Increasing Power Levels Research Articles

Response surface method-based optimization of the shroud of an axial cooling fan for high performance and low noise

We optimized the shroud of an axial cooling fan in a mechanical room of a household refrigerator using the response surface method (RSM) based on numerical predictions in terms of high flow rate and low noise. Computational fluid dynamics (CFD) techniques and an acoustic analogy were used to predict the volume flow rate (VFR) and noise in the system. The numerical methods were validated by comparing their VFR and acoustic power level predictions with the measured data. Then, the RSM was used to optimize the design parameters of the shroud of an axial cooling fan. The numerical prediction using optimum design obtained for maximum VFR from the RSM showed that the VFR can be increased by 21.8% at the cost of an increase in the acoustic power level by 1 dB. The prediction for minimum noise reveals that the acoustic power level can be reduced by 3.55 dB at the same flow rate as the original model. The orifice length of the shroud and the serrated structure are found to contribute significantly to the flow rate and radiated noise, respectively. Physical reasons for these observations are given based on detailed investigations of the variations of flow fields due to the design parameters.

SWITCHABLE MICROWAVE BAND-STOP TO ALL PASS FILTER USING STEPPED IMPEDANCE RESONATOR

Electronically switchable microwave fllters are attracting more attention for research and development because of their importance in increasing the capability of wireless communication and cognitive radios. In this paper, novel switchable microwave band- stop to all pass fllters are designed by using stepped impedance resonator. Commercially available Pin diodes are used in order to allow the fastest switching between band-stop and all pass responses. The theoretical analysis is presented in this paper, and its feasibility has been experimentally verifled with a micro-strip prototype. The design was also characterized by measuring the fllter performance with increasing power levels of 20, 15, 10, 5, and 0dBm. The results have shown that the switchable fllter is immune to power saturation efiects. Nonlinear measurements at higher power levels are also performed and the switchable fllter produced low power inter-modulation product. The main advantage of this fllter is its capability to switch between band-stop and all pass mode of operation. Other advantages include being small in size, and low in cost.

HERMITIAN SYMMETRY BASED FIBER NON-LINEARITY COMPENSATION IN OPTICAL OFDM NETWORKS

Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique which is now used in most new and emerging broadband wired and wireless communication systems such as standard 802.11a/b/g/n, Digital Video Broad casting Television (DVB-TV), and Long Term Evolution (LTE) in the next mobile generation, due to its capacity in solving the problems of Inter-Symbol Interference (ISI) caused by the effects of the dispersive channel. Very recently researches focus on applying OFDM technology in optical fiber communication systems. Optical OFDM is well suited for high speed transmission systems with high spectral efficiency and attracted significant attention from the optical communication community. One of the major issues that degrade the performance of optical OFDM networks is its fiber non-linearity. Fiber non-linearities represent the fundamental limiting mechanisms to the amount of data that can be transmitted on a single optical fiber. Non-linear effects arise as optical fiber data rates, transmission lengths, number of wavelengths, and optical power level increases. Therefore, the effect of non-linearity in high data rate optical networks needs to be controlled to enhance link performances. In this paper, a nonlinearity compensation technique (Hermitian Symmetry) is implemented to improve the performance of OFDM based optical networks. This would provide high spectral efficiency, low ISI and very good Bit Error Rate (BER) performances without increasing the complexity of the network. The optical OFDM transmission system with fiber non-linearity compensation is simulated using Virtual Photonics Integrated (VPI) software.

An experimental investigation on a multilevel inverter for solar energy applications

The main objective of the proposed work is to design, develop and test a three phase multilevel inverter with the modern power electronic switches to reduce the power quality issues in solar power conversion system. Due to the increased usage of power electronic converters for processing the power in all walks of our life, the power quality problem become the hot research topic in the recent years. As the power level increases, the voltage level is increased accordingly to obtain satisfactory efficiency. The multilevel power converter has shown growing popularity. The fundamental advantages of multilevel converter topologies are low distorted output waveforms and limited voltage stress on the switching devices and hence the reduced electromagnetic interferences. The main disadvantages are higher complexity and more difficult control; it can be overcome by using modern digital controllers. In this paper, the performance parameters are analyzed with the developed prototype of the three phase cascaded multilevel inverter for solar energy conversion designed with digital controller for reduced power quality issues with three phase AC motor drive. The main objective is to obtain the better quality of output waveform on the inverter output with suitable control strategy on the experimental hardware setup.

Marking, Ablating, Cleaning, Cutting and even Micro Welding!

