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Uncertainty and geographical diversity of wind speeds create risk for a wind power generation company (WGenco) to make the maximum profit from power market trading. A probabilistic approach is proposed to estimate the profit of a WGenco considering geographical diversity and uncertainty of wind speeds and market prices. The objective of the optimization problem is to assist a WGenco to do the optimal bidding in market trading in order to make the maximum profit under various market and wind speed uncertainties. The point estimate method (PEM) has been improved to facilitate stochastic modeling of the aggregated power output of wind turbine generators in different locations in the problem formulation. The principal component analysis (PCA) is used to manage correlated wind speeds. [ABSTRACT FROM AUTHOR]

Introduction: Ocular motor nerve palsies are one of the leading causes of ocular morbidity in the neuro-ophthalmology clinic. Objective: This study was aimed to determine the aetiology of ocular motor nerve palsies in a tertiary referral eye center of Nepal. Methods: This hospital based cross-sectional descriptive study was carried out over a period of one and a half years. All cases of ocular motor nerve palsies were evaluated and relevant laboratory investigations and imaging studies were done. Results: Ninety-one patients with ocular motor nerve palsies were examined, of which 53 (58%) were males and 38(42%) were females. The mean age was 39.4 years +18.29 years. Majority of the cases (n=78, 86%) had unilateral involvement and the most common chief complaint was double vision (n=58, 63.7%). The sixth cranial nerve palsy was most commonly seen (n=49, 53.85%) followed by third nerve palsy (n=22, 24.18%). Fourth cranial nerve palsy and combined cranial nerve palsies accounted for 10.99% each (n=10). Aetiology of ocular motor nerve palsies could not be determined in 31.8% of the cases. Among the identifiable etiologies were vascular diseases (n=24, 26.3%), infections (n=14, 15.3%), trauma (n=14, 15.3%) and neoplasms (n=9, 9.8%). Imaging studies were done in 92 %(n=84) of cases. In cases of combined cranial nerve palsies, positive diagnostic findings were noted in 50% (n=5) of the cases with imaging studies. Conclusion: The sixth cranial nerve palsy was the most common ocular motor nerve palsy in our study. The most common identifiable aetiology was vascular diseases followed by trauma. Besides ophthalmic examination, neurological evaluation and imaging plays an important role in diagnosis. [ABSTRACT FROM AUTHOR]

This study presents a new approach to bidding for Gencos participating in a competitive market, which takes account of both the uncertainty as well as the cost characteristics of the generating units in an effort to make a reasonable profit from the operation. The price uncertainty is accounted for by representing the price appropriate statistical distributions. Such statistical representation of market price is utilised to enable a Genco to be successful in a bidding process with a specified degree of confidence. The screening curve commonly used in planning and operation of generators in traditional operation of power systems to characterise the economic merits of the generating units are utilised in this study to account for the costs incurred by the Genco in its operation and establish the desired level of bidding success in the market place. The logical development of the strategy is illustrated by implementing it for a Genco with three generating units, which are chosen to have competitive cost characteristics with respect to the market price. The results of the Genco operation are presented to illustrate that the methodology succeeds in securing reasonable profit. The simulation is extended to illustrate how the accuracy of the price modelling is important to ensure better profits. [ABSTRACT FROM AUTHOR]

Price uncertainty is faced by Gencos in the scheduling of their units in competitive power markets. The proper way to deal with the uncertainty depends on the risk preference of the Genco. Two important means to manage the price uncertainty are (i) suitable flexible bids and (ii) the use of hedging tools such as forward contracts. The influence of these factors in the Genco's short-term generation planning and the corresponding profit performances is studied. The market price is represented by lognormal distribution, Genco risk behaviour is represented by exponential utility functions, the bid functions are taken to be flexible and simple contracts for hedging are assumed available. The unit commitment problem is combined with the hedging problem to obtain the optimal solution. Formulation of the problem to maximise profit in the spot market and its extension to incorporate the risk behaviour of the Gencos and the forward contacts for hedging is presented. Solution method based on genetic algorithms is implemented in MATLAB. It is observed through numerical examples that the flexible outputs and the forward contracts can be used to hedge against price risks to achieve desired profit performance according to Gencos' risk behaviour. [ABSTRACT FROM AUTHOR]

