Generation of variational standard plant room solutions

We have used the object-based CAD programming to take advantage of standardisation to handle the selection, sizing, layout and (potentially) pipe routing for Low-Pressure Hot Water (LPHW) plant rooms in buildings. Our approach combines automation and interactivity. From a simple specification of the plant room geometry (an orthogonal polygon with known obstructions, openings and external walls), and the heating load in kW, our software proceeds through a number of steps. First, the number and size of standard modular boilers, pumps, etc., are determined from the heat load. Then, a compatible optimising 3D variational solution is generated, using Constraint Logic Programming. To do this, we firstly enumerate a satisfactory topological solution, and then refine it to form a compatible geometrical solution. The final step generates pipe routes, using optimisation techniques to minimise the length of pipes and the number of bends. The solution obtained can be modified or improved by the designer, for which we have interactivity. Modifying the topology of the solution or the geometry of the plant room is done directly through the graphic interface, e.g. modifying a boiler position is done by dragging; the system automatically updates the 3D model including the pipe routing while maintaining all the design rules. The solutions generated by our prototype have been tested against conventional solutions in a benchmarking exercise. Advantages have been underlined and suggestions for further development have been made.     

Novel adaptation of the critical clearing angle formula for faults on a three phase and a six phase line

Enhanced power transfer through polyphase conversion of a transmission line, specially three to six phase, as an alternative to upgrading the conventional three phase power transmission voltage is becoming an area of growing interest in the power industry. Among others this conversion will have an impact on the system stability. While the well-known symmetrical component method has been found suitable in modelling the unsymmetrical faults of a three phase system for transient stability analysis it appeared as difficult-to-apply for six phase system. In this paper a new technique has been proposed to determine the stability in terms of critical clearing angles for both three and six phase line faults. The method has been validated by applying it first for the faults on a 132 kV three phase double circuit line of a given practical power system and comparing the results with those obtained through the symmetrical component method. Then it has been applied for the faults on the same line but considered to have been converted into a 132 kV six phase single circuit line. The method, though an approximate one, is straightforward, simpler and faster than the symmetrical component method and provides sufficiently accurate results.     

Nuclear data sheets for A = 183

The 1975 evaluation of A=183 has been revised using experimental decay and reaction data received by the date given below.     

Thin film coatings which inhibit spin relaxation of polarized potassium atoms

A new technique is being developed at Argonne National Laboratory to produce a beam of polarized deuterium atoms. A part of the apparatus consists of a small cell which contains potassium vapor. The potassium atoms are polarized by circularly polarized light from a high-power cw laser. A port feeds deuterium into the cell and the polarization of the potassium is transferred to the deuterium by spin-exchange scattering. It is important that the potassium and deuterium atoms do not lose polarization by scattering from the walls of the exchange cell. We have tried various coatings of the exchange walls in order to inhibit losses from spin relaxation. Methods used to produce these coatings as well as their success will be described.     

Diffusion model for simultaneous mass and heat transfer in partially miscible liquid systems: Experimental findings and numerical simulation

A coupled diffusion model has been numerically solved to obtain temperature profiles when two partially miscible liquids are contacted at a planar interface. The proposed model includes the presence of a heat source at the interface due to the heat of solution which is considered to have a non-linear relationship with concentration. As a result, a system of four partial differential equations is obtained which is numerically solved with the DISPL software package. This DISPL package solves systems of PDEs by means of a Galerkin procedure. This procedure reduces these PDE systems to ODEs which are, in turn, solved by a multistep stiff ODE solver. The basis of the method of solution involves defining new variables to transform the domain so that the interface conditions can be treated as boundary conditions. The temperature difference predictions calculated with this model were compared to experimental data obtained for eight partially miscible liquid systems. The agreement proved to be remarkable in some instances and only qualitatively adequate in others. Further improvements in the predictions would be expected if a microconvection mechanism close to the interface and heat losses were incorporated into the model.     

The history and future of Lake Champlain's fishes and fisheries

In the last two centuries, physical, chemical, and biological alterations of Lake Champlain have resulted in the loss of two species, addition of 15 fish species, and listing of 16 species as endangered, threatened or of special concern. The lake currently supports 72 native fish species; lake trout (Salvelinus namaycush) and Atlantic salmon (Salmo salar) were extirpated by 1900, American eel (Anguilla rostrata) and lake sturgeon (Acipenser fulvescens) populations are extremely low, and walleye (Sander vitreum) are declining. Dams on several rivers, and ten causeways constructed in the mid 1800s to early 1900s, cut off access to critical spawning areas and may have limited fish movements. Siltation and sediment loading from agricultural activity and urban growth have degraded substrates and led to noxious algal blooms in some bays. A commercial fishery targeting spawning grounds of lake whitefish (Coregonus clupeaformis), lake trout, and walleye probably reduced numbers of these species prior to its closure in 1912. Non-native species introductions have had ecosystem-wide impacts. Sea lamprey (Petromyzon marinus) populations were very high prior to successful control, possibly as a consequence of ecological imbalance and habitat changes. A paucity of historic survey data or accurate species accounts limits our understanding of the causes of current fish population trends and status; in particular, the effects of habitat fragmentation within the lake and between the lake and its watershed are poorly understood. Holistic, ecosystem management, including pollution reduction and examination of habitat impacts, is necessary to restore the general structure of native biological assemblages.     

夏季投肥对混养鱼塘水质影响研究

为明确夏季投加氮肥、磷肥对鱼塘水质的影响,对投肥前后鱼塘水质进行监测,并选取pH值、溶解氧(DO)、化学需氧量(COD)、铵态氮、硝酸盐氮、亚硝酸盐氮、总氮、有效磷8项因子,研究投肥前后鱼塘上层、下层水质变化。结果表明:鱼塘投入氮肥、磷肥后湖水的pH值、溶解氧含量、COD、总氮含量、亚硝酸盐含量均显著增加(P0.05)。投肥后第1天下层湖水铵态氮含量显著增加(P0.05),水体的硝态氮含量略有下降,但不显著(P0.05)。投肥后第3天湖水铵态氮含量显著降低(P0.05),硝态氮含量显著升高(P0.05)。与投肥前相比,鱼塘投肥后上、下两层湖水有效磷含量均有所下降,但不显著(P0.05)。     

Measurement of Diporeia respiration rate for Lake Superior

The freshwater amphipod Diporeia is a dominant macroinvertebrate species in Lake Superior’s benthic community and an important prey item for many fish. A capacity to predict growth and production rates of Diporeia using a bioenergetics model requires information on physiological processes of the species. The objective of this study is to quantify oxygen consumption of Lake Superior Diporeia and to determine if respiration rate changes with body length. Diporeia were collected from Lake Superior and kept over natural sediment maintained at 4 °C. Dissolved oxygen levels for groups of immature (2 mm), juvenile (4 mm), and adult (6 mm) Diporeia in 20 ml microcosms were measured using a polarographic microelectrode. Mass-specific respiration rates for Lake Superior Diporeia ranged from 32.0 to 44.7 mg O₂ g DW^− 1 day ⁻¹. A significant relationship between body length and mass-specific respiration rate (p > 0.1) was not found. The estimate of Diporeia respiration presented here is significantly higher (p < 0.05) than previous findings from populations in Lakes Michigan and Ontario. This study provides new data on respiration rates of Lake Superior Diporeia and compares findings to studies for other connecting Great Lakes.