Research on shell-side heat and mass transfer with multi-component in LNG spiral-wound heat exchanger under sloshing conditions

The spiral-wound heat exchanger(SWHE) is the primary low-temperature heat exchanger for large-scale LNG plants due to its high-pressure resistance, compact structure, and high heat exchange efficiency. This paper studied the shell-side heat and mass transfer characteristics of vapor-liquid two-phase mixed refrigerants in an SWHE by combining a multi-component model in FLUENT software with a customized multicomponent mass transfer model. Besides, the mathematical model under the sloshing condition was obtained through mathematical derivation, and the corresponding UDF code was loaded into FLUENT as the momentum source term. The results under the sloshing conditions were compared with the relevant parameters under the steady-state condition. The shell-side heat and mass transfer characteristics of the SWHE were investigated by adjusting the component ratio and other working conditions. It was found that the sloshing conditions enhance the heat transfer performance and sometimes have insignificant effects. The sloshing condition is beneficial to reduce the flow resistance. The comprehensive performance of multi-component refrigerants has been improved and the improvement is more significant under sloshing conditions, considering both the heat transfer and pressure drop.These results will provide theoretical support for the research and design of multi-component heat and mass transfer enhancement of LNG SWHE under ocean sloshing conditions.

内窥镜下改良球形头硅胶管插管与泪囊鼻腔吻合术治疗鼻泪管阻塞的比较

目的:比较内窥镜下球形头硅胶管插管(SHSI)与泪囊鼻腔吻合术(En-DCR)治疗鼻泪管阻塞(NLDO)的疗效与经济效益。方法:将43例50眼NLDO患者随机分为SHSI组(21例25眼)和En-DCR组(22例25眼),比较两组患者术中出血量、单眼手术时间、手术不适及住院时间,随访至术后12mo,根据末次随访时溢泪与泪道灌洗情况评估临床疗效,并采用成本-效果比(C/E)进行经济效益评估。结果:SHSI组患者术中出血量与手术不适视觉模拟评分显著低于En-DCR组(4.96±1.989mL vs 27.60±14.950mL,2.84±0.64分vs 4.88±0.84分),单眼手术时间与住院时间显著短于En-DCR组(13.40±6.007min vs 59.64±12.786min,0.50±0.010h vs 137.280±23.085h)(均P<0.001)。末次随访时,两组患者临床有效率无差异(88%vs 96%,P>0.05),但SHSI组患者C/E(13.57)远小于En-DCR(121.50)。结论:内窥镜下SHSI与En-DCR均为NLDO的有效手术治疗方法,但SHSI手术难度相对更低且具有明显的成本效益优势。

Germinomas of the basal ganglia and thalamus: Four case reports

BACKGROUND The early diagnosis of basal ganglia and thalamus germinomas is often difficult due to the absence of elevated tumor markers,and atypical clinical symptoms and neuroimaging features.CASE SUMMARY Four male children aged 8 to 15 years were diagnosed with germinomas in the basal ganglia and thalamus by stereotactic biopsy from 2017 to 2019.All patients developed hemiplegia except patient 4 who also had cognitive decline,speech disturbance,nocturnal enuresis,polydipsia,polyuria,precocious puberty and abnormalities of thermoregulation.All four cases were alpha-fetoprotein and beta-human chorionic gonadotrophin(p-HCG)negative except patient 3 who had slightly elevated p-HCG in cerebrospinal fluid(CSF).No malignant cells were detected in the patients'CSF.Brain magnetic resonance imaging findings were diverse in these patients with the exception of the unique and common characteristics of ipsilateral hemisphere atrophy,especially in the cerebral peduncle.All patients were diagnosed with germinomas of the basal ganglia and thalamus by stereotactic brain biopsy.CONCLUSION Stereotactic brain biopsy is necessary to confirm the diagnosis of ectopic germinomas.Serial neuroimaging studies can not only differentiate disease but also determine the biopsy site.

