The scarcity of land resources and food security challenges have prompted more effective uses of the rooftop as well as façade spaces in the urban city of Singapore. Urban rooftop spaces are used for mechanical and electrical (M&E) amenities such as air-conditioning cooling units and water tanks, so the spacious span of the roof area on HDB flats in Singapore is not available. Urban-metabolic farming modules (UmFm) built on 1.5 to 2 m terrace-step terrains have been modelled using BIM Revit to mimic such constraints in rooftop spaces. CFD simulation was conducted for the structure with consideration of the prevailing wind directions at different months of the year. The airflow with the inclusion of mesh netting and varying tiltings of the polycarbonate side façade was simulated to understand their impact on airflow in the growth envelope of the UmFm units under different prevailing wind directions. The amount of solar irradiance received by the crops at different heights in the UmFm due to the sun’s path, and shading of crops grown on the A-frame, was studied using Climate Studio. A comparative verification was done with a scaffold modular unit mounted with temperature, humidity, airflow, and Photosynthesis Photon Flux Density (PPFD) sensors. The digital model of the UmFm unit enables a prior assessment of site feasibility before actual physical implementation on an existing rooftop. It also facilitates plug and play for the UmFm unit to generate an eco-resilient farmscape for an urban city.
The effect of different grazing intensity(nongrazed,light grazing,moderate grazing and heavy grazing) on soil physical properties and chemical properties was conducted in a desert steppe in Ningxia.Grazing disturbance had significant effect on soil physical properties and chemical properties in desert steppe.Soil moisture and porosity decreased with the increase of grazing intensity,while soil bulk density and pH showed a sharp linear increase with grazing intensity increasing.As compared with nongrazed plots,grazed plots(heavy grazing,moderate grazing and light grazing) resulted in significant decrease of soil moisture(0-30 cm) and porosity by 21.1%,12.0%,4.7% and 3.2%,2.5%,2.1%.With the increase of soil depth,soil moisture increased under different grazing intensity.Soil organic carbon and C/N decreased with grazing intensity increasing.Compared with nongrazed plots,heavy grazing decreased soil organic carbon of 0-10 cm and 10-20 cm by 20.6% and 14.1%,and soil C/N decreased by 43.4% and 34.1%,respectively.With the increase of grazing intensity,soil total phosphorus,available phosphorus and total kalium increased,while soil electric conductivity and soil total nitrogen decreased after an initial increase.It was suggested that reasonable grazing can improve soil structure and soil nutrient in desert steppe and restrain the degradation of soil in desert steppe.
This paper presents an ultra-low power mixed-signal neural data acquisition (MSN-DAQ) system that enables a novel low-power hybrid-domain neural decoding architecture for implantable brain-machine interfaces with high channel count. Implemented in 180nm CMOS technology, the 32-channel custom chip operates at 1V supply voltage and achieves excellent performance including 1.07µW/channel, 2.37/5.62 NEF/PEF and 88dB common-mode rejection ratio (CMRR) with significant back-end power-saving advantage compared to prior works. The fabricated prototype was further evaluated with in vivo human tests at bedside, and its performance closely follows that of a commercial recording system.
Abstract Desertification, one of the most severe types of land degradation in the world, is of great importance because it is occurring, to some degree, on approximately 40% of the global land area and is affecting more than 1 billion people. In this study, we used a space-for-time method to quantify the impact of five different desertification regimes (potential (PD), light (LD), moderate (MD), severe (SD), and very severe (VSD)) on a desert steppe ecosystem in northern China to examine the relationship between the productivity of the vegetation and soil properties and to determine the mechanism underlying the effects of desertification on productivity. Our results showed that the effects of desertification on TP (total phosphorus) and AP (available phosphorus) were not significant, and desertification decreased productivity in the desert steppe as a result of direct changes to soil physical properties, which can directly affect soil chemical properties. Therefore, intensive grassland management to improve soil quality may result in the long-term preservation of ecosystem functions and services.
Fast stepwise procedures of selection of variables by using AIC and BIC criteria are proposed inthis paper. We shall use a short name for these new procedures. FSP are similar to the well-known stepwise regression procedures in computing steps. But FSP have two advantages. One of theseadvantages is that FSP are definitely convergent with a faster rate in finite computing steps. Anotheradvantage is that ESP can be used for large number of candidate variables. In this paper we alsoshow some asymptotic properties of FSP, and some simulation results.
