Diamond-type Research Articles

불규칙 피로 하중을 받는 자전거 프레임에 대한 연구

Abstract : In this study, 3 kinds of models about bike frame are simulated with static structural analysis, And fatigue life, damage and durability according to fatigue load are analyzed. A bike frame model with diamond type is compared with another model on the reinforced support with its type. In case of the reinforced support type, maximum equivalent stress or total deformation is shown with 10% or 20% more than the diamond type respectively. At both types of models, the trends of fatigue life and damage at both types are same. ‘SAE bracket history’ with the severest change of load becomes most unstable but ‘Sample history’ becomes most stable among the cases of nonuniform fatigue loads. In case of ‘Sample history’ with the average stress of 0 to -1MPa and the amplitude stress of 0 to 1MPa, the possibility of maximum damage becomes 3%. This stress state can be shown with 6 times more than the damage possibility of ‘SAE Bracket history’ or ‘SAE transmission’. In case of the reinforced support type, fatigue life becomes shorter and damage probability becomes larger at the right side installed with support than diamond type. The structural result of this study can be effectively utilized with the design on bike frame by investigating prevention and durability against its damage.

Electrooxidation of the Reactive Orange 16 Dye Using Boron Doped Diamond and DSA Type Electrodes

The comparison of the efficiencies for boron-doped diamond (BDD) and for DSA-Cl2® type electrodes to degrade the reactive orange 16 (RO16) dye is presented. The results for the dye electrochemical degradation were investigated by spectroscopic techniques UV/VIS analysis, Total Organic Carbon (TOC), and High Performance Liquid Chromatography (HPLC). The BDD electrode showed the higher performance in the whole range of current densities studied for the color removal as well as in the mineralization of organic materials present in such dye.

Discrete maximum principle based on repair technique for diamond type scheme of diffusion problems

SUMMARYIn this paper, two repair techniques are proposed for diamond schemes of anisotropic diffusion problems to ensure that the repaired solutions satisfy the discrete maximum principle. One of them is an extension of that in [Liska R, Shashkov M. Enforcing the discrete maximum principle for linear finite element solutions of second‐order elliptic problems. Communications in Computational Physics 2008; 3(4):852–877.] for linear finite element solutions, which is a local repair technique, and another is a new global repair technique. Both of them keep total energy conservation and are easy to be implemented in existing codes. Numerical examples show that these two repair techniques do not destroy the accuracy of solution for the diamond schemes on distorted meshes. Copyright © 2012 John Wiley & Sons, Ltd.

Electrong-factor anisotropy in symmetric (110)-oriented GaAs quantum wells

We demonstrate by spin quantum beat spectroscopy that in undoped symmetric (110)-oriented GaAs/AlGaAs single quantum wells even a symmetric spatial envelope wavefunction gives rise to an asymmetric in-plane electron Land\'e-g-factor. The anisotropy is neither a direct consequence of the asymmetric in-plane Dresselhaus splitting nor of the asymmetric Zeeman splitting of the hole bands but is a pure higher order effect that exists as well for diamond type lattices. The measurements for various well widths are very well described within 14 x 14 band k.p theory and illustrate that the electron spin is an excellent meter variable to map out the internal -otherwise hidden- symmetries in two dimensional systems. Fourth order perturbation theory yields an analytical expression for the strength of the g-factor anisotropy, providing a qualitative understanding of the observed effects.

A Study of the Diamond Tools for Grinding Polycrystalline Diamond

The purpose of this paper was to investigate the grinding performance of two types of cobalt and vitrified bond diamond tools produced by the hot press for the vertical flat grinding polycrystalline diamond. The worn diamond type and the diamond protrusion observed by the toolmaker or SEM after grinding under two different feed rates of 1 and 5 mm/min and the depth of cut of 2 µm with total depth of 10µm were studied. In addition, the grinding efficiency and the workpiece surface roughness produced were analyzed as well. The experiment results showed that when the feed rate of 1 mm/min during the flat grinding PCD was used, a lower percentage of the good diamond, a higher percentage of flat diamond and pulled-out hole on the worn surface of the cobalt bond diamond tool were obtained. For the vitrified bond diamond tool, the good diamond produced showed a higher percentage and flat grit and pulled-out hole displayed a relatively lower percentage. This may be due to the result of the relatively moderate strength and grit retention of the vitrified bond. Furthermore, the diamond protrusion and the grinding efficiency produced for the vitrified bond diamond tool were better than those for the cobalt bond tool. And the PCD surface roughness obtained was better as well.

