The interaction mechanism between coal and rock masses with supporting materials is significant in roadway control, especially in deep underground mining situations where dynamic hazards frequently happened due to hig...The interaction mechanism between coal and rock masses with supporting materials is significant in roadway control, especially in deep underground mining situations where dynamic hazards frequently happened due to high geo-stress and strong disturbed effects. This paper is to investigate the strain energy evolution in the interaction between coal and rock masses with self-designed energy-absorbing props and rock bolts by numerical modeling with the finite difference method. The interaction between rock and rock bolt/prop is accomplished by the cables element and the interface between the inner and outer props. Roadway excavation and coal extraction conditions in deep mining are numerically employed to investigate deformation, plastic zone ranges, strain energy input, accumulation, dissipation,and release. The effect on strain energy input, accumulation, dissipation, and release with rock deformation, and the plastic zone is addressed. A ratio of strain energy accumulation, dissipation, and release with energy input a, β, γ is to assess the dynamic hazards. The effects on roadway excavation and coal extraction steps of a, β, γ are discussed. The results show that:(1) In deep high geo-stress roadways, the energyabsorbing support system plays a dual role in resisting deformation and reducing the scope of plastic zones in surrounding rock, as well as absorbing energy release in the surrounding rock, especially in the coal extraction state to mitigate disturbed effects.(2) The strain energy input, accumulation is dependent on roadway deformation, the strain energy dissipation is relied on plastic zone area and disturbed effects, and strain energy release density is the difference among the three. The function of energyabsorbing rock bolts and props play a key role to mitigate strain energy release density and amount, especially in coal extraction condition, with a peak density value from 4×10^(4) to 1×10^(4)J/m^(3), and amount value from 3.57×10^(8) to 1.90×10^(6)J.(3) When mining is advanced in small steps, the strain energy accumulation is dominated. While in a large step, the released energy is dominant, thus a more dynamic hazards proneness. The energy-absorbing rock bolt and prop can reduce three times strain energy release amount, thus reducing the dynamic hazards. The results suggest that energy-absorbing props and rock bolts can effectively reduce the strain energy in the coal and rock masses, and prevent rock bursts and other hazards.The numerical model developed in this study can also be used to optimize the design of energyabsorbing props and rock bolts for specific mining conditions.展开更多
The creep behaviors in deep underground engineering structures,especially in soft rocks,have a remarkable impact on the long-term stability of the excavations,which finally leads to the high risk and failure of it.Acc...The creep behaviors in deep underground engineering structures,especially in soft rocks,have a remarkable impact on the long-term stability of the excavations,which finally leads to the high risk and failure of it.Accordingly,it is essential to recognize the time-dependent deformation through the investigation of this phenomenon.In this study,the creep behaviors of soft rocks were examined to help understand the underlying mechanism of the extended time-dependent deformation.Due to the limited results about the time-dependent properties of the constituents of the rock that reveal their heterogeneity,the targeting nanoindentation technique(TNIT),was adopted to investigate the viscoelastic characteristics of kaolinite and quartz in a two-constituent mudstone sample.The TNIT consists of identifications of mineralogical ingredients in mudstone and nanoindentation experiments on each identified constituent.After conducting experiments,the unloading stages of the typical indentation curves were analyzed to calculate the hardness and elastic modulus of both elements in mudstone.Additionally,the 180 s load-holding stages with the peak load of 50 mN were transformed into the typical creep strain-time curves for fitting analysis by using the Kelvin model,the standard viscoelastic model,and the extended viscoelastic model.Fitting results show that the standard viscoelastic model not only can perfectly express the nanoindentation creep behaviors of both kaolinite and quartz but also can produce suitable constants used to measure their creep parameters.The creep parameters of kaolinite are much smaller than that of quartz,which causes the considerable time-dependent deformation of the soft mudstone.Eventually,the standard viscoelastic model was also verified on the quartz in a sandstone sample.展开更多
