Search results

This study aims to introduce the achievements and benefits of applying wheel/rail-force–based maintenance interval extension of the C80 series wagon in China.

Chinese wagons' existing maintenance strategy had left a certain safety margin for the characteristics of widely running range, unstable service environment and submission to transportation organization requirements. To reduce maintenance costs, China railway (CR) has attempted to extend the maintenance interval since 2020. The maintenance cycle of C80 series heavy haul wagons is extended by three months (no stable routing) or 50,000 km (regular routing). However, in the meantime, the alarming rate of the running state, a key index to reflect the severe degree of hunting stability, by the train performance detection system (TPDS) for the C80 series heavy haul wagons has increased significantly.

The present paper addresses a big data statistical way to evaluate the risk of allowing the C80 series heavy haul wagons to remain in operation longer than stipulated by the maintenance interval initial set. Through the maintenance and wayside-detector data, which is divided into three stages, the extension period (three months), the current maintenance period and the previous maintenance period, this method reveals the alarming rate of hunting was correlated with maintenance interval. The maintainability of wagons will be achieved by utilizing wagon performance degradation modeling with the state of the wheelset and the often-contact side bearing. This paper also proposes a statistical model to return to the average safety level of the previous maintenance period's baseline through correct alarming thresholds for unplanned corrective maintenance.

The paper proposes an approach to reduce safety risk due to maintenance interval extension by effective maintenance program. The results are expected to help the railway company make the optimal solution to balance safety and the economy.

Previous commonly used author co-citation analysis (ACA) methods have limited the ability to deal with accidental co-citation in constructing a raw co-citation matrix. Therefore, the purpose of this paper is to propose a new method, called author tri-citation analysis (ATA), to better map knowledge domains and depict scientific intellectual structures.

Different from the previous method of using ACA that captures author co-citation relationships, the ATA method seeks tri-citation relationships among authors. Compared with ACA, ATA can ignore some accidental co-citation relationships between authors and can improve the accuracy of mapping knowledge domains.

Although ATA does not mine more sub-fields than ACA does, the results of the empirical studies show that ATA, the newly proposed method, performs better in knowledge domain maps based on publications in the field of computer science.

The definition of ATA in this article is simple and still insufficiently informative. Many other pieces of information can be involved; for example, all authors’ information, authors’ sequence in the author list, reference published time and similar. These can be enhanced in future studies.

This research will enrich the methods of mapping knowledge domains due to its new perspective.

Knowledge domain mapping is important to understand a discipline, and this research provides more potential methods for this, which benefits the performance of the maps.

ATA can provide a methodological awareness for mapping knowledge domains. This value lies in not only a tri-citation perspective, but also author bibliographic tripling and author tri-operation perspectives (“tri-” perspectives).

The purpose of this paper is to investigate thermal protection provided by the fire fighting fabric systems with different layer under high-level thermal hazards with a typical temperature range of 800-1,000°C. The purpose of these fabric systems was to provide actual protection against burn injuries using garments worn by industrial workers, fire fighters and military personnel, etc.

The fabric system was consist of glass with aluminum foil as an outer layer, non-woven basalt, non-woven glass fabric containing NaCl-MgCl₂ and Galactitol phase change materials (PCM) which simulate multilayer fire fighter protective clothing system. Thermal protective performance tests were applied for thermal analysis and used as an attempt to quantify the insulating characteristics of fabrics under conditions of flash over temperature. The surface of fire fighting multilayer protective fabric has been characterized using the UV-Vis-NIR (ultraviolet-visible-near infrared) spectrophotometer

The clothing shows good thermal insulation and high-temperature drop during flash over environment and avoid second degree burn. The current PCM obvious advantages such as the ability to work in high temperature, high efficiency a long period of practical performance.

Using this design of composite multilayer technology incorporating two stages of PCM may provide people with better protection against the fire exposure and increasing the duration time which was estimated to be more than five minutes to prevent burn injuries.

High performance aramid fibers display high tenacity, modulus and temperature resistance under various end-use applications. Since no scientific research papers on the subject of Kermel fibers are found, the thermal degradation properties of Kermel and poly-p-phenylenebenzobisoxazole (PBO) fibres are therefore compared in this paper. When heated to temperatures of 100°C, 200 °C, 300°C, and 400°C for 1.5 hours, the tenacity and extension-to-break properties of PBO and Kermel fibres both decrease with temperature, but the modulus first increases, and then decreases until 300°C. By using a scanning electron microscope (SEM) to observe the effect of heat treatment on these fibres, the morphologies of PBO and Kermel fibres exhibit fractures when they are ruptured and fibrils are found in their cores.

