Control law for variable damping device defined by a non-linear differential equation

This paper proposes a non-linear control law for a variable damping device (VDD) aimed at reducing structural seismic responses. The VDD is attached to the structure by an auxiliary spring element composing a non-linear Maxwell element. The VDD's damping coefficient is adjusted to control the reactive internal force in the non-linear Maxwell element. A large controlled force is thus produced with little external power required to adjust the VDD's damping coefficient. The proposed control law defines the rate or increment of the VDD's damping coefficient at a certain moment by a differential equation or its discretized form. The controlled force vs. deformation relation plots parallelogram-like hysteretic curves, which indicates quick action and energy dissipation. Fundamental characteristics of an SDOF model with the VDD controlled by the proposed law are examined for impulse, sin and seismic excitations. The law for the SDOF model is extended to one for an MDOF model. The control effect for a 3DOF model is examined by numerical experiments. Copyright © 1999 John Wiley & Sons, Ltd.     

A GIS‐based variable source area hydrology model

Effective control of nonpoint source pollution from contaminants transported by runoff requires information about the source areas of surface runoff. Variable source hydrology is widely recognized by hydrologists, yet few methods exist for identifying the saturated areas that generate most runoff in humid regions. The Soil Moisture Routing model is a daily water balance model that simulates the hydrology for watersheds with shallow sloping soils. The model combines elevation, soil, and land use data within the geographic information system GRASS, and predicts the spatial distribution of soil moisture, evapotranspiration, saturation‐excess overland flow (i.e., surface runoff), and interflow throughout a watershed. The model was applied to a 170 hectare watershed in the Catskills region of New York State and observed stream flow hydrographs and soil moisture measurements were compared to model predictions. Stream flow prediction during non‐winter periods generally agreed with measured flow resulting in an average r² of 0·73, a standard error of 0·01 m³/s, and an average Nash‐Sutcliffe efficiency R² of 0·62. Soil moisture predictions showed trends similar to observations with errors on the order of the standard error of measurements. The model results were most accurate for non‐winter conditions. The model is currently used for making management decisions for reducing non‐point source pollution from manure spread fields in the Catskill watersheds which supply New York City's drinking water. Copyright © 1999 John Wiley & Sons, Ltd.     

Photometric variability of the Herbig Ae/Be star HD 200775

We present results of photometric monitoring of HD 200775 in the passbands X and V of the VILGEN system obtained over the period from September 1994 to May 1995. It is shown that the star varies with a period of 10.225±0.041 days and an amplitude of 0.02 mag in X passband. The variations on the time scale of several hours and/or days are also confirmed.     

准噶尔盆地南缘楼庄子地区头屯河组水文地质条件与铀成矿的关系

前人在准噶尔盆地南缘楼庄子地区发现头屯河组砂岩型铀矿化,针对该地区铀成矿前景及找矿方向进行了论述,但铀控矿因素尚不明朗。砂岩型铀矿作为一种水成矿产,研究水文地质条件与铀成矿关系对铀成矿规律和找矿靶区的预测至关重要。本文利用铀矿勘探和煤田钻孔资料,分析了楼庄子地区头屯河组含水层特征并对其进行了划分;通过分析研究区地下水演化特征,推断出铀成矿地质时期;通过分析含水层发育特征（砂岩含水层厚度、沉积特征、砂泥比,连通性、渗透性等）、“天窗”特征,揭示了不同区域水循环交替强度、铀成矿水文地质条件的差异;综合有利成矿信息,预测头屯河组有利成矿的区域和含水层,经过钻孔验证,楼庄子地区中部铀矿化较好,东部次之,西部较差,仅Ⅲ含水层见工业铀矿化,取得了良好的勘探效果。     

海渔况信息产品的制作原理及其应用

海渔况信息产品对于渔业资源的研究、调查、预测、评估具有重要意义。利用计算机制作的海渔况图对于信息的表达一目了然,具有速度快、时效新、反应及时等特点,因此计算机制图已经成为目前海渔况信息产品的主要制作手段。论文将以《太平洋大眼金枪鱼延绳钓渔场与SST叠加分布图集》和《东海中心渔场预报图》为例,简要介绍海渔况信息产品的制作原理及其应用。     

内蒙古获青公路沿线地质环境特征与地质灾害防治

拟建的内蒙古获青公路是半干旱山区线路工程的典型代表。公路沿线最主要的地质环境特征是气候条件恶劣、地质条件复杂、岩体破碎、岩堆发育、高陡边坡密布。潜在的地质灾害主要有岩堆失稳、高边坡变形破坏和峡谷路基洪涝灾害。相应的防治措施建议为:绕避I类岩堆;采取优化线路布设与岩堆加固相结合方式处理III、II类岩堆;高边坡常规处理;按不同河段,以适当抬高路面标高,或设置较大过水断面桥涵,并辅以相应防洪措施防治峡谷路基洪涝灾害。     

关于边界层阻力定律在非定常均匀条件下的推广

用自由大气实际风速取代地转风,得到了非定常均匀条件下阻力定律和边界层内参数的一些性质及相似性函数Ａ、Ｂ的特性。该方法和结果可应用于大气模式中的边界层参数化以及与相似性函数有关的一些研究。     

基础隔震建筑混合控制的变结构趋近律方法

本文对叠层胶支座基础震建筑的混合振动控制问题进行了研究。利用控制律设计的变结构趋近律方法,给出了相应的闭环控制律表示式。     

吉林省松原地区1119年6 3／4级地震的发震构造条件

１９９９年６ ３／４级地震是东北地区震级在的地震,目前对其发震构造背景缺乏深入的研究。本文从深部构造背景,浅层构造条件和深浅部构造关系等方面,对１１１９年地震的发震构造背景作了剖析。研究认为,本次地震的宏观震中位于扶余－前郭一带,地质构造上,该区处于松辽盆地中央凹陷和东南隆起的交接部位;深部构造背景上,该区是莫霍面起伏的拐点,存在北东向基底断鲜明和弱西向深部断裂,前者规模较大,晚新生代有弱活动,是