Causes of Forest Encroachment: An Analysis of Bangladesh

Deforestation is a major cause of environmental degradation. Tropical countries with huge population pressure and widespread poverty are main frontier of deforestation. Bangladesh, being one the most densely populated country with diminishing tropical forestland, supports lowest per capita forestland. The forests are depleting mainly due to illegal logging and conversion to non-forestry uses. In this paper encroachment of forestland by individuals has been dealt with. The socioeconomic causes and pattern of encroachment have been analyzed. Limited land availability and unemployment have been identified as the major proximate causes of encroachment and, if no measures are adopted within next three decades the existing natural forests might be encroached.Part of thesis of the first author submitted for the partial fulfillment of the Master of Science in Forestry in the Khulna University, Bangladesh in 2001 (Iftekhar, 2001). Some of the findings have been presented in the World Forestry Congress XIII, Canada, held from 21 to 28 September 2003 (Iftekhar et al., 2003).     

High-Resolution Observations in B1-IRS: Ammonia, Ccs and Water Masers

We present a study of the structure and dynamics of the star-forming region B1-IRS (IRAS 03301+3057) using the properties of different molecules at high angular resolution (4). We have used VLA observations of NH₃, CCS, and H₂O masers at 1 cm. CCS emission shows three clumps around the central source, with a velocity gradient from red to blue-shifted velocities towards the protostar, probably due to the interaction with outflowing material. Water maser emission is elongated in the same direction as a reflection nebula detected at 2 m by 2MASS, with the maser spots located in a structure of some hundreds of AU from the central source, possibly tracing a jet. We propose a new outflow model to explain all our observations, consisting of a molecular outflow near the plane of the sky. Ammonia emission is extended and anticorrelated with CCS. We have detected for the first time this anticorrelation at small scales (1400 AU) in a star-forming region.     

Evidence for Co-Propagation of 4765- and 1720-MHz OH Masers in Star-Forming Regions

Two star-forming regions Cepheus A and W75N, were searched for the 4765-MHz OH maser emission using the multi-element radio linked interferometer network (MERLIN). The excited OH emission has an arc-like structure of 40 mas in Cep A and a linear structure of size 45 mas in W75N. We also found the 1720-MHz line in Cep A and Hutawarakorn [MNRAS 330 (2002) 349] reported the 1720-MHz emission in W75N. The 1720- and 4765-MHz OH spots coincided in space within 60 mas and in velocity within 0.3 km s^–1 in both targets implying that both maser transitions arise from the same region. According to the modelling by Gray [MNRAS 252 (1991) 30] the 1720/4765-MHz co-propagation requires a low density, warm environment. The masers lie at the edges of H II regions where such conditions are expected.     

An integrated decision method for prediction of tropical cyclone movement by using genetic algorithm

Typhoon disaster is one of the most influentialnatural disasters. The strong storm surge of Bangla-desh cyclone, which happened in November 1970,resulted in 300000 deaths. Asia and the western Pa-cific can be regarded as an area where is affected mostseverely by the disasters of tropical storms[1]. Themost important thing is to improve the accuracy oftyphoon tracks prediction internationally. Lande-sea,C.[2] pointed out that for a successful forecast oftropic cyclone (TC) tracks, it is not …     

Discovery of double-peaking potassic volcanic rocks in Langshan Group of the Tanyaokou hydrothermal-sedimentary deposit,Inner Mongolia,and its indicating significance

Since the mid-1980s,Tanyaokou large Zn-Cu-Fe sulfides deposit,located at the southwest end of Langshan-Zhaertaishan-Bayan Obo Mesoproterozoic metallogenic belt in the west section of the northern margin of the North China Platform[1?9](Fig.1),has been confirmed to be submarine volcanic exhalative-sedimentary metamorphosed deposit hosted in the miogeosynclinal mud-carbonaceous formation of the Langshan Group(LG)[1],or submarine volcanic exha-lative-deposition-altered deposit[2]or stratabo…     