Time-domain hydrodynamic analysis of pontoon-plate floating breakwater

The hydrodynamic behaviors of a floating breakwater consisting of a rectangular pontoon and horizontal plates are studied theoretically. The fluid motion is idealized as two-dimensional linear potential flow. The motions of the floating breakwater are assumed to be two-dimensional in sway, heave, and roll. The solution to the fluid motion is derived by transforming the governing differential equation into the integral equation on the boundary in time domain with the Green＇s function method. The motion equations of the floating breakwater are established and solved with the fourth-order Runge-Kutta method to obtain the displacement and velocity of the breakwater. The mooring forces are computed with the static method. The computational results of the wave transmission coefficient, the motion responses, and the mooring forces of the pontoon-plate floating breakwater are given. It is indicated that the relative width of the pontoon is an important factor influencing the wave transmission coefficient of the floating breakwater. The transmission coefficient decreases obviously as the relative width of the pontoon increases. The horizontal plates help to reduce the wave transmission over the floating breakwater. The motion responses and the mooring forces of the pontoon-plate floating breakwater are less than those of the pontoon floating breakwater. The mooring force at the offshore side is larger than that at the onshore side.

视网膜中央静脉阻塞后发生新生血管性青光眼的危险因素和预测模型建立

目的:探讨视网膜中央静脉阻塞(CRVO)后发生新生血管性青光眼(NVG)的危险因素,在基础上构建预测模型。方法:选择2016-02/2020-03我院眼科收治的483例527眼CRVO患者临床资料并随访至2021-06,统计CRVO合并NVG情况。采用多因素Logistic回归分析CRVO后发生NVG的危险因素。根据危险因素回归系数构建CRVO后发生NVG的风险预测模型,Hosmer-Lemeshow(H-L)检验、受试者工作特征(ROC)曲线法评价预测模型。结果:患者失访15例23眼,随访15~64(中位数35)mo,其中70例86眼发生NVG(NVG组),398例418眼未发生NVG(非NVG组)。回归分析结果显示缺血型CRVO、首次就诊时IOP≥18mmHg、高血压、首次就诊时相对性瞳孔传入缺陷(RAPD)≥0.75logU、首次就诊时裸眼视力(UCVA)>0.30(LogMAR)是CRVO后发生NVG的危险因素(P<0.01),抗VEGF治疗是CRVO后发生NVG的保护因素(P<0.01)。CRVO后发生NVG的风险预测模型具有较好的符合度(H-L检验P>0.05)以及判别度(曲线下面积为0.877,95%CI:0.830~0.924,灵敏度为84.3%,特异度为88.9%)。进一步构建预测评分模型,其CRVO后发生NVG的临界值为5分,曲线下面积为0.844(95%CI:0.790~0.898),灵敏度为78.6%,特异度为87.4%。结论:缺血型CRVO、首次就诊时IOP≥18mmHg、高血压、首次就诊时RAPD≥0.75logU、首次就诊时UCVA>0.30(LogMAR)、抗VEGF治疗与CRVO后发生NVG密切相关,据此建立预测模型具有较好的预测效能。

An Evolutionary Algorithm with Multi-Local Search for the Resource-Constrained Project Scheduling Problem

This paper introduces a hybrid evolutionary algorithm for the resource-constrained project scheduling problem (RCPSP). Given an RCPSP instance, the algorithm identifies the problem structure and selects a suitable decoding scheme. Then a multi-pass biased sampling method followed up by a multi-local search is used to generate a diverse and good quality initial population. The population then evolves through modified order-based recombination and mutation operators to perform exploration for promising solutions within the entire region. Mutation is performed only if the current population has converged or the produced offspring by recombination operator is too similar to one of his parents. Finally the algorithm performs an intensified local search on the best solution found in the evolutionary stage. Computational experiments using standard instances indicate that the proposed algorithm works well in both computational time and solution quality.