Understanding the material flow facilitated by tool geometry in friction stir welds is challenging for quality weld production in industrial applications.The optimal tool shoulder and pin design combination,which play...Understanding the material flow facilitated by tool geometry in friction stir welds is challenging for quality weld production in industrial applications.The optimal tool shoulder and pin design combination,which plays a vital role in material flow was addressed.The flow of plasticized material was analyzed using a marker insert technique.The results show that the knurling shoulder design with square and hexagonal pin design facilitated constant stability force with reference to weld length/time.The uniform mixing and distribution of plasticized material were facilitated by the knurling shoulder design with square tool pin shape(TK)S(sticking length minimum)below which fragmented copper was observed.(TK)S tool facilitated higher mechanical properties for the welds,i.e.strength(182 MPa)and hardness(HV 78)in stir zone.展开更多
Background: Anatomic single bundle is a widely accepted technique for anterior cruciate ligament (ACL) reconstruction. The research question: are transverse pins safe to fix the ACL graft on the femoral side in anatom...Background: Anatomic single bundle is a widely accepted technique for anterior cruciate ligament (ACL) reconstruction. The research question: are transverse pins safe to fix the ACL graft on the femoral side in anatomic single bundle ACL reconstruction? Material and Methods: Ten cadaveric femoral dry bones were tested in this study. Thirty mm long sockets were prepared in the center of the anatomic ACL footprints. Transverse pin guide for soft tissue graft was used to prepare pin sites through the femoral sockets using three different positions. The positions (A) and (B) had a lateral entry point and differ in their inclination in relation to the joint line;while (A) has a 15° open laterally plane, (B) has a 15° closed laterally. The last position (C) had a medial entry point for the transverse pins. The relations of the transverse pins to the anatomic landmarks (lateral epicondyle and articular cartilage) in addition to the path of the pins within the femoral sockets were recorded. Results: Pins inserted while the guide in position (A) crossed the center of the femoral sockets and were fully seated within the bone of the distal femur. Distal pins inserted through inclination (B) were found to penetrate the posterior cortex of the distal femur proximal to the lateral femoral condyle. Pins inserted from the medial side (C) achieved central position through the femoral tunnel. The entry point for transverse pins through lateral entry points was very close to the attachment of the lateral collateral ligament at the lateral epicondyle while medial entry point avoided important structures. Conclusion: Transverse pins inserted through the lateral entry point carry the risk of penetrating the posterior cortex of the femur and/or damage the attachment of the lateral collateral ligament. Medial entry point may give a safer approach but needs further adjustments of the guides and clinical trials of the technique.展开更多
Heat transfer to pins swimming in non-isothermal fluidic systems is theoretically analyzed. Four different cases are considered: [A] pins aligned longitudinally in flowing fluid having constant temperature gradient, [...Heat transfer to pins swimming in non-isothermal fluidic systems is theoretically analyzed. Four different cases are considered: [A] pins aligned longitudinally in flowing fluid having constant temperature gradient, [B] pins aligned transversely in flowing fluid flow with constant temperature gradient, [C] pins moving longitudinally towards a heated surface, and [D] pins moving transversely towards the heated surface. The Appropriate unsteady energy transport equations are solved and closed form solutions for the fin temperatures are obtained. Accordingly, different performance indicators are calculated. It is found that heat transfer to the swimming fin increases as the fin thermal length, Peclet number and fluid temperature difference along the fin length increase. It decreases as fluid temperature index along the motion direction increases. Moreover, the swimming pins of case C are found to produce the maximum system effective thermal conductivity. In addition, pins of case B with thermal lengths above 11 produce system thermal conductivity independent on the thermal length. Meanwhile, pins of case A having thermal lengths above 10 produce system thermal conductivities less responsive to the thermal length. The system thermal conductivity is noticed to increase as the thermal length and Peclet number increase. Eventually, pins of case D produce system thermal conductivities that are independent on the transverse temperature. Finally, the results of this work provide a basis for modeling super convective fluidic systems that can be used in cooling of electronic components.展开更多
