Microcontroller Based Variable Frequency Power Inverter

The variable frequency inverters have been used in wide applications, such as speed control of induction motors. The variable speed operation of a single phase and three-phase induction motors suffer from large harmonic and limited speed range. Therefore, intensive researches were carried out in order to eliminate the harmonic distortion, simplify the motor speed control task over a wide range, and to reduce the overall system cost. This work investigates performance of the microcontroller based variable frequency power inverter to reduce the Total Harmonic Distortion (THD) for the overall system. The fully controlled single phase and three-phase bridge voltage source inverter have been designed and implemented with semiconductors power devices Insulated Gate Bipolar Transistor. The microcontroller has been employed in this inverter to provide SPWM signal that controls the applied voltage on the gate drive, which provides the desired SPWM frequency at the output of the power inverter. The Matlab simulation results for the proposed system have been achieved with different SPWM frequencies. From the results a stable AC voltage with variable frequency over wide range has been obtained with fewer harmonics and a good agreement has been found between the simulation and hardware results of a single phase and three-phase inverter. Also, the result obtained has been compared with previous work and it shown a good agreement too. Therefore, this system can be considered as variable frequency voltage source power inverter, with low total harmonic distortion (THD <2)

On the traffic offloading in Wi-Fi supported heterogeneous wireless networks

Heterogeneous small cell networks (HetSNet) comprise several low power, low cost (SBSa), (D2D) enabled links wireless-fidelity (Wi-Fi) access points (APs) to support the existing macrocell infrastructure, decrease over the air signaling and energy consumption, and increase network capacity, data rate and coverage. This paper presents an active user dependent path loss (PL) based traffic offloading (TO) strategy for HetSNets and a comparative study on two techniques to offload the traffic from macrocell to (SBSs) for indoor environments: PL and signal-to-interference ratio (SIR) based strategies. To quantify the improvements, the PL based strategy against the SIR based strategy is compared while considering various macrocell and (SBS) coverage areas and traffic–types. On the other hand, offloading in a dense urban setting may result in overcrowding the (SBSs). Therefore, hybrid traffic–type driven offloading technologies such as (WiFi) and (D2D) were proposed to en route the delay tolerant applications through (WiFi) (APs) and (D2D) links. It is necessary to illustrate the impact of daily user traffic profile, (SBSs) access schemes and traffic–type while deciding how much of the traffic should be offloaded to (SBSs). In this context, (AUPF) is introduced to account for the population of active small cells which depends on the variable traffic load due to the active users

Teaching percutaneous renal biopsy using unfixed human cadavers

Background: Percutaneous renal biopsy (PRB) is an important diagnostic procedure. Despite advances in its safety profile there remains a small but significant risk of bleeding complications. Traditionally, operators train to perform PRB through tutor instruction and directly supervised PRB attempts on real patients. We describe an approach to teaching operators to perform PRB using cadaveric simulation. Methods: We devised a full day course hosted in the Clinical Anatomy Skills Centre, with places for nine candidates. Course faculty consisted of two Consultant Nephrologists, two Nephrology trainees experienced in PRB, and one Radiologist. Classroom instruction included discussion of PRB indications, risk minimisation, and management of complications. Two faculty members acted as models for the demonstration of kidney localisation using real-time ultrasound scanning. PRB was demonstrated using a cadaveric model, and candidates then practised PRB using each cadaver model. Results: Written candidate feedback was universally positive. Faculty considered the cadaveric model a realistic representation of live patients, while the use of multiple cadavers introduced anatomical variation. Conclusions: Our model facilitates safe simulation of a high risk procedure. This might reduce serious harm associated with PRB and improve patient safety, benefiting trainee operators and patients alike

Spectral Efficiency Improvements in HetNets by Exploiting Device-to-Device Communications