In order to investigate the failure mechanism of the reinforced muddy soft rock under the influence of the hydration reaction when ground water is present,a series of confined compressive tests and Acoustic Emission(A...In order to investigate the failure mechanism of the reinforced muddy soft rock under the influence of the hydration reaction when ground water is present,a series of confined compressive tests and Acoustic Emission(AE)recordings were conducted subject to various moisture content levels and lateral confining stresses.It was found that the failure modes of the reinforced rock specimen were affected by the moisture content level and the lateral stress σ_(2) in a way that the load bearing capacity of the reinforced rock would increase with the lateral stress σ_(2) but decrease as the moisture content increased.An increase in the moisture content would reduce the extent of the influence of the lateral stress on the load bearing capacity of the reinforced rock.In addition,much less AE counts were recorded when the moisture content increased indicating that the crack initiation and propagation in this case was easier due to the reduction of the required external input energy.With increasing moisture content,the failure mode of the specimen gradually changes from sudden and brittle to progressive and ductile.Moreover,the hydration reaction became more significant leading to a complete debonding between the grout and the rock.Consequently,the reinforcement provided by the rock bolt to the rock became negligible.展开更多
In coal mining industry,with the depth growing of coal mines,the creep behaviours of coal and rock can extensively affect the mining safety,coalbed methane recovery and geo-sequestration.To acquire a better insight in...In coal mining industry,with the depth growing of coal mines,the creep behaviours of coal and rock can extensively affect the mining safety,coalbed methane recovery and geo-sequestration.To acquire a better insight into their creep characteristics,an efficient and robust researching technique,nanoindentation,was applied to investigate the creep performances of coal and rock samples obtained from two coal mines in the east of China.Creep characteristics were reflected by evaluating the curves of creep depth versus creep time of nanoindentation tests during the load-holding period at the peak load of 30 mN.These curves can be divided into two stages:transient stage and steady stage;and the time of load-holding period of 5 s,which is the dividing point between two stages,can efficiently avoid the influence of creep displacement on the unloading curves.The exponential function can perfectly fit creep curves and Kelvin model can be used to calculate the rheological parameters of coal and rock samples.Calculated results yield values for the creep modulus and viscosity terms of coal and rock.This study also settled a particular emphasis on the selection of the positions of indentations to obtain the rheological properties of mineralogical constituents in heterogonous coal and rock samples and their elastic aftereffect.展开更多
In the loose and fractured coal seam with particularly low uniaxial compressive strength(UCS),driving a roadway is extremely difficult as roof falling and wall spalling occur frequently.To address this issue,the jet g...In the loose and fractured coal seam with particularly low uniaxial compressive strength(UCS),driving a roadway is extremely difficult as roof falling and wall spalling occur frequently.To address this issue,the jet grouting(JG)technique(high-pressure grout mixed with coal particles)was first introduced in this study to improve the self-supporting ability of coal mass.To evaluate the strength of the jet-grouted coal-grout composite(JG composite),the UCS evolution patterns were analyzed by preparing 405 specimens combining the influential variables of grout types,curing time,and coal to grout(C/G)ratio.Furthermore,the relationships between UCS and these influencing variables were modeled using ensemble learning methods i.e.gradient boosted regression tree(GBRT)and random forest(RF)with their hyperparameters tuned by the particle swarm optimization(PSO).The results showed that the chemical grout composite has higher short-term strength,while the cement grout composite can achieve more stable strength in the long term.The PSO-GBRT and PSO-RF models can both achieve high prediction accuracy.Also,the variable importance analysis demonstrated that the grout type and curing time should be considered carefully.This study provides a robust intelligent model for predicting UCS of JG composites,which boosts JG design in the field.展开更多
Cement-based grouting has been widely used in mining engineering;its constitutive law has not been comprehensively studied.In this study,a novel constitutive law of cement-grouted coal specimens(CGCS)was developed usi...Cement-based grouting has been widely used in mining engineering;its constitutive law has not been comprehensively studied.In this study,a novel constitutive law of cement-grouted coal specimens(CGCS)was developed using hybrid machine learning(ML)algorithms.Shear tests were performed on CGCS for the analysis of stress-strain curves and the preparation of the dataset.To maintain the interpretation of the trained ML models,regression tree(RT)was used as the main technique.The effect of maximum RT depth(Maxdepth)on its performance was studied,and the hyperparameters of RT were tuned using the genetic algorithm(GA).The RT performance was also compared with ensemble learning techniques.The optimum correlation coefficient on the training set was determined as 0.835,0.946,0.981,and 0.985 for RT models with Maxdepth=3,5,7,and 9,respectively.The overall correlation coefficient was over 0.9 when the Maxdepth≥5,indicating that the constitutive law of CGCS can be well described.However,the failure type of CGCS could not be captured using the trained RT models.Random forest was found to be the optimum algorithm for the constitutive modeling of CGCS,while RT with the Maxdepth=3 performed the worst.展开更多
