Aspect ratio effects of an adiabatic rectangular obstacle on natural convection and entropy generation of a nanofluid in an enclosure

G. A. Sheikhzadeh,M. Nikfar 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.11

In the present study, aspect ratio (AR) effects of a centered adiabatic rectangular obstacle numerically investigated on natural convection and entropy generation in a differentially heated enclosure filled with either water or nanofluid (Cu-water). The governing equations are solved numerically with finite volume method using the SIMPLER algorithm. The study has been done for Rayleigh numbers between 103 and 106, the aspect ratio of 1/3, 1/2, 1, 2 and 3 and for base fluid as well as nanofluid. It is found that, using the nanofluid leads to increase the flow strength, average Nusselt number and entropy generation and decrease the Bejan number especially at high Rayleigh numbers. At low Rayleigh numbers entropy generation is very low. By increasing Rayleigh number, entropy generation and Bejan number increases. It is observed that the viscose entropy generation is more considerable than the thermal entropy generation and has dominant role in total entropy generation. The maximum entropy generation occurs at AR = 1/3 and 3 and the minimum entropy generation occurs at AR = 1 and 1/2. It is observed that the effect of AR on Nusselt number, entropy generation and Bejan number depends on Rayleigh number.

정보 생성 예술로서의 바이오아트 : 엔트로피와 노이즈, 그리고 생물학적 변이의 예술적 활용에 관한 연구

신종천,윤준성 한국기초조형학회 2018 기초조형학연구 Vol.19 No.1

This study looks into the aesthetic discussions that explore the characteristics of artworks focusing on entropy, and presents the ultimate form of contemporary art as bio-art that utilizes biological variations. In the explanation, bio-art is analyzed as the art form that does not transmit fixed information but generate information in order to meet aesthetic goals. To clearly define 'openness' to which contemporary art aspires, Umberto Eco analyzed the characteristics of artworks using the concept of entropy. In his book <The Open Work>, since the direct link between disorder and information can be found in art as well as everyday life, he used information, like Claude Shannon, as the concept of entropy which means the possibility of statistical aspects. However, the openness of artworks requires the concept of 'informatization of noise' or 'information generation', in that it involves not only the uncertainty experienced in the selection process but also the uncertainty interfered in the process of information transmission. In addition, the information generation can also be observed in biological variations of life phenomena, because a biological mutation is related to a biological variation changed by the involvement of noise in the existing genetic information. In this regard, bio-art, which combines the life phenomena with the form of art, is a useful tool to show how entropy of life and entropy of art can be mixed to generate information. The information generation in life and art ultimately confirms that the essence of life is not different from that of art. In particular, Eduardo Kac's <Genesis> and Pei-Ying Lin's <Smallpox Syndrome> show how genetic information and bodily information can be generated in artworks, and present the potential value of bio-art. 본 연구는 엔트로피를 중심으로 예술 작품의 특성을 탐구하는 미학적 논의들을 살펴보고, 현대 예술이 궁극적으로 도달하고자 하는 형태를 생물학적 변이를 활용하는 바이오아트를 통해 제안하고자 한다. 그 과정에서 바이오아트는 고정된 정보를 전달하는 것이 아니라 정보를 생성시켜 미학적 목표를 충족시킬 수 있는 예술의 한 형태로 제시되고 분석되어진다. 움베르코 에코(Umberto Eco)는 현대 예술이 추구하고 있는 작품의 ‘개방성’을 좀 더 명확하게 규정하고자 엔트로피 개념을 활용해 예술 작품의 형태적 특성들을 분석했다. 그는 그의 저서 <The Open Work>에서 무질서와 정보가 직접적으로 연관되는 현상은 일상생활에서 뿐만 아니라 예술에서도 통상적으로 찾아볼 수 있기 때문에, 클로드 섀넌(Claude Shannon)처럼 정보를 통계학적 측면의 가능성을 의미하는 엔트로피의 개념으로 사용하는 것이 타당하다고 보았다. 하지만 에코가 말하는 예술 작품의 개방성은 선택 상황에서 경험하는 불확실성뿐만 아니라 정보 전달 과정에서 개입되는 불확실성까지도 포함하는 문제라는 점에서, ‘노이즈의 정보화’ 또는 ‘정보 생성’의 개념을 필요로 한다. 그리고 그와 같은 정보 생성은 생명 현상의 생물학적 변이를 통해서도 경험될 수 있다. 일반적으로 생물학에서의 돌연변이는 유전 정보에 노이즈가 개입되어 유전자의 모습이나 성질이 변하는 것을 의미하기 때문이다. 그런 점에서, 생명 현상과 예술의 형태적 특성이 결합된 바이오아트는 생명 자체의 엔트로피와 예술 자체의 엔트로피가 어떤 방식으로 혼합되어 정보를 생성시킬 수 있는가를 보여주는 유용한 도구이다. 그리고 바이오아트 안에서 실험되는 생명과 예술의 정보 생성은 궁극적으로 생명의 본질과 예술의 본질이 다르지 않다는 것을 확인시켜 준다. 특히, 에두아르도 카츠(Eduardo Kac)의 <Genesis>나 페이-잉 린(Pei-Ying Lin)의 <Smallpox Syndrome>은 작품 속에서 유전 정보와 신체 정보가 어떤 방식으로 생성될 수 있는가를 보여주고, 아직 익숙하지 않은 바이오아트의 잠재적 가치를 제시한다.

