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  • Hangseng Che added an answer in MPPT:
    How can the reactive power be controlled in PV systems during MPPT?

    The active power can be controlled in many ways for MPPT such as control of DC output of the PV terminal voltage, I would like to control the injected reactive power to the grid at the same time.

    Hangseng Che · University of Malaya

    Based on your question, I am not sure if you have a full picture of the PV converter system. So, I would just like to raise a few important points with regards to your question of MPPT and reactive power injection.

    1) PV is a DC power source. In this case, there is no reactive power associated with PV itself. When a PV is connected to a load via a dc/dc converter, the voltage and current of the PV can be varied by the converter, such that active power can be control. The ideal case will be to extract the maximum active power from the case, and such control will be known as MPPT. A dc/dc converter cannot inject or absorb any reactive power.

    2) Reactive power is a concept unique in AC power system. When an inverter is used, the reactive power can be injected into the grid by varying the magnitude and angle of the inverter voltage. If voltage-oriented control (VOC) method is used to control the inverter, reactive power can be controlled by controlling the d-axis current. 

    3) in order to perform MPPT and Q injection at the same time, an inverter must be used. Two common structures will be possible: single stage power conversion or two stage power conversion:

    A) In single stage power conversion, the PV is connected directly to the inverter without any dc/dc converter (hence termed single stage). In the case if VOC is used for the inverter control, q-axis current will be controlled to vary the active power, hence to achieve MPPT. At the same time, d-axis current will be used to control the reactive power injection. Take note that in this structure, the dc-link of the inverter is connected directly to the PV terminals, and will fluctuate with the PV voltage. 

    B) In a two stage system, PV panel is connected first to a dc/dc converter, then to an inverter. The dc/dc converter will perform the MPPT task to extract maximum active power from the PV. The inverter on the other hand still control the active and reactive power. However, in this case, the inverter is not doing the MPPT, but merely injecting active power to the grid (by controlling q-axis current) to maintain a fixed dc-link voltage (dc-link voltage control). At the same time, d-axis current is controlled to vary the reactive power. In this structure, the dc-link voltage of the inverter is maintained at a constant value all the time.

  • Ajay Singh asked a question in Petrology:
    Anyone can tell me how to use Petrolog software for Olivine geothermometer ?

    I have analysed olivene for major oxides and now I am trying to find out  temperature of melt. 

  • Chen tiam foo added an answer in Plasma Chemistry:
    How can increase the quantity of monomer flow into the reactor chamber and reduce the leakage of the piping connection at the monomer inlet?

    The monomer I used was heptylamine.

    I did for warming up the monomer by immersed the bottom flask in the water bath. I used the heating tape to warmed the SS piping as well and the SS piping had the heptylamine odor strongly.

    However, it showed air plasma reaction (pink color) once turned on the RF power. Heptylamine seem doesn't flow into the chamber because it doesn't have any odour of Heptylamine inside the chamber.

    How can I improve the system to gain more monomer flow into the chamber? Any methods to tighten the bottom flask to holds the stainless piping?(Figure 1)

    Chen tiam foo · National University of Malaysia

    Dear Anton Manakhov,

    Thanks for your advice.

    Can you share again for the link about the calculation of flowrate?  

    I couldn't find the link you mention in above.

    Hope to hear from you. Thank.



  • Francesco Maoli added an answer in T4:
    What could be the reason for ligation not working with Insert that has new restriction sites placed on it via PCR?

    I have a vector with the restriction sites PAC1/SGS1 that I plan to use in order to ligate my insert which does not have these sites on it. 

    In order to make the sites I used two primers (one forward, one reverse) at 10uM concentration that contain the beginning and end of the sequence of my insert with the PAC1/SGS1 restriction sites added on the ends. A few nucleotides were added past the restriction sites in each sample which was suggested by my professor who got results using this procedure with the same sequence. However he was not placing the PAC1/SGS1 restrictions sites specifically.

    The PCR samples, for the insert, have a total volume of 25uL and used the following program setup:

    1. 95C 2:00min
    2. 95C 0:30min
    3. 56.7C 0:30min
    4. 72C 2:00min
    5. GOTO step 2, 20 times
    6. 72C 3:00min
    7. 4C (Infinite hold until samples can be retrieved)

    I have confirmed through electro-gel phoresis & gel purification that I retrieve ample PCR samples at the correct band size. Agarose Gel was 1% in 1X TAE solution and ran 100V constant for 45min.

