Abstract— A sudden postural change may produce symptoms or even syncope mainly due to orthostatic hypotension. To date, most hemodynamic studies in postural change focus on the response of static and definite postures. To quantify cardiovascular hemodynamics characteristics during continuous posture, we developed a three-dimensional fluid-structure interaction mathematical model of hemodynamics with continuous posture. In this model, the rotating inertial forces were introduced. By the finite element method, the distribution of blood flow pressure (DBFP) in the inner carotid artery in ±90° postures was numerically simulated with rotation and gravity concerned or not. The simulations are as follows: (1) whether gravity was considered or not, the DBFP varied from two-dimensional axisymmetrical distribution without rotation to three-dimensional asymmetrical one with rotation considered, and extreme pressures occurred in the same positions in the two cases. (2) The effect intensity of rotation is larger than the effect intensity of gravity. So, unlike gravity, rotation affected the DBFP. This indicates that hemodynamic characteristics in certain position during dynamic change of posture obviously differ from that in static and definite posture. This study may provide a novel way to characterize hemodynamics during continuous posture, and consequently help to evaluate the syncope patients, astronauts or pilots and athletes with unexplained syncope more accurately.
Keywords— Blood flow pressure, Continuous posture, Gravity, Hemodynamics, Mathematical Model, Rotation, Syncope.
Abstract— The estimation of areal rainfall is an important part of solving various hydrological problems utilizing rainfall-runoff and other models. Traditionally used Thiessen polygons (TP) method proved to be inaccurate mainly in mountainous areas and in catchments with insufficient number of rainfall gauges. One of the alternative to this method is an inverse distance weighting (IDW) method giving better estimates of areal rainfall even on places with rugged orography. However, this and similar methods are far less efficient than the simple TP method restraining its use to tasks where computational efficiency is not important. In this study a new algorithm accelerating the traditional IDW method is proposed and applied to three mountainous catchments situated in the central part of Slovakia. The method is compared with traditional IDW and TP methods in terms of both computational efficiency and estimated values. The results showed that while the new method gives the same results as the traditional IDW method it is far more efficient when the computational time was in all three catchments reduced by more than 96%.
Keywords – areal rainfall, inverse distance weighting, interpolation, Thiessen polygons.
Abstract— Zirconia with tetragonal phase is a widely used functional material to toughen ceramics. At room temperature zirconia usually presents in the less stable form of monoclinic phase. In this paper, room temperature single tetragonal phase zirconia stabilized by yttria was successfully synthesized by a sol-gel route at a relative low temperature (≤1000oC). The calcination mechanism of zirconia was determined by thermogravimetric analysis and differential scanning calorimetry, which indicated that phase formation of zirconia started above 600oC. X-ray diffraction patterns showed stabilized with 3mol % yttria was insufficient to obtain fully single tetragonal phase zirconia. As the content of the stabilizer increased, single tetragonal phase zirconia was obtained as observed by Raman spectrum and X-ray diffraction. With 4mol% yttria content, zirconia remains stable with the desired tetragonal phase at room temperature.
Keywords— Zirconia, tetragonal phase, sol-gel, phase characterization.
- nYSZ (n=3, 3.5, and 4) were synthesized by Pechini sol-gel route successfully.
- The phase status of 3YSZ, 3.5YSZ, and 4YSZ was investigated.
- The 4YSZ with the pure tetragonal phase at room temperature was obtained.
Colossal and frequency stable permittivity of barium titanate nanoceramics derived from mechanical activation and SPS sintering
Abstract— Highly dense barium titanate nanoceramics have been successfully prepared via a mechanical activation synthesis method and Spark Plasma sintering. Attractive electrical properties have been evidenced in these materials: a colossal permittivity, (3.5. 105) and low loss (0.07) at room temperature and 1 kHz, that are stable over a wide frequency range (from 40 Hz to 40 kHz). Surprisingly, the ferroelectric transition is still observed, for the first time to our knowledge, in these colossal permittivity materials.
Keywords— Barium titanate, ball milling, spark plasma sintering, nanoceramics, dielectric properties.
Abstract— The Curve Number (CN) method used for estimating direct runoff depths from rainstorms (developed by NRCS in 1954) is based on a CN parameter (representing the hydrological properties of a catchment) and a λ parameter (representing the initial abstraction ratio Ia/S). In this paper, the CN parameter is determined for 10 small Slovak basins using the original SCS-CN method (CNtabulated) and empirically from rainfall-runoff events for a 13-year period using four different approaches (asymptotic fitting, arithmetic, median, and a method used by Hawkins et al. ) for both natural and ordered P-Q pairs (CNempirical). The CNempirical numbers were evaluated and consequently used to determine the direct runoff for both λ equal to 0.2 and 0.05. The results show differences among the selected approaches that indicate variances in the direct runoff computed. The large range of the empirical CN numbers indicates uncertainty. However, the NRCS does not define the uncertainty of the tabulated curve numbers either, and the original data is not available. As a result, this paper will highlight the uncertainty of tabulated CN numbers.
Keywords— Curve Number method, Rainfall-runoff events, Asymptotic fitting.
Abstract— NASA´s spacecraft, Galileo, discovered large amount of water on Europa, one of the Jupiter´s icy moons. Several works claim the existence of a liquid water ocean under the Europa icy crust. Europa is one of the most important regions in the Solar System and might reveal primitive forms of life in its oceans. At the present days, several technologies can be used to design the travel, prepare the landing and build the pressure hull of the submarine. A deep region of ice crust could be melted by an ice breaker, which would reach a liquid ocean and then a small submarine would be released. In this short communication, a preliminary design of both ice breaker and a small submarine for Europa’s ocean exploration is considered. Additionally, communication between the submarine and a structure left over the icy crust will be discussed too. Results reveal that a small submarine with less than 80 cm and 2.4 m for diameter and beam, respectively, are required for moderate melting time. A submarine hull in ceramic composite is required to have adequate reserve buoyancy. Several alternatives are analysed for both submarine propulsion problems and underwater communication systems.
