Compressive performance of laminated bamboo

This study investigated the compressive performance of 24 laminated bamboo specimens made from three different growth portions of the source bamboo. The cross-section of each specimen was 100 mm × 100 mm. The load–strain and load–displacement relationships are obtained from compression tests, and the detailed failure modes, compressive strength and elastic modulus for all specimens are reported. The results show that the mean compressive strength increases with growth portion height, but that the variation in compressive strength also increases with growth portion height. The net result is that the characteristic strength (typically used in the design process) decreases slightly with growth portion height, but not significantly. In contrast, laminated bamboo manufactured from the middle growth portion exhibits the highest elastic modulus, with the variation again increasing with height. Although the source growth portion has a clear effect on the behaviour of laminated bamboo under compression, the paper concludes that the effect is not significant from a design perspective. The results of all the tests are combined to produce a model stress–strain relationship suitable for predicting the performance of laminated bamboo under compression for design purposes. The stress–strain relationship shows that under compression laminated bamboo fails in a ductile manner. Based on the compressive properties obtained in this research, laminated bamboo is a suitable construction material for engineering structures.     

热处理对竹材理化性能影响研究进展

目的 归纳国内外现有热处理工艺对竹材理化性能的影响的研究进展,分析不足,并提出热处理竹材作为代木材料在包装领域的未来研究趋势。方法 综述不同热处理竹材工艺(包含时间条件、温度条件、介质种类)的研究现状,总结竹材理化性能的变化特点。结果 当前热处理技术作为环保简易的竹改性技术表现出一定优势,但单一的工艺条件对竹材原有性能会产生负向影响,需对工艺参数和反应条件进行开发改进,并设计相应的制备装置。结论 采用热处理条件多线程综合工艺可以在优化竹材性能的同时,保持甚至降低中高温对竹结构的破坏,从而增加热处理竹材的使用年限,并拓展其使用领域。     

Analysis of traffic accidents at urban intersections in Riyadh

Previous studies have shown that intersection-related accidents account for about 50% of all accidents registered annually in Riyadh, the capital of the Kingdom of Saudi Arabia (KSA). More than half of these accidents are classified as severe. In this study, an attempt was made to investigate traffic accidents that occurred at both intersections and non-intersection sites. The goal was to analyze the nature of such accidents to determine their characteristics so that remedies could be sought or at least future research could be suggested. For this purpose, a sample of 1774 reported accidents was collected in a systematic random manner for the period 1996-1998 (651 severe accidents (accidents resulting in at least one personal injury or fatality) and 1123 property-damage-only (PDO) accidents). Conditional probability and contingency table analyses were used to make inferences from the data. The study found that improper driving behavior is the primary cause of accidents at signalized urban intersections in Riyadh; running a red light and failing to yield are the primary contributing causes. The analysis indicates that there is an urgent need to review existing intersection geometry along with the traffic control devices installed at these sites. In addition, public education campaigns and law enforcement strategies are urgently needed.     

A suggested color scheme for reducing perception-related accidents on construction work sites

Changes in workforce demographics have led to the need for more sophisticated approaches to addressing the safety requirements of the construction industry. Despite extensive research in other industry domains, the construction industry has been passive in exploring the impact of a color scheme; perception-related accidents have been effectively diminished by its implementation. The research demonstrated that the use of appropriate color schemes could improve the actions and psychology of workers on site, thereby increasing their perceptions of potentially dangerous situations. As a preliminary study, the objects selected by rigorous analysis on accident reports were workwear, safety net, gondola, scaffolding, and safety passage. The colors modified on site for temporary facilities were adopted from existing theoretical and empirical research that suggests the use of certain colors and their combinations to improve visibility and conspicuity while minimizing work fatigue. The color schemes were also tested and confirmed through two workshops with workers and managers currently involved in actual projects. The impacts of color schemes suggested in this paper are summarized as follows. First, the color schemes improve the conspicuity of facilities with other on site components, enabling workers to quickly discern and orient themselves in their work environment. Secondly, the color schemes have been selected to minimize the visual work fatigue and monotony that can potentially increase accidents.     

