Series design of compressors for two-stage centrifugal chiller

A preliminary series design of compressors for a two-stage centrifugal chiller is suggested. Six groups of hydrodynamically similar compressors, ranging from 233RT to 1,200RT, are introduced. Flow rates, impeller diameters, and wheel speeds for each group are determined from hydrodynamic similarity to share impellers of adjacent groups. It is expected that these compressors can have the same performance and efficiency from the smallest model to the largest one.     

A finite element beam analysis by interface matching

An alternative way of finite element beam analysis is presented. The beam deflection in an element is represented by the sum of general solution and particular solution. The general solution is approximated by using Hermite polynomials and the particular solution is obtained by applying zero boundary conditions at element boundaries. The inter-element stiffness matrices are obtained by requiring the continuity of moment and shear force across element boundaries. The inter-element stiffness matrices do not overlap each other to form the global stiffness matrix. The boundary conditions are explicitly specified. Numerical examples are provided for various boundary conditions and load conditions.

     

Stress Response of Mouse Embryonic Fibroblasts Exposed to Polystyrene Nanoplastics

Polystyrene (PS) nanoplastic exposure has been shown to affect the viability of neuronal cells isolated from mouse embryonic brains. However, the viability of mouse embryonic fibroblasts (MEFs) was not affected although PS nanoplastics accumulated in the cytoplasm. It is currently unknown whether MEFs do not respond to PS nanoplastics or their cellular functions are altered without compromising viability. Here, we found that PS nanoplastics entered the cells via endocytosis and were then released into the cytoplasm, probably by endosomal escape, or otherwise remained in the endosome. Oxidative and inflammatory stress caused by intracellular PS nanoplastics induced the antioxidant response pathway and activated the autophagic pathway. However, colocalization of the autophagic marker LC3B and PS nanoplastics suggested that PS nanoplastics in the cytoplasm might interfere with normal autophagic function. Furthermore, autophagic flux could be impaired, probably due to accumulation of PS nanoplastic-containing lysosomes or autolysosomes. Intriguingly, the level of accumulated PS nanoplastics decreased during prolonged culture when MEFs were no longer exposed to PS nanoplastics. These results indicate that accumulated PS nanoplastics are removed or exported out of the cells. Therefore, PS nanoplastics in the cytoplasm affect cellular functions, but it is temporal and MEFs can overcome the stress caused by PS nanoplastic exposure.     

Synthesis and characteristics of NH<Subscript>2</Subscript>-functionalized polymer films to align and immobilize DNA molecules

We developed a method to use NH₂-functionalized polymer films to align and immobilize DNA molecules on a Si substrate. The plasma-polymerized cyclohexane film was deposited on the Si substrate according to the radio frequency plasma-enhanced chemical vapor deposition method using a single molecular precursor, and it was then treated by the dielectric barrier discharge method in a nitrogen environment under atmospheric pressure. Changes in the chemistry of the surface functional groups were studied using X-ray photoelectron spectroscopy and Fourier transformed infrared spectroscopy. The wettability of the surfaces was examined using dynamic contact angle measurements, and the surface morphology was evaluated using atomic force microscopy.     

Fine liquid blowing: A high Reynolds number,high production rate nanofiber manufacturing technique

A novel gas-assisted jetting process, term fine liquid blowing, is used to improve the production rate of making nanofiber from polymer solution. A high-velocity gas stream is introduced through a central protruding core needle, while a liquid is introduce via an adjacent satellite needle. This arrangement avoids passing the high-velocity gas over the surface of the slow flowing liquid and results in the stable acceleration of the liquid flow on its approach to the tip of the core needle, where it interacts with the high-velocity gas, initiating numerous liquid jets at elevated Reynolds numbers of up to more than 800. The method was used to produce poly (vinyl alcohol) nonwoven fiber mats at polymer solution feed rates of up to 900 mL h, surpassing other conventional methods. The produced fibers were of diameters ranging from 96 to 430 nm. Over the tested range, polymer flow rate did not show significant influence on the resulting fiber diameter. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47384.     

Effects of the alkylamine functionalization of graphene oxide on the properties of polystyrene nanocomposites

Alkylamine-functionalized graphene oxides (FGOs) have superior dispersibility in low-polar solvents and, as a result, they interact with low-polar polymers such as polystyrene. In this work, the functionalization of graphene oxide using three types of alkylamines, octylamine (OA), dodecylamine (DDA), and hexadecylamine (HDA), was performed, and nanocomposites of polystyrene (PS) and FGOs were prepared via solution blending. Different dispersions of FGOs over PS were obtained for the three alkylamines, and the properties of the PS composites were influenced by the length of the alkylamine. A better thermal stability was observed with a longer chain length of the alkylamine. On the other hand, functionalization with the shortest chain length alkylamine resulted in the highest increase in the storage modulus (3,640 MPa, 140%) at a 10 wt.% loading of FGO.