The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform

Alistair J Gunn - One of the best experts on this subject based on the ideXlab platform.

  • randomized controlled trial of a car safety Seat Insert to reduce hypoxia in term infants
    Pediatrics, 2013
    Co-Authors: Christine G Mcintosh, Shirley L Tonkin, Alistair J Gunn
    Abstract:

    OBJECTIVE: To test the hypothesis that a foam plastic Insert that allows the infant head to rest in a neutral position in sleep may prevent obstruction of the upper airway and thus reduce episodes of reduced oxygenation in term infants in car Seats. METHODS: Healthy full-term babies were randomized to be studied during sleep while restrained in an infant car safety Seat either with or without the Insert, with continuous polysomnographic recordings with sleep video. RESULTS: Seventy-eight infants (39 in each group) had polysomnogram recordings at a mean of 8 days of age. Both groups showed a small fall in mean hemoglobin oxygen saturation (SpO2) over the first hour of sleep. There was no difference between Insert and no Insert in the rate of moderate desaturations (a fall in SpO2 ≥4% lasting for ≥10 seconds, mean ± SEM, 17.0 ± 1.5 vs 17.2 ± 1.5/hour), or mean SpO2 during sleep. The Insert was associated with a significant reduction in the rate of obstructive apnea (0.3 ± 0.1 vs 0.9 ± 1.5/hour, P < .03), the severity of desaturation events (minimum SpO2 82% ± 1% vs 74% ± 2%, P < .001), and time with SpO2 <85% (0.6% ± 0.3% vs 1.8% ± 1.4%, P = .03). CONCLUSIONS: In full-term newborn infants, a car Seat Insert that helps the head to lie in a neutral position was associated with reduced severity of desaturation events but not the overall rate of moderate desaturations. * Abbreviations: SpO2 — : hemoglobin oxygen saturation

  • Randomized Controlled Trial of a Car Safety Seat Insert to Reduce Hypoxia in Term Infants
    Pediatrics, 2013
    Co-Authors: Christine G Mcintosh, Shirley L Tonkin, Alistair J Gunn
    Abstract:

    OBJECTIVE: To test the hypothesis that a foam plastic Insert that allows the infant head to rest in a neutral position in sleep may prevent obstruction of the upper airway and thus reduce episodes of reduced oxygenation in term infants in car Seats. METHODS: Healthy full-term babies were randomized to be studied during sleep while restrained in an infant car safety Seat either with or without the Insert, with continuous polysomnographic recordings with sleep video. RESULTS: Seventy-eight infants (39 in each group) had polysomnogram recordings at a mean of 8 days of age. Both groups showed a small fall in mean hemoglobin oxygen saturation (SpO2) over the first hour of sleep. There was no difference between Insert and no Insert in the rate of moderate desaturations (a fall in SpO2 ≥4% lasting for ≥10 seconds, mean ± SEM, 17.0 ± 1.5 vs 17.2 ± 1.5/hour), or mean SpO2 during sleep. The Insert was associated with a significant reduction in the rate of obstructive apnea (0.3 ± 0.1 vs 0.9 ± 1.5/hour, P < .03), the severity of desaturation events (minimum SpO2 82% ± 1% vs 74% ± 2%, P < .001), and time with SpO2

  • Can we reduce episodes of haemoglobin desaturation in full-term babies restrained in car Seats?
    Acta Paediatrica, 2007
    Co-Authors: Shirley L Tonkin, Christine G Mcintosh, Gillian M. Nixon, Simon Rowley, Alistair J Gunn
    Abstract:

    Objectives: To determine whether episodes of haemoglobin oxygen (SpO2) desaturation in full-term infants restrained in car Seats can be reduced by a simple foam plastic infant car Seat Insert designed to push the body forward, with space for the protuberant occiput to lie behind the spine, and so reduce flexion of the infant's head on the trunk. Methods: Eighteen healthy full-term babies were evaluated while restrained in an infant car safety Seat with, and without, the foam Insert. Infants were monitored in each position for 30 min with continuous polygraphic recording of respiratory and heart rate, nasal airflow and SpO2. Results: Placement of the Insert in the car Seat was associated with a significant reduction in the rate of apneas with a fall in SpO2 >5% (median, interquartile range: 4.4 (0, 10.6) vs. 9.2 (5.4, 15.2) events per hour, p = 0.03). The one clinically severe episode of apnea, with a fall in SpO2 of more than 30%, occurred in the car Seat without the Insert. Conclusions: A car Seat Insert that allows the newborn's head to lie in a neutral position during sleep may reduce the frequency of mild episodes of reduced SpO2 in some full-term newborn babies.

