The present work compares microstructures of hot work steels made by different processes, that is, by sprayforming,by casting, and a commercially supplied H13 steel. Material benefits are recognized by sprayforming ho...The present work compares microstructures of hot work steels made by different processes, that is, by sprayforming,by casting, and a commercially supplied H13 steel. Material benefits are recognized by sprayforming hot working tools such as die inserts for hot forging. The sprayformed hot work steels present a fine and homogeneous microstructure,which implies that, at a similar toughness level, the sprayformed steel can be higher alloyed, so that the thermal fatigue and wear resistance at elevated temperatures can be improved. A series of steels with higher vanadium content than commercial hot work steels are developed. There are no segregation and carbide network problems usually encountered in conventional ingot/forging processed high-vanadium steels. Microstructure and hardness of the new sprayformed steels are studied under different heat treatment conditions. It is justified that these sprayformed steels can be directly used for tooling without high temperature hardening. Sprayforming the tool steels onto a precision ceramic mould is demonstrated to extend the technoeconomical benefits, so that a net shape production tool can be rapidly made.Features of the rapid tooling process are also discussed.展开更多
A simple and rapid assay for the detection of Classical swine fever virus(CSFV)was established using reverse transcription loop-mediated isothermal amplification(RT-LAMP).This study describes the amplification of the ...A simple and rapid assay for the detection of Classical swine fever virus(CSFV)was established using reverse transcription loop-mediated isothermal amplification(RT-LAMP).This study describes the amplification of the genomic RNA of CSFV under isothermal conditions(63℃)within one hour,using a set of six primers(two outer primers,two inner primers and two loop primers).This RT-LAMP assay showed 100-fold higher sensitivity than the standard RT-PCR method and identified eighteen additional positive cases that were negative when tested by RT-PCR.This RT-LAMP was able to detect all the 13 strains of CSFV but not the BVDV.PRRSV.SIV. PRV-PCV,thus showed a good specificity.Products amplified by RT-LAMP can be visualized by agarose gel electrophoresis and in addition,either as a white precipitate at the bottom of the tube after a pulse spin or as a color change when dyed with SYBR Green I which are visible to the naked eye.Because RT-LAMP is low-cost and produces rapid results,it has the potential to be an excellent tool for CSFV surveillance in the field,especially in developing countries.展开更多
A process to convert models made by rapid prototypi ng techniques like SL (stereolitography) and LOM (laminated object manufacturing) or by conventional techniques (silicones, resins, wax, etc.) into metallic mould s ...A process to convert models made by rapid prototypi ng techniques like SL (stereolitography) and LOM (laminated object manufacturing) or by conventional techniques (silicones, resins, wax, etc.) into metallic mould s or tools has been developed. The main purpose of this technique is to rapidly obtain the first prototypes of parts, for plastics injection, forging or any oth er manufacturing process using the tools produced by casting a metal into a cera mic mould. Briefly, it can be said that the ceramic moulds are produced by mixing in variab le proportions, depending on the type of ceramics employed, strength and roughne ss desired, a ceramic mixture composed by alumina and/or zirconium silicates bon ded with silica coming from a liquid binder, based on ethyl silicate. A catalyst is added to the slurry in order to produce a sol-gel reaction. The liquid slur ry is poured into the box containing the mould to be reproduced. After a short p eriod of time, controlled by the amount of gelling agent, the ceramic mixture ac quires a rubber consistency. The pattern is removed from the ceramic mould, whic h is fired to stop the gelation reaction. After this stabilization the ceramic m ould is sintered at high temperatures in order to generate an inert mould wi th the desired strength in which almost all metallic alloys can be cast. The effect of ceramic materials (shape, granulometric distribution, chemical com position, etc.), processing parameters (proportion binder/ceramic/catalyst, sint ering conditions, etc.) and casting conditions (mould pre-heating temperature a nd pouring temperature) were studied in order to obtain metallic moulds or tools with tailored properties (high dimensional accuracy, low roughness and high mec hanical strength).展开更多
