Experimental and Numerical Analyses of Thermal Storage Tile-Bricks for Efficient Thermal Management of Buildings

Due to the tremendous increase in the population and emerging energy crisis, the surging demand for the thermal management of buildings has become essential. Thermal management of buildings is of high importance for maintaining optimum thermal comfort and controlling the drastic environmental impacts. To avoid high energy consumption strategies and continuous operation such as active air heaters and air conditioners, passive strategies driven by phase change material-based thermal storage are expected to leverage the energy challenges. This work attempts to present the form-stabilized thermal storage tile-bricks (TSTBs) that are fabricated by a combination of octadecane, phosphogypsum, kaolin clay and cement. The optimal percent contents of each entity were found with respect to the design criterion of form-stability and effective temperature control capacity. Two TSTBs with a thickness of 10 mm and 15 mm were constructed, which are then applied on ordinary clay bricks to build a prototype wall. The optimal TSTBs are experimentally and numerically evaluated by subjecting them to transient thermal performance analysis, providing longer temperature retardation (~3000 s) compared with ordinary clay bricks (~400 s). It is thus implied that TSTBs can provide a viable solution against energy mismanagement by inhibiting the heating in summer and reserving the cold in winter.

Specification and Evaluation of Plasticizer Migration Simulants for Human Blood Products: A Delphi Study

Potentially toxic plasticizers are commonly added to polyvinyl chloride medical devices for transfusion in order to improve their flexibility and workability. As the plasticizers are not chemically bonded to the PVC, they can be released into labile blood products (LBPs) during storage. Ideally, LBPs would be used in laboratory studies of plasticizer migration from the medical device. However, short supply (i.e., limited stocks of human blood in collection centres) has prompted the development of specific simulants for each type of LBP in the evaluation of new transfusion devices. We performed a Delphi study with a multidisciplinary panel of 24 experts. In the first (qualitative) phase, the panel developed consensus definitions of the specification criteria to be met by each migration simulant. Next, we reviewed the literature on techniques for simulating the migration of plasticizers into LBPs. A questionnaire was elaborated and sent out to the experts, and the replies were synthesized in order to obtain a consensus. The qualitative study established specifications for each biological matrix (whole blood, red blood cell concentrate, plasma, and platelet concentrate) and defined the criteria required for a suitable LBP simulant. Ten criteria were suggested: physical and chemical characteristics, opacity, form, stability, composition, ability to mimic a particular clinical situation, ease and safety of use, a simulant–plastic interaction correlated with blood, and compatibility with analytical methods. The questionnaire data revealed a consensus on the use of natural products (such as pig’s blood) to mimic the four LBPs. Opinions diverged with regard to synthetic products. However, an isotonic solution and a rheological property modifier were considered to be of value in the design of synthetic simulants. Consensus reached by the Delphi group could be used as a database for the development of simulants used to assess the migration of plasticizers from PVC bags into LBPs.

Physicochemical compatibility studies of triclosan and flurbiprofen with excipients of pharmaceutical formulation using binary, ternary, and multi-combination approach

Background The aim of the study was to evaluate the suitability of triclosan (TCS) and flurbiprofen (FLB) with poly-ε-caprolactone (PCL), chitosan (CS), and Kolliphor® P188 (KP) for possible application in the design of nano-formulations. Results Differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), and scanning electron microscopy (SEM) revealed the physical characteristics of the various sample compositions without any apparent interaction. The Fourier transform infrared spectroscopy (FTIR)’s spectra of the physical mixtures showed their characteristic absorption bands with broadening and overlapping of bands in some instances, but no appearance of new bands was observed. Conclusion The study revealed the physical form stability of the evaluated components after the storage period and lack of definite pharmaceutical incompatibility between them. Thus, the selected drugs and excipients could be used for the development of pharmaceutical nano-formulations.

Investigation of shape stability of semi-finished samples in the form of a ring made of plastic ceramic material based on SiC, obtained by injection molding

The concept of form stability is considered. A semifinished product in the form of a ring from a thermoplastic mass based on SiC powder has been made on the installation for injection molding developed at the Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine in accordance with the established technological parameters optimized by the results of computer modeling. Schemes of loading and dividing the ring into samples in the form of prismatic segments are presented. A technique for the preparation of experimental samples is proposed. The study of the compressive strength of the samples from the injected semi-finished product has been carried out on the FP-5 mechanical test machine and a corresponding здще of its change has been constructed. The formation of a barrel shape during compression tests of samples, both along the radial and tangential directions, has been established. The values of the minimum and maximum loads at which the samples are destroyed have been determined. An increase in the compaction of the thermoplastic mass around the injection point has been experimentally proved. The scheme and the actual image of crack distribution as a result of destruction of samples have been presented. It is shown that the failure occurs in the area of the presence of the calculated parting lines, which have become stress concentrators.

Stability Constraints on Practical Implementation of Parity-Time-Symmetric Electromagnetic Systems

Recently, several applications leveraging unconventional manipulation of electromagnetic radiation based on parity-time symmetry have been proposed in the literature. Typical examples include systems with unidirectional invisibility and asymmetric refraction. Such applications assume an inherent system stability and no occurrence of unbounded signal growth or unwanted self-oscillations. Here, a general instability issue of parity-time-symmetric systems is investigated, with particular emphasis on a recently proposed system based on resistive metasurfaces. Explicit closed-form stability criterion is derived, crosschecked and verified by both time-domain transient simulations and the measurements on an experimental demonstrator operating in a lower radiofrequency range. Results of this study lead to the conclusion that any parity-time-symmetric system is necessarily marginally stable. Finally, it is shown that such a marginally stable system may easily become unstable if not designed carefully.

Adaption of 3D Printing for Rapid Tooling

Over the course of the last decade 3D printing has become a more established technology in terms of prototype development (rapid prototyping). The current effort is focused on transferring this knowhow into a product driven approach in order to manufacture even small batch sizes more economic. In terms of this work, this idea is adapted for the development of injection molds (rapid manufacturing). Hereby, a hardened polymer is used to create a forming cavity instead of tool-steel. In order to fulfil the mechanical process requirements of micro injection molding such as form stability under temperature and pressure this cavity is nevertheless integrated into a metal housing. A first set of experiments has been carried out using this develop mold to verify the capabilities of the developed prototype as well as molding process. Based on these first results, an optimization is carried out to improve the next iteration of this molding tool.

ASSESSMENT OF THE FORMAL STABILITY OF KNITTED FABRICS ON THE CYLINDRICAL BEND OF THE PLATES

The article analyzes the results of theoretical studies of the dimensional stability of knitted fabrics with different fibrous composition. The coefficient of form stability Кф according to the deformability data of knitted fabrics, modeled in the form of bending of a rectangular plate along a cylindrical surface, is proposed.