Heat exchanger is an important equipment used in process industries for cooling and heating purposes. Its design configuration which involves the flow of cold and hot fluids within the exchanger subjects it to corrosi...Heat exchanger is an important equipment used in process industries for cooling and heating purposes. Its design configuration which involves the flow of cold and hot fluids within the exchanger subjects it to corrosion attack. The article utilized the principle of mass and energy conservation in the development of weight and temperature models to study the effect of corrosion on mild steel coupon inside the exchanger containing water and Mono ethanol amine (MEA). The models developed were resolved analytically using Laplace Transform and simulated using Excel as simulation tool and data obtained from experiment in the laboratory to obtain profiles of weight loss and temperature as a function of time. The weight loss and performance of mild steel under various corrosive conditions were examined which indicates the effect of corrosion on the mild steel heat exchanger in water and MEA media. The result shows that water is more corrosive than MEA at higher temperatures and at lower temperatures of 35°C and 1 atm, MEA has inhibitive properties than water as indicated by the weight loss result with time. The comparative analysis between the results obtained from the model simulation and experimental results shows that the result obtained from the model is more reliable and demonstrated better performance characteristics as it clearly shows mild steel heat exchanger experiences more corrosive effect in water medium than MEA at higher temperatures. And at lower temperatures, MEA becomes more inhibitive and less corrosive than water. The model simulation results correlate with various literatures and hence, it is valid for future referencing.展开更多
Nonlinear effect is of importance to waves propagating from deep water to shallow water. The non-linearity of waves is widely discussed due to its high precision in application. But there are still some problems in de...Nonlinear effect is of importance to waves propagating from deep water to shallow water. The non-linearity of waves is widely discussed due to its high precision in application. But there are still some problems in dealing with the nonlinear waves in practice. In this paper, a modified form of mild-slope equation with weakly nonlinear effect is derived by use of the nonlinear dispersion relation and the steady mild-slope equation containing energy dissipation. The modified form of mild-slope equation is convenient to solve nonlinear effect of waves. The model is tested against the laboratory measurement for the case of a submerged elliptical shoal on a slope beach given by Berkhoff et al. The present numerical results are also compared with those obtained through linear wave theory. Better agreement is obtained as the modified mild-slope equation is employed. And the modified mild-slope equation can reasonably simulate the weakly nonlinear effect of wave propagation from deep water to coast.展开更多
Through investigating the effect of mild hypothermia on activity of nitric oxide snythase (NOS) in cortical neurons and glycemia levels of neonatal rats with hypoxic ischemic brain damage (HIBD). We studied the mecha...Through investigating the effect of mild hypothermia on activity of nitric oxide snythase (NOS) in cortical neurons and glycemia levels of neonatal rats with hypoxic ischemic brain damage (HIBD). We studied the mechanism of protecting hypoxic ischemic neurons of mild hypothermia. We established neonatal rat HIBD models, used NOS immunohistochemistry and glycemia determination by micromethod. The number of cortical NOS positive neurons after hypoxic ischemia was significantly decreased as compared with controls. The glycemia levels was significantly increased than that controls. No significant difference was found in number of cortical NOS positive neurons and glycemia levels between 31℃ and 34℃ mild hypothemia. The results imply that hypothermia can decrease overproduction of NO through inhibiting the increase of the activity of NOS, and increase the glycemia levels, thus protect the hypoxic ischemic neurons.展开更多
This work investigates the relative aggressiveness of nitrate solutions at different pH values on mild steel towards stress corrosion cracking (SCC) and general corrosion. Electrochemical behavior and stress corrosion...This work investigates the relative aggressiveness of nitrate solutions at different pH values on mild steel towards stress corrosion cracking (SCC) and general corrosion. Electrochemical behavior and stress corrosion cracking sus-ceptibility measurements were carried out in 52 Wt% ammonium nitrate solutions at 368° K and various pH values ranging from 0.77 to 9.64. Constant load stress corrosion test at 90% yield stress was conducted. Tested specimens were prepared and examined using the scanning electron microscope (SEM). The potentiodynamic polarization curves for different pH values again emphasized the validity of the gravimetric measurements and hence the mechanism of cracking was attributed to the stress that assisted the dissolution process.展开更多
