Follow up on Literature Reviews

In thinking about my own experience with writing literature reviews and re-reading my earlier post Those old papers are worth something…, I’ve realized I have more to say about this topic. I forgot an important detail about how to actually do the writing of literature reviews. It’s probably worth a deep dive so let me give a little history on this and then walk you thought how to use the modern tools.

I completed my graduate degrees between 2003 to 2008. I’m confident to say that I was probably the last group of graduate students who needed to physically go to the library to find the older books and scan in articles. After that time internet search engines improved, and libraries offered services to scan articles. In recent history, I’ve only gone to the library to retrieve some books that have too many pages to offer a digital copy or old enough that the digital copies that exist online are poor quality such that I need the figures in real life.

Ok, so here we are in the present with a need to do a good literature review and great tools to accomplish it but relatively underdeveloped skills in using these tools. Maybe this is not a problem for you, so please offer your tips but here are my own. First, use internet search tools or library database tools to find your favorite reference using a keyword search. I teach in a metallurgical engineering field so I’m going to pick out something interesting to me. In fact, I’m going to give you a pickup line to use, “Are you made of copper and tellurium? Because you are CuTe.” Corny I know, but what temperature does this alloy melt at? I want to know how hot CuTe really is.

Step 1 go ahead and do a keyword search for “CuTe phase diagrams.” Realize the first 10 articles are generic resources on phase diagrams because those are way more popular than copper tellurium alloys. If you scroll down far enough or revise your search for “copper tellurium phase diagrams” you will find articles related to what you were looking for.

Step 2 after the keyword search, we have everything we need right? Why would anyone really need to know this info besides the pickup line requirement? Cu₂Te has semiconductor properties in a liquid state so maybe that’s cool for you. This is about literature reviews so let’s work through this. Maybe you are interested in liquid semiconductors, so we could do one or two more searches using these new keywords. However, in our case I’m going to recommend a different plan. Who wrote the article? The search engines for searching papers are much better at finding authors than looking for every combination of keywords. Typically, a graduate student or advisor develops a theme on certain topics. Therefore, you can see the evolution of the research area if you follow a certain research group or set of people. Also, you can track the topic in time both backwards and forward from the article that you start with. If the individual only wrote one paper, then you are complete. If there are more, you can collect all the articles that author has written. Then you can also look at co-authors as well as the references for that work.

Step 3 I need to emphasize this again, using keyword searches on internet search engines will never reveal all the reference articles. You must find the papers the same way that they are written, by authors! Eventually authors will write other papers or wander off into other areas. So, what we end up with are small groupings of papers that are relevant to your research topic. I also generally advise to add papers until the reference set is “complete” for me complete is that there are no other authors or groups that have anything else to say on the topic. If you have too many papers then you don’t have enough specifics and if you don’t have enough, then you need to widen the search. I use a rule of thumb that about 100 papers is usually enough to define the edges of my research topic.

Step 4 don’t stop looking for papers. Eventually using keywords, author searching, and references gathering you will find a complete set of papers. Then you may have reviewers that reveal complete new sets of literature related to your topic.

Image analysis casting manufacturing

We’ve found that image analysis techniques are interesting for developing manufacturing routes for castings. William Warriner is developing all of the routines shown below to be used in his PhD work. For example, watershed segmentation of the solidification profile of a casting geometry is quite illustrative. Below, at left is a component, shown transparent, and at right are the watershed segments of the component’s solidification profile overlaid on the component. Essentially the segments tell us what regions of the casting can be fed by the same feeder or group of feeders. Feeding will occur from segment boundaries where solidification begins and proceeds the thickest section.

Using attributes of each segment and the solidification profile, we can apply known feeder design guidelines to generate feeder geometries. Below are the feeders generated from the segments. In practice, feeders that interfere with geometry can be replaced by side-attachment feeders, or by gating directly to the location of the feeder. In the meantime, it is still worth visually reporting that a feeder is required.

