摘要：In this paper a novel log-domain current-mode integrator based on MOS transistors in subthreshold is proposed. The integrator's time-constant is tunable by varying a reference bias current. By use of the integrator, a fifth-order Chebyshev lowpass filter with 0.1dB ripples is designed. The simulation results demonstrate that the proposed filter has such advantages as low power supply(1.5V), very low power dissipation (μW level), nearly ideal frequency response, very small sensitivity to components in passband, and adjustable cut-off frequency over a wide *** circuit is composed of NMOS transistors and grounded capacitors which make it suitable for fully integrated circuit implementation.

摘要：Through the survey of plant landscapes on eight representative squares in Tianjin City,the paper had pointed out that plant landscapes on Tianjin squares were improper in terms of plants richness,cultivation layer and color *** had suggested selecting regional characteristic tree species,applying salt-tolerant plants,emphasizing the diversity of plants species,highlighting the application of towering arbors,stressing the use of color-leaved plants,and creating abundant plant communities,so as to provide citizens with a more practical and ornamental square landscape environment through improving plant landscapes on squares in Tianjin City.

摘要：After the analysis of the development situation of urban landscape planning and design, the paper has summarized characteristics of current landscape planning, design and construction; and pointed out primary problems existing in modern urban landscape planning and design. It considers that the general planning and design level of modern landscape is to be improved, landscape construction is lacked of technological innovation, urban landscape construction and eco-environment efficiency have not been unified, plant species for landscaping are not reasonable, and construction has been emphasized while management been neglected in landscape planning. Through discussing the development tendency of modern urban landscape planning and design, it highlights that it should establish an ecological landscape idea corresponding with modern urban development requirements; set a long-term target based on modern urban development requirement; achieve the combination of bio-diversity, science and art; take social, ecological and social benefit into consideration; identify humanistic theme for landscape design; and pay attention to highly integrated application of multiple disciplines.

摘要：The effects of the composite-collector structure and the δ-doping density in InGaAs/InP DHBT on the Kirk current have been *** effective grade layer in the discretely graded layer goes into the InGaAs setback *** formulas of the maximum doping density,the maximum Kirk current,and the corresponding δ-doping density are derived under different Kirk-effect *** the maximum collector doping density and the maximum Kirk current are dependent on the δ-doping *** opti-mizing the delta doping,the Kirk current density can be greatly increased.

摘要：A study of coccolith assemblages from a box core from the central South Yellow Sea（SYS） was performed revealing fluctuations on their relative abundance（%） that can be related to climatic and hydrographic changes over the last 230 years（1780–2011）. Total coccolith abundances ranged from 7.0 to 55.1×10^6 coccoliths·g^-1sediment. Although the abundance of different species varied widely throughout the core, seven taxa dominated the assemblage. Among these species, Gephyrocapsa oceanica was the most dominant species, and it showed an average percentage of 50.1%. The pattern of G. oceanica（eutrophic species） was opposite to that of the combined percentage of Braarudosphaera bigelowii and Umbilicosphaera sibogae（both oligotrophic species）, indicating that in the Yellow Sea（YS）, the distribution pattern of G. oceanica might be characteristic of nutrient *** patterns between G. oceanica and the Siberian High were observed on an inter-decadal time scale,indicating that the East Asian Winter Monsoon（EAWM） may be an important driver of ecological changes in the YS. When the EAWM prevails, both the Yellow Sea Coastal current（YSCC） and Yellow Sea Warm current（YSWC）strengthen, and the increasing nutrient availability and warmer water brought by the strengthened YSWC favor eutrophic and warm-water coccolithophore species, such as G. oceanica. This likely mechanism demonstrates that coccolith assemblages can be used as benign and reliable proxy for climate change and surface oceanography.