AbstractDespite outstanding beam qualities, air cooled pulsed fiber lasers were previously mainly used for marking purposes due to their limited average power level. Increasing power levels enable those laser sources now to be used for applications that required totally different (more sophisticated/more complex) laser sources in the past. These latest developments will lead to a name change for the devices now called laser markers (source plus scanner) to “fine process lasers”, as they are able to mark, cut and weld small parts in the medical, automotive and defense industry sectors.

Microwave drying of ginger (Zingiber officinaleRoscoe) and its effects on polyphenolic content and antioxidant activity

SummaryThe effects of microwave (MW) drying on the total polyphenol content (TPP) and antioxidant properties of ginger extract (column extraction using 50% ethanol at room temperature) were evaluated using the Folin–Ciocalteau's method, 2, 2′‐diphenyl‐1‐picryl‐hydrazyl assay, reducing power, antioxidant capacity and ferric reducing ability of plasma assay. The results were compared to that of the convective cross‐flow drying (CD) at 50 ± 4 °C. Extract yield, TPP content (59–80 mg GAE per g) of the MW‐dried samples increased with increase in MW power levels (PL 40, 60, 80 and 100), which might be as a result of MW energy causing breakdown of cellular constituents. The MW‐dried (PL100, 800W) extract showed the highest quantity (1.5 fold) in TPP, [6]‐gingerol content and antioxidant activity, when compared to the CD extract. Hence, it might be concluded that the optimal MW PL for drying of ginger slices with respect to retention of nonvolatiles such as TPP including [6]‐gingerol was PL 100.

Investigation on Surface and Biological Properties of Silver Containing Diamond Like Carbon Films on Polyethylene Terephthalate Film Surface by Hybrid Reactive Sputtering Method

Silver containing diamond like carbon films were coated on the surface of polyethylene film (PET) using novel hybrid sputtering method. Polymeric substrates can create soft, flexible, highly absorbent and cost-effective materials by selecting or controlling their molecular structures. The material silver is known to be a potential antibacterial material. The silver containing coating has been potentially recommended for synthesis biomedical materials. In the present work, we discussed the antibacterial activity of the silver containing DLC film coated PET film surfaces which was coated as a function of deposition power level. The surface morphology of the Ag-DLC was analysed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The atomic concentration and structure of the Ag-DLC was measured by energy dispersive X-ray (EDX) and Raman spectroscopy. The hydrophilicity of the films was measured by contact angle analysis. The antibacterial activity of Ag–DLC films were evaluated by bacterial eradication tests withEscherichia coliat incubation time of one day. In addition, blood compatibility of the Ag-DLC films were studied byIn Vitroblood compatibility tests. It was found that the surface of the obtained Ag-DLC decreases with increasing the deposition power level. The antibacterial and hemocompatibility of the silver containing DLC film increase gradually with increase of deposition power level. Our results revealed that the Ag-incorporated DLC films are potentially useful as biomedical devices having good antibacterial and hemocompatibility.

ADORE-GA: Genetic algorithm variant of the ADORE algorithm for ROP detector layout optimization in CANDU reactors

The regional overpower protection (ROP) systems protect CANDU® reactors against overpower in the fuel that could reduce the safety margin-to-dryout. The overpower could originate from a localized power peaking within the core or a general increase in the global core power level. The design of the detector layout for ROP systems is a challenging discrete optimization problem. In recent years, two algorithms have been developed to find a quasi optimal solution to this detector layout optimization problem. Both of these algorithms utilize the simulated annealing (SA) algorithm as their optimization engine. In the present paper, an alternative optimization algorithm, namely the genetic algorithm (GA), has been implemented as the optimization engine. The implementation is done within the ADORE algorithm. Results from evaluating the effects of using various mutation rates and crossover parameters are presented in this paper. It has been demonstrated that the algorithm is sufficiently robust in producing similar quality solutions.

Microwave annealing of YAG: Ce nanophosphors

Y3Al5O12:Ce3+ nanophosphor powders were synthesized via a solvothermal method. The pure YAG:Ce crystalline phase was found after solvothermal method at 220°C/2h and postannealing at 1150W using a single-mode cavity of 2.45GHz microwaves. The average crystallite sizes of powders were in the range of 39–51nm. The photoluminescence (PL) emission intensity increased with increasing power levels. The microwave annealed sample at 1150W showed higher PL emission intensity than conventionally annealed sample (1500°C/4h).

