Strengthening QC relaxations of optimal power flow problems by exploiting various coordinate changes

Motivated by the potential for improvements in electric power system economics, this dissertation studies the AC optimal power flow (AC OPF) problem. An AC OPF problem optimizes a specified objective function subject to constraints imposed by both the non-linear power flow equations and engineering limits. The difficulty of an AC OPF problem is strongly connected to its feasible space\u27s characteristics. This dissertation first investigates causes of nonconvexities in AC OPF problems. Understanding typical causes of nonconvexities is helpful for improving AC OPF solution methodologies. This dissertation next focuses on solution methods for AC OPF problems that are based on convex relaxations. The quadratic convex (QC) relaxation is one promising approach that constructs convex envelopes around the trigonometric and product terms in the polar representation of the power flow equations. This dissertation proposes several improvements to strengthen QC relaxations of OPF problems. The first group of improvements provides tighter envelopes for the trigonometric functions and product terms in the power flow equations. Methods for obtaining tighter envelopes includes implementing Meyer and Floudas envelopes that yield the convex hull of trilinear monomials. Furthermore, by leveraging a representation of line admittances in polar form, this dissertation proposes tighter envelopes for the trigonometric terms. Another proposed improvement exploits the ability to rotate the base power used in the per unit normalization in order to facilitate the application of tighter trigonometric envelopes. The second group of improvements propose additional constraints based on new variables that represent voltage magnitude differences between connected buses. Using \u27bound tightening\u27 techniques, the bounds on the voltage magnitude difference variables can be significantly tighter than the bounds on the voltage magnitudes themselves, so constraints based on voltage magnitude differences can improve the QC relaxation --Abstract, page iv

The Relationship of Alexithymia and Cognitive Failure with Spiritual Health in Male Students of Ardabil Payam-e Noor University

Background & Objectives: Students with a high spiritual health can adapt to the problems in their personal life. The purpose of this study was to investigate the relationship of alexithymia and cognitive failure with spiritual health in male students of Ardabil Payam-e Noor University. Methods: This descriptive-analytic study was performed on 268 male students of Ardabil Payam-e Noor University selected through multistage multi-cluster random sampling. Data collection tools included questionnaires of alexithymia (20 items), cognitive failure (25 items), and spiritual well-being (20 questions). Data were entered into SPSS version 23 and analyzed using inferential statistics tests, Pearson Correlation Coefficient and Multiple Regression tests. Results: There was no statistically significant relationship between demographic variables (age, educational level and field, occupation and marital status) and spiritual health among male students. However, alexithymia and cognitive failure showed significant statistical relationships with spiritual well-being. According to multiple regression results, alexithymia and cognitive failure have the potential for predicting spiritual well-being in male students (P <0.05). Conclusion: Considering the effect of alexithymia and cognitive failure on students’ spiritual health, it is recommended to help students to improve their spiritual health by overcoming alexithymia and cognitive failure. Key¬words: Affective Symptoms, Cognition, Health, Students Citation: Narimani M, Samadifard HR. The Relationship of Alexithymia and Cognitive Failure with Spiritual Health in Male Students of Ardabil Payam-e Noor University. Journal of Health Based Research 2017; 3(2): 163-173

Improving QC Relaxations of OPF Problems via Voltage Magnitude Difference Constraints and Envelopes for Trilinear Monomials

AC optimal power flow (AC~OPF) is a challenging non-convex optimization problem that plays a crucial role in power system operation and control. Recently developed convex relaxation techniques provide new insights regarding the global optimality of AC~OPF solutions. The quadratic convex (QC) relaxation is one promising approach that constructs convex envelopes around the trigonometric and product terms in the polar representation of the power flow equations. This paper proposes two methods for tightening the QC relaxation. The first method introduces new variables that represent the voltage magnitude differences between connected buses. Using "bound tightening" techniques, the bounds on the voltage magnitude difference variables can be significantly smaller than the bounds on the voltage magnitudes themselves, so constraints based on voltage magnitude differences can tighten the relaxation. Second, rather than a potentially weaker "nested McCormick" formulation, this paper applies "Meyer and Floudas" envelopes that yield the convex hull of the trilinear monomials formed by the product of the voltage magnitudes and trignometric terms in the polar form of the power flow equations. Comparison to a state-of-the-art QC implementation demonstrates the advantages of these improvements via smaller optimality gaps.Comment: 8 pages, 1 figur

The relationship between quality of life with metacognitive belief and cognitive fusion in couples

