데이터 센터에서 IT 장비의 액체냉각에 따른 총 소유비용

Vali Sorel,Bill Carter,Roy Zeighami,Susan F. Smith,Robin Steinbrecher,박창용(번역자) 대한설비공학회 2016 설비저널 Vol.45 No.2

수냉식 방법은 서버 집적도 향상, 자연 냉각방식 사용 증가, 장치 성능 및 단위 전력당 성능증가를 가능하도록 하여 총 소유비용을 감소시킬 수 있다. 이코노마이저가 설치된 칠러 시스팀, 효율적인 공기 제어장치, 찬 공기와 더운 공기를 분리하는 복도구조, 최적화된 운전 등을 갖춘 공랭식 데이터 센터의 총 소유비용은 하이브리드 냉각방식을 적용한 경우의 총 소유비용과 거의 유사함을 보여주었다. 각 데이터센터 소유자는 각각의 복잡한 운전 및 지역의 특성에 맞는 최상의 냉각방식을 선택하여 이윤을 극대화할 수 있을 것이다. 본 연구는 이러한 복잡한 특성에 대해 설명하고 수냉식 시스템을 설치하게 되는 경우 기존 공랭식에 대한 비용적 비교 방법을 제시하였다. 비록 본 연구에서는 공랭식과 하이브리드 냉각방식에서 총 소유비용의 차이가 크지 않았지만, 수냉식에 최적화된 구성요소를 적용하지 않은 결과이기 때문에 수냉식에 최적화된 상태에서 비교한다면 더 높은 총 소유비용 특성을 보여줄 가능성이 존재한다. 하이브리드 냉각이 운전부하에 대한 성능을 향상시키고 소프트웨어 관련 비용을 감소시켜 데이터센터 운영에 필요한 지출을 줄일 수 있다. 높은 IT 장비밀도가 요구되며, 공랭식의 활용이 어려운 고밀도 및 고성능 환경에서 수냉식 시스템의 적용이 확대되길 기대하며, 여러분의 총 소유비용 분석과정에서 본 연구가 도움이 되길 바란다.

Effect of different binders on cold-bonded artificial lightweight aggregate properties

Vali, Kolimi Shaiksha,Murugan, S. Bala Techno-Press 2020 Advances in concrete construction Vol.9 No.2

The present investigation is to identify an optimum mix combination amongst 28 different types of artificial lightweight aggregates by pelletization method with aggregate properties. Artificial aggregates with different combinations were manufactured from fly ash, cement, hydrated lime, ground granulated blast furnace slag (GGBFS), silica fume, metakaolin, sodium bentonite and calcium bentonite, at a standard 17 minutes pelletization time, with 28% of water content on a weight basis. Further, the artificial aggregates were air-dried for 24 hours, followed by hardening through the cold-bonding (water curing) process for 28 days and then testing with different physical and mechanical properties. The results found the lowest impact strength value of 16.5% with a cement-hydrated lime (FCH) mix combination. Moreover, the lowest water absorption of 16.5% and highest individual pellet crushing strength of 36.7 MPa for 12 mm aggregate with a hydrated lime-GGBFS (FHG) mix combination. The results, attained from different binder materials, could be helpful for manufacturing high strength artificial aggregates.

Transformation of the Coplanar Waveguide Bandpass Filter to Band Stop Filter by Serpentine Shape Shunt/Open Stubs

Sk. Shoukat Vali,K. Srinivasa Rao 한국전기전자재료학회 2022 Transactions on Electrical and Electronic Material Vol.23 No.6

In this paper, the design and simulation of a new compact bandpass filter (BPF) has been implemented with serpentine meandershunt stub on coplanar waveguide technology. The inductive loading is improved by serpentine meander, thus the size of the BPF is reduced. The size of the proposed BPF structure is 4 × 2.6 mm 2 . The behaviour of the proposed structure and eff ects on the frequency response of BPF while changing the dimensions is carried out with an electromagnetic (EM) simulator. The equivalent circuit model describes the proposed BPF and exhibits the center frequency, bandwidth, and insertion loss of 20, 8 GHz, and< 0.1 dB respectively. The device-level and equivalent lumped model simulations are done by using the HFSS and ADStools. The proposed BPF is transformed into the bandstop filter, while the serpentine shunt type meander is convertedinto an open stuband also the coupling capacitance gap has vanished. The frequency response of bandstop filter (BSF) is also carried out with both EM and equivalent simulations, these simulations are disclosed the excellent agreement between the electromagnetic (EM) and lumped equivalent model simulations for both BPF and BSF over a frequency range of (15–30) GHz. Hence the proposed structure is recommended for K band (18–26) GHz applications.