The debate is still on regarding the rationale for transmission expansion in deregulated power markets. Transmission planning with social welfare as the objective would lead to a different optimal expansion plan compared to the planning deemed optimal by individual merchants acting on market forces with profits as their objective. This issue remains to be resolved amid varying rationales and conflicting interests. Fundamental formulations and analyses for long-term network expansion are presented under the paradigms of (i) system-wide social cost minimisation under central planning, and (ii) profit maximising objectives of merchant entrants covering a range of market structures. Distinct planning outcomes under centralised (regulated monopoly) and decentralised (merchant transmission) network managements, and the relation between these optimal solutions have been quantified analytically. These fundamental formulations would be useful for detailed policy studies, and in the formulation of practical regulatory frameworks in the context of transmission sector market liberalisation. Simple and clear examples are presented to illustrate the theoretical results. [ABSTRACT FROM AUTHOR]

Bidding plays an important role for Gencos participating in competitive electricity markets with the objective of maximising profit. While making bidding strategies, factors like characteristics of generators and price uncertainty need to be considered as they have direct impact on the expected profit. In this work, a method of building an optimal bid curve under price uncertainty using price-based unit commitment (PBUC) is presented. The results indicate a simple yet an effective bidding method. [ABSTRACT FROM AUTHOR]

A framework for obtaining an optimal network reinforcement scheme to jointly meet both long-term transmission capacity requirements as well as the alleviation of short- or medium-term congestion in a competitive power market is presented. A value-based network expansion strategy is formulated in which long-term network investment cost is justified by the long-term congestion cost saving. Network expansions and flexible AC transmission system (FACTS) device installations are investigated as possible alternatives for network reinforcement. These alternatives are considered separately as well as in different combinations. Two types of FACTS devices namely the phase shifter and the series compensator are explored for the purpose. The solution methodology is implemented using the generalised Benders decomposition technique in which the master problem is the network investment cost minimisation and the operational subproblem is the social cost minimisation in network constrained power dispatch. Case studies have been carried out on the modified IEEE 24-bus system to illustrate the features of the proposed technique and to demonstrate the ability of the technique to produce good network reinforcement schemes under various conditions. [ABSTRACT FROM AUTHOR]

This paper addresses the optimal management of hydropower resources on medium term. The objective is to maximize the expected revenue of a producer, and the decision variables are generation and forward contracts in each period for each scenario. Stochastic linear and nonlinear programming has been used as a framework for modeling and solution. Results are exposited for a Norwegian power producer participating in Nord Pool, the Nordic power exchange. [ABSTRACT FROM AUTHOR]

A framework for transmission planning in a deregulated power market environment is discussed. The level of congestion in the network is utilized as the driving signal for the need of network expansion. A compromise between the congestion cost and the investment cost is used to determine the optimal expansion scheme. The long-term network expansion problem is formed as the decoupled combination of: 1)the master problem (minimization of investment costs subject to investment constraints and the Benders cuts generated by the operational problem (power pool) and 2) the operational problem, whose solution provides congestion details and associated multipliers A proper power-pool model is developed and solved for congestion cost, congestion revenue, and transmission shadow prices. Linear programming is utilized to solve the investment subproblem, while the quadratic programming technique has been used to Solve the operational problem. The algorithm has been developed for the complete planning process, which provides the expansion schemes for the planning horizon. The technique has been applied to Illustrate the network planning study for a modified IEEE 24-bus test System. [ABSTRACT FROM AUTHOR]

Ramp rates of generators are. generally specified within elastic range of the strength of the shaft to safeguard the rotor from fatigue. These limits can, however, be exceeded, albeit at the risk of reducing the rotor life. Such effects on the rotor life can be compensated by incorporating appropriate ramping costs. Power demand and power price in deregulated power markets have shown a tendency of sudden wide excursions over short intervals of time. The ability to respond to such fast change in demand and price can be quite rewarding. This provides the motivation to utilize the ramping rates beyond traditional elastic limits. This paper studies the strategic use of ramping rates beyond elastic limits in a power producer's self-dispatch in a power market with price and demand volatility A set of ramping processes has been developed. from ramping-cost versus ramping time relationships to derive the total operation cost including ramping costs for various levels of ramping rates exceeding elastic limits. A thorough theoretical analysis has been conducted for the selection of the optimal ramping process under different conditions. A numerical example is presented to highlight the potential benefits from the optimal use of these ramping processes. It is seen that the benefit from the strategic use of lamp rates beyond elastic limits not only depends on the high price in the power market hut also on the initial loading of the generator which limits the capacity available for dispatch. [ABSTRACT FROM AUTHOR]

