Novel Designs for Photovoltaic Arrays to Reduce Partial Shading Losses and to Ease Series Arc Fault Detection

A mismatch in a photovoltaic array implies differences in the I-V characteristics of the modules forming the array which can lead to significant energy losses known as mismatch losses. The sources of mismatch losses could be easy- or difficult-to-predict sources. This thesis proposes novel designs for photovoltaic arrays to reduce mismatch losses. The mismatch from easy-to-predict sources and its resulting losses can be reduced by altering the interconnection of the array. Therefore, this thesis proposes an optimal total-cross-tied interconnection, based on a thorough mathematical formulation, which can significantly reduce mismatch losses from easy-to-predict sources. Application examples of the operation of the optimal total-cross-tied interconnection under partial shading are presented. The effect of partial shading caused by easy- or difficult-to-predict sources can be considerably reduced by photovoltaic array reconfiguration. This thesis proposes a novel mathematical formulation for the optimal reconfiguration of photovoltaic arrays to minimize partial shading losses. The thesis formulates the reconfiguration problem as a mixed integer quadratic programming problem and finds the optimal solution using branch-and-bound algorithm. The proposed formulation can be used for equal or non-equal number of modules per row. Moreover, it can be used for fully reconfigurable or partially-reconfigurable arrays. Application examples of the operation of the reconfigurable photovoltaic array under partial shading are presented. Finally, the recently updated American National Electric Code requires the presence of a series arc fault detector in any Photovoltaic installation operating at a voltage greater than or equal to 80V. However, the Photovoltaic market nowadays lacks the presence of an accurate series arc fault detector that can detect series arc faults and discriminate between them and partial shading. The work in this thesis proposes an algorithm that can detect series arc faults and discriminate between them and partial shading in total-cross-tied arrays. This algorithm is based on the measurement of instantaneous row voltages.1 yea

Facilities and activities financed by associated expenditure in Egyptian universities : their relationship to the academic and professional development of student teachers

The present research aims to: (i) Calculate the average total educational expenditure per student in Egyptian universities. (ii) Identify characterise and quantify the provision of facilities and activities financed by associated expenditure, as distinct from other educational expenditure in Egyptian universities. (iii) Analyse the relationships between: (a) The amounts of associated expenditure and the extent of involvement of undergraduate students in faculties of education with facilities and activities financed by this expenditure; (b) The nature and extent of involvement of undergraduate students in faculties of education with facilities and activities financed by associated expenditure and their professional development during their university courses as evident in staff and student opinions; and (c) The nature and extent of involvement of undergraduate students in faculties of education with facilities and activities financed by associated expenditure and their success in their university courses in terms of the standard of their academic awards. From the material mentioned above and to facilitate the understanding of the present research, it can be said that there are two major aspects which have to be investigated: the first one is economic which focuses on calculating the average total educational expenditure per student as well as associated expenditure per student and earnings foregone by students in Egyptian universities; and the second aspect is educational which focuses on investigating the relationships which are mentioned in (a), (b), and (c) above. Research instruments have been designed to investigate these two aspects and these instruments have been applied in Ain Shams, Minia, and Assiut Universities in Egypt. These instruments are six in number, two questionnaires and four interviews. Questionnaire no.1 was designed to collect data about the earnings of students from part-time employment during their university courses. Questionnaire no.2 investigates the extent of involvement of undergraduate students in faculties of education with the facilities and activities financed by associated expenditure as well as the relationship between the nature and extent of the involvement of those students in faculties of education with facilities and activities financed by associated expenditure and their professional development during their university courses. Interview schedule no.1 was designed for Egyptian university academic staff in faculties of education to help in distinguishing associated expenditure from other sorts of educational expenditure. Interview schedule no.2 was designed for academic staff in Egyptian faculties of education to help in further investigation of the relationship between the extent of involvement of undergraduate students with facilities and activities financed by associated expenditure and the development of their professional skills during their university courses. Interview schedule no.3 was designed for undergraduate students in Egyptian faculties of education to investigate the same issue as questionnaire no.2. Interview schedule no.4 was designed for university administrative staff who are responsible for the facilities and activities financed by associated expenditure to help in revealing the nature and scale of these facilities and activities. It is found that the average total educational expenditure per student in 1984 is E&#156459;.495 in Ain Shams, E&#156929;.178 in Minia, and E&#156798;.141 in Assiut, the earnings foregone per student in 1984 are E&#15666;.17 in Ain Shams, E&#156194;.03 in Minia, and E&#156210;.93 in Assiut, and the associated expenditure per student in 1984 is (roughly) E&#15611;.5 in Ain Shams, E&#15698;.2 in Minia, and E&#15657;.6 in Assiut. It is also found that relationships (a) and (b) are positive, but relationship (c) is not. The researcher put forward some suggestions for improving facilities and activities financed by associated expenditure and recommended further related research.</p