    Both the vector and insert, with new restriction sites form PCR, were then digested using PAC1/SGS1 in a 20uL volume and incubated at 37C for 20min using a warm water bath. Reaction mix is as detailed below:

    • 1uL of enzyme (one with both enzymes, another with 1 enzyme)
    • 2uL of Green Buffer
    • 1ug of DNA
    • ddH2O to fill to volume requirements

    I confirmed using the same gel procedure as above that the desired bands had been obtained and extracted/purified the samples from the gel for use in the ligation.
    The ligation uses T4 Ligase and had the following reagents:
    50ng Vector DNA

    • 1:1, 1:3, 1:5, 1:7.5, & 1:10 Insert DNA (Respective to Vector amount)
    • 2uL 10X T4 DNA Ligase Buffer
    • 1 Weiss U(5 Weiss U/uL stock) T4 DNA Ligase
    • ddH2O to fill to total volume if needed
    1. Incubated for 10min. at 22C
    2. Used 5uL of micture for transformation of 50uL XL-10 cells
    3. Plated onto LB w/ AMP Agar plates

    I observed colonies in my positive control and no colonies in my negative control. I also observed no colonies in my other samples except for a single colony in the 1:3 and two colonies in the 1:5. I retrieved some samples of the colonies for a plasmid prep:

    1. 5mL LB w/ 10uL AMP
    2. One negative control w/ no bacteria
    3. Put a pipette tip w/ XL-10 samples into media
    4. Samples all placed in incubator at 37C shaking at 200rpm overnight

    I retrieved the overnight inoculations and used a plasmid prep kit in order to retrieve DNA sample and measured the samples on a nano-drop to determine the purity. The absorption rates came out fine.

    The samples were then digested with PAC1/SGS1 using the same procedure as above.

    The digest samples where then run through a 1% Agarose Gel in 1XTAE solution set to 100V constant for 45min. A sample of digested vector/insert were also run in the gel in order to compare band size to the ligated samples.

    The gels have always resulted in a recombination that seems to be a common way for the XL-10 cells to form resistance to AMP and proliferate. So far I have not seen ligation of my insert/vector.

    I sent the insert sample to be sequenced however the primers were not able to run far along enough to determine if the primers placed the proper restriction sites on the insert.

    I am currently going to try another ligation which I will then digest again to determine if the ligation is working properly. I am also creating new competent cells just in-case the ones I am working with are not able to take up the plasmid due to loss in competency. I have also ordered new primers with no extra nucleotides at the end to see if that may also be an issue.

    I have a feeling that the problem may be the extra nucleotides although I don't know why it would've worked for my professor who carried out a successful ligation before me doing the same thing. The plasmid I am using to retrieve the insert is actually from his ligation.

    Might there be something I am missing here? Could it really be as simple as removing the extra nucleotides at the end of the primers or is there a problem with my methods?

    Francesco Maoli · University of South Carolina

    What I am trying now is some different primers with poly A tails as well as 8-12nt attached beyond the restriction site on the 5' end. I made sure to leave at least 15nt on the 3' end to attach to the target sequence.

    Using this site https://www.embl.de/pepcore/pepcore_services/cloning/pcr_strategy/primer_design/ I was able to determine this is the best course of action and so the truncated primers I created with no extra nt on the 5' end are not useful to the experiment.

    Also I am using G. FD Buffer which according to the thermoscientific website is 100% efficiency, sorry for that confusion.

    I will be checking the ligation step soon now that I have the new primers, thank you for all the help.

  • Arezoo sh. dadkhah asked a question in Liquid Crystals:
    Polyphenylene oxide is not a liquid crystal polymer, but its structure similar to LCPs. why?

    PPO isnt a LCP. 

  • Perps Idehen added an answer in Soxhlet Extraction:
    What is the typical amount of solvent that a GC can analyse at once?Also,Using Soxhlet extraction to extract the hydrocarbons first, how much samples?

    im extracting hydrocarbons from soil using soxhlet extraction, after which, will analyse with GC-FID.

    Perps Idehen · The University of Manchester

    Hi Pramote, So what is the conc that elutes?

  • Amr M. Sadek added an answer in Gamma Irradiation:
    What are the best approach to analyze a glow curve?

