Chapter Tidal Turbine Generators

Recently, tidal stream turbines have become a preferable mode of harvesting tidal energy. The main issue for low utilization of tidal energy is the high levelized cost of energy (LCoE) from tidal stream turbines. A major reason for this is the high operation and maintenance costs for submerged installations. A possible way of minimizing the LCoE and improving the availability is to use a flooded (or a wetgap) generator rather than a conventional airgap generator. Inside flooded generators, the gap between the stator and rotor is filled with the seawater. This architecture has the potential to improve cooling and reduce reliance on ancillary systems (e.g., bilge system), thereby improving reliability. The chapter begins with a brief description of the generator systems used in current tidal stream turbines. The focus of the chapter is, however, to give a basic insight into the design aspects of the flooded generators, and compares it with the currently used sealed airgap generators in tidal turbine systems

Penerimaan Kesaksian Tanpa Sumpah Dalam Perkara Cerai Talak (Analisis Putusan Hakim Tingkat Banding Nomor 45/Pdt.G/2017/MS.Aceh)

Abstrak: Sumpah adalah suatu pernyataan yang khidmat yang diucapkan pada waktu saksi memberi keterangan dengan mengingat akan sifat Maha Kuasa Tuhan dan percaya bahwa siapa yang memberi keterangan yang tidak benar akan dihukum-Nya. Jadi, pada hakikatnya sumpah merupakan tindakan yang bersifat keagamaan yang digunakan dalam peradilan. Suatu sumpah yang diperintahkan oleh salah satu pihak yang berperkara kepada pihak lawannya, mempunyai suatu kekuatan pembuktian yang memaksa, jika sumpah itu telah diangkat. Namun pada prakteknya di persidangan, terdapat hakim yang menerima kesaksian para saksi tanpa disumpah terlebih dahulu sebelum memberikan keterangan. Hal ini diperkuat dengan putusan hakim tingkat banding yang juga menerima keterangan para saksi tanpa disumpah, sebagaimana terdapat dalam putusan hakim tingkat banding nomor 45/Pdt.G/2017/MS-Aceh, tentang Perkara Cerai Talak di Mahkamah Syar’iyah Aceh tahun 2017. Oleh karena itu, penulis ingin mengetahui dasar pertimbangan hakim tentang penerimaan kesaksian tanpa sumpah dalam perkara cerai talak dan bagaimana tinjauan hukum Islam tentang kesaksian tanpa sumpah dalam perkara cerai talak. Dalam penelitian ini, metode penelitian yang digunakan adalah deskriptif normatif yang bersifat kualitatif. Berdasarkan hasil penelitian, pertimbangan hakim mengenai penerimaan kesaksian tanpa sumpah adalah karena majelis hakim Mahkamah Syar’iyah Aceh merasa bahwa apa yang telah dipertimbangkan oleh majelis hakim tingkat pertama tentang alat bukti saksi yang dihadirkan oleh tergugat telah relevan dan menguatkan dalil-dalil gugatan tergugat, sehingga pertimbangan hukum oleh majelis hakim tingkat pertama diambil alih sepenuhnya oleh majelis hakim tingkat banding. Adapun tinjauan hukum Islam terhadap putusan hakim banding nomor 45/Pdt.G/2017/MS-Aceh tidak bisa diterima karena saksi yang diajukan tergugat sebagai alat bukti tidak memenuhi salah satu kewajiban saksi yaitu disumpah sebelum memberikan kesaksian. Namun, dapat diterima hanya sebagai bahan persangkaan saja bukan sebagai alat bukti utuh karena kesaksian tanpa sumpah masih diragukan kebenarannya karena dikhawatirkan adanya kesaksian palsu yang mengarah kepada sumpah palsu.Abstract: The oath is a reverent statement spoken at the time the witness describes by remembering the nature of the Almighty God and believing that who gives the unrighteous information will be punished by him. Thus, the oath is a religious act used in the judiciary. An oath commanded by one of the parties to his opponent, having a force of proof that forces if the oath has been lifted. But in practice at the trial, there was a judge who received the testimony of the witnesses without being sworn in before giving the caption. This is strengthened by the decision of the appellate judge who also received the testimony of the witnesses without oath, as in the decision of the appellate Judge number 45/Pdt. G/2017/MS-ACEH, on the matter of divorce in the court of Shar'iyah Aceh year 2017. Therefore, the author wanted to know the basic judgment of the judges on the acceptance of the unsworn testimony in the divorce and how the Islamic law review of the testimony without oath in the case of divorce. In this study, the research methods used are normative descriptive which is qualitative. Based on the results of the study, the judges ' consideration of the acceptance of the unsworn testimony was because the Assembly of the Supreme Court judges was felt that what had been considered by the first-tier judges of the witness evidence presented by the defendant had been relevant and strengthened the evidence of the defendant's lawsuit so that the legal consideration by the first-tier judges was taken over entirely The review of Islamic law on the decision of Judge No. 45/PDT. G/2017/MS-ACEH is not acceptable because the witnesses who are asked to be the defendant as a means of evidence does not meet one of the obligations of witnesses is sworn before bearing testimony. However, it can be accepted only as a matter of mere substance not as a tool of complete evidence because the unsworn testimony is still doubtful of its truthfulness. After all, it is feared a false witness that leads to a false oath

