• Journal of the Optical Society of Korea
• /
• 제18권5호
• /
• pp.531-537
• /
• 2014

Through-silicon vias (TSVs) are fine, deep holes fabricated for connecting vertically stacked wafers during three-dimensional packaging of semiconductors. Measurement of the TSV geometry is very important because TSVs that are not manufactured as designed can cause many problems, and measuring the critical dimension (CD) of TSVs becomes more and more important, along with depth measurement. Applying white-light scanning interferometry to TSV measurement, especially the bottom CD measurement, is difficult due to the attenuation of light around the edge of the bottom of the hole when using a low numerical aperture. In this paper we propose and demonstrate four bottom CD measurement methods for TSVs: the cross section method, profile analysis method, tomographic image analysis method, and the two-dimensional Gaussian fitting method. To verify and demonstrate these methods, a practical TSV sample with a high aspect ratio of 11.2 is prepared and tested. The results from the proposed measurement methods using white-light scanning interferometry are compared to results from scanning electron microscope (SEM) measurements. The accuracy is highest for the cross section method, with an error of 3.5%, while a relative repeatability of 3.2% is achieved by the two-dimensional Gaussian fitting method.

• Korean Journal of Optics and Photonics
• /
• 제32권4호
• /
• pp.172-179
• /
• 2021

A near-normal-incidence ellipsometer (NNIE) is suggested as an optical critical dimension (OCD) measurement system that is highly sensitive to the bottom defect of a sample with high-aspect-ratio structured patterns. Incident light passes through a polarizer and a phase retarder in sequence, and the reflected light from the sample also passes through them, but in reverse order. The operating principle of this NNIE, where a single polarizer and a single phase retarder are shared by the incident and reflected light, is studied, and a method to determine the ellipsometric constants from the measured intensities at proper combinations of the azimuthal angles of polarizer and retarder is presented.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• 제33권2호
• /
• pp.61-70
• /
• 2023

This paper examines the way of thinking and limitations of physicists regarding the phenomenon of superconductivity and outlines how room-temperature and ambient-pressure superconductors can be developed through the statistical thermodynamic background of the liquid state theory. In hypothesis, the number of electron states should be limited by confining them to a state close to one-Dimension. Simultaneously, the electron-electron interactions should be frequent enough for the electrons to have liquid-like properties. As an example of implementing the hypothesis, our team reports the development of room-temperature and ambient-pressure superconductivity of a material named LK-99 (superconducting compound name developed in the research), whose structure was revealed through numerous experiments with a clue found by chance. Moreover, we summarize the theoretical and experimental basis for the characteristics and discovery of the world's first superconducting material surpassing the critical temperature of 97℃ at atmospheric pressure.

• Proceedings of the KIEE Conference
• /
• 대한전기학회 2009년도 제40회 하계학술대회
• /
• pp.1491_1492
• /
• 2009

The impedance of a vertical grounding electrode is not lowered by expanding the dimension of the grounding electrode, and the length of thr vertical grounding electrode which shows the minimum value of the grounding impedance for each condition of frequency and soil characteristics is existent, and it is defined as Critical length. In this paper, the critical lengths for the vertical grounding electrodes are calculated by using the distributed parameter circuit model. The adequacy of the simulations has been confirmed by comparing the simulated results with the measured results.

• Bulletin of the Korean Mathematical Society
• /
• 제53권4호
• /
• pp.1087-1094
• /
• 2016

On a compact n-dimensional manifold M, it has been conjectured that a critical point of the total scalar curvature, restricted to the space of metrics with constant scalar curvature of unit volume, is Einstein. In this paper, after derivng an interesting curvature identity, we show that the conjecture is true in dimension three and four when g is weakly Einstein. In higher dimensional case $n{\geq}5$, we also show that the conjecture is true under an additional Ricci curvature bound. Moreover, we prove that the manifold is isometric to a standard n-sphere when it is n-dimensional weakly Einstein and the kernel of the linearized scalar curvature operator is nontrivial.

• Progress in Superconductivity and Cryogenics
• /
• 제14권3호
• /
• pp.5-8
• /
• 2012

Superconducting windings of synchronous machine have to be operated in below the critical temperature, critical current density and critical magnetic field. If one of these characteristics does not satisfied, then the quench occurred in superconducting winding. Especially the armature current dramatically increased as the superconducting generator is short-circuited at the rated load condition and magnetic field in field winding increased due to the armature current. Therefore, damper is required to reduce the magnetic field of field winding which increases reliability of the superconducting generator. Damper dimension can be decided by time constant[1-2]. In this paper the basic model is high-power and low-speed superconducting generator. Damper time constant was calculated from the changed damper thickness and material. Magnetic flux of field coil at the basic model and changed damper time constant model is analyzed.

