Partially Damaged Research Articles

Task-Based Configuration Synthesis of an Underactuated Resilient Robot

A resilient robot can recover its original function after partial damage of the system. This paper develops an underactuated resilient robot that utilizes a combination of passive joints, active joints, adjustable links, and passive links. A novel method based on the genetic algorithm was proposed to determine the goal configuration of a partially damaged robot. The novelty of the method lies in the integration of both discrete and continuous variables. This model is illustrated by a 3-DOF robot manipulator in the simulation.

Fail-safe topology optimization for multiscale structures

This paper presents a novel fail-safe topology optimization method for multiscale structures. The partial damage of both macroscopic and microscopic scales is considered for structural design. To ensure precision, the effective elasticity tensor obtained by the homogenization method is fitted as a high-order polynomial function. Meanwhile, the simplified models of partially damaged truss-like microstructure are employed to reduce the computational cost and the difficulty of fitting. Moreover, Heaviside projection is applied to speed up the convergence and yield a relatively clear configuration. Three numerical examples are tested to demonstrate that the optimized multiscale structures successfully obtain comprehensive performances than optimized solid structures when appropriate microstructure configurations are chosen. Besides, multiscale structures are more self-supporting than solid structures and thus more suitable for additive manufacturing due to the large number of gray elements diffused.

Simulated partial predation on the largest-seeded oak: Effects of seed morphology and size on early establishment

Plant recruitment is limited by seed predation. However, seeds that are only partially consumed can still contribute to regeneration provided the embryo remains viable. Seed size and shape are important traits that influence the relative location of the embryo, as well as its survival and further development. Yet, it is unclear whether the interaction of seed size and shape affects seed tolerance to partial damage and initial seedling performance. We evaluated the effects of simulated partial damage in three different acorn shapes (flattened, triangular and typical) on early seedling establishment in the threatened Quercus insignis, the largest-seeded oak species worldwide. We also distinguished between lateral acorn damage (pericarp damage only) and cotyledon damage (1/3 of the reserves), using acorn size as a covariate. For this, we recorded the germination, emergence and performance (total height, basal diameter, specific leaf area, total leaf area, above and belowground dry biomass) of each seedling after 110 days of growth.Seed shape influenced the rate and percentage of acorn germination, seedling emergence and performance. Typical-shaped acorns germinated at higher rates and produced more seedlings with higher performance. Simulated damage increased the rate and percentages of germination and emergence, but did not affect performance (except for specific leaf area). Seed size favored performance but not germination or emergence, and no significant interaction was found between acorn shape and seed size with respect to germination, emergence or performance, depending on each damage treatment. Our results suggest that acorn size allows tolerance to partial seed predation, since low to moderate acorn damage (<1/3 of cotyledon lost) had no negative effect on germination or emergence. Larger seed size could therefore not only support seedling performance, but also help to meet the nutritional requirements of small and mid-size predators without risking the integrity or development of the embryo. Acorn shape should therefore be considered in basic and applied oak ecology since seed morphology seems to influence not only germination and emergence, but also seedling performance. These results may have important eco-evolutionary implications in the context of seed-predator interactions, since certain shapes tolerate damage better than others and may thus benefit from the selection pressures exerted by seed foragers, both predators and dispersers. In addition to acorn size, managers should consider acorn shape and its relationship to early seedling establishment, as well as the potential for using partially damaged acorns in oak forest restoration projects.

Effects of stud connection failure on displacement responses of partially damaged bridges

Stud connections in composite bridges are traditionally modeled with rigid links or surface constraints, without considering potential failures. In this study, the effects of stud connection failure were investigated to determine if the failure behaviors were required for a partially damaged bridge or not. Detailed finite-element (FE) bridge models, including stud connection failure behaviors and material inelasticity, were developed to analyze the displacement responses of the bridge. The accuracy of the FE bridge models was verified using full-scale bridge fracture test results obtained from other studies. The analysis results show that the stud connection failure can significantly affect the bridge displacement responses even if a bridge girder suffers partial damage.

