The presence of horizontal layered rocks in tunnel engineering significantly impacts the stability and strength of the surrounding rock mass,leading to floor heave in the tunnel.This study focused on preparing layered...The presence of horizontal layered rocks in tunnel engineering significantly impacts the stability and strength of the surrounding rock mass,leading to floor heave in the tunnel.This study focused on preparing layered specimens of rock-like material with varying thickness to investigate the failure behaviors of tunnel floors.The results indicate that thin-layered rock mass exhibits weak interlayer bonding,causing rock layers near the surface to buckle and break upwards when subjected to horizontal squeezing.With an increase in the layer thickness,a transition in failure mode occurs from upward buckling to shear failure along the plane,leading to a noticeable reduction in floor heave deformation.The primary cause of significant deformation in floor heave is upward buckling failure.To address this issue,the study proposes the installation of a partition wall in the middle of the floor to mitigate heave deformation of the rock layers.The results demonstrate that the partition wall has a considerable stabilizing effect on the floor,reducing the zone of buckling failure and minimizing floor heave deformation.It is crucial for the partition wall to be sufficiently high to prevent buckling failure and ensure stability.Through simulation calculations on an engineering example,it is confirmed that implementing a partition wall can effectively reduce floor heave and enhance the stability of tunnel floor.展开更多
BACKGROUND Pelvic floor dysfunction(PFD)is related to muscle fiber tearing during childbirth,negatively impacting postpartum quality of life of parturient.Appropriate and effective intervention is necessary to promote...BACKGROUND Pelvic floor dysfunction(PFD)is related to muscle fiber tearing during childbirth,negatively impacting postpartum quality of life of parturient.Appropriate and effective intervention is necessary to promote PFD recovery.AIM To analyze the use of hydrogen peroxide and silver ion disinfection for vaginal electrodes in conjunction with comprehensive rehabilitation therapy for postpartum women with PFD.METHODS A total of 59 women with PFD who were admitted to the hospital from May 2019 to July 2022 were divided into two groups:Control group(n=27)received comprehensive rehabilitation therapy and observation group(n=32)received intervention with pelvic floor biostimulation feedback instrument in addition to comprehensive rehabilitation therapy.The vaginal electrodes were disinfected with hydrogen peroxide and silver ion before treatment.Intervention for both groups was started 6 weeks postpartum,and rehabilitation lasted for 3 months.Pelvic floor muscle voltage,pelvic floor muscle strength,vaginal muscle voltage,vaginal muscle tone,pelvic floor function,quality of life,and incidence of postpartum PFD were compared between the two groups.RESULTS Before comprehensive rehabilitation treatment,basic data and pelvic floor function were not significantly different between the two groups.After treatment,the observation group showed significant improvements in the maximum voltage and average voltage of pelvic floor muscles,contraction time of type I and type II fibers,pelvic floor muscle strength,vaginal muscle tone,vaginal muscle voltage,and quality of life(GQOLI-74 reports),compared with the control group.The observation group had lower scores on the pelvic floor distress inventory(PFDI-20)and a lower incidence of postpartum PFD,indicating the effectiveness of the pelvic floor biostimulation feedback instrument in promoting the recovery of maternal pelvic floor function.CONCLUSION The combination of the pelvic floor biostimulation feedback instrument and comprehensive rehabilitation nursing can improve pelvic floor muscle strength,promote the recovery of vaginal muscle tone,and improve pelvic floor function and quality of life.The use of hydrogen peroxide and silver ion disinfectant demonstrated favorable antibacterial efficacy and is worthy of clinical application.展开更多
BACKGROUND Spastic pelvic floor syndrome(SPFS)is a refractory pelvic floor disease characterized by abnormal(uncoordinated)contractions of the external anal sphincter and puborectalis muscle during defecation,resultin...BACKGROUND Spastic pelvic floor syndrome(SPFS)is a refractory pelvic floor disease characterized by abnormal(uncoordinated)contractions of the external anal sphincter and puborectalis muscle during defecation,resulting in rectal emptation and obstructive constipation.The clinical manifestations of SPFS are mainly characterized by difficult defecation,often accompanied by a sense of anal blockage and drooping.Manual defecation is usually needed during defecation.From physical examination,it is commonly observed that the patient's anal muscle tension is high,and it is difficult or even impossible to enter with his fingers.AIM To investigate the characteristics of anorectal pressure and botulinum toxin A injection combined with biofeedback in treating pelvic floor muscle spasm syndrome.METHODS Retrospective analysis of 50 patients diagnosed with pelvic floor spasm syndrome.All patients underwent pelvic floor surface electromyography assessment,anorectal dynamics examination,botulinum toxin type A injection 100 U intramuscular injection,and two cycles of biofeedback therapy.RESULTS After the botulinum toxin A injection combined with two cycles of biofeedback therapy,the patient's postoperative resting and systolic blood pressure were significantly lower than before surgery(P<0.05).Moreover,the electromyography index of the patients in the resting stage and post-resting stages was significantly lower than before surgery(P<0.05).CONCLUSION Botulinum toxin A injection combined with biofeedback can significantly reduce pelvic floor muscle tension in treating pelvic floor muscle spasm syndrome.Anorectal manometry is an effective method to evaluate the efficacy of treatment objectively.However,randomized controlled trials are needed.展开更多
