Valve recession: From experiment to predictive model

Increasing demands on engine performance and cost reductions have meant that advances made in materials and production technology are often outpaced This frequently results in wear problems occurring with engine components. Few models exist for predicting wear, and consequently each wear problem has to be investigated, the cause isolated and remedial action taken. The objective of this work was to carry out experimental studies to investigate valve and seat insert wear mechanisms and use the test results to develop a recession prediction tool to assess the potential for valve recession and solve problems that occur more quickly. Experimental apparatus has been developed that is capable of providing a valid simulation of the wear of diesel automotive inlet valves and seats. Test methodologies developed have isolated the effects of impact and sliding. A semi-empirical wear model for predicting valve recession has been developed based on data gathered during the bench testing. A software program, RECESS, was developed to run the model. Model predictions are compared with engine dynamometer tests and bench tests. The model can be used to give a quantitative prediction of the valve recession to be expected with a particular material pair or a qualitative assessment of how parameters need to be altered in order to reduce recession. The valve recession model can be integrated into an industrial environment in order to help reduce costs and timescales involved in solving valve/seat wear problems

Friction and wear response of vegetable oils and their blends with mineral engine oil in a reciprocating sliding contact at severe contact conditions

Although many studies investigating the tribological performance of pure vegetable oils have been conducted, a better understanding of vegetable oil tribological performance at extreme conditions is still needed. Similarly, little work has been carried out to study the influence of the vegetable oils on the performance of a lubricant formed from a blend of vegetable oil and conventional mineral engine oil. This work presents the tribological performance of vegetable oils, and their blends with mineral oil, in a high temperature and contact pressure reciprocating contact. Palm and soybean based vegetable oils were mixed with a commercial mineral engine oil at a 1:1 ratio by volume. The conventional mineral oil was also tested to provide a benchmark. The pure palm oil exhibited lower friction than soybean oil, but for wear performance, this was reversed. The friction performance of the palm oil was competitive to that of the mineral engine oil. The mineral engine oil was far superior in wear resistance over both vegetable oils. When blended with mineral engine oil both vegetable oils demonstrated a reduction in coefficient of friction when compared to their pure oil states. An improvement in wear performance was observed for both a blend of palm oil and mineral engine oil (25% improvement) and that of soybean and mineral engine oil (27% improvement). This work shows that for palm oil and soybean oil, the performance of a blended oil is influenced by its vegetable oil component and that tribological characteristics of vegetable oils are dominant. That said, the significant limitation of these vegetable oils is their ability to provide a satisfactory level of wear resistance. It is suggested that any future work in this area should have a greater emphasis on the enhancement of wear resistance

Friction and wear response of vegetable oils and their blends with mineral engine oil in a reciprocating sliding contact at severe contact conditions

Although many studies investigating the tribological performance of pure vegetable oils have been conducted, a better understanding of vegetable oil tribological performance at extreme conditions is still needed. Similarly, little work has been carried out to study the influence of the vegetable oils on the performance of a lubricant formed from a blend of vegetable oil and conventional mineral engine oil. This work presents the tribological performance of vegetable oils, and their blends with mineral oil, in a high temperature and contact pressure reciprocating contact. Palm and soybean based vegetable oils were mixed with a commercial mineral engine oil at a 1:1 ratio by volume. The conventional mineral oil was also tested to provide a benchmark. The pure palm oil exhibited lower friction than soybean oil, but for wear performance, this was reversed. The friction performance of the palm oil was competitive to that of the mineral engine oil. The mineral engine oil was far superior in wear resistance over both vegetable oils. When blended with mineral engine oil both vegetable oils demonstrated a reduction in coefficient of friction when compared to their pure oil states. An improvement in wear performance was observed for both a blend of palm oil and mineral engine oil (25% improvement) and that of soybean and mineral engine oil (27% improvement). This work shows that for palm oil and soybean oil, the performance of a blended oil is influenced by its vegetable oil component and that tribological characteristics of vegetable oils are dominant. That said, the significant limitation of these vegetable oils is their ability to provide a satisfactory level of wear resistance. It is suggested that any future work in this area should have a greater emphasis on the enhancement of wear resistance

