Robot-Assisted Image-Guided Interventions

Image guidance is a common methodology of minimally invasive procedures. Depending on the type of intervention, various imaging modalities are available. Common imaging modalities are computed tomography, magnetic resonance tomography, and ultrasound. Robotic systems have been developed to enable and improve the procedures using these imaging techniques. Spatial and technological constraints limit the development of versatile robotic systems. This paper offers a brief overview of the developments of robotic systems for image-guided interventions since 2015 and includes samples of our current research in this field

Robot-Assisted Image-Guided Interventions

Image guidance is a common methodology of minimally invasive procedures. Depending on the type of intervention, various imaging modalities are available. Common imaging modalities are computed tomography, magnetic resonance tomography, and ultrasound. Robotic systems have been developed to enable and improve the procedures using these imaging techniques. Spatial and technological constraints limit the development of versatile robotic systems. This paper offers a brief overview of the developments of robotic systems for image-guided interventions since 2015 and includes samples of our current research in this field

A Four-step Approach for Selecting a Genetically Diverse Group of Animals from Pedigree Data using the Example of Endangered Austrian Goat Breeds

A four-step approach using pedigree data to create genetically diverse groups of animals for genotyping from a limited pool of available samples was developed and applied to a data set comprising five endangered Austrian goat breeds. Animals were selected according to their raw gene contribution, number of offspring, average relatedness to the living population and relatedness to other selected animals. Not all criteria could be applied to the same degree to all breeds due to small number of available samples. Methods to cope with this circumstance are presented in the paper. Inbreeding coefficient was lower in the selection groups than in the total populations in all breeds. Genotype data derived from the selected animals will be used to analyse diversity parameters and compare with available data from other Alpine goat breeds

A Four-step Approach for Selecting a Genetically Diverse Group of Animals from Pedigree Data using the Example of Endangered Austrian Goat Breeds

A four-step approach using pedigree data to create genetically diverse groups of animals for genotyping from a limited pool of available samples was developed and applied to a data set comprising five endangered Austrian goat breeds. Animals were selected according to their raw gene contribution, number of offspring, average relatedness to the living population and relatedness to other selected animals. Not all criteria could be applied to the same degree to all breeds due to small number of available samples. Methods to cope with this circumstance are presented in the paper. Inbreeding coefficient was lower in the selection groups than in the total populations in all breeds. Genotype data derived from the selected animals will be used to analyse diversity parameters and compare with available data from other Alpine goat breeds

Numerical Simulation of the 3d Transient Temperature Evolution Inside a Domestic Single Zone Wine Storage Cabinet With Forced Air Circulation

This work is carried out in order to investigate the air flow and temperature stratification in the compartment of a single zone wine storage cabinet with forced ventilation for domestic use. The appliance used in this work has a total gross capacity of approximately 135 liters. A single zone wine cooler should achieve evenly distributed temperature for all bottles inside the appliance. To analyze the temperature distribution, a numerical simulation of the air flow and the temperature field can be very helpful. The numerical simulations are carried out applying commercial CFD (Computational Fluid Dynamic) software using the finite volume method. Therefore, the following assumptions are made: the evaporator is modelled by means of a time-varying but locally constant temperature obtained from measurements, the ambient temperature is constant. Concerning the air flow, turbulent conditions are considered. The energy equation is solved transiently and the flow field is calculated assuming steady-state conditions at specific points in time in order to reduce computing time. Furthermore, the air flow in the air channel behind the rear and the top wall of the compartment, where the fan and the freely suspended evaporator are located, is also simulated. The compartment is investigated for different configurations: firstly, an empty wine cooler only with wooden grid shelves and secondly, an appliance loaded with test packages. Temperature measurements with several thermocouples inside the compartment and the air channel are carried out for each arrangement to verify the results of the numerical simulations

A Numerical Investigation of the Oil Pump Suction Behaviour in a Hermetic Reciprocating Compressor

In addition to the adequate lubrication of the moving parts, the oil flow in a hermetic reciprocating compressor has a significant influence on the thermal characteristics of a compressor. The present work is concerned with the investigation of the oil pump system of a reciprocating hermetic compressor used in household refrigeration appliances. The considered oil pump system consists of a centrifugal pump immersed in the oil sump of the hermetic compressor and a helical groove machined on the crankshaft. The focus of this work lies on the immersed part of the centrifugal oil pump and its interaction with the oil in the oil sump. To analyse the flow in the immersed area of the oil pump, the commercial computational fluid dynamics (CFD) software ANSYS Fluent is used. The free surface of the oil flow is modelled with the volume of fluid (VOF) method. A numerical investigation is used to study the influence of the immersion depth and the oil pump design on oil mass flow rate and flow field at the oil pump intake. To evaluate the oil pump regarding the applicability in variable speed compressors, the influence of the rotational speed on the oil mass flow is also explored