External lumbar drainage (ELD) has gained wide popularity in neurosurgical practice since its’ first introduction by F. Vourc’h in 1963. It manifests encouraging prospects in control of refractory intracranial hyper...External lumbar drainage (ELD) has gained wide popularity in neurosurgical practice since its’ first introduction by F. Vourc’h in 1963. It manifests encouraging prospects in control of refractory intracranial hypertension, prevention of complications secondary to aneurysmal subarachnoid hemorrhage, prediction of shunt respondency in normal pressure hydrocephalus, management of cerebrospinal fluid (CSF) leakage, and application in bacterial meningitis and ventriculitis. But many questions on the efficacy and safety of ELD are remained to be answered by future studies. CSF overdrainage and ELD-related meningitis are the two most common and fatal complications due to inappropriate usage of ELD. Randomized control ed trials are badly in need to more safely and rational y guide the clinical application of ELD.展开更多
In the present work,a numerical investigation on the coaxial shallow borehole heat exchanger based on Com-putational Fluid Dynamics(CFD)technique in Hefei city of China has been performed.The effects of design paramet...In the present work,a numerical investigation on the coaxial shallow borehole heat exchanger based on Com-putational Fluid Dynamics(CFD)technique in Hefei city of China has been performed.The effects of design parameters,including inlet flow rate,inlet fluid temperature,inner pipe material and outer pipe diameter,on the heat transfer performance were systematically studied.Besides,the thermal behavior along the pipe has been carefully examined with focus on the thermal short-circuiting phenomena.When the fluid inlet velocity is less than the critical value,the turbulence intensity increases and the Nusselt number increases with the inlet flow rate increasing.However,there is sufficient time for heat transfer between the fluid in inner pipe and outer pipe because of low flow rates,leading to large heat loss,i.e.,thermal short-circuiting phenomenon.It is found that with the inlet flow rate increasing,the heat transfer increases first and then decreases,and the rate of reduction slows down gradually.When the inlet flow rate increases,the pumping power undergoes exponential growth.As the inlet temperature increasing,the heat transfer decreases almost linearly.Moreover,when the soil temperature at the top of the casing is lower than that of the fluid in the casing,heat is transferred from the fluid in the casing to the soil,and the heat loss increases with the increase of the inlet fluid temperature.The material of inner pipe with high heat conductivity would result in large heat loss under the influence of thermal short-circuiting.The heat load increases while the pumping power required decreases with the increasing of outer pipe diameter.This study is very beneficial for the coaxial shallow borehole exchanger designs and energy conservation of buildings.展开更多
Ruptured aneurysms with a presentation of intracerebral hemorrhage (ICH) and/or intraventricular hemorrhage (IVH)without subarachnoid hemorrhage (SAH) are rarely reported.Issues on the clinical characteristics,mechani...Ruptured aneurysms with a presentation of intracerebral hemorrhage (ICH) and/or intraventricular hemorrhage (IVH)without subarachnoid hemorrhage (SAH) are rarely reported.Issues on the clinical characteristics,mechanism,diagnosis,treatment and prognosis of this rare entity are obscure to us.We present two cases of ruptured aneurysms with a presentation of isolated ICH.A systematic review of the literature was also conducted.There were 21 cases plus our cases.Good recovery was achieved in 10 patients (47.6 ％).Pertaining to location,38 ％ of presenting aneurysms were on the right side,52 ％ were on the left side,and 10 ％ were midline.Anterior circulation aneurysms were identified in 81％ of patients (7 PComA,8 MCA,1 ICA,1 AComA) and posterior in 19 ％ of patients (3 PCA,1 BA).Sizes of the aneurysms ranged from 3 mm to 40 mm (16.21 ± 8.45).Ruptured aneurysms at the main trunks of the Willis cycle with a presentation of isolated ICH and/or IVH without SAH is extremely rare.The cause of this rare entity is multifactorial.The diagnosis and management of this entity pose a great challenge to us.The prognosis was discouraging based on the now available data.展开更多
基金the National Natural Science Foundation of China(Nos.52204114,52274145,U22A20165,and 52174089)the Natural Science Foundation of Jiangsu Province(No.BK20210522)+2 种基金the National Key Research and Development Program of China(No.2022YFE0128300)the China Postdoctoral Science Foundation(No.2023M733758)the Shandong Postdoctoral Science Foundation(No.SDCX-ZG-202302037).