Recently the manufacture of epoxy coating and flooring materials begun to be under strong pressure to use more environmentally friendly raw materials in its composition.First tendency to reduce of solvents and diluent...Recently the manufacture of epoxy coating and flooring materials begun to be under strong pressure to use more environmentally friendly raw materials in its composition.First tendency to reduce of solvents and diluents contained in the materials appeared at the end of 90´s.This situation was supported by the Council of Europe in 2004 to reduce VOC emissions to zero till 2020.Solvent materials were thus largely replaced by solvent free materials from which the volatile substances are not released into the air.But pressure continued to increase,and over the past decade began to take centre stage water-based epoxy.On the Czech market solvent based material is still occasionally used,but predominant are solvent free materials.There are no commonly used materials containing wastes as fillers in new water-borne and solvent-free epoxy materials.Characteristics identification of the waste material as a potential filler is a set of properties that determine the limits of secondary raw materials or waste as a filler.This paper describes the basic characteristics which must be selected to meet the requirements,to affect negatively the workability,sedimentation,properties and behavior of the final floor system.Some materials must comply with special requirements,such as resistance to chemicals,etc.Next part of paper talks about utilization of polymer floors and their mechanical properties.展开更多
Machining is as old as humanity, and changes in temperature in both the machine’s internal and external environments can be of great concern as they affect the machine’s thermal stability and, thus, the machine’s d...Machining is as old as humanity, and changes in temperature in both the machine’s internal and external environments can be of great concern as they affect the machine’s thermal stability and, thus, the machine’s dimensional accuracy. This paper is a continuation of our earlier work, which aimed to analyze the effect of the internal temperature of a machine tool as the machine is put into operation and vary the external temperature, the machine floor temperature. Some experiments are carried out under controlled conditions to study how machine tool components get heated up and how this heating up affects the machine’s accuracy due to thermally induced deviations. Additionally, another angle is added by varying the machine floor temperature. The parameters mentioned above are explored in line with the overall thermal stability of the machine tool and its dimensional accuracy. A Robodrill CNC machine tool is used. The CNC was first soaked with thermal energy by gradually raising the machine floor temperature to a certain level before putting the machine in operation. The machine was monitored, and analytical methods were deplored to evaluate thermal stability. Secondly, the machine was run idle for some time under raised floor temperature before it was put into operation. Data was also collected and analyzed. It is observed that machine thermal stability can be achieved in several ways depending on how the above parameters are joggled. This paper, in conclusion, reinforces the idea of machine tool warm-up process in conjunction with a carefully analyzed and established machine floor temperature variation for the approximation of the machine tool’s thermally stability to map the long-time behavior of the machine tool.展开更多
Lower groups of coal seams are presently being mined from water-inrush from coal floors in order to have safe production in the Yanzhou coal mining area. We need to evaluate the risk in the lower groups of coal seams ...Lower groups of coal seams are presently being mined from water-inrush from coal floors in order to have safe production in the Yanzhou coal mining area. We need to evaluate the risk in the lower groups of coal seams in mines. Based on a systematic collection of hydrogeological data and some data from mined working faces in these lower groups, we evaluated the factors affecting water-inrush from coal floors of the area by a method of dimensionless analysis. We obtained the order of the factors affecting water-inrush from coal floors and recalculated data on depths of destroyed floors by multiple linear regression analysis and obtained new empirical formulas. We also analyzed the water-inrush coefficient of mined working faces of the lower groups of coal seams and improved the evaluation standard of the water-inrush coefficient method. Finally, we made a comprehensive evaluation of water-inrush risks from coal floors by using the water-inrush coefficient method and a fuzzy clustering method. The evaluation results provide a solid foundation for preventing and controlling the damage caused by water of an Ordovician limestone aquifer in the lower group of coal seams in the mines of Yanzhou. It provides also important guidelines for lower groups of coal seams in other coal mines.展开更多
The failure depth of the coal seam floor is one important consideration that must be kept in mind when mining is carried out above a confined aquifer.Determining the floor failure depth is the essential precondition f...The failure depth of the coal seam floor is one important consideration that must be kept in mind when mining is carried out above a confined aquifer.Determining the floor failure depth is the essential precondition for predicting the water-resisting ability of the floor.We have used a high-precision microseismic monitoring technique to overcome the limited amount of data available from field measurements. The failure depth of a coal seam floor,especially an inclined coal seam floor,may be more accurately estimated by monitoring the continuous,dynamic failure of the floor.The monitoring results indicate the failure depth of the coal seam floor near the workface conveyance roadway(the lower crossheading) is deeper and that the failure range is wider here compared to the coal seam floor near the return airway(the upper crossheading).The results of micro-seismic monitoring show that the dangerous area for water-inrush from the coal seam floor may be identified.This provides an important field measurement that helps ensure safe and highly efficient mining of the inclined coal seam above the confined aquifer at the Taoyuan Coal Mine.展开更多
