Realization of electronically tunable voltage-mode/current-mode quadrature sinusoidal oscillator using ZC-CG-CDBA

a b s t r a c t This paper presents a first of its kind canonic realization of active RC (ARC) sinusoidal oscillator with non-interactive/independent tuning laws, which simultaneously provides buffered quadrature voltage outputs and explicit quadrature current outputs. The proposed circuit is created using a new active building block, namely the Z-copy controlled-gain current differencing buffered amplifier (ZC-CG-CDBA). The circuit uses three resistors and two grounded capacitors, and provides independent/non-interactive control of the condition of oscillation (CO) and the frequency of oscillation (FO) by means of different resistors. Other advantageous features of the circuit are the inherent electronic tunability of the FO via controlling current gains of the active elements and the suitability to be employed as a low-frequency oscillator. A non-ideal analysis of the circuit is carried out and experimental results verifying the workability of the proposed circuit are included

Test Arrangement of Small-scale Shear Tests of Composite Slabs

Composite slab consists of the layer of concrete above the trapezoidal sheeting. The sheeting serves as a lost formwork as well as a tension bearing member after the hardening of concrete. The interaction between the sheeting and the concrete is necessary for composite action and can be ensured by prepressed embossments in the sheeting. According to nowadays codes, full scale bending tests are required in the design of the new sheeting of this type of composite slabs. An alternative longitudinal shear tests of a small part of the slab have already been derived by many authors. However, the testing arrangement is not unified. The results of the shear tests can be influenced by the magnitude and the way of application of the clamping force, the loading speed, the interface conditions and others. This paper presents a proposal of the testing arrangement and the recommendations for the testing procedure of small-scale shear tests. The recommendations are posted based on the results of several series of performed laboratory tests

Cast Screws as Shear Anchors for Composite Slabs

Composite slabs consist of trapezoidal steel sheeting and concrete cover. The steel sheeting serves as both, a lost framework and a tension bearing member after hardening of concrete. The longitudinal shear between the sheeting and the concrete must be ensured by a mechanical interlock, for example shear studs or prepressed embossments in the sheeting. The traditional massive shear studs have to be welded to the supporting construction of the slab. Alternatively, thin screws can be drilled through the sheeting and cast into the concrete to ensure the composite action or to strengthen the composite slab in reconstructions locally. The usage of the screws is not limited to the steel supporting frames. This paper describes laboratory tests of the composite slabs with cast screws of various diameters and the effect of the screws on the bending capacity of the slab in combination with prepressed embossments

Response Analysis of a Piezoelectric Ceramic Transducer Pair Excited by Phase-Modulated Signals for Improved Echo Measurement

The article is mainly devoted to the analysis of the transient process during the phase change of the intra-impulse modulated signal of the system, which is composed of a pair of piezoelectric ceramic transducers. In the introductory part, this article is focused on the most accurate determination of the parameters of electrical equivalent circuit of piezoelectric ceramic transducers commonly available on the market of electrical components and less economically demanding. Based on the determination of these parameters, a system consisting of the piezoelectric ceramic transducer, transmitter - environment - piezoelectric ceramic transducer, receiver is then assembled and represented by transfer function. This system is subjected to simulation. An intra-impulse modulated signal with phase modulation is connected to the system input. The response to this signal is subsequently analyzed and compared with the real response of a real system. The goal is therefore to verify the suitability of the simulation model and, on the basis of this analysis, to determine the possibility of using specific piezoelectric ceramic transducers for application of intra-impulse modulated signal. As a method of verification, main parameter analysis of a cross-correlation function was selected. Based on this analysis it was found that this method is relevant for this purpose

An Experimental and numerical study of the load distribution effect on composite slab shear resistance

The design codes prescribe “a close simulation” of the uniformly distributed loads for bending tests, since, applying an ideal uniform load on the slab surface, is not technically as simple as applying concentrated loads by spreader beams. The 4-point bending test used in both standard methods m-k and PCM to determine the shear resistance of composite slabs is currently the most conventional loading arrangement. This article presents the comparison between the 4-point bending and uniform load results, obtained from both experimental tests and numerical simulations. Two groups of specimens, made with a common trapezoidal steel profile and concrete, including short and long spans, have been tested under the two loading setups. The numerical analysis of these slabs has been carried out through modelling the realistic interaction of steel and concrete. For the 4-point bending simulation, predefined vertical cracks are modelled representing the real crack inducers, whereas, for the uniform load case, the Willam-Warnke model is used. Both the experimental and the numerical results indicated that the 4-point bending test provides higher shear strength than uniform load. The experimental part was conducted by LERMA (Universitat Politècnica de Catalunya – BarcelonaTech) in collaboration with AdMaS-BUT at Brno University of Technology. The 3D FEM of composite slabs has been made through ANSYS software.Peer Reviewe