文摘The interaction mechanism between coal and rock masses with supporting materials is significant in roadway control, especially in deep underground mining situations where dynamic hazards frequently happened due to high geo-stress and strong disturbed effects. This paper is to investigate the strain energy evolution in the interaction between coal and rock masses with self-designed energy-absorbing props and rock bolts by numerical modeling with the finite difference method. The interaction between rock and rock bolt/prop is accomplished by the cables element and the interface between the inner and outer props. Roadway excavation and coal extraction conditions in deep mining are numerically employed to investigate deformation, plastic zone ranges, strain energy input, accumulation, dissipation,and release. The effect on strain energy input, accumulation, dissipation, and release with rock deformation, and the plastic zone is addressed. A ratio of strain energy accumulation, dissipation, and release with energy input a, β, γ is to assess the dynamic hazards. The effects on roadway excavation and coal extraction steps of a, β, γ are discussed. The results show that:(1) In deep high geo-stress roadways, the energyabsorbing support system plays a dual role in resisting deformation and reducing the scope of plastic zones in surrounding rock, as well as absorbing energy release in the surrounding rock, especially in the coal extraction state to mitigate disturbed effects.(2) The strain energy input, accumulation is dependent on roadway deformation, the strain energy dissipation is relied on plastic zone area and disturbed effects, and strain energy release density is the difference among the three. The function of energyabsorbing rock bolts and props play a key role to mitigate strain energy release density and amount, especially in coal extraction condition, with a peak density value from 4×10^(4) to 1×10^(4)J/m^(3), and amount value from 3.57×10^(8) to 1.90×10^(6)J.(3) When mining is advanced in small steps, the strain energy accumulation is dominated. While in a large step, the released energy is dominant, thus a more dynamic hazards proneness. The energy-absorbing rock bolt and prop can reduce three times strain energy release amount, thus reducing the dynamic hazards. The results suggest that energy-absorbing props and rock bolts can effectively reduce the strain energy in the coal and rock masses, and prevent rock bursts and other hazards.The numerical model developed in this study can also be used to optimize the design of energyabsorbing props and rock bolts for specific mining conditions.
基金The work presented in this paper was supported by the projects of"the Fundamental Research Funds for the Central Universities(2020ZDPY0221)""the Guizhou Science and Technology Department([2020]2Y026)".The authors are also grateful to the anonymous reviewers for carefully reading the manuscript and providing many helpful comments.Sun Changlun acknowledges,in particular,the powerful support received from his wife,Zhou Fan,over the years.
文摘The creep behaviors in deep underground engineering structures,especially in soft rocks,have a remarkable impact on the long-term stability of the excavations,which finally leads to the high risk and failure of it.Accordingly,it is essential to recognize the time-dependent deformation through the investigation of this phenomenon.In this study,the creep behaviors of soft rocks were examined to help understand the underlying mechanism of the extended time-dependent deformation.Due to the limited results about the time-dependent properties of the constituents of the rock that reveal their heterogeneity,the targeting nanoindentation technique(TNIT),was adopted to investigate the viscoelastic characteristics of kaolinite and quartz in a two-constituent mudstone sample.The TNIT consists of identifications of mineralogical ingredients in mudstone and nanoindentation experiments on each identified constituent.After conducting experiments,the unloading stages of the typical indentation curves were analyzed to calculate the hardness and elastic modulus of both elements in mudstone.Additionally,the 180 s load-holding stages with the peak load of 50 mN were transformed into the typical creep strain-time curves for fitting analysis by using the Kelvin model,the standard viscoelastic model,and the extended viscoelastic model.Fitting results show that the standard viscoelastic model not only can perfectly express the nanoindentation creep behaviors of both kaolinite and quartz but also can produce suitable constants used to measure their creep parameters.The creep parameters of kaolinite are much smaller than that of quartz,which causes the considerable time-dependent deformation of the soft mudstone.Eventually,the standard viscoelastic model was also verified on the quartz in a sandstone sample.
