是“失之”,不是“有失”

张定远认为。长期以来，对于中小学生语文能力(包括作文能力)的评估一直存在两种误区。一种是“不可知”论，即作文难以评估的说法：一种是“精确化”法，即实行完全的量化。在他看来，这两种看法都有失偏颇．不太可取。(《作文考级：社会质疑官方反对挡不住家长欢迎》，《中国青年报》2004年12月6日A6版）

“有失”与“失之”的区别和用法

在带领高三学生进行高考语文复习备考的时候．笔者遇到了这样一道试题。

“失之于……”和“有失于……”

周海婴所著<鲁迅和我七十年>一书中有这样一句话……但是对于母亲的无端指斥,我觉得这位前辈不仅太伤人,失之一于厚道,简直是在信口污蔑人.

“有失”与“失之”辨

“有失”与“失之”是两个文言意味很浓的词语，一般辞书均无单独的词条及解释，由于其表意简洁，媒体上时有所见。但一些人（包括一些文化人）由于不了解其意义和用法，常常错用，以辞害意。例如：

Research on Automatic Test System of Engine Blade Natural Frequency

Blades are one of the important components on aircraft engines.If they break due to vibration failure,the normal operation of the entire engine will be offected.Therefore,it is necessary to measure their natural frequency before installing them on the engine to avoid resonance.At present,most blade vibration testing systems require manual operation by operators,which has high requirements for operators and the testing process is also very cumbersome.Therefore,the testing efficiency is low and cannot meet the needs of efficient testing.To solve the current problems of low testing efficiency and high operational requirements,a high-precision and high-efficiency automatic test system is designed.The testing accuracy of this system can reach ±1%,and the testing efficiency is improved by 37% compared to manual testing.Firstly,the influence of compression force and vibration exciter position on natural frequency test is analyzed by amplitude-frequency curve,so as to calibrate servo cylinder and fourdimensional motion platform.Secondly,the sine wave signal is used as the excitation to sweep the blade linearly,and the natural frequency is determined by the amplitude peak in the frequency domain.Finally,the accuracy experiment and efficiency experiment are carried out on the developed test system,whose results verify its high efficiency and high precision.

Numerical Investigations on Dynamic Stall Characteristics of a Finite Wing

The paper examines the dynamic stall characteristics of a finite wing with an aspect ratio of eight in order to explore the 3D effects on flow topology,aerodynamic characteristics,and pitching damping.Firstly,CFD methods are developed to calculate the aerodynamic characteristics of wings.The URANS equations are solved using a finite volume method,and the two-equation k-ωshear stress transport(SST)turbulence model is employed to account for viscosity effects.Secondly,the CFD methods are used to simulate the aerodynamic characteristics of both a static,rectangular wing and a pitching,tapered wing to verify their effectiveness and accuracy.The numerical results show good agreement with experimental data.Subsequently,the static and dynamic characteristics of the finite wing are computed and discussed.The results reveal significant 3D flow structures during both static and dynamic stalls,including wing tip vortices,arch vortices,Ω-type vortices,and ring vortices.These phenomena lead to differences in the aerodynamic characteristics of the finite wing compared with a 2D airfoil.Specifically,the finite wing has a smaller lift slope during attached-flow stages,higher stall angles,and more gradual stall behavior.Flow separation initially occurs in the middle spanwise section and gradually spreads to both ends.Regarding aerodynamic damping,the inboard sections mainly generate unstable loading.Furthermore,sections experiencing light stall have a higher tendency to produce negative damping compared with sections experiencing deep dynamic stall.

DAMAGES AND FAILURES OF SMART STRUCTURES

According to some observed dama ge phenomena in the smart structure systems, the issues related to the damage and failures of smart structures are addressed in this paper. A few possible damage patterns and the definition of the failure of the smart structures are given. It is pointed out that more attentions should be paid to the functional failures o f smart structures. The effects on the control the static deformation due to par tial debonding of PZT actuators are analyzed by the finite element method. Preli minary numerical results show that partial debonding of PZT actuators may have a p preciate reduction on their actuating ability thus reducing the control ability and accuracy of the smart structures.

Finite element analysis of stress distribution and burst failure of SiC_f/Ti-6Al-4V composite ring

A three-dimensional cyclic symmetry finite element model of titanium-matrix composites（TMCs） ring was developed to investigate the stress distribution and burst failure. The effects of fiber volume fractions, reinforced areas, thermal residual stresses and two different temperatures on stress distribution were studied. The burst speed was obtained through analyzing the hoop tensile stresses under a series of rotating speeds. The results indicate that at the two different temperatures, the influences of fiber volume fractions and reinforced areas on stress level and distribution are different. Some proposals are provided for the structure design of the TMCs ring. With regard to thermal residual stresses, a larger reinforced area is an advisable choice for design of the ring at higher temperature.

