Search results

The purpose of this paper is to provide the details of developments to research works in the distribution characteristics of the air gaps within firefighters’ clothing and research methods to evaluate the effect of air gaps on the thermal protective performance of firefighters’ clothing.

In this paper, the distribution of air gaps within firefighters’ clothing was first analyzed, and the air gaps characteristics were summarized as thickness, location, heterogeneity, orientation and dynamics. Then, the evaluation of the air gap on the thermal protective performance of fighters’ clothing was reviewed for both experimental and numerical studies.

The air gaps within clothing layers and between clothing and skin play an important role in determining the thermal protective performance of firefighters’ protective clothing. It is obvious that research works on the effects of actual air gaps entrapped in firefighters’ clothing on thermal protection are comparatively few in number, primarily focusing on static and uniform air gaps at the fabric level. Further studies should be conducted to define the characteristic of air gap, deepen the understand of mechanism of heat transfer and numerically simulate the 3D dynamic heat transfer in clothing to improve the evaluation of thermal protective performance provided by the firefighters’ clothing.

Air gaps within thermal protective clothing play a crucial role in the protective performance of clothing and provide an efficient way to provide fire-fighting occupational safety. To accurately characterize the distribution of air gaps in firefighters’ clothing under high heat exposure, the paper will provide guidelines for clothing engineers to design clothing for fighters and optimize the clothing performance.

This paper is offered as a concise reference for researchers’ further research in the area of the effect of air gaps within firefighters’ clothing under thermal exposure.

The purpose of this paper is to determine the effect of flash fire exposure on the mechanical properties of single-layer thermal protective clothing.

The full-scale flame manikin tests were performed to simulate flash fire exposure. Two typical fire-resistant fabrics were investigated. The manikin was divided into seven body parts and the specimens meeting the requirements of tensile and tear strength standards were sampled. Fabric thickness, mass per unit area, tensile strength and tear strength were measured and analyzed.

The results revealed the significant influence of heat flux on both of tensile and tear strength. However, the regression analysis indicated the low R² of the liner models. When the tensile and tear strength retention were reorganized based on the body parts, both of the multiple linear regression models for tensile and tear strength showed higher R² than the one-variable linear regressions. Furthermore, the R² of the multiple linear regression model for tear strength retention was remarkably higher than that of the tensile strength.

The findings suggested that greater attention should be paid to the local part of human body and more factors such as the air gap should be considered in the future thermal aging of firefighters’ clothing studies.

The outcomes provided useful information to evaluate the mechanical properties of thermal protective clothing and predict its service life.

In order to solve the problems faced by First Order Reliability Method (FORM) and First Order Saddlepoint Approximation (FOSA) in structural reliability optimization, this paper aims to propose a new Reliability-based Design Optimization (RBDO) strategy for offshore engineering structures based on Original Probabilistic Model (OPM) decoupling strategy. The application of this innovative technique to other maritime structures has the potential to substantially improve their design process by optimizing cost and enhancing structural reliability.

In the strategy proposed by this paper, sequential optimization and reliability assessment method and surrogate model are used to improve the efficiency for solving RBDO. The strategy is applied to the analysis of two marine engineering structure cases of ship cargo hold structure and frame ring of underwater skirt pile gripper. The effectiveness of the method is proved by comparing the original design and the optimized results.

In this paper, the proposed new RBDO strategy is used to optimize the design of the ship cargo hold structure and the frame ring of the underwater skirt pile gripper. According to the results obtained, compared with the original design, the structure of optimization design has better reliability and stability, and reduces the risk of failure. This optimization can also better balance the relationship between performance and cost. Therefore, it is recommended for related RBDO problems in the field of marine engineering.

In view of the limitations of FORM and FOSA that may produce multiple MPPs for a single performance function, the new RBDO strategy proposed in this study provides valuable insights and robust methods for the optimization design of offshore engineering structures. It emphasizes the importance of combining advanced MPP search technology and integrating SORA and surrogate models to achieve more economical and reliable design.

The chapter will address comparative teacher preparation programs for teachers who wish to teach in inclusive settings, including those in the United States and People’s Republic of China. Consideration will be given to developing course objectives and outcomes for teacher preparation programs through the alignment of teacher standards and content standards. Further, discussion will review assessing pre-service teacher candidates for inclusive settings. It will conclude with recommendations for inclusive teacher preparation programs.

