Nominal Roll Research Articles

Contributory Pension Scheme and Performance of Employee of Unity Schools in South East Nigeria (2005-2019)

This paper critically examines the implementation of the contributory pension scheme in Unity Schools in the south east of Nigeria. The specific objectives were: to determine the extent of implementation of the contributory pension scheme; how it has helped in motivating staff and the challenges confronting the implementation of the scheme in Unity Schools in the South East. Population of the study was 1,091 based on the nominal rolls of the five schools in Enugu and Anambra States. The Sample Size of 293 was determined using the Taro Yamane’s statistical formula of 1964. Three hypotheses were formulated and tested using t-test statistics. Findings of the study revealed that: Contributory Pension Scheme has been fully implemented in Unity Schools; Contributory Pension Scheme has no significant effect on the motivation of workers for efficiency in the discharge of their duties and that Federal Government inconsistency in prompt remittance of its share of the contributions and it’s borrowing from the fund for infrastructural development among others constitute challenges to the implementation of the scheme. Based on the findings, the study recommended that: the Pension Reform Act be further amended to include the payment of gratuity; increase employers contributions from ten percent (10%) to fifteen percent (l5%), and the removal of the 16years limit on pension. The Contributory Pension Scheme is a welcome idea which when properly implemented will eradicate the pensioners’ harsh lives thereby making their dream a reality.

Analysis and remedies for factors responsible for time between overhaul: a case study of Do-228 aircraft starter generator

The starter generator is used for cranking the engine and to produce electricity for the aircraft system after a sustainable speed. A review of relevant literature reveals the time between the overhaul of the Do-228 aircraft starter generator but did not go in-depth to unravel the factors responsible. A survey research method is adopted to elicit information on the factors. Raosoft sample technique calculator: a software that primarily calculates or generates the sample size of a research or survey was used to obtain the minimum sample size from the study population with the nominal rolls of the technicians as the sampling frame. The questionnaire was vetted and validated by a professional focus group discussion team. The result shows that the factors responsible for the time between overhaul of the starter generator are Environmental Factors (10%), Mechanical Factors (20%), Poor Maintenance Factors (17%), Time Due (25%), Usage/Life Cycle (16%) and Aging (12%). 75% overhaul is unscheduled. It is recommended that the overhauling of the aircraft starter generators be done at 900 as against 1000 flight hour intervals to mitigate unscheduled maintenance.

Influence of process layouts of multi-roll solid-liquid cast-rolling bonding process on circumferential performance uniformity during fabricating metal cladding materials

The twin-roll casting (TRC) process is typically used to fabricate laminated metal cladding strips with rectangular cross-sections, and it has the advantages of short flow, low energy consumption, green environmental protection, etc. Recently, a twin-roll solid-liquid cast-rolling bonding (TRSLCRB) process was proposed based on the TRC process to fabricate metal cladding materials with round cross-sections. However, the nonuniformity of heat transfer and mass transfer along the circumferential direction finally influences the performance uniformity. Therefore, a multi-roll solid-liquid cast-rolling bonding (MRSLCRB) process was proposed integrating cast-rolling bonding technology and multi-roll groove rolling technology. The steady-state thermal resistance network was established, and the influences of nominal roll radius, groove radius, and molten pool height on the heat transfer and mass transfer were studied systematically. 3-D steady-state thermal-fluid coupled simulation models of twin-roll, three-roll, and four-roll layouts were established. The results indicate that increasing casting roll number can improve the nominal cast-rolling velocity, service life of the casting roll, temperature uniformity, strain uniformity, and strain rate uniformity through regulating the heat transfer and mass transfer. Considering the manufacturing feasibility, the MRSLCRB equipment based on the three-roll layout was designed. Cu/steel cladding bars with uniform circumferential performance were fabricated, and the forming mechanism was revealed. The multi-field coupled analysis method provides a way to control heat and mass transfer uniformity, and the successful attempts of various typical metal cladding materials inspire exploring new forming processes.

