During the low-pressure casting of extra-large size C95800 copper alloy components,traditional linear pressurization technique leads to a rapid surge of liquid metal inlet velocity at the regions where the mold cavity...During the low-pressure casting of extra-large size C95800 copper alloy components,traditional linear pressurization technique leads to a rapid surge of liquid metal inlet velocity at the regions where the mold cavity cross-section enlarges.This rapid increasement of liquid metal inlet velocity causes serious entrapment of gas and oxide films,and results in various casting defects such as the bifilm defects.These defects detrimentally deteriorate mechanical properties of the castings.To address this issue,an innovative nonlinear pressurization strategy timely matching to the casting structure was proposed.The pressurization rate decreases at sections where the cross-section widens,but it gradually increases as the liquid metal level rises.By this way,the inlet velocity remains below a critical threshold to prevent the entrapment of gas and oxide films.Comparative analyses involving numerical simulations and casting verification illustrate that the nonlinear pressurization technique,compared to the linear pressurization,effectively diminishes both the size and number of bifilm defects.Furthermore,the nonlinear pressurization method enhances the casting yield strength by 10%,tensile strength by 14%,and elongation by 10%.Examination through scanning electron microscopy highlights that the bifilm defects arising from the linear pressurization process result in the reduction of the castings’mechanical properties.These observations underscore the efficacy of nonlinear pressurization in enhancing the quality and reliability of gigantic castings,as exemplified by a 5.4-ton extra-large sized C95800 copper alloy propeller hub with complex structures in the current study.展开更多
Kafka shows people the image of the gigantic insect according to the description of characteristics of its figure,action,language,food,etc and psychology.It seems to be absurd,but this phenomena discloses the reality ...Kafka shows people the image of the gigantic insect according to the description of characteristics of its figure,action,language,food,etc and psychology.It seems to be absurd,but this phenomena discloses the reality of people's alienation in that society.The protagonist Gregor is similar to the gigantic insect in weakness,loneliness and the tragedy of the two is just an epitome of that times.Gregor,like the gigantic insect,cannot control his own fate and can just be trapped in the disaster caused by the cruel society of intense industrialization,which leads to his tragic end.展开更多
BACKGROUND Gigantism,characterized by excessive growth and height is due to increased secretion of growth hormone,most commonly from a pituitary adenoma.In addition to the surgical and anesthetic complexity,the extrem...BACKGROUND Gigantism,characterized by excessive growth and height is due to increased secretion of growth hormone,most commonly from a pituitary adenoma.In addition to the surgical and anesthetic complexity,the extreme stature of these patients presents a unique challenge for kidney transplantation in deciding whether to proceed with a single or dual kidney transplantation.The lack of relevant literature further adds to the dilemma.CASE SUMMARY A 45-year-old patient with untreated gigantism and end stage renal failure on renal replacement therapy was waitlisted for a deceased donor dual kidney transplantation due to the extreme physical stature(Height-247 cm and weight-200 kg).He was offered 2 kidneys from a 1-0-1 HLA mismatched 24-year-old DCD donor(Height-179 cm and weight-75 kg),and was planned for a bilateral retroperitoneal implantation into the recipient external iliac vessels.The immunosuppression consisted of alemtuzumab induction(50 mg)and steroidfree maintenance with tacrolimus.The donor’s right kidney was uneventfully implanted extra-peritoneally into the right external iliac vessels.On contralateral exposure,the left common and external iliac arteries were ectatic and frail.A complex vascular reconstruction was not preferred in order to preserve the arterial supply to the left lower limb,to minimise the cold ischemia time and prevent additional warm ischemic insult to the second kidney.Hence,it was decided not to proceed with dual transplantation.Amidst concerns of nephron mass insufficiency,the graft function was remarkable with a serum creatinine of 120μmol/L within a month from transplantation and 94μmol/L at 1-year post transplantation,and without proteinuria.CONCLUSION To our knowledge,this is the first case report on kidney transplantation in gigantism.Although it is believed that dual kidney transplantation is ideal,a single kidney transplantation from an appropriately selected donor can provide sufficient functioning nephron mass in patients with gigantism.展开更多
基金supported by the National Natural Science Foundation of China(Granted Nos.51827801,52371152)the Foundation of National Key Laboratory of Precision Hot Processing of Metals(Granted No.DCQQ2790100724).