Optimization of Hard Disk Drive Heads Cleaning by Using Ultrasonics and Prevention of Its Damage

This paper investigates the optimization of hard disk drive heads under various experimental conditions such as ultrasonic frequency, sonication time, ultrasonic power and cleaning solvent. The ranges of frequency and ultrasonic power studied were 40 – 132kHz and 100 – 500W respectively. Three solvents were tested to compare the cleaning efficiency and parts damage (low boiling point solvent: acetone and high boiling point solvent: N- Methyl Pyrolidone (NMP) around 200°C and mixture of acetone 30% and NMP 70%). The best cleaning condition obtained from the experiments are 40kHz with 5min followed by 58kHz 5min followed by 132kHz with 4min followed by 58/132kHz with 4min. The removal efficiency (85%) is high for multiple frequencies with shorter cleaning time of each frequency compared to single frequency (70%) with longer cleaning time of same frequency (58kHz). The surface damage induced by Ultrasonics at the contact area is almost 0 for the best cleaning condition irrespective of the solvent used (∼0.01% for acetone). As the power level increases, damage of parts also increases. The cavitation intensity is higher for higher power level. Therefore, the parts undergo more vibration and leads to more parts damage. The parts damage is more for acetone as compared to NMP. The result also indicates that the removal efficiency is high for Co-solvent (acetone +NMP) comapred to acetone or NMP alone. The AlTiC surface profile of the burned parts can be measured by using Atomic Force Microscope technique (AFM). The result indicates that the surface roughness value (Ra) obtained from AFM analysis for good and burned slider was 2.294nm and 8.288nm respectively. The Ra value was almost 4 times higher for burned slider. The defects/contamination on the AlTiC surface can be detected by using Energy Dispersive X-Ray (EDX) analysis

Quantification of surface area and intrinsic mass transfer coefficient for ultrasound-assisted dissolution process of a sparingly soluble solid dispersed in aqueous solutions

The efficacy of power ultrasound of 20 kHz in enhancing the volumetric mass transfer coefficient was investigated in this study. Breakage and dissolution of sparingly soluble benzoic acid dispersed in either water or 24% aqueous glycerol was monitored as a function of time and ultrasound power input. Particle size measurements were carried out at intermediate times during the experiment to estimate the mean particle size and surface area. Linear combination of lognormal distributions was found to fit the experimental particle size distribution data. The De Brouckere mean diameters ( d 43) obtained from the particle size distributions decreased with increase in the ultrasonic power level. Empirical correlations were developed for the evolution of surface area as a function of ultrasonic energy input per unit mass. The effect of ultrasound on the intrinsic mass transfer coefficient ( k c) could be decoupled from the volumetric mass transfer coefficient ( k c a) as the surface area was also estimated. Different approaches involving either constant or variable intrinsic mass transfer coefficients were employed when carrying out the delineation. Mass transfer rates were enhanced due to both higher ultrasound induced intrinsic convective mass transfer coefficient and additional surface area created from particle breakage. To delineate the effects of particle breakage from solid dissolution, experiments were also carried out under non-mass transfer conditions by pre-saturating the solvents with benzoic acid. Both the solid–liquid systems examined in the present study attained saturation concentration when the ultrasonic energy input per unit mass was approximately 60 kJ/kg, irrespective of the ultrasonic power level setting.

Microwave drying and moisture diffusivity of white mulberry: experimental and mathematical modeling

The literature surveyed revealed that drying kinetics of white mulberry under microwave treatment has not been investigated. In present study, both experimental study and mathematical modeling on microwave drying of white mulberry was performed. The microwave drying process which reduced the moisture content of mulberry from 3.76 to 0.25 (g water/g dry matter) was carried out at 90, 180, 360, 600, and 800 W in a modified microwave drying set-up. The effects of microwave drying technique on the moisture ratio and drying rate of white mulberry were investigated experimentally. Both the effects of microwave power level (under the range of 90–800W) and initial sample weight (50–150g) were studied. No constant rate period was observed. Mathematical modeling of thin layer drying kinetics of white mulberry under microwave treatment was also investigated by fitting the experimental drying data to eight thin layer drying models. Among the models proposed, Midilli et al. model precisely represented the microwave drying behavior of white mulberry with the coefficient of determination higher than 0.999 and mean square of deviation (χ2) and root mean square error (RMSE) lower than 1.1×10−4 and 8.9×10−3, respectively for all the microwave drying conditions studied. The effective moisture diffusivity (Deff) of white mulberry varied from 0.45×10−8 to 3.25×10−8 m2s−1. Both the drying constant (k) and Deff increased with the increase of microwave power level.

