Electroless deposition has been used to deposit Ni-P films on glass slides using the reducing agent sodium hypophosphite. This has been done with a purpose to use Ni-P films as back contact for silicon carbide radiati...Electroless deposition has been used to deposit Ni-P films on glass slides using the reducing agent sodium hypophosphite. This has been done with a purpose to use Ni-P films as back contact for silicon carbide radiation detectors. By keeping deposition time, temperature, pH and concentration of the precursor solution constant, the film deposition has been done. XPS studies were done to analyze the composition and stoichiometry of Ni-P thin films.展开更多
The criticality of transformers and reactors in the power transmission network and the paramount importance of ensuring their reliability through maintenance of the insulating oil is known. This paper presents a compr...The criticality of transformers and reactors in the power transmission network and the paramount importance of ensuring their reliability through maintenance of the insulating oil is known. This paper presents a comprehensive examination of the efficacy and economic viability of a dielectric oil regeneration system, as implemented by the Transmission System Maintenance Department (TSMD) of the Independent Power Transmission Operator (IPTO), Greece’s sole transmission operator. Through a detailed chemical analysis and performance evaluation, we assess the impact of the regeneration system on treated insulating oil quality over multiple cycles. The study reveals that the electrical properties of the insulating oil are fully restored after regeneration, negating the need to fully replace it, while the investment becomes cost-neutral within weeks from the commissioning of the regeneration system. This economic analysis, coupled with the system’s environmental benefits of reducing waste oil generation, positions the dielectric oil regeneration system as a compelling solution for the maintenance of power transmission assets.展开更多
This paper deals with a digest on electrical treeing degradation in nanocomposite of magnesium oxide(MgO) added to a low-density polyethylene(LDPE).The objective is to elucidate the"visual"aspects of runaway...This paper deals with a digest on electrical treeing degradation in nanocomposite of magnesium oxide(MgO) added to a low-density polyethylene(LDPE).The objective is to elucidate the"visual"aspects of runaway stage of final treeing breakdown mechanisms,and to ensure that the existence of MgO filler itself is responsible for this aspect instead of voltage application changes.The"visual"aspect of treeing breakdown was investigated by applying ac ramp voltage with continuous rising speed of 0.5 kV/s.As soon as tree had been incepted,the voltage was kept constant to observe the tree propagation until breakdown.The tree propagations were also described by their fractal dimension. To ensure the responsibility of MgO filler on the"visual"aspect results,the experiment was repeated using the same rate of ac ramp voltage.However,as soon as tree had been incepted,the voltage was either increased or decreased to a constant value of mean tree inception voltage obtained from the preceding results to observe its propagation to breakdown. As a result,the tree inception voltage was increased with the filler concentration in LDPE.The filler is considered not only acted as a physical obstacle for tree to propagate,but also as a chemical obstacle in which the free electron might be trapped to cause difficulties for electron avalanche occurrence.This consideration could also be valid for tree propagation up to breakdown.During propagation,due to the filler,the tree structure is accompanied by more branches.Since the branches are closely placed each other,the tree tips become relatively uniform field compares to pure LDPE.This would produce the higher local breakdown strength at the tree tips,leads to the suppression of propagation.The"visual"aspect of breakdown could be achieved by applying voltage exactly at the inception level. After bridging the tree would not breakdown until a short period of time lag.Within this period,the tree channel will be eroded by internal flashover(IFO) and become thicker.MgO filler could still restrain the IFO at the small diameter; however there will be a maximum diameter above which the effect of MgO would be very small.Lastly,it is confirmed that the MgO filler itself excels to suppress the tree degradation instead of the voltage application changes.The polymer nanocomposite appears to be more resistive to treeing degradation than their base material.展开更多
The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the incre...The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the increase of sintering temperature offers a reduced capacitive effect from 0.460 nF to 0.321 nF.Furthermore,the grain sizes of varistors were varied from 6.8μm to 9.8μm.The consequence of such smaller grain sizes provided a better voltage gradient of about 895 V/mm for the disc sintered at 900°C and fallen drastically to 410 V/mm for the sample sintered at 1050°C.In addition,there was an increase of non-linearity index to a maximum value of 36.0 and reduced leakage current of 0.026 mA/cm2.However,the density of the varistor decreased with an increase of temperature from 5.41 g/cm3 to 5.24 g/cm3.With this base,the influence of varistor capacitance and high voltage gradient were scrutinized and it led an improved transition speed of the varistor assembly from non-conduction to conduction mode during intruding nanosecond transients.展开更多
In this work, a total of 322 tests were taken on young volunteers by performing 10 different falls, 6 different Activities of Daily Living (ADL) and 7 Dynamic Gait Index (DGI) tests using a custom-designed Wireless Ga...In this work, a total of 322 tests were taken on young volunteers by performing 10 different falls, 6 different Activities of Daily Living (ADL) and 7 Dynamic Gait Index (DGI) tests using a custom-designed Wireless Gait Analysis Sensor (WGAS). In order to perform automatic fall detection, we used Back Propagation Artificial Neural Network (BP-ANN) and Support Vector Machine (SVM) based on the 6 features extracted from the raw data. The WGAS, which includes a tri-axial accelerometer, 2 gyroscopes, and a MSP430 microcontroller, is worn by the subjects at either T4 (at back) or as a belt-clip in front of the waist during the various tests. The raw data is wirelessly transmitted from the WGAS to a near-by PC for real-time fall classification. The BP ANN is optimized by varying the training, testing and validation data sets and training the network with different learning schemes. SVM is optimized by using three different kernels and selecting the kernel for best classification rate. The overall accuracy of BP ANN is obtained as 98.20% with LM and RPROP training from the T4 data, while from the data taken at the belt, we achieved 98.70% with LM and SCG learning. The overall accuracy using SVM was 98.80% and 98.71% with RBF kernel from the T4 and belt position data, respectively.展开更多
