Concentrations of natural radionuclides in imported zirconium minerals

The natural radioactivity in imported zircon samples used as glaze for ceramic tiles in the ceramics industry has been presented in this paper. The measurements were made by gamma spectrometry with a high purity germanium detector. The average activity concentrations of 238U and 232Th determined in the measured samples (3250 Bq/kg, and 556 Bq/kg, respectively) are much higher than the concentrations found in the Earth’s crust. The activity concentration of 226Ra is also high in all analyzed samples, while 40K was not detected. The gamma index, I, the external hazard index, Hex, the internal hazard index, Hin, and the radium equivalent activity, Raeq, were calculated. Due to relatively high activity concentration level of uranium in imported zircon samples, specific regulations are necessary for zircon compound used in ceramic industry. It can be concluded that the investigated samples can be used as the component of ceramic glaze in the concentrations not above 3%

Analytical and experimental determination of the temperature field on the surface of wall heating panels

This paper presents experimental verification of the accuracy and acceptability of Faxen-Rydberg-Huber analytical expression for determining thermal characteristics of the heating panels. The verification of accuracy of the Faxen-Rydberg-Huber expression, which describes the 2-D temperature field in the wall with series of embedded heated pipes having uniform temperature, was performed by comparing the temperatures on the surface of three types of heating wall panels, differing in structure and geometric characteristics. The analysis of results has shown high accuracy of Faxen-Rydberg-Huber expression in describing the temperature field. Also, it was noted that small changes in heating fluid temperature, occurring along the pipe in the heated panel, have a negligible influence on the accuracy of prediction by the expression. This confirmed that the Faxen-Rydberg-Huber expression can be used to describe the temperature field in the wall heating panels. At the same time, this expression has proven to be extremely sensitive primarily to thermophysical characteristics of the panel layers, as well as to the geometric parameters of the panels

Indoor environmental quality in non-residential buildings - experimental investigation

This paper presents the part of the research that has been done at the Universities both in Belgrade and Thessaloniki, Greece, taking into account indoor environmental quality in office buildings and classrooms. The measurements that are presented were done in Process Equipment Design Laboratory at Aristotle University Thessaloniki, during March 2015. Indoor environmental quality regarding air temperature, relative humidity, and CO2 concentration in two representative offices is observed. The similar offices are located one on the north-east and the other one on the south-west side of the University building, so as to be representative of the orientation's impact. Furthermore, the impact of natural ventilation on CO2 concentration and temperature is monitored, together with the offices' occupancy. Recommended parameters for indoor air quality are compared and discussed on the base of several standards: SRPS EN 15251:2010, ASHRAE standards 55 and 62.1, and ISO 7730. The main objectives, as set from these standards are discussed, together with the investigation results

Indoor environmental quality in non-residential buildings - experimental investigation

This paper presents the part of the research that has been done at the Universities both in Belgrade and Thessaloniki, Greece, taking into account indoor environmental quality in office buildings and classrooms. The measurements that are presented were done in Process Equipment Design Laboratory at Aristotle University Thessaloniki, during March 2015. Indoor environmental quality regarding air temperature, relative humidity, and CO2 concentration in two representative offices is observed. The similar offices are located one on the north-east and the other one on the south-west side of the University building, so as to be representative of the orientation's impact. Furthermore, the impact of natural ventilation on CO2 concentration and temperature is monitored, together with the offices' occupancy. Recommended parameters for indoor air quality are compared and discussed on the base of several standards: SRPS EN 15251:2010, ASHRAE standards 55 and 62.1, and ISO 7730. The main objectives, as set from these standards are discussed, together with the investigation results

Analytical and experimental determination of the temperature field on the surface of wall heating panels

This paper presents experimental verification of the accuracy and acceptability of Faxen-Rydberg-Huber analytical expression for determining thermal characteristics of the heating panels. The verification of accuracy of the Faxen-Rydberg-Huber expression, which describes the 2-D temperature field in the wall with series of embedded heated pipes having uniform temperature, was performed by comparing the temperatures on the surface of three types of heating wall panels, differing in structure and geometric characteristics. The analysis of results has shown high accuracy of Faxen-Rydberg-Huber expression in describing the temperature field. Also, it was noted that small changes in heating fluid temperature, occurring along the pipe in the heated panel, have a negligible influence on the accuracy of prediction by the expression. This confirmed that the Faxen-Rydberg-Huber expression can be used to describe the temperature field in the wall heating panels. At the same time, this expression has proven to be extremely sensitive primarily to thermophysical characteristics of the panel layers, as well as to the geometric parameters of the panels

Possibilities of reconstruction and implant-prosthetic rehabilitation following mandible resection

Introduction. Mandible reconstruction is still very challenging for surgeons. Mandible defects could be the consequence of ablative surgery for malignancies, huge jaw cysts, infection and trauma. Segmental resection of the mandible may compromise orofacial function and often lead to patients psychological disorders. Despite very frequent use of microvascular flaps, autogenous bone grafts are still very reliable technique for mandible reconstruction. Comprehensive therapy means not only mandible reconstruction, but prosthodontic rehabilitation supported by dental implants, which can significantly improve patients quality of life. The aim of this paper was to evaluate possible techniques of mandible reconstruction and to present a patient who had been submitted to mandible resection and reconstruction with autogenous iliac bone graft and prosthodontic rehabilitation with fixed denture anchoraged by disc-shaped implants in early loading protocol. Case report. Mandible reconstruction was performed simultaneously with resection. Autogenous iliac bone graft was taken, reshaped and placed in two parts, to the required optimal contour of the mandible. After graft consolidation, decision was made for prosthodontics rehabilitation with fixed dentures supported by implants. In addition to the standard preoperative procedures, planning was done based on a biomodel gained by rapid prototyping after CT scan. It offered a real 3D planning to obtain a proper shape, dimension and the position of implants. Conclusion. If bone dimensions of a reconstructed mandible are insufficient, like in the presented case, the use of basal osseointegrated implants may be a method of choice. Avoiding bone augmentation procedures, as well as early loading protocol for this type of implants, shorten the total rehabilitation time, which is very convenient for patients. Fixed denture supported by dental implants is the best solution for comprehensive rehabilitation after mandible resection. [Projekat Ministarstva nauke Republike Srbije, br. 175075

The Exchange of Tritiated Water Between Zn-A Zeolitevand the Surrounding Water

Zeolites are considered as adsorbents for tritiated waste water. The sorption capacity of 4A zeolite is increased, and the speed of tritium release, as THO, decreased if sodium ions in 4A zeolite are replaced with small divalent cations. The exchange kinetics THO/H20 between Zn-A zeolite containing tritiated water and the surrounding water was investigated at 30-60 De, using zinc-exchanged 4A zeolite beads of 0.8 and 1.6 mm radius. The kinetics was controlled by the diffusion of water in the solid particle and interpreted in terrns of the Boyd - Reichenberg diffusion model. Effective self-diffusion coefficients of water in the zeolite beads were obtained and the kinetic data are discussed from the point of view of using zeolites as sorbents and storage material for tritiated waste water