  • simple car Seat Insert to prevent upper airway narrowing in preterm infants a pilot study
    Pediatrics, 2003
    Co-Authors: Shirley L Tonkin, Christine G Mcintosh, Simon Rowley, Wendy Hadden, Caroline Dakin, Alistair J Gunn
    Abstract:

    OBJECTIVES: To test prospectively the hypothesis that an infant car Seat modification to allow the infant's head to rest in a neutral position on the trunk would prevent narrowing of the upper airway and thus reduce oxygen desaturation in preterm infants who are restrained in car Seats. METHODS: Seventeen preterm infants who were approved for discharge were evaluated in a car Seat for newborns, with and without a foam Insert that provided a slot for the back of the infants' head. Respiration timed inspiratory radiographs for assessment of upper airway dimensions were taken during quiet sleep in each position. Infants were monitored in each position for 30 minutes with continuous polygraphic recording of respiratory, cardiac, and nasal airflow activity and pulse oximetry. RESULTS: Placement of the Insert in the car Seat was associated with a larger upper airway space (mean +/- standard deviation, 5.2 +/- 1.3 vs 3.6 +/- 1.4 mm). This radiologic improvement was associated with a significant reduction in the frequency of episodes of oxygen desaturation to <85% (1.5 +/- 2.1 vs 3.5 +/- 3.5 episodes/infant), of bradycardia <90 bpm (0.1 +/- 0.3 vs 1 +/- 1.7), and of arousal (median [25th, 75th], 2.5 [1.3, 4.0] vs 5.0 [4.0, 7.0]). CONCLUSIONS: The cause of oxygen desaturation in preterm infants who are restrained in car Seats is multifactorial. The present data strongly support the hypothesis that flexion of the head on the body is a significant contributor to these episodes and that the mechanism is posterocephalic displacement of the mandible, leading to narrowing of the upper airway. Critically, this pilot study demonstrates that the frequency of episodes of desaturation in a standard newborn car Seat can be substantially reduced by placement of a simple foam Insert that allows the infant to maintain the head in a neutral position on the trunk during sleep.

  • SIMPLE CAR Seat Insert TO PREVENT UPPER AIRWAY NARROWING IN PRETERM INFANTS: A PILOT STUDY
    Pediatrics, 2003
    Co-Authors: Shirley L Tonkin, Christine G Mcintosh, Simon Rowley, Wendy Hadden, Caroline Dakin, Alistair J Gunn
    Abstract:

    OBJECTIVES: To test prospectively the hypothesis that an infant car Seat modification to allow the infant's head to rest in a neutral position on the trunk would prevent narrowing of the upper airway and thus reduce oxygen desaturation in preterm infants who are restrained in car Seats. METHODS: Seventeen preterm infants who were approved for discharge were evaluated in a car Seat for newborns, with and without a foam Insert that provided a slot for the back of the infants' head. Respiration timed inspiratory radiographs for assessment of upper airway dimensions were taken during quiet sleep in each position. Infants were monitored in each position for 30 minutes with continuous polygraphic recording of respiratory, cardiac, and nasal airflow activity and pulse oximetry. RESULTS: Placement of the Insert in the car Seat was associated with a larger upper airway space (mean +/- standard deviation, 5.2 +/- 1.3 vs 3.6 +/- 1.4 mm). This radiologic improvement was associated with a significant reduction in the frequency of episodes of oxygen desaturation to

Krzysztof Siczek - One of the best experts on this subject based on the ideXlab platform.

  • THE RESEARCHES ON THE TRIBOLOGICAL PROPERTIES OF ELEMENTS OF THE Seat Insert-VALVE-VALVE GUIDE ASSEMBLY
    Journal of KONES, 2020
    Co-Authors: Krzysztof Siczek
    Abstract:

    The researches have been carried out, where the object has been the elements of valve trains in the different combustion engines. Those elements have been valve, valve guide and Seat Insert. The analysed valves have been driven by special camshaft, with the cams of trapezoid shape. The special research stand has been elaborated and its scheme has been presented in the article. The mentioned research stand has been driven by electric motor. The rotational velocity of the camshaft has been controlled and measured. The aim of the researches has been to obtain values of wear for valve, Seat Insert, valve guide vs. valve lift, and rpm of camshaft. The dynamic parameters have been analyzed for the Seat Insert – valve – valve guide assembly, experimentally and by simulation either. During researches the values of valve lift, of valve acceleration, of temperature for Seat Insert and additionally sound level have been measured. The wear of valve, Seat Insert and valve guide has been measured, basing on their initial and post-research geometry. The results of experimental researches obtained for different materials for valve, valve guide and Seat Insert have been presented in the article. The simulation model of the analyzed Seat Insert – valve – valve guide assembly has been elaborated and presented in the article. Such model has been needed to calculate the values of the settle velocity for the analyzed valve. The wear of titanium valve has been a little greater than of the steel valve, the wear of cast iron Seat Insert mating with steel valve has been much greater than for titanium valve case. The wear of valve guides, made of bronze has been several times less than those of cast iron.