A theory of seepage instability was used to estimate the harmfulness of water-inrush from a coal seam floor in a particular coal mine of the Mining Group,Xuzhou. Based on the stratum column chart in this coal mine,the...A theory of seepage instability was used to estimate the harmfulness of water-inrush from a coal seam floor in a particular coal mine of the Mining Group,Xuzhou. Based on the stratum column chart in this coal mine,the distribu-tion of stress in mining floors when the long-wall mining was respectively pushed along to 100 m and to 150 m was simulated by using the numerical software (RFPA2D). The permeability parameters of the coal seam floor are described given the relationship between permeability parameters. Strain and the water-inrush-indices were calculated. The wa-ter-inrush-index was 67.2% when the working face was pushed to 100 m,showing that water-inrush is possible and it was 1630% when the working face was pushed to 150 m,showing that water-inrush is quite probable. The results show that as long-wall mining is pushed along,the failure zone is enlarged,the strain increased,and fissures developed cor-respondingly,resulting in the formation of water-inrush channels. Accompanied by the failure of the strata,the perme-ability increased exponentially. In contrast,the non-Darcy flow β factor and the acceleration coefficient decreased ex-ponentially,while the increase in the water-inrush-index was nearly exponential and the harmfulness of water-inrush in the coal mine increased accordingly.展开更多
The mechanism of mine water inrushes in coal mines in China differs considerably from that in other countries.In China, most water inrushes occur from floor strata, where the water-inrush sources are karstic limestone...The mechanism of mine water inrushes in coal mines in China differs considerably from that in other countries.In China, most water inrushes occur from floor strata, where the water-inrush sources are karstic limestone aquifers.Our study describes the mechanism of mine water inrushes through a fault in the mine floor using principles of strata mechanics and the path of water inrush from an aquifer to the working face.A criterion to judge whether a ground water inrush will occur through a fault or not is also described, together with a case history of water inflow in the Feicheng coalfield, China.展开更多
In order to study the water-inrush mechanism of concealed collapse pillars from the mechanical view, a mechanical model for water-inrush of collapse pillars has been established based on thick plate theory of elastic ...In order to study the water-inrush mechanism of concealed collapse pillars from the mechanical view, a mechanical model for water-inrush of collapse pillars has been established based on thick plate theory of elastic mechanics in this paper.By solving this model the deformation of water-resistant rock strata under the action of water pressure and the expression of critical water pressure for collapse pillar waterinrush have been obtained The research results indicate that:the boundary conditions and strength of water-resistant strata play important roles in influencing water-inrush of collapse pillars.The critical water-inrush pressure is determined by both relative thickness and absolute thickness of water-resistant strata.展开更多
To investigate the water-inrush process due to floor heave,simulation model was made and factors of mining height,immediate roof strength,water pressure,depth and strength of confiningbed,excavation step distance and ...To investigate the water-inrush process due to floor heave,simulation model was made and factors of mining height,immediate roof strength,water pressure,depth and strength of confiningbed,excavation step distance and bury depth were analyzed by using UDEC software.Five zones theory (containing two maximum main stress circles and three maximum main stress stratiform zones) along excavation direction was proposed, and two-ends-fixed beam mechanical model in maximum main stress circle was estab- lished.It is found that water inrush always occurs at the end of the beam where shear stress is higher,that is to say,it always occurs at near the starting cut and working face. Water pressure,height and strength of confiningbed are the determined factors,and min- ing height,immediate roof strength,excavation step distance and bury depth effect water inrush process due to floor heave.展开更多
Used numerical simulation method to study the floor water-inrush mechanism in working face which was influenced by fault structure, and set up many kinds of models and performs numerical calculation by fully using lar...Used numerical simulation method to study the floor water-inrush mechanism in working face which was influenced by fault structure, and set up many kinds of models and performs numerical calculation by fully using large finite element soft-ANSYS and element birth-death method. The results show that the more high the underground water pressure, the more big the floor displacement and possibility of water-inrush; the floor which has fault structure is more prone to water-inrush than the floor which not has fault structure, the floor which has multi-groups cracks is more prone to water-inrush than the floor which has single-group cracks. The numerical simulation result forecasts the water-inrush in working face preferably.展开更多
