Operating risk analysis of wind integrated generation systems

Wind power installations are growing rapidly throughout the world due to environmental concerns associated with electric power generation from conventional generating units. Wind power is highly variable and its uncertainty creates considerable difficulties in system operation. Reliable operation of an electric power system with significant wind power requires quantifying the uncertainty associated with wind power and assessing the capacity value of wind power that will be available in the operating lead time. This thesis presents probabilistic techniques that utilize time series models and a conditional probability approach to quantify the uncertainty associated with wind power in a short future time, such as one or two hours. The presented models are applied to evaluate the risk of committing electric power from a wind farm to a power system. The impacts of initial wind conditions, rising and falling wind trends, and different operating lead times are also assessed using the developed methods. An appropriate model for day-ahead wind power commitment is also presented. Wind power commitment for the short future time is commonly made equal to, or a certain percentage, of the wind power available at the present time. The risk in meeting the commitment made in this way is different at various operating conditions, and unknown to the operator. A simplified risk based method has been developed in this thesis to assist the operator in making wind power commitments at a consistent level of risk that is acceptable to the system. This thesis presents a methodology to integrate the developed short-term wind models with the conventional power generation models to evaluate the overall operational reliability of a wind integrated power system. The area risk concept has been extended to incorporate wind power, evaluate the unit commitment risk and the well- being indices of a power system for a specified operating lead time. The method presented in this thesis will assist the operator to determine the generator units and the operating reserve required to integrate wind power and meet the forecast load for a short future time while maintaining an acceptable reliability criterion. System operators also face challenges in load dispatch while integrating wind power since it cannot be dispatched in a conventional sense, and is accepted as and when present in current operational practices. The thesis presents a method to evaluate the response risk and determine the unit schedule while satisfying a specified response risk criterion incorporating wind power. Energy storage is regarded as an effective resource for mitigating the uncertainty of wind power. New methods to incorporate energy storage with wind models, and with wind-integrated power system models to evaluate the wind power commitment risk and unit commitment risk are presented in this thesis. The developed methods and the research findings should prove useful in evaluating the operating risks to wind farm operators and system operators in wind integrated power systems

Validation of a Preoperative Scoring System to Predict Difficult Laparoscopic Cholecystectomy: A Nepalese Perspective

Introduction: Preoperative prediction of the factors leading to difficulty or conversion in cholecystectomy could help plan the surgical strategies and possible outcomes beforehand. The present study aimed to predict and analyze risk factors using a scoring system deemed responsible for surgical difficulties in patients undergoing cholecystectomy for symptomatic cholelithiasis. Methods: This hospital based prospective study was conducted at Department of Surgery, Lumbini Medical College and Teaching Hospital, Nepal. Various factors considered preoperatively were gender, age, previous history of hospitalization, impacted stone, obesity, gall bladder wall thickness, pericholecystic collection, previous abdominal scar and palpable gall bladder. Results: Among 177 cases operated, the mean age ±SD of the patients was 47.72±17.54 years. Conversion rate was 7.9 %. At preoperative score of 5; sensitivity, specificity, positive predictive value and negative predictive value were 89.40% (CI: 83.36%-93.82%), 69.23% (CI: 48.21 %-85.67%), 94.41%(CI: 90.44%-96.79%) and 52.94% (CI: 39.85%-65.64%) respectively{Area under curve– 0.74, p=0.0001, CI (0.637-0.846)}. Multivariate analysis showed abdominal scar {p=0.02, OR (CI): 5.2 (1.2-21.8)}, previous hospitalization {p=0.001, OR(CI): 6.8(2.2-20.8)} and thickened gall bladder wall {p= 0.03, OR(CI): 3.6(1.1-11.5)} to be statistically significant risk factors. Conclusion: With possible prediction beforehand, high risk group of patients can be identified and dealt accordingly to generate good surgical outcome avoiding complications

Metabolic Syndrome and Benign Prostatic Hyperplasia: A Nepalese Perspective

Introduction: Metabolic syndrome is defined as the presence of at least 3 of the following parameters: (1) waist circumference ≥ 90 cm, (2) triglycerides > 150 mg/dl or treatment for hypertriglyceridemia, (3) HDL-cholesterol < 40 mg/dl or treatment for reduced HDL-cholesterol, (4) blood pressure ≥ 130/85 mmHg or current use of antihypertensive medications, (5) fasting blood glucose ≥ 110 mg/dl or previous diagnosis of type-2 diabetes mellitus. It is closely associated with many diseases and recent studies have also shown its association with benign prostatic hyperplasia and lower urinary tract symptoms. Our study aimed to investigate association between metabolic syndrome and its components with benign prostatic hyperplasia among patients managed surgically in a tertiary centre in Western Nepal. Methods: One hundred and four patients above 50 years with benign prostatic hyperplasia managed in the department of Surgery over one year were included in the study. Results: Twenty-seven patients had metabolic syndrome (25.96%). There was association between metabolic syndrome and mean prostate size and among components of metabolic syndrome, high serum triglyceride and low HDL Cholesterol were found to be associated. There was increase in mean prostate size with increase in number of metabolic syndrome components which was statistically significant. Conclusion: Metabolic syndrome along with its two components, serum triglyceride and HDL Cholesterol were associated with increase in mean prostate size

