Flow and Noise Characteristics of Centrifugal Fan in Low Pressure Environment

The influence of low-pressure environment on centrifugal fan’s flow and noise characteristics was studied experimentally and numerically. A testbed was established to conduct the experimental test on the performance of a centrifugal fan, and the characteristic curve and power consumption curve of the fan under different pressure were obtained. Then the simulation model of the centrifugal fan was established, which was used to simulate the working process of centrifugal fan under different negative pressures. The results showed that the total pressure and static pressure of the fan decrease with the decrease of the ambient pressure. The total and static pressures of the fan under 60 kPa pressure condition decreased by 42.3% and 38.3%, respectively, compared with those of fan under the normal pressure. The main reason for this phenomenon is that the decrease of the environmental pressure leads to the decrease of air density. Besides, with the drop of environmental pressure, the sound pressure and sound power of the fan noise decreases.

Electricity Safety Analysis and Improvement Based on User Classification

Analyzing electricity consumption behavior by classifying user groups and knowing each group’s characteristics are an important way to realize intelligent power consumption. This paper firstly classifies different types of users based on power consumption data and grasps the power consumption behavior of typical users. The main causes of accidents and alarms are then discussed based on the recorded events and power consumption curve. Finally, the corresponding solutions, which take the user’s social attributes and electricity consumption behavior into consideration are put forward to avoid the potential accidents.

Design of Negative Pressure Spiral Feeding Device for Tangential and Longitudinal Axial Intersection of Combine Harvester

A difficult problem occurred with straw clogging at the tangential and longitudinal axial intersection of rice combine harvesters, which seriously affected the efficiency and reliability of the threshing cylinder. The primary objective of this paper was to design a negative pressure spiral feeding device by CFD (computational fluid dynamics). The negative pressure spiral feeding combined structure of the tangential threshing cylinder and longitudinal axial threshing cylinder was established by Pro/E software. Then, the flow path model of the negative pressure spiral feeding device was analyzed by CFD. The airflow velocity distribution of the spiral feed head semicircular cross section and power consumption of the longitudinal axial spiral feeding head were used to verify the effectiveness and rationality of the negative pressure spiral feeding device. The results showed that the two-blade spiral structure and 30 mm pitch shroud structure were more suitable to ensure the smooth flow of straw at the tangential and longitudinal axial intersection. The resistance of the feeding head would cause the power consumption curve fluctuation. The power consumption curve of the improved shroud spiral feed structure was a stable regular fold line without upward trend. When the power consumption curve has an always upward trend, it means that congestion is about to happen. The characteristics of the power consumption curve indicated that the shroud negative pressure spiral feed device designed in this paper was reasonable and effective.

Conditional Bias Robust Estimation of the Total of Curve Data by Sampling in a Finite Population: An Illustration on Electricity Load Curves

For marketing or power grid management purposes, many studies based on the analysis of total electricity consumption curves of groups of customers are now carried out by electricity companies. Aggregated totals or mean load curves are estimated using individual curves measured at fine time grid and collected according to some sampling design. Due to the skewness of the distribution of electricity consumptions, these samples often contain outlying curves which may have an important impact on the usual estimation procedures. We introduce several robust estimators of the total consumption curve which are not sensitive to such outlying curves. These estimators are based on the conditional bias approach and robust functional methods. We also derive mean square error estimators of these robust estimators, and finally, we evaluate and compare the performance of the suggested estimators on Irish electricity data.

A New Type of Countermeasure against DPA in Multi-Sbox of Block Cipher

The Internet of Things (IoT) provides the network for physical devices, like home appliances, embedded with electronics, sensors, and software, to share and exchange data. With its fast development, security of IoT has become a crucial problem. Among the methods of attack, side-channel attack has proven to be an effective tool to compromise the security of different devices with improving techniques of data processing, like DPA and CPA. Meanwhile, many countermeasures have risen accordingly as well, such as masking and noise addition. However, their common deficiency was that every single countermeasure might not be able to protect the key information completely after statistical analysis. Sensitive information will be disclosed during differential power analysis of Sbox, since it is the only nonlinear component in block cipher. Thus, how to protect Sbox effectively was the highlight of researches. Based on Sbox-reuse concept proposed by Bilgin, this paper put forward a new type of a countermeasure scheme against DPA in multi-Sbox of block cipher. We first converted the multi-Sbox into 4 × 4 permutations and then reused permutation with the algebraic degree of more than one so as to turn it into a special reusable Sbox and then numbered 4 × 4 permutation input. Finally, we made these inputs of permutations completely random by masking. Since it was necessary to make the collected power consumption curve subject to alignment process in DPA by chosen-plaintext attack, this scheme combined the concept from DPA countermeasures of masking and noise addition. After the experiment with the proposed implementation, successful prevention of the attacker from accurately aligning the power consumption curve of the target Sbox has been proven, and the level of security has been improved by adding more random noise to protect key information and decrease the accuracy of statistical analysis.

Power Window

This article analyzes the energy identity crisis in some oil-producing countries. It highlights that the retail price for gasoline in countries such as Libya, Saudi Arabia, Bahrain, and Yemen was at or below the cost on the world market of the petroleum needed to produce it. However, Egypt went from an exporter of more than 300,000 barrels of oil a day in 1999 to a net importer beginning in 2009. And as a consequence, the prices for gasoline in Egypt went from below the raw material cost in 2006 to being comparable to those in the United States. Tunisia shifted from an exporter to an importer in 2000. Thanks to strong consumption growth, Bahrain has also seen its exports plummet from more than 30,000 barrels a day in the 1990s to around 3500 today. The Saudi consumption curve is climbing at about 4% per year, and unless the country can raise production above 11 million barrels a day, its exports will disappear by 2050.