A method for balancing thermal and electrical packaging requirements for gallium nitride (GaN) high power amplifier (HPA) modules is presented. The goal is to find a design approach that minimizes the junction tempera...A method for balancing thermal and electrical packaging requirements for gallium nitride (GaN) high power amplifier (HPA) modules is presented. The goal is to find a design approach that minimizes the junction temperature of the GaN so that it is reliable and has interconnects that meet electrical performance requirements. One benefit of GaN is that it can simultaneously achieve high power density and operate at microwave and millimeter-wave frequencies. However, the power density can be so high that the necessary thermal solutions can have negative impact on electrical performance. This is especially a concern for the electrical interconnects required for the input/ output ports on high power amplifier devices. This is because the signal interconnects must operate at GHz frequencies, which means that special care must be taken to avoid problems such as undesired signal coupling and ground path inductance. Therefore, this work focuses on GaN packaging and its integration into a module. The results show that an optimum thickness for the GaN heat spreader exits for thermal performance but the electrical design is impacted negatively if the optimum thermal design is chosen. Therefore, a balanced design is chosen which meets overall system level requirements.展开更多
A simple equation for heat spreading angle is derived which is useful for cases with a single layer thermal spreader. The derivation starts with Fourier’s heat transfer law. Heat spreading in two dimensions is then i...A simple equation for heat spreading angle is derived which is useful for cases with a single layer thermal spreader. The derivation starts with Fourier’s heat transfer law. Heat spreading in two dimensions is then introduced which results in a quadratic equation relative to spreading angle. The result is a closed form equation for heat spreading angle. Calculations using the equation are compared to 3D finite element simulations which show agreement acceptable for most practical applications and over a wide range of physical dimensions and thermal conductivities. A norma-lized dimensional parameter is defined which is used to generate a curve fit equation of the spreading angle. A three step procedure is then presented which allows the calculation of the spreading angle and temperature rise in the thermal spreader. The result has application for initial calculations of temperature rise in microwave hybrid modules and electronic packages such as heat sinks for high power amplifiers. This is because it is common for these types of modules and packages to use a single layer heat spreader in copper-tungsten (CuW) or copper-molybde-num (CuMo) connected to a cold plate. An important benefit of this method is that it allows microwave hybrid designers and high power amplifier packaging engineers a method to quickly perform trade studies to determine the maximum mounting temperature for integrated circuits.展开更多
Background:Coronary artery bypass grafting(CABG)is a coronary revascularization technique associated with diminished pulmonary function.During the first week after CABG,slow vital capacity(SVC)decreases by 30%–60%.Sc...Background:Coronary artery bypass grafting(CABG)is a coronary revascularization technique associated with diminished pulmonary function.During the first week after CABG,slow vital capacity(SVC)decreases by 30%–60%.Scalene muscles affect pulmonary function because they attach to the 1st and 2nd ribs.Shorter scalene muscles can decrease inhalation volume and chest expansion.Very few studies have assessed the effects of scalene stretching on SVC and chest expansion in patients post-CABG.Therefore,this study was aimed at determining the effects of scalene muscle stretching on SVC and chest expansion in such patients.Methods:A total of 74 patients post-CABG(phase 2)meeting the inclusion criteria were randomly allocated to two groups:an intervention group(n=30)performing scalene muscle stretching and a control group(n=30)performing active neck exercise.Pre&Post SVC and chest expansion were measured in all patients.A total of 14 patients wereexcluded.Statistical analysis was conducted in SPSS software(version 20.0).Results:SVC showed significant increase(P<0.05)in the intervention group compared with the control group.Chest expansion was statistically non-significant between groups(P>0.05).Conclusion and clinical implications:Scalene muscle stretching improves SVC in patients post-CABG(phase 2).Hence,scalene stretching should be included in programs for improving respiratory function.展开更多