  • Chapter 7 – Valve train tribology
    Tribological Processes in the Valvetrain Systems with Lightweight Valves, 2016
    Co-Authors: Krzysztof Siczek
    Abstract:

    In the chapter the term tribology was explained. It was discussed the tribological problems occurring in the guide-lightweight valve-Seat Insert subsystem. The basic concepts related to the friction were shown, including the dry, boundary, mixed and liquid friction and tribofilms. It was also presented guidelines for the design of the model for the guide-valve-Seat Insert assembly treated as a tribological system. It was created the model of friction in friction pairs the system including the valve head–oil–pollutant-Seat Insert subsystem and the valve stem–oil-pollutant-guide subsystem. Different models of friction and method of friction compensation were discussed. Also the wear process of friction pairs the mentioned system was analyzed and related model of wear was created.

  • Research on valve trains
    Tribological Processes in the Valvetrain Systems with Lightweight Valves, 2016
    Co-Authors: Krzysztof Siczek
    Abstract:

    This chapter presents testing methods and testers used during studies on the valve train and its components, friction, wear, and noise therein. It also discusses the computer simulation of friction and wear at the nodes valve–guide and valve–Seat Insert. The chapter analyzes the effect of the wear of components of the studied system on the sum of flows in the gap between the valve stem and guide and between the Seat faces of the valve and its Insert. The chapter also presents the simplified simulation algorithm for the analyzed system. In subsequent iterations, the geometrical and material parameters of the system components can be changed, which makes the model very flexible. On the basis of calculations carried out by this algorithm, a rough estimation of how much time is required for the repair of the Seat Insert–lightweight valve–guide system can be obtained.

  • Valve train kinetic effects
    Tribological Processes in the Valvetrain Systems with Lightweight Valves, 2016
    Co-Authors: Krzysztof Siczek
    Abstract:

    In the chapter was described the control cycle of valve motion, consisting of: Run-up Phase (elimination of valve clearance), Operating motion Phase, Run-down Phase (formation of valve clearance), Cut-off the drive Phase. It was also discussed operating conditions of the valve train components. Special attention was put on valve rotation and auxiliary rotation system used in modern engines. It was also analysed the effect of misalignment of Seat Insert relative to valve guide, forces loading elements of valve train, especially of the friction nature. Also it was discussed the role of stiffness of valve train, contact between cam and follower, cam profile, valve spring, lash adjusters and hydraulic chain tensioners. It was also discussed the friction phenomena in the nodes of the cam valve train with fixed phases. In the chapter it was presented the criteria for the tribological quality of the system. It was explained, that the optimum valve motion is possible if it is obtained the required values of quality indicators, including: filling of the area under the curve of valve lift, the extreme value of the positive geometric acceleration, an extreme negative acceleration, extreme geometric speed, the speed of valve settling, rhe radius of curvature of the cam track, determination of the angle ϕ1 of the maximum speed of the valve (modified Turkish and Derdinger criterion), the intensity ratio of vibrations generated by the cam extortion of drive motion throughout the cam.

  • Friction Resistance between Valve Made of TiAl Alloy and its Guide Made of Phosphor Bronze
    Applied Mechanics and Materials, 2013
    Co-Authors: Adam Rylski, Krzysztof Siczek
    Abstract:

    A lightweight valve is often made of TiAl alloys and its stem can be solid or hollow. Such valves can mate with guides made of cast iron or of phosphor bronze at different conditions in their contact zone valve/quide. The aim of the research was to measure the friction force in the sliding contact between the valve stem made of TiAl alloy and its guide made of phosphor bronze, in the absence of oil. The experiment was conducted at room temperature and in static air under normal pressure. The investigations were conducted with use of the tester, which is presented in this article. The loading of contact zone has varied periodically during series. The displacement and acceleration of valve and the force during its impact into Seat Insert have been measured during tests. Additionally the sound level has been measured, either. Tests have been provided for different frequency of driving force. Additionally, researches on the tribotester pin-on-disc, presented in the article, have been provided, with the pin made of Ti6Al4V alloy and the disc made of phosphor bronze. The model of research stand has been elaborated for the simulation of dynamics for the material sample rotating plate assembly. The aim of such researches has been to obtain values of coefficient of friction for such tribological pair and to simulate dynamics of the material sample rotating plate assembly, characteristic for used research stand. The obtained courses of coefficient of friction vs. loading, slide velocity, duration of motion of material sample in respect to the rotating plate have been presented in the article. On the base of simulation results the values of damping coefficient have been estimated, which allow to obtain the value for the amplitude of the modeled motion for the material sample in respect to the rotating plate near to the value of the amplitude for the real motion. Such estimation allows forecasting the dynamics of the mentioned assembly for other values of velocity and loading.

Shirley L Tonkin - One of the best experts on this subject based on the ideXlab platform.

