高航速下带自由面滑行艇粘性流场数值计算方法研究

针对滑行艇高航速下姿态变化显著、数值计算时艇底易于出现气-水异常现象的问题,基于雷诺平均纳维-斯托克斯(RANS)方法及动网格技术,采用人工干预结合六自由度(6-DOF)运动模型解决自由面与网格的匹配问题,采用高分辨率交界面捕捉技术结合流体体积模型(HRIC-VOF)的方法计算气-液相分布,通过探索HRIC-VOF的角度因子、锐化因子、库朗数上界值、库朗数下界值、时间步长等对艇底气-液相分布及总阻力的影响规律,获得可有效计算高速下滑行艇阻力及自由面兴波的数值计算方法。通过与试验结果进行对比,在模型速度V_(m)=2~13 m/s(F_(V)=0.96~5.78)时的阻力计算误差小于4.5%。

Properties of high cis-1,4 content hydroxyl-terminated polybutadiene and its application in composite solid propellants

In this paper,high cis-1,4 content hydroxyl-terminated polybutadiene(cis-HTPB)with different molecular weights was prepared through the oxidative cracking process using cis-butadiene rubber as raw material.Firstly,this article comprehensively compared the differences between cis-HTPB and conventional I-HTPB in terms of molecular weight distribution,functionality,viscosity,molecular polarity,and other physicochemical properties,which provided effective data support for its subsequent application.In addition,the reaction kinetics study showed that cis-HTPB with isocyanate curing agent has high reactivity,allowing it to be rapidly cured at low temperatures,and the cured elastomers had excellent mechanical properties,with tensile strength and elongation up to 1.89 MPa and 1100%,respectively.It was also found that cis-HTPB has extremely excellent low-temperature resistance,and the glass transition temperature(T_(g))of its cured elastomer is as low as-101℃.Based on the above studies,cis-HTPB is applied as a binder in composite solid propellants for the first time to investigate its practical performance,and the results indicated that cis-HTPB-based propellants have excellent process and mechanical properties.

Integrated strategies for chemotherapy cycles in nasopharyngeal carcinoma patients: Real-world data from two epidemic centers guiding decision-making

objective:Two cycles of induction chemotherapy(IC)followed by 2 cycles of platinum-based concurrent chemoradiotherapy(CCRT)(2IC+2CCRT)for locoregionally advanced nasopharyngeal carcinoma(LA-NPC)is widely adopted but not evidence-confirmed.This study aimed to determine the clinical value of 2IC+2CCRT regarding efficacy,toxicity and cost-effectiveness.Methods:This real-world study from two epidemic centers used propensity score matching(PSM)and inverse probability of treatment weighting(IPTW)analyses.The enrolled patients were divided into three groups based on treatment modality:Group A(2IC+2CCRT),Group B(3IC+2CCRT or 2IC+3CCRT)and Group C(3IC+3CCRT).Long-term survival,acute toxicities and cost-effectiveness were compared among the groups.We developed a prognostic model dividing the population into high-and low-risk cohorts,and survivals including overall survival(OS),progression-free survival(PFS),distant metastasis-free survival(DMFS)and locoregional relapse-free survival(LRRFS)were compared among the three groups according to certain risk stratifications.Results:Of 4,042 patients,1,175 were enrolled,with 660,419,and 96 included in Groups A,B and C,respectively.Five-year survivals were similar among the three groups after PSM and confirmed by IPTW.Grade 3-4 neutropenia and leukocytopenia were significantly higher in Groups C and B than in Group A(52.1%vs.41.5%vs.25.2%;41.7%vs.32.7%vs.25.0%)as were grade 3-4 nausea/vomiting and oral mucositis(29.2%vs.15.0%vs.6.1%;32.3%vs.25.3%vs.18.0%).Cost-effective analysis suggested that 2IC+2CCRT was the least expensive,while the health benefits were similar to those of the other groups.Further exploration showed that 2IC+2CCRT tended to be associated with a shorter PFS in high-risk patients,while 3IC+3CCRT potentially contributed to poor PFS in low-risk individuals,mainly reflected by LRRFS.Conclusions:In LA-NPC patients,2IC+2CCRT was the optimal choice regarding efficacy,toxicity and costeffectiveness;however,2IC+2CCRT and 3IC+3CCRT probably shortened LRRFS in high-and low-risk populations,respectively.

