Aim: The data on semen analysis of subjects attending the Fertility Clinic at NIHFW (National Institute of Health and Family Welfare) Munirka, New Delhi for the last 11 years were analyzed to verify the claims and spe...Aim: The data on semen analysis of subjects attending the Fertility Clinic at NIHFW (National Institute of Health and Family Welfare) Munirka, New Delhi for the last 11 years were analyzed to verify the claims and speculations on declining sperm counts in men. Methods: Approximately 10 % of the records every year starting from 1990 to 2000 (numbering 1176 in total) were randomly selected for analysis. Subjects with azoospermia or severe oligozoospermia were excluded from analysis. Results: The average age of the men attending the infertility clinic was 31.2 years. The average semen volume and sperm count were found to be (2.6 ±0.1) mL and (60.6 ± 0.9) × 106/mL, respectively. No significant decline in sperm counts was observed in any year during the entire study period. Only 1.8 % of the total number of sperm counts in the random sampling were less then 20 × 106/mL. On the basis of WHO criteria on motility, the total percentage of non-progressive and non-motile sperm in the ejaculate was higher (63 %) as compared to the combined categories of slow and rapid linear progressive. Conclusion: The present study has confirmed similar findings from other different countries that declining sperm counts in humans is not a global phenomenon.展开更多
In order to control the ferrite and austenite percentage in duplex stainless steel welding, many researchers try to change the laser welding parameters and cooling medium, but ignore to study the influence of heat sin...In order to control the ferrite and austenite percentage in duplex stainless steel welding, many researchers try to change the laser welding parameters and cooling medium, but ignore to study the influence of heat sink effect on weld strength. In this work, the effect of aluminium heat sink and varying cooling medium on the laser welding of duplex stainless steel (DSS) 2205 is studied. The 2 mm thick DSS sheets welded with pulsed Nd: YAG laser welding machine by varying the cooling medium (air and oil) and an aluminium plate used as a heat sink. The welded specimens tested for tensile strength, micro-hardness, distortion, microstructure and radiography analysis. The faster cooling rate in the oil quenching process enhances the ferrite percentage compared with air-cooled samples. But the faster cooling rate in oil quenching leads to more distortion and using aluminium as a heat sink influenced positively the distortion to a small extent. The lower cooling rate in air quenching leads to a higher tensile strength of the welded specimen. The objective of this work is to analyse experimentally the effect of cooling medium and heat sink in the mechanical and metallurgical properties of laser welded duplex stainless steel.展开更多
The hot deformation behaviour of extruded magnesium-zinc oxide nano composite has been studied using hot compression test.The test was conducted in the temperature range of 250-400℃ and in the strain rate range of 0....The hot deformation behaviour of extruded magnesium-zinc oxide nano composite has been studied using hot compression test.The test was conducted in the temperature range of 250-400℃ and in the strain rate range of 0.01 to 1.5 s^(−1).The processing map was obtained using the power dissipation efficiency with the functions of temperature and strain rate.The workability and instability domains were observed in the processing map for a nano composite.The optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)images were used to confirm the formation of dynamic recrystallization(DRX),dynamic recovery(DRY)and instability regions.The workability region of the composite was identified at a working temperature of 400℃ and the strain rate of 0.01 s^(−1) from the processing map.The instability regions were observed at higher strain rates(>0.1 s^(−1))and temperatures(250-400℃).展开更多
文摘Aim: The data on semen analysis of subjects attending the Fertility Clinic at NIHFW (National Institute of Health and Family Welfare) Munirka, New Delhi for the last 11 years were analyzed to verify the claims and speculations on declining sperm counts in men. Methods: Approximately 10 % of the records every year starting from 1990 to 2000 (numbering 1176 in total) were randomly selected for analysis. Subjects with azoospermia or severe oligozoospermia were excluded from analysis. Results: The average age of the men attending the infertility clinic was 31.2 years. The average semen volume and sperm count were found to be (2.6 ±0.1) mL and (60.6 ± 0.9) × 106/mL, respectively. No significant decline in sperm counts was observed in any year during the entire study period. Only 1.8 % of the total number of sperm counts in the random sampling were less then 20 × 106/mL. On the basis of WHO criteria on motility, the total percentage of non-progressive and non-motile sperm in the ejaculate was higher (63 %) as compared to the combined categories of slow and rapid linear progressive. Conclusion: The present study has confirmed similar findings from other different countries that declining sperm counts in humans is not a global phenomenon.
文摘In order to control the ferrite and austenite percentage in duplex stainless steel welding, many researchers try to change the laser welding parameters and cooling medium, but ignore to study the influence of heat sink effect on weld strength. In this work, the effect of aluminium heat sink and varying cooling medium on the laser welding of duplex stainless steel (DSS) 2205 is studied. The 2 mm thick DSS sheets welded with pulsed Nd: YAG laser welding machine by varying the cooling medium (air and oil) and an aluminium plate used as a heat sink. The welded specimens tested for tensile strength, micro-hardness, distortion, microstructure and radiography analysis. The faster cooling rate in the oil quenching process enhances the ferrite percentage compared with air-cooled samples. But the faster cooling rate in oil quenching leads to more distortion and using aluminium as a heat sink influenced positively the distortion to a small extent. The lower cooling rate in air quenching leads to a higher tensile strength of the welded specimen. The objective of this work is to analyse experimentally the effect of cooling medium and heat sink in the mechanical and metallurgical properties of laser welded duplex stainless steel.
文摘The hot deformation behaviour of extruded magnesium-zinc oxide nano composite has been studied using hot compression test.The test was conducted in the temperature range of 250-400℃ and in the strain rate range of 0.01 to 1.5 s^(−1).The processing map was obtained using the power dissipation efficiency with the functions of temperature and strain rate.The workability and instability domains were observed in the processing map for a nano composite.The optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)images were used to confirm the formation of dynamic recrystallization(DRX),dynamic recovery(DRY)and instability regions.The workability region of the composite was identified at a working temperature of 400℃ and the strain rate of 0.01 s^(−1) from the processing map.The instability regions were observed at higher strain rates(>0.1 s^(−1))and temperatures(250-400℃).
