已知$f(t) \Longleftrightarrow F(j\omega)$,则$f(4-3t) $的傅立叶变换为 A: $\frac{1}{3} F(-j \frac{\omega}{3}) e^{-j \frac{4}{3} \omega}$ B: $3F(-j3\omega) e^{-j \frac{3}{4} \omega}$ C: $\frac{1}{3} F(j \frac{\omega}{3}) e^{-j \frac{4}{3} \omega}$ D: $3F(j3\omega) e^{-j \frac{3}{4} \omega}$

（4）唱片获得了动能多大？ A: $mR^{2}\omega^{2}/4$ B: $mR^{2}\omega^{2}/2$ C: $mR^{2}\omega^{2}$ D: $mR^{2}\omega^{2}/3$

（接上题）（4）唱片获得了动能多大？ A: $mR^{2}\omega^{2}/4$ B: $mR^{2}\omega^{2}/2$ C: $mR^{2}\omega^{2}$ D: $mR^{2}\omega^{2}/3$

下列信号中，（ ）信号的频谱是连续的。 A: $x(t) = A\sin (\omega t + {\varphi _1}) + B\sin (3\omega t + {\varphi _2})$ B: $x(t) = 5\sin 30t + 3\sin \sqrt {50} t$ C: $x(t) = {e^{ - at}}\sin {\omega _0}t$

最大值为______ $\Omega$。

We evaluated the associations between serum omega-3 and omega-6 poly-unsaturated fatty acid levels and colon cancer risk in a study conducted between 1997 and 2002. We included 363 cases of colon cancer and 498 disease-free controls. Serum omega-3 poly-unsaturated fatty acid levels were inversely associated with colon cancer risk. Subjects in the upper 33% of serum omega-3 poly-unsaturated fatty acids had a 33% lower risk of colon cancer as compared with subjects in the lower 33% of serum omega-3 poly-unsaturated fatty acids. In contrast, the risk of colon cancer was increased by omega-6 poly-unsaturated fatty acids by 68%. This is the first study that simultaneously finds an inverse association of serum omega-3 poly-unsaturated fatty acids and a positive association of omega-6 poly-unsaturated fatty acids with colon cancer. The study design is a:

设\( \Omega \) 是由\( 1 \le x \le 2 \) ，\( 0 \le y \le 1 \) ，\( 0 \le z \le 2 \) 所围区域，则\( \mathop{\int\!\!\!\int\!\!\!\int}\limits_{\kern-5.5pt \Omega } { { x^2}yz} dv \) =\( {7 \over 3} \)

偏心因子的定义式（ ） A: [img=166x25]1802e152dc71db3.png[/img] B: \omega =-lg(P^s_r)_{T_r=0.8}-1 C: \omega =-lg(P^s_r)_{T_r=0.7}-2 D: \omega =-lg(P^s_r)_{T_r=0.7}

3、$R_{\rm i}=R_{\rm s}+R_{\rm b<br/>}//r_{\rm {be}}\approx 4\rm{k\Omega}$，。 A: Yes B: No

设$A$是与刚体固结坐标系与定系的转换矩阵，则刚体运动时角速度定义为_____。 A: $\bar{\omega }=\dot{A}A^{T}$ B: $\underline{\omega }=\dot{A}A^{T}$ C: $\omega=\dot{A}A^{T}$ D: 以上都不正确