EFFECT OF CHARGE DENSITY ON SPRAY CHARACTERISTICS, COMBUSTION PROCESS, AND EMISSIONS OF HEAVY-DUTY DIESEL ENGINES

Bin Yang Wu,Qiang Zhan,Xiao Yang Yu,Wen Yu Gu,Min Zhang,Wanhua Su 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.4

In-cylinder charge density at top dead center is an important parameter of diesel engines and is influenced by intake pressure, intake temperature, and compression ratio. The effects of charge density on fuel spray, combustion process, and emissions were investigated by using a constant volume bomb and a heavy-duty diesel engine. Spray development resistance increased with the increase of the charge density in the constant volume bomb. It was found that short spray penetration was accompanied by a large spray cone angle in the former stage with high charge density. However, the equivalence ratio was lowered and the degree of homogeneity of the mixture was increased in the later stage owing to the rapid interaction of fuel and gas at a high mixing rate. Combining the first law of thermodynamics and the second law of thermodynamics for analysis, as the charge density increased, the gross indicated thermal efficiency (ITEg) was improved. However, pumping loss had to be considered with higher charge density. Under this condition, the brake thermal efficiency (BTE) trend was increased initially and decreased subsequently. Under high-load operation (1200 r/min BMEP, 2.0 MPa), the minimum charge density value of 44.8 kg/m3 was found to be reasonable. This charge density was suitable for combustion and brought about minimum exhaust energy and trade-off emissions. Moreover, by analyzing two operation conditions in terms of the maximum BTE with the Miller and the conventional cycles, compression temperature and combustion temperature were reduced in the Miller cycle with the charge density 44.8 kg/m3. A high C p/C v could improve the cylinder exergy/power conversion process by its positive effect of increasing the specific heat ratio. Owing to the interaction between a high C p/C v and exergy loss to heat transfer, the condition with the minimal charge density could produce more piston work.

Optimum Conditions of the Plasma Density for the Generation of the Maximum Bunch Charge in a Laser Wakefield Accelerator

유승훈,신현수,김근주,김재훈 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.7

The plasma density effects on the bunch charge in the laser wakefield accelerator were investigated by experiments and simulations. We measured the energy and charge of the quasi-mono energetic electron bunch with energy spectrometer and ICT. Also the plasma density was measured using a biprism interferometer. The measured electron energy showed that the electron energy decreased with increasing plasma density due to the dephasing effect. The results of the bunch charge measurement showed that the effect of the plasma density on the bunch charge was separated into two different density regimes. In the low density regime (<i>cτ/λ_p</i> < 2), the bunch charge increased with the plasma density. In the high density regime (<i>cτ/λ_p</i> > 2), bunch charge decreased with increasing plasma density. There exists an optimum plasma density to generate a high bunch charge. Particle-In-Cell simulations show that the multi-cavitation of the plasma wake wave results in the maximum generation of the bunch charge in the laser wakefield accelerator.

매립용량 산정을 위한 일반폐기물의 물성조사

장성호 密陽産業大學校 農業技術開發硏究所 1999 農業技術開發硏究所報 Vol.3 No.1

국내 일반폐기물의 약 70%가 매립에 의존하고 있으며, 매립장의 매립기한은 폐기물의 밀도에 가장 큰 영향을 받는다. 본 연구는 매립장의 효율적인 관리 및 매립장의 계획. 설계시 매립용량 및 매립기한 산정을 위한 기초자료로서 활용하고자 매립장으로 반입되는 일반폐기물을 매립 부지에 적하시의 적하밀도를 조사 분석하였다. 전체 폐기물의 차량적재밀도 및 적하밀도는 각각 0.375 ton/㎥, 0.408 ton/㎥로 조사되었으며, 성상별로는 소각재의 밀도가 가장 높게 조사되었다. 그리고 요일별에 따른 폐기물의 밀도차이는 본 연구당시의 폐기물의 구성비의 차이 때문인 것으로 생각하며, 종량제 쓰레기 등의 일반 쓰레기가 전체 쓰레기의 배출밀도에 미치는 영향이 가장 큰 것으로 나타났으며, 젖은 폐기물이 반입이 금지된 이후( '97.9 이후)의 전체 폐기물의 차량적재밀도 및 적하밀도는 0.299 ton/㎥, 0.263 ton/㎥로 추정 가능하다. The majority of general wastes have been treated by landfill method in Korea and the length of landfill site was influenced by waste's density. The purpose of this study was to investigate waste's vehicle charged density and throw down density for plan, design and management of landfill site. Vehicle charged density and throw down density of total waste was 0.375 ton/㎥, 0.408 ton/㎥, respectively and incinerated ash's density was higher than the others. Difference of density with a day of the week was due to distinction of waste's composition ratio at the time of investigation. Total waste's density was extremely influenced by garbage' density. General waste's vehicle charge density and throw down density carried in SG landfill site(after'97. 9) was assumed 0.299 ton/㎥, 0.263 ton/㎥ respectively.