To study the effect of mild hypothermia on glucose metabolism and glycerol of brain tissue in patients with severe traumatic brain injury (sTBI).Methods All 33 patients with sTBI(GCS≤8) were randomly divided into hyp...To study the effect of mild hypothermia on glucose metabolism and glycerol of brain tissue in patients with severe traumatic brain injury (sTBI).Methods All 33 patients with sTBI(GCS≤8) were randomly divided into hypothermic group and control group.Microdialysis catheters were inserted into the cerebral cortex of perilesion,relative normal brain tissue and subcutaneous tissue of abdomen in order to analyze the concentrations of lactate/pyruvate (L/P),lactate/glucose (L/G) and the glycerol(Gly) in extracellular fluid (ECF).Results In comparison with the control group,the concentration of L/G,L/P and Gly in periphery and that of L/P in ECF of the “normal brain tissue” were significantly decreased in the hypothermic group.In control group,concentration of L/G,L/P and Gly in periphery were higher than those in relative normal brain.In the hypothermic group,L/P concentration in periphery was higher than that in relative normal brain.Conclusion Mild hypothermia protects brain by decreasing concentrations of L/G,L/P and Gly in periphery and L/P concentration in “normal brain tissue”.The energy crisis and membrane phospholipid breakage in periphery are easier to happen after TBI,where mild hypothermia exerts significant protgective role.12 refs,3 tabs.展开更多
The effect of varying the temperature and the concentration of ammonium nitrate solution on the stress corrosion cracking (SCC) susceptibility of mild steel is studied. An increase in the temperature causes a decrease...The effect of varying the temperature and the concentration of ammonium nitrate solution on the stress corrosion cracking (SCC) susceptibility of mild steel is studied. An increase in the temperature causes a decrease in the stress corrosion life. It appears that the susceptibility in the range 368 K to 380 K was greater than at other temperatures. Near the boiling point corrosion and stress corrosion occurs, at the boiling point, the cracking was associated with a high rate of general corrosion. Microscopic examination after stress corrosion testing in 10Wt%, 20Wt%, and 52Wt% NH4NO3 solution revealed that in all cases there was severe intergranular attack, especially at the high concentration.展开更多
AIM: To assess the prevalence of mild gastrointestinal disorders in milk-fed infants in paediatric practice, and to evaluate the effectiveness and satisfaction with dietetic treatment.METHODS: A cross-sectional epidem...AIM: To assess the prevalence of mild gastrointestinal disorders in milk-fed infants in paediatric practice, and to evaluate the effectiveness and satisfaction with dietetic treatment.METHODS: A cross-sectional epidemiological study was first carried out. A total of 285 paediatricians included 3487 children seen during a period of one week. In a second phase an observational, prospective and multicentre study was conducted and 2069 milk-fed infants with mild gastrointestinal disorders (colic, constipation, regurgitation and diarrhoea) were included. There was a baseline visit (start of treatment) and a final visit four weeks later. The effectiveness of the various Novalac formulas, as well as the satisfaction of the parents/tutors and paediatricians with the dietetic treatment were assessed at the final visit.RESULTS: The prevalence of mild gastrointestinal disorders was 27.8% of all paediatrician consultations (9.2%, 7.8%, 6.1% and 4.6% in relation to colic, constipation, regurgitation and diarrhoea, respectively). The several Novalac adapted milk formulas resolved 88.4% of the mild gastrointestinal disorders. Depending on the type of disorder, differences in response rate were observed. The highest effectiveness was recorded with respect to diarrhoea (92.6%), followed by constipation (91.6%), colic (87.6%) and regurgitation (81%). Overall, 91% of the paediatricians and 88.8% of the parents/tutors were satisfied or very satisfied with the Novalac adapted milk formulas.CONCLUSION: Mild gastrointestinal disorders show a high prevalence in paediatric practice. The Novalac adapted milk formulas have been shown to be effective in treating mild gastrointestinal disorders in milk-fed infants in the context of routine clinical practice.展开更多
文摘Heat exchanger is an important equipment used in process industries for cooling and heating purposes. Its design configuration which involves the flow of cold and hot fluids within the exchanger subjects it to corrosion attack. The article utilized the principle of mass and energy conservation in the development of weight and temperature models to study the effect of corrosion on mild steel coupon inside the exchanger containing water and Mono ethanol amine (MEA). The models developed were resolved analytically using Laplace Transform and simulated using Excel as simulation tool and data obtained from experiment in the laboratory to obtain profiles of weight loss and temperature as a function of time. The weight loss and performance of mild steel under various corrosive conditions were examined which indicates the effect of corrosion on the mild steel heat exchanger in water and MEA media. The result shows that water is more corrosive than MEA at higher temperatures and at lower temperatures of 35°C and 1 atm, MEA has inhibitive properties than water as indicated by the weight loss result with time. The comparative analysis between the results obtained from the model simulation and experimental results shows that the result obtained from the model is more reliable and demonstrated better performance characteristics as it clearly shows mild steel heat exchanger experiences more corrosive effect in water medium than MEA at higher temperatures. And at lower temperatures, MEA becomes more inhibitive and less corrosive than water. The model simulation results correlate with various literatures and hence, it is valid for future referencing.