Relations of Microstructural Attributes and Strength-Ductility of Zirconium Alloys with Hydrides

As the first safety barrier of nuclear reactors,zirconium alloy cladding tubes have attracted extensive attention because of its good mechanical properties.The strength and ductility of zirconium alloy are of great significance to the service process of cladding tubes,while brittle hydrides precipitate and thus deteriorate the overall performance.Based on the cohesive finite element method,the effects of cohesive strength,interfacial characteristics,and hydrides geometric characteristics on the strength and ductility of two-phase material(zirconium alloy with hydrides)are numerically simulated.The results show that the fracture behavior is significantly affected by the cohesive strength and that the overall strength and ductility are sensitive to the cohesive strength of the zirconium alloy.Furthermore,the interface is revealed to have prominent effects on the overall fracture behavior.When the cohesive strength and fracture energy of the interface are higher than those of the hydride phase,fracture initiates in the hydrides,which is consistent with the experimental phenomena.In addition,it is found that the number density and arrangement of hydrides play important roles in the overall strength and ductility.Our simulation provides theoretical support for the performance analysis of hydrogenated zirconium alloys during nuclear reactor operation.

Practices and Empirical Insights from the National Research Program for Key Issues in Air Pollution in Beijing-Tianjin-Hebei and Surrounding Areas

1.Introduction The United States began implementing policies against air pollution in earnest starting in the early 1970s,taking several decades and an economic recession to achieve reductions in air pollution.In contrast,China has reduced its air pollution by the same amount in only seven years[1].Compared with foreign countries.

微沟槽形貌对水润滑轴承混合润滑特性影响的研究

建立了计入轴承内表面微沟槽形貌的水润滑轴承混合润滑(Mixed-EHDL)数值计算模型,着重研究了不同运行工况下,半椭圆形、矩形、等腰三角形、左三角形、右三角形等多种微沟槽形貌对水润滑轴承混合润滑特性的影响.研究表明:在所有微沟槽形貌中,混合润滑性能与承载性能优劣排序依次为右三角形、等腰三角形、左三角形、半椭圆形、矩形;在弹流润滑阶段,微沟槽形貌对水润滑轴承摩擦系数几乎无影响,而在混合润滑阶段,不同微沟槽形貌下接触载荷以及摩擦系数之间的差异随转速的增加呈现出先增大后减小最后趋于统一的规律性;在承载区,由于沟槽内水膜增压能力以及抽吸作用的不同引起了水润滑轴承混合润滑性能的差异,其中右三角形表现最优,而矩形最差.

倾斜轴颈滑动轴承混合热弹流研究

为了研究重载工况下滑动轴承混合润滑行为,综合考虑轴-润滑介质-轴承-环境之间的耦合热传导效应,建立考虑轴颈受载倾斜的滑动轴承混合热弹流(mixed-TEHD)数值计算模型。模型预测出轴颈受载倾斜及对中状态下的润滑界面油膜压力、油膜厚度、接触压力、摩擦因数、热(弹性)变形以及轴承温度场。研究结果表明:轴颈在受载倾斜状态下,油膜压力、弹性变形、油膜厚度沿轴向呈非对称分布,接触压力集中于轴承末端;轴颈在受载倾斜状态下,轴承圆周方向与轴向温度分布的不均匀性比对中状态的严重,温度比对中状态时的大,同时,沿油膜最高温度处的圆周方向截面与轴向截面内热变形分布具有非对称性,其热变形也明显大于对中状态时的大;在混合流润滑阶段,轴颈受载倾斜对接触载荷、摩擦因数、轴承最高温度以及最大热变形的影响较大。

SpyGlass DS胆道镜联合射频消融在肝外胆管癌诊治中的应用

目的探讨SpyGlass DS胆道镜联合射频消融在肝外胆管癌诊断和治疗中的作用。方法对临床疑诊为胆管癌的患者进行SpyGlass DS胆道镜检查,直视下观察胆管病变及活检,病理学检查证实胆管癌,不能手术切除的患者,接受胆管腔内射频消融(RFA)治疗。结果15例患者成功进行SpyGlass DS胆道镜下活检病理学检查,3例外科手术治疗,12例完成胆管腔内RFA治疗,平均操作时间(36.8±4.2)min,无相关并发症。结论SpyGlass DS胆道镜可以取得胆管癌标本,并明确病理学诊断,可进行胆管腔内RFA治疗,临床安全可行,疗效肯定,值得进一步推广。