Shear transfer behavior in composite slabs under 4-point standard and uniform-load tests

The 4-point bending test, prescribed by most standards, is the conventional test used to determine the shear resistance of steel-concrete composite slabs, whereas loading requirements are commonly specified in terms of uniform load in standard codes. This article shows a comparison between the results of these two load arrangements. This comparison has been made through both experimental tests and FEM simulations points of view. Both approaches show that the 4-point load arrangement provides higher shear strength than uniform load. The cause of this difference has been studied by means of a realistic FEM approach focusing on the slip mechanics and the 3D contact forces in the steel-concrete interface: longitudinal (shear), transversal (interlocking) and vertical (clamping). It has been concluded that the distribution of contact forces is different from the one load arrangement to the other, mainly because of differences in the distribution of concrete cracks. This article is the result of cooperation between UPC-BarcelonaTech, where the 4-point bending tests and the FEM models were developed, and AdMaS-BUT where the uniform load tests were carried out by means of a vacuum system. The slabs were made with conventional open-rib trapezoidal profile and the Eurocode-4 provisions have been followed in both testing procedures.Peer ReviewedPostprint (author's final draft

Shear transfer behavior in composite slabs under 4-point standard and uniform-load tests

The 4-point bending test, prescribed by most standards, is the conventional test used to determine the shear resistance of steel-concrete composite slabs, whereas loading requirements are commonly specified in terms of uniform load in standard codes. This article shows a comparison between the results of these two load arrangements. This comparison has been made through both experimental tests and FEM simulations points of view. Both approaches show that the 4-point load arrangement provides higher shear strength than uniform load. The cause of this difference has been studied by means of a realistic FEM approach focusing on the slip mechanics and the 3D contact forces in the steel-concrete interface: longitudinal (shear), transversal (interlocking) and vertical (clamping). It has been concluded that the distribution of contact forces is different from the one load arrangement to the other, mainly because of differences in the distribution of concrete cracks. This article is the result of cooperation between UPC-BarcelonaTech, where the 4-point bending tests and the FEM models were developed, and AdMaS-BUT where the uniform load tests were carried out by means of a vacuum system. The slabs were made with conventional open-rib trapezoidal profile and the Eurocode-4 provisions have been followed in both testing procedures.Peer Reviewe

Fatigue and depression predict health-related quality of life in patients with pediatric-onset multiple sclerosis

Background: Fatigue, depression and loss in health-related quality of life (HRQoL) have been reported to occur in a substantial amount of patients with pediatric-onset MS (POMS). This study aims to evaluate depression, fatigue and HRQoL and its relationship in a cohort of patients with POMS and matched healthy controls (HCs). Methods: In a multicenter cross-sectional study, Beck Depression Inventory II, Depressionstest fur Kinder, the Pediatric Quality of Life Inventory (PedsQL (TM)) 4.0 Generic Core Scale and the PedsQL (TM) Multidimensional Fatigue Scale were performed. Results: In a cohort of 106 patients with POMS and 210 matched HCs, patients were significantly more often depressed (21.7% vs. 11.4%, p = 0.014) experienced greater fatigue (40.6% vs. 17.3%, p < 0.001) and a greater loss of HRQoL (43.4% vs. 15%, p < 0.001) than controls. Depression predicted 51.8% of variance of fatigue. Fatigue was also predicted by female gender. Loss of HRQoL was predicted by EDSS, depression and fatigue. Depression and fatigue together explained 67.7% of variance of HRQoL. Conclusion: Patients with POMS are at a significant increased risk for depression, fatigue and loss of HRQoL. Furthermore, fatigue and depression significantly predict reduced HRQoL in POMS, suggesting that testing for these symptoms and early therapy is of utmost importance in all patients with POMS