• Korean Journal of Human Ecology
• /
• 제20권6호
• /
• pp.1185-1198
• /
• 2011

This research explores the consumers' experience in retailing channel(offline channel and online channel) using the critical incident technique. This research aims to clarify the common incidents within retailing channels which implies decisive factors over the channels, and to clarify the contrasts between channels to compare advantages and disadvantages. Therefore, the research is designed to collect the consumers' narrative of those who have used both channels in 3 months. Classifications are conducted with other researchers majoring consumer science. The results address how impressive experiences are constructed on each channel in three dimensions: product, information search, and the purchase-service dimension. These results are able to provide implications for offline and online retailers and directions for future research.

• Transactions of the Korean Society of Automotive Engineers
• /
• 제9권3호
• /
• pp.131-142
• /
• 2001

A wrinkling is the instability phenomenon influenced by material properties, shape geometry, forming conditions, stress state, etc. The wrinkling is considered as a critical defect in appearance of product. Many wrinkling prediction methods using thickness strain distribution and farming analysis have been proposed. The wrinkling, however, is not easily predicted precisely by these methods. In this study, the region in the biaxial plane stress state is modeled with a rectangular plate introducing the effective dimension, and critical stress values for the wrinkling are calculated. Prediction index for the wrinkling is then evaluated by normalizing the actual stress with respect to the critical stress. In order to show the validity and efficiency of the method proposed, the wrinkling prediction for a squared sheet in the uniaxial tensile stress and auto-body front finder panel is performed.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제9권3호
• /
• pp.315-325
• /
• 2017

The design dimension may not be satisfactory at the final stage due to the welding during the assembly stage, leading to cutting or adding the components in large structure constructions. The productivity is depend on accuracy of the welding quality especially at assembly stage. Therefore, it is of utmost importance to decide the component dimension during each assembly stage considering the above situations during the designing stage by exactly predicting welding deformation before the welding is done. Further, if the system that predicts whether welding deformation is equipped, it is possible to take measures to reduce deformation through FE analysis, helping in saving time for correcting work by arresting the parts which are prone to having welding deformation. For the FE analysis to predict the deformation of a large steel structure, calculation time, modeling, constraints in each assembly stage and critical welding length have to be considered. In case of fillet welding deformation, around 300 mm is sufficient as a critical welding length of the specimen as proposed by the existing researches. However, the critical length in case of butt welding is around 1000 mm, which is far longer than that suggested in the existing researches. For the external constraint, which occurs as the geometry of structure is changed according to the assembly stage, constraint factor is drawn from the elastic FE analysis and test results, and the magnitude of equivalent force according to constraint is decided. The comparison study for the elastic FE analysis result and measurement for the large steel structure based on the above results reveals that the analysis results are in the range of 80-118% against measurement values, both matching each other well. Further, the deformation of fillet welding in the main plate among the total block occupies 66-89%, making welding deformation in the main plate far larger than the welding deformation in the longitudinal and transverse girders.

• International Journal of Computer Science & Network Security
• /
• 제22권11호
• /
• pp.331-337
• /
• 2022

Smart learning is augmented with digital, context-aware, and adaptable technologies to encourage students to learn better and faster. To ensure that digital learning is successful and that implementation is efficient, it is critical that the dimensions of digital learning are arranged correctly and that interactions between the various elements are merged in an efficient and optimal manner. This paper builds and discusses a basic framework for smart learning in the digital age, aimed to improve students' abilities and performance in learning. The proposed framework consists of five dimensions: Teacher, Technology, Learner, Digital content, and Evaluation. The Teacher and Learner dimensions operate on two levels: (a) an abstract level to fit in knowledge and skills or interpersonal characteristics and (b) a concrete level in the form of digital devices used by teachers and learners. Moreover, this paper proposes asynchronous online course delivery model. An Arabic smart learning platform has been developed, based on these smart learning core dimensions and the asynchronous online course delivery model, because despite the official status of this language in many countries, there is a lack of Arabic platforms to teach Arabic. Moreover, many non-native Arabic speakers around the world have expressed an interest in learning it. The Arabic digital platform consists of over 70 lessons classified into three competence levels: beginner, intermediate, and advanced, delivered by Arabic experts and Arabic linguists from various Arab countries. The five dimensions are described for the Arabic platform in this paper. Learner dimension is the Arabic and non-Arabic speakers, Teacher dimension is Arabic experts and Arabic linguistics, Technology dimension consists of technology for Arabic platform that includes web design, cloud computing, big data, etc. The digital contents dimension consists of web-based video, records, etc. The evaluation dimension consists of Teachers rating, comments, and surveys.