Argon Cluster and Graphene Collision Simulation Experiment

Argon Cluster and Graphene Collision Simulation Experiment Formation of Nanopore in a Suspended Graphene Sheet with Argon Cluster Bombardment: A Molecular Dynamics Simulation study Abstract: Formation of a nanopore in a suspended graphene sheet using an argon gas beam was simulated using molecular dynamics (MD) method. The Lennard-Jones (LJ) two-body potential and Tersoff–Brenner empirical potential energy function are applied in the MD simulations for different interactions between particles. The simulation results demonstrated that the incident energy and cluster size played a crucial role in the collisions. Simulation results for the Ar55 –graphene collisions show that the Ar55 cluster bounces back when the incident energy is less than 11ev/atom, the argon cluster penetrates when the incident energy is greater than 14 ev/atom. The two threshold incident energies, i.e. threshold incident energy of defect formation in graphene and threshold energy of penetration argon cluster were observed in the simulation. The threshold ene rgies were found to have relatively weak negative power law dependence on the cluster size. The number of sputtered carbon atoms is obtained as a function of the kinetic energy of the cluster. Keywords: Nanopore, Suspended graphene sheet, Argon cluster, Molecular dynamics simulation Introduction The carbon atoms in graphene condense in a honeycomb lattice due to sp 2-hybridized carbon bond in two dimensions [1]. It has unique mechanical [2], thermal [3-4], electronic [5], optical [6], and transport properties [7], which leads to its huge potential applications in nanoelectronic and energy science [8]. One of the key obstacles of pristine graphene in nanoelectronics is the absence of band gap [9-10]. Theoretical studies have shown that chemical doping of graphene with foreign atoms can modulate the electronic band structure of graphene and lead to the metal to semiconductor transition and break the polarized transport degeneracy [11-12]. Also, computational studies have demonstr ated that some vacancies of carbon atoms within the graphene plane could induce a band-gap opening and Fermi level shifting [13-14]. Graphene nanopores can have potential applications in various technologies, such as DNA sequencing, gas separation, and single-molecule analysis [15-16]. Generating sub-nanometer pores with precisely-controlled sizes is the key difficulty in the design of a graphene nanopore device. Several method have been employed to punch nanopores in graphene sheets, including electron beam from a transmission electron microscope (TEM) and heavy ion irradiation. Using electron beam technique, Fischbein et al.[17] drilled nanopores with the width of several nanometers and demonstrated that porous graphene is very stable; but, this method cannot be widely used because of its low efficiency and high cost. Russo et al. [18] used energetic ion exposure technique to create nanopores with radius as small as 3Å. S. Zhao et al. [19] indicated that energetic cluster irra diation was more effective in generating nanopores in graphene, because their much larger kinetic energy could be transferred to the target atoms. Recent experimental works have further confirmed that cluster irradiation is a feasible and promising way in the generation of nanopores [20]. Numerical simulations have demonstrated that, by choosing a suitable cluster species and controlling its energy, a nanopores of desired sizes and qualities can be fabricated in a graphene sheet [19].

Education in developing countries Assignment Example | Topics and Well Written Essays - 750 words

Education in developing countries - Assignment Example This part of investment by any firm can defines any part of then organization labor ability and it is very essential for the productivity of any firm. To be noted is that not the whole world population is referred to as the working population but only that portion that is able, willing and working on agreed wage rate. In any developing country and economy work force is a necessity that is required to propel its growth. This makes human capital very essential as it is cheap and readily available in the developing countries (Becker, 1993). Q.2 Explain some of the reasons why developing countries have not realized a greater positive development impact from their higher education programs. In this context, why should the development of a solid elementary education system take precedence over an expansion of the university system in developing countries? Developing countries need a solid base for elementary education because majority of the jobs are not technical. Industries are not well developed and casual works are the basis f their economy. Higher education though needed is for the few who are only needed to supervise the majority who only require elementally education and knowledge. Developing countries can import these few university graduates but it will cost more if they were to do the same for the unskilled human work force (Becker, 1993). Therefore, elementary education should be invested for more by these countries. Like wise due to underdevelopment and poor governance productivity of these nations is poor and they heavily depend on imports thus their production is for raw materials. Q.3 In developing countries higher educational facilities have tended to expand to the point where social benefits exceed private benefits. What is the economic explanation for this? Due to poor governance and unplanned occurrences social benefits have exceeded private benefits as organizations and external investor try to compensated the void. This has diluted the gap making these organizations bend towards social benefits rather than have private motives. This has made an economic impact as there is investment in the education sector that is very essential in the growth of any economy. Furthermore, there is direct investment that is injecting money directly into the economy as well as offering employment to the citizens. These institutions also pay taxes directly to the central government and this helps in the management of the economy through government expenditures. Q 4.Explain how a better-educated population will also tend to be a healthier, and vice versa, that a healthier population will tend to be better educated. In this context, how can an increase in human capital lead to an increase in GDP? Why might it not lead to an increase in GDP? Educated populations will always be healthier as this adds to their knowledge, experience and time management. Good investment options can only be made through well thought ides and these skills require educat ion in order for them to materialize. Higher education therefore contributes to a higher GDP for the developing countries as productivity is achieved and also by them using their own citizens cutting on importation of labor. However, this may not be the case if everybody acquires higher education as majority would not fit in their job description and as earlier stated the economies

Longitudinal method compared with 5 other methods in text book Research Paper - 1

Longitudinal method compared with 5 other methods in text book - Research Paper Example In essence, longitudinal studies usually allow tracking of people; therefore, different longitudinal surveys given people are less likely to be the true reflection of cultural or behavior different over a given period (Jin and Rounds, 2012). Longitudinal research methods allow observation of changes in a more accurate way; therefore, it can be applied in different fields particularly business field among other fields (Bryman, 2012). Notably, longitudinal studies often allow accurate observation of changes that occur during the study in numerous fields. In nursing and medicine fields, the study is often designed to reveal the predictors of certain diseases. In marketing, the same study is often applied to identify the needed changes to advertisements due to attitude and behavior changes within the targeted audience. Longitudinal studies are classified among the observational studies; thus, it its application cannot allow the manipulation of variables of the study (Lee and Xia, 2011). In some instances, it has been noted that the longitudinal studies are less powerful to detect any causal relationship between variables than other experimental research methods (Wagner, 2010). However, due to their repeated observations at individual levels, longitudinal studies are more powerful than other cross-sectional observational studies. Additionally, longitudinal studies are capable of excluding time invariants within the unobservable individual difference, and they allow temporal observation of order of events (Morrow, 2011). Nonetheless, the longitudinal studies are every expensive since they take a longer period to be accomplished; thus, making it less convenient research method. Additionally, longitudinal studies may lack accuracy since sometimes they experience changes in variables especially in case of death of a particular data set. These underlying differences and similarities between longitudinal research studies allows to compared with