• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.4-7
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• 2015

In this paper, we propose a matrix completion algorithm for Internet of Things (IoT) localization. The proposed algorithm recovers the Gram matrix of sensors by performing optimization over the Riemannian manifold of fixed-rank positive semidefinite matrices. We compute and show the closed forms of all the differentially geometric components required for applying nonlinear conjugate gradients combined with Armijo line search method. The numerical experiments show that the performance of the proposed algorithm in solving IoT localization is outstanding compared with the state-of-the-art matrix completion algorithms both in noise and noiseless scenarios.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.741-749
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• 1994

The planar solid oxide fuel cell(SOFC) contains several ceramic materials depending on its structure and has rdfractory metal parts for manifolds, shrouds and current leads. Among ceramic materials for planar SOFC, joining of lanthanum chromite separator and yttria stabilized zirconia(YSZ) electoyte in planar SOFC stack to give strong gas tight seals is necessary for satisfactory operation and high performance. Nevertheless, for planar SOFC/sub s/, how to seal the cell stack and gas manifold remains as one of the unsolved problems. Therefore, in this study. we investigated the joining of sintered lanthanum chromite and YSZ pellets using unsintered lanthanum chromite green films as sealent. Scanning electron microscopy(SEM) and energy dispersive X-ray analysis(EDX) revealed that Ca in the sealing material diffused and dissolved into YSZ and sintered lanthanum chromite, and unsintered lanthanum chromite green films reacted with YSZ to from a new phase at the interface. Also, the densification of unsintered lanthanum chromite green films was inpeded by the Ca migration.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.4
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• pp.223-228
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• 2005

Tube hydroforming provides a number of advantages over conventional stamping process, including fewer secondary operation, weight reduction, assembly simplification, adaptability to forming of complex structural components and improved structural strength and stiffness. It can produce wide range of products such as subframe, engine cradle, and exhaust manifold. In this study, the effect of the heat treatment conditions such as post seam annealing (PSA) and bright annealing (BA) on the ovality and hydro-formability of steel tubes has been investigated. Hydroformabilities have been estimated by the bulging heights obtained at various processing parameters such as internal pressure, axial feeding and heat treatment conditions. The ovality and forming height are strongly influenced by material properties after heat treatments.

• Bulletin of the Korean Mathematical Society
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• v.26 no.1
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• pp.1-9
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• 1989

In 1980 and 1983, it was proved that P $D^{2}$-groups are surface groups ([2], [3]). Since then, topologists have been positively studying about P $D^{n}$ -groups (or $D^{n}$ -groups). For example, let a topological space X have a right .pi.-action, where .pi. is a multiplicative group. If each x.memX has an open neighborhood U such that for each u.mem..pi., u.neq.1, U.cap. $U_{u}$ =.phi., this right .pi.-action is said to be proper. In this case, if X/.pi. is compact then (1) .pi.$_{1}$(X/.pi).iden..pi.(X:connected, .pi.$_{1}$: fundamental group) ([4]), (2) if X is a differentiable orientable manifold with demension n and .rho.X (the boundary of X)=.phi. then $H^{k}$ (X;Z).iden. $H_{n-k}$(X;Z), ([6]), where Z is the set of all integers.s.

• The Pure and Applied Mathematics
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• v.28 no.2
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• pp.143-153
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• 2021

In this paper, we study some curvature properties of Sasakian 3-manifolds associated to Ƶ-tensor. It is proved that if a Sasakian 3-manifold (M, g) satisfies one of the conditions (1) the Ƶ-tensor is of Codazzi type, (2) M is Ƶ-semisymmetric, (3) M satisfies Q(Ƶ, R) = 0, (4) M is projectively Ƶ-semisymmetric, (5) M is Ƶ-recurrent, then (M, g) is of constant curvature 1. Several consequences are drawn from these results.

