193 research outputs found
An innovative cost modelling system development for laser drilling process
Get PDFPoster presented at Cranfield University’s 2019 Manufacturing Doctoral Community event
Evaluation of UDP and SCTP for SIP-T and TCP, UDP and SCTP with constant traffic
No full textIn recent years, Voice over IP (VoIP) has gained a lot of popularity. Signaling being an important part of VoIP has been addressed by the (IETF) SIGTRAN working group to meet Quality of Service as given by Public Switched Telephone Network (PSTN), so that both PSTN and VoIP can co-exit and work together in a seamless manner SIP (Session Initiation Protocol) developed by IETF for VoIP signaling is a communication control protocol capable of running on different transport layers, e.g., TCP, UDP or SCTP. Today’s SIP application is mostly operating over the unreliable transport protocol UDP. In lossy environment such as wireless networks and congested Internet networks, SIP messages can be lost or delivered out of sequence. The SIP application then has to retransmit the lost messages and re-order the received packets. This additional processing overhead can degrade the performance of the SIP application. Therefore to solve this problem, the researchers are looking for a more appropriate transport layer for SIP. SCTP, a transport protocol providing acknowledged, error-free, non-duplicated transfer of messages, has been proposed to be an alternative to UDP [1] and TCP [2]. The multi-streaming and multi-homing features of SCTP are especially attractive for applications that have stringent performance and high reliability requirements and an example is the SIP proxy server. In this research, we have analyzed the performance offered by SCTP for SIP message delivery in the perspective of historic research work as well as determined call setup time using UDP and SCTP by simulating SIP traffic in Network Simulator-2 (ns-2). We also evaluate TCP, UDP and SCTP traffic with constant bit rate of traffic through ns-2Muhammad Sarfraz C/o Ahsan Haroon ,87 Kungsmarksvagen , LGH 869, 37144 karlskrona Sweden 004673589535
Development of a non-living model system for cell membranes and investigation of its mechanical and tribological properties
Get PDFWhile our exposure to nanomaterials (NMs) has increased with advancements in nanotechnology, understanding harmful effects of such materials on humans is still wanting. Here we have proposed and developed a non-living model system for cell membranes which is suitable for elucidating interactions between NMs and living cells. In contrast to existing model systems for cell membranes, PAAm hydrogel was used as soft support for the lipid. Grafting of lipid with PAAm was achieved through layer by layer deposition of alternating poly(allylamine hydrochloride) (PAH)and poly(sodium 4-styrenesulfonate) (PSS) polyelectrolyte multilayers (PEM). Single step bilayer formation was observed under QCM on the PAAm-PEM support owing to high electrostatic interactions between the PEM and lipid vesicles with frequency and dissipation changes of ~-30 Hz and ~0.8x10-6, respectively. It is also shown that the PEM architecture is robust and reproducible on gels of different elastic modulus. AFM images confirm bilayer formation on top of PAAm-PEM supports with uniform bilayer patches of ~ 0.5 μm. AFM indentation experiments show significant differences in the elastic modulus and adhesion forces for systems with soft underlying supports compared to systems having a hard substrate. The physiological relevance of the developed system is clear from its mechanical characterization via AFM, where the system undergoes considerable deformation before and after bilayer rupture. This behavior is similar to behavior of real cells, in which deformation of cytoskeleton is dominant over that of the cell membrane. The model cell membrane system was also used to study shear forces at the interface of the lipid bilayer on hydrogel, which gave insights into the frictional behavior of the system and its mechanical interactions with nanoprobes.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-12-01The student, Tooba Shoaib, accepted the attached license on 2016-07-22 at 08:53.The student, Tooba Shoaib, submitted this Thesis for approval on 2016-07-22 at 10:40.This Thesis was approved for publication on 2016-07-22 at 15:06.DSpace SAF Submission Ingestion Package generated from Vireo submission #10071 on 2017-02-28 at 14:35:29Made available in DSpace on 2017-03-01T16:36:31Z (GMT). No. of bitstreams: 2
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Phytopharmacological evaluation of different solvent extract/fractions From<i> Sphaeranthus indicus</i> L. flowers:From traditional therapies to bioactive compounds