Roll Bonding of Al-Based Composite Reinforced with C10 Steel Expanded Mesh Inlay

The most complex issue related to the design of high efficiency composite materials is the behavior of the reinforcing component during the bonding process. This study presents numerical and experimental investigations of the shape change in the reinforcing inlay in an aluminum-steel mesh-aluminum composite during roll-bonding. A flat composite material consisting of two outer strips of an EN AW 1050 alloy and an inlay of expanded C10 steel mesh was obtained via hot roll bonding with nominal rolling reductions of 20%, 30%, 40% and 50% at a temperature of 500 °C. The experimental procedure was carried out using two separate rolling mills with diameters equal to 135 and 200 mm, respectively. A computer simulation of the roll bonding was performed using the finite element software QForm 9.0.10 by Micas Simulations Limited, Oxford, UK. The distortion of the mesh evaluated via the change in angle between its strands was described using computer tomography scanning. The dependence of the absorbed impact energy of the roll bonded composite on the parameters of the deformation zone was found. The results of the numerical simulation of the steel mesh shape change during roll bonding concur with the data from micro-CT scans of the composites. The diameter of rolls applied during the roll bonding, along with rolling reduction and temperature, have an influence on the resulting mechanical properties, i.e., the absorbed bending energy. Generally, the composites with reinforcement exhibit up to 20% higher impact energy in comparison with the non-reinforced composites.

Investigation of main bearing operating conditions in a three-Point mount wind turbine drivetrain

Wear-related failures of spherical roller bearings in the main bearing position of three-point mount wind turbines have been higher than expected and can contribute to higher than anticipated operation-and-maintenance costs. In this paper, the operational conditions of such a main bearing—including measured axial displacement and velocity subject to the estimated axial loads—are described for an instrumented, commercial wind turbine. The field measurements suggest a maximum axial speed between the bearing rings that is less than 2 millimeters per second. It is estimated that the axial speed between the ring and rollers is approximately 25% of this value. When compared to a speed of rolling from approximately 200–352 millimeters per second, the measured axial sliding is therefore significantly less than 1% of the speed of rolling. Previous numerical studies of lubricant film formation in rolling contacts have shown that the effect of axial sliding starts to be noticeable only when this ratio exceeds 10%; therefore, the axial velocity represents only a small disturbance to the nominal pure rolling case, and the influence on oil film building can be neglected. A simple analytic model of the main bearing motion was also developed and demonstrated similar displacement and velocity characteristics.

Effects of axle load transfer on wheel rolling contact fatigue of high-power AC locomotives with oblique traction rods

Severe wheel rolling contact fatigue (RCF) has been observed on two types of high-power AC locomotives with CO-CO axle arrangement and running in complicated environments in China. This RCF occurs as continuous lateral surface cracks in the zone approximately centered at the nominal rolling circle of wheels and can propagate downward up to 14.5 mm deep. To figure out the causes, field observations, monitoring tests and numerical simulations have been conducted in the past years together with systematic comparisons between two types of locomotives. Statistics have shown an interesting phenomenon, among others, that wheels on axles 3 and 4 are most susceptible to RCF cracks on Type B locomotives, but not so on Type A. It has been found that complicated running environments such as sharp curves and large slopes are the root causes of RCF. The axle load transfer among axles, which is aggravated by oblique traction rods, and inappropriate electrical compensation, and the curving behavior determine the axle preference of RCF on Type B locomotives. This explains the phenomenon that similar RCF damage has not been reported on Type B locomotives running in mild environments. At the end, the electrical compensation is optimized numerically with a purpose of easing RCF damage of Type B locomotives.

‘Sinn Féin permits … in the heels of their shoes’: Cumann na mBan emigrants and transatlantic revolutionary exchange

AbstractThe emigration of female revolutionary activists has largely eluded historical studies; their global movements transcend dominant national and regional conceptions of the Irish Revolution and challenge established narratives of political exile which are often cast in masculine terms. Drawing on Cumann na mBan nominal rolls and U.S. immigration records, this article investigates the scale of post-Civil War Cumann na mBan emigration and evaluates the geographical origins, timing and push-pull factors that defined their migration. Focusing on the United States in particular, it also measures the impact of the emigration and return migration of female revolutionaries – during the revolutionary period and in its immediate aftermath – on both the republican movement in Ireland and the fractured political landscapes of Irish America. Ultimately, this article argues that the cooperative transatlantic exchange networks of Cumann na mBan, and the consciously gendered revolutionary discourse they assisted in propagating in the diaspora, were integral to supporting the Irish Revolution at home and abroad.

Effects analysis of suspension parameters, different wheel conicities and wheel nominal rolling radii on the derailment safety and ride comfort

Using a modified heuristic nonlinear creep model with different wheel conicities and nominal rolling radii, a 31 degrees-of-freedom railway vehicle system with rail irregularities in the lateral and vertical directions is modelled and analysed. The effect of suspension system parameters, different wheel conicities and nominal rolling radius on the derailment quotient, the offload factor and the ride comfort index are illustrated and compared. Generally, the derailment risk is underestimated and ride comfort is overestimated when the linear creep model is used for dynamic analysis of a railway vehicle system. The derailment risk is increased and the ride comfort performance is decreased when a worn wheel that has a different wheel nominal rolling radius is used. Finally, for a softer primary and secondary suspension system, the derailment risk for a worn wheel is also increased.