Melt Electrospinning Writing of Highly Ordered Large Volume Scaffold Architectures

The additive manufacturing of highly ordered, micrometer‐scale scaffolds is at the forefront of tissue engineering and regenerative medicine research. The fabrication of scaffolds for the regeneration of larger tissue volumes, in particular, remains a major challenge. A technology at the convergence of additive manufacturing and electrospinning–melt electrospinning writing (MEW)–is also limited in thickness/volume due to the accumulation of excess charge from the deposited material repelling and hence, distorting scaffold architectures. The underlying physical principles are studied that constrain MEW of thick, large volume scaffolds. Through computational modeling, numerical values variable working distances are established respectively, which maintain the electrostatic force at a constant level during the printing process. Based on the computational simulations, three voltage profiles are applied to determine the maximum height (exceeding 7 mm) of a highly ordered large volume scaffold. These thick MEW scaffolds have fully interconnected pores and allow cells to migrate and proliferate. To the best of the authors knowledge, this is the first study to report that z‐axis adjustment and increasing the voltage during the MEW process allows for the fabrication of high‐volume scaffolds with uniform morphologies and fiber diameters.     

西南地区竹编工艺数字化平台建构及创新应用研究

目的 从设计学角度提出西南地区竹编工艺数字化的设计策略,通过“艺术设计+数字平台”来实现竹编工艺的创新设计与应用,助推传统竹编工艺的保护、传承、传播与创新。方法 在对西南地区传统竹编工艺发展现状研究的基础上,将西南竹编工艺进行梳理与分类,并对工艺特征进行衍生设计,以非物质化形式构建起竹编工艺数据库平台,进而通过具体的设计实践在实现竹编工艺创新应用的同时,也验证了竹编工艺数字化设计策略的可行性。结果 通过研究建立起了西南竹编工艺数据库,将有效地推动西南地区竹编工艺的设计产出与实践应用,拓宽了竹编工艺的应用范畴。结论 设计与技术的结合,实现了传统手工艺的在地创新设计与在线推广传播,多元化的手段促进了传统手工艺的创造性转化和创新性发展,更好地助力乡村振兴。     

筒型基础平台气浮拖航的影响因素分析

为研究筒型基础海洋平台气浮拖航运动特性, 以筒型基础抢修平台为原型, 采用水动力学软件MOSES对其进行模拟分析。建立了1:20 的平台缩尺试验模型, 其分析结果与模型试验结果吻合很好, 表明MOSES 模型计算结果有较高的可靠性。为消除模型试验中模型尺寸对平台拖航运动分析的影响, 按平台实际尺寸建立平台原型气浮拖航模型, 进而分析不同系缆点位置、波浪状态等因素对平台拖航的影响。MOSES 计算结果表明为提高平台拖航稳性, 系缆点位置应尽量靠近平台浮心所在平面, 以减小拖缆力产生的倾覆力矩;波浪高度对筒型基础海洋平台拖缆力和垂向运动影响较大, 当波高超过2m 时不宜进行拖航;顺浪拖航比顶浪拖航更加有利于拖航安全。     

现代竹结构的研究与工程应用

竹材是世界上为数不多的可再生资源,是建筑行业的理想材料。随着经济社会的发展、科学技术的进步、国家政策的推动,全生命周期均可实现与生态环境协调共存的竹结构是未来发展方向之一。虽然从基本方法与手段上,竹结构的研究可以从已经较为成熟的传统结构研究中汲取经验,但是,竹材的特殊使得竹结构在构件、节点以及体系构成上与传统结构存在显著差别,且目前针对竹结构的研究尚缺乏统一材料本构,手段也较为单一,节点连接形式局限性大,均限制了竹结构在工程中的广泛应用。结合已有成果,对竹结构中所涉及的竹材、竹构件、节点的力学性能作出分析;结合现代科技,对竹结构体系进行研究、总结。提出一种喷涂复合砂浆-原竹骨架组合结构体系,其整体力学性能好,功能性和适应能力强,施工速度快,可代替传统砖混结构,在低层房屋及村镇建筑中应用,具有较高的推广价值。     

