3. the load pan. A very common


Working principle of Electronic Weight Scale Electronic weight scale are equipped with electronic measuring modules. The electronic weighing machines operate based on the following principle: the force exerted by the load situated on the balance pan is transmitted to the load cell (one or more) which in turn emits an electric signal whose intensity is proportional with the force. The electrical signal is picked up by the electronic balance block, processed, amplified and transmitted to a digital display system (digital mass indicator), the result representing the weight of the mass located on the load pan. A very common solution is to use strain gauges (strain-sensitive transducers). These are generally used for commercial weighing devices with low resolution. The strain gauges are wired as a Wheatstone-bridge to balance for temperature changes .When the pan is not loaded by any object all four resistors are the same and the input of the amplifier is zero. When an object is placed on the pan R4 and R1 are compacted and their resistance decreasing, R2 and R3 are strained and their resistance is increasing.

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This becauses a voltage difference at the input of the amplifier, proportional to the weight of the object. The strain gauges are wired as a Wheatstone-bridge to compensate for temperature changes .1 : Spring body 2 : Weighing pan3 : Mounting plate (housing) 4 : Placing and wiring of the strain gauges (R3 and R4 can also be placed on the under side of the beam)The advantages of electronic/digital weight scale are the plain fact that digital scales are considerably effortless to read. Besides, electronic weight scale will give more precision of reading value. Here are some disadvantages to electronic/digital scales, most likely the very regular one being incorrect readings.

Several people have criticising that when they stand on the scale at one spot and obtain a reading and when they get back after few seconds they get a different reading altogether. Commonly , digital scales are good if just anybody make use of it since the mechanism could become worn out after regular use. This instrument need to calibrate after years to get better accuracy.

3.1 The survey was carried out only


1 Dimension of Research Research design is the framework or plan for a study which guides the selection of sources and types of information. It outlines procedures for every research activity. Research designs are classified into three traditional categories: descriptive, exploratory or explanatory. The descriptive research method was used in gathering the needed information for this study. The characteristics of descriptive research are that it makes a clear statement of the problem, defines clearly the information needed and that the research is pre-planned and structured. This method enables the researchers to interpret the theoretical meaning of the findings and hypothesis development for further studies.

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Specifically under descriptive design, Survey Questionnaire was used to gather data on Brand consciousness.3.2 Time Orientation The data was collected only once in the time specification due to limited time constrains. This technique was ideal for the research as study does not aim to identify the changes in target population overtime and the study only aim to acquire information about the brand consciousness in target population.

The survey was carried out only for one week and only responses gathered during this time period were included in analyzing the research outcome.3.3 Data Collection In this study, structured questionnaire as a research design was applied. Questions were presented with exact same wording and in the same order to all respondents.

In this research, the reason for standardizing the questions was to ensure that all respondents were replying to the same questions and the data could be presented in Quantitative form. The questionnaire used in this research was designed by defining the information needed to answer the research objectives and questions. In addition, the questionnaire was structured, designed, formed and modified based on the theory about measuring brand consciousness among students. The Questionnaire consisted of 15 Questions which were first distributed to 10 participants to identify any error in the questionnaire. The finalized Questionnaire was then formed on Google Docs and link was shared among target population for responses. The questionnaire type chosen for this quantitative research is a self-administered questionnaire.

As these are administrated electronically through internet so they provided easy access to respondents to answer from all devices.3.4 Sample Split A sample is a subgroup of the target population that the researcher plans to study for the purpose of making generalizations about the target population. It would be impractical and time consuming to survey the entire population and that is why a sampling technique was applied.

The research was conducted among the university students of different faculties; business, science, fashion designing and humanities. In this research, the sample size of above 100 students was targeted to collect the data, and the survey link was sent to each of the students by emails and messages. The sample population for this research was restricted to the city of Karachi due to limited time constrain. To ensure the diversity in survey population, research included respondents from both gender and from different ethnic and religious background.

3.5 Data Reliability Reliability of a questionnaire refers to its ability to yield the same data when it is re-administered under the same conditions. The reliability of data is important as it helps to generalize the findings of study to the wider population and provide accurate understanding of results of the research objective. Data reliability therefore was checked through random sampling to get clear checks on the information to be presented and provided within the Thesis.3.6 Data Analysis Data analysis means to organize , provide structure and elicit meaning.

These data analyses were based on the research questions and on the research design selected for the study. The study utilized first hand data which comes from the chosen respondents who answered the survey-questionnaires given to them. The responses from the respondents were edited and some of the responses were omitted as they were either not filled or filled incompletely or not done properly. Since the research only provides quantitative data, so the data analysis technique included summary descriptive statistics and inferential statistical tests. Pie chart and Tables were used to present the result as they provide better and concise understanding of the responses.

