MTJ based MRAM Core Cell

Wanjun Park 한국자기학회 2002 Journal of Magnetics Vol.7 No.3

MRAM (Magnetoresistive Random Access Memory) is a promising candidate for a universal memory that meets all application needs with non-volatile, fast operational speed, and low power consumption. The simplest architecture of MRAM cell is a series of MTJ (Magnetic Tunnel Junction) as a data storage part and MOS transistor as a data selection part. This paper is for testing the actual electrical parameters to adopt MRAM technology in the semiconductor based memory device. The discussed topics are an actual integration of MRAM core cell and its properties such as electrical tuning of MOS/MTJ for data sensing and control of magnetic switching for data writing. It will be also tested that limits of the MRAM technology for a high density memory.

Influence of Processing on Morphology, Electrical Conductivity and Flexural Properties of Exfoliated Graphite Nanoplatelets-Polyamide Nanocomposites

Wanjun Liu,In-Hwan Do,Hiroyuki Fukushima,Lawrence T. Drzal 한국탄소학회 2010 Carbon Letters Vol.11 No.4

Graphene is one of the most promising materials for many applications. It can be used in a variety of applications not only as a reinforcement material for polymer to obtain a combination of desirable mechanical, electrical, thermal, and barrier properties in the resulting nanocomposite but also as a component in energy storage, fuel cells, solar cells, sensors, and batteries. Recent research at Michigan State University has shown that it is possible to exfoliate natural graphite into graphite nanoplatelets composed entirely of stacks of graphene. The size of the platelets can be controlled from less than 10 nm in thickness and diameters of any size from sub-micron to 15 microns or greater. In this study we have investigated the influence of melt compounding processing on the physical properties of a polyamide 6 (PA6) nanocomposite reinforced with exfoliated graphite nanoplatelets (xGnP). The morphology, electrical conductivity, and mechanical properties of xGnP-PA6 nanocomposite were characterized with electrical microscopy, X-ray diffraction, AC impedance, and mechanical properties. It was found that counter rotation (CNR) twins crew processed xGnP/PA6 nanocomposite had similar mechanical properties with co-rotation (CoR) twin screw processed or with CoR conducted with a screw design modified for nanoparticles (MCoR). Microscopy showed that the CNR processed nanocomposite had better xGnP dispersion than the (CoR) twin screw processed and modified screw (MCoR) processed ones. It was also found that the CNR processed nanocomposite at a given xGnP content showed the lowest graphite X-ray diffraction peak at 26.5˚ indicating better xGnP dispersion in the nanocomposite. In addition, it was also found that the electrical conductivity of the CNR processed 12 wt.% xGnP-PA6 nanocomposite is more than ten times higher than the CoR and MCoR processed ones. These results indicate that better dispersion of an xGnP-PA6 nanocomposite is attainable in CNR twins crew processing than conventional CoR processing.

그린워싱 및 그린 구매의도: 그린 구전과 그린 위험 지각의 매개 역할

Wanjun Gu,임형록 사단법인 한국융합기술연구학회 2023 아시아태평양융합연구교류논문지 Vol.9 No.4

As environmental problems become more and more serious, customers are increasingly likely to buy eco-friendly goods. However, many businesses want to attract them to buy products by greenwashing. This research investigated the connection between greenwashing and green purchase intention by the mediating impacts of green word of mouth and green perceived risk. This study employs the questionnaire survey method to collect data from 556 participants who purchased energy-efficient appliances in China. Through the analysis, we obtained the following conclusions. First, greenwashing has a negative impact on green word of mouth. Second, greenwashing has a positive impact on green perceived risk. Third, greenwashing has a negatively impacts on green purchase intentions. Fourth, green word of mouth has a positive impact on green purchase intentions. Fifth, green perceived risk has a negatively impacts on green purchase intentions. This research find that it is essential to reduce all forms of misinformation and increase the reliability and credibility of green messages so that companies can increase their customers' green purchase intentions. In addition, by engaging in green marketing, businesses must prevent overpromising. Reducing greenwashing can improve green word of mouth and reduce green perceived risk, eventually, green purchase intentions. 환경 문제가 갈수록 심화되면서 친환경 상품 구매에 대한 소비자의 욕구와 가능성은 점차 증가하고 있다. 한편, 많은 기업은 제품의 판매하기 위해 그린워싱을 통해 소비자들을 끌어들이기를 희망한다. 본 연구에서는 그린 구전 및 그린 위험 지각의 매개 효과를 통해 그린워싱과 그린 구매의도의 상관관계를 연구하였다. 본 연구는 설문조사를 통해 중국 내에서 고효율 전기제품을 구매한 소비자 데이터 556개를 수집하였다. 분석을 통해 도출된 결론은 다음과 같다. 첫째, 그린워싱은 그린 구전에 부정적인 영향을 미친다. 둘째, 그린워싱은 그린 위험 지각에 긍정적인 영향을 미친다. 셋째, 그린워싱은 그린 구매의도에 부정적인 영향을 미친다. 넷째, 그린 구전은 그린 구매의도에 긍정적인 영향을 미친다. 다섯째, 그린 위험 지각은 그린 구매의도에 부정적인 영향을 미친다. 본 연구의 결과는 기업이 소비자의 그린 구매의도를 높이기 위해서는 모든 형태의 잘못된 정보를 줄이고 그린 메시지에 대한 신뢰도를 높이는 것이 필수적임을 증명했다. 또한, 그린 마케팅에 참여하는 기업들은 과도한 약속을 자제해야 한다. 이러한 방법을 통해 그린워싱을 감소시키면, 그린 구전을 개선하고 그린 위험 지각을 감소시킬 수 있으며, 이는 결국 그린 구매의도를 감소하게 만들 것이다.

