• Korean Journal of Mathematics
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• 제29권1호
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• pp.13-24
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• 2021

For a finite commutative ring R with identity 1 ≠ 0, the zero divisor graph ��(R) is a simple connected graph having vertex set as the set of nonzero zero divisors of R, where two vertices x and y are adjacent if and only if xy = 0. We find the signless Laplacian spectrum of the zero divisor graphs ��(ℤn) for various values of n. Also, we find signless Laplacian spectrum of ��(ℤn) for n = pz, z ≥ 2, in terms of signless Laplacian spectrum of its components and zeros of the characteristic polynomial of an auxiliary matrix. Further, we characterise n for which zero divisor graph ��(ℤn) are signless Laplacian integral.

• Journal of Power Electronics
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• 제9권2호
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• pp.156-163
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• 2009

In this paper a family of zero current transition PWM converters which employs a simple auxiliary circuit is introduced. This soft switched auxiliary circuit is only composed of a switch and a capacitor. The proposed converters are analyzed and various operating modes of the ZCT flyback converter are discussed. Design considerations are presented and the experimental results of the ZCT flyback converter laboratory prototype are illustrated. The experimental results confirm the validity of theoretical analysis.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.646-652
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• 2003

AS a main Power Supply of the Railroad Vehicles, a three-Level ZVZCS DC/DC Converter is proposed in this paper. The proposed three-Level DC/DC Converter achieves zero voltage and zero current switching for the main switches. Its attribute is that the voltage across the switches is half the value of the input voltage. Also. using a diode and secondary side of the transformer, and simple auxiliary circuits it achieves zero current switching of the auxiliary switches. The principle operation and simulation results are included.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2204-2206
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• 1997

A novel zero voltage and zero current switching (ZVZCS) full bridge (FB) PWM converter with a low output current ripple is proposed. The proposed circuit improve the demerits of the previously presented ZVBCS-FB-PWM converters[5-8] such as use of lossy components or additional active switches. A simple auxiliary circuit which includes neither lossy components nor active switches provides ZVZCS conditions to primary switches, ZVS for leading-leg switches and ZCS for lagging-leg switches. In addition, this proposed circuit reduces a output current ripple considerably. Many advantages including simple circuit topology, high efficiency, low cost and low current ripple make the new converter attractive far high power (> 1kW) applications.

• 한국통신학회논문지
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• 제31권1A호
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• pp.38-47
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• 2006

본 논문에서는 주파수 영역에서의 간단한 zero-forcing 기법을 이용한 속도 적응형 채널 추정 기법을 제안한다. 제안된 기법은 최적의 채널 추정 기법인 Wiener 필터의 주파수 응답을 구형(rectangular)으로 근사화하여 유도된다. 채널 추정 과정은 수신 신호에서 최대 도플러 주파수보다 큰 주파수 성분들을 제거함으로써 수행된다. 제안된 기법은 채널 계수와 이동체 속도에 대한 동시 추정 기법으로 확장 가능하며, 하나의 FFT 구조를 사용하여 효과적으로 구현 가능하다. 실험 결과를 통해 제안된 채널 추정 기법은 기존의 속도 적응형 채널 추정 기법들보다 넓은 속도 범위에서 낮은 채널 추정 MSE 성능을 보여주며, 확장된 동시 추정 기법은 다양한 채널 환경에서 안정된 추정 성능을 보인다. 마지막으로 제안된 기법에 대한 MSE 성능이 수식적으로 유도된다.

• 대한수학회지
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• 제60권1호
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• pp.167-193
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• 2023

Let f be a self-dual primitive Maass or modular forms for level 4. For such a form f, we define N^s_f(T):=|{ρ ∈ ℂ : |𝕵(ρ)| ≤ T, ρ is a non-trivial simple zero of L_f(s)}|.. We establish an omega result for N^s_f(T), which is $N^s_f(T) = \Omega(T^{\frac{1}{6}-{\epsilon}})$ for any ∊ > 0. For this purpose, we need to establish the Weyl-type subconvexity for L-functions attached to primitive Maass forms by following a recent work of Aggarwal, Holowinsky, Lin, and Qi.

