Lactation Performance of Primiparous Nubian Ewes and Yunling Black Ewes

[ Objective] To evaluate lactation performance of primiparous Nubian ewes and Yunling Black ewes. [ Method] Healthy primiparous Nubian ewes （20 ewes lambing twins and 19 ewes lambing single） and Yunling Black ewes （4 ewes lambing twins and 15 ewes lambing single） were used to study the effects of breeds and litter size on lactation performance. [Result] The total milk yield of the Nubian ewes lambing twins was 14.81% higher than that of the Nubian ewes lambing single （ P 〈 0.05） and 22.93% higher than that of the Yunling Black ewes lambing twins （ P 〈 0.05）. The total milk yield of the Yunling Black ewes lambing twins was 32.80% higher than that of the Yunling Black ewes lambing single （ P〈 0.05 ）, but the total milk yield of the Nubian ewes lambing single was 42.20% higher than that of the Yunling Black ewes lambing single （ P 〈 0.05）. The Nubian goats and the Yunling Black goats had similar lactation curves. The milk yield gradually increased during the early lactation period （5 - 15 d post partum）, and the lactation peak lasted for 20 d （15 -35 d post partum）. Then the milk yield gradually decreased. The predicted values showed the milk yield of the ewes may rapidly decrease during 80 -120 d post partum. Until Day 70 post partum, the Nubian ewes lambing twins had lost 3.06% more body weight than those lambing single had （P〈0.05）; the Yunling Black ewes lambing twins had lost 0.89% more body weight than those lambing single had （P〈0.05）. The Nubian ewes lambing lost 3.22% -5.39% more body weight than those with the same litter size did （ P 〈 0.05）. [ Conclusion] The regular pattern of primiparous lactation is similar between the Nubian ewes and the Yunling Black ewes, and their lactation performance is closely related to breeds and litter size.

The Biological and Economical Feasibility of Feeding Barley Green Fodder to Lactating Awassi Ewes

The objective of this research was to investigate the biological and economical values of hydroponic barley (HB) on lactating Awassi ewes. A total of 48 lactating ewes were used in a feeding trial in two groups. The first was fed a regular lactation TMR ration while ewes in the second treatment were fed similar ration except that regular wheat hay was totally replaced by HB for 120 days feeding trial. Results of the experiment showed that the green fodder yield in 8 days germination cycle was 7.5 kg per 1 kg barley grains of green fodder. HB had no effects on feed intake (FI), body weight changes, milk yield, and milk composition;however, HB had positive effects on ewe’s health conditions, mortalities, conception rates and abortion. In conclusion, HB can be used as feed for lactating sheep as cost of feed can be reduced by 42%.

Plasma and cerebrospinal fluid interleukin-1β during lipopolysaccharide-induced systemic inflammation in ewes implanted or not with slow-release melatonin