基金financially supported by the National Natural Science Foundation of China(U22A20165,12072102,52174089).
文摘In order to investigate the failure mechanism of the reinforced muddy soft rock under the influence of the hydration reaction when ground water is present,a series of confined compressive tests and Acoustic Emission(AE)recordings were conducted subject to various moisture content levels and lateral confining stresses.It was found that the failure modes of the reinforced rock specimen were affected by the moisture content level and the lateral stress σ_(2) in a way that the load bearing capacity of the reinforced rock would increase with the lateral stress σ_(2) but decrease as the moisture content increased.An increase in the moisture content would reduce the extent of the influence of the lateral stress on the load bearing capacity of the reinforced rock.In addition,much less AE counts were recorded when the moisture content increased indicating that the crack initiation and propagation in this case was easier due to the reduction of the required external input energy.With increasing moisture content,the failure mode of the specimen gradually changes from sudden and brittle to progressive and ductile.Moreover,the hydration reaction became more significant leading to a complete debonding between the grout and the rock.Consequently,the reinforcement provided by the rock bolt to the rock became negligible.
基金the projects of the Fundamental Research Funds for the Central Universities(2020ZDPY0221)the Guizhou Science and Technology Department([2020]2Y026)。
文摘In coal mining industry,with the depth growing of coal mines,the creep behaviours of coal and rock can extensively affect the mining safety,coalbed methane recovery and geo-sequestration.To acquire a better insight into their creep characteristics,an efficient and robust researching technique,nanoindentation,was applied to investigate the creep performances of coal and rock samples obtained from two coal mines in the east of China.Creep characteristics were reflected by evaluating the curves of creep depth versus creep time of nanoindentation tests during the load-holding period at the peak load of 30 mN.These curves can be divided into two stages:transient stage and steady stage;and the time of load-holding period of 5 s,which is the dividing point between two stages,can efficiently avoid the influence of creep displacement on the unloading curves.The exponential function can perfectly fit creep curves and Kelvin model can be used to calculate the rheological parameters of coal and rock samples.Calculated results yield values for the creep modulus and viscosity terms of coal and rock.This study also settled a particular emphasis on the selection of the positions of indentations to obtain the rheological properties of mineralogical constituents in heterogonous coal and rock samples and their elastic aftereffect.
基金financially supported by the Fundamental Research Funds for the Central Universities(2020ZDPY0221)。
文摘In the loose and fractured coal seam with particularly low uniaxial compressive strength(UCS),driving a roadway is extremely difficult as roof falling and wall spalling occur frequently.To address this issue,the jet grouting(JG)technique(high-pressure grout mixed with coal particles)was first introduced in this study to improve the self-supporting ability of coal mass.To evaluate the strength of the jet-grouted coal-grout composite(JG composite),the UCS evolution patterns were analyzed by preparing 405 specimens combining the influential variables of grout types,curing time,and coal to grout(C/G)ratio.Furthermore,the relationships between UCS and these influencing variables were modeled using ensemble learning methods i.e.gradient boosted regression tree(GBRT)and random forest(RF)with their hyperparameters tuned by the particle swarm optimization(PSO).The results showed that the chemical grout composite has higher short-term strength,while the cement grout composite can achieve more stable strength in the long term.The PSO-GBRT and PSO-RF models can both achieve high prediction accuracy.Also,the variable importance analysis demonstrated that the grout type and curing time should be considered carefully.This study provides a robust intelligent model for predicting UCS of JG composites,which boosts JG design in the field.
基金financially supported by Fundamental Research Funds for the Central Universities(No.2020ZDPY0221)State Key Laboratory for Geo Mechanics and Deep Underground Engineering,China University of Mining&Technology(No.SKLGDUEK2002)+1 种基金Fundamental Research Funds for the Central Universities(No.2021QN1003)National Natural Science Foundation of China(Nos.52104106,52174089)。
文摘Cement-based grouting has been widely used in mining engineering;its constitutive law has not been comprehensively studied.In this study,a novel constitutive law of cement-grouted coal specimens(CGCS)was developed using hybrid machine learning(ML)algorithms.Shear tests were performed on CGCS for the analysis of stress-strain curves and the preparation of the dataset.To maintain the interpretation of the trained ML models,regression tree(RT)was used as the main technique.The effect of maximum RT depth(Maxdepth)on its performance was studied,and the hyperparameters of RT were tuned using the genetic algorithm(GA).The RT performance was also compared with ensemble learning techniques.The optimum correlation coefficient on the training set was determined as 0.835,0.946,0.981,and 0.985 for RT models with Maxdepth=3,5,7,and 9,respectively.The overall correlation coefficient was over 0.9 when the Maxdepth≥5,indicating that the constitutive law of CGCS can be well described.However,the failure type of CGCS could not be captured using the trained RT models.Random forest was found to be the optimum algorithm for the constitutive modeling of CGCS,while RT with the Maxdepth=3 performed the worst.
