This paper studies optimal shape design of pressure vessel head subject to internal uniform pressure.The optimization aims at minimizing its maximum stress while the volume of the vessel head remains no less than the ...This paper studies optimal shape design of pressure vessel head subject to internal uniform pressure.The optimization aims at minimizing its maximum stress while the volume of the vessel head remains no less than the standard ellipsoidal head.Super-ellipse curve is selected to describe the middle surface shape of the vessel head because it represents a large family of curves with only two or three parameters and makes the design and manufacture easy.The performance of different elements and element sizes of FEM modeling is carefully studied in view of computational cost,accuracy and noises of von Mises stress.The response surface of the maximum stress vs.shape design parameters is approximated by a Kriging surrogate model with EI criterion for sampling adding,based on the parameter optimization which is carried out to search the optimal shape.Finally,it is shown by numerical comparison that the super-ellipsoidal head is better than the standard ellipsoidal head and the other vessel heads in the literature.展开更多
To investigate the content and dynamics of nitric oxide (NO) in the cerebrospinal fluid (CSF) of patients with acute head injury and to clarify the relationship of NO with clinical features and intracranial pressure (...To investigate the content and dynamics of nitric oxide (NO) in the cerebrospinal fluid (CSF) of patients with acute head injury and to clarify the relationship of NO with clinical features and intracranial pressure (ICP) as well as outcomes, 38 adults with acute head injury were studied. Glasgow Coma Scale (GCS) obtained at admission and Glasgow Outcome Scale (GOS) 3 months after injury was assessed. ICP was surveyed via intraventricular catheter and lumbar puncture and CSF samples were obtained simultaneously. NO was determined with Griess reagents. Results showed that NO peak content in the head injury group was significantly higher than that of the control group. During dynamic research, no peak content of mildly injured cases and severely injured ones appeared in different time windows respectively. The peak value of NO was distinctly higher in the severe group than in the mild group. NO peak value of the raised ICP group was remarkably higher than that of the normal ICP group. The peak value of NO was considerately higher in the poor outcome group than in the good outcome group. When the content of NO was over 6. 5 μmol/L, the rate of poor outcome was increased. There existed a correlation between NO and GCS, ICP and GOS. It is concluded that the content of NO was increased in patients with acute head injury and the changes of NO had different time windows in severely injured patients and mildly injured ones. The more sever the injury, the higher the NO content; and the more serious the secondary brain injury and brain edema, the worse the outcomes. When NO is combined with GCS, GOS and ICP, it increases the accuracy of judgement to the degree of head injury and outcome.展开更多
Samarahan has transformed from a small village into education hub for the past 2 decades. Rapid development and population growth had led to speedy growth in water demand. The situation is getting worse as the pipes a...Samarahan has transformed from a small village into education hub for the past 2 decades. Rapid development and population growth had led to speedy growth in water demand. The situation is getting worse as the pipes are deteriorating due to pipe aging. Therefore, there is a need to study the adequacy of water supply and relationships among roughness coefficient (C) values in Hazen Williams’ Equation with head loss and water pressure due to pipe aging at Uni-Central, a residential area located at Samarahan Sarawak. Investigations were carried out with Ductile Iron, Abestos Cement and Cast Iron pipes at age categories of 0 - 10 years, 10 - 30 years, 30 - 50 years, 50 - 70 years and >70 years. Six critical nodes named as A, B, C, D, E and F were identified to study the water pressure and head loss. Model was developed with InfoWorks Water Supply (WS) Pro software. The impact of pipe aging and materials to water pressure and head loss was not significant at Nodes A, B, C and F. However, max water pressure at Nodes D and F were only reaching 6.30 m and 7.30 m, respectively for all investigations. Therefore, some improvement works are required. Results also show that Asbestos Cement pipe has the least impact on the head loss and water pressure, followed by Ductile Iron pipe and lastly Cast Iron pipe. Simulation results also revealed that older pipes have higher roughness coefficients, indicated with lower “C” values, thus increase the head loss and reduce the water pressure. In contrast, as “C” values increased, head loss will be reduced and water pressure will be increased.展开更多
