A practical approach to EMC education at the undergraduate level

In view of the importance of electromagnetic compatibility (EMC), universities worldwide are paying more attention to training electronic engineers with good EMC design knowledge. As part of the EMC training, a practical printed circuit board (PCB) layout project has been offered as an elective to the undergraduates in the authors' universities. The project requires the students to design the PCB layout of a standard digital circuit twice, the first time with no EMC consideration at all, and the second time with careful EMC consideration. The significant difference in the levels of radiated emissions of the two layouts allows the students to appreciate the importance of EMC design at an early stage of product development.     

Influence of the characteristics of a water-in-CO2 microemulsion on the separation of metal species

In this study, AOT [sodium bis(2-ethylhexyl) sulfosuccinate] combined with fluorinated cosurfactant or alcohol was used to form a water-in-CO₂ (W/C) microemulsion. The amount of water uptake in the microemulsion was closely related to the PFPE-PO₄/AOT (P/A) ratio. The stability of the microemulsion decreased with the amount of water. Lower temperature and higher pressure stabilize W/C microemulsions. The extraction efficiencies of metals (Cd, Co, Cu, Pb, Zn), when this W/C microemulsion method was used, exceeded 90% (AOT + octanol). The efficiencies for the extraction of Eu, La, and Sr could exceed 94% (AOT + PFPE-PO₄) in sc-CO_2.     

直流脉宽调速系统中回馈能量的研究及泵升电路的设计

本文通过对直流脉宽调速系统制动时回馈能量产生机理的分析，推导了泵升电压与脉宽调制放大器主回路各参数之间的函数关系。在此基础上，提出了泵升电路的设计准则。     

Reliability by Robust Design for optical alignment in a CD pickup

Micron-level alignment of optical components in the laser pickup of a compact disc (CD) system is critical for its performance. The robustness of the rotational alignment of the laser/diffraction grating unit (LDGU) is studied in detail using finite element analysis and Robust Design tools. Robust design simulations were constructed in terms of the process capability indices C_p, C_pk, and yield of the clamping arms used to hold the LDGU in place. Effects of force and torsional load from the actual process were taken into consideration during the simulations. Experimental measurement was used to verify the finite element analysis. The results from both experimental and theoretical analyzes were applied to concurrently modify the design of the clamping arms, reducing the fall-off rate in the production of the laser pickup by 10%. It is demonstrated that the finite element analysis together with the Robust Design approach form a very powerful tool for the designer to achieve the required reliability targets for the product     

Knowledge through participation: the triumphs and challenges of transferring Integrated Pest and Disease Management (IPDM) technology to cocoa farmers in Papua New Guinea

Income from cocoa is the main source of cash used to purchase food and services in many communities in the tropical lowlands of Papua New Guinea (PNG). Despite the availability of improved management technology, there has been poor transfer and uptake of these technologies among smallholder cocoa farmers, and potentially high bean yields and farmer incomes remain unrealised. A series of IPDM options that were shown to improve crop management and cocoa bean yield in research trials were demonstrated to farmers using an on-farm participatory approach that enabled farmers to evaluate the costs and benefits of each strategy before committing to adoption. The options were designed to provide several levels of entry to improved management, and ranged from no inputs (Option 1), manual inputs (Option 2: pruning, sanitation, weed management and regular complete pod harvesting), high level inputs (Option 3: pruning, sanitation, weed management, regular complete pod harvesting and fertiliser application), to intensive management (Option 4: pruning, sanitation, weed management, regular complete pod harvesting, and the application of fertiliser, fungicide and pesticide). Farmers from East New Britain, Madang and Bougainville, the three main cocoa growing provinces in PNG, participated in on-farm IPDM training and surveys to monitor changes in knowledge and management practice. Farmers opted in or out of the training as their commitments or level of interest changed, and new farmers joined in after observing changes in the cocoa blocks. Farmers were trained in epidemiology and crop management, were shown how to apply the IPDM inputs in their own cocoa blocks, and were given a simple training manual. Surveys conducted prior to, and 3 years after the training, showed an improvement in the farmers’ knowledge of cocoa management and a better understanding of cocoa pest and disease epidemiology. Three years after the training, pest and disease incidence in participating cocoa blocks had declined and cocoa yields had increased by an average of 30%. Trained farmers were encouraged to demonstrate improved management to neighbouring farmers, and the program has now been officially adopted as the national strategy to improve cocoa production in PNG. The participatory approach is an effective way of disseminating information and technology to farmers, however, it requires frequent follow-up visits by trained extension staff. We also discuss the significant challenges associated with conducting farmer surveys.     

电机拖动系统中的传导性电磁干扰噪声的测试

针对电机拖动系统中日益严重的电磁兼容问题,提出了用于传导性电磁干扰噪声诊断的噪声分离网络和噪声智能处理软件平台,并对电机拖动系统中的传导噪声进行特征提取和模态分析,以便为噪声抑制及电磁兼容综合解决方案提供必要信息。此外,对开关磁阻电机构成的风机调速系统进行传导性电磁兼容测试,并对试验数据进行了对比和分析。     

电机拖动系统中的传导性电磁干扰噪声的测试

针对电机拖动系统中日益严重的电磁兼容问题，提出了用于传导性电磁干扰噪声诊断的噪声分离网络和噪声智能处理软件平台，并对电机拖动系统中的传导噪声进行特征提取和模态分析，以便为噪声抑制及电磁兼容综合解决方案提供必要信息。此外，对开关磁阻电机构成的风机调速系统进行传导性电磁兼容测试，并对试验数据进行了对比和分析。     

The Annealing Effects in the Iron-Based Superconductor FeTe0.8Se0.2 Prepared by the Self-Flux Method

FeTe_0.8Se_0.2 single crystals as-cast and post-annealed were prepared by the self-flux method. We have investigated the structural properties of samples by using the XRD, scanning electron microscope (SEM), energy dispersive X-ray (EDX), and magnetic techniques. The SEM results clearly demonstrate that Te ions are quite well substituted for Se ions in the FeSe lattice for the samples. From the XRD and EDX spectra of the both samples, it has been concluded that the post-annealing causes no change in the tetragonal structure of FeTe_0.8Se_0.2. According to M–H measurements, the perfect diamagnetism has been observed only in low field at 5 and 10 K temperatures. The trend of the magnetization versus temperature curves, measured under a magnetic field of 10 Oe, also support our conclusion about diamagnetic contribution in FeTe_0.8Se_0.2 single crystal explored in this study. The as-cast and post-annealed samples show the onset of diamagnetism at temperatures, \(T_{\mathrm {c.on}}^{\text {mag}}\) , 12.45 and 13.27 K, respectively. In addition, those curves indicate that the high field value and some impurities reveal ferromagnetic interactions.     

Degradation of Superconducting Properties in MgB2 by Formation of the MgB4 Phase

Superconducting MgB₂ polycrystalline samples have been fabricated under two different conditions in order to determine the effect of MgB₄ phase. A series of samples was placed in an α-alumina container closed with a cup and fired under high purity argon gas. The other series of samples was placed in an α-alumina boot without any lid and fired under similar conditions. For the first series of samples, we have found pure MgB₂ phase formation and a narrow transition width at 0.4 K. For the second series of samples, significant amount of MgB₄ phase were formed and the T _zero was decreased to 27 K. For both the group of samples magnetization hysteresis loops obtained at various temperature range and applied field up to 2 T. The best J _cmag for the first series of samples was 1.9 × 10⁵ A/cm² at 10 K and 0 T, and for the second series of samples was 0.7 × 10⁴ A/cm² at 10 K and 0 T.