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
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
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
In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and pro...In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and process with computer graphics parameters design. The results that, as long as the appropriate parameters, using the above method not only can punch the square hole, can also be processed triangle, the five angle and hexagonal regular polygon holes. The square hole processing method can provide theoretical basis and engineering reliable reference for related engineering and technical personnel.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.
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.
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In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and process with computer graphics parameters design. The results that, as long as the appropriate parameters, using the above method not only can punch the square hole, can also be processed triangle, the five angle and hexagonal regular polygon holes. The square hole processing method can provide theoretical basis and engineering reliable reference for related engineering and technical personnel.
