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Today, they are students in colleges and universities. Tomorrow, they will be engineers in various industrial sectors. One of the primary goals of education is to prepare people for successful careers in the real world. As in every course, students want to obtain the maximum value of a CAD related course for their future careers. They want to obtain knowledge and skills that are most practical and useful to them when they become engineers. College professors and teachers also want to provide the maximum value for students in their CAD courses. The question is: what should be included in such a CAD curriculum. This paper tries to answer some critical questions related to developing such a curriculum, from an industrial perspective, based on the authors' survey results and the first author's own (rather limited) experiences as a R&D staff for a CAD vendor. It focuses on issues related to teaching and training students on CAD systems. These include, for different roles, how much underlying mathematical foundations in CAD systems should be taught, how much computer skills and engineering knowledge the students should know, how much design methodologies related to CAD systems should be taught, and how much ability the students should develop in order to specify their CAD needs and to evaluate and choose the CAD systems most suitable for their specific applications. The paper then shares some personal experiences and suggestions from long-term CAD veterans on the essential topics of CAD education. Based on the survey results, last section concludes the paper by authors' suggestions on what should be included in CAD curriculums for different levels of students.

In this paper, multiresolution models are employed in the context of reverse engineering for feature line extraction. Starting with a proper triangulation of the cloud point data as a priori, our feature line extraction algorithm has three steps: (1) establishing a Gauss normal sphere and creating multiresolution models for the Gauss sphere based on different levels of subdivisions for the sphere regions; (2) mapping the unit normal vectors of triangular faces in the multiresolution Gauss sphere and merging those connected triangular faces whose unit normal vectors fallen on the same Gauss sphere region with a given resolution to form super-faces (the collection of triangular facets with similar normal); and (3) extracting the boundaries from the super-faces and generating the feature lines from the extracted boundaries. We then use these feature lines as a base for tracing boundary curves for B-spline surface construction. Since feature lines maintain the characteristics of the original product models, in this way, we have a good chance to reconstruct B-spline surfaces with high quality. Examples are given in the paper to show the feature line extraction, the influence of the feature lines extracted under different resolutions, and the final reconstructed B-spline surfaces based on these feature lines.

Wild-type p53-induced phosphatase 1 (Wip1) negatively regulates several tumour suppressor and DNA damage response pathways. However, the impact of Wip1 on haematopoietic stem cell (HSC) homeostasis and aging remains unknown. Here we show that Wip1 is highly expressed in HSCs but decreases with age. Wip1-deficient (Wip1(-/-)) mice exhibited multifaceted HSC aging phenotypes, including the increased pool size and impaired repopulating activity. Deletion of p53 rescued the multilineage repopulation defect of Wip1(-/-) HSCs without affecting cellular senescence or apoptosis, indicating that the Wip1-p53 axis regulates HSC differentiation in a manner independent of conventional p53 pathways. However, p53 deletion did not influence the increased HSC pool size in Wip1(-/-) mice. Interestingly, the expansion of HSCs in Wip1(-/-) mice was due to an mTORC1-mediated HSC proliferation. Thus, our study reveals a mechanism of stem cell aging, in which distinct effects of p53 and mTORC1 pathways on HSC aging are governed by Wip1.

It is well known that that source inductance could significantly increase turn-on and turn-off time, and therefore increase switching power loss. Also, it is well understood that switching loop inductance could reduce voltage stress during turn-on and increase voltage stress during turn-off. In this paper, a new inductive switching loss model that includes source inductance and switching loop inductance has been derived and thoroughly analyzed. The new model shows that source inductance causes a “visual gate charge”, which is equivalent to physical gate charge, when look from the driver. For high current switching conditions, the visual source charge dominates total gate charge and is the main factor for switching time. Simulations and experiments show that the model has very good accuracy.

MODPEX is widely used in industry and universities to produce Pspice model for power semiconductor devices, including MOSFETs. However, the model generated by MODPEX for MOSFETs does not include channel charge at strong inversion condition. This paper presents a modified MODPEX model for MOSFETs, which includes channel charge at strong inversion condition. A process based on genetic algorithm (GA) implemented in Microsoft Office Excel is developed to optimize parameters of the modified MODPEX model. Static and dynamic validation proves that the modified MODPEX model improves simulation accuracy in both switching loss and driver loss.

This paper presents a method to optimize gate resistance of low side MOSFET in terms of damping phase node ringing for high efficiency synchronous buck converter. This method analyzes damping effect of low side gate resistance in the network of parasitic capacitances of MOSFET die and parasitic inductances of MOSFET package. Optimization equations for low side gate resistance are derived based on parasitic inductances and capacitances. Experiment proves the validity of this optimization design for low side gate resistance.