Hematopoietic Stem Cell Transplantation for Primary Immunodeficiencies

The field of primary immunodeficiencies has pioneered many of the advances in haematopoietic stem cell transplantation and cellular therapies over the last 50 years. The first patients to demonstrate sustained benefit and prolonged cure from the primary genetic defect following allogeneic haematopoietic stem cell transplantation were patients with primary immunodeficiencies. Although primary immunodeficiency patients began the modern era of haematopoietic stem cell transplantation, the history is nevertheless short-in answer to the question "what is the long term outcome of patients transplanted for primary immunodeficiencies?" we often have to say that we do not know. We believe that most patients who undergo haematopoietic stem cell transplantation for primary immunodeficiencies should live a normal lifespan with a fully corrected immune system. We are now beginning to understanding long term outcomes, the relationship to the underlying genetic defect, age, and pre-morbid condition of the patient at time of transplantation, stem cell source and donor, and effect of pre-transplant cytoreductive chemotherapy conditioning. The long term consequences of post-transplant complications such as graft vs. host disease, veno-occlusive disease, or immune dysregulation are also being recognized. Additionally, some genetic defects have a systemic distribution, and we are learning the natural history of these defects once the immunodeficiency has been removed

Too much of a good thing: a review of primary immune regulatory disorders

Primary immune regulatory disorders (PIRDs) are inborn errors of immunity caused by a loss in the regulatory mechanism of the inflammatory or immune response, leading to impaired immunological tolerance or an exuberant inflammatory response to various stimuli due to loss or gain of function mutations. Whilst PIRDs may feature susceptibility to recurrent, severe, or opportunistic infection in their phenotype, this group of syndromes has broadened the spectrum of disease caused by defects in immunity-related genes to include autoimmunity, autoinflammation, lymphoproliferation, malignancy, and allergy; increasing focus on PIRDs has thus redefined the classical ‘primary immunodeficiency’ as one aspect of an overarching group of inborn errors of immunity. The growing number of genetic defects associated with PIRDs has expanded our understanding of immune tolerance mechanisms and prompted identification of molecular targets for therapy. However, PIRDs remain difficult to recognize due to incomplete penetrance of their diverse phenotype, which may cross organ systems and present to multiple clinical specialists prior to review by an immunologist. Control of immune dysregulation with immunosuppressive therapies must be balanced against the enhanced infective risk posed by the underlying defect and accumulated end-organ damage, posing a challenge to clinicians. Whilst allogeneic hematopoietic stem cell transplantation may correct the underlying immune defect, identification of appropriate patients and timing of transplant is difficult. The relatively recent description of many PIRDs and rarity of individual genetic entities that comprise this group means data on natural history, clinical progression, and treatment are limited, and so international collaboration will be needed to better delineate phenotypes and the impact of existing and potential therapies. This review explores pathophysiology, clinical features, current therapeutic strategies for PIRDs including cellular platforms, and future directions for research

The effectiveness of chalk as a friction modifier for finger pad contact with rocks of varying roughness

The application of chalk (magnesium carbonate) in rock climbing is common practice as climbers attempt to improve their grip by removing moisture from their hands with the aim of increasing friction at the finger pad-rock interface. This novel work investigated the effectiveness of chalk as a friction modifier on four different rocks (sandstone, granite, dark limestone, and light limestone) typically found in areas of the U.K. where the sport of climbing is undertaken, with varying surface roughness. The static coefficient of friction was measured for dry and wet fingertip conditions with and without chalk, under normal (“grip”) forces of 5 N, 10 N and 15 N. Results showed that the effectiveness of chalk as a friction modifier is dependent on a number of factors such as moisture level and the gradient of the asperity at the rock surface, however, in general chalk applied to dry fingertips had a more positive effect on the static coefficient of friction than in simulated sweaty conditions. During lab tests, chalk was also seen to be beneficial by making the static coefficient of friction more consistent across most test conditions. The results of this study, and the explanation of friction mechanisms involved, provides guidance for the use of chalk with consideration of the type of rock which is being climbed

Learning tethered perching for aerial robots

Aerial robots have a wide range of applications, such as collecting data in hard-to-reach areas. This requires the longest possible operation time. However, because currently available commercial batteries have limited specific energy of roughly 300 W h kg -1 , a drone's flight time is a bottleneck for sustainable long-term data collection. Inspired by birds in nature, a possible approach to tackle this challenge is to perch drones on trees, and environmental or man-made structures, to save energy whilst in operation. In this paper, we propose an algorithm to automatically generate trajectories for a drone to perch on a tree branch, using the proposed tethered perching mechanism with a pendulum-like structure. This enables a drone to perform an energy-optimised, controlled 180° flip to safely disarm upside down. To fine-tune a set of reachable trajectories, a soft actor critic-based reinforcement algorithm is used. Our experimental results show the feasibility of the set of trajectories with successful perching. Our findings demonstrate that the proposed approach enables energy-efficient landing for long-term data collection tasks