成本改善新技术Tear Down技法研究

通过对TearDown技法的作用和流程介绍,分析了成本改善对成本管理的贡献,提出了TearDown技法在我国先进制造企业应用的几点启示。

Effects of diamagnetic drift on nonlinear interaction between multi-helicity neoclassical tearing modes

A numerical study of the diamagnetic drift effect on the nonlinear interaction between multi-helicity neoclassical tearing modes(NTMs) is carried out using a set of four-field equations including two-fluid effects.The results show that,in contrast to the single-fluid case,5/3 NTM cannot be completely suppressed by 3/2 NTM with diamagnetic drift flow.Both modes exhibit oscillation and coexist in the saturated phase.To better understand the effect of the diamagnetic drift flow on multiple-helicity NTMs,the influence of typical relevant parameters is investigated.It is found that the average saturated magnetic island width increases with increasing bootstrap current fraction f_(b) but decreases with the ion skin depth δ.In addition,as the ratio of parallel to perpendicular transport coefficients χ_(‖)/χ_(⊥) increases,the average saturated magnetic island widths of the 3/2 and 5/3 NTMs increase.The underlying mechanisms behind these observations are discussed in detail.

Assessment of tear film parameters post-treatment with commercial eyelid cleaning wipes:a pilot study

AIM:To investigate the short-term effects of commercially available eyelid-cleaning wipes on film parameters.METHODS:This study enrolled 48 healthy participants aged 20-35y(both males and females).Clinical assessment included the Ocular Surface Disease Index(OSDI)questionnaire,non-invasive tear break-up time(NITBUT),tear meniscus height(TMH),and lipid layer pattern(LLP).Based on these initial results,participants were categorized as either non-dry eye or dry eye.Participants in each group were randomly allocated to either Blephaclean■or Systane■treatments.Changes in NITBUT,TMH,and LLP levels before and after lid wipe treatment were assessed.RESULTS:The dry eye group exhibited significantly higher OSDI scores and lower NITBUT and TMH levels than in the non-dry eye group(P<0.001).Following the application of eyelid wipes(Systane■wipes),dry eye subjects experienced a significant improvement in NITBUT levels(P=0.0014)compared to the non-dry eye individuals.Although the remaining participants showed a marginal increase in TMH and NITBUT levels,these changes did not achieve statistical significance(P>0.05).Similarly,the LLP levels were significantly improved with Systane■(P<0.001)post-treatment compared to individuals in the non-dry eye group.However,the dry eye subjects showed higher posttreatment LLP levels than the untreated group(P<0.02).CONCLUSION:The short-term effects of Systane®eyelid wipes on tear film parameters suggest their effectiveness in dry eye disease.Nonetheless,further exploration of their long-term impact is essential to justify their cost effectiveness and efficacy in treating both aqueous deficiency and evaporative dryness.

Microstructure and Hot Tearing Sensitivity Simulation and Parameters Optimization for the Centrifugal Casting of Al-Cu Alloy

Four typical theories on the formation of thermal tears:strength,liquid film,intergranular bridging,and solidifica-tion shrinkage compensation theories.From these theories,a number of criteria have been derived for predicting the formation of thermal cracks,such as the stress-based Niyama,Clyne,and RDG(Rapaz-Dreiser-Grimaud)criteria.In this paper,a mathematical model of horizontal centrifugal casting was established,and numerical simulation analysis was conducted for the centrifugal casting process of cylindrical Al-Cu alloy castings to investigate the effect of the centrifugal casting process conditions on the microstructure and hot tearing sensitivity of alloy castings by using the modified RDG hot tearing criterion.Results show that increasing the centrifugal rotation and pouring speeds can refine the microstructure of the alloy but increasing the pouring and mold preheating temperatures can lead to an increase in grain size.The grain size gradually transitions from fine grain on the outer layer to coarse grain on the inner layer.Meanwhile,combined with the modified RDG hot tearing criterion,the overall distribution of the castings’hot tearing sensitivity was analyzed.The analysis results indicate that the porosity in the middle region of the casting was large,and hot tearing defects were prone to occur.The hot tearing tendency on the inner side of the casting was greater than that on the outer side.The effects of centrifugal rotation speed,pouring temperature,and preheating temperature on the thermal sensitivity of Al-Cu alloy castings are summarized in this paper.This study revealed that the tendency of alloy hot cracking decreases with the increase of the centrifugal speed,and the maximum porosity of castings decreases first and then increases with the pouring temperature.As the preheating temperature increases,the overall maximum porosity of castings shows a decreasing trend.

