**Acknowledgements**

The present author expresses his appreciation to three European scientists: Dr. Judit Angster of Fraunhofer-Institute fur Bauphysik, in Stuttgart, for her long-term support to carry out the PIV measurement; Prof. Avraham Hirschberg of Technishe Universiteit Eindhoven for his kind offer of the picture used as **Figure 12(c)** and helpful comments to the author's journal papers from the aeroacoustical viewpoint; and Prof. Andreas Bamberger of Freiburg University for his effective comments and suggestions on the PIV. Also, the author thanks Keita Arimoto and Takayasu Ebihara of Yamaha Corporation, in Hamamatsu, Japan, for their sincere support and appropriate comments to the manuscript.

**Author details**

Shigeru Yoshikawa

**75**

Kyushu University, Dazaifu, Japan

\*Address all correspondence to<EMAIL_ADDRESS>
*Vortices on Sound Generation and Dissipation in Musical Flue Instruments*

*DOI: http://dx.doi.org/10.5772/intechopen.91258*

provided the original work is properly cited.

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Vortices on Sound Generation and Dissipation in Musical Flue Instruments DOI: http://dx.doi.org/10.5772/intechopen.91258*


6. Conclusions and future work

Our contributions are threefold. Firstly, comparing the predicting results of the Gray-Markov model and the time series model and the original value, respectively, we can find that the fitting effect of the former (GMM) is better than the latter (TSM) and so does its scientific and practical importance. Secondly, the predicting results of GMM show that the level of foreign investment in China has been increasing by years. Thirdly, in order to further enhance Chinese international status and attract more foreign investment, the government should play a role at a macro level to reduce excessive market administrative intervention, establish a service-oriented government, and reduce the relevant approval procedures for international investment.

In the future work, the Gray-Markov model and time series model can be combined with other predicting model (e.g., support vector machine and dynamic Bayesian) to improve the accuracy. Also these models have the potential to be applied in the other areas such as finance (e.g., stocks, funds, and security), risk (e.g., financial risk and operational risk), and business (e.g., consumer price index and incomes).

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**1. Introduction**

Scroll compressors have been extensively employed in air conditioning and refrigeration since the 1980s. Their success is mostly related to a low level of noise and vibrations, together with a small number of moving parts and a compact design. In the last decade, scroll compressors and other positive displacement machines (PDMs, e.g., piston, screw, and vane machines) have been operated as expanders in Organic Rankine Cycles (ORCs) to generate power from waste heat and renewable energies [1]. Compared to its alternatives, the scroll expander is generally characterized by higher pressure ratios and efficiency and by lower flow rates and rotational speeds [2]. On the other hand, one of the major drawbacks of this technology is the maximum working temperature (maximum temperature of 250 ◦C reported by Seher et al. [3]): higher temperatures would increase excessively the thermal expansion of scroll spirals, leading to significant increments of internal leakages [4].

Scroll expanders are frequently adopted in micro-ORCs with power outputs up to 2 kW, as described in different literature works reporting experimental tests. Wang et al. [5] have tested a scroll expander with R134a over a wide range of rotational speeds, reaching a shaft work output close to 1 kW. Experimental characterizations of scroll expanders with R245fa are described in References [6,7], with maximum isoentropic efficiencies of 66.5% and 75.7%, respectively. Other tests using HCFC-123 and R134a as working fluids are analyzed in References [8,9].

The architecture of the scroll geometry is the cornerstone of the design and optimization of the whole machine. The inventor of this technology, Léon Creux, has introduced in 1905 a scroll profile based on the involute of a circle, which is still the most spread solution [10]. However, various alternative profile shapes have been developed during the XX century [11–13].

