SESTON AND DISSOLVED ORGANIC CARBON DYNAMICS DURING MICROCYSTIS BLOOM WITH SPECIAL REFERENCE TO THE EFFECTS OF THREE CHINESE DOMESTIC FISHES IN EXPERIMENTAL ENCLOSURES

The Microcystis bloom that once disappeared from Donghu Lake, a shallow eutrophic Chinese lake,was successfully resumed with the use of the enclosure method. Seston and dissolved organic carbon (DOC)dynamics during the Microcystis bloom were investigated with particular emphasis on the effect of three Chinese domestic fishes (silver carp, bighead carp and grass carp). The results showed that the change of chlorophyll a obviously reated to the fish species and its stocking density. Du to the relare of exracelular ogranic carbon and increased bacterial activity, DOC increased apparently after silver and bighead carps were introduced. POC/DOC dropped considerably in the enclosures containing silver and bighead carps and in the surrounding lake water, which implied that the bacterial acivity was more pronounced in such ecosystems. Statistical analytis indicated that the linear relationship between POC and chiorophyll a could reflect the state of algal growth and nutrient metabolism. It was expected that this study would provide some information on biomanipulation in the shallow eutrophic lakes.

Computing the Enclosures Eigenvalues Using the Quadratic Method

In this article, we compute the enclosures eigenvalues (upper and lower bounds) using the quadratic method. The Schrodinger operator (A) (harmonic and anharmonic oscillator model) has used as an example. We study a new technique to get more accurate bounds. We compare our results with Boulton and Strauss method.

The pathway and fate of the heavy metal mixture in Xiamen marine experiment enclosures

The pathway and fate of heavy metals were studied in 10m3 enclosures at Xiamen Bay in 1985. The dissolved metals added are removed rather quickly during the first days, and their half-removal times ( t1/2) (d) are as follows: Pb 5. 4-5. 8, Hg 6. 7-14, Zn 11-22, Cu 16 - 29, and Cd 30-89. Zinc is transferred biologically to particles during phytoplankton bloom. The main Fate of added metals after 27 days is as follows; over 80% Cd and 60% Cu remain in dissolved phase, more than 60% Pb and 50% Hg transfer to settling settlement, while Zn is equally distributed in dissolved phase and settling settlement. The wall uptake is less than 2% of the total metals added. Organic materials play an essential role in the partition and the transfer of heavy metals in water column. Terrigenous and autochthonous particles show different affinities to different metals. Most heavy metals associate weakly with zooplankton. The Binding of Cd, Pb, Zn and Cu to the particles shows distinctive features related to the diagenetic alteration.

Effect of flow rate on environmental variables and phytoplankton dynamics:results from field enclosures

To investigate the effects of flow rate on phytoplankton dynamics and related environment variables,a set of enclosure experiments with different fl ow rates were conducted in an artificial lake. We monitored nutrients,temperature,dissolved oxygen,p H,conductivity,turbidity,chlorophyll-a and phytoplankton levels. The lower biomass in all flowing enclosures showed that flow rate significantly inhibited the growth of phytoplankton. A critical flow rate occurred near 0.06 m/s,which was the lowest relative inhibitory rate. Changes in flow conditions affected algal competition for light,resulting in a dramatic shift in phytoplankton composition,from blue-green algae in still waters to green algae in flowing conditions. These findings indicate that critical flow rate can be useful in developing methods to reduce algal bloom occurrence. However,flow rate significantly enhanced the inter-relationships among environmental variables,in particular by inducing higher water turbidity and vegetative reproduction of periphyton( Spirogyra). These changes were accompanied by a decrease in underwater light intensity,which consequently inhibited the photosynthetic intensity of phytoplankton. These results warn that a universal critical flow rate might not exist,because the effect of flow rate on phytoplankton is interlinked with many other environmental variables.

Comparison between Two Vertical Enclosures Filled With Porous Media under the Effect of Radiation and Magnetohydrodynamics

A numerical study has been carried out to investigate the temperature distribution and the natural convection heat transfer in axisymmetric two-dimensional vertical saturated porous cylinder with steady state laminar flow. A comparison between two situations is done under the effect of MHD （magnetohydrodynamics） and radiation. In the two situations, the vertical walls of the cylinder are cooled with constant wall temperature and a constant heat generation subjected along the centerline of the cylinder. The first case for cylinder with insulated upper surface and cooled bottom surface while the second case for cylinder with cooled upper surface and insulated bottom surface. The governing equations used are continuity, momentum and energy equations which are transformed to dimensionless equations. The finite difference approach is used to obtain all the computational results using the MATLAB-7 programming. The parameters affected the system are Rayleigh number ranging within （102≤ Ra ≤104）, radiation parameter （0≤ Rd ≤ 2） and magnetohydrodynamics MHD （Mn） （0 ≤ Mn≤ 2）.The results show that the temperature of Case 1 is more than that in Case 2 at constant Ra, Mn and Rd while the value of the stream in Case 2 is greater than that in Case 1. Nu increase with the increase of Rd and increasing Mn caused the temperature to increase and the streamline dropped while Nu decreased. A correlation has been set up to give the average Nusselt number variation with Ra, Rd and Mn for which the results are found to be in good agreement with previously published researches.