文摘Nonlinear effect is of importance to waves propagating from deep water to shallow water. The non-linearity of waves is widely discussed due to its high precision in application. But there are still some problems in dealing with the nonlinear waves in practice. In this paper, a modified form of mild-slope equation with weakly nonlinear effect is derived by use of the nonlinear dispersion relation and the steady mild-slope equation containing energy dissipation. The modified form of mild-slope equation is convenient to solve nonlinear effect of waves. The model is tested against the laboratory measurement for the case of a submerged elliptical shoal on a slope beach given by Berkhoff et al. The present numerical results are also compared with those obtained through linear wave theory. Better agreement is obtained as the modified mild-slope equation is employed. And the modified mild-slope equation can reasonably simulate the weakly nonlinear effect of wave propagation from deep water to coast.
文摘Through investigating the effect of mild hypothermia on activity of nitric oxide snythase (NOS) in cortical neurons and glycemia levels of neonatal rats with hypoxic ischemic brain damage (HIBD). We studied the mechanism of protecting hypoxic ischemic neurons of mild hypothermia. We established neonatal rat HIBD models, used NOS immunohistochemistry and glycemia determination by micromethod. The number of cortical NOS positive neurons after hypoxic ischemia was significantly decreased as compared with controls. The glycemia levels was significantly increased than that controls. No significant difference was found in number of cortical NOS positive neurons and glycemia levels between 31℃ and 34℃ mild hypothemia. The results imply that hypothermia can decrease overproduction of NO through inhibiting the increase of the activity of NOS, and increase the glycemia levels, thus protect the hypoxic ischemic neurons.
文摘This work investigates the relative aggressiveness of nitrate solutions at different pH values on mild steel towards stress corrosion cracking (SCC) and general corrosion. Electrochemical behavior and stress corrosion cracking sus-ceptibility measurements were carried out in 52 Wt% ammonium nitrate solutions at 368° K and various pH values ranging from 0.77 to 9.64. Constant load stress corrosion test at 90% yield stress was conducted. Tested specimens were prepared and examined using the scanning electron microscope (SEM). The potentiodynamic polarization curves for different pH values again emphasized the validity of the gravimetric measurements and hence the mechanism of cracking was attributed to the stress that assisted the dissolution process.
文摘To study the effect of mild hypothermia on glucose metabolism and glycerol of brain tissue in patients with severe traumatic brain injury (sTBI).Methods All 33 patients with sTBI(GCS≤8) were randomly divided into hypothermic group and control group.Microdialysis catheters were inserted into the cerebral cortex of perilesion,relative normal brain tissue and subcutaneous tissue of abdomen in order to analyze the concentrations of lactate/pyruvate (L/P),lactate/glucose (L/G) and the glycerol(Gly) in extracellular fluid (ECF).Results In comparison with the control group,the concentration of L/G,L/P and Gly in periphery and that of L/P in ECF of the “normal brain tissue” were significantly decreased in the hypothermic group.In control group,concentration of L/G,L/P and Gly in periphery were higher than those in relative normal brain.In the hypothermic group,L/P concentration in periphery was higher than that in relative normal brain.Conclusion Mild hypothermia protects brain by decreasing concentrations of L/G,L/P and Gly in periphery and L/P concentration in “normal brain tissue”.The energy crisis and membrane phospholipid breakage in periphery are easier to happen after TBI,where mild hypothermia exerts significant protgective role.12 refs,3 tabs.