AIM: To analyze changes of the optic nerve head(ONH) and peripapillary region during intraocular pressure(IOP) elevation in patients using spectral domain optical coherence tomography(SD-OCT).METHODS: Both an optic di...AIM: To analyze changes of the optic nerve head(ONH) and peripapillary region during intraocular pressure(IOP) elevation in patients using spectral domain optical coherence tomography(SD-OCT).METHODS: Both an optic disc 200×200 cube scan and a high-definition 5-line raster scan were obtained from open angle glaucoma patients presented with monocular elevation of IOP(≥30 mm Hg) using SD-OCT. Additional baseline characteristics included age, gender, diagnosis,best-corrected visual acuity, refractive error, findings of slit lamp biomicroscopy, findings of dilated stereoscopic examination of the ONH and fundus, IOP, pachymetry findings, and the results of visual field.RESULTS: The 24 patients were selected and divided into two groups: group 1 patients had no history of IOP elevation or glaucoma(n =14), and group 2 patients did have history of IOP elevation or glaucoma(n =10). In each patient, the study eye with elevated IOP was classified into group H(high), and the fellow eye was classified into group L(low). The mean deviation(MD)differed significantly between groups H and L when all eyes were considered(P =0.047) and in group 2(P =0.042), not in group 1(P =0.893). Retinal nerve fiber layer(RNFL) average thickness(P =0.050), rim area(P =0.015),vertical cup/disc ratio(P =0.011), cup volume(P =0.028),inferior quadrant RNFL thickness(P =0.017), and clockhour(1, 5, and 6) RNFL thicknesses(P =0.050, 0.012, and0.018, respectively), cup depth(P =0.008), central prelaminar layer thickness(P =0.023), mid-inferior prelaminar layer thickness(P =0.023), and nasal retinal slope(P =0.034)were significantly different between the eyes with groups H and L.CONCLUSION:RNFLaveragethickness,rim area,vertical cup/disc ratio, cup volume, inferior quadrant RNFL thickness, and clock-hour(1, 5, and 6) RNFL thicknesses significantly changed during acute IOP elevation.展开更多
Super-high pressure(SHP)technique plays an increasing role in the fields of materials science and engineering.Herein,the Mg_(97)Zn_(1)Y_(2) alloy was heat-treated under SHP(6 GPa)by cubic-anvil large-volume press with...Super-high pressure(SHP)technique plays an increasing role in the fields of materials science and engineering.Herein,the Mg_(97)Zn_(1)Y_(2) alloy was heat-treated under SHP(6 GPa)by cubic-anvil large-volume press with six rams for 2 h in the temperature range of 500–1200℃.The microstructure and mechanical properties were investigated.The results indicated that the as-cast sample consists of α-Mg equiaxed dendrites and continuous lamellar long period stacking ordered(LPSO)phase in grain boundaries.After the SHP treatment,the LPSO phase is gradually replaced by eutectic phase(Mg,Zn)_(3)Y with increasing temperature.The microhardness and strength of sample prepared at 1100℃ under SHP treatment are significantly improved compared with the as-cast one at room temperature.The improved mechanical behaviors are mainly attributed to LPSO phase kink-banding strengthening at low temperature and the precipitation strengthening of a large amount of fine(Mg,Zn)_(3)Y particles at high temperature after SHP treatment.It reveals the SHP is an effective approach to prepare high performance Mg alloys.展开更多
The design operating conditions of rubber dams were analyzed,and it is found that the operating conditions are similar to the actual operating conditions of changes in the internal pressure ratio of a specific rubber ...The design operating conditions of rubber dams were analyzed,and it is found that the operating conditions are similar to the actual operating conditions of changes in the internal pressure ratio of a specific rubber dam bag in the process of filling and draining. Based on this,the linear relationship curve between the internal pressure head H0 and the real-time dam height H and its approximate analytical formula can be obtained,which can be used as a supplement and correction method for the measurement method of real-time dam height during rubber dam operation,and provides reference for rubber dam project managers.展开更多