Fast bolometer built in an artificial HPHT diamond matrix

A fast bolometer built in a plate of diamond grown at high pressure by the gradient growth method is developed and fabricated. The parameters of this structure are compared with these of the structures investigated earlier, which were fabricated based on chemical vapour deposited (CVD) diamond and natural type IIa diamond.

The entrepreneurial journey: From entrepreneurial intent to opportunity realization

The entrepreneurial process of new business creation starts when a business opportunity is discovered or created by nascent entrepreneurs. This process involves a journey of improvising and coping with uncertainty. There are many obstacles as well as pulling, pushing, and driving forces that the entrepreneur may encounter along the way. In this paper, There need the internal driving forces that solves these problems by taking entrepreneurial actions to actualize new business potential against all odds. The series of entrepreneurs' autonomous, innovative, and improvised actions throughout the entrepreneurial process will consist the entrepreneurial journey. This journey will be viewed as a combination of volitional and emergent process of transforming potentiality into actuality, that is, opportunity realization. This paper attempts to explain the internal driving forces that direct, drive, and sustain entrepreneurial processes with and against internal and external conditions and changes. An entrepreneurial process is composed of driving forces of activity and a number of activities related with resource and opportunity. In this paper, we conceptualize the obsessive motivation and internal driving forces that catalyzes the entrepreneurial journey as entrepreneurial intent: entrepreneurial mindset that can be defined as an aroused state of entrepreneurial motivation to initiate, drive and sustain the entrepreneurial journey til the opportunity is completely transformed to real business. A case study method that implements a modified version of the grounded theory method is applied to identify the multidimensional and emergent processes of this entrepreneurial journey. This study examines a sample of high-tech venture firms in Korea. The results show that entrepreneurial intent toward a new opportunity emerges as collective actions for combining new resources to create new value. In the journey, entrepreneurial intent can be considered as internal driving force because it is at the center of underlying layers of the emergent process of opportunity realization. In successful journeys, entrepreneurial intent seems to be an extreme level of entrepreneurial motivation because it is characterized by more energetic functions of motivation: arousal, direction, and duration of entrepreneurial activity. In this paper, these three functions will be referred to as the 3C Effects: the channeling (arousal), the concentrating (direction), and the continuing (duration) of entrepreneurial action. This mechanism converts the actions of the entrepreneur and his/her firm into entrepreneurial ones that aim to seize every chance to make the opportunity into reality. The entrepreneurial actions, increase the chances of serendipity in the external process of creating, attracting, and combining resources to meet the value criteria of market opportunity. Cases of entrepreneurial journey are analyzed in layered and diamond type frameworks. In summary, the volitional and emergent journey can be illuminated by frameworks consisting of multiple phases, dimensions and layers of entrepreneurial process that interact with various kinds of external conditions including business opportunities.

Morphological evolution of polished single crystal (100) diamond surface exposed to microwave hydrogen plasma

It is shown that exposure of polished single crystal diamond surfaces to microwave hydrogen plasma at optimized conditions may be applied as a very efficient method for the smoothing out of single crystal diamond surfaces. The effect of microwave (MW) hydrogen plasma exposure on the morphology of mechanically polished natural single crystal (100) oriented diamond type 2a surfaces is reported. It is shown that the surface morphology is very sensitive to plasma power and exposure time. Under appropriate plasma exposure conditions the diamond surfaces smooth out as reflected in the decrease in the number and depth of the polishing scratches or lines. However adverse effects on the surface morphology through the formation of pits were found to occur upon long exposure times and high plasma power. A systematic study of the influence of hydrogen microwave plasma power and exposure time on the diamond surface morphology is presented. The morphology of the diamond surfaces at the different stages was monitored with sub-nano-metric resolution by atomic force microscopy and scanning electron spectroscopy.

Planarization of natural single crystal diamond polishing lines by microwave hydrogen plasma

AbstractThe effect of microwave hydrogenated (MW‐H) plasma exposure on the morphology of mechanically polished natural single crystal (100) oriented diamond type 2a surfaces is reported. It is shown that the surface morphology is very sensitive to plasma power and exposure time. Under appropriate plasma exposure conditions the diamond surfaces smooth out as reflected in the decrease in the number and depth of the polishing lines. A systematic study of the influence of hydrogen MW plasma power and exposure time on the diamond surface morphology is presented. The morphology of the diamond surfaces at the different stages was monitored with sub‐nano‐metric resolution by atomic force microscopy and scanning electron spectroscopy.

