[FBG Self-Chirped Based on an Sine-Structure].

Considerting that the uniform grating can be induced chirp effect under non-uniform strain, a method of making chirp grating by uniform grating with the use of sine structure is proposed. The sine structure was designed as basal material while the fiber Bragg and grating was pasted in the strain non-uniform area of basal material. the strain it produced was introducied into FBG gate area by applying tensile load to achieve FBG produce chirp effect. FBG was made with multiple peaks and wide bandwidth of the chirp grating. The finite element software was used to simulate the strain of sine-structure under tensile loading to get strain contours of the sinusoidal structure in different positions; The experimental results showd that the bandwidth has been increased five times when the displacement load was up to 8 mm and the chirp grating reflection spectrum with multiple peaks; The transfer matrix method to reflection spectrum of chirp grating was combined for spectrum simulation reconstruction and the simulation spectrum spectrum trend was consistent with the experimental results. The chirp grating made in this method has an important application in complex strain field multiple parameters and achieving sense of temperature without compensation by the use of the bandwidth of the chirp grating at the same time.

[Progressive damage monitoring of corrugated composite skins by the FBG spectral characteristics].

In the present paper, a method of monitoring progressive damage of composite structures by non-uniform fiber Bragg grating (FBG) reflection spectrum is proposed. Due to the finite element analysis of corrugated composite skins specimens, the failure process under tensile load and corresponding critical failure loads of corrugated composite skin was predicated. Then, the non-uniform reflection spectrum of FBG sensor could be reconstructed and the corresponding relationship between layer failure order sequence of corrugated composite skin and FBG sensor reflection spectrums was acquired. A monitoring system based on FBG non-uniform reflection spectrum, which can be used to monitor progressive damage of corrugated composite skins, was built. The corrugated composite skins were stretched under this FBG non-uniform reflection spectrum monitoring system. The results indicate that real-time spectrums acquired by FBG non-uniform reflection spectrum monitoring system show the same trend with the reconstruction reflection spectrums. The maximum error between the corresponding failure and the predictive value is 8.6%, which proves the feasibility of using FBG sensor to monitor progressive damage of corrugated composite skin. In this method, the real-time changes in the FBG non-uniform reflection spectrum within the scope of failure were acquired through the way of monitoring and predicating, and at the same time, the progressive damage extent and layer failure sequence of corru- gated composite skin was estimated, and without destroying the structure of the specimen, the method is easy and simple to operate. The measurement and transmission section of the system are completely composed of optical fiber, which provides new ideas and experimental reference for the field of dynamic monitoring of smart skin.

[A comprehensive surveillance on HIV among 1,237 men who have sex with men in thirteen cities of Yunnan].

OBJECTIVE: To understand the knowledge, risk behaviors and HIV prevalence in men who have sex with men (MSM) in thirteen cities. METHODS: Target samples were chosen using the snowball-rolling method, with transverse KABP and HIV-antibody testing developed for those MSM in thirteen cities of Yunnan. RESULTS: A total of 1237 valid questionnaires and 1129 blood samples were collected. Basic knowledge on HIV and the rate of the response was 93.2%. 81.1% of the respondents had anal sex with male partners in the last six months, of them 49.7% could persistently using condoms in each anal sex episode. 29.0% of the respondents had sex with female partners in the last six months. The HIV prevalence among the studied MSM was 8.2% and the prevalence of syphilis among them was 3.9%. Most risky factors of those MSM infected by HIV would include: not persistently use condom when having sex and co-infection of syphilis. CONCLUSION: Both rates of HIV infection associated risk behaviors and HIV prevalence were high in MSM under study that called for more work on HIV prevention and control MSM in Yunnan.

[Spectral analysis of fiber bragg grating modulated by double long period grating and its application in smart structure monitoring].

Spectrum of fiber bragg grating (FBG) sensor modulated by double long period grating (LPFG) is proposed in the paper. Double LPFG consists of two LPFGS whose center wavelengths are the same and reflection spectrum of FBG sensor is located in linear range of double LPFG transmission spectrum. Based on spectral analysis of FBG and double LPFG, reflection spectrum of FBG modulated by double LPFG is obtained and studied by use of band-hider filter characteristics for double LPFG. An FBG sensor is attached on the surface of thin steel beam, which is strained by bending, and the center wavelength of FBG sensor will shift. The spectral peak of FBG sensor modulated by double LPFG is changed correspondingly, and the spectral change will lead to variation in exit light intensity from double LPFG. Experiment demonstrates that the relation of filtering light intensity from double LPFG monitored by optical power meter to center wavelength change of FBG sensor is linear and the minimum strain of material (steel beam) detected by the modulation and demodulation system is 1.05 microepsilon. This solution is used in impact monitoring of optical fibre smart structure, and FBG sensor is applied for impulse response signal monitoring induced by low-velocity impact, when impact pendulum is loaded to carbon fiber-reinforced plastics (CFP). The acquired impact response signal and fast Fourier transform of the signal detected by FBG sensor agree with the measurement results of eddy current displacement meter attached to the FBG sensor. From the results, the present method using FBG sensor is found to be effective for monitoring the impact. The research provides a practical reference in dynamic monitoring of optical fiber smart structure field.