潜艇近水面航行自由液面干扰效应数值研究

针对潜艇近水面航行艇体水动力呈现显著变化的问题,本文在验证数值计算方法可行性的基础上,开展不同潜深及航速下潜艇粘性流场的数值模拟,获取艇体阻力、垂向力及纵倾力矩随水深及航速的变化规律。模拟结果表明:潜深是影响潜艇近水面与深水状态水动力性能差异的决定性因素,当潜深与艇体直径的比值H/D≤1.3时,近水面效应显著;而当H/D≥2.9时,可认为潜艇水动力性能与深水状态无显著差异;近自由液面条件下(H/D≤1.3),潜艇所受阻力及垂向力系数随航速的增大均呈现明显波动现象,这主要是由于自由面的兴波干扰使得艇体表面压力变化所引起。

任意偏斜下水润滑橡胶艉轴承混合润滑性能

为探究大偏心率(ε≥1)下水润滑橡胶艉轴承沿端面偏斜的混合润滑性能,综合考虑表面粗糙度、弹性变形、接触压力、偏斜角对水润滑橡胶轴承混合润滑特性的影响,提出大偏心率(ε≥1)下滑动轴承沿端面任意偏斜的膜厚计算方法,并应用于艉轴承缩比模型混合润滑分析。通过数值模拟研究重载条件下水润滑橡胶艉轴承水膜压力、接触压力随偏斜角的变化规律,分析偏斜角、偏斜方向角等对水润滑橡胶轴承混合润滑性能参数的影响。研究表明:在混合润滑条件下,轴颈沿端面偏斜对流体载荷影响相对较小,但会显著增强润滑界面的接触效应从而恶化其润滑性能;横向偏斜一定程度上会提高直槽式水润滑橡胶轴承的承载能力,偏斜角增加到一定程度时会引起最大水膜压力沿偏斜端反向移动;偏斜角对水润滑轴承润滑特性的影响在混合润滑阶段内较为显著,在弹流润滑阶段其影响将会削弱。

Clinical findings and imaging features of 67 nasopharyngeal carcinoma patients with postradiation nasopharyngeal necrosis

Postradiation nasopharyngeal necrosis is an important late effect of radiotherapy that affects prognosis in patients with nasopharyngeal carcinoma.In the present study,we reviewed the clinical and imaging features of 67 patients with pathologically diagnosed postradiation nasopharyngeal necrosis who were treated at Sun Yat-sen University Cancer Center between June 2006 and January 2010.Their clinical manifestations,endoscopic findings,and imaging features were analyzed.Early nasopharyngeal necrosis was limited to a local site in the nasopharyngeal region,and the tissue defect was not obvious,whereas deep parapharyngeal ulcer or signs of osteoradionecrosis in the basilar region was observed in serious cases.Those with osteoradionecrosis and/or exposed carotid artery had a high mortality.In conclusion,Postradiation nasopharyngeal necrosis has characteristic magnetic resonance imaging appearances,which associate well with clinical findings,but pathologic examination is essential to make the diagnosis.

Randomized study of sinusoidal chronomodulated versus flat intermittent induction chemotherapy with cisplatin and 5-fluorouracil followed by traditional radiotherapy for locoregionally advanced nasopharyngeal carcinoma