A robotic wheelchair is assumed to be capable of doing tasks like navigation, obstacle detection, etc. using sensors and intelligence. The initial part of the work was development of a cap controlled wheelchair to tes...A robotic wheelchair is assumed to be capable of doing tasks like navigation, obstacle detection, etc. using sensors and intelligence. The initial part of the work was development of a cap controlled wheelchair to test and verify the gesture operation. Following that, a real time operating wheelchair was developed consisting of mode changing option between joystick control mode and head gesture control mode as per as the user’s requirement. The wheelchair consists of MPU6050 sensor, joystick module, RF module, battery, dc motor, toggle switch and Arduino. The movement of the head is detected by MPU6050 and the signal is transmitted to the microcontroller. Then the signal is processed by controller and motion of wheelchair is enabled for navigation. The wheelchair was capable of moving left, right, forward and backward direction. The speed of the wheelchair was 4.8 km/h when tested. Design objective of the wheelchair included cost effectiveness without compromising safety, flexibility and mobility for the users.展开更多
A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO2 gate stack. Impacts of the two kinds of scatterings on mob...A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO2 gate stack. Impacts of the two kinds of scatterings on mobility degradation are investigated. Effects of interlayer （SiO2） thickness and permittivities of the high-k dielectric and interlayer on carrier mobility are also discussed. It is shown that a smooth interface between high-k dielectric and interlayer, as well as moderate permittivities of high-k dielectrics, is highly desired to improve carriers mobility while keeping alow equivalent oxide thickness. Simulated results agree reasonably with experimental data.展开更多
Combined cycle plants (CCs) are broadly used all over the world. The inclusion of CCs into the optimal resource scheduling causes difficulties because they can be operated in different operating configuration modes ba...Combined cycle plants (CCs) are broadly used all over the world. The inclusion of CCs into the optimal resource scheduling causes difficulties because they can be operated in different operating configuration modes based on the number of combustion and steam turbines. In this paper a model CCs based on a mixed integer linear programming approach to be included into an optimal short term resource optimization problem is presented. The proposed method allows modeling of CCs in different modes of operation taking into account the non convex operating costs for the different combined cycle mode of operation.展开更多
We have demonstrated and analyzed the methane gas sensor based on octagonal cladding and hexagonal hybrid porous core photonic crystal fiber (HPC-PCF) for gas detection purpose. The proposed design of HPC-PCF has been...We have demonstrated and analyzed the methane gas sensor based on octagonal cladding and hexagonal hybrid porous core photonic crystal fiber (HPC-PCF) for gas detection purpose. The proposed design of HPC-PCF has been numerically investigated by COMSOL Multiphysics software through utilizing the full vectorial finite element method (FEM). The optical characteristics of HPC-PCF as well as confinement loss, relative sensitivity and refractive index, effective area, nonlinearity and numerical aperture are optimized properly by changing the geometrical parameters as well as air filling ratio, air hole diameter, pitch constant of cladding and porosity of the core. In this simulation work, we have achieved optimum relative sensitivity of 21.2%, and confinement loss of 0.000025 dB/m at 3 μm pitch, 0.7 air filling ratio of the cladding and 29% porosity of the core for 3.5 μm absorption wavelength of CH4 gas. This proposed design of HPC-PCF will keep exclusive contribution for detecting the CH4 gas accurately.展开更多
In this paper, a new method for discovering the candidate car license plate locations is presented. First, the image is decomposed using a Haar wavelet to get the HL band with vertical edges. Then, the HL band image i...In this paper, a new method for discovering the candidate car license plate locations is presented. First, the image is decomposed using a Haar wavelet to get the HL band with vertical edges. Then, the HL band image is binarized using an Otsu threshold. Next a black top-hat algorithm is applied to reduce the effects of interfering large continuous features other than the license plate. At this time, a moving window based modified variance score calculation is made for areas with white pixels. This work found that the top 3 detected rectangle windows correctly locate the license plate regions with a success rate of about 98.2%. Moreover, the proposed method is robust enough to locate the plates in cases where the rough vehicle position has not been previously discovered and the cars are not centered in the image.展开更多
A very compact (80 - 100 μm2) integrated power splitting devices with two outputs (1 × 2), four outputs (1 × 4) and six outputs (1 × 6) channel has been designed, simulated and optimized for Telecommun...A very compact (80 - 100 μm2) integrated power splitting devices with two outputs (1 × 2), four outputs (1 × 4) and six outputs (1 × 6) channel has been designed, simulated and optimized for Telecommunication purpose with T-Junction, Y-Junction, PC line defect waveguides integrated with multimode interference block (PCLD-MMI) and multiple line defect PC waveguides (MLDPCW) configurations. The optical modeling of these proposed structures was investigated by finite difference time domain (FDTD) simulation. With the optimization of the parameters (Hole Radius, R = 0.128 μm, Input Diameter, D = 1.02 μm, Input wavelength, λ = 1.55 μm, Substrate Reflective Index, nsub = Si(1.52), Photonic Crystal Material, npcs = InAs(3.45), and Rectangular crystal structure), 1 × 2 for Y-Junction (100%), 1 × 4 for T-Junction (92.8%) and 1 × 6 configuration for MLDPCW (81%) show maximum power transmission.展开更多