    Figure shows a glow curve of a material after gamma irradiation. According to shifts of Tm with increasing dose, one can predict that the glow curve does not obey first order of kinetics. Tm-Tstop method was applied with heating rate of 5K/s to distinguish  peaks positions, approximately. But  as the samples is heated towards the higher Tstop, the Tm shifts continuously towards the higher temperatures. This behavior is known to be a strong indication of the presence of overlapping TL peaks, possibly forming a continuum of closely located energy states.

    Which one of practical methods can be applied to this kind of glow curve?

    If anyone knows, please also recommend a simple and user friendly software for calculating glow curve peak parameters?

    Thanks for your attentions

    Amr M. Sadek · National Institute of Standards (Egypt)

    Perhaps the non-universal agreement in the values of the kinetic parameters is due to the different algorithms utilized in the analysis procedures. Moreover, the limitations of the TL models restricts the usage of these models in analyzing the TL glow-curves. Most  of the TL expressions employed in the deconvolution is derived based, directly or non-directly, on the OTOR model. While, it is very rare to find a glow-curve that is described by single glow-peak. In other words, is it possible to assume that the glow-curve signal is the results of the super positions of its components? We have a lot of evidence that this assumption does not hold in many cases.

    However, I do not suggest to stop analyzing the glow-curve. Because, we will be, perhaps, the only community that does not analyze their spectrum. Instead, I see that we shall keep going in developing the TL models and the analysis method till we reach the optimum model and optimum method to analyze and extract all the information from the glow-curve with quite accepted accuracy and precision.

  • Leona M. Ungerer added an answer in E-Portfolio:
    Where can I find a literature review on e-portfolio use in higher and/or vocational education?

    I'm also looking for studies, which focussed the effect of e-portfolio use on the developent of critical thinking or meta-cognitive skills.

    Leona M. Ungerer · University of South Africa

    Dear Martina, I am particularly enthusiastic about the use of e-portfolios as assessment tools in a higher education environmnent. I did a quick search about your topics. Please see the embedded links.

  • What were the theoretical issues when Marx and Marxian economists criticized John Stuart Mill as vulgarizer of classical system?

    What is the real content of vulgarization, when they claim that J.S. Mill vulgarized Ricardo's teachings? In what sense is he blamed to have opened the way to neoclassical economics?

    Béla Balassa once wrote in his paper "Karl Marx and John Stuart Mill" (Weltwirtschaftliches Archiv, Bd. 83, (1959), pp. 147-165):

    •  Marx's treatment of John Stuart Mill is one of the great puzzles of history of economic thought. Reading Marx (and his followers) one gets the impression that Mill was an insignificant figure whose writings exemplify the "decline" of Ricardian economics. Whenever Marx mentions Mill's name (which does not happen very frequently) he v\never forgets to add some derogatory comment. (p.147)

    In another paper (John Stuart Mill and the Law of Markets, The Quarterly Journal of Economics Vol. 73, No. 2 (May, 1959), pp. 263-274) he wrote:

    • For present-day economists [Mill] represents a "half-way house" between Ricardo and Marshall; for Marxists he is the apologist personified, sharing the responsibility with many others for the "decline" of Ricardian economics.(p.263)

    I wonder why John Stuart Mill was so undully ill-treated by Marx and Marxain economists.

    Yoshinori Shiozawa · Osaka City University

    All information combined, is it possible that Marx denounced John Stuart Mill, not by his theory but his ambiguous political stand?  

  • Erwin Vermeij added an answer in Steel:
    Which kind of steel is this?

    Composition: 0.1% Cr, 0.5% Mn, 0.1% Ni, 0.2%Cu. Si and C unknown.

    See also the ECC-image below

    Erwin Vermeij · Netherlands Forensic Institute

    It is definitely not SS. I thought it was some kind of tempered martensite, but steel is not my field of expertise.

  • Jarina De Deckere asked a question in Speaking:
    How can you calculate the floor and ceiling effect?

    I would like to calculate if the measurements I used have a floor or ceiling effect. When can we decide if there is a floor or ceiling effect: from 70%, 75%, 80%?

  • Does a gravitation wave change propagation direction passing near a massive gravitation center (star)?

    As we know light wave passing near a gravitation center (star) changes its propagation direction. Is this true for a gravitation wave? 

  • Sara Lebid asked a question in Desalination:
    Why not build in complex Desalination plans/Saltworks ?

    The impact of the desalination plants rejections on seawater has not be fully considered for different reasons. However I suppose that increasing the concentration of salts in a given location constitutes a major threat to both flora and fauna of this place, resulting in a scenario of the Dead Sea. I say just in a little spot.
    So why not achieve, right next to the desalination plants, sea salt recovery stations for a domestic use.

