Design of controllers for linear parameter-varying systems by the gain scheduling technique

AbstractDesign of controllers for linear multi-input multi-output systems whose dynamics depend on a time-varying parameter is studied. Design algorithms for the state feedback control law based on the gain scheduling technique are proposed. State feedback control laws are designed so that one of the following goals is achieved: (i) the poles of the closed-loop system for all fixed parameter values are placed in a small neighborhood of a set of desired closed-loop poles; (ii) the stability of the closed-loop system for all fixed parameter values guarantees that the of the system (with the time-varying parameter), independent of the rate of change of the parameter. Rigorously justified and computationally appealing design algorithms are developed

Compressible flow structures interaction with a two-dimensional ejector: a cold-flow study

An experimental study has been conducted to examine the interaction of compressible flow structures such as shocks and vortices with a two-dimensional ejector geometry using a shock-tube facility. Three diaphragm pressure ratios ofP4 =P1 = 4, 8, and 12 have been employed, whereP4 is the driver gas pressure andP1 is the pressure within the driven compartment of the shock tube. These lead to incident shock Mach numbers of Ms = 1:34, 1.54, and 1.66, respectively. The length of the driver section of the shock tube was 700 mm. Air was used for both the driver and driven gases. High-speed shadowgraphy was employed to visualize the induced flowfield. Pressure measurements were taken at different locations along the test section to study theflow quantitatively. The induced flow is unsteady and dependent on the degree of compressibility of the initial shock wave generated by the rupture of the diaphragm

Control of Cavity-Induced Drag Using Steady Jets

Separated shear layer oscillations in open cavities can induce drag, noise and vibration. This issue has many aerospace applications such as Landing gears and control surfaces [1]. Recently, phase-cancellation [1] and offinstability frequency excitation [2] & [3] approaches have been incorporated in different open-loop and feedback control systems. Despite the high control performance of these systems, further enhancement is still possible. In this study, steady jets, as shown in fig. 1, are forced through 2mm, two-dimensional slots at the leading and trailing edges of the cavity. In order to study the performance of this novel approach, different cases will be examined, including: jet combination (blowing from cavity leading edge, suction from cavity leading edge and blowing-suction), jet angle (parallel or deflected jet) and jet-to-free stream velocity factor /.

Transverse jet-cavity interactions with the influence of an impinging shock

For high-speed air breathing engines, fuel injection and subsequent mixing with air is paramount for combustion. The high freestream velocity poses a great challenge to efficient mixing both in macroscale and microscale. Utilising cavities downstream of fuel injection locations, as a means to hold the flow and stabilise the combustion, is one mechanism which has attracted much attention, requiring further research to study the unsteady flow features and interactions occurring within the cavity. In this study we combine the transverse jet injection upstream of a cavity with an impinging shock to see how this interaction influences the cavity flow, since impinging shocks have been shown to enhance mixing of transverse jets. Utilising qualitative and quantitative methods: schlieren, oilflow, PIV, and PSP the induced flowfield is analysed. The impinging shock lifts the shear layer over the cavity and combined with the instabilities generated by the transverse jet creates a highly complicated flowfield with numerous vertical structures. The interaction between the oblique shock and the jet leads to a relatively uniform velocity distribution within the cavity

Quantum Hall Effect on the Grassmannians Gr2(CN)\mathbf{Gr}_2(\mathbb{C}^N)

Quantum Hall Effects (QHEs) on the complex Grassmann manifolds $\mathbf{Gr}_2(\mathbb{C}^N)$ are formulated. We set up the Landau problem in $\mathbf{Gr}_2(\mathbb{C}^N)$ and solve it using group theoretical techniques and provide the energy spectrum and the eigenstates in terms of the $SU(N)$ Wigner ${\cal D}$-functions for charged particles on $\mathbf{Gr}_2(\mathbb{C}^N)$ under the influence of abelian and non-abelian background magnetic monopoles or a combination of these thereof. In particular, for the simplest case of $\mathbf{Gr}_2(\mathbb{C}^4)$ we explicitly write down the $U(1)$ background gauge field as well as the single and many-particle eigenstates by introducing the Pl\"{u}cker coordinates and show by calculating the two-point correlation function that the Lowest Landau Level (LLL) at filling factor $\nu =1$ forms an incompressible fluid. Our results are in agreement with the previous results in the literature for QHE on ${\mathbb C}P^N$ and generalize them to all $\mathbf{Gr}_2(\mathbb{C}^N)$ in a suitable manner. Finally, we heuristically identify a relation between the $U(1)$ Hall effect on $\mathbf{Gr}_2(\mathbb{C}^4)$ and the Hall effect on the odd sphere $S^5$, which is yet to be investigated in detail, by appealing to the already known analogous relations between the Hall effects on ${\mathbb C}P^3$ and ${\mathbb C}P^7$ and those on the spheres $S^4$ and $S^8$, respectively.Comment: 34 pages, revtex 4-1, Minor Correction