Get PDFSphaeranthus indicus L. is a medicinal herb having widespread traditional uses for treating common ailments. The present research work aims to explore the in-depth phytochemical composition and in vitro reactivity of six different polarity solvents (methanol, n-hexane, benzene, chloroform, ethyl acetate, and n-butanol) extracts/fractions of S. indicus flowers. The phytochemical composition was accomplished by determining total bioactive contents, HPLC-PDA polyphenolic quantification, and UHPLC-MS secondary metabolomics. The reactivity of the phenolic compounds was tested through the following biochemical assays: antioxidant (DPPH, ABTS, FRAP, CUPRAC, phosphomolybdenum, and metal chelation) and enzyme inhibition (AChE, BChE, α-glucosidase, α-amylase, urease, and tyrosinase) assays were performed. The methanol extract showed the highest values for phenolic (94.07 mg GAE/g extract) and flavonoid (78.7 mg QE/g extract) contents and was also the most active for α-glucosidase inhibition as well as radical scavenging and reducing power potential. HPLC-PDA analysis quantified rutin, naringenin, chlorogenic acid, 3-hydroxybenzoic acid, gallic acid, and epicatechin in a significant amount. UHPLC-MS analysis of methanol and ethyl acetate extracts revealed the presence of well-known phytocompounds; most of these were phenolic, flavonoid, and glycoside derivatives. The ethyl acetate fraction exhibited the highest inhibition against tyrosinase and urease, while the n-hexane fraction was most active for α-amylase. Moreover, principal component analysis highlighted the positive correlation between bioactive compounds and the tested extracts. Overall, S. indicus flower extracts were found to contain important phytochemicals, hence could be further explored to discover novel bioactive compounds that could be a valid starting point for future pharmaceutical and nutraceuticals applications.</p
Investigation of productivity, energy efficiency, quality and cost for laser drilling
Get PDFLaser drilling is a high speed, non-contact advanced machining process and has
proven to be an important industrial process for producing cooling holes in various
aeroengine components; in particular high-pressure turbine blades, combustor
liners and nozzle guide vanes. However, an increase in the number of cooling
holes demands the need for effective utilisation of laser drilling process capability.
Material removal rate (MRR), specific energy consumption (SEC), hole taper and
the drilling cost are the basic performance indicators to meet this goal. Hence,
this research aims to examine the laser drilling process in terms of the mentioned
performance measures.
Taking into account the significance of material removal quantity, energy
efficiency, product quality and manufacturing cost, this study is performed in the
form of an experimental investigation for three laser drilling processes, namely,
single-pulse drilling, percussion and trepanning. Two different laser drilling setups
were prepared to produce holes in Inconel 718 superalloy sheets using
flashlamp-pumped Nd:YAG laser and Quasi-CW fibre laser.
This research contributes to an evaluation of the influence of laser drilling process
parameters on the MRR, SEC, hole quality and drilling cost. Moreover, the
performance of laser drilling methods has been compared in relation to the
selected performance measures. To further understand the significance of laser
sources, the performance of laser drilling was compared for the mentioned drilling
setups. This research also introduced a detailed cost analysis to explore the
economic implications of the laser drilling process. In addition, optimal drilling
conditions were determined aiming to maximise the MRR and minimise hole taper
and drilling cost.Manufacturin
A stabilized discontinuous Galerkin method for variational embedding of physics-based data
Get PDFA stabilized variational framework that admits overlapping as well as non overlapping coupling of domains for a variety of Partial Differential Equations (PDEs) is employed in this work. This method accommodates non-matching meshes across the interfaces between the subdomain boundaries and allows for sharp changes in mechanical material properties. Interface coupling operators that emanate via embedding of Discontinuous Galerkin ideas in the continuous Galerkin framework provide a unique avenue to embed physics-based data in the modeling and analysis of the system. Physics-based data, either in discrete or in distributed form can be embedded via the interface operators that are otherwise devised to enforce continuity of the fields across internal discontinuities. The least-squares form of the interface coupling operators is exploited for its inherent linear regression type structure, and it is shown that it helps improve the overall accuracy of the numerical solution. Method is applicable to multi-PDE class of problems wherein different PDEs are operational on adjacent domains across the common interface. The method also comes equipped with a residual based error estimation method which is shown to be applicable to test problems employed. Different test cases are employed to investigate the mathematical attributes of the method.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-08-01The student, Shoaib Ahmad Goraya, accepted the attached license on 2019-07-12 at 16:53.The student, Shoaib Ahmad Goraya, submitted this Thesis for approval on 2019-07-12 at 16:54.This Thesis was approved for publication on 2019-07-15 at 14:47.DSpace SAF Submission Ingestion Package generated from Vireo submission #14260 on 2019-11-26 at 14:03:50Made available in DSpace on 2019-11-26T20:59:45Z (GMT). No. of bitstreams: 3
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Uncertainties in adoption of model-based definition and enterprise for high-value manufacturing
Get PDFIncorrect spelling of the author name in the paper: should be Ahmed Al-Ashaab.The world is adopting digital technologies at a rapid pace which are the
key enablers to improve every walk of life in the modern era. This quest for
digitization has equal rigor within the manufacturing industry. 2D drawings have
been used historically to define the specifications of a product for manufacturing.
