Backward Load Research Articles

Optimization of Energy Loss Cost of Distribution Networks with the Optimal Placement and Sizing of DSTATCOM Using Differential Evolution Algorithm

This paper presents an optimization of energy loss cost (ELC) of distribution networks (DN) with the optimal allocation and sizing of DSTATCOM to maximizing the total net profit (TNP)/cost savings by using the differential evolution algorithm per annum and planning horizon of DSTATCOM installation scheme. In this approach, the optimal reactive power compensation is the main vital role in solving the objective function. The optimal reactive power compensation with the optimal placement and sizing of DSTATCOM and the improvement in voltage profile of the DN are obtained based on certain objectives such as best reduction in network power loss and the total ELC and the maximization of TNP. The modeling on the size of DSTATCOM is used and was incorporated in DN through the forward–backward sweep load flow technique to evaluate the parameters of load flows in DN. Present worth factor is instigated to evaluate the TNP of the DSTATCOM installation scheme. The proposed method is validated on the 30, 33, and 69-bus DN.

Kinematics of the lever arm swing in myosin VI

Myosin VI (MVI) is the only known member of the myosin superfamily that, upon dimerization, walks processively toward the pointed end of the actin filament. The leading head of the dimer directs the trailing head forward with a power stroke, a conformational change of the motor domain exaggerated by the lever arm. Using a unique coarse-grained model for the power stroke of a single MVI, we provide the molecular basis for its motility. We show that the power stroke occurs in two major steps. First, the motor domain attains the poststroke conformation without directing the lever arm forward; and second, the lever arm reaches the poststroke orientation by undergoing a rotational diffusion. From the analysis of the trajectories, we discover that the potential that directs the rotating lever arm toward the poststroke conformation is almost flat, implying that the lever arm rotation is mostly uncoupled from the motor domain. Because a backward load comparable to the largest interhead tension in a MVI dimer prevents the rotation of the lever arm, our model suggests that the leading-head lever arm of a MVI dimer is uncoupled, in accord with the inference drawn from polarized total internal reflection fluorescence (polTIRF) experiments. Without any adjustable parameter, our simulations lead to quantitative agreement with polTIRF experiments, which validates the structural insights. Finally, in addition to making testable predictions, we also discuss the implications of our model in explaining the broad step-size distribution of the MVI stepping pattern.

Kinematics of the Lever Arm Swing in Myosin VI

Similarly to other myosins, Myosin VI (MVI) uses the energy stored in ATP to move on the actin filament. During the power stroke, a structural transition initiated in the motor domain leads to the movement of the converter, which is exaggerated by the swinging lever arm. MVI, like Myosin V, can form dimers that walk processively on actin. The uniqueness of MVI emerges from the details of its motion: MVI walks towards the pointed end of the actin filament, and it does so undergoing an erratic stepping pattern, in which backward steps are combined with hand-over-hand and inchworm-like forward steps. Experimental evidence suggested that the lever arm of the leading head of a MVI dimer is uncoupled from the motor domain. We developed a model of the power stroke of MVI and we show that it occurs in two steps: first the motor domain, including the converter, reaches the post-stroke conformation without directing the lever arm forward. Secondly, the lever arm undergoes a diffusion towards its post-stroke orientation, which is only weakly biased by the motor domain. The uncoupling of the lever arm during the power stroke occurs even without backward load, suggesting that it is a mechanism encoded in MVI strucutre. Also, a backward load compatible with the largest estimated interhead tension in a MVI dimer prevents the second step of the power stroke, suggesting that a MVI dimer leading head lever arm is uncoupled from the motor domain. Our model, without any adjustable parameters, provides results that are in quantitative agreement with polTIRF experiments monitoring the orientation of a calmodulin-bound probe, and they suggest that the two-step mechanism with an uncoupled lever arm might contribute to explaining the experimentally-observed combination of hand-over-hand and inchworm-like steps.