Background： Interleukin-1β（IL-1β） is important mediator of inflammatory-induced suppression of reproductive axis at the hypothalamic level. At the beginning of inflammation, the main source of cytokines in the cerebrospinal fluid（CSF） is peripheral circulation, while over time, cytokines produced in the brain are more important. Melatonin has been shown to decrease pro-inflammatory cytokines concentration in the brain. In ewes, melatonin is used to advance the onset of a breading season. Little is known about CSF concentration of IL-1β in ewes and its correlation with plasma during inflammation as well as melatonin action on the concentration of IL-1β in blood plasma and the CSF, and brain barriers permeability in early stage of lipopolysaccharide（LPS）-induced inflammation.Methods： Systemic inflammation was induced through LPS administration in melatonin-and sham-implanted ewes. Blood and CSF samples were collected before and after LPS administration and IL-1β and albumin concentration were measured. To assess the functions of brain barriers albumin quotient（QAlb） was used.Expression of IL-1β（Il1B） and its receptor type Ⅰ（Il1r1） and type Ⅱ（Il1r2） and matrix metalloproteinase（Mmp） 3 and 9 was evaluated in the choroid plexus（CP）.Results： Before LPS administration, IL-1β was on the level of 62.0 ± 29.7 pg/mL and 66.4 ± 32.1 pg/mL in plasma and 26.2 ± 5.4 pg/mL and 21.3 ± 8.7 pg/mL in the CSF in sham-and melatonin-implanted group, respectively.Following LPS it increased to 159.3 ± 53.1 pg/mL and 197.8 ± 42.8 pg/mL in plasma and 129.8 ± 54.2 pg/mL and139.6 ± 51.5 pg/mL in the CSF. No correlations was found between plasma and CSF IL-1β concentration after LPS in both groups. The QAlb calculated before LPS and 6 h after was similar in all groups. Melatonin did not affected m RNA expression of Il1B, Il1r1 and Il1r2 in the CP. The m RNA expression of Mmp3 and Mmp9 was not detected.Conclusions： The lack of correlation between plasma and CSF IL-1β concentration indicates that at the beginning of inflammation the local synthesis of IL-1β in the CP is an important source of IL-1β in the CSF. Melatonin from slow-release implants does not affect IL-1β concentration in plasma and CSF in early stage of systemic inflammation.

Changes in energetic profile of pregnant ewes in relation with the composition of the fetal fluids

Objective: To evaluate the energetic profile of fetal fluids and to make comparisons of the concentrations of the constituents present with those in the maternal plasma.Methods: A study was conducted in 102 gravid sheep uteri. The four stages of gestation as Stage I(0–60 days), Stage II(61–90 days), Stage III(91–120 days) and Stage IV(121–145 days) were identified based on the crown anus length of the embryo/fetus. The amniotic and allantoic fluids collected from the gravid uteri of each group were subjected to biochemical analysis of glucose, cholesterol and triglyceride.Results: The levels of glucose and triglyceride in maternal plasma were lower(P < 0.05)on late pregnancy as well as in amniotic and allantoic fluids. No significant variation(P > 0.05) of plasma cholesterol levels was detected between the sampling periods.Contrariwise, cholesterol concentrations of fetal fluids were higher in Stages III and IV of pregnancy when compared with the Stages I and II.Conclusions: The influence of pregnancy on the biochemical composition of fetal fluids was statistically significant.

The proteome of IVF-induced aberrant embryo-maternal crosstalk by implantation stage in ewes

Background:Implantation failure limits the success of in vitro fertilization and embryo transfer(IVF-ET).Wellorganized embryo-maternal crosstalk is essential for successful implantation.Previous studies mainly focused on the aberrant development of in vitro fertilized(IVF)embryos.In contrast,the mechanism of IVF-induced aberrant embryo-maternal crosstalk is not well defined.Results:In the present study,using ewes as the model,we profiled the proteome that features aberrant IVF embryo-maternal crosstalk following IVF-ET.By comparing in vivo(IVO)and IVF conceptuses,as well as matched endometrial caruncular(C)and intercaruncular(IC)areas,we filtered out 207,295,and 403 differentially expressed proteins(DEPs)in each comparison.Proteome functional analysis showed that the IVF conceptuses were characterized by the increased abundance of energy metabolism and proliferation-related proteins,and the decreased abundance of methyl metabolism-related proteins.In addition,IVF endometrial C areas showed the decreased abundance of endometrial remodeling and redox homeostasis-related proteins;while IC areas displayed the aberrant abundance of protein homeostasis and extracellular matrix(ECM)interaction-related proteins.Based on these observations,we propose a model depicting the disrupted embryo-maternal crosstalk following IVF-ET:Aberrant energy metabolism and redox homeostasis of IVF embryos,might lead to an aberrant endometrial response to conceptus-derived pregnancy signals,thus impairing maternal receptivity.In turn,the suboptimal uterine environment might stimulate a compensation effect of the IVF conceptuses,which was revealed as enhanced energy metabolism and over-proliferation.Conclusion:Systematic proteomic profiling provides insights to understand the mechanisms that underlie the aberrant IVF embryo-maternal crosstalk.This might be helpful to develop practical strategies to prevent implantation failure following IVF-ET.