Spatial Distribution of Fractures in the Asmari Formation of Iran in Subsurface Environment: Effect of Lithology and Petrophysical Properties

The distribution of fractures and its dependence on lithology and petrophysical properties of rock in the Asmari Formation were examined using three wells data of one of the largest oil fields of southwestern Iran. Fractures were measured on cut cores. Mineral content and petrophysical data were obtained through thin section study and core plug measurement respectively. Influence of mineral composition and petrophysical property of rocks on fracture density was explored statistically. Increasing quartz (sand) and anhydrite content of rocks decrease and dolomite increases the threshold of fracture densities, however no significant relation was observed between calcite content of rock and fracture density. Increasing porosity and permeability of rock decrease the threshold of fracture density in some of the defined lithology groups. There are significant differences between the lithology groups in terms of fracture density, although the results in the three wells are not the same. In whole data, the highest fracture density can be observed in dolostone. Limestone and impure carbonates hold broader spaced fractures and sandstones display the least fracture density. The average fracture densities in the wells are strictly different. These differences are the result of the structural position of the wells and also the trend of the well and fractures. The distribution of fractures in most lithology groups can be explained by the function: , where F is relative frequency, D is fracture density and a, b, and c are constants.     

Canonical Modelling of Relative Spacecraft Motion Via Epicyclic Orbital Elements

This paper presents a Hamiltonian approach to modelling spacecraft motion relative to a circular reference orbit based on a derivation of canonical coordinates for the relative state-space dynamics. The Hamiltonian formulation facilitates the modelling of high-order terms and orbital perturbations within the context of the Clohessy–Wiltshire solution. First, the Hamiltonian is partitioned into a linear term and a high-order term. The Hamilton–Jacobi equations are solved for the linear part by separation, and new constants for the relative motions are obtained, called epicyclic elements. The influence of higher order terms and perturbations, such as Earth’s oblateness, are incorporated into the analysis by a variation of parameters procedure. As an example, closed-form solutions for J₂-invariant orbits are obtained.     

钱塘江水系的形成和变迁

本文根据控制钱塘江水系发育的最后一期构造的发生时间；根据古地面的形成和水系发育的相互关系；根据水系沉积物性质和古生物等推断钱塘江水系的雏形发生于晚白垩世，整体水系形成于始—渐新世。钱塘江水系形成以后，主、支流在平原河口段的改道却相当频繁。其总体趋势是由向北转为向东。河流长度且随海水进退而消长。长江的输沙作用及杭州—临安东西向构造带造成的地形条件是形成杭州湾三角港的决定因素。文中还根据河口湾环境的出现，推断了钱塘涌潮形成的时间。     

Is the Universe flat?

The evidence for unseen mass (which is briefly reviewed) suggests that the cosmological density parameter Ω is at least 0.1–0.2. An Einstein-de-Sitter ‘flat’ universe with Ω = 1 — which is appealing for theoretical reasons — can only be reconciled with the data if the galaxies are more ‘clumped’ than the overall mass distribution, and are poor tracers of the unseen mass even on scales of several Mpc. Possible forms for the unseen mass are discussed; and feedback processes are outlined whereby galaxy formation can be suppressed in underdense regions.     

花江喀斯特峡谷地区石漠化成因初探

花江喀斯特峡谷区地下水埋藏深,地表干旱,存在显著的人为加速土壤侵蚀过程,植被次生性明显,生境干热特征显著,是已石漠化和半石漠化的生态系统。其中地质构造、地貌演化、岩溶形态、可开发利用的水资源、植被群落可能是石漠化过程的主要自然成因,以土地利用为表现形式的强烈人类活动是石漠化的驱动力。基于此,提出了石漠化地区的土地利用方式和生态恢复过程的建议,旨在为石漠化的演化研究及生态重建提供参考。