ResearchGate Q&A lets scientists and researchers exchange questions and answers relating to their research expertise, including areas such as techniques and methodologies.
Browse by research topic to find out what others in your field are discussing.
- 6I have a dataset of 1444 images.How to divide the dataset of training & testing set.Suggest me the count of images in training set and in testing set?
Data set of 1444 images = training set + testing set.
suggest me the number of training images and number of testing images.
Generally, I work with 50/50 and 75/25 ...
I believe that are good choise .....Following
- 3Do you know of any package/algorithm/referenced threshold for item selection (for "every" test taker, not per test taker) based on IRT estimates?
Context : Performance test, dichotomous, one-dimensional (at least in theory), at least 3PL (variable pseudo-guessing). Theta is assumed normal. But I'm also interested in answers in general in IRT.
Problem : It seems to me that EFA factor loadings provide clear guidelines to rank/select a subset of items from a pool (with referenced rules of thumb, etc.) when one does not have any prior info/assumption of theta (aka for "all" test-takers).
On the other hand, IRT is, in my opinion, a much more accurate representation of the psychological situation that underlies test situations, but it seems to me that there are a variety (especially in IRT-3PL / 4PL) of parameters to take into account all at once to select items, at least without any prior estimation of theta.
So I'm wondering if you knew of any guidelines/packages that can be referenced as a clear basis (meaning, not eye-balling item response functions) for item selection there. At this stage I'm thinking of a very non-parsimonious solution, like generating all item subsets possible (I'd get a LOT of models, but why not) -> fit IRT model -> compute marginal reliability (and/or...Information, of why not CFI, RMSEA, etc.) for thetas ranging between -3SD and +3SD -> Rank the subsets by descending marginal reliability (but I'm afraid it would bias towards more items, so I'd have to weight per item count maybe).
Anyway, you get the idea. Any known referenced procedures/packages?
What often happens is that the IRT parameters, the proportion correct, and DIF statistics are used on field items and all taken into account when constructing the final test taking into account what the items are one (since often field tests will have several items for one content area but only a few for others). So, these are "eye-balling" them, but they start with criterion from psychometricians but the decisions are often by the test developers. This is for large scale tests.
As far as packages, I'm not sure exactly what you want (if it is just choose your thresholds for various statistics, that could be coded fairly easily), but a big list of IRT packages is on:
- 3How long is sectioned brain tissue good for something?
Bird brains cryosectioned and kept in cryoprotectant in a -20C freezer for ~5 years. It was preserved with acrolein and some sections were used for IHC right away. What can I do with the rest of it, besides toss it?
Can proteomics be done? Cresyl violet anatomical staining?
Thank you both for your input! It sounds like there is just too much uncertainty to make it worth while to stain for anything. The quality is likely far below most tissues kept in a lab setting. The sections have been floating in liquid cryoprotectant and exposed to varying temperatures over the years. The steps needed to validate any staining would be out of my reach at the moment too since I don't have freshly preserved tissues. They were left over from my dissertation experiments. My options were to junk them before I left or take them with me and hope for the best. I've carried the weight long enough, I guess! I just wanted to hear from others with more experience in this area that there was NOT a sure thing I was walking away from. Thank you for taking the time to respond.Following
- 4Image enhancement using harmony search algorithm?
I was applied an evolutionary algorithm (Harmony search algorithm) for image enhancement (edge preserving), and there are three criteria for evaluating the results which are (number of edges, summation of intensity around the edge and entropy) I got all of them criteria are max but the output image has many noise (not smooth) please give me your opinon if there any method to get smooth output
I apply Harmony Search in the image restoration context. Follow the paper:
- 5Can systematic lupus erythromatosus (SLE) is curable?? if yes then whats parameters??
Dear Sir/mam... I want to research on SLE it epidemiology pathology treatment about all its aspects and extract a right treatment for this.
thanks to all ov youFollowing
- 9How to apply deep learning on image classes?
I have two image classes, one is positive class images and other is negative class images. Positive class is the image regions of target object, whereas negative class is non target images. As a result i want in test image target region should be detected? is it possible?
I want to apply deep learning algorithm using matlab. I don' know much about deep learning? which algorithm to use? how to implement?
Can any one will help?
Do you know Caffe?
Caffe is very powerfull framework, however we need map the class label to natural number (> 0).
- 4During Machine learning for object Detection, How can I simulate the effect of different day illumination on my training dataset?
I have my vehicle training dataset, but in real situation the vehicles are subjected to different intensity of light , how can I simulate or remove the effect of light?
You have three possibilities, they are:
1) Use HSV representation and use the Hue
2) Train the machine learning algortihm with different illumination scenario
3) Normalize/Equalize the imageFollowing
- 9I-type granite and S-type granite , how can we distinguish in these granite.
I-type granite formed by the igneous and S-type granite formed by melting of metasedimentary rocks. if they are generated from different continental settings and from different magma so can we see any difference in behavior in element in these two types of rocks.
For the petrolographic observation:
S-type granites have Al-rich minerals such as garnet, cordierite, muscovite and Al-rich biotite, while I-type granites have hornblend and biotite.