Maxillary sinus floor augmentation using lateral window and crestal technique is considered as predictable methods to increase the residual bone height;however,this surgery is commonly complicated by Schneiderian memb...Maxillary sinus floor augmentation using lateral window and crestal technique is considered as predictable methods to increase the residual bone height;however,this surgery is commonly complicated by Schneiderian membrane perforation,which is closely related to anatomical factors.This article aimed to assess anatomical factors on successful augmentation procedures.After review of the current evidence on sinus augmentation techniques,anatomical factors related to the stretching potential of Schneiderian membrane were assessed and a decision tree for the rational choice of surgical approaches was proposed.Schneiderian membrane perforation might occur when local tension exceeds its stretching potential,which is closely related to anatomical variations of the maxillary sinus.Choice of a surgical approach and clinical outcomes are influenced by the stretching potential of Schneiderian membrane.In addition to the residual bone height,clinicians should also consider the stretching potential affected by the membrane health condition,the contours of the maxillary sinus,and the presence of antral septa when evaluating the choice of surgical approaches and clinical outcomes.展开更多
This study aimed to introduce a minimally invasive technique for maxillary sinus floor elevation using the lateral approach(lSFE)and to determine the factors that influence the stability of the grafted area in the sin...This study aimed to introduce a minimally invasive technique for maxillary sinus floor elevation using the lateral approach(lSFE)and to determine the factors that influence the stability of the grafted area in the sinus cavity.Thirty patients(30 implants)treated with lSFE using minimally invasive techniques from 2015 to 2019 were included in the study.Five aspects of the implant(central,mesial,distal,buccal,and palatal bone heights[BHs])were measured using cone-beam computed tomography(CBCT)before implant surgery,immediately after surgery(T0),6 months after surgery(T1),and at the last follow-up visit(T2).Patients’characteristics were collected.A small bone window(height,(4.40±0.74)mm;length,(6.26±1.03)mm)was prepared.No implant failed during the follow-up period(3.67±1.75)years.Three of the 30 implants exhibited perforations.Changes in BH of the five aspects of implants showed strong correlations with each other and BH decreased dramatically before second-stage surgery.Residual bone height(RBH)did not significantly influence BH changes,whereas smoking status and type of bone graft materials were the potentially influential factors.During the approximate three-year observation period,lSFE with a minimally invasive technique demonstrated high implant survival rate and limited bone reduction in grafted area.In conclusion,lSFE using minimally invasive techniques was a viable treatment option.Patients who were nonsmokers and whose sinus cavity was filled with deproteinized bovine bone mineral(DBBM)had significantly limited bone resorption in grafted area.展开更多
The test floor effects seen in standardised tests lead to a standardised score of 1 or less with a flat profile that hides a child’s individual strengths and needs. The Griffiths III community of practitioners reques...The test floor effects seen in standardised tests lead to a standardised score of 1 or less with a flat profile that hides a child’s individual strengths and needs. The Griffiths III community of practitioners requested advice on the reporting of children’s development below the floor of the test, so that individual strengths and needs can be described. This paper reports the third phase of research following an earlier Scoping Review and a wider literature review. To confirm quality control, Phase 3 was conducted in a retrospective manner using the same methodology as the earlier phases but in a reverse direction. Peer reviewer comments and key elements from the Scoping Review and keywords from the publications were tabulated. Data analysis included a change of perspective to that of the child and their individual rights with respect to the literature themes already described in Phase 2. These confirmed that there is little specific guidance in the literature, but that computational advances for homogeneous populations and especially disaggregated data offer some solutions. A greater balance between broad biopsychosocial models and standardised models of assessment should be sought by practitioners together with the use of disaggregated data to highlight issues that pertain to individual subsets of results. This will ensure that the child’s right for their individual strengths and needs to be described together with a plan for management, may be met.展开更多
In order to better meet the objective requirements of the use safety of the high-rise glulam building floor structure and the living comfort of the residents,the transient excitation,environmental excitation and frequ...In order to better meet the objective requirements of the use safety of the high-rise glulam building floor structure and the living comfort of the residents,the transient excitation,environmental excitation and frequency spectrum identification methods were used to carry out experimental modal test in-site on the three rooms numbered A,B and C of the same glulam structural building.The three rooms have different functions,different floor sizes and different floor supporting structures.The research results have shown that the first-order bending frequency of the floor structure of Room A is 27.50 Hz,the transverse second-order bending frequency is 34.75 Hz,the longitudinal second-order bending frequency is 53.25 Hz,and the first-order torsional frequency is 56.25 Hz.The reinforced wooden beam at the bottom of the floor of Room A increases the transverse stiffness of the floor structure,but does not offset the anisotropy caused by the longitudinally installed glulam floors.The fundamental frequency values of the floor structures of the three rooms numbered A,B,and C are 27.5,13 and 18 Hz,respectively.This has a relatively high innovation and reference significance for integrating the theory of structural dynamic characteristics with the dynamic testing technology,improving the design level of high-rise glulam structure buildings,and improving the living comfort of residents.展开更多