Keywords— Spacecraft, submarine, Europa, ice breaker, pressure hull.
Abstract— This study is based on the experimental method to investigate the gas water heater cycling piping system, In this experiment, the accelerated corrosion rate of laboratory immersion corrosion test of metal and electrochemical methods, three kinds of water quality to pure water, tap water, groundwater as a corrosion observed. Flow field experiments rectangular boxes, copper tube and acrylic sheet components, In order to visualize the flow, the shadowgraph technique is used. In order to understand the structure of the flow field and flow field of temperature and concentration measurement analysis and mass transfer rates.
Keywords— Flow Field, Electrochemical, Immersion Corrosion Test, temperature, concentration.
Abstract— This study is research of gas water heater cycling system with piping the heat transfer simulation analysis of water heater pipeline flow channel system the mold flow software of numerical calculation is FLUENT6.2 the geometric shape and computational grid for quarter bend, When the fluid passes through the shape changed flow field, under the effect of pressure distribution and geometric shape change of the flow field, there will be a recirculation zone. In the flow field of a quarter bend, To understand the structure of the flow field and flow field of temperature a analysis.
Keywords— Gas Water Heater Cycling System, Quarter Bend, Flow Field, Numerical Calculation.
Bacteria Associated with the Spoilage of Salad, their resistotyping and Potential Public Health Implications
Abstract— A study of bacteria associated with spoilage of various types of salads purchased from 3 different restaurants in Uyo metropolis was carried out between the months August and October, 2008 using standard microbiological procedures. The mean microbial load in vegetable salad was (3.5±0.25) x 107cfu/g with the sample from food affairs having the highest load (3.7 x 107cfu/g). The mean microbial load in garlic salad was (3.2±0.25) x 107cfu/g also with the sample from food affairs having the highest load (3.6 x 107cfu/g). However, fruit salad samples from Mr. Biggs had the highest microbial load (3.9 x 107cfu/g) out of the mean value of (3.6±0.25) x 107 cfu/g. Analysis of the frequency of occurrence of the isolates revealed that Staphylococcus aureus (33%), Micrococcus spp. (20%), Bacillus spp. (20%), Proteus spp. (13%), Pseudomonas spp. (13%) and Escherichia coli (7%) were the most encountered organisms in both spoiling and fresh (control) salad. The resistotyping of 20 % of tested bacteria were resistant to 5 antibiotics. The presence of Escherichia coli and some potential pathogenic microorganisms in all the samples collected are indications of faecal contamination and unhygienic method of food handling. This suggests that salad should be properly managed during and after preparations to avoid outbreak of food borne diseases. Also the food handlers should be trained and educated on the importance of sanitary condition during food production.
Keywords— Bacteria, salad, spoilage, Staphylococcus species, Escherichia coli, resistotyping.
Abstract— A successfully designed bike should possess safety and comfort for the riders. A safe bike means that its structure must be strong enough to prevent from damage due to various external loads and a comfortable bike means that its suspension systems must be excellent enough to reduce the transmissibility of disturbance coming from the uneven roads to the rider. In order to achieve the above goals, various methods have been presented; however, most of them assumed that each part of a bike is a “rigid body” except the helical (coil) springs. For the last reason, this paper tries to use more versatile finite element method (FEM) to perform the static and free vibration analysis of a bike. It is believed that a finite element model with all parts of a bike replaced by the “elastic” elements or lumped masses should be more realistic. In this paper, the entire bike structure is modeled by using three kinds of beam elements: pinned-pinned (P-P), pinned-clamped (P-C) and clamped-clamped (C-C) beam elements. Among the main parts of a bike structure, the main frame and rim are modeled by the C-C elements, the elastic effect of each tire is modeled by using a P-C element, and each spoke or each “spring-damper unit” is modeled by a P-P element. The key point of this paper is to study the influence of some pertinent parameters on the lowest several natural frequencies and mode shapes of the bike. It is found that the radius of the hub (disks), the pretension of each spoke, the mass of various attachments or rider, and the riding gesture of a rider have significant influence on the free vibration characteristics, the static deformations and internal forces (and moments) of the pertinent structural members of a bike. Because the mass of a rider is much greater than that of the bike structure itself, the static and dynamic characteristics of a bike with and without a rider on it must be studied, separately.
Keywords— Rider, Bike, Suspension System, Finite Element Method, Elastic Element, Lumped Mass, Main Frame, Rim, Tire, Spoke, Natural Frequency, Mode Shape
Abstract— A digital low-dropout regulator (D-LDO) with reduced transient response time and overshoot/undershoot is proposed. The reduction of response time is achieved by using transient response boost technique. The loop gain is increased at the time of deviations exceeding the limit and the loop gain is returned after the output voltage is settled. On comparing LDO with and without transient response boost technique the settling time is reduced. The regulation is done in time mode with the help of high linear voltage to time convertor (VTC) and time to digital convertor. The time domain analog to digital conversion achieves high resolution at low power and small area. And multibit cyclic TDC for high level current efficiency is used.
Key words—Current efficiency, cyclic TDC, digital low-dropout regulator (D-LDO), transient-response boost mode (TRBM), voltage-to-time converter (VTC).