Targeted neuromodulation of pelvic floor nerves in aging and multiparous rabbits improves continence

Pelvic floor muscle stretch injury during pregnancy and birth is associated with the incidence of stress urinary incontinence (SUI), a condition that affects 30–60% of the female population and is characterized by involuntary urine leakage during physical activity, further exacerbated by aging. Aging and multiparous rabbits suffer pelvic nerve and muscle damage, resulting in alterations in pelvic floor muscular contraction and low urethral pressure, resembling SUI. However, the extent of nerve injury is not fully understood. Here, we used electron microscopy analysis of pelvic and perineal nerves in multiparous rabbits to describe the extent of stretch nerve injury based on axon count, axon size, myelin-to-axon ratio, and elliptical ratio. Compared to young nulliparous controls, mid-age multiparous animals showed an increase in the density of unmyelinated axons and in myelin thickness in both nerves, albeit more significant in the bulbospongiosus nerve. This revealed a partial but sustained damage to these nerves, and the presence of some regenerated axons. Additionally, we tested whether electrical stimulation of the bulbospongiosus nerve would induce muscle contraction and urethral closure. Using a miniature wireless stimulator implanted on this perineal nerve in young nulliparous and middle age multiparous female rabbits, we confirmed that these partially damaged nerves can be acutely depolarized, either at low (2–5 Hz) or medium (10–20 Hz) frequencies, to induce a proportional increase in urethral pressure. Evaluation of micturition volume in the mid-age multiparous animals after perineal nerve stimulation, effectively reversed a baseline deficit, increasing it 2-fold (p = 0.02). These results support the notion that selective neuromodulation of pelvic floor muscles might serve as a potential treatment for SUI.

Feasibility of studying 460 MPa high-strength steel affected by strain aging with acoustic emission method

Strain aging significantly influences the behavior of partially damaged structural steel. The effects of strain aging can be determined based on mechanical experiments, but the sampling process causes further damage to the structures. To explore the possibility of using nondestructive testing (NDT) technology to distinguish the strain aging effects on steel materials, this study investigates the characteristics of acoustic emission (AE) signals for high-strength steel (HSS) affected by strain aging. First, different strain aging effects were applied to 460 MPa HSS specimens. Second, pencil lead break (PLB) tests were performed on the specimens with strain aging, and the generated AE signals were recorded. Finally, tensile tests were conducted, that the strain aging effects on mechanical behavior were determined. The obtained AE signals were compared by extracting the AE parameters and analyzed in the frequency and time-frequency domains with a fast Fourier transform (FFT) and a wavelet transform (WT), respectively. The study shows that the strain aging effects change the characteristics of the AE signals. Compared to the prestrain, the aging time has a more pronounced impact on the AE behaviors. This research proposes a possible NDT method to determine the effects of strain aging on steel materials. Experimental data are provided to detect the degree of partial damage to 460 MPa HSS owing to strain aging using the AE method.

Effect of elevated temperature on the mechanical properties of high-strain-rate-induced partially damaged concrete and CFSTs

The present research investigates the effect of high temperatures on the mechanical properties of plain concrete as well as steel-concrete composite samples which have previously sustained partial damage under high-strain-rate loading. With the rise of interest in investigating extreme loading events such as post-impact-fire scenarios, this study will help in evaluating whether partially damaged concrete and composite elements can further sustain additional stresses in case of a subsequent fire outbreak. Unconfined self- compacting concrete (SCC) and SCC-filled mild steel tube (CFST) samples are subjected to a dual-phase testing procedure where they undergo interrupted compressive loading at impact rates of strain, controlled locally at pre-defined damage levels to account for different deformation states. Damaged specimens are subsequently exposed to elevated temperatures and the residual mechanical properties of the samples are measured under quasi-static compression test conditions. Results indicate that for concrete and CFSTs, variation of residual properties is dependent on the level of pre-induced damage as well as exposed temperature, with the effect of pre-deformation losing significance at very high temperatures. Residual characteristics of CFSTs are shown to be reliant on rate and temperature dependency of both constituent materials. Furthermore, X-ray imaging has been utilized to investigate the extent of cracking and crack propagation at different damage levels.

Strain ageing effect on the temperature dependent mechanical properties of partially damaged structural mild-steel induced by high strain rate loading

This study presents the significant effect of strain ageing on the mechanical response of partially damaged structural steel under extreme loading conditions. Once partial damage occurs in a structure, it takes a while to start the repair process. This lapsed time can substantially affect the strength and ductility of the material. Since the strain ageing effect has not effectively been considered in design guidelines, an understanding of its effect on partly damaged structures is essential. In this paper, a multi-phase loading scenario including high strain rate and quasi-static loadings is applied to the structural mild steel in which partial damage is made to the specimens under high strain rate loading (Phase I). Considering different ageing times ranging from no-age to 7days, the specimens undergo subsequent quasi-static tensile tests at ambient and elevated temperature (up to 600°C) until failure (Phase II). Three different damage levels are introduced to examine the damage level effect on strain ageing. It is shown that the variations of ultimate strength and strain values are significantly dependent on ageing time. Presenting a numerical example, the effect of strain ageing on global behaviour of a typical structural component is studied.