奥灰岩溶裂隙含水层是影响华北型煤矿深部开采的重要水害,在水-岩相互作用下奥灰含水层易导致煤层底板突水。为进一步认识奥灰岩溶突水问题,文章以新集矿区深部1煤层开采为例,利用矿区近些年最新积累的奥灰钻孔资料,选取断层强度指数、...奥灰岩溶裂隙含水层是影响华北型煤矿深部开采的重要水害,在水-岩相互作用下奥灰含水层易导致煤层底板突水。为进一步认识奥灰岩溶突水问题,文章以新集矿区深部1煤层开采为例,利用矿区近些年最新积累的奥灰钻孔资料,选取断层强度指数、断层交叉点与尖灭点、含水层水压、富水性、隔水层等效厚度、脆塑比7个因素作为奥灰岩溶突水的主控因素,并结合层次分析法(analytic hierarchy process,AHP)确定各主控因素影响权重。运用地理信息系统(geographic information system,GIS)空间分析功能建立各主控因素专题图,通过对专题栅格图归一化处理,将各主控因素按照权重进行空间复合叠加,最终获得1煤层底板奥灰岩溶突水危险性评价分区结果。将评价结果与突水系数法计算结果对比分析可知,基于GIS的煤层底板突水危险性评价方法更符合矿区实际地质情况,可以为矿区深部煤层开采与水害防治工作提供参考依据。展开更多
基金supported by the Key Program of National Natural Science Foundation of China(No.U23A202579)the National Natural Science Foundation of China(No.42277187,42007276,41972297)the Natural Science Foundation of Hebei Province(No.D2021202002)。
文摘The presence of horizontal layered rocks in tunnel engineering significantly impacts the stability and strength of the surrounding rock mass,leading to floor heave in the tunnel.This study focused on preparing layered specimens of rock-like material with varying thickness to investigate the failure behaviors of tunnel floors.The results indicate that thin-layered rock mass exhibits weak interlayer bonding,causing rock layers near the surface to buckle and break upwards when subjected to horizontal squeezing.With an increase in the layer thickness,a transition in failure mode occurs from upward buckling to shear failure along the plane,leading to a noticeable reduction in floor heave deformation.The primary cause of significant deformation in floor heave is upward buckling failure.To address this issue,the study proposes the installation of a partition wall in the middle of the floor to mitigate heave deformation of the rock layers.The results demonstrate that the partition wall has a considerable stabilizing effect on the floor,reducing the zone of buckling failure and minimizing floor heave deformation.It is crucial for the partition wall to be sufficiently high to prevent buckling failure and ensure stability.Through simulation calculations on an engineering example,it is confirmed that implementing a partition wall can effectively reduce floor heave and enhance the stability of tunnel floor.
文摘BACKGROUND Pelvic floor dysfunction(PFD)is related to muscle fiber tearing during childbirth,negatively impacting postpartum quality of life of parturient.Appropriate and effective intervention is necessary to promote PFD recovery.AIM To analyze the use of hydrogen peroxide and silver ion disinfection for vaginal electrodes in conjunction with comprehensive rehabilitation therapy for postpartum women with PFD.METHODS A total of 59 women with PFD who were admitted to the hospital from May 2019 to July 2022 were divided into two groups:Control group(n=27)received comprehensive rehabilitation therapy and observation group(n=32)received intervention with pelvic floor biostimulation feedback instrument in addition to comprehensive rehabilitation therapy.The vaginal electrodes were disinfected with hydrogen peroxide and silver ion before treatment.Intervention for both groups was started 6 weeks postpartum,and rehabilitation lasted for 3 months.Pelvic floor muscle voltage,pelvic floor muscle strength,vaginal muscle voltage,vaginal muscle tone,pelvic floor function,quality of life,and incidence of postpartum PFD were compared between the two groups.RESULTS Before comprehensive rehabilitation treatment,basic data and pelvic floor function were not significantly different between the two groups.After treatment,the observation group showed significant improvements in the maximum voltage and average voltage of pelvic floor muscles,contraction time of type I and type II fibers,pelvic floor muscle strength,vaginal muscle tone,vaginal muscle voltage,and quality of life(GQOLI-74 reports),compared with the control group.The observation group had lower scores on the pelvic floor distress inventory(PFDI-20)and a lower incidence of postpartum PFD,indicating the effectiveness of the pelvic floor biostimulation feedback instrument in promoting the recovery of maternal pelvic floor function.CONCLUSION The combination of the pelvic floor biostimulation feedback instrument and comprehensive rehabilitation nursing can improve pelvic floor muscle strength,promote the recovery of vaginal muscle tone,and improve pelvic floor function and quality of life.The use of hydrogen peroxide and silver ion disinfectant demonstrated favorable antibacterial efficacy and is worthy of clinical application.
文摘BACKGROUND Spastic pelvic floor syndrome(SPFS)is a refractory pelvic floor disease characterized by abnormal(uncoordinated)contractions of the external anal sphincter and puborectalis muscle during defecation,resulting in rectal emptation and obstructive constipation.The clinical manifestations of SPFS are mainly characterized by difficult defecation,often accompanied by a sense of anal blockage and drooping.Manual defecation is usually needed during defecation.From physical examination,it is commonly observed that the patient's anal muscle tension is high,and it is difficult or even impossible to enter with his fingers.AIM To investigate the characteristics of anorectal pressure and botulinum toxin A injection combined with biofeedback in treating pelvic floor muscle spasm syndrome.METHODS Retrospective analysis of 50 patients diagnosed with pelvic floor spasm syndrome.All patients underwent pelvic floor surface electromyography assessment,anorectal dynamics examination,botulinum toxin type A injection 100 U intramuscular injection,and two cycles of biofeedback therapy.RESULTS After the botulinum toxin A injection combined with two cycles of biofeedback therapy,the patient's postoperative resting and systolic blood pressure were significantly lower than before surgery(P<0.05).Moreover,the electromyography index of the patients in the resting stage and post-resting stages was significantly lower than before surgery(P<0.05).CONCLUSION Botulinum toxin A injection combined with biofeedback can significantly reduce pelvic floor muscle tension in treating pelvic floor muscle spasm syndrome.Anorectal manometry is an effective method to evaluate the efficacy of treatment objectively.However,randomized controlled trials are needed.
