71 research outputs found
A study on the effect of frequency in delamination of CFRP
No full textFatigue damage is considered to be one of the most critical phenomenon, contributing to the failure of an aircraft structure. Understanding the fatigue mechanism is essential for considering the different technical conditions that influence the fatigue life of structures. In recent years, fatigue tests are accelerated in order to reduce the testing time of materials/structures being developed, which in turn can reduce the time to market. However, an ideal fatigue experiment should involve testing the structure at its service conditions. Increasing the frequency of the fatigue test can alter the fatigue mechanisms that attribute to damage initiation and propagation. One possible solution to overcome this problem is to understand the effect of frequency on fatigue. By doing so, tests can be carried out at high frequencies and influence of frequency on damage progression can be taken into account during damage prediction. The scope of this thesis is narrowed down to carbon fibre reinforced plastics and aimed at understanding the effect of frequency on damage propagation through energy principles.Fatigue can be seen as a material degradation process through which the applied work in the form of strain energy is dissipated into damage and other energy dissipation mechanisms. Experiments were performed for Mode I delamination on double cantilever beam specimens manufactured from carbon/epoxy laminate. Within a single fatigue cycle, energy dissipation (energy that is supplied during loading phase and not returned back during unloading phase) and crack growth are mutual. In other words, crack growth occurs with the consumption of dissipated energy and energy is dissipated in creating new crack surface. For simplification of calculation, energy loss and crack growth occurring in one cycle are averaged over that cycle. The averaged quantities dU/dN and da/dN are correlated with each other for different frequencies.For the calculation of strain energy loss, strain energy at maximum displacement position is calculated from the area under load-displacement plots of the fatigue cycle. For the fatigue tests carried out at a frequency of 5 Hz, assumption that the load-displacement response is linear, holds good. For higher frequencies, the response becomes non-linear due to hysteresis effect. When strain energy was calculated for all the tests with the assumption of linear P-d response, no particular trend on the effect of frequency could be observed in da/dN vs dU/dN plots. Accounting for the non linearity in load-displacement response due to hysteresis provided light on the characterization of frequency effects. The size of hysteresis loop was approximated for different frequencies based on the observations during the experiments. It was also found that, more energy was dissipated to grow a unit crack (more crack growth resistance, 퐺∗) for a higher frequency test.Two possible mechanisms were investigated to find a suitable explanation for the observed increase in G∗ with the increase in frequency: heat dissipation and internal heat generation that would cause a rise in specimen temperature. Measurements from thermocouple and infra red camera showed that no significant temperature rise occurred in the specimen during fatigue. This confirmed that, for CFRP under mode I fatigue loading, the hysteresis energy due to high frequency fatigue testing did not heat up the specimen, but either got dissipated as heat at a rapid rate or by some other mechanism which is still not clear.When results were compared with the conceptual model formulated in this thesis, it was found that increasing the frequency increases the available energy, dU/dN and the crack growth resistance, G∗ such that crack growth rate may either increase or decrease (depending on the interaction between the two parameters). Further, a model based on quantitative measurements of heat dissipation at higher fre- quencies and determination of exact coordinates of the hysteresis loop evolution in load-displacement relationship of the fatigue cycles are recommended to fully understand the effect of test frequency in fatigue damage propagation.Aerospace Engineerin
Area Efficient Floating Point Addition Unit With Error Detection Logic
No full textAbstractApplications that involve large dynamic range make use of the floating point operations. Addition is one of the complex operation in a floating point unit. This paper proposes an area efficient floating-point addition unit with error detection logic. Existing Leading Zero Anticipators (LZA) and error detection logics helps to reduce the delay of the general floating point unit, but are not area efficient. Here a single precision area efficient floating point addition unit is designed using an efficient Carry Select Adder together with the error detection logic. Efficient Carry Select Adder is developed using Binary to Excess-1 Converter instead of Ripple Carry Adder for cin=‘1’. The proposed design is simulated using ModelSim and is tested on Xilinx
An analytical study of 100 cases of penetrating injuries.
No full textNature offers protection to the eye, anatomically by its situation in
the elastic fatty tissues of the orbital cavity and sturdy bony projections of
the orbital rim and the nose, physiologically by the vigilance exercised by
the blink reflex and the head – turning reflex on the approach of objects.