This paper describes a current sharing technique for digitally controlled multiphase buck DC-DC converters. The effective duty cycle mismatches and resistance mismatches are digitally compensated to achieve equal current sharing without sensing currents. Effects of various non-idealities on the current sharing performance are discussed. Experimental results are shown for a four-phase synchronous buck converter with 9V input voltage, and 1.5 V, 0–1.5A output.

In order to extract more abundant information carried by the explosion seismic signals in seismic exploration, the mathematical method of multi-fractal analysis was proposed. The relevant parameter diagrams of seismic signals were obtained through theoretical derivation and calculation by programming in MATLAB software. Then the partial singularity characteristic of the explosion seismic signals was analyzed. The results show that: The single fractal box dimension can't reflect essence of the explosion seismic signal; Multi-fractal can describe the partial feature of explosion seismic signals in more detail. The singularity characteristic and the distribution of explosion seismic signals can be depicted accurately. The data extracted by multi-fractal could provide analysis and forecasting for seismic exploration.

This paper researched the propagation laws of blasting seismic wave under the action of damping ditch, with the help of blasting vibration test and wavelet transform method. Blasting seismic wave is short-time non-stationary random signal. According to the time-frequency characteristics and the multi-resolution decomposition of discrete wavelet transform, the time history signal of blasting vibration was expressed by different leave reconstruction signals. The results show that, using wavelet transform method can reflect the time-frequency domain properties better than the classical method in the analysis of blasting vibration; the damping ditch has different effects in different frequency components of the vibration signal. It provided the principles of weaken vibration and lower frequency.

A novel SiC junction field effect transistor (JFET) model is proposed that uses a unified description of linear and saturated conduction modes. Advantages of the proposed model are improved robustness and convergence, inclusion of fielddependent mobility effects, and more physical description of the current saturation phenomenon. The model is validated against a normally-off JFET sample over a wide temperature range. Finite element simulation are used to demonstrate the physicsbased nature of the proposed model.

A practical parameter extraction procedure for power junction field effect transistor (JFET) is presented. The carrier mobility and carrier concentrations are very important parameters, strongly affecting the current capability and dynamic characteristics of the device for a given design. When modeling JFETs, values of these parameters usually are based on assumptions and given by a vendor in a range. As a result, model accuracy is compromised. In this paper, a step-by-step parameter extraction procedure is described that includes extraction of the mobility and the carrier concentration in the channel and drift regions based on knowledge of the device geometrical parameters. For the first time, carrier mobility in channel and drift regions of power JFET are extracted individually. It is found that channel and drift region mobilities can be very different for a given device, since they are strongly fabrication-process dependent. The developed procedure includes extraction of parameters for proposed empirical temperature dependencies of mobilities in the channel and drift regions. A simple static I-V characterization and C-V measurements are the only measurements required for the parameter extraction.

In this work a physical model for a SiC Junction Field Effect Transistor (JFET) is presented. The novel feature of the model is that the mobility dependence on both temperature and electric field is taken into account. This is particularly important for high-current power devices, where the maximum conduction current is limited by drift velocity saturation in the channel. The model equations are described in detail, emphasizing the differences introduced by the field-dependent mobility model. The model is then implemented in Pspice. Both static and dynamic simulation results are given. The results are validated with experimental results under static conditions and under resistive switching conditions.

This paper worked on decomposing the decision-making problem structure and the group structure by the method of work breakdown structure, in complex large group, analyzed the linear tree-like hierarchical structure of decision-making group structured decomposition and decision-making problem structured decomposition, then analyzed the synthesis of decision-making problempsilas results, integrated humanpsilas qualitative analysis ability and computerpsilas quantitative data processing ability. A framework was proposed that can be suitable for software implementation requirement, and can realize the human-computer combination of decision-making problems decomposition, decision-making groups decomposition, synthesis of results, parallel solution and level-driven. Based on this research, the complex large group decision support system (CLGDSS) is designed.

A compact trench-gate insulated-gate bipolar transistor model that captures MOS-side carrier injection is developed. The model retains the simplicity of a 1-D solution to the ambipolar diffusion equation, but at the same time, captures the MOS-side carrier injection and its effects on steady-state carrier distribution in the drift region and on switching waveforms.

Swept volume has been applied to many applications areas such as NC machining simulation and verification, robot workspace analysis, collision detection, and CAD. The numerical computation of swept volume remains to be a very challenging problem in terms of simplicity, efficiency and accuracy. The paper presents a novel swept volume approximation method for revolution generator solids sweeping along curved trajectories. This algorithms consists of the following main steps: (1) Discretization of the trajectory curve and establishments of reference frames; (2) Extraction and approximation of envelop profile at each discretized position based on the velocity vector calculated; and (3) Generation of envelop surfaces from the extracted envelop profile curves, and attachment of the ingress and egress surfaces to the envelop surface to form the SV Solid. Examples show that our algorithm is simple, efficient and accurate.