3.1 will take for whole project which

3.1 PROJECT MANAGERThe responsibility of the project manager is to inspect, establish and coordinate the entire project and the staff who are work on site. This is to finish the project within budget set by employer, and complete work on schedule and the quality of workmanship. Through the life of the project, Project manager is to observe the provided quality control measures are executed and preserved. Besides, project manager also ensure the stock and the expropriations for subcontract are ready and hand over on time.3.

1 SITE MANAGERThe responsibilities of site manager is make sure that the cost of construction project within budget and can accomplished on time. In construction site, site manager usually begin its work before construction. For the senior construction manager, they will take for whole project which known as project manager. Beside for the junior site managers will just be responsible for only part of a project. The roles of the site manager include inspecting the direction of the project and assuring that fulfill all the specification and requirement from the client.

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Site manager discuss the project cost with the quantity surveyor. Site manager also choosing the materials and tools, coordinate and manage construction worker. Site manager keep quality controls and procedures.

3.2 SITE ENGINEERThe role of the site engineers is to supply site engineering duties for project within the area. Site engineer will set up the level and the detailed works to make sure that the check are made. Site Engineer ensures that records are precise and accomplish with organizational and legal requirements. They also analyze all the technical difficulties which unexpected and other problems that may appear.

Besides, site engineer ensure records are precise and accomplish with organizational and legal requirements. Site engineer discuss with the procurement department and prepare procurement schedules for the jobs to make sure site have sufficient of resources to accomplish the tasks.3.3 SITE SUPERVISORThe responsible of the site supervisor is to supervise a building project. Beside that the duties and responsibilities of the site supervisor is to make sure to produce high standard of work consistently by the way of regular quality inspections with sub-contractors which according to the specification and quality standards. To assuring the appliance of common operational procedures, site supervisor should supervise sub-contractor every day. Site supervisor must ensure that material expropriation in sufficient time to comply construction procedures. Site supervisor should also check and control all materials and plant once in every week.

3.5 SITE CLERKThe role of the Site Clerk is to support the Construction Site Staff with administrative duties, frame walk-throughs and site documentation. They also help the Site Superintendents in the Activities in every day of an Active Construction Site.

Besides, site clerk need to plan and retain communication and documentation.3.4 ARCHITECT MANAGERThe responsible of architect manager is to guiding the whole project of architectural including budget and implementation of the project. They giving recommendations during site visit and execute site inspection. Other than that, before the project design get approval, architect manager conduct discussions and meeting with professionals of the organization and different members. The responsibilities of architect manager also include obtaining construction bids, employing and choosing contractors and arbitrating construction contracts.3.

6 SITE QUANTITY SURVEYORSite quantity surveyors ensure the commitment with contractual requirements and the Company’s ‘Three Pillar’ objectives and supply commercial support to project teams and retaining commercial information. Other than that, Quantity surveyor are responsible to communicate with third parties on commercial issues and representative of customer about the agreement of variations, any additional payments and claims. The responsibilities of quantity surveyor include precise and timely cost and value informing at both project and business.

Site quantity surveyor also conduct cost management including, cost and commercial plans and predicting Update the monthly CVR. Site quantity surveyor keenly tried to enhance procedures and processes. 3.7 SAFETY OFFICERMain Duties of a Safety Officer is to supervise the commissioning preventative maintenance, repair services and installation. Safety Officer makes sure onsite and compliance that are outage for all maintenance activities that are planned. The Health, Environmental procedures and Safety are insures compliance with the customer by the Safety Officer.

Besides, Safety Officer prepares and carries out the Health Plan and Site Safety. Safety Officer develops measure to ensure worker’s personnel safety. Safety Officer also responsibilities in evaluate and observe dangerous and unsettled situations.

3. in percentage 4. Figure 4 Energy

3. Table of Contents1. Title page 12. Acknowledgments 23. Table of Contents 34. List of Figures 45.

List of Equations 56. List of Tables 67. List of Acronyms and Abbreviations 78. Internship background 88.1 MASEN STATUS 88.2 STRATEGY IN THE FIELD OF ENERGY 88.

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6 PROTECTING THE ENVIRONMENT 118.7 KEY DATES 128.8 PROJECTS 139. Internship plan 149.

1 CSP vs PV – technologies 149.2 CSP vs PV – Energy Storage and efficiency 149.3 Key performance indicators (KPIs) 159.3.