Neoadjuvant chemotherapy plus radiotherapy is the most common treatment regimen for advanced nasopharyngeal carcinoma(NPC).Whether chronomodulated infusion of chemotherapy can reduce its toxicity is unclear.This study aimed to evaluate the toxic and therapeutic effects of sinusoidal chronomodulated infusion versus flat intermittent infusion of cisplatin(DDP)and 5-fluorouracil(5-FU)followed by radiotherapy in patients with locoregionally advanced NPC.Patients with biopsy-diagnosed untreated stages III and IV NPC(according to the 2002 UICC staging system)were randomized to undergo2 cycles of sinusoidal chronomodulated infusion(Arm A)or flat intermittent constant rate infusion(Arm B)of DDP and 5-FU followed by radical radiotherapy.Using a"MELODIE"multi-channel programmed pump,the patients were given 12-hour continuous infusions of DDP(20 mg/m2)and 5-FU(750 mg/m2)for 5days,repeated every 3 weeks for 2 cycles.DDP was administered from 10:00 am to 10:00 pm,and 5-FU was administered from 10:00 pm to 10:00 am each day.Chronomodulated infusion was performed in Arm A,with the peak deliveries of 5-FU at 4:00 am and DDP at 4:00 pm.The patients in Arm B underwent a constant rate of infusion.Radiotherapy was initiated in the fifth week,and both arms were treated with the same radiotherapy techniques and dose fractions.Between June 2004 and June 2006,125 patients were registered,and 124 were eligible for analysis of response and toxicity.The major toxicity observed during neoadjuvant chemotherapy was neutropenia.The incidence of acute toxicity was similar in both arms.During radiotherapy,the incidence of stomatitis was significantly lower in Arm A than in Arm B(38.1%vs.59.0%,P=0.020).No significant differences were observed for other toxicities.The 1-,3-,and 5-year overall survival rates were 88.9%,82.4%,and 74.8%for Arm A and 91.8%,90.2%,and 82.1%for Arm B.The 1-,3-,and 5-year progression-free survival rates were 91.7%,88.1%,and 85.2%for Arm A and 100%,94.5%,and 86.9%for Arm B.The 1-,3-,and 5-year distant metastasis-free survival rates were 82.5%,79.1%,and 79.1%for Arm A and 90.2%,85.2%,and 81.7%for Arm B.Chronochemotherapy significantly reduced stomatitis but was not superior to standard chemotherapy in terms of hematologic toxicities and therapeutic response.

Favorable prognosis of female patients with nasopharyngeal carcinoma

The female sex is traditionally considered a favorable prognostic factor for nasopharyngeal carcinoma (NPC). However, no particular study has reported this phenomenon. To explore the prognostic impact of gender on patients with NPC after definitive radiotherapy, we reviewed the clinical data of 2,063 consecutive patients treated between 1st January 2000 and 31st December 2003 in the Sun Yat-sen University Cancer Center. The median follow-up for the whole series was 81 months. The female and male patients with early stage disease comprised 49.4% and 28.1% of the patient population, respectively. Both the 5-year overall survival (OS) and disease-specific survival (DSS) rates of female patients were significantly higher than those of male patients (OS: 79% vs. 69%, P < 0.001; DSS: 81% vs. 70%, P < 0.001). For patients with locoregionally advanced NPC, the 5-year OS and DSS rates of female vs. male patients were 74% vs. 63% (P < 0.001) and 76% vs. 64%, respectively (P < 0.001). A multivariate analysis showed that gender, age, and TNM stage were independent prognostic factors for the 5-year OS and DSS of NPC patients. The favorable prognosis of female patients is not only attributed to the early diagnosis and treatment but might also be attributed to some intrinsic factors of female patients.

Nb2C MXene-Functionalized Scaffolds Enables Osteosarcoma Phototherapy and Angiogenesis/Osteogenesis of Bone Defects

Early surgical resection and chemotherapy of bone cancer are commonly used in the treatment of bone tumor,but it is still highly challenging to prevent recurrence and fill the bone defect caused by the resection site.In this work,we report a rational integration of photonic-responsive two-dimensional(2D)ultrathin niobium carbide(Nb2C)MXene nanosheets(NSs)into the 3D-printed bone-mimetic scaffolds(NBGS)for osteosarcoma treatment.The integrated 2D Nb2C-MXene NSs feature specific photonic response in the second near-infrared(NIR-II)biowindow with high tissue-penetrating depth,making it highly efficient in killing bone cancer cells.Importantly,Nb-based species released by the biodegradation of Nb2C MXene can obviously promote the neogenesis and migration of blood vessels in the defect site,which can transport more oxygen,vitamins and energy around the bone defect for the reparative process,and gather more immune cells around the defect site to accelerate the degradation of NBGS.The degradation of NBGS provides sufficient space for the bone remodeling.Besides,calcium and phosphate released during the degradation of the scaffold can promote the mineralization of new bone tissue.The intrinsic multifunctionality of killing bone tumor cell and promoting angiogenesis and bone regeneration makes the engineered Nb2C MXeneintegrated composite scaffolds a distinctive implanting biomaterial on the efficient treatment of bone tumor.

