AIM： To retrospectively evaluate the effectiveness of impedance monitoring for predicting popping during radiofrequency ablation （RFA） using internally cooled electrodes. METHODS： We reviewed 140 patients （94 mal...AIM： To retrospectively evaluate the effectiveness of impedance monitoring for predicting popping during radiofrequency ablation （RFA） using internally cooled electrodes. METHODS： We reviewed 140 patients （94 males, 46 females; age range 73.0 ＋ 11.1 year） who underwent RFA between February 2006 and November 2008 with a modified protocol using a limited power delivery rather than a conventional one to avoid popping. All the patients provided their written informed consent, and the study was approved by the institutional review board. Intraprocedural impedances were measured for the study subjects, and the tumors were classified into three types according to the characteristics of their impedance curves： increasing, flat, or decreasing. The tumors were further sorted into seven subtypes （A-G） depending on the curvature of the impedance curve＇ s increase or decrease. Relative popping rates were determined for the three types and seven subtypes. A chi-square test was performed to estimate statistical significance.RESULTS： A total of 148 nodules treated by RFA were analyzed. The study samples included 132 nodules of hepatocellular carcinoma, 14 nodules of metastatic liver cancer, and two nodules of intrahepatic cholangio- carcinoma. The numbers of nodules with each imped- ance curve type were as follows： 37 increasing-type nodules, 43 fiat-type nodules, and 68 decreasing-type nodules. Popping occurrence rates were 24.3%, 46.5% and 64.7%, respectively. Flat-type nodules exhibited a significantly higher rate of popping compared to increasing-type nodules （P = 0.039）. Decreasing-type nodules exhibited a significantly higher rate of popping compared to increasing-type nodules （P 〈 0.0001）. No- tably, nodules that showed a sharp decrease in imped- ance in the latter ablation period （subtype E） exhibited a significantly higher rate of popping compared to other subtypes. CONCLUSION： Intraprocedural impedance monitoring can be a useful tool to predict the occurrence of pop- ping during liver tumor RFA performed with internally cooled electrodes.展开更多
Internally-cooled dehumidifiers are efficient liquid desiccant dehumidifiers, whose performance is mainly determined by the device structure and operating conditions. Based on energy and mass conservation in the air, ...Internally-cooled dehumidifiers are efficient liquid desiccant dehumidifiers, whose performance is mainly determined by the device structure and operating conditions. Based on energy and mass conservation in the air, solution, and cooling water in the device, mathematical models are built and their theoretical performance is simulated and analyzed in this paper. A novel measure of dehumidification efficiency is introduced to evaluate the performance of internally-cooled dehumidifiers, in which the equilibrium humidity ratio of the inlet solution is calculated according to the minimum temperature in the inlet solution and the cooling water. Numerical simulations show that a counter flow between air and solution is always the most efficient, followed by cross flow, and parallel flow is the least efficient. Cooling water with the same flow direction as the solution performs better than that with a counter flow, with approximately a 5% improvement in efficiency. Compared with Ca Cl2, the dehumidification efficiency of a Li Cl solution is greater by 60%, while its exergy efficiency is less by 16%. Dehumidification efficiency can be improved with the number of air-solution heat transfer units(NTUa-s) increasing, and reduced with the air mass flow rate raised. With NTUa-s increasing, exergy efficiency can be improved, and an increase in mass flow rate of cooling water results in a decrease of efficiency. Higher solution concentration and lower inlet temperature of solution and air can achieve both higher dehumidification efficiency and exergy efficiency.展开更多
A theoretical model is developed to establish an indepth understanding of the performance of a three-stage wind tower with a bypass system for indoor cooling in rural dry and hot climates. Model simulations are presen...A theoretical model is developed to establish an indepth understanding of the performance of a three-stage wind tower with a bypass system for indoor cooling in rural dry and hot climates. Model simulations are presented for a wide range of ambient conditions that include inlet wind speed, inlet temperature and relative humidity. Simulation results provide an insight into the desirable water flow rates and air-to-water loadings for comfort zone tem-peratures and relative humidity levels at the exit of the wind tower. Simulations show wind towers with variable cross-sections provide an increase in the cooling power for the same inlet wind speed, inlet air temperature and relative humidity when compared to wind towers with a constant cross-section. The study shall lead to a better understanding to designing wind towers that are both environmentally friendly and energy efficient.展开更多
