Composition and Properties of Biodegradable Materials

The important possibility of fabricating biodegradable materials by incorporating different bio- and photodegradable additives in the polymer is demonstrated. Changes were found in the structure and properties of degradable materials during exposure to soil microorganisms, air, and UV radiation for different times. The results obtained can serve as the basis for a more in-depth investigation of the mechanism of degradation of PCM.     

Safe Landing Analysis of a Quadrotor Aircraft With Two Legs

We proposed a multi-propeller multifunction aerial robot (MMAR) that is composed of a quadrotor with two legs. The legs can increase the function of the robot. We found that the legs can increase the safety region of the robot during the landing. To study the safety problem, the dynamics of MMAR interacting with environment should be solved. On the basis of the interaction dynamics, this paper investigates the velocity constraint for safe landing of MMAR. The investigation begins from the kinematics and dynamics of MMAR in flight mode. Then the impact dynamics of MMAR during landing is developed. Furthermore, the landing safety problem is formulated by a series of constraint equations which can give a safety region of the velocity during landing. The safety region can give the safe velocity of the aerial robot before landing. Finally, simulation examples are presented using the proposed methodology. In the examples, a detailed safety region of a simulated MMAR is constructed and shown.     

Mechanism of growth of silicon nitride crystals in combustion of ferrosilicon in nitrogen

The process of nitride formation in burning of iron-silicon melt in gaseous nitrogen was investigated. It was found that silicon nitride is synthesized at temperatures (2100°C) which are much higher than the temperature of appearance of the liquid phase (1206°C). Silicon is in the liquid state during synthesis in the form of an iron-silicon melt and a gaseous melt. The electron-microscopic studies showed that silicon nitride crystals grow according to two mechanisms: vapor-liquid-crystal and crystallization from iron-silicon melt. The ratio of the contributions of these mechanisms to structural formation of silicon nitride is determined by the conditions of synthesis. __________ Translated from Steklo i Keramika, No. 8, pp. 18–21, August, 2007.     

Automatic inpainting by removing fence-like structures in RGBD images

Recent inpainting techniques usually require human interactions which are labor intensive and dependent on the user experiences. In this paper, we introduce an automatic inpainting technique to remove undesired fence-like structures from images. Specifically, the proposed technique works on the RGBD images which have recently become cheaper and easier to obtain using the Microsoft Kinect. The basic idea is to segment and remove the undesired fence-like structures by using both depth and color information, and then adapt an existing inpainting algorithm to fill the holes resulting from the structure removal. We found that it is difficult to achieve a satisfactory segmentation of such structures by only using the depth channel. In this paper, we use the depth information to help identify a set of foreground and background strokes, with which we apply a graph-cut algorithm on the color channels to obtain a more accurate segmentation for inpainting. We demonstrate the effectiveness of the proposed technique by experiments on a set of Kinect images.     

Stabilizing bit-rates in networked control systems with decentralized event-triggered communication

In a decentralized event-triggered networked control system (NCS), an agent samples and transmits its local state information to the controller when some local event occurs. Such event-triggered NCSs were expected to be more efficient than traditional periodically sampled system in terms of communication channel usage. This paper studies the stability of decentralized event-triggered NCS in the presence of quantization and delays. We point out some potential issues in decentralized event-triggered design and propose an alternative decentralized event with a linear-affine threshold, which avoids infinitely fast data transmission. Conditions on quantizer and communication channel are derived, which, when satisfied, can guarantee stability of the resulting NCS. Based on these conditions, finite stabilizing bit-rates are provided.     

Bifurcation analysis of a two-dimensional simplified Hodgkin–Huxley model exposed to external electric fields

In this paper, the dynamical behaviors of a two-dimensional simplified Hodgkin–Huxley (H–H) model exposed to external electric fields are investigated through qualitative analysis and numerical simulation. A necessary and sufficient condition is proposed for the existence of the Hopf bifurcation. Saddle-node bifurcations and canards of the simplified model with the coefficients of different linear forms are also discussed. Finally, the bifurcation curves with the coefficients of different linear forms are shown. The numerical results demonstrate that some linear forms can retain the bifurcation characteristics of the original model, which is of great use to simplify the H–H model for the real-world applications.     

Effect of composition of metallurgical powder on the slopes and hearths of electric arc furnaces

Summary To reduce the sliding of fettling powders from the slopes of electric furnaces, it is desirable to use powders with not more than 10% of the fraction finer than 0.088 mm, and the SiO₂ content should be about 4.5–6%. Addition to the magnesite powder of coarse dolomite fraction 15-0.5 mm, and also 6–7% coal tar pitch, reduces the mobility of the powders.The rational composition of metallurgical powders used for fettling slopes and hearths of electric arc furnaces largely depends on the grade of steel being melted.The increase in the life of the slopes and hearths of an electric furnace in which stainless steel was being melted, fettled with MPMZ powder, was due to the increase in the content of periclase bonded with melilite and mervinite in the slopes and melilite and forsterite in the hearths.During the melting of steel of changing sorts, the increase in the life of the slopes and hearths, fettling with magnesite-dolomite powders is due to the presence of crystals of periclase bonded mainly with highly refractory dicalcium silicate.When fettling is done with MPMZ powder the structure of the slopes and hearths is identical. The use of chromemagnesite, magnesite-chromite and magnesite-dolomite powders give rise to the formation of a heterogeneous structure in the slopes and hearths which leads to their irregular wearing away.To prolong the service of the hearths and slopes of electric furnaces it is necessary to continue investigating the wear resistance of fettling materials in furnaces of different capacities, where steels of different types are being melted, typifying the life of the powders by the consumption per ton of steel melted, the burn-out profile of the lining, the interrepair periods and other factors.     

生物发酵过程中SSVIP-NNI软测量方法

生物发酵过程中关键生化变量难以直接检测,提出了一种利用基于敏感性与特异性的变量投影重要性(SSVIP)方法优化神经网络逆系统(NNI)的软测量方法。根据逆系统理论建立软测量模型,采用VIP变量优选方法,对软测量模型中的辅助变量进行优化。为了进一步提高VIP方法优选变量的性能,利用模型敏感性与特异性的概念,重新定义了VIP筛选阈值,确定最优的发酵过程软测量模型的变量。构造神经网络近似最优逆系统软测量模型,实现对发酵过程中关键过程变量的估计。通过Pensim仿真平台进行实验研究,结果表明经过辅助变量优选的神经网络逆系统软测量模型具有更高的估计精度和泛化能力。     

模拟三相流化床中颗粒尺寸对单气泡传质系数的影响

本文在模拟三相流化床中,测量了单气泡的传质系数,实验结果表明颗粒直径对气-液传质系数影响显著。颗粒直径较大时,传质系数有明显提高。