The safety and feasibility of simultaneous robotic repair of an inguinal hernia during robotic-assisted laparoscopic prostatectomy: a systematic review and meta-analysis

Purpose This study intended to assess the safety and feasibility of performing concurrent robotic-assisted laparoscopic prostatectomy (RALP) and robotic inguinal hernia repair (RIHR). Method We systematically searched the PubMed, Embase and Cochrane Library database up to the year 2020 to identify studies that assessed patients who underwent RALP and RIHR in the same settings. Results Thirteen studies were considered suitable for a systematic review and seven for Meta-analysis. RALP and RIHR were associated with significantly longer operative time. RIHR added on average 26 min to the operation time (8, 45 95% CI, p = 0.005, I2 97%). Concurrent RALP and RIHR was not associated with a higher incidence of blood loss (−13, 6 95% CI, p = 0.43, I2 18%), length of stay (−0.08, 0.06 95% CI, p = 0.73, I2 0%) or early postoperative complications. Conclusion Concurrent robotic repair of an inguinal hernia during RALP appears feasible and safe. Urologists should be encouraged to repair hernias encountered during RALP keeping in mind possible complications including wound infection, mesh infection, chronic inguinal pain and recurrence of hernia

Finite element analysis of unreinforced masonry walls with different bond patterns

Masonry is the oldest building material, yet it is also the least understood due to the non-linear and composite nature of masonry, which consists of brick units, mortar, and unit-mortar contact. In this paper, the response of a two-dimensional masonry wall with a window opening subjected to an in-plane lateral pushover loading is simulated by varying the interface properties of brick such as crushing, elastic, cracking, and shear properties. The simplified micro-modeling technique with the Engineering Masonry model for bricks and linear stiffness properties for the interfaces in the bed and head joints is employed to investigate the geometric nonlinear behavior of the masonry wall. The pushover curves obtained from the numerical simulations indicate that there is a significant influence on the lateral load response of the wall due to elastic, crushing, and shear parameters while the cracking parameters have less impact on the ductile capacity of the structure. Moreover, the study is also extended to examine the effect of bond patterns such as English, Stretcher, Flemish, and Header bond with varied aspect ratios of 1,1.5 and 0.75. In all four bond patterns, it was observed that the walls with lower aspect ratios exhibited higher strength. Further, in comparison to the other bond patterns, walls with the Flemish bond pattern demonstrated higher strengths at both lower and higher aspect ratios

Survival Prediction of Children Undergoing Hematopoietic Stem Cell Transplantation Using Different Machine Learning Classifiers by Performing Chi-squared Test and Hyper-parameter Optimization: A Retrospective Analysis

Bone Marrow Transplant, a gradational rescue for a wide range of disorders emanating from the bone marrow, is an efficacious surgical treatment. Several risk factors, such as post-transplant illnesses, new malignancies, and even organ damage, can impair long-term survival. Therefore, technologies like Machine Learning are deployed for investigating the survival prediction of BMT receivers along with the influences that limit their resilience. In this study, an efficient survival classification model is presented in a comprehensive manner, incorporating the Chi-squared feature selection method to address the dimensionality problem and Hyper Parameter Optimization (HPO) to increase accuracy. A synthetic dataset is generated by imputing the missing values, transforming the data using dummy variable encoding, and compressing the dataset from 59 features to the 11 most correlated features using Chi-squared feature selection. The dataset was split into train and test sets at a ratio of 80:20, and the hyperparameters were optimized using Grid Search Cross-Validation. Several supervised ML methods were trained in this regard, like Decision Tree, Random Forest, Logistic Regression, K-Nearest Neighbors, Gradient Boosting Classifier, Ada Boost, and XG Boost. The simulations have been performed for both the default and optimized hyperparameters by using the original and reduced synthetic dataset. After ranking the features using the Chi-squared test, it was observed that the top 11 features with HPO, resulted in the same accuracy of prediction (94.73%) as the entire dataset with default parameters. Moreover, this approach requires less time and resources for predicting the survivability of children undergoing BMT. Hence, the proposed approach may aid in the development of a computer-aided diagnostic system with satisfactory accuracy and minimal computation time by utilizing medical data records.Comment: 25 pages, 14 figures, 38 table