Cardiovascular diseases are the most common cause of death worldwide over the last few decades in the developed as well as underdeveloped and developing countries. Early detection of cardiac diseases and continuous su...Cardiovascular diseases are the most common cause of death worldwide over the last few decades in the developed as well as underdeveloped and developing countries. Early detection of cardiac diseases and continuous supervision of clinicians can reduce the mortality rate. However, accurate detection of heart diseases in all cases and consultation of a patient for 24 hours by a doctor is not available since it requires more sapience, time and expertise. In this?study, a tentative design of a cloud-based heart disease prediction system had been proposed to detect impending heart disease using Machine learning techniques. For the accurate detection of the heart disease, an efficient machine learning technique should be used which had been derived from a distinctive analysis among several machine learning algorithms in a Java Based Open Access Data Mining Platform, WEKA. The proposed algorithm was validated using two widely used open-access database, where 10-fold cross-validation is applied in order to analyze the performance of heart disease detection. An accuracy level of 97.53% accuracy was found from the SVM algorithm along with sensitivity and specificity of 97.50% and 94.94%respectively. Moreover, to monitor the heart disease patient round-the-clock by his/her caretaker/doctor, a real-time patient monitoring system was developed and presented using Arduino, capable of sensing some real-time parameters such as body temperature, blood pressure, humidity, heartbeat. The developed system can transmit the recorded data to a central server which are updated every 10 seconds. As a result, the doctors can visualize the patient’s real-time sensor data by using the application and start live video streaming if instant medication is required. Another important feature of the proposed system was that as soon as any real-time parameter of the patient exceeds the threshold, the prescribed doctor is notified at once through GSM technology.展开更多
This paper addresses the problem of single-channel speech enhancement in the adverse environment. The critical-band rate scale based on improved multi-band spectral subtraction is investigated in this study for enhanc...This paper addresses the problem of single-channel speech enhancement in the adverse environment. The critical-band rate scale based on improved multi-band spectral subtraction is investigated in this study for enhancement of single-channel speech. In this work, the whole speech spectrum is divided into different non-uniformly spaced frequency bands in accordance with the critical-band rate scale of the psycho-acoustic model and the spectral over-subtraction is carried-out separately in each band. In addition, for the estimation of the noise from each band, the adaptive noise estimation approach is used and does not require explicit speech silence detection. The noise is estimated and updated by adaptively smoothing the noisy signal power in each band. The smoothing parameter is controlled by a-posteriori signal-to-noise ratio (SNR). For the performance analysis of the proposed algorithm, the objective measures, such as, SNR, segmental SNR, and perceptual evaluations of the speech quality are conducted for the variety of noises at different levels of SNRs. The speech spectrogram and objective evaluations of the proposed algorithm are compared with other standard speech enhancement algorithms and proved that the musical structure of the remnant noise and background noise is better suppressed by the proposed algorithm.展开更多
Considering the geographical location and one of the very densely populated countries in the world, Bangladesh is very vulnerable to climate change and its adaptability. This paper has been designed with an attempt to...Considering the geographical location and one of the very densely populated countries in the world, Bangladesh is very vulnerable to climate change and its adaptability. This paper has been designed with an attempt to inform the policy maker of Bangladesh regarding the potentiality of MSW as a renewable source of energy in Bangladesh. It deals with modern waste collection, management and incineration practices based on densely populated cities or towns like Bogura Municipality and Chattogram City Corporation. Waste to Energy (WtE) conversions not only reduce the land pressure problem in urban areas, but also generate electricity and heat to supply to the surrounding urban areas. The increase in generation of methane (CH<sub>4</sub>) from municipal solid wastes (MSW) alarms the world to take suitable initiative for the sustainable management of MSW, as it is stronger than carbon dioxide (CO<sub>2</sub>). By burning one mole of CH<sub>4</sub>, 890 kJ·mol<sup>-1</sup> heat is produced which is a major source of energy. This treatment technology is used in destruction of solid waste by controlled burning at high temperatures. With the release of heat, it can be accompanied and this heat from combustion can be converted into energy. This type of incineration is a high-quality treatment for Municipal or City Corporation solid waste like Bangladesh where were over crowded cities, towns and it can reduce the quantity and volume of a large amount of waste to landfill, which can recover energy and dispose in the compact zone. The results also examined that the total amount of solid waste produced in Bogura municipality is lower than that of Chattogram City Corporation. The percentage compositions of waste patterns are shown in both the Cities. The paper discusses these problems, analyses and finally, a recommendation has been proposed in order to understand the industrial situation enhanced.展开更多