  • How can I approach an optimization problem, where there are no mathematical expression as such that connects the variables and the output?

    In the absence of mathematical expression, how can i optimize a problem with minimum effort ? Which technique to use ? What will be the approach like ?

    Will DOE ( Design Of Experiments), may be taguchi method, be helpful ? If yes how ?

    Thanks !


    Rajesh Alayil · Indian Institute of Technology Madras

    @ Farhad, thanks for the info.

    I will go through it. Appreciate your help.

  • xu ye asked a question in Social Psychology:
    Can someone provide recent information about the reason of cheated ?

    Actually,I am doing research about social psychology,I want to know why the old people get cheated easily in China. I need some news to give me some ideas.  Hope to get some answer very soon...   Best wishes  

  • Elmer Rich added an answer in Cognitive Systems:
    Is Chalmers' so-called "hard problem" in consciousness real?

    In his 2014 book "Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts" Stanislas Dehaene wrote "Chalmers, a philosopher of the University of Arizona, is famous for introducing a distinction between the easy and the hard problems. The easy problem of consciousness, he argues, consists in explaining the many functions of the brain: how do we recognize a face, a word, or a landscape? How do we extract information form the senses and use it to guide our behavior? How do we generate sentences to describe what we feel?

    “Although all these questions are associated with consciousness,” Chalmers argues, “they all concern the objective mechanisms of the cognitive system, and consequently, we have every reason to expect that continued work in cognitive psychology and neuroscience will answer them. By contrast the hard problem is the “question of how physical processes in the brain give rise to subjective experience … the way things feel for the subject. When we see for example, we experience visual sensations, such as that of vivid blue. Or think of the ineffable sound of a distant oboe, the agony of an intense pain, the sparkle of happiness or the meditative quality of a moment lost in thought … It is these phenomena that poses the real mystery of the mind”."

    Stanislas Dehaene's opinion is "that Chalmers swapped the labels: it is the “easy” problem that is hard, while the “hard” problem just seems hard because it engages ill-defined intuitions. Once our intuition is educated by cognitive neuroscience and computer simulations, Chalmers’ “hard problem” will evaporate".

    Personally, I agree with Stanislas Dehaene's opinion.

    Elmer Rich · Rich & Company

    "hypothesis of a thalamic consciousness 'center'?" - but only in humans?  Gee, how did that evolve?  Magic?

  • Why electromagnetic field propagates via void vacuum?

    Water wave propagates via the water. Sound wave propagates via matters in solid, liquid or gas states. It is pretty logical.

    "Electromagnetic field propagates via void vacuum" is commonly accepted. In this case, void vacuum is media for light. If vacuum is true void, why it can be a media for carrying electromagnetic wave? Can you provide a logical answer?

    I was waiting for your post....You seem keen at pointing to faults.

    Actually what I call particles is nothing more than the old material point of mechanics : a material body with an internal structure that one can neglect at the scale of the study (it can be a solar system or an atom). It is matter,and it occupies a geometric point.

    You were taught that photons are particles...Well, I did not notice that you were so attached to academic views. Photons have been invented to account for bizarre phenomena : they seem to be located at one point, travel, have a momentum...This does not mean that they are particles, and to my knowledge bosons have some particles properties but are distinct from fermions. So we have to see how we can represent the phenomena, and link them to specific objects of physics.

    When a particle is accelerated in our frame they radiate (the field changes), this does not mean that it emits a photon. In the bremstrahlung effect (that is a brutal change of the field) actually the photon is detected when it interfers with matter, and we can conceive that there is a distinct discontinuous process : it is detected because the variation of the field is large, with respect to the monochromatc field. The photon is a discontinuity of the field, so it propagates as the field (for the EM field at the speed of light), and its propagation is not related to the motion of the particle.

  • Ian Kennedy added an answer in Human Resources:
    What is the best strategy for dealing with bad bosses?
    I advise coworkers and clients regarding career issues, how to deal with bad bosses, self-directed career planning, hard skill development and so forth. Usually the answers are linked to organizational behavior, because my goal is to assist with career advancement. I would like to draw upon the HR intelligence of RG. Please, let me know your thoughts.
    Ian Kennedy · Independent Researcher

    @Lola-Peach: Excellent reply!

    Is a bad boss one who e.g., conforms to the institutional mentality of only reporting good news upwards?