1. ROI (Return on investment) 159.3.

2. NPV (Net present value) 159.3.3. IRR – Internal rate of return 169.3.4.

PR – Performance ratio 16PA – Plant availability 17MTTR – Mean time to repair 18MTBF – Mean time between failures 18DCC – DC Capacity – Direct Current 18ACC – AC Capacity- Alternating Current 18TT – Ticket Types % 19V – Variance between expected kWh and actual kWh 199.3. PI – Peak Irradiance 19PSH – Peak Solar Hours 1910.

Lessons learned 2011. Conclusions 2012. References 204. List of Figures 1. Figure 1 The institutional architecture of the renewable energy sector2. Figure 2 Masen objectives in Megawatts 3. Figure 3 Masen objectives in percentage 4.

Figure 4 Energy dependence on other countries and oil products5. Figure 5 Per capita electricity (2000-2015)6. Figure 6 Power’s Noor III CSP tower plant5.

List of Equations 1. Equation 1 ROI (Return on investment) formula2. Equation 2 NPV (Net present value) formula3. Equation 3 IRR (Internal rate of return) formula4. Equation 4 PR (Performance ratio) formula5. Equation 5 Energy Output per Area formula6.

List of Tables1. Table 1 MASEN status2. Table 2 Projects 3. Table 3 Key dates7. List of Acronyms and AbbreviationsMASEN: Moroccan agency for Solar Energy CSP: Concentrated Solar PowerPV: PhotovoltaicsGG: Greenhouse gas tCO2: The ton of CO2 equivalenttoe: The ton of oil equivalent ONEE: National Office for Electricity and Potable WaterMW: Megawatts GWH: Gigawatts/hoursKPIs: Key performance indicators ROI: Return on investment NPV: Net present value IRR: Internal rate of returnPR: Performance ratioE: EnergyA: Area h: yearly sum of global irradiance8.

Internship background8.1 MASEN STATUS Legal name MASEN (Moroccan agency for sustainable energy)business entity S.A. (corporation)Creation March 2010Seat RabatChief executive officer Mustapha Bakkoury (President)Obaid Amrane (Member of the Direction)Shareholder Moroccan stateSIE (Société d’investissements énergétiques)ONEE (Office national de l’électricité et de l’eau potable)Investment fund Hassan IIActivity Renewable energyProject Noor Ouarzazate INoor Ouarzazate IINoor Ouarzazate IIINoor Ouarzazate IVNoor LaayouneNoor BoujdourSubsidiary Masen ServicesMasen CapitalTable 1 MASEN status8.

2 STRATEGY IN THE FIELD OF ENERGYMorocco is ineffectively invested with customary vitality assets and imports 96% of its vitality. Nevertheless, the Kingdom must take care of a developing demand (around 7% every year) as a result of its economic development and population increase. To address these difficulties, the Ministry of Energy, Mines, Water and Environment has built up a new national energy plan to secure energy supply while adopting a sustainable development approach. This plan also targets to preserve economical prices and better control demand.As part of this strategy, several orientations have been adopted:• The implementation of an optimized electricity mix around reliable and competitive technological choices;• The mobilization of national resources thanks to the rise of renewable energies;• The promotion of energy efficiency, established as a national priority;• Regional integration.8.3 COMPANY PRESENTATIONMASEN (Moroccan Agency for Sustainable Energy) was set up for the application of the strategyMorocco launched by His Majesty King MOHAMMED VI on November 2, 2009 Ouarzazate.

It is in charge of doing this extend by creating by producing 5 solar power plants which will be located in various locations and through the foundation and development of specialized program of incorporated power age ventures from energy solar and to organize the solar development strategy of the nation’s renewable energy plan, alongside the National Office of Electricity and Potable Water. Figure 1 The institutional architecture of the renewable energy sectorThe Kingdom of Morocco has traditionally been the largest importer of non-renewable energy sources in North Africa and relying on foreign sources for more than 97 per cent of its energy and Masen is instrumental in serving to turn that around.Masen drives ventures went for making an extra 3,000 MW of clean electrical power generation capacity by 2020, and an additional 6,000 MW after that. By 2030, the national objective is to produce at least 52 percent of the kingdom’s energy mix from renewable sources. Figure 2 Masen objectives in Megawatts 8.

4 MASEN, OR THE APPLICATION OF THE RENEWABLE ENERGY STRATEGY Figure 3 Masen objectives in percentage Masen targets to share its best practices in order to increase and help of the development of renewable energy in nations that have the resources; nonetheless, not yet the capacity, to fully profit from the power of the sun.8.5 RENEWABLE ENERGY A RESPONSEThe concern of the necessities for a socioeconomic development of the kingdom and the obligation to protect the environment have led to the harnessing of renewables for the energy required for a sustainable development of the country in the long-term. As choice doesn’t suggest necessarily concession, the Nation has opted for low carbon development without abandoning productivity. The Kingdom aim to transform its renewable energy into its strength in order to sustain a continuous socioeconomic growth.