The expander is designed with a fixed built-in volume ratio, which is the volume of the discharge chamber at the beginning of the discharge phase divided by the volume of the suction chamber at its maximum extension. The built-in volume ratio determines the theoretical pressure ratio of the fluid expansion. Nonetheless, leakage flows, off-design operating conditions, and wear could commonly force the expander to work in under- or over-expansion conditions. The expander works in conditions of under-expansion when the internal pressure ratio imposed by the chambers volumes variation is lower than the system pressure ratio. Consequently, the pressure in the working chamber at the end of the expansion is higher than the pressure in the discharge area. This phenomenon produces a significant flow rate peak at the expander output when the discharge phase occurs. On the contrary, over-expansion occurs when the internal pressure ratio of the expander is higher than the system pressure ratio. The fluid is then forced to flow back, leading to a recompression, which is particularly detrimental for the machine performance [8].

Currently, the most used methods for the design and the prediction of scroll expanders performance are based on theoretical modeling, thermodynamic analysis, and experimental studies. Shaffer et al. [14] have presented a control volume approach to model the geometry of a scroll machine. The analytical and thermodynamic modeling of scroll compressors is extensively treated in References [15–19], with and without experimental validation. For what concerns the scroll expander, Ma et al. [20] have presented a dynamic model with experimental validation, introducing an overall dynamic friction coefficient of the machine to enhance the model adaptability. Lately, Bell et al. and Ziviani et al. have presented [21] and demonstrated the capabilities [22] of an open-source general framework for the simulation of various positive displacement machines, including scrolls. When the geometry of the scroll expander is not exactly known, deterministic models similar to the ones reported above are not suitable options. Lemort et al. [8] have developed and validated a semi-empirical model that requires a limited number of parameters. Examples of similiar studies for scroll and other positive displacement expanders are reported in References [23–27].

Recently, industries and researches have began to include Computational Fluid Dynamics (CFD) analyses in scroll machine designs and optimizations [28–33]. This tool allows to retrieve information about leakage flows nature, temperature distribution, and three-dimensional behavior of the flow inside the expander/compressor. Moreover, CFD could be employed to tune analytical and thermodynamic models as low-cost alternatives to experimental campaigns. One of the most challenging aspects of computational analyses of scroll machines (and positive displacement machines in general) is the grid generation process.

The nature of the problem imposes to adopt a dynamic mesh approach in order to correctly model the moving parts of the machines. Casari et al. [34] have reviewed different approaches for the dynamic mesh treatment in screw machines numerical analyses, including immersed boundary, adaptive remeshing, and key-frame remeshing. Most of the techniques presented in their work are suitable also for scroll expanders and compressors, but the most popular approach is certainly the custom predefined mesh generation [35]. This technique consists in the realization of a user-defined number of grids per rotor pitch. Each grid represents a set of control points (coordinates) through which the mesh nodes has to pass during the simulation. Several examples of this approach can be found in the literature, including applications to screw machines [36–39], root machines [40,41], and scroll machines [28,31,42,43].

In this work, the authors present a C++ library for the generation of structured body-fitted meshes of scroll compressors and expanders. Starting from the scroll profiles and main dimensions, the meshes are generated by means of an elliptic grid generation algorithm. This library has been realized in accordance with the coding standards of the open-source CFD software OpenFOAM. Furthermore, the authors have performed a full three-dimensional CFD analysis of a scroll expander suitable for micro-ORC applications. The library developed can be a useful tool for the development of structured meshes of scroll machines. One of the possible outcomes of this work could be the realization of advanced numerical analysis of ORC systems, such as the Whole ORC Model (WOM) presented in Reference [44].


**Abstract**

The objective of this work is to verify the design of an existing die for the manufacture of an extruded profile using the simulation of the flow in the head using a simulation software that uses computational fluid dynamics and also the experimental design and construction of a calibrator by means of the extrusion the geometry and desired dimensions of the profile. The rheological behavior of rigid PVC in the extruded molten state was investigated, which in itself is a difficult target due to the intrinsic weakness of this polymer that degrades when heated above 140°C. By means of a special capillary rheometer, rheological data, *k* and *n* of the power law, were obtained to introduce them, together with the process input parameters and the flow channel geometry in the simulation software. The flow channel was drawn with the head and calibrator using CAD-3D software. The different parts of the calibrator were manufactured and assembled into the equipment. The extrusion was performed with the process parameters: screw speed and material temperature used in the simulation software. The results obtained by the extrusion, geometry and final dimensions of the profile, mass flow, pressure, and temperature in the head were compared with those delivered by the software, being the same satisfactory.

