A note on the dynamics of population density gradients

The aim of this paper is to show how the density gradient can be modified to take account of population increase and income growth (reflected in a decline in the slope of the gradient). It is shown that central city densities and the slope of gradient are related exponentially. Given certain assumptions about the income elasticity of demand for space, it is possible to draw inferences about the relative contribution of income growth and population growth. An illustration using four American cities suggested population changes have been more important than income, effects, especially since 1930.     

Measurement of density gradients and space-filling in urban systems

New digital data sources for urban analysis are becoming available, which are far more disaggregate, comprehensive and frequently updated than those used hitherto in regional science. Urban theory in regional science has often been founded upon notions of settlement density that are not fully deliberated in theoretical terms, and which in practice are often shackled to inappropriate and overly coarse zonations. Clearer conception and better measurement of density and the related concept of space-filling are seen as central to applied analysis in regional science. In this spirit we probe the uncertain and ambiguous conception of urban ‘density’ and space-filling, and illustrate how new data sources permit sensitivity analysis of measurements of these properties. We illustrate our arguments with an extensive, if necessarily preliminary, analysis of some characteristics of a large UK city, including a sensitivity analysis of density profiles and fractal measures. Received: 20 July 1999 / Accepted: 4 June 2001     

Location-specific amenities,topography, and population migration

Despite the increased attention devoted to amenities in the migration literature, most studies that even consider amenities only include 1 or 2. Generally a single temperature or sunshine variable has had to suffice. Topographical characteristics, including such major features as proximity to mountains or major coastlines, have virtually been ignored. This paper focuses on the importance of several location-specific amenities, including mountains and coastlines. All of these amenities appear to significantly influence migration flows. Specifically, summer temperature at the destination is potentially the most important determinant of destination choice, with very hot summers being repulsive. Migrants are strongly attracted to sunny locations and strongly repulsed by very cold winters. Although of less relative importance, migrants are significantly influenced by windiness, humidity, terrain, and proximity to major coastlines. There does not appear to be a general tendency for migration to be equilibrating with respect to location-specific amenities     

Land development and amenities: A predator-prey interaction

How land development in the form of land improvements and locational amenities interact in time, at any point in space characterized as a tourist area, is the topic of this rather brief investigation. The strong, non linear, interactive dynamics between the two entities is viewed in a general ecological predator-prey formulation, under a series of scenarios. Mildly cyclical and eventually unstable dynamics are portrayed under numerical simulation to be perhaps the most likely of the various scenarios explored. Windows of opportunity for governmental intervention are shown to exist, in the case where complex scale effects and significant externalities take place between the two. This paper presents an effective framework to fruitfully examine issues of sustainable development. Received: January 1998/Accepted: October 1998     

Hazardous goods and their environmental impact

The paper reviews the problems generated by transportation, handling and storing of hazardous goods in harbours and their surroundings. It expands on the heretofore narrow topic of direct dangers and consequences for the environment and examines secondary effects and potential remedies.     

Integrating scenic and recreational amenities into numerical forest planning

This study proposes an operational way of computing the amenity value of a forest area that consists of several stands or compartments. Such a method produces an amenity index suitable for numerical optimization. With this method of computation, amenity is divided into scenic and recreation values. Scenic value of the forest depends on the visibility, area, and scenic beauty score of different compartments. Recreation value of the forest is a weighted mean of variety and the area-weighted mean recreation value of compartments. Variety is described by the total length of boundaries between distinctly different compartments. Recreation value of a compartment is the product of accessibility and recreation score of the compartment. Recreation and scenic beauty scores are computed from stand characteristics using empirical models. The study describes a complete planning system that uses the developed amenity index as a decision criterion, and relates a case study to illustrate the effect of amenity objective on choice of treatments for compartments.     

Nature's Neighborhood: Urban Environmental History and Neighborhood Planning

The physical form of an urban settlement is a product of the reciprocal relationship between the humans and the ecological systems in the area which act together to create an urban landscape that changes through time. While many of the interactions between the natural world and the built environment occur at the regional level, the quality of life experienced by residents is in large part a function of environmental conditions in the neighborhood. This article explores the benefits to neighborhood planning from incorporating urban environmental history. It reviews the conceptual territory of urban environmental history and presents a framework for its application to neighborhood planning. An environmental history completed for a neighborhood is highlighted to illustrate the technique.     