In Morocco, rising energy needs concomitant with structural sectoral plans, national consumption and the electrification of rural regions (99% in 2015) are being confronted by the country’s high energy dependence. In fact, 95% of energy consumed in Morocco in 2014 was imported and the considerable unpredictability of the price of non-renewable energy sources threatens the economic development and stability. The major defy is hence to control the energy needs and combats climate changes.8.6 PROTECTING THE ENVIRONMENTThe consciousness of the requirement to stop climate change and protect the environment is now a global concern. Furthermore, renewable energy are recognized as being the crucial answer for diminishing its effects.

In Morocco, greenhouse gas (GG) emissions are not high. In 2011, the global average per capita was around 5 tons of CO2 equivalent (tCO2) compared with approximately 1.7 tCO2 for Morocco. However, affected by the effects of climate change and preoccupied by this problem, Morocco started to control its GG emissions, in accordance with the United Nations Framework Convention on Climate Change (UNFCCC).During COP21, the Kingdom definite a national objective of a 13% decrease in GG emissions by 2030.The use of renewable energy implies that by 2020, Morocco could avert the emission of no less than 9.3 million tCO2 (2.5 million tons of oil equivalent – toe), including 3.

7 million through the progress of solar energy ventures and 5.6 through wind energy ventures8.7 KEY DATES2009 December: Mustapha Bakkoury became Chairman of the Management Board of Masen.November: Launch by His Majesty King Mohammed VI of the Solar Plan Noor (with the goal of reaching at least of 2000 MW by 2020).2010 March: promulgation of the law of creation of Masen, Moroccan Agency for Solar Energy.2011 The plant selection procedure Noor Ouarzazate I is startedLaunch of the realization of the complex infrastructures of the complex Noor Ouarzazate.Implementation of the integrated approach for the development of solar projects2012 May: Launch of the Solar Atlas, developed by Masen, tool indispensable for the accurate evaluation of the solar deposit and its spatial and temporal distribution on a large scale.2013 Start of the selection process for Noor Ouarzazate II and Noor Ouarzazate III.

May: launch of construction works of the Noor plant Ouarzazate I by His Majesty King Mohammed VI.2014 June: creation of the Cluster, a platform that aims to synergize actors in the ENR ecosystem in Morocco (institutions, companies, and R & D / training).2015 End 2015: completion of all infrastructures common Noor Ouarzazate complex. Starting the selection process for Noor PV I (Noor Ouarzazate VI, Noor Laayoune and Noor Boujdour).2016 November: adjudication of Noor PV I (Noor Ouarzazate IV, Noor Boujdour, Noor Laayoune).

August: extension of Masen’s prerogatives, from solar to all energies Renewable. Masen becomes the central and integrated player of renewable energies in Morocco.February: inauguration of the Noor Ouarzazate I power plant by His Majesty King Mohammed VI.Launch of the construction works of Noor Ouarzazate II and Noor Ouarzazate III.2017 April: launch of the works of Noor Ouarzazate IV, last central solar complex Noor Ouarzazate and first phase photovoltaic project Noor PV I.Table 2 Key dates8.8 PROJECTSProject Superficies ha Technology used CO2 avoided tCO2/an POWER MW Project commissioningNoor Ouarzazate I 480 CSP 280000 160 2014Noor Ouarzazate II 610 CSP 300000 200 2018Noor Ouarzazate III 582 CSP 222000 150 2018Noor Ouarzazate IV 137 PV 86539 72 2018Noor Laayoune 240 PV 104300 85 2018Noor Boujdour 60 PV 23855 20 2018Table 3 Projects 9. Internship planLearning Objectives:Understand the functioning of a PV plant How to perform a PV plant operation analysis (Performance, Availability …)How using and produce a KPI and Performance report of a PV plant 9.

1 CSP vs PV – technologiesConcentrated Solar Thermal systems (CSP) and Photovoltaic panels are different as CSP systems concentrate radiation of the sun to heat a liquid substance that is then used to increase the temperature of an engine and drive an electric generator. Alternating current (AC) is generated this indirect method from, which can be easily disseminated on the power network.Photovoltaic (PV) solar panels diverge from solar thermal systems because they do not utilize the sun’s heat to produce electrical power. Rather, they utilize sunlight through the ‘photovoltaic effect’ to create direct electric current (DC) in a direct electricity generation process. In order to be distributed on the power network, the DC is then converted to AC (inverter). 9.2 CSP vs PV – Energy Storage and efficiency Figure 6 Power’s Noor III CSP tower plantCSP systems are able of storing energy by utilization of Thermal Energy Storage technologies (TES) and using it at times of low or no sunlight like in night, to generate electric power. This ability expands the diffusion of solar thermal technology in the power production industry as it is a solution to overcome intermittency issues due to environmental variations.