Presents a study on strategic bidding using the operational parameter, minimum output, submitted by power suppliers in a deregulated environment. Features of the power market environment; Effect of minimum outputs of on the market; Optimal strategic bidding; Numerical example; Conclusion.

A linear optimal controller is designed to implement Variable Series Compensation (VSC) in transmission network of interconnected power systems. The proposed controller is used to dampen inter-area oscillations and enhance power system stability. The effectiveness of the linear optimal controller to properly control such a variable series reactance is demonstrated through mode shapes and digital simulation studies on a two-machine system. The digital simulation studies are conducted using a PSCAD/EMTDC software package. The mode shapes and simulation results show that the controller contributes significantly to the damping of inter-area oscillations and the power stability enhancement. [ABSTRACT FROM AUTHOR]

Context: Most of the world's refugees are displaced within the developing world. The impact of torture on such refugees is unknown.Objective: To examine the impact of torture on Bhutanese refugees in Nepal.Design: Case-control survey. Interviews were conducted by local physicians and included demographics, questions related to the torture experienced, a checklist of 40 medical complaints, and measures of posttraumatic stress disorder (PTSD), anxiety, and depression.Setting: Bhutanese refugee community in the United Nations refugee camps in the Terai in eastern Nepal.Participants: A random sample of 526 tortured refugees and a control group of 526 nontortured refugees matched for age and sex.Main Outcome Measures: The Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition (DSM-III-R) criteria for PTSD and the Hopkins Symptom Checklist-25 (HSCL-25) for depression and anxiety.Results: The 2 groups were similar on most demographic variables. The tortured refugees, as a group, suffered more on 15 of 17 DSM-III-RPTSD symptoms (P<.005) and had higher HSCL-25 anxiety and depression scores (P<.001) than nontortured refugees. Logistic regression analysis showed that history of torture predicted PTSD symptoms (odds ratio [OR], 4.6; 95% confidence interval [CI], 2.7-8.0), depression symptoms (OR, 1.9; 95% CI, 1.4-2.6), and anxiety symptoms (OR, 1.5; 95% CI, 1.1-1.9). Torture survivors who were Buddhist were less likely to be depressed (OR, 0.5; 95% CI, 0.3-0.9) or anxious (OR, 0.7; 95% CI, 0.4-1.0). Those who were male were less likely to experience anxiety (OR, 0.66; 95% CI, 0.44-1.00). Tortured refugees also presented more musculoskeletal system- and respiratory system-related complaints (P<.001 for both).Conclusion: Torture plays a significant role in the development of PTSD, depression, and anxiety symptoms among refugees from Bhutan living in the developing world. [ABSTRACT FROM AUTHOR]

Describes the main features of four design modules that form part of the curriculum for the final year power engineering students at the Nanyang Technological University, Singapore. Generating capacity expansion planning; Rectifier and dc motor control; Power system operations planning; Security enhancement using optimal power flow.

Background: Malignant melanoma of uveal tract is a rare ocular malignancy. It is one of the significant causes of ocular morbidity and mortality which is less commonly seen in children., Case: We report an unusual case of orbital recurrence of malignant melanoma in a 14-year old boy who had previously undergone enucleation of the left painful blind eye 8 months ago. He was diagnosed to have uveal malignant melanoma elsewhere which was confirmed by histopathology. Orbital recurrence was managed with modified exenteration with adjuvant chemotherapy and radiotherapy., Conclusion: In all treated cases of uveal melanoma, close follow up examination and monitoring is necessary for early diagnosis of the recurrence and to plan for further management., (© NEPjOPH.)