Cervical dilation and improvement of reproductive performance in fat-tailed ewes via cervical dilator treatments

Objective:To determine the effect of different cervical dilators on cervical dilation and reproductive performance of fat-tailed ewes.Methods: In experiment 1140 ewes were divided into seven groups with seven different treatments as following: 10 mL normal saline (control group), 100 IU oxytocin (OT group), 100 μg estradiol and 100 IU oxytocin (E2+OT group), 5 mL relaxin (R group), 2 mL sensiblex (SEN group), 200 μg misoprostol (MIS group) or 200 μg dinoprostone (DIN group). In experiment 2, artificial insemination was applied for evaluation of reproductive performance in experimental groups.Results: In experiment 1, the highest cervical dilation was observed in OT (90%) and E2+OT (100%) groups (P<0.05), while no significant differences was found among DIN, MIS, SEN and R groups (80%, 75%, 70% and 65%, respectively). In addition, the lowest cervical dilation was observed in control group. Experiment 2 found no significant differences among control, OT and E2+OT groups. The highest pregnancy rate, parturition rate and lambing rate were observed in OT groups (60%, 60% and 70%, respectively) and E2+OT groups (65%, 60% and 70%, respectively) compared to SEN, R, MIS and DIN groups (P<0.05).Conclusions:Oxytocin treatment alone or with estradiol could be used as a suitable dilator for improving reproductive efficiency during artificial insemination in fat-tailed ewes.

Effect of Geographic Location and Age on Levels of Some Biochemical Parameters of Ewes in Southern of Iraq

A total of one hundred and ten healthy dry ewes of Arabi sheep diffusive in three geographic locations in the north of Basrah (AL-Qurna, Al-Midaina and Al-Uazair) were divided into three different age groups: 3 years old, to investigate the influence of geographic location and age on the concentration of some biochemical parameters of sheep in the south of Iraq. The results showed significant (P < 0.05) changes among geographic locations in some bio-chemical parameters such as cholesterol, glucose, estridol and growth hormone concentrations. No significant differences were presented in concentrations of total protein, albumin, Fe, phosphorus, ascorbic acid, LH, T3 and T4 hormones in the blood of ewes in different geographic locations. The concentrations of cholesterol, T3 and T4 hormones decreased significantly (P < 0.05), while, the concentrations of glucose and estradiol hormone increased significantly (P < 0.01) in adult ewes compared with younger ewes.

L-Arginine Supplementation Alters Maternal Blood Biochemical Attributes and Milk Composition Relative to Neonatal Traits of <i>Najdi</i>Ewes

In a 2 × 3 factorial arrangement, 3 levels of L-arginine (0, 75 and 150 mg/kg BW per day) were tested at two stages of pregnancy (Early 60 days vs. Late 60 days) on the maternal blood metabolites and postnatal milk composition relative to the newborn traits of Najdi ewes. Thirty adult pregnant Najdi ewes were randomly assigned into 6 treatments (n = 5). Control early (CE) ewes were orally administered 50 mL normal saline (0.9% NaCl) daily during the first 60 days of pregnancy;control late (CL) ewes were similar to CE except saline was given at the last 60 days of pregnancy;low dose of L-arginine at early pregnancy (LE);low dose of L-arginine at late pregnancy (LL);high dose of L-arginine at early (HE) and high dose of L-arginine at late pregnancy (HL). Blood and milk samples were collected on a weekly basis. Data of lambing and newborn traits were considered. There were non-significant differences in litter size due to L-arginine;however lamb birth and weaning weights increased by 35% in LE-ewes. Arginine did not change blood protein and albumin. Low arginine decreased lipid fractions, creatinine, urea, and milk fat;however, it increased AST, ALT, milk lactose and milk ash. Administration of L-arginine at 75 mg/Kg BW per day for 60 days at an early gestation in ewes improved the maternal body health and milk composition for the welfare of the neonates.

