. The effluent quality met The Reuse of Urban Recycling Water - Water Quality Standard for Scenic Environment Use （GB/T 18921-2002） even when the HLR was as high as 10 cm/d. Hydraulic conductivity, oxidation reduction potential （ORP）, the quantity of nitrifying bacteria, and the pollutant removal rate of NH3-N increased with the decrease of the RWD. For the pollutant removal rates of TP, BOD, and COD, there were no significant difference （p 〈 0.05） under different RwDS. The suggested RWD was 1.0. Relative contribution of the pretreatment and SWlS to the pollutant removal was examined, and more than 80% removal of NH3-N, TN, TP, COD, and BOD occurred in the SWIS.
基金The National Natural Science Foundation of China under contract Nos 41276198,41076135 and 41003036the Scientific Research Fund of Second Institute of Oceanography,SOA under contract Nos JG1323 and JG1023the Chinese Polar Environment Comprehensive Investiga-tion and Assessment Programs under contract Nos 20130403 and 20130304
文摘CHEMTAX analysis of high-performance liquid chromatography （HPLC） pigment was conducted to study phytoplankton community structure in the northern Bering Sea shelf, where a seasonal subsurface cold pool emerges. The results showed that fucoxanthin （Fuco） and chlorophyll a （Chl a） were the most abundant diagnostic pigments, with the integrated water column values ranging from 141 to 2160 μg/m2 and 477 to 5 535 μg/m2, respectively. Moreover, a diatom bloom was identified at Sta. BB06 with the standing stock of Fuco up to 9214 μg/m3. The results of CHEMTAX suggested that the phytoplankton community in the northern Bering Sea shelf was dominated by diatoms and chrysophytes with an average relative contribu- tion to Chl a of 80% and 12%, respectively, followed by chlorophytes, dinoflagellates, and cryptophytes. Dia- toms were the absolutely dominant algae in the subsurface cold pool with a relative contribution exceeding 90%, while the contribution of chrysophytes was generally higher in oligotrophic upper water. Additionally, the presence of a cold pool would tend to favor accumulation of diatom biomass and a bloom that occurred beneath the halocline would be beneficial to organic matter sinks, which suggests that a large part of the phytoplankton biomass would settle to the seabed and support a rich benthic biomass.
基金support from the China National Space Administration.
文摘China's Mars probe,named Tianwen-1,including an orbiter and a landing rover,will be launched during the July-August 2020 Mars launch windows.Selected to be among the rover payloads is a Subsurface Penetrating Radar module(RoSPR).The main scientific objective of the RoSPR is to characterize the thickness and sub-layer distribution of the Martian soil.The RoSPR consists of two channels.The low frequency channel of the RoSPR will penetrate the Martian soil to depths of 10 to 100 m with a resolution of a few meters.The higher frequency channel will penetrate to a depth of 3 to 10 m with a resolution of a few centimeters.This paper describes the design of the instrument and some results of field experiments.
基金Financial supports from the National Natural Science Foundation of China (Grants No.51575084)the Science Fund for Creative Research Groups of NSFC (Grants No.51621064) are gratefully acknowledged
文摘Single-crystal silicon is an important material in the semiconductor and optical industries.However,being hard and brittle,a silicon wafer is vulnerable to subsurface cracks(SSCs)during grinding,which is detrimental to the performance and lifetime of a wafer product.Therefore,studying the formation of SSCs is important for optimizing SSC-removal processes and thus improving surface integrity.In this study,a statistical method is used to study the formation of SSCs induced during grinding of silicon wafers.The statistical results show that grinding-induced SSCs are not stochastic but anisotropic in their distributions.Generally,when grinding with coarse abrasive grains,SSCs form along the cleavage planes,primarily the{111}planes.However,when grinding with finer abrasive grains,SSCs tend to form along planes with a fracture-surface energy higher than that of the cleavage planes.These findings provide a guidance for the accurate detection of SSCs in ground silicon wafers.