AIM: To describe a newly-recognized entity, illustrated by five cases of glaucoma in whom trauma to the head, but not the eye, resulted in marked, transient elevation of intraocular pressure (IOP). METHODS: Retrospect...AIM: To describe a newly-recognized entity, illustrated by five cases of glaucoma in whom trauma to the head, but not the eye, resulted in marked, transient elevation of intraocular pressure (IOP). METHODS: Retrospective case series. Chart review. RESULTS: All five cases had a diagnosis of primary open-angle glaucoma prior to the experience of trauma to the head. All cases had an unusual elevation of IOP (around 70 percent) for days to weeks following the trauma, after which the IOP fell to pre-accident levels. No cause other than the trauma could be determined. CONCLUSION: The relationship between head trauma and elevation of IOP appears real.展开更多
Foot pressure measurements were performed during standing and level walkingon a series of 30 normal subjects (15 males, 15 females, a total of 60 feet) with amean age of 37.6 yrs and a mean body weight of 66.3 kg. A s...Foot pressure measurements were performed during standing and level walkingon a series of 30 normal subjects (15 males, 15 females, a total of 60 feet) with amean age of 37.6 yrs and a mean body weight of 66.3 kg. A significant difference wasfound in the peak pressure under the second metatarsal head between males and femaleswith females showing higher pressures than males daring walking (P【0. 01). The meanpeak pressure and standard deviation for all 7 areas selected for 30 adult subjects duringstanding and walding were obtained. The rise time to peak pressure at each selected areafor walking was recorded and analysed. The practical application and clinical significanceof these data were also discussed.展开更多
Normal pressure hydrocephalus is a devious phenomenon. It is a disease that is difficult to diagnose and difficult to treat, the only treatment being a ventriculo-peritoneal shunt, though good shunting results rarely ...Normal pressure hydrocephalus is a devious phenomenon. It is a disease that is difficult to diagnose and difficult to treat, the only treatment being a ventriculo-peritoneal shunt, though good shunting results rarely pass a 70% level of effectiveness. We need to understand its pathophysiology better before things will improve. Although some colleagues know it as a possible “reversible dementia” others hardly know about its existence. Solutions would also have value for the general understanding of hydrocephalus of other types. Many theories have been published recently in the search for the missing pieces in this puzzle and I feel that my own postulations could turn out to be useful. After years of diagnosing and operating on hydrocephalus patients I propose that: 1) There is reason to believe that patients with the Apoprotein E3/3 genotype and a high head size percentile are particularly vulnerable to developing idiopathic normal pressure hydrocephalus (iNPH). 2) The classical theory that the arachnoid granulations (AG) transport cerebrospinal fluid (CSF) into the venous circulation is wrong. I postulate, that the AG essentially are sensors, registering the pressure differences between the CSF in the subarachnoidal space at the top of the skull and the venous pressure in the sagittal sinus. The AG’s endothelium produces nitric oxide (NO) as a messenger that is received by the vagus nerve at the jugular foramen. 3) The disease has its fundamental pathology in the subpial space in the large cisternas and along the large vessels under the brain. Here the intravenous absorption of cerebrospinal fluid (CSF) takes place. Cerebrospinal fluid is transported into the subpial venules and veins, driven by the pulse pressure of the subpial arteries. Morphological changes in the pial/subpial anatomy explain the existence of acquired normal pressure hydrocephalus (aNPH).展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.9121620111128205)+1 种基金the National Program on Key Basic Research Project(Grant No.2011CB610304)the Fundamental Research Funds for the Central Universities(Grant No.DUT 11 ZD(G)04)
文摘This paper studies optimal shape design of pressure vessel head subject to internal uniform pressure.The optimization aims at minimizing its maximum stress while the volume of the vessel head remains no less than the standard ellipsoidal head.Super-ellipse curve is selected to describe the middle surface shape of the vessel head because it represents a large family of curves with only two or three parameters and makes the design and manufacture easy.The performance of different elements and element sizes of FEM modeling is carefully studied in view of computational cost,accuracy and noises of von Mises stress.The response surface of the maximum stress vs.shape design parameters is approximated by a Kriging surrogate model with EI criterion for sampling adding,based on the parameter optimization which is carried out to search the optimal shape.Finally,it is shown by numerical comparison that the super-ellipsoidal head is better than the standard ellipsoidal head and the other vessel heads in the literature.
