The dynamics of neighborhood property crime rates

We investigate theoretically and empirically the inter-temporal dynamics of neighborhood property crime, a prime contributor to the quality of life and the vitality of markets in urban areas. We develop a microeconomic model of year-to-year changes in crime rates that incorporates endogenous relationships between the recruitment of criminals and deterrent effects spawned by responses of neighborhood residents and/or police. We operationalize the model using annual panel data for census tracts in Cleveland, Detroit, and Seattle, and use dynamic panel econometric procedures to estimate parameters. Although the details vary across cities, all estimated models demonstrate a time path that converges to a stable state within 10 years and often sooner, ceteris paribus, regardless of the size of disequilibrating shock. The Cleveland and Detroit models provide evidence of nonlinear, endogenous deterrence response effects. The Detroit model provides evidence of an endogenous net fear response producing threshold instability for large increases in neighborhood property crime rates.     

Multilevel Programmable Oxide Diode for Cross-Point Memory by Electrical-Pulse-Induced Resistance Change

A multilevel one-time programmable (OTP) oxide diode for cross-point memory is introduced. The oxide diode is composed of a thin-film p-CuO/n-InZnOx (IZO). By applying negative electrical pulses, the p-CuO/n-IZO diode exhibited multilevel resistance states, and such characteristics of the p-CuO/n-IZO diode could be utilized as the cell of OTP cross-point memory. The resistance-change properties of the p-CuO/n-IZO diode originated possibly from a back-to-back diode phenomenon by oxygen ion migration in the IZO thin film.     

A390铝合金汽车发动机缸套静载拉伸时的断裂行为

分别通过金属型重力铸造和挤压铸造制备了成分相同而显微组织不同的A390合金汽车发动机缸套,并用原位拉伸试验法研究了缸套试样在静载拉伸时的裂纹萌生与扩展行为。试验结果表明,在金属型铸造的合金样品中,微裂纹最初萌生于初生Si上,但未扩展到基体上;主裂纹的萌生来源于基体的剪切带变形,具有较大长宽比的共晶Si为主裂纹提供了快速扩展通道,即具有较大长宽比的共晶Si比初生Si更易扩展主裂纹;在挤压铸造的合金样品中,最初的微裂纹同样萌生于初生Si上,但这些微裂纹扩展到基体上并相互连接成为一条主裂纹;此外,挤压铸造合金中的微裂纹几乎不出现在球状共晶Si上,而初生Si被主裂纹穿过的现象更为普遍。分析结果表明,过共晶Al-Si合金中的初生Si和共晶Si的尺寸大小与形貌分布需要合理搭配与相互协调才能获得更好的力学性能。     

Stress-induced domain dynamics and phase transitions in epitaxially grown VO₂ nanowires

We demonstrate that surface stresses in epitaxially grown VO? nanowires (NWs) have a strong effect on the appearance and stability of intermediate insulating M? phases, as well as the spatial distribution of insulating and metallic domains during structural phase transitions. During the transition from an insulating M1 phase to a metallic R phase, the coexistence of insulating M? and M? phases with the absence of a metallic R phase was observed at atmospheric pressure. In addition, we show that, for a VO? NW without the presence of an epitaxial interface, surface stresses dominantly lead to spatially inhomogeneous phase transitions between insulating and metallic phases. In contrast, for a VO? NW with the presence of an epitaxial interface, the strong epitaxial interface interaction leads to additional stresses resulting in uniformly alternating insulating and metallic domains along the NW length.     

In Situ Study of γ‐TiAl Lamellae Formation in Supersaturated α2‐Ti3Al Grains

In situ heating transmission electron microscopy (TEM) was used to investigate the initial stage of γ‐TiAl lamellae formation in an intermetallic Ti–45Al–7.5Nb alloy (in at.%). The material was heat treated and quenched in a non‐equilibrium state to consist mainly of supersaturated, ordered α₂‐Ti₃Al grains. Subsequently, specimens were annealed inside a TEM up to 750 °C. The in situ TEM study revealed that ultra‐fine γ‐TiAl laths precipitate in the α₂‐matrix at ≈730 °C which exhibit the classical Blackburn orientation relationship, i.e. (0001)α₂//(111)γ and [$11{\bar {2}}0$ ]α₂//<110]γ. The microstructural development observed in the in situ TEM experiment is compared to results from conventional ex situ TEM studies. In order to investigate the precipitation behavior of the γ‐phase with a complementary method, in situ high energy X‐ray diffraction experiments were performed which confirmed the finding that γ‐laths start to precipitate at ≈730 °C from the supersaturated α₂‐matrix.     

van der Waals epitaxy of MoS₂ layers using graphene as growth templates

We present a method for synthesizing MoS(2)/Graphene hybrid heterostructures with a growth template of graphene-covered Cu foil. Compared to other recent reports, (1, 2) a much lower growth temperature of 400 °C is required for this procedure. The chemical vapor deposition of MoS(2) on the graphene surface gives rise to single crystalline hexagonal flakes with a typical lateral size ranging from several hundred nanometers to several micrometers. The precursor (ammonium thiomolybdate) together with solvent was transported to graphene surface by a carrier gas at room temperature, which was then followed by post annealing. At an elevated temperature, the precursor self-assembles to form MoS(2) flakes epitaxially on the graphene surface via thermal decomposition. With higher amount of precursor delivered onto the graphene surface, a continuous MoS(2) film on graphene can be obtained. This simple chemical vapor deposition method provides a unique approach for the synthesis of graphene heterostructures and surface functionalization of graphene. The synthesized two-dimensional MoS(2)/Graphene hybrids possess great potential toward the development of new optical and electronic devices as well as a wide variety of newly synthesizable compounds for catalysts.     

Mass sensitivity calculation of the protein layer using love wave SAW biosensor

Love waves, a variety of surface acoustic waves (SAWs), can be used to detect very small biological surface interactions and so have a wide range of potential applications. To demonstrate the practicality of a Love wave SAW biosensor, we fabricated a 155-MHz Love wave SAW biosensor and compared it with a commercial surface Plasmon resonance (SPR) using glycerol-water solution with known densities and viscosities to calibrate the response signals of the biosensors. And the mass per unit area of anti-mouse IgG bound with protein G onto the sensitive layer of the biosensor was calculated on the basis of the calibration result. The sensitivity of the Love wave SAW biosensor was the same as or greater than that of the SPR biosensor. Furthermore, the Love wave SAW biosensor was capable of measuring a much wider range of viscosities than the SPR biosensor. Although the operating principle of the Love wave SAW biosensor is completely different from that of the SPR biosensor, the subtle changes in the viscoelastic properties of the biological layer that accompany biological binding reactions on the sensitive layer can be monitored and measured in the same ways as with the SPR biosensor.