In This paper a ground-state cooling method for bad optomechanical systems is proposed. Previous authors show that an optical Cavity with equal loss and gain has a parity-time reversal (PT) symmetry. We introduced an optomechanical Cavity coupled to the two modes of a PT symmetry and a passive optical Cavity. A quarter-wave plate provides linear mixing interaction between the PT symmetry and passive cavities. In this study, our proposed system improved the cooling rate by utilizing two effects: energy localization and quantum interference. These two impacts increase the cooling rate while the system is red or blue-detuned. It is demonstrated that optomechanical cooling occurs in both the bad-Cavity limit and the weak optomechanical coupling regime. These innovations can be attained by parameter management of the system.

Oral malignant melanoma (OMM) accounts for 5% of all oral  malignancies. It is a rareaggressive neoplasm usually found on the hard palate and gingiva. The etiology is unknown, but tobacco and chronic irritation are suggested as probable causative factors. Over 30% of the cases have been reported to arise from pre-existing pigmented lesions. A biopsy is required to establish the diagnosis and the treatment of choice is surgery which may be affected by several factors such as size of the lesion and anatomic location. Despite aggressive resection and  djuvant treatments such as chemotherapy and immunotherapy, the five-year survival rate of this malignancy is poor.

The flow field which results from an expansion wave entering a Cavity from an upstream tube, and the focusing effect which occurs, is investigated. Different Cavity geometries, different expansion wave pressure ratios and different expansion wave widths are explored. As the expansion wave propagates into the Cavity it induces flow in the opposite direction and back down the walls. The flow experiences compression as it flows out back into the tube because of the concave surface of the Cavity it encounters. This can result in the formation of shock waves which can propagate back up into the Cavity. Very low pressure and temperature regions can develop because of the focusing action of the expansion. A convenient way of generating an expansion wave numerically and/or experimentally is in a shock tube. This consists of a tube divided into two compartments, one at high pressure and one at low pressure separated by a frangible diaphragm. On bursting the diaphragm, a shock wave travels in one direction and an expansion in the other towards the Cavity. Whilst ideal boundary conditions can be imposed in numerical simulation laboratory experiments are complicated by the diaphragm being curved and having a finite opening time. The effect of an initially curved diaphragm is briefly considered. The expansion wave pressure ratio was altered by changing the initial pressure ratio across the diaphragm. For an initially high pressure ratio, supersonic flow can occur behind the trailing edge of the expansion wave which has a marked influence on the flow. The width of the wave is dependent on the distance of the diaphragm from the Cavity and also has a significant influence on the flow. As the width of the wave increases and the density gradient decreases, focusing effects becomes significantly weaker. Correspondence between experiment and simulation is examined.