Introduction: Lamellar Ichthyosis is an autosomal recessive, inherited skin disorder characterized by thickening, fissuring and scaling of the skin., Objective: To report a case of lamellar icthyosis and highlight the importance of monitoring corneal health in these patients., Case: We report a rare case of bilateral spontaneous corneal perforation in a patient with lamellar ichthyosis .The patient presented with complaints of diminution of vision, foreign body sensation, watering and discharge in both of his eyes for the last three months followed by pain and redness for one week. Visual acuities were light perception in both the eyes. Cicatricial ectropion was seen in both the lower eyelids. Corneal perforation was seen in both the eyes. Lamellar ichthyosis was diagnosed on the basis of scaling and excessive dryness of the entire body skin and was confirmed by skin biopsy. Peneterating keratoplasty of both eyes was done with cataract surgery of the right. The systemic anti-ichthyosis therapy was started. Ectropion of the right eye was corrected, and on follow-up at three months, the patient had a visual acuity of 4 /60 and CFCF in the right and the left eye respectively., Conclusion: In patients with cicatricial ectropion and dry eye secondary to ichthyosis, corneal health should be closely monitored because of the perforation risk., (© NEPjOPH.)

Background: Ocular complications of herpes zoster ophthalmicus (HZO) may lead to substantial visual disability, severe post-herpetic neuralgia and rarely fatal cerebral complications., Aim: To identify the pattern of ocular manifestation in herpes zoster ophthalmicus., Materials and Methods: A cross-sectional descriptive study was under taken including the clinically diagnosed cases of HZO. All of them underwent a complete ophthalmological evaluation., Results: Sixty-eight cases of HZO were examined, of which 37 (54.4 %) were male and 31 (45.6%) female. The mean age was 48.7 ± 18.5 years. Most of the patients (64.7 %) were above the age of 40 years. 77.94 % of the patients had some form of ocular involvement. Pain (77.9 %) was the commonest ocular complaint. In young patients less than 35 years, HIV was the most common risk factor (19.3 %).Visual status was good in the majority (73.5 %) of patients at presentation. Lid and adnexal findings (45.8 %) were most common ocular involvement followed by conjunctivitis (41.1 %). Corneal complication was seen in 38.2 % of cases, uveitis in 19.1 % and post-herpetic neuralgia (PHN) and secondary glaucoma each in 5.8 %., Conclusion: Eyelid and ocular adnexal involvement is most commonly found in patients with herpes zoster ophthalmicus followed by corneal complication and uveitis. There needs to be awareness of ocular involvement, which can be sight threatening, among the HZO patients and other medical departments and an increased emphasis on regular ophthalmic examination., (© NEPjOPH.)

Introduction: Patients of breast diseases of female are very common cases attending surgical out patient department for treatment at NGMC, Banke, Nepal., Objectives: To find out the magnitude of the breast diseases, its frequency distribution in different age group among the patients attending surgical OPD for surgical consultation., Material and Method: This is a prospective study conducted at NGMC, Nepalgunj, Nepal. Patients attending surgical OPD for one or another breast problem were included. They were assessed clinically and their diagnosis was confirmed by cytological (FNAC) or histopathological (biopsy) examination. Then they were subjected to appropriate treatment. It must be mentioned at the outset that no clinical mammography could be done in the case of this study as these facilities are not available at NGMC., Results: 264 cases of breast disease were diagnosed. This includes 232 female and 32 male patients. The ratio between benign and malignant lesions was 13.6:1. The benign breast diseases (BBD) were the commonest lesions of the breast found in this study (93.2%) whereas malignant lesion was infrequent (6.8%). Among BBD, the commonest lesion was fibroadenoma (32.57%) followed by breast abscess (24.19%), Aberration of Normal Development and Involution (ANDI) which was 16.63% and gynecomastia (11.34%). 18 cases (6.80%) were of malignant lesion. This includes 16 female and 2 male cases. The common ages for BBD were, 20-40 years for fibroadenoma, 15-40 years for breast abscess, 18-40 years for ANDI and 10-19, 50-59 for gynecomastia respectively, whereas carcinoma breast was common in the age group of forties and fifties., Conclusion: We conclude from this study that BBD were the most frequent breast lesion. Among the BBD fibroadenoma was the commonest lesion. Breast carcinoma cases were less frequent and reached to the hospital in very late stage of the disease.