Dynamic assessment of partially damaged historic masonry bridges under blast-induced ground motion using multi-point shock spectrum method

We studied the partial damage effects on historic masonry bridges exposed to blast-induced ground motion. For this purpose, a historic masonry bridge in Turkey was selected to estimate its shock spectral behaviour. In order to determine these results, first, various damage was created on the restored bridge finite element model. This damage was generally selected by searching for damaged historic masonry bridges in the literature. Various critical regions on an example bridge were detected and corresponding regions were removed from the restored finite element model. Thus, partially damaged historic masonry bridge models were obtained. Dynamic calculations of the bridge are presented by using the multi-point shock response spectrum method obtained from ground motions due to a blast load. Acceleration time histories of blast-induced ground motions are obtained depending on a deterministic shape function and a stationary process. Shock response spectra determined from ground shock time histories are simulated using a MATLAB-based BlastGM computer program developed by us. The frequency-varying shock response spectra are applied to each support of the two-span historic masonry bridge. The influences of various charge weights and distances from the charge centre are also investigated in the analyses. The results from the analyses demonstrate the importance of partial damage on the historic masonry bridge, blast-induced ground motion effects, and charge weight and distance from the blast centre.

Effect of strain ageing on the mechanical properties of partially damaged structural mild steel

This paper addresses the strain ageing effects on the mechanical properties of the partially damaged structural mild steel. Since repairing partly damaged structures may not occur immediately, the strain ageing effect can significantly influence the structural behaviour. The changes due to this effect have not so far been considered in the civil engineering design guidelines. In order to investigate strain ageing effects, two-stage experimental tests are carried out on the mild-steel specimens. In the first stage, partial damage is made using quasi-static loading. During the second stage, the strength and ductility of the specimens are examined after 2 and 7days ‘ageing’ at room temperature and the results are compared with the corresponding no-age samples. The microstructure of the specimens is examined using scanning electron microscopy (SEM). To illustrate the effect of strain ageing on the global behaviour of steel structures, a numerical example is provided in which strain ageing impacts on loading capacity and deflection of a steel beam. Finally, the stress–strain relation of partially damaged mild-steel material incorporating strain ageing effects is expressed by calibrating the parameters of Ramberg–Osgood model.

Performance of Unstiffened Welded Steel I-Beam to Hollow Tubular Column Connections Under Seismic Loading

Earthquake causes wide and severe damage to building structures, due to not just the great ground motion but also secondary actions, such as impact, blast or fire, occurring after earthquake. The extreme combined loading scenario should be considered for safety of buildings and lives. Taking fire for example, the combined load can be considered as an event in which the structures are first partially damaged under an earthquake and then attacked by fire. In order to investigate the post-earthquake loading scenario, it is important to assess the partial damage caused by earthquake on different components of structures. The behavior of welded steel I-beam to hollow square tubular columns is investigated herein. A detailed experimental study is presented in which two groups of unstiffened welded steel connections, with the same configurations, subjected to static and cyclic loading are considered. The flexibility and strength of the connections are measured, while the damage phenomena and failure modes are explored during the tests. The connection damage is found to be a cumulative fracture developing process which leads to significant gradual degradation of the mechanical properties of the connection. The quantificational evaluations of the cyclic loading induced damage are also carried out to investigate the connection damage level according to different loading intensities. A finite element modeling numerical study is also carried out to validate the experimental results and a good agreement is achieved. The test results and FE modeling provide a benchmark data for the unstiffened welded connections and can be used for further investigations of the connections subjected to combined actions such as post-earthquake fire.

부분 손상과 기하학적 공격에 강인한 워터마킹 방법

In this paper, we propose a robust watermarking method against geometric attack even though the watermarked image is partially damaged. This method consists of standard image normalization which transforms any image into a predefined standard image and embedding watermark in DCT domain of standard normalized image using spread spectrum technique. The proposed standard image normalization method has an improvement over existing image normalization method, so it is robust to partial damage and geometric attack. The watermark embedding method using spread spectrum technique also has a robustness to image losses such as blurring, sharpening and compressions. In addition, the proposed watermarking method does not need an original image to detect watermark, so it is useful to public watermarking applications. Several experimental results show that the proposed watermarking method is robust to partial damage and various attacks including geometric deformation.

Unilateral Headache with Visual Aura from a Wallenberg Syndrome

Symptomatic migraine or migraine‐like headache due to a brainstem lesion is rarely reported, and limited reports of brainstem lesions with migraine‐like headache onset are all directed to the pons or midbrain [1, 2]. We describe a new onset of recurrent unilateral headache whose clinical features were similar to that of migraine with aura in a patient who had a lateral medullary infarction, i.e., Wallenberg syndrome.

