TEMPORAL AND GEOMORPHIC VARIATIONS OF STREAM STABILITY AND MORPHOLOGY: MAHOGANY CREEK,NEVADA1

ABSTRACT: Detailed studies of long-term management impacts on rangeland streams are few because of the cost of obtaining detailed data replicated in time. This study uses government agency aquatic habitat, stream morphologic, and ocular stability data to assess land management impacts over four years on three stream reaches of an important rangeland watershed in northwestern Nevada. Aquatic habitat improved as riparian vegetation reestablished itself with decreased and better controlled livestock grazing. However, sediment from livestock disturbances and road crossings and very low stream flows limited the rate of change. Stream type limited the change of pool variables and width/depth ratio, which are linked to gradient and entrenchment. Coarse woody debris removal due to previous management limited pool recovery. Various critical-element ocular stability estimates represented changes with time and differences among reaches very well. Ocular stability variables tracked the quantitative habitat and morphologic variables well enough to recommend that ocular surveys be used to monitor changes with time between more intensive aquatic surveys.     

INTEGRATED RIVER BASIN OPTIMIZATION: MODELING ECONOMIC AND HYDROLOGIC INTERDEPENDENCE1

ABSTRACT: This paper presents an integrated optimal control model that optimizes economic performance of reservoir management in watersheds in which there are significant economic and hydrologic interdependencies. The model is solved using the General Algebraic Modeling System (GAMS). Results show that application of this model to New Mexico's Rio Chama basin can increase total system benefits over historical benefits by exploiting complementarities between hydroelectricity production, instream recreation, and downstream lake recreation.     

青藏高原北缘P波波形线性度的动态跟踪及其变化的物理机制初探

利用数字化近震Ｐ波波形资料，追踪研究了青藏高原北缘１９９０年２月～１９９５年８月Ｐ波波形时间线性度的变化过程。发现该区较大地震发生前线性度有一定程度的下降现象。分析认为：大震前孕震区应力场的不均匀分布可使通过孕震区及其周缘的地震波产生频散，可能是较大地震前波形时间线性度下降的物理本质     

北京地区15000年以来环境变迁中灾害性气候突变事件的讨论

通过高分辨率孢粉分析及烧失量、炭屑实验结果的统计分析，结合１４Ｃ、古地磁等，对北京房山东甘池１５０００ａ以来植被变化和环境变迁进行了较为深入的研究，特别强调气候变化的灾害性突变事件。初步得知约在１４１００～１４０００ａＢ．Ｐ．前后曾出现与哥得堡反转相对应的事件，在１００００ａＢ．Ｐ．左右出现类似与新仙女木事件相对应的事件，在大约５７７０ａＢ．Ｐ．和４５６０ａＢ．Ｐ．左右及２８５０～２６５０ａＢ．Ｐ．出现了大暖期的突然降温事件。     

Thermal and mechanical properties of poly(lactic Acid) and poly(ethylene/butylene Succinate) blends

In this study, blends of poly (lactic acid) (PLA) with poly(ethylene/butylene succinate) (Bionolle) have been investigated for their thermal and mechanical properties as a function of the concentration of Bionolle. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and tensile tests were used to characterize the blends. From the results of the DMA and DSC, it was found that this blend system was not miscible within the compositions studied. DSC results showed that adding Bionolle aids in crystallization of PLA. It was observed that increasing the Bionolle concentration led to a slight increase in the strain-at-break of the blends but a decrease in the Young’s modulus and ultimate tensile strength. Biaxially oriented films showed an increase in tensile strength, modulus, and strain-at-break.     

Pressure- volume- temperature relationships of soy protein isolate/starch plastic

The use of pressure-volume-temperature (PVT) studies in processing of a biodegradable plastic composition made from soy protein isolate and corn starch is described. The ability of PVT measurements to predict the combined effects of pressure, volume, and temperature effects is demonstrated. The results show that the PVT relations of the plastic can be predicted by using a regression analysis similar to the Tait equations of state. A change in slope of the PVT curves was observed at around 80‡C, which is ascribed to the glass-transition process of the plastic. Evidence of onset of thermal degradation of the plastic was observed at ca. 160‡C under 0 to 200 MPa isobaric pressure. This thermal degradation precluded determination of the crystal melting point of the plastic.     

