The number of patients with gastric cancer has more than doubled since 1985 in developing countries. Thus, the questions of whether it can be predicted from gastritis morphology, who is at risk and who has a lower ris...The number of patients with gastric cancer has more than doubled since 1985 in developing countries. Thus, the questions of whether it can be predicted from gastritis morphology, who is at risk and who has a lower risk of developing gastric carcinoma are raised. H pylori-infection leads to erosions, ulcerations, carcinoma, mucosa associated lymphoid tissue (MALT)- lymphoma and extragastric diseases only in some individuals. The frequency of ulcerations among H pylori-infected individuals is estimated to be 13%, gastric cancer about 1% and MALT lymphoma around 0.1%. In the literature a multistep model from chronic active H pylori -infection through multifocal atrophy, intestinal metaplasia, dysplasia (intraepithelial neoplasia) and carcinoma has been described. But this model cannot be applied to all routine cases. Since risk factors such as metaplasia and atrophy are paracancerous rather than precancerous conditions, this raises the question whether there is a better morphological marker. Differences in topography, grade and activity of Helicobacter gastritis in the antrum and corpus might be good markers for identifying those who are at risk of developing gastric cancer. It is known that the so-called corpus dominant H pylori gastritis is found more frequently among individuals with early and advanced gastric cancer and within high risk populations. This is valid both for first- degree relatives of gastric cancer patients and for patients with gastric adenoma and hyperplastic polyps. In conclusion, corpus-dominant H pylori gastritis is significantly more common in patients with advanced and early gastric cancer, first-degree relatives of patients with gastric cancer, patients with gastric adenoma and gastric hyperplastic polyps. Therefore, all these patients are at risk of developing gastric cancer. Next, the question of who is at risk of developing corpus-dominant gastritis is raised. It appears that patients with a low acid output more frequently develop gastric cancer. Eradication therapy is never performed t展开更多
Given the“carbon neutralization and carbon peak”policy,enhancing the low voltage ride-through(LVRT)capability of wind farms has become a current demand to ensure the safe and stable operation of power systems in the...Given the“carbon neutralization and carbon peak”policy,enhancing the low voltage ride-through(LVRT)capability of wind farms has become a current demand to ensure the safe and stable operation of power systems in the context of a possible severe threat of large-scale disconnection caused by wind farms.Currently,research on the LVRT of wind farms mainly focuses on suppressing rotor current and providing reactive current support,while the impact of active current output on LVRT performance has not been thoroughly discussed.This paper studies and reveals the relation-ship between the limit of reactive current output and the depth of voltage drop during LVRT for doubly-fed induction generator(DFIG)based wind farms.Specifically,the reactive current output limit of the grid-side converter is inde-pendent of the depth of voltage drop,and its limit is the maximum current allowed by the converter,while the reac-tive current output limit of the DFIG stator is a linear function of the depth of voltage drop.An optimized scheme for allocating reactive current among the STATCOM,DFIG stator,and grid-side converter is proposed.The scheme maximizes the output of active current while satisfying the standard requirements for reactive current output.Com-pared to traditional schemes,the proposed LVRT optimization strategy can output more active power during the LVRT period,effectively suppressing the rate of rotor speed increase,and improving the LVRT performance and fault recov-ery capability of wind farms.Simulation results verify the effectiveness of the proposed scheme.展开更多
An ultra-low-power CMOS temperature sensor with analog-to-digital readout circuitry for RFID applications was implemented in a 0.18-μm CMOS process. To achieve ultra-low power consumption, an error model is proposed ...An ultra-low-power CMOS temperature sensor with analog-to-digital readout circuitry for RFID applications was implemented in a 0.18-μm CMOS process. To achieve ultra-low power consumption, an error model is proposed and the corresponding novel temperature sensor front-end with a new double-measure method is presented. Analog-to-digital conversion is accomplished by a sigma-delta converter. The complete system consumes only 26 μA @ 1.8 V for continuous operation and achieves an accuracy of ±0.65 °C from –20 to 120 °C after calibration at one temperature.展开更多