엔트로피 생성을 고려한 능동형 자기 재생기의 성능특성에 관한 연구

김영권(Youngkwon Kim),정상권(Sangkwon Jeong) 대한설비공학회 2010 대한설비공학회 학술발표대회논문집 Vol.2010 No.6

Application of the Second Law of Thermodynamics to Energy Systems

Kuan Chen 한국에너지기후변화학회 2007 에너지기후변화학회지 Vol.2 No.2

The second law of thermodynamics has been applied to the analyses and optimizations of various energy systems. The increase of entropy principle-perhaps the most commonly used second-law statement-when applied to a composite thermodynamic system, is only a necessary, not a sufficient, condition for the second law to be satisfied. Negative entropy generation in some regions in a composite system may be cancelled by the positive entropy generation in other regions. In this case the total entropy generation of the system may be positive, but the second law of thermodynamics, which is a local and instantaneous law and should be satisfied everywhere and at ally instant, is violated in the regions of negative entropy generation.

Implication of Magneto-hydrodynamics and Melting Heat Transfer in Cubic Autocatalytic Reactive Flow with Entropy Generation

Sohail A. Khan,M. Ijaz Khan,Sami Ullah Khan,M. Y. Malik,A. Ghareeb 한국자기학회 2021 Journal of Magnetics Vol.26 No.3

The theme of this article is to investigate hydrodynamic flow of an incompressible second grade nanoliquid by a curved stretched sheet. Energy expression is developed through dissipation and Joule heating. Brownian and thermophoresis diffusion are also scrutinized. Physical feature of entropy generation is discussed. Isothermal cubic autocatalytic chemical reactions are discussed. Suitable transformations are used to develop the ordinary differential system. To develop a convergent series solution we employed the Optimal Homotopy Analysis Technique (OHAM). Graphical description of velocity, entropy generation, temperature distribution and concentration versus sundry parameters are discussed. An opposite behavior in velocity field is noted for magnetic and curvature parameters. Temperature distribution and velocity field have reverse trends for melting parameter. An augmentation in temperature is observed for radiation parameter. Larger magnetic variable lead to improve the entropy generation. Entropy optimization is boosted versus higher magnetic parameter.

Entropy analysis for nanofluid flow over a stretching sheet in the presence of heat generation/absorption and partial slip

Aminreza Noghrehabadi,Mohammad Reza Saffarian,Rashid Pourrajab,Mohammad Ghalambaz 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.3

The boundary layer heat transfer and entropy generation of a nanofluid over an isothermal linear stretching sheet with heat genera-tion/absorption have been analyzed. In the nanofluid model, the development of nanoparticles concentration gradient due to slip mecha-nisms, the effects of Brownian motion and thermophoresis, are taken into account. The dependency of the local Nusselt number and entropy generation number on the non-dimensional parameters is numerically investigated. The results show that the increase of heat generation parameter, Brownian motion parameter, or thermophoresis parameter decreases the entropy generation number in the vicinity of the sheet.

Entropy measurement of a large format lithium ion battery and its application to calculate heat generation

Doh, Chil-Hoon,Ha, Yoon-Cheol,Eom, Seung-wook Pergamon Press 2019 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>As large format lithium ion batteries are used in EV and ESS applications, the temperature control of a battery is important to achieve a safe and long cycle life operation. To control the temperature properly, we need to know the heat generation characteristics. Heat generation of a battery mainly depends on the applied current, internal resistance, temperature and entropy of the battery. However, it is not easy to measure the entropy, because they depend on SOC and temperature simultaneously. Here, we suggested a new way to measure the entropy, on the assumption of adiabatic condition and calculate the heat generation. Internal resistance, specific heat capacity, OCCP values are also measured experimentally. The entropy (F ∂E<SUB>OC</SUB> ∂T<SUP>−1</SUP>) at a given SOC were measured from the variation of OCCP with temperature and expressed via a polynomial equation. The temperature dependence of the internal resistance were also expressed in the same procedure. The battery temperature variations calculated from the above parameters showed a good agreement with those from experiments. This suggested method provides a simple and reliable temperature estimation of lithium ion batteries.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Entropy generation analysis for multi-walled carbon nanotube (MWCNT) suspended nanofluid flow over wedge with thermal radiation and convective boundary condition

