1,722,874 research outputs found
Comparison of Efficacy of Intralesional Tranexamic Acid Verses Topical 4% Hydroquinone in Treating Melasma
No full textData of study conducted spanning from 16th October 2019 to 16th April 2020 in a tertiary care hospital of Pakistan for comparison of 2 different treatment modalities. This data will help other researchers to conduct similar study and to apply right treatment modality for melasma treatmentData of study conducted spanning from 16th October 2019 to 16th April 2020 in a tertiary care hospital of Pakistan for comparison of 2 different treatment modalities. This data will help other researchers to conduct similar study and to apply right treatment modality for melasma treatmentData of study conducted spanning from 16th October 2019 to 16th April 2020 in a tertiary care hospital of Pakistan for comparison of 2 different treatment modalities. This data will help other researchers to conduct similar study and to apply right treatment modality for melasma treatmentData of study conducted spanning from 16th October 2019 to 16th April 2020 in a tertiary care hospital of Pakistan for comparison of 2 different treatment modalities. This data will help other researchers to conduct similar study and to apply right treatment modality for melasma treatmentData of study conducted spanning from 16th October 2019 to 16th April 2020 in a tertiary care hospital of Pakistan for comparison of 2 different treatment modalities. This data will help other researchers to conduct similar study and to apply right treatment modality for melasma treatmen
Optimal Processing Pathway for Microalgal Biorefinery based on Nannochloropsis sp.
No full textIn this study, a superstructure based optimization model of microalgae-based biorefinery is proposed. The proposed biorefinery superstructure is based on Nannochloropsis sp. and it consists of major processing steps for the biofuels production such as cultivation, harvesting of biomass, pretreatment of harvested biomass, extraction of lipids from biomass, transesterification, post-transesterification, and microalgae residue conversion. The mixed integer nonlinear programming (MINLP) model is formulated to find the optimal process option in each processing step among the various potential technological alternatives available for the production of biofuels from microalgae. The proposed MINLP model is solved by applying on a specific case with different objective functions. The results showed the optimal configuration of biorefinery depending on the implemented objective function
Onboard Communication Systems for Low Cost Small Satellites
No full textThe development of a large number of Nano and Pico-satellite missions, with spacecrafts of mass lower than 10 kg and 1 kg respectively, started in the beginning of this century due to the availability of low-cost piggyback launch opportunities. Such small satellites are usually built using commercially available electronic components that are not qualified for the space environment. This approach reduces the total cost of the satellite missions but at the expense of design effort which is needed not to compromise the reliability of the designed spacecrafts. One of the foremost design efforts in this regard is the design re-use method which extends the cost reduction to
the system level, and helps in simplifying the development cycle for a space mission. The on-board communication subsystem consist of critical set of elements common to every mission, and therefore is not exempt from such a design philosophy. The on-board networks, on-board transceivers, and the protocols are all critical elements for a spacecraft mission and, at the same time, some of the most specialized and complex ones. Innovative data communication systems are therefore desirable for the future space missions.
The size of the satellites keeps reducing as the time progresses, therefore the harness mass and complexity inside the satellite becomes a prime challenge. An innovative approach to smart harness is therefore necessary which reduces the wiring harness for intra-satellite communication.
This thesis copes with several problems related to spacecraft subsystem development, integration and testing and proposes some solutions that can help in both keeping system development and production cost low while still achieving good performances.
Chapter 1 starts with the design goals of the work and introduction to the Modular Architecture of Small Satellites (AraMiS) project. The biggest design goals of space systems of current era are the cost, time and complexity issues. Modularity
and cost-sharing between multiple missions will appear as optimal solutions for reducing development costs, while the use of commercial components (COTS) will be presented as a way to simplify procurement and further lower system cost
In Chapter 2, the smart harness approach is proposed which reduces the traditional harness complexities inside the small spacecrafts. The chapter focuses on the design of small spacecrafts which are completely modular and flexible. Modularity at mechanical, electrical and testing level will be discussed in this chapter.
Chapter 3 addresses the complete life cycle of a subsystem module i.e. from conception to the final design and testing. The module life cycle uses a variety of Unified Modelling Language (UML) diagrams to fulfill different design stages.
Chapter 4 proposes different types of spacecraft configurations based on smart harness approaches including physical module based, satellite on demand and reusable design configurations.A design trade-off is also performed for these configurations.
Chapter 6 proposes the design technique of physical module based spacecraft configuration which is based on physical plug and play connectors and logical slots for the subsystem modules. A honeycomb based tile is discussed in this chapter
which is used for larger and more demanding spacecraft structures.
In Chapter 7, the requirement of data communication across different subsystems of the spacecrafts are described. The use cases have been discussed and the implementation rules have been defined in this Chapter.
