This paper presents a universal biquadratic circuit employing only positive current output operational trans-conductance amplifiers (OTAs). The circuit enables low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) responses by the selection and addition of the circuit currents. Moreover the circuit parameters ω₀ and Q can be set orthogonally by adjusting the bias currents of the OTAs. The biquadratic circuit enjoys very low sensitivity with respect to the circuit components. The achievement examples are given together with simulation results by PSPICE">

This paper presents a universal biquadratic circuit employing only plus current output devices (i.e. operational trans-conductance amplifiers (OTAs) and a current follower (CF)). The circuit enables low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) responses by the selection and addition of the circuit currents with no component matching constraints. Moreover the circuit parameters ω₀ and Q can be set orthogonally by adjusting the bias currents of the OTAs. The biquadratic circuit enjoys very low sensitivity with respect to the circuit components. The achievement examples are given together with simulation results by PSPICE. 

Fuel cells have the characteristics of pollution-free, renewable and high efficiency, and are the main development direction of new energy vehicles in the future. However, fuel cell vehicles have many system components and have great differences in temperature control, so compared with traditional vehicles, the design of the vehicle thermal management system is much more difficult. Therefore, the energy consumption of each component is reduced under the condition of reasonable temperature control of the vehicle  system, which has become a research hotspot today.

In this paper, we will simulate and simulate the thermal management of a fuel cell bus, and analyze the heat generation and heat dissipation mechanism of the fuel cell and the heat load of the cabin. Theoretical calculations and overall operating models of the thermal management system are carried out to provide the basis for the design and analysis of the thermal management system. Then, based on AMESim, the thermal management model of the whole vehicle is established, and the operation mode of the whole system is formulated. Finally, the model was simulated under NEDC conditions at different temperatures in winter and summer, and the simulation results were comprehensively analyzed.

The results show that the temperature of the crew compartment can be controlled within a reasonable range under different temperatures in winter and summer, and the cabin can be well cooled or heated in different temperature environments. At the same time, the temperature of the fuel cell can also be within a reasonable range. The simulation results show that the system is reasonable in controlling the temperature of the passenger compartment and the fuel cell.

Truck powertrain matching and overall design is an important part of truck research and development design, and runs through the whole vehicle research and development, is conducive to improving the quality of vehicle research and development and promote the process of vehicle research and development, and affects the stability of vehicle powertrain work, can overall focus on the whole vehicle research and development bias, It has certain practical application significance for a certain type of truck powertrain matching and overall design. This paper uses the main basic parameters of the truck prescribed to calculate the main index parameters of the truck powertrain of each part and determine the vehicle type, and then according to the main target parameters to choose the model of the powertrain system components, and the powertrain system and the main components of the vehicle are rationally arranged, the use of CAD software to draw the general layout of the truck. Finally, according to the parameters of the selected model of each component of the vehicle's power, fuel economy and other performance parameters were calculated, the results basically meet the requirements.

The study investigates the performance characteristics of laterized concrete made from cement blended with glass powder. The quest for shelter as one of the basic needs of man is on the increase as population increases geometrically. High cost of building materials in Nigeria has made housing out of reach of the average citizen. This difficulty has led to inward sourcing of some local wastes as alternatives to conventional materials in the construction industry. Cement is one of the chief ingredients used to produce concrete for building construction for man and animal. However, the production process of cement is not ecofriendly hence, several pozolanic materials have been exploited to partially replace cement. Glass has very short usage life span and are found all around especially dumpsites constituting source of harm to both man and animal in the environment. The reuse of these waste products will help to save our environment from environmental pollution and severe ecological (green) problem. Concrete cubes were produced using cement, glass powder, laterite and granite measured using 1:2:4 ratio, and the percentage of cement replacement used are 0%, 10%, 20% and 30% respectively. the mixture was thoroughly mixed with water to achieve plastic form, it was then poured into mould in three steps and compacted manually by tapping on a flat surface, after  24 hours, it was demoulded and cured  in water under room temperature. The strength was tested in three replicates for 7, 14, 21, and 28days, respectively. The absorption test was carried out after curing the concrete for 28 days and air dried for 60 days to determine the water holding capacity of the concrete cubes. Each sample was weighed before immersion in water for twenty four hours. The samples were removed and weighed again. The procedure was replicated three times. The compressive strength increased with the age of curing in all the specimen. On 28th day, the specimen with 10% replacement had highest compressive strength of 10.0N/mm² while the lowest compressive strength of 2.5N/mm² was observed in the 30% replacement. The absorption capacity of the specimen 0,10, 20 and 30% are 5.12, 7.38, 9.76 and 9.58, respectively. The results showed that all cubes produced satisfied the maximum water absorption 12% recommended by Nigerian Industrial Standard NIS (2004) and 12.5% water absorption recommended by the Nigerian Building and Road Research Institute NBRRI (2006). Therefore, glass powder can effectively replace cement up to 10%.