Endogenous determination of historical amenities and the residential location choice

Brueckner et al. (Econ Rev 43:91–107, 1999) remark that city’s historical amenities, which are considered exogenous today, may have been formed endogenously over time. This paper develops a simple two-period model based on this idea. It assumes there are two locations in a city and two income types. Lot sizes are decided myopically in the first period and cannot be adjusted later. Without historical amenities, locations of the rich and the poor are never reversed (the poor always locate closer to the center) for increasing population, income and utility levels of each type. If the rich leave some “historical amenity” behind for the residents in the second period, locations are reversed when the population of the first period is moderate, income disparity between the two types is low and the rich is sensitive to amenity. An earlier version of this paper was presented at International Symposium on Spatial Economics and Transportation, Sendai, Japan, June 13, 2005. The paper has benefited greatly from the comments of Dr. Jan Brueckner, who participated in the symposium, and Dr. Charles de Bartolomé, my academic adviser in the University of Colorado at Boulder.     

Wages,local amenities and the rise of the multi-skilled city

This paper examines a set of necessary and sufficient conditions under which equilibrium involves mixing multiple types of workers in cities. Multi-skilled cities emerge if workers gain more from labor complementarities than they lose if they cannot consume their most preferred local amenities. A review of the different approaches to the presence of equilibrium in local public good economies is also provided.     

社区公园的声景观研究

通过对杭州市翠苑一区社区公园的使用后评价,该公园声景观现状、使用者行为及其空间分布得到了全面的分析,并在声景观要寨选择、空间分区和管理等几个方面加以阐述．形成了完整的社区公园声景观设计方法。居民对该公园声景观的好感度和协调度的评价结果说明了声景观设计应着重考虑与周围环境的相互配合,同时声景观空间分区也具有相对的重要性。该研究成果不仅对社区公园的景观设计提供了基础资料和分析手法,而且通过建成环境的使用后评价丰富了当前的声景观研究。     

Properties of water at hydrophobic surfaces and their impact on wedging pressure

A hypothesis on the impact of water density at hydrophobic surfaces on the electrostatic component of their interaction is proposed. A theoretical model of the double electric layer and wedging pressure at variable density and consequently water permittivity has been developed. It was shown that reduction of permittivity at interphase surfaces determined by their hydrophobicity results in the compression of double electric layers and the weakening of the interaction of the latter.     

Different glazing systems and their impact on human thermal comfort—Indian scenario

In the present communication, fifteen different glazing systems ranging from 3 mm single glazed clear glass to double glazed with low-e and solar control coating, have been analysed in terms of their human thermal comfort impact. Thermal comfort is measured in term of PMV (predicted mean vote) and PPD (predicted percentage of dissatisfied). Study encompasses all the six climatic zones of India. By using OPTICS 5.0 and WINDOW 5.0, U-values, solar heat gain coefficient, inside glazing surface temperatures and inside solar radiation have been computed. Depending upon different climatic zones, six sets of different design conditions, in terms of ambient temperatures, solar radiation and wind velocity, have been chosen. Typical values of metabolic rate and clothing insulation taken are 1.2 met and 0.5 clo for summer and 1.0 met and 1.0 clo for winter, respectively. Inside room air velocity is taken as 0.15 m s⁻¹ round the year. Room temperature is taken as 20 °C in winter and 25 °C in summer. It is found that for cold station (e.g. Leh) all glazings except solar control glazings, ensure thermal comfort and total PPD is less than 10% (|PMV|?0.5). For warm and hot climates, solar control glazings are thermally suitable. Results for winter night of Delhi shows that all the 15 glazings are inadequate for thermal comfort and PPD, due to cold feeling, varies between 27% and 33% approximately.     

Characterization of various cement grinding aids and their impact on grindability and cement performance

The aim of the present research work was the evaluation of six commercial grinding additives, which were used for the production of Portland cement (ground in a ball mill at a laboratory stage). For this purpose, a reference sample was also produced without using any admixture. The characterization of the grinding aids (GA) was carried out by Fourier transform infra-red spectroscopy (FT-IR) and gas chromatography/mass spectrometry (GC/MS). All the cement mixtures were tested for initial and final setting times, consistency of standard paste, flow of normal mortar and compressive strengths after 2, 7 and 28 days. In all cases the addition of grinding aids resulted in improvement of the specific surface and grindability index, a fact that was attributed to the additive ability not only to reduce resistance to comminution, but also to prevent agglomeration and powder coatings of ball and mill. The mortars made with cements ground with the addition of commercial additives, which contained triisopropanolamine (TIPA), exhibited higher strength at any age and higher setting times. On the other hand, the presence of triethanolamine (TEA) on the commercial grinding additives did not affect the mechanical properties of the produced cements but slightly decreased their setting times.     