Effects of Enclosure on Grassland Ecological and Economic Benefits in Northern China

Grasslands in northern China serve the country as both an ecological barrier and a livestock production base.There,installing enclosures has been becoming the major grassland restoration measure adopted by many local governments.However,the effects of restoration on both ecological and production benefits of grassland remain unclear for implemented grassland restoration policies.Therefore,a representative rangeland in northern China,the Maodeng pasture in Inner Mongolia Autonomous Region was selected as the study area,and remote sensing monitoring analyses were carried out to quantify the ecological benefits and economic benefits from 2015 to 2021.The results showed that:1) in terms of ecological benefits,the grassland area with a grassland coverage rate of more than 60% accounts for 32.3% of the regional area,and 86.4% of its grassland grew significantly better than the same period in2015,showing a significant improvement in grassland growth.Using the average amount of carbon per unit area as the ecological benefit evaluation index,it increased by 27.1% to 32.48Tg C/yr from 2015 to 2021.2) In terms of economic benefits,both theoretical grass production and livestock carrying capacity increased from 2015 to 2021.Compared to 2015,the theoretical grass production in 2021 increased by 24.8% to 71 900 t.The livestock carrying capacity reached 52 100 sheep units in 2021,nearly 11 000 sheep units more than that in 2015.During the study period,multiple economic indicators(on a per capita basis of permanent residents) for the pastoral area of Xilinhot City to which the Maodeng pasture belongs,have grown steadily.Per capita total income rose from 29 630 yuan(RMB) in2015 to 62 859 yuan(RMB) in 2021.Relying on grassland resources to develop the pastoral ecology also broadens the potential economic development space.Overall,the establishment of the reserve and the experiment of implanting an enclosure policy have had a significant and positive impact on Maodeng pasture’s development from both an ecological and economic perspective.With the support of scientific evidence,enclosure policy can be extended to more than 110 000 km~2 of grasslands in northern China with similar precipitation and temperature conditions,enhancing the productive and ecological potential of grasslands.The above research results will contribute to the scientific formulation of grassland pasture quality improvement plans in northern China.

FORMULAE OF SOUND FIELD IN ENCLOSURES

It is considered necessary that an additional term representing the direct sound be introduced into the classical normal mode solution of sound field in enclosures , to accord with practice and to make the formula more useful.

Steady-state sound field in enclosures

The classical normal-mode theory expresses the steady-state sound field in an enclosure produced by a sound source as a series of normal modes of vibration. Experimental facts are not often explained by this theory, and it was conjectured that the normal-mode expression is not the complete solution of the wave equation in the enclosure, but only the reverberant part of it, and there should be an additional term representing the direct spherical radiation to make the solution complete. The problem is examined by critically reviewing the derivation of the normal-mode expression, and by theoretical analysis of the steady-state sound field in the room and experimental measurements therein. The conjecture is thus confirmed, and it is definitely shown that the sound field should contain the direct wave as well as the standing waves (normal modes) formed by the confinement of the boundary surfaces. Relevant mathematical expressions are derived.

On Identical Problems of Natural Convection in Enclosures and Applications of the Identity Character

In this paper, a concept of 'identical problems' of natural convection in enclosures is presented. A pair of problems of natural convection in enclosures is said to be identical if they look different in appearance but with appropriate selection of coordinates and appropriate definition of dimensionless variables for each problem, they will have identical geometric configurations and identical dimensionless governing equations and related boundary conditions. The identical characteristics of a pair of problems of natural convection in enclosures with an internal isolated island are demonstrated via dimensionless mathematical formulation and flow visualization results. Numerical computations are performed and the predicted streamlines agree with the flow visualization results. A number of other possible pairs of identical problems are also presented. Applications of the identical character are provided and assumptions under which the identical problems may exist are discussed.

Numerical investigation on thermal effects by adding thin compartmental plates into cooling enclosures with heat-leaking walls

Adding thin compartmental plates near the internal walls of enclosures has been nttmerically modeled using the lattice Boltzmann method. This practice was found to be an effective way to fitrther suppress the disadvantageous effects of heat leak, along with the application of insulation materials on the external surfaces. A modified extrapolation scheme for handling the thermal boundary of the thin plate was proposed and verified by comparison with the conventional coupled boundary scheme. The simulation of the natural convection during the cooling down processes and at steady states in the enclosure indicates that the existence of the plates leads to a higher cooling rate and a more favorable temperature uniformity. For a typical case, the one with plates takes 6% less time to reach the halfway point of the steady state and has 26% less temperature variance. Effects by the plates＇ positions and sizes were parametrically investigated, in order to find an optimal geometrical configuration. In addition, the fluid＇s intrinsic characteristics and the relative heat leak by using the Raylcigh number and Nussclt number, respectively, have been discussed in detail through hydrodynamic and convective heat transfer analyses.