Chapters 8,9 and 10 focus on module design for intra-satellite communication purposes. The modules have been designed for wired as well as wireless data communication. The wired solution is based on on-board data bus module for inter-tile
data communication. Wireless solutions included both optical and radio frequency
based solutions. The optical module has been designed for optical free space as well as glass fiber based communication purposes. The comparison between theoretical and practical results has been made. The radio frequency based module is based on commercial module and simpliciTI protocol stack.
In Chapter 11, the functional testing of modules, tiles and whole satellites is discussed. The testing scheme of functional test board is also highlighted in this
chapter
Spark plasma sintered hydroxyapatite / bioglass composite for improved biological performance / Muhammad Rizwan
No full textThe most common biomaterials employed in orthopaedic and dental surgery are calcium phosphate (CaP) based, such as hydroxyapatite (HA) and β-tricalcium phosphate (TCP). Although HA exhibits tremendous biocompatibility, its close resemblance with the mineralized phase of natural bone affects the bioresorption rate in the body. Furthermore, the in vitro reactivity of HA is insufficient, and several in vivo studies confirmed the inadequate development of osseous tissues. Several attempts were made to combine HA with bioactive glasses, with the aim to obtain composite materials with improved bioactivity, controllable resorption rate and enhanced osseointegration. However, the high-temperature treatments required to sinter HA-based composites causes the bioactive glass to crystallize into a glass–ceramic and/ or react excessively with HA, exhibiting possible negative effects on its bioactivity, resorption and osseointegration. In this study, Bioglass®45S5 (BG) has been added into the HA matrix. BG exhibits the highest bioactivity (IB>8) among all bioceramics and forms very strong bonds with the surrounding tissues. Composite scaffolds containing BG powder (0 to 30 wt %) and BG fibers (0-20 wt %) were prepared using Spark Plasma Sintering (SPS) and conventional sintering. The SPS simultaneously compacts and sinters at relatively less severe processing conditions (compared to the conventional route), yielding novel findings related to the ability to prevent glass devitrification and excessive reactions between the constituents. The avoidance of excessive reactions and devitrification is critical, as the unique characteristics of BG (high bioactivity and extremely high osseointegration) and HA (similarity with the mineralized phase of natural bone) are lost or significantly deteriorated as a result of excessive reaction and devitrification. XRD analysis confirmed the absence of any crystalline phase (other than HA and β-TCP) resulting from the excessive reaction between HA and BG in SPSed scaffolds. On the other hand, the conventionally processed composites are composed of the β-TCP, Rhenanite and glassy phases. FESEM and EDAX analysis confirmed the presence of glassy phase with rounded morphology in the SPSed samples, which changed to a longer shape resembling the fibrous morphology when the BG fibers were used as reinforcement. Bulk density analysis of the composites was conducted using the Archimedes’ principle. Microhardness indentation was used to evaluate the hardness of each phase in the samples. The in vitro bioactivity analysis of the composite samples by immersion in simulated body fluid (SBF) showed enhanced bioactivity of the composite samples with higher BG content. The formation of biomimetic carbonated HA (CHA) on the composite samples has been confirmed by FESEM, EDAX and FTIR analysis. The in vitro resorption behavior was analyzed by immersion of the samples in Tris solution. The in vitro biological behavior of SPSed composite samples was evaluated in human bone marrow derived mesenchymal stromal cells (hBMSCs). The in vitro hBMSCs attachment (using SEM), mineralization (using EDAX) and proliferation (using Alamar blue staining) were evaluated initially. In next stage, the osteogenic differentiation (evaluating BMP-2, collagen I and Osterix formation) was analyzed by confocal laser scanning microscopy (CLSM). The SPSed HA-BG samples showed improved in vitro biological performance with higher BG content (particularly containing 30 wt % BG)
Smart honeycomb tile for small satellites
No full textTraditional satellite technologies integrate solar
panels, thermo mechanical subsystems, power management,
data processing and harness subsystems together in a late stage
of design. More recently this approach has become inefficient
and its limitation can easily be overcome with modern
manufacturing technologies. This paper proposes an innovative
approach to embed power, signal processing and harness
together with thermo mechanical subsystem(s) and when
required, solar panels. The approach has been developed for
the AraMiS architecture for low-cost modular satellites, but it
can easily be adapted to other architectures, missions and
spacecraft sizes. The architecture consists of tiles or panel
bodies containing solar panels on exterior side and all necessary
electronic subsystems on the interior side. The proposed
approach uses very thin commercial PCBs (0.2 or 0.3mm thick)
as the lateral skins for honeycomb structure. The interior side
also contains commercial tile processors and plug & play
connectors for any desired subsystem placement. The
processors implement common functionalities for signal
processing, data communication and control operation. The
interior side can also host power conversion, for an improved
fault-tolerant interface of solar panels with the power
management subsystem. A high-performance power
distribution bus has also been tested, for a distributed
approach to satellite power management. The proposed design
uses exclusively the UML diagrams for illustration purpose and
software handling of housekeeping data
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