房地产企业BIM 技术采纳影响因素研究

为解决房地产企业BIM 技术采纳不理想的问题,基于信息技术采纳相关理论,将个体采纳层面的技术接受与应用统一理论与组织采纳层面的任务技术匹配模型相结合,同时考虑房地产企业特征及BIM 技术特征。在此基础上提出相关假设,建立房地产企业BIM 技术采纳模型。利用SPSS 及Amos 软件对所收集的328 份有效问卷数据进行分析。最终得到影响房地产企业BIM 技术采纳的影响因素及各因素之间的相互关系,并提出针对性建议以期对决策者提供参考。     

基于人工神经网络的房地产市场预警模型研究 ——以成都市为例

随着社会的不断进步,房地产业迅速繁荣,对房地产市场进行有效的调控显得尤为重要。结合成都市房地产市场的特点,以及人工神经网络容错性、易操作等特性,利用人工神经网络建立房地产市场预警模型。选取成都市房地产业 2000~2014 年的数据,建立BP 人工神经网络模型,将2000~2013 年的数据作为训练样本,2014 年的数据作为检测样本。通过5000 次训练,在第263 次时得到最佳结果,实现了误差小于1e-6 的训练目标,其仿真效果具有较高的可信度。该BP 人工神经网络模型在有效进行市场预测、促进房地产市场可持续发展等方面有较高的实际意义。     

改进GM(1,1)模型在建筑工程现金流预测中的应用

准确的建筑工程现金流预测是提高建筑行业投资和融资决策效果、获得稳定收益的前提,合理的现金流预测方法是确保预测结果准确的关键。引入灰色预测和"1/4:1/3"现金流预测理论,提出基于权重因子的背景值构造,并以实地收集的10余个建筑工程项目为样本,采用黄金分割法和对半分割法对GM(1,1)模型进行改进,以提高GM(1,1)模型在建筑工程现金流预测实践中的适用性和适应性。实证结果表明,改进后的灰色预测模型能够以较高精度预测建筑工程现金流,从而为公司投资、融资决策以及资金管理提供可靠依据。     

基于灰色模型的房地产开发企业战略成本管理风险评价

在房地产开发企业存在多个子公司、子公司有多个在建项目的条件下,针对房地产开发企业战略成本风险管理水平较难评判的情况进行研究。通过专家访谈与文献综合,以标准住宅的特征价格与项目战略成本对比作为专家评判的依据,建立了多项目房地产开发企业战略成本风险管理灰色综合评判模型,通过专家打分并对打分结果进行处理,从而评判房地产开发企业战略成本风险管理水平,减少了对风险管理水平判断的主观性。从实证结果来看,该方法较准确地判断出了当前企业的战略成本风险管理水平,为企业制定相关发展战略提供了依据,效果较显著,其科学性及实用性得到了初步验证。     

Evaluation of prestress losses in prestressed concrete specimens subjected to freeze–thaw cycles

Prestressed concrete structures are considered to be reliable and durable. However, their long-term performance when subjected to frost attack is still unclear. In this work, experiments were carried out to evaluate the prestress losses in post-tensioned prestressed concrete specimens subjected to freeze–thaw cycles (FTCs). Two cases were considered: in one case, a series of specimens were prepared and tested in a freeze–thaw chamber; in the second case, the same series of specimens were tested in an indoor environment (outside the chamber). The difference between the prestress losses of the specimens inside the freeze–thaw chamber and those outside the chamber equalled the prestress losses due to FTCs. When using mathematical models to predict the prestress losses due to the FTCs, it was found that they were relatively small when the concrete was slightly damaged. However, they increased rapidly when the FTCs were repeated. The eccentricity of the prestress wires led to larger prestress losses when subjected to FTCs. Moreover, the same cross section and eccentricity resulted in similar prestress losses due to the FTCs, and the relatively high-strength concrete could withstand more FTCs.     

