Maintenance of an abrupt boundary between needle-leaved and broad-leaved forests in a wetland near coast

There is an abrupt boundary between two well-developed wetland forests, a stand consisting of a broad-leaved, nitrogen-fixer Alnusjaponica and a stand of the needle-leaved Picea glehnii Masters, in eastern Hokkaido, Japan. To clarify maintenance mechanisms, we studied the forest profile, water level, groundwater and precipitation chemistry, seedling establishment patterns in relation to microhabitats, and seed migration. The profile of groundwater level insufficiently explained the abrupt boundary formation, while the groundwater chemistry differed significantly between the two forests ; i.e., EC, Na^＋, K^＋, Mg^2＋, Ca^2＋ and Cl^- were higher in P. glehnii forest and pH was lower. Precipitation in P. glehnii forest contained richer Na＋, Ca^2＋ and Cl^-, indicating that the differences in surface-water chemistry were mostly derived from precipitation. Solar radiation was less than 2.2 MJ.m^-2.d^-1 on P. glehnii forest in late June, while that was patchily distributed in A.japonica forest with a range from 1.0 to 3.7 MJ＇m^-2＇d^-1. Moss cover on the soil surface, most of which were made of Sphagnum spp., was 60% in P. glehnii forest, but was 10% in A. japonica forest. Surface water chemistry represented by pH was considered to determine the development of Sphagnum moss. About 70% of P. glehnii seedlings 〈 1.3 m in height established on moss cover. Seed-sowing experiments suggested that seed germination and seedling survival for both species were significantly higher in P. glehnii forest. Therefore, the regeneration of P. glehnii in A. japonica forest was negligible, owing to the paucity of favorable microhabitats and low seedling establishment. A. japonica regenerated only by resprouting, and the seedlings were few in both forests. In addition, A. japonica seed migration into the P. glehnii forests was greatly restricted, and low solar radiation in the P. glehnii forest contributed to low seedling survival. Based on those results, we concluded that Picea glehnii and Alnusjaponica could develop distinct and selfish environments being unsuitable for the other species and inhibit natural afforestation of another species each other by excluding invasion.

Speed-assigned Position Tracking Control of SRM With Adaptive Backstepping Control

A novel speed-assigned method is applied to the position tracking control of switched reluctance motor(SRM).A speed control freedom can be drawn into the position control through speed assignment. Adaptive backstepping control is used to design the position controller for the SRM. The accuracy of position tracking of the SRM can be enhanced with speed assignment. A disturbance observer is further designed to enhance the estimation accuracy of the unknown load torque. Simulation results certify that the design scheme is right and effective.

Maintenance of an abrupt boundary between needle-leaved and broad-leaved forests in a wetland near coast

There is an abrupt boundary between two well-developed wetland forests, a stand consisting of a broad-leaved, nitrogen-fixer Alnus japonica and a stand of the needle-leaved Picea glehnii Masters, in eastern Hokkaido, Japan.To clarify maintenance mechanisms, we studied the forest profile, water level, groundwater and precipitation chemistry, seedling establishment patterns in relation to microhabitats, and seed migration.The profile of groundwater level insufficiently explained the abrupt boundary formation, while the groundwater che-mistry differed significantly between the two forests;i.e., EC, Na+, K+, Mg2+, Ca2+ and Cl-were higher in P.glehnii forest and pH was lower.Precipitation in P.glehnii forest contained richer Na+, Ca2+ and Cl-, indicating that the differences in surface-water chemistry were mostly derived from precipitation.Solar radiation was less than 2.2 MJ·m-2·d-1 on P.glehnii forest in late June, while that was patchily distributed in A.japonica forest with a range from 1.0 to 3.7 MJ·m-2·d-1.Moss cover on the soil surface, most of which were made of Sphagnum spp., was 60% in P.glehnii forest, but was 10% in A.japonica forest.Surface water chemistry represented by pH was considered to determine the development of Sphagnum moss.About 70% of P.glehnii seedlings < 1.3 m in height established on moss cover.Seed-sowing experiments suggested that seed germination and seedling survival for both species were significantly higher in P.glehnii forest.Therefore, the regeneration of P.glehnii in A.japonica forest was negligible, owing to the paucity of favorable microhabitats and low seedling establishment.A.japonica regenerated only by resprouting, and the seedlings were few in both forests.In addition, A.japonica seed migration into the P.glehnii forests was greatly restricted, and low solar radiation in the P.glehnii forest contributed to low seedling survival.Based on those results, we concluded that Picea glehnii and Alnus japonica could develop distinct and selfish environments being unsuitable for the other species and inhibit natural afforestation of another species each other by excluding invasion.

Experiment on Leader Propagation Characteristics of Air Gaps in UHVDC Transmission Towers Under Positive Switching Impulse Voltages

Rapid developments in EHV/UHV transmission systems require a deeper understanding of the mechanism of long air gap discharge.Leader propagation is one of the main processes in long gap breakdown.In this paper,the leader propagation characteristics of real size±800 kV UHVDC transmission tower gaps under positive switching impulse voltages(185/2290μs)are investigated.An integrated observation platform consisting of an impulse voltage divider,a coaxial shunt,a high-speed video camera,and a set of integrated optical electric field sensors(IOES),is established.The waveforms of impulse voltage,discharge current,electric field variation at specific positions,and time-resolved photographs of discharge morphology are recorded.Axial leader velocity and the relationship between leader advancements and injected charge are obtained.The typical value of leader stable propagation velocity is 1.7–2.2 cm/μs,which varies slightly with the gap length and applied voltage amplitude.The leader velocity in the re-illumination process is much higher,and is seen as varying from 5 cm/μs to 30 cm/μs,with an average value around 10 cm/μs.The charge in leader channel per unit length is 20–40μC/m,which illustrates a near-direct proportion relationship between discharge current and leader velocity.The observed parameters are important for further simulation of the tower gap breakdown processes.