Suppression of the m/n=2/1 tearing mode by electron cyclotron resonance heating on J-TEXT

Stabilization of tearing modes and neoclassical tearing modes is of great importance for tokamak operation.Electron cyclotron waves(ECWs)have been extensively used to stabilize the tearing modes with the virtue of highly localized power deposition.Complete suppression of the m/n=2/1 tearing mode(TM)by electron cyclotron resonance heating(ECRH)has been achieved successfully on the J-TEXT tokamak.The effects of ECW deposition location and power amplitude on the 2/1 TM suppression have been investigated.It is found that the suppression is more effective when the ECW power is deposited closer to the rational surface.As the ECW power increases to approximately 230 k W,the 2/1 TM can be completely suppressed.The island rotation frequency is increased when the island width is reduced.The experimental results show that the local heating inside the magnetic island and the resulting temperature perturbation increase at the O-point of the island play dominant roles in TM suppression.As the ECW power increases,the 2/1 island is suppressed to smaller island width,and the flow shear also plays a stabilizing effect on small magnetic islands.With the stabilizing contribution of heating and flow shear,the 2/1 TM can be completely suppressed.

Effects of counter-current driven by electron cyclotron waves on neoclassical tearing mode suppression

Through theoretical analysis,we construct a physical model that includes the influence of counter-external driven current opposite to the plasma current direction in the neoclassical tearing mode(NTM).The equation is used with this model to obtain the modified Rutherford equation with co-current and counter-current contributions.Consistent with the reported experimental results,numerical simulations have shown that the localized counter external current can only partially suppress NTM when it is far from the resonant magnetic surface.Under some circumstances,the Ohkawa mechanism dominated current drive(OKCD)by electron cyclotron waves can concurrently create both co-current and counter-current.In this instance,the minimal electron cyclotron wave power that suppresses a particular NTM was calculated by the Rutherford equation.The result is marginally less than when taking co-current alone into consideration.As a result,to suppress NTM using OKCD,one only needs to align the co-current with a greater OKCD peak well with the resonant magnetic surface.The effect of its lower counter-current does not need to be considered because the location of the counter-current deviates greatly from the resonant magnetic surface.

Hot tearing behavior of AZ91D magnesium alloy

Hot tearing is a serious destructive solidification defect of magnesium alloys and other casting metals.Quantitative and controllable measurements on the thermal and the mechanical behavior of an alloy during its solidification process are crucial for the understanding of hot tearing formation.We developed a new experimental method and setup to characterize hot tearing behavior via controlled cooling and active loading to force hot hearing formation on cooling at selected fractions of solid.The experimental setup was fully instrumented so that stress,strain,strain rate,and temperature can be measured in-situ while hot tearing was developing.An AZ91D magnesium alloy,which is prone to hot tearing,was used in this study.Results indicate that when hot hearing occurred,the local temperature,critical stress,and cumulative strain were directly affected by strain rate.Depending on the applied strain rate,hot tearing of the AZ91D magnesium alloy could occur in two solidification stages:one in the dendrite solidification stage(fS∼0.81-0.82)and the other in the eutectic solidification stage(fS∼0.99).AZ91D alloy exhibited distinct mechanical behaviors in these two ranges of fraction solid.

The Incidence and Risk Factors of Third- and Fourth-Degree Perineal Tears in Ministry of Health in Bahrain over 5 Years