Next generation cellular networks require huge capacity, ubiquitous coverage and maximum energy efficiency. In order to meet these targets, Device-to-device (D2D) communication is being considered for future heterogeneous networks (HetNets). In this paper, we consider a three tier hierarchical HetNet by exploiting D2D communication in traditional HetNet. D2D communication is deployed within the HetNet where closely located mobile users are engaged in direct communication without routing the traffic through cellular access network. The proposed configuration mandates to reduce the interference offered by the resultant HetNet by reducing the transmitter-receiver distance and ensuring that the mobile users are transmitting with adaptive power subject to maintaining their desired link quality. In this context, we analyzed and compared the spectral efficiency improvements in hierarchical HetNet against traditional HetNet. Simulation results show that D2D communication offers much higher spectral efficiency as compared to traditional HetNet

The influence of EDFA’s configurations on the behavioral trends of gain and noise figure

Various configurations have been conceived and tested for improvement of the gain and noise figures in Erbium doped fiber amplifiers (EDFA’s). Single pass (SP), double pass (DP), triple pass (TP) and quadruple pass (QP), are employed in the investigation. The highest gain and highest noise figure (NF) of 54dB and 7dB respectively are obtained at -50 dBm input power with 90 mW pump power using the QP configuration, while and the lowest gain of 23dB and lowest NF of 3dB are obtained at -50 dBm input power with 90 mW pump power for SP configuration

New erbium-doped fiber laser with a double tunable bandpass filter

A new configuration for an erbium-doped fiber laser is reported. It incorporates a linear cavity with fiber loopback and a tunable bandpass filter (TBF). This configuration suppresses the amplified spontaneous emission and achieves a highly stable output power of more than 18 dBm at 1560 nm. A standard spectrum is obtained with TBF adjustment

Comparison of the effect structure on ring and linear cavity lasers of erdoped optical fibers

Two erbium doped fiber laser configurations are conceived and constructed; A ring fiber laser and a linear cavity fiber loop laser. A comparative investigation tests were carried out. It is found that both the output power and the side mode suppression ratio (SMSR) for the two structures were significantly different. The measured laser power and the side mode suppression ratio (SMSR) of 11 mW and 75 dB respectively were higher for the linear cavity configuration. A lower output power and SMSR of 3 mW and 61.5 dB respectively were obtained with the ring laser configuration. Both lasers were pumped with a 90 mW pump power, and had a reflectivity of 90%

Spam image email filtering using K-NN and SVM

The developing utilization of web has advanced a simple and quick method for e-correspondence. The outstanding case for this is e-mail. Presently days sending and accepting email as a method for correspondence is prominently utilized. Be that as it may, at that point there stand up an issue in particular, Spam mails. Spam sends are the messages send by some obscure sender just to hamper the improvement of Internet e.g. Advertisement and many more.  Spammers introduced the new technique of embedding the spam mails in the attached image in the mail. In this paper, we proposed a method based on combination of SVM and KNN. SVM tend to set aside a long opportunity to prepare with an expansive information set. On the off chance that "excess" examples are recognized and erased in pre-handling, the preparation time could be diminished fundamentally. We propose a k-nearest neighbor (k-NN) based example determination strategy. The strategy tries to select the examples that are close to the choice limit and that are effectively named. The fundamental thought is to discover close neighbors to a question test and prepare a nearby SVM that jelly the separation work on the gathering of neighbors. Our experimental studies based on a public available dataset (Dredze) show that results are improved to approximately 98%

A high gain EDFA using double-pass dual-stage amplification

A new configuration of an Erbium Doped Fiber Amplifier is proposed. Double-Pass amplification in a Dual-Stage using a fiber loop-back is incorporated with a Tunable Band Pass Filter. Spontaneous emission is filtered-out in the mid-section to ensure efficient amplification of the signal as it propagates along the fiber. High gain of 54dB is achieved for - 50dBm signal power at 1550nm. The two stages were pumped by laser diodes operating at 980nm with 10mW and 90mW respectively