  • Remi Cornwall added an answer in Genius:
    What is the BJT emitter voltage Ve, when the emitter is floating?

    Dear Genius Ladies and Gentlemen,

    Suppose two circuits of bjt connections (e.g. pnp, see attached figure below):

    a) open base
    The base is floating (no external leakage current).
    The supply current is Iceo.
    The base voltage Vb is settled to one diode below VDD,
    let say Vb~2.5V at VDD=3V.

    b) open emitter
    Now, the emitter is floating (no external leakage current).
    The supply current is Icbo:

    The question is:
    To which voltage Ve is settled in the circuit b)?
    Is it equal to VDD, to GND, or to what, and why? 

  • Abbas Cheddad added an answer in Image Processing:
    How to restore a thinned image?

    Hello Every one,

    I have obtained the desired thinned image by using matlab built in function. After removing branch points, i got several segments with out any branch. Now i want to restore the refined thinned image into its original shape. 

    But i can not find any help regarding this.

    i have tried to thicken it by again using matlab built in utility but the result is not what i desire. Instead it is a chaos.

    So can any one guide me how can i restore thinned image?

    Thank you.

    Abbas Cheddad · Karolinska Institutet

    You are welcome Jim!

  • Raj Kumar added an answer in XRD Analysis:
    How can I get the percent of crystallinity from Powder XRD data?
    I have done XRD and having data file and drawn xrd patterns using Powder X software. I need % crystallinity.
    Raj Kumar · Indian Institute of Technology Mandi

    u calculate the area using origin or if there is any characteristic peak for ur samples then calculated the area of that peak for all sample and with respect raw sample calculate the %crystallinity assuming as the raw has 100 % crystalline, or take the intensity of peak of characteristic for samples based on intensity also you can calculated the % crystallinity.

  • Salam Abbas asked a question in ArcSWAT:
    Differences between inlet and point source in SWAT ?


    can anyone tell me the difference between added inlet or point source in watershed delineation in ArcSWAT hydrological modelling ?

    Many thanks in advance,

  • Raghuram Kandimalla added an answer in HPLC-UV:
    Are you familiar with quantitative analysis of flavanoids in medicinal plants using HPLC and UV/VIS?

    Can anyone help me with list of methods for quantitative analysis of flavanoids in medicinal plants using HPLC and UV/VIS?

    Raghuram Kandimalla · Institute of Advanced Study in Science and Technology

    Hydro alcoholic extract is preferable, This might be different for plant to plant but try with Water and Ethanol in 1:1 ratio to extract the active principles. 

  • Can we use the perceived behavioral control as the mediator variable between attitude and intention?

    Can we use and focus the perceived behavioral control as the mediator variable between attitude and intention?

    Based on the theory of planned behavior, perceived behavioral control and attitude are used as the predictors of intention. Even though, some scholars pointed that, perceived behavioral control is considered as the unique and better predictor of Behavior directly without having intention. These issues make me raise the question in my research mind like

    Can we use and focus the perceived behavioral control as the powerful mediator variable between attitude and intention?

    Attitude, it is the evaluation towards subject or object or issues (may be favorable or unfavorable). Beyond attitude, perceived behavioral control is taken the important place in the creation of intention, which refers to the extent to which individuals believe that their actions make a different in solving problem.  These facts make me think that, perceived behavioral control might give the better pathway to create the intention from the attitude (Attitude – Perceived behavioral control- intention).   Or, other way, PBC might bridge the gap between attitude and intention successfully.

    Please guide me perfectly with recent empirical findings!

  • Hanno Krieger added an answer in Productivity:
    What is the impact of overtime and long working hours on an employee?

    To meet deadlines, some times one is forced for work on long hours every day.  Some people work overtime regularly, and it helps them to learn some extra income.

    If working overtime or working for long hours on a regular basis, what may be their impact on an employee?

    Has any study been done on this?! Your views are welcome!

    Best wishes, Sundar

    Hanno Krieger · retired from Justus-Liebig-Universität Gießen

     lot of errors by the workers, descending quality of the products and all the already mentioned health problems.

  • What is the management for teenager sufferring recent onset transient concomitant exotropia ?

    What is the management for teenager sufferring recent onset transient concomitant exotropia ?

    14  y.o. girl's parents revealed  2 yeras ago strabismus in her dauther- transient alternating exodeviation dominantly in her left eye, more prominent when girl is tired.

