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Dong Han,Huanyu Guang,Zheng Yang,XingCai Lu,Zhen Huang 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.8
The effects of fuel/air equivalence ratio and CO2 concentration in fuel/air charge on the ignition process of gasoline and diesel-like fuel (n-heptane) blends on a rapid compression machine are investigated in this study. Results showed that the effects of equivalence ratio on ignition delays of two ignition stages are varied. As equivalence ratio increases from 0.3 to 0.5, the first stage ignition delay slightly increases because the increased equivalence ratio improves the mixture heat capacity, reducing the in-cylinder temperature and weakening the low-temperature heat release process of the fuel. The second stage ignition delay is shortened with the increased equivalence ratio because increased fuel concentration facilitates mixture reactivity. CO2 addition to the cylinder charge can effectively reduce the peak cylinder pressure and the two stage pressure rise rates, as well as extend the durations of ignition delays of two ignition stages.
Dong Han,Yoshiho Yamada,Shinichi Yokota,Joon-wan Kim 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.5
Previously, we described a single layer fabrication combining thick photoresist (KMPR) micromolding and electroformingto fabricate ECF micropumps with triangular prism and slit electrode pairs (TPSEs). However, the fabricated TPSEs have aheight limitation due to the limitation of KMPR’s aspect ratio caused by serious swelling and deformation of KMPR micromolds. To solve this problem and realize high-aspect-ratio TPSEs, we propose to utilize the multilayer fabrication instead ofthe single layer one. After each prior micromolding layer fabrication, the precision surface grinding technique is introducedto achieve the excellent planarization of the KMPR micromolds and electroplated TPSEs between the fi rst layer and thesecond one. We apply this method to successfully fabricate the 3D-integration ECF micropump (3D-EMP) with TPSEs of880 μm in height. Also, we validate this method by experimentally investigating and comparing the output performance ofECF micropumps composed of double layer TPSEs and previous single layer ones. The novel MEMS fabrication methodcombining multilayer micromolding and electroforming with the planarization is promising and applicable to a broad rangeof high-aspect-ratio metallic microstructures.
Dong Han,Tadahiko Shinshi,Makoto Kine 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.1
The challenges of developing a micro electromagnetic power generator are to increase the flux density from the thin permanent magnet and reduce the resistance of the micro high-winding-density coil. To overcome these challenges, we propose a novel MEMS power generator for low-frequency-vibration energy harvesting employing a 16-poles thin magnet plate and a high-aspect-ratio spiral micro array coil. Transient magnetic analysis has proved that the multi-pole magnet thin plate (8.9 × 8.9 × t0.5 mm) magnetized by laser assisted heating helps increase the output power from the generator compared with the unidirectional one. The high-aspect-ratio spiral micro array coil (width: 80 μm, thickness: 160 μm, total turns: 144) fabricated by the combination of multilayer SU-8 micro moldings, copper plating, and silver paste screen printing is beneficial for increasing coil density and reducing resistance, thus improving output power. The vibration experiment showed that in terms of no consideration of spring and guideway structure, when the magnet is directly vibrated by an actuator, the induced voltage, generated power, and power density were 1.63 mV, 0.12 μW and 1.03 μW/cm 3, respectively at an excitation frequency of 10 Hz with an amplitude of 2 mm. When a 3D-printed cantilever beam was adopted as the spring and guideway structure for the resonant prototype, the counterparts were 8.48 mV, 3.34 μW and 5.22 μW/cm 3, respectively at 38 Hz and 2 mm excitation (corresponding to a vibration acceleration peak of 11.6 g).
A Low Power Analog to Digital Interface for Digitally Controlled DC-DC Converter
Dong Han,Liansoon Ng,Lam YH Yvonne 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
This paper presents a novel low power analog to digital interface (ADI) for digitally controlled DC-DC converter. The whole ADI has been implemented in commercial 0.18 ㎛ CMOS process design kit. Simulation results validate the design concept. The proposed ADI consumes 7.5 ㎂ current under 1 V supply voltage with 500 ㎑ sampling rate and 4-bit resolution. It is very suitable for digitally controlled pulse width modulation (PWM) mode DC-DC converter.
