Low-Velocity Impact Localization on a Honeycomb Sandwich Panel Using a Balanced Projective Dictionary Pair Learning Classifier.

Carbon-fiber aluminum honeycomb sandwich panels are vulnerable to low-velocity impacts, which can cause structural damage and failures that reduce the bearing performance and reliability of the structure. Therefore, a method for locating such impacts through a sensor network is very important for structural health monitoring. Unlike composite laminates, the stress wave generated by an impact is damped rapidly in a sandwich panel, meaning that the signal qualities measured by different sensors vary greatly, thereby making it difficult to locate the impact. This paper presents a method for locating impacts on carbon-fiber aluminum honeycomb sandwich panels utilizing fiber Bragg grating sensors. This method is based on a projective dictionary pair learning algorithm and uses structural sparse representation for impact localization. The measurement area is divided into several sub-areas, and a corresponding dictionary is trained separately for each sub-area. For each dictionary, the sensors are grouped into main sensors within the sub-area and auxiliary sensors outside the sub-area. A balancing weight factor is added to optimize the proportion of the two types of sensor in the recognition model, and the algorithm for determining the balancing weight factor is designed to suppress the negative effects on the positioning of the sensors with poor signal quality. The experimental results show that on a 300 mm × 300 mm × 15 mm sandwich panel, the impact positioning accuracy of this method is 96.7% and the average positioning error is 0.85 mm, which are both sufficient for structural health monitoring.

[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.

[Change trend of HIV/AIDS related risk factors and influencing factors among men who have sex with men in Yunnan, 2010-2013].

OBJECTIVE: To understand the change trend of the awareness rate of HIV/AIDS related knowledge, risk behaviors among men who have sex with men (MSM) in Yunnan and the factors influencing their condom use, and evaluate the effect of comprehensive intervention. METHODS: The data about the MSM's demographic information, HIV/AIDS related knowledge awareness, and sex behavior, condom use, drug use and intervention receiving were obtained from AIDS sentinel surveillance among MSM in Yunnan province during 2010-2013 to conduct change trend and influencing factor analysis. RESULTS: A total of 9 073 MSM were surveyed. The awareness rate of the HIV/AIDS related knowledge, homosexual behavior and condom use rate increased year by year (P < 0.01). The condom use rate was lower in heterosexual behavior, and the drug use rate and sexually transmitted disease prevalence declined with year (P < 0.01). Multivariate logistic regression analysis indicated that cohabiting, low awareness of HIV/AIDS related knowledge, being from other provinces, local residence for <1 year, low education level, receiving no intervention, frequent anal sex and receiving no HIV/AIDS detection were the risk factors influencing persistent condom use among MSM. CONCLUSION: The effect of HIV/AIDS comprehensive intervention was observed after 4 years implantation, but most of the index were at low level. More attention should be paid to the intervention among MSM with cohabiting habit, low education level, frequent anal sex, and heterosexual sex. It is necessary to expand intervention coverage, strengthen HIV test and promote condom use among MSM.

[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.

Wavelet packet energy characterization of low velocity impacts and load localization by optical fiber Bragg grating sensor technique.

The low velocity impacts (LVIs) monitoring based on optical fiber Bragg grating (FBG) sensors have attracted more attention in recent years. The center wavelength migrations of FBG sensors were determined by strain and residual strain during and after LVI on composite material structure. We presented a method to discriminate the energy characters of LVI response signals related to LVI locations. By analyzing the wavelet packet energy spectra of LVI response signals monitored by FBG sensors, the sixth node's energy was found to be sensitive to LVI location. Thus, the sixth node's energies as LVI feature values, were used to predict the LVI locations by the method of support vector regression (SVR). By optimization of the SVR models' free parameters, predicting accuracy was 4.62% in the work.

[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.

Spontaneous formation of graphene-like stripes on high-index diamond C(331) surface.

We employ first-principles density functional theory calculations to study the surface reconstruction, energetic stability, and electronic structure of diamond C(331) surface. Spontaneous formation of graphene-like stripes on the reconstructed surface is found to occur as the surface terrace C atoms transform from sp3 to sp2 hybridization upon structural relaxation. The comparison of the calculated absolute surface energies of C(331), C(111), and C(110) surfaces demonstrates the energetic stability of the graphitic-like C(331) surface. Local density of electronic states analysis reveals the occurrence of localized electronic states near the Fermi level, which may have a significant impact on the surface conductivity.

B and T lymphocyte attenuator down-regulation by HIV-1 depends on type I interferon and contributes to T-cell hyperactivation.