基金supported by the project"OKTAEDR-partnership and building network."Project registration number is cz.1.07./2.4.00/31.0012.
文摘Recently the manufacture of epoxy coating and flooring materials begun to be under strong pressure to use more environmentally friendly raw materials in its composition.First tendency to reduce of solvents and diluents contained in the materials appeared at the end of 90´s.This situation was supported by the Council of Europe in 2004 to reduce VOC emissions to zero till 2020.Solvent materials were thus largely replaced by solvent free materials from which the volatile substances are not released into the air.But pressure continued to increase,and over the past decade began to take centre stage water-based epoxy.On the Czech market solvent based material is still occasionally used,but predominant are solvent free materials.There are no commonly used materials containing wastes as fillers in new water-borne and solvent-free epoxy materials.Characteristics identification of the waste material as a potential filler is a set of properties that determine the limits of secondary raw materials or waste as a filler.This paper describes the basic characteristics which must be selected to meet the requirements,to affect negatively the workability,sedimentation,properties and behavior of the final floor system.Some materials must comply with special requirements,such as resistance to chemicals,etc.Next part of paper talks about utilization of polymer floors and their mechanical properties.
文摘Machining is as old as humanity, and changes in temperature in both the machine’s internal and external environments can be of great concern as they affect the machine’s thermal stability and, thus, the machine’s dimensional accuracy. This paper is a continuation of our earlier work, which aimed to analyze the effect of the internal temperature of a machine tool as the machine is put into operation and vary the external temperature, the machine floor temperature. Some experiments are carried out under controlled conditions to study how machine tool components get heated up and how this heating up affects the machine’s accuracy due to thermally induced deviations. Additionally, another angle is added by varying the machine floor temperature. The parameters mentioned above are explored in line with the overall thermal stability of the machine tool and its dimensional accuracy. A Robodrill CNC machine tool is used. The CNC was first soaked with thermal energy by gradually raising the machine floor temperature to a certain level before putting the machine in operation. The machine was monitored, and analytical methods were deplored to evaluate thermal stability. Secondly, the machine was run idle for some time under raised floor temperature before it was put into operation. Data was also collected and analyzed. It is observed that machine thermal stability can be achieved in several ways depending on how the above parameters are joggled. This paper, in conclusion, reinforces the idea of machine tool warm-up process in conjunction with a carefully analyzed and established machine floor temperature variation for the approximation of the machine tool’s thermally stability to map the long-time behavior of the machine tool.
基金supports from the Natural Science Foundation of Shandong Province (No.Y2007F46)the Doctor Disciplines Special Scientific Research Foundation of Ministry of Education (No.20070424005)+1 种基金China Coal Industry Association Science and Technology Research Instructive Plan (No.MTKJ2009-290) the National Natural Science Foundation of China (No.50539080)
文摘Lower groups of coal seams are presently being mined from water-inrush from coal floors in order to have safe production in the Yanzhou coal mining area. We need to evaluate the risk in the lower groups of coal seams in mines. Based on a systematic collection of hydrogeological data and some data from mined working faces in these lower groups, we evaluated the factors affecting water-inrush from coal floors of the area by a method of dimensionless analysis. We obtained the order of the factors affecting water-inrush from coal floors and recalculated data on depths of destroyed floors by multiple linear regression analysis and obtained new empirical formulas. We also analyzed the water-inrush coefficient of mined working faces of the lower groups of coal seams and improved the evaluation standard of the water-inrush coefficient method. Finally, we made a comprehensive evaluation of water-inrush risks from coal floors by using the water-inrush coefficient method and a fuzzy clustering method. The evaluation results provide a solid foundation for preventing and controlling the damage caused by water of an Ordovician limestone aquifer in the lower group of coal seams in the mines of Yanzhou. It provides also important guidelines for lower groups of coal seams in other coal mines.
基金supported by the National Basic Research Program ofChina(No.2010CB202210)the National Natural Science Foundation of China(No.50874103)+1 种基金the Natural Science Foundation of Jiangsu Province(No.KB2008135)as well as by the Qinglan Project of Jiangsu Province
文摘The failure depth of the coal seam floor is one important consideration that must be kept in mind when mining is carried out above a confined aquifer.Determining the floor failure depth is the essential precondition for predicting the water-resisting ability of the floor.We have used a high-precision microseismic monitoring technique to overcome the limited amount of data available from field measurements. The failure depth of a coal seam floor,especially an inclined coal seam floor,may be more accurately estimated by monitoring the continuous,dynamic failure of the floor.The monitoring results indicate the failure depth of the coal seam floor near the workface conveyance roadway(the lower crossheading) is deeper and that the failure range is wider here compared to the coal seam floor near the return airway(the upper crossheading).The results of micro-seismic monitoring show that the dangerous area for water-inrush from the coal seam floor may be identified.This provides an important field measurement that helps ensure safe and highly efficient mining of the inclined coal seam above the confined aquifer at the Taoyuan Coal Mine.