This paper is concerned with global practical stabilization of the double integrator system with an imperfect sensor and subject to an additive bounded output disturbance.The imperfect sensor nonlinearity possesses th...This paper is concerned with global practical stabilization of the double integrator system with an imperfect sensor and subject to an additive bounded output disturbance.The imperfect sensor nonlinearity possesses the nonlinear characteristics of saturation and dead zone.Because of the presence of output dead zone and the additive disturbance,the states cannot be expected to driven into an arbitrarily small neighborhood of the origin.To solve the global practical stabilization problem,we proposes a low gain-based linear dynamic output feedback law,under which the first state enters and remains in a bounded set whose size is depended on the bound of disturbance and the range of dead zone and the second state enters and remains in a pre-specified arbitrarily small set,both in finite time.Simulation results illustrate the effectiveness of our proposed control method.展开更多
为了找到一种复杂度低和适应性强的载噪比估计算法,本文在分析了宽窄带功率比值法和方差求和法两种典型算法的基础上,提出了一种载噪比估计算法。对I支路二阶矩分布和I、Q四阶矩分布进行了的推导,得到了载噪比估计的精确表达式;论证了...为了找到一种复杂度低和适应性强的载噪比估计算法,本文在分析了宽窄带功率比值法和方差求和法两种典型算法的基础上,提出了一种载噪比估计算法。对I支路二阶矩分布和I、Q四阶矩分布进行了的推导,得到了载噪比估计的精确表达式;论证了两种不同推导方法的一致性;从估计偏差、算法实现复杂度、输出时延、适应性四个方面对本文的方法进行了理论仿真和实测数据验证。结果表明:本文提出的算法估计误差小于1 d B,同时解决了宽窄带功率比值法不能直接应用于BD系统以及方差求和法在实际应用时实现较复杂的问题。本文提出的算法在保证一定性能的前提下,极大地降低了算法实现复杂度和输出时延,提升了适应性,可广泛应用于北斗等GNSS系统中。展开更多
AIM:To compare the outcomes of conservative vs surgical treatment of enterocutaneous fistulae(ECF) in a community teaching hospital over a decade.METHODS:All cases of ECF between 1997 and 2007 were reviewed for manage...AIM:To compare the outcomes of conservative vs surgical treatment of enterocutaneous fistulae(ECF) in a community teaching hospital over a decade.METHODS:All cases of ECF between 1997 and 2007 were reviewed for management strategy.RESULTS:Of the 83 patients with ECF,60(72%) were postoperative.Sixty-six patients(79.5%) were treated initially with conservative measures.Eighteen patients failed to respond to conservative treatment and required later(secondary) exploration;this group consisted of an equal number of low vs high output fistulae.Seventeen(20.5%) patients underwent initial(primary) def initivesurgery secondary to anastomotic leak and peritonitis.Surgical procedures included resection of ECF with anastomosis(24),exclusion(6) and direct-drainage(4).No signif icant difference was seen in the recurrence rate for conservative(10%) vs operative-treatment(20%).role as an initial management in both low and high output fistulae.In selective cases only,early primary exploration is recommended.展开更多
In recent years, with the growth of wind energy resources,the capability of wind farms to damp low-frequency oscillations(LFOs) has provided a notable advantage for the stabilityenhancement of the modern power grid. M...In recent years, with the growth of wind energy resources,the capability of wind farms to damp low-frequency oscillations(LFOs) has provided a notable advantage for the stabilityenhancement of the modern power grid. Meanwhile, owingto variations in the power system operating point (OP), thedamping characteristics of LFOs may be affected adversely. Inthis respect, this paper presents a coordinated robust proportional-integral-derivative (PID) based damping control approachfor permanent magnet synchronous generators (PMSGs)to effectively stabilize LFOs, while considering power system operationaluncertainties in the form of a polytopic model constructedby linearizing the power system under a given set ofOPs. The proposed approach works by modulating the DC-linkvoltage control loop of the grid-side converter (GSC) via a supplementaryPID controller, which is synthesized by transformingthe design problem into H-infinity static output feedback(SOF) control methodology. The solution of H-infinity SOF controlproblem involves satisfying linear matrix inequality (LMI)constraints based on the parameter-dependent Lyapunov functionto ensure asymptotic stability such that the minimal H-infinityperformance objective is simultaneously accomplished forthe entire polytope. The coordinated damping controllers forthe multiple wind farms are then designed sequentially by usingthe proposed approach. Eigenvalue analysis confirms the improveddamping characteristics of the closed-loop system forseveral representative OPs. Afterward, the simulation results, includingthe performance comparison with existing approaches,validate the higher robustness of the proposed approach for awide range of operating scenarios.展开更多