Assessing the Impact of Advanced Technologies on Utilization Improvement of Substations
Dong Han,Zheng Yan,Dao-Tian Zhang,Yi-Qun Song 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.5
The smart substation is the heart of a transmission system, which is particularly emphasized as the most significant composition of smart grids in China. In order to assess the functionality performance of substation technologies, this paper presents methods used to identify the most promising solutions for smart substation design and to evaluate the technical levels of available technologies. The multi-index optimization model is presented to address the issue of smart substation planning. A mathematical model of the planning decision problem is established with multiple objectives consisting of economic, reliability, and green key indices, and many kinds of concerns including physical and environmentally friendly operations are formulated as a set of constraints. With respect to the assessment of the technical level regarding integration of advanced technologies into a substation, a modified grey whitenization weight function is adopted to structure a novel grey clustering method. The proposed grey clustering approach is used to overcome the difficulty of insufficient quantitative assessment capacity for traditional methods. The evaluation of technical effects provides the classification definition for the development phase and the maturity level of the smart substation. The effectiveness of the proposed approaches in planning decision-making and evaluation of construction efforts is demonstrated with case studies involving the actual smart substation projects of Wenchongkou substation in China Southern Power Grid (CSG) and Mengzi substation in State Grid Corporation of China (SGCC).
( Donghan Kim ),( Jeong Gwan Cho ),( Ki Hong Lee ),( Min Goo Lee ),( Keun Ho Park ),( Doo Sun Sim ),( Nam Sik Yoon ),( Hyun Ju Yoon ),( Kye Hun Kim ),( Young Joon Hong ),( Ju Han Kim ),( Youngkeun Ahn 대한내과학회 2011 대한내과학회 추계학술대회 Vol.2011 No.1
Background and study objective: The anterior ischemic pattern such as negative T wave is most frequent Electrocardiographic (ECG) sign of pulmonary thromboembolism (PTE) or anterior wall acute myocardial infarction (AMI). The aim of the present study was to evaluate the distinguishable findings between AMI and PTE in patients with negative T wave in anterior lead. Subject and methods: We analyzed 12-lead ECG, echocardiography and laboratory finding of 151 patients (PTE group; n=51, AMI group; n=100) with the diagnosis of PTE and AMI confirmed by computed tomography or coronary angiography, at Chonnam National University Hospital, between July 2008 and July 2011. The ECG analysis included S1Q3T3 complex(negative S waves in lead I and negative Q or T waves in lead III), sinus tachycardia(>100 beats/min), right bundle branch block (RBBB), low QRS voltage in peripheral leads and pulmonary P wave in lead II. Echocardiographic findings was included both ventricular systolic function and right ventricular systolic pressure (RVSP). We compared the ECG, echocardiography and biomarkers to distinguish from PTE and AMI. Results: S1Q3T3 was the most frequent ECG finding (42%), and was more common in PTE than AMI (42% vs. 8.1%, p<0.001). Also sinus tachycardia (36% vs. 6.1%, p<0.001), low QRS in peripheral leads (24% vs. 8.1%, p=0.011), pulmonary P wave in lead II (10% vs. 1%, p=0.016) was more common in AMI than PTE. In echocardiography, RVSP (56 mmHg vs. 29.85 mmHg, p<0.001) and systolic function (65.64% vs. 56.41%, p<0.001) were significantly higher in PTE than AMI. In laboratory findings, D-dimer (0.7851 vs. 0.2112, p<0.001) was significantly higher and Troponin-I was significantly lower (0.4814 vs. 5.7928, p<0.001) in PTE than AMI. Conclusion: The S1Q3T3 in ECG, elevated RVSP in echocardiography, and D-dimer in laboratory findings were useful to distinguish AMI from PTE in patients with negative T wave in anterior lead.