Residents' preferences for private amenities and trade-offs associated with various spatial densities and patterns

ABSTRACT

Northwest Arkansas planning policies, like a number of communities across the country, have identified goals working toward more sustainable, livable, and subsequently denser development patterns. However, the understanding of residents’ perceptions of such living arrangements is limited. This study provides a more nuanced understanding of Northwest Arkansas residents’ spatial preferences through a survey of residents’ preferences for private amenities and their trade-off with various spatial densities and patterns in support of sustainability. Results of the survey indicate a preference for, and experience with, single-family residential living arrangements and amenities, with the preponderance (80%) of survey respondents currently living in single-family housing. There is a preference for low-density neighborhoods even if it means sacrificing other amenities. This study is in alignment with previous research suggesting that people may learn to prefer where they live. Additionally, while the majority of survey respondents indicated a preference for communal greenspaces, renters are more likely to prefer communal greenspaces when compared to homeowners. This study indicates that attached, multi-family development and renter development in Northwest Arkansas should consider the provision of communal green spaces, walkable access to transit, and walkable access to services as desired amenities for those residents.     

高性能碳基储能材料的设计、合成与应用

电化学储能器件的性能很大程度上决定于其电极材料。碳材料具有来源广泛、化学稳定性好、易于调控、环境友好等优点，被广泛应用于各类能量存储系统，但仍存在能量密度低、倍率性能差等问题。本文从碳材料孔结构调控、杂原子掺杂、与金属氧化物复合三个角度，综述了构建高性能碳基储能材料的设计合成策略，介绍了其在锂/钠离子二次电池、超级电容器等领域的研究进展，对几种方法策略的优缺点进行了总结，并对未来的研究方向进行了展望。本文对高性能碳基储能电极材料的设计开发具有积极意义。     

Estimating the system efficiency of the multifunctional hydrogen complex at nuclear power plants

The paper deals with the primary current frequency regulation in the energy system (ES) as well as the basic requirements for NPP power units (PUs) under the conditions of involvement into the primary regulation. According to these requirements, NPP operation is related to the unloading and corresponding decrease in efficiency. It has been shown in this connection that combining NPP with a hydrogen complex (HEC) allows excluding the inefficient unloading mode. This enables the steam turbine and reactor equipment to operate in the basic mode at nominal power level. Besides, the conditions for producing and storing hydrogen and oxygen during the day as well as additionally during the night-time of off-peak electrical load may be created, which allows using them for generating peak power.In the paper, the systemic economic benefit as a result of involving NPP combined with HEC into primary regulation of the current frequency in ES with allowance for expending resources for the main equipment has been estimated. In this regard, the paper gives grounds for cyclic loadings of HEC main equipment including metal tanks for storing hydrogen and oxygen, compressors, hydrogen-oxygen combustion chamber (HOCC) for hydrogen-steam superheating of the actuating medium in the NPP steam turbine cycle. Methodological grounds for evaluating the equipment endurance under cyclic loading with involving into the primary frequency regulation by the criterion of the fatigue crack growth rate are described. It has been shown that in terms of HEC equipment, the highest load intensity occurs in HOCC due to high thermal stresses.Also, the systemic economic benefit has been estimated, and the impact of the equipment deterioration under conditions of cyclic loading has been demonstrated. It is shown that when combining NPP PUs with HEC, the efficiency of primary regulation may significantly depend on such factors as the cost of equipment exposed to cyclic loads, the frequency and intensity of cyclic loads, and the relation between the peak electricity tariff and the cost price of electric energy produced by NPP.It has been shown on the basis of novel methods for estimating the efficiency of involving NPP with HEC into the primary frequency regulation with allowance for damage to the equipment, that the use of HEC may provide a considerable economic benefit, as compared to the version of NPP unloading when involving directly into frequency regulation.     