Background and need for the research:High-normal blood pressure(i.e.,130–139/85–89 mmHg)hashazardous ratio for both coronary heart disease and stroke,because of day to day variations in blood pressure;consequently,p...Background and need for the research:High-normal blood pressure(i.e.,130–139/85–89 mmHg)hashazardous ratio for both coronary heart disease and stroke,because of day to day variations in blood pressure;consequently,prevention through lifestyle modification is essential.Although numerous studies have examined stretching and myo-fascial release to lower blood pressure,no consensus has been reached regarding which technique is superior for immediate lowering blood pressure.The aim of this study was to evaluate and compare the immediate effects of self-performed foam rolling and active-stretching on blood pressure and myocardial oxygen demand.Methods:A total of 98 patients with high normal blood pressure(20–40 years of age)meeting the inclusion criteria were randomly divided into two groups.Group 1(n=49)performed foam rolling,and group 2(n=49)performed TheraBand-assisted active stretching of the calf muscle.The pre and post blood pressure,heart rate,and the rate pres-sure product were assessed.Statistical analysis was conducted in SPSS software(version 20.0).Results:Systolic and diastolic blood pressure significantly decreased in both groups(P<0.05),and the decrease was greater in the active stretching group than the foam rolling group.In the foam rolling group,the heart rate signifi-cantly increased,whereas no changes were observed in the active stretching group.The Rate Pressure Product was notsignificant within and between two groups.Conclusion and clinical implications:Active stretching as part of a self-performed daily exercise routineappears safer for immediate lowering blood pressure,without affecting myocardial oxygen demand.Ethics committee approval:Reference No.:EC/Approval/08/Physio/21/06/2023.展开更多
A dual optical time domain reflectometry （OTDR） system, which employs two different continuous waves at the optical line terminal and a pair of fiber Bragg gratings at the end of each optical network unit, is propos...A dual optical time domain reflectometry （OTDR） system, which employs two different continuous waves at the optical line terminal and a pair of fiber Bragg gratings at the end of each optical network unit, is proposed in a time-division multiplexing passive optical network （PON）. The proposed scheme accomplishes the fiber fault monitoring by comparing the different wavelength＇s testing curves. Complete complementary code is utilized to measure multiple wavelength signals simultaneously with only one receiver and to improve the dynamic range of this system. The PON system consisting of 20 km feeding fiber and a 1：16 splitter is investigated by the experiments. The experimental results show that the faulty branch can be successfully identified by using our scheme. What is more, we also demonstrate that our scheme can be applied to the multi-stage PON.展开更多
文摘A method for balancing thermal and electrical packaging requirements for gallium nitride (GaN) high power amplifier (HPA) modules is presented. The goal is to find a design approach that minimizes the junction temperature of the GaN so that it is reliable and has interconnects that meet electrical performance requirements. One benefit of GaN is that it can simultaneously achieve high power density and operate at microwave and millimeter-wave frequencies. However, the power density can be so high that the necessary thermal solutions can have negative impact on electrical performance. This is especially a concern for the electrical interconnects required for the input/ output ports on high power amplifier devices. This is because the signal interconnects must operate at GHz frequencies, which means that special care must be taken to avoid problems such as undesired signal coupling and ground path inductance. Therefore, this work focuses on GaN packaging and its integration into a module. The results show that an optimum thickness for the GaN heat spreader exits for thermal performance but the electrical design is impacted negatively if the optimum thermal design is chosen. Therefore, a balanced design is chosen which meets overall system level requirements.
文摘A simple equation for heat spreading angle is derived which is useful for cases with a single layer thermal spreader. The derivation starts with Fourier’s heat transfer law. Heat spreading in two dimensions is then introduced which results in a quadratic equation relative to spreading angle. The result is a closed form equation for heat spreading angle. Calculations using the equation are compared to 3D finite element simulations which show agreement acceptable for most practical applications and over a wide range of physical dimensions and thermal conductivities. A norma-lized dimensional parameter is defined which is used to generate a curve fit equation of the spreading angle. A three step procedure is then presented which allows the calculation of the spreading angle and temperature rise in the thermal spreader. The result has application for initial calculations of temperature rise in microwave hybrid modules and electronic packages such as heat sinks for high power amplifiers. This is because it is common for these types of modules and packages to use a single layer heat spreader in copper-tungsten (CuW) or copper-molybde-num (CuMo) connected to a cold plate. An important benefit of this method is that it allows microwave hybrid designers and high power amplifier packaging engineers a method to quickly perform trade studies to determine the maximum mounting temperature for integrated circuits.