Effects of Charge Density on Water Splitting at Cation-Exchange Membrane Surface in the Over-Limiting Current Region

문승현,강문성,최용진 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.1

To determine the corelation betwen surface properties and concentration polarization (CP) behaviors,cation exchange membranes with varying fixed charge densities were prepared and characterized by using severalelectrochemical analyses such as chronopotentiometry, zeta potential, and current-voltage measurements. Resultsshowed that CP behavior depended mainly on surface charge density. With higher surface charge density, strongerelectroconvection was observed, suggesting that an increase in the surface charge density increased the concentrationof the counter ions at the membrane surface. As such, the electric field around the membrane surface was strengthenedat a curent over the limiting curent density. Water spliting was also proportional to the surface charge density. Thisresult was consistent with the classical electric field-enhanced water spliting theory, indicating that water splitingincreased due to increases in the electric field and prepolarization of water molecules at the membrane-solution interfaceof the cation-exchange membrane.

매립장내 일반 폐기물의 밀도조사에 관한 연구

박진식,장성호,김수생 동아대학교 법학연구소 1999 硏究報告 Vol.22 No.2

The majority of general wastes have been treated by landfill method in Korea and the landfill period of landfill site was influenced by waste's density. The aim of this study was to investigate waste's vehicle charge density and throw down density for plan, design and management of landfill site. Vehicle charge density and throw down density of total waste was 0.375 ton/ ㎥, 0.408 ton/ ㎥, respectively and incinerated ash's density was higher than the others. Difference of density with a day of the week was due to distinction of waste's composition ratio at the time of investigation. Total waste's density was extremely influenced by garbage' density. General waste's vehicle charge density and throw down density carried in SG landfill site(after '97. 9) was assumed 0.299 ton/ ㎥, 0.263 ton/ ㎥ respectively.

The effect of charge density on the velocity and attenuation of ultrasound waves in human cancellous bone

Elsevier 2018 Journal of biomechanics Vol.79 No.-

<P><B>Abstract</B></P> <P>Cancellous bone is a highly porous material, and two types of waves, fast and slow, are observed when ultrasound is used for detecting bone diseases. There are several possible stimuli for bone remodelling processes, including bone fluid flow, streaming potential, and piezoelectricity. Poroelasticity has been widely used for elucidating the bone fluid flow phenomenon, but the combination of poroelasticity with charge density has not been introduced. Theoretically, general poroelasticity with a varying charge density is employed for determining the relationship between wave velocity and attenuation with charge density. Fast wave velocity and attenuation are affected by porosity as well as charge density; however, for a slow wave, both slow wave velocity and attenuation are not as sensitive to the effect of charge density as they are for a fast wave. Thus, employing human femoral data, we conclude that charged ions gather on trabecular struts, and the fast wave, which moves along the trabecular struts, is significantly affected by charge density.</P>

Superlattice-induced ferroelectricity in charge-ordered La_1/3Sr_2/3FeO₃

Park, Se Young,Rabe, Karin M.,Neaton, Jeffrey B. National Academy of Sciences 2019 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.116 No.48

