A Unified Approach to Maximum Power Point Tracking and I-V Curve Determination of Photovoltaic Arrays from Real-time Measurements

In recent years we have seen a considerable increase in the installed capacity of Photovoltaic (PV) power generating plants worldwide. This increase is primarily attributed to the decrease in the cost of installation and the awareness towards the sustainable power generation. However, the efficiency of the PV modules is still low. The Current vs. Voltage (I-V) characteristics of the PV generators is non-linear and changes with irradiance and temperature. For optimal utilization of PV sources, Maximum Power Point Trackers (MPPTs) are used. When the array is under uniform illumination, there is a single peak on the Power vs. Voltage (P-V) curve of the PV array. This peak is easily tracked by conventional MPPTs. However, under Partial Shading Conditions (PSC), multiple peaks appear on the P-V curve. Out of these, there is one Global Peak (GP) while the others are Local Peaks (LP). When the MPPT algorithm is trapped at LP, considerable power loss occurs. Special MPPTs are designed for finding the GP when the array is under PSC. It is also important to periodically find the I-V curve of the array under the field conditions for monitoring and control of the PV generators. For this purpose, specialized tests are performed. During these tests, the generation of power from the PV arrays is halted. Similarly, the speed of performance of these tests is also important as the environmental conditions may change quickly during finding of the curve. Any change in the surroundings during the performance of finding the characteristic curve may affect the results. In this thesis, two algorithms are proposed that perform the MPP tracking and measurement of the I-V curve under any kind of irradiance. The first algorithm performs these tasks by using the module voltages as the parameter. In the second method, the input filter capacitor of buck or buck-boost converter is used. Simulation and experimental results confirm the performance of the proposed methods

Performance Evaluation and Simulation of M-Ary Quadrature Amplitude Modulation Schemes with VisSim/Comm Software

M-ary modulation schemes are considered one of widely used digital modulation in practice because of its high efficiency in power and bandwidth. Therefore, this necessity the need to study and evaluate the performance of M-ary schemes using simulation techniques. In this paper, the performance of M-ary modulations schemes M-ary quadrature amplitude modulation (QAM) is considered. Because of its efficiency in power and bandwidth, M-ary QAM (M-QAM) is one of the widely used modulation techniques in practice. Therefore, a need for studying and evaluating the performance of QAM modulation schemes is an important task for designers. In this paper, M-QAM modulation schemes for even number of bits per symbol (16, 62, and 256-QAM) and an odd number of bits per symbol (32- and 128-QAM), over Additive White Gaussian Noise channel, are studied. A VisSim/Comm simulation[1] model for M-QAM is designed. Theoretical and simulation results for bit error ratio (BER) performance of QAM modulation schemes are obtained using VisSim/Comm software. The results are evaluated and compared

Frequency of Impacted Third Molar in Mandibular Angle Fractures in Patients Presenting to Ayub Teaching Hospital

Mandibular fractures are one of the commonest maxillofacial injury. Fractures take place at various locations. Mandibular angle fracture susceptibility in addition to being associated to the type and direction of impact is also associated with impacted 3rd molar.The objective of the study is to determine the frequency of impacted third molar in mandibular angle fracture.This descriptive cross-sectional study was performed for a period of six months on one hundred and twenty-two patients with mandibular. OPG was done to determine the state of 3rd molar tooth. The states of 3rd molar tooth along with its inclination were noted on a proforma.The frequency of 3rd molar impaction in fractures of angle of mandible was 36.1%. Young age (less than 31 years in this study) was significantly associated with development of impacted 3rd molar tooth (p < 0.05).Individuals with impacted 3rd molar should be educated about the possibility of the fracture of mandibular angle so that preventive measures can be adopted

Efficacy of Epidural Dexamethasone for Prevention of Post Dural Puncture Headache: A Randomized Controlled Trial

Objective: To evaluate the efficacy of epidural dexamethasone for prevention of post dural puncture headache.Study Design: Randomized Controlled TrialPlace and Duration: Department of anaesthesia Holy Family, hospital, Rawalpindi from January 2017 to September 2017, in a period of nine months.Methodology: The patients were selected from general, orthopedic, urology, and gynecology services. In study group an intervention was made through a prophylactic dose of epidural dexamethasone injection in a dose of (2 ml, 8 mg) and in control group 2 ml normal saline was injected at the time of anesthesia along with standard spinal anesthesia. The anesthesia was administered between third and fourth vertebral spaces L3 and L4 in sitting position. The dose of anesthetic was standardized at 75mg Lindocaine 5% and 25mg Fentanyl, which was administered using a 25-gauge disposable needle. The incidence of a headache was the main outcome of the study and it was measured in first 24 hours, 72 hours and 7 days after spinal anesthesia.Results: The mean age in the intervention group was 32.18 ± 5.64 years, and control group it was 31.63 ± 6.24 years. It was observed that 3 (5.56%) patients in intervention group and 7 (12.96%) patients in control group had post dural puncture headache. The rate of a headache was significantly higher in control group after 72 hours of operation. The rate of post dural puncture headache after 7 days was significantly greater (20.37% versus 38.89%, p-value < 0.05) in control group. The comparison of mean VAS scores of pain at 24 hours and 72 hours showed that mean pain score was significantly (p-value < 0.05) lower in the intervention group. There was no statistically significant (p-value > 0.05) difference in the mean value of pain score after 7 days.  Conclusions: It was observed that epidural administration of dexamethasone during spinal anesthesia is effective and useful in preventing headaches. So intravenous epidural dexamethasone is suggested for prevention of headaches in patients who undergo spinal anesthesia