A model to predict the risk of lethal nasopharyngeal necrosis after re-irradiation with intensity-modulated radiotherapy in nasopharyngeal carcinoma patients

Background:For patients with nasopharyngeal carcinoma(NPC) who undergo re-irradiation with intensity-modulated radiotherapy(IMRT),lethal nasopharyngeal necrosis(LNN) is a severe late adverse event.The purpose of this study was to identify risk factors for LNN and develop a model to predict LNN after radical re-irradiation with IMRT in patients with recurrent NPC.Methods:Patients who underwent radical re-irradiation with IMRT for locally recurrent NPC between March 2001 and December 2011 and who had no evidence of distant metastasis were included in this study.Clinical characteristics,including recurrent carcinoma conditions and dosimetric features,were evaluated as candidate risk factors for LNN.Logistic regression analysis was used to identify independent risk factors and construct the predictive scoring model.Results:Among 228 patients enrolled in this study,204 were at risk of developing LNN based on risk analysis.Of the 204 patients treated,31(15.2%) developed LNN.Logistic regression analysis showed that female sex(P = 0.008),necrosis before re-irradiation(P = 0.008),accumulated total prescription dose to the gross tumor volume(GTV) ≥ 145.5 Gy(P = 0.043),and recurrent tumor volume >25.38 cm3(P = 0.009) were independent risk factors for LNN.A model to predict LNN was then constructed that included these four independent risk factors.Conclusions:A model that includes sex,necrosis before re-irradiation,accumulated total prescription dose to GTV,and recurrent tumor volume can effectively predict the risk of developing LNN in NPC patients who undergo radical re-irradiation with IMRT.

Detection of nasopharyngeal carcinoma using surface-enhanced laser desorption and ionization mass spectrometry profiles of the serum proteome

Background and Objective: Early diagnosis of nasopharyngeal carcinoma (NPC) is difficult due to the insufficient specificity of the conventional examination method. This study was to investigate potential and consistent biomarkers for NPC, particularly for early detection of NPC. Methods: A proteomic pattern was identified in a training set (134 NPC patients and 73 control individuals) using the surface-enhanced laser desorption and ionization-mass spectrometry (SELDI-MS), and used to screen the test set (44 NPC patients and 25 control individuals) to determine the screening accuracy. To confirm the accuracy, it was used to test another group of 52 NPC patients and 32 healthy individuals at 6 months later. Results: Eight proteomic biomarkers with top-scored peak mass/charge ratios (m/z) of 8605 Da, 5320 Da, 5355 Da, 5380 Da, 5336 Da, 2791 Da, 7154 Da, and 9366 Da were selected as the potential biomarkers of NPC with a sensitivity of 90.9% (40/44) and a specificity of 92.0% (23/25). The performance was better than the current diagnostic method by using the Epstein-Barr virus (EBV) capsid antigen IgA antibodies (VCA/IgA). Similar sensitivity (88.5%) and specificity (90.6%) were achieved in another group of 84 samples. Conclusion: SELDI-MS profiling might be a potential tool to identify patients with NPC, particularly at early clinical stages.

Structural, mechanical, and electronic properties of 25 kinds of Ⅲ–Ⅴbinary monolayers: A computational study with first-principles calculation

Using first-principle calculations, we investigate the mechanical, structural, and electronic properties and formation energy of 25 kinds of Ⅲ–V binary monolayers in detail. A relative radius of the binary compound according to the atomic number in the periodic table is defined, and based on the definition, the 25 kinds of Ⅲ–V binary compounds are exactly located at a symmetric position in a symmetric matrix. The mechanical properties and band gaps are found to be very dependent on relative radius, while the effective mass of holes and electrons are found to be less dependent. A linear function between Young’s modulus and formation energy is fitted with a linear relation in this paper. The change regularity of physical properties of B–V(V = P, As, Sb, Bi) and Ⅲ–N(Ⅲ = Al, Ga, In, Tl) are found to be very different from those of other Ⅲ–V binary compounds.