  • randomized controlled trial of a car safety Seat Insert to reduce hypoxia in term infants
    Pediatrics, 2013
    Co-Authors: Christine G Mcintosh, Shirley L Tonkin, Alistair J Gunn
    Abstract:

    OBJECTIVE: To test the hypothesis that a foam plastic Insert that allows the infant head to rest in a neutral position in sleep may prevent obstruction of the upper airway and thus reduce episodes of reduced oxygenation in term infants in car Seats. METHODS: Healthy full-term babies were randomized to be studied during sleep while restrained in an infant car safety Seat either with or without the Insert, with continuous polysomnographic recordings with sleep video. RESULTS: Seventy-eight infants (39 in each group) had polysomnogram recordings at a mean of 8 days of age. Both groups showed a small fall in mean hemoglobin oxygen saturation (SpO2) over the first hour of sleep. There was no difference between Insert and no Insert in the rate of moderate desaturations (a fall in SpO2 ≥4% lasting for ≥10 seconds, mean ± SEM, 17.0 ± 1.5 vs 17.2 ± 1.5/hour), or mean SpO2 during sleep. The Insert was associated with a significant reduction in the rate of obstructive apnea (0.3 ± 0.1 vs 0.9 ± 1.5/hour, P < .03), the severity of desaturation events (minimum SpO2 82% ± 1% vs 74% ± 2%, P < .001), and time with SpO2 <85% (0.6% ± 0.3% vs 1.8% ± 1.4%, P = .03). CONCLUSIONS: In full-term newborn infants, a car Seat Insert that helps the head to lie in a neutral position was associated with reduced severity of desaturation events but not the overall rate of moderate desaturations. * Abbreviations: SpO2 — : hemoglobin oxygen saturation

  • Randomized Controlled Trial of a Car Safety Seat Insert to Reduce Hypoxia in Term Infants
    Pediatrics, 2013
    Co-Authors: Christine G Mcintosh, Shirley L Tonkin, Alistair J Gunn
    Abstract:

    OBJECTIVE: To test the hypothesis that a foam plastic Insert that allows the infant head to rest in a neutral position in sleep may prevent obstruction of the upper airway and thus reduce episodes of reduced oxygenation in term infants in car Seats. METHODS: Healthy full-term babies were randomized to be studied during sleep while restrained in an infant car safety Seat either with or without the Insert, with continuous polysomnographic recordings with sleep video. RESULTS: Seventy-eight infants (39 in each group) had polysomnogram recordings at a mean of 8 days of age. Both groups showed a small fall in mean hemoglobin oxygen saturation (SpO2) over the first hour of sleep. There was no difference between Insert and no Insert in the rate of moderate desaturations (a fall in SpO2 ≥4% lasting for ≥10 seconds, mean ± SEM, 17.0 ± 1.5 vs 17.2 ± 1.5/hour), or mean SpO2 during sleep. The Insert was associated with a significant reduction in the rate of obstructive apnea (0.3 ± 0.1 vs 0.9 ± 1.5/hour, P < .03), the severity of desaturation events (minimum SpO2 82% ± 1% vs 74% ± 2%, P < .001), and time with SpO2

  • Can we reduce episodes of haemoglobin desaturation in full-term babies restrained in car Seats?
    Acta Paediatrica, 2007
    Co-Authors: Shirley L Tonkin, Christine G Mcintosh, Gillian M. Nixon, Simon Rowley, Alistair J Gunn
    Abstract:

    Objectives: To determine whether episodes of haemoglobin oxygen (SpO2) desaturation in full-term infants restrained in car Seats can be reduced by a simple foam plastic infant car Seat Insert designed to push the body forward, with space for the protuberant occiput to lie behind the spine, and so reduce flexion of the infant's head on the trunk. Methods: Eighteen healthy full-term babies were evaluated while restrained in an infant car safety Seat with, and without, the foam Insert. Infants were monitored in each position for 30 min with continuous polygraphic recording of respiratory and heart rate, nasal airflow and SpO2. Results: Placement of the Insert in the car Seat was associated with a significant reduction in the rate of apneas with a fall in SpO2 >5% (median, interquartile range: 4.4 (0, 10.6) vs. 9.2 (5.4, 15.2) events per hour, p = 0.03). The one clinically severe episode of apnea, with a fall in SpO2 of more than 30%, occurred in the car Seat without the Insert. Conclusions: A car Seat Insert that allows the newborn's head to lie in a neutral position during sleep may reduce the frequency of mild episodes of reduced SpO2 in some full-term newborn babies.

  • simple car Seat Insert to prevent upper airway narrowing in preterm infants a pilot study
    Pediatrics, 2003
    Co-Authors: Shirley L Tonkin, Christine G Mcintosh, Simon Rowley, Wendy Hadden, Caroline Dakin, Alistair J Gunn
    Abstract:

    OBJECTIVES: To test prospectively the hypothesis that an infant car Seat modification to allow the infant's head to rest in a neutral position on the trunk would prevent narrowing of the upper airway and thus reduce oxygen desaturation in preterm infants who are restrained in car Seats. METHODS: Seventeen preterm infants who were approved for discharge were evaluated in a car Seat for newborns, with and without a foam Insert that provided a slot for the back of the infants' head. Respiration timed inspiratory radiographs for assessment of upper airway dimensions were taken during quiet sleep in each position. Infants were monitored in each position for 30 minutes with continuous polygraphic recording of respiratory, cardiac, and nasal airflow activity and pulse oximetry. RESULTS: Placement of the Insert in the car Seat was associated with a larger upper airway space (mean +/- standard deviation, 5.2 +/- 1.3 vs 3.6 +/- 1.4 mm). This radiologic improvement was associated with a significant reduction in the frequency of episodes of oxygen desaturation to <85% (1.5 +/- 2.1 vs 3.5 +/- 3.5 episodes/infant), of bradycardia <90 bpm (0.1 +/- 0.3 vs 1 +/- 1.7), and of arousal (median [25th, 75th], 2.5 [1.3, 4.0] vs 5.0 [4.0, 7.0]). CONCLUSIONS: The cause of oxygen desaturation in preterm infants who are restrained in car Seats is multifactorial. The present data strongly support the hypothesis that flexion of the head on the body is a significant contributor to these episodes and that the mechanism is posterocephalic displacement of the mandible, leading to narrowing of the upper airway. Critically, this pilot study demonstrates that the frequency of episodes of desaturation in a standard newborn car Seat can be substantially reduced by placement of a simple foam Insert that allows the infant to maintain the head in a neutral position on the trunk during sleep.

  • SIMPLE CAR Seat Insert TO PREVENT UPPER AIRWAY NARROWING IN PRETERM INFANTS: A PILOT STUDY
    Pediatrics, 2003
    Co-Authors: Shirley L Tonkin, Christine G Mcintosh, Simon Rowley, Wendy Hadden, Caroline Dakin, Alistair J Gunn
    Abstract:

    OBJECTIVES: To test prospectively the hypothesis that an infant car Seat modification to allow the infant's head to rest in a neutral position on the trunk would prevent narrowing of the upper airway and thus reduce oxygen desaturation in preterm infants who are restrained in car Seats. METHODS: Seventeen preterm infants who were approved for discharge were evaluated in a car Seat for newborns, with and without a foam Insert that provided a slot for the back of the infants' head. Respiration timed inspiratory radiographs for assessment of upper airway dimensions were taken during quiet sleep in each position. Infants were monitored in each position for 30 minutes with continuous polygraphic recording of respiratory, cardiac, and nasal airflow activity and pulse oximetry. RESULTS: Placement of the Insert in the car Seat was associated with a larger upper airway space (mean +/- standard deviation, 5.2 +/- 1.3 vs 3.6 +/- 1.4 mm). This radiologic improvement was associated with a significant reduction in the frequency of episodes of oxygen desaturation to

Jaesoo Hong - One of the best experts on this subject based on the ideXlab platform.

  • Study on exhaust valve and Seat Insert wear depending on fuel type
    International Journal of Precision Engineering and Manufacturing, 2012
    Co-Authors: Jaesoo Hong, Keyoungjin Chun
    Abstract:

    This study used a dedicated wear tester to verify the cause and amount of wear depending on fuel type such as LPG and gasoline. Test conditions for general commercial vehicles, such as number of cycles (2 × 10 6 ), test speed (25Hz), temperature (350°C), and force (1960N) were applied to the specimens. This study utilized LPG and gasoline as test fuels. The maximum depth of wear (Dmax) of the exhaust valve and the Seat Insert was 74.7 (± 3.9)μm and 82.9 (± 2.9)μm, respectively, in the case of the test using LPG, and 64.6 (± 4.0)μm and 59.4 (± 1.2)μm, respectively, in the case of the test using gasoline. The result of the analysis performed on the compositions of the combustion products appearing on the exhaust valve and the Seat Insert using EDS (Energy Dispersive Spectroscopy) indicated that, in the case of the test performed with LPG, O and S were detected from the test specimen, and that in the case of the test specimen performed with gasoline, O, P, and Ca were detected from the test specimen. The analysis results from the composition of the Seating faces indicated that the Seating face of the exhaust valve had Cu and Mo existing only in the Seat Insert regardless of the type of fuel used. In addition, Si and Mn, which existed only in the exhaust valve, were detected in the Seating face of the Seat Insert. The mean Dmax of the exhaust valve and the Seat Insert, for which the test was performed with LPG fuel, was greater than that of the exhaust valve and the Seat Insert for which the test was performed with gasoline fuel, 14.5% and 29.4%, respectively. The adhesive wear and tribochemical reaction products were observed regardless as to whether the fuel type was LPG or gasoline. However, the abrasive wear was observed only at the Seating face of the Seat Insert for which the test was performed with LPG fuel. From the analysis performed based on the above results, it is thought that since LPG fuel has less combustion products that act as a gum component that lubricates the valve and the Seat Insert Seating faces than gasoline fuel. The direct metal-to-metal collision between the valve and the Seat Insert Seating faces may generate more particles with LPG fuel. Therefore, The abrasive wear was observed only in the specimen for the test performed with LPG fuel, however it was not observed in the specimen for the test performed with gasoline fuel.