In a three phase power system, the voltages at the generation side are in sinusoidal and equal in magnitude with 120? phase difference between the phases. However, at the load side voltages may become unbalanced due t...In a three phase power system, the voltages at the generation side are in sinusoidal and equal in magnitude with 120? phase difference between the phases. However, at the load side voltages may become unbalanced due to unequal voltage magnitudes at the fundamental frequency, phase angle deviations or unequal distribution of single phase loads. The voltage unbalance is a major power quality issue, because a small unbalance in the phase voltages can cause a larger unbalance in the phase currents. A completely balanced three-phase three wire system contains only positive sequence components of voltage, current and impedance, whereas unbalanced system contains both positive and negative sequence components of voltages and currents. The negative sequence component of current in the unbalanced system increases the temperature and losses in the equipments. Hence, it is necessary to mitigate this problem by supplying the negative sequence current to the load at the load side and keep the source side balanced. This paper proposes the shunt connected, current injecting Distribution Static Synchronous Compensator (DSTATCOM) with appropriate controller to mitigate the unbalanced load current. The symmetrical components based Hysteresis Current Controller (HCC) is designed for DSTATCOM to diminish the unbalances in a three-phase three-wire system. The performance of the controller is studied by simulating the entire system in the MATLAB/Simulink environment. The DSTATCOM with HCC is found to be better than other controllers because it is suitable for compensating both balanced and unbalanced loads.展开更多
There is increasing public concern about biological interactions with and the potential health effects of low frequency electric and magnetic fields. Recently, the ICNIRP （International Commission on Non-Ionizing Rad...There is increasing public concern about biological interactions with and the potential health effects of low frequency electric and magnetic fields. Recently, the ICNIRP （International Commission on Non-Ionizing Radiation Protection） has published new exposure guidelines with regard to these fields. The aim of this paper is to demonstrate the calculation of the currents and electric fields induced in the human body by external electric fields at 60 Hz, using numerical human models of anatomically-realistic human bodies, and to compare those results with the basic restrictions proposed by the new guidelines. As a result, in the case that a human is exposed to an electric field of 1 kV/m at 60 Hz the short-circuit current of 18 μA flows though the ankles. Furthermore, the electric field of 40 mV/m in the nervous tissue of the adult model is induced by exposure to external electric fields at the reference level, which is enough smaller than the basic restrictions established in the ICNIRP guidelines for occupational exposure.展开更多
Wireless Sensor Networks (WSNs) are used to sense certain parameters in an environment, manipulate the acquired data and transmit/receive the information in an intra or inter communication network. Innovative research...Wireless Sensor Networks (WSNs) are used to sense certain parameters in an environment, manipulate the acquired data and transmit/receive the information in an intra or inter communication network. Innovative researches in WSNs have resulted in the increase of application scenarios, which, at a time instant, were not even well-thought-of to be automated by WSNs. With this advent, it becomes necessary to customize sensor nodes depending on node specific characteristics and the deployment environment. Challenges for designing a WSN depend on the scenario in which it is implemented. Commercially available wireless motes are mostly generalized for usage in most of the applications. This survey work aims to provide an insight on the various wireless motes available in the market. This will enhance future researchers to select wireless modules which might be most suitable for their application needs. Various parameters related to the technical and implementation characteristics of WSNs were considered in this survey. This survey also concentrates with the survey on individual RF modules based on certain parameters like frequency of operation, transmission power, receiver sensitivity, interface mechanism, data rate, active, sleep & power-down current consumptions, range and cost involved.展开更多
The effect of an external electric field on the bandgap is observed for two proposed heterostructures graphitic carbon nitride-graphene-hexagonal boron nitride(g-C_3N_4/G/h-BN) in hexagonal stack(AAA) and graphene-gra...The effect of an external electric field on the bandgap is observed for two proposed heterostructures graphitic carbon nitride-graphene-hexagonal boron nitride(g-C_3N_4/G/h-BN) in hexagonal stack(AAA) and graphene-graphitic carbon nitridehexagonal boron nitride(G/g-C_3N_4/h-BN) in Bernal stack(ABA). Their inter-layer distance, binding energy and effective mass has also been calculated. The structure optimization has been done by density functional theory(DFT) with van der Waals corrections. The inter-layer distance, bandgap, binding energy and effective mass has been listed for these heterostructures and compared with that of bilayer graphene(BLG), graphene-hexagonal boron nitride(G/h-BN) hetero-bilayer, graphene-graphitic carbon nitride(G/g-C_3N_4) hetero-bilayer and graphitic carbon nitride-graphene-graphitic carbon nitride(g-C_3N_4/G/g-C_3N_4) heterostructure in Bernal and hexagonal stack. g-C_3N_4/G/h-BN is found to offer lower effective mass and larger bandgap opening among the considered heterostructures.展开更多
In this paper, a threshold voltage model for high-k gate-dielectric metal-oxide-semiconductor field-effect transistors （MOSFETs） is developed, with more accurate boundary conditions of the gate dielectric derived th...In this paper, a threshold voltage model for high-k gate-dielectric metal-oxide-semiconductor field-effect transistors （MOSFETs） is developed, with more accurate boundary conditions of the gate dielectric derived through a conformal mapping transformation method to consider the fringing-field effects including the influences of high-k gate-dielectric and sidewall spacer. Comparing with similar models, the proposed model can be applied to general situations where the gate dielectric and sidewall spacer can have different dielectric constants. The influences of sidewall spacer and high-k gate dielectric on fringing field distribution of the gate dielectric and thus threshold voltage behaviours of a MOSFET are discussed in detail.展开更多