• Journal of Korean Medical classics
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• v.37 no.2
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• pp.1-10
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• 2024

Objectives : The Wenyilun is the first specialized text on warm disease, written by Wuyouke from the Ming period in 1642. Methods : This paper examines the newly discovered manuscript of the Wenyilun called the Yeonreungjip, focusing on its bibliography and content. In addition, the original script of the Yeonreungjip was studied philologically. Results : 1. The Yeonreungjip was transcribed in the early 20th century. 2. The Jongbaegmuusan formula is a tried and tested prescription unique to Korea. 3. The original script of the Yeonreungjip is affiliated with the Chinese Liuchang edition. It is uncertain when this edition was introduced to Korea. 4. The contents of the Yeonreungjip referenced the Siququanshu edition series. Conclusions : In conclusion, the Yeonreungjip is the only transcribed version of the specialized Chinese warm disease text from the Joseon period that is known today. Its implication in the research of warm disease introduction to Korea is manifold.

• Journal of applied mathematics & informatics
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• v.42 no.4
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• pp.879-897
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• 2024

The emergence of generalized square metrics in Finsler geometry can be attributed to various classification concerning (𝛼, 𝛽)-metrics. They have excellent geometric properties in Finsler geometry. Within the scope of this research paper, we have conducted an investigation into the generalized square metric denoted as $F(x,y)=\frac{[{\alpha}(x,y)+{\beta}(x,y)]^{n+1}}{[{\alpha}(x,y)]^n}$, focusing specifically on its application to the Finslerian hypersurface. Furthermore, the classification and existence of first, second, and third kind of hyperplanes of the Finsler manifold has been established.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.1
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• pp.57-67
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• 1989

Acoustic intensity method is applied to a 4-cylinder gasoline engine in order to identify the noise sources and the response characteristics. Acoustic intensity is analyzed by 1/3 octave band filter for each center frequency. Radiational characteristics of acoustic intensity at overall and the maximum intensity level are represented by using the contour and three-dimensional plot. It is verified that this method is effective to the assessment of engine noise. It can be found that the maximum intensity is radiated from the front side of the engine under idling condition and the right side of it under 2, 000 rpm running with no loading condition at overall level, and also that the maximum intensity is radiated from the oil pan and the intake and exhaust manifold at the center frequency of 100 Hz.

• Solar Energy
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• v.9 no.3
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• pp.37-43
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• 1989

This paper dealt with thermal storage efficiency due to difference ($T_{\infty}-Ti$) between the mean temperature of water in the storage tank [$0.5m{\times}0.5m{\times}1.0m$] and the temperature of water flowing into the tank, flow rate of water flowing into the tank and shape of porous manifold which water flow into the tank through. As results of experiments; (1) When the flow rate was constant and the diameter of porous section decreased by 8mm, 6mm, and 4mm, the thermal storage efficiency increased. (2) When the diameter of porous section was constant and the difference ($T_{\infty}-Ti$) between the mean temperature of water in the storage tank and the temperature of water flowing into the tank increased by -30, -20, -10, 5, 10, 15 ($^{\circ}C$), the thermal storage efficiency increased. (3) When the($T_{\infty}-Ti$) was constant and the flow rate decreased by 0.8, 0.4, 0.25(LPM), the thermal storage efficiency increased. (4) When the shape of porous section was rigid, the thermal storage efficiency was the most effective, and with establishing flexible porous section or mesh, the effective thermal storage efficiency was obtained.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.6
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• pp.1260-1271
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• 2001

The simulation program which predicts the gas behavior in a spark ignition engine has been developed and verified by the comparison with the experimental results foy the MPI engine, naturally aspirated and turbochared engines with a carburettor. First paper describes the calculations of the behavior of gas in the intake and exhaust system. The generalized method of characteristics including friction, heat transfer, area change and entropy gradients was used to analyse the pipe flow The constant-Pressure model was applied for the analysis of the flow through engine valved, and the constant-pressure perfect-mixing model was applied for the flow at manifold junction. The concept of the sudden area change was used for the muffler and catalytic convertor. Fer the plenum chamber in an MPI engine, constant-pressure model and constant-volume model were both examined. Through the comparison of predicted results with experiments, the simulation program was verified by showing good prediction of the behavior of IC engine qualitatively and quantitatively under wide range of operating conditions.