• International Journal of Air-Conditioning and Refrigeration
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• 제7권
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• pp.33-44
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• 1999

Enthalpy transport in a pulse tube was investigated by two-dimensional analysis of mass, momentum and energy equations assuming that the axial temperature gradient in the pulse tube was constant. The time-averaged second-order conservation equations of mass, momentum and energy were used to show the existence of steady mass and enthalpy streaming. Effects of the axial temperature gradient, velocity amplitude ratio, and heat transfer between the gas and the tube wall On the steady mass and enthalpy streaming were shown. Enthalpy loss due to the steady mass streaming is zero for basic and orifice pulse tube refrigerators, but it is proportional to the axial temperature gradient and steady mass flow rate through a pulse tube for double inlet pulse tube refrigerators.

• KIEE International Transaction on Systems and Control
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• 제2D권2호
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• pp.108-114
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• 2002

This paper describes the design of a robust adaptive controller for a nonlinear dynamical system with unknown nonlinearities. These unknown nonlinearities are approximated by multilayered neural networks (MNNs) whose parameters are adjusted on-line, according to some adaptive laws far controlling the output of the nonlinear system, to track a given trajectory. The main contribution of this paper is a method for considering input constraint with a rigorous stability proof. The Lyapunov synthesis approach is used to develop a state-feedback adaptive control algorithm based on the adaptive MNN model. An overall control system guarantees that the tracking error converges at about zero and that all signals involved are uniformly bounded even in the presence of input saturation. Theoretical results are illustrated through a simulation example.

• 한국환경과학회지
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• 제15권12호
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• pp.1087-1091
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• 2006

This paper describes the current spatial patterns of the net primary productivity (NPP) of the terrestrial vegetation and carbon emission (C) in the world due to the burning of fossil fuels in order to clarify the amount of expansion of human activity. The C/NPP value varies spatially from almost zero to several tens of thousand times the local NPP. C/NPP is higher under the condition of extensive human activities due to a high human population density or when the local NPP is extremely low in severe climatic zones. In contrast, the low C/NPP areas are distributed mainly in sparsely populated districts, loading to a low impact of human activity. Although the area where C/NPP is less than 10% accounts for about 70% of the entire land area, one-third of these areas cannot contribute to carbon absorption because of low NPP with a shortage of climatic resources. Since more than half of the areas of the remaining areas are agricultural land and forest ecosystems with high NPP, the possible afforestation area was evaluated to be maximum of $30{\times}10^{6}\;km^{2}$; here only sequestrate carbons that correspond to 2% of the global total NPP are present. These analyses revealed that presently most of the areas where the NPP is high are those exclusively used by humans and that it is difficult for large-scale forest plantations to absorb a substantial amount of the carbon emitted annually by humans.

• 산업경영시스템학회지
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• 제25권5호
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• pp.9-14
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• 2002

A capital investment problem is essentially one of determining whether the anticipated cash inflows from a proposed project are sufficiently attractive to invest funds in the project. The net present value(NPV) criterion and internal rate of return(IRR) criterion are widely used as means of making investment decisions. A positive NPV means the equivalent worth of the inflows is greater than the equivalent worth of outflows, so, the project makes profit. Business people are familiar with rates of return because they all borrow money to finance ventures, even if the money they borrow is their own. Thus they are apt to use the IRR in preference to the NPV. The IRR can be defined as the discount rate that causes the net present value of a cash flow to equal zero. Why the project are accepted if the project's IRR is greater than the investor's minimum attractive rate of return\ulcorner Against the NPV, the definition cannot distinctly explain the concept of the IRR as decision criterion. We present a new definition of the IRR as the ratio of profit on the invested capital.

• Journal of applied mathematics & informatics
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• 제34권1_2호
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• pp.75-84
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• 2016

The objective of this work is to perform a geometric analysis of the net present value (NPV) and Internal Rate of Return (IRR), defining analytics and in verifying the relationship between geometric properties of such functions. For this simulation, was used the values of the cash flows for each period identical and equal to US$ 200.00 cash, the initial investment US$ 1,000.00 and investments of each identical and equal to US$ 50.00 period. In addition, the discount rate and time were considered a maximum of 2 years (24 months) at a rate between 0 and 100%. The geometric analysis of the characteristics obtained from the expressions of the Net Present Value and Internal Rate of Return possible to observe that besides the analytical dependence between these quantities , the geometric relationships are relevant when studied in relation to the zero NPV and expressed a great contribution the sense of a broad vision for the administrator in the analysis of analytical variables that in uences the balance sheet of the company.