Two acetylene polymers containing cyanobiphenyl-based mesogens, poly{10-[((4'-cyano-4-biphenylyl)oxy)carbonyl]-1-decyne} (PA8CN), which has a relatively flexible polyalkyne backbone, and poly {[4-(((12-((4'-cy...Two acetylene polymers containing cyanobiphenyl-based mesogens, poly{10-[((4'-cyano-4-biphenylyl)oxy)carbonyl]-1-decyne} (PA8CN), which has a relatively flexible polyalkyne backbone, and poly {[4-(((12-((4'-cyano-4-biphenylyl)oxy)dodecyl)oxy) carbonyl) phenyl]-acetylene} (PB12CN), which has a fairly rigid poly(phenylacetylene) backbone, were synthesized using respectively WCl6 and [Rh(nbd)Cl](2) as the catalysts. PA8CN exhibits enantiotropic interdigitated smectic A phase (S-Ad) over a temperature range as wide as ca. 100 degrees C, whereas PB12CN is non-mesomorphic, demonstrating that the backbone rigidity plays an important role in determining the liquid crystallinity of the polyacetylenes.展开更多
文摘Electroless deposition has been used to deposit Ni-P films on glass slides using the reducing agent sodium hypophosphite. This has been done with a purpose to use Ni-P films as back contact for silicon carbide radiation detectors. By keeping deposition time, temperature, pH and concentration of the precursor solution constant, the film deposition has been done. XPS studies were done to analyze the composition and stoichiometry of Ni-P thin films.
文摘The criticality of transformers and reactors in the power transmission network and the paramount importance of ensuring their reliability through maintenance of the insulating oil is known. This paper presents a comprehensive examination of the efficacy and economic viability of a dielectric oil regeneration system, as implemented by the Transmission System Maintenance Department (TSMD) of the Independent Power Transmission Operator (IPTO), Greece’s sole transmission operator. Through a detailed chemical analysis and performance evaluation, we assess the impact of the regeneration system on treated insulating oil quality over multiple cycles. The study reveals that the electrical properties of the insulating oil are fully restored after regeneration, negating the need to fully replace it, while the investment becomes cost-neutral within weeks from the commissioning of the regeneration system. This economic analysis, coupled with the system’s environmental benefits of reducing waste oil generation, positions the dielectric oil regeneration system as a compelling solution for the maintenance of power transmission assets.
基金Supported by the Ministry of Education,Culture, Sports,Science,and Technology(Monbukagakusho) Japanthe 21st Century COE Program"Intelligent Human Sensing",Toyohashi University of Technology,Japan
文摘This paper deals with a digest on electrical treeing degradation in nanocomposite of magnesium oxide(MgO) added to a low-density polyethylene(LDPE).The objective is to elucidate the"visual"aspects of runaway stage of final treeing breakdown mechanisms,and to ensure that the existence of MgO filler itself is responsible for this aspect instead of voltage application changes.The"visual"aspect of treeing breakdown was investigated by applying ac ramp voltage with continuous rising speed of 0.5 kV/s.As soon as tree had been incepted,the voltage was kept constant to observe the tree propagation until breakdown.The tree propagations were also described by their fractal dimension. To ensure the responsibility of MgO filler on the"visual"aspect results,the experiment was repeated using the same rate of ac ramp voltage.However,as soon as tree had been incepted,the voltage was either increased or decreased to a constant value of mean tree inception voltage obtained from the preceding results to observe its propagation to breakdown. As a result,the tree inception voltage was increased with the filler concentration in LDPE.The filler is considered not only acted as a physical obstacle for tree to propagate,but also as a chemical obstacle in which the free electron might be trapped to cause difficulties for electron avalanche occurrence.This consideration could also be valid for tree propagation up to breakdown.During propagation,due to the filler,the tree structure is accompanied by more branches.Since the branches are closely placed each other,the tree tips become relatively uniform field compares to pure LDPE.This would produce the higher local breakdown strength at the tree tips,leads to the suppression of propagation.The"visual"aspect of breakdown could be achieved by applying voltage exactly at the inception level. After bridging the tree would not breakdown until a short period of time lag.Within this period,the tree channel will be eroded by internal flashover(IFO) and become thicker.MgO filler could still restrain the IFO at the small diameter; however there will be a maximum diameter above which the effect of MgO would be very small.Lastly,it is confirmed that the MgO filler itself excels to suppress the tree degradation instead of the voltage application changes.The polymer nanocomposite appears to be more resistive to treeing degradation than their base material.
文摘The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the increase of sintering temperature offers a reduced capacitive effect from 0.460 nF to 0.321 nF.Furthermore,the grain sizes of varistors were varied from 6.8μm to 9.8μm.The consequence of such smaller grain sizes provided a better voltage gradient of about 895 V/mm for the disc sintered at 900°C and fallen drastically to 410 V/mm for the sample sintered at 1050°C.In addition,there was an increase of non-linearity index to a maximum value of 36.0 and reduced leakage current of 0.026 mA/cm2.However,the density of the varistor decreased with an increase of temperature from 5.41 g/cm3 to 5.24 g/cm3.With this base,the influence of varistor capacitance and high voltage gradient were scrutinized and it led an improved transition speed of the varistor assembly from non-conduction to conduction mode during intruding nanosecond transients.