Many mobile devices today are equipped with diversified sensors that enable the acquisition of rich user context (e.g. GPS location, phone activity) for application utilization. With the growing usage of mobile devices in daily life, the problem of conveniently and promptly searching a piece of content that a user has viewed on his/her device before becomes more and more crucial. This paper aims to propose a context‐based query processing framework called UCQP that supports unstructured queries for content search in a user's access history.

Beyond the keywords related to the content properties, a context query in the framework is specified with freeform phrases that describe high‐level mobile contexts of the user at a previous time when the user viewed the searched content.

Experimental results on a prototype system of the framework illustrate its good accuracy and small response time.

To tolerate the incompleteness and inaccuracy in user query texts caused by fading human memory, the authors develop several semantic query parsers that are tailored for different types of contexts using natural language processing and information retrieval techniques. The authors further propose a similarity model to rank the multiple result contents of a query by comparing context entities specified in the query and historical context values associated with each result.

Based on the social interaction theory and trust theory, this study investigates the switching of users on social question and answer (Q&A) platforms from knowledge seekers to knowledge contributors.

We used Python to gather data from Zhihu, performed hypothesis testing on the models using Poisson regression and finally conducted a mediation effect analysis.

The findings reveal that knowledge seeking impacts users' motivation for information interaction, emotional interaction and trust. Notably, information interaction and trust exhibit a chained mediation effect that subsequently influences knowledge contribution.

Current studies on user knowledge behavior typically examine individual actions, rarely connecting knowledge seeking and knowledge contribution. However, the balance of knowledge inflow and outflow is crucial for social Q&A platforms. To cover this gap, this paper empirically investigates the switching between knowledge seeking and knowledge contribution based on the social interaction theory and trust theory.

The purpose of this study is to trace time variation paths in risk sensitivities of bank stock returns over the period of 1990-2014, which covers one of most serious financial crises in the history of the USA.

This study programs the flexible least squares (FLS) approach (Kalaba and Testfatsion, 1988, 1989 and 1990) with R, a free statistical computing and graphics software, to estimate the three-factor model developed by He and Reichert (2003) to examine changes in risk sensitivities of bank stocks to the stock market, bond market and real estate market.

Both FLS and ordinary least squares (OLS) results indicate that the bond market (interest rate) sensitivity of bank stock returns experiences dramatic changes. It is significantly positive before the 2006 subprime mortgage crisis (11/1990 to 5/2006), reduces to insignificant in a short period of 11/2006 to 10/2008 and turns into significantly negative during the period of 11/2008-11/2014. Further, results of this study indicate that bank stocks negatively respond to changes in housing prices in the period of 11/1990-1/1994 and after that the sensitivity turns into significantly positive. The significant shifts in risk sensitivities of banks stock returns coincide with alterations in long-term interest rates and monetary policy, especially the enormously stimulative monetary policy after the financial crisis in 2008.

This study programs the FLS approach with R and uses the FLS approach to demonstrate the time variation paths of risk sensitivities of bank stocks over a period that covers the 2008 financial crisis. The OLS results verify the significant shifts in risk sensitivities suggested by the FLS estimates.

The purpose is to explore the improvement mechanism of coating and laser micro-texture on the surface properties of cemented carbide, so as to give full play to the technical advantages of both and improve the overall surface properties of the material.

The surface hardness of the coating was measured by a microhardness tester, the surface element composition of the coating was tested by an energy spectrum analyzer and the phase was measured by an X-ray diffractometer to observe the surface morphology after the friction and wear experiment.

Laser will generate new oxide and nitride films on the surface of the coating, which will improve the hardness of the coating surface and the bonding strength between the coating and the substrate. The surface micro-texture can collect wear debris during the friction process, reduce abrasive wear and play a good role in inhibiting the expansion of the coating failure zone.

Most of the research on traditional laser coating is to process micro-texture first and then coating. This study is the opposite. In this paper, the modification effect of laser on the coating surface is explored, and the parameters of laser and coating are optimized, which paves the way for the subsequent milling experiments of textured coating tools.