[Current situation and influential factors concerning the sexual transmission of HIV in Dehong prefecture, Yunnan province].

OBJECTIVE: To investigate the current situation of the sexual transmission of HIV in Dehong prefecture, analyze the influential factors, and provide support for drafting pertinent preventive interventions in the future. METHODS: We had analyzed the data of case report from 2005 to 2007, and the prostitutes surveillance data from 2003 to 2007. A special survey was conducted from October 26 to November 7, 2007. Totally 685 people including prostitutes, the clients of prostitutes, people who were HIV positive and their partners, key insiders were interviewed in order to better understand the influential factors related to sexual transmission of HIV. RESULTS: Among 1636 cases reported from January 1 to September 20, 2007, 52% were infected through sexual transmission. Among 586 cases infected through sexual transmission, 40.6% had commercial sexual behavior and 28.6% had unmarried sexual behavior. And the average rate of condom use was below 30%. The prostitutes' surveillance data from 2003 to 2007 showed that the HIV positive rate in prostitutes was 3.3% - 5.5%. The rate of condom use in the last month was 29.4% - 84.4% during commercial sexual activity, but it was 9.5% - 34.8% with fixed sexual partners. Although the rate of HIV and AIDS-related knowledge among prostitutes was 95.0%, there were still many misunderstanding regarding certain aspects of HIV and AIDS awareness. CONCLUSION: Sexual transmission has become one of the main transmission routes of HIV in Dehong prefecture. The main factors involved in the sexual transmission of HIV in Dehong prefecture might include the wide spreading of sexual services, cohabitation among unmarried couples, having multiple partners, casual sexual behavior, and the low rate of condom use.

[Analysis of the epidemiologic patterns of HIV transmission in Dehong prefecture, Yunnan province].

OBJECTIVE: To uncover the transmission patterns of the HIV epidemic in Dehong prefecture. METHODS: The reviewed case reports, data of sentinel surveillance, testing and special survey were analyzed by SAS 8.0 program. The transmission patterns were modeled by utilizing data including sizes of the whole population and the high risk groups, high risk behavior data from 1989 to 2007, and the population index such as sex ratio and fertility rate. RESULTS: In 2005, case reports showed the proportion of people infected with HIV through sexual contact was 39.1%, and 46.9% in 2006. Among 1636 cases reported between January 1 to September 20, 2007, the proportion of people infected with HIV through sexual contact was 52%. From 1989 to 2007, the proportion of HIV infection among drug users was declining, while HIV infection through sexual contact was rising after standardizing the population tested/surveyed. The Asian Epidemic Model has shown that the proportions of incident HIV infections through sexual transmissions were 50.6%, 52.3% and 52.7% respectively from 2005 to 2007. Correspondingly, the proportions of incident cases by injecting drug user were 48.9%, 47.2% and 46.7% respectively during this period. Moreover, the Workbook method has shown that, among adults living with HIV in 2007, 50.3% were infected through injecting drugs and 48.4% through unsafe sexual activity. CONCLUSION: The rapid rise in HIV infections through injecting drug in Dehong prefecture has been initially curbed. HIV epidemic has already witnessed a change from predominantly through drug injecting-related activity to an almost equally fuelled epidemic by sexual and drug-related transmission.

[Analysis for epidemic trend of acquired immunodeficiency syndrome in Yunnan Province of China].

OBJECTIVE: To understand epidemiologic characteristics and changes in epidemic trend of human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) in different areas and populations of Yunnan Province. METHODS: Seroepidemiological studies were conducted in injection drug users (IDUs), women sex workers, whoring goers, patients with sexually transmitted disease (STD), patients with tuberculosis, pregnant women and blood donors with sentinel surveillance, ad hoc investigations, regular case-finding and data collection during 1989 to 2003 in Yunnan Province. RESULTS: Relatively high prevalence of HIV/AIDS was firstly found in IDUs from border areas of the province in 1989. By December of 2003, totally 14 905 cases with HIV infection were reported in 121 counties of 16 prefectures in Yunnan Province. Prevalence of HIV infection ranged from 21.2% to 27.8% in IDUs, over 40% in IDUs from six areas, and 1.23% to 6.67% and 0.3% to 1.8% in underground prostitutes and whoring goers, respectively. Prevalence of HIV infection was 2.1% to 2.7%, 10.8% in specific areas, in male patients with STD, and was 0.14% to 0.25% in pregnant women during 1993 to 2002 and increased to 0.37% in 2003. Prevalence of HIV infection ranged 1.5% to 1.6% in patients with tuberculosis and 0.01% in blood donors during 1999 to 2000 and increased to 0.07% in 2003. CONCLUSIONS: Epidemic of HIV infection began in late 1980s in Yunnan, then spread from border areas to inland through IDUs, maintaining a higher prevalence in them to date. Sexual transmission of HIV/AIDS showed an increasing trend in them, with a low prevalence in general population, but appeared a wide spread in local areas.