• Energy Research

This paper investigates the application of widely used K-Medoids based clustering algorithm on data collected through CoMon facility for the PlanetLab testbed. The averaged values of various metrics in passively collected slice-centric data has been considered for clustering purposes. Various groups of slices, depicting similar resource usage patterns have been identified in original data set. These clusters have been represented in reduced dimensional space formed by first two principal components of original data set. In order to capture variations in pattern of resource usage by various slices at a PlanetLab node, clustering of standard deviations of various metrics have also been carried out. It has been found that K-medoid based clustering can effectively split the original data space into various sub-spaces of different resource usage behaviour of slices. Thus, it can lead to better resource management and control in publicly available testbeds.

Currently, Pakistan is facing severe energy crises and global warming effects. Hence, there is an urgent need to utilize renewable energy generation. In this context, Pakistan possesses massive wind energy potential across the coastal areas. This paper investigates and numerically analyzes coastal areas’ wind power density potential. Eight different state-of-the-art numerical methods, namely an (a) empirical method, (b) graphical method, (c) wasp algorithm, (d) energy pattern method, (e) moment method, (f) maximum likelihood method, (g) energy trend method, and (h) least-squares regression method, were analyzed to calculate Weibull parameters. We computed Weibull shape parameters (WSP) and Weibull scale parameters (WCP) for four regions: Jiwani, Gwadar, Pasni, and Ormara in Pakistan. These Weibull parameters from the above-mentioned numerical methods were analyzed and compared to find an optimal numerical method for the coastal areas of Pakistan. Further, the following statistical indicators were used to compare the efficiency of the above numerical methods: (i) analysis of variance (R2), (ii) chi-square (X2), and (iii) root mean square error (RMSE). The performance validation showed that the energy trend and graphical method provided weak performance for the observed period for four coastal regions of Pakistan. Further, we observed that Ormara is the best and Jiwani is the worst area for wind power generation using comparative analyses for actual and estimated data of wind power density from four regions of Pakistan.

It is imperative to find new places other than Earth for the survival of human beings. Mars could be the alternative to Earth in the future for us to live. In this context, many missions have been performed to examine the planet Mars. For such missions, planetary precision landing is a major challenge for the precise landing on Mars. Mars landing consists of different phases (hypersonic entry, parachute descent, terminal descent comprising gravity turn, and powered descent). However, the focus of this work is the powered descent phase of landing. Firstly, the main objective of this study is to minimize the landing error during the powered descend landing phase. The second objective involves constrained optimization in a predictive control framework for landing at non-cooperative sites. Different control algorithms like PID and LQR have been developed for the stated problem; however, the predictive control algorithm with constraint handling’s ability has not been explored much. This research discusses the Model Predictive Control algorithm for the powered descent phase of landing. Model Predictive Control (MPC) considers input/output constraints in the calculation of the control law and thus it is very useful for the stated problem as shown in the results. The main novelty of this work is the implementation of Explicit MPC, which gives comparatively less computational time than MPC. A comparison is done among MPC variants in terms of feasibility, constraints handling, and computational time. Moreover, other conventional control algorithms like PID and LQR are compared with the proposed predictive algorithm. These control algorithms are implemented on quadrotor UAV (which emulates the dynamics of a planetary lander) to verify the feasibility through simulations in MATLAB.