However, PV systems do not generate or stock thermal energy as they directly create electricity and electrical power cannot be easily stored, such as in batteries.During the day, CSP systems can generate surplus energy store it for use over the night, thus energy storage abilities can not only improve economic effectiveness but also dispatch capacity of solar power and flexibility in the power system. Hence, CSP systems are much more interesting for large scale power generation since thermal energy storage technologies are more productive than electricity storage technologies.9.3 Key performance indicators (KPIs) Key performance indicators (KPIs) are used evaluate, study and exploit the maximum performance of their ventures by development and operation.

This information are essential and can help understand the strength and weakness of your existing ventures and make the necessary to maximize their performance.Some examples of commonly used KIPs:9.3.1. ROI (Return on investment)The ratio is a basic calculation consisting on the project’s expected earnings over its initial investment. This ratio can be applied to decide if a project is profitable or should be abandoned.

Equation 1 ROI (Return on investment) formula9.3.2. NPV (Net present value)The NPV is used to estimate the feasibility of a project. The future revenue of the project can be determined by this calculation in today’s currency.

Equation 2 NPV (Net present value) formula9.3.3. IRR – Internal rate of return IRR can be seen as more efficient version of return on investment (ROI). It’s essential to check the IRR throughout a venture to guarantee good returns are being realized. IRR can be viewed as an interest on your investment.

Equation 3 IRR (Internal rate of return) formula9.3.4. PR – Performance ratioThe performance ratio is the actual electricity produced over the theoretical estimation (Targeted).

The actual performance will be smaller due to several factors, such as weather. A low PR can means that there are technical problems that are preventing an asset from performing well.9.3.

4.1 Target YieldThe target yield can be defined as the hypothetical annual energy production, only taking into consideration the energy of the received light and the module’s nominal efficiency. 9.3.

4.2 Performance RatioThe Performance Ratio is the ratio between actual yield and the target yield: Equation 4 PR (Performance ratio) formula The performance ration or “Quality Factor”, is not related to the irradiation and therefore useful to compare systems. It consider all losses, such as losses from pre-conversion. It is advantageous to measure the performance ratio during the functioning of the system, as a drop could help identify reasons of yield losses.9.3.

4.3 Energy Output per AreaThe energy, E, delivered by a system with area A can be estimated from: Equation 5 (Energy Output per Area) formulaThe pre-conversion efficiency reflects the losses experienced before the beam hits the actual semiconductor material, provoked by the environment, such as shading and glass. The system efficiency can be defined as the electrical losses provoked by wiring, inverter and transformer. PA – Plant availabilityThe PA is a percentage that represent the time that the power plant is available to provide energy to the grid. It can be understood as the up-time of the plant. Little downtime often occur because solar PV plants has high percentage of availability.

The plant availability factor and the capacity factor are not the same. MTTR – Mean time to repairThe mean of time it takes for maintenance. It is calculated by dividing the total time the equipment is not working for maintenance (preventive and corrective) over the number of failure or breakdown event of plant. MTBF – Mean time between failuresMTBF is the mean of operating time that is the sum of the productive time and productions delays over the number of failure or breakdown event of plant.

MTBF represents the risk of failure of the plant. DCC – DC Capacity – Direct CurrentThe capacity is commonly describe the maximum energy that can be produced in direct current and the unit used for the calculation is the watts. ACC – AC Capacity- Alternating CurrentCompared to DC, the AC capacity is smaller because of the energy loss during the conversion from DC to AC. If we take in consideration both measurements together, an operator can observe an energy loss due to conversion of current through the inverter.

TT – Ticket Types %Tickets are produced from diverse problems from several sources. Reduce negative impact Following the Ticket Types as a rate helps with recognizing and keeping up control over issues by examination from every period. V – Variance between expected kWh and actual kWhForecasting energy generation as accurately as possible is essential for plant operations. Although there will always be variances between the expected kWh vs the actual kWh, monitoring the variance over a period of time could shine light on incorrect data or lead to other problems such as weather or hardware.9.3. PI – Peak IrradianceThe peak irradiance represent the maximum calculated solar irradiance.

Solar irradiance is the energy of the sunlight and can be measured by calculating the solar energy in watt per unit area, commonly a square meter (W/m2). PSH – Peak Solar HoursThe PSH should not be confused with total daylight hours. The difference between daylight hours and PSH is that PSH is defined in hours the duration of sunlight that exceeds 1 kW / m2.Although annual or quarterly targets are communicated to the O;M team, it is often difficult for team members to scale these targets into daily or hourly goals. KPIs provides that missing link where everyone on the team can gauge their efforts towards the target. When looking at performance measurements on a granular level, it allows for the company to measure the maintainers performance on a daily basis as well as increase the reactiveness and proactiveness towards the success of a high performing PV plant

3.The taken from ETH Zurich Research Report.