Hamza Berrehal,Abdelaziz Maougal 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1

We performed entropy generation analysis for a carbon nanotube (CNT) suspended nanofluid flow by a wedge with thermal radiation and convective boundary condition. The multi-wall carbon nanotube (MWCNT) with water as the base fluid was considered. Twodimensional governing equations were transformed by similarity method into a set of coupled nonlinear ODEs and then solved analytically using optimal homotopy asymptotic method (OHAM). Moreover, solutions of these equations were further utilized in a dimensionless equation of entropy generation. The analytical results indicated that the entropy generation can be reduced by increasing radiation parameter and reducing the convection through boundaries, while nanoparticles have influence to increase the entropy production.

Theoretical Investigations of Entropy Optimization in Electro-Magneto Nonlinear Mixed Convective Second Order Slip Flow

M. Ijaz Khan,Sumaira Qayyum,S. Kadry,W. A. Khan,S. Z. Abbas 한국자기학회 2020 Journal of Magnetics Vol.25 No.1

Here nonlinear mixed convective entropy based nanofluid second order slip flow of magnetic and electric field is addressed. Both electric and magnetic field is considered for the problem formulation and the flow is generated by a stretched surface. Important slip factors, i.e., Brownian and thermophoresis diffusions are accounted. Total entropy rate subject to four types of irreversibilities (i) heat transfer (ii) chemical reaction (iii) fluid friction (iv) Joule or Ohmic heating is obtained through second law of thermodynamics. Thermal radiation, heat generation/absorption, dissipation, Brownian motion, Joule or Ohmic heating and thermophoresis effects are considered in the development of the energy equation. Activation energy to undergo the physical transportation or chemical transformation of atoms or molecules is further considered in the analysis of concentration. Firstly ordinary differential system is found, then numerically solved for flow field, entropy generation, concentration, temperature, skin friction, Nusselt number, Bejan number and Sherwood number through built-in- Shooting method.

엔트로피를 이용한 분산 서비스 거부 공격 탐지에 효과적인 특징 생성 방법 연구

김태훈(Tae-hun Kim),서기택(Ki-taek Seo),이영훈(Young-hoon Lee),임종인(Jong-in Lim),문종섭(Jong-sub Moon) 한국정보보호학회 2010 정보보호학회논문지 Vol.20 No.4

최근 분산 서비스 거부 공격의 근원인 악성 봇 프로그램이 널리 유포되고 있으며 보안이 유지되지 않는 PC를 통하여 악성 봇이 설치된 PC의 수가 기하급수적으로 증가하고 있다. 이를 통한 분산 서비스 거부 공격이 계속적으로 발생하고 있으며 최근 금품을 요구하는 사례도 발견되었다. 따라서 분산 서비스 거부 공격에 대응하기 위한 연구가 필요하며 본 논문에서는 네트워크 패킷 헤더의 속성에 대해 불확실성을 나타내는 척도인 엔트로피를 이용하는, 분산 서비스 거부 공격 탐지에 효과적인 특징 생성 방법을 제안한다. DARPA 2000 데이터셋과 직접 실험을 통해 구성한 분산 서비스 거부 공격 데이터셋에 대해 향상된 엔트로피 수식과 효율적인 엔트로피 계산 기법, 다양한 엔트로피 특징 값을 사용하는 제안 기법을 적용해보고 베이지안 네트워크 분류기를 이용하여 분류함으로써 제안하는 방법이 효과적인지를 검증해 본다. Malicious bot programs, the source of distributed denial of service attack, are widespread and the number of PCs which were infected by malicious bot program are increasing geometrically thesedays. The continuous distributed denial of service attacks are happened constantly through these bot PCs and some financial incident cases have found lately. Therefore researches to response distributed denial of service attack are necessary so we propose an effective feature generation method for distributed denial of service attack detection using entropy. In this paper, we apply our method to both the DARPA 2000 datasets and also the distributed denial of service attack datasets that we composed and generated ourself in general university. And then we evaluate how the proposed method is useful through classification using bayesian network classifier.