The dynamic ionic charge of zincblende type crystals

Abstract : The ionic charges of zincblende type crystals are discussed. Since the static ionic charges are, in general, quite small in these crystals, the magnitudes of the dynamic ionic charge, (e* sub T), are attributed largely to the effects of charge redistribution. The fairly sizeable values of (e* sub T) in Se and Te trigonal crystals must, in fact, be attributed entirely to charge redistribution effects since their static ionic charges are identically zero. Efforts to account for the (e* sub T) values in ZnS type crystals using either the shell model or the deformation dipole model have not been too successful. It is urged that theorists turn their attention to ab-initio energy band calculations of long wavelength dynamical properties of zincblende and diamond type crystals, namely: the first order electric moment (infrared) tensor; the first order electric susceptibility (Raman) tensor; and the change in the electric susceptibility with interatomic distance (piezo-optic) tensor. (Author)

A numerical study on heat transfer and friction in rectangular channel with inclined perforated baffles

AbstractA three‐dimensional numerical study on the turbulent flow and heat transfer characteristics in the rectangular channel with different types of baffles is carried out. The inclined baffles have the width of 19.8 cm, the square diamond type hole having one side length of 2.55 cm, and the inclination angle of 5°. Reynolds number is varied between 23 000 and 57 000. The SST k − ω turbulence model is used in the method to predict turbulent flow. The validity of the numerical results is confirmed by measurement. Numerical results show that the flow patterns around the different baffle type are entirely different and it significantly affects the local heat transfer characteristics. The heat transfer and friction factor characteristics are significantly affected by the perforation density of the baffle plate. The present study demonstrates that the battle type II (3 holes) can enhance the greatest heat transfer rates with advantages from the overall efficiency point of view.

Coordination Frictions and the Financial Crisis

In this note I argue that the desirability of fiscal policy in response to the current crisis depends on whether one views the current crisis as a temporary deviation from a unique equilibrium or as a bad equilibrium out of multiple equilibria. The paper presents a simple Diamond (1982) type of model where firms must find an (investment) bank to finance their projects and the investment banks sell risky assets to get capital from investors. Due to coordination frictions, the economy can get stuck in an inefficient low-trade equilibrium. Finally, I briefly discuss some of the policies that have recently been put forward to stimulate the economy in the context of this model.

A Numerical Study on Heat Transfer and Friction in Rectangular Channel with Inclined Perforated Baffles

A three dimensional numerical study has been applied to predict the turbulent fluid flow and heat transfer characteristics for the rectangular channel with different types of baffles. Four different types of the baffles are used. The inclined baffles have the width of 19.8 ㎝, the square diamond type hole having one side length of 2.55 ㎝, and the inclination angle of 5o. Reynolds number is varied between 23,000 and 57,000. The SST k -ω turbulence model is used in the present numerical study. The validity of the numerical results is examined with the experimental data. The numerical results of the flow field depict that the flow patterns around the different baffle type are entirely different and it significantly affects the local heat transfer characteristics. The heat transfer and friction factor depend significantly on the number of baffle holes. It is found that the heat transfer enhancement of baffle type Ⅱ (3 hole baffle) has the best values.

Germanium-Based Ferromagnetic Semiconductor Ge1-xFex for Silicon Spintronics

Ferromagnetic semiconductor Ge1-xFex thin films were grown on Si(001) substrates by low-temperature molecular beam epitaxy. The crystal structure of the Ge1-xFex films was of diamond type for 0 {less than or equal to} x {less than or equal to} 17.5%. Magnetic circular dichroism (MCD) characterizations revealed that the origin of the ferromagnetic ordering in the Ge1-xFex films comes only from the diamond lattice phase with the cooperation of s,p-d exchange interactions. The Ge1-xFex films clearly exhibited the anomalous Hall effect at lower temperatures, and their ferromagnetic behavior was consistent with the results of the MCD observations. As the Fe content increased, the resistivity of the film monotonically decreased and simultaneously the Curie temperature monotonically increased. All the experimental results indicate that the Ge1-xFex films grown on Si(001) have the properties of intrinsic ferromagnetic semiconductor.