文摘The effect of varying the temperature and the concentration of ammonium nitrate solution on the stress corrosion cracking (SCC) susceptibility of mild steel is studied. An increase in the temperature causes a decrease in the stress corrosion life. It appears that the susceptibility in the range 368 K to 380 K was greater than at other temperatures. Near the boiling point corrosion and stress corrosion occurs, at the boiling point, the cracking was associated with a high rate of general corrosion. Microscopic examination after stress corrosion testing in 10Wt%, 20Wt%, and 52Wt% NH4NO3 solution revealed that in all cases there was severe intergranular attack, especially at the high concentration.
文摘目的将共享随机效应模型(shared random-effect model,SREM)应用于轻度认知障碍(mild cognitive impairment,MCI)向认知正常(normal cognition,NC)逆转的研究,比较不同纵向认知标志物对MCI逆转的预测性能,并评价影响因素的协变量效应。方法SREM模型包括两个子模型,其中纵向子模型采用线性混合效应模型对纵向认知标志物的变化轨迹建模,生存子模型采用比例风险模型对生存过程建模。基于对数似然函数值和信息准则进行模型拟合优度检验,采用ROC曲线下面积(area under the curve,AUC)评价不同纵向认知标志物(MMSE、CDRSB、FAQ、ADAS11、ADAS13和ADASQ4)对MCI逆转的预测性能;同时进行纵向子模型和生存子模型的影响因素分析。结果843名MCI患者中72名(8.54%)在随访结束后逆转为NC。以spline-PH-GH参数分布为基准风险函数的SREM模型对数似然函数值最大,AIC和BIC最小;以CDRSB为纵向认知标志物建立的SREM模型拟合最好,在不同时间的AUC值均表现良好,范围为0.797~0.852,且预测误差最小,范围为0.0427~0.0429;年龄、性别、受教育程度、婚姻状况和APOEε4基因均会影响MCI患者的认知功能和日常活动功能,六种纵向认知标志物均会影响MCI患者的逆转。结论CDR评分对MCI患者的认知功能和逆转预测性能最佳;认知功能和日常活动功能可作为MCI逆转的动态监测指标。
文摘AIM: To assess the prevalence of mild gastrointestinal disorders in milk-fed infants in paediatric practice, and to evaluate the effectiveness and satisfaction with dietetic treatment.METHODS: A cross-sectional epidemiological study was first carried out. A total of 285 paediatricians included 3487 children seen during a period of one week. In a second phase an observational, prospective and multicentre study was conducted and 2069 milk-fed infants with mild gastrointestinal disorders (colic, constipation, regurgitation and diarrhoea) were included. There was a baseline visit (start of treatment) and a final visit four weeks later. The effectiveness of the various Novalac formulas, as well as the satisfaction of the parents/tutors and paediatricians with the dietetic treatment were assessed at the final visit.RESULTS: The prevalence of mild gastrointestinal disorders was 27.8% of all paediatrician consultations (9.2%, 7.8%, 6.1% and 4.6% in relation to colic, constipation, regurgitation and diarrhoea, respectively). The several Novalac adapted milk formulas resolved 88.4% of the mild gastrointestinal disorders. Depending on the type of disorder, differences in response rate were observed. The highest effectiveness was recorded with respect to diarrhoea (92.6%), followed by constipation (91.6%), colic (87.6%) and regurgitation (81%). Overall, 91% of the paediatricians and 88.8% of the parents/tutors were satisfied or very satisfied with the Novalac adapted milk formulas.CONCLUSION: Mild gastrointestinal disorders show a high prevalence in paediatric practice. The Novalac adapted milk formulas have been shown to be effective in treating mild gastrointestinal disorders in milk-fed infants in the context of routine clinical practice.