Information on the paper, Chappell and White (1992), would be useful for you for their geochemical characteristics.Following
- 4Help in feature/attribute selection?
I am working on machine learning for Bonet detection, I have a dataset, the problem I am facing is the attribute/feature selection to use in weka. Also how can I convert PCAP file into ARFF format ?
In this paper i present some comparison between methods of feature selection. I believe that can be useful...
- NewWhat is the relationship between communities of practice and communities of inquiry? Can they co-exist?
I am researching the formation of communities of learning and need clarification as I can't find much literature on this. Thanks.Following
- 9What are the tools are available for pattern recognition?
I am working on biometric with MATLAB. It is really hard for me. So what are the tools are available for pattern recognition?
I suggest the scikit in Python.... is very easy and powerful framework.
- 1AIC discordance in mixed effects modeling: which to prioritize?
I'd like to ask about mixed effects models. I'm modeling based on the significance of the likelihood ratio, within R. As a primary criterion I use the p-significance of the model comparison (anova()). Yet, with any significant comparison, I'll also check the AIC difference separately. As I understand it, this last check helps to avoid overfitting. For a couple of times already, I have encountered the infamous discordance between the two, with a model comparison that is significant and then a general AIC difference that falls below 2 points (see image attached).
So, I wonder how come that the model comparison doesn't pick up the overfitting... That is, do I definitely have to lighten up the model?
Thanks a lot for any advice
There are lots of different ways to compare models (e.g., cross validation). From your variable names I assume this is neuroscience and you have a large number of channels and many repeated measures. You will often get "significance" for these when the effect size is small. Can you give a few more details of your design?Following
- 1I need to know the most recent Artificial Intelligent (AI) and Evolutionary Algorithm (EA) Optimization methods (Published in 2015 and 2016) ?
I need to know the most recent Artificial Intelligent (AI) and Evolutionary Algorithm (EA) Optimization methods to solve Optimal Power Flow Optimization problem.
Follow my recent publications about this theme
I believe that those papers can help ....
- 1In SPSS when we are doing EFA, Under Extraction Method, which one to Select Whether Correlation Matrix or Covariance Matrix and why?
In SPSS when we are doing Exploratory factor analysis (EFA), Under Extraction Method window, in analyze sub-window which one to Select Whether Correlation Matrix or Covariance Matrix and why?
It depends if you are assuming all the variables are on the same scale. If so, using the correlation would lose information. However, for many (perhaps most) applications of EFA you would not be assuming that these are on the same scale so the correlation matrix should be used (otherwise the ones with the largest standard deviations will tend to dominate the solution). I think SPSS' default is correlation, but when using other packages you would need to calculate the correlation mtrix first.Following
- 4What is the relationship between the leaf P50 and the leaf turgor loss point (πtlp)?
The leaf P50 and leaf water turgor loss point (πtlp) were used to access the plant drought tolerance in xylem and leaf tissue level, respecitively. However, in conifers, both of them were measured on current-year shoots, I think the relationship between them should be concerned. Here, I wondered was that what if a species had a lower πtlp but less negative P50, then how to quantify the leaf drought tolerance ?
But I prefer to consider a negative correlation between them. Because I think the osmoregulation and the capable of keep water transport safety might be a trade off in a certain extent.Following
- 7How to define the catalogue of criteria in a meta-analysis?
I want to make a meta-analysis and my question is: How should I define the catalogue of criteria to distinguish relevant studies from irrelevant ones?
I'd say : Use criteria that address to your research question (and nothing else).
- What measures address it?
- What designs address it?
- What statistical reportings address it?
- What samples address it?
I find it better to have strict criteria and be more exclusive, that narrows down your research question to something specific and feels less like a take-all (unless it narrows down to 3 studies...)Following
- 20Which elements/ions are highly responsible to increase soil EC/soil salinity?
Soil-1: have large amount of Ca2+ and less amount of Na+, Mg2+, K+ and others
Soil-2: have large amount of Na+, SO4- and less amount Ca2+, and others
Total concentration of ions is about same in both soils but soil EC is higher in soil-2 than soil-1.
What are the reasons/mechanisms for higher soil EC?
I agree with Steve Trotter statement and Bikash. These are the important factor developing soil salinity. Salinity or EC mostly depends on the amount of soluble ions rather on the ions in the exchangeable sites. However, sodium salts are more soluble than other salts. For this reason when a soil enriched with sodium salts rather than calcium salt obviously salinity of earlier soil will be higher than the later. EC does not indicate the amount of specific ions in a solution but the total soluble ions in the solution.Following
- 3Western blot detection of nuclear proteins?
Hi im trying to detect by western blot a nuclear protein. I have been trying yo do this with no success until i realised that nuclear proteins may require different way to prepare and detect. Below is how i prepare my cell lysate for western blot detection typically please advise on the centrifugation part to detect nuclear protein.
Remove media from culture dish and add PBS. Remove pbs and add 50ul of lysis buffer into cells. Scrape to detach and then homogenize with syringe. Transfer contents into ependorf tube and centrifuge for 14000 rpm for 15 mins. The supernatant is normally used for western blot detection. Now is there any advise on how to modify this centrifugation step to enrich for nuclear proteins?
