• East Asian mathematical journal
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• v.33 no.1
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• pp.103-113
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• 2017

We provide quantitative two weight estimates for the commutator of the Hilbert transform under certain conditions on a pair of weights (u, v) and b in $Carl_{u,v}$. In [10] and [11], Bloom's inequality is shown in a modern setting, and the boundedness of the commutators is provided by assuming both weights u, v are $A_2$ and $b{\in}BMO_{\rho}$. In the present paper we show that the condition on b can be replaced by $Carl_{u,v}$ by using the joint $A^d_2$ condition.

• East Asian mathematical journal
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• v.38 no.3
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• pp.339-346
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• 2022

In this paper, a comparison of two types of quantitative two weight conditions for the boundedness of the dyadic paraproduct and the commutator of the Hilbert transform is provided. In the case of the commutator [b, H], the conditions of the well-known Bloom's inequality [2] and the slightly different types of two weight inequality introduced in [1] are compared around the A₂-conditions on weights and the novel conditions on the function b.

• Bulletin of the Korean Mathematical Society
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• v.61 no.4
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• pp.1053-1066
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• 2024

In this paper, we study the boundedness of the commutator H^b_Ω formed by the rough Hardy operator H_Ω and a locally integrable function b from homogeneous Herz spaces to homogeneous weak Herz spaces. In addition, the weak boundedness of H^b_Ω on central Morrey spaces is also established.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.4
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• pp.67-74
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• 2012

This paper presents the novel design and implementation of a switched reluctance motor with commutator. Unlike typical switched reluctance motor, this motor doesn't require semi-conductor devices and inverter circuits for driving. Instead, the brushes and commutator can make rotating field for driving the switched reluctance motor. Moreover, because this motor has no magnet, the total cost for manufacturing the motor is very cheap. In order to verify the usability of the proposed motor, the authors manufactured the prototype motor, and showed the torque-speed curve of the motor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.57-62
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• 2013

Because of high torque and easiness of speed control, Direct Current(DC) motors have been used for a long time. But, its applications are limited in circumstance and performance, since they contained brush and commutator. The commutation characteristic gives effect to life and performance of the DC motor. Naturally, the commutation characteristic analysis is strongly required. In this paper, With the result of finite element analysis, The inductance is calculated each rotor position and applied to the voltage equations coupled with commutation equation. Also, contact resistances of brush/commutator assembly are considered using contact area and brush width converted with commutator segments. The time derivative term in the differential equation is solved in time difference method. This algorithm was applied to 2-pole shunt DC motor. We considered commutation characteristic by changing contact resistance between brush and commutator segment.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.114-121
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• 2009

Mobile phone is a representative personal communication tool among wireless communication devices. Recently, with the miniaturization and light-weight trend of mobile phone, the vibration motor has been replaced by coin type. The required performances of coin type vibration motor needed by user are long life, higher vibration, and thin thickness. Also the most important factor determines the performance of vibration motor is long-term reliability, which is mainly related to PCB plating technique for commutator. In this study, three types of fault were categorized to analyze the cause for malfunction of vibration motor. And, hardness and surface morphology on plating surface are also investigated to optimize the plating method and plating conditions. As a result, new plating method and conditions were proposed to increase the durability of PCB commutator.

• Bulletin of the Korean Mathematical Society
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• v.59 no.6
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• pp.1471-1493
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• 2022

The goal of this paper is to establish the boundedness of bilinear Calderón-Zygmund operator BT and its commutator [b₁, b₂, BT] which is generated by b₁, b₂ ∈ BMO(ℝⁿ) (or ${\dot{\Lambda}}_{\alpha}$(ℝⁿ)) and the BT on generalized variable exponent Morrey spaces 𝓛^p(·),𝜑(ℝⁿ). Under assumption that the functions 𝜑₁ and 𝜑₂ satisfy certain conditions, the authors proved that the BT is bounded from product of spaces 𝓛^{p₁(·),𝜑₁}(ℝⁿ)×𝓛^{p₂(·),𝜑₂}(ℝⁿ) into space 𝓛^p(·),𝜑(ℝⁿ). Furthermore, the boundedness of commutator [b₁, b₂, BT] on spaces L^p(·)(ℝⁿ) and on spaces 𝓛^p(·),𝜑(ℝⁿ) is also established.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.2
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• pp.123-136
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• 2013

Objectives: This paper was prepapred to report airborne asbestos fiber concentrations in asbestos textile, brake-lining, commutator, and building materials manufacturing industries, and some other asbestos related industries in Korea from 1994 to 2006. Methods: Airborne asbestos data that have been sampled and analyzed in the above industries during 1994-2006 were collected. These data were reviewed to scrutinize the qualified data based on the records such as sampling and analyzed method and quality control procedures. All asbestos data were generated using the National Institute for Occupational Safety & Health (NIOSH) Method 7400. Results: Average concentration of asbestos fiber was 2.14 fibers/cc(0.02-15.6 fibers/cc) in the asbestos textile industry, 0.26 fibers/cc(0.01-1.01 fibers/cc) in the building-materials industry, 0.15 fibers/cc(0.01-0.93 fibers/cc) in the brake-lining manufacturing industry, and 0.14 fibers/cc(0.03-1.36 fibers/cc) in the commutator producing industry. For these industries, the percentage of samples of which asbestos fiber concentrations above the limit of exposure(0.1 fibers/cc) was 97.6% in the asbestos textile industry, 62.3% in the building-materials industry, 53.5% in the brake-lining manufacturing industry, and 34.3% in the commutator producing industry. Asbestos fiber concentration was below the limit of exposure in the gasket producing, petrochemistry, musical instrument producing industries, and the brake-lining exchange operations. Conclusions: Airborne asbestos fiber level in the asbestos textile, brake-lining producing, commutator and building-material producing industries was above the limit of exposure, but in the gasket producing, petrochemistry, musical instrument producing industries and the brake-lining exchange operations were below the limit of exposure.

• Journal of the Korean Mathematical Society
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• v.55 no.4
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• pp.939-962
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• 2018

In this paper, we show that the commutator of the intrinsic square function with BMO symbols is bounded on the variable exponent Lebesgue spaces $L^{p({\cdot})}({\mathbb{R}}^n)$ applying a generalization of the classical Rubio de Francia extrapolation. As a consequence we further establish its boundedness on the variable exponent Morrey spaces $\mathcal{M_{p({\cdot}),u}$, Morrey-Herz spaces $M{\dot{K}}^{{\alpha}({\cdot}),{\lambda}}_{q,p({\cdot})}({\mathbb{R}}^n)$ and Herz type Hardy spaces $H{\dot{K}}^{{\alpha}({\cdot}),q}_{p({\cdot})}({\mathbb{R}}^n)$, where the exponents ${\alpha}({\cdot})$ and $p({\cdot})$ are variable. Observe that, even when ${\alpha}({\cdot}){\equiv}{\alpha}$ is constant, the corresponding main results are completely new.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.720-722
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• 2000

Single phase series commutator motors is widely used in various home appliances, such as vacuum cleaner, electric mixers, electrical tools, etc. This paper deals with the characteristics of single phase series commutator motors of which parameters varied with stator turns and stack length to find optimal electric and magnetic loading. We try to measure these data through the experiments with several prototype motors. The experimental results show some specific stator turns and stack length with which this motor has the highest efficiency.