• International Journal of Internet, Broadcasting and Communication
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• 제14권1호
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• pp.136-141
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• 2022

A very complex task in deep learning such as image classification must be solved with the help of neural networks and activation functions. The backpropagation algorithm advances backward from the output layer towards the input layer, the gradients often get smaller and smaller and approach zero which eventually leaves the weights of the initial or lower layers nearly unchanged, as a result, the gradient descent never converges to the optimum. We propose a two-factor non-saturating activation functions known as Bea-Mish for machine learning applications in deep neural networks. Our method uses two factors, beta (𝛽) and alpha (𝛼), to normalize the area below the boundary in the Mish activation function and we regard these elements as Bea. Bea-Mish provide a clear understanding of the behaviors and conditions governing this regularization term can lead to a more principled approach for constructing better performing activation functions. We evaluate Bea-Mish results against Mish and Swish activation functions in various models and data sets. Empirical results show that our approach (Bea-Mish) outperforms native Mish using SqueezeNet backbone with an average precision (AP50val) of 2.51% in CIFAR-10 and top-1accuracy in ResNet-50 on ImageNet-1k. shows an improvement of 1.20%.

• Tribology and Lubricants
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• 제2권1호
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• pp.30-38
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• 1986

In the paper, static characteristics of spiral grooved seal is theoretically obtained by Using Navier-Stokes equation. In the analysis, inertia term of fluid is considered and the flow and pressure in the steady state are obtained for the groove direction and vertical to the groove direction. As the journal rotating frequency increases, the leakage flow decreases. Therefore, zero net leakage flow is possible at the region of some rotating frequency.

• Ecology and Resilient Infrastructure
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• 제7권4호
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• pp.248-255
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• 2020

본 연구에서는 국내 음식물쓰레기 (food waste, FW) 분야에 대한 재활용 현황을 분석하고 green house gases (GHG) 배출 관리방안에 대해 고찰하였다. 연구 결과, FW의 자원 활용성을 향상시키고 GHG 배출을 부가적으로 저감시키기 위해서는 적절한 선순환체계가 필요하다는 결론을 얻었다. 효과적인 퇴비화를 위해서 우선 GW의 활용이 고려되었다. 특히 3세대 바이오매스로써의 GW (phytoplankton, periphyton, macrophyte etc.)는 퇴비화 공정에서 FW의 단점을 보완하고 질적 능력을 향상시킬 수 있는 좋은 기능성 첨가제로 판단된다. 또 하나의 접근법은 최종산물 (예: 토양개량제)을 오염물질 완충이 가능한 bio-filter로 가공하여 그린인프라에 적용하는 방안이다. 이러한 생태공학적 접근과 시도는 안정화된 재활용 산물의 기존 활용 이외에도 FW 자원화에 대한 새로운 적용처를 제시할 수 있으므로 향후 효과적인 탄소 넷제로 (Net-Zero) 시스템 구축에 기여할 수 있을 것으로 판단된다.

• 산업진흥연구
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• 제9권1호
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• pp.47-55
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• 2024

교통분야에서 탄소중립 달성을 위한 전략으로 자동차 총 주행거리 감축과 승용차 교통량 감축을 제시하고 있다. 이를 위해서는 대중교통 활성화를 목표로 MaaS 서비스를 적극적으로 추진하여야 한다. MaaS를 추진하기 위해서는 개인의 이동에 대한 이용수단, 경로뿐만 아니라, 개인의 이용 수단의 전환 등 개인별 누적 이동 데이터가 필요하다. 하지만 국내에서는 개인의 이동에 대한 데이터를 수집하고 이를 활용하는데 있어서 법적인 한계가 존재한다. 2023년 개정된 개인정보보호법에 개인정보 전송요구권이 신설됨에 따라 개인의 이동에 대한 데이터를 수집하고 활용하기 위한 법률이 마련되었지만, 시행령, 세부 규칙, 지침, 가이드라인 등이 마련되어야 하며, 마이데이터수집을 위한 데이터 형식 및 전송체계의 표준화가 선행될 필요가 있다.

• 해양환경안전학회지
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• 제30권1호
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• pp.135-145
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• 2024

MEPC 80차 회의에서 IMO는 더욱 강화된 온실가스 감축 전략을 제시하였다. 기존의 72차 회의에서 제시하였던 초기전략보다 구체적이고 강화된 감축 전략이다. IMO는 2050년 무렵까지 국제 해운으로부터 온실가스 배출을 'Net Zero'에 도달하도록 전략을 세웠다. 이 논문에서는 대표적인 친환경 연료로 구분되는 LNG, 수소, 메탄올, 암모니아의 위험도 평가를 진행하였다. 전문가들의 설문조사를 통한 결과를 퍼지 기법을 적용하여 주관적인 모호성을 해결하였다. 또한 TOPSIS 기법을 통해서 퍼지의 긍정적인 해와 부정적인 해를 도출하였다. 이를 통해서 Vertex 방법을 이용하여 대체 연료의 근접계수 값을 최종적으로 구하여 결정하였다. 그 결과, 메탄올, LNG, 수소, 암모니아 순으로 선호하였다. 이 연구는 제안된 접근 방식이 대체 연료를 결정을 위한 집단 의사결정 방법으로 이용할 수 있음을 보여준다.