A Numerical Friction Loss Analysis of the Journal Bearings in a Hermetic Reciprocating Compressor

In addition to the electrical and the thermodynamic losses in hermetic compressors, mechanical losses have a significant influence on the performance of the compressor. In the present paper the friction losses in the journal bearings of a hermetic reciprocating compressor are investigated using numerical methods. A dynamic model is set up to solve the Reynolds equation using a finite volume approach to calculate the pressure field in each journal bearing. The calculation of the fluid film thickness is accomplished with the formulas of the parallel gap. The resulting hydrodynamic forces are equated with forces obtained by a dynamic multibody model of the compressor crank drive to calculate the transient orbit movement of the bearing. Based on the movement of the crankshaft at steady-state conditions, the shear stresses in the gap between crankshaft and housing can be calculated. Thus the cycle averaged friction power loss can be determined. To consider effect such as surface roughness of the bearings or possible contacts between the solids, correlations found in the literature are implemented. The present method is used to assess the friction power loss of the journal bearings during the operation with different oil viscosities. The simulated data is verified with simple analytical friction loss calculations based on shear stresses in the Couette flow between bearing and housing

Experimental Study on the Thermal Behavior of a Domestic Refrigeration Compressor during Transient Operation in a Small Capacity Cooling System

Generally, domestic refrigerators and freezers are running in non-continuous operation mode most of the time, which is a necessity to match cooling capacity to thermal loads. In currently available domestic appliances it can be observed, that this matching is mainly realized in two different ways: On the one hand, a simple on/off control of the hermetic compressor is installed in lower priced appliances with limited energy efficiency for the mass market. On the other hand, modern top efficiency class appliances have a variable frequency controlled compressor installed. Both control strategies have a repetitive and transient change of thermodynamic states of the refrigerant in common. For better understanding of these cyclic patterns in terms of internal temperature distribution, a state of the art domestic refrigeration compressor with a displacement of approximately 6 cubic centimeters is integrated in a commercial freezer. The compressor which has an on/off control is equipped with extensive measurement instrumentation. Several temperature probes are inserted and temperatures on surfaces inside and outside the compressor as well as refrigerant temperatures are logged for both cyclic and steady state behavior. Finally, a comparison between transient experimental data and steady-state data from a standardized calorimeter test bench is done

Thermal Analysis of a Hermetic Reciprocating Compressor Using Numerical Methods

Comprehensive knowledge about the heat transfer mechanisms and the temperature field inside hermetic compressors is very important for the thermal management and thus their performance. A numerical model to predict the temperature field in a hermetic reciprocating compressor for household refrigeration appliances is presented in this work. The model combines a high resolution three-dimensional heat conduction formulation of the compressor’s solid parts, a three-dimensional computational fluid dynamics (CFD) approach for the gas line domain and lumped formulations of the shell gas and the lubrication oil. Heat transfer coefficients are determined by applying CFD to the gas line side and correlations from the literature on the shell gas and oil side, respectively. The valve in the gas line simulation is modelled as a parallel moving flat plate. By means of an iterative loop the temperature field of the solid parts acts as boundary condition for the CFD calculation of the gas line which returns a cycle averaged quantity of heat to the solid parts. Using an iteration method which is based on the temperature deviation between two iteration steps, the total number of iterations and consequently the computational time can be reduced. The loop is continued until a steady-state temperature field is obtained. Calculated temperatures of the solid parts are verified against temperature measurements of a calorimeter test bench. The numerical results show reasonable agreement with the measured data

Calibration Strategies And Limitations Of Cycle Simulations Representing Complex Domestic Cooling Devices

Transient cycle simulations are commonly said to be a tool for improving and understanding the operating behavior of cooling cycles. Assuming a properly working simulation tool, simple cycle configurations which are driven by On/Off-controlled compressors can meanwhile be modelled with relatively high effort. Given the growing complexity of today\u27s modern refrigeration appliances – in particular cooling/freezing combinations – it is getting more and more challenging to represent these in a satisfactory manner. Fans for ventilation, variable speed drives and switchable capillary tubes are in interaction and follow a sensor-controlled, prescribed logic. The focus of this paper lies on the simulation of a particular real world appliance, which features all before-mentioned actuators. The simulation tool comprises component models beyond state of the art which have been validated both independently and in a simple cycle configuration. The attempt of modelling the cooling/freezing combination leads to new knowledge concerning the approach of calibrating the model. Measurement data (temperature, pressure, electric power, state variables) is available and used as reference. It can be shown, that it is possible to shape the model to follow the order of switching commands of the real appliance. Effects like heat conduction from walls to the sensors, delay caused by the thermal inertia of the sensors or temperature stratification pose the main obstacle on the way to obtain a comparable energy consumption