**Keywords:** simulation, extrusion, PVC (polyvinyl chloride), process, design, rheology


**5. Paediatric diagnostic reference levels (PDRLs)**

The International Commission on Radiological Protection (ICRP) Publication 73 was first to introduce the term 'Diagnostic Reference Level' (DRL) in 1996, a concept that was further developed further. The DRL has been proven to be an effective tool towards the optimisation of protection in the medical exposure of patients in diagnostic procedures.

#### **5.1 Planar-SPECT imaging procedures**

For planar nuclear medicine imaging, DRLs have been set either by administered activity (MBq) or by administered activity per body weight (MBq/kg).

For SPECT imaging procedures, DRL values should be used in the same way as for planar nuclear medicine procedures. DRL values for SPECT studies are usually slightly higher than for the same radiopharmaceuticals used for planar imaging.

#### **5.2 Positron emission tomography (PET)**

Specific radiopharmaceuticals are used for PET imaging, depending on the scope of the study. F18-fluorodeoxyglucose (F18-FDG) is used for diagnosing, staging and assessing therapeutical schemes in cancer, inflammation, viable myocardium and brain diseases by revealing relative glucose metabolic activity in tissues and organs. N13-ammonia or Rb82-chloride assesses myocardial perfusion. Ga68-DOTATATE and DOTATOC in neuroendocrine tumours reflecting the status of somatostatin receptors. As the physical half-lives of radionuclides and biological half-times of radiopharmaceuticals are different, DRL values have to be set for each one.

European guidelines provide a calculation system according to body weight, image acquisition method (two-, or three-dimensional), scan speed (minutes per table position) and table overlap during the following PET acquisitions.

### **5.3 Hybrid imaging (PET-CT, SPECT-CT and PET-MRI, SPECT-MRI)**

PET and SPECT have been combined with the modality of CT generating the so-called hybrid systems of PET-CT and SPECT-CT accordingly. Nowadays, they have been combined with the Magnetic Resonance Imaging (MRI) modality too, as these combinations increase diagnostic accuracy by providing both functional and anatomical images of the body.

The acquisition of accurately co-registered anatomical and functional images is a major strength of combined modality (hybrid imaging) devices. The patient dose from a PET-CT or SPECT-CT examination is the combination of the radiation exposures caused by the radiopharmaceutical and by the CT study via the exposure to ionising radiation.

The MRI component of PET/MRI or SPECT/MRI does not increase the patient dose considering that it uses non-ionising radiation, so from a radiation protection point of view, this hybrid imaging is preferable in paediatric examinations.

In the framework of a PET/CT or SPECT/CT, the CT portion of the examination consists of a localiser radiograph and the helical CT scan. If a CT is solely performed for attenuation correction and co-localisation, the acquisition parameters (tube current, voltage, slice thickness, rotation time, and pitch) should be selected in order to minimise the patient's radiation exposure. A low-dose CT used in hybrid imaging is sufficient for attenuation correction and anatomic localisation and proper for paediatric examinations.


*4.8. Trichoderma viride*

*Trichoderma viride* is an Ascomycota fungus belonging to the order Hypocreales, family Hypocreaceae. It is capable of producing a brown colored pigment, identified as furfural (only one study and this should be confirmed) [89]. It is mostly used as a biological control agent against soil-borne plant pathogenic fungi. It is also capable of synthesizing emodin, a yellow pigment. *T. polysporum* is the only fungi capable of producing emodin in culture media. A phytotoxicity assay proved the nontoxic nature of *T. viride* on the germination of *Phaseolus aureus* Roxb. The pigment, i.e., furfural, produced by *Trichoderma viride*, has possible wide applications in various industries [89].