Epitaxial Growth and Magnetic Properties of Ferromagnetic Semiconductor Ge1-xFex Thin Films Epitaxially Grown on Si(001) Substrates

Ferromagnetic semiconductor Ge1-xFex thin films were grown on Si(001) substrates by low-temperature molecular beam epitaxy. The crystal structure of the Ge1-xFex films was of diamond type for 0≤x≤17.5%, and their lattice constant monotonically decreased with increasing Fe content x. No precipitations of any other Fe–Ge phase were detected in structural characterizations. Magnetic circular dichroism (MCD) characterizations revealed that the origin of the ferromagnetic ordering in the Ge1-xFex films comes from the diamond-type semiconductor phase. The anomalous Hall effect was clearly observed and their ferromagnetic behavior was consistent with the results of the MCD observations. As the Fe content increased, the resistivity of the film monotonically decreased, and simultaneously, the Curie temperature monotonically increased. All the experimental results indicate that the Ge1-xFex films grown on Si(001) have the properties of intrinsic ferromagnetic semiconductor.

Reactive ion etching of waveguide structures in diamond

Waveguide structures were fabricated in both nanocrystalline CVD diamond (NCD) and HPHT type 1b single crystal diamond using photolithography and reactive ion etching. The combination of these techniques allows the patterning of many long photonic structures simultaneously, making it easily scalable. Emphasis has been placed on reducing sidewall roughness to prevent loss due to scattering. In single crystal diamond a peak-to-peak roughness of approximately 10 nm (estimated from SEM images) was achieved for the majority of the structure sidewall.

Enhancement of heat transfer in a typical pressurized water reactor by different mixing vanes on spacer grids

The flow mixing devices on a grid spacer are designed to enhance the turbulence and heat transfer in sub-channels. The present study evaluates the effects of different mixing vane configurations on flow pattern and heat transfer in the downstream of the mixing vanes in the sub-channels of fuel assembly. This is done by obtaining velocity and pressure fields, turbulent intensity and the heat transfer coefficient using a three-dimensional CFD analysis. Two blade groups, two-dimensional and three-dimensional, were modeled. The two-dimensional blades are classified in ring type, diamond type, square type, homographic type and multiply type. Three-dimensional blades containing split vane, ripped open, trumpet shaped and split trumpet shaped are applied in a 2 × 2 rod bundle array. Also, a 3 × 3 rod bundle array is modeled to evaluate the neighborhood effects on the thermo-hydraulic parameters. The latter model shows a good comparison with the available experimental data by 5–12% difference. A standard K-epsilon model is used as a turbulence model and the symmetry condition is set as boundary conditions. It was confirmed that the turbulence in the sub-channel was significantly promoted by spacer and mixing devices. However, their effects rapidly decreased to a fully developed level after passing approximately 10 times the hydraulic diameter downstream of the spacer. The CFD results showed good agreement with the measurements. The static pressure of the fluid in the flow direction drops rapidly, then in a very short distance rise up, followed by a decrease near to the linear slope down stream. The split trumpet vane was the best with a 14% increase in the heat transfer coefficient, however regarding the manufacturing possibilities, the split vane spacers are expected to significantly enhance the overall heat transfer of a nuclear fuel assembly about 9.82% with a reasonable increase in the pumping cost.

X-ray diffraction study of the structure of detonation nanodiamonds

The spatial structure of aggregates formed by detonation nanodiamonds is investigated using the wide-angle and small-angle X-ray scattering techniques. The effective sizes of crystallites and the crystallite size distribution function are determined. The shape of scattering aggregates is restored from the small-angle X-ray scattering data. An analysis of the results obtained allowed the conclusion that the nanodiamond aggregates have an extended spatial structure composed of nine to ten clusters, each involving four to five crystallites with a crystal lattice of the diamond type.

Evaluation of continuous grinding tests on some marble and limestone units with silicon carbide and diamond type abrasives

This paper deals with the results of continuous grinding tests carried out with two different grinding machines on some marble and limestone units with silicon carbide and diamond type abrasives. The results showed that the relationship between the surface roughness and the surface glossiness of stones with homogeneous structure are independent of abrasive types. However, this argument is not valid for stones giving orange peel effect and not going through entire ductile behaviour due to their softer mineral and other materials content. Appropriate series of abrasives and operational conditions should be chosen for obtaining desired surface quality. For this reason, the results of surface quality measurements should be used in conjunction with stone properties.

Reswitching of Techniques in an Intertemporal Equilibrium Model with Overlapping Generations

We study an overlapping generation model of Diamond's type. In contrast to Diamond, we do not assume that the technology can be represented by an aggregate neoclassical production function. Rather, we study the case in which (i) the technology consists of a finite number of constant coefficient productive activities, (ii) there are capital goods physically heterogeneous with respect to each other and to the economy's only consumption good and (iii) there are two alternative production methods for obtaining the consumption good. We explore the possible linkage between reswitching of techniques and the multiplicity of stationary state equilibria of the model.