Heterogeneous cross-project defect prediction (HCPDP) aims to learn a prediction model from a heterogeneous source project and then apply the model to a target project. Existing HCPDP works mapped ...the data of the source and target projects in a common space. However, the pre-defined forms of mapping methods often limit prediction performance and it is difficult to measure the distance between two data instances from different feature spaces. This paper introduced optimal transport (OT) theory for the first time to build the relationship between source and target data distributions, and two prediction algorithms were proposed based on OT theory. In particular, an algorithm based on the Gromov-Wasserstein (EGW) entropic discrepancy was developed to perform the HCPDP model. The proposed EGW model measures the distance between two metric spaces by learning an optimal transfer matrix with the minimum data transfer cost and avoids measuring the distance of two instances of different feature spaces. Then, to improve EGW performance, an EGW+ transport algorithm based on EGW was developed by integrating target labels. Experimental results showed the effectiveness of EGW and EGW+ methods, and proved that our methods can support developers to find the defects in the early phase of software development.
This study proposes a novel incremental learning algorithm called distribution matching ensemble (DME) in context of adaptive weighted ensemble learning. In particular, DME estimates the distribution ...of each received data block by Gaussian mixture model (GMM) and reserves the corresponding distribution information, as well it maintains a group of classifiers in a buffer. When we receive a new data block which is required to be predicted, the similarity between its distribution and each reserved distribution will be calculated by Kullback-Leibler (KL) divergence, and then the similarities can be used to guide the weight assignment of each corresponding classifier to further make adaptive ensemble decision. DME gets rid of the underlying hypothesis that the most recent labeled data block always has the most similar distribution with the current unlabeled data block. In addition, to avoid infinite extension of ensemble buffer during incremental learning, we also develop two dynamic classifier update rules. Experiments results on some synthetic and real-world streaming datasets show that the proposed DME algorithm is able to track and adapt to various types of concept drift just in time. Especially, on data stream with frequent reoccurring drifts, the DME significantly outperforms to several state-of-the-art algorithms, indicating its superiority.
The pressure–viscosity coefficient (the
α
value), which represents the variation of viscosity as a function of pressure, is an important parameter for elastohydrodynamic lubrication analyses. The ...properties of hydrocarbons in the C
20
–C
40
mass range are of fundamental importance as they are basic constituents of synthetic- and mineral-based lubricant stocks. The conventional acquisition of the
α
value requires preparation of lubricant samples and experimental testing by means of a high-pressure viscometer. In this paper, we present a method to obtain the
α
value of a typical base oil (1-Decene trimer) based solely on the molecular dynamics simulations. Non-equilibrium molecular dynamics (NEMD) simulations were performed to calculate the shear viscosity of the lubricant at various temperatures and pressures up to 1 GPa. Elevated temperatures and time–temperature superposition (TTS)-based extrapolations were applied to further extend the ability of the NEMD simulations, and the rotational relaxation time was calculated and used to determine the validity of the NEMD calculations. The
α
value at 100 °C was calculated and compared with experimental results. Effectiveness of the extrapolation was evaluated with a 95 % confidence interval.
Obvious differences are observed between simulation and experimental results for series-connected insulated-gate bipolar transistors (IGBTs) using current IGBT models. Here, the cause of these errors ...is analyzed in detail. A physical model based on more effective assumptions for a 2-D structure is proposed in this paper. The relationship between carrier concentration and lifetime is considered in the model in order to achieve an accurate description for excess carrier distribution. Testing was performed in a buck converter using series-connected non-punch-through (NPT) planar-gate 6500 V/600 A high-voltage IGBTs (HVIGBTs) at various bus voltages using an asynchronous control signal. The accuracy of HVIGBT transient model is verified by comparing experimental and simulation results in buck converters using two and three series-connected IGBTs. The function of the RC snubber circuit is also evaluated using the proposed model.
During the operation of boom sprayers in the field, it is crucial to ensure that the entire boom is maintained at an optimal height relative to the ground or crop canopy. Active suspension is usually ...used to adjust the height. A control system for double-pendulum active suspension was developed in this paper. The control system consisted of a main control node, two distance measurement nodes, a vehicle inclination detection node, and an execution node. Communication between nodes was carried out using a CAN bus. The hardware was selected, and the interface circuits of the sensors and the actuator were designed. The transfer functions of the active suspension and electric linear actuator were established. In order to enhance the efficiency of the control system, the particle swarm optimization (PSO) algorithm was employed to optimize the initial parameters of the fuzzy PID controller. The simulation results demonstrated that the PSO-based fuzzy PID controller exhibited improvements in terms of reduced overshoot and decreased settling time when compared to conventional PID and fuzzy PID controllers. The experimental results showed that the active suspension system equipped with the control system could effectively isolate high-frequency disturbances and follow low-frequency ground undulations, meeting the operational requirements.
In video coding, temporal correlations between pictures are utilized by short-term and long-term reference, which are limited inside a random access segment and cannot cross random access points ...(RAPs). To improve coding efficiency, correlations across RAPs are exploited by some novel video coding schemes. The cross-random-access prediction structure results in alterable dependency between pictures, which is affected by random access and different from the fixed dependency in conventional video coding standard. However, current media streaming scheme, such as Dynamic Adaptive Streaming over HTTP (DASH), cannot describe dependency across RAPs. This paper introduces the cross-random-access dependency description in DASH syntax. With dependency information, client can download segments in proper temporal order but may re-download segments. This paper further improves downloading management in client. Experiments show that improved DASH system transmitting stream with cross-random-access prediction structure can save 22.1% on maximum and 14.3% on average transmission bits in contrast to conventional DASH system.
Although the maximum collector-emitter voltage of a high-voltage insulated-gate bipolar transistor (HV-IGBT) reaches 3300 V or higher, it still cannot satisfy the requirements of some high-voltage ...high-power converters. Applying power semiconductor devices in series connection can effectively improve the voltage rating and power rating of a power electronic converter. The key issue of device series connection is voltage balancing in static switching state and dynamic switching state. In this paper, a three-level converter based on series-connected HV-IGBTs is presented, its voltage-balancing subcircuits are analyzed, and the parameter design method for the converter is proposed. During the design process, key performance indexes of the series connection circuit, such as the voltage-balancing effect, loss of the voltage-balancing circuit, switching loss, and switching time, are comprehensively considered. Moreover, component parameters of the three-level converter are calculated considering the influence of the voltage-balancing circuit. The proposed parameter design method is applied in the development of a three-level HV-IGBT (4500 V/600 A) series connection test platform with 10 000-V rated dc-link voltage. Experimental results verify the validity of the proposed method.
The insulated gate bipolar transistor (IGBT) physical models are studied in details. The difference between low-voltage IGBT (LVIGBT) and high-voltage IGBT (HVIGBT) is analyzed and the shortage of ...the LVIGBT model used for HVIGBT is discussed. The physical model considering the effect of carrier concentrate on excess carrier lifetime is established for HVIGBT. The HVIGBT transient model is presented with different excess carrier lifetime in the base. The new description of steady-state U-I characteristics is also obtained with numerical method. The test experiment was performed in a Buck converter using 6500 V HVIGBT with different bus voltage and load current. The accuracy of the transient model of HVIGBT is verified by experiment and simulation results. The verification of some key parameters to describe the external characteristics is also given in the paper.
PDF