Relating the effect of safety measures to expected number of accidents

Traffic engineers have long believed that the effectiveness (percentage reduction in accidents) of a safety measure is greater at locations which had many accidents than at those which had few. That this type of belief has often translated into warrants is evidence of the strength of this belief. Recent research has raised doubts as to whether this phenomenon is real or merely a manifestation of regression-to-the-mean. This paper addresses this issue in the context of an examination of the safety effect of converting 222 intersections in Philadelphia, PA, U.S.A. from two-way to all-way stop control. The results indicate that the conversions were more effective at intersections expected to have many accidents than at the relatively safe intersections. One of the important implications of this finding is that, for measures for which this phenomenon exists, effectiveness cannot be specified as a single accident reduction factor as is currently the practice.     

The 2.5 s Microgravity Drop Tower at National Centre for Combustion Research and Development (NCCRD), Indian Institute of Technology Madras

Space missions involving humans require a better understanding of various phenomena happening in space environments. A number of experiments need to be conducted in microgravity for addressing various issues encompassing safety (primarily fire) and better understanding of fluid and material behaviour. Of the various methods used for obtaining microgravity conditions, drop towers offer ground based microgravity platform. They provide a cost effective platform for doing short duration, repeatable, high quality microgravity experiments. This paper describes key factors that influence the design of a drop tower. The salient features of 2.5 s microgravity tower set up at National Centre for Combustion Research and Development (NCCRD), IIT Madras (IITM) are discussed. Primary features of the three critical elements, namely the drop capsule, the release unit and the decelerator unit are described along with review of these elements in existing drop towers. The IITM drop tower operates in ambient atmospheric conditions to minimise the cost of operation. In order to achieve good quality microgravity levels, a dual capsule configuration is adopted. The shape of the outer capsule is arrived at by detailed transient computational fluid dynamic analysis of the drag shield under free fall condition over the drop height. A pneumatic mechanism is used for capsule release and brought to rest at the end of fall in a carefully designed decelerator unit. The decelerator unit consists of an airbag with controlled air outflow for smooth deceleration.     

数字乡村战略下龙普村彝族竹编品牌建设研究

目的 探索数字乡村战略下品牌建设对龙普村彝族竹编工艺传承与乡村发展赋能的价值内涵和现实路径。方法 对云南红河龙普村进行实地考察,发现当地彝族竹编产业具备发展竹编品牌的条件和前景,拥有优势显著的竹资源、民族文化资源、地理条件资源。依据田野调查,总结龙普村彝族竹编的发展现状与困境,并挖掘龙普村彝族竹编品牌建设的价值内涵,力求推进彝族竹编活态传承与乡村振兴目标。结果 在实践层面上,分别从品牌架构、品牌形象、数字平台三个方面探索龙普村彝族竹编品牌建设现实路径。结论 龙普村彝族竹编品牌建设有利于延续龙普村彝族竹编活力与传承能力,同时增强农村内生发展动力,从而推动乡村振兴。     

Dialysis of persistent organic pollutants and polycyclic aromatic hydrocarbons from semipermeable membranes. A procedure using an accelerated solvent extraction device

