Second-order theories for extensional vibrations of piezoelectric crystal plates and strips.

An infinite system of two-dimensional (2-D) equations for piezoelectric plates with general symmetry and faces in contact with vacuum is derived from the 3-D equations of linear piezoelectricity in a manner similar to that of previous work, in which an infinite system of 2-D equations for plates with electroded faces was derived. By using a new truncation procedure, second-order equations for piezoelectric plates with faces in contact with either vacuums or electrodes are extracted from the aforementioned infinite systems of equations, respectively. The second-order equations for plates with or without electrodes are shown to predict accurate dispersion curves by comparing to the corresponding curves from the 3-D equations in a range up to the cut-off frequencies of the first symmetric thickness-stretch and the second symmetric thickness-shear modes without introducing any correction factors. Furthermore, a system of 1-D second-order equations for strips with rectangular cross section is deduced from the 2-D second-order equations by averaging variables across the narrow width of the plate. The present 1-D equations are used to study the extensional vibrations of barium titanate strips of finite length and narrow rectangular cross section. Predicted frequency spectra are compared with previously calculated results and experimental data.

Extensional, thickness-stretch and symmetric thickness-shear vibrations of piezoceramic disks.

A set of two-dimensional (2-D), second-order approximate equations for extensional, thickness-stretch and symmetric thickness-shear vibrations of piezoelectric ceramic plates with electroded faces is extracted from the infinite system of 2-D equations deduced previously. The new truncation procedure developed recently is used for it improves the accuracy of calculated dispersion curves. Closed-form solutions are obtained for free vibrations of circular disks of barium titanate. Dispersion curves calculated from the present approximate 2-D equations are compared with those obtained from the 3-D equations, and the predicted resonance frequencies are compared with experimental data. Both comparisons show good agreement without any corrections. The frequencies of the edge modes calculated from the present 2-D equations are very close to the experimental data. Furthermore, mode shapes at various frequencies are calculated in order to identify the frequency segments of the spectrum at which one of the coupled modes--i.e., the radial extension (R), edge mode (Eg), thickness-stretch (TSt), and symmetric thickness-shear (s.TSh)--is predominant.

[Distribution of allergens in patients with allergic rhinitis in Hebei villagers and Tianjin citizens].

OBJECTIVE: To investigate the epidemiology of allergic rhinitis (AR) and the distribution of allergens in villagers who lived in Hebei Province (Hebei villagers) and the citizens who lived in the city of Tianjin (Tianjin citizens). METHODS: From April 2007 to May 2010, face to face investigation and serum specific IgE (sIgE) examination were conducted among Hebei villagers and Tianjin citizens by randomly multi-stage and cluster sampling, and the results were analyzed. RESULTS: A total of 1524 cases were investigated, among them, 1024 cases in Hebei and 500 cases in Tianjin, the prevalence of the sIgE test was 27.2% (279/1024) and 21.2% (106/500), and the difference was of statistical significance (χ(2) = 7.13, P < 0.01). The prevalence of AR was 9.2% (94/1024) and 9.0% (45/500), the difference was of no statistical significance (χ(2) = 0.01, P > 0.05). The most common allergens were dog epithelium and cat epithelium, the next were dust mites, house dust mites, birch and forage grasses in rural areas of Hebei Province. The most common allergens in Tianjin city were dust mites and house dust mites, the next were dog epithelium, cat epithelium, birch and forage grasses. The prevalence of allergens between Hebei villagers and Tianjin citizens had significant difference, which from high to low were house dust mites, dust mites and dog epithelium (χ(2) value were 11.36, 9.14, 5.28, all P < 0.05). The incidence of AR caused by dog epithelium in Hebei was higher than that in Tianjin, however, the dust mites in Tianjin was higher than that in Hebei. CONCLUSIONS: Allergen plays an important role in the prevalence of AR. The allergens have differences not only in areas but also in urban and village. The key factor is contact with allergens frequently.

[Analysis of the correlation of prevalence in allergic rhinitis and other allergic diseases].

OBJECTIVE: To obtain the prevalence of allergic rhinitis (AR) in different regions of northern China, to analyze the correlation and interaction between AR and bronchial asthma (BA) or atopic dermatitis (AD), and to provide reference for the prevention and treatment of allergic diseases such as AR. METHODS: To obtain the indexes including age, occupation, atopic physical fitness, smoking, alcohol, lifestyle and so on. To explore the correlation between AR and BA or AD. From April 2007 to May 2010, the serum specific IgE (sIgE) was investigated in different regions (rural areas of Qingxian, Hebei; coastal fishing village of Bohai Bay, Huanghua; area of Wuling Mountain, Chengde; urban areas of Tianjin) by randomly multi-stage and cluster sampling, with total population of 1524. RESULTS: The prevalence of AR, BA and AD were 9.1%, 5.4% and 6.0%. The prevalence of BA and AD were 30.9% and 29.5% in AR patients, but were 2.9% and 3.7% in non-AR, and the differences were of statistical significance (χ(2) values were 192.97 and 148.40, respectively, all P < 0.01). The risk of people with BA suffering from AR was as 8.619 times as those free from BA, the risk of people with AD suffering from AR was as 1.817 times as those free from AD and, the risk of workers suffering from AR was as 2.320 times as farmers in terms of working factor by analysis of Logistic regression for AR and BA, AD, age, occupation, atopic physical fitness and other factors. CONCLUSIONS: The prevalence of AR are correlated with BA and AD. It is greater between BA and AR than AD and AR in the strength of correlation.

[Research on prevalence and related factors in allergic rhinitis].

OBJECTIVE: To obtain the prevalence and related factors in allergic rhinitis (AR) and other allergic diseases in rural area in China through epidemiological investigation with large sample and multi-faceted survey data. METHODS: Face to face survey was conducted in different regions (rural areas of Cangzhou, Hebei, coastal fishing village of Bohai Bay, area of Wuling Mountain, Chengde, urban areas of Tianjin) from April 2007 to May 2009. In the same time, serum specific IgE (sIgE) was detected in the digits of every 0, 1or 5 in them. SPSS 13.0 software was used to analyze the data. RESULTS: Five thousand and ten cases were investigated. There were 823 cases with the symptoms or signs of AR (16.4%). Four hundred and two cases were found to have positive serum sIgE antibody in 1576 detected cases (25.5%). One hundred and fourty-six cases with nasal allergic symptoms or signs were diagnosed as AR. The incidence of AR was 9.3% (146/1576). The occurrence of allergic symptoms or signs had a significant statistical difference with factors such as age, occupation, atopic constitution (χ(2) value were 7.96, 9.73, 16.53, 8.95 respectively, all P < 0.05), and it was closely related to lower respiratory tract allergies (ß = 2.544, P < 0.01). The most common allergens were dog and cat epithelium in rural areas and dust mites in city. CONCLUSIONS: The incidence of AR is higher whether in urban or rural areas, it should be taken seriously as the impact on human health. The occurrence is closely related to physical characteristics and environmental factors.