Recombinant PBD-1 (porcine beta-defensin 1) expressed in the milk by transplanting transgenic mES-like-derived cells into mouse mammary gland

ES (embryonic stem)-derived cells have been investigated in many animal models of severe injury and degenerative disease. However, few studies have examined the ability of ES-derived cells to improve functional outcome following partially damaged breast and also the modification of mammary tissue to produce costly proteins. This study investigates the feasibility of implanting mES-dK (mouse ES-derived keratinocytes-like) cells stably transfected with a mammary gland special expression vector for the PBD-1 (porcine beta-defensin 1) in developing mammary glands. Our aim was to assess the ability of cell grafting to improve functional outcome following partial damage of the breast, also on the breast modification mammary tissue in mice for the production of PBD-1 protein secreted in the milk. Our results showed that the ratios of the surviving cells labelled with the myoepithelial or luminal cell markers, EMA (epithelial membrane antigen) and CALLA, were 41.7 +/- 15.2% and 28.4 +/- 9.6%, respectively, which revealed that transplanted mES-dK cells survived, integrated in vivo and differentiated into myoepithelial or luminal cells. In addition, Western blot analysis showed that 37.5% (3 out of 8) female transplanted mice had PBD-1 expression in their milk and reached 0.4998, 0.5229 and 0.5195 microg/ml, respectively.

How does silviculture affect storm damage in forests of south-western Germany? Results from empirical modeling based on long-term observations

Storms represent the most important disturbance factor in forests of Central Europe. Using data from long-term growth and yield experiments in Baden-Wuerttemberg (south-western Germany), which permit separation of storm damage from other causes of mortality for individual trees, we investigated the influence of soil, site, forest stand, and tree parameters on storm damage, especially focusing on the influence of silvicultural interventions. For this purpose, a four-step modeling approach was applied in order to extract the main risk factors for (1) the general stand-level occurrence of storm damage, (2) the occurrence of total stand damage, and (3) partial storm damage within stands. The estimated stand-level probability of storm damage obtained in step 3 was then offset in order to describe the damage potential for the individual trees within each partially damaged stand (4). Generalized linear mixed models were applied. Our results indicate that tree species and stand height are the most important storm risk factors, also for characterizing the long-term storm risk. Additionally, data on past timber removals and selective thinnings appear more important for explaining storm damage predisposition than for example stand density, soil and site conditions or topographic variables. When quantified with a weighting method (summarizing the relative weight of single predictors or groups of predictors), removals could explain up to 20% of storm risk. The stepwise modeling approach proved an important methodological feature of the analysis, since it enabled consideration of the large number of observations without damage (“zero inflation”) in a statistically correct way. These results form a reliable basis for quantifying forest management’s direct impact on the risk of storm damage.

Fatigue is More Damaging than Creep in Ligament Revealed by Modulus Reduction and Residual Strength

Following injury of a complementary joint restraint, ligaments can be subjected to higher than normal stresses. Normal ligaments are exposed to static (creep) and cyclic (fatigue) loading from which damage can accumulate at these higher than normal stresses. This study tracked damage accumulation during creep and fatigue loading of normal rabbit medial collateral ligaments (MCLs) over a range of stresses, using modulus reduction as a marker of damage. Creep tests were interrupted occasionally with unloading/reloading cycles to measure modulus. Test stresses were normalized to ultimate tensile strength (UTS): 60%, 30%, and 15% UTS. Not all creep and fatigues tests progressed until rupture but were stopped and followed by an assessment of the residual strength of that partially damaged ligament using a monotonic failure test. Fatigue loading caused earlier modulus reduction than creep. Modulus reduction occurred at lower increases in strain (strain relative to initial strain) for fatigue than creep. In other words, at the same time or increase in strain, fatigue is more damaging than creep because the modulus ratio reduction is greater. These findings suggest that creep and fatigue have different strain and damage mechanisms. Ligaments exposed to creep or fatigue loading which produced a modulus reduction had decreased residual strength and increased toe-region strain in a subsequent monotonic failure test. This finding confirmed that modulus reduction during creep and fatigue is a suitable marker of partial damage in ligament. Cyclic loading caused damage earlier than static loading, likely an important consideration when ligaments are loaded to higher than normal magnitudes following injury of a complementary joint restraint.