基金Projects 50225414 supported by the National Outstanding Youth Foundation50574090, 50674087 and 50490270 by the National Natural Science Foundation of China
文摘A theory of seepage instability was used to estimate the harmfulness of water-inrush from a coal seam floor in a particular coal mine of the Mining Group,Xuzhou. Based on the stratum column chart in this coal mine,the distribu-tion of stress in mining floors when the long-wall mining was respectively pushed along to 100 m and to 150 m was simulated by using the numerical software (RFPA2D). The permeability parameters of the coal seam floor are described given the relationship between permeability parameters. Strain and the water-inrush-indices were calculated. The wa-ter-inrush-index was 67.2% when the working face was pushed to 100 m,showing that water-inrush is possible and it was 1630% when the working face was pushed to 150 m,showing that water-inrush is quite probable. The results show that as long-wall mining is pushed along,the failure zone is enlarged,the strain increased,and fissures developed cor-respondingly,resulting in the formation of water-inrush channels. Accompanied by the failure of the strata,the perme-ability increased exponentially. In contrast,the non-Darcy flow β factor and the acceleration coefficient decreased ex-ponentially,while the increase in the water-inrush-index was nearly exponential and the harmfulness of water-inrush in the coal mine increased accordingly.
基金Projects Y2007F46 supported by the Natural Science Foundation of Shandong Province20070424005 by the Doctor Disciplines Special Scientific Researc Foundation of the Ministry of Education+1 种基金108158 by the Key Project of the Ministry of Education of China50539080 by the National Natural Scienc Foundation of China
文摘The mechanism of mine water inrushes in coal mines in China differs considerably from that in other countries.In China, most water inrushes occur from floor strata, where the water-inrush sources are karstic limestone aquifers.Our study describes the mechanism of mine water inrushes through a fault in the mine floor using principles of strata mechanics and the path of water inrush from an aquifer to the working face.A criterion to judge whether a ground water inrush will occur through a fault or not is also described, together with a case history of water inflow in the Feicheng coalfield, China.
基金Projects are supported by the National Basic Research Program of China(No.2007CB209400)the National Natural Science Foundation of China(Nos.50974115,50904065 and 50974107)the 111 Project(No.B07028).
文摘In order to study the water-inrush mechanism of concealed collapse pillars from the mechanical view, a mechanical model for water-inrush of collapse pillars has been established based on thick plate theory of elastic mechanics in this paper.By solving this model the deformation of water-resistant rock strata under the action of water pressure and the expression of critical water pressure for collapse pillar waterinrush have been obtained The research results indicate that:the boundary conditions and strength of water-resistant strata play important roles in influencing water-inrush of collapse pillars.The critical water-inrush pressure is determined by both relative thickness and absolute thickness of water-resistant strata.
基金the National Natural Science Foundation of China(10572047)
文摘To investigate the water-inrush process due to floor heave,simulation model was made and factors of mining height,immediate roof strength,water pressure,depth and strength of confiningbed,excavation step distance and bury depth were analyzed by using UDEC software.Five zones theory (containing two maximum main stress circles and three maximum main stress stratiform zones) along excavation direction was proposed, and two-ends-fixed beam mechanical model in maximum main stress circle was estab- lished.It is found that water inrush always occurs at the end of the beam where shear stress is higher,that is to say,it always occurs at near the starting cut and working face. Water pressure,height and strength of confiningbed are the determined factors,and min- ing height,immediate roof strength,excavation step distance and bury depth effect water inrush process due to floor heave.
文摘Used numerical simulation method to study the floor water-inrush mechanism in working face which was influenced by fault structure, and set up many kinds of models and performs numerical calculation by fully using large finite element soft-ANSYS and element birth-death method. The results show that the more high the underground water pressure, the more big the floor displacement and possibility of water-inrush; the floor which has fault structure is more prone to water-inrush than the floor which not has fault structure, the floor which has multi-groups cracks is more prone to water-inrush than the floor which has single-group cracks. The numerical simulation result forecasts the water-inrush in working face preferably.
基金supported by grants from:1.Young Clinical Research Fund of the Chinese Stomatological Association[grant number CSA-SIS2022-19]Sichuan Science and Technology Program:[grant number 2023NSFSC0567].
文摘Maxillary sinus floor augmentation using lateral window and crestal technique is considered as predictable methods to increase the residual bone height;however,this surgery is commonly complicated by Schneiderian membrane perforation,which is closely related to anatomical factors.This article aimed to assess anatomical factors on successful augmentation procedures.After review of the current evidence on sinus augmentation techniques,anatomical factors related to the stretching potential of Schneiderian membrane were assessed and a decision tree for the rational choice of surgical approaches was proposed.Schneiderian membrane perforation might occur when local tension exceeds its stretching potential,which is closely related to anatomical variations of the maxillary sinus.Choice of a surgical approach and clinical outcomes are influenced by the stretching potential of Schneiderian membrane.In addition to the residual bone height,clinicians should also consider the stretching potential affected by the membrane health condition,the contours of the maxillary sinus,and the presence of antral septa when evaluating the choice of surgical approaches and clinical outcomes.