BACKGROUND Infection at the pin tract is a frequent and feared complication of external fixators(EF).The type of pin material and coatings have been regarded as possibly influencing infection rates.Over the last 20 ye...BACKGROUND Infection at the pin tract is a frequent and feared complication of external fixators(EF).The type of pin material and coatings have been regarded as possibly influencing infection rates.Over the last 20 years,few prospective clinical studies and systematic reviews addressed the role of coated pins on the rate of pin site infection in human clinical studies.AIM To assess the EF literature over the past 20 years on the clinical benefits of pins manufactured from varied materials and coating systems and their possible role in pin tract infection rates.METHODS We performed a systematic review according to the PRISMA and PICOS guidelines using four scientific platforms:PubMed,LiLacs,SciELO,and Cochrane.We searched the literature for related publications over the past 20 years.RESULTS A literature search yielded 29 articles,among which seven met the inclusion criteria.These studies compared stainless-steel pins and pins coated with hydroxyapatite(HA),titanium and silver.The pin tract infection definitions were arbitrary and not standardized among studies.Most studies included a low number of patients in the analysis and used a short follow-up time.Three metaanalyses were carried out,comparing stainless steel vs silver pins,stainless steel vs HA-coated pins,and titanium vs HA-coated pins.None of this analysis resulted in statistically significant differences in pin tract infection rates.CONCLUSION Currently,no clinical evidence supports the advantage of EF pins manufactured with materials other than stainless steel or coated over uncoated pins in reducing the rates of pin tract infections.A standardized definition of pin tract infection in external fixation is still lacking.展开更多
This work investigates the impact of biomechanical wear and abrasion on the antibiotic release profiles of hydroxyapatite (HA) coated fixation pins during their insertion into synthetic bone. Stainless steel fixation ...This work investigates the impact of biomechanical wear and abrasion on the antibiotic release profiles of hydroxyapatite (HA) coated fixation pins during their insertion into synthetic bone. Stainless steel fixation pins are coated with crystalline TiO2 by cathodic arc evaporation forming the bioactive layer for biomimetic deposition of Tobramycin containing HA. Tobramycin is either introduced by co-precipitation during HA formation or by adsorption-loading after HA deposition. The samples containing antibiotics are inserted into bone mimicking polyethylene foam after which the drug release is monitored using high performance liquid chromatography. This analysis shows that HA coating wear and delamination significantly decrease the amount of drug released during initial burst, but only marginally influence the sustained release period. Spalled coating fragments are found to remain within the synthetic bone material structure. The presence of HA within this structure supports the assumption that the local release of Tobramycin is not only expected to eliminate bacteria growth directly at the pin interface but as well at some distance from the implant. Furthermore, no negative effect of gamma sterilization could be observed on the drug release profile. Overall, the observed results demonstrate the feasibility of a multifunctional implant coating that is simultaneously able to locally deliver clinically relevant doses of antibiotics and an HA coating capable of promoting osteoconduction. This is a potentially promising step toward orthopaedic devices that combine good fixation with the ability to treat and prevent post-surgical infections.展开更多
Background: Pediatric supracondylar humerus fractures are the most common elbow fractures in children. Operative management includes closed reduction and placement of 2 to 3 laterally based pins. Occasionally, a media...Background: Pediatric supracondylar humerus fractures are the most common elbow fractures in children. Operative management includes closed reduction and placement of 2 to 3 laterally based pins. Occasionally, a medial pin is used to create a crossed fixation pattern, despite risk of nearly 10% iatrogenic ulnar nerve injury. The objective of this study was to assess the trends and outcomes in the operative management of pediatric supracondylar humerus fractures at a level one academic trauma center. Materials & Methods: A retrospective review was performed on all children sustaining a Gartland type II or III supracondylar humerus fractures treated by closed or open reduction and percutaneous pinning in 2006-2008 and 2009-2011 at a level one academic trauma center by two of the authors (JTR, LMT). Pin placement patterns were evaluated and compared based on year performed. Outcomes