Percutaneous Endoscopic Discectomy for Far Lateral Lumbar Disc Herniations: Prospective Study and Outcome of 66 Patients

Extraforaminal disc herniations represent up to 11% of all lumbar herniated discs. Numerous surgical approaches have been described. Percutaneous endoscopic discectomy (PED) is one of the minimally invasive techniques; after mastering this procedure it is a practical method that is used for treatment of foraminal or extraforaminal disc herniation. The outcome of PED for treatment of foraminal or extraforaminal disc herniation has been studied. A total of 66 patients with foraminal or extraforaminal lumbar disc herniation was treated by applying the PED technique between January 1998 and June 2005. The positions of the herniated disc levels were L2-3 (n=5, 8%), L3-4 (n=19, 28%) and L4-5 (n=42; 64%). The selected patients had no previous surgery, appropriate conservative therapies were done before the operations, and MRI was the main diagnostic method with the clinical findings. Evaluation of the patients with clinical examinations, visual analogue pain scale (VAS) and Oswestry scale was performed preoperatively, on postoperative day 7 and in the postoperative 6-12 months period. In two patients (n=1, L4-5 and n=1, L3-4) disc material could not be removed with PED, so discectomy was performed with microscopic visualization during the same session. Three patients (n=3, L4-5) were reoperated on three to six months after primary surgery due to recurring disc problems with microscope visualization. In two patients (n=2, L4-5) root nerves were partially damaged, and in two patients (n=2, L4-5) root nerves were impinged by the working channel. These 4 patients had dysesthesias from just after surgery to a mean of 45 days after surgery. One of recurrent cases was among these patients. Neurological examinations showed minimal muscle weakness of the quadriceps femoris and diminished sensation of the L4 dermatomal area in patients with partial nerve root damage. This patient improved and the neurologic examination became normal with disappearance of the dysesthesia. There was no sign of reflex sympathetic dystrophy (RDS). With these two patients VAS and Oswestry scales scores decreased significantly early in the postoperative follow-up. The postoperative 6-month average scores are favourable in comparison with the average score at postoperative day 7. The postoperative 12-month scores showed no significant differences to those of postoperative month 1. Percutaneous endoscopic discectomy is a minimally invasive method and offers many benefits to the patient, but extensive surgical practice is needed to become a capable surgeon. Consequently this technique can only be a treatment option on appropriate patients. This study reconfirmed that the removal of fragmented disc material is achieved and offers a pain-free status.

Restoration of vision by training of residual functions.

A new paradigm emerges: visual field defects after optic nerve or brain injury are partially reversible. Using high-resolution visual field tests, areas of residual vision can be identified which are characterized by impaired vision (relative defect) with some residual capacities. By repetitively stimulating these partially damaged areas with daily computer-based visual restitution training it is now possible to enlarge the visual field. Average border shifts of 5 degrees (range, 0 to 20 degrees) have been found in clinical trials, and training is effective even when started years after the injury. Visual restitution training is useful for the treatment of patients with stroke, head injury, or partial optic nerve damage, as long as the patient presents some residual vision. The improved vision is maintained in most patients after training is discontinued. Brain plasticity is likely to provide the substrate for restoration of vision, opening new opportunities to treat partial blindness, which has been considered irreversible.

Potential of two-cell mouse embryos to develop to term despite partial damage after cryopreservation

Approximately 18% of cryopreserved 2-cell mouse embryos of 26 different batches showed various degrees of morphological damage after the freeze-thaw process. Normal and damaged morphology were assessed by light microscopy and the ability of an embryo to develop in vitro to a blastocyst, or to develop to term, after transfer to foster mothers. Using vital stains such as Fluorescein-diacetate (FDA) and 4', 6-Diamidino-2-Phenylindole (DAPI) it was found that in approximately 82% of the cases, both of the 2 blastomeres of the cryopreserved embryos survived the freeze-thaw process; in 10% only one cell survived the process; and in 8% none survived. Normally, only intact 2-cell embryos are considered for transfer. Here it was shown that over 60% of the partially damaged embryos developed in vitro to the blastocyst stage and, of those, 26% developed to term after transfer to suitable foster mothers. Although the inner cell mass (ICM) appeared to remain smaller during culture after the transfer of partially damaged 2-cell stage embryos, no difference during gestation period was found compared with intact embryos.

Radiofrequency Ablation for the Fast Pathway of Atrioventricular Node Reentry: Evidence for Partial Damage to the Fast and Lower Common Pathways

Radiofrequency ablation was attempted in a 30-year-old woman with atrioventricular (AV) node reentry of the common variety. Energy was delivered to ablate a fast pathway. After energy delivery, the atrio-His interval prolonged following transient AV node block. Retrograde conduction was no longer present. However, dual AV nodal physiology and AV node reentry with similar retrograde atrial activation sequence could be shown post-ablation. These observations suggest that both fast and lower common pathways were partially damaged by ablation.