<P><B>Significance</B></P><P>Charge-order–driven ferroelectrics are an emerging class of materials with promise for high-frequency electron-dominated polarization switching, distinct from conventional ferroelectrics. However, only a few systems exhibiting this behavior have been experimentally realized thus far. With continued development of layer-by-layer growth techniques with a high level of composition control, the exploration of charge-ordered ferroelectrics can be extended to artificially structured superlattices. Here, we use density-functional theory to explore an experimentally realized bulk perovskite iron-oxide solid solution with robust charge ordering and find that in superlattices formed by layered cation ordering, bulk charge ordering is maintained and can lead to charge-order–driven ferroelectricity. Our results suggest that other broad classes of mixed valence materials may be promising candidates for discovery of electronic ferroelectrics.</P><P>Charge-order–driven ferroelectrics are an emerging class of functional materials, distinct from conventional ferroelectrics, where electron-dominated switching can occur at high frequency. Despite their promise, only a few systems exhibiting this behavior have been experimentally realized thus far, motivating the need for new materials. Here, we use density-functional theory to study the effect of artificial structuring on mixed-valence solid-solution La<SUB>1/3</SUB>Sr<SUB>2/3</SUB>FeO<SUB>3</SUB> (LSFO), a system well studied experimentally. Our calculations show that A-site cation (111)-layered LSFO exhibits a ferroelectric charge-ordered phase in which inversion symmetry is broken by changing the registry of the charge order with respect to the superlattice layering. The phase is energetically degenerate with a ground-state centrosymmetric phase, and the computed switching polarization is 39 [Formula]C/[Formula], a significant value arising from electron transfer between [Formula] octahedra. Our calculations reveal that artificial structuring of LSFO and other mixed valence oxides with robust charge ordering in the solid solution phase can lead to charge-order–induced ferroelectricity.</P>

Real-space charge distribution of the cobalt ion and its relation with charge and spin states

김봉재 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.78 No.4

The charge state of an ion provides a simplified electronic picture of the bonding in compounds, and heuristically explains the basic electronic structure of a system. Despite its usefulness, the physical and chemical definition of a charge state is not a trivial one, and the essential idea of electron transfer is found to be not a realistic explanation. Here, we study the realspace charge distribution of a cobalt ion in its various charge and spin states, and examine the relation between the formal charge/spin states and the static charge distribution. Taking the prototypical cobalt oxides, La/SrCoO3 , and bulk Co metal, we confirm that no prominent static charge transfer exists for different charge states. However, we show that small variations exist in the integrated charges for different charge states, and these are compared to the various spin state cases.

Evaluation of the Effective Charge Density on Low Pressure Nanofiltration with the Separation Characteristics of Monovalent and Divalent Solutes in the Production of Drinking Water

Jeong Ik Oh,Urase Taro 대한환경공학회 2011 Environmental Engineering Research Vol.16 No.1

The electric charge on a membrane was investigated by analyzing the experimental rejection of various monovalent and divalent ionic solutes. The characteristics of the separation of ionic solutes using various nanofiltration membranes were obtained from an experimental nanofiltration set-up, with a surface area of 40 cm2 under the operational pressures between 0.25-0.3 MPa. The state of the membrane electric charge was observed using separation coefficients, i.e., the permeation ratio of monovalent to divalent ions. To confirm the state of the membrane charge observed via the separation coefficient, a calculation using the extended Nernst-Planck equation, coupled with the Donnan equilibrium, assuming different electric charge states of the membrane, was compared with the experimental rejection of ionic solutes. The examination of the characteristics of separation using three types of nanofiltration membranes showed that one of the membranes carried a negative/positive double charge density inside, while other two membranes carried either a positive or negative charge density.

Effects of Charge Density on Water Splitting at Cation-Exchange Membrane Surface in the Over-Limiting Current Region

Kang, Moon-Sung,Choi, Yong-Jin,Moon, Seong-Hyeon 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.1

To determine the correlation between surface properties and concentration polarization (CP) behaviors, cation exchange membranes with varying fixed charge densities were prepared by using several electrochemical analyses such as chronopotentiometry, zeta potential, and current-voltage measurements. Results showed that CP behavior depended mainly on surface charge density. With higher surface charge density, stronger electroconvection was observed, suggesting that an increase in the surface charge density increased the concentration of the counter ions at the membrane surface. As such, the electric field around the membrane surface was strengthened at a current over the limiting current density. Water splitting was also proportional to the surface charge density. This results was consistent with the classical electric field-enhanced water splitting theory, indicating that water splitting increased due to increases in the electric field and prepolarization of water molecules at the membrane-solution interface of the cation-exchange membrane.