Issues on Design of Piled Raft Foundation

A piled raft foundation consists of a thick concrete slab reinforced with steel which covers the entire contact area of the structure, in which the raft is supported by a group of piles or a number of individual piles. Bending moment on raft, differential and average settlement, pile and raft geometries are the influencing parameters of the piled raft foundation system. In this paper, a detailed review has been carried out on the issues on the raft foundation design. Also, the existing design procedure was explained

The role of mechanical environment in regulating vascular network formation

Introduction: The integration of engineered tissues after implantation is limited due to the lack of a vascular network. When vascular networks are included, they generally are not organized, or lose their initial organization fast1. Due to the ability of cells to sense their environment by mechanotransduction, signaling, maturation, organization and cell survival is regulated. The objective of this study is to analyze the combinatory effect of substrate stiffness and fluid flow on vascular organization and maturation to find the basic parameters for pre-vascularization of engineered tissue. Methods A microfluidic PDMS framed system was used, which makes it possible to investigate different hydrogel compositions in parallel. Pre-glycation by D-(-)-Ribose allowed for the use of one type of hydrogel in the same concentration but with different modulated mechanical properties. During the polymerization process of the hydrogels, needles were integrated into the gels to create hollow channels by their removing afterwards. The down and top side of the system were sealed with thin cover glasses to ensure the visibility of the inner system. The fluid-flow channels were coated with 0.1% Gelatin to improve the cell attachment and seeded with Smooth muscle cells. Afterwards Human Umbilical Vein Endothelial Cells (HUVECs) were seeded on top of the smooth muscle cells to mimic the physiological blood vessel structure. An additional channel was filled with VEGF (50 ng/mL), which is known as one of the main angiogenic factors which diffuse into the hydrogel over time2. Different fluid-flow profiles were applied to the cell seeded channels. The newly formed capillary network was analyzed by ImageJ. Results: The pre-glycation by incubation of different concentrations of D-(-)-Ribose resulted in an increase of stiffness of the same type of hydrogel by additionally crosslinking of the different hydrogels components. The use of different modulated hydrogels allowed for the simultaneous analysis of the effect of fluid flow on the vascular sprouting into the hydrogels triggered by the diffused VEGF. Different mechanical properties in combination with different fluid flow patterns affected the ability of HUVEC to migrate and organize into the hydrogels and show differences in the sprouting morphology. Outlook: To mimic the physiological state, different Endothelial cell types (e.g. HUVECs, HMECs, HIAEC) will be integrated into the fluid flow channels. This will allow us to see if different endothelial cell origins leads to a different sprouting behavior or if the already described endothelial plasticity leads to similar results

Regulation of cytochrome P-450 messenger RNA and apoprotein levels by heme

2-Allylisopropylacetamide, a porphyrinogen which decreases the microsomal and cytosolic heme pools, is a phenobarbitone-like inducer of cytochrome P-450(b + e) messenger RNAs in rat liver. The porphyrinogen, however, does not affect the nuclear heme pool and enhances the transcription of cytochrome P-450(b + e) messenger RNAs strikingly. Inhibitors of heme biosynthesis, such as CoCl2 and 3-amino-1,2,4-triazole, which decrease the total heme levels including that of the nuclear heme pool, block the 2-allylisopropylacetamide- or phenobarbitone-mediated increase in the transcription of cytochrome P-450(b + e) messenger RNAs. Administration of exogenous heme at a very low concentration (25 μg/100 g) is able to counteract the inhibitory effects of the heme biosynthetic inhibitors. Addition of heme in vitro to heme-depleted nuclei leads to a significant increase in the transcription rates for cytochrome P-450(b + e) messenger RNAs. 2-Allylisopropylacetamide, unlike phenobarbitone, fails to increase the levels of cytochrome P-450b protein at 12 h after the drug administration, although there is a striking increase in the messenger RNA levels. Under conditions of 2-allylisopropylacetamide treatment, the cytochrome P-450 messenger RNA is translated, but the newly synthesized apoprotein undergoes rapid degradation. It is concluded that heme is a positive modulator of cytochrome P-450 gene transcription and is also required to stabilize the freshly synthesized apoprotein

Investigations of AC Microgrid Energy Management Systems Using Distributed Energy Resources and Plug-in Electric Vehicles

The world has witnessed a rapid transformation in the field of electrical generation, transmission and distribution. We have been constantly developing and upgrading our technology to make the system more economically efficient. Currently, the industry faces an acute shortage of energy resources due to overconsumption by industries worldwide. This has compelled experts to look for alternatives to fossil fuels and other conventional sources of energy to produce energy in a more sustainable manner. The microgrid concept has gained popularity over the years and has become a common sight all over the world because of the ability of a microgrid to provide power to a localized section without being dependent on conventional resources. This paper focuses on development of such an AC hybrid microgrid, which receives power from distributed energy resources (DERs) such as a PV array alongside a battery storage system, and also uses an emergency diesel generator system and an online uninterruptible power supply (UPS) system to provide power to predefined loads under different conditions. This paper also addresses on the power flow to the loads under two main modes of operation—on grid and off grid—and investigates the microgrid in different states and sub-states. The final objective is to design an efficient microgrid model such that it can sustain the multiple loads simultaneously under all operating conditions

Three-phase series resonant DC-DC boost converter with double LLC resonant tanks and variable frequency control

This paper proposes a three-phase inverter combined with two LLC resonant tanks series resonant DC-DC boost converter with variable frequency control. The three-phase inverter side of the proposed circuit is connected to identical two-level LLC tanks to ensure balanced resonant currents. The proposed converter requires less switching devices and transformers as compared to the conventional interleaved LLC resonant converter, which competitively offers higher efficiency and reduced size and cost. Furthermore, the proposed converter works above the resonant frequency to achieve zero voltage switching (ZVS) for the entire operating frequency range {(42.5kHz < }{f}{s}{ < 50kHz)} for all switches. Variable frequency controller is considered in order to obtain better stability for diverse loads. Therefore, the proposed converter will have the ability to respond to the load changes by varying the switching frequency to the value that fulfils the requirement. In order to verify the improvement of the proposed converter, the converter performance is compared to conventional interleaved LLC resonant converter. The theoretical outcomes are confirmed through simulation studies using MATLAB/SIMULINK and validated experimentally using a laboratory prototype. Selected results are presented to verify the effectiveness of the proposed converter

Analysis and Investigation of Hybrid DC–DC Non-Isolated and Non-Inverting Nx Interleaved Multilevel Boost Converter (Nx-IMBC) for High Voltage Step-Up Applications: Hardware Implementation

In significant cases, the generated voltage needs to be step-up with high conversion ratio by using the DC-DC converter as per the requirement of the load. The drawbacks of traditional boost converter are it required high rating semiconductor devices and have high input current ripple, low efficiency, and reverse recovery voltage of the diodes. Recently, the family of Multilevel Boost Converter suggested and suitable configuration to overcome the above drawbacks. In this article, hybrid DC-DC non-isolated and non-inverting Nx Interleaved Multilevel Boost Converter (Nx-IMBC) is analyzed in Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM) with boundary condition and investigated in detail. The Nx-IMBC circuit combined the features of traditional Interleaved Boost Converter (IBC) and Nx Multilevel Boost Converter (Nx-MBC). The modes of operation, design of Nx-IMBC and the effect of the internal resistance of components are presented. The comparison study with various recent DC-DC converters is presented. The experimental and simulation results are presented with or without perturbation in input voltage, output power and output reference voltage which validates the design, feasibility, and working of the converter