  • a study of wear and matching of diesel engine exhaust valve and Seat Insert depending on valve materials
    Journal of the Korean Society for Precision Engineering, 2008
    Co-Authors: Keyoungjin Chun, Jaesoo Hong, Dongteak Chung
    Abstract:

    The wear on engine valve and Seat Insert is one of the most important factors affecting engine performance. The engine valve and Seat Insert must be able to withstand the severe environment that is created by: high temperature exhaust gases generated while the engine is running, rapid movement of the valve spring, high pressure generated in the explosive process. In order to study such problems, a simulator has been developed to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and Seat Insert wear process with various speeds during engine activity. This work focused on the test of various degrees of wear on four different exhaust valve materials such as HRV40, HRV40-FNV (face nitrided valve), STL #32, STL #6,. Throughout all tests performed in this study, the outer surface temperature of the Seat Insert was controlled at , the cycle number was , the test load was 6860 N, the fuel was LPG the test speed was 20 Hz (2400 RPM) and the Seat Insert material was HVS1-2. The mean (standard deviation) maximum roughness of the exhaust valve and Seat Insert was and at the HRV40, and at the HRV40-FNV, and at the STL #32, and at the STL #6, respectively. It was discovered that the maximum roughness of exhaust valve was lower as the high temperature hardness of the valve material was higher under the same test conditions such as temperature, test speed, cycle number, test load and Seat Insert material. The set of the HRV40-FNV exhaust valve and the HVS1-2 Seat Insert showed the best wear resistance.

  • a study of exhaust valve and Seat Insert wear depending on cycle numbers
    Wear, 2007
    Co-Authors: Keyoungjin Chun, Jaesoo Hong
    Abstract:

    Abstract This study investigated the wear of the Seating faces of the exhaust valve and Seat Insert that have influence on an engine's performance depending on mileage (cycle numbers). Exhaust valves and Seat Inserts that are commonly used for commercial vehicles were used as test specimens. The cycle numbers for tests were 2 × 10 6 , 4 × 10 6 , 6 × 10 6 and 8 × 10 6 , and the test speeds were 10 and 25 Hz. All other parameters such as temperature (350 °C), fuel (LPG) and load (1960 N) were fixed. The 10 Hz tests indicated that the average maximum roughness (Rmax) of the valve increased at the rate of 7.76 μm/10 6 cycles starting from 29.42 μm at the 2 × 10 6 cycles, and that the average Rmax of the Seat Insert increased at the rate of 8.57 μm/10 6 cycles starting from 34.19 μm at the 2 × 10 6 cycles. The 25 Hz tests indicated that the average Rmax of the valve increased at the rate of 1.58 μm/10 6 cycles starting from 74.2 μm at the 2 × 10 6 cycles, and that the average Rmax of the Seat Insert increased at the rate of 1.25 μm/10 6 cycles starting from 83.95 μm at the 2 × 10 6 cycles. The tribochemical reaction product covered the base metals of the valve and Seat Insert, preventing the wear of the base metals, and included O, V, S and Al, which are the compositions of the two base metals. The tribochemical reaction product observed on the valve had cracks, and it was also noticed that the Seat Inserts were laid one upon another. As cycle numbers became greater, the Rmax of the Seating faces of the valve and Seat Insert also increased, and the wear rate rose significantly depending on the Hz (RPM). The wear mechanism of the valve and Seat Insert was investigated through the tribochemical reaction.

  • Comparison of the wear exerted on engine valves and Seat Inserts under various speeds and mileages
    Proceedings of the Institution of Mechanical Engineers Part D: Journal of Automobile Engineering, 2006
    Co-Authors: Keyoungjin Chun, Jaesoo Hong
    Abstract:

    Under actual engine driving conditions, there is a possibility of engine valve and Seat Insert wear occurring as a result of various speed changes and accumulation of mileage. It is therefore necessary to examine the wear-related problems of engine valves and Seat Inserts and to determine by comparison whether speed or mileage inflicts the greater wear. This work focuses on the various degrees of wear produced at three different singular test speeds (10 Hz, 25 Hz, and multi-Hz) and two different cycle numbers (2.1 x 10 6 and 6.0 x 10 6 ). Throughout all tests performed in this study, the temperature of the outer surface of the Seat Insert was controlled at 350 °C and the test load was 1960 N. Wear depths were measured using a confocal laser microscope, and wear mechanisms were observed using a scanning electron microscope. The extent of wear produced at higher speeds (25 Hz) was found to be greater than that produced at lower speeds (10 Hz) under identical test conditions (temperature, valve displacement, cycle number, and test load). Although test cycle numbers were increased by a factor of 3, for example from 2.1 x 10 6 to 6.0 x 10 6 , the wear depths were not proportionally increased. Wear occurred rapidly during the initial stages of the test and wear depths increased less significantly with each cycle number. Wear depth of the 2.1 x 10 6 cycle number test at 25 Hz was much larger than that of the 6.0 x 10 6 cycle number test at 10 Hz in both the valve and the Seat Insert. Therefore, this result indicates that speed (Hz) might have a greater effect than mileage (cycle number) on the valve and Seat Insert while the engine is running. As the cycle number was increased, the wear depth at multi-Hz showed a tendency to near the wear depth at 25 Hz (high speed) rather than that at 10 Hz (low speed). Adhesive wear and shear strain were observed in the wear mechanisms of the valves. Furthermore, adhesive wear and surface fatigue wear were observed in the wear mechanisms of the Seat Inserts.