Finite element model analysis of thermal failure in connector

Thermal analysis and thermal diagnose are important for small power connector especially in electronic devices since their structure is usually compact. In this paper thermal behavior of small power connector was investigated. It was found that the contact resistance increased due to the Joule beating, and that increased contact resistance produced more Joule heating; this mutual action causes the connector to lose efficiency. The thermal distribution in the connector was analyzed using finite element method （FEM）. The failure mechanism is discussed. It provides basis for improving the structure. The conclusion was verified by experimental results.

Image Distortion Metric Based on Total Bounded Variation

Image definition measurement plays an important role in various image processing applications.And a reliable objective image definition metrics is critical for evaluating the definition of the restored image.In this paper,a novel image distortion metric based on minimal Total Bounded Variation(TBV) is presented.It is clarified that when the restored image approximates to the original clear image,the smaller the TBV is,the better the definition of the restored image is.Furthermore,the difference between the restored image and the original clear image is the smallest when the TBV is minimum.In numerical results,the TBV of the original clear image,blur image and restored image are presented and compared,and the results demonstrate the validity of the distortion metric proposed.

Impacts of distorted fishery statistical data on assessments of three surplus production models

We evaluated the effect of various error sources in fishery harvest/effort data on the maximum sustainable yield （MSY） and corresponding fishing effort （EMsv） using Monte Carlo simulation analyses. A high coefficient of variation （CV） of the catch and effort values biased the estimates of MSY and EMsv. Thus, the state of the fisheries resource and its exploitation was overestimated. We compared the effect using three surplus production models, Hilborn-Waters （H-W）, Schnute, and Prager models. The estimates generated using the H-W model were significantly affected by the CV. The Schnute model was least affected by errors in the underlying data. The CVof the catch data had a greater impact on the assessment than the CV of the fishing effort. Similarly, the changes in CV had a greater impact on the estimated maximum sustainable yield （MSY） than on the corresponding estimate of fishing effort （EMsY）. We discuss the likely effect of these biases on management efforts and provide suggestions for the improvement of fishery evaluations.

Applications of Graph Theory to Gross Error Detection for GPS Geodetic Control Networks

This paper describes a broad perspective of the application of graph theory to establishment of GPS control networks whereby the GPS network is considered as a connected and directed graph with three components.In this algorithm the gross error detection is undertaken through loops of different spanning trees using the "Loop Law" in which the individual components Δ X, Δ Y and Δ Z sum up to zero.If the sum of the respective vector components ∑X,∑Y and ∑Z in a loop is not zero and if the error is beyond the tolerable limit (ε>w),it indicates the existence of gross errors in one of the baselines in the loop and therefore the baseline must be removed or re_observed.After successful screening of errors by graph theory,network adjustment can be carried out.In this paper,the GPS data from the control network established as reference system for the HP Dam at Baishan county in Liaoning province is presented to illustrate the algorithm.

Nonlinear buckling finite element analysis of stiffened B-Al plates

Nonlinear buckling behavior of stiffened composite B-Al plates was analyzed by means of finite element analysis(FEA) method. In the method, the composite material was taken as B matrix into which Al fibers were embedded in different configurations. The laminated B-Al material in the form of rectangular plates was subjected to lateral compressive loading. It is observed that stiffeners have significant effect on the buckling behavior of plates under compressive loading and for various geometrical configurations. The stiffeners used in the modeling are one-sided and have rectangular cross-sections. It is found that there are physically important loading intervals and the critical buckling modes make transitions back and forth between stable and unstable states. Bifurcation buckling regions resulting from various configurations of fiber orientations and different plate aspect ratios are determined. The whole analysis is performed by using ANSYS finite element computations. Only the buckling patterns of stiffened plate configurations under simply supported boundary conditions are studied. Distributions of compressive stresses(σx) vs in-plane contractions(u) and compressive stresses(σx) vs out-of plane deflections(δ) are obtained. Nonlinear analysis of the C2 fiber configuration yields the safest critical buckling stress amongst C1, C2, C3 and C4 configurations. It is concluded that FEA method for the nonlinear buckling analysis generates accurate results.

Finite element analysis of contact fatigue and bending fatigue of a theoretical assembling straight bevel gear pair

The aim of this work is to propose a 3D FE model of a theoretical assembling straight bevel gear pair to analyze the contact fatigue on the tooth surface and the bending fatigue in the tooth root. Based on the cumulative fatigue criterion and the stress-life equation, the key meshing states of the gear pair were investigated for the contact fatigue and the bending fatigue. Then, the reliability of the proposed model was proved by comparing the calculation result with the simulation result. Further study was performed to analyze the variation of the contact fatigue stress and the bending fatigue stress under different loads. Furthermore, the roles of the driving pinion and the driven gear pair were evaluated in the fatigue life of the straight bevel gear pair and the main fatigue failure mode was determined for the significant gear. The results show that the fatigue failure of the driving pinion is the main fatigue failure for the straight bevel gear pair and the bending fatigue failure is the main fatigue failure for the driving pinion.