measured were rates of ulnar nerve symptoms, non-union, re-operation, and varus malalignment. Data analysis was performed using a Fisher exact test on STATA software. Results: A total of 49 patients met inclusion criteria. Of 22 patients treated in 2006-2008, 5 (23%) were type II and 17 (77%) were type III. From 2009-2011, 16 (59%) were type II and 11 (41%) were type III. Comparison of pinning pattern in type II fractures between 2006-2008 and 2009-2011 did not indicate statistical significance (p = 0.429). Comparison of pinning pattern in type III fractures during the same time period did show that there was a statistically significant decrease (p = 0.010) in the number of cross pin fixations. There were no ulnar nerve injuries, non-unions, re-operations, or varus malalignment in any patient on final follow-up. Conclusion: This study shows that there has been a significant decrease in cross pin fixation for pediatric type III supracondylar humerus fractures with equivalent clinical outcomes at a Level I trauma center. Furthermore, performing lateral pinning for type III fractures has eliminated the risk of iatrogenic ulnar nerve injury. Level of Evidence: Level III—Retrospective cohort study.展开更多
The patch antennas with an array of pins （pin array patch antennas） with excellent radiation characteristics are investigated for various substrate thicknesses. The radiation in the horizontal plane of a pin array p...The patch antennas with an array of pins （pin array patch antennas） with excellent radiation characteristics are investigated for various substrate thicknesses. The radiation in the horizontal plane of a pin array patch antenna is very small compared to that of a conventional patch antenna. And the increase of forward radiation and the decrease of backward radiation of a pin array patch antenna are obtained than those conventional one＇s. Also the half-power beamwidth of E -plane radiation pattern of a pin array patch antenna is narrower compared to that of the conventional so that the directivity is improved.展开更多
Background: Foreign body aspiration is a common yet preventable health problem. Headscarf pin aspiration is a unique example of aspirated foreign bodies in young Muslim women usually removed using the rigid bronchosco...Background: Foreign body aspiration is a common yet preventable health problem. Headscarf pin aspiration is a unique example of aspirated foreign bodies in young Muslim women usually removed using the rigid bronchoscope. However, the flexible bronchoscope is increasingly used for this purpose. This prospective study was conducted in Sulaimaniyah Teaching Hospital, Sulaimaniyah, Iraq and aimed to evaluate the usefulness of fiberoptic bronchoscope for removal of aspirated headscarf pins in view of the relevant literature. Methodology: Fifty female patients with headscarf pin aspiration were managed by fiberoptic bronchoscopy over an 8-year period (January 2008 to December 2015). The procedure was performed under local anesthesia and conscious sedation through the mouth. Results: The age ranged from 10 to 45 years with a mean of 27.5. All patients had cough, five had unilateral wheeze (10%) while haemoptysis occurred twice (4%). Fiberoptic bronchoscopy succeeded in 45 cases (90%). Rigid bronchoscopy under general anesthesia was necessary in (n = 4, 8%) while one patient (2%) required thoracotomy. ?Conclusion: Fiberoptic bronchoscopy is safe and effective in removal of aspirated headscarf pins and should be tried first.展开更多
Cooling methods are needed for turbine blade tips to ensure a long durability and safe operation.A common way to cool a tip is to use serpentine passages with 180-deg turn under the blade tip-cap taking advantage of t...Cooling methods are needed for turbine blade tips to ensure a long durability and safe operation.A common way to cool a tip is to use serpentine passages with 180-deg turn under the blade tip-cap taking advantage of the threedimensional turning effect and impingement like flow.Improved internal convective cooling is therefore required to increase the blade tip lifetime.In the present study,augmented heat transfer of an internal blade tip with pin-fin arrays has been investigated numerically using a conjugate heat transfer method.The computational domain includes the fluid region and the solid pins as well as the tip regions.Turbulent convective heat transfer between the fluid and pins,and heat conduction within pins and tip are simultaneously computed.The main objective of the present study is to observe the effect of the pin material on heat transfer enhancement of the pin-finned tips.It is found that due to the combination of turning,impingement and pin-fin crossflow,the heat transfer coefficient of a pin-finned tip is a factor of 2.9 higher than that of a smooth tip at the cost of an increased pressure drop by less than 10%.The usage of metal pins can reduce the tip temperature effectively and thereby remove the heat load from the tip.Also,it is found that the tip heat transfer is enhanced even by using insulating pins having low thermal conductivity at low Reynolds numbers.The comparisons of overall performances are also included.展开更多