• 대한수학회논문집
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• 제32권1호
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• pp.7-17
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• 2017

Let R be a commutative ring with zero-divisors Z(R). The extended zero-divisor graph of R, denoted by $\bar{\Gamma}(R)$, is the (simple) graph with vertices $Z(R)^*=Z(R){\backslash}\{0\}$, the set of nonzero zero-divisors of R, where two distinct nonzero zero-divisors x and y are adjacent whenever there exist two non-negative integers n and m such that $x^ny^m=0$ with $x^n{\neq}0$ and $y^m{\neq}0$. In this paper, we consider the extended zero-divisor graphs of idealizations $R{\ltimes}M$ (where M is an R-module). At first, we distinguish when $\bar{\Gamma}(R{\ltimes}M)$ and the classical zero-divisor graph ${\Gamma}(R{\ltimes}M)$ coincide. Various examples in this context are given. Among other things, the diameter and the girth of $\bar{\Gamma}(R{\ltimes}M)$ are also studied.

• 한국태양에너지학회 논문집
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• 제30권2호
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• pp.39-45
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• 2010

Zero Emission Building is abuilding which emits virtually '0(zero)' carbon dioxide. Although simple in concept, ZEB requires totally different approach from conventional building in terms of design, engineering, construction and operation. There are few research on ZEB design process as ZEB design requires understanding and knowledge regarding energy and technology. The study aims to propose a design process of Zero Emission Building for architects. The study examined the concept of Zero Emission Building through intensive literature search. The examples of Zero Emission Buildings were investigated, and strategies and technologies applied to the buildings were analyzed. Various conventional design processes were identified and analyzed to examine the applicability to ZEB design, Finally, a new design process which effectively accommodate the requirement of Zero Emission Building was proposed.

• Journal of Power Electronics
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• 제12권5호
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• pp.723-730
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• 2012

This paper presents a new ZVS single phase bridgeless (Power Factor Correction) PFC, using an active clamp to achieve zero-voltage-switching for all main switches and diodes. Since the presented PFC uses a bridgeless rectifier, most of the time, only two semiconductor components are in the main current path, instead of three in conventional single-switch configurations. This property significantly reduces the conduction losses,. Moreover, zero voltage switching removes switching loss of all main switches and diodes. Also, auxiliary switch turns on zero current condition. The presented converter needs just a simple non-isolated gate drive circuitry to drive all switches. The eight stages of each switching period and the design considerations and a control strategy are explained. Finally, the converter operation is verified by simulation and experimental results.

• International Journal of Internet, Broadcasting and Communication
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• 제14권3호
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• pp.193-204
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• 2022

The 2018 Seoul Zero Pay is a policy actively promoted by the government as an economic stimulus package for small business owners and the self-employed who are experiencing economic depression due to COVID-19. However, the controversy over the effectiveness of Zero Pay continues even after two years have passed since the implementation of the policy. Zero Pay is a joint QR code mobile payment service introduced by the government, Seoul city, financial companies, and private simple payment providers to reduce the burden of card merchant fees for small business owners and self-employed people who are experiencing economic difficulties due to the economic downturn., it was attempted in the direction of economic revitalization for the return of alleyways[1]. Therefore, this study intends to draw implications for improvement measures so that the ongoing zero-pay can be further activated and the economy can be settled normally. The analysis results of this study are as follows. First, it shows the effect of increasing the income of small business owners by inducing consumption in alleyways through the economic revitalization policy of Zero Pay. Second, the issuance and distribution of Zero Pay helps to revitalize the local economy and contribute to the establishment of a virtuous cycle system. Third, stable operation is being realized by the introduction of blockchain technology to the Zero Pay platform. In terms of academic significance, the direction of Zero Pay's policies and systems was able to identify changes in the use of Zero Pay through big data analysis. The implementation of the zero-pay policy is in its infancy, and there are limitations in factors for examining the consumer image perception of zero-pay as there are insufficient prior studies. Therefore, continuous follow-up research on Zero Pay should be conducted.