An Analytical Development of the Hyperbolic Behaviour of Micro Thermoelectric Coolers

The transient behaviour of a micro thermoelectric cooler is described in the present paper through the theory of the thermal wave, involving the relaxation time. The internal heat generation due to the sudden application of the electric current is taken into account by means of the Heaviside function. The governing equations of both the semiconductors are solved by a modified Separation of Variables Method that allows us to have a better description of the device which can be obtained at early times. As regards the performances, the cooling load shows discontinuities due to the contributions of the travelling wave fronts of both the semiconductors. The results show that the coefficient of performance (COP) of the device obtained with the hyperbolic model is lower than that provided by the parabolic model at early times

Influence of Carding and Pressing on Hygrothermal Properties and Fire Reaction of Hemp Fiber Nonwoven Mats

This article depicts the effect of carding and pressing on hygrothermal properties of hemp fibers nonwoven mats, trying to understand if their implementation can improve their behavior when employed as insulation materials in buildings. Hemp fibers belonging to Cannabis Sativa species and coming from local area (Apulia - Italy) were examined, then samples of carded and pressed hemp fibers nonwoven mats were prepared. According to European standards, the thermal conductivity, the vapor permeability and the fire reaction of hemp fibers samples were measured. Results were compared to each other and with those of a commercial nonwoven mat made with hemp (90 wt. %) and synthetic fibers (10 wt. %), used as reference. We observed that carded and pressed hemp fibers were characterized by a lower thermal conductivity when compared to unprocessed hemp fibers, likely because the removing of wood elements. On the other hand, not processed hemp fibers show higher breathability when compared to carded and pressed ones, as well as with respect to the commercial nonwoven mat. Moreover, it was proved that the absence of synthetic commingled fibers in hemp fibers allows a better behavior in fire reaction. At last, the improvement in terms of insulation properties of a hollow brick when filled with hemp fibers was verified, by comparing the thermal conductivities of an empty and a filled hollow brick; as expected, the filled hollow brick shows a lower thermal conductivity, underlining the effectiveness of hemp fibers as insulation material

Characterization in expected working environments of recyclable fire-resistant materials

This study focuses on the development of multi-material solutions for fire-resistant structural materials for transport and thermal insulation in the construction field. Special attention was paid to combining recyclable and bio-mass derived raw materials without interfering with an easy end-of-life separation, recycling and reuse. Fire-resistant biomass derived resins were associated with basalt derived Mineral Fibres (BDMF) in the form of prepregs, which were studied as semi-finished materials. Fire-resistance was obtained by associating these prepregs with thin gres tiles in the case of fire-resistant thermal insulating facades and with aluminum layers (giving origin to Fibre Metal Laminates-FML) in the case of structural components for transport applications. Thermophysical characterization of the solutions was carried out to assess both thermal conductivity and thermal diffusivity. Fire resistance tests were performed on FML to determine the number of Al layers needed to ensure fire resistance. Results suggest that fire resistance depends primarily on the number of Al layers, rather than on their thickness. Accelerated ageing tests (salty mist and freeze-thaw) were executed to predict durability in the expected working conditions. Results suggest a durability issue in FML with preceramic interface in salty environments

Joining of SiC, alumina, and mullite by the Refractory Metal—Wrap pressure‐less process

The aim of this work was to discuss the suitability of the joining process called “RMWrap” (RM = Refractory Metals, ie, Mo, Nb, Ta, Zr) as a pressure-less and tailorable technique to join several different ceramics such as SiC, alumina, and mullite (3Al2O3.2SiO2). In the RM-Wrap joining technique the refractory metal foil is used as a wrap containing one or more silicon foils. It is performed at 1450°C, under flowing argon, and the resulting joining materials are in situ formed composites made of refractory metal disilicides (MoSi2, NbSi2, TaSi2, or ZrSi2) embedded in a siliconrich matrix; their coefficient of thermal expansion has been calculated and the Laser Flash Method was used to measure the thermal diffusivity of one of them (MoSi2/Si) in 25°C-1000°C range, then to calculate its thermal conductivity. All the obtained joints are uniform, continuous, and crack free. Some preliminary oxidation tests were carried out on all joints at 1100°C, 6 hours in air, giving unchanged morphology of the interface and the joining materials itself; the joint strength of RM-Wrap joined SiC was measured at room temperature using three different mechanical tests: (a) single lap (SL), (b) single lap off-set (SLO) and (c) torsion on hourglass-shaped samples (THG) (on Mo-wrap joined SiC)

Factors associated with climacteric symptoms in women around menopause attending menopause clinics in Italy

Objective: To obtain data on correlates of climacteric symptoms in women around menopause attending menopause clinics in Italy. Methods: Since 1997 a large cross sectional study has been conducted on the characteristics of women around menopause attending a network of first level menopause outpatient's clinics in Italy. A total of 66,501 (mean age 54.4 years) women are considered in the present paper. Results: The odds ratios of moderate and severe hot flashes/night sweats were lower in more educated women and (for severe symptoms only) in women reporting regular physical activity. Depression, difficulty to sleep, forgetfulness and irritability tended to be less frequent in more educated women and (depression only) in women reporting regular physical activity. Parous women reported more frequently these symptoms. Conclusions: This large study confirms in Southern European population that low education, body mass index and low physical activity are associated with climacteric symptoms. Parous women are at greater risk of psychological symptoms

Risk factors for type 2 diabetes in women attending menopause clinics in Italy: a cross-sectional study

OBJECTIVE: To analyze risk factors for type 2 diabetes among women attending menopause clinics in Italy for counselling about the menopause. SUBJECTS: Women attending a network of first-level outpatient menopause clinics in Italy for general counselling about menopause or treatment of menopausal symptoms. METHODS: Cross-sectional study with no exclusion criteria. Type 2 diabetes was defined according to National Diabetes Data Groups Indications and the fasting blood glucose at an oral glucose tolerance test within the previous year. RESULTS: Out of the 44 694 considered in this analysis, 808 had a diagnosis of diabetes type 2 (1.8%). In comparison with women aged or = 57 years. Type 2 diabetes was less frequently reported in more educated women (OR high school/university vs. primary school = 0.44 (95% CI, 0.36-0.55)). Being overweight was associated with an increased risk of type 2 diabetes. In comparison with women reporting a low level of physical activity, the multivariate OR of type 2 diabetes was 0.67 (95% CI, 0.54-0.84) for women reporting regular physical activity. In comparison with premenopausal women, the multivariate OR of type 2 diabetes was 1.38 (95% CI, 1.03-1.84) in women with natural menopause. This finding was present also after allowing for the potential confounding effect of age. The multivariate OR of diabetes for users of hormonal replacement therapy was 0.58 (95% CI, 0.46-0.73). CONCLUSIONS: This large cross-sectional study suggests that postmenopausal women are at higher risk of type 2 diabetes after allowance for the effect of age. Other main determinants of risk of type 2 diabetes in women around menopause were low socioeconomic status and being overweight. Diabetes was found less frequently in those taking hormone replacement therapy

Risk factors for type 2 diabetes in women attending menopause clinics in Italy: a cross-sectional study

To analyze risk factors for type 2 diabetes among women attending menopause clinics in Italy for counselling about the menopause