文摘Background:Coronary artery bypass grafting(CABG)is a coronary revascularization technique associated with diminished pulmonary function.During the first week after CABG,slow vital capacity(SVC)decreases by 30%–60%.Scalene muscles affect pulmonary function because they attach to the 1st and 2nd ribs.Shorter scalene muscles can decrease inhalation volume and chest expansion.Very few studies have assessed the effects of scalene stretching on SVC and chest expansion in patients post-CABG.Therefore,this study was aimed at determining the effects of scalene muscle stretching on SVC and chest expansion in such patients.Methods:A total of 74 patients post-CABG(phase 2)meeting the inclusion criteria were randomly allocated to two groups:an intervention group(n=30)performing scalene muscle stretching and a control group(n=30)performing active neck exercise.Pre&Post SVC and chest expansion were measured in all patients.A total of 14 patients wereexcluded.Statistical analysis was conducted in SPSS software(version 20.0).Results:SVC showed significant increase(P<0.05)in the intervention group compared with the control group.Chest expansion was statistically non-significant between groups(P>0.05).Conclusion and clinical implications:Scalene muscle stretching improves SVC in patients post-CABG(phase 2).Hence,scalene stretching should be included in programs for improving respiratory function.
文摘Background and need for the research:High-normal blood pressure(i.e.,130–139/85–89 mmHg)hashazardous ratio for both coronary heart disease and stroke,because of day to day variations in blood pressure;consequently,prevention through lifestyle modification is essential.Although numerous studies have examined stretching and myo-fascial release to lower blood pressure,no consensus has been reached regarding which technique is superior for immediate lowering blood pressure.The aim of this study was to evaluate and compare the immediate effects of self-performed foam rolling and active-stretching on blood pressure and myocardial oxygen demand.Methods:A total of 98 patients with high normal blood pressure(20–40 years of age)meeting the inclusion criteria were randomly divided into two groups.Group 1(n=49)performed foam rolling,and group 2(n=49)performed TheraBand-assisted active stretching of the calf muscle.The pre and post blood pressure,heart rate,and the rate pres-sure product were assessed.Statistical analysis was conducted in SPSS software(version 20.0).Results:Systolic and diastolic blood pressure significantly decreased in both groups(P<0.05),and the decrease was greater in the active stretching group than the foam rolling group.In the foam rolling group,the heart rate signifi-cantly increased,whereas no changes were observed in the active stretching group.The Rate Pressure Product was notsignificant within and between two groups.Conclusion and clinical implications:Active stretching as part of a self-performed daily exercise routineappears safer for immediate lowering blood pressure,without affecting myocardial oxygen demand.Ethics committee approval:Reference No.:EC/Approval/08/Physio/21/06/2023.
基金supported by the National 863Program of China(No.2015AA017002)the Research Foundation of Wuhan Science and Technology Bureau(No.2015010303010141)+1 种基金the Open Foundation of State Key Laboratory of Optical Communication Technologies and Networks(W.R.I.)the Accelink Technologies Company Ltd
文摘A dual optical time domain reflectometry （OTDR） system, which employs two different continuous waves at the optical line terminal and a pair of fiber Bragg gratings at the end of each optical network unit, is proposed in a time-division multiplexing passive optical network （PON）. The proposed scheme accomplishes the fiber fault monitoring by comparing the different wavelength＇s testing curves. Complete complementary code is utilized to measure multiple wavelength signals simultaneously with only one receiver and to improve the dynamic range of this system. The PON system consisting of 20 km feeding fiber and a 1：16 splitter is investigated by the experiments. The experimental results show that the faulty branch can be successfully identified by using our scheme. What is more, we also demonstrate that our scheme can be applied to the multi-stage PON.