Keeping up with the latest fads in China is like trying to swim without getting wet. Things happen way too fast here and seen through a foreigner’s eyes more often than not these fads are kitsch, but occasionally the...Keeping up with the latest fads in China is like trying to swim without getting wet. Things happen way too fast here and seen through a foreigner’s eyes more often than not these fads are kitsch, but occasionally they get downright bizarre.展开更多
Background:The purpose of this study is to present our experience with the modified pins and rubber band traction system, discuss problems encountered, and make recommendations to optimize outcomes. Methods:Data was c...Background:The purpose of this study is to present our experience with the modified pins and rubber band traction system, discuss problems encountered, and make recommendations to optimize outcomes. Methods:Data was collected prospectively from November 2013 to March 2017 at a tertiary referral hospital in Melbourne, Australia. Patients with closed complex proximal interphalangeal joint fracture dislocations that were considered unsuitable for other surgical options were included in the study. Patients underwent dynamic skeletal distraction using the modified (Deshmukh) pins rubber band traction system. Outcomes were measured using the Nominal Rating Scale for pain;Disabilities of the Arm, Shoulder, and Hand (DASH) score;active and passive range of motion;patient rating scale;and complications. Results:Twenty patients underwent the procedure, and 19 were included in analyses. At the final follow-up assessment, an average of 62° and 77° was achieved for proximal interphalangeal joint active and passive range of motion, respectively. Pain levels were low (median score of 0 at rest and 1 ranging, out of 10). Four patients suffered minor pin site infections. Conclusion:Distraction ligamentotaxis is a useful part of the armamentarium, especially in the absence of more suitable procedures. It is important to select appropriate patients, educate, and ensure adherence to postoperative therapy. Employing the Deshmukh frame modification streamlines the theatre processes, and removal of wires at approximately 4 weeks minimizes risk of pin site infection.展开更多
英语对话:A:It seems you’re on pins and needles today.Anything troubling you?B:Yeah.I don’t know why bad things keep happening to me .You see,mycar was stolen and the warehouse had been broken into.I can’t keep myfi...英语对话:A:It seems you’re on pins and needles today.Anything troubling you?B:Yeah.I don’t know why bad things keep happening to me .You see,mycar was stolen and the warehouse had been broken into.I can’t keep myfinger on the causes of this damned thing.A:There must be someone who had planned that.Do you have a partieularperson in mind?展开更多
In this investigation,the effects of pin geometry and number of passes on macrostructure,microstructure,wear rate and also microhardness profile of 6061-T6 aluminum alloy surface composites fabricated via friction sti...In this investigation,the effects of pin geometry and number of passes on macrostructure,microstructure,wear rate and also microhardness profile of 6061-T6 aluminum alloy surface composites fabricated via friction stir processing(FSP)were discussed by reinforcement particles of silicon carbide(SiC).The results show that after each FSP pass,a modify distribution of SiC particles is acquired and the increase in the number of passes reduces the average grain size in stir zone(SZ).Furthermore,it is discovered that pin geometry and pass number play a dominant role in the grain size of SZ and distribution of SiC particles in SZ.It is found that after each FSP pass,wear rate is improved due to the uniform distribution of SiC particles in surface of Al/SiC composite.Additionally,the results show that the square pin and smooth(straight)cylindrical pin have the highest and lowest resistance to wear,respectively.展开更多
文摘Understanding the material flow facilitated by tool geometry in friction stir welds is challenging for quality weld production in industrial applications.The optimal tool shoulder and pin design combination,which plays a vital role in material flow was addressed.The flow of plasticized material was analyzed using a marker insert technique.The results show that the knurling shoulder design with square and hexagonal pin design facilitated constant stability force with reference to weld length/time.The uniform mixing and distribution of plasticized material were facilitated by the knurling shoulder design with square tool pin shape(TK)S(sticking length minimum)below which fragmented copper was observed.(TK)S tool facilitated higher mechanical properties for the welds,i.e.strength(182 MPa)and hardness(HV 78)in stir zone.