文摘AIM： To retrospectively evaluate the effectiveness of impedance monitoring for predicting popping during radiofrequency ablation （RFA） using internally cooled electrodes. METHODS： We reviewed 140 patients （94 males, 46 females; age range 73.0 ＋ 11.1 year） who underwent RFA between February 2006 and November 2008 with a modified protocol using a limited power delivery rather than a conventional one to avoid popping. All the patients provided their written informed consent, and the study was approved by the institutional review board. Intraprocedural impedances were measured for the study subjects, and the tumors were classified into three types according to the characteristics of their impedance curves： increasing, flat, or decreasing. The tumors were further sorted into seven subtypes （A-G） depending on the curvature of the impedance curve＇ s increase or decrease. Relative popping rates were determined for the three types and seven subtypes. A chi-square test was performed to estimate statistical significance.RESULTS： A total of 148 nodules treated by RFA were analyzed. The study samples included 132 nodules of hepatocellular carcinoma, 14 nodules of metastatic liver cancer, and two nodules of intrahepatic cholangio- carcinoma. The numbers of nodules with each imped- ance curve type were as follows： 37 increasing-type nodules, 43 fiat-type nodules, and 68 decreasing-type nodules. Popping occurrence rates were 24.3%, 46.5% and 64.7%, respectively. Flat-type nodules exhibited a significantly higher rate of popping compared to increasing-type nodules （P = 0.039）. Decreasing-type nodules exhibited a significantly higher rate of popping compared to increasing-type nodules （P 〈 0.0001）. No- tably, nodules that showed a sharp decrease in imped- ance in the latter ablation period （subtype E） exhibited a significantly higher rate of popping compared to other subtypes. CONCLUSION： Intraprocedural impedance monitoring can be a useful tool to predict the occurrence of pop- ping during liver tumor RFA performed with internally cooled electrodes.
基金Project supported by the National Natural Science Foundation of China(No.51766010)the Knowledge Innovative Team of High-efficient Refrigeration in Nanchang City of China(No.2018-CXTD-004)+2 种基金the Special Fund Project for Graduate Innovation of Nanchang University(No.CX2018058)the Zhihui Zhengzhou 1125 Talent Gathering Plan Innovation and Entrepreneurship Leading Teamthe Study Plan for Young and Middle-aged Teachers in Nanchang University,China
文摘Internally-cooled dehumidifiers are efficient liquid desiccant dehumidifiers, whose performance is mainly determined by the device structure and operating conditions. Based on energy and mass conservation in the air, solution, and cooling water in the device, mathematical models are built and their theoretical performance is simulated and analyzed in this paper. A novel measure of dehumidification efficiency is introduced to evaluate the performance of internally-cooled dehumidifiers, in which the equilibrium humidity ratio of the inlet solution is calculated according to the minimum temperature in the inlet solution and the cooling water. Numerical simulations show that a counter flow between air and solution is always the most efficient, followed by cross flow, and parallel flow is the least efficient. Cooling water with the same flow direction as the solution performs better than that with a counter flow, with approximately a 5% improvement in efficiency. Compared with Ca Cl2, the dehumidification efficiency of a Li Cl solution is greater by 60%, while its exergy efficiency is less by 16%. Dehumidification efficiency can be improved with the number of air-solution heat transfer units(NTUa-s) increasing, and reduced with the air mass flow rate raised. With NTUa-s increasing, exergy efficiency can be improved, and an increase in mass flow rate of cooling water results in a decrease of efficiency. Higher solution concentration and lower inlet temperature of solution and air can achieve both higher dehumidification efficiency and exergy efficiency.
文摘A theoretical model is developed to establish an indepth understanding of the performance of a three-stage wind tower with a bypass system for indoor cooling in rural dry and hot climates. Model simulations are presented for a wide range of ambient conditions that include inlet wind speed, inlet temperature and relative humidity. Simulation results provide an insight into the desirable water flow rates and air-to-water loadings for comfort zone tem-peratures and relative humidity levels at the exit of the wind tower. Simulations show wind towers with variable cross-sections provide an increase in the cooling power for the same inlet wind speed, inlet air temperature and relative humidity when compared to wind towers with a constant cross-section. The study shall lead to a better understanding to designing wind towers that are both environmentally friendly and energy efficient.