Despite these protection injuries to the eyes are common and may involve
any tissue1. Moreover, the effects of such injuries are much more severe
than in any other parts of the body, because of the delicacy of the ocular
tissues. Ocular injuries therefore assume marked social and economic
importance involving a huge cost in human unhappiness and economic
inefficiency.
In our study males were predominantly affected by penetrating injuries
The age group 16-45yrs was the most common group to get penetrating
injuries.
The majority of penetrating injuries were occupational. Metal was the most
common object involved in causing penetrating injuries.
Patients who presented immediately within 24hrs of injury had good visual
prognosis than those presented late.
Though Wound repair is the most common intervention in the primary
procedure some patients underwent cataract extraction and IOL implantation,
foreign body removal.
Traumatic cataract was the most common complication associated with
penetrating injuries. Five patients in our study had Endophthalmitis.
Cataract extraction with IOL implantation is the most common secondary
procedure in our study.
Visual acuity at the time of presentation is one of the most important
prognostic factors in predicting visual outcome.
Patients who presented with RAPD had poor visual outcome.
Zone I is the commonest location of laceration followed by Zone II and then
Zone III. Patients who had Zone I injury had better visual prognosis than
those with Zone II or Zone III injuries.
Visual acuity at the time of presentation, presence of Relative afferent
pupillary defect, Zone of involvement and the size of laceration are the
important factors in predicting the visual prognosis.
Importance should be laid on preventive measures by educating people
on ocular trauma, use of protective eyewear and timely management
Sub-Nyquist Sampling of Acoustic Signals Based on Chaotic Compressed Sensing
No full textAbstractCompressed sensing (CS) is a new approach to signal sampling that allows signal recovery from an incomplete set of samples. For the faithful reconstruction of the signal from few measurements or samples, the sensing matrix must satisfy the restricted isometry property (RIP). The random matrices obey this property, but the practical implementation is expensive. Chaotic sequences are used to construct the sensing matrix and exact reconstruction is, under specific conditions, possible with high probability. In this paper, a chaotic compressive sampler is employed to sample the acoustic signals at sub-Nyquist rate. In contrast with traditional Nyquist sampling and linear reconstruction, orthogonal matching pursuit (OMP) algorithm is applied to recover the signal from the chaotic measurements. This paper shows that the chaotic compressive sampler outperforms the random demodulator architecture in terms of the reconstruction accuracy
Aurolab aqueous drainage implant: My surgical technique
No full textAurolab aqueous drainage implant is a nonvalved tube implant used to treat refractory glaucoma. Although implanting the device could be surgically more demanding than certain other drainage devices, the author aims to describe the techniques which enable him to perform the surgery safely and efficiently
Alkaloids from Alstonia scholaris and Ficus schwarzii
No full textAlkaloids, which are the most studied secondary metabolites, are structurally diverse and well known for their biological activity. The aim of the present study is to perform phytochemical investigations on the alkaloidal composition of two selected plant species, namely, Ficus schwarzii (Moraceae) and Alstonia scholaris (Apocynaceae). (specimen from the West Coast of Peninsular Malaysia). The previously unexplored phytochemistry of F. schwarzii and the phytochemical variation of A. scholaris due to locality have motivated research into the two species collected from Peninsular Malaysia.
Phytochemical investigation of the leaves of F. schwarzii yielded nine novel alkaloids, namely, schwarzinicines A−G (1−7), and schwarzificusines A and B (8 and 9). The schwarzinicine alkaloids represent the first examples of 1,4 diarylbutanoid−phenethylamine conjugates, while schwarzificusines A and B (8 and 9) represent a pair of new diastereomeric 1-phenyl-3-aminotetralins that are structurally related to the schwarzinicines alkaloids. The structures of alkaloids 1–9 were elucidated by detailed analysis of their HRMS and NMR data. Plausible biogenetic pathways that furnish the skeletons of the schwarzinicine and schwarzifiscusine alkaloids were proposed.