Road Accidents and Prevention

Road accidents cannot be stopped despite providing the best possible roads and intersections, however there are ways to reduce the impact of road accidents on road-users and the vehicles plying on the road.The incidence of accidental deaths has shown an increasing trend during the period 2005 - 2015 with an increase of 54.3 in the year 2015 as compared to 2005 increase in the rate of accidental deaths during the same period was 25.5.A total of 4,00,517 accidental deaths were reported in the country during 2015 (5,535 more than such deaths reported in 2014) showing an increase of 1.4 as compared to 2014. However, the average rate of Accidental Deaths has remained same 32.6 in 2014 and 2015.In the stretches we studied the road accidents are increasing rapidly .We studied accidental records of various police-stations ,identified the black-spots of accidents and then analyzed the geometric features of those spots whose observation is given in this paper .The identification of such points provides us ease to work on some section of road which is most prone to accidents .We analyzed the geometric deficiencies and they recommended ways to reduce their affects. The findings indicated that large radii right-turn curves were more dangerous than left curves, in particular, during lane changing maneuvers. However sharper curves are more dangerous in both left and right curves. Moreover, motorway carriageways with no or limited shoulders have the highest CR when compared to other carriageway width. Proper traffic guidance and control system to guide road users ensuring safe movement of vehicles has been recommended and some of the facilities such as pedestrian crossings and median openings, acceleration and deceleration lanes were re-designed in order to improve the safety of the road and minimize the accidents

Acute Appendicitis among Saudi and Non-Saudi Patients: A Cross-Sectional Based Study

Objective: We conduct this study to discuss the differences between Saudi and non- Saudi patients with acute appendicitis.Background: Acute appendicitis is one of emergency surgeries in developing and developed countries. Its symptoms are vomiting, lower abdominal pain and decreased appetite. Appendicitis needs urgent surgical prouder to avoid its perforation and associated complications which may lead to death. Method: We conduct cross-sectional based study in one of khamis Mushayt, Saudi Araba. 136 patients diagnosed with acute appendicitis were included and their medical records were reviewed after getting their informed consent.Results: We included 136 patients, 90 were non-Saudi and 46 were Saudi. There were no statistically differences in their diagnosis but the distribution of the diagnosis was different.Conclusion: Acute appendicitis was more prevalent among non-Saudi patients, the diagnosis between both was with no significant differences. Keywords: acute appendicitis, Saudi, non-Saudi, diagnosis, cross-sectional, Saudi Arabia and khamis Mushayt

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Thermal Cycling in Converter IGBT Modules with Different Cooling Systems in Pitch- and Active Stall-Controlled Tidal Turbines

This paper compares active and passive cooling systems in tidal turbine power electronic converters. The comparison is based on the lifetime of the IGBT (insulated gate bipolar transistor) power modules, calculated from the accumulated fatigue due to thermal cycling. The lifetime analysis accounts for the influence of site conditions, namely turbulence and surface waves. Results indicate that active cooling results in a significant improvement in IGBT lifetime over passive cooling. However, since passive cooling systems are inherently more reliable than active systems, passive systems can present a better solution overall, provided adequate lifetime values are achieved. On another note, the influence of pitch control and active speed stall control on the IGBT lifetime was also investigated. It is shown that the IGBT modules in pitch-controlled turbines are likely to have longer lifetimes than their counterparts in active stall-controlled turbines for the same power rating. Overall, it is demonstrated that passive cooling systems can provide adequate cooling in tidal turbine converters to last longer than the typical lifetime of tidal turbines (>25 years), both for pitch-controlled and active speed stall-controlled turbines

Three dimensional Finite Element Modeling of a Brushless Doubly-fed Induction Machine

As we move deeper into offshore waters to harness more of wind energy there is a need to keep the total operational and maintenance costs to a minimum, of which expenditures related to the generators form a major share. Brushless Doubly-fed Induction machine used as a generator, due to the requirement of a lower rating converter, and the absence of brush-gear and slip-ring arrangement can help in mitigating those costs. 2D models of the BDFIM have been developed to arrive at a better design so that the machine is able to compete with and possibly, outperform other solutions in the market. However, much like 2D models of the other machines, these models usually neglect or at best approximate certain practical aspects. These aspects mostly include effects arising due to physical features such as end windings, laminated structure of the iron, skew in the conductors, etc. 3D modeling can allow us to more accurately model these effects and perhaps, result in an even more efficient design. However, there are some caveats in this approach. 3D models, as expected, are mathematically more complex to formulate and solve. Besides, there is a multifold increase in the number of unknowns to be solved for which poses a significant challenge in terms of the memory requirement and the time cost of the model. The methods adopted to solve 2D problems hitherto, magnetostatic as well as transient, are not suitable to solve large scale 3D models. The objective of this thesis is primarily to present a strategy to efficiently solve such 3D problems. In this regard, different magnetic potential formulations were considered, and the mathematical properties of the matrix system resulting from each formulation were outlined. Special emphasis is placed on the implementation of iterative solvers and multigrid preconditioning. Also, it will be demonstrated that a formulation resulting in fewer degrees of freedom does not necessarily translate into a memory and/or time efficient model. This approach is then extended to estimate the axial flux in the BDFIM arising from the skewed rotor. In the 3D model, we consider the axial flux component and anisotropy of the iron which are neglected by the 2D multi-slice model. Upon analysis, it was observed that incorporating these effects leads to minimal improvement over the 2D multi-slice model which, however, more than outweighs this improvement by being computationally less expensive