Objectives: Rapid and accurate identification of persons infected with SARS-CoV-2 which causes COVID-19 is key to managing the pandemic. The urgent need to scale up access to COVID-19 testing in Nigeria has led to the...Objectives: Rapid and accurate identification of persons infected with SARS-CoV-2 which causes COVID-19 is key to managing the pandemic. The urgent need to scale up access to COVID-19 testing in Nigeria has led to the government’s introduction of the use of COVID-19 Ag rapid diagnostic test (RDT) across various settings in the country. However, field performance evaluation of the rapid SARS-CoV-2 antigen detection test is required to be conducted periodically and compared with the gold standard real-time reverse transcription-polymerase chain reaction (RT-PCR) test for diagnosis of COVID-19 cases. Design: A prospective COVID-19 screening and un-blinded verification of the performance of the STANDARD Q COVID-19 Ag test kit. Setting: The rapid SARS-CoV-2 antigen detection test, Standard<sup>TM</sup> Q COVID-19 Ag kit was compared with the RT-PCR test for detection of SARS-CoV-2 in nasopharyngeal samples for COVID-19 screening from persons and personnel attending a national youth camp orientation exercise during the second wave of the COVID-19 outbreak (January to March 2021) in Ondo state, southwest Nigeria. Participants: Three hundred fifty-one persons and personnel were screened for COVID-19 infection. Results: Of 351 respondents screened, 68 (19.4%) were positive, and 264 (75.2%) were negative for both COVID-19 Ag RDT and RT-PCR assay. The rapid SARS-CoV-2 antigen detection test’s sensitivity and specificity were 78.16% (95% CI = 68.02% - 86.31%) and 100.0% (95% CI = 98.61% - 100.0%), respectively and the diagnostic accuracy was 94.59% (95% CI: 92 - 97). Respondents that were symptomatic had a higher test sensitivity of 78.6% (49.2 - 95.3) compared to those without symptoms 78.1% (66.9 - 86.9) (p Conclusions: Our study shows evidence that Standard<sup>TM</sup> Q COVID-19 Ag kit can be an appropriate rapid antigen test that could be used to screen for positive COVID-19 tests to guide decision-making for clinical management of persons infected with COVID-19, especially for closed settings and other clinical care settings.展开更多
The paper is to outline a new process for manufacturing rapid graphite electrode. It detailsthe steps in Providing integration with Rapid Prototyping (RP) into rapid electrode abrading Process.The key to this combinat...The paper is to outline a new process for manufacturing rapid graphite electrode. It detailsthe steps in Providing integration with Rapid Prototyping (RP) into rapid electrode abrading Process.The key to this combination is the successful model or patted creating using the RP technology.Significantly reduced lead-time, shortened learns curve, lowered revision changes cost and eliminatedor reduced mold polishing are the consequent results. high quality Electrical Discharge Machining(EDM) electrodes are sometimes difficult to be manufactured rapidly and are very time-consumingby conventional methods, even using Computer Numerical Control (CNC) machines. Abradingprovides a simple way to create etuemely detailed and complex electrode to make molds in toolingmaking industries. Integration with the rapid development of the Rapid Prototyping & Manufacturing(RP&M) technology, the rapid electrode abrading process has been regarded as one of the majorbreakthrough in tooling making technology.展开更多
文摘The present work compares microstructures of hot work steels made by different processes, that is, by sprayforming,by casting, and a commercially supplied H13 steel. Material benefits are recognized by sprayforming hot working tools such as die inserts for hot forging. The sprayformed hot work steels present a fine and homogeneous microstructure,which implies that, at a similar toughness level, the sprayformed steel can be higher alloyed, so that the thermal fatigue and wear resistance at elevated temperatures can be improved. A series of steels with higher vanadium content than commercial hot work steels are developed. There are no segregation and carbide network problems usually encountered in conventional ingot/forging processed high-vanadium steels. Microstructure and hardness of the new sprayformed steels are studied under different heat treatment conditions. It is justified that these sprayformed steels can be directly used for tooling without high temperature hardening. Sprayforming the tool steels onto a precision ceramic mould is demonstrated to extend the technoeconomical benefits, so that a net shape production tool can be rapidly made.Features of the rapid tooling process are also discussed.
基金The National Science and Technology supporting plan of the Eleventh Five-year(2006BAD06A18 and 2006BAD06A03)Beijing Natural Science Foundation(5072041)
文摘A simple and rapid assay for the detection of Classical swine fever virus(CSFV)was established using reverse transcription loop-mediated isothermal amplification(RT-LAMP).This study describes the amplification of the genomic RNA of CSFV under isothermal conditions(63℃)within one hour,using a set of six primers(two outer primers,two inner primers and two loop primers).This RT-LAMP assay showed 100-fold higher sensitivity than the standard RT-PCR method and identified eighteen additional positive cases that were negative when tested by RT-PCR.This RT-LAMP was able to detect all the 13 strains of CSFV but not the BVDV.PRRSV.SIV. PRV-PCV,thus showed a good specificity.Products amplified by RT-LAMP can be visualized by agarose gel electrophoresis and in addition,either as a white precipitate at the bottom of the tube after a pulse spin or as a color change when dyed with SYBR Green I which are visible to the naked eye.Because RT-LAMP is low-cost and produces rapid results,it has the potential to be an excellent tool for CSFV surveillance in the field,especially in developing countries.
