• Journal of the Korean Mathematical Society
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• v.55 no.2
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• pp.391-413
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• 2018

In this paper we introduce a new tensor named semi-projective curvature tensor which generalizes the projective curvature tensor. First we deduce some basic geometric properties of semi-projective curvature tensor. Then we study pseudo semi-projective symmetric manifolds $(PSPS)_n$ which recover some known results of Chaki [5]. We provide several interesting results. Among others we prove that in a $(PSPS)_n$ if the associated vector field ${\rho}$ is a unit parallel vector field, then either the manifold reduces to a pseudosymmetric manifold or pseudo projective symmetric manifold. Moreover we deal with semi-projectively flat perfect fluid and dust fluid spacetimes respectively. As a consequence we obtain some important theorems. Next we consider the decomposability of $(PSPS)_n$. Finally, we construct a non-trivial Lorentzian metric of $(PSPS)_4$.

• International Journal of Automotive Technology
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• v.7 no.6
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• pp.757-762
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• 2006

Reliability of automotive parts has been one of the most interesting fields in the automotive industry. Especially, a small DC motor was issued because of the increasing adoption for passengers' safety and convenience. For several years, small DC motors have been studied and some problems of a life test method were found out. The field condition was not considered enough in the old life test method. It also needed a lot of test time. For precise life estimation and accelerated life test, new life test procedure was developed based on measured field condition. The vibration condition on vehicle and latent force on fan motor shaft were measured and correlated with each other. We converted the acceleration data into the load data and calculated the equivalent load from integrated value. We found the relationship which can be used for accelerated life test without changing the severity by using different loading factors.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.12-15
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• 1987

The study on Electrostatics represents the first scientific interest of human being on electrical phenomena, and it led to enormous progress of electrical and electronic science and engineering up to the current levels. Electrostatics, however, has been long forgotten in the stream of this history as a tribial minor field. Interesting enough, this minor sector has regained recently its new life, in particular in the area of high-technologies, and Electrostatics is going to become one of the most important field in the future of electrical and electronics engineerings. It is impossible to cover the entire trend of this emerging field in a limited space, so that spot lights shall be focused on several important topics in this paper.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.987-995
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• 1996

The time components of the operations were investigated on the rice paddy field operations by radio controlled helicopter. The net time of operations, seeding and application, were less than a quarter of the required total time in the field of 1 ha. The most interesting is how to decrease the time of hop-off and landing. In this paper the seeding density itself is taken under a new look and its describing method is discussed. Voronoi diagram was introduced to consider individual plant of rice paddy. Extremely wide ranges of the distribution of seeding density are not supposed by the common indexes based on the concept of mean values and discussed on the aggregate of plants.

• Journal of applied mathematics & informatics
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• v.2 no.1
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• pp.3-10
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• 1995

Nonlinear hyperbolic differenctial equations have been a subject of intense research in the field of gas dynamics due to many engineering problems associated with high-speed airplanes missiles materials processing etc. Recently phenomena known from gas dy-namics are found to occur also in the microeletronic devices such as MOSFET. Here a few interesting mathematical problems are presented along with future areas of research.

• Broadcasting and Media Magazine
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• v.5 no.1
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• pp.59-71
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• 2000

This paper presents a survey of the CMOs-based image sensor and its applications to various real field digital camera. CMOS image sensor, called active pixel sensor (APS), has many interesting properties such ash I회 sensitivity, high speed readout, random access and lower power consumption when it is compared with CCd. this paper also addresses the state-of-the-art of CMOS image sensor, and gives some examples of its application to digital camera and special-purpose cameras. with the advancement of semiconductor technology, CMOS image sensor is a future technology for imaging system, and will be widely used in the filed of image capturing for consumer electronics and scientific measurements.

• Proceedings of the Optical Society of Korea Conference
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• 1991.07a
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• pp.5-8
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• 1991

New nonliner organic materials have been developed for all-optical signal processing. The organic materials possess many interesting features for this purpose. Unlike inorganic molecules the delocalized $\pi$-electron distribution and intramolecular charge transfer mevhanism allows certain organic molecules to respond highly anharmonically to an external field. In the present paper the origins of nonlinear phenomena, advantages of orgnic materials and structures of organic devices will be discussed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.201-205
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• 1999

An analytical study on the stability of steel plates in the presence of magnetic fields is carried out based on a model which accounts for the nonlinear field-structure interaction. The resultant force system arising from the interaction between the magnetic fields and ferromagnetic plates is derived using the variational principle. The bending and buckling problems of steel plates in oblique magnetic fields are investigated with the aid of the finite element method. Numerical results reveal some interesting features of the magnetoelastic buckling phenomenon.

• Proceedings of the Korean Biophysical Society Conference
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• 2002.06b
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• pp.25-26
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• 2002

The goal of radiation therapy is to maximize the tumor dose and to minimize the dose of normal tissue. In order to achieve this goal, the new radiation therapy techniques such as three dimensional conformal therapy or intensity modulated radiation therapy has been developed and tried to clinical application. The relationship between radiation dose and normal tissue response is an interesting subject in the radiation therapy field.(omitted)

• Kyungpook Mathematical Journal
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• v.56 no.1
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• pp.173-184
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• 2016

Mock theta functions are the most interesting topic mentioned in Ramanujan's Lost Notebook, due to its emerging application in the field of Number theory, Quantum invariants theory and etc. In the present research articles we have made an attempt to develop continued fractions representation of all the existing Mock theta functions.