Spatial Integration,Adjustment, and Structural Transformation in Sub‐Saharan Africa: Some Linkage Pattern Changes in Ghana     

J. Henry Owusu 《The Professional geographer》2001,53(2):230-247

In 1983, Ghana embarked on a program of structural adjustment under the auspices of the World Bank and the International Monetary Fund, to resuscitate the economy and to foster development. This paper utilizes the Lagos Plan of Action, a comprehensive, continent‐wide effort and African‐led policy strategy for the economic development of the African continent, to examine the contribution of adjustment to the development of an integrated economy in Ghana. Adjustment is examined as a form of structural transformation, as evidenced by the emergent intranational (intra‐ and inter‐sectoral) and international linkages in the formal wood processing industry, a key sector with tremendous potential for such linkages. Intranationally, this study shows that, as in the pre‐adjustment years, inter‐sectoral linkages, although important, were not dynamic enough to play a significantly galvanizing role in the nation's economic development. However, intra‐sectorally, a dramatic expansion in lumber exports led to an unprecedented constriction in the traditional forward linkage between sawmills and downstream processors. This forced the latter to depend on the informal sector for inputs. Internationally, Ghanaian firms operated as subcontractors of convenience for firms overseas (particularly in Europe) via an expanded forward linkage, reflecting a new “colonial relationship” under the program.  相似文献   

The impact of small-scale wood harvesting on neem Azadirachta indica A. Juss stands in the coastal savanna of Ghana     

Michael O'Neal Campbell 《Area》2005,37(1):8-16

Although the introduced neem tree Azadirachta indica A. Juss is a very important energy source in the coastal savanna of Ghana, the sustainability of small-scale wood harvesting (SSWH) has not been investigated with regard to this species. This paper assesses the sustainability of SSWH on neem stands in the coastal savanna, using a socio-economic and ecological survey. The results show that SSWH, incorporating coppicing, stand tolerance, balanced with total bole cutting and root removal, and based on socio-cultural supports, has created a modified yet sustainable system of SSWH. It is concluded that these systems may contribute to tree stand conservation.  相似文献   

Large wood potential,piece characteristics,and flood effects in Swiss mountain streams     

Christian Rickli  Alexandre Badoux  Dieter Rickenmann  Nicolas Steeb  Peter Waldner 《自然地理学》2018,39(6):542-564

We present results of two studies on the (1) potential wood load in steep headwater streams and (2) properties of large wood (LW) transported in mountain rivers during the large August 2005 flood event in Switzerland. Ten headwater reaches of 1000 m length were surveyed in different regions of Switzerland. The potential wood load was estimated for in-channel deadwood, and possible driving factors were explored. Correlations were found with dead wood volume on hillslopes and mean channel width. We established size distributions of LW pieces and identified probable recruitment processes. Four reaches were resurveyed after an exceptionally severe flood in August 2005, showing limited LW transport in channels but considerable wood input by mass wasting processes. In addition, characteristics of deposits of LW along mountain rivers affected by the 2005 flood were investigated. Diameter and length distribution of transported and deposited pieces were comparable to those of LW from steep headwater streams, yet with considerably fewer long pieces in the deposits of mountain rivers. Most LW pieces were fresh wood, indicating that the portion of in-channel deadwood transported during the 2005 flood was limited. Findings of the study contribute to a better understanding of LW dynamics in Alpine mountain streams.  相似文献   

基于ANSYS的木框架有限元静力弹塑性分析   总被引：1，自引：0，他引：1  

阿肯江·托呼提  亓国庆 《地震工程与工程振动》2007,27(4):167-171

采用大型有限元软件ANSYS10.0对单调水平荷载作用下一榀门式木框架及其各种加固方案进行了静力弹塑性计算分析。通过各种加固方式屈服荷载、极限荷载大小的比较以及相对于未加固木框架提高程度的比较,从中得出了对门式木框架加固的最佳方案,为木柱、梁-土坯组合墙体的抗震加固提供方案。  相似文献   

Gas and Particle Partitioning Behavior of Aldehyde in the Presence of Diesel Soot and Wood Smoke Aerosols     

Sangdon?Lee  Richard?M.?Kamens  Myoseon?JangEmail author 《Journal of Atmospheric Chemistry》2005,51(2):223-234

Outdoor smog chamber experiments were performed to investigate gas/particle (G/P) partitioning behavior of aldehyde compounds in atmospheric acidic aerosols. Diesel soot and wood smoke aerosols were selected as acidic aerosols and octanal, decanal, undecanal, and cis-pinonaldehyde for aldehydes compounds. Aerosol acidity was measured with the equivalent sulfuric acid amounts in aerosol mass: 0.2–0.6 wt% in diesel soot and 0.04–0.1 wt% in wood smoke aerosols. Experimentally determined partitioning coefficients of aldehyde along with other classes of semivolatile organic compounds (SOCs) were compared with the estimation. All experimental G/P partitioning coefficients of aldehyde compounds were 10–200 times higher than estimated partitioning coefficients. Aldehyde partitioning coefficients in wood soot were similar or less than diesel soot aerosols.  相似文献   