Magnetic refrigeration: a promising new technology for energy saving

Magnetic refrigeration is an emerging, environment-friendly technology based on a magnetic solid that acts as a refrigerant by magnetocaloric effect. The reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative refrigeration). In this paper, attention is directed towards the near-room-temperature range. We compare the energetic performance of a commercial R134a refrigeration plant to that of a magnetic refrigerator working with an AMR cycle. The comparison is carried out by means of a mathematical model. In these simulations, we consider different solid magnetic refrigerants, namely, Gd, Gd_0.95Dy_0.05, Gd_0.9Tb_0.1,Gd₅Si₂Ge₂, MnAs_0.9Sb_0.1, and MnAs_0.95Sb_0.05. We compared two different geometries of the regenerator: a porous medium and a flat plate. In the former, the Coefficient of Performance (COP) of the AMR cycle is better than that of the vapour compression plant only in the low mass flow-rate range. Whereas in a flat plate regenerator, the COP of the AMR cycle is better than that of the vapour compression plant only in the high mass flow-rate range.     

Stress among South African construction professionals: a job demand-control-support survey

Research into workplace stress in the construction industry has been dominated by studies undertaken in Hong Kong, England and Australia, with relatively little attention having been paid to African countries. A purposively selected sample of thirty-six construction professionals (comprising architects, project managers, construction managers, engineers and quantity surveyors) based in Cape Town, South Africa, were surveyed regarding their perceptions about, and experiences of, workplace stress. The purpose was to identify and rank job demand, job control and job support factors and to analyse these by gender and professional grouping, both in terms of how respondents perceived them, as well as in terms of how frequently they had experienced them. The main finding was that respondents’ perceptions about the importance of job demand, job control and job support factors were largely consistent with their own experience of these factors. Distinguishing between perceptions and experience of stressors and moderators of stress was, however, considered valuable because the fact that differences were found indicates the need for precision in the design of scales. The highest ranked factors were, respectively, ‘critical time constraints’, ‘volume of work’ and ‘adequate compensation (salary)’. Women and men ranked items differently, as did the various professional groups. The main conclusions were that the construction project environment is a time-pressured, complex, environment in which work-life balance is negatively affected, particularly for women. Control over the type, flow and volume of work were perceived to be the main moderators of stress, whilst salary and career path opportunities were perceived to be the main job support moderators of stress. The applicability of using the job demand–control–support framework was confirmed given that the main stressors, control and support moderators were found to be to be largely consistent with the findings of previous studies. Future research taking a gendered approach should anticipate issues important to female respondents and should consider the benefits of qualitative methods. The design of research focusing on construction professionals should consider using the project team as the unit of analysis to ensure that the influence of the interconnectedness of participants’ roles is taken into account.     

铁矿井塔钢筋混凝土模型的试验研究

铁矿井塔属于重载高层构筑物,为探讨强度和稳定性,利用异质模型,国内不少单位用力学手段进行过许多研究,由于泊松比不一致,给实验带来误差.本文针对一井塔,利用钢筋混凝土同质模型,对井塔进行了强度、稳定性分析,为工程设计提供了重要资料.     

框支连续墙梁抗震试验与分析

做了三榀两跨框支墙梁1/2比例模型试验;对模型在竖向及反复水平荷载作用下的破坏过程、破坏机理和水平承载力等进行了分析;根据试验与分析结果,论述了这种结构的抗震性能.     

饮用水氯化中氯仿形成的动力学模式

以黄腐酸（ＦＡ）为卤仿前驱物质，分别测定不同投氯量、ＴＯＣ水平、温度以及ｐＨ值对ＣＨＣｌ３形成速率的影响，确定出ＣＨＣｌ３形成的动力学模式。该模式可用于预测投氯后的管网水中ＣＨＣｌ３的形成量，以便采取必要措施保证饮用水符合国家规定ＣＨＣｌ３〈６０μｇ／Ｌ的标准。