Several of the sections are close and it is believed that number of feeders is correlated with increased cost and with decreased ease of manufacturing. One goal could be to decrease the number of feeders. One way to do so is to provide connections, or feed pads, between segments. Creating feed pads can be accomplished by drawing a solid tube between the feeder locations of neighboring segments. Below at left are the connecting tubes overlaid on the component. At right is the same image with greater visibility of the tubes.

One strategy for reducing the number of feeders is to cluster their segments by proximity. From the perspective of connector tubes, that would mean removing longer tubes and retaining shorter ones. Below at left are the original set of tubes, and at right are the reduced set. Note that currently there isn’t an obvious quantitative metric for doing this without human intervention. The tube removal process here is based purely on human intuition and is intended to illustrate the usefulness of the tubes.

Now that the connector tubes have been pared down to several clusters, it should be possible to reduce the number of feeders so that each cluster is fed by only one feeder. An example, purely for illustration purposes, is shown below. The number of feeders has decreased from 16 to 6. Note that the connector tubes are quite crude, and would almost certainly not be able to be implemented as they appear here.

A casting designer would have to work closely with a product designer to rework the original geometry. They would likely incorporate the connector tubes as wall thickness changes in appropriate locations. Any changes would have to avoid altering features that must remain as-cast. There is also the consideration of avoiding more net-shape machining by adding material in locations where machining is not required.

Ideas made simple

One of the things that I cannot stand is describing something as complicated or complex. That is to say, there are some really complicated and complex things in this world but that should never be the way your research or presentation should pass on information. I challenge myself to take anything that I’m trying to explain and make it as clear as tying my shoes…

In fact, that is not a bad way to practice explaining yourself. If you choose something you are comfortable with like cooking, playing a sport, or tying your shoes and then explain it in video or using a presentation then you will get some practice with handling more difficult topics for example your PhD research proposal or defense. I recommend to have a steady diet of TED talks and 3MT to give yourself the cultural context to communicate your ideas. Remember, that the evidence that you have been successful is not making it through your material but instead hearing that same concept passed on by an understanding audience.

Just don’t practice without any content, I’d rather you be boring than say nothing.

Those old papers are worth something…

So, other than the desktop cnc mill that I appear to be spending all my time on… I try to teach and research too. When I find an article like this one, I like to share it with my graduate students and offer some thoughts on a positive side. This thought is to offer some context to protect our research group from similar pitfalls. So, what am I talking about.

Inadequate literature reviews can get you retracted!

Even innocent co-authors are impacted by retraction!

Science corrects false information slower than you expect!

Thanks to Craig Beard at UAB Library for being a good resource for me. I think the best thing to do is to make sure your work is your own and that you’ve made the best possible effort to get criticism from the best experts in the field to make sure you haven’t missed any details that catch you by surprise. And I admit, engineering seems to be weaker at this than you would expect based on knowing all the work we put into the studies we do and the tests and experiments we run. I think there are just too many ways to publish this information and strong disagreements about what is a contribution enough to publish.

I’ve been looking for better tools for making this easier for my students and myself. Heres a short list of ideas if you are also interested in the world of bibliometrics and systematic review.

1. Use a reference manager, several I’ve tried include Jabref, Bibdesk, Papers, Mendeley, and Zotero. Most of these will let you exchange via a .bibtex file so you won’t really lose time playing around with all of them until you get one you like. Once you find the solution though, I’d stick with it because it makes it super easy to add comments to papers you want to use in writing.
2. Explore bibliometrics software, for example, Bibliometrix for R, SciMAT, VOSviewer, Network Workbench, and CiteSpace may work for you. I’ve had varying degrees of progress getting these tools to work.
3. Make you own mind map using Docear,  FreeMind, or other. Honestly, when I first discovered mind mapping I though “wow! this is going to be so useful” but I think my engineering mind is just wired up to sort information as I receive it. So whenever I mind map it just turns into an exercise of prioritization of how important the information I get is.
4. Define a stopping point, don’t use your research as a jumping off point to connect to every paper ever written. Use the papers you do find to narrow the scope of your research until what you say gives you the references you intended to find. In other words, the first thing you write to describe your research is probably not correct.