Phytochemical investigation of the leaves, bark and flowers of A. scholaris cultivated on the West Coast of Peninsular Malaysia provided a total of 17 alkaloids, of which five are new, namely, alstoscholactine (10), alstolaxepine (11), N-formylyunnanensine (12), scholaphylline (13), and alstobrogaline (19). Alstoscholactine (10), alstolaxepine (11), and alstobrogaline (19) were established to contain novel ring systems. Alstoscholactine (10) represents a rearranged stemmadenine alkaloid with an unprecedented C-6-C-19 connectivity, while alstolaxepine (11) represents a 6,7-seco-angustilobine B-type alkaloid incorporating a rare γ-lactone-bridged oxepane ring system. On the other hand, alstobrogaline (19) is an unusual monoterpenoid indole alkaloid incorporating a third N atom, and possessing an aldimine as well as a nitrone function. N-Formylyunnanensine (12) is the N-formyl derivative of the known alkaloid yunnanensine, and it was isolated as a pair of unseparable E/Z-formamide rotamers. Scholaphylline (13) represents the first member of the secostemmadenine-secovallesamine-type bisindole alkaloid. The 12 known alkaloids obtained from Alstonia scholaris are 19,20-E-vallesamine (14), 19,20-Z-vallesamine (15), 19,20-E-vallesamine N-oxide (16), 6,7-secoangustilobine B (17), and 6,7-seco-19,20-epoxyangustilobine B (18), tetrahydroalstonine (20), picrinine (21), 16R-19,20-Z-isositsirikine (22), 16R-19,20-E-isositsirikine (23), scholaricine (24), N-demethylalstogustine N-oxide (25), and E/Z-vallesiachotamine (26)
Peace and value education: a comparative understanding from Montessori and Freire
No full textAbstract: The thesis entitled ‘Peace and Value Education- A comparative understanding from Montessori and Freire’ is an effort in knowing the foundation of peace and value education via possible application of the ideas from Maria Montessori and Paulo Freire. The context of work is around the experience of the author while working with concepts and practices from ‘peace classes’ provided by the association- Education Globale et Développement asbl. These peace classes are the weekly activity sessions organized all through the year in various class groups mainly in primary schools from different provinces of French speaking region of Belgium. Those relevant concepts and practices from Montessori and Freire which directly or indirectly are either applied or have their potential for application is analyzed here. The beginning is made conceptualizing and understanding peace and value concepts, its education and requirement in present social context. Thereafter, Freire and Montessori are analyzed by presenting briefly their lives, explaining one of their books each and upon that their individual and later their complementary and shared comparative relevance towards peace and value education. This analysis is supplemented with relevant concept and practice examples from the organization of peace classes. The taken research question of ‘What is the foundation of the work of peace classes whose aim is to develop peaceful, morally developed individuals who are active promotors of peace in order to develop a peaceful, united and progressive world?’ Montessori and Freire are analyzed to see how their approaches can help us to answer this research question. Whether young people or adults from Montessori or Freire respectively, the central understanding gained in relevance and harmony with peace class objective is that- to progress people have to become the conscious subjects of their own development. Educators should themselves go through this conscious transformation in order to bring the same in their population. The question in relevance to peace classes is often the attitude of teacher or educator in the schools which is in disharmony with the objective and state of mind for peace classes and which requires being more positive thereby encouraging young people and adults in their conscious development. Peace within and without an individual and group are the twin facets of the same peace and value education objective. Cooperative learning approach is the suggested methodology in harmony and as a mean in best fulfilling this objective applying it both within and without the class-room context at individual and collective dimensions including family and community. A positive and encouraging attitude for young people and for educators towards themselves is found to be the key in arriving sufficiently fulfilling this goal.Master [120] en sciences de l'éducation, Université catholique de Louvain, 2016La diffusion de ce mémoire n'est pas autorisée par l'institutio
Alkaloids from Alstonia scholaris and Ficus schwarzii
No full textAlkaloids, which are the most studied secondary metabolites, are structurally diverse and well known for their biological activity. The aim of the present study is to perform phytochemical investigations on the alkaloidal composition of two selected plant species, namely, Ficus schwarzii (Moraceae) and Alstonia scholaris (Apocynaceae). (specimen from the West Coast of Peninsular Malaysia). The previously unexplored phytochemistry of F. schwarzii and the phytochemical variation of A. scholaris due to locality have motivated research into the two species collected from Peninsular Malaysia.