文摘In this work, a total of 322 tests were taken on young volunteers by performing 10 different falls, 6 different Activities of Daily Living (ADL) and 7 Dynamic Gait Index (DGI) tests using a custom-designed Wireless Gait Analysis Sensor (WGAS). In order to perform automatic fall detection, we used Back Propagation Artificial Neural Network (BP-ANN) and Support Vector Machine (SVM) based on the 6 features extracted from the raw data. The WGAS, which includes a tri-axial accelerometer, 2 gyroscopes, and a MSP430 microcontroller, is worn by the subjects at either T4 (at back) or as a belt-clip in front of the waist during the various tests. The raw data is wirelessly transmitted from the WGAS to a near-by PC for real-time fall classification. The BP ANN is optimized by varying the training, testing and validation data sets and training the network with different learning schemes. SVM is optimized by using three different kernels and selecting the kernel for best classification rate. The overall accuracy of BP ANN is obtained as 98.20% with LM and RPROP training from the T4 data, while from the data taken at the belt, we achieved 98.70% with LM and SCG learning. The overall accuracy using SVM was 98.80% and 98.71% with RBF kernel from the T4 and belt position data, respectively.
文摘A robotic wheelchair is assumed to be capable of doing tasks like navigation, obstacle detection, etc. using sensors and intelligence. The initial part of the work was development of a cap controlled wheelchair to test and verify the gesture operation. Following that, a real time operating wheelchair was developed consisting of mode changing option between joystick control mode and head gesture control mode as per as the user’s requirement. The wheelchair consists of MPU6050 sensor, joystick module, RF module, battery, dc motor, toggle switch and Arduino. The movement of the head is detected by MPU6050 and the signal is transmitted to the microcontroller. Then the signal is processed by controller and motion of wheelchair is enabled for navigation. The wheelchair was capable of moving left, right, forward and backward direction. The speed of the wheelchair was 4.8 km/h when tested. Design objective of the wheelchair included cost effectiveness without compromising safety, flexibility and mobility for the users.
基金Project supported by the National Natural Science Foundation of China （Grant No 60776016）, the RGC of HKSAR, China （Grant No HKU7142/05E）, and Open Foundation of State Key Laboratory of Advanced Technology for Materials Synthesis and Processing （Grant No WUT2006M02）.
文摘A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO2 gate stack. Impacts of the two kinds of scatterings on mobility degradation are investigated. Effects of interlayer （SiO2） thickness and permittivities of the high-k dielectric and interlayer on carrier mobility are also discussed. It is shown that a smooth interface between high-k dielectric and interlayer, as well as moderate permittivities of high-k dielectrics, is highly desired to improve carriers mobility while keeping alow equivalent oxide thickness. Simulated results agree reasonably with experimental data.
文摘Combined cycle plants (CCs) are broadly used all over the world. The inclusion of CCs into the optimal resource scheduling causes difficulties because they can be operated in different operating configuration modes based on the number of combustion and steam turbines. In this paper a model CCs based on a mixed integer linear programming approach to be included into an optimal short term resource optimization problem is presented. The proposed method allows modeling of CCs in different modes of operation taking into account the non convex operating costs for the different combined cycle mode of operation.
文摘We have demonstrated and analyzed the methane gas sensor based on octagonal cladding and hexagonal hybrid porous core photonic crystal fiber (HPC-PCF) for gas detection purpose. The proposed design of HPC-PCF has been numerically investigated by COMSOL Multiphysics software through utilizing the full vectorial finite element method (FEM). The optical characteristics of HPC-PCF as well as confinement loss, relative sensitivity and refractive index, effective area, nonlinearity and numerical aperture are optimized properly by changing the geometrical parameters as well as air filling ratio, air hole diameter, pitch constant of cladding and porosity of the core. In this simulation work, we have achieved optimum relative sensitivity of 21.2%, and confinement loss of 0.000025 dB/m at 3 μm pitch, 0.7 air filling ratio of the cladding and 29% porosity of the core for 3.5 μm absorption wavelength of CH4 gas. This proposed design of HPC-PCF will keep exclusive contribution for detecting the CH4 gas accurately.
文摘In this paper, a new method for discovering the candidate car license plate locations is presented. First, the image is decomposed using a Haar wavelet to get the HL band with vertical edges. Then, the HL band image is binarized using an Otsu threshold. Next a black top-hat algorithm is applied to reduce the effects of interfering large continuous features other than the license plate. At this time, a moving window based modified variance score calculation is made for areas with white pixels. This work found that the top 3 detected rectangle windows correctly locate the license plate regions with a success rate of about 98.2%. Moreover, the proposed method is robust enough to locate the plates in cases where the rough vehicle position has not been previously discovered and the cars are not centered in the image.
