Abstract: This paper presents a means for reducing the torque
variation during the revolution of a vertical-axis water turbine
(VAWaterT) by increasing the blade number. For this purpose, twodimensional
CFD analyses have been performed on a straight-bladed
Darrieus-type rotor. After describing the computational model and
the relative validation procedure, a complete campaign of
simulations, based on full RANS unsteady calculations, is proposed
for a three, four and five-bladed rotor architectures, characterized by
a NACA 0025 airfoil. For each proposed rotor configuration, flow
field characteristics are investigated at several values of tip speed
ratio, allowing a quantification of the influence of blade number on
flow geometric features and dynamic quantities, such as rotor torque
and power. Finally, torque and power curves are compared for the
three analyzed architectures, achieving a quantification of the effect
of blade number on overall rotor performance.
Abstract: Nanostructured Iron Oxide with different
morphologies of rod-like and granular have been suc-cessfully
prepared via a solid-state reaction in the presence of NaCl, NaBr, NaI
and NaN3, respectively. The added salts not only prevent a drastic
increase in the size of the products but also provide suitable
conditions for the oriented growth of primary nanoparticles. The
formation mechanisms of these materials by solid-state reaction at
ambient temperature are proposed. The photocatalytic experiments
for congo red (CR) have demonstrated that the mixture of α-Fe2O3
and Fe3O4 nanostructures were more efficient than α-Fe2O3
nanostructures.
Abstract: Gold passbook is an investing tool that is especially
suitable for investors to do small investment in the solid gold. The gold
passbook has the lower risk than other ways investing in gold, but its
price is still affected by gold price. However, there are many factors
can cause influences on gold price. Therefore, building a model to
predict the price of gold passbook can both reduce the risk of
investment and increase the benefits. This study investigates the
important factors that influence the gold passbook price, and utilize
the Group Method of Data Handling (GMDH) to build the predictive
model. This method can not only obtain the significant variables but
also perform well in prediction. Finally, the significant variables of
gold passbook price, which can be predicted by GMDH, are US dollar
exchange rate, international petroleum price, unemployment rate,
whole sale price index, rediscount rate, foreign exchange reserves,
misery index, prosperity coincident index and industrial index.
Abstract: Heat powered solid sorption is a feasible alternative to
electrical vapor compression refrigeration systems. In this paper,
activated carbon (powder type Maxsorb and fiber type ACF-A10)-
CO2 based adsorption cooling cycles are studied using the pressuretemperature-
concentration (P-T-W) diagram. The specific cooling
effect (SCE) and the coefficient of performance (COP) of these two
cooling systems are simulated for the driving heat source
temperatures ranging from 30 ºC to 90 ºC in terms of different
cooling load temperatures with a cooling source temperature of 25
ºC. It is found from the present analysis that Maxsorb-CO2 couple
shows higher cooling capacity and COP. The maximum COPs of
Maxsorb-CO2 and ACF(A10)-CO2 based cooling systems are found
to be 0.15 and 0.083, respectively. The main innovative feature of
this cooling cycle is the ability to utilize low temperature waste heat
or solar energy using CO2 as the refrigerant, which is one of the best
alternative for applications where flammability and toxicity are not
allowed.
Abstract: Arc welding creates a weld pool to realize continuity between pieces of assembly. The thermal history of the weld is dependent on heat transfer and fluid flow in the weld pool. The metallurgical transformation during welding and cooling are modeled in the literature only at solid state neglecting the fluid flow. In the present paper we associate a heat transfer – fluid flow and metallurgical model for the 16MnD5 steel. The metallurgical transformation model is based on Leblond model for the diffusion kinetics and on the Koistinen-Marburger equation for Marteniste transformation. The predicted thermal history and metallurgical transformations are compared to a simulation without fluid phase. This comparison shows the great importance of the fluid flow modeling.
Abstract: This paper presents the results of a study aimed at
establishing the temperature distribution during the welding of
magnesium alloy sheets by Pulsed Current Gas Tungsten Arc
Welding (PCGTAW) and Constant Current Gas Tungsten Arc
Welding (CCGTAW) processes. Pulsing of the GTAW welding
current influences the dimensions and solidification rate of the fused
zone, it also reduces the weld pool volume hence a narrower bead. In
this investigation, the base material considered was 2mm thin AZ 31
B magnesium alloy, which is finding use in aircraft, automobile and
high-speed train components. A finite element analysis was carried
out using ANSYS, and the results of the FEA were compared with
the experimental results. It is evident from this study that the finite
element analysis using ANSYS can be effectively used to model
PCGTAW process for finding temperature distribution.
Abstract: Decentralized eco-sanitation system is a promising and sustainable mode comparing to the century-old centralized conventional sanitation system. The decentralized concept relies on an environmentally and economically sound management of water, nutrient and energy fluxes. Source-separation systems for urban waste management collect different solid waste and wastewater streams separately to facilitate the recovery of valuable resources from wastewater (energy, nutrients). A resource recovery centre constituted for 20,000 people will act as the functional unit for the treatment of urban waste of a high-density population community, like Singapore. The decentralized system includes urine treatment, faeces and food waste co-digestion, and horticultural waste and organic fraction of municipal solid waste treatment in composting plants. A design model is developed to estimate the input and output in terms of materials and energy. The inputs of urine (yellow water, YW) and faeces (brown water, BW) are calculated by considering the daily mean production of urine and faeces by humans and the water consumption of no-mix vacuum toilet (0.2 and 1 L flushing water for urine and faeces, respectively). The food waste (FW) production is estimated to be 150 g wet weight/person/day. The YW is collected and discharged by gravity into tank. It was found that two days are required for urine hydrolysis and struvite precipitation. The maximum nitrogen (N) and phosphorus (P) recovery are 150-266 kg/day and 20-70 kg/day, respectively. In contrast, BW and FW are mixed for co-digestion in a thermophilic acidification tank and later a decentralized/centralized methanogenic reactor is used for biogas production. It is determined that 6.16-15.67 m3/h methane is produced which is equivalent to 0.07-0.19 kWh/ca/day. The digestion residues are treated with horticultural waste and organic fraction of municipal waste in co-composting plants.
