This paper documents design and modeling of a grid-connected emergency back-up power supply for medium power applications. Back-up power supplies are very important in regard to support electrical loads in the events ...This paper documents design and modeling of a grid-connected emergency back-up power supply for medium power applications. Back-up power supplies are very important in regard to support electrical loads in the events of grid power outage. However, grid-integration of a back-up power supply substantiates continual power transfer to the loads, especially to the critical loads, which should not suffer from power interruptions. Therefore, design and circuit modeling of switching converters based reliable grid-tied emergency back-up power supply are presented in this paper. There are a rectifier-link boost derived battery charging circuit and a 4-switch push-pull power inverter circuit which are controlled by high frequency pulse width modulation (PWM) signals. This paper presents a state averaging model and Laplace domain transfer function of the charging circuit and a switching converter model of the power inverter circuit. A changeover relay based transfer switch controls the power flow towards the utility loads. During off-grid situations, loads are fed power by the proposed inverter circuit and during on-grid situations, battery is charged by an ac-link rectifier-fed boost converter. However, there is a relay switching circuit to control the charging phenomenon of the battery. The proposed design is simulated in PLECS and the simulation results corroborate the reliability of the presented framework.展开更多
Aim: The purpose of this article is to advocate standard skull base technique for removing the clinoidal meningioma and to delineate the technique's advantages that aid in achieving an improved extent of tumor res...Aim: The purpose of this article is to advocate standard skull base technique for removing the clinoidal meningioma and to delineate the technique's advantages that aid in achieving an improved extent of tumor resection and enhancing the patients' overall outcome, specially their visual outcome. Methods: A retrospective analysis was performed on 10 consecutive patients with clinoidal meningiomas who underwent surgical resection at the Bangabandhu Sheikh Mujib Medical University and other private clinics between May 2013 and July 2016. A standard pterional craniotomy technique consisting of extradural anterior clinoidectomy, coupled with optic canal unroofing and optic nerve sheath opening was used in all patients. All patients had thorough preoperative and postoperative ophthalmological evaluations. The follow-up period ranged from 6 to 42 months. Results: Total resection was achieved in 5 (50.0%) of the 10 patients in this series. The majority of the patients with preoperative visual impairment experienced significant visual improvement 7 of 10 patients;70.0%). Conclusion: In the majority of patients with clinoidal meningiomas, total resection may be achieved with minimal complications. For large tumors encasing the optic nerve and internal carotid artery, or for those tumors causing preoperative visual impairment, use of the cranial base technique delineated in this study may lead to significant improvement in the patients' visual and overall outcomes.展开更多
Azygos anterior cerebral artery (ACA) is type I variation of ACA with a reported incidence of < 1% in population(1)This variation predisposes to the formation of aneurysm especially at the bifurcation zone. The ane...Azygos anterior cerebral artery (ACA) is type I variation of ACA with a reported incidence of < 1% in population(1)This variation predisposes to the formation of aneurysm especially at the bifurcation zone. The aneurysm develops because of double hemodynamic pressure supplying medial surface of both cerebral hemispheres. However reported incidence of saccular aneurysm in azygos ACA is between 13% and 71%(2,3)It is often associated with other central nervous system (CNS) malformations like agenesis of corpus callosum, hydranencephaly and other vascular malformations[4].展开更多
文摘This paper documents design and modeling of a grid-connected emergency back-up power supply for medium power applications. Back-up power supplies are very important in regard to support electrical loads in the events of grid power outage. However, grid-integration of a back-up power supply substantiates continual power transfer to the loads, especially to the critical loads, which should not suffer from power interruptions. Therefore, design and circuit modeling of switching converters based reliable grid-tied emergency back-up power supply are presented in this paper. There are a rectifier-link boost derived battery charging circuit and a 4-switch push-pull power inverter circuit which are controlled by high frequency pulse width modulation (PWM) signals. This paper presents a state averaging model and Laplace domain transfer function of the charging circuit and a switching converter model of the power inverter circuit. A changeover relay based transfer switch controls the power flow towards the utility loads. During off-grid situations, loads are fed power by the proposed inverter circuit and during on-grid situations, battery is charged by an ac-link rectifier-fed boost converter. However, there is a relay switching circuit to control the charging phenomenon of the battery. The proposed design is simulated in PLECS and the simulation results corroborate the reliability of the presented framework.
文摘Aim: The purpose of this article is to advocate standard skull base technique for removing the clinoidal meningioma and to delineate the technique's advantages that aid in achieving an improved extent of tumor resection and enhancing the patients' overall outcome, specially their visual outcome. Methods: A retrospective analysis was performed on 10 consecutive patients with clinoidal meningiomas who underwent surgical resection at the Bangabandhu Sheikh Mujib Medical University and other private clinics between May 2013 and July 2016. A standard pterional craniotomy technique consisting of extradural anterior clinoidectomy, coupled with optic canal unroofing and optic nerve sheath opening was used in all patients. All patients had thorough preoperative and postoperative ophthalmological evaluations. The follow-up period ranged from 6 to 42 months. Results: Total resection was achieved in 5 (50.0%) of the 10 patients in this series. The majority of the patients with preoperative visual impairment experienced significant visual improvement 7 of 10 patients;70.0%). Conclusion: In the majority of patients with clinoidal meningiomas, total resection may be achieved with minimal complications. For large tumors encasing the optic nerve and internal carotid artery, or for those tumors causing preoperative visual impairment, use of the cranial base technique delineated in this study may lead to significant improvement in the patients' visual and overall outcomes.
文摘Azygos anterior cerebral artery (ACA) is type I variation of ACA with a reported incidence of < 1% in population(1)This variation predisposes to the formation of aneurysm especially at the bifurcation zone. The aneurysm develops because of double hemodynamic pressure supplying medial surface of both cerebral hemispheres. However reported incidence of saccular aneurysm in azygos ACA is between 13% and 71%(2,3)It is often associated with other central nervous system (CNS) malformations like agenesis of corpus callosum, hydranencephaly and other vascular malformations[4].