FENC: Fast and Efficient Opportunistic Network Coding in wireless networks

( Peyman Pahlavani ),( Vali Derhami ),( Ali Mohammad Zareh Bidoki ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.1

Network coding is a newly developed technology that can cause considerable improvements in network throughput. COPE is the first network coding approach for wireless mesh networks and it is based on opportunistic Wireless Network Coding (WNC). It significantly improves throughput of multi-hop wireless networks utilizing network coding and broadcast features of wireless medium. In this paper we propose a new method, called FENC, for opportunistic WNC that improves the network throughput. In addition, its complexity is lower than other opportunistic WNC approaches. FENC utilizes division and conquer method to find an optimal network coding. The numerical results show that the proposed opportunistic algorithm improves the overall throughput as well as network coding approach.

Extracellular Synthesis of Magnetite and Metal-Substituted Magnetite Nanoparticles

Roh, Y.,Vali, H.,Phelps, T. J.,Moon, J.-W. American Scientific Publishers 2006 Journal of Nanoscience and Nanotechnology Vol.6 No.11

<P>We have developed a novel microbial process that exploits the ability of Fe(III)-reducing microorganisms to produce copious amounts of extracellular magentites and metal-substituted magnetite nanoparticles. The Fe(III)-reducing bacteria (<I>Theroanaerobacter ethanolicus</I> and <I>Shewanella</I> sp.) have the ability to reduce Fe(III) and various metals in aqueous media and form various sized magnetite and metal-substituted magnetite nano-crystals. The Fe(III)-reducing bacteria formed metal-substituted magnetites using iron oxide plus metals (e.g., Co, Cr, Mn, Ni) under conditions of relatively low temperature (<70 °C), ambient pressure, and pH values near neutral to slightly basic (pH = 6.5 to 9). Precise biological control over activation and regulation of the biosolid-state processes can produce magnetite particles of well-defined size (typically tens of nanometers) and crystallographic morphology, containing selected dopant metals into the magnetite (Fe3−<I>y</I>X<I>y</I>O4) structure (where X = Co, Cr, Mn, Ni). Magnetite yields of up to 20 g/L per day have been observed in 20-L vessels. Water-based ferrofluids were formed with the nanometer sized, magnetite, and metal-substituted biomagnetite particles.</P>

Some extension results concerning analytic and meromorphic multivalent functions

Ali Ebadian,Vali Soltani Masih,Shahram Najafzadeh 대한수학회 2019 대한수학회보 Vol.56 No.4

Let $\mathscr{B}_{p,n}^{\upeta, \upmu}\left(\upalpha\right)$; $\left( \upeta, \upmu\in \mathbb{R}, n,p\in \mathbb{N}\right) $ denote all functions $f$ class in the unit disk $\mathbb{U}$ as $f(z)=z^p+\sum_{k=n+p}^{\infty}a_kz^k$ which satisfy: \begin{align*} & \left| \left[ \frac{f'(z)}{pz^{p-1}}\right]^{\upeta} \left[ \frac{z^p}{f(z)}\right] ^{\upmu}-1\right| <1-\frac{\upalpha}{p}; \quad \left( z\in \mathbb{U}, \: 0\leq \upalpha<p\right). \intertext{ And $\mathscr{M}_{p,n}^{\upeta,\upmu}\left(\upalpha\right)$ indicates all meromorphic functions $h$ in the punctured unit disk $\mathbb{U}^{\ast}$ as $h(z)=z^{-p}+\sum_{k=n-p}^{\infty}b_kz^k$ which satisfy:} & \left| \left[ \frac{h'(z)}{-pz^{-p-1}}\right]^{\upeta} \left[ \frac{1}{z^p h(z)}\right]^{\upmu}-1\right| <1-\frac{\upalpha}{p}; \quad \left( z\in \mathbb{U}, \: 0\leq \upalpha<p\right). \end{align*} In this paper several sufficient conditions for some classes of functions are investigated. The authors apply Jack's Lemma, to obtain this conditions. Furthermore, sufficient conditions for strongly starlike and convex $p$-valent functions of order $\gamma$ and type $\beta$, are also considered.

