Effect of Si3N4 Additive on Microstructure and Mechanical Properties of Ti(C,N)-Based Cermet Cutting Tools.

Development of high-performance cutting tool materials is one of the critical parameters enhancing the surface finishing of high-speed machined products. Ti(C,N)-based cermets reinforced with and without different contents of silicon nitride were designed and evaluated to satisfy the requirements. In fact, the effect of silicon nitride addition to Ti(C,N)-based cermet remains unclear. The purpose of this study is to investigate the influence of Si3N4 additive on microstructure, mechanical properties, and thermal stability of Ti(C,N)-based cermet cutting tools. In the present work, α-Si3N4 "grade SN-E10" was utilized with various fractions up to 6 wt.% in the designed cermets. A two-step reactive sintering process under vacuum was carried out for the green compact of Ti(C,N)-based cermet samples. The samples with 4 wt.% Si3N4 have an apparent solid density of about 6.75 g/cm3 (relative density of about 98 %); however, the cermet samples with 2 wt.% Si3N4 exhibit a superior fracture toughness of 10.82 MPa.m1/2 and a traverse rupture strength of 1425.8 MPa. With an increase in the contents of Si3N4, the Vickers hardness and fracture toughness of Ti(C,N)-based cermets have an inverse behavior trend. The influence of Si3N4 addition on thermal stability is clarified to better understand the relationship between thermal stability and mechanical properties of Ti(C,N)-based cermets.

[Study on the comparison of high risk behaviors related to AIDS among different status of income in men who have had sex with men].

OBJECTIVE: To explore the risk sexual behaviors related to AIDS among different status of income among men who have had sex with men and to provide relevant interventions for AIDS control and prevention. METHODS: Study objectives were recruited through target sampling and anonymous questionnaires were adopted. Men's sexual behaviors were reported under the categories as high, mid or low-income. RESULTS: The total number of same-gender partners with high and mid-income was 110.17 with an average of 71.97. Among high and mid-income men, the number of partners for oral sex was 62.45, with an average of 46.6 respectively. The number of partners having anal intercourse was 52.21, with an average of 32.3, obviously more than in the low-income group (P < 0.01). The rates of condom use among high-income and mid-income men were 79.03% and 77.29% respectively and were higher than that those among low-income men (P < 0.01). The percentage of high-income men who recently had had sex with male sex workers was 3.81%, higher than that of the mid-income and the low-income men (P < 0.01). The rates of high-income and mid-income men who had paid for sex from men were 24.27% and 14.7% respectively and were all higher than that of the low-income men with the highest in the high-income group (P < 0.01). The rates of high-income and mid-income men who were male sex workers were 6.72% and 11.05% respectively, which were all lower than that from the low-income group (P < 0.01). CONCLUSION: The characteristics of sexual behaviors related to AIDS were different in the three groups. In high-income group, risk sexual behaviors also existed, suggesting that different interventions for different people should be developed.

[Study on 1389 men who have sex with men regarding their HIV high-risk behaviors and associated factors in mainland China in 2004].

OBJECTIVE: To study the HIV related high-risk behaviors and associated factors on the spread of HIV among men having sex with men(MSM) who lived in mainland China and to provide evidence for developing related policies and intervention measures. METHODS: Questionnaires were distributed at gay bars and volunteer activity venues in six big cities of China. Data on 1389 valid cases was collected and urine HIV screening test was provided. Data was analyzed with SPSS 11.0. RESULTS: The respondents were 27.62 year olds on average with an average age for first intercourse at 19.18. The most commonly available way of finding a sex partner was through internet(43.07%), followed by gay bar and public bathrooms(35.29 % ). 6 months prior to the study, the average number of their male sex partners was 5.69 including 4.37 unfamiliar sex partners and the average number of anal-intercourse was 4.33 with 11.61 per cent of them had experienced group sex. 13 cases of them showed positive results for preliminary urine HIV screening test. In the prior 6 months, 32.46 per cent of those who had experienced intercourse using condom every time while 76.37 per cent of them during the last sex episode. In the previous 6 months, 47.18 per cent of those who had experienced intercourse with women never used condoms. CONCLUSION: HIV high-risk behaviors are ubiquitous among MSM and AIDS intervention measures should be significantly strengthened in reaching MSM via a wide variety of conduits, especially internet. Meanwhile, a gay-friendly environment for prevention and control of AIDS is vital.