VIBRO-ACOUSTIC RESPONSE OF A CIRCULAR ISOTROPIC CYLINDRICAL SHELL UNDER A THERMAL ENVIRONMENT

This paper presents numerical simulation studies on the vibration and acoustic response-characteristics of an isotropic cylindrical shell under a thermal environment using commercial softwares ANSYS and SYSNOISE. First, the critical buckling temperature is obtained, followed by modal and harmonic response analyses considering pre-stress due to the thermal field in the cylindrical shell, with the critical buckling temperature as a parameter. The vibration response predicted is then used to compute the sound radiation. It is found that there is a significant change in the vibration mode shapes and ring frequency towards the lowest natural frequency with an increase in temperature. There is a sudden increase in overall sound power level near the critical buckling temperature and significant changes in mode shapes with temperature does not affect the overall sound power level.

Thin layer drying kinetics of Gundelia tournefortii L.

The literature surveyed revealed that the drying kinetics of Gundelia tournefortii has not been investigated. In this study, mathematical modeling of the thin layer drying kinetics of G. tournefortii is investigated for both the microwave and open sun drying conditions. Five different microwave power levels ranging from 90 to 800W were used for the microwave drying. Solar radiation for the open sun drying varied from 350 to 1100W/m2. Drying took place in the falling rate period. Increasing the microwave power caused a significant decrease in drying time. The experimental moisture loss data were fitted to the 14 thin layer drying models. Among the models proposed, the Midilli model precisely represented the microwave drying behavior of G. tournefortii with the coefficient of determination higher than 0.996 and mean square of deviation (χ2), root mean square error (RMSE) and mean bias error (MBE) lower than 1.82×10−4, 12×10−3 and 1.4×10−4, respectively for all the microwave drying conditions studied. Values of drying constant (k) were in the range of 0.0098–0.2943min−1 and the effective moisture diffusivities (Deff) of G. tournefortii ranged from 5.5×10−8 to 3.5×10−7m2/s. The values of k and Deff increased with the increase of microwave power level. The logarithmic model was found to best describe the open sun drying kinetics of G. tournefortii. The effective diffusivity of G. tournefortii under the sun drying condition was determined as 2.48×10−10m2/s.

Designing power heterojunction bipolar transistors with non-uniform emitter finger lengths to achieve high thermal stability

With the aid of a thermal-electrical model, a practical method for designing multi-finger power heterojunction bipolar transistors with finger lengths divided in groups is proposed. The method can effectively enhance the thermal stability of the devices without sacrificing the design time. Taking a 40-finger heterojunction bipolar transistor for example, the device with non-uniform emitter finger lengths is optimized and fabricated. Both the theoretical and the experimental results show that, for the optimum device, the peak temperature is lowered by 26.19 K and the maximum temperature difference is reduced by 56.67% when compared with the conventional heterojunction bipolar transistor with uniform emitter finger length. Furthermore, the ability to improve the uniformity of the temperature profile and to expand the thermal stable operation range is strengthened as the power level increases, which is ascribed to the improvement of the thermal resistance in the optimum device. A detailed design procedure is also summarized to provide a general guide for designing power heterojunction bipolar transistors with non-uniform finger lengths.

Degradation of Diethyl Phthalate by Sono-Fenton Process and its Dependence on the Power Density

The first-order rate constants of diethyl phthalate (DEP) degradation by sonochemical, Fenton and sono-Fenton processes were compared, and the synergistic effect of the combined sono-Fenton process and the dependence of the degradation rate on the power density (80, 180, and 330 W L-1) were investigated. The rate constants for the individual sonochemical and Fenton processes were 10-3 to 10-2 and 1.02 ×10-2 min-1, respectively. The synergy from the combined process increased significantly as the applied power density increased, and it was 1.97 with the input of ultrasonic energy of 330 W L-1. This increase was attributed to the higher efficiency of hydroxyl radical production from several pathways. The relationship between the degradation rate constant and power density was linear because the cavitation rate increased with increasing power level of the applied ultrasound.