Optimal Phase Angle Injection for Reactive Power Compensation of Distribution Systems with the Allocation of Multiple Distribution STATCOM

In this paper, the optimal phase angle model and allocation technique of multiple distribution STATCOM (DSTATCOM) in distribution systems for the optimal reactive power compensation is presented. The objective function formulated is the minimization of the active power loss of radial distribution systems (RDS) so as to determine the optimal location(s), optimal phase angle(s), and rating(s) for DSTATCOM, to provide the optimal reactive power compensation. The new modeling of DSTATCOM is developed and is suitably integrated in the forward–backward sweep load flow algorithm so as to determine the line currents, node voltages and the power loss of RDS. Differential evolution algorithm is used as the optimal solution scheme for the optimization of the power loss. The IEEE-69 node RDS is used to validate the efficacy of the proposed approach. The results demonstrate that the proposed technique is more effective in compensating the reactive power to reduce the power loss compared to some of the previous approaches.

Planning of unbalanced radial distribution systems using differential evolution algorithm

This paper presents a planning approach for unbalanced radial distribution systems using differential evolution algorithm (DE) so as to determine the optimal phase balancing and conductor sizes. The objective functions used in the planning are minimization of: (1) total complex power unbalance, (2) total power loss, (3) average voltage drop, (4) voltage unbalance factor, and (5) total neutral current. The optimization is done under the constraints of minimum and maximum voltage limits for each bus voltage and thermal limit of each line. A three phase forward–backward sweep load flow algorithm is developed and used for the determination of these objective functions. The effectiveness of the proposed planning algorithm is corroborated on 19-bus and IEEE 25-bus unbalanced radial distribution systems. The results show that significant improvements in power loss and voltage drop with simultaneous optimization for phase balancing and conductor sizes. The performance of DE is found to be better and consistent as compared to some other meta-heuristic algorithms studied here.

Genetic Algorithm Based Network Reconfiguration in Distribution Systems with Multiple DGs for Time Varying Loads

Abstract This paper describes the implementation of an algorithm which predicts optimum reconfiguration plan for power distribution system with multiple PV generators. Since network reconfiguration is a multi objective and multi constrained problem, genetic algorithm is used for optimization. Forward backward load flow method with time varying load condition is considered. The objective function of the genetic algorithm incorporates all the objectives and constraints required for the reconfiguration plan. The algorithm developed predicts the switching pattern for reconfiguration which gives minimum loss and minimum voltage deviation. It also reduces the number of switching operations along with satisfying the defined limit constraints.

Load-Sharing Mechanism of Cytoplasmic Dynein

Cytoplasmic dynein is a homodimeric AAA+ motor protein responsible for minus end-directed transport along microtubules. The two heads of dynein are not strictly coordinated during processive motility, unlike those of dimeric kinesins and myosins. Therefore, tail-tethered optical trapping experiments yield insufficient information about the force production of individual heads. Here, we connected a trapped bead to a dynein dimer through a rigid DNA tether and directly measured the stepping motion of a single head under load. We observed that even though the step size of a head decreases under load, the head only stalls at half the stall force of the dimer and must rely on its partner head to walk against near-stall loads. The bulk of the force is produced when a head is bound to the microtubule, and stepping direction in the unbound state can be reversed by as little as 0.5 pN of backward load. Force-velocity curves indicate that the forward stepping rate of a dynein head is strongly inhibited by external force, while the backward rate is slow and nearly force-independent. Our results provide evidence for tension gating in dynein motility and lead us to propose a load-sharing mechanism between the two heads of a dynein dimer.

A Forming Load Prediction Model in BMG Micro Backward Extrusion Process Considering Size Effect

The size effect was considered in order to improve the prediction accuracy of forming load in the micro backward extrusion process of a Zr55Cu30Al10Ni5 BMG cup-shaped specimen. The ratio of the billet surface to volume near the working land of backward extrusion punch was proposed as size effect factor. Then the size effect factor was complemented into a backward extrusion load prediction formula of conventional macroscopic parts. The micro-sized BMG cups with different sidewall thickness varying from 20 μm to 125 μm were deformed in supercooled liquid state. The initial diameter of the billets is 600 μm and the experiments were conducted at Zwick/Roell Z200 Press. The forming loads were recorded and compared with the calculated values from the proposed prediction model. The results showed that the proposed model can predict the forming load with very small deviation.