Effects analysis of suspension parameters, different wheel conicities and wheel nominal rolling radii on the derailment safety and ride comfort

Using a modified heuristic nonlinear creep model with different wheel conicities and nominal rolling radii, a 31 degrees-of-freedom railway vehicle system with rail irregularities in the lateral and vertical directions is modelled and analysed. The effect of suspension system parameters, different wheel conicities and nominal rolling radius on the derailment quotient, the offload factor and the ride comfort index are illustrated and compared. Generally, the derailment risk is underestimated and ride comfort is overestimated when the linear creep model is used for dynamic analysis of a railway vehicle system. The derailment risk is increased and the ride comfort performance is decreased when a worn wheel that has a different wheel nominal rolling radius is used. Finally, for a softer primary and secondary suspension system, the derailment risk for a worn wheel is also increased.

Strain dependent grain growth during cold rolling deformation of gradient nanograined nickel

The effect of the rolling strain on grain growth behavior of two gradient nanograined nickel samples (average grain size ranging from 20~90nm) with symmetrical structure was investigated by scanning electron microscope/transmission electron microscopy observation, X-ray line profile analysis and microhardness measurement. In both gradient microstructures, under the same volume fraction, the layer with small grains and the layer with large grains was systematically compared. Quantitative analysis indicated that at a given nominal rolling strain small grains seem to grow more slowly than large grains, which can be attributed to the fact that the “hard” small grains sustain less deformation when the gradient are deformed to a certain strain.

On the wheel rolling contact fatigue of high power AC locomotives running in complicated environments

Severe rolling contact fatigue (RCF), occurring continuously around the nominal rolling circle of a wheel as lateral cracks up to 14.5 mm deep, has been observed on some high-power (≥7200 kW) AC locomotives in China. Its characteristics are first explained with data collected during field observations and monitoring tests. Then, a multi-body dynamic model is developed, in combination with the shakedown map and Tγ model, to reveal its initiation mechanisms. It is found that unqualified sand used for adhesion enhancement and complicated environments such as sharp curves and steep slopes are the main causes for RCF.

Field measurements of the evolution of wheel wear and vehicle dynamics for high-speed trains

ABSTRACTThis investigation demonstrates the wheel wear evolution and related vehicle dynamics of high-speed trains with an operating distance (OD) of around two million kilometres. A long-term experimental test lasting two years was conducted to record the wheel profiles and structural vibrations of various trainsets. The wheel wear, namely the profile shape, worn distribution and wheelset conicity, is investigated for several continuous reprofiling cycles. Typical results are illustrated for the stability analysis, and the ride quality is examined with increasing OD. In addition, the vibration transition characteristics between suspensions are investigated in both the time and frequency domains. The experiments show that the dominant wear concentrates on the nominal rolling radius, and the wear rate increases with OD because of the surface softening resulting from the loss of wheel material. The vibration of structural components is aggravated by the increase of the equivalent conicity of the wheelset, which rises approximately linearly with the wheel wear and OD. High-frequency vibrations arise in the bogie and car body related to the track arrangement and wheel out-of-roundness, causing the ride comfort to worsen significantly. Additionally, the system vibration characteristics are strongly dependent on the atmospheric temperature. Summaries and conclusions are obtained regarding the wheel wear and related vehicle dynamics of high-speed trains over long operating times and distances.

Experimental investigation of mass transfer performance in laboratory- and pilot-scale structured-packing columns under roll motion

Influence of roll motion on the mass transfer performance in laboratory- and pilot-scale structured-packing columns was investigated. A six-degree-of-freedom motion parallel platform was adopted to mimic different sea states of roll motion, and the relative change in the mass-transfer area caused by roll motion was obtained using an air-NaOH system. The experimental results showed that both enhanced and deteriorative mass transfer phenomena could be induced by roll motion, which results from the combined effect involving the operating conditions, packing types and sea states. Based on these results, a nominal maximum rolling velocity was proposed. The nominal maximum rolling velocity was positively correlated with the relative change in the mass-transfer area. Furthermore, the results indicated that tilt could be regarded as an extreme sea state of roll motion.