Pu-breeding feasibility in irradiation channels of research reactors

The breeding potential in the irradiation channels of research reactors is of safeguards concern, because of lacking continuous supervision on the type of experiments in all the irradiation channels. Moreover, the irradiation time can be optimized in order to breed high quality weapon grade plutonium. With regard to the safeguards measures currently adopted, IAEA concentrates its efforts on those reactors whose thermal power is greater than 25 MWth, because it was calculated that a 25 MWth LEU-fuelled reactor produces not more than one Significant Quantity of Pu (8 kg)/year in its spent fuel and a HEU-fuelled reactor of this power would require an annual reload of not more than one Significant Quantity of U 235 (25 kg). In order to investigate whether it would be possible to determine an analogous power level threshold to estimate the clandestine plutonium production capability of different research reactors, the Monte Carlo method was used to determine the neutron flux in the irradiation channels and to calculate the plutonium breeding potential for three different reactor types: (1) a Triga Mark II with 250 kWth, representative for a small size research reactor; (2) a Material Test Reactor (MTR) with 5 MWth, representative for a medium size research reactor; (3) a High Flux Reactor (HFR) with 45 MWth, representative for a large size research reactor. It was observed that the most important factors for plutonium breeding are the neutron flux (to which reaction rates are proportional) and the available space to place irradiation samples. The breeding capability scales fairly well with the reactor power level and from about 10 MWth onwards the proliferation concern raises with increasing power level and available sample space.

The importance of uncertainties in the ROP detector layout design process for CANDU reactors

In CANDU® reactor design, the regional overpower protection (ROP) systems protect the reactor against overpower in the fuel which could reduce the safety margin-to-dryout. The increase in fuel power could be caused by a localized power peaking within the core (for example, as a result of a certain reactivity device configuration) or a general increase in the core power level during a slow-loss-of-regulation (SLOR) event. This overpower could lead to fuel sheath dryout. In the CANDU® 600 MW (CANDU 6) design, there are two ROP systems in the core, one for each fast-acting shutdown system. Each ROP system includes a number of fast-responding, self-powered flux detectors suitably distributed throughout the core within vertical and horizontal assemblies. A new methodology for designing the detector layout for the ROP system, called the DETPLASA algorithm, has been developed recently. This method utilizes the simulated annealing (SA) technique to optimize the placement of the detectors in the core. The evaluation of the trip setpoint (TSP) corresponding to each detector layout configuration ( i.e., each history in the SA algorithm) is performed probabilistically using the ROVER-F code. In this evaluation, there are uncertainties related to both the detector components ( i.e., related to the margin-to-trip) and to the fuel channel components ( i.e., related to the margin-to-dryout). In this paper, the importance of these uncertainties on the outcome of the detector layout optimization process is evaluated. Some parametric studies have been performed to quantify the effect of uncertainties on the resulting detector layout. Two types of investigations have been performed. First, a given detector layout will be used to explicitly determine the effect of changing the uncertainty values. In this study, 343 sets of uncertainty values are used to produce the corresponding TSP values. The variation in the TSP values is analyzed. Second, three sets of uncertainty values (a subset of uncertainties from the first study) are used in independent DETPLASA executions. The resulting detector layout configurations will be examined to observe the effect of these uncertainties on the final design. Results from these investigations are presented in this paper.

Thermal properties of diamond/Ag composites fabricated by eletroless silver plating

Thermal management in microelectronic technology has become an important issue due to the increase of device power and integration levels. Diamond and silver were selected for the fabrication of composites with high thermal conductivity and low coefficient of thermal expansion (CTE). Diamond reinforcement powders with varied types, shapes and sizes were electroless plated by silver. Then these powders were hot-pressed in air at 600 °C, 500 MPa for 30 min to produce bulk silver matrix composites. The thermal conductivity and the CTEs of the composite at 20 vol.% are 420 W/m K and 12 ppm/K, respectively. These diamond/Ag composites have potential applications for the high integration electronic devices.

Methodologies for optimizing ROP detector layout for CANDU® reactors

The regional overpower protection (ROP) systems protect CANDU® reactors against overpower in the fuel that would reduce the safety margin-to-dryout. Both a localized power peaking within the core (for example, as a result of certain reactivity device configuration) or a general increase in the core power level during a slow-loss-of-regulation (SLOR) event could cause overpower in the fuel. This overpower could lead to fuel sheath dryout. In the CANDU® 600 MW (CANDU 6) design, there are two ROP systems in the core, one for each fast-acting shutdown systems. Each ROP system includes a number of fast-responding, self-powered flux detectors suitably distributed throughout the core within vertical and horizontal assemblies. Traditionally, the placement of these detectors was done using a method called the detector layout optimization (DLO). A new methodology for designing the detector layout for the ROP system has been developed recently. The new method, called the DETPLASA algorithm, utilizes the simulated annealing (SA) technique to optimize the placement of the detectors in the core. Both methodologies will be discussed in detail in this paper. Numerical examples are employed to better illustrate how each method works. Results from some sensitivity studies on three SA parameters are also presented.