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After one generation of entrepreneurship, Chinese family firms will gradually usher in the peak of intergenerational succession, and the success of intergenerational succession will also determine the rise and fall of family firms. The principal-agent chain of family firms is short and the cost is small, which can effectively avoid the principal-agent problem. With the gradual improvement of the governance of family firms, whether the family development model,"Being success for no more than three generations", be effectively improved? In this paper, We select Chinese listed family firms in A-share market as research samples to test the market reaction of the intergenerational succession by using the event research method. The empirical results show that the second-generation succession of family firms can often obtain excess returns.

The flow-induced noise near the expansion device can be very disturbing to users. Studies related to the relationship between the flow-induced noise and flow regimes are calling more and more attention in recent decades. However, current studies lack a quantitative relationship between flow characteristics and the flow-induced noise. Therefore, in this paper, a noise-prediction model is proposed to predict the sound pressure level of flow-induced noise. The paper utilizes a pumped R134a loop with a needle valve for synchronized measurements between flow-induced noise and flow regimes. Synchronized high-speed measurements obtained from a microphone and a high-speed camera enable simultaneous investigation of flow-induced noise and flow regimes. Both the experimental results and the modeling results show that the sound pressure level of gurgling noise increases as the flow quality increases or the system mass flux increases. The relative error of the model for most prediction of flow-induced noise is less than 15%. However, in some high-quality cases, such as annular flow-induced noise, the prediction does not predict the noise well.

The flow-induced noise can be very disturbing to the users in the HVAC&R system. The flow-induced noise varies with the flow regimes near the expansion device, especially related to the flow regimes before entering the expansion device. The flow regimes are not only related to the mass flow rate of the flow and the quality of the flow but also related to the gravity orientation of the flow. Therefore, the flow regimes in the tube with different orientations can be different. In this paper, the comparison of the psychoacoustic annoyance of flow-induced noise with different needle valve installations is studied. A needle valve is connected to the system, and the microphone is used as the noise measuring technique. The installation includes the horizontal tube directions, the vertical upward tube directions, the 45o inclined upward tube directions, the 45o inclined downward tube directions, and the vertical downward tube directions. Also, the flow-induced noise generated by an angle valve is used to compare with the straight valve. The results show that the annoyance of flow-induced noise increases as the flow quality increases. Also, it shows that it is the void fraction of the flow other than the quality of the flow that influences the intensity of flow-induced noise. The vertical upward tube installation is the best installation of all five options. The possible explanation is that the flow's void fraction is the lowest as the flow goes vertical upwards. In this case, the intensity of the noise of the case should be the lowest as well. An angle valve is installed as a comparison. It shows that the inlet flow regimes are the primary influence of flow-induced noise for flow-induced noise. The annoyance of which is close to the flow-induced noise of straight valve with horizontal direction.

Flow-induced noise produced by expansion devices can be very disturbing to the user, especially when the device is in the close vicinity of the occupants. This paper characterizes the relationship between flow-induced noise and the flow regime, which may aid the design process of future geometry improvements of thermostatic expansion valves (TXV). A refrigerant loop using pumped R134a with appropriate pre-conditioning sections to vary inlet and outlet conditions is connected to a TXV and an automotive microchannel evaporator. The experiment is set up in a semi-anechoic chamber using microphones, accelerometer, and high-speed pressure transducers. Noise spectrum analysis is performed using the Fast-Fourier-Transform method. Visual access is made through transparent test sections. To the authors’ best knowledge, it is the first-time noise measurements have been linked with two-phase flow regime information for TXV with an adjacent evaporator published in the open literature. A gurgling noise vibrating at 4.4 kHz and 6.0 kHz and a hissing noise at 10.3 kHz is observed. The gurgling noise mostly appeared in the wavy and slug flow regimes, while the hissing noise appeared in all kinds of flow regime. The acceleration signal and microphone signal matched each other perfectly, meaning that the acceleration signal could be used to simulate the flow-induced noise. This paper also proposes some possible geometry improvements based on the results, which could be applied to the industry after further experimental testing.

Flow-induced noise in expansion devices is always a severe problem in HVAC&R applications, such as the TXV noise in an automobile where users are sensitive to noise emissions. This paper introduces a CFD based model for exploring the geometry optimization of an orifice tube using R134a. Relevant parameters including diameter and internal geometry features are discussed in the paper. When the flow is going through the constrained section, liquid R134a turns into vapor. In this paper, the internal fluid flow is solved separately as large eddies and small scales with 3D large eddy method. Phase change that happens in the orifice is computed using mass transfer between liquid R134a and vapor R134a that is similar to what happens in cavitation. The cavitation model is used together with a simplified multiphase model – mixture model. The fluid model and structure model interact with each other with two interactive surfaces within each solving step. Natural frequency describes the vibration of the orifice tube when the interior flow is going through, while vortex shedding frequency is generated when internal flow hits bluff geometry features. The modification of internal geometry significantly mitigates the flow-induced noise by reducing the turbulence of flow field. Increasing the tube wall thickness also weakens the flow-induced noise by lowering resonance with structure vibration. The results are references for geometry optimization of other types of expansion devices, such as manual expansion valve and TXV.