Stability of Switched Positive Descriptor Systems with Average Dwell Time Switching

In this paper, the problems of stability for a class of switched positive descriptor systems(SPDSs)with average dwell time(ADT) switching are investigated. First, based on the equivalent switched system and the properties of the projector matrix, sufficient stabilities are given for the underlying systems in both continuoustime and discrete-time contexts. Then, a sufficient stability condition for the SPDS with both stable and unstable subsystems is obtained. The stability results for the SPDSs are represented in terms of a set of linear programmings(LPs) by the multiple linear co-positive Lyapunov function(MLCLF) approach. Finally, three numerical examples are given to illustrate the effectiveness of the obtained theoretical results.

Regional Stability of Positive Switched Linear Systems with Multi-equilibrium Points

This paper studies the regional stability for positive switched linear systems with multi-equilibrium points （PSLS-MEP）. First, a sufficient condition is presented for the regional stability of PSLS-MEP via a common linear Lyapunov function. Second, by establishing multiple Lyapunov functions, a dwell time based condition is proposed for the regional stability analysis. Third, a suprasphere which contains all equilibrium points is constructed as a stability region of the considered PSLS-MEP, which is less conservative than existing results. Finally, the study of an illustrative example shows that the obtained results are effective in the regional stability analysis of PSLS-MEP.

An UPLC-MS/MS method for simultaneous determination of multiple constituents in Guizhi Fuling capsule with ultrafast positive/negative ionization switching

Guizhi Fuling capsule(GFC), a traditional Chinese medicine(TCM) with effects of promoting blood circulation and dissipating blood stasis, has been widely used in the clinic. Because of the complex matrix and various chemical structure types, quality control of GFC remains great challenge. In the present study, an ultra performance liquid chromatography hybrid triple-quadrupole mass spectrometry(UPLC-QQQ MS) method with ultrafast positive/negative ionization switching was developed for simultaneous determination of 18 bioactive components in GFC, including methyl gallate, ethyl gallate, oxypaeoniflorin, benzoic acid, albiflorin, paeonolide, paeoniflorin, 1, 2, 3, 4, 6-pentagalloylglucose, mudanpioside C, benzoyloxypaeoniflorin, benzoylpaeoniflorin, pachymic acid, amygdalin, cinnamaldehyde, paeonol, cinnamic acid, 4-hydroxybenzoic acid, and gallic acid. Separation was performed on an Agilent Zorbax Extend–C18 column(2.1 mm × 50 mm, 1.8 μm), using a gradient elution with acetonitrile and water containing 0.1% formic acid. Cholic acid was selected as the internal standard. This newly developed method was fully validated for linearity, precision, accuracy, and stability, and then applied to quality assessment of GFC. Finally, the batch-to-batch reproducibility of GFC samples was evaluated by the cosine ration and Euclidean distance method, which showed high quality consistency. The results demonstrated that the developed method provided a reasonable and powerful manner for quality control of GFC.

Guaranteed Cost Finite-Time Control of Fractional-Order Nonlinear Positive Switched Systems with D-Perturbations via MDADT

This paper is concerned with the problem of guaranteed cost finite-time control of fractionalorder nonlinear positive switched systems (FONPSS) with D-perturbation. Firstly, the proof of the positivity of FONPSS with D-perturbation is given, the definition of guaranteed cost finite-time stability is firstly given in such systems. Then, by constructing linear copositive Lyapunov functions and using the mode-dependent average dwell time (MDADT) approach, a static output feedback controller is constructed, and sufficient conditions are derived to guarantee that the corresponding closed-loop system is guaranteed cost finite-time stable (GCFTS). Such conditions can be easily solved by linear programming. Finally, an example is provided to illustrate the effectiveness of the proposed method.

Event-Triggered L1-Gain Control of Nonlinear Positive Switched Systems

This paper is concerned with the event-triggered L1-gain control of a class of nonlinear positive switched systems.First,an event-triggering condition in the form of 1-norm is presented for the systems.By virtue of the event-triggering strategy,the original system is transformed into an interval uncertain system.An event-triggered L1-gain controller is designed by decomposing the controller gain matrix into the sum of nonnegative and non-positive components.Under the design controller,the resulting closed-loop systems are positive and L1-gain stable.The obtained approach is developed for the systems subject to input saturation.All presented conditions are solvable in terms of linear programming.Finally,two examples are provided to verify the effectiveness of the design.

Event-triggered Control of Positive Switched Systems with Actuator Saturation and Time-delay

This paper investigates the event-triggered control of positive switched systems with randomly occurring actuator saturation and time-delay,where the actuator saturation and time-delay obey different Bernoulli distributions.First,an event-triggering con-dition is constructed based on a 1-norm inequality.Under the presented event-triggering scheme,an interval estimation method is utilized to deal with the error term of the systems.Using a co-positive Lyapunov functional,the event-triggered controller and the cone attraction domain gain matrices are designed via matrix decomposition techniques.The positivity and stability of the resulting closed-loop systems are reached by guaranteeing the positivity of the lower bound of the systems and the stability of the upper bound of the systems,respectively.The proposed approach is developed for interval and polytopic uncertain systems,respectively.Finally,two examples are provided to illustrate the effectiveness of the theoretical findings.