• International Journal of Aeronautical and Space Sciences
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• v.15 no.4
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• pp.444-453
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• 2014

A throttleable rocket engine enables operational possibilities such as the docking of spacecraft, maneuvering in a certain orbit and landing on a planet's surface, altitude control, and entrance to atmosphere-less planets. Thus, throttling methods have long been researched. However, dual-manifold injectors, which represent one throttling method, have been investigated less than others. In this study, dual-manifold and single-manifold injectors were compared to determine the characteristics of dual-manifold injectors. Also, the effects of gas injection were investigated with various F/O ratios. To investigate the characteristics, mass flow rate, spray pattern, spray angle, and droplet size were measured. The spray angle and droplet size were captured by indirect photography. About 30 images were taken to assess the spray patterns and spray angle. Also, 700 images were analyzed to understand the droplet distribution and targeting area, moving to the right from the centerline with 1.11-cm intervals. The droplet size was obtained from an image processing procedure. From the results, the spray angle showed two transition regions, due to swirl momentum in the swirl chamber regardless of the F/O ratio. The droplet size showed similar trends in both dual-manifold and single-manifold injectors except in the low mass flow rate region. In the case of the dual- manifold injector, the spray cone was not fully developed in the low mass flow rate region due to low angular momentum in the swirl chamber.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.3
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• pp.22-30
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• 2011

There is a many way of LPRE throttling methods, high-pressure-drop systems, dual-manifold injector, gas injection, multiple chambers, pulse modulation and movable injector components. Especially dual-manifold injector is essentially combines two fixed-area injectors into a common structure, with independent feed systems controlling flow to each injector manifold. In this paper, using indirect photography and liquid film thickness measurement with various injection pressure and tangential entry diameter to decide stability of spray over a wide thrust range in dual manifold injector.

• Korean Journal of Mathematics
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• v.13 no.1
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• pp.51-59
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• 2005

Let (M, $g$) be a compact oriented self-dual 4-dimensional Einstein manifold with positive sectional curvature. Then we show that, up to rescaling and isometry, (M, $g$) is $S^4$ or $\mathbb{C}\mathbb{P}_2$, with their cannonical metrics.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.5
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• pp.2607-2627
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• 2017

Nonnegative matrix factorization (NMF) has received considerable attention due to its effectiveness of reducing high dimensional data and importance of producing a parts-based image representation. Most of existing NMF variants attempt to address the assertion that the observed data distribute on a nonlinear low-dimensional manifold. However, recent research results showed that not only the observed data but also the features lie on the low-dimensional manifolds. In addition, a few hard priori label information is available and thus helps to uncover the intrinsic geometrical and discriminative structures of the data space. Motivated by the two aspects above mentioned, we propose a novel algorithm to enhance the effectiveness of image representation, called Dual graph-regularized Constrained Nonnegative Matrix Factorization (DCNMF). The underlying philosophy of the proposed method is that it not only considers the geometric structures of the data manifold and the feature manifold simultaneously, but also mines valuable information from a few known labeled examples. These schemes will improve the performance of image representation and thus enhance the effectiveness of image classification. Extensive experiments on common benchmarks demonstrated that DCNMF has its superiority in image classification compared with state-of-the-art methods.

• Honam Mathematical Journal
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• v.46 no.2
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• pp.224-236
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• 2024

This study inspects the structure of CR-product of a holomorphic statistical manifold. Findings concerning geodesic submanifolds and totally geodesic foliations in the context of dual connections have been demonstrated. The integrability of distributions in CR-statistical submanifolds has been characterized. The statistical version of CR-product in the holomorphic statistical manifold has been researched. Additionally, some assertions for curvature tensor field of the holomorphic statistical manifold have been substantiated.

• Bulletin of the Korean Mathematical Society
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• v.40 no.1
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• pp.109-122
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• 2003

In this paper we give a characterization of an irreducible connection with harmonic curvature over a connected Kaehler manifold to be self-dual. Also we introduce new notions of $c_{i}-self-dual$ or Kaehler Yang-Mills connections on compact Kaehler manifolds and investigate some fundamental properties of this kind of new connections. Moreover, on a compact odd dimensional Riemannian manifold we give a property of generalized monopole.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.6
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• pp.787-798
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• 1995

We implement the E-plane T-juncition manifold mutiplexer having low insertion loss for output multiplexer of Ku-band satellite transponder. Manifold multiplexer implemented here is composed of 2 channel filters, T-junctions, half-wave waveguide connecting channel filters and manifold, and manifold itself.[1-4] Considering the mass and volume of the satellite transponder, the channel filters are designed to dual-mode.[5-13] And Elliptic filter function is used, which has good characteristics of suppressing the interference between 2 channels. Since the performance of manifold multiplexer depends on the manifold waveguide transmission line length, it's necessary proper analysis. In this paper, we do optimization process of T-junction and other elements by using CAD and implement the manifold multiplexer. An experiment shows that characteristic response of multiplexer matches wel its modeling result.

• Bulletin of the Korean Mathematical Society
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• v.28 no.2
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• pp.225-229
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• 1991

Our final purpose may be to introduce generalized differential forms on the space Map(S, M) of mappings from a manifold S into a manifold M and discuss the differential geometry of the space Map(S, M) from the point of the generalized forms. Here we take a subspace X of the space Map(S,M) and we introduce the generalized differential forms on X, taking the dual to the chain space with the flat norm. This method of construction allows us to discuss a sufficient condition for a subspace Y of X to admit the generalized differential forms and the natural integration as the dual operation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.10
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• pp.868-874
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• 2015

Thrust variation is an essential parameter in a space mission such as landing on an atmosphereless planet or docking a spacecraft. In order to achieve the thrust variation control, using throttleable injector is a representative and general method. A dual-manifold injector, one of throttleable injectors, was used to control mass flow rate. Five kinds of injectors were designed and investigated in order to compare the spray characteristics of the dual-manifold injector with various tangential entries. Spray angles and patterns were measured to determine external flow characteristics and film thicknesses were measured in order to investigate the internal flow patterns.

• Korean Journal of Mathematics
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• v.31 no.2
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• pp.133-137
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• 2023

Consider a Riemannian manifold M equipped with a metric g. In this article, we study a notion for statistical manifolds (M, g, ∇), which can have a nonzero torsion, abbreviated to SMT. Then it turns out that the tensor fields ∇g and ${\tilde{\nabla}}g$ obtained from two different SMT-connections are different.