新昌硅化木揭示的早白垩世东南沿海地区古气候特征分析     

薛根元娄伟平  张维祥吴春华 何凤翩 《南京气象学院学报》2005,28(5):666-671

根据浙江省新昌硅化木的分布与特点，应用硅化木记录的可知性和植物学的类比原理，通过该地区硅化木、其他植物化石和岩性组合等综合分析，初步探讨了早白垩世新昌盆地南洋杉型木的生态环境，以此研究该时期东南沿海地区的古气候主要特征。研究表明：该地区早白垩世古气候的主要特点是温暖、湿润及有时存在相对干旱的季节，同时呈现由温湿逐渐转变为干旱炎热的气候变化趋势；新昌硅化木中有明显的树木年轮，表明这种古气候可能存在一定的季节变化。  相似文献   

北京延庆硅化木的矿物学特征分析     

程素珍 《地质与资源》2022,31(1):21-27

通过X射线荧光、红外光谱和X射线衍射等检测方法分析了延庆硅化木的矿物学特征.结果表明:2个不同植物种属但在同一埋藏地形成硅化木标本成因相似,其颜色与所含元素种类及含量密切相关.X射线衍射分析表明,不同颜色和植物种属的硅化木主要组成物相一致,为SiO2,其他矿物极其微量.2个硅化木标本的红外吸收谱带基本一致,均显示典型的...  相似文献   

现代测量技术在古树名木保护中的应用     

吴洁 《东北测绘》2014,(2):206-208

以上海市为例,简要介绍在古树名木保护工作中,应用航测立体采集的方法有效提高内业数据处理工作效率和成果精度。实践证明,采用航测立体采集技术可以较低的成本获取高精度和信息丰富的古树名木现状数据,为绿化市容部门开展古树名木的保护提供准确的基础数据。  相似文献   

Shaking‐table tests of a full‐scale single‐story masonry veneer wood‐frame structure     

Hussein O. Okail  P. Benson Shing  William M. McGinley  Richard E. Klingner  Seongwoo Jo  David I. McLean 《地震工程与结构动力学》2011,40(5):509-530

This paper presents the findings of shaking‐table experiments conducted to examine the seismic performance of a full‐scale, one‐story, wood‐framed structure with masonry veneer. The structure was designed and constructed in accordance with current U.S. code provisions. The veneer was attached to the wood backing with two kinds of metal anchors, corrugated ties fastened with 8d nails and rigid ties fastened with #8 screws. The tests have shown that the use of nails to fasten veneer anchors to the wood studs is highly unreliable due to the high variation of the nail extraction capacity, which can be influenced by the moisture content of the wood. Other than this, both the wood frame and the masonry veneer performed well under severe ground motions far exceeding a design level earthquake for Seismic Design Category D. Good performance was observed for the rigid veneer ties, which were attached to the wood studs with screws. The results have shown that the veneer walls parallel to the direction of shaking helped to restrain the motion of the wood structure and therefore should not be simply treated as added mass. The detailing of wood roof diaphragms requires special attention in consideration of the out‐of‐plane inertia force of the veneer that can be transmitted through the top plate of the wood‐stud wall to the rim joist. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Seismic performance of wood‐frame houses in south‐western British Columbia     

Katsuichiro Goda  Gail M. Atkinson 《地震工程与结构动力学》2011,40(8):903-924

The seismic performance of conventional wood‐frame structures in south‐western British Columbia is analytically investigated through incremental dynamic analysis by utilizing available UBC‐SAWS models, which were calibrated based on experimental test results. To define an adequate target response spectrum that is consistent with information from national seismic hazard maps, record selection/scaling based on the conditional mean spectrum (CMS) is implemented. Furthermore, to reflect complex seismic hazard contributions from different earthquake sources (i.e. crustal events, interface events, and inslab events), we construct CMS for three earthquake types, and use them to select and scale an adequate set of ground motion records for the seismic performance evaluation. We focus on the impacts of adopting different record selection criteria and of using different shear‐wall types (Houses 1–4; in terms of seismic resistance, House 1>House 2>House 3>House 4) on the nonlinear structural response. The results indicate that the record selection procedures have significant influence on the probabilistic relationship between spectral acceleration at the fundamental vibration period and maximum inter‐story drift ratio, highlighting the importance of taking into account response spectral shapes in selecting and scaling ground motion records. Subjected to ground motions corresponding to the return period of 2500 years, House 1 is expected to experience very limited extent of damage; Houses 2 and 3 may be disturbed by minor damage; whereas House 4 may suffer from major damage occasionally. Finally, we develop statistical models of the maximum inter‐story drift ratio conditioned on a seismic intensity level for wood‐frame houses, which is useful for seismic vulnerability assessment. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献