Background: Perineal trauma and vaginal laceration are considered a common complication associated with vaginal delivery. Well established risk factors, recognized by the Royal College of Obstetricians and Gynecologists, are ethnicity, birth weight over 4 kg persistent occipital posterior position, null parity, induction of labor, shoulder dystocia, instrumental delivery. There are other risk factors that were suggested in the literature, but data are conflicting, such as prolonged second stage of labor, episiotomy and obesity. Objective: To evaluate third- and fourth-degree perineal rears rates and the impact of related risk factors on perineal tears in Ministry of health in Bahrain over 5 years (which includes Salmanyia Medical complex (SMC) and Jidhafs maternity hospital (JMH)). Methods: This retrospective descriptive cross-sectional study analyzed all vaginal deliveries from January 2015 to December 2019 in Obstetrics and Gynecology department in Salmanyia Medical Complex (the main hospital in Kingdom of Bahrain which received all kinds of cases including low and high risks) and Jidhafs Maternity Hospital (tertiary hospital which received only low risk cases), Kingdom of Bahrain. During the period of interest 33,694 records were identified. Data were extracted from observational recording from SMC and JMH labour registry books. Results: There was no statistically significant difference between groups according to age (p = 0.199). On the other hand, there was statistically significant higher cases of >40 weeks at gestational age, obesity > 35 kg/mr, vacuum delivery, pushing stage > 90 min, birth weight > 4 kg, head circumference > 34 cm, fetal length at birth > 50 cm, episiotomy and lower cases of nulliparity in study group compared to control group 16 (66.7%) vs. 13,805 (41.0%), 3 (12.5%) vs. 1448 (4.3%), 3 (12.5%) vs. 1414 (4.2%), 4 (16.7%) vs. 1751 (5.2%), 3 (12.5%) vs. 1751 (5.2%), 12 (50.0%) vs. 15,926 (47.3%), 15 (62.5%) vs. 20,135 (59.8%) and 17 (70.8%) vs. 29,024 (86.2%);(p = 0.027, 0.009, Conclusion: Gestational age > 40 weeks, obesity > 35 kg/mr, pushing stage > 90 min, birth weight > 4 kg, head circumference > 34 cm, fetal length at birth > 50 cm and using of vacuum increase incidence of 3rd and 4th degree perineal tears with vaginal delivery however maternal age and nulliparity have no significant role. Finally, episiotomy did not represent as protective factor for perineal damage. .

Risk Factors Associated with Obstetric Perineal Tear in a Maternity Ward of the Communal Medical Center of Ratoma-Conakry-Guinea

Introduction: Obstetric perineal tears are a common complication during childbirth. The objectives of this study were to describe the sociodemographic characteristics, the different types of perineal tears and to identify the associated risk factors. Patients and Method: The maternity of the CMC of Ratoma served as a setting for carrying out this study. This was a prospective study of a descriptive and analytical type, which took place over a period of 6 months from July 1, 2021 to January 1, 2022. Results: The frequency of perineal tear was 9%. The average age of the patients concerned was 23.99 years ± 5.18 years, with extremes of 15 and 38 years. Housewives were the most numerous (30.88%). Most of our parturient had undergone excision (99.6%) and they were more frequently primiparous (40.44%) and pauciparous (47.79%). The multiplicity of risk factors was a remarkable fact (scarred perineum, edematous, short, and infected). The presentation was cephalic in 96.33%, posterior variety in 3.81% and the variety of positions could not be specified by the health worker who provided care to the parturient in 46.56%. The expulsion took place in OP (92.37%) and in OS (2.30%). In most cases, midwives carried out deliveries (93%). Perineal tears were 1st degree (54.41%), 2nd degree (39.70%), 3rd degree (5.15%) and 4th degree (0.74%). Conclusion: Prevention of perineal obstetric injuries is based on better knowledge of risk factors and delivery by qualified personnel. The main limitation of this study is the impossibility of highlighting occult perineal lesions due to the weakness of the technical platform.

The Prevalence Type of the Meniscus Tear in Patients with Anterior Cruciate Ligament (ACL) Injury, in Abu Arish General Hospital, Jazan, KSA

Background: The anterior cruciate ligament (ACL) is the main structure that prevents the forward movement of the tibia about the femur Meniscus tear which is a common finding in patients with anterior cruciate ligament (ACL) injury. Aim: To investigate the prevalence of types of meniscus tears in patients with Anterior Cruciate Ligament (ACL) Injury. Methods: A retrospective study was conducted among inpatients. Clinical evaluation included side-to-side difference in anterior tibial translation (ATT) as measured by a KT-1000 arthrometer (MEDmetric Corp) and a grade of pivot-shift test at final follow-up in all patients. Subsequent meniscal tear was defined by symptoms of joint line pain and/or locking or joint effusion requiring surgical treatment. Results: Most of patients were males (92.6%). The patients were categorized into 5 groups according to age with a mean of age 32.8 ± 10.6. The most common causes of ACL injury were falling down (43.2%), trauma (38.1%) or knee torsion (18.8%). Medial meniscal tear was found in 92 knees (55.7%), while lateral meniscal tear was found in 19 knees (10.8%) and the most common type was the longitudinal tear that was found in 31 knees (17.6%). Similarly, 66.7% of the meniscal flap tears and half of the meniscal bucket-handle tears were significantly associated with loose body (P Conclusion: The present study demonstrated that meniscus tears are more common in individuals with chronic ACL rupture. The main factors contributing to ACL injury were classified as falls, trauma, and knee torsion. Gender was identified as a critical determinant in the etiology of ACL injury. The occurrence of a ramp lesion was associated longitudinal meniscal tears, whereas chodoral injury was associated with the majority of meniscal flap tears and meniscal bucket-handle tears.