文摘The number of patients with gastric cancer has more than doubled since 1985 in developing countries. Thus, the questions of whether it can be predicted from gastritis morphology, who is at risk and who has a lower risk of developing gastric carcinoma are raised. H pylori-infection leads to erosions, ulcerations, carcinoma, mucosa associated lymphoid tissue (MALT)- lymphoma and extragastric diseases only in some individuals. The frequency of ulcerations among H pylori-infected individuals is estimated to be 13%, gastric cancer about 1% and MALT lymphoma around 0.1%. In the literature a multistep model from chronic active H pylori -infection through multifocal atrophy, intestinal metaplasia, dysplasia (intraepithelial neoplasia) and carcinoma has been described. But this model cannot be applied to all routine cases. Since risk factors such as metaplasia and atrophy are paracancerous rather than precancerous conditions, this raises the question whether there is a better morphological marker. Differences in topography, grade and activity of Helicobacter gastritis in the antrum and corpus might be good markers for identifying those who are at risk of developing gastric cancer. It is known that the so-called corpus dominant H pylori gastritis is found more frequently among individuals with early and advanced gastric cancer and within high risk populations. This is valid both for first- degree relatives of gastric cancer patients and for patients with gastric adenoma and hyperplastic polyps. In conclusion, corpus-dominant H pylori gastritis is significantly more common in patients with advanced and early gastric cancer, first-degree relatives of patients with gastric cancer, patients with gastric adenoma and gastric hyperplastic polyps. Therefore, all these patients are at risk of developing gastric cancer. Next, the question of who is at risk of developing corpus-dominant gastritis is raised. It appears that patients with a low acid output more frequently develop gastric cancer. Eradication therapy is never performed t
基金supported by the National Natural Science Foundation of China 52177108。
文摘Given the“carbon neutralization and carbon peak”policy,enhancing the low voltage ride-through(LVRT)capability of wind farms has become a current demand to ensure the safe and stable operation of power systems in the context of a possible severe threat of large-scale disconnection caused by wind farms.Currently,research on the LVRT of wind farms mainly focuses on suppressing rotor current and providing reactive current support,while the impact of active current output on LVRT performance has not been thoroughly discussed.This paper studies and reveals the relation-ship between the limit of reactive current output and the depth of voltage drop during LVRT for doubly-fed induction generator(DFIG)based wind farms.Specifically,the reactive current output limit of the grid-side converter is inde-pendent of the depth of voltage drop,and its limit is the maximum current allowed by the converter,while the reac-tive current output limit of the DFIG stator is a linear function of the depth of voltage drop.An optimized scheme for allocating reactive current among the STATCOM,DFIG stator,and grid-side converter is proposed.The scheme maximizes the output of active current while satisfying the standard requirements for reactive current output.Com-pared to traditional schemes,the proposed LVRT optimization strategy can output more active power during the LVRT period,effectively suppressing the rate of rotor speed increase,and improving the LVRT performance and fault recov-ery capability of wind farms.Simulation results verify the effectiveness of the proposed scheme.
文摘An ultra-low-power CMOS temperature sensor with analog-to-digital readout circuitry for RFID applications was implemented in a 0.18-μm CMOS process. To achieve ultra-low power consumption, an error model is proposed and the corresponding novel temperature sensor front-end with a new double-measure method is presented. Analog-to-digital conversion is accomplished by a sigma-delta converter. The complete system consumes only 26 μA @ 1.8 V for continuous operation and achieves an accuracy of ±0.65 °C from –20 to 120 °C after calibration at one temperature.