文摘A very compact (80 - 100 μm2) integrated power splitting devices with two outputs (1 × 2), four outputs (1 × 4) and six outputs (1 × 6) channel has been designed, simulated and optimized for Telecommunication purpose with T-Junction, Y-Junction, PC line defect waveguides integrated with multimode interference block (PCLD-MMI) and multiple line defect PC waveguides (MLDPCW) configurations. The optical modeling of these proposed structures was investigated by finite difference time domain (FDTD) simulation. With the optimization of the parameters (Hole Radius, R = 0.128 μm, Input Diameter, D = 1.02 μm, Input wavelength, λ = 1.55 μm, Substrate Reflective Index, nsub = Si(1.52), Photonic Crystal Material, npcs = InAs(3.45), and Rectangular crystal structure), 1 × 2 for Y-Junction (100%), 1 × 4 for T-Junction (92.8%) and 1 × 6 configuration for MLDPCW (81%) show maximum power transmission.
文摘Cardiovascular diseases are the most common cause of death worldwide over the last few decades in the developed as well as underdeveloped and developing countries. Early detection of cardiac diseases and continuous supervision of clinicians can reduce the mortality rate. However, accurate detection of heart diseases in all cases and consultation of a patient for 24 hours by a doctor is not available since it requires more sapience, time and expertise. In this?study, a tentative design of a cloud-based heart disease prediction system had been proposed to detect impending heart disease using Machine learning techniques. For the accurate detection of the heart disease, an efficient machine learning technique should be used which had been derived from a distinctive analysis among several machine learning algorithms in a Java Based Open Access Data Mining Platform, WEKA. The proposed algorithm was validated using two widely used open-access database, where 10-fold cross-validation is applied in order to analyze the performance of heart disease detection. An accuracy level of 97.53% accuracy was found from the SVM algorithm along with sensitivity and specificity of 97.50% and 94.94%respectively. Moreover, to monitor the heart disease patient round-the-clock by his/her caretaker/doctor, a real-time patient monitoring system was developed and presented using Arduino, capable of sensing some real-time parameters such as body temperature, blood pressure, humidity, heartbeat. The developed system can transmit the recorded data to a central server which are updated every 10 seconds. As a result, the doctors can visualize the patient’s real-time sensor data by using the application and start live video streaming if instant medication is required. Another important feature of the proposed system was that as soon as any real-time parameter of the patient exceeds the threshold, the prescribed doctor is notified at once through GSM technology.
文摘This paper addresses the problem of single-channel speech enhancement in the adverse environment. The critical-band rate scale based on improved multi-band spectral subtraction is investigated in this study for enhancement of single-channel speech. In this work, the whole speech spectrum is divided into different non-uniformly spaced frequency bands in accordance with the critical-band rate scale of the psycho-acoustic model and the spectral over-subtraction is carried-out separately in each band. In addition, for the estimation of the noise from each band, the adaptive noise estimation approach is used and does not require explicit speech silence detection. The noise is estimated and updated by adaptively smoothing the noisy signal power in each band. The smoothing parameter is controlled by a-posteriori signal-to-noise ratio (SNR). For the performance analysis of the proposed algorithm, the objective measures, such as, SNR, segmental SNR, and perceptual evaluations of the speech quality are conducted for the variety of noises at different levels of SNRs. The speech spectrogram and objective evaluations of the proposed algorithm are compared with other standard speech enhancement algorithms and proved that the musical structure of the remnant noise and background noise is better suppressed by the proposed algorithm.
文摘Considering the geographical location and one of the very densely populated countries in the world, Bangladesh is very vulnerable to climate change and its adaptability. This paper has been designed with an attempt to inform the policy maker of Bangladesh regarding the potentiality of MSW as a renewable source of energy in Bangladesh. It deals with modern waste collection, management and incineration practices based on densely populated cities or towns like Bogura Municipality and Chattogram City Corporation. Waste to Energy (WtE) conversions not only reduce the land pressure problem in urban areas, but also generate electricity and heat to supply to the surrounding urban areas. The increase in generation of methane (CH<sub>4</sub>) from municipal solid wastes (MSW) alarms the world to take suitable initiative for the sustainable management of MSW, as it is stronger than carbon dioxide (CO<sub>2</sub>). By burning one mole of CH<sub>4</sub>, 890 kJ·mol<sup>-1</sup> heat is produced which is a major source of energy. This treatment technology is used in destruction of solid waste by controlled burning at high temperatures. With the release of heat, it can be accompanied and this heat from combustion can be converted into energy. This type of incineration is a high-quality treatment for Municipal or City Corporation solid waste like Bangladesh where were over crowded cities, towns and it can reduce the quantity and volume of a large amount of waste to landfill, which can recover energy and dispose in the compact zone. The results also examined that the total amount of solid waste produced in Bogura municipality is lower than that of Chattogram City Corporation. The percentage compositions of waste patterns are shown in both the Cities. The paper discusses these problems, analyses and finally, a recommendation has been proposed in order to understand the industrial situation enhanced.
