Method for altering deformational characteristics of controlled-clearance piston-cylinders

A new controlled-clearance pressure balance has been developed to improve the hydraulic pressure standard for pressures up to 1 GPa. For several controlled-clearance (CC) piston-cylinders, characterization experiments based on the Heydemann-Welch (H-W) model were performed to estimate the pressure dependence of the effective area. The results of the experiments, specifically, the changes in the piston fall-rate and the generated pressure in response to the applied jacket pressure, are summarized for CC piston-cylinders of different pressure ranges. At pressures higher than a few hundred MPa, the characteristics of some piston-cylinders differed from those predicted by the H-W model. In this paper, a method for altering the deformational characteristics of CC piston-cylinders is examined. It was found that adjusting the area of the outer surface of the cylinder to which the jacket pressure is applied is an effective method for obtaining deformational characteristics that satisfy the conditions of the H-W model.     

液压随动平衡系统的设计与实现

根据机床垂直运动坐标随动平衡的要求。提出一种双向运动等扭矩液压实现的方法，解决负载不平衡带来的诸多问题。     

Evaluation of thermodynamic properties using GAB model to describe the desorption process of cocoa beans

The desorption isotherms and thermodynamic properties of cocoa beans were obtained during the drying process of this product. The isotherms were determined by dynamic method for various temperature (25, 35, 45 and 55 °C) and relative humidity (RH) conditions (30, 40, 50, 60, 70 and 80%). Equilibrium moisture content data were correlated by the Guggenheim–Anderson–de Boer (GAB) model, which presented good fit to the data, according to statistical procedures. Equilibrium moisture content ranged from 5.90 to 16.67 d.b.; it increased with an increment in the RH and decreased with increased temperature at a constant RH. Enthalpy values for each model coefficient were encountered, ranging from ?90.05 to 545.96 kJ kg^?1. The integral isosteric heat of desorption and differential entropy increased with decreased equilibrium moisture content, a tendency also found for Gibbs free energy.     

Evaluation of the dynamic performance variation of a serial manipulator after eliminating the self-weight influence

Manipulators used in the industrial field usually have a very stiff structure but without an equivalent payload on their end-effectors. This is because the stiff structure is used to prevent excessive deformation which will negatively impact the positioning accuracy of the manipulator, especially when the manipulator is fully extended. However, the stiff structure increases the weight of the manipulator and consumes much of the output of the constituent joint actuators in order to overcome the gravitational force resulting from the heavy structure. To cope with this problem, the concept of gravity balance was proposed decades ago, and there have been several approaches suggested to eliminate the influence of the self-weight of the structure. With the help of gravity balance, the output of the constituent joint actuators can fully be used to drive the manipulator and save considerable energy when the manipulator is in static or low-speed applications.For decades, many papers have discussed how to make a manipulator in gravity balance or how to design and apply a gravity balance mechanism to satisfy a certain application. However, none of them discuss what the influence on the dynamic performance of a manipulator is after it is equipped with a gravity balance mechanism or how to evaluate that influence. To rectify this insufficiency, this article utilizes acceleration radius to be the index of measuring the dynamic performance before and after a manipulator is equipped with a gravity balance mechanism and proposes a new index, the maneuverability ratio, to provide quantitative information to measure whether the dynamic performance of the manipulator increases or not after the gravity balance mechanism is applied.     

A dimensionless approach for the urban-scale evaluation of domestic rainwater harvesting systems for toilet flushing and garden irrigation

A dimensionless methodology to evaluate the water saving obtainable from large-scale implementation of domestic rain water harvesting (RWH) systems in urban areas is presented. The methodology combines the use of regressive relationships for water saving evaluation based on the results of the dimensionless rainwater tank water balance and of catchment-wide information obtained from geospatial databases. The adopted RWH scheme included internal use of rainwater for toilet flushing and external use for garden irrigation. An application to a portion of the city of Rome, Italy showed the methodology to allow systematic and accurate evaluation of RWH system performance at the selected urban scale. Results pointed out high water saving potential for toilet flushing ranging between 38–65% for tank sizes within 1–50 m³. Furthermore, more than one third of the systems provided water saving benefit for irrigation larger than 20% by using a 50 m³ tank.     

Computational Studies on Nitro-Azaboriridine—A High-Energetic Material

Nitrogen heterocycles and their derivatives are one of the classes of compounds that have been widely used in developing high-energetic materials. The energy content of the heterocycle ring systems can be increased by inclusion of nitro, cyano, and azido groups. In the present study nitro derivatives of small three-membered B-N-C ring compounds, viz. 1-nitro-1,2-azaboriridine, 1,3-dinitro-1,2-azaboriridine, and 1,3,3-trinitro-1,2-azaboriridine, have been considered. Thermodynamic properties and energetics of the above compounds have been taken for detailed computational study using G2, G3, and CBSQB3 compound methods. Studies reveal that these compounds can be considered for use as high-energetic materials. Detonation velocity (D) and detonation pressure (P) of the title compounds have also been evaluated using the Kamlet-Jacobs method based on the theoretical densities and heats of formation calculated at G3 level. Calculation shows that 1,3,3-trinitro-1,2-azaboriridine yields a detonation velocity of 9.14 km/s and a detonation pressure of 40.2 GPa at a loading density of 1.91 g/cm³ that is comparable to powerful commercial explosives such as HMX (9.10 km/s, 1.91 g/cm³, 39.0 GPa) and RDX (8.75 km/s, 1.82 g/cm³, 34.0 GPa).     

多级离心输油泵平衡装置设计的模糊综合评价

将模糊多目标决策方法应用于多级离心泵平衡装置设计方案的评价,使设计方案的优选更趋于合理。     

建筑雨水利用系统的设计

本文结合工程实际，对雨水利用系统进行介绍，提出在设计中应考虑的问题及解决办法。     

热水采暖系统的故障分析与处理

以设计和安装角度分析了造成室内热水采暖系统故障的原因，指出其影响因素是多方面的，在排除故障时应对其逐一分析，并提出一些可行性建议。     

Expanded Polystyrene Foam Formed from Polystyrene Beads Coated with a Nanocrystalline SiO2 Film and the Analysis of Its Moisture Adsorption and Resistance to Mechanical Stress

Conventional expanded polystyrene can absorb moisture, which significantly degrades its properties. In the present study, it was demonstrated that SiO₂ can be deposited on polystyrene beads before pre-expansion and molding steps. Under the applied test conditions, expanded polystyrene with nanocrystalline SiO₂ additives had approximately 10% lower moisture adsorption and an 8.4% better resistance to deformation. Expanded polystyrene analysis suggested that the observed improvements were caused by the hydrophobic nature of nanocrystalline SiO₂ and, even more importantly, because SiO₂ acted as an amalgamation catalyst and significantly increased adhesion between the expanded polystyrene beads during the expanded polystyrene molding process.