Abstract: In this paper is study the possibility of successfully
implementing of hollow roller concept in order to minimize inertial
mass of the large bearings, with major results in diminution of the
material consumption, increasing of power efficiency (in wind power
station area), increasing of the durability and life duration of the large
bearings systems, noise reduction in working, resistance to
vibrations, an important diminution of losses by abrasion and
reduction of the working temperature. In this purpose was developed
an original solution through which are reduced mass, inertial forces
and moments of large bearings by using of hollow rollers. The
research was made by using the method of finite element analysis
applied on software type Solidworks - Nastran. Also, is study the
possibility of rapidly changing the manufacturing system of solid and
hollow cylindrical rollers.
Abstract: This paper proposes the numerical simulation of the
investment casting of gold jewelry. It aims to study the behavior of
fluid flow during mould filling and solidification and to optimize the
process parameters, which lead to predict and control casting defects
such as gas porosity and shrinkage porosity. A finite difference
method, computer simulation software FLOW-3D was used to
simulate the jewelry casting process. The simplified model was
designed for both numerical simulation and real casting production.
A set of sensor acquisitions were allocated on the different positions
of the wax tree of the model to detect filling times, while a set of
thermocouples were allocated to detect the temperature during
casting and cooling. Those detected data were applied to validate the
results of the numerical simulation to the results of the real casting.
The resulting comparisons signify that the numerical simulation can
be used as an effective tool in investment-casting-process
optimization and casting-defect prediction.
Abstract: This work evaluated the effect of temperature on headspace solid-phase microextraction of volatile and furanic compounds in coated fish sticks. The major goal was the analysis of the samples as consumed, to reproduce volatile compounds people feel when consuming those products. Extraction at 37 ºC (the human body temperature) throughout the HS-SPME analysis of volatile and furanic compounds in coated fish was compared with higher extraction temperatures, which are frequently used for this kind of determinations. The profile of volatile compounds found in deepfried (F) and non-fried (NF) coated fish at 37 and 50 ºC was different from that obtained at 80 ºC. Concerning furan and its derivatives, an extra formation of these compounds was observed at higher extraction temperatures. The analysis of volatile and furanic compounds in fish coated sticks simulating the cooking and eating conditions can be reliably carried out setting the headspace absorption temperature at 37 ºC.
Abstract: In this article, the phenomenon of nonlinear
consolidation in saturated and homogeneous clay layer is studied.
Considering time-varied drainage model, the excess pore water
pressure in the layer depth is calculated. The Generalized Differential
Quadrature (GDQ) method is used for the modeling and numerical
analysis. For the purpose of analysis, first the domain of independent
variables (i.e., time and clay layer depth) is discretized by the
Chebyshev-Gauss-Lobatto series and then the nonlinear system of
equations obtained from the GDQ method is solved by means of the
Newton-Raphson approach. The obtained results indicate that the
Generalized Differential Quadrature method, in addition to being
simple to apply, enjoys a very high accuracy in the calculation of
excess pore water pressure.
Abstract: Rapid Prototyping (RP) is a technology that produces models and prototype parts from 3D CAD model data, CT/MRI scan data, and model data created from 3D object digitizing systems. There are several RP process like Stereolithography (SLA), Solid Ground Curing (SGC), Selective Laser Sintering (SLS), Fused Deposition Modeling (FDM), 3D Printing (3DP) among them SLS and FDM RP processes are used to fabricate pattern of custom cranial implant. RP technology is useful in engineering and biomedical application. This is helpful in engineering for product design, tooling and manufacture etc. RP biomedical applications are design and development of medical devices, instruments, prosthetics and implantation; it is also helpful in planning complex surgical operation. The traditional approach limits the full appreciation of various bony structure movements and therefore the custom implants produced are difficult to measure the anatomy of parts and analyze the changes in facial appearances accurately. Cranioplasty surgery is a surgical correction of a defect in cranial bone by implanting a metal or plastic replacement to restore the missing part. This paper aims to do a comparative study on the dimensional error of CAD and SLS RP Models for reconstruction of cranial defect by comparing the virtual CAD with the physical RP model of a cranial defect.
Abstract: In seismic survey, the information regarding the
velocity of compression wave (Vp) as well as shear wave (Vs) are
very useful especially during the seismic interpretation. Previous
studies showed that both Vp and Vs determined by above methods
are totally different with respect to each other but offered good
approximation. In this study, both Vp and Vs of consolidated granite
rock were studied by using ultrasonic testing method and seismic
refraction method. In ultrasonic testing, two different condition of
rock are used which is dry and wet. The differences between Vp and
Vs getting by using ultrasonic testing and seismic refraction were
investigated and studied. The effect of water content in granite rock
towards the value of Vp and Vs during ultrasonic testing are also
measured. Within this work, the tolerance of the differences between
the velocity of seismic wave getting from ultrasonic testing and the
velocity of seismic wave getting from seismic refraction are also
measured and investigated.
Abstract: the work contains the results of complex investigation
related to the evaluation of condition of working blades of gas turbine
engines during fatigue tests by applying the acoustic emission
method. It demonstrates the possibility of estimating the fatigue
damage of blades in the process of factory tests. The acoustic
emission criteria for detecting and testing the kinetics of fatigue crack
distribution were detected. It also shows the high effectiveness of the
method for non-destructive testing of condition of solid and cooled
working blades for high-temperature gas turbine engines.