文摘External lumbar drainage (ELD) has gained wide popularity in neurosurgical practice since its’ first introduction by F. Vourc’h in 1963. It manifests encouraging prospects in control of refractory intracranial hypertension, prevention of complications secondary to aneurysmal subarachnoid hemorrhage, prediction of shunt respondency in normal pressure hydrocephalus, management of cerebrospinal fluid (CSF) leakage, and application in bacterial meningitis and ventriculitis. But many questions on the efficacy and safety of ELD are remained to be answered by future studies. CSF overdrainage and ELD-related meningitis are the two most common and fatal complications due to inappropriate usage of ELD. Randomized control ed trials are badly in need to more safely and rational y guide the clinical application of ELD.
基金This work was supported by the Natural Science Foundation of China,Grant#11947012Anhui Provincial Natural Science Foundation,Grant#1908085MA08+1 种基金Open fund from State Key Laboratory of Aero-dynamics,Grant#PA2018GKSK0046Fundamental Research Funds for the Central Universities,Grant#JZ2019HGTA0035.
文摘In the present work,a numerical investigation on the coaxial shallow borehole heat exchanger based on Com-putational Fluid Dynamics(CFD)technique in Hefei city of China has been performed.The effects of design parameters,including inlet flow rate,inlet fluid temperature,inner pipe material and outer pipe diameter,on the heat transfer performance were systematically studied.Besides,the thermal behavior along the pipe has been carefully examined with focus on the thermal short-circuiting phenomena.When the fluid inlet velocity is less than the critical value,the turbulence intensity increases and the Nusselt number increases with the inlet flow rate increasing.However,there is sufficient time for heat transfer between the fluid in inner pipe and outer pipe because of low flow rates,leading to large heat loss,i.e.,thermal short-circuiting phenomenon.It is found that with the inlet flow rate increasing,the heat transfer increases first and then decreases,and the rate of reduction slows down gradually.When the inlet flow rate increases,the pumping power undergoes exponential growth.As the inlet temperature increasing,the heat transfer decreases almost linearly.Moreover,when the soil temperature at the top of the casing is lower than that of the fluid in the casing,heat is transferred from the fluid in the casing to the soil,and the heat loss increases with the increase of the inlet fluid temperature.The material of inner pipe with high heat conductivity would result in large heat loss under the influence of thermal short-circuiting.The heat load increases while the pumping power required decreases with the increasing of outer pipe diameter.This study is very beneficial for the coaxial shallow borehole exchanger designs and energy conservation of buildings.
文摘Ruptured aneurysms with a presentation of intracerebral hemorrhage (ICH) and/or intraventricular hemorrhage (IVH)without subarachnoid hemorrhage (SAH) are rarely reported.Issues on the clinical characteristics,mechanism,diagnosis,treatment and prognosis of this rare entity are obscure to us.We present two cases of ruptured aneurysms with a presentation of isolated ICH.A systematic review of the literature was also conducted.There were 21 cases plus our cases.Good recovery was achieved in 10 patients (47.6 ％).Pertaining to location,38 ％ of presenting aneurysms were on the right side,52 ％ were on the left side,and 10 ％ were midline.Anterior circulation aneurysms were identified in 81％ of patients (7 PComA,8 MCA,1 ICA,1 AComA) and posterior in 19 ％ of patients (3 PCA,1 BA).Sizes of the aneurysms ranged from 3 mm to 40 mm (16.21 ± 8.45).Ruptured aneurysms at the main trunks of the Willis cycle with a presentation of isolated ICH and/or IVH without SAH is extremely rare.The cause of this rare entity is multifactorial.The diagnosis and management of this entity pose a great challenge to us.The prognosis was discouraging based on the now available data.
