摘要：At present,the architecture of a digital-to-analog converter(DAC) in essence is based on the weight current,and the average value of its D/A signal current increases in geometric series according to its digital signal bits increase,which is 2^(n-1) times of its least weight *** for a dual weight resistance chain type DAC,by using the weight voltage manner to D/A conversion,the D/A signal current is fixed to chain current I_(cha);it is only 1/2^(n-1) order of magnitude of the average signal current value of the weight current type *** principle is:n pairs dual weight resistances form a resistance chain,which ensures the constancy of the chain current;if digital signals control the total weight resistance from the output point to the zero potential point,that could directly control the total weight voltage of the output point,so that the digital signals directly turn into a sum of the weight voltage signals;thus the following goals are realized:(1) the total current is less than 200μA;(2) the total power consumption is less than 2 m W;(3) an 18-bit conversion can be realized by adopting a multi-grade structure;(4) the chip area is one order of magnitude smaller than the subsection current-steering type DAC;(5) the error depends only on the error of the unit resistance,so it is smaller than the error of the subsection current-steering type DAC; (6) the conversion time is only one action time of switch on or off,so its speed is not lower than the present DAC.

摘要：A temperature-based method is usually applied in displacement ventilation (DV) design when overheating is the primary indoor climate concern. Different steady-state models have been developed and implemented to calculate airflow rate in rooms with DV. However, in practical applications, the performance of DV depends on potentially dynamic parameters, such as strength, type and location of heat gains and changing heat gain schedule. In addition, thermal mass affects dynamically changing room air temperature. The selected steady-state and dynamic models were validated with the experimental results of a lecture room and an orchestra rehearsal room. Among the presented models, dynamic DV model demonstrated a capability to take into account the combination of dynamic parameters in typical applications of DV. The design airflow rate is calculated for the case studies of dynamic DV design in the modelled lecture room in both dynamic and steady-state conditions. In dynamic conditions of heavy construction in 2–4 hours occupancy periods, the actual airflow rate required could be 50% lower than the airflow rate calculated with the steady-state models. The difference between steady-state and dynamic multi-nodal model is most significant with heavyweight construction and short occupancy period (17%–28%). In cases with light construction, the dynamic DV model provides roughly the same airflow rates for four-hour occupancy period than the Mund’s model calculates. The dynamic model can significantly decrease the design airflow rate of DV, which can result in a reduction of investment costs and electrical consumption of fans.

摘要：A numerical investigation of thin-walled complex section steel columns with intermediate stiffeners was performed using finite element analysis. An accurate and reliable finite element model was developed and verified against test results. Veri-fication indicates that the model could predict the ultimate strengths and failure modes of the tested columns with reasonable accuracy. Therefore,the developed model was used for the parametric study. In addition,the effect of geometric imperfection on column ultimate strength and the effect of boundary conditions on the elastic distortional buckling of complex section columns were investigated. An equation for the elastic distortional buckling load of fixed-ended columns having different column lengths was proposed. The elastic distortional buckling load obtained from the proposed equation was used in the direct strength method to calculate the column ultimate strength. Generally,it is shown that the proposed design equation conservatively predicted the ultimate strengths of complex section columns with different column lengths.

摘要：Based on the characteristics of sewage from beauty salons,a simulation model of a small sewage source heat pump triple supply system that can be applied to such places is established to optimize the operating conditions of the *** results show that with the increase of sewage temperature and flow,the performance of the system also *** summer conditions,the system provides cooling,recovers waste heat and condensed heat from sewage,with a COP value of 8.97;in winter conditions,the system heats and produces hot water,with a COP value of 2.44;in transitional seasons,only hot water is *** COP value is *** with the traditional systems which refers to the air source heat pump and hot water boiler system currently used in beauty salons,this system can save energy by 50.9%.

摘要：Proton conductivity of proton exchange membranes(PEMs)strongly relies on microscopic morphology,which can be modulated by engineering the distribution of ionic ***,poly(arylene ether)s with densely distributed allyl functionalities are polymerized from a tetra-allyl bisphenol A *** subsequent thiol-ene addition with sodium 3-mercapto-1-propanesulfonate yields comb-shaped sulfonated fluorinated poly(arylene ether)s(SFPAEs)with ion exchange capacities(lECs)ranging from 1.29 mmol·g^-1 to 1.78 mmol g^-*** SFPAEs exhibit superior proton conductivity over the whole temperature range,which is attributed to the enhanced hydrophilic/hydrophobic phase separation as evidenced by small angle X-ray scattering *** SFPAE-4-40 with an IEC of 1.78 mmol·g^-1 shows the largest proton conductivity of 93 mS-crrr1 at room temperature under fully hydrated condition,higher than that of Nafion ***,the vanadium redox flow battery(VRFB)assembled with SFPAE-4-40 separator exhibits higher energy efficiency than the VRFB assembled with Nafion 212.