PBO and p-aramids fibers were compared on thermal degradation in TG and DTG experiments, and PBO fiber showed the highest degradation temperature in both air and nitrogen atmosphere. Annealed under high temperature of 100°C, 200°C, 300°C and 400°C for 1.5 hours, the tenacity of these samples all decreased with the temperature, while PBO fiber showed the best tensile retention property. Whereas using the xenon arc light to simulate sunlight irradiated on the PBO and Kevlar samples for different time respectively, PBO showed the worst tensile retention property. In contrast, the p-aramid fibers showed their relatively good mechanical stability when exposed to the simulated sunlight. Therefore, the application of PBO fibers should be careful in the state of sunlight irradiation although PBO has the highest original mechanical and thermal property.

This paper studies the effects of stretching slenderization on the structure and properties of yak hair using an optical microscope, scanning electron microscope (SEM), Raman spectroscopy, tensile curves and dyeability. The SEM results show that stretching slenderization can decrease the diameter of yak hair, and the scale of the fibres is elongated and thinner. As well, the structure of the fibre scale is looser after stretching, and some scale cells are damaged. The stretching process results in the structural transformation of yak hair from an α-keratin to a predominantly β-keratin crystalline structure by the Raman analysis. Through the tensile curves, the slenderizing of the yak hair at different stretching rates is analyzed. The breaking tenacity increases gradually in terms of the stretching rate and breaking elongation decreases. Optical microscope photographs and dyeing rate analysis are used to observe the changes in the dyeability of yak hair before and after the stretching. The results show that after stretching, there is a significant improvement in the dyeing properties of yak hair.

This paper presents the related theories and current situation of regenerated keratin materials, as well as fibre reinforced composite materials, which are used to evaluate the feasibility of glass fibres and whisker reinforced wool keratin films. Although blending biopolymers is the traditional way to improve the mechanical properties of keratin materials, wool keratin, which consists of only a few percentages in composite materials, would not have an outstanding performance biologically. In this article, we examine the processes of developing fibre reinforced keratin materials, including the dissolution of wool fibres, dispersion of reinforcements, and interface study of the reinforcements/matrix. The results suggest that both glass fibres and whiskers distribute uniformly and bond well with keratin matrix through observations with an optical microscope and scanning electron microscope (SEM). Moreover, the effects of reinforcement alignment, as well as fibre concentration, can be used to predict the tensile strength (TS) of regenerated keratin materials for further experiments.

In this paper, a method of designing flexible multilayer insulation is analyzed and discussed, with focus on reducing the three basic modes of heat transfer (thermal radiation, solid spacer and residual gas conduction). The foundation for designing the new flexible thermal insulation material is provided. The insulation performances of different types (by choosing different reflection shields and spacers) of flexible multilayer insulation materials are obtained through measurements using a KES-F7 Thermal Labo II apparatus. The thermal performance of flexible multilayer insulation materials at different layers are also presented, and the best is about 20∼25 layers. To improve the thermal performance of multilayer insulation materials, treble spacers between double aluminized shields are applied. Aluminized shields with air, meshes, wool fibres, etc. are compared with each other. The aluminized shields with meshes fixed with down can reduce thermal contact, which reduces the radiation heat transfer more fully and can be more steady than the other spacers in the project applications. With the same layers and spacers, the thermal conductivity of crinkled aluminized shields is lower than that of the smooth aluminized shields. The effects of compressive loads on layer density and thermal performance are also investigated.

The purpose of this paper is to describe a new apparatus for testing acoustic insulating, air permeating and water vapor transfer properties of fibrous assemblies with density variation.

An apparatus is designed and built in order to investigate the acoustic insulating, air permeating and water vapor transfer properties of fiber assemblies with density variation. The apparatus mainly consists of three chambers, just like the structure of a syringe. The three properties can be measured by placing different sensors at the corresponding chambers. The material density variation can be realized by compression.

The new apparatus can realize the measurement of the three properties with density variation, which provides a new perspective to study the physical property of fibrous assemblies.

The paper introduces a new apparatus for testing acoustic insulating, air permeating and water vapor transfer properties of fibrous assemblies with density variation.

The purpose of this paper is to describe a new transient approach for testing water vapor diffusivity of fabrics and fibrous assemblies.

An apparatus was designed and built in order to investigate the transient water vapor diffusivity of fabrics and fibrous assemblies, and the apparatus is validated by applying a theoretical model and comparing the result obtained by the desiccant cup method.

The transient water vapor diffusion test method permits rapid testing of small quantities of fabrics in a short amount of time. The method has an excellent correlation and agreement with the desiccant cup method. The variation of the new method is much smaller than the desiccant method. It also provided a way to study water vapor transfer through fibrous assemblies.

The paper introduces a new approach for testing water vapor diffusivity of fabrics and fibrous assemblies.