Axial Torsion and Meckel’s Diverticulitis: A Diagnostic Conundrum

Introduction: Meckel’s diverticulum is one the most common congenital anomalies of gastrointestinal tract that mimics acute appendicitis, gastroenteritis, peptic ulcer disease. Complications related to it can be haemorrhage, intestinal obstruction, perforation while axial torsion is one of the rarest complications. So, this paper objectifies a rare clinical scenario that we encountered in our practice and highlights on the possible management strategies. Case : An 11 year boy presented with a history of pain at peri-umbilical region for four days with 2-3 episodes of vomiting. Abdominal examination revealed tenderness at suprapubic area with a mass around 5x3 cm along hypogastrium. Ultrasonography abdomen revealed an avascular structure in central area with clumping of bowel and omentum over the lesion while computed tomography scan of abdomen revealed blind ended gas filled structure at hypogastrium with thickened enhancing irregular wall associated with adjacent mesenteric fat plane stranding and prominent adjacent axial vessels supplying inflammatory lesion. Exploratory laparotomy showed axial twisting of diverticulum about 10x5 cm arising from anti-mesenteric border around 50 cm proximal to ileo-caecal junction with a fibrous band attached to the fundus and ileum leading to gangrenous diverticulum with clumping of bowel loops along with omental covering. De-twisting and adhesiolysis along with excision of the diverticulum was done with two layered closure of the defect. Conclusion: Axial torsion is the rarest of the complication of MD and should be managed with utmost caution. Excision of the twisted diverticulum with or without wedge resection of the involved ileum is the procedure of choice

Corporate governance reform and risk-taking:evidence from a quasi-natural experiment in an emerging market

Existing studies suggest that stricter Corporate Governance Reform (CGR) reduces corporate risk-taking, primarily due to higher compliance costs and expanded liabilities of insiders or managers. We revisit the relationship between CGR and risk-taking in an emerging market set-up characterized by weaker market forces of corporate scrutiny and greater insider ownership, which encourages firms to pursue investment conservatism. Using a quasi-natural experiment, we find that stricter CGR leads to greater corporate risk-taking. We further show that risk-taking is an important channel through which CGR enhances firm value. Our findings support the view that stricter CGR can have a positive effect on corporate risk-taking and corporate investment decisions in an evolving regulatory environment

International equity portfolio allocations and stock market development

This paper examines whether the widely reported phenomena of home and foreign biases (i.e. sub-optimal international equity portfolio diversification) hold any ramifications for the development of stock markets. The results, analysed using macro- and micro-level data, support the view that stock markets that are characterised by a higher degree of home bias are associated with lower levels of development. On the other hand, markets where foreign investors show a higher degree of allocation preference, relative to the prescribed benchmark (foreign bias), are found to be more developed. The results, which are robust to the use of shock based identification strategy, indicate that policy measures that promote optimal international equity portfolio diversification could be crucial in developing the depth and breadth of domestic stock markets

Predictive Factors for Post-Operative Bleeding in Percutaneous Nephrolithotomy.

Introduction: Post-operative bleeding is a serious complication necessitating prompt attention inPercutaneous Nephrolithotomy (PCNL). A number of factors dictate the severity of post-PCNL bleeding.Identification of these risk factors helps prevent bleeding complications. Methods: In this observationalcross-sectional study, a total of 126 patients with renal stones >10mm or stag-horn stones underwent PCNL.All the relevant pre- and intra-operative factors were noted and analyzed. Hemoglobin differences betweenpre- and post-operative levels were considered for the evaluation of blood loss. Univariate and multivariablelogistic regression analysis was done. The strength of association was examined using Odds Ratio and95% confidence intervals derived from the logistic regression. A p value <0.05 was considered statisticallysignificant. Results: The mean age of the patients was 31.9 ±4.47 years. The mean drop in hemoglobinwas 1.83 ±0.98 gm/dl. Age, stone size, number of tracts, size of Amplatz sheath and number of stonessignificantly affected the blood loss in univariate analysis. Among the variables mentioned above only, thenumber of stones could maintain the significance in multivariable analysis (p<0.05). The number of stonesincrease the risk of bleeding post PCNL by 4.4 times. Conclusion: Stone size, number of tracts, size ofAmplatz sheath and the number of stones significantly affect the blood loss post PCNL. Identification ofthese risk factors should be considered for minimizing bleeding in PCNL

Do foreign institutional investors improve board monitoring?

Exploiting the global financial crisis of 2007–08 as an exogenous shock that resulted in a significant decline in the ownership of foreign institutional investors (FIIs) in the Indian equity market, we find evidence of a causal link between FIIs’ ownership and different dimensions of board monitoring. Specifically, the empirical results suggest that higher FIIs ownership leads to lower board size, busyness, network size, CEO power, CEO pay, and improved board diligence. However, we also document a negative link between FIIs’ ownership and board independence, indicating that FIIs do not view independent directors as effective monitors. In terms of implications, our results suggest that improved board monitoring, induced by higher FIIs’ ownership, leads to higher firm valuation and innovation activities

Firm quality or market sentiment: What matters more for IPO investors?

a b s t r a c t This paper investigates the investment decisions of IPO investors when equipped with information on both the quality of the firm and the market sentiment. Unique regulatory provisions allow IPO investors in India to have access to the independent assessment of firm quality and information on the participation of other investors, including institutional investors. At the same time, an active grey market reveals market sentiment before the application for subscription is closed. The results, which are robust to alternative model specifications, suggest that the institutional investors' decision is guided almost exclusively by firm quality while the retail investors' decision to participate in IPOs is strongly influenced by market sentiment, even in a highly transparent market where both sets of information are freely available