Dietary rumen-protected L-arginine or N-carbamylglutamate enhances placental amino acid transport and suppresses angiogenesis and steroid anabolism in underfed pregnant ewes

This study aimed to investigate the effects of dietary supplementation of underfed Hu ewes from d 35 to110 of gestation with either rumen-protected L-arginine(RP-Arg)or N-carbamylglutamate(NCG)on placental amino acid(AA)transport,angiogenic gene expression,and steroid anabolism.On d 35 of gestation,32 Hu ewes carrying twin fetuses were randomly divided into four treatment groups,each consisting of eight ewes,and were fed the following diets:A diet providing 100%of NRC’s nutrient requirements for pregnant ewes(CON);A diet providing 50%of NRC’s nutrient requirements for pregnant ewes(RES);RES diet plus 5 g/d NCG(RES+NCG);or RES diet plus 20 g/d RP-Arg(RES+ARG).On the d 110 of pregnancy,blood samples were taken from the mother,and samples were collected from type A cotyledons(COT;the fetal portions of the placenta).The levels of 17β-estradiol and progesterone in the maternal serum and both the capillary area density(CAD)and capillary surface density(CSD)in type A COT were decreased in response to Arg or NCG supplementation when compared to the RES group.The concentrations of arginine,leucine,putrescine and spermidine in type A COT were higher(P<0.05)in the RES+ARG or RES+NCG group than in the RES group.The mRNA expression levels of inducible nitric oxide synthase(iNOS)and solute carrier family 15,member 1(SLC15A1)were increased(P<0.05)while those of progesterone receptor(PGR)and fibroblast growth factor 2(FGF2)were decreased in type A COT by supplementation with either NCG or RP-Arg compared to the RES group.The results suggest that providing underfed pregnant ewes from d 35 to 110 of gestation with a diet supplemented with NCG or RP-Arg improves placental AA transport,and reduces the expression of angiogenic growth factor genes and steroid anabolism,leading to better fetal development.

Effect of hormonal status and metabolic changes of restricted ewes during late pregnancy on their fetal growth and development

This study investigated the effects of hormonal status and metabolic changes of restricted ewes during late pregnancy on the ovine fetus growth and development. One hundred Mongolian ewes, synchro- nized for oestrus and mated, were divided into three groups and offered 0.175 MJME·kgw-0.75·d-1 (Re- stricted Group 1, RG1), 0.33 MJME·kgw-0.75·d-1 (Restricted Group 2, RG2) and ad libitum access to feed (Control Group, CG) during their late pregnancy respectively. The results suggested that with the sup- ply of exogenous energy decreasing during late pregnancy, maternal body weight and net body weight loss in RG2 and RG1 were lower than those of CG (P<0.01). The insulin and IGF-1 concentrations of ewes in RG2 and RG1 tended to be lower than those of CG (P>0.05), but the GH concentrations in RG2 and RG1 were enhanced and there was significant difference between RG1 and CG on d 120 of gesta- tion (P<0.05). The glucose concentration of ewes in RG2 and RG1 was decreased throughout the feed restriction period, and the differences were observed between RG1 and CG on d 120 of gestation (P<0.05). In addition, the nonesterified fatty acid (NEFA) and total amino acid (TAA) concentrations of ewes in RG2 tended to increase, but there was no significant difference (P>0.05). However, the NEFA and FAA concentrations of ewes in RG1 were reduced from d 90 to d 120 of gestation, then enhanced from d 120 to d 140 of gestation. During the late pregnancy, with the supply of nutrition decreasing, the negatively physiological and biochemical maternal reactions to restriction became worse, which sig- nificantly reduced the average lamb birth weight and daily growth rate of fetus in RG2 (P<0.05) and RG1 (P<0.01).

