*2.4.2 Platform-as-a-service (PaaS)*

The capability provided to the consumer is the deployment of consumer-created or acquired applications created by means of programming languages, libraries, services, and tools supported by the PaaS provider. The consumer does not manage or control the underlying cloud infrastructure, including network, servers, operating systems, or storage, but has control over the deployed applications and possibly the configuration settings for the application-hosting environment.

**Figure 4.** *A hybrid cloud composed of an on-premise private cloud and a public cloud.*

*Network Function Virtualization over Cloud-Cloud Computing as Business Continuity Solution DOI: http://dx.doi.org/10.5772/intechopen.97369*

#### *2.4.3 Software-as-a-service (SaaS)*

Within a SaaS context, the consumer can run SaaS provider's applications in a cloud infrastructure. The applications are accessible from various client devices through either a thin client interface, such as a web browser (for example, webbased email), or a program interface. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings.

In the SaaS model, a provider hosts an application centrally in the cloud and offers it to multiple consumers for use as a service. The consumers do not own or manage any aspect of the cloud infrastructure. In a SaaS context, a given version of an application, with a specific configuration (hardware and software) typically provides services to multiple consumers by partitioning their individual sessions and data. SaaS applications execute in the cloud and usually do not need installation on end-point devices. This enables a consumer to access the application on demand from any location and use it through a web browser on a variety of end-point devices. Some SaaS applications may require a client interface to be locally installed on an endpoint device. Customer Relationship Management (CRM), email, Enterprise Resource Planning (ERP), and office suites are examples of applications delivered through SaaS. **Figure 5** illustrates the three cloud service models.

### *2.4.4 Mobile "backend" as a service (MBaaS)*

In the mobile "backend" as a service (m) model, also known as backend as a service (BaaS), web app and mobile app developers are provided with a way to link their applications to cloud storage and cloud computing services with application programming interfaces (APIs) exposed to their applications and custom software development kits (SDKs). Services include user management, push notifications, integration with social networking services [6] and more. This is a relatively recent model in cloud computing [7] with most BaaS startups dating from 2011 or later [8] but trends indicate that these services are gaining significant mainstream traction with enterprise consumers.

**Figure 5.** *Cloud service models.*


4.2.1. Analysis of Microstructure for the Weld Beads

The grain size is very important for the material characteristics, especially for the metals. The influence of grain size on the materials characteristics actually resulted from the influence of the grain boundary surface area. A smaller grain size denotes a bigger grain boundary surface area, and larger influence on the materials characteristics. In general, smaller grain size means higher strength and stiffness, as well as higher toughness and ductility for the metals in room temperature. This is because a plastic deformation can occur in more grains when the grain sizes are smaller, which can make the deformation more equal. Moreover, smaller grain size means more overall grain

boundary surfaces, and boundaries are more complex, which can make the combination of different grains may more compacted. Under this circumstance, the propagation and growth of the cracks may be effectively prevented, which means that the metal has good strength and toughness.

To explore the materials characteristics, above nine weld beads can be observed by Phenom pro-electron microscopy (Thermo Fisher Scientific Inc, Waltham, MA, USA), which has 2000 multiplication times. The observations can be seen in Figure 4. In addition, to clearly present the grain sizes of the weld beads, the grain length was introduced to describe the grain size. In general, smaller grain length meant smaller grain size. For these nine weld beads, the corresponding grain length were 10.8, 10.38, 11.74, 9.64, 7.94, 9.00, 8.44, 6.53 and 6.75 μm from the weld beads from L1 to L9. It can be noticed that all the microstructures were cellular grain structure. The grain sizes of the weld bead of L1–L3 were larger, while the grain sizes of weld beads of L4–L6 were relatively smaller. In addition, the grain size of weld bead of L4 was a little larger than that of L5 and L6, and the weld beads of L7–L9 have the smallest grain sizes.

**Figure 4.** Microstructures of the weld bead observed by electron microscopy. (**a**) The weld bead of L1, (**b**) the weld bead of L2, (**c**) the weld bead of L3, (**d**) the weld bead of L4, (**e**) the weld bead of L5, (**f**). the weld bead of L6, (**g**) the weld bead of L7, (**h**) the weld bead of L8, (**i**) the weld bead of L9.


**Author details**

In fact, the studies described above do not reveal information about the full complexity of subsurface defect distribution effects. Therefore, there remains a wide number of uncertainties, e.g., the fundamental problem of whether or not the ultrasonic processing exploiting high acoustic powers is capable of promoting

To improve the photovoltaic response of Si wafers, SiGe and amorphous silicon (a-Si)/SiGe surfaces, a sonochemical treatment in hydrocarbon solutions of chloroform (CHCl3) and dichloromethane (CH2Cl2) can be employed. The use of the sonochemical reaction slows down the observed surface photovoltage decay and enhances its magnitude in SiGe and a-Si/SiGe thin layers grown on Si. The average surface-integrated photovoltage and decay time can increase up to 50%. This effect is not observed in distilled water, indicative of the fact that CH-containing radicals can lead to the observed improvements. It is suggested that the effect can be explained as follows. The hydrocarbon solution is decomposed and produces hydrocarbon chains, which are then decomposed further away into hydrogen and carbon. The reactive Si dangling bonds revealed on the surface of Si, a-Si or SiGe alloy layers are saturated by the hydrocarbon species to passivate the surface.

More work needs still to be done beyond the description of a very few links that have been highlighted above. In particular, the following experiments could pave the way for new mechanisms of surface passivation, activation of the interphase regions dangling bonds as well as cleaning of surfaces due to the ultrasonic

The work at Kyiv was funded by the Ministry of Education and Science of Ukraine (0119U100303). Financial support from the University of Vienna is also

effective cleaning without surface deterioration effects.

*Solar Cells - Theory, Materials and Recent Advances*

processing.

acknowledged.

**152**

**Acknowledgements**

**Conflict of interest**

The authors declare no conflict of interest.

Andriy Nadtochiy1 , Artem Podolian1 , Oleg Korotchenkov1 and Viktor Schlosser2 \*

1 Faculty of Physics, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine

2 Department of Electronic Properties of Materials, Faculty of Physics, University of Vienna, Austria

\*Address all correspondence to<EMAIL_ADDRESS>
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