Effects of Y on hot tearing susceptibility of Mg-Zn-Y-Zr alloys

The hot tearing susceptibility of MgZn2.5YxZr0.5 （x=0.5, 1, 2, 4, 6） alloys was evaluated by thermodynamic calculations based on Clyne-Davies model. The microstructure and morphology of hot tearing regions of the alloys were observed by X-ray diffraction and scanning electron microscopy. The solidification temperature and shrinkage stress during the solidification of MgZn2.5YxZr0.5 alloys in the“T”type hot tearing permanent-mold were acquired with the attached computer. The effect factors of hot tearing susceptibility of MgZn2.5YxZr0.5 alloys, such as the solidification temperature interval, the variation of solid fraction in vulnerable region, the residual liquid fraction in the final stage, the type of the second phase of the alloys were discussed based on the above calculation and observation. The results demonstrated that the hot tearing susceptibility in the investigated alloys was found as follows：MgZn2.5Y2Zr0.5＆gt;MgZn2.5Y0.5Zr0.5＆gt;MgZn2.5Y4Zr0.5＆gt;MgZn2.5Y6Zr0.5＆gt;MgZn2.5Y1Zr0.5. The highest hot tearing susceptibility of MgZn2.5Y2Zr0.5 alloy related to the following reasons： the largest freezing range, the biggest changing of the variation of solid fraction in vulnerable region, the least liquid film in the final stage of solidification, the formation of the second phase which worsens the liquid flow and interdendritic feeding after dendrite coherency.

Effect of pouring and mold temperatures on hot tearing susceptibility of AZ91D and Mg-3Nd-0.2Zn-Zr Mg alloys

Pouring and mold temperatures are two important parameters during casting magnesium components. The present study examined their influence on hot tearing susceptibility （HTS） of commercial AZ91D and newly developed Mg-3Nd-0.2Zn-Zr （mass fraction, %; NZ30K） magnesium alloys in gravity permanent mold casting condition. The results indicate that mold temperature shows much more significant influence on the HTS of both alloys than pouring temperature whose influence only can be distinguished at low mold temperature （341 K for AZ91D alloy and 423 K for NZ30K alloy）. Hot tearing susceptibility prediction model concerning feeding parameters, grain size and solidification range, is more suitable to estimate the HTS of different magnesium alloys than the model only concerning feeding parameters. In order to achieve better hot tearing resistance, the ranges of pouring and mold temperatures are suggested to be 961-991 K and≥641 K for AZ91D alloy, 1003-1033 K and≥623 K for NZ30K alloy, respectively.

Solidification characteristics and hot tearing susceptibility of Ni-based superalloys for turbocharger turbine wheel

The solidification characteristics and the hot tearing susceptibility were investigated on two Ni-based superalloys for turbocharger turbine wheel, K418 and K419. The segregation behaviors of the alloying elements and the precipitation phases were also studied. The results show that the solidification behavior of K419 alloy is complicated when compared with K418 due to the interdendritic segregation of many kinds of strong interdendritic partitioning elements in the remaining liquid at the final stage of solidification. The segregation of multiple elements in interdendritic liquid results in an extremely low solidus in K419. A long residual liquid stage is found during the solidification of K419, giving rise to reduced cohesion strength of dendrites and increased sensitivity to hot tearing. A hot tearing susceptibility coefficient（HTS） criterion is proposed based on a hot tearing sensitive model. The HTS value of K419 alloy is larger than that of K418 alloy.