摘要：In coastal areas with complicated flow movement, deposition and scour readily occur in submarine excavation projects. In this study, a smallscale model, with a high resolution in the vertical direction, was used to simulate the tidal current around a submarine excavation project. The finite volume method was used to solve Navier-Stokes equations and the Reynolds stress transport equation, and the entire process of the tidal current was simulated with unstructured meshes, generated in the irregular shape area, and structured meshes, generated in other water *** meshes near the bottom and free surface were densified with a minimum layer thickness of 0.05 m. The volume of fluid method was used to track the free surface, the volume fraction of cells on the upstream boundary was obtained from the volume fraction of adjacent cells, and that on the downstream boundary was determined by the water level process. The numerical results agree with the observed data, and some conclusions can be drawn: after the foundation trench excavation, the flow velocity decreases quite a bit through the foundation trench, with reverse flow occurring on the lee slope in the foundation trench; the swirling flow impedes inflow, leading to the occurrence of dammed water above the foundation trench; the turbulent motion is stronger during ebbing than in other tidal stages, the range with the maximum value of turbulent viscosity, occurring on the south side of the foundation trench at maximum ebbing, is greater than those in other tidal stages in a tidal cycle, and the maximum value of Reynolds shear stress occurs on the south side of the foundation trench at maximum ebbing in a tidal cycle. The numerical calculation method shows a strong performance in simulation of the hydrodynamic characteristics of tidal currents in the foundation trench, providing a basis for submarine engineering construction in coastal areas.

摘要：Concept of agritourism was analyzed and it was stressed that significance of agritourism has been highlighted as the living standards are improved, then concept of creative agritourism design was introduced due to the need of improving grade of agritourism and developing competitive tourism products. Creative design of agritourism was taken as the key point of agritourism planning, its significance was analyzed, and it was stressed that novel, special and comfortable tourist products and experience should be developed. On this basis, agritourism development and problems of Beijing City were introduced, foundation of creative resources in Beijing was analyzed, then content of the creative agritourism design was discussed under supervision principles of natural and cultural creative designs. Creative agritourism design was specifically elaborated from the following aspects:creative and strategic cultural planning, enhancement of humanistic and natural landscapes, constructed landscapes, design of tourism cultures, scientific and technological originality, festival and event planning, planning and design of tourist products, design of propaganda materials and website.

摘要：A common current source, generally used to bias cross-coupled differential amplifiers in a transconductor, controls third harmonic distortion (HD3) poorly. Separate current sources are shown to provide better control on HD3) . In this paper, a detailed design and analysis is presented for a transconductor made using this biasing technique. The transconductor, in addition, is made to offer high Gm, low power dissipation and is designed for linearly tunable Gm with current mode load as one of the applications. The circuit exhibits HD3) of less than –43.7 dB, high current efficiency of 1.18 V-1 and Gm of 390 μS at 1 VGp-p @ 50 MHz. UMC 0.18 μm CMOS process technology is used for simulation at supply voltage of 1.8 V.

摘要：As an important carrier of the construction of campus spiritual civilization,college national orchestra can not only enhance the popularity of the school,the level of art education,but also improve the students’aesthetics of music through the professional training of national *** paper analyzes the current situation of national orchestra of Sichuan Minzu College from different perspectives,and in view of the problems explores the form and trend of its future development in order to achieve better development of national orchestra in colleges and universities.

摘要：This paper presents a systematic approach of optimal design and control of a surface-mount, permanent-magnet synchronous torque motor for the next-generation machine tools. A step-by-step procedure of optimization integrates multiple performance objectives and constraints to help the designer make the best decision on the final motor geometry from both design and control perspectives. In the perspective of design, a torque motor with concentrated windings and similar numbers of slots and poles may achieve the desired performance after optimization for multiple objectives, leading to a sinusoidal flux density for a nearly ripple-free torque distribution. From the control perspective, an optimal current waveform with an ideal shift angle is determined for each phase by aligning the current excitation with the back electromotive force. Both design and control of the surface-mount, permanent magnet machine are verified by the finite element method, and a prototype is fabricated for performance validation.