  • A study on wear and wear mechanism of exhaust valve and Seat Insert depending on different speeds using a simulator
    Journal of Mechanical Science and Technology, 2006
    Co-Authors: Jaesoo Hong, Keyoungjin Chun, Young Han Youn
    Abstract:

    The wear of engine valve and Seat Insert is one of the most important factors which affect engine performance. Because of higher demands on performance and the increasing use of alternative fuel, engine valve and Seat Insert are challenged with greater wear problems than in the past. In order to solve the above problems, a simulator was developed to be able to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and Seat Insert wear process with various speeds during engine activity. This work focuses on the different degrees of wear at three different singular test speeds (10 Hz, 25 Hz & multi-Hz). For this study, the temperature of the outer surface of the Seat Insert was controlled at 350°C, and the test load was 1960 N. The test cycle number was 6.0×10^6. The mean (±standard error) wear depth of the valve at 10 Hz and 25 Hz was 45.1 (±3.7)μm and 81.7 (±2.5)μm, respectively. The mean wear depth of the Seat Insert at 10 Hz and 25 Hz was 52.7 (±3.9) μm and 91.2 (±2.7) μm, respectively. In the case of multi-Hz it was 70.7 (±2.4)/on and 77.4 (±3.8) μm, respectively. It was found that higher speed (25 Hz) cause a greater degree of wear than lower speed (10 Hz) under identical test condition (temperature, valve displacement, cycle number and test load). In the wear mechanisms of valves, adhesive wear, shear strain and abrasive wear could be observed. Also, in the wear mechanisms of Seat Inserts, adhesive wear, surface fatigue wear and abrasive wear could be observed.

Christine G Mcintosh - One of the best experts on this subject based on the ideXlab platform.

  • randomized controlled trial of a car safety Seat Insert to reduce hypoxia in term infants
    Pediatrics, 2013
    Co-Authors: Christine G Mcintosh, Shirley L Tonkin, Alistair J Gunn
    Abstract:

    OBJECTIVE: To test the hypothesis that a foam plastic Insert that allows the infant head to rest in a neutral position in sleep may prevent obstruction of the upper airway and thus reduce episodes of reduced oxygenation in term infants in car Seats. METHODS: Healthy full-term babies were randomized to be studied during sleep while restrained in an infant car safety Seat either with or without the Insert, with continuous polysomnographic recordings with sleep video. RESULTS: Seventy-eight infants (39 in each group) had polysomnogram recordings at a mean of 8 days of age. Both groups showed a small fall in mean hemoglobin oxygen saturation (SpO2) over the first hour of sleep. There was no difference between Insert and no Insert in the rate of moderate desaturations (a fall in SpO2 ≥4% lasting for ≥10 seconds, mean ± SEM, 17.0 ± 1.5 vs 17.2 ± 1.5/hour), or mean SpO2 during sleep. The Insert was associated with a significant reduction in the rate of obstructive apnea (0.3 ± 0.1 vs 0.9 ± 1.5/hour, P < .03), the severity of desaturation events (minimum SpO2 82% ± 1% vs 74% ± 2%, P < .001), and time with SpO2 <85% (0.6% ± 0.3% vs 1.8% ± 1.4%, P = .03). CONCLUSIONS: In full-term newborn infants, a car Seat Insert that helps the head to lie in a neutral position was associated with reduced severity of desaturation events but not the overall rate of moderate desaturations. * Abbreviations: SpO2 — : hemoglobin oxygen saturation

  • Randomized Controlled Trial of a Car Safety Seat Insert to Reduce Hypoxia in Term Infants
    Pediatrics, 2013
    Co-Authors: Christine G Mcintosh, Shirley L Tonkin, Alistair J Gunn
    Abstract:

    OBJECTIVE: To test the hypothesis that a foam plastic Insert that allows the infant head to rest in a neutral position in sleep may prevent obstruction of the upper airway and thus reduce episodes of reduced oxygenation in term infants in car Seats. METHODS: Healthy full-term babies were randomized to be studied during sleep while restrained in an infant car safety Seat either with or without the Insert, with continuous polysomnographic recordings with sleep video. RESULTS: Seventy-eight infants (39 in each group) had polysomnogram recordings at a mean of 8 days of age. Both groups showed a small fall in mean hemoglobin oxygen saturation (SpO2) over the first hour of sleep. There was no difference between Insert and no Insert in the rate of moderate desaturations (a fall in SpO2 ≥4% lasting for ≥10 seconds, mean ± SEM, 17.0 ± 1.5 vs 17.2 ± 1.5/hour), or mean SpO2 during sleep. The Insert was associated with a significant reduction in the rate of obstructive apnea (0.3 ± 0.1 vs 0.9 ± 1.5/hour, P < .03), the severity of desaturation events (minimum SpO2 82% ± 1% vs 74% ± 2%, P < .001), and time with SpO2