Mechanical Properties with the Functional Group of Additives for Starch/PVA Blend Film

This paper deals with the mechanical properties and degree of swelling (DS) of starch/PVA blend film with the functional groups i.e., hydroxyl and carboxyl group, of additives. Starch/PVA blend films were prepared by using the mixing process. Glycerol (GL) with 3 hydroxyl group, sorbitol (SO) with 6 hydroxyl group, succinic acid (SA) with 2 carboxyl group, malic acid (MA) with 1 hydroxyl and 2 carboxyl group, tartaric acid (TA) with 2 hydroxyl and 2 carboxyl group and citric acid (CA) with 1 hydroxyl and 3 carboxyl group were used as additives. The results of measured tensile strength (TS) and elongation (%E) verified that both hydroxyl and carboxyl group as a functional groups increased the flexibility and strength of the film. Values of DS for GL-added and SA-added films were low. However, DS values of the films added MA, TA or CA with both hydroxyl and carboxyl group were comparatively high. When the film was dried at low temperature, the properties of the films were evidently improved. The reason is probably because the hydrogen bonding was activated at low temperature.     

The New Jersey Toxics Reduction Workplan for Ny-Nj Harbor: Distribution of Pcdd/Fs in Ambient Waters

As part of the NJ Toxics Reduction Workplan for NY-NJ Harbor, ambient water samples were collected at fifteen locations along the tidal portions of the Hackensack, Passaic, Raritan, Rahway and Elizabeth Rivers, and in Newark Bay, the Arthur Kill, and Kill van Kull. A Trace Organics Platform Sampler was used to collect a total of 75 suspended sediment phase samples between June 2000 and May 2002. These samples were analyzed for spatial and wet vs. dry weather trends in the 17 polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs; modified USEPA Method 1613b). Mean total PCDD/F (tPCDD/F) concentrations at the sampling locations ranged between 3.8 and 41.5 ng/g. On average, OCDD accounted for almost 80% of the tPCDD/F concentrations; mean total [PCDD/F – OCDD] concentrations ranged between 0.84 and 5.20 ng/g at the sampling locations. Mean 2,3,7,8-TCDD concentrations ranged between 0.003 and 0.28 ng/g, with the highest concentrations (> 0.10 ng/g) along the tidal Passaic and lower Hackensack Rivers, and in upper Newark Bay. Mean tPCDD/F Toxic Equivalency Quotients (TEQ) ranged between 45 and 344 TEQ pg/g, with the highest levels found in the lower Passaic River. Toxicity was primarily driven by 2,3,7,8-TCDD concentrations in the Passaic and Hackensack Rivers, and in Newark Bay. Examples of congener distribution patterns at some of the sampling locations are also presented.     

我院电子阅览室利用情况分析

分别按专业、系部、年级、性别等方面统计了学生的开户情况，在不同的时间段调查了学生上机的目的，然后对学生在电子阅览室的开户情况和上机行为进行了深入分析，在此基础上，对我院电子阅览室的管理提出了几点建议。     

枇杷核中提取苦杏仁甙的研究

研究了3个枇杷品种的出核率，利用高效液相色谱检测苦杏仁甙的含量，以及从枇杷核中提取苦杏仁甙的工艺。结果表明，3个品种烘干后核的得率存在显著差异，干核的年产量很大，有综合开发利用价值；提取溶剂以乙醇为好，最合理的工艺组合为：在原料中按料液比1：10加入浓度为80％的乙醇，在65℃时回流提取50min。在40℃功率为80W的条件下超声处理25min。合理选择品种是提高苦杏仁甙得率的关键。