Primary Ewing sarcoma of the kidney mimicking cystic papillary renal cell carcinoma in an older patient:A case repor

BACKGROUND Ewing’s sarcoma(ES)is a neuroectodermal tumor that typically occurs in the bones and soft tissues of children and young adults.Primary renal ES is rare;only a few cases and a small case series have been documented,and only four cases involved primary renal ES in older people(>65 years old).CASE SUMMARY Herein,we describe the radiological and pathological features of primary renal ES in an older person.A 76-year-old man complained of poor oral intake and was found to have a large cystic renal mass with indistinct margins on computed tomography.Ultrasound-guided biopsy revealed that the tumor contained small round blue cells.The patient underwent a right radical nephrectomy.The tumor cells showed diffuse membranous CD99,and nuclear friend leukemia integration 1 transcription factor and NK2 Homeobox 2.Fluorescence in situ hybridization revealed EWSR1 translocation.Postoperatively,18F-fluorodeoxyglucose positron emission tomography revealed no evidence of metastasis.The patient was diagnosed with primary renal ES.Six months following the surgery,local recurrence and distant metastasis were observed.Primary renal ES is rare and often lethal in older individuals.The specific imaging findings are unknown,and treatment protocols have not been standardized.CONCLUSION This case report describes the radiological and pathological features of primary renal ES in an older person.

EW75镁合金镧掺杂硫酸盐稀土转化膜的防护性能研究

通过析氢测试、扫描电子显微镜、全浸实验和电化学测试等手段探究优化稀土转化液配方对稀土转化膜性能的提升。配方中加入硫酸根离子可以有效地改善稀土转化膜无法均匀成膜且与基体结合力不好的现象,改善了膜层成膜均匀性和结合力。在析氢实验中,改进的膜层耐蚀性能有了显著提升,浸泡14天腐蚀速率依旧恒定,说明膜层具有长期稳定的保护作用。全浸实验中经过阶段性腐蚀,膜层仍然完整均匀,无脱落现象出现。动电位极化测试中,改进膜层自腐蚀电位正移,腐蚀电流约为2.152×10^(−5)A/cm^(2),阻抗测试中改进膜层也呈现更好的耐腐蚀性能。

Behavioral response of pregnant ewes to high ambient temperature in loose housing system

In order to investigate the behavioral responses of pregnant ewes to high ambient temperature in a loose housing system,eighty-seven pregnant ewes(Chinese little fat-tailed sheep,Ovis aries)from the same loose house were chosen,and nine ewes with the similar body weight and age were marked for later individual behavioral observation.The ambient temperature and relative humidity were recorded,and the individual behaviors of the pregnant ewes were observed continuously from 04:50 to 20:00 once every other day for 14 days.The behavioral state of all the pregnant ewes was recorded once every hour from 5:00 to 20:00,the number of pregnant ewes selecting specific lying areas(designated as area A and area B),was recorded at 15 minute intervals from 12:00 to 17:00 everyday.The final results show that the behavioral durations are significantly different in eating and drinking,rumination,rest,and locomotion for pregnant ewes(P<0.05).The time spent in lying for rumination or rest is significantly longer than that for locomotion(P<0.05).Temperature has a significant effect on the number of pregnant ewes lying on the floor(P<0.05).There are significant differences for pregnant ewes’preference of area A and area B for lying at temperatures ranging from 27.0℃to 31.0℃(P<0.05).The results indicate that the lying behavior is significantly more than the locomotion behavior for the pregnant ewes in the loose housing systems under the high ambient temperature.