  • Can we reduce episodes of haemoglobin desaturation in full-term babies restrained in car Seats?
    Acta Paediatrica, 2007
    Co-Authors: Shirley L Tonkin, Christine G Mcintosh, Gillian M. Nixon, Simon Rowley, Alistair J Gunn
    Abstract:

    Objectives: To determine whether episodes of haemoglobin oxygen (SpO2) desaturation in full-term infants restrained in car Seats can be reduced by a simple foam plastic infant car Seat Insert designed to push the body forward, with space for the protuberant occiput to lie behind the spine, and so reduce flexion of the infant's head on the trunk. Methods: Eighteen healthy full-term babies were evaluated while restrained in an infant car safety Seat with, and without, the foam Insert. Infants were monitored in each position for 30 min with continuous polygraphic recording of respiratory and heart rate, nasal airflow and SpO2. Results: Placement of the Insert in the car Seat was associated with a significant reduction in the rate of apneas with a fall in SpO2 >5% (median, interquartile range: 4.4 (0, 10.6) vs. 9.2 (5.4, 15.2) events per hour, p = 0.03). The one clinically severe episode of apnea, with a fall in SpO2 of more than 30%, occurred in the car Seat without the Insert. Conclusions: A car Seat Insert that allows the newborn's head to lie in a neutral position during sleep may reduce the frequency of mild episodes of reduced SpO2 in some full-term newborn babies.

  • simple car Seat Insert to prevent upper airway narrowing in preterm infants a pilot study
    Pediatrics, 2003
    Co-Authors: Shirley L Tonkin, Christine G Mcintosh, Simon Rowley, Wendy Hadden, Caroline Dakin, Alistair J Gunn
    Abstract:

    OBJECTIVES: To test prospectively the hypothesis that an infant car Seat modification to allow the infant's head to rest in a neutral position on the trunk would prevent narrowing of the upper airway and thus reduce oxygen desaturation in preterm infants who are restrained in car Seats. METHODS: Seventeen preterm infants who were approved for discharge were evaluated in a car Seat for newborns, with and without a foam Insert that provided a slot for the back of the infants' head. Respiration timed inspiratory radiographs for assessment of upper airway dimensions were taken during quiet sleep in each position. Infants were monitored in each position for 30 minutes with continuous polygraphic recording of respiratory, cardiac, and nasal airflow activity and pulse oximetry. RESULTS: Placement of the Insert in the car Seat was associated with a larger upper airway space (mean +/- standard deviation, 5.2 +/- 1.3 vs 3.6 +/- 1.4 mm). This radiologic improvement was associated with a significant reduction in the frequency of episodes of oxygen desaturation to <85% (1.5 +/- 2.1 vs 3.5 +/- 3.5 episodes/infant), of bradycardia <90 bpm (0.1 +/- 0.3 vs 1 +/- 1.7), and of arousal (median [25th, 75th], 2.5 [1.3, 4.0] vs 5.0 [4.0, 7.0]). CONCLUSIONS: The cause of oxygen desaturation in preterm infants who are restrained in car Seats is multifactorial. The present data strongly support the hypothesis that flexion of the head on the body is a significant contributor to these episodes and that the mechanism is posterocephalic displacement of the mandible, leading to narrowing of the upper airway. Critically, this pilot study demonstrates that the frequency of episodes of desaturation in a standard newborn car Seat can be substantially reduced by placement of a simple foam Insert that allows the infant to maintain the head in a neutral position on the trunk during sleep.

  • SIMPLE CAR Seat Insert TO PREVENT UPPER AIRWAY NARROWING IN PRETERM INFANTS: A PILOT STUDY
    Pediatrics, 2003
    Co-Authors: Shirley L Tonkin, Christine G Mcintosh, Simon Rowley, Wendy Hadden, Caroline Dakin, Alistair J Gunn
    Abstract:

    OBJECTIVES: To test prospectively the hypothesis that an infant car Seat modification to allow the infant's head to rest in a neutral position on the trunk would prevent narrowing of the upper airway and thus reduce oxygen desaturation in preterm infants who are restrained in car Seats. METHODS: Seventeen preterm infants who were approved for discharge were evaluated in a car Seat for newborns, with and without a foam Insert that provided a slot for the back of the infants' head. Respiration timed inspiratory radiographs for assessment of upper airway dimensions were taken during quiet sleep in each position. Infants were monitored in each position for 30 minutes with continuous polygraphic recording of respiratory, cardiac, and nasal airflow activity and pulse oximetry. RESULTS: Placement of the Insert in the car Seat was associated with a larger upper airway space (mean +/- standard deviation, 5.2 +/- 1.3 vs 3.6 +/- 1.4 mm). This radiologic improvement was associated with a significant reduction in the frequency of episodes of oxygen desaturation to