BACKGROUND: Quality of life (QOL) is one of the most important factors of family stability. The objective in this study is to investigate the relationship between metacognitive belief and cognitive fusion with QOL among couples in Ardabil City, Iran.METHODS: This was a descriptive-correlational study in which the statistical population included all couples in Ardabil in 2016 who were selected by the convenience sampling method (54 couples). Data were collected using questionnaires and were analysed using Pearson correlation coefficient.RESULTS: The results showed that there was a significant relationship between metacognitive belief and fusion cognitive with QOL of the couples (P &lt; 0.05).CONCLUSION: It can be concluded from this study that couples with higher levels of metacognitive beliefs and cognitive fusion have a lower QOL compared to their peers

The role of spiritual well-being and Religious Adherence in predicting marital satisfaction among nurses

زمینه و هدف: رضایت زناشویی از جمله عوامل مرتبط با سلامت روان و استرس شغلی پرستاران است. پژوهش حاضر با هدف تعیین نقش بهزیستی معنوی و پایبندی مذهبی در پیش بینی رضامندی زناشویی پرستاران صورت گرفته است. روش بررسی: در این مطالعه توصیفی تحلیلی، 176 نفر از پرستاران شاغل در بیمارستان های اردبیل در سال 93 به ‌صورت نمونه‌گیری خوشه‌ای چند مرحله ای انتخاب شدند. برای جمع ‌آوری داده‌ها از پرسش‌نامه های بهزیستی معنوی پالوتزیان و الیسون، پایبندی مذهبی و رضامندی زناشویی بر اساس معیارهای اسلامی استفاده شد. داده‌های به‌دست‌آمده با آزمون ضریب همبستگی پیرسون و تحلیل رگرسیون همزمان مورد تجزیه و تحلیل قرار گرفتند. یافته ها: بین پایبندی مذهبی و بهزیستی معنوی با رضامندی زناشویی رابطه مثبت و معناداری وجود داشت. همچنین نتایج تحلیل رگرسیون نشان داد که 3/32 درصد رضامندی زناشویی پرستاران، براساس پایبندی مذهبی و بهزیستی معنوی قابل تبیین است (001/0

Relationship Between Post-traumatic Growth and Illness Perception and Emotion Regulation in Patients with Cancer

Background: Cancer diagnosis causes emotional problems and profound psychological helplessness in patients. We aimed to investigate the relationship between post-traumatic growth and disease perception and emotion regulation in patients with cancer.Methods: The statistical population of this correlation study was all patients aged 18-65 years with breast, leukemia, and gastrointestinal cancer going to the oncology ward of Omid and Imam Khomeini hospitals in Urmia in the first half of 2021. 250 people (121 women and 129 men) were selected by the purposeful sampling method. Data collection tools included a post-traumatic growth questionnaire, a modified illness perception questionnaire, and the emotion regulation process strategies questionnaire. Pearson’s correlation test and multiple regression analysis were used for data analysis.Results: The results showed that negative illness perception had a significant and negative relationship, and optimistic illness perception had a positive, meaningful relationship with post-traumatic growth (P &lt; 0.05). Emotion regulation had a significant and positive association with post-traumatic growth (P &lt; 0.05).Conclusion: How to perceive the disease and emotion regulation strategies in patients with cancer have an influential role in promoting post-traumatic growth

Tightening QC Relaxations of AC Optimal Power Flow Problems via Complex Per Unit Normalization

Optimal power flow (OPF) is a key problem in power system operations. OPF problems that use the nonlinear AC power flow equations to accurately model the network physics have inherent challenges associated with non-convexity. To address these challenges, recent research has applied various convex relaxation approaches to OPF problems. The QC relaxation is a promising approach that convexifies the trigonometric and product terms in the OPF problem by enclosing these terms in convex envelopes. The accuracy of the QC relaxation strongly depends on the tightness of these envelopes. This paper presents two improvements to these envelopes. The first improvement leverages a polar representation of the branch admittances in addition to the rectangular representation used previously. The second improvement is based on a coordinate transformation via a complex per unit base power normalization that rotates the power flow equations. The trigonometric envelopes resulting from this rotation can be tighter than the corresponding envelopes in previous QC relaxation formulations. Using an empirical analysis with a variety of test cases, this paper suggests an appropriate value for the angle of the complex base power. Comparing the results with a state-of-the-art QC formulation reveals the advantages of the proposed improvements

Multi-Objective Dynamic Economic Dispatch with Demand Side Management of Residential Loads and Electric Vehicles

In this paper, a multi-objective optimization method based on the normal boundary intersection is proposed to solve the dynamic economic dispatch with demand side management of individual residential loads and electric vehicles. The proposed approach specifically addresses consumer comfort through acceptable appliance deferral times and electric vehicle charging requirements. The multi-objectives of minimizing generation costs, emissions, and energy loss in the system are balanced in a Pareto front approach in which a fuzzy decision making method has been implemented to find the best compromise solution based on desired system operating conditions. The normal boundary intersection method is described and validated