A combined M5P tree and hazard-based duration model for predicting urban freeway traffic accident durations

The duration of freeway traffic accidents duration is an important factor, which affects traffic congestion, environmental pollution, and secondary accidents. Among previous studies, the M5P algorithm has been shown to be an effective tool for predicting incident duration. M5P builds a tree-based model, like the traditional classification and regression tree (CART) method, but with multiple linear regression models as its leaves. The problem with M5P for accident duration prediction, however, is that whereas linear regression assumes that the conditional distribution of accident durations is normally distributed, the distribution for a “time-to-an-event” is almost certainly nonsymmetrical. A hazard-based duration model (HBDM) is a better choice for this kind of a “time-to-event” modeling scenario, and given this, HBDMs have been previously applied to analyze and predict traffic accidents duration. Previous research, however, has not yet applied HBDMs for accident duration prediction, in association with clustering or classification of the dataset to minimize data heterogeneity. The current paper proposes a novel approach for accident duration prediction, which improves on the original M5P tree algorithm through the construction of a M5P-HBDM model, in which the leaves of the M5P tree model are HBDMs instead of linear regression models. Such a model offers the advantage of minimizing data heterogeneity through dataset classification, and avoids the need for the incorrect assumption of normality for traffic accident durations. The proposed model was then tested on two freeway accident datasets. For each dataset, the first 500 records were used to train the following three models: (1) an M5P tree; (2) a HBDM; and (3) the proposed M5P-HBDM, and the remainder of data were used for testing. The results show that the proposed M5P-HBDM managed to identify more significant and meaningful variables than either M5P or HBDMs. Moreover, the M5P-HBDM had the lowest overall mean absolute percentage error (MAPE).     

Applicability of Kocks–Mecking approach for tensile work hardening in P9 steel

Abstract

Work hardening behaviour of P9 steel in the temperature range 300–873 K has been examined in the framework of Kocks–Mecking (K–M) approach. At all temperatures, P9 steel exhibited two-stage work hardening behaviour characterised by a rapid decrease in instantaneous work hardening rate (i.e. θ?=?dσ/d?, where σ is the true stress and ? is the true plastic strain) with stress at low stresses (transient stage) followed by a gradual decrease at high stresses (stage III). Stage III work hardening of P9 steel was adequately described by K–M approach. The variations of work hardening parameters associated with K–M approach for stage III with temperature indicated three distinct temperature regimes. At all temperatures, good correlations between the respective work hardening parameters evaluated using K–M approach and from Voce equation and its derivative have been obtained for P9 steel.     

The life of a plant builder in the modern metals industry

Abstract

The 2007 SMEA Celebrity Lecture (Sheffield Metallurgical and Engineering Association) was given by Roy Tazzyman, the outgoing Managing Director of Siemens VAI–UK, on 4 July 2007 at the University of Sheffield, in conjunction with the Association's annual conference. Ken Ridal summarises the proceedings.     

Effect of Cu addition on microstructure and impact toughness in the simulated coarse-grained heat-affected zone of high-strength low-alloy steels

The effects of Cu content on microstructure and impact toughness in the simulated coarse-grained heat-affected zone (CGHAZ) of high-strength low-alloy steels were investigated. It has been observed that the microstructure in the simulated CGHAZ of Cu-free steel is dominated by a small proportion of acicular ferrite and predominantly bainite with martensite–austenite constituent. Whereas, in the 0.45 and 1.01% Cu-containing steels, the acicular ferrite increased significantly due to the effective nucleation on intragranular inclusions with outer layer of MnS and CuS. The formation of acicular ferrite is attributed to superior high heat-affected zone impact toughness in the 0.45% Cu-containing steel. Furthermore, the increasing martensite–austenite constituent and ε-Cu precipitates in the simulated CGHAZ of 1.01% Cu-containing steel caused degradation in impact toughness.     

Precipitation behaviour of oxide in directionally solidified aerospace bearing steel

The directional solidification enables independently control of the holding temperature and withdrawal rate over a given range. This technology was used to investigate the precipitation behaviour of oxide in aerospace bearing steel M50NiL. Most of the oxides are Si–Al–Mn–Ti–O complex inclusions with spherical shape. With the increase of withdrawal rate, the size and volume fraction of oxides decrease. In contrast, the diameter and volume fraction increase remarkably with the increase of holding temperature. The composition of oxides with different sizes varies with holding temperature. The holding temperature of 1550°C accompanied with a cooling rate over 95.7°C?min^?1 is deemed as the optimal solidification parameters for M50NiL steel, which can significantly reduce the size and volume fraction of oxides.     

Award for distinguished scientific applications of psychology.

The American Psychological Association's Award for Distinguished Scientific Applications of Psychology is presented to a person who, in the opinion of the Committee on Scientific Awards, has made distinguished theoretical or empirical advances leading to the understanding or amelioration of important practical problems. The 2010 award was given to David M. Clark. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimal design of catalytic distillation columns: A case study on synthesis of TAEE

The design of catalytic distillation (CD) columns is a challenging task because of the superposition of chemical reaction and distillation in one apparatus. In this work, a method to design a cost-optimal CD column for chemical systems with large number of components and chemical reactions is presented. The method is based on the following steps: (1) estimation of the number of theoretical stages and catalyst volume by the decomposition of the CD column into a sequence of chemical reactors and non-reactive distillation columns, (2) estimation of the column diameter and operating conditions using an equilibrium stage model, and (3) design of the column applying an optimisation algorithm and using a rigorous non-equilibrium stage model to represent the CD process. The method is applied to determine the optimal column configuration and operating conditions for the synthesis of tert-amyl ethyl ether from ethanol and isoamylenes. Eight components and four chemical reactions were selected to represent the chemical system in the simulations.     

通过核糖核苷酸还原酶M2逆转肝癌细胞对5-氟尿嘧啶耐药

目的：探讨核糖核苷酸还原酶M2（RRM2）在肝癌细胞对5-氟尿嘧啶（5-FU）耐药中的作用,并开发潜在的策略来提高肝癌细胞对5-FU的敏感性。方法：利用Western blot检测5-FU耐药肝癌细胞（BEL/5-FU）与非耐药肝癌细胞（BEL7402）中RRM2蛋白的表达差异;通过用RNA干扰技术下调BEL/5-FU细胞中RRM2的表达或RRM2抑制剂3-AP（Triapine）抑制RRM2活性;CCK-8和集落形成实验用于检测细胞的增殖能力;使用高内涵细胞成像系统仪检测与分析细胞凋亡。结果：BEL/5-FU细胞中RRM2的表达量是BEL7402细胞的2.5倍。RNA干扰技术能够下调BEL/5-FU细胞中RRM2的表达,并使5-FU对BEL/5-FU细胞的半数抑制浓度（IC50）下降约50%,同时细胞集落形成能力也显著减弱。3-AP与5-FU联合处理BEL/5-FU细胞,使5-FU对BEL/5-FU细胞的IC50下降约40%,细胞集落形成能力减弱,并促进5-FU导致的细胞凋亡。结论：RRM2与肝癌细胞对5-FU的耐药相关,本研究通过抑制RRM2的活性来逆转肝癌细胞对5-FU的耐药,为提高肝癌的5-FU化疗疗效提供新靶点和新思路。