In my process and I think I’m pretty quick at this, I typically take an idea or hypothesis and find the best paper I can possibly find. This means that this first, key paper is highly cited, published in a reputable journal (not on a blog site), written by researchers with proven background in the field. Then use that first paper to search for related material (a) in it’s reference section, (b) by the same authors, (c) citing this paper. That is the start of your comprehensive literature review. You will probably find in that initial search about 10-20 papers. Hopefully another paper you find will also be pretty key and important to you. Take this second key paper and do the same thing. Repeat perhaps a 3rd or 4th time. Hopefully you will find that if you have a good scope to your research work that you can define your stopping point now and you should have by the 4th time about 80 papers or so. Now it may take me a couple weeks to really digest this information for a new field… But, you can be smarter than about 99% of everyone on a topic using this approach in about 3-4 hours if you have access to the references. The other benefit to this… You will also know who are the 1% of people that are smarter than you on that same topic. Use these skills carefully, because you only get to make first impressions once.

As Charles Caleb Colton and Oscar Wilde said “imitation is the sincerest form of flattery that mediocrity can pay to greatness.” Don’t be mediocre, be great.

Mold Lock

In the effort to develop pattern making expertise, I was disappointed in the lack of information about various types of mold and pattern locks to align the cope and drag sand molds for a flaskless sand casting process. The most common discussion I’ve seen is the flask alignment approaches which are primarily used in green sand. There are some really good backyard casting websites that overview the process. Let me start by acknowledging them, hats off to Gingery Foundry, Workshopshed, Backyardmetalcasting, kylehausladen’s instructables, Steven Chastain’s book, AFS Patternmaker’s Manual and others I’m sure to forget to include links. Let me give the caveat that I’m looking specifically for good strategies for pattern/mold alignment that I can just build into the patten for a flaskless mold.

Let me tell you things that don’t seem to work well, to start out with. First, you could depend on the edges of the mold to align the pattern. If there are no features in the either the cope or the drag then I believe this method would work well. That’s an obvious one. Second, you could add “pins” to the pattern. In fact, there are options like the Freeman Concentric Mold-Lock Buttons that are commercially available. I think a solution like this would work well if you take care to install them both in the right location and with three of them that are not symmetric so that the orientation of the mold cannot be reversed. But frankly, I really want to discuss an alternative mold lock that I’ve been playing with. Using Onshape, I created a 1/2 inch platform that the cope and drag patterns could be built from. This is simply a “picture frame” approach to aligning the cope and drag. The drag lock is simply creating a raised surface which when matched with the cope lock which creates a recessed surface. The outer edge is 10.5″ square which is roughly the limit on the desktop milling machine. One corner has been prepared with a corner knocked off to make sure the mold is oriented properly.

Drag lock in Onshape.com

Cope lock from Onshape.com

Please note that I’m probably a little premature in claiming this is my solution for this alignment issue. But the example below is the cope side of a little cast knife project I’m working on to see if we can cast some steel knives as part of an AFS student activity.

Rapid Melting Applied to High‑Pressure Die‑Casting

… is the title of Carlos Larrazabal PhD dissertation work that he successfully defended last Thursday. Of interest was the power outage that occurred immediately after his presentation. The committee continued to question him in the dark and everyone persevered until he answered all aspects of his work.

Stay tuned for his first publication that is focused on modeling the electromagnetic and thermal aspects of induction heating a cylindrical billet of aluminum. This work is the basis for designing a rapid melting system. We believe that this effort will serve as a building block for designing several heating stages toward delivery of high-quality aluminum on-demand.