有源带通滤波器的设计、调试与应用

所述的有源带通滤波器是采用现代网络理论，通过查图表反复计算数值调试并利用多项式综合滤波器的设计理论得到的设计结果，从频率响应特性曲线和电路结构可见，它完全满足了设计时所提供的各项技术指标的要求。文中详细地讨论了由单元电路到全极点多反馈滤波网络电路设计时的理论根据，各支路参数实际的计算和调试方法。这种电路结构简单合理，调试和维修十分方便，代替了无源滤波器中的大型电感和电容，有利于设备小型化。     

油气形成的构造动力学理论和油气藏勘探的地球动力学方法综述

综述了石油和天然气形成构造动力学理论，其中包括构造挤压是有机质演化所需能量的重要来源、构造挤压的最重要伴生效应－力化学作用促进了有机质演化、构造挤压对烃类运移和 烃类资源分布有重要影响等观点。还综述了油气藏勘探的地球动力方法，其中包括这一方法的理论基础，可行性和具体任务以及应用前景等。     

Multichannel analysis of surface wave method with the autojuggie

The shear (S)-wave velocity of near-surface materials and its effect on seismic-wave propagation are of fundamental interest in many engineering, environmental, and groundwater studies. The multichannel analysis of surface wave (MASW) method provides a robust, efficient, and accurate tool to observe near-surface S-wave velocity. A recently developed device used to place large numbers of closely spaced geophones simultaneously and automatically (the ‘autojuggie’) is shown here to be applicable to the collection of MASW data. In order to demonstrate the use of the autojuggie in the MASW method, we compared high-frequency surface-wave data acquired from conventionally planted geophones (control line) to data collected in parallel with the automatically planted geophones attached to steel bars (test line). The results demonstrate that the autojuggie can be applied in the MASW method. Implementation of the autojuggie in very shallow MASW surveys could drastically reduce the time required and costs incurred in such surveys.     

Conflicting rights to the city in New York's community gardens

In the mid-1990s, New York City initiated what would prove to be a long, highly visible struggle involving rights claims related to property, housing, and public space in the form of community gardens. The competing discourses of rights were part of a struggle over the kind of city that New York was to become, and more specifically, whether it would be one in which difference is accepted and in which access to the city and the public realm would be guaranteed. Using interviews with participants in the conflict over community gardens, we evaluate how the resolution to the gardens crisis, which in part occurred through the privatization of what are often taken to be public or community rights to land, transform not only the legal status of the gardens but also, potentially, their role as places where different `publics' can both exercise their right to the city and solidify that right in the landscape.     

Permafrost science and secondary education: direct involvement of teachers and students in field research

Permafrost and periglacial geomorphology are absent from the science curriculum in most secondary schools in the United States. This is an unfortunate situation given the recent increases in development and environmental concerns in northern latitudes and high-mountain areas, and the interesting examples of basic scientific principles found in the history of research on periglacial geomorphology and permafrost. In 1997 and 1998, a University of Delaware research group studying permafrost and periglacial geomorphology in northern Alaska participated in the National Science Foundation's (NSF) Teachers Experiencing the Antarctic and Arctic (TEA) Program. In each of these years, a high school teacher and a student traveled as part of the research team to the North Slope of Alaska. They learned about the landscape, collected active-layer thickness and temperature measurements, and assisted in data analysis. Results from studies of active-layer thickness variability and ground temperature contributed to a series of long-term observations and international research on the impacts of global climate change. Since their expeditions, the teachers have shared their experiences with their classrooms and communities in several ways, including public lectures and the Internet. Classroom activities are available to the public through the TEA web site (http://tea.rice.edu). This experience may heighten public awareness of permafrost and contribute to it becoming a useful part of the secondary curriculum.     

Thermal inertia mapping of Mars from 60°S to 60°N

Twenty-micrometer brightness temperatures are used to derive the thermal inertia for 81% of the Martian surface between latitudes ±60°. These data were acquired by the two Viking Infrared Thermal Mappers in 1977 and 1978 following the two global dust storms of 1977. The spatial resolution used is 2° in latitude by 2° in longitude and the total range in derived inertia is $\text{1}\text{to}\text{15 × 10}{}^{\mathrm{?3}}\text{cal cm}{}^{\mathrm{?2}}\text{sec}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{°}\text{K}{}^{\mathrm{?1}}$. The distribution of thermal inertia is strongly bimodal with all values of thermal inertia less than $\text{4 × 10}{}^{\mathrm{?3}}\text{cal cm}{}^{\mathrm{?2}}\text{sec}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{°}\text{K}{}^{\mathrm{?1}}$ being associated with three disjoint bright regions mostly in the northern hemisphere. Sufficient dust is raised in global storms to provide fine material adequate to produce these low-inertia areas but the specific deposition mechanism has not been defined. At the low resolution used, no complete exposures of clean rock were found. There is some tendency for darker material to be associated with higher thermal inertia, although the trend is far from one to one. The distribution of high- and low-inertia areas is sufficiently nonrandom to produce a variation in whole-disk brightness temperature with central meridian longitude. This variation and the change in surface kinetic temperature associated with dust storms are factors in establishing the whole-disk brightness temperature at radio and infrared wavelengths and will be important for those who use Mars as a calibration source.