Finite-Element Simulation and Experimental Investigation of Isothermal Backward Extrusion of 7075 Al Alloy

This paper reports on an experimental and finite-element analysis of a backward extrusion process of 7075 Al alloy. The influence of punch speed and billet temperatures on the backward extrusion process was investigated. DEFORM-3D software was used for finite-element simulations. A backward extrusion die was designed and manufactured for the purpose of experimental research. From simulation, the forming load and stress/strain distribution of the billet were obtained. The simulation results show that the effective stress/strain distributions are inhomogeneous in the deformed billet. Finite-element method has been used successfully to predict the backward extrusion load, indicating the good accuracy of the simulation results. In this study, the effects of the different temperatures and punch speeds on the effective stress/strain distribution and forming load during forming process were investigated.

Kramers-type elastic ratchet model for ATP gating during kinesin’s mechanochemical cycle

ATP binding, acting as a gate, plays an important role in kinesin stepping. To understand the physical mechanism of the ATP gate, we propose a Kramers-type elastic ratchet model in which the free head undergoes a biased diffusive search. By first passage time analysis, we investigate the dependence of the mean dwell time on the load force for forward steps of kinesin and find that the forward dwell time varies exponentially with the backward load force which is consistent with the data of Carter and Cross, Nature 435 (2005) 308. Our work suggests that the gating mechanism triggered by ATP binding involves both Kramers-type elastic ratchet mechanism and power stroke movement.

前方軸・後方缶の組合せ押出し鍛造における荷重<br>に及ぼすビレット高さ/直径比の影響

Combined extrusion forging is effective in decreasing load and process simplification. However, combined forging is not used widely. The reason for this seems to be the load and metal flow being difficult to assume. Many research studies have been conducted to solve this problem. Although it is considered that extrusion load and metal flow are affected by the shape ratio of a billet (ho/do), research on this subject is insufficient. In this study, the effect of the shape ratio of a billet on extrusion load was examined by experiment and analysis. The extrusion load in both single extrusion and combined extrusion increases with the shape ratio of a billet. When the shape ratio is 1.5, the combined extrusion load corresponded to either of the forward extrusion load or the backward extrusion load, smaller. When the shape ratio is 0.4, the combined extrusion load was smaller than both of the forward extrusion load and the backward extrusion load. When the diameter and height of the billet based on the size of the product were given, the method of predicting a combined extrusion load was proposed.

Stepping behavior of two-headed kinesin motors

The stepping behavior of the dimeric kinesin is studied by using our model based on previous biochemical, X-ray crystallography and cryo-electron microscopy studies. It is shown that, when a Pi is released from the trailing head, a forward step is made under a backward load smaller than the stall force; while when a Pi is released from the leading head, no stepping is made under a forward load or no load, and a backward step is made under a backward load. The forward stepping time, i.e., the time from the release of Pi in the trailing head to the binding of the ADP head to next binding site, is much smaller than the dwell time even under the backward load near the stall force. Thus the movement velocity of the kinesin dimer can be considered to be only dependent on ATPase rates of the two heads. The duration of the rising phase, i.e., the actual time taken by the ADP head to transit from the trailing to leading positions, is on the time scale of microseconds under any backward load smaller than the stall force. This is consistent with available experimental results.