Accelerated solvent extraction (ASE) is one of the most recent solid-phase extraction methods and has caught on all over the world in numerous laboratories. Until now it was not known that this device is also very suitable for performing dialysis. In this study, development of a rapid dialysis procedure (RDP) was described that is based on the dialysis of persistent organic xenobiotics from triolein-containing semipermeable membrane devices (SPMDs) using ASE. All the operating parameters were optimized within the framework of usage. The RDP procedure was compared with the conventional dialytic recovery of target analytes under atmospheric pressure using spiked analytes and real field samples of SPMDs exposed to urban air. The main advantages of the RDP in comparison to the conventional dialysis are the speed, with up to 70 times faster taking only 40 min, and the considerable reduction in solvent consumption (by two-thirds) when SPMDs with standard configuration are used. Moreover, the RDP is also suitable as an analytical cleanup procedure for the same analytes from various types of lipid samples and other difficult matrixes using semipermeable membranes.     

Failure analysis of connecting bolts in collapsed tower crane

The use of tower cranes can cause critical accidents during large building construction projects. Failure of the tower crane results in critical injuries to crane operators and other workers at the construction site. Issues that often cause the fatal collapse of tower cranes include the damage and fracture of the mast (or tower) and turntable parts, and the tower crane slewing‐unit‐support fleeing. Without systematic investigations and proper prevention procedures in place, this type of crane accident, which often leads to worker fatalities, will continue to occur. Therefore, more proactive, specialized and systematic research needs to be performed in terms of forensic engineering to minimize the occurrence of similar disasters. In this research, the tower crane collapse accidents are thoroughly investigated and the exact cause of the damaged crane parts is also identified using fractography and mechanical/chemical characterizations techniques, including visual inspections, field research, scanning electron microscopes and optical microscopes. Specifically, instrumented indentation technique is employed to evaluate the material properties, and energy spectrum analysis is used to determine the chemical characteristics. Based on thorough investigations, it has been identified that the connecting bolts of the tower crane are very vulnerable. It is recommended to improve the reliability of the bolts and to implement additional regulations to check their maintenance and safety. This research clearly provides guidance for investigating crane collapse accidents and contributes to the prevention of similar types of accidents. Several corrective actions and recommendations are suggested to reduce the risk of the tower crane failures.     

Fatalities and injuries in the Kuwaiti construction industry

This paper presents an analysis of construction accidents in Kuwait along with accident causation and injuries that can be considered serious or fatal, so that corrective measures can be taken to decrease casualties, resulting in a safer construction industry. The paper evaluates the existing injury and cost reporting-investigation system of construction accidents in government agencies and private firms.

This research confirms that construction is the most hazardous industry in Kuwait, with accidents accounting for 48%, 38% and 34% of all disabling injuries and 62%, 38% and 42% of all fatalities in 1994, 1995 and 1996, respectively. These rates are considered high and can be compared to construction accident statistics in the U.S.A. which accounted for 14% of all work-related deaths and 9% of disabling injuries in 1993. Based on the study, falling from a height appears to be the major cause of construction injuries and fatalities in Kuwait. Poor accident records and reporting systems hide the extent of the construction safety problem in Kuwait. In addition, many people at management level are unaware of accident-related costs and the effectiveness of a safety program in reducing project costs.     

Progressive image transmission using a prefilter and a modified difference pyramid structure

Abstract

Pyramid data structures have played an important role in progressive image transmission. Over the years, the reduced difference pyramid (RDP) has been found to be one of the best data structure. The RDP takes the differences between the neighboring nodes at the same level. The new modified difference pyramid (MDP) data structure, developed in this paper, takes the differences between successive levels. Simulation results show that both the bit rate and the complexity of the receiver for the MDP structure are lower than those for the RDP structure at the same quality.

An MDP coding process which incorporates a prefilter is also proposed in this paper. Simulation results show it can provide good quality (in a subjective sense) reconstructed images at a lower bit rate than the unfiltered scheme can. Also, acceptable intermediate images are interpolated via the repetition method and via the cubic convolution method to get images which are the same size as the original. Results are compared.     