BACKGROUND: Nonspecific T-cell hyperactivation is the main driving force for human immunodeficiency virus (HIV)-1 disease progression, but the reasons why the excess immune response is not properly shut off are poorly defined. METHODS: Eighty-five HIV-1-infected individuals were enrolled to characterize B and T lymphocyte attenuator (BTLA) expression and function. Infection and blockade assays were used to dissect the factors that influenced BTLA signaling in vitro. RESULTS: BTLA expression on overall CD4(+) and CD8(+) T cells was progressively decreased in HIV-1 infection, which was directly correlated with disease progression and CD4(+) T-cell differentiation and activation. BTLA(+)CD4(+) T cells from HIV-1-infected patients also displayed an altered immune status, which was indicated by reduced expression of naive markers but increased activation and exhaustion markers. Cross-linking of BTLA can substantially decrease CD4(+) T-cell activation in vitro. This responsiveness of CD4(+) T cells to BTLA-mediated inhibitory signaling was further found to be impaired in HIV-1-infected patients. Furthermore, HIV-1 NL4-3 down-regulated BTLA expression on CD4(+) T cells dependent on plasmacytoid dendritic cell (pDC)-derived interferon (IFN)-α. Blockade of IFN-α or depletion of pDCs prevents HIV-1-induced BTLA down-regulation. CONCLUSIONS: HIV-1 infection potentially impairs BTLA-mediated signaling dependent on pDC-derived IFN-α, which may contribute to broad T-cell hyperactivation induced by chronic HIV-1 infection.

A novel non-alcoholic steatohepatitis animal model featured with insulin resistance, hepatic inflammation and fibrosis.

OBJECTIVE: There is no animal model that displays the features of non-alcoholic steatohepatitis (NASH) characterized by insulin resistance (IR) and fibrosing steatohepatitis. This study aimed to develop a novel IR-associated rat model of NASH. MATERIAL AND METHODS: Male Sprague-Dawley rats were fed with the high-fat diet (HFD) supplemented with 0.25% propylthiouracil for 2, 4, 6, 8 and 12 weeks. The IR-associated metabolic parameters, histological assessment and the expression of key insulin signaling molecules were determined. The circulating and tissue pro-inflammatory factors and adipocytokines were examined. RESULTS: In the HFD-fed rats, the systemic and multiple-organ IR was developed after 4 weeks, whereas the histological changes characterized by steatohepatitis, inflammatory response in the visceral adipose tissue and proliferative pancreatic islet ß-cells appeared after 6 weeks, concomitant with altered expression of key insulin signaling molecules. In addition, the elevated levels of serum tumor necrosis factor α (TNF-α), soluble TNF receptor2, interleukin (IL)-6, CC-chemokine ligand (CCL)2 and resistin were parallel with the severity of hepatic inflammation, while the levels of serum adiponectin, leptin and TNF-α, but not resistin, were correlated with IR. CONCLUSIONS: We have developed a systemic IR-associated NASH model of rats, with impaired insulin signaling, systemic inflammation and appropriate pathology characterized by human NASH, and provided a realistic experimental model for elucidating the association between IR and the pathogenesis of NASH.

The HIV epidemic in Yunnan Province, China, 1989-2007.

OBJECTIVE: To investigate the characteristics and trends in the HIV epidemic in Yunnan province, China, between 1989 and 2007. METHODS: Statistical analysis of serological data from voluntary testing and counseling sites, medical case reports, mass screenings, sentinel surveillance, and other sources. RESULTS: By 2007, a cumulative total of 57,325 cases of HIV infection were reported in Yunnan, and unsafe drug injection practices and unsafe sexual behaviors were identified as the dominant modes of transmission. HIV affects injecting drug users most, particularly in Jingpo, Dai, and Yi ethnicities, more than 40% in 7 counties. HIV prevalence rates among female sex workers (FSWs) increased from 0.5% in 1995 to 4.0% in 2007; among men who have sex with men, from 4.0% in 2005 to 13.2% in 2007; among male clients of FSWs, from 0% in 1995-1997 to 1.8% in 2007; among male sexually transmitted disease clinic attendees, from 0% in 1992 to 2.1% in 2007; among pregnant women from 0.16% in 1992 to 0.5% in 2007; and among blood donors, from 0.0075% in 1992 to 0.084% in 2007. CONCLUSIONS: The HIV epidemic in Yunnan has progressed to a concentrated epidemic. Future efforts must focus on not only groups at risk for primary infection (injecting drug users, men who have sex with men, and FSWs) but also on their low-risk sexual partners.

[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.