A Fast-Transient Repetitive Control Strategy for Programmable Harmonic Current Source

Wanjun Lei,Cheng Nie,Mingfeng Chen,Huajia Wang,Yue Wang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

The repetitive control (RC) strategy is widely used in AC power systems because of its high performance in tracking period signal and suppressing steady-state error. However, the dynamic response of RC is determined by the fundamental period delay T0 existing in the internal model. In the current study, a (nk ± i)-order harmonic RC structure is proposed to improve dynamic performance. The proposed structure has less data memory and can improve the tracking speed by n/2 times. T0 proves the effectiveness of the (nk ± i)-order RC strategy. The simulation and experiments of (6k ± 1)-order and (4k ± 1)-order RC strategy used in the voltage source inverter is conducted in this study to control the harmonic current source, which shows the validity and advantages of the proposed structure.

Technology of MRAM (Magneto-resistive Random Access Memory) Using MTJ(Magnetic Tunnel Junction) Cell

Wanjun Park,I-Hun Song,Sangjin Park,Teawan Kim 대한전자공학회 2002 Journal of semiconductor technology and science Vol.2 No.3

Integration of Carbon Nanotubes for the Electronic Device Applications

Wanjun Park 한국진공학회 2008 한국진공학회 학술발표회초록집 Vol.2008 No.2

Bidirectional Trapezoidal Versus Unidirectional Spiral Groove Performance in Dry Gas Seals

Wanjun Xu,Yongwei Tian,Ying Song,Yaoyao Xu 한국유체기계학회 2021 International journal of fluid machinery and syste Vol.14 No.3

The gas film characteristics of bidirectional dry gas seals with trapezoidal grooves were studied by comparing with the traditional spiral grooved gas seals. The two-dimensional compressible Reynolds equation was solved by finite difference method. The typical performance parameters including gas film force, leakage, gas film stiffness, and torque were compared under different parametrical conditions. The pattern of trapezoidal grooves wasted part of groove area in bidirectional operation; though the grooves were designed by overlapping trapezoids to make up for the performance loss, the resulting decrease in gas film stiffness was notable. The resisting disturbance ability of trapezoidal grooved seals was poorer than that of spiral grooved seals, while the load-carrying capacity, sealing ability, and power consumption of trapezoidal grooved seals differed slightly from those of spiral grooved seals. The trapezoidal grooved seals are not recommended in unidirectional rotational compressors due to the decreasing stability.

Preparation of γ-alumina nanoparticle modified polyacrylamide composite and study on its solid phase extraction of Sunset Yellow

Wanjun Li,Qiong Jia,Zhenyu Zhang,Yuanpeng Wang 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.4

An organic-inorganic composite, γ-alumina nanoparticle modified polyacrylamide, was synthesized in this study. The composite was characterized by scanning electron microscope, nitrogen adsorption-desorption measurement, thermal gravimetric analyzer, differential scanning calorimetry, and Fourier-transformed infrared spectrometer. A novel solid-phase extraction method with the synthesized composite as the adsorbent was developed for the enrichment of Sunset Yellow coupled with ultraviolet-visible spectrophotometry. To obtain the optimum extraction efficiency, the experimental parameters in the processes of preparation of the adsorbent and solid-phase extraction were studied including synthesis temperature, synthesis time, the dosage of γ-alumina nanoparticles, sample flow rate, sample pH, eluant concentration, and eluant flow rate. Under the optimum conditions, the detection limit of the developed method was calculated to be 0.037 μg mL−1 with intra-day and inter-day relative standard deviation values of 2.57% and 3.89%, respectively. When the method was applied to the determination of Sunset Yellow in beverages, satisfactory recoveries were obtained in the range of 92.3-109.8%.

Explicit solution of gas film pressure for performance calculation of spiral grooved gas seals

Wanjun Xu,Jian Gang Yang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

The study presents an explicit solution to a narrow groove theory for compressible spiral grooved gas seals. The explicit solution was derived from Muijderman’s narrow groove theory by employing Cauchy’s integral theorem. It expresses the gas film pressure as a function of gas film radius. Using this process, the initial value problem of Muijderman’s equations is avoided, and the gas film pressure can be obtained directly in contrast to the traditional Runge-Kutta method. A complete analytical procedure of the explicit solution is presented. The accuracy of the explicit solution was validated using published results.

Technology of MRAM (Magneto-resistive Random Access Memory) Using MTJ(Magnetic Tunnel Junction) Cell

Park, Wanjun,Song, I-Hun,Park, Sangjin,Kim, Teawan The Institute of Electronics and Information Engin 2002 Journal of semiconductor technology and science Vol.2 No.3

DRAM, SRAM, and FLASH memory are three major memory devices currently used in most electronic applications. But, they have very distinct attributes, therefore, each memory could be used only for limited applications. MRAM (Magneto-resistive Random Access Memory) is a promising candidate for a universal memory that meets all application needs with non-volatile, fast operational speed, and low power consumption. The simplest architecture of MRAM cell is a series of MTJ (Magnetic Tunnel Junction) as a data storage part and MOS transistor as a data selection part. To be a commercially competitive memory device, scalability is an important factor as well. This paper is testing the actual electrical parameters and the scaling factors to limit MRAM technology in the semiconductor based memory device by an actual integration of MRAM core cell. Electrical tuning of MOS/MTJ, and control of resistance are important factors for data sensing, and control of magnetic switching for data writing.