2023年土耳其7.8级强震前烟台台伸缩仪EW分量固体潮畸变

烟台台SS-Y伸缩仪EW分量在2023-02-06土耳其7.8级双震前2 d开始出现急速上升趋势变化,至6日凌晨开始下降,变化幅度达到9.58×10^(-8),震后维持快速上升趋势。对烟台台伸缩仪稳定性指标进行判定,认为仪器稳定;经现场核实,未发现环境干扰。最后对烟台台伸缩仪固体潮畸变特征进行分析,并基于畸变与远震前兆的关系进行初步探讨。

鼻腔骨外尤文氏肉瘤误诊1例

骨外尤文氏肉瘤(extraskeletal Ewing’s sarcoma,EES)是一种少见的软组织恶性小圆细胞肿瘤,来源于神经外胚层,由于其与骨尤文氏肉瘤镜下形态学、超微结构相似以及染色体变异相同,因此其相当于骨尤文氏肉瘤的特殊表现形式,临床上十分罕见。由于该病在术前均缺乏明确的组织病理学诊断,故该病的误诊率非常高[1],国内更有报道骨外尤文氏肉瘤的术前诊断明确率为零[2]。本文报道了一例病变局限在鼻腔内而未侵犯鼻窦的骨外尤文氏肉瘤,该患者未行术前活检,且未行术中冰冻,因而误诊为鼻腔出血性息肉。

西藏阿里阿鲁错地堑系的第四纪活动性、最新同震地表破裂及其地震地质意义

藏北高原非常薄弱的活断层调查程度和不完整的历史地震资料等,限制了对青藏高原内部活动构造的变形机制及强震活动特征等问题的深入认识。文中通过综合地质、遥感和地震等资料对阿里北部进行详细的活断层解译,重点对阿鲁错地堑系南段昆楚克错地堑西侧边界正断层的第四纪活动性、新发现的最新同震地表破裂及其震级与形成时间等进行了深入分析。研究结果表明,阿里北部第四纪期间以近EW向伸展变形为主,发育了以近SN向正断层和由NW向与NE向走滑断层构成的共轭走滑断层为主的高密度活断层系统。沿昆楚克错地堑西缘主边界正断层新发现的最新同震地表破裂整体沿NNW向雁列展布,总长约400m,最大垂直位移约0.8m,平均垂直位移为0.3~0.4m。结合历史地震记录和经典的“地表破裂位移与震级”统计关系式推断,该破裂应是震源深度为35km的1955年革吉县纳屋错东M_(W)6.5强震事件的结果。综合该地表破裂的发育特点推断,震源深度对地表破裂参数存在显著影响,震源偏深时的地表破裂长度可远小于震源破裂的最大长度,表明在活断层的地震复发模式研究中应注意随机性较强的断层局部破裂行为或小位移破裂事件。

自主神经功能障碍对卒中后睡眠障碍的影响

目的探讨急性脑卒中睡眠觉醒障碍的早期诊断与自主神经系统(ANS)功能障碍的关系。方法本研究是一项横断面观察研究,使用Ewing试验评估ANS功能障碍的严重程度,并应用PSQI评分评估脑卒中后3个月的失眠程度。分析首次缺血性脑卒中后自主神经系统功能变化与睡眠障碍的相关性。将缺血性卒中患者的脑成像标志物与自主神经系统(ANS)功能障碍联系起来,分析缺血性卒中合并ANS功能障碍、睡眠障碍对预后的影响以及相关因素。结果本研究共纳入52例急性缺血性脑卒中患者,其中男44例(84.6%),年龄(58.85±9.52)岁。ANS功能障碍的比例高达90.4%,10例(19.2%)严重ANS功能障碍患者在脑干卒中患者中睡眠障碍的发生率最高。经过3个月的随访,发现与非严重ANS功能障碍组相比,严重ANS功能障碍组的神经功能障碍和日常生活能力受损更严重,但未发现严重的ANS功能障碍与睡眠障碍之间的联系。结论急性缺血性脑卒中普遍存在ANS功能障碍,尚未发现严重的ANS功能障碍与睡眠障碍之间的关系。ANS调节可能是急性缺血性脑卒中的一个治疗方向。