基金supported by National Natural Science Foundation of China(81970986,81771125)Exploration and R&D Project of West China Hospital of Stomatology(LCYJ2020-DC-1)+1 种基金Sichuan University Postdoctoral Innovation Fund(2023SCU12040)China Postdoctoral Science Foundation funded project(2022TQ0222).
文摘This study aimed to introduce a minimally invasive technique for maxillary sinus floor elevation using the lateral approach(lSFE)and to determine the factors that influence the stability of the grafted area in the sinus cavity.Thirty patients(30 implants)treated with lSFE using minimally invasive techniques from 2015 to 2019 were included in the study.Five aspects of the implant(central,mesial,distal,buccal,and palatal bone heights[BHs])were measured using cone-beam computed tomography(CBCT)before implant surgery,immediately after surgery(T0),6 months after surgery(T1),and at the last follow-up visit(T2).Patients’characteristics were collected.A small bone window(height,(4.40±0.74)mm;length,(6.26±1.03)mm)was prepared.No implant failed during the follow-up period(3.67±1.75)years.Three of the 30 implants exhibited perforations.Changes in BH of the five aspects of implants showed strong correlations with each other and BH decreased dramatically before second-stage surgery.Residual bone height(RBH)did not significantly influence BH changes,whereas smoking status and type of bone graft materials were the potentially influential factors.During the approximate three-year observation period,lSFE with a minimally invasive technique demonstrated high implant survival rate and limited bone reduction in grafted area.In conclusion,lSFE using minimally invasive techniques was a viable treatment option.Patients who were nonsmokers and whose sinus cavity was filled with deproteinized bovine bone mineral(DBBM)had significantly limited bone resorption in grafted area.
文摘The test floor effects seen in standardised tests lead to a standardised score of 1 or less with a flat profile that hides a child’s individual strengths and needs. The Griffiths III community of practitioners requested advice on the reporting of children’s development below the floor of the test, so that individual strengths and needs can be described. This paper reports the third phase of research following an earlier Scoping Review and a wider literature review. To confirm quality control, Phase 3 was conducted in a retrospective manner using the same methodology as the earlier phases but in a reverse direction. Peer reviewer comments and key elements from the Scoping Review and keywords from the publications were tabulated. Data analysis included a change of perspective to that of the child and their individual rights with respect to the literature themes already described in Phase 2. These confirmed that there is little specific guidance in the literature, but that computational advances for homogeneous populations and especially disaggregated data offer some solutions. A greater balance between broad biopsychosocial models and standardised models of assessment should be sought by practitioners together with the use of disaggregated data to highlight issues that pertain to individual subsets of results. This will ensure that the child’s right for their individual strengths and needs to be described together with a plan for management, may be met.
文摘In order to better meet the objective requirements of the use safety of the high-rise glulam building floor structure and the living comfort of the residents,the transient excitation,environmental excitation and frequency spectrum identification methods were used to carry out experimental modal test in-site on the three rooms numbered A,B and C of the same glulam structural building.The three rooms have different functions,different floor sizes and different floor supporting structures.The research results have shown that the first-order bending frequency of the floor structure of Room A is 27.50 Hz,the transverse second-order bending frequency is 34.75 Hz,the longitudinal second-order bending frequency is 53.25 Hz,and the first-order torsional frequency is 56.25 Hz.The reinforced wooden beam at the bottom of the floor of Room A increases the transverse stiffness of the floor structure,but does not offset the anisotropy caused by the longitudinally installed glulam floors.The fundamental frequency values of the floor structures of the three rooms numbered A,B,and C are 27.5,13 and 18 Hz,respectively.This has a relatively high innovation and reference significance for integrating the theory of structural dynamic characteristics with the dynamic testing technology,improving the design level of high-rise glulam structure buildings,and improving the living comfort of residents.
文摘奥灰岩溶裂隙含水层是影响华北型煤矿深部开采的重要水害,在水-岩相互作用下奥灰含水层易导致煤层底板突水。为进一步认识奥灰岩溶突水问题,文章以新集矿区深部1煤层开采为例,利用矿区近些年最新积累的奥灰钻孔资料,选取断层强度指数、断层交叉点与尖灭点、含水层水压、富水性、隔水层等效厚度、脆塑比7个因素作为奥灰岩溶突水的主控因素,并结合层次分析法(analytic hierarchy process,AHP)确定各主控因素影响权重。运用地理信息系统(geographic information system,GIS)空间分析功能建立各主控因素专题图,通过对专题栅格图归一化处理,将各主控因素按照权重进行空间复合叠加,最终获得1煤层底板奥灰岩溶突水危险性评价分区结果。将评价结果与突水系数法计算结果对比分析可知,基于GIS的煤层底板突水危险性评价方法更符合矿区实际地质情况,可以为矿区深部煤层开采与水害防治工作提供参考依据。