Clinical significance of immunohistochemical expression of DDR1 and β-catenin in colorectal carcinoma

Abstract Background Despite recent advances in therapy modalities of colorectal cancer (CRC), it is still the third cause of cancer-related deaths worldwide. Thus, the search for new target therapies became mandatory. DDR1 is a collagen receptor that has a suggested role in cellular proliferation, tumor invasion, and metastasis. Material and methods Forty-eight cases of CRC, 20 of CR adenoma, and 8 cases of non-tumoral colonic tissue were subjected to immunohistochemistry by DDR1 and β-catenin antibodies. Results were compared among the different studied groups and correlated with clinicopathologic data and available survival data. Also, the expression of both proteins was compared versus each other. Results were compared among the 3 studied groups and correlated with clinicopathologic and survival data. Results It revealed a stepwise increase of DDR1 expression among studied groups toward carcinoma (P = 0.006). DDR1 expression showed a direct association with stage D in the modified Dukes’ staging system (P = 0.013), higher-grade histologic types (P = 0.008), and lymph node invasion (P = 0.028) but inverse correlation with the presence of intratumoral inflammatory response (TIR) (P = 0.001). The shortest OS was associated with strong intensity of DDR1 (P = 0.012). The DDR1 and β-catenin expressions were significantly correlated (P = 0.028), and the combined expression of both was correlated with TNM staging (P = 0.017). Conclusion DDR1 overexpression is a frequent feature in CRC and CR adenoma. DDR1 is a poor prognostic factor and a suppressor of the TIR. DDR1 and β-catenin seem to have a synergistic action

Photovoltaic mismatch losses caused by moving clouds

Mismatch losses is a major issue in the photovoltaic (PV) system and are mainly caused by partial shading; largest mismatch losses are caused by sharp shadows. These shadows are a typical problem for rooftop and residential installations. In large-scale PV plants, partial shading is mostly caused by moving clouds which produce gentle irradiance transitions causing typically only minor irradiance differences between adjacent PV modules. This paper presents a study of the mismatch losses of PV arrays with various layouts and electrical configurations during around 27,000 irradiance transitions identified in measured irradiance data. The overall effect of the mismatch losses caused by moving clouds on the energy production of PV plants was also studied. The study was conducted using a mathematical model of irradiance transitions and an experimentally verified MATLAB/Simulink model of a PV module. The relative mismatch losses during the identified irradiance transitions ranged from 1.4% to 4.0% depending on the electrical configuration and layout of the PV array. The overall effect of the mismatch losses caused by moving clouds on the total electricity production of PV arrays was about 0.5% for the PV array with strings of 28 PV modules and substantially smaller for arrays with shorter strings. The proportions of the total mismatch losses caused by very dark or highly transparent clouds were small. About 70% of the total mismatch losses were caused by shadow edges with shading strengths ranging between 40% and 80%. These results indicate that the mismatch losses caused by moving clouds are not a major problem for large-scale PV plants. An interesting finding from a practical point of view is that the mismatch losses increase the rate of power fluctuations compared to the rate of irradiance fluctuations.Peer reviewe

Morphological and histopathological study of hypertrophied inferior nasal turbinate in Egyptian patients: in clinical perspective

Abstract Background The inferior nasal turbinates have important role in the maintenance of nasal breathing function by providing the nasal valve mechanism necessary for the regulation of air flow through the nose. Hypertrophied inferior nasal turbinates are the second most common cause of chronic nasal obstruction. Our aim of this study is to evaluate the morphological and histopathological features of hypertrophied inferior nasal turbinate in Egyptian patients. Methods Our descriptive comparative study was carried on 30 patients presented with hypertrophied inferior nasal turbinate by clinical and radiological assessment. Patients are divided into two groups according to CT scan and endoscopic examination as group A for patients with deviated nasal septum with compensatory hypertrophied inferior nasal turbinate and group B for patients with hypertrophied inferior nasal turbinate due to allergic rhinosinusitis. Both groups underwent the same operation which partial controlled posterior inferior turbinectomy. During the period from June 2018 till May 2019, patients were selected from out-patient’s clinic of Otorhinolaryngology Department at Menoufia University Hospital and Shebin El-Kom Teaching Hospital, and Military Hospital. Results By histopathological examination of the specimens, we found out that the bony layer thickness was more prominent in group A and the mucosal layer thickness was more prominent in group B. The prominent inflammatory cells were lymphocytes in group A and eosinophils plus mast cells in group B. Conclusion The bony layer thickness should be excised during the surgical treatment of cases presented with deviated nasal septum with hypertrophied inferior turbinate where in cases of allergic rhinitis with hypertrophied inferior turbinate, the mucosal layer is enough to be excised