文摘During the low-pressure casting of extra-large size C95800 copper alloy components,traditional linear pressurization technique leads to a rapid surge of liquid metal inlet velocity at the regions where the mold cavity cross-section enlarges.This rapid increasement of liquid metal inlet velocity causes serious entrapment of gas and oxide films,and results in various casting defects such as the bifilm defects.These defects detrimentally deteriorate mechanical properties of the castings.To address this issue,an innovative nonlinear pressurization strategy timely matching to the casting structure was proposed.The pressurization rate decreases at sections where the cross-section widens,but it gradually increases as the liquid metal level rises.By this way,the inlet velocity remains below a critical threshold to prevent the entrapment of gas and oxide films.Comparative analyses involving numerical simulations and casting verification illustrate that the nonlinear pressurization technique,compared to the linear pressurization,effectively diminishes both the size and number of bifilm defects.Furthermore,the nonlinear pressurization method enhances the casting yield strength by 10%,tensile strength by 14%,and elongation by 10%.Examination through scanning electron microscopy highlights that the bifilm defects arising from the linear pressurization process result in the reduction of the castings’mechanical properties.These observations underscore the efficacy of nonlinear pressurization in enhancing the quality and reliability of gigantic castings,as exemplified by a 5.4-ton extra-large sized C95800 copper alloy propeller hub with complex structures in the current study.
文摘Kafka shows people the image of the gigantic insect according to the description of characteristics of its figure,action,language,food,etc and psychology.It seems to be absurd,but this phenomena discloses the reality of people's alienation in that society.The protagonist Gregor is similar to the gigantic insect in weakness,loneliness and the tragedy of the two is just an epitome of that times.Gregor,like the gigantic insect,cannot control his own fate and can just be trapped in the disaster caused by the cruel society of intense industrialization,which leads to his tragic end.
文摘BACKGROUND Gigantism,characterized by excessive growth and height is due to increased secretion of growth hormone,most commonly from a pituitary adenoma.In addition to the surgical and anesthetic complexity,the extreme stature of these patients presents a unique challenge for kidney transplantation in deciding whether to proceed with a single or dual kidney transplantation.The lack of relevant literature further adds to the dilemma.CASE SUMMARY A 45-year-old patient with untreated gigantism and end stage renal failure on renal replacement therapy was waitlisted for a deceased donor dual kidney transplantation due to the extreme physical stature(Height-247 cm and weight-200 kg).He was offered 2 kidneys from a 1-0-1 HLA mismatched 24-year-old DCD donor(Height-179 cm and weight-75 kg),and was planned for a bilateral retroperitoneal implantation into the recipient external iliac vessels.The immunosuppression consisted of alemtuzumab induction(50 mg)and steroidfree maintenance with tacrolimus.The donor’s right kidney was uneventfully implanted extra-peritoneally into the right external iliac vessels.On contralateral exposure,the left common and external iliac arteries were ectatic and frail.A complex vascular reconstruction was not preferred in order to preserve the arterial supply to the left lower limb,to minimise the cold ischemia time and prevent additional warm ischemic insult to the second kidney.Hence,it was decided not to proceed with dual transplantation.Amidst concerns of nephron mass insufficiency,the graft function was remarkable with a serum creatinine of 120μmol/L within a month from transplantation and 94μmol/L at 1-year post transplantation,and without proteinuria.CONCLUSION To our knowledge,this is the first case report on kidney transplantation in gigantism.Although it is believed that dual kidney transplantation is ideal,a single kidney transplantation from an appropriately selected donor can provide sufficient functioning nephron mass in patients with gigantism.