L'utilisation à long terme de l'huile de transformateur détériore les propriétés thermiques et diélectriques de l'huile. L'objectif principal de notre travail est de trouver un substitut approprié à l'huile minérale avec des caractéristiques supérieures. L'oxyde de titane (TiO 2 ), l'oxyde de zinc (ZnO) et l'oxyde d'aluminium (Al 2 O 3 ) Les nanoparticules (NP) sont utilisées à l'intérieur de l'huile minérale vierge pour former des nanofluides (NF). Les NF sont soumis à un multi-vieillissement accéléré (thermique et électrique) pendant 1000 heures. Les chambre de vieillissement spéciale est conçue pour appliquer des contraintes électriques et thermiques à l'huile considérée.Les caractéristiques thermiques et diélectriques des NF sont déterminées à l'aide de tests de tension de claquage, de teneur en eau, de tan delta, de point d'éclair, de viscosité et de point d'écoulement.Les tests susmentionnés sont effectués avant et après le vieillissement accéléré des échantillons.Les caractéristiques thermiques et diélectriques des NF à base de ZnO sont supérieures à celles des autres NP.Les NP de ZnO présentent la tension de claquage la plus élevée et des valeurs minimales de teneur en eau, de tan delta, de point d'écoulement et de viscosité.La valeur la plus élevée du point d'éclair a confirmé la supériorité du ZnO NF par rapport aux autres NF, même après un multi-vieillissement accéléré.Par conséquent, les l'analyse expérimentale a conclu que les NF à base de ZnO possèdent des propriétés thermiques et diélectriques remarquablement bonnes en remplacement de l'huile minérale dans le fonctionnement du transformateur. El uso de aceite de transformador a largo plazo deteriora las propiedades térmicas y dieléctricas del aceite. El objetivo principal de nuestro trabajo es encontrar un reemplazo adecuado para el aceite mineral con características superiores. Las nanopartículas (NP) de óxido de titanio (Tío 2), óxido de zinc (ZnO) y óxido de aluminio (Al 2 O 3) se utilizan dentro del aceite mineral virgen para formar nano fluidos (NF). Las NF se someten a multienvejecimiento acelerado (térmico y eléctrico) durante 1000 horas. la cámara de envejecimiento especial está diseñada para aplicar tensiones eléctricas y térmicas al aceite bajo consideración. Las características térmicas y dieléctricas de las NF se determinan utilizando pruebas de voltaje de ruptura, contenido de agua, tan delta, punto de inflamación, viscosidad y punto de fluidez. Las pruebas antes mencionadas se realizan antes y después del envejecimiento acelerado de las muestras. Las características térmicas y dieléctricas de las NF a base de ZnO se encuentran superiores a otras NP. Las NP de ZnO muestran el voltaje de ruptura más alto y los valores mínimos de contenido de agua, tan delta, punto de fluidez y viscosidad. El valor más alto del punto de inflamación confirmó la superioridad de ZnO NF sobre otras NF incluso después del envejecimiento múltiple acelerado. Por lo tanto, el análisis experimental concluyó que los NF basados en ZnO poseen propiedades térmicas y dieléctricas notablemente buenas como reemplazo del aceite mineral en la operación del transformador. Long-term transformer oil usage deteriorates the thermal and dielectric properties of the oil.The main aim of our work is to find a suitable replacement for mineral oil with superior characteristics.Titanium Oxide (TiO 2 ), Zinc Oxide (ZnO), and Aluminum Oxide (Al 2 O 3 ) Nano Particles (NPs) are used inside the virgin mineral oil to form Nano Fluids (NFs).NFs are subjected to accelerated multi-aging (thermal and electrical) for 1000 hours.The special aging chamber is designed to apply electrical and thermal stresses to the oil under consideration.Thermal and dielectric characteristics of the NFs are determined using breakdown voltage, water content, tan delta, flash point, viscosity, and pour point tests.The aforementioned tests are conducted before and after the accelerated aging of the samples.Thermal and dielectric characteristics of ZnO based NFs are found superior to other NPs.ZnO NPs show the highest breakdown voltage and minimum values of water content, tan delta, pour point, and viscosity.The highest value of flash point confirmed the superiority of ZnO NF over other NFs even after accelerated multi-aging.Therefore, the experimental analysis concluded that ZnO based NFs possess remarkably good thermal and dielectric properties as a replacement of mineral oil in the transformer operation. يؤدي استخدام زيت المحولات على المدى الطويل إلى تدهور الخصائص الحرارية والعازلة للزيت. الهدف الرئيسي من عملنا هو إيجاد بديل مناسب للزيوت المعدنية ذات الخصائص الفائقة. يتم استخدام أكسيد التيتانيوم (TiO 2 ) وأكسيد الزنك (ZnO) وأكسيد الألومنيوم (Al 2 O 3 ) وجسيمات النانو (NPs) داخل الزيت المعدني البكر لتشكيل سوائل النانو (NFs). تتعرض NFs لتسارع متعدد الأعمار (الحرارية والكهربائية) لمدة 1000 ساعة. تم تصميم غرفة التقادم الخاصة لتطبيق الضغوط الكهربائية والحرارية على الزيت قيد النظر. يتم تحديد الخصائص الحرارية والعزل الكهربائي لـ NFs باستخدام جهد الانهيار، ومحتوى الماء، ودلتا السمرة، ونقطة الاشتعال، واللزوجة، واختبارات نقطة الصب. يتم إجراء الاختبارات المذكورة أعلاه قبل وبعد التقادم المتسارع للعينات. تم العثور على الخصائص الحرارية والعزل الكهربائي لـ NFs القائمة على ZnO متفوقة على NPs الأخرى. تُظهر ZnO NPs أعلى جهد للانهيار والقيم الدنيا لمحتوى الماء، ودلتا السمرة، ونقطة الصب، واللزوجة. أكدت أعلى قيمة لنقطة الوميض تفوق ZnO NFs على NFs الأخرى حتى بعد التسارع المتعدد. لذلك، فإن خلص التحليل التجريبي إلى أن NFs القائمة على ZnO تمتلك خصائص حرارية وعازلة جيدة بشكل ملحوظ كبديل للزيت المعدني في عملية المحول.