The evolution in digital technologies has made it possible to improve the way of
representing these specifications in the form of 3D models which is known as
Model-Based Definition (MBD). However, the 2D representation is still the
authoritative source within the industry for engineering definition and related
documents in the product lifecycle. Though MBD has been adopted in design,
discrete part manufacturing, and inspection stages to some extent, the industry
heavily relies on the conventional 2D representation of product definition. The
digitization process of product definition lies within the adoption of MBD as the
authoritative source for all the enterprise activities which is referred to as Modelbased
Enterprise (MBE). However, there are several uncertainties and risks in this
process. In this work, it is ascertained to formulate the key uncertainties in the
transformation towards MBD/E. These uncertainties are categorized and analyzed
further for visualization.18th International Conference on Manufacturing Research, incorporating the 35th National Conference on Manufacturing Researc
Performance evaluation of Cu-Ni 90/10 alloyed structures exposed to various seawater compositions and their remaining service life estimation
Get PDF11th International Conference on Through-life Engineering Services - TESConf 2022, 8-9 November 2022, Cranfield UKThe Cu-Ni 90/10 alloy is extensively used in seawater applications mainly because of its excellent heat transferability, resistance toward corrosion and marine fouling. The corrosion resistance of Cu-Ni 90/10 has been found to be far superior in open natural seawater, however, several premature failures have often been reported during their exposure in the pollutant-rich seawater typically found near harbours, jetties and coastlines. This paper investigates the corrosion behaviour of Cu-Ni 90/10 alloyed coupons exposed to natural seawater, and pollutant-rich harbour seawater in a submerged position. Moreover, this research also investigates the corrosion mechanism on marine heat exchanger tubes of material that failed prematurely while operating in similar seawater compositions. The field experimental results for short-term corrosion results from coupons, and the long-term corrosion results from heat exchanger tubes have been evaluated, to formulate a relationship and corrosion modelling.DMG Mor
Softmatter tribology: Understanding the microstructure to property relationships of hydrogel-like materials
Get PDFBiological tribosystems are excellent examples of nature leveraging soft matter properties to achieve exceptional lubrication for prolonged periods of activity. In these systems, lubrication is provided by sparsely crosslinked, polymeric surface layers imbibed with an aqueous lubricant. A prominent biological tribosystem is the articular cartilage, an avascular tissue consisting of an extracellular matrix made of collagen fibrils and proteoglycans, with a small number of chondrocyte cells. However, in this tissue, there exists a gradient in the orientation of the collagen fibers and water content as a function of the distance from the bone, which emphasizes the importance of the microstructure in cartilage’s functionality, i.e. a load-bearing tissue that maintains low friction and wear. In fact, recent studies have shown that the cartilage’s articulating surface comprises of a network of highly hydrated mucins, polysaccharides, glycoproteins, and phospholipids, which play a key role in maintaining low friction in boundary lubrication. This has been evident in studies performed on multiple other biphasic, non-biological hydrogels as well, where a prominent effect of the interfacial microstructure is observed on their mechanical and tribological properties. Yet, not only there is a lack of knowledge but also wide discrepancy about the fundamental underlying mechanisms relating the dynamic and static frictional dissipation to the microstructure of these materials. Conversely, this fundamental gap in knowledge also limits progress in the design of functional replacements, based on hydrogel-like materials.
Our aim was to not only advance the existing knowledge about the frictional dissipation of hydrogels, by precisely correlating the role of microstructure to the tribological performance, but also, to establish design principles that can help combat some of the existing challenges related to their application as tribological biomaterials. In light of this, the doctoral work presented here has achieved the following specific goals:
I. Studied, modeled and quantified influence of the microstructure, crosslinking degree and stiffness of the polymer on the dynamic and static frictional response
II. Scrutinized the relation between friction force and interfacial rheology of hydrogels
III. Elucidated the pathways of network formation in double network hydrogels which lead to enhanced mechanical and frictional response
IV. Scrutinized mechanical and tribological response of biological hydrogels in physiologically relevant conditions
By combining powerful state-of-the-art experimental techniques such as the Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM) and extended surface forces apparatus (SFA), we have demonstrated that the main mechanisms behind the frictional dissipation of hydrogels arise directly from their biphasic nature – the polymeric network and the imbibing fluid. In the context of dynamic friction, the viscous-adhesive model developed here quantifies the hydrogel’s frictional response by considering an interplay of adhesive and viscous dissipation directly arising from the hydrogel’s microstructure. The model accounts for confinement effects, poroelastic deformation, and the influence of the polymer on the viscous friction force, and helps reconcile seemingly contradictory models proposed previously. The adhesive contribution was modeled as a combination of reversible, transient adhesive bonds between the hydrogel and the countersurface and the poroelastic deformation of the hydrogel during shear, while the role of viscous dissipation was revealed to be directly related to the rheological performance of the hydrogel’s interface. In the latter, the polymer and imbibed fluid, both dictated viscous dissipation. Scrutiny of the rheological behavior of hydrogel thin films in tandem with nanotribology was conducted to show that the effective viscosity measured in rheology agrees with the friction behavior, although it is not sufficient to capture the rich frictional response of hydrogels as a function of sliding velocity. In the context of static friction, the combined effects of microstructure, interfacial shear stresses, interfacial ageing, and temperature were all tied together into a conceptual phase diagram for the static friction of hydrogels. Feasibility of the models developed for the dynamic and static friction was validated by extending the concepts to other hydrogel systems such as physically crosslinked agarose and cartilage, thereby demonstrating the universality of the proposed mechanisms for biphasic soft materials.