文摘In a three phase power system, the voltages at the generation side are in sinusoidal and equal in magnitude with 120? phase difference between the phases. However, at the load side voltages may become unbalanced due to unequal voltage magnitudes at the fundamental frequency, phase angle deviations or unequal distribution of single phase loads. The voltage unbalance is a major power quality issue, because a small unbalance in the phase voltages can cause a larger unbalance in the phase currents. A completely balanced three-phase three wire system contains only positive sequence components of voltage, current and impedance, whereas unbalanced system contains both positive and negative sequence components of voltages and currents. The negative sequence component of current in the unbalanced system increases the temperature and losses in the equipments. Hence, it is necessary to mitigate this problem by supplying the negative sequence current to the load at the load side and keep the source side balanced. This paper proposes the shunt connected, current injecting Distribution Static Synchronous Compensator (DSTATCOM) with appropriate controller to mitigate the unbalanced load current. The symmetrical components based Hysteresis Current Controller (HCC) is designed for DSTATCOM to diminish the unbalances in a three-phase three-wire system. The performance of the controller is studied by simulating the entire system in the MATLAB/Simulink environment. The DSTATCOM with HCC is found to be better than other controllers because it is suitable for compensating both balanced and unbalanced loads.
文摘There is increasing public concern about biological interactions with and the potential health effects of low frequency electric and magnetic fields. Recently, the ICNIRP （International Commission on Non-Ionizing Radiation Protection） has published new exposure guidelines with regard to these fields. The aim of this paper is to demonstrate the calculation of the currents and electric fields induced in the human body by external electric fields at 60 Hz, using numerical human models of anatomically-realistic human bodies, and to compare those results with the basic restrictions proposed by the new guidelines. As a result, in the case that a human is exposed to an electric field of 1 kV/m at 60 Hz the short-circuit current of 18 μA flows though the ankles. Furthermore, the electric field of 40 mV/m in the nervous tissue of the adult model is induced by exposure to external electric fields at the reference level, which is enough smaller than the basic restrictions established in the ICNIRP guidelines for occupational exposure.
文摘Wireless Sensor Networks (WSNs) are used to sense certain parameters in an environment, manipulate the acquired data and transmit/receive the information in an intra or inter communication network. Innovative researches in WSNs have resulted in the increase of application scenarios, which, at a time instant, were not even well-thought-of to be automated by WSNs. With this advent, it becomes necessary to customize sensor nodes depending on node specific characteristics and the deployment environment. Challenges for designing a WSN depend on the scenario in which it is implemented. Commercially available wireless motes are mostly generalized for usage in most of the applications. This survey work aims to provide an insight on the various wireless motes available in the market. This will enhance future researchers to select wireless modules which might be most suitable for their application needs. Various parameters related to the technical and implementation characteristics of WSNs were considered in this survey. This survey also concentrates with the survey on individual RF modules based on certain parameters like frequency of operation, transmission power, receiver sensitivity, interface mechanism, data rate, active, sleep & power-down current consumptions, range and cost involved.
文摘The effect of an external electric field on the bandgap is observed for two proposed heterostructures graphitic carbon nitride-graphene-hexagonal boron nitride(g-C_3N_4/G/h-BN) in hexagonal stack(AAA) and graphene-graphitic carbon nitridehexagonal boron nitride(G/g-C_3N_4/h-BN) in Bernal stack(ABA). Their inter-layer distance, binding energy and effective mass has also been calculated. The structure optimization has been done by density functional theory(DFT) with van der Waals corrections. The inter-layer distance, bandgap, binding energy and effective mass has been listed for these heterostructures and compared with that of bilayer graphene(BLG), graphene-hexagonal boron nitride(G/h-BN) hetero-bilayer, graphene-graphitic carbon nitride(G/g-C_3N_4) hetero-bilayer and graphitic carbon nitride-graphene-graphitic carbon nitride(g-C_3N_4/G/g-C_3N_4) heterostructure in Bernal and hexagonal stack. g-C_3N_4/G/h-BN is found to offer lower effective mass and larger bandgap opening among the considered heterostructures.
基金Project supported by the National Natural Science Foundation of China （Grant No 60376019）.
文摘In this paper, a threshold voltage model for high-k gate-dielectric metal-oxide-semiconductor field-effect transistors （MOSFETs） is developed, with more accurate boundary conditions of the gate dielectric derived through a conformal mapping transformation method to consider the fringing-field effects including the influences of high-k gate-dielectric and sidewall spacer. Comparing with similar models, the proposed model can be applied to general situations where the gate dielectric and sidewall spacer can have different dielectric constants. The influences of sidewall spacer and high-k gate dielectric on fringing field distribution of the gate dielectric and thus threshold voltage behaviours of a MOSFET are discussed in detail.
基金This work was in part supported by the Hong Kong RGC grants HKUST597/95P and HKUST6149/97P.
文摘Two acetylene polymers containing cyanobiphenyl-based mesogens, poly{10-[((4'-cyano-4-biphenylyl)oxy)carbonyl]-1-decyne} (PA8CN), which has a relatively flexible polyalkyne backbone, and poly {[4-(((12-((4'-cyano-4-biphenylyl)oxy)dodecyl)oxy) carbonyl) phenyl]-acetylene} (PB12CN), which has a fairly rigid poly(phenylacetylene) backbone, were synthesized using respectively WCl6 and [Rh(nbd)Cl](2) as the catalysts. PA8CN exhibits enantiotropic interdigitated smectic A phase (S-Ad) over a temperature range as wide as ca. 100 degrees C, whereas PB12CN is non-mesomorphic, demonstrating that the backbone rigidity plays an important role in determining the liquid crystallinity of the polyacetylenes.