Effects of Gully Erosion and Gully Filling on Soil Degradation in the Black Soil Region of Northeast China

Gully erosion has caused soil degradation and even reduced soil productivity. However, only few studies on the effects of gully erosion and artificial controlling measures on soil degradation in the Black Soil Region of Northeast China are available. Thus, this study explores the relationships between gully erosion, gully filling and soil parameters. Two sets of soil samples were collected in the field at： （1） 72 sample points in the gully erosion study area, 60 sample points in the ephemeral and classical gully erosion area （3,518 m2）, 12 sample points in the deposition zone （443 m2）, （2）1o reference points along a slope unaffected by gully erosion representing the original situation before the gully was formed. All soil samples were analyzed for gravel content （GC）, soil organic matter （SOM）, total nitrogen （TN）, available nitrogen （AN）, available phosphorus （AP）, and available potassium （AK）. The soil property values on unaffected slope were fitted by the polynomial curves as the reference values in no gully erosion area. The interpolated soil property values in gully eroded study area were compared with these polynomial curves, respectively, and then, changes of soil property values were analyzed. Gully erosion caused an increase in GC and a decrease in SOM, TN, AN, AP and AK. The change of GC, SOM, TN, AN, AP, AK was 8.8%, -9.04 g kg-1, -0.92 g kg-1, -62.28 mg kg-1, -29.61 mg kg% -79.68 mg kg-1. The soil property values in the study area were below optimal values. Thus, we concluded that gully erosion and gully filling caused both on-site and off-site soil degradation. Soil degradation area was 0.65 % of the cultivated land. In addition, it was proved that gully filling were an improper soil and water conservation measure, which seems to exacerbate the problem. Thus, it is suggested that soil where soil is deep is moved to fill the gully, and then the area around the filled gullies should be covered by grass for preventing the formation and development of the gully.

Effects of working parameters on gasoline engine exergy balance

To improve the energy utilization efficiency of internal combustion （IC） engine, exergy analysis was conducted on a passenger car gasoline engine. According to the thermodynamic theory of IC engine, in-cylinder exergy balance model was built. The working processes of gasoline engine were simulated by using the GT-power. In this way, the required parameters were calculated and then gasoline engine exergy balance was obtained by programming on computer. On this basis, the influences of various parameters on exergy balance were analyzed. Results show that, the proportions of various forms of exergy in gasoline engine from high to low are irreversible loss, effective work, exhaust gas exergy and heat transfer exergy. Effective exergy proportion fluctuates with cylinder volumetric efficiency at full load, while it always increases with break mean effective pressure （BMEP） at part load. Exhaust gas exergy proportion is more sensitive to speed, and it increases with speed increasing except at the highest speed. The lower proportion of heat transfer exergy appears at high speed and high load. Irreversible loss is mainly influenced by load. At part load, higher BMEP results in lower proportion of irreversible loss; at full load, the proportion of irreversible loss changes little except at the highest speed.

The Knee Wear Prediction of UHMWPE Tibial Insert Using VIPRO Platform

The failure mechanism was postulated as a combination of the high level of loading during normal activities and a non-conforming contact mechanism between the femoral condyles and the tibial insert. The question that arises is： could be this phenomenon evaluated quantitatively a priori, e.g., could be the failure due to delamination wear predicted？ In order to do some finite element simulations were performed to dynamically determinate the contact area and contact pressure for three different activities. The results obtained using VIPRO platform lead to the conclusion that many clinically reported failures of the tibial tray are caused by the adhesive and fatigue wear.

Distributed Generators Location and Capacity Effect on Voltage Profile Improvement and Power Losses Reduction Using Genetic Algorithm

This paper presents a powerful approach to find the optimal size and location of distributed generation units in a distribution system using GA （Genetic Optimization algorithm）. It is proved that GA method is fast and easy tool to enable the planners to select accurate and the optimum size of generators to improve the system voltage profile in addition to reduce the active and reactive power loss. GA fitness function is introduced including the active power losses, reactive power losses and the cumulative voltage deviation variables with selecting weight of each variable. GA fitness function is subjected to voltage constraints, active and reactive power losses constraints and DG size constraint.

Losses Calculation of an Aerospace Retraction Wheel Motor with Regarding to Electromagnetic-Field Analysis Investigation

A 3-D FEA （finite element analysis） transient and steady-state design proposal for high-speed with Nd-Fe-Br （reversible） magnets in aerospace application will be examined under design considerations of n = 12,000 rpm, short-duty, sinusoidal drive, low cogging, high efficiency at peak torque, and etc. for an ARWM （aerospace retraction wheel motor）. In construction, the PMs （permanent magnets） fixed on the rotor core which is surface-mOunted magnets retained by a carbon-fiber bandage. Redundant windings, resistant to fault propagation have accounted. Besides, an axial water-jacket housing without end-cap cooling has involved. All performed characteristic performances of the correlated ARWM will verify by comparison through 2-D and 3-D FEA results. In this paper, design process has dealing with determination of various kinds of losses such as electromagnetic and mechanical losses. In terms of both classified losses, copper, stator back iron, stator tooth, PM, rotor back iron, air-friction and sleeve losses were calculated. The 3-D end-winding effects were included in the modeled ARWM by the authors.