Laboratory batch experiments of the combined effects of ultrasound and air stripping in removing CCl4 and 1,1,1-TCA from water

Ultrasonic and air-stripping techniques for removal of carbon tetrachloride (CCl₄) and 1,1,1-trichloroethane (1,1,1-TCA) from water were studied in batch experiments. Ultrasound (US) is effective for destroying organic compounds in aqueous solutions whereas air stripping (AS) efficiently transfers volatile compounds from the liquid to the gas phase. In simultaneous US and AS experiments, synergistic effects were observed and attributed to the effect of US on the mass transfer process. Using a photographic method, ultrasonic break up of gas bubbles and changes in gas holdup ratios were examined. In the two different gas-sparging systems studied, ultrasonic waves did not break up gas bubbles. In contrast, bubbles from the smaller porous size diffuser were coalesced due to sonication. In addition, both photographic and gas holdup experiments demonstrated that ultrasonic irradiation increased the gas holdup ratio. The enhancement observed in the removal of the compounds appeared to be due to this greater ultrasonic gas holdup ratio.     

An analysis of value function learning with piecewise linear control

Reinforcement learning (RL) algorithms attempt to learn optimal control actions by iteratively estimating a long-term measure of system performance, the so-called value function. For example, RL algorithms have been applied to walking robots to examine the connection between robot motion and the brain, which is known as embodied cognition. In this paper, RL algorithms are analysed using an exemplar test problem. A closed form solution for the value function is calculated and this is represented in terms of a set of basis functions and parameters, which is used to investigate parameter convergence. The value function expression is shown to have a polynomial form where the polynomial terms depend on the plant's parameters and the value function's discount factor. It is shown that the temporal difference error introduces a null space for the differenced higher order basis associated with the effects of controller switching (saturated to linear control or terminating an experiment) apart from the time of the switch. This leads to slow convergence in the relevant subspace. It is also shown that badly conditioned learning problems can occur, and this is a function of the value function discount factor and the controller switching points. Finally, a comparison is performed between the residual gradient and TD(0) learning algorithms, and it is shown that the former has a faster rate of convergence for this test problem.     

Is unilateral breast enlargement always a sign of cancer?

Breast swelling is caused by many etiological factors, but should alert central vein occlusion in hemodialysis patients when the permanent vascular access is in the same arm. The swelling of the breast is caused by venous hypertension in the venous plexus draining the breast. Endovascular treatment relieves venous hypertension and related clinical signs. Additional diagnostic workup or invasive interventions such as a biopsy should be avoided in such patients, as diagnosis is straightforward with the presence of a functioning arteriovenous fistula in the same arm.     

Second law analysis of wind turbine power plants: Cesme, Izmir example

In this study, the energy and exergy efficiency results of the Wind Turbine Power Plants (WTPPs) are presented. Exergy, energy and technical availability analysis are performed. The case study includes the actual system data taken from the system in Cesme, Izmir WTPP. General energy, exergy and other performance parameters are also presented. Investigated WTPP is Turkey’s first installed (1998) wind plant (1.50 MW) located in Izmir. Exergy efficiency of the power plant found to be between 0% and 68.20%. The monthly average technical availabilities are 96.11%, 98.71%, 98.52% for turbine 1, turbine 2, and turbine 3, respectively. Furthermore, authors developed some correlations, which are capable of predicting the values of exergy efficiencies of the WTPP for different power factor value.     

The influence of ventilation variables on the volume rate of airflow delivered to the face of long drivages

Auxiliary ventilation is performed by carrying intake or return air in ducts. The complete elimination of air leakage from or into the ducting system is impossible due to duct quality and numerous joints in ducting system. The auxiliary ventilation systems for long drivages often require the use of multiple fans. Fans are installed in series and separated from each other in fixed or variable lengths. There are many methods proposed for the analysis air flow problems in leaky ducts. Due to the lengthy calculations, computers are often needed to conduct the analyses. In this study, a method known as “series–parallel combination of the duct and leakage path” has been introduced and a computer program has been developed based on this method.In order to design the conditions of an auxiliary ventilated drivage, in situ measurement have been made in Western Lignite Enterprises (GLI) OMERLER underground coal mine (Turkey) and the related data necessary for this study was collected. The presently developed program was tested using these data, and it was found that the measured and calculated values are quite close.The effective operational parameters governing auxiliary ventilation have been investigated and the effects of these variables on the volume rate of air flow reaching long drivage face have been examined by using linear regression analysis. Finally, it was concluded that the increase of duct diameter has prime importance in achieving the adequate air flow to the face and that for the auxiliary fans considered in this study the selection of fan does not greatly affect the volume rate reaching the face in a long duct line.     

A parametrical study on the energetic and exergetic assessment of a solar-assisted vertical ground-source heat pump system used for heating a greenhouse

An energetic and exergetic modeling of a solar-assisted vertical ground-source heat pump (GSHP) greenhouse heating system (SAGSHPGHS) for system analysis and performance assessment is presented in this study. Energy (heating coefficient of performance ‘COP’) and exergy efficiencies at various reference and entering water temperatures are also determined. The actual thermal data collected are utilized for the model calculations at different reference temperature values in the range of −0.69 to 25 °C. Furthermore, the performance of a SAGSHPGHS, installed in Solar Energy Institute of Ege University, Izmir, Turkey, is evaluated to show, how energy and exergy efficiencies values change with system. The exergy destructions in the overall SAGSHPGHS are quantified, particularly for a reference temperature of −0.69 °C on 7 January 2004 for comparison purposes. Based upon the measurements made in the heating mode from the 16th of December 2003 till 31st of March 2004, average heating COPs of the GSHP unit and the overall system are obtained to be 2.84 and 2.27, respectively. The best (peak) COP of the GSHP and system were found to be 3.14 and 2.79 on 7 January 2004, respectively. Average exergy efficiency of the system is determined to be 68.11%, while the best exergy efficiency peak values for the GSHP unit and the whole system on a product/fuel basis are obtained to be 76.2% and 75.6%, respectively.     

Modeling and performance evaluation of ground source (geothermal) heat pump systems

This study deals with the energetic and exergetic modeling of ground source heat pump (GSHP) systems for the system analysis and performance assessment. The analysis covers two various GSHPs, namely a solar assisted vertical GSHP and horizontal GSHP. The performances of both GSHP systems are evaluated using energy and exergy analysis method based on the experimental data. Energy and exergy specifications are also presented in tables. Some thermodynamic parameters, such as fuel depletion ratio, relative irreversibility, productivity lack and exergetic factor, are investigated for both systems. The results obtained are discussed in terms of energetic and exergetic aspects. The values for COP_HP ranged from 3.12 to 3.64, while those for COP_sys varied between 2.72 and 3.43. The exergy efficiency peak values for both whole systems on a product/fuel basis were in the range of 80.7% and 86.13%. It is expected that the model presented here would be beneficial to everyone dealing with the design, simulation and testing of GSHP systems.     

Methods of Measuring Bruise Volume of Pear (Pyrus Communis L.)

The grade of injures can be determined or measured by bruise volume using a sectioning and imaging analysis technique and different methods for calculating the size of pear bruises. The calculation methods were not consistent, with large calculation errors at small bruise sizes. The calculation of bruise volume was improved when the surface shape of the bruise was an ellipse instead of a circle. In this study, various methods are recommended for the calculation of the bruise volume depending on the range of the bruise sizes being investigated.