Purpose  A robotic intraoperative laser guidance system with hybrid optic-magnetic tracking for skull base surgery is presented. It provides in situ augmented reality guidance for microscopic interventions at the lateral skull base with minimal mental and workload overhead on surgeons working without a monitor and dedicated pointing tools. Methods  Three components were developed: a registration tool (Rhinospider), a hybrid magneto-optic-tracked robotic feedback control scheme and a modified robotic end-effector. Rhinospider optimizes registration of patient and preoperative CT data by excluding user errors in fiducial localization with magnetic tracking. The hybrid controller uses an integrated microscope HD camera for robotic control with a guidance beam shining on a dual plate setup avoiding magnetic field distortions. A robotic needle insertion platform (iSYS Medizintechnik GmbH, Austria) was modified to position a laser beam with high precision in a surgical scene compatible to microscopic surgery. Results  System accuracy was evaluated quantitatively at various target positions on a phantom. The accuracy found is 1.2 mm ± 0.5 mm. Errors are primarily due to magnetic tracking. This application accuracy seems suitable for most surgical procedures in the lateral skull base. The system was evaluated quantitatively during a mastoidectomy of an anatomic head specimen and was judged useful by the surgeon. Conclusion  A hybrid robotic laser guidance system with direct visual feedback is proposed for navigated drilling and intraoperative structure localization. The system provides visual cues directly on/in the patient anatomy, reducing the standard limitations of AR visualizations like depth perception. The custom- built end-effector for the iSYS robot is transparent to using surgical microscopes and compatible with magnetic tracking. The cadaver experiment showed that guidance was accurate and that the end-effector is unobtrusive. This laser guidance has potential to aid the surgeon in finding the optimal mastoidectomy trajectory in more difficult interventions.

The paper presents an advanced concept for a computer model of partial discharge (PD) in insulation. The advanced model concept is based on a well-known model, using condensers for modeling of electrical network and the cavity where discharge occurs. The fundamental advancement is the modeling of initial conditions of each discharge event by introducing a controlled voltage source and modeling its control, the modeling of parameters of PD current pulse, and advanced modeling of all circuit elements. The paper presents basic analysis of PD processes and the analysis of basic shortcomings of the well-known model. The elements of the advanced model are established, and the way to implement it. It is shown that commercial software packages for electric circuits analysis are indeed suitable for PD modeling. Physical and electrical parameters of PD pulse are established, as well as the response of observed object's electric network to the ensuing excitation. The results of the model show the possibility of modeling of PD current pulse in a wide range of parameters.

SUMMARY The paper deals with thermal modelling of transformers with automatic control of the cooling system. The case study was done on 725 MVA transformer with OFAF cooling, having eight compact coolers, each of them with their own pump and hysteresis control: four coolers, when top oil temperature drops below 30 °C, and six coolers, when top oil temperature rises above 45 °C. The consequence of operation with different number of coolers is change of thermal characteristics of the transformer. Additional phenomenon causing change of thermal characteristics is fouling of the coolers. These variable thermal characteristics are included in mathematical models used for the calculation of top oil and hot‐spot temperatures in all applications of such calculation algorithms: protection, monitoring, estimation of overload capability, calculation of thermal ageing, etc. Copyright © 2012 John Wiley & Sons, Ltd.

Due to the large number of power transformers (ETs) in the distribution system, there is a need for a relatively simple representation of the status of each unit in order to more easily determine where and how to allocate the budget for preventive and corrective maintenance. In recent years, the concept of the transformer health index (HI) as an integral part of resource management was adopted for the condition assessment and ranking of ETs. HI algorithms take different forms and can be determined based on a large number of specific parameters. However, the main problem in HI methodology or any modern diagnostic technique is the existence of regular measurements and inspections and accurate test results. The paper proposes a solution in the form of the upgraded HI and the novel methodology for ET ranking including the value of available information to describe ET current state. The confidence to the measurement results is calculated using evidential reasoning (ER) algorithm based on Dempster–Shafer theory. The contribution to the ER methodology is the calculation of the initial degrees of belief using Markov chains. The aging process of an ET and transition probabilities from state to state are modelled using the statistical data for the population of 300 ETs and 20 years monitoring data. The proposed methodology is tested on the real data for 110/35 kV transformer, and in the second case, compared to the sample of 30 110/x kV transformers with traditional HI calculation.

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SUMMARYThe basic goal of this research was to evaluate sociocultural influence of parents on general body dissatisfaction among their adolescent children. The sample comprised (N = 228) of both male and female adolescents aged between 16-19 years. In this study, two measuring instruments were applied: Body image and body change inventory and the Perceived Sociocultural Influences on Body Image and Body Change Questionnaire. These instruments show internal consistency of high reliability, which makes them applicable to the Serbian population. According to results of the correlational analysis, there is a mild correlation between predictor variables (influence of mother and influence of father) and the criteria general body dissatisfaction. The applied hierarchical regression analysis showed that predictor variables explain 22% of the total variance of general body dissatisfaction. It was also established that variables (female gender, sociocultural influence of parents on body image and change in physical appearance) present significant predictors of overall body dissatisfaction in late adolescence. The majority of the obtained findings is in accordance with results from previous studies, and should provide directions for predicting body image and perceptive sociocultural contributions on body image, as well as designing programs of prevention regarding body dissatisfaction in adolescents of both genders.

In this article, we investigate a two-hop relaying communication where all nodes are equipped with antenna arrays. We derive the multiple-input multiple-output (MIMO) processing matrices using the mean-squared-error cost function and assuming that each node uses only locally available channel state information estimates. Spatial processing at the base station and at the user terminals is same as in the case of a direct communication. The emphasis is on the design of the MIMO precoding matrix at the relay as it has to process the noise and the interference on the first and on the second hop at the same time. The resulting system performance is close to the performance of the system that jointly optimizes matrices at the source and at the relay. The proposed solution requires significantly less computational power and feedback overhead than the solutions proposed in the literature.

The aim of this research is to confirm differences in the anthropometric characteristics and motor abilities of schoolchildren aged 9 and 10 compared by sex and age. The sample comprised 341 schoolchildren, divided into two subgroups of third (172) and fourth (169) graders. The research is of a transversal character and includes the measurement of anthropometric characteristics and motor abilities by applying the Eurofit fitness testing battery. The results show a significant difference based on sex in terms of body mass (t = 2.148), and as for motor abilities, there is a difference in the Shuttle run test (t = -3.709). A statistically significant difference considering the age of the tested population was observed in height (t = -10.327) and body mass (Z = -5,991), while in terms of motor abilities there was a statistically significant difference in the values of all the tests: Hand tapping (t = 4.735), the Standing long jump (Z = -3,575), Shuttle run (t = 12,248), the Flexed arm hang (Z = -2,167), 406),. The research shows a higher statistically significant difference observed in body composition, but also in the motor area of the studied group in terms of age, and in relation to the statistically significant difference that was revealed by gender.