I have worked with proteins from cell extract.
I advice you use RIPA buffer for the lysis (with proteasa inhibitors), incubated on ice 30 min and passed through a 20G gauge needle to facilitate cell breaking-up. After, centrifuge for 10000 rpm for 10 min and 4ºC.
Supernatant contains cytoplasmic proteins.
Pellet contains nuclear proteins
- 19Are there academic values to Marquis Who's Who in the World publications on bibliographic basis?I wonder if there are any literary values to biographies.
I was just invited to this. This thread is helpful in trying to de-mystify the merit of this organization.Following
- 1Can rainfall data be presented along a linear strip?
Dear RG members
I want to know/get information regarding.
please make your question a bit more elaborate to invite what you exactly need hereFollowing
- 6The ratio between available nitrogen and total nitrogen after vermicomposting is higher 90 percent?
The available nitrogen content in initial substrate of my study is about equal 27% total nitrogen. After vermicomposting process, it increased from 27% to 90%. I suspect the result was wrong because i had some problems in nitrogen analyzing process.
Mr.Thien,Good question.The proportion of available N in total N depends on feed N and the transformation of N in the gut of earthworm and subsequently in the wormcasts during maturation period of composting.Many workers reported high amount of N in vermicompost ranging from 1.5 -3.5 % N(slightly higher than what Dr.Tarafdar has mentioned).I think that the C:N ratio of 5:1 is difficult to achieve(I have not comeacross in literature).It can be around 10:1.Because of gut enzymes and also microbiological activty the mineralization of N is fast and high in the gut .But the mineralized N can not be 90% of the total N in the vermicompost.It is also reported that the nitrate N content will be much higher than ammoniacal N(because of nitrification process).In one example from USA, the total N in vermicompost was 3.81%.The nitrate N was 4871 mg/kg and ammoniacal N 139 mg/kg.Total mineral N is 5010mg/kg or 5g/kg. Mineral N as a proportion of total N 3810:5.So mineral N can not be so high.However I am not familiar with the methods used for estimating total N and the mineral N by Mr.Thien.He can give more details of methods used.Following
- 2Is it ok to re-code the ordinal variables to fit a multiple regression analysis?
I have 3 independent variables which are categorical and ordinal in nature (my dependent variable is interval), is it ok to re-code the ordinal variables to fit a multiple regression analysis? I have already re-coded the categorical variable and I want all my variables in one model.
Which of the 2 re-coding options is the best for the regression analysis? there are 14 questions in this likert scale.Following
- 8Can somebody help me, How can I maintenance Agrobacterium rhizogenes stain ICMP-8640?
New stain of Agrobacterium rhizogenes ICMP 8640 bought from new Zealand, Now its need to maintains virulence and preserved long time. Which actual protocol we should follow for maintenance?
I resent it for you as a private message. Please check it, and if it is not opening send me your e-mail to send it again.
- 3How microRNAs move from one cell to another cell in Animals?
In plants, microRNAs translocate from one cell to another cell through small pores called Plasmodesmata. What about Animals?
The comunication or send by microRNAs between animal cells is proposed by microvesicles, micropasticles or exosomes
- NewWhat are the differences between green freshwater algae and marine one in related to cell's organic contents?
in case of identifying organic substance in algal cellsFollowing
- NewI need friends (lecturer or researcher) who are interested to do a research about family communication? My campus has fund to do it. Anyone?
Family communication in any field. Extended Communication, Communication, Divorce Family, Single Parent Family, Different Religion Family, Different Culture FamilyFollowing
- 3How to calculate accumulated energy in mw/cm2 ?
Can any one help me how to calculate the accumulation of energy in mW/cm2 used in photocatalysis. i have the data of sunlight wavelength measured by using radiometer at different time intervals. but i dont know how to calculate accumulation energy using that value.
- Just want to add: Total number of photons (m2/s)=(total irradiance)/(total energy of photons)
- 2How to calculate the flow rate for sephadex G-50 superfine packed gel filtration column using Darcy's law?
I have packed a column with ~50 mL (height=28.5 cm) sephadex G-50 superfine, as required for the high resolution chromatography of a ~9.5 kDa peptide, in a BIORAD econo-column (d=1.5 cm, h=30 cm, max. backpressure 0.1 MPa). I randomly selected a flow rate of 0.8 mL/min which doesn't create a backpressure of more than 0.1 MPa on Akta Prime Plus system for packing. I wanted to know how to calculate the maximum flow rate that can be applied on the column using Darcy's Law
U = K x delta P x L-1
L know the value of, L= bed height= 28.5 cm
I dont know what to put or how to get the value of delta P, which is pressure drop over the packed bed expressed in cm water.
and K which is constant for the proportionality depending on the properties of the bed material and the buffer, which is given as 36 for sephadex G-50, fine but not for the superfine. Which I can assume reduces by a factor of 3.33 as that of sephadex G-25, so 10.8.
The value of P and other useful information is given here:
pressure drop cm H2O/bed height=15Following