Modelling the transport disengagement height in fluidized beds

Bubbles bursting at the surface of a bubbling gas fluidized bed (BFB) project particles into the freeboard. Coarser particles fall back, the solids loading declines with height in the freeboard, and fines are ultimately carried over. The height of declining solids loading is the transport disengagement height (TDH), measured in this research by positron emission particle tracking, and modelled from a balance of forces on ejected particles. Model predictions and PEPT-data are in good agreement. Almost all of the empirical equations overestimate the TDH.     

SBA-15 ordered mesoporous silica inside a bioactive glass–ceramic scaffold for local drug delivery

The paper reports the synthesis of an ordered silica mesostructure of the SBA-15 type inside a macroporous bioactive glass-ceramic scaffold of the type SiO(2)-CaO-K(2)O, to combine the bioactivity of the latter with the release properties of the former, in view of local drug delivery from implants designed for tissue engineering. The standard procedure for SBA-15 synthesis has been modified to minimize the damage to the scaffold caused by the acidic synthesis medium. The composite system has been characterized by means of Scanning Electron Microscopy (coupled with EDS analysis), Small Angle X-Ray Diffraction, Thermogravimetry analysis and Infrared Spectroscopy: the formation of a well ordered hexagonal mesostructure was confirmed. Ibuprofen has been chosen as model drug. The uploading properties have been investigated of the scaffold-mesoporous silica composite as compared with the scaffold as such, and a five-fold increase in the adsorbing properties toward ibuprofen was found, due to the presence of the ordered mesoporous silica. The ibuprofen release to a SBF solution in vitro is complete in 1 day. Retention of bioactivity from the glass-ceramic scaffold after the silica mesostructure incorporation has been observed.     

Cellular automata-based forecasting of the impact of accidental fire and toxic dispersion in process industries

The strategies to prevent accidents from occurring in a process industry, or to minimize the harm if an accident does take place, always revolve around forecasting the likely accidents and their impacts. Based on the likely frequency and severity of the accidents, resources are committed towards preventing the accidents. Nearly all techniques of ranking hazardous units, be it the hazard and operability studies, fault tree analysis, hazard indice, etc.--qualitative as well as quantitative--depend essentially on the assessment of the likely frequency and the likely harm accidents in different units may cause. This fact makes it exceedingly important that the forecasting the accidents and their likely impact is done as accurately as possible. In the present study we introduce a new approach to accident forecasting based on the discrete modeling paradigm of cellular automata. In this treatment an accident is modeled as a self-evolving phenomena, the impact of which is strongly influenced by the size, nature, and position of the environmental components which lie in the vicinity of the accident site. The outward propagation of the mass, energy and momentum from the accident epicenter is modeled as a fast diffusion process occurring in discrete space-time coordinates. The quantum of energy and material that would flow into each discrete space element (cell) due to the accidental release is evaluated and the degree of vulnerability posed to the receptors if present in the cell is measured at the end of each time element. This approach is able to effectively take into account the modifications in the flux of energy and material which occur as a result of the heterogeneous environment prevailing between the accident epicenter and the receptor. Consequently, more realistic accident scenarios are generated than possible with the prevailing techniques. The efficacy of the approach has been illustrated with case studies.     

Characteristics of low speed accidents with buses in public transport

Low-speed accidents with buses in public transport in the city of Uppsala during the years 1986-2000 are coded in 17 variables concerning mainly physical properties of the accident. The taxonomy uses classifications from existing schemes, but some are altered and some new are added to capture common features of reports of bus accidents in this population. It is found that side contacts and singles are the most common accidents, and that more than a quarter of all accident involvements occurs at bus stops. Inter-rater reliability calculations for the categories show that all except one have reliabilities above 80%. The level of internal validity, calculated as agreement of frequencies between time periods, is acceptable, despite many possible sources of change and bias. It is argued that the validity of this database far exceeds that of the, for research purposes normally used, non-company self-reports, state- and police-archives, due to more extensive reporting and corroborating evidence. The practical usefulness of these results and accident taxonomies in general is discussed.