文摘Background: Anatomic single bundle is a widely accepted technique for anterior cruciate ligament (ACL) reconstruction. The research question: are transverse pins safe to fix the ACL graft on the femoral side in anatomic single bundle ACL reconstruction? Material and Methods: Ten cadaveric femoral dry bones were tested in this study. Thirty mm long sockets were prepared in the center of the anatomic ACL footprints. Transverse pin guide for soft tissue graft was used to prepare pin sites through the femoral sockets using three different positions. The positions (A) and (B) had a lateral entry point and differ in their inclination in relation to the joint line;while (A) has a 15° open laterally plane, (B) has a 15° closed laterally. The last position (C) had a medial entry point for the transverse pins. The relations of the transverse pins to the anatomic landmarks (lateral epicondyle and articular cartilage) in addition to the path of the pins within the femoral sockets were recorded. Results: Pins inserted while the guide in position (A) crossed the center of the femoral sockets and were fully seated within the bone of the distal femur. Distal pins inserted through inclination (B) were found to penetrate the posterior cortex of the distal femur proximal to the lateral femoral condyle. Pins inserted from the medial side (C) achieved central position through the femoral tunnel. The entry point for transverse pins through lateral entry points was very close to the attachment of the lateral collateral ligament at the lateral epicondyle while medial entry point avoided important structures. Conclusion: Transverse pins inserted through the lateral entry point carry the risk of penetrating the posterior cortex of the femur and/or damage the attachment of the lateral collateral ligament. Medial entry point may give a safer approach but needs further adjustments of the guides and clinical trials of the technique.
文摘Heat transfer to pins swimming in non-isothermal fluidic systems is theoretically analyzed. Four different cases are considered: [A] pins aligned longitudinally in flowing fluid having constant temperature gradient, [B] pins aligned transversely in flowing fluid flow with constant temperature gradient, [C] pins moving longitudinally towards a heated surface, and [D] pins moving transversely towards the heated surface. The Appropriate unsteady energy transport equations are solved and closed form solutions for the fin temperatures are obtained. Accordingly, different performance indicators are calculated. It is found that heat transfer to the swimming fin increases as the fin thermal length, Peclet number and fluid temperature difference along the fin length increase. It decreases as fluid temperature index along the motion direction increases. Moreover, the swimming pins of case C are found to produce the maximum system effective thermal conductivity. In addition, pins of case B with thermal lengths above 11 produce system thermal conductivity independent on the thermal length. Meanwhile, pins of case A having thermal lengths above 10 produce system thermal conductivities less responsive to the thermal length. The system thermal conductivity is noticed to increase as the thermal length and Peclet number increase. Eventually, pins of case D produce system thermal conductivities that are independent on the transverse temperature. Finally, the results of this work provide a basis for modeling super convective fluidic systems that can be used in cooling of electronic components.
文摘BACKGROUND Infection at the pin tract is a frequent and feared complication of external fixators(EF).The type of pin material and coatings have been regarded as possibly influencing infection rates.Over the last 20 years,few prospective clinical studies and systematic reviews addressed the role of coated pins on the rate of pin site infection in human clinical studies.AIM To assess the EF literature over the past 20 years on the clinical benefits of pins manufactured from varied materials and coating systems and their possible role in pin tract infection rates.METHODS We performed a systematic review according to the PRISMA and PICOS guidelines using four scientific platforms:PubMed,LiLacs,SciELO,and Cochrane.We searched the literature for related publications over the past 20 years.RESULTS A literature search yielded 29 articles,among which seven met the inclusion criteria.These studies compared stainless-steel pins and pins coated with hydroxyapatite(HA),titanium and silver.The pin tract infection definitions were arbitrary and not standardized among studies.Most studies included a low number of patients in the analysis and used a short follow-up time.Three metaanalyses were carried out,comparing stainless steel vs silver pins,stainless steel vs HA-coated pins,and titanium vs HA-coated pins.None of this analysis resulted in statistically significant differences in pin tract infection rates.CONCLUSION Currently,no clinical evidence supports the advantage of EF pins manufactured with materials other than stainless steel or coated over uncoated pins in reducing the rates of pin tract infections.A standardized definition of pin tract infection in external fixation is still lacking.