Effect of initial crystallization temperature and surface diffusion on formation of GaAs multiple concentric nanoring structures by droplet epitaxy

GaAs multiple concentric nano-ring structures(CNRs)are prepared with multistep crystallization procedures by droplets epitaxy on GaAs(001)to explore the influence of different initial crystallization temperatures on CNRs morphology.Atomic force microscope(AFM)images show that GaAs nanostructures are more likely to form elliptical rings due to diffusion anisotropy.Meanwhile,with the increase of initial crystallization temperature,the inner ring height and density of CNRs are increased,and outer rings are harder to form.In addition,the mechanism of formation of CNRs is discussed by classical nucleation theory and diffusion theory.The method can be used to calculate the diffusion activation energy of gallium atoms(0.7±0.1 eV)on the GaAs(001)surface conveniently.

Microstructure,optical,and photoluminescence properties ofβ-Ga_(2)O_(3)films prepared by pulsed laser deposition under different oxygen partial pressures

Theβ-Ga_(2)O_(3)films are prepared on polished Al_(2)O_(3)(0001)substrates by pulsed laser deposition at different oxygen partial pressures.The influence of oxygen partial pressure on crystal structure,surface morphology,thickness,optical properties,and photoluminescence properties are studied by x-ray diffraction(XRD),atomic force microscope(AFM),scanning electron microscope(SEM),spectrophotometer,and spectrofluorometer.The results of x-ray diffraction and atomic force microscope indicate that with the decrease of oxygen pressure,the full width at half maximum(FWHM)and grain size increase.With the increase of oxygen pressure,the thickness of the films first increases and then decreases.The room-temperature UV-visible(UV-Vis)absorption spectra show that the bandgap of theβ-Ga_(2)O_(3)film increases from4.76 e V to 4.91 e V as oxygen pressure decreasing.Room temperature photoluminescence spectra reveal that the emission band can be divided into four Gaussian bands centered at about 310 nm(~4.0 e V),360 nm(~3.44 e V),445 nm(~2.79 e V),and 467 nm(~2.66 e V),respectively.In addition,the total photoluminescence intensity decreases with oxygen pressure increasing,and it is found that the two UV bands are related to self-trapped holes(STHs)at O1 sites and between two O2-s sites,respectively,and the two blue bands originate from V_(Ga)^(2-)at Ga1 tetrahedral sites.The photoluminescence mechanism of the films is also discussed.These results will lay a foundation for investigating the Ga_(2)O_(3)film-based electronic devices.

顺铂、氟尿嘧啶加或不加紫杉烷的诱导化疗对局部区域晚期鼻咽癌的影响:回顾性、倾向评分匹配分析

背景与目的比较局部区域晚期鼻咽癌(nasopharyngeal carcinoma,NPC)不同诱导化疗(induction chemotherapy,IC)方案的文献中缺乏可用数据。本研究旨在评价接受紫杉烷、顺铂和5-氟尿嘧啶(taxane,cisplatin and 5?fuorouracil,TPF)或顺铂和5-氟尿嘧啶(cisplatin and 5?fuorouracil,PF)方案的IC后进行同步放化疗(concurrent chemoradiotherapy,CCRT)的局部区域晚期鼻咽癌患者的结局。方法前瞻性维护数据库中共1879例接受了IC和CCRT治疗的局部区域晚期鼻咽癌患者被纳入此观察性研究。我们采用倾向评分法比较了总生存期(overall survival,OS)、疾病特异生存期(disease-specific survival,DSS)、无远处转移生存期(distant metastasis?free survival,DMFS)和无局部区域复发生存期。结果共1256例患者接受了TPF或PF作为IC方案。多因素分析中,TPF组比PF组表现出显著更好的OS[风险比(hazard ratio,HR)=0.660;95%置信区间(confdence interval,CI):0.442–0.986;P=0.042]、DSS(HR=0.624;95%CI:0.411–0.947;P=0.027)和DMFS(HR=0.589;95%CI:0.406–0.855;P=0.005)。倾向评分匹配在每个队列中确定了294例患者,并证实了TPF组比PF组表现出显著改善的5年OS率(88.1%vs. 80.7%;P=0.042)、DSS率(88.5%vs.80.7%;P=0.021)和DMFS率(87.9%vs. 78.6%;P=0.012)。匹配前后的局部区域无复发生存率无显著差异。结论在我们的研究中,与PF方案相比,TPF方案IC结合CCRT改善了局部区域晚期鼻咽癌患者的长期生存。然而,有必要进行前瞻性随机临床试验来验证这些发现。