3.The framework of This Study:To analyze the security and performance implications of different consensus and network layer protocol author has prepared a quantitative framework to carry out this study. Author’s framework is a combination of two key elements.Figure:6 Components of Study Framework ** Pictures taken from ETH Zurich Research Report.They are (i) POW Blockchain and (ii) Security Model. A blackchin instance is a proof of work blockchain instantiated by consensus layer and network layer parameter. As discussed earlier a consensus mechanism is what all the blocks in the network follow to validate a transaction.

For example, Bitcoin uses a POW consensus layer mechanism which searches for a nonce value such that the current target value should be lesser than the hash value. In network layer two most important parameters for POW blockchain is Block size: This defines how many transactions can be put into each block. If the block size is bigger then block propagation speed decreases. On the other side, it increases the stale block rate.

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Information Propagation mechanism: This shows how information is delivered in peer to peer network. There are four types of standard information propagation mechanism:Send Headers: Peers can directly issue a send header to directly receive block headers from its peer in future.Unsolicited Block Push: A mechanism of broadcasting blocks by the miners without advertisement. Relay Networks: It enhances the synchronization of miners of the common pool of transaction. Hybrid Push/Advertisement System: A system which combines the use of push and advertisement system.

In the left-hand side, POW blockchain takes consensus and network parameters as input and gives output like block propagation time, throughput. To realistically capture the output of this POW based blockchain authors have put this blockchain on the simulators they have developed. These simulators take input parameter such as block interval, mining power as well as block size, propagation protocol, the location of miner’s etc.

Stale block rate is an important output from this POW based blockchain because it gives the efficiency of peer to peer connection of an honest network. This Stale block rate is taken as an input to Security model. This model also takes different security parameters as input such as adversarial mining power, mining cost, number of required confirmation. The main objective of this model is to holistically compare the security and performance of different POW blockchain with different parameters as input. This security model is based on Markov decision Process and provides an optimal adversarial strategy for double spending and selfish mining as an output.

3.1Security Model: Parameters for the Security Model:Stale Block Rate: Stale block rate captures information propagation mechanism.Mining Power: This is typically used in the study model to capture the fraction of the total mining power possessed by the adversary. Block Confirmation Number: Total number of blocks required to confirm a transaction.Impact of Eclipse Attack: This study model accounts for eclipse attack as well.

3.2 Markov Decision Process: (MDP)The right tool for a problem which deals with “states” and “discrete events” with a certain probability is a Markov Decision Process (MDP). MDPs are a mathematical model which decides the best policy means in what sequence the actions should be implemented to maximize a goal. An MDP model has multiple states and actions. Actions are the transitions between states. In MDP each transition can happen with some probability.

In this model, some actions might provide a reward or loss to occur. Figure 7 shows a graphical depiction of a Markov Decision Process. In the intended security and performance of POW study, MDP is based on four tuples. It is represented as follows M:=<S, A, P, R>. Where S represents state space, A is for representing actions, P is the stochastic transition matrix and R is the reward matrix.Figure 7: A graphical depiction of MDP with states s_0, s_1, S_2 and action a_0, a_1.The two rewards are -1 and +5. (Figure created by MistWiz on WikiCommons).

In this model an adversary can perform the below actions:Adopt: If an adversary thinks it can never win over an honest miner then it performs this action.Override: If adversaries chain is longer than the honest miner then it overrides the honest mining chain.Match: if the length of adversarial chain and honest chain are same then adversary perform this action.Wait: If an adversary has not yet found a block then it continues mining until it finds one.

Exit: This action is performed during the double-spending attack. Now state space S also has four-tuple namely length of honest chain, length of adversarial chain, blocks mined by eclipsed victim and fork. In the research, paper MDPs were built such a way which could provide justification when a rational attacker successfully double-spend or selfish mine.Selfish Mining vs Double Spending: Main goal in selfish mining is to increase the relative share of the adversarial block in the main chain.

In double spending, the adversary is more focused on earning maximum revenue. It is also found in the study that selfish mining is not always rational. Following an adversarial strategy for mining 1000 blocks with 30% hash power, an adversary can mine 209 blocks, but an honest miner can mine 300 blocks. In honest mining, an adversary can earn by mining a block. It also loses it’s reward if a block is adopted by the main chain. As the main chain poses maximum hash power, the probability is always high for an adversary to lose the competition. Eclipse Attack: In this type of attack attacker takes control of peer to peer network and obscure target node’s view of the blockchain. The researcher has found attacker can saturate the connection to a target victim.