    VA 1.0

    Concomitant strabismius 10-15 degree . Anterior and posterior without abnormality. The girl has headaches without localization Neurologist reject any pathology.

    What is your opinion ?

  • Platinum resistance in ovarian cancer due to increased Nucleotide excision repair?

    I am reading about platinum resistance in ovarian cancer. The papers state that increased Nucleotide excision repair may cause platinum resistance but I am not able to understand how. The platinum based chemotherapy works by the platinum binding to DNA, creating crosslinks which are recognised by DNA binding proteins which then recruits DNA repair pathway and clear any damage . The NER helps in doing this so how can increased NER lead to resistance to the platinum based drug???

    Thanks beforehand :)

    Victor C. Kok · Asia University

    Hi Vrushali,

    To my understanding, NER will be activated after single-strand break of DNA induced by platinum in the setting of acquired resistance; if repair is unsuccessful, the cancer cells will enter apoptosis. Nevertheless, if the repair is successful, then the cancer cells survive. So when increased NER such as in the setting of ERCC1 hyper-expression or polymorphism state, more cancer cells will survive through an effective repair from the platinum adducts single strand break.

  • Basant Subba asked a question in QualNet Simulator:
    Is there any site that provides a free Linux version of Qualnet Simulator?

    Qualnet is an advance version of well known GloSim simulator used for simulating many wireless network protocols. I googled and searched extensively for a free version but couldn't find one. Can anyone provide me with a link from where I can download it.

  • Christoph Wolf asked a question in Chem:
    CH3NH3PbBr3 first principles calculation - what is a good starting configuration?

    Dear Colleagues!

    Recently I have been trying to calculate the electronic band structure of a organic-inorganic lead halide perovskite structure, namely CH3NH3PbBr3.

    I am not an expert in band structure calculation and I only worked with Wien2k years ago. Unfortunately I don't have access to that license anymore and I am now learning Quantum Espresso.

    I tried following the work of Y.H. Chang (Journal of the Korean Physical Society, Vol 44, No 4, April 2004, pp 889~893) and a more recent one by Mosconi et al. (Phys Chem Chem Phys 2014, 16. 16137), however when I am trying to structurally optimize my starting position the calculation goes haywire and all my hydrogen atoms vanish and the calculation runs until nstep.I tried aligning the C-N bond of  H3C--NH3 along the cubes basic (100 direction) axis, and alongside the diagonal (111 direction), but this does not help. Mosconi gives a different starting configuration but I did not figure out how to use it properly (I am really new to this kind of material)!

    If someone could help me with a reliable starting position that would extremely glad (if this results in anything useful proper credit will be, of course, given, but so far I am mainly playing around out of curiosity).

    For the MD calculation I used the example03 that comes with QE.



  • Farhad Tari added an answer in Optimization Methods:
    Does anyone know how to select the initial guess for the steepest descent method loop to arrive the minimal point?

    Hi there,

    I was looking for a publicly available code for steepest descent method for minimization and I came up the web site whose address is 

    http://www.math.colostate.edu/~gerhard/classes/331/lab/newton2d.html .

    I am running the same code structure by implementing the function,


    which is known as Rosenbrock’s “banana” function. 

    I removed the "&n<100" part in "while" line to be able to still work it until the code reaches the condition and I am trying to hit the optimum point by changing initial guess, "a" and error but in my every attempt, gradient values and others  go to infinity after a few iterations. 

    So, I am gently asking you if you can guide me. Thanks.

    The codes that I implemented is here.


    n = 0; % initialize iteration counter
    eps = 1; % initialize error
    a = 0.09; % set iteration parameter

    x1 = -.5; % first component of the 2D space
    x2 = -.5; % second component of the 2D space
    x = [x1;x2]; % set starting value
    % Computation loop
    while eps>1e-10
    gradf=[400*(x(1))^3 - 400*x1*x2 + 2*x1-2 ; -200*(x(1))^2 + 200*x(2)] % gradf(x)
    eps=abs(gradf(1))+abs(gradf(2)); % error
    x_iterated=x-a*gradf; % iterate
    x=x_iterated; % update x
    n=n+1 % counter+1

    Farhad Tari · Sharif University of Technology

    If you have an initial state of the problem, the best initial point is the variable values of the current state. otherwise it is better to find it by trail and error. That is, by selecting several initial solution and seeing which one performs better. Otherwise there may not be a general rule for finding the initial guess.