Analysis of the wheel/rail rolling contact fatigue of a high-speed train under the transient mechanism

The Rolling contact fatigue (RCF) damage of high-speed wheels is a main factor that affects railway safety. This paper presents a Finite element model (FEM) of high-speed transient rolling contact that considers kinetic parameters as initial conditions. This model is used to calculate wheel/rail RCF. With a CRH2 high-speed train as the research object, a head car model is established with the multibody dynamics software UM. The train is driven on a straight track at a speed of 300 km/h. Different contact geometric parameters, such as lateral displacement and attack angle, are obtained. A 3D high-speed transient elastic-plastic FEM of wheel/rail rolling contact is then developed by using ABAQUS with the initial dynamic contact geometric parameters. The actual geometries of the wheel tread and rail head as well as the elastic-plastic properties are considered in this model. This consideration makes the model highly suitable for solving 3D transient rolling contact behavior. The normal force, creep force, and contact area in the contact patch are solved and used in the fatigue model. Owing to the hunting movement of wheels, the wheel/rail force and lateral displacement change significantly at 0.2 and 0.5 s. The longitudinal and lateral creep force increase sharply with the increase in shear stress. The work states of the wheel/rail at 0.2 and 0.5 s easily reach the ratchet effect zone, and the fatigue index is large. The fatigue damage of the wheels is generally near the nominal rolling circle.

Wheel nominal rolling radius difference on hunting stability of railway vehicle system under a speed-dependent nonlinear creep model

This study presents the hunting stability of a railway vehicle system in a speed-dependent nonlinear creep model with varying wheel conicity and nominal rolling radius. Integrating Kalker’s linear theory, Hertz contact theory, and the heuristic nonlinear creep model, the speed-dependent nonlinear creep model, including the semi-axis lengths and nonconstant creep coefficients with the varying vehicle speed, is investigated. Modeling and dynamic analysis are performed in the 28 degrees-of-freedom railway vehicle system. Lyapunov’s indirect method is used to calculate critical hunting speed of a railway vehicle system. The effects of suspension system parameters, various wheel conicities, and nominal rolling radii on the hunting stability are illustrated and compared. Critical hunting speeds calculated for the original design wheel are consistently better than those obtained from worn wheels with differences in wheel conicity and wheel rolling radius. Notably, critical hunting speeds calculated for a softer stiffness and damping decrease as wheel nominal rolling radius difference increases. Furthermore, the critical hunting speed calculated by the harder stiffness and damping increase as wheel nominal rolling radius difference increases. Analysis of hunting stability further shows that vehicle running speed must be considered when the wheel nominal rolling radius is less than the origin design wheel radius. Therefore, the effects of various wheel nominal rolling radius differences on hunting stability is an important research issue.

Surgeons of the Royal Naval Medical Service in the First World War: producing a nominal roll

In 2014, I acquired from a South African auction house the three World War One (WW1) medals awarded to Fleet Surgeon George Ley Royal Navy (see [Figure 1][1]). These were the first medals awarded to a naval surgeon that I had been fortunate enough to obtain. On attempting to research this man’s

Does optimal access to dental care counteract the oral health-related quality of life social gradient?

The aim of this study was to determine if an oral health-related quality of life (OHRQoL) social gradient existed when Australian Defence Force (ADF) members have universal and optimal access to dental care. A nominal roll included 4089 individuals who were deployed to the Solomon Islands as part of Operation ANODE and a comparison group of 4092 ADF personnel frequency matched to the deployed group on gender, age group and service type, from which 500 deployed and 500 comparison individuals were randomly selected. The dependent variables were the OHIP-14 summary measures. Rank was used to determine socioeconomic status. The demographic variables selected were: gender and age. The response rate was 44%. Of the individual OHIP-14 items, being self-conscious, painful aching and having discomfort when eating were the most common problems. Mean OHIP-14 severity was 2.8. In bivariate analysis, there was not a significant difference in mean OHIP-14 severity (p = 0.52) or frequency of OHIP-14 impacts (p = 0.57) by military rank. There was a significant increasing OHIP-14 extent score from commissioned officer to non-commissioned officer to other ranks (0.07, 0.19, 0.40, p = 0.03). Even with optimal access to dental care, there was an OHRQoL social gradient between military ranks in the ADF.