文摘To investigate the content and dynamics of nitric oxide (NO) in the cerebrospinal fluid (CSF) of patients with acute head injury and to clarify the relationship of NO with clinical features and intracranial pressure (ICP) as well as outcomes, 38 adults with acute head injury were studied. Glasgow Coma Scale (GCS) obtained at admission and Glasgow Outcome Scale (GOS) 3 months after injury was assessed. ICP was surveyed via intraventricular catheter and lumbar puncture and CSF samples were obtained simultaneously. NO was determined with Griess reagents. Results showed that NO peak content in the head injury group was significantly higher than that of the control group. During dynamic research, no peak content of mildly injured cases and severely injured ones appeared in different time windows respectively. The peak value of NO was distinctly higher in the severe group than in the mild group. NO peak value of the raised ICP group was remarkably higher than that of the normal ICP group. The peak value of NO was considerately higher in the poor outcome group than in the good outcome group. When the content of NO was over 6. 5 μmol/L, the rate of poor outcome was increased. There existed a correlation between NO and GCS, ICP and GOS. It is concluded that the content of NO was increased in patients with acute head injury and the changes of NO had different time windows in severely injured patients and mildly injured ones. The more sever the injury, the higher the NO content; and the more serious the secondary brain injury and brain edema, the worse the outcomes. When NO is combined with GCS, GOS and ICP, it increases the accuracy of judgement to the degree of head injury and outcome.
文摘Samarahan has transformed from a small village into education hub for the past 2 decades. Rapid development and population growth had led to speedy growth in water demand. The situation is getting worse as the pipes are deteriorating due to pipe aging. Therefore, there is a need to study the adequacy of water supply and relationships among roughness coefficient (C) values in Hazen Williams’ Equation with head loss and water pressure due to pipe aging at Uni-Central, a residential area located at Samarahan Sarawak. Investigations were carried out with Ductile Iron, Abestos Cement and Cast Iron pipes at age categories of 0 - 10 years, 10 - 30 years, 30 - 50 years, 50 - 70 years and >70 years. Six critical nodes named as A, B, C, D, E and F were identified to study the water pressure and head loss. Model was developed with InfoWorks Water Supply (WS) Pro software. The impact of pipe aging and materials to water pressure and head loss was not significant at Nodes A, B, C and F. However, max water pressure at Nodes D and F were only reaching 6.30 m and 7.30 m, respectively for all investigations. Therefore, some improvement works are required. Results also show that Asbestos Cement pipe has the least impact on the head loss and water pressure, followed by Ductile Iron pipe and lastly Cast Iron pipe. Simulation results also revealed that older pipes have higher roughness coefficients, indicated with lower “C” values, thus increase the head loss and reduce the water pressure. In contrast, as “C” values increased, head loss will be reduced and water pressure will be increased.
文摘AIM: To analyze changes of the optic nerve head(ONH) and peripapillary region during intraocular pressure(IOP) elevation in patients using spectral domain optical coherence tomography(SD-OCT).METHODS: Both an optic disc 200×200 cube scan and a high-definition 5-line raster scan were obtained from open angle glaucoma patients presented with monocular elevation of IOP(≥30 mm Hg) using SD-OCT. Additional baseline characteristics included age, gender, diagnosis,best-corrected visual acuity, refractive error, findings of slit lamp biomicroscopy, findings of dilated stereoscopic examination of the ONH and fundus, IOP, pachymetry findings, and the results of visual field.RESULTS: The 24 patients were selected and divided into two groups: group 1 patients had no history of IOP elevation or glaucoma(n =14), and group 2 patients did have history of IOP elevation or glaucoma(n =10). In each patient, the study eye with elevated IOP was classified into group H(high), and the fellow eye was classified into group L(low). The mean deviation(MD)differed significantly between groups H and L when all eyes were considered(P =0.047) and in group 2(P =0.042), not in group 1(P =0.893). Retinal nerve fiber layer(RNFL) average thickness(P =0.050), rim area(P =0.015),vertical cup/disc ratio(P =0.011), cup volume(P =0.028),inferior quadrant RNFL thickness(P =0.017), and clockhour(1, 5, and 6) RNFL thicknesses(P =0.050, 0.012, and0.018, respectively), cup depth(P =0.008), central prelaminar layer thickness(P =0.023), mid-inferior prelaminar layer thickness(P =0.023), and nasal retinal slope(P =0.034)were significantly different between the eyes with groups H and L.CONCLUSION:RNFLaveragethickness,rim area,vertical cup/disc ratio, cup volume, inferior quadrant RNFL thickness, and clock-hour(1, 5, and 6) RNFL thicknesses significantly changed during acute IOP elevation.
基金NSFC(51101142 and 50821001)New Century Excellent Talents in University of Ministry of Education of China(NCET-12-0690)+1 种基金Hebei province scientific program(13961002D and Y2012019)Hebei Province Technology Foundation for Selected Overseas Chinese and Outstanding Young Scholar.