Phytochemical investigation of the leaves of F. schwarzii yielded nine novel alkaloids, namely, schwarzinicines A−G (1−7), and schwarzificusines A and B (8 and 9). The schwarzinicine alkaloids represent the first examples of 1,4 diarylbutanoid−phenethylamine conjugates, while schwarzificusines A and B (8 and 9) represent a pair of new diastereomeric 1-phenyl-3-aminotetralins that are structurally related to the schwarzinicines alkaloids. The structures of alkaloids 1–9 were elucidated by detailed analysis of their HRMS and NMR data. Plausible biogenetic pathways that furnish the skeletons of the schwarzinicine and schwarzifiscusine alkaloids were proposed.
Phytochemical investigation of the leaves, bark and flowers of A. scholaris cultivated on the West Coast of Peninsular Malaysia provided a total of 17 alkaloids, of which five are new, namely, alstoscholactine (10), alstolaxepine (11), N-formylyunnanensine (12), scholaphylline (13), and alstobrogaline (19). Alstoscholactine (10), alstolaxepine (11), and alstobrogaline (19) were established to contain novel ring systems. Alstoscholactine (10) represents a rearranged stemmadenine alkaloid with an unprecedented C-6-C-19 connectivity, while alstolaxepine (11) represents a 6,7-seco-angustilobine B-type alkaloid incorporating a rare γ-lactone-bridged oxepane ring system. On the other hand, alstobrogaline (19) is an unusual monoterpenoid indole alkaloid incorporating a third N atom, and possessing an aldimine as well as a nitrone function. N-Formylyunnanensine (12) is the N-formyl derivative of the known alkaloid yunnanensine, and it was isolated as a pair of unseparable E/Z-formamide rotamers. Scholaphylline (13) represents the first member of the secostemmadenine-secovallesamine-type bisindole alkaloid. The 12 known alkaloids obtained from Alstonia scholaris are 19,20-E-vallesamine (14), 19,20-Z-vallesamine (15), 19,20-E-vallesamine N-oxide (16), 6,7-secoangustilobine B (17), and 6,7-seco-19,20-epoxyangustilobine B (18), tetrahydroalstonine (20), picrinine (21), 16R-19,20-Z-isositsirikine (22), 16R-19,20-E-isositsirikine (23), scholaricine (24), N-demethylalstogustine N-oxide (25), and E/Z-vallesiachotamine (26)
Damage analysis of CF-PEKK composite during ultrasonic fatigue loading
No full textFiber architecture, matrix material as well as layup sequences have a strong influence on damage initiation and propagation. This is especially the case with High- (HCF) and Very- High Cycle Fatigue (VHCF) regimes where damage initiation and accumulation occurs at the weakest links with the highest stress concentration. Constant amplitude (CA) fatigue experiments under displacement control were performed on orthotropic laminates produced from 5-H satin fabric carbon fibers reinforced with PEKK polymer. Poly-Ether-Ketone-Ketone (PEKK) is a semi-crystalline thermoplastic polymer that belongs to the family of Polyketones. It has a glass transition temperature (Tg) of about 160 °C and melting temperature (Tm) of about 340 °C which makes it a suitable matrix material for applications requiring elevated service temperatures. Fatigue experiments were carried out with a pulse-pause sequence in the in-house developed ultrasonic three-point fatigue test system. A single-point laser vibrometer was used to measure the dynamic displacement during ultrasonic loading. Infra-red thermography was employed to capture the temperature evolution in the specimen surface during loading at locations where maximum shear stresses occur. Additionally, residual stiffness characterization and optical microscopy were performed by interrupting the tests at different stages of fatigue lives of specimens. Based on the results, the damage states and their influence on the residual stiffness of the specimen were analyzed
The lymphocyte as a cellular model to study insights into the pathophysiology of diabetes and its complications
No full textBlood cells from subjects with hypertension and/or diabetes mellitus have been successfully studied in the past to gain insight into pathological alterations of several signal transduction pathways. Diabetes mellitus is also considered to be a disease of abnormal cellular Ca2+ metabolism, as metabolic derangements of Ca2+ transport have been noticed both in the prediabetic state and as a consequence of hyperglycemia and oxidative stress. In this report, we used peripheral blood lymphocytes from type 2 diabetes patients and control subjects to study and delineate different mechanisms of Ca2+ turnover that determine the level of cytosolic calcium (Cai). While demonstrating the specific Ca2+ turnover alterations, we suggest that insights into the pathophysiology of diabetic complications originating from signal transduction defects could be conveniently studied using blood cell types such as lymphocytes and that such studies could lead to the identification of new molecular drug targets
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