A descriptive study on the perception of health care workers to dental treatment at a tertiary hospital in Lagos, Nigeria

Aims: Many oral diseases have a strong connection with systemic conditions while effective delivery of health care often requires the combined efforts of all health professionals. Due to the problems of access to dental care, patients may consult other primary health care providers for their oral health needs. This study was undertaken to assess the oral health knowledge, attitude and practices among various health professionals working in Lagos State University Teaching Hospital, (LASUTH). Methods: This cross-sectional study was conducted at the LASUTH Ikeja, Lagos, Nigeria. A stratified probability sampling method was used to categorize the different health professionals in LASUTH and about 20% of the health workers in each category were enlisted using the nominal roll as a sampling frame. A total of 148 questionnaires were administered during the study on subjects who met the inclusion criteria and gave their informed consent. Results: Females and younger respondents were more likely to visit the dentist than males for routine dental check-up even though the association was not significant. The oral health knowledge and attitude among the various health professionals surveyed in LASUTH was found to be inadequate even though Medical doctors had the overall best responses. There was a significant difference between the attitude of the Medical Doctors and other health professionals on questions about extractions (p = 0.024); dental treatments (p = 0.008); dental fillings (p = 0.000); artificial teeth (p = 0.013); bleeding gums (p = 0.002) and replacement of lost teeth (p = 0.004). Conclusion: All health professionals can promote oral health by disseminating accurate oral health messages, being appropriate role models by paying attention to their own oral health, encouraging appropriate dental visits and participating in oral health promotion within their scope of duties. It is also recommended that dental items feature more frequently in hospital ground rounds and clinical meetings of to address this deficit.

Numerical simulation of wheel wear evolution for heavy haul railway

The prediction of the wheel wear is a fundamental problem in heavy haul railway. A numerical methodology is introduced to simulate the wheel wear evolution of heavy haul freight car. The methodology includes the spatial coupling dynamics of vehicle and track, the three-dimensional rolling contact analysis of wheel-rail, the Specht’s material wear model, and the strategy for reproducing the actual operation conditions of railway. The freight vehicle is treated as a full 3D rigid multi-body model. Every component is built detailedly and various contact interactions between parts are accurately simulated, taking into account the real clearances. The wheel-rail rolling contact calculation is carried out based on Hertz’s theory and Kalker’s FASTSIM algorithm. The track model is built based on field measurements. The material loss due to wear is evaluated according to the Specht’s model in which the wear coefficient varies with the wear intensity. In order to exactly reproduce the actual operating conditions of railway, dynamic simulations are performed separately for all possible track conditions and running velocities in each iterative step. Dimensionless weight coefficients are introduced that determine the ratios of different cases and are obtained through site survey. For the wheel profile updating, an adaptive step strategy based on the wear depth is introduced, which can effectively improve the reliability and stability of numerical calculation. At last, the wear evolution laws are studied by the numerical model for different wheels of heavy haul freight vehicle running in curves. The results show that the wear of the front wheelset is more serious than that of the rear wheelset for one bogie, and the difference is more obvious for the outer wheels. The wear of the outer wheels is severer than that of the inner wheels. The wear of outer wheels mainly distributes near the flange and the root; while the wear of inner wheels mainly distributes around the nominal rolling circle. For the outer wheel of front wheelset of each bogie, the development of wear is gradually concentrated on the flange and the developing speed increases continually with the increase of traveled distance.

Wheel reprofiling of a high-speed electric-multiple-unit train based on a multi-objective optimization strategy

An approach to optimize the wheel reprofiling of a high-speed electric multiple unit (EMU) train is presented; it has three functions as objectives: the critical speed of the train, the contact stress that affects the contact fatigue of wheel/rail wear and the diameter of the nominal rolling circle of the wheel. The vertical coordinates of the control points on the curve of the wheel profile are used as design variables and the upper and lower values of each control point are utilized as additional limiting conditions of the curve, with the height, thickness and contact angle of the wheel flange as well as the derivative of the curve acting as constraints on the geometry parameters. A multi-objective optimization model is established for the wheel reprofiling of a high-speed EMU train; three models are created: standard, worn and optimized wheel profiles. Comparisons of wheel/rail contact, running stability and curving performance of the vehicle are performed. It is shown that the wheel profile obtained from the reprofiling optimization model satisfies the constraints and its corresponding dynamic performance has a good agreement with that of a standard wheel profile with a 30 mm thick wheel flange. A performance close to that of a standard wheel profile can be obtained even though the worn wheel is not reprofiled to have the standard profile. Also, the amount of diameter reduction in the direction of the nominal rolling circle is reduced and service life-time is extended by employing the proposed wheel reprofiling approach based on the multi-objective optimization strategy.