文摘A process to convert models made by rapid prototypi ng techniques like SL (stereolitography) and LOM (laminated object manufacturing) or by conventional techniques (silicones, resins, wax, etc.) into metallic mould s or tools has been developed. The main purpose of this technique is to rapidly obtain the first prototypes of parts, for plastics injection, forging or any oth er manufacturing process using the tools produced by casting a metal into a cera mic mould. Briefly, it can be said that the ceramic moulds are produced by mixing in variab le proportions, depending on the type of ceramics employed, strength and roughne ss desired, a ceramic mixture composed by alumina and/or zirconium silicates bon ded with silica coming from a liquid binder, based on ethyl silicate. A catalyst is added to the slurry in order to produce a sol-gel reaction. The liquid slur ry is poured into the box containing the mould to be reproduced. After a short p eriod of time, controlled by the amount of gelling agent, the ceramic mixture ac quires a rubber consistency. The pattern is removed from the ceramic mould, whic h is fired to stop the gelation reaction. After this stabilization the ceramic m ould is sintered at high temperatures in order to generate an inert mould wi th the desired strength in which almost all metallic alloys can be cast. The effect of ceramic materials (shape, granulometric distribution, chemical com position, etc.), processing parameters (proportion binder/ceramic/catalyst, sint ering conditions, etc.) and casting conditions (mould pre-heating temperature a nd pouring temperature) were studied in order to obtain metallic moulds or tools with tailored properties (high dimensional accuracy, low roughness and high mec hanical strength).
文摘Objectives: Rapid and accurate identification of persons infected with SARS-CoV-2 which causes COVID-19 is key to managing the pandemic. The urgent need to scale up access to COVID-19 testing in Nigeria has led to the government’s introduction of the use of COVID-19 Ag rapid diagnostic test (RDT) across various settings in the country. However, field performance evaluation of the rapid SARS-CoV-2 antigen detection test is required to be conducted periodically and compared with the gold standard real-time reverse transcription-polymerase chain reaction (RT-PCR) test for diagnosis of COVID-19 cases. Design: A prospective COVID-19 screening and un-blinded verification of the performance of the STANDARD Q COVID-19 Ag test kit. Setting: The rapid SARS-CoV-2 antigen detection test, Standard<sup>TM</sup> Q COVID-19 Ag kit was compared with the RT-PCR test for detection of SARS-CoV-2 in nasopharyngeal samples for COVID-19 screening from persons and personnel attending a national youth camp orientation exercise during the second wave of the COVID-19 outbreak (January to March 2021) in Ondo state, southwest Nigeria. Participants: Three hundred fifty-one persons and personnel were screened for COVID-19 infection. Results: Of 351 respondents screened, 68 (19.4%) were positive, and 264 (75.2%) were negative for both COVID-19 Ag RDT and RT-PCR assay. The rapid SARS-CoV-2 antigen detection test’s sensitivity and specificity were 78.16% (95% CI = 68.02% - 86.31%) and 100.0% (95% CI = 98.61% - 100.0%), respectively and the diagnostic accuracy was 94.59% (95% CI: 92 - 97). Respondents that were symptomatic had a higher test sensitivity of 78.6% (49.2 - 95.3) compared to those without symptoms 78.1% (66.9 - 86.9) (p Conclusions: Our study shows evidence that Standard<sup>TM</sup> Q COVID-19 Ag kit can be an appropriate rapid antigen test that could be used to screen for positive COVID-19 tests to guide decision-making for clinical management of persons infected with COVID-19, especially for closed settings and other clinical care settings.
文摘The paper is to outline a new process for manufacturing rapid graphite electrode. It detailsthe steps in Providing integration with Rapid Prototyping (RP) into rapid electrode abrading Process.The key to this combination is the successful model or patted creating using the RP technology.Significantly reduced lead-time, shortened learns curve, lowered revision changes cost and eliminatedor reduced mold polishing are the consequent results. high quality Electrical Discharge Machining(EDM) electrodes are sometimes difficult to be manufactured rapidly and are very time-consumingby conventional methods, even using Computer Numerical Control (CNC) machines. Abradingprovides a simple way to create etuemely detailed and complex electrode to make molds in toolingmaking industries. Integration with the rapid development of the Rapid Prototyping & Manufacturing(RP&M) technology, the rapid electrode abrading process has been regarded as one of the majorbreakthrough in tooling making technology.
