Multiple and quantitative measurements using computed tomography images reveal the factors associated with chronic subdural hematoma recurrence

Objective: The aim of this retrospective single–center study was to quantitatively assess chronic subdural hematomas (CSDHs), reveal the correlations between multiple and quantitative values calculated from computed tomography images, and determine the risk factors for CSDH recurrence. Methods: We enrolled 225 patients who underwent 304 burr-hole surgeries between April 2005 and October 2021 at Otemae Hospital. Patients′ medical records and quantitative values including preoperative CSDH volume (ml), thickness (mm), computed tomography values (CTV), postoperative CSDH volume (ml), and air volume (ml) were evaluated. The locations of CSDH thickness and burr holes were also assessed quantitatively using Montreal Neurological Institute coordinates. Univariate and multivariate regression analyses and receiver operating characteristic (ROC) analyses were performed. Results: Thirty–seven patients (12%) showed CSDH recurrence requiring reoperation. Preoperative CSDH volume was positively correlated with age, preoperative CSDH thickness, CTV, postoperative CSDH volume, and air volume. Univariate Cox proportional hazards regression analysis showed that age, preoperative CSDH volume, Glasgow Coma Scale score (3–14), postoperative hemiplegia, and gait disturbance were risk factors for recurrence requiring reoperation, and a higher CTV (hazard ratio 0.95, 95% confidence interval 0.91–0.99) was associated with a lower risk of recurrence requiring reoperation. Only preoperative CSDH volume was a significant risk factor for recurrence requiring reoperation in multivariate regression analyses. The postoperative air volume and locations of CSDH thickness and burr hole had no influence on recurrence requiring reoperation. ROC curve analysis revealed that the optimal preoperative CSDH volume cut-off value as a predictor was 155 ml, the thickness was approximately 36.3 mm calculated from a regression line. Conclusions: A larger and more hypodense CSDH has a high risk of recurrence requiring reoperation. Residual air volume after surgery and locations of CSDH and burr hole had no influence on recurrence requiring reoperation.

Direct-Contact Air, Gravel, Ground Heat Exchanger in Air Treatment Systems for Cowshed Air Conditioning

This paper describes the analysis of the possibility of use of the direct-contact air, gravel, ground heat exchanger (acronym GAHE), patented at the Wroclaw University of Science and Technology, as a means of improving microclimate parameters in dairy cows’ barns. Different possibilities of introducing GAHE to the standard mechanical ventilation system of cowsheds have been proposed and investigated. Based on literature data, the required air parameters in the barns of dairy cows were determined and discussed. Computer simulations were carried out and the results obtained were compared to the baseline model. Year-round changes in microclimate parameters, especially air temperature, relative humidity, and THI index were investigated. The benefits of GAHE use were indicated. The possible increase in the minimum air volume of ventilation during the winter season and the decrease in the maximum values of this parameter in the summer were presented. Indications were made of the systems where the application of GAHE could be the most beneficial. A further research path has been proposed.

Atmospheric Pressure Change Measurement: An Observational Study

Introduction: The aim of the study was to show an atmospheric pressure change by indirect measurement in hermetically closed vessels during four years of follow-up.Methods: Study design: an observational study. In hermetically sealed elastic bottles with different liquids were measured differences in liquid and air volumes from baseline to final follow-up period. The physical law of flotation was used to measure liquid and air volume above liquid in bottles. To measure liquid and air (above liquid) volumes in each bottle was used the physical law of buoyancy. The follow-up period was four years.Results: The volumes of liquid and air in all bottles were decreased after the follow-up period to 14.38±2.40 and 36.25±3.37 ml, respectively. Air volume in comparison to liquid volume decreased more than two times significantly (P=0.0007) after the follow-up period.Conclusions: Thus, atmospheric pressure increased during the last 4-year follow-up period. Further investigations are needed.

Optimal Control Method of Variable Air Volume Terminal Unit System

This study reviewed the existing studies on the types of variable air volume (VAV) terminal units, control and operation methods, prediction models, and sensor calibration methods. As a result of analyzing the existing research trends on the system type, characteristics, and control method of VAV terminal units studies such as theoretical verification and energy simulation were conducted to improve the existing control methods, reset the set value using a mathematical model, and add a monitoring sensor for the application of control methods. The mathematical model used in the study of VAV terminal unit control methods was used to derive set values for minimum air volume, supply temperature, ventilation requirements, and indoor comfort. The mathematical model has a limitation in collecting input information for professional knowledge and model development, and development of a building environment prediction model using a black box model is being studied. The VAV terminal unit system uses a sensor to control the device, and when an error occurs in the sensor, indoor comfort problems and energy waste occur. To solve this problem, sensor calibration techniques have been developed using statistical models, mathematical models, and Bayesian statistical models. The possibility of developing a method for calibrating the variable air volume terminal unit sensor using the prediction model was confirmed. In conclusion, the VAV terminal unit system is one of the most energy efficient systems. The energy saving potential of current VAV systems can still be improved through control methods, the use of predictive models, and sensor calibration methods.

A review of common human errors in design, installation, and operation of multiple-zone VAV AHU systems

Faults in air-based heating, ventilation, and air conditioning (HVAC) systems lead to energy waste and discomfort. While the emphasis of fault detection and diagnostic (FDD) research has been on hard faults in actuators, sensors, and equipment, faults arising from human errors account for a significant portion of faults occurring in HVAC systems. In this paper, human errors occurring in air handling units (AHUs) and variable air volume (VAV) thermal zones during design, construction, and operation phases are identified through a review of the literature. Then, the faults are divided into six main categories. Based on case studies investigating these faults, the impact of each fault category on occupant comfort, energy consumption, and equipment life is discussed. The authors provide recommendations to minimize human errors in AHUs and VAV zones throughout the building life cycle.

Preliminary symptoms assessment of typical faults related to the fans and humidifiers of HVAC systems based on experimental data collected during Italian summer and winter

The symptoms associated to the occurrence of typical faults in a heating, ventilation and air-conditioning (HVAC) system, including a single duct dual fan constant air volume air-handling unit, have been experimentally characterized. The operation of the HVAC unit with 3 artificially forced faults ((1) reduced velocity of the supply air fan, (2) reduced velocity of the return air fan, (3) the valve supplying the humidifier kept always closed) has been analysed and compared with that of healthy operation of the same plant under very similar boundary conditions (outside air temperature and initial indoor air temperature) during Italian summer and winter in order to preliminarily assess (i) the effects on the main operating parameters, and (ii) generate preliminary operation data to assist further research in fault detection and diagnosis of HVAC systems.