多房棘球蚴RNA结合蛋白EWS的原核表达及其细胞定位与功能的初步鉴定

通过对多房棘球绦虫(Echinococcus multilocularis)RNA结合蛋白EWS(EmEWS)基因的原核表达、抗体制备、细胞定位等研究,初步探究EmEWS基因特征以及与RNA的结合能力。根据Wormbase数据库中EmEWS基因序列设计引物,利用RT-PCR扩增EmEWS基因并构建重组表达质粒,诱导表达、纯化重组蛋白,制备EmEWS多克隆抗体后进行Western blot、实时荧光定量PCR、免疫荧光定位、双荧光测定。结果表明,EmEWS基因长度为1485 bp,编码495个氨基酸,在多房棘球蚴原代细胞中表达量较高,在原头蚴中最低。生物信息学分析表明,细粒棘球蚴EWS与EmEWS相似性高达98.3%,且EmEWS的RBD结构域在绦虫中高度保守。EmEWS重组蛋白大小约为54 ku,制备的多克隆抗体可识别多房棘球绦虫中天然EmEWS蛋白。细胞定位显示EmEWS主要分布在细胞膜上。双荧光试验证明EmEWS可以与结合富含UG的RNA序列结合。综合上述结果,推测EmEWS可能作为转录调控因子参与小RNA的形成,同时有助于核蛋白的运输。

The mechanism to reform dynamic performance of an elastic wave-front in a piezoelectric semiconductor by the wave-carrier interaction induced from static biasing fields

The propagation of an elastic wave(EW)in a piezoelectric semiconductor(PSC)subjected to static biasing fields is investigated.It is found that there exist two coupling waves between electric field and charge carriers.One is stimulated by the action of the polarized electric field in the EW-front on charge carriers(EFC),and the other is stimulated by the action of initial electric field in biasing fields on dynamic carriers(IEC).Obviously,the latter is a man-made and tunable wave-carrier interaction.A careful study shows that IEC can play a leading role in remaking dynamic performance of the wave-front and an inter-medium role in transferring energy from biasing fields to EW-fronts.Hence,a method is proposed to reform the EW performance by biasing-fields:reforming the dispersivity of EW-fronts by promoting competition between IEC and EFC and inverting the dissipation by the IEC to transfer energy from biasing fields to EWfronts.The corresponding tuning laws on the phase-frequency characteristics of an EW show that the wave velocity can be regulated smaller than the pure EW velocity at a lowfrequency and larger than the pure piezoelectric wave velocity at a high-frequency.As for regulating the amplitude-frequency characteristics of the EW by the IEC,analyses show that EWs can obtain amplification only for those with relatively high vibration frequencies(small wave lengths).The studies will provide guidance for theoretical analysis of waves propagating in PSCs and practical application and design of piezotronic devices.

Optimization of extended warranty cost for multi-component systems with economic dependence based on group maintenance

During extended warranty(EW)period,maintenance events play a key role in controlling the product systems within normal operations.However,the modelling of failure process and maintenance optimization is complicated owing to the complex features of the product system,namely,components of the multi-component system are interdependent with each other in some form.For the purpose of optimizing the EW pricing decision of the multi-component system scientifically and rationally,taking the series multi-component system with economic dependence sold with EW policy as a research object,this paper optimizes the imperfect preventive maintenance(PM)strategy from the standpoint of EW cost.Taking into consideration adjusting the PM moments of the components in the system,a group maintenance model is developed,in which the system is repaired preventively in accordance with a specified PM base interval.In order to compare with the system EW cost before group maintenance,the system EW cost model before group maintenance is developed.Numerical example demonstrates that offering group maintenance programs can reduce EW cost of the system to a great extent,thereby reducing the EW price,which proves to be a win-win strategy to manufacturers and users.