文摘This work investigates the impact of biomechanical wear and abrasion on the antibiotic release profiles of hydroxyapatite (HA) coated fixation pins during their insertion into synthetic bone. Stainless steel fixation pins are coated with crystalline TiO2 by cathodic arc evaporation forming the bioactive layer for biomimetic deposition of Tobramycin containing HA. Tobramycin is either introduced by co-precipitation during HA formation or by adsorption-loading after HA deposition. The samples containing antibiotics are inserted into bone mimicking polyethylene foam after which the drug release is monitored using high performance liquid chromatography. This analysis shows that HA coating wear and delamination significantly decrease the amount of drug released during initial burst, but only marginally influence the sustained release period. Spalled coating fragments are found to remain within the synthetic bone material structure. The presence of HA within this structure supports the assumption that the local release of Tobramycin is not only expected to eliminate bacteria growth directly at the pin interface but as well at some distance from the implant. Furthermore, no negative effect of gamma sterilization could be observed on the drug release profile. Overall, the observed results demonstrate the feasibility of a multifunctional implant coating that is simultaneously able to locally deliver clinically relevant doses of antibiotics and an HA coating capable of promoting osteoconduction. This is a potentially promising step toward orthopaedic devices that combine good fixation with the ability to treat and prevent post-surgical infections.
文摘Background: Pediatric supracondylar humerus fractures are the most common elbow fractures in children. Operative management includes closed reduction and placement of 2 to 3 laterally based pins. Occasionally, a medial pin is used to create a crossed fixation pattern, despite risk of nearly 10% iatrogenic ulnar nerve injury. The objective of this study was to assess the trends and outcomes in the operative management of pediatric supracondylar humerus fractures at a level one academic trauma center. Materials & Methods: A retrospective review was performed on all children sustaining a Gartland type II or III supracondylar humerus fractures treated by closed or open reduction and percutaneous pinning in 2006-2008 and 2009-2011 at a level one academic trauma center by two of the authors (JTR, LMT). Pin placement patterns were evaluated and compared based on year performed. Outcomes measured were rates of ulnar nerve symptoms, non-union, re-operation, and varus malalignment. Data analysis was performed using a Fisher exact test on STATA software. Results: A total of 49 patients met inclusion criteria. Of 22 patients treated in 2006-2008, 5 (23%) were type II and 17 (77%) were type III. From 2009-2011, 16 (59%) were type II and 11 (41%) were type III. Comparison of pinning pattern in type II fractures between 2006-2008 and 2009-2011 did not indicate statistical significance (p = 0.429). Comparison of pinning pattern in type III fractures during the same time period did show that there was a statistically significant decrease (p = 0.010) in the number of cross pin fixations. There were no ulnar nerve injuries, non-unions, re-operations, or varus malalignment in any patient on final follow-up. Conclusion: This study shows that there has been a significant decrease in cross pin fixation for pediatric type III supracondylar humerus fractures with equivalent clinical outcomes at a Level I trauma center. Furthermore, performing lateral pinning for type III fractures has eliminated the risk of iatrogenic ulnar nerve injury. Level of Evidence: Level III—Retrospective cohort study.
文摘The patch antennas with an array of pins （pin array patch antennas） with excellent radiation characteristics are investigated for various substrate thicknesses. The radiation in the horizontal plane of a pin array patch antenna is very small compared to that of a conventional patch antenna. And the increase of forward radiation and the decrease of backward radiation of a pin array patch antenna are obtained than those conventional one＇s. Also the half-power beamwidth of E -plane radiation pattern of a pin array patch antenna is narrower compared to that of the conventional so that the directivity is improved.
文摘Background: Foreign body aspiration is a common yet preventable health problem. Headscarf pin aspiration is a unique example of aspirated foreign bodies in young Muslim women usually removed using the rigid bronchoscope. However, the flexible bronchoscope is increasingly used for this purpose. This prospective study was conducted in Sulaimaniyah Teaching Hospital, Sulaimaniyah, Iraq and aimed to evaluate the usefulness of fiberoptic bronchoscope for removal of aspirated headscarf pins in view of the relevant literature. Methodology: Fifty female patients with headscarf pin aspiration were managed by fiberoptic bronchoscopy over an 8-year period (January 2008 to December 2015). The procedure was performed under local anesthesia and conscious sedation through the mouth. Results: The age ranged from 10 to 45 years with a mean of 27.5. All patients had cough, five had unilateral wheeze (10%) while haemoptysis occurred twice (4%). Fiberoptic bronchoscopy succeeded in 45 cases (90%). Rigid bronchoscopy under general anesthesia was necessary in (n = 4, 8%) while one patient (2%) required thoracotomy. ?Conclusion: Fiberoptic bronchoscopy is safe and effective in removal of aspirated headscarf pins and should be tried first.
