This is actually a model of the arrival process in an interactive environment, rather than a model of a parallel workload. Its distinction lies in modeling the daily cycle of job submittals, with peaks in the morning and afternoon, and a drop at lunchtime.
Additional details are available in the referenced paper.
Note that this model is suitable for a time-driven simulation, where one wishes to simulate the correct number of arrivals for each minute of the day. Some work is needed to transform this for use in an event-driven simulation, where you actually need the distribution of interarrival times.