Amphiphilic molecules, comprised of both hydrophilic and hydrophobic domains, have been extensively developed and investigated for various biomedical applications. In this dissertation, polymeric and small molecular weight amphiphiles were rationally designed and utilized as atherosclerotic therapeutics, antimicrobials, and liposome stabilizing agent. Atherosclerosis, a leading cause of mortality in developed countries, is characterized by the buildup of oxidized low-density lipoprotein (oxLDL) within the vascular intima, unregulated oxLDL uptake by macrophages, and ensuing formation of arterial plaque. Amphiphilic macromolecules (AMs) comprised of a branched hydrophobic domain and a hydrophilic poly(ethylene glycol) (PEG) tail have shown promising anti-atherogenic effects through direct inhibition of oxLDL uptake by macrophages. In this study, five AMs with controlled variations were evaluated for their micellar and structural stability in the presence of serum and lipase, respectively, to develop underlying structure-atheroprotective activity relations. In parallel, molecular dynamics simulations were performed to explore the AM conformational preferences within an aqueous environment. Notably, AMs with ether linkages between the hydrophobic arms and sugar backbones demonstrated enhanced degradation stability and storage stability, and also elicited enhanced anti-atherogenic bioactivity. Additionally, AMs with increased hydrophobicity elicited increased atheroprotective bioactivity in the presence of serum. These studies provide key insights for designing more serum-stable polymeric micelles as prospective cardiovascular nanotherapies. The rapid emergence of antibiotic-resistant bacteria and lack of efficacious treatments have prompted extensive research in development of novel antimicrobial agents. Inspired by the unique membrane-targeting mechanism of naturally occurring antimicrobial peptides (AMPs), two series of cationic amphiphiles (CAms) were strategically designed with hydrophilic head groups and non-polar domains segregated to opposite sides of the amphiphiles’ backbone, known as a facially amphiphilic conformation. This orientation has been determined to be critical to elicit membrane-lytic properties. The CAms self-assembled into supramolecular nanostructures above their respective critical micelle concentrations (CMCs) upon direct dissolution. By systematically tuning the hydrophobicity, CAms with optimized compositions exhibited potent activity against both Gram-positive and Gram-negative bacteria as well as displaying negligible hemolytic activity. Scanning electron microscope and transmission electron microscope images revealed the morphology and ultrastructure changes of bacterial membranes induced by CAm treatment and further attested to their membrane-disrupting mechanism. Additionally, an all-atom molecular dynamics simulation was employed to understand the CAm-membrane interaction on a molecular level. This study shows that these CAms can serve as viable scaffolds for rationally designing the next generation of AMP mimics as effective antimicrobials to combat drug-resistant pathogens. Sterically stabilized liposomes have been widely used as long-circulating delivery vehicles. They are typically prepared with poly(ethylene glycol)- (PEG-) modified lipids, where the lipid portion is inserted in the lipid bilayers as an anchor and the hydrophilic PEG coats the surface to prevent liposome aggregation and rapid clearance in vivo. However, these steric protection effects are compromised upon systemic administration due to low retention of PEGylated lipids within liposome membranes upon dilution. Bolaamphiphiles (bolas), comprised of two hydrophilic head groups connected by a hydrophobic domain, can predominantly adopt a membrane-spanning configuration that confers robust bilayer retention. Hence, a series of PEG-bolas were developed to increase retention in the lipid bilayer, presumably leading to enhanced integrity of the PEG protective layer, and thus improved colloidal and biological stability (i.e., phagocytosis by macrophages) of resulting liposome formulations. We hypothesized that PEG-bolas with a sufficiently long hydrophobic domain and rigid central group could preferentially extend across lipid bilayers. Liposomes stabilized by PEG-bolas comprised of a biphenyl core and twelve-carbon alkyl chain exhibited similar storage and biological stability compared to conventional PEGylated lipid stabilized liposomes, but with significantly improved retention upon dilution. In this thesis, bioinspired amphiphiles were rationally designed by mimicking key characteristics of relevant biological molecules. Through systematic structure-activity relationship studies, the physicochemical properties and bioactivity of amphiphiles can be optimized for specific applications.