基金supported by the National Natural Science Foundation of China(Nos.62022055,62373249).
文摘This paper is concerned with global practical stabilization of the double integrator system with an imperfect sensor and subject to an additive bounded output disturbance.The imperfect sensor nonlinearity possesses the nonlinear characteristics of saturation and dead zone.Because of the presence of output dead zone and the additive disturbance,the states cannot be expected to driven into an arbitrarily small neighborhood of the origin.To solve the global practical stabilization problem,we proposes a low gain-based linear dynamic output feedback law,under which the first state enters and remains in a bounded set whose size is depended on the bound of disturbance and the range of dead zone and the second state enters and remains in a pre-specified arbitrarily small set,both in finite time.Simulation results illustrate the effectiveness of our proposed control method.
文摘为了找到一种复杂度低和适应性强的载噪比估计算法,本文在分析了宽窄带功率比值法和方差求和法两种典型算法的基础上,提出了一种载噪比估计算法。对I支路二阶矩分布和I、Q四阶矩分布进行了的推导,得到了载噪比估计的精确表达式;论证了两种不同推导方法的一致性;从估计偏差、算法实现复杂度、输出时延、适应性四个方面对本文的方法进行了理论仿真和实测数据验证。结果表明:本文提出的算法估计误差小于1 d B,同时解决了宽窄带功率比值法不能直接应用于BD系统以及方差求和法在实际应用时实现较复杂的问题。本文提出的算法在保证一定性能的前提下,极大地降低了算法实现复杂度和输出时延,提升了适应性,可广泛应用于北斗等GNSS系统中。
文摘AIM:To compare the outcomes of conservative vs surgical treatment of enterocutaneous fistulae(ECF) in a community teaching hospital over a decade.METHODS:All cases of ECF between 1997 and 2007 were reviewed for management strategy.RESULTS:Of the 83 patients with ECF,60(72%) were postoperative.Sixty-six patients(79.5%) were treated initially with conservative measures.Eighteen patients failed to respond to conservative treatment and required later(secondary) exploration;this group consisted of an equal number of low vs high output fistulae.Seventeen(20.5%) patients underwent initial(primary) def initivesurgery secondary to anastomotic leak and peritonitis.Surgical procedures included resection of ECF with anastomosis(24),exclusion(6) and direct-drainage(4).No signif icant difference was seen in the recurrence rate for conservative(10%) vs operative-treatment(20%).role as an initial management in both low and high output fistulae.In selective cases only,early primary exploration is recommended.
基金supported by the Major Program of National Natural Science Foundation of China(No.U2166601)the General Program of National Natural Science Foundation of China(No.52077196).
文摘In recent years, with the growth of wind energy resources,the capability of wind farms to damp low-frequency oscillations(LFOs) has provided a notable advantage for the stabilityenhancement of the modern power grid. Meanwhile, owingto variations in the power system operating point (OP), thedamping characteristics of LFOs may be affected adversely. Inthis respect, this paper presents a coordinated robust proportional-integral-derivative (PID) based damping control approachfor permanent magnet synchronous generators (PMSGs)to effectively stabilize LFOs, while considering power system operationaluncertainties in the form of a polytopic model constructedby linearizing the power system under a given set ofOPs. The proposed approach works by modulating the DC-linkvoltage control loop of the grid-side converter (GSC) via a supplementaryPID controller, which is synthesized by transformingthe design problem into H-infinity static output feedback(SOF) control methodology. The solution of H-infinity SOF controlproblem involves satisfying linear matrix inequality (LMI)constraints based on the parameter-dependent Lyapunov functionto ensure asymptotic stability such that the minimal H-infinityperformance objective is simultaneously accomplished forthe entire polytope. The coordinated damping controllers forthe multiple wind farms are then designed sequentially by usingthe proposed approach. Eigenvalue analysis confirms the improveddamping characteristics of the closed-loop system forseveral representative OPs. Afterward, the simulation results, includingthe performance comparison with existing approaches,validate the higher robustness of the proposed approach for awide range of operating scenarios.