The study was further extended to DN hydrogels and biological hydrogels. Systematic investigations of the DN hydrogels comprising of agarose and polyacrylamide hydrogels as independent, interpenetrating networks revealed the design limitations of achieving high strength and high lubricity, simultaneously. Lastly, the novel experimental study on the gel-like surface of the articular cartilage was conducted as a direct application of this research. The graded response of the cartilage’s gel-like articulating surface in elevated calcium concentrations was traced back to changes in the surface and sub-surface microstructure, which was reported to subsequently modulate the mechanical and tribological response of the material.
In summary, through its collective experimental studies and comprehensive models, this doctoral work provides the basic framework to understand lubrication mechanisms of hydrogel-like materials in light of their microstructure. Furthermore, it also helps provide the basic design principles for fabricating hydrogels capable of achieving low friction coefficients and augmented wear resistance through the precise control of their microstructure. Lastly, the novel methodologies and protocols stemming from this dissertation open up previously unexplored research avenues and hence can influence diverse areas of inquiries, not only limited to biolubrication and biomedical applications but soft robotics and microelectromechanical devices.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2023-08-01The student, Tooba Shoaib, accepted the attached license on 2021-07-14 at 11:30.The student, Tooba Shoaib, submitted this Dissertation for approval on 2021-07-14 at 11:37.This Dissertation was approved for publication on 2021-07-16 at 11:52.DSpace SAF Submission Ingestion Package generated from Vireo submission #16930 on 2022-01-12 at 12:55:05Made available in DSpace on 2022-01-12T22:35:15Z (GMT). No. of bitstreams: 2
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Electronic properties of corundum-like Ir2O3 and Ir2O3-Ga2O3 alloys
No full textThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Shoaib Khalid, Anderson Janotti; Electronic properties of corundum-like Ir2O3 and Ir2O3-Ga2O3 alloys. Appl. Phys. Lett. 11 November 2024; 125 (20): 202102. https://doi.org/10.1063/5.0232445 and may be found at https://doi.org/10.1063/5.0232445.
© 2024 Author(s). Published under an exclusive license by AIP Publishing.
This article will be embargoed until 11/11/2025.In the hexagonal, corundum-like structure, -Ga2O3 has a bandgap of 5.1 eV, which, combined with its relatively small electron effective mass, high Baliga's figure of merit, and high breakdown field, makes it a promising candidate for power electronics. Ga2O3 is easy to dope n-type, but impossible to dope p-type, impeding the realization of some electronic device designs. Developing a lattice-matched p-type material that forms a high-quality heterojunction with n-type Ga2O3 would open new opportunities in electronics and perhaps optoelectronic devices. In this work, we studied Ir2O3 as a candidate for that purpose. Using hybrid density functional theory calculations we predict the electronic band structure of -Ir2O3 and compare that to -Ga2O3, and study the stability and electronic properties of -(IrxGa1−x)2O3 alloys. We discuss the band offset between the two materials and compare it with recently available experimental data. We find that the Ir d bands that compose the top of the valence band in -Ir2O3 are much higher in energy than O p bands in -Ga2O3, possibly enabling effective p-type doping. Our results provide an insight into using the Ir2O3 or Ir2O3-Ga2O3 alloys as p-type material lattice-matched to -Ga2O3 for the realization of p–n heterojunctions.This work was supported by the Laboratory Directed Research and Development (LDRD) Program (Project No. 800025) at Princeton Plasma Physics Laboratory under U.S. Department of Energy Prime Contract No. DE-AC02-09CH11466. A.J. was supported by the NSF through the UD-CHARM University of Delaware Materials Research Science and Engineering Center (MRSEC) Grant No. DMR-2011824. The calculations were carried out at the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility located at the Lawrence Berkeley National Laboratory, operated under Contract No. DE-AC02-05CH11231 using NERSC award BES-ERCAP27253, the Stellar Cluster at Princeton University, and the DARWIN computing system at the University of Delaware, using the NSF Grant No. 1919839
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