摘要：The hydro-hammer sampler is a new type of sampler compared with traditional ones. An important part of this new offshore sampler is that the structure of the core cutter has a significant effect on penetration and core recovery. In our experiments, a commercial finite element code with a capability of simulating large-strain frictional contact between two or more solid bodies is used to simulate the core cutter-soil interaction. The effects of the cutting edge shape, the diameter and the edge angle on penetration are analyzed by non-liner transient dynamic analysis using a finite element method （FEM）. Simulation results show that the cutter shape clearly has an effect on the penetration and core recovery. In addition, the penetration of the sampler increases with an increase in the inside diameter of the cutter, but decreases with an increase in the cutting angle. Based on these analyses, an optimum structure of the core cutter is designed and tested in the north margin of the Dalian gulf. Experiment results show that the penetration rate is about 16.5 m/h in silty clay and 15.4 m/h in cohesive clay, while the recovery is 68% and 83.3% resoectively.

摘要：This paper presents a wide supply voltage range, high speed true random number generator（TRNG） based on ring oscillators, which have different prime number of inverters. And a simple Von Neumann corrector as post processing is also realized to improve data randomness. Prototypes have been implemented and fabricated in 0.18 μm complementary metal oxide semiconductor（CMOS） technology with a wide range of supply voltage from 1.8 V to 3.6 V. The circuit occupies 4 500 μm2, and dissipates minimum 160 μW of power with sampling frequency of 20 MHz. Output bit rate range is from 100 kbit/s to 20 Mbit/s. Statistical test results, which were achieved from the die Hard battery of tests, demonstrate that output random numbers have a well characteristic of randomness.

摘要：We evaluate the hydrogen depletion ability of the hydrogen depletion system for Chinese Pressurized Reactor 1000(CPR1000), which has been applied in nuclear power plants with pressurized water reactors;moreover, we introduce a new device that can continuously monitor hydrogen concentration inside the CPR1000 containment building. Experimental studies show that a moveable hydrogen autocatalytic recombiner alone can sufficiently deplete hydrogen under the condition of a design-basis accident, and 33 passive autocatalytic recombiners placed in the areas of high hydrogen concentration satisfy the hydrogen depletion requirements under the condition of a beyond-design-basis ***, the hydrogen concentration monitoring system is designed and installed based on the approach of detecting the temperature increase caused by the catalytic reaction of hydrogen. In conclusion, the hydrogen depletion capacity of the CPR1000 meets the requirements, and the system's safety can be enhanced by the improved hydrogen concentration monitoring system.

摘要：The overuse of and heavy dependency on a technology will result in the rigidity of thinking, which is true of computer-aided drawing. Due to the similarities in computer graphics, freehand sketching has attracted the public attention again. In this paper, the necessity and importance of freehand sketching were reaffirmed, and suggestions for teaching reform in terms of learning interest, methods, quantity, and achievements were put forward, so as to help students to comprehensively improve their skills and accomplishment in their learning and practice.

摘要：Anti-ram bollard systems, which are installed around buildings and infrastructure, can prevent unauthorized vehicles from entering, maintain distance from vehicle-borne improvised explosive devices （VBIED） and reduce the corresponding damage. Compared with a fixed bollard system, a removable bollard system provides more flexibility as it can be removed when needed. This paper first proposes a new type of K4-rated removable anti-ram bollard system. To simulate the collision of a vehicle hitting the bollard system, a finite element model was then built and verified through comparison of numerical simulation results and existing experimental results. Based on the orthogonal design method, the factors influencing the safety and economy of this proposed system were examined and sorted according to their importance. An optimal design scheme was then produced. Finally, to validate the effectiveness of the proposed design scheme, four dynamic impact tests, including two front impact tests and two side impact tests, have been conducted according to BSI Specifications. The residual rotation angles of the specimen are smaller than 30~ and satisfy the requirements of the BSI Specification.