Role of tensile forces in hot tearing formation of cast Al-Si alloy

The instrumented applied rod casting apparatus （ARCA） was developed to investigate the effects of tensile forces in the hot tearing formation of cast AI-Si alloys. The obtained data of tensile forces/temperature was used to identify hot tearing initiation and propagation and the fracture surface of samples was also investigated. The result shows that the applied tensile forces have a complex effect on load onset for the hot tearing initiation and propagation. During the casting solidification, the tensile forces are gradually increased with the increase of solid fraction. Under the action of tensile forces, there will appear hot tearing and crack propagation on the surface of the sample. When the tensile forces exceed the inherent strength of alloys, there will be fractures on the sample. As for the A356 alloy, the critical fracture stress is about 0.1 MPa. The hot tearing surface morphology shows that the remaining intergranular bridge and liquid films are thick enough to allow the formation of dendrite-tip bumps on the fracture surface.

A review on hot tearing of magnesium alloys

Hot tearing is often a major casting defect in magnesium alloys and has a significant impact on the quality of their casting products.Hot tearing of magnesium alloys is a complex solidification phenomenon which is still not fully understood,it is of great importance to investigate the hot tearing behaviour of magnesium alloys.This review attempts to summarize the investigations on hot tearing of magnesium alloys over the past decades.The hot tearing criteria including recently developed Kou’s criterion are summarized and compared.The numeric simulation and assessing methods of hot tearing,factors influencing hot tearing,and hot tearing susceptibility(HTS)of magnesium alloys are discussed.

Changes of tear film and tear secretion after phacoemulsification in diabetic patients

Objective: To evaluate tear film stability and tear secretion in patients with diabetes after phacoemulsification. Methods: Twenty-five diabetic cataract patients and 20 age-matched non-diabetic cataract patients as control underwent pha- coemulsification. Tear film break-up time (TFBUT), Schirmer I test (SIT), corneal fluorescein staining, and dry eye symptoms were measured pre- and postoperatively. Results: Diabetics had a decreased preoperative TFBUT and SIT. TFBUT was reduced on Day 1 and recovered on Day 180 postoperatively in both groups. SIT was increased after phacoemulsification, but returned to preoperative levels by Day 180 in non-diabetics, whereas it was lower than preoperative level in diabetics. Positive corneal fluo- rescein staining was elevated in both groups, and returned to preoperative levels only in controls. Dry eye symptoms were similar to fluorescein staining in both groups. Conclusion: Tear secretion was reduced in diabetic cataract patients after phacoe- mulsification, which worsened dry eye symptoms and predisposed those patients to ocular damage.

Rotator cuff tears: An evidence based approach

Lesions of the rotator cuff(RC) are a common occurrence affecting millions of people across all parts of the globe. RC tears are also rampantly prevalent with an agedependent increase in numbers. Other associated factors include a history of trauma, limb dominance, contralateral shoulder, smoking-status, hypercholesterolemia, posture and occupational dispositions. The challenge lies in early diagnosis since a high proportion of patients are asymptomatic. Pain and decreasing shoulder power and function should alert the heedful practitioner in recognizing promptly the onset or aggravation of existing RC tears. Partial-thickness tears(PTT) can be bursalsided or articular-sided tears. Over the course of time, PTT enlarge and propagate into full-thickness tears(FTT) and develop distinct chronic pathological changes due to muscle retraction, fatty infiltration and muscle atrophy. These lead to a reduction in tendon elasticity and viability. Eventually, the glenohumeral joint experiences a series of degenerative alterations- cuff tear arthropathy. To avert this, a vigilant clinician must utilize and corroborate clinical skill and radiological findings to identify tear progression. Modern radio-diagnostic means of ultrasonography and magnetic resonance imaging provide excellent visualization of structural details and are crucial in determining further course of action for these patients. Physical therapy along with activity modifications, antiinflammatory and analgesic medications form the pillars of nonoperative treatment. Elderly patients with minimal functional demands can be managed conservatively and reassessed at frequent intervals. Regular monitoring helps in isolating patients who require surgical interventions. Early surgery should be considered in younger, active and symptomatic, healthy patients. In addition to being costeffective, this helps in providing a functional shoulder witha stable cuff. An easily reproducible technique of maximal strength and sturdiness should by chosen among the armamentarium of the shoulder surgeon. Grade 1 PTTs do well with debridement while more severe lesions mandate repair either by trans-tendon technique or repair following conversion into FTT. Early repair of repairable FTT can avoid appearance and progression of disability and weakness. The choice of surgery varies from surgeon-to-surgeon with arthroscopy taking the lead in the current scenario. The double-row repairs have an edge over the single-row technique in some patients especially those with massive tears. Stronger, costeffective and improved functional scores can be obtained by the former. Both early and delayed postoperative rehabilitation programmes have led to comparable outcomes. Guarded results may be anticipated in patients in extremes of age, presence of comorbidities and severe tear patters. Overall, satisfactory results are obtained with timely diagnosis and execution of the appropriate treatment modality.