The variation of soil properties, the fractal dimension of soil particle size, and the relationships between fractal dimension of soil particle size and soil properties in the process of desertification in desert grassland of Ningxia were discussed. The results showed that the fractal dimension (D) at different desertification stages in desert grassland varied greatly, the value of D was between 1.69 and 2.62. Except for the 10-20 cm soil layer, the value of D gradually declined with increa sing desertification of desert grassland at 0-30 cm soil layer. In the process of desertification in de-sert grassland, the grassland had the highest values of D , the volume percentage of clay and silt, and the lowest values of the volume percentage of very fine sand and fine sand. However, the mobile dunes had the lowest value of D , the volume percentage of clay and silt, and the highest value of the volume percentage of very fine sand and fine sand. There was a significant positive correlation between the soil fractal dimension value and the volume percentage of soil particles <50 μm, and a significant negative correlation between the soil fractal dimension value and the volume percentage of soil particles >50 μm. The grain size of 50 μm was the critical value for deciding the relationship between the soil particle fractal dimension and the volume percentage. Soil organic matter (SOM) and total nitrogen (TN) decreased gradually with increasing desertification of desert grassland, but soil bulk density increased gradually. Qualitative change from fixed dunes to semi fixed dunes with the rapid decrease of the volume percentage of clay and silt, SOM, TN and the rapid increase of volume percentage of very fine sand and fine sand, soil bulk density. Fractal dimension was significantly correlated to SOM, TN and soil bulk density. Fractal dimension 2.58 was a critical value of fixed dunes and semi fixed dunes. So, the fractal dimension of 2.58 could be taken as the desertification indicator of desert grassland.研究宁夏荒漠草原沙漠化过程中土壤性状、土壤粒径分形维数的变化特征，以及分形维数与土壤性状的关系.结果表明：草地沙漠化对土壤分形维数(D)影响显著，D值为1.69～2.62.除在10～20 cm土层出现较小波动外，随着沙漠化程度加剧，0～30 cm土层D值整体呈减小趋势.在荒漠草原沙漠化过程中，荒漠草地D 值最大，黏粒和粉粒体积百分含量最高，极细砂粒和细砂粒体积百分含量最低；流动沙地D值最小，黏粒和粉粒体积百分含量最小，极细砂粒和细砂粒体积百分含量最高.D与<50 μm和>50 μm粒径的土壤颗粒存在显著正相关和负相关，表明50 μm粒径是决定草地沙漠化过程中土壤分形维数与土壤粒径关系的临界粒径.随着荒漠草原沙漠化加剧，土壤有机质和全氮含量逐渐降低，土壤容重逐渐升高，固定沙地至半固定沙地是荒漠草原沙漠化的质变过程，其中土壤粘粒体积百分含量、粉粒体积百分含量、土壤有机质含量、土壤全氮含量骤减，极细砂粒体积百分含量、细砂粒体积百分含量和土壤容重骤增.分形维数与土壤有机质、土壤全氮和土壤容重显著相关，固定沙地与半固定沙地分形维数的临界值为2.58，因此分形维数2.58可作为荒漠草原沙漠化的退化指标.
The conditions and factors which determine and affect the temporature peak in the materials during infrared heating are discussed. The temperature fields in dry materials with constant thermal properties during infrared heating are calculated bynumerical method with a transient one-dimensional combined radiative-conductive heat transfer model. The results show that the radiation is the main factor to cause the temperature peak, and the essential conditions for the existence of the temporature peak are the following: (a) there is irradiation on the surface; (b) the transmissivity of the surface is not equal to zero; (c)the material is semi-transparent; (d)the heated surface is cooled by convective heat transfor. The effects of absorption coefficient, refractive index, heat conductivity, convective heat-transfer coefficient and radiative properties of the surf ace on the temperature field are discussed too.
X-ray study, density measurement and estimation of aoousto-optic properties of the compounds in PbO-Nb2O5 system were carried out. Existence of the six PbO-NbaOs compounds reported by Roth was confirmed by X-ray analysis. Cell parameters and powder diffraction data were accurately measured for the compounds P3N and P5N2. It was found that in the mixture of PbO and Nb2O5 with a composition of P5N2 heated at 900~1150℃ there exists P3N as an intormediate phase. In this system the compounds P3N, P5N2, P2N and P3N2 with high PbO contents all possess large values of acousto-optio figures of merit and thus are promising new aoousto-optic materials.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