Numerical Simulation of Natural Convection in Circular Enclosures with Inner Polygonal Cylinders,with Confirmation by Experimental Results

Numerical computations are performed for the natural convection in circular enclosures with inner polygonal cylinders.The polygon surface and the outer envelope are at constant but different temperatures,A body-fitted coordinate system is used,The coordinate system is generated via simple algebraic equations.The transformed governing equations are discretized on a control volume basis with power-law finite difference scheme.The SIMPLE-like algorithm is used to deal with the linkage between pressure and velocities.The numerical results are compared with the experimental data available in the literature,and the agreement between the numerical and experimental results are very good.

Numerical Study of Natural Convective Heat Transfer in an Air Filled Square Cavity Heated from Below and Symmetrically Cooled from the Sides with a Partition in the Hot Wall

A two-dimensional numerical study of laminar natural convection in a square enclosure filled with air with a wall partially heated on the bottom is presented.The heat source is located on the lower wall with different heated widths varied from 20 to 80%(ε=0.2–0.8)of the total width of the lower wall and different heights h=H/4 and H/2 of the partition.The effect of the partition height on the main system dynamics is investigated through solution of the two-dimensional Navier-Stokes equations and the energy equation by means of a finite volume method based on the SIMPLE algorithm.The influence of the Rayleigh number(Ra=10^(3) to 10^(6))and the hot wall length is also examined.It is shown that the average Nusselt number grows whenεincreases and when h decreases.For a given value ofεand h,the average Nusselt number increases as Ra increases.It is concluded that the partition height causes a decrease in the average Nusselt number.

Simulation of Natural Convection Flow with Magneto-Hydrodynamics in a Wavy Top Enclosure with a Semi-Circular Heater

Natural convection flow in enclosure has different applications such as room ventilation, heat exchangers, the cooling system of a building etc. The Finite-Element method based on the Galerkin weighted residual approach is used to solve two-dimensional governing mass, momentum and energy-equations for natural convection flow in the presence of a magnetic field on a roof top with semi-circular heater. In the enclosure the horizontal lower wall was heated, the vertical two walls were adiabatic, inside the semi-circular heater, the wavy top wall cooled. The parameters Rayleigh number, Hartmann number and Prandtl number are considered. The effects of the Hartmann number and Rayleigh number on the streamlines, isotherms, velocity profiles and average Nusselt number are examined graphically. The local Nusselt number and the average Nusselt number of the heated portion of the enclosure with the semi-circular heater are presented in this paper. Finally, for the validation of the existing work, the current results are compared with published results and the auspicious agreement is achieved.

ACTIVE STRUCTURAL ACOUSTIC CONTROL IN ENCLOSURE USING RADIATION MODES

The problem of active structural acoustic control in an enclosure using radiation mode is investigated. The response of the coupled enclosure is derived in terms of radiation modes. The potential energy in the enclosure can be decomposed into independent parts and the radiation modes contribute to potential energy independently. The control strategy for minimizing first G radiation modes with large radiation efficiency is proposed, and the optimal model of control forces is presented. Finally, a numerical simulation for minimizing sound transmission into a rectangular enclosure using the proposed method is conducted. Simulation results indicate that one control force can control one radiation mode and controlling the first four-order radiation modes with four control forces can achieve significant potential energy reduction at the low frequency range.

Impact of enclosure management on soil properties and microbial biomass in a restored semi-arid rangeland, Kenya

Rangeland degradation is a serious problem throughout sub-Saharan Africa and its restoration is a challenge for the management of arid and semi-arid areas. In Lake Baringo Basin of Kenya, communities and individual farmers are restoring indigenous vegetation inside enclosures in an effort to combat severe land degradation and address their livelihood problems. This study evaluated the impact of enclosure management on soil properties and microbial biomass, being key indicators of soil ecosystem health. Six reseeded communal enclosures using soil embankments as water-harvesting structures and strictly regulated access were selected, varying in age from 13 to 23 years. In six private enclosures, ranging from 3 to 17 years in age, individual farmers emulated the communal enclosure strategy and restored areas for their exclusive use. Significant decreases in bulk density, and increases in the soil organic carbon, total nitrogen and microbial biomass contents and stocks were found in the enclosures as compared with the degraded open rangeland. In the private enclosures, the impact of rehabilitation on the soil quality was variable, and soil quality was in general lower than that obtained under communal management. The significant increase of absolute stocks of carbon, nitrogen and microbial biomass compared to the degraded open rangeland indicates the potential for the restoration of soil quality through range rehabilitation. Over-sowing with indigenous legume fodder species could improve total nitrogen content in the soil and nutritional value of the pastures as well.

