Checkpoint

Ship Type Length,m Extent of Testing - Number of Checkpoints ... 

The results showed that some yards used ultrasonics to examine thousands of checkpoints for quality control purposes whilst others were content to examine the almost the minimum number that would be accepted. It is cleeu from the results that the minimum extent of NDE recommended by Classification Societies falls some way short of that applied for quality control purposes by some shipbuilders. 

The reasoning behind the first change is that NDE made for Class should be a sample of the QC programme rather than a separate exercise. In this way the original purpose of the Classification checkpoints is restored and the overall quality level of welding can be monitored. 

Intersections of butts and seams of fabrication and section welds Throughout hull envelope, longitudinal and transverse bulkheads, inner bottom and hopper bottom The summation of checkpoint lengths (see note 2) examined at intersections is to be L where L is the overall length of the ship in metres... 

Sampling of checkpoints during the review exercise confirmed some predictable features, notably that radiography would miss planar defects such as lack of side wall fusion, and that ultrasonic operators tended not to report undercut, porosity or the smaller slag inclusions. 

The Surveyor will discuss with the shipbuilder and the owners a plan showing the intended checkpoints for ultrasonic and radiographic testing. 

During the construction of a ship the Surveyor monitors NDE results for completeness of testing and overall quality of welding. This role includes the evaluation of checkpoints taken specifically for classification purposes but also includes the monitoring of additional checkpoints taken for quality control purposes by the builder. In the case of tankers built to LR Class since 1994 and for bulk carriers built to Class since January 1996 the Surveyor will witness the actions listed as part of the ShipRight Construction Monitoring procedure that is now mandatory. 

The molecular structures were rendered with good-quality shading on a blue background. Isosurfaces produced from cube files or checkpoint files also looked nice. Molecular vibrations can be animated on screen and vibrational displacement vectors displayed. The vibrational line spectrum may be displayed too, but the user has no control over the axes. There is no way to set the background color. The display can be saved using several image file formats. 

As it passed checkpoints, the car was observed to be releasing plumes of carbon dioxide from the safety valve, after which the tank exploded 15 m (50 ft) in front of a group of other rail cars. Other evidence indicates that the explosion occurred after impact with these cars. 

How many formal checkpoints does this system require For example, a system for maintaining MSDSs may require multiple reviews of each new entry, or be consolidated as a single person s responsibility. Results may be forwarded to a centralized checkpoint, or may remain at the facility or division level. 

OptsReadFC Read in the initial force constants from the checkpoint file created... 

If you have saved the checkpoint file, then it is also possible to restart a faile optimization, using the Opl=Restart keyword. See the Gaussian User s Reference for details. 

You can retrieve an intermediate structure from the output log file manually. Alternatively, you may use the Geom=(Check,Step=n) keyword to retrieve the structure corresponding to step n from a checkpoint file. 

You will need to run these jobs for benzene and for TMS (if you want to run the jobs for both molecules simultaneously, you will need to specify different names for the checkpoint file in each input file). 

Optimize the structure of acetyl radical using the 6-31G(d) basis set at the HF, MP2, B3LYP and QCISD levels of theory. We chose to perform an Opt Freq calculation at the Flartree-Fock level in order to produce initial force constants for the later optimizations (retrieved from the checkpoint file via OptsReadFC). Compare the predicted spin polarizations (listed as part of the population analysis output) for the carbon and oxygen atoms for the various methods to one another and to the experimental values of 0.7 for the C2 carbon atom and 0.2 for the oxygen atom. Note that for the MP2 and QCISD calculations you will need to include the keyword Density=Current in the job s route section, which specifies that the population analysis be performed using the electron density computed by the current theoretical method (the default is to use the Hartree-Fock density). 

Perform the IRC calculation (requested with the IRC keyword). This job will help you to verify that you have the correct transition state for the reaction when you examine the structures that are downhill from the saddle point. In some cases, however, you will need to increase the number of steps taken in the IRC in order to get closer to the minimum the AAoxPoinb option specifies the number of steps to take in each direction as its argument. You can also continue an IRC calculation by using the lRC=(ReStorhMaxPointe=n) keyword, setting n to some appropriate value (provided, of course, that you have saved the checkpoint file). 

Retrieving them from the checkpoint file from a previous frequency calculation (IRCrRCFC). 

In order to save computation time, set up the second and subsequent jobs to extract the electron density from the checkpoint file by using the Geom=Checlcpoint and Densiiy=(Checkpoint/AP2) keywords in the route section. You will also need to include Den iiy=MP2 for the first job, which specifies that the population analysis should be performed using the electron density computed at the MP2 level (the default is to use the Hartree-Fock density). 

The first job step computes the energies of the three lowest excited states. The second job step uses its results to begin the optimization by including the Read option to the CIS keyword, Geom=Check, and Guess=Read (and of course the commands to name and save the checkpoint file). The Freq keyword computes the frequencies at the optimized structure. 

Finally, run another CASSCF 6,5)/6-31G(d) job to predict the energy of the ground state, using the same strategy as for the excited state. Retrieve the initial guess from the checkpoint file from the excited state calculation. 

Solution We ll look at the input files for this exercise more closely than we often do. Here is the structure of the first set of jobs designed for examining the orbitals and planning the active space (note that we save the checkpoint file for later reuse) ... 

The %Chk command in each job step specifies the name for the checkpoint file—one of Gaussian s scratch files—and it tells the program to save the file after the job finishes (normally, all scratch files are deleted automatically). The %NoSave command in the second job step tells the program to delete the checkpoint file after that step concludes even though %Chk has been included. 

The most common purpose for specifying and saving the checkpoint file is so that molecular structures and other calculation results can be retrieved from it for use in a... 

As an example, here is an output from Gaussian 98 on CH3F (Figure 17.2). I forced the finite field method by choice of Polar = Enonly (Polar = Energy only) in the route. The geometry was first optimized and stored in a checkpoint file. 

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