Price relationships between qualitatively differentiated agricultural products: organic and conventional wheat in Germany

Organic agriculture, which produces commodities that can be qualitatively differentiated from conventional food products, has grown into an important market in many countries. The dynamics of commodity prices in both sectors are partly interdependent, but are also shaped by independent determinants and have rarely been studied. We analyze organic food markets and their interdependencies with conventional markets in the context of wheat markets in Germany, which have been subject to a number of fundamental changes during the last two decades. Based on institutional market characteristics, we suggest a flexible Markov‐switching asymmetric time series model. We find a pronounced temporal sequence of market phases that differ in their asymmetric dynamics and the extent to which the organic price is influenced by the conventional price. Organic wheat prices tend to be increasingly connected to prices of conventional wheat.     

构建生态型政府:理论体系与实践路径研究

立足于生态文明建设与生态型政府创建的关键时期,通过生态型政府的理论内涵,深入探讨构建生态型政府应坚持的动态平衡原则、尊重多样性与公平原则、开放原则、协同原则;提出生态型政府应符合节约型政府、有限责任政府、开放透明政府、解制型政府的基本范式,勾勒出创建生态型政府应遵循的理论依据。基于理论体系的探讨,进一步从生态优先的执政理念、职能体系、体制创新、利益相关的多元治理模式、坚持绿色GDP的绩效考核体系等方面阐述了构建生态型政府的实践路径。     

The moderating role of nationality on destination experience

ABSTRACT

Differences in tourists’ cultural values are significant factors in their product and service choices, yet they have generally been neglected in the literature. Therefore, this study examined how tourists’ nationalities influence their perceptions of service quality, affective image perceptions, and revisiting intentions. Activities were found to be more determinant on a destination’s affective image for Russian tourists, whereas accommodation, hospitality, and language communication services had a larger effect on German tourists.     

Buchbesprechung

Buchbesprechung

Buchbesprechung     

Analysis of congress destinations' competitiveness using importance performance competitor analysis

To be competitive and successful in congress tourism, destinations must learn which congress tourism-related attributes are important and how they perform against their main competitors. This study identifies the importance and performance of destination attributes in Antalya, Turkey, and compares the position of these attributes to those of its main rival in congress tourism, ?stanbul. Importance performance competitor analysis results show that, according to domestic participants, Antalya has to focus on “sight-seeing and cultural attractions” and “outside entertainment.” For international participants, “climate,” “choice of meeting and housing properties,” and “suitability of conference facilities” exhibit higher performance in Antalya than ?stanbul.     

Operating Strategies for Battery Storage Systems in Low-Voltage Grids to Limit the Feed-In Power of Solar Power Systems Using Fuzzy Control

Germany’s energy turnaround is leading to an increasing integration of photovoltaics (PVs) throughout its distribution grid. To ensure safe grid operation in times of high solar radiation, PV plants must either be throttled back to comply with the feed-in limitation or store a portion of their excess electricity in batteries. This paper presents a grid-optimized operating strategy for PV storage systems based on a Fuzzy Logic Controller that reduces peak feed-in and thus also PV curtailment losses. The Fuzzy Logic Controller uses data on PV power surplus and battery charge level as input variables. To obtain good results, the set of numerical parameters of the membership functions is enhanced by evolutionary programming.The energetic assessment shows that even small electrical storage capacities (<<5?kWh) reduce curtailment losses considerably when using the grid-optimized operating strategy. The economic assessment shows that, in 2016, investments in PV storage systems with large PV plants and small batteries have small (positive) Internal Rates of Return. The system efficiency of the battery storage has a small impact on the profitability of PV storage systems, whereas the cycle stability and the electricity purchase price have a large impact. Moreover, there is an economic benefit for plant operators to switch from the simple to the grid-optimized operating strategy. Solar forecast inaccuracies and variations in load and generation profiles have a negligible impact on the performance of the control algorithm.     

城市土地空间结构演变及其驱动机制分析

城市土地利用空间结构及其演变一直是城市地理学、城市经济学、城市规划学、土地利用学等学科研究的核心与热点问题.当前我国城市土地利用正处在快速城市化的开端,在未来近半个多世纪的时期中,将一直处于急剧突变进程之中.加强对我国城市土地空间结构演变及其驱动机制的研究,有助于我们从城市用地结构演变的根源分析问题.本文简要概括了城市土地利用空间结构的相关研究,分析了城市用地空间结构演变在空间上的两种表现形式,并在此基础上分析了城市用地空间结构演变的动力主体、驱动力和驱动机制,以期为更好地促进城市土地利用结构的优化提供相应的参考.