文摘Super-high pressure(SHP)technique plays an increasing role in the fields of materials science and engineering.Herein,the Mg_(97)Zn_(1)Y_(2) alloy was heat-treated under SHP(6 GPa)by cubic-anvil large-volume press with six rams for 2 h in the temperature range of 500–1200℃.The microstructure and mechanical properties were investigated.The results indicated that the as-cast sample consists of α-Mg equiaxed dendrites and continuous lamellar long period stacking ordered(LPSO)phase in grain boundaries.After the SHP treatment,the LPSO phase is gradually replaced by eutectic phase(Mg,Zn)_(3)Y with increasing temperature.The microhardness and strength of sample prepared at 1100℃ under SHP treatment are significantly improved compared with the as-cast one at room temperature.The improved mechanical behaviors are mainly attributed to LPSO phase kink-banding strengthening at low temperature and the precipitation strengthening of a large amount of fine(Mg,Zn)_(3)Y particles at high temperature after SHP treatment.It reveals the SHP is an effective approach to prepare high performance Mg alloys.
文摘The design operating conditions of rubber dams were analyzed,and it is found that the operating conditions are similar to the actual operating conditions of changes in the internal pressure ratio of a specific rubber dam bag in the process of filling and draining. Based on this,the linear relationship curve between the internal pressure head H0 and the real-time dam height H and its approximate analytical formula can be obtained,which can be used as a supplement and correction method for the measurement method of real-time dam height during rubber dam operation,and provides reference for rubber dam project managers.
文摘AIM: To describe a newly-recognized entity, illustrated by five cases of glaucoma in whom trauma to the head, but not the eye, resulted in marked, transient elevation of intraocular pressure (IOP). METHODS: Retrospective case series. Chart review. RESULTS: All five cases had a diagnosis of primary open-angle glaucoma prior to the experience of trauma to the head. All cases had an unusual elevation of IOP (around 70 percent) for days to weeks following the trauma, after which the IOP fell to pre-accident levels. No cause other than the trauma could be determined. CONCLUSION: The relationship between head trauma and elevation of IOP appears real.
文摘Foot pressure measurements were performed during standing and level walkingon a series of 30 normal subjects (15 males, 15 females, a total of 60 feet) with amean age of 37.6 yrs and a mean body weight of 66.3 kg. A significant difference wasfound in the peak pressure under the second metatarsal head between males and femaleswith females showing higher pressures than males daring walking (P【0. 01). The meanpeak pressure and standard deviation for all 7 areas selected for 30 adult subjects duringstanding and walding were obtained. The rise time to peak pressure at each selected areafor walking was recorded and analysed. The practical application and clinical significanceof these data were also discussed.
文摘Normal pressure hydrocephalus is a devious phenomenon. It is a disease that is difficult to diagnose and difficult to treat, the only treatment being a ventriculo-peritoneal shunt, though good shunting results rarely pass a 70% level of effectiveness. We need to understand its pathophysiology better before things will improve. Although some colleagues know it as a possible “reversible dementia” others hardly know about its existence. Solutions would also have value for the general understanding of hydrocephalus of other types. Many theories have been published recently in the search for the missing pieces in this puzzle and I feel that my own postulations could turn out to be useful. After years of diagnosing and operating on hydrocephalus patients I propose that: 1) There is reason to believe that patients with the Apoprotein E3/3 genotype and a high head size percentile are particularly vulnerable to developing idiopathic normal pressure hydrocephalus (iNPH). 2) The classical theory that the arachnoid granulations (AG) transport cerebrospinal fluid (CSF) into the venous circulation is wrong. I postulate, that the AG essentially are sensors, registering the pressure differences between the CSF in the subarachnoidal space at the top of the skull and the venous pressure in the sagittal sinus. The AG’s endothelium produces nitric oxide (NO) as a messenger that is received by the vagus nerve at the jugular foramen. 3) The disease has its fundamental pathology in the subpial space in the large cisternas and along the large vessels under the brain. Here the intravenous absorption of cerebrospinal fluid (CSF) takes place. Cerebrospinal fluid is transported into the subpial venules and veins, driven by the pulse pressure of the subpial arteries. Morphological changes in the pial/subpial anatomy explain the existence of acquired normal pressure hydrocephalus (aNPH).