Neck Injury Mechanisms During Direct Face Impact

Digitized measurements of the intervertebral motions using cervical cineradiographs of 10 volunteers during direct impacts applied to their faces. To clarify the cervical spine motion during direct face impact and postulate some mechanisms of neck injuries. Neck injury occurs mostly in traffic or falling accidents. Hyperextension of the neck is considered the most common mechanism of the injury because most victims have lacerations or contusions on their faces. A low-level backward impact load was applied to 10 healthy male volunteers' faces at the forehead and maxilla via a strap using a free-falling small mass. Cervical vertebral motion was recorded by radiograph cineradiography during the impact. The upper cervical spine showed a flexion motion for both conditions. Consequently, the cervical spine had an S-shaped curvature similar to that in cervical retraction. Intervertebral motions of the cervical spine were evaluated using an radiograph frame taken at the maximum cervical retraction. For the forehead load, intervertebral motion at C1-C2 was flexion, and motions of the lower cervical spine were extension. For the maxilla load, intervertebral motions from occiput-C1 through C4-C5 were flexion. The inflection point of the curvature was influenced by the impact location. We detected a flexion motion of the upper or middle cervical spine during direct face impact. In an actual accident, if the cervical spine is forced into similar motion, we speculate that neck injury would occur in this retraction-like curvature of the cervical spine.

Model for kinetics of wild-type and mutant kinesins

A hand-over-hand model is presented for the processive movement of two-headed kinesin based on previous structural and biochemical studies. In the model, the ATPase activities of the two heads are regulated by forces, both from internal elasticity and external load, exerted on their neck linkers. The results from the model show that the two heads may be partially coordinated in their ATPase cycles: in the case of backward load or low forward load, the ATPase cycles of its two heads are well coordinated, whereas in the case of high forward load, they are no longer well coordinated. The model gives results that show good quantitative agreement with both previous biochemical and mechanical experimental results such as the limping of homodimers and the dependences of mean velocity on [ATP] and on loads (both positive and negative). Furthermore, using the model we study the kinetics of a number of mutant kinesin homodimers and heterodimers, showing that the two heads’ ATPase activities of some of these molecules are not well coordinated and they move processively with low mechanochemical coupling efficiencies even under no load. The theoretical results of ATPase rate per head, moving velocity, and stall force of the motors show good quantitative agreement with the experimental ones. The puzzling dynamic behaviours of mutant homodimeric and heterodimeric kinesins become understandable.

Force-Dependent Stepping Kinetics of Myosin-V

Myosin-V is a processive two-headed actin-based motor protein involved in many intracellular transport processes. A key question for understanding myosin-V function and the communication between its two heads is its behavior under load. Since in vivo myosin-V colocalizes with other much stronger motors like kinesins, its behavior under superstall forces is especially relevant. We used optical tweezers with a long-range force feedback to study myosin-V motion under controlled external forward and backward loads over its full run length. We find the mean step size remains constant at ∼36 nm over a wide range of forces from 5 pN forward to 1.5 pN backward load. We also find two force-dependent transitions in the chemomechanical cycle. The slower ADP-release is rate limiting at low loads and depends only weakly on force. The faster rate depends more strongly on force. The stronger force dependence suggests this rate represents the diffusive search of the leading head for its binding site. In contrast to kinesin motors, myosin-V’s run length is essentially independent of force between 5 pN of forward to 1.5 pN of backward load. At superstall forces of 5 pN, we observe continuous backward stepping of myosin-V, indicating that a force-driven reversal of the power stroke is possible.

Unconstrained Steps of Myosin VI Appear Longest among Known Molecular Motors

Myosin VI is a two-headed molecular motor that moves along an actin filament in the direction opposite to most other myosins. Previously, a single myosin VI molecule has been shown to proceed with steps that are large compared to its neck size: either it walks by somehow extending its neck or one head slides along actin for a long distance before the other head lands. To inquire into these and other possible mechanism of motility, we suspended an actin filament between two plastic beads, and let a single myosin VI molecule carrying a bead duplex move along the actin. This configuration, unlike previous studies, allows unconstrained rotation of myosin VI around the right-handed double helix of actin. Myosin VI moved almost straight or as a right-handed spiral with a pitch of several micrometers, indicating that the molecule walks with strides slightly longer than the actin helical repeat of 36 nm. The large steps without much rotation suggest kinesin-type walking with extended and flexible necks, but how to move forward with flexible necks, even under a backward load, is not clear. As an answer, we propose that a conformational change in the lifted head would facilitate landing on a forward, rather than backward, site. This mechanism may underlie stepping of all two-headed molecular motors including kinesin and myosin V.