Relationships between project governance and information technology governance and their impact on project performance

This research endeavors to address the question of how to enhance project performance through exploring the relationships among information technology (IT) governance, project governance and project performance. The research utilizes an empirical survey methodology. The survey of 533 working professionals in various industries renders 282 usable responses or a response rate of 53.91%. The results suggest that both IT governance and project governance have a positive impact on project performance. Moreover, we found that three dimensions of IT governance (i.e., strategy setting, value delivery, and performance management) are positively associated with project performance while all three dimensions of project governance (i.e., portfolio direction, project sponsorship as well as project effectiveness & efficiency, and disclosure & reporting) are positively associated with project performance. Additionally, the alignment between IT governance and project governance is also found to be positively associated with project performance. These findings provide evidence to project management professionals in regard to IT governance and project governance being part of the operational strategy in facilitating the success of projects. It also demonstrates the importance of the alignment strategy between IT governance and project governance in enhancing project performance.     

新加坡邻里中心模式研究

邻里中心是一种体现以人为本,注重社区交往的住区公共服务设施的规划模式。在新加坡的新市镇建设中广为运用,是其顺利开展并得以成功的重要因素。我国苏州工业园区的规划设计借鉴了新加坡经验,并结合我国国情进行了有益探索。本文探讨了邻里中心的概念,详细分析了新加坡邻里中心的规划模式并介绍其在我国苏州工业园区的实践经验,最后归纳总结了邻里中心规划思想的借鉴意义。     

基于慢行的城市社区适老公共服务设施配置

以南京五个城市社区为例,基于老龄人口慢行出行特征界定其活动范围、进行公共服务设施使用调查、对服务设施进行适老性评价。发现目前社区缺乏自身完整服务设施体系、适老服务设施存在不均衡性等问题,最终提出相应的配置建议。     

汉口“星分”研究之二：泰兴星与同兴里

该文简要介绍了汉口近代里分泰兴里与同兴里的概况和历史。采用比较研究的方法,将两个里分从规划布局,建筑形态等角度进行对比分析,指出泰兴里与同兴里不同的房地产开发模式对现代地产开发模式的借鉴作用。     

Initial studies of oxidation processes on filter surfaces and their impact on perceived air quality

Used filters can be a strong sensory pollutant source. Oxidation processes, especially those initiated by ozone, may contribute to the pollutants emitted from such filters. In the present study, ozone was added to the airstream passing through used ventilation filters. Two flow rates were examined. While the upstream ozone concentration was approximately 75 ppb, the concentrations downstream of the filter were initially 35-50% lower. However, within an hour downstream concentrations were only 5-10% lower than those upstream. These filter samples were then placed for 48 h in nitrogen, ambient air containing less than 5 ppb ozone, or ambient air at an elevated temperature. This resulted in partial regeneration of the ozone removal capability of the filter. In analogous experiments, lower ozone removal occurred when the filter samples were first ventilated for 24 h with ozone-free air before making the measurements. Samples from a new filter removed <10% of the ozone in the airstream, and removal remained relatively constant over time. In companion studies, human subjects assessed the air passing through various used filter samples. In the initial evaluation each of the four filter samples, taken from the same filter and ventilated for 24 h, were assessed to be equivalent. The next evaluation was immediately after the samples had been kept for 24 h in either nitrogen, air, air at an elevated temperature or ozone. The nitrogen-treated filter was assessed to be best, while the ozone-treated filter was assessed to be the worst. The final evaluation occurred after ambient air had passed through the 'treated' filters for 2 h. All such ventilated filters were assessed to be more acceptable than immediately after the 24-h treatments; the ozonized and air-treated filters were the most polluting of the four. Practical Implications The present paper supports previous findings that loaded ventilation filters can be significant sources of sensory pollution. Replacing a loaded filter with a new filter temporarily removes this source of pollution. However, the present study does not provide an answer to how frequently changes are needed under different conditions. The results indicate that in cases of intermittent operation of ventilation systems, the airflow through the polluted filters should be restarted in sufficient time prior to occupancy to purge odorous pollutants that have accumulated on the filter surface. Removal of ozone upstream of the particle filters may further improve perceived air quality in the space downstream of the filter bank. Future efforts related to the development and application of low-polluting filtration systems are warranted.     

Absorptive,innovative and adaptive capabilities and their impact on project and project portfolio performance

This study explores how absorptive, innovative and adaptive capabilities within early project phases affect project and portfolio performances in pharmaceutical and biotechnology R&D organizations. A sequential qualitative–quantitative mixed method was used with 18 interviews and 80 responses to an online survey. The results show effects of absorptive, innovative and adaptive capabilities on short- and long-term project performance and portfolio performance. Absorptive and adaptive capabilities are the primary contributors to the performance outcome, whereas innovative capabilities are a minor contributor. Managerial and theoretical implications are discussed.