Management of tear trough deformity with and without tear trough-orbicularis retaining ligament complex release in transconjunctival blepharoplasty: a comparative study

AIM: To evaluate the effect of releasing the orbicularis retaining ligament(ORL) complex of the tear trough combined with the transconjunctival blepharoplasty in the surgical management of tear trough deformity compared with the effect of blepharoplasty alone. METHODS: A prospective, randomized(by closed envelope technique), controlled surgical trial which included 50 patients(100 eyes) with bilateral visible tear trough deformity and lower eyelid fat bulging, was divided into two groups where 25 patients(50 eyes) had tear trough-ORL release with blepharoplasty and 25 patients(50 eyes) didn't. Qualitative and quantitative assessments of tear trough deformity were done at 6 mo postoperatively, achieving grade 0 or 1 of Barton's classification was considered a success. Standardized photographic documentation of each patient was done pre and postoperatively, also assessment of the patients' satisfaction postoperatively was done and ranked as excellent, very good, good or fair. RESULTS: There was statistically significant difference between the two groups in the overall aesthetic results postoperatively regarding the qualitative and quantitative analysis of the tear trough deformity, where patients who had tear trough-ORL complex release had more successful outcomes than those of the second group. CONCLUSION: ORL release should be done in patients with tear trough deformity in order to release the tethering effect of this ligament which causes the prominence of the naso jugal groove.

Treatment of meniscal tears: An evidence based approach

Treatment options for meniscal tears fall into three broad categories;non-operative,meniscectomy or meniscal repair.Selecting the most appropriate treatment for a given patient involves both patient factors(e.g.,age,co-morbidities and compliance)and tear characteristics(e.g.,location of tear/age/reducibility of tear).There is evidence suggesting that degenerative tears in older patients without mechanical symptoms can be effectively treated non-operatively with a structured physical therapy programme as a first line.Even if these patients later require meniscectomy they will still achieve similar functional outcomes than if they had initially been treated surgically.Partial meniscectomy is suitable for symptomatic tears not amenable to repair,and can still preserve meniscal function especially when the peripheral meniscal rim is intact.Meniscal repair shows 80%success at 2 years and is more suitable in younger patients with reducible tears that are peripheral(e.g.,nearer the capsular attachment)and horizontal or longitudinal in nature.However,careful patient selection and repair technique is required with good compliance to post-operative rehabilitation,which often consists of bracing and non-weight bearing for 4-6 wk.

Changes of tear film lipid layer thickness by 3% diquafosol ophthalmic solutions in patients with dry eye syndrome

AIM: To evaluate the quantitatively changes in lipid layer thickness(LLT) when 3% diquafosol eye drop is used for dry eye patients using the tear film interferometer. METHODS: A total 124 participants(32 males, 92 females;mean age, 28.9 y) diagnosed with dry eye disease(DED) received topical instillation of 4 ophthalmic solutions in one eye: diquafosol, normal saline, 0.1% sodium hyaluronate and 0.3% gatifloxacin, in a masked manner. LLT was measured using an interferometer at baseline and 20 min after the instillation of each ophthalmic solutions.RESULTS: Changes of LLT after instillation(nm, mean± standard error) were as follows: 12.6±2.0 for diquafosol(P<0.001), 1.2±2.2 for normal saline(P=0.301), 1.5±2.0 for hyaluronate(P=0.495), and 0.5±3.2 for gatifloxacin(P=0.884).CONCLUSION: Topical instillation of diquafosol increases tear film LLT in DED patients. Diquafosol 3% eye drop might be effective treatment option of evaporative DED with meibomian gland dysfunction.