Uterine sarcoma diagnose and treatment: Review article

Uterine sarcomas comprise a group of rare tumors with different tumor biology, natural history and response to treatment, contain just 3-7 of total uterine malignancies and about 1 of all gynecologic cancers. Although they cause important part of women death due gynecologic cancers. These tumors have aggressive behavior and high recurrence rate, even when confined to the uterine corpus at the time of diagnosis. The most common of uterine sarcomas is leiomyosarcoma. The incidence of leiomyosarcoma is increased after age 50. Traditionally, carcinosarcomas were named as Malignant Mixed Mullerian tumor (MMMT), but in recent classification according to their pathologic structure and its behavior, these tumors are classified as carcinomas. The rare group of sarcomas is endometrial stromal sarcoma (ESS), which occurres in younger women. In a medical studies search from 2000 to 2017, all kinds of uterine sarcomas, pathologic diagnostic methods, primary treatment and supportive treatment have been analyzed. Last histological classification is based on FIGO 2009 and WHO. According to such classification, sarcomas divided into three subtypes: leiomyosarcoma, endometrial stromal sarcoma and carcinosarcomas. Diagnosis of sarcoma before treatment and discrimination from benign myoma by current diagnostic methods is difficult. Preoperative endometrial sampling identifies only 25 of sarcomas. It may be the myometrial origin of tumor. Currently, MRI, ultrasound and PET scan may be used for the diagnosis of tumor. The gold standard of treatment is complete and intact resection of tumor considereing free margins. In advanced or recurrence disease, cytoreductive surgery followed by chemotherapy is the choice of treatment. If technically it is not possible or there are extra abdominal metastases, palliative chemotherapy should be considered. Combination of gemcitabine and docetaxel is an acceptable choice. Recent studies are going to approve the effective role for targeted agents with or without cytotoxic chemotherapy in these group of aggressive tumors. The only drug in this group has approval is pazopanib. However, it did not achieved acceptable responses in phase I, II studies. As regards of tumor biology and inappropriate response to chemotherapy and radiotherapy, sarcoma have poor prognosis in all stages. © 2018, Tehran University of Medical Sciences. All rights reserved

Control of Cavity-Induced Drag Using Steady Jets

Separated shear layer oscillations in open cavities can induce drag, noise and vibration. This issue has many aerospace applications such as Landing gears and control surfaces [1]. Recently, phase-cancellation [1] and offinstability frequency excitation [2] & [3] approaches have been incorporated in different open-loop and feedback control systems. Despite the high control performance of these systems, further enhancement is still possible. In this study, steady jets, as shown in fig. 1, are forced through 2mm, two-dimensional slots at the leading and trailing edges of the cavity. In order to study the performance of this novel approach, different cases will be examined, including: jet combination (blowing from cavity leading edge, suction from cavity leading edge and blowing-suction), jet angle (parallel or deflected jet) and jet-to-free stream velocity factor /.

Suspended liquid particle disturbance on laser-induced blast wave and low density distribution

The impurity effect of suspended liquid particles on the laser-induced gas breakdown was experimentally investigated in quiescent gas. The focus of this study is the investigation of the influence of the impurities on the shock wave structure as well as the low density distribution. A 532 nm Nd:YAG laser beam with an 188 mJ/pulse was focused on the chamber filled with suspended liquid particles 0.9 ± 0.63 μm in diameter. Several shock waves are generated by multiple gas breakdowns along the beam path in the breakdown with particles. Four types of shock wave structures can be observed: (1) the dual blast waves with a similar shock radius, (2) the dual blast waves with a large shock radius at the lower breakdown, (3) the dual blast waves with a large shock radius at the upper breakdown, and (4) the triple blast waves. The independent blast waves interact with each other and enhance the shock strength behind the shock front in the lateral direction. The triple blast waves lead to the strongest shock wave in all cases. The shock wave front that propagates toward the opposite laser focal spot impinges on one another, and thereafter a transmitted shock wave (TSW) appears. The TSW interacts with the low density core called a kernel; the kernel then longitudinally expands quickly due to a Richtmyer-Meshkov-like instability. The laser-particle interaction causes an increase in the kernel volume which is approximately five times as large as that in the gas breakdown without particles. In addition, the laser-particle interaction can improve the laser energy efficiency

Effect of dimples on glancing shock wave turbulent boundary layer interactions

An experimental study has been conducted to examine the control effectiveness of dimples on the glancing shock wave turbulent boundary layer interaction produced by a series of hemi-cylindrically blunted fins at Mach numbers 0.8 and 1.4, and at angles of sweep 0°, 15°, 30° and 45°. Schlieren photography, oil flow, pressure sensitive paints, and pressure tappings were employed to examine the characteristics of the induced flow field. The passive control technique used a series of 2 mm diameter, 1 mm deep indents drilled across the hemi-cylindrical leading edge at angles 0°, 45° and 90°. The effects of dimples were highly dependent on their orientation relative to the leading edge apex, and the local boundary layer properties

Influence of shock wave propagation on dielectric barrier discharge plasma actuator performance

Interest in plasma actuators as active flow control devices is growing rapidly due to their lack of mechanical parts, light weight and high response frequency. Although the flow induced by these actuators has received much attention, the effect that the external flow has on the performance of the actuator itself must also be considered, especially the influence of unsteady high-speed flows which are fast becoming a norm in the operating flight envelopes. The primary objective of this study is to examine the characteristics of a dielectric barrier discharge (DBD) plasma actuator when exposed to an unsteady flow generated by a shock tube. This type of flow, which is often used in different studies, contains a range of flow regimes from sudden pressure and density changes to relatively uniform high-speed flow regions. A small circular shock tube is employed along with the schlieren photography technique to visualize the flow. The voltage and current traces of the plasma actuator are monitored throughout, and using the well-established shock tube theory the change in the actuator characteristics are related to the physical processes which occur inside the shock tube. The results show that not only is the shear layer outside of the shock tube affected by the plasma but the passage of the shock front and high-speed flow behind it also greatly influences the properties of the plasma