It means all the connection to the victim would be bottlenecked and passed through attacker nodes so that it can manipulate the connections. Following eclipse attack scenarios are captured by our model: No Eclipse Attack: This study model captures this case. Isolate the Victim: This captures those cases where total mining power decreases. In return, it increases the fraction of mining power possessed by an adversary.Exploit the eclipsed victim: Adversary uses victims mining power to expand its own chain.3.3 Selfish Mining MDP: As discussed previously the main goal of a selfish miner is to increase the relative number of adversary block in the main chain. In this study, the model author has captured that by optimizing the relative revenue.

But there is a problem of applying single player MDP in this particular case because selfish miner deals with relative revenue. To overcome this problem the author has applied Sapirshtein el. Sapirshtein el proposes that an adversary with less than 33% of total hash power can make a profit from the network. This model captures various parameter such as block propagation time, block generation interval, block size and eclipse attack.3.3.

1 Optimal Strategies For Selfish Mining : Authors have used MDP solver for finite state space MDP’s. The output author received from the model is below. Here the author tries to find the impact of stale block rate on selfish mining. Figure 8: Selfish mining (Relative revenue vs Adversarial mining power)** Pictures taken from ETH Zurich Research Report. In Figure 8 author tries to understand how adversarial mining power influences the relative revenue of an attacker. For this he has put the adversarial mining power is in X-axis and relative revenue in the Y axis.

The graph is drawn for a stale block rate of 1% and 10%. It is seen from this diagram that relative revenue increase with the increase of adversarial mining power. An upper bound is also taken in this diagram to understand the cases when the relative revenue of a selfish miner maximized by overriding a block of an honest chain. Figure 8 shows the upper bound exceeded when network delays and parameters are captured.Figure 9: Relative revenue vs Stale rate** Pictures taken from ETH Zurich Research Report.

In Figure 9 author tries to understand the relationship between stale block rate and relative revenue. He compares relative revenue in Y axis with stale block rate in X-axis for a mining power ? of .1 and .3 respectively. This diagram suggests a nonlinear relationship between relative revenue and stale block rate.Author has also studied the impact of the eclipse attack in selfish mining. Figure 9 explains the relationship between eclipsed mining power ? and adversarial mining power ?.

In this study the cases considered are 1. where adversary uses victims mining power ?2. When an adversary uses honest miners blocks to advance its own chain.It is seen for higher ? values selfish mining capability also increases. In this graph, an exceptional case is also observed for ?=.3 and ?=.38. For this situation, it is more profitable for an adversary not to include some of the victim’s blocks.

Here victim’s blocks are accounted as a reward for the honest chain. This, in turn, reduces the block share of an adversary. Figure 10: Eclipsed mining power vs Adversarial mining power ** Pictures taken from ETH Zurich Research Report.3.

4 Double Spending MDP: As discussed earlier in the double-spending rational adversary tries to maximize its profit. In double spending, it is assumed that loss in operational cost is less because the adversary can earn some goods or money in exchange for a transaction. In double spending, exit state can only be reached if the length of an adversarial chain is at least a block longer than the honest chain (la ; lh ) after k block confirmation for an honest chain with 1?? mining power. This is described in the below table 2. A question can arise during this study as the adversary is rational it is hard to reach an exit state. But it is found that in exit state adversary can earn a reward of blocks.** Pictures taken from ETH Zurich Research Report.3.

4.1 Optimal Strategies for Double Spending: To create optimal strategies author has used the pymdtoolbox library and applied PolicyIteration algorithm. By this block confirmation value, k is received which is sufficient to make a safe transaction in presence of rational adversary in the network. To decide in a certain scenario if a rational adversary would do double spend or selfish mining, a minimum value of double spend vd must be determined. For achieving that author start with high double spending value so that exit state is reachable in optimal double spending strategy. Author has done this because the presence of exit state in policy ensures double spending is highly profitable. In this below Table -3 an example is shown for optimal strategy.Table 3: Optimal Strategies for double spending.

** Pictures taken from ETH Zurich Research Report.Here ? = 0.3,? = 0,rs = 0.41%,cm = ?,? = 0 and vd = 19.

5. Length of adversary chain is la, taken as rows. Length of honest chain is lh. Three values of each entry are irrelevant, relevant and active. * means unreachable and w, a, e represents wait, adopt and exit respectively. In this example cut off value for honest chain and adversarial is taken as 20.