我国矿业海外直接投资区位分布与空间经济效应研究——以世界主要经济体为例

以我国矿业对世界主要经济体直接投资为例, 基于2009~2018年投资存量数据, 在多区域结构分析框架下, 运用投资多样性指数、动态时空模型、灰色系统预测模型分别对投资区位分布特征、空间经济效应以及未来分布趋势进行了研究。结果显示: ① 2009~2018年, 我国矿业对世界主要经济体直接投资区位分布呈现出“由高度集中转向渐进扩散”“高者仍高、低者仍低”的集团俱乐部式时空分布特征;② 投资区位分布受到了来自于其他国家(地区)全局效应和相邻效应的影响;③ 2019~2020年, 在空间经济效应作用下, 投资渐进扩散趋势仍将持续, 集团俱乐部式分布有所减弱;我国矿业对欧盟、俄罗斯联邦、东盟、美国的投资机会及热度将有所增加。依据研究结果, 提出了我国矿业海外直接投资的启示及建议。     

电爆喷涂粒子的约束调控机制及对沉积行为的影响

采用对喷涂粒子进行槽内约束的电爆喷涂方法,研究了喷涂粒子在垂直槽中的约束调控机制及其沉积行为。结果表明:约束深度达20mm时,即喷涂距离为丝径的100倍时,仍可获得连续、均匀的涂层。约束宽度从6mm减小至2 mm,涂层表面呈现出由粗糙的"丘壑状"形貌向均匀的"薄饼状"形貌逐渐过渡的演变趋势,且涂层厚度显著提高;能量密度从57 J/mm~3提高至152 J/mm~3,同样可提高涂层厚度并改善涂层均匀性。对喷涂粒子进行收集,发现减小约束宽度和提高能量密度均可有效细化喷涂粒子并使喷涂粒子粒径分布更加均匀。分析认为,由焦耳加热导致的"热膨胀效应"和击穿电弧伴生的"压力效应"共同决定电爆冲击波和喷涂粒子的形成,并随能量密度和约束参数的变化,对喷涂粒子表现出不同的约束调控作用,使其沉积行为产生显著差异。     

内河船舶LNG发动机-蓄电池混合动力系统性能仿真

为改善船舶天然气发动机动力系统调速性能，提高内河液化天然气（LNG）燃料动力船舶的操纵性及安全性，提出构建天然气发动机-蓄电池混合动力系统。分别针对LNG发动机动力系统及混合动力系统建立Matlab/Simulink仿真模型，并实现了船舶起动和变负荷过程。对两种仿真系统的仿真结果进行分析，结果表明：采用该混合动力系统的船舶变负荷过程航速变化区间变大，系统达到稳定时间缩短；采用设计的控制策略，天然气的消耗最多降低19.6%；NOx、CO、HC排放分别最多降低22.1%、18.5%、23.6%。     

Winners and losers of rapid growth in Turkey: Analysis of the spatial variability of convergence

This paper investigates spatial variability of regional convergence for the 2004-2017 period in Turkey. Results from neoclassical convergence model which are robust to inclusion of a spatial battery points out the existence of convergence. However, additional results highlight that regional convergence is spatially heterogeneous. While underdeveloped regions exhibit higher convergence, convergence speed is not distributed evenly among these underdeveloped eastern regions. These findings point out that, last epoch of Turkish transformation fails to have equity enhancing effects at local level, rather there are winners and losers of the rapid growth of 2000s.     

Environmental Engel curves in Italy: A spatial econometric investigation

This paper adopts a spatial econometric methodology to investigate the relationship between income and direct household emissions in Italy, as posited by the environmental Engel curve. The spatial approach is motivated by an expanding strand of studies that have detected significant spatial interactions in household-polluting activities responsible for the generation of direct household emissions. Our results suggest the presence of significant spatial dependence for household emissions emerging among regions. At the same time, increases in the level of income do not seem to be coupled with a higher demand for environmental quality by Italian households.     

Evaluating the role of resilience in reducing economic losses from disasters: A multi-regional analysis of a seaport disruption

Models to estimate economic impacts of disasters have recently been augmented to include resilience. However, most research has incorporated only a limited set of resilience tactics and has not estimated their individual loss reduction effect. We present a comprehensive framework for estimating the relative effects of a broad set of post-disaster resilience tactics. Our methodological innovation is illustrated by adapting the TERM multi-regional CGE model for a seaport disruption, distinguishing inherent resilience working through the price system from adaptive resilience and other inherent tactics to cope with input shortages. We also overcome a path-dependency problem in the modelling process.     

双PWM变频调速系统在矿井提升机中的应用

针对目前大部分矿井提升机仍采用转子串电阻调速方法造成能量浪费的现状,提出了一种双PWM变频调速方案:三相电压型PWM整流器采用电压、电流双闭环控制,其中电流环引入前馈解耦控制,并结合空间矢量脉宽调制(SVPWM)算法来提高直流电压利用率。仿真实验的结果表明,该双PWM变频调速系统控制精度高、动态响应快、抗扰能力强,能有效地实现矿井提升机的节能降耗。