1D-Coordination Polymer Formed by Structural Conversion of an Oxazolidine Ligand in Reaction with the Copper(II) Halides

Zahra Mardani,Vali Golsanamlou,Zahra Jabbarzadeh,Keyvan Moeini,Cameron Carpenter-Warren,Alexandra M. Z. Slawin,J. Derek Woollins 대한화학회 2018 대한화학회지 Vol.62 No.5

A 1D-coordination polymer of 1D-{Cu(μ-picolinato)2}{Hakimi, 2012 #73}n (1), was prepared by the reactions between 2-(2-(pyridin-2-yl)oxazolidin-3-yl)ethanol (AEPC) ligand and CuCl2 or CuBr2. The product was characterized by elemental analysis, UV-Vis, FT-IR spectroscopy and single-crystal X-ray diffraction. The X-ray analysis results revealed that the AEPC ligand, after reactions with the copper(II) chloride or bromide, gives the same product - 1D-{Cu(μ-picolinato)2}n (1). The coordination modes for various picolinate-based ligands were extracted from the Cambridge Structural Database (CSD). In the crystal structure of 1, the copper atom has a CuN2O4 environment and octahedral geometry, which is distorted by elongation of the axial bond lengths due to the Jahn-Teller effect.

Coordination of Active Front Steering and Direct Yaw Control Systems Using MIMO Sliding Mode Control

Ebrahim Muhammad,Ahmad Reza Vali,Abdorreza Kashaninia,Vahid Behnamgol 제어·로봇·시스템학회 2024 International Journal of Control, Automation, and Vol.22 No.1

This paper investigates an integrated multi-input multi-output (MIMO) sliding mode control strategy to coordinate the active front steering (AFS) and direct yaw control (DYC) system of a vehicle. The proposed control method aims to enhance the lateral dynamics of the vehicle, especially in the presence of tire-road friction coefficient variations as parameter uncertainties. The proposed integrated control strategy consists of two control layers. The upper layer coordinates the AFS and DYC systems and produces the corrective yaw moment and additive front steering angle. At the lower layer, the slip controller based on sliding mode control (SMC) converts the yaw moment into the desired longitudinal slip and generates the final distributed braking torques. Simulations of two scenarios in various road conditions were conducted to ensure that the proposed control is robust against road condition changes in the proposed method. Results from the simulation during the J-turn maneuver on the slippery road compared the performance of the suggested sliding mode integrated controller with an adaptive integrated controller. The simulation results showed that the proposed control system improved the stability and handling of the system’s tracking performance in various maneuvers.

Microstructure and Mechanical Properties of AM60 Magnesium Alloy Processed by a New Severe Plastic Deformation Technique

Siroos Ahmadi,Ghader Faraji,Vali Alimirzaloo,Ali Donyavi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8

The mechanical properties and microstructure of AM60 Magnesium alloy processed by a new cyclic extrusion channelangular pressing (CECAP) technique were investigated in this research. In this novel method, a low extrusion ratio stage wasadded at the end of the CECAP process to enhance the hydrostatic stresses and equivalent strain. The structure was refinedfrom the average grain size of ~ 76 μm for the annealed samples to 2.63 μm in the new CECAP after four passes. Whilefor the CECAP and ECAP processes, it was 3.43 and 6.98 μm, respectively. Experimental results of the proposed CECAPprocess showed an improvement in the mechanical properties after the second pass that were stopped for the ECAP process. However, the hardness of the CECAP-processed and proposed samples was constantly increasing. This increase in hardnesswas 196% and 175% for the proposed CECAP and CECAP processes after four passes compared to the unprocessedsample, respectively. Moreover, the compressive yield stress and ultimate compressive strength of the CECAP-processedsamples were higher in all passes; however, they were smaller than those of the proposed CECAP process. The hydrostaticcompressive stresses and higher plastic strain in the proposed technique helped in further refining of the grains, which caneffectively improve the mechanical properties.

Stabilized marine and desert sands with deep mixing of cement and sodium bentonite

Saberian, Mohammad,Moradi, Mojtaba,Vali, Ramin,Li, Jie Techno-Press 2018 Geomechanics & engineering Vol.14 No.6

Road construction is becoming increasingly important in marine and desert areas due to population growth and economic development. However, the load carrying capacity of pavement is of gear concern to design and geotechnical engineers because of the poor engineering properties of the soils in these areas. Therefore, stabilization of the soils is regarded as an important issue. Besides, due to the fuels combustion and carbonate decomposition, cement industry generates around 5% of global $CO_2$ emission. Thus, using bentonite as a natural pozzolan in soil stabilization is more eco-friendly than using cement. The aim of this research is to experimentally study of the stabilized marine and desert sands using deep mixing method by ordinary Portland cement and sodium bentonite. Different partial percentages of cement along with different weight percentages of sodium bentonite were added to the sands. Unconfined compression test (UCS), Energy Dispersive X-ray (EDX), and Scanning Electron Microscope (SEM) were conducted on the specimens. Moreover, a mathematical model was developed for predicting the strength of the treated soils.