This suggests both this chain length cannot be greater than the defined cut-off value. So what is the main goal of this analysis? The attacker must overcome a threshold if it wants to double spend with profit for a fixed number of confirmed block k. In the other cases it is more profitable to do honest mining. This result is illustrated in Figure 10. The x-axis shows how the adversarial mining power is influencing the threshold.

Different values of k (the desired number of confirmations) lead to different curves.The y-axis in Figure 10 shows how many successive blocks are needed to be mined before a double spending attack to be successful. For an adversary, around 30% mining power needs 6 block confirmation and the expected number of blocks is roughly 100.An adversary with mining power of more than .25 needed less than 1000 blocks to successfully carry out double-spending attack.

Figure:10 Expected blocks for double spending rs = 0.41%, ? = 0, cm = ? and ? = 0.** Pictures taken from ETH Zurich Research Report.

Here stale block rate is represented by rs. ?, cm represents the propagation parameter and maximum mining costs respectively.Impact of Propagation Parameter: Propagation parameter signifies the connectivity efficiency in an adversarial chain.

It suggests if connectivity increases in the adversarial network then adversarial mining power also increases. Author has put adversarial mining power in the X-axis and shown double spending transaction should have a threshold value. If transaction value is more than the threshold value, then only double spending is profitable. It can also be seen from Figure 11 that higher the propagation parameter ? lower the transaction value an adversary expects to double spend.Figure:11 Impact of propagation parameter ? with respect to double spending transaction value.

** Pictures taken from ETH Zurich Research Report.In this graph double spending value(vd) is taken in Y-axis and adversarial mining power(?) in the X-axis. If ? increase vd decreases.

Impact of mining costs: From the study, it is found that mining cost has a negligible impact on adversarial strategy. It is shown by the below Figure 12.Figure 12: Impact of mining cost.** Pictures taken from ETH Zurich Research Report.Value of double spend (Vd) is in the Y-axis and adversarial mining power(?) in the X-axis. rs = 0.

41%, ? = 0, ? = 0 Cm represents maximum mining cost ?vd is the difference in costs.Impact of Stale Block Rate: In Figure 13 impact of stale block rate is explained for double spending. This below experiment is carried out for a mining power of .

1 and .3 respectively. It can be seen if stale block rate grows the value of double spend decreases. Author has found double spending value of an adversary decreases from 9.

2 to 6.4 block reward with mining power .3 and a stale block rate of 10% and 20 %. Figure:13 Impact of stale block rate.** Pictures taken from ETH Zurich Research Report.Here Vd is the value of double spend in the Y-axis, Stale block rate in X-axis and adversarial mining power is represented by ?.Impact of Eclipse Attack: The impact of eclipse attack is represented by Figure 14.

It is assumed that an adversary attacks an honest block with ? eclipsed mining power. It can be observed eclipsed mining power increases with the increase of adversarial mining power. So eclipse attack is beneficial for an adversary. For example, an adversary with an adversary with ?=.

025 and ? =.1 reduces the double spending value (vd) from 880 block reward to .75 block.Figure 14: Full eclipse attack ** Pictures taken from ETH Zurich Research Report.In Figure 14 eclipse mining power ? is in Y axis and adversarial mining power is in X axis and , rs = 0.

41%, ? = 0 and cm = 0.Bitcoin vs Ethereum: Figure 15 shows the reward required for a double spending attack to make a profit. The y-axes show the reward required from fraudulent behavior as multiples of the block reward, i.e. multiples of the reward of non-fraudulent behavior. The figure also contrasts between Ethereum and Bitcoin. As a consensus algorithm both this chain uses proof of work, but the key difference is the block time.

i.e. the duration between the generation of two blocks.

Stale block rate increases because of shorter block times. It means the time gap between finding two blocks is much shorter in Ethereum. Thus, participant blocks more often return finding the same block which increases the stale block rate in the network.Below points are observed by the author in the study.

First: Figure 15 shows 6 Bitcoin block confirmation is more resilient to double spending than that of 12 Ethereum block.Second: Ethereum’s double spending resilience is better only for an adversary with less than 11% hash power.Third: If block reward goes up blockchain is more resilient to double spending attack. Figure 15: Double spending resistance of Ethereum vs Bitcoin** Pictures taken from ETH Zurich Research Report.

Block reward is in the Y-axis and Adversarial mining power in the X-axis. Ethereum (k ?{6,12}) vs. Bitcoin (k = 6).Author has also tried to compare both this block chains by equalling their stale block rate. It is observed that Ethereum’s security is lower in caparison to bitcoin Figure 16 explains the following.Figure 16: Comparison between Ethereum and Bitcoin.** Pictures taken from ETH Zurich Research Report.

Value of double spend is on the Y-axis and Adversarial mining power is in the X-axis. Here k is 6, rs = 6.8% and their difference is ?vd.


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