基金The research has been funded by the Swedish Energy Agency,Siemens Industrial Turbomachinery AB and Volvo Aero Corporation through the Swedish research program TURBO POWER,the support of which is gratefully acknowledged.
文摘Cooling methods are needed for turbine blade tips to ensure a long durability and safe operation.A common way to cool a tip is to use serpentine passages with 180-deg turn under the blade tip-cap taking advantage of the threedimensional turning effect and impingement like flow.Improved internal convective cooling is therefore required to increase the blade tip lifetime.In the present study,augmented heat transfer of an internal blade tip with pin-fin arrays has been investigated numerically using a conjugate heat transfer method.The computational domain includes the fluid region and the solid pins as well as the tip regions.Turbulent convective heat transfer between the fluid and pins,and heat conduction within pins and tip are simultaneously computed.The main objective of the present study is to observe the effect of the pin material on heat transfer enhancement of the pin-finned tips.It is found that due to the combination of turning,impingement and pin-fin crossflow,the heat transfer coefficient of a pin-finned tip is a factor of 2.9 higher than that of a smooth tip at the cost of an increased pressure drop by less than 10%.The usage of metal pins can reduce the tip temperature effectively and thereby remove the heat load from the tip.Also,it is found that the tip heat transfer is enhanced even by using insulating pins having low thermal conductivity at low Reynolds numbers.The comparisons of overall performances are also included.
文摘Keeping up with the latest fads in China is like trying to swim without getting wet. Things happen way too fast here and seen through a foreigner’s eyes more often than not these fads are kitsch, but occasionally they get downright bizarre.
文摘Background:The purpose of this study is to present our experience with the modified pins and rubber band traction system, discuss problems encountered, and make recommendations to optimize outcomes. Methods:Data was collected prospectively from November 2013 to March 2017 at a tertiary referral hospital in Melbourne, Australia. Patients with closed complex proximal interphalangeal joint fracture dislocations that were considered unsuitable for other surgical options were included in the study. Patients underwent dynamic skeletal distraction using the modified (Deshmukh) pins rubber band traction system. Outcomes were measured using the Nominal Rating Scale for pain;Disabilities of the Arm, Shoulder, and Hand (DASH) score;active and passive range of motion;patient rating scale;and complications. Results:Twenty patients underwent the procedure, and 19 were included in analyses. At the final follow-up assessment, an average of 62° and 77° was achieved for proximal interphalangeal joint active and passive range of motion, respectively. Pain levels were low (median score of 0 at rest and 1 ranging, out of 10). Four patients suffered minor pin site infections. Conclusion:Distraction ligamentotaxis is a useful part of the armamentarium, especially in the absence of more suitable procedures. It is important to select appropriate patients, educate, and ensure adherence to postoperative therapy. Employing the Deshmukh frame modification streamlines the theatre processes, and removal of wires at approximately 4 weeks minimizes risk of pin site infection.
文摘英语对话:A:It seems you’re on pins and needles today.Anything troubling you?B:Yeah.I don’t know why bad things keep happening to me .You see,mycar was stolen and the warehouse had been broken into.I can’t keep myfinger on the causes of this damned thing.A:There must be someone who had planned that.Do you have a partieularperson in mind?
文摘In this investigation,the effects of pin geometry and number of passes on macrostructure,microstructure,wear rate and also microhardness profile of 6061-T6 aluminum alloy surface composites fabricated via friction stir processing(FSP)were discussed by reinforcement particles of silicon carbide(SiC).The results show that after each FSP pass,a modify distribution of SiC particles is acquired and the increase in the number of passes reduces the average grain size in stir zone(SZ).Furthermore,it is discovered that pin geometry and pass number play a dominant role in the grain size of SZ and distribution of SiC particles in SZ.It is found that after each FSP pass,wear rate is improved due to the uniform distribution of SiC particles in surface of Al/SiC composite.Additionally,the results show that the square pin and smooth(straight)cylindrical pin have the highest and lowest resistance to wear,respectively.