TEKO通用机壳

TEKO Enclosures公司推出可容纳所有类型小型电子装置的ENCLOS型机壳。典型应用包括：遥控和袖珍型仪表。这些通用机壳以黑色ABS(UL94HB)材料模铸而成，带有可以嵌入顶部凹陷处的铝质面板。该凹陷处也可用来安装薄膜小键盘或产品标签。这种产品有3种尺寸3．34英寸×2．85英寸，高度分别为0．98英寸、

Buckeye平板金属机箱

BuckeyeEnclosures公司开始提供全系列平板金属(SM系列)机箱，用于轨架安装应用。该系列由0．062英寸的铝制成，经过铬钝化表面处理(alodine finish)。其面板尺寸宽19英寸，材料为0．125英寸经腐蚀的阳极化铝材。具有不带通风孔型、侧向板机柜安装孔型或带顶部和底部通风孔或侧向面板机柜安装孔等型号。

Convection Heat Transfer from Heated Thin Cylinders Inside a Ventilated Enclosure

Experimental study was conducted to determine the effect of velocity of axial fan,outlet vent height,position,area,and aspect ratio(h/w)of ventilated enclosure on convection heat transfer.Rectangular wooden ventilated enclosure having top and front transparent wall was made up of Perspex for visualization,and internal physical dimensions of box were 200 mm×200 mm×400 mm.Inlet vent was at bottom while outlet vents were at the side and top wall.Electrically heated cylindrical heat source having 6.1 slenderness ratio was fabricated and hanged at the centre of the enclosure.To calculate heat transfer rates,thermocouples were attached to the inner surface of heat source with silica gel.Heat source was operated at constant heat flux in order to quantify the effect of velocity of air on heat transfer.It was observed that average Nusselt number was increased from 68 to 216 by changing velocity from 0 to 3.34 m/s at constant modified Grashof number i.e.5.67E+09.While variation in outlet height at the front wall did not affect heat transfer in forced convection region.However,Nusselt number decreased to 5%by changing the outlet position from top to the front wall or by 50%reduction in outlet area during forced convection.Mean rise in temperature of enclosure increased from 8.19 K to 9.40 K by increasing aspect ratio of enclosure from 1.5 to 2 by operating heat source at constant heat flux i.e.541.20 w/m^(2).

EXPERIMENTAL STUDIES ON THE ROLE OF PLANKTIVOROUS FISHES IN THE ELIMINATION OF MICROCYSTIS BLOOM FROM DONGHU LAKE USING ENCLOSURE METHOD

The hypertrophic subtropic Donghu Lake’s dense water bloom(of mainly Microcystis Anaabaena andOscillatoria)that occurred annually from the beginning of the 1970s, has disappeared since 1985. The infiuenceof planktivorous fishes (silver and bighead carps) on the water bloom was studied for three years usingthe enclosure method. The enclosures stocked densely with bighead and/or silver carp were free of waterbloom during the experimental period. The water bloom that appeared in the fish-free enclosures was completelyeliminated in 10-20 days by introduction of silver and/or bighead carp(grass carp was not effectivein controlling water bloom).This study showed clearly that grazing pressure by planktivorous fishes is a keyfactor in eliminating water bloom from the lake.

Variations in microbial community during nitrogen removal by in situ oxygen-enhanced indigenous nitrogen-removal bacteria

In this study, the enclosure system exhibited perfect nitrogen removal performance with in situ oxygen-enhanced indigenous aerobic denitrifying bacteria in an enclosure experiment. We explored changes in the microbial community during the nitrogen removal process using the MiSeq high-throughput sequencing technology. The results revealed a total of 7974 and 33653 operational taxonomic units(OTUs) for water and sediment systems, respectively, with 97% similarity. The OTUs were found to be affiliated with eight main phyla(Proteobacteria, Actinobacteria, Cyanobacteria, Bacteroidetes, Planctomycetes, Chloroflexi, Firmicutes, and Actinobacteria). The diversity of the enhanced system was found to be higher than that of the control system. Principal component analysis(PCA) revealed that significant spatial and temporal differences were exhibited in the microbial community during nitrogen removal in the enclosure experiment. Redundancy analysis(RDA)indicated that physical parameters(temperature, dissolved oxygen, and pH), nitrogen(total nitrogen and nitrate), functional genes(nirK and nirS), and dissolved organic carbon(DOC) were the most important factors affecting bacterial community